As-synthesized Zinc Oxide Nanoparticles Research Articles

Photocatalytic and Biological Activity of ZnO Nanoparticles Using Honey

The innovation and development of water purification methods have been at the center of extensive research for several decades. Many nanoparticles are frequently seen in industrial waste water. In this research, zinc oxide nanoparticles (ZnO) were synthesized following an autocombustion method with and without honey capping. Structural crystallinity and bonding structure were examined via X-ray diffraction (XRD) analysis and Fourier transform infrared (FTIR) spectroscopy. Optical behavior was analyzed using ultraviolet–visible (UV–Vis) spectroscopy and photoluminescence (PL). Size estimation and surface morphology were studied using scanning electron microscopy (SEM), while energy-dispersive spectroscopy (EDS) was performed to analyze the sample purity and elemental composition. The photocatalytic degradation of methylene blue (MB) by ZnO was assessed as it is an efficient water treatment process with high potential. The biological activity of ZnO nanoparticles was also investigated in terms of antibacterial and antifungal activities against different bacterial and fungal species. Surprisingly, the as-synthesized ZnO nanoparticles were found to be substantially bioactive compared to conventional drugs. Honey-mediated nanoparticles displayed 86% dye degradation efficiency, and that of bare ZnO was 60%. Therefore, the involvement of honey in the synthesis of ZnO nanoparticles has great potential due to its dual applicability in both biological and environmental remediation processes.

A fast-response and transparent solution–processed ultraviolet photodetector based on ZnO quantum–sized nanoparticles

Solution-processed ultraviolet (UV) photodetectors with high performance have great potential in many practical applications. In this paper, quantum-sized zinc oxide (ZnO) nanoparticles (~ 5.5 nm) were synthesized by a simple and low-cost chemical reflux method. The crystalline structure, morphologies, and optical properties of ZnO nanoparticles were investigated in detail. The results showed that the as-synthesized ZnO nanoparticles were wurtzite-structured (hexagonal) ZnO and had specific surface area as high as 68.3 m2/g, the ZnO nanoparticulate thin films had a strong absorption in UV region and optical bandgap of 3.28 eV. Furthermore, an UV photodetector was fabricated using the as-prepared ZnO nanoparticles, the device revealed stable, rapid and repeatable photoresponse towards 365 nm UV light, the sensitivity (S), responsivity (R), rise time (Tr), and decay time (Td) of the photodetector was 11.4 at − 0.25 V, 22.1 A/W at 3 V, 1.8 s and 47.2 s, respectively. In addition, the photoresponsive mechanism of this UV photodetector was systematically illuminated according to the adsorption-photodesorption theory of oxygen in ZnO nanoparticles.

Phytogenic Synthesis of Band Gap-Narrowed ZnO Nanoparticles Using the Bulb Extract of Costus woodsonii

The use of biomass for functional nanomaterial is fascinating. Costus woodsonii was used as a green approach to synthesize zinc oxide (ZnO) nanoparticles from its bulb (flower). The as-synthesized ZnO nanoparticles were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), and transmission electron microscopy (TEM). XRD showed that the commercial ZnO (C-ZnO) and as-synthesized ZnO nanoparticles were of high purity and displayed a hexagonal wurtzite and well crystalline structure. XPS confirms that Zn was in the + 2 chemical state. FT-IR spectroscopy showed some additional peaks on the as-synthesized ZnO only due to a surface coating of the components of the bulb extract. TEM revealed the morphology, particle size, and high purity of the ZnO nanoparticles. The UV-Vis DRS of the as-synthesized ZnO showed a red shift compared to C-ZnO, which was attributed to the surface coating of the as-synthesized ZnO nanoparticles. These studies confirmed the synthesis of ZnO nanoparticles with a lower band gap, i.e., Eg = 2.66–2.79 eV. Therefore, phytogenic synthesis could be a new or alternate pathway for the synthesis of different types of novel nanomaterials with unique characteristics without altering the basic and fundamental structure.

Photophysical study of the interaction between ZnO nanoparticles and globular protein bovine serum albumin in solution and in a layer-by-layer self-assembled film

In this study, we investigated the spectroscopic properties of the water-soluble globular protein bovine serum albumin (BSA) while interacting with zinc oxide (ZnO) semiconductor nanoparticles (NPs) in aqueous medium and in a ZnO/BSA layer-by-layer (LbL) self-assembled film fabricated on poly (acrylic acid) (PAA)-coated quartz or a Si substrate via electrostatic interactions. BSA formed a ground state complex due to its interaction with ZnO NPs, which was confirmed by ultraviolet–visible absorption, and steady state and time-resolved fluorescence emission spectroscopic techniques. However, due to its interaction with ZnO, the photophysical properties of BSA depend significantly on the concentration of ZnO NPs in the mixed solution. The quenching of the fluorescence intensity of BSA in the presence of ZnO NPs was due to the interaction between ZnO and BSA, and the formation of their stable ground state complex, as well as energy transfer from the excited BSA to ZnO NPs in the complex nano-bioconjugated species. Multilayer growth of the ZnO/BSA LbL self-assembled film on the quartz substrate was confirmed by monitoring the characteristic absorption band of BSA (280 nm), where the nature of the film growth depends on the number of bilayers deposited on the quartz substrate. BSA formed a well-ordered molecular network-type morphology due to its adsorption onto the surface of the ZnO nanostructure in the backbone of the PAA-coated Si substrate in the LbL film according to atomic force microscopic study. The as-synthesized ZnO NPs were characterized by field emission scanning electron microscopy, X-ray powder diffraction, and dynamic light scattering techniques.

A review on bio-synthesized zinc oxide nanoparticles using plant extracts as reductants and stabilizing agents

In the age of technology, nanoparticles have proven to be one of the essential needs for development. These nanoparticles have the potential to be used for a wide variety of applications, thereby, development in improving the quality of nanoparticles, to make them more application specific, is still under research. In this regard, an important point to note is that the procedures employed in synthesizing nanoparticles require to be cost-effective and less-steps involved and have an additional advantage, i.e. they should be eco-friendly. This means that the synthesis procedure needs avoiding the use of harmful chemicals, and negligible generation of any noxious by-products. The green synthesis (biosynthesis) method employs simple procedures, easily available raw materials and ambiance for the synthesis process, where the precursors used are safe, with minute possibility for the production of harmful by-products. Considering these advantages, the current review includes a brief description on the various chemical and physical synthesis method of zinc oxide (ZnO) nanoparticles with emphasis on the biosynthesis of ZnO nanoparticles using plant extracts (and briefly microbes), the phytochemicals present in the plant extracts, the plausible mechanisms involved in the formation of ZnO nanoparticles and applications of the as-synthesized ZnO nanoparticles as photocatalysts and microbial inhibitors.

Band gap engineering of transition metal (Ni/Co) codoped in zinc oxide (ZnO) nanoparticles

Here we report on tunable bandgap engineering of single phase (Ni/Co) codoped ZnO nanoparticles controlled by different dopant concentrations. The as-synthesized ZnO nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–visible near infrared spectroscopy (UV-VIS-NIR), photoluminescence (PL) spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). In absorption spectra, a clear blue shift of 15 nm for the Ni/Co codoped ZnO nanoparticles was observed compared to pure ZnO nanoparticles. Moreover, it demonstrates that the value of energy bandgap changes from 3.55 eV to 3.71 eV by varying the dopant concentrations. Compared to pure ZnO nanoparticles, green emission PL peak intensity is significantly reduced in the doped ZnO nanoparticles, attributed to the significant decrease in intrinsic defects. Our results improve the understanding of optical and structural properties of Ni and Co codoped ZnO nanoparticles as these nanocrystalline structures could be potential candidates for optoelectronic devices.

One-pot green synthesis of zinc oxide nano rice and its application as sonocatalyst for degradation of organic dye and synthesis of 2-benzimidazole derivatives

In this paper, we report novel and green approach for one-pot biosynthesis of zinc oxide (ZnO) nanoparticles (NPs). Highly stable and hexagonal phase ZnO nanoparticles were synthesized using seeds extract from the tender pods of Parkia roxburghii and characterized by XRD, FT-IR, EDX, TEM, and N2 adsorption-desorption (BET) studies. The present method of synthesis of ZnO NPs is very efficient and cost effective. The powder XRD pattern furnished evidence for the formation of hexagonal close packing structure of ZnO NPs having average crystallite size 25.6nm. The TEM image reveals rice shapes ZnO NPs are with an average diameter of 40–60nm. The as-synthesized ZnO NPs has proved to be an excellent sonocatalysts for degradation of organic dye and synthesis of 2-benzimidazole derivatives.

Photocatalytic degradation of methylene blue dye by zinc oxide nanoparticles obtained from precipitation and sol-gel methods.

Zinc oxide (ZnO) nanoparticles were synthesized by precipitation and sol-gel methods. The aim of this study was to understand how different synthetic methods can affect the photocatalytic activity of ZnO nanoparticles. As-synthesized ZnO nanoparticles were characterized by X-ray diffraction (XRD) and UV-Visible spectroscopic techniques. XRD patterns of ZnO powders synthesized by precipitation and sol-gel methods revealed their hexagonal wurtzite structure with crystallite sizes of 30 and 28nm, respectively. Their photocatalytic activities were evaluated by photocatalytic degradation of methylene blue, a common water pollutant, under UV radiation. The effects of operational parameters such as photocatalyst load and initial concentration of the dye on photocatalytic degradation of methylene blue were investigated. While the degradation of dye decreased over the studied dye concentration range of 20 to 100mg/L, an optimum photocatalyst load of 250mg/L was needed to achieve dye degradation as high as 81 and 92.5% for ZnO prepared by precipitation and sol-gel methods, respectively. Assuming pseudo first-order reaction kinetics, this corresponded to rate constants of 8.4×10-3 and 12.4×10-3min-1, respectively. Hence, sol-gel method is preferred over precipitation method in order to achieve higher photocatalytic activity of ZnO nanostructures. Photocatalytic activity is further augmented by better choice of capping ligand for colloidal stabilization, starch being more effective than polyethylene glycol (PEG).

Facile synthesis and characterization of zinc oxide nanoparticles and studies of their catalytic activity towards ultrasound-assisted degradation of metronidazole

A novel and facile approach for synthesis of zinc oxide (ZnO) nanoparticles (NPs) employing homogeneous chemical precipitation followed by hydrothermal heating technique is reported. The present method of synthesis of ZnO NPs is very efficient and cost effective. As-synthesized ZnO NPs were characterized by XRD, FT-IR, EDX, TEM, and N2 adsorption–desorption (BET) studies. The powder XRD pattern furnished evidence for the formation of hexagonal close packing structure of ZnO NPs having average crystallite size 21.93nm. The shapes of synthesized ZnO NPs are mostly quasi-cylindrical with sizes 20–50nm. These ZnO NPs were used as catalysts for the degradation of a pharmaceuticals waste, metronidazole under ultrasound irradiation.

Preparation of Monodisperse ColloidalZnONanoparticles and their Optical Properties

Monodisperse colloidal zinc oxide ( ZnO ) nanospheres with a narrow size distribution were synthesized via a developed two-stage solution method. We controlled the size of the as-synthesized ZnO nanoparticles by varying the amount of ZnO /ethanol suspension added. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) revealed that the diameter of the as-synthesized ZnO nanoparticles was in the range of 60–140 nm with a polydispersity index less than 5%. On high-resolution TEM images, we clearly observed that the ZnO nanospheres were actually composed of tiny ZnO subunits, several nanometers in size. Powder X-ray diffraction and TEM-selected area electron diffraction analysis showed that the spheres consisted of polycrystalline nanoparticles. The size of the subunits, which was confirmed by ultraviolet (UV)-visible spectroscopy, increased as the amount of ZnO /ethanol suspension added was decreased. A UV emission at about 374 nm was observed, and this emission of ZnO nanoparticles is found to depend on particle size due to the confinement effect. A red emission at about 651 nm, which has been reported for undoped ZnO , appeared due to the excess oxygen on the particles from O – H or C = O groups. The intensity of the red emission increased as the relative oxygen content increased. The formation mechanism of such ZnO nanospheres was also considered.

Pulsed electrical discharge synthesis of red photoluminescence zinc oxide nanoparticles

Zinc oxide (ZnO) nanoparticles have been prepared using a pulsed electrical discharge in a liquid medium. The effects of the processing parameters, including liquid media, current, frequency of the electrical discharge and electrode gap distance exert significant effects on the characteristic and properties of ZnO nanoparticles. The synthesized ZnO nanoparticles are characterized using a combination of transmission electron microscopy (TEM), energy dispersive X-ray (EDS) and photoluminescence (PL) spectroscopy. The average size of ZnO nanoparticles varies between 10–25 nm depending on the processing parameters. It is found that an increase in the arc current plays a great role in particle growth and results in a significant increase in average particles size. Both frequency of discharge and electrode gap distance can influence the average particle size and distribution due to the variation in the cooling rate. The PL spectrum for all as-synthesized ZnO nanoparticles exhibits an ultraviolet emission (~3.4 eV) and a red visible emission (~1.98 eV). The blue shift is independent of the average size of the ZnO nanoparticles. However, the intensity of visible emission is significantly enhanced with the decrease of the particle sizes. The porous structure and irregular particle surface are suggested to contribute significantly to the visible red emission.

Comparison of optical and photovoltaic properties of ZnO chemically synthesized by using different hydrolyzing agents

Two zinc oxide (ZnO) nanoparticles ZS with hexagonal sheet and ZN having nanorod-like morphologies were prepared by precipitation technique using two different hydrolyzing agents viz. water (ZS) and ethanol (ZN). The physicochemical properties of both of the as-synthesized ZnO nanoparticles were investigated by UV–vis, powder X-ray diffraction (pXRD) and field emission scanning microscopy (FESEM). The as-synthesized ZnO nanoparticulates were successfully employed as photoanode material in dye-sensitized solar cells (DSSCs). The photoanode fabricated by using ZN in DSSC showed two times better cell efficiency with enhanced photocurrent and open circuit potential in comparison to the photoanode fabricated using ZS. The improved efficiency of ZN over ZS is due to high active surface area for greater dye loading.

Effect of the temperature on structural and optical properties of zinc oxide nanoparticles.

Zinc nitrate hexahydrate, Zn(NO3)2 x 6H2O was used as a precursor with urea NH2CONH2 to prepare hydrozincite Zn5(CO3)2(OH)6 powder using hydrothermal method for 8 h at 90 degrees C. Zinc oxide (ZnO) nanoparticles (NPs) were prepared by thermal annealing of hydrozincite powder at different annealing temperatures, i.e., 350, 550 750 and 950 degrees C in air for 2 h. The resulting materials were characterized by X-ray diffraction, scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA). The optical properties of the products were characterized by Fourier transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy and photoluminescence (PL) spectra. It was found that the particle size increased from - 33 to 250 nm with increasing in the annealing temperatures. FTIR results showed that the standard peaks of zinc oxide were presented at 428.17 and 532.32 cm(-1). Thermal analysis study showed that the primary weight loss starts at - 93 degrees C is due to solvent evaporation. The secondary weight loss, observed at - 378 degrees C, is due to phase transition from hydrated zinc oxide to zinc oxide. The band gaps of the products were in the range - 3.26-3.30 eV. The PL spectrum showed that the as-synthesized ZnO nanoparticles had UV (381 nm) and green (537 nm) emissions.

Influence of dipole moment of capping molecules on the optoelectronic properties of ZnO nanoparticles

Thiol-stabilized zinc oxide nanoparticles were synthesized via an aqueous route under moderate temperature to obtain better crystalline material. The work has been focused to study the effect of molecular dipole moment on optoelectronic properties of these nanoparticles. Three different organic thiols such as 1-thioglycerol, thioglycolic acid and 2-mercaptoethanol possessing different dipole moment were used as capping molecules. These nanoparticles were characterized by X-ray diffraction, optical absorption, photoluminescence, energy dispersive analyses of X-ray, infrared spectroscopy and scanning electron microscopy. X-ray diffraction results revealed that as-synthesized zinc oxide nanoparticles had pure hexagonal wurtzite structure and 2-mercaptoethanol capping gives smallest particle size. Colloids of these nanoparticles clearly emit violet color under ultraviolet light irradiation. The role of dipole moment and its orientation on ZnO surface has been investigated. It has been observed that a static electric field due to dipole moment on these nanoparticles significantly affects the photoluminescence properties.

Low-temperature synthesis of ZnO nanoparticles for inverted polymer solar cell application

Zinc oxide (ZnO) nanoparticles were synthesized by a simple wet chemical method at low temperature. Morphologies, crystalline structure, and optical transmission of ZnO nanoparticles were investigated. The results showed that the average diameter of as-synthesized ZnO nanoparticles was about 4.9 nm, the nanoparticles were wurtzite-structured (hexagonal) ZnO and had optical band gap of 3.28 eV. Very high optical transmission (>80 %) in visible light region of ZnO nanoparticulate thin films was achieved. Furthermore, an inverted polymer solar cell consisted of ZnO nanoparticles and polymer were fabricated. The device exhibited an open circuit voltage (Voc) of 0.50 V, a short circuit current density (Jsc) of 1.76 mA/cm2, a fill-factor of 38 %, and a power conversion efficiency of 0.42 %.

Glutathione Coated Zinc Oxide Nanoparticles: A Promising Material for Pesticide Detection

Extensive research studies are being carried out to significantly improve the sensing characteristics of pesticide sensors (chloropyrifos, organophosphates (OP)) especially at ultra low concentrations using advance fabrication and characterization techniques. We report feasibility study of pesticide sensing, using nanostructured zinc oxide (ZnO) and acetylcholinesterase (AChE) immobilized ZnO films, at ultra low concentrations (10 to 1000 ppb). ZnO nanoparticles (NPs) were synthesized by non-aqueous sol–gel method. Reduced glutathione (GSH) was coated on as-synthesized ZnO NPs by physical mixing. FESEM observation revealed spherical particles of about 10–20 nm in diameter having fairly uniform shape distribution. Thick films of these powders were printed on pre-printed electrodes using conventional screen printing technique. AChE was immobilized on the films by physical adsorption method. It is found that bare ZnO NPs are insensitive to pesticides while GSH coated ZnO NPs exhibit monotonous increase of sensitivity as a function of OP concentration over the wide range (10 ppb to 1000 ppb) with sensitivity of 2.1 A/ppm/cm2, detection limit of 3 ppb and regression coefficient of 0.92. Electrochemical measurement indicated that sensors can be used for few times due to the known inhibitory nature of OP and AChE reaction.

Antimicrobial Activity of 6.5 MeV Electron-Irradiated ZnO Nanoparticles Synthesized by Microwave-Assisted Method

ABSTRACT Zinc oxide (ZnO) nanoparticles were synthesized by a microwave method and were tailored using an energy electron irradiation method at 6.5 MeV. ZnO nanoparticles with a size of 40 nm were exposed to different fluences of 6.5 MeV electrons over the range from 5 × 1014 to 3.5 × 1015 electron/cm2. These electron-irradiated ZnO nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The XRD results showed that the ZnO nanoparticles retained the hexagonal phase with a wurtzite structure. However, the particle size decreased continuously from 40 to 15 nm with increasing electron fluence. The TEM results also supported for the reduction of the ZnO nanoparticles by 6.5 MeV electron irradiation. The antimicrobial activities of the as-synthesized and electron-irradiated ZnO nanoparticles on the fungus Candida albicans were studied. In this case, the electron-irradiated ZnO nanoparticles showed higher antimicrobi...

Synthesis of ZnO Nanoparticles and Their Ink-Jetting Behavior

Zinc oxide (ZnO) nanoparticles were synthesized by ultrasonically-assisted solution process without using any surfactants. The as-synthesized spherical ZnO nanoparticles with diameter of 20 +/- 5 nm possessed crystalline nature with wurtzite hexagonal phase and showed a blue-shifted near band-edge ultra-violet absorption at -340 nm due to quantum confinement effect of ZnO nanoparticles. The as-synthesized ZnO nanoparticles were further formulated as an ink for ink-jet printing application. Jetting and writing of various line patterns on Si and ITO substrates were demonstrated using the as-formulated ZnO ink. UV-treated substrates showed an improvement in the fixation of ink on substrate due to decreased contact angle with controlled surface wettability.

Preparation and Properties of Polyvinylpyrrolidone / Zinc Oxide Composite Nanofibers

Zinc Oxide (ZnO) nanoparticles were firstly synthesized by the hydration of alkoxide. The as-synthesized ZnO were dispersed in the polyvinylpyrrolidone (PVP) solution. PVP/ZnO composite nanofibers were prepared via electrospinning the PVP/ZnO mixed solution. The morphology of ZnO nanoparticles and as-spun nanofibers was measured by scanning electron microscopy (SEM). The as-synthesized ZnO nanoparticles were homogeneous and stable, and their size ranged from 30 to 40 nm. The composite nanofibers showed a uniform and continuous morphology. With the increase of the ZnO content in the composite nanofibers, the diameter distribution of the composite nanofibers became wider. Transmission electron microscopy (TEM) images clearly showed that ZnO nanoparticles were distributed uniformly in the PVP/ZnO composite nanofibers without any aggregation, although the ZnO content reached as highly as 6 wt. %. The structures and properties of the composite nanofibers were investigated using X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and Combined Stead State Fluorescence and Phosphorescence Lifetime Spectrometer (FLSP).