S Lefebvre

D Grancher

L Alves De Oliveira

You said "gastro-intestinal" food ? Approach of petfood diversity during a student-conducted consultation.

You said "gastro-intestinal" food ? Approach of petfood diversity during a student-conducted consultation.

Introduction:

The choice of a petfood adapted to a clinical case is often difficult to perform by veterinary students. Indeed, between marketing, labelling, clinical data and the wide choice among available products, it is easy to be lost and to base their prescriptions on cognitive bias instead of scientific data. This presentation reports a case of protein-losing enteropathy with intestinal lymphangiectasia and its dietary management. Beyond the clinical aspect the authors want to discuss educational aspects.

Consultation:

The consultation was performed by a student in the 4th year of the curriculum. As a part of case history was available before the consultation, a briefing based on literature was done before the consultation [1]. The aim of this briefing was to give students the necessary knowledge to perform the clinical reflexion, and thus to allow them to conduct the consultation as far as possible. One student took the history and led the physical examination under supervision. To help the student in the case assessment, he had a nutrition software and diagrams of available food characteristics (tools are presented in this congress [2]). Figure 1 presents some of these diagrams, the given food being number 4. According to this diagram and the briefing presenting the interest of fat reduction in management of protein-losing enteropathy with intestinal lymphangiectasia, the student easily assessed that this food was not the most appropriate for this case. With help of other diagrams, he proposed to change food for the number 9 (Hill's i/d low fat). Then, with the software (figure 2), he estimated the MER at 1257 Kcal ME/d (MER=130xBW 0.75 /d) and made sure that needs were covered-(main nutrient intake calculated in sofware are resumed in table 1. Three days after the food change, diarrhoea stopped. One month later, prednisolone dose was decreased to 0.5 mg/kg BW and the calorie intake increased to 1450 Kcal ME to recover its optimal weight.

Conclusion: More than clinical success, we report an approach that may popularize clinical nutrition reflexion among veterinarians by making it more achievable with the help of two complementary tools:

Case History:

Diet (petfood diagram number) Initial (n°4) Prescribed (n°9)
Calorie intake (kcal of ME) 1 357 1 272

Protein intake (g/kg BW 0.75 ) 12.3 8.5

Fat intake (g/kg BW 0.75 ) 7.9 2.8 Here specific-purpose petfoods for gastrointestinal disorders

  Introduction Sébastien Lefebvre, Denis Grancher, L Alves de Oliveira To cite this version: Sébastien Lefebvre, Denis Grancher, L Alves de Oliveira. You said "gastro-intestinal" food ? Approach of petfood diversity during a student-conducted consultation. Introduction. 23rd congress of the European Society of Veterinary and Comparative Nutrition (ESVCN 2019), Sep 2019, Turin, Italy. . hal-02295150

Figure 2 :

 2 Figure 2: VetNutri software interface

Table 1 :Figure 1 :

 11 Figure 1: samples of the diagrams used to assess petfoods. Here specific-purpose petfoods for gastrointestinal disorders


Mickaël Mateos

Marie-Donga Tchangaï

Rita Meunier-Prest

Olivier Heintz

Frédéric Herbst

Jean-Moïse Suisse

Marcel Bouvet

Low Conductive Electrodeposited Poly(2,5-dimethoxyaniline) as a Key Material in a Double Lateral Heterojunction, for Sub-ppm Ammonia Sensing in Humid Atmosphere

The low conductive electrodeposited poly(2,5-dimethoxyaniline) as a key material in a double lateral heterojunction, for sub-ppm ammonia sensing in humid atmosphere Mickaël Mateos a , Marie-Donga Tchangaï a , Rita Meunier-Prest a *, Olivier Heintz b , Frederic Herbst b , Jean-Moïse Suisse a , Marcel Bouvet a *.

a Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB), UMR CNRS 6302, Université Bourgogne Franche-Comté, 9 avenue Alain Savary, 21078 Dijon cedex, France. Tel: +33-380-396-086; E-mail: marcel.bouvet@u-bourgogne.fr, rita.meunier-prest@u-bourgogne.fr b Laboratoire Interdisciplinaire Carnot de Bourgogne (LICB), UMR CNRS 6303, Université Bourgogne Franche-Comté, 9 avenue Alain Savary, 21078 Dijon cedex, France KEYWORDS. Electrochemistry, conducting polymer, polyaniline, impedance spectroscopy, conductometric transducer, relative humidity, ammonia sensor.

ABSTRACT:

We present a new device called double lateral heterojunction (DLH) as ammonia sensor in humid atmosphere. It combines polyaniline derivatives in their poor conducting state with a highly conductive molecular material, lutetium bisphthalocyanine, LuPc2. The polyaniline and poly(2,5-dimethoxyaniline) are electrodeposited on ITO interdigitated electrodes, leading to an original device that can be obtained only by electrochemistry and not by other solution processing techniques. Both polymers lead to highly conducting materials that require a neutralization step before their covering by LuPc2. While the device based on polyaniline shows an ohmic behavior, the non-linear I-V characteristics of poly(2,5-dimethoxyaniline)based DLH proves the existence of energy barriers at the interfaces, as demonstrated by impedance spectroscopy. It exhibits a particularly interesting sensitivity to ammonia, at room temperature and in a broad relative humidity range. Thanks to its higher energy barriers, the poly(2,5-dimethoxyaniline)/LuPc2 DLH is the most sensitive device with a limit of detection of 320 ppb. This work paves the way for the use of substituted polyanilines in conductometric sensors not only in the field of air quality monitoring but also in the field of health diagnosis by measurement in human breath.

Conductometric gas sensors are mostly resistors using inorganic materials, such as metallic oxides. However, molecular materialbased resistors also reveal to be highly sensitive devices, with the advantage to operate at room temperature. Beside organic resistors, field-effect transistors (OFET) and p-n junctions were used as conductometric transducers. These devices were developed after their inorganic counterparts. In most of the cases, complex apparatus are necessary, which involve high vacuum and/or high temperature processes. On the contrary, solution processing techniques are particularly suitable for large areas and low cost processes. [START_REF] De Gans | Inkjet Printing of Polymers: State of the Art and Future Developments[END_REF][START_REF] Ha | One-Step Interface Engineering for All-Inkjet-Printed, All-Organic Components in Transparent, Flexible Transistors and Inverters: Polymer Binding[END_REF] Metal oxidebased heterojunctions were considerably studied as gas sensors. [START_REF] Miller | Nanoscale Metal Oxide-Based Heterojunctions for Gas Sensing: a Review[END_REF] Heterojunctions between inorganic and organic materials were also used as gas sensors, e.g. towards liquefied petroleum gas, with n-CdS/PANI. [START_REF] Dhawale | Room Temperature Liquefied Petroleum Gas (LPG) Sensor[END_REF] Discoid SnO2 with reduced graphene oxide was also used to detect NO2. [START_REF] Xiao | Improvement of NO2 Gas Sensing Performance Based on Discoid Tin Oxide Modified by Reduced Graphene Oxide[END_REF] Conducting polymers, polyaniline (PANI), polypyrrole and polythiophene, were associated with nanostructured metal oxides to detect a series of VOCs, leading generally to better performances than with the isolated components in resistors. [START_REF] Geng | Characterization and Gas Sensitivity Study of Polyaniline/SnO2 Hybrid Material Prepared by Hydrothermal Route[END_REF][START_REF] Xu | Gas Sensing Properties of SnO2 Hollow Spheres/Polythiophene Inorganic-Organic Hybrids[END_REF][START_REF] Ebrahimiasl | Electrochemical Synthesis, Characterization and Gas Sensing Properties of Hybrid Ppy/CS Coated ZnO Nanospheres[END_REF][START_REF] Hatchett | Composites of Intrinsically Conducting Polymers as Sensing Nanomaterials[END_REF] We can also cite phthalocyanines combined with ZnS. [START_REF] Chowdhury | Nanostructured Organic-Inorganic Heterojunction Diodes as Gas Sensors[END_REF] Organic Schottky diodes were widely reported as gas sensors, [START_REF] Potje-Kamloth | Semiconductor Junction Gas Sensors[END_REF] unlike heterojunctions combining two molecular materials. We can mention phthalocyanine-based p-n heterojunctions, [START_REF] Muzikante | A Novel Gas Sensor Transducer Based on Phthalocyanine Heterojunction Devices[END_REF] which behave electrically as classical p-n diodes, and a particular conductometric transducer, called MSDI, for Molecular Semiconductor -Doped Insulator heterojunction. [START_REF] Parra | Molecular Semiconductor-Doped Insulator (MSDI) Heterojunctions: an Alternative Transducer for Gas Chemosensing[END_REF][START_REF] Parra | Semiconductor Transducer and Its Use in a Sensor for Detecting Electron-Donor or Electron-Acceptor Species[END_REF] Besides, beyond its synthetic interest, 15 electrochemistry became highly popular to modify electrode surfaces. [START_REF] Bélanger | Electrografting: a Powerful Method for Surface Modification[END_REF] In the case of conducting polymers, electrochemistry ensures the synthesis and the preparation of materials in a unique step, as exemplified by phthalocyanine-polypyrrole hybrid materials used as sensing material for the detection of NH3. [START_REF] Sizun | Microstructured Electrodeposited Polypyrrole-Phthalocyanine Hybrid Material, From Morphology to Ammonia Sensing[END_REF] In the case of polyanilines, the control of their conducting state, related to their doping state, determines their electrical and optical properties. [START_REF] Epstein | Polyaniline Versus Polyacetylene, or, Rings Versus Bonds and the Roles of Barriers and Crystallinity[END_REF] The electronic and physico-chemical properties of conducting polymers are highly dependent on the nature of substituents. Thus, polyanilines were synthesized from aniline bearing electronwithdrawing and electron-donating substituents such as fluorine atoms [START_REF] Cihaner | Electrochemical Behaviour and Electrochemical Polymerization of Fluoro-Substituted Anilines[END_REF] and alkoxy groups. [START_REF] D'aprano | Synthesis and Characterization of Polyaniline Derivatives: Poly(2-Alkoxyanilines) and Poly(2,5-Dialkoxyanilines)[END_REF] In this paper, we report on a new device called double lateral heterojunction (DLH) that implies a double interface between two molecular materials: a poor conductive polymer around the electrodes and a molecular semiconductor, the lutetium bisphthalocyanine, LuPc2, as a top layer (Figure 1). Actually, we reported recently a first example of DLH, using the poly-(tetrafluoroaniline), PTFANI, starting from tetrafluoroaniline. [START_REF] Mateos | Comprehensive Study of Poly(2,3,5,6-Tetrafluoroaniline): From Electrosynthesis to Heterojunctions and Ammonia Sensing[END_REF] The main drawback with PTFANI was the difficulty to obtain homogeneous films, due to its insulating nature. Among phthalocyanines, LuPc2, because of its radical nature, exhibits a unique high intrinsic conductivity and a particularly high sensitivity to redox active species. [START_REF] Parra | Molecular Semiconductor-Doped Insulator (MSDI) Heterojunctions: an Alternative Transducer for Gas Chemosensing[END_REF] We develop two DLH differing in the polymer electroplated on ITO interdigitated electrodes (IDE): the poly(2,5-dimethoxyaniline) (PDMA) and the nonsubstituted polyaniline (PANI). Thanks to the electrochemical method, the polymer is deposed selectively onto the electrodes and not on all the substrate area. After vacuum evaporation of LuPc2, the devices consist in DLH (Fig. 1). They were characterized thanks to electrical measurements like impedance spectroscopy and current-voltage characteristics, I(V). Finally, we compared the sensing properties of PANI-DLH and PDMA-DLH through ammonia sensing experiments in humid atmosphere.

Experimental section

Chemicals 2,5-Dimethoxyaniline (DMA), 70% perchloric acid and potassium hydroxide were purchased from Sigma Aldrich and absolute ethanol (analaR normapur) was purchased from Carlo Erba. Aniline (Aldrich) was distilled at a boiling temperature of 120 °C under the reduced pressure before use. Ammonia gas, at 985 ppm and 98 ppm (mol/mol) in synthetic air, and synthetic air were used from standard gas cylinders, purchased from Air Liquide, France. Lutetium bisphthalocyanine (LuPc2) was synthesized according to a previously reported method. [START_REF] Kirin | Formation of Unusual Phthalocyanines of the Rare-Earth Elements[END_REF]

Electrochemical methods

All electrochemical experiments were performed with a PGSTAT302N (Metrohm) potentiostat and the collected data analyzed using Nova® 2.1 software. Cyclic voltammetry (CV) and chronoamperometry (ChA) were carried out by means of a three-electrode setup consisting of an ITO plate or ITO interdigitated electrodes (IDE, deposited onto a 1 x 1 cm² floated glass substrate and separated by 75 m with 50 nm thickness) as working electrode, a platinum wire as counter electrode and a saturated calomel electrode (SCE) as reference electrode. Potentials were reported versus SCE. PANI films were deposited on ITO plates by ChA at 1 V in a solution of 0.15 M aniline in 2 M HClO4 (consumed charge of 415 mC.cm -2 ), then rinsed with 0.2 M HClO4, absolute EtOH and dried under vacuum at room temperature. They were also deposited on IDE by ChA at 0.9 V (consumed charge of 115 mC.cm -2 ) under similar conditions. PDMA films were deposited on ITO plates by CV from -0.3 V to 1 V at a scan rate of 40 mV.s -1 , in a 50 mM DMA solution in 2 M HClO4. The CV was stopped at 0 V after consuming 1 C.cm -2 , then the polymer films were rinsed with 0.2 M HClO4, absolute EtOH and dried under vacuum at room tem-perature. They were also deposited on IDE in the same conditions but with a consumed charge of 250 mC.cm -2 . To obtain their neutral forms the films were rinsed with 1 mM KOH, water and dried under vacuum at room temperature.

SEM images and XPS analysis

SEM images were performed with a scanning electronic microscope JEOL JSM6400F with 2 kV of acceleration voltage. XPS analysis of the polymer films was performed on a SIA100 spectrometer (Cameca Riber apparatus) using non-monochromated Al Kα X-ray source (1486.6 eV photons). All spectra were calibrated using the normalized In(3d5/2) XPS signal from In2O3 at 444.9 eV 23 and all deconvolutions were performed using contributions with a nearly constant width at half maximum (± 0.2 eV).

Electrical and chemosensing measurements

The top layer was coated over the neutralized polymer sublayer prepared on IDE, by sublimation of LuPc2 in an UNIVEX 250 thermal evaporator (Oerlikon, Germany), under secondary vacuum (ca. 10 -6 mbar), by heating in a temperature range of 400-500 °C, at a rate of 1 Å.s -1 . Impedance data were obtained using a Solartron SI 1260 impedance analyzer. The frequency range was 10 Hz to 10 MHz with a fixed ac oscillation amplitude of 300 mV and a bias ranging from 0 V to 10 V. A commercial software Zview from Ametek was used for impedance data fitting and parameter extraction. The apparatus used for NH3 exposure, at different relative humidity (RH) values, was described previously. [START_REF] Gaudillat | Bias and Humidity Effects on the Ammonia Sensing of Perylene Derivative/Lutetium Bisphthalocyanine MSDI Heterojunctions[END_REF] The total flow was in the range 0.5-0.55 NL.min -1 depending on ammonia concentration and the volume of the test chamber was 12 cm 3 . Gas sensing experiments were carried out in a dynamic way, by alternating 4 min-long rest periods and 1 min-long exposure periods.

Results and Discussion

Film formation

The electrodeposition of PDMA on ITO electrodes was carried out by cyclic voltammetry in an acidic solution containing the monomer (Figure 2). DMA was irreversibly oxidized at 0.62 V. Repetitive scanning leaded to a new redox system, at around 0.37 and 0.2 V, attributed to the polymer formation. [START_REF] Storrier | Chemical and Electrochemical Syntheses, and Characterization of Poly(2,5-Dimethoxyaniline) (PDMA) -a Novel, Soluble, Conducting Polymer[END_REF][START_REF] Palys | Influence of Anions on Formation and Electroacitivity of Poly-2,5-Dimethoxyaniline[END_REF] Its intensity and the corresponding charge consumed (inset in Figure 2) grew rapidly with the number of scans. This was characteristic of a polymer having a good conductivity like PANI. [START_REF] D'aprano | Synthesis and Characterization of Polyaniline Derivatives: Poly(2-Alkoxyanilines) and Poly(2,5-Dialkoxyanilines)[END_REF] Previous EQCM results revealed a partially protonated emeraldine form with a doping ratio of 1 ClO4 -/ 2 DMA units. [START_REF] D'aprano | Synthesis and Characterization of Polyaniline Derivatives: Poly(2-Alkoxyanilines) and Poly(2,5-Dialkoxyanilines)[END_REF]

SEM images and XPS analysis

PDMA films electrodeposited on ITO plates had a broccoli shape structure (Figure 3). [START_REF] Suephatthima | Effect of Electrolytes on Electrochromic Properties and Morphology of Poly(2,5-Dimethoxy Aniline) Films[END_REF] This porous structure can be explained by the high conductivity of PDMA in its emeraldine salt form that enabled a fast growth on itself, as previously reported for PANI, which lead to fibers of a few hundred nanometers in length. [START_REF] Mateos | Comprehensive Study of Poly(2,3,5,6-Tetrafluoroaniline): From Electrosynthesis to Heterojunctions and Ammonia Sensing[END_REF] The atomic ratio has been calculated from XPS spectra, using peak areas of C(1s), N(1s), O(1s) and Cl(2p) (N(1s) used as a reference, Figure S1). The C/N ratio of 8.4 was closed to the expected value of 8. The Cl/N ratio (0.7) demonstrates the presence of ClO4 -counterions that indicates an important acid-base doping (protonation of amine/imine bridges). Furthermore, after subtracting the oxygen contribution from the two methoxy groups, the obtained O/Cl ratio (4) matched with ClO4 -anions. The O(1s), Cl(2p) and C1s spectra are analyzed in Figure S2, S3 and S4, respectively. The deconvolution of N(1s) spectrum showed three components at 399.4, 401 and 403.5 eV, that can be attributed to the neutral amine, the protonated imine and the protonated amine, respectively (Figure 4a). [START_REF] Amin | Metastable and Stable Pitting Events on Al Induced by Chlorate and Perchlorate Anions-Polarization, XPS and SEM Studies[END_REF][START_REF] Han | Highly Conductive and Electroactive Fluorine-Functionalized Polyanilines[END_REF][START_REF] Neoh | Thermal Degradation Studies of Perchlorate-Doped Conductive Polymers[END_REF][START_REF] Kang | The Intrinsic Redox States in Polypyrrole and Polyaniline: a Comparative Study by XPS[END_REF][START_REF] Wei | XPS Study of Highly Sulfonated Polyaniline[END_REF] It is worth noting that, in our case, the neutral imine peak, expected at 398 eV, [START_REF] Sui | Self-Assembly of Poly(o-Methoxyaniline) Hollow Nanospheres From a Polymeric Acid Solution[END_REF][START_REF] Hasik | Poly(o-Methoxyaniline)-Palladium Systems: Effect of Preparation Conditions on Physico-Chemical Properties[END_REF] was absent because all imine bridges were protonated. The acid-base doping was calculated by addition of the contributions of the protonated molecules at 401 and 403.5 eV. Charged species rates of 52% for PANI and 54% for PDMA were obtained. This was lower than the chlorine ratio obtained from XPS semi-quantitative analysis (0.7) because the Cl/N ratio also provided for traces of electrolyte not fully eliminated by the rinsing step with absolute EtOH. Otherwise, we demonstrated that PDMA and PANI had a -N= / -NH-ratio near to 1 in accordance with their emeraldine salt form.

Electrical properties

Inspired by the behavior of MSDI that include a low conductive sublayer, we decided to build heterojunctions, with PANI and PDMA in their low conductive form. Therefore, 1 µm thick polymer films of PDMA and PANI were electrodeposited on IDE, then neutralized by KOH, leading to their poor conductive state (emeraldine base form). A LuPc2 upper layer was then added by vacuum sublimation to obtain DLH (Figure 1). The normalized I(V) characteristics of PDMA/LuPc2 DLH, defined as the ratio of the current with its maximum value at 10 V, showed a non-linear behavior compared to the ohmic characteristic of a LuPc2 resistor (Figure 5). This new lateral configuration forces the charges to cross twice the ITO/polymer and polymer/LuPc2 interfaces, and creates energy barriers. The threshold voltage, Uth, provides an evaluation of the non-linear character of the PDMA -DLH. It is determined by extrapolation to zero of the tangent to the curve at high bias (Figure 5). The obtained value of 3.4 V was higher than that of the poly(2,3,5,6-tetrafluoroaniline) (PTFANI)based device (threshold voltage of 2 V calculated from ref. [START_REF] Mateos | Comprehensive Study of Poly(2,3,5,6-Tetrafluoroaniline): From Electrosynthesis to Heterojunctions and Ammonia Sensing[END_REF] ). Despite the lower current in the PANI/LuPc2 heterojunction (2 µA at 10 V, Figure S5) than in the LuPc2 resistor (20 µA at 10 V), this device kept an ohmic I(V) characteristic, suggesting that all the interfaces formed ohmic contacts.

We explored the transport properties thanks to impedance spectroscopy, a conventional technique in electrochemistry, with recently growing applications in organic electronics. [START_REF] Kuwabara | Characterization of Inverted-Type Organic Solar Cells with a ZnO Layer as the Electron Collection Electrode by AC Impedance Spectroscopy[END_REF][START_REF] Kim | Impedance Spectroscopy on Copper Phthalocyanine Diodes with Surface-Induced Molecular Orientation[END_REF] Thereafter, we will discuss the complex plane representation, called the Nyquist plot, of the impedance Z defined as: Z = Re(Z) + jIm(Z), where Re(Z) and Im(Z) are the real and imaginary parts of Z, respectively. As shown in Figure 6, Nyquist plots of PDMA -DLH exhibited two intermixed non-ideal semicircles, which have different behaviors depending on the bias. The first one, at high frequency (HF), was practically independent of the bias, whereas the second one, at low frequency (LF), collapsed as the bias increased. It is worth noting that the LuPc2 resistor exhibits only one semicircle unaffected by the bias. This means that the electrical properties of the resistor remain constant, [START_REF] Bouvet | Revisiting the Electronic Properties of Molecular Semiconductor -Doped Insulator (MSDI) Heterojunctions Through Impedance and Chemosensing Studies[END_REF] suggesting that the charge transport is dominated by the bulk material, and not by interfacial traps. [START_REF] Miller | Electrode Independent Chemoresistive Response for Cobalt Phthalocyanine in the Space Charge Limited Conductivity Regime[END_REF] In the PDMA -DLH, when focusing on the diameter of the LF semicircle, the major part of the collapse occurred when the bias was lower than 3 V. This bias corresponds to the abovementioned threshold voltage of 3.4 V, deduced from the I(V) curves (Figure 5). Our working assumption, supported by previous studies, [START_REF] Bouvet | Revisiting the Electronic Properties of Molecular Semiconductor -Doped Insulator (MSDI) Heterojunctions Through Impedance and Chemosensing Studies[END_REF][START_REF] Braga | Organic Metal-Semiconductor Field-Effect Transistor (OMESFET) Fabricated on a Rubrene Single Crystal[END_REF] was that, at low bias, the LF semicircle represents the interfacial behavior, whereas the HF semicircle represents properties from the bulk materials. For the present heterojunctions, with two non-ideal semicircles, the data were modeled by an equivalent circuit consisting of two Ri-CPEi elements in series (Figure 6). A constant-phase element (CPEi) can be regarded as an imperfect capacitor [START_REF] Raistrick | Theory, Experiment, and Applications[END_REF] of which the impedance ZCPEi is defined as follows (equation 1):

𝑍 𝐶𝑃𝐸𝑖 = 1 𝑄 𝑖 * (𝑗𝜔) 𝛼 𝑖 (1)
with ω = 2πf, where f is the frequency, Qi the non-ideal capacitance, and αi a value between 0 and 1 that reflects the nonideality of the capacitive element. When αi = 1, a CPE corresponds to an ideal capacitor. As expected from the Nyquist plots, all the parameters (R1, Q1 and α1) of the R1-CPE1 element remain nearly constant with the bias (Figure 7). This confirms that part of the properties of the bulk materials are modeled by this element. The collapse of the second semicircle observed in the Nyquist plot (Figure 6) results from the decrease of R2 with the bias. This resistance is the key parameter to explain the energy barrier abovementioned and the non-linear behavior observed in the I(V) characteristics.

Indeed, the strong non-linear behavior (Figure 5) observed with PDMA sublayers results from the high value of R2 at low bias (Figure 7). To be more specific, R2 decreased from 18.3 MΩ to 0.6 MΩ and R1 remained stable at 1.1 MΩ. The large part of the R2 drop occurred for bias below 3 V, which corresponds to the threshold voltage of 3.4 V (Figure 5). To confirm that the interfacial phenomena were mainly represented by the R2-CPE2 element associated with the LF semicircle, we calculated the effective capacitance Ceffi, (equation 2), of the Ri-CPEi element (Figure 7) referring to a reported method. [START_REF] Hsu | Technical Note: Concerning the Conversion of the Constant Phase Element Parameter Y0 Into a Capacitance[END_REF] 𝐶 𝑒𝑓𝑓 𝑖 = 𝑅 𝑖

1 𝛼 𝑖 -1 * 𝑄 𝑖 1 𝛼 𝑖 (2)
Actually, the parameter Qi has no physical sense because its unit depends on αi. It is worth noting that a R-C element attributed to an interfacial behavior should have a larger capacitance than the bulk capacitance, because an interfacial layer should have a smaller thickness compared to that of the device. [START_REF] Braga | Organic Metal-Semiconductor Field-Effect Transistor (OMESFET) Fabricated on a Rubrene Single Crystal[END_REF] It appeared that Ceff1 had a constant value of 8 pF whereas Ceff2 declined from 1.4 nF at 0 V to 120 pF at 10 V, which is hundreds time higher than Ceff1. Furthermore, the PANI -DLH that exhibited an ohmic characteristic (Figure S5) displays a Nyquist plot with essentially one semicircle, as the second one was scarcely visible, reflecting the absence of interfacial energy barrier (Figure S6). Indeed, R2 decreased from 970 kΩ at 0 V to 474 kΩ whereas R1 remained almost stable at 1 MΩ (Figure S7). So R2 was lower than R1 whatever the bias. It means that interfacial barriers play a minor role in the electrical transport in the device, which is corroborated by its ohmic behavior. All these observations confirmed our starting hypothesis that the R2-CPE2 block, associated to the LF semicircle, modeled the role of the interfaces.

Gas sensing

Under exposure to NH3 (Figure 8), the PDMA -DLH showed a current drop, which demonstrated that the transport properties are governed by positive charge carriers. The current decrease depended on the NH3 concentration whatever the RH. The ΔI response, corresponding to the difference between the current at the end of the exposure phase If (1 min) and that of the recovery phase I0 (4 min) was not linear in this NH3 concentration range. Indeed, at 50% RH, ΔI went from -14 nA at 90 ppm NH3 to -5.5 nA at 10 ppm. This suggested that the sensor worked in overloaded regime. All along this experiment, the I0 value decreased with the RH value, but at each RH value I0 was very stable during the exposure-recovery cycles. The device exhibited the same behavior when exposed to different RH values without NH3 (Figure S8). We also studied the devices at lower NH3 concentrations, between 1 and 9 ppm, at 50% RH (Figure 9). The sensor continued to show a large current decrease, depending on the NH3 concentration, with a stable current baseline. The I value at 1 ppm was 1 nA, with a good signal-tonoise ratio, suggesting that the limit of detection (LOD) was not reached yet. The relative response, RR, defined in equation 3 from the mean value over four exposure / recovery cycles at each NH3 concentration, reached 29% at 90 ppm NH3, against 7%, for the PANIbased device.

𝑅𝑅 (%) =

Conclusion

ammonia decreases when the relative humidity tends to dry atmosphere, but the LOD remains in the sub-ppm range, even at 10 % RH. It is worth noting that a RH value of 10% is rarely encountered in applications of ammonia sensors. We demonstrated a new application of conducting polymers, in their poor conducting state, as a component of lateral heterojunctions. The PDMAbased sensors were more sensitive to NH3 than the phthalocyanine-based heterojunctions that inspired this work.

Figure 1 .

 1 Figure 1. Schematic view of the double lateral heterojunction (DLH); the arrow indicates the main channel for charge carriers.

Figure 2 .

 2 Figure 2. Cyclic voltammogram of 50 mM DMA in 2 M HClO4 on an ITO electrode, at 0.04 V.s -1 . Consumed charge in inset.

Figure 3 .

 3 Figure 3. SEM images of PDMA on ITO plates with a zoom (x8) in inset.

Figure 4 .

 4 Figure 4. N(1s) XPS high resolution spectra of a) PDMA, b) PANI films electrodeposited on ITO plates.

Figure 5 .

 5 Figure 5. Normalized I(V) characteristics in ambient atmosphere of a LuPc2 resistor and a PDMA -DLH with the threshold voltage, Uth.

36

 36

Figure 6 .

 6 Figure 6. Nyquist plot as a function of the bias (0.33 V to 10 V) of a PDMA -DLH, with the equivalent circuit for data modelling in inset.

Figure 7 .

 7 Figure 7. Variations of the extracted circuit parameters as a function of the bias for PDMA -DLH.

Figure 8 .

 8 Figure 8. Current response of PDMA -DLH exposed to NH3, in humid air, from 70% RH to 10% RH, during exposure/recovery cycles (1 min / 4 min).

Figure 9 .

 9 Figure 9. Current response of a PDMA -DLH exposed to NH3 (9, 6, 4, 3, 2 and 1 ppm), in air at 50 % RH, during exposure / recovery cycles (1 min / 4 min).

Figure 10 .

 10 Figure 10. Relative response of PDMA -DLH and PANI -DLH as a function of the NH3 concentration in the 1-90 ppm range, in air at 50 % RH. The data of the linear fits for both devices (green table) and of the Langmuir modelling for the PDMA-DLH (blue table) are given in insets.

Table 1 .

 1 Sensitivities (S) of the present devices compared to those of a series of heterojunctions (MSDI and DLH) and resistors. sensitivity drops after few days in ambient air, b) in dry air, c) at 40% RH and d) at 450 °C

M. Mateos et al., ACS Sensors 2019, DOI 10.1021/acssensors.9b00109

The authors acknowledge the Agence Nationale de la Recherche for funding through the ANR project OUTSMART ANR-2015-CE39-0004-03 and the MENESR for a PhD grant (M. M.). Financial support from the European Union (FEDER) and the Conseil Régional de Bourgogne through the FABER and the CDEA program is gratefully acknowledged. We also acknowledge the Conseil Régional de Bourgogne through the CPER program.

ASSOCIATED CONTENT

O(1s), Cl(2p) and C(1s) XPS spectra of PDMA film; I(V) characteristics of PANI/LuPc2, PDMA/LuPc2 heterojunction and LuPc2 resistor; Nyquist plot as a function of the bias of PANI/LuPc2 ; variation of the circuit parameters as a function of the bias for PANI/LuPc2 and response of PDMA/LuPc2 to RH. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Authors

Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB), UMR CNRS 6302, Université Bourgogne Franche-Comté, 9 av. Alain Savary, 21078 Dijon cedex, France. Tel: +33-380-396-086; E-mail: marcel.bouvet@u-bourgogne.fr, rita.meunier-prest@u-bourgogne.fr

Author Contributions

All authors have given approval to the final version of the manuscript.

ACKNOWLEDGMENT