S. Ghazal

Preparation of pure and Se/WO3-NRDs was successfully carried out using the sol-gel route. In a typical process, 3.30 g Na2WO4.2H2O was dissolved in 80 mL distilled water, and an appropriate amount of Na2SeO3 (0.057, 0.095, or 0.133 g) was dissolved in 20 mL distilled water to prepare 3, 5, or 7% doping solution. The Na2SeO3 salt solution was added drop by drop to the Na2WO4 salt solution under constant stirring. In the next step, 0.25 g chitosan powder as stabilizer was dissolved in 25 ml 5% acetic acid solution at ambient temperature, and it was added drop by drop to the mixed salt solution. Then the pH of the mixture was lowered to 1.5 by dropwise addition of HCl, 2.0 M, and the obtained gel stirred for 16 h at ambient temperature. The powder produced was filtered off and carefully washed five times with distilled water, and the last time, it was ethanol. The filtrate was dried in an oven at 70 °C overnight and then calcined at 550 °C for two hours. The pure sample was prepared by dissolving the same amount of Na2WO4.2H2O in 100 mL of distilled water without the addition of Na2SeO3, with the same procedure.
The UV-Vis spectrophotometer (Perkin-Elmer, Lambda 365) in the 200-800 nm range was used for the optical evaluation. FESEM/EDX (Zeiss, Sigma 300-HV) and PXRD (Bruker, D8-Advance) analysis were used to investigate the prepared samples' morphology, surface composition, and crystal structures. The FT-IR (Thermo Nicolet, AVATAR 370), and Raman (Avantes) were also used to characterize the samples.