Morphology Of ZnO Research Articles

Growth and Characterization of Sputtered ZnO:ZnGa2O4 Dual-Phase Films on Sapphire Substrates for NO Gas-Sensing Applications

Nitric oxide (NO) released from combustion facilities and automobiles adversely affects the respiratory systems and environment. Hence, the development of a NO gas sensor with high sensing response to measure NO gas levels is significantly commendable. Herein, we report the growth of ZnO:ZnGa2O4 dual-phase films on the c-plane sapphire substrates using radio-frequency magnetron sputtering for NO gas sensors. The microstructures and morphology of ZnO:ZnGa2O4 films were systematically investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy. The XRD patterns revealed the polycrystalline nature of the ZnO:ZnGa2O4 film with (222) preferred orientation. The SEM micrographs showed the presence of grain boundaries in the nanostructures over the surface of the film due to the recrystallization of grains upon annealing the film at 700 °C. This ZnO:ZnGa2O4 film was employed to fabricate the NO gas sensor, which demonstrates significantly high sensor response of 28.6 at 400 °C operating temperature with the quick response time of 8 s and recovery time of 140 s upon exposure to 100 ppm NO gas concentration. The ZnO:ZnGa2O4-based gas sensor is found to be highly selective for NO gas among NO, CO2, and SO2 gases. The gas-sensing mechanism behind the high response of ZnGa2O4-based NO gas sensors is described. The results achieved in this study are particularly important in terms of the development of technologies for the early detection of poisonous and hazardous gases from polluting industries and metropolises, which is crucial for environmental security.

Preparation and performance of epoxy resin-based thermal conductive composites with different morphologies of ZnO

Preparation and performance of epoxy resin-based thermal conductive composites with different morphologies of ZnO

Nitrogen-doped ZnO microspheres with a yolk-shell structure for high sensing response of triethylamine

Triethylamine is a kind of volatile organic compounds, which is harmful and toxic to the environment and people. Therefore, triethylamine gas sensors are increasingly demanded in practical applications. In this work, we synthesized the nitrogen-doped ZnO yolk-shell microspheres with mesoporous distribution by a facile strategy of hydrothermal-annealing. The influence of the amount of hexamethylene tetramine on the morphology of yolk-shell ZnO was studied and the yolk-shell ZnO (YSZ-3) prepared with 0.3 g hexamethylene tetramine showed the best gas sensing performances for triethylamine at 370 ℃. The response to 100 ppm triethylamine was 133. Moreover, a low triethylamine detection limit was achieved (1 ppm), with a response value of 2.6. The prepared yolk-shell ZnO showed an excellent selectivity to triethylamine, over ethanol, methanol, acetone, formaldehyde, ammonia, and toluene. Furthermore, YSZ-3 offered a low theoretical detection limit (42.4 ppb) and a fast response and recovery (20 s/5 s). Finally, the growth mechanism and gas sensing mechanism of yolk-shell ZnO were discussed.

Green Synthesis of ZnO and V-Doped ZnO Nanoparticles Using Vinca rosea Plant Leaf for Biomedical Applications.

The present work focused on the synthesis of Vinca rosea leaf extract derived ZnO and vanadium-doped ZnO nanoparticles (V-ZnO NPs). The chemical composition, structural, and morphology of ZnO and vanadium-doped ZnO NPs were examined by FTIR, XRD, and SEM-EDX. The FTIR confirmed the presence of functional groups corresponding to ZnO and vanadium-doped ZnO NPs. SEM-EDX clearly indicated the morphology of synthesised NPs; the hexagonal crystal of NPs was confirmed from XRD. In addition, the cytotoxic effect of ZnO and V-ZnO NPs was estimated against the breast cancer (MCF-7) cell line. From the assay, Vinca rosea (V. rosea) capped ZnO NPs have shown improved cytotoxic activity than that of Vinca rosea capped V-ZnO NPs. ZnO and vanadium-doped ZnO NPs showed the strongest antibacterial activity against Enterococcus, Escherichia coli, Candidaalbicans, and Aspergillus niger. The α-amylase inhibition assays demonstrated antidiabetic activity of synthesised NPs. From the assay test, results obtained Vinca rosea capped ZnO nanoparticles prepared using the green approach showed high effective antioxidant, antidiabetic activity, and anticancer activity than vanadium-doped ZnO NPs.

Hydrothermally synthesized CeO2/ZnO nanocomposite photocatalysts for the enhanced degradation of Reactive Orange 16 dye

In this work, in order to improve the photocatalytic efficiency of ZnO, the optimal CeO2 content in ZnO powders was determined by varying the quantity of CeO2 from 0 to 10 mol%. The structural, microstructural, optical, textural, and photocatalytic properties of the hydrothermally obtained ZnO and CeO2/ZnO nanocomposites have been investigated by using the XRPD, FESEM, HRTEM/SAED, BET, and UV–Vis techniques. Detailed characterization revealed that CeO2, having spherical nanodots of about 5 nm with a large surface area, was distributed onto the ZnO surface, whose crystallites displayed a bimodal distribution, from nano-to micro-crystals. The morphology of ZnO is a combination of nanograins and microrods that further makes a 3-D tie-like morphology. The nanocomposite containing 5 mol% of CeO2 showed about 30% better photocatalytic efficiency in the degradation of Reactive Orange 16 dye compared to other samples under simulated solar radiation. In addition, the kinetics and mechanism of photocatalytic degradation were also proposed based on the photocatalytic activity and scavenger tests.

Nanoporous ZnO structure prepared by HiPIMS sputtering for enhanced ozone gas detection

A high performance ozone gas sensor is fabricated using high power impulse magnetron sputtering (HiPIMS) process with nanoporous ZnO as the sensing material which is deposited on micro electro mechanical systems (MEMS) device. The morphology and nanostructure properties of ZnO were tested with XRD, SEM, TEM, EDS and XPS. As the sensor is tested at different temperatures, the sensor showed high sensing response at 200 °C operating temperature and with 400 °C annealed sample of nanoporous ZnO sensor. Low concentrations of ozone were chosen to obtain best possible sensing response characteristics ranging from 50 ppb to 1000 ppb. At 1000 ppb, sensor recorded a high 638% sensing response at 200 °C optimal temperature. Selectivity test and effects of relative humidity data is presented in the study, where sensor had high selectivity towards O3 gas and the sensing response showed decreasing trend with increase in relative humidity. The reason behind sensing mechanism of the nanoporous ZnO sensor is explained due to the adsorption and desorption phenomenon on the surface of ZnO sensor.

Experimental investigation of nanofluids for heat pipes used in solar photovoltaic panels

The current study is aimed to measure and analyze the impact of temperature (10°C < T < 90°C) and particle concentration (0.05% < ϕ < 1.5%) on thermo-physical properties of TiO2, ZnO and CuO nanoparticles suspended in Therminol-55. The nanoparticles were characterized by using various techniques, including TEM, XRD, FTIR, TGA/DSC. TEM images reveal that the morphology of TiO2 and ZnO as spherical nanoparticles whereas that of CuO is in the form of flakes. XRD pattern for TiO2, ZnO and CuO nanoparticles possess anatase, heaxagonal and monoclinic phase respectively. TGA results show that that TiO2 losses less mass than the ZnO and CuO nanoparticles at each stage of decomposition. Thereby making it more stable thermally as compared to the other samples. Two-step method has been employed to formulate stable Therminol-55 based nanofluids containing TiO2, ZnO and CuO nanoparticles for varying particle concentrations. Results show that the thermal conductivity of suspensions containing solid conducting particles increase with increasing nanoparticle content and temperature of dispersions in the fluid. The thermal conductivity of TiO2/Therminol-55, ZnO/Therminol-55 and CuO/Therminol-55 nanofluids increases up to 17.62%, 21.55% and 24.32% at particle concentration of 1.5 wt%. Further, the experimental results demonstrate that the density of nanofluids increased significantly with increase in concentration and decreased with temperature. Surface tension of nanofluids shows decrease with increase in particle concentration. This indicates that adding nanoparticles improve thermo-physical properties of nanofluid, making it suitable for use in heat pipe. The measured data for thermal conductivity and density are compared with existing theoretical models of nanofluids to check the effectivity of conventional models. A multi-variable new generalized correlations for thermal conductivity and density of Therminol-55 based nanofluids containing TiO 2, ZnO and CuO nanoparticles are proposed.

UV Suppression in photoluminescence emission and improved photocatalytic activity under sunlight in nanoassemblies and nanocrystals of ZnO

The objective of present study is to analyse the impact of alterations in the shape and size of ZnO on PL emission and photocatalytic activity of ZnO nanostructures. The study also aims at addressing the knowledge gap between synthesis approach and its role in governing the optical, morphological and photocatalytic behaviour. Here, we report the facile and controlled synthesis of nanoassemblies (NA) and nanocrystals (NC) of ZnO via soft chemical approach. The synthesized ZnO nanostructures were characterized using TEM, SEM, UV–vis and photoluminescence (PL) measurement. The morphology of ZnO is tuned by adjusting the molar ratio of DEG and water whose impact is also noticed on the PL emission spectra. PL analysis revealed that the UV emission (378 nm) and defect levels attributed to Zn interstitial (Zni) and oxygen interstitial (Oi) are stabilized at ambient condition. However, UV band gap emission peak is significantly reduced making it lesser distinct by introducing appropriate amount of water in diethylene glycol (DEG) solvent during ZnO synthesis. Such controlled nanostructured growth demonstrates potential for sustainable photocatalytic activity under both UV and Sunlight irradiation. The study shows 100% photodegradation efficiency for ZnO NA and it get completely irradiated methylene blue dye within 90 min under UV light, whereas only 70% dye is degraded in 100 min for ZnO NC. Under natural Sunlight, ZnO NA has been achieved 97% degradation efficacy in 75 min; however, ZnO NC has degraded only 89% of dye. Further, the degradation of dye over ZnO was observed to follow pseudo first order reaction kinetic model that is used to determine the rate constant of the reaction.

Effect of Mg Doping on the Structural, Optical and NO<sub>2</sub>-sensing Properties of ZnO Thin Films Prepared by Modified SILAR Method

In this report, we have prepared undoped and Mg-doped ZnO thin films by a modified successive ionic layer adsorption and reaction (SILAR) method. The structural, surface morphological, chemical compositional, and optical properties of pure and Mg-doped ZnO thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), ultraviolet-visible (UV-VIS) spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy. The XRD patterns of undoped and doped films have wurtzite crystal structures with preferential orientation along the (101) plane, without any secondary phases. Addition of Mg into host ZnO influenced surface morphology of the film. Predominant nanorods-like surface morphology of undoped ZnO turned to be predominant nanoflowers-like surface morphology after addition of Mg. UV-VIS spectra showed that the energy band gap of films increased with increase Mg doping concentration. EDS and FT-IR spectroscopy confirmed the successful Mg doping. Gas sensing properties of the undoped and Mg-doped ZnO thin films were tested based on the electrical resistance changes upon exposure to different concentrations of a NO2 gas at 200°C operating temperature. Mg-doped ZnO (3 wt%) showed higher response compared to other wt% and exhibited the highest responses of 2.95, 9.51, and 9.93 when exposed to 25, 50, and 100 ppm concentrations of the NO2 gas at 200°C, respectively. The response/recovery time of the Mg-doped ZnO thin film were 6/75, 14/88, and 14/89 s at 25, 50, and 100 ppm, respectively.

Solvothermal synthesis of ZnO with controllable morphology

ZnO structures were prepared by a two-step procedure. Firstly ZnO were synthesized by hydrothermal method with methanol as solvent and then annealed in air. The structure and morphology of the samples were analyzed by XRD and SEM. The chemical composition of the samples was determined by XPS. The optical properties were analyzed by fluorescence spectroscopy. The results show that the reaction time has an important influence on the morphology, chemical composition and optical properties of ZnO.

A Green Synthesis Method to Tune the Morphology of CuO and ZnO Nanostructures

Background: Green synthesis of nanomaterials has gained interest over the years as it has many benefits compared to conventional methods. Green methods are non-toxic and economic due to the use of aqueous extracts as reducing agents. Yerba mate is a widely used herb in South America, showing an available and economical alternative to conventional methods Methods: Different copper and zinc nanostructures were obtained using yerba mate extract (Ilex paraguariensis) as a reducing and capping agent. Furthermore, adjusting NaCl concentration and temperature, it was possible to successfully tune and examine the morphology of the resulting nanostructures by Scanning Electron Microscopy (SEM). Phenolic oxidation was evaluated by Raman spectroscopy and Fourier Transform Infrared Spectroscopy (FT-IR) to assess the role of yerba mate extract in the reaction. Moreover, antimicrobial activity versus Pseudomonas aeruginosa was assayed, and antioxidant activity was performed by the DPPH method. Results and Conclusion: The present study reveals a powerful method to obtain zinc and copper nanostructures, showing a logarithmic reduction of Pseudomonas aeruginosa of 2.14 and 5.92 CFU/mL at 96 hours respectively and scavenger activity of 42% and 22%, respectively. These properties highlight the potential of the nanomaterials for applications in catalysis, textile, biomedical and agricultural fields.

Influence of Mechanical Properties on the Piezoelectric Response of UV-Cured Composite Films Containing Different ZnO Morphologies

ZnO flower-like (ZFL) and needle (ZLN) structures were synthesized and embedded into UV-curable acrylic resin (EB), with the aim to study the effect of filler loading on the piezoelectric properties of the resulting composite films. The composites showed uniform dispersion of fillers within the polymer matrix. However, by increasing the filler amount, the number of aggregates increased, and ZnO fillers appeared not to be perfectly embedded in polymer film, indicating poor interaction with acrylic resin. The filler content increase caused an increase in glass transition temperature (Tg) and a decrease in storage modulus in the glassy state. In particular, compared with pure UV-cured EB (Tg = 50 °C), 10 wt.% ZFL and ZLN presented Tg values of 68 and 77 °C, respectively. The piezoelectric response generated by the polymer composites was good when measured at 19 Hz as a function of the acceleration; the RMS output voltages achieved at 5 g were 4.94 and 1.85 mV for the composite films containing ZFL and ZLN, respectively, at their maximum loading levels (i.e., 20 wt.%). Further, the RMS output voltage increase was not proportional to the filler loading; this finding was attributable to the decrease in the storage modulus of the composites at high ZnO loading rather than the dispersion of filler or the number of particles on the surface.

Contribution of surface carboxyl of cellulose in the formation mechanism and interfacial catalysis activity of ZnO/cellulose nanocomposites

The morphology, structure, and dispersion of photocatalysts play important roles in tailoring the surface active sites, photocatalytic productivity, and light utilization efficiency. Cellulose has been widely used in supporting and dispersing ZnO catalysts. However, surface groups of cellulose were ignored as a factor governing ZnO morphology. This work aims to explore the effects of cellulose surface groups on the formation and properties of ZnO catalysts. The reactivity, electronegativity, ion adsorption, and dispersion of the cellulose are improved after the introduction of carboxyl groups, which is beneficial to observe the induction of cellulose surface charge on the growth of ZnO. The results indicate that the diameter, sheet number, and thickness of flower-like ZnO in porous ZnO/cellulose nanocomposites are increased with the enhancement of cellulose surface electronegativity. The ZnO/cellulose nanocomposites with surface carboxyl content of 1.63 mmol*g−1 and zeta potential of –52.6 mV (ZnO/TOCNF3) have the highest photocatalytic activities and recycling for MO degradation due to the exposure of the interfacial active sites and strong electrostatic adsorption between carboxyl and ZnO. These findings provide a green method to regulate the formation and properties of catalysts by adjusting the surface electronegativity of cellulose nanofibers.

The Application of GaN/ZnO Heterojunction in Water Splitting

Different morphology of ZnO were deposited on GaN substrate using magnetron sputtering method by changing deposition conditions. The ZnO and GaN can form II-type heterojunction due to its higher conduction and lower valence band compared to GaN. The electric field generated by space charge region can separate the photo generated carriers more promptly. In the photocatalytic test, the best performance of GaN/ZnO photoanode with fine crystal quality is about 1.39 times compared to planar GaN. Our research paves a new way for the application of GaN in water splitting performance.

Morphological effect of one-dimensional ZnO nanostructures on the photocatalytic activity

The chemical and physical properties, including photocatalytic activity, can be tuned by altering the morphology of the ZnO nanostructures. Herein, the correlation between the physical properties (optical and shape) of various one-dimensional (1-D) ZnO and their photocatalytic performance was evaluated. The 1-D ZnO nanostructure (nanorods (NRs), nanowires (NWs), and nanotubes (NTs)) on a glass substrate were successfully synthesized using a hydrothermal method with varying precursor concentrations and reaction temperatures. By reducing the seeding precursor concentration, the morphology of ZnO changed from NRs to NWs, whereas the NRs were transformed into NTs when the incubation time was prolonged. XRD and SEM analysis confirmed the formation of hexagonal wurtzite ZnO NRs, NWs, and NTs with trunk diameters of 151 nm, 60 nm, and 157 nm, respectively. Furthermore, the UV-light photocatalytic efficiency test using methylene blue exhibited that the one with the highest degradation efficiency was ZnO NTs (67.43%), followed by ZnO NWs (53.76%) and ZnO NRs (46.10%). The morphology and physicochemical properties study revealed that the large polar face owned by ZnO NT, which is augmented by the high UV absorption and large photocurrent density, enhanced their photocatalytic efficiency.

Scalable hierarchical wood/ZnO nanohybrids for efficient mechanical energy conversion

Owing to the hierarchical structure, easy multi-functionalization and favorable mechanical properties, wood could harvest electricity from mechanical energy through piezoelectric behavior. In this work, a scalable method to synthesize wood/ZnO composite with multilayered ZnO morphologies is reported for efficient mechanical energy conversion. The synthesis includes charged wood template fabrication, precursor infiltration, and ZnO hydrothermal growth, resulting in controlled ZnO morphologies and distributions while maintaining the hierarchical structure of the wood. Stereo-digital image correlation (stereo-DIC) investigated the relationship between deformation and piezoelectric performance, which revealed the homogeneous distribution of multilayered ZnO enhance piezoelectric performance. The output voltage of wood/ZnO was 1.5 V under periodic mechanical compression (8–10 N) for 300 cycles, while the output current was 2.91 nA. The scalable synthesis strategy and piezoelectric performance are significant for the design of advanced wood nanocomposites for sustainable and efficient energy conversion systems.

Promoted catalytic activity of CO oxidation at low temperatures by tuning ZnO morphology for optimized CuO/ZnO catalysts

Catalytic oxidation of CO is an effective route to eliminate the pollution of automobile exhaust. Tuning the fraction of exposed polar and non-polar crystal facets in ZnO provides an effective strategy to tailor metal-oxide interfacial active sites. Herein, the morphology of ZnO support was tuned to alter the fraction of exposed (002) polar/(100), (101) non-polar facets. ZnO nanodisks and nanorods were prepared, followed by deposition of ∼3.1 ± 0.9 nm CuO nanoparticles. The impact of the ZnO morphology upon CuO deposition and catalytic activity towards CO oxidation were investigated. The CuO/ZnO derived from ZnO nanodisks (NDs) with the most exposed (002) polar plane exhibited more than 2 folds higher catalytic activity at 150 °C than that over CuO/ZnO with commercial ZnO support (CuO/ZnO-C), highlighting the morphology influence of ZnO. For its enhanced catalytic activity and cyclic stability, the CuO/ZnO-NDs could be a promising catalyst for CO oxidation.

Preparation and Photocatalysis Characteristics of Flower-like ZnO by Microwave Method

Flower-like ZnO was prepared by a simple and efficient microwave method at different microwave times. The effect of microwave time on the structure and morphology of the flower-like ZnO was analyzed systematically by XRD, SEM, PL and other equipment, the photocatalysis properties of flower-like ZnO were analyzed systematically through the degradation effect of ZnO on methyl orange. With the increase of microwave time, the shape of flower-ZnO was changed, it was bud at 10 min, then became flower-like gradually, and stacked reunion at 40 min. photoluminescence results showed green emission peaks at 536nm, photoluminescence intensity of ZnO prepared at 20 min was weakest, the photocatalytic efficiency of ZnO were not the same at different times, photocatalytic efficiency of ZnO prepared at 20 min and 40 min were 67% and 58.3% respectively, and photocatalytic efficiency of ZnO prepared at 10 min, 15 min, 30 min were 86.7%, 87.1%, 82.1% respectively.

Development of Eco-Friendly TiO2 Doped ZnO Nanorods Based Dual Functional Sensor for the Sewage System Monitoring

Pertaining to the drainage of urban runoff and the expulsion of sewage, sewer systems are a vital component of urban engineering. Owing to this, a dual functional sensor to detect the toxic gases and pipeline leakages was developed with TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> doped (1, 3 and 5Wt. %) ZnO nanorods using a wet chemical approach. The morphological and structural analysis depicts the formation of nanorods morphology and characteristic ZnO hexagonal wurtzite structure (dominant (002) peak plane) despite doping. A decrease in bandgap (optical analysis −3.03 eV) and internal resistance (Nyquist plot–74 Ω) was observed when doped with 5Wt.% of TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . A distinguishing p-n junction curve was observed in all the doped samples during the photoconductivity (J-V) study. A systematic experimental exploratory of the developed sensors at room temperature unfolds the improved dual functional property of the developed sensors when exposed to target gases (10 ppm) (CH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> –0.60 and CO–0.64) and acceleration (2.45 V at 1 g).

Flower-like and nanorods ZnO deposited on rGO as efficient photocatalysts for removal of polychlorinated biphenyls (PCBs)

PCBs were used for several decades as coolants, lubricants in transformers, plasticizers, and dielectric fluids, being highly carcinogenic and representing a severe environmental problem in soil and water. Pure and modified TiO2 has been the most studied photocatalyst looking to degrade PCBs into less toxic products. Lately, ZnO-graphene composites have played an essential role in the photocatalytic degradation of various toxic organic compounds. In this work, ZnO nanostructures were coupled with reduced graphene oxide (ZnO-rGO) via a one-pot microwave-assisted hydrothermal route. As a result, the composites exhibited improved photocatalytic performance for PCBs degradation compared to ZnO nanoparticles. Thus, this research provides an in-situ method to grow different morphologies of ZnO on rGO.