Dendritic Silica Nanospheres Loaded with Red-Emissive Enhanced Carbon Dots for Zika Virus Immunoassay

Enhanced red emissive carbon dots (CDs) and their enrichment in spheres are ideal for sensing applications. Here, we propose a novel strategy for enhancing the red emission of CDs and enriching it in dendritic SiO2 nanospheres. The surface carboxylated and red emissive CDs obtained by alkali/acid treatment of blue emissive CDs are dissolved in N-beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane for silanization. Electron injection and long chain passivation greatly enhance the red emission of CDs. Through the reaction of silane with the hydroxyl groups of dendritic SiO2 spheres, the silanized CDs can be enriched in dendritic SiO2 spheres. Encapsulation of composite spheres with (3-Aminopropyl)-trimethoxysilane protects CDs and facilitates bioconjugation. These fluorescence SiO2 spheres exhibit high quantum yields in red emission (48.5 % for aqueous solution and 35.7 % for solid state) and maintain good monodispersity. It is further used as a signal of lateral flow test strips to target Zika virus, and demonstrates an ultra-sensitive, specific and effective immunoassay. And considerable results have been achieved in the analysis of actual samples.