Synthesis of composite gold/tin-oxide nanoparticles by nano-soldering

Composite Au-SnO2 nanoparticles (NPs) are synthesized by nano-soldering of pure Au and SnO2 NPs. The multi-step process involves synthesis of pure Au and SnO2 NPs separately by nanosecond pulse laser ablation of pure gold and pure tin targets in deionized water and post-ablation laser heating of mixed solution of Au colloidal and SnO2 colloidal to form nanocomposite. Transmission Electron Microscopy (TEM) and High-Resolution Transmission Electron Microscopy (HRTEM) were used to study the effect of laser irradiation time on morphology of the composite Au-SnO2 NPs. The spherical particles of 4 nm mean size were obtained for 5 min of post-laser heating. Increased mean size and elongated particles were observed on further laser heating. UV-vis spectra of Au-SnO2 nanocomposites show red shift in the plasmon resonance absorption peak and line shape broadening with respect to pure Au NPs. The negative binding energy shift of Au 4f(7/2) peak observed in X-ray Photoelectron Spectra (XPS) indicates charge transfer in the nano-soldered Au-SnO2 between gold and tin oxide and formation of soldered nanocomposite.