Preparing high chroma colored silica nanoparticles based on layer-by-layer self-assembled technique

In this paper, monodisperse high chroma colored silica nanoparticles (SiNPs) were efficiently prepared by layer-by-layer (LbL) self-assembled technique. Poly(sodium-p-styrenesulfonate) (PSS) and Poly(ethyleneterephthalate) (PEI) were respectively used as polyanion and polycationic electrolytes. The monodisperse SiNPs with negative charge on the surface were used as the matrix. Direct dye (C.I Direct Red 224) was deposited on the SiNPs surface by means of LbL electrostatic adsorption. PEI and C.I. Direct Red 224 were electrostatically adsorbed on the surface of SiNPs. Then PSS and PEI were adsorbed on SiNPs surface to make the red SiNPs positive negative, respectively. And multilayer film-coated high chroma red SiNPs were prepared by repeating the above steps 4 times. The effects of concentration of polyelectrolyte, supporting salt (NaCl), amount of C.I Direct Red 224 and deposition time on dye coupling rate were studied. The multilayer film-coated high chroma red SiNPs were characterized using Scanning Electron Microscopy (SEM), Nano ZS potential laser particle analyzer and UV–vis spectrophotometer. The nanoparticles show good dispersibility due to the mutual repulsion of the same charge, and deep color. In addition, dense nano-film formed prevents the detachment of the dye and prevent the dye from falling off. This high chroma red SiNPs is expected to become a probe of visual marker and amplify the signal in immunoassay.