Rapid Deposition and Controlled Clustering of Gold Nanoparticles on Surfaces and Micro-Patterned Substrates.

A method is reported for depositing gold nanoparticles (AuNPs) rapidly and uniformly onto centimeter-scale substrates. AuNPs functionalized with a low-density coating of poly(ethylene glycol) (PEG) are first dispersed into dichloromethane (DCM) containing cetyltrimethylammonium chloride (CTAC) then deposited onto hydroxyl terminated surfaces using centrifugal force. The degree of clustering on the surface is found to be controllable by varying the concentration of CTAC. The sparse coating of PEG stabilizes the AuNPs in DCM at sub-μM concentrations of CTAC, enabling deposition of AuNPs as a nonagglomerated submonolayer. Hence, the method can be used for rapid, scalable, and uniform deposition of isolated AuNPs as well as clustered agglomerates with tunable morphology and optical response. The approach is extended for depositing citrate- and PEG-capped AuNPs into the nanowells of topographically patterned substrates. Centrifugal deposition is first used to deposit AuNPs onto the patterned substrate. Wiping with a tissue selectively removes AuNPs from the top surface. This yields AuNPs deposited uniformly into nanowells of the substrate. The overall approach may be useful for large-scale selective deposition of AuNPs onto patterned surfaces that are attractive for SERS and sensors.