Ion Cr3 Research Articles

INVESTIGATION OF THE IMPACT OF NATURAL ANTIOXIDANTS FOUND IN COFFEE LEAVES, YERBA MATE, AND JAMBOLAN PULP ON THE INDUCTION PERIOD AND RATE CONSTANT OF BIODIESEL OXIDATION REACTION IN THE PRESENCE OF METALLIC IONS

The present study describes the antioxidant potential of ethanolic extracts of yerba mate (Ilex paraguariensis), coffee leaves (Coffea arabica) and jambolan pulp (Syzygium cumini Lamarck) when added to biodiesel, with and without chromium (Cr3+), manganese (Mn2+) and cobalt (Co2+) metal ions, measuring the induction period (IP) and the rate constant (k) of the oxidation reaction at 110 °C. Antioxidant activity was observed in all extracts, as they reduced k and increased the IP compared to the control sample. The coffee leaves extract had the most pronounced positive effect, increasing the IP to 12.42 h and reducing k by 5.9 times. However, biodiesel containing metallic ions of chromium, manganese and cobalt, both with and without natural extracts, reduced the IP in all assays conducted in this study. The natural yerba mate extract was the most affected by the manganese ion (Mn2+), reducing the IP by 41.61%. The chromium ion (Cr3+) had the least impact on the biodiesel oxidation process in the presence of coffee leaves extract, increasing the rate constant by 3.55%. Furthermore, the alcoholic jambolan pulp extract was the one that presented the best antioxidant properties in the presence of metal ions.

First-Principles study for the influence of ion vacancies on the doped Cr3+ and transition dipole moment in anti-perovskite structure La3(SiN2O2)N

Typically, the luminescence properties of doped luminescent centers, such as rare earth ions or transition metal ions, are significantly influenced by the properties of the luminescent host materials. In this study, we focus on how the electronic band structure and transitions between the valence band maximum (VBM) and conduction band minimum (CBM) are affected by the formation of individual VLa or VSi, as well as the coexistence of VLa with VSi in La3(SiN2O2)N. The doped Cr3+ as luminescent centers preferentially substitutes for Si4+ rather than La3+.The band gap characteristics of La3(SiN2O2)N, associated with its absorption properties, can be modified by the presence of ion vacancies and doped Cr3+. Additionally, the computed transition dipole moment of La3(SiN2O2)N: VSi, Cr3+ is the highest. This indicates the maximal transition between VBM and CBM, resulting in the most robust charge transfer from the p orbital of N3− to the d orbital of Cr3+.Enhanced charge transfer can also result in effective luminescence. Therefore, it can be concluded that La3(SiN2O2)N with individual VSi is suitable as a luminescent host material for Cr3+ doping. The study of La3(SiN2O2)N with different ion vacancies and Cr3+ doping provides information for the development of new luminescent materials that exhibit strong luminescence.

First-Principles Investigation of the Optical Transition Energies of Cr3+ Impurity Ion

First-principles Investigation of the Optical Transition Energies of Cr3+ Impurity Ion Cr3+ - transition metal ion impurity in crystals have been extensively studied for numerous technological application such as in medical diagnostics, food analysis, horticultural lighting, night vision, etc. [1]. Together with experimental studies, theoretical investigation is also a prerequisite for gaining a better insight into their optical properties and interpreting the available experimental information to develop an efficient Cr3+-doped phosphors, and thereby improving their potential for application.In this talk, we will discuss about the evaluation of the optical transition energies of Cr3+ impurity ionin garnets systems using first-principles calculations in the framework a DFT by employing different kinds of the exchange-correlation functionals in order to test their ability to reproduce geometrical and electronic structures. We found that absolute values of the calculated optical transitions are not correct by analyzing electronic density of states (DOS) diagram approach, which overestimates the optical transition energies even with wrongly estimated trend. Furthermore, we presented the excited-state calculation with appropriately constraining the electron occupation for obtaining the equilibrium geometric structures of the ground and excited states. The opportunity excited state calculation method within DFT that can bring accurate information on structural properties of the ground state and the excited states, consequently, optical transitions for Cr3+ impurity will be pointed out.Reference T. Basore, W.G. Xiao, X.F. Liu, J.H. Wu, J.R. Qiu. Broadband near-infrared garnet phosphors with near-unity internal quantum efficiency, Adv. Opt. Mater. 8 (2020) 2000296.

Nucleic acid-functionalized upconversion luminescence biosensor based on strand displacement-mediated signal amplification for the detection of trivalent chromium ions

BackgroundRapid industrial development has generated serious pollution, including the presence of toxic and harmful heavy metal ions. Among them, trivalent chromium ion (Cr3+) is a very important element that poses a threat to life and health in our industrial wastewater pollution. Thus, it is important to develop efficient fluorescence methods for Cr3+ detection. In this study, an upconversion luminescence biosensor for detecting Cr3+ was constructed based on a DNAzyme, strand displacement reaction (SDR), and DNA-functionalized upconversion nanoparticles (UCNPs). ResultsThe sulfonate-rich poly (sodium 4-styrene sulfonate) (PSS) was modified onto the surface of UCNPs, forming UCNPs@PSS. Then, NH2-Capture probe DNA (NH2-Cp) was further modified onto the UCNPs@PSS surface through sulfonylation, resulting in UCNPs@PSS@NH2-Cp. The DNAzyme activated by Cr3+ triggered the release of the primer probe (Pp), which initiated the SDR system cycle, thereby releasing a tetramethylrhodamine (TAMRA)-modified signal probe (TAMRA-Sp). Finally, UCNPs@PSS@NH2-Cp bound to TAMRA-Sp through complementary base pairing, causing UCNPs and TAMRA to approach each other. Because of the luminescence resonance energy transfer (LRET) mechanism, the upconversion luminescence (UCL) signal of the UCNPs was quenched by TAMRA, enabling the detection of Cr3+ by the change of I585/I545 ratio. This biosensor has good stability, selectivity, and sensitivity, with a linear range of 0.5–75 nM and a detection limit of 0.135 nM for Cr3+. Significance and noveltyFirstly, based on LRET between UCNPs and TAMRA, the quantitative analysis of Cr3+ is achieved through the changes of ratio fluorescence. Secondly, the specificity of the biosensor is improved by utilizing the specific recognition of DNA enzymes. Thirdly, the signal amplification technology of the SDR cycle greatly improves the sensitivity of biosensor. This biosensor will be useful for future environmental safety monitoring and biopsy of biological fluids.

Thermally stable NIR broad emission of Cr3+ doping phosphor with a high output power

The anti-thermal quenching of Cr3+ is determined by the attribution of the defect level, which originates from the coupling between the doped ion Cr3+ and the VO. NIR pc-LED achieves an NIR output power of 59.67 mW with working current of 150 mA.

Plasmon-enhanced fluorescence of gold nanoparticle/graphene quantum dots for detection of Cr3+ ions

Graphene quantum dots (GQDs), fascinating semiconductors with stable photoluminescence (PL), have important potential applications in the fields of biology, medicine, and new semiconductor devices. However, it is still challenging to overcome the weak PL intensity. Here, we report a strategy for selective resonance enhancement of GQD fluorescence using gold nanoparticles (AuNPs) as plasmas. Interestingly, the addition of low concentration AuNP makes AuNP/GQDs exhibit significant fluorescence enhancement of 2.67 times in the visible range. The addition of high concentration AuNP leads to the formation of an excitation peak at 421 nm and selectively enhances certain radiation modes. We concluded that the main reason for the selective enhancement of PL intensity in high concentration AuNP is the transfer of generous hot electrons at high energy states from AuNP to GQD and relaxation to the ground state. The electron resonance of low concentration AuNP transfers to GQD and relaxes to lower energy levels, exhibiting an overall enhancement of PL intensity. We apply it for detection of the heavy metal ion Cr3+, and verify that it has a correlation coefficient of 97.36%. We believe AuNP/GQDs can be considered excellent candidates for heavy metal detection and high fluorescence bio-imaging.

Insight into the Effect of Counterions on the Chromatic Properties of Cr-Doped Rutile TiO2-Based Pigments.

Rutile TiO2 pigments codoped with chromophore ion Cr3+ and various charge-balancing ions (i.e., counterions species of Sb, Nb, W and Mo) were prepared by a solid-phase reaction method. The effects of the counterions and calcination temperatures on the phase structure, color-rendering and spectroscopic properties, microstructure, and stability of the synthesized pigments were investigated in detail. The results showed that the introduction of 5–10% counterions improved the solubility of Cr3+ in the TiO2 lattice to form the single-phase rutile pigments calcined at 1100 °C for 2 h. The 10% Cr-doped pigment showed a dark brown color. Depending on the content and type of counterions, the color of the codoped pigments was tailored from yellow to reddish or yellowish-orange to black with different brightness and hue. The influence mechanism of counterions was ascribed to the lattice distortion and variation in the charge balance condition. It was found that the addition of Sb, Nb, or Mo resulted in a remarkable improvement in the NIR reflectance of pigments. The grain growth was inhibited with the codoping of Cr/Sb and Cr/Nb to achieve the nano-sized pigments. In addition, the prepared pigments exhibited good acid and alkali corrosion resistance as well as excellent stability and coloring performance in transparent ceramic glazes.

Pyrolysis of Biomass Wastes into Carbon Materials

This study presents the results of the biomass pyrolysis process focusing on biochar production and its potential energetic (as solid fuel) and material (as adsorbent) applications. Three kinds of biomass waste were investigated: wheat straw, spent coffee grounds, and brewery grains. The pyrolysis process was carried out under nitrogen atmosphere at 400 and 500 °C (residence time of 20 min). A significant increase in the carbon content was observed in the biochars, e.g., from 45% to 73% (at 400 °C) and 77% (at 500 °C) for spent coffee grounds. In addition, the structure and morphology were investigated using scanning electron microscopy. Thermal properties were studied using a simultaneous thermal analysis under an oxidising atmosphere. The chemical activation was completed using KOH. The sorption properties of the obtained biochars were tested using chromium ion (Cr3+) adsorption from liquid solution. The specific surface area and average pore diameter of each sample were determined using the BET method. Finally, it was found that selected biochars can be applied as adsorbent or a fuel. In detail, brewery grains-activated carbon had the highest surface area, wheat straw-activated carbon adsorbed the highest amount of Cr3+, and wheat straw chars presented the best combustion properties.

A novel strategy to fabricate nylon 6 based flame retardant microfiber nonwoven fabric with durability

A fundamental challenge in nylon-6-based microfiber non-woven fabrics (NWFs) are their flammability, which limits their industrial application in different fields. Inspired by chrome tanned leather with excellent flame retardancy, we developed a photo-grafting method to introduce carboxyl groups (–COOH) onto polyurethane-impregnated nylon-6-based microfiber nonwoven fabric (PNWF). By simulating the chrome tanning process of natural leather, we utilized a coordination reaction between chromium ion (Cr3+) and -COOH to fabricate the flame retardant PNWF. Compared with the control sample, the modified PNWF show an increased the limited oxygen index (LOI) value from 19.9% to 27.1%, and their peak heat release rate (pk-HRR) and peak smoke production rate (pk-SPR) were reduced by 32.1% and 54.2% respectively, suggesting a significant improvement in flame retardancy and the amelioration of smoke inhibition. In addition, we employed scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) to evaluate the flame retardant mechanisms of modified PNWF. EDS and XPS analysis of the chars of PNWFs after cone calorimetry tests showed the formation of a Cr2O3 protective layer for Cr3+-crosslinked PNWF and the coordination between Cr3+ and –COOH enhances the degree of graphitization of char residue, both promoting the flame retardancy of PNWF. Due to the chemical bonding between Cr3+ and –COOH, the resultant PNWF retained 95.01% of the original LOI after undergoing the laundering procedure 50 times, revealing durable flame retardant characteristics.

Luminescence spectroscopy of Cr3+ in an oxide: A strong or weak crystal-field phosphor?

Various Cr3+-activated oxide phosphors can be classified into two groups: a strong crystal field group [E(2Eg)ZPL < E(4T2g)ZPL] and a weak crystal field group [E(2Eg)ZPL > E(4T2g)ZPL] from an equality relation of the zero-phonon line (ZPL) energies of 2Eg and 4T2g. Obtaining reliable Racah parameters for the 3d3 ion (Cr3+) usually needs accurate information on the three excited-state ZPL energies, E(2Eg)ZPL, E(4T2g)ZPL, and E(4T1g,a)ZPL. However, an exact determination of such ZPL energies is a very difficult problem. Because of an accumulation with adjacent excited states along with the presence of charge transfer band, this is especially for E(4T1g,a)ZPL. An importance of accurate determination of the excited-state energies to be used in the Racah parameter calculation is discussed in detail with demonstrating a risk of erroneous conclusion of whether Cr3+-activated oxide phosphor belongs to a strong or weak crystal-field phosphor.

Ingenious aspartic acid-functionalized gold nanoparticles by one-pot protocol for the sensitive detection of chromium (III) ions

In this work, we report an effective one-pot strategy for synthesizing aspartic acid-functionalized gold nanoparticles (Asp-AuNPs) and constructing chromium (III) ion (Cr3+) colorimetric sensing system. Aspartic acid, acting as a reductant and stabilizer, was used directly to synthesize functionalized AuNPs without additional surface modification procedure. The Asp-AuNPs possesses the same good stability and optical properties as citrate-stabilized AuNPs, which become a new option for preparing AuNPs. More importantly, aspartic acid exhibits superior performance than citrate and other succinic acid derivatives because of its Cr3+identifying property. The Asp-AuNPs was used for the sensitive and selective detection of Cr3+ based on the aggregation-induced color change of AuNPs from wine red to blue-gray. Under optimal conditions, the absorbance ratios (A660 nm/A520 nm) show good linearity with Cr3+ concentrations with a limit of detection of 0.6 nM. Furthermore, the proposed method was applied for the analysis of Cr3+ in environmental water samples successfully with a reliable recovery of 95.4%-105.1%. Besides, the scanometric analysis model based on three primary colors change was established to deal with the requirement for the rapid quantitative determination of Cr3+ inenvironmental emergencies.

A New Cr3+ Electrochemical Sensor Based on ATNA/Nafion/Glassy Carbon Electrode.

A new electrochemical sensor of metal cation in an aqueous solution based on homobifunctional tridentate disulfide Schiff base and named 1,1′-(-((disulfanediylbis(2,1-phenylene))bis(azaneylylidene))bis(methaneylylidene))bis(naphthalene-2-ol) (ATNA) was easily obtained quantitatively from the condensation reaction of 2-hydroxy-1-naphthaldehyde and 2-aminothiophenol, and then fully characterized by spectroscopic techniques for structure elucidation. The molecular structure of ATNA was also confirmed by a single-crystal X-ray diffraction study to reveal a new conformation in which the molecule was stabilized by the O–H…N type intramolecular hydrogen bonding interactions in both moieties. The ATNA was used as a selective electrochemical sensor for the detection of chromium ion (Cr3+). A thin film of ATNA was coated on to the flat surface of glassy carbon electrode (GCE) followed by 5 % ethanolic Nafion in order to make the modified GCE (ATNA/Nafion/GCE) as an efficient and sensitive electrochemical sensor. It was found to be very effective and selective against Cr3+ cations in the company of other intrusive heavy metal cations such as Al3+, Ce3+, Co2+, Cu2+, Ga3+, Hg2+, Mn2+, Pb2+, and Y3+. The detection limit at 3 S/N was found to be 0.013 nM for Cr3+ ions within the linear dynamic range (LDR) (0.1 nM–10.0 mM) of Cr3+ ions with r2 = 0.9579. Moreover; this work instigates a new methodology for developing the sensitive as well as selective electrochemical toxic cationic sensors in the field of environmental and health care.

Preparation of Zeolite‐g‐Polyacrylamide using Radiation Induced Grafting and Its Adsorption Isotherms Study on Several Heavy Metal Ions

AbstractZeolite‐g‐polyacrylamide is prepared by using the radiation induced grafting technique. Clinoptilotite, a natural zeolite, is used as the base matrix. In order to increase the degree of grating of polyacrylamide into the zeolite, its surface is modified with silane compound before the grafting reaction and applied a poor solvent method in the grafting reaction, i.e., a mixture of toluene and H2O. The irradiation doses are varied from 10 to 50 kGy. The grafting parameters are 40% w/w acrylamide, temperature 60 °C and 3 h grafting time. The highest degree of grafting is 93% at an irradiation dose of 25 kGy. The zeolite‐g‐polyacrylamide is then characterized with FTIR spectroscopy and SEM observation. Batch experiments are also carried out to investigate the adsorption capacity for ion Cr3+, Pb2+, and Zn2+. The maximum adsorption capacities of zeolite‐g‐polyacrylamide are 544, 345, and 1046 mg g−1 for ion Cr3+, Pb2+, and Zn2+, respectively. The equilibrium data are also tested with Langmuir and Freundlich isotherm to find the best suitable adsorption isotherm system.

First-principle study of the microstructure and electronic properties for Cr3+ doped yttrium orthoaluminate

Chromium ion (Cr3+) doped YAlO3 host crystal shows strong prospects for the exploitation of new optical materials. However, the microstructure of Cr3+ doped of YAlO3 is still unclear. In this work, we systematically explore the structural evolutions of Cr3+ doped of YAlO3 system by using the CALYPSO method and density functional theory. A novel cage-like structure with P-1 space group is identified for the first time. The impurity Cr3+ ion can naturally substitute the Al3+ ion of the central site in the crystal lattice. The result show that the impurity Cr3+ concentration is determined to be 6.25%, which is almost comparable to the experiments. The perfect agreement between our simulated X-ray diffraction patterns and the measured ones demonstrates the validity of the ground-state structure. The calculation of electronic band structure for Cr3+ doped YAlO3 reveals a closure of the insulator band gap, forming an energy gap of 2.94 eV. The result of electronic density of states shows that it is the impurity Cr3+ ion that leads to a transition from insulator to semiconductor. By analyzing the electron localization function of Cr3+ doped of YAlO3 crystal, we conclude that the Cr–O interaction is dominantly ionic bond. The obtained results could provide an important understanding of the transition-metal doped host materials.

Colorimetric determination of chromium in aluminium alloys by diphenylcarbazide method

A concise method for the determination of chromium in aluminium alloys colorimetrically by the use of diphenylcarbazide is described. The method is based on measurement of the violet colour formed between chromate III ion (Cr3+) and diphenylcarbazide. The diphenylcarbazide forms a violet complex which absorbs at 540 nm. Other interfering metal ions including manganese and iron were masked by making alkaline with sodium hydroxide (NaOH). Potassium heptaoxodichromate (VI) K2Cr2O7 solution (283ppm) was used as standard. Three aliquots (2ml, 5ml and 10ml) of standards were used for measurement. The solutions of samples were made in aquaregia and colour reagent added. Absorbance of standard as well as samples was measured at 540 nm using a colorimeter. A working curve obtained from known concentrations of standard was used to calculate the concentration of chromium in each sample. The findings show that colorimetric determination of chromium by diphenylcarbazide method is a simple, effective and valuable alternative method for the determination of chromium in aluminium alloys.

Ultratrace Naked-Eye Colorimetric Ratio Assay of Chromium(III) Ion in Aqueous Solution via Stimuli-Responsive Morphological Transformation of Silver Nanoflakes.

In this work, we discover an effective domino-effect-based detection mechanism for the rapid, high-selectivity, and ultrasensitive naked-eye colorimetric ratio assay of chromium(III) ion (Cr3+) in aqueous solutions. This naked-eye colorimetric ratio assay to Cr3+ relies on changes in absorbance properties that are due to the stimuli response of Cr3+ for the morphological transformation of silver nanoflakes. In the presence of Cr3+, large silver nanoflakes can be stimulated to transform to small nanoparticles (NPs), which promoted a color change in solution from bright yellow to wine red that was detected by the naked eye and spectroscopic absorption methods. The proposed naked-eye sensing strategy was coupled with an ultraviolet (UV)-spectroscopic chemosensor for the detection of trace Cr3+. The detection method showed an ultralow detection limit of 1.4 nM (nanomole) for Cr3+ in ultrapure water and 11.5 nM in human serum sample, respectively. On the basis of colorimetry, the lowest concentration of ∼50 nM for Cr3+ in ultrapure water and human serum can be detected by the naked eye. This naked-eye-based colorimetric ratio assay for accurate and selective identification and high sensitivity of Cr3+ is expected to have large potential and wide applications such as pharmaceutical analysis, clinical diagnosis, and environmental monitoring.

Modulating energy transfer between transition metal and rare earth ions in nanostructured glass to promote ultrabroadband infrared emission

Researching broadband amplification materials and modulating energy transfer processes between two active ions have attracted immense attention for photoluminescence applications in recent years. In this work, transition metal (Cr) and rare earth (Er) ions codoped glasses and glass ceramics with ten nanometer length scale β-Zn2SiO4 crystals have been successfully prepared. The analysis of valence state change and surroundings of Cr ions proves two points: 1) Cr3+ ions always stay in amorphous surroundings, 2) a part of Cr3+ ions change to Cr4+ occupied in the nanocrystal phase. To the best of our knowledge, it is demonstrated for the first time that an active ion (Cr3+) does not produce the radiative processes by emitting photons, while it can store pumping energy and transfer to neighboring active ions (RE: Er3+ ions here) for infrared emission. Four times enhanced infrared intensity of 1530 nm emission and super-ultrabroadband emisison in the region of 1100–1700 nm have been obtained finally. Meanwhile, an approach in nanometer length scale to control ET processes between two simultaneous active ions has been proposed for futher studies on photoluminescence applications.

Implications of including a magnetic ion (Cr3+ and Fe3+) at the vanadium site in a geometrically frustrated spinel MgV2O4: magnetic and catalytic properties.

The vanadium sublattice in a geometrically frustrated MgV2O4 is substituted partially with Cr3+ and Fe3+. With a successful Rietveld refinement of the powder X-ray diffraction patterns of MgVCrO4 and MgVFeO4, Cr and Fe occupy the octahedral sites of a spinel structure. Extensive field-dependent and temperature magnetic measurements on these samples reveal exciting results. MgV2O4 remains paramagnetic till 3 K, with a small divergence at around 20 K between ZFC and FC data. MgVCrO4 exhibits antiferromagnetic behavior with a Néel temperature of 13.6 K. MgVFeO4 shows spin-glass behavior resulting from the frustration with a glass transition temperature of 194 K. This sample shows a typical ferromagnetic behavior, with a coercivity of 194.5 Oe within an applied field of ±2 kOe. All three systems have been found to have a frustration index in the range of 1-25, and the effective magnetic moment decreases in the order MgVFeO4 > MgVCrO4 > MgV2O4. While the inclusion of chromium does not alter the bandgap of MgV2O4, iron substitution increases the bandgap. The partial replacement of V3+ with Cr3+ and Fe3+ increases the catalytic ability of the system in terms of the oxidative degradation of methylene blue dye. The catalytic efficiency follows the order MgVFeO4 > MgVCrO4 > MgV2O4, matching well with the trend noticed in the porosity, surface area, and redox ability of Fe3+, Cr3+ and V3+ in these samples. The degradation pathway has been followed by analyzing the intermediates from these experiments by mass spectrometry, and a plausible mechanism is proposed.

Crystal field study of Chromium(III) ions doped antimony phosphate glass: Fano’s antiresonnance and Neuhauser models

The absorption spectrum of antimony phosphate glass doped with Cr3+ is characterized by the presence of features on the 4T2g(4F) absorption band. These features result from the interaction of the 2Eg(2G) and 2T1g(2G) sharp levels with the vibrationally broadened 4T2g(4F) quasi-continuum via spin-orbit coupling called interference dips. We have analyzed this phenomenon through two models: Fano’s antiresonance and Neuhauser models. This analysis permits us to determine the electronic structure of the chromium ion Cr3+ based on the crystal field theory. As a result, Racah and crystal-field parameters have been reliably obtained. A good agreement between the theoretical and the experimental energy levels are obtained.

Effect of transition metal ion (Cr3+, Mn2+ and Cu2+) doping on the photocatalytic properties of ZnWO4 nanoparticles

In this work, we report the effect of transition metal ion doping on the photocatalytic properties of ZnWO4 nanoparticles. Undoped and transition metal (Cr3+, Mn2+ and Cu2+) doped ZnWO4 nanoparticles have been synthesized sonochemically and have been characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). Band gap has been estimated using UV–vis diffuse reflectance spectroscopy (DRS) which shows a red shift with doping which could be attributed to doping effects and lattice variation. The photocatalytic efficiency of the samples was tested for Methylene blue (MB) degradation under simulated solar light (150 W Xe arc lamp) which showed improvement with doping. The best results were obtained for ZnWO4:Cr3+(2 mol%) and ZnWO4:Cu2+(2 mol%) samples which was a result of proper band gap tuning and enhanced separation of the photogenerated electron/hole pairs leading to effective degradation of the MB dye solution. The photocatalytic mechanism has been elucidated and it could be inferred that photogenerated holes and hydroxide radicals play a major role in the photocatalysis process.