Nano-ZnS photocatalytically active both under UV and solar radiation: A comparison of conventional and microwave-assisted hydrothermal syntheses with various reaction conditions

Influence of reaction conditions on properties of nano-ZnS was investigated. The nano-ZnS was synthesized from ZnCl2 and Na2S via conventional hydrothermal (H) and microwave-assisted hydrothermal (M) method with reaction times 90, 150, 210 min and 10, 20, 30 min, respectively. For all reaction times, three nZn:nS molar ratios (1:1; 1.5:1; 2:1) were tested. Samples were characterized by XRPD, FTIR, Raman microspectroscopy, UV-VIS and SEM. Photocatalytic activity (PA) was determined on Acid orange 7 under UV radiation (λ = 365 nm), and for selected samples also under the sunlight. After 360 min of UV radiation, PA 96% (H; 210 min; 1:1, 1.5:1 or 2:1) and 92% (M; 30 min; 1.5:1 or 2:1) was reached. Under the sunlight, PA 96% (H; 210 min; 2:1) and 92% (M; 20 min; 2:1) was achieved after 120 and 540 min, respectively. M-synthesized nano-ZnS is promising for outdoor applications not requiring a fast PA effect.