Surface- and tip-enhanced Raman spectroscopy for catalysis: Fundamentals and applications

Abstract

ZnO:Tb nanoparticles are synthesized by solvothermal method. And the structure and optical and photocatalysis property are identified by XRD patterns, SEM, TEM, photoluminescence spectrum and Raman spectrum. For ZnO:Tb calcined at 450 °C, two splits for 544 nm luminescence peak are found by laser stimulated luminescence spectrum, while for doped sample calcined at 550 °C or 700 °C, this peak splits to 4. The site symmetry Tb3+ occupied in samples calcined at high temperature is much lower than that of sample calcined at 450 °C. Tb2O3 is found to separate from host ZnO lattice for doped sample calcined at high temperature by XRD and Raman spectra. Vacancy O and interstitial Zn related peaks are observed by photoluminescence spectra, in which vacancy O and interstitial Zn related peaks are confirmed to play an important media role on energy transfer from ZnO to Tb3+. All as-prepared samples have good photocatalysis property in which ZnO:Tb calcined at 700 °C has the best degradation rate. As the size of ZnO:Tb calcined at 700 °C is much bigger and surface area of 700 °C calcined smaple is much smaller. The best degradation rate should originate other reasons. Because distinct defect excitation states are found in the energy gap, trap of electrons from conduction band to these states promotes the charge separation, which favors good photocatalytic performance. As the difficult separation process and low degradation speed, as-prepared samples are unsuitable for repeated applications.