title: Label-free optical characterization methods for detecting amine silanization-driven gold nanoparticle self-assembly.
abstract: Fluorescence lifetime correlation spectroscopy (FLCS) is presented as a single-step label-free detection method for probing the amine silanization-driven spontaneous 3D self-assembly of freestanding gold nanoparticles (GNPs) in solution. Unlike the conventional methods of studying self-assembly, for example, UV-vis spectroscopy and electron microscopy, FLCS utilizes the intrinsic gold fluorescence. The significance of this approach is to amalgamate the measurement of optical and hydrodynamic size properties simultaneously to achieve a more coherent description of the self-assembly pathway. GNP self-assembly has two-stage kinetics. Electrostatic interaction drives the initial amine silanization, and this is followed by siloxane bond formation between hydrolyzed ethoxy groups of GNP-attached APTES, resulting in the formation of micrometer-sized superstructures. The self-assembly has resulted in a 5-fold increase in the fluorescence lifetime (FL), and the FLCS study has shown an 8- to 10-fold increase in the diffusion coefficient using the pure diffusion model. This result is consistent with the transmission electron microscopy (TEM) observation, which shows a few hundred fold increase in the diameter due to assembly formation by the GNPs.
authors.affiliation: National Biophotonics and Imaging Platform, School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland.
authors.forename: Shibsekhar
authors.initials: S
authors.lastname: Roy
authors.forename: Chandra K
authors.initials: CK
authors.lastname: Dixit
authors.forename: Robert
authors.initials: R
authors.lastname: Woolley
authors.forename: Richard
authors.initials: R
authors.lastname: O'Kennedy
authors.forename: Colette
authors.initials: C
authors.lastname: McDonagh
mesh_terms: D000588:Amines / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D055095:Optics and Photonics; D010316:Particle Size; D012821:Silanes / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013499:Surface Properties
chemical_list: D000588:Amines; D012821:Silanes; D006046:Gold