Metal-enhanced fluorescence effect of Ag and Au nanoparticles modified with rhodamine derivative in detecting Hg2+

In this study, two metal-enhanced fluorescence chemosensors, metal mesoporous materials (hexagonal mesoporous silica (HMS) material loading with Ag and Au NPs were defined as Ag-HMS and Au-HMS) functionalized by rhodamine derivative R, have been prepared by a simple and effective impregnation-reduction method and used for Hg2+ detection in aqueous media. These materials were characterized by transmission electron microscopy (TEM), N2 physical adsorption-desorption, X-ray powder diffraction (XRD), UV-Vis spectrum and Fourier transform infrared spectroscopy (FT-IR). Both HMS-Ag-R and HMS-Au-R chemosensors have high selectivity toward Hg2+ in presence of interfering ions. According to the results, the suitable content of Ag and Au NPs is 2 wt% in the metal nanocomposite Ag-HMS and Au-HMS, respectively. In this paper, HMS-Ag-R shows a higher enhancement factor (EF) of 4.58 comparing with HMS-Au-R (EF = 2.93) in presence of 100 ppb Hg2+. The detection limits of HMS-Ag-R and HMS-Au-R for Hg2+ were determined as 0.9 and 1.4 ppb, respectively. Furthermore, the fluorescence lifetime of R reduced slightly after introducing Ag and Au NPs, and the localized surface plasmon resonance spectra of Ag and Au NPs all exhibited blueshift after immobiling rhodamine derivative R. It can be concluded that the metal-enhanced fluorescence effect of Ag-HMS is more powerful than Au-HMS.