Green Synthesis and Characterization of CuO Nanoparticles Derived from Papaya Peel Extract for the Photocatalytic Degradation of Palm Oil Mill Effluent (POME)

Sustainable Utilization of Food Biowaste (Papaya Peel) Extract for Gold Nanoparticle Biosynthesis and Investigation of Its Multi-Functional Potentials

Papaya contains high amounts of vitamins A, C, riboflavin, thiamine, niacin, ascorbic acid, potassium, and carotenoids. It is confirmed by several studies that all food waste parts such as the fruit peels, seeds, and leaves of papaya are potential sources of phenolic compounds, particularly in the peel. Considering the presence of numerous bioactive compounds in papaya fruit peels, the current study reports a rapid, cheap, and environmentally friendly method for the production of gold nanoparticles (AuNPs) employing food biowaste (vegetable papaya peel extract (VPPE)) and investigated its antioxidant, antidiabetic, tyrosinase inhibition, anti-inflammatory, antibacterial, and photocatalytic degradation potentials. The phytochemical analysis gave positive results for tannins, saponins, steroids, cardiac steroidal glycoside, protein, and carbohydrates. The manufactured VPPE-AuNPs were studied by UV-Vis scan (with surface plasmon resonance of 552 nm), X-ray diffraction analysis (XRD) (with average crystallite size of 44.41 nm as per the Scherrer equation), scanning electron microscopy-energy-dispersive X-ray (SEM-EDS), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), particle size, zeta potential, etc. The mean dimension of the manufactured VPPE-AuNPs is 112.2 d.nm (PDI-0.149) with a -26.1 mV zeta potential. The VPPE-AuNPs displayed a significant antioxidant effect (93.24% DPPH scavenging and 74.23% SOD inhibition at 100 µg/mL); moderate tyrosinase effect (with 30.76%); and substantial α-glucosidase (95.63%) and α-amylase effect (50.66%) at 100 µg/mL. Additionally, it was found to be very proficient in the removal of harmful methyl orange and methylene blue dyes with degradation of 34.70% at 3 h and 24.39% at 5 h, respectively. Taken altogether, the VPPE-AuNPs have been proven to possess multiple biopotential activities, which can be explored by the food, cosmetics, and biomedical industries.

Benign-by-design plant extract-mediated preparation of copper oxide nanoparticles for environmentally related applications

A facile, cost-competitive, scalable and novel synthetic approach is used to prepare copper oxide (CuO) nanoparticles (NPs) using Betel leaf (Piper betle) extracts as reducing, capping, and stabilizing agents. CuO-NPs were characterized using various analytical techniques, including Fourier-transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), as well as photoluminescence (PL) measurements. The activity of CuO-NPs was investigated towards Congo red dye degradation, supercapacitor energy storage and antibacterial activity. A maximum of 89% photodegradation of Congo red dye (CR) was obtained. The nanoparticle modified electrode also exhibited a specific capacitance (Csp) of 179 Fg-1. Furthermore, the antibacterial potential of CuO NPs was evaluated against Bacillus subtilis and Pseudomonas aeruginosa, both strains displaying high antibacterial performance.

Biosynthesis of green CuO@C nanocomposite using Combretum indicum flower extract for organic dye removal: adsorption performance, modeling, and recyclability studies

Water contamination becomes one of the most high-priority environmental concerns, calling for the efficient treatment techniques. Bionanocomposites can be robust adsorbents, but the synthesis requires toxic chemicals or energy consuming and cause the secondary pollution. Green nanocomposites can be biogenically synthesized using the plant extract to end up with a critically safe strategy. Herein, we used the flower extract of Combretum indicum plant as a bio-based reductant and carbonaceous source for the green CuO@C nanocomposite. This green nanoadsorbent obtained a specific surface area of 17.33 m2/g, good crystallinity, and functional group-containing surface, i.e., -OH and -CONH-. We also conducted the optimization of parameters, i.e., concentration, CuO@C dose, pH, time, and temperature, and reached removal efficiencies towards malachite green (MG, 83.23%), Congo red (CR, 84.60%), brilliant blue (BB, 71.39%), and methylene blue (MB, 23.67%). The maximum adsorption capacities were found as ordered, MG (46.387 mg/g) > MB (23.154 mg/g) > BB (22.8 mg/g) > CR dye (11.063 mg/g). Through the intra-particle diffusion kinetic model, MG and BB adsorption endured a three-step process, while CR and MB adsorption was a two-step process. The recyclability of the green CuO@C nanocomposite was three cycles with 67.54% for the final cycle of BB removal. Moreover, the nanoadsorbent displayed a high stability, checked by X-ray diffraction, FT-IR analysis, EDX spectra, and SEM images. It is recommended that the green CuO@C nanocomposite biosynthesized using the Combretum indicum flower extract can be a good alternative for the dye treatment from wastewater.

Impact of Diverse Parameters on the Physicochemical Characteristics of Green-Synthesized Zinc Oxide-Copper Oxide Nanocomposites Derived from an Aqueous Extract of Garcinia mangostana L. Leaf

Compared to conventional metal oxide nanoparticles, metal oxide nanocomposites have demonstrated significantly enhanced efficiency in various applications. In this study, we aimed to synthesize zinc oxide-copper oxide nanocomposites (ZnO-CuO NCs) using a green synthesis approach. The synthesis involved mixing 4 g of Zn(NO3)2·6H2O with different concentrations of mangosteen (G. mangostana) leaf extract (0.02, 0.03, 0.04 and 0.05 g/mL) and 2 or 4 g of Cu(NO3)2·3H2O, followed by calcination at temperatures of 300, 400 and 500 °C. The synthesized ZnO-CuO NCs were characterized using various techniques, including a UV-Visible spectrometer (UV-Vis), photoluminescence (PL) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD) analysis and Field Emission Scanning Electron Microscope (FE-SEM) with an Energy Dispersive X-ray (EDX) analyzer. Based on the results of this study, the optical, structural and morphological properties of ZnO-CuO NCs were found to be influenced by the concentration of the mangosteen leaf extract, the calcination temperature and the amount of Cu(NO3)2·3H2O used. Among the tested conditions, ZnO-CuO NCs derived from 0.05 g/mL of mangosteen leaf extract, 4 g of Zn(NO3)2·6H2O and 2 g of Cu(NO3)2·3H2O, calcinated at 500 °C exhibited the following characteristics: the lowest energy bandgap (2.57 eV), well-defined Zn-O and Cu-O bands, the smallest particle size of 39.10 nm with highest surface area-to-volume ratio and crystalline size of 18.17 nm. In conclusion, we successfully synthesized ZnO-CuO NCs using a green synthesis approach with mangosteen leaf extract. The properties of the nanocomposites were significantly influenced by the concentration of the plant extract, the calcination temperature and the amount of precursor used. These findings provide valuable insights for researchers seeking innovative methods for the production and utilization of nanocomposite materials.

Biogenic Synthesis of Copper Nanoparticles: A Systematic Review of Their Features and Main Applications

Nanotechnology is an innovative field of study that has made significant progress due to its potential versatility and wide range of applications, precisely because of the development of metal nanoparticles such as copper. Nanoparticles are bodies composed of a nanometric cluster of atoms (1-100 nm). Biogenic alternatives have replaced their chemical synthesis due to their environmental friendliness, dependability, sustainability, and low energy demand. This ecofriendly option has medical, pharmaceutical, food, and agricultural applications. When compared to their chemical counterparts, using biological agents, such as micro-organisms and plant extracts, as reducing and stabilizing agents has shown viability and acceptance. Therefore, it is a feasible alternative for rapid synthesis and scaling-up processes. Several research articles on the biogenic synthesis of copper nanoparticles have been published over the past decade. Still, none provided an organized, comprehensive overview of their properties and potential applications. Thus, this systematic review aims to assess research articles published over the past decade regarding the antioxidant, antitumor, antimicrobial, dye removal, and catalytic activities of biogenically synthesized copper nanoparticles using the scientific methodology of big data analytics. Plant extract and micro-organisms (bacteria and fungi) are addressed as biological agents. We intend to assist the scientific community in comprehending and locating helpful information for future research or application development.

Metal Oxide Nanostructures (MONs) as Photocatalysts for Ciprofloxacin Degradation

In recent years, organic pollutants have become a global problem due to their negative impact on human health and the environment. Photocatalysis is one of the most promising methods for the removal of organic pollutants from wastewater, and oxide semiconductor materials have proven to be among the best in this regard. This paper presents the evolution of the development of metal oxide nanostructures (MONs) as photocatalysts for ciprofloxacin degradation. It begins with an overview of the role of these materials in photocatalysis; then, it discusses methods of obtaining them. Then, a detailed review of the most important oxide semiconductors (ZnO, TiO₂, CuO, etc.) and alternatives for improving their photocatalytic performance is provided. Finally, a study of the degradation of ciprofloxacin in the presence of oxide semiconductor materials and the main factors affecting photocatalytic degradation is carried out. It is well known that antibiotics (in this case, ciprofloxacin) are toxic and non-biodegradable, which can pose a threat to the environment and human health. Antibiotic residues have several negative impacts, including antibiotic resistance and disruption of photosynthetic processes.

Green synthesis of highly efficient and stable copper oxide nanoparticles using an aqueous seed extract of Moringa stenopetala for sunlight-assisted catalytic degradation of Congo red and alizarin red s

Environmental pollution by organic pollutants because of population growth and industrial expansion is a global concern. Following this, the fabrication of single and efficient nanomaterials for pollution control is highly demanded. Under this study, highly efficient and stable copper oxide nanoparticles (CuO NPs) were synthesized through the green method using Moringa stenopetala seed extract. XRD, UV-vis, FT-IR, and SEM were applied to characterize the synthesized material. From XRD data, the average particle size was found to be 6.556 nm, and the nanoparticles are crystalline in nature. The formation of CuO NPs was demonstrated by FT-IR spectra of Cu-O in different bending vibration bands at 535 cm-1 and 1122 cm-1, as well as stretching vibration of Cu-O at 1640 cm-1. From UV-visible spectroscopic measurements, the energy band gap of greenly synthesized CuO NPs was found to be 1.73 eV. The SEM result shows that the nanoparticles' surfaces are rough, with some of the particles having spherically random orientation. The photodegradation efficiency of green synthesized CuO NPs photocatalyst was found to be 98.35% for Congo red at optimum experimental parameters (initial concentration, 25 mg/L; exposure time, 120 min; catalyst dose, 0.2 g; and pH, 5) and 95.4% for Alizarin Red S at optimum experimental parameters (catalyst dose, 0.25 g; initial concentration, 40 mg/L; exposure time, 120 min; and pH, 4.6). The COD values determined for the degraded product strongly support the complete mineralization of the dyes toward nontoxic materials. Reusability of the catalyst was investigated for five cycles, and the results clearly indicate the green synthesized CuO NPs are highly stable, can be used for several times, and are cost-effective as well. The degradation of Congo red and Alizarin red S on the surface of the CuO NPs follows the MBG kinetic model.

The photocatalytic, cytotoxicity, and antibacterial properties of zinc oxide nanoparticles synthesized using Trigonella foenum-graecum L extract

In this study, the manufacture of zinc oxide nanoparticles (ZnO-NPs) was completed via the sol-gel method with Trigonella foenum-graecum L extract for the first time to function as the stabilizing and reducing agent. The obtained product was investigated by various analyzing procedures such as TGA/DTG, FT-IR, UV-Vis, XRD, and EDX/FESEM. The calcination of our product was conducted at temperatures of 400, 500, and 600 °C. In conformity to the XRD pattern, heightening the temperature of calcination caused an enlargement in the size of nanoparticles. The photocatalytic performance of ZnO-NPs was evaluated to degrade methylene blue and Eriochrome black T (EBT) dyes under UV light, which resulted in a degradation percentage of about 96% and 94%, after 90 min, respectively. There has been some evidence suggesting that the green synthesis of ZnO-NPs has increased their use in medicine. The outcomes of examining the cytotoxicity effect of this product against the Huh-7 cell line by the performance of the MTT assay were indicative of an IC₅₀ of around 62.5 µg/mL. Finally, according to the results of the broth microdilution method, which was performed to assess the antibacterial activity of ZnO-NPs towards gram-positive and gram-negative bacteria, the value of MIC was in the range of 31 to 125 µg/mL. The obtained results from biological studies confirm the antibacterial and anticancer properties of ZnO-NPs, which are promising for applying NPs in medical fields.

Synergistic Effect of Iron and Copper Oxides in the Removal of Organic Dyes Through Thermal Induced Catalytic Degradation Process

This study proposes a new method for producing α-Fe2O3–CuO nanocatalyst that is both cost-effective and ecologically benign. The α-Fe2O3–CuO nanocomposite was prepared via moderate thermal oxidative decomposition of copper hexacyanoferrate. Its structure and surface morphology are affirmed via XRD, SEM, FTIR, EDX, TEM, XPS, and VSM. In the presence of H2O2, α-Fe2O3–CuO is employed as a heterogeneous catalyst to stimulate thermally induced degradation of dyes such as direct violet 4, rhodamine b, and methylene blue. The synergistic effect of Fe2O3 and CuO enhanced the catalytic activity of the nanocomposite compared to Fe2O3 and CuO separately. The effectiveness of DV4 degradation is optimized by evaluating multiple reaction parameters. The reaction rate increased substantially with the temperature, revealing its key role in the degradation process. Higher H2O2 levels and the inclusion of inorganic anions like chloride or nitrate also sped up the degradation process. While sulfate and humic acid, particularly at high doses, slowed it. The mechanism of H2O2 activation on α-Fe2O3–CuO is studied. The measurements of chemical oxygen demand and total organic carbon indicate that all dyes are highly mineralized. The remarkable performance and stability of this nanocomposite in removing diverse dyes render it a promising option for wastewater remedy.

Effect of Calcination Temperature on Structural, Morphological and Optical Properties of Copper Oxide Nanostructures Derived from Garcinia mangostana L. Leaf Extract

Synthesis of copper oxide (CuO) nanostructures via biological approach has gained attention to reduce the harmful effects of chemical synthesis. The CuO nanostructures were synthesized through a green approach using the Garcinia mangostana L. leaf extract and copper (II) nitrate trihydrate as a precursor at varying calcination temperatures (200-600 °C). The effect of calcination temperatures on the structural, morphological and optical properties of CuO nanostructures was studied. The red shifting of the green-synthesized CuO nanoparticles' absorption peak was observed in UV-visible spectrum, and the optical energy bandgap was found to decrease from 3.41 eV to 3.19 eV as the calcination temperatures increased. The PL analysis shown that synthesized CuO NPs calcinated at 500 °C has the maximum charge carriers separation. A peak located at 504-536 cm^-1 was shown in FTIR spectrum that indicated the presence of a copper-oxygen vibration band and become sharper and more intense when increasing the calcination temperature. The XRD studies revealed that the CuO nanoparticles' crystalline size was found to increase from 12.78 nm to 28.17 nm, and dislocation density decreased from 61.26 × 10¹⁴ cm^-1 to 12.60 × 10¹⁴ cm^-1, while micro strain decreased from 3.40 × 10^-4 to 1.26 × 10^-4. From the XPS measurement, only CuO single phase without impurities was detected for the green-mediated NPs calcinated at 500 °C. The morphologies of CuO nanostructures were examined using FESEM and became more spherical in shape at elevated calcination temperature. More or less spherical nanostructure of green-mediated CuO calcinated at 500 °C were also observed using TEM. The purity of the green-synthesized CuO nanoparticles was evaluated by EDX analysis, and results showed that increasing calcination temperature increases the purity of CuO nanoparticles.

Preparation and modification methods of defective titanium dioxide-based nanoparticles for photocatalytic wastewater treatment-a comprehensive review

The rapid population growth and industrial expansion worldwide have created serious water contamination concerns. To curb the pollution issue, it has become imperative to use a versatile material for the treatment. Titanium dioxide (TiO₂) has been recognized as the most-studied nanoparticle in various fields of science and engineering due to its availability, low cost, efficiency, and other fascinating properties with a wide range of applications in modern technology. Recent studies revealed the photocatalytic activity of the material for the treatment of industrial effluents to promote environmental sustainability. With the wide band gap energy of 3.2 eV, TiO₂ can be activated under UV light; thus, many strategies have been proposed to extend its photoabsorption to the visible light region. In what follows, this has generated increasing attention to study its characteristics and structural modifications in different forms for photocatalytic applications. The present review provides an insight into the understanding of the synthesis methods of TiO₂, the current progress in the treatment techniques for the degradation of wide environmental pollutants employing modified TiO₂ nanoparticles, and the factors affecting its photocatalytic activities. Further, recent developments in using titania for practical applications, the approach for designing novel nanomaterials, and the prospects and opportunities in this exciting area have been discussed.

Biogenic Synthesis of Copper-Based Nanomaterials Using Plant Extracts and Their Applications: Current and Future Directions

Plants have been used for multiple purposes over thousands of years in various applications such as traditional Chinese medicine and Ayurveda. More recently, the special properties of phytochemicals within plant extracts have spurred researchers to pursue interdisciplinary studies uniting nanotechnology and biotechnology. Plant-mediated green synthesis of nanomaterials utilises the phytochemicals in plant extracts to produce nanomaterials. Previous publications have demonstrated that diverse types of nanomaterials can be produced from extracts of numerous plant components. This review aims to cover in detail the use of plant extracts to produce copper (Cu)-based nanomaterials, along with their robust applications. The working principles of plant-mediated Cu-based nanomaterials in biomedical and environmental applications are also addressed. In addition, it discusses potential biotechnological solutions and new applications and research directions concerning plant-mediated Cu-based nanomaterials that are yet to be discovered so as to realise the full potential of the plant-mediated green synthesis of nanomaterials in industrial-scale production and wider applications. This review provides readers with comprehensive information, guidance, and future research directions concerning: (1) plant extraction, (2) plant-mediated synthesis of Cu-based nanomaterials, (3) the applications of plant-mediated Cu-based nanomaterials in biomedical and environmental remediation, and (4) future research directions in this area.

Photocatalytic Activity Induced by Metal Nanoparticles Synthesized by Sustainable Approaches: A Comprehensive Review

Nanotechnology is a fast-expanding area with a wide range of applications in science, engineering, health, pharmacy, and other fields. Among many techniques that are employed toward the production of nanoparticles, synthesis using green technologies is the simplest and environment friendly. Nanoparticles produced from plant extracts have become a very popular subject of study in recent decades due to their diverse advantages such as low-cost synthesis, product stability, and ecofriendly protocols. These merits have prompted the development of nanoparticles from a variety of sources, including bacteria, fungi, algae, proteins, enzymes, etc., allowing for large-scale production with minimal contamination. However, nanoparticles obtained from plant extracts and phytochemicals exhibit greater reduction and stabilization and hence have proven the diversity of properties, like catalyst/photocatalyst, magnetic, antibacterial, cytotoxicity, circulating tumor deoxy ribo nucleic acid (CT-DNA) binding, gas sensing, etc. In the current scenario, nanoparticles can also play a critical role in cleaning wastewater and making it viable for a variety of operations. Nano-sized photocatalysts have a great scope toward the removal of large pollutants like organic dyes, heavy metals, and pesticides in an eco-friendly and sustainable manner from industrial effluents. Thus, in this review article, we discuss the synthesis of several metal nanoparticles using diverse plant extracts, as well as their characterization via techniques like UV–vis (ultraviolet–visible), XRD (X-ray diffraction), SEM (scanning electron microscopy), TEM (transmission electron microscopy), FTIR (Fourier transform infrared spectroscopy), etc., and catalytic activity on various hazardous systems.

Green synthesis of nanoparticles from biodegradable waste extracts and their applications: a critical review

The contemporary world is concerned only with non-biodegradable waste management which needs more sophisticated procedures as compared to biodegradable waste management. Biodegradable waste has the potential to become useful to society through a simple volarization technique. The researchers are behind sustainable nanotechnology pathways which are made possible by using biodegradable waste for the preparation of nanomaterials. This review emphasizes the potentialities of biodegradable waste produced as a viable alternative to create a sustainable economy that benefits all humans. Volarization results in the utilization of biowastes as well as provides safer and hazard-free green methods for the synthesis of nanoparticles. Starting from different sources to the application which includes therapeutics, food industry and water treatment. The review hovers over the pros and cons of biowaste-mediated nanoparticles and concludes with possible advances in the application. In the present scenario, the combination of green synthesis and biowaste can bring about a wide variety of applications in nanotechnology once the hurdles of bulk-scale industrial production are resolved. Given these points, the review is focused on the cost-effective synthesis of metal and metal oxide nanoparticles.

Photocatalytic activity of CuO nanoparticles for organic and inorganic pollutants removal in wastewater remediation

Heterogeneous photocatalysis is a promising technology for eradicating organic, inorganic, and microbial pollutants in water and wastewater remediation. It is a more preferable method to other conventional wastewater treatment approaches on account of its low cost, environmental benignity, ability to proceed at ambient temperature and pressure conditions, and capability to completely degrade pollutants under appropriate conditions into environmentally safe products. In heterogeneous photocatalysis, pollutant removal is mainly induced by in-situ generated reactive radicals and their subsequent attack when energetic radiation impinges on the semiconductor catalyst. As such, for the effective and economical removal of wastewater pollutants, the employed catalyst should have high photonic efficiency, less toxic, abundant, chemically and photochemically stableand visible light active. Copper (II) oxide (CuO) is one among such promising compounds and its photocatalytic performance has been hampered primarily by rapid recombination and slow mobility of photogenerated charge carriers. So, this review provides an overview of the strategies adopted to mitigate the aforementioned drawbacks and also other operational parameters to boost its catalytic activity towards the elimination of toxic organic and inorganic metal ion contaminants in an aqueous media.

A Review on Current Designation of Metallic Nanocomposite Hydrogel in Biomedical Applications

In the past few decades, nanotechnology has been receiving significant attention globally and is being continuously developed in various innovations for diverse applications, such as tissue engineering, biotechnology, biomedicine, textile, and food technology. Nanotechnological materials reportedly lack cell-interactive properties and are easily degraded into unfavourable products due to the presence of synthetic polymers in their structures. This is a major drawback of nanomaterials and is a cause of concern in the biomedicine field. Meanwhile, particulate systems, such as metallic nanoparticles (NPs), have captured the interest of the medical field due to their potential to inhibit the growth of microorganisms (bacteria, fungi, and viruses). Lately, researchers have shown a great interest in hydrogels in the biomedicine field due to their ability to retain and release drugs as well as to offer a moist environment. Hence, the development and innovation of hydrogel-incorporated metallic NPs from natural sources has become one of the alternative pathways for elevating the efficiency of therapeutic systems to make them highly effective and with fewer undesirable side effects. The objective of this review article is to provide insights into the latest fabricated metallic nanocomposite hydrogels and their current applications in the biomedicine field using nanotechnology and to discuss the limitations of this technology for future exploration. This article gives an overview of recent metallic nanocomposite hydrogels fabricated from bioresources, and it reviews their antimicrobial activities in facilitating the demands for their application in biomedicine. The work underlines the fabrication of various metallic nanocomposite hydrogels through the utilization of natural sources in the production of biomedical innovations, including wound healing treatment, drug delivery, scaffolds, etc. The potential of these nanocomposites in relation to their mechanical strength, antimicrobial activities, cytotoxicity, and optical properties has brought this technology into a new dimension in the biomedicine field. Finally, the limitations of metallic nanocomposite hydrogels in terms of their methods of synthesis, properties, and outlook for biomedical applications are further discussed.

Phytochemical-Assisted Green Synthesis of Nickel Oxide Nanoparticles for Application as Electrocatalysts in Oxygen Evolution Reaction

Electrocatalytic water splitting is a promising solution to resolve the global energy crisis. Tuning the morphology and particle size is a crucial aspect in designing a highly efficient nanomaterials-based electrocatalyst for water splitting. Herein, green synthesis of nickel oxide nanoparticles using phytochemicals from three different sources was employed to synthesize nickel oxide nanoparticles (NiOx NPs). Nickel (II) acetate tetrahydrate was reacted in presence of aloe vera leaves extract, papaya peel extract and dragon fruit peel extract, respectively, and the physicochemical properties of the biosynthesized NPs were compared to sodium hydroxide (NaOH)-mediated NiOx. Based on the average particle size calculation from Scherrer’s equation, using X-ray diffractograms and field-emission scanning electron microscope analysis revealed that all three biosynthesized NiOx NPs have smaller particle size than that synthesized using the base. Aloe-vera-mediated NiOx NPs exhibited the best electrocatalytic performance with an overpotential of 413 mV at 10 mA cm−2 and a Tafel slope of 95 mV dec−1. Electrochemical surface area (ECSA) measurement and electrochemical impedance spectroscopic analysis verified that the high surface area, efficient charge-transfer kinetics and higher conductivity of aloe-vera-mediated NiOx NPs contribute to its low overpotential values.

Muntingia calabura Leaves Mediated Green Synthesis of CuO Nanorods: Exploiting Phytochemicals for Unique Morphology

In this study, phytochemical assisted nanoparticle synthesis was performed using Muntingia calabura leaf extracts to produce copper oxide nanoparticles (CuO NPs) with interesting morphology. Scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis of the biosynthesized CuO NPs reveal formation of distinct, homogeneous, and uniform sized CuO nanorods structure with thickness and length of around 23 nm and 79 nm, respectively. Based on Fourier-transform infrared (FTIR) analysis, the unique combinations of secondary metabolites such as flavonoid and polyphenols in the plant extract are deduced to be effective capping agents to produce nanoparticles with unique morphologies similar to conventional chemical synthesis. X-ray diffraction (XRD) analysis verified the monoclinical, crystalline structure of the CuO NPs. The phase purity and chemical identity of the product was consolidated via X-Ray photoelectron spectroscopy (XPS) and Raman spectroscopic data which indicate the formation of a single phase CuO without the presence of other impurities. The direct and indirect optical band gap energies of the CuO nanorods were recorded to be 3.65 eV and 1.42 eV.

Mo-Doped CuO Nanomaterial for Photocatalytic Degradation of Water Pollutants under Visible Light

Recently, metal oxide-based nano-photocatalysts have gained much attention in waste water remediation due to their outstanding properties. In this report, a novel Mo-doped CuO nanomaterial was successfully prepared and utilized for the degradation of methylene blue water pollutant. The molybdenum content was varied from 1–5 wt.% to obtain the desired modified CuO based nanomaterials. The crystalline structures of as prepared materials were investigated by XRD diffraction technique, which explored the successful fabrication of monoclinic structure based CuO nanomaterials. For morphological study, SEM and HRTEM techniques were probed, which had also proved the successful preparation of nanoparticles-based material. SAED is used to check the crystallinity of the sample. The EDX and XPS analysis were performed to evaluate the elemental composition of Mo-doped CuO nanomaterials. The optical characteristics were explored via UV-vis and PL techniques. These studies have showed that the energy bandgap of CuO was decreased from 1.55 eV to 1.25 eV due to Mo doping. The photocatalytic efficiency of Mo-doped CuO nanomaterials was evaluated by degrading methylene blue (MB) under visible light-irradiation. Among different Mo-doped CuO based nanomaterials, the 4 wt.% Mo-doped CuO sample have shown highest degradation activity against MB dye. These results verified that the optimized material can be used for photocatalytic applications, especially for the purification of waste water.