Nanocomposites of ZnO with p-type NiO and n-type SnO2 in the equimolar ratio were prepared by microwave assisted method inorder to reduce the fast recombination rate of ZnO. XRD reveals the formation of nanocomposites of ZnO. The photocatalytic activity of nanocomposites against RhB is poor compared to control ZnO. The control ZnO nanocrystals exhibit 100% degradation efficiency and is mainly ascribed to the decrease in band gap and increase in surface defects. The decolorization of RhB follows the pseudo-first order kinetics and the mechanism is explained on the basis of charge trapping through defect sites.
C-N-S tridoped TiO2 nanoparticles were synthesized by sol-gel method using thiourea as a source compound for carbon (C), nitrogen (N) and sulphur (S). The crystalline phase and morphology of the doped and undoped TiO2 nanoparticles are analyzed by XRD and FESEM. FTIR confirms the bonding interaction of C, N and S in TiO2 lattice. Compared to the doped samples undoped sample annealed at 600°C shows more absorbance in the visible region due to the existence of rutile phase. Presence of oxygen vacancy is confirmed from the photoluminescence spectra. XPS indicates the existence of the carbon atom in the form of carbonaceous species on the surface of the TiO2 and absorbs the visible light to enhance the photocatalytic activity. The photocatalytic activity of C-N-S tridoped TiO2 nanoparticles were evaluated for the degradation of Rhodamine B organic dye under the visible light irradiation. Maximum of ~ 100% degradation exhibits for the C-N-S tridoped sample (D4) calcined at 600°C. This highly active photocatalytic performance is associated with the existence of oxygen vacancies, the acidic sites on the surface (SO42-) and the mixed phases of anatase and rutile in TiO2 lattices.
Nanocomposite of metal oxide semiconductors are multifunctional and one such nanocomposite ZnO/ Mn3O4 (2:1) was synthesized ZMA4 (ZnO: Mn3O4 using ammonia), ZMH4 (ZnO: Mn3O4 using hexamine) by the coprecipitation route. In addition pure ZnO was prepared using ammonia (ZA) and hexamine (ZH). XRD reveals the crystal structure of ZnO/Mn3O4 and the average crystallite size is estimated as 43, 12, 42 and 18 nm for ZA, ZMA4, ZH and ZMH4 respectively. FTIR bands at 440-490 and 616-621cm-1 are due to Zn-O and Mn-O vibrational bands. Presence of manganese in nanocomposites is confirmed by EDS. SEM micrographs indicate the formation of nanoparticles (ZA and ZMA4) and nanorods (ZH-98 nm length, 63 nm dia). Excitonic absorption peaks at 370 and 290 nm in the UV-Vis spectra are attributed to ZnO/Mn3O4 nanocomposite. The bandgap is estimated as 2.7, 2.3, 2.6 and 3.0 eV for ZA, ZMA4, ZH and ZMH4 respectively. FL spectra of ZA, ZMA4 expose the emission at 366 and 396 nm owing to the near band edge (NBE) and zinc interstitial at 468 nm. ZH nanorods show the emission at 386, 468 and 558 nm which are attributed to NBE, zinc interstitial and oxygen vacancy respectively. The reduction of oxygen vacancy is observed in ZMH4 as manganese effectively changes the morphology from nanorod to nanoparticle. The second harmonic generation efficiency measured for ZA and ZH is 0.6 and 0.9 times KDP using Q - switched Nd: YAG laser (1064nm, 10 Hz, 9 ns).
The semicarbazone of p-dimethylamino benzaldehyde (SCPDB) is a potential organic nonlinear optical material. SCPDB has been synthesized and the solubility studies were carried out in the temperature range 30-60°C. Following the slow evaporation technique, single crystals of SCPDB have been grown and the unit cell parameters have been evaluated by single crystal x-ray diffraction technique. The UV-Vis-NIR transmittance spectrum was recorded in the range 200-1100nm. Fourier transform IR and Fourier transform Raman spectra were recorded in the range 400-4000 cm-1 and the characteristic vibrational frequencies of the functional groups present in the system have been assigned. Second Harmonic Generation efficiency measurements were carried out using Nd:YAG laser.