Influence of the Physical Properties on the Antibacterial and Photocatalytic Behavior of Ag-Doped Indium Sulfide Film Deposited by Spray Pyrolysis

Belgacem Tiss,Daniel Cristea,Ioana Ghiuta,Catalin Croitoru,Sahbi Alaya,Mabrouk Kraini,Noureddine Bouguila,Delia Patroi,Cacilda Moura,Youssef Moualhi,Luís Cunha

doi:10.3390/coatings11040370

Abstract

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.

Highlights

Environmental pollution, energy efficiency, pharmaceutical research, and biomaterials are some of the hot topics of today’s world
With or without silver doping, deposited by spray pyrolysis are polycrystalline, with the crystallite sizes around 20 nm and 32 nm
Electrical characterization confirms the films as semiconductors; the Ag doping leads to an increase in conductivity

Summary

Introduction

Environmental pollution, energy efficiency, pharmaceutical research, and biomaterials are some of the hot topics of today’s world. One of the most promising solutions for the degradation of various types of antibiotic contaminants is performed by semiconductor-based heterogeneous photocatalysis. This approach has received considerable attention, because it is an environmentally friendly technology [3,4,5]. Spray pyrolysis is a good choice to obtain In2S3 nanostructured layers and has the capacity to prepare thin films on large surfaces, and with low cost. Other authors observed that Ag incorporation affects the physical properties of In2S3, the electrical properties, leading to decrease of the electrical resistivity due to an increase of the concentration of electric charge carriers [40,41,42,43]

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