Exploring the dual role of TEMPO-oxidized cellulose nanofibers in CdSe quantum dot synthesis for biocomposites in metal ion chemosensing

Abstract

TEMPO-oxidized cellulose nanofibers (TOCNs) are commonly used to develop hybrid functional materials. Aldehyde moieties in TOCNs allow them to act as reducing agents for the in situ synthesis of Ag, Pt, Au, and Pd NPs (NPs). However, no reports exist on using TOCNs as reducing agents for synthesizing semiconducting quantum dots (QDs). This study presents the simultaneous use of TOCNs as a reducing and stabilizing agent for synthesizing thioglycerol CdSe QD (QTC) biocomposites. In the presence of TOCNs, the synthesis of CdSe–TG QDs proceeds rapidly, eliminating the need for an additional reducing agent. TEM analysis shows that a thirty-minute reaction at 100 °C in aqueous media containing TOCNs produces homogeneously dispersed CdSe–TG QD biocomposites with a crystallite size of approximately 2.3 nm, whereas a reaction without TOCNs using NaBH₄ as a reducing agent takes 12 to 15 hours and results in larger nanostructures. QTC bionanocomposites were tested as chemosensors for metal ion detection in water using absorption and fluorescence spectroscopy. The hybrid material displayed high selectivity and sensitivity toward copper ions (Cu²⁺) with a detection limit as low as 320 ppb.