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Disulfide-linked gold nanoparticles (AuNP) were synthesized by reacting dithiobis[succinimidylpropionate] (DSP) coated nanoparticles with glutathione disulfide. AuNP-cross-linking was monitored by the red shift and broadening of the AuNP's localized surface plasmon absorption resonance (LSPR) spectrum. The exposure of the disulfide-linked AuNPs to a variety of free thiols with systematically varying molecular weight revealed a AuNP-disulfide stability to reduction by thiols up to a critical molecular weight, M(c), of >300 Da thus making the disulfide-linked AuNP the first reagent that can discriminate thiols based on their size.

Rooney, P.; Rezaee, A.;Xu, S.; Manifar, T.; and Rangan, Chitra. (2008 We present experimental and theoretical results for the changes in the optical-plasmon resonance of goldnanoparticle dimers immobilized on a surface when coated with an organic dielectric material. The plasmon band of a nanoparticle dimer shifts to a higher wavelength when the distance between neighboring particles is decreased, and a well-separated second peak appears. This phenomenon is called cross-talk. We find that an organic coating lets cross-talk start at larger separation distances than for uncoated dimers by bridging the gap between immobilized nanoparticles ͑creating optical clusters͒. We study this optical clustering effect as a function of the polarization of the applied light, of the inter-particle distance, of the surrounding environment, and of the optical properties of the coating layer. Theoretical discrete-dipole approximation calculations support the experimental absorption spectroscopy results of gold nanoparticles on glass substrates and on optical waveguides.

One application of octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs) is its use as thin film resists. In this work, we demonstrated that OTS SAMs can be reliable resists for organo-metallic chemical vapor deposition (OMCVD) grown gold nanoparticles (Au NPs). In optical sensing applications based on Au NPs, one candidate system consists of patterned OTS SAMs and precisely grown OMCVD Au NPs for achieving a high sensitivity. As an initial step, the OTS SAMs need to perfectly resist the OMCVD Au NP growth. Hence the optimized formation of the OTS SAMs affected by different assembly times and baking temperatures was studied by contact angle, ellipsometry, XPS, SEM, and atomic force microscopy (AFM). To demonstrate the ability of the OTS SAMs to resist OMCVD Au NP growth, the OMCVD process was carried out on two sets of samples: OTS SAMs fabricated under optimized conditions on one set and the other set without OTS SAMs. High-resolution XPS, RBS, SEM, and ultraviolet-visible (UV-Vis) spectroscopy were applied to study the growth of Au NPs on the samples with and without OTS SAM resists.