Growth Of Zinc Oxide Nanorods Research Articles

Growth of variable aspect ratio ZnO nanorods by hydrothermal technique

Zinc oxide (ZnO) nanorods were successfully prepared by hydrothermal process. The influence of the solution temperature on the ZnO nanorods aspect ratio is investigated in the present work. The x-ray diffraction (XRD) and scanning electron microscopy (SEM) results and analysis reveal the formation of ZnO nanorods owing hexagonal Wurtzite structure with preferential orientation along the c-axis. We found that the solution temperature is a key parameter controlling the aspect ratio of the formed ZnO nanorods. The later increases linearly with the preparation temperature. The rod length is thermally activated with an activation energy of 0.48 eV, which corresponds to the activation energy of the reaction forming ZnO, indicating that the nanorods growth is controlled by the surface reaction rather than by mass transport. While, the rods diameter is reduced with increasing temperature, its activation energy of 0.23 eV is equal to the species diffusion activation energy in the solution and to the crystallite size activation energy suggesting, thereafter that the rod diameter variation is controlled by the nucleation dynamic.

Point-of-Care Electrochemical Immunosensor Applied against Nosocomial Infection: Staphylococcus aureus Detection in Human Hand Skin.

Staphylococcus aureus is an important pathogen that causes nosocomial infections, resulting in unacceptable morbidity and mortality rates. In this work, we proposed the construction of a nanostructured ZnO-based electrochemical immunosensor for qualitative and semiquantitative detection of S. aureus using simple methods for growing zinc oxide nanorods (ZnO NRs) on a sensor board and immobilizing the anti-S. aureus antibody on ZnO NRs through cystamine and glutaraldehyde. The immunosensor detected S. aureus in the 103-107 colony-forming unit (CFU) mL-1 range and showed a limit of detection (LoD) around 0.792 × 103 CFU mL-1. Beyond a satisfactory LoD, the developed immunosensor presented other advantages, such as high versatility for point-of-care assays and a suitable selective factor that admits the detection of the S. aureus concentration range in human hand skin after washing. Moreover, the immunosensor showed the potential to be an excellent device to control nosocomial infection by detecting the presence of S. aureus in human hand skin.

Highly Controllable Fabrication of Gold Composite Nanostructures by Multiple Electroplating for High‐Performance Electrochemical and Raman Scattering Measurements

Morphology‐controlled nanostructures are important functional materials in multidisciplinary research fields, such as sensing, imaging, catalysis, and energy harvesting. However, existing nanofabrication methods have limitations in terms of controllability, diversity, cost, and efficiency. Here, a novel nanofabrication approach is proposed to construct Au nanostructures with high controllability, cost‐efficiency, and high‐performance sensing and energy harvesting. The fabrication incorporates electric field‐assisted hydrothermal growth of zinc oxide nanorods (ZnO NRs) with two‐step gold electroplating. The ZnO NRs serve as a dissolvable template during the electroplating formation of gold nanostructures for eventually synthesizing pure gold nanostructures on electrodes. The synthesized gold nanostructures take unique composite shape of nanospheres (hundreds of nanometers) covered with tinier nanostructures (tens of nanometers) like floccules, grains, lamellas, or rods, which are highly controlled by regulating electroplating parameters. The gold composite nanostructures provide high‐performance sensing and energy harvesting, such as enhanced electrochemical sensing interface (electric double‐layer impedance decrease up to 97.1%), excellent surface‐enhanced Raman scattering (SERS enhancement factor up to ), and preferable visible–near‐infrared light harvesting (absorptivity near to 90%). For the first time, the application of tumor cell photothermal therapy with nanostructured electrodes and in situ bimodal monitoring of single‐cell impedance and SERS‐based molecular expression during therapy is demonstrated.

The Fast and One-Step Growth of ZnO Nanorods on Cellulose Nanofibers for Highly Sensitive Photosensors.

Cellulose is the most abundant organic material on our planet which has a key role in our daily life (e.g., paper, packaging). In recent years, the need for replacing fossil-based materials has expanded the application of cellulose and cellulose derivatives including into electronics and sensing. The combination of nanostructures with cellulose nanofibers (CNFs) is expected to create new opportunities for the development of innovative electronic devices. In this paper, we report on a single-step process for the low temperature (<100 °C), environmentally friendly, and fully scalable CNF-templated highly dense growth of zinc oxide (ZnO) nanorods (NRs). More specifically, the effect of the degree of substitution of the CNF (enzymatic CNFs and carboxymethylated CNFs with two different substitution levels) on the ZnO growth and the application of the developed ZnO NRs/CNF nanocomposites in the development of UV sensors is reported herein. The results of this investigation show that the growth and nature of ZnO NRs are strongly dependent on the charge of the CNFs; high charge promotes nanorod growth whereas with low charge, ZnO isotropic microstructures are created that are not attached to the CNFs. Devices manufactured via screen printing/drop-casting of the ZnO NRs/CNF nanocomposites demonstrate a good photo-sensing response with a very stable UV-induced photocurrent of 25.84 µA. This also exhibits excellent long-term stability with fast ON/OFF switching performance under the irradiance of a UV lamp (15 W).

Enhancing Dye-Sensitized Solar Cell Performance with Different Sizes of ZnO Nanorods Grown Using Multi-Step Growth

In this study, we employed a chemical solution method to grow zinc oxide (ZnO) nanorods on SnO2:F (FTO) substrates as photoelectrodes for dye-sensitized solar cells (DSSCs). The influence of varying ZnO nanorod dimensions on cell performance was investigated. Specifically, we explored the effects of nanorod length and diameter on dye adsorption capacity and photovoltaic conversion efficiency. Characterization techniques such as electrochemical impedance spectroscopy (EIS), X-ray diffraction (XRD), and field-emission scanning electron microscopy (FE-SEM) were utilized to analyze the ZnO nanorods. Our results demonstrate that the sequential growth technique allows for control over the length and diameter of ZnO nanorods, thereby modulating their optoelectronic properties. XRD and FE-SEM analyses revealed that the surface morphology of the ZnO nanorods impacts dye adsorption capacity and photovoltaic conversion efficiency. EIS measurements further indicated a significant influence of dye adsorption on the electron lifetime of ZnO nanorods. Overall, this study highlights the potential of multi-step growth of ZnO nanorods to optimize the performance of dye-sensitized solar cells by tuning their morphology and surface properties.

Effect of Ga Concentration on the Output Performance of ZnO Piezoelectric Nanorods Nanogenerator

In this study, a self-assembled monolayer of octyltriethoxysilane was grown on ITO glass. Subsequently, a hydrothermal method was employed to grow low-density gallium (Ga)-doped zinc oxide (ZnO) nanorod structures. In this growth process, the undoped pure ZnO nanorods and ZnO nanorods doped with five different Ga concentrations were developed. After growing the nanorods, X-ray diffraction (XRD) analysis was conducted on both undoped pure ZnO and Ga-doped ZnO nanorods to observe the influence of Ga concentration on the crystalline structure of the ZnO nanorods. Additionally, scanning electron microscopy (SEM) was utilized to examine changes in the surface and cross-sectional growth of ZnO nanorods with varying Ga concentrations, thereby investigating the impact of Ga concentration on the growth of ZnO nanorods. Finally, a thin Pt film was sputtered onto the ZnO nanorod structures to assemble nanogenerators. Ultrasonic excitation was applied to develop these nanogenerators for electrical measurements, allowing us to explore the effects of metal doping on the nanorods’ electrical properties.

Crystal polarity enhanced by interactions between antiparallel crystal dipoles

From zinc acetates dispersed within monolayers of poled polymer ferroelectric lamellar crystals, the growth of zinc oxide nanorods has been surprisingly identified subject to antiparallel match between crystal dipoles, unveiling a new type of non-contact epitaxial relationship therefore. The involved phase interactions between antiparallel crystal dipoles significantly enhance reversible piezoelectric strains of both interacting crystals, and the achieved piezoelectric constants of polymer ferroelectric crystals are increased by one order of magnitude. As two interacting crystals are further separated, achieved piezoelectricity of individual crystals declines accordingly, similar to the influences of noncovalent interactions between molecules. Upon guided crystal clustering, the available phase interactions significantly increase dielectric constants of prepared monolayers from 23 to more than 100. In addition to separation distance, the number and size of interacting crystals have been experimentally clarified critical also for reached levels of piezoelectric responses. Conceivably, unveiled phase interactions are dependent on the augmentation and enhancement of electric fields yielded by interacting crystal dipoles.

Synthesis of ZnO Nanorods at Very Low Temperatures Using Ultrasonically Pre-Treated Growth Solution

This paper investigates how the pre-treatment of the growth solution with ultrasonic energy affects the annealing temperatures and the growth temperatures of zinc oxide (ZnO) nanorods. The ultrasonic pre-treatment of the growth solution resulted in the successful growth of ZnO nanorods at a very low annealing temperature of 40 °C. The size and density of ZnO nanorods were found to increase proportionally with the increasing duration of pre-ultrasonic treatment, as indicated by characterisations performed with a scanning electron microscope (SEM). At an annealing temperature of 40 °C, coupled with ultrasonic waves, the SEM results showed that ZnO nanorods’ length and diameter increased by 37 and 25%. A similar pattern was also observed at an annealing temperature of 60 and 80 °C, where the length and diameter of ZnO nanorods increased. In addition, the conductivity and acidity of the aqueous solution that had been sonicated were measured. The results showed that solution conductivity and acidity increased as the ultrasonic treatment continued for longer periods. After 3 min of sonication, the final conductivity and acidity of the solutions were found to be 9164 µS/cm and 6.64, respectively. The results also indicated that the ultrasonic pre-treatment of the growth solution increased the zinc nutrient concentration, which would affect the formation of ZnO nanorods. In addition to the ultrasonic effect, the annealing temperature influenced the active nucleation sites essential to the ZnO nanorods’ expansion.

Towards a Highly Efficient ZnO Based Nanogenerator.

A nanogenerator (NG) is an energy harvester device that converts mechanical energy into electrical energy on a small scale by relying on physical changes. Piezoelectric semiconductor materials play a key role in producing high output power in piezoelectric nanogenerator. Low cost, reliability, deformation, and electrical and thermal properties are the main criteria for an excellent device. Typically, there are several main types of piezoelectric materials, zinc oxide (ZnO) nanorods, barium titanate (BaTiO3) and lead zirconate titanate (PZT). Among those candidate, ZnO nanorods have shown high performance features due to their unique characteristics, such as having a wide-bandgap semiconductor energy of 3.3 eV and the ability to produce more ordered and uniform structures. In addition, ZnO nanorods have generated considerable output power, mainly due to their elastic nanostructure, mechanical stability and appropriate bandgap. Apart from that, doping the ZnO nanorods and adding doping impurities into the bulk ZnO nanorods are shown to have an influence on device performance. Based on findings, Ni-doped ZnO nanorods are found to have higher output power and surface area compared to other doped. This paper discusses several techniques for the synthesis growth of ZnO nanorods. Findings show that the hydrothermal method is the most commonly used technique due to its low cost and straightforward process. This paper reveals that the growth of ZnO nanorods using the hydrothermal method has achieved a high power density of 9 µWcm-2.

Highly efficient Zinc Oxide nanostructure based gas sensor for domestic application

In this work, Zinc Oxide (ZnO) nanorods with high surface to volume ratio were fabricated through the hydrothermal synthesis process on a glass slide and highly conductive alumina ceramic based gold interdigitated electrode (IDE). The ZnO nanorods structure on substrates were characterized through X-ray diffraction (XRD) and UV absorption spectroscopy followed by growth verification by Scherrer’s equation. The sensitivity characterization of fabricated sensor was determined for 2000 ppm and 4000 ppm natural gas in the air through high resistance electrometer at room temperature. The 2000 ppm concentration of gas shows 11.3% sensitivity, response time of 66 seconds and recovery time of 92 seconds to the sensor. The 4000 ppm concentration of gas shows 64% sensitivity, the response time of 106 seconds and a recovery time of 174 seconds to the sensor. The higher sensitivities with slow response and recovery times exhibit the behavior of redox reactions of sensor surface to the higher concentration of natural gas. The minute reduction in resistance and with the fast response and recovery time of the sensor show the 11.3% sensitivity to lower concentration. The more concentration of natural gas in the air would show a higher sensitivity of the sensor. The experimental results indicate the growth of ZnO nanorods on substrates and their sensitivity to natural gas.  Â

Bio-compatible piezoelectric material based wearable pressure sensor for smart textiles

With the rapid advancement of flexible wearable technology, bio-compatible textile piezoelectric pressure sensors are a promising candidates for next-generation sensing platforms to monitor human health. Smart textiles can be easily incorporated into our daily wear clothing in a breathable and conformable manner. In this study, a novel structural hierarchy consisting of a piezoelectric composite film Glycine–Chitosan (GC) sandwiched between two Zinc Oxide (ZnO) nanorods patterned conductive textile electrodes was developed. A low temperature hydrothermal method was used to grow ZnO nanorods directly on the conductive fabric, and a simple solvent casting technique was employed to form a GC film. Scanning electron microscopy and x-ray diffraction analyses were performed to investigate the growth of the bio-compatible piezoelectric materials. Under periodic deformation, the fabricated sensor exhibited a good piezoelectric response over a wide range of sensing pressures. The use of non-toxic, bio-compatible piezoelectric materials in the development of textile pressure sensors paves the way for the development of eco-friendly wearables.

Rapid growth of zinc oxide nanorods on kanthal wires by direct heating method and its photocatalytic performance in pollutants removal

Immobilization of photocatalysts on supporting substrates to prevent the loss and deterioration of photocatalytic performances is an issue to be addressed by researchers. However, the common synthesis techniques such as chemical vapour deposition, sol-gel, or hydrothermal are time- and cost inefficient. A lot of heat is loss to environment when the heat generated outside the reactor is transferring into the reactor and precursor solution. In this work, ZnO nanorods were grown on kanthal wires using direct heating (DH) technique. DH technique offers many advantages as compared to common synthesis techniques such as chemical vapor deposition, sol–gel and hydrothermal to produce ZnO nanorods. The heat was generated directly on the substrate itself, providing effective heating, low electric consumption (≤0.060 kWh), and rapid synthesis (15 min) of ZnO nanorods. The presence of ZnO nanorods on kanthal wires are verified by XRD, FESEM, TEM/HRTEM, XPS and RTPL analyses. The ZnO nanorods demonstrated good photocatalytic performance in degradation of RhB dye and heavy metal ions under UV light. Thus, DH is a potential synthesis technique for mass production of wastewater treatment module.

Correlation between crystal defects and room temperature ferromagnetism of hydrothermally grown Eu substituted ZnO nanorods

The hydrothermal method has been used to grow zinc oxide nanorods on a glass substrate with different Europium (Eu) concentrations. The Eu doping effect on the structural, optical, and magnetic properties of the samples was systematically investigated. The undoped sample exhibited diamagnetic behaviour, while soft room temperature ferromagnetism was observed in all the Eu substituted samples. With regard to the hysteresis loops, the highest coercivity, saturated magnetic moment, and retentive magnetic moment values were observed to be 41.64 Oe, 18.86 × 10−6 emu, and 2.17 × 10−6 emu, respectively, for ZnO:Eu 7%. According to the relationships between the magnetic properties, Eu doping levels, and defects concentrations, it can be concluded that the room temperature ferromagnetism observed in the samples is caused by crystal point defects including oxygen vacancies and zinc interstitials, rather than carrier-mediated exchange interactions, which is also consistent with the bound magnetic polarons theory.

Novel Synthesis of Sensitive Cu-ZnO Nanorod-Based Sensor for Hydrogen Peroxide Sensing.

We aimed to synthesize sensitive electrochemical sensors for hydrogen peroxide sensing by using zinc oxide nanorods grown on a fluorine-doped tin oxide electrode by using the facial hydrothermal method. It was essential to keep the surface morphology of the material (nanorods structure); due to its large surface area, the concerned material has enhanced detection ability toward the analyte. The work presents a non-enzymatic H2O2 sensor using vertically grown zinc oxide nanorods on the electrode (FTO) surfaces with Cu nanoparticles deposited on zinc oxide nanorods to enhance the activity. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-Ray (EDX), X-ray diffraction (XRD), and electrochemical methods were used to characterize copper–zinc oxide nanorods. In addition to the high surface area, the hexagonal Cu-ZnO nanorods exhibited enhanced electrochemical features of H2O2 oxidation. Nanorods made from Cu-ZnO exhibit highly efficient sensitivity of 3415 μAmM−1cm−2 low detection limits (LODs) of 0.16 μM and extremely wide linear ranges (0.001–11 mM). In addition, copper-zinc oxide nanorods demonstrated decent reproducibility, repeatability, stability, and selectivity after being used for H2O2 sensing in water samples with an RSD value of 3.83%. Cu nanoparticles decorated on ZnO nanorods demonstrate excellent potential for the detection of hydrogen peroxide, providing a new way to prepare hydrogen peroxide detecting devices.

Reduced Graphene Oxide/MXene-Derived TiO2 Hybrid Interface Layer for the Improvement of Zinc Oxide Nanorod Growth and Their Applications in Glutathione Sensing

Photoelectrochemical (PEC) sensor is an important type of biosensor widely used in glutathione (GSH) sensing. The PEC properties of the photoanode present in the sensor are critical to its sensing performance. Zinc oxide (ZnO) is an excellent semiconductor with a suitable band gap and light absorption ability for photoanode applications. Meanwhile, the interfacial layer is also important in the separation and transportation process of the excitons. In this work, high-quality ZnO nanorods were grown on the indium tin oxide (ITO) substrates. An interfacial layer consisting of reduced graphene oxide (RGO) or MXene (a two-dimensional transition metal carbide)-derived TiO2 was introduced. Our results show that the introduction of the RGO/TiO2 hybrid interfacial layer can promote both the high-quality growth of ZnO nanorods and also provides suitable band gap grading for efficient excitons separation and transportation. The GSH sensing performance of the PEC sensor based on the ZnO nanorods grown on the RGO/TiO2 hybrid layer-coated ITO photoanode can dramatically improve the photocurrent strength and linearity.

Nanocomposite Film Development Based on Chitosan/Polyvinyl Alcohol Using ZnO@Montmorillonite and ZnO@Halloysite Hybrid Nanostructures for Active Food Packaging Applications.

The global turn from the linear to the circular economy imposes changes in common activities such as food packaging. The use of biodegradable materials such as polyvinyl alcohol, natural raw materials such as clays, and food byproducts such as chitosan to develop novel food packaging films attracts the interest of industrial and institutional research centers. In this study, novel hybrid nanostructures were synthesized via the growth of zinc oxide nanorods on the surface of two nanoclays. The obtained nanostructures were incorporated with chitosan/polyvinyl alcohol composite either as nanoreinforcement or as an active agent to develop packaging films. The developed films were characterized via XRD, FTIR, mechanical, water-vapor diffusion, water sorption, and oxygen permeability measurements. Antimicrobial activity measurements were carried out against four different pathogen microorganisms. XRD indicated the formation of an intercalated nanocomposite structure for both types of nanoclays. Furthermore, improved tensile, water/oxygen barrier, and antimicrobial properties were recorded for all films compared to the pure chitosan/polyvinyl alcohol film. Overall, the results indicated that the use of the bio-based developed films led to an extension of food shelf life and could be used as novel active food packaging materials. Among them, the most promising film was the 6% wt. ZnO@halloysite.

Influence of N2O plasma treatment on PET-based flexible bending sensors with ZnO nanorod array cross-linked with interdigitated electrode structures

We present a highly sensitive bending sensor fabricated with hydrothermally grown zinc oxide nanorod (NR) arrays cross-linked with interdigitated electrode patterns on polyethylene terephthalate substrates. To examine the effects of microstructural change in NR arrays on the device characteristics, N2O plasma treatment (PT) was carried out for 3 and 6 min for the seed layers. Negative resistance change (ΔR) was obtained in the case of convex bending, while positive ΔR was measured under the concave bending from every device prepared under different PT conditions, which is due to the change in the number of cross-linkings between the NRs. The device with no PT condition showed the highest gauge factor of 196 at a bending strain of 1.75% in the convex direction.

Impact of shock waves on the physical and chemical properties of aligned zinc oxide structures grown over metal-sheets

Zinc oxide (ZnO) nanorods were developed on stainless steel (SS) sheets as well as glass substrates in two steps by adopting well-established two different chemical methods namely, spray pyrolysis and chemical bath deposition techniques. Then, the structures were exposed to dynamically generated shock waves in a home-built shock tunnel. All the as-grown and shock waves exposed structures were characterized with advanced analytical techniques. Surface morphology and structural studies reveal that the as-grown nanostructured films over the both SS and glass substrates possess nanorods-like surface morphology; however, they exhibited (101) and (001) orientations as predominant orientations, respectively. From micro Raman analysis, it is noticed that the nanorod structures grown on both surfaces have good phase purity and crystalline quality. On the other hand, the cathodoluminescence studies show that these hydrothermally grown ZnO nanorods possess a large number of native defects. Finally, the ZnO nanorods exposed to shock waves generated with a temperature and pressure of ca. ∼20,000 K and ∼6 MPa for a short duration of 2–3 ms exhibited superb sustainability in terms of surface morphology as well as crystalline quality, which is mainly attributed to the slantly overlapped morphology as well as the high melting temperature of ZnO nanorods.

Cytotoxicity and apoptosis response of hexagonal zinc oxide nanorods against human hepatocellular liver carcinoma cell line

Hexagonal zinc oxide nanorods (ZnO-NRs) were prepared via solution process using zinc nitrate hexahydrate (Zn(NO3)2·6H2O, 0.25 M), hexamethylenetetramine (HMT) and sodium hydroxide at low concentration (4 × 10-3 M in 100 ml of distilled water) and refluxed at 100 °C for an hour. The HMT was used because its act as a template for the nucleation and growth of zinc oxide nanorods. The X-ray diffraction patterns (XRD) clearly reveal that the grown product is pure zinc oxide. The diameters and lengths of the synthesized nanorods lie between 200 and 250 nm and 2–3 μm respectively as observed from the field emission scanning electron microscopy (FESEM). The chemical functional properties was analyzed by Fourier Transform infra-red (FTIR) spectroscopy. This study was designed to show the possible effect of ZnO-NRs in human liver cancer (HepG2) cells. It induces cytotoxicity via reactive oxygen species (ROS), mitochondrial membrane potential. For gene expression analysis, it induces apoptotic gene marker P53, Bax, caspase3, Bcl2 genes. Based on analysis and observations, it concludes that the ZnO-NRs were utilized for toxicity at dose dependent via ROS generation against human hepato cellular liver carcinoma cell line.

Enhanced structural and morphological properties of ZnO nanorods using plant extract-assisted solution immersion method

Zinc oxide nanorods were successfully synthesized via a modified biosynthesis approach using plant extract. It consisted of two sections: first, the deposition of biosynthesized zinc oxide seed layer’s solution on a glass substrate using the spin-coat method. (using zinc nitrate hexahydrate and Pandanus amaryllifolius as a precursor and stabilizer). Second, the growth of zinc oxide nanorods on deposited biosynthesized zinc oxide seed layer using the solution immersion method. All samples were annealed at a temperature of 100 °C, 200 °C, 300 °C, 400 °C and 500 °C to observe the effect of annealing temperature on structural and morphological properties of the samples. The hexagonal wurtzite structure of zinc oxide was evident. A primary three peaks occur at 2θ = 31.78, 34.47, and 36.26, which resemble the (100), (002), and (101) zinc oxide crystallographic planes, respectively using X-ray diffraction (XRD) characterization. By using field emission scanning electron microscopy (FESEM), the smallest diameter (290 nm) of zinc oxide nanorods were demonstrated when annealed at 400 °C compared to other annealing temperatures. In addition, uniform dense rods structures were developed as annealing temperatures were increased. This study is the first to report on the ability of Pandanus amaryllifolius as an alternative stabilizer to investigate thedevelopment ofa highly crystalline and dense zinc oxide nanorods structure. It reveals that zinc oxide nanorods successfully synthesized on the biosynthesized zinc oxide seed layer. An elevated annealing temperature have demonstrated the enhancement of the structural and morphological properties of the samples. The advantages from the findings would be towards the optoelectronic applications such as ultra-violet sensors.