Zinc Oxide Composites Research Articles

Antibacterial properties and mechanism of nanometer zinc oxide composites

Nanometer zinc oxide (nano ZnO) is frequently added as an antibacterial agent to matrix materials used widely in packaging applications such as food. Two antibacterial films were prepared with high antibacterial activity achieved through low doping: ZnO/linear low-density polyethylene (ZnO/LLDPE) and ZnO/polycarbonate (ZnO/PC). The antibacterial rates of both films against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were greater than 99.9 %, and their antibacterial performance value (R) was ≥ 5.9. Experiments were conducted using LLDPE and PC with varying chain mobility to verify that the commonly known three antibacterial mechanisms, namely soluble Zn2+ ions, reactive oxygen species (ROS), and direct contact between nano ZnO and bacteria, are not the primary mechanisms responsible for the antibacterial properties of the nano ZnO composite film. Furthermore, a new mechanism of inhibiting bacteria by nano ZnO irradiated photons was proposed to explain the high antibacterial rate of ZnO/PC films under the condition of limited nano ZnO migration. Understanding the antibacterial mechanism of nano ZnO in polymers will aid in the development of ZnO antibacterial agents that can effectively exert high antibacterial effects in matrix materials.

Photodegradation of ceftriaxone using g-C3N4-ZnO nanocomposite as an efficient photocatalyst

The entrance of emerging contaminants (ECs) (hormones, dyes, pesticides, pharmaceuticals, etc.) into natural waters threatens public health and the ecosystem due to their longer half-life and low biodegradability. Particular interest is placed on antibiotics, whose presence in aqueous systems notoriously increased the recent COVID-19 pandemic and, thus, the risk for various organisms and other collateral implications. This work evaluates the photocatalytic activity of graphitic carbon nitride (g-C3N4)-zinc oxide (ZnO) composites (CNZO), compared to bare photocatalytic materials, to degrade Ceftriaxone (CEF) antibiotic. The synthesis methodology of materials comprised the obtention of bare photocatalysts using hydrothermal (ZnO) and thermal polymerization (g-C3N4) methods, whereas, for CNZO composites, wet impregnation methodology was employed. The impact of g-C3N4 wt% content (10, 25, 50, and 75%) in composites was investigated by correlating variations in their structural, morphological, chemical, and optical properties with their photocatalytic activity under UV and visible irradiation. The results showed an optimal relation between ZnO and g-C3N4 wt% content (CNZO (25–75) sample), resulting in complete molecule degradation in 60 min and 93 % of degradation in 180 min under UV and visible radiation, respectively. The reusability of the CNZO (25–75) sample was tested in five consecutive ceftriaxone-degradation cycles, where no deactivation phenomena in the sample (92% of degradation) was observed, suggesting its good stability and potential application in practical experiments. The enhanced photocatalytic activity is attributed to decreasing recombination of the charge carriers evidenced by PL spectra, which confirms the heterojunction formation between ZnO and g-C3N4. Based on the results, a schematic photocatalytic mechanism was proposed, which describes the enhanced electron-hole separation at the materials interface. These results provide a guideline for obtaining composites with superior photocatalytic activity. Additionally, their visible light-active feature might be helpful towards the use of sunlight, overcoming conventional photocatalysts (ZnO, TiO2, etc.) drawbacks.

Comparative study for removal of toxic hexavalent chromium by zinc oxide nanoparticles, chitosan, chitin and zinc-chitosan nano-biocomposite

Hexavalent chromium is classified as a human carcinogen and its removal is crucial from wastewater. A comparative study was done to remove Cr (VI) from an aqueous solution by synthesized nanoparticles such as chitin, chitosan, zinc oxide (at various temperatures 500 °C, 600 °C and 700 °C), and ZnO-chitosan composite. Among all the synthesized materials the maximum uptake of chromium (VI) was observed in ZnO-chitosan nano-biocomposite (ZnO-CS NC). The adsorption variables like initial concentration, adsorbent dosage, adsorption time, and pH were examined. The batch adsorption studies revealed the best result in 20 ppm concentration dosage of 0.5 g/l, pH 3 at 60 min. The characterization of nanoparticles and nanocomposite was done by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Fourier Transform Infrared (FTIR) techniques Langmuir isotherm models were best fitted due to the highest R2 value. Among all adsorbent, ZnO-chitosan nano-biocomposite was best adsorbent for chromium (VI) removal. ZnO-chitosan adsorption capacity and adsorption efficiency were 69.5 mg/g and 96.5% respectively. ZnO nanoparticles showed the potential for antibacterial activity. Electrostatic attraction between chromium and ZnO-chitosan biocomposite was the main cause for the removal of chromium from aqueous solution and it could be a promising material for sustainable treatment of wastewater.

Tailoring Structural, Chemical, and Photocatalytic Properties of ZnO@β-SiC Composites: The Effect of Annealing Temperature and Environment.

For achieving unified functionalities of rare-earth free materials, the development of innovative zinc oxide and β-silicon carbide (ZnO@β-SiC) composites by a solid-state reaction method is presented. The evolution of zinc silicate (Zn2SiO4) is evidenced by X-ray diffraction when annealed in air beyond 700 °C. Detailed X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analyses reveal the involvement of silicon dioxide in forming Zn2SiO4. Transmission electron microscopy and the associated energy-dispersive X-ray spectroscopy elucidate the evolution of the zinc silicate phase at the ZnO/β-SiC interface, though it can be averted by vacuum annealing. These results manifest the importance of air in oxidizing SiC before a chemical reaction with ZnO from 700 °C. Finally, ZnO@β-SiC composites are found to be promising for methylene blue dye degradation under ultraviolet radiation, but the annealing above 700 °C is detrimental due to the evolution of a potential barrier in the presence of Zn2SiO4 at the ZnO/β-SiC interface.

Impact of carbon nanotubes concentrations on the performance of carbon nanotubes/zinc oxide nanocomposite for photoelectrochemical water splitting

Under the influence of visible light, the photoelectrochemical (PEC) method of water splitting offers a green method for producing sustainable hydrogen. In this work, several volume ratios of carbon nanotubes (CNTs) were incorporated in the zinc oxide (ZnO) matrix to prepare ZnO/CNTs nanocomposites on a glass substrate as photoelectrodes for hydrogen production. These electrodes were synthesized via the spray pyrolysis technique and chemical vapor deposition. Various approaches were used to analyze the chemical composition, crystal structure, morphology, and optical properties of pure ZnO and ZnO/CNTs nanocomposites. The structural properties showed that crystallite size is decreased from 44.2 nm to 36.8 nm, and the optical shows that the energy bandgap (Eg) enhanced from 3.07 to 2.87 eV for pure ZnO and the optimum sample of ZnO/7 mL CNTs nanocomposite, respectively. The maximum photocurrent density (Jph) was found for the 7 mL CNTs among the produced ZnO/X CNTs nanostructures. The value of Jph for ZnO/7 mL CNTs (200.7 µA/cm2) is around 33 times greater compared with pure ZnO (6.96 µA/cm2). At 490 nm, the incident photon-to-current efficiency (IPCE) of ZnO/7 mL CNTs is roughly 9.85 %. The ZnO/CNTs photoelectrode showed a hydrogen evolution rate of 4.34 mmole/h.cm2. The improved photoelectrode additionally exhibits strong chemical stability and a lengthy lifetime under visible light without photo-corrosion. Finally, the electrochemical impedance spectroscopy and the PEC water-splitting mechanism for ZnO/CNTs were discussed. This study presents a simple method that enables the fabrication of inexpensive and efficient ZnO/CNTs photoelectrode for renewable energy applications.

MoS2-ZnO Nanocomposite Mediated Immunosensor for Non-Invasive Electrochemical Detection of IL8 Oral Tumor Biomarker

In order to support biomolecule attachment, an effective electrochemical transducer matrix for biosensing devices needs to have many specialized properties, including quick electron transfer, stability, high surface area, biocompatibility, and the presence of particular functional groups. Enzyme-linked immunosorbent assays, gel electrophoresis, mass spectrometry, fluorescence spectroscopy, and surface-enhanced Raman spectroscopy are common techniques used to assess biomarkers. Even though these techniques provide precise and trustworthy results, they cannot replace clinical applications because of factors such as detection time, sample amount, sensitivity, equipment expense, and the need for highly skilled individuals. For the very sensitive and targeted electrochemical detection of the salivary oral cancer biomarker IL8, we have created a flower-structured molybdenum disulfide-decorated zinc oxide composite on GCE (interleu-kin-8). This immunosensor shows very fast detection; the limit of detection (LOD) for interleukin-8 (IL8) detection in a 0.1 M phosphate buffer solution (PBS) was discovered to be 11.6 fM, while the MoS2/ZnO nanocomposite modified glassy carbon electrode (GCE) demonstrated a high catalytic current linearly from 500 pg to 4500 pg mL-1 interleukin-8 (IL8). Therefore, the proposed biosensor exhibits excellent stability, high accuracy sensitivity, repeatability, and reproducibility and shows the acceptable fabrication of the electrochemical biosensors to detect the ACh in real sample analysis.

Electrochemical Aptasensor Based on ZnO-Au Nanocomposites for the Determination of Ochratoxin A in Wine and Beer

Ochratoxin A (OTA) is positively correlated with an increased risk of developing cancer in nephrotoxic and hepatotoxic patients. Therefore, it is of great significance for the highly sensitive, highly selective, and timely detection of OTA. We described here an electrochemical aptasensor for OTA analysis, which took advantage of the favorable properties of gold nanoparticles (AuNPs) functionalized zinc oxide (ZnO) composites and the intercalative binding between methylene blue (MB) and nucleic acid. There were two label-free aptamers: one to capture OTA and another serving as complementary DNA (cDNA), enabling connection to the ZnO-Au composite’s immobilized electrode. Once OTA was present, the aptamer could capture OTA and detach from the electrode interface, thus, preventing MB from accessing electrode surface for efficient electron transfer; a decreased peak current was monitored by differential pulse voltammetry. The aptasensor presented nice analytical performance for OTA detection in the range of 0.1–30,000 pg·mL−1, with a detection limit of 0.05 pg·mL−1. Moreover, the developed biosensor could be applied to actual sample (wine and beer) analysis.

Colorimetric sensor for formaldehyde detection using thiol-functionalized polydiacetylene and zinc oxide nanocomposites

Formaldehyde is a toxic pollutant that harmful effect on human health. This work focus on the development of a colorimetric sensor to detect formaldehyde solution using composites of polydiacetylene (PDA), thiol-functionalized polydiacetylene (PDA-SH) and zinc oxide (ZnO) nanosheets. The as-prepared PDA/PDA-SH/ZnO vesicles exhibit a blue color, and change to a red color in the presence of formaldehyde solution. With increasing formaldehyde concentrations, the optical absorption spectra show the decreasing of absorption intensity at 640 nm wavelength, and new absorption peak occurred at 540 nm wavelength with increasing its intensity. Additionally, the PDA/PDA-SH/ZnO sensor exhibit high selective to formaldehyde and its color transition is easily observed by the naked-eye. These results indicate a possibility to use PDA/PDA-SH/ZnO sensor for on-site monitoring formaldehyde in an environment.

ZnO-Enhanced Reduced Graphene Oxide Electrodes from Cocoa Shell: Nanoarchitectonics Platform for Photoelectrocatalytic Detection of Methylene Blue.

In this study, we report the successful preparation of reduced graphene oxide modified zinc oxide (rGO-ZnO) composites from cocoa shells. Synthesis of rGO-ZnO was carried out using the Hummer method and thermal reduction. The electrode material was comprehensively characterized using fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy & Energy Dispersive X-ray (SEM-EDX). The photoelectrocatalytic performance of the prepared composite electrodes was evaluated using various electrochemical techniques, including Linear Sweep Voltammetry (LSV), Cyclic Voltammetry (CV), and Multi Pulse Amperometry (MPA). The FTIR analysis of rGO-ZnO exhibited distinct bands corresponding to C-O at 1022 cm-1, C=C at 1600 cm-1, and Zn-O at 455 cm-1. The XRD analysis revealed characteristic peaks at 26.6º, 29.2º, 36.2º, 44.04º, 47.58º, and 64.4º, confirming the presence of key crystalline phases. SEM-EDX analysis of rGO-ZnO revealed a rough surface morphology with bright white and black regions, signifying the coexistence of ZnO and rGO with carbon, oxygen, and zinc contents of 78.98%, 17.46%, and 3.56%, respectively. The investigations involved the photoelectrochemical profiles of methylene blue organic dyes at different concentrations, ranging from 0.5 ppm to 3.0 ppm. The acquired findings offer valuable understanding into the photoelectrocatalytic effectiveness of the composite electrodes containing rGO-ZnO, suggesting their potential use in potential scenarios involving the revitalization of the environment in industrial water systems.

Electrical Properties of Jackfruit Seed Starch and Polyvinyl Alcohol Blend with Different Composition of Zinc Oxide

A biopolymer electrolyte made from natural polymer consists of jackfruit seed starch (JSS) and polyvinyl alcohol (PVA) with a different composition of zinc oxide (ZnO) was prepared using the solution casting method. The incorporation of metal oxides such as ZnO into natural polymers can improve the electrical properties, which can produce biodegradable energy storage devices. This innovation may aid in the reduction of the use of electronic devices, which generate e-waste. Thus, this study was conducted to investigate the effect of ZnO addition to the biopolymer in terms of its electrical properties. The samples were prepared by using the solution casting method. Different percentages of ZnO were mixed with JSS, PVA, hydrocloric acid, sodium hydroxide, and glycerol before being moulded in a petri dish and dried at room temperature. The electrical properties of the blends were then characterized by using an Agilent 4284a Precision LCR meter. The highest ionic conductivity value for JSS and PVA after the addition of ZnO is 1.10x10-6 Scm-1 with 10% of ZnO, and the lowest conductivity is 2.11x10-7 Scm-1 with 14% of ZnO. The dielectric and electric modulus were further studied in order to understand the electrode polarization effect.

The effect of zinc oxide and Curcuma heyneana Val. combination on stability and sun protection factor (SPF) of lotion

Indonesian people risk-averse effects of Ultraviolet (UV) exposure, so they need skin protection agents. Zinc Oxide (ZnO) is an effective UV reflection, but at a concentration of more than 10%, it can cause skin irritation. Combining ZnO with other UV protective agents is necessary, so its concentration can be reduced but still effective. The flavonoid in C. heyneana has potential as a sunscreen because chromophore groups can absorb UV B and UV A light. This study aims to examine the effect of the combination of ZnO and C. heyneana on the stability and SPF value of lotion. The lotion is made in five variations of the composition of ZnO and C. heyneana , F1 of 100: 0%; F2 of 0:100%; F3 of 50:50%; F4 of 25:75%; and F5 of 75:25% respectively. Test parameters include organoleptic, pH, spreadability, viscosity, and SPF. The test is recorded before and after the cycling test. Statistical analysis using Paired Sample T-Test. The combination of ZnO and C. heyneana affected organoleptic, viscosity, spreadability, and SPF value but did not affect pH. The higher concentration of ZnO will increase the viscosity, pH, and SPF but decrease the spreadability. The formula with a combination of ZnO and C. heyneana of 50%:50% is selected because it has an SPF value of 13.24 and; a viscosity of 48.67 d.Pas; pH of 7.1; and spreadability of 3.81 cm.

Electrochemiluminescence detection of Cu2+ ions by nitrogen-doped carbon quantum dots and zinc oxide composites

In this study, nitrogen-doped carbon quantum dots and ZnO (N-CQDs/ZnO) composites were prepared to improve the electrochemiluminescence (ECL) performance of carbon quantum dots (CQDs) for detecting copper ions. Nitrogen-doped carbon quantum dots (N-CQDs) were prepared by a pyrolysis method using glucosamine as a carbon source and urea as a nitrogen source. In addition, N-CQDs/ZnO composites were prepared using zinc acetate in the same way, and they were characterized by the ECL method. The ECL performance of composite ZnO materials with paper-based modified electrodes improved, and the principle of signal enhancement of the N-CQDs/ZnO composite material was demonstrated. The paper electrode was modified with the composite material to detect copper ions via the quenching reaction. The results show that the sensitivity and detection limit (6.13 × 10−9 M) of the paper ECL sensor improved across a wide linear detection range (1.0 × 10−8–1.0 × 10−3 M). Therefore, N-CQDs/ZnO composites prepared by this method have potential applications in ECL signal amplification.

Investigation of mechanical properties and antibacterial behavior of WE43 magnesium-based nanocomposite

The aim of this study is to develop a biodegradable magnesium-based nanocomposite with enhanced mechanical and antibacterial properties. To achieve this goal, nano- and micro-scale zinc oxide (ZnO) and copper-zinc oxide (Cu/ZnO) reinforcements were incorporated into WE43 magnesium alloy, as the matrix of the nanocomposite. High purity ZnO and Cu/ZnO were synthesized by solution combustion with citric acid fuel using conventional and microwave heating, resulting in nanometer and micrometer particles, respectively. Friction stir processing (FSP) was employed to develope the magnesium-based composites. ZnO and Cu/ZnO powders were implemented into the WE43 base plate with either drilling holes or machining grooves. Hole-inserted additives resulted in more uniform particle distribution than groove-inserted ones. In addition, nanoscale ZnO and Cu/ZnO particles showed more uniform distribution compared to microscale ZnO. The addition of Cu/ZnO particles yielded the highest level of antibacterial activity, compressive strength and micro hardness of the composite. The antibacterial performance of the composite was in line with the fact that Cu/ZnO powder showed more pronounced antibacterial properties than ZnO powders. In addition, groove-inserted Cu/ZnO composite showed compressive strength of 527 MPa and hardness of 90.7 Hv, which were significantly higher than the values of 300 MPa and 78.7 Hv obtained for groove-inserted ZnO composites. It should be noted that the un-processed monolithic WE43 alloy had a compressive strength of 138 MPa and hardness of 66.8 Hv.

Development of a Conductometric Sensor Based on Al,Ca-Doped ZnO for the Detection of Formaldehyde.

In the present study, the development of a conductometric gas sensor based on Al,Ca-doped zinc oxide composite which is finalized to the detection of formaldehyde (HCHO) at a low concentration in air is investigated. The electrical and sensing properties of the composite based on ZnO doped with different loadings of Al and/or Ca (from 0 up to 5 at%) were evaluated. The gas-sensing mechanism of Al,Ca-doped zinc oxide nanocomposite-based sensors was also discussed. The optimized 3%Al,3%Ca-ZnO sensor displayed a formaldehyde response of 3.5 (@ 4 ppm HCHO/air) and an experimental low detection limit of 125 ppb HCHO/air, at the operating temperature of 400 °C. The sensor was also shown to be selective to HCHO with respect to many interferent indoor gases, but NO2 changed the baseline resistance in an opposite way compared to the target gas. The developed device for monitoring HCHO in indoor and workplace environments has the advantage of a simple planar structure and can be easily fabricated for mass production by using low-cost materials and easy fabrication methods.

Long-term Photo-degradation of Nanofibrous Composites Based on Poly(3-hydroxybutyrate) Electrospun Fibers Loaded with Zinc Oxide Nanoparticles

Composite mats based on submicron biopolyester fibers, such as poly(3-hydroxyalkanoate)s, and zinc oxide (ZnO) nanoparticles have been exploited in medicine and environmental areas, as antibacterial wound dressings or filters. Generally, the resulting mats have to be subjected to UV irradiation in order to promote the formation of reactive oxygen species, thus activating the antimicrobial or photocatalytic effect of ZnO. Therefore, investigation related to the influence of ZnO on poly(3-hydroxyalkanoate)s photo-degradation is required. In this context, the present paper addresses the long-term photo-degradation of nanofibrous poly(3-hydroxybutyrate) (PHB)/ZnO composites derived from two complementary electro-hydrodynamic techniques, namely electrospinning or electrospinning/electrospraying tandem processes. A thorough investigation of the as-obtained PHB/ZnO fibrous composites implying the utilization of ATR-FTIR, SEC, and SEM analysis pre- and post-aging under UV irradiation (313 nm) for a period of time of 500 h to study the effect of electro-hydrodynamic technique utilized and the ZnO content on the UV shielding properties of PHB mats.

Highly sensitive and fully printable humidity sensor on a flexible substrate based on a zinc oxide and polyethylenimine composite

We report a highly sensitive and fully printable capacitive humidity sensor based on a zinc oxide (ZnO) and polyethylenimine (PEI) composite. The sensor has a simple structure, consisting only of a layer of the ZnO:PEI composite, coated using an ethanol solution, on a layer of silver inter-digital electrodes that have been pre-printed on a polyethyleneterephthalate substrate. The sensor with ZnO:PEI in the ratio of 2:1 by volume exhibits a response of 43 907 000% at maximum humidity, with a detection range of 15%–95% relative humidity, higher than other sensors fully made by wet-coating processes. Fourier transform infrared spectroscopy, atomic force microscopy, and scanning electron microscopy measurements suggest that the high response likely arises from the use of a hydrophilic polymer with a high dipole moment which facilitates dipole-dipole interactions with water molecules and from the highly granular morphology of the composite which leads to a high surface-to-volume ratio and more-numerous water adsorption sites. The fabricated sensor also demonstrates short response/recovery times (5 s/3 s), good repeatability over multiple humidification and desiccation cycles, and only 5% loss in response after being kept in the ambient for three weeks.

High-performance water vapor barriers via amorphous alumina-polycrystalline zinc oxide hybrids with a self-wrinkling morphology

This work presents a materially and structurally designed barrier thin film with a self-wrinkling morphology, which consists of composites of amorphous alumina (a-Al2O3) and polycrystalline zinc oxide (ZnO). The pure ZnO, Al2O3 films, and Al2O3-ZnO composited film are deposited on polyethylene terephthalate (PET) by magnetron co-sputtering at room temperature. The water vapor transmission rate (WVTR) for the composited film with about 30 % ratio of Al2O3 to ZnO is down to 0.026 g·m−2·day−1 from 1.184 g·m−2·day−1 of pure ZnO film at 38 °C/90 % RH, indicating that the nanocomposite structure of amorphous Al2O3 and crystalline ZnO can significantly improve the water-resistance performance. Theoretical calculations demonstrate that the amorphous Al2O3 can dramatically suppress the defect fraction within ZnO from 4.65 % to 0.08 %. Furthermore, a self-wrinkling morphology with Al2O3-ZnO composited film deposited on PET/acrylic is designed to have the WVTR value as low as 1.30 × 10−3 g·m−2·day−1. Due to the stress release when forming micro-scale wrinkles, the more smooth and dense Al2O3-ZnO composited film can markedly sharpen up the barrier property. The low WVTR barriers via amorphous and crystalline hybrid composites with self-wrinkling morphology by magnetron sputtering potentially serve as a low-cost and large-scale production path for electronics encapsulation as compared to atomic layer deposition (ALD) and plasma-enhanced chemical vapor deposition (PECVD).

Evaluation of Mechanical Properties for Epoxy reinforced with palm oil /Zinc oxide composites

In this research, the effect of reinforcing epoxy resin composites with a filler derived from chopped agriculture waste from oil palm (OP). Epoxy/OP composites were formed by dispersing (1, 3, 5, and 10 wt%) OP filler using a high-speed mechanical stirrer utilizing a hand lay-up method. The effect of adding zinc oxide (ZnO) nanoparticles, with an average size of 10-30 nm, with different wt% (1,2,3, and 5wt%) to the epoxy/oil palm composite, on the behavior of an epoxy/oil palm composite was studied with different ratios (1,2,3, and 5wt%) and an average size of 10-30 nm. Fourier Transform Infrared (FTIR) spectrometry and mechanical properties (tensile, impact, hardness, and wear rate) were used to examine the composites. The FTIR results show a strong interaction between ZnO and oil palm fiber and epoxy resin. Tensile strength was reduced from 22.78 MPa to 19.03 MPa for the epoxy/OP composite as the wt% of OP was increased but increased to 29.224MPa for epoxy /oil palm / 5% ZnO samples. Young modulus increased from 1.9 MPa to 4.3 MPa while elongation decreased (9.6 to 6.8 %) with the increase of wt% OP and ZnO. The impact and hardness increased for all composites between (6.94 - 10.8 KJ/m2) and between (80.8- 84.55 KJ/m2) respectively. Also, wear resistance of the epoxy/OP and epoxy/OP/ZnO samples increased with the increase of wt% OP and ZnO. This studied in order to provide a new step in the utilization of green nanoparticle fillers for sustainable and renewable structural products for biodegradability.

Biogenic Synthesis of CuO, ZnO, and CuO-ZnO Nanoparticles Using Leaf Extracts of Dovyalis caffra and Their Biological Properties.

Biogenic metal oxide nanoparticles (NPs) have emerged as a useful tool in biology due to their biocompatibility properties with most biological systems. In this study, we report the synthesis of copper oxide (CuO), zinc oxide (ZnO) nanoparticles (NPs), and their nanocomposite (CuO–ZnO) prepared using the phytochemical extracts from the leaves of Dovyalis caffra (kei apple). The physicochemical properties of these nanomaterials were established using some characterization techniques including X-ray diffraction analysis (XRD), ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). The XRD result confirmed the presence of a monoclinic CuO (Tenorite), and a hexagonal ZnO (Zincite) nanoparticles phase, which were both confirmed in the CuO–ZnO composite. The electron microscopy of the CuO–ZnO, CuO, and ZnO NPs showed a mixture of nano-scale sizes and spherical/short-rod morphologies, with some agglomeration. In the constituent’s analysis (EDX), no unwanted peak was found, which showed the absence of impurities. Antioxidant properties of the nanoparticles was studied, which confirmed that CuO–ZnO nanocomposite exhibited better scavenging potential than the individual metal oxide nanoparticles (CuO, and ZnO), and ascorbic acid with respect to their minimum inhibitory concentration (IC50) values. Similarly, the in vitro anticancer studies using MCF7 breast cancer cell lines indicated a concentration-dependent profile with the CuO–ZnO nanocomposite having the best activity over the respective metal oxides, but slightly lower than the standard 5-Fluorouracil drug.

Polypyrrole Decorated Flower-like and Rod-like ZnO Composites with Improved Microwave Absorption Performance.

In this study, zinc oxide (ZnO)/polypyrrole (PPy) composites with flower- and rod-like structures were successfully fabricated by in situ polymerization and the hydrothermal method and used as microwave absorption (MWA) materials. The surface morphologies, crystal structures, and electromagnetic features of the as-prepared samples were measured by field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and vector network analyzer (VNA). The results show that the conductive polymer PPy was successfully decorated on the surface of ZnO substrates. The MWA ability of flower- and rod-like ZnO/PPy composites is significantly enhanced after introduction of PPy. Rod-like ZnO/PPy composites exhibited superior MWA properties than those of flower-like ZnO/PPy. The former achieved a minimum reflection loss (RLmin) of −59.7 dB at 15.8 GHz with a thickness of 2.7 mm, and the effective absorption bandwidth (EAB, RL < −10 dB) covered 6.4 GHz. PPy addition and stacked structure of rod-like ZnO/PPy composites can effectively improve the dielectric properties, form multiple reflections of incident electromagnetic waves, and generate an interfacial polarization effect, resulting in improved MWA properties of composite materials.