Ultraluminescent gold core–shell nanoparticles applied to individual bacterial detection based on metal-enhanced fluorescence nanoimaging

Abstract

Gold core–shell nanoparticles were synthesized based on metallic cores, variable silica shell spacers covered with modified fluorescent silica layers. Ultraluminescent properties were obtained based on metal-enhanced fluorescence (MEF). Different silica spacers were synthesized to optimize the MEF enhancement factor (MEFEF). An optimal MEFEF was determined equal to 9.5 for shorter silica spacers (d−SiO2−=10 nm). These nanoparticles were deposed on Escherichia coli bacteria at different concentration levels for Bioimaging generation over their surfaces. The best luminescent nanoparticles were deposed on intermediate and higher bacteria concentrations. In the presence of intermediate bacteria concentrations, the ultraluminescent nanoparticles adsorbed showed an increase of 35% to 45% compared with individual nanoparticles. To modify the surface of individual bacteria, diluted samples of bacteria were used in which a 20% decrease in fluorescence emission was measured. In the presence of higher bacteria concentrations, fewer clear and bright images were obtained. At diluted ultraluminescent nanoparticle concentrations, a decrease in brightness and image detail was observed; and in the absence of nanoparticle deposition, no image was recorded. Accordingly, these ultraluminescent gold core–shell nanoparticles have been shown to be useful as platforms for biodetection and tracking applications.