Article

# Low Temperature Solution Synthesis and Characterization of ZnO Nano-Flowers

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## Abstract

Synthesis of flower-shaped ZnO nanostructures composed of hexagonal ZnO nanorods was achieved by the solution process using zinc acetate dihydrate and sodium hydroxide at very low temperature of 90 °C in 30 min. The individual nanorods are of hexagonal shape with sharp tip, and base diameter of about 300–350 nm. Detailed structural characterizations demonstrate that the synthesized products are single crystalline with the wurtzite hexagonal phase, grown along the [0 0 0 1] direction. The IR spectrum shows the standard peak of zinc oxide at 523 cm−1. Raman scattering exhibits a sharp and strong E2 mode at 437 cm−1 which further confirms the good crystallinity and wurtzite hexagonal phase of the grown nanostructures. The photoelectron spectroscopic measurement shows the presence of Zn, O, C, zinc acetate and Na. The binding energy ca. 1021.2 eV (Zn 2p3/2) and 1044.3 eV (Zn 2p1/2), are found very close to the standard bulk ZnO binding energy values. The O 1s peak is found centered at 531.4 eV with a shoulder at 529.8 eV. Room-temperature photoluminescence (PL) demonstrate a strong and dominated peak at 381 nm with a suppressed and broad green emission at 515 nm, suggests that the flower-shaped ZnO nanostructures have good optical properties with very less structural defects.

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... ZnO has been extensively investigated over the years as thin films or nanostructures and in fact, several ZnO structures have been described at the nanoscale. The most common are one-dimensional nanostructures, such as nanorods, nanotubes, nanofibers, nanowires, but also nanoplates, nanosheets, nanospheres, tetrapods, and nanoflowers, among others, have been described (Figure 11) [204][205][206][207][208][209]. To produce such a variety of structures, numerous and distinct techniques have been reported, including direct precipitation [210], the sol-gel method [211,212], hydrothermal [213,214] and solvothermal syntheses [101], microwave synthesis [96,97,215], chemical bath deposition [216], electrospinning [217], electrodeposition [218], electrospinning [102,105], magnetron sputtering [219,220], and spray pyrolysis [221], among others. ...
... To produce such a variety of structures, numerous and distinct techniques have been reported, including direct precipitation [210], the sol-gel method [211,212], hydrothermal [213,214] and solvothermal syntheses [101], microwave synthesis [96,97,215], chemical bath deposition [216], electrospinning [217], electrodeposition [218], electrospinning [102,105], magnetron sputtering [219,220], and spray pyrolysis [221], among others. [204], (b,c) ZnO nanoplates [204], (d) ZnO tetrapods [222], (e) ZnO nanosheets [205], (f) ZnO nanospheres [206], (g) ZnO nanotubes [207], (h) ZnO nanoflowers [209], and (i) aligned ZnO nanowire arrays [208]. Reprinted with permission from direct growth of freestanding ZnO tetrapod networks for multifunctional applications in photocatalysis, UV photodetection, and gas sensing, ACS Appl. ...
... SEM images of several ZnO nanostructures. (a) ZnO nanorods [204], (b,c) ZnO nanoplates [204], (d) ZnO tetrapods [222], (e) ZnO nanosheets [205], (f) ZnO nanospheres [206], (g) ZnO nanotubes [207], (h) ZnO nanoflowers [209], and (i) aligned ZnO nanowire arrays [208]. Reprinted with permission from direct growth of freestanding ZnO tetrapod networks for multifunctional applications in photocatalysis, UV photodetection, and gas sensing, ACS Appl. ...
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The interest in advanced photocatalytic technologies with metal oxide-based nanomaterials has been growing exponentially over the years due to their green and sustainable characteristics. Photocatalysis has been employed in several applications ranging from the degradation of pollutants to water splitting, CO2 and N2 reductions, and microorganism inactivation. However, to maintain its eco-friendly aspect, new solutions must be identified to ensure sustainability. One alternative is creating an enhanced photocatalytic paper by introducing cellulose-based materials to the process. Paper can participate as a substrate for the metal oxides, but it can also form composites or membranes, and it adds a valuable contribution as it is environmentally friendly, low-cost, flexible, recyclable, lightweight, and earth abundant. In term of photocatalysts, the use of metal oxides is widely spread, mostly since these materials display enhanced photocatalytic activities, allied to their chemical stability, non-toxicity, and earth abundance, despite being inexpensive and compatible with low-cost wet-chemical synthesis routes. This manuscript extensively reviews the recent developments of using photocatalytic papers with nanostructured metal oxides for environmental remediation. It focuses on titanium dioxide (TiO2) and zinc oxide (ZnO) in the form of nanostructures or thin films. It discusses the main characteristics of metal oxides and correlates them to their photocatalytic activity. The role of cellulose-based materials on the systems’ photocatalytic performance is extensively discussed, and the future perspective for photocatalytic papers is highlighted.
... Herein, we report the synthesis of nanoparticles possess with different compositions (α-Fe 2 O 3 : ZnO = 1:1, 2:1, and 1:2) through a simple and facile chemical route and subsequently studies the degradation of methylene blue dye under solar energy. The synthesis has been carried out by following two steps particularly calcination of iron (II) oxalate complex at 500°C to form α-Fe 2 O 3 nanoparticles [34] followed by the chemical precipitation of ZnO nanoparticles at 90°C [35]. ...
... ZnCl 2 (3 g) was dissolved in 50 mL of de-ionized water under stirring at 90°C and further, 3 M sodium hydroxide solution was added dropwise till the pH of the solution attained the value ∼ 12 [35]. It led to a white milky precipitate which was further refluxed for 3 h at 90°C. ...
Article
The present report illustrates the photocatalytic degradation of methylene blue dye under solar energy through α-Fe2O3 - ZnO composite synthesized by adopting a facile and simple chemical method. Various characterization techniques particularly X-ray diffraction (XRD), Transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR), etc., have been employed to characterize the as-synthesized composite. The XRD reveals the successful formation of the as-synthesized sample. The TEM studies illustrate the agglomeration of particles with sizes in the range of ∼10–60 nm. HRTEM micrograph indemnifies the formation of lattice fringes pertaining to inter-planner spacing∼ 0.149 nm and ∼0.138 nm corresponding to (214) reflection plane of hematite and (112) reflection plane of ZnO, respectively. The as-synthesizedα-Fe2O3 – ZnO composite shows double absorption edges which correspond to the bandgap of α-Fe2O3 (2.2 eV) and ZnO (3.2 eV). Furthermore, α-Fe2O3 - ZnO composite shows a remarkable enhanced degradation capacity than bare hematite nanoparticles and zinc oxide nanoparticles, and α-Fe2O3 – ZnO (1:2) composite demonstrates the best degradation performance among all the variants. Moreover, it clearly suggests that the UV part of solar light plays a vital role in the catalytic degradation of methylene blue whereas the visible part of light remains unresponsive.
... 20−22 In the past decade, a variety of synthesis methods of ZnONPs with different morphologies have been reported, creating such moities as nanoparticles, nanorods, 23 nanotubes, 24 nanobelts, 25 nanoplates, 26 nanorings, and even nanoflowers. 27,28 The usual methods to synthesize ZnONPs include sol−gel, 29 hydrothermal, 30 mechanochemical, 31 vapor-phase method (VPM), coprecipitation, 32 and via solution. 33 These methods all have a common limitation that the product could not disperse well or rapid subsidence in water, and this prevents ZnONPs from being useful in biological fields. ...
... The high concentration of OHincreased the growth and density of ZnO rods, which led to form flower-type morphologies when the length of nanorods is reduced (Figure 3 a-l) [56]. Baruah and coworkers have reported that flower-like nanostructures are typical of ZnO [57] and they can be composed either of hexagonal nanorods [58] or nanosheet petals [59], which are derived as a result of the increase of the pH above 9. Thus, the high VW X/VZ5 Q[ X ratio explains the flower type morphology due to an excess of the OH groups in the reaction medium. ...
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The main purpose of this work was to synthesize ZnO nanoparticles (NPs) in situ into a chitosan (CS) matrix to obtain highly dispersed antibacterial composites by the sol-gel technique. These composites were characterized by their thermal, structural, morphological and optical properties. NPs were subsequently used and added into polyvinyl alcohol (PVA) in order to obtain electrospun fibers. Previously, it was determined the adequate PVA/CS ratio and changes in their morphological features in dependence of molecular weight of PVA and electrospinning parameters to avoid the beads and spindle-like defects in the final fibers. Then, optimal conditions were used to fabricate PVA/in situ ZnO:CS nanofiber composites. The hydrogen bonding interaction governs the ZnO:CS system, which forms a combination between flower-type and agglomerated rod morphologies. It was found that CS promotes the crystallinity of ZnO NPs maintaining the hexagonal phase. The addition of ZnO into the CS matrix was performed via weak interactions by stabilizing the hybrid compound after the second decomposition stage when the mass loss is above 50 %. Free-defects uniform fibers with an improvement in hardness as well as in the elastic modulus was obtained in the electrospun PVA/in situ ZnO:CS fibers. The presence of ZnO NPs improves the spinnability in the fiber nanocomposites with an average diameter of 223 nm. PVA/in situ ZnO:CS mats displayed an inhibition of bacterial growth of E. coli and S. aureus.
... ZnO with the wide bandgap energy (3.37 eV) and the high exciton binding energy (60 meV) could absorb a larger fraction of the UV spectrum to oxidize harmful organic substances in wastewater effectively [21][22][23]. e photocatalytic mechanism for degradation of organic pollutants of ZnO nanomaterials has been indicated in previous studies [12,[24][25][26]. Upon the UV irradiation with the photonic energy (hʋ) equal to or greater than the bandgap energy (E g ) of ZnO, the electrons in the valence band can be excited (e−) and transfer to the conduct band, leading to holes (h + ) generation in the VB. e electrons can active molecular oxygen to form superoxide anion radicals • O 2 − , whereas the photogenerated holes react with either water (H 2 O) or hydroxyl ions (OH − ) to produce hydroxyl radicals ( • OH). e formation of • OH, • O 2 − radicals, which are powerful oxidizing agents, will attack the pollutants adsorbed on the surface of ZnO through hydroxylation, oxidation, and mineralization processes to create finally harmless compounds of CO 2 and H 2 O. ...
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In this study, the physical properties of ZnO were facile controlled by the synthesis method with the addition of capping and precipitation agents. As-prepared ZnO samples had different morphologies such as carnation flower-like ZnO (CF-ZnO), rose-flower-like ZnO (RF-ZnO), rod-like ZnO (R-ZnO), and nanoparticle ZnO (N-ZnO) and were characterized by SEM, XRD, N2 adsorption/desorption isotherms, FT-IR, and DR/UV-vis. All samples had a crystallite structure of hexagonal wurtzite type. The CF-ZnO and RF-ZnO samples had the hierarchical structure like a carnation flower and a beautiful rose, respectively. R-ZnO was composed of many hexagonal rods and few spherical particles, while N-ZnO microstructures were made up of nanoparticles with approximately 20–30 nm, exhibiting the largest surface area, pore volume, and pore width among as-prepared samples, and their crystal size and bandgap energy were 17.8 nm and 3.207 eV, respectively. The catalytic performances of ZnO samples were evaluated by degradation of Tartrazine (TA) and Caffeine (CAF) under low UV irradiation (15 W). N-ZnO showed a high photocatalytic activity compared to other samples. Besides, the reaction kinetics was investigated by the first-order kinetic model, and the catalytic performance of ZnO was evaluated through several organic pollutants.
... Various methods are used to synthesize nanomaterials which include chemical synthesis methods [20][21][22], and physical synthesis methods [23][24][25]. These methods for synthesis include, hydrothermal synthesis [26], solution precipitation method [27], spray pyrolysis [28], physical vapor deposition [29], chemical vapor deposition [23], microemulsion method [30], and sol-gel process [31]. All these methods utilize toxic reducing agents, sophisticated and costly equipment, lengthy and harsh synthesis procedures, etc. ...
Article
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Zinc oxide nanostructures (ZnO NSs) have been extensively studied because of their many applications in different fields. In this study, an attempt has effectively been made for the synthesis of ZnO nanostructures by using fast and environment-friendly microplasma electrochemical technique. The prepared nanostructures were examined in terms of their morphological, optical, structural, electrical, and compositional properties by using different characterization techniques. Results demonstrated that the highly crystalline ZnO nanostructures were produced with a single hexagonal (wurtzite structure) phase. Results also indicated the crystallite size increases with increasing precursor concentration. The optical band gap of ZnO is found to decrease (from 3.48eV to 3.40 eV) with increasing crystallite size. I-V characteristics of ZnO are measured by two probe technique which shows semiconducting behavior of prepared ZnO. The antibacterial and photocatalytic properties of the synthesized nanostructures were also investigated. It was observed that the degradation efficiency of zinc oxide photocatalyst increases with the irradiation time. About 85% of Rhd B dye was degraded by ZnO after 120 min at a rate of 0.01339 min⁻¹ under direct sunlight irradiation. The antibacterial activity of ZnO was carried out against different gram-positive and gram-negative bacterial strains, by using the diffusion well method. Higher antibacterial activities were observed against gram-negative bacteria as well as for a higher concentration of ZnO. This study will be helpful to synthesize low-cost and effective materials to remove microorganisms and toxic industrial organic dyes which is a serious threat to terrestrial and aquatic life.
... Figure 10 shows the UV-Visible spectra of PEG capped pure and Silver (1-5%) doped ZnO nanoparticles. PEG capped pure ZnO nanoparticles showed strong UV absorption around 382 nm that could be related to the wurtzite crystal structure of ZnO (Wahab et al. 2007). PEG capped Ag doped ZnO nanoparticles exhibit the absorption band towards higher wavelength. ...
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Utilization of natural waste for energy conversion offers the method for clean energy production with sustainable development. The pomegranate peels are the natural waste generated every day and we describe the conversion of this waste into electricity by a simple and cost-effective method. Dye Sensitized Solar Cells (DSSCs) offer simple and cost-effective method for the preparation of solar cells. The advantages include easy to fabrication, lower cost of the materials and electricity generation under low illumination indoor conditions. DSSCs involve two Transparent Conducting Oxide (TCO) photoelectrodes acting as photoanode and photocathode. In one photoelectrode, Semiconducting oxide (TiO 2 /ZnO) and dye (Natural/Organometallic) are coated that acts as photo-absorbing materials. The role of dyes and semiconducting material play an important role in determining the photovoltaic conversion efficiency of fabricated solar cells. In this work, hydrothermal method has been adopted for the preparation of pure and silver doped ZnO nanoparticles using polyethylene glycol (PEG) as capping agent via wet chemical route. The structural and optical properties of the prepared samples were studied using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Analysis (EDAX) and UV-Visible absorption spectra. A Natural dye from the peels of pomegranate was extracted and dye sensitized solar cells were fabricated with pure and Ag-doped nanoparticles. Both the materials showed the photovoltaic conversion capabilities and showed photoconversion efficiencies. The solar cell fabricated with Ag-doped ZnO semiconducting nanoparticle showed higher short circuit current density as compared to the pure ZnO-nanoparticle synthesized in this study. The photoconversion efficiency of the DSSC based on Ag-doped ZnO showed 30% more conversion efficiency than the cell without silver doping.
... The non-toxicity and low-cost sol-gel processing conditions for depositing ZnO makes it attractive for the development of n-FETs. As such, several methods such as atomic layer deposition [1], pulsed laser deposition [2,3], spray pyrolysis [4], hydrothermal deposition [5], and chemical and other physical vapor deposition methods [6] have been used to deposit hierarchical architectures of ZnO in addition to sol-gel processes [7,8]. ...
Article
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The use of high κ dielectrics lowers the operating voltage in organic field-effect transistors (FETs). Polymer ferroelectrics open the path not just for high κ values but allow processing of the dielectric films via electrical poling. Poled ferroelectric dielectrics in p-type organic FETs was seen to improve carrier mobility and reduce leakage current when compared to unpoled devices using the same dielectric. For n-type FETs, solution-processed ZnO films provide a viable low-cost option. UV–ozone-treated ZnO films was seen to improve the FET performance due to the filling of oxygen vacancies. P-type FETs were fabricated using the ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) as the dielectric along with a donor–acceptor polymer based on diketopyrrolopyrrole (DPP-DTT) as the semiconductor layer. The DPP-DTT FETs yield carrier mobilities upwards of 0.4 cm2/Vs and high on/off ratios when the PVDF-TrFE layer is electrically poled. For n-type FETs, UV–ozone-treated sol–gel ZnO films on SiO2 yield carrier mobilities of 10−2 cm2/Vs. DPP-DTT-based p- and ZnO-based n-type FETs were used in a complementary voltage inverter circuit, showing promising characteristic gain. A basic inverter model was used to simulate the inverter characteristics, using parameters from the individual FET characteristics.
... These morphologies have also been obtained experimentally in Refs. [1,13,14,32,[51][52][53][54][55][56][57][58][59][61][62][63]. Furthermore, the model proposed considers synthesis routes in solution, hydrothermal or aqueous medium, in which a zinc salt reacts under a basic medium to form. ...
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DOI: 10.1016/j.mtcomm.2021.102748 Zinc oxide nanoparticles (ZnONPs) synthesis was studied in multiscale modeling, proposing a reaction-diffusion system based on its three-stage reaction mechanism by the hydrothermal method: (1) dissociation of the precursor, (2) formation of the anion complex, and (3) obtaining the ZnO nanoparticle. Chemical compounds present in the reaction mechanism were evaluated under the Density Functional Theory (DFT) to find its reactivity through the B3LYP/6-311+G method. Reaction-diffusion model Computational simulation and numerical solution allow reproducing ZnONPs three-dimensional morphologies reported experimentally, such as rods, spheres, pseudo-spheres, octahedral, sheet-like, nut-like, and hollow spheres.
... In Al 2 O 3 , OH-stretching attributed to the wide peaks found at 2979 to 3276 cm − 1 . Presence of atmospheric moisture can be confirmed by the peak at 1385 cm − 1 [25,26]. Stretching vibrations of terminal M − O bonds lead to the occurrence of the peak at 1073 cm − 1 [24]. ...
Article
Mn-based photocatalyst and antimicrobial agent was synthesized by ultrasonic-assisted co-precipitation method by keeping MnO2 as active compound and Al2O3 was adopted as catalyst support. XRD and HRTEM analysis verified the co-existence of MnO2 and Al2O3 and the crystalline nature of NCs. The XPS and EDAX revealed the chemical states of elements namely Mn2p, Al2p and O1s. The presence of Mn–O and Al–O–Al bonds were noted through FTIR. The photon absorption ability of NCs in visible region was favoured by the energy bandgap of 2.51 eV. Photoluminescence revealed that the charge carriers in NCs showed an improvement in life time. The NCs exhibited enhanced photocatalytic effect due to its synergetic effect and the photocatalytic performance can be ordered as MnO2/Al2O3 > MnO2 > Al2O3. The enhancement in photocatalysis rate in NCs was attributed by the formation of heterostructure and it prevent the recombination of charge carriers. The OH· radical was the dominant species in dye degradation. The NCs showed high photostability and recyclability, and almost same photocatalytic activity preserved even after sixth recycle. In addition to that, the antimicrobial activity of MnO2/Al2O3 was demonstrated to be efficient in their action against the strains of gram positive and gram negative bacteria than that of the individual MnO2 and Al2O3 NPs. Thus, this multifunctional MnO2/Al2O3 can be used as an efficient candidate for the photocatalytic degradation of toxic dyes and an antimicrobial agent.
... The presence of ZnO, which showed the hexagonal wurtzite structure, in condensed phases was confirmed by X-Ray Diffraction (XRD) analysis. Some of the XRD results are shown in Fig. 4, and the peaks are indexed according to JCPDS card No. 79-2205 and 36-1451 [33,34]. The peak referring to [0 0 2] reflection is overwhelmingly higher than the other peaks indicating that the condensed ZnO has a strongly preferential growth direction along the (0 0 2) plane. ...
Article
Fuels used in combustion and gasification, such as coal, biomass and wastes, yield large amounts of trace elements , which can cause both technological and environmental concerns. This work provides an in-depth insight into the condensation behavior of the trace element zinc under gasification-like conditions in atmospheres containing the HCl and H2S trace gases. A lab-scale quartz reactor with a multi-stage cooling zone was used to determine the condensation content and species distribution of the zinc deposition in different gasification atmospheres. The Scheil-Gulliver cooling model was used to simulate the zinc condensation process, since it provides a good reference to analyze the degree of supercooling during the condensation process. Competition of the gaseous species HCl and H2S with respect to the ZnO condensation behavior has been observed. HCl leads to significant supercooling of the ZnO condensation. It is shown that this can be compensated by ZnS acting as nucleation sites for ZnO if significant amounts of H2S are present. It is further shown that there is a significant bypass effect, i.e. even after nucleation has started there is a significant amount of Zn remaining in the gas phase which significantly extends the condensation regime to lower temperatures. To visualize both effects, a H2S-temperature-transition diagram is proposed. The potential applications including the prevention of problematic depositions (slagging and fouling) and sorbent selection as well as design for removal of trace element zinc from the syngas in IGCC power plants are proposed and discussed in the light of developing clean power technologies.
... These morphologies have also been obtained experimentally in Refs. [1,13,14,32,[51][52][53][54][55][56][57][58][59][61][62][63]. Furthermore, the model proposed considers synthesis routes in solution, hydrothermal or aqueous medium, in which a zinc salt reacts under a basic medium to form. ...
Article
Full-text available
Zinc oxide nanoparticles (ZnONPs) synthesis was studied in multiscale modeling, proposing a reaction-diffusion system based on its three-stage reaction mechanism by the hydrothermal method: (1) dissociation of the precursor, (2) formation of the anion complex, and (3) obtaining the ZnO nanoparticle. Chemical compounds present in the reaction mechanism were evaluated under the Density Functional Theory (DFT) to find its reactivity through the B3LYP/6-311+G method. Reaction-diffusion model Computational simulation and numerical solution allow reproducing ZnONPs three-dimensional morphologies reported experimentally, such as rods, spheres, pseudo-spheres, octahedral, sheet-like, nut-like, and hollow spheres.
... FTIR spectrum of ZnO nanostructures was obtained from sample deposited at 500 rpm corresponding to 120 nm thickness. Figure 6 shows the infrared spectrum of the sample of ZnO Figure 7 and Figure 8 which is similar to results reported [7,11,15,[25][26][27][28][29][30][31][32] (Table 1). ...
... The peak at 597.15 cm −1 in the FT-IR diagram of the synthesis adsorbent is due to the metallic group [37]. This peak can be attributed to the presence of ZnO in the adsorbent. ...
Article
... The rod formation takes place to maintain the minimum surface energy and keep the symmetry in the crystal structure of wurtzite ZnO. This observation is in close agreement with earlier reports where zinc ions reacts with hydroxyl ion at ambient or hydrothermal conditions to form zinc oxide flower comprises of zinc oxide rods [35][36][37][38]. Based on the above observation, it is found that the discharging time is an important factor to control the shape/size of the ZnO. ...
Article
In the present work, the field emission characteristics of zinc oxide (ZnO) rods extracted from waste primary alkaline batteries is demonstrated. ZnO rods were extracted from anode component of the waste primary battery via eco-friendly process using water as solvent for the first time. Earlier, synthesis of ZnO nanoparticles using waste primary battery was done using complex hydrometallurgical processes. The fabrication of ZnO based field emitter was achieved via coating of ZnO on silicon substrate using scalable spin coating process. The turn on field for ZnO rods was 4.9 Vμm⁻¹ with field enhancement factor 4655 in the high field regime. This process would certainly be of interest for the researchers working in the field of materials chemistry and environmental waste management.
... The obtained UV-vis spectrophotometer results were in agreement with Dobrucka et al. [33], who reported that the maximum absorption of about 310 nm, which is a characteristic band of pure ZnO, verified the presence of ZnONPs biologically with the use of the extract of Chelidonium majus. Furthermore, there was no additional peak in the spectrum, confirming that the produced products were pure ZnO [34,35]. In addition, Perveen et al. [36] reported that UV-visible spectroscopy investigation showed a peak at 300 nm, which corresponded to the wavelength of ZnO quantum dots' surface plasmon resonance. ...
Article
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ZnO-based nanomaterials have high antifungal effects, such as inhibition of growth and reproduction of some pathogenic fungi, such as Fusarium sp., Rhizoctonia solani and Macrophomina phaseolina. Therefore, we report the extracellular synthesis of ZnONPs using a potential fungal antagonist (Trichoderma harzianum). ZnONPs were then characterized for their size, shape, charge and composition by visual analysis, UV–visible spectrometry, X-ray diffraction (XRD), Zeta potential, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX). The TEM test confirmed that the size of the produced ZnONPs was 8–23 nm. The green synthesized ZnONPs were characterized by Fourier transform infrared spectroscopy (FTIR) studies to reveal the functional group attributed to the formation of ZnONPs. For the first time, trichogenic ZnONPs were shown to have fungicidal action against three soil–cotton pathogenic fungi in the laboratory and greenhouse. An antifungal examination was used to evaluate the bioactivity of the mycogenic ZnONPs in addition to two chemical fungicides (Moncut and Maxim XL) against three soil-borne pathogens, including Fusarium sp., Rhizoctonia solani and Macrophomina phaseolina. The findings of this study show a novel fungicidal activity in in vitro assay for complete inhibition of fungal growth of tested plant pathogenic fungi, as well as a considerable reduction in cotton seedling disease symptoms under greenhouse conditions. The formulation of a trichogenic ZnONPs form was found to increase its antifungal effect significantly. Finally, the utilization of biocontrol agents, such as T. harzianum, could be a safe strategy for the synthesis of a medium-scale of ZnONPs and employ it for fungal disease control in cotton.
... In line with JCPDS card no. 36-1415, the diffraction patterns are indexed to hexagonal wurtzite ZnO phase [x = 0] [46]. The XRD patterns revealed no traces of secondary phases or contaminants, confirming the phase purity of all the compositions. ...
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Present study portrays, physicochemical investigations of pristine and Pd²⁺ modified ZnO nanoflowers (NFs) compositional series [Zn(1−x)PdxO NFs; where x = 0, 0.01, 0.03, 0.05, and 0.07] synthesized via sol–gel reaction route. X-ray diffractogram of all the compositions displayed hexagonal wurtzite type crystallinity with P63mc space group without any traces of impurities as confirmed from Rietveld refinement technique. It was found that the average crystallite size increased from 32 to 74 nm with Pd²⁺ intrusion in the crystal lattice framework of ZnO. FESEM micrographs depicted that the surface morphology of pure and Pd modified compositions exhibit flower-shaped surface morphology. The optical properties of as-synthesized NFs were carried out using UV–vis spectroscopy and it was observed that optical energy bandgap (Eg) decreased minutely by Pd²⁺ doping. To determine the gas sensing behavior of synthesized NFs, the prepared gel during material fabrication was used to cast thin films. The thin films were calcined at 600 °C for LPG gas sensing activity and it was observed that the transient curve shows a high response for the composition x = 0.03 for the concentration of 2000 ppm. The present result illustrates that synthesized NFs showed potential candidature for LPG gas sensing. The present study reveals synthesized NFs showed potential candidature for LPG gas sensing 80 °C with a gas sensitivity of 315%.
... The binding energies of N 1 s of BZAC before adsorption were 399.89 eV and 398.34 eV, respectively, which increased by 0.33 eV and 0.6 eV after adsorption, thereby suggesting that uranyl ions strongly interacted with C = N-and -NH-groups and that a peak that may belong to N-O-U appears, which was consistent with the infrared peak observed at 3119 cm -1 ( Fig. 10a and b) (Wang et al. 2018a, b, c). Figure 9d shows that the 1044.75 eV and 1021.74 eV of Zn 2p in the spectrum belonged to Zn 2p3/2 and Zn 2p1/2, respectively (Wahab et al. 2007). Their binding energies slightly increased after adsorption, thereby indicated that Zn also participated in the adsorption of uranyl ions. ...
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... A major sharp peak was detected at 447 cm −1 , which is characteristic of hexagonal wurtzite ZnO. This peak corresponds to the Raman active optical phonon mode E2 (high) [51]. Other small peaks were observed at 334.6 cm −1 and 584.7 cm −1 . ...
Article
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Fabrication of porous materials from the standard sacrificial template method allows metal oxide nanostructures to be produced and have several applications in energy, filtration and constructing sensing devices. However, the low surface area of these nanostructures is a significant drawback for most applications. Here, we report the synthesis of ZnO/carbon composite monoliths in which carbon is used as a sacrificial template to produce zinc oxide (ZnO) porous nanostructures with a high specific surface area. The synthesized porous oxides of ZnO with a specific surface area of 78 m2/g are at least one order of magnitude higher than that of the ZnO nanotubes reported in the literature. The crucial point to achieving this remarkable result was the usage of a novel ZnO/carbon template where the carbon template was removed by simple heating in the air. As a high surface area porous nanostructured ZnO, these synthesized materials can be useful in various applications including catalysis, photocatalysis, separation, sensing, solar energy harvest and Zn-ion battery and as supercapacitors for energy storage.
... The FTIR spectra of BiVO 4 , Ag-BiVO 4 NPs and Ag-BiVO 4 -rGO composite were recorded in the range of 4000 to 400 cm − 1 as showed in [63]. In Ag-BiVO 4 NPs (Fig. 3b) the intensity of peak is reduced and slight shift in the position of the band toward lower frequencies is associated with changes in bond length owing to the formation of Ag NPs on the surface of BiVO 4 NPs. ...
Article
Recently, the development of multifunctional heterostructured nanocomposites has recieved significant interest due to their numerous applications. In this study, BiVO4, Ag-BiVO4 and Ag-BiVO4-rGO photocatalysts were synthesised using Citrus bergamia through solution combustion technique. Prepared nanomaterials were characterized by PXRD, FTIR, Raman, UV- visible DRS, TEM, SEM and EDX spectroscopy studies. The materials were assessed for photocatalytic MB dye degradation. Ag-BiVO4-rGO photocatalyst was found to degrade MB dye completely in 60 min whereas BiVO4 and Ag-BiVO4 NPs degraded the dye in 150 and 180 min respectively. Photoluminescence spectra evidenced the efficient charge separation in Ag-BiVO4-rGO composite compared to BiVO4 and Ag-BiVO4 NPs. The electrochemical nitrite sensing studies revealed that Ag-BiVO4-rGO composite was a promising electrocatalyst with a significant anodic peak current 57.43 μA at the potential of 0.867 V. The limit of detection of nitrate was observed to be 8.7517 μM. Further, the composite material exhibited better biological activities such as antioxidant, erythrocytes lysis, anticoagulant, anti-platelet and antibacterial properties. The superior properties of Ag-BiVO4-rGO are ascribed to reduction in the energy gap as well as crystallite size by incorporation of Ag into the crystal lattice and presence of rGO. The present study demonstrates a novel approach to develop multifunctional Ag-BiVO4-rGO nano hybrid material for photocatalytic dye degradation, photoluminescence, electrocatalytic nitrite detection and selected biomedical applications.
... Highresolution O1s and Zn2p spectrum were shown in Fig. 4b and c respectively. The binding energy located at 531.8 eV and 531.0 eV can [35,36]. Furthermore, the EDS spectra was used to provide more elemental distribution information, as shown in Fig. 4d. ...
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It remains a great challenge to design and achieve fluorine-free superhydrophobic materials for multifunctional applications through facile and substrate-independent approaches. Herein, environmental-friendly superhydrophobic composite coating was fabricated with the combination of nano zinc oxide (nano-ZnO) and polydimethylsiloxane (PDMS) via a versatile spray-coating method. The surface wettability, micro-nano morphologies and chemical compositions of the superhydrophobic [email protected] coating were investigated through contact angle meter, FE-SEM, AFM, EDS, XPS and FTIR techniques. The optimal superhydrophobic [email protected] coating with water contact angle (WCA) of 158.3±1.7° and sliding angle of 6.2 ± 1.8° can be achieved with the nano-ZnO/PDMS mass ratio of 1.5:1. The self-cleaning and anti-fouling ability was evaluated based on the solid and liquid contaminants. The electrochemical impendence spectroscopy (EIS) results verified that the superhydrophobic [email protected] coating exhibits a larger capacitive arc diameter, enhanced charge transfer resistance and |Z|0.01 Hz value at the low frequency, suggesting an improvement of anti-corrosion performance. Besides, the mechanical robustness and stability of the superhydrophobic [email protected] coating were evaluated through tape-peeling and sandpaper abrasion tests, which provides potential applications towards real-world applications.
... The shape and position of SPR bands depends on various parameters such as shape, particle size, dielectric constant and medium [40]. The ZnO NPs exhibits strong UV absorption edge at 374 nm that could be related to wurtize crystal structure of ZnO [41]. By decorating Au to the surface of the ZnO NPs, the absorption edge moved towards the longer wavelength (red shifted). ...
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... Transmission peaks observed at 1320 cm −1 were proposed to be contributed by the stretching of C-O bonds of carbonyl groups and/or C-O of alcoholic groups and glycosidic linkages of the phytochemical constituents of Kakadu plum. Finally, there was a strong transmission peak that appeared around 500 cm −1 is correlated to Zn-O [35][36][37][38][39]. ...
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... The EDX micrograph of ZnO9 nanoparticles has been shown in Fig 5( Fig 5(b). The weight and atomic ratio of Zn:O were 4.69 and 1.14, respectively, which had been in agreement with the similar results reported elsewhere [55][56]. ...
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In this investigation, highly crystalline and mesoporous Zinc oxide (ZnO) nanoparticles with the large surface area were synthesized without calcination. Furthermore, the effects of different pH values on structural, physicochemical and textural properties of ZnO nanoparticles were comprehensively investigated. Rietveld refinement implied that the pH variation had significant effects on the crystal structure of ZnO nanoparticles. The phase, molecular and elemental structures confirmed the formation of ZnO as a major phase in all nanopowders. The morphology of ZnO nanoparticles was irregular with an average size of 45± 9 nm. Both phase and atomic structures confirmed the polycrystalline arrangement of ZnO nanoparticles. Moreover, isotherms confirmed the mesoporous structure of all ZnO nanoparticles with superior specific surface area and porosity volume. Thus, owing to the concoction of high crystallinity, superior surface area and porosity volume, resultant ZnO nanoparticles can be effectively employed for diverse multifunctional therapeutic applications.
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This paper investigated the degradation of the pharmaceutical drug Valsartan (VS) using non-equilibrium atmospheric pressure plasma (NEAPP) with various operating conditions. The heterogeneous photocatalyst ZnO nanoparticles (NP's) were synthesized using a hydrothermal process. The morphology, chemical composition and structure of as-synthesized ZnO NPs were examined by Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. Then, VS degradation was examined in three subsequent treatment conditions including plasma treatment alone, the combination of plasma with as-prepared ZnO NPs and various environments (air, oxygen and hydrogen peroxide) at fixed plasma operating potential and treatment time. The degradation efficiency of plasma-treated VS by various conditions was observed using UV-visible spectroscopy. Optical Emission Spectrometry (OES) was used to characterize the distribution and emission intensity of various reactive species (OH˙, N2-SPS and O) during the degradation processes which plays a vital role in the degradation of VS. The role of OH˙ and H2O2 during the degradation process was further examined by chemical dosimetry and spectroscopic techniques. Furthermore, pH, conductivity and TOC of the untreated and plasma-treated VS were also investigated. The results on the degradation of VS showed that plasma treatment combined with ZnO NP's has a significant effect on degradation of molecules of VS than degradation processes carried out by other experimental conditions due to the formation of higher concentrations of various reactive oxygen and nitrogen species during the degradation processes.
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Bacteria induced wound infection has become fatal healthcare issues needed to be resolved urgently. It is of vital importance to develop multifunctional therapeutic platforms to fight against increased bacterial antibiotic resistance. Herein, a titanium carbide (MXene)/zeolite imidazole framework-8 (ZIF-8)/polylactic acid (PLA) composite membrane (MZ-8/PLA) was fabricated through in-situ growth of ZIF-8 on MXene and the subsequent electrospinning process. It indicated MZ-8 can generate singlet oxygen and hyperthermia at photothermal (PTT) convention efficiency of 80.5 % with bactericidal rate of more than 99.0%. In addition, MZ-8 showed remarkable antitumor efficiency in vitro and in vivo based on the combined photodynamic/photothermal therapy. Theoretical calculation illustrated MZ-8 could improve the laser activation process by acceleration of intermolecular charge transfer, reducing excitation energy, stabilizing excited states and increasing intersystem crossing rate. After incorporated into electrospun scaffolds, MZ-8/PLA exhibited potent PTT and photodynamic therapy (PDT) properties under 808 nm laser irradiation. The antibacterial rates of MZ-8/PLA were up to 99.9% and 99.8% against Escherichia coli and Methicillin-resistant staphylococcus aureus, respectively. In-vivo experimental results further confirmed that MZ-8/PLA can accelerate bacteria infected wound healing without observable resistance. This work opens a new avenue to design promising platforms for fighting against extremely drug resistant bacterial infection.
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Lithium (Li) metal is considered as the best anode candidate for next-generation high-energy batteries due to its ultralow electrochemical potential and extremely high theoretical capacity. However, issues arising from the undesired growth of lithium dendrites and infinite volumetric change have seriously hindered the practical application of lithium metal batteries (LMBs). Here, we designed a super-lithiophilic amorphous zinc oxide-doped carbon nanofiber framework with uniformly-distributed and parallel multichannels ([email protected]) to achieve the homogeneous distribution of electric field and Li⁺ flux. By the assistances of COMSOL Multiphysics simulations and ex-situ scanning electron microscopy, we reveal that the Li metal preferentially deposits into the porous nanochannels inside the nanofibers, followed by its even distribution on the lithiophilic surface of [email protected] Furthermore, the conductive multichannels of the carbon nanofiber skeleton can effectively minimize the partial current density, thereby effectively avoiding the electrochemical polarization and assisting the uniform metallic deposition. As a result, [email protected] exhibits a stable CE over 99.2% as the substrate after 500 cycles at the current density of 1 mA cm⁻². The symmetrical cell of lithium-loaded [email protected] composite electrodes can stably operate over 3300 h at 0.5 mA cm⁻², indicating the great potential of [email protected] for stabilizing lithium metal anodes in practical applications of LMBs.
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Zinc oxide (ZnO) nanostructures can be synthesized in nanoforms of spheres, rods, flowers, disks, walls, etc., among which nanoflowers have gained special attention due to their versatile biomedical and pollutant remedial applications in waste water and air. ZnO nanoflowers have an ultrasmall size with a huge surface area to volume ratio due to their hexagonal petal structures which render them superior compared to the nanoparticles of other shapes. The ZnO nanoflowers have bandgap energy equivalent to a semiconductor that makes them have unique photophysical properties. We have used the appropriate keywords in Google Scholar and PubMed to obtain the recent publications related to our topic. We have selected the relevant papers and utilized them to write this review. The different methods of synthesis of ZnO nanoflowers are chemical vapor deposition, facile hydrothermal, thermal evaporation, chemical reduction, bio route of synthesis, and solvothermal method, etc. which are mentioned in this review. ZnO nanoparticles are used in paints, cosmetics, and other products due to their high photocatalytic activity. The different applications of ZnO nanoflowers in the diagnosis of disease biomarkers, biosensors, catalysts, and the therapeutic process along with wastewater remediation and gas sensing applications will be discussed in this review.
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The solution-based technique is recently gaining momentum for the fabrication of optoelectronic materials due to its cost-effectiveness, fabrication of large-scale thin films, processing at low temperature, low cost and simplicity of the process requirements. The properties of thin films depend on the diverse parameters like substrate, deposition time, source materials, doping agent, pH and temperature at which the process is done. ZnO nanostructured thin film has been widely used in organic and hybrid solar cells due to its precise characters such as reduced cost, simple processing, non-toxicity, better optoelectronic properties and good stability. In this review article, we have focused on different solution-based methods which are capable of yielding good quality thin films of ZnO with different morphology for various applications.
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Damage to the skin makes the body vulnerable to microorganisms; wound dressings with desirable properties such as antibacterial activity is used in order to accelerate the healing of the injury. An available natural substance investigated for its antibacterial property is honey; also, zinc-oxide nanoparticles (ZnO-NPs) have shown great antibacterial activities. This study investigated some properties of PU-Gel nanofibrous membranes, loaded with honey and ZnO-NPs, including antibacterial activity against Staphylococcus aureus, Escherichia coli, and Bacillus subtilis, mechanical properties and cell proliferation. The results indicate that PU/Gel/ZnO and PU/Gel/ZnO/H are suitable in inhibiting bacterial growth compared with PU/Gel/H and control membranes. Moreover, PU/Gel/H membranes had considerable antibacterial effect on E-coli. The addition of ZnO-NPs improved the mechanical properties. Cell culture studies (MTT test) proved the biocompatibility of the developed nanofibrous membranes. The obtained nanofibrous membrane PU/Gel/ZnO/H is a promising candidate for the development of improved bandage materials.
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Nanoparticles (NPs) have acquired significance in technological breakthroughs due to their unique properties, such as size, shape, chemical composition, physiochemical stability, crystal structure, and larger surface area. There is a huge demand for packaging materials that can keep food fresher for extended periods of time. The incorporation of nanoscale fillers in the polymer matrix would assists in the alleviation of packaging material challenges while also improving functional qualities. Increased barrier properties, thermal properties like melting point and glass transition temperatures, and changed functionalities like surface wettability and hydrophobicity are all features of these polymers containing nanocomposites. Inorganic nanoparticles also have the potential to reduce the growth of bacteria within the packaging. By incorporating nano-sized components into biopolymer-based packaging materials, waste material generated during the packaging process may be reduced. The different inorganic nanoparticles such as titanium oxide, zinc oxide, copper oxide, silver, and gold are the most preferred inorganic nanoparticles used in food packaging. Food systems can benefit from using these packaging materials and improve physicochemical and functional properties. The compatibility of inorganic nanoparticles and their various forms with different polymers make them excellent components for package fortification. This review article describes the various aspects of developing and applying inorganic nanoparticles in food packaging. This study provides diverse uses of metals and metal oxides nanoparticles in food packaging films for the development of improved packaging films that can extend the shelf life of food products. These packaging solutions containing nanoparticles would effectively preserve, protect, and maintain the quality of the food material.
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The zinc oxide (ZnO) nanostructures are highly influential material and exhibit numerous properties. Numerous physicochemical applications for instance electronic, catalyst, solar cells, hydrogen fuels and energy evolution. Besides the large application in various directions very few reports are available for the cytotoxic evaluations and their compression with nano particles (NPs) and nanrorods (NRs) against the breast (MCF-7) cancer cells. The ZnO-NPs and NRs were produced through solution process in a short time span and were well characterized. The cells viability was tested with MTT and NRU assays. A series of different concentrations (2 μg/mL, 5 μg/mL, 10 μg/mL, 25 μg/ mL, 50 μg/mL, 100 μg/mL and 200μg/mL) of NRs and NPs were employed against cancer cells for to evaluvate the % activity of sustained and non-sustained cells. The morphology of treated and control cells were observed via microscopy respectively. Including this, the genetic studies were also scrutinized, cell-cycle analysis express the upsurge in the apoptotic peak after a 24-h. Quantitative PCR (qPCR) data revealed that the mRNA levels of apoptotic genes such as p53, bax, and caspase-3 were upregulated, whereas bcl-2, an anti-apoptotic gene, was downregulated; therefore, apoptosis was mediated through the p53, bax, caspase-3, and bcl-2 pathways.
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This work describes the facile synthesis of silver nanoparticle-decorated zinc oxide nanocomposite through a simple glycol reduction method. The silver nanoparticle-decorated zinc oxide nanocomposite-based pencil graphite electrode has been validated as a perceptive electrochemical sensing podium towards nitrite. The morphology of the prepared nanocomposite has been characterized via specific spectroscopic and electrochemical techniques. The sensor exhibits a notable enhancement in the cyclic voltammetric response to nitrite oxidation at an ideal peak potential of 0.76 V in pH 6.0 acetate buffer. Under optimum conditions of nitrite directly expanded with their concentration in the range from 30 to 1400 μM with a detection limit of 14 μM.
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Hexagonal zinc oxide nanorods (ZnO-NRs) were prepared via solution process using zinc nitrate hexahydrate (Zn(NO3)2.6H2O, 0.25M), 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 200-250 nm and 2-3 μm respectively as observed from the field emission scanning electron microscopy (FESEM). The chemical composition 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.
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During the low-temperature atomic layer deposition (ALD) process, residual carbon from the un-reacted ligand of precursors causes deterioration in the properties of grown materials. This study proposed a simple approach using a base solution as a reactant to reduce residual carbon and improve the low-temperature ALD reaction. NaOH dissolved in H2O was used as the reactant base solution and diethyl zinc was used as a reactant. The effects of the base-reactant on the ZnO film growth were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and thin-film transistor (TFT) measurements. The crystallinity, grain size, and Zn and O contents of the ZnO thin films gradually increased as the concentration of NaOH increased (0 wt.%, 10 wt.%, 20 wt.%, 30 wt.%). Residual carbon occupying Zn sites were reduced as NaOH concentrations increased. The unintended heavily doped state induced by the residual carbon during the low-temperature ALD process was improved, and the ZnO TFT device fabricated with the NaOH/H2O solution also showed improvements in its field-effect mobility and the on/off current ratio. This simple approach, using the base solution as the reactant during the low-temperature ALD process, effectively improved the quality of the grown film with low carbon impurities. This article is protected by copyright. All rights reserved.
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Ag nanoparticle-integrated ZnO nanoflakes (ZnO/Ag nanocomposite) were synthesized by a simple green method using Beta vulgaris (beetroot) extract and assessed for their potential in in vitro anticancer activity. Four Ag contents (2.5, 5, 7.5, and 10%) were used in the composite (ZnO/Ag-2.5, ZnO/Ag-5, ZnO/Ag-7.5, and ZnO/Ag-1.0, respectively) to examine the effects of Ag on the surface, structural, morphological, and bio-activities of the ZnO/Ag nanocomposite. Bandgap narrowing was observed due to the introduction of silver in the ZnO/Ag composites. These nanocomposites were examined for their cytotoxic effects in the cervical (HeLa) and ovarian (SKOV-3) carcinoma cell lines. The dose-dependent cytotoxicity was investigated by studying the cell viability assay, ROS generation, and adenosine triphosphate (ATP) contents when the cell lines were exposed to the ZnO/Ag composites for 48 h. Among the various ZnO/Ag composites produced, the ZnO/Ag 7.5 composite exhibited superior anticancer activity against HeLa and SKOV-3 cell lines. The Cell viability and ATP contents were reduced significantly in a dose-dependent manner, whereas ROS generation was increased appreciably.
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The annealing process was carried out for the Nano composed oxides (zinc and nickel) at different temperatures (200 ° C, 500 ° C, 700 ° C) and for a specific time of one hour for each temperature change in order to get rid of the internal pressures and the change in their physical and chemical properties and study the structural properties. The optical and surface diffraction results of the nanocrystalline oxides after each temperature change, as the results of the X-ray diffraction of zinc oxide showed that it has a polycrystalline structure and of the hexagonal type and the X-ray diffraction of nickel oxide showed that it has a polycrystalline structure of the cubic type. After the annealing process using Brake law and calculating the average Crystallite size by Debye Shearer method, it was observed that there was an increase in the average crystal size after each temperature change and the results of FTIR showed the emergence of the chemical Zn-O band of zinc oxide, as most Studies indicate the emergence of a (Zn-O) band within the (cm-1) spectral range (400-700) and the emergence of a (Ni-O) chemical bond of nickel oxide, where the peak intensity of this bond decreases due to the hot change. Get up in temperatures. The results of (FESEM) images showed that it is within the nanoscale and that the grain size increases after each temperature change process..
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ZnO spheres were synthesized by solid state oxidation of ZnS microspheres at different oxidation temperatures of 600 and 700 °C in an ambient atmosphere. The high temperature transformation of ZnS microspheres into hexagonal structured and highly crystalline ZnO microspheres comprising interconnected nanoparticles facilitating efficiently electron transport as well as charge collection through an intended path in the solar cell. The comparative physico-chemical and photovoltaic studies were done for synthesized ZnO microspheres. The structural study by x-ray diffraction of ZnO confirmed the hexagonal ZnO; the UV–Visible spectroscopy study showed λ max varying from 410 to 413 nm and 397 to 407 nm for ZnO microspheres synthesized by heating at 600 and at 700 °C, respectively. Additionally, crystalline and electronic structures were validated by density functional theory studies. The computational studies also revealed growth of hexagonal ZnO, where the bandgap varied with the oxidation temperature. The photovoltaic properties of ZnO microspheres synthesized at 600 °C exhibited better performance than the ones synthesized at 700 °C due to high surface roughness leading to enhanced dye loading and favorable charge collection. Dye-sensitized solar cells fabricated from ZnO microspheres synthesized at 600 and 700 °C exhibited the maximum power conversion efficiency of 3.38% and 3.06% correspondingly.
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Here, we report high output piezoelectric voltage generation using ZnO nanowires oxidized at high temperature. The study has been carried out to observe behavior of ZnO nanowires in the presence of strong oxidizing gases (O, CO2, and NO2) at elevated temperature. The focus of the research was to generate high piezoelectric voltage by using surface modified ZnO nanowires. VING (vertically integrated nanowire generator) has been exposed to oxidizing gases. ZnO nanowires oxidized with O2 have shown maximum high output voltage of 3.36 V at 200o C, showing net rise of 0.762 V as compared to voltage generated at room temperature. Similarly, ZnO nanowires modified with CO2 molecules have generated piezoelectric voltage of 2.589 V at 200o C, exhibiting a rise of 0.778 V as compared to the values recorded at room temperature and ZnO nanowires modified with NO2 have generated maximum output voltage of 3.307 V at 150o C, indicating net rise of 0.59 V to the voltage values achieved at room temperature.
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This study illustrates preparation of well-formed TiO2 and Ag/TiO2 nanoparticles (NPs) by green combustion process using Cucumis melo (Muskmelon) juice as unique fuel. Polycrystalline Ag/TiO2 NPs outline the superior photocatalytic action towards the degradation of methylene blue dye and antioxidant activity through hindrance of free radical scavenging. The PXRD pattern illustrates the existence of Ag in the TiO2 crystal lattice with the average crystallite measure of 9.09 nm and 22.8 nm for TiO2 and Ag/TiO2 respectively. FTIR spectral studies showed a decrease in the intensity upon doping with Ag owing to the arrangement of Ag NPs on the surface of TiO2 NPs. The TEM image of Ag/TiO2 exhibited almost spherical shape with average particle measure of 9.12 nm. Further, HRTEM studies evidence enhancement of the lattice fringe width upon doping and d-spacing values are in conformity with XRD results illustrating successful doping of Ag into TiO2 lattice. PL spectrum of both the NPs exhibited intense peak at 458 nm (2.69 eV) and weak peaks at 486 nm (2.53 eV) and 700 nm (1.76 eV) in the visible region. Ag/TiO2 NPs showed predominant photocatalytic property for the MB dye decomposition compared to TiO2 NPs. This is possibly owing to aid of Ag Surface Plasmon Resonance in expanding the light assimilation of TiO2 NPs from near UV region to visible range driving to better light-absorbing capability and considerably enhances charge separation in TiO2 due to doping. The results manifested that Ag/TiO2 NPs possess conformity surface structure, better photocatalytic property compared to un-doped TiO2. Both the NPs proved to have considerable DPPH free radical scavenging activities.
Chapter
This chapter describes the synthesis of (ZnO) nanocrystals by different chemical methods and physical methods. A brief overview of various approaches, including precipitation, hydrothermal, solvothermal, sol–gel, microemulsion, combustion, electrochemical, sonochemical, laser ablation, magnetron sputtering, and spray pyrolysis, has been given. Among these synthesis methods, solution approaches are being used widely due to being cost-effective, appropriate, and their superhomogeneousness and high production of the metal oxide nanocrystals. There is keen attention paid toward the preparation procedure of ZnO nanocrystallites with the specific well-ordered shape and size because of the precise requirements in various applications.
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These three volumes provide comprehensive information about the instrument, the samples, and the methods used to collect the spectra. The spectra are presented on a landscape format and cover a wide variety of elements,polymers, semiconductors, and other materials. Offers a clear presentation of spectra with the rightamount of experimental detail. All of the experiments have been conducted under controlled conditions on the same instrument by aworld-renowned expert.
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A large quantity of nanosized ZnO tubular structures was prepared using a very simple thermal evaporation of mixed Zn-ZnO powders under a wet oxidation condition. The ZnO nanotubes have a hollow core with crystalline wall of 8-20 nm in thickness. Optical properties of ZnO nanotubes were studied at room temperature. Raman peaks arising from the ZnO nanotubes were analyzed, which correspond well to that of the bulk ZnO sample. The photoluminescence measurements of ZnO nanotubes revealed an intensive UV peak at 377 nm corresponding to the free exciton emission, and a broad peak at about 500 nm arising from defect-related emission. (C) 2003 American Institute of Physics.
Article
By decomposing Zn(OH)(4)(2-) or Zn(NH3)(4)(2+) precursor in various solvents at suitable reaction conditions, zinc oxide with a diversity of well-defined morphologies was synthesized. Flowerlike ZnO built up by nanorods was obtained by treating Zn(OH)(4)(2-) precursor in water at 180 degreesC for 13 h. Whereas a replacement of the solvent by n-heptane yields snow flakelike ZnO. The prismlike and the prickly spherelike ZnO were also prepared, respectively, by decomposing Zn(NH3)(4)(2+) or Zn(OH)(4)(2-) in ethanol at 100 degreesC for 13 h. The rodlike ZnO was produced at 180 degreesC under the same condition for preparing prickly spherelike product. Besides these typical samples, ZnO in other morphologies was studied manipulatively by changing the reaction conditions of our solution route. Systematical condition-dependent experiments were compared comprehensively to reveal the formation and detailed growth process of ZnO nanosized crystallites and aggregates. The experimental results studied by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy indicated that the solvent, precursor, solution basicity, and reaction temperature as well as time are responsible for the variations of ZnO morphologies.
Article
A new hydrothermal process—hydrothermal salt solution pressure-relief—was introduced, and ZnO powder with the size of 15 nm and ZnO fiber with length/diameter=16∶1 were prepared by this process. The change of particle size of ZnO powder and the formation mechanism of ZnO fiber were investigated. It is proposed that the main factor affecting the particle size of powders is nucleation rate, that is, the bigger the nucleation rate is, the smaller the particle is: the main factors affecting the formation of fiber include whether hydrothermal reaction proceeds under the condition of pressure-relief or not and the crystallization degree of powders before pressure-relief.
Article
Atmospheric pressure vapor-phase epitaxy of ZnO thin films using ZnI2 and O2 as starting materials has been examined: thin films of ZnO deposited onto sapphire (0001) substrates at 1023 K have smooth surfaces free from cracks; the photoluminescence spectra of the ZnO thin film prepared under atmospheric pressure show for the first time an ultraviolet emission centered at 381.0 nm at room temperature.
Article
In the present work, single-crystalline hexagonal prism ZnO nanorods have been successfully synthesized via a PEG-assisted hydrothermal route at 140 °C. The structure of the products has been characterized by XRD. TEM and SEM images indicated that the as-synthesized nanorods are wurtzite ZnO with diameters ranging from 60 to 120 nm and lengths of hundreds of nanometers. The smooth prismatic side planes and tips of the rods have been observed. The results also show that short-chain polymer PEG plays a crucial role in the formation of 1D ZnO nanostructures. This facile, reproducible, and effective low-cost approach should promise us a future large-scale synthesis of ZnO nanostructures for many important applications in nanotechnology.
Article
Flowerlike ZnO nanostructures were deposited on Si substrate by choosing hexamethylenetetramine as the nucleation control reagent and ethylenediamine as the chelating and capping reagent. Structural and optical measurements reveal that obtained ZnO exhibits well-defined flowerlike morphology, hexagonal wurtzite structure, uniform distribution on substrate, and strong photoluminescence in ultraviolet band. The well-arrayed pedals of each ZnO flower possess the typical tapering feature, and are built up by many well-aligned ZnO nanorods. Moreover, each single nanorod building up the pedal exhibits the single crystal nature and the growth direction along c-axis. Effects of the precursor composition on the morphology of ZnO were discussed.
Article
The Raman effect in zinc oxide has been measured using the continuous helium-neon and ionized argon lasers as sources. The frequency and symmetry character of the fundamental modes have been determined. The results are: two ${E}_{2}$ vibrations at 101 and 437 ${\mathrm{cm}}^{$-${}1}$; one transverse ${A}_{1}$ at 381 ${\mathrm{cm}}^{$-${}1}$ and one transverse ${E}_{1}$ at 407 ${\mathrm{cm}}^{$-${}1}$; one longitudinal ${A}_{1}$ at 574 ${\mathrm{cm}}^{$-${}1}$ and one longitudinal ${E}_{1}$ at 583 ${\mathrm{cm}}^{$-${}1}$.
Article
Zinc oxide pompom-like particles were crystallized by heating solutions of zinc amino complexes in open air. The nature of the precursor (nitrate, hydroxide or a mixture of both) changes the precipitation pH and the growth mechanism, involving in the case of nitrate salts ramified branches and stratified tips, whereas hexagonal rods with flat ends grow from zinc hydroxide precursors.
Article
ZnO nanorods were grown on Si substrates by metal-organic chemical vapor deposition (CVD). The ZnO nanorods were characterized by scanning electron microscopy, transmission electron microscopy (TEM), and X-ray diffraction. It was found that highly oriented ZnO single-crystalline nanorods were formed only on the substrate coated with a gold film. Without the gold, ZnO was deposited as a continuous film. No Au was observed on top of the ZnO nanorods, implying that the Au plays no role as catalytic metal in vapor–liquid–solid mechanism for formation of ZnO nanorods. In CVD, oriented ZnO nanorods along the c-axis were grown as a result of 〈111〉 textured Au. High-resolution TEM shows that the gold layer and ZnO are in orientation relationship of Au {111} planes//ZnO (0002) basal planes.
Article
ZnO nanowires were mass produced using a physical vapor deposition approach. The ZnO nanowire monocrystallites have an average diameter around 60 nm and length up to a few micrometers. The unidirectional growth of the ZnO nanowires was controlled by the conventional vapor-liquid-solid mechanism. Intensive UV light emission peaked around 3.27 eV was observed at room temperature, which was assigned to emission from free exciton under low excitation intensity. The observed room temperature UV emission was ascribed to the decrease in structure defects as compared to bulk ZnO materials, and in particularly to the size effect in the ZnO wires. © 2001 American Institute of Physics.
Article
In the vapor−liquid−solid (VLS) growth of 1D nanostructures, the electronic structure of the substrate surface may critically affect the morphology of the grown nanowires/nanorods. In this paper, using a model system of the Sn-catalyzed growth of ZnO nanostructures on a single-crystal ZnO substrate, we demonstrate the effect of substrate surface termination on nanowire growth. Symmetric nanoribbons have been grown on the nonpolar surfaces of ±(21̄1̄0) (or ±(011̄0)), but the polar surface ±(0001) substrates have asymmetrically grown nanostructures. For the Zn-terminated (0001) substrate surface, uniform, long, and epitaxially aligned nanowires have been grown. For the oxygen-terminated (0001̄) substrate surface, short nanotrunks have been grown. These asymmetrical growth features are related to the atomic termination of the substrate, surface charges, and interface adhesion. These observations provide some insight into the physical chemical process in VLS growth.
Article
By decomposing Zn(OH)42- or Zn(NH3)42+ precursor in various solvents at suitable reaction conditions, zinc oxide with a diversity of well-defined morphologies was synthesized. Flowerlike ZnO built up by nanorods was obtained by treating Zn(OH)42- precursor in water at 180 °C for 13 h. Whereas a replacement of the solvent by n-heptane yields snow flakelike ZnO. The prismlike and the prickly spherelike ZnO were also prepared, respectively, by decomposing Zn(NH3)42+ or Zn(OH)42- in ethanol at 100 °C for 13 h. The rodlike ZnO was produced at 180 °C under the same condition for preparing prickly spherelike product. Besides these typical samples, ZnO in other morphologies was studied manipulatively by changing the reaction conditions of our solution route. Systematical condition-dependent experiments were compared comprehensively to reveal the formation and detailed growth process of ZnO nanosized crystallites and aggregates. The experimental results studied by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy indicated that the solvent, precursor, solution basicity, and reaction temperature as well as time are responsible for the variations of ZnO morphologies.
Article
Different shapes of ZnO microcrystals have been achieved controllably by a capping-molecule-assisted hydrothermal process. The flowerlike, disklike, and dumbbell-like ZnO microcrystals of hexagonal phase have been obtained respectively using ammonia, citric acid (CA), and poly(vinyl alcohol) (PVA) as the capping molecules. Only a very strong UV emission at 380 nm is observed in the photoluminescence (PL) spectra of the three kinds of ZnO microcrystals, indicative of their high crystal quality. The formation mechanisms for the hydrothermally synthesized microcrystals in different morphologies have been phenomenologically presented.
Article
The structural ordering of ZnO nanoparticles into a flower-type morphology was discussed. A peptide with both an affinity for ZnO and the ability to generate ZnO nanoparticles that assemble into a highly ordered flower-type structure was identified using a combinatorial library approach. The selected peptide recognizes ZnO, but not ZnS or Eu2O3. ZnO can be selectively immobilized on a substrate in neutral solution at room temperature by the ZnO-recognizing peptide. The peptide can condense Zn(OH)2 sol, and the conjugate of the ZnO-recognizing peptide with glycine linker (GGGSC) enables the homogeneous creation of a flower-type morphology composed of ZnO nanoparticles.
Article
Patterned nanowire networks of photoluminescent highly crystalline ZnO nanowires were produced via the vapor-liquid-solid mechanism using gold as catalyst. The diameters of the nanowires were controlled by varying the thickness of the gold layer. Wire size influenced the emission characteristics.
Article
Growth behaviors of ZnO nanorods synthesized by catalyst-free metalorganic chemical vapor deposition were studied as functions of various growth parameters such as growth temperature, precursor ratio and substrate type. We found that their sizes, shapes and alignment nature were strongly dependent on such parameters. However, individual ZnO nanorods were of single-crystalline nature as well as of high optical quality. Field effect transistors (FETs) using single ZnO nanorods were fabricated to study their electrical properties. Ultraviolet illumination and vacuum environment resulted in a significant increase of mobile electrons. Investigation on temperature-dependent electrical transport revealed that thermionic emission dominated as a current transport mechanism in the FETs.
Article
The synthesis of hybrid bulk-heterojunction solar cells from zinc oxide (ZnO) nanocrystalline (nc) particles and a conjugated polymer, poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene ] (MDMO-PPV), was investigated. The cells exhibited an incident photon to current conversion efficiency up to 40%. The photoinduced charge separation of the MDMO-PPV:nc-ZnO mixture was analyzed using photoinduced absorption (PIA) spectroscopy. The kinetics of charge generation of the mixture was investigated with pump-probe spectroscopy by monitoring the intensity of low-density radical cation absorption band at 2200 nm (0.56 eV). Transmission electron microscopy (TEM) was used to analyze the morphology of the MDMO-PPV:ncZnO blend.
Article
A convenient hydrogen-assisted thermal evaporation method to synthesize nano-ribbons of the semiconductor ZnS is introduced. As such, the synthetic reaction is carried out in a quartz tube furnace using high-purity Ar premixed with 5% H2 as carrier gas at 1100°C and sphalerite ZnS as source. The results presented a new compound semiconductor nanoribbon, different from silicon or oxides, which may provide a guide for obtaining other non-oxide semiconductor nanoribbons.
Article
Current research into semiconductor clusters is focused on the properties of quantum dots-fragments of semiconductor consisting of hundreds to many thousands of atoms-with the bulk bonding geometry and with surface states eliminated by enclosure in a material that has a larger band gap. Quantum dots exhibit strongly size-dependent optical and electrical properties. The ability to join the dots into complex assemblies creates many opportunities for scientific discovery.
Article
Effect of confinement is investigated on optical phonons of different symmetries in the nanoparticles of zinc oxide with wurtzite structure using Raman spectroscopy. An optical phonon confinement model is used for calculating the theoretical line shapes, which exhibit different asymmetric broadening and shifts, depending on the symmetries of phonon and their dispersion curves. The best fit to the data is found for particle diameters consistent with those estimated using x-ray diffraction. © 2000 American Institute of Physics.
Article
We explore the interrelationships between the green 510 nm emission, the free‐carrier concentration, and the paramagnetic oxygen‐vacancy density in commercial ZnO phosphors by combining photoluminescence, optical‐absorption, and electron‐paramagnetic‐resonance spectroscopies. We find that the green emission intensity is strongly influenced by free‐carrier depletion at the particle surface, particularly for small particles and/or low doping. Our data suggest that the singly ionized oxygen vacancy is responsible for the green emission in ZnO; this emission results from the recombination of a photogenerated hole with the singly ionized charge state of this defect. © 1996 American Institute of Physics.
Article
Ordered semiconductor ZnO nanowire arrays embedded in anodic alumina membranes (AAM) were fabricated by generating alumina templates with nanochannels, electrodepositing Zn in them, and then oxidizing the Zn nanowire arrays. The polycrystalline ZnO nanowires with the diameters ranging from 15 to 90 nm were uniformly assembled into the hexagonally ordered nanochannels of the AAM. Photoluminescence (PL) measurements show a blue PL band in the wavelength range of 450–650 nm caused by the singly ionized oxygen vacancy in ZnO nanowires. © 2000 American Institute of Physics.
Article
Star-shaped ZnO nanostructures were grown over Au-coated Si (1 0 0) substrate by a cyclic feeding chemical vapor deposition method. Transmission electron microscopy image and selected area electron diffraction pattern showed that these nanostructures were single crystalline with wurtzite hexagonal structure and preferentially oriented in the c-axis direction. Photoluminescence (PL) spectra of the as-grown structures measured at room temperature showed a suppressed UV emission at 380 nm and a strong and broad green emission at 520 nm, but showed reversibly a drastic change in the PL intensity when the samples were annealed in an oxygen atmosphere at 500 °C.
Article
Room-temperature free excition absorption and luminescence are observed in ZnO thin films grown on sapphire substrates by the laser molecular beam epitaxy technique. At moderate optical pumping intensities, an excition-exciton collision induced stimulated emission peak is observed at 390 nm. The existence of this peak is related to the presence of closely packed hexagonally shaped microcrystallites in these films. Stimulated emission due to electron-hole plasma recombination process is also observed at higher pumping intensities.
Article
AbstractSingle crystalline ZnO nanorods were prepared by the hydrothermal method with synthesized ZnCl2·4Zn(OH)2 as the precursor. Morphologies of the nanorods were controlled by various reaction conditions with cetyltrimethylammonium bromide (CTAB) as the modifying agent. The nanorods were characterized by XRD, TEM, UV-Vis spectra, and IR spectra. The microstructure of holes in nanosize was observed on the surface of the nanorods. The UV-Vis spectra indicate that the as-prepared ZnO nanorods have absorption of visible-light as well as ultraviolet-light. Therefore, these nanorods may be good candidates for visible-light photocatalysis materials from the viewpoint of practical applications. The reason for visible-light absorption was discussed in this article.
Article
In the present paper, ZnO nanorods with the mean size of 50 nm × 250 nm were successfully synthesized via a hydrothermal synthesis route in the presence of cetyltrimethylammonium bromide (CTAB). ZnCl2 and KOH were used as the starting materials and zinc oxide nanorods were obtained at 120 °C for 5 h. The product was characterized by means of X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The optical properties of the product were studied. Some factors affecting the morphologies and optical properties were also investigated.
Article
The emission spectrum of high quality ZnO epilayers is studied from room temperature up to 550 K. At room temperature and low excitation power a single emission peak is observed which may be identified with the free exciton from its peak energy and dependence on temperature. However, when excitation intensities exceed 400 kW cm-2 a sharp peak emerges at lower energy which we attribute to exciton-exciton scattering. At higher excitation intensities (>800 kW cm-2) a second stimulated emission peak emerges at even lower energies: we attribute this peak to be stimulated emission of an electron hole plasma. Similar features are observed for all temperatures up to 550 K.
Article
We report the observation of optically pumped lasing in ZnO at room temperature. Thin films of ZnO were grown by plasma-enhanced molecular beam epitaxy on (0001) sapphire substrates. Laser cavities formed by cleaving were found to lase at a threshold excitation intensity of 240 kW cm(-2). We believe these results demonstrate the high quality of ZnO epilayers grown by molecular beam epitaxy while clearly demonstrating the viability of ZnO based light emitting devices. (C) 1997 American Institute of Physics.
To evaluate the relationship between unilateral renal agenesis and auditory abnormality, and to determine the clinical spectrum of hearing impairment in such patients. Seventy-five children with unilateral renal agenesis underwent auditory examinations. The subjects comprised 35 males and 40 females. Fourteen females had mullerian abnormalities. Another 75 schoolchildren with the same gender profile were selected for audiometric testing as a control group. Children with sonographically evident urogenital system abnormalities were excluded from the control group. The prevalence of auditory abnormalities in children with unilateral renal agenesis (4/75) (5.3%) was higher than in the control group (0%). The prevalence in children with urogenital anomalies was significantly higher in patients with renal agenesis than in the normal population (28.5%). Audiometric results showed that four of the 75 children manifested ipsilateral sensorineural hearing impairment, particularly in the high-frequency range. All were females with coexisting genital abnormalities. Two were diagnosed with mild sensorineural hearing impairment while the other two had moderate hearing loss. The results of our study suggest that neurosensory hearing loss was found to be associated with renal agenesis. Further audiometric follow-up of children with renal agenesis seems worthwhile.
Article
Scanning electron microscope (SEM) and UV spectrum methods were used to identify Kochia scoparia and its substitutes, including the fruits of Chenopodium album, Chenopodium serotinum and Kochia scoparia (L.) Schrad. f. trichophila Schirz. et Thell. The results showed that kochia scoparia differed from the substitutes in utride, trichome, stoma and shape of seed under SEM. The UV spectrum of Kochia scoparia was similar to that of Kochia scoparia f. trichophila, but significantly different from that of Chenopodium album and Chenopodium serotinum.
Article
Bulk heterojunction photovoltaic devices based on blends of a conjugated polymer poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) as electron donor and crystalline ZnO nanoparticles (nc-ZnO) as electron acceptor have been studied. Composite nc-ZnO:MDMO-PPV films were cast from a common solvent mixture. Time-resolved pump-probe spectroscopy revealed that a photoinduced electron transfer from MDMO-PPV to nc-ZnO occurs in these blends on a sub-picosecond time scale and produces a long-lived (milliseconds) charge-separated state. The photovoltaic effect in devices, made by sandwiching the active nc-ZnO:MDMO-PPV layer between charge-selective electrodes, has been studied as a function of the ZnO concentration and the thickness of the layer. We also investigated changing the degree and type of mixing of the two components through the use of a surfactant for ZnO and by altering the size and shape of the nc-ZnO particles. Optimized devices have an estimated AM1.5 performance of 1.6% with incident photon to current conversion efficiencies up to 50%. Photoluminescence spectroscopy, atomic force microscopy, and transmission electron microscopy have been used to gain insight in the morphology of these blends.
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