Water pollution caused by pollutants like organic dyes and heavy metal ions is accountable for problems related to health, economy, and environmental degradation. Metal oxide nanomaterials such as ZnO have extensive potential to tackle water pollution. In the present study, pure, 3 and 6 at% Fe-doped ZnO nanoparticles were synthesized via high-energy ball mill cum solid-state reaction route. The samples were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, Brunauer-Emmett-Teller (BET) technique, UV-visible and photoluminescence spectroscopies. The crystallite size decreased, whereas structural defects increased with Fe concentration. The band gap narrowing (3.36-3.23 eV) has been observed with an increase in Fe doping. The light-emission properties of samples were analyzed using CIE plots. Also, DFT+U calculations were performed to predict the impact of Fe-doping on the crystal structure and electronic & band structure of ZnO. Photocatalytic degradation ability of the nanostructures towards methylene blue (MB) dye was improved from 59.8 % to 90.7 % with Fe doping, and degradation follows pseudo-1st order kinetics. With Fe-doping, Ni ions removal capability of ZnO from water enhanced from 14.7 % to 48 %, and DFT studies of Ni-adsorption on the pure and Fe-ZnO surfaces also predicted this trend.

Environmental concern essentially demands solemn consideration of industrial waste -water containing organic dyes. To develop efficient photocatalysts for degradation of organic dyes in waste water, metal -oxide nanostructures are the promising candidate owing to their tunable physical properties. The present work emphasizes on the experimental and first -principle (DFT + U) studies to understand the impact of magnesium doping on the structural, optical and electrical properties, and photocatalytic degradation tendency of zinc oxide (ZnO) nanoceramics. The ZnO lattice contraction endorsed by Mg -doping, has been examined mutually from the first principle calculations and Rietveld refinement investigations. The decrease in crystallite -size (93 to 88 nm) and enrichment in structural imperfections of Zn1-xMgxO nanostructures were analyzed with Williamson -Hall peak profile methods. The band gap broadening of ZnO with Mg doping was demonstrated by UV-visible spectroscopy (3.32 to 3.43 eV) which was further confirmed from DFT + U (3.39 to 3.55 eV) calculations. The increase in dielectric constant and reduction in ac conductivity has been observed due to Mg addition. The photocatalytic performance of Zn1-xMgxO nanostructures was evaluated under sunlight for Methylene -blue (MB) and Congo -red (CR) dyes. The performance has been optimally improved with 6 mol% Mg content leading to degradation of 86.2 % and 58.3 % of MB and CR dyes respectively in 160 min.

The present manuscript emphasizes the versatility of Mg-doped CuO nanostructures for environmental remediation (photocatalytic degradation of pollutants) and biomedical applications (anticancer activity) thus highlighting their potential impact in addressing societal and health challenges. The primary focus of the manuscript is the synthesis, characterization, and applications of Mg-doped CuO nanostructures. In order to meet this purpose, pure and Mg doped CuO nanostructures were synthesized using the solid-state reaction method and ball milling techniques. To characterize the prepared samples, X-ray diffraction, transmission electron microscopy, UV-Visible, photoluminescence, and Raman spectroscopy techniques were utilized. A profusion of structural defects and the reduction in crystallite size have been observed in CuO nanomaterial’s due to the dopant's complete incorporation into the CuO lattice. Additionally, the band gap of CuO has been observed to decrease as a result of Mg doping. Density functional theory was employed to simulate the effect of Mg on the properties of CuO. The efficiency of photocatalytic degradation aided by sunlight against methylene blue increased from 50.8% to 89.5%. MCF-7, a cell line representing human breast adenocarcinoma, was utilized to assess the cytotoxicity of Mg/CuO samples. CuO nanoparticles enriched with Mg are viable biocompatible anti-cancer agents and prospective photocatalyst for the removal of environmental pollutants from aqueous solutions, according to the findings of this study.

We prepared the pristine and Sm3+-doped ZnO nanostructures using an eco-friendly ball milling technique and investigated the physical properties of nanostructures by experimental methods and density functional theory approach. The reduction in crystallite size and increment in structural defects was witnessed due to Sm-doping. Decrease in band gap (from 3.27 to 3.02 eV) and enhancement of magnetic properties were observed with the increase in dopant concentration. The photocatalytic degradation potential of the samples towards the pollutants methylene blue (dye) and ciprofloxacin (antibiotic) improved with Sm3+ doping. The best performance was witnessed for the sample doped with 4 mol% of Sm2O3, which degraded the 93% and 95% of methylene blue (50 ppm) and ciprofloxacin (25 ppm) in 150 min and 210 min, respectively. Antibacterial activity towards the Escherichia coli and Staphylococcus aureus bacteria was also enhanced with the increase of Sm-content. Thus, Sm-doped ZnO nanostructures show good potential for photocatalytic and antibacterial applications.

In this paper, we report structural, vibrational and toluene sensing properties of pristine and Al-doped NiO. Pristine and Al-doped (1, 3 and 5 wt%) NiO samples were successfully synthesized using coprecipitation method at room temperature. X-ray diffraction analysis revealed cubic structure of all the samples. Raman spectroscopy confirmed the presence of maximum number of nickel vacancies in 3 wt% Al-doped sample. FESEM of pristine and 3 wt% aluminium-doped nickel oxide confirmed that aluminium doping in host lattice of nickel oxide altered the morphology from micro-rods to nanoparticles. The surface areas of all the samples have been analyzed using Brunauer–Emmett–Teller technique which confirmed the largest specific surface area of 3 wt% Al-doped NiO. Sensors fabricated using pristine and Al-doped NiO exhibited optimum sensing response towards toluene at 230 °C and 180 °C, respectively. Aluminium doping improved the sensing performance of nickel oxide by reducing optimum operating temperature to 180 °C and made it operable at temperatures from 90 to 300 °C. The device fabricated using 3 wt% Al-doped NiO exhibited optimum sensor response of 29 towards 10 ppm toluene. Doping with aluminium improved the selectivity, sensitivity and reduced the optimum operating temperature of nickel oxide. Small crystallite size, large specific surface area and numerous nickel vacancies play important role in improving the toluene sensing performance of 3 wt% Al-doped NiO sensor. The detailed study of NiO-based toluene sensor is presented in this paper.

Nitrogen oxide (NOx) is one of the prominent toxic air pollutants originating from fertilized soils. Considering the excellent properties of semiconducting metal oxides like wide band gap, intrinsic oxygen vacancies, high chemical and thermal stability, they have been investigated in gas sensors to detect toxic gases. Further, MXenes have established as excellent sensing materials in recognition of its tunable surface termination groups, modulating work function and highly conducting nature. Herein, we demonstrate the interfacial engineering of semiconductor metal oxide (SnO2) with MXene (Ti3C2TX) (SnO2/Ti3C2TX) synthesized using hydrothermal method towards the enhancement in the gas sensitivity of low-cost nitrogen oxide (NOx) gas sensor. The structural and morphological characterization of SnO2/Ti3C2TX nanostructures have been performed using X-ray diffraction, field-emission scanning electron microscopy, and Brunauer-Emmett-Teller techniques. Further, SnO2/Ti3C2TX nanostructure have been investigated for gas sensing toward different gases (isopropanol, methane, nitrogen oxide, ammonia, ethanol and acetone) at room temperature and estimated their sensitivity and selectivity. SnO2/Ti3C2TX sensor demonstrated excellent selectivity toward NOx and exhibited high sensing response of 203% with improved response/recovery time of 156/115 s toward NO2 in comparison to pristine SnO2 (56%) and Ti3C2TX (24%)-based sensors, suggesting a promising application prospect in soil released NOx sensing.

The ion beam induced modified gallium doped ZnO thin films are studied for their gas sensing applications. The Ag9+ and Si6+ irradiated gallium doped zinc oxide thin films were exposed to various concentrations of ethanol and acetone gas for gas sensing applications. The Ag9+ ion irradiated Ga-doped ZnO thin was optimized at different operating temperature. It was observed that gas sensing response for both ethanol and acetone gas increases with increasing Ag9+ ion fluence. This indicates that the swift heavy ions have improved the sensitivity of Ga-doled ZnO thin film by reducing the particle size. The Si6+ ion irradiated Ga-doped ZnO thin films were also exposed to ethanol and acetone gas for gas sensing applications. In comparison to Ag9+ ion irradiated thin film, the film irradiated with Si6+ ion beam exhibits a greater sensing response to both ethanol and acetone gas.

In the present work, we have investigated the role of calcination temperature in altering the structural, optical and antibacterial properties of ball mill synthesized Co 3 O 4 nanoparticles. The outcomes of X-ray diffraction patterns and their Rietveld refinement confirm the presence of spinel cubic phase of Co 3 O 4 and lattice expansion with increase in calcination temperature. The crystallite size and micro-strain values obtained from Williamson-Hall plot method, show increasing and decreasing trends respectively with increase in calcination temperature. The Raman spectra of the samples exhibit vibrational modes related to the Co 3 O 4 cubic structure only. The particle size and morphology of the nanoparticles have been examined with the help of scanning electron microscopy and these results are consistent with the XRD findings. The red shift in the optical band gap of the nanoparticles has been observed with increasing calcination temperature. Important optical parameters such as refractive index, extinction coefficient, dielectric constant and conductivity are found to be dependent on the calcination temperature. The existence of various types of defects and vacancies has been confirmed from the results of photoluminescence spectroscopy. The bactericidal activity of the Co 3 O 4 samples has been examined towards the Escherichia coli and Staphylococcus aureus bacteria. This study shows that the optical and antibacterial properties are strongly correlated to the structural properties of Co 3 O 4 nanoparticles which can be tuned by varying calcination temperature.

The present work focuses on the detailed investigation of the structural, optical and antibacterial properties of undoped and Ni-doped CuO nanostructures. The CuO nanostructures with different mol% (0, 1 and 3) of nickel oxide have been synthesized using the ball milling for 20 h, followed by calcination for 4 h at 500 °C. The X-ray diffraction patterns reveal that all the samples contain only CuO with a monoclinic phase and indicate the successful doping of Ni into the host matrix. The Rietveld refinement of the XRD patterns indicates the decrease in structural parameters with increase in dopant concentration. The results of the Williamson–Hall method reveal the decrease in crystallite size and increase in micro-strain with Ni-doping. The optical band energy of the CuO nanoparticles has been obtained with the help of UV–visible data, and it is found to increase with the increase in Ni content. The detection of various types of defects and vacancies in CuO nanoparticles has been carried out using photoluminescence spectra. The antibacterial activity of the synthesized CuO nanostructures has been investigated against pathogenic bacteria (S. aureus and E. coli) using the agar well diffusion method.

Iron and vanadium co-doped ZnO nano-structures have been synthesized by solid state reaction method and the influence of Fe content on their structural, optical, dielectric and transport properties was investigated. The structural and optical characterizations of samples have been carried out by X-ray diffraction (XRD), trans-mission electron microscopy, Raman, UV-Visible and photoluminescence spectroscopy. Rietveld refinement of XRD data revealed that the lattice parameters and unit cell volume of the wurtzite ZnO decreased with Fe doping. The decrease in crystallite size and increase in micro-strain with doping have been observed from Williamson-Hall and size-strain analysis. The red shift in the band gap (from 3.29 to 3.24 eV) and increase in the dc activation energy (from 0.196 to 0.207 eV) with increase in Fe concentration are attributed to the enhancement of structural disorder/defects. The decrement in dielectric constant from 160 to 25 and ac conductivity from 16.6 x 10(-6) to 1.4 x 10(-6) at 10 kHz have been observed with Fe doping. The modulus and impedance studies revealed the presence of non-Debye relaxation, and contribution of grains and grain boundaries to the polarization. The study also revealed that the addition of Fe significantly modified structural, optical, dielectric and transport properties of the samples.

In this work, V-doped and (Sm, V) co-doped ZnO samples have been synthesized using ball milling method followed by heat treatment. The dependence of structural, optical, electrical and dielectric properties of V:ZnO samples on the Sm doping concentration has been explored. The structural properties have been studied by means of X-ray diffraction (XRD) and Rietveld refinement. Oxidation states of the elements present in the samples are determined using X-ray photoelectron spectroscopy. Raman spectra of the samples further verified the observations obtained from XRD. The crystallite size and microstrain have been estimated from the Williamson-Hall analysis. Microstrain increases from 0.814 x 10(-3) to 1.01 x 10(-3) with increase in the Sm doping level. The morphology of the grains is significantly affected by the Sm doping. The enhancement of defect density with Sm doping is responsible for the observed red shift (3.29-3.19 eV) in the band gap. The frequency dependence of the dielectric properties has been studied at various fixed temperatures ranging from 25 to 350 degrees C. The increase in real dielectric constant with dopant content indicates the enhancement of energy storage capacity. The ac conductivity follows Jonscher's power law and it increases up to 1 mol% Sm concentration. Further increase in Sm extent leads to the decrease in ac conductivity. The impedance spectroscopy has been performed to understand electrical behavior of samples and Cole-Cole plots are fitted against the equivalent circuit model. The electrical activation energy values for conduction and relaxation vary in the range: 0.281-0.269 eV and 0.260-0.243 eV, respectively.

The physicochemical properties of SnO 2 obtained by different methods (sol–gel, solvothermal and CVD synthesis) from different precursors were investigated. The synthesized samples were characterized by X-ray diffraction analysis, electron spectroscopy, FTIR, low-temperature nitrogen adsorption–desorption and their optical bandgap and volt-ampere characteristics were determined. It was shown that the synthesis method and its parameters have a significant effect on the properties of the obtained SnO 2 powders. The type of reaction medium significantly affects structural and adsorption characteristics of samples. SnO 2 synthesized by the solvothermal method is characterized by the smallest crystallite sizes, larger specific surface, and more diverse structural characteristics in comparison with the powders obtained by sol–gel and CVD methods. Mesoporous powders of tin (IV) oxide were obtained using sol–gel method, macroporous SnO 2 monocrystalline powders were produced by CVD method. The found values of the optical bandgap for the tin (IV) oxide, obtained by different methods, differ from the theoretical bandgap value. The influence of all parameters on the electrical properties of SnO 2 was observed.

In the present study, we report gas sensing properties of Zinc doped nickel oxide nanoparticles. The Zn doped NiO samples were successfully synthesized by chemical co-precipitation method at room-temperature. Raman studies revealed the presence of defects such as nickel vacancies, which encourage the better sensing results. These defects are essential for providing active sites for adsorption of gaseous molecules and assists in improving the sensing parameters. Further, the sensor response of device has been found to be 7.2 when exposed to 100 ppm of methanol at 260 °C. Obtained Zn doped NiO sensor was found to be selective towards methanol as compared to other volatile compounds including, ethanol, acetone, ammonia and hydrogen.

The high thermal conductivity, high electron mobility, the direct wide band gap, and large exciton binding energy of zinc oxide (ZnO) make it appropriate for a wide range of device applications like light-emitting diodes, photodetectors, laser diodes, transparent thin-film transistors, and so forth. Among the semiconductor metal oxides, zinc oxide (ZnO) is one of the most commonly used gas-sensing materials. The gas sensor made of nanocomposite ZnO and Ga-doped ZnO (ZnO:Ga) thin films was developed by the sol–gel spin coating method. The gas sensitivity of gallium-doped ZnO thin films annealed at 400, 700, and 900 °C was studied for ethanol and acetone gases. The variation of electrical resistance of gallium-doped ZnO thin films with exposure of ethanol and acetone vapors at different concentrations was estimated. Ga:ZnO thin films annealed at 700 °C show the highest sensitivity and shortest response and recovery time for both ethanol and acetone gases. This study reveals that the 5 at. % Ga-doped ZnO thin film annealed at 700 °C has the best sensing property in comparison to the film annealed at 400 and 900 °C. The sensing response of ZnO:Ga thin films was found higher for ethanol gas in comparison to acetone gas.

Despite the high prevalence of tin oxide (SnO2) based sensors for detection of numerous toxic gases, they suffer from issues of cross-sensitivity and high operating temperatures. Herein, SnO2 lattice has been modified with highly catalytic erbium (Er) based rare earth metal to address aforementioned issues. Thin films of undoped and 1, 3, 5 wt% Er-doped SnO2 nanoparticles have been deposited by electron beam evaporation technique and influence of Er on structural and optical characteristics of SnO2 films has been investigated for gas sensing applications. The incorporation of Er in SnO2 thin films has been found to tune the concentration of oxygen vacancies, which can enhance the gas sensing parameters. The sensor with an optimized amount of Er (3 wt%) exhibits a maximum sensing response for 1 ppb of NO2 at room temperature (25 degrees C) with improved selectivity and stability against humidity.

We have systemically examined the impact of Ga doping on structural, optical, and ethanol sensing properties of NiO nanoparticles. X-ray diffraction study demonstrated cubic structure of pure as well as Ga-doped NiO nanoparticles. Brunauer Emmett Teller results indicated that Ga doping increases the surface area of NiO. Fascinatingly, dopant altered the surface morphology of NiO from micro rods to large area nanoparticles which eventually improved the sensing properties of Ga-doped NiO nanoparticles. Raman and photoluminescence spectroscopy indicated huge number of defects in 3% Ga-doped NiO nanoparticles. The catalytic effect of Ga reduced the activation energy of Ga-doped NiO which further improved sensing properties of doped samples for 50 ppm of ethanol. The improvement in sensor response and selectivity of 3% Ga-doped NiO sensor to ethanol is accredited to larger surface area, augmented defect concentration, and excellent catalytic effect of the sensor. The sensing results revealed that 3% Ga-doped NiO sensor was able to detect even 10 ppm of ethanol. The astonishing response of 3% Ga-doped NiO nanoparticles suggested that they can be utilized for producing high performance ethanol gas sensing devices.

Fabrication of atomically thin p-n junctions has proved to be a challenging job as the conventional processes such as ion implantation and doping for the realization of p and n type regions in bulk crystals are no longer viable. By considering their pressing demands, there is a requirement to look for vibrant strategies for fabrication of p-n junctions in two dimensional materials and to observe their applications. Herein, in this work, we explore the possibility of formation of atomically thin p-n homojunction diodes in an exfoliated graphenic medium based on asymmetrical structure induced self-doping. Our fabricated p-n homojunction diode exhibits satisfactory rectifying properties with a rectification ratio of similar to 10(5) with ideality factor of 1.46 indicative of defect-free interface between n-layered/m-layered (n m) graphene sheets. Our results unfold the potential of desired device characteristics based on various stacking patterns of graphene layers. The novelty of this work lies in the fact that the formation of atomically thin p-n homojunction diodes in graphene is devoid of any ion implantation, chemical treatment, electrostatic gating techniques etc.