Sustainable Catalysts from Gold-Loaded Polyamidoamine Dendrimer-Cellulose Nanocrystals

Generation 6.0 polyamidoamine (G6 PAMAM) dendrimer-grafted cellulose nanocrystals (CNCs) (CNC-PAMAM) were synthesized and employed as supports for gold nanoparticles. The successful grafting of PAMAM dendrimers was confirmed by conductometric-potentiometric titration and pH-dependent zeta-potential analyses. Gold nanoparticles with diameters of approximately 2 to 4 nm were synthesized with the PAMAM dendrimers playing the role of nanoreactors and NaBH4 as the reducing agent. More importantly, gold nanoparticles were successfully prepared at pH 3.3 with the PAMAM dendrimers playing the functional role of reducing agent. Temperature and the concentration of CNC-PAMAM had an impact on the resulting size of gold nanoparticles. The gold nanoparticles immobilized on CNC-PAMAM displayed superior catalytic properties toward the reduction of 4-nitrophenol to 4-aminophenol. The enhanced catalytic behavior may be attributed to the improved dispersity and accessibility of gold nanoparticles within the PAMAM dendrimer domain. This work has demonstrated the versatility of CNC-PAMAM, both as an effective nanoreactor and a reducing agent.