Stéphanie Bonilauri

Benoît Chevrier

Asgari Asghar

Makhameh Khaneghah

Roozbeh Abolfathi

Robab Ejlalipour

Gilles Sadeghinegad

Berillon

Asghar Asgari Khaneghah

Makhameh Abolfathi

Roozbeh Ejlalipour

Robab Sadeghi

Gilles Berillon

Garm Roud 2, Iran : bladelet production and cultural features of a key Upper Palaeolithic site south of the Caspian Sea

Keywords: Upper Paleolithic, Garm Roud, Northern Iran, Baledet production, Bladelets, Lithic industries Paléolithique supérieur, Garm Roud, Iran du Nord, Production lamellaire, Lamelles, Industries lithiques

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

INTRODUCTION

Due to its location between the Caspian Sea and the Persian Gulf and between the Middle East and East Asia, the Iranian Central Plateau and neighboring areas, the Zagros and Alborz mountains are of particular importance to issues relating to Palaeolithic settlement and mobility. This large region of Central Asia was probably occupied very early since the Lower Paleolithic (e.g., Biglari, Shidrang, 2006;[START_REF] Biglari | Ganj Par: the first evidence for Lower Palaeolithic occupation in the Southern Caspian Basin, Iran[END_REF][START_REF] Coon | Cave Explorations in Iran 1949[END_REF][START_REF] Hole | The Prehistory of South-western Iran: a preliminary report[END_REF]Olszewski, Dibble, 1993;[START_REF] Smith | Palaeolithic Archaeology in Iran[END_REF]. Many sites are located in the Zagros Mountains, mainly from the Middle and Upper Palaeolithic (e.g., [START_REF] Conard | The Paleolithic of Iran[END_REF][START_REF] Coon | Cave Explorations in Iran 1949[END_REF][START_REF] Hole | The Prehistory of South-western Iran: a preliminary report[END_REF]Olszewski, Dibble, 1993;[START_REF] Otte | Origines du Paléolithique supérieur en Asie occidentale[END_REF][START_REF] Smith | Palaeolithic Archaeology in Iran[END_REF], but the quality of the archaeological information is highly variable. New international programs have been running in the country for more two decades. In addition to new surface discoveries, previously known sites have been revisited and several new stratified settlements have been identified and excavated (e.g., [START_REF] Asgari Khaneghah | Prehistoric settlements of Iran. First results of the joint French and Iranian Palaeoanthropological Program at Yazd, Damavand and Amol[END_REF][START_REF] Bazgir | Test excavations and initial results at the Middle and Upper Paleolithic sites of Gilvaran, Kaldar, Ghamari caves and Gar Arjene Rockshelter, Khorramabad Valley, western Iran[END_REF][START_REF] Berillon | Discovery of new open-air Paleolithic localities in Central Alborz, Northern Iran[END_REF][START_REF] Berillon | Late Pleistocene Prehistory in Central Alborz: Preliminary results of the French and Iranian Palaeoanthropological Programme 2006 on the excavation of Garm Roud 2 (Amol, Mazandaran)[END_REF][START_REF] Biglari | Test excavations at the Middle Paleolithic sites of Qaleh Bozi, Southwest of Central Iran, A preliminary report[END_REF][START_REF] Conard | Report on the 2005 Survey of the TübingenIranian Stone Age Research Project in the Provinces of Esfahan, Fars and Kohgiluyeh-Boyerahmad[END_REF]Gashidian et al., 2009;[START_REF] Jaubert | New Research on Paleolithic of Iran: Preliminary Report of 2004 Iranian-French Joint Mission[END_REF][START_REF] Jaubert | The Middle Palaeolithic occupation of Mar-Tarik, a new Zagros Mousterian site in Bisotun massif (Kermanshah, Iran)[END_REF]Otte et al., 2007[START_REF] Otte | Origines du Paléolithique supérieur en Asie occidentale[END_REF]Roustai et al., 2004;[START_REF] Vahdati Nasab | Paleolithic Archaeology in Iran[END_REF][START_REF] Vahdati Nasab | The Upper Paleolithic of the Iranian Central Desert: the Delazian Sites, Semnan Province -a Case Study[END_REF][START_REF] Vahdati Nasab | The open-air Paleolithic site of Mirak, nothern edge of the Iranian Central Desert (Semnan, Iran): Evidence of repeated human occupations during the late Pleistocene[END_REF]. Much more reliable archaeological assemblages and chronological data have thus been obtained and have renewed perceptions of the Palaeolithic in Iran and Central Asia. As regards the Upper Palaeolithic, reconsideration of the Zagros sites began in the 2000s after a reassessment of the Warwasi collections [START_REF] Olszewski | The Early Upper Palaeolithic in the Zagros Mountains[END_REF]Olszewski, Dibble, 1993[START_REF] Olszewski | The Zagros Aurignacian[END_REF], 2006;[START_REF] Otte | La place du Baradostien dans l'origine du Paléolithique supérieur d'Eurasie[END_REF], 2007;[START_REF] Otte | Origines du Paléolithique supérieur en Asie occidentale[END_REF][START_REF] Otte | L'Aurignacien de la grotte Yafteh et son contexte (fouilles 2005-2008)[END_REF]. This raised the question of the origin and cultural area of the Aurignacian: some authors suggest that the Aurignacian originated in Iran, from a local Mousterian, and then spread to the Near East and Europe [START_REF] Otte | La place du Baradostien dans l'origine du Paléolithique supérieur d'Eurasie[END_REF], 2007, 2009), while others maintain that it is clearly distinct from the Middle Palaeolithic and/or hypothesise that Upper Palaeolithic cultures in Iran are very diverse and not only Aurignacian (Bordes, Shidrang, 2009[START_REF] Demidenko | The great North Black Sea region Early Upper Paleolithic and human migrations into the region from different territories[END_REF][START_REF] Conard | The Rostamian cultural group and the taxonomy of the Iranian Upper Palaeolithic[END_REF][START_REF] Ghasidian | Excavations at Ghar-e-Boof in the Fars Province of Iran and its bearing on models for the evolution of the Upper Palaeolithic in the Zagros Mountains[END_REF][START_REF] Olszewski | Whither the Aurignacian in the Middle East? Assessing the Zagros Upper Paleolithic[END_REF][START_REF] Tsanova | The beginning of the Upper Paleolithic in the Iranian Zagros. A taphonomic approach and techno-economic comparison of Early Baradostian assemblages from Warwasi and Yafteh (Iran)[END_REF]. But the debate was mostly limited to caves and rock shelters from Zagros including Warwasi (Otte, Koslowski, 2007;[START_REF] Tsanova | The beginning of the Upper Paleolithic in the Iranian Zagros. A taphonomic approach and techno-economic comparison of Early Baradostian assemblages from Warwasi and Yafteh (Iran)[END_REF], Yafteh (Bordes, Shidrang, 2009;Hole, Flanney, 1967;[START_REF] Otte | New radiocarbon dates for the Zagros Aurignacian from Yafteh cave, Iran[END_REF][START_REF] Otte | L'Aurignacien de la grotte Yafteh et son contexte (fouilles 2005-2008)[END_REF], Gar Arjeneh [START_REF] Bazgir | Test excavations and initial results at the Middle and Upper Paleolithic sites of Gilvaran, Kaldar, Ghamari caves and Gar Arjene Rockshelter, Khorramabad Valley, western Iran[END_REF][START_REF] Hole | The Prehistory of South-western Iran: a preliminary report[END_REF][START_REF] Otte | Témoin aurignaciens dans le Zagros, Iran[END_REF], Gar-é-Boof [START_REF] Conard | The Rostamian cultural group and the taxonomy of the Iranian Upper Palaeolithic[END_REF][START_REF] Conard | Report on the 2005 Survey of the TübingenIranian Stone Age Research Project in the Provinces of Esfahan, Fars and Kohgiluyeh-Boyerahmad[END_REF]Gashidian et al., 2017), Guilvaran and Kaldar [START_REF] Bazgir | Test excavations and initial results at the Middle and Upper Paleolithic sites of Gilvaran, Kaldar, Ghamari caves and Gar Arjene Rockshelter, Khorramabad Valley, western Iran[END_REF](Bazgir et al., , 2017;;[START_REF] Becerra-Valdivia | Chronometric investigations of the Middle to Upper Paleolithic transition in the Zagros Mountains using AMS radiocarbon dating and Bayesian age modelling[END_REF] or Gar-é-Khar [START_REF] Shidrang | Continuity and change in the late Pleistocene lithic industries of the central Zagros: a typo-technological analysis of lithic assemblage from Ghar-e Khar cave, Bisotun, Iran[END_REF][START_REF] Young | Research in the prehistory of Central Western Iran[END_REF]. Out of Zagros, Upper Paleolithic sites are almost absent and the debate is thus limited. Only 3 sites are currently know (they are mostly surface open-air sites and unfortunately they didn't yield chronostratigraphic data): Sefid-ab [START_REF] Shidrang | A typo-technological study of an Upper Paleolithic collection from Sefid-Ab, Central Iran[END_REF], Delazian (Albofathi et al., 2018;[START_REF] Vahdati Nasab | The Upper Paleolithic of the Iranian Central Desert: the Delazian Sites, Semnan Province -a Case Study[END_REF] in the northern zone of the Iranian Central Plateau. In the same area, Mirak was originally described as Middle Paleolithic surface site [START_REF] Rezvani | Settlement patterns of prehistoric cultures in Semnan[END_REF][START_REF] Rezvani | A major Middle Paleolithic open-air site at Mirak, Semnan Province, Iran[END_REF]; recent excavations by the joint French-Iranian Palaeoanthropological Program yielded to the discovery of in situ archaeological assemblages including an upper and an intermediate assemblages with Upper Paleolithic affinities (Vadhati-Nasab et al., 2019). Garm Roud 2 appears to be the only know in Central Alborz [START_REF] Asgari Khaneghah | Prehistoric settlements of Iran. First results of the joint French and Iranian Palaeoanthropological Program at Yazd, Damavand and Amol[END_REF][START_REF] Berillon | Discovery of new open-air Paleolithic localities in Central Alborz, Northern Iran[END_REF][START_REF] Berillon | Late Pleistocene Prehistory in Central Alborz: Preliminary results of the French and Iranian Palaeoanthropological Programme 2006 on the excavation of Garm Roud 2 (Amol, Mazandaran)[END_REF]Berillon, Asgari Khanegha, 2016). The site of Garm Roud 2 was discovered in 2005 and was excavated from 2006 to 2008 by the French-Iranian Palaeoanthropological Program (FIPP). The digs yielded a rich assemblage, from an in situ and stratigraphically clear archaeological level relating to the end of OIS 3, and corresponding to a short occupation related to a hunting halt [START_REF] Berillon | Discovery of new open-air Paleolithic localities in Central Alborz, Northern Iran[END_REF][START_REF] Berillon | Late Pleistocene Prehistory in Central Alborz: Preliminary results of the French and Iranian Palaeoanthropological Programme 2006 on the excavation of Garm Roud 2 (Amol, Mazandaran)[END_REF]Berillon, Asgari Khanegha, 2016). Preliminary studies provided a large lithic assemblage, focused on a bladelet production, with evident Upper Paleolithic affinities (Albofathi et al., 2018;[START_REF] Berillon | Late Pleistocene Prehistory in Central Alborz: Preliminary results of the French and Iranian Palaeoanthropological Programme 2006 on the excavation of Garm Roud 2 (Amol, Mazandaran)[END_REF][START_REF] Chevrier | Moghanak, Otchounak, GarmRoud 2 : nouveaux assemblages paléolithiques dans le Nord de l'Iran. Premières caractérisations typo-technologiques et attributions chrono-culturelles[END_REF][START_REF] Chevrier | L'assemblage lithique de Garm Roud / The lithic assemblage from Garm Roud[END_REF]. Its location outside the Zagros, in central Alborz, and the quality and dating of its context, the lithic assemblage of Garm Roud 2 as a whole, expanded with the material collected from the excavations, appeared to be informative and able to bring material to the debate. In this context it was necessary to reconsider the entire lithic assemblage by a systematic and extensive examination of the lithic typo-technological diversity and the reduction sequences and to compare it to available assemblages from the Iranian Central Plateau and the Zagros to the Middle East and Central Asian regions.

BACKGROUND OF GARM ROUD 2

Garm Roud 2 is an open-air site in a clear stratigraphic context located in the province of Mazandaran, 20 km south of the Caspian Sea, near the city of Amol [START_REF] Berillon | Garm Roud, une halte de chasse en Iran[END_REF][START_REF] Berillon | Discovery of new open-air Paleolithic localities in Central Alborz, Northern Iran[END_REF] (fig. 1). The single 5 cm-thick archaeological deposit (unit 8) is preserved in a valley bottom palaeosol. It appears in the Baliran fluvial sedimentary sequence, which is about 15 m-thick at the location of the site [START_REF] Antoine | Tuf calcaire et séquence alluviale en contexte tectonique actif: la formation de Baliran (province du Mazandaran, Iran)[END_REF][START_REF] Antoine | La séquence stratigraphique de Garm Roud / The stratigraphic sequence at Garm Roud[END_REF]. The weighted average of three radiocarbon dates obtained from in situ charcoal situates the archaeological level at 33,878 ± 3,300 Cal BP [START_REF] Antoine | La séquence stratigraphique de Garm Roud / The stratigraphic sequence at Garm Roud[END_REF] (fig. 2). The 18m 2 excavation yielded a significant concentration of nearly 50,000 archaeological remains including 11,148 lithic artefacts. The minor vertical dispersion and the good preservation of the archaeological remains indicates minor post-depositional disturbance [START_REF] Berillon | Garm Roud, une halte de chasse en Iran[END_REF]. Technical homogeneity of the lithic assemblage was expected and addressed by the two first analyses of a selection of this assemblage [START_REF] Abolfathi | Histoire récente du Paléolithique supérieur dans le Zagros et dans l'Alborz[END_REF][START_REF] Chevrier | L'assemblage lithique de Garm Roud / The lithic assemblage from Garm Roud[END_REF].

MATERIAL AND METHOD

As the quantity of lithic material is very large (11,148 artefacts), this study relates to the whole lithic assemblage coordinated in situ during the 3 campaigns (2006)(2007)(2008) (2,516 pieces); additional observations were made on those without coordinates (8,418 artefacts) (tabl.1 and tabl.2). The procedure focused on cores, blanks production (flakes, blades and bladelets), tools and retouched pieces. We discarded waste, undetermined pieces and most damaged fragments as well as chips and flakes smaller than 2.5 cm long. Finally after this whittling down, the lithic series contains 899 pieces (tabl.2). Using a classical technological approach, the aim of this analyse is to understand the overall process of the technical system, from the procurement of raw material to the production aims.

This article presents thus a study of the raw material and the different technological classes that has produced an overall and dynamic view of the lithic production at Garm Roud 2.

RESULTS

Raw material

The raw materials in the Garm Roud 2 assemblage are varied and can be divided into limestone, chert/flint, quartz, siltstone and rhyolite (tabl.3). Limestone and chert/flint are broadly are dominant (85.8%). These raw materials are locally available in the channel of coarse gravel located near the site as pebbles of various size and colours. Knapping quality is generally medium to good. Some excellent and probably exogenous chert/flint of various colours seem also have been used. This is an important argument discussing the mobility of Garm Roud 2 group(s). However, the small number of these pieces precludes discussion about the original morphology of the blocks. A more detailed petrographic study and identification of raw material outcrops would be necessary in the future. In the typo-technological study that follows, we specify the nature of the raw materials only when they do not seem to be local or when they are of superior quality.

Blank production

The lithic assemblage thus include 899 artefacts and is composed of two main blank categories: mainly bladelets and flakes. Although more rare, some blades are also present.

Flakes

Flakes represent more than 40% of the selected assemblage (n=372). Two broad categories can be distinguished: products from flake cores and waste from bladelet reduction. The first category relate to thick flake ranging from 25 mm to 80 mm long and removed by hard stone percussion. These products present frequent cortical surfaces and various morphologies: short, wide, elongated and débordant. They are linked to the unidirectional, bidirectional and multidirectional flakes cores present in the assemblage (n=14) and mainly made on pebbles (fig. 3). Some of them can be considered as blanks for bladelet cores as. We therefore have to consider two purposes for these flakes, as both core blanks and blank tools.

The second category relates to waste from bladelet production. Indeed the assemblage is also composed of some core microtablets and flakes with one or several straight and/or twisted bladelet scars (fig. 8).

Blades

Ranging from 30 to 40 mm long, blades represent less than 6% of the selected lithic series (n=49). This group includes two blades categories produced by soft percussion: mainintended blades and preparation/maintenance blades for bladelet or blade production (fig.4, n°17 to 20, 26 and 28). The main-intended blades are characterized by various morphologies (with convergent or parallel edges) and various side face, mainly straight and in some cases curve or twist. The direction of the removal on their dorsal face is unidirectional testifying a production on prismatic cores. All blade are made on exogenous raw material (flint -or highquality chert -is over-represented). The absence of blade cores and blade preparation / maintenance indicates that they were produced at another site and imported into Garm Roud 2. Some blades (around 7 or 8 pieces) relate to preparation and maintenance phases but especially for bladelet production. These display the remains of crest hinged scars on their ventral face. Among them, some pieces clearly reflect perfectly controlled production of twisted bladelets, usually carried out on excellent exogenous raw materials (fig. 4,n°20).

Bladelets

Bladelets represent more than 45% of the selected lithic production (n=435) and can be classified in two main categories: main-intended bladelets (n=327) and preparation / maintenance bladelets (n=108). The raw materials are the same for all bladelets and soft percussion was used as confirmed several "bulb spallings" on proximal part of the products [START_REF] Pelegrin | Les techniques de débitage laminaire au Tardiglaciaire: critères de diagnose et quelques réflexions[END_REF]. Among the main-intended bladelets and despite the high percentage of broken bladelets (n=301, 69.2%) it is possible to distinguish two subgroups: straight and twisted bladelets. They result from several reduction strategies: a main in situ production and a secondary outside production.

Straight bladelets

Straight bladelets represent 54,7% of the main-intended bladelet production (n=179/327).

Ranging from 12 to 38 mm long and from 3,5 to 7 mm wide with an average of 5.5 mm in width, these pieces have various morphologies and are more or less regular (fig. 4 Parallel bladelets and some bladelets with convergents edges have been produced from parallel bladelet cores on flakes (around 8 pieces) (fig. 5 n°2 and n°3; fig. 7). The bladelets were removed from a wide, flat surface, on an edge. Débitage is unidirectional but one core shows scars in two opposite directions (possibly indicating maintenance of the flaking surface). Series of removals are often short but we cannot exclude the hypothesis of longer series. Again, hinged scars are frequent due to consumption of the carina (fig. 5,n°2). The striking platform is always flat and is either a natural surface, a large removal or part of a lower face. In only one or two cases, it has been maintained by one or more scars. Some cores (around 4 pieces) have several flaking surfaces in association (convergent and/or parallel). The production may be similar or different on the same core, but never occur over the entire block (fig. 5 n°1 and n°2). Besides these main types of cores, are also presents more complex prismatic bladelet cores (around 4 pieces) (fig. 5,n°6). Limestone and chert/flint were used, both local and exogenous.

The cores display a relatively long series of convergent and/or parallel removals on a wide and slightly convex flaking surface. Preparation of the cores would have been an important phase during which crests, especially posterior ones, were probably made. Maintenance focused on the striking platforms, with the removal of core microtablets from the flaking surface on at least one piece (fig. 5,n°6).

Twisted bladelet

Twisted bladelets represent 45,3% of the main-intended bladelet (n=148/327) and are characterized by a marked twist (n=61) or a moderate twist (n=87) (fig. 4, n°10 to 16). They are mainly ranging from 14 and 38 mm long and from 4,5 to 7 mm wide (for an average of 5.5 mm in width). Apart from a few pieces in which fortuitous torsion occurred during production, the bladelets with a marked twist indicate high-quality and perfectly controlled production. For example, some of these bladelets have short proximal scars: these were needed to shift the guide ridge and the required impact point to twist the removals (fig. 4, n°13 and 15). The direction of the twist is overwhelmingly counter-clockwise (n=55, 90.2%). As regards the moderately twisted bladelets (fig. 4, n°13 and 16), without a matching core, it is difficult to demonstrate intentional production. Several assumptions need to be considered such as: an intentional production; an opportunistic production mixed in with other bladelets; unintended by-products. Although some pieces are probably in the last category, the large number of these bladelets supports the first two hypotheses. A brief review of the direction of the twists shows that it is mostly counter-clockwise, as in the bladelets with a marked twist.

Given the cores studied, the presence of twisted bladelets is surprising as they do not relate to any identified core in Garm Roud 2. It seems that some of the twisted baldelets were imported into the site. However, some maintenance flakes and blades present at Garm Roud 2 show twisted bladelet scars suggesting that twisted bladelets were also produced on the site. Moreover, given that some waste flakes display both straight and twisted bladelet scars, the hypothesis of opportunistic twisted bladelet débitage is also possible.

Preparation and maintenance bladelets

Some bladelets are clearly linked with the preparation or maintenance of bladelet cores. Among them are present bladelets with a thick triangular or trapezoidal section, crested and sub-crested bladelets relating the early stages of production (fig.8 n°1, n°2, n°3, n°4, n°5, n°9). Regarding maintenance phases, some bladelets were used to restore lateral and distal convexities. It is thus possible to recognise thick, narrow bladelets with convergent or parallel edges, on which hinged removals can be observed on the proximal part, and sometimes one or two abrupt side edges (fig. 8,n°6).

Tools

Most of the main-intended bladelets, blades and flakes are not retouched and represents probably the main tools of the lithic assemblage of Garm Roud 2.

Retouched tools are mainly made up of retouched bladelets (n=64) (tabl.4; fig.4, n°1 to 3, 5, 7, 9, 13 to 16, 28). It should be note that the twisted retouched bladelets are over-represented compared to their percentage in the total number of bladelets (n=31/64, 48.4%). This could indicate imports of a larger number of finalised twisted bladelets than straight bladelets, which is also suggested by the absence of cores and the very few remains from twisted bladelet debitage. The retouches are located on the dorsal face of the blanks, on one or both sides and are often short and semi-abrupt. None of them can be considered as stricto sensu Dufour bladelet (for a review of the different definitions of Dufour bladelet, see [START_REF] Lucas | Les lamelles Dufour du Flageolet 1 (Bézenac, Dordogne) dans le contexte aurignacien[END_REF] and only one (uncoordinated) bladelet shows a convergent retouch forming an Arjeneh point.

The percentage of broken retouched bladelets (n=55/64, 85.9%) is much higher than for all bladelets (69.2%). Their condition may partly explain why they were left behind at Garm Roud 2, but a specific intention cannot be excluded, which could be tested through a study of the fractures. The length of the unbroken retouched bladelets ranges from 15.5 to 33.5 mm. Analysis of their mesial width shows a high degree of homogeneity, with 45 retouched bladelets between 4.5 and 6 mm wide (70.3%) . Apart from modifications due to wear and tear, the retouches therefore seem to have been made to adjust the morphology of the bladelet, especially in width, rather than to create a cutting edge. It is therefore likely that some unretouched bladelets were also used for similar purposes because they were of a suitable size.

We also note the presence of some common tools: two endscrapers on flakes (fig. 4, n°25), a dihedral burin on a blade produced with an excellent and probably exogenous raw material (fig. 4, n°26), five retouched blades, two burins on small flakes (although they could be accidental removals) and four retouched flakes with a marginal retouch.

DISCUSSION

Main contributions

The technological analysis of the Garm Roud 2 lithic assemblage show a variety of chaînes opératoires mainly focused on bladelet production and to some extent on flakes. Representing more than 45% of the blanks, bladelets, straight or twisted, show a homogeneity and regularity of their mesial widths around 4.5 and 6 mm. Their mesial width is controlled either during débitage or by a short or very short, direct, semi-abrupt or more rarely abrupt retouch.

As regards straight bladelets, parallel or with convergent edges, all stages of production are represented at Garm Roud, from the acquisition of the raw material through the exploitation of the blocks and the production of blanks and tools. Indeed, as regards flake cores and some bladelet cores, the raw materials were collected locally. These blocks are flaked or broken, and while the flakes may have been retouched to make tools (e.g. endscrapers), they were mainly used as blanks for simple convergent and parallel bladelet cores. As regard twisted bladelets, no twisted bladelet cores have been identified: it seems that some of the twisted bladelets were imported into Garm Roud 2, but it is likely that débitage of such bladelets occured on the site. The presence of a large number of these bladelets and of some maintenance flakes and blades points to several production patterns: very well controlled débitage of bladelets and probably opportunistic production in combination with other kinds of bladelets. A small number of cores relate to prismatic or pyramidal designs and also produced bladelets. These point to more complex technical intentions requiring more preparation and maintenance. It is possible that these cores were prepared and partially used elsewhere, then imported to Garm Roud 2 before being left on the site. Apart from bladelets and flakes, some blades mainly made on exogenous raw material are also present at Garm Roud 2. No evidence supports the idea of a continuity of blade and bladelet reduction strategy: the absence of blade cores and preparation / maintenance blades therefore shows that production was done elsewhere, on exogenous raw materials of excellent quality.

As regards tools, straight and twisted bladelets, unretouched or retouched, are the main components of the toolkit. These are associated with rare common tools related to domestic use (endscrapers, burins). We note the absence of Dufour bladelet and Arjeneh points, two major components of the Zagros Aurignacian industries.

Based on these observations as well as on all archaeological data (e.g. remains of large fragmented mammals with marks of percussion and cut marks, burned bone fragments and lithic artefacts in association with numerous charcoal fragments) the assemblage has been interpreted as representing a single and fairly brief occupation most likely linked to butchering activities and to hunting-related trips [START_REF] Berillon | Garm Roud, une halte de chasse en Iran[END_REF]. In the future, a micro wear analysis of the tools as well as of the retouched bladelets's breakages will allow us to discuss whether this industry is linked only to specialized activities (butchery and/or hunting) and short occupation and/or due to the small excavation area and/or to a cultural tradition.

Regional comparisons

The Upper Paleolithic sites are, in the Central Iranian Plateau and neighbouring areas, mainly concentrated in the Zagros and its foothills. If we consider only stratified sites that have delivered reliable information (Shanidar, Yafteh, Warwasi, Ghār-e Boof, Kaldar), these are very few in number and for old excavations, lithostratigraphic methods have seldom been used, so that the assemblages from some of these sites (e.g. Yafteh, Warwasi) relate to artificial collections, covering different settlements [START_REF] Braidwood | Prehistoric Investigations in Iraqi Kurdistan[END_REF][START_REF] Braidwood | The Iranian prehistoric project[END_REF][START_REF] Conard | The Rostamian cultural group and the taxonomy of the Iranian Upper Palaeolithic[END_REF]Olszewski, Dibble, 1993;[START_REF] Otte | L'Aurignacien de Zagros[END_REF]Otte et al., 2007;[START_REF] Demidenko | The great North Black Sea region Early Upper Paleolithic and human migrations into the region from different territories[END_REF][START_REF] Solecki | Prehistory in Shanidar Valley, Northern Iraq[END_REF]. However, they help to understand evolutionary trends and reflect the presence or the absence of some classes in these archaeological sequences.

Yafteh is currently the best known site in Zagros thanks to new excavation campaigns in the late 2000s [START_REF] Otte | New radiocarbon dates for the Zagros Aurignacian from Yafteh cave, Iran[END_REF][START_REF] Otte | L'Aurignacien de la grotte Yafteh et son contexte (fouilles 2005-2008)[END_REF]. The whole sequence relates only to the Upper Palaeolithic and the dates from Hole and Flannery's excavations (29,000-38,000 BP) have been reassessed [START_REF] Otte | New radiocarbon dates for the Zagros Aurignacian from Yafteh cave, Iran[END_REF][START_REF] Zwyns | Les fouilles 2005-2008 à Yafteh et la chronologie radiocarbone[END_REF], as new samples are now considered to link the entire sequence to a single early phase dated to 33,000 to 35,000 BP, i.e. 37,000 to 39,000 Cal BP. These results may match the earliest Shanidar (Iraq) layer C dates, at 28,000 to 36,000 BP [START_REF] Solecki | Prehistory in Shanidar Valley, Northern Iraq[END_REF]. With these new data, we can dismiss the idea of a comparison with the most recent Garm Roud 2 lithic assemblage (33,878 ± 3,300 Cal BP) and discard the previously suggested hypothesis of a possible link based on the most recent dates from Hole and Flannery's excavations [START_REF] Berillon | Discovery of new open-air Paleolithic localities in Central Alborz, Northern Iran[END_REF][START_REF] Chevrier | Moghanak, Otchounak, GarmRoud 2 : nouveaux assemblages paléolithiques dans le Nord de l'Iran. Premières caractérisations typo-technologiques et attributions chrono-culturelles[END_REF][START_REF] Otte | New radiocarbon dates for the Zagros Aurignacian from Yafteh cave, Iran[END_REF][START_REF] Zwyns | Les fouilles 2005-2008 à Yafteh et la chronologie radiocarbone[END_REF]. Moreover, the new results on the Garm Roud 2 reduction sequences confirm the distinction between this site on the one hand and the Zagros Aurignacian (Yafteh, Warwasi, Shanidar C in particular) linked to the Levantine Aurignacian on the other hand [START_REF] Olszewski | Whither the Aurignacian in the Middle East? Assessing the Zagros Upper Paleolithic[END_REF][START_REF] Otte | La place du Baradostien dans l'origine du Paléolithique supérieur d'Eurasie[END_REF], 2007). If the high proportion of typological burins is still a constant criterion, the significant number of endscrapers, carinated pieces, pointed bladelets such as Arjeneh points and lamelle Dufour in the Zagros Aurignacian, means that Garm Roud 2 must be distinguished from this complex. Furthermore, the technological analysis of the Yafteh industries describes a stratigraphically lower set composed of long, straight or curved bladelets and pointed and lamelle Dufour on the one hand, and an upper complex with small twisted bladelets, lamelle Dufour and burins on the other hand (Bordes, Shidrang, 2009[START_REF] Demidenko | The great North Black Sea region Early Upper Paleolithic and human migrations into the region from different territories[END_REF], which also suggests clear differences with Garm Roud 2. Otherwise, the recent investigations carried out in Kaldar cave and Gilvaran cave and the data relating to the Upper Paleolithic lithic industries, clearly attributed to the Zagros Aurignacian [START_REF] Bazgir | Test excavations and initial results at the Middle and Upper Paleolithic sites of Gilvaran, Kaldar, Ghamari caves and Gar Arjene Rockshelter, Khorramabad Valley, western Iran[END_REF][START_REF] Bazgir | Understanding the emergence of modern humans and the disappearance of Neanderthals: Insights from Kaldar Cave (Khorramabad Valley, Western Iran)[END_REF], also show clear differences with Garm roud 2. N.J. [START_REF] Conard | The Rostamian cultural group and the taxonomy of the Iranian Upper Palaeolithic[END_REF] and [START_REF] Ghasidian | Excavations at Ghar-e-Boof in the Fars Province of Iran and its bearing on models for the evolution of the Upper Palaeolithic in the Zagros Mountains[END_REF] have put forward the hypothesis of a cultural group that differs from the Zagros Aurignacian: the Rostamian. This is located in the southern Zagros and has been defined from the Ghār-e Boof site in particular, where bladelet debitage on blocks using soft stone percussion and wide twisted bladelets with a direct abrupt or semi-abrupt retouch on one or both sides, called Rostamian bladelets, have been recognised. These were found together with small twisted retouched bladelets, a few inverse-retouched bladelets, endscrapers and a very few Arjeneh points. These features clearly distinguish Garm Roud 2 from the Rostamian assemblages, which is also suggested by the early dates of Ghār-e Boof: 31,000-37,000 BP, i.e. 35,000 to 41,000 Cal BP. Out of Zagros, in the Iranian Plateau, Sefid-ab has yielded no date because the assemblage was collected on the surface [START_REF] Otte | L'Aurignacien de Zagros[END_REF][START_REF] Shidrang | A typo-technological study of an Upper Paleolithic collection from Sefid-Ab, Central Iran[END_REF]. However, based on the presence of bladelet Dufour, carinated burins and endscrapers, it has been linked to a recent phase of the Zagros Aurignacian. The Garm Roud 2 assemblage therefore cannot be linked with the Sefid-Ab collection. At last, in the northern fringe of the Iranian Central Plateau, the lithic assemblages of the open-air sites of Delazian and Mirak -the nearest Paleolithic sites to Garm Roud 2 -are the witness of several occupations by different entities during the Upper Paleolithic [START_REF] Vahdati Nasab | The Upper Paleolithic of the Iranian Central Desert: the Delazian Sites, Semnan Province -a Case Study[END_REF][START_REF] Vahdati Nasab | The open-air Paleolithic site of Mirak, nothern edge of the Iranian Central Desert (Semnan, Iran): Evidence of repeated human occupations during the late Pleistocene[END_REF]. The lithic industry of Delazian, although collect on the surface, is focus on straight bladelet production mainly from prismatic cores and on twisted bladelets knapped from carinated cores. The toolkit is various and composed of diverse retouched bladelets including bladelet Dufour and numerous endscrapers, carinated endscrapers and burins [START_REF] Abolfathi | Histoire récente du Paléolithique supérieur dans le Zagros et dans l'Alborz[END_REF]. If this assemblage share clear affinities with the lower and the recent phases of the Zagros Aurignacian [START_REF] Abolfathi | Histoire récente du Paléolithique supérieur dans le Zagros et dans l'Alborz[END_REF][START_REF] Vahdati Nasab | The Upper Paleolithic of the Iranian Central Desert: the Delazian Sites, Semnan Province -a Case Study[END_REF], its typo-technological features distinguish Delazian from Garm Roud 2.

In the same area, the open-air site of Mirak, recently excavated yielded in situ archaeological assemblages including an upper assemblage with Upper Paleolithic affinities but disturbed and poorly preserved and an intermediate assemblage with a mixt of artefacts with Upper and Middle Paleolithic affinities [START_REF] Vahdati Nasab | The open-air Paleolithic site of Mirak, nothern edge of the Iranian Central Desert (Semnan, Iran): Evidence of repeated human occupations during the late Pleistocene[END_REF]. This intermediate assemblage, which may be affiliate to an Early Upper Paleolithic or even to an Initial Upper Paleolithic is characterized by a production of Levallois flakes (points and flakes), blades and straight, curve and some twisted bladelets knapped from unidirectionnal -prismatic -cores and narrow-face cores on flakes. These two assemblages are dated by OSL in the ranges of 21-28ky and 26-33ky respectively (Heydary et al., 2020). Despite a difficult comparison between the assemblage of Garm Roud 2 and those of Mirak, their composition and the sharing of some common features as well as ages highlight how complex the question of Upper and Early Upper Paleolithic in the area.

How to explain the presence of such different typo-technological entities in the different Iranian area? Do connections exist -expansions of humans and/or ideas -between Garm Roud 2 and this part of the Alborz with the neighboring or more distant regions during the Early Upper and Upper Paleolithic? Or do these different entities reflect independent technocultural developments carried out during these Paleolithic periods? To the west of the Iranian regions, in the Levant, two main technocomplexes from the Early Upper Paleolithic are present, the Early Ahmarian focus on blade/bladelet industries and the Aurignacian focus on flake industries [START_REF] Gilead | Upper Palaeolithic tool assemblages from the Negev and Sinai[END_REF][START_REF] Marks | The Upper Paleolithic of the Levant. Synthesis[END_REF]. The Early Ahmarian seem to be around 43-42 ka BP (Belfer-Cohen, Goring-Morris, 2014) with a multiplication of occupations around 34 to 30 ka BP including those, for example, of Qadesh Barnea [START_REF] Gilead | Early upper paleolithic sites in the Qadesh Barnea area, NE Sinaï[END_REF] in the southern, Umm el Tlel area 2 (e.g. layer I4'c') [START_REF] Ploux | Umm el Tlel, une séquence du Paléolithique supérieur en Syrie centrale. Industries lithiques et chronologie culturelle[END_REF] and Wadi Khara 16R [START_REF] Kadowaki | Variability in Early Ahmarian lithic technology and its implications for the model of a Levantine origin of the Protoaurignacian[END_REF] in the northern inland regions, Ksar-Akil X-XI [START_REF] Douka | Chronology of Ksar Akil (Lebanon) and implications for the colonization of Europe by Anatomically Modern Humans[END_REF][START_REF] Bergman | Ksar Akil, Libanon. A technological and typological analysis of the later Palaeolithic levels of Ksar Akil : levels XIII-VI[END_REF] and Üçagizli (Khun et al., 2009) in the mediterranean zone. Despite regional differences, the Early Ahamarian industries share an emphasis on bladelets production, straight and slightly curve, parallel or with convergent edges. Bladelets are modified into retouched (with fines and semi-steep or steep retouches) and backed bladelets as well as into points including El Wad point types. If the core reduction srategies can be focus on a bi-directional blade/bladelet knapping method to a single plateform core or on an opposed platform, mainly for the northern assemblages (Goring-Morris, [START_REF] Goring-Morris | Straight to the point: Upper Paleolithic Ahmarian Lithic Technology in the Levant[END_REF], the bladelet production is, for almost all Early Ahmarian assemblages, based on an unidirectionnal knapping method to a single palteform from the narrow face of a core (Belfer-Cohen, Goring-Morris, 2014) such as, for example, in Nahal Nizza III, industry from which the concept of "narrow fronted core with tyical Y-shaped configuration" was proposed [START_REF] Davidzon | Sealed in stone: the Upper Palaeolithic Early Ahmarian knapping method in the light of refitting studies at Nahal Nizzana XIII, Western Negev, Israel[END_REF]. In almost assemblages, a single core strategy contiuously produces blades and bladelets [START_REF] Kadowaki | Variability in Early Ahmarian lithic technology and its implications for the model of a Levantine origin of the Protoaurignacian[END_REF]. Based on these typo-technological elements, the Garm Roud 2 assemblage can be compared to some Early Ahmarian assemblages, such as that of Umm el Tlel area 2 (I4'c'). Similarities relate to some reduction scheme (unidirectionnal knapping method from a narrow face of a core) as well as the tool kit based in both cases on lightly retouched bladelets (broken for many of them) and charactrized by the absence of El Wad types points [START_REF] Ploux | Umm el Tlel, une séquence du Paléolithique supérieur en Syrie centrale. Industries lithiques et chronologie culturelle[END_REF]. However, the Garm Roud 2 blade/bladelet production remain quite different and a link with the Early Ahmarian industries seem unlikely. The reduction schemes are various and autonomous from cores and flakes and a high number of baldelets have a twist profile. Based on the bladelets technological characteristics and despite important typological differences, the assemblage from Garm Roud 2 share some similarities with the early facies of the Levantine Aurignacian formerly called "A" [START_REF] Copeland | The Middle and Upper Palaeolithic of Lebanon and Syria in the light of recent research[END_REF][START_REF] Goring-Morris | A hard look at the "Levantine Aurignacian: how real is the taxon?[END_REF] as represented by the industries of Ksar-Akil XI-XIII [START_REF] Bergman | Ksar Akil, Libanon. A technological and typological analysis of the later Palaeolithic levels of Ksar Akil : levels XIII-VI[END_REF][START_REF] Williams | Upper Paleolithic Levels XIII-VI (A and B) from the 1937-1938 and 1947-1948 Boston College excavations and the Levantine Aurignacian at Ksar Akil, Lebanon[END_REF], likely Kebara I-II [START_REF] Bar-Yosef | The dating of the Upper Paleolithic layers in Kebara Cave[END_REF] and Umm el Tlel area 5 [START_REF] Ploux | Umm el Tlel, une séquence du Paléolithique supérieur en Syrie centrale. Industries lithiques et chronologie culturelle[END_REF]. The Ksar Akil XI-XIII assemblage, dated for the XII level around 40-39 ka cal BP [START_REF] Douka | Chronology of Ksar Akil (Lebanon) and implications for the colonization of Europe by Anatomically Modern Humans[END_REF] and the Umm el Tlel area 5 industry are based on blades and bladelets production with a high number of twisted bladelets modified into retouched bladelets. The bladelets production modalities are autonomous and diverse -carinated pieces, cores on flakes, unidirectionnal primatic cores including the lateral carinated scraper [START_REF] Bergman | Ksar Akil, Libanon. A technological and typological analysis of the later Palaeolithic levels of Ksar Akil : levels XIII-VI[END_REF]. These assemblages are typologically characterized by a high number of burins and then by end-scrpers, notches and retouched bladelets including, except for the Umm el Tlel tool kit, El Wad points. Nevertheless and despite some technological similarities between the assemblage from Gram Roud 2 and the Early Ahmarian and the Levantine Aurignacian "A" technocomplexes, the differences do not allow to group this industry within the Early Upper Paleolithic traditions of the Levant.

To the east, in Central Asia, the recently studies and discoveries of the Upper Paleolithic sites of Kulbulak, Dodekatym-2 and Shugnou [START_REF] Kolobova | The Upper Paleolithic site of Dodekatym-2 in Uzbekistan[END_REF][START_REF] Kolobova | The Kulbulak bladelet tradition in the Upper Paleolithic of Central Asia[END_REF][START_REF] Ranov | The Upper Paleolithic assemblages of Shugnou, Tadjikistan[END_REF] allowed to highlight a new cultural-technlogical tradition called Kulbulakian which share meany features in common with the Baradostian / Zagros Aurignacian and the Rostamian technocompelxes (Kolobova, Krivoshapkin, 2014) as well as some typo-technological similarities with the lithic assemblage of Garm Roud 2. The early/middle stage complexes of the Kulbulak tradition, estimated possibly around 35-25 ka BP, is characterized by the development of flakes, straight small blades and bladelets from prismatic and narrow-face cores and by non-straight bladelets mainly knapped from carinated cores (Kolobova et al., 2014 ;Kolobova, Krivoshapkin, 2014). The tool kits is composed of many common tools on flakes, numerous retouched blades and bladelets including Dufour bladelets as well as some backed bladelets (Kolobova, Krivoshapkin, 2014). Although the lithic assemblage from Garm Roud 2 share many technological attributes with the early and middle Kulbulakian technocomplex, the significant typological differences prevent us from fully affiliating the assemblage of Garm Roud 2 within this techno-cultural tradition.

Finally, it maybe with some Early Upper Paleolithic assemblages from the northern region of the Caucasus that the techno-typological similarities seem most obvious. In 2012, Y.E. Demidenko have proposed connections between "Southern Caucasus Early Upper Paleolithic" industries and some assemblages of the Southern Zagros (e.g. Garh-e-Bof Cave AH IV-III) and of the Alborz region such as Garm Roud 2 [START_REF] Demidenko | The great North Black Sea region Early Upper Paleolithic and human migrations into the region from different territories[END_REF]. The majority of the "southern Caucasus EUP" assemblages including those of Dzudzuana cave Units D (35-32 ka cal BP) and Ortval Klde rock-shleter layers 4d-4c (40-26 ka cal BP) in the southern as well as Mezmaiskaya cave (35-34 ka BP) in the northern, share similar technical traits based on fine or narrow bladelet and microbladelet production mainly from unidirectionnal -prismatic or pyramidal -cores and narrow-flakes bladelet cores on flakes (e.g. Meshvilani et al., 2004;[START_REF] Bar-Yosef | The implications of the Middle-Upper Paleolithic chronological boundary in the Caucasus to Eurasian prehistory[END_REF]Alder et al., 2008;[START_REF] Golovanova | The Earlier Upper Paleolithic of the Caucasus in the West Eurasian Context[END_REF][START_REF] Demidenko | The great North Black Sea region Early Upper Paleolithic and human migrations into the region from different territories[END_REF]. In all these assemblages, the most distinctive tools types are small (or microliths) finely retouched bladelets (around 2-4 mm wide), fine backed bladelets and light points with bilateral fines retouches. In the eastern part of the southern Caucasus , the assemblage of Aghitu 3 cave AH VI-III (36-24 ka cal BP) [START_REF] Kandel | The Upper Paleolithic settlement of the Armenian Highlands[END_REF][START_REF] Kandel | The earliest evidence for Upper Paleolithic occupation in the Armenian Highlands at Aghitu-3 Cave[END_REF] share also close typotechnological affinities with assemblages mentionned above (e.g. Dzudzuana cave) and offer perhaps the best comparison to Garm Roud 2. Througouht the sequence, the industry show an emphasis on small or narrow bladelet production mainly from unidrectionnal palteform cores. The tools types are mainly represented by laterally finelly retouched bladelets (or one or both edges) while other tools types including a variety of backed bladelets, burins and carinated scrapers are rare as are cores. Additionnally, we can highlight here the presence of narrow bladelets often twisted [START_REF] Kandel | The Upper Paleolithic settlement of the Armenian Highlands[END_REF].

CONCLUSION

The technological analysis of the artefacts collected at Garm Roud 2 presented here has produced a dynamic view of the site's productions and toolkit. Distinctive Upper Palaeolithic features have been identified: straight and twisted bladelets, bladelet cores, retouched bladelets, laminar blanks and some common tools such as burins and endscrapers. If the assemblage of Garm Roud 2 appear to be different from the Zagros Aurignacian, it share common features with some Upper Paleolithic or Early Upper Paleolithic assemblages from peripheral regions : the diversity of knapping patterns and bladelet production, the balanced combination of straight and twisted bladelets, the debitage of numerous flake blanks and the high percentage of bladelets with direct, short, semi-abrupt or even abrupt retouches. Its likely function as a hunting camp (Berillon, Asgari Khanegah, 2016) necessarily influenced the components of the industry and the proportions of cores and tools, but the differences remain significant. One would be tempted to consider Garm Roud 2 as one site within a local techno-complex, which may be peculiar to the Caspian region and later than the Zagros Aurignacian and the Rostamian. However, although a techno-cultural mosaic is usually obvious, it seems premature to define such a complex when few Upper Palaeolithic sites have been surveyed or excavated in the area. A major challenge must now be to find new stratigraphically welllocated sites in northern Iran that could yield reliable dates to further our understanding of cultural relationships between Upper Palaeolithic groups in Central Asia.

Although the Garm Roud 2 settlement, given its late chronology, does not provide new information about the emergence of bladelet debitage, this study has produced new data about the development of these industries and the Upper Palaeolithic groups concerned. Thanks to its precise stratigraphic framework, the Garm Roud 2 site has to be considered as a key site for defining and understanding the evolution of Upper Paleolithic cultural complexes in the Central Iranian Plateau and neighbouring areas and more widely in Central Asia.

Figure 1 .

 1 Figure 1. Location of Garm Roud 2 and main sites listed in the paper

Figure 3 .

 3 Figure 3. Garm Roud 2. Flakes cores on pebble (photo B. Chevrier)

  , n°1 to 9 and n° 21 to 23). Two sub-categories can be distinguished: badelets with convergent edges and points and parallel bladelets. Most of them have been produced in situ and result from different débitage modalities. Mainly baldelets with convergent edges have been produced from convergent bladelet cores on flakes (around 17 pieces) (fig.5). Unidirectional baldelet reduction took place along a dihedral narrow face of the flake (fig.5n°1 -right view; fig.6) or along a wide or a flat surface. In this case the removals are located on the ridges of the wide or flat surface (fig.5 n°1 -left view; fig.5 n°4, n°5; fig.7). In both case, the series of narrow and convergent removal are short (10 to 41 mm long) and followed by numerous hinged scars. Convergent bladelet cores show few preparation stigmas and only one or two cores shows unilateral cresting. The striking platforms may be flat (large scar, cortical or fracture surface) or prepared.

Figure 4 .

 4 Figure 4. Garm Roud 2. Bladelets, blades and tools. N°1 to 9, 21 to 23: straight bladelets (n°1 to 3, 5, 7 and 9: retouched bladelets). N°10 to 16: twisted bladelets (n°13 to 16: retouched bladelets). N°17 to 20, 26 to 28: blades (n°26: burin; n°28: retouch blade on the proximal part). N°24: refitting of bladelets n°21 to 23. N°25: endscraper on flake (drawing B. Chevrier)

Figure 6 .

 6 Figure 6. Garm Roud 2. Summary of the preparation, intended volumes, production and maintenance of the convergent bladelet cores

Table 1 -

 1 Number and composition of the coordinated and uncoordinated artefacts of Garm Roud 2 during the 2005 survey and the 2006-2008 excavations

		N 2006-2008	N 2005 (from survey;	Summ
			Berillon et al., 2007)
	Uncoordinated	8418	-	8418
	artefacts
	Coordinated artefacts	2516	214	2730
	Flakes cores	14	-	14
	Bladelet cores	29	2	31
	Bladelets	505	27	532
	Blades	49	2	51
	Flakes, fragments,	1491	68	1559
	chips
	Waste	362	114	476
	Undetermined	66	1	67
	Summ	10934	214	11148
	Coordinated artefacts	N 2006-2008 sample
	Flakes cores	14
	Bladelet cores	29
	Bladelets	435
	Blades	49
	Flakes	372
	Summ	899

Table 2 -

 2 Composition of the lithic assemblage of Garm Roud 2 after shorting(2006-2008 sample)

Table 3 -

 3 Raw materials composition of the Garm Roud 2 lithic assemblage

Table 4 -

 4 Number of retouched tools at Garm Roud 2

ACKNOWLEDGEMENTS

The authors thank the French Ministry of Foreign Affairs (research grants for archaeological excavations of French-Iranian Palaeoanthropological Program -FIPP), the Service of Cooperation and Cultural Action of the French Embassy in Iran (PAI Gundishapur and student trainings), the Ministry of Science, Research and Technology of the Islamic Republic of Iran (PAI Gundishapur), the Iranian National Science Foundation (INSF), the Center for International Scientific Studies and Collaboration (CISSC), the University of Tehran, the Insitute of Social Studies and Research of the University of Tehran, the UPR 2147 of CNRS and the UMR 7194 CNRS-MNHN-UPVD. We are also grateful to the Iranian Organisation for Cultural Heritage and Tourism, in particular Dr. Massoud Azarnouche and Dr. Hassan Fazeli, successive directors of the Iranian Centre of Archaeological Research during the field research of the FIPP and for permission to study the archaeological material collected in Garm Roud 2. We thank the regional archaeological offices of Mazandaran and Amol. We give thanks to Dr. Marie Soressi for her scientific advice and suggestions and Ilona Bossanyi for linguistic proof reading.


Yanhui Wang

Sanghoon Kim

Nicolas Louvain

Johan G Alauzun

P Hubert Mutin

Acetic anhydride as oxygen donor in the non-hydrolytic sol-gel synthesis of mesoporous TiO2 with high electrochemical lithium storage performances

An original, halide-free non-hydrolytic sol-gel route to mesoporous anatase TiO2 with hierarchical porosity and high specific surface area is reported. This route is based on the reaction at 200 °C of titanium (IV) isopropoxide with acetic anhydride, in the absence of a catalyst or of a solvent. NMR studies indicated that this method provides an efficient, truly non-hydrolytic and aprotic route to TiO2. Formation of the oxide involves acetoxylation and condensation successive reactions, both with ester elimination. The resulting TiO2 materials were nanocrystalline, even before calcination. Small (10 nm) anatase nanocrystals spontaneously aggregated to form mesoporous micron sized particles with high specific surface area (260 m 2 g -1 before calcination). Evaluation of the lithium storage performances showed a high reversible specific capacity, particularly for the non-calcined sample with the highest specific surface area favoring pseudo-capacitive storage: 253 mAh g -1 at 0.1C and 218 mAh g -1 at 1C (C = 336 mA g -1 ). This sample also showed good cyclability (>92% retention after 200 cycles at 336 mA g - 1 ) with a high coulombic efficiency (99.8 %). Synthesis in the presence of a solvent (toluene or squalane) offers the possibility to tune the morphology and texture of the TiO2 nanomaterials.

Introduction

Nanostructured, mesoporous metal oxides are in high demand for advanced applications such as energy storage, photovoltaic conversion, (photo)catalysis or sensing. Due to its outstanding electronic and optical properties, high chemical stability, low toxicity and low cost, nanostructured titanium dioxide is one of the most studied oxide nanomaterials in all of these fields. [1,2] In particular, mesoporous anatase TiO2 is a promising anode material for Li-ion batteries owing to its good capacity, cyclability and safety. [3][4][5] The elaboration of advanced nanostructured materials depends on the development of powerful synthetic methodologies. The sol-gel process is the most common method used to synthesize mesoporous oxides, as it offers the possibility to obtain metastable phases, with control over composition, homogeneity, and texture. Conventional sol-gel based on hydrolysis and condensation reactions naturally predominates, but non-hydrolytic (or non-aqueous) sol-gel (NHSG) chemistry has been found to provide simple and powerful alternative routes notably for the synthesis of mixed oxides, of nanoparticles, and of mesoporous materials. [6][7][8][9][10][11] Among the various NHSG routes described in the literature, two main routes have proven particularly successful: i) the so-called benzyl alcohol route, based on the reaction of metal chloride or alkoxide precursors with benzyl alcohol acting as solvent and oxygen donor [12,13] and ii) the alkyl halide elimination route, based on the reaction of metal or silicon chlorides with alkoxide or ether oxygen donors. The benzyl alcohol route has been used mainly in the preparation of crystalline metal oxide nanoparticles, [7,14] while the alkyl halide elimination route has been used both for the preparation of oxide nanoparticles (in the presence of capping agents [15,16] or in dilute conditions [17,18] ) and for the synthesis of non-ordered mesoporous oxides or mixed oxides. [19,20] Ester elimination between acetate and alkoxide precursors (equation 1) is one of the early routes proposed in NHSG. This route appears seducing because it does not involve chloride precursors. However, the only oxide materials prepared by this route were ZrO2 and SiO2-ZrO2. [21] This limited success was most likely due to the lack of commercially available anhydrous metal acetates. Generating acetoxy groups in situ would be of great interest to widen the scope of the ester elimination route, but the first reaction that comes to mind, the reaction of metal alkoxides with acetic acid, does not afford a non-hydrolytic solgel method as water will form by esterification of acetic acid with the alcohol released (equations 2 and 3). [9,22,23] Water formation can only be avoided in atomic layer deposition methods, where reactants and by-products are flushed after each alternate pulse of metal alkoxide and acetic acid. [24,25] In 1996, Vioux et al. proposed to form acetoxy groups in situ by reaction of acetic anhydride with an alkoxide (equation 4). [26] However, at that time, the reaction was found too slow to be practical and this route remained practically unexplored. Thus, in the case of the reaction of Ti(O i Pr)4 with acetic anhydride, no solid formed even after 7 days at 140 °C in the absence of TiCl4 catalyst. [26] The same reaction catalyzed by TiCl4 was later used by Fox and coworkers to prepare TiO2 nanomaterials in supercritical CO2 at 110 °C, but before calcination only amorphous, poorly condensed powders were obtained. [27] In the present work we revisit the use of acetic anhydride as an oxygen donor. We found that reacting Ti(O i Pr)4 with a stoichiometric amount of Ac2O at 200 °C, in the absence of a catalyst or a solvent, leads in high yield to mesoporous anatase TiO2. The reactions involved were identified, and the morphology, structure, texture and lithium ion storage performances of this mesoporous TiO2 (before and after calcination) were investigated in details. Mesoporous TiO2 samples were also prepared in the presence of toluene or squalane to study the influence of added solvent.

Results and discussion

Reactions involved and nature of residual groups

The first aim of this work was to show that the reaction of a metal alkoxide precursor with acetic anhydride could afford in the absence of a catalyst a valuable route to mesoporous metal oxides. After testing several reaction temperatures, we found that at 200 °C the reaction of Ti(O i Pr)4 with a stoichiometric amount of acetic anhydride (2 equivalents) led after 12 h to mesoporous TiO2 in high yields (90% on isolated product after calcination). To elucidate the reaction mechanism, the liquid by-products of the reaction were analyzed by NMR. According to 1 H and 13 C NMR spectra (Figure 1a,b), the liquid phase contained mainly isopropyl acetate (95 mol%). The formation of this major byproduct is consistent with a 2-step mechanism, involving acetoxylation (equation 5) and condensation (equation 6) reactions, with in both cases elimination of isopropyl acetate.

A small amount of acetic acid (5 mol%) was also detected, possibly resulting from hydrolysis reactions during the isolation of the by-products. It is noteworthy that neither propylene, isopropanol nor water were detected, indicating that thermal decomposition of titanium isopropoxide [28] followed by condensation of the resulting Ti-OH groups was negligible under our conditions (Scheme S1 in ESI). Both 13 C CPMAS NMR and FTIR spectroscopies of the solid xerogel showed the presence of residual acetoxy groups, consistent with this non-hydrolytic mechanism (Figure 1c,d). The solid state 13 C NMR spectrum of the washed and dried TiO2-NS-nc powder displayed resonances at 20 and 180 ppm, ascribed to the methyl and carboxylate groups, respectively. The ATR-FTIR spectrum displayed two strong absorption bands at 1445 cm -1 and 1526 cm -1 attributed to the symmetric and asymmetric stretching vibration of surface carboxylate groups, respectively. The separation of the two bands (Δʋ = 81 cm -1 ) suggests that these carboxylate groups are in a bidentate chelating mode. [22] The broad absorption around 3400 cm -1 characteristic of O-H stretching vibrations is comparatively very weak, indicating a very low amount of surface hydroxyl groups or adsorbed water, possibly resulting from the hydrolysis of residual surface groups during washing or manipulations in air. A very weak vibration at 2937 cm -1 (barely visible in figure 1d) is ascribed to C-H stretching vibrations, possibly in CH3 groups of residual acetoxy groups.

Thermogravimetric analysis of TiO2-NS-nc in air (Figure S1 in ESI) indicated a 9% weight loss at 800 °C. Assuming the presence of residual acetoxy groups only, this weight loss would correspond to a degree of condensation of 96% (conversion of TiO1.92(OAc)0.16 into TiO2). Accordingly, the reaction of titanium isopropoxide with acetic anhydride at 200 °C provides an efficient, truly non-hydrolytic route to titanium dioxide with a very high condensation degree. Representative SEM images of the TiO2-NS samples before and after calcination are displayed in Figure 2. As shown by these images, the morphology of the samples was not affected by the calcination treatment. Both TiO2-NS-nc and TiO2-NS-c samples showed an interesting hierarchical morphology: small rounded primary nanoparticles with diameters of 10 nm self-assembled to form spherical secondary particles with diameters of about 3 to 6 µm. The XRD patterns of the TiO2-NS powders (Figure 3) showed the presence of anatase nanocrystals mainly (JCPDS 21-1272), along with traces of brookite (JCPDS 29-1360) evidenced by the low-intensity peak at 30.8°. The crystallite size, estimated from the Scherrer equation for the (101) reflection, increased slightly from 9.5 to 10.5 nm upon calcination, indicating limited grain growth. These sizes are similar to the sizes observed by SEM (Figure 2) or HR-TEM (Figure 4), showing that the primary nanoparticles in SEM images were anatase nanocrystals. The nitrogen physisorption isotherms of TiO2-NS samples before and after calcination are reported in Figure 5a. Composite Type IVa + Type II isotherms are observed, indicating the presence of mesopores between the primary particles and of macropores between the micronic spherical aggregates. [29] Similar isotherms have been reported for hierarchically mesoporous anatase spheres prepared using a TiO2-CdSO4 composite as intermediate. [30] BJH analysis (Figure 5b) or DFT (Figure S2) confirmed the presence of mesopores with a broad pore size distribution. The BET specific surface area of the noncalcined TiO2-NS sample was 260 m 2 g -1 , which is very high for a crystalline TiO2 material. For comparison, mesoporous TiO2 materials prepared by conventional sol-gel are usually amorphous before calcination, and when crystalline their specific surface areas are usually below 150 m 2 g -1 . [31] Specific surface area of more than 300 m 2 g -1 have already been reported for TiO2 materials, but these materials were prepared either by elaborated hydrolytic sol-gel protocols [32,33] or by non-hydrolytic sol-gel in dilute conditions from TiCl4 and benzyl alcohol [12] or from TiCl4 and diisopropyl ether. [18] Calcination of TiO2-NS-nc led to a decrease of the specific surface area from 260 to 190 m 2 g -1 and to an increase of the average pore diameter from 4.1 to 7.7 nm, suggesting that some sintering of the primary nanoparticles took place. The electrochemical lithium storage performance of the TiO2-NS samples was investigated by galvanostatic cycling in a half-cell configuration and compared to that of a commercial TiO2 sample (TiO2-Comm, anatase, 85 m 2 g -1 , see Experimental Section). Figures 6a and6b show galvanostatic charge-discharge voltage profiles of the non-calcined and calcined samples, respectively. The discharge profiles show the three distinct regions characteristic of anatase TiO2 cycled versus lithium. [5,31] In region I the initial fast potential drop to 1.8 V is ascribed to the formation of a LiTiO2 solidsolution. In region II the constant voltage plateau at approxiamtely 1.8 V corresponds to the two-phase region where lithium-poor (Li0.05TiO2) and lithium-rich (Li0.5TiO2) solid solutions coexist. In region III, the sloped curve below 1.7 V is attributed to reversible surface lithium storage.

Characterization

Electrochemical performance

Interestingly, the presence of organic residual groups in TiO2-NS-nc did not hamper electrochemical cycling, even at high C-rates (Figure 6c). Although TiO2-NS-nc contained 9 wt% of organics its specific capacity was higher than that of TiO2-NS-c. The specific capacities at 0.1C on the 10 th discharge curve were very high: 253 mAh g -1 for TiO2-NS-nc and 238 mAh g -1 for TiO2-NS-c. These values are nearly twice higher than that found for TiO2-Comm (119 mAh g -1 ) (Figure S3 in SI), and they compare well with the best values reported in the literature for nanostructured TiO2 prepared by various methods. [5,31,34,35] The specific capacity arising from reversible surface lithium storage in Region III can be estimated to be 115 mAh g -1 and 95 mAh g -1 for TiO2-NS-nc and TiO2-NS-c, respectively, compared to 30 mAh g -1 for TiO2-Comm. Accordingly, the differences in specific capacity between TiO2-NS-nc, TiO2-NS-c, and TiO2-Comm are mostly related to surface lithium storage, which depends on the specific surface area of the materials. [31,36] The acetate groups of TiO2-NS-nc were possibly exchanged or decomposed during the 1 st discharge as suggested by the shoulder in the galvanostatic curve (indicated by an arrow in Figure 6a). As a result, the initial coulombic efficiency of TiO2-NS-nc was slightly lower than that of TiO2-NS-c (70.0 % vs 76.1%). In the subsequent cycles, however, both TiO2-NS samples showed an excellent coulombic efficiency (>99.7 %). It is noteworthy that after cycling at higher rates, both TiO2 samples recovered their initial capacity at 0.1C, meaning that these TiO2 materials were not significantly degraded. The long term cyclability of TiO2-NS-nc was particularly good: its capacity remained constant over 50 cycles at 0.1C, while a slight continuous capacity decrease was observed for TiO2-NS-c (Figure 6c). As shown in Figure S4, TiO2-NS-nc was also stable at higher rate (1C) with a discharge capacity of 201 mAh g -1 after 200 cycles (corresponding to 92 % capacity retention) and a coulombic efficiency of 99.8 %. TiO2-NS-nc and TiO2-NS-c samples were further analyzed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (Figure 7). The Nyquist plots of both TiO2 samples (Figure 7a,b) displayed an arc in the middle-to high-frequency range, corresponding to the charge-transfer resistance (Rct) and solid electrolyte interphase resistance (RSEI), and an angled line in the low-frequency region corresponding to the lithium diffusion in the electrode. [37] The semicircles for the non-calcined samples were similar whatever the number of cycles, and smaller than those for the calcined sample, particularly for the first cycles. Simulation of the Nyquist plots after the 10 th cycle using an equivalent model circuit (Figure S5) showed that both Rct and RSEI values were significantly smaller for TiO2-NS-nc (Rct = 17.4 Ω and RSEI = 11.4 Ω) than for TiO2-NS-c (Rct = 23.8 Ω and RSEI = 21.7 Ω). This suggests that the residual acetate groups and their decomposition products not only did not hamper electrochemical cycling but could also improve electrochemical performance, probably because the SEI formation could be different from that of TiO2-Ns-c. Cyclic voltammetry was performed at different sweep rates (Figure 7c). In TiO2 anatase nanomaterials, pseudo-capacitive storage can become important when the nanoparticle size decreases. [38,39] The relative contributions of capacitive and intercalation behavior was evaluated by analysis of cyclic voltammetry curves from 1.2 to 1.8 V according to:

i = a b ( 1
)
where i stands for measured current,  for sweep rate and a, b are adjustable parameters. For a lithium intercalation mechanism b = 0.5, while for a a purely capacitive mechanism b = 1.0. [40,[START_REF] Bard | Electrochemical Methods: Fundamentals and Applications[END_REF] As can be seen in Figure 7d, at the peak potential of 1.7 V, b-values for both TiO2-NS samples are very close to 0.5 indicating that the current results mainly from lithium intercalation reactions (plateau in the galvanostatic curve in Figure 6a-b). Conversely, below 1.7 V b-values increase, indicating that the capacitive mechanism becomes more and more important, and predominates below 1.6 V. Between 1.2 and 1.6 V the b-values found for TiO2-NS-nc are higher than those found for TiO2-NS-c, indicating a larger contribution of capacitive storage for TiO2-NS-nc, most likely due to its higher specific surface area.

Influence of the addition of a solvent

Although the possibility to prepare TiO2 materials in the absence of solvent is a major advantage of our acetic anhydride route, additional experiments were done to investigate the influence a solvent (namely toluene or squalane) on the characteristics of the materials. As shown by the SEM images in Figure 8 and S6, the morphology of the samples strongly depended on the presence of a solvent and on its nature. The TiO2 sample prepared in toluene consisted of shapeless aggregates built of short nanorods up to 40 nm in length. According to HR-TEM images (Figure S7), these nanorods were well-crystallized, with diameters of 6-7 nm. The sample prepared in squalane showed an interesting hierarchical morphology: short nanorods were assembled to form spindles, which themselves further aggregated to build spiky spheres, about 2.5 to 5 µm in diameter. Images of broken spheres indicated that they were hollow. The XRD patterns of the TiO2-Tol-nc and TiO2-Squ-nc samples (Figure S8) showed the presence of anatase nanocrystals, with sizes 10 nm which increased slightly upon calcination to 11 nm (Table 1). The higher intensity of the (004) reflection compared to the (200) reflection is consistent with the nanorod morphology observed by SEM for these samples. [23,[START_REF] Liu | [END_REF] It is well known in nanoparticle synthesis that both the morphology of the particles can be tuned by the addition of small amounts of ligands or by changing synthesis conditions. In our case, the impact of the solvent on the morphology could arise from preferential adsorption of solvent molecules (or of impurities in the solvent) during crystal growth. Another possibility would be that the solvent favors oriented attachment of anatase crystallites. [43] Unfortunately, as already noted for the non-hydrolytic synthesis of nanocrystalline metal oxides by the benzyl alcohol route, [8] the role of the organic species during the growth of the inorganic nanoparticles is not well understood. Thus, playing on the reaction conditions offers us the possibility to tune the morphology of our samples, but predicting this morphology is not yet possible.

The texture of the TiO2 samples is also impacted by the use of a solvent (Figure S9-S10). The physisorption isotherms of the samples prepared in toluene were of type IVa, characteristic of mesoporous adsorbents, while for the samples prepared in squalane, composite Type IVa + Type II isotherms were observed, indicating the presence of mesopores between the primary particles and of macropores between the spherical aggregates. The textural data for the different TiO2 samples prepared in this work are compared in Table 1. The specific surface areas of the samples prepared in the presence of a solvent were similar (170 m 2 g -1 before calcination, 120 m 2 g -1 after calcination), significantly lower than those of the samples prepared without solvent.

Table 1. Comparison of anatase crystallite size and textural data for the different TiO2 samples, before and after calcination. To complete this study, the electrochemical lithium storage performance of TiO2-Tol-c and TiO2-Squ-c was investigated. The rate performance of both samples were nearly identical (Figure S11a), with capacities ranging from 150 mA h g -1 at 0.1 C to 95 mA h g -1 at 2 C. These values are significantly lower than those found for TiO2-NS-c (238 and 152 mA h g -1 ) and only marginally better than those of TiO2-Comm. Comparison of the discharge profiles in Figures 6b and S11b revealed that the lower capacity of TiO2-Tol-c and TiO2-Squ-c over TiO2-NS-c arises largely from their lower specific surface area. Indeed, the specific capacity arising from reversible surface lithium storage in Region III can be estimated to be 45 mAh g -1 for TiO2-Tol-c and TiO2-Squ-c, compared to 95 mAh g -1 for TiO2-NS-c.

Conclusions

The reaction of Ti(O i Pr)4 with acetic anhydride at 200 °C provides an efficient, truly non-hydrolytic and aprotic route leading to highly condensed nanocrystalline TiO2 materials. Using acetic anhydride as an oxygen donor allows the in situ formation of intermediate acetoxy groups which further condense with alkoxide groups. The TiO2 nanocrystalline materials prepared in the absence of solvent by this halideand template-free method exhibited very high specific surface areas and high electrochemical lithium storage performances. The presence of residual acetate groups in the non-calcined samples did not hamper electrochemical cycling. Synthesis in the presence of a solvent allows tuning the morphology of the materials, leading to mesoporous samples with lower specific surface area and electrochemical performances. This ester elimination route avoids the use of metal acetate precursors and should be easily extended to other metal oxide systems.

Experimental Section

Materials

All manipulations were carried out in a glovebox under argon atmosphere (<10 ppm of water and O2). Titanium (IV) isopropoxide (Ti(O i Pr)4, 97%) and acetic anhydride (Ac2O, 99%) were obtained from Sigma-Aldrich and were used without further purification. Squalane (98%) was purchased from Alfa Aesar. Commercial titanium oxide nanoparticles (labeled TiO2-Comm in the following) were purchased from Tronox (AK-1, anatase, SBET = 85 m 2 g -1 , average crystallite size 17.5 nm). Toluene (Sigma-Aldrich, 99.7%) was dried over a PureSolve MD5 solvent purification system (H2O <10 ppm, controlled with a Karl Fischer coulometer).

Synthesis of TiO2 materials

Ti(O i Pr)4, (3.41 g, 12.0 mmol) and Ac2O, (2.45 g, 24.0 mmol) were mixed in a stainless steel digestion vessel equipped with a PTFE lining (23 mL). Then the sealed autoclave was heated in an oven at 200 °C for 12 h under autogenous pressure. After reaction, the resulting white precipitate was washed with acetone (30 mL, 5 times). The precipitate was dried under vacuum at room temperature and then ground into a fine white powder. Calcination of selected samples was carried out at 380 °C (heating rate 5 °C/min) for 5 h in dry air (flow rate of 50 mL/min). The non-calcined sample is referred to as TiO2-NS-nc, the calcined one as TiO2-NS-c, where NS stands for 'no solvent'. Two samples were prepared using the same procedure but with addition of 10 mL of a solvent. The samples prepared in toluene are referred to as TiO2-Tol-nc (or c) and those prepared in squalane as TiO2-Squ-nc (or c).

Materials characterization

Fourier-transform infrared (FTIR) spectra were collected in ATR mode on a Spectrum II Perkin-Elmer spectrometer. The powder X-ray diffraction (XRD) patterns were collected with a PANalytical X'Pert Pro MPD diffractometer (CuKα1 = 0.1540598 nm). The scanning electron microscopy (SEM) images were obtained with a Hitachi S-4800 electron microscope. The low-and high-resolution transmission electron microscopy (TEM) images were obtained using a JEOL JEM-ARM 200F transmission electron microscope. Nitrogen adsorption and desorption isotherms were measured at 77 K with a Micrometrics Triflex apparatus; the specific surface area was determined by the BET method, pore size distribution by the BJH method from the desorption branch or by DFT assuming cylindrical pore geometry. 1 H and 13 C NMR spectra in solution were recorded using a Bruker AVANCE 400 MHz spectrometer. Solid state 13 C CPMAS NMR spectra were recorded on a VARIAN VNMRS 300 MHz spectrometer using a 3.2 mm T3 2 channels probe. Rotors were spun at 12 kHz.

Electrochemical characterization

Galvanostatic electrochemical characterizations were performed at room temperature on a BTS3000 instrument from Neware Battery. TiO2 electrodes were composed of the active material (80 wt%), Super P (14 wt%), and sodium carboxymethyl cellulose (CMC, 6 wt%). After stirring in water, the slurry was ball-milled in a Pulverisette 7 Planetary Micro Mill from Fritsch using an agate grinding jar (1 h at 500 rpm), then tape casted uniformly at 150 µm onto a copper current collector (0.018 mm, >99.96%, Prometor) using a 3540 bird film applicator from Elcometer. Electrodes (diameter 12.7 mm) were cut with a disk cutter and then dried under vacuum at 80 °C for 15 h. The loading weight of active material was 1.5 mg cm -2 . CR2032 coin-type cells were assembled in a glove box under Ar atmosphere (O2 <0.5 ppm, H2O <0.5 ppm), using lithium metal as both reference and counter electrode. The electrolyte was LP30 (1 M LiPF6 in ethylene carbonate and dimethyl carbonate in a 1:1 vol. ratio. A glass fiber separator (Whatman) was used. The electrochemical galvanostatic measurements were taken in the voltage range of 2.5-1.2 V versus Li + /Li at different current densities. Cyclic voltammetry (CV) measurements were carried out on a VSP-300 instrument with sweep rate of 0.2 mV s -1 to 10 mV s -1 . Electrochemical impedance spectroscopy (EIS) studies were performed on a VSP-300 instrument, from 100 kHz to 20 mHz, with a 10 mV amplitude.

Figure 1 .

 1 Figure 1. a) 1 H NMR and b) 13 C NMR spectra in CDCl3 of the liquid by-products after reaction of Ti(O i Pr)4 with Ac2O (no solvent) at 200 °C for 12h; c) solid-state 13 C CPMAS-NMR and d) ATR-FTIR spectra of TiO2-NS-nc.

Figure 2 .

 2 Figure 2. SEM images of a) non-calcined and b) calcined TiO2-NS samples.

Figure 3 .

 3 Figure 3. Powder XRD patterns of non-calcined and calcined TiO2-NS samples. The reflection marked by an asterisk arises from traces of brookite)

Figure 4 .

 4 Figure 4. HRTEM images of TiO2-NS-c.

Figure 5 .

 5 Figure 5. a) N2 physisorption isotherms at 77 K and b) BJH mesopore size distribution of non-calcined and calcined TiO2-NS samples. The filled and open symbols refer to adsorption and desorption, respectively

Figure 6 .

 6 Figure 6. Galvanostatic charge-discharge voltage profiles at C/10 between 1.2 and 2.5 V of a) TiO2-NSnc, b) TiO2-NS-c;. c) Rate capability and long term cyclability test. Filled and open symbols refer to reduction (discharge) and oxidation (charge), respectively, C = 336 mA g -1 .

Figure 7 .

 7 Figure 7. a) Nyquist plots obtained at discharged state of a) TiO2-NS-nc and b) TiO2-Ns-c cycled at 0.1C (33.6 mA g -1 ), c) cyclic voltammetry curves of TiO2-NS-nc at various scan rates, d) Calculated b-values for TiO2-NS-nc and TiO2-NS-c as a function of the potential for cathodic sweeps (lithium insertion).

Figure 8 .

 8 Figure 8. SEM images of calcined TiO2 samples produced from Ti(O i Pr)4 and Ac2O at 200 °C a) in squalane (TiO2-Squ-c) and b) in toluene (TiO2-Tol-c).

a

  crystallite size estimated by the Scherrer equation from the (101) reflection; b specific surface area; c total pore volume at P/P0 = 0.99; d BJH average pore diameter calculated from the desorption branch.

Acknowledgements

The authors acknowledge the Agence Nationale pour la Recherche (project ANR-16-CE08-0015 SYNCOPE) and the European Commission (POROUS4APP project GA no. 666157), the University of Montpellier and CNRS for financial support.

Conflicts of interest

The authors declare no conflict of interest.

Keywords: non-hydrolytic sol-gel . acetic anhydride route . anatase . mesoporous . Li-ion batteries