Shape Of AgNPs Research Articles

Mycosynthesis of Silver Nanoparticles by an Endophytic Fungus Alternaria tenuissima and Evaluation of Their Antimicrobial and Antioxidant Effect

GREEN synthetic strategies have been receiving a great interest for metal nanoparticles synthesis. In the current study, extracellular synthesis of silver nanoparticles (AgNPs) using the cell filtrate of the endophytic fungus, Alternaria tenuissima AUMC 13621 isolated from healthy leaves of Ruta graveolens plant, was achieved. The biosynthesized AgNPs were characterized by UV–visible spectroscopy, transmission electron microscopy (TEM), dynamic light scattering analysis (DLS), and fourier transform infra-red (FT-IR), The UV–visible spectrum shows a maximum absorption peak at 416nm. TEM photography showed the spherical shape of AgNPs with an average size 9.8nm. FT-IR indicates bounding of silver nanoparticles with the supernatant molecules of A. tenuissima and provides evidence for the presence of proteins and biomolecules responsible for reduction of Ag+ to Ag0, capping and stabilizing the synthesized AgNPs. Parametric optimization for the biosynthesis process showed maximum absorbance of 400–408nm at pH-12, 70oC using 1mM AgNO3 concentration. By studying the effect of gamma irradiation on AgNPs biosynthesis, the results showed that, the obtained peak became more sharper and narrower moreover, the absorbance intensity increased by increasing irradiation dose from 0.5 to 3.0kGy. The synthesized Ag NPs have a potent antimicrobial activity to some tested pathogenic bacterial strains and Candida albicans ATCC1023. Additionally, they had excellent free radical scavenging activity. The AgNPs antioxidant activity at 100μg/ml was of 65.99% inhibition that was close to the result obtained for ascorbic acid (67.39%).

Synthesis and biological characterization of silver nanoparticles derived from the cyanobacterium Oscillatoria limnetica

Using aqueous cyanobacterial extracts in the synthesis of silver nanoparticle is looked as green, ecofriendly, low priced biotechnology that gives advancement over both chemical and physical methods. In the current study, an aqueous extract of Oscillatoria limnetica fresh biomass was used for the green synthesis of Ag-NPs, since O. limnetica extract plays a dual part in both reducing and stabilizing Oscillatoria-silver nanoparticles (O-AgNPs). The UV-Visible absorption spectrum, Fourier transforms infrared (FT-IR), transmission electron microscopy (TEM) and scanning electron microscope (SEM) were achieved for confirming and characterizing the biosynthesized O-AgNPs. TEM images detected the quasi-spherical Ag-NPs shape with diverse size ranged within 3.30–17.97 nm. FT-IR analysis demonstrated the presence of free amino groups in addition to sulfur containing amino acid derivatives acting as stabilizing agents as well as the presence of either sulfur or phosphorus functional groups which possibly attaches silver. In this study, synthesized Ag-NPs exhibited strong antibacterial activity against multidrug-resistant bacteria (Escherichia coli and Bacillus cereus) as well as cytotoxic effects against both human breast (MCF-7) cell line giving IC50 (6.147 µg/ml) and human colon cancer (HCT-116) cell line giving IC50 (5.369 µg/ml). Hemolytic activity of Ag-NPs was investigated and confirmed as being non- toxic to human RBCs in low concentrations.

Effect of nanoparticle shape on the conductivity of Ag nanoparticle poly(vinyl alcohol) composite films

AbstractIn this work, the shape effect of silver nanoparticles (AgNPs) on photocatalysis and electrical conductivity was investigated. Different shapes of AgNPs achieved using various concentrations of NaBH4 were characterized using particle size analysis, UV–visible spectroscopy and high‐resolution transmission electron microscopy. The colours of colloidal solutions were found to be influenced by the shape of the nanoparticles. Yellow and blue AgNPs were spherical and triangular in shape, respectively, whereas distorted spherical particles showed a red colour and the presence of both particles in one solution resulted in a green colloidal solution. The AgNPs were used to prepare Ag/poly(vinyl alcohol) (PVA) composite films and their electrical conductivity was investigated. Owing to their better charge carrier generation, uniform distribution in the PVA matrix and enhanced surface plasmon resonance, blue AgNPs (triangular shaped) exhibited superior conductivity performance compared to the other nanoparticles. The values for maximum conductivity for the blue and yellow AgNPs were 3.45 × 10−4 Ω−1 cm−1 and 2.67 × 10−4 Ω−1 cm−1respectively. © 2019 Society of Chemical Industry

Eco-friendly green synthesis of silver nanoparticles and their potential applications as antioxidant and anticancer agents

Eco-friendly green synthesis of nanoparticles using medicinal plants gained immense importance due to its potential therapeutic uses. In the current study, silver nanoparticles (AgNPs) were synthesized using water extract of Jurinea dolomiaea leaf and root at room temperature. MTT assay was used to study anticancer potential of AgNPs against cervical cancer cell line (HeLa), breast cancer cell lines (MCF-7), and mouse embryonic fibroblast (NIH-3 T3) cell line for toxicity evaluation. The antioxidant potential was evaluated using stable DPPH radicals. In addition, the apoptotic nuclear changes prompted by AgNPs in more susceptible HeLa cells were observed using fluorescence microscope through DAPI and PI staining. Physiochemical properties of biosynthesized AgNPs were characterized using various techniques. AgNPs were formed in very short time and UV–vis spectra showed characteristic absorption peak of AgNPs. SEM and TEM showed spherical shape of AgNPs and XRD revealed their crystalline nature. EDX analysis revealed high percentage of silver in green synthesized AgNPs. FTIR analysis indicated involvement of secondary metabolites in fabrication of AgNPs. In vitro cytotoxic and antioxidant study revealed that herb and biosynthesized AgNPs exhibited significant dose-dependent and time-dependent anticancer and antioxidant potential. Furthermore, study on normal cell line and microscopic analysis of apoptosis revealed that AgNPs exhibited good safety profile as compared to cisplatin and induces significant apoptosis effect. Based on the current findings, it is strongly believe that use of J. dolomiaea offers large scale production of biocompatible AgNPs that can be used as alternative anticancer agents against cancer cell lines tested.

Electrospinning of hyaluronan/polyvinyl alcohol in presence of in-situ silver nanoparticles: Preparation and characterization

Novel nanofibers mats were fabricated by electrospinning of polyvinyl alcohol/hyaluronan (PVA/HA) solutions in the presence of silver nanoparticles (AgNPs). The AgNPs were synthesized by in-situ chemical reduction of silver ions (Ag+) using HA as a reducing and stabilizing agent. Narrow size distribution and spherical shape of AgNPs were achieved by optimizing the initial silver nitrate concentration (0.01 to 1 M) and reaction time (10–60 min). HA-AgNPs nanocomposite and PVA/HA-AgNPs nanofibrous mats were fabricated by electrospinning technique from aqueous solution containing a different mass ratio of PVA and HA-AgNPs and characterized by UV/Vis spectroscopy, SEM, TEM, DLS, XRD, TGA, and ATR-FTIR. Mechanical and rheological properties were also investigated and discussed. The novel nanofibrous mats show great potential in skin regeneration and drug carrier applications.

Plant Mediated Green Synthesis, Catalytic Activity and Antibacterial Assay of Silver Nanoparticles

Plant mediated green synthesis of silver nanoparticles (AgNPs) was carried out with the plant extract of Vitex negundo Linn., a simple method without using harmful chemicals. Herein, a root bark extract is used as reducing and capping agent for synthesizing AgNPs from silver nitrate solution. The characterization of AgNPs were obtained by UV-visible spectrophotometer, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive spectroscopy. The results were confirmed the presence of silver nanoparticles with UV-visible absorption peak at around 433-443 nm and its crystalline nature by XRD analysis. The FTIR spectrum confirmed that the synthesized AgNPs are stabilized and protected by various functional groups of biomolecules in extract. The SEM morphology showed the triangular or spherical shape of AgNPs with the size in the range of 80-100 nm and EDS confirmed the presence of elemental silver in the sample. The catalytic activity of AgNPs was investigated in the synthesis of 5-substituted 1H-tetrazole. Furthermore, antibacterial profile showed that biopotent AgNPs exhibited moderate to good antibacterial activity.

Thermoreversible Fibrous Hydrogel of Benzene‐Centered Tris‐dodecylimidazolium Bromide: A Dual Role as Stabilizer and Directing Agent for Silver Dendrites.

AbstractBenzene centered tris‐alkylimidazolium bromide salts, denoted as BTIm(R)3Br3 ; where R=C12H25 and C14H29 have been prepared and structurally characterised. The hydrogelation ability and stabilizer role of these salts for the synthesis of silver nanoparticles (AgNPs) via chemical reduction method is described. A worth note that the BTIm(C12)3Br3 compound could lead a thermoreversible fibrous‐hydrogel in water, which plays a dual role as stabilizer and directing agent for silver dendritic nanostructures. While the partial‐hydrogel of BTIm(C12)3Br3 contributes silver nanospheres. The non‐gel solutions of BTIm(C12)3Br3 in dichloromethane, and BTIm(C14)3Br3 in water as stabilizers did not show control over the shape of AgNPs, and they lead mixed morphology. The experimental conditions, i. e. temperature, heating‐cooling process and the physical state of the stabilizer play a key role in the thermoreversible hydrogel and partial‐hydrogel control over the morphology of Ag nanostructures. Overall, the outcome of the present study provides new possibility for the use of thermoreversible fibrous gels to prepare Ag dendrites.

Bioengineering of Piper longum L. extract mediated silver nanoparticles and their potential biomedical applications.

The present investigation highlights the strong antioxidant, anticancer and larvicidal potential of green synthesized silver nanoparticles (AgNPs) using aqueous leaf extract of Piper longum L. for their diverse therapeutic applications. The optimum conditions for the synthesis of AgNPs were recorded as 1 mM AgNO3, 60 ± 2 °C at pH 6 for 120 min. Synthesized AgNPs proved to be highly stable and monodispersed as characterized through various techniques. UV-Vis spectrum of biosynthesized AgNPs showed a maximum absorption peak at 420 nm. Field emission-Scanning electron microscopy (FE-SEM) and High resolution-Transmission electron microscopy (HR-TEM) micrographs showed the spherical shape of AgNPs with mean diameter size of 28.8 nm. Existence of crystallographic AgNPs was proved by X-ray diffraction (XRD) pattern analysis. Presence of phenolics, terpenoids and flavonoids compounds which act as bioreducing agents were confirmed by Fourier-transform infrared spectroscopy (FTIR) analysis. Furthermore, the AgNPs and leaf extracts prepared individually in different solvents such as methanol, ethyl acetate, chloroform, hexane and aqueous were assessed for their bio-efficacies. AgNPs showed the enhanced antioxidant (IC50 67.56 μg) and radical-scavenging activities (IC50 196.8 μg) as compared to the crude leaf extracts. Anticancer activity revealed the strong and dose-dependent cytotoxic effect of AgNPs against the HeLa cells showing maximum IC50 value being 5.27 μg/mL after 24 h and was also found to be non-toxic to normal cells (HEK). The AgNPs induced the fragmentation of DNA in the cells, indicating the occurrence of apoptosis and necrosis. Subsequently, an efficient larvae mortality was also recorded against Anopheles stephensi having LC50 and LC90 values being 8.969 and 16.102 ppm, followed by Aedes aegypti (LC50;14.791 and LC90;28.526 ppm) and Culex quinquefasciatus (LC50;18.662 and LC90;40.903 ppm) after 72 h of exposure. Besides, they showed no toxicity against Mesocyclops thermocyclopoides (non-target organism). This is the first report showing strong anti-tumorous and larvicidal activity of AgNPs synthesized using P. longum leaf extract against cervical cancer cell line and mosquito vectors causing dengue, malaria and filariasis. Based on our findings, we suggest that AgNPs derived using P. longum leaf extract possessed excellent anti-cancerous and mosquito larvicidal potential and therefore, can be bioprospected further for the management of these hazardous health diseases. This study has given a new insight for the novel drug designing after conducting experiments on the in vivo models.

Ionic-liquid-based microextraction method for the determination of silver nanoparticles in consumer products.

A simple method to determine hazardous silver nanoparticles (AgNPs) based on ionic liquid (IL) dispersive liquid-liquid microextraction and back-extraction is described. This approach involves AgNP stabilization using a cationic surfactant followed by extraction from the sample matrix by means of an IL as an extraction phase. Certain ILs have high affinity for metals, and preliminary experiments showed that those ILs consisting of imidazolium cation efficiently extracted AgNPs in the presence of a cationic surfactant and a chelating agent. Afterward, histamine was used as a dispersing agent to promote phase transfer of differently coated AgNPs from the IL in aqueous solution to be subsequently analyzed by UV-visible spectrometry. The analytical procedure allows AgNPs to be recovered from the sample matrix in an aqueous medium, the enrichment factor being up to 4, preserving both AgNP size and AgNP shape as demonstrated by transmission electron microscopy images and the localized surface plasmon resonance band characteristic of each AgNP. The present method exhibited a linear response for AgNPs in the range from 3 to 20 μg/mL, the limit of detection being 0.15 μg/mL. Method efficiency was assessed in spiked orange juice and face cream, yielding recoveries ranging from 75.7% to 96.6%. The method was evaluated in the presence of other nanointerferents (namely, gold nanoparticles). On the basis of diverse electrophoretic mobilities and surface plasmon resonance bands for metal nanoparticles, capillary electrophoresis was used to prove the lack of interaction of the target AgNPs with gold nanoparticles during the whole protocol; thus, interferents do not affect AgNP determination. As a consequence, the analytical approach described has great potential for the analysis of engineered nanosilver in consumer products. Graphical abstract Simple protocol for the determination of silver nanoparticles (AgNPs) based on dispersive liquid-liquid extraction with a specific short alkyl side chain ionic liquid and their quantitative detection with a UV-visible spectrometer. HMIM•PF6 1-hexyl-3-methylimidazolium hexafluorophosphate, NP nanoparticle, SPR surface plasmon resonance.

Silver Nanoparticles Based Ink with Moderate Sintering in Flexible and Printed Electronics.

Printed electronics on flexible substrates has attracted tremendous research interest research thanks its low cost, large area production capability and environmentally friendly advantages. Optimal characteristics of silver nanoparticles (Ag NPs) based inks are crucial for ink rheology, printing, post-print treatment, and performance of the printed electronics devices. In this review, the methods and mechanisms for obtaining Ag NPs based inks that are highly conductive under moderate sintering conditions are summarized. These characteristics are particularly important when printed on temperature sensitive substrates that cannot withstand sintering of high temperature. Strategies to tailor the protective agents capping on the surface of Ag NPs, in order to optimize the sizes and shapes of Ag NPs as well as to modify the substrate surface, are presented. Different (emerging) sintering technologies are also discussed, including photonic sintering, electrical sintering, plasma sintering, microwave sintering, etc. Finally, applications of the Ag NPs based ink in transparent conductive film (TCF), thin film transistor (TFT), biosensor, radio frequency identification (RFID) antenna, stretchable electronics and their perspectives on flexible and printed electronics are presented.

Green Synthesis, Characterization and Antibacterial Activity of Silver Nanoparticles Using Amorphophallus paeoniifolius Leaf Extract

In this study, silver nanoparticles (Ag NPs) were profitably synthesized from aqueous Amorphophallus paeoniifolius leaf extract at room temperature, using one step and eco-friend green synthesis. The leaf extract acts as reducing agent to the formation of Ag NPs from Ag+ ions. The development of Ag NPs through aqueous medium was confirmed by UV–Vis spectroscopy and the spectra show characteristic surface plasmon resonance of Ag NPs at 428 nm. Crystalline nature of the synthesized samples was affirmed by the XRD studies. The particles are predominantly grown via (111) plane of Ag crystal and the particles size was fall in the range of 20–26 nm calculated by Scheerrer’s formula. Size and shape of Ag NPs were observed from the SEM and TEM characterization. The samples are almost having spherical shape particles and the size of the particles is lies between 20 and 30 nm. The energy peak at 3 keV in the EDS spectrum strongly supported that the synthesized sample is Ag. FTIR spectra exhibit the leaf extract containing various characteristic functional groups which should responsible for the reduction of Ag+ ions. Synthesized Ag NPs displayed as potential antibacterial candidate against both gram positive and gram negative bacterial.

Green synthesis of silver nanoparticle by cauliflower extract: characterisation and antibacterial activity against storage

Green synthesis of silver nanoparticles (AgNPs) was accomplished using different volumes of cauliflower extract and 0.001 M silver nitrate solution at 80°C for 15 min. A brownish-red solution of AgNPs formed was tested by ultraviolet–visible absorption spectroscopy, Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Surface plasmon resonance of AgNPs appeared at 416 nm. Also, the kinetic of AgNPs formation was studied and follows a sigmoidal pattern. Storing time was studied for the freshly prepared AgNPs after 60 days. FTIR analysis shows the adsorption of active components on AgNPs surface, and these components are responsible for reduction besides working as a stabiliser like a capping agent, also FTIR analysis of AgNPs after storage showed no change in peaks location. The SEM exhibited a globular shape of AgNPs, and the particle size ranged from 25 to 100 nm, while the XRD particle size calculation was 25 nm with cubic phase lattice.The antibacterial activity was tested against Gram-positive and -negative bacteria showed an inhibition zone of 16–27 mm and the antibacterial activity tested for the same bacteria after storage for about 10 months showed an inhibition zone of 6–10 mm.

Occurrence and significance of natural ore-related Ag nanoparticles in groundwater systems

Occurrences of Ag nanoparticles (Ag NPs) in the groundwater system have gradually gained extensive attention recently, owing to the wide application and considerable discharge of engineered Ag NPs. However, naturally produced Ag NPs related to metal deposits, which are supposed to have a large source, have largely been ignored. To fill this gap in the research, deep groundwater and nearby well-water samples were collected in several Ag-bearing deposits and subsequently tested using high-resolution transmission electron microscopy (HRTEM). Many approximately spherical shapes of Ag NPs were detected in both types of water media. The characteristics of most Ag NPs in well-water samples were highly consistent with those Ag NPs in deep groundwater samples, both in their morphology features and chemical composition, indicating that those Ag NPs were homologous and originally from the deep concealed Ag-bearing ore bodies. The potential fate of Ag NPs in the groundwater system were addressed, as well, such as their formation in geological processes, separation from the host minerals, migration as a result of water flow and deposition in particular environments. Consequently, Ag NPs in the groundwater systems are supposed to be of great significance in the prospecting for concealed Ag-bearing deposits and the formation of secondary Ag-bearing deposits.

Facile Interpretation of Catalytic Reaction between Organic Dye Pollutants and Silver Nanoparticles with Different Shapes

In this study, various shapes of silver nanoparticles (Ag NPs) were synthesized via simple methods in aqueous solution. The size and shape of Ag NPs were measured by TEM image and DLS, and the crystalline form of Ag NPs was confirmed by XRD. From ATR-IR and zeta potential, the Ag NPs were found to be well surrounded by PVP. In addition, the catalytic activity of Ag NPs was evaluated using model dyes. Unlike the conventional catalysts, the model dyes with absorption peaks that did not overlap with the SPR peaks of the Ag NPs were selected to evaluate the catalytic activity without removal of the Ag NPs from the dye solution.

Controllable biosynthesis of silver nanoparticles using actinobacterial strains

Abstract We report the effect of various parameters, namely substrate concentration, time, pH and temperature, on the biosynthesis of silver nanoparticles (AgNPs) by using the extract of actinobacterial strains, which were isolated from the sediments of Lonar Crater Lake in India. It was found that the formation of AgNPs and its morphology depended on synthesis conditions. Visual observation of the reaction mixture, ultraviolet-vis spectroscopic analysis and mass of synthesized AgNPs indicated that 25°C, pH 7 and 3 days of incubation time were optimal for its efficient synthesis. The transmission electron microscopy (TEM) analysis revealed aggregation and irregular shape of AgNPs both at acidic pH and below 25°C. It was found that alkaline pH and temperature higher than optimal fostered the formation of nanoparticle aggregates. Based on the obtained results, it was concluded that the efficiency of biological synthesis by using actinobacteria as well as the size and shape of fabricated nanoparticles can be manipulated by controlled conditions of synthesis process. The use of desired nanoparticles increases its potential for medical applications.

Determination of the Activity of the Green Synthesized Silver Nanoparticles Against Multidrug Resistant Bacteria Isolated from Children with Diarrhea under Five Years

Background: Bacterial resistance to wide range of antibiotics increased dramatically in the last decade. The most serious of such resistant is the multidrug resistance that leads to failure of treatment and increase in morbidity and mortality.Aim: To evaluate the synergistic inhibition of combination of nano particles with antibiotics against multidrug resistant bacteria.Materials and methods: One hundred twenty stool specimens were collected from children under five years old with diarrhea. These samples were collected during the period from May 2015 to October 2015 from different hospitals in Baghdad (Child Central Hospital, Children's Welfare Hospital and AL-Karama Hospital). Isolation and identification of bacterial isolates were carried out according to the morphology and biochemical characteristics. Antibiotic susceptibility test for 116 bacterial isolates was performed using disk diffusion method.Results: The highest rate of diarrhea (61.2%) was recorded at age group less than 12 months. Bacterial isolation frequency was 34.48% for Escherichia coli, 2.68% for Salmonella typhi, 9.48% Proteus mirabilis, 9.48% Pseudomonas aeruginosa, 9.48% Klebsiella pneumonia, 5.17% Citrobacter freundii, 5.17% Enterobacter aerogenes , 2.58% Shigella sonnei, 2.58% Serratia marcescens and 0.86% Hafnia alvei. Results showed a dissimilar resistance rates towards different antibiotics, ten bacterial isolates were collected for each bacterial species to study their resistance patterns, the ones with the highest resistance rate were selected for further study. Meanwhile, easy and cheap green method using the banana peel extract (BPE) was applied to synthesize silver nanoparticles (AgNPs). Phytochemicals of banana peel extract were screened by standard methods. The results verified the existence of alkaloids, flavonoids, and glycosides in it. These components acted as a reducing agent, stabilizing and capping agents for AgNO3 with the assistance of the microwave. The successful preparation of AgNPs was established by ultraviolet–visible spectroscopy which showed the absorption peak at 415 nm. The size and shape of AgNPs were characterized by Transmission Electron Microscopy (TEM), which indicated spherical shaped of AgNPs with size of around 9-15 nm. Dynamic light scattering (DLS) demonstrated the average size of colloidal AgNPs which was around 40.5 nm. Also Fourier Transform Infrared Spectroscopy (FTIR) measurements confirmed the role of BPE as a reducing and capping agent of silver ions. In addition zeta potential was measured to evaluate the stability of particles and showed that the stability was about -30.99 mv. Moreover, penicillin G - AgNPs and chloramphenicol-AgNPs nanocomposite were synthesized (separately) and characterized via employing UV-Vis Spectroscopy, DLS and FTIR spectroscopy to confirm successful preparation of nanocomposite. The antibacterial activity of the AgNPs and the nanocomposite effects of biosynthesis AgNPs with penicillin G and chloramphenicol antibiotics against multidrug resistance (MDR) bacteria were studied by using disk diffusion method. Results showed a good effect against MDR isolates. The synergistic effects of biosynthesis AgNPs at different concentrations with different standard antibiotic discs (Tobramycin, Chloramphenicol, Nitrofurantoin, Ampicillin- sulbactam and Nalidixic acid) against MDR bacteria were also investigated.Conclusion: This study showed that there was the synergistic action of AgNPs and antibiotics led to enhancement of antibacterial activity. So, the dose of an antibiotic administered can be reduced and subsequently decrease the adverse effects.

THE INFLUENCE OF SILVER NANOPARTICLES SYNTHESIS ON THEIR PROPERTIES

Application of green methods to replace physical and chemical methods for synthesis of silver nanoparticles (AgNPs) has become necessary not only from economic aspect but especially due to its significant impact on ecosystem. The properties of biologically synthesized AgNPs using green algae Parachlorella kessleri (P. kessleri) and chemically prepared were investigated and compared. The UVvis analysis confirmed a high stability of biosynthesized AgNPs as well as chemically synthesized gelatin modified citrate-AgNPs. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) revealed different sizes and shapes of AgNPs synthesized in different ways. Biosynthesized AgNPs have similar inhibitory antimicrobial activity as gelatin/sodium citrate–AgNPs.

Anti-biofilm Activity Against Gram-Positive Bacteria by Biologically Synthesized Silver Nanoparticles Using Curcuma longa.

To assess the biofilm inhibition activity of biosynthesized silver nanoparticles (AgNPs) using Curcuma longa. Characterizations of these biogenic nanoparticles were done by UV-Vis spectroscopy, TEM, EDX and nanoparticles tracking analyzer. The antibiofilm activity of AgNPs against S. aureus and S. pneumoniae was carried out by 96 well plate method. Further, the combined effect of AgNPs with the antibiotic was studied against S. aureus and S. pneumoniae. UV-spectroscopic analysis showed a surface plasmon resonance peak at 415nm. The shape of AgNPs is spherical with an average size of 20-40 nm while the elemental silver was confirmed by EDX analysis. These biosynthesized AgNPs have anti-biofilm activity against S. aureus and S. pneumoniae. Furthermore, the combined effect of AgNPs with an antibiotic, showed enhanced anti-biofilm activity against both the strains under study. C. longa mediated AgNPs showed potent anti-biofilm activity.

Microwave-Assisted Synthesis and Characterization of an Agriculturally Derived Silver Nanocomposite and Its Derivatives

Nanocomposites and activated carbons are well known and tested effective adsorbents in the areas of water purification and water treatment. However, commercial nanocomposites and activated carbons are expensive; therefore, it has become increasingly pertinent to produce affordable nanocomposites and activated carbons. Herein, we report a microwave assisted synthesis of an agriculturally derived nanocomposite, maize tassel-silver (MtAg) nanocomposite. Controlled growth of silver nanoparticles (AgNPs) was formed with maize tassel powder (a lignocellulosic material) and silver nitrate in the ratio (1:1) and optimized microwave conditions of 1 h, 60 °C and 800 W. The MtAg nanocomposite was activated physically and chemically using air at 400 °C and nitrogen at 600 °C and H3PO4 at 500 °C respectively. The activated and non-activated MtAg nanocomposite were characterized using energy dispersive X-ray spectroscopy, scanning electron microscopy, transmission electron microscopy (TEM), thermogravimetric analysis, Brunauer–Emmett–Teller (BET) and powder X-ray diffraction (XRD). The irregular sized, spherical shape of AgNPs was confirmed on the newly formed MtAg nanocomposite material using TEM. The XRD patterns showed diffraction peaks at 2θ of about 37.8°, 43.6°, 64.6°, 76.8° and 81.3°. The synthesized MtAg nanocomposite (ratios 1:1, 3:1 and 5:1/maize tassel vs. silver nitrate) exhibited low BET surface areas of 0.42, 0.36 and 0.13 m2/g, respectively. Upon physical activation, a BET surface area (86.27 m2/g) was recorded and this increased significantly to 331 m2/g, with chemical activation. The synthesized MtAg nanocomposite was found to be an improved form of the original tassel material in terms of thermal stability, crystallinity and structural morphology.

Green synthesis of stable silver nanoparticles by the main reduction component of green tea (Camellia sinensis L.).

Recently the use of medicinal plants potential in the production of nanoparticles has received serious attention. Here, the main component of Camellia sinensis L. (green tea) extract was detected by spectroscopy and the optimal conditions were determined for their performance in green synthesis of silver nanoparticles at room temperature. Epigallocatechin gallate was identified as the dominant component in the extract as determined by spectroscopy, and it was established that its oxidation was a function of the solution pH. Transmission electron microscopy, dynamic light scattering, and visible absorption spectroscopy (UV-Vis) confirmed the reduction in silver ions to silver nanoparticles (Ag NPs). Controlling over Ag NPs shape and narrow size distribution was achieved with 10 ml green tea leaf extract solution and in different reaction pH. Spherical colloidal Ag NPs with well-defined hydrodynamic diameters (with average hydrodynamic size of 27.9-50.2 nm) were produced. Silver nitrate concentrations used in this study were lower than that of reported in similar works, and synthesis efficiency was also higher. Nanoparticles were perfectly spherical and their uniformity, compared to similar studies, was much higher. These NPs showed higher degree of stability and were aqueously stable for >10 months in dark glasses at 4°C.