Synthesis of protein-assisted aqueous Ag2S quantum dots in the bovine serum albumin solution

A one-step method was developed for preparing Ag2S quantum dots (QDs) using a common protein [bovine serum albumin (BSA)] to entrap QDs precursors (BSA-Ag+). Fluorescence (FL) and ultraviolet spectra showed that the molar ratio of Ag+/BSA, temperature, and pH are the crucial factors for the quality of QDs. The QDs absorption wavelength and emission wavelength were about 340 and 450 nm. The average QDs particle size was estimated to be less than 5 nm, determined by transmission electron microscopy. The X-ray power diffraction and XPS results showed that the synthesized product was indeed monoclinic Ag2S. With Fourier transform infrared spectra and thermogravimetry analysis, there might be conjugated bonds between Ag2S QDs and -OH, -NH, and -SH groups in BSA. In addition, FL spectra suggest that the designed QDs can produce static quenching with BSA and the Stern-Volmer quenching constant (K-sv) was calculated as 2.145 x 10(4). Copyright (c) 2014 John Wiley & Sons, Ltd.