Near-Infrared (NIR) Silver Sulfide (Ag 2 S) Semiconductor Photocatalyst Film for Degradation of Methylene Blue Solution.

A silver sulfide (Ag 2 S) semiconductor photocatalyst film has been successfully synthesized using a solution casting method. To produce the photocatalyst films, two types of Ag 2 S powder were used: a commercialized and synthesized powder. For the commercialized powder (CF/comAg 2 S), the Ag 2 S underwent a rarefaction process to reduce its crystallite size from 52 nm to 10 nm, followed by incorporation into microcrystalline cellulose using a solution casting method under the presence of an alkaline/urea solution. A similar process was applied to the synthesized Ag 2 S powder (CF/syntAg 2 S), resulting from the co-precipitation process of silver nitrate (AgNO 3 ) and thiourea. The prepared photocatalyst films and their photocatalytic efficiency were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and UV-visible spectroscopy (UV-Vis). The results showed that the incorporation of the Ag 2 S powder into the cellulose films could reduce the peak intensity of the oxygen-containing functional group, which indicated the formation of a composite film. The study of the crystal structure confirmed that all of the as-prepared samples featured a monoclinic acanthite Ag 2 S structure with space group P 21 /C. It was found that the degradation rate of the methylene blue dye reached 100% within 2 h under sunlight exposure when using CF/comAg 2 S and 98.6% for the CF/syntAg 2 S photocatalyst film, and only 48.1% for the bare Ag 2 S powder. For the non-exposure sunlight samples, the degradation rate of only 33-35% indicated the importance of the semiconductor near-infrared (NIR) Ag 2 S photocatalyst used.