Thierry Bouche

Evelyne Miot

Célia Vaudaine

The Launch of Centre Mersenne, a Technical Infrastructure to Support the Move Towards Diamond Open Access

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

The Centre Mersenne for Open Scientific Publishing is a non-profit initiative that has been publicly launched in January 2018. Its goal is to build a comprehensive Open Access publishing infrastructure for scientific communities publishing in LaTeX 1 [START_REF] Bouche | Le centre Mersenne pour l'édition scientifique ouverte[END_REF]. It is developed by Cellule Mathdoc, a joint service unit of the mathematical institute of CNRS 2 and Université Grenoble Alpes (UGA) located in Grenoble (France), in partnership with UGA Éditions 3 .

The Centre Mersenne consists of a dissemination platform for scientific publications and a set of modular publishing services for editorial teams. Those services enable editorial committees or small organisations to professionally manage a publication, with all features relevant to their scientific communities without employing a commercial publisher.

Eligible scientific publications can be journals, proceedings, or books, in any scientific domain with a local or international base, provided they are engaged towards Diamond Open Access (aka no APC 4 Gold OA: no subscription fee to read, no submission or publication fee to publish), and the documents are formatted in LaTeX, two principles that are the DNA of the project.

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The Centre Mersenne homepage

CNRS

Context Background: From Cedram Dissemination Platform to the Centre Mersenne for Open Scientific Publishing

Several years ago, the French mathematical community joined forces to set-up a highquality online publishing platform for academically published research math journals [START_REF] Bouche | L'édition sans drame[END_REF]: the Cedram 5 [START_REF] Cherhal-Cleverly | MathDoc and the Electronic Publishing of Mathematics[END_REF] was built by Cellule Mathdoc 6 , a public structure mainly staffed by CNRS, also supported by the university of Grenoble and developing various services towards French librarians and mathematicians, among which Numdam [START_REF] Bouche | The New Numdam Platform[END_REF] 7 (the reference French digital mathematics library), an archive containing digitised journals, proceedings, theses and monographs (58,000 articles and 1,000,000 pages).

The Cedram comprised a dissemination platform and a few other services for mathematical journals publishing in LaTeX [START_REF] Bouche | A PdfLaTeX-based automated journal production system[END_REF], it was launched in 2005. Cedram originally offered editorial teams services such as online posting, a LaTeX production workflow for serials, creation and maintenance of LaTeX styles, production of PDFs for print and web with XML/MathML metadata, DOI 8 registration, reference linking… This publishing platform progressively evolved and extended its services range to OJS 9 maintenance and LaTeX typesetting. To give some figures, in 2017, it contained 9 journals, one book, and 6 proceedings series and was producing and publishing 200 articles and 6,000 pages per year (8,500 articles, 200,000 pages currently online).

The Centre Mersenne is thus built on the expertise gained from the Cedram experience and intends to offer a more comprehensive structure, providing a stronger technical platform, opening up to international journals, to scientific disciplines outside mathematics (but with similar publishing practices), and offering more services.

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Open Access As a Founding Principle 7

The decision to make Diamond Open Access a founding principle of the Centre Mersenne is also an answer to a growing scientific community's call for alternative open access publishing solutions.

Researchers and academic libraries are indeed increasingly challenging the traditional system of scientific publishing, marked by the for-profit publishers oligopoly, where researchers have to pay to access and share their own publications and where libraries and institutions have to face ever rising costs of the "Big Deal" journal subscriptions. Those "Big Deals" are indeed being more and more questioned and cancelled. 9

In parallel, researchers (university or research staff, grant recipients) are progressively required by governments, institutions and funders in Europe [START_REF]Towards a Competitive and Sustainable OA Market in Europe: A Study of the Open Access Market and Policy Environment[END_REF], United States, Canada… to make their published, peer-reviewed journal articles and proceedings papers free to access (mandates). Meanwhile, more journals are converting to open access to meet these requirements [START_REF]Converting Scholarly Journals to Open Access: A Review of Approaches and Experiences[END_REF].

The general idea is that publishing is part of the research activity and should be considered as a research infrastructure, thus controlled by the scientific community and essentially funded by research institutions. The Centre Mersenne is struggling to offer an effective and sustainable alternative open access publishing solution, in a similar fashion to initiatives such as OpenEdition 10 , Episciences 11 (France), SciPost 12 (Netherlands), ELibM 13 (Germany).

The project A new dissemination platform

Being more than a decade old, the Cedram system was starting to show its age. A new platform for hosting and disseminating digital content has been rewritten from scratch during the last two years. It has been first released for the Numdam Digital Library early 2017, and is now adapted to Centre Mersenne's publications. One important feature of the platform is that it uses internally a very standardised structure, but allows for a wide versatility in appearance, so as to endow each journal with a well recognised identity.

All of its content is open access, free for everyone to read and download.

A range of services to facilitate journals management

The Centre Mersenne offers services that provide the necessary technical and editorial tools to help editorial teams publish their journals or books: Some are considered part of the infrastructure, thus are made available for free:

• Online publication and dissemination of articles on the Mersenne platform, including the creation of a specific web site for each publication but also DOI registration, reference linking (zbMATH 14 , Crossref 15 ), interoperability through an OAI-PMH 16 server (to allow anybody to search and reuse metadata) and long term preservation through the CLOCKSS solution 17 , a non-profit "dark archive" that ensures long-term preservation of the content.

• Creation of a LaTeX style template within the Cedram class.

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• Installation of Open Journal System (OJS) for managing submissions and the refereeing process, including customisation of a dedicated instance adapted to the editorial board's evaluation process, maintenance and support but also documentation and training.

Other services, depending on each journal's publishing flow, will be charged, to make the infrastructure sustainable. Here are typical examples:

• Copy editing;

• LaTeX structure and layout editing;

• Managing editor, for journal workflow assistance;

• Plagiarism detection, through Crossref Similarity Check's tool;

• Printing (on demand or a posteriori).

A team

The team is headed by mathematicians, and comprises about ten people bringing diverse skills: IT specialists, a project manager, a LaTeX typesetter… The Centre Mersenne's team has been drawing on the expertise acquired through previous activities of Cellule Mathdoc (the Numdam digital library, the Cedram dissemination platform for mathematical publications).

Governance

The Centre Mersenne isn't a publisher but a platform and service provider. It relies on its governance bodies in order to decide on resource allocation. Two governing bodies are responsible for selecting the publications joining it: the scientific committee, composed of reputable scientists, and the steering committee. Applications of journals wishing to join the Centre Mersenne are considered by the scientific committee on a regular basis. It gives an opinion on the scientific and operational quality of the project, it also helps prioritise the journals' applications and advise on development plans. The final decision is taken by the steering committee taking into account available financial, technical and human resources.

Selection criteria

The Centre Mersenne's governance sets its policy: publications should be peer-reviewed research publications; the articles are selected on behalf of a competent, scientifically independent editorial board; the publication's title is owned by a non-profit organisation (which can be an editorial board, a society…); journals web sites comply with OASPA 18 's "Principles of transparency and best practice in scholarly publishing 19 ", the European Mathematical Society 20 Code of Practice 21 (if applicable)…

These are mostly aligned with Fair Open Access Alliance's principles 22 , while maybe less prescriptive on some issues, as the Centre Mersenne also intends to leave room for innovation.

Business model

The Diamond Open Access model is one of the many names of Gold OA without APC. This means that publication costs should not be covered by authors nor by readers. But, they still have to be covered in some way.

In the Centre Mersenne's case, the structure of costs is as follows:

1. Infrastructure and maintenance, coordination; The institutions supporting Mathdoc (CNRS, UGA) provide the Centre Mersenne all the staff necessary for the development and running of the infrastructure [START_REF] Bouche | Le centre Mersenne pour l'édition scientifique ouverte[END_REF]. They shall also support ( 2) and ( 3), with the existing resources, for about 4 journals a year.

In order for the service to be scalable and sustainable, running costs (4) will have to be borne by the journal. Its team will be responsible for finding funding for its running costs in order to operate smoothly. The typical scenario would be the case of a journal, sustained by an institution that engages its name and resources. That institution will get some visibility in return. Another scenario would be a publication selected by a consortium of libraries willing to encourage transition to Diamond Open Access or any other mechanism as long as they are scientifically sound and economically viable.

The Centre Mersenne is eager to evaluate and discuss any proposed model.

Beginning of the Centre Mersenne

The Centre Mersenne has been inaugurated in January 2018 with the publication of the first issue of the new journal Algebraic Combinatorics 23 . Algebraic Combinatorics was founded by the former editorial board of the Springer-published Journal of Algebraic Combinatorics who resigned in July 2017 and flipped their journal to fair OA. As the editors didn't have any formal (legal) publisher, the MathOA foundation 24 , which also helped with the flipping, took this role.

Three journals are currently applying to join the Centre Mersenne:

• a newly-created generalist mathematics journal, supported by French public institutions, willing to enlarge the number of alternative venues for Diamond OA;

• An existing journal published by a learned society, already OA but willing to get a more professional support;

• A new journal meant as an OA companion to an existing journal, thus anticipating a move to OA for a community quite removed from mathematics. This would be the first publication outside of mathematics discipline for the Centre Mersenne.

All the Cedram publications will be gradually migrated to the Centre Mersenne as its mathematical facet. This migration is expected to be completed before the end of this year.

The Algebraic Combinatorics journal homepage

CNRS

The Centre Mersenne Member Journals

CNRS

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Conclusion

29 The Centre Mersenne for open scientific publishing has gone public since January 2018. It is designed to be an open access scientific publishing infrastructure for the scientific communities publishing in LaTeX. The new platform has already been used to launch a new journal, and should disseminate about 15 journals, some of them new, some of them well established before the end of the year. We currently anticipate a growth of about 4 journals per year, with a balance between newly-created and pre-existing journals, as well as from across all scientific fields.

30 We hope this new venture will be one of the small incremental steps that shall eventually change the landscape of scientific publishing and enable the scientific communities to regain control over it.

BIBLIOGRAPHY at: https://dash.harvard.edu/bitstream/handle/1/27803834/DASH%20Version-Journal-flippingfinal-Aug4-2016-print-2.pdf?sequence=3 NOTES 1. LaTeX is a high-quality typesetting system; it includes features designed for the production of technical and scientific documentation. It is very popular in the scientific community because it enables to effectively typeset mathematics formulas.

CNRS for

2 .

 2 Initial set-up costs per publication; 3. Training of editorial teams and staff; 4. Running costs for each publication, depending on the level of service, editorial organisation, and volume published.

  Centre National de la Recherche Scientifique -the French National Center for Scientific Research. CNRS' website address: http://www.cnrs.fr/ 3. The newly-created university press of UGA, resulting from a merger of the publishing services in Grenoble in Human and Social Science and Science/Technical/Medical. UGA Editions' website address: https://www.uga-editions.com. 4. Article processing Charges: fees required by a publisher from the author to publish his/ her article in a journal. Cellule Mathdoc or Cellule de coordination documentaire nationale pour les mathematiques, develops services towards French librarians and research mathematicians such as Numdam or Cedram. Mathdoc's website address: http:// www.mathdoc.fr/ 7. Numdam's website address: http://www.numdam.org/ 8. DOI (Digital Object Identifier): a unique and long-lasting identifier for an electronic document or a dataset assigned by Crossref, of which the Centre Mersenne is a member. 9. Open Journal System, an open source journal management and publishing software, developed by the Public Knowledge Project. OJS website address: https://pkp.sfu.ca/ojs/. The Launch of Centre Mersenne, a Technical Infrastructure to Support the Move... The European Mathematical Society (EMS) is a learned society representing mathematicians throughout Europe. It promotes the development of all aspects of mathematics in Europe, in particular mathematical research. EMS' website address: http://euro-math-soc.eu/. Algebraic Combinatorics' website address: https://alco.centre-mersenne.org/ 24. MathOA is a foundation aimed at facilitating and accelerating the switch to open access publishing in mathematics (broadly interpreted), using the principles of what we call Fair Open Access. MathOA's website address: http://www.mathoa.org/ABSTRACTS The aim of this paper is to present the Centre Mersenne for Open Scientific Publishing, a new open access scientific publishing infrastructure for publications written in LaTeX. The Centre Mersenne was launched in January 2018 with the first volume of the newly-created journal Algebraic Combinatorics.This non-profit initiative hosted by French public institutions was created to address a growing need within the scientific community for alternative solutions simultaneously scalable, sustainable, trustworthy, of high quality and at fair price.The Centre Mersenne supports publications such as journals, books and proceedings from any scientific discipline, provided they are written in LaTeX and engaged towards Diamond open access. Electronic publishing, Publishing platform, Scientific publishing infrastructure, Open Access, Open access scientific publishing, LaTeX, Open access publishing, Scientific publishing,The Launch of Centre Mersenne, a Technical Infrastructure to Support the Move...

	20. 21. EMS code of practice is available at: http://euro-math-soc.eu/system/files/uploads/
	COP-approved.pdf
	22. Fair Open Access Alliance (FOAA) is composed of a group of scholars and librarians
	aimed at coordinating efforts towards sustainable open access scholarly publishing,
	following the principles of Fair Open Access. Fair Open Access' website address: https://
	www.fairopenaccess.org/. FOAA principles are available at: https://
	www.fairopenaccess.org/
	10. OpenEdition's website address: https://www.openedition.org/?lang=en 11. Episciences' website address: https://episciences.org/ 12. Scipost's website address: https://scipost.org/ 13. ELibM's website address: https://www.elibm.org/ 14. Zentralblatt Math (zbMATH) is an international abstracting and reviewing service in pure and applied mathematics. It contains about 4 million bibliographic entries. ZbMATH's website address: https://zbmath.org/ 15. Crossref is an official Digital Object Identifier (DOI) Registration Agency of the International DOI Foundation. Crossref's website address: https://www.crossref.org/ 16. The Open Archive Protocol for Metadata Harvesting (OAI-PMH) is a mechanism developed for harvesting metadata descriptions of records in an archive to make all publications available to a broader academic public. 17. CLOCKSS (the Controlled-Lots of Copy Keep Stuff Safe) is a non-profit "dark archive" founded by research libraries and academic publishers to ensure long-term preservation 23. Scientific publication, Open sciences
	of online scholarly content. CLOCKSS' website address: https://www.clockss.org/clockss/
	Home 18. OASPA is a OSAPA (Open Access Scholarly Publishers Association) an association AUTHORS
	aiming to support and represent the interests of Open Access (OA) journal and book THIERRY BOUCHE
	publishers globally in all scientific, technical, and scholarly disciplines. OASPA's website Université Grenoble Alpes, France
	thierry.bouche@univ-grenoble-alpes.fr
	ELPUB 2018 ELPUB 2018

5. Cedram's website address: http://www.cedram.org/ 6. address: https://oaspa.org/. 19. OASPA's criteria are available at: https://oaspa.org/membership/membershipcriteria/ INDEX Keywords:

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EVELYNE MIOT

Centre national de la recherche scientifique (CNRS-French National Center for Scientific Research), France evelyne.miot@univ-grenoble-alpes.fr

CÉLIA VAUDAINE

Université Grenoble Alpes, France celia.vaudaine@univ-grenoble-alpes.fr (corresponding author)

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Nothing to do with medicine? Ordinary life, stories and beliefs as educational tools for physicians in Antiquity, Middle Ages and Renaissance

In his treatise On the powers of simple drugs, Galen (2 nd cent.) criticizes the "Sophists'" method of demonstration based on induction and example. Yet he himself resorts to examples, giving them a prominent place in the demonstrative process.

Rāzī (9 th cent.) exemplifies causation, diagnosis, therapy, and relation between the patient, his or her milieu and the physician resorting to stories from all kinds of people, inside or outside the medical milieu. Some of them are examples, like the Galenic ones, some others are telling anecdotes providing guidance, especially moral.

Both Galen and Rāzī transform real-life situations into pieces of medical evidence.

However, "real life" is not independent of time and place. In the Renaissance, the humanists had to reconcile their respect for Galen's medical authority with their own intellectual and social context. Less erudite works aimed at "professionals" engage with religion as part of the readers' "real life", without an explicit link to piety.

Our aim is to study a selection of examples and stories in their context. We would like to focus on the transformation of their nature and use in the framework of knowledge transmission and innovation.

Our study is based on:

• two commented editions of Galen's four treatises On the differentiae and causes of diseases and symptoms: by François Valleriole (1504-1580; edition published in Lyon, 1540), a practicing physician who spent almost all his life in Arles (southern France); and by Leonhart Fuchs (1501-1566; edition published in Paris, 1550), born in Tübingen where he spent almost all his life teaching medicine in the university; • Fuchs's Paradoxa medicinae (Paris, 1555), a work on "errors" committed by the Arabs and the physicians of his time; • The Promptuaire des médecines simples (Tours 1537; Paris 1544) by the French druggist Thibault Lespleigney (1496-1550). • Razi's Spiritual book (Kitāb ṭibb al-ruḥanī), Aphorisms (Fuṣūl), On smallpox and measles, Comprehensive book (Al-Ḥāwī).

We will examine: images explaining the human body and its functioning; Galen's concept of "nature"; the use of Christian concepts/images/storiees; Razi's moral stories; and some "trivial" facts simplifying complex contents.

I.

Understanding the human body thanks to images explaining it 1) Galen refutes the Atomists' opinion (K. 6, 839-840): "the body of living creatures1 is not like the atom (ἄτομος, insectilis) of Epicurus or one of the anarma (ἄναρμα, incompacta, literally "without joints") of Asclepiades. It is therefore in all aspects composite". Disease is the disruption of this composition.

Galen's example: the affection of "a house, made from impassible stones" concerns only their combination; the body is made from sensitive elements, and therefore its affection concerns both the elements and the composition.

The house represents the living body, the stones its components. This concrete image of real life facilitates the understanding of Galen's critique against the medicophilosophical theory of the atomists.

In his comment, Fuchs provides "an example for the sake of clarity" from Galen's De elementis (K. 1, 429-431 = De Lacy V 1,2 72-74): the house made of bricks, stones and timbers and the heap made of wheat, barley, chickpeas and beans. If the components are merely put side by side but remain the same, it is impossible to produce a whole whose qualities are changed; the "sentient" body is something different because it is not the mere product of combination of unchanged components.

The comprehension of these examples seems to Fuchs as obvious as to the Roman reader of the 2 nd cent. B.C.

2) Galen presents the causes of the "cold diseases" and indicates that the right way to preserve the body's internal heat located in the heart (K. 7, 10-13 and 15) is to avoid excess of cold and nourishing, or prevent obstruction of the pharynx and the pores of the skin. Extinction of this heat can be fatal to the "animal".

Galen's examples:

• a flame is immediately extinguished if one pours on it snow/cold water • an oil lamp is extinguished if exposed to too cold surrounding air, as the one in the "Istros" region in winter • too much wood extinguishes the fire; too much oil extinguishes the lamp • a stove cover or a cupping-glass on a flame interrupts the communication with the surrounding air and destroys it because it hinders its respiration • blocking the openings of a furnace produces the same result Both Fuchs and Valleriole comment on "Istros": "the famous river of our Germania which bathes the Illyricum; its other name is Danube" (Fuchs); "the famous German river whose other name is Danube" (Valleriole). Valleriole also refers to the ancient authors (Pliny [Fuchs mentions Pliny too], Strabo and Solinus) for further information about "Istros", as if this were the central point in Galen's example.

Fuchs explains the Greek word πνιγεύς (literally "what drowns/strangles") thanks to "Phavorinus and the Souda". He often explains terms referring to the Greek-Greek lexicon of Phavorinus (cf. also "according to Phavorinus and Souda" for ἀποκύησις K. 7, 27)2 , without translating the Greek lemmas.

Fuchs considers obvious the similitude between the flame and the heat in the heart. Yet the extinction of the flame is the result of a deliberate action (one puts/pours something on it), while the obstruction is the result of a dysfunction of the body (nobody does something to destroy the heat): is the Galenic example accurate? Fuchs does not discuss this point.

One can also pose the question of whether an oil lamp or a furnace, the latter used by Romans as a warming-place3 , are still familiar to the Renaissance reader, and therefore accurate representations of the living body.

3) Galen presents the causes of the hot diseases (K. 7, 3-4) and explains how the heat (which is indispensable for life) becomes fire and the fire a destructive element.

Galen's examples:

• wood or stone rubbed together can light a fire • putrefaction can light a fire: "I myself saw putrefied pigeon's feces kindle intofire"

Valleriole comments on concentration that increases heat, "what people living in cold places like Germania experience in the vaporaria/hypocausta".

Fuchs also refers to the "hypocausta et caldaria nostra": the possessive adjective implies that baths similar to the Roman ones actually exist in his country (Germania). Both Valleriole and Fuchs are comfortable with the comparison between the body and the Roman vaporarium/caldarium. Antiquarianism was quite widespread in some Renaissance milieus, in order to emphasize the positive aspects of ancient culture, including material one: see for instance Girolamo Marcuriale's association with antiquarians in Rome and the illustrations of his work by the artist Pirro Ligorio, which "reconstruct" ancient monuments4 .

Fuchs mentions the whole story narrated by Galen (De temperamentis K. 1, 657-658) about the house in Mysia, which was burnt down because the putrefied pigeon's feces kindled a fire. He casts no doubt about the veracity of this story, which refers to life in Galen's time and place (Asia Minor). It seems obvious to him that his reader can easily transpose this example to his own time and place.

4) In his treatise On smallpox and measles, Razi resorts to facts everyone may have seen e.g. in a garden or a kitchen, in order to explain how a child suddenly breaks out in spots: the child's blood is compared to the juice of a fruit; a ripe fruit produces gas which bursts out suddenly, like spots on the skin. This example makes it easier for the physician (and the patient) to understand the disease.

II. The functioning of the human body

Diseases, symptoms and their causes the physician should recognize and heal.

1) Galen explains the diseases "arising in a dyscrasia of qualities", This may be the result of: (a) too much heat (K. 6, 849). It is easily detected either in the whole body, or in a particular limb. Galen's examples: • legs of people walking too long • hands of people working too hard, e.g. rowing (ἐρέσσειν) or digging (σκάπτειν) • burning sun • heat beside a fire (παρὰ πυρὶ θάλψις) Neither Valleriole, nor Fuchs comments on the two painful open-air activities.

In Valleriole's comment on the marches under the sun we find the story of the bishop of Toul (Tullensis episcopus) a "distinguished" man of "extraordinary probity", a high profile patient, who has been marching for a long time in scorching heat (canicula) without a head cover. Is a bishop supposed to go walking in such circumstances without protection? Or is the example only mentioned to update Galen's one? Or Valleriole just seized this opportunity to contrast the extremely careful (summa diligentia) physician who immediately moistened and refrigerated the patient with the careless bishop? Razi relates a comparable experience: a nurse confronted him about his capacity to heal a child who had contracted measles. Her doubts were removed thanks to Razi's interest in the child's eyes. As the main risk in case of measles is blindness, Razi was actually a skilled physician, the right person to heal the child.

(b) too much cold (K. 6, 850). In case of the whole body, Galen gives the example of people walking too long in too cold places: either they died en route, or they reached a lodging house or their home "half dead and frozen" (ἡμιθανεῖς τε καὶ κατεψυγμένοι).

Fuchs relates a story he knew, shifting the focus from a person walking to a prisoner, i.e. an immobile one, exposed to extreme cold. This "miserable" man was left without clothes or other protection to die in the cold prison because the guard, a "rascal" (nebulo), wanted to abuse his wife. Moreover, the judge was "unaware" of the guard's infamy. Fuchs's update of the initial example includes a moral appreciation that complies with the spirit of his times and readers.

2) Galen presents lethal conditions caused by: (a) "bad appetites of the stomach" (K. 7, 135) such as unquenched thirst. Examples:

• people on a ship, forced to drink sea water • people bitten by the serpent dipsas and reapers intoxicated by wine contaminated by this serpent.

Both Fuchs and Valleriole comment on dipsas, relating the detailed story of how Galen tried to find out if this kind of serpent actually exists in Italy: he questioned the "Marsoi", the serpent hunters, whose answer was negative, but he was not sure about that (De simpl med K. 12, 316-317).

Because of Galen's incertitude, Valleriole cites other sources (Dioscorides, Nicander, Paulus, Aetius, Lucan) and Niccolò Leoniceno's, the expert's, description of the dipsas5 .

Fuchs adds another rural scene, citing Vergil's Eclogues (2, 10-11) and relating the "old reapers'" recipe to avoid intoxication if ever the venomous serpent creeps into the vase when they fall asleep: they add wild thyme (serpyllum) and other ingredients to their food and wine. Both Valleriole and Fuchs take for granted the examples related to the Roman world as if life remained unchanged. Fuchs does not question the efficacy of the reapers' recipe. The commentators provide no information about the actual existence of the dipsas in the 16 th century France or Germany.

(b) changing qualities of a nutriment (K. 7, 227-228). Galen's example: the lethal "Persian plant" which became edible when transported to Egypt.

Thanks to ancient Latin authors, Valleriole explains that the change of qualities depends on the place. He continues with a list of the best regional Italian products, even though he lives in Arles and his audience is supposed to know France better than Italy.

According to Fuchs's commentary, this plant is mentioned in Pliny. The actual reference is in Dioscorides (1, 129, 1-6). It is "an Egyptian tree" Galen saw in Alexandria (De alimentorum facultatibus K. 6, 617). In the Paradoxa (Book 1, c. 27) Fuchs confirms that the plant is not "Persian", but its name, "Persaia" can be misleading.

The two commentaries are "static", while Galen's example is about moving. In the Paradoxa, Fuchs recommends avoiding "exotic" pharmaceutical ingredients and seems not interested in novelties. Such an attitude may be surprising in an era of navigations and discoveries. Fuchs's authorities are almost exclusively ancient, as if a medical student and scholar needed no other culture. This is the reason why one is quite surprised to find twice in the Paradoxa a near-contemporary authority, the Venetian navigator Luis de Cadamosto or Alvise Da Mosto (Aloysius Cadamustus Venetus Patricius 1432-1488)6 author of Navigationes 7 : firstly for the right description of the "blood of the dragon" and secondly for the saccharon/zuccharon, the sweet juice of the bamboo Cadamustus saw in the island of Madera.

III. "Nature", Christian faith and good behavior

This section examines what one can broadly call "Galen's beliefs" and how the humanists cope with them, in an era marked by the importance of the Christian religion.

1) Learned commentaries and treatises

(a) According to Galen, nature (φύσις) "does nothing in vain" (K. 6, 856). "We shall be attributing a certain reasoning (λογισμόν) and purpose (νοῦν) to the nature" (K. 7, 23), because it moves "what is not useful from the important to the unimportant parts" of the body.

Galen's concept of nature is described in detail in his treatise On the function of the parts (De usu partium K. 3, 1-939 and 4, 1-366) 8 .

Valleriole opposes nature to the "powerful yet variable", "perfidious and slippery" Fortuna who is always changing justice to injustice 9 . He cites a poem attributed to Vergil 10 , a "condiment" added to "the sacred theory of medicine", even though it has nothing to do with Galen's passage.

Valleriole develops the topic of the "sacred" medicine in his speech publicly given in Avignon, a lavish praise of Galen and medicine, which is included in the edition of Galen's commentary and whose target audience is the city's authorities. The divine origin of medicine is confirmed by the fact that Jesus proved himself a doctor healing all kinds of people. These healings are not alluded to as "miracles", because Valleriole aims at underlining their medical character. The physician, who preserves human life, is a continuator of God who created life. Valleriole's actual purpose is to prompt the authorities to attract skilled doctors to Avignon, to scrupulously follow their prescriptions as they do their religious obligations, and remunerate them well. "Christianizing" medicine helps him to reach his audience.

In the Paradoxa, Fuchs thinks that the physician, who, according to Galen, is "a minister of nature", should "observe the movement of nature". He then repeats one of his favorite topics, considering his contemporary physicians incompetent "bandits" who enjoy "a complete impunity". He also criticizes the principes who spend their time "drinking and hunting" (compotationes et venationes) and the courtiers (aulici) who are always "chatting, boasting, making promises, speaking nonsense and lying"11 .

In Valleriole's commentary on Galen's recommendation (K. 7, 208-209) to eat meals at regular times, one can also find a rejection of the gluttony and intemperance of people spending their time "taking breakfasts, drinking, taking luncheons, afternoon luncheons, dinners, lunches before the main meal, Bacchanalian revels"12 .

In general, Fuchs and Valleriole adapt Galen's examples to their time when it comes to society. Criticism on their contemporaries' way of life or moral decay provides medical students /scholars with rules of good behavior.

(b)

According to Razi, we can control desire and keep the spirit "healthy" thanks to education, reflection and strong will. These "spiritual" capacities may also be used advisedly, turning a morally reprehensible situation into something positive. Examples:

• adults are able to control evacuation of liquid or solid excrements from the body; This is not the case of for children or animals . • one should be able to suppress or control anger; unable to do that, Galen's mother was always slapping people or breaking objects; yet it is a pity that a person who recovered from anger stopped playing with his beard: this amusing habit was pleasant to the prince • one should not tell lies or boast, like people who relate extravagant stories to attract attention; yet a bizarre story kept the Prince calm and prevented an execution. Saving a life makes the reprehensible attitude actually acceptable.

2) A non-learned treatise intended for druggists: the Promptuaire des médecines simples, by Thibault Lespleigney13 .

Lespleigny educates his "brothers apothicaries" who should know the qualities and use of medicinal substances thanks to narratives from the Bible, systematically rewritten. Religion attracts the attention of the reader who may not have read the Bible, but certainly knows the stories because the majority of them are part of the religious education. Who ignores the burial of Jesus (aloe and myrrh) or the visit of the Magi to the Holy Infant (incense and myrrh)? Or the religious use of incense, "a pleasure for God" used to "chase the evil spirits"? Or even the anointment of Jesus' body with nard/spikenard by Saint Magdalene?

Lespleigny does not limit himself to religious examples. He abundantly refers to Greek, Latin and Arabic authors, using the same method of rewriting their texts. He thus creates a common understanding on how professionals should work.

IV.

"Trivial" facts 1) Galen (K. 7, 229-230) thinks that the cause of the affection (πάθημα) of "what is nourished" is the nutriment, which is in turn "assimilated and changed". Affection and change do not only depend on the balance of power, i.e. strength over weakness/ a large quantity over a small one, but also on "the passage of time": prolonged duration of the action of a weak element modifies a strong one. Galen's examples: • sharp iron "is dulled to some degree in cutting the softest flesh" (duration)

• "stone has some hollow if stuck by a drop of water" (duration)

• pouring "a cotyle of cold into an amphora of boiling water" or "a cotyle of boiling water into an amphora of cold water" affects both (mixture).

Fuchs comments on the hollowed stone thanks to a Latin and Greek proverb and to Erasmus' Adagia (or Chiliades III, III, 3). While Galen's example is simple, Fuchs's explanation is a learned reference intended to be shared with learned readers.

Concerning the mixture of cold and hot water, instead of explaining the measures used by Galen (cotyla/amphora), Fuchs insists on an error of translation (cotyla is not the equivalent of hemina) and encourages the reader to read his annotations in Galen's De sanitate tuenda. Indeed, in the 1541 annotated edition of this treatise, there is a detailed explanation of the terms, followed by a comparison between the Greek and Roman volume measures. Yet it would be difficult for the medical scholar/student of Fuchs's time to understand Galen's example, unless he were familiar with the ancient measures.

Valleriole refers to Latin authors (Cicero, Horace, and the veterinarian Columella) who are supposed to give a concrete idea of the volumes mentioned by Galen. He also uses a near-contemporary learned reference, Georgius Agricola's14 , De ponderis et mensuribus (1533). Yet this is a treatise on ancient Greek and Roman measures, not on their contemporary equivalents.

2) The physician should be able to make a diagnosis thanks to the sounds emitted by the body when a "superfluity" is evacuated (K. 7, 241). One of them can be compared, Galen says, to the sound of the "clarinet" the "tomb singers" (τυμβαῦλαι) play.

Fuchs explains that the "tomb singers" played in the deceased St. Lazarus' house when Jesus came in to resurrect him. How is the physician supposed to recognize this sound that nobody ever heard and compare it to the one emitted by the body of his patient?

Valleriole, on the contrary, mentions the musical instruments of his time (nostra musica instrumenta) and a lively scene: choral songs accompanying the "plebeians'" dances in the streets of Montpellier. He thus facilitates the comprehension of the sound.

3) The allegedly medicinal substance called "mumia": according to Fuchs's Paradoxa, Razes and Serapion, medieval Arab authors, explain it as a kind of "gore" (sanies), a discharge from a dead body mixed with the aloe and myrrh used to coat it.

Fuchs gives no details about the therapeutic use of the "mumia", but insists that in his time it is used as if the Arab authors were right. His contemporaries are stupid and deceitful. Some of them replace aloe and myrrh, rare and expensive ingredients, with crow's excrements. Some others expose corpses as a kind of public entertainment.

Fuchs re-establishes the "truth": mumia is in fact Dioscorides's pissasphaltos (Materia medica 1, 73-74,). Galen mentions the combined effect of pitch (pissa) and asphalt (De simpl med K. 11, 520), and recipes of composed medicines 15 . Pissasphaltos is a mineral medicinal substance that has nothing to do with "gore". The German term is "Tirschenblut": Georgius Transtetter Collimitius, a physician, cartographer and natural scientist from Innsbruck (1482-1535), sent Fuchs an authentic sample.

Therefore, "people must not regard our shops (officinae nostrae) as dens of vultures or cannibals (anthropophagarum), where a human substance is sold as a medicine".

This description has a twofold purpose:

• to underline that medical education includes both behavior and skill;

• to highlight the error of Razes, Serapion and their followers, which is the source of this "commerce with corpses". This gives Fuchs the opportunity to criticize an actual phenomenon of his time, without posing the question of a probable change in nature and use of substances from Antiquity to Middle Ages and Renaissance.

Conclusion

The humanists shift the focus of their comments according to what is at stake. And what is at stake depends not only on the theme dealt with in Galen, but also on whether this theme is open to further interpretation, social criticism, or controversy. But the humanists are also men of their age, and the sixteenth century concerns are not the same as those of the Roman age.

Bookish culture stands in the forefront. The humanists disseminate it to students and scholars, but they do not completely neglect reality, including religion. This can be regarded as their particular method to "update" Galen and share medical culture 16 .

Razi takes advantage of all kinds of experience, even the most futile, but remains rooted in his time and place, even in cases of philosophical advice and moral prescriptions. The latter may be compared to the way the humanists "update" Galen, aiming at professional education and ethical behavior.

Does medical education transcend time and place? Yes, as far as the Greek sources are concerned. No, as far as scientific and social stances are put forward, in particular the complex relation between the humanists and the Medieval past. The rhetoric of persuasion, including thoughtful engagement with "real life", plays a crucial role for this education, which links past, present and future.

Dina Bacalexi and Mehrnaz Katouzian-Safadi 15 De compositione medicamentum secundum locos K. 13, 320 and De compositione medicamentum per genera K. 13, 372, 548, 558, 560, 740, 754. 16 An overview of medical education/professional formation: Siraisi (2004), 30-36.

Galen, On diseases and symptoms, Ian Johnston, Cambridge

2006, 136, translation: "of the

"Phavorinus": Favorino Varino (Guarinus Camers) bishop of Nocera (1450-1537). He compiled a Greek Lexicon fist published in Rome, 1523: https://onb.digital/result/10305AAD

https://urlz.fr/m4aB

Nancy G. Siraisi, "The Fielding H. Garrison Lecture: Medicine and the Renaissance World ofLearning" BHM 78, no. 1 (2004), 24-27 doi:10.1353/bhm.2004.0045

Leoniceno wrote a treatise On the serpents (1518).

https://www.treccani.it/enciclopedia/alvise-da-mosto_%28Enciclopedia-Italiana%29/ and

"garriendo, iactando, pollicendo, nugando, mentiendo"

"in ientaculis, compotationibus, prandiis, merendis, coenis, antecoeniis, et comissationibus"

We studied his work in our Scientiae 2018 and 2021 talks.

Georg Bauer, physician, natural scientist, mineralogist and philologist: Wilhelm Pieper, "Agricola, Georgius" in Neue Deutsche Biographie 1 (1953), 98-100 https://urlz.fr/m4dm

https://www.treccani.it/enciclopedia/alvise-da-mosto_%28Dizionario-Biografico%29/ This important Venetian navigator (part of an old family, patricians since 1207) explored the Western Mediterranean starting from Madera, and then the Western coast of Africa (Gambia, Senegal). His travel relation, Paesi novamente ritrovati et novo mondo da Alberico Vesputio Florentino intitulato, was first published in Italian in Venice (1507), then translated into Latin (1550), German, French and Portuguese. 7 This is the Latin translation of Da Mosto's work cf. https://urlz.fr/m4ap 8 See discussion by Rebecca Fleming: "Emperor and Demiurge" in Galen and the world of knowledge, ed. by Christopher Gill, Tim Whitmarch, John Wilkins, Cambridge, 2009, 59-84. 9 O Fortuna potens, tam variabilis 10 It continued to circulate in the next century: it is included in Iconologia Deorum (Nurnberg, 1680, p. 162), by Joachim Sandrart, German painter and art historian, (1606-1688), director of the Academy of Nurnberg since 1674). Digitized https://onb.digital/result/10573CD7


Victor Malgras

Yoshitaka Matsushita

Joel Henzie

Yoshiyuki Sugahara

Yusuke Yamauchi

Free-standing membranes from the chemical exfoliation of mesoporous amorphous titania thin film

Thin films are typically bound to their substrate, limiting their integration on rough, porous, curved or chemically/thermally sensitive surfaces. Instead of employing tedious and expensive back-etching processes, certain chemical routes can enable the exfoliation of such thin structures. Herein, we demonstrate that an alkaline treatment can exfoliate a hybrid thin film comprising amorphous titania embedded in well-ordered block-copolymer micelles, which can be redeposited elsewhere. We provide sufficient evidence of the preservation of pore ordering and the importance of neutralizing the solution to spare the system from the redissolution of the titania species.

Several studies have demonstrated the fabrication of mesoporous oxide films through self-assembled softtemplating approaches. [1][2][3][4] Their high surface area, pore size, and ordering are properties that have applications in a wide range of applications, such as sensing, 5,6 biomedical, 7 catalysis, [8][9][10] and self-cleaning coatings. 11 These films are of interest as processing 12 and morphology control are continuously improving. 13 Recently, vertically oriented mesoporous TiO 2 films with long-range ordering have been fabricated by exploiting the unidirectional contraction of a cubic-centered pore geometry (Im m).

14

This example highlights how the features of some nanostructured films are related to the substrate they are adhered to. There are instances, however, where transferring such films on a support with a non-planar surface can be useful; for example, a macroporous substrate for hierarchical filtration membrane and concave electrodes of a battery. Some approaches can achieve free-standing mesoporous organo-silica films at the water/air interface 15 ; however, the lack of subsequent demonstrations and implementations suggests that further processing may be challenging. Manipulating these thin freestanding films in liquid media can be rather challenging. 16 Exfoliation-assisted transfer is a common practice for transferring graphene from the synthesis platform for characterization or device integration, 17,18 where simple, inexpensive, and non-destructive methods are generally favored. Herein, we demonstrate that mesoporous amorphous titania films can be exfoliated from their Si substrate by using an alkaline treatment and further transferred onto a new substrate, while retaining its mesoporous morphology. This approach employs soft forces as tools to separate the substrate from the film: while the former is maintained, face down, at the air-water interface through capillarity, the latter is pulled downward by gravity. We also emphasize the importance of controlling the pH of the final solution before extracting the free-standing film, which helps preserving the Ti-O x scaffold. The as-synthesized mesoporous titania film, of thickness 100 nm (± 10 nm), was selected because of its toughness, longrange pore ordering, and the ability to contract and generate vertical porosity upon annealing, which presents promising aspects for nano-/microfiltration membrane technology (SEM and AFM images are shown in Fig. 1). 14 In such systems, the predominant aqueous phase containing the Ti 4+ species induces the formation of spherical micelles from the selfassembly of a polystyrene-b-poly(ethylene oxide) (PS-b-PEO) block copolymer, where the hydrophobic PS tails are oriented Please do not adjust margins Please do not adjust margins inside while the hydrophilic PEO heads remain outside to interact with water. The presence of water can ensure, at least, partial hydration of the native SiO 2 layer, which lies above the silicon wafer, into silanol terminals (Si-OH). Because the PS blocks are allocated within the micelles, the adhesion of the film is expected to rely mostly on the hydrogen bonds (H-bonds) between the ether oxygen from the PEO blocks and the acidic silanol groups from the hydrated silica (Fig. 2, top-left). [START_REF] Fleer | Reagents in Mineral Technology[END_REF] The hydrolysis reaction described by equation 1 is fast, resulting in low probability to observe titanium hydroxychloride species.

20

(1)

The condensation reaction (equation 2) can proceed slowly if performed in highly acidic aqueous media, 21 however, it is generally completed rapidly during evaporation-induced selfassembly as the removal of water drives the process, resulting in amorphous titania, likely in the form TiO x (OH) y , embedded in polymeric micelles.

(

) 2
While the ether oxygen-silanol H-bonds take place immediately as the film is cast on the substrate, other adhesive interactions can arise from the inorganic components of the film after condensation, such as H-bonds between silanol and Ti-OH or -O-terminals (Fig. 2, top-right). Deprotonation of anchoring H-bonds can be achieved using an alkaline agent, such as NaOH, to trigger the desorption of PEO and titanium oxyhydroxide species from the surface.

22,23

Heating the film at temperatures higher than 100 °C was found to be necessary to consolidate the structure by triggering titania condensation, increasing the x/y ratio, and thus preventing complete dissolution during the alkaline treatment. Si-O-Ti bonds, are known to form at relatively low temperature, 24,25 and can logically take place from the proximity of silanols and titanium hydroxides terminals (equation 3).

(

) 3
Beyond 150 °C, however, their abundant formation is expected to be responsible for firmly fastening the titania film to the substrate, thus suppressing subsequent exfoliation. The effect of temperature on the film integrity and exfoliability is described in more detailed in Fig. 2. This approach was also experimented on films fabricated using Pluronic® poly(ethylene oxide)-b-poly(propylene oxide)b-poly(ethylene oxide) F127 and P123 according to methods reported in references 4 and 26, respectively. In such case, despite the preliminary thermal treatment, the film whether dissolves (≤ 120 °C), or become insensitive to the alkaline exfoliation (≥ 150 °C), highlighting the importance of a sturdy and interconnected amorphous titania backbone. The ultra flat surface of Si and the weak interactions with silanol groups appear to be critical factors enabling exfoliation, since other substrates with higher roughness and different surface Please do not adjust margins Please do not adjust margins chemistry, such as glass and ITO-coated glass, did not permit the release of the film.

Under optimal conditions, the film exfoliates within 30 min (Fig. 3a and videos in supplementary information) and can be collected on a substrate of choice, such as another Si chip. We selected a film with holes (from spin-coating defects) to show that patterns are kept intact and do not propagate during the exfoliation. The integrity of the mesoporous network was evaluated through TEM observation. Assuming that the freestanding membrane preserved the body-centered cubic Im m porous structure (a = 23.3 nm), the hexagonal and cubic patterns observed in Fig. 3b andc can be assigned to the and planes, respectively. It is believed that the inherent sturdiness of the parent mesoporous TiO 2 film is partially responsible for maintaining the pore structure during exfoliation. Grazing-incidence small-angle X-ray scattering (GI-SAXS) patterns of the film at the different stages of the process can be observed in Fig. 4, with a special focus on the in-plane ordering (white rectangle on the 2D patterns, inset). The as-deposited film annealed at 120 °C exhibits a lattice of 16.3 nm, which is retained after exfoliation and redeposition. Following redeposition, two different annealing steps are applied in order to study their impact on pore-topore spacing. The shift induced by subsequent heating steps is assigned to a slight reduction of the lattice to 15.1 nm at 150 °C and 14.6 nm at 400 °C. While the former shift could be directly attributed to the loss of volume following water evaporation, the latter is more likely to be caused by crystallization-driven contractions. Annealing the as-deposited film, firmly attached to the substrate, has been reported to induce unidirectional contraction without affecting the lateral pore lattice, 14 however, the loosely adhered membrane appears to undergo isotropic stress which could explain the shift observed. In addition, the expansion of the spot width and length along the semi-circular shape suggests a broader size distribution and a loss of verticality (e.g., slanted, tortuous), respectively.

The chemistry of the free-standing films was investigated by X-ray photoelectron spectroscopy (XPS) to understand the implications of annealing, exfoliation, and neutralization treatments on chemical coordination (O 1s and Ti 2p in Fig. 5, C 1s in Fig. S1,ESI †). In addition to the usual adventitious carbon, the contribution to the C 1s in the pristine sample is expected to include the organic skeleton still present in the film (as PS-b-PEO block copolymer). This participation is reduced after annealing treatments because of the removal of most aliphatic coordinated carbon and partial oxidation of remaining organic moieties (shifted toward higher binding energies, at approximately 288.8 eV). This is accompanied by an increase in Ti-O x contribution in the O 1s signal, observed at ~530.5 eV, caused by the crystallization of TiO 2 . The increasing Ti 2p intensity is attributed to the significantly higher density in the TiO 2 crystal. After exfoliation, the alkaline treatment appears to disturb TiO 2 condensation during the final annealing step, as can be deduced from the loss of the Ti-O x signal in both O 1s and Ti 2p contribution. This can be expected as under high-pH conditions (>14), excess concentration of OH -can selectively dissolve amorphous titania from the surface, while sparing the bulk Ti-O-Ti network. The dissolution of titanate under basic conditions is at the core of the hydrothermal chemistry responsible for the formation of TiO 2 nanotubes. 27 The presence of Na in the To circumvent this effect, we sought to alter the pH conditions so condensation can be favored within the vicinity of the isoelectric point of TiO 2 (pH 4.5 -6.8). [START_REF] Anpo | Studies in Surface Science and Catalysis[END_REF]29 Therefore, an Please do not adjust margins Please do not adjust margins additional neutralization step is performed immediately following exfoliation, where 0.1 M HCl is added dropwise until neutral pH is reached. This should reduce considerably the concentration of OH -responsible for dissolving the titania species. This has a critical impact on how the free-standing film condenses, as the Ti-O x signal (O 1s and Ti 2p) is almost identical to the annealed film (unexfoliated). We also observe a dramatic reduction of the Na species contribution (1s and KLL), washed off by the acid neutralization (Fig. S2, ESI †). Finally, the weak C 1s intensity suggests that most organic compounds have been efficiently removed, and the resulting surface chemistry seems to limit the adsorption of adventitious carbons. X-ray diffraction (XRD) was employed to assess the crystallization of each sample (Fig. S3, ESI †). Although the clear XPS signal confirms the presence of Ti-O x in the neutralized sample after annealing, the crystallinity of TiO 2 cannot be detected by XRD. At this stage, it is impossible to confirm whether the crystallite size is confined below the diffraction detection limit (nanocrystalline, semicrystalline), or some other mechanism acts as crystallization inhibitor. Instead, the sharp reflections observed on the XRD pattern can be assigned to the Si substrate and to NaCl crystals, as previously suggested.

This study is a step forward to establish effective protocols to transfer mesoporous (semiconducting) oxides to different substrates (non-planar, chemically/thermally sensitive). Alkaline treatment is leveraged to break the hydrogen bonds responsible for the adhesion of the organic template/titania film on parent substrates. Such approach preserves the mesoporous structure and pore-to-pore distance, and the dissolution of Ti 4+ can be inhibited through an additional neutralization step, however further work is necessary to optimize the chemistry driving the crystallization of TiO 2 .

Fig. 1

 1 Fig. 1 a) SEM images of the mesoporous amorphous titania film (annealed at 150 °C) before exfoliation. b) AFM image of the mesoporous TiO2 film annealed at 400 °C.100 nm

Fig. 2

 2 Fig. 2 Schematic illustration highlighting the major components responsible for adhering the film on the Si substrate. The film is composed of orderly packed spherical micelles embedded in partially condensed titania (top). N.B. A single micellar layer is represented for simplification, in reality 25 to 30 layers are stacked on one another. Briefly, H-bonds between silanol terminals and the PEO groups from the block copolymers (top left) as well as titanium oxyhydroxides (top right) are expected to accommodate adherence prior to any thermal treatment. Annealing at < 100 °C does not achieve sufficient condensation, thus alkaline treatment dissociates condensed domains and the film dissolves. Between 100 and 150 °C, the formation of larger Ti-O-Ti networks prevents dissolution, and exfoliation can take place as the H-bonds with the silanol terminals are weakened through deprotonation. Beyond 150 °C, exfoliation can no more be achieved due to the formation of abundant Si-O-Ti bonds fastening the TiO2 scaffold on the substrate. The chemical configurations at the bottom illustrate the assumptions of bond breaking during alkaline treatment, and bond formation (in purple) during annealing.

  exfoliated structure is confirmed from the strong Na 1s signal (Fig. S2, ESI †) at 1071.45 eV and can be attributed to the development of TiO-Na terminals, or the formation of NaCl crystals when the residual Cl -ions (HCl) present in the sol film are immersed in the alkaline solution.

Fig. 3 a

 3 Fig. 3 a) Photograph of the amorphous titania film during exfoliation process. TEM images of the as-exfoliated free-standing film, exhibiting b) hexagonal ordering from the (111) plane and c) cubic ordering from the (100 plane of the Im m structure.

Fig. 4

 4 Fig.4SAXS patterns corresponding to the integration shown in the insets (right), highlighting the retained mesoporous structure and pore-to-pore distance.

Fig. 5

 5 Fig.5XPS resolved around O 1s and Ti 2p for films annealed at 120 and 400 °C, and exfoliated films without and with neutralization, followed by 400 °C thermal treatment.

Acknowledgments

This work was supported by the JST-ERATO Yamauchi Materials Space-Tectonics Project (JPMJER2003), the Queensland Node of the Australian National Fabrication Facility (ANFF-Q), and the NIMS ICYS. TEM observations were carried out by the TEM station, XPS and XRD have been performed by the Surface Analysis Platform (NIMS).


Victor Malgras

Yasuhiro Shirai

Toshiaki Takei

Yusuke Yamauchi

Coalescence-driven verticality in mesoporous TiO 2 thin films with long-range ordering

Keywords: mesoporous, TiO 2, block copolymers, soft-template, films, pore ordering, vertical pore

Mesoporous semiconducting films with continuous interconnectivity and minimal tortuosity, such as densely ordered arrays of vertical channels, are ideal for ensuring a maximal surface area at the heterojunction to increase the density of charges or photons (absorption/emission). While designing these films with nanostructures below 50 nm using modern lithography is not feasible, continuously perpendicular pores can be obtained throughout a TiO 2 film using a traditional soft-templating approach and lyotropic crystal engineering. We demonstrate here that a polystyrene-b-polyethylene oxide block copolymer in a three-solvent system can self-assemble into a body-centered cubic Im m template. The long-range threedimensional periodicity of the template combined with a high degree of vertical contraction results in coalescence of the pores into orthogonal channels that are strongly interconnected with their nearest neighbors in the ( ) plane. This work presents evidence of lateral long-range ordering with continuously transverse vertical porosity in a TiO 2 material, which will enable functional applications, such as filtration, sensing, catalysis, and optoelectronics. To this end, we demonstrate the ability of the films to template and host methylammonium lead iodide perovskite nanocrystals.

Introduction

Nanofabrication technology has been at the center of scientific research for several decades and has opened the door to ever downsizing circuitry. Most optoelectronic devices heavily rely on the heterojunction interface between two semiconductors. While typical technologies leverage "clean" planar junctions, increasing the interfacial surface density by texturing the junction can enhance the charge separation and optical in/output. However, traditional fabrication methods, such as lithography and nano-etching, are not only time-and energy-inefficient, require the use of toxic chemicals, and produce a significant amount of waste but also face limitations when the feature size is less than 100 nm. Although modern techniques such as optical and electron-beam lithography can theoretically achieve a resolution of 10 nm, their throughput and consistency make these techniques relatively unattractive for commercial applications. Molecular self-assembly has been recognized as a promising bottom-up alternative to creating materials with a wide variety of nanoscale patterns on a large scale using a simple chemical apparatus. [START_REF] Malgras | Templated Synthesis for Nanoarchitectured Porous Materials[END_REF][START_REF] Malgras | Nanoarchitectures for Mesoporous Metals[END_REF] These networks can act as soft templates to host precursors and shape the negative replica of various inorganic materials. TiO 2 is an example of a semiconducting oxide with remarkable properties for electronic devices and catalysis that can be shaped through softtemplating. [START_REF] Vivero-Escoto | Recent Progress in Mesoporous Titania Materials: Adjusting Morphology for Innovative Applications[END_REF][START_REF] Ismail | Mesoporous Titania Photocatalysts: Preparation, Characterization and Reaction Mechanisms[END_REF] In particular, highly ordered and interconnected mesoporous materials have an ideal structure to generate large accessible surface areas. A simple design consisting of perpendicular cavity arrays with minimal tortuosity, which could form one of the two combs from a three-dimensional (3D) interdigitated heterojunction, can be used for various types of (opto-)electronic devices, such as photovoltaics, LEDs, lasers, and transistors. [START_REF] Wang | Continuous Fabrication of Free-Standing TiO 2 Nanotube Array Membranes with Controllable Morphology for Depositing Interdigitated Heterojunctions[END_REF][START_REF] Zhao | Interdigitated CuS/TiO 2 Nanotube Bulk Heterojunctions Achieved via Ion Exchange[END_REF][START_REF] Zhao | Conformal Filling of TiO 2 Nanotubes with Dense M x S y Films for 3D Heterojunctions: The Anion Effect[END_REF] An interfacial texture with a high aspect ratio is known to enhance the density of both transferred charges and absorbed/emitted photons. While verticality enables accessibility, anisotropy, and the space necessary to connect the mesoporous surface with the substrate, high-ordering allows for density, consistency, and possibly coupling (plasmonic, photonic crystals, polarization). [START_REF] Molenkamp | Highly Polarized Luminescence from Optical Quality Films of a Semiconducting Polymer Aligned within Oriented Mesoporous Silica[END_REF][START_REF] Haberkorn | Templated Organic and Hybrid Materials for Optoelectronic Applications[END_REF] Such vertical features can also be leveraged in membranes, where straight transversal channels with monodisperse aperture sizes and catalytically active walls would be attractive functionalities for various microfiltration, sensing, and catalytic applications.

Unlike SiO 2 , however, molding TiO 2 remains challenging. [START_REF] Soler-Illia | Chemical Strategies to Design Textured Materials: From Microporous and Mesoporous Oxides to Nanonetworks and Hierarchical Structures[END_REF] The condensation rate and pH of the precursor phase constitute a dynamic system, and predicting the final configuration outside equilibrium is difficult. In traditional two-dimensional (2D)-hexagonal packing, the denser {10} lattice planes (parallel to the cylindrical pores) have a lower surface energy and primarily lie flat on the substrate. This affinity generally prevents channel-like structures from orienting perpendicular to the substrate. It is well known that the mesophase can transition from one state to another during the drying process as it moves beyond the critical micelle concentration. [START_REF] Brinker | Evaporation Induced Self-Assembly: Nanostructures Made Easy[END_REF] Grosso et al. determined that in cetyltrimethylammonium bromide or Brij 58 templates, the mesophase transitions from P6 3 /mmc (3D-hexagonal close packing) to Pm n (face-centered cubic close packing) and finally to P6m (2D-hexagonal packing). [START_REF] Grosso | A First Insight in the Mechanisms Involved in the Self-Assembly of 2D-Hexagonal Templated SiO 2 and TiO 2 Mesostructured Films during Dip-Coating[END_REF][START_REF] Grosso | Fundamentals of Mesostructuring Through Evaporation-Induced Self-Assembly[END_REF] In addition, the template calcination temperature can be close to the crystallization point, and crystal growth tends to cause the mesoporous structure to collapse. Therefore, the films can undergo several transformations during the annealing process, which can result in unexpected features.

The use of block copolymers based on poly(ethylene oxide) and poly(propylene oxide) (i.e., PEO x -b-PPO y -b-PEO x ) as template materials has been reported for the fabrication of mesoporous TiO 2 films by Wu et al., specifically Pluronic® P123 block copolymers (x/y = 20/70). [START_REF] Wu | Formation of Highly Ordered Mesoporous Titania Films Consisting of Crystalline Nanopillars with Inverse Mesospace by Structural Transformation[END_REF] Because of the small PEO hydrophilic block size, the pore walls are relatively thin and are subject to considerable migration during the thermal treatment, resulting in well-ordered vertical TiO 2 nanopillars. By contrast, when the films are templated with F127 (x/y = 106/70), the resulting thicker walls accommodate crystal expansion during annealing, which maintains the pore shape.

Several groups have reported the formation of orthogonal features, although it remains unclear whether the vertical cavities are continuous throughout the entire thickness, and limited evidence of long-range ordering is available. [START_REF] Grosso | Highly Porous TiO 2 Anatase Optical Thin Films with Cubic Mesostructure Stabilized at 700[END_REF][START_REF] Koganti | Generalized Coating Route to Silica and Titania Films with Orthogonally Tilted Cylindrical Nanopore Arrays[END_REF][START_REF] Shan | A Facile Approach for Controlling the Orientation of One-Dimensional Mesochannels in Mesoporous Titania Films[END_REF] It is not uncommon for vertical features to remain localized at the surface of the film; [START_REF] Jiang | Synthesis of Highly Ordered Mesoporous Alumina Thin Films and Their Framework Crystallization to γ-Alumina Phase[END_REF][START_REF] Weng | A High-Speed Passive-Matrix Electrochromic Display Using a Mesoporous TiO 2 Electrode with Vertical Porosity[END_REF] therefore, surface measurement techniques, such as scanning electron microscopy (SEM) or grazing-incidence small-angle X-ray diffraction (GISAXS), when considered alone can be misleading unless supported by cross-sectional imaging.

Hence, soft-templated mesoporous crystalline TiO 2 with vertical/transversal porosity and longrange lateral ordering represents a fabrication challenge. Here, we report a detailed approach to synthesizing mesoporous TiO 2 films through a soft-template approach using poly(styrene)-b-PEO (PS-b-PEO) amphiphilic block copolymers in a multi-solvent environment, which sets the conditions for effective evaporation-induced self-assembly. We carefully monitored the evolution of the pore ordering throughout the annealing process to explain the formation of channels with a high degree of ordering and verticality and demonstrated the ability of the film to isolate the formation of monodisperse perovskite nanocrystals.

Results and discussion

The mesoporous TiO 2 films were formed by adding a hydrolyzing aqueous TiO 2 precursor to the PS-b-PEO block copolymer fully dissolved in a tetrahydrofuran (THF)/ethanol solvent mixture. During the deposition, the sequential evaporation of volatile solvents (THF followed by ethanol) packs the micelles in a well-ordered fashion. After aging under atmospheric conditions (~23 °C, relative humidity between 30 and 50 %), gentle condensation was induced by annealing at a low temperature (100 °C) to ensure sufficient contrast during electron microscope observations and to limit possible damage during focused ion beam (FIB) cross-sectional cutting.

The surfaces and cross-sections of the resulting films were observed by field emission SEM (FE-SEM, Figure 1A) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM, Figure 1B), respectively, which showed the long-range ordering of the pores in all directions. While the pore ordering at the surface span domains of 1.5 to 5 µm before changing direction (boundaries are highlighted by dashed lines in Figure 1A andB), it is continuous and consistent throughout the film thickness. The mesoporous ordering, which is maintained over the entire sample but simply rotated around the vertical axis from domain to domain, can be assigned to the (011) plane of a distorted body-centered cubic structure (bcc, Im m). This structure was previously reported for mesoporous SiO 2 based on a PS-b-PEO block polymer with a similar block size and mesoporous TiO 2 based on Pluronic F127. [START_REF] Grosso | Highly Porous TiO 2 Anatase Optical Thin Films with Cubic Mesostructure Stabilized at 700[END_REF][START_REF] Yu | Syntheses of Silica/Polystyrene-block-Poly(ethylene oxide) Films with Regular and Reverse Mesostructures of Large Characteristic Length Scales by Solvent Evaporation-Induced Self-Assembly[END_REF] Despite annealing the samples at a low temperature, the volume loss resulting from the complete removal of solvents caused a significant distortion. The observed spacing was measured to be 5.8 nm. Because the film contraction left the surface relatively intact, the lattice parameter of the undistorted cubic cell, nm, could be estimated from the observed , , and (Figure 1C-E). From the calculated undistorted ( nm), the film contracted to ~ 36 % of its original thickness. This conclusion is supported by the ellipsoidal shape adopted by the pores, with a minor-to-major pore diameter ratio of 0.42.

FE-SEM and GISAXS were used to monitor the surface and mesostructural changes as a function of annealing temperature (Figure 2). Before any thermal treatment (left image), when the film is still fully hydrated and no contraction has occurred, and on the GISAXS pattern are equidistant, resulting in a hemispherical shape for the spot dispersion of an ideal Im m structure. As the applied temperature increases to 300 °C, the X-ray scattering pattern gradually elongates in the q z direction. The compressed lattice spacing and pore shape resulting from the aforementioned film contraction is inverted in reciprocal space and appears as a vertical elongation of both the pattern and reflection spot shape. Meanwhile, the condensation and solidification of TiO 2 affords a clear contrast and is responsible for further shrinking the pore-topore vertical distance. While the surface remained mostly unchanged for calcination temperatures up to 400 °C, we observed a sudden switch from 3D to 2D ordering in the GISAXS patterns between 300 °C and 350 °C, suggesting that the isolated pores ultimately merged with their nearest neighbors along the [ ] axis. The films calcined at 400 °C exhibited three distinct spots on the q x,y axis associated with the ( ), ( ), and ( ) diffraction planes (see intensity plot in supplementary information Figure S1). Above 450 °C, gradual collapse of the mesostructure was observed, both from the FE-SEM image and loss of GISAXS contrast.

Further coalescence of inter-pores and inter-walls causes the formation of 1D arrays of nanotrenches. The samples annealed at 400 °C, which represented an optimal compromise between mesostructure and crystallinity, were further studied. The FE-SEM image of the surface magnified at 7.00k (line scan spacing of ~ 14.5 nm) reveals clear contrast patterns forming domains of 1.5 to 4 µm in size (Figure 3A). These Moiré fringes are generated from the overlap between two similar regular patterns with slight mismatching and/or rotated pitch, i.e., the linear raster of the electron beam and the periodic arrangement of pores within each domain. [START_REF] Yamauchi | Generation of Electron Moiré Fringes on Designed Nanoporous Anodic Alumina Films and Their Replicated Ni Cone Arrays: Exploration of Domain Sizes and Nanopore Arrangements[END_REF][START_REF] Wang | Formation of Secondary Moiré Patterns for Characterization of Nanoporous Alumina Structures in Multiple Domains with Different Orientations[END_REF] Note that Moiré domains with low (or no) contrast are not a sign of poor arrangement, but simply indicate that the Moiré conditions are not fulfilled (relative rotation > 20°). The FE-SEM image magnified at 50k provides a clear view of an entire domain (Figure 3B) used to generate the fast Fourier transform (FFT) shown in the inset, where several orthogonal planes can be readily assigned with a close match to and from the GISAXS patterns (Figure 2). We believe that various factors are responsible for such a leap in long-range lateral ordering compared with previous works. 1) The influence of the hydrophilic-lipophilic balance (HLB) of block copolymer assemblies has been widely investigated in systems under thermodynamic equilibrium but scarcely when it comes to mesoporous thin films. [START_REF] Kozlov | Relationship between Pluronic Block Copolymer Structure, Critical Micellization Concentration and Partitioning Coefficients of Low Molecular Mass Solutes[END_REF] Amphiphilic molecules with small HLB values yield dense mesophases (e.g., lamellar) at lower concentrations and can be more difficult to control than those with larger HLBs. Once the lyotropic crystalline phase is reached the more hydrophobic the core is, the more robust the micelle, and thus the harder it is to achieve electrostatic assembly. [START_REF] Wan | Designed Synthesis of Mesoporous Solids via Nonionic-Surfactant-Templating Approach[END_REF] Compared with F127 (PEO 106 -PPO 70 -PEO 106 ), the PS 36 -b-PEO 113 amphiphilic molecules have similar head and tail lengths but a tail that is twice as hydrophobic (HBL F127 = 22, HBL PS-b-PEO = 11.4), [START_REF] Kadam | Micelles from PEO-PPO-PEO Block Copolymers as Nanocontainers for Solubilization of a Poorly Water Soluble Drug Hydrochlorothiazide[END_REF][START_REF] Grunenwald | Hydrophobic Mesostructured Organosilica-Based Thin Films with Tunable Mesopore Ordering[END_REF] which is likely to promote the long-range cohesive assembly of rigid spherical micelles. 2) Inspired by research on solvent vapor annealing, [START_REF] Sinturel | Solvent Vapor Annealing of Block Polymer Thin Films[END_REF] we noticed that the reproducibility and long-range ordering were improved by aging the films for 10 to 20 min in a sealed container containing a petri dish with THF immediately after spin-coating. This step, which has rarely been reported, partially re-dissolves the PS blocks, thereby softening the micelles and enabling enough mobility for the system to relax thermodynamically in a state approaching equilibrium.

The cross-sectional HAADF-STEM image highlights the presence of linear mesochannels continuously connecting the surface pores to the bottom substrate (Figure 3C). Note that the channels have a high degree of verticality and low tortuosity and that the top surface roughness is negligible. Under these synthetic conditions, the thickness of the film is c.a. 130 nm, but this can be easily tuned between 30 and 210 nm by adjusting the block copolymer concentration or the spin-coating speed; however, a high concentrations can lead to a disordered structure, whereas a slower rotation speed can yield irregular coating. The pore wall crystallinity can be assessed from the high-resolution transmission electron microscopy (TEM) image in Four distinct events were distinguished from the thermogravimetric analysis (Figure 4B). Note that we kept the timeline on the x-axis to highlight the effect of the temperature plateau. The initial event A, a 20% mass loss accompanied by an endothermic peak at 50 °C, can be attributed to the evaporation of trapped ethanol. Event B (30% mass loss) likely includes the desorption/evaporation of water, which is known to occur up to 200 °C, as well as other chlorinated species (HCl, Cl -) as side products from the hydrolysis/condensation reactions.

Events C and D are expected to arise from the decomposition of hydroperoxide radicals and from the breakdown of oxidized carbon species into their volatile forms, respectively. These events are caused by the pyrolysis in air of the PS-b-PEO block copolymer. Although previous works have reported the decomposition of similar polymers at temperatures higher than 400 °C, [START_REF] Gutierrez | Hybrid Titanium Dioxide/PS-b-PEO Block Copolymer Nanocomposites Based on Sol-Gel Synthesis[END_REF][START_REF] Scalarone | Porous and Worm-like Titanium Dioxide Nanostructures from PS-b-PEO Block Copolymer Micellar Solutions[END_REF] the extremely slow heating ramp used in our method (1 °C/min) and long plateau could cause these processes to occur at lower temperatures. Finally, the exothermic peak at 365 °C corresponds to crystallization into anatase TiO 2 . The successful formation of vertical channels relies on highly dynamic mechanisms such as the differential evaporation rate of each solvent under the set temperature and humidity. THF, the only solvent in the present system that can fully dissolve the PS block, promotes complete dispersion and prevents aggregation. The presence of ethanol is crucial for efficient wetting of the substrate but also alleviates the transition caused from the rapid evaporation of THF, allowing the system to adjust and reorganize into the appropriate mesophase with a cubic Im m arrangement. Increasing the water content would affect the TiO 2 hydrolysis/condensation reaction; therefore, ethanol acts as an ideal surrogate to dilute the lyotropic liquid crystal. For example, a low ethanol content (10 v/v%) generally leads to disordered porosity (Figure S2A)

and discontinuous vertical features (Figure S2B). On the other hand, an excessive amount of ethanol (75 v/v%) results in large domains with loosely packed square symmetry (Figure S2C).

Similar to the previous sample, the vertical features do not span the whole thickness of the film.

The in-plane spots observed in the GISAXS patterns generated from these discontinuous structures were usually obliquely elongated (Figure S2D).

We also investigated the possibility of tuning the diameter of the vertical channels by selecting PS-b-PEO block copolymers with various PS block sizes (Figure 5). We observed a strong correlation between the PS block size and the pore diameter (measured from the FE-SEM images), as evidenced by the linear trend in Figure 5F (black). Although the pore-to-pore distance dependence upon the PEO block size also seems to be linear (white), the trend fails for molecules where the PS block is significantly larger than the PEO block (PS 130 -b-PEO 91 , pentagon). Most importantly, we observed three levels of mesoscopic ordering: disorder, shortrange order, and long-range order. As opposed to long-range ordering, short-range ordering is characterized by slightly tilted and larger spots on the GISAXS pattern. We noticed that lateral and vertical long-range ordering do not strongly depend on the PS/PEO molecular weight ratio Other space groups were considered because the hexagonal pore geometry observed at the surface could theoretically be the ( ) plane of a face-centered cubic structure (Fm m) or the ( ) plane of a hexagonal (close-packed) structure (P6 3 /mmc). However, the most intense spots on the GISAXS patterns correspond to the dominant diffraction features of the ( ) and ( ) plane families and would not match that of the face-centered cubic nor hexagonal structures. [START_REF] Gonzalez Solveyra | 2D-SAXS in Situ Measurements as a Tool to Study Elusive Mesoporous Phases: The Case of p6mm TiO 2[END_REF] In addition, the location of the pores just below the surface is critical in determining the space group assignment. In a close-packed configuration, the subsequent pores should sit precisely in the middle space between three (for P6 3 /mmc) or four (for Fm m) nearest neighbors from the surface plane. Here, the high magnification FE-SEM image in Figure 6A reveals dark areas that can be differentiated from the top pores (in black) and the pore walls (light gray). These darkgray spots are positioned between two neighboring pores within the same ( ) plane and constitute cavities from calcined micelles located either above (shallow rift) or below the surface (thinning of the TiO 2 layer). This observation corresponds to the ( ) plane of a bcc structure (see inset). These intercalated pores not only afford the ( ) orthogonal planes a high pore density, which justifies the high diffraction intensity but are also expected to bridge the two adjacent vertical channels with a certain degree of microporosity, as illustrated in Figure 6C.

This is also consistent with the surfaces observed after treatment at higher temperatures (450 °C and 500 °C), where further mass movement and the collapse of the mesoporous roof revealed the underlying nano-trenches. Various mechanisms are involved in the film contraction; the major ones are summarized in Figure 6B, where the experimental -spacings are plotted against temperature. After the rapid evaporation of THF, spherical micelles form with the hydrophobic PS blocks at the core due to the remaining ethanol/water mixed solvent. The mesogen concentration is such that selfassembly occurs via loose packing, but the subsequent evaporation of ethanol brings the micelles together in a tighter fashion through unidirectional contraction. [START_REF] Grosso | Highly Porous TiO 2 Anatase Optical Thin Films with Cubic Mesostructure Stabilized at 700[END_REF] This is followed by condensation of TiO 2 , water evaporation and, at a later stage, decomposition of the PEO blocks.

By contrast, the thermal stability of the PS blocks is believed to keep the structure from collapsing until complete decomposition. The coalescence observed in Figure 2 takes place simultaneously with the crystallization into the anatase phase (Figure 4), suggesting that a high atomic mobility facilitates the displacement of TiO 2 nucleation from the forming channels toward the pore walls. We presume this event can only occur if the walls between two neighboring pores in the [011] direction (separated by ) is extremely thin ( h pore ).

Therefore, the balance between pore size, pore-to-pore distance, and contraction dynamics is critical.

We demonstrated the ability of these films to host individual methylammonium lead iodide nanocrystals within their pores. The method is inspired by the screen-printing approach, where ink is spread and pressured through a mesh using a rubber squeegee. Here, a soft polydimethylsiloxane (PDMS) blade was used to drive the perovskite precursor into the pores while cleaning excess material from the surface. The films were then annealed at 100 °C for 15 min to remove the solvent and allow the perovskite to crystallize. FE-SEM images of our mesoporous TiO 2 film, along with a well-known TiO 2 nanopillar film, [START_REF] Wu | Formation of Highly Ordered Mesoporous Titania Films Consisting of Crystalline Nanopillars with Inverse Mesospace by Structural Transformation[END_REF] show the state of the surface before and after perovskite infiltration (Figure S3A-D). Because of the large and irregular spaces between the nanopillars in the well-known TiO 2 film, the formation of polydisperse perovskite crystals (Figure S3B) led to a broad photoluminescence emission band (Figure S3E), with each crystal size emitting at a different wavelength. By contrast, the pores from the mesoporous film appeared to be uniformly filled to some extent (Figure S2D), with negligible agglomeration. As a result, the emission wavelength was clearly blue shifted from the traditional bulk emission (from 745 to 682 nm) with a narrow bandwidth. Therefore, the TiO 2 film with vertically aligned nano-channels can act as both a host template and electron transport material, which can be leveraged in optoelectronic devices in the future.

Conclusions

We have studied in detail the formation of mesoporous TiO 2 films with pore diameters ranging from 10 to 20 nm that are ordered over several micrometers and vertically oriented, as well as strongly interconnected throughout the entire thickness of the film. The soft-template approach uses under-explored low-molecular-weight PS-b-PEO block copolymers that form spherical micelles (PS-core and PEO-shell) packed in a bcc (Im m) structure upon the sequential evaporation of THF and ethanol. From our studies on the temperature, solvent composition, and polymer block size, we conclude that the formation of vertical channels results directly from the coalescence of well-aligned pores in the orthogonal direction [011] due to thermally induced film contraction. The relatively sizeable pore-to-pore distance and slow annealing process allow for crystallization and crystal expansion without jeopardizing the film integrity for temperatures up to 400 °C. As a result, nanocrystalline anatase TiO 2 with crystallites on the order of ~15 nm can be obtained. While the pore size and pore-to-pore distance were observed to be linearly dependent on the PS and PEO block sizes, we could not establish a connection between the PS/PEO molecular ratio and the stability of the system. Instead, it seems that maintaining the PEO block size between 4000 and 6000 mol/g while changing the PS block size to tune the pore diameter can ensure sufficient ordering to generate the post-calcination vertical cavities. The role of ethanol as a PS swelling agent might also represent an interesting subject of study. The clear formation of monodisperse perovskite nanocrystals with the mesoporous film represents promising evidence that it is possible to form an interdigitated structure with a surface area improved by 15-fold compared with its planar counterpart (estimated from pore density, depth, and diameter).

Experimental details

Materials

The PS n -b-PEO m diblock copolymers ({n, m} = {14, 54}, {22, 70}, {36, 113}, {86, 227}, {120, 317}) were purchased from Polymer Source. Methylammonium iodide (MAI) and lead iodide (PbI 2 ) were obtained from Sigma Aldrich. All other chemicals were of reagent grade and acquired from Fujifilm Wako Pure Chemical.

Methods

Si substrates were cut and cleaned through successive sonication in acetone and ethanol prior to deposition. In a typical fabrication process, the first mixture was prepared by dissolving 30 mg of PS 36 -b-PEO 113 block copolymer in 1.2 mL of THF, after which 0.8 mL of ethanol was added.

The hydrolyzing TiO 2 precursor was prepared by slowly adding 150 µL of cold TiCl 4 to 200 µL of concentrated HCl. After redissolution of the rapidly formed precipitate, 300 µL of deionized water was added. The precursor solution was then added to the block-copolymer mixture and stirred for 30 min before being spin-coated on Si substrates at 3000 rpm for 30 s. The films were aged for 15 min under a THF atmosphere, followed by 2 h in a temperature/humidity chamber (IW222, Yamato) at 23 °C and 40% RH, and finally calcined in air at 400 °C for 4 h at a 1 °C/min ramp.

TiO 2 nanopillar films were fabricated according a previously reported procedure. [START_REF] Wu | Formation of Highly Ordered Mesoporous Titania Films Consisting of Crystalline Nanopillars with Inverse Mesospace by Structural Transformation[END_REF] For the perovskite hosting experiment, an equimolar solution of MAI and PbI 2 in γ-butyrolactone (1 M) was prepared and left to stir overnight. A drop of the precursor was drop-cast onto the film, and a PDMS blade was used to manually spread and clean the surface, followed by heating at 100 °C for 10 min.

Material characterization

The surfaces of the films were observed using a scanning electron microscope (Hitachi SU8230) at an operating voltage of 15 kV, working distance of 8.0 mm, and pressure of 2 × 10 -8

Pa. High-resolution TEM and HAADF-STEM images were observed using a transmission electron microscope (JEM-2100F, JEOL) at an acceleration voltage of 200 kV and spot size of 0.7 nm (for STEM). The cross-sections were processed by a FIB (Ga) (Hitachi FB-2100) and thinned to ~80 nm. 2D GISAXS profiles were obtained with a Rigaku NANO-Viewer (microfocus rotating anode; Cu Kα radiation; 40 kV, 30 mA) using a camera length of 680 mm.

ASSOCIATED CONTENT

Supporting Information. Contains 2D integration of small-angle X-ray diffraction data and 3Drendered atomic force microscopy images.

AUTHOR INFORMATION

Corresponding Author

*Victor Malgrasmagras.victor@nims.go.jp* For table of content only

Figure 1 .

 1 Figure 1. A) FE-SEM image and B) cross-sectional HAADF-STEM image of the mesoporous

Figure 2 .

 2 Figure 2. FE-SEM images (top) and GISAXS 2D profiles (bottom) of the mesoporous TiO 2

Figure 3D.

  The crystal lattice, indexed to anatase from the FFT pattern shown in Figure3E, spans the entire wall thickness (~ 8.5 nm) and can reach lengths of up to 30 nm. This was further supported by X-ray diffraction (XRD, Figure4A), where TiO 2 anatase reflection peaks appeared when the films were annealed at temperatures higher than 350 °C. The crystallite size calculated from the Scherrer equation (assuming spherically shaped crystals, K = 0.89) is 14.0 ± 0.7 nm for the samples annealed between 350 and 450 °C and 17.0 ± 0.7 nm for those annealed at 500 °C, which are between the wall thickness and maximum crystal length observed along the channels by TEM.

Figure 3 .

 3 Figure 3. FE-SEM images of the mesoporous TiO 2 film surface at A) 7k and B) 50k

Figure 4 .

 4 Figure 4. A) XRD patterns of mesoporous TiO 2 films annealed at various temperatures. The

  (δ). PS 14 -b-PEO 54 , PS 22 -b-PEO 70 , PS 36 -b-PEO 114 , PS 86 -b-PEO 227 , and PS 120 -b-PEO 318 all have δ between 0.63 and 0.90; PS 22 -b-PEO 70 and PS 86 -b-PEO 227 have short-range ordering (Figure 5C); and, PS 14 -b-PEO 54 and PS 120 -b-PEO 318 are disordered (Figure 5A, E). By contrast, fixing the PEO block size to 4000-5000 mol/g results in long-range ordering, although the δ-values are significantly different (Figure5B, D). Therefore, we can conclude that the ability of the template to adopt and retain long-range ordering is predominantly attributable to the inter-micellar distance dictated by the PEO block size, which later ensures oriented coalescence. We further observed that the films exhibiting a disordered porous surface also lacked continuous vertical channels, highlighting the importance of pore alignment for coalescing in straight anisotropic shapes.

Figure 5 .

 5 Figure 5. FE-SEM images of mesoporous TiO 2 films fabricated from PS n -b-PEO m with different

Figure 6 . 2 .

 62 Figure 6. A) High-magnification FE-SEM images of mesoporous TiO 2 films. Dashed circles

Namiki Foundry and the TEM station facilities from NIMS were both involved in the preparation of samples (FIB) and TEM observations. 3D modeling of the porous structure was carried out using Vesta (ver. 3.3.2). [START_REF] Momma | VESTA 3 for Three-Dimensional Visualization of Crystal, Volumetric and Morphology Data[END_REF]