Shift Of Edge Research Articles

Ga based Sillenite-TiO2 composite for efficient sunlight induced photo reduction of Cr (VI) and photo degradation of ampicillin

This work reports the design and development of an efficient sillenite based visible light photoactive Bi24Ga2O39–TiO2 (BGT) heterostructure. Structural and morphological studies based on X-ray diffraction (XRD) and high-resolution scanning electron microscopy (HRSEM) confirm the formation of combined phase as well the overall morphology of composite BGT. Additionally, X-ray photoelectron spectroscopy (XPS) results confirm the presence of Bi3+, Ga3+, Ti4+ & O2−. The composite exhibits a shift in the absorbance edge towards visible region of electromagnetic spectrum when compared to that of TiO2. Suitable band edge positions in the composite facilitate the formation of type-1 heterojunction enhancing visible light photocatalytic property. The photocatalytic activity is evident from photo reduction of Cr (VI) (95% reduction in 180 min). The composite also plays an improved and effective role in the degradation of persistent drug ampicillin-cloxacillin (AMC) with a rate constant of 0.02 min−1. Photocatalytic experiments conducted at different pH values showed higher performance at lower pH ∼3. Trapping experiments performed on the sample confirm the role of holes as the main active species during photocatalysis. Appreciable recyclability of BGT composite was noted with respect to AMC drug degradation.

Modifications in the structural, morphological, optical properties of Ag45Se40Te15 thin films by proton ion irradiation for optoelectronics and nonlinear applications

This current work reports the 30 keV proton ion irradiation induced structural, morphological, and optical properties change in Ag45Se40Te15 films at different fluences. The thin films were irradiated with different ion fluences, such as 5 × 1015 ions/cm2,1 × 1016 ions/cm2 and 5 × 1016 ions/cm2. The electronic loss (Se) dominates over the nuclear loss (Sn) in proton irradiation. The X-ray diffraction study shows the phase transformation from amorphous to crystalline upon ion irradiation. The Raman analysis confirms the change in chemical and vibrational bonds due to structural alterations in the films. The surface morphology has been studied by field emission scanning electron microscopy and the composition of the films has been checked by the energy dispersive X-ray analysis. The particle size increased upon the increase in ion irradiation fluence. The surface roughness of the films has been studied by atomic force microscopy. The transmission data is used to calculate the linear optical parameters. The absorption edge shifts towards the high wavelength region inferring the reduction in the optical bandgap. The linear refractive index of the films increased with ion fluence. The optical density increased at the high wavelength region while the skin depth decreased with fluence. The carrier concentration per effective mass decreased while the plasma frequency increased with proton irradiation. The nonlinearity (χ (3) and n2) values increased significantly with the increase in fluences. Such kind of materials with optimization in their optical parameters are primarily essential for cutting-edge photonic, optoelectronic, and nonlinear optical applications.

Effect of Al doped ZnO on optical and photovoltaic properties of the p-Cu2O/n-AZO solar cells

Metal oxide thin films have fared so well in the semiconductor industry because of their superior physical, electrical, and optical properties. The applications of these materials in solar cells, biosensors, biomedicine, supercapacitors, photocatalysis, luminous materials, and laser systems are becoming increasingly popular. In this study, the influence of Al concentration on Cu2O/AZO heterojunction thin films was examined systematically. First, arrays of n-ZnO and AZO rods were produced on an ITO substrate using a hydrothermal technique at 140 °C. Then, using an alkaline cupric lactate solution, a thin films of p-Cu2O were electrodeposited at 60 °C onto the ZnO arrays. The structure and morphology of the produced materials and the solar cells were studied using X-ray diffraction and scanning electron microscopy. The optical measurements demonstrate a shift in the absorption edge with increasing Al content. Solar cells have been created with a device structure of ITO/ZnO/Cu2O/Al and ITO/Al-doped ZnO/Cu2O/Al configurations. The power conversion efficiency (ɳ) of the inorganic solar cell with 6% Al-doped ZnO is ɳ = 0.282%, which is greater than the ɳ of the ZnO-based solar cell (ɳ = 0.17%).

Short-range order and charge transport in silicon-rich pyrolytic silicon oxynitride

Amorphous SiOxNy films were grown by pyrolysis in a reduced pressure reactor at T = 800 °C for different SiH2Cl2/NH3 ratios from 1/5 to 1/1. The resulting analysis for the photoelectron spectra showed that, in addition to silicon and nitrogen, the samples composition includes oxygen, apparently, due to the presence of residual traces of oxygen and/or water. The red shift of the fundamental absorption edge indicates the presence of Si-Si bonds in SiOxNy. In a wide range of electric fields and temperatures, the charge transport mechanisms in SiOxNy are experimentally studied. The experimental results are compared with the calculation based on different trap ionization models. The best agreement between the experiment and calculation was obtained using the model of phonon-assisted tunneling between neighboring traps. The increase in the SiOxNy leakage current, when changing the SiH2Cl2/NH3 ratio from 1/5 to 1/1, is explained by the trap concentration increase.

Third order nonlinear optical absorption studies of Cr3+ doped PbWO4 nanostructures

We report the synthesis of Cr3+ doped PbWO4 nanoparticles with different concentration of Cr3+ through chemical method. The structural, morphological and optical characterization was studied through X-ray diffraction (XRD), Raman, UV–Visible spectra, Photoluminescence, X-ray photo electron spectroscopy (XPS) and Transmission electron Microscopy (HR-TEM). The XRD patterns revealed the tetragonal phase of stolzite and the peaks are highly crystalline structure with no segregation of Cr3+. UV–Vis absorption spectra reveal that the shift of absorption band edge towards higher wavelength upon doping of Cr3+ions. The average particle size of the nanostructure as revealed by the TEM image lies around 47 nm. Third order nonlinearity of Cr3+ doped PbWO4 nanoparticles were analysed by the standard Z-scan technique using 532 nm Nd: YAG laser. The observed nonlinear absorption (NLA) and nonlinear refraction (NLR) behavior is caused by thermal nonlinear effects due to localized heating. Experimental results have demonstrated that an increase in optical nonlinearity occurs with higher Cr3+ concentrations. Based on the observed nonlinearity it is suggested that the synthesized nanostructures could be used in various optical device applications.

Field-Effect Tuning of Electrochemistry at 2D Semiconductor Electrodes: Charge Transfer Kinetics Can be Modulated with a Back Gate Voltage

Semiconductor electrodes are widely used in electrocatalytic reactions. The ability to improve and modulate the heterogeneous charge transfer kinetics on semiconducting electrodes is a major challenge for the electrochemical application of these materials. Instead of changing the electronic occupation of the semiconductor by chemical doping, we adopt an electronic method to modulate band edge alignment and solution electrochemistry at 2D ZnO working electrodes.In our approach, a field-effect transistor with ultrathin ZnO semiconductor (3-5 nm) is fabricated, the heart of which is a metal-insulator-semiconductor (MIS) stack. A high-dielectric-constant material (HfO2) is used as the insulator to realize low-voltage tunability of the device. The ZnO layer of the device functions as the working electrode (WE) for electrochemical reactions. By applying a back gate voltage to this MIS field-effect transistor, charge carriers are electrostatically induced and the ZnO band edges shift at the front face of the ZnO in contact with electrolyte. These effects can be exploited to manipulate the charge transfer kinetics on the ZnO electrode at a given electrode potential. We demonstrate this by focusing on outer-sphere redox chemistry. In order to eliminate mass transfer effects, microfluidic flow cells are coupled to the ZnO devices. Steady state kinetic analysis is carried out to extract the electron transfer rate constant of the redox process as a function of both electrochemical and back gate potentials. The heterogeneous electron transfer rate can be tuned by over an order of magnitude using the back gate voltage. The work demonstrates that a back gate provides another degree of freedom in determining electrochemical reaction kinetics at ultrathin semiconductor working electrodes. The method also opens possibilities for control over a wider range of semiconductor electrochemistry, such as electrocatalytic reactions. Figure 1

One-pot ultrasonicated synthesized lead-less hybrid perovskite nanocrystals: structural, morphological and optical analysis

In contemporary years, hybrid lead halide perovskites nanocrystals (HPNCs) have emerged as core materials for low-cost solution-processable photovoltaic, light-emitting devices as well as in other optoelectronic fields, such as high-efficiency perovskite fluorescent quantum dots (quantum dot, QD). Although the high efficiency makes them an attractive active material, reducing the Pb-toxicity and enhancing the stability while sustaining the efficiency of the HPNCs devices is important for their successful commercialization in future. Here, we report for the first time the fabrication of excellent quality Pb-less, MAPb1-x Sn x Br3 (x = 0 to 0.50) perovskite NCs by one-pot ultrasonication method. Interestingly, an outstanding photoluminescence quantum yield (PLQY) of 94% and better lifetime performance than 100% Pb-based HPNCs is obtained for Pb-less HPNCs. The successful incorporation of Sn MAPb1-x Sn x Br3 HPNCs is confirmed by energy-dispersive x-ray (EDX) and x-ray photoelectron spectroscopy (XPS) analysis. Although the particle size for Pb-less HPNCs was different, the change in morphology and structure was minimal as confirmed by transmission electron microscopy (TEM) analysis. The optical analysis indicated bandgap tuning, which is evident by the blue shift of the band edge in absorbance spectra and photoluminescence peak after incorporating Sn2+. To the best of our knowledge, this is the highest achieved PLQY for Sn-substituted hybrid Pb-based HPNCs. The synthesis by using one pot ultrasonication method might be helpful for large-scale HPNCs production and can pave the way for future research on less-toxic and stable alternatives to Pb-based HPNCs.

Effect of indium doping on the optoelectronic properties of ZnSe films

Polycrystalline In:ZnSe films were prepared by the thermal co-evaporation method, where high purity ZnSe and In2Se3 powders are taken as source materials. Orderly change in the X-ray diffraction peak position and red shift in the optical absorption edge have confirmed the incorporation of the dopant in the system. Photoluminescence spectra showed that the doped system has a Zn vacancy, which is in line with energy dispersive spectroscopy measurements. The chemical state of the doped films i.e., Zn2+, In3+ and Se2− was analysed by Raman and X-ray photoelectron spectroscopy (XPS); XPS has also indicated the incorporation of oxygen in small fractions which improves the conductivity of the films. The electrical investigation has revealed that electrical properties altered by doping and majority charge carriers are electrons and carrier density is in the order of 1015 cm−3. Films with 15 at. % In exhibited good photoresponse in the visible range and suitable for photodetector applications.

Periodic dynamics in superconductors induced by an impulsive optical quench

A number of experiments have evidenced signatures of enhanced superconducting correlations after photoexcitation. Initially, these experiments were interpreted as resulting from quasi-static changes in the Hamiltonian parameters, for example, due to lattice deformations or melting of competing phases. Yet, several recent observations indicate that these conjectures are either incorrect or do not capture all the observed phenomena, which include reflectivity exceeding unity, large shifts of Josephson plasmon edges, and appearance of new peaks in terahertz reflectivity. These observations can be explained from the perspective of a Floquet theory involving a periodic drive of system parameters, but the origin of the underlying oscillations remains unclear. In this paper, we demonstrate that following incoherent photoexcitation, long-lived oscillations are generally expected in superconductors with low-energy Josephson plasmons, such as in cuprates or fullerene superconductor K3C60. These oscillations arise from the parametric generation of plasmon pairs due to pump-induced perturbation of the superconducting order parameter. We show that this bi-plasmon response can persist even above the transition temperature as long as strong superconducting fluctuations are present. Our analysis offers a robust framework to understand light-induced superconducting behavior, and the predicted bi-plasmon oscillations can be directly detected using available experimental techniques.

Lattice strain and band overlap of the thermoelectric composite Mg2Si1−xSnx

${\mathrm{Mg}}_{2}{\mathrm{Si}}_{1\text{\ensuremath{-}}x}{\mathrm{Sn}}_{x}$ solid solutions show enhanced thermoelectric performance when the Sn mole fraction $x$ is approximately $x=0.7$. This has been discussed in terms of complexity of the electronic structure arising from the crossover of two bottom conduction bands, but direct detailed understanding of the origins and the precise nature of this band convergence is limited. Here, we report first-principles calculations of the band edge changes analyzed by band unfolding and crystal orbital Hamilton population techniques. We find that strain is particularly important at this crossing. ${\mathrm{Mg}}_{2}\mathrm{Si}$ and ${\mathrm{Mg}}_{2}\mathrm{Sn}$ show opposite trends in the conduction band edge shifts leading to a band crossover at $x\ensuremath{\sim}0.625$. However, there are also important effects due to disorder. Transport calculations show that enhancement of the figure of merit $ZT$ value owes to the combined effects of lattice strain, band edge overlap, composition change, and disorder.

Improvement in optical absorption and emission characteristics of polymethyl methacrylate in solution cast polymethyl methacrylate/polyvinyl carbazole polyblends

Polymer blends have got considerable attention for their potential optoelectronic and photonic applications due to several advantages such as easy processing, low cost, flexibility, and good mechanical properties. This work reports the structure and optical properties of solution cast binary blends of poly (methyl methacrylate) (PMMA) and poly (vinyl carbazole) (PVK). Here, the position and/or intensity of characteristic FTIR peaks reveal the changes of the structure of PMMA on PVK content while the surface morphology changes from highly smooth for pure PMMA to flaky structured (PVK 5%) and then to agglomerated morphologies for these blends. A red shift in optical absorption edge and decrease in optical transmission with PVK content in PMMA based blends. The emission spectra exhibit intensity escalation by 340 times with respect to PMMA for PVK-15 blends and then decreases with further addition of PVK in these blends. These results are very important for the advent of new optoelectronic functionalities for these polymer blends.

Electro-optical properties of APS and APhS linkers on silicon thin film: A DFT study

APS (3-Aminopropyl) trimethoxysilane) and APhS (p-Aminophenyl) trimethoxysilane) are the most commonly used linkers on a silicon surface. We investigate the surface properties of the structures, including APS or APhS on a silicon substrate. The studied structures consist of APS or APhS linkers with one, two, or three bonds with a substrate, which is a thin layer of Si with crystal orientation 〈100〉 or 〈111〉. Using a first-principles study based on density functional theory (DFT), we investigated the electronic and optical properties of the silicon-linker interface, such as interface states, orbital location, dielectric function, and photon absorption. The effects of linker type, number of linker-substrate bonds, and crystal orientation on density of states are investigated as a most important electrical property. In addition, we calculated the orbital location and dielectric function in the structures consisting of the substrate with the linker molecules. In this study, we propose techniques to reduce band edge shifts due to surface states and enhance the current mobility in structures with APS or APhS on a silicon substrate. The obtained results show that the use of APS linker molecules instead of APhS can reduce the conduction band shift by up to 50% and the density of interface states are sharply reduced at a depth of approximately 5 Å from the silicon surface. Also, simulation results show that the effect of linkers on the dielectric function can be negligible in the case of using linkers with one or two bonds with the substrate at low energies (lower than 5 eV).

Oxygen hyper stoichiometric trimetallic titanium doped magnesium ferrite: Structural and photocatalytic studies

Oxygen hyper stoichiometric titanium doped magnesium ferrite, Mg 1-x Ti x Fe 2 O 4+δ (x = 0–1.0) nanoparticles (NPs) were synthesized using sol-gel method. XRD analysis revealed a decrease in the lattice parameter from 8.9 to 8.3 Å and confirmed the incorporation of Ti 4+ , a smaller ionic radius dopant. Presence of M-O vibrational bands at tetrahedral and octahedral sites were authenticated by FT-IR analysis. The observed reduction in saturation magnetization values from 23.3 emug −1 to 18.3 emug −1 was ascribed to the doping of non-magnetic Ti 4+ ions in MgFe 2 O 4 NPs. BET studies corroborated the mesoporous nature of the NPs and doped ferrite NPs displayed larger surface area (53.0–73.0 m 2 g -1 ) as compared to pristine ferrite NPs (32.8–39.0 m 2 g -1 ). Optical studies displayed red shift in the absorption edge of the Ti 4+ doped MgFe 2 O 4 NPs in contrast to pristine NPs. Oxygen hyper stoichiometry in the doped ferrite NPs was determined experimentally. Photoluminescence emission spectra exhibited reduction in the emission intensity in case of Ti 4+ doped NPs which supported their higher light capturing potential. Among synthesized doped ferrite NPs Mg 0.5 Ti 0.5 Fe 2 O 4.5 NPs exhibited maximum (98%) photodegradation capacity for rhodamine B. The • O 2 − and • OH were the main reactive species in the photodegradation. The present studies have clearly shown the potential of tuning the composition of oxygen hyper stoichiometric ferrite Mg 0.5 Ti 0.5 Fe 2 O 4.5 for the removal of toxic organic contaminants from water.

Gamma radiation effects on plastic optical fibers

• The effect of gamma-ray irradiation on the Plastic Optical Fibers (POFs). • Irradiated POFs had optical losses significantly higher at 535 nm than at 650 nm. • The POFs could be used to connect up to 20 m if gamma-ray does not exceed 17.6 kGy. • The POFs could be used to connect up to 10 m if gamma-ray does not exceed 28.6 kGy. • The absorption edge shifts towards the higher wavelengths due to gamma radiation. We report on our study of the effect of gamma-ray irradiation on Plastic Optical Fibers with a 1 mm diameter for short reach communication. For the study, we used gamma-radiation facilities with 60 Co sources for slow long-term irradiation with a low dose speed of around 70 Gy/hrs and a maximum dose up to 62.90 kGy and a higher speed irradiation dose of around 1 kGy/hrs with a maximum dose up to 51.30 kGy. The optical losses measurement showed that the losses increased linearly during the irradiation and began to decrease immediately after the end of being irradiated. Higher doses of irradiation cause a higher value of the optical loss, and at the dose of 62.9 kGy, the loss was unmeasurably high. A low dose of gamma radiation (1.24 kGy) increased optical losses only slightly and the gamma-ray irradiation at 17.6 kGy for the 20 m long fiber had optical losses of −15.5 dB at 650 nm. The results of the relaxation measurements also showed that optical losses measured at wavelength 535 nm are significantly higher than those at 650 nm. Spectral characteristics measurement done during the irradiation showed that the intensity of the transmitted light decreased and the absorption edge shifted towards the higher wavelengths. Spectral characteristics measured after irradiation during the relaxation period showed that the intensity increased and also that the absorption edge was shifted towards the lower wavelengths, but the same values as before the irradiation were not achieved.

First principles study of biaxially deformed hexagonal buckled XS (X=Ge and Si) monolayers with light absorption in the visible region

In the present letter, we report the structural, electronic and optical properties of hexagonal buckled GeS and SiS monolayers under in-plane biaxial strain. The hybrid functional was adopted to calculate more accurate band gaps. The calculated electronic structures using Heyd–Scuseria–Ernzerhof (Perdew-Burke-Ernzerhof) methods show that both GeS and SiS monolayers display indirect band gap of 3.30 and3.03 eV (2.49 and 2.19 eV), respectively. We show that the buckling height, electronic structure and optical absorption of hexagonal buckled GeS and SiS monolayers can be tuned by applying in-plane biaxial strain. The band gap of SiS monolayer decreases by applying the tensile or compressive strain. The band gap of GeS monolayer reaches its maximum value under -2% strain and it decreases when the structure is more compressed or stretched. Both GeS and SiS monolayers exhibit optical absorption with energy covering ultraviolet light and partial visible light. By increasing the biaxial tensile strain, the absorption in visible region is expanded and enhanced due to the red shift of absorption edge.

Elliptical vibration cutting of large-size thin-walled curved surface parts of pure iron by using diamond tool with active cutting edge shift

Large-size thin-walled curved surface parts of pure iron are crucial in aerospace, national defense, energy and precision physical experiments. However, the high machining accuracy and surface quality are difficult to achieve due to the serious tool wear and deformation when machining the parts with conventional cutting tools. In this paper, an elliptical vibration cutting (EVC) with active cutting edge shift (ACES) based on a long arbor vibration device is proposed for ultra-precision machining the pure iron parts by using diamond tool. Compared with cutting at a fixed cutting edge, the influence of ACES on the EVC was analyzed. Experiments in EVC of pure iron with ACES were conducted. The evolutions of the surface roughness, surface topography, and chip morphology with tool wear in EVC with ACES are revealed. The reasonable parameters of ultra-precision machining the pure iron parts by EVC with ACES were determined. It shows that the ACES has a slight influence on the machined surface roughness and surface topography. The diamond tool life can be significantly prolonged in EVC of pure iron with ACES than that with a fixed cutting edge, so that high profile accuracy and surface quality could be obtained even at higher nominal cutting speed. A typical thin-walled curved surface pure iron part with diameter ∅240 mm, height 122 mm, and wall thickness 2 mm was fabricated by the presented method, and its profile error and surface roughness achieved PV 2.2 μm and Ra less than 50 nm, respectively.

Estimation of spectral responses and chlorophyll based on growth stage effects explored by machine learning methods

Estimation of leaf chlorophyll content (LCC) by proximal sensing is an important tool for photosynthesis evaluation in high-throughput phenotyping. The temporal variability of crop biochemical properties and canopy structure across different growth stages has great impacts on wheat LCC estimation, known as growth stage effects. It will result in the heterogeneity of crop canopy at different growth stages, which would mask subtle spectral response of biochemistry variations. This study aims to explore spectral responses on the growth stage effects and establish LCC models suited for different growth stages. A total number of 864 pairwise samples of wheat canopy spectra and LCC values with 216 observations of each stage were sampled at the tillering, jointing, booting and heading stages in 2021. Firstly, statistical analysis of LCC and spectral response presented different distribution traits and typical spectral variations peak at 470, 520 and 680 nm. Correlation analysis between LCC and reflectance showed typical red edge shifts. Secondly, the testing model of partial least square (PLS) established by the entire datasets to validate the predictive performance at each stage yielded poor LCC estimation accuracy. The spectral wavelengths of red edge (RE) and blue edge (BE) shifts and the poor estimation capability motivated us to further explore the growth stage effects by establishing LCC models at respective growth periods. Finally, competitive adaptive reweighted sampling PLS (CARS-PLS), decision tree (DT) and random forest (RF) were used to select sensitive bands and establish LCC models at specific stages. Bayes optimisation was used to tune the hyperparameters of DT and RF regression. The modelling results indicated that CARS-PLS and DT did not extract specific wavelengths that could decrease the influences of growth stage effects. From the RF out-of-bag (OOB) evaluation, the sensitive wavelengths displayed consistent spectral shifts from BE to GP and from RE to RV from tillering to heading stages. Compared with CARS-PLS and DT, results of RF modelling yielded an estimation accuracy with deviation to performance (RPD) of 2.11, 2.02, 3.21 and 3.02, which can accommodate the growth stage effects. Thus, this study explores spectral response on growth stage effects and provides models for chlorophyll content estimation to satisfy the requirement of high-throughput phenotyping.

Abnormal red shift in photoluminescence emission of ZnO nanowires

In this study, ZnO nanowires (NWs) have been synthesized through a simple chemical method and their optical properties were investigated using UV–vis, photoluminescence (PL) and Raman spectroscopy. PL studies revealed the red shift in the near band edge (NBE) emission peak with increasing diameter from 170 nm to 560 nm. By taking the sample with diameter d = 170 nm as a reference, the value of this red shift was found to be varied from 55 meV to 149 meV with the increase in diameter. Furthermore, this red shift shows the direct relation with the width of extra Zinc interstitial (Zni) or metal clusters related defect depletion layer at the boundary walls of nanowires. In this paper, the explanation for this red shift in PL is established by band bending at the edges of NWs caused by the depletion layer of excess Zn related defects. The confinement of the electrons at the surface of NWs was also found to be responsible for this red shift.

One-pot synthesis of flower-like Bi2WO6/BiOCOOH microspheres with enhanced visible light photocatalytic activity

Herein, flower-like Bi2WO6/BiOCOOH heterojunction photocatalysts were synthesized by one-pot method. Morphological characterizations had demonstrated that the Bi2WO6 nanoparticles were tightly anchored on the surface of BiOCOOH, which indicated that the successful synthesis of the Bi2WO6-BiOCOOH photocatalysts. Compared with pure BiOCOOH and Bi2WO6, the Bi2WO6/BiOCOOH photocatalysts had exhibited a red shift in absorption edge and enhanced visible light absorption. EIS, PL and photocurrent response results suggested that the form of the Bi2WO6-BiOCOOH heterojunction facilitated the separation of photogenerated electron and hole pairs. Furthermore, the photoactivity of Bi2WO6/BiOCOOH were evaluated by the photocatalytic degradation of tetracycline (TC) and ciprofloxacin (CIP) under the simulated sunlight irradiation. The results manifested that the W/Bi-2 photocatalyst exhibited the best photocatalytic activity, which TC was degraded by 88 % within 75 min and CIP was degraded by 90 % within 90 min. The improvement of photocatalytic activity was mainly attributed to the decrease in the composite rate of photo-induced electron-hole pairs. Radical trapping experiments and EPR results indicated that holes (h+) and superoxide radicals (·O2–) were dominant during the degradation of TC. The possible photocatalytic mechanism was discussed based on the band structures of BiOCOOH and Bi2WO6.

Superior dielectric behaviour and band gap tuning of Zn doped MgO nanoparticles

ABSTRACT The primary aim was to study the doping effect of Zn in MgO nanoparticles (NPs) prepared by the co-precipitation method. X-ray diffraction (XRD) results inferred the cubic structure of MgO with good crystallinity, which changed with dopant additions. Scanning electron microscope (SEM) images exposed the development of NPs with decreasing size and dimensions with little agglomeration on doping. Fourier transform infrared (FTIR) results revealed the Mg-O bond formation, which is associated with Zn-O bond on increasing dopant content. UV Vis studies showed the red shift in absorption edge and decreased band gap with percentage of Zn dopant additions. The dielectric results exposed the dielectric constant, dielectric loss and ac conductivity of Zn-doped MgO NPs. Dopant addition led to the higher dielectric constant and low dielectric loss at lower frequency due to oxygen vacancies generation. The impedance behaviour in different frequency regimes illustrated the effective contribution of conductive grains and insulating grain boundaries.