Core-satellite Ag/TiO2/Ag composite nanospheres for multiple SERS applications in solution by a portable Raman spectrometer

Herein, the robust core-satellite Ag/TiO 2 /Ag composite nanospheres were successfully developed. We firstly fabricated large silver nanoparticles with sufficient plasmonic activity as cores and then encapsulated uniform titanium dioxide interlayer shell around Ag cores, which serves as the highly functionalized substrates to achieve uniform and plentiful surface chemical properties. Next, the outer shell of small silver satellites was formed in-situ via controllable reduction of AgNO 3 by n -butylamine, which acts as the remarkable enhancer for surface enhanced Raman scattering (SERS). The Ag/TiO 2 /Ag composite nanospheres with exceptional SERS sensitivity were easily prepared via facilely tuning the coverage and grain sizes of silver satellites. Then the optimized Ag/TiO 2 /Ag composite nanospheres were employed to quantitatively detect methylene blue (MB) in solution. The results showed good linear relationship between SERS intensities and logarithm concentrations of MB and the limit of detection is low to 10 −10  M. Moreover, the highly uniform and robust Ag/TiO 2 /Ag composite nanospheres display outstanding reproducibility (RSD = 4.02%) and highly storage stability. Owing to the intrinsic catalytic activity of small Ag satellites, Ag/TiO 2 /Ag nanospheres were further applied to effectively follow the degradation reaction process of crystal violet by SERS. Altogether, the core-satellite Ag/TiO 2 /Ag nanospheres present multiple SERS application potential in various fields, such as quantitative chemical analysis, trace detection of pollutants and in-situ reaction monitoring.