Growth Of Zinc Oxide Nanorods Research Articles

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.

Double Layer Growth of ZnO Nanorods by a Low Temperature Solution Method: Synthesis and Photoluminescence Properties

In the present work, double layer Zinc Oxide (ZnO) nanorods (NRs) were fabricated hydrothermally and their photoluminescence (PL) properties were investigated. Two different recipes and their combination were used to obtain double layer vertically well-aligned ZnO NRs. These recipes include polyethylenimine (PEI) and citrate as additives in the growth solution resulting long NRs with a broad defect emission and relatively short NRs with a near band-edge ultraviolet (UV) emission, respectively. Double layer growth of long-long (LL), long-short (LS) and short-short (SS) ZnO NRs were considered. Grown samples were annealed in a forming gas atmosphere for a better quality NR structure. LL ZnO NRs (long ZnO NRs grown on a long ZnO NR layer) with a 65 µm thickness showed a broad yellow-orange PL emission and no any near band-edge UV emission was observed. LS ZnO NRs representing short ZnO NRs grown on a long ZnO NR layer (LS1= 36 µm, LS2= 48 µm and LS3= 44 µm) showed an enhanced near band-edge UV emission when compared to that of the long ZnO NRs. The UV intensity was found to decrease with the increase in thickness of the NRs in LS samples. Finally, SS ZnO NR sample, (short ZnO NRs grown on a short ZnO NR layer) which has a thickness of 33 µm, displayed a stronger near band-edge UV emission with a negligible broad emission than that of as-grown SS ZnO NRs (UV peak intensity ratio 59). This study should be important for applications where longer NRs with enhanced PL properties are strictly required.

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.

Influence of Refresh Hydrothermally Grown ZnO Nanorods for Vibration Sensing Application

This research report investigates the effect of fabrication methodology in the sensitivity performance of the ZnO (Zinc Oxide)-based piezoelectric vibration sensor. For that, two types of synthesising techniques, namely, normal hydrothermal (H) method and refresh hydrothermal (R) methods were used for the growth of ZnO nanorods on rigid substrates. Insights into the structural and morphological properties of the active layer (ZnO) evidence the formation of hexagonal ZnO wurtzite structure and growth of 1D nanorods in both the samples. Optical analysis reveals a decreased bandgap and better crystal quality of the refresh hydrothermal method compared to the normal hydrothermal method. Electrical analysis confirms the formation of a p-n junction in both the devices. The fabricated vibration sensors were subjected to a vibration sensing experiment where a max output voltage of 2.52 V at 9 Hz resonant frequency was recorded for the R sensor. The sensitivity of the R sensor was ∼3.54V/g which is 11% times higher than that of H.

Aligned vertical growth of zinc oxide nanorods on glass substrates using optimum hydrothermal synthesis technique

<div>This paper reported an optimized hydrothermal synthesis technique to grow zinc oxide (ZnO) nanorods vertically on the normal microscope glass. ZnO nanorods exhibited various advantages such as strong binding energy, non toxicity, large surface to volume ratio and versatility for optical detections. However, the growth of nanorods which aligned vertically on the glass substrates is rather complicated. It required a thorough process based on optimized concentration, growth duration, growth temperature and solvent variations. The morphological structure result has shown an exceptional vertical growth of the nanorods on the glass surfaces which increase the nanorods density. The optimized synthesis technique produced high density ZnO nanorods up to 3 𝑥 10<sup>13</sup> nanorods/m2 which is double as compared to conventional synthesis technique.</div>

Photocatalytic Degradation of Methylene Blue Using Zinc Oxide Nanorods Grown on Activated Carbon Fibers

In this work, the synthesis, characterization, and photocatalytic performance of zinc oxide/activated carbon fiber nanocomposites prepared by hydrothermal method were investigated. Zinc oxide nanoparticles (ZnO-NP) were deposited as seeds on porous activated carbon fiber (ACF) substrates. Then, zinc oxide nanorods (ZnO-NR) were successfully grown on the seeds and assembled on the fibers’ surface in various patterns to form ZnO-NR/ACF nanocomposites. The nanocomposites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrometry, UV–vis diffuse reflectance spectra (DRS), and Brunauer–Emmett–Teller (BET) surface area analysis. SEM images showed that brush-like and flower-like ZnO-NR patterns were grown uniformly on the ACF surface with sizes depending on the ZnO-NP concentration, growth time, and temperature. The FTIR spectrum confirmed the presence of the major vibration bands, especially the absorption peaks representing the vibration modes of the COOH (C = O and C = C) functional group. Adsorption and photocatalytic activities of the synthesized catalytic adsorbents were compared using methylene blue (MB) as the model pollutant under UV irradiation. ZnO-NR/ACF nanocomposites showed excellent photocatalytic activity (~99% degradation of MB in 2 h) compared with that of bare ZnO-NR and ACF. Additionally, a recycling experiment demonstrated the stability of the catalyst; the catalytic degradation ratio of ZnO-NR/ACF reached more than 90% after five successive runs and possessed strong adsorption capacity and high photocatalytic ability. The enhanced photocatalytic activities may be related to the effects of the relatively high surface area, enhanced UV-light absorption, and decrease of charge carrier recombination resulting from the synergetic adsorption–photocatalytic degradation effect of ZnO and ACF.

Zinc oxide nanostructures and stearic acid as surface modifiers for flax fabrics in polylactic acid biocomposites

Different surface treatments including mercerization, stearic acid and growth of zinc oxide nanorods as well as their combinations were exploited to address their effects on the properties of green composites based on polylactic acid (PLA) and flax fabrics. The resulting fabrics were morphologically (SEM), crystallographically (XRD) and thermally (TGA) characterized, showing no significant changes with respect to the untreated samples. In contrast, tensile and flexural properties of composites produced by compression moulding were significantly influenced. A combination of mercerization and environmentally friendly stearic acid treatment turned the character of the flax fabric from hydrophilic to hydrophobic, and led to improved bending and tensile strengths by 20% and 12%, respectively, compared to untreated composites. The presence of ZnO nanorods promoted an increase in flexural and tensile stiffness by 58% and 31%, respectively, but at the expense of strength, with reductions ascribed to the degradation of polylactic acid under high-temperature conditions favoured by ZnO, as confirmed by a reduction in the initial thermal degradation temperature up to 26%. These latter composites can be suggested in those applications where a suitable combination of flexural properties and a shorter persistence in the environment is desired.

Morphology, Structure, and Optical Properties of ZnO nanorods/Eosin-y Grown via Microwave-assisted Hydrothermal Method

Zinc Oxide (ZnO) was a highly attractive semiconductor material because it has a lot of properties such as non-toxic oxide, a friend of the environment, and stability for biological and biomedical applications. ZnO nanoparticle was deposited on the FTO substrates using sol-gel and spin-coating techniques and microwave-assisted hydrothermal methods were used to grow ZnO nanorods (ZNRs) from the seed layer. After that, the surface of ZNRs was modified using organic Eosin-y dye with different concentrations (0.5, 1, and 3) mM to enhance the surface of ZNRs. The XRD patterns of the as-synthesized ZNRs were indicated that the wurtzite hexagonal structure and the diameter of ZNRs will be increased after coated with Eosin-y and the surface becomes rough. The ZNRs/Eosin-y adsorbed more than 50% incident light and the electronic properties of ZNRs/1mM Eosin-y were studied using Photoluminescence (PL) spectrum and the results proved that 1 mM was the optimum concentration of Eosin-y dye that lead to increase the defects which could be enhanced the properties of ZNRs surface.

C-axis oriented ZnO nanorods based quantum dot solar cells

In this work, for the growth of ZnO (Zinc Oxide) nanorod thin films, the seed layer is prepared by sol-gel dip coating and spin coating methods. We studied the effect of seed layer on structural and optical properties of the ZnO nanorods. FESEM image revealed the difference between the growth of ZnO nanorods on spin and sol-gel dip coated seed layers. It has been observed that ZnO nanorods with uniform size and highly oriented along the c-axis have been grown on spin coated seed layer. HRTEM and Transmission electron microscopy study shows that the ZnO nanorods have an average length of 300 nm and the average diameter is 50 nm, the interplanner spacing is found to be d = 2.63 Å. The X-ray diffraction pattern revealed that the ZnO nanorods are of hexagonal structure. Absorption spectra showed that the ZnO nanorods exhibit UV absorption with absorption peak at 365 nm and the optical band gap has been found to be 3.23 eV. PL spectra indicated the presence of UV and visible emission lying in the range of 380–550 nm. ZnO nanorods based solar cells have been constructed using CdSe quantum dots.

Effect of zinc oxide nucleation on flexible bio based carbon nanotube cotton via chemical bath deposition method

The preparation and characterization of zinc oxide nanorods on flexible bio-based carbon nanotubes cotton (CNTC) was investigated. CNTC was synthesized via floating catalyst chemical vapor deposition reactor using waste cooking palm oil as hydrocarbon source. One sided CNTC facet was used as substrate hosting the growth of zinc oxide nanorods. The zinc oxide (ZnO) nucleation seed layer was deposited onto the CNTC using 99.9% Zn target and ZnO nanorods were synthesized via chemical bath deposition method. It was observed that the average diameter and length of nanorods increased proportionally to the increase of seed layer thickness. However, the aspect ratio decreased with the escalation of seed layer thickness due to its diameter significant enlargement. The highest aspect ratio is 9.4 and the lowest is 6.3 for seed layer thickness at 117 nm and 282 nm respectively. The electrical conductivity measurement showed that sample with thicker seed layer yielded better conductive value due to the ease of electrical charges movement with lower energy gap. Conclusively, ZnO nanorods have been successfully grown on CNTC surface via facile synthesis route with minimal sample pre-preparation exertion. The hybrid of ZnO/CNTC offers promising future as CNTC is flexible, readily available and incurs lower cost than other substrates.

Effect of zinc acetate dihydrate concentration on morphology of ZnO seed layer and ZnO nanorods grown by hydrothermal method

Fine-tuning zinc oxide (ZnO) nanostructures using a simple methodology will give benefits in designing efficient optoelectronic devices. In this paper, the effect of zinc acetate dihydrate (ZAD) concentration on the deposition of the ZnO seed layer by drop-casting and the growth of ZnO nanorods (ZnO NRs) was studied. As the concentration of ZAD increases, the more aggregation of ZnO nucleation centers in the seed layer. Growth of ZnO NRs using concentration 0.01 M results in the highest aspect ratio and nanorod density due to the aggregation process resulting in more nucleation sites with smaller grain sizes. X-ray diffraction (XRD) done on the four samples show that 0.001 M concentration demonstrates the highest intensity of vertically aligned (002) ZnO NRs. Photoluminescence (PL) spectra show ZnO NRs grown using 0.01 M ZAD solution exhibits the highest intensity in near band edge (NBE) emission compared to other samples.

Effect of an applied electric field during the oxidation process of zinc thin films on growth and properties of ZnO nanorods

In recent years, metal oxide semiconductors have been one of the most remarkable subjects in science and technology. Present research investigates the growth and characterization of Zinc Oxide (ZnO) nanorods (NRs) as one of the metal oxide semiconductors with a broad range of applications. In this work, ZnO NRs preparation includes two steps. In the first step, Zn thin layers were deposited by thermal evaporation method on soda lime glass (SLG) substrate under an electric field of 134 kV/m. The second step contains the oxidation process of the Zn layers under electric fields of 0, 48 and 84 kV/m in air. Then, samples were characterized by X-ray Diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDX), Field Emission Scanning Electron Microscopy (FESEM), Raman and UV–Visible Spectroscopy. XRD study showed that all samples were crystallized in a hexagonal wurtzite crystal structure. EDX analysis showed that Zn and O atomic ratio, with a good approximation, are close to the ratio expected for ZnO (1:1). FESEM images illustrated that by applying the electric field, diameter of ZnO NRs decreased. Moreover, Raman spectra indicated a shift towards higher wavenumbers due to decreasing the crystallite size and vice versa. In addition, the results obtained from optical measurement demonstrated a reversed behavior of the samples' band gap energy with crystallite size.

Zinc Oxide Nanorod Surface-Enhanced Raman Scattering Substrates without and with Gold Nanoparticles Fabricated through Pulsed-Laser-Induced Photolysis

We fabricated surface-enhanced Raman scattering (SERS) substrates using gold nanoparticle (AuNP)-decorated zinc oxide (ZnO) nanorods (NRs). Prior to decoration with AuNPs, ZnO NRs on the glass substrate fabricated using the sol–gel method could enhance the SERS signal for detecting 10−5 M rhodamine 6G (R6G). Microscopic analysis revealed that the thermal-annealing process for fabricating the seed layers of ZnO facilitated the growth of ZnO NRs with the highly preferred c-axis (002) orientation. A decrease in the diameter of ZnO NRs occurred because of the use of annealed seek layers further increased the surface-to-volume ratio of ZnO NRs, resulting in an increase in the SERS signal for R6G of 10−5 M. To combine the localized surface plasmon resonance (LSPR) mode with the charge transfer (CT) mode, ZnO NRs were decorated with AuNPs through pulsed-laser-induced photolysis (PLIP). However, the preferred vertical (002) orientation of ZnO NRs was prone to the aggregation of AuNPs, which hindered the SERS signal. The experimental results revealed that ZnO NRs with the crystalline structure of horizontal (100) and (101) orientations facilitated the growth of homogeneous, independent and isolated AuNPs which serves as “hot spots” for SERS signal of detecting R6G at a low concentration of 10−9 M. Comparing to previous fabrication of SERS substrate, our method has advantage to fabricate AuNP-decorated ZnO NR in a short time. Moreover, the optimization of the SERS behaviors for different fabrication conditions of AuNPs using the PLIP method was investigated in detail.

Modeling and Piezoelectric Analysis of Nano Energy Harvesters.

The expedient way for the development of microelectromechanical systems (MEMS) based devices are based on two key steps. First, perform the simulation for the optimization of various parameters by using different simulation tools that lead to cost reduction. Second, develop the devices with accurate fabrication steps using optimized parameters. Here, authors have performed a piezoelectric analysis of an array of zinc oxide (ZnO) nanostructures that have been created on both sides of aluminum sheets. Various quantities like swerve, stress, strain, electric flux, energy distribution, and electric potential have been studied during the piezo analysis. Then actual controlled growth of ZnO nanorods (NRs) arrays was done on both sides of the etched aluminum rod at low-temperature using the chemical bath deposition (CBD) method for the development of a MEMS energy harvester. Micro creaks on the substrate acted as an alternative to the seed layer. The testing was performed by applying ambient range force on the nanostructure. It was found that the voltage range on topside was 0.59 to 0.62 mV, and the bottom side was 0.52 to 0.55 mV. These kinds of devices are useful in low power micro-devices, nanoelectromechanical systems, and smart wearable systems.

Effect of the Seeding Thickness on the Growth of ZnO Nanorods prepared by CBD

Zinc Oxide (ZnO) nanostructure (NS), with nanorods (NRs) forward-facing alignment were deposited by chemical bath deposition (CBD) method on seeded glass substrates. Two different ZnO seed layer thickness, 100 nm and 200 nm, prepared by RF sputtering were employed to investigate the effect of seed layer thickness on the characteristics of the grown ZnO NRs. The investigations on physical, structural, and optical properties were carried out through field emission scanning electron microscope (FESEM) with integrated energy dispersive X-ray (EDX), X-Ray Diffraction (XRD), and UV and visible (UV-Vis) analyses. The morphological results reveal that with a thicker seed layer, the grown NRs diameter increased double while the NRs height was maintained at 1.5 μm. From EDX, the stoichiometric ratios of Zn:O were mostly towards 1:1. While the XRD evaluates that the preferred structure was wurtzite hexagonal with c-axis orientation along (002) plane. The UV-Vis analysis showed the increased in optical band gap energy closes to the bulk ZnO at 3.37 eV, for the ZnO NRs grown on the thicker seed layer. The obtained results illustrated high quality single-crystal ZnO NRs with different diameters were realized by only adjusting the seed layer thickness.

Humidity Effects on the Growth of ZnO Nanorods using Hydrothermal Method

The effects of ZnO nanorod samples with different growth times samples to the morphological structures and output light intensity are reported. The proposed structure comprises of silica microfiber integrated with Zinc Oxide (ZnO) nanorods coated glass surface. The silica microfiber is tapered into constant waist diameter of 10 μm using flame brushing technique. While the glass surface is coated with ZnO nanorods using hydrothermal method for 6 hours, 9 hours, 12 hours, 15 hours and 18 hours growth times. The samples are exposed to the different humidity levels ranging from 35%RH to 85%RH to observe the effect of the morphological structures such as length, diameter and density and the output light intensity. The resulted measurements provide the correlation between the growth time during the synthesis process to the ZnO nanorods physical structure as well as the output light intensity in different humidity levels. It utilizes the unique features of the scattering and surface absorption of the microfiber and ZnO nanomaterials coated glass surface to alter the output light intensity. The reported results may contribute to the optimal ZnO nanorods growth time for humidity sensing applications.

Growth of ZnO nanorods on different substrates using hydrothermal method

Zinc oxide (ZnO) nanorods have been grown on different substrates, i.e. gold film-coated BK-7 glass (Au-film/BK7), microscope glass slide (MGS), silicon oxide film-coated silicon (SiO2-film/Si), to investigate the effects of different substrates on its material properties. The growth process was started by dipping substrates in zinc acetate solution to fabricate a seed layer, followed by growing the ZnO nanorods in zinc nitrate tetrahydrate solution based on hydrothermal method at 95 °C for 6 hour. In this process, seed layer and ZnO nanorods were annealed at 350 °C for 2 hours. The characterization results using X-ray diffraction and field effect scanning electron microscope showed that ZnO nanorods were successfully grown homogenously and mostly in vertical direction with hexagonal wurtzite structure. The diameter size of ZnO nanorods was significantly influenced by the type of material substrate. ZnO nanorods on Au-film/BK-7 glass have the smallest diameter size of (239±51) nm, while the average diameter size of ZnO nanorods on MGS is of (269±53) nm and ZnO nanorods on SiO2-film/Si have the largest diameter size of (354±80) nm. The effect of substrates on different size of ZnO nanorods may be regarded to the intrinsic thermal conductivity of substrate material. Hence, the synthesis and growth parameters for the different substrates differ from each other and need to be optimized in order to grow ZnO nanostructures

Optimization of ZnO Nanorods Growth on Polyetheresulfone Electrospun Mats to Promote Antibacterial Properties.

Zinc oxide (ZnO) nanorods grown by chemical bath deposition (CBD) on the surface of polyetheresulfone (PES) electrospun fibers confer antimicrobial properties to the obtained hybrid inorganic–polymeric PES/ZnO mats. In particular, a decrement of bacteria colony forming units (CFU) is observed for both negative (Escherichia coli) and positive (Staphylococcus aureus and Staphylococcus epidermidis) Grams. Since antimicrobial action is strictly related to the quantity of ZnO present on surface, a CBD process optimization is performed to achieve the best results in terms of coverage uniformity and reproducibility. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) provide morphological and compositional analysis of PES/ZnO mats while thermogravimetric analysis (TGA) is useful to assess the best process conditions to guarantee the higher amount of ZnO with respect to PES scaffold. Biocidal action is associated to Zn2+ ion leaching in solution, easily indicated by UV–Vis measurement of metallation of free porphyrin layers deposited on glass.

Influence of pH on the photocatalytic activity of ZnO nanorods

Zinc oxide (ZnO) nanorods were prepeared on glass substrates through the chemical bath deposition (CBD) method. The growth of vertically array ZnO nanorods was promoted by seeding the substrates with ZnO nanoparticle layers. Surface morphology that investagated through field-emission scanning electron microscopy (FESEM) show that hexagonal ZnO nanorods (wurtzite) are formed with diameters ranging from 10 nm to 130 nm. The optical absorption of the grown ZnO nanorods exhibited high absorption edge with an energy gap of 3.26 eV. The photocatalytic activity of the prepared ZnO nanorods was investigated against methylene blue dye at room temperature using different pH values and UV exposure times. Degradation ratio of dye increased when irradiation time and pH were increased. The degradation ratio for dye with pH 6 increased from 42% to 89% when exposure time increased from 30 min to 240 min, whereas the degradation ratio of the dye with pH 11 increased from 65% to 94% under the same exposure time.