Rethinking Nanoparticle Synthesis: A Sustainable Approach vs. Traditional Methods

This review portrays a comparison between green protocols and conventional nanoparticle (NP) synthesis strategies, highlighting each method's advantages and limitations. Various top-down and bottom-up methods in NP synthesis are described in detail. The green chemistry principles are emphasized for designing safe processes for nanomaterial synthesis. Among the green biogenic sources plant extracts, vitamins, enzymes, polysaccharides, fungi (Molds and mushrooms), bacteria, yeast, algae, and lichens are discussed. Limitations in the reproducibility of green protocols in terms of availability of raw material, variation in synthetic protocol, and selection of material due to geographical differences are elaborated. Finally, a conclusion is drawn utilizing green chemical principles, & a circular economy strategy to minimize waste generation, offering a promising framework for the synthesis of NPs emphasizing sustainability.

Green synthesis of copper nanoparticles by using pineapple peel waste: in vitro characterizations and antibacterial potential

A considerable amount of fruit waste is being produced every day worldwide. The green synthesis of metal nanoparticles from fruit peel waste can be an innovative, cost-effective, and eco-friendly alternative to traditional methods. Copper nanoparticles (CuNPs) were synthesized by a green method using the pineapple peels extract (PLX) and copper sulfate pentahydrate. The formation of CuNPs was visually identified and detected by UV-Visible spectroscopy. The CuNPs were characterized by Fourier-transform infrared (FTIR) spectroscopy, particle size analyzer, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The antioxidant and reducing power of CuNPs were conducted by %DPPH scavenging and electron transfer-based ferric reducing antioxidant power (FRAP) assay, respectively. The antibacterial properties of CuNPs were determined in gram-positive, and gram-negative bacteria. The results showed that the CuNPs were spherical in shape with mean particle size 290.5 nm. The zeta potential of the nanoparticles was found to be - 12.3 mV indicating the instability in the colloidal state. The FTIR study confirmed the peaks of phytochemicals present in the PLX and the nanoparticles supporting the use of pineapple peels as stabilizing, reducing and capping agents. Both the DPPH and reducing power assay depicted that the synthesized CuNPs had significant antioxidant activity. However, the synthesized CuNPs had strong inhibitory capacity against both gram-positive and gram-negative test organisms. Thus, the CuNPS could be used for its viable antibacterial potential to preserve fruits, flowers, and vegetables from bacterial contamination.

Employing Piper longum extract for eco-friendly fabrication of PtPd alloy nanoclusters: advancing electrolytic performance of formic acid and methanol oxidation

Advancement in bioinspired alloy nanomaterials has a crucial impact on fuel cell applications. Here, we report the synthesis of PtPd alloy nanoclusters via the hydrothermal method using Piper longum extract, representing a novel and environmentally friendly approach. Physicochemical characteristics of the synthesized nanoclusters were investigated using various instrumentation techniques, including X-ray photoelectron spectroscopy, X-ray diffraction, and High-Resolution Transmission electron microscopy. The electrocatalytic activity of the biogenic PtPd nanoclusters towards the oxidation of formic acid and methanol was evaluated chronoamperometry and cyclic voltammetry studies. The surface area of the electrocatalyst was determined to be 36.6 m2g-1 by Electrochemical Surface Area (ECSA) analysis. The biologically inspired PtPd alloy nanoclusters exhibited significantly higher electrocatalytic activity compared to commercial Pt/C, with specific current responses of 0.24 mA cm - 2 and 0.17 mA cm - 2 at synthesis temperatures of 180 °C and 200 °C, respectively, representing approximately four times higher oxidation current after 120 min. This innovative synthesis approach offers a promising pathway for the development of PtPd alloy nanoclusters with enhanced electrocatalytic activity, thereby advancing fuel cell technology towards a sustainable energy solution.

Sonochemical-assisted synthesis of copper oxide nanoparticles with the plant-mediated approach and comparative evaluation of some biological activities

The present study reported a green approach for the sonochemical-assisted synthesis (SAS) of copper oxide nanoparticles (CuO NPs) by using the aqueous extract of the Ficus johannis plant. The aqueous extract was obtained using ultrasonic-assisted extraction (15 min, 45 °C) and microwave-assisted extraction (15 min, 450 w). Next, the as-prepared extracts were used in a plant-mediated approach for the green synthesis of CuO NPs. The synthesized CuO NPs have been characterized via different techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering (DLS), ultraviolet-visible absorption, photoluminescence, and Fourier-transformed infrared (FT-IR) spectroscopic techniques. As observed, a broad absorption band around 375 nm clarified the successful synthesis of CuO NPs. From the SEM analysis, the average particle size of the prepared CuO NPs was estimated below 50 nm. In addition, the antimicrobial, antioxidant, and antifungal properties of the aqueous extracts as well as the as-prepared CuO NPs were evaluated by different assays. These included the release of protein, nucleic acids, disk diffusion method, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), and time-killing assays.

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.

Polyvinyl alcohol/citric acid/β-cyclodextrin/CuONP composite nanofibers as an effective and green absorbent for the simultaneous extraction of three antidepressant drugs in biological fluids prior to GC-FID analysis

Composite nanofibers, namely, polyvinyl alcohol (PVA), citric acid (CA), β-cyclodextrin (β-CD), and copper oxide nanoparticles (PVA/CA/β-cyclodextrin/CuO NPs), were developed as a novel, green, and efficient adsorbent in the pipette tip-micro-solid-phase extraction method (PT-µSPE), for the simultaneous extraction of three antidepressants drugs namely imipramine (IMP), citalopram (CIT), and clozapine (CLZ) in biological fluids before quantification by gas chromatography (GC-FID). Based on the obtained results from field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD), the successful synthesis of composite nanofibers was approved. Due to the presence of β-cyclodextrins and CuO NPs rich of functional groups on their surface, the nanofibers have high extraction efficiency. Under the optimal conditions, the linear range for imipramine, citalopram, and clozapine was 0.1 to 1000.0 ng mL^-1 with a determination coefficient ≥ 0.99. The limits of detection (LODs) were in the range 0.03 to 0.15 ng mL^-1. The relative standard deviation was 4.8 to 8.7% (within-day, n = 4) and 5.1 to 9.2% (between-day, n = 3) for 3 consecutive days. In addition, excellent clean-up was achieved which is a great advantage over other sample preparation methods. Finally, the ability of the developed method to extract the target analytes from the biological samples was evaluated.

Concurrent Tissue Engineering for Wound Healing in Diabetic Rats Utilizing Dual Actions of Green Synthesized CuO NPs Prepared from Two Plants Grown in Egypt

Purpose

Diabetes mellitus is among the disrupting factors of orchestrated events in wound healing. This necessitates the urge for tailored medications, which are continually offered by nano-sized materials. Herein, we present greenly synthesized copper oxide nanoparticles (CuO NPs), obtained from either Punica granatum L. (PG) or Pisidium guajava L. (GV) extract, to function as potent bactericidal and fungicidal materials that promote regeneration and healing of the targeted diabetic wounded tissues.

Methods

PG or GV plant extracts were compared as source of reducing agents for CuO NPs synthesis process. The yield and photocatalytic degradation potential were compared. NPs obtained from the superior extract, PG, were characterized using particles size, zeta potential, XRD, TEM, SEM, and EDX. The antimicrobial effects were evaluated on multidrug-resistant human pathogens and then the percentage biofilm inhibitory concentration was determined. The cytotoxicity and wound scratch study were conducted on a normal human skin cell line. In-vivo wound healing activity in diabetic rats was assessed along with histopathological and immunohistochemical examination of CD45 and α-SMA.

Results

The greenly synthesized CuO NPs are spherical in shape having a diameter of 233nm. CuO NPs (250µg/mL) acted as promising biocontrol agent against a variety of multidrug-resistant human pathogens. They significantly exhibited 29.460±0.811% healing of the scratched wound compared to only 2.001±0.155% for the control. Wound healing experiments revealed the safety of a low CuO NPs concentration in a diabetic animal model as well as on human normal skin fibroblast cell line. The treated group with a dose of 2mg/cm2 showed superior results with a WC50 value of 7.2 days, and 92% wound contraction after 13-days. Immunohistochemical investigation of the same group demonstrated well-established fibrous tissue (5.7±3.7/HPF), and an amplified granulation tissue of recently developed blood vessels (70±1.5/HPF).

Conclusion

Green synthesized CuO NPs could overcome drug resistance and promote wound healing process effectively.

Antibacterial and in vivo toxicological studies of Bi2O3/CuO/GO nanocomposite synthesized via cost effective methods

In this research work, Bi2O3, Bi2O3/GO and Bi2O3/CuO/GO nanocomposites have been synthesized via an eco-friendly green synthesis technique, solgel route and co-precipitation method respectively for the assessment of antibacterial activity as well as in vivo toxicity. The XRD patterns confirm the formation of Bi2O3, Bi2O3/GO and Bi2O3/CuO/GO nanocomposites showing monoclinic structures. Crystallite size and lattice strain are calculated by Scherrer equation, Scherrer plot and Willimson Hall plot methods. Average crystallite size measured for Bi2O3, Bi2O3/GO and Bi2O3/CuO/GO nanocomposites by Scherrer equation, Scherrer plot and WH-plot methods are (5.1, 13.9, 11.5)nm, (5.4, 14.2, 11.3)nm and (5.2, 13.5, 12.0)nm respectively. Optical properties such as absorption peaks and band-gap energies are studied by UV-vis spectroscopy. The FTIR peaks at 513 cm-1, 553 cm-1 and 855 cm-1 confirms the successful synthesis of Bi2O3, Bi2O3/GO and Bi2O3/CuO/GO nanocomposites. The antibacterial activity of synthesized Bi2O3, Bi2O3/GO and Bi2O3/CuO/GO nanocomposites is examined against two gram-negative (Escherichia coli and pseudomonas) as well as gram-positive bacteria (Bacillus cereus and Staphylococcus aureus) at dose 25 mg/kg and 40 mg/kg by disk diffusion technique. Zone of inhibition for Bi2O3, Bi2O3/GO and Bi2O3/CuO/GO at dose 40 mg/kg against E. coli (gram - ve) are 12 mm, 17 mm and 18 mm respectively and against Pseudomonas (gram - ve) are 28 mm, 19 mm and 21 mm respectively. While the zone of inhibition for Bi2O3/GO and Bi2O3/CuO/GO at dose 40 mg/kg against B. cereus (gram + ve) are 8 mm and 8.5 mm respectively and against S. aureus (gram + ve) are 5 mm and 10.5 mm respectively. These amazing results reveal that Bi2O3, Bi2O3/GO and Bi2O3/CuO/GO nanocomposite as a kind of antibacterial content, have enormous potential for biomedical applications. In addition, the in vivo toxicity of synthesized Bi2O3/CuO/GO nanocomposite is investigated on Swiss Albino mice at dose of 20 mg/kg by evaluating immune response, hematology and biochemistry at the time period of 2, 7, 14 and 30 days. No severe damage is observed in mice during whole treatment. The p value calculated by statistical analysis of hematological and biochemistry tests is nonsignificant which ensures that synthesized nanocomposites are safe and non-toxic as they do not affect mice significantly. This study proves that Bi2O3/CuO/GO nanocomposites are biocompatible and can be explored further for different biomedical applications.

Decolourisation of triphenylmethane dyes by biogenically synthesised iron nanoparticles from fungal extract

In this study, the extract from endophytic Fusarium proliferatum was used to synthesise iron nanoparticles (Fe-NPs). The properties of the biogenically synthesised Fe-NPs were then characterised by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR). The efficacy of the synthesised Fe-NPs in decolourizing triphenylmethane dyes was evaluated. Results revealed that fungal extract from F. proliferatum was successfully used to synthesise Fe-NPs. The Fe-NPs produced were 20-50 nm in size, and consist of substantial elemental Fe content (14.83%). The FTIR spectra revealed the presence of amino acids and proteins on the surface of the Fe-NPs, confirming the biogenic synthesis of the Fe-NPs. When tested for decolourisation, the Fe-NPs were most effective in decolourising Methyl Violet (28.9%), followed by Crystal Violet (23.8%) and Malachite Green (18.3%). This study is the first few to report the biogenic synthesis of Fe-NPs using extracts from an endophytic Fusarium species and their corresponding dye decolourisation activities.

New frontiers in the plant extract mediated biosynthesis of copper oxide (CuO) nanoparticles and their potential applications: A review

Copper oxide nanoparticles (CuO NPs) are one of the most widely used nanomaterials nowadays. CuO NPs have numerous applications in biological processes, medicine, energy devices, environmental remediation, and industrial fields from nanotechnology. With the increasing concern about the energy crisis and the challenges of chemical and physical approaches for preparing metal NPs, attempts to develop modern alternative chemistry have gotten much attention. Biological approaches that do not produce toxic waste and therefore do not require purification processes have been the subject of numerous studies. Plants may be extremely useful in the study of biogenic metal NP synthesis. This review aims to shed more light on the interactions between plant extracts and CuO NP synthesis. The use of living plants for CuO NPs biosynthesis is a cost-effective and environmentally friendly process. To date, the findings have revealed many aspects of plant physiology and their relationships to the synthesis of NPs. The current state of the art and potential challenges in the green synthesis of CuO NPs are described in this paper. This study found a recent increase in the green synthesis of CuO NPs using various plant extracts. As a result, a thorough explanation of green synthesis and stabilizing agents for CuO NPs made from these green sources is given. Additionally, the multifunctional applications of CuO NPs synthesized with various plant extracts in environmental remediation, sensing, catalytic reduction, photocatalysis, diverse biological activities, energy storage, and several organic transformations such as reduction, coupling, and multicomponent reactions were carefully reviewed. We expect that this review could serve as a useful guide for readers with a general interest in the plant extract mediated biosynthesis of CuO NPs and their potential applications.

Transformation of CuS/ZnS nanomaterials to an efficient visible light photocatalyst by 'photosensitizer' graphene and the potential antimicrobial activities of the nanocomposites

We report the growth of CuS/ZnS (CZS) nanoparticles (NPs) on the graphene sheet by a facile green synthesis process. The CuS/ZnS-graphene (CZSG) nanocomposites exhibit enhanced visible light photocatalytic activity towards organic dye (methylene blue) degradation than that of CZS nanoparticles. To find the reason for the enhanced photo-activity, we propose a new photocatalytic mechanism where graphene in the CZSG nanocomposites acts as a 'photosensitizer' for CZS nanoparticles. This distinctive photocatalytic mechanism is noticeably different from all other previous research works on semiconductor-graphene hybrid photocatalysts where graphene behaves as an electron reservoir to capture the electrons from photo-excited semiconductor. This novel idea of the photocatalytic mechanism in semiconductor-graphene photocatalysts could draw a new track in thinking for designing of graphene-based photocatalysts for solving environmental pollution problems and they also show remarkable antimicrobial activities.

Bioengineered Matricaria recutita Extract-Assisted Palladium Nanoparticles for the Congo Red Dye Degradation and Catalytic Reduction of 4-Nitrophenol to 4-Aminophenol

The green chemistry method is the preferred approach for synthesizing metal and metal oxide nanoparticles because of its low toxicity, environmental friendliness, feasibility, and safety to human health compared with other chemical or physical methods. The present work reports the phytogenic synthesis of palladium nanoparticles (PdNPs) using an aqueous extract of Matricaria recutita (Chamomile). The phytochemical-mediated synthesis of PdNPs is an economical and eco-friendly approach without using toxic elements as reducing and capping or stabilizing agents. The UV-visible spectroscopic characterization was initially used to confirm the preparation of PdNPs using an aqueous extract of M. recutita flowers as a bioreductant for the reduction of Pd2+ to Pd0 without using any extra capping and reducing agents. The appearance of surface plasmon resonance (SPR) peak at 286 nm confirmed the formation of M. recutita extract-based PdNPs. Furthermore, the PdNPs were characterized by TEM, SEM, EDX, XRD, XPS, and FTIR to confirm their proper synthesis. The thermogravimetric analysis (TGA) was implemented to interpret the decomposition pattern and thermal stability of as-synthesized PdNPs. The biosynthesized PdNPs were further applied as a nanocatalyst in degradation of an azo dye Congo red (CR) in the presence of NaBH4. The catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) was also investigated in the presence of NaBH4. All the catalytic reactions were performed in water, and no significant loss in catalytic activity was observed after recovery and reusability of the biosynthesized PdNPs.

Microwave-Assisted Synthesis of CuO Nanoparticles Using Cordia africana Lam. Leaf Extract for 4-Nitrophenol Reduction

Copper-oxide-based nanomaterials play an important role as a low-cost alternative to nanoparticles of precious metals for the catalytic reduction of 4-nitrophenols. In this study, CuO nanoparticles were synthesized by a microwave-assisted method using Cordia africana Lam. leaf extract for reduction or stabilization processes. The synthesized CuO nanoparticles (NPs) were characterized using X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The analysis indicated that nanocrystals of the monoclinic CuO phase having a cluster of agglomerated morphology with a crystallite size of about 9 nm were synthesized. We also evaluated the catalytic performance of CuO NPs against 4-nitrophenol (4-NP) reduction. The catalyst has shown excellent performance completing the reaction within 12 min. Furthermore, the performance of CuO NPs synthesized at different pH values was investigated, and results indicated that the one synthesized at pH 7 reduced 4-NP effectively in shorter minutes compared to those obtained at higher pH values. The CuO NPs synthesized using Cordia africana Lam. leaf extract exhibited a better reducing capacity with an activity parameter constant of 75.8 min−1·g−1. Thus, CuO synthesized using Cordia africana Lam. holds a potential application for the catalytic conversion of nitroarene compounds into aminoarene.

Valorisation of Fruits, their Juices and Residues into Valuable (Nano)materials for Applications in Chemical Catalysis and Environment

One of the most abundant wastes from all around the world is nutrient resources. Among them, fruits, their extracts, and residues comprise a major portion, which contain many valuable components that get lost during disposal or become burden on the shrinking landfills. These concerns are addressed by seeking sustainable processing methods that would have a minimal environmental impact. The crops contain renewable chemicals which are useful for catalysis, wastewater treatment, or preparation of nanomaterials; there has been an upsurge for the industrial applications of (nano)materials as their environmental and catalytic appliances is a fascinating subject to design cheaper and safer catalytic systems. Due to the excellent chemical properties of the fruit extracts, they have garnered attention as cost-effective catalysts and support materials. This review focuses on the preparation of (nano)materials and their catalytic and environmental applications and highlights the potential appliances and industrial benefits derived from these low-cost renewable and sustainable greener sources thus essentially converting waste into wealth.

A decennary update on applications of metal nanoparticles (MNPs) in the synthesis of nitrogen- and oxygen-containing heterocyclic scaffolds

Heterocycles have been found to be of much importance as several nitrogen- and oxygen-containing heterocycle compounds exist amongst the various USFDA-approved drugs. Because of the advancement of nanotechnology, nanocatalysis has found abundant applications in the synthesis of heterocyclic compounds. Numerous nanoparticles (NPs) have been utilized for several organic transformations, which led us to make dedicated efforts for the complete coverage of applications of metal nanoparticles (MNPs) in the synthesis of heterocyclic scaffolds reported from 2010 to 2019. Our emphasize during the coverage of catalyzed reactions of the various MNPs such as Ag, Au, Co, Cu, Fe, Ni, Pd, Pt, Rh, Ru, Si, Ti, and Zn has not only been on nanoparticles catalyzed synthetic transformations for the synthesis of heterocyclic scaffolds, but also provide an inherent framework for the reader to select a suitable catalytic system of interest for the synthesis of desired heterocyclic scaffold.

Green synthesis and characterization of copper nanoparticles using Piper retrofractum Vahl extract as bioreductor and capping agent

The copper nanoparticles (CuNPs) have attracted much attention due to their application in diverse fields. The applications of CuNPs depend on their physical and chemical properties. This study presents the first report for the use of medicinal fruit extract of Piper retrofractum Vahl as an eco-friendly reagent in the synthesis of CuNPs using copper sulfate as a starting material. Piper retrofractum Vahl extract was employed as a bioreductor as well as a capping agent in the formation of CuNPs. The reaction process was assisted by sonication and stirring. The influences of extract concentration, pH, temperature, and reaction time on the size of CuNPs were studied in detail. The morphology and structure of synthesized CuNPs were characterized by UV-Vis, FT-IR, SEM-EDS, TEM, and XRD. The UV-Vis measurement showed the surface plasmon resonance (SPR) peak at 234-255 nm, whereas FTIR characteristic peaks of metal-oxygen (Cu-O) were confirmed in the range 550-570 cm-1 and Cu-O-H bonds led to bending absorptions in the region 870-880 cm-1. The synthesized CuNPs possess the spherical shapes and high content of copper (70.3%) as confirmed by SEM-EDS. From the TEM micrograph, it can be seen that the particle size distribution of CuNPs has a high uniformity with a size of 2-10 nm under the optimum condition. The crystalline nature of CuNPs as confirmed by XRD showed the crystallinity phase of 26.4%. The synthesized CuNPs have relatively good stability and could inhibit Escherichia coli and Staphylococcus aureus. The results proved that Piper retrofractum Vahl fruit extract could be applied for a greener synthesis of CuNPs with high uniformity of particle sizes.

Green synthesis of copper oxide nanoparticles for biomedical application and environmental remediation

Recent development in nanoscience and nanotechnology has contributed to the wide applications of metal and metal oxides nanoparticles in several field of sciences, research institutes and industries. Among all metal oxides, copper oxide nanoparticles (CuONPs) has gained more attention due to its distinctive properties and applications. The high cost of reagents, equipment and environmental hazards associated with the physical and chemical methods of synthesizing CuONPs has been a major setback. In order to puffer solution to the aforementioned challenges by reducing environmental pollution and production of cheaper nanoparticles with good properties and efficiency, this review focus on collection of comprehensive information from recent developments in the synthesis, characterization and applications from previous scientific findings on biological method of synthesizing CuONPs due to the acclaimed advantages of been cheap, environmentally friendly, convenient and possibility of been scale up in into large scale production reported by numerous researchers. Our finding also support the synthesis of CuONPs from plant sources due to relative abundance of plants for the production of reducing and stabilizing agents required for CuONPs synthesis, potential efficiency of plant biomolecules in enhancing the toxicity effect of CuONPs against microbes, prevention of environmental pollution due of nontoxic chemicals and degradation effectiveness of CuONPs synthesized from plant sources. Furthermore, this study provide useful information on the rapid synthesis of CuONPs with desired properties from plant extracts.

Pd-based nanoparticles: Plant-assisted biosynthesis, characterization, mechanism, stability, catalytic and antimicrobial activities

Among various metal nanoparticles, palladium nanoparticles (Pd NPs) are one of the most important and fascinating nanomaterials. An important concern about the preparation of Pd NPs is the formation of toxic by-products, dangerous wastes and harmful pollutants. The best solution to exclude and/or minimize these toxic substances is plant mediated biosynthesis of Pd NPs. Biogenic Pd-based NPs from plant extracts have been identified as valuable nanocatalysts in various catalytic reactions because of their excellent activities and selectivity. They have captured the attention of researchers owing to their economical, sustainable, green and eco-friendly nature. This review attempts to cover the recent progresses in the fabrication, characterization and broad applications of biogenic Pd NPs in environmental and catalytic systems. In addition, the stability of biosynthesized Pd NPs and mechanism of their formation are investigated.

Green synthesis of copper oxide nanoparticles and mosquito larvicidal activity against dengue, zika and chikungunya causing vector Aedes aegypti

In the present study, high purity copper oxide nanoparticles (NPs) were synthesised using Tridax procumbens leaf extract. Green syntheses of nano-mosquitocides rely on plant compounds as reducing and stabilising agents. Copper oxide NPs were characterised using X-ray diffraction (XRD) analysis, Fourier transform infrared (FT-IR), Field-emission scanning electron microscopy with energy dispersive spectroscopy, Ultraviolet-visible spectrophotometry and fluorescence spectroscopy. XRD studies of the NPs indicate crystalline nature which was perfectly matching with a monoclinic structure of bulk CuO with an average crystallite size of 16 nm. Formation of copper oxide NPs was confirmed by FT-IR studies and photoluminescence spectra with emission peaks at 331, 411 and 433 nm were assigned to a near-band-edge emission band of CuO in the UV, violet and blue region. Gas chromatography-mass spectrometry studies inferred the phytochemical constituents of the leaf extract. Larvicidal activity of synthesised NPs using T. procumbens leaf extract was tested against Aedes aegypti species (dengue, chikungunya, zika and yellow fever transmit vector).

Cytotoxic, antioxidant and antibacterial activities of copper oxide incorporated chitosan-neem seed biocomposites

In this study biopolymer-inorganic material of chitosan‑copper oxide-neem seed (CS-CuO-NS) biocomposite was successfully synthesized by simple precipitation method and characterized by FT-IR, XRD, HR-SEM, TEM and TGA analyses. From HR-SEM and TEM analysis, CS-CuO-NS biocomposite shows flower and needle like structure respectively. The size of the as prepared CS-CuO-NS biocomposite is found to be 20-100 nm. All the synthesized materials were tested for antibacterial activity against both gram positive like Staphylococcus aureus (S. aureus) and Streptococcus pyogenes (S. pyogenes) and gram negative like Escherichia coli (E. coli) and Klebsiella aerogenes (K. aerogenes) bacterial strains. The maximum zone of inhibition is obtained for CS-CuO-NS biocomposite against S. aureus (23 mm), S. pyogenes (21 mm), E. coli (22 mm) and K. aerogenes (20 mm). The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were determined. The antioxidant activity was determined by free radicals scavenging such as 1, 1-Diphenyl-2-picryhydrazyl (DPPH) and 2, 2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). Furthermore, the cytotoxicity effect was investigated against human breast cancer (MCF-7) cell line and the highest cytotoxicity (IC₅₀:16.33 μg/mL) is found to be in biocomposite. From the results of antibacterial, antioxidant and cytotoxic activities, it is concluded that CS-CuO-NS biocomposite may be suitable for biomedical applications.

Low-temperature phyto-synthesis of copper oxide nanosheets: Its catalytic effect and application for colorimetric sensing

The last decade has seen a remarkable detonation in modifying chemical processes for nanomaterial synthesis to make them 'green'. Owing to the unique properties of nanomaterial and with regard to environmental issues, in this study, a new alternative and fast eco-friendly approach for the synthesis of copper oxide nanosheets (CuO-NSs) using Terminalia catappa (Indian almond) leaf extract as a renewable and non-toxic reducing agent and efficient stabilizer was reported. It is noteworthy to mention that the present fabrication process can open up the possibility of fast, low cost and high efficiency synthesis of CuO nanostructures with an interesting morphology of nanosheets at ambient temperature and pressure. Optimization of important factors such as pH, the quantity of leaf extract, copper precursor concentration, incubation time and temperature on the formation of CuO-NSs were investigated. The formation of bioreduced CuO-NSs was certified by UV-Vis spectroscopy, XRD, TEM analysis and FT-IR spectroscopy. Due to good stability, and excellent catalytic activity of the synthesized CuO-NSs, they are exerted to degrade of MB dye in water as a model color pollutant in the presence of NaBH₄ at room temperature. Furthermore, color properties of CuO nanostructures aid us to apply these biosynthesized nanomaterials in the design of optical sensors for detection of Fe²⁺ and Fe³⁺ ions. In view of many advantages of the current optical sensors based on CuO-NSs, such as eco-friendly, cost-effective, and straightforward design, the sensing system presents a potential application in environmental science.

Green synthesis of Au nanoparticles using an aqueous extract of Stachys lavandulifolia and their catalytic performance for alkyne/aldehyde/amine A3 coupling reactions

High reaction rate and easy availability make green synthesis of metal nanoparticles noticeable. In the present study, gold nanoparticles with wide applications in different fields were synthesized by an ecofriendly method at room temperature using Stachys lavandulifolia extract as the reducing agent. Properties of the synthesized gold nanoparticles (GNP) were identified by different analytical techniques including: UV-Vis absorption spectroscopy verified presence of Au NPs in the solution while functional groups of its extract and synthesized Au NPs were determined by FT-IR. Its crystalline analysis with a fcc plane was verified by X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) determined elements in the sample. Surface morphology, diverse shapes and sizes of the Au NPs were shown by scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). Beginning and end destruction temperatures of the Au/S. lavandulifolia NPs were determined by thermal gravimetric analysis (TGA). The Au nanoparticles were capped with extracts, preventing them from oxidation and agglomeration and were used as an efficient heterogeneous nanocatalyst for a three-component reaction of amines, aldehydes, and alkynes (A3 coupling). A diverse range of propargylamines were obtained in good yields. Furthermore, the separation and recycling of Au/S. lavandulifolia NPs was very simple, effective, and economical.

Biosynthesis of Copper Oxide (CuO) Nanowires and Their Use for the Electrochemical Sensing of Dopamine

A facile one-step, eco-friendly, and cost-effective approach for the formation of copper oxide (CuO) nanowires by a green method using saponin-rich Sapindus mukorossi fruit extract (SMFE). The physio-chemical characteristics of the synthesized CuO nanowires have been characterized by X-ray Diffractometry (XRD), X-ray Photoelectron Spectroscopy (XPS), FT-IR (Fourier Transform Infrared Spectroscopy, FE-SEM (Scanning Electron Microscopy), and High-Resolution Transmission Electron Microscopy (HR-TEM). Further, the electrocatalytic activity of the CuO nanowires synthesized with SMFE has been investigated, and they have been used as dopamine (DA) sensors. Because of their unique properties, the CuO nanowires/GCE exhibited remarkable electrochemical response for the detection of DA with enhanced current response. The anodic current demonstrated that the CuO nanowires/GCE linearly detects the concentration of DA over the range of 0.1 µM to 0.105 mM of DA with a regression co-efficient of 0.9960. The obtained results illustrated that the synthesized CuO nanowires can easily stimulate the electron transfer reaction between DA and the nanowires modified electrode with the improvement of the conductivity and stability of the electrode. This remarkable electrocatalytic property of CuO nanowires makes it a unique electrochemical sensor for the detection of DA. Furthermore, the sensor is free from the interference of ascorbic acid, uric acid, and other interfering species. Moreover, the anti-interference performance also showed that the CuO nanowires/GCE could be employed for the determination of DA in real samples with good selectivity and sensitivity.