As-prepared ZnO Nanoparticles Research Articles

Antioxidant and Anti-inflammatory Applications of Aerva persica Aqueous-Root Extract-Mediated Synthesis of ZnO Nanoparticles.

In the present study, ZnO nanoparticles were synthesized by using aqueous extracts of Aerva persica roots. Characterization of as-prepared ZnO nanoparticles was carried out using different techniques, including powder X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and BET surface area analysis. Morphological analysis confirmed the small, aggregated flake-shaped morphology of as-synthesized ZnO nanostructures. The as-prepared ZnO nanoparticles were analyzed for their potential application as anti-inflammatory (using in vivo inhibition of carrageenan induced paw edema) and antioxidant (using in vitro radical scavenging activity) agents. The ZnO nanoparticles were found to have a potent antioxidant and anti-inflammatory activity comparable to that of standard ascorbic acid (antioxidant) and indomethacin (anti-inflammatory drug). Therefore, due to their ecofriendly synthesis, nontoxicity, and biocompatible nature, zinc oxide nanoparticles synthesized successfully from roots extract of the plant Aerva persica with potent efficiencies can be utilized for different biomedical applications.

Biosynthesis of ZnO nanoparticles using Melia azedarach seed extract: Evaluation of the cytotoxic and antimicrobial potency

ZnO nanoparticles (NPs) synthesized by using an aqueous extract of Melia azedarach seed are reported in this paper. The structural, morphological, compositional, and optical properties of the NPs were evaluated. A hexagonal phase with spherical morphology and an average crystallite size of 57.74 nm was obtained. Optical studies indicated a maximum absorption peak around 296 nm and bandgap energy of 3.88 eV. Cytotoxicity assay of both the plant extract and the as-prepared ZnO nanoparticles against the human hepatoma (HepG2) cell line showed that the M. azedarach seed-mediated ZnO nanoparticles were less toxic compared to ZnO synthesized by the conventional method, while the plant itself showed dose-dependent low toxicity. ZnO nanoparticles by the green route also exhibited good antibacterial activity, with higher efficiency for Gram-negative bacteria than Gram-positive bacteria.

ZnO nanoparticles and β-cyclodextrin containing molecularly imprinted polymers for gravimetric sensing of very-low-density lipoprotein

The elevated level of very-low-density lipoprotein (VLDL) in the blood is associated with coronary heart disease; therefore, its detection is of significant clinical importance. In this work, molecularly imprinted polymer (MIP) layers fabricated with ZnO nanoparticles are developed for gravimetric sensing of VLDL. The use of methacrylic acid and β-cyclodextrin as functional co-monomers in an optimized ratio of 1:1 for MIP synthesis controls the hydrophilicity/hydrophobicity; thus, yielding highly tailored recognition sites having adequate stability. The as-prepared ZnO nanoparticles are characterized by scanning electron microscopy, Fourier transformation infrared, and x-ray diffraction before incorporating into the MIP matrix. The template concentration in MIP is also varied to select its optimal amount, i.e. 50 µl of 50 µg ml−1 VLDL solution for enhanced sensor performance. Sensor measurements reveal that the ZnO-MIP has a sensitivity of 19.285 Hz ng−1 ml−1 for VLDL, which is about 16-fold higher than the reference ZnO-non-imprinted polymer channel. Furthermore, the ZnO-MIP sensor exhibits high selectivity for VLDL as the sensor response is 6 and 3 times higher compared to α1-acid glycoprotein and human serum albumin, respectively. Finally, the performance of the developed sensor setup is evaluated for the detection of VLDL in human serum samples indicating its potential for reliable analysis of VLDL in complex biofluids.

Evaluation of Bioactive Potential of a Tragia involucrata Healthy Leaf Extract @ ZnO Nanoparticles

The aim of the present work is to prepare ZnO nanoparticles (NPs) from Tragia involucrata leaf extract by low-cost technology. The extracted ZnO NPs were calcined at different temperatures such as 400 °C (TZ 1), 450 °C (TZ 2), and 500 °C (TZ 3). The as-prepared ZnO NPs were characterized using techniques such as TG-DTA, XRD, FTIR, and SEM. Based on the observations made using the above techniques, the calcination temperature was fixed at 450 °C and EDS, HR-TEM, and VSM studies were made for these samples. The XRD analysis revealed the hexagonal structure with the average crystallite size being ~ 27 nm for the different samples (TZ 1, TZ 2, and TZ 3). The occurrence of FTIR peaks in the region 600–450 cm−1 confirmed the presence of the Zn–O bond. SEM and HR-TEM images indicated the rod and conical shapes for the bio-synthesized ZnO NPs, and the d-spacing value has been found to be 0.24 nm with (1 0 1) lattice plane, matching very well with that of XRD. The SAED pattern clearly portrayed annular rings indicating the single crystalline nature. The results of VSM studies indicated a diamagnetic nature at room temperature. The green synthesized ZnO NPs were screened for antibacterial and antifungal activities. Among the bacteria used, Klebsiella pneumoniae has secured maximum sensitivity (22 mm) and Proteus vulgaris has secured minimum sensitivity (12 mm). In the case of fungal studies, Aspergillus niger showed a maximum sensitivity (16 mm) as compared to Aspergillus flavus (15 mm). Thus, it is concluded that the bio-synthesized ZnO NPs using Tragia involucrata leaf extract may serve as a potential candidate for biomedical applications.

Synthesis, characterization and photocatalytic activity of SnO2, ZnO nanoparticles against congo red: A comparative study

Nanoparticles of SnO2 and ZnO were successfully synthesised by simple solution route via environmental friendly approach using Simarouba Glauca leaf extract as biosolvent. The products were characterized by XRD, FTIR, UV, SEM, and TEM. The photocatalytic activities of the as-prepared SnO2 and ZnO nanoparticles were evaluated by degradation of Congo Red (CR), a common textile dye, under sunlight irradiation.

Thermal Degradation of Polystyrene (PS) Nanocomposites Loaded with Sol Gel-Synthesized ZnO Nanorods.

Thermal degradation of polystyrene/ZnO (PS/ZnO) nanocomposites was investigated in this study. PS/ZnO polymer nanocomposites were prepared by using ZnO nanorods as nanofillers that were prepared via the sol-gel route. The as-prepared ZnO nanoparticles showed nanocrystallites in rod-like shapes with a non-uniform hexagonal cross-section and diameter varying from 40 to 75 nm. PS/ZnO nanocomposites with ZnO nanoparticles content ranging from 0–3 wt% are prepared via the common casting method. Even dispersion for ZnO nanoparticles within as-prepared PS/ZnO nanocomposites was verified through SEM/EDX measurements. Thermal degradation of the samples was checked by using the thermogravimetric (TG) analysis and differential scanning calorimetry (DSC) under non-isothermal conditions and a constant heating rate of 10 °C min. The thermal stability of the nanocomposite is elevated compared to that of pristine PS due to the addition of the ZnO nanoparticles. The homogeneity of the PS/ZnO nanocomposites is verified by systematic increases in thermal degradation with increasing ZnO content. The characterization degradation temperatures at different weight loss percentages of ZnO nanoparticles increase at high ZnO wt%. Static activation energy of decomposing is based on TGA data. Activation energies showed some enhancement after the addition of ZnO nanorods into the PS matrix. Enhancing the thermal stability of PS with ZnO addition within the investigated ZnO concentration range is verified by TG, DSC results.

A facile fabrication and high-performance electromagnetic microwave absorption of ZnO nanoparticles

Abstract Electromagnetic microwave absorption materials are highly desired in electronics application in recent years. Herein, ZnO nanoparticles were successfully fabricated via sonochemical process using zinc acetate dihydrate (Zn(CH3COO)2·2H2O) and ammonia water as raw materials. The as-prepared ZnO nanoparticles annealed at 120 °C for 8 h had significantly enhanced electromagnetic microwave absorption properties. This could be attributed to dielectric loss originating from interface polarization, and dipole polarization due to oxygen vacancy defects. The minimum reflection coefficient reached −37.7 dB at 8.96 GHz with a small thickness of 2.1 mm. This work provides a new idea of preparing electromagnetic microwave absorption materials (MAMs) with strong absorbing properties.

Characterization and photocatalysis of visible-light-driven Dy-doped ZnO nanoparticles synthesized by tartaric acid-assisted combustion method

ZnO samples containing different contents of Dy dopant were synthesized by a tartaric acid-assisted combustion method. The as-synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The samples with and without Dy dopant were specified as hexagonal wurtzite ZnO. The particle sizes of samples were decreased from 113 ± 31 nm for ZnO to 15 ± 3 nm for 5 wt% Dy-doped ZnO but the specific surface areas were increased from 3.58 m2·g−1 for ZnO to 28.35 m2·g−1 for 5 wt% Dy-doped ZnO. Both ZnO and 5 wt% Dy-doped ZnO samples revealed the strongest vibration peak of Zn–O stretching vibration E2H mode. Photocatalytic activities of the as-prepared ZnO and Dy-doped ZnO nanoparticles were investigated through photodegradation of methylene blue (MB) under UV visible light irradiation. The 5 wt% Dy-doped ZnO nanoparticles showed the highest photocatalytic activity for MB degradation of 97% within 75 min. The direct mass spectrometry specified that the MB solution was degraded by photocatalysis within 75 min.

ZnO nanodispersion as pseudohomogeneous catalyst for alcoholysis of polyethylene terephthalate

Chemical depolymerization and recycling of polyethylene terephthalate (PET) is a sustainable way to preserve the resources and protect the environment. In this work, methanol and ethylene glycol dispersions of ultrasmall ZnO nanoparticles are firstly adopted as pseudohomogeneous catalysts for alcoholysis of PET. The as-prepared ZnO nanoparticles have a uniform size of 4 nm and can be stable in dispersions for 6 months. In the methanolysis process of PET, the effects of various parameters on the conversion of PET and the yield of dimethyl terephthalate (DMT) were investigated. The results show that higher temperature (170 °C) was beneficial to the conversion of PET and the yield of DMT, which can reach about 97% and 95% after 15 min, respectively. The excellent activity of 553 g PET h−1 (g ZnO)−1 was achieved. Furthermore, the methanolysis of PET have shorter reaction time (1/4) and higher activity (4.7 times) than the glycolysis of PET.

Synthesis, characterization, and catalytic properties of zinc oxide nanoparticles for the treatment of wastewater in the presence of natural sunlight

Zinc oxide nanoparticles were synthesized using monochloro acetic acid as a complexing agent. These synthesized nanoparticles were characterized by X-ray diffraction, scanning electron microscopy, UV–visible, energy-dispersive X-ray, Fourier transform infrared spectroscopy analysis, and BET techniques. As-prepared ZnO nanoparticles show crystalline nature with hexagonal dominant crystal phase. The SEM image shows the formation of homogenous micro-porous nanoparticles of ZnO. The photocatalytic activity of ZnO materials was measured on UV–visible spectrophotometer under natural sunlight irradiation and shows the efficiency (ɳ) of 56.80% in 150 min of time. A ZnO nanoparticle shows an excellent photocatalytic activity and can be used for the treatment of wastewater.

Effective adsorptive removal of azo dyes over spherical ZnO nanoparticles

To minimize the detrimental effects of contaminated water, technology-based smart treatment processes are prerequisite for sustainable supply of drinking water. Nano-sized metal oxides are the best choice futuristic adsorbents for the removal of water toxins as such materials are associated with the characteristics of simplicity, versatility, efficacy and high surface reactivity. In this study, we describe a nanostructured ZnO adsorbent, which displays remarkable efficiency toward the removal of widely used azo dyes, methyl orange (MO) and amaranth (AM), from aqueous systems. The ZnO nanoparticles (ZnO-NPs) were prepared by simple co-precipitation method, and the structural morphology of the as-prepared NPs was revealed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform IR (FTIR) and Brunauer–Emmett–Teller (BET). After complementary characterization, as-prepared ZnO-NPs were further used as adsorbent for the removal of toxic azo dyes (MO and AM) from water. The results revealed that an amount of 0.3g ZnO-NPs showed maximum removal efficiency of each dye (40ppm) at pH 6. It was further confirmed that the adsorption of both dyes on ZnO-NPs strongly followed the Langmuir model whereas the kinetics studies revealed that each adsorption process was pseudo second order. Moreover, the findings suggested that R-SO3– groups were active sites and the electrostatic attraction between the dyes (MO–, AM–) and ZnO-NPs+ may be the prime adsorption mechanism of designated removal systems.

Effect of ZnO nanoparticles doping on the optical properties of TiS2 discs

As-synthesized sample of TiS2 discs and ZnO doped TiS2 discs have been prepared by solid-state reaction method. XRD studies confirm that the polycrystalline nature of as-synthesized discs. The doping of ZnO nanoparticles in TiS2 discs has been verified by the XRD spectra. UV–vis studies reveal a direct band-gap and its value increases after the doping of ZnO nanoparticles in TiS2 discs. The evaluated value of optical band gap (Eg) of TiS2 discs is 2.01 eV and after the doping of ZnO nanoparticles its values increases from 2.07 eV to 2.31 eV. PL emission spectra of as-prepared TiS2 discs and ZnO nanoparticles doped TiS2 discs have been studied at room temperature for the wavelength range of (300–550) nm. PL emission spectra suggest the blue shift, which decreases after increasing concentration of ZnO nanoparticles in TiS2 discs. Optical constants such as refractive index (n) & extinction (k) coefficient have been evaluated. The value of k of TiS2 discs & ZnO nanoparticles doped TiS2 discs increases while the value of n decreases with increase in photon energy.

Microwave induced facile synthesis and characterization of ZnO nanoparticles as efficient antibacterial agents

Microwave assisted synthesis of ZnO nanoparticles was performed at varying pH of the synthesis medium. At pH 8 and 10, uniform and crystalline ZnO nanoparticles were formed whereas at pH 6, layered basic zinc acetate (LBZA) was obtained. The present work proposes a new strategy to synthesize LBZA via microwave irradiation method. As-prepared ZnO nanoparticles were used to study antibacterial behavior against pathogenic Gram-negative and Gram-positive bacteria viz. E. coli, P. aeruginosa, S. aureus and E. faecalis under dark condition. The results show a significant decrease in viability of pathogenic bacterial cells with increase in interaction time with ZnO nanoparticles.

Degradation of 4-Chlorophenol Under Sunlight Using ZnO Nanoparticles as Catalysts

Herein we demonstrate a simplistic microwave assisted chemical precipitation approach regarding the synthesis of zinc oxide nanoparticles. As-prepared ZnO nanoparticles (NPs) were characterized by UV–visible spectroscopy, Fourier transform infra-red spectroscopy, atomic force microscopy and x-ray diffractometry and scrutinized as photo-catalysts for degradation of 4-chlorophenol (4-CP) under sunlight. The study substantiated that 98.5% of 4-CP was degraded within 20 min in the absence of initiator like H2O2 which reflects an outstanding prospective use for ZnO NPs as photo-catalysts. The nanocatalysts were recycled four times and still showed catalytic efficiency up to 95.5% for degradation of 4-CP in the specified 20 min.

Suppression of Red Luminescence in Wire Explosion Derived Eu:ZnO

Europium oxide (Eu2O3) is coated on zinc (Zn) wire using the electrophoretic deposition process. The coated Zn wire is subjected to the wire explosion process (WEP) which is rapid (< 15 min), and chimie douce (soft chemical, low temperature), in nature; this results in the formation of Eu doped ZnO. The explosion chamber contains oxygen (99.9%) at atmospheric pressure. Electron micrographs indicate that the particle sizes are ∼ 80 nm. Diffractogram-based analysis suggests that the crystallite size is ~ 18–20 nm in the as-prepared doped ZnO nanoparticles. Electron paramagnetic resonance shows the presence of Zn vacancies and the cryo-photoluminescence spectrum indicates that Eu exists in the + 3 state. A combined Williamson–Hall plot and Kisielowski’s model based analysis indicates that Eu is a substitutional dopant in WEP derived Eu:ZnO particles. It is estimated that this material has ∼ 0.24 at.% doping. This analysis also shows that, unlike another popular material GaN, in the case of ZnO, Eu3+ strictly substitutes for Zn2+ (i.e., dopant replacing a cation–anion pair does not seem possible). It may be noted that Eu3+ in a suitable host is oftentimes reported to be an efficient luminophore. The IR spectra show a band shift from 486 cm−1 to 493 cm−1; with peak shifts from 436 cm−1 to 430 cm−1 in Raman spectra. These too indicate the presence of Eu in the samples. However, at room temperature, only green luminescence (centered at 534 nm) is observed from the sample indicating (1) high concentrations of OZn anti-site defects and Zn vacancies, and (2) concomitant quenching of the luminescence at room temperature. Our results suggest that WEP is viable for synthesizing rare earth doped ceramic materials. However, obtaining efficient phosphors using this approach will likely require, (1) reduction of defect densities, and (2) appropriate passivation using post-processing.

Synthesis and electrochemical investigation of highly dispersed ZnO nanoparticles as anode material for lithium-ion batteries

Highly dispersed ZnO nanoparticles were prepared by a versatile and scalable sol-gel synthetic technique. High-resolution transmission electronic microscopy (HRTEM) showed that the as-prepared ZnO nanoparticles are spherical in shape and exhibit a uniform particle size distribution with the average size of about 7 nm. Electrochemical properties of the resulting ZnO were evaluated by galvanostatic discharge/charge cycling as anode for lithium-ion battery. A reversible capacity of 1652 mAh g−1 was delivered at the initial cycle and a capacity of 318 mAh g−1 was remained after 100 cycles. Furthermore, the system could deliver a reversible capacity of 229 mAh g−1 even at a high current density of 1.5 C. This outstanding electrochemical performance could be attributed to the nano-sized features of highly dispersed ZnO particles allowing for the better accommodation of large strains caused by particle expansion/shrinkage along with providing shorter diffusion paths for Li+ ions upon insertion/deinsertion.

Wet chemical synthesis of ZnO nanocoating on the surface of bamboo timber with improved mould-resistance

With the increasing emphasis on sustainable development, bamboo is receiving an increasing attention as a kind of forest resource. But bamboo is readily discoloured by mould fungi, which greatly limits the applications of bamboo. In this research, ZnO nanoparticles were successfully fabricated on the surface of bamboo timber by a simple low-temperature wet chemical method. The morphology, chemical structure, and crystalline structure of the samples were characterized by using scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). XRD studies confirmed that the as-prepared ZnO nanoparticles were wurtzite. The microstructure and hydroxyl groups in the bamboo timber surface at the wet state provided cavities and affinity for the creation and the immobilization of ZnO nanoparticles on the bamboo timber surface through electrostatic and hydrogen bonding interactions. Moreover, the mould-resistance of ZnO coated bamboo timber was also in focus on the present study. The results indicated that bamboo timber treated with ZnO had a better resistance against Aspergillus niger V. Tiegh (A. niger) and Penicillium citrinum Thom (P. citrinum), but poor against Trichoderma viride Pers. ex Fr (T. viride).

Preparation and characterization of self-cleaning and anti-reflection ZnO-SiO2 nanometric films

Unlike the general anti-reflection and self-cleaning film such as SiO2 and TiO2-SiO2, the ZnO-SiO2 nanometric film used as a substrate of excellent transparency in visible region and effective photo-catalytic self-cleaning under UV illumination is seldom studied in the application as a substrate; however, it has a lot of advantages including high transmittance and low refractivity. In this paper, a self-cleaning and anti-reflection ZnO-SiO2 nanometric film is successfully fabricated by using a sol-gel dip-coating method. The morphology, crystal structure, surface microstructure and light transmittance of the obtained products are characterized by techniques such as TEM, SAD, XRD, SEM, DTA and UV-vis. Photo-catalytic degradation of the methylene blue (MB) in aqueous solution is used as probe reaction to evaluate the photo-catalytic activity of ZnO-SiO2 nanometric film. The TEM images reveal that the as-prepared ZnO nanoparticles are spherical grains with diameters of 12-20 nm, the average grain diameter is about 14.51 nm. ZnO nanoparticles obtained are of hexagonal wurtzite structure revealed by XRD pattern and there exist no other diffraction peaks, Furthermore, the SAD results show that ZnO microstructurs have good crystallinity. In addition, the ZnO grain size is about 14.41 nm by using the Scherrer formula calculation, which is consistent with the TEM results by the Gauss simulation. The UV-vis spectra reveal that the ultraviolet characteristic absorption peak of ZnO-SiO2 composite films is located at 368 nm and 375 nm after annealing at different temperatures such as 300℃ and 450℃, corresponding to the band gaps of 3.37 eV and 3.31 eV, respectively. It is highly consistent with that obtained from pure ZnO nanoparticles. Increasing the annealing temperature results in a lower refractive index and the increases of the porosity in of the ZnO-SiO2 composite films. It has a uniformly refractive index value about 1.23-1.25 and a high porosity value about 50.3-54.7% when the annealing temperature is 450 ℃. Experimental results show that the ZnO-SiO2 composite film can enhance the light transmittance of the quartz substrate, due to its lower reflective index and higher porosity. Compared with the quartz substrate, the average optical transmission rate of the quartz glass coated with ZnO-SiO2composite films is increased by about 4.17% at 400-800 nm, which favors greatly anti-reflection characteristics in a wide spectrum range. Meanwhile, the ZnO-SiO2 composite films are found to be efficient for photo-catalytically degradation of methylene blue dye under UV illumination, which favors greatly the self-cleaning function.

Hydrothermal tuning of the morphology and particle size of hydrozincite nanoparticles using different counterions to produce nanosized ZnO as an efficient adsorbent for textile dye removal

The current study aimed to investigate the effect of counterions on hydrothermally synthesized hydrozincite (zinc hydroxide carbonate), which was thermally converted to generate ZnO nanostructures, which are an efficient nanoadsorbent for the removal of Reactive Black 5 (RB5) dye from wastewater. Hydrozincite nanospheres and flower-like structures were hydrothermally prepared using various zinc salts (sulfate, acetate, and nitrate) and ammonium carbonate in a molar ratio of 1:3, respectively, at 120 °C for 3 h. The morphology and crystallite size of the hydrozincite precursor were effectively controlled via the parameters of the hydrothermal reaction. Interestingly, sulfate was the optimum counterion, as zinc sulfate salt produced pure hydrozincite nanospheres with the smallest crystallite size (∼13.57 nm), which were consequently thermally decomposed at 400 °C for 1 h to produce pure nanosized ZnO (∼10 nm). The compositions of the as-synthesized products were determined by means of FT-IR, FE-SEM, HR-TEM, XRD, zeta potential, BET, and thermal analyses. An adsorption study showed a much higher adsorption capacity (80.9 mg g−1) of the as-prepared ZnO nanoparticles toward RB5 dye. The adsorption of RB5 dye followed pseudo-second-order kinetics. In addition, the equilibrium adsorption of RB5 dye was best described by a Langmuir isotherm model and the calculated thermodynamic parameters, ΔG0 (from −4.027 to −7.533 kJ mol−1), ΔH0 (30.798 kJ mol−1), and Ea (29.105 kJ mol−1), indicate the spontaneous, endothermic, and physisorptive nature of the adsorption process.

Morphological transformation of ZnO nanoparticle to nanorods via solid–solid interaction at high temperature annealing and functional properties

Highly monodispersed ZnO nanoparticles with an average diameter of 8–10nm were prepared using N-Methylaniline as an organic ligand by chemical route. Thermal stability of the size confined ZnO nanoparticles was investigated by annealing at high temperatures. Morphology of the ZnO nanoparticles has been transformed from spherical particles to nanorods at 600°C by solid–solid interaction. Crystallinity was improved by increasing annealing temperature. As-prepared ZnO nanoparticles exhibited strong ultraviolet emission at 380nm and annealed samples had strong green emission. X-ray photoelectron spectra results showed that ZnO had more oxygen defects at higher annealing temperatures.