Doped ZnO Nanostructures Research Articles

Ultrasensitive Room Temperature Formaldehyde Sensors Based on F Doped ZnO Nanostructures Activated by UV Light

Ultrasensitive Room Temperature Formaldehyde Sensors Based on F Doped ZnO Nanostructures Activated by UV Light

Enhancement of CO gas sensing with ZnO nanostructures on MWCNTs films

CO gas sensing properties of 1-D ZnO nanostructures deposited on films of Multi-Wall carbon nanotubes were investigated using a vapor transport approach. X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, energy dispersive X-ray, Raman spectroscopy, diffused reflectance spectroscopy, and photoluminescence, techniques were used to carry out the structural, morphological, and optical characterizations. The development of carbon-doped hybrid MWCNTs/ZnO nanostructures was demonstrated by the current results. The synthesized nanostructures were dense tapering belts and pedal-like crystalline structures as evidenced by their structural and morphological characteristics. Multiple networks of pure ZnO and hybrid MWCNTs-ZnO nanostructures were used to synthesize the gas sensors. Doped ZnO nanostructures sensing technique for CO gas detection was investigated in the present study. The combined impact of ZnO and MWCNTs was shown to be beneficial in boosting the response towards CO gas, as the response to CO gas at a concentration of 20 parts per million (ppm) was found to be five-times greater than that of ZnO sensors with good stability.

Facile synthesis, morphological, optical, catalytic and photocatalytic properties of Ag nanoparticles decorated Ce doped ZnO hybrid plasmonic nanorods

Designing plasmonic metal–semiconductor hybrid nanostructures for photodecomposition of industrial textile effluent has been considered as a great way to boost the catalytic and photocatalytic capability by promoting effective separation of photoexcited charge carriers. Herein, fabrication of Ag nanoparticles decorated Ce doped ZnO nanostructures were demonstrated via facile wet chemical method. The morphology and structure of the fabricated photocatalysts were analysed using FESEM, XRD and Raman spectroscopy whereas PL, TRPL and UV–vis absorption spectroscopy were employed to examine their optical behaviour. Catalytic response of the synthesized catalysts was studied for 4-NP to 4-AP reduction and the results are more favourable for Ag loaded Ce doped ZnO catalysts and achieved 96.4 % reduction of 4-NP in only 4 min. Photocatalytic measurements showed that higher Ag NP loading onto Ce doped ZnO nanostructures led to superior photodegradation ability over other photocatalysts for the degradation of synthetic dyes and levofloxacin antibiotic. The sunlight driven photodecolorization of harmful synthetic dyes and levofloxacin were studied and efficacy of 97.5, 97.1, 85.1, and 70.9 % were achieved for MG, MB, RhB and MO dyes, respectively in 12 min and 97.2 % efficiency for degradation of levofloxacin was achieved in 20 min of sunlight exposure. Furthermore, the key reactive species was identified and tentative photodegradation process was explained. This work provides an excellent plasmonic-semiconductor catalyst and photocatalyst with good photostability and practical applicability indicating its enormous potential for application in environmental remediation.

Interlinking the Fe doping concentration, optoelectronic properties, and photocatalytic performance of ZnO nanostructures

Doping is one of the effective strategies to modulate the optoelectronic properties and photocatalytic activity of photocatalysts. In this study, the effect of Fe doping (0–10 %) on morphology, optical and electronic properties, and photocatalytic activity of ZnO nanostructures is studied. The X-ray diffraction analysis shows that >5 % Fe doping, ZnFe2O4 is segregated as a secondary phase. The crystalline size decreases from 50.8 nm to 21.4 nm and the micro-strain increases with increasing the Fe concentration. The Fe doping-induced electronic restructuring facilitates visible light absorption through the O 2p → Fe 3d transition and the suppression of charge recombination by efficiently trapping conduction band electrons. Density functional theory (DFT) calculations are employed to unravel the underlying electronic changes induced by Fe doping in ZnO. The formation of shallow donor levels below the conduction band originates from the Fe 3d state. Photoluminescence spectra of pristine and Fe-doped ZnO nanostructures show characteristic emission peaks at approximately 384 nm and 570 nm, indicating the recombination of free excitons and oxygen interstitial defects, respectively. The results of the photocatalytic activity tests confirm that the 1 % Fe-doped ZnO nanostructures can exhibit the highest efficiency compared to the heavily doped ZnO nanostructures. The high efficiency in photocatalytic activity of 1 % Fe-doped ZnO nanostructures is ascribed to the modulated electronic structure and defect density. The adsorption affinity of methylene blue and water molecules to the surfaces of pristine and Fe-doped ZnO is simulated using the Monte-Carlo method. This study emphasizes the importance of controlling the dopant concentration to enhance the photocatalytic activity of various photocatalysts.

Bicone nanoflower evolution and multi-peak emission of polymer caped Cu doped ZnO.

A low-temperature polymer-assisted wet chemical method was used to synthesise Cu-doped ZnO bicone nanoflowers at three different PEG concentrations.The effects of PEG concentration on the structural, morphological and optical properties of Cu doped ZnO nanostructures were studied. X-ray diffraction studies revealed that the as-synthesized ZnO nanostructures are highly crystalline with a hexagonal wurtzite phase. The scanning electron microscopy (SEM) analysis showed that the prepared nanostructures have bicone-nanoflower morphology and PEG concentration has strongly influenced the size as well the shape of nanoflowers. The surface passivation effect of PEG on the band gap energies was studied by analysing UV -visible spectra of all the samples. The room-temperature fluorescent spectra of all the nanoflowers showed multiple peak emissions, both in the ultra-violet and visible regions, with varying intensities.These recasted multiple peaks are attributed to the morphological modification caused by the PEG addition.&#xD.

Fabrication of alcohol sensor using undoped and Al doped ZnO nanostructure film with polymer electrolyte gating

We report the fabrication of two terminal and three terminal gas sensor using Al-doped ZnO nanostructured-films and polymer electrolyte gate dielectric on glass substrate using vacuum free chemical method. The Al doped ZnO films are characterized by UV–vis Spectrometer, SEM, EDX and XRD. The characterization results have revealed the polycrystalline structure of both undoped and doped ZnO; with loosely packed, porous, and spherical granny nanostructure with mean grain size 20–10 nm and bandgap of the films is within the range of 3.12–3.16 eV. The conductivity of the ZnO film is tuned by Al concentration and the maximum value of conductivity was observed in 3 % Al doped ZnO films. Similarly, the best performance index of TFT such as current ON/OFF ratio, high transconductance and low threshold voltage was observed in 3 % Al doping concentration. The ordinary (two-terminal) sensor and three-terminal (FET) sensors' responses towards three different concentrations 50, 250, 500 ppm of ethanol and methanol vapors have been studied. The sensitivity of the film is modulated by Al concentration and higher value of sensitivity was achieved at 3 % Al doped ZnO films. The use of polymer electrolyte enhanced the sensitivity of the device which is more effective in methanol vapor. The Response-Recovery time of the sensor is significantly improved in three terminal devices than the two terminal devices.

Highly sensitive and selective room temperature acetone sensing properties of Co doped ZnO nanostructure films

Highly sensitive and selective room temperature acetone sensing properties of Co doped ZnO nanostructure films

Synergistic effects of La-doping on ZnO nanostructured photocatalysts for enhanced MB dye degradation

In this work, we present the design and characterization of pristine and La-doped ZnO photocatalysts, prepared via a facile co-precipitation technique. A comprehensive range of characterization techniques was employed to analyze the physicochemical properties of these synthesized nanostructured photocatalysts. The slight shift in the position of peaks in the X-ray diffraction (XRD) pattern confirms successful doping (La3+) of ZnO. Additionally, the identified wurtzite phase further validates the presence of ZnO nanostructures. Subsequent photocatalytic investigations were conducted using model solutions of water and methylene blue (MB) dyes under solar irradiation, meticulously comparing the performance of pure ZnO with La3+ doped ZnO. Over the time span of 90 min, the 5 % La-doped ZnO photocatalysts exhibited an impressive 98 % degradation efficiency for MB dye, surpassing the performance of the pristine ZnO counterpart (0 % La), which achieved only 51 % degradation. This emphasizes the pronounced enhancement resulting from the incorporation of La ions. The photoluminescence (PL) spectra insights with 5 % La3+doping exhibit significant quenching, caused by the suppression of charge carrier recombination, which enhances the photocatalyst's charge transport. X-ray photoelectron spectroscopy (XPS) spectra provided crucial insights into the elemental composition and chemical states of the 5 % La3+ doped ZnO nanostructures. Through systematic reusability assessments, it was established that the 5 % La-doped ZnO photocatalysts maintain their efficiency for up to four cycles, without displaying a significant reduction in removal efficacy. This emphasizes the inherent reliability and robustness of the developed photocatalysts.

Green Valorization of Waste Plastics to Graphene as an Upcycled Eco-Friendly Material for Advanced Gas Sensing

The valorization technique successfully transformed waste polyethylene terephthalate (PET) into valuable carbon nanomaterial (CN)/graphene, while doped and undoped ZnO nanopowders were synthesized via sol–gel methods. Utilizing XRD, BET, TEM, EDX, FTIR, and TGA analyses, the synthesis of sp2 2D sheet, pristine, and doped ZnO nanostructures was confirmed. Solid-state gas sensor devices, tested under 51% relative humidity (RH), 30 °C ambient temperature, and 0.2 flow rate, exhibited a 3.4% enhanced response to H2 gas compared to CO2 at 50 ppm concentrations over time. Notably, the ZnO/CN sensor surpassed CN and ZnO alone, attributed to CN dopant integration with decreasing order of response performance as ZnO/CN > CN > ZnO. This study underscores the efficacy of valorization techniques in generating high-value carbon nanomaterials and their efficacy in bolstering gas sensor performance, with ZnO/CN demonstrating superior response capabilities.

Study of structural and optical properties of Gd doped ZnO nanostructures synthesized by one-step, mass-scale productive method

In the present work, one-step, mass-scale productive solid state reaction method has been employed for the preparation of gadolinium (Gd) doped ZnO (GZOx: x = 0, 2, 4, 6, 8 wt%) nanostructures. The prepared GZOx samples have been studies their structural, morphological, elemental diffusion profile and optical properties using P-XRD, FE-SEM, EDS, FTIR, and photoluminescence (PL) spectroscopy. The powder X-ray diffractometer (P-XRD) results clearly indicate strong and sharp diffraction peaks with broadening that confirms the formation of hexagonal nanocrystalline structure of ZnO and Gd doped ZnO. The hexagonal morphology formation of the grains after doping of Gd contents into the ZnO nanostructures system is seen from the FE-SEM micrographs and the sizes of the grains are found to close to the results obtained from XRD patterns. The presence of Gd contents in ZnO matrix confirms its doping by EDS spectrum of 4 wt% Gd doped ZnO nanostructures. Fourier transform infrared (FTIR) results confirm the presence of functional groups and chemical bonding of ZnO at room temperature. Investigation of optical emission is interesting and the PL spectra reveal two emission peaks, one in UV-region located in the range of ∼385 to 395 nm and other is defects related emission centred at ∼450, ∼468, ∼503 and ∼562 nm in visible region for all the samples. The enhanced PL intensity is observed in the higher doped Gd contents in ZnO nanostructures and can be attributed to the presence of Gd ions into ZnO lattice. The detailed structural and luminescence analysis has been carried out and correlated. The study of structural and optical properties GZOx samples suggest the luminescent optoelectronic applications.

Improved humidity sensing performances of boron doped ZnO nanostructured thin films depending on boron concentration

Abstract This study details the production and analysis of undoped zinc oxide (uZnO) and boron (B) doped zinc oxide nanostructured thin films, with a specific focus on assessing the influence of varying B doping concentrations on humidity sensing performance. The synthesis of undoped ZnO and B doped ZnO nanoparticles was carried out using sol–gel method. B doping concentrations within the ZnO lattice were adjusted to 1, 3, 4, 5, and 10 mol%. Subsequently, nanostructured thin films were obtained through the spin coating technique on glass substrates. X-ray diffraction analysis revealed a hexagonal wurtzite structure for all nanostructured thin films. Notably, a change in preferential orientation from the (002) plane to the (100) plane occurred when B doping concentration exceeded 5 mol%. Scanning electron microscopy showcased nano-sized grains and capillary nanopores on the surface of each thin film. Energy dispersive X-ray spectra confirmed the presence of zinc, oxygen, and boron elements in the nanostructured thin films. Humidity sensing performance was assessed through electrical resistance measurements in the range of 45%–90% relative humidity at room temperature. All fabricated sensors exhibited sensitivity to humidity. Remarkably, the sensor with a 5 mol% B doping concentration demonstrated the highest humidity sensitivity (438.44 times) and the fastest response (2.0 s) and recovery times (14.2 s). The study concluded that the optimal B doping concentration for designing a highly efficient humidity sensor was determined to be 5 mol%. Overall, the study underscores the potential of B doped ZnO nanostructures for humidity sensor applications, given their exceptional sensor performance.

Mg doped ZnO Nanostructures: application as an environmental photo-catalyst

In this era, metal oxide nanoparticles with appliances in solar, catalysis, sensors, actuators, and many other fields, are highly sought-after because of their wide band gap. This study examines the Mg doped ZnO nanoparticles for the structural, electrical transportation and photo-catalytic behaviour. The XRD, FT-IR (Infrared Spectroscopy), PL (Photoluminescence), and Complex Impedance Spectroscopy were used to characterise the prepared sample. The wurtzite hexagonal structure in space group P63mc was shown by the XRD data. The analyzed crystallite sizes, planner distances, and cell volumes of Mg doped ZnO nanoparticles are 35.2 nm, 2.6122 Å, and 60.91 Å3, respectively. The aggregation in sample is visible in the micrographs. The PL spectra was traced at an excitation wavelength of 330 nm (λ) using a PL spectrometer. Using the FTIR approach, IR spectra with acmes about 520–640 cm-1 were traced, leading to Zn–O bond stretching. Using a photocatalytic reactor, the photocatalytic degradation of magnesium-doped ZnO nanoparticles was measured for two hours. For the Mg doped ZnO sample, the degradation efficiencies (ɳ%) is 67 percent.

Enhanced photocatalytic activity of Er doped ZnO nanospindles and nanorods for degradation of organic pollutants

Rare earth doping in ZnO is an efficient way to improve the photocatalytic performance. In the present work, Er doped ZnO nanospindles and nanorods were prepared through a simple cost effective wet chemical approach and were thoroughly characterized by FESEM, XRD, Raman spectroscopy, UV–vis-DRS, UV–vis absorption and PL spectroscopy. Nanospindle and nanorod-like morphologies of the fabricated samples were revealed by FESEM. XRD analyses revealed hexagonal wurtzite structure of Er doped ZnO nanostructures and confirmed Er doping into ZnO. PL studies showed increased defect concentration in ZnO nanostructures doped with Er ions. The photodegradation ability of nanostructures was investigated using cationic and anionic dyes and photodecomposition rate of 0.042 min−1 was achieved for MB decolorization using 0.5 % Er doped ZnO sample upon 32 min of solar light illumination. The probable photodecomposition mechanism supported by in-situ radical trapping experiments and repeatability test have also been discussed and results suggest that Er doped ZnO photocatalyst exhibit potential for use as commercial solar-active photocatalysts.

Diode characteristics, piezo-photocatalytic antibiotic degradation and hydrogen production of Ce3+ doped ZnO nanostructures

Piezo-photocatalysis of ZnO nanostructures had recently well attracted due to their exceptional potential in degrading the antibiotics and scalable hydrogen production. Here, we have synthesized the Ce3+ doped ZnO nanospheres in a facile wet chemical strategy. Dopant ions induced morphological evolution and optical bandgap tuning had observed in our experiment. Optical absorbance spectrum had confirmed the bandgap shortening occurs with Ce3+ doped ZnO specimens. The bandgap gap value had reduced to 2.82 eV from 3.05eV confirming the visible light responsivity of ZnO nano specimens. Obtained Zn(1-x)CexO nanospheres were utilized to fabricate the p-Si/n- Zn(1-x)CexO heterojunction diodes as well studied the improved electrical conductivity for the Ce3+ specimen-based diodes. Besides, ideality factor and barrier height values of the heterojunction diodes ZnO/p-Si, Zn0.99Ce0.01O/p-Si, Zn0.97Ce0.03O/p-Si, and Zn0.95Ce0.05O/p-Si are 15.97 & 0.43 eV, 15.47 & 0.44 eV, 8.02 & 0.46 eV and 5.21 & 0.47 eV, respectively. Direct sunlight assisted piezo-photocatalytic tetracycline (TC) degradation efficiency of ZnO, Zn0.99Ce0.01O, Zn0.97Ce0.03O, and Zn0.95Ce0.05O nanostructures respectively are 64%, 69%, 74% and 82%. We have produced the hydrogen quantity of 1234 μ mol h−1, 1490 μ mol h−1, 1750 μ mol h−1 and 1980 μ mol h−1 with 0%, 1%, 3% and 5% Ce3+ doped ZnO specimens under the direct sunlight assisted piezo-photocatalytic H2 production from H2S splitting.

Fe3+ doped ZnO nanostructures for improved photocatalytic degradation of malachite green, crystal violet and antibacterial activity

Fe3+ doped ZnO nanostructures for improved photocatalytic degradation of malachite green, crystal violet and antibacterial activity

TeO2 doped ZnO nanostructure for the enhanced NO2 gas sensing on MEMS sensor device

Severe health issues occur when human beings are exposed to NO2 gas, which is formed from combustion processes and reactions facilitated by sunlight. In order for safety measurements, NO2 gas sensors are highly needed at low concentration gas detections. ZnO gas sensor with the doping of TeO2 is developed using co-sputtering technique. ZnO/TeO2 heterojunction nanostructure is analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS) for structural study. Gas sensing properties were tested with Micro electro mechanical system (MEMS) devices, on which ZnO/TeO2 nanostructure is developed. This study focused on doping of 4 different variations of TeO2 with ZnO such as 0%, 2%, 4% and 8% atomic weight percentage (at.w%) of TeO2. Upon testing, 4% ZnO/TeO2 transpired to be best possible parameter for NO2 gas sensing. With maximum NO2 gas concentration of 1 ppm, 4% ZnO/TeO2 sensor exhibited 80% sensing response and with 200 ppb of minimum gas concentration, sensor had 42% response at optimal temperature of 100 oC. TeO2 doped ZnO sensor exhibits superior performance over pure ZnO sensor and has good selectivity over NO2 gas.

Enhancement in photocatalytic activity and biological properties of Sm doped ZnO nanostructures by the increase in Sm contents

The impact of Sm on the photocatalytic and biological properties of ZnO was explored in this study. The sol–gel approach was used to produce undoped and Sm-doped ZnO nanostructures by using Sm 6–10 wt%. The functional groups that appeared in the prepared nanostructures were identified by FTIR. Sm-doped ZnO exhibited a hexagonal wurtzite ZnO structure and Sm ions were successfully embedded into the ZnO matrix. The size of the crystallites was enhanced as the Sm content was increased, pointing to potential applications in photocatalysis and biological science. These nanocrystals were expected to break down bacterial and chemical pollutants in water when exposed to visible sunshinewavelengths. 9 wt% Sm in ZnO had shown the best photocatalytic performance. The effects of Sm concentration on antibacterial activity against Escherichia coli (E. coli), Pseudomonas aeruginosa (K. Pneumonia) and Staphylococcus aureus (S. aureus) were probed in this research through agar well diffusion method. Sm doped ZnO nanostructures were effective against all selected bacterial strains. The development of sensors, photovoltaic panels, wastewater treatment and water-splitting applications are the few applications of Sm-doped ZnO.

Development of Ag doped ZnO nanostructure and tranexamic acid infused chitosan-guargum film: A multifunctional antimicrobial dressing with haemostatic and wound closure potential

Modern wound care requires multifunctional dressings that can efficiently control bleeding and subsequent infection, facilitating faster healing which reduces the healthcare costs. Our study aimed to develop a nanocomposite biopolymeric film composed of Ag doped ZnO nanoparticle and drug tranexamic acid (TRA) loaded into chitosan guargum matrix (CGT/AgZnO) for obtaining improved antibacterial, antibiofilm and haemostatic properties, along with potential wound healing effects.The films were developed via solution casting method and characterized by various standard biophysical techniques such as X-ray diffraction, infrared spectroscopy, electron microscopy imaging etc. The polymeric nanocomposite films exhibited strong antibacterial efficacy against bacteria such as E. coli, P. aeruginosa, S. aureus and B. subtilis. The films loaded with 3 wt% of nanoparticles (CGT/AgZnO3) exhibited remarkable growth inhibition i.e. 90% and 94% against gram-negative and gram-positive bacteria, respectively. These films also demonstrated excellent antibiofilm activity, with CGT/AgZnO3 inhibiting over 80% of bacterial biofilm formation after 72 h. The nanocomposite films exhibited a strong hemostatic effect as indicated by their blood clotting index (BCI) value. The in vitro hemocompatibility and cytocompatibility study (against the mouse fibroblast cells- L929 cell line) showed the films were highly biocompatible. The wound closure potential of the films was evaluated using in vitro scratch assays, exhibiting enhanced cell migration (100%) after 24 h, as compared to the control groups (66%). These findings confirmed that the developed CGT/AgZnO films have the potential as an excellent wound dressing material with high antibacterial, hemostatic, and wound healing properties.

Morphological properties of ZnO nanostructures doped with Ag and Li for piezoelectric applications

The development of a facile method to obtain materials with piezoelectric properties, through a green synthesis, as an alternative to lead-free materials, was the main objective of this work. Piezo active materials were grown by chemical methods on two types of metal substrates: Pt/Ti/SiO2/Si and the Ti foil. Ag and Li-doped ZnO nanostructures were prepared by hydrothermal method at low temperature on metallic substrates which were previously covered with ZnO seed layer deposited by spin coating sol-gel method. The newly prepared materials were covered with a polymer layer and were morphological characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The piezoelectric properties were estimated by measuring the direct piezoelectric coefficient d33. The test results show that the doped ZnO nanostructures synthesized using a green route exhibit a piezoelectric response so the established method can be considered a promising approach for obtaining piezoelectric materials on large surfaces. Piezo active nanostructures could be of interest for integration into piezoelectric devices.

Synthesis, structural, photoluminescence, ultraviolet blocking and antibacterial performances of Ba-doped ZnO nanostructures

In the current experimental work, pure ZnO and Ba-doped ZnO nanorods have been prepared by implementing a facile wet chemical technique. XRD study reveals the formation of the hexagonal wurtzite phase of pure ZnO and Ba-doped ZnO nanorods. Interestingly, Ba-doped ZnO nanorods show very good absorption in the UVA (93% at 351 nm), UVB (90% at 300 nm) and UVC (61% at 220 nm) regions. The obtained results of the UV–visible absorbance study validate in such a way that the Ba-doped ZnO nanorods could be a better bet to be utilized as a UV blocker for the next generation of UV shielding materials. The Photoluminescence spectrum of Ba-doped ZnO nanoparticles reveals widespread UV–Visible bands between 350 and 600 nm. Also, the zone of inhibition is found to be 15 nm for both bacterial strains S.aures and E.coli and implies excellent antibacterial activity. Interestingly, the outcome as observed in the zone of inhibition towards S. aureus and E. coli in the present study is found to be higher than many doped ZnO and Ba-doped metal oxide nanostructures. The observed experimental results via the aforementioned characterizations imply that the synthesized samples possess the potential ingredients required for the applications related to the field of health care.