In situ sonochemical synthesis of luminescent Sn@C-dots and a hybrid Sn@C-dots@Sn anode for lithium-ion batteries

A facile sonochemical approach is employed for the in situ formation of C-dots via ultrasonic irradiation of polyethylene glycol (PEG) solvent and its decomposition. Metallic bulk tin was added to the reaction vessel and heated to its melting point (234 degrees C) in the presence of polyethylene glycol 400. The two-phase mixture was sonicated to yield Sn@C-dots and subsequently to achieve Sn nanoparticles decorated with Sn@C-dots (Sn@C-dots@Sn). The fluorescence (luminescence) properties of Sn@C-dots are different from those of the C-dots alone and change as a function of excitation wavelength. The as-synthesized Sn@C-dots@Sn nanoparticles were directly deposited on the copper foil current collector as a promising anode for Li-ion batteries. Encouraging lithiation and delithiation properties are obtained with high coulombic efficiency and enhanced rate capabilities for the hybrid Sn@C-dots@Sn nanoparticles, owing to the conducting carbon dot network on the tin nanoparticles minimizing pulverization effects. Methodical studies on morphology (SEM, TEM), structure (XRD, HR-TEM) and compositions (XPS, EDS) are carried out on the Sn@C-dots and electroactive Sn@C-dots@Sn nanoparticles to understand the reaction mechanism and their luminescence and battery anode properties.