Size control and characterization of Au nanoparticle agglomeration during encapsulation in sol–gel matrices

Abstract Gold nanoparticles were encapsulated in sol–gel matrices with different amine cross-linker molecules in order to determine the cross-linker influence on nanoparticle agglomeration behaviour during encapsulation. The role of a stabilizing surfactant (SDS) was also investigated. The NP aggregate sizes were tracked using the UV surface plasmon resonance band (SPR), which red-shifts with increased particle size. It was found that use of long carbon chain cross-linkers such as 1,4-diaminobutane resulted in large Au NP aggregates, compared to short-chain analogs such as 1,2-diaminoethane, with which almost no agglomeration was observed. The SPR splitting pattern observed in samples with nanoparticle agglomeration is consistent with formation of nanodimensional objects with major and minor axes similar to nanowires during encapsulation within the cross-linked sol–gel material. The cross-linkers diethylenetriamine and triethylenetetraamine containing both terminal and internal amines demonstrated nanoparticle stabilization beyond that observed for similar sized diamine cross-linkers. This is ascribed to the multiple cross-linking sites available on these polyamines and the resulting reduction in matrix void volume.