Near Infrared Emission of Ag2S Quantum Dots and their Fluorescence Quenched by Gold Nanoparticles

Abstract

The near-infrared emitting Ag 2 S quantum dots (QDs) coated with L-cysteine were prepared by one-pot aqueous synthesis at room temperature. Several characterization methods including X-ray diffraction (XRD), transmission electron microscopy (TEM), fluorescence spectrophotometer (PL) and ultraviolet -visible spectrophotometer (UV-vis) were used to characterize the structure, morphology and optical properties of the samples. The effects of gold nanoparticles on the fluorescence of Ag 2 S QDs were systematically investigated, it was found that gold nanoparticles could enhance or quench the fluorescence intensity of Ag 2 S QDs in some situation. Within a certain range, the fluorescence intensity of Ag 2 S QDs shows a linear quenching proportional to the colloidal gold concentration. Under the optimized experimental conditions, the linear range was obtained for colloidal gold concentration from 5.93 -27.09 ×10 -6 mol/l (r 2 = 0.9956). The determined detection limit (LOD) was about 5.08×10 -6 mol/l. The quenching mechanism of Ag 2 S QDs is discussed. Gold nanoparticles also have similar effects on Ag 2 Te QDs. A new method for the quantitative detection of inorganic nanoparticles was established, and it provides a new way for the bio-analytical applications.

Novel and effective synthesis protocol of AgNPs functionalized using L-cysteine as a potential drug carrier

“…It is well known that silver sulfide exhibits quantum dots properties. Xiulan Wu et.al ( 2015 ) have shown that for spherical Ag 2 S nanoparticles of 5 nm in diameter, the maximum emission peak appears at the wavelength of ca. 750 nm, after excitation at 520 nm.…”