Abstract
The range of applicability of nanoparticle aggregates in surface enhanced Raman spectroscopy (SERS) sensing is limited. Therefore, in this work, an alternative route is developed consisting in a deposition of positively charged gold nanoparticles on silica carrier microparticles in an electrostatic interaction driven colloidal self-assembly process. The obtained composite particles of a raspberry structure and controlled gold nanoparticle coverage are utilized as SERS substrates in the sensing of rhodamine B. It is shown that the composites show significantly larger enhancement efficiency compared to gold nanoparticle aggregates produced in a conventional way. This effect was attributed to the adsorption of rhodamine B molecules at an available silica particle surface in the vicinity of immobilized gold nanoparticles. The results obtained in this work show that nanoparticle immobilization may be an efficient strategy to increase SERS sensing efficiency.
Highlights
As shown in some works [1,2,3], the use of gold nanoparticles (AuNPs) as SERS substrates requires a surface cleaning from adsorbed stabilizers which may result in particle aggregation
These values correspond to the polydispersity index (PDI) value equal to 0.07 and 0.25 for SiO2Ps and AuNPs, respectively
The diffusion coefficients and electrophoretic mobilities of the particles were measured for a broad range of ionic strength using dynamic light scattering (DLS) and laser Doppler velocimetry (LDV) methods
Summary
As shown in some works [1,2,3], the use of gold nanoparticles (AuNPs) as SERS substrates requires a surface cleaning from adsorbed stabilizers which may result in particle aggregation. This can significantly influence the optical properties of nanoparticles by affecting the maximum of localized surface plasmon resonance (LSPR) band [4,5] or even may result in loss of their plasmonic properties [6]. One can expect that the use of AuNPs aggregates in real SERS analyses is limited [12] For this reason, new reproducible strategies for the generation of hot-spots in SERS substrates are still needed
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