Influence of the physical properties on the antibacterial and photocatalytic behavior of Ag-doped indium sulfide film deposited by spray pyrolysis

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

Heterostructured S-TiO₂/g-C₃N₄ Photocatalysts with High Visible Light Photocatalytic Activity

Novel heterojunctions associating graphitic carbon nitride g-C3N4 and S-doped TiO2 nanoparticles were successfully designed and prepared via a hydrothermal method and used for photocatalytic degradations. The loading in S-TiO2 nanoparticles on g-C3N4 was varied (5, 10 and 20 wt%), and the photocatalysts were characterized by XRD, FT-IR, solid-state UV-visible diffuse reflectance, photoluminescence, XPS, TEM and SEM. The S-TiO2 (5%)/g-C3N4 catalyst exhibits the highest activity for the photocatalytic degradation of the methylene blue (MB) dye under visible light irradiation. The high photocatalytic performance originates from the enhanced separation and transfer of photogenerated charge carriers. The S-TiO2 (5%)/g-C3N4 photocatalyst is stable and can be reused five times without a sharp drop in activity, indicating its high potential for wastewater remediation

Conductometric H₂S Sensors Based on TiO₂ Nanoparticles

High-performance hydrogen sulfide (H2S) sensors are mandatory for many industrial applications. However, the development of H2S sensors still remains a challenge for researchers. In this work, we report the study of a TiO2-based conductometric sensor for H2S monitoring at low concentrations. TiO2 samples were first synthesized using the sol-gel route, annealed at different temperatures (400 and 600 °C), and thoroughly characterized to evaluate their morphological and microstructural properties. Scanning electronic microscopy, Raman scattering, X-ray diffraction, and FTIR spectroscopy have demonstrated the formation of clusters of pure anatase in the TiO2 phase. Increasing the calcination temperature to 600 °C enhanced TiO2 crystallinity and particle size (from 11 nm to 51 nm), accompanied by the transition to the rutile phase and a slight decrease in band gap (3.31 eV for 400 °C to 3.26 eV for 600 °C). Sensing tests demonstrate that TiO2 annealed at 400 °C displays good performances (sensor response Ra/Rg of ~3.3 at 2.5 ppm and fast response/recovery of 8 and 23 s, respectively) for the detection of H2S at low concentrations in air

Organic FETs using biodegradable almond gum as gate dielectric: A promising way towards green electronics

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

Experimental and Theoretical Studies on Optical Properties of Tetra(Imidazole) of Palladium (II) Phthalocyanine

In this work, the optical properties of tetra(imidazole) of palladium phthalocyanine (PdPc(Im)4) in solution form and thin films on glass and fluorine-doped tin oxide (FTO) substrates were investigated via the thermal evaporation technique. The optical band gap was evaluated by ultraviolet–visible spectroscopy (UV-Vis). The energy band gap values were determined based on the Tauc graph. In addition, time-dependent density functional theory (TD-DFT) was used to simulate the UV-Vis absorption spectrum of the (PdPc(Im)4) molecule in the Dimethyl Sulfoxide (DMSO) solution phase. A good correlation was found between the DFT results and the experimental optical results. The band gap values between the experimental and DFT-simulated values are presented. The energy band gap of (PdPc(Im)4) obtained from the DFT calculations showed that it can be efficiently regulated. Frontier molecular orbitals and molecular electrostatic potentials were also proposed in this work. The surface study of the layers deposited on FTO was considered by atomic force microscopy (AFM) and scanning electron microscopy (SEM), and the results demonstrated good homogeneity covering the entire surface. The SEM image showed a homogeneous distribution of the grains with some spherical or rod-shaped structures and no agglomeration structures. This work rendered a strategy for regulating the energy band gap and compared the experimental observations obtained with theoretical studies, which provides a fundamental insight into the optical band for optoelectronic and thin-film solar cells

Influence of silver doping on physical properties of sprayed In2S3 films for solar cells application

A set of silver-doped indium sulphide (In2S3:Ag) thin films were deposited by spray pyrolysis technique, at 350 degrees C, to analyze the effects of the Ag doping on the physical properties of the films. Within the limits of the analyzed dopant concentration, X-ray diffraction (XRD) revealed the polycrystalline nature of the films, crystalizing in the beta-In2S3 cubic phase, regardless the level of doping. Both XRD and Raman spectroscopy confirmed the absence of secondary phases. Optical absorption spectra evidenced that the films are opaque to ultraviolet radiation, but transparent in visible and near infrared regions of the electromagnetic spectrum. According to absorption and extinction coefficients variations, the films are smooth and homogeneous. The forbidden bandgap (E-g) increases with increasing Ag concentration. Photoluminescence measurements reveal that the films exhibit seven emissions related to In2S3 defects. The films are semiconductor and the transport phenomena are assisted via small polaron hopping. The photovoltaic effect in Ag/In2S3(n)/Si(p)/Ag is confirmed by I-V characterization in dark and under illumination.This research was partly supported by the projects HP-NANOBIO Project PID2019-111163RB-100, granted by Spanich Ministry of Science, and Project CIVP18A3940, granted by Fundación Ramón Areces, Spain. CVV thanks Xunta de Galicia (Spain) for the AEMAT (ED431E-2018/08) Strategic Partnership and the use of RIAIDT-USC analytical facilities. CVV belongs to the Galician Competitive Research Group ED431C-2017/22, co-funded by FEDER. Part of this work was also supported by the Portuguese Foundation for Science and Technology (FCT) in the frame work of the Strategic Funding UIDB/04650/2020

Electrical behavior and photocatalytic ativity of ag-doped in2S3 thin films

Indium sulfide thin films with different amounts of silver doping were deposited by spray pyrolysis. The samples were tested as potential photocatalysts by degrading methylene blue (MB) dye aqueous solution under the effect of light. Samples were prepared using precursors with Ag/In ratios of 0 at.%, 4 at.%, and 6 at.%, corresponding to a measured and normalized Ag concentration in the films of 0.0 at.%, 1.4 at.%, and 2.3 at.%, respectively. Scanning electron microscopy revealed that the surface of the films was homogeneous and compact. Within the energy resolution of dispersive x-ray spectroscopy, the films were revealed to be stoichiometric with an S/In ratio of 1.50 ± 0.05. The films exhibited semiconductor behavior, and the best direct-current (DC) conductance was achieved for the film with 1.4 at.% Ag doping. Changes in the Ag concentration led to the activation of different conduction mechanisms, from correlated barrier hopping (for the undoped and for 1.4 at.% Ag-doped film) to overlapping large-polaron tunneling (for the 2.3 at.% Ag-doped film). After immersing the samples in MB solution and exposing them to visible light for 270 min, a significant decrease of the MB absorption was observed. The lowest absorption (and thus highest photodegradation efficiency) was measured for the solution containing the sample with 1.4 at.% Ag doping, showing a photodegradation efficiency of 83%. Considering their performance and relatively low manufacturing cost, such In2S3:Ag films could contribute to the solution of environmental problems related to wastewater via photodegradation of contaminants under illumination by sunlight.This work was supported by Tunisian Ministry of Higher Education and Scientific Research, Spanish Ministry of Science and Innovation—FEDER Funds (MODENA Project CTQ2016-79461-R) and Fundacio´n Ramo´n Areces (Spain, Project CIVP18A3940). NANOMAG group belongs to Galician Competitive Research Group ED431C-2017/22, programme cofunded by FEDER, and AEMAT Strategic Partnership (ED431E-2018/08, Xunta de Galicia, Spain). 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. Cristea and C. Croitoru 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

Chlorine doping impact on the photocatalytic and antibacterial activity of sprayed In2S3 films

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.Part of this work was supported by the Portuguese Foundation for Science and Technology in the framework of the Strategic Funding UIDB/04650/2020. D.C. and I.G. acknowledge the structural fund project PRO-DD (POS-CCE, O.2.2.1., ID123, SMIS 2637, contract number 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. V.C. acknowledges the Romanian Ministry of Research, NUCLEU Program LAPLAS VI (contract number 16N/2019) and ELI-RO_2020_12