Polarization-dependent fluorescence of CdSe/ZnS quantum dots coupling to a single gold-silver alloy nanotube

Highlights: • SP of Au-Ag alloy nanotube shows less polarization dependent than that of Ag nanowire. • Ag content in alloy nanotube affects its SP polarization dependent behavior. • SP energies of both Ag and Au nanotubes are found to penetrate into their interiors. • Microwave heating can improve the productivity of chemical synthesis of alloy nanotubes. The fluorescence intensities of CdSe/ZnS quantum dots on a silver nanowire and a gold-silver alloy nanotube with different molar ratios of gold and silver are investigated under excitation with different polarization angles. The ratio of the fluorescence intensity of perpendicular and parallel polarization excitations is measured to be 4.05 for a silver nanowire and decreases to 1.30, 1.10 and 1.07 for nanotube with Au:Ag molar ratios of 1:4.0, 1:2.5 and 1:1.5, respectively. The numerical simulation results show that the aforementioned experimental phenomena can be attributed to the variation in the distribution of the surface plasmon electromagnetic field under perpendicular polarized light excitation. The electromagnetic field is primarily distributed on the outer surface of the silver nanowire, while the field partially penetrates the interior of the silver nanotube and becomes completely concentrated at the interior of the gold nanotube. This research also found that the productivity and robustness of the chemical synthesis of the alloy nanotubes can be greatly improved by using a microwave reactor.