Current insights into the green synthesis, in planta characterization and phytoeffects of nickel nanoparticles and their agricultural implications

The intensifying production and release into the environment as well as the increasing potential in agricultural applications make the relationship between plants and nickel nanoparticles (Ni NPs) a relevant and timely topic. The aim of this review is to give an overview and discuss the latest findings about the relationship of Ni NPs and plants. Ni NPs can be synthesized using phytochemicals derived from plant parts in an environmentally friendly manner. There are several ways for these nanoparticles to enter plant cells and tissues. This can be demonstrated through various imaging and chemical mapping approaches (e.g., transmission electron microscopy, X-ray fluorescence spectroscopy etc.). NiO NPs affect plants at multiple levels, including subcellular, cellular, tissue, organ, and whole-plant levels. However, the effects of Ni NPs on plants' ecological partners (e.g., rhizobiome, pollinators) remain largely unknown despite their ecotoxicological significance. The main cause of the Ni NPs-triggered damages is the reactive oxygen species imbalance as a consequence of the modulation of antioxidants. In non-tolerant plants, the toxicity of NiO NPs can be mitigated by exogenous treatments such as the application of silicon, salicylic acid, or jasmonic acid, which induce defense mechanisms whereas Ni-hypertolerant plant species possess endogenous defense systems, such as cell wall modifications and nitrosative signaling against NiO NP stress. Research highlights the role of Ni NPs in managing fungal diseases, showcasing their antifungal properties against specific pathogens. Due to the essentiality of Ni, the application of Ni NPs as nanofertilizers might be promising and has recently started to come into view.

Biologically Derived Gold Nanoparticles and Their Applications

Nanotechnology is a rapidly evolving discipline as it has a wide variety of applications in several fields. They have been synthesized in a variety of ways. Traditional processes such as chemical and physical synthesis have limits, whether in the form of chemical contamination during synthesis operations or in subsequent applications and usage of more energy. Over the last decade, research has focused on establishing easy, nontoxic, clean, cost-effective, and environmentally friendly techniques for nanoparticle production. To achieve this goal, biological synthesis was created to close this gap. Biosynthesis of nanoparticles is a one-step process, and it is ecofriendly in nature. The metabolic activities of biological agents convert dissolved metal ions into nanometals. For biosynthesis of metal nanoparticles, various biological agents like plants, fungus, and bacteria are utilized. In this review paper, the aim is to provide a summary of contemporary research on the biosynthesis of gold nanoparticles and their applications in various domains have been discussed.

Recent advances on botanical biosynthesis of nanoparticles for catalytic, water treatment and agricultural applications: A review

Green synthesis of nanoparticles using plant extracts minimizes the usage of toxic chemicals or energy. Here, we concentrate on the green synthesis of nanoparticles using natural compounds from plant extracts and their applications in catalysis, water treatment and agriculture. Polyphenols, flavonoid, rutin, quercetin, myricetin, kaempferol, coumarin, and gallic acid in the plant extracts engage in the reduction and stabilization of green nanoparticles. Ten types of nanoparticles involving Ag, Au, Cu, Pt, CuO, ZnO, MgO, TiO₂, Fe₃O₄, and ZrO₂ with emphasis on their formation mechanism are illuminated. We find that green nanoparticles serve as excellent, and recyclable catalysts for reduction of nitrophenols and synthesis of organic compounds with high yields of 83-100% and at least 5 recycles. Many emerging pollutants such as synthetic dyes, antibiotics, heavy metal and oils are effectively mitigated (90-100%) using green nanoparticles. In agriculture, green nanoparticles efficiently immobilize toxic compounds in soil. They are also sufficient nanopesticides to kill harmful larvae, and nanoinsecticides against dangerous vectors of pathogens. As potential nanofertilizers and nanoagrochemicals, green nanoparticles will open a revolution in green agriculture for sustainable development.

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.

Green Synthesis of Gold Nanoparticles Using Polianthes tuberosa L. Floral Extract

The developments of green-based metallic nanoparticles (gold) are gaining tremendous interest, having potential applications in health care and diagnosis. Therefore, in the present study, Polianthes tuberosa flower filtered extract was used as a reducing and stabilizing agent to synthesize gold nanoparticles (PtubAuNPs). The PtubAuNPs were extensively characterized by UV-visible spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, and X-ray diffraction. The antibacterial activity of PtubAuNPs was determined by the agar well diffusion method; the PtubAuNPs performed extreme antagonistic activity against the tested pathogens. Furthermore, the cytotoxicity of the PtubAuNPs was evaluated in MCF 7 cells by MTT assay. The PtubAuNPs induced toxicity in MCF 7 cells with the least concentration of 100 µg/mL in a dose-dependent method by inducing apoptosis. Overall, the study manifested that PtubAuNPs are a potent nanomaterial that can be employed as an antimicrobial and anticancer agent.

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.

A review of plant metabolites with metal interaction capacity: a green approach for industrial applications

Rapid industrial development is responsible for severe problems related to environmental pollution. Many human and industrial activities require different metals and, as a result, great amounts of metals/heavy metals are discharged into the water and soil making them dangerous for both human and ecosystems and this is being aggravated by intensive demand and utilization. In addition, compounds with metal binding capacities are needed to be used for several purposes including in activities related to the removal and/or recovery of metals from effluents and soils, as metals' corrosion inhibitors, in the synthesis of metallic nanoparticles and as metal related pharmaceuticals, preferably a with minimum risks associated to the environment. Plants are able to synthesize an uncountable number of compounds with numerous functions, including compounds with metal binding capabilities. In fact, some of the plants' secondary metabolites can bind to various metals through different mechanisms, as such they are excellent sources of such compounds due to their high availability and vast diversity. In addition, the use of plant-based compounds is desirable from an environmental and economical point of view, thus being potential candidates for utilization in different industrial activities, replacing conventional physiochemical methods. This review focuses on the ability of some classes of compounds that can be found in relatively high concentrations in plants, having good metal binding capacities and thus with potential utilization in metal based industrial activities and that can be involved in the progressive development of new environmentally friendly strategies.

Lignin, lipid, protein, hyaluronic acid, starch, cellulose, gum, pectin, alginate and chitosan-based nanomaterials for cancer nanotherapy: Challenges and opportunities

Although nanotechnology-driven drug delivery systems are relatively new, they are rapidly evolving since the nanomaterials are deployed as effective means of diagnosis and delivery of assorted therapeutic agents to targeted intracellular sites in a controlled release manner. Nanomedicine and nanoparticulate drug delivery systems are rapidly developing as they play crucial roles in the development of therapeutic strategies for various types of cancer and malignancy. Nevertheless, high costs, associated toxicity and production of complexities are some of the critical barriers for their applications. Green nanomedicines have continually been improved as one of the viable approaches towards tumor drug delivery, thus making a notable impact on which considerably affect cancer treatment. In this regard, the utilization of natural and renewable feedstocks as a starting point for the fabrication of nanosystems can considerably contribute to the development of green nanomedicines. Nanostructures and biopolymers derived from natural and biorenewable resources such as proteins, lipids, lignin, hyaluronic acid, starch, cellulose, gum, pectin, alginate, and chitosan play vital roles in the development of cancer nanotherapy, imaging and management. This review uncovers recent investigations on diverse nanoarchitectures fabricated from natural and renewable feedstocks for the controlled/sustained and targeted drug/gene delivery systems against cancers including an outlook on some of the scientific challenges and opportunities in this field. Various important natural biopolymers and nanomaterials for cancer nanotherapy are covered and the scientific challenges and opportunities in this field are reviewed.

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.

Biradical o-iminobenzosemiquinonato(1-) complexes of nickel(ii): catalytic activity in three-component coupling of aldehydes, amines and alkynes

The six-coordinated bis-o-iminosemiquinone complex, NiL2 BIS, in which LBIS is the o-iminosemiquinone 1-electron oxidized form of the tridentate o-aminophenol benzoxazole-based ligand H2LBAP, was synthesized and characterized. The crystal structure of the complex reveals octahedral geometry with a NiN4O2 coordination sphere in which Ni(ii) has been surrounded by two tridentate LBIS ligands. This compound exhibits (S Ni = 1) with both spin and orbital contribution to the magnetic moment and antiferromagnetic coupling between two electrons on two LBIS ligands which results in a triplet spin ground state (S = 1). The electronic transitions and the electrochemical behavior of this open-shell molecule are presented here, based on experimental observations and theoretical calculations. The electrochemical behavior of NiL2 BIS was investigated by cyclic voltammetry and indicates ligand-centered redox processes. Three-component coupling of aldehydes, amines and alkynes (A3-coupling) was studied in the presence of the NiL2 BIS complex, and the previously reported four-coordinated bis-o-iminosemiquinone NiL2 NIS. Furthermore, among these two o-iminobenzosemiquinonato(1-) complexes of Ni(ii) (NiL2 NIS and NiL2 BIS), NiL2 NIS was found to be an efficient catalyst in A3-coupling at 85 °C under solvent-free conditions and can be recovered and reused for several cycles with a small decrease in activity.

The first PdO nanoparticle catalyzed one pot synthesis of propargylamine through A3-coupling of an aldehyde, alkyne and amine

Palladium(ii) oxide (PdO) nanoparticles (Nps) were prepared by an environmentally benign hydrothermal method with a new capping agent quercetin.

Phytosynthesized nanoparticles as a potential cancer therapeutic agent

Plants are the well-known sources for the hyper-accumulation and reduction of metallic ions. Analysis of various plant extracts has justified the presence of different types of phytochemicals that possess the stabilization and reduction functionalities of precursors to form nanoparticles. Such characteristics make plants as an attractive source for synthesizing eco-friendly nanoparticles (NPs) with potentially less toxicity to the body. Recently, phytosynthesized nanoparticles have been explored for targeted inhibition and diagnosis of cancer cells without affecting non-cancerous healthy cells. The aim of this review is to discuss the characteristic performance of NPs synthesized from various plant sources for the diagnosis and inhibition of cancer. The mode of action of phytosynthesized nanoparticles for anti-cancer applications are also discussed.

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.

Green synthesis of copper nanoparticles using Celastrus paniculatus Willd. leaf extract and their photocatalytic and antifungal properties

This research aimed to explore the eco-friendly green synthesis of copper nanoparticles (CuNPs) using Celastrus paniculatus leaves extract. Primarily, the biosynthesized CuNPs characterized by UV-vis spectroscopy showed an absorption peak at 269 nm. Further, The SEM and TEM studies revealed the spherical shape of particles with size ranged between 2-10 nm with an average particle diameter of 5 nm. FT-IR analysis confirmed the presence of functional groups -OH, C[bond, double bond]C and C-H triggers the synthesis of CuNPs. The negative zeta potential -22.2 mV indicated the stability of CuNPs was confirmed by DLS and the composition and purity by EDS studies. Further, the photocatalytic property of the CuNPs was divulged by their methylene blue dye degradation potential. The reaction kinetics followed pseudo-first-order with k-values (rate constant) 0.0172 min-1. In addition, this material was found to be a good antifungal agent against plant pathogenic fungi Fusarium oxysporum showed 76.29 ± 1.52 maximum mycelial inhibition.

Green and cost-effective synthesis of copper nanoparticles by extracts of non-edible and waste plant materials from Vaccinium species: Characterization and antimicrobial activity

The aim of this work was the green synthesis of copper nanoparticles (Cu-NPs) using aqueous extracts of (i) bilberry (Vaccinium myrtillus L.) waste residues from the production of fruit juices and (ii) non-edible "false bilberry" fruits (Vaccinium uliginosum L. subsp. gaultherioides). Different cupric salts (CuCl₂, Cu(CH₃COO)₂ and Cu(NO₃)₂) were used for the synthesis. The formation of stable nanoparticles (CuNPs) was assessed by transmission electron microscopy and the oxidation state of copper in these aggregates was followed by X-ray photoelectron spectroscopy. The polyphenol composition of the extracts was characterized, before and after the synthesis, using spectrophotometric methods (i.e. total soluble polyphenols and total monomeric anthocyanins) and high-performance liquid chromatography coupled with tandem mass spectrometry (i.e. individual anthocyanins). Polyphenol concentration in the extracts was found to decrease after the synthesis, indicating their active participation to the processes, which led to the formation of Cu-NPs. The antimicrobial activity of Cu-NPs, berry extracts, and cupric ion solutions were analysed by broth microdilution and time-kill assays, on prokaryotic and eukaryotic models. The antimicrobial activity of Cu-NPs, especially those derived from bilberry waste residues, appeared to be higher for both Gram-negative and Gram-positive bacteria, and for fungi, compared to the ones of its single components (cupric salts and berry extracts). Therefore, Cu-NPs from the green synthesis here proposed can be considered as a cost-effective sanitization tool with a wide spectrum of action.

Gold nanoparticles stabilized by PEG-tagged imidazolium salts as recyclable catalysts for the synthesis of propargylamines and the cycloisomerization of γ-alkynoic acids

Water-soluble gold nanoparticles prepared in the presence of PEG-tagged tris-imidazolium bromide, containing Au(0) and Au(i) species, are reusable catalysts.

Plant-based gold nanoparticles; a comprehensive review of the decade-long research on synthesis, mechanistic aspects and diverse applications

The worldwide focus on research in the field of green nanotechnology has resulted in the environmentally and biologically safe applications of a diversity of nanomaterials. Nanotechnology, in general, implies the production of nanoparticles having different but regular shapes, sizes, and properties. A lot of studies have been conducted on the synthesis of metal nanoparticles through biological, chemical, and physical methods. Owing to its safety, both environmental and in vivo, as well as the ease of synthesis, biogenic routes especially the plant-based synthesis of metal nanoparticles has been preferred as the best strategy. Among the metal nanoparticles, gold nanoparticles are recognized as the most potent, biocompatible and environment-friendly. A decade of research work has attempted the production of gold nanoparticles mediated by different parts of various plants. Further, these nanoparticles have been engineered through modification in the sizes and shapes for attaining enhanced activity and optimal performance in many different applications including biomedical, antimicrobial, diagnostics and environmental applications. This article reviews the fabrication strategies for gold nanoparticles via plant-based routes and highlights the diversity of the applications of these materials in bio-nanotechnology. The review article also highlights the recent developments in the synthesis and optical properties of gold nanoparticles.

Metal nanoparticles fabricated by green chemistry using natural extracts: biosynthesis, mechanisms, and applications

Nanoparticles (NPs) are new inspiring clinical targets that have emerged from persistent efforts with unique properties and diverse applications. However, the main methods currently utilized in their production are not environmentally friendly. With the aim of promoting a green approach for the synthesis of NPs, this review describes eco-friendly methods for the preparation of biogenic NPs and the known mechanisms for their biosynthesis. Natural plant extracts contain many different secondary metabolites and biomolecules, including flavonoids, alkaloids, terpenoids, phenolic compounds and enzymes. Secondary metabolites can enable the reduction of metal ions to NPs in eco-friendly one-step synthetic processes. Moreover, the green synthesis of NPs using plant extracts often obviates the need for stabilizing and capping agents and yields biologically active shape- and size-dependent products. Herein, we review the formation of metallic NPs induced by natural extracts and list the plant extracts used in the synthesis of NPs. In addition, the use of bacterial and fungal extracts in the synthesis of NPs is highlighted, and the parameters that influence the rate of particle production, size, and morphology are discussed. Finally, the importance and uniqueness of NP-based products are illustrated, and their commercial applications in various fields are briefly featured.

Ficus retusa-stabilized gold and silver nanoparticles: Controlled synthesis, spectroscopic characterization, and sensing properties

Ficus retusa was used as reducing and stabilizing agent in the green synthesis of silver and gold nanoparticles with high dispersion stability and controllable size and shape. The controlling of reaction conditions i.e. contact time, extract quantity, metal concentration, and pH value enables the tuning of the particle size and size distribution of the metal nanoparticles. UV-visible spectroscopy was used to follow the spectral profile changes of the surface plasmon resonance of the metal nanoparticles due to different treatments. The surface plasmon resonance varies between 400 and 432 nm and between 522 and 554 nm for silver and gold nanoparticles, respectively, depending on the different reaction parameters. Atomic force and transmission electron microscopy results confirmed the success of preparation of spherical silver (15 nm) and gold (10-25 nm) nanoparticles with narrow size-distribution. Fourier transform infrared spectroscopy suggested the phenolic compounds play the key role in the reduction and stabilizing of metal ions. The colorimetric sensitivity of silver and gold nanoparticles to detect the presence of heavy metals in water was studied.

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.

Copper(i)/succinic acid cooperatively catalyzed one-pot synthesis of organoselenium-propargylamines via A3-coupling

Selenium propargylamines were synthesized via an A³-coupling approach using piperidine, p-methoxybenzaldehyde, and trimethylsilyl selenium–acetylene, catalyzed by copper(i) chloride and succinic acid as an additive, in good to excellent yields.

Synthesis paradigm and applications of silver nanoparticles (AgNPs), a review

Nanoscience is an inspiring and influential discipline of science which have accessible numerous novel and cost-effective yields and applications. Currently, nanotechnology research has been empowering more in agricultural sector, food process and medicinal industries. The surface area to volume ratio of nanoparticles is quite large which have 1–100 nm size. Nanomaterials have superior bioavailability than larger particles, resulting in greater utilization in single cells, tissues and organs. Referable to the growing demand of nanoparticles, it is essential to build up synthetic method which is profitable, environmentally sustainable and which can substitutes with effective and competent technology to synthesis environmentally benign nanoparticles (NPs). Nanomaterials are “deliberately engineered” to direct the enhancement of special properties at the nanoscale. Nanoparticles have been known to be used for abundant physical, biological, and pharmaceutical applications. Nano-silver is the most studied and utilized nanoparticle. Silver nanoparticles (AgNPs) have been the topics of researchers because of their unique properties. Thus, this review presents various synthesis methods of AgNPs and its application in different sectors.

Enhancing reducing ability of α-zein by fibrillation for synthesis of Au nanocrystals with continuous flow catalysis

Green low-cost synthesis and efficient recyclability are two major hindrances for Au nanocrystals as catalysts applying in diverse industrial reaction processes. By the use of low-cost α-zein (i.e. a major storage protein of corn) as the reductant, capping agent and stabilizer, Au nanocrystals with tunable catalytic activity were synthesized in a wet-chemical approach. Fibrillation of α-zein further enhanced its reducing ability due to larger specific surface area and more hydrophilic groups exposed on the surfaces. The obtained Au nanocrystals had biocompatibility, high stability in various solvents, unique solubility in aqueous alcohol and high catalytic ability, being able to detect ethanol composition in aqueous ethanol as well as H₂O₂ for diagnosis of diabetes mellitus. These advantages also enable efficient recyclability of Au nanocrystals with continuous flow catalysis in different solvents and environments. Thus, the use of α-zein offered Au nanocrystals not only with green low-cost synthesis, but also with tunable catalytic activities, ethanol-responsiveness and efficient recyclability, which may be applicable in diverse fields.