2.8. Steady-state photoluminescence
Steady-state photoluminescence (PL) spectra were excited by A939572 diode-pumped solid-state laser at 325 nm. PL was collected at normal incidence to the surface of samples through a fiber, dispersed in a spectrometer (Princeton Instruments, SpectraPro 300i), and detected using a Peltier cooled charge coupled device (CCD) camera (PIXIS 100F). A long pass filter (Thorlabs) with a nominal cut-on wavelength of 365 nm was used to remove the laser line at monochromator inlet. Three measures for each sample were collected.
3. Results and discussion
Hydrothermal growth of ZnO NWs consists in hydrolysis of zinc nitrate in presence of an amine . During this process, ZnO(NO3)2, a water soluble salt, dissociates to form free Zn2+ ions and the HTMA hydrolyzes into formaldehyde and ammonia. OH− ions are supplied from the dissociation of NH3 into NH4+ and OH−, i.e. the OH− ions are supplied by the HTMA that acts as a pH buffer. Finally, Zn2+reacts with OH− to form Zn(OH)2 which leads to ZnO + H2O. The hydrothermal process is summarized by the following reactions:(CH2)6N4 + 6H2O → 6COH2 + 4NH3NH3 + H2O ↔ NH4+ + OH−2OH− + Zn2+ → Zn(OH)2Zn(OH)2 → ZnO + H2O