Rod-like Zinc Oxide Research Articles

Tailoring of Zinc Oxide-based microstructures to efficiently promote piezocatalytic water oxidation and oxygen production

Two zinc oxide (ZnO) nanomaterials, exhibiting distinct morphologies, were synthesized in wurtzite phase through chemical precipitation. The elongated shape rod-like ZnO (R-ZnO) exhibited more pronounced piezoelectric characteristics compared to the more compact flower-like ZnO (F-ZnO). Detailed characterization including piezoforce microscopy, finite element simulation, revealed that the remarkable piezoelectric properties of R-ZnO are due to its strongly anisotropic structure, enabling significant mechanical deformation under ultrasound in aqueous suspension. The piezocatalytical degradation of these materials was assessed using methylene blue as a test organic dye across various ultrasound frequencies, with R-ZnO consistently outperforming F-ZnO. This highlighted the impact of structural deformability on piezocatalytic efficiency. Additionally, the capability of R-ZnO to facilitate oxygen evolution from water through ultrasound-induced stress was explored in an oxygen-free environment. Our findings demonstrate that R-ZnO can effectively catalyze water oxidation and produce oxygen directly, showcasing its potential as a standalone catalyst for environmental remediation and sustainable chemical processes.

Antibacterial effect of novel dental resin composites containing rod-like zinc oxide

Abstract Dental resin composite materials are widely used as dental fillings; however, the accumulation of microbes and the resulting secondary caries often leads to filling failure. ZnO, an inorganic antibacterial material, exhibits effective antibacterial properties and is considered safe for use. In this study, rod-like ZnO was prepared by using the atmospheric-pressure hydrothermal method, and its microstructure and antibacterial effects on Streptococcus mutans were studied. Subsequently, we created modified resins by incorporating rod-like ZnO at varying mass fractions and analyzed their morphological characteristics and elemental distributions. The antibacterial effectiveness, biocompatibility, and mechanical properties of these materials were examined using in vitro experiments. The results indicated that the rod-like ZnO exhibited a complete hexagonal wurtzite structure, with columnar dimensions of approximately 2.5 μm in length, 0.8 μm in diameter, and a lattice spacing of 0.2544 nm. The growth, biofilm formation, and biofilm destruction of S. mutans were significantly inhibited at 1/4, 1/2, 3/4, and 1 times the minimum inhibitory concentration. The rod-like modified resin, with mass fractions of 2.5, 5, and 7.5 wt%, exhibited evident inhibitory effects on S. mutans biofilm formation. These modified resins demonstrated no cytotoxicity toward HGF-1 cells and exhibited enhanced compressive strength. Therefore, rod-like ZnO modified resin has promising potential for the treatment of dental caries.

Polypyrrole Decorated Flower-like and Rod-like ZnO Composites with Improved Microwave Absorption Performance.

In this study, zinc oxide (ZnO)/polypyrrole (PPy) composites with flower- and rod-like structures were successfully fabricated by in situ polymerization and the hydrothermal method and used as microwave absorption (MWA) materials. The surface morphologies, crystal structures, and electromagnetic features of the as-prepared samples were measured by field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and vector network analyzer (VNA). The results show that the conductive polymer PPy was successfully decorated on the surface of ZnO substrates. The MWA ability of flower- and rod-like ZnO/PPy composites is significantly enhanced after introduction of PPy. Rod-like ZnO/PPy composites exhibited superior MWA properties than those of flower-like ZnO/PPy. The former achieved a minimum reflection loss (RLmin) of −59.7 dB at 15.8 GHz with a thickness of 2.7 mm, and the effective absorption bandwidth (EAB, RL < −10 dB) covered 6.4 GHz. PPy addition and stacked structure of rod-like ZnO/PPy composites can effectively improve the dielectric properties, form multiple reflections of incident electromagnetic waves, and generate an interfacial polarization effect, resulting in improved MWA properties of composite materials.

Dendrite-suppressing separator with high thermal stability by rod-like ZnO coating for lithium batteries

The application of lithium (Li) metal as an anodic electrode for potential use in Li batteries has of late attracted much attention. This is because of its higher theoretical energy capacity (3860 mAh g−1) and negative potential (−3.04 V vs. standard hydrogen electrode (SHE)). However, Li metal anode possesses its own problem and chief being the formation of Li dendrites. Acuminate Li dendrites can pierce through the polyolefin separator causing the battery to short and this can potentially lead to fire. To buttress this problem, we synthesized and applied rod-like zinc oxide (ZnO) nanoparticles as a coating material on separators for suppressed dendrite formation in Li metal batteries. The cells with the coated separator showed improved electrochemical performance with an 83.4% capacity retention compared to the pristine separator with 65.5% after 100 cycles. This was due to suppressed dendrite formation. These results show that rod-like ZnO nanoparticle is a potential candidate for use as a coating material for separators in Li metal batteries.

Low temperature structure tunability of zinc oxide nanostructures using milk protein casein

Spherical, flower and rod-like zinc oxide nanostructures have been successfully biosynthesized at 70 °C in the presence of milk protein casein through a simple precipitation method. The concentration of casein in an alkaline medium determines the structure of zinc oxide. The chemical synthesis of highly crystalline zinc oxide nanostructures is accomplished at relatively low processing temperature using casein. X-ray diffraction studies confirm the phase purity and crystalline nature of zinc oxide nanostructures. Morphological changes in the samples were identified through electron microscopic images. Casein linkage with the ZnO nanostructures was confirmed by Fourier Transform Infra-red spectroscopy. The role of casein on the morphological features has been explained on the basis of its self-assembling nature, copolymerization, and secondary structure formation. The effects of morphological change in the optical properties are studied using a UV-visible absorption and photoluminescence spectroscopy. The results indicate that casein is a good mediator for the morphology-controlled growth of nanostructures at moderately low temperatures.

In-Suspension Growth of ZnO Nanorods with Tunable Length and Diameter Using Polymorphic Seeds

Nanostructured zinc oxide (ZnO) is an important material that finds application in numerous fields spanning from catalysis to optoelectronics. Rodlike ZnO nanostructures are of particular interest,...

Photocatalyst ZnO nanorod arrays on glass substrates: the critical role of seed layer in nanorod alignment and photocatalytic efficiencies

The surfaces of the wet-etched and activated glass substrates were first seeded by a simple dip-coating method using the zinc acetate precursor solutions with and without polyvinyl alcohol (PVA). Then, the substrates with two kinds of freshly prepared seed layers (i.e. with and without PVA) were annealed at 250 and 400 °C. Seed-mediated growth of rod-like zinc oxide (ZnO) nanostructure arrays by a chemical bath deposition was carried out as the second step in the formation of continuous ZnO films. PVA, which was added to the seed precursor solution, increased the vertical alignment of the ZnO nanorods along the c-axis. This was confirmed by the appearance of the strong (002) X-ray diffraction peak and by the cross-sectional scanning electron microscope (SEM) images of the films. Even though the well-aligned nanorods were synthesized on the PVA-modified seed layer, they exhibited poor photocatalytic activities in the degradation of C.I. Acid Red 88 azo dye compared with the more randomly aligned ones. The color removal efficiencies of the “random” nanorods (i.e. without PVA modification) under ultraviolet A light illumination were nearly two times higher than those of the well-aligned nanorods.

Zinc oxide with dominant (1 0 0) facets boosts vulcanization activity

The effect of zinc oxide (ZnO) with different crystal facets on the vulcanization activity efficiency was studied via experiments and theoretical calculation. Two types of ZnO particle with the similar size and specific surface, one with more (0 0 1) facets (table-like ZnO) and the other with more (1 0 0) facets (rod-like ZnO), were used to investigate the effects of different facets on the vulcanization activity. The results of curing rate index (CRI) suggested that rod-like ZnO has a faster cure rate than table-like ZnO and rod-like ZnO has a higher vulcanization activity efficiency than table-like ZnO because of higher cross-link density in the styrene butadiene rubber (SBR) composites cured by rod-like ZnO crystal. The DFT calculation results showed that the value of ZnO binding energy on the crystal face of rod-like ZnO was lower than that of table-like ZnO, which indicated that more Zn2+ would be released into the rubber matrix during the process of vulcanization and it would efficiently promote the curing process. It was proposed that the vulcanization activity of ZnO was highly relative with the ZnO exposed facets, which is in the order of (1 0 0)1 > (0 0 1) > (1 0 0)2 > (0 0 1¯), which was consistent with the experiment results.

Enhanced sunlight photocatalytic degradation of methylene blue by rod-like ZnO-SiO2 nanocomposite

This work aims to develop a novel and economical rod-like zinc oxide–silicon dioxide (ZS) nanocomposite by a simple co-precipitation method with different surfactants, such as cationic surfactant cetyl triethylammonium bromide (CTAB), non-ionic polymer polyvinyl pyrrolidone (PVP), and an anionic surfactant sodium dodecyl sulfate (SDS). The phase identification, surface topography and optical properties were analyzed by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), UV-Visible and Photoluminescence Spectroscopy. The photocatalytic degradation efficiency of the prepared nanocomposite was measured using model organic pollutant of methylene blue (MB) in water under sun light irradiation. Due to surface plasmon resonance (SPR) effect of SiO2 nanoparticles, ZS nanocomposite shows an absorption peak (434 nm) in the visible region. Hence the maximal MB degradation efficiency of 97.8% was achieved under 90 min of sunlight irradiation. Among the three surface-active agents, cationic surfactant shows the highest degradation ability with ZS nanocomposite. This work will open a new platform for further development of ZS-based nanocomposites to solve the global photocatalytic and waste water treatment problem.

Controllable preparation and photocatalytic activity of ZnO microstructures with different morphology

Zinc oxide (ZnO) microstructures were successfully prepared by hydrothermal synthesis with PEG4000 at 120°C for 24 h. The crystalline phase and morphology of ZnO microstructures were characterised by X-ray diffraction and scanning electron microscopy. The results show that the rod-like, flower-like and dumbbell-shaped ZnO microstructures can be easily controlled by varying the amount of PEG4000. The photoluminescence spectra of ZnO microstructures with different morphology at room temperature show four emission peaks at about 362, 389, 421 and 487 nm. The photocatalytic activities of ZnO microstructures are evaluated by degradation of methylene blue (MB) under ultraviolet light irradiation, and the degradation rates of MB with rod-like, flower-like and dumbbell-shaped ZnO microstructures reached 94.8, 95.4 and 70.9%, respectively.

A photoelectrochemical biosensor for determination of DNA based on flower rod-like zinc oxide heterostructures

The work describes a photoelectrochemical (PEC) biosensor for the detection of DNA. It employs oriented hierarchical ZnO flower-rod architectures (ZnO FRs) and DNA dendrimers. ZnO FRs act as photoactive material that yields a photocurrent of up to 23 μA. The photogenerated electron transfer is inhibited once the probe DNA and the target DNA oligonucleotides hybridize, and this results in a reduced photocurrent. The use of DNA dendrimers with scores of DNA branches further amplifies the signal of the PEC biosensor. The PEC sensor displays a response that is linear in the DNA concentration range from 10 fM to 0.1 μM with a detection limit of 3.7 fM (at S/N = 3). The sensor was applied to the determination of DNA in human serum samples and was found to work with acceptable accuracy. Due to the use of ZnO FRs and DNA dendrimers, the assay is highly sensitive, rapid, and repeatability.

Efficient Electron Injection by Size- and Shape-Controlled Zinc Oxide Nanoparticles in Organic Light-Emitting Devices

Three different sized zinc oxide (ZnO) nanoparticles were synthesized as spherical ZnO (S-ZnO), rodlike ZnO (R-ZnO), and intermediate shape and size ZnO (I-ZnO) by controlling the reaction time. The average sizes of the ZnO nanoparticles were 4.2 nm × 3.4 nm for S-ZnO, 9.8 nm × 4.5 nm for I-ZnO, and 20.6 nm × 6.2 nm for R-ZnO. Organic light-emitting devices (OLEDs) with these ZnO nanoparticles as the electron injection layer (EIL) were fabricated. The device with I-ZnO showed lower driving voltage and higher power efficiency than those with S-ZnO and R-ZnO. The superiority of I-ZnO makes it very effective as an EIL for various types of OLEDs regardless of the deposition order or method of fabricating the organic layer, the ZnO layer, and the electrode.

Composite of acicular rod-like ZnO nanoparticles and semiconducting polypyrrole photoactive under visible light irradiation for methylene blue dye photodegradation

Nanoparticles of zinc oxide (ZnO) with acicular rod-like morphology were synthesized using a bicontinuous microemulsion and coated with polypyrrole (PPy), by polymerization in the presence of dioctyl sodium sulfosuccinate (AOT) surfactant with ammonium persulfate as oxidizing agent to obtain nanocomposites of ZnO/PPy. The resulting material was characterized by FTIR, Raman spectroscopy, and scanning electron microscopy. The synthesized nanocomposite consisted of ZnO nanoparticles immersed in a polypyrrole matrix with a conductivity of 6.4 × 10−6 S/cm. The synthesized nanocomposite was tested in the photodegradation of methylene blue (MB) dye under visible light irradiation resulting in photodegradation efficiency of 95.2 % after 60 min of irradiation using 3.6 g/L of nanocomposite in an aqueous solution of MB at 20 mg/L. Pseudo first-order kinetics were used to describe the photodegradation reactions.

Enhanced gas sensing properties of flower-like ZnO nanostructure to acetylene

Well dispersed flower-like and rod-like zinc oxide (ZnO) microstructures were successfully synthesised by hydrothermal method with the assistance of hexadecyl trimethyl ammonium bromide. Microstructures and surface morphologies for both samples were characterised by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and high resolution transmission electron microscopy. Gas sensors were fabricated by screenprinting the as prepared ZnO nanostructures onto planar ceramic substrates. Then, their gas sensing properties were systematically investigated towards acetylene gas (C2H2). The products exhibit a high, reversible and fast response to C2H2 gas, and the flower-like ZnO architecture exhibits a better activity.

Blue-emitting photoluminescence of rod-like and needle-like ZnO nanostructures formed by hot-water treatment of sol–gel derived coatings

The morphological evolution of the zinc oxide (ZnO) nanostructures generated by hot-water treatment (HWT) of sol–gel derived coatings as a function of temperature from 30 to 90°C was investigated. With increasing HWT temperature, the ZnO crystals evolved from nanoparticles to rod-like and needle-like nanostructures. High-resolution transmission electron microscope observations of rod-like and needle-like nanostructures generated at 60 and 90°C indicated single crystal ZnO wurtzite structure was obtained. All the hot-water treated samples exhibited blue emission at approximately 440nm in room temperature. The intensity of blue emission increased with higher HWT temperatures. The unique photoluminescence emission characteristic remained even after heat-treatment at 400°C for 1h. As the emission peak obtained in our work is approximately 440nm (2.82eV), the emission peak is corresponding to the electron transition from the interstitial Zn to the top of valence band. This facile formation of blue-emitting ZnO nanostructures at low-temperature can be utilized on substrate with low thermal stability for optoelectronic applications such as light emitting devices and biological fluorescence labeling.

Preparation of ZnO nanopowder by a novel ultrasound assisted non-hydrolytic sol–gel process and its application in photocatalytic degradation of C.I. Acid Red 249

Abstract Rod-like zinc oxide (ZnO) nanopowder was synthesized from zinc acetate via an ultrasound assisted non-hydrolytic sol–gel process. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–vis spectroscopy. X-ray diffraction confirmed that the as-prepared nanopowder was excellently crystallized. TEM images displayed the samples consisting of rod-like nanocrystallites of about 30 nm width and 50–70 nm length. A plausible nonhydrolytic alcoholysis route based on the well-known ester-elimination reaction that involved the nucleophilic attack of the hydroxyl group of diethylene glycol on the carbonyl carbon atom of zinc acetate was proposed and confirmed by gas chromatography–mass spectroscopy (GC–MS) analysis. Diethylene glycol not only acted as a solvent, but also acted as a reactant and as a capping agent, limiting particles growth and preventing their agglomeration. Photocatalytic degradation of C.I. Acid Red 249 (AR249) was carried out with synthesized ZnO nanopowder. The blank experiments showed that both UV illumination and the catalyst were necessary for the decomposition of AR249. The influences of various operational parameters such as catalyst dose, dye concentration, pH of the solution on percentage photodegradation of AR249 were investigated. The degradation of AR249 was found to be effective in alkaline media and the kinetic of photodegradation followed pseudo-first-order kinetic model. The rate constant for degradation of AR249 was calculated to be 0.01369 min − 1 .

The effect of solvent on the morphology of ZnO nanostructure assembly by dielectrophoresis and its device applications

Different zinc oxide nanostructured morphologies were grown on photolithographically patterned silicon/silicon dioxide substrates by dielectrophoresis technique using different solvents, such as water and ethanol, obtaining rod-like and net-like nanostructures, respectively. The formation of continuous nanostructures was confirmed by scanning electron microscopic, atomic force microscopic images, and electrical characterizations. The rod-like zinc oxide nanostructures were observed in the 10 μm gap between the fingers in the pattern, whereas net-like nanostructures were formed independently of microgap. A qualitative study about the mechanism for the assembly of zinc oxide continuous nanostructures was presented. Devices were electrically characterized, at room temperature, in controlled environment to measure the conductance behavior in ultraviolet and humidity environment. Devices based on zinc oxide nanostructures grown in ethanol medium show better responses under both ultraviolet and humidity, because of the net-like structure with high surface-to-volume ratio.

Kinetic Study of Organic Dye Degradation Using ZnO Particles with Different Morphologies as a Photocatalyst

Zinc oxide (ZnO) particles were successfully synthesized via sol-gel approach using zinc acetate dihydrate (Zn(CH3COO)2·2H2O) and ammonia (NH4OH) solution as precursors. By adjusting the reaction parameters such as amount of ammonia and reaction time as well as complexing agent aluminium sulphate Al2(SO4)3, ZnO particles with different morphologies, that is, rodlike, ricelike and disklike could be synthesized. The effectiveness of ZnO particles with different morphologies (rodlike, ricelike and disklike) on the photocatalytic activity has been studied. The results showed that rodlike ZnO particles were the most effective in degrading the Rhodamine B (RhB) solution under the illumination of ultraviolet (UV) light. The rate constant was found to be first order, with rodlike particles the highest (0.06329 min−1), followed by rice-like ZnO particles (0.0431 min−1) and disk-like ZnO particles (0.02448 min−1).

Testing of the superhydrophobicity of a zinc oxide nanorod array coating on wood surface prepared by hydrothermal treatment

Abstract Natural wood surface is hydrophilic and can easily absorb moisture. Inorganic nanometer-scale metal oxides can be controlled and fabricated on wood surface to serve as a protective coating. In the present study, a superhydrophobic surface consisting of zinc oxide (ZnO) nanorod array was successfully attached on wood via a cosolvent hydrothermal method at low temperature. By means of X-ray diffraction pattern and Fourier transform infrared spectroscopy, the presence of the hexagonal wurtzite phase of ZnO was detected and characterized. Field-emission scanning electron microscopy showed uniform, large-scale rod-like ZnO crystal whiskers on the wood surface. The wettability of the wood surface after treatment became superhydrophobic, with a water contact angle of 153°. The prepared coating also showed an anti-contamination effect against milk, cola, soya sauces and coffee.

Synthesis of zinc oxide nanoparticles elaborated by microemulsion method

Zinc oxide (ZnO) nanoparticles were synthesized by a reverse microemulsion system formed from sodium bis(2-ethylhexyl)sulfosuccinate (Aerosol OT, or AOT):glycerol:n-heptane. The zinc precursor was zinc acetate dihydrate. The formation of ZnO nanoparticles was achieved by calcination of premature zinc glycerolate microemulsion product in air at 300, 400 and 500 °C. The crystal structure and the morphology of the ZnO nanoparticles were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Thermal analysis was employed to reveal structural and chemical changes during calcination. Both surfactant concentrations – AOT – in the initial microemulsion formulation and the calcination temperature influenced the morphology and size of the ZnO nanoparticles. Low surfactant concentrations (5:5:90, AOT:glycerol:n-heptane, wt.%) resulted in formation of spherical ZnO nanoparticles. The average particle size increased from 15 ± 1 to 24 ± 1 nm with calcination temperature, but spherical morphology remained unchanged after all calcination treatments. The microemulsion system containing higher surfactant amount (30:5:65, AOT:glycerol:n-heptane, wt.%) resulted in rod-like ZnO nanostructures after calcination at 300 and 400 °C, with a diameter of 22 ± 3 and 28 ± 1 nm; and with a length of 66 ± 3 and 72 ± 1 nm, respectively. Further increase in the calcination temperature to 500 °C initiated rod-to-sphere shape transformation for the ZnO nanoparticles produced using this particular microemulsion formulation. For all ZnO microemulsion products, the photoluminescence measurements suggested a high defect concentration which increases with calcination temperature.