Three‑Dimensional Ordered Mesoporous Carbon Spheres Modified with Ultrafine Zinc Oxide Nanoparticles for Enhanced Microwave Absorption Properties

Currently,electromagnetic radiation and interference have a significant effect on the operation of electronic devices and human health systems.Thus,developing excellent microwave absorbers have a huge significance in the material research field.Herein,a kind of ultrafine zinc oxide(ZnO)nanoparticles(NPs)supported on three-dimensional(3D)ordered mesoporous carbon spheres(ZnO/OMCS)is prepared from silica inverse opal by using phenolic resol precursor as carbon source.The prepared lightweight ZnO/OMCS nanocomposites exhibit 3D ordered carbon sphere array and highly dispersed ultrafine ZnO NPs on the mesoporous cell walls of carbon spheres.ZnO/OMCS-30 shows microwave absorbing ability with a strong absorption(−39.3 dB at 10.4 GHz with a small thickness of 2 mm)and a broad effective absorption bandwidth(9.1 GHz).The outstanding microwave absorbing ability benefits to the well-dispersed ultrafine ZnO NPs and the 3D ordered mesoporous carbon spheres structure.This work opened up a unique way for developing lightweight and high-efficient carbon-based microwave absorbing materials.

Zinc Oxide Nanoparticles in Bacterial Growth Medium: Optimized Dispersion and Growth Inhibition of <i>Pseudomonas putida</i>

The majority of nanoparticles tend to agglomerate in bacterial growth media. Thus, nanoparticle-specific characteristics can get lost. To investigate the influence of nanoparticles on bacteria, these particles should remain in their nanoparticulate state. The present study demonstrates the stabilization of commercially available zinc oxide (ZnO) with sodiumhexametaphosphate (SHMP) in bacterial growth medium (LB) to avoid agglomeration of these particles after the addition to LB. This established method is appropriate to stabilize ZnO agglomerates as small as 43 nm. The method of fractionated centrifugation was used to obtain stable agglomerates (also stable in the presence of bacteria) with different mean diameters. The SHMP-stabilized ZnO inhibits the growth of Pseudomonas putida with increasing concentration (up to 500 mg/L) and decreasing agglomerate size (43 - 450 nm).

Microbial synthesis of zinc oxide nanoparticles and their potential application as an antimicrobial agent and a feed supplement in animal industry: a review

In recent years, zinc oxide nanoparticles(ZnO NPs) have gained tremendous attention attributed to their unique properties. Notably, evidence has shown that zinc is an important nutrient in living organisms. As such, both prokaryotes and eukaryotes including bacteria, fungi and yeast are exploited for the synthesis of ZnO NPs by using microbial cells or enzyme, protein and other biomolecules compounds in either an intracellular or extracellular route. ZnO NPs exhibit antimicrobial properties, however, the properties of nanoparticles(NPs) are depended upon on their size and shape, which make them specific for various applications. Nevertheless, the desired size and shape of NPs can be obtained through the optimization process of microbes mediated synthesis by manipulating their reaction conditions. It should be noted that ZnO NPs are synthesized by various chemical and physical methods.Nonetheless, these methods are expensive and not environmentally friendly. On that account, the microbes mediated synthesis of ZnO NPs have rapidly evolved recently where the microbes are cleaner, eco-friendly, nontoxic and biocompatible as the alternatives to chemical and physical practices. Moreover, zinc in the form of NPs is more effective than their bulk counterparts and thus, they have been explored for many potential applications including in animals industry. Notably, with the advent of multi-drug resistant strains, ZnO NPs have emerged as the potential antimicrobial agents. This is mainly due to their superior properties in combating a broad spectrum of pathogens. Moreover, zinc is known as an essential trace element for most of the biological function in the animal’s body. As such, the applications of ZnO NPs have been reported to significantly enhance the health and production of the farm animals. Thus, this paper reviews the biological synthesis of ZnO NPs by the microbes, the mechanisms of the biological synthesis, parameters for the optimization process and their potential application as an antimicrobial agent and feed supplement in the animal industry as well as their toxicological hazards on animals.

Structural and photoluminescence properties of terbium-doped zinc oxide nanoparticles

We present in this paper a study of the structural and photoluminescence （PL） properties of terbium （Tb） doped zinc oxide （ZnO） nanoparticles synthesized by a simple low temperature chemical precipitation method, using zinc acetate and terbium nitrate in an isopropanol medium with diethanolamine （DEA） as the capping agent at 60 ℃. The as-prepared samples were heat treated and the PL of the annealed samples were studied. The prepared nanoparticles were characterized with X-ray diffraction （XRD）. The XRD patterns show the pattern of typical ZnO nanoparticles and correspond with the standard XRD pattern given by JCPDS card No. 36-1451, showing the hexagonal phase structure. The PL intensity was enhanced due to Tb^3＋ doping, and it decreased at higher concentrations of Tb^3＋ doping after reaching a certain optimum concentration. The PL spectra of Tb^3＋ doped samples exhibited blue, bluish green, and green emissions at 460 nm （5^D3 - 7^F3）, 484 nm （5^D4 - 7^F6）, and 530 nm （5^D4 - 7^F5）, respectively, which were more intense than the emissions for the undoped ZnO sample. Based on the results, an energy level schematic diagram was proposed to explain the possible electron transition processes.

Synthesis and Characterization of Zinc Oxide and Zinc Oxide Doped with Chlorine Nanoparticles as Novel <i>α</i>-Amylase Inhibitors

In this study we used a chemical solution method from oxalic acid (OX. acid) and zinc acetate (ZnAc) to prepare Zinc Oxide nanoparticles (ZnONPs) and Zinc Oxide nanoparticles doped with Chlorine (Cl:ZnONPs). The characterizations (FTIR, X-ray, SEM, TEM) of ZnONPs and Cl:ZnONPs were determined. Amylase inhibitors of ZnONPs and Cl:ZnONPs also were determined. SEM indicated that the ZnONPs and Cl:ZnONPs have an average particle size of 46.65 - 74.64 nm. TEM images of the ZnONPs and Cl:ZnONPs showed the round shaped. Compounds b, d and e exhibited significant inhibitory activity against amylase enzyme (from 69.21 ± 1.44 to 76.32 ± 0.78), respectively, and were comparable with that of acarbose (86.32 ± 0.63) at 1000 μg, thereby, projecting ZnONPs and Cl:ZnONPs as α-amylase inhibitors.

Synthesis of Zinc Oxide Nanoparticles with Good Photocatalytic Activities under Stabilization of Bovine Serum Albumin

Zinc oxide nanoparticles were synthesized using bovine serum albumin as stabilizers through a facile one-pot strategy in aqueous media. The morphology and crystal phase of the zinc oxide nanoparticles were determined by transmission electron microscopy, X-ray diffractograms, and Fourier transform infrared spectroscopy. The synthesized ZnO nanoparticles exhibited strong absorption and photoluminescence properties in the visible wavelength region based on the fluorescence and UV-visible spectroscopy. Based on the results, the zinc oxide nanoparticles could effectively degrade the organic dyes through the mediation of the hydroxyl radical under visible light irradiation. Furthermore, the zinc oxide nanoparticles show good recycling stability during the photocatalytic experiments. These results suggested that the as-prepared zinc oxide nanoparticles might be used as a potential photocatalyst to efficiently treat the organic pollutants.

Biosynthesis of Zinc Oxide Nanoparticles Using Ixora Coccinea Leaf Extract—A Green Approach

Green synthesis of metal oxide nanoparticles using plant extract is a promising alternative to traditional method of chemical synthesis. In this paper, we report the synthesis of nanostructured zinc oxide particles by biological method. Highly stable and spherical zinc oxide nanoparticles are produced by using zinc acetate and Ixora coccinea leaf extract. Formation of zinc oxide nanoparticles has been confirmed by UV-Vis absorption spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Dynamic light scattering analysis (DLS), zetapotential study and Scanning Electron Microscope with the Energy Dispersive X-ray studies (EDX). Dynamic light scattering analysis shows average particle size of 145.1 nm whereas high zeta potential value confirms the stability of formed zinc oxide nanoparticles. The Scanning Electron Microscope reveals spherical morphology of nanoparticles and Energy Dispersive X-ray analysis confirms the formation of highly pure zinc oxide nanoparticles. The zinc oxide nanoparticles from Ixora coccinea leaves are expected to have applications in biomedical, cosmetic industries, biotechnology, sensors, medical, catalysis, optical device, coatings, drug delivery and water remediation, and also may be applied for electronic and magneto-electric devices. This new eco-friendly approach of synthesis is a novel, cheap, and convenient technique suitable for large scale commercial production.

Effect of Zinc Oxide Nanoparticles on Denitrification and Denitrifying Bacteria Communities in Typical Estuarine Sediments

For revealing the effects of increasing of zinc oxide nanoparticles(ZnO NPs)on denitrification and denitrifying bacteria communities in estuarine sediments,the surface sediments of two typical estuaries(the Yangtze River Estuary and the Yellow River Estuary)were added with medium concentration(170mgL−1)and high concentration(1700mgL−1)of ZnO NPs for anaerobic cul-ture in laboratory.The concentration of NO_(3)^(−)and NO_(2)^(−),the reductase activity and denitrification rate were measured by physico-chemical analysis,nirS gene abundance and denitrifying bacteria communities by molecular biological methods.The results showed that ZnO NPs inhibited NO_(3)^(−), NO_(2)^(−)reduction process and NO_(3)^(−), NO_(2)^(−)reductase activity,and a stronger inhibition effect resulting from the higher ZnO NPs concentration.ZnO NPs decreased nirS gene abundance and community diversity of denitrifying bacteria.In addition,the inhibition degree of ZnO NPs on the denitrification process of sediments in different estuaries was different.These results were of great significance for evaluating the potential ecological toxicity and risks of nanomaterials in estuaries.

Ameliorative effects of melatonin and zinc oxide nanoparticles treatment against adverse effects of busulfan induced infertility in male albino mice

Testicular damage is one of the most hazardous effects as it’s associated with azoospermia.Busulfan(Bu)is a highly toxic chemotherapeutic drug that affects testis.Thirty male Swiss albino mice divided into six groups of 5 animals each.Control(oral 0.9%saline daily for 75 days);Mel(20 mg/kg/day orally for 30 days);ZnO NPs(5 mg/kg/day i.p.for 30 days);BU(single i.p.injection of 40 mg/kg and then left for 45 days);BU+Mel(single 40 mg/kg dose of BU and left for 45 days followed by 20 mg/kg/day Mel for 30 days);BU+ZnO NPs(single dose of 40 mg/kg of BU and left for 45 days,then 5 mg/kg/day ZnO NPs for 30 days).Preparation and Characterization of ZnO NPs.Specimens from testis prepared for ultrastructural investigations using TEM after Masson’s trichrome and toluidine blue staining.BU induced histological and ultrastructural damage of the testis.Moreover,the present results could be concluded that Mel or ZnO NPs can protect the testicular tissue against ultrastructural alterations induced by BU by its antioxidant and anti-apoptotic effects.

Zinc oxide nanoparticles reduce the chemoresistance of gastric cancer by inhibiting autophagy

BACKGROUND Gastric cancer(GC)is a common malignancy that results in a high rate of cancerrelated mortality.Cisplatin(DDP)-based chemotherapy is the first-line clinical treatment for GC therapy,but chemotherapy resistance remains a severe clinical challenge.Zinc oxide nanoparticle(ZnO-NP)has been identified as a promising anti-cancer agent,but the function of ZnO-NP in GC development is still unclear.AIM To explore the effect of ZnO-NP on chemotherapy resistance during GC progression.METHODS ZnO-NP was synthesized,and the effect and underlying mechanisms of ZnO-NP on the malignant progression and chemotherapy resistance of GC cells were analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)assays,colony formation assays,transwell assays,wound healing assays,flow cytometry,and Western blot analysis in GC cells and DDP-resistant GC cells,and by tumorigenicity analyses in nude mice.RESULTS Our data revealed that ZnO-NP was able to inhibit proliferation,migration,and invasion and induce apoptosis of GC cells.Meanwhile,ZnO-NP significantly reduced the half maximal inhibitory concentration(IC50)of DDP for the inhibition of cell proliferation of DDP-resistant SGC7901/DDP cell lines.Autophagy was increased in DDP-resistant GC cells,as demonstrated by elevated light chain 3-like protein 2(LC3II)/LC3I and Beclin-1 expression and repressed p62 expression in SGC7901/DDP cells compared to SGC7901 cells.Mechanically,ZnO-NP inhibited autophagy in GC cells and treatment with DDP induced autophagy,which was reversed by ZnO-NP.Functionally,ZnO-NP attenuated the tumor growth of DDP-resistant GC cells in vivo.CONCLUSION We conclude that ZnO-NP alleviates the chemoresistance of GC cells by inhibiting autophagy.Our findings present novel insights into the mechanism by which ZnO-NP regulates the chemotherapy resistance of GC.ZnO-NP may serve as a potential therapeutic candidate for GC treatment.The potential role of ZnO-NP in the clinical treatment of GC needs clarification in future investigations.

Zinc oxide nanoparticles and epibrassinolide enhanced growth of tomato via modulating antioxidant activity and photosynthetic performance

Nanotechnology has greatly expanded the applications of nanoparticles(NPs)domain in the scientific field.In this context,the zinc oxide nanoparticles(ZnO-NPs)and 24-epibrassinolide(EBL)has been revealed to positively regulate plant metabolism and growth.In the present study,we investigated the role of ZnO-NPs and EBL in the regulation of plant growth,photosynthetic efficiency,enzymes activities and fruit yield in tomato.Foliar treatment of ZnO-NPs at three levels(10,50 or 100 ppm)and EBL(10^(−8) M)were applied separately or in combination to the foliage of plant at 35-39 days after sowing(DAS);and the control plants were treated with double distilled water(DDW)only at the same time interval.Among different tested concentrations of ZnO-NPs and/or EBL,the combined spray of 50 ppm of ZnO-NPs and 10^(−8) M of EBL proved to be best,and considerably increased the growth,photosynthetic efficiency,biochemical enzymes activities as well as fruit yield.Besides,the performance of the antioxidant enzymes viz catalase,peroxidase and superoxide dismutase were also increased after the combined application of ZnO-NPs and EBL in Lycopersicon esculentum.Therefore,it is suggested that combined application of 50 ppm of ZnO-NPs and 10−8 M of EBL is the best combination can be applied to increase the performance and yield of L.esculentum.

Mass Synthesis in Polyol of Tailored Zinc Oxide Nanoparticles for Photovoltaic Applications

Zinc oxide nanoparticles with different sizes and shapes have been synthesized in polyol using a bottom-up approach. We have studied the scale-up of the process to massively produce high quality nanoparticles of controlled size and shape. The scale-up strategy required the effective mixing of reagents using either axial or radial mixing configurations and was experimentally validated by comparing structural properties of particles obtained in a small and a large size reactor. In addition, the flow patterns in these reactors have been calculated using three-dimensional turbulent computational fluid dynamics (CFD) simulations. Our results indicate a strong connection between the flow patterns, as obtained by CFD simulations, and the size and shape of the particles. Actually, our pilot scale reactor allowed producing sample aliquots of ~50 grams with nanoparticle sizes ranging from 8 nm to 600 nm and aspect ratio varying from 1 (nanospheres) to 20 (nanorods). After their synthesis, these two nanoparticle classes have been tested as building blocks in D149-dye-sensitized solar cell (DSSC). The measured power conversion efficiency (PCE) was 4.66% for nanorods shaped particles and 4.21% for nanospheres. These values were significantly higher than the 3.90% PCE obtained with commercial Degussa VP20 ZnO nanoparticles.

Effects of Zinc Oxide Particles with Different Sizes on Root Development in Oryza sativa

Given the consistent release of zinc oxide(ZnO)nanoparticles into the environment,it is urgent to study their impact on plants in depth.In this study,grains of rice were treated with two different concentrations of ZnO nanoparticles(NP-ZnO,10 and 100 mg/L),and their bulk counterpart(B-ZnO)were used to evaluate whether ZnO action could depend on particle size.To test this hypothesis,root growth and development assessment,oxidative stress parameters,indole-3-acetic acid(IAA)content and molecules/enzymes involved in IAA metabolism were analyzed.In situ localization of Zn in control and treated roots was also performed.Though Zn was visible inside root cells only following nanoparticle treatment,both materials(NP-ZnO and B-ZnO)were able to affect seedling growth and root morphology,with alteration in the concentration/pattern of localization of oxidative stress markers and with a different action depending on particle size.In addition,only ZnO supplied as bulk material induced a significant increase in both IAA concentration and lateral root density,supporting our hypothesis that bulk particles might enhance lateral root development through the rise of IAA concentration.Apparently,IAA concentration was influenced more by the activity of the catabolic peroxidases than by the protective action of phenols.

Unravel the potential of zinc oxide nanoparticle-carbonized sawdust matrix for removal of lead(Ⅱ) ions from aqueous solution

Zinc oxide nanoparticles(ZnOnp) are molecular nanoparticles synthesized by a chemical precipitation method from zinc nitrate tetrahydrate and sodium hydroxide.Carbonized sawdust(CSD) was prepared from sawdust obtained from a local wood mill.The matrix of both provides a better material as an adsorbent.The present study applied the functionality of ZnOnp,CSD,and ZnOnp-CSD matrix as adsorbent materials for the removal of Pb(Ⅱ) ions from aqueous solution.The method of batch process was employed to investigate the potential of the adsorbents.The influence of pH,contact time,initial concentration of adsorbate,the dosage of adsorbents,and the temperature of adsorbate-adsorbent mixture on the adsorption capacity were revealed.The adsorption isotherm studies indicate that both Freundlich and Langmuir isotherms were suitable to express the experimental data obtained with theoretical maximum adsorption capacities(q_(m)) of 70.42,87.72,and 92.59 mg·g^(-1) for the adsorption of Pb(Ⅱ) ions onto ZnOnp,CSD,and ZnOnp-CSD matrix,respectively.The separation factors(R_(L)) calculated showed that the use of the adsorbents for the removal of Pb(Ⅱ) ions is a feasible process with R_(L) <1.The thermodynamic parameters obtained revealed that the processes are endothermic,feasible,and spontaneous in nature at 25-50℃.Evaluation of the kinetic model elected that the processes agreed better with pseudo-second order where the values of rate constant(k_2) obtained for the adsorption of Pb(Ⅱ) ions onto ZnOnp,CSD,and ZnOnp-CSD matrix are 0.00149,0.00188,and 0.00315 g·mg^(-1)·min^(-1),respectively.The reusability potential examined for four cycles indicated that the adsorbents have better potential and economic value of reuse and the ZnOnp-CSD matrix indicates improved adsorbent material to remove Pb(Ⅱ) ions from aqueous solution.

Metal Ion Release of Manufactured Metal Oxide Nanoparticles Is Involved in the Allergic Response to Inhaled Ovalbumin in Mice

The aim of the present study was to establish the mechanism of the allergy aggravation effect. Our previous study showed that soluble ZnO nanoparticles caused allergy aggravation, but insoluble TiO2 and SiO2 nanoparticles did not induce an allergic response. Metal ion release is associated with the cytotoxicity of manufactured nanoparticles;however, the role of metal ion release in allergy aggravation remains to be elucidated. Therefore, we examined the allergy aggravation potential of several soluble manufactured nanoparticles (ZnO, CuO, NiO, MgO, and CaCO3). These nanoparticles were administered to mouse lungs by pharyngeal aspiration and subsequently, the mice inhaled ovalbumin (OVA). We also compared the properties of soluble NiO nanoparticles with insoluble micro-scale NiO particles. NiO nanoparticles markedly increased the levels of OVAspecific immunoglobulin (Ig) E but micro-scale NiO particles did not. Among the nanoparticles (ZnO, CuO, MgO, and CaCO3), ZnO induced increase of OVA-specific IgE level. CuO showed tendency to increase OVA-specific IgE;however, no significant difference was observed. Additionally, ZnO and NiO nanoparticles enhanced expression of a gene related to inflammation (Cxcl2), heavy metal detox (metallothionein 2), and oxidative stress (heme oxygenase-1). Gene expression of arginase1, which is enhanced by T helper 2 cytokine, was remarkably enhanced in mice administered ZnO and NiO particles. These effects were not observed in mice administered MgO and CaCO3 nanoparticles. In conclusion, the solubility and type of metal ion released from the nanoparticles influence the allergy aggravation effect. The results showed that the release of Zn2+ and Ni2+ aggravated the allergic reaction.

Production and characterization of ZnO nanoparticles and porous particles by ultrasonic spray pyrolysis using a zinc nitrate precursor

ZnO nanoparticles and porous particles were produced by an ultrasonic spray pyrolysis method using a zinc nitrate precursor at various temperatures under air atmosphere. The effects of reaction temperature on the size and morphology of ZnO particles were investi- gated. The samples were characterized by energy dispersive spectroscopy, X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. ZnO particles were obtained in a hexagonal crystal structure and the crystallite shapes changed from spherical to hex- agonal by elevating the reaction temperature. The crystallite size grew by increasing the temperature, in spite of reducing the residence time in the heated zone. ZnO nanoparticles were obtained at the lowest reaction temperature and ZnO porous particles, formed by aggregation of ZnO nanoparticles due to effective sintering, were prepared at higher temperatures. The results showed that the properties of ZnO particles can be controlled by changing the reaction temperature in the ultrasonic spray pyrolysis method.

Comparison of the In Vitro and In Vivo Toxic Effects of Three Sizes of Zinc Oxide(ZnO)Particles Using Flounder Gill(FG)Cells and Zebrafish Embryos

Nano-sized zinc oxide(n ZnO) particles are one kind of the most commonly used metal oxide nanoparticles(NPs). This study compared the cytotoxic and embryotoxic effects of three increasing sized ZnO particles(φ30 nm, 80-150 nm and 2 μm) in the flounder gill(FG) cells and zebrafish embryos, and analyzed the contribution of size, agglomeration and released Zn^(2+) to the toxic effects. All the tested ZnO particles were found to be highly toxic to both FG cells and zebrafish embryos. They induced growth inhibition, LDH release, morphological changes and apoptosis in FG cells in a concentration-, size-and time-dependent manner. Moreover, the release of LDH from the exposed FG cells into the medium occurred before the observable morphological changes happened. The ultrasonication treatment and addition of serum favored the dispersion of ZnO particles and alleviated the agglomeration, thus significantly increased the corresponding cytotoxicity. The released Zn^(2+) ions from ZnO particles into the extracellular medium only partially contributed to the cytotoxicity. All the three sizes of ZnO particles tested induced developmental malformations, decrease of hatching rates and lethality in zebrafish embryos, but size-and concentration-dependent toxic effects were not so obvious as in FG cells possibly due to the easy aggregation of ZnO particles in freshwater. In conclusion, both FG cells and zebrafish embryos are sensitive bioassay systems for safety assessment of ZnO particles and the environmental release of ZnO particles should be closely monitored as far as the safety of aquatic organisms is concerned.

Enhancement of thermal stability and UV resistance of halloysite nanotubes using zinc oxide functionalization via a solvent-free approach

The aim of this study was to synthesize and evaluate the thermal properties and ultraviolet(UV)resistance of zinc oxide-functionalized halloysite nanotubes(HNT–ZnO).The HNT–ZnO was synthesized using a facile solvent-free route.The properties of the HNT–ZnO nanofillers were characterized using zeta-potential measurement,X-ray diffraction(XRD),field-emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FTIR),and thermogravimetric analysis(TGA).The immobilization of ZnO nanoparticles onto HNT is feasible even at the lowest mass ratio of HNT/ZnO.The TGA results indicate that the thermal stability of the HNT–ZnO nanofillers is higher than that of the HNT.Furthermore,UV?Vis diffuse reflectance spectroscopy(UV-DRS)results show that the HNT–ZnO achieve a total reflectance as high as approximately 87.5%in the UV region,as compare with 66.9%for the HNT.In summary,the immobilization of ZnO onto HNT is a viable approach for increasing the thermal stability and improving the UV shielding of HNT.

Photocatalytic Degradation of Azure A Using N-Doped Zinc Oxide

Photocatalysis has been predicted as a promising technology for waste water treatment. N-doped zinc oxide has been used as an effective catalyst for carrying out number of chemical reactions, but limited work has been reported on use of N-doped ZnO as photocatalyst. In the present work, the photocatalytic degradation of Azure A was carried out in the presence of N-doped zinc oxide and the progress of the reaction was observed spectrophotometrically. The morphologies and structures of the as-synthesized nanomaterials were investigated by using FT-IR and DRS techniques. On the basis of observations, a tentative mechanism has been proposed for the photocatalytic degradation of dye.