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APTES Duality and Nanopore Seed Regulation in Homogeneous and Nanoscale-Controlled Reduction of Ag Shell on SiO2 Microparticle for Quantifiable Single Particle SERS
journal contribution
posted on 2018-10-11, 08:13 authored by Daragh Rice, Rabah Mouras, Matthew Gleeson, Ning Liu, Syed A. M. Tofail, Tewfik Soulimane, Christophe SilienNoble-metal
nanoparticles size and packing density are critical
for sensitive surface-enhanced Raman scattering (SERS) and controlled
preparation of such films required to achieve reproducibility. Provided
that they are made reliable, Ag shell on SiO2 microscopic
particles (Ag/SiO2) are promising candidates for lab-on-a-bead
analytical measurements of low analyte concentration in liquid specimen.
Here, we selected nanoporous silica microparticles as a substrate
for reduction of AgNO3 with 3-aminopropyltriethoxysilane
(APTES). In a single preparation step, homogeneous and continuous
films of Ag nanoparticles are formed on SiO2 surfaces with
equimolar concentration of APTES and silver nitrate in ethanol. It
is discussed that amine and silane moieties in APTES contribute first
to an efficient reduction on the silica and second to capping the
Ag nanoparticles. The high density and homogeneity of nanoparticle
nucleation is further regulated by the nanoporosity of the silica.
The Ag/SiO2 microparticles were tested for SERS using self-assembled
4-aminothiophenol monolayers, and an enhancement factor of ca. 2 ×
106 is measured. Importantly, the SERS relative standard
deviation is 36% when a single microparticle is considered and drops
to 11% when sets of 10 microparticles are considered. As prepared,
the microparticles are highly suitable for state-of-the-art quantitative
lab-on-a-bead interrogation of specimens.