Doped ZnO Nanowires Research Articles

Investigation of highly efficient self-powered photo-detector performance of all inorganic lead-free halide perovskites (CsSnCl3) nanocrystals (NCs) decorated Er: ZnO nanowires (NWs)/Si heterojunctions

In this study, a zero-biased or self-powered heterojunction photodetector is fabricated by using the combination of lead-free halide-based inorganic perovskite (CsSnCl3) and erbium (Er)-doped ZnO nanowires (NWs) on Si platform. The main advantages of such types of heterojunctions are cost-effective fabrication procedure, highly stable and responsive photoresponse, and, such devices exhibit low dark current and high photo-to-dark current ratio of >102. The HRTEM images confirm that CsSnCl3 perovskites nanocrystals (NCs) are randomly decorated over the ZnO NWs. The UV–visible spectroscopy shows the absorption edges and bandgaps of perovskites NCs, ZnO NWs, and combined heterojunctions. The structural, chemical compositional, and defect-related optical transitions are studied in detail by employing XRD, XPS, and PL results. The highest zero-biased photo-response at 374 nm is achieved for the 1%Er: ZnO–CsSnCl3 NWs/Si heterojunction and corresponding calculated responsivity and detectivity values are obtained to be 0.196 A/W and 2.48 × 1011 Jones, respectively. Along with it, such selective Er-doped NWs perovskites heterojunction exhibits relatively superior linear dynamic range (LDR) (51.76 dB) and rapid response speed (rise time: fall time = 83 ms:63 ms) as compared to reported values. Hence, current work demonstrates that Er-doped oxide-perovskite heterojunctions can be a promising candidate for developing high-performance UV/Visible photodetector under self-powered mode.

Facile synthesis of Ce doped ZnO nanowires for efficient photocatalytic removal of organic pollutants from water

Facile synthesis of Ce doped ZnO nanowires for efficient photocatalytic removal of organic pollutants from water

Solvothermal synthesis of magnetically separable Co–ZnO nanowires for visible light driven photocatalytic applications

Magnetically retrievable Cobalt doped ZnO nanowires were synthesised by simple solvothermal method. The prepared Co–ZnO nanowires were analysed with several characterization instruments such as FESEM, XRD, FTIR, VSM, UV–vis spectroscopy, XPS and PL spectroscopy. No other phase has been identified besides wurtzite phase, according to the structural analysis of pure ZnO and Co–ZnO nanowires. As the concentration of Co doping increased, ZnO nanowires' band gap energy dropped. Moreover, ZnO's absorption peak has a minor wavelength shift toward longer wavelengths. Green light emission was detected by PL analysis of ZnO nanowires and also the PL intensity of ZnO nanowires was decreased after cobalt doping. Co–ZnO nanowires exhibited ferromagnetic property. The coercivity and retentivity of Co–ZnO nanowires were increased with increase of Cobalt concentration. Improved visible light photocatalytic activity for the breakdown of methyl orange dye was achieved by Co–ZnO nanowires.

Co-doped ZnO nanowires: Synthesis, photocatalytic performance, and cytotoxic activity against human brain glioblastoma cells

In this paper, we introduced a green method for the preparation of pure and 1, 3, 7, and 10 % cobalt doped zinc oxide (Co-doped ZnO) Nanowires through the application of Salvadora persica aqueous extract. The synthesis of nanorods was confirmed by the results of PXRD, UV–vis, FESEM, EDX, and Raman analyses. The existence of well doped cobalt within the structure of zinc oxide was affirmed by the results of PXRD, EDX, and UV–vis. The FESEM analysis displayed the length and diameter of pure ZnO Nanowires to be 500 ± 0.2 nm and 25 ± 5 nm, while an enlargement was observed in the length and diameter of doped Nanowires due to the doping of cobalt into ZnO. The photocatalytic activity of synthesized samples indicated the culmination of doped cobalt into ZnO in increasing the rate of photocatalyst performance. The optimum sample was 1 % Co-doped ZnO Nanowires that eliminated 89 % of MB with a concentration of 20 mg/Lit in pH = 7. The toxicity effect of synthesized Nanowires on brain glioblastoma cells (U87) was investigated by the means of WST-1 test. Accordingly, the doped ZnO Nanowires induced a more toxic impact on U87 cells when compared to the case of pure zinc oxide Nanowires. Thus, performing a doping process on the nanostructure of ZnO led to increasing its inhibitory effect against U87 cells and intensifying its photocatalytic activity on MB dye.

Effects of As, P and Sb on the output voltage generation of ZnO nanowires based nanogenerator: Mitigation of screening effect by using surface modified ZnO nanowires

Here, we report high output voltage generation by employing p-type ZnO nanowires as an integral part of vertically integrated nanowire generators (VING). Study has been carried out to generate high piezoelectric voltage by introducing impurities to ZnO nanowires from group V (P, As, Sb) elements which worked as acceptor impurities for intrinsically n-type ZnO nanowires by which reverse leakage current through nanowires has been minimized. Three distinct doping concentrations (2, 4 and 6 wt %) of (P, As, and Sb) have been incorporated in ZnO nanowires at room temperature. X-ray photoelectron spectra (XPS) has indicated the presence of SbZn–2VZn, PZn + 2VZn, AsZn–2VZn complexes acceptors for Sb, P, As doping respectively. Gradual rise in piezoelectric output voltage has been observed. P/ZnO nanowires generated output voltages of 0.9 V, 1.45 V and 1.85 V respectively. For As/ZnO nanowires, output voltages are 1.25 V, 1.51 V and 1.92 V and with Sb doping recorded voltage values are 1.78 V 2.1 V and 2.5 V respectively. To Acquire optimal output voltage doped ZnO nanowires have been further oxidized (with O2) to mitigate the screening effect and maximum voltage generated by oxidized ZnO are 2.38 V, 2.86 V, and 3.45 V respectively.

Investigation of the growth of Na+-Doped ZnO nanorods using hydrothermal method and their photoluminescence properties

In this study, the hydrothermal method was used to synthesize Na[Formula: see text]-doped ZnO nanowires with different concentrations of Na[Formula: see text] ions under different synthesis temperatures. First, ZnO films with a thickness of about 300 nm were deposited on glass substrates as a seed layer, and C6H[Formula: see text]N4, Na(NO[Formula: see text]H2O, and Zn(NO[Formula: see text]H2O were used as source materials to grow the Na[Formula: see text]-doped ZnO nanowires using different Na[Formula: see text] concentrations and under different synthesis temperatures. After the Na[Formula: see text]-doped ZnO nanowires were synthesized, their XRD patterns were obtained to analyze their crystal phases. FESEM observations were used to observe the synthesized morphologies, and a fluorescence spectrophotometer was used to show the photoluminescence excitation (PLE) and photoluminescence (PL) emission properties of the Na[Formula: see text]-doped ZnO nanowires. We showed that Na[Formula: see text] precursor concentrations and synthesis temperatures had considerable effects on the crystal phase, surface morphologies, and PL emission and PLE properties of the Na[Formula: see text]-doped ZnO nanowires.

Theoretical examination of defect structures and spin Hamiltonian parameters of manganese (II)- and cobalt (II)-doped ZnO nanowires

This study theoretically investigates the defect structures of Mn2+ at 3 and 10 at. % as well as those of Co2+ at 5 at. % in ZnO nanowires by analyzing their experimental spin Hamiltonian parameters (g factors, hyperfine structure constants A, and zero-field splitting D) based on perturbation formulae in trigonally distorted tetrahedral 3 d5 and 3 d7 clusters, respectively. Unlike the trigonal distortion of the host Zn2+ site in ZnO nanowires, the impurities Mn2+ and Co2+ underwent displacements ΔZ (≈0.0223 and 0.0233 Å for Mn2+, and 0.040 and 0.043 Å for the two Co2+ centers) away from the ligand oxygen triangles along the C3 axis at 3 and 10 at. %, and at 5 at. %, respectively. In light of the significant covalent interactions of the two Co2+ centers, their contributions to the spin Hamiltonian parameters due to the charge transfer mechanism need to be included in the theoretical calculations. The defect structures and spectral properties are also discussed in view of the different crystalline morphologies of the doped samples, which indicate that the values of ΔZ of the Mn2+ centers decreased in low-dimensional materials, whereas those of the Co2+ centers remained nearly constant owing to strong covalence.

PL study of Mn-doped ZnO nanowires

Mn-doped ZnO nanowires have been fabricated through a high temperature vapor-solid deposition process. The low-temperature photoluminescence spectra of the samples show that there are multipeak emissions at the ultra- violet (UV) region (about 3.4–3.0 eV). The excitonic and phonon-assisted transitions in Mn-doped ZnO nanowires were investigated. The results show that there is an obvious oscillatory structure emission at the UV region under low temperature from 12–125 K. The oscillatory structure has an energy periodicity about 70 meV and the oscillatory structure is mainly attributed to longitudinal optical (LO) phonon replicas of free excitons (FX). The multipeak emissions at 12 K are attributed to a donor-bound exciton (DBX, 3.3617 eV), 1LO-phonon replicas of a free exciton (FX- 1LO, 3.3105 eV), 2LO-phonon replicas of a free exciton (FX-2LO, 3.2396 eV), and 3LO-phonon replicas of a free exciton (FX-3LO, 3.1692 eV), respectively. The intensity of UV emission and the efficiency of emission from the Mn- doped ZnO nanowires are improved.

Sensory analysis of hepatitis B virus DNA for medicinal clinical diagnostics based on molybdenum doped ZnO nanowires field effect transistor biosensor; a comparative study to PCR test results

In this paper, a bio-sensing setup for investigating hepatitis B virus deoxyribonucleic acid (HBV DNA) diagnosis including rapid testing and field effect transistor (FET) in label free assay is proposed. The FET biosensor was fabricated by molybdenum doped ZnO nanowires (NWs) in easy method and cost-free approach. The materialized NWs were synthesized by physical vapor deposition (PVD) growth mechanism. The molybdenum dopant could bring about vacancy sites for DNA adsorption and electric charge transfer. The capability of the fabricated biosensor was evaluated by investigating the PCR-verified samples known as True Positive (TP), True Negative (TN), False Positive (FP) and False Negative (FN). The FET biosensor could materialize the clinical tests on samples TP, TN, FP and FN and could distinguish the clinical samples from each other. The designed biosensor showed more precision than the PCR-outcomes by exhibiting more sensitivity on labeled samples known as FN. This research has analytical and comparative study on fabricated biosensor performance. The achieved results show that the biosensor had significant response to samples which have not been carefully detected by PCR test. The fabricated biosensor showed high accuracy, precision, sensitivity, specificity and reproducibility for differentiating (TP), (TN), (FP) and (FN) samples from healthy and normal sample. The response sensitivity was calculated and biosensor showed a detection limit (LOD) of 1 pM. The biosensor demonstrated high response and satisfied signal in the concentration ranges from 1 pM to 10 μM.

Enhanced Organic Gas Sensor Based on Cerium and AU Doped Zno Nanowires Via Low Temperature One-Pot Synthesis

Enhanced Organic Gas Sensor Based on Cerium and AU Doped Zno Nanowires Via Low Temperature One-Pot Synthesis

Optimization of aluminum doped ZnO nanowires for photoelectrochemical water splitting

Undoped and aluminum-doped ZnO nanowire (NW) arrays with high aspect ratio and doping concentration up to 2.0 at.% in Al, were prepared by chemical bath deposition (CBD) technique onto FTO/glass substrates. The morphological, structural, and optical properties of the as-grown NWs were investigated by using electron microscopy, diffraction, and spectroscopic techniques. The prepared samples were used as photoanodes in a photoelectrochemical cell and their effectiveness for water splitting was evaluated. The optimum doping concentration was found to be 0.5 at.%. The increase of the photocurrent density normalized by the specific surface reaches up to 110% (in relation to the neat ZnO photoanode at 1.23 V) for this concentration The improved photocurrent density cannot be accounted for solely by the improvement of the conductivity by Al doping and the change in morphology; hence, the promoting effect of Al ions and the photoactivation of a larger fraction of sites has been evoked.

PbS doped ZnO nanowires films synthesis by thermal evaporation method: Morphological, structural and optical properties

Thermal evaporation technique has been used to prepare PbS doped ZnO Nanowires films growth on Si (100) and glass substrates. EDX technique was employed to investigate the element’s contents of the films materials. Pb and S concentration in the Nanowires films were about at 8% for each one. The XRD pattern showed the structure of ZnO is wurtzite with (002) preferred orientation. Thickness and morphology of the films were explored from cross section of the surface films, respectively, using scanning electron microscopy images. Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) images confirmed the ZnO Nanowires and modifications of the morphology when adding PbS. The film deposited without doping (0 ​wt %) was dense structured. However, PbS: ZnO was Nanowires structure. The optical band gap increased with increase the concentrations of PbS. Photoluminescence measurements PL used to estimate band gap for prepared films. Raman and EDX indicate ZnO Nanowires stoichiometry film.

Fabrication of low Mg content MgxZn1-xO nanowires ultraviolet photosensors via chemical vapour deposition method

To solve the problem that ZnO ultraviolet photosensors is poor in detecting deep ultraviolet light, a method of fabricating Mg doped ZnO nanowires was proposed to adjust the ZnO energy band, so as to improve the sensitivity of ZnO ultraviolet photosensors in detecting deep ultraviolet light. The MgZnO nanowires were characterized by scanning electron microscope(SEM), energy spectrum analysis(EDS), transmission electron microscope(TEM) and other characterization methods. The results show that MgZnO nanowires were successfully prepared. The ZnO nanowire detector and the Mg doped ZnO nanowire detector were test with the 254 nm deep ultraviolet light, and the test results show that the photoresponse of the Mg doped ZnO detector to the 254 nm deep ultraviolet light was enhanced, the photocurrent increased from 0.02 μA to 0.57 μA. The detector is prepared by Mg doped ZnO nanowires, which can effectively improve the ZnO nanowires detectability in detecting deep ultraviolet light. It will provide beneficial reference for the design and preparation of deep ultraviolet detectors.

Significance of Ni doping on structure-morphology-photoluminescence, optical and photocatalytic activity of CBD grown ZnO nanowires for opto-photocatalyst applications

In this work, we study bare and Nickel (Ni) doped ZnO nanostructured thin films synthesized by the chemical bath approach. The as-prepared thin films were characterized extensively by XRD, SEM, PL, and UV–visible spectroscopy before and after Ni incorporation. Finally, the photocatalytic action of all catalysts was assessed using methylene blue (MB) dye degradation under the visible light irradiation. X-ray diffraction analysis approves wurtzite hexagonal structure with predominant orientation along (002) plane, and crystallite size was noticed to reduce from 34 to 32 nm by Ni-doping. The SEM images proved the formation of well-defined nanowire structures. Photoluminescence analysis confirmed the band-edge and defect-related emission peaks. The intensity of PL spectra ensured a decreased value after Ni-doping, suggesting delayed electron-hole pair recombination, which influences the decolorization activity. The 3 wt% Ni-doped ZnO thin film possessed the least optical bandgap value of 3.21 eV. It was observed that the Ni (3%) doped ZnO nanowires showed a significantly improved photocatalytic performance (96%) compared to the pure ZnO nanostructure (83%).

Zinc Vacancy–Hydrogen Complexes as Major Defects in ZnO Nanowires Grown by Chemical Bath Deposition

Crystal defects in unintentionally doped ZnO nanowires grown by chemical bath deposition (CBD) play a capital role on their optical and electrical properties, governing the performances of many nan...

Nitrogen plasma irradiation of Fe doped ZnO nanowire arrays for improved optical properties

This work reports on the ability to improve the optical properties of hydrothermally grown, vertically-aligned arrays of wurzite ZnO and Fe doped ZnO nanowires by means of nitrogen doping during high-powered plasma irradiation. The morphology, structural and optical properties of ZnO, Fe:ZnO NWs and N2 – Fe:ZnO NWs are studied by scanning electron microscopy, grazing incidence X-ray diffraction and UV–visible spectroscopy, respectively, whereas elemental doping of the nanostructures are investigated by means of X-ray photo-electron spectroscopy. SEM micrographs show no discernible morphological differences between the ZnO, Fe:ZnO NWs and N2-Fe:ZnO NWs, however a clear increase in light transmission over the visible to UV range, accompanied by a decrease in optical band gap of 3.261 eV for ZnO NWs to 3.255 eV for Fe:ZnO NWs and ultimately 3.250 eV for N2-Fe:ZnO nanowires is observed. This band gap reduction is ascribed to the presence of a high density of shallow donor states in the bandgap of the ZnO lattice, subsequently causing an overall reshape of the conduction band minimum, caused by filling of oxygen vacancies and substitutional replacement of lattice oxygen by the highly kinetic α-N species during oxynitride, O-Zn-N bond formation. The results suggest that nitrogen doping during plasma irradiation provides a controlled method of deep lattice nitrogen doping that is favorable for improved photo-electrochemical, photovoltaic and photo-response applications of ZnO nanowires.

Growth of n-Ga doped ZnO nanowires interconnected with disks over p-Si substrate and their heterojunction diode application

In this paper, the heterojunction diode based on n-Ga doped ZnO nanowires interconnected with disks/p-Si assembly was fabricated and their low-temperature electrical properties were examined. The Ga-doped ZnO nanowires interconnected with disks were grown over p-Si substrate and studied by numerous techniques to understand the structural, compositional and morphological characteristics. Electrical properties, at lowtemperatures ranging from 77 K–295 K, were examined for the fabricated heterojunction diode assembly both in reverse and forward biased conditions which exhibited an excellent stability over all the temperature range. The detailed electrical characterizations revealed that the current decreases gradually from 1.9 μA, to 0.87 μA to 0.84 μA when temperature increases from 77 K, 100 K to 150 K and then increases gradually from 1.86 μA–3.36 μA and to 9.95 μA when temperature increases from 200 K–250 K and to 295 K, respectively. Both the highest rectifying ratio at 100 K and the lowest one at 295 K occur in the voltage range of 2–5 V.

The highly sensitive impedimetric biosensor in label free approach for hepatitis B virus DNA detection based on tellurium doped ZnO nanowires

The highly sensitive impedimetric biosensor in label free approach for hepatitis B virus DNA (HPV DNA) detection based on tellurium doped ZnO nanowires was fabricated. The NWs were grown by hybrid thin film oxidation in the physical vapor deposition (PVD) mechanism. The morphology characterization of the synthesized NWs was performed by field emission scanning electron microscopy (FESEM) and the images demonstrated that the diameter and the length of the materialized NWs were around 50 nm and several micrometers, respectively. The high-resolution transmission electron microscopy (HRTEM) image indicated that the fabricated NWs were crystalline and their phase characterization was validated by the X-ray diffraction pattern (XRD pattern). The single-stranded DNA (ss DNA) probe was immobilized on the surface of the Te-ZnO NWs. The electrochemical impedance spectra (EIS) measurements showed high response sensitivity after hybridization with complementary oligonucleotides. The biosensor could distinguish complementary target from non-complementary and mismatch oligonucleotides. The HBV biosensor could respond to complementary target in the concentrations range from 1 pM to 1 μM. The limit of detection (LOD) of the biosensor was 0.1 pM. The stability of the HBV DNA biosensor was investigated and biosensor could show 95% of its initial responses after 8 weeks maintenance.

Temperature- and diameter-dependent electrical conductivity of nitrogen doped ZnO nanowires

A modified formula to calculate the axial conductivity of nanowires was proposed based on the one-dimensional quantum state density distribution and Boltzmann transport theory. Numerical simulations of the ZnO nanowires (ZnONWs) and Nitrogen-doped ZnO nanowires (N-ZnONWs) were implemented using data from the first principles calculation. The results indicate that ZnONWs are low-conductivity wide band-gap semiconductors owing to their low carrier concentrations at room temperature, with N-doping increasing the conductivity. The N-ZnONWs carrier concentrations increased with increasing temperature, and possessed significantly higher carrier concentrations than ZnONWs. With an increase in diameter, the ZnONWs conductivities increased, whereas the N-ZnONWs conductivities decreased.

Chemical vapor deposition synthesis of Ge doped ZnO nanowires and the optical property investigation

Ge-doped ZnO nanowires with high quality were prepared with simple chemical vapor deposition method. The morphology, crystal structure and elemental distribution were characterized using SEM (scanning electron microscopy), HRTEM (high resolution transmission electron microscopy) and EDS (energy dispersive spectrometry) mapping approaches. The optical properties were investigated with combination of room-temperature CL (cathode ray luminescence) and variable temperature micro-PL methods. It is found for the first time that a tapered Ge doped nanowire exhibits a thickness-dependent spectrum shift under a cathode-ray excitation, which was interpreted by the electron-lattice interaction model and the band-filling effect of semiconductors. The exciting power dependent emission spectra (lux-luminescent characteristics) at varied temperatures reveal a varied radiative recombination mechanism. At 83 K, free excitons contribute to the emission spectrum, while at 300 K while at 300 K multi-levels related non-radiative transition process largely contributed. The optical property indicates an excellent crystallization of the nanowires with a small amount of defects.