pH‐Dependent Metal‐Enhanced Fluorescence from CdTe@PAA Nanospheres near the Au Nanoparticles in Aqueous Solution

Abstract

Metal-enhanced fluorescence of semiconductor nanocrystals (NCs) is the current investigation focus. In this work, we directly observed metal-enhanced fluorescence of CdTe@PAA nanaospheres in aqueous solution. The enhanced magnitude of photoluminescence (PL) was closely related to solution pH values, and the maximal PL enhancement is about 9 times compared with the ones without Au NPs. Furthermore, based on the results of absorptions and fluorescence lifetimes of CdTe@PAA-Au mixed solution at different pH values, we studied the mechanisms and physics processes of pH-dependent enhanced PL induced by Au NPs. The pH-dependent PL of CdTe@PAA-Au mixed solutions are due to the constantly changing distances between Au NPs and CdTe@PAA nanaospheres with pH. In the CdTe@PAA-Au mixed solutions, CdTe@PAA nanospheres in close proximity to the Au NPs are exposed to the increased electric fields in between and around the NPs, effectively resulting in significant increases in their absorption cross section. This lends itself to a subsequent increase in the excitation and eventually in the fluorescence emission from the CdTe@PAA nanospheres.