Eric S. Agorku

Enhanced visible-light photocatalytic activity of multi-elements-doped ZrO2 for degradation of indigo carmine

Abstract In this study, C,N,S-doped ZrO 2 and a series of Eu doped C,N,S-ZrO 2 photocatalysts were synthesized by a coprecipitation method using thiourea as the source of C, N and S and Eu(NO 3 )·6H 2 O as source of Eu. The materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), UV-visible diffuse reflectance spectroscopy, scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). Indigo carmine (IC) was chosen as a model for organic pollutants and used to evaluate the photocatalytic performance of the photocatalysts under simulated solar light. Commercial ZrO 2 was used as a reference material. XRD and Raman results indicated the formation of both tetragonal and monoclinic phase ZrO 2 with particle size ranging from 8-30 nm. Multi-element doping had a great influence on the optical responses manifested as red shift in the absorption edge. The highest photocatalytic activity towards IC was observed for the Eu,C,N,S-doped ZrO 2 (0.6 mol.% Eu) sample ( k =1.09×10 −2 min −1 ). The commercial ZrO 2 showed the lowest photodegradation activity ( k =5.83×10 −4 min −1 ). The results showed that the control of Eu doping in the C,N,S-ZrO 2 was very important in reducing electron-hole recombination. The synergistic effect of Eu, C, N, and S in the ZrO 2 matrix led to enhanced utilization of simulated solar energy for the degradation of IC through narrowing of bandgaps.

Synthesis, characterization and photoluminescence properties of Ce3+-doped ZnO-nanophosphors

The present study involves the synthesis of Ce3+ doped ZnO nanophosphors by the zinc nitrate and cerium nitrate co-precipitation method. The synthesized nanophosphors were characterized with respect to their crystal structure, crystal morphology, particle size and photoluminescence (PL) properties using X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive X-ray (EDX), transmission electron microscopy (TEM)/Energy-dispersive X-ray spectroscopy (EDS) and PL-spectroscopy respectively. XRD results revealed that ZnO nanophosphors are single phase and cubic type structures. Further, PL spectra of ZnO:Ce3+ nanophosphors showed green emission because of the charge transfer at single occupied oxygen vacancies with ZnO holes and red emission due to the cerium ion transitions. Intensity and fine structure of the Ce3+ luminescence and its temperature dependence are strongly influenced by the doping conditions. The formation of ZnO:Ce3+ nanophosphors was confirmed by Fourier transform infrared (FTIR) and XRD spectra.

Fabrication of photocatalyst based on Eu3+-doped ZnS-SiO2 and sodium alginate core shell nanocomposite

This research paper reports the photocatalytic properties of Zn-SiO2-Eu3+ and sodium alginate (Alg) based nanocomposites for the degradation of indigo carmine dye. Initially, Eu3+ doped ZnS-SiO2 nanophorphor was synthesized and after that it was incorporated within the grafted crosslinked polymer matrix of Alg with acrylamide-co-acrylic acid in different concentrations. Synthesized materials were characterized using XRD, Raman spectroscopy, FTIR, SEM/EDX, TEM and UV-vis diffuse reflectance spectroscopy. XRD and TEM analyses confirmed the formation of nanoparticles as well as the uniform distribution of the nanoparticles within the polymer matrix. The UV-vis and UV-vis DRS spectral analysis indicated that Eu3+ doping causes a red-shift in the absorption band, resulting in the reduction in band gaps. The synergic effect of ZnS and Eu3+ in the SiO2 evidenced the photocatalytic performance of the catalyst. Alg-cl-poly(AAM-co-MAA)/ZnS-SiO2-Eu3+ nanocomposites were found to be very effective for the degradation of indigo carmine under visible light. Highest photocatalytic performance (93.4%) was shown by the nanocomposite with the 20% concentration of the nanoparticle after 5h. The photocatalytic activity was mainly attributed to the intense light absorption in the visible region and narrow band gap energy.

Sulfur/Gadolinium-Codoped TiO2 Nanoparticles for Enhanced Visible-Light Photocatalytic Performance

A series of S/Gd-codoped TiO 2 photocatalysts were synthesized by a modified sol-gel method. The materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), UV-visible diffuse reflectance spectroscopy, scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM)/energy-dispersive spectroscopy (EDS). Laboratory experiments with Indigo Carmine chosen as a model for organic pollutants were used to evaluate the photocatalytic performance of S/Gd-codoped TiO 2 under visible-light with varying concentrations of Gd ions in the host material. XRD and Raman results confirmed the existence of anatase phase TiO 2 with particle size ranging from 5 to 12 nm. Codoping has exerted a great influence on the optical responses along with red shift in the absorption edge. S/Gd-codoped TiO 2 showed significant visible-light induced photocatalytic activity towards Indigo Carmine dye compared with S-TiO 2 or commercial TiO 2 . TiO 2 -S/Gd (0.6% Gd) degraded the dye (k a = 5.6 × 10 min) completely in 50min.

Sulfur/Gadolinium-Codoped TiO2Nanoparticles for Enhanced Visible-Light Photocatalytic Performance

A series of S/Gd-codoped TiO 2 photocatalysts were synthesized by a modified sol-gel method. The materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), UV-visible diffuse reflectance spectroscopy, scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM)/energy-dispersive spectroscopy (EDS). Laboratory experiments with Indigo Carmine chosen as a model for organic pollutants were used to evaluate the photocatalytic performance of S/Gd-codoped TiO 2 under visible-light with varying concentrations of Gd ions in the host material. XRD and Raman results confirmed the existence of anatase phase TiO 2 with particle size ranging from 5 to 12 nm. Codoping has exerted a great influence on the optical responses along with red shift in the absorption edge. S/Gd-codoped TiO 2 showed significant visible-light induced photocatalytic activity towards Indigo Carmine dye compared with S-TiO 2 or commercial TiO 2 . TiO 2 -S/Gd (0.6% Gd) degraded the dye (k a = 5.6 × 10 min) completely in 50min.

Sulfur/Gadolinium-Codoped TiO 2 nanoparticles for enhanced visible-light photocatalytic performance

A series of S/Gd-codoped TiO 2 photocatalysts were synthesized by a modified sol-gel method. The materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), UV-visible diffuse reflectance spectroscopy, scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM)/energy-dispersive spectroscopy (EDS). Laboratory experiments with Indigo Carmine chosen as a model for organic pollutants were used to evaluate the photocatalytic performance of S/Gd-codoped TiO 2 under visible-light with varying concentrations of Gd ions in the host material. XRD and Raman results confirmed the existence of anatase phase TiO 2 with particle size ranging from 5 to 12 nm. Codoping has exerted a great influence on the optical responses along with red shift in the absorption edge. S/Gd-codoped TiO 2 showed significant visible-light induced photocatalytic activity towards Indigo Carmine dye compared with S-TiO 2 or commercial TiO 2 . TiO 2 -S/Gd (0.6% Gd) degraded the dye (k a = 5.6 × 10 min) completely in 50min.