Surface Plasmon Resonance of Silver Nanocrystals in Ethylene Glycol: Regulation by Multiple Thermodynamic Factors.

Silver (Ag) nanocrystals are appealing due to their excellent antimicrobial properties. Synthesis of harmless Ag nanocrystals by low toxic reagents remains significant. Herein, an environmentally benign solvothermal process was applied to synthesize Ag nanocrystals in ethylene glycol (EG) dissolving silver nitrate and sodium oleate. Silver ions were reduced by EG to zero-valent Ag atoms that underwent nucleation and growth to form oleate-stabilized Ag nanocrystals. Multiple experimental parameters including the reaction time, temperature, concentration of Ag precursor, and the molar ratio of sodium oleate and silver nitrate were investigated to probe their effects on morphological structures and surface plasmon resonance (SPR) properties of resulting Ag nanocrystals. Results from UV–Vis absorption spectra and TEM images show that structural and SPR features of Ag nanocrystals are extremely sensitive to the reaction temperature as well as the molar ratio of sodium oleate and silver nitrate. Especially, two absorption bands appeared. The short wavelength (~ 450 nm) represents the characteristic SPR of Ag nanospheres. While, the plasmon absorption at long wavelength (500–700 nm depending on reaction conditions) indicates the anisotropic or heterogeneous structures of Ag nanocrystals that maybe pave their potential applications in asymmetric catalysis, selective growth of coating materials, nanomedicine and optoelectronics. [ABSTRACT FROM AUTHOR]