Green Synthesis

In recent years, the green synthesis of silver nanoparticles using various plant extracts has attracted great attention. This is because these methods are simple, inexpensive, environment benign, nontoxic and large scale up process. Green synthesis method of nanoparticles is evolution from the Nano biotechnology. Development of green nanotechnology is generating interest of researches toward eco-friendly biosynthesis of nanoparticles. In this study, it was observed that silver ions were reduced by Ageratina adenophora leaf extract by refluxing method around 2 hours until leading to the formation of crystalline silver nanoparticles. A.adenophora is known as Crofton weed or sticky snakeroot, Mexican devil, eupatory, eupatorium adenophorum is a synonym. The green synthesized AgNPs were characterized using physical-chemical techniques viz., (UV-Vis) ultraviolet-visible spectroscopy, (XRD) X-ray diffraction, (SEM) scanning electron microscope coupled with (EDX) X-ray energy dispersive spectroscopy and (FTIR) Fourier transform-infrared spectroscopy.

Cerium oxide (CeO 2) and 1%, 5% and 10% tin-doped CeO 2 nanoparticles (Sn-doped CeO 2 NPs) were synthesized using aqueous leaf extracts of Pometia pinnata. UV-Vis diffuse reflectance spectroscopy showed band gap energies of 2.47-2.66 eV. X-ray diffraction results confirmed the formation of a fluorite phase of CeO 2 and Sn-doped CeO 2 NPs with average crystallite sizes between 6 and 19 nm. X-ray photoelectron spectroscopy (XPS) analysis further established the synthesis of CeO 2 and Sn-doped CeO 2 NPs. The density of states was proposed accordingly using the valence band-XPS data. Scanning electron microscopic and transmission electron microscopic studies showed almost spherical shaped particles with average particle sizes around 15-20 nm. All synthesized nanomaterials were tested for photoantioxidant activity under visible light and in the dark and showed improved photoantioxidant activity under visible light irradiation for dose and time-dependent studies. The synthesized nanomaterials were also tested for antibiofilm activities and exhibited significant concentration-dependent antibiofilm activity against Gram-positive pathogenic bacteria such as Staphylococcus aureus and Listeria monocytogenes. The 10% Sn-doped CeO 2 NPs and S-CeO 2 NPs also exhibited bactericidal activity against Staphylococcus aureus. These studies showed that S-CeO 2 and Sn-doped CeO 2 NPs have both good antioxidant and antibacterial properties.

An improved, safe, and scalable isolation process for (substituted) pyridine and quinoline N-oxides in quantitative yields along with high purities using the m-CPBA−NH 3 (g) system is described. The safety was assessed by reaction calorimetry and differential scanning calorimetry studies for possible hazards during the conversion and isolation steps. Careful interpretation of the data substantiated the safety and scalability. The process flow is simplified to meet the industrial requirements of safety, cost-effectiveness, and utility minimization. The reaction was safely demonstrated at a 2.5 kg scale.

A series of Dihydropyrimidinone (DHPM) derivatives were synthesized using urea, ethyl acetoacetate
with electron rich as well as electron deficient aromatic aldehydes through Biginelli reaction in an eco friendly
and green condition. Their antimicrobial evaluations were performed against some common pathogenic
microorganisms. It was observed that the electronic factor of the phenyl ring of DHPM has significant influence
on their antimicrobial properties.

The development of nanotechnology is making the interest of researchers towards the synthesis of nanoparticles for bioapplication. In recent years, metal oxides such as ZnO have received increasing attention as antibacterial materials because of their stability under harsh processing conditions. They are generally regarded as safe materials for human beings and animals. Zinc activates  300 enzymes, and it plays a role in many other phenomena like growth,  membrane stability, bone mineralization, tissue growth and repair, wound healing and cell signalling. Many studies have shown that ZnO nanoparticles have enhanced antibacterial activity. The use of plant and plant materials to synthesise Zinc nanoparticles is a relatively new and exciting research field.  Various plants were used for the synthesis of nanoparticles using the green synthesis method.  Nanoparticles were synthesized from all the plant parts separately like stem,  flower,  leaf, latex, root,  peel, stem bark and fruits.  The prepared Zinc oxide nanoparticles were characterized by using  XRD,  FTIR,  UV-VIS Spectroscopy,  EDAX,  Particle size analyzer, TGA, and  SEM. The objective of this review was to report on the synthesis of Zinc oxide nanoparticles by using different plant extracts and their significance in different fields.

Developing an environment friendly process for synthesis of nanoparticles is a significant step in the field of nanotechnology. Nanotechnology involves the tailoring of materials at the atomic level to attain unique properties, which can be suitably manipulated for the desired applications. Among the all metallic nanoparticles silver nanoparticles draw more attention due to its unique physical, chemical and biological properties. Green protocol of synthesizing nanoparticles has emerged as an alternative to overcome the limitation of conventional methods. Plant and microorganisms are majorly applied for green synthesis of metallic nanoparticles. Using plants towards synthesis of nanoparticles are emerging and also beneficial compared to microbes with the presence of broad variability of bio-molecules in plants which can act as capping/stabilizing and reducing agents and so increases the rate of reduction and stabilization of synthesized nanoparticles. Among all organisms plants seem to be the best candidates for biosynthesis of silver nanoparticles and they are suitable for large-scale biosynthesis. Nanoparticles produced by plants are more stable and the rate of synthesis is faster than in the case of microorganisms. This review focuses on the green synthesis of silver nanoparticles using various plant sources.

Narrow band gap zinc oxide (ZnO) nanoparticles (NPs) were synthesized using unboiled and boiled leaf extracts of Costus woodsonii. The as-synthesized NPs were characterized using a range of techniques. The as-synthesized ZnO NPs were crystalline with a hexagonal wurtzite structure similar to the commercial ZnO (ZnO-C). The maximum absorbance was observed at ~390 nm for ZnO-C and the as-synthesized ZnO NPs (ZnO-UL and ZnOBL) showed a red shift, i.e. ~448 nm to ~462 nm, hence, a lower band gap of ~2.68–2.77 eV. The band gap energy of the as-synthesized ZnO NPs was lower than that of commercial ZnO. The surface of ZnO was coated/modified with the components of the leaf extract. The as-synthesized ZnO NPs showed similar particle sizes and were spherical in shape. These studies confirmed the green synthesis of ZnO NPs using Costus woodsonii and the significantly reduced band gap (Eg =~2.68 eV to ~2.77 eV) of the as-synthesized ZnO NPs compared to the ZnO-C (Eg =3.18 eV).

In view of advantages of green synthesis, a novel green route for the synthesis and stabilization of copper nanoparticles (CuNPs) using aqueous extract of Citrus limon fruits at room temperature was reported. The formation of CuNPs is monitored by recording the UV-vis absorption spectra for surface Plasmon resonance (SPR) peak (∼579 nm). X-ray diffraction (XRD) pattern of the CuNPs agrees with the reported data for Cu metal and the crystallite average size is ~30 nm. Scanning and transmission electron microscopic (SEM and TEM) show uniform spherical particles obtained by this green method. The antimicrobial activity is found to be effective of CuNPs. Results revealed that the green synthesis is an efficient for the preparation of CuNPs as an active antimicrobial agent for practical applications.

The present study reports the synthesis and characterization of ZnO nanoparticles by green synthesis method. The capping agent of Ocimum tnuiflorum leaf extract was used as a reducing agent in the preparation of ZnO nanoparticles. The synthesized ZnO nanoparticles were characterized by X-Ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), scanning electron microscope (SEM) and Energy Dispersive Analysis of X−rays (EDAX). The obtained results reveal that the crystalline size, morphology and composition match well with the standard values and will be useful for antibacterial applications.

The aim of present study is based on low cost, efficient, non-toxic and ecofriendly method for green synthesis of copper oxide nanoparticles (CuONPs) using Bougainvillea leaves aqueous extract. The green synthesized nanoparticles were subjected to characterization techniques UV-visible spectroscopy (UV-vis), X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FT-IR) and transmission electron microscope (TEM). The synthesized CuONPs were pure, predominantly spherical with sizes ranges from 8-20 nm. CuONPs showed excellent antimicrobial activity against various bacterial strains Escherichia coli, Enterococcus faecalis, and Staphylococcus aureus. Moreover, E. coli and E. faecalis exhibited the highest sensitivity to CuONPs while Staphylococcus aureus was the least sensitive. Possible mechanisms of antimicrobial activity of CuONPs should be further investigated.

Nanotechnology is a rapidly developing field because of its wide range of applications in science, nanoscience and biotechnology. Nanobiotechnology deals with nanomaterials synthesised or modified using biotechnology. Fungi are used to synthesise metal nanoparticles and they have vast applications in wound healing, pathogen detection and control, food preservation, textiles, fabrics, etc. The present review describes the different types of fungi used for the biosyntheses of silver nanoparticles (AgNPs), along with their characterisation and possible biological applications. AgNPs synthesised by other physical and chemical methods are expensive and have toxic substances adsorbed onto them. Therefore, green, simple and effective approaches have been chosen for the biosynthesis of AgNPs, which are very important because of their lower toxicity and environmentally friendly behaviour. AgNPs synthesised using fungi have high monodispersity, specific composition and a narrow size range. In this regard, among the different biological methods used for metal nanoparticle synthesis, fungi are considered to be a superior biogenic method owing to their diversity and better size control. To further understand the biosynthesis of AgNPs using various fungi and evaluate their potential applications, this review discusses the antimicrobial, antibacterial, antifungal, antiviral, antidermatophytic, anti-inflammatory, antitumor, hepatoprotective, cytotoxic, hypotensive, and immunomodulatory activities of these AgNPs. The synthesis of AgNPs using fungi is a clean, green, inexpensive, eco-friendly, reliable, and safe method that can be used for a range of applications in real life for the benefit of human beings.

Nanotechnology is an escalating field, which has an growing impact in each and every sector. There are many ways for synthesizing nanoparticles but biosynthetic route of nanoparticle synthesis is emerging as a new and safer alternative to the conventional methods. Ocimum basilicum Lamiaceae (OBL) is an age old herb native to Southeast Asia and Central African countries. These plants are generally known to be used in different cuisines worldwide. The aroma emitted from the leaves and the twigs of the fresh and dried plants are well known to have insect repellent property. Estragole, citronellal, limonene and nerolidol are the natural volatile compounds present in the basil leaves which acts as repellents. This plant is also widely used as a scent through which it netted its title Queen (basileus) of aromatic herbs. In present study the Green synthesis of some metal oxide nanoparticles have been synthesized by Ocimum Basilicum-Lamiaceae (Thiru Neetru Pathilai).These methods are completely green methods, free from toxic and harmful solvent. Note and measure visual observation of the nanoparticle solutions, preliminary test of electrical conductivity(EC), pH change of the reaction mixture and total dissolved suspend(TDS) in the reaction were measured and recorded. I. INTRODUCTION Over the last decade, novel synthesis approaches/methods for nanomaterials (such as metal nanoparticles, quantum dots (QDs), carbon nanotubes (CNTs), graphene, and their composites) have been an interesting area in nanoscience and technology [1-9]. To obtain nanomaterials of desired sizes, shape, and functionalities, two diferent fundamental principles of synthesis (i.e., top down and bottom up methods) have been investigated in the existing literature (Fig. 1). In the former, nanomaterials/nanoparticles are prepared through diverse range of synthesis approaches like lithographic techniques, ball milling, etching, and sputtering [10]. Te use of a bottom up approach (in which nanoparticles are grown from simpler molecules) also includes many methods like chemical vapor deposition, sol-gel processes, spray pyrolysis, laser pyrolysis, and atomic/molecular condensation. Interestingly, the morphological parameters of nanoparticles (e.g., size and shape) can be modulated by varying the concentrations of chemicals and reaction conditions (e.g., temperature and pH). Nevertheless, if these synthesized nanomaterials are subject to the actual/ specifc applications, then they can sufer from the following limitation or challenges: (i) stability in hostile environment, (ii) lack of understanding in fundamental mechanism and modeling factors, (iii) bioaccumulation/ toxicity features, (iv) expansive analysis requirements, (v) need for skilled operators, (vi) problem in devices assembling and structures, and (vii) recycle/reuse/regeneration. In true world, it is desirable that the properties, behavior, and types of nanomaterials should be improved to meet the aforementioned points. On the other hand, these limitations are opening new and great opportunities in this emerging feld of research. To counter those limitation, an new era of 'green synthesis' approaches/methods is gaining great attention in current research and development on materials science and technology. Basically, green synthesis of materials/nonmaterial, produced through regulation, control, clean up, and remediation process, will directly help uplift their environmental friendliness. Some basic principles of "green synthesis" can thus be explained by several components like prevention/minimization of waste, reduction of derivatives/pollution, and the use of safer (or non-toxic) solvent/auxiliaries as well as renewable feedstock. 'Green synthesis' are required to avoid the production of unwanted or harmful by-products through the build-up of reliable, sustainable, and eco-friendly synthesis procedures. Te use of ideal solvent systems and natural resources (such as organic systems) is essential to achieve this goal. Green synthesis of metallic nanoparticles has been adopted to accommodate various biological materials (e.g., bacteria, fungi, algae, and plant extracts).

"green chemistry, green synthesis, nanomaterials, environmental catalysis

10.1002/9783527628698.hgc092
"

Abstract

The sections in this article are

Introduction
Green Synthesis of Nanophase Inorganic Materials
Metal Oxide Nanoparticles
Hydrothermal Synthesis
Reflux Synthesis
Microwave-Assisted Synthesis
Green Synthesis of Metallic Nanoparticles
Green Chemistry Applications of Inorganic Nanomaterials
Manganese Oxides
Titanium Dioxide
Environmental Applications of Nanomaterials
Background
Titanium Dioxide Nanomaterials
Zinc Oxide Nanomaterials
Iron-Based Nanomaterials
Conclusion and Future Perspectives
Acknowledgment

Keywords:
nanophase inorganic materials;metallic nanoparticles;metal oxide nanoparticles;inorganic nanomaterials;environmental applications;catalysis;green synthesis;green chemistry

Phase-transfer catalyst (PTC) has been popular for more than four decades in synthetic chemistry. The PT catalysis uses the PTC in a catalytic amount and it allows to react the reactants of two different phases via facilitating transfer of reactants from interface, which are not miscible and itself regenerated again and the cycle is repeated. The use of PTC is wide from liquid-liquid, solid-liquid to liquid-gas system. Due to its diversified application, PTC is also combined with other rate enhancing techniques like microwave, electro-organic synthesis, sono-chemistry, photochemistry and many more are exploring. The PTC application in the field of manufacturing of the fine chemicals and organic intermediates are unlimited.

Cerium oxide nanoparticles (CeO2 NPs) are a sought-after material in numerous fields due to their potential applications such as in catalysis, cancer therapy, photocatalytic degradation of pollutants, sensors, polishing agents. Green synthesis usually involves the production of CeO 2 assisted by organic extracts obtained from plants, leaves, flowers, bacteria, algae, food, fruits, etc. The phytochemicals present in the organic extracts adhere to the NPs and act as reducing and/or oxidizing agents and capping agents to stabilize the NPs, modify the particle size, morphology and band gap energy of the as-synthesized materials, which would be advantageous for numerous applications. This review focuses on the green extract-mediated synthesis of CeO 2 NPs and discusses the effects on CeO 2 NPs of various synthesis methods that have been reported. Several photocatalytic, antimicrobial, antioxidant and cytotoxicity applications have been evaluated, compared and discussed. Future prospects are also suggested.

A  new  and  novel  approach  for  the  green  synthesis  of  silver
nanoparticles  is  the  need  of  the  hour.  Use  of  plant  parts  for  the
synthesis of silver nanoparticles is ecofriendly, economic and cost
effective. In the present paper, silver nanoparticles were synthesized
using  aqueous  stem  extract  of Cassia  roxburghii DC  as  a  reducing
agent.  The  biosynthesized  AgNPs  were  characterized  by  various
spectral analysis like UV–Vis, FTIR, XRD, TEM and Zeta potential
measurement. UV–vis spectra showed maxima absorption peak at
432  nm.  XRD  and  TEM  analysis  revealed  AgNPs  to  be  facecentered, cubic structures spherical in shape with an average particle
size of 32-35 nm.
The synergistic antibacterial activity was evaluated against two Gram
positive,  two  Gram  negative  bacteria  and  four  fungi  with  fifteen
commercial antibiotics alone and antibiotics plus synthesized AgNPs.
Antioxidant  activity  of  AgNPs  was  evaluated  by  ABTS  and  FRAP
assay.  The  AgNPs  showed  synergistic  antibacterial  activity  even
better than some antibiotics and also good  antioxidant activity. The
results suggest that Cassia roxburghii stem could be exploited for the
fabrication  of  AgNPs  with  potential  therapeutic  application  in
nanomedicine especially against multi drug resistant microorganisms
which  are  cost  effective  and  ecofriendly  and  simple.  They  can  be
definitely used in cosmetics, medical and pharmaceutical applications

Sulfur nanoparticles (S-NPs) were prepared using rosemary (Rosmarinus officinalis) leaves aqueous extract and sodium thiosulfate pentahydrate (Na2S2O3.5H2O) at room temperature. The S-NPs were characterized by UV–visible spectrophotometer, Fourier transform infrared (FT-IR), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and X-ray diffraction (XRD) techniques. The sulfur nanoparticles are crystalline in nature with average size of 40 nm. The morphology of S-NPs could be controlled by tuning the amount of rosemary leaves aqueous extract and sulfur ions. The cytotoxic effects of the S-NPs on hatching of second stage root-knot and mortality of second stage of root-knot nematode (Meloidogyne javanica) were tested. These results confirmed that the S-NPs synthesized using rosemary leaves aqueous extract and could possibility be used as nematicidal to manage M. javanica infestation.

In this study, zinc ferrite nanoparticles (ZF-NPs) were synthesized using aqueous seed extract of Piper nigrum as a bio-reducing and stabilizing agent. FTIR, SEM, FE-SEM, XRD, and TGA have been used for characterizing ZF-NPs. The results showed that Piper nigrum stabilized ZF-NPs have high purity and size range of 60-80 nm. The performance of the ZF-NPs has been investigated by photocatalytic reduction of methylene blue (MB) in the presence of sunlight. The factors responsible for affecting the degradation values of the reaction were also explored for developing a better understanding of the phenomenon.

To cite this article: Gloria Aderonke Otunola & Anthony Jide Afolayan (2018): In vitro antibacterial, antioxidant and toxicity profile of silver nanoparticles green-synthesized and characterized from aqueous extract of a spice blend formulation, Biotechnology & Biotechnological Equipment,

A critical investigation on the fabrication of metal oxide nanoparticles (NPs) such as ZnO, SnO2, and CeO2 NPs synthesized from green and phytogenic method using plants and various plant parts have been compiled. In this review, diferent plant extraction methods, synthesis methods, characterization techniques, efects of plant extract on the physical, chemical, and optical properties of green synthesized ZnO, SnO2, and CeO2 NPs also have been compiled and discussed. Efect of several parameters on the size, morphology, and optical band gap energy of metal oxide have been explored. Moreover, the role of solvents has been found important and discussed. Extract composition i.e. phytochemicals also found to afect the morphology and size of the synthesized ZnO, SnO2, and CeO2 NPs. It was found that, there is no universal extraction method that is ideal and extraction techniques is unique to the plant type, plant parts, and solvent used.

Nanoscale zerovalent iron (nZVI) particles represent an important material for diverse environmental applications because of their exceptional electron donating properties, which can be utilized, e.g., for reduction, catalysis, adsorption and degradation of a broad range of pollutants. The synthesis and assembly of nZVI using biological and natural sustainable resources is an attractive option for alleviating environmental contamination worldwide. In this review, various green synthesis pathways for generating nZVI particles are summarized and compared with conventional chemical and physical methods. In addition to describing the latest environmentally benign methods for the synthesis of nZVI, their properties and interactions with diverse biomolecules are discussed, especially in the context of environmental remediation and catalysis. Future prospects in the field are also considered.

El uso de las nanopartículas (NPs) de oro se remonta al el siglo IV d.C, en la copa de Licurgo fabricada artesanalmente por los romanos. El proceso para la síntesis de NPs no era sencillo de estandarizar, hasta que Turkevich en 1953 estableció los criterios que deben seguirse para tener mayor control de la morfología y tamaño de NPs obtenidas (en su caso cuasi-esferas de ∼15nm de diámetro). La desventaja de su método es que genera residuos tóxicos al medio ambiente. Por ello una vertiente actual de investigación consiste en la búsqueda de métodos verdes de síntesis mediante compuestos capaces de efectuar la misma labor que los reactivos químicos con cierta toxicidad, pero que sean amigables con el ambiente. Una alternativa a explorar son las algas, las cuales se componen mayormente de polisacáridos y en particular las de clase Phaeophyceae, como la Egregia menziesii que además contiene metabolitos secundarios aplicables en biomedicina. En el presente trabajo se buscó sintetizar NPs de oro usando un extracto del alga E. menziesii como reactivo reductor de un precursor de oro. También se presenta la caracterización de las muestras obtenidas, utilizando espectrofotometría UV-Visible y microscopía electrónica de transmisión (TEM). Se evaluó la estabilidad de las NPs en dispersión coloidal. Y se elaboraron histogramas de distribución del diámetro de las NPs con morfología cuasi-esférica. Se propone entonces, que el extracto de E. menziesii no solo funge como agente reductor para la síntesis de las NPs de oro, sino que además participa como agente estabilizante de las mismas. Es así que se comprobó que el extracto de E. menziesii es capaz de sintetizar NPs de oro y obtener dispersiones altamente estables con distribuciones de tamaño cuya dispersión resulta ser angosta.

The hazardous effects of current nanoparticle synthesis methods have steered researchers to focus on the development of newer environmentally friendly and green methods for synthesizing nanoparticles using nontoxic chemicals. The development of environmentally friendly methods of nanoparticle synthesis with different sizes and shapes is one of the pressing challenges for the current nanotechnology. Several novel green approaches for the synthesis of AuNPs have been explored using different natural sources, such as plants, algae, bacteria, and fungi. Among organisms, algae and blue–green algae are of particular interest for nanoparticle synthesis. Gold nanoparticles (AuNPs) have a range of applications in medicine, diagnostics, catalysis, and sensors because of their significant key roles in important fields. AuNPs have attracted a significant interest for use in a variety of applications. The widespread use of AuNPs can be accredited to a combination of optical, physical, and chemical properties as well as the miscellany of size, shape, and surface composition that has been adopted through green synthesis methods.

Conference Presentation 10.12.2021 on Intrnational Forum of Alternative Energy and Carbon Neutrality.
:
VHTGCR Very High Temperature Gas-Cooled Reactor (inherently safe) and HTE (High Temperature Electrolysis Water Steam (SOEC Solid Oxide Electrolysis Cell)

This research work presents a facile and green route for synthesis silver sulfide (Ag2SNPs) nanoparticles from silver nitrate (AgNO3) and sodium sulfide nonahydrate (Na2S.9H2O) in the presence of rosemary leaves aqueous extract at ambient temperature (27 oC). Structural and morphological properties of Ag2SNPs nanoparticles were analyzed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The surface Plasmon resonance for Ag2SNPs was obtained around 355 nm. Ag2SNPs was spherical in shape with an effective diameter size of 14 nm. Our novel approach represents a promising and effective method to large scale synthesis of eco-friendly antibacterial activity silver sulfide nanoparticles.

Nanoscale iron particles have attracted substantial interest due to their unique physical and chemical properties. Over the years, various physical and chemical methods have been developed to synthesize these nanostructures which are usually expensive and potentially harmful to human health and the environment. Synthesis of iron nanoparticles (INPs) by using plant extract is now of great interest in order to develop a novel and sustainable approach toward green chemistry. In this method the chemical compounds and organic solvents are replaced with phytochemicals and aqueous matrixes, respectively. Similar to any chemical and biochemical reaction, factors such as reaction temperature, concentration of iron precursor, concentration of leaf extract, and reaction time have critical effects on the reaction yield. This review focuses on the novel approaches used for green synthesis of INPs by using plant resources. The currently available statistics including the factors affecting the synthesis process and potential applications of the fabricated nanoparticles are discussed. Recommendations are also given for areas of future research in order to improve the production process.

Silver nanoparticles (AgNPs) are an important class of nanomaterials for a wide range of industrial and biomedical applications. AgNPs have been used as an antimicrobial and disinfectant agents due its detrimental effect. The aim our study was to determine the cytotoxic effects of biologically synthesized AgNPs using hot aqueous extracts of the mycelia of Ganoderma neo-japonicum Imazeki on MDA-MB-231 human breast cancer cells.  Here, we developed a green method for the synthesis of water-soluble AgNPs by treating silver ions with hot aqueous extract of mycelia of G.neo-japonicum. The formation of silver nanoparticles was characterized by ultraviolet and visible absorption spectroscopy (UV-Vis), X-ray diffraction, dynamic light scattering (DLS) and transmission electron microscopy. Furthermore, the toxicity of synthesized AgNPs was evaluated using a series of assays like cell viability, LDH leakage, ROS generation, caspase-3, DNA laddering and TUNEL in human breast cancer cells (MDA-MB-231).  The ultraviolet and visible absorption spectroscopy results show a strong resonance centered on the surface of AgNPs at 420 nm. The X-ray diffraction analysis confirmed that the synthesized AgNP are single crystalline, corresponding to the result of transmission electron microscopy. Treatment of MDA-MB-231 breast cancer cells with various concentrations of AgNPs (1 to 10 μg/mL) for 24 h revealed that AgNPs could inhibit the cell viability and induces membrane leakage in a dose dependent manner. Cells exposed to AgNPs showed increased reactive oxygen species and hydroxyl radical production. Furthermore, the apoptotic effects of AgNPs were confirmed by activation of caspase-3 and DNA nuclear fragmentation.  The results indicate that AgNPs possess cytotoxic effects with apoptotic features and suggest that the ROS generated by AgNPs have a significant role in apoptosis. The present findings suggest that AgNPs may contribute to the development of a suitable anticancer drug and the presented results here may lead to develop novel nanomedicine for treatment of cancers.

Out of all metals, silver has been widely recognized for its antimicrobial activity over centuries of years. In more recent times, silver was found to be even more effective in antimicrobial activity when it was at nanoscale. A novel protocol was developed for green synthesis of silver nanoparticles and their anti-bacterial activity was experimentally validated. This protocol is different from the prior art in a way that the green synthesis from non-polar organic plant extracts is now possible for the first time. The raw material was the dichloromethane extract of Plectranthus zeylanicus, a widely used medicinal plant in Sri Lanka. Scanning electron microscopy (SEM) images of the formulation revealed that the synthesized objects were predominantly of spherical shape and approximately 100 nm in size. Energy dispersive X-ray (EDX) spectrum confirmed the presence of elemental silver in it. The presence of phytochemical classes that could be responsible for the green synthesis of nano silver was detected by standard qualitative phytochemical screening assays. The antibacterial activity of the compound was assessed by the agar well diffusion method against Gram positive and Gram negative bacteria including the methicillin resistant Staphylococcus aureus (MRSA). These new formulations exhibited profound antibacterial activity against all the tested microorganisms in comparison to aqueous silver ion solution and commercial disinfectants that contain silver ions as active ingredients. This is the first time the anti-MRSA potential of silver nanoparticles synthesized via a green route is documented. Present findings point towards the possible application of biogenic silver nanoparticles as an effective antimicrobial agent against nosocomial infections.

A new corrosion inhibitor namely, 2-amino-3-((4-((S)-2-amino-2-carboxyethyl)-1H-imidazol-2-yl)thio)propionic acid (AIPA) has been synthesized and its inhibition action on corrosion of mild steel in 1 M HCl has been investigated using Electrochemical impedance spectroscopy (EIS),Potentiodynamic polarization, Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) and Atomic force microscopy(AFM) methods. The results obtained from above methods reveal that AIPA is an excellent inhibitor. It gives a maximum inhibition efficiency of 96.52% at 0.456 mM/L (125 ppm; 125 mg L −1) and inhibits corrosion by adsorbing at the mild steel surface. Polarization study suggested that AIPA acts as mixed type inhibitor with some cathodic predominance. SEM and AFM analyses showed improved morphology of the mild steel surface in presence AIPA. Quantum chemicals parameters such as E HOMO , E LUMO , ΔE, global hardness and softness, electronegativity and fraction of electron transfer (ΔN) were calculated using DFT method to correlate the electronic properties with the adsorp-tion and inhibition behavior of AIPA.

A green, cost-effective and eco-friendly method for the synthesis of copper oxide nanoparticles (CuO NPs) using Bougainvillea flower aqueous extract at room temperature was reported. The synthesized CuO NPs were characterized by UVvisible spectroscopy, fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray diffraction (XRD) tecniques. The synthesized particles were highly stable, spherical in shape with an average diameter of 12±4 nm. The CuO NPs were explored for their antifungal activity against Aspergillus niger and responses revealed that CuO NPs are highly efficient to inhibit the fungal growth and zone of inhibition were comparable with standard drug. The green route for the synthesis of CuO NPs is suggested in view of promising antifungal activity.

Synthesized cerium oxide nanoparticles (S-CeO 2 NPs) and 1%, 5% and 10% zirconium doped CeO 2 (Zr-doped CeO 2) NPs were fabricated using aqueous leaf extract of Pometia pinnata. The synthesized NPs were characterized using standard techniques which confirmed successful synthesis of NPs with particle size ranging from 12 to 23 nm and band gap energy of 2.54-2.66 eV. Photoantioxidant activities showed enhanced activities under visible light irradiation in comparison to the dark condition in the dose-dependent study. Biofilm inhibition studies showed ~ 73% biofilm inhibition of Staphylococcus aureus at 512 µg/mL for S-CeO 2 , whereas 10% Zr-doped CeO 2 NPs showed biofilm inhibition of 52.7%. The bactericidal tests showed killing properties at 1024 µg/mL of S-CeO 2 NPs and at 512 µg/mL of 1% Zr-doped CeO 2. Reduced bactericidal activities were observed for 5% and 10% Zr-doped CeO 2. These studies showed that the fabricated NPs have both good photoantioxidant and antibacterial properties.

Eco-Friendly green synthesis of nanoparticles is a fast-growing area of research in nanotechnology. This study aims to synthesize Aloe vera mediated silver nanoparticles (AV-AgNPs) and evaluates in-vitro and in-vivo antioxidant potentials. Also examines the phytochemical screening of aqueous Aloe vera leaves extract (AVLE). The AV-AgNPs were characterized by UV–visible spectroscopy and scanning electron microscopy. However, the phytochemical screening of AVLE was performed by standard protocols. In-vitro antioxidant activities were determined through lipid peroxidation inhibition, DPPH (1,1-diphenyl-2-picrylhydrazyl), and reducing power assays. Whereas, in-vivo antioxidant activities were studied in rats (180-220g b.w), received AV-AgNPs (10 mg/kg b.w) via oral gavage for 28 days.  After euthanization of rats, blood and kidneys were collected and used for biochemical (urea, creatinine) and antioxidant (MDA, SOD, CAT, and GSH) investigations. Results showed the maximum absorption of AV-AgNPs at 400 nm and 20-24 nm particle size with spherical morphology. Whereas, flavonoid, glycosides, phenols, saponin, tannins, and terpenoids phytochemicals were present in AVLE. Both in-vitro and in-vivo studies exhibited the significant potentials of AV-AgNPs as an antioxidant and free radical scavengers thus it could be proposed for many biomedical and environmental applications such as for drug encapsulation or purification of water.

One-pot synthesis of some pyranocoumarins and biscoumarins using graphene oxide nanosheets as efficient
catalyst has been investigated. The green methods offer appealing attributes such as excellent yields,
short reactions times, use of a safe and recyclable catalyst, and a simple workup procedure.

The facile green synthesis method has been employed for the synthesis of biocompatible Fe3O4 magnetic nanoparticles (MNPs) using green tea extract. The effective reduction of ferric ions (Fe3+) were done using an aqueous green tea extract where it acts as reducing as well as a capping agent. The effect of iron precursor to green tea extract ratio and the reaction temperature was studied. The MNPs were characterized by x-ray diffraction, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, dynamic light scattering, and vibrating sample magnetometer. It was observed that the reaction temperature strongly affects the magnetic and structural properties of MNPs. The magnetic measurements study showed that Fe3O4 MNPs are superparamagnetic at 300 K, while at 60 K have ferromagnetic as well as superparamagnetic contributions.

A cost-effective phytogenic fabrication of zinc oxide (ZnO) and copper-doped zinc oxide (Cu-doped ZnO) using aqueous leaf extract of Ziziphus mauritiana Lam. was successfully demonstrated. The structural, morphological and optical studies have been carried out using various techniques. XPS, XRD analysis and FT-IR spectroscopic studies confirmed the successful synthesis, crystalline nature and purity of synthesized ZnO and Cu-doped ZnO. UV–visible diffuse reflectance spectra showed reduction of band gap energies from 3.11 to 2.54 eV as Cu doping increases from 0% to 5%. SEM images revealed the synthesized ZnO and Cu-doped ZnO are irregular and spherical shaped, respectively. Antibacterial property of the synthesized materials were evaluated against Gram positive Staphylococcus aureus and Gram negative Escherichia coli using different concentrations. This investigation revealed that the synthesized materials were able to inhibit the activity of Staphylococcus aureus better than Escherichia coli under both dark and visible light conditions with the highest inhibition of 9.33 ± 0.58 mm under light irradiation. The synthesized materials were also found to effectively scavenge 2,2-diphenyl-1-picrylhydrazyl radicals in the dark and an enhancement of the scavenging activity was observed under visible light irradiation.

Green procedure for synthesizing silver nanoparticles (AgNPs) is currently considered due to its economy and toxic-free effects. Several existing works on synthesizing AgNPs using leaves extract still involve the use of physical or mechanical treatment such as heating or stirring, which consume a lot of energy. To extend and explore the green extraction philosophy, we report here the synthesis and antibacterial evaluations of a purely green procedure to synthesize AgNPs using Carica papaya, Manihot esculenta, and Morinda citrifolia leaves extract without the aforementioned additional treatment. The produced AgNPs were characterized using the ultraviolet– visible spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and antibacterial investigations. For antibacterial tests, two bacteria namely Escherichia coli and Bacillus cereus were selected. The presently employed method has successfully produced spherical AgNPs having sizes ranging from 9 to 69 nm, with plasmonic characteristics ranging from 356 to 485 nm, and energy-dispersive X-ray peak at approximately 3 keV. In addition, the smallest particles can be produced when Manihot esculenta leaves extract was applied. Moreover, this study also confirmed that both the leaves and synthesized AgNPs exhibit the antibacterial capability, depending on their concentration and the bacteria type.