Barbated Skullcup herb extract-mediated biosynthesis of gold nanoparticles and its primary application in electrochemistry

Efficient removal of environmental pollutants by green synthesized metal nanoparticles of Clitoriaternatea

Prevention and management of water pollution are becoming a great challenge in the present scenario. Different conventional methods like carbon adsorption, ion exchange, chemical precipitation, evaporation, and biological treatments remove water pollutants. Nowadays, the requirement for effective, non-toxic and safe waste management strategies is very high. Nanomaterials have been explored in various fields due to their unique characteristics. Green synthesis of nanomaterial is becoming more popular due to their safety, non-toxicity, and ease of scale-up technology. Metal nanoparticles can be synthesized using a green synthesis method using biological sources provided by eco-friendly, non-hazardous nanomaterials with superior properties to bulk metals. Hence, this study has designed a green synthesis of magnetic (cobalt oxide) and noble (gold) nanoparticles from the fresh flowers of Clitoria ternatea. The flavonoids and polyphenols in the extract decreased the energy band gap of cobalt oxide and gold nanoparticles; hence, the capping of the natural constituents in Clitoria ternatea helped form stable metal nanoparticles. The cobalt oxide and gold nanoparticles are evaluated for their potential for eliminating organic pollutants from industrial effluent. The novelty of this present work represents the application of cobalt oxide nanoparticles in the removal of organic pollutants and a comparative study of the catalytic behaviour of both metal nanoparticles. The degradation of bromophenol blue, bromocresol green, and 4-nitrophenol in the presence of gold nanoparticles was completed in 120, 45, and 20 min with rate constants of 3.7 × 10-3/min, 6.9 × 10-3/min, and 16.5 × 10-3/min, respectively. Similarly, the photocatalysis of bromophenol blue, bromocresol green, and 4-nitrophenol in the presence of cobalt oxide nanoparticles was achieved in 60, 90, and 40 min with rate constants of 2.3 × 10-3/min, 1.8 × 10-3/min, and 1.7 × 10-3/min, respectively. The coefficient of correlation (R2) values justify that the degradation of organic pollutants follows first-order kinetics. The significance of the study is to develop green nanomaterials that can be used efficiently to remove organic pollutants in wastewater using a cost-effective method with minimal toxicity to aquatic animals. It has proved to be useful in environmental pollution management.

Collision of herbal medicine and nanotechnology: a bibliometric analysis of herbal nanoparticles from 2004 to 2023

BACKGROUND

Herbal nanoparticles are made from natural herbs/medicinal plants, their extracts, or a combination with other nanoparticle carriers. Compared to traditional herbs, herbal nanoparticles lead to improved bioavailability, enhanced stability, and reduced toxicity. Previous research indicates that herbal medicine nanomaterials are rapidly advancing and making significant progress; however, bibliometric analysis and knowledge mapping for herbal nanoparticles are currently lacking. We performed a bibliometric analysis by retrieving publications related to herbal nanoparticles from the Web of Science Core Collection (WoSCC) database spanning from 2004 to 2023. Data processing was performed using the R package Bibliometrix, VOSviewers, and CiteSpace.

RESULTS

In total, 1876 articles related to herbal nanoparticles were identified, originating from various countries, with China being the primary contributing country. The number of publications in this field increases annually. Beijing University of Chinese Medicine, Shanghai University of Traditional Chinese Medicine, and Saveetha University in India are prominent research institutions in this domain. The Journal "International Journal of Nanomedicine" has the highest number of publications. The number of authors of these publications reached 8234, with Yan Zhao, Yue Zhang, and Huihua Qu being the most prolific authors and Yan Zhao being the most frequently cited author. "Traditional Chinese medicine," "drug delivery," and "green synthesis" are the main research focal points. Themes such as "green synthesis," "curcumin," "wound healing," "drug delivery," and "carbon dots" may represent emerging research areas.

CONCLUSIONS

Our study findings assist in identifying the latest research frontiers and hot topics, providing valuable references for scholars investigating the role of nanotechnology in herbal medicine.

Green Synthesis, Characterization and Bioactivity of Mangifera indica Seed-Wrapped Zinc Oxide Nanoparticles

In the realm of nanoparticles, metal-based nanoparticles have traditionally been regarded as the pioneering category. Compared to other nanoparticles, zinc oxide nanoparticles have several advantages, including optical and biological properties, which provide them a significant competitive advantage in clinical and biological applications. In the current investigation, we used an aqueous Mangifera indica seed extract to synthesize nanoparticles of zinc oxide (ZnO NPs). UV-Vis spectroscopy, Fourier transform infrared spectroscopy analysis, atomic force spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to characterize the synthesized ZnO NPs. The nanoparticles were assessed for their potential to inhibit bacterial growth and protect cells from free radical damage. According to the current study's findings, zinc oxide nanoparticles that had been modified with the aid of mango seeds were very efficient in preventing the development of the tested bacteria and were also powerful antioxidants.

Photocatalysis of environmental organic pollutants and antioxidant activity of flavonoid conjugated gold nanoparticles

The unique properties of nanomaterials have the potential application in different fields of biomedical application along with the management of environmental pollutants. This research work involved the isolation of hesperidin from the orange peel and the preparation of hesperidin gold nanoparticles by the chemical reduction method. The high substrate specificity and lower band gap enable the excitation of gold nanoparticles in visible light. Hence gold nanoparticles are chosen nowadays for the management and removal of organic pollutants. The efficacy of hesperidin gold nanoparticles was evaluated by the photocatalytic activity on organic dyes and pollutants like methyl orange, methylene blue, bromocresol green, and 4 - nitro phenol with sodium borohydride as reducing agent and the antioxidant study by scavenging of free radicals of DPPH, ABTS, and hydroxyl free radicals of hydrogen peroxide. The kinetics of photocatalytic degradation of organic dyes and 4 - nitro phenol was found to follow the first order with rate constants of 10 × 10^-3, 37 × 10^-3, 23 × 10^-3 and 49 × 10^-3 min^-1 for methyl orange, methylene blue, bromocresol green and 4 - nitro phenol respectively. The hesperidin gold nanoparticles showed significant antioxidant activity as compared to ascorbic acid as standard. The flavonoid conjugated gold nanoparticles can be an efficient antioxidant and photocatalyst for the management of different diseases and wastewater treatment respectively.

Sonochemical-Assisted Biogenic Synthesis of Theophrasite β-Ni(OH)2 Nanocluster Using Chia Seeds Extract: Characterization and Anticancer Activity

Theophrasite β-Ni(OH)₂ nanocluster were fabricated via the sonochemical-assisted biogenic method using chia seeds extract as a reducing and stabilizing agent. The optical and morphological feature of the synthesized nanocluster was characterized using UV-Vis, FTIR, FE-SEM-EDS, HR-TEM, DLS, XPS, and XRD analysis. According to FE-SEM and HR-TEM images of the synthesized materials, β-Ni(OH)₂ nanocluster illustrates the hexagonal particle shape with an average size of 5.8 nm, while the EDS results confirm the high purity of the synthesized nanocluster. Moreover, the XRD pattern of the synthesized materials shows typical peaks that match the reference pattern of the Theophrasite form of β-Ni(OH)₂ with a hexagonal crystal system. The XPS analysis illustrates that the prepared samples exhibit both Ni²⁺ and Ni³⁺ with the predominance of Ni²⁺ species. Additionally the in-vitro cytotoxic activity of β-Ni(OH)₂ nanocluster is tested against the MCF7 cell lines (breast cancer cells). The MTT assay results proved that the synthesized β-Ni(OH)₂ nanocluster has potent cytotoxic activity against breast cancer cell lines (IC₅₀: 62.7 μg/mL).

Biomedical Applications of Chinese Herb-Synthesized Silver Nanoparticles by Phytonanotechnology

Recent advances in nanotechnology have opened up new avenues for the controlled synthesis of nanoparticles for biomedical and pharmaceutical applications. Chinese herbal medicine is a natural gift to humanity, and it has long been used as an antibacterial and anticancer agent. This study will highlight recent developments in the phytonanotechnological synthesis of Chinese herbal medicines to utilize their bioactive components in biomedical and therapeutic applications. Biologically synthesized silver nanoparticles (AgNPs) have emerged as a promising alternative to chemical and physical approaches for various biomedical applications. The comprehensive rationale of combinational or synergistic effects of Chinese herb-based AgNPs synthesis was investigated with superior physicochemical and biological properties, and their biomedical applications, including antimicrobial and anticancer activity and wound healing properties. AgNPs can damage the cell ultrastructure by triggering apoptosis, which includes the formation of reactive oxygen species (ROS), DNA disintegration, protein inactivation, and the regulation of various signaling pathways. However, the anticancer mechanism of Chinese herbal medicine-based AgNPs is more complicated due to the potential toxicity of AgNPs. Further in-depth studies are required to address Chinese herbs' various bioactive components and AgNPs as a synergistic approach to combat antimicrobial resistance, therapeutic efficiency of drug delivery, and control and prevention of newly emerged diseases.

Understanding and advancement in gold nanoparticle targeted photothermal therapy of cancer

The present communication summarizes the importance, understanding and advancement in the photothermal therapy of cancer using gold nanoparticles. Photothermal therapy was used earlier as a single line therapy, but using a combination of photothermal therapy with other therapies like immunotherapy, chemotherapy, photodynamic therapy; efficient therapy management can be achieved. As it was discussed in many studies that gold nanoparticles are treated as idyllic photothermal transducers due to their structural dimensions, which enables them to strongly absorb near infrared light. Gold nanoparticles which are mediated for photothermal therapy can warn cancer cells to chemotherapy, regulate genes and immunotherapy by enhancing the cell permeability and intracellular delivery. The necrosis process and apoptosis depend on the power of laser and temperature within the cancerous tissues which are reached during irradiation. Cells death mechanism is also important because the cells which died through the process of necrosis can endorse secondary tumor growth while the cells which died through apoptosis may provoke the immune response to inhibit the development of secondary tumor growth. To decrease the in vivo barriers, gold nanostructures are again modified with targeting ligand and bio-responsive linker. The manuscript summarizes that the use of gold nanoparticles is capable of inhibiting the growth of cancerous cells by using photothermal therapy which has lesser adverse effects compared to other line therapies.

Green synthesis of silver nanoparticles using pollen extract: Characterization, assessment of their electrochemical and antioxidant activities

In the present study, a simple, cheaply and environmental friendly method was evaluated for the synthesis of silver nanoparticle via Cupressus sempervirens L. (CSPE) pollen extract as reducing and stabilizing agent. Various parameters such as volume of CSPE, temperature and reaction time on AgNPs formation were investigated spectrophotometrically to optimize reaction conditions. The electrochemical behavior of the biosynthesized AgNPs were investigated by cyclic voltammetry and square wave voltammetry techniques. An electrosensor based on AgNPs modified glassy carbon electrode were constructed and tested on electro reduction of hydrogen peroxide in phosphate buffer medium. The prepared electrosensor could detect the H₂O₂ in the range of 5.0 μM - 2.5 mM with a detection limit of 0.23 μM. In addition, the antioxidant activity of biosynthesized AgNPs were evaluated against DPPH free radical. Results obtained from the antioxidant study suggested that CSPE mediated AgNPs exhibit a good antioxidant effect.

Ammonia-controlled synthesis of monodispersed N-doped carbon nanoparticles

The presence of ammonia slowing down the acid-catalysed Schiff base formation as well as control the monodispersity through the separation of nucleation and growth stages.

A Review of Bark-Extract-Mediated Green Synthesis of Metallic Nanoparticles and Their Applications

Nanoparticles are intensely studied because of their importance in diverse fields of biotechnology, especially in medicine. This paper highlights that waste bark can be a cheap source of biocompounds, with high recovery and functionalization potential in nanoparticle synthesis. Due to their biocompatibility and activity as antioxidant, antimicrobial, and anticancer agents, the green synthesis of metallic nanoparticles is of great importance. This review aims to bring together the diversity of synthesized metallic nanoparticles mediated by bark extracts obtained from different woody vascular plants, the phytoconstituents responsible for the reduction of metal salts, and the activity of metallic nanoparticles as diverse agents in combating the microbial, oxidant, and cancer activity. The literature data highlight the fact that metallic nanoparticles obtained from natural compounds are proven reducing agents with multiple activities. Thus, the activity of natural components in environmental protection and human health is confirmed.

Batch process biosynthesis of silver nanoparticles using Equisetum arvense leaf extract

The plant extract of Equisetum arvense is applied to reduce silver ions to silver nanoparticles (AgNPs) in the batch method. When mixed with silver nitrate (AgNO3), the extract changed color from yellow to dark brown, and AgNPs were synthesized in 24 h. Plant extracts applied to synthetize metal NPs, provide a simple and eco-friendly approach and the biomolecules are used as reducing and capping agents. The nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy, ultraviolet spectroscopy and X-ray diffraction (XRD) analyses. The dark brown solution showed a surface plasmon resonance of AgNPs around 448 nm. The XRD pattern showed the crystalline nature and high purity of AgNPs. Fourier transform infrared spectroscopy was employed to measure particular functional groups that reduce silver nitrate as AgNPs are formed. TEM revealed that the size of AgNPs was around 18–20 nm. Antibacterial activity assays with Escherichia coli and Staphylococcus aureus demonstrated that AgNPs reduced bacterial growth and produced well-defined inhibition zones.

Green synthesis of gold nanoparticles using Citrus maxima peel extract and their catalytic/antibacterial activities

The peel of Citrus maxima (C. maxima) is the primary byproducts during the process of fruit or juice in food industries, and it was always considered as biomass waste for further treatments. In this study, the authors reported a simple and eco-friendly method to synthesise gold nanoparticles (AuNPs) using C. maxima peel extract as reducing and capping agents. The synthesised AuNPs were characterised by UV-visible spectrum, X-ray diffraction (XRD), transmission electron microscope (TEM) and Fourier-transform infrared spectroscopy (FTIR). The UV-visible spectrum of the AuNPs colloid showed a characteristic peak at 540 nm. The peaks of XRD analysis at (2θ) 38.30°, 44.28°, 64.62°, 77.57° and 81.75° were assigned to (111), (200), (220), (311) and (222) planes of the face-centered cubic (fcc) lattice of gold. The TEM images showed that AuNPs were nearly spherical in shape with the size of 8-25 nm. The FTIR spectrum revealed that some bioactive compounds capped the surface of synthesised AuNPs. The biosynthesised AuNPs performed strong catalytic activity in degradation of 4-nitrophenol to 4-aminophenol and good antibacterial activity against both gram negative (Escherichia coli) and gram positive (Staphylococcus aureus) bacterium. The synthesis procedure was proved simple, cost effective and environment friendly.

Green synthesis of anisotropic gold nanoparticles using hordenine and their antibiofilm efficacy against Pseudomonas aeruginosa

Pseudomonas aeruginosa is a notorious pathogen that causes biofilm aided infections in patients with cystic fibrosis and burn wounds, resulting in significant mortality in immunocompromised individuals. This study reports a novel one-step biosynthesis of gold nanoparticles using phytocompound, hordenine (HD), as a reducing and capping agent. The synthesis of the anisotropic hordenine-fabricated gold nanoparticles (HD-AuNPs) with an average particle size of 136.87 nm was achieved within 12 h of incubation at room temperature. Both HD and HD-AuNPs exhibited significant antibiofilm activity against P. aeruginosa PAO1, although greater biofilm inhibition was observed for the nanoparticles as compared to hordenine alone. In the microtitre plate assay and tube method, the nanoparticles significantly inhibited the biofilm formation by 73.69 and 78.41%, respectively. The exopolysaccharide production by the test pathogen was arrested by 68.46% on treatment with the nanoparticles. Further, the effect of HD and HD-AuNPs on the biofilm architecture of P. aeruginosa was revealed by light and confocal laser-scanning microscopy micrographs. The overall results of this study suggested the synergistic antibiofilm effect of AuNPs and HD for the treatment of chronic bacterial infections caused by biofilms forming pathogens.

Green gold nanoparticles from plant-derived materials: an overview of the reaction synthesis types, conditions, and applications

Many studies have examined metallic nanoparticles (NPs) produced according to the principles of green chemistry. Gold NPs have drawn much more attention than other metallic NPs in recent years. Moreover, among all gold NP synthesis studies, using plant-derived molecules is one of the commonly used reductants in studies on NP synthesis because of its convenience in terms of shape, size control advantage, and nontoxic specifications. The present review focused on studies of the synthesis of gold NP types, including single gold atom NPs, alloyed AU NPs, and core-shell Au NPs as well as their conditions and applications. The effect of those structures on application fields such as catalysis, antifungal action, antibacterial activities, sensors and so on are also summarized. Furthermore, the morphology and synthesis conditions of the primer and secondary NP were discussed. In addition to synthesis methods, characterization methods were analyzed in the context of the considerable diversity of the reducing agents used. As the reducing agents used in most studies, polyphenols and proteins usually play an active role. Finally, the challenges and drawbacks in plant-derived agent usage for the preparation of Au NPs at various industries were also discussed.

Vapreotide-mediated hierarchical mineralized Ag/Au nanoshells for photothermal anti-tumor therapy

A new type of vapreotide-templated Ag/Au bimetallic nanoshells (Vap@Ag/AuNSs) were successfully designed and fabricated based on polypeptide-directed mineralization and hierarchical self-assembly mechanisms under mild synthetic conditions. The nanoparticles with polypeptides serving as a core and coated Ag/Au bimetallic nanoshells exhibit diverse advantages, such as excellent biocompatibility, tumor targeting and low-cost. The Vap@Ag/AuNSs share excellent dispersibility, uniform size (120 nm) and a positive zeta potential (36.74 ± 4.49 mV), hence they easily accumulate in negatively charged tumor tissue. The results of thermal imaging, temperature variation assays and photothermal conversion efficiency (41.6%) indicated that Vap@Ag/AuNSs have excellent photothermal conversion capability. Based on their photothermal response, as well as biocompatibility determined by MTT assay, the prominent anti-tumor effects of Vap@Ag/AuNSs have been verified by fluorescein diacetate staining. Therefore, Vap@Ag/AuNSs are novel and promising candidates for photothermal tumor therapy.

Metal-plant frameworks in nanotechnology: An overview

BACKGROUND

Since ancient times, potential of plants in research and medicine have found pronounced applications, due to better therapeutic value. To meet the mounting demands for commercial nanoparticles, novel eco-friendly methods of synthesis has led to a remarkable progress via unfolding a green synthesis protocol towards metallic nanoparticles synthesis.

HYPOTHESIS/PURPOSE

This review highlights the biological synthesis of various metallic nanoparticles as safe, cost effective process, where the phytochemicals present in extract such as flavonoid, phenols, terpenoids act as capping, reducing and stabilizing agents. Moreover, due to their nano size, the nanoparticles directly bind to bacterial strains leading to higher antimicrobial activity.

CONCLUSION

Nano-sized dosage systems have a potential for enhancing the activity and overcoming problems associated with phyto medicines. Hence, synthesis of metallic nanoparticles using various plant extracts, emerge as safe alternative to conventional methods for biomedical applications.

Biogenic gold nanoparticles synthesis mediated by Mangifera indica seed aqueous extracts exhibits antibacterial, anticancer and anti-angiogenic properties

During the last few decades, gold nanoparticles (AuNP's) have gained considerable attention in nanomedicine and expanded its application in clinical diagnosis and as therapeutics. Employing plant extract for synthesising gold nanoparticles proves to be an eco-friendly technology for large scale production. It is highly economical and suitable for biological applications by negating the use of chemicals involved in conventional route. In this study, AuNP's was prepared by a simple one step method of employing aqueous Mangifera indica seed extract as a reducing agent. Scanning electron microscopy and transmission electron microscopy revealed spherical shaped nanoparticles and dynamic light scattering analysis indicated the AuNP's to be approximately 46.8 nm in size. AuNP's efficiently inhibited the growth of E. coli and S. aureus by its inherent ability to generate reactive oxygen species (ROS) and exhibited detrimental effects towards the tested bacterial species. Biocompatibility assessment indicated the non-toxic nature of AuNP's towards mesenchymal stem cells at 25 μg/ml and interestingly, suppressed the growth of human gastric cancer cells under in vitro culture conditions. AuNP's significantly exhibited anti-angiogenic property in chick chorioallantoic membrane model (CAM) by downregulating Ang-1/Tie2 pathway. Overall, the synthesized AuNP's exhibited antibacterial and anti-angiogenic properties with high biocompatibility thereby supporting its candidature for various biomedical applications. It can be employed in suppressing tumor growth, combat inflammatory diseases that necessitate the involvement of angiogenesis suppression, and antibacterial activity is suitable for its clinical translation to negate surgery associated infections.

Photocatalytic reduction of organic pollutant under visible light by green route synthesized gold nanoparticles

We report a rapid method of green chemistry approach for synthesis of gold nanoparticles (AuNPs) using Lagerstroemia speciosa leaf extract (LSE). L. speciosa plant extract is known for its effective treatment of diabetes and kidney related problems. The green synthesis of AuNPs was complete within 30min at 25°C. The same could also be achieved within 2min at a higher reaction temperature (80°C). Both UV-visible spectroscopy and transmission electron microscopy results suggest that the morphology and size distribution of AuNPs are dependent on the pH of gold solution, gold concentration, volume of LSE, and reaction time and temperature. Comparison between Fourier transform infrared spectroscopy (FT-IR) spectra of LSE and the synthesized AuNPs indicate an active role of polyphenolic functional groups (from gallotannins, lagerstroemin, and corosolic acid) in the green synthesis and capping of AuNPs. The green route synthesized AuNPs show strong photocatalytic activity in the reduction of dyes viz., methylene blue, methyl orange, bromophenol blue and bromocresol green, and 4-nitrophenol under visible light in the presence of NaBH₄. The non-toxic and cost effective LSE mediated AuNPs synthesis proposed in this study is extremely rapid compared to the other reported methods that require hours to days for complete synthesis of AuNPs using various plant extracts. Strong and stable photocatalytic behavior makes AuNPs attractive in environmental applications, particularly in the reduction of organic pollutants in wastewater.

Biofabrication of platinum nanoparticles using Fumariae herba extract and their catalytic properties

Due to the increasing popularity of using plant extract in the synthesis of nanoparticles, this study presented the synthesis of platinum nanoparticles using Fumariae herba extract. The formation of platinum nanoparticles was confirmed by UV–visible spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with EDS profile. Transmission electron micrograph presented the hexagonal and pentagonal shape of the synthesized nanoparticles sized about 30 nm. Moreover, platinum nanoparticles presented good catalytic properties in the reduction of methylene blue and crystal violet.

Biosynthesis of gold nanoparticles: A green approach

Nanotechnology is an immensely developing field due to its extensive range of applications in different areas of technology and science. Different types of methods are employed for synthesis of nanoparticles due to their wide applications. The conventional chemical methods have certain limitations with them either in the form of chemical contaminations during their syntheses procedures or in later applications and use of higher energy. During the last decade research have been focussed on developing simple, clean, non-toxic, cost effective and eco-friendly protocols for synthesis of nanoparticles. In order to get this objective, biosynthesis methods have been developed in order to fill this gap. The biosynthesis of nanoparticles is simple, single step, eco-friendly and a green approach. The biochemical processes in biological agents reduce the dissolved metal ions into nano metals. The various biological agents like plant tissues, fungi, bacteria, etc. are used for biosynthesis for metal nanoparticles. In this review article, we summarised recent literature on biosynthesis of gold nanoparticles which have revolutionised technique of synthesis for their applications in different fields. Due to biocompatibility of gold nanoparticles, it has find its applications in biomedical applications. The protocol and mechanism of biosynthesis of gold nanoparticles along with various applications have also been discussed.

Castor leaf mediated synthesis of iron nanoparticles for evaluating catalytic effects in transesterification of castor oil

A castor (Ricinus communis) leaf extract mediated process was developed for the synthesis of iron nanoparticles. The phytosynthesized iron nanoparticles were used as a catalyst for castor biodiesel production.

Green and energy-efficient methods for the production of metallic nanoparticles

In the last decade, researchers paid great attention to the concept of "Green Chemistry", which aims at development of efficient methods for the synthesis of nanoparticles (NPs) in terms of the least possible impact on human life and environment. Generally, several reagents including precursors, reducing agents, stabilizing agents and solvents are used for the production of NPs and in some cases, energy is needed to reach the optimum temperature for reduction. Therefore, to develop a green approach, researchers had the opportunity to investigate eco-friendly reagents and new energy transfer techniques. In order to substitute the harmful reagents with green ones, researchers worked on different types of saccharides, polyols, carboxylic acids, polyoxometalates and extracts of various plants that can play the role of reducers, stabilizers or solvents. Also, there are some reports on using ultraviolet (UV), gamma and microwave irradiation that are capable of reducing and provide uniform heating. According to the literature, it is possible to use green reagents and novel energy transfer techniques for production of NPs. However, these new synthesis routes should be optimized in terms of performance, cost, product quality (shape and size distribution) and scale-up capability. This paper presents a review on most of the employed green reagents and new energy transfer techniques for the production of metallic NPs.

Novel green synthesis of gold nanoparticles using Citrullus lanatus rind and investigation of proteasome inhibitory activity, antibacterial, and antioxidant potential

Biological synthesis of nanoparticles using nontoxic, eco-friendly approaches is gaining importance owing to their fascinating biocompatibility and environmentally benign nature. This study describes the green synthesis approach for synthesis of gold nanoparticles (ANPs) using aqueous extract of the rind of watermelon as a fruit waste and evaluate its biopotential in terms of proteasome inhibitory activity, antibacterial, and antioxidant potential. The synthesized ANPs were characterized using UV–vis spectroscopy, scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The surface plasmon resonance spectra of ANPs were obtained at 560 nm. Scanning electron microscopy image revealed that particles had a spherical shape and have a size distribution of 20–140 nm, followed by the elemental analysis by energy-dispersive X-ray spectroscopy. X-ray diffraction analysis confirmed the crystallite nature of the ANPs and Fourier-transform infrared spectroscopy revealed the involvement of bioactive compounds from watermelon rind in the synthesis, capping, and stabilization of ANPs. ANPs exhibited potential antibacterial activity against five different foodborne pathogenic bacteria with diameter of inhibition zones ranged between 9.23 and 11.58 mm. They also displayed strong synergistic antibacterial activity together with kanamycin (11.93–21.08 mm inhibition zones) and rifampicin (10.32–24.84 mm inhibition zones). ANPs displayed strong antioxidant activity in terms of DPPH radical scavenging (24.69%), nitric oxide scavenging (25.62%), ABTS scavenging (29.42%), and reducing power. Significantly high proteasome inhibitory potential of the ANPs (28.16%) could be highly useful for cancer treatment and targeted cancer drug delivery. Overall, results highlight a potential low-cost green method of synthesizing ANPs from food waste materials. Significant biopotentials of synthesized ANPs could make it a potential candidate for its application in the biomedical, pharmaceutical, cosmetics, and food sectors.

Size dependent catalytic activities of green synthesized gold nanoparticles and electro-catalytic oxidation of catechol on gold nanoparticles modified electrode

A green and facile method for the synthesis of gold nanoparticles with efficient catalytic activity.

Applications of biosynthesized metallic nanoparticles - a review

We present a comprehensive review of the applications of biosynthesized metallic nanoparticles (NPs). The biosynthesis of metallic NPs is the subject of a number of recent reviews, which focus on the various "bottom-up" biofabrication methods and characterization of the final products. Numerous applications exploit the advantages of biosynthesis over chemical or physical NP syntheses, including lower capital and operating expenses, reduced environmental impacts, and superior biocompatibility and stability of the NP products. The key applications reviewed here include biomedical applications, especially antimicrobial applications, but also imaging applications, catalytic applications such as reduction of environmental contaminants, and electrochemical applications including sensing. The discussion of each application is augmented with a critical review of the potential for continued development.

Optimization and stabilization of gold nanoparticles by using herbal plant extract with microwave heating

In this study, we have synthesized the gold nanoparticles by using Hibiscus rosa-sinensis, a medicinal plant. The gold nanoparticles were synthesized rapidly by the involvement of microwave heating. By changing of plant extract concentration, gold solution concentration, microwave heating time and power of microwave heating the optimized condition was identified. The surface Plasmon resonance found at 520 nm confirmed the gold nanoparticles synthesis. The spherical sized nanoparticles in the size range of 16-30 nm were confirmed by Transmission Electron Microscope (TEM). The stability of the nanoparticles is very well proved in the invitro stability tests. The biochemical like alkaloids and flavonoids play a vital role in the nanoparticles synthesis was identified using the Fourier Transform Infrared Spectroscopy (FTIR). Combining the phytochemical and microwave heating, the rapid synthesis of gold nanoparticles is the novel process for the medically applicable gold nanoparticles production.

Green synthesis and spectral characterization of silver nanoparticles from Lakshmi tulasi (Ocimum sanctum) leaf extract

A simple method for the green synthesis of silver nanoparticles (AgNPs) using aqueous extract of Lakshmi tulasi (Ocimum sanctum) leaf as a reducing and stabilizing agent. AgNPs were rapidly synthesized using aqueous extract of tulasi leaf with AgNO(3) solution within 15 min. The green synthesized AgNPs were characterized using physic-chemical techniques viz., UV-Vis, X-ray diffraction (XRD), scanning electron microscope (SEM) coupled with X-ray energy dispersive spectroscopy (EDX) and Fourier transform-infrared spectroscopy (FT-IR). Characterization data reveals that the particles were crystalline in nature and triangle shaped with an average size of 42 nm. The zeta potential of AgNPs were found to be -55.0 mV. This large negative zeta potential value indicates repulsion among AgNPs and their dispersion stability.