Wet chemical synthesis of TGA capped Ag2S nanoparticles and their use for fluorescence imaging and temperature sensing in living cells

In this work, we describe a simple wet chemical route for preparing silver sulfide nanoparticles (Ag2S) encapsulated with thioglycolic acid (TGA). By using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray (EDS) microanalysis, transmission electron microscopy (TEM), and dynamic light scattering (DLS), we have found that these nanoparticles were enrobed by TGA molecules and they have an Ag/S ratio nearly equal to 2.2 and a nearly spherical shape with two average size populations. Photoluminescence (PL) spectroscopy has shown that these nanoparticles are highly luminescent, photostable and photobleaching resistant and they emit in the first biologic window with a band peaking in the NIR region at 915 nm. We have demonstrated through a 3-(4,5-dimethyl-thiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) assay protocol and using U-87 MG human living cells that these nanoparticles are biocompatible with a viability ratio higher than 80% for a concentration equal to 100 mu g mL(-1). By investigating the effect of pH, ionic strength and thermal quenching on the PL emission, we have shown that these nanoparticles provide a convenient stable tool to measure temperature in the biological range with a relative thermal sensitivity higher than 5% per C-degrees and they may be used as suitable fluorescent probes for living cell imaging and intracellular temperature mapping.

Automated summary

This work describes a simple wet chemical route to synthesize silver sulfide nanoparticles encapsulated with thioglycolic acid. The nanoparticles exhibit a nearly spherical shape with two average size populations, and are enrobed by TGA molecules. They have been found to be highly luminescent, photostable and photobleaching resistant, emitting in the NIR region at 915 nm. The nanoparticles are biocompatible and can be used as fluorescent probes for living cell imaging and intracellular temperature mapping.