Cu\({}_{2}\)ZnSnS\({}_{4}\) Nanoparticles as an Efficient Photocatalyst for the Degradation of Diclofenac in Water  
[PERSON]  
1 Department of Materials Science, Solar Energy Research Center (MIB-SOLAR), University of Milano-Bicocca, Via Cozzi 55, 20125 Milan, Italy; [EMAIL_ADDRESS] (A.H.H. ); [EMAIL_ADDRESS] (A.L. ); [EMAIL_ADDRESS] (S.B.) [PERSON]  
1 Department of Materials Science, Solar Energy Research Center (MIB-SOLAR), University of Milano-Bicocca, Via Cozzi 55, 20125 Milan, Italy; [EMAIL_ADDRESS] (A.H.H. ); [EMAIL_ADDRESS] (A.L. ); [EMAIL_ADDRESS] (S.B.) [PERSON]  
1 Department of Materials Science, Solar Energy Research Center (MIB-SOLAR), University of Milano-Bicocca, Via Cozzi 55, 20125 Milan, Italy; [EMAIL_ADDRESS] (A.H.H. ); [EMAIL_ADDRESS] (A.L. ); [EMAIL_ADDRESS] (S.B.) [PERSON]  
1 Department of Materials Science, Solar Energy Research Center (MIB-SOLAR), University of Milano-Bicocca, Via Cozzi 55, 20125 Milan, Italy; [EMAIL_ADDRESS] (A.H.H. ); [EMAIL_ADDRESS] (A.L. ); [EMAIL_ADDRESS] (S.B.) [PERSON]  
1 Department of Materials Science, Solar Energy Research Center (MIB-SOLAR), University of Milano-Bicocca, Via Cozzi 55, 20125 Milan, Italy; [EMAIL_ADDRESS] (A.H.H. ); [EMAIL_ADDRESS] (A.L. ); [EMAIL_ADDRESS] (S.B.) from photo/electro-catalytic water splitting to CO2 reduction, as well as from photosynthesis to environmental remediation [5]. The photocatalytic materials conventionally used are represented by common metal oxide semiconductors, and the most representative of them is TiO2 [6; 7; 8; 9; 10; 11; 12]. However, due to their large energy gap, these compounds can only efficiently absorb the UV portion of the solar spectrum, affecting their photocatalytic performance. Kesterite, Cu2 ZnSnS4 (CZTS), is a p-type semiconductor that is well known in photovoltaics, and it has drawn the scientific community's attention thanks to its excellent absorption coefficient, cost-effectiveness, and environmental sustainability [13; 14]. CZTS shows a bandgap of around 1.5 eV, so it can efficiently harvest an abundant portion of the solar spectrum, especially in the visible region [15; 16]. Except for PV technologies, this class of semiconductors has been recently reported to be an efficient photocatalyst for organic dye degradation [17; 18; 19; 20; 21; 22; 23]. While, for PV applications, CZTS is usually produced by sol-gel methods or high-vacuum depositions [24; 25; 26; 27; 28; 29; 30; 31; 32; 33], in the few photocatalytic applications reported, it is mainly provided in the form of nanoparticles or nanocrystals to enhance the contact surface and, therefore, make the active sites easily reachable. Back in 2014, [PERSON] et al. [17] demonstrated how CZTS nanocrystals could efficiently degrade methyl orange, and a few years later, methylene blue was degraded by hydrothermally synthesized CZTS nanoparticles in a study by [PERSON] and co-workers [18]. [PERSON] et al. also reported excellent photocatalytic efficiencies [19] in a study on the degradation of azo dyes in the presence of nanocrystalline kesterite. More recently, [PERSON] suggested that the use of CZTS nanocrystals could be considered as a novel approach for the remediation of water from organic pollutants and industrial wastes, but still, only organic dyes have been used to test this system, with there being no development of any analytic methodology to test and assess CZTS photocatalytic activity in the degradation of a truly encountered micropollutant [20]. In another study, Rhodamine B (RRB) was degraded with around 52% efficiency through photocatalysis mediated by a layered microstructure of CZTS synthesized by a hydrothermal method [34]. The same RhB was photodegraded under visible light by [PERSON] et al. [35] with an efficiency of 79% in 4 h using CZTS films obtained through using chemical spray pyrolysis equipment. Additionally, the CTZS nanoparticles prepared through a solvothermal method by [PERSON] and co-workers showed an efficiency of 83% in 100 min of RhB degradation under visible light [36].