Green Synthesis of Silver Nanoparticles Using Aqueous Orange and Lemon Peel Extract and Evaluation of Their Antimicrobial Properties

Green synthesis of silver nanoparticles (AgNPs) using aqueous extracts of orange and lemon peels, as a reducing agent, and silver nitrate salts as a source of silver ions is a promising field of research due to the versatility of biomedical applications of metal nanoparticles. In this paper, AgNPs were synthetized at different reaction parameters such as the type and concentration of the extracts, metal salt concentration, temperature, speed stirring, and pH. The antibacterial properties of the obtained silver nanoparticles against E. coli, as well as the physical and chemical characteristics of the synthesized silver nanoparticles, were investigated. UV-Vis spectroscopy was used to confirm the formation of AgNPs. In addition to green biogenic synthesis, chemical synthesis of silver nanoparticles was also carried out. The optimal temperature for extraction was 65˚C, while for the synthesis of AgNPs was 35˚C. The synthesis is carried out in an acidic environment (pH = 4.7 orange and pH = 3.8 lemon), neutral (pH = 7) and alkaline (pH = 10), then for different concentrations of silver nitrate solution (0.5 mM - 1 mM), optimal time duration of the reaction was 60 min and optimal stirring speed rotation was 250 rpm on the magnetic stirrer. The physical properties of the synthesized silver nanoparticles (conductivity, density and refractive index) were also studied, and the passage of laser light through the obtained solution and distilled water was compared. Positive inhibitory effect on the growth of new Escherichia coli colonies have shown AgNPs synthesized at a basic pH value and at a 0.1 mM AgNO3 using orange or lemon peel extract, while for a 0.5 mM AgNO3 using lemon peel extract.

Exploring the nano-fungicidal efficacy of green synthesized magnesium oxide nanoparticles(MgO NPs)on the development,physiology,and infection of carrot(Daucus carota L.)with Alternaria leaf blight(ALB):Molecular docking

In this research,green synthesized magnesium oxide nanoparticles(MgO NPs)from lemon fruit extracts and their fungicidal potential was evaluated against Alternaria dauci infection on carrot(Daucus carota L.)under greenhouse conditions.The scanning and transmission electron microscopy(SEM and TEM)and ultra-violet(UV)visible spectroscopy were used to validate and characterize MgO NPs.The crystalline nature of MgONPs was determined using selected area electron diffraction(SAED).MgO NPs triggered substantial antifungal activity against A.dauci when exposed to 50 and 100 mg L^(–1)concentrations but the higher antifungal potential was noticed in 100 mg L^(–1)under invitro conditions.In fungal inoculated plants,a marked decrease in growth,photosynthetic pigments,and an increase in phenol,proline contents,and defense-related enzymes of carrot were seen over control(distilled water).However,foliar application of MgO NPs at 50 and 100 mg L^(–1)resulted in significant improvement of plant growth,photosynthetic pigments,phenol and proline contents,and defense enzymes activity of carrots with and without A.dauci infection.Spraying of MgO NPs at 100 mg L^(–1)had more plant length(17.11%),shoot dry weight(34.38%),plant fresh weight(20.46%),and root dry weight(49.09%)in carrots when challenged with A.dauci over inoculated control.The leaf blight indices and percent disease severity were also reduced in A.dauci inoculated plants when sprayed with MgO NPs.The non-bonding interactions of Alternaria genus protein with nanoparticles were studied using molecular docking.

Green Synthesis of Titanium Oxide Nanoparticles Using Natural Extracts

Green synthesis is an alternative method for obtaining nanoparticles for environmentally friendly purposes. The present work describes the synthesis and characterization of titanium oxide nanoparticles, starting from three natural sources: orange peel, hibiscus rosa sinensis and Aloe vera. Titanium (IV) tetrabutoxide in ethanol solution was used as precursor. The methodology used was based on the sol-gel technique, through which TiO2 nanoparticles were obtained in the anatase phase. The characterization of the nanoparticles was carried out by means of x-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared spectrophotometry (FTIR), which allowed the identification of a good degree of purity and crystallinity of the samples obtained.

Green Synthesis and Antibacterial Properties of Silver Nanoparticles from Eugenia uniflora Fruit Extract

The synthesis of nanoparticles by biological methods using microorganisms, enzymes, or plant extracts has been suggested as a possible ecofriendly alternative to chemical and physical methods that involve the use of harmful reducing agents. Green synthesis of silver nanoparticles (AgNPs) was achieved using Eugenia uniflora ripe fruit extract, which was characterized by phytochemical screening revealing the presence of polyphenols (quinones, flavonoids, and tannins), reducing compounds, and terpenes. These excellent antioxidants reduced silver nitrate to give the AgNPs, which were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), and ζ potential analysis. The diameter of the AgNPs ranged from 10.56 ± 1.2 nm to 107.56 ± 5.7 nm. The antibacterial activity of the AgNPs was evaluated using a modification of the Kirby-Bauer technique with Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The inhibition halos were 11.12 ± 0.02 mm, 13.96 ± 0.07 mm, and 11.29 ± 0.76 mm, respectively. The synthesis using E. uniflora is an ecofriendly and low cost method of obtaining silver nanoparticles that could be used in health sciences because of their activity against bacteria with antibiotic resistance.

Green Synthesis and Luminescent Properties of Mn4+ Doped Red Phosphor for WLED

Herein, the K3MoO2F5.2H2O:Mn4+ phosphor was synthesized by using low toxic NH4HF2 and HCl instead of highly toxic HF. The K3MoO2F5.2H2O:Mn4+ phosphor has a blocky structure and exhibits sharp red emission at the range of 580 to 670 nm excited by the blue light at 470 nm. The fabricated WLED device at 20 mA current has low correlation color temperature (CCT = 3608 K) and high color rendering index (Ra = 90.1), which can significantly improve the electroluminescence performance of cold WLED devices. These results indicate that the K3MoO2F5.2H2O:Mn4+ phosphor has potential application value in warm WLED excited by blue light chip. .

Green synthesis and characterization of palladium nanoparticles and its conjugates from solanum trilobatum leaf extract

An important area of research in nanotechnology deals with the synthesis of nanoparticles of different chemical compositions,sizes and controlled monodispersity.Currently,there is a growing need to develop environmentally benign nanoparticle synthesis in which no toxic chemicals are used in the synthesis protocol.Palladium nanoparticles(Pd Np) are of interest because of their catalytic properties and affinity for hydrogen.Our protocol for the phyto-synthesis of Pd Np under moderate p H and room temperature offers a new means to develop environmentally benign nanoparticles.Solanum trilobatum is enlightened in our present study as it is enriched with phytochemicals to reduce palladium chloride ions.Poly MVA a dietary supplement based on the nontoxic chemotherapeutic lipoic acid-palladium complex(LA-Pd) is been hypothesized as the new paradigm of cancer therapy.Hence forth we successfully conjugated lipoic acid(S-Pd Np-LA) and vitamins(S-Pd Np-Vitamin-LA) to palladium nanoparticles synthesised from Solanum trilobatum leaf extract.These nanoparticles(S-Pd Np,S-Pd Np-LA,S-Pd Np-Vitamin-LA) were characterized with UV-Vis Spectroscopy,SEM and FTIR analysis,which revealed that S-Pd Np are polydisperse and of different morphologies ranging from 60?70 nm(S-Pd Np),65?80 nm(S-Pd Np-LA) and 75?100 nm(S-Pd Np-Vitamin-LA) in size.

Green Synthesis of Nitrogen-to-Ammonia Fixation: Past, Present, and Future

The nitrogen(N2)-to-ammonia(NH3)fixation driven by renewable energy has an attractive prospect to relieve the global warming and reduce the consumption of fossil fuels.Ideally,photocatalytic,electrochemical,and photoelectrochemical approaches are developed as the next-generation NH3 synthesis technologies to substitute the Haber–Bosch method.However,the NH3 yield rate of nitrogen reduction reaction(NRR)by green approaches is extremely low,resulting in the current dilemma of NRR and contamination issues.Thus,in this mini review,the past advances on the sustainable NRR are briefly summarized in the three aspects as follows:the selectivity and adjustment of various catalysts,the type of electrolyte/solvent system,and the investigation of reaction conditions.Subsequently,the recent critical activities in the area of sustainable NH3 synthesis are analyzed and discussed deeply,and a perspective for rational and healthy development of this area is provided positively。

Green synthesis of bentonite-supported iron nanoparticles as a heterogeneous Fenton-like catalyst:Kinetics of decolorization of reactive blue 238 dye

This study aimed to synthesize green tea nano zero-valent iron(GT-NZVI)and bentonite-supported green tea nano zero-valent iron(BGT-NZVI)nanoparticles using green tea extracts in an environmentally sustainable way.Bentonite was used as a support material because it disperses and stabilizes GT-NZVI,and it helps to reduce the cost,increase the adsorption capacity of GT-NZVI,and decrease the optimum amount of GT-NZVI used in Fenton-like oxidation.A scanning electron microscope,an atomic force microscope,and a Fourier transform infrared spectroscope were used to characterize GT-NZVI and B-GT-NZVI,while the zeta potential was measured to evaluate the stability of iron nanoparticles.The decolorization kinetics of reactive blue 238(RB 238)dye in the aqueous phase in the Fenton-like oxidation process were investigated as well.The effects of various experimental conditions such as reaction time,dosages of catalysts,concentration of H2O2,temperature,addition of inorganic salts,and other parameters were investigated.The results show that the oxidative degradation efficiencies of RB 238 dye catalyzed by GT-NZVI and B-GT-NZVI were 93.5%and 96.2%,respectively,at the optimum reaction conditions as follows:c(H2O2)¼5 mmol/L,r(GT-NZVI)¼0.5 g/L or r(B-GT-NZVI)¼0.5 g/L,c(RB 238 dye)¼0.05 mmol/L,and pH¼2.5 at 180 min.The best catalytic performance was exhibited when B-GT-NZVI was used.Three kinetic models were employed,and the second-order model was found to be the best model representing the experimental kinetic data of RB 238 dye.The value of activation energy decreased from 38.22 kJ/mol for GT-NZVI to 14.13 kJ/mol for B-GT-NZVI.This indicates that the effect of B-GT-NZVI in decreasing the energy barrier is more pronounced than that of the GT-NZVI catalyst,leading to improved Fenton-like oxidation processes.©2020 Hohai University.Production and hosting by Elsevier B.V.This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).

Antiplasmodial activity of silver nanoparticles: A novel green synthesis approach

Objective:To synthesize silver nanoparticles using silver nitrate by a green technique which involves different compositions of aqueous leaf extracts of Azadirachta indica(neem)and Ocimum sanctum(tulsi).Methods:Their shape and size were determined using transmission electron microscopy and UV-visible spectroscopy.Their antiplasmodial activity was studied using the malarial parasite strain(Plasmodium falciparum,3D7).The parasite strain(3D7)was collected and revived in vitro using Trager and Jensen method in RPMI 1640 medium for 7-8cycles.Half maximal effective concentration values were calculated by nonlinear regression analysis.Results:Transmission electron microscopy results confirmed the formation of silver nanoparticles with size ranging from 4.74-39.32 nm and their size differs by varying the concentrations from 20%to 100%of neem extract in neem and tulsi extracts.It was observed that samples B and C showed half maximum effective concentration of about 0.3μM.Conclusions:It can be easily established that the aqueous leaf extracts of neem and tulsi in combination can be a good source for synthesis of silver nanoparticles with small size possessing appreciable antiplasmodial activity.

A Facile and Green Synthesis of Sulforaphane

The compound sulforaphane （SFN, 1） has been synthesized via a facile and green synthetic strategy based on the modification of previous methods. Because of its high bioactivities and rare content in nature, the present work is of great important significance.

Green Synthesis of Silver Nanoparticles: A Review

The bio-molecules from various plant components and microbial species have been used as potential agents for the synthesis of silver nanoparticles (AgNPs). In spite of a wide range of bio-molecules assisting in the process, synthesizing stable and widely applicable AgNPs by many researchers still poses a considerable challenge to the researchers. The biological agents for synthesizing AgNPs cover compounds produced naturally in microbes and plants. More than 100 different biological sources for synthesizing AgNPs are reported in the past decade by various authors. Reaction parameters under which the AgNPs were being synthesized hold prominent impact on their size, shape and application. Available published information on AgNPs synthesis, effects of various parameters, characterization techniques, properties and their application are summarised and critically discussed in this review.

Green Synthesis of Silver Nanoparticles Using Plectranthus Amboinicus Leaf Extract for Preparation of CMC/PVA Nanocomposite Film

In the present study,the biogenic silver nanoparticles have been synthesized using aqueous leaf extract of Plectranthus amboinicus(PA),which acted as both reducing and stabilizing agents.The PA synthesized silver nanoparticles were blended with carboxymethyl cellulose/polyvinyl alcohol(CMC/PVA)biocomposite.The prepared AgNPs as well as the biogenic AgNPs incorporated CMC/PVA films were investigated using UV-visible spectrophotometry,Fourier-transform infrared spectroscopy(FT-IR),dynamic light scattering(DLS),scanning electron microscope(SEM),and X–ray diffraction(XRD).The DLS results showed that biogenic AgNPs had the average particle size of 65.70 nm with polydispersity index of 0.44.The surface plasmon resonance of AgNPs,which was determined by UV-vis spectrophotometry,showed the value of 410.00 nm.These results therefore confirmed the reduction Ag+into Ag°and the formation of AgNPs in the medium.The SEM imaging showed that AgNPs was quasi-spherical and monodisperse.The XRD peaks at 33.07°,44.19°,64.58°and 77.47°confirmed the crystalline nature and presence of AgNPs.The CMC/PVA films that incorporated with AgNPs displayed best mechanical strength and morphological properties than the pure CMC/PVA film.The film of CMC/PVA-AgNPs exhibited significant antibacterial activities against Bacillus spizizenii,Staphylococcus aureus,Salmonella typhi and Escherichia Coli.

Green Synthesis of Silver Nanoparticles from Abronia villosa as an Alternative to Control of Pathogenic Microorganisms

The aim of this study was to evaluate the antibacterial and antifungal activities of eco-friendly synthesized silver nanoparticles.The silver nanoparticles were synthesized by biological method using aqueous extract of Abronia villosa.Synthesis of silver nanoparticles was confirmed by color change and characterized using UV-visible spectroscopy,scanning electron microscope(SEM),energy dispersive X-ray spectroscopy(EDX),dynamic light scattering(DLS),and zeta potential analysis.The SEM analysis revealed the presence of spherical silver nanoparticles of the size range 21 to 33 nm.Synthesized silver nanoparticles were used to evaluate their antibacterial effects at different concentrations(25,50,75 and 100μg/ml)on gram negative and gram positive bacteria.The biggest halo zone was observed at 75 and 100μg/ml concentrations of silver nanoparticles against both gram positive and gram negative bacteria.Antifungal activity of biosynthesized silver nanoparticles was evaluated against seven different phytopathogenic fungi.AgNPs showed high inhibition of radial growth toward all tested fungi.The highest inhibition of fungal growth by AgNPs was recorded against Macrophomina phaseolina(86.06±0.92%).Biosynthesized AgNPs using plant extract are a promising to use safety for various biomedical and agricultural applications.

Green Synthesis of Silver Nanoparticles Using Cannabis sativa Extracts and Their Anti-Bacterial Activity

A procedure for the green synthesis of silver nanoparticles (AgNPs) using Cannabis sativa (hemp plant) as a stabilizing media was developed and antibacterial activity was tested. Within 30 minutes of heating the mixture of silver nitrate and hemp extract, the formation of silver nanoparticles took place under the complete absence of a chemical reducing or an additional stabilizing agent. The so-formed AgNPs were characterized using different optical spectroscopy and electron microscopy techniques. The initial formation of AgNPs was established from UV-Vis data based on surface plasmon resonance (SPR) of AgNPs at ~417 nm. The exact size, shape, and elemental composition of AgNPs were established from ESEM images and EDS data. The antibacterial activity of these nanoparticles was studied on Gram-positive Staphylococcus aureus, and Gram-negative Escherichia coli following Disk diffusion and Minimum Inhibitory Concentration (MIC) tests. Results showed that the biosynthesis of silver nanoparticles using hemp extract could be a simple,inexpensive, and biocompatible method.

Green Synthesis of Magnetite Nanoparticles Using Aqueous Leaves Extracts of <i>Azadirachta indica</i>and Its Application for the Removal of As(V) from Water

Because of various disadvantages of chemical synthesis processes, these days people are attracting towards green synthesis processes as it is devoid of toxic by-products, cost-effective and eco-friendly. In this study, a simple green synthesis method is applied for the synthesis of magnetite (Fe3O4) nanoparticles (MNPs) by co-precipitation of FeCl3·6H2O and FeSO4·7H2O in the molar ratio of 2:1 using Azadirachta indica leaves extract under nitrogen environment. FTIR, XRD, SEM etc. were used to characterize the synthesized MNPs. Batch adsorption experiments were carried out to determine adsorption equilibrium of As(V) as a function of pH, adsorbent dose, contact time and different initial concentrations. Kinetics results were best described by pseudo-second order model with rate constant value 0.0052 g/(mg·min). The equilibrium adsorption isotherm was best fitted with Langmuir adsorption isotherm model. The maximum adsorption capacity was found to be 62.89 mg/g at pH 2. MNPs showed a high affinity for As(V) and avoids filtration for solid-liquid separation, thus it would be employed as a promising material for the removal of As(V) from water.

Light Induced Green Synthesis of Silver Nanoparticles Using Aqueous Extract of Prunus amygdalus

Light driven, photon mediated green synthesis of silver nano-particles (AgNPs) was carried out using aqueous silver nitrate solution (1 mM) and aqueous extract of almond (Prunus amygdalus). Experiments were carried out in dark, diffused sunlight and direct sunlight to study the influence of light intensity as well as by wrapping the reaction tubes with colored cellophane filters (violet, green, yellow and red) to investigate the effect of light color on AgNP synthesis. It was observed that the violet filter enhanced the AgNPs synthesis appreciably. The FTIR spectroscopic analysis confirmed participation of bio-molecules with hydroxyl and amide groups present in the almond extract as reducing and capping or stabilizing agents, respectively. Dynamic light scattering (DLS) studies revealed the particle size distribution of nano-particles as 2 – 400 nm, and scanning electron microscopy (SEM) confirmed their spherical shape with an average size of about 20 nm. Growth analysis of AgNPs revealed an increase in number of nano-particles with time, whereas their rate of growth decreased gradually. The AgNP suspension was stable even beyond 3 weeks.

Recent progress in the green synthesis of rare-earth doped upconversion nanophosphors for optical bioimaging from cells to animals

Rare-earth doped upconversion nanophosphors(UCNPs), which convert low energy near-infrared(NIR) photons into high energy photons such as ultraviolet, visible light and NIR light, have found various applications in optical bioimaging. In this review article, we summarize recent advances in the synthesis and applications of UCNPs achieved by us and other groups in the past few years. The approaches for the synthesis of UCNPs are presented,with an emphasis on the role of green chemistry in the advancement of this field, followed by a focused overview on their latest applications in optical bioimaging from subcellular structures through cells to living animals. Challenges and opportunities for the use of UCNPs in biomedical diagnosis and therapy are discussed.

Effect of storage conditions on long-term stability of Ag nanoparticles formed via green synthesis

Spherical Ag nanoparticles(AgNPs) with a diameter of 20 nm or smaller were biologically synthesized using algae Parachlorella kessleri. The effect of storage conditions on the long-term stability of AgNPs was investigated. UV/Vis spectrophotometry, transmission electron microscopy, and dynamic light scattering measurements revealed that the long-term stability of AgNPs was influenced by light and temperature conditions. The most significant loss of stability was observed for the AgNPs stored in daylight at room temperature. The AgNPs stored under these conditions began to lose their stability after approximately 30 d; after 100 d, a substantial amount of agglomerated particles settled to the bottom of the Erlenmeyer flask. The AgNPs stored in the dark at room temperature exhibited better long-term stability. Weak particle agglomeration began at approximately the 100 th day. The AgNPs stored in the dark at about 5℃ exhibited the best long-term stability; the AgNPs stored under such conditions remained spherical, with a narrow size distribution, and stable(no agglomeration) even after 6 months. Zeta-potential measurements confirmed better dispersity and stability of AgNPs stored under these conditions.

Green Synthesis of Aryl Thioethers through Cu-catalysed C-S Coupling of Thiols and Aryl Boronic Acids in Water

An efficient, practical, highly selective and environmentally benign method is reported for the synthesis of aryl thioethers via the coupling of thiols with aryl boronic acids in the presence of NaOH and a catalytic amount of CuSO4 at 130 ℃ using water as a green solvent. The products were obtained in moderate to excellent yields;more importantly, the use of toxic ligands and solvents was avoided. A broad range of aryl boronic acids and scalable processes make this methodology valuable and versatile for the synthesis of a broad range of aryl sulfides.

Applications of lignin-derived catalysts for green synthesis

This review intends to introduce the application of lignin-derived catalyst for green organic synthesis over latest two decades and aims to present a renewable alternative for conventional catalyst for future industry application. The structure of lignin is initially introduced in this review. Then, various pretreatment and activation technologies of lignin are systematically presented, which includes physical activation for the formation of well-developed porosity and chemical activation to introduce catalytic active sites. Finally, the catalytic performances of various lignin-derived catalysts are rationally assessed and compared with conventional catalysts, which involves lignin-derived solid acids for hydrolysis, hydration, dehydration(trans)esterification, multi-component reaction and condensation, lignin-derived solid base for Knoevenagel reaction, lignin-derived electro-catalysts for electro-oxidation, oxygen reduction reaction, and lignin-derived supported transition metal catalysts for hydrogenation, oxidation, coupling reaction, tandem reaction, condensation reaction, ring-opening reaction, Friedel-Crafts-type reaction,Fischer–Tropsch synthesis, click reaction, Glaser reaction, cycloaddition and(trans)esterification. The above lignin-derived catalysts thus successfully promote the transformations of organic compounds, carbon dioxide, biomass-based cellulose, saccharide and vegetable oil into valuable chemicals and fuels. At the end of this review, some perspectives are given on the current issues and tendency on the lignin-derived catalysts for green chemistry.