Synthesis of Cadmium Selenide Nanoparticles

Cellulose acetate (MW ∼100,000 Da; acetyl content ~39.7 wt%) and acetone were purchased from VWR International (Radnor, PA, USA).
Based on the slow reaction between Cd²⁺ and Se²⁻ ions in an aqueous basic bath with pH > 10, the CdSe nanoparticles were synthesized using a chemical bath deposition process. Cadmium sulfate (CdSO₄) and sodium selenosulfite (Na₂SSeO₃) were used as the sources for Cd²⁺ and Se²⁻, respectively. Na₂SSeO₃ was prepared by dissolving elemental Se in the form of fine powder in an aqueous solution of sodium sulfite heated to 60 °C. The solution was stirred well until the Se was completely dissolved. The pH of the solution was adjusted by adding excess NaOH. CdSe was formed in 2 h at a temperature of 70 °C. The obtained CdSe powder was washed using deionized water, centrifuged repeatedly, and subsequentially dried in a vacuum oven.
Because CdSe is considered toxic to human cells, it was handled with the utmost care during this study [18 (link)]. CdSe toxicity has been mainly attributed to the release of Cd²⁺ ions from the CdSe to surrounding cells [18 (link)]. The method of exposure by which this diffusion occurs highly alters how significantly the affected cells react to CdSe [18 (link)]. Consequently, equipment in contact with CdSe was cleaned thoroughly, waste was properly disposed of, and the CdSe NPs were properly labeled and stored before and after use.