Photocatalytic activity of ZnO nanoparticles and the role of the synthesis method on their physical and chemical properties

Phytochemical fabrication of ZnO nanoparticles and their antibacterial and anti-biofilm activity

The synthesis of metal nanoparticles through bio-reduction is environmentally benign and devoid of impurities, which is very important for biological applications. This method aims to improve ZnO nanoparticle's antibacterial and anti-biofilm activity while reducing the amount of hazardous chemicals used in nanoparticle production. The assembly of zinc oxide nanoparticles (ZnO NPs) is presented via bio-reduction of an aqueous zinc nitrate solution using Echinochloacolona (E. colona) plant aqueous leaf extract comprising various phytochemical components such as phenols, flavonoids, proteins, and sugars. The synthesized nano ZnO NPs are characterized by UV-visible spectrophotometer (UV-vis), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (X-RD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and elemental composition by energy-dispersive x-ray spectroscopy (EDX). The formation of biosynthesized ZnO nanoparticles was confirmed by the absorbance at 360-370 nm in the UV-vis spectrum. The average crystal size of the particles was found to be 15.8 nm, as calculated from XRD. SEM and TEM analysis of prepared ZnO NPs confirmed the spherical and hexagonal shaped nanoparticles. ZnO NPs showed antibacterial activity against Escherichia coli and Klebsiella pneumoniae with the largest zone of inhibition (ZOI) of 17 and 18 mm, respectively, from the disc diffusion method. Furthermore, ZnO NPs exhibited significant anti-biofilm activity in a dose-dependent manner against selected bacterial strains, thus suggesting that ZnO NPs can be deployed in the prevention of infectious diseases and also used in food preservation.

Origin of the Improved Photoelectrochemical and Photocatalytic Activity in a ZnO-TiO2 Nanohybrid Revealed by Experimental and Density Functional Theory Studies

Heterojunctions of metal oxides have attracted a great deal of attention as photo (electro) catalysts owing to their excellent photoactivity. While multiple fundamental studies have been dedicated to heteroaggregation, self-assembly of oppositely charged particles to obtain heterojunctions for energy applications has been underexplored. Herein, we report the synthesis of ZnO-TiO2 heterojunctions using the electrostatic self-assembly approach. The synthesized ZnO-TiO2 heterojunctions were characterized by using multiple experimental techniques. Density functional theory calculations were conducted to establish the heterojunction formation mechanism and electronic properties. The ZnO-TiO2 nanohybrid was tested for the photodegradation of rhodamine B dye and water splitting applications. The photocatalytic performance of the ZnO-TiO2 nanohybrid is 3.5 times higher than that of bare ZnO. In addition, the heterostructure exhibited an excellent photocurrent density of 2.4 mA cm-2 at a low onset potential during photoelectrochemical oxygen evolution. The performance improvements are attributed to the formation of the type II heterojunction between ZnO and TiO2, which suppresses carrier recombination and enhances carrier transport, boosting the catalytic activity.

Defects in Nitrogen-Doped ZnO Nanoparticles and Their Effect on Light-Emitting Diodes

In this study, the effect of defects on the acceptor properties of nitrogen-doped ZnO nanoparticles (NPs) was investigated through the fabrication of light-emitting diodes (LEDs). Nitrogen-doped ZnO NPs were synthesized by an arc discharge in-gas evaporation method and post-annealed at 800 °C in an oxygen and nitrogen atmosphere. The annealed ZnO NPs were characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and photoluminescence spectroscopy. It was found that the annealing of nitrogen-doped ZnO NPs in a nitrogen environment increased the number of zinc vacancies, while annealing in an oxygen environment increased the number of oxygen vacancies due to nitrogen desorption. The output characteristics of LEDs fabricated with oxygen-annealed NPs were degraded, while those with nitrogen-annealed NPs were significantly improved. From these results, the contribution of zinc vacancies to acceptor formation in ZnO NPs was confirmed for the first time in actual pn junction devices.

Photocatalytic Degradation of Organic Pollutants-Nile Blue, Methylene Blue, and Bentazon Herbicide-Using NiO-ZnO Nanocomposite

Water pollution poses a significant threat to both human health and ecosystem integrity. Chemical pollutants such as dyes and pesticides affect the water quality and endanger aquatic life. Among the methods for water purification from organic pollutants, photodegradation is certainly a valid technique to decrease such contaminants. In this work, pristine NiO, ZnO, and NiO-ZnO photocatalysts were synthesized by the homogeneous co-precipitation method. X-ray diffraction confirms the formation of a photocatalyst consisting of ZnO (Hexagonal) and NiO (Cubic) structures. The crystalline size was calculated by the Scherrer formula, which is 19 nm for the NiO-ZnO photocatalyst. The band gap measurements of the prepared samples were obtained using the Tauc Plot, equation which is 2.93 eV, 3.35 eV and 2.63 eV for NiO, ZnO, and NiO-ZnO photocatalysts, respectively. The photocatalytic performance of NiO-ZnO nanocomposite was evaluated through the degradation of Methylene Blue and Nile Blue dyes under sunlight, and Bentazon herbicide under a UV light. Photocatalyst degradation efficiency was 95% and 97% for Methylene Blue and Nile Blue in 220 min under sunlight while a degradation of 70% for Bentazon after 100 min under UV light source was found.

Green synthesis of ZnO nanoparticles from ball moss (Tillandsia recurvata) extracts: characterization and evaluation of their photocatalytic activity

Green synthesis (GS), referred to the synthesis using bioactive agents such as plant materials, microorganisms, and various biowastes, prioritizing environmental sustainability, has become increasingly relevant in international scientific practice. The availability of plant resources expands the scope of new exploration opportunities, including the evaluation of new sources of organic extracts, for instance, to the best of our knowledge, no scientific articles have reported the synthesis of zinc oxide nanoparticles (ZnO NPs) from organic extracts of T. recurvata, a parasitic plant very common in semiarid regions of Mexico.This paper presents a greener and more efficient method for synthesizing ZnO NPs using T. recurvata extract as a reducing agent. The nanoparticles were examined by different techniques such as UV-vis spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and BET surface analysis. The photocatalytic and adsorptive effect of ZnO NPs was investigated against methylene blue (MB) dye in aqueous media under sunlight irradiation considering an equilibrium time under dark conditions. ZnO nanoparticles were highly effective in removing MB under sunlight irradiation conditions, showing low toxicity towards human epithelial cells, making them promising candidates for a variety of applications. This attribute fosters the use of green synthesis techniques for addressing environmental issues.This study also includes the estimation of the supported electric field distributions of ZnO NPs in their individual spherical or rounded shapes and their randomly oriented organization, considering different diameters, by simulating their behavior in the visible wavelength range, observing resonant enhancements due to the strong light-matter interaction around the ZnO NPs boundaries.

Phase controlled green synthesis of wurtzite (P63mc) ZnO nanoparticles: interplay of green ligands with precursor anions, anisotropy and photocatalysis

Green approaches for nanosynthesis often lack the precise control of synthetic outcomes, which is primarily due to the poorly defined reaction protocols. Herein, we investigated the use of lignocellulosic agro-waste, sugarcane press mud (PM), for the synthesis of ZnO nanoparticles using three different precursor salts and their further application in the photocatalytic degradation of rhodamine dyes. This approach resulted in the formation of ZnO nanoparticles with two different morphologies, i.e., sheet-like structure from the zinc sulphate and nitrate precursors, whereas sphere-like structures from zinc acetate. In all three cases, the wurtzite phase (P63mc) of ZnO nanoparticles remained consistent. Also, the ZnO nanoparticles were found to be positively charged ("ζ" = +8.81 to +9.22 mv) and nearly monodispersed, with a size and band gap in the range of ∼14-20 nm and 3.78-4.1 eV, respectively. Further, the potential photocatalytic activity of these nanoparticles was investigated under direct sunlight. At the same photocatalyst dose of 0.1 g L-1, the three ZnO nanoparticles showed varying efficiencies due to their shape anisotropy. The ZnO NPs from acetate salt (∼20 nm, sheet like) showed the highest dye degradation efficiency (90.03%) in 4.0 hours, indicating the role of the catalyst-dye interface in designing efficient photocatalysts.

Principles of Photocatalysts and Their Different Applications: A Review

Human existence and societal growth are both dependent on the availability of clean and fresh water. Photocatalysis is a type of artificial photosynthesis that uses environmentally friendly, long-lasting materials to address energy and environmental issues. There is currently a considerable demand for low-cost, high-performance wastewater treatment equipment. By changing the structure, size, and characteristics of nanomaterials, the use of nanotechnology in the field of water filtration has evolved dramatically. Semiconductor-assisted photocatalysis has recently advanced to become among the most promising techniques in the fields of sustainable energy generation and ecological cleanup. It is environmentally beneficial, cost-effective, and strictly linked to the zero waste discharge principle used in industrial effluent treatment. Owing to the reduction or removal of created unwanted byproducts, the green synthesis of photoactive nanomaterial is more beneficial than chemical synthesis approaches. Furthermore, unlike chemical synthesis methods, the green synthesis method does not require the use of expensive, dangerous, or poisonous ingredients, making it a less costly, easy, and environmental method for photocatalyst synthesis. This work focuses on distinct greener synthesis techniques utilized for the production of new photocatalysts, including metals, metal doped-metal oxides, metal oxides, and plasmonic nanostructures, including the application of artificial intelligence and machine learning to the design and selection of an innovative photocatalyst in the context of energy and environmental challenges. A brief overview of the industrial and environmental applications of photocatalysts is also presented. Finally, an overview and recommendations for future research are given to create photocatalytic systems with greatly improved stability and efficiency.

Anomalous catalytic and antibacterial activity confirmed by molecular docking analysis of silver and polyacrylic acid doped CeO2 nanostructures

This research presents the novel synthesis of CeO2 nanostructures (NSs) doped with a fixed amount of capping agent (polyacrylic acid-PAA) and different concentrations (0.01 and 0.03) of silver (Ag). This work aimed to examine the catalytic and antibacterial efficacy with evidential molecular docking analysis of Ag/PAA doped CeO2. Systematic characterization was used to analyze the effect of Ag and a capping agent on crystal structure, morphology, absorbance wavelength, and the exciton recombination rate of CeO2. The silver metal and capping agent (PAA) were added into CeO2 to reduce the size of NSs, enhancing the catalytic efficacy. These binary dopants (Ag-PAA) based CeO2 revealed remarkable results for catalytic de-colorization of rhodamine B dye and antimicrobial potential as the dopants provide more active sites. Notably, (0.03) Ag/PAA doped CeO2 NSs exhibited a substantial catalytic reduction (98.9%) of rhodamine B dye in an acidic medium. The higher doped CeO2 revealed a significant inhibition zone (3.75 mm) against Escherichia coli at maximal concentration. Furthermore, in silico docking showed the possible inhibitory impact of produced nanomaterials on the fatty acid biosynthesis enzymes FabI and FabH.

Hydrothermal Synthesis of Fe-Doped Cadmium Oxide Showed Bactericidal Behavior and Highly Efficient Visible Light Photocatalysis

Cationic dyes present in industrial effluents significantly reduce the effectiveness of remediation operations. Considering the terrible impact of these pollutants on environment and biodiversity, investigating strategies to remove potentially harmful compounds from water is becoming an increasingly intriguing issue. In this work, we employed a simple hydrothermal technique to synthesize Fe-doped CdO (2, 4, and 6 wt %) nanostructures and assessed their efficacy in degrading methylene blue (MB) dye and inhibiting the growth of Staphylococcus aureus and Escherichia coli, respectively. Structural, morphological, and optical characterization of produced nanomaterials was also performed using X-ray diffraction, TEM, and UV absorption spectra. The photocatalytic decomposition of MB was significantly enhanced (58.8%) by using Fe (6 wt %)-doped CdO catalysts for 80 min under irradiation. In addition, 2.05-5.05 mm inhibitory zones were seen against Gram-positive bacteria (S. aureus), whereas the range for Gram-negative bacteria (E. coli) was 1.65-2.75 mm. These nanostructures were shown to be very effective inhibitors of beta-lactamase, d-alanine-d-alanine ligase B, and fatty acid synthase inhibitor by in silico molecular docking investigations.

Experimental and computational study of metal oxide nanoparticles for the photocatalytic degradation of organic pollutants: a review

Photocatalysis is a more proficient technique that involves the breakdown or decomposition of different organic contaminants, various dyes, and harmful viruses and fungi using UV or visible light solar spectrum. Metal oxides are considered promising candidate photocatalysts owing to their low cost, efficiency, simple fabricating method, sufficient availability, and environment-friendliness for photocatalytic applications. Among metal oxides, TiO2 is the most studied photocatalyst and is highly applied in wastewater treatment and hydrogen production. However, TiO2 is relatively active only under ultraviolet light due to its wide bandgap, which limits its applicability because the production of ultraviolet is expensive. At present, the discovery of a photocatalyst of suitable bandgap with visible light or modification of the existing photocatalyst is becoming very attractive for photocatalysis technology. However, the major drawbacks of photocatalysts are the high recombination rate of photogenerated electron-hole pairs, the ultraviolet light activity limitations, and low surface coverage. In this review, the most commonly used synthesis method for metal oxide nanoparticles, photocatalytic applications of metal oxides, and applications and toxicity of different dyes are comprehensively highlighted. In addition, the challenges in the photocatalytic applications of metal oxides, strategies to suppress these challenges, and metal oxide studied by density functional theory for photocatalytic applications are described in detail.

Synthesis of Planar-Type ZnO Powder in Non-Nano Scale Dimension and Its Application in Ultraviolet Protection Cosmetics

ZnO is one of the most widely used inorganic sunscreens, owing to its fine particle size and UV light shielding capability. However, powders at nanosizes can be toxic and cause adverse effects. The development of non-nanosized particles has been slow. The present work investigated synthesis methods of non-nanosized ZnO particles for ultraviolet protection application. By altering the starting material, KOH concentration, and input speed, the ZnO particles can be obtained in different forms, including needle type, planar type, and vertical wall type. Cosmetic samples were made by mixing different ratios of synthesized powders. The physical properties and the UV blockage efficacy of different samples were evaluated using scanning electron microscopy (SEM), X-ray diffraction (XRD), particle size analyzer (PSA), and ultraviolet/visible (UV/Vis) spectrometer. The samples with 1:1 ratio of needle-type ZnO and vertical wall-type ZnO exhibited superior light blocking effect owing to improved dispersibility and prevention of particle agglomeration. The 1:1 mixed sample also complied with the European nanomaterials regulation due to the absence of nanosized particles. With superior UV protection in the UVA and UVB regions, the 1:1 mixed powder showed potential to be used as a main ingredient in UV protection cosmetics.

The synergetic effect of lanthanide (La and Ce) and N co-doping of ZnO NPs for high-rate photocatalytic phenol degradation

Simultaneously, lanthanide and N-modified ZnO NPs were synthesized and applied for the photocatalytic phenol degradation under LED irradiation. Among La and Ce, Ce-doped ZnO exhibited more efficiently photocatalytic activity. XRD analysis confirmed that most of Ce³⁺ was oxidized to Ce₂O₃/CeO₂ over the photocatalyst surface as a secondary phase. This is due to the larger ionic radius of Ce³⁺ relative to that of Zn²⁺. Ce and N co-doping of ZnO led to narrowing the band gap and suppressing charge recombination rate. The effect of key variables, dopant type, dopant concentration, catalyst loading, initial dye concentration, light source power, solution pH, and H₂O₂ content on the photocatalytic degradation of phenol was systematically investigated. The utmost conversion of phenol, 100%, was observed by ZnO-Ce5-N0.33 sample under optimum conditions. Kinetics investigation revealed that under the optimum conditions, photodegradation of phenol follows a pseudo-first-order kinetics model with rate constant of 0.0631 min^-1. Given the fact that the ZnO-Ce5-N0.33 is a heterostructure composed of Zn_1-xCe_xO_1-yN_y and Ce₂O₃ and CeO₂, a double Z-scheme pattern is suggested as a plausible charge transfer mechanism.

Comprehensive study upon physicochemical properties of bio-ZnO NCs

In this study, for the first time, the comparison of commercially available chemical ZnO NCs and bio-ZnO NCs produced extracellularly by two different probiotic isolates (Latilactobacillus curvatus MEVP1 [OM736187] and Limosilactobacillus fermentum MEVP2 [OM736188]) were performed. All types of ZnO formulations were characterized by comprehensive interdisciplinary approach including various instrumental techniques in order to obtain nanocomposites with suitable properties for further applications, i.e. biomedical. Based on the X- ray diffraction analysis results, all tested nanoparticles exhibited the wurtzite structure with an average crystalline size distribution of 21.1 nm (CHEM_ZnO NCs), 13.2 nm (1C_ZnO NCs) and 12.9 nm (4a_ZnO NCs). The microscopy approach with use of broad range of detectors (SE, BF, HAADF) revealed the core-shell structure of bio-ZnO NCs, compared to the chemical one. The nanoparticles core of 1C and 4a_ZnO NCs are coated by the specific organic deposit coming from the metabolites produced by two probiotic strains, L. fermentum and L. curvatus. Vibrational infrared spectroscopy, photoluminescence (PL) and mass spectrometry (LDI-TOF-MS) have been used to monitor the ZnO NCs surface chemistry and allowed for better description of bio-NCs organic coating composition (amino acids residues). The characterized ZnO formulations were then assessed for their photocatalytic properties against methylene blue (MB). Both types of bio-ZnO NCs exhibited good photocatalytic activity, however, the effect of CHEM_ZnO NCs was more potent than bio-ZnO NCs. Finally, the colloidal stability of the tested nanoparticles were investigated based on the zeta potential (ZP) and hydrodynamic diameter measurements in dependence of the nanocomposites concentration and investigation time. During the biosynthesis of nano-ZnO, the increment of pH from 5.7 to around 8 were observed which suggested possible contribution of zinc aquacomplexes and carboxyl-rich compounds resulted in conversion of zinc tetrahydroxy ion complex to ZnO NCs. Overall results in present study suggest that used accessible source such us probiotic strains, L. fermentum and L. curvatus, for extracellular bio-ZnO NCs synthesis are of high interest. What is important, no significant differences between organic deposit (e.g. metabolites) produced by tested strains were noticed-both of them allowed to form the nanoparticles with natural origin coating. In comparison to chemical ZnO NCs, those synthetized via microbiological route are promising material with further biological potential once have shown high stability during 7 days.

ZnO Nanoparticles from Different Precursors and Their Photocatalytic Potential for Biomedical Use

Semiconductor photocatalysts, particularly ZnO nanoparticles, were synthesized via the precipitation method using four different precursors (zinc acetate/zinc nitrate/zinc sulfate/zinc chloride) and compared, according to their optical, structural, photocatalytic, and anticancer properties. The materials were characterized via X-ray Diffraction method (XRD), micro-Raman, Fourier Transform Infrared Spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), Dynamic Light Scattering (DLS), and Field Emission Scanning Electron Microscope (FESEM) analysis. Photocatalysis was conducted under UV and visible light irradiation, using Rhodamine B as the organic pollutant. It was observed that the highest photocatalysis efficiency was obtained by the nanoparticles synthesized from the zinc acetate used as precursor material. A cell-dependent anticancer efficiency of the tested ZnO nanoparticles was also observed, that was also attributed to the different precursors and the synthesis method, revealing that the nanoparticles that were synthesized from zinc acetate were more bioactive among the four tested precursors. Overall, the data revealed that both the enhanced photocatalytic and biological activity of ZnO nanoparticles derived from zinc acetate precursor could be attributed to the reduced crystalline size, increased surface area, as well as the observed hexagonal crystalline morphology.

ZnO Nano-swirlings for Azo Dye AR183 photocatalytic degradation and antimycotic activity

The sol-gel technique was used to fabricate ZnO Nano-swirlings (ZNsw) at a predetermined agitation rate (of >> 1900 rpm), with around 21.94 gm of zinc acetate dihydrate and 0.2 g cetyltrimethylammoniumbromide (CTAB) and a cationic surfactant (drop-wise). The impact of the predetermined agitation condition on the molecular size and morphology of ZNsw is examined, and the outcomes are dissected by useful characterization tools and techniques viz. XRD, SEM embedded with EDS, TEM, FT-IR and UV-visible. The SEM and TEM results suggest that the product formed into a big cluster of adequate ZNsw, containing a significant quantity of folded long thread-lengths. Each group indicated a fair amount of the volume of these lengths. The photocatalytic process of ZNsw was carried out as a result of the irradiation time due to the deterioration of Azo Dye AR183, resulting in approximately 79 percent dye discoloration following an 80-min UV light irradiation in the presence of ZNsw. Additionally, the synthesized ZNsw was tested for antagonistic activity, and the growth hindrance of two plant pathogenic fungal strains found. Per cent inhibition in growth of Rhizoctonia solani and Alternaria alternata were observed in response to ZNsw.

Halloysite-Zinc Oxide Nanocomposites as Potential Photocatalysts

The synthesis and structural characterization of synthetic zinc oxide and halloysite-based zinc oxide nanocomposites (with 2–28 m/m% ZnO content) are presented. The chemical precipitation of zinc hydroxide precursors and its subsequent drying at 80 °C yielded dominantly zinc oxide (zincite). Thermal treatment at 350 °C completely transformed the remaining precursor to ZnO without causing structural dehydroxylation of the halloysite support. The procedure yielded zinc oxide nanoparticles with 10–22 nm average size having quasi-spherical scale-like morphology. The specific surface area of the synthetic zinc oxide was found to be low (13 m2/g), which was significantly enhanced after nanocomposite preparation (27–47 m2/g). The photocatalytic activity of the prepared nanocomposites was probed by the degradation of a phenolic compound (4-nitrophenol) upon UV irradiation in liquid phase. Compared to their individual constituents, an increased activity of the nanocomposites was observed, while the SSA-normalized photocatalytic activity revealed a synergic effect in nanocomposites above 9 m/m% ZnO content. The nanocomposites were found to be stable at pH = 5.6, with a minor and major mobilization of zinc ions at pH = 12.4 and pH = 1.9, respectively. The toxicity of leachates in different pH environments by Vibrio fischeri bioluminescence indicated low toxicity for ZnO nanoparticles and insignificant toxicity for the nanocomposites. The enhanced photocatalytic activity together with the lower toxicity of the halloysite-ZnO nanocomposites highlight their application potential in water treatment.

Performance Enhancement of Self-Cleaning Cotton Fabric with ZnO NPs and Dicarboxylic Acids

In this paper, we explore the self-cleaning and washing durability of green-prepared ZnO NPs combined with cotton fabrics. Honeysuckle extract was used to prepare ZnO NPs with an average particle size of 15.3 nm. Cotton fabrics were then treated with oxalic acid (OA), tartaric acid (TA), and succinic acid (SA) as cross-linking agents, sodium hypophosphite as a catalyst, and after that, the ZnO NPs were applied to the cross-linked cotton fabrics by the padding to prepare the self-cleaning cotton fabrics. The morphology and structure of the fabric samples were characterized using FTIR, scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), and XRD. The optical properties of the cotton fabric samples were discussed by UV-vis diffuse reflectance spectrum, and the self-cleaning performance, wrinkle recovery angle and ultraviolet protection performance of the cotton fabric samples were analyzed. The results showed that the carboxyl groups of TA, OA, and SA were esterified with hydroxyl groups of the cotton fiber and formed a film on the surface of the cotton fabrics. ZnO NPs were successfully loaded onto the cotton fabrics by strong electrostatic interaction, causing the improvement of the washing resistance of the cross-linked fabrics. In addition, compared with uncross-linked fabrics, the wrinkle recovery performance of the cross-linked fabrics had also been greatly improved, and the UV protection factor reached 50+, thus obtaining an excellent self-cleaning, multifunctional cotton-based textile with anti-wrinkle and anti-ultraviolet properties.

Facile synthesis of ZnO nanoparticles by Actinidia deliciosa fruit peel extract: Bactericidal, anticancer and detoxification properties

Synthesis of nanoparticles by eco-friendly method pulled an extensive concern worldwide due its biocompatibility and wide range of applications as catalysts, microbicidal agents, cancer treatment, sensors etc. Though different chemical methods available for preparation of ZnO nanoparticles, synthesis by utilizing plant material is an excellent substitute and green method as well. The present study describes preparation of ZnO nanoparticles by low-cost green synthetic way using Actinidia deliciosa (kiwi) fruit peel extract and its excellent biological and catalytic properties. The synthesized nanoparticles were well characterized by UV visible spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Energy-dispersive X-ray spectroscopy (EDAX). The bactericidal activity of the ZnO nanoparticles was determined by using Staphylococcus aureus (S. aureus), while mechanism of cell death was studied by SEM images. Superior anticancer activity was also observed in inhibiting the colon cancer cells (HCT116) by the ZnO nanoparticles. In addition, ZnO nanoparticles showed efficient photocatalytic activity towards degradation of p-bromophenol, about 96.3% within 120 min. Furthermore, phytotoxicity of the intermediate products was analyzed using Vigna radiata (V. radiata) as a model plant. About 8.0% of germination index (GI) was observed in pure p-BP while it increased to 82.3%, and exhibited that the detoxification of p-BP was attained after 120 min of degradation. Thus, the present study demonstrates ZnO nanoparticles prepared from simple, rapid, inexpensive, eco-friendly and efficient green method gives alternative root for biomedicine and wastewater treatment technologies.

A state of the art review on the synthesis, antibacterial, antioxidant, antidiabetic and tissue regeneration activities of zinc oxide nanoparticles

Recently, zinc oxide nanoparticles (ZnONPs) are gaining much interest of nanobiotechnologists due to their profound biomedical applications. ZnONPs are used as antibacterial agents, which cause both gram-positive and negative bacterial cell death through the generation of reactive free radicals as well as membrane rupture. ZnONPs show excellent antioxidant properties in normal mammalian cells via the scavenging of reactive free radicals and up-regulation of antioxidant enzyme activities. Besides, it also shows hypoglycaemic effect in diabetic animals via pancreatic β-cells mediated increased insulin secretion and glucose uptake by liver, skeletal muscles and adipose tissues. Among the other potential applications, ZnONPs-induced bone and soft-tissue regeneration open a new horizon in the field of tissue engineering. Here, first we reviewed the complete synthesis routes of ZnONPs by physical, chemical, and biological pathways as well as outlined the advantages and disadvantages of the techniques. Further, we discussed the several important aspects of physicochemical analysis of ZnONPs. Additionally, we extensively reviewed the important biomedical applications of ZnONPs as antibacterial, antioxidant, and antidiabetic agents, and in the field of tissue engineering with special emphasis on their mechanisms of actions. Furthermore, the future perspectives of the ZnONPs are also discussed.

Livistona jekinsiana fabricated ZnO nanoparticles and their detrimental effect towards anthropogenic organic pollutants and human pathogenic bacteria

An environment-friendly and economically sound method was developed to achieve a multi-functional ZnO nanoparticles (ZnO NPs) using water extract of Livistona jekinsiana. The ZnO NPs absorbed maximum wavelength of light at 332 nm in UV-Visible spectroscopy (UV/Vis). X-Ray Diffraction (XRD) pattern revealed the crystallinity of the nanoparticles with the crystallite size around 22.45 nm. The geometry, shape, size, and elemental composition were determined by Transmission Electron Microscope (TEM) and Energy Dispersive Spectroscopy (EDS). The presence of phytochemicals and the typical zinc-oxygen group in the ZnO NPs was implied by Fourier Transform Infrared spectroscopy (FTIR). Photo luminescence spectroscopy (PL), and Dynamic Light Scattering (DLS) techniques were also used to characterize and study the different features of ZnO NPs. The multifunctional ZnO NPs showed an efficient photodegradative effect towards the degradation of two anthropogenic dyes, methyl orange (MO) and methylene blue (MB) under solar radiation. The degradation reaction of MO and MB was compliantwithzero-order kinetics and first-order kinetics respectively. Also, Livistona jekinsiana fabricated ZnO NPs showed potential Antibacterial activity against S. aureus, B. subtilis, E. coli and K. pneumonia bacteria and effective antioxidant activity using DPPH scavenging assay. The mechanism of the antibacterial activity was established by estimating the ROS generation and percentage of DNA in K. pneumonia cell. The study illustrated the reducing and stabilizing property of the Livistona jekinsiana extract as a novel source and potential photodegradative and therapeutic effects of the ZnO NPs.

Ecofriendly Green Synthesis of the ZnO-Doped CuO@Alg Bionanocomposite for Efficient Oxidative Degradation of p-Nitrophenol

In the present study, ecofriendly green synthesized ZnO/CuO nanorods were prepared by using the stabilizing and reducing characteristics of the alginate biopolymer. The bionanocomposite (BNC) material was characterized by various sophisticated analytical tools such as Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy-energy dispersive X-ray spectroscopy, transmission electron microscopy, UV-visible spectroscopy, differential scanning calorimetry, and the Brunauer-Emmett-Teller (BET) method. The composition of ZnO/CuO@Alg BNC was found to be C (16.16 ± 0.42%), O (42.26 ± 1.87%), Cu (31.96 ± 1.05%), and Zn (9.62 ± 0.48%), which also supports the approximate 3:1 ratio of Cu2+ and Zn2+ taken as the precursor. The nanocrystalline spinel ferrite was found to have a BET specific surface area of 19.24 m2 g-1 with a total pore volume of 0.075 cm3 g-1 and 1.45 eV as the band gap energy (E g). Further, the material was applied for the photodegradation of p-nitrophenol (PNP) under the advanced oxidative process (AOP) under visible sunlight irradiation. The visible light radiation was used for the degradation of PNP under pH 2 conditions and resulted in 98.38% of the photocatalytic efficiency of the ZnO/CuO@Alg catalyst within 137 min of irradiation time. The photocatalytic reaction was best defined by the pseudo-first-order kinetics which involves the adsorption of the PNP molecule on the surface of the catalyst, thereby demineralizing it in the presence of advanced active •OH radicals. The values of rate constant for the pseudo-first-order model (k 1) were calculated as 0.013, 0.016, 0.019, 0.021, and 0.023 min-1 with half-life periods of 53.31, 43.31, 36.47, 33.00, and 30.13 min for 10-50 mg L-1 PNP concentrations. The presence of t-butyl alcohol decreases the photocatalytic efficiency, which suggests that the degradation of PNP was accomplished by the •OH oxidative radical.