ZnAl2O4 Samples Research Articles

Photocatalytic performance of Fe‐substituted ZnAl2O4 powders under sunlight irradiation on degradation of industrial dyes

AbstractUsing the sol–gel auto combustion method with diethanolamine (DEA) as fuel, a sequence of iron‐substituted zinc aluminates, ZnFexAl2‐xO4 powders, including variable Fe3+ ion concentrations (0 ≤ x ≤ 2) were effectively prepared. X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), the Brunauer–Emmett–Teller (BET) method, UV–visible diffuse reflectance spectroscopy (UV‐DRS), and vibrating sample magnetometer (VSM) were employed to examine the structures, chemical bonds, morphologies, composition, surface area, and optical properties as well as the magnetic behavior of the obtained samples. A single‐phase spinel structure was obtained for the calcined aluminate powders with different interplanar spacing and crystallite sizes, as revealed by the classification results. The bandgap energy (Eg) of adapted aluminates was in the range of 2.04‐3.14 eV, identified as being much lower compared to the pure sample (5.60 eV). Thus, Fe3+‐substituted ZnAl2O4 samples could be successfully photoexcited using both ultraviolet and visible light, as suggested by the results. Examination of how the four main pollutant types decay when irradiated by sunlight was carried out to assess the samples and establish photocatalytic activity. These contaminants included rhodamine B (RhB), methylene blue (MB), methyl orange (MO), and methyl red (MR). The performance of photocatalytic degradation reached 98% after 150 min for all optimal samples of organic dyes. Besides, each of the altered photocatalysts could be recycled and displayed high stability. The S‐shaped curve of ferrimagnetism can result in those samples as found by the magnetic measurements, though pure ZnAl2O4 displays diamagnetic characteristics. The adapted samples show intense improvement in the remanent magnetization (Mr) when compared to pure ZnAl2O4, signifying that magnetic photocatalyst recovery by applying an external magnetic field is easy. Thus, these results offer a convincing sign that ZnAl2O4 powders replaced by Fe3+ could provide the ability to aid in the ecologically friendly collection of solar energy.

Development of magnetic recyclable spinel photocatalysts with enhanced sunlight‐driven degradation of industrial dyes

AbstractNanocrystalline nickel and copper‐substituted zinc aluminate spinel powders (NixZn1−xAl2O4 and CuxZn1−xAl2O4) with different additional ion concentrations (0 ≤ x ≤ 1) were successfully synthesized by the sol‐gel auto combustion method using diethanolamine (DEA) as a fuel. The structures, chemical bonds, morphologies, composition, surface area, and optical properties including the magnetic behavior of the obtained samples were investigated by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), the Brunauer‐Emmett‐Teller (BET) method, UV‐visible diffuse reflectance spectroscopy (UV‐DRS), and vibrating sample magnetometer (VSM). All characterization results confirmed that a single‐phase spinel structure was obtained for all calcined aluminate powders with various crystallite sizes and lattice constants. The band gap energy (Eg) of all modified aluminates is in the range of 2.99‐3.15 eV, which was found to be much lower than that of the pure sample (5.60 eV). These results indicate that the Ni2+ and Cu2+‐substituted ZnAl2O4 samples could be effectively photoexcited by both the ultraviolet and visible light. Evaluation of the samples to determine the photocatalytic activity was carried out through investigation of the way the four main pollutant types decompose when irradiated by sunlight. These pollutants were rhodamine B (RhB), methylene blue (MB), methyl orange (MO), and methyl red (MR). For all optimum samples of organic dyes, the efficiency of photocatalytic degradation achieved 96% by the end of 150 min. Furthermore, each of the modified photocatalysts could be reused and showed a high degree of stability. According to magnetic measurements, the S‐shaped curve of ferrimagnetism can arise in those samples with the optimum concentration, although pure ZnAl2O4 exhibits diamagnetic properties. In comparison to pure ZnAl2O4, the modified samples exhibit high enhancement in the remanent magnetization (Mr), which indicates that it is easy to recover those magnetic photocatalyst through the use of an external magnetic field application. These findings therefore serve as a strong indication that ZnAl2O4 powders substituted by both Ni2+ and Cu2+ may offer the capability to serve in environmentally beneficial harvesting of solar energy.

Luminescence of MgAl2O4 and ZnAl2O4 spinel ceramics containing some 3d ions

The luminescence properties of ceramic phosphors based on two spinel hosts MgAl2O4 and ZnAl2O4 doped with manganese ions have been studied. It has been found that the spectral properties of these phosphors can be strongly varied by changing synthesis conditions. Both types of doped ceramic spinel can serve as efficient Mn2+ green-emitting phosphors having peak emissions at 525 and 510 nm, respectively. Mn-doped MgAl2O4 spinel can also be prepared as an efficient Mn4+ red-emitting phosphor having peak emission at ~651 nm by using specific temperatures of heat treatment in air. It has also been shown that the conversion of Mn2+ to Mn4+ and viсe versa, as well as the coexistence of Mn2+ green and Mn4+ red emissions, can be accomplished by properly chosen annealing conditions of the same initially synthesized MgAl2O4:Mn sample. Manganese doped MgAl2O4 spinel with an optimal intensity ratio of green and red emissions can be a promising single-phase bicolor phosphor suitable for the development of warm white phosphor-converted LED lamps. On the other hand, it has been determined that perfectly normal ZnAl2O4 spinel cannot be doped with Mn4+ ions in contrast to partially inverse MgAl2O4 spinel. However, ZnAl2O4 samples unintentionally doped with impurity Cr3+ ions show emission spectra in the far-red region with well pronounced R, N and vibronic lines of Cr3+ luminescence due to the perfect normal spinel structure of synthesized ZnAl2O4 ceramics. Also, by partially substituting Al3+ cations for Mg2+ in ZnAl2O4 there is an opportunity to obtain Mn4+ doped or Mn4+/Cr3+ codoped far-red emitting phosphors which can be suitable for indoor plant growth lighting sources.

Study of ZnAl2O4 spinel nanoparticles synthesized using gelatin as organic precursor

Abstract In this work, zinc aluminate spinel powders were prepared by a fast, simple, eco-friendly and low-cost modified Pechini method using commercial gelatin as the organic precursor. The materials were calcinated at 600, 700 and 800 °C and characterized by thermogravimetric analysis, in situ and ex situ X-ray diffraction (XRD), N2-adsorption/desorption isotherms and scanning electron microscopy. The results showed that single phase ZnAl2O4 particles with spinel structure were successfully obtained resulting in a high purity, nanometric, homogeneous and mesoporous materials. The in situ XRD results showed that the crystalline spinel structure of ZnAl2O4 started forming at a temperature lower than 600 °C, revealing powders with crystallite size smaller than 40 nm, which increased with increasing the temperature (91% of increase between 600 and 800 °C). The effect of calcination time showed that the materials calcinated at 600 °C for 3 h presented the higher percentage of crystallite growth due to the increase of crystallinity. The ZnAl2O4 samples retained their pore size up to 700 °C.

High surface area ZnAl2O4/reduced graphene oxide nanocomposites with enhanced photocatalytic performance

AbstractIn this study, the fabrication of ZnAl2O4/reduced graphene oxide nanocomposites is reported for the initial time. Two nanocomposites, ZnAl2O4/reduced graphene oxide‐50 and ZnAl2O4/reduced graphene oxide‐100, with different reduced graphene oxide contents (50 mg/ml and 100 mg/ml initial graphene oxide concentration respectively) were synthesized via a hydrothermal route; and characterized with the aid of suitable characterization and analytical techniques. For comparative purposes, two pure ZnAl2O4 samples were fabricated by citrate sol‐gel and urea combustion methods. The photocatalytic activity of the synthesized pure nanospinels and nanocomposites was studied for the degradation of rhodamine B dye under ultraviolet–A light irradiation. Compared to pure ZnAl2O4 nanoparticles, ZnAl2O4/reduced graphene oxide nanocomposites exhibited superior photocatalytic activity. The highest efficiency was observed for ZnAl2O4/reduced graphene oxide‐100 composite, where; full degradation of rhodamine B occurred after 45 min. The enhancements of the photocatalytic performance of ZnAl2O4/reduced graphene oxide composites were mainly attributed to unique electronic and surface properties of reduced graphene oxide.

Synchrotron X-ray absorption spectroscopy and cation distribution studies of NiAl2O4, CuAl2O4, and ZnAl2O4 nanoparticles synthesized by sol-gel auto combustion method

An array of modern approaches to X-ray including X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) were employed to examine the local atomic structure, cation distribution, and degree of inversion of nanocrystalline metal aluminate MAl2O4 (M = Ni, Cu, Zn) powders produced using the sol-gel auto combustion technique. All samples were revealed to display single-phase cubic spinel structure with Fd-3m space group, as established by the XRD results. The cation distribution within these aluminate spinel structures were completely unique as suggested by the divergent disparity in comparative intensity between (220), (400), (422), and (440) diffraction plans for each XRD pattern. Rietveld refinement examination of the XRD data validates the ZnAl2O4 samples as having normal spinel structure, while CuAl2O4 and NiAl2O4 samples comprise partially-inverse spinel structures with low and high degree of inversion, respectively. The investigative findings gained from experimental Ni, Cu, Zn, and Al K-edge XANES spectra accommodated with the hypothetical computation of absorption spectra using the FEFF9.7 code reinforce this. Four-fold synchronization with oxygen atoms was demonstrated by all Zn ions discovered in the ZnAl2O4 samples. Conversely, the Ni and Cu ions located in the NiAl2O4 and CuAl2O4 samples tend to be synchronized in both tetrahedral and octahedral fashion by four or six oxygen atoms, respectively. Additionally, M2+ altering from Zn2+ ions to be Cu2+ and Ni2+ ions caused a substantial translocation of divalent metal (M2+) ions from the tetrahedral (A) sites to octahedral (B) sites, as clearly demonstrated by the EXAFS spectra. Specifically, the degree of inversion in these metal aluminates is completely dissimilar and identified as 0.83 for NiAl2O4, 0.42 for CuAl2O4 and 0 for ZnAl2O4, as indicated by the curve-fitting analysis of Ni, Cu, and Zn K-edge EXAFS spectra. These values comprise vital data for comprehension of numerous pertinent properties.

Optical characteristics of samarium doped ZnAl2O4 nanomaterials synthesized by vibrational milling process

Optical and fluorescence properties of samarium (Sm) doped zinc aluminate host matrix (Sm:ZnAl2O4) was studied. Sm:ZnAl2O4 nanopowder was synthesized by vibrational milling process assisted with calcination treatment. Structural and optical properties of Sm:ZnAl2O4 nanopowders were investigated via the crucial parameter of different doping concentration. Structural properties of as-synthesized samples and Sm: ZnAl2O4 powders were characterized by X-ray diffraction and scanning electron microscope. For optical properties, Sm: ZnAl2O4 phosphor materials were analyzed via diffuse reflectance and photoluminescence spectroscopy. The preliminary results suggested that Sm: ZnAl2O4 powders were identically in spinel crystalline phase as host ZnAl2O4 structure affirmed by XRD result. SEM images indicated the Sm:ZnAl2O4 after the synthesis distinctly obtained in ultrafine power due to the effect of several milling round and sintering process. The optical properties in reflectance mode of Sm:ZnAl2O4 samples were significantly increased by the presence of Sm dopant in ZnAl2O4 structure. Meanwhile, the luminescent materials showed red emissions under visible light excitation in range of 650-730 nm by PL spectra. The improvement of ZnAl2O4 photoluminescence property was obviously obtained at 0.5 wt.% Sm due to photon transfer from Sm to host material.

Trap level spectroscopic investigations of U: ZnAl2O4: Role of defect centres in the TSL process

In order to evaluate the trap level spectroscopic properties of Uranium in ZnAl2O4 spinel host, undoped and Uranium doped ZnAl2O4 samples were synthesized. From photoluminescence (PL) data it was confirmed that uranium gets stabilized in the system as UO66− (octahedral uranate). Electron spin resonance (ESR) studies for the gamma irradiated sample suggested the formation of O2−, F+ and V centres. From the TSL (thermally stimulated luminescence) data, the trap parameters such as frequency factor and activation energy etc. were evaluated. From ESR-TSL correlation it was confirmed that the destruction of O2− ion coincides with TSL glow peak appeared at 332 K.

Effect of Cu2+ doping on the structural, electronic and optical properties of ZnAl2O4: A combined experimental and DFT+U study

Using the sol-gel technique, undoped and Cu2+ doped ZnAl2O4 samples were prepared at 0≤x≤1.24 Cu2+ percentages. X-ray diffraction (XRD) analysis confirmed that the prepared samples were cubic and that there was no phase segregation. Energy dispersive X-rays (EDS) was then used to investigate and confirm the purity of Zn, Al, O and Cu samples with no other characteristic peaks. From the XRD spectra of Cu2+ at different concentrations, Cu2+ doping was found not to lead to significant lattice distortion an observation that was corroborated with density functional theory (DFT) calculations. As the Cu2+ concentration was increased a slight shift to higher angles was recorded in XRD analysis, suggesting a larger ionic radius atom substituted by a smaller ionic radius atom. At 283nm excitation, the doped samples were found to emit in the blue region (at 425nm and 480nm) of the color spectrum. Theoretically using DFT with the Hubbard correction term U, the doped system was found to emit at 435nm which is within the emission range observed experimentally. From the calculated substitutional energies, Ovac was found to have negative formation energies indicating ease of formation form in ZnAl2O4. The binding energy for CuZn+Ovac was negative indicating that these two point defects don’t exist as pair inside ZnAl2O4.

Synthesis of single‐phase ZnAl2O4 nanoparticles via a wet chemical approach and evaluation of crystal structure characteristics

Single‐phase ZnAl2O4 nanoparticles were hydrothermally synthesized utilizing improvements to the preparation of the precursor materials. This synthesis differs from more general syntheses of ZnAl2O4 nanoparticles in that it minimizes the presence of ZnO impurities. The higher purity of our ZnAl2O4 nanoparticles allowed for more comprehensive X‐ray diffraction analysis as well as more sensitive spectroscopic evaluation. Moreover, pH control of the precursor solution dramatically improved the reproducibility of the synthesis. The lattice constant of the ZnAl2O4 samples synthesized by our technique is different from what is observed in particles fabricated using more common solid state reactions. This difference in lattice constants indicates the occurrence of a site exchange phenomenon between Zn2+ and Al3+ and/or oxygen deficiency. This suggests the possibility of tailoring novel functional spinel oxides for a wide array of future applications.

Luminescence of divalent europium activated spinels synthesized by combustion and the enhanced afterglow by dysprosium incorporation

Herein we report a luminescent phenomenon of Eu2+ in the spinel MgAl2O4 and ZnAl2O4 samples which are successfully synthesized via a combustion method. The XRD shows cubic spinel structure is obtained from the prepared samples. The mean crystal sizes estimated from XRD data are 30 and 10nm for MgAl2O4 and ZnAl2O4 respectively, and the large grain particles are the agglomeration of crystallites. The Eu2+ ions show a blue emission at around 480nm and an afterglow phenomenon is observed after the removal of excitation. The afterglow spectrum of MgAl2O4: Eu2+, Dy3+ shows two emissions at 480 and 520nm while only one at 480nm is observed in ZnAl2O4: Eu2+, Dy3+. The afterglow intensity and the persisting duration can be substantially enhanced by the Dy3+ incorporation because the trapping ability of the electron traps is reinforced. This is confirmed by the TL curves of the samples.

Aloe vera Plant Extracted Green Synthesis, Structural and Opto-Magnetic Characterizations of Spinel Co(x)Zn₁₋xAl₂O₄Nano-Catalysts.

Spinel Co(x)Zn₁₋xAl₂O₄ (0 ≤ x ≤ 1) nano-catalysts were synthesized by a simple Aloe vera plant extracted green synthesis route. Powder XRD patterns and Rietveld analysis confirmed the formation of single phase, cubic spinel gahnite structure without other impurities. The lattice parameter increased from 8.089 to 8.125 A with increasing CO²⁺ content. The average crystallite sizes were estimated using Scherrer's method, and it was found to be in the range of 15.72 nm to 26.53 nm. FT-IR spectra showed vibrational stretching frequencies corresponding to the spinel structure. HR-SEM and HR-TEM images showed the features of well particle shaped crystals with nano-sized grains. The elemental compositions of Co, Zn, Al and O were quantitatively obtained from EDX analysis. The band gap energy estimated using Kubelka-Munk method by UV-Visible DRS method, and the values are decreased with increasing the Co²⁺ content (4.12 eV to 3.67 eV), due to the formation of sub bands in between the energy gap. PL spectra showed emission bands in UV as well as in the visible regions for ZnAl₂O₄ and Co-doped ZnAl₂O4, due to the defect centers acting as the trap levels. VSM measurements revealed that pure ZnAl₂O₄ has diamagnetic, while Co doped ZnAl₂O₄ samples (x = 0.2 to 0.8) have superparamagnetism, whereas the sample CoAl₂O₄ has ferromagnetic in nature. Catalytic oxidation of benzyl alcohol to benzaldehyde was found that the sample Co₀.₆Zn₀.₄Al₂O₄ showed 93.25% conversion with 99.56% selectivity, whereas for pure ZnAl₂O₄, the conversion was only 86.31% with 92.85% selectivity.

A comparative study of ZnAl2O4 nanoparticles synthesized from different aluminum salts for use as fluorescence materials.

Three ZnAl2O4 samples were prepared via a modified polyacrylamide gel method using a citric acid solution with different aluminum salt starting materials, including AlCl3∙6H2O, Al2(SO4)3∙18H2O, and Al(NO3)3∙9H2O under identical conditions. The influence of different aluminum salts on the morphologies, phase purity, and optical and fluorescence properties of the as-prepared ZnAl2O4 nanoparticles were studied. The experimental results demonstrate that the phase purity, particle size, morphology, and optical and fluorescence properties of ZnAl2O4 nanoparticles can be manipulated by the use of different aluminum salts as starting materials. The energy bandgap (Eg) values of ZnAl2O4 nanoparticles increase with a decrease in particle size. The fluorescence spectra show that a major blue emission band around 400 nm and two weaker side bands located at 410 and 445 nm are observed when the excitation wavelength is 325 nm. The ZnAl2O4 nanoparticles prepared from Al(NO3)3∙9H2O exhibit the largest emission intensity among the three ZnAl2O4 samples, followed in turn by the ZnAl2O4 nanoparticles prepared from Al2(SO4)3∙18H2O and AlCl3∙6H2O. These differences are attributed to combinational changes in Eg and the defect types of the ZnAl2O4 nanoparticles.

Study of Nanocrystalline ZnAl<sub>2</sub>O<sub>4</sub> and ZnFe<sub>2</sub>O<sub>4</sub> with SiO<sub>2</sub> on Structural and Optical Properties Synthesized by Sol-Gel Method

Zinc aluminate (ZnAl2O4) and zinc ferrite (ZnFe2O4) nanocrystalline structures dispersed into SiO2 matrix were prepared by sol-gel method. Phase formation of ZnAl2O4 and ZnFe2O4 was confirmed by X-ray diffraction (XRD) analysis. The crystallite sizes was determine using Scherer’s equation from the broadening of dominant peak at (311) plane. It was found the crystallite size of both compound decreased due to the decrement compositions of Zn2+ ion and Al3+ / Fe3+ ions. The crystallite sizes for ZnAl2O4 and ZnFe2O4 was calculated to be around ~ 14.16 – 11.27 nm and ~ 11.27 – 4.72 nm, respectively. FTIR analysis was done to determine the formation of spinel structures. FTIR results analysis confirmed that the formation of spinel structure where it has been observed that the bands around 800 cm-1 was associated to the vibrations of aluminum-oxygen and metal-oxygen-aluminum bonds. This characteristic was identified to the formation of zinc aluminate spinel structure. The optical properties have been done to determine the energy bandgap of ZnAl2O4 and ZnFe2O4 samples. The Uv-Visible absorption spectra have been done within wavelength 300 – 800 nm and the graph was plotted into the Tauc plot. This new dielectric material was purposed to improve the value of dielectric permittivity with addition of SiO2 where it can be applied as microwave dielectric material without changing the original spinel structures.

Microstructure of sol–gel derived Mn-doped gahnite: Correlation of TEM and XRD investigations

Powder ZnAl2O4 (gahnite) samples doped with 0, 4.3, 7.6 and 11.7at% Mn (in relation to Zn) were prepared by a sol–gel technique followed by thermal treatment. The effect of manganese doping on microstructure of the samples has been investigated by transmission electron microscopy and X-ray diffraction. Diffraction patterns showed that all samples were cubic with a spinel structure, space group Fd3¯m. Diffraction lines were broadened indicating nanocrystalline samples. Transmission electron microscopy investigations confirmed that the samples were nanocrystalline. Particles (grains) in the samples, as observed by transmission electron microscopy, were evenly shaped and grain size distribution could be fitted to a lognormal function. Grain sizes determined by TEM analysis and crystallite sizes obtained from diffraction line-broadening analysis were similar. Both decreased with increasing manganese doping level. Increase in doping level from 0 to 11.7at% Mn caused the change in grain size from 25.0(7)nm to 14.2(3)nm and the change in crystallite size from 24.1(1)nm to 18.0(1)nm. Doping Mn2+ cations acted as defects in the gahnite structure that increased lattice strain from 0.07(1)% for undoped sample to 0.21% for sample doped with 11.7at% Mn, and disturbed the crystallites to grow.

Synthesis and characterization of some acetoxime-modified hetero-metal alkoxide precursors of zinc(II) and aluminum(III) for sol–gel transformation to nano-sized ZnAl2O4

Reactions of [ZnAl2(OPri)8] [A] with acetoxime in different molar ratios in refluxing anhydrous benzene, yield complexes of the type [ZnAl2(OPri)8−n{(CH3)2CNO}n] {where, n = 1–4}. All the complexes are transparent viscous/foamy solids. They were characterized by elemental analyses, FT-IR and NMR (1H, 13C {1H}) spectral studies. 27Al NMR spectrum of [ZnAl2(OPri)4{(CH3)2CNO}4] [4] in CDCl3 suggests presence of four coordination around both the aluminum atoms. IR spectra suggest that the oximato ligands bind the aluminum atoms in a side on manner in all the complexes. The ESI-mass spectrum of the representative derivative [4] suggests its monomeric nature while the thermo-gravimetric curve shows its low thermal stability. Sol–gel transformations of the precursors (A), (1), and (4) yielded nano-sized ZnAl2O4 samples (a), (b) and (c) at ~500 °C, respectively. The XRD patterns of (a), (b) and (c) indicate formation of cubic phase nano-sized zinc aluminate in all the samples. Surface morphologies of these samples were investigated by SEM images. IR spectra as well as EDX analyses indicate formation of pure zinc aluminate in all the cases. TEM image of sample (c) shows spherical (~5–8 nm) morphology.

Impulsive Excitation Of Mechanoluminescence In γ-ray Irradiated ZnAl2O4:Dy Phosphors synthesized By Solution Combustion Technique

The mechanoluminescence (ML) of γ-irradiated ZnAl2O4: Dy phosphor has been studied. ZnAl2O4 samples having different concentrations of Dy were prepared by solution combustion technique by using hydrazine as a fuel. ML was excited impulsively by dropping a load onto the sample. Two distinct peaks have been observed in the ML intensity versus time curve. Maximum intensity is obtained for 0.1 mol% of Dy doped ZnAl2O4 phosphor. ML spectra of the phosphors show two distinct peaks around 482 nm and 585 nm which is characteristic emission of Dy 3+ . It is also observed that the ML intensity of the samples increases almost linearly with increasing mass of the sample and gamma ray doses given to the sample. Experimental results suggest that the ML excitation is related to the movement of dislocation with defect centres and it may be used for dosimeter applications. Copyright © 2013 VBRI press.

Photocatalytic performances and activities in Ag-doped ZnAl2O4nanorods studied by FTIR spectroscopy

Porous and rod-shaped nanostructures of ZnAl2O4 were successfully synthesized by a simple hydrothermal method. The Ag-doped ZnAl2O4 catalyst, based on porous ZnAl2O4, was prepared by the incipient wetness impregnation strategy and showed an excellent photoelectric property and catalytic activity. The structural properties of the samples were systematically investigated by X-ray powder diffraction (XRD), Brunauer–Emmet–Teller (BET), transmission electron microscopy (TEM), Electron spin resonance (ESR), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) techniques. The photocatalytic degradation of toluene by the Ag-doped ZnAl2O4, ZnAl2O4 and P25 TiO2 samples was comparatively studied under UV lamp irradiation. The results indicate that the Ag-doped ZnAl2O4 sample synthesized at pH = 6 exhibited a higher capacity for the degradation of toluene. No obvious deactivation of the Ag-doped ZnAl2O4 nanorods was observed during the prolonged operation of 6 h. The Ag-doped ZnAl2O4 nanorods could be potentially applied in environmental purification in the near future.

ChemInform Abstract: Structure, Microstructure and Photoluminescence of Nanocrystalline Ti‐Doped Gahnite.

AbstractTi‐doped ZnAl2O4 (gahnite) samples with doping levels of 0, 1.8, 3.8, 5.4, and 11.6 at.% Ti relative to Al are synthesized from Zn(NO3)2, Al(O‐sBu)3, and Ti(O‐Bu)4 by a sol—gel method followed by thermal treatment (800 °C, 2 h).

Structure, microstructure and photoluminescence of nanocrystalline Ti-doped gahnite

A series of Ti-doped ZnAl2O4 (gahnite) samples with doping levels of 0, 1.8, 3.8, 5.4 and 11.6at.% Ti in relation to Al were prepared by a sol–gel technique. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), EPR spectroscopy, UV–vis reflectance spectroscopy and photoluminescence (PL) studies. Diffraction patterns indicated that all samples were nanocrystalline, with a spinel-type structure, space group Fd3¯m. Titanium doping of gahnite caused an increase of unit-cell parameter and diffraction line broadening. The structure of samples was refined by the Rietveld method, simultaneously with the analysis of diffraction line broadening. TEM investigations confirmed that samples had spinel-type structure, and showed that samples contained evenly shaped particles of about 20nm in size. Ti-doped samples exhibited strong absorption at wavelength <400nm, and blue photoluminescence under excitation with λexc=308nm.