Tailoring anisotropic ZnO/wood-structural holocellulose hybrids for dye degradation through nanoinsertion controlled

Nanostructured inorganic/wood-structural holocellulose hybrids offer new potential applications, including mechanical energy conversion, superhydrophobic materials, gas adsorption and so on. Owing to the anisotropy of wood, controlled the morphology of mineral particles inside porous holocellulose scaffold is still far from satisfactory. In this work, a homogeneous zinc oxide (ZnO) decoration inside wood-structural holocellulose scaffold was presented while the morphology, distribution and content of ZnO micro-nano particles were controllable through changing the conditions of hydrothermal growth. The holocellulose scaffold was prepared through delignification and periodate oxidation, which is favorable for Zn2+ capture and ZnO nuclei form because of the surface charge increased. The controlled ZnO insertion were realized by changing metal salt concentration, temperature and hydrothermal time. The obtained multilayer ZnO could provide multiple light refractions and reflections and enhance the utilization of light. Consequently, with a minor ZnO loading (15 wt%), the ZnO/wood-structural hybrids could totally degraded methyl orange and methyl blue in 6 h. This novel and scalable synthesis method shows potential in both the design and photocatalytic activity of holocellulose hybrids.

Synthesis of cobalt- ferrite and zinc oxide metal nanoparticles based-bentonite using SDS and their investigation as catalysts in synthesis of benzylbarbiturocoumarins

In this research, a suitable and efficient CoFe2O4@ZnO@Bentonite nano-catalyst was designed and synthesized by using zinc oxide (ZnO) and cobalt ferrite (CoFe2O4) nanoparticles and bentonite by microwave irradiation. Characteristics of the synthesized nanocomposite were investigated by Fourier transform infrared (FT-IR), scanning electron microscope (SEM), energy dispersive X-ray (EDX), transmission electron microscope (TEM), X-ray diffraction (XRD), Bruner- Emmett-Teller (BET) and vibrating sample magnetometer (VSM) techniques. The produced catalyst was effectively employed as a supported solid acid catalyst in mildly agitated three-component reactions involving aromatic aldehydes, 4-hydroxycoumarin, and 1,3-dimethyl-barbituric acid in a single pot to produce benzylbarbiturocoumarins. Starting materials were condensed via three C-C bond formation by CoFe2O4@ZnO@Bentonite as an efficient, recyclable, and environmentally safe nanocatalyst to obtain target products. The advantages of this method include using a natural substrate, small amounts of catalyst, aqueous media, performing reactions at ambient temperature, simple separation and purification of products, and good yields with short reaction times.

Highly Efficient and Reproducible Sonochemical Synthesis of ZnO Nanocrystals

Sonochemical synthesis can be a facile, fast, efficient, versatile and economical way to prepare a large variety of conventional or novel nanostructured materials (metallic, magnetic, semiconducting, polymeric, etc.). In this work, zinc oxide nanocrystals were synthesized by irradiating and heating at 90 °C in a commercial ultrasonic bath a water solution of zinc nitrate hexahydrate and ammonia solution or hexamethylenetetramine as base catalysts. The evolution of the powder morphology and its crystalline structure were investigated at different times of ultrasonic irradiation (0-9 hours) and compared with those of samples obtained by only heating the solutions in a muffle furnace in order to enlighten the growth mechanism. It resulted that: i) the crystal morphology depends on the selected base, ii) for samples obtained by using ultrasounds, the homogeneity of the powders depends on the irradiation time, iii) by comparing all samples obtained at 7 hours of heating, the aspect ratio of the crystals is higher for those that also underwent to ultrasounds.

Cutting-edge developments in zinc oxide nanoparticles: synthesis and applications for enhanced antimicrobial and UV protection in healthcare solutions

This paper presents a comprehensive review of recent advancements in utilizing zinc oxide nanoparticles (ZnO NPs) to enhance antimicrobial and UV protective properties in healthcare solutions. It delves into the synthesis techniques of ZnO NPs and elucidates their antimicrobial efficacy, exploring the underlying mechanisms governing their action against a spectrum of pathogens. Factors impacting the antimicrobial performance of ZnO NPs, including size, surface characteristics, and environmental variables, are extensively analyzed. Moreover, recent studies showcasing the effectiveness of ZnO NPs against diverse pathogens are critically examined, underscoring their potential utility in combatting microbial infections. The study further investigates the UV protective capabilities of ZnO NPs, elucidating the mechanisms by which they offer UV protection and reviewing recent innovations in leveraging them for UV-blocking applications in healthcare. It also dissects the factors influencing the UV shielding performance of ZnO NPs, such as particle size, dispersion quality, and surface coatings. Additionally, the paper addresses challenges associated with integrating ZnO NPs into healthcare products and presents future perspectives for overcoming these hurdles. It emphasizes the imperative for continued research efforts and collaborative initiatives to fully harness the potential of ZnO NPs in developing advanced healthcare solutions with augmented antimicrobial and UV protective attributes. By advancing our understanding and leveraging innovative approaches, ZnO NPs hold promise for addressing pressing healthcare needs and enhancing patient care outcomes.

Study on the Synthesis of Nano Zinc Oxide Particles under Supercritical Hydrothermal Conditions

The supercritical hydrothermal synthesis of nanomaterials has gained significant attention due to its straightforward operation and the excellent performance of the resulting products. In this study, the supercritical hydrothermal method was used with Zn(CH3COO)2·2H2O as the precursor and deionized water and ethanol as the solvent. Nano-ZnO was synthesized under different reaction temperatures (300~500 °C), reaction times (5~15 min), reaction pressures (22~30 MPa), precursor concentrations (0.1~0.5 mol/L), and ratios of precursor to organic solvent (C2H5OH) (2:1~1:4). The effects of synthesis conditions on the morphology and size of ZnO were studied. It was found that properly increasing hydrothermal temperature and pressure and extending the hydrothermal time are conducive to the more regular morphology and smaller size of ZnO particles, which is mainly achieved through the change of reaction conditions affecting the hydrothermal reaction rate. Moreover, the addition of ethanol makes the morphology of nano-zno more regular and significantly inhibits the agglomeration phenomenon. In addition to the change in physical properties of the solvent, this may also be related to the chemical bond established between ethanol and ZnO. The results show that the optimum synthesis conditions of ZnO are 450 °C, 26 MPa, 0.3 mol/L, 10 min, and the molar ratio of precursor to ethanol is 1:3.

Control of ZnO nanowires growth in flexible perovskite solar cells: A mini-review

Due to their excellent properties, Zinc oxide nanowires (ZnO NW) have been attractive and considered as a promising electron-transporting layer (ETL) in flexible Perovskite Solar Cells (FPSCs). Since the first report on ZnO NWs-based FPSCs giving 2.6 % power conversion efficiency (in 2013), great improvements have been made, allowing to reach up to∼15 % nowadays. However, some issues still need to be addressed, especially on flexible substrates, to achieve uniform and well-aligned ZnO NWs via low-cost chemical solution techniques. Several parameters, such as the growing method (time, temperature, precursors concentration), addition of seed layer (thickness, roughness, annealing temperature) and substrate (rigid or flexible), play a crucial role in ZnO NWs properties (i.e., length, diameter, density and aspect ratio). In this review, these parameters allowing to control the properties of ZnO NWs, like the growth techniques, utilization of seed layers and the growing method (time or precursors concentration) have been summarized. Then, a particular focus on the ZnO NW's role in FPSCs as well as the use of these results on the development of ZnO NWs-based FPSCs have been highlighted.

Progress towards blue emitting MgO-ZnO-Ga2O3 nanocomposites synthesized by bio mediated route

MgO-ZnO-Ga2O3 nanocomposites are synthesized by solution combustion method using Aloe Vera gel as a reducing agent to increase the efficiency of blue emission. The appearance of Bragg reflections corresponding to MgO, ZnO and Ga2O3 clearly indicates the formation of nanocomposites. The surface morphology consists irregular shape and sized NPs. The Energy dispersive X-ray analysis confirms the purity of the sample. The band energy gap was tuned to 3.1 eV. The Photoluminescence excitation and emission spectra was discussed and compared it with emission spectra of individual oxides as well as with other reported blue emitted nanophosphors. Further, the chromaticity coordinates and Color correlated temperature coordinates clearly confirms their warm blue emission. Further, the powder dusting method was employed to collect the latent fingerprints on the pores and non-pores surfaces. The synthesized MgO-ZnO-Ga2O3 nanocomposites exhibits well-resolved ridge patterns that can be used to identify latent finger prints with clarity. From all these results, the present synthesized MgO-ZnO-Ga2O3 nanocomposite might find an application in display technology as a blue nanophosphor material and for latent finger print detection in crime investigation.

Antibacterial Hydrophilic ZnO Microstructure Film with Underwater Oleophobic and Self-Cleaning Antifouling Properties

Super-hydrophilic and oleophobic functional materials can prevent pollution or adsorption by repelling oil, and have good circulation. However, traditional strategies for preparing these functional materials either use expensive fabrication machines or contain possibly toxic organic polymers, which may prohibit the practical application. The research of multifunctional ZnO microstructures or nanoarrays thin films with super-hydrophilic, antifouling, and antibacterial properties has not been reported yet. Moreover, the exploration of underwater oleophobic and self-cleaning antifouling properties in ZnO micro/nanostructures is still in its infancy. Here, we prepared ZnO microstructured films on fluorine-doped tin oxide substrates (F-ZMF) for the development of advanced self-cleaning type super-hydrophilic and oleophobic materials. With the increase of the accelerators, the average size of the F-ZMF microstructures decreased. The F-ZMF shows excellent self-cleaning performance and hydrophilic (water contact angle ≤ 10°) and oleophobic characteristics in the underwater antifouling experiment. Under a dark condition, F-ZMF-4 showed good antibacterial effects against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) with inhibition rates of 99.1% and 99.9%, respectively. This study broadens the application scope of ZnO-based material and provides a novel prospect for the development of self-cleaning super-hydrophilic and oleophobic materials.

ZnO nanostructured matrix as nexus catalysts for the removal of emerging pollutants

Water pollution stands as a pressing global environmental concern, elevating the significance of innovative, dependable, and sustainable solutions. This study represents an extensive review of the use of photocatalytic zinc oxide nanoparticles (ZnO NPs) for the removal of emerging pollutants from water and wastewater. The study examines ZnO NPs' different preparation methods, including physical, chemical, and green synthesis, and emphasizes on advantages, disadvantages, preparation factors, and investigation methods for the structural and morphological properties. ZnO NPs demonstrate remarkable properties as photocatalysts; however, their small dimensions pose an issue, leading to potential post-use environmental losses. A strategy to overcome this challenge is scaling up ZnO NP matrices for enhanced stability and efficiency. The paper introduces novel ZnO NP composites, by incorporating supports like carbon and clay that serve as photocatalysts in the removal of emerging pollutants from water and wastewater. In essence, this research underscores the urgency of finding innovative, efficient, and eco-friendly solutions for the removal of emerging pollutants from wastewater and highlights the high removal efficiencies obtained when using ZnO NPs obtained from green synthesis as a photocatalyst. Future research should be developed on the cost-benefit analysis regarding the preparation methods, treatment processes, and value-added product regeneration efficiency.

The Interplay of Growth Mechanism and Properties of ZnO Nanostructures for Different Applications

This review provides a background on the structure and properties of ZnO nanostructures. ZnO nanostructures are advantageous for many applications in sensing, photocatalysis, functional textiles, and cosmetic industries, which are described in this review. Previous work using UV Visible (UV-vis) spectroscopy and scanning electron microscopy (SEM) for ZnO nanorod growth analysis in-solution and on a substrate for determination of optical properties and morphology is discussed, as well as their results in determining the kinetics and growth mechanisms. From this literature review, it is understood that the synthesis process greatly affects nanostructures and properties; and hence, their applications. In addition, in this review, the mechanism of ZnO nanostructure growth is unveiled, and it is shown that by having greater control over their morphology and size through such mechanistic understanding, the above-mentioned applications can be affected. The contradictions and gaps in knowledge are summarized in order to highlight the variations in results, followed by suggestions for how to answer these gaps and future outlooks for ZnO nanostructure research.

Relevance of alcoholic solvents in the growth of ZnO nanoparticles and ZnO hierarchical nanorod structures on their optical and opto-electrical properties

We report on the synthesis of ZnO nanoparticles and ZnO hierarchical nanorod structures using four different alcohols i.e. methanol, isopropanol, ethanol, and aqueous ethanol (70% alcohol, 30% water). The syntheses of the nanoparticles were carried out by non-aqueous and hydrothermal routes. In general, absolute alcohol allows a better control of the synthesis reaction and nanoparticles as small as 5 nm were obtained, confirmed by TEM. XPS analysis elucidated the chemical states that were correlated to the synthesis reaction. For the nanorod growth, these four alcohols were used as seeding solvents, followed by hydrothermal ZnO nanorod growth. Here, the seed layer tailored the nanorod diameters and surface defects, which were studied by SEM and photoluminescence spectroscopy. Subsequently, the ZnO nanorods were electrically characterized and exhibited persistent photoconductivity under UV irradiation of 365 nm. The differences in conductivity in dark and under UV irradiation were attributed to the size of the nanorods, defect states, semiconductor band bending and oxygen adsorption-desorption mechanisms. Parameters such as photoresponse and photosensitivity are also calculated in order to evaluate their applicability in UV sensors. This work demonstrates optimization of the physical, chemical, electrical and optical properties of both ZnO nanostructures via the use of alcoholic solvents.

Influence of Synthesis Conditions on the Properties of Zinc Oxide Obtained in the Presence of Nonionic Structure-Forming Compounds

This work investigated the influence of synthesis conditions, including the use of nonionic structure-forming compounds (surfactants) with different molecular weights (400-12,600 g/mol) and various hydrophilic/hydrophobic characteristics, as well as the use of a glass substrate and hydrothermal exposure on the texture and structural properties of ZnO samples. By X-ray analysis, it was determined that the synthesis intermediate in all cases is the compound Zn5(OH)8(NO3)2∙2H2O. It was shown that thermolysis of this compound at 600 °C, regardless of the physicochemical properties of the surfactants, leads to the formation of ZnO with a wurtzite structure and spherical or oval particles. The particle size increased slightly as the molecular weight and viscosity of the surfactants grew, from 30 nm using Pluronic F-127 (MM = 12,600) to 80 nm using Pluronic L-31 (MM = 1100), PE-block-PEG (MM = 500) and PEG (MM = 400). Holding the pre-washed synthetic intermediates (Zn5(OH)8(NO3)2∙2H2O) under hydrothermal conditions resulted in the formation of hexagonal ZnO rod crystal structures of various sizes. It was shown that the largest ZnO particles (10-15 μm) were observed in a sample obtained during hydrothermal exposure using Pluronic P-123 (MM = 5800). Atomic adsorption spectroscopy performed comparative quantitative analysis of residual Zn2+ ions in the supernatant of ZnO samples with different particle sizes and shapes. It was shown that the residual amount of Zn2+ ions was higher in the case of examining ZnO samples which have spherical particles of 30-80 nm. For example, in the supernatant of a ZnO sample that had a particle size of 30 nm, the quantitative content of Zn2+ ions was 10.22 mg/L.

ZnO microrods sandwiched between layered CNF matrix: Fabrication, stress transfer, and mechanical properties

Functional metal oxide particles are often added to the polymers to prepare flexible functional polymer composites with adequate mechanical properties. ZnO and cellulose nanofibrils (CNF) outstand among these metal oxides and the polymer matrices respectively due to their various advantages. Herein, we in situ prepare ZnO microrods in the presence of CNF, which resultes in a layered composite structure. The ZnO microrods are sandwiched between the CNF layers and strongly bind to highly charged CNF, which provides a better stress transfer during mechanical activity. Digital image correction (DIC) and finite element analysis-based computational homogenization methods are used to investigate the relationship between mechanical properties and composite structure, and the stress transfer to the ZnO microrods. Full-field strain measurements in DIC reveal that the in situ ZnO microrods preparation leads to their homogenous distribution in the CNF matrix unlike other methods, which require external means such as ultrasonication. The computational homogenization technique provides a fairly good insight into the stress transfer between constituents in microstructure as well as a good prediction of macroscopic mechanical properties, which otherwise, would be challenging to be assessed by any ordinary mechanical testing in the layered composites. Finally, we also demonstrate that these composites could be used as physiological motion sensors for human health monitoring.

Synthesis and optical properties of phosphorus doped ZnO: X-ray absorption, X-ray emission, and X-ray excited optical luminescence studies

Over the past decades, zinc oxide semiconductor and its derivatives have been extensively developed because of its optoelectronic properties. Since ZnO is an intrinsic n-type semiconductor, how to synthesize high-quality p-type ZnO semiconductors and investigate their optoelectronic properties and local chemical structures are important and necessary. In this article, two studies of synthesizing both undoped and phosphorus-doped ZnO nanostructures by hydrothermal method and chemical vapor deposition (CVD) technique are presented. Scanning electron microscopy (SEM) and laboratory X-ray diffraction (XRD) are used to track the surface morphology and the crystalline structure of both undoped and phosphorus doped ZnO nanostructures, respectively. X-ray absorption near edge structures (XANES), X-ray emission spectroscopy (XES) and X-ray excited optical luminescence (XEOL) are also used to determine the local chemical information of both undoped and phosphorus-doped ZnO nano/microstructures such as local symmetry and optical properties. It is found that the phosphorus is successfully doped into the surface of ZnO and substituted the Zn. The phosphorus-doped ZnO products have better crystallinity and less oxygen vacancies on the surface. These two are correlated as one leads to the other. The XEOL results suggest that the average bandgap for undoped and phosphorus doped ZnO is the same, 3.24 eV. The second derivative of the absorption-emission spectra yields the fundamental bandgap for undoped ZnO and phosphorus-doped ZnO is 3.25 eV. The implication of this observation is discussed.

Aluminium doped ZnO nanostructures for efficient photodegradation of indigo carmine and azo carmine G in solar irradiation

Aluminium doped zinc oxide (AZO) nanomaterials (AlxZn1-xO) with x fraction varying as 0.02 and 0.04 were synthesized using the auto-combustion method using glycine as a fuel. The synthesized catalysts were characterized with X-ray diffraction (XRD), UV–Visible Spectroscopy (UV–Vis), Raman spectroscopy, Photoluminescence (PL) spectroscopy, and High Resolution Transmission Electron Microscopy (HR-TEM). XRD results showed that synthesized materials possessed good crystallinity, while UV–VIS was employed to find the band gaps of synthesized materials. Raman was used to determine the vibrational modes in the synthesized nanoparticles, while TEM analysis was performed to study the morphology of the samples. Industrial effluents such as indigo carmine and azo carmine G were used to test the photodegradation ability of synthesised catalysts. Parameters such as the effect of catalyst loading, dye concentration and pH were studied. The reduction in crystallite size, band gap and increased lattice strain for the 4% AZO was the primary reason for the degradation in visible irradiation, degrading 97 and 99% equimolar concentrations of indigo carmine and azo carmine G in 140 min. The Al doped ZnO was found to be effective in faster degradation of dyes as compared to pure ZnO in presence of natural sunlight.

Facile Fabrication of Oxygen-Defective ZnO Nanoplates for Enhanced Photocatalytic Degradation of Methylene Blue and In Vitro Antibacterial Activity

In this study, we examined whether catalysts with many defects have excellent photoactivity. We prepared ZnO nanoplates with varying degrees of defects in a short time of 4 h by varying the crystal growth temperature at 50, 100, 150, and 200 °C under a strong alkali NaOH atmosphere of 4.0 M. During high-temperature preparation of ZnO, crystal defects were reduced and crystallinity was further increased. In crystallized systems over 100 °C, rhombic nanoplates were used to control particle shape and induce growth in only two axes. The PL, Raman, and XPS analyses confirmed the presence of strong oxygen vacancies in all ZnO nanoplates, and the vacancies decreased with increasing crystallization temperatures. Methylene blue (MB) dye was initially fixed at 50 mg/L with a peak decrease in absorption at 600–700 nm, confirming its decomposition over time. For the 5 h reaction, the MB removal concentration follows the following order: ZnO-50 < ZnO-100 < ZnO-150 < ZnO-200. The study confirms that ZnO-200 nanoplates with fewer oxygen vacancies decompose MB more quickly. ZnO-200 nanoplates synthesized at 200 °C provided the best sterilization performance when tested against gram-positives and gram-negatives, Escherichia coli and Staphylococcus aureus, respectively. ZnO-200 nanoplates after 3 h showed a high sterilization performance of 96.95% (86.67% in a dark room) for staphylococcus aureus and 95.82% (74.66% in a dark room) for Escherichia coli when irradiated with light. Particularly noteworthy in this study is that ·OH and ·O2− radicals are generated more strongly in ZnO-200 than in ZnO-50 nanoplates. These results show that too-strong oxygen vacancies rather inhibit the antibacterial performance, and that the virtue of moderation also exists in the catalytic activity.

Evaluation of scolicidal potential of salicylate coated zinc nanoparticles against Echinococcus granulosus protoscoleces

Echinococcosis is a zoonotic disease caused by larval stages of the Echinococcus genus (metastasis). In this study, salicylate-coated Zinc oxide nanoparticles (SA-ZnO-NPs) were fabricated and characterized by SEM, FTIR and XRD analytical techniques. After that, different doses of SA-ZnO-NPs, SA and ZnO-NPs were taken to assess scolicidal potency. Scanning electron microscopy (SEM) micrographs were also used to evaluate the morphological deformities of treated protoscoleces. Furthermore, Caspase-3&7 inductions were examined in protoscoleces cysts treated with all formulations. Based on SEM and DLS analyses, the size of SA-ZnO-NPs was between 30 and 40 nm, with a spherical shape. The FTIR spectrum verified the presence of SA functional groups on the ZnO coating. At 20 min, SA-ZnO-NPs at 2000 μg/ml exhibited the greatest activity on protoscolices with 100% mortality, followed by ZnO-NPs at 1500 μg/ml at 10 min and SA alone at 2000 μg/ml at 30 min. The activation of Caspase-3&7 apoptotic enzyme was determined for 2000 μg/ml of SA-ZnO-NPs, ZnO-NPs and SA to be 16.4, 31.4, and 35.7%, respectively. The SEM image revealed apoptogenic alterations and the induction of tegument surface wrinkles, as well as abnormalities in rostellum protoscolices. According to the current study, SA-ZnO-NPs have a high mortality rate against hydatid cyst protoscolices. As a result, further studies on the qualitative assessment of these nanoformulations in vivo and preclinical animal trials seem to be required. Furthermore, the adoption of nano-drugs potentially offers alternative therapeutic approaches to combat hydatid cysts.

Traditional vs. Microfluidic Synthesis of ZnO Nanoparticles

Microfluidics provides a precise synthesis of micro-/nanostructures for various applications, including bioengineering and medicine. In this review article, traditional and microfluidic synthesis methods of zinc oxide (ZnO) are compared concerning particle size distribution, morphology, applications, reaction parameters, used reagents, and microfluidic device materials. Challenges of traditional synthesis methods are reviewed in a manner where microfluidic approaches may overcome difficulties related to synthesis precision, bulk materials, and reproducibility.

Hydroponic Ginseng ROOT Mediated with CMC Polymer-Coated Zinc Oxide Nanoparticles for Cellular Apoptosis via Downregulation of BCL-2 Gene Expression in A549 Lung Cancer Cell Line

The unique and tailorable physicochemical features of zinc oxide nanoparticles (ZnO-NPs) synthesized from green sources make them attractive for use in cancer treatment. Hydroponic-cultured ginseng-root-synthesized ZnO-NPs (HGRCm-ZnO NPs) were coated with O-carboxymethyl chitosan (CMC) polymer, which stabilized and enhanced the biological efficacy of the nanoparticles. Nanoparticles were characterized by X-ray diffraction (XRD), UV-Vis spectroscopy, transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), and energy-dispersive X-ray spectroscopy (EDS). The flower-shaped nanoparticles were crystalline in nature with a particle size of 28 nm. To evaluate if these NPs had anti-lung cancer activity, analysis was performed on a human lung carcinoma cell line (A549). HGRCm-ZnO nanoparticles showed less toxicity to normal keratinocytes (HaCaTs), at concentrations up to 20 µg/mL, than A549 cancer cells. Additionally, these NPs showed dose-dependent colony formation and cell migration inhibition ability, which makes them more promising for lung cancer treatment. Additionally, Hoechst and propidium iodide dye staining also confirmed that the NP formulation had apoptotic activity in cancer cells. Further, to evaluate the mechanism of cancer cell death via checking the gene expression, HGRCm ZnO NPs upregulated the BAX and Caspase 3 and 9 expression levels but downregulated Bcl-2 expression, indicating that the nanoformulation induced mitochondrial-mediated apoptosis. Moreover, these preliminary results suggest that HGRCm ZnO NPs can be a potential candidate for future lung cancer treatment.

Rational construction of porous marigold flower-like nickel molybdenum phosphates via ion exchange for high-performance long-lasting hybrid supercapacitors

The assembled hybrid supercapacitor device using the urea-based nickel molybdenum phosphate nanopetals embedded microspheres electrode exhibits outstanding long-term cycling stability, demonstrating its practical applications.

Deep-Level Emission Tailoring in ZnO Nanostructures Grown via Hydrothermal Synthesis

Zinc oxide (ZnO) nanostructures are widely used in various fields of science and technology due to their properties and ease of fabrication. To achieve the desired characteristics for subsequent device application, it is necessary to develop growth methods allowing for control over the nanostructures' morphology and crystallinity governing their optical and electronic properties. In this work, we grow ZnO nanostructures via hydrothermal synthesis using surfactants that significantly affect the growth kinetics. Nanostructures with geometry from nanowires to hexapods are obtained and studied with photoluminescence (PL) spectroscopy. Analysis of the photoluminescence spectra demonstrates pronounced exciton on a neutral donor UV emission in all of the samples. Changing the growth medium chemical composition affects the emission characteristics sufficiently. Apart the UV emission, nanostructures synthesized without the surfactants demonstrate deep-level emission in the visible range with a peak near 620 nm. Structures synthesized with the use of sodium citrate exhibit emission peak near 520 nm, and those with polyethylenimine do not exhibit the deep-level emission. Thus, we demonstrate the correlation between the hydrothermal growth conditions and the obtained ZnO nanostructures' optical properties, opening up new possibilities for their precise control and application in nanophotonics, UV-Vis and white light sources.

Hydrothermal Synthesis of Zinc Oxide Nanoparticles Using Different Chemical Reaction Stimulation Methods and Their Influence on Process Kinetics

The aim of this work was to study the effect of the applied chemical reaction stimulation method on the morphology and structural properties of zinc oxide nanoparticles (ZnONPs). Various methods of chemical reaction induction were applied, including microwave, high potential, conventional resistance heater and autoclave-based methods. A novel, high potential-based ZnONPs synthesis method is herein proposed. Structural properties-phase purity, grain size-were examined with XRD methods, the specific surface area was determined using BET techniques and the morphology was examined using SEM. Based on the results, the microwave and autoclave syntheses allowed us to obtain the desired phase within a short period of time. The impulse-induced method is a promising alternative since it offers a non-equilibrium course of the synthesis process in an highly energy-efficient manner.

L-cysteine embedded core-shell ZnO microspheres composed of nanoclusters enhances anticancer activity against liver and breast cancer cells

Nano-based products have become an apparent and effective option to treat liver cancer, which is a deadly disease, and minimize or eradicate these problems. The Core-shell ZnO microspheres composed of nanoclusters (ZnOMS-NCs) have shown that it is very worthwhile to administer the proliferation rate in HepG2 and MCF-7 cancer cells even at a very low concentration (5 μg/mL). ZnOMS-NCs were prepared through hydrothermal solution process and well characterized. The MTT assay revealed that the cytotoxic effects were dose-dependent (2.5 μg/mL-100 μg/mL) on ZnOMS-NCs. The diminished activity in cell viability induces the cytotoxicity response to the ZnOMS-NCs treatment of human cultured cells. The qPCR data showed that the cells (HepG2 and MCF-7) were exposed to ZnOMS-NCs and exhibited up-and downregulated mRNA expression of apoptotic and anti-apoptotic genes, respectively. In conclusion, flow cytometric data exhibited significant apoptosis induction in both cancer cell lines at low concentrations. The possible mechanism also describes the role of ZnOMS-NCs against cancer cells and their responses.

Adsorptive and photocatalytic remediation of hazardous organic chemical pollutants in aqueous medium: A review

The provision of clean water is still a major challenge in developing parts of the world, as emphasized by the United Nation Sustainable Development Goals (SDG 6), and has remained a subject of extensive research globally. Advancements in science and industry have resulted in a massive surge in the amount of industrial chemicals produced within the last few decades. Persistent and emerging organic pollutants are detected in aquatic environments, and conventional wastewater treatment plants have ineffectively handled these trace, bioaccumulative and toxic compounds. Therefore, we have conducted an extensive bibliometric analysis of different materials utilized to combat organic pollutants via adsorption and photocatalysis. The classes of pollutants, material synthesis, mechanisms of interaction, merits, and challenges were comprehensively discussed. The paper highlights the advantages of various materials used in the removal of hazardous pollutants from wastewater with activated carbon having the highest adsorption capacity. Dyes, pharmaceuticals, endocrine-disrupting chemicals, pesticides and other recalcitrant organic pollutants have been successfully removed at high degradation efficiencies through the photocatalytic process. The photocatalytic degradation and adsorption processes were compared by considering factors such as cost, efficiency, ease of application and reusability. This review will be good resource material for water treatment professionals/scientists, who may be interested in adsorptive and photocatalytic remediation of organic chemicals pollutants.

A non-enzymatic electrochemical hydrogen peroxide sensor based on copper oxide nanostructures

This article describes the synthesis of nanostructured copper oxide on copper wires and its application for the detection of hydrogen peroxide. Copper oxide petal nanostructures were obtained by a one-step hydrothermal oxidation method. The resulting coating is uniform and dense and shows good adhesion to the wire surface. Structure, surface, and composition of the obtained samples were studied using field-emission scanning electron microscopy along with energy-dispersive spectroscopy and X-ray diffractometry. The resulting nanostructured samples were used for electrochemical determination of the H2O2 content in a 0.1 M NaOH buffer solution using cyclic voltammetry, differential pulse voltammetry, and i-t measurements. A good linear relationship between the peak current and the concentration of H2O2 in the range from 10 to 1800 μM was obtained. The sensitivity of the obtained CuO electrode is 439.19 μA·mM-1. The calculated limit of detection is 1.34 μM, assuming a signal-to-noise ratio of 3. The investigation of the system for sensitivity to interference showed that the most common interfering substances, that is, ascorbic acid, uric acid, dopamine, NaCl, glucose, and acetaminophen, do not affect the electrochemical response. The real milk sample test showed a high recovery rate (more than 95%). According to the obtained results, this sensor is suitable for practical use for the qualitative detection of H2O2 in real samples, as well as for the quantitative determination of its concentration.

Tailoring ZnO nanowire crystallinity and morphology for label-free capturing of extracellular vesicles

Zinc oxide (ZnO) nanowires have shown their potential in isolation of cancer-related biomolecules such as extracellular vesicles (EVs), RNAs, and DNAs for early diagnosis and therapeutic development of diseases. Since the function of inorganic nanowires changes depending on their morphology, previous studies have established strategies to control the morphology and have demonstrated attainment of improved properties for gas and organic compound detection, and for dye-sensitized solar cells and photoelectric conversion performance. Nevertheless, crystallinity and morphology of ZnO nanowires for capturing EVs, an important biomarker of cancer, have not yet been discussed. Here, we fabricated ZnO nanowires with different crystallinities and morphologies using an ammonia-assisted hydrothermal method, and we comprehensively analyzed the crystalline nature and oriented growth of the synthesized nanowires by X-ray diffraction and selected area electron diffraction using high resolution transmission electron microscopy. In evaluating the performance of label-free EV capture in a microfluidic device platform, we found both the crystallinity and morphology of ZnO nanowires affected EV capture efficiency. In particular, the zinc blende phase was identified as important for crystallinity, while increasing the nanowire density in the array was important for morphology to improve EV capture performance. These results highlighted that the key physicochemical properties of the ZnO nanowires were related to the EV capture performance.

Shape-controlled synthesis of zinc nanostructures mediating macromolecules for biomedical applications

Zinc nanostructures (ZnONSs) have attracted much attention due to their morphological, physicochemical, and electrical properties, which were entailed for various biomedical applications such as cancer and diabetes treatment, anti-inflammatory activity, drug delivery. ZnONS play an important role in inducing cellular apoptosis, triggering excess reactive oxygen species (ROS) production, and releasing zinc ions due to their inherent nature and specific shape. Therefore, several new synthetic organometallic method has been developed to prepare ZnO crystalline nanostructures with controlled size and shape. Zinc oxide nanostructures' crystal size and shape can be controlled by simply changing the physical synthesis condition such as microwave irradiation time, reaction temperature, and TEA concentration at reflux. Physicochemical properties which are determined by the shape and size of ZnO nanostructures, directly affect their biological applications. These nanostructures can decompose the cell membrane and accumulate in the cytoplasm, which leads to apoptosis or cell death. In this study, we reviewed the various synthesis methods which affect the nano shapes of zinc particles, and physicochemical properties of zinc nanostructures that determined the shape of zinc nanomaterials. Also, we mentioned some macromolecules that controlled their physicochemical properties in a green and biological approaches. In addition, we present the recent progress of ZnONSs in the biomedical fields, which will help centralize biomedical fields and assist their future research development.

A Review on the Effects of ZnO Nanowire Morphology on the Performance of Interpenetrating Bulk Heterojunction Quantum Dot Solar Cells

Interpenetrating bulk heterojunction (IBHJ) quantum dot solar cells (QDSCs) offer a direct pathway for electrical contacts to overcome the trade-off between light absorption and carrier extraction. However, their complex three-dimensional structure creates higher requirements for the optimization of their design due to their more difficult interface defect states control, more complex light capture mechanism, and more advanced QD deposition technology. ZnO nanowire (NW) has been widely used as the electron transport layer (ETL) for this structure. Hence, the optimization of the ZnO NW morphology (such as density, length, and surface defects) is the key to improving the photoelectric performance of these SCs. In this study, the morphology control principles of ZnO NW for different synthetic methods are discussed. Furthermore, the effects of the density and length of the NW on the collection of photocarriers and their light capture effects are investigated. It is indicated that the NW spacing determines the transverse collection of electrons, while the length of the NW and the thickness of the SC often affect the longitudinal collection of holes. Finally, the optimization strategies for the geometrical morphology of and defect passivation in ZnO NWs are proposed to improve the efficiency of IBHJ QDSCs.

Effect of ZnO surface morphology on its electrochemical performance

The purpose of this paper is to bridge the gap between ZnO surface morphology and its electrochemical performance. For this reason, ZnO nanowires (NWs) of different length were synthesized using an electrochemical method. Then, the electrochemical performance of the synthesized ZnO surfaces was studied using cyclic voltammetry and electrochemical impedance spectroscopy. The electrochemical analysis results revealed that the increase of ZnO NW length contributes to the retrogression of electrochemical performance. Indeed, the electrochemical performance is mainly related to the wettability behavior of the ZnO nanowire surfaces. When the ZnO NWs length increases, the surface become more hydrophobic, therefore, charge transfers between the electrode/electrolyte decrease. To improve the electrochemical performance of ZnO, we propose a new strategy combining NWs and microsheets (μSs) for further improving the morphology. Finally, the surfaces based on the double structure of ZnO provide good propagation of charge at the surface, good transfer in the electrode, good stability, and excellent scanning ability. In the present work we intend to pave the way for achieving high electrochemical performance ZnO-based layers.

The purpose of this paper is to bridge the gap between ZnO surface morphology and its electrochemical performance.

Efficient and Rapid Photocatalytic Degradation of Methyl Orange Dye Using Al/ZnO Nanoparticles

ZnO and Aluminum doped ZnO nanoparticles (Al/ZnO NPs) were successfully synthesized by the sol-gel method. Together with the effect of calcination temperatures (200, 300 and 400 °C) and Al dosage (1%, 3%, 5% and 10%) on structural, morphological and optical properties of Al/ZnO NPs, their photocatalytic degradation of methyl orange (MO) dye was investigated. The calcination temperatures at 200, 300 and 400 °C in forming structure of ZnO NPs led to spherical nanoparticle, nanorod and nanoflake structures with a well-crystalline hexagonal wurtzite, respectively. The ZnO NPs calcined at 200 °C exhibited the highest specific surface area and light absorption property, leading to the MO removal efficiency of 80% after 4 h under the Ultraviolet (UV) light irradiation. The MO removal efficiency was approximately two times higher than the nanoparticles calcined at 400 °C. Furthermore, the 5% Al/ZnO NPs exhibited superior MO removal efficiency of 99% in only 40 min which was approximately 20 times enhancement in photocatalytic activity compared to pristine ZnO under the visible light irradiation. This high degradation performance was attributed to the extended light absorption, narrowed band gap and effective suppression of electron-hole recombination through an addition of Al metal.

Metal Oxide-Based Photocatalytic Paper: A Green Alternative for Environmental Remediation

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.

Adsorption and photocatalytic activity of biosynthesised ZnO nanoparticles using Aloe Vera leaf extract

In this article, we demonstrates the growth of phase pure ZnO nanostructures from Aloe-Vera leaf extract and degradation of an organic dye-Malachite Green (MG)- from aqueous medium using the same as catalyst. Adsorption mechanisms were evaluated using Lagergren’s pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. X-Ray diffraction data showed that the synthesised ZnO is crystalline with hexagonal wurtzite phase. Average crystallite size and lattice strain was estimated from Scherrer equation and Williamson-Hall analysis with the help of Rietveld refinement data. Crystallite size obtained from Scherrer method is 12.62 nm while that from Williamson-Hall analysis is 19.27 nm. Uniform growth of ZnO nano-sheets were confirmed by FE-SEM analysis. Optical characterisation was carried by UV-Visible spectroscopy and the band gap ZnO nanoparticles was found to be 3.19 eV. Zn-O stretching vibrations were recorded at 550 cm−1 using FTIR spectrophotometer. Results showed that biosynthesised ZnO nanosheets are particularly effective for the degradation of MG dye.

Controlled titration-based ZnO formation

Hexamethylenetetramine (HMTA) is commonly used as a base releasing agent for the synthesis of ZnO under mild aqueous conditions. HMTA hydrolysis leads to gradual formation of a base during the reaction. Use of HMTA, however, does have limitations: HMTA hydrolysis yields both formaldehyde and ammonia, it provides no direct control over the ammonia addition rate or the total amount of ammonia added during the reaction, it results in a limited applicable pH range and it dictates the accessible reaction temperatures. To overcome these restrictions, this work presents a direct base titration strategy for ZnO synthesis in which a continuous base addition rate is maintained. Using this highly flexible strategy, wurtzite ZnO can be synthesized at a pH >5.5 using either KOH or ammonia as a base source at various addition rates and reaction pH values. In situ pH measurements suggest a similar reaction mechanism to HMTA-based synthesis, independent of the varied conditions. The type and concentration of the base used for titration affect the reaction product, with ammonia showing evidence of capping behaviour. Optimizing this strategy, we are able to influence and direct the crystal shape and significantly increase the product yield to 74% compared to the ∼13% obtained by the reference HMTA reaction.

Efficient photocatalytic degradation of dyes using photo-deposited Ag nanoparticles on ZnO structures: simple morphological control of ZnO

In this work, morphology-controlled ZnO structures were prepared via a hydrothermal method by simple adjustments in the NaOH concentration. The NaOH concentration variation from 0.2 to 1.2 M resulted in the formation of ZnO structures in shapes such as walnut, spherical flower, flower, rod, and urchin-like. The extent of OH- ions is the main factor influencing the growth of ZnO structures. Well-defined morphologies, good crystallinity, and optical properties were obtained for all ZnO structures. Among these ZnO structures, ZnOsf (spherical flower-like) structure showed a greater percentage of photodegradation of methyl orange and rhodamine B dyes. Surface plasmon resonance was achieved by modifying the surface of ZnO with Ag nanoparticles. ZnOsf was loaded with Ag nanoparticles by a facile photo-deposition method. Ag-ZnOsf showed superior photoactivity and recyclability for the degradation of methyl orange and rhodamine B. Therefore, modification of different ZnO structures can help realize potential catalysts for future environmental applications.

pH-Dependent Formation of Oriented Zinc Oxide Nanostructures in the Presence of Tannic Acid

To crucially comprehend the relaying factors behind the growth mechanism of ZnO nanostructures, the needs to understand the cause of preferences in the enhancement of desired physicochemical properties are essential. The particular oriented attachment (OA) is believed to become the cause of the classical growth pattern of ZnO nanostructures which is mainly controlled by the Ostwald ripening (OR) process. In the present work, the concerns over the systematic changes in size and the morphological surface of ZnO nanostructures upon exposure to tannic acid (TA) prepared by drop-wise method turns the particles to different surface adjustment state. Here, we assessed the TA capping ability and its tendency to influence the OA process of the ZnO nanostructures. The detailed process of the growth-based TA system via transmission electron microscopy (TEM), scanning electron microscopy (SEM), and FFT autocorrelation revealed the pH effect on their physical properties which proved the transition surface properties state of the particles from rough to smooth states due to oriented attachment. For pure ZnO nanostructures, the surface is almost smooth owing to the strong bonding particles which are then changed to coarsened surface structures upon the introduction of TA. Strong surface adsorption of Zn cations and phenol ligands mediated the agglomerated nanocrystals, surprisingly with smaller nanostructures dimension.

Thermophysiological comfort of zinc oxide nanoparticles coated woven fabrics

This study investigates physicochemical impact of ultrasonic irradiations on surface topography of woven fabrics. In a simultaneous in-situ sonochemical method, the synthesis and coating of zinc oxide nanoparticles (ZnO NPs) on woven textiles were successfully achieved. Different instruments i.e. Alambeta, moisture management tester, air permeability tester and permetester were utilised during experimentation for thermal evaluation, moisture transportation and air permeation. The results regarding thermophysiological comfort of ZnO coated fabrics were evaluated on the basis of thickness and ZnO NPs coated amount on fabrics. In addition, the achieved results depict the impact of sonication (pressure gradient) on surface roughness of cotton and polyester. The coating of ZnO NPs on fabrics, crystal phase identification, surface topography and fluctuations in surface roughness were estimated by inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray Diffractometry (XRD), ultrahigh-resolution scanning electron microscopy (UHR-SEM) and energy dispersive X-ray (EDX). Moreover, thermophysiological properties i.e. thermal conductivity, absolute evaporative resistance, thermal absorptivity, air permeability, overall moisture management capacity and relative water vapour permeability of untreated and ZnO treated samples were evaluated by standard test methods.