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Biopolymers obtained from renewable resources became the center of public interest by virtue of their environmental and commercial advantages. Natural polymers such as starch, almond gum, chitosan and arabic gum were investigated to get fully or partially biodegradable dielectric material. Thus, in this article we study the material properties of cashew gum. This biopolymer is an exudate collected from occidental anacardium tree. For this investigation, scanning electron microscopy of powder and thin film cashew gum showed homogenous and slightly rough surface morphology with visible wrinkles. The thermal analyses such as thermogravimetric (TGA) and differential scanning calorimeter were realized. thermogravimetric thermogram shows two distinct stages of decomposition. The first around 150°C is attributed to moisture evaporation with loss in weight of 9.7%. The second transition, between 255°C and 330°C, is related to the decomposition of cashew gum with loss in weight of 50%. UV-visible spectra of the cashew gum thin film show a low absorbance and high transmittance. For this material, we obtained a direct optical band gap around 4.56 eV. In addition, the dielectric and electrical characterizations lead to conclude that cashew gum may be interesting for transistor applications as a gate dielectric.

In this study, the surface chemistry and morphology and the photocatalytic and antibacterial potential of pure and chlorine (Cl)-doped indium sulfide (In2S3) thin films, produced by spray pyrolysis, were analyzed. The root-mean-square roughness seemed not to be affected significantly by the chlorine concentration in three of the doped films (around 12 nm). The roughness seemed not to affect the characteristics of the films analyzed in this study. The samples presented a photocatalytic efficiency higher than 80%, but no correlation with the chlorine concentration was found. The antibacterial potential of the films was assessed against the multidrug-resistant bacteria Pseudomonas aeruginosa, responsible for serious infections, which are extremely difficult to treat in hospitals. The obtained results evidence an increase in antibacterial activity with the increase in chlorine concentration. These results encourage further studies to support the potential of this material to be used in biomedical applications.

In2S3 thin films were grown on indium tin oxide (ITO) glass substrate by chemical spray pyrolysis technique at 360°C. The structural analysis of the deposited films shows a combination of tetragonal and cubic structures. The average crystallite size is about 25 nm. The electrical properties of In2S3 thin films have been investigated in a wide frequency (40Hz-100MHz) and temperature (400 K-660 K) ranges.We find that the electrical conductance of the In2S3 thin films is frequency and temperature dependent. The dc conductance shows a semi-conductor behavior for In2S3 films over the explored range of temperature and it follows the Arrhenius law with different activation energies. The variation of ac conductance and the frequency exponent `s’ are explained by the correlated barrier hopping (CBH) model. The Nyquist plots of impedance exhibit semicircle arcs and an electrical equivalent circuit has been suggested to interpret the impedance results.

In this paper, we study the dielectric and material properties of almond gum, a natural biopolymer material collected from almond trees. The dielectric properties are investigated by mean of impedance spectroscopy in the ranges of frequency 40 Hz-10MHz and temperature 300 K–400 K. The resulting responses provided valuable information about the material and revealed that the dielectric parameters are both temperature and frequency dependent. The calculated dielectric constant is around 8 at temperature T = 300 K and frequency f = 1 kHz. UV–visible spectrum of the almond gum thin films recorded from 300 nm to 2500 nm, showed a high transmittance with an optical band gap around 3.4eV. X-ray fluorescence showed that almond gum contained oxides such as CaO, SiO2, K2O, etc, with a significant concentration of CuO (63.72%) and several other chemical elements in trace such as strontium, rubidium, chlorine, cadmium, sulfur, etc. Thermal properties studies such as thermogravimetric analysis and differential scanning calorimetry conducted on almond gum powder revealed two stages of decomposition with a glass transition at 58.5 °C. In order to study the surface properties of almond gum thin films, we have carried out contact angle measurements and scanning electron microscopy analysis. The results showed hydrophobic surfaces. Our findings in this study lead to conclude that almond gum may be an interesting candidate for electronic applications especially for gate dielectric and encapsulating layer.

Spray pyrolysis was used to deposit indium sulfide (In2S3) films, with or without silver doping. The films are polycrystalline, and the inclusion of Ag in the In2S3 structure leads to the formation of a solid solution, with the crystallite size of the order of tens of nanometers. In2S3 films exhibit a semiconductive behavior, and the incorporation of Ag leads to an increase of the charge carrier concentration, enhancing the electrical conductivity of the films. The small polaron hopping mechanism, deduced by the fittings according to the double Jonscher variation, explains the evolution of the direct current (dc) conductivity at high temperature of the Ag-doped indium sulfide. From impedance spectroscopy, it was found that the doped film presents dielectric relaxation, and Nyquist diagrams indicate the importance of the grain and the grain boundaries’ contributions to the transport phenomena. The physical characteristics of the films have an influence on the photocatalytic performance, achieving photodegradation efficiency above 80% (85.5% in the case of Ag doping), and on the antibacterial activity. The obtained results indicate that indium sulfide films are good candidates for environmental and biological applications, confirming a multifunctional nature., Part of this work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020”. D.C. and I.G. acknowledge the structural funds project PRO-DD (POS-CCE, O.2.2.1., ID123, SMIS 2637, ctr. no 11/2009) for providing some of the infrastructure used in this work. Part of this work was supported by a grant of the Romanian Ministry of Education and Research, CNCS - UEFISCDI, project number PN-III-P1-1.1-TE-2019-1209, within PNCDI III.

Green electronics is an emerging field of research which aims to manufacture devices in an environmentally friendly and sustainable way. Usually, the involved electronic materials are naturally occurring and non-toxic. Also, they can be processed using simple, low energy deposition processes and fabrication techniques. In this work, we present low voltage organic field-effect transistors (OFETs) using almond gum (AG) as the gate dielectric. AG is a natural, biodegradable insulator material that can be directly collected from almond trees and used without any further purification. Moreover, AG possesses interesting properties such as water solubility, ease of processing, good insulation, low leakage current, good film quality, and high capacitance making it a promising dielectric for OFET devices. Bottom gate/bottom contact p-channel OFETs have been processed on glass substrates with poly (3,6-di (2-thien-5-yl)-2,5-di (2-octyldodecyl)-pyrrolo [3,4-c] pyrrole-1,4-dione)thieno [3,2-b] thiophene) (DPPTTT) polymethyl methacrylate (PMMA) blend as the active layer and gold as the source and drain electrodes. The transistors operate at low voltage (VGS ≤ 3 V), with threshold voltages Vth as low as −0.8 V, saturated field effect mobilities μsat above 0.75 cm2 V−1 s−1, subthreshold swings SS around 270 mV/dec and ON/OFF current ratio equal to 103. The combined favourable properties of both almond gum and low voltage operated OFET devices have a high potential to pave a way towards using naturally occurring, biodegradable electronic materials in future disposable sensors or throwaway, low-end electronics.

In2S3 films have been grown on glass substrates by spray pyrolysis technique. The deposition was carried out in a 300–500 °C substrate temperature and the molar ratio S/In is fixed to 2. The characteristics of these films have been determined by X-ray diffraction, energy dispersive spectroscopy, atomic force microscopy and spectrophotometer. These properties are related to the substrate temperature. X-ray diffraction spectra show that the films are polycrystalline and the obtained material is In2S3 with a cubic phase and oriented preferentially towards (400). The film grain size increases from 25 to 31 nm whereas the microstrain decreases from 4.68 × 10−3 to 3.85 × 10−3 with increasing substrate temperature. The average surface roughness passes through a minimum at 340 °C. Optical transmission of 80 % has been achieved in the visible and near infrared regions. The band gap energy has been found in the range of 2.33–2.65 eV. The static refractive index n(λ), the oscillation energy gap E0 and the dispersion energy Ed were determined by the Wemple-Didomenico model. The complex dielectric constants of In2S3 films have been calculated in the investigated wavelength range. It was found that the refractive index dispersion data obeyed to the single oscillator of the Wemple-Didomenico model, from which the dispersion parameters, the oscillation energy values and the high-frequency dielectric constant were determined. Hall effect measurements were carried out for higher substrate temperatures.

In2S3 thin films with different S/In molar ratios (from 1.5 to 3.5) were deposited via a spray pyrolysis technique on glass substrates at 340∘C. Then, the obtained films were annealed at the same temperature 400∘C for 2[Formula: see text]h. X-ray diffraction study reveals the formation of cubic [Formula: see text]-In2S3 phase with (400) as preferred orientation. The crystallite size varies in the range 64–97[Formula: see text]nm. Optical analysis exhibits that transmittance in visible and near infrared regions is higher than 65% for all films. The optical band gap varied from 2.58[Formula: see text]eV to 2.67[Formula: see text]eV. The optical parameters (refractive index, extinction coefficient, dielectric constants) were calculated through the transmittance ([Formula: see text]) and reflectance ([Formula: see text]). Dispersion parameters ([Formula: see text], [Formula: see text]), high frequency dielectric constant ([Formula: see text]), refractive index ([Formula: see text]), oscillator length strength ([Formula: see text]), average oscillator wavelength ([Formula: see text]) and optical moments ([Formula: see text]) were determined by Wemple–DiDomenico model. The surface and volume energy losses with photon energy were also calculated. The optical and electrical conductivities were estimated. These properties of In2S3 films are important for photovoltaic applications.

Tin-doped indium sulfide films were grown on glass substrates by spray pyrolysis technique at low different Sn:In atomic ratio in the starting solution and optimum experiment conditions ([Formula: see text]C, S:[Formula: see text]). The tin to indium molar ratio Sn:In was varied from 0 to [Formula: see text] in the solution. The obtained films with 2[Formula: see text][Formula: see text]m of thickness, are perfectly adhered, homogenous and uniform on the substrates. X-ray diffraction study reveals that all the films are formed in [Formula: see text] phase grown preferentially along (400). These films lose the orientation with increasing tin doping level. The crystallite size of undoped film was 48.8[Formula: see text]nm, which increases to 59.2[Formula: see text]nm corresponding to the film grown with Sn:[Formula: see text]. Raman analysis shows different peaks related to In2S3 phase. Optical analysis shows that these films are transparent in the visible and near IR with a transmittance higher than 85%. The optical gap energy is found to be direct and varies from 2.61[Formula: see text]eV to 2.76[Formula: see text]eV with the increase of Sn:In ratio from 0 to [Formula: see text]. The films are [Formula: see text] type and Sn doping improves considerably their conductivity. The photoluminescence behavior of In2S3:Sn films was also studied.