Gold nanoparticles deposited on silica microparticles - Electrokinetic characteristics and application in SERS

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.