Dialdehyde cellulose nanocrystals act as multi-role for the formation of ultra-fine gold nanoparticles with high efficiency

Gold nanoparticles (AuNPs) within 10 nm prepared and stabilized by environmentally friendly reducing and supporting agents are highly desired to obtain excellent catalytic properties for organic transformation. In this paper, a rapid and mild strategy for synthesizing ultra-fine AuNPs is reported by using dialdehyde cellulose nanocrystals (DACNCs) as both efficient reductant, dispersant and template for the first time. DACNCs with higher content of aldehyde groups, acting as multi-role player, are crucial to limit the size of AuNPs within 10 nm. Furthermore, AuNPs with average diameter of 5.1 ± 1.0 nm are quantitative obtained at ambient temperature by reducing chloroauric acid within 1 h under conditions of pH= 10.8, 53% aldehyde content, 0.4% DACNCs and 0.25 mM gold ions. In addition, a quantitative method for monitoring the exhaustion of gold ions is established to clarify the synthetic mechanism of AuNPs. Finally, reduction of 4-nitrophenol under AuNPs catalysis is conducted to verify the superiority of as-prepared ultra-fine AuNPs.