Biosynthesis and Characterization of AgNPs-Silk/PVA Film for Potential Packaging Application.

PubMed

Tao, Gang; Cai, Rui; Wang, Yejing; Song, Kai; Guo, Pengchao; Zhao, Ping; Zuo, Hua; He, Huawei

2017-06-17

Bionanocomposite packaging materials have a bright future for a broad range of applications in the food and biomedical industries. Antimicrobial packaging is one of the bionanocomposite packaging materials. Silver nanoparticle (AgNP) is one of the most attractive antimicrobial agents for its broad spectrum of antimicrobial activity against microorganisms. However, the traditional method of preparing AgNPs-functionalized packaging material is cumbersome and not environmentally friendly. To develop an efficient and convenient biosynthesis method to prepare AgNPs-modified bionanocomposite material for packaging applications, we synthesized AgNPs in situ in a silk fibroin solution via the reduction of Ag⁺ by the tyrosine residue of fibroin, and then prepared AgNPs-silk/poly(vinyl alcohol) (PVA) composite film by blending with PVA. AgNPs were synthesized evenly on the surface or embedded in the interior of silk/PVA film. The prepared AgNPs-silk/PVA film exhibited excellent mechanical performance and stability, as well as good antibacterial activity against both Gram-negative and Gram-positive bacteria. AgNPs-silk/PVA film offers more choices to be potentially applied in the active packaging field.

Multifunctional Ag-decorated porous TiO2 nanofibers in dye-sensitized solar cells: efficient light harvesting, light scattering, and electrolyte contact.

PubMed

Hwang, Sun Hye; Song, Hee; Lee, Jungsup; Jang, Jyongsik

2014-09-26

Designing the photoanode structure in dye-sensitized solar cells (DSSCs) is vital to realizing enhanced power conversion efficiency (PCE). Herein, novel multifunctional silver-decorated porous titanium dioxide nanofibers (Ag/pTiO2 NFs) made by simple electrospinning, etching, and chemical reduction processes are introduced. The Ag/pTiO2 NFs with a high surface area of 163 m(2)  g(-1) provided sufficient dye adsorption for light harvesting. Moreover, the approximately 200 nm diameter and rough surface of the Ag/pTiO2 NFs offered enough light scattering, and the enlarged interpores among the NFs in the photoanode also permitted electrolyte circulation. Ag nanoparticles (NPs) were well dispersed on the surface of the TiO2 NFs, which prevented aggregation of the Ag NPs after calcination. Furthermore, a localized surface plasmon resonance effect by the Ag NPs served to increase the light absorption at visible wavelengths. The surface area and amount of Ag NPs was optimized. The PCE of pTiO2 NF-based DSSCs was 27 % higher (from 6.2 to 7.9 %) than for pure TiO2 NFs, whereas the PCE of Ag/pTiO2 NF-based DSSCs increased by about 12 % (from 7.9 to 8.8 %). Thus, the PCE of the multifunctional pTiO2 NFs was improved by 42 %, that is, from 6.2 to 8.8 %. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Antimicrobial and anticancer activity of AgNPs coated with Alphonsea sclerocarpa extract.

PubMed

Doddapaneni, Suman Joshi D S; Amgoth, Chander; Kalle, Arunasree M; Suryadevara, Surya Narayana; Alapati, Krishna Satya

2018-03-01

The synthesis and characterization of an aggregate of AgNPs coated with plant extract (PE) from Alphonsea sclerocarpa and its significant antimicrobial activity and inhibition on K562 (blood cancer) cells have been appended in the article. Synthesis of aggregate [(AgNPs)-(PE)] has been followed by a facile eco-friendly approach without using any harmful chemicals. The morphology of an aggregate [(AgNPs)-(PE)] was confirmed by TEM and SEM microscopic characterizations. Properties like solid state, the presence of functional groups, and elemental composition have been characterized through the XRD, FTIR, and EDAX. The biocompatibility of synthesized aggregate of [(AgNPs)-(PE)] was confirmed by the MTT assay. An in vitro cell (HEK293)-based studies were performed for the biocompatibility tests and it is found that the aggregate [(AgNPs)-(PE)] is not harmful to normal/healthy cells. Even though A. sclerocarpa show the antimicrobial (antibacterial and antifungal) activity, it has been further enhanced with the developed aggregate of [(AgNPs)-(PE)]. Furthermore, it has been extended to examine the cellular inhibition on K562 cells and obtained > 75% cell inhibition for 24 h treated cells.

Antifungal Effects of Silver Nanoparticles (AgNPs) against Various Plant Pathogenic Fungi.

PubMed

Kim, Sang Woo; Jung, Jin Hee; Lamsal, Kabir; Kim, Yun Seok; Min, Ji Seon; Lee, Youn Su

2012-03-01

This research is concerned with the fungicidal properties of nano-size silver colloidal solution used as an agent for antifungal treatment of various plant pathogens. We used WA-CV-WA13B, WA-AT-WB13R, and WA-PR-WB13R silver nanoparticles (AgNPs) at concentrations of 10, 25, 50, and 100 ppm. Eighteen different plant pathogenic fungi were treated with these AgNPs on potato dextrose agar (PDA), malt extract agar, and corn meal agar plates. We calculated fungal inhibition in order to evaluate the antifungal efficacy of silver nanoparticles against pathogens. The results indicated that AgNPs possess antifungal properties against these plant pathogens at various levels. Treatment with WA-CV-WB13R AgNPs resulted in maximum inhibition of most fungi. Results also showed that the most significant inhibition of plant pathogenic fungi was observed on PDA and 100 ppm of AgNPs.

Bacterial adhesion and inactivation on Ag decorated TiO2-nanotubes under visible light: Effect of the nanotubes geometry on the photocatalytic activity.

PubMed

Hajjaji, A; Elabidi, M; Trabelsi, K; Assadi, A A; Bessais, B; Rtimi, S

2018-06-05

This study investigates the effect of the diameter of TiO 2 nanotubes and silver decorated nanotubes on optical properties and photocatalytic inactivation of Escherichia coli under visible light. The TiO 2 nanotubes (TiO 2 -NTs) were prepared using the electrochemical method varying the anodization potential starting from 20 V until 70 V. The Ag nanoparticles were carried out using the photoreduction process under the same experimental conditions. The diameter size was determined using the scanning electronic microscopy (SEM). TiO 2 -NTs diameter reached ∼100 nm at 70 V. Transmission electronic microscopy (TEM) imaging confirmed the TiO 2 -NTs surface decoration by silver nanoparticles. The Ag-NPs average size was found to be equal to 8 nm. The X-Ray diffraction (XRD) analysis confirm that all TiO 2 -NTs crystallize in the anatase phases regardless the used anodization potential. The decrease of the photoluminescence (PL) intensity of Ag NPs decorated TiO 2 -NTs indicates the decrease of the specific area when the nanotubes diameter increases. The UV-vis absorbance show that the absorption edges was bleu shifted with the increasing of nanotubes diameter, which can be explained by the increase of the crystallites average size. The bacterial adhesion and inactivation tests were carried in the dark and under light. Bacteria were seen to adhere on TiO 2 -NTs in the dark; however, under light the bacteria were killed before they establish a strong contact with the TiO 2 -NTs and Ag/TiO 2 -NTs surfaces. Bacterial inactivation kinetics were faster when the anodizing potential of the NTs-preparation increases. A total bacterial inactivation was obtained on ∼100 nm nanotubes diameter within 90 min. This result was attributed to the enhancement of the TNTs crystallinity leading to reduced surface defects. Redox catalysis was seen to occur under light on the TiO 2 -NTs and Ag/TiO 2 -NTs. the photo-induced antibacterial activity on the AgO/Ag 2 O decorated Ti

Structural mechanical and antibacterial properties of HPMC/SF-AgNPs nanocomposite films

NASA Astrophysics Data System (ADS)

Harish, K. V.; Rao, B. Lakshmeesha; Asha, S.; Vipin, C.; Sangappa, Y.

2018-04-01

In the present study, Hydroxypropyl Methylcellulose (HPMC) pure and HPMC/SF-AgNPs biopolymer nanocomposite films were prepared by simple solution casting method. The prepared nanocomposite films were characterized using UV-Visible spectroscopy(UV-Vis), X-ray diffraction (XRD) measurements. The mechanical properties of HPMC/SF-AgNPs nanocomposites were found to be decrease with increase in the AgNP's concentrations. The HPMC/SF-AgNPs nanocomposites showed very good antibacterial activity against human pathogens P. aeruginosa, E.coli, and S.aureus.

Seed-mediated photodeposition route to Ag-decorated SiO2@TiO2 microspheres with ideal core-shell structure and enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Ma, Jianqi; Guo, Xiaohua; Ge, Hongguang; Tian, Guanghui; Zhang, Qiang

2018-03-01

Ag-decorated SiO2@TiO2 microspheres (SiO2@TiO2-Ag) with ideal core-shell structure and enhanced photocatalytic activity were successfully fabricated by combining both coating anatase TiO2 on the surface of SiO2 spheres and subsequent depositing face-centered cubic Ag nanoparticles (NPs) on the coated TiO2 surface via novel sol-gel method and Ag-seed-mediated photodeposition (PD) route, respectively. The morphology, structure, composition and optical properties of the resulting composites were characterized in detail. The results reveal that the monodisperse SiO2 spheres of ∼260 nm were covered uniformly and perfectly by the TiO2 nanoparticle coating layer with the thickness of ca. 55 nm by the novel sol-gel method. Further, homogeneously and highly dispersed Ag NPs with an average size of 8 ± 1.5 nm were strongly anchored onto the TiO2 surface in SiO2@TiO2 core-shell spheres by the modified PD process (Ag-seed-mediated PD route), whereas polydispersed Ag aggregates and detached Ag NPs were irregularly deposited over the TiO2 surface in previous works, which is the inherent problem and has not been effectively solved for depositing noble metal NPs such as Au, Ag, Pt, Pd on TiO2 surface by conventional PD method. The formation mechanism of small and uniformly dispersed Ag NPs with narrow size distribution via the modified PD method is tentatively explained by both nucleation kinetics and growth kinetics. The key reason is that the pre-deposited seeds firmly tethered on SiO2@TiO2 spheres served as nucleation sites and anchoring points for the further nucleation and subsequent growth of Ag via photoreduction of Ag+.

Both Enhanced Biocompatibility and Antibacterial Activity in Ag-Decorated TiO2 Nanotubes

PubMed Central

Lan, Ming-Ying; Liu, Chia-Pei; Huang, Her-Hsiung; Lee, Sheng-Wei

2013-01-01

In this study, Ag is electron-beam evaporated to modify the topography of anodic TiO2 nanotubes of different diameters to obtain an implant with enhanced antibacterial activity and biocompatibility. We found that highly hydrophilic as-grown TiO2 nanotubes became poorly hydrophilic with Ag incorporation; however they could effectively recover their wettability to some extent under ultraviolet light irradiation. The results obtained from antibacterial tests suggested that the Ag-decorated TiO2 nanotubes could greatly inhibit the growth of Staphylococcus aureus. In vitro biocompatibility evaluation indicated that fibroblast cells exhibited an obvious diameter-dependent behavior on both as-grown and Ag-decorated TiO2 nanotubes. Most importantly, of all samples, the smallest diameter (25-nm-diameter) Ag-decorated nanotubes exhibited the most obvious biological activity in promoting adhesion and proliferation of human fibroblasts, and this activity could be attributed to the highly irregular topography on a nanometric scale of the Ag-decorated nanotube surface. These experimental results demonstrate that by properly controlling the structural parameters of Ag-decorated TiO2 nanotubes, an implant surface can be produced that enhances biocompatibility and simultaneously boosts antibacterial activity. PMID:24124484

Multifunctional AgNPs@Wool: colored, UV-protective and antioxidant functional textiles

NASA Astrophysics Data System (ADS)

Shabbir, Mohd; Mohammad, Faqeer

2018-02-01

Nanomaterials have great impact on textile industry for multifunctional and smart clothing as per the need of present, and further, green nanotechnology is the current hotspot of research and industrial developments. Silver nanoparticles (AgNPs) are synthesized (in situ) by using natural compounds of plant extracts (naphthoquinones, phenolics/flavonoids, polyphenols) as reducing or stabilizing agents, and simultaneously deposited on wool fabric for coloration, UV protection and antioxidant properties. UV-visible spectroscopy is used to monitor the route of biosynthesis of nanoparticles and transmission electron microscopy for morphological characteristics of synthesized AgNPs. Spherical and almost oval-shaped AgNPs were synthesized by naphthoquinones, polyphenols and flavonoids, respectively. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction pattern (XRD) and Fourier transform infrared spectroscopy were used for the AgNPs@Wool fabrics characterization. SEM-EDX analysis and XRD patterns confirmed the successful deposition of silver nanoparticles on wool. Coloration characteristics in terms of color strength (K/S) and CIEL*a*b*c*h° values, UV protection abilities in terms of UV transmittance and UV protection factor, and % antioxidant activity of AgNPs@Wool are suggestive of good-to-excellent results.

Enhancing the photoelectrochemical response of TiO2 nanotubes through their nanodecoration by pulsed-laser-deposited Ag nanoparticles

NASA Astrophysics Data System (ADS)

Trabelsi, K.; Hajjaji, A.; Gaidi, M.; Bessais, B.; El Khakani, M. A.

2017-08-01

We report on the pulsed laser deposition (PLD) based nanodecoration of titanium dioxide (TiO2) nanotube arrays (NTAs) by Ag nanoparticles (NPs). We focus here on the investigation of the effect of the number of laser ablation pulses (NLP) of the silver target on both the average size of the Ag-NPs and the photoelectrochemical conversion efficiency of the Ag-NP decorated TiO2-NT based photoanodes. By varying the NLP, we were able to not only control the size of the PLD-deposited Ag nanoparticles from 20 to ˜50 nm, but also to increase concomitantly the surface coverage of the TiO2 NTAs by Ag-NPs. The red-shifting of the surface plasmon resonance peak of the PLD-deposited Ag-NPs deposited onto quartz substrates confirmed the increase of their size as the NLP is increased from 500 to 10 000. By investigating the photo-electrochemical properties of Ag-NP decorated TiO2-NTAs, by means of linear sweep cyclic voltammetry under UV-Vis illumination, we found that the generated photocurrent is sensitive to the size of the Ag-NPs and reaches a maximum value at NLP =500 (i.e.,; Ag-NP size of ˜20 nm). For NLP = 500, the photoconversion efficiency of the Ag-NP decorated TiO2-NTAs is shown to reach a maximum of 4.5% (at 0.5 V vs Ag/AgCl). The photocurrent enhancement of Ag-NP decorated TiO2-NTAs is believed to result from the additional light harvesting enabled by the ability of Ag-NPs to absorb visible irradiation caused by various localized surface plasmon resonances, which in turn depend on the size and interdistance of the Ag nanoparticles.

A biodynamic understanding of dietborne and waterborne Ag uptake from Ag NPs in the sediment-dwelling oligochaete, Tubifex tubifex

USGS Publications Warehouse

Tangaa, Stine Rosendal; Winther-Nielsen, Margrethe; Selck, Henriette; Croteau, Marie-Noele

2018-01-01

Metal nanoparticles (Me-NPs) are increasingly used in various products, such as inks and cosmetics, enhancing the likelihood of their release into aquatic environments. An understanding of the mechanisms controlling their bioaccumulation and ecotoxicity in aquatic biota will help support environmental risk assessment. Here we characterized unidirectional parameters for uptake and elimination of silver (Ag) in the sediment-dwelling oligochaete Tubifex tubifex after waterborne (0.01–47 nmol Ag/L) and dietborne (0.4–482 nmol Ag/g dw sed.) exposures to Ag NPs and AgNO3, respectively. Worms accumulated Ag from AgNO3more efficiently than from Ag NPs during waterborne exposure. The Ag uptake rate constants from water were 8.2 L/g/d for AgNO3 and 0.34 L/g/d for Ag NPs. Silver accumulated from both forms was efficiently retained in tissues, as no significant loss of Ag was detected after up to 20 days of depuration in clean media. High mortality (~50%) during depuration (i.e. after 17 days) was only observed for worms exposed to waterborne AgNO3 (3 nmol/L). Sediment exposures to both Ag forms resulted in low accumulation, i.e., the uptake rate constants were 0.002 and 0.005 g/g/d for AgNO3 and Ag NPs, respectively. Avoidance was only observed for worms exposed to sediment amended with AgNO3. Incorporation of the estimated rate constants into a biodynamic model predicted that sediment is likely the most important route of uptake for Ag in both forms in ecologically relevant aquatic environments. However, inference of bioavailability from our estimations of Ag assimilation efficiencies (AE) suggests that Ag (AE: 3–12% for AgNO3 and 0.1–0.8% for Ag NPs) is weakly bioavailable from sediment for this species. Thus, Ag amended to sediment as NPs might not pose greater problems than 'conventional' Ag for benthic organisms such as T. tubifex.

Voltammetric studies of Azathioprine on the surface of graphite electrode modified with graphene nanosheets decorated with Ag nanoparticles.

PubMed

Asadian, Elham; Iraji Zad, Azam; Shahrokhian, Saeed

2016-01-01

By using graphene nanosheets decorated with Ag nanoparticles (AgNPs-G) as an effective approach for the surface modification of pyrolytic graphite electrode (PGE), a sensing platform was fabricated for the sensitive voltammetric determination of Azathioprine (Aza). The prepared AgNPs-G nanosheets were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis and Raman spectroscopy techniques. The electrochemical behavior of Aza was investigated by means of cyclic voltammetry. Comparing to the bare PGE, a remarkable enhancement was observed in the response characteristics of Aza on the surface of the modified electrode (AgNPs-G/PGE) as well as a noticeable decrease in its reduction overpotential. These results can be attributed to the incredible enlargement in the microscopic surface area of the electrode due to the presence of graphene nanosheets together with strong adsorption of Aza on its surface. The effect of experimental parameters such as accumulation time, the amount of modifier suspension and pH of the supporting electrolyte were also optimized toward obtaining the maximum sensitivity. Under the optimum conditions, the calibration curve studies demonstrated that the peak current increased linearly with Aza concentrations in the range of 7 × 10(-7) to 1 × 10(-4)mol L(-1) with the detection limit of 68 nM. Further experiments revealed that the modified electrode can be successfully applied for the accurate determination of Aza in pharmaceutical preparations. Copyright © 2015 Elsevier B.V. All rights reserved.

Green Synthesis of AgNPs Stabilized with biowaste and their antimicrobial activities

PubMed Central

Jasuja, Nakuleshwar Dut; Gupta, Deepak Kumar; Reza, Mohtashim; Joshi, Suresh C.

2014-01-01

In the present study, rapid reduction and stabilization of Ag+ ions with different NaOH molar concentration (0.5 mM, 1.0 mM and 1.5 mM) has been carried out in the aqueous solution of silver nitrate by the bio waste peel extract of P.granatum. Generally, chemical methods used for the synthesis of AgNPs are quite toxic, flammable and have adverse effect in medical application but green synthesis is a better option due to eco-friendliness, non-toxicity and safe for human. Stable AgNPs were synthesized by treating 90 mL aqueous solution of 2 mM AgNO3 with the 5 mL plant peels extract (0.4% w/v) at different NaOH concentration (5 mL). The synthesized AgNPs were characterized by UV-Vis spectroscopy, TEM and SEM. Further, antimicrobial activities of AgNPs were performed on Gram positive i.e. Staphylococcus aureus, Bacillus subtilius and Gram negative i.e. E. coli, Pseudomonas aeruginosa bacteria. The AgNPs synthesized at 1.5 mM NaOH concentration had shown maximum zone of inhibition (ZOI) i.e. 49 ± 0.64 in E. coli, whereas Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilius had shown 40 ± 0.29 mm, 28 ± 0.13 and 42 ± 0.49 mm ZOI respectively. The MIC value of 30 μg/mL observed for E. coli Whereas, Staphylococcus aureus, Bacillus subtilius and Pseudomonas aeruginosa had shown 45 μg/mL, 38 μg/mL, 35 μg/mL respectively. The study revealed that AgNPs had shown significant antimicrobial activity as compared to Streptomycin. PMID:25763037

Green Synthesis of AgNPs Stabilized with biowaste and their antimicrobial activities.

PubMed

Jasuja, Nakuleshwar Dut; Gupta, Deepak Kumar; Reza, Mohtashim; Joshi, Suresh C

2014-01-01

In the present study, rapid reduction and stabilization of Ag+ ions with different NaOH molar concentration (0.5 mM, 1.0 mM and 1.5 mM) has been carried out in the aqueous solution of silver nitrate by the bio waste peel extract of P.granatum. Generally, chemical methods used for the synthesis of AgNPs are quite toxic, flammable and have adverse effect in medical application but green synthesis is a better option due to eco-friendliness, non-toxicity and safe for human. Stable AgNPs were synthesized by treating 90 mL aqueous solution of 2 mM AgNO₃ with the 5 mL plant peels extract (0.4% w/v) at different NaOH concentration (5 mL). The synthesized AgNPs were characterized by UV-Vis spectroscopy, TEM and SEM. Further, antimicrobial activities of AgNPs were performed on Gram positive i.e. Staphylococcus aureus, Bacillus subtilius and Gram negative i.e. E. coli, Pseudomonas aeruginosa bacteria. The AgNPs synthesized at 1.5 mM NaOH concentration had shown maximum zone of inhibition (ZOI) i.e. 49 ± 0.64 in E. coli, whereas Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilius had shown 40 ± 0.29 mm, 28 ± 0.13 and 42 ± 0.49 mm ZOI respectively. The MIC value of 30 μg/mL observed for E. coli Whereas, Staphylococcus aureus, Bacillus subtilius and Pseudomonas aeruginosa had shown 45 μg/mL, 38 μg/mL, 35 μg/mL respectively. The study revealed that AgNPs had shown significant antimicrobial activity as compared to Streptomycin.

Influence of salinity on the toxicity of silver nanoparticles (AgNPs) and silver nitrate (AgNO3) in halophilic microalgae, Dunaliella salina.

PubMed

Johari, Seyed Ali; Sarkheil, Mehrdad; Behzadi Tayemeh, Mohammad; Veisi, Shakila

2018-06-13

This study aim to evaluate the potential toxic effects of citrate coated silver nanoparticles (AgNPs) and ionic silver (AgNO 3 ) on marine microalgae Dunaliella salina under three different salinities (35, 70, and 140 g/L). The toxicity was investigated according to modified OECD guideline (No. 201) by 72 h exposure of microalgae to various concentrations of each of the chemicals in Walne's saline media. According to the results, the growth inhibitory effects of AgNPs and AgNO 3 increased significantly coincidence with increasing time and concentration compared to control (P < 0.05). The values of median inhibitory concentrations (IC 50 ) of AgNPs and AgNO 3 based on average specific growth rate and yield for D. salina increased significantly with elevation of water salinity from 35 to 140 g/L (P < 0.05). Toxicity of AgNO 3 based on IC 50 to D. salina was significantly higher than AgNPs at all salinities (P < 0.05). In conclusion, both AgNPs and AgNO 3 inhibited the growth of D. salina at different saltwater medium. Copyright © 2018 Elsevier Ltd. All rights reserved.

The impact of anticancer activity upon Beta vulgaris extract mediated biosynthesized silver nanoparticles (ag-NPs) against human breast (MCF-7), lung (A549) and pharynx (Hep-2) cancer cell lines.

PubMed

Venugopal, K; Ahmad, H; Manikandan, E; Thanigai Arul, K; Kavitha, K; Moodley, M K; Rajagopal, K; Balabhaskar, R; Bhaskar, M

2017-08-01

The present study tried for a phyto-synthetic method of producing silver nanoparticles (Ag-NPs) with size controlled as and eco-friendly route that can lead to their advanced production with decorative tranquil morphology. By inducing temperature fluctuation of the reaction mixture from 25 to 80°C the plasmon resonance band raised slowly which had an ultimate effect on size and shape of Ag-NPs as shown by UV-visible spectroscopy and TEM results. The biosynthesized nanoparticles showed good cytotoxic impact against MCF-7, A549 and Hep2 cells compared to normal cell lines. Compared to control plates, the percentage of cell growth inhibition was found to be high with as concentrations of Ag-NPs becomes more as determined by MTT assay. The AO/EtBr staining observations demonstrated that the mechanism of cell death induced by Ag-NPs was due to apoptosis in cancer cells. These present results propose that the silver nanoparticles (Ag-NPs) may be utilized as anticancer agents for the treatment of various cancer types. However, there is a need for study of in vivo examination of these nanoparticles to find their role and mechanism inside human body. Further, studies we plan to do biomarker fabrication from the green synthesized plant extract nanoparticles like silver, gold and copper nanoparticles with optimized shape and sizes and their enhancement of these noble nanoparticles. Copyright © 2017. Published by Elsevier B.V.

Mimetic Ag nanoparticle/Zn-based MOF nanocomposite (AgNPs@ZnMOF) capped with molecularly imprinted polymer for the selective detection of patulin.

PubMed

Bagheri, Nafiseh; Khataee, Alireza; Habibi, Biuck; Hassanzadeh, Javad

2018-03-01

Here, Ag nanoparticle/flake-like Zn-based MOF nanocomposite (AgNPs@ZnMOF) with great peroxidase-like activity was applied as an efficient support for molecularly imprinted polymer (MIP) and successfully used for selective determination of patulin. AgNPs@ZnMOF was simply synthesized by creating Ag nanoparticles (Ag NPs) inside the nano-pores of flake-like (Zn)MOF. The high surface area of MOF remarkably improved the catalytic activity of Ag NPs which was assessed by fluorometric, colorimetric and electrochemical techniques. Furthermore, it was observed that patulin could strangely reduce the catalytic activity of AgNPs@ZnMOF, probably due to its electron capturing features. This outcome was the motivation to design an assay for patulin detection. In order to make a selective interaction with patulin molecules, MIP layer was created on the surface of AgNPs@ZnMOF by co-polymerization reaction of 3-aminopropyl triethoxysilane (APTES) and tetraethyl orthosilicate (TEOS) monomers wherein patulin was applied as template agent. Combination between the selective identifying feature of MIP and outstanding peroxidase-like activity of novel AgNPs@ZnMOF nanocomposite as well as the sensitive fluorescence detection system was led to the design of a reliable probe for patulin. The prepared MIP-capped AgNPs@ZnMOF catalyzed the H 2 O 2 -terephthalic acid reaction which produced a high florescent product. In the presence of patulin, the fluorescence intensity was decreased proportional to its concentration in the range of 0.1-10µmolL -1 with a detection limit of 0.06µmolL -1 . The proposed method was able to selectively measure patulin in a complex media without significant interfering effects from analogue compounds. Copyright © 2017 Elsevier B.V. All rights reserved.

Halloysite Nanotubes Supported Ag and ZnO Nanoparticles with Synergistically Enhanced Antibacterial Activity

NASA Astrophysics Data System (ADS)

Shu, Zhan; Zhang, Yi; Yang, Qian; Yang, Huaming

2017-02-01

Novel antimicrobial nanocomposite incorporating halloysite nanotubes (HNTs) and silver (Ag) into zinc oxide (ZnO) nanoparticles is prepared by integrating HNTs and decorating Ag nanoparticles. ZnO nanoparticles (ZnO NPs) and Ag nanoparticles (Ag NPs) with a size of about 100 and 8 nm, respectively, are dispersively anchored onto HNTs. The synergistic effects of ZnO NPs, Ag NPs, and HNTs led to the superior antibacterial activity of the Ag-ZnO/HNTs antibacterial nanocomposites. HNTs facilitated the dispersion and stability of ZnO NPs and brought them in close contact with bacteria, while Ag NPs could promote the separation of photogenerated electron-hole pairs and enhanced the antibacterial activity of ZnO NPs. The close contact with cell membrane enabled the nanoparticles to produce the increased concentration of reactive oxygen species and the metal ions to permeate into the cytoplasm, thus induced quick death of bacteria, indicating that Ag-ZnO/HNTs antibacterial nanocomposite is a promising candidate in the antibacterial fields.

Ag-Decorated Localized Surface Plasmon-Enhanced Ultraviolet Electroluminescence from ZnO Quantum Dot-Based/GaN Heterojunction Diodes by Optimizing MgO Interlayer Thickness.

PubMed

Chen, Cheng; Chen, Jingwen; Zhang, Jun; Wang, Shuai; Zhang, Wei; Liang, Renli; Dai, Jiangnan; Chen, Changqing

2016-12-01

We demonstrate the fabrication and characterization of localized surface plasmon (LSP)-enhanced n-ZnO quantum dot (QD)/MgO/p-GaN heterojunction light-emitting diodes (LEDs) by embedding Ag nanoparticles (Ag-NPs) into the ZnO/MgO interface. The maximum enhancement ration of the Ag-NP-decorated LEDs in electroluminescence (EL) is 4.3-fold by optimizing MgO electron-blocking layer thickness. The EL origination was investigated qualitatively in terms of photoluminescence (PL) results. Through analysis of the energy band structure of device and carrier transport mechanisms, it suggests that the EL enhancement is attributed to the increased rate of spontaneous emission and improved internal quantum efficiency induced by exciton-LSP coupling.

Ag-Decorated Localized Surface Plasmon-Enhanced Ultraviolet Electroluminescence from ZnO Quantum Dot-Based/GaN Heterojunction Diodes by Optimizing MgO Interlayer Thickness

NASA Astrophysics Data System (ADS)

Chen, Cheng; Chen, Jingwen; Zhang, Jun; Wang, Shuai; Zhang, Wei; Liang, Renli; Dai, Jiangnan; Chen, Changqing

2016-10-01

We demonstrate the fabrication and characterization of localized surface plasmon (LSP)-enhanced n-ZnO quantum dot (QD)/MgO/p-GaN heterojunction light-emitting diodes (LEDs) by embedding Ag nanoparticles (Ag-NPs) into the ZnO/MgO interface. The maximum enhancement ration of the Ag-NP-decorated LEDs in electroluminescence (EL) is 4.3-fold by optimizing MgO electron-blocking layer thickness. The EL origination was investigated qualitatively in terms of photoluminescence (PL) results. Through analysis of the energy band structure of device and carrier transport mechanisms, it suggests that the EL enhancement is attributed to the increased rate of spontaneous emission and improved internal quantum efficiency induced by exciton-LSP coupling.

Enhanced antimicrobial activities of silver-nanoparticle-decorated reduced graphene nanocomposites against oral pathogens.

PubMed

Peng, Jian-Min; Lin, Jia-Cheng; Chen, Zhuo-Yu; Wei, Meng-Chao; Fu, Yuan-Xiang; Lu, Shu-Shen; Yu, Dong-Sheng; Zhao, Wei

2017-02-01

As a means of capitalizing on the synergistic properties between reduced graphene nanosheets (R-GNs) and silver nanoparticles (AgNPs), an efficient and convenient chemical reduction method was used to prepare silver-nanoparticle-decorated reduced graphene nanocomposites (R-GNs/Ag). The products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy, which confirmed the loading of well-dispersed silver nanoparticles on reduced graphene sheets. Their antimicrobial activities against oral pathogens such as Candida albicans, Lactobacillus acidophilus, Streptococcus mutans, and Aggregatibacter actinomycetemcomitans were investigated by MIC determination, the counting of colony-forming units (CFU), agar diffusion tests, and growth curve observation. Compared with pure R-GNs and AgNPs, R-GNs/Ag composites exhibited enhanced antimicrobial properties owing to highly dispersed AgNPs on R-GNs. Copyright © 2016 Elsevier B.V. All rights reserved.

Role of silver nanoparticles (AgNPs) on the cardiovascular system.

PubMed

Gonzalez, Carmen; Rosas-Hernandez, Hector; Ramirez-Lee, Manuel Alejandro; Salazar-García, Samuel; Ali, Syed F

2016-03-01

With the advent of nanotechnology, the use and applications of silver nanoparticles (AgNPs) have increased, both in consumer products as well as in medical devices. However, little is known about the effects of these nanoparticles on human health, more specific in the cardiovascular system, since this system represents an important route of action in terms of distribution, bioaccumulation and bioavailability of the different circulating substances in the bloodstream. A collection of studies have addressed the effects and applications of different kinds of AgNPs (shaped, sized, coated and functionalized) in several components of the cardiovascular system, such as endothelial cells, isolated vessels and organs as well as integrative animal models, trying to identify the underlying mechanisms involved in their actions, to understand their implication in the field of biomedicine. The purpose of the present review is to summarize the most relevant studies to date of AgNPs effects in the cardiovascular system and provide a broader picture of the potential toxic effects and exposure risks, which in turn will allow pointing out the directions of further research as well as new applications of these versatile nanomaterials.

Dose-dependent effect of silver nanoparticles (AgNPs) on fertility and survival of Drosophila: An in-vivo study

PubMed Central

Raj, Akanksha; Shah, Prasanna

2017-01-01

Silver nanoparticles (AgNPs) containing consumer products have been proliferating in the market due to its unique antimicrobial property, however, lack of in-depth knowledge about their potential effect on human health in a longer run is of great concern. Therefore, we investigated dose-dependent in vivo effect of AgNPs using Drosophila as a model system. Drosophila, a genetically tractable organism with distinct developmental stages, short life cycle and significant homology with human serves as an ideal organism to study nanomaterial-mediated toxicity. Our studies suggest that ingestion of AgNPs in Drosophila during adult stage for short and long duration significantly affects egg laying capability along with impaired growth of ovary. Additionally, dietary intake of AgNPs from larval stage has more deleterious effects that result in reduced survival, longevity, ovary size and egg laying capability at a further lower dosage. Interestingly, the trans-generational effect of AgNPs was also observed without feeding progeny with AgNPs, thereby suggesting its impact from previous generation. Our results strongly imply that higher doses of AgNPs and its administration early during development is detrimental to the reproductive health and survival of Drosophila that follows in generations to come without feeding them to AgNPs. PMID:28542630

Dose-dependent effect of silver nanoparticles (AgNPs) on fertility and survival of Drosophila: An in-vivo study.

PubMed

Raj, Akanksha; Shah, Prasanna; Agrawal, Namita

2017-01-01

Silver nanoparticles (AgNPs) containing consumer products have been proliferating in the market due to its unique antimicrobial property, however, lack of in-depth knowledge about their potential effect on human health in a longer run is of great concern. Therefore, we investigated dose-dependent in vivo effect of AgNPs using Drosophila as a model system. Drosophila, a genetically tractable organism with distinct developmental stages, short life cycle and significant homology with human serves as an ideal organism to study nanomaterial-mediated toxicity. Our studies suggest that ingestion of AgNPs in Drosophila during adult stage for short and long duration significantly affects egg laying capability along with impaired growth of ovary. Additionally, dietary intake of AgNPs from larval stage has more deleterious effects that result in reduced survival, longevity, ovary size and egg laying capability at a further lower dosage. Interestingly, the trans-generational effect of AgNPs was also observed without feeding progeny with AgNPs, thereby suggesting its impact from previous generation. Our results strongly imply that higher doses of AgNPs and its administration early during development is detrimental to the reproductive health and survival of Drosophila that follows in generations to come without feeding them to AgNPs.

Facile and eco-friendly fabrication of AgNPs coated silk for antibacterial and antioxidant textiles using honeysuckle extract.

PubMed

Zhou, Yuyang; Tang, Ren-Cheng

2018-01-01

Recently, there is a growing trend towards the functionalization of silk through nanotechnology for the prevention of fiber damage from microbial attack and the enhancement of hygienic aspects. Considering sustainable development and environmental protection, the eco-friendly fabrication of silver nanoparticles (AgNPs)-modified silk using natural extracts has currently become a hot research area. This study presents a facile strategy for the fabrication of colorful and multifunctional silk fabric using biogenic AgNPs prepared by honeysuckle extract as natural reductant and stabilizing agents. The influences of pH and reactant concentrations on the AgNPs synthesis were investigated. The color characteristics and functionalities of AgNPs treated silk were evaluated. The results revealed that the particle size of AgNPs decreased with increasing pH. The diameter of AgNPs decreased with increasing amount of honeysuckle extract and reducing amount of silver nitrate. The transmission electron microscopy image showed that the AgNPs were spherical in shape with a narrow size distribution. The treated silk showed excellent antibacterial activities against E. coli and S. aureus, and certain antioxidant activity. Both of the antibacterial and antioxidant activities were well maintained even after 30 washing cycles. This work provides a sustainable and eco-friendly approach to the fabrication of AgNPs coated silk for colorful and long-term multifunctional textiles using honeysuckle extract. Copyright © 2017 Elsevier B.V. All rights reserved.

Efficient removal of herbicide 2,4-dichlorophenoxyacetic acid from water using Ag/reduced graphene oxide co-decorated TiO2 nanotube arrays.

PubMed

Tang, Yanhong; Luo, Shenglian; Teng, Yarong; Liu, Chengbin; Xu, Xiangli; Zhang, Xilin; Chen, Liang

2012-11-30

A new photocatalyst, Ag nanoparticles (NPs) and reduced graphene oxide (RGO) co-decorated TiO(2) nanotube arrays (NTs) (Ag/RGO-TiO(2) NTs), was designed and facilely produced by combining electrodeposition and photoreduction processes. The structures and properties of the photocatalysts were characterized. The ternary catalyst exhibited almost 100% photocatalytic removal efficiency of typical herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) from water under simulated solar light irradiation. The photodegradation rate toward 2,4-D over Ag/RGO-TiO(2) NTs is 11.3 times that over bare TiO(2) NTs. After 10 successive cycles with 1600 min of irradiation, Ag/RGO-TiO(2) NTs maintained as high 2,4-D removal efficiency as 97.3% with excellent stability and easy recovery, which justifies the photocatalytic system a promising application for herbicide removal from water. Copyright © 2012 Elsevier B.V. All rights reserved.

Rapid Biosynthesis of AgNPs Using Soil Bacterium Azotobacter vinelandii With Promising Antioxidant and Antibacterial Activities for Biomedical Applications

NASA Astrophysics Data System (ADS)

Karunakaran, Gopalu; Jagathambal, Matheswaran; Gusev, Alexander; Torres, Juan Antonio Lopez; Kolesnikov, Evgeny; Kuznetsov, Denis

2017-07-01

Silver nanoparticles (AgNPs) are applied in various fields from electronics to biomedical applications as a result of their high surface-to-volume ratio. Even though different approaches are available for synthesis of AgNPs, a nontoxic method for the synthesis has not yet been developed. Thus, this study focused on developing an easy and ecofriendly approach to synthesize AgNPs using Azotobacter vinelandii culture extracts. The biosynthesized nanoparticles were further characterized by ultraviolet-visible (UV-Vis) spectroscopy, x-ray diffraction (XRD), Fourier transform infrared (FTIR), energy-dispersive spectrum, particle size distribution (PSD), and transmission electron microscopy (TEM). UV absorption noticed at 435 nm showed formation of AgNPs. The XRD pattern showed a face-centered cubic structure with broad peaks of 28.2°, 32.6°, 46.6°, 55.2°, 57.9°, and 67.8°. The FTIR confirmed the involvement of various functional groups in the biosynthesis of AgNPs. The PSD and TEM analyses showed spherical, well-distributed nanoparticles with an average size of 20-70 nm. The elemental studies confirmed the existence of pure AgNPs. The bacterial extract containing extracellular enzyme nitrate reductase converted silver nitrate into AgNPs. AgNPs significantly inhibited the growth of pathogenic bacteria such as Streptomyces fradiae (National Collection of Industrial Microorganisms (NCIM) 2419), Staphylococcus aureus (NCIM 2127), Escherichia coli (NCIM 2065), and Serratia marcescens (NCIM 2919). In addition, biosynthesized AgNPs were found to possess strong antioxidant activity. Thus, the results of this study revealed that biosynthesized AgNPs could serve as a lead in the development of nanomedicine.

Influence of silver content on rifampicin adsorptivity for magnetite/Ag/rifampicin nanoparticles

NASA Astrophysics Data System (ADS)

Ivashchenko, Olena; Coy, Emerson; Peplinska, Barbara; Jarek, Marcin; Lewandowski, Mikołaj; Załęski, Karol; Warowicka, Alicja; Wozniak, Anna; Babutina, Tatiana; Jurga-Stopa, Justyna; Dolinsek, Janez; Jurga, Stefan

2017-02-01

Magnetite nanoparticles (NPs) decorated with silver (magnetite/Ag) are intensively investigated due to their application in the biomedical field. We demonstrate that the increase of silver content on the surface of nanoparticles improves the adsorptivity of antibiotic rifampicin as well as antibacterial properties. The use of ginger extract allowed to improve the silver nucleation on the magnetite surface that resulted in an increase of silver content. Physicochemical and functional characterization of magnetite/Ag NPs was performed. Our results show that 5%-10% of silver content in magnetite/Ag NPs is already sufficient for antimicrobial properties against Streptococcus salivarius and Staphylococcus aureus. The rifampicin molecules on the magnetite/Ag NPs surface made the spectrum of antimicrobial activity wider. Cytotoxicity evaluation of the magnetite/Ag/rifampicin NPs showed no harmful action towards normal human fibroblasts, whereas the effect on human embryonic kidney cell viability was time and dose dependent.

Synthesis of Ag-NPs impregnated cellulose composite material: its possible role in wound healing and photocatalysis.

PubMed

Ali, Attarad; Haq, Ihsan Ul; Akhtar, Javeed; Sher, Muhammad; Ahmed, Naveed; Zia, Muhammad

2017-06-01

Cellulose is the natural biopolymer normally used as supporting agent with enhanced applicability and properties. In present study, cellulose isolated from citrus waste is used for silver nanoparticles (Ag-NPs) impregnation by a simple and reproducible method. The Ag-NPs fabricated cellulose (Ag-Cel) was characterised by powder X-rays diffraction, Fortier transform infrared spectroscopy and scanning electron microscopy. The thermal stability was studied by thermo-gravimetric analysis. The antibacterial activity performed by disc diffusion assay reveals good zone of inhibition against Staphylococcus aureus and Escherichia coli by Ag-Cel as compared Ag-NPs. The discs also displayed more than 90% reduction of S. aureus culture in broth within 150 min. The Ag-Cel discs also demonstrated minor 2,2-diphenyl 1-picryl-hydrazyl radical scavenging activity and total reducing power ability while moderate total antioxidant potential was observed. Ag-Cel effectively degrades methylene-blue dye up to 63.16% under sunlight irradiation in limited exposure time of 60 min. The Ag-NPs impregnated cellulose can be effectively used in wound dressing to prevent bacterial attack and scavenger of free radicals at wound site, and also as filters for bioremediation and wastewater purification.

A novel multifunctional electrochemical platform for simultaneous detection, elimination, and inactivation of pathogenic bacteria based on the Vancomycin-functionalised AgNPs/3D-ZnO nanorod arrays.

PubMed

Yang, Zhiqing; Wang, Yi; Zhang, Dun

2017-12-15

A novel fast, sensitive, and specific multifunctional electrochemical platform has been proposed for simultaneous detection, elimination, and inactivation of pathogenic bacteria for the first time. The platform is constituted with three-dimensional ZnO nanorod arrays (3D-ZnO) decorated with sliver nanoparticles (AgNPs) and functionalized with vancomycin (Van). Based on the specific recognition of Van for Gram-positive bacteria, the fabricated electrochemical platform has presented high detection sensitivity to Staphylococcus aureus with a low detection limit of 330cfu/mL and adaptable bacterial-elimination efficiency (50%) at low concentrations (1000-2000cfu/mL). Moreover, the platform has shown high antibacterial activity (99.99%) arising from the synergistic germicidal effect of the composited antibacterial AgNPs and Van units. The current work could provide new strategies to construct advanced platforms for simultaneous detection, elimination, and inactivation of various pathogenic bacteria. Copyright © 2017 Elsevier B.V. All rights reserved.

High-performance SERS substrate based on hybrid structure of graphene oxide/AgNPs/Cu film@pyramid Si

PubMed Central

Li, Zhe; Xu, Shi Cai; Zhang, Chao; Liu, Xiao Yun; Gao, Sai Sai; Hu, Li Tao; Guo, Jia; Ma, Yong; Jiang, Shou Zhen; Si, Hai Peng

2016-01-01

We present a novel surface-enhanced Raman scattering (SERS) substrate based on graphene oxide/silver nanoparticles/copper film covered silicon pyramid arrays (GO/AgNPs/PCu@Si) by a low-cost and simple method. The GO/AgNPs/PCu@Si substrate presents high sensitivity, good homogeneity and well stability with R6G molecules as a probe. The detected concentration of Rhodamine 6 G (R6G) is as low as 10−15 M. These sensitive SERS behaviors are also confirmed in theory via a commercial COMSOL software, the electric field enhancement is not only formed between the AgNPs, but also formed between the AgNPs and Cu film. And the GO/AgNPs/PCu@Si substrates also present good property on practical application for the detection of methylene blue (MB) and crystal violet (CV). This work may offer a novel and practical method to facilitate the SERS applications in areas of medicine, food safety and biotechnology. PMID:27924863

High-performance SERS substrate based on hybrid structure of graphene oxide/AgNPs/Cu film@pyramid Si

NASA Astrophysics Data System (ADS)

Li, Zhe; Xu, Shi Cai; Zhang, Chao; Liu, Xiao Yun; Gao, Sai Sai; Hu, Li Tao; Guo, Jia; Ma, Yong; Jiang, Shou Zhen; Si, Hai Peng

2016-12-01

We present a novel surface-enhanced Raman scattering (SERS) substrate based on graphene oxide/silver nanoparticles/copper film covered silicon pyramid arrays (GO/AgNPs/PCu@Si) by a low-cost and simple method. The GO/AgNPs/PCu@Si substrate presents high sensitivity, good homogeneity and well stability with R6G molecules as a probe. The detected concentration of Rhodamine 6 G (R6G) is as low as 10-15 M. These sensitive SERS behaviors are also confirmed in theory via a commercial COMSOL software, the electric field enhancement is not only formed between the AgNPs, but also formed between the AgNPs and Cu film. And the GO/AgNPs/PCu@Si substrates also present good property on practical application for the detection of methylene blue (MB) and crystal violet (CV). This work may offer a novel and practical method to facilitate the SERS applications in areas of medicine, food safety and biotechnology.

High-performance SERS substrate based on hybrid structure of graphene oxide/AgNPs/Cu film@pyramid Si.

PubMed

Li, Zhe; Xu, Shi Cai; Zhang, Chao; Liu, Xiao Yun; Gao, Sai Sai; Hu, Li Tao; Guo, Jia; Ma, Yong; Jiang, Shou Zhen; Si, Hai Peng

2016-12-07

We present a novel surface-enhanced Raman scattering (SERS) substrate based on graphene oxide/silver nanoparticles/copper film covered silicon pyramid arrays (GO/AgNPs/PCu@Si) by a low-cost and simple method. The GO/AgNPs/PCu@Si substrate presents high sensitivity, good homogeneity and well stability with R6G molecules as a probe. The detected concentration of Rhodamine 6 G (R6G) is as low as 10 -15 M. These sensitive SERS behaviors are also confirmed in theory via a commercial COMSOL software, the electric field enhancement is not only formed between the AgNPs, but also formed between the AgNPs and Cu film. And the GO/AgNPs/PCu@Si substrates also present good property on practical application for the detection of methylene blue (MB) and crystal violet (CV). This work may offer a novel and practical method to facilitate the SERS applications in areas of medicine, food safety and biotechnology.

Silver nanoparticles (AgNPs) biosynthesized using pod extract of Cola nitida enhances antioxidant activity and phytochemical composition of Amaranthus caudatus Linn

NASA Astrophysics Data System (ADS)

Azeez, Luqmon; Lateef, Agbaje; Adebisi, Segun A.

2017-02-01

This study investigates the influence of different concentrations of AgNPs biologically synthesized using pod extract of Cola nitida on antioxidant activity, phenolic contents, flavonoid contents and compositions of Amaranthus caudatus L. AgNPs of 25, 50, 75, 100 and 150 ppm were utilized in growing A. caudatus while water was used as control. Delayed germination for two days was observed for A. caudatus grown with 150 ppm of AgNPs, while others showed no difference. There were 43.3, 38.7, 26.7 and 6.48% improvements in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant activity of A. caudatus grown with 25, 50, 75 and 100 ppm of AgNPs, respectively, compared to control. Antioxidant activity of A. caudatus grown with AgNPs reduced with increase in the concentrations of AgNPs. A. caudatus grown with 50 ppm of AgNPs was the most potent with the least IC50 of 0.67 mg/ml. Significant improvements obtained for phenolic and flavonoid contents grown with AgNPs were concentration dependent. Enhancements of 21.9, 68.19, and 1.98% in phenolic contents were achieved in treatments with 25, 50 and 75 ppm AgNPs, respectively, while 32.58, 35.80, and 7.20% improvement in flavonoids were obtained for 25, 50 and 100 ppm treatments, respectively. Kaempferol and quercetin were the most abundant flavonoids in A. caudatus treated with 50 ppm of AgNPs, showing the highest flavonoid composition. This further confirms A. caudatus grown with 50 ppm of AgNPs as the most potent. This study has shown that concentration-dependent AgNPs can be used to boost antioxidant activity and phytochemical contents of vegetables.

Hydrodynamic chromatography coupled to single-particle ICP-MS for the simultaneous characterization of AgNPs and determination of dissolved Ag in plasma and blood of burn patients.

PubMed

Roman, Marco; Rigo, Chiara; Castillo-Michel, Hiram; Munivrana, Ivan; Vindigni, Vincenzo; Mičetić, Ivan; Benetti, Federico; Manodori, Laura; Cairns, Warren R L

2016-07-01

Silver nanoparticles (AgNPs) are increasingly used in medical devices as innovative antibacterial agents, but no data are currently available on their chemical transformations and fate in vivo in the human body, particularly on their potential to reach the circulatory system. To study the processes involving AgNPs in human plasma and blood, we developed an analytical method based on hydrodynamic chromatography (HDC) coupled to inductively coupled plasma mass spectrometry (ICP-MS) in single-particle detection mode. An innovative algorithm was implemented to deconvolute the signals of dissolved Ag and AgNPs and to extrapolate a multiparametric characterization of the particles in the same chromatogram. From a single injection, the method provides the concentration of dissolved Ag and the distribution of AgNPs in terms of hydrodynamic diameter, mass-derived diameter, number and mass concentration. This analytical approach is robust and suitable to study quantitatively the dynamics and kinetics of AgNPs in complex biological fluids, including processes such as agglomeration, dissolution and formation of protein coronas. The method was applied to study the transformations of AgNP standards and an AgNP-coated dressing in human plasma, supported by micro X-ray fluorescence (μXRF) and micro X-ray absorption near-edge spectroscopy (μXANES) speciation analysis and imaging, and to investigate, for the first time, the possible presence of AgNPs in the blood of three burn patients treated with the same dressing. Together with our previous studies, the results strongly support the hypothesis that the systemic mobilization of the metal after topical administration of AgNPs is driven by their dissolution in situ. Graphical Abstract Simplified scheme of the combined analytical approach adopted for studying the chemical dynamics of AgNPs in human plasma/blood.

The structural conversion from α-AgVO3 to β-AgVO3: Ag nanoparticle decorated nanowires with application as cathode materials for Li-ion batteries.

PubMed

McNulty, David; Ramasse, Quentin; O'Dwyer, Colm

2016-09-15

The majority of electrode materials in batteries and related electrochemical energy storage devices are fashioned into slurries via the addition of a conductive additive and a binder. However, aggregation of smaller diameter nanoparticles in current generation electrode compositions can result in non-homogeneous active materials. Inconsistent slurry formulation may lead to inconsistent electrical conductivity throughout the material, local variations in electrochemical response, and the overall cell performance. Here we demonstrate the hydrothermal preparation of Ag nanoparticle (NP) decorated α-AgVO 3 nanowires (NWs) and their conversion to tunnel structured β-AgVO 3 NWs by annealing to form a uniform blend of intercalation materials that are well connected electrically. The synthesis of nanostructures with chemically bound conductive nanoparticles is an elegant means to overcome the intrinsic issues associated with electrode slurry production, as wire-to-wire conductive pathways are formed within the overall electrode active mass of NWs. The conversion from α-AgVO 3 to β-AgVO 3 is explained in detail through a comprehensive structural characterization. Meticulous EELS analysis of β-AgVO 3 NWs offers insight into the true β-AgVO 3 structure and how the annealing process facilitates a higher surface coverage of Ag NPs directly from ionic Ag content within the α-AgVO 3 NWs. Variations in vanadium oxidation state across the surface of the nanowires indicate that the β-AgVO 3 NWs have a core-shell oxidation state structure, and that the vanadium oxidation state under the Ag NP confirms a chemically bound NP from reduction of diffused ionic silver from the α-AgVO 3 NWs core material. Electrochemical comparison of α-AgVO 3 and β-AgVO 3 NWs confirms that β-AgVO 3 offers improved electrochemical performance. An ex situ structural characterization of β-AgVO 3 NWs after the first galvanostatic discharge and charge offers new insight into the Li + reaction

Eco-friendly decoration of graphene oxide with biogenic silver nanoparticles: antibacterial and antibiofilm activity

NASA Astrophysics Data System (ADS)

de Faria, Andreia Fonseca; de Moraes, Ana Carolina Mazarin; Marcato, Priscyla Daniely; Martinez, Diego Stéfani Teodoro; Durán, Nelson; Filho, Antônio Gomes Souza; Brandelli, Adriano; Alves, Oswaldo Luiz

2014-02-01

This work reports on preparation, characterization, and antibacterial activity of graphene oxide (GO) decorated with biogenic silver nanoparticles (Bio-AgNPs) produced by the fungus Fusarium oxysporum. This nanocomposite (Bio-GOAg) was prepared by an ex situ process through the physical mixture of a GO dispersion with the previously prepared Bio-AgNPs. The adsorption of the Bio-AgNPs onto the GO sheets was confirmed by transmission electron microscopy. The average size of the Bio-AgNPs anchored onto the GO surface was found to be 3.5 nm. The antibacterial activity of the Bio-GOAg nanocomposite against Gram-positive and Gram-negative microorganisms was investigated and a very promising result was found for the Gram-negative strains. In addition, the Bio-GOAg nanocomposite displayed a very strong biocidal activity against the Salmonella typhimurium strain at a concentration of 2.0 μg/mL. The antibiofilm activity toward S. typhimurium adhered on stainless steel surfaces was also investigated. The results showed 100 % inhibition of the adhered cells after exposure to the Bio-GOAg nanocomposite for 1 h.

The effect of silver nanoparticles (AgNPs) on proliferation and apoptosis of in ovo cultured glioblastoma multiforme (GBM) cells.

PubMed

Urbańska, Kaja; Pająk, Beata; Orzechowski, Arkadiusz; Sokołowska, Justyna; Grodzik, Marta; Sawosz, Ewa; Szmidt, Maciej; Sysa, Paweł

2015-01-01

Recently, it has been shown that silver nanoparticles (AgNPs) provide a unique approach to the treatment of tumors, especially those of neuroepithelial origin. Thus, the aim of this study was to evaluate the impact of AgNPs on proliferation and activation of the intrinsic apoptotic pathway of glioblastoma multiforme (GBM) cells cultured in an in ovo model. Human GBM cells, line U-87, were placed on chicken embryo chorioallantoic membrane. After 8 days, the tumors were divided into three groups: control (non-treated), treated with colloidal AgNPs (40 μg/ml), and placebo (tumors supplemented with vehicle only). At the end of the experiment, all tumors were isolated. Assessment of cell proliferation and cell apoptosis was estimated by histological, immunohistochemical, and Western blot analyses. The results show that AgNPs can influence GBM growth. AgNPs inhibit proliferation of GBM cells and seem to have proapoptotic properties. Although there were statistically significant differences between control and AgNP groups in the AI and the levels of active caspase 9 and active caspase 3, the level of these proteins in GBM cells treated with AgNPs seems to be on the border between the spontaneous apoptosis and the induced. Our results indicate that the antiproliferative properties of silver nanoparticles overwhelm proapoptotic ones. Further research focused on the cytotoxic effect of AgNPs on tumor and normal cells should be conducted.

Revelation of susceptibility differences due to Hg(II) accumulation in Streptococcus pyogenes against CX-AgNPs and Cefixime by atomic force microscopy.

PubMed

Rasheed, Wasia; Shah, Muhammad Raza; Perveen, Samina; Ahmed, Shakil; Uzzaman, Sami

2018-01-01

Solution based method for the formation of chemically modified silver nanoparticles (CX-AgNPs) using Cefixime as stabilizing and reducing agent was developed. The CX-AgNPs were characterized by AFM, UV-visible, FT-IR and MALDI-TOF MS. Bactericidal efficiency of CX-AgNPs and Cefixime against Streptococcus pyogenes was evaluated. Afterwards, susceptibility differences of Streptococcus pyogenes due to accumulation of Hg(II) against CX-AgNPs and Cefixime were estimated and validated through Atomic force microscopy. Selectivity and sensitivity of CX-AgNPs against Hg(II) was evaluated in a systematic manner. The CX-AgNPs was titrated against optically silent Hg(II) which induced enhancement in the SPR band of CX-AgNPs. The increase in intensity of SPR band of CX-AgNPs was determined to be proportionate to the concentration of Hg(II) in the range of 33.3-700µM obeying linear regression equation of y = 0.125x + 8.962 with the detection limit of 0.10µM and the coefficient of determination equals to 0.985 (n = 3). The association constant Ka of CX-AgNPs-Hg(II) was found to be 386.0095mol -1 dm 3 by using the Benesi Hildebrand plot. Copyright © 2017 Elsevier Inc. All rights reserved.

A novel glucose biosensor platform based on Ag@AuNPs modified graphene oxide nanocomposite and SERS application.

PubMed

Gupta, Vinod Kumar; Atar, Necip; Yola, Mehmet Lütfi; Eryılmaz, Merve; Torul, Hilal; Tamer, Uğur; Boyacı, Ismail Hakkı; Ustündağ, Zafer

2013-09-15

This study represents a novel template demonstration of a glucose biosensor based on mercaptophenyl boronic acid (MBA) terminated Ag@AuNPs/graphene oxide (Ag@AuNPs-GO) nanomaterials. The nanocomposites were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) method. The TEM image shows that Ag@AuNPs in the nanocomposite is in the range of diameters of 10-20 nm. The nanocomposite was used for the determination of glucose through the complexation between boronic acid and diol groups of glucose. Thus, a novel glucose biosensor was further fabricated by immobilizing glucose oxidase (GOD) into MBA terminated Ag@AuNPs-GO nanocomposite film (MBA-Ag@AuNPs-GO). The linearity range of glucose was obtained as 2-6mM with detection limit of 0.33 mM. The developed biosensor was also applied successfully for the determination of glucose in blood samples. The concentration value of glucose in blood samples was calculated to be 1.97±0.002 mM from measurements repeated for six times. Copyright © 2013 Elsevier Inc. All rights reserved.

Disinfection of waterborne viruses using silver nanoparticle-decorated silica hybrid composites in water environments.

PubMed

Park, SungJun; Ko, Young-Seon; Jung, Haeyong; Lee, Cheonghoon; Woo, Kyoungja; Ko, GwangPyo

2018-06-01

Silver nanoparticles (AgNPs) have been reported as an effective alternative for controlling a broad-spectrum of pathogenic viruses. We developed a micrometer-sized silica hybrid composite decorated with AgNPs (AgNP-SiO 2 ) to prevent the inherent aggregation of AgNPs, and facilitated their recovery from environmental media after use. The production process had a high-yield, and fabrication was cost-effective. We evaluated the antiviral capabilities of Ag30-SiO 2 particles against two model viruses, bacteriophage MS2 and murine norovirus (MNV), in four different types of water (deionized, tap, surface, and ground). MNV was more susceptible to Ag30-SiO 2 particles in all four types of water compared to MS2. Furthermore, several water-related factors, including temperature and organic matter content, were shown to affect the antimicrobial capabilities of Ag30-SiO 2 particles. The modified Hom model was the best-fit disinfection model for MNV disinfection in the different types of water. Additionally, this study demonstrated that the effects of a certain level of physical obstacles in water were negligible in regards to the use of Ag30-SiO 2 particles. Thus, effective use of AgNPs in water disinfection processes can be achieved using our novel hybrid composites to inactivate various waterborne viruses. Copyright © 2018 Elsevier B.V. All rights reserved.

Rapid visual detection of quaternary ammonium surfactants using citrate-capped silver nanoparticles (Ag NPs) based on hydrophobic effect.

PubMed

Zheng, Li-Qing; Yu, Xiao-Dong; Xu, Jing-Juan; Chen, Hong-Yuan

2014-01-01

In this work, a rapid, sensitive and low-cost colorimetric method for detection of quaternary ammonium surfactants using citrate-capped silver nanoparticles (Ag NPs) was developed. The quaternary ammonium surfactants induce the aggregation of Ag NPs through the hydrophobic effect, which is a novel aggregation mechanism of Ag NPs. The addition of cationic surfactant results in color change of Ag NPs solution from yellow to red and finally to colorless, which is due to the broadening of the surface plasmon band. The color change was monitored using a UV-vis spectrophotometer. The LOD of different cationic surfactants was in the range of 0.5-5 µM. More importantly, this detection method was successfully utilized to the disinfectant residual sample. Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved.

Development of polyethersulfone (PES)/silver nanoparticles (AgNPs)/polyethylene glycol (PEG) nanofiltration membrane

NASA Astrophysics Data System (ADS)

Johary, Fasihah; Jamaluddin, Nur Adibah; Rohani, Rosiah; Hassan, Abdul Rahman; Sharifuddin, Syazrin Syima; Isa, Mohd Hafez Mohd

2018-06-01

Nanofiltration is a membrane-based separation process that has been used widely in the separation and purification fields for various applications such as dye desalting, applications of water softening, pharmaceuticals and wastewater treatment. In this research, polyethersulfone (PES), polyethylene glycol (PEG), Pluronic F108 and silver nanoparticles (AgNPs) nanofiltration membrane was prepared using casting solution technique with N-methyl-2-pyrrolidone (NMP) was used as a solvent. The effects of Pluronic F108 and silver nanoparticles (AgNPs) concentrations in the casting solutions on the membrane performance/properties were also studied. The membrane pure water permeation (PWP) and salt rejection tests were carried out for membrane performance analysis. Scanning electron microscopy (SEM) was used for the membrane morphology characterization. Fourier transform infrared spectroscopy was utilized to identify functional groups in the membrane. Membrane with 2.0 wt.% of Pluronic F108 and 0.05 wt.% of AgNPs showed the best performances for both PWP (40.89 L/m2h) as well as permeation flux of salts solution of NaCl (43.95 L/m2h), Na2SO4 (21.16 L/m2h), MgCl2 (26.46 L/m2h) and MgSO4 (20.41 L/m2h). All fabricated membranes with different formulation of dope composition obtained high salts rejection in the range of 79% to 91%. SEM images showed addition of AgNPs has improved fabricated membrane morphology with higher pore density and larger macro-void structure.

Ag-NP@Ge-nanotaper/Si-micropillar ordered arrays as ultrasensitive and uniform surface enhanced Raman scattering substrates

NASA Astrophysics Data System (ADS)

Liu, Jing; Meng, Guowen; Li, Zhongbo; Huang, Zhulin; Li, Xiangdong

2015-10-01

Surface-enhanced Raman scattering (SERS) is considered to be an excellent candidate for analytical detection schemes, because of its molecular specificity, rapid response and high sensitivity. Here, SERS-substrates of Ag-nanoparticle (Ag-NP) decorated Ge-nanotapers grafted on hexagonally ordered Si-micropillar (denoted as Ag-NP@Ge-nanotaper/Si-micropillar) arrays are fabricated via a combinatorial process of two-step etching to achieve hexagonal Si-micropillar arrays, chemical vapor deposition of flocky Ge-nanotapers on each Si-micropillar and decoration of Ag-NPs onto the Ge-nanotapers through galvanic displacement. With high density three-dimensional (3D) ``hot spots'' created from the large quantities of the neighboring Ag-NPs and large-scale uniform morphology, the hierarchical Ag-NP@Ge-nanotaper/Si-micropillar arrays exhibit strong and reproducible SERS activity. Using our hierarchical 3D SERS-substrates, both methyl parathion (a commonly used pesticide) and PCB-2 (one congener of highly toxic polychlorinated biphenyls) with concentrations down to 10-7 M and 10-5 M have been detected respectively, showing great potential in SERS-based rapid trace-level detection of toxic organic pollutants in the environment.Surface-enhanced Raman scattering (SERS) is considered to be an excellent candidate for analytical detection schemes, because of its molecular specificity, rapid response and high sensitivity. Here, SERS-substrates of Ag-nanoparticle (Ag-NP) decorated Ge-nanotapers grafted on hexagonally ordered Si-micropillar (denoted as Ag-NP@Ge-nanotaper/Si-micropillar) arrays are fabricated via a combinatorial process of two-step etching to achieve hexagonal Si-micropillar arrays, chemical vapor deposition of flocky Ge-nanotapers on each Si-micropillar and decoration of Ag-NPs onto the Ge-nanotapers through galvanic displacement. With high density three-dimensional (3D) ``hot spots'' created from the large quantities of the neighboring Ag-NPs and large-scale uniform

Biochar alleviates the toxicity of imidacloprid and silver nanoparticles (AgNPs) to Enchytraeus albidus (Oligochaeta).

PubMed

Nyoka, Ngitheni Winnie-Kate; Kanyile, Sthandiwe Nomthandazo; Bredenhand, Emile; Prinsloo, Godfried Jacob; Voua Otomo, Patricks

2018-04-01

The present study investigated the use of biochar for the alleviation of the toxic effects of a nanosilver colloidal dispersion and a chloronicotinyl insecticide. The survival and reproduction of the potworm Enchytraeus albidus were assessed after exposure to imidacloprid and silver nanoparticles (AgNPs). E. albidus was exposed to 0, 25, 50, 100, 200, and 400 mg imidacloprid/kg and 0, 5, 25, 125, and 625 mg Ag/kg for 21 days in 10% biochar amended and non-biochar amended OECD artificial soil. In both exposure substrates, the effects of imidacloprid on survival were significant in the two highest treatments (p < 0.01). No biochar effect was observed as survival was statistically similar in both soils after exposure to imidacloprid. In the case of AgNPs, significant mortality was only observed in the highest AgNP treatments in both the amended and non-amended soils (p < 0.05). Nevertheless, statistically greater survival occurred in the biochar-amended treatment (p < 0.05). Reproduction results showed a more pronounced biochar effect with an EC 50  = 22.27 mg imidacloprid/kg in the non-amended soil and a higher EC 50  = 46.23 mg imidacloprid/kg in the biochar-amended soil. This indicated a 2-fold decrease in imidacloprid toxicity due to biochar amendment. A similar observation was made in the case of AgNPs where a reproduction EC 50  = 166.70 mg Ag/kg soil in the non-amended soil increased to an EC 50  > 625 mg Ag/kg soil (the highest AgNP treatment) in the amended soil. This indicated at least a 3.7-fold decrease in AgNPs toxicity due to biochar amendment. Although more studies may be needed to optimize the easing effects of biochar on the toxicity of these chemicals, the present results show that biochar could be useful for the alleviation of the toxic effects of imidacloprid and silver nanoparticles in the soil.

One-Pot Green Synthesis of Ag-Decorated SnO2 Microsphere: an Efficient and Reusable Catalyst for Reduction of 4-Nitrophenol.

PubMed

Hu, Min; Zhang, Zhenwei; Luo, Chenkun; Qiao, Xiuqing

2017-12-01

In this paper, hierarchical Ag-decorated SnO 2 microspheres were synthesized by a facile one-pot hydrothermal method. The resulting composites were characterized by XRD, SEM, TEM, XPS, BET, and FTIR analysis. The catalytic performances of the samples were evaluated with the reduction of 4-nitrophenol to 4-aminophenol by potassium borohydride (KBH 4 ) as a model reaction. Time-dependent experiments indicated that the hierarchical microspheres assembled from SnO 2 and Ag nanoparticles can be formed when the react time is less than 10 h. With the increase of hydrothermal time, SnO 2 nanoparticles will self-assemble into SnO 2 nanosheets and Ag nanoparticles decorated SnO 2 nanosheets were obtained. When evaluated as catalyst, the obtained Ag-decorated SnO 2 microsphere prepared for 36 h exhibited excellent catalytic performance with normalized rate constant (κ nor ) of 6.20 min -1 g -1 L, which is much better than that of some previous reported catalysts. Moreover, this Ag-decorated SnO 2 microsphere demonstrates good reusability after the first five cycles. In addition, we speculate the formation mechanism of the hierarchical Ag-decorated SnO 2 microsphere and discussed the possible origin of the excellent catalytic activity.

Silver nanoparticles (AgNPs) as a contrast agent for imaging of animal tissue using swept-source optical coherence tomography (SSOCT)

NASA Astrophysics Data System (ADS)

Mondal, Indranil; Raj, Shipra; Roy, Poulomi; Poddar, Raju

2018-01-01

We present noninvasive three-dimensional depth-resolved imaging of animal tissue with a swept-source optical coherence tomography system at 1064 nm center wavelength and silver nanoparticles (AgNPs) as a potential contrast agent. A swept-source laser light source is used to enable an imaging rate of 100 kHz (100 000 A-scans s-1). Swept-source optical coherence tomography is a new variant of the optical coherence tomography (OCT) technique, offering unique advantages in terms of sensitivity, reduction of motion artifacts, etc. To enhance the contrast of an OCT image, AgNPs are utilized as an exogeneous contrast agent. AgNPs are synthesized using a modified Tollens method and characterization is done by UV-vis spectroscopy, dynamic light scattering, scanning electron microscopy and energy dispersive x-ray spectroscopy. In vitro imaging of chicken breast tissue, with and without the application of AgNPs, is performed. The effect of AgNPs is studied with different exposure times. A mathematical model is also built to calculate changes in the local scattering coefficient of tissue from OCT images. A quantitative estimation of scattering coefficient and contrast is performed for tissues with and without application of AgNPs. Significant improvement in contrast and increase in scattering coefficient with time is observed.

Synthesis and improved SERS performance of silver nanoparticles-decorated surface mesoporous silica microspheres

NASA Astrophysics Data System (ADS)

Jiang, Tao; Wang, Xiaolong; Zhang, Li; Zhou, Jun; Zhao, Ziqi

2016-08-01

This study reported the improved Raman enhancement ability of silver nanoparticles (Ag NPs) decorated on surface mesoporous silica microspheres (MSiO2@Ag) than that of Ag NPs on solid silica microspheres (SSiO2@Ag). These two kinds of hybrid structures were prepared by a facile single-step hydrothermal reaction with polyvinylpyrrolidone (PVP) serves as both a reductant and stabilizer. The as-synthesized MSiO2@Ag microspheres show more significant surface-enhanced Raman scattering (SERS) activity for 4-mercaptobenzoic acid (4MBA) than SSiO2@Ag microspheres with enhancement factors as 9.20 × 106 and 4.39 × 106, respectively. The proposed reason for the higher SERS activity is estimated to be the contribution of more Raman probe molecules at the mesoporous channels where an enhanced electromagnetic field exists. Such a field was identified by theoretical calculation result. The MSiO2@Ag microspheres were eventually demonstrated for the SERS detection of a typical chemical toxin namely methyl parathion with a detection limit as low as 1 × 10-3 ppm, showing its promising potential in biosensor application.

Reactive oxygen species acts as executor in radiation enhancement and autophagy inducing by AgNPs.

PubMed

Wu, Hao; Lin, Jun; Liu, Peidang; Huang, Zhihai; Zhao, Peng; Jin, Haizhen; Ma, Jun; Wen, Longping; Gu, Ning

2016-09-01

Malignant glioma is one of the most common intracranial tumor with a dismal prognosis. The radiosensitizing effect of silver nanoparticles (AgNPs) on glioma both in vitro and in vivo were demonstrated in the previous studies of our group. However, the underlying mechanism is still unclear. In this present study, the use of antioxidants is employed for the regulating of reactive oxygen species (ROS) in U251 cells treated with various agents, and the results shows that ROS played an essential role in the autophagy inducing and radiosensitization effect of AgNPs. Moreover, the inhibition of protective autophagy with 3-MA is another way to increase ROS, resulting in the increasing of cell death and apoptosis. Taken together, understanding the relationship between the elevated ROS and autophagy and the effect of ROS should be useful to the clinical applications of AgNPs. These findings could potentially be exploited for new therapeutic strategies in glioma radiotherapy. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ambient-Stable and Durable Conductive Ag-Nanowire-Network 2-D Films Decorated with a Ti Layer.

PubMed

Kim, Yoon-Mi; Hwang, Bu-Yeon; Lee, Ki-Wook; Kim, Jin-Yeol

2018-05-11

Highly stable and durable conductive silver nanowire (Ag NW) network electrode films were prepared through decoration with a 5-nm-thick Ti layer. The Ag NW network 2-D films showed sheet resistance values as low as 32 ohm/sq at 88% transparency when decorated with Ti. These 2-D films exhibited a 30% increase in electrical conductivity while maintaining good stability of the films through enhanced resistance to moisture and oxygen penetration as a result of the protective effect of the Ti layer.

Plumbago auriculata leaf extract-mediated AgNPs and its activities as antioxidant, anti-TB and dye degrading agents.

PubMed

Jaryal, Neeraj; Kaur, Harpreet

2017-11-01

In the present work, silver nanoparticles have been biosynthesized by utilizing the alcoholic extract of Plumbago auriculata. The optimization of reaction conditions was carried out by monitoring the reactions with the help of UV-Visible absorption spectroscopy. The characterization of AgNP was carried out by infrared spectroscopy, transmission electron microscopy and X-Ray diffraction (XRD) studies. The biogenic AgNPs were tested against Mycobacterium tuberculosis using Microplate Almar Blue assay (MABA) and their antioxidant activity was also evaluated. The silver nanoparticles were also assessed for their reducing activity against organic dyes. The AgNPs were spherical in shape with size ranging from 15 to 45 nm with face centered cubic geometry as revealed by XRD analysis. The AgNPs possessed good antitubercular activity with MIC value of 1.6 μg/ml and these also exhibited promising antioxidant activity with IC 50 value of 28.2. Furthermore, AgNPs also reduced congo red within 2 h and malachite green was degraded within 40 min. The present work demonstrated the utilization of P. auriculata for biosynthesis of AgNP which could be a potential candidate for antitubercular drug development and it could also be used as an antioxidant agent. The application of AgNP in reducing agent can be further extended and evaluated for purification of effluent water from textile industries.

Preparation, characterization, and antibacterial activity of silver nanoparticle-decorated graphene oxide nanocomposite.

PubMed

Shao, Wei; Liu, Xiufeng; Min, Huihua; Dong, Guanghui; Feng, Qingyuan; Zuo, Songlin

2015-04-01

In this work, we report a facile and green approach to prepare a uniform silver nanoparticles (AgNPs) decorated graphene oxide (GO) nanocomposite (GO-Ag). The nanocomposite was fully characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectra, ultraviolet-visible (UV-vis) absorption spectra, and X-ray photoelectron spectroscopy (XPS), which demonstrated that AgNPs with a diameter of approximately 22 nm were uniformly and compactly deposited on GO. To investigate the silver ion release behaviors, HEPES buffers with different pH (5.5, 7, and 8.5) were selected and the mechanism of release actions was discussed in detail. The cytotoxicity of GO-Ag nanocomposite was also studied using HEK 293 cells. GO-Ag nanocomposite displayed good cytocompatibility. Furthermore, the antibacterial properties of GO-Ag nanocomposite were studied using Gram-negative E. coli ATCC 25922 and Gram-positive S. aureus ATCC 6538 by both the plate count method and disk diffusion method. The nanocomposite showed excellent antibacterial activity. These results demonstrated that GO-Ag nanocomposite, as a kind of antibacterial material, had a great promise for application in a wide range of biomedical applications.

Thermal conductivity enhancements and viscosity properties of water based Nanofluid containing carbon nanotubes decorated with ag nanoparticles

NASA Astrophysics Data System (ADS)

Gu, Yanni; Xu, Sheng; Wu, Xiaoshan

2018-01-01

The water based nanofluid containing carbon nanotube (CNT) decorated with Ag nanoparticles (Ag/CNT) is prepared. Its thermal conductivity (k) enhancement increases with the thermal filler loading and the decoration quantity of Ag nanoparticles. The low absolute CNT content will decrease the tangles or aggregations among the CNTs, and it will be good at the Brownian motion of CNTs in the water. It has positive effects on the thermal conductivity of nanofluid. With the increase of Ag loading, the average size of Ag nanoparticles increased, and further results in the decrease of dispersing amount of Ag/CNT as the weight of Ag/CNT is fixed. Little dispersing quantity of Ag/CNT makes it possible that the Ag/CNT particles disperse well in the fluid. So it is not easy for CNTs to form aggregation. The high intrinsic k of CNT and the effective thermal conductive networks forming by CNTs and Ag nanoparticles are good at the k enhancement. With temperature increase the k of Ag/CNT nanofluid appears improvement. The study results make it possible to develop high-efficiency nanofluid for advanced thermal management regions.

Thermal conductivity enhancements and viscosity properties of water based Nanofluid containing carbon nanotubes decorated with ag nanoparticles

NASA Astrophysics Data System (ADS)

Gu, Yanni; Xu, Sheng; Wu, Xiaoshan

2018-06-01

The water based nanofluid containing carbon nanotube (CNT) decorated with Ag nanoparticles (Ag/CNT) is prepared. Its thermal conductivity ( k) enhancement increases with the thermal filler loading and the decoration quantity of Ag nanoparticles. The low absolute CNT content will decrease the tangles or aggregations among the CNTs, and it will be good at the Brownian motion of CNTs in the water. It has positive effects on the thermal conductivity of nanofluid. With the increase of Ag loading, the average size of Ag nanoparticles increased, and further results in the decrease of dispersing amount of Ag/CNT as the weight of Ag/CNT is fixed. Little dispersing quantity of Ag/CNT makes it possible that the Ag/CNT particles disperse well in the fluid. So it is not easy for CNTs to form aggregation. The high intrinsic k of CNT and the effective thermal conductive networks forming by CNTs and Ag nanoparticles are good at the k enhancement. With temperature increase the k of Ag/CNT nanofluid appears improvement. The study results make it possible to develop high-efficiency nanofluid for advanced thermal management regions.

UV-visible light-activated Ag-decorated, monodisperse TiO2 aggregates for treatment of the pharmaceutical oxytetracycline.

PubMed

Han, Changseok; Likodimos, Vlassis; Khan, Javed Ali; Nadagouda, Mallikarjuna N; Andersen, Joel; Falaras, Polycarpos; Rosales-Lombardi, Pablo; Dionysiou, Dionysios D

2014-10-01

Noble metal Ag-decorated, monodisperse TiO2 aggregates were successfully synthesized by an ionic strength-assisted, simple sol-gel method and were used for the photocatalytic degradation of the antibiotic oxytetracycline (OTC) under both UV and visible light (UV-visible light) irradiation. The synthesized samples were characterized by X-ray diffraction analysis (XRD); UV-vis diffuse reflectance spectroscopy; environmental scanning electron microscopy (ESEM); transmission electron microscopy (TEM); high-resolution TEM (HR-TEM); micro-Raman, energy-dispersive X-ray spectroscopy (EDS); and inductively coupled plasma optical emission spectrometry (ICP-OES). The results showed that the uniformity of TiO2 aggregates was finely tuned by the sol-gel method, and Ag was well decorated on the monodisperse TiO2 aggregates. The absorption of the samples in the visible light region increased with increasing Ag loading that was proportional to the amount of Ag precursor added in the solution over the tested concentration range. The Brunauer, Emmett, and Teller (The BET) surface area slightly decreased with increasing Ag loading on the TiO2 aggregates. Ag-decorated TiO2 samples demonstrated enhanced photocatalytic activity for the degradation of OTC under UV-visible light illumination compared to that of pure TiO2. The sample containing 1.9 wt% Ag showed the highest photocatalytic activity for the degradation of OTC under both UV-visible light and visible light illumination. During the experiments, the detected Ag leaching for the best TiO2-Ag photocatalyst was much lower than the National Secondary Drinking Water Regulation for Ag limit (0.1 mg L(-1)) issued by the US Environmental Protection Agency.

Electrostatic Assemblies of Well-Dispersed AgNPs on the Surface of Electrospun Nanofibers as Highly Active SERS Substrates for Wide-Range pH Sensing.

PubMed

Yang, Tong; Ma, Jun; Zhen, Shu Jun; Huang, Cheng Zhi

2016-06-15

Surface-enhanced Raman scattering (SERS) has shown high promise in analysis and bioanalysis, wherein noble metal nanoparticles (NMNPs) such as silver nanoparticles were employed as substrates because of their strong localized surface plasmon resonance (LSPR) properties. However, SERS-based pH sensing was restricted because of the aggregation of NMNPs in acidic medium or biosamples with high ionic strength. Herein, by using the electrostatic interaction as a driving force, AgNPs are assembled on the surface of ethylene imine polymer (PEI)/poly(vinyl alcohol) (PVA) electrospun nanofibers, which are then applied as highly sensitive and reproducible SERS substrate with an enhancement factor (EF) of 10(7)-10(8). When p-aminothiophenol (p-ATP) is used as an indicator with its b2 mode, a good and wide linear response to pH ranging from 2.56 to 11.20 could be available, and the as-prepared nanocomposite fibers then could be fabricated as excellent pH sensors in complicated biological samples such as urine, considering that the pH of urine could reflect the acid-base status of a person. This work not only emerges a cost-effective, direct, and convenient approach to homogeneously decorate AgNPs on the surface of polymer nanofibers but also supplies a route for preparing other noble metal nanofibrous sensing membranes.

Ag nanodots decorated SiO2 coated ZnO core-shell nanostructure with enhanced luminescence property as potential imaging agent

NASA Astrophysics Data System (ADS)

Gupta, Jagriti; Barick, K. C.; Hassan, P. A.; Bahadur, Dhirendra

2018-04-01

Ag decorated silica coated ZnO nanocomposite (Ag@SiO2@ZnO NCs) has been synthesized by soft chemical approach. The physico-chemical properties of Ag@SiO2@ZnO NCs are investigated by various sophisticated characterization techniques such as X-ray diffraction, Transmission electron microscopy, X-ray photoelectron spectroscopy, UV-visible absorption and photoluminescent spectroscopy. X-ray diffraction confirms the phase formation of ZnO and Ag in nanocomposite. TEM micrograph clearly shows that Ag nanodots are well decorated over silica coated ZnO NCs. The photoluminescent study reveals the enhancement in the photoluminance property when the Ag nanodots are decorated over silica coated ZnO nanocomposite due to an electromagnetic coupling between excitons and plasmons. Furthermore, the photoluminescent property is an important tool for bio-imaging application, reveal that NCs give green and red emission after excitation with 488 and 535 nm. Therefore, low cytotoxicity and excellent fluorescence stability in vitro makes it a more suitable material for both cellular imaging and therapy for biomedical applications.

Succinic acid functionalized silver nanoparticles (Suc-Ag NPs) for colorimetric sensing of melamine

NASA Astrophysics Data System (ADS)

Rajar, Kausar; Sirajuddin; Balouch, Aamna; Bhanger, M. I.; Shah, Muhammad Tariq; Shaikh, Tayyaba; Siddiqui, Samia

2018-03-01

In this study, a quantitative colorimetric sensing strategy is developed for the rapid, sensitive and selective determination of melamine. The sensing system relies on the application of succinic acid as a selective recognition probe functionalized over Ag NPs. The synthesized Ag NPs were modified with cysteamine to induce positively charged atmosphere which allowed easy and favorable functionalization of succinic acid. The di-carboxyl nature of succinic acid enabled its binding to both cysteamine and melamine. The strong and favorable linkage between succinic acids carbonyl and amine moieties of melamine triggered aggregation of silver NPs producing a significant shift in the measured absorption excitation. This change in the excitation along with the colorimetric response was found linearly proportional to the melamine concentration in the range of 0.1-1.2 μM. The developed sensor system is simple and unlike electrostatic attraction based sensor system utilize selective linkage for the recognition of melamine. In addition to this, the developed optical probe can efficiently be used for the determination of melamine in milk samples.

Ag-NP@Ge-nanotaper/Si-micropillar ordered arrays as ultrasensitive and uniform surface enhanced Raman scattering substrates.

PubMed

Liu, Jing; Meng, Guowen; Li, Zhongbo; Huang, Zhulin; Li, Xiangdong

2015-11-21

Surface-enhanced Raman scattering (SERS) is considered to be an excellent candidate for analytical detection schemes, because of its molecular specificity, rapid response and high sensitivity. Here, SERS-substrates of Ag-nanoparticle (Ag-NP) decorated Ge-nanotapers grafted on hexagonally ordered Si-micropillar (denoted as Ag-NP@Ge-nanotaper/Si-micropillar) arrays are fabricated via a combinatorial process of two-step etching to achieve hexagonal Si-micropillar arrays, chemical vapor deposition of flocky Ge-nanotapers on each Si-micropillar and decoration of Ag-NPs onto the Ge-nanotapers through galvanic displacement. With high density three-dimensional (3D) "hot spots" created from the large quantities of the neighboring Ag-NPs and large-scale uniform morphology, the hierarchical Ag-NP@Ge-nanotaper/Si-micropillar arrays exhibit strong and reproducible SERS activity. Using our hierarchical 3D SERS-substrates, both methyl parathion (a commonly used pesticide) and PCB-2 (one congener of highly toxic polychlorinated biphenyls) with concentrations down to 10(-7) M and 10(-5) M have been detected respectively, showing great potential in SERS-based rapid trace-level detection of toxic organic pollutants in the environment.

A novel surface plasmon resonance biosensor based on the PDA-AgNPs-PDA-Au film sensing platform for horse IgG detection

NASA Astrophysics Data System (ADS)

Wang, Ning; Zhang, Di; Deng, Xinyu; Sun, Ying; Wang, Xinghua; Ma, Pinyi; Song, Daqian

2018-02-01

Herein we report a novel polydopamine-silver nanoparticle-polydopamine-gold (PDA-AgNPs-PDA-Au) film based surface plasmon resonance (SPR) biosensor for horse IgG detection. The PDA-AgNPs-PDA-Au film sensing platform was built on Au-film via layer-by-layer self-assembly. Ag ion was reduced in situ to AgNPs in presence of PDA. The top PDA layer can prevent AgNPs from being oxidized and connect with antibody via Schiff alkali reaction directly. The morphology and thickness of the modified gold film were characterized using scanning electron microscope and Talystep. Experimental results show that the PDA-AgNPs-PDA-Au film sensing platform is stable, regenerative and sensitive for horse IgG detection. The detection limit of horse IgG obtained with the present biosensor is 0.625 μg mL- 1, which is 2-fold and 4-fold lower than that obtained with biosensor based on PDA modified Au film and conventional biosensor based on MPA, respectively. Furthermore, when challenged to real serum samples, our sensor exhibited excellent specificity to horse IgG, suggesting its potential for industrial application.

Building an Electronic Bridge via Ag Decoration To Enhance Kinetics of Iron Fluoride Cathode in Lithium-Ion Batteries.

PubMed

Li, Yu; Zhou, Xingzhen; Bai, Ying; Chen, Guanghai; Wang, Zhaohua; Li, Hui; Wu, Feng; Wu, Chuan

2017-06-14

As a typical multielectron cathode material for lithium-ion batteries, iron fluoride (FeF 3 ) and its analogues suffer from poor electronic conductivity and low actual specific capacity. Herein, we introduce Ag nanoparticles by silver mirror reaction into the FeF 3 ·0.33H 2 O cathode to build the electronic bridge between the solid (active materials) and liquid (electrolyte) interface. The crystal structures of as-prepared samples are characterized by X-ray diffraction and Rietveld refinement. Moreover, the density of states of FeF 3 ·0.33H 2 O and FeF 3 ·0.33H 2 O/Ag (Ag-decorated FeF 3 ·0.33H 2 O) samples are calculated using the first principle density functional theory. The FeF 3 ·0.33H 2 O/Ag cathodes exhibit significant enhancements on the electrochemical performance in terms of the cycle performance and rate capability, especially for the Ag-decorated amount of 5%. It achieves an initial capacity of 168.2 mA h g -1 and retains a discharge capacity of 128.4 mA h g -1 after 50 cycles in the voltage range of 2.0-4.5 V. It demonstrates that Ag decoration can reduce the band gap, improve electronic conductivity, and elevate intercalation/deintercalation kinetics.

Direct synthesis of mesostructured carbon nanofibers decorated with silver-nanoparticles as a multifunctional membrane for water treatment

NASA Astrophysics Data System (ADS)

Aboueloyoun Taha, Ahmed

2015-12-01

One-dimensional (1D) porous carbon nanofibers (CNFs) decorated by silver (Ag) nanoparticles (NPs) were prepared using a one-pot/self-template synthesis strategy by combining electrospinning and carbonization methods. The characterization results revealed that AgNPs were homogenously distributed along the CNFs and possessed a relatively uniform nano-size of about 12 nm. The novel membrane distinctively displayed enhanced photocatalytic activity under visible-light irradiation. The membrane exhibited excellent dye degradation and bacteria disinfection in batch experiments. The high photocatalytic activity can be attributed to the highly accessible surface areas, good light absorption capability, and high separation efficiency of photogenerated electron-hole pairs. The as-prepared membranes can be easily recycled because of their 1D property.

Photoconversion of 4-nitrophenol in the presence of hydrazine with AgNPs-TiO2 nanoparticles prepared by the sol-gel method.

PubMed

Hernández-Gordillo, Agileo; Arroyo, Missael; Zanella, R; Rodríguez-González, V

2014-03-15

The photocatalytic properties of functionalized TiO2 with silver nanoparticles (AgNPs) for the conversion of 4-nitrophenol to 4-aminophenol in the presence of hydrazine were investigated. The TiO2 semiconductor synthesized by the sol-gel method was functionalized with AgNPs at different loadings, and their structural and optical properties were characterized by several techniques. The functionalized TiO2 with 1.5wt% AgNPs presented the highest photocatalytic activity for the conversion of 4-nitrophenol with appropriate hydrazine concentrations (0.5M). The photoefficiency enhancement under UV light irradiation was attributed to the electron transfer from the TiO2 semiconductor surface to the adsorbed acceptor reactant (4-nitrophenol) through the deposited AgNPs. Copyright © 2014 Elsevier B.V. All rights reserved.

W{sub 18}O{sub 49} nanorods decorated with Ag/AgCl nanoparticles as highly-sensitive gas-sensing material and visible-light-driven photocatalyst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun Shibin; Chang Xueting, E-mail: xuetingchang@yahoo.cn; Dong Lihua

2011-08-15

A novel gas-sensing material and photocatalyst was successfully obtained by decorating Ag/AgCl nanoparticles on the W{sub 18}O{sub 49} nanorods through a clean photochemical route. The as-prepared samples were characterized using combined techniques of X-ray diffractometry, electron microscopy, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy. Gas-sensing measurements indicate that the Ag/AgCl/W{sub 18}O{sub 49} NRs sensors exhibit superior reducing gas-sensing properties to those of bare W{sub 18}O{sub 49} NRs, and they are highly selective and sensitive to NH{sub 3}, acetone, and H{sub 2}S with short response and recovery times. The Ag/AgCl/W{sub 18}O{sub 49} NRs photocatlysts also possess higher photocatalytic performance thanmore » bare W{sub 18}O{sub 49} NRs for degradation of methyl orange under simulated sunlight irradiation. Possible mechanisms concerning the enhancement of gas-sensing and photocatalytic activities of the Ag/AgCl/W{sub 18}O{sub 49} NRs composite were proposed. - Graphical Abstract: The Ag/AgCl nanoparticles adhered well to the W{sub 18}O{sub 49} nanorod. The Ag could act as transfer center of the photoexcited carriers, prohibiting their recombinations in both W{sub 18}O{sub 49} and AgCl. Highlights: > Ag/AgCl/W{sub 18}O{sub 49} NRs were successfully obtained via a clean photochemical route. > The Ag/AgCl nanoparticles decorated on the W{sub 18}O{sub 49} NRs possessed cladding structure. > The Ag/AgCl/W{sub 18}O{sub 49} NRs exhibited excellent gas-sensing and photocatalytic properties.« less

Promising biocidal activity of thymol loaded chitosan silver nanoparticles (T-C@AgNPs) as anti-infective agents against perilous pathogens.

PubMed

Manukumar, H M; Umesha, S; Kumar, H N Naveen

2017-09-01

The advent of biodegradable polymer-encapsulated drug nanoparticles has made an exciting area of drug delivery research. The present study investigated novel and simple route for synthesis of thymol loaded chitosan silver nanoparticles (T-C@AgNPs) using chitosan and thymol as reducing, capping agent respectively to understand the therapeutic efficacy. The UV-vis spectroscopy, DLS, FT-IR, SEM, EDS, XRD used for characterization and radical scavenging activity, anti-microbial and biocompatibility was taken to ascertain an efficacy of novel T-C@AgNPs. The T-C@AgNPs intense peak at 490nm indicates the formation of nanoparticles and had average particle size of 28.94nm with spherical shape, monodisperse state in water, also exhibited excellent biocompatibility of cubic shaped pure silver element containing T-C@AgNPs. The antibacterial activity was studied for gram positive and gram negative food-borne pathogens and effective inhibition at 100μgmL -1 to S. aureus, S. epidermidis, S. haemolyticus (10.08, 10.00, 11.23mm) and S. typhimurium, P. aeruginosa and S. flexneri (9.28, 9.33, 12.03mm) compared to antibiotic Streptomycin. This study revealed the efficacy against multiple food-borne pathogens and therapeutic efficacy of T-C@AgNPs offers a valuable contribution in the area of nanotechnology. This proved to be a first-class novel antimicrobial material for the first time in this study. Copyright © 2017 Elsevier B.V. All rights reserved.

An eco-benign synthesis of AgNPs using aqueous extract of Longan fruit peel: Antiproliferative response against human breast cancer cell line MCF-7, antioxidant and photocatalytic deprivation of methylene blue.

PubMed

Khan, Arif Ullah; Yuan, Qipeng; Khan, Zia Ul Haq; Ahmad, Aftab; Khan, Faheem Ullah; Tahir, Kamran; Shakeel, Muhammad; Ullah, Sadeeq

2018-05-07

Plants mediated synthesis of noble metal nanoparticles is encountered as a clean, environment friendly, lucrative and benign loom. The current study consists of clean and green synthesis of Silver nanoparticles (AgNPs). Phytoconstituents from Longan (Euphorbia longana Lam.) fruit peel were used to reduce Ag + into AgNPs. Different analytical techniques i.e. UV-vis Spectroscopy, X-ray diffraction spectroscopy (XRD), electron dispersive X-ray (EDX), High-resolution transmission electron microscopy (HRTEM) and Fourier transform infrared spectroscopy (FTIR) were used to analyze the synthesized AgNPs. AgNPs have localized surface plasmon resonance (LSPR) peak at 445 nm which is confirmed by UV-vis spectroscopy. HRTEM showed that the prepared AgNPs are spheroid in shape and well dispersed while XRD results showed that the AgNPs are face centered cubic crystalline. EDX confirmed the elemental composition of AgNPs. The antiproliferative response of AgNPs was assayed by an exhaustive MTT assay. AgNPs showed potent anticancer activity (88%) against breast cancer cells MCF-7. Moreover, the green produced AgNPs effectively scavenged 91% of the stable and harmful 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical which confirms its' efficient antioxidant nature. AgNPs have profound photocatalytic degradation (99%) of methylene blue in a short period of time (7 min). The noteworthy biological and photocatalytic responses of the green and cleanly produced AgNPs are encountered to their well dispersion, petite volume and round shaped structure. Copyright © 2018 Elsevier B.V. All rights reserved.

Synthesis, kinetics and photocatalytic study of "ultra-small" Ag-NPs obtained by a green chemistry method using an extract of Rosa 'Andeli' double delight petals.

PubMed

Suárez-Cerda, Javier; Alonso-Nuñez, Gabriel; Espinoza-Gómez, Heriberto; Flores-López, Lucía Z

2015-11-15

This paper reports the effect of different concentrations of Rosa 'Andeli' double delight petals aqueous extract (PERA) in the synthesis of silver nanoparticles (Ag-NPs), using an easy green chemistry method. Its kinetics study and photocatalytic activity were also evaluated. The Ag-NPs were obtained using an aqueous silver nitrate solution (AgNO3) with 9.66% w/v, 7.25% w/v, and 4.20% w/v PERA as both reducing-stabilizing agent. The formation of the Ag-NPs was demonstrated by analysis of UV-vis spectroscopy, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). TEM analysis shows spherical nanoparticles in shape and size between ∼0.5 and 1.4nm. A comparative study was done to determine which concentration was the best reducing-stabilizing agent, and we found out that "ultra-small" nanoparticles (0.5-1.1nm) were obtained with 9.66% w/v of PERA. The size of the Ag-NPs depends on the concentration of PERA and Ag(I). The reaction of formation of "ultra-small" Ag-NPs, proved to be first order for metallic precursor (silver) and second order for reducing-stabilizing agent (PERA). The Ag-NPs showed photocatalytic activity, in degradation of commercial dye with an efficiency of 95%. Copyright © 2015 Elsevier Inc. All rights reserved.

Visible light photo catalytic inactivation of bacteria and photo degradation of methylene blue with Ag/TiO2 nanocomposite prepared by a novel method.

PubMed

Tahir, Kamran; Ahmad, Aftab; Li, Baoshan; Nazir, Sadia; Khan, Arif Ullah; Nasir, Tabassum; Khan, Zia Ul Haq; Naz, Rubina; Raza, Muslim

2016-09-01

Water purification is one of the worldwide problem and most of the conventional methods are associated with a number of drawbacks. Therefore it is the need of the day to develop new methods and materials to overcome the problem of water purification. In this research work we present a simple and green approach to synthesize silver decorated titanium dioxide (Ag/TiO2) nanocomposite with an efficient photo catalytic activities. Phytochemicals of the Cestrum nocturnum leaf extract were used to synthesize silver nanoparticles (AgNPs), Titanium dioxide (TiO2) and Ag/TiO2 nanocomposite. To confirm the formation, crystal structure, particle size and shape of green synthesized nanoparticles and nanocomposite, they were characterized by UV-visible spectroscopy (UV-vis), X-ray diffraction spectroscopy (XRD), high resolution transmission electron microscopy (HRTEM), Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The AgNPs, TiO2 and Ag/TiO2 were evaluated for photo degradation of methylene blue (MB) and photo inhibition of Bacteria. The bio-synthesized Ag/TiO2 nanocomposite was observed to have strong catalytic activities for photo reduction of MB and photo inactivation of bacteria as compared to bare AgNPs and TiO2. In the presence of Ag/TiO2, 90% of MB was degraded only in 40min of irradiation. Alternatively the bare AgNPs and TiO2 degraded less than 30% and 80% respectively of MB even in more than 100min of irradiation. Similarly the Ag/TiO2 has very strong photo inhibition efficiency towards Escherichia coli and Pseudomonas aeruginosa. The zone of inhibition of irradiated Ag/TiO2 nanocomposites against E. coli and P. aeruginosa was 19mm and 17mm respectively which was two times higher than in dark. These promising photocatalytic activities of nanocomposite may be due to the highly decorated AgNPs over the surface of TiO2. Copyright © 2016 Elsevier B.V. All rights reserved.

Biological studies and electrical conductivity of paper sheet based on PANI/PS/Ag-NPs nanocomposite.

PubMed

Youssef, A M; Mohamed, S A; Abdel-Aziz, M S; Abdel-Aziz, M E; Turky, G; Kamel, S

2016-08-20

Polyaniline (PANI) with/without polystyrene (PS), was successfully manufactured in the occurrence of dispersed pulp fibers via the oxidative polymerization reaction of aniline monomer to produce conductive paper sheets containing PANI, PANI/PS composites. Additionally, sliver nitrate (Ag-NO3) was added by varied loadings to the oxidative polymerization of aniline monomer to provide sliver nanoparticles (Ag-NPs) emptied into the prepared paper sheets. The prepared paper sheets were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD) and infrared spectroscopy (IR), the mechanical properties of the prepared paper sheets were evaluated. Moreover, the electrical conductivity and biological studies such as cellulases assay, Microorganism & culture condition and detection of the released of Ag-NPs were evaluated. Furthermore, the prepared paper sheets were displayed good antibacterial properties contrary to gram positive and gram negative bacteria. Consequently, the prepared paper sheet may be used as novel materials for packaging applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Synthesis and characterization of PVK/AgNPs nanocomposites prepared by laser ablation.

PubMed

Abd El-Kader, F H; Hakeem, N A; Elashmawi, I S; Menazea, A A

2015-03-05

Nanocomposites of Poly (n-vinylcarbazole) PVK/Ag nanoparticles were prepared by laser ablation of a silver plate in aqueous solution of chlorobenzene. The influences of laser parameters such as; time of irradiation, source power and wavelength (photon energy) on structural, morphological and optical properties have been investigated using X-ray diffraction (XRD), Transmission electron microscopy (TEM), Ultraviolet-visible (UV-Vis) and Photoluminescence (PL). A correlation between the investigated properties has been discussed. XRD, TEM and PL indicated that the complexation between AgNPs and PVK in the composite system is possible. Only the reflection peak at 2θ=38° of AgNPs appeared in the composite nanoparticles while the other reflection peaks were destroyed. The nanoparticles shape and size distribution were evaluated from TEM images. TEM analysis revealed a lower average particle size at long laser irradiation time 40min and short laser wavelength 532nm together with high laser power 570mW. From UV-Visible spectra the values of absorption coefficient, absorption edge and energy tail were calculated. The reduction of band tail value with increasing the laser ablation parameters confirms the decrease of the disorder in such composite system. The PL and UV-Vis. spectra confirm that nanocomposite samples showed quantum confinement effect. Copyright © 2014 Elsevier B.V. All rights reserved.

Silver Nanoparticle-Decorated Shape-Memory Polystyrene Sheets as Highly Sensitive Surface-Enhanced Raman Scattering Substrates with a Thermally Inducible Hot Spot Effect.

PubMed

Mengesha, Zebasil Tassew; Yang, Jyisy

2016-11-15

In this study, an active surface-enhanced Raman scattering (SERS) substrate with a thermally inducible hot spot effect for sensitive measurement of Raman-active molecules was successfully fabricated from silver nanoparticle (AgNP)-decorated shape-memory polystyrene (SMP) sheets. To prepare the SERS substrate, SMP sheets were first pretreated with n-octylamine for effective decoration with AgNPs. By varying the formulation and condition of the reduction reaction, AgNP-decorated SMP (Ag@SMP) substrates were successfully prepared with optimized particle gaps to produce inducible hot spot effects on thermal shrink. High-quality SERS spectra were easily obtained with enhancement factors higher than 10 8 by probing with aromatic thiols. Several Ag@SMP substrates produced under different reaction conditions were explored for the creation of inducible hot spot effects. The results indicated that AgNP spacing is crucial for strong hot spot effects. The suitability of Ag@SMP substrates for quantification was also evaluated according to the detection of adenine. Results confirmed that prepared Ag@SMP substrates were highly suitable for quantitative analysis because they yielded an estimated limit of detection as low as 120 pg/cm 2 , a linear range of up to 7 ng/cm 2 , and a regression coefficient (R 2 ) of 0.9959. Ag@SMP substrates were highly reproducible; the average relative standard deviation for all measurements was less than 10%.

Development of HA/Ag-NPs Composite Coating from Green Process for Hip Applications.

PubMed

Lozoya-Rodríguez, Denisse A; de Lima, Renata; Fraceto, Leonardo F; Ledezma Pérez, Antonio; Bazaldua Domínguez, Mercedes; Gómez Batres, Roberto; Reyes Rojas, Armando; Orozco Carmona, Víctor

2017-08-08

In the present study, biological hydroxyapatite (HA) was obtained from bovine bones through a thermal process. A total of 0% and 1% of silver nanoparticles (Ag-NPs) synthesized from Opuntia ficus (nopal) were added to the biological hydroxyapatite coatings using an atmospheric plasma spray (APS) on a Ti6Al4V substrate. Following this, its antimicrobial efficiency was evaluated against the following bacterial strains: Escherichia coli , Staphylococcus aureus , and Pseudomonas aeruginosa . This was conducted according to the Japanese Industrial Standard (JIS) Z2801:2000 "Antimicrobial Product-Test for Antimicrobial Activity and Efficacy". Scanning electron microscopy (SEM) showed that the silver nanoparticles (Ag-NPs) were evenly distributed on the coating surface. Energy dispersive X-ray spectroscopy (EDX) shows that apatite deposition occurs on a daily basis, maintaining a Ca/P rate between 2.12 and 1.45. Biocompatibility properties were evaluated with osteoblast-like cells (MC3T3-E1) by single-cell gel electrophoresis assay and Tali image cytometry.

Synthesis of Silver nanoparticles (AgNPs) with Antibacterial Activity

NASA Astrophysics Data System (ADS)

Campillo Gloria, E.; Ederley, Vélez; Gladis, Morales; César, Hincapié; Jaime, Osorio; Oscar, Arnache; Uribe José, Ignacio; Franklin, Jaramillo

2017-06-01

The synthesis of nanomaterials is currently one of the most active in nanoscience branches; especially those help improve the human quality life. Silver nanoparticles (AgNPs) are an example of this as it is known to have inhibitory and bactericidal effects. In this work, we report the synthesis of silver nanoparticles by chemical reduction method of silver nitrate (AgNO3) from aqueous solution, using a mix of polivinyl pyrrolidone (PVP) - Aloe Vera as reducing agent and for stabilization and control of particle size. Silver nanoparticles obtained were characterized by Scanning Electron Microscopy (SEM), UV-visible spectroscopy and measurements using Zetasizer Nano ZS were applied to size estimation. The existence of surface plasmon resonance peak at λmax ~ 420 nm is evidence of silver nanoparticles formation. It was possible to standardize an appropriate protocol for the evaluation of bactericidal activity of the nanoparticles, for mesophilic microorganisms. Bactericidal activity above 90% against these kinds of bacteria was demonstrated.

Wafer-Scale Hierarchical Nanopillar Arrays Based on Au Masks and Reactive Ion Etching for Effective 3D SERS Substrate.

PubMed

Men, Dandan; Wu, Yingyi; Wang, Chu; Xiang, Junhuai; Yang, Ganlan; Wan, Changjun; Zhang, Honghua

2018-02-04

Two-dimensional (2D) periodic micro/nanostructured arrays as SERS substrates have attracted intense attention due to their excellent uniformity and good stability. In this work, periodic hierarchical SiO₂ nanopillar arrays decorated with Ag nanoparticles (NPs) with clean surface were prepared on a wafer-scale using monolayer Au NP arrays as masks, followed by reactive ion etching (RIE), depositing Ag layer and annealing. For the prepared SiO₂ nanopillar arrays decorated with Ag NPs, the size of Ag NPs was tuned from ca. 24 to 126 nanometers by controlling the deposition thickness of Ag film. Importantly, the SiO₂ nanopillar arrays decorated with Ag NPs could be used as highly sensitive SERS substrate for the detection of 4-aminothiophenol (4-ATP) and rhodamine 6G (R6G) due to the high loading of Ag NPs and a very uniform morphology. With a deposition thickness of Ag layer of 30 nm, the SiO₂ nanopillar arrays decorated with Ag NPs exhibited the best sensitive SERS activity. The excellent SERS performance of this substrate is mainly attributed to high-density "hotspots" derived from nanogaps between Ag NPs. Furthermore, this strategy might be extended to synthesize other nanostructured arrays with a large area, which are difficult to be prepared only via conventional wet-chemical or physical methods.

The effect of biologically and chemically synthesized silver nanoparticles (AgNPs) on biofilm formation

NASA Astrophysics Data System (ADS)

Chojniak, Joanna; Biedroń, Izabela; Mendrek, Barbara; Płaza, Grażyna

2017-11-01

Bionanotechnology has emerged up as integration between biotechnology and nanotechnology for developing biosynthetic and environmental-friendly technology for synthesis of nanomaterials. Different types of nanomaterials like copper, zinc, titanium, magnesium, gold, and silver have applied in the various industries but silver nanoparticles have proved to be most effective against bacteria, viruses and eukaryotic microorganisms. The antimicrobial property of silver nanoparticles are widely known. Due to strong antibacterial property silver nanoparticles are used, e.g. in clothing, food industry, sunscreens, cosmetics and many household and environmental appliances. The aim of the study was to compare the effect of silver nanoparticles (AgNPs) synthesized biologically and chemically on the biofilm formation. The biofilm was formed by the bacteria isolated from the water supply network. The commonly used crystal violet assay (CV) was applied for biofilm analysis. In this study effect of biologically synthesized Ag-NPs on the biofilm formation was evaluated.

FRET based integrated pyrene-AgNPs system for detection of Hg (II) and pyrene dimer: Applications to environmental analysis

NASA Astrophysics Data System (ADS)

Walekar, Laxman S.; Hu, Peidong; Vafaei Molamahmood, Hamed; Long, Mingce

2018-06-01

The integrated system of pyrene and cetyltrimethyl ammonium bromide (CTAB) capped silver nanoparticles (AgNPs) with a distance (r) of 2.78 nm has been developed for the detection of Hg (II) and pyrene dimer. The interaction between pyrene and AgNPs results in the fluorescence quenching of pyrene due to the energy transfer, whose mechanism can be attributed to the Forster Resonance Energy Transfer (FRET) supported by experimental observation and theoretical calculations. The developed probe shows a highly selective and sensitive response towards Hg (II) probably due to the amalgam formation, which results in the fluorescence recovery (90%) of pyrene and color change of solution from yellowish brown to colorless. The addition of Hg (II) may increase the distance between pyrene and AgNPs undergoes the 'FRET OFF' process. This system gives a selective response towards Hg (II) over other competing metal ions. Under the optimal condition, the system offers good linearity between 0.1 and 0.6 μg mL-1 with a detection limit of 62 ng mL-1. In addition, the system also provides an effective platform for detection of pyrene in its dimer form even at very low concentrations (10 ng mL-1) on the surface of AgNPs. Therefore, it could be used as effective alternatives for the detection of Hg (II) as well as pyrene simultaneously.

Rapid colorimetric sensing of gadolinium by EGCG-derived AgNPs: the development of a nanohybrid bioimaging probe.

PubMed

Singh, Rohit Kumar; Mishra, Sourav; Jena, Satyapriya; Panigrahi, Bijayananda; Das, Bhaskar; Jayabalan, Rasu; Parhi, Pankaj Kumar; Mandal, Dindyal

2018-04-17

Polyphenol functionalized silver nanoparticles (AgNPs) have been developed and demonstrated as colorimetric sensors for the selective detection of gadolinium. The newly obtained AgNP-Gd3+ conjugates exhibit high aqueous dispersibility and excitation dependent fluorescence emission. The conjugates offer multicolor bioimaging potential owing to their excellent luminescence properties.

Simultaneous determination of epinephrine and dopamine by electrochemical reduction on the hybrid material SiO₂/graphene oxide decorated with Ag nanoparticles.

PubMed

Cincotto, Fernando H; Canevari, Thiago C; Campos, Anderson M; Landers, Richard; Machado, Sérgio A S

2014-09-21

This paper describes the synthesis, characterization and applications of a new hybrid material composed of mesoporous silica (SiO2) modified with graphene oxide (GO), SiO2/GO, obtained by the sol-gel process using HF as the catalyst. The hybrid material, SiO2/GO, was decorated with silver nanoparticles (AgNPs) with a size of less than 20 nanometres, prepared directly on the surface of the material using N,N-dimethylformamide (DMF) as the reducing agent. The resulting material was designated as AgNP/SiO2/GO. The Ag/SiO2/GO material was characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and high-resolution transmission electron microscopy (HR-TEM). A glassy carbon electrode modified with AgNP/SiO2/GO was used in the development of a sensitive electrochemical sensor for the simultaneous determination of epinephrine and dopamine employing electrocatalytic reduction using squarewave voltammetry. Well-defined and separate reduction peaks were observed in PBS buffer at pH 7. No significant interference was seen for primarily biological interferents such as uric acid and ascorbic acid in the detection of dopamine and epinephrine. Our study demonstrated that the resultant AgNP/SiO2/GO-modified electrode is highly sensitive for the simultaneous determination of dopamine and epinephrine, with the limits of detection being 0.26 and 0.27 μmol L(-1), respectively. The AgNP/SiO2/GO-modified electrode is highly selective and can be used to detect dopamine and epinephrine in a human urine sample.

Superabsorbent cryogels decorated with silver nanoparticles as a novel water technology for point-of-use disinfection.

PubMed

Loo, Siew-Leng; Fane, Anthony G; Lim, Teik-Thye; Krantz, William B; Liang, Yen-Nan; Liu, Xin; Hu, Xiao

2013-08-20

This paper reports the preparation of poly(sodium acrylate) (PSA) cryogels decorated with silver nanoparticles (AgNPs) for point-of-use (POU) water disinfection. The PSA/Ag cryogels combine the high porosity, excellent mechanical and water absorption properties of cryogels, and uniform dispersion of fine AgNPs on the cryogel pore surface for rapid disinfection with minimal Ag release (<100 μg L(-1)). They were used in a process that employed their ability to absorb water, which subsequently could be released via application of mild pressure. Their antibacterial performance was evaluated based on the disinfection efficacies of E. coli and B. subtilis . The PSA/Ag cryogels had excellent disinfection efficacies showing close to a 3 log reduction of viable bacteria after a brief 15 s contact time. They were highly reusable as there was no significant difference in the disinfection efficacies over five cycles of operation. The biocidal action of the PSA/Ag cryogels is believed to be dominated by surface-controlled mechanisms that are dependent on direct contact of the interface of PSA/Ag cryogels with the bacterial cells. The PSA/Ag cryogels are thought to offer a simpler approach for drinking water disinfection in disaster relief applications.

Template-free synthesis of porous ZnO/Ag microspheres as recyclable and ultra-sensitive SERS substrates

NASA Astrophysics Data System (ADS)

Liu, Yanjun; Xu, Chunxiang; Lu, Junfeng; Zhu, Zhu; Zhu, Qiuxiang; Manohari, A. Gowri; Shi, Zengliang

2018-01-01

The porous structured zinc oxide (ZnO) microspheres decorated with silver nanoparticles (Ag NPs) have been fabricated as surface-enhanced Raman scattering (SERS) substrate for ultra-sensitive, highly reproducible and stable biological/chemical sensing of various organic molecules. The ZnO microspheres were hydrothermally synthesized without any template, and the Ag NPs decorated on microspheres via photochemical reaction in situ, which provided stable Ag/ZnO contact to achieve a sensitive SERS response. It demonstrates a higher enhancement factor (EF) of 2.44 × 1011 and a lower detection limit of 10-11 M-10-12 M. This porous SERS substrate could also be self-cleaned through a photocatalytic process and then further recycled for the detection of same or different molecules, such as phenol red (PhR), dopamine (DA) and glucose (GLU) with ultra-low concentration and it possessed a sensitive response. The excellent performances are attributed to morphology of porous microspheres, hybrid structure of semiconductor/metal and corresponding localized field enhancement of surface plasmons. Therefore, it is expected to design the recyclable ultra-sensitive SERS sensors for the detection of biological molecules and organic pollutant monitoring.

MoS2 quantum dots decorated g-C3N4/Ag heterostructures for enhanced visible light photocatalytic activity

NASA Astrophysics Data System (ADS)

Fu, Yanhui; Liang, Wei; Guo, Jinqiu; Tang, Hua; Liu, Shuaishuai

2018-02-01

A novel MoS2 quantum dots (QDs) decorated g-C3N4/Ag heterostructured photocatalyst has been synthesized via a two-step method including in situ microemulsion-assisted reduction and wetness impregnation method. The obtained heterostructure photocatalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS) and photoluminescence spectrosxopy (PL). The photocatalytic activity was evaluated by the degradation of methyl orange (MO) under visible-light irradiation. The MoS2 QDs decorated hybrid photocatalysts exhibited significantly enhanced photocatalytic performance. The concentration of Ag and MoS2 QDs showing the optimal photocatalytic performance was determined to be 10% and 0.3% respectively, which exceeded the photocatalytic performance of pure g-C3N4 by more than 4.7 times. Recycling experiments confirmed that the hybrid catalysts had superior cycle performance and stability. The enhanced photocatalytic activity of MoS2 QDs decorated g-C3N4/Ag hybrid photocatalysts can be mainly ascribed to enhanced visible-light absorption, the efficient separation of photogenerated charge carriers and the stronger oxidation and reduction ability through a Z-scheme system composed of g-C3N4, Ag and MoS2 QDs, in which Ag nanoparticles act as the charge separation center. The evidence of the Z-scheme photocatalytic mechanism of the composite photocatalysts was obtained from the active species trapping experiments.

Electrical response from nanocomposite PDMS-Ag NPs generated by in situ laser ablation in solution

NASA Astrophysics Data System (ADS)

Kalyva, Maria; Kumar, Susmit; Brescia, Rosaria; Petroni, Simona; La Tegola, Carola; Bertoni, Giovanni; De Vittorio, Massimo; Cingolani, Roberto; Athanassiou, Athanassia

2013-01-01

Laser ablation technique is employed in order to generate polydimethylsiloxane (PDMS)/Ag NPs in situ, starting from a silver target in a solution of PDMS prepolymer and toluene. The produced surfactant-free nanoparticles are characterized by high resolution transmission electron microscopy (HRTEM) and scanning TEM-high angle annular dark field (STEM-HAADF) imaging modes, showing the majority of them to be of the order of 4 nm in diameter with a small percentage of larger Ag-AgCl multidomain NPs, embedded into a PDMS matrix. Low concentrations of carbon onion-like nanoparticles or larger fibers are also formed in the toluene-PDMS prepolymer solution. In accordance with this, UV-vis spectra shows no peak from silver NPs; their small size and their coverage by the PDMS matrix suppresses the signal of surface plasmon absorption. Inductively coupled plasma measurements reveal that the concentration of silver in the polymer is characteristically low, ˜0.001% by weight. The electrical properties of the PDMS nanocomposite films are modified, with current versus voltage (I-V) measurements showing a low current of up to a few tenths of a pA at 5 V. The surface resistivity of the films is found to be up to ˜1010 Ω/sq. Under pressure (e.g. stress) applied by a dynamic mechanical analyzer (DMA), the I-V measurements demonstrate the current decreasing during the elastic deformation, and increasing during the plastic deformation.

Role of Au(NPs) in the enhanced response of Au(NPs)-decorated MWCNT electrochemical biosensor

PubMed Central

Mehmood, Shahid; Ciancio, Regina; Carlino, Elvio; Bhatti, Arshad S

2018-01-01

Background The combination of Au-metallic-NPs and CNTs are a new class of hybrid nanomaterials for the development of electrochemical biosensor. Concentration of Au(nanoparticles [NPs]) in the electrochemical biosensor is crucial for the efficient charge transfer between the Au-NPs-MWCNTs modified electrode and electrolytic solution. Methods In this work, the charge transfer kinetics in the glassy carbon electrode (GCE) modified with Au(NPs)–multiwalled carbon nanotube (MWCNT) nanohybrid with varied concentrations of Au(NPs) in the range 40–100 nM was studied using electrochemical impedance spectroscopy (EIS). Field emission scanning electron microscopy and transmission electron microscopy confirmed the attachment of Au(NPs) on the surface of MWCNTs. Results The cyclic voltammetry and EIS results showed that the charge transfer mechanism was diffusion controlled and the rate of charge transfer was dependent on the concentration of Au(NPs) in the nanohybrid. The formation of spherical diffusion zone, which was dependent on the concentration of Au(NPs) in nanohybrids, was attributed to result in 3 times the increase in the charge transfer rate ks, 5 times increase in mass transfer, and 5% (9%) increase in Ipa (Ipc) observed in cyclic voltammetry in 80 nM Au(NP) nanohybrid-modified GCE from MWCNT-modified GCE. The work was extended to probe the effect of charge transfer rates at various concentrations of Au(NPs) in the nanohybrid-modified electrodes in the presence of Escherichia coli. The cyclic voltammetry results clearly showed the best results for 80 nM Au(NPs) in nanohybrid electrode. Conclusion The present study suggested that the formation of spherical diffusion zone in nanohybrid-modified electrodes is critical for the enhanced electrochemical biosensing applications. PMID:29713161

Ag nanoparticles-decorated ZnO nanorod array on a mechanical flexible substrate with enhanced optical and antimicrobial properties

NASA Astrophysics Data System (ADS)

Chen, Yi; Tse, Wai Hei; Chen, Longyan; Zhang, Jin

2015-03-01

Heteronanostructured zinc oxide nanorod (ZnO NR) array are vertically grown on polydimethylsiloxane (PDMS) through a hydrothermal method followed by an in situ deposition of silver nanoparticles (Ag NPs) through a photoreduction process. The Ag-ZnO heterostructured nanorods on PDMS are measured with an average diameter of 160 nm and an average length of 2 μm. ZnO NRs measured by high-resolution transmission electron microscope (HRTEM) shows highly crystalline with a lattice fringe of 0.255 nm, which corresponds to the (0002) planes in ZnO crystal lattice. The average diameter of the Ag NPs in situ deposited on the ZnO NRs is estimated at 22 ± 2 nm. As compared to the bare ZnO NRs, the heterostructured Ag-ZnO nanorod array shows enhanced ultraviolet (UV) absorption at 440 nm, and significant emission in the visible region (λem = 542 nm). In addition, the antimicrobial efficiency of Ag-ZnO heterostructured nanorod array shows obvious improvement as compared to bare ZnO nanorod array. The cytotoxicity of ZnO nanorod array with and without Ag NPs was studied by using 3 T3 mouse fibroblast cell line. No significant toxic effect is imposed on the cells.

Ag nanoparticles-decorated ZnO nanorod array on a mechanical flexible substrate with enhanced optical and antimicrobial properties.

PubMed

Chen, Yi; Tse, Wai Hei; Chen, Longyan; Zhang, Jin

2015-01-01

Heteronanostructured zinc oxide nanorod (ZnO NR) array are vertically grown on polydimethylsiloxane (PDMS) through a hydrothermal method followed by an in situ deposition of silver nanoparticles (Ag NPs) through a photoreduction process. The Ag-ZnO heterostructured nanorods on PDMS are measured with an average diameter of 160 nm and an average length of 2 μm. ZnO NRs measured by high-resolution transmission electron microscope (HRTEM) shows highly crystalline with a lattice fringe of 0.255 nm, which corresponds to the (0002) planes in ZnO crystal lattice. The average diameter of the Ag NPs in situ deposited on the ZnO NRs is estimated at 22 ± 2 nm. As compared to the bare ZnO NRs, the heterostructured Ag-ZnO nanorod array shows enhanced ultraviolet (UV) absorption at 440 nm, and significant emission in the visible region (λem = 542 nm). In addition, the antimicrobial efficiency of Ag-ZnO heterostructured nanorod array shows obvious improvement as compared to bare ZnO nanorod array. The cytotoxicity of ZnO nanorod array with and without Ag NPs was studied by using 3 T3 mouse fibroblast cell line. No significant toxic effect is imposed on the cells.

Antimicrobial kinetics of Alstonia scholaris bark extract-mediated AgNPs

NASA Astrophysics Data System (ADS)

Supraja, N.; Prasad, T. N. V. K. V.; David, E.; Giridhara Krishna, T.

2016-06-01

Nanobiotechnology is considered as one of the important branches of nanotechnology, and research on synthesis of nanoscale materials, silver in particular, using plant and plant parts has been progressing rapidly. Herein, we used bark extract of Alstonia scholaris one of the most important medicinal plants to synthesize silver nanoparticles (AgNPs) which exhibited excellent antimicrobial properties against biofilm formed in drinking water PVC pipes. The biosynthesis of silver nanoparticles was done by treating 90 mL of 1 mM AgNO3 aqueous solution with 10 mL of 5 % bark extract. As-prepared silver nanoparticles were characterized using the biophysical techniques such as UV-Vis spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, transmission electron microscopy, and dynamic light scattering for the measurement of hydrodynamic diameter and zeta potential. The kinetics of the antimicrobial activity against PVC biofilm of prepared silver nanoparticles were done using comparative solution suspension time-killing assessments and which are evidenced in Epi-fluorescent microscopic observations.

Ambipolar transport of silver nanoparticles decorated graphene oxide field effect transistors

NASA Astrophysics Data System (ADS)

Sarkar, Kalyan Jyoti; Sarkar, K.; Pal, B.; Kumar, Aparabal; Das, Anish; Banerji, P.

2018-05-01

In this article, we report ambipolar field effect transistor (FET) by using graphene oxide (GO) as a gate dielectric material for silver nanoparticles (AgNPs) decorated GO channel layer. GO was synthesized by Hummers' method. The AgNPs were prepared via photochemical reduction of silver nitrate solution by using monoethanolamine as a reducing agent. Morphological properties of channel layer were characterized by Field Effect Scanning Electron Microscopy (FESEM). Fourier Transform Infrared Spectroscopy (FTIR) was carried out to characterize GO thin film. For device fabrication gold (Au) was deposited as source-drain contact and aluminum (Al) was taken as bottom contact. Electrical measurements were performed by back gate configuration. Ambipolar transport behavior was explained from transfer characteristics. A maximum electron mobiliy of 6.65 cm2/Vs and a hole mobility of 2.46 cm2/Vs were extracted from the transfer characteristics. These results suggest that GO is a potential candidate as a gate dielectric material for thin film transistor applications and also provides new insights in GO based research.

Aggregation-based colorimetric sensor for determination of prothioconazole fungicide using colloidal silver nanoparticles (AgNPs)

NASA Astrophysics Data System (ADS)

Ivrigh, Zahra Jafar-Nezhad; Fahimi-Kashani, Nafiseh; Hormozi-Nezhad, M. Reza

2017-12-01

There is a growing interest in developing high-performance sensors monitoring fungicides, due to their broadly usage and their adverse effects on humans and wildlife. In the present study, a colorimetric probe has been proposed for detection of prothioconazole based on aggregation of unmodified silver nanoparticles (AgNPs). Under optimized condition, linear relationships between the concentration of prothioconazole and the absorbance ratio of A500/A395 were found over the range of 0.01 μg·mL- 1 to 0.4 μg·mL- 1 with quantification limit as low as 1.7 ng·mL- 1. Furthermore, AgNPs color change from yellow to pink-orange in presence of prothioconazole, indicates highly sensitive naked-eye colorimetric assay for quantifying prothioconazole in real applications. The proposed approach was successfully used for the determination of prothioconazole in wheat flour and paddy water sample.

Nanoparticle-density-dependent field emission of surface-decorated SiC nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Qizheng; School of Materials and Chemical Engineering, Ningbo University of Technology, Ningbo City 315016; State Key Lab of New Fine Ceramics and Fine Processing, Tsinghua University, Beijing City 100084

2016-08-22

Increasing the electron emission site density of nanostructured emitters with limited field screening effects is one of the key issues for improving the field emission (FE) properties. In this work, we reported the Au-nanoparticles-density-dependent field emission behaviors of surface-decorated SiC nanowires. The Au nanoparticles (AuNPs) decorated around the surface of the SiC nanowires were achieved via an ion sputtering technique, by which the densities of the isolated AuNPs could be adjusted by controlling the fixed sputtering times. The measured FE characteristics demonstrated that the turn-on fields of the SiC nanowires were tuned to be of 2.06, 1.14, and 3.35 V/μm withmore » the increase of the decorated AuNPs densities, suggesting that a suitable decorated AuNPs density could render the SiC nanowires with totally excellent FE performances by increasing the emission sites and limiting the field screening effects.« less

Red light emitting nano-PVP fibers that hybrid with Ag@SiO2@Eu(tta)3phen-NPs by electrostatic spinning method

NASA Astrophysics Data System (ADS)

Zhang, Xiaolin; Tang, Jianguo; Li, Haidong; Wang, Yao; Wang, Xinzhi; Wang, Yanxin; Huang, Linjun; Belfiore, Laurence A.

2018-04-01

This work demonstrated red light emitting nano-PVP fibers that incorporated with novel three-layer nanostructure of Ag@SiO2@Eu(tta)3phen nanoparticles (Ag@SiO2@Eu(tta)3phen-NPs), and the hybrid nano-PVP fibers were fabricated via a remarkably simple electrostatic spinning method. For Ag@SiO2@Eu(tta)3phen-NPs, the thickness of SiO2 is optimized to obtain the maximum luminescent intensity, as results, the optimized thickness of SiO2 is 20 nm. And the corresponding luminescent intensity (612 nm) of the Ag@SiO2@Eu(tta)3phen-NPs is enhanced up to 10 times compared with the pure Eu(tta)3phen complex, which indicates that with 20 nm SiO2 thickness, the localized surface plasmon resonance (LSPR) effect of Ag@SiO2 exhibits highest performance for enhancing luminescence. Moreover, the luminescent PVP fibers emit bright red light under the fluorescence microscope, which definitely confirms that the microenvironment provided by PVP polymer is absolutely suitable for the fluorescent composites.

Pathway and mechanism of nitrogen transformation during composting: Functional enzymes and genes under different concentrations of PVP-AgNPs.

PubMed

Zeng, Guangming; Zhang, Lihua; Dong, Haoran; Chen, Yaoning; Zhang, Jiachao; Zhu, Yuan; Yuan, Yujie; Xie, Yankai; Fang, Wei

2018-04-01

Polyvinylpyrrolidone coated silver nanoparticles (PVP-AgNPs) were applied at different concentrations to reduce total nitrogen (TN) losses and the mechanisms of nitrogen bio-transformation were investigated in terms of the nitrogen functional enzymes and genes. Results showed that mineral N in pile 3 which was treated with AgNPs at a concentration of 10 mg/kg compost was the highest (6.58 g/kg dry weight (DW) compost) and the TN loss (47.07%) was the lowest at the end of composting. Correlation analysis indicated that TN loss was significantly correlated with amoA abundance. High throughput sequencing showed that the dominant family of ammonia-oxidizing bacteria (AOB) was Nitrosomonadaceae, and the number of Operational Taxonomic Units (OTUs) reduced after the beginning of composting when compared with day 1. In summary, treatment with AgNPs at a concentration of 10 mg/kg compost was considerable to reduce TN losses and reserve more mineral N during composting. Copyright © 2017 Elsevier Ltd. All rights reserved.

Antibacterial properties of amino acid functionalized silver nanoparticles decorated on graphene oxide sheets

NASA Astrophysics Data System (ADS)

Chandraker, Kumudini; Nagwanshi, Rekha; Jadhav, S. K.; Ghosh, Kallol K.; Satnami, Manmohan L.

2017-06-01

Graphene oxide (GO) sheets decorated with amino acid L-cysteine (L-cys) functionalized silver nanoparticles (GO-L-cys-Ag) was synthesized by AgNO3, trisodium citrate, and NaBH4. GO-L-cys-Ag nanocomposite was characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectra, ultraviolet-visible (UV-vis) absorption spectra, which demonstrated that a diameter of L-cys-AgNPs compactly deposited on GO. Antibacterial activity tests of GO-L-cys-Ag nanocomposite were carried out using Escherichia coli MTCC 1687 and Staphylococcus aureus MTCC 3160 as model strains of Gram-negative and Gram-positive bacteria, respectively. The effect of bactericide dosage on antibacterial activity of GO-L-cys-Ag nanocomposite was examined by plate count, well diffusion and broth dilution methods. Morphological observation of bacterial cells by scanning electron microscope (SEM) showed that GO-L-cys-Ag nanocomposite was more destructive to cell membrane of Escherichia coli than that of Staphylococcus aureus. The above technique establish that the bactericidal property of GO-L-cys-Ag nanocomposite with wide range of applications in biomedical science.

Comparative effects on rat primary astrocytes and C6 rat glioma cells cultures after 24-h exposure to silver nanoparticles (AgNPs)

NASA Astrophysics Data System (ADS)

Salazar-García, Samuel; Silva-Ramírez, Ana Sonia; Ramirez-Lee, Manuel A.; Rosas-Hernandez, Hector; Rangel-López, Edgar; Castillo, Claudia G.; Santamaría, Abel; Martinez-Castañon, Gabriel A.; Gonzalez, Carmen

2015-11-01

The aim of this work was to compare the effects of 24-h exposure of rat primary astrocytes and C6 rat glioma cells to 7.8 nm AgNPs. Glioblastoma multiforme (GBM) is the most aggressive primary brain tumor and current treatments lead to diverse side-effects; for this reason, it is imperative to investigate new approaches, including those alternatives provided by nanotechnology, like nanomaterials (NMs) such as silver nanoparticles. Herein, we found that C6 rat glioma cells, but no primary astrocytes, decreased cell viability after AgNPs treatment; however, both cell types diminished their proliferation. The decrease of glioma C6 cells proliferation was related with necrosis, while in primary astrocytes, the decreased proliferation was associated with the induction of apoptosis. The ionic control (AgNO3) exerted a different profile than AgNPs; the bulk form did not modify the basal effect in each determination, whereas cisplatin, a well-known antitumoral drug used as a comparative control, promoted cytotoxicity in both cell types at specific concentrations. Our findings prompt the need to determine the fine molecular and cellular mechanisms involved in the differential biological responses to AgNPs in order to develop new tools or alternatives based on nanotechnology that may contribute to the understanding, impact and use of NMs in specific targets, like glioblastoma cells.

Structural and biological evaluation of a multifunctional SWCNT-AgNPs-DNA/PVA bio-nanofilm.

PubMed

Subbiah, Ramesh P; Lee, Haisung; Veerapandian, Murugan; Sadhasivam, Sathya; Seo, Soo-Won; Yun, Kyusik

2011-04-01

A bio-nanofilm consisting of a tetrad nanomaterial (nanotubes, nanoparticles, DNA, polymer) was fabricated utilizing in situ reduction and noncovalent interactions and it displayed effective antibacterial activity and biocompatibility. This bio-nanofilm was composed of homogenous silver nanoparticles (AgNPs) coated on single-walled carbon nanotubes (SWCNTs), which were later hybridized with DNA and stabilized in poly(vinyl alcohol) (PVA) in the presence of a surfactant with the aid of ultrasonication. Electron microscopy and bio-AFM (atomic force microscopy) images were used to assess the morphology of the nanocomposite (NC) structure. Functionalization and fabrication were examined using FT-Raman spectroscopy by analyzing the functional changes in the bio-nanofilm before and after fabrication. UV-visible spectroscopy and X-ray powder diffraction (XRD) confirmed that AgNPs were present in the final NC on the basis of its surface plasmon resonance (370 nm) and crystal planes. Thermal gravimetric analysis was used to measure the percentage weight loss of SWCNT (17.5%) and final SWCNT-AgNPs-DNA/PVA (47.7%). The antimicrobial efficiency of the bio-nanofilm was evaluated against major pathogenic organisms. Bactericidal ratios, zone of inhibition, and minimum inhibitory concentration were examined against gram positive and gram negative bacteria. A preliminary cytotoxicity analysis was conducted using A549 lung cancer cells and IMR-90 fibroblast cells. Confocal laser microscopy, bio-AFM, and field emission scanning electron microscopy (FE-SEM) images demonstrated that the NCs were successfully taken up by the cells. These combined results indicate that this bio-nanofilm was biocompatible and displayed antimicrobial activity. Thus, this novel bio-nanofilm holds great promise for use as a multifunctional tool in burn therapy, tissue engineering, and other biomedical applications.

Synthesis of novel benzodioxane midst piperazine moiety decorated chitosan silver nanoparticle against biohazard pathogens and as potential anti-inflammatory candidate: A molecular docking studies.

PubMed

Karthik, C S; Manukumar, H M; Ananda, A P; Nagashree, S; Rakesh, K P; Mallesha, L; Qin, Hua-Li; Umesha, S; Mallu, P; Krishnamurthy, N B

2018-03-01

Nanoparticles (NPs) are currently being investigated along with the use of biodegradable polymer containing active agents in many areas of medicine for targeted applications. The present study was aimed to synthesize novel compound Benzodioxane midst piperazine (BP) and characterization of a BP decorated chitosan silver nanoparticles (BP*C@AgNPs) and shown effective against hazardous pathogens, and also having anti-inflammatory property. It was further evaluated for molecular docking proofs, and toxicity. The BP*C@AgNPs had spherical shape with size of 36.6nm with wide biocidal activity against hazardous Gram-positive and Gram-negative bacteria with excellent inhibition at 100μg/mL for S. aureus (10.08±0.05mm ZOI), and E. coli (10.03±0.04mm ZOI) compared to antibiotic Streptomycin. The anti-inflammatory activity exhibited IC 50 value of 71.61±1.05μg/mL for BP*C@AgNPs compared to indomethacin (IC 50 =40.15±1.21μg/mL). Also, the docking study of BP showed excellent score for COX1 and DNA gyrase. This in silico study confirmed the achieved efficacy of BP, with less toxicity against normal PMBCs in vitro and in vivo studies. This study concludes that, the novel synthesized BP*C@AgNPs had excellent biocidal property and as anti-inflammatory candidate revealed by docking studies, it confirms BP*C@AgNPs for first-class therapeutic applications in the area of medicinal nanotechnology for the coming days. Copyright © 2017 Elsevier B.V. All rights reserved.

Piezoresistive Sensor with High Elasticity Based on 3D Hybrid Network of Sponge@CNTs@Ag NPs.

PubMed

Zhang, Hui; Liu, Nishuang; Shi, Yuling; Liu, Weijie; Yue, Yang; Wang, Siliang; Ma, Yanan; Wen, Li; Li, Luying; Long, Fei; Zou, Zhengguang; Gao, Yihua

2016-08-31

Pressure sensors with high elasticity are in great demand for the realization of intelligent sensing, but there is a need to develope a simple, inexpensive, and scalable method for the manufacture of the sensors. Here, we reported an efficient, simple, facile, and repeatable "dipping and coating" process to manufacture a piezoresistive sensor with high elasticity, based on homogeneous 3D hybrid network of carbon nanotubes@silver nanoparticles (CNTs@Ag NPs) anchored on a skeleton sponge. Highly elastic, sensitive, and wearable sensors are obtained using the porous structure of sponge and the synergy effect of CNTs/Ag NPs. Our sensor was also tested for over 2000 compression-release cycles, exhibiting excellent elasticity and cycling stability. Sensors with high performance and a simple fabrication process are promising devices for commercial production in various electronic devices, for example, sport performance monitoring and man-machine interfaces.

Selective hydrodechlorination of 1,2-dichloroethane catalyzed by trace Pd decorated Ag/Al2O3 catalysts prepared by galvanic replacement

NASA Astrophysics Data System (ADS)

Sun, Jingya; Han, Yuxiang; Fu, Heyun; Wan, Haiqin; Xu, Zhaoyi; Zheng, Shourong

2018-01-01

Ag catalysts decorated by trace Pd supported on γ-Al2O3 with different structure and chemical properties were prepared using a combined impregnation and galvanic replacement method. For comparison, monometallic Ag/γ-Al2O3 and Pd/γ-Al2O3 catalysts were prepared using the impregnation method. Gas-phase catalytic hydrodechlorination of 1,2-dichloroethane to ethylene was investigated on those catalysts. The structures and chemical compositions of bimetallic Pd-Ag particles in the catalysts were controlled by adjusting Pd replacement amount. The as-prepared catalysts were characterized by X-ray diffraction, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and in-situ FTIR spectroscopy of CO adsorption. The results demonstrated that contiguous Pd sites dominated in the monometallic Pd/γ-Al2O3 catalyst, while Pd atoms were separately decorated on the surface of Ag particles in the bimetallic Pd-Ag/γ-Al2O3 catalysts when Pd replacement amount was below 0.30 wt.%. At Pd replacement amount of 0.30 wt.%, Pd ensembles with contiguous Pd sites developed in the bimetallic catalyst. Thus, monometallic Pd/γ-Al2O3 catalyst displayed negligible ethylene selectivity toward the catalytic hydrodechlorination of 1,2-dichloroethane, while bimetallic Pd-Ag/γ-Al2O3 catalyst with a Pd replacement amount of 0.13 wt.% exhibited 94.6% of ethylene selectivity. Furthermore, selectivity to incompletely dechlorinated byproduct chloroethylene decreased with Pd replacement amount, due to the enhanced decoration effect of Pd on large Ag ensembles. Findings in this work provide a promising bimetallic catalyst prepared by galvanic replacement for the selective catalytic hydrodechlorination of 1,2-dichloroethane.

Preparation of Hierarchical Porous Silicalite-1 Encapsulated Ag NPs and Its Catalytic Performance for 4-Nitrophenol Reduction

NASA Astrophysics Data System (ADS)

Wang, Bin; Wang, Haojiang; Zhang, Fengwei; Sun, Tijian

2018-06-01

A facile and efficient strategy is presented for the encapsulation of Ag NPs within hierarchical porous silicalite-1. The physicochemical properties of the resultant catalyst are characterized by TEM, XRD, FTIR, and N2 adsorption-desorption analytical techniques. It turns out that the Ag NPs are well distributed in MFI zeolite framework, which possesses hierarchical porous characteristics (1.75, 3.96 nm), and the specific surface area is as high as 243 m2 · g-1. More importantly, such catalyst can rapidly transform the 4-nitrophenol to 4-aminophenol in aqueous solution at room temperature, and a quantitative conversion is also obtained after being reused 10 times. The reasons can be attributed to the fast mass transfer, large surface area, and spatial confinement effect of the advanced support.

Lanthanum doped titania decorated with silver plasmonic nanoparticles with enhanced photocatalytic activity under UV-visible light

NASA Astrophysics Data System (ADS)

Dal'Toé, Adrieli T. O.; Colpani, Gustavo Lopes; Padoin, Natan; Fiori, Márcio Antônio; Soares, Cíntia

2018-05-01

Lanthanum doped titanium dioxide decorated with silver plasmonic nanoparticles (Ag-La/TiO2 NPs) materials were prepared using a simple ultrasound-assisted wet impregnation method followed by silver photodeposition. The obtained photocatalysts with different Ag contents were characterized by XRD, FE-SEM, EDX, TEM, BET, XPS, DRS and PL techniques. Moreover, the size distribution of the nanoparticles aggregates was assessed. The characterization analysis revealed that La doping slightly changed the crystalline phase of TiO2, increased the amount of surface hydroxyl groups and interacted with TiO2 nanoparticles via Ti-O-La bond, while Ag photodeposition enhanced the absorption of visible light due to the effects of localized surface plamon resonance and significantly decreased electronic recombination rate by the Schottky junction. Furthermore, the combination of Ag-La induced the formation of oxygen vacancies, which increased the amount of adsorbed surface hydroxyl groups in Ag-La/TiO2. In addition, Ag-La possibly decreased the semiconductor surface energy, which acted positively in the reduction of NPs aggregation. These features along with better textural properties (greater surface areas) played a fundamental role in the enhancement of the photocatalytic activity of Ag-La/TiO2 composites for the decolorization of methylene blue under UV-visible irradiation compared to the mono-metallic (La/TiO2 and Ag/TiO2) modified photocatalysts. Finally, a mechanism for the transfer of charge carriers in Ag-La/TiO2 photocatalyst under UV-visible irradiation was proposed.

Superhydrophobic Ag decorated ZnO nanostructured thin film as effective surface enhanced Raman scattering substrates

NASA Astrophysics Data System (ADS)

Jayram, Naidu Dhanpal; Sonia, S.; Poongodi, S.; Kumar, P. Suresh; Masuda, Yoshitake; Mangalaraj, D.; Ponpandian, N.; Viswanathan, C.

2015-11-01

The present work is an attempt to overcome the challenges in the fabrication of super hydrophobic silver decorated zinc oxide (ZnO) nanostructure thin films via thermal evaporation process. The ZnO nanowire thin films are prepared without any surface modification and show super hydrophobic nature with a contact angle of 163°. Silver is further deposited onto the ZnO nanowire to obtain nanoworm morphology. Silver decorated ZnO (Ag@ZnO) thin films are used as substrates for surface enhanced Raman spectroscopy (SERS) studies. The formation of randomly arranged nanowire and silver decorated nanoworm structure is confirmed using FESEM, HR-TEM and AFM analysis. Crystallinity and existence of Ag on ZnO are confirmed using XRD and XPS studies. A detailed growth mechanism is discussed for the formation of the nanowires from nanobeads based on various deposition times. The prepared SERS substrate reveals a reproducible enhancement of 3.082 × 107 M for Rhodamine 6G dye (R6G) for 10-10 molar concentration per liter. A higher order of SERS spectra is obtained for a contact angle of 155°. Thus the obtained thin films show the superhydrophobic nature with a highly enhanced Raman spectrum and act as SERS substrates. The present nanoworm morphology shows a new pathway for the construction of semiconductor thin films for plasmonic studies and challenges the orderly arranged ZnO nanorods, wires and other nano structure substrates used in SERS studies.

Low-dose AgNPs reduce lung mechanical function and innate immune defense in the absence of cellular toxicity.

PubMed

Botelho, Danielle J; Leo, Bey Fen; Massa, Christopher B; Sarkar, Srijata; Tetley, Terry D; Chung, Kian Fan; Chen, Shu; Ryan, Mary P; Porter, Alexandra E; Zhang, Junfeng; Schwander, Stephan K; Gow, Andrew J

2016-01-01

Multiple studies have examined the direct cellular toxicity of silver nanoparticles (AgNPs). However, the lung is a complex biological system with multiple cell types and a lipid-rich surface fluid; therefore, organ level responses may not depend on direct cellular toxicity. We hypothesized that interaction with the lung lining is a critical determinant of organ level responses. Here, we have examined the effects of low dose intratracheal instillation of AgNPs (0.05 μg/g body weight) 20 and 110 nm diameter in size, and functionalized with citrate or polyvinylpyrrolidone. Both size and functionalization were significant factors in particle aggregation and lipid interaction in vitro. One day post-intratracheal instillation lung function was assessed, and bronchoalveolar lavage (BAL) and lung tissue collected. There were no signs of overt inflammation. There was no change in surfactant protein-B content in the BAL but there was loss of surfactant protein-D with polyvinylpyrrolidone (PVP)-stabilized particles. Mechanical impedance data demonstrated a significant increase in pulmonary elastance as compared to control, greatest with 110 nm PVP-stabilized particles. Seven days post-instillation of PVP-stabilized particles increased BAL cell counts, and reduced lung function was observed. These changes resolved by 21 days. Hence, AgNP-mediated alterations in the lung lining and mechanical function resolve by 21 days. Larger particles and PVP stabilization produce the largest disruptions. These studies demonstrate that low dose AgNPs elicit deficits in both mechanical and innate immune defense function, suggesting that organ level toxicity should be considered.

Simultaneous and sensitive determination of ascorbic acid, dopamine, uric acid, and tryptophan with silver nanoparticles-decorated reduced graphene oxide modified electrode.

PubMed

Kaur, Balwinder; Pandiyan, Thangarasu; Satpati, Biswarup; Srivastava, Rajendra

2013-11-01

In this paper, we report the synthesis of silver nanoparticle-decorated reduced graphene oxide composite (AgNPs/rGO) by heating the mixture of graphene oxide and silver nitrate aqueous solution in the presence of sodium hydroxide. This material was characterized by means of X-ray diffraction, UV-vis spectroscopy, and transmission electron microscopy. AgNPs/rGO based electrochemical sensor was fabricated for the simultaneous determination of ascorbic acid, dopamine, uric acid, and tryptophan. Electrochemical studies were carried out by using cyclic voltammetry, linear sweep voltammetry, and chronoamperometry. AgNPs/rGO modified electrode exhibited excellent electrocatalytic activity, stability, sensitivity, and selectivity with well-separated oxidation peaks toward ascorbic acid, dopamine, uric acid, and tryptophan in the simultaneous determination of their quaternary mixture. The analytical performance of this material as a chemical sensor was demonstrated for the determination of ascorbic acid and dopamine in commercial pharmaceutical samples such as vitamin C tablets and dopamine injections, respectively. The applicability of this sensor was also extended in the determination of uric acid in human urine samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Ag-NPs embedded in two novel Zn3/Zn5-cluster-based metal-organic frameworks for catalytic reduction of 2/3/4-nitrophenol.

PubMed

Wu, Xue-Qian; Huang, Dan-Dan; Zhou, Zhi-Hang; Dong, Wen-Wen; Wu, Ya-Pan; Zhao, Jun; Li, Dong-Sheng; Zhang, Qichun; Bu, Xianhui

2017-02-21

By utilizing symmetrical pentacarboxylate ligands, 3,5-di(2',5'-dicarboxylphenyl)benzoic acid (H 5 L1) and 3,5-di(2',4'-dicarboxylphenyl)benzoic acid (H 5 L2), two novel porous Zn-MOFs, [Zn 5 (μ 3 -H 2 O) 2 (L1) 2 ]·3DMA·4H 2 O (CTGU-3) and [Zn 3 (μ 3 -OH)L2(H 2 O) 3 ]·H 2 O (CTGU-4) have been synthesized under solvothermal conditions. CTGU-3 and CTGU-4 exhibit 3D microporous frameworks with flu and dia topologies and possess unique secondary building units [Zn 5 (μ 3 -H 2 O) 2 (RCO 2 ) 6 ] and [Zn 3 (μ 3 -OH)(RCO 2 ) 3 ], respectively. Such porous systems create a unique space or surface to accommodate Ag nanoparticles (Ag NPs), which could efficiently prevent Ag NPs from aggregation and leaching. In this work, two new Ag@Zn-MOF composites, denoted as Ag@CTGU, have been successfully fabricated through solution infiltration, for the reduction of nitrophenol. Compared with CTGU-4, CTGU-3 shows enhanced catalytic efficiency toward the reaction when it is used as a catalyst support of Ag NPs. Moreover, gas sorption and luminescence properties of two compounds were also investigated.

Magnesium nanoparticles with transition metal decoration for hydrogen storage

NASA Astrophysics Data System (ADS)

Pasquini, Luca; Callini, Elsa; Brighi, Matteo; Boscherini, Federico; Montone, Amelia; Jensen, Torben R.; Maurizio, Chiara; Vittori Antisari, Marco; Bonetti, Ennio

2011-11-01

We report on the hydrogen storage behaviour of Mg nanoparticles (NPs) (size range 100 nm-1 μm) with metal-oxide core-shell morphology synthesized by inert gas condensation and decorated by transition metal (TM) (Pd or Ti) clusters via in situ vacuum deposition. The structure and morphology of the as-prepared and hydrogenated NPs is studied by electron microscopy, X-ray diffraction including in situ experiments and X-ray absorption spectroscopy, in order to investigate the relationships with the hydrogen storage kinetics measured by the volumetric Sieverts method. With both Pd and Ti, the decoration deeply improves the hydrogen sorption properties: previously inert NPs exhibit complete hydrogenation with fast transformation kinetics, good stability and reversible gravimetric capacity that can attain 6 wt%. In the case of Pd-decoration, the occurrence of Mg-Pd alloying is observed at high temperatures and in dependence of the hydrogen pressure conditions. These structural transformations modify both the kinetics and thermodynamics of hydride formation, while Ti-decoration has an effect only on the kinetics. The experimental results are discussed in relation with key issues such as the amount of decoration, the heat of mixing between TM and Mg and the binding energy between TM and hydrogen.

Spherical LDH-Ag°-montmorillonite heterocoagulated system with a pH-dependent sol-gel structure for controlled accessibility of AgNPs immobilized on the clay lamellae.

PubMed

Deák, Ágota; Janovák, László; Tallósy, Szabolcs Péter; Bitó, Tamás; Sebők, Dániel; Buzás, Norbert; Pálinkó, István; Dékány, Imre

2015-02-17

Aqueous suspensions of spherical ZnMgAl-layered double hydroxides [LDH(sph)] and antibacterial silver nanoparticles (AgNPs) deposited on the lamellae of montmorillonite were used for the synthesis of composites, which behave like coherent gels at low pH (≲4.5) and incoherent sols at higher pH (≳4.5). The composition of the composite was chosen as LDH(sph)/Ag°-montm. = 25:75 wt % in order to ensure a sol-gel transition that can also be characterized by viscometry. This pH-sensitive heterocoagulated system consisting of oppositely charged colloid particles was suitable for the release of antimicrobial AgNPs immobilized on the clay lamellae via a pH-controlled gel-sol transition. The heterocoagulation process was also characterized by surface charge titration measurements. Spherical LDH/Ag°-montmorillonite composite samples were identified by X-ray diffraction (XRD) measurements. The morphological properties of the composites were studied, and the presence of the heterocoagulated structure was confirmed by scanning electron microscopy (SEM). The nanoscale structure of the LDH(sph)-Ag°-montmorillonite composite obtained was also verified by small-angle X-ray scattering (SAXS), and the rheological characteristics were studied at various pH values. The viscosity and yield value of the composite decreased by an order of magnitude upon increasing the pH from 3.0 to 5.5. The sol-gel transition of the composite suspension was reversible in the previously mentioned pH range.

Autoclave mediated one-pot-one-minute synthesis of AgNPs and Au-Ag nanocomposite from Melia azedarach bark extract with antimicrobial activity against food pathogens.

PubMed

Pani, Alok; Lee, Joong Hee; Yun, Soon-Ii

2016-01-01

The increasing use of nanoparticles and nanocomposite in pharmaceutical and processed food industry have increased the demand for nontoxic and inert metallic nanostructures. Chemical and physical method of synthesis of nanostructures is most popular in industrial production, despite the fact that these methods are labor intensive and/or generate toxic effluents. There has been an increasing demand for rapid, ecofriendly and relatively cheaper synthesis of nanostructures. Here, we propose a strategy, for one-minute green synthesis of AgNPs and a one-pot one-minute green synthesis of Au-Ag nanocomposite, using Melia azedarach bark aqueous extract as reducing agent. The hydrothermal mechanism of the autoclave technology has been successfully used in this study to accelerate the nucleation and growth of nano-crystals. The study also presents high antimicrobial potential of the synthesized nano solutions against common food and water born pathogens. The multistep characterization and analysis of the synthesized nanomaterial samples, using UV-visible spectroscopy, ICP-MS, FT-IR, EDX, XRD, HR-TEM and FE-SEM, also reveal the reaction dynamics of AgNO3, AuCl3 and plant extract in synthesis of the nanoparticles and nanocomposite. The antimicrobial effectiveness of the synthesized Au-Ag nanocomposite, with high gold to silver ratio, reduces the dependency on the AgNPs, which is considered to be environmentally more toxic than the gold counterpart. We hope that this new strategy will change the present course of green synthesis. The rapidity of synthesis will also help in industrial scale green production of nanostructures using Melia azedarach.

Ammonia-modified graphene sheets decorated with magnetic Fe3O4 nanoparticles for the photocatalytic and photo-Fenton degradation of phenolic compounds under sunlight irradiation.

PubMed

Boruah, Purna K; Sharma, Bhagyasmeeta; Karbhal, Indrapal; Shelke, Manjusha V; Das, Manash R

2017-03-05

Synthesis of easily separable and eco-friendly efficient catalyst with both photocatalytic and photo-Fenton degradation properties is of great importance for environment remediation application. Herein, ammonia-modified graphene (AG) sheets decorated with Fe 3 O 4 nanoparticles (AG/Fe 3 O 4 ) as a magnetically recoverable photocatalyst by a simple in situ solution chemistry approach. First, we have functionalized graphene oxide (GO) sheets by amide functional group and then Fe 3 O 4 nanoparticles (NPs) are doped onto the functionalized GO surface. The AG/Fe 3 O 4 nanocomposite showed efficient photocatalytic activity towards degradation of phenol (92.43%), 2-nitrophenol (2-NP) (98%) and 2-chlorophenol (2-CP) (97.15%) within 70-120min. Consequently, in case of photo-Fenton degradation phenomenon, 93.56% phenol, 98.76% 2-NP and 98.06% of 2-CP degradation were achieved within 50-80min using AG/Fe 3 O 4 nanocomposite under sunlight irradiation. The synergistic effect between amide functionalized graphene and Fe 3 O 4 nanoparticles (NPs) enhances the photocatalytic activity by preventing the recombination rate of electron-hole-pair in Fe 3 O 4 NPs. Furthermore, the remarkable reusability of the AG/Fe 3 O 4 nanocomposite was observed up to ten cycles during the photocatalytic degradation of these phenolic compounds. Copyright © 2016 Elsevier B.V. All rights reserved.

Reducing Strength Prevailing at Root Surface of Plants Promotes Reduction of Ag+ and Generation of Ag0/Ag2O Nanoparticles Exogenously in Aqueous Phase

PubMed Central

Pardha-Saradhi, Peddisetty; Yamal, Gupta; Peddisetty, Tanuj; Sharmila, Peddisetty; Nagar, Shilpi; Singh, Jyoti; Nagarajan, Rajamani; Rao, Kottapalli S.

2014-01-01

Potential of root system of plants from wide range of families to effectively reduce membrane impermeable ferricyanide to ferrocyanide and blue coloured 2,6-dichlorophenol indophenol (DCPIP) to colourless DCPIPH2 both under non-sterile and sterile conditions, revealed prevalence of immense reducing strength at root surface. As generation of silver nanoparticles (NPs) from Ag+ involves reduction, present investigations were carried to evaluate if reducing strength prevailing at surface of root system can be exploited for reduction of Ag+ and exogenous generation of silver-NPs. Root system of intact plants of 16 species from 11 diverse families of angiosperms turned clear colorless AgNO3 solutions, turbid brown. Absorption spectra of these turbid brown solutions showed silver-NPs specific surface plasmon resonance peak. Transmission electron microscope coupled with energy dispersive X-ray confirmed the presence of distinct NPs in the range of 5–50 nm containing Ag. Selected area electron diffraction and powder X-ray diffraction patterns of the silver NPs showed Bragg reflections, characteristic of crystalline face-centered cubic structure of Ag0 and cubic structure of Ag2O. Root system of intact plants raised under sterile conditions also generated Ag0/Ag2O-NPs under strict sterile conditions in a manner similar to that recorded under non-sterile conditions. This revealed the inbuilt potential of root system to generate Ag0/Ag2O-NPs independent of any microorganism. Roots of intact plants reduced triphenyltetrazolium to triphenylformazon and impermeable ferricyanide to ferrocyanide, suggesting involvement of plasma membrane bound dehydrogenases in reduction of Ag+ and formation of Ag0/Ag2O-NPs. Root enzyme extract reduced triphenyltetrazolium to triphenylformazon and Ag+ to Ag0 in presence of NADH, clearly establishing potential of dehydrogenases to reduce Ag+ to Ag0, which generate Ag0/Ag2O-NPs. Findings presented in this manuscript put forth a novel, simple

Effect of cysteine and humic acids on bioavailability of Ag from Ag nanoparticles to a freshwater snail

USGS Publications Warehouse

Luoma, Samuel N.; Tasha Stoiber,; Croteau, Marie-Noele; Isabelle Romer,; Ruth Merrifeild,; Lead, Jamie

2016-01-01

Metal-based engineered nanoparticles (NPs) will undergo transformations that will affect their bioavailability, toxicity and ecological risk when released to the environment, including interactions with dissolved organic material. The purpose of this paper is to determine how interactions with two different types of organic material affect the bioavailability of silver nanoparticles (AgNPs). Silver uptake rates by the pond snail Lymnaea stagnalis were determined after exposure to 25 nmol l-1 of Ag as PVP AgNPs, PEG AgNPs or AgNO3, in the presence of either Suwannee River humic acid or cysteine, a high-affinity thiol-rich organic ligand. Total uptake rate of Ag from the two NPs was either increased or not strongly affected in the presence of 1 – 10 mg 1-1 humic acid. Humic substances contain relatively few strong ligands for Ag explaining their limited effects on Ag uptake rate. In contrast, Ag uptake rate was substantially reduced by cysteine. Three components of uptake from the AgNPs were quantified in the presence of cysteine using a biodynamic modeling approach: uptake of dissolved Ag released by the AgNPs, uptake of a polymer or large (>3kD) Ag-cysteine complex and uptake of the nanoparticle itself. Addition of 1:1 Ag:cysteine reduced concentrations of dissolved Ag, which contributed to, but did not fully explain the reductions in uptake. A bioavailable Ag-cysteine complex (> 3kD) appeared to be the dominant avenue of uptake from both PVP AgNPs and PEG AgNPs in the presence of cysteine. Quantifying the different avenues of uptake sets the stage for studies to assess toxicity unique to NPs.

Modified pulse laser deposition of Ag nanostructure as intermediate for low temperature Cu-Cu bonding

NASA Astrophysics Data System (ADS)

Liu, Ziyu; Cai, Jian; Wang, Qian; Liu, Lei; Zou, Guisheng

2018-07-01

To lower the Cu-Cu bonding temperature and save the time of the bonding process applied for 3D integration, the Ag nanostructure deposited by pulsed laser deposition (PLD) was designed and decorated on the Cu pads as intermediate. Influences of different PLD process parameters on the designed Ag nanostructure morphology were investigated in this work. The large nanoparticles (NP) defects, NPs coverage rate on the Cu pad, and NPs size distribution were adopted to evaluate the PLD parameters based on the NPs morphology observation and the Cu-Cu bonding quality. The medium laser power of 0.8 W, smaller distance between target and substrate, and protective container should be applied in the optimized PLD to obtain the Ag nanostructure. Then a loose 3D mesh Ag nanostructure consisted of the protrusions and grooves was formed and the morphology observation proved the nanostructure deposition mechanism was contributed to the block of nano-film nucleation and nanoparticles absorption. Finally, the relationship between the bonding temperature and pressure suitable for the Ag nanostructure had been determined based on shear strength and interface observation. The results revealed the combination of higher bonding temperature (250 °C) and lower pressure (20 MPa), or lower bonding temperature (180 °C) and higher pressure (50 MPa) can both achieve the bonding process with the short bonding time of 5 min and annealing at 200 °C for 25 min in vacuum furnace.

Insight into the localized surface plasmon resonance property of core-satellite nanostructures: Theoretical prediction and experimental validation.

PubMed

Song, Dongxing; Jing, Dengwei

2017-11-01

Regulation of the localized surface plasmon resonance (LSPR) of nanoparticles by changing the dielectric constant of the surrounding medium has been exploited in many practical applications. In this study, using Ag-nanodot-decorated SiO 2 nanoparticles (Ag-decorated SiO 2 NPs) with different solvents, we investigated the potential of using such core-satellite nanostructures as a liquid sensor for the determination of melamine. The dielectric constant effect of the surrounding medium on the LSPR property was given particular attention. It was found that colloids with water as solvent display a LSPR shift of 14nm, and this value was 18nm for ethanol. For colloids with methanol and glycol as solvents, the peak shifts are negligible. Finite-difference time-domain (FDTD) simulations were used to assign the LSPR peaks of Ag-decorated SiO 2 NPs and to monitor the effect of the substrate and solvent on the LSPR properties. In the calculations, the wavelength positions of the LSPR peaks for Ag-decorated SiO 2 NPs in various solvents were successfully predicted in the order methanolAg nanodots and their relative positions on the SiO 2 substrate with respect to the incident light were also found to be crucial to the characteristic LSPR peak positions. The LSPR peak undergoes a shift in the presence of different concentrations of melamine. We proposed a multi-mode absorption model to describe the effect of melamine absorption on the LSPR peak shifts of Ag-decorated SiO 2 NPs. Based on this model, we were able to quantitatively explain the LSPR peak shift of Ag-decorated SiO 2 NPs in the presence of various concentrations of melamine. Our work is expected to be valuable for theoretical guidance in design of new materials and devices based on LSPR effects. Copyright © 2017 Elsevier Inc. All rights reserved.

Surface modification of nanoporous alumina layers by deposition of Ag nanoparticles. Effect of alumina pore diameter on the morphology of silver deposit and its influence on SERS activity

NASA Astrophysics Data System (ADS)

Pisarek, Marcin; Nowakowski, Robert; Kudelski, Andrzej; Holdynski, Marcin; Roguska, Agata; Janik-Czachor, Maria; Kurowska-Tabor, Elżbieta; Sulka, Grzegorz D.

2015-12-01

Self-organized Al2O3 nanoporous/nanotubular (Al2O3-NP) oxide layers decorated with silver nanoparticles (Ag-NPs) exhibiting specific properties may serve as attractive SERS substrates for investigating the interactions between an adsorbate and adsorbent, or as stable platforms for detecting various organic compounds. This article presents the influence of the size of the alumina nanopores with a deposit of silver nanoparticles obtained by the magnetron sputtering technique on the morphology of silver film. Moreover, the effect of pore diameter on the intensity of SERS spectra in Ag-NPs/Al2O3-NP/Al composites has also been estimated. For such investigations we used pyridine as a probe molecule, since it has a large cross-section for Raman scattering. To characterize the morphology of the composite oxide layer Ag-NPs/Al2O3-NP/Al, before and after deposition of Ag-NPs by PVD methods (Physical Vapor Deposition), we used scanning electron microscopy (SEM) and atomic force microscopy (AFM). The surface analytical technique of surface-enhanced Raman spectroscopy (SERS) was used to investigate the surface activity of the composite. The results obtained show that, for a carefully controlled amount of Ag (0.020 mg/cm2 - deposited on the top of alumina nanopores whose average size varies from ∼86 nm up to ∼320 nm) in the composites investigated, pore size significantly affects SERS enhancement. We obtained distinctly higher intensities of SERS spectra for substrates with an Ag-NPs deposit having a larger diameter of the alumina nanopores. AFM results suggest that both the lateral and perpendicular distribution of Ag-NPs within and on the top of the largest pores is responsible for the highest SERS activity of the resulting Ag-NPs/Al2O3-NP/Al composite layer, since it produces a variety of cavities and slits which function as resonators for the adsorbed molecules. The Ag-NPs/MeOx-NP/Me composite layers obtained ensure a good reproducibility of the SERS measurements.

Gas sensing properties of MWCNT layers electrochemically decorated with Au and Pd nanoparticles

PubMed Central

Alvisi, Marco; Rossi, Riccardo; Cassano, Gennaro; Di Franco, Cinzia; Palmisano, Francesco; Torsi, Luisa

2017-01-01

Multiwalled carbon nanotube (MWCNT)-based chemiresistors were electrochemically decorated with Au and Pd nanoparticles (NPs), resulting in an improvement in the detection of gaseous pollutants as compared to sensors based on pristine MWCNTs. Electrophoresis was used to decorate MWCNTs with preformed Au or Pd NPs, thus preserving their nanometer-sized dimensions and allowing the metal content to be tuned by simply varying the deposition time. The sensing response of unmodified and metal-decorated MWCNTs was evaluated towards different gaseous pollutants (e.g., NO2, H2S, NH3 and C4H10) at a wide range of concentrations in the operating temperature range of 45–200 °C. The gas sensing results were related to the presence, type and loading of metal NPs used in the MWCNT functionalization. Compared to pristine MWCNTs, metal-decorated MWCNTs revealed a higher gas sensitivity, a faster response, a better stability, reversibility and repeatability, and a low detection limit, where all of these sensing properties were controlled by the type and loading of the deposited metal catalytic NPs. Specifically, in the NO2 gas sensing experiments, MWCNTs decorated with the lowest Au content revealed the highest sensitivity at 150 °C, while MWCNTs with the highest Pd loading showed the highest sensitivity when operated at 100 °C. Finally, considering the reported gas sensing results, sensing mechanisms have been proposed, correlating the chemical composition and gas sensing responses. PMID:28382249

Development of a novel tridentate ligand for colorimetric detection of Mn2+ based on AgNPs.

PubMed

Wei, Jianyu; Chen, Jinfan; Yue, Guozong; Hu, Liangsheng; Zhao, Danqing; Zhu, Jing; Yang, Luming; Huang, Deshun; Zhao, Pengxiang

2018-05-09

A novel tridentate ligand nitrilotris(methylene)tris(1,2,3-triazole)triacetate (NTTTA) has been synthesized by click reaction and followed with ester hydrolysis reaction. The silver nanoparticles (AgNPs) were then modified and stabilized by this ligand, and subsequently been employed for the highly selective and sensitive colorimetric detection of Mn 2+ in aqueous solution. The presence of Mn 2+ can cause the aggregation of AgNPs, which leads to the color change of the dispersion from yellow to brown, as well as the decrease and red-shift of the surface plasmon resonance absorption. The detection limit of Mn 2+ was as approximately 0.5 μM by the naked eyes. UV-vis spectroscopy analysis showed a good linear relationship between the logarithm of the ratios (A 550 /A 395 ) and the concentration of Mn 2+ over the range of 0.05 μM-10 μM, and the LOD was calculated to be 12.6 nM (S/N = 3). The present assay showed good simplicity without the need of adjusting the pH value. The feasibility of this technique was evaluated for successful detection of Mn 2+ in tap water and lake water samples, with good recoveries. Copyright © 2018 Elsevier B.V. All rights reserved.

Synthesis and characterization of Ag+-decorated poly(glycidyl methacrylate) microparticle design for the adsorption of nucleic acids.

PubMed

Erol, Kadir; Uzunoglu, Aytekin; Köse, Kazım; Sarıca, Büşra; Avcı, Emre; Köse, Dursun A

2018-04-01

In this study, we report on the adsorption of RNA and DNA molecules by exploiting the high binding affinity of these nucleic acids to Ag + ions anchored on magnetic poly(glycidyl methacrylate) (PGMA) microparticles. PGMA microparticles were synthesized and modified with nicotinamide which enabled to anchor Ag + ions on the surface. The successful preparation of PGMA was confirmed by the presence of characteristic FTIR peaks. The ESR results showed that the incorporation of FeNi salt to the polymeric structure provided a magnetic property to the microparticles. The amount of nicotinamide and Ag + ions used to modify the surface of the particles were found to be 1.79 wt% and 52.6 mg Ag/g microparticle, respectively. The high affinity of nucleic acids to Ag + ions were exploited for the adsorption studies. At the optimum working conditions, the adsorption capacity of microparticles was found to be 40.1 and 11.48 mg nucleic acid/g microparticle for RNA and DNA, respectively. Our study indicated that the use of novel Ag + -decorated magnetic PGMA particles can be successfully employed as adsorbents for fast, easy, and cost-friendly adsorption of nucleic acids with high purity as well as high in quantity. Copyright © 2018 Elsevier B.V. All rights reserved.

Biosynthesis of AgNPs using Carica Papaya peel extract and evaluation of its antioxidant and antimicrobial activities.

PubMed

Kokila, T; Ramesh, P S; Geetha, D

2016-12-01

Waste fruit peel mediated synthesis of silver nanoparticles (AgNPs) is a green chemistry approach that links nanotechnology and biotechnology. Using biological medium such as peel extract for the biosynthesis of nanoparticles is an ecofriendly and emerging scientific trend. With this back drop the present study focused on the biosynthesis of AgNPs using Carica Papaya peel extract (CPPE) and evaluation of its antimicrobial potentials of the nanoparticles against different human pathogens and to investigate the free radical scavenging activity. Water soluble antioxidant constituents present in Carica Papaya peel extract were mainly responsible for the reduction of silver ions to nanosized Ag particles. UV-vis spectral analysis shows surface plasmon resonance band at 430nm. The presence of active proteins and phenolic groups present in the biomass before and after reduction was identified by Fourier transform infrared spectroscopy. X-ray diffraction study shows the average size of the silver nanoparticles is in the range of 28nm, as well as revealed their face centered cubic structure. Atomic force microscope image gives the 3D topological characteristic of silver nanoparticles and the particle size ranges from 10 to 30nm. The average particle size distribution of silver nanoparticles is 161nm (Dynamic light scattering) and the corresponding average zeta potential value is -20.5mV, suggesting higher stability of silver nanoparticles. Biologically synthesized nanoparticles efficiently inhibited pathogenic organisms both gram-positive and gram-negative bacteria. The biosynthesized nanoparticles might serve as a potent antioxidant as revealed by DPPH and ABT S+ assay. Copyright © 2016 Elsevier Inc. All rights reserved.

Comparative Cytotoxicity Study of Silver Nanoparticles (AgNPs) in a Variety of Rainbow Trout Cell Lines (RTL-W1, RTH-149, RTG-2) and Primary Hepatocytes

PubMed Central

Connolly, Mona; Fernandez-Cruz, Maria-Luisa; Quesada-Garcia, Alba; Alte, Luis; Segner, Helmut; Navas, Jose M.

2015-01-01

Among all classes of nanomaterials, silver nanoparticles (AgNPs) have potentially an important ecotoxicological impact, especially in freshwater environments. Fish are particularly susceptible to the toxic effects of silver ions and, with knowledge gaps regarding the contribution of dissolution and unique particle effects to AgNP toxicity, they represent a group of vulnerable organisms. Using cell lines (RTL-W1, RTH-149, RTG-2) and primary hepatocytes of rainbow trout (Oncorhynchus mykiss) as in vitro test systems, we assessed the cytotoxicity of the representative AgNP, NM-300K, and AgNO3 as an Ag+ ion source. Lack of AgNP interference with the cytotoxicity assays (AlamarBlue, CFDA-AM, NRU assay) and their simultaneous application point to the compatibility and usefulness of such a battery of assays. The RTH-149 and RTL-W1 liver cell lines exhibited similar sensitivity as primary hepatocytes towards AgNP toxicity. Leibovitz’s L-15 culture medium composition (high amino acid content) had an important influence on the behaviour and toxicity of AgNPs towards the RTL-W1 cell line. The obtained results demonstrate that, with careful consideration, such an in vitro approach can provide valuable toxicological data to be used in an integrated testing strategy for NM-300K risk assessment. PMID:26006119

Strong damping of the localized surface plasmon resonance of Ag nanoparticles by Ag2O.

PubMed

Wu, Qingmen; Si, Mengting; Zhang, Bing; Zhang, Kang; Li, Huanhuan; Mi, Longfei; Jiang, Yang; Rong, Yan; Chen, Junling; Fang, Yingcui

2018-07-20

By studying oxidation of AgNPs (Ag nanoparticles) and decomposition of the produced silver oxide, we demonstrate that the localized surface plasmon resonance (LSPR) of AgNPs was damped by Ag 2 O produced during oxygen plasma irradiation (OPI). The AgNPs were fabricated by evaporation of high pure silver under high vacuum. The oxidation was conducted in oxygen plasma generated by radio frequency glow discharging in vacuum, and the decomposition was performed by annealing the silver oxide in nitrogen ambient at temperatures ranging from room temperature to 450 °C. Samples were characterized by color, absorption spectra, surface enhanced Raman scattering, x-ray photoelectron spectroscopy, and field emission scanning electron microscopy. The bandgap of the silver oxide was calculated. We propose that AgNPs are only partially oxidized into silver oxide during OPI, and the LSPR of the AgNPs left without being oxidation is strongly damped by the produced silver oxide. This LSPR damping is responsible for the transparency of the sample after OPI for 2 s.

Strong damping of the localized surface plasmon resonance of Ag nanoparticles by Ag2O

NASA Astrophysics Data System (ADS)

Wu, Qingmen; Si, Mengting; Zhang, Bing; Zhang, Kang; Li, Huanhuan; Mi, Longfei; Jiang, Yang; Rong, Yan; Chen, Junling; Fang, Yingcui

2018-07-01

By studying oxidation of AgNPs (Ag nanoparticles) and decomposition of the produced silver oxide, we demonstrate that the localized surface plasmon resonance (LSPR) of AgNPs was damped by Ag2O produced during oxygen plasma irradiation (OPI). The AgNPs were fabricated by evaporation of high pure silver under high vacuum. The oxidation was conducted in oxygen plasma generated by radio frequency glow discharging in vacuum, and the decomposition was performed by annealing the silver oxide in nitrogen ambient at temperatures ranging from room temperature to 450 °C. Samples were characterized by color, absorption spectra, surface enhanced Raman scattering, x-ray photoelectron spectroscopy, and field emission scanning electron microscopy. The bandgap of the silver oxide was calculated. We propose that AgNPs are only partially oxidized into silver oxide during OPI, and the LSPR of the AgNPs left without being oxidation is strongly damped by the produced silver oxide. This LSPR damping is responsible for the transparency of the sample after OPI for 2 s.

Room-temperature synthesis of carnation-like ZnO@AgI hierarchical nanostructures assembled by AgI nanoparticles-decorated ZnO nanosheets with enhanced visible light photocatalytic activity.

PubMed

Huang, He; Huang, Ni; Wang, Zhonghua; Xia, Guangqiang; Chen, Ming; He, Lingling; Tong, Zhifang; Ren, Chunguang

2017-09-15

The preparation of highly efficient visible-light-driven photocatalyst for the photodegradation of organic pollutants has received much attention due to the increasing global energy crises and environmental pollution. In this study, carnation-like ZnO@AgI hierarchical nanostructures assembled by AgI nanoparticles-decorated ZnO nanosheets were successfully prepared via a room-temperature route. The as-prepared ZnO@AgI nanostructures exhibited highly efficient photocatalytic activity under visible light irradiation (λ>400nm). Under optimized AgI content, the ZnO@AgI-5% sample showed high photocatalytic activity, which was 25.7 and 1.5 times the activity of pure ZnO and pure AgI, respectively. Mechanism studies indicated that superoxide anion radicals (O 2 - ) was the main reactive species in the photocatalytic process. The high photocatalytic activity of the ZnO@AgI nanostructures is attributed to the highly active AgI nanoparticles and the heterojunction between AgI nanoparticles and ZnO nanosheets. The heterojunction structure reduced the recombination of the photogenerated electron-hole pairs in the conduction band (CB) and valence band (VB) of AgI nanoparticles by transferring the electrons from the CB of AgI nanoparticles to the CB of ZnO nanosheets. The composite of ZnO and AgI not only improves photocatalytic efficiency but also reduces photocatalyst cost, which is beneficial for practical application. Copyright © 2017 Elsevier Inc. All rights reserved.

Construction of AgBr nano-cakes decorated Ti3+ self-doped TiO2 nanorods/nanosheets photoelectrode and its enhanced visible light driven photocatalytic and photoelectrochemical properties

NASA Astrophysics Data System (ADS)

Deng, Xiaoyong; Zhang, Huixuan; Guo, Ruonan; Cheng, Xiuwen; Cheng, Qingfeng

2018-05-01

In the study, AgBr nano-cakes decorated Ti3+ self-doped TiO2 nanorods/nanosheets (AgBr-Ti3+/TiO2 NRs/NSs) photoelectrode with enhanced visible light driven photocatalytic (PC) and photoelectrochemical (PECH) performance has been successfully fabricated by hydrothermal reaction, followed by sodium borohydride reduction and then successive ionic layer adsorption and reaction (SILAR) treatment. Afterwards, series of characterizations were conducted to study the physicochemical properties of AgBr-Ti3+/TiO2 NRs/NSs photoelectrode. Results indicated that AgBr nano-cakes with sizes varying from 110 to 180 nm were uniformly decorated on the surface of Ti3+/TiO2 NRs/NSs to form AgBr-Ti3+/TiO2 NRs/NSs photoelectrode. Moreover, PC activity of AgBr-Ti3+/TiO2 NRs/NSs photoelectrode was measured by degradation of methylene blue (MB). It was found that AgBr-Ti3+/TiO2 NRs/NSs photoelectrode exhibited higher PC activity (98.7%) than that of other samples within 150 min visible light illumination, owing to the enhancement of visible light harvesting and effective separation of photoproduced charges. Thus, AgBr nano-cakes and Ti3+ exerted a huge influence on the PC and PECH properties of AgBr-Ti3+/TiO2 NRs/NSs photoelectrode. Furthermore, the possible enhanced visible light driven PC mechanism of AgBr-Ti3+/TiO2 NRs/NSs was proposed and confirmed.

Experimental and theoretical study on field emission properties of zinc oxide nanoparticles decorated carbon nanotubes

NASA Astrophysics Data System (ADS)

Li, Xin; Zhou, Wei-Man; Liu, Wei-Hua; Wang, Xiao-Li

2015-05-01

Field emission properties of zinc oxide (ZnO) nanoparticles (NPs) decorated carbon nanotubes (CNTs) are investigated experimentally and theoretically. CNTs are in situ decorated with ZnO NPs during the growth process by chemical vapor deposition using a carbon source from the iron phthalocyanine pyrolysis. The experimental field emission test shows that the ZnO NP decoration significantly improves the emission current from 50 μA to 275 μA at 550 V and the reduced threshold voltage from 450 V to 350 V. The field emission mechanism of ZnO NPs on CNTs is theoretically studied by the density functional theory (DFT) combined with the Penn-Plummer method. The ZnO NPs reconstruct the ZnO-CNT structure and pull down the surface barrier of the entire emitter system to 0.49 eV so as to reduce the threshold electric field. The simulation results suggest that the presence of ZnO NPs would increase the LDOS near the Fermi level and increase the emission current. The calculation results are consistent with the experiment results. Project supported by the National Natural Science Foundation of China (Grant Nos. 91123018, 61172040, and 61172041) and the Natural Science Foundation of Shaanxi Province, China (Grant No. 2014JM7277).

Guazuma ulmifolia bark-synthesized Ag, Au and Ag/Au alloy nanoparticles: Photocatalytic potential, DNA/protein interactions, anticancer activity and toxicity against 14 species of microbial pathogens.

PubMed

Karthika, Viswanathan; Arumugam, Ayyakannu; Gopinath, Kasi; Kaleeswarran, Periyannan; Govindarajan, Marimuthu; Alharbi, Naiyf S; Kadaikunnan, Shine; Khaled, Jamal M; Benelli, Giovanni

2017-02-01

In the present study, we focused on a quick and green method to fabricate Ag, Au and Ag/Au alloy nanoparticles (NPs) using the bark extract of Guazuma ulmifolia L. Green synthesized metal NPs were characterized using different techniques, including UV-Vis spectroscopy, FT-IR, XRD, AFM and HR-TEM analyses. The production of Ag, Au and Ag/Au alloy NPs was observed monitoring color change from colorless to brown, followed by pink and dark brown, as confirmed by UV-Vis spectroscopy characteristic peaks at 436, 522 and 510nm, respectively. TEM shed light on the spherical shapes of NPs with size ranges of 10-15, 20-25 and 10-20nm. Biosynthesized NPs showed good catalytic activity reducing two organic dyes, 4-nitrophenol (4-NP) and Congo red (CR). UV-vis spectroscopy, fluorescence, circular dichroism spectroscopy and viscosity analyses were used to investigate the NP binding with calf thymus DNA. The binding constant of NPs with DNA calculated in UV-Vis absorption studies were 1.18×10 4 , 1.83×10 4 and 2.91×10 4 M -1 , respectively, indicating that NPs were able to bind DNA with variable binding affinity: Ag/Au alloy NPs>Ag NPs>Au NPs. Ag/Au alloy NPs also showed binding activity to bovine serum albumin (BSA) over the other NPs. Ag and Ag/Au alloy NPs exhibited good antimicrobial activity on 14 species of microbial pathogens. In addition, the cytotoxic effects of Ag/Au alloy NPs were studied on human cervical cancer cells (HeLa) using MTT assay. Overall, our work showed the promising potential of bark-synthesized Ag and Ag/Au alloy NPs as cheap sources to develop novel and safer photocatalytic, antimicrobial and anticancer agents. Copyright © 2017. Published by Elsevier B.V.

Antibacterial activity of N-halamine decorated mesoporous silica nanoparticles

NASA Astrophysics Data System (ADS)

Xu, Jiarong; Zhang, Yu; Zhao, Yanbao; Zou, Xueyan

2017-09-01

N-halamine decorated mesoporous silica nanoparticles (mSiO2/halamine NPs) were prepared by coating mSiO2 NPs with poly (1-allylhydantoin-co-methyl methacrylate) (AH-co-MMA) by the aid of the radical polymerization, followed by chlorination treatment. The sterilizing effect on the bacterial strain is investigated by incubating Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Results indicated that the mSiO2/halamine NPs had excellent antibacterial activity and no significant change occurred in antibacterial efficiency after five recycle experiments.

Synergistic effect of shape-selective silver nanostructures decorating reduced graphene oxide nanoplatelets for enhanced cytotoxicity against breast cancer.

PubMed

Derakhshi, Maryam; Ashkarran, Ali Akbar; Bahari, Ali; Bonakdar, Shahin

2018-07-13

Graphene-based nanomaterials contain unique physicochemical properties and have been widely investigated due to a variety of applications particularly in cancer therapy. Furthermore, Ag has been known for its extensive historical background for biomedical applications. Therefore, conjugation of shape-selective Ag nanostructures with graphene may provide new horizons for pharmaceutical applications such as cancer treatments. Here we report on the synthesis of Ag nanoparticles (NPs)/reduced graphene oxide (AgNPs/RGO) conjugate nanomaterials containing various shapes of AgNPs by a novel and simple synthesis route using the deformation of dimethylformamide (DMF) as the reducing and coupling agent. The cytotoxicity and anticancer properties of AgNPs, AgNPs/RGO conjugate nanomaterials, RGO and graphene oxide (GO) were probed against MDA-MB-231 cancer and MCF-10A normal human breast cells in vitro. The AgNPs/RGO nanocomposites exhibited a strong anticancer effect by penetration and apoptosis in cancer cells as well as the lowest influence on the viability of normal cells. It was found that cancer cell viability not only depends on the geometry of Ag nanostructures but also on the interaction between AgNPs and RGO nanoplatelets. It is suggested that AgNPs/RGO conjugate nanomaterials with various shapes of AgNPs is a promising therapeutic platform for cancer therapy.

Synergistic effect of shape-selective silver nanostructures decorating reduced graphene oxide nanoplatelets for enhanced cytotoxicity against breast cancer

NASA Astrophysics Data System (ADS)

Derakhshi, Maryam; Ashkarran, Ali Akbar; Bahari, Ali; Bonakdar, Shahin

2018-07-01

Graphene-based nanomaterials contain unique physicochemical properties and have been widely investigated due to a variety of applications particularly in cancer therapy. Furthermore, Ag has been known for its extensive historical background for biomedical applications. Therefore, conjugation of shape-selective Ag nanostructures with graphene may provide new horizons for pharmaceutical applications such as cancer treatments. Here we report on the synthesis of Ag nanoparticles (NPs)/reduced graphene oxide (AgNPs/RGO) conjugate nanomaterials containing various shapes of AgNPs by a novel and simple synthesis route using the deformation of dimethylformamide (DMF) as the reducing and coupling agent. The cytotoxicity and anticancer properties of AgNPs, AgNPs/RGO conjugate nanomaterials, RGO and graphene oxide (GO) were probed against MDA-MB-231 cancer and MCF-10A normal human breast cells in vitro. The AgNPs/RGO nanocomposites exhibited a strong anticancer effect by penetration and apoptosis in cancer cells as well as the lowest influence on the viability of normal cells. It was found that cancer cell viability not only depends on the geometry of Ag nanostructures but also on the interaction between AgNPs and RGO nanoplatelets. It is suggested that AgNPs/RGO conjugate nanomaterials with various shapes of AgNPs is a promising therapeutic platform for cancer therapy.

Tailoring the light absorption of Ag-PZT thin films by controlling the growth of hexagonal- and cubic-phase Ag nanoparticles

NASA Astrophysics Data System (ADS)

Hu, Tao; Wang, Zongrong; Ma, Ning; Du, Piyi

2017-12-01

PbZr0.52Ti0.48O3 thin films containing hexagonal and cubic Ag nanoparticles (Ag NPs) of various sizes were prepared using the sol-gel technique. During the aging process, Ag ions were photo-reduced to form hexagonal Ag NPs. These NPs were uniform in size, and their uniformity was maintained in the thin films during the heat treatment process. Both the total volume and average size of the hexagonal Ag NPs increased with an increasing Ag ion concentration from 0.02 to 0.08 mol l-1. Meanwhile, the remaining Ag ions were reduced to form unstable Ag-Pb alloy particles with Pb ions during the early heating stage. During subsequent heat treatment, these alloys decomposed to form cubic Ag NPs in the thin films. The absorption range of the thin films, quantified as the full width at half maximum in the ultraviolet-visible absorption spectrum, expanded from 6.3 × 1013 Hz (390-425 nm) to 8.4 × 1013 Hz (383-429 nm) as the Ag NPs/PZT ratio increased from 0.2 to 0.8. This work provides an effective way to broaden the absorption range and enhance the optical properties of such films.

Au nanostructure-decorated TiO2 nanowires exhibiting photoactivity across entire UV-visible region for photoelectrochemical water splitting.

PubMed

Pu, Ying-Chih; Wang, Gongming; Chang, Kao-Der; Ling, Yichuan; Lin, Yin-Kai; Fitzmorris, Bob C; Liu, Chia-Ming; Lu, Xihong; Tong, Yexiang; Zhang, Jin Z; Hsu, Yung-Jung; Li, Yat

2013-08-14

Here we demonstrate that the photoactivity of Au-decorated TiO2 electrodes for photoelectrochemical water oxidation can be effectively enhanced in the entire UV-visible region from 300 to 800 nm by manipulating the shape of the decorated Au nanostructures. The samples were prepared by carefully depositing Au nanoparticles (NPs), Au nanorods (NRs), and a mixture of Au NPs and NRs on the surface of TiO2 nanowire arrays. As compared with bare TiO2, Au NP-decorated TiO2 nanowire electrodes exhibited significantly enhanced photoactivity in both the UV and visible regions. For Au NR-decorated TiO2 electrodes, the photoactivity enhancement was, however, observed in the visible region only, with the largest photocurrent generation achieved at 710 nm. Significantly, TiO2 nanowires deposited with a mixture of Au NPs and NRs showed enhanced photoactivity in the entire UV-visible region. Monochromatic incident photon-to-electron conversion efficiency measurements indicated that excitation of surface plasmon resonance of Au is responsible for the enhanced photoactivity of Au nanostructure-decorated TiO2 nanowires. Photovoltage experiment showed that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was attributable to the effective surface passivation of Au NPs. Furthermore, 3D finite-difference time domain simulation was performed to investigate the electrical field amplification at the interface between Au nanostructures and TiO2 upon SPR excitation. The results suggested that the enhanced photoactivity of Au NP-decorated TiO2 in the UV region was partially due to the increased optical absorption of TiO2 associated with SPR electrical field amplification. The current study could provide a new paradigm for designing plasmonic metal/semiconductor composite systems to effectively harvest the entire UV-visible light for solar fuel production.

Hyaluronan-decorated polymer nanoparticles targeting the CD44 receptor for the combined photo/chemo-therapy of cancer

NASA Astrophysics Data System (ADS)

Maiolino, Sara; Moret, Francesca; Conte, Claudia; Fraix, Aurore; Tirino, Pasquale; Ungaro, Francesca; Sortino, Salvatore; Reddi, Elena; Quaglia, Fabiana

2015-03-01

In the attempt to develop novel concepts in designing targeted nanoparticles for combination therapy of cancer, we propose here CD44-targeted hyaluronan-decorated double-coated nanoparticles (dcNPs) delivering the lipophilic chemotherapeutic docetaxel (DTX) and an anionic porphyrin (TPPS4). dcNPs are based on electrostatic interactions between a negative DTX-loaded nanoscaffold of poly(lactide-co-glycolide), a polycationic shell of polyethyleneimine entangling negatively-charged TPPS4 and finally decorated with hyaluronan (HA) to promote internalization through CD44 receptor-mediated endocytosis. DTX/TPPS4-dcNPs, prepared through layer-by-layer deposition, showed a hydrodynamic diameter of around 180 nm, negative zeta potential and efficient loading of both DTX and TPPS4. DTX/TPPS4-dcNPs were freeze-dried with trehalose giving a powder that could be easily dispersed in different media. Excellent stability of dcNPs in specific salt- and protein-containing media was found. Spectroscopic behavior of DTX/TPPS4-dcNPs demonstrated a face-to-face arrangement of the TPPS4 units in non-photoresponsive H-type aggregates accounting for an extensive aggregation of the porphyrin embedded in the shell. Experiments in MDA-MB-231 cells overexpressing the CD44 receptor demonstrated a 9.4-fold increase in the intracellular level of TPPS4 delivered from dcNPs as compared to free TPPS4. Light-induced death increased tremendously in cells that had been treated with a combination of TPPS4 and DTX delivered through dcNPs as compared with free drugs, presumably due to efficient uptake and co-localization inside the cells. In perspective, the strategy proposed here to target synergistic drug combinations through HA-decorated nanoparticles seems very attractive to improve the specificity and efficacy of cancer treatment.In the attempt to develop novel concepts in designing targeted nanoparticles for combination therapy of cancer, we propose here CD44-targeted hyaluronan-decorated double

Sensing of low concentration of ammonia at room temperature by decorated multi-walled carbon nanotube: fabrication and characteristics

NASA Astrophysics Data System (ADS)

Hasnahena, S. T.; Roy, M.

2018-01-01

A chemical sensor based on multi-walled carbon nanotube (MWCNT) decorated with densely populated thiol-capped gold nanoparticles (AuNPs) with sizes smaller than 3 nm for sensing low concentrations of ammonia gas is reported. The functionalized MWCNTs, subsequently decorated with AuNPs following an easy fabrication route were exposed to NH3 gas at the room temperature and the electrical resistance of the sensor changed upon exposure. The sensor also partially recovered the initial state after sensing in the normal air environment (without any dry air or N2 gas purge). The gold nanoparticles decoration is found to enhance the sensitivity and selectivity of MWCNT towards NH3 gas under ambient conditions with a reduced response and recovery time. The material was structurally characterized by Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy. Thermal stability of the sensor till 574 °C was demonstrated by TGA analysis. This papers describes how thiol-capped AuNPs are uniformly decorated on the outer walls of the MWCNTs with a separation of 2-3 nm making use of the ionic nature of Au and how this uniform distribution of AuNPs increases the active sites for absorption of NH3 gas molecules leading to sensing its low concentrations.

Electrochemical Fabrication of Nanostructures on Porous Silicon for Biochemical Sensing Platforms.

PubMed

Ko, Euna; Hwang, Joonki; Kim, Ji Hye; Lee, Joo Heon; Lee, Sung Hwan; Tran, Van-Khue; Chung, Woo Sung; Park, Chan Ho; Choo, Jaebum; Seong, Gi Hun

2016-01-01

We present a method for the electrochemical patterning of gold nanoparticles (AuNPs) or silver nanoparticles (AgNPs) on porous silicon, and explore their applications in: (1) the quantitative analysis of hydroxylamine as a chemical sensing electrode and (2) as a highly sensitive surface-enhanced Raman spectroscopy (SERS) substrate for Rhodamine 6G. For hydroxylamine detection, AuNPs-porous silicon can enhance the electrochemical oxidation of hydroxylamine. The current changed linearly for concentrations ranging from 100 μM to 1.32 mM (R(2) = 0.995), and the detection limit was determined to be as low as 55 μM. When used as SERS substrates, these materials also showed that nanoparticles decorated on porous silicon substrates have more SERS hot spots than those decorated on crystalline silicon substrates, resulting in a larger SERS signal. Moreover, AgNPs-porous silicon provided five-times higher signal compared to AuNPs-porous silicon. From these results, we expect that nanoparticles decorated on porous silicon substrates can be used in various types of biochemical sensing platforms.

Ag@AgHPW as a plasmonic catalyst for visible-light photocatalytic degradation of environmentally harmful organic pollutants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Wenhui; Cao, Minhua, E-mail: caomh@bit.edu.cn; Li, Na

2013-06-01

Graphical abstract: Ag@Ag{sub x}H{sub 3−x}PW12O40 (Ag@AgHPW) nanoparticles (NPs), a new visible-light driven plasmonic photocatalyst, are prepared by a green photoreduction strategy without the addition of any surfactant, which show a high activity and stability for the degradation of methyl blue (MB) under visible light irradiation. - Highlights: • A new visible-light driven photocatalyst Ag@Ag{sub x}H{sub 3−x}PW{sub 12}O{sub 40} was designed. • The photocatalyst shows a high activity for the degradation of methyl blue. • The high activity can be ascribed to the synergy of photoexcited AgHPW and Ag. - Abstract: Ag@Ag{sub x}H{sub 3−x}PW{sub 12}O{sub 40} (Ag@AgHPW) nanoparticles (NPs), a newmore » visible-light driven plasmonic photocatalyst, are prepared by a green photoreduction strategy without the addition of any surfactant. They show strong absorption in the visible region because of the localized surface plasmon resonance (LSPR) of Ag NPs. This plasmonic photocatalyst shows a high activity and stability for the degradation of methyl blue (MB) under visible light irradiation, which could be attributed to the highly synergy of photoexcited Ag{sub x}H{sub 3−x}PW{sub 12}O{sub 40} (AgHPW) and plasmon-excited Ag NPs and the confinement effects at interfaces between polyoxometalates (POMs) and silver. POM anions have redox ability and high photocatalytic activity, whereas Ag NPs could effectively accelerate the separation of electrons and holes, both of which contribute to their high activity.« less

Biotin-decorated silica coated PbS nanocrystals emitting in the second biological near infrared window for bioimaging

NASA Astrophysics Data System (ADS)

Corricelli, M.; Depalo, N.; di Carlo, E.; Fanizza, E.; Laquintana, V.; Denora, N.; Agostiano, A.; Striccoli, M.; Curri, M. L.

2014-06-01

Nanoparticles (NPs) emitting in the second biological near infrared (NIR) window of the electromagnetic spectrum have been successfully synthesized by growing a silica shell on the hydrophobic surface of OLEA/TOP PbS nanocrystals (NCs), by means of a reverse microemulsion approach, and subsequently decorated with biotin molecules. The fabrication of very uniform and monodisperse NPs, formed of SiO2 shell coated single core PbS NCs, has been demonstrated by means of a set of complementary optical and structural techniques (Vis-NIR absorption and photoluminescence spectroscopy, transmission electron microscopy) that have highlighted how experimental parameters, such as PbS NC and silica precursor concentration, are crucial to direct the morphology and optical properties of silica coated PbS NPs. Subsequently, the silica surface of the core-shell NPs has been grafted with amino groups, in order to achieve covalent binding of biotin to NIR emitting silica coated NPs. Finally the successful reaction with a green-fluorescent labelled streptavidin has verified the molecular recognition response of the biotin molecules decorating the PbS@SiO2 NP surface. Dynamic light scattering (DLS) and ζ-potential techniques have been used to monitor the hydrodynamic diameter and colloidal stability of both PbS@SiO2 and biotin decorated NPs, showing their high colloidal stability in physiological media, as needed for biomedical applications. Remarkably the obtained biotinylated PbS@SiO2 NPs have been found to retain emission properties in the `second optical window' of the NIR region of the electromagnetic spectrum, thus representing attractive receptor-targeted NIR fluorescent probes for in vivo tumour imaging.Nanoparticles (NPs) emitting in the second biological near infrared (NIR) window of the electromagnetic spectrum have been successfully synthesized by growing a silica shell on the hydrophobic surface of OLEA/TOP PbS nanocrystals (NCs), by means of a reverse microemulsion

Preparation of silver nanoparticles loaded graphene oxide nanosheets for antibacterial activity

NASA Astrophysics Data System (ADS)

T, T. T., Vi; Lue, S. J.

2016-11-01

A simple, facile method to fabricate successfully silver nanoparticle (AgNPs) decorated on graphene oxide (GO) layers via grafted thiol groups. Samples were prepared with different concentrations of AgNO3. Resulting AgNPs were quasi-spherical in shape and attached on the layers of GO. Physical properties were confirmed by X-ray diffraction (XRD), zeta potential, dynamic light scattering (DLS), Fourier transform infrared (FTIR) spectra, thermogravimetric analyzer (TGA), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM). Antimicrobial test was effectively showed using MRSA (Staphylococcus areus). The GO-Ag NPs with appropriate Ag NPs content of 0.2 M AgNO3 exhibited the strongest antibacterial activity at 48.77% inhibition after 4 hours incubation.

Surface decoration by Spirulina polysaccharide enhances the cellular uptake and anticancer efficacy of selenium nanoparticles.

PubMed

Yang, Fang; Tang, Quanming; Zhong, Xueyun; Bai, Yan; Chen, Tianfeng; Zhang, Yibo; Li, Yinghua; Zheng, Wenjie

2012-01-01

A simple and solution-phase method for functionalization of selenium nanoparticles (SeNPs) with Spirulina polysaccharides (SPS) has been developed in the present study. The cellular uptake and anticancer activity of SPS-SeNPs were also evaluated. Monodisperse and homogeneous spherical SPS-SeNPs with diameters ranging from 20 nm to 50 nm were achieved under optimized conditions, which were stable in the solution phase for at least 3 months. SPS surface decoration significantly enhanced the cellular uptake and cytotoxicity of SeNPs toward several human cancer cell lines. A375 human melanoma cells were found extremely susceptible to SPS-SeNPs with half maximal (50%) inhibitory concentration value of 7.94 μM. Investigation of the underlying mechanisms revealed that SPS-SeNPs inhibited cancer cell growth through induction of apoptosis, as evidenced by an increase in sub-G(1) cell population, deoxyribonucleic acid fragmentation, chromatin condensation, and phosphatidylserine translocation. Results suggest that the strategy to use SPS as a surface decorator could be an effective way to enhance the cellular uptake and anticancer efficacy of nanomaterials. SPS-SeNPs may be a potential candidate for further evaluation as a chemopreventive and chemotherapeutic agent against human cancers.

Effect of chemically and biologically synthesized Ag nanoparticles on the algae growth inhibition

NASA Astrophysics Data System (ADS)

Anna, Mražiková; Oksana, Velgosová; Jana, Kavuličová

2017-12-01

Over the past few years green methods for preparation of silver nanoparticles has become necessary due to its friendly influence on ecosystem. In the present work antimicrobial properties of biologically synthesized silver nanoparticles (Bio-AgNPs) using green algae extract and chemically synthesized silver nanoparticles (Chem-AgNPs) using sodium citrate against algae Parachlorella kessleri is investigated. Both used Bio-AgNPs and Chem-AgNPs exhibit long-term stability as demonstrated by UV-vis spectroscopy measurements. The results revealed stronger toxic effects of Bio-AgNPs on agar plates what was confirmed clear inhibition zone around wells impregnated with Bio-AgNPs. On the other hand Bio-AgNPs were confirmed to be less toxic in aquatic environments for the growths of green algae P. kessleri comparing to Chem-AgNPs.

Gold decorated porous biosilica nanodevices for advanced medicine.

PubMed

Terracciano, Monica; Napolitano, Michela; De Stefano, Luca; De Luca, Anna Chiara; Rea, Ilaria

2018-06-08

Diatomite is a fossil material made of amorphous porous silica. In this work, polyethylene glycol (PEG)-modified diatomite NPs (PEG-DNPs) are decorated with gold NPs (AuNPs) by one-pot liquid-phase synthesis. Nanocomplexes (PEG-DNPs@AuNPs), with an average size of about 450 nm, are characterized by dynamic light scattering, electron microscopy, nitrogen adsorption/desorption analysis, UV-vis and photoluminescence spectroscopies. Preliminary studies on the use of the nanocomplex in nanomedicine are also presented. Tests performed incubating PEG-DNPs@AuNPs in physiological conditions reveal a good stability of material. Cellular uptake of labeled PEG-DNPs@AuNPs is investigated by confocal microscopy after incubation with human cervix epithelioid carcinoma (HeLa) cells up to 48 h: an efficient cytoplasmic localization is observed. In vitro cytotoxicity of nanocomplexes with a concentration up to 400 μg ml -1 for 72 h is also evaluated. The results suggest the use of PEG-DNPs@AuNPs as advanced nanodevices adding imaging features to the nanocomplexes, due to AuNPs as contrast agent.

Gold decorated porous biosilica nanodevices for advanced medicine

NASA Astrophysics Data System (ADS)

Terracciano, Monica; Napolitano, Michela; De Stefano, Luca; Chiara De Luca, Anna; Rea, Ilaria

2018-06-01

Diatomite is a fossil material made of amorphous porous silica. In this work, polyethylene glycol (PEG)-modified diatomite NPs (PEG-DNPs) are decorated with gold NPs (AuNPs) by one-pot liquid-phase synthesis. Nanocomplexes (PEG-DNPs@AuNPs), with an average size of about 450 nm, are characterized by dynamic light scattering, electron microscopy, nitrogen adsorption/desorption analysis, UV–vis and photoluminescence spectroscopies. Preliminary studies on the use of the nanocomplex in nanomedicine are also presented. Tests performed incubating PEG-DNPs@AuNPs in physiological conditions reveal a good stability of material. Cellular uptake of labeled PEG-DNPs@AuNPs is investigated by confocal microscopy after incubation with human cervix epithelioid carcinoma (HeLa) cells up to 48 h: an efficient cytoplasmic localization is observed. In vitro cytotoxicity of nanocomplexes with a concentration up to 400 μg ml‑1 for 72 h is also evaluated. The results suggest the use of PEG-DNPs@AuNPs as advanced nanodevices adding imaging features to the nanocomplexes, due to AuNPs as contrast agent.

Glancing-incidence X-ray diffraction of Ag nanoparticles in gold lustre decoration of Italian Renaissance pottery

NASA Astrophysics Data System (ADS)

Bontempi, E.; Colombi, P.; Depero, L. E.; Cartechini, L.; Presciutti, F.; Brunetti, B. G.; Sgamellotti, A.

2006-06-01

Lustre is known as one of the most significant decorative techniques of Medieval and Renaissance pottery in the Mediterranean basin, characterized by brilliant gold and red metallic reflections and iridescence effects. Previous studies by various techniques (SEM-EDS and TEM, UV-VIS, XRF, RBS and EXAFS) demonstrated that lustre consists of a heterogeneous metal-glass composite film, formed by Cu and Ag nanoparticles dispersed within the outer layer of a tin-opacified lead glaze. In the present work the investigation of an original gold lustre sample from Deruta has been carried out by means of glancing-incidence X-ray diffraction techniques (GIXRD). The study was aimed at providing information on structure and depth distribution of Ag nanoparticles. Exploiting the capability of controlling X-ray penetration in the glaze by changing the incidence angle, we used GIXRD measurements to estimate non-destructively thickness and depth of silver particles present in the first layers of the glaze.

Decoration of vertical graphene with aerosol nanoparticles for gas sensing

NASA Astrophysics Data System (ADS)

Cui, Shumao; Guo, Xiaoru; Ren, Ren; Zhou, Guihua; Chen, Junhong

2015-08-01

A facile method was demonstrated to decorate aerosol Ag nanoparticles onto vertical graphene surfaces using a mini-arc plasma reactor. The vertical graphene was directly grown on a sensor electrode using a plasma-enhanced chemical vapor deposition (PECVD) method. The aerosol Ag nanoparticles were synthesized by a simple vapor condensation process using a mini-arc plasma source. Then, the nanoparticles were assembled on the surface of vertical graphene through the assistance of an electric field. Based on our observation, nonagglomerated Ag nanoparticles formed in the gas phase and were assembled onto vertical graphene sheets. Nanohybrids of Ag nanoparticle-decorated vertical graphene were characterized for ammonia gas detection at room temperature. The vertical graphene served as the conductance channel, and the conductance change upon exposure to ammonia was used as the sensing signal. The sensing results show that Ag nanoparticles significantly improve the sensitivity, response time, and recovery time of the sensor.

Organic memory capacitor device fabricated with Ag nanoparticles.

PubMed

Kim, Yo-Han; Jung, Sung Mok; Hu, Quanli; Kim, Yong-Sang; Yoon, Tae-Sik; Lee, Hyun Ho

2011-07-01

In this study, it is demonstrated that an organic memory structure using pentacene and citrate-stabilized silver nanoparticles (Ag NPs) as charge storage elements on dielectric SiO2 layer and silicon substrate. The Ag NPs were synthesized by thermal reduction method of silver trifluoroacetate with oleic acid. The synthesized Ag NPs were analyzed with high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) for their crystalline structure. The capacitance versus voltage (C-V) curves obtained for the Ag NPs embedded capacitor exhibited flat-band voltage shifts, which demonstrated the presence of charge storages. The citrate-capping of the Ag NPs was confirmed by ultraviolet-visible (UV-VIS) and Fourier transformed infrared (FTIR) spectroscopy. With voltage sweeping of +/-7 V, a hysteresis loop having flatband voltage shift of 7.1 V was obtained. The hysteresis loop showed a counter-clockwise direction. In addition, electrical performance test for charge storage showed more than 10,000 second charge retention time. The device with Ag NPs can be applied to an organic memory device for flexible electronics.

Effect of toxicity of Ag nanoparticles on SERS spectral variance of bacteria

NASA Astrophysics Data System (ADS)

Cui, Li; Chen, Shaode; Zhang, Kaisong

2015-02-01

Ag nanoparticles (NPs) have been extensively utilized in surface-enhanced Raman scattering (SERS) spectroscopy for bacterial identification. However, Ag NPs are toxic to bacteria. Whether such toxicity can affect SERS features of bacteria and interfere with bacterial identification is still unknown and needed to explore. Here, by carrying out a comparative study on non-toxic Au NPs with that on toxic Ag NPs, we investigated the influence of nanoparticle concentration and incubation time on bacterial SERS spectral variance, both of which were demonstrated to be closely related to the toxicity of Ag NPs. Sensitive spectral alterations were observed on Ag NPs with increase of NPs concentration or incubation time, accompanied with an obvious decrease in number of viable bacteria. In contrast, SERS spectra and viable bacterial number on Au NPs were rather constant under the same conditions. A further analysis on spectral changes demonstrated that it was cell response (i.e. metabolic activity or death) to the toxicity of Ag NPs causing spectral variance. However, biochemical responses to the toxicity of Ag were very different in different bacteria, indicating the complex toxic mechanism of Ag NPs. Ag NPs are toxic to a great variety of organisms, including bacteria, fungi, algae, protozoa etc., therefore, this work will be helpful in guiding the future application of SERS technique in various complex biological systems.

Digestive cell lysosomes as main targets for Ag accumulation and toxicity in marine mussels, Mytilus galloprovincialis, exposed to maltose-stabilised Ag nanoparticles of different sizes.

PubMed

Jimeno-Romero, A; Bilbao, E; Izagirre, U; Cajaraville, M P; Marigómez, I; Soto, M

2017-03-01

Bioavailability and toxicity of maltose-stabilised AgNPs of different sizes (20, 40 and 100 nm) in mussels were compared with bulk and aqueous forms of the metal through a two-tier experimental approach. In the first tier, mussels were exposed for 3 d to a range of concentrations (0.75, 75, 750 μg Ag/l) in the form of Ag20-Mal, Ag40-Mal, Ag100-Mal, bulk Ag and aqueous Ag (as AgNO 3 ), as well as to the concentrations of maltose used in the formulation of NPs. Mortality, bioaccumulation, tissue and cell distribution and lysosomal responses were investigated. In the second tier, mussels were exposed for 21 d to Ag20-Mal, Ag100-Mal, bulk Ag and aqueous Ag at the lowest effective concentration selected after Tier 1 (0.75 μg Ag/l), biomarkers and toxicopathic effects were investigated. Aqueous Ag was lethal within 3 d at 75 μg Ag/l; Ag NPs or bulk Ag did not produce significant mortality at 750 μg Ag/l. Ag accumulation was limited and metallothionein gene transcription was not regulated although metal accumulation occurred in digestive, brown and stomach epithelial cells and in gut lumen after exposure to AgNPs and aqueous Ag starting at low concentrations after 1 d. Electrondense particles (<10 nm) in lysosomes and residual bodies after exposure to AgNPs contained Ag and S (X-ray). Intralysosomal metal accumulation and lysosomal membrane destabilisation were enhanced after exposure to all the forms of Ag and more marked after exposure to Ag20-Mal than to larger NPs. 21 d exposure to AgNPs provoked digestive cell loss and loss of digestive gland integrity, resulting in atrophy-necrosis in digestive alveoli and oedema/hyperplasia in gills (Ag NP), vacuolisation in digestive cells (aqueous Ag) and haemocyte infiltration of connective tissue (all treatments). Intralysosomal metal accumulation, lysosomal responses and toxicopathic effects are enhanced at decreasing sizes and appear to be caused by Ag +  ions released from NPs, although the metal was not

Formation of Ag nanoparticles and enhancement of Tb3+ luminescence in Tb and Ag co-doped lithium-lanthanum-aluminosilicate glass

NASA Astrophysics Data System (ADS)

Piasecki, Patryk; Piasecki, Ashley; Pan, Zhengda; Mu, Richard; Morgan, Steven H.

2010-12-01

Tb3+ and Ag co-doped glass nano-composites were synthesized in a glass matrix Li2O-LaF3-Al2O3-SiO2 (LLAS) by a melt-quench technique. The growth of Ag nanoparticles (NPs) was controlled by a thermal annealing process. A broad absorption band peaking at about 420 nm was observed due to surface plasmon resonance (SPR) of Ag NPs. The intensity of this band grows with increasing annealing time. The transmission electron microscopic image (TEM) reveals the formation of Ag NPs in glass matrix. Photoluminescence (PL) emission and excitation spectra were measured for glass samples with different Ag concentrations and different annealing times. Plasmon enhanced Tb3+ luminescence was observed at certain excitation wavelength regions. Luminescence quenching was also observed for samples with high Ag concentration and longer annealing time. Our luminescence results suggest that there are two competitive effects, enhancement and quenching, acting on Tb3+ luminescence in the presence of Ag NPs. The enhancement of Tb3+ luminescence is mainly attributed to local field effects due to SPR. The quenching of luminescence suggests an energy transfer from Tb3+ ions to Ag NPs.

Surface decoration by Spirulina polysaccharide enhances the cellular uptake and anticancer efficacy of selenium nanoparticles

PubMed Central

Yang, Fang; Tang, Quanming; Zhong, Xueyun; Bai, Yan; Chen, Tianfeng; Zhang, Yibo; Li, Yinghua; Zheng, Wenjie

2012-01-01

A simple and solution-phase method for functionalization of selenium nanoparticles (SeNPs) with Spirulina polysaccharides (SPS) has been developed in the present study. The cellular uptake and anticancer activity of SPS-SeNPs were also evaluated. Monodisperse and homogeneous spherical SPS-SeNPs with diameters ranging from 20 nm to 50 nm were achieved under optimized conditions, which were stable in the solution phase for at least 3 months. SPS surface decoration significantly enhanced the cellular uptake and cytotoxicity of SeNPs toward several human cancer cell lines. A375 human melanoma cells were found extremely susceptible to SPS-SeNPs with half maximal (50%) inhibitory concentration value of 7.94 μM. Investigation of the underlying mechanisms revealed that SPS-SeNPs inhibited cancer cell growth through induction of apoptosis, as evidenced by an increase in sub-G1 cell population, deoxyribonucleic acid fragmentation, chromatin condensation, and phosphatidylserine translocation. Results suggest that the strategy to use SPS as a surface decorator could be an effective way to enhance the cellular uptake and anticancer efficacy of nanomaterials. SPS-SeNPs may be a potential candidate for further evaluation as a chemopreventive and chemotherapeutic agent against human cancers. PMID:22359460

Bioinspired anchoring AgNPs onto micro-nanoporous TiO2 orthopedic coatings: Trap-killing of bacteria, surface-regulated osteoblast functions and host responses.

PubMed

Jia, Zhaojun; Xiu, Peng; Li, Ming; Xu, Xuchen; Shi, Yuying; Cheng, Yan; Wei, Shicheng; Zheng, Yufeng; Xi, Tingfei; Cai, Hong; Liu, Zhongjun

2016-01-01

The therapeutic applications of silver nanoparticles (AgNPs) against biomedical device-associated infections (BAI), by local delivery, are encountered with risks of detachment, instability and nanotoxicity in physiological milieus. To firmly anchor AgNPs onto modified biomaterial surfaces through tight physicochemical interactions would potentially relieve these concerns. Herein, we present a strategy for hierarchical TiO2/Ag coating, in an attempt to endow medical titanium (Ti) with anticorrosion and antibacterial properties whilst maintaining normal biological functions. In brief, by harnessing the adhesion and reactivity of bioinspired polydopamine, silver nanoparticles were easily immobilized onto peripheral surface and incorporated into interior cavity of a micro/nanoporous TiO2 ceramic coating in situ grown from template Ti. The resulting coating protected the substrate well from corrosion and gave a sustained release of Ag(+) up to 28 d. An interesting germicidal effect, termed "trap-killing", was observed against Staphylococcus aureus strain. The multiple osteoblast responses, i.e. adherence, spreading, proliferation, and differentiation, were retained normal or promoted, via a putative surface-initiated self-regulation mechanism. After subcutaneous implantation for a month, the coated specimens elicited minimal, comparable inflammatory responses relative to the control. Moreover, this simple and safe functionalization strategy manifested a good degree of flexibility towards three-dimensional sophisticated objects. Expectedly, it can become a prospective bench to bedside solution to current challenges facing orthopedics. Copyright © 2015 Elsevier Ltd. All rights reserved.

Gold nanoparticles-decorated electrospun poly(N-vinyl-2-pyrrolidone) nanofibers with tunable size and coverage density for nanomolar detection of single and binary component dyes by surface-enhanced raman spectroscopy

NASA Astrophysics Data System (ADS)

Kurniawan, Alfin; Wang, Meng-Jiy

2017-09-01

The application of the electrospun nanomaterials to surface-enhanced Raman spectroscopy (SERS) is a rapidly evolving field which holds potential for future developments in the generation of portable plasmonic-based detection platforms. In this study, a simple approach to fabricate electrospun poly(N-vinylpyrrolidone) (PVP) mats decorated with gold nanoparticles (AuNPs) by combining electrospinning and calcination was presented. AuNPs were decorated on the fiber mat surface through electrostatic interactions between positively charged aminosilane groups and negatively charged AuNPs. The size and coverage density of AuNPs on the fiber mats could be tuned by varying the calcination temperature. Calcination of AuNPs-decorated PVP fibers at 500 °C-700 °C resulted in the uniform decoration of high density AuNPs with very narrow gaps on every single fiber, which in turn contribute to strong electromagnetic SERS enhancement. The robust free-standing AuNPs-decorated mat which calcined at 500 °C (500/AuNPs-F) exhibited high SERS activity toward cationic (methylene blue, MB) and anionic (methyl orange, MO) dyes in single and binary systems with a detection range from tens of nM to a few hundred μM. The fabricated SERS substrate demonstrated high reproducibility with the spot-to-spot variation in SERS signal intensities was ±10% and ±12% for single and binary dye systems, respectively. The determination of MB and MO in spiked river water and tap water with 500/AuNPs-F substrate gave satisfactory results in terms of the percent spike recoveries (ranging from 92.6%-96.6%) and reproducibility (%RSD values less than 15 for all samples).

Gas Sensing Analysis of Ag-Decorated Graphene for Sulfur Hexafluoride Decomposition Products Based on the Density Functional Theory

PubMed Central

Zhang, Xiaoxing; Huang, Rong; Gui, Yingang; Zeng, Hong

2016-01-01

Detection of decomposition products of sulfur hexafluoride (SF6) is one of the best ways to diagnose early latent insulation faults in gas-insulated equipment, and the occurrence of sudden accidents can be avoided effectively by finding early latent faults. Recently, functionalized graphene, a kind of gas sensing material, has been reported to show good application prospects in the gas sensor field. Therefore, calculations were performed to analyze the gas sensing properties of intrinsic graphene (Int-graphene) and functionalized graphene-based material, Ag-decorated graphene (Ag-graphene), for decomposition products of SF6, including SO2F2, SOF2, and SO2, based on density functional theory (DFT). We thoroughly investigated a series of parameters presenting gas-sensing properties of adsorbing process about gas molecule (SO2F2, SOF2, SO2) and double gas molecules (2SO2F2, 2SOF2, 2SO2) on Ag-graphene, including adsorption energy, net charge transfer, electronic state density, and the highest and lowest unoccupied molecular orbital. The results showed that the Ag atom significantly enhances the electrochemical reactivity of graphene, reflected in the change of conductivity during the adsorption process. SO2F2 and SO2 gas molecules on Ag-graphene presented chemisorption, and the adsorption strength was SO2F2 > SO2, while SOF2 absorption on Ag-graphene was physical adsorption. Thus, we concluded that Ag-graphene showed good selectivity and high sensitivity to SO2F2. The results can provide a helpful guide in exploring Ag-graphene material in experiments for monitoring the insulation status of SF6-insulated equipment based on detecting decomposition products of SF6. PMID:27809269

As-synthesis of nanostructure AgCl/Ag/MCM-41 composite

NASA Astrophysics Data System (ADS)

Sohrabnezhad, Sh.; Pourahmad, A.

2012-02-01

In this work, we present the simple synthetic route for silver chloride/silver nanoparticles (AgCl/Ag-NPs) using as-synthesis method. The structure, composition and optical properties of such material were investigated by transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (UV-vis DRS), X-ray diffraction (XRD) and FTIR. Powder X-ray diffraction showed that when AgNO 3 content is below 0.1 wt.% in synthetic gel, the guest AgCl/Ag-NPs is formed on the silica channel wall, and lower exists in the crystalline state. When AgNO 3 content exceeds this value, AgCl/Ag nanoparticles can be observed in high crystalline state. The absorption at 327 nm ascribed to the characteristic absorption of the AgCl semiconductor. Ag nanoparticles have been shown to exist in the nanocomposite at 375 nm. When AgNO 3 content is above 0.1 wt.% in synthetic gel, spectra exhibited stronger absorption at 450-700 nm that was attributed to the surface plasmonic resonance of silver nanoparticles. The obtained AgCl/Ag/MCM-41 sample exhibit enhanced photocatalytic activity for the degradation of methylene blue under visible-light irradiation.

The role of exopolymeric substances in the bioaccumulation and toxicity of Ag nanoparticles to algae

NASA Astrophysics Data System (ADS)

Zhou, Kaijun; Hu, Yi; Zhang, Luqing; Yang, Kun; Lin, Daohui

2016-09-01

Exopolymeric substances (EPS) have an important role in bioaccumulation and toxicity of nanoparticles (NPs) to algae, which warrants specific studies. The interaction of EPS with citrate and polyvinyl pyrrolidone (PVP) coated AgNPs (C-AgNPs and P-AgNPs, respectively) and its roles in bioaccumulation and toxicity of the AgNPs to Chlorella pyrenoidosa were investigated. The amino and aromatic carboxylic groups in the EPS were involved in the EPS-AgNP interactions. Compared with Ag+, C-AgNPs had comparable total bioaccumulation but greater absorption by intact algae with EPS; P-AgNPs had the smallest total bioaccumulation and were mainly adsorbed on algal surfaces. With EPS removed, the total bioaccumulations and surface adsorptions for the three Ag species decreased but the cell internalizations increased; the 96 h half growth inhibition concentrations decreased, indicating EPS alleviated the algal toxicity of Ag. The cell-internalized but not the adsorbed AgNPs could contribute to the nanotoxicity. The EPS could bind both AgNPs and Ag+, and thus inhibited the cell internalization and the nanotoxicity. However, the EPS-bound Ag on the cell surfaces would migrate along with the algae and be biologically amplified in the aquatic food chains, presenting ecological risks. These results are helpful for understanding the fate and ecological effects of NPs.

Ag/AgO Nanoparticles Grown via Time Dependent Double Mechanism in a 2D Layered Ni-PCP and Their Antibacterial Efficacy

NASA Astrophysics Data System (ADS)

Agarwal, Rashmi A.; Gupta, Neeraj K.; Singh, Rajan; Nigam, Shivansh; Ateeq, Bushra

2017-03-01

A simple synthesis route for growth of Ag/AgO nanoparticles (NPs) in large quantitative yields with narrow size distribution from a functional, non-activated, Ni (II) based highly flexible porous coordination polymer (PCP) as a template has been demonstrated. This template is a stable storage media for the NPs larger than the pore diameters of the PCP. From EPR study it was concluded that NPs were synthesized via two mechanisms i.e. acid formation and the redox activity of the framework. Size range of Ag/AgO NPs is sensitive to choice of solvent and reaction time. Direct use of Ag/AgO@Ni-PCP shows influential growth inhibition towards Escherichia coli and the pathogen Salmonella typhimurium at extremely low concentrations. The pristine template shows no cytotoxic activity, even though it contains Ni nodes in the framework.

Carbon Nanoparticles decorated with cupric oxide Nanoparticles prepared by laser ablation in liquid as an antibacterial therapeutic agent

NASA Astrophysics Data System (ADS)

Khashan, Khawla S.; Jabir, Majid S.; Abdulameer, Farah A.

2018-03-01

Carbon nanoparticles (CNPs) decorated with cupric oxide nanoparticles (CuO NPs) were prepared by laser ablation in water, and their antibacterial activity was examined. X-ray diffraction measurements demonstrated the presence of carbon phases and different CuO phases, and results were confirmed by Fourier transform infrared analysis. Energy- Dispersive spectra showed the presence of C, O, and Cu in the final product. Transmission electron micrographs revealed that the CNPs were 10-80 nm in size and spherical; after being decorated with CuO NPs, particles became 5-50 nm in size and uniform in shape. The absorption spectrum of decorated Nanoparticles indicated the appearance of a new peak at 254-264 nm in addition to the fundamental peak at 228 nm. We then examined the antibacterial activity of the decorated CNPs for both gram-negative and -positive bacteria using the agar-well-diffusion method. The mode of action was determined using acridine orange-ethidium bromide staining to detect reactive oxygen species, and bacterial morphological change was studied by scanning electron microscopy. Results showed that CNPs decorated with 43% CuO NPs had the highest antibacterial activity for gram-positive bacteria. The CNPs acted on the cytoplasmic membrane and nucleic acid of bacteria, which led to a loss of cell-wall integrity, increased cell-wall permeability, and nucleic acid damage. The results offer a novel way to synthesis Carbon nanoparticles decorated with cupric oxide nanoparticles and could use them as novel antibacterial agent in future for pharmaceutical and biomedical applications.

Synthesis of silver nanoparticles by solar irradiation of cell-free Bacillus amyloliquefaciens extracts and AgNO3.

PubMed

Wei, Xuetuan; Luo, Mingfang; Li, Wei; Yang, Liangrong; Liang, Xiangfeng; Xu, Lin; Kong, Peng; Liu, Huizhou

2012-01-01

Silver nanoparticles (AgNPs) were obtained by solar irradiation of cell-free extracts of Bacillusamyloliquefaciens and AgNO3. Light intensity, extract concentration, and NaCl addition influenced the synthesis of AgNPs. Under optimized conditions (solar intensity 70,000 lx, extract concentration 3 mg/mL, and NaCl content 2 mM), 98.23±0.06% of the Ag+ (1 mM) was reduced to AgNPs within 80 min, and the ζ-potential of AgNPs reached -70.84±0.66 mV. TEM (Transmission electron microscopy) and XRD (X-ray diffraction) analysis confirmed that circular and triangular crystalline AgNPs with mean diameter of 14.6 nm were synthesized. Since heat-inactivated extracts also mediated the formation of AgNPs, enzymatic reactions are likely not involved in AgNPs formation. A high absolute ζ-potential value of the AgNPs, possibly caused by interaction with proteins likely explains the high stability of AgNPs suspensions. AgNPs showed antimicrobial activity against Bacillussubtilis and Escherichiacoli in liquid and solid medium. Copyright © 2011 Elsevier Ltd. All rights reserved.

Surface-enhanced Raman scattering from AgNP-graphene-AgNP sandwiched nanostructures

NASA Astrophysics Data System (ADS)

Wu, Jian; Xu, Yijun; Xu, Pengyu; Pan, Zhenghui; Chen, Sheng; Shen, Qishen; Zhan, Li; Zhang, Yuegang; Ni, Weihai

2015-10-01

We developed a facile approach toward hybrid AgNP-graphene-AgNP sandwiched structures using self-organized monolayered AgNPs from wet chemical synthesis for the optimized enhancement of the Raman response of monolayer graphene. We demonstrate that the Raman scattering of graphene can be enhanced 530 fold in the hybrid structure. The Raman enhancement is sensitively dependent on the hybrid structure, incident angle, and excitation wavelength. A systematic simulation is performed, which well explains the enhancement mechanism. Our study indicates that the enhancement resulted from the plasmonic coupling between the AgNPs on the opposite sides of graphene. Our approach towards ideal substrates offers great potential to produce a ``hot surface'' for enhancing the Raman response of two-dimensional materials.We developed a facile approach toward hybrid AgNP-graphene-AgNP sandwiched structures using self-organized monolayered AgNPs from wet chemical synthesis for the optimized enhancement of the Raman response of monolayer graphene. We demonstrate that the Raman scattering of graphene can be enhanced 530 fold in the hybrid structure. The Raman enhancement is sensitively dependent on the hybrid structure, incident angle, and excitation wavelength. A systematic simulation is performed, which well explains the enhancement mechanism. Our study indicates that the enhancement resulted from the plasmonic coupling between the AgNPs on the opposite sides of graphene. Our approach towards ideal substrates offers great potential to produce a ``hot surface'' for enhancing the Raman response of two-dimensional materials. Electronic supplementary information (ESI) available: Additional SEM images, electric field enhancement profiles, Raman scattering spectra, and structure-dependent peak ratios. See DOI: 10.1039/c5nr04500b

Hollow Au-Ag Nanoparticles Labeled Immunochromatography Strip for Highly Sensitive Detection of Clenbuterol

NASA Astrophysics Data System (ADS)

Wang, Jingyun; Zhang, Lei; Huang, Youju; Dandapat, Anirban; Dai, Liwei; Zhang, Ganggang; Lu, Xuefei; Zhang, Jiawei; Lai, Weihua; Chen, Tao

2017-01-01

The probe materials play a significant role in improving the detection efficiency and sensitivity of lateral-flow immunochromatographic test strip (ICTS). Unlike conventional ICTS assay usually uses single-component, solid gold nanoparticles as labeled probes, in our present study, a bimetallic, hollow Au-Ag nanoparticles (NPs) labeled ICTS was successfully developed for the detection of clenbuterol (CLE). The hollow Au-Ag NPs with different Au/Ag mole ratio and tunable size were synthesized by varying the volume ratio of [HAuCl4]:[Ag NPs] via the galvanic replacement reaction. The surface of hollow Ag-Au NPs was functionalized with 11-mercaptoundecanoic acid (MUA) for further covalently bonded with anti-CLE monoclonal antibody. Overall size of the Au-Ag NPs, size of the holes within individual NPs and also Au/Ag mole ratio have been systematically optimized to amplify both the visual inspection signals and the quantitative data. The sensitivity of optimized hollow Au-Ag NPs probes has been achieved even as low as 2 ppb in a short time (within 15 min), which is superior over the detection performance of conventional test strip using Au NPs. The optimized hollow Au-Ag NPs labeled test strip can be used as an ideal candidate for the rapid screening of CLE in food samples.

Gracilaria lemaneiformis polysaccharide as integrin-targeting surface decorator of selenium nanoparticles to achieve enhanced anticancer efficacy.

PubMed

Jiang, Wenting; Fu, Yuanting; Yang, Fang; Yang, Yufeng; Liu, Ting; Zheng, Wenjie; Zeng, Lilan; Chen, Tianfeng

2014-08-27

The poor permeability of glioma parenchyma represents a major limit for antiglioblastoma drug delivery. Gracilaria lemaneiformis polysaccharide (GLP), which has a high binding affinity to αvβ3 integrin overexpressed in glioma cells, was employed in the present study to functionalize selenium nanoparticles (SeNPs) to achieve antiglioblastoma efficacy. GLP-SeNPs showed satisfactory size distribution, high stability, and selectivity between cancer and normal cells. In U87 glioma cell membrane, which has a high integrin expression level, GLP-SeNPs exhibited significantly higher cellular uptake than unmodified SeNPs. As expected, U87 cells exhibited a greater uptake of GLP-SeNPs than C6 cells with low integrin expression level. Furthermore, the internalization of GLP-SeNPs was inhibited by cyclo-(Arg-Gly-Asp-Phe-Lys) peptides, suggesting that cellular uptake into U87 cells and C6 cells occurred via αvβ3 integrin-mediated endocytosis. For U87 cells, the cytotoxicity of SeNPs decorated by GLP was enhanced significantly because of the induction of various apoptosis signaling pathways. Internalized GLP-SeNPs triggered intracellular reactive oxygen species downregulation. Therefore, p53, MAPKs, and AKT pathways were activated to advance cell apoptosis. These findings suggest that surface decoration of nanomaterials with GLP could be an efficient strategy for design and preparation of glioblastoma targeting nanodrugs.

Preparation and antibacterial properties of Ag@polydopamine/graphene oxide sheet nanocomposite

NASA Astrophysics Data System (ADS)

Zhou, Hao; Liu, Yunfang; Chi, Weidong; Yu, Changyuan; Yu, Yingjie

2013-10-01

Immobilization of silver nanoparticles (Ag NPs) on poly-dopamine (PDA) functionalized graphene oxide sheets (GOSs) were carried out by an easy in situ reduction method. The PDA layer was coated on the surface of the GOSs via the self-polymerization of dopamine under atmosphere condition. The PDA layer not only works as the chemisorption and reduction sites for silver ions to form Ag NPs but also stabilizes them. High-resolution transmission electron microscopy observation shows that the average size of the Ag NPs anchored on the PDA/GOS composite is about 2.8 nm. The inhibition zone diameter of the Ag@PDA/GOS nanocomposite is about 23.7 mm, whereas said diameter of the Ag NPs is only 18.5 mm. The minimum bactericidal concentration of the Ag@PDA/GOS nanocomposite is about 25 μg/ml that is only half of said concentration of the Ag NPs. The Ag@PDA/GOS nanocomposite exhibits an excellent antibacterial property.

Halloysite nanotubes with immobilized silver nanoparticles for anti-bacterial application.

PubMed

Jana, Subhra; Kondakova, Anastasiya V; Shevchenko, Svetlana N; Sheval, Eugene V; Gonchar, Kirill A; Timoshenko, Victor Yu; Vasiliev, Alexander N

2017-03-01

Halloysite nanotubes (HNTs) with immobilized silver (Ag) nanoparticles (NPs) were prepared by methods of wet chemistry and were characterized by using the transmission electron microscopy, x-ray diffraction, optical spectroscopy and experiments with E. coli bacteria in-vitro. It was found that Ag NPs with almost perfect crystalline structure and sizes from ∼9nm were mainly attached over the external surface of HNTs. The optical absorption measurement revealed a broad plasmonic resonance in the region of 400-600nm for HNTs with Ag NPs. The later samples exhibit bactericidal effect, which is more pronounced under illumination. A role of the plasmonic excitation of Ag NPs for their bioactive properties is discussed. The obtained results show that Ag NPs-decorated HNTs are promising agents for the antibacterial treatment. Copyright © 2016 Elsevier B.V. All rights reserved.

Antifungal mechanisms of ZnO and Ag nanoparticles to Sclerotinia homoeocarpa

NASA Astrophysics Data System (ADS)

Li, Junli; Sang, Hyunkyu; Guo, Huiyuan; Popko, James T.; He, Lili; White, Jason C.; Parkash Dhankher, Om; Jung, Geunhwa; Xing, Baoshan

2017-04-01

Fungicides have extensively been used to effectively combat fungal diseases on a range of plant species, but resistance to multiple active ingredients has developed in pathogens such as Sclerotinia homoeocarpa, the causal agent of dollar spot on cool-season turfgrasses. Recently, ZnO and Ag nanoparticles (NPs) have received increased attention due to their antimicrobial activities. In this study, the NPs’ toxicity and mechanisms of action were investigated as alternative antifungal agents against S. homoeocarpa isolates that varied in their resistance to demethylation inhibitor (DMI) fungicides. S. homoeocarpa isolates were treated with ZnO NPs and ZnCl2 (25-400 μg ml-1) and Ag NPs and AgNO3 (5-100 μg ml-1) to test antifungal activity of the NPs and ions. The mycelial growth of S. homoeocarpa isolates regardless of their DMI sensitivity was significantly inhibited on ZnO NPs (≥200 μg ml-1), Ag NPs (≥25 μg ml-1), Zn2+ ions (≥200 μg ml-1), and Ag+ ions (≥10 μg ml-1) amended media. Expression of stress response genes, glutathione S-transferase (Shgst1) and superoxide dismutase 2 (ShSOD2), was significantly induced in the isolates by exposure to the NPs and ions. In addition, a significant increase in the nucleic acid contents of fungal hyphae, which may be due to stress response, was observed upon treatment with Ag NPs using Raman spectroscopy. We further observed that a zinc transporter (Shzrt1) might play an important role in accumulating ZnO and Ag NPs into the cells of S. homoeocarpa due to overexpression of Shzrt1 significantly induced by ZnO or Ag NPs within 3 h of exposure. Yeast mutants complemented with Shzrt1 became more sensitive to ZnO and Ag NPs as well as Zn2+ and Ag+ ions than the control strain and resulted in increased Zn or Ag content after exposure. This is the first report of involvement of the zinc transporter in the accumulation of Zn and Ag from NP exposure in filamentous plant pathogenic fungi. Understanding the molecular

Laminarin based AgNPs using brown seaweed Turbinaria ornata and its induction of apoptosis in human retinoblastoma Y79 cancer cell lines

NASA Astrophysics Data System (ADS)

Remya, R. R.; Radhika Rajasree, S. R.; Suman, T. Y.; Aranganathan, L.; Gayathri, S.; Gobalakrishnan, M.; Karthih, M. G.

2018-03-01

Biosynthesis of nanoparticles using isolated compounds from various sources is accepting interest due to their broad array of biological activities and biocompatibility. This paper presents a simple; cost effective and green synthesis of silver nanoparticles (AgNPs) using the polysaccharide, laminarin a storage compound obtained from the brown algae Turbinaria ornata (T. ornata). Initially, the water soluble polysaccharide, laminarin was extracted, purified and analyzed using Matrix Assisted Laser Desorption Ionization Time-of-Flight Mass Spectroscopy (MALDI-TOF MS) and Proton Nuclear Magnetic Resonance (1H NMR). Further, the silver nanoparticles (AgNPs) were synthesized using the isolated laminarin and were characterized by Ultraviolet - visible (UV-vis) spectrophotometer, colour value analysis, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD) and High Resolution Transmission Electron Microscopy (HR-TEM). The free radical scavenging activities were performed and the effect of cytotoxicity against retinoblastoma Y79 cell lines was also evaluated by in vitro studies. Induction of apoptosis was evident by the percentage of cells arrested in G2/M phase using flow cytometry analysis and was further confirmed by DNA fragmentation study which identified the presence of double strand break.

Silver bioaccumulation dynamics in a freshwater invertebrate after aqueous and dietary exposures to nanosized and ionic Ag

USGS Publications Warehouse

le Croteau, Marie-Noe; Misra, Superb K.; Luoma, Samuel N.; Valsami-Jones, Eugenia

2011-01-01

We compared silver (Ag) bioavailability and toxicity to a freshwater gastropod after exposure to ionic silver (Ag+) and to Ag nanoparticles (Ag NPs) capped with citrate or with humic acid. Silver form, exposure route, and capping agent influence Ag bioaccumulation dynamics in Lymnaea stagnalis. Snails efficiently accumulated Ag from all forms after either aqueous or dietary exposure. For both exposure routes, uptake rates were faster for Ag+ than for Ag NPs. Snails efficiently assimilated Ag from Ag NPs mixed with diatoms (assimilation efficiency (AE) ranged from 49 to 58%) and from diatoms pre-exposed to Ag+ (AE of 73%). In the diet, Ag NPs damaged digestion. Snails ate less and inefficiently processed the ingested food, which adversely impacted their growth. Loss rates of Ag were faster after waterborne exposure to Ag NPs than after exposure to dissolved Ag+. Once Ag was taken up from diet, whether from Ag+ or Ag NPs, Ag was lost extremely slowly. Large Ag body concentrations are thus expected in L. stagnalis after dietborne exposures, especially to citrate-capped Ag NPs. Ingestion of Ag associated with particulate materials appears as the most important vector of uptake. Nanosilver exposure from food might trigger important environmental risks.

Tobramycin mediated silver nanospheres/graphene oxide composite for synergistic therapy of bacterial infection.

PubMed

Ullah, Sadeeq; Ahmad, Aftab; Subhan, Fazli; Jan, Aminullah; Raza, Muslim; Khan, Arif Ullah; Rahman, Aziz-Ur; Khan, Usman Ali; Tariq, Muhammad; Yuan, Qipeng

2018-06-01

Graphene-based materials have attracted a significant attention in constructing hybrid systems for drug delivery with enhanced antimicrobial activities. In our work, we demonstrated the formation of silver nanoparticles (AgNPs) on graphene oxide (GO) using tobramycin (TOB), an aminoglycoside antibiotic, as reducing and decorating agent. The TOB decorated GO AgNPs (TOB-GO-Ag) composite was used as an antibacterial agent against multi-drug resistant Gram-negative E-coli (BL21 DE3). The reversal of surface potential from -30 mV (GO) to +20 mV confirms the successful reduction of GO by TOB. Atomic force microscopy (AFM) and high-resolution transmission electron microscopic (HRTEM) analyses confirmed the formation of uniformly distributed AgNPs on the reduced GO with an approximate particle size of 5 nm. The as-synthesized nanocomposite displayed significant antibacterial activity as compared to pure AgNPs and TOB. The positively charged TOB-GO-Ag interacts with the negatively charged E. coli membrane and inhibit bacterial growth by the antibacterial actions of the released silver, GO and tobramycin from the TOB-GO-Ag composite. The significant loss of bacterial membrane potential from -52 ± 2 mV (control) to -2 ± 1 mV (treated) indicates a severe cell wall damage caused by TOB-GO-Ag composite. Furthermore, fluorescence study also demonstrated a severe membrane disruption in bacterial cells treated with TOB-GO-Ag composite as compared to pure AgNPs and GO. In conclusion, the development of such hybrid systems would help in enhancing the efficacy of available drugs and eradicating the emerging bacterial resistance. Copyright © 2018 Elsevier B.V. All rights reserved.

Limitations and possibilities of green synthesis and long-term stability of colloidal Ag nanoparticles

NASA Astrophysics Data System (ADS)

Velgosová, Oksana; Mražíková, Anna

2017-12-01

In this paper the influence of algae life cycle and the solutions pH on the green synthesis of colloidal Ag nanoparticles (AgNPs) as well as effect of different storage conditions on AgNPs long-term stability was investigated. Silver nanoparticles were biologically synthesized using extracts of Parachlorella kessleri algae cultivated 1, 2, 3 and 4 weeks. The formation of AgNPs was monitored using a UV-vis spectrophotometer and verified by TEM observation. The results confirmed formation of polyhedron and/or near polyhedron AgNPs, ranging between 5 and 60 nm in diameter. The age of algae influenced the synthesis rate and an amount of AgNPs in solution. The best results were obtained using tree weeks old algae. UV-vis analysis and TEM observation also revealed that the size and the stability of AgNPs depend on the pH of solution. AgNPs formed in solutions of higher pH (8 and 10) are polyhedron, fine, with narrow size interval and stabile. Nanoparticles formed in solutions of low pH (2, 4 and 6) started to lose their stability on 10th day of experiment, and the particle size interval was wide. The long-term stability of AgNPs can be influenced by light and temperature conditions. The most significant stability loss was observed at day light and room temperature (21°C). After 200-days significant amount of agglomerated particles settled on the bottom of the Erlenmeyer flask. AgNPs stored at dark and room temperature showed better long-term stability, weak particles agglomeration was observed. AgNPs stored at dark and at temperature 5°C showed the best long-term stability. Such AgNPs remained spherical, fine (5-20 nm), with narrow size interval and stable (no agglomeration) even after more than six months.

Bactericidal impact of Ag, ZnO and mixed AgZnO colloidal nanoparticles on H37Rv Mycobacterium tuberculosis phagocytized by THP-1 cell lines.

PubMed

Jafari, Alireza; Mosavari, Nader; Movahedzadeh, Farahnaz; Nodooshan, Saeedeh Jafari; Safarkar, Roya; Moro, Rossella; Kamalzadeh, Morteza; Majidpour, Ali; Boustanshenas, Mina; Mosavi, Tahereh

2017-09-01

The purpose of this research project was to infection of human macrophages (THP-1) cell lines by H 37 Rv strain of Mycobacterium tuberculosis (H 37 RvMTB) and find out the ratio/dilution of mixture silver (Ag NPs) and zinc oxide nanoparticles (ZnO NPs) whose ability to eliminate phagocytized bacteria compared to rifampicin. The colloidal Ag NPs and ZnO NPs were synthesized and their characteristics were evaluated. The THP-1 cell lines were infected with different concentration of H 37 RvMTB. Next, the infected cells were treated with different ratios/dilutions of Ag NPs, ZnO NPs and rifampicin. The THP-1 were lysed and were cultured in Lowenstein-Jensen agar medium, for eight weeks. The TEM and AFM images of NPs and H 37 RvMTB were supplied. It is observed that Ag NPs, 2 Ag :8 ZnO and 8 Ag :2 ZnO did not have any anti-tubercular effects on phagocytized H 37 RvMTB. Conversely, ZnO NPs somehow eliminated 18.7 × 10 4  CFU ml -1 of H 37 RvMTB in concentration of ∼ 0.468 ppm. To compare with 40 ppm of rifampicin, ∼ 0.663 ppm of 5 Ag :5 ZnO had the ability to kill of H 37 RvMTB, too. Based on previous research, ZnO NPs had strong anti-tubercular impact against H 37 RvMTB to in-vitro condition, but it was toxic in concentration of ∼ 0.468 ppm to both of THP-1 and normal lung (MRC-5) cell lines. It also seems that 5 Ag :5 ZnO is justified because in concentration of ∼ 0.663 ppm of 5 Ag :5 ZnO , phagocytized H 37 RvMTB into the THP-1 had died without any toxicity effects against THP-1 and also MRC-5 cell lines. It is obvious that the mixture of colloidal silver and zinc oxide NPs with ratio of 5 Ag :5 ZnO would be trustworthy options as anti-tubercular nano-drugs in future researches. Copyright © 2017. Published by Elsevier Ltd.

Gold Decorated Graphene for Rapid Dye Reduction and Efficient Electro Catalytic Oxidation of Ethanol

NASA Astrophysics Data System (ADS)

Siddhardha, R. S.; Kumar v, Lakshman; Kaniyoor, A.; Podila, R.; Kumar, V. S.; Venkataramaniah, K.; Ramaprabhu, S.; Rao, A.; Ramamurthy, S. S.; Clemson University Team; Sri Sathya Sai Institute of Higher Learning Team; IITMadras Team

2013-03-01

A well known disadvantage in fabrication of metal-graphene composite is the use of surfactants that strongly adsorb on the surface and reduce the performance of the catalyst. Here, we demonstrate a novel one pot synthesis of gold nanoparticles (AuNPs) by laser ablation of gold strip and simultaneous decoration of these on functionalized graphene derivatives. Not only the impregnation of AuNPs was linker free, but also the synthesis by itself was surfactant free. This resulted in in-situ decoration of pristine AuNPs on functionalized graphene derivatives. These materials were well characterized and tested for catalytic applications pertaining to dye reduction and electrooxidation. The catalytic reduction rates are 1.4 x 102 and 9.4x102 times faster for Rhodamine B and Methylene Blue dyes respectively, compared to earlier reports. The enhanced rate involves synergistic interplay of electronic relay between AuNPs and the dye, also charge transfer between the graphene system and dye. In addition, the onset potential for ethanol oxidation was found to be more negative ~ 100 mV, an indication of its promising application in direct ethanol fuel cells.

Layer-by-Layer-Assembled AuNPs-Decorated First-Generation Poly(amidoamine) Dendrimer with Reduced Graphene Oxide Core as Highly Sensitive Biosensing Platform with Controllable 3D Nanoarchitecture for Rapid Voltammetric Analysis of Ultratrace DNA Hybridization.

PubMed

Jayakumar, Kumarasamy; Camarada, María Belén; Dharuman, Venkataraman; Rajesh, Rajendiran; Venkatesan, Rengarajan; Ju, Huangxian; Maniraj, Mahalingam; Rai, Abhishek; Barman, Sudipta Roy; Wen, Yangping

2018-06-27

The structure and electrochemical properties of layer-by-layer-assembled gold nanoparticles (AuNPs)-decorated first-generation (G1) poly(amidoamine) dendrimer (PD) with reduced graphene oxide (rGO) core as a highly sensitive and label-free biosensing platform with a controllable three-dimensional (3D) nanoarchitecture for the rapid voltammetric analysis of DNA hybridization at ultratrace levels were characterized. Mercaptopropinoic acid (MPA) was self-assembled onto Au substrate, then GG1PD formed by the covalent functionalization between the amino terminals of G1PD and carboxyl terminals of rGO was covalently linked onto MPA, and finally AuNPs were decorated onto GG1PD by strong physicochemical interaction between AuNPs and -OH of rGO in GG1PD, which was characterized through different techniques and confirmed by computational calculation. This 3D controllable thin-film electrode was optimized and evaluated using [Fe(CN) 6 ] 3-/4- as the redox probe and employed to covalently immobilize thiol-functionalized single-stranded DNA as biorecognition element to form the DNA nanobiosensor, which achieved fast, ultrasensitive, and high-selective differential pulse voltammetric analysis of DNA hybridization in a linear range from 1 × 10 -6 to 1 × 10 -13 g m -1 with a low detection limit of 9.07 × 10 -14 g m -1 . This work will open a new pathway for the controllable 3D nanoarchitecture of the layer-by-layer-assembled metal nanoparticles-functionalized lower-generation PD with two-dimensional layered nanomaterials as cores that can be employed as ultrasensitive and label-free nanobiodevices for the fast diagnosis of specific genome diseases in the field of biomedicine.

Kinetic trapping through coalescence and the formation of patterned Ag-Cu nanoparticles

NASA Astrophysics Data System (ADS)

Grammatikopoulos, Panagiotis; Kioseoglou, Joseph; Galea, Antony; Vernieres, Jerome; Benelmekki, Maria; Diaz, Rosa E.; Sowwan, Mukhles

2016-05-01

In recent years, due to its inherent flexibility, magnetron-sputtering has been widely used to synthesise bi-metallic nanoparticles (NPs) via subsequent inert-gas cooling and gas-phase condensation of the sputtered atomic vapour. Utilising two separate sputter targets allows for good control over composition. Simultaneously, it involves fast kinetics and non-equilibrium processes, which can trap the nascent NPs into metastable configurations. In this study, we observed such configurations in immiscible, bi-metallic Ag-Cu NPs by scanning transmission electron microscopy (S/TEM) and electron energy-loss spectroscopy (EELS), and noticed a marked difference in the shape of NPs belonging to Ag- and Cu-rich samples. We explained the formation of Janus or Ag@Cu core/shell metastable structures on the grounds of in-flight mixed NP coalescence. We utilised molecular dynamics (MD) and Monte Carlo (MC) computer simulations to demonstrate that such configurations cannot occur as a result of nanoalloy segregation. Instead, sintering at relatively low temperatures can give rise to metastable structures, which eventually can be stabilised by subsequent quenching. Furthermore, we compared the heteroepitaxial diffusivities along various surfaces of both Ag and Cu NPs, and emphasised the differences between the sintering mechanisms of Ag- and Cu-rich NP compositions: small Cu NPs deform as coherent objects on large Ag NPs, whereas small Ag NPs dissolve into large Cu NPs, with their atoms diffusing along specific directions. Taking advantage of this observation, we propose controlled NP coalescence as a method to engineer mixed NPs of a unique, patterned core@partial-shell structure, which we refer to as a ``glass-float'' (ukidama) structure.In recent years, due to its inherent flexibility, magnetron-sputtering has been widely used to synthesise bi-metallic nanoparticles (NPs) via subsequent inert-gas cooling and gas-phase condensation of the sputtered atomic vapour. Utilising two

CVD graphene sheets electrochemically decorated with "core-shell" Co/CoO nanoparticles

NASA Astrophysics Data System (ADS)

Bayev, V. G.; Fedotova, J. A.; Kasiuk, J. V.; Vorobyova, S. A.; Sohor, A. A.; Komissarov, I. V.; Kovalchuk, N. G.; Prischepa, S. L.; Kargin, N. I.; Andrulevičius, M.; Przewoznik, J.; Kapusta, Cz.; Ivashkevich, O. A.; Tyutyunnikov, S. I.; Kolobylina, N. N.; Guryeva, P. V.

2018-05-01

The paper reports on the first successful fabrication of Co-graphene composites by electrochemical deposition of Co nanoparticles (NPs) on the sheets of twisted graphene. Characterization of the surface morphology and element mapping of twisted graphene decorated with Co NPs by transmission and scanning electron microscopy in combination with the energy-dispersive X-ray spectroscopy reveals the formation of isolated quasi-spherical oxidized Co NPs with the mean diameter 〈 d〉 ≈ 220 nm and core-shell structure. X-ray photoelectron spectroscopy indicates that the core of deposited NPs consists of metal Co while the shell is CoO. Composite Co-graphene samples containing core-shell NPs reveal an exchange bias field up to 160 Oe at 4 K as detected by vibrating sample magnetometry after the field cooling procedure.

Preparation and antibacterial performance testing of Ag nanoparticles embedded biological materials

NASA Astrophysics Data System (ADS)

Li, Xiaoyun; Gao, Guanhui; Sun, Chengjun; Zhu, Yaoyao; Qu, Lingyun; Jiang, Fenghua; Ding, Haibing

2015-03-01

In this study, we developed an environmentally friendly chemistry strategy to synthesize Ag nanoparticles (Ag-NPs) embedded biological material, powdered mussel shell (PMS). With the PMS as scaffolds and surfactant, Ag nanoparticles of controllable size dispersed uniformly on it via liquid chemical reduction approach. Morphologies and characteristics of synthesized Ag-NPs/PMS hybrids were analyzed with TEM, SEM and XPS. Antibacterial properties were investigated with Gram-positive bacteria (Arthrobacter sulfureus (A. sulfureus) YACS14, Staphylococcus aureus (S. aureus)) and Gram-negative bacteria (Vibrio anguillarum (V. anguillarum) MVM425, Escherichia coli (E. coli)). The antimicrobial results illustrated that Ag-NPs/PMS composites have antibacterial effect on both sea water and fresh water bacteria with a better effect on sea water bacteria. The degree of antibacterial effect is directly related to the amount of Ag released from Ag-NPs/PMS.

Modulation of Morphology and Optical Property of Multi-Metallic PdAuAg and PdAg Alloy Nanostructures

NASA Astrophysics Data System (ADS)

Pandey, Puran; Kunwar, Sundar; Sui, Mao; Bastola, Sushil; Lee, Jihoon

2018-05-01

In this work, the evolution of PdAg and PdAuAg alloy nanostructures is demonstrated on sapphire (0001) via the solid-state dewetting of multi-metallic thin films. Various surface configurations, size, and arrangements of bi- and tri-metallic alloy nanostructures are fabricated as a function of annealing temperature, annealing duration, film thickness, and deposition arrangements such as bi-layers (Pd/Ag), tri-layers (Pd/Au/Ag), and multi-layers (Pd/Au/Ag × 5). Specifically, the tri-layers film shows the gradual evolution of over-grown NPs, voids, wiggly nanostructures, and isolated PdAuAg alloy nanoparticles (NPs) along with the increased annealing temperature. In contrast, the multi-layers film with same thickness show the enhanced dewetting rate, which results in the formation of voids at relatively lower temperature, wider spacing, and structural regularity of alloy NPs at higher temperature. The dewetting enhancement is attributed to the increased number of interfaces and reduced individual layer thickness, which aid the inter-diffusion process at the initial stage. In addition, the time evolution of the Pd150 nm/Ag80 nm bi-layer films at constant temperature show the wiggly-connected and isolated PdAg alloy NPs. The overall evolution of alloy NPs is discussed based on the solid-state dewetting mechanism in conjunction with the diffusion, inter-diffusion, alloying, sublimation, Rayleigh instability, and surface energy minimization. Depending upon their surface morphologies, the bi- and tri-metallic alloy nanostructures exhibit the dynamic reflectance spectra, which show the formation of dipolar (above 700 nm) and quadrupolar resonance peaks ( 380 nm) and wide dips in the visible region as correlated to the localized surface plasmon resonance (LSPR) effect. An absorption dip is readily shifted from 510 to 475 nm along with the decreased average size of alloy nanostructures.

Enhancement of Ag nanoparticles concentration by prior ion implantation

NASA Astrophysics Data System (ADS)

Mu, Xiaoyu; Wang, Jun; Liu, Changlong

2017-09-01

Thermally grown SiO2 layer on Si substrates were singly or sequentially implanted with Zn or Cu and Ag ions at the same fluence of 2 × 1016/cm2. The profiles of implanted species, structure, and spatial distribution of the formed nanoparticles (NPs) have been characterized by the cross-sectional transmission electron microscope (XTEM) and Rutherford backscattering spectrometry (RBS). It is found that pre-implantation of Zn or Cu ions could suppress the self sputtering of Ag atoms during post Ag ion implantation, which gives rise to fabrication of Ag NPs with a high density. Moreover, it has also been demonstrated that the suppressing effect strongly depends on the applied energy and mobility of pre-implanted ions. The possible mechanism for the enhanced Ag NPs concentration has been discussed in combination with SRIM simulations. Both vacancy-like defects acting as the increased nucleation sites for Ag NPs and a high diffusivity of prior implanted ions in SiO2 play key roles in enhancing the deposition of Ag implants.

Water-dispersible silver nanoparticles-decorated carbon nanomaterials: synthesis and enhanced antibacterial activity

NASA Astrophysics Data System (ADS)

Dinh, Ngo Xuan; Chi, Do Thi; Lan, Nguyen Thi; Lan, Hoang; Van Tuan, Hoang; Van Quy, Nguyen; Phan, Vu Ngoc; Huy, Tran Quang; Le, Anh-Tuan

2015-04-01

In recent years, a growing number of outbreak of infectious diseases have emerged all over the world. The outbreak of re-emerging and emerging infectious diseases is a considerable burden on global economies and public health. Nano-antimicrobials have been studied as an effective solution for the prevention of infectious diseases. In this work, we demonstrated a modified photochemical approach for the preparation of carbon nanotubes-silver nanoparticles (CNTs-Ag) and graphene oxide-silver nanoparticles (GO-Ag) nanocomposites, which can be stably dispersible in aqueous solution. The formation of silver nanoparticles (Ag-NPs) on the functionalized CNTs and GO nanosheets was analyzed by X-ray diffraction, transmission electron microscopy, Raman spectroscopy and UV-Vis measurements. These analyses indicated that the average particle sizes of Ag-NPs deposited on GO/CNTs nanostructures were ~6-7 nm with nearly uniform size distribution. Moreover, these nanocomposites were found to exhibit enhanced antibacterial activity against two strains of infectious bacteria including Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria as compared to bare Ag-NPs. Our obtained studies showed a high potential of GO-Ag and CNTs-Ag nanocomposites as effective and long-term disinfection solution to eliminate infectious bacterial pathogens.

Picosecond laser fabricated Ag, Au and Ag-Au nanoparticles for detecting ammonium perchlorate using a portable Raman spectrometer

NASA Astrophysics Data System (ADS)

Byram, Chandu; Moram, Sree Sathya Bharathi; Soma, Venugopal Rao

2018-04-01

In this paper, we present the results from fabrication studies of Ag, Au, and Ag-Au alloy nanoparticles (NPs) using picosecond laser ablation technique in the presence of liquid media. The alloy formation in the NPs was confirmed from UV-Visible measurements. The shape and crystallinity of NPs were investigated by using high resolution transmission electron microscopy (HRTEM), selected area diffraction pattern (SAED) and energy dispersive spectroscopy (EDS). The SERS effect of fabricated NPs was tested with methylene blue and an explosive molecule (ammonium perchlorate) using a portable Raman spectrometer and achieved EFs of ˜106.

Effects of Ag Nanoparticles on Growth and Fat Body Proteins in Silkworms (Bombyx mori).

PubMed

Meng, Xu; Abdlli, Nouara; Wang, Niannian; Lü, Peng; Nie, Zhichao; Dong, Xin; Lu, Shuang; Chen, Keping

2017-12-01

Ag nanoparticles (AgNPs), a widely used non-antibiotic, antibacterial material, have shown toxic and other potentially harmful effects in mammals. However, the deleterious effects of AgNPs on insects are still unknown. Here, we studied the effects of AgNPs on the model invertebrate organism Bombyx mori. After feeding silkworm larvae different concentrations of AgNPs, we evaluated the changes of B. mori body weights, survival rates, and proteomic differences. The results showed that low concentrations (<400 mg/L) of AgNPs promoted the growth and cocoon weights of B. mori. Although high concentrations (≥800 mg/L) of AgNPs also improved B. mori growth, they resulted in silkworm death. An analysis of fat body proteomic differences revealed 13 significant differences in fat body protein spots, nine of which exhibited significantly downregulated expression, while four showed significantly upregulated expression. Reverse transcription-polymerase chain reaction results showed that at an AgNP concentration of 1600 mg/L, the expression levels of seven proteins were similar to the transcription levels of their corresponding genes. Our results suggest that AgNPs lowered the resistance to oxidative stress, affected cell apoptosis, and induced cell necrosis by regulating related protein metabolism and metabolic pathways in B. mori.

Synthesis of silver nanoparticles (Ag NPs) for anticancer activities (MCF 7 breast and A549 lung cell lines) of the crude extract of Syzygium aromaticum.

PubMed

Venugopal, K; Rather, H A; Rajagopal, K; Shanthi, M P; Sheriff, K; Illiyas, M; Rather, R A; Manikandan, E; Uvarajan, S; Bhaskar, M; Maaza, M

2017-02-01

In the present report, silver nanoparticles were synthesized using Piper nigrum extract for in vitro cytotoxicity efficacy against MCF-7 and HEP-2 cells. The silver nanoparticles (AgNPs) were formed within 20min and after preliminarily confirmation by UV-Visible spectroscopy (strong peak observed at ~441nm), they were characterized by using FT-IR and HR-TEM. The TEM images show spherical shape of biosynthesized AgNPs with particle size in the range 5-40nm while as compositional analysis were observed by EDAX. MTT assays were carried out for cytotoxicity of various concentrations of biosynthesized silver nanoparticles and Piper nigrum extract ranging from 10 to 100μg. The biosynthesized silver nanoparticles showed a significant anticancer activity against both MCF-7 and Hep-2 cells compared to Piper nigrum extract which was dose dependent. Our study thus revealed an excellent application of greenly synthesized silver nanoparticles using Piper nigrum. The study further suggested the potential therapeutic use of these nanoparticles in cancer study. Copyright © 2016. Published by Elsevier B.V.

Silver nanocrystal-decorated polyoxometalate single-walled nanotubes as nanoreactors for desulfurization catalysis at room temperature.

PubMed

Zhang, Hao; Xu, Xiaobin; Lin, Haifeng; Ud Din, Muhammad Aizaz; Wang, Haiqing; Wang, Xun

2017-09-14

Ultrathin nanocrystals generally provide a remarkable catalytic performance due to their high specific surface area and exposure of certain active sites. However, deactivation caused by growth and gathering limits the catalytic application of ultrathin nanocrystals. Here we report Ag nanocrystal-decorated polyoxometalate (Ag-POM) single-walled nanotubes assembled via a concise, surfactant-free soaking method as a new kind of well-defined core-sheath nanoreactor. The diameter of Ag nanocrystals inside polyoxometalate nanotubes can be controlled via simply adjusting the reactant concentration. Ag-POM provided outstanding oxidative desulfurization (ODS) catalytic performance for aromatic sulfocompounds at room temperature. It was suggested that Ag nanocrystals decorated on the inner surface played a key role in adjusting the electronic distribution and enhancing the catalytic activity. The as-prepared Ag-POM nanotubes are promising candidate catalysts with enhanced performance for practical catalytic applications in the gasoline desulfurization industry.

Interactions of aqueous Ag+ with fulvic acids: mechanisms of silver nanoparticle formation and investigation of stability.

PubMed

Adegboyega, Nathaniel F; Sharma, Virender K; Siskova, Karolina; Zbořil, Radek; Sohn, Mary; Schultz, Brian J; Banerjee, Sarbajit

2013-01-15

This study investigated the possible natural formation of silver nanoparticles (AgNPs) in Ag(+)-fulvic acid (FA) solutions under various environmentally relevant conditions (temperature, pH, and UV light). Increase in temperature (24-90 °C) and pH (6.1-9.0) of Ag(+)-Suwannee River fulvic acid (SRFA) solutions accelerated the appearance of the characteristic surface plasmon resonance (SPR) of AgNPs. The rate of AgNP formation via reduction of Ag(+) in the presence of different FAs (SRFA, Pahokee Peat fulvic acid, PPFA, Nordic lake fulvic acid, NLFA) and Suwannee River humic acid (SRHA) followed the order NLFA > SRHA > PPFA > SRFA. This order was found to be related to the free radical content of the acids, which was consistent with the proposed mechanism. The same order of AgNP growth was seen upon UV light illumination of Ag(+)-FA and Ag(+)-HA mixtures in moderately hard reconstituted water (MHRW). Stability studies of AgNPs, formed from the interactions of Ag(+)-SRFA, over a period of several months showed that these AgNPs were highly stable with SPR peak reductions of only ~15%. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements revealed bimodal particle size distributions of aged AgNPs. The stable AgNPs formed through the reduction of Ag(+) by fulvic and humic acid fractions of natural organic matter in the environment may be transported over significant distances and might also influence the overall bioavailability and ecotoxicity of AgNPs.

Modulation of Morphology and Optical Property of Multi-Metallic PdAuAg and PdAg Alloy Nanostructures.

PubMed

Pandey, Puran; Kunwar, Sundar; Sui, Mao; Bastola, Sushil; Lee, Jihoon

2018-05-16

In this work, the evolution of PdAg and PdAuAg alloy nanostructures is demonstrated on sapphire (0001) via the solid-state dewetting of multi-metallic thin films. Various surface configurations, size, and arrangements of bi- and tri-metallic alloy nanostructures are fabricated as a function of annealing temperature, annealing duration, film thickness, and deposition arrangements such as bi-layers (Pd/Ag), tri-layers (Pd/Au/Ag), and multi-layers (Pd/Au/Ag × 5). Specifically, the tri-layers film shows the gradual evolution of over-grown NPs, voids, wiggly nanostructures, and isolated PdAuAg alloy nanoparticles (NPs) along with the increased annealing temperature. In contrast, the multi-layers film with same thickness show the enhanced dewetting rate, which results in the formation of voids at relatively lower temperature, wider spacing, and structural regularity of alloy NPs at higher temperature. The dewetting enhancement is attributed to the increased number of interfaces and reduced individual layer thickness, which aid the inter-diffusion process at the initial stage. In addition, the time evolution of the Pd 150 nm /Ag 80 nm bi-layer films at constant temperature show the wiggly-connected and isolated PdAg alloy NPs. The overall evolution of alloy NPs is discussed based on the solid-state dewetting mechanism in conjunction with the diffusion, inter-diffusion, alloying, sublimation, Rayleigh instability, and surface energy minimization. Depending upon their surface morphologies, the bi- and tri-metallic alloy nanostructures exhibit the dynamic reflectance spectra, which show the formation of dipolar (above 700 nm) and quadrupolar resonance peaks (~ 380 nm) and wide dips in the visible region as correlated to the localized surface plasmon resonance (LSPR) effect. An absorption dip is readily shifted from ~ 510 to ~ 475 nm along with the decreased average size of alloy nanostructures.

Facile preparation of silver nanoparticle decorated chitosan cryogels for point-of-use water disinfection.

PubMed

Fan, Meikun; Gong, Lin; Huang, Yuting; Wang, Dongmei; Gong, Zhengjun

2018-02-01

In this study, silver nanoparticle decorated chitosan (CS/Ag NP) cryogels were fabricated through a simple freeze-drying process for point-of-use (POU) water disinfection. The CS/Ag NP cryogels showed high porosity, good mechanical properties, an excellent water absorption capability, and most importantly, an efficient bactericidal feature. The absorption capacity for water was found to be 47g/g, approximately 90% of which was recovered by simple squeezing. Three different sizes of Ag NPs were compared regarding their bactericidal capability against both Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis). Under optimum conditions, a 3 log reduction of bacteria was observed by holding the bacteria suspension (10 8 colony forming units (cfu)/mL) in the cryogels for 5min. Reduction was further increased to a 4 log when the contact time was doubled. The silver content in the cryogels was found to only be 7.5mg/g. Furthermore, the total Ag in processed water was found to only be 22μg/L, half of the safety limit set by China (<50μg/L). The bactericidal effectiveness of the material for real surface water samples was also demonstrated by treating water samples with different water quality matrices, including lake water and sewage water samples. In all three treated lake water samples, both the total bacteria and E. coli met the regulations for drinking water in China (<100cfu/mL for total bacteria and negative for E. coli). CS/Ag NP cryogels can be used for drinking water disinfection during disaster relief and in contingency water supply applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Large enhancement of UV luminescence emission of ZnO nanoparticles by coupling excitons with Ag surface plasmons

NASA Astrophysics Data System (ADS)

Kuiri, Probodh K.; Pramanik, Subhamay

2018-04-01

For an emitter based on bandgap emission, defect mediated emission has always been considered as the most important loss. Here, a novel approach which can overcome such emission loss is proposed using films of ZnO nanoparticles (NPs) on Ag NPs embedded in silica. The effects of the size of Ag NPs on the enhancement of ultra-violet (UV) photoluminescence (PL) of ZnO NPs for such a system have been studied. For the ZnO NPs without Ag NPs, two emission bands have been seen: one in the UV region and the other one in the visible region. This UV PL emission intensity has been seen to increase significantly with a drastic reduction of the visible PL emission intensity in the case of the sample containing ZnO NPs on silica embedded Ag NPs. A linear increase in UV emission with increase in the size of Ag NPs has been found. For the largest size of Ag NPs (˜10 nm, considered in the present study), the PL emission enhancement becomes about 4 times higher than that of sample without Ag NPs. The observed enhancement of the UV PL emission was caused by coupling between spontaneous emission in ZnO and surface plasmons of Ag. The larger Ag NPs provided a larger scattering cross section in coupling surface plasmons to light leading to an increase in UV emission. Thus, it is possible to convert the useless defect emission to the useful excitonic emission with a large enhancement factor.

In-situ synthesis of AgNPs in the natural/synthetic hybrid nanofibrous scaffolds: Fabrication, characterization and antimicrobial activities.

PubMed

Maharjan, Bikendra; Joshi, Mahesh Kumar; Tiwari, Arjun Prasad; Park, Chan Hee; Kim, Cheol Sang

2017-01-01

Silver nanoparticles embedded within a nanofibrous polymer matrix have significant attention in recent years as an antimicrobial wound dressing materials. Herein, we have fabricated a novel Ag-polyurethane-zein hybrid nanofibrous scaffold for wound dressing applications. AgNPs were synthesized in-situ via reduction of silver nitrate in electrospinning solution. Varying mass composition of the components showed the pronounced effect on the morphology and physicochemical properties of the composite fibers. Field-Emission Scanning Electron Microscopy (FESEM) images revealed that PU and zein with mass ratio 2:1 produced the bead-free continuous and uniformly distributed nanofibers. Fourier-transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD) and Thermogravimetric Analysis (TGA) confirmed the well interaction between component polymers. Compared to the pristine PU nanofibers, composite fibers showed enhanced tensile strength, young׳s modulus and surface wettability. The antibacterial capacity of the nanofibrous membrane was evaluated against gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacterial strains via a zone of inhibition test, and the results showed high antibacterial performance for Ag incorporated composite mat. Experimental results of cell viability assay and microscopic imaging revealed that as-fabricated scaffolds have an excellent ability for fibroblast cell adhesion, proliferation and growth. Overall, as-fabricated antibacterial natural/synthetic composite scaffold can be a promising substrate for repairing skin defects. Copyright © 2016. Published by Elsevier Ltd.

Demonstrating approaches to chemically modify the surface of Ag nanoparticles in order to influence their cytotoxicity and biodistribution after single dose acute intravenous administration.

PubMed

Pang, Chengfang; Brunelli, Andrea; Zhu, Conghui; Hristozov, Danail; Liu, Ying; Semenzin, Elena; Wang, Wenwen; Tao, Wuqun; Liang, Jingnan; Marcomini, Antonio; Chen, Chunying; Zhao, Bin

2016-01-01

With the advance in material science and the need to diversify market applications, silver nanoparticles (AgNPs) are modified by different surface coatings. However, how these surface modifications influence the effects of AgNPs on human health is still largely unknown. We have evaluated the uptake, toxicity and pharmacokinetics of AgNPs coated with citrate, polyethylene glycol, polyvinyl pyrolidone and branched polyethyleneimine (Citrate AgNPs, PEG AgNPs, PVP AgNPs and BPEI AgNPs, respectively). Our results demonstrated that the toxicity of AgNPs depends on the intracellular localization that was highly dependent on the surface charge. BPEI AgNPs (ζ potential = +46.5 mV) induced the highest cytotoxicity and DNA fragmentation in Hepa1c1c7. In addition, it showed the highest damage to the nucleus of liver cells in the exposed mice, which is associated with a high accumulation in liver tissues. The PEG AgNPs (ζ potential = -16.2 mV) showed the cytotoxicity, a long blood circulation, as well as bioaccumulation in spleen (34.33 µg/g), which suggest better biocompatibility compared to the other chemically modified AgNPs. Moreover, the adsorption ability with bovine serum albumin revealed that the PEG surface of AgNPs has an optimal biological inertia and can effectively resist opsonization or non-specific binding to protein in mice. The overall results indicated that the biodistribution of AgNPs was significantly dependent on surface chemistry: BPEI AgNPs > Citrate AgNPs = PVP AgNPs > PEG AgNPs. This toxicological data could be useful in supporting the development of safe AgNPs for consumer products and drug delivery applications.

Simple and Sensitive Colorimetric Assay for Pb2+ Based on Glutathione Protected Ag Nanoparticles by Salt Amplification.

PubMed

Chen, Zhang; Li, Huidong; Chu, Lin; Liu, Chenbin; Luo, Shenglian

2015-02-01

A simple and sensitive colorimetric assay for Pb2+ detection has been reported using glutathione protected silver nanoparticles (AgNPs) by salt amplification. The naked AgNPs aggregate under the influence of salt. Glutathione (GSH) can bind to AgNPs via Ag-S bond, helping AgNPs to against salt-induced aggregation. However, GSH binding to AgNPs can be compromised by the interaction between Pb2+ and GSH. As a result, Pb2+-mediated aggregation of AgNPs under the influence of salt is reflected by the UV-Visible spectrum, and the qualitative and quantitative detection for Pb2+ is accomplished, with the detection range 0.5-4 µM and a detection limit of 0.5 µM. At the same time, Pb2+ in real water sample is detected. Furthermore, the high selectivity and low cost of the assay means it is promising for enviromental applications.

MEMS based highly sensitive dual FET gas sensor using graphene decorated Pd-Ag alloy nanoparticles for H2 detection.

PubMed

Sharma, Bharat; Kim, Jung-Sik

2018-04-12

A low power, dual-gate field-effect transistor (FET) hydrogen gas sensor with graphene decorated Pd-Ag for hydrogen sensing applications was developed. The FET hydrogen sensor was integrated with a graphene-Pd-Ag-gate FET (GPA-FET) as hydrogen sensor coupled with Pt-gate FET as a reference sensor on a single sensor platform. The sensing gate electrode was modified with graphene by an e-spray technique followed by Pd-Ag DC/MF sputtering. Morphological and structural properties were studied by FESEM and Raman spectroscopy. FEM simulations were performed to confirm the uniform temperature control at the sensing gate electrode. The GPA-FET showed a high sensing response to hydrogen gas at the temperature of 25~254.5 °C. The as-proposed FET H 2 sensor showed the fast response time and recovery time of 16 s, 14 s, respectively at the operating temperature of 245 °C. The variation in drain current was positively related with increased working temperature and hydrogen concentration. The proposed dual-gate FET gas sensor in this study has potential applications in various fields, such as electronic noses and automobiles, owing to its low-power consumption, easy integration, good thermal stability and enhanced hydrogen sensing properties.

Fiber optic surface plasmon resonance sensor for detection of E. coli O157:H7 based on antimicrobial peptides and AgNPs-rGO.

PubMed

Zhou, Chen; Zou, Haimin; Li, Ming; Sun, Chengjun; Ren, Dongxia; Li, Yongxin

2018-06-05

A fiber optic surface plasmon resonance (FOSPR) sensor was developed for detection of Escherichia coli O157:H7 (E. coli O157:H7) in water and juice, based on antimicrobial peptides (AMP), Magainin I, as recognition elements and silver nanoparticles-reduced graphene oxide (AgNPs-rGO) nanocomposites assisted signal amplification. The uniform AgNPs-rGO was fixed on the surface of optical fiber and covered with gold film. Not only was the SPR response greatly enhanced, but also the AgNPs was prevented from being oxidized. The FOSPR showed a sensitivity of about 1.5 times higher than that fabricated only with gold film. In the assay, Magainin I, immobilized on the surface of gold film, could specifically capture E. coli O157:H7, resulting in the wavelength shift of the SPR absorption peak. Under the optimized conditions, the SPR resonance wavelength exhibited a good linear relationship with natural logarithm of the target bacteria concentration in the range of 1.0 × 10 3 to 5.0 × 10 7 cfu/mL with the detection limit of 5.0 × 10 2 cfu/mL (S/N = 3). The FOSPR sensor showed good specificity for E. coli O157:H7 detection compared to other bacteria similar to the target bacterial species. Furthermore, the FOSPR sensor was successfully applied to the detection of E. coli O157:H7 in water, fruit and vegetable juice with the satisfactory recoveries of 88-110%. This assay for E. coli O157:H7 detection possesses high sensitivity, good selectivity, reproducibility and stability. In addition, the AMP based SPR biosensing methodology could be extended to detect a wide variety of foodborne pathogens. Therefore, the versatile method might become a potential alternative tool in food analysis and early clinical diagnosis. Copyright © 2018 Elsevier B.V. All rights reserved.

Phytosynthesis of stable Au, Ag and Au-Ag alloy nanoparticles using J. Sambac leaves extract, and their enhanced antimicrobial activity in presence of organic antimicrobials

NASA Astrophysics Data System (ADS)

Yallappa, S.; Manjanna, J.; Dhananjaya, B. L.

2015-02-01

A green chemistry approach for the synthesis of Au, Ag and Au-Ag alloy nanoparticles (NPs) using the corresponding metal precursors and Jasminum sambac leaves extract as both reducing and capping media, under microwave irradiation, is reported. During the formation, as expected, the reaction mixture shows marginal decrease in pH and an increase in solution potential. The formation of NPs is evident from their surface plasmon resonance (SPR) peak observed at ∼555 nm for Au, ∼435 nm for Ag and ∼510 nm for Au-Ag alloy. The XRD pattern shows fcc structure while the FTIR spectra indicate the presence of plant residues adsorbed on these NPs. Such a bio-capping of NPs is characterized by their weight loss, ∼35% due to thermal degradation of biomass, as observed in TG analysis. The colloidal dispersion of NPs is stable for about 6 weeks. The near spherical shape of NPs (ϕ20-50 nm) is observed by FE-SEM/TEM images and EDAX gives the expected elemental composition. Furthermore, these NPs showed enhanced antimicrobial activity (∼1-4-fold increase in zone of inhibition) in combination with antimicrobials against test strains. Thus, the phytosynthesized NPs could be used as effective growth inhibitors for various microorganisms.

Ferritin Decorated PLGA/Paclitaxel Loaded Nanoparticles Endowed with an Enhanced Toxicity Toward MCF-7 Breast Tumor Cells.

PubMed

Turino, Ludmila N; Ruggiero, Maria R; Stefanìa, Rachele; Cutrin, Juan C; Aime, Silvio; Geninatti Crich, Simonetta

2017-04-19

Polylactic and glycolic acid nanoparticles (PLGA-NPs), coated with L-ferritin, are exploited for the simultaneous delivery of paclitaxel and an amphiphilic Gd based MRI contrast agent into breast cancer cells (MCF7). L-ferritin has been covalently conjugated to the external surface of PLGA-NPs exploiting NHS activated carboxylic groups. The results confirmed that nanoparticles decorated with L-ferritin have many advantages with respect to both albumin-decorated and nondecorated particles. Ferritin moieties endow PLGA-NPs with targeting capability, exploiting SCARA5 receptors overexpressed by these tumor cells, that results in an increased paclitaxel cytotoxicity. Moreover, protein coating increased nanoparticle stability, thus reducing the fast and aspecific drug release before reaching the target. The theranostic potential of the nanoparticles has been demonstrated by evaluating the signal intensity enhancement on T 1 -weighted MRI images of labeled MCF7 cells. The results were compared with that obtained with MDA cells used as negative control due to their lower SCARA5 expression.

Loading Ag nanoparticles on Cd(II) boron imidazolate framework for photocatalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Min; State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002; Zhang, De-Xiang

2016-05-15

An amine-functionalized Cd(II) boron imidazolate framework (BIF-77) with three-dimensional open structure has been successfully synthesized, which can load Ag nanoparticles (NPs) for photocatalytic degradation of methylene blue (MB). - Graphical abstract: An amine-functionalized neutral Cd(II) boron imidazolate framework can load Ag NPs and show excellent photocatalytic degradation behavious for MB. - Highlights: • Amine-functionalization. • Neutral boron imidazolate framework. • Loading Ag nanoparticles (NPs). • Photocatalytic degradation of methylene blue.

Graphene oxide-Ag nanoparticles-pyramidal silicon hybrid system for homogeneous, long-term stable and sensitive SERS activity

NASA Astrophysics Data System (ADS)

Guo, Jia; Xu, Shicai; Liu, Xiaoyun; Li, Zhe; Hu, Litao; Li, Zhen; Chen, Peixi; Ma, Yong; Jiang, Shouzhen; Ning, Tingyin

2017-02-01

In our work, few layers graphene oxide (GO) were directly synthesized on Ag nanoparticles (AgNPs) by spin-coating method to fabricate a GO-AgNPs hybrid structure on a pyramidal silicon (PSi) substrate for surface-enhanced Raman scattering (SERS). The GO-AgNPs-PSi substrate showed excellent Raman enhancement effect, the minimum detected concentration for Rhodamine 6G (R6G) can reach 10-12 M, which is one order of magnitude lower than the AgNPs-PSi substrate and two order of magnitude lower than the GO-AgNPs-flat-Si substrate. The linear fit calibration curve with error bars is presented and the value of R2 of 612 and 773 cm-1 can reach 0.986 and 0.980, respectively. The excellent linear response between the Raman intensity and R6G concentrations prove that the prepared GO-AgNPs-PSi substrates can serve as good SERS substrate for molecule detection. The maximum deviations of SERS intensities from 20 positions of the GO-AgNPs-PSi substrate are less than 8%, revealing the high homogeneity of the SERS substrate. The excellent homogeneity of the enhanced Raman signals can be attributed to well-separated pyramid arrays of PSi, the uniform morphology of AgNPs and multi-functions of GO layer. Besides, the uniform GO film can effectively protect AgNPs from oxidation and endow the hybrid system a good stability and long lifetime. This GO-AgNPs-PSi substrate may provide a new way toward practical applications for the ultrasensitive and label-free SERS detection in areas of medicine, food safety and biotechnology.

3D ZnO/Ag Surface-Enhanced Raman Scattering on Disposable and Flexible Cardboard Platforms

PubMed Central

Pimentel, Ana; Araújo, Andreia; Águas, Hugo; Martins, Rodrigo; Fortunato, Elvira

2017-01-01

In the present study, zinc oxide (ZnO) nanorods (NRs) with a hexagonal structure have been synthesized via a hydrothermal method assisted by microwave radiation, using specialized cardboard materials as substrates. Cardboard-type substrates are cost-efficient and robust paper-based platforms that can be integrated into several opto-electronic applications for medical diagnostics, analysis and/or quality control devices. This class of substrates also enables highly-sensitive Raman molecular detection, amiable to several different operational environments and target surfaces. The structural characterization of the ZnO NR arrays has been carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical measurements. The effects of the synthesis time (5–30 min) and temperature (70–130 °C) of the ZnO NR arrays decorated with silver nanoparticles (AgNPs) have been investigated in view of their application for surface-enhanced Raman scattering (SERS) molecular detection. The size and density of the ZnO NRs, as well as those of the AgNPs, are shown to play a central role in the final SERS response. A Raman enhancement factor of 7 × 105 was obtained using rhodamine 6 G (R6G) as the test analyte; a ZnO NR array was produced for only 5 min at 70 °C. This condition presents higher ZnO NR and AgNP densities, thereby increasing the total number of plasmonic “hot-spots”, their volume coverage and the number of analyte molecules that are subject to enhanced sensing.

Chitosan based polymer matrix with silver nanoparticles decorated multiwalled carbon nanotubes for catalytic reduction of 4-nitrophenol.

PubMed

Alshehri, Saad M; Almuqati, Turki; Almuqati, Naif; Al-Farraj, Eida; Alhokbany, Norah; Ahamad, Tansir

2016-10-20

A novel catalyst for the reduction of 4-nitrophenol (4-NP) was prepared using carboxyl group-functionalized multiwalled carbon nanotubes (MWCNTs), polymer matrix, and silver nanoparticles (AgNPs). The AgNPs were prepared by the reduction of silver nitrate by trisodium citrate in the MWCNTs-polymer nanocomposite; the size of the synthesized AgNPs was found to be 3nm (average diameter). The synthesized nanocomposites were characterized using several analytical techniques. Ag@MWCNTs-polymer composite in the presence of sodium borohydride (NaBH4) in aqueous solution is an effective catalyst for the reduction of 4-NP. The apparent kinetics of reduction has a pseudo-first-order kinetics, and the rate constant and catalytic activity parameter were found to be respectively 7.88×10(-3)s(-1)and 11.64s(-1)g(-1). The MWCNTs-polymer nanocomposite renders stability to AgNPs against the environment and the reaction medium, which means that the Ag@MWCNTs-polymer composite can be re-used for many catalytic cycles. Copyright © 2016 Elsevier Ltd. All rights reserved.

In-site synthesis of monodisperse, oleylamine-capped Ag nanoparticles through microemulsion approach

NASA Astrophysics Data System (ADS)

Chen, Shun; Ju, Yanyun; Guo, Yi; Xiong, Chuanxi; Dong, Lijie

2017-03-01

Ag NPs were in-site synthesized through microemulsion method by reducing silver acetate with oleylamine-mediated at 70 °C with highly monodisperse and narrow size from 10 to 20 nm. The synthesis of Ag NPs was aided by oleylamine and the role of oleylamine was researched. This in-site synthesis approach to Ag NPs was reproducibility and high yield more than 80% with stable store about 6 months.

Cerium Oxide Nanoparticles Decorated Graphene Nanosheets for Selective Detection of Dopamine.

PubMed

Nayak, Pranati; Santhosh, P N; Ramaprabhu, S

2015-07-01

The fabrication of a novel amperometric biosensor based on selective determination of dopamine (DA) using nafion coated cerium oxide nanoparticles (NPs) decorated graphene nanosheets (CeO2-HEG-nafion) as a transducer candidate is reported. Graphene was synthesized by hydrogen exfoliation technique. Decoration of CeO2NPs over graphene nanosheets was done by chemical reduction method. The electrochemical impedance spectroscopy (EIS) study shows the enhanced electron transfer kinetics of the composite compared to HEG modified and bare glassy carbon electrode (GCE). The response of the composite towards dopamine displays a lower oxidation potential of 0.23 V and a high oxidation current. The sensor exhibits linearity from 10 µM to 780 µM with a detection limit of 1 µM. In the presence of nafion, it shows excellent selectivity for coexisting interference species like Ascorbic acid (AA) and Uric acid (UA). The excellent performance of the biosensor can be attributed to large active surface area, enhanced electron transfer kinetics and high catalytic activity of the composite.

High-efficient catalytic reduction of 4-nitrophenol based on reusable Ag nanoparticles/graphene-loading loofah sponge hybrid.

PubMed

Liu, Y Y; Zhao, Y H; Zhou, Y; Guo, X L; Chen, Z T; Zhang, W J; Zhang, Y; Chen, J; Wang, Z M; Sun, L T; Zhang, T

2018-08-03

Noble metal nanoparticles (NPs) such as Au and Ag have shown many applications in the field of catalysis, sensing etc. due to their excellent photoelectric properties. But agglomeration and a low recovery rate are big problems for their applications. In this research, a novel Ag NPs/graphene (reduced graphene oxide)-loading loofah sponge (Ag NPs/RGO-LS) was synthesized through a one-step reduction method. Where the RGO is used as a nano-support with the high specific surface area and the high conductivity to prevent the agglomeration of Ag NPs and provide a conductive layer. The natural, green, low-cost and high-yield LS is designed as a macro-support to reduce the loss of Ag NPs during recycling. The as-prepared Ag NPs/RGO-LS is stable, uniform, and exhibits high efficiency and reusability in the catalytic reduction of 4-nitrophenol (4-NP) with a high rate constant of 1.893 min -1 as well as an average conversion of 98% in 6 min during five cycles. The results have not only paved the way for the wide application of Ag NPs but also provide a new road for the application of other metal NPs.

Synergistic influence of polyoxometalate surface corona towards enhancing the antibacterial performance of tyrosine-capped Ag nanoparticles

NASA Astrophysics Data System (ADS)

Daima, Hemant K.; Selvakannan, P. R.; Kandjani, Ahmad E.; Shukla, Ravi; Bhargava, Suresh K.; Bansal, Vipul

2013-12-01

We illustrate a new strategy to improve the antibacterial potential of silver nanoparticles (AgNPs) by their surface modification with the surface corona of biologically active polyoxometalates (POMs). The stable POM surface corona was achieved by utilising zwitterionic tyrosine amino acid as a pH-switchable reducing and capping agent of AgNPs. The general applicability of this approach was demonstrated by developing surface coronas of phosphotungstic acid (PTA) and phosphomolybdic acid (PMA) around AgNPs. Our investigations on Gram negative bacterium Escherichia coli demonstrate that in conjugation with AgNPs, the surface corona of POMs enhances the physical damage to the bacterial cells due to synergistic antibacterial action of AgNPs and POMs, and the ability of tyrosine-reduced AgNPs (AgNPsY) to act as an excellent carrier and stabiliser for the POMs. The further extension of this study towards Gram positive bacterium Staphylococcus albus showed a similar toxicity pattern, whereas these nanomaterials were found to be biocompatible for PC3 epithelial mammalian cells, suggesting the potential of these materials towards specific antimicrobial targeting for topical wound healing applications. The outcomes of this work show that facile tailorability of nanostructured surfaces may play a considerable role in controlling the biological activities of different nanomaterials.We illustrate a new strategy to improve the antibacterial potential of silver nanoparticles (AgNPs) by their surface modification with the surface corona of biologically active polyoxometalates (POMs). The stable POM surface corona was achieved by utilising zwitterionic tyrosine amino acid as a pH-switchable reducing and capping agent of AgNPs. The general applicability of this approach was demonstrated by developing surface coronas of phosphotungstic acid (PTA) and phosphomolybdic acid (PMA) around AgNPs. Our investigations on Gram negative bacterium Escherichia coli demonstrate that in conjugation

Biotin decorated PLGA nanoparticles containing SN-38 designed for cancer therapy.

PubMed

Mehdizadeh, Mozhdeh; Rouhani, Hasti; Sepehri, Nima; Varshochian, Reyhaneh; Ghahremani, Mohammad Hossein; Amini, Mohsen; Gharghabi, Mehdi; Ostad, Seyed Nasser; Atyabi, Fatemeh; Baharian, Azin; Dinarvand, Rassoul

2017-05-01

Active targeted chemotherapy is expected to provide more specific delivery of cytotoxic drugs to the tumor cells and hence reducing the side effects on healthy tissues. Due to the over expression of biotin receptors on cancerous cells as a result of further requirement for rapid proliferations, biotin can be a good candidate as a targeting agent. In this study, biotin decorated PLGA nanoparticles (NPs) containing SN-38 were prepared and in vitro studies were evaluated for their improved anti-cancer properties. In conclusion, biotin targeted PLGA NPs containing SN-38 showed preferential anticancer properties against tumor cells with biotin receptor over expression.

Three-dimensional nanoporous MoS2 framework decorated with Au nanoparticles for surface-enhanced Raman scattering

NASA Astrophysics Data System (ADS)

Sheng, Yingqiang; Jiang, Shouzhen; Yang, Cheng; Liu, Mei; Liu, Aihua; Zhang, Chao; Li, Zhen; Huo, Yanyan; Wang, Minghong; Man, Baoyuan

2017-08-01

The three-dimensional (3D) MoS2 decorated with Au nanoparticles (Au NPs) hybrids (3D MoS2-Au NPs) for surface-enhanced Raman scattering (SERS) sensing was demonstrated in this paper. SEM, Raman spectroscopy, TEM, SAED, EDX and XRD were performed to characterize 3D MoS2-Au NPs hybrids. Rhodamine 6G (R6G), fluorescein and gallic acid molecules were used as the probe for the SERS detection of the 3D MoS2-Au NPs hybrids. In addition, we modeled the enhancement of the electric field of MoS2-Au NPs hybrids using Finite-difference time-domain (FDTD) analysis, which can further give assistance to the mechanism understanding of the SERS activity.

Preparation of Rh/Ag bimetallic nanoparticles as effective catalyst for hydrogen generation from hydrolysis of KBH4

NASA Astrophysics Data System (ADS)

Huang, Liang; Jiao, Chengpeng; Wang, Liqiong; Huang, Zili; Liang, Feng; Liu, Simin; Wang, Yuhua; Zhang, Haijun; Zhang, Shaowei

2018-01-01

ISOBAM-104 protected Rh/Ag bimetallic nanoparticles (NPs) with average diameter less than 3.0 nm were synthesized by a co-reduction method. Ultraviolet-visible spectroscopy, transmission electron microscopy (TEM), high-resolution TEM and x-ray photoelectron spectroscopy (XPS) were employed to characterize the structure, particle size, and electronic structure of the prepared bimetallic NPs. The catalytic activities of prepared bimetallic NPs for hydrogen generation from hydrolysis of a basic KBH4 solution were evaluated in detail. The results indicated that as-prepared Rh/Ag bimetallic NPs showed a higher catalytic activity than corresponding monometallic NPs. Among all the monometallic NPs and bimetallic NPs, Rh80Ag20 bimetallic NPs exhibited the highest catalytic activity with a value of 6010 mol-H2·h-1·mol-catalyst-1 at pH = 12 and 303 K. The high catalytic activities of Rh/Ag bimetallic NPs could be attributed to presence of negatively charged Rh atoms and positively charged Ag atoms, which is supported by the results of XPS and density functional theory calculation. Based on the kinetic study, the apparent activation energy for the hydrolysis reaction of the basic KBH4 solution catalyzed by Rh80Ag20 bimetallic NPs was about 47.0 ± 3.9 kJ mol-1.

The Antimicrobial Properties of Silver Nanoparticles in Bacillus subtilis Are Mediated by Released Ag+ Ions

PubMed Central

Hsueh, Yi-Huang; Lin, Kuen-Song; Ke, Wan-Ju; Hsieh, Chien-Te; Chiang, Chao-Lung; Tzou, Dong-Ying; Liu, Shih-Tung

2015-01-01

The superior antimicrobial properties of silver nanoparticles (Ag NPs) are well-documented, but the exact mechanisms underlying Ag-NP microbial toxicity remain the subject of intense debate. Here, we show that Ag-NP concentrations as low as 10 ppm exert significant toxicity against Bacillus subtilis, a beneficial bacterium ubiquitous in the soil. Growth arrest and chromosomal DNA degradation were observed, and flow cytometric quantification of propidium iodide (PI) staining also revealed that Ag-NP concentrations of 25 ppm and above increased membrane permeability. RedoxSensor content analysis and Phag-GFP expression analysis further indicated that reductase activity and cytosolic protein expression decreased in B. subtilis cells treated with 10–50 ppm of Ag NPs. We conducted X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses to directly clarify the valence and fine structure of Ag atoms in B. subtilis cells placed in contact with Ag NPs. The results confirmed the Ag species in Ag NP-treated B. subtilis cells as Ag2O, indicating that Ag-NP toxicity is likely mediated by released Ag+ ions from Ag NPs, which penetrate bacterial cells and are subsequently oxidized intracellularly to Ag2O. These findings provide conclusive evidence for the role of Ag+ ions in Ag-NP microbial toxicity, and suggest that the impact of inappropriately disposed Ag NPs to soil and water ecosystems may warrant further investigation. PMID:26669836

Speciation and Lability of Ag-, AgCl- and Ag2S-Nanoparticles in Soil Determined by X-ray Absorption Spectroscopy and Diffusive Gradients in Thin Films

EPA Science Inventory

Long-term speciation and lability of silver (Ag-), silver chloride (AgCl-) and silver sulfide nanoparticles (Ag₂S-NPs) in soil were studied by X-ray absorption spectroscopy (XAS), and newly developed "nano" Diffusive Gradients in Thin Films (DGT) devices. These nano-D...

Monocrystalline solar cells performance coated by silver nanoparticles: Effect of NPs sizes from point of view Mie theory

NASA Astrophysics Data System (ADS)

Elnoby, Rasha M.; Mourad, M. Hussein; Elnaby, Salah L. Hassab; Abou Kana, Maram T. H.

2018-05-01

Solar based cells coated by nanoparticles (NPs) acknowledge potential utilizing as a part of photovoltaic innovation. The acquired silicon solar cells (Si-SCs) coated with different sizes of silver nanoparticles (Ag NPs) as well as uncoated were fabricated in our lab. The sizes and optical properties of prepared NPs were characterized by spectroscopic techniques and Mie theory respectively. The reflectivity of Si-SCs showed reduction of this property as the size of NPs increased. Electrical properties as open circuit current, fill factor and output power density were assessed and discussed depending on point of view of Mie theory for the optical properties of NPs. Also, photostabilities of SCs were assessed using diode laser of wavelength 450 nm and power 300 mW. Coated SCs with the largest Ag NPs size showed the highest Photostability due to its highest scattering efficiency according to Mie theory concept.

Third-order optical nonlinearity studies of bilayer Au/Ag metallic films

NASA Astrophysics Data System (ADS)

Mezher, M. H.; Chong, W. Y.; Zakaria, R.

2016-05-01

This paper presents nonlinear optical studies of bilayer metallic films of gold (Au) and silver (Ag) on glass substrate prepared using electron beam evaporation. The preparation of Au and Ag nanoparticles (NPs) on the substrate involved the use of electron beam deposition, then thermal annealing at 600 °C and 270 °C, respectively, to produce a randomly distributed layer of Au and a layer of Ag NPs. Observation of field-effect scanning electron microscope images indicated the size of the NPs. Details of the optical properties related to peak absorption of surface plasmon resonance of the nanoparticle were revealed by use of UV-Vis spectroscopy. The Z-scan technique was used to measure the nonlinear absorption and nonlinear refraction of the fabricated NP layers. The third-order nonlinear refractive index coefficients for Au and Ag are (-9.34 and  -1.61)  ×  10-11 cm2 W-1 given lower n 2, in comparison with bilayer (Au and Ag) NPs at  -1.24  ×  10-10 cm2 W-1. The results show bilayer NPs have higher refractive index coefficients thus enhance the nonlinearity effects.

Colloidal lithography with electrochemical nickel deposition as a unique method for improved silver decorated nanocavities in SERS applications

NASA Astrophysics Data System (ADS)

Petruš, Ondrej; Oriňak, Andrej; Oriňaková, Renáta; Orságová Králová, Zuzana; Múdra, Erika; Kupková, Miriam; Kovaľ, Karol

2017-11-01

Two types of metallised nanocavities (single and hybrid) were fabricated by colloid lithography followed by electrochemical deposition of Ni and subsequently Ag layers. Introductory Ni deposition step iniciates more homogenous decoration of nanocavities with Ag nanoparticles. Silver nanocavity decoration has been so performed with lower nucleation rate and with Ag nanoparticles homogeinity increase. By this, two step Ni and Ag deposition trough polystyrene nanospheres (100, 300, 500, 700, 900 nm), the various Ag surfaces were obtained. Ni layer formation in the first step of deposition enabled more precise controlling of Ag film deposition and thus final Ag surface morphology. Prepared substrates were tested as active surfaces in SERS application. The best SERS signal enhancement was observed at 500 nm Ag nanocavities with normalised thickness Ni layer ∼0.5. Enhancement factor has been established at value 1.078 × 1010; time stability was determined within 13 weeks; charge distribution at nanocavity Ag surfaces as well as reflection spectra were calculated by FDTD method. Newly prepared nanocavity surface can be applied in SERS analysis, predominantly.

Synergistic influence of polyoxometalate surface corona towards enhancing the antibacterial performance of tyrosine-capped Ag nanoparticles.

PubMed

Daima, Hemant K; Selvakannan, P R; Kandjani, Ahmad E; Shukla, Ravi; Bhargava, Suresh K; Bansal, Vipul

2014-01-21

We illustrate a new strategy to improve the antibacterial potential of silver nanoparticles (AgNPs) by their surface modification with the surface corona of biologically active polyoxometalates (POMs). The stable POM surface corona was achieved by utilising zwitterionic tyrosine amino acid as a pH-switchable reducing and capping agent of AgNPs. The general applicability of this approach was demonstrated by developing surface coronas of phosphotungstic acid (PTA) and phosphomolybdic acid (PMA) around AgNPs. Our investigations on Gram negative bacterium Escherichia coli demonstrate that in conjugation with AgNPs, the surface corona of POMs enhances the physical damage to the bacterial cells due to synergistic antibacterial action of AgNPs and POMs, and the ability of tyrosine-reduced AgNPs (AgNPs(Y)) to act as an excellent carrier and stabiliser for the POMs. The further extension of this study towards Gram positive bacterium Staphylococcus albus showed a similar toxicity pattern, whereas these nanomaterials were found to be biocompatible for PC3 epithelial mammalian cells, suggesting the potential of these materials towards specific antimicrobial targeting for topical wound healing applications. The outcomes of this work show that facile tailorability of nanostructured surfaces may play a considerable role in controlling the biological activities of different nanomaterials.

Size-dependent melting modes and behaviors of Ag nanoparticles: a molecular dynamics study

NASA Astrophysics Data System (ADS)

Liang, Tianshou; Zhou, Dejian; Wu, Zhaohua; Shi, Pengpeng

2017-12-01

The size-dependent melting behaviors and mechanisms of Ag nanoparticles (NPs) with diameters of 3.5-16 nm were investigated by molecular dynamics (MD). Two distinct melting modes, non-premelting and premelting with transition ranges of about 7-8 nm, for Ag NPs were demonstrated via the evolution of distribution and transition of atomic physical states during annealing. The small Ag NPs (3.5-7 nm) melt abruptly without a stable liquid shell before the melting point, which is characterized as non-premelting. A solid-solid crystal transformation is conducted through the migration of adatoms on the surface of Ag NPs with diameters of 3.5-6 nm before the initial melting, which is mainly responsible for slightly increasing the melting point of Ag NPs. On the other hand, surface premelting of Ag NPs with diameters of 8-16 nm propagates from the outer shell to the inner core with initial anisotropy and late isotropy as the temperature increases, and the close-packed facets {111} melt by a side-consumed way which is responsible for facets {111} melting in advance relative to the crystallographic plane {111}. Once a stable liquid shell is formed, its size-independent minimum thickness is obtained, and a three-layer structure of atomic physical states is set up. Lastly, the theory of point defect-pair (vacancy-interstitial) severing as the mechanism of formation and movement of the solid-liquid interface was also confirmed. Our study provides a basic understanding and theoretical guidance for the research, production and application of Ag NPs.

Biosynthesis and Characterization of AgNPs–Silk/PVA Film for Potential Packaging Application

PubMed Central

Tao, Gang; Cai, Rui; Wang, Yejing; Song, Kai; Guo, Pengchao; Zhao, Ping; Zuo, Hua; He, Huawei

2017-01-01

Bionanocomposite packaging materials have a bright future for a broad range of applications in the food and biomedical industries. Antimicrobial packaging is one of the bionanocomposite packaging materials. Silver nanoparticle (AgNP) is one of the most attractive antimicrobial agents for its broad spectrum of antimicrobial activity against microorganisms. However, the traditional method of preparing AgNPs-functionalized packaging material is cumbersome and not environmentally friendly. To develop an efficient and convenient biosynthesis method to prepare AgNPs-modified bionanocomposite material for packaging applications, we synthesized AgNPs in situ in a silk fibroin solution via the reduction of Ag+ by the tyrosine residue of fibroin, and then prepared AgNPs–silk/poly(vinyl alcohol) (PVA) composite film by blending with PVA. AgNPs were synthesized evenly on the surface or embedded in the interior of silk/PVA film. The prepared AgNPs–silk/PVA film exhibited excellent mechanical performance and stability, as well as good antibacterial activity against both Gram-negative and Gram-positive bacteria. AgNPs–silk/PVA film offers more choices to be potentially applied in the active packaging field. PMID:28773026

Antitumor Activity of Alloy and Core-Shell-Type Bimetallic AgAu Nanoparticles

NASA Astrophysics Data System (ADS)

Shmarakov, Igor; Mukha, Iuliia; Vityuk, Nadiia; Borschovetska, Vira; Zhyshchynska, Nelya; Grodzyuk, Galyna; Eremenko, Anna

2017-05-01

Nanoparticles (NPs) of noble metals, namely gold and silver, remain promising anticancer agents capable of enhancing current surgery- and chemotherapeutic-based approaches in cancer treatment. Bimetallic AgAu composition can be used as a more effective agent due to the synergetic effect. Among the physicochemical parameters affecting gold and silver nanoparticle biological activity, a primary concern relates to their size, shape, composition, charge, etc. However, the impact of metal components/composition as well as metal topological distribution within NPs is incompletely characterized and remains to be further elucidated and clarified. In the present work, we tested a series of colloidal solutions of AgAu NPs of alloy and core-shell type for an antitumor activity depending on metal molar ratios (Ag:Au = 1:1; 1:3; 3:1) and topological distribution of gold and silver within NPs (AucoreAgshell; AgcoreAushell). The efficacy at which an administration of the gold and silver NPs inhibits mouse Lewis lung carcinoma (LLC) growth in vivo was compared. The data suggest that in vivo antitumor activity of the studied NPs strongly depends on gold and silver interaction arising from their ordered topological distribution. NPs with Ag core covered by Au shell were the most effective among the NPs tested towards LLC tumor growth and metastasizing inhibition. Our data show that among the NPs tested in this study, AgcoreAushell NPs may serve as a suitable anticancerous prototype.

High-value utilization of lignin to synthesize Ag nanoparticles with detection capacity for Hg²⁺.

PubMed

Shen, Zuguang; Luo, Yuqiong; Wang, Qun; Wang, Xiaoying; Sun, Runcang

2014-09-24

This study reports the rapid preparation of silver nanoparticles (AgNPs) from Tollens' reagent under microwave irradiation. In the synthesis, lignin with reducing groups and spatial three-dimensional structure was used as reducing and stabilizing agents without other chemical reagents, and the effects of the ratio of lignin to Ag(+), reaction temperature, and heating time on the synthesis of AgNPs were investigated. The obtained AgNPs were further characterized by UV-vis, Malvern particle size, TEM, XRD, and XPS analyses. The structural changes of lignin before and after reaction were also studied by FT-IR, (1)H NMR, (13)C NMR, and GC-MS. The results revealed that the obtained AgNPs were mostly spherical with diameters of around 24 nm. The optimum reaction conditions were a ratio 50 mg of lignin to 0.3 mM of Ag(+), a microwave irradiation temperature of 60 °C, and a heating time of 10 min. Moreover, AgNPs redispersed well in water and ethanol after centrifugation for the removal of lignin. During the formation of AgNPs, lignin was oxidized, and the side chains of lignin were partly disrupted into small molecules, such as hydrocarbon and alcohol. The resultant lignin-AgNPs showed highly selective sensing detection for Hg(2+), and the color of the lignin-AgNP solution containing Hg(2+) decreased gradually with increasing amounts of Hg(2+) within seconds, but the other 19 metal ions had little effect on the color and surface plasmon absorption band of the lignin-AgNPs. Also, there was a linear relationship between the absorbance and Hg(2+) concentration, with a limit of detection concentration of 23 nM. This study provides not only a new way to take advantage of agricultural and forestry residues, but also a green and rapid method for the synthesis of AgNPs to detect the toxic ion Hg(2+) selectively and sensitively.

Fabrication of high aspect ratio nanogrid transparent electrodes via capillary assembly of Ag nanoparticles

NASA Astrophysics Data System (ADS)

Kang, Juhoon; Park, Chang-Goo; Lee, Su-Han; Cho, Changsoon; Choi, Dae-Geun; Lee, Jung-Yong

2016-05-01

In this report, we describe the fabrication of periodic Ag nanogrid electrodes by capillary assembly of silver nanoparticles (AgNPs) along patterned nanogrid templates. By assembling the AgNPs into these high-aspect-ratio nanogrid patterns, we can obtain high-aspect-ratio nanogratings, which can overcome the inherent trade-off between the optical transmittance and the sheet resistance of transparent electrodes. The junction resistance between the AgNPs is effectively reduced by photochemical welding and post-annealing. The fabricated high-aspect-ratio nanogrid structure with a line width of 150 nm and a height of 450 nm has a sheet resistance of 15.2 Ω sq-1 and an optical transmittance of 85.4%.In this report, we describe the fabrication of periodic Ag nanogrid electrodes by capillary assembly of silver nanoparticles (AgNPs) along patterned nanogrid templates. By assembling the AgNPs into these high-aspect-ratio nanogrid patterns, we can obtain high-aspect-ratio nanogratings, which can overcome the inherent trade-off between the optical transmittance and the sheet resistance of transparent electrodes. The junction resistance between the AgNPs is effectively reduced by photochemical welding and post-annealing. The fabricated high-aspect-ratio nanogrid structure with a line width of 150 nm and a height of 450 nm has a sheet resistance of 15.2 Ω sq-1 and an optical transmittance of 85.4%. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01896c

Immunomodulatory of selenium nano-particles decorated by sulfated Ganoderma lucidum polysaccharides.

PubMed

Wang, Jianguo; Zhang, Yifeng; Yuan, Yahong; Yue, Tianli

2014-06-01

In this study, we employed a one-step method to prepare selenium nanoparticles (SeNPs) decorated by the water-soluble derivative of Ganoderma lucidum polysaccharides (SPS). The SeNPs-SPS complexes were stable, and the diameter of the SeNPs was homogeneous at around 25 nm. We investigated the anti-inflammatory activity of SeNPs-SPS against murine Raw 264.7 macrophage cells induced by LPS. SeNPs-SPS were found to significantly inhibit LPS-stimulated nitric oxide (NO) production against Raw 264.7 macrophages. RT-PCR results reveal the down-regulation of mRNA gene expressions for pro-inflammatory cytokines, including inducible NO synthase (iNOS), interleukin (IL)-1 and TNF-α in a dose-dependent manner. However, the anti-inflammation cytokine IL-10 was markedly increased. In the NF-κB signal pathway, SeNPs-SPS significantly inhibited the phosphorylation of Iκ-Bα. Similar results were observed for inhibition of the phosphorylation of JNK1/2 and p38 mitogen-activated protein kinase(MAPKs), whereas ERK1/2 MAPK was not apparently affected by SeNPs-SPS. All of these results suggest that SeNPs-SPS complexes have anti-inflammatory potential modulating pro-/anti-inflammation cytokine secretion profiles, and that the mechanism is partially due to inhibition of activations of NF-κB, JNK1/2 and p38 MAPKs. Copyright © 2014 Elsevier Ltd. All rights reserved.

Ameliorative role of nano-ceria against amine coated Ag-NP induced toxicity in Labeo rohita

NASA Astrophysics Data System (ADS)

Khan, Muhammad Saleem; Qureshi, Naureen Aziz; Jabeen, Farhat

2018-03-01

Silver nanoparticles (Ag-NPs) and its byproducts can spread pollution in aquatic habitat. Liver and gills are key target for toxicity. Oxidative stress, tissue alterations, and hemotoxicity are assumed to be associated with Ag-NPs in target animals. Cerium oxide nanoparticles (nano-ceria) show antioxidant potential in scavenging the free radicals generated in Ag-NP-induced oxidative stress. We determined ameliorated role of nano-ceria against Ag-NP-induced toxicity in fresh water Labeo rohita (L. rohita). Four groups were used in study including control, nano-ceria, Ag-NPs, and Ag-NPs + nano-ceria. Ag-NPs (30 mg l-1) and nano-ceria (50 µg kg-1) were given through water and prepared feed, respectively. The samples were taken after 28 days. Results demonstrated that pre-treatment of nano-ceria recovered L. rohita from Ag-NP-induced toxicity and oxidative stress. Nano-ceria pre-treatment actively mimics the activity of GST, GSH, CAT, and SOD. Furthermore, Ag-NPs' treatment caused severe inflammation and necrosis in hepatic parenchyma which leaded to congestion of blood in hepatic tissues. Accumulation of a yellow pigment in hepatic tissue was also seen due to necrosis of affected cells. In nano-ceria pre-treatment, there was no congestion in hepatic tissue. Vacuolization of cells and necrosis in some area was recorded in nano-ceria pre-treated group, but the gill and hepatic tissue showed improvement against Ag-NP-induced damage. Nano-ceria pre-treatment also improved hematological parameters in Ag-NP-treated fish. This study concluded that Ag-NP-induced toxicity in treated fish and pre-treatment of nano-ceria show ameliorative role.

Synthesis, characterization and multifunctional properties of plasmonic Ag-TiO2 nanocomposites

NASA Astrophysics Data System (ADS)

Prakash, Jai; Kumar, Promod; Harris, R. A.; Swart, Chantel; Neethling, J. H.; Janse van Vuuren, A.; Swart, H. C.

2016-09-01

We report on the synthesis of multifunctional Ag-TiO2 nanocomposites and their optical, physio-chemical, surface enhanced Raman scattering (SERS) and antibacterial properties. A series of Ag-TiO2 nanocomposites were synthesized by sol-gel technique and characterized by x-ray diffraction, scanning and transmission electron microscopy, energy-dispersed x-ray analysis, photoluminescence, UV-vis, x-ray photoelectron and Raman spectroscopy and Brunauer-Emmett-Teller method. The Ag nanoparticles (NPs) (7-20 nm) were found to be uniformly distributed around and strongly attached to TiO2 NPs. The novel optical responses of the nanocomposites are due to the strong electric field from the localized surface plasmon (LSP) excitation of the Ag NPs and decreased recombination of photo-induced electrons and holes at Ag-TiO2 interface providing potential materials for photocatalysis. The nanocomposites show enhancement in the SERS signals of methyl orange (MO) molecules with increasing Ag content attributed to the long-range electromagnetic enhancement from the excited LSP of the Ag NPs. To further understand the SERS activity, molecular mechanics and molecular dynamics simulations were used to study the geometries and SERS enhancement of MO adsorbed onto Ag-TiO2 respectively. Simulation results indicate that number of ligands (MO) that adsorb onto the Ag NPs as well as binding energy per ligand increases with increasing NP density and molecule-to-surface orientation is mainly flat resulting in strong bond strength between MO and Ag NP surface and enhanced SERS signals. The antimicrobial activity of the Ag-TiO2 nanocomposites was tested against the bacterium Staphylococcus aureus and enhanced antibacterial effect was observed with increasing Ag content explained by contact killing action mechanism. These results foresee promising applications of the plasmonic metal-semiconductor based nano-biocomposites for both chemical and biological samples.

Two-dimensional ZnO ultrathin nanosheets decorated with Au nanoparticles for effective photocatalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Jin; You, Ning; Yu, Zhe

Two-dimensional (2D) materials, especially the inorganic 2D nanosheets (NSs), are of particular interest due to their unique structural and electronic properties, which are favorable for photoelectronic applications such as photocatalysis. Here, we design and fabricate the ultrathin 2D ZnO NSs decorated with Au nanoparticles (AuNPs), though molecular modelling 2D hydrothermal growth and followed by surface modification are used as an effective photocatalyst for photocatalytic organic dye degradation and hydrogen production. The ultrathin 2D nature enables ultrahigh atom ratio near surface to proliferate the active sites, and the Au plasmon plays a promoting role in the visible-light absorption and photogenerated chargemore » separation, thus integrating the synergistic benefits to boost the redox reactions at catalyst/electrolyte interface. The AuNPs-decorated ZnO NSs yield the impressive photocatalytic activities such as the dye degradation rate constant of 7.69 × 10{sup −2} min{sup −1} and the hydrogen production rate of 350 μmol h{sup −1} g{sup −1}.« less

Graphene-supported Ag-based core-shell nanoparticles for hydrogen generation in hydrolysis of ammonia borane and methylamine borane.

PubMed

Yang, Lan; Luo, Wei; Cheng, Gongzhen

2013-08-28

Well-dispersed magnetically recyclable core-shell Ag@M (M = Co, Ni, Fe) nanoparticles (NPs) supported on graphene have been synthesized via a facile in situ one-step procedure, using methylamine borane (MeAB) as a reducing agent under ambient condition. Their catalytic activity toward hydrolysis of ammonia borane (AB) were studied. Although the Ag@Fe/graphene NPs are almost inactive, the as-prepared Ag@Co/graphene NPs are the most reactive catalysts, followed by Ag@Ni/graphene NPs. Compared with AB and NaBH4, the as-synthesized Ag@Co/graphene catalysts which reduced by MeAB exert the highest catalytic activity. Additionally, the Ag@Co NPs supported on graphene exhibit higher catalytic activity than the catalysts with other conventional supports, such as the SiO2, carbon black, and γ-Al2O3. The as-synthesized Ag@Co/graphene NPs exert satisfied catalytic activity, with the turnover frequency (TOF) value of 102.4 (mol H2 min(-1) (mol Ag)(-1)), and the activation energy Ea value of 20.03 kJ/mol. Furthermore, the as-synthesized Ag@Co/graphene NPs show good recyclability and magnetically reusability for the hydrolytic dehydrogenation of AB and MeAB, which make the practical reusing application of the catalysts more convenient. Moreover, this simple synthetic method indicates that MeAB could be used as not only a potential hydrogen storage material but also an efficient reducing agent. It can be easily extended to facile preparation of other graphene supported metal NPs.

Mildly reduced graphene oxide-Ag nanoparticle hybrid films for surface-enhanced Raman scattering

PubMed Central

2012-01-01

Large-area mildly reduced graphene oxide (MR-GO) monolayer films were self-assembled on SiO2/Si surfaces via an amidation reaction strategy. With the MR-GO as templates, MR-GO-Ag nanoparticle (MR-GO-Ag NP) hybrid films were synthesized by immersing the MR-GO monolayer into a silver salt solution with sodium citrate as a reducing agent under UV illumination. SEM image indicated that Ag NPs with small interparticle gap are uniformly distributed on the MR-GO monolayer. Raman spectra demonstrated that the MR-GO monolayer beneath the Ag NPs can effectively quench the fluorescence signal emitted from the Ag films and dye molecules under laser excitation, resulting in a chemical enhancement (CM). The Ag NPs with narrow gap provided numerous hot spots, which are closely related with electromagnetic mechanism (EM), and were believed to remarkably enhance the Raman signal of the molecules. Due to the co-contribution of the CM and EM effects as well as the coordination mechanism between the MR-GO and Ag NPs, the MR-GO-Ag NP hybrid films showed more excellent Raman signal enhancement performance than that of either Ag films or MR-GO monolayer alone. This will further enrich the application of surface-enhanced Raman scattering in molecule detection. PMID:22471923

Synthesis of Metal Nanoparticle-decorated Carbon Nanotubes under Ambient Conditions

NASA Technical Reports Server (NTRS)

Lin, Yi; Watson, Kent A.; Ghose, Sayata; Smith, Joseph G.; Connell, John W.

2008-01-01

This viewgraph presentation reviews the production of Metal Nanoparticle-decorated carbon Nanotubes. Multi-walled carbon nanotubes (MWCNTs) were efficiently decorated with metal nanoparticles (e.g. Ag, Pt, etc.) using the corresponding metal acetate in a simple mixing process without the need of chemical reagents or further processing. The conversion of acetate compounds to the corresponding metal reached over 90%, forming nanoparticles with average diameters less than 10 nm under certain conditions. The process was readily scalable allowing for the convenient preparation of multi-gram quantities of metal nanoparticle-decorated MWCNTs in a matter of a few minutes. These materials are under evaluation for a variety of electrical and catalytic applications. The preparation and characterization of these materials will be presented. The microscopic views of the processed MWCNTs are shown

Role of catalytic protein and stabilising agents in the transformation of Ag ions to nanoparticles by Pseudomonas aeruginosa.

PubMed

Ali, Jafar; Hameed, Abdul; Ahmed, Safia; Ali, Muhammad Ishtiaq; Zainab, Shama; Ali, Naeem

2016-10-01

Biological routes of synthesising metal nanoparticles (NPs) using microbes have been gaining much attention due to their low toxicity and eco-friendly nature. Pseudomonas aeruginosa JP2 isolated from metal contaminated soil was evaluated towards extracellular synthesis of silver NPs (AgNPs). Cell-free extract (24 h) of the bacterial isolate was reacted with AgNO 3 for 24 h in order to fabricate AgNPs. Preliminary observations were recorded in terms of colour change of the reaction mixture from yellow to greyish black. UV-visible spectroscopy of the reaction mixture has shown a progressive increase in optical densities that correspond to peaks near 430 nm, depicting reduction of ionic silver (Ag + ) to atomic silver (Ag 0 ) thereby synthesising NPs. X-ray diffraction spectra exhibited the 2θ values to be 38.4577° confirming the crystalline and spherical nature of NPs [9.6 - 26.7 (Ave. = 17.2 nm)]. Transmission electron microscopy finally confirmed the size of the particles varying from 5 to 60 nm. Moreover, rhamnolipids and proteins were identified as stabilising molecules for the AgNPs through Fourier transform-infrared spectroscopy. Characterisation of bacterial crude and purified protein fractions confirmed the involvement of nitrate reductase (molecular weight 66 kDa and specific activity = 3.8 U/mg) in the Synthesis of AgNPs.

Synthesis, characterization, and thermal stability of SiO2/TiO2/CR-Ag multilayered nanostructures

NASA Astrophysics Data System (ADS)

Díaz, Gabriela; Chang, Yao-Jen; Philipossian, Ara

2018-06-01

The controllable synthesis and characterization of novel thermally stable silver-based particles are described. The experimental approach involves the design of thermally stable nanostructures by the deposition of an interfacial thick, active titania layer between the primary substrate (SiO2 particles) and the metal nanoparticles (Ag NPs), as well as the doping of Ag nanoparticles with an organic molecule (Congo Red, CR). The nanostructured particles were composed of a 330-nm silica core capped by a granular titania layer (10 to 13 nm in thickness), along with monodisperse 5 to 30 nm CR-Ag NPs deposited on top. The titania-coated support (SiO2/TiO2 particles) was shown to be chemically and thermally stable and promoted the nucleation and anchoring of CR-Ag NPs, which prevented the sintering of CR-Ag NPs when the structure was exposed to high temperatures. The thermal stability of the silver composites was examined by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). Larger than 10 nm CR-Ag NPs were thermally stable up to 300 °C. Such temperature was high enough to destabilize the CR-Ag NPs due to the melting point of the CR. On the other hand, smaller than 10 nm Ag NPs were stable at temperatures up to 500 °C because of the strong metal-metal oxide binding energy. Energy dispersion X-ray spectroscopy (EDS) was carried out to qualitatively analyze the chemical stability of the structure at different temperatures which confirmed the stability of the structure and the existence of silver NPs at temperatures up to 500 °C.

Core-shell AgSiO2-protoporphyrin IX nanoparticle: Effect of the Ag core on reactive oxygen species generation

NASA Astrophysics Data System (ADS)

Lismont, M.; Pá; ez-Martinez, C.; Dreesen, L.

2015-03-01

Photodynamic therapy (PDT) for cancer is based on the use of a light sensitive molecule to produce, under specific irradiation, toxic reactive oxygen species (ROS). A way to improve the therapy efficiency is to increase the amount of produced ROS near cancer cells. This aim can be achieved by using a metal enhanced process arising when an optically active molecule is located near a metallic nanoparticle (NP). Here, the coupling effect between silver (Ag) NPs and protoporphyrin IX (PpIX) molecules, a clinically approved photosensitizer, is studied compared first, to PpIX fluorescence yield and second, to ROS production efficiency. By applying a modified Stöber process, PpIX was encapsulated into a silica (SiO2) shell, surrounding a 60 nm sized Ag core. We showed that, compared to SiO2-PpIX NPs, Ag coated SiO2-PpIX NPs dramatically decreased PpIX fluorescence together with singlet oxygen production efficiency. However, after incubation time in the dark, the amount of superoxide anions generated by the Ag doped sample was higher than the control sample one.

Fabrication of PANI/Ag/AgCl/ITO-PET Flexible Film and Its Crystallinity and Electrical Properties

NASA Astrophysics Data System (ADS)

Diantoro, M.; Rohmiani, F.; Mustikasari, A. A.; Sunaryono

2018-05-01

Abstrak. PANI as one of the conductive polymers which have been widely using in electronics or storage devices such as a supercapacitor. PANI has recently become an option because of its potential for a broad area of application. Protonation or introduce a dopant can control the electrical properties of PANI. However, researcher facing a disadvantage since PANI also active in acidic conditions. To control the conductivity and the stability in an acidic environment, the researcher has introduced Ag/AgCl to PANI. We report the synthesis and analyses of silver nanoparticles (AgNPs), PANI, and PANI/Ag/AgCl/ITO-PET films. PANI was synthesized by chemical polymerization, while AgNPs were synthesized via a reductive chemical method using NaBH4 as an AgNO3 reductor. The resulting PANI was characterized using FTIR to determine the functional group, while to obtain the purity of the Ag phase was checked by using XRD. The preparation of PANi/Ag/AgCl solution was carried out by mixing method with the variation of the mass of AgNO3. The precipitate was carried out by using ITOPET substrate. PANI/Ag/AgCl/ITO-PET films were characterized by using FTIR, XRD, SEMEDX, and capacitance meters. It has was found that crystallinity increases with the addition of Ag films to PANI/Ag/AgCl/ITO-PET. The crystallinity reached 29.85 %. It was also revealed that the dielectric constant decreased with increasing Ag in PANi/Ag/AgCl/ITO-PET films.

Nanoparticle-Enhanced Silver-Nanowire Plasmonic Electrodes for High-Performance Organic Optoelectronic Devices.

PubMed

Kim, Taehyo; Kang, Saewon; Heo, Jungwoo; Cho, Seungse; Kim, Jae Won; Choe, Ayoung; Walker, Bright; Shanker, Ravi; Ko, Hyunhyub; Kim, Jin Young

2018-05-21

Improved performance in plasmonic organic solar cells (OSCs) and organic light-emitting diodes (OLEDs) via strong plasmon-coupling effects generated by aligned silver nanowire (AgNW) transparent electrodes decorated with core-shell silver-silica nanoparticles (Ag@SiO 2 NPs) is demonstrated. NP-enhanced plasmonic AgNW (Ag@SiO 2 NP-AgNW) electrodes enable substantially enhanced radiative emission and light absorption efficiency due to strong hybridized plasmon coupling between localized surface plasmons (LSPs) and propagating surface plasmon polaritons (SPPs) modes, which leads to improved device performance in organic optoelectronic devices (OODs). The discrete dipole approximation (DDA) calculation of the electric field verifies a strongly enhanced plasmon-coupling effect caused by decorating core-shell Ag@SiO 2 NPs onto the AgNWs. Notably, an electroluminescence efficiency of 25.33 cd A -1 (at 3.2 V) and a power efficiency of 25.14 lm W -1 (3.0 V) in OLEDs, as well as a power conversion efficiency (PCE) value of 9.19% in OSCs are achieved using hybrid Ag@SiO 2 NP-AgNW films. These are the highest values reported to date for optoelectronic devices based on AgNW electrodes. This work provides a new design platform to fabricate high-performance OODs, which can be further explored in various plasmonic and optoelectronic devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface Plasmon Enhanced Photocatalysis of Au/Pt-decorated TiO2 Nanopillar Arrays

NASA Astrophysics Data System (ADS)

Shuang, Shuang; Lv, Ruitao; Xie, Zheng; Zhang, Zhengjun

2016-05-01

The low quantum yields and lack of visible light utilization hinder the practical application of TiO2 in high-performance photocatalysis. Herein, we present a design of TiO2 nanopillar arrays (NPAs) decorated with both Au and Pt nanoparticles (NPs) directly synthesized through successive ion layer adsorption and reaction (SILAR) at room temperature. Au/Pt NPs with sizes of ~4 nm are well-dispersed on the TiO2 NPAs as evidenced by electron microscopic analyses. The present design of Au/Pt co-decoration on the TiO2 NPAs shows much higher visible and ultraviolet (UV) light absorption response, which leads to remarkably enhanced photocatalytic activities on both the dye degradation and photoelectrochemical (PEC) performance. Its photocatalytic reaction efficiency is 21 and 13 times higher than that of pure TiO2 sample under UV-vis and visible light, respectively. This great enhancement can be attributed to the synergy of electron-sink function of Pt and surface plasmon resonance (SPR) of Au NPs, which significantly improves charge separation of photoexcited TiO2. Our studies demonstrate that through rational design of composite nanostructures one can harvest visible light through the SPR effect to enhance the photocatalytic activities initiated by UV-light, and thus realize more effectively utilization of the whole solar spectrum for energy conversion.

Fabrication of Ag nanoparticle catalyst supported on graphene for effective H2O2 nonenzymatic detection powered by chemical energy

NASA Astrophysics Data System (ADS)

Zhang, Hulin; Xie, Yuhang; Zhang, Shangjie; Wen, Yige; Chen, Changyong; Ye, Wenhao; Lin, Yuan

2017-06-01

Ag nanoparticles/graphene nanosheets (Ag NPs/GNs) have been fabricated using graphene nanosheets (GNs) as frames for the growth of Ag nanoparticles (Ag NPs). The graphene nanostructures adsorbed with a large number of Ag NPs and were synthesized via a facile redox reaction. The prepared nanocatalysts were characterized using x-ray diffraction, Raman spectroscopy, field electron scanning electron microscopy and transmission electron microscopy. The electrochemical activity of the Ag NPs/GNs for the detection of H2O2 was explored using cyclic voltammetry and chronoamperometry, indicating that the Ag NPs/GNs can remarkably facilitate H2O2 redox in phosphate buffer solution. Further comparative investigations show that the as-prepared Ag nanocatalysts exhibit a wide linear range, a high response, and a short response time for H2O2 detection. To further exploit the practical applications in H2O2 detection, the homemade electrochemical cells were employed to power the Ag NPs/GNs electrode sensor by chemical energy without external power sources. The results expand the applications of the graphene-based sensors and propose a feasible self-powered biochemical sensing approach independent of conventional power sources.

Fabrication of Ag-Au bimetallic nanoparticles by laser-induced dewetting of bilayer films

NASA Astrophysics Data System (ADS)

Oh, Yoonseok; Lee, Jeeyoung; Lee, Myeongkyu

2018-03-01

We here show that Ag-Au bimetallic nanoparticles (NPs) can be produced by dewetting an Ag/Au bilayer film coated on glass using a nanosecond-pulsed laser beam. Elemental analysis revealed that the obtained bimetallic NPs are Ag-Au alloys, with two elements well mixed over the whole volume of the particle. The composition of the produced particles was controllable by changing the relative thickness of each layer. The localized surface plasmon resonance (LSPR) peak was red-shifted with an increasing Au content and the LSPR wavelength could be tuned from 415 to 525 nm by varying the alloy composition. A film area of several square centimeters could be transformed into Ag-Au NPs by a single laser pulse of 6 ns duration. This study provides a facile and scalable route to prepare bimetallic NPs for plasmonic and other applications.

One-step fabrication of recycled Ag nanoparticles/graphene aerogel with high mechanical property for disinfection and catalytic reduction of 4-nitrophonel.

PubMed

Zhang, Yi; Yang, Jia-Cheng E; Fu, Ming-Lai; Yuan, Baoling; Gupta, Kiran

2018-05-15

Fabrication of smart composites with expected removal property and excellent recycle performance for micro-pollutants including microbes and organic contaminants without formation of second-pollutants is highly desired. In this work, Ag nanoparticles (Ag NPs) homogenously loaded on graphene aerogel (GA) as Ag NPs/GA was facilely fabricated by a one-step process and the composite was characterized in detail. The bactericidal performance of the composite towards escherichia coli (E. coli) was evaluated and the catalytic activity was probed for the reduction of 4-nitrophenol (4-NP). Results showed that the composite contains about 44.4 wt% of well-dispersed Ag NPs with diameters ranging from 10 to 100 nm. Compared with the bare Ag particles or GA, Ag NPs/GA exhibited an enhanced bactericidal performance for 8-lg of E. coli cells with 100% inactivation rate and catalytic activity for 4-NP with 96.6% degradation rate, respectively. Impressively, the 100% inactivation rates for 8-lg of E. coli remained after 7 recycles and the releasing silver was negligible compared with the loaded Ag NPs. Moreover, the used Ag NPs/GA for the catalytic reduction of 4-NP can be regenerated easily by calcination in inert atmosphere. Hence, Ag NPs/GA can be regarded as a promising and cost-efficient composite for environmental remediation.

Continuous-flow biosynthesis of Au-Ag bimetallic nanoparticles in a microreactor

NASA Astrophysics Data System (ADS)

Liu, Hongyu; Huang, Jiale; Sun, Daohua; Odoom-Wubah, Tareque; Li, Jun; Li, Qingbiao

2014-11-01

Herein, a microfluidic biosynthesis of Au-Ag bimetallic nanoparticle (NP) in a tubular microreactor, based on simultaneous reduction of HAuCl4 and AgNO3 precursors in the presence of Cacumen Platycladi ( C. Platycladi) extract was studied. The flow velocity profile was numerically analyzed with computational fluid dynamics. Au-Ag bimetallic NPs with Ag/Au molar ratios of 1:1 and 2:1 were synthesized, respectively. The alloy formation, morphology, structure, and size were investigated by UV-Vis spectra analysis, transmission electron microscopy (TEM), high resolution TEM, scanning TEM, and energy-dispersive X-ray analysis. In addition, the effects of volumetric flow rate, reaction temperature, and concentration of C. Platycladi extract and NaOH on the properties of the as-synthesized Au-Ag bimetallic NPs were investigated. The results indicated that these factors could not only affect the molar ratios of the two elements in the Au-Ag bimetallic NPs, but also affect particle size which can be adjusted from 3.3 to 5.6 nm. The process was very rapid and green, since a microreactor was employed with no additional synthetic reagents used. This work is anticipated to provide useful parameters for continuous-flow biosynthesis of bimetallic NPs in microreactors.

Ag Nanoparticle-Functionalized Open-Ended Freestanding TiO₂ Nanotube Arrays with a Scattering Layer for Improved Energy Conversion Efficiency in Dye-Sensitized Solar Cells.

PubMed

Rho, Won-Yeop; Chun, Myeung-Hwan; Kim, Ho-Sub; Kim, Hyung-Mo; Suh, Jung Sang; Jun, Bong-Hyun

2016-06-15

Dye-sensitized solar cells (DSSCs) were fabricated using open-ended freestanding TiO₂ nanotube arrays functionalized with Ag nanoparticles (NPs) in the channel to create a plasmonic effect, and then coated with large TiO₂ NPs to create a scattering effect in order to improve energy conversion efficiency. Compared to closed-ended freestanding TiO₂ nanotube array-based DSSCs without Ag or large TiO₂ NPs, the energy conversion efficiency of closed-ended DSSCs improved by 9.21% (actual efficiency, from 5.86% to 6.40%) with Ag NPs, 6.48% (actual efficiency, from 5.86% to 6.24%) with TiO₂ NPs, and 14.50% (actual efficiency, from 5.86% to 6.71%) with both Ag NPs and TiO₂ NPs. By introducing Ag NPs and/or large TiO₂ NPs to open-ended freestanding TiO₂ nanotube array-based DSSCs, the energy conversion efficiency was improved by 9.15% (actual efficiency, from 6.12% to 6.68%) with Ag NPs and 8.17% (actual efficiency, from 6.12% to 6.62%) with TiO₂ NPs, and by 15.20% (actual efficiency, from 6.12% to 7.05%) with both Ag NPs and TiO₂ NPs. Moreover, compared to closed-ended freestanding TiO₂ nanotube arrays, the energy conversion efficiency of open-ended freestanding TiO₂ nanotube arrays increased from 6.71% to 7.05%. We demonstrate that each component-Ag NPs, TiO₂ NPs, and open-ended freestanding TiO₂ nanotube arrays-enhanced the energy conversion efficiency, and the use of a combination of all components in DSSCs resulted in the highest energy conversion efficiency.

Synthesis of novel cellulose- based antibacterial composites of Ag nanoparticles@ metal-organic frameworks@ carboxymethylated fibers.

PubMed

Duan, Chao; Meng, Jingru; Wang, Xinqi; Meng, Xin; Sun, Xiaole; Xu, Yongjian; Zhao, Wei; Ni, Yonghao

2018-08-01

A novel cellulose-based antibacterial material, namely silver nanoparticles@ metal-organic frameworks@ carboxymethylated fibers composites (Ag NPs@ HKUST-1@ CFs), was synthesized. The results showed that the metal-organic frameworks (HKUST-1) were uniformly anchored on the fiber's surfaces by virtue of complexation between copper ions in HKUST-1 and carboxyl groups on the carboxymethylated fibers (CFs). The silver nanoparticles (Ag NPs) were immobilized and well-dispersed into the pores and/or onto the surfaces of HKUST-1 via in situ microwave reduction, resulting in the formation of novel Ag NPs@ HKUST-1@ CFs composites. The antibacterial assays showed that the as-prepared composites exhibited a much higher antibacterial activity than Ag NPs@ CFs or HKUST-1@ CFs samples. Copyright © 2018 Elsevier Ltd. All rights reserved.

Natural ageing process accelerates the release of Ag from functional textile in various exposure scenarios

PubMed Central

Ding, Dahu; Chen, Lulu; Dong, Shaowei; Cai, Hao; Chen, Jifei; Jiang, Canlan; Cai, Tianming

2016-01-01

Natural ageing process occurs throughout the life cycle of textile products, which may possess influences on the release behavior of additives such as silver nanoparticles (Ag NPs). In this study, we assessed the releasability of Ag NPs from a Ag NPs functionalized textile in five different exposure scenarios (i.e. tap water (TW), pond water (PW), rain water (RW), artificial sweat (AS), and detergent solution (DS) along with deionized water (DW) as reference), which were very likely to occur throughout the life cycle of the textile. For the pristine textile, although the most remarkable release was found in DW (6–15 μg Ag/g textile), the highest release rate was found in RW (around 7 μg Ag/(g textile·h)). After ageing treatment, the total released Ag could be increased by 75.7~386.0% in DW, AS and DS. Morphological analysis clearly showed that the Ag NPs were isolated from the surface of the textile fibre due to the ageing treatment. This study provides useful information for risk assessment of nano-enhanced textile products. PMID:27869136

Natural ageing process accelerates the release of Ag from functional textile in various exposure scenarios

NASA Astrophysics Data System (ADS)

Ding, Dahu; Chen, Lulu; Dong, Shaowei; Cai, Hao; Chen, Jifei; Jiang, Canlan; Cai, Tianming

2016-11-01

Natural ageing process occurs throughout the life cycle of textile products, which may possess influences on the release behavior of additives such as silver nanoparticles (Ag NPs). In this study, we assessed the releasability of Ag NPs from a Ag NPs functionalized textile in five different exposure scenarios (i.e. tap water (TW), pond water (PW), rain water (RW), artificial sweat (AS), and detergent solution (DS) along with deionized water (DW) as reference), which were very likely to occur throughout the life cycle of the textile. For the pristine textile, although the most remarkable release was found in DW (6-15 μg Ag/g textile), the highest release rate was found in RW (around 7 μg Ag/(g textile·h)). After ageing treatment, the total released Ag could be increased by 75.7~386.0% in DW, AS and DS. Morphological analysis clearly showed that the Ag NPs were isolated from the surface of the textile fibre due to the ageing treatment. This study provides useful information for risk assessment of nano-enhanced textile products.

Functionalized layered double hydroxide with nitrogen and sulfur co-decorated carbondots for highly selective and efficient removal of soft Hg2+ and Ag+ ions.

PubMed

Asiabi, Hamid; Yamini, Yadollah; Shamsayei, Maryam; Molaei, Karam; Shamsipur, Mojtaba

2018-05-28

A facile composite was fabricated via direct assembly of nitrogen and sulfur co-decorated carbon dots with abundant oxygen-containing functional groups on the surface of the positively charged layered double hydroxide (N,S-CDs-LDH). The novel N,S-CDs-LDH demonstrates highly selective bindings (M-S) and an extremely efficient removal capacity for soft metal ions such as Ag + and Hg 2+ ions. N,S-CDs-LDH displayed a selectivity order of Ag + > Hg 2+ > Cu 2+ > Pb 2+ > Zn 2+ > Cd 2+ for their adsorption. The enormous capacities for Hg 2+ (625.0 mg g -1 ) and Ag + (714.3 mg g -1 ) and very high distribution coefficients (K d ) of 9.9 × 10 6 mL g -1 (C 0  = 20 mg L -1 ) and 2.0 × 10 7 mL g -1 (C 0  = 20 mg L -1 ) for Hg 2+ and Ag + , respectively, place the N,S-CDs-LDH at the top of LDH based materials known for such removal. The adsorption kinetic curves for Hg 2+ and Ag + fitted well with the pseudo-second order model. For Hg 2+ and Ag + , an exceptionally rapid capture with removal ∼100% within 80 min was observed (C ions  = 30 mg L -1 and V/m ratio of 1000). The adsorption isotherms were well described using Langmuir isotherm. The N,S-CDs-LDH was successfully applied to highly efficient removal of Hg 2+ and Ag + from aqueous solutions. Copyright © 2018 Elsevier B.V. All rights reserved.

Simplifying the growth of hybrid single-crystals by using nanoparticle precursors: the case of AgI

NASA Astrophysics Data System (ADS)

Xu, Biao; Wang, Ruji; Wang, Xun

2012-03-01

We report the synthesis of a series of AAgmIn single-crystals within 24 h, at room temperature, utilizing AgI nanoparticles (NPs) as the precursor. The AgI NPs impart high reactivity under mild conditions and favor the growth kinetics. 0D, 1D and 2D iodoargentate crystals can be obtained. This work represents the first application of NPs in the field of organo-metal-halide crystals and will inspire the design of other AMmXn crystals.We report the synthesis of a series of AAgmIn single-crystals within 24 h, at room temperature, utilizing AgI nanoparticles (NPs) as the precursor. The AgI NPs impart high reactivity under mild conditions and favor the growth kinetics. 0D, 1D and 2D iodoargentate crystals can be obtained. This work represents the first application of NPs in the field of organo-metal-halide crystals and will inspire the design of other AMmXn crystals. Electronic supplementary information (ESI) available: XPS spectra of AgI NPs, schematic representation of the formation process of [Ag4I8]4- in 2, UV-Vis spectra of the DTMA-Ag-I clusters, analysis of force balance of a crystal at the interface between H2O and CH2Cl2 and crystal structure depiction of 1-4. CIF files of 1-4 are also provided. CCDC reference numbers 863848, 863849, 863850 and 863851. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2nr30139c

Plasmon enhanced water splitting mediated by hybrid bimetallic Au-Ag core-shell nanostructures.

PubMed

Erwin, William R; Coppola, Andrew; Zarick, Holly F; Arora, Poorva; Miller, Kevin J; Bardhan, Rizia

2014-11-07

In this work, we employed wet chemically synthesized bimetallic Au-Ag core-shell nanostructures (Au-AgNSs) to enhance the photocurrent density of mesoporous TiO2 for water splitting and we compared the results with monometallic Au nanoparticles (AuNPs). While Au-AgNSs incorporated photoanodes give rise to 14× enhancement in incident photon to charge carrier efficiency, AuNPs embedded photoanodes result in 6× enhancement. By varying nanoparticle concentration in the photoanodes, we observed ∼245× less Au-AgNSs are required relative to AuNPs to generate similar photocurrent enhancement for solar fuel conversion. Power-dependent measurements of Au-AgNSs and AuNPs showed a first order dependence to incident light intensity, relative to half-order dependence for TiO2 only photoanodes. This indicated that plasmonic nanostructures enhance charge carriers formed on the surface of the TiO2 which effectively participate in photochemical reactions. Our experiments and simulations suggest the enhanced near-field, far-field, and multipolar resonances of Au-AgNSs facilitating broadband absorption of solar radiation collectively gives rise to their superior performance in water splitting.

Microwave-synthesized freestanding iron-carbon nanotubes on polyester composites of woven Kevlar fibre and silver nanoparticle-decorated graphene

PubMed Central

Hazarika, Ankita; Deka, Biplab K.; Kim, DoYoung; Kong, Kyungil; Park, Young-Bin; Park, Hyung Wook

2017-01-01

We synthesized Ag nanoparticle-decorated multilayered graphene nanosheets (Ag-graphene) from graphite nanoplatelets and silver nitrate through 90–100 s of microwave exposure, without the use of any mineral acids or harsh reducing agents. Fe nanoparticle-decorated carbon nanotubes (Fe-CNTs) were grown on polypyrrole (PPy) deposited on woven Kevlar fibre (WKF), using ferrocene as a catalyst, under microwave irradiation. Fe-CNTs grown on WKF and Ag-graphene dispersed in polyester resin (PES) were combined to fabricate Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites by vacuum-assisted resin transfer moulding. The combined effect of Fe-CNTs and Ag-graphene in the resulting composites resulted in a remarkable enhancement of tensile properties (a 192.56% increase in strength and 100.64% increase in modulus) as well as impact resistance (a 116.33% increase). The electrical conductivity significantly increased for Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites. The effectiveness of electromagnetic interference shielding, which relies strongly on the Ag-graphene content in the composites, was 25 times higher in Ag-graphene/Fe-CNT/PPy-coated WKF/PES than in neat WKF/PES composites. The current work offers a novel route for fabricating highly promising, cost effective WKF/PES composites through microwave-assisted synthesis of Fe-CNTs and Ag-graphene. PMID:28074877

Microwave-synthesized freestanding iron-carbon nanotubes on polyester composites of woven Kevlar fibre and silver nanoparticle-decorated graphene

NASA Astrophysics Data System (ADS)

Hazarika, Ankita; Deka, Biplab K.; Kim, Doyoung; Kong, Kyungil; Park, Young-Bin; Park, Hyung Wook

2017-01-01

We synthesized Ag nanoparticle-decorated multilayered graphene nanosheets (Ag-graphene) from graphite nanoplatelets and silver nitrate through 90-100 s of microwave exposure, without the use of any mineral acids or harsh reducing agents. Fe nanoparticle-decorated carbon nanotubes (Fe-CNTs) were grown on polypyrrole (PPy) deposited on woven Kevlar fibre (WKF), using ferrocene as a catalyst, under microwave irradiation. Fe-CNTs grown on WKF and Ag-graphene dispersed in polyester resin (PES) were combined to fabricate Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites by vacuum-assisted resin transfer moulding. The combined effect of Fe-CNTs and Ag-graphene in the resulting composites resulted in a remarkable enhancement of tensile properties (a 192.56% increase in strength and 100.64% increase in modulus) as well as impact resistance (a 116.33% increase). The electrical conductivity significantly increased for Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites. The effectiveness of electromagnetic interference shielding, which relies strongly on the Ag-graphene content in the composites, was 25 times higher in Ag-graphene/Fe-CNT/PPy-coated WKF/PES than in neat WKF/PES composites. The current work offers a novel route for fabricating highly promising, cost effective WKF/PES composites through microwave-assisted synthesis of Fe-CNTs and Ag-graphene.

Microwave-synthesized freestanding iron-carbon nanotubes on polyester composites of woven Kevlar fibre and silver nanoparticle-decorated graphene.

PubMed

Hazarika, Ankita; Deka, Biplab K; Kim, DoYoung; Kong, Kyungil; Park, Young-Bin; Park, Hyung Wook

2017-01-11

We synthesized Ag nanoparticle-decorated multilayered graphene nanosheets (Ag-graphene) from graphite nanoplatelets and silver nitrate through 90-100 s of microwave exposure, without the use of any mineral acids or harsh reducing agents. Fe nanoparticle-decorated carbon nanotubes (Fe-CNTs) were grown on polypyrrole (PPy) deposited on woven Kevlar fibre (WKF), using ferrocene as a catalyst, under microwave irradiation. Fe-CNTs grown on WKF and Ag-graphene dispersed in polyester resin (PES) were combined to fabricate Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites by vacuum-assisted resin transfer moulding. The combined effect of Fe-CNTs and Ag-graphene in the resulting composites resulted in a remarkable enhancement of tensile properties (a 192.56% increase in strength and 100.64% increase in modulus) as well as impact resistance (a 116.33% increase). The electrical conductivity significantly increased for Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites. The effectiveness of electromagnetic interference shielding, which relies strongly on the Ag-graphene content in the composites, was 25 times higher in Ag-graphene/Fe-CNT/PPy-coated WKF/PES than in neat WKF/PES composites. The current work offers a novel route for fabricating highly promising, cost effective WKF/PES composites through microwave-assisted synthesis of Fe-CNTs and Ag-graphene.

Infrared light-assisted preparation of Ag nanoparticles-reduced graphene oxide nanocomposites for non-enzymatic H{sub 2}O{sub 2} sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ji, Ye; State Key Laboratory of Transducer Technology, Chinese Academy of Sciences; Zhang, Yong

2015-12-15

Graphical abstract: An infrared light irradiation method has been developed for preparation of AgNPs/rGO nanocomposites for electrochemical detection of H{sub 2}O{sub 2}. - Highlights: • AgNPs/rGO nanocomposites have been prepared by photochemical method. • AgNPs/rGO nanocomposites exhibit good sensing performances for detection of H{sub 2}O{sub 2}. • The present work provides a simple and green method for preparation of rGO-based materials. - Abstract: A green method has been developed for preparation of Ag nanoparticles/reduced graphene oxide (AgNPs/rGO) nanocomposites by infrared light irradiation. The characterizations indicate the successful preparation of AgNPs/rGO nanocomposites. Most importantly, AgNPs/rGO nanocomposites exhibit excellent electrocatalytic activity formore » reduction of H{sub 2}O{sub 2}, leading to a high-performance non-enzymatic H{sub 2}O{sub 2} sensor with linear detection range and detection limit about 0.1 mM to 140 mM (r = 0.9896) and 3.0 μM, respectively.« less

Preparation of core-shell Ag@CeO2 nanocomposite by LSPR photothermal induced interface reaction

NASA Astrophysics Data System (ADS)

Zhong, H. X.; Wei, Y.; Yue, Y. Z.; Zhang, L. H.; Liu, Y.

2016-04-01

The core-shell structure of Ag@CeO2 was prepared by a novel and facile method, which was based on the photothermal effect of localized surface plasmon resonance (LSPR). Nanoparticles (NPs) of Ag were dispersed in a solution containing citric acid, ethylene glycol and cerium nitrate, then under irradiation, Ag NPs generated heat from LSPR and the heat-induced polymerization reaction in the interface between Ag and the sol resulted in cerium gel formation only on the surface of the Ag NPs. After calcination, Ag@CeO2 was successfully obtained, then Ag@CeO2/SiO2 was prepared by loading Ag@CeO2 on SiO2. The resultant catalyst exhibited favorable activity and stability for CO oxidation. The preparation method proposed here should be extendable to other composites with metallic cores and oxide shells in which the metallic nanoparticle possesses LSPR properties.

Use of Single-Layer g-C3N4/Ag Hybrids for Surface-Enhanced Raman Scattering (SERS)

PubMed Central

Jiang, Jizhou; Zou, Jing; Wee, Andrew Thye Shen; Zhang, Wenjing

2016-01-01

Surface-enhanced Raman scattering (SERS) substrates with high activity and stability are desirable for SERS sensing. Here, we report a new single atomic layer graphitic-C3N4 (S-g-C3N4) and Ag nanoparticles (NPs) hybrid as high-performance SERS substrates. The SERS mechanism of the highly stable S-g-C3N4/Ag substrates was systematically investigated by a combination of experiments and theoretical calculations. From the results of XPS and Raman spectroscopies, it was found that there was a strong interaction between S-g-C3N4 and Ag NPs, which facilitates the uniform distribution of Ag NPs over the edges and surfaces of S-g-C3N4 nanosheets, and induces a charge transfer from S-g-C3N4 to the oxidizing agent through the silver surface, ultimately protecting Ag NPs from oxidation. Based on the theoretical calculations, we found that the net surface charge of the Ag atoms on the S-g-C3N4/Ag substrates was positive and the Ag NPs presented high dispersibility, suggesting that the Ag atoms on the S-g-C3N4/Ag substrates were not likely to be oxidized, thereby ensuring the high stability of the S-g-C3N4/Ag substrate. An understanding of the stability mechanism in this system can be helpful for developing other effective SERS substrates with long-term stability. PMID:27687573

Green synthesis of Pt and Ag nanoparticles and their use towards nitric oxide abatement

NASA Astrophysics Data System (ADS)

Castegnaro, Marcus V.; Alexandre, Jéssica; Baibich, Ione M.; Alves, Maria C. M.; Morais, Jonder

2014-12-01

Pt and Ag nanoparticles (NPs) were synthesized by eco-friendly room-temperature chemical reduction routes based on trisodium citrate and L-ascorbic acid (for Pt NPs) and on gelatin and trisodium citrate (for Ag NPs). The as-prepared NPs were characterized by UV-visible absorption spectroscopy and transmission electron microscopy analyses, which confirmed the formation of sub-10 nm metal particles. Then, the colloidal solutions were used to obtain activated carbon-supported catalysts (metal/AC) for direct NO decomposition. X-ray photoelectron spectroscopy and x-ray diffraction measurements proved that the NPs hosted on the support surface were present in the metallic chemical state. In situ infrared absorption spectroscopy investigations during NO reduction catalytic reactions showed that the Pt/AC and Ag/AC catalysts were highly active at 373 K. At 573 K, we observed different behaviors for each catalyst. While Ag/AC performed similarly to the reaction at 373 K, Pt/AC was found to participate in a redox mechanism, where the catalyst’s active sites were oxidized by NO and reduced by carbon, thus emitting CO2 and enhancing its catalytic activity, an effect that we have also observed in carbon-supported Pd NPs.

Electroactive Au@Ag nanoparticles driven electrochemical sensor for endogenous H2S detection.

PubMed

Zhao, Yuan; Yang, Yaxin; Cui, Linyan; Zheng, Fangjie; Song, Qijun

2018-05-26

In this work, a novel and facile electrochemical sensor is reported for the highly selective and sensitive detection of dissolved hydrogen sulfide (H 2 S), attributing to the redox reaction between Au@Ag core-shell nanoparticles (Au@Ag NPs) and H 2 S. Electroactive Au@Ag NPs not only possess excellent conductivity, but exhibit great electrochemical reactivity at 0.26 V due to the electrochemical oxidation from Ag° to Ag + . In the presence of H 2 S, the Ag shell of Au@Ag NPs can be oxidized to Ag 2 S, resulting in the decrease of differential pulse voltammetry (DPV) peak at 0.26 V. The electrochemical sensor exhibits a wide linear response range from 0.1 nM to 500 nM. The limit of detection (LOD) for H 2 S is as low as 0.04 nM. The developed sensor shows significant prospects in the study of pathological processes related to the mechanism of H 2 S production. Copyright © 2018. Published by Elsevier B.V.

Multidimensional Co3O4 nano sponge for the highly sensitive SERS applications

NASA Astrophysics Data System (ADS)

Zhao, Miao-miao; Liu, Wen-yao; Du, Jian-gong; Guo, Xu-dong; Wang, Lei; Xia, Mei-jing; Tang, Jun

2017-01-01

In this work, surface enhanced Raman spectroscopy (SERS) substrates with Ag nanoparticles (NPs) decorated Co3O4 nanowires (NWs) grafted on the three-dimensional (3D) network architecture of Ni foam (denoted as Ag-NP@Co3O4-NW/Ni-foam) arrays are manufactured. In the experiment, the hierarchical Ag-NP@Co3O4-NW/Ni-foam arrays exhibit strong SERS activity due to the higher density of the "hot spots" created from the large quantities of neighboring Ag NPs. Using this hierarchical 3D SERS substrates, the crystal violet (a banned drug of aquaculture) with concentration down to 10-14 mol/L can be detected, which shows potential application in SERS-based rapid trace-level detection of harmful food additives.

Alignment of Gold Nanoparticle-Decorated DNA Origami Nanotubes: Substrate Prepatterning versus Molecular Combing.

PubMed

Teschome, Bezu; Facsko, Stefan; Gothelf, Kurt V; Keller, Adrian

2015-11-24

DNA origami has become an established technique for designing well-defined nanostructures with any desired shape and for the controlled arrangement of functional nanostructures with few nanometer resolution. These unique features make DNA origami nanostructures promising candidates for use as scaffolds in nanoelectronics and nanophotonics device fabrication. Consequently, a number of studies have shown the precise organization of metallic nanoparticles on various DNA origami shapes. In this work, we fabricated large arrays of aligned DNA origami decorated with a high density of gold nanoparticles (AuNPs). To this end, we first demonstrate the high-yield assembly of high-density AuNP arrangements on DNA origami adsorbed to Si surfaces with few unbound background nanoparticles by carefully controlling the concentrations of MgCl2 and AuNPs in the hybridization buffer and the hybridization time. Then, we evaluate two methods, i.e., hybridization to prealigned DNA origami and molecular combing in a receding meniscus, with respect to their potential to yield large arrays of aligned AuNP-decorated DNA origami nanotubes. Because of the comparatively low MgCl2 concentration required for the efficient immobilization of the AuNPs, the prealigned DNA origami become mobile and displaced from their original positions, thereby decreasing the alignment yield. This increased mobility, on the other hand, makes the adsorbed origami susceptible to molecular combing, and a total alignment yield of 86% is obtained in this way.

Fabrication of Ag-decorated BiOBr-mBiVO4 dual heterojunction composite with enhanced visible light photocatalytic performance for degradation of malachite green

NASA Astrophysics Data System (ADS)

Regmi, Chhabilal; Dhakal, Dipesh; Kim, Tae-Ho; Yamaguchi, Takutaro; Wohn Lee, Soo

2018-04-01

A visible light active Ag-decorated BiVO4-BiOBr dual heterojunction photocatalyst was prepared using a facile hydrothermal method, followed by the photodeposition of Ag. The photocatalytic activity of the synthesized samples was investigated by monitoring the change in malachite green (MG) concentration upon visible light irradiation. The synthesized sample was highly effective for the degradation of non-biodegradable MG. The enhanced activity observed was ascribed to the efficient separation and transfer of charge carriers across the dual heterojunction structure as verified by photoluminescence measurements. The removal of MG was primarily initiated by hydroxyl radicals and holes based on scavenger’s effect. To gain insight into the degradation mechanism, both high performance liquid chromatography and high resolution-quantitative time of flight, electrospray ionization mass spectrometry measurements during the degradation process were carried out. The degradation primarily followed the hydroxylation and N-demethylation process. A possible reaction pathway is proposed on the basis of all the information obtained under various experimental conditions.

Novel biosynthesis of Ag-hydroxyapatite: Structural and spectroscopic characterization

NASA Astrophysics Data System (ADS)

Ruíz-Baltazar, Álvaro de Jesús; Reyes-López, Simón Yobanny; Silva-Holguin, Pamela Nair; Larrañaga, Daniel; Estévez, Miriam; Pérez, Ramiro

2018-06-01

Silver-doped hydroxyapatite (Ag-HAP) was obtained by green synthesis route. The dopant silver nanoparticles (AgNPs) were obtained by biosynthesis based on Melissa officinalis extract. This research is focused on the characterization and the use of the nontoxic and environment-friendly Ag-HAP nanocomposite. The structural and morphological characterization of Ag-HAP nanocomposite was carried out by scanning electron microscopy (SEM), X-ray diffraction, Fourier-transform infrared (FT-IR) and Raman spectroscopy. The obtained nanoparticles exhibited a great interaction with the HAP matrix, performing an Ag-HAP nanocomposite. Changes in the structure of the Ag-HAP nanocomposite were corroborated by the different characterization techniques. Additionally, a homogeneous distribution of the AgNPs on the HAP structure was observed. The heterogeneous nucleation process employed to doping the HAP, offer a functional route to obtain a green composite with potentials applications in multiple fields, such as tissue engineering, bone repair as well as protein. These properties can be evaluated in subsequent studies.

γ-Irradiation assisted synthesis of graphene oxide sheets supported Ag nanoparticles with single crystalline structure and parabolic distribution from interlamellar limitation

NASA Astrophysics Data System (ADS)

Yue, Yunhao; Zhou, Baoming; Shi, Jie; Chen, Cheng; Li, Nan; Xu, Zhiwei; Liu, Liangsen; Kuang, Liyun; Ma, Meijun; Fu, Hongjun

2017-05-01

This paper reported a method to fabricate graphene oxide sheets supported Ag nanoparticles (AgNPs/GOS) with single crystalline structure and parabolic distribution without surfactant or functional agent. We used imidazole silver nitrate as intercalation precursor into the layers of graphite oxide, and subsequently reduction and growth of interlamellar AgNPs were induced via γ-irradiation. The results illustrated that the synergism of interlamellar limitation of graphite oxide and fragmentation ability of γ-irradiation could prevent coalescent reaction of AgNPs with other oligomeric clusters, and the single crystalline and small-sized (below 13.9 nm) AgNPs were prepared. Moreover, the content and size of AgNPs exhibited parabolic distribution on GOS surface because the graphite oxide exfoliated to GOS from the edge to the central area of layers. In addition, complete exfoliation degree of GOS and large-sized AgNPs were obtained simultaneously under suitable silver ions concentration. Optimized composites exhibited outstanding surface-enhanced Raman scattering properties for crystal violet with enhancement factor of 1.3 × 106 and detection limit of 1.0 × 10-7 M, indicating that the AgNPs/GOS composites could be applied to trace detection of organic dyes molecules. Therefore, this study presented a strategy for developing GOS supported nanometal with single crystalline structure and parabolic distribution based on γ-irradiation.

Bromelain-decorated hybrid nanoparticles based on lactobionic acid-conjugated chitosan for in vitro anti-tumor study.

PubMed

Wei, Bing; He, Le; Wang, Xin; Yan, Guo Qing; Wang, Jun; Tang, Rupei

2017-08-01

In this work, lactobionic acid-modified chitosan (CLA) was chosen as an initial material to prepare tumor-targeted nanoparticles (CLA NPs). To improve the nanoparticles' tumor penetration ability, bromelain was then decorated on the surface of CLA NPs to give CLAB NPs. The micromorphology of CLA and CLAB NPs was observed by transmission electron microscopy and scanning electron microscopy. The stability of CLA and CLAB NPs was then investigated at different pH values (4.0-9.0) and physiological environment by dynamic light scattering. Doxorubicin as a model drug was successfully encapsulated into these two nanoparticles and drug release profiles were also investigated at pH 5.5, 6.5 and 7.4, respectively. Cellular uptake and MTT results against HepG2 and SH-SY5Y cells demonstrated that the LA-conjugated tumor-targeting NPs can be efficiently internalized into hepatoma carcinoma cells, leading to higher cytotoxicity than free doxorubicin. CLAB NPs show considerable cell cytotoxicity and are expected to improve the penetration ability and therapeutic effect in the subsequent in vivo studies.

Preparation and characterization of Fe3O4-Ag2O quantum dots decorated cellulose nanofibers as a carrier of anticancer drugs for skin cancer.

PubMed

Fakhri, Ali; Tahami, Shiva; Nejad, Pedram Afshar

2017-10-01

The Best performance drug delivery systems designed with Fe 3 O 4 -Ag 2 O quantum dots decorated cellulose nanofibers which that grafted with Etoposide and Methotrexate. Morphology properties were characterized by Scanning and Transmittance electron microscopy. The crystalline structure of prepared sample was evaluated using by X-ray diffraction. The vibrating sample magnetometer analysis was used for magnetic behavior of samples. The size distributions of Fe 3 O 4 -Ag 2 O QDs/Cellulose fibers nanocomposites indicate that the average diameter was 62.5nm. The Saturation magnetization (Ms) indicates the Fe 3 O 4 -Ag 2 O QDs/Cellulose fibers nanocomposites have ferromagnetic properties in nature. For make carrier, the Iron and Silver should be binds to cellulose nanofibers and to drug molecules and observe in UV-vis spectroscopy. The drug release kinetics was studied in vitro as spectrophotometrically. The release of Etoposide and Methotrexate were carried out with a constant speed, and the equilibrium reached at 24 and 30h with a total amount 78.94% and 63.84%, respectively. The results demonstrated that the obtained Fe 3 O 4 -Ag 2 O quantum dots/cellulose fibers nanocomposites could be applied for drug delivery systems. Cytotoxicity and antioxidant study confirmed the activity of the drug incorporated in nanocomposites. In addition, the cytotoxicity of drug was increased when loaded on nanocomposites, compared to pure Fe 3 O 4 -Ag 2 O quantum dots/cellulose fibers nanocomposites. Copyright © 2017 Elsevier B.V. All rights reserved.

Pt@Ag and Pd@Ag core/shell nanoparticles for catalytic degradation of Congo red in aqueous solution

NASA Astrophysics Data System (ADS)

Salem, Mohamed A.; Bakr, Eman A.; El-Attar, Heba G.

2018-01-01

Platinum/silver (Pt@Ag) and palladium/silver (Pd@Ag) core/shell NPs have been synthesized in two steps reaction using the citrate method. The progress of nanoparticle formation was followed by the UV/Vis spectroscopy. Transmission electron microscopy revealed spherical shaped core/shell nanoparticles with average particle diameter 32.17 nm for Pt@Ag and 8.8 nm for Pd@Ag. The core/shell NPs were further characterized by FT-IR and XRD. Reductive degradation of the Congo red dye was chosen to demonstrate the excellent catalytic activity of these core/shell nanostructures. The nanocatalysts act as electron mediators for the transfer of electrons from the reducing agent (NaBH4) to the dye molecules. Effect of reaction parameters such as nanocatalyst dose, dye and NaBH4 concentrations on the dye degradation was investigated. A comparison between the catalytic activities of both nanocatalysts was made to realize which of them the best in catalytic performance. Pd@Ag was the higher in catalytic activity over Pt@Ag. Such greater activity is originated from the smaller particle size and larger surface area. Pd@Ag nanocatalyst was catalytically stable through four subsequent reaction runs under the utilized reaction conditions. These findings can thus be considered as possible economical alternative for environmental safety against water pollution by dyes.

Internally dispersed synthesis of uniform silver nanoparticles via in situ reduction of [Ag(NH3)2]+ along natural microfibrillar substructures of cotton fiber

USDA-ARS?s Scientific Manuscript database

Silver nanoparticles (Ag NPs) are known to have efficient antimicrobial properties, but the direct application of Ag NPs onto the surface of textiles has shown to be ineffective and raise environmental concerns because Ag NPs leach out during washing. In this study, non-leaching and stable Agcotton ...

Frequency upconversion in Er3+ doped tungsten tellurite glass containing Ag nanoparticles

NASA Astrophysics Data System (ADS)

Mahajan, S. K.; Parashar, J.

2018-05-01

The frequency upconversion emission in Er3+ doped TeO2-WO3-Li2O containing Ag nanoparticle (TWLEOAG) glasses at 980nm excitation is reported. The absorption spectra reveal not only the peaks due to Er3+ ions, but also the surface plasmon resonance band of silver NPs located around 525nm and 650 nm. The spherical AgNPs with average size ˜38 nm in the glassy matrix is evidenced from the TEM measurement. Under 980nm laser excitation upconversion emission spectra show two major emission at 550nm and 638nm originating from 4S3/2 and 4F9/2 energy levels of the Er3+ ions, respectively was observed. Upconversion emission enhancement factor 7 fold has been measured for sample heat treated during 40h. However for 18h heat treated TWLEOAG sample under 980 nm flash lamp excitation produced Intense green compare to red emission. Since the 980nm frequency is far from the AgNPs surface plasmon resonance frequency, visible emission ehancement is attributed to local field increase in proximity of the Ag NPs and not energy tranfer from NPs to emitters. Possible energy transfer upconversion mechanism has been also discussed.

Catalytic Activity of Silicon Nanowires Decorated with Gold and Copper Nanoparticles Deposited by Pulsed Laser Ablation

PubMed Central

Casiello, Michele; Fusco, Caterina; Irrera, Alessia; Trusso, Sebastiano; Cotugno, Pietro

2018-01-01

Silicon nanowires (SiNWs) decorated by pulsed laser ablation with gold or copper nanoparticles (labeled as AuNPs@SiNWs and CuNPs@SiNWs) were investigated for their catalytic properties. Results demonstrated high catalytic performances in the Caryl–N couplings and subsequent carbonylations for gold and copper catalysts, respectively, that have no precedents in the literature. The excellent activity, attested by the very high turn over number (TON) values, was due both to the uniform coverage along the NW length and to the absence of the chemical shell surrounding the metal nanoparticles (MeNPs). A high recyclability was also observed and can be ascribed to the strong covalent interaction at the Me–Si interface by virtue of metal “silicides” formation. PMID:29385761

Catalytic Activity of Silicon Nanowires Decorated with Gold and Copper Nanoparticles Deposited by Pulsed Laser Ablation.

PubMed

Casiello, Michele; Picca, Rosaria Anna; Fusco, Caterina; D'Accolti, Lucia; Leonardi, Antonio Alessio; Lo Faro, Maria Josè; Irrera, Alessia; Trusso, Sebastiano; Cotugno, Pietro; Sportelli, Maria Chiara; Cioffi, Nicola; Nacci, Angelo

2018-01-30

Silicon nanowires (SiNWs) decorated by pulsed laser ablation with gold or copper nanoparticles (labeled as AuNPs@SiNWs and CuNPs@SiNWs) were investigated for their catalytic properties. Results demonstrated high catalytic performances in the C aryl -N couplings and subsequent carbonylations for gold and copper catalysts, respectively, that have no precedents in the literature. The excellent activity, attested by the very high turn over number (TON) values, was due both to the uniform coverage along the NW length and to the absence of the chemical shell surrounding the metal nanoparticles (MeNPs). A high recyclability was also observed and can be ascribed to the strong covalent interaction at the Me-Si interface by virtue of metal "silicides" formation.

Biotic and abiotic interactions in aquatic microcosms determine fate and toxicity of Ag nanoparticles. Part 1. Aggregation and dissolution.

PubMed

Unrine, Jason M; Colman, Benjamin P; Bone, Audrey J; Gondikas, Andreas P; Matson, Cole W

2012-07-03

To better understand their fate and toxicity in aquatic environments, we compared the aggregation and dissolution behavior of gum arabic (GA) and polyvinylpyrrolidone (PVP) coated Ag nanoparticles (NPs) in aquatic microcosms. There were four microcosm types: surface water; water and sediment; water and aquatic plants; or water, sediment, and aquatic plants. Dissolution and aggregation behavior of AgNPs were examined using ultracentrifugation, ultrafiltration, and asymmetrical flow field flow fractionation coupled to ultraviolet-visible spectroscopy, dynamic and static laser light scattering, and inductively coupled plasma mass spectrometry. Plants released dissolved organic matter (DOM) into the water column either through active or passive processes in response to Ag exposure. This organic matter fraction readily bound Ag ions. The plant-derived DOM had the effect of stabilizing PVP-AgNPs as primary particles, but caused GA-AgNPs to be removed from the water column, likely by dissolution and binding of released Ag ions on sediment and plant surfaces. The destabilization of the GA-AgNPs also corresponded with X-ray absorption near edge spectroscopy results which suggest that 22-28% of the particulate Ag was associated with thiols and 5-14% was present as oxides. The results highlight the potential complexities of nanomaterial behavior in response to biotic and abiotic modifications in ecosystems, and may help to explain differences in toxicity of Ag observed in realistic exposure media compared to simplified laboratory exposures.

Ag nanoparticles loading of polypyrrole-coated superwetting mesh for on-demand separation of oil-water mixtures and catalytic reduction of aromatic dyes.

PubMed

Yihan, Sun; Mingming, Liu; Guo, Zhiguang

2018-05-19

Herein, a catalytic mesh with unique wettability, high oil-water separation efficiency and excellent catalytic performance towards aromatic dyes was fabricated. Polypyrrole (PPy) was firstly pre-coated on pristine stainless-steel mesh (SSM) surface via cyclic voltammetry approach. Subsequently, a simple electrodeposition process was performed to prepare and anchor Ag nanoparticles (AgNPs) onto the PPy-coated SSM surface. The PPy-coated mesh with anchored AgNPs was denoted as PPy/AgNPs-coated SSM. The obtained PPy/AgNPs-coated SSM exhibited dual superlyophobic properties and were able to achieve on-demand separation to deal with various of light oil (ρ oil  < ρ water ) and heavy oil (ρ oil  > ρ water )-water mixtures. Importantly, benefitting from AgNPs on mesh surface, the obtained PPy/AgNPs-coated SSM exhibits exceptional catalytic activity. As proof-of-concept three typical aromatic dye molecules (methylene blue, rhodamine B and Congo red) can be effectivity degraded. Additionally, the degradation of aromatic dyes and oil-water separation were achieved simultaneously when the PPy/AgNPs-coated SSM was converted to water-removing mode. Therefore, the present work is of great significance to the development of novel oil-water filtration membranes and can open a new avenue towards the practicability of metal nanoparticle catalysts in wastewater treatment. Copyright © 2018 Elsevier Inc. All rights reserved.

Understanding the adsorptive and photoactivity properties of Ag-graphene oxide nanocomposites.

PubMed

Martínez-Orozco, R D; Rosu, H C; Lee, Soo-Wohn; Rodríguez-González, V

2013-12-15

Nanocomposites of graphene oxide (GO) and silver nanoparticles (AgNPs) were synthetized using a practical photochemical silver functionalization. Their photocatalytic activities were evaluated with two dyes, Rhodamine B and Indigo Carmine, under visible-light irradiation. The prepared nanocomposites were characterized by HRTEM, FESEM, XRD, Raman, FTIR and UV-vis absorption spectroscopy. These nanocomposites present new defect domains of sp(3) type in combination with several graphitic functional groups that act as nucleation sites for anchoring AgNPs, while the sp(2)-sp(3) edge defects domains of GO generate the photoactivity. Furthermore, their photocatalytic performances are governed by their large adsorption capacity, and strong interaction with dye chromophores. A comprehensive photocatalytic way underlying the importance of adsorption is suggested to explain the low visible-light responsive photoactivity of the AgNPs-GO nanocomposites and the possible binding-site saturation. Then, the usage of H2SO4 allows the production of ionic species and helps to confirm the strong adsorption of both dyes. The ability to synthesize AgNPs-GO nanocomposites with extensive adsorptive capacity is certainly of interest for the efficient removal of hazardous materials. Copyright © 2013 Elsevier B.V. All rights reserved.

Thin silica shell coated Ag assembled nanostructures for expanding generality of SERS analytes

PubMed Central

Kang, Yoo-Lee; Lee, Minwoo; Kang, Homan; Kim, Jaehi; Pham, Xuan-Hung; Kim, Tae Han; Hahm, Eunil; Lee, Yoon-Sik; Jeong, Dae Hong

2017-01-01

Surface-enhanced Raman scattering (SERS) provides a unique non-destructive spectroscopic fingerprint for chemical detection. However, intrinsic differences in affinity of analyte molecules to metal surface hinder SERS as a universal quantitative detection tool for various analyte molecules simultaneously. This must be overcome while keeping close proximity of analyte molecules to the metal surface. Moreover, assembled metal nanoparticles (NPs) structures might be beneficial for sensitive and reliable detection of chemicals than single NP structures. For this purpose, here we introduce thin silica-coated and assembled Ag NPs (SiO2@Ag@SiO2 NPs) for simultaneous and quantitative detection of chemicals that have different intrinsic affinities to silver metal. These SiO2@Ag@SiO2 NPs could detect each SERS peak of aniline or 4-aminothiophenol (4-ATP) from the mixture with limits of detection (LOD) of 93 ppm and 54 ppb, respectively. E-field distribution based on interparticle distance was simulated using discrete dipole approximation (DDA) calculation to gain insight into enhanced scattering of these thin silica coated Ag NP assemblies. These NPs were successfully applied to detect aniline in river water and tap water. Results suggest that SiO2@Ag@SiO2 NP-based SERS detection systems can be used as a simple and universal detection tool for environment pollutants and food safety. PMID:28570633

Antibacterial Activity Of ternary semiconductor compounds AgInSe2 Nanoparticles Synthesized by Simple Chemical Method

NASA Astrophysics Data System (ADS)

Shehab, A. A.; Fadaam, S. A.; Abd, A. N.; Mustafa, M. H.

2018-05-01

In this objective AgInSe2Nanoparticles (AgInSe2 NPs) were prepared by a simple chemical method (SCM). The optica structural l and morphological properties of the synthesized AgInSe2 NPs swere investigated by using UVVI absorption atomic force microscopy AFMmf, Fourier Transform Infrared Spectroscopy and x-ray diffraction. The resistance of bacteria represents a trouble and the outlook for the use of antibiotics in the future until now uncertain. Measures must be taken to decrease this problem. Antibacterial activity of the AgInSe2 nanoparticles were exposed against several pathogenic bacteriaa including Klebsiella pneumonia KPa, Staphylococcus aureus, Bacillus subtili, Enterobacter Cloacae and Esherichia Coliby. Using a good spread method the results showed that AgInSe2 NPs had inhibitory effect versus some pathogenic bacteria with suppression area 18, 14 and 17 mm for SAgInSe2 NPs had an inhibitory effect against S Bacillus Subtilis 11 mm K EnterobactercCloacae 12 mm.

Synthesis and Complete Antimicrobial Characterization of CEOBACTER, an Ag-Based Nanocomposite

PubMed Central

Vasquez-Peña, M.; Raymond-Herrera, O.; Villavicencio-García, H.; Petranovskii, V.; Vazquez-Duhalt, R.; Huerta-Saquero, A.

2016-01-01

The antimicrobial activity of silver nanoparticles (AgNPs) is currently used as an alternative disinfectant with diverse applications, ranging from decontamination of aquatic environments to disinfection of medical devices and instrumentation. However, incorporation of AgNPs to the environment causes collateral damage that should be avoided. In this work, a novel Ag-based nanocomposite (CEOBACTER) was successfully synthetized. It showed excellent antimicrobial properties without the spread of AgNPs into the environment. The complete CEOBACTER antimicrobial characterization protocol is presented herein. It is straightforward and reproducible and could be considered for the systematic characterization of antimicrobial nanomaterials. CEOBACTER showed minimal bactericidal concentration of 3 μg/ml, bactericidal action time of 2 hours and re-use capacity of at least five times against E. coli cultures. The bactericidal mechanism is the release of Ag ions. CEOBACTER displays potent bactericidal properties, long lifetime, high stability and re-use capacity, and it does not dissolve in the solution. These characteristics point to its potential use as a bactericidal agent for decontamination of aqueous environments. PMID:27824932

E-beam deposited Ag-nanoparticles plasmonic organic solar cell and its absorption enhancement analysis using FDTD-based cylindrical nano-particle optical model.

PubMed

Kim, Richard S; Zhu, Jinfeng; Park, Jeung Hun; Li, Lu; Yu, Zhibin; Shen, Huajun; Xue, Mei; Wang, Kang L; Park, Gyechoon; Anderson, Timothy J; Pei, Qibing

2012-06-04

We report the plasmon-assisted photocurrent enhancement in Ag-nanoparticles (Ag-NPs) embedded PEDOT:PSS/P3HT:PCBM organic solar cells, and systematically investigate the causes of the improved optical absorption based on a cylindrical Ag-NPs optical model which is simulated with a 3-Dimensional finite difference time domain (FDTD) method. The proposed cylindrical Ag-NPs optical model is able to explain the optical absorption enhancement by the localized surface plasmon resonance (LSPR) modes, and to provide a further understanding of Ag-NPs shape parameters which play an important role to determine the broadband absorption phenomena in plasmonic organic solar cells. A significant increase in the power conversion efficiency (PCE) of the plasmonic solar cell was experimentally observed and compared with that of the solar cells without Ag-NPs. Finally, our conclusion was made after briefly discussing the electrical effects of the fabricated plasmonic organic solar cells.

Rich variety of substrates for surface enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Nguyen, Bich Ha; Hieu Nguyen, Van; Nhung Tran, Hong

2016-09-01

The efficiency of the application of surface enhanced Raman spectroscopy (SERS) technique to each specified purpose significantly depends on the choice of the SERS substrate with an appropriate structure as well as on its performance. Until the present time a rich variety of SERS substrates was fabricated. They can be classified according to their structures. The present work is a review of main types of SERS substrates for using in the trace analysis application. They can be classified into 4 groups: (1) Substrates using gold nanoparticles (AuNPs) with spherical shape such as colloidal AuNPs, AuNPs fabricated by pulsed laser deposition, by sputtering or by capillary force assembly (CFA), substrates fabricated by electrospinning technique, substrates using metallic nanoparticle arrays fabricated by electron beam lithography combined with CFA method, substrates using silver nanoparticle (AgNP) arrays grain by chemical seeded method, substrates with tunable surface plasmon resonance, substrates based on precies subnanometer plasmonic junctions within AuNP assemblies, substrates fabricated by simultaneously immobilizing both AuNPs and AgNPs on the same glass sides etc. (2) Substrates using nanostructures with non-spherical shapes such as gold nanowire (NW), or highly anisotropic nickel NW together with large area, free-standing carpets, substrates with obviously angular, quasi-vertically aligned cuboid-shaped TiO2 NW arrays decorated with AgNPs, substrates using gold nanoprism monolayer films, substrates using silver nanocube dimmers or monodisperse close-packed gold nanotriangle monolayers. (3) Substrates using multiparticle complex nanostructure such as nanoparticle cluster arrays, gold nanoflowers and nanodendrites. (4) Flexible substrate such as paper-based swab with gold nanorods, adhesive polymer tapes fabricated by inkjet printing method and flexible and adhesive SERS tapes fabricated by decorating AuNPs via the conventional drop-dry method.

Bio-inspired sustainable and green synthesis of plasmonic Ag/AgCl nanoparticles for enhanced degradation of organic compound from aqueous phase.

PubMed

Devi, Th Babita; Ahmaruzzaman, M

2016-09-01

In the current study, we report the utilization of the biogenic potential of Benincasa hispida (ash gourd) peel extract for the synthesis of Ag embedded AgCl nanoparticles nanoparticles (Ag/AgCl NPs) without the use of any external organic solvents. The appearance of dark brown color from the pale yellow color confirmed the formation of Ag/AgCl nanoparticles which was further validated by absorbance peak using UV-visible spectroscopy. The phytochemicals (flavones) present in the B. hispida peel extract acts as a reducing/stabilizing agents. The morphology and size of the synthesized NPs were characterized by transmission electron microscope (TEM), selected area electron microscope (SAED) and high resolution transmission electron microscope (HR-TEM). FT-IR spectra of the B. hispida peel extract and after the development of nanoparticles are determined to identify the functional groups responsible for the conversion of metal ions to metal nanoparticles. The synthesized nanoparticles showed an excellent photocatalytic property in the degradation of toxic dye like malachite green oxalate under sunlight irradiation. For the first time, malachite green oxalate dye was degraded by Ag/AgCl nanoparticles under sunlight irradiation.

Detecting decompositions of sulfur hexafluoride using reduced graphene oxide decorated with Pt nanoparticles

NASA Astrophysics Data System (ADS)

Chen, Dachang; Tang, Ju; Zhang, Xiaoxing; Fang, Jiani; Li, Yi; Zhuo, Ran

2018-05-01

The resistance-typed gas sensing material of Pt nanoparticles (PtNPs) decorated reduced graphene oxide (RGO) synthesized by one-step chemical reduction for the detection of four types of SF6 decompositions was explored. The PtNPs disperse uniformly on RGO with particle size near 2–4 nm and a small number of particles are larger than 10 nm. Gas sensing tests suggest that the introduction of PtNPs increases the response to SO2, SOF2 and H2S compared to pure RGO and PtNPs-RGO experiences resistance reducing in SO2 and SOF2 while presenting the opposite case in H2S. Elevating the temperature enhances the recovery properties to SO2 and H2S but lowers the sensitivity. The sensing mechanism for Pt-RGO in low oxygen and water environment depends mainly on the charge transfer between gas and adsorbent and the solvent on material surface. The work provides experimental investigation of Pt-RGO to detect SF6 decompositions.

A colorimetric assay for measuring iodide using Au@Ag core-shell nanoparticles coupled with Cu(2+).

PubMed

Zeng, Jingbin; Cao, Yingying; Lu, Chun-Hua; Wang, Xu-Dong; Wang, Qianru; Wen, Cong-Ying; Qu, Jian-Bo; Yuan, Cunguang; Yan, Zi-Feng; Chen, Xi

2015-09-03

Au@Ag core-shell nanoparticles (NPs) were synthesized and coupled with copper ion (Cu(2+)) for the colorimetric sensing of iodide ion (I(-)). This assay relies on the fact that the absorption spectra and the color of metallic core-shell NPs are sensitive to their chemical ingredient and dimensional core-to-shell ratio. When I(-) was added to the Au@Ag core-shell NPs-Cu(2+) system/solution, Cu(2+) can oxidize I(-) into iodine (I2), which can further oxidize silver shells to form silver iodide (AgI). The generated Au@AgI core-shell NPs led to color changes from yellow to purple, which was utilized for the colorimetric sensing of I(-). The assay only took 10 min with a lowest detectable concentration of 0.5 μM, and it exhibited excellent selectivity for I(-) over other common anions tested. Furthermore, Au@Ag core-shell NPs-Cu(2+) was embedded into agarose gels as inexpensive and portable "test strips", which were successfully used for the semi-quantitation of I(-) in dried kelps. Copyright © 2015 Elsevier B.V. All rights reserved.

Ag-ZnO nanostructure for ANTA explosive molecule detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaik, Ummar Pasha; Sangani, L. D. Varma; Gaur, Anshu

2016-05-23

Ag/ZnO nanostructure for surface enhanced Raman scattering application in the detection of ANTA explosive molecule is demonstrated. A highly rough ZnO microstructure was achieved by rapid thermal annealing of metallic Zn film. Different thickness Ag nanostructures are decorated over these ZnO microstructures by ion beam sputtering technique. Surface enhanced Raman spectroscopic studies carried out over Ag/ZnO substrates have shown three orders higher enhancement compared to bare Ag nanostructure deposited on the same substrate. The reasons behind such huge enhancement are discussed based on the morphology of the sample.

Ag Nanoparticles (Ag NM300K) in the Terrestrial Environment: Effects at Population and Cellular Level in Folsomia candida (Collembola)

PubMed Central

Mendes, Luís André; Maria, Vera L.; Scott-Fordsmand, Janeck J.; Amorim, Mónica J. B.

2015-01-01

The effects of nanomaterials have been primarily assessed based on standard ecotoxicity guidelines. However, by adapting alternative measures the information gained could be enhanced considerably, e.g., studies should focus on more mechanistic approaches. Here, the environmental risk posed by the presence of silver nanoparticles (Ag NM300K) in soil was investigated, anchoring population and cellular level effects, i.e., survival, reproduction (28 days) and oxidative stress markers (0, 2, 4, 6, 10 days). The standard species Folsomia candida was used. Measured markers included catalase (CAT), glutathione reductase (GR), glutathione S-transferase (GST), total glutathione (TG), metallothionein (MT) and lipid peroxidation (LPO). Results showed that AgNO3 was more toxic than AgNPs at the population level: reproduction EC20 and EC50 was ca. 2 and 4 times lower, respectively. At the cellular level Correspondence Analysis showed a clear separation between AgNO3 and AgNP throughout time. Results showed differences in the mechanisms, indicating a combined effect of released Ag+ (MT and GST) and of AgNPs (CAT, GR, TG, LPO). Hence, clear advantages from mechanistic approaches are shown, but also that time is of importance when measuring such responses. PMID:26473892

Insights into the proteomic response of soybean towards Al₂O₃, ZnO, and Ag nanoparticles stress.

PubMed

Hossain, Zahed; Mustafa, Ghazala; Sakata, Katsumi; Komatsu, Setsuko

2016-03-05

Understanding the complex mechanisms involved in plant response to nanoparticles is indispensable in assessing the impact of nano-pollutants on environment. The present study compares the phytotoxicity of three different metal-based nanoparticles (Al2O3, ZnO, and Ag) in soybean seedling at proteome level. Plant growth, rigidity of roots, and root cell viability were markedly affected by ZnO- and Ag-NPs stress; while, Al2O3-NPs challenged soybean maintained normal seedling growth like control. Moreover, severe oxidative burst was evident in ZnO-NPs and Ag-NPs treatments. Gel-free proteomic analysis of NPs stressed soybean roots revealed 104 commonly changed proteins primarily associated with secondary metabolism, cell organization, and hormone metabolism. Oxidation-reduction cascade related genes, such as GDSL motif lipase 5, SKU5 similar 4, galactose oxidase, and quinone reductase were up-regulated in Al2O3-NPs challenged roots and down-regulated in ZnO- and Ag-NPs treatments. In comparison to root, 16 common proteins were found to be significantly changed in leaves of NPs exposed soybean that were predominantly associated to photosystem and protein degradation. The proteomic findings suggest that high abundance of proteins involved in oxidation-reduction, stress signaling, hormonal pathways related to growth and development might be the principal key for optimum growth of soybean under Al2O3-NPs stress. Copyright © 2015 Elsevier B.V. All rights reserved.

Pt decorated MoS2 nanoflakes for ultrasensitive resistive humidity sensor

NASA Astrophysics Data System (ADS)

Burman, Debasree; Santra, Sumita; Pramanik, Panchanan; Guha, Prasanta Kumar

2018-03-01

In this work, we report the fabrication of a low power, humidity sensor where platinum nanoparticles (NPs) decorated few-layered molybdenum disulphide (MoS2) nanoflakes have been used as the sensing layer. A mixed solvent was used to exfoliate the nanoflakes from the bulk powder. Then the Pt/MoS2 composites were prepared by reducing Pt NPs from chloroplatinic acid hexahydrate using a novel reduction technique using sulphide salt. The successful reduction and composite preparation were confirmed using various material characterization tools like scanning electron microscopy, atomic force microscopy, transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, Raman spectroscopy and UV-visible spectroscopy. The humidity sensors were prepared by drop-coating the Pt-decorated MoS2 on gold interdigitated electrodes and then exposed to various levels of relative humidity (RH). Composites with different weight ratios of Pt were tested and the best response was shown by the Pt/MoS2 (0.25:1) sample with a record high response of ˜4000 times at 85% RH. The response and recovery times were ˜92 s and ˜154 s respectively with repeatable behaviour. The sensor performance was found to be stable when tested over a few months. The underlying sensing mechanisms along with detailed characterization of the various composites have been discussed.

Homogeneous synthesis of Ag nanoparticles-doped water-soluble cellulose acetate for versatile applications.

PubMed

Cao, Jie; Sun, Xunwen; Zhang, Xinxing; Lu, Canhui

2016-11-01

We report a facile and efficient approach for synthesis of well-dispersed and stable silver nanoparticles (Ag NPs) using water-soluble cellulose acetate (CA) as both reductant and stabilizer. Partially substituted CA with highly active hydroxyl groups and excellent water-solubility is able to reduce silver ions in homogeneous aqueous medium effectively. The synthesized Ag NPs were characterized by UV-vis spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and energy dispersive X-ray spectroscope analysis. The as-prepared Ag NPs were well-dispersed, showing a surface plasmon resonance peak at 426nm. The resulted Ag NPs@CA nanohybrids exhibit high catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH 4 . Meanwhile, the nanohybrids are also effective in inhibiting the growth of bacterial. This environmentally friendly method promotes the use of renewable natural resources to prepare a variety of inorganic-organic materials for catalysis, antibacterial, sensors and other applications. Copyright © 2016 Elsevier B.V. All rights reserved.

RGO/Au NPs/N-doped CNTs supported on nickel foam as an anode for enzymatic biofuel cells.

PubMed

Zhang, He; Zhang, Lingling; Han, Yujie; Yu, You; Xu, Miao; Zhang, Xueping; Huang, Liang; Dong, Shaojun

2017-11-15

In this study, three-dimensional reduced graphene oxide/Au NPs/nitrogen-doped carbon nanotubes (RGO/Au NPs/N-doped CNTs) assembly supported on nickel foam was utilized as an anode for enzymatic biofuel cells (EBFCs). 3D RGO/Au NPs was obtained by electrodepositing reduced graphene oxide on nickel foam (Ni foam), while Au NPs were co-deposited during the process. Afterwards, nitrogen doped CNTs (N-CNTs) were allowed to grow seamlessly on the surfaces of 3D RGO/Au NPs via a simple chemical vapor deposition (CVD) process. In this nanostructure, Au NPs co-deposition and nitrogen doping offer more active sites for bioelectrocatalysis. Additionally, N-CNTs were demonstrated providing high specific surface area for enzyme immobilization and facilitating the electron transfer between glucose oxidase (GOx) and electrode. The resulting bioanode achieved efficient glucose oxidation with high current densities of 7.02mAcm -2 (0.3V vs. Ag/AgCl). Coupling with a Pt cathode, the fabricated glucose/air biofuel cell exhibited an open-circuit potential of 0.32V and generated a maximum power density 235µWcm -2 at 0.15V. This novel electrode substrate achieved high performance in current density at bioelectrochemical systems and could be useful for further exploiting the application of three dimensional carbon-based nanomaterials in EBFCs. Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis, structural and optical properties of silver nanoparticles uniformly decorated ZnO nanowires

NASA Astrophysics Data System (ADS)

Zhang, Ke-Xin; Wen, Xing; Yao, Cheng-Bao; Li, Jin; Zhang, Meng; Li, Qiang-Hua; Sun, Wen-Jun; Wu, Jia-Da

2018-04-01

Silver (Ag) nanoparticles decorated Zinc oxide (A-ZnO) nanowires have been successfully synthesized by two-step chemical vapour deposition and magnetron sputtering method. The X-ray diffraction patterns revealed their hexagonal wurtzite structure. SEM images indicated the Ag nanoparticles are distributed uniformly on the surface of A-ZnO nanowires. By extending the sputtering time, the atomic percent of Ag increased gradually. Moreover, the photoluminescence results demonstrated two major emission peaks for the A-ZnO nanowires. Where, the visible emission peaks were stronger than those of unmodified ZnO nanowires. These studies promise their potential applications in multifunctional optical devices.

Self-decorated Au nanoparticles on antireflective Si pyramids with improved hydrophobicity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saini, C. P.; Barman, A.; Kanjilal, A., E-mail: aloke.kanjilal@snu.edu.in

2016-04-07

Post-deposition annealing mediated evolution of self-decorated Au nanoparticles (NPs) on chemically etched Si pyramids is presented. A distinct transformation of Si surfaces from hydrophilic to hydrophobic is initially found after chemical texturing, showing an increase in contact angle (CA) from 58° to 98° (±1°). Further improvement of hydrophobicity with CA up to ∼118° has been established after annealing a 10 nm thick Au-coated Si pyramids at 400 °C that led to the formation of Au NPs on Si facets along with self-ordering at the pyramid edges. Detailed x-ray diffraction studies suggest the evolution of crystalline Au NPs on strained Si facets. Microstructuralmore » studies, however, indicate no mixing of Au and Si atoms at the Au/Si interfaces, instead of forming Au nanocrystals at 400 °C. The improved hydrophobicity of Si pyramids, even with Au NPs can be explained in the light of a decrease in solid fractional surface area according to Wenzel's model. Moreover, a sharp drop in specular reflectance from Si pyramids in the range of 300–800 nm, especially in the ultraviolet region up to ∼0.4% is recorded in the presence of Au NPs by ultraviolet-visible spectroscopy, reflecting the possible use in photovoltaic devices with improved antireflection property.« less

Mussel-inspired functionalization of graphene for synthesizing Ag-polydopamine-graphene nanosheets as antibacterial materials

NASA Astrophysics Data System (ADS)

Zhang, Zhe; Zhang, Jing; Zhang, Bailin; Tang, Jilin

2012-12-01

Mussels have been shown to attach to virtually all types of inorganic and organic surfaces via their adhesive proteins. The adhesive proteins secreted by mussels contain high concentrations of catechol and amine functional groups, which have similar functional groups with polydopamine (PDA). Inspired by mussels, a mild and environmentally friendly method was used to synthesize Ag nanoparticles (Ag NPs) on functionalized PDA-graphene nanosheets (PDA-GNS) with uniform and high dispersion. First, a uniform layer of PDA was coated on graphene oxide (GO) by polymerizing dopamine (DA) at room temperature. During the process GO was reduced by the DA. The PDA layer on the surface of GNS can be used as a nanoscale guide to form uniform Ag NPs on the surface of PDA-GNS. The obtained Ag-PDA-GNS hybrid materials are characterized by atomic force microscopy, transmission electron microscopy, UV-vis spectroscopy, Raman spectroscopy, X-ray photo-electron spectroscopy, X-ray diffraction, and thermal gravimetric analysis. The resultant Ag-PDA-GNS hybrid materials exhibited strong antibacterial properties to both Gram-negative and Gram-positive bacteria due to the synergistic effect of GNS and Ag NPs.Mussels have been shown to attach to virtually all types of inorganic and organic surfaces via their adhesive proteins. The adhesive proteins secreted by mussels contain high concentrations of catechol and amine functional groups, which have similar functional groups with polydopamine (PDA). Inspired by mussels, a mild and environmentally friendly method was used to synthesize Ag nanoparticles (Ag NPs) on functionalized PDA-graphene nanosheets (PDA-GNS) with uniform and high dispersion. First, a uniform layer of PDA was coated on graphene oxide (GO) by polymerizing dopamine (DA) at room temperature. During the process GO was reduced by the DA. The PDA layer on the surface of GNS can be used as a nanoscale guide to form uniform Ag NPs on the surface of PDA-GNS. The obtained Ag

Palladium nanoparticle-decorated 2-D graphene oxide for effective photodynamic and photothermal therapy of prostate solid tumors.

PubMed

Thapa, Raj Kumar; Soe, Zar Chi; Ou, Wenquan; Poudel, Kishwor; Jeong, Jee-Heon; Jin, Sung Giu; Ku, Sae Kwang; Choi, Han-Gon; Lee, You Mie; Yong, Chul Soon; Kim, Jong Oh

2018-05-23

Intratumoral injection of nanoparticles is a viable alternative for treating solid tumors. In this study, we used intratumorally-injected palladium nanoparticle (Pd NP)-decorated graphene oxide (GO) (GO-Pd NPs) for the treatment of solid prostate tumors. GO was synthesized using the modified Hummer's method and GO-Pd NPs were prepared using the one pot synthesis method. Studies on physicochemical characterization and in vitro/in vivo anticancer properties were performed using GO-Pd NPs. Successful preparation of GO-Pd NPs was confirmed by transmission electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Compared to GO or Pd NPs alone, GO-Pd NPs showed higher cytotoxic effects in prostate cancer 3 (PC3) cells. Irradiation of treated cells with near infrared (NIR) laser considerably enhanced apoptosis induced by synergistic photothermal effect and reactive oxygen species (ROS) generation. Intratumorally-injected GO-Pd NPs showed promising in vivo localized distribution, photothermal ablation, and anti-tumor effects in the PC3 xenograft mouse model. Furthermore, the minimal organ toxicity of GO-Pd NPs was an added advantage. Hence, GO-Pd NPs could be a potential formulation for localized treatment of prostate solid tumors. Copyright © 2018. Published by Elsevier B.V.

Synthesis of a novel Au nanoparticles decorated Ni-MOF/Ni/NiO nanocomposite and electrocatalytic performance for the detection of glucose in human serum.

PubMed

Chen, Jingyuan; Xu, Qin; Shu, Yun; Hu, Xiaoya

2018-07-01

A nonenzymatic glucose electrochemical sensor was constructed based on Au nanoparticles (AuNPs) decorated Ni metal-organic-framework (MOF)/Ni/NiO nanocomposite. Ni-MOF/Ni/NiO nanocomposite was synthesized by one-step calcination of Ni-MOF. Then AuNPs were loaded onto the Ni-based nanocomposites' surface through electrostatic adsorption. Through characterization by transmission electron microscopy (TEM), high resolution TEM (HRTEM) and energy disperse spectroscopy (EDS) mapping, it is found that the AuNPs were well distributed on the surface of Ni-based nanocomposite. Cyclic voltammetric (CV) study showed the electrocatalytic activity of Au-Ni nanocomposite was highly improved after loading AuNPs onto it. Amperometric study demonstrated that the Au-Ni nanocomposites modified glassy carbon electrode (GCE) exhibited a high sensitivity of 2133.5 mA M -1 cm -2 and a wide linear range (0.4-900 μM) toward the oxidation of glucose with a detection limit as low as 0.1 μM. Moreover, the reproducibility, selectivity and stability of the sensor all exhibited outstanding performance. We applied the as-fabricated high performance sensor to measure the glucose levels in human serum and obtained satisfactory results. It is believed that AuNPs decorated Ni MOF/Ni/NiO nanocomposite provides a new platform for developing highly performance electrochemical sensors in practical applications. Copyright © 2018 Elsevier B.V. All rights reserved.

A novel approach for the synthesis of ultrathin silica-coated iron oxide nanocubes decorated with silver nanodots (Fe3O4/SiO2/Ag) and their superior catalytic reduction of 4-nitroaniline

NASA Astrophysics Data System (ADS)

Abbas, Mohamed; Torati, Sri Ramulu; Kim, Cheolgi

2015-07-01

A novel sonochemical approach was developed for the synthesis of different core/shell structures of Fe3O4/SiO2/Ag nanocubes and SiO2/Ag nanospheres. The total reaction time of the three sonochemical steps for the synthesis of Fe3O4/SiO2/Ag nanocubes is shorter than that of the previously reported methods. A proposed reaction mechanism for the sonochemical functionalization of the silica and the silver on the surface of magnetic nanocubes was discussed in detail. Transmission electron microscopy revealed that the surface of Fe3O4/SiO2 nanocubes was decorated with small Ag nanoparticles of approximately 10-20 nm in size, and the energy dispersive spectroscopy mapping analysis confirmed the morphology of the structure. Additionally, X-ray diffraction data were used to confirm the formation of both phases of a cubic inverse spinel structure for Fe3O4 and bcc structures for Ag in the core/shell structure of the Fe3O4/SiO2/Ag nanocubes. The as-synthesized Fe3O4/SiO2/Ag nanocubes showed a high efficiency in the catalytic reduction reaction of 4-nitroaniline to 4-phenylenediamine and a better performance than both Ag and SiO2/Ag nanoparticles. The grafted silver catalyst was recycled and reused at least fifteen times without a significant loss of catalytic efficiency.A novel sonochemical approach was developed for the synthesis of different core/shell structures of Fe3O4/SiO2/Ag nanocubes and SiO2/Ag nanospheres. The total reaction time of the three sonochemical steps for the synthesis of Fe3O4/SiO2/Ag nanocubes is shorter than that of the previously reported methods. A proposed reaction mechanism for the sonochemical functionalization of the silica and the silver on the surface of magnetic nanocubes was discussed in detail. Transmission electron microscopy revealed that the surface of Fe3O4/SiO2 nanocubes was decorated with small Ag nanoparticles of approximately 10-20 nm in size, and the energy dispersive spectroscopy mapping analysis confirmed the morphology of the

Preparation and antibacterial activities of Ag/Ag+/Ag3+ nanoparticle composites made by pomegranate (Punica granatum) rind extract

NASA Astrophysics Data System (ADS)

Yang, Hui; Ren, Yan-yu; Wang, Tao; Wang, Chuang

Nano-silver and its composite materials are widely used in medicine, food and other industries due to their strong conductivity, size effect and other special performances. So far, more microbial researches have been applied, but a plant method is rarely reported. In order to open up a new way to prepare AgNP composites, pomegranate peel extract was used in this work to reduce Ag+ to prepare Ag/Ag+/Ag3+ nanoparticle composites. UV-Vis was employed to detect and track the reduction of Ag+ and the forming process of AgNPs. The composition, structure and size of the crystal were analyzed by XRD and TEM. Results showed that, under mild conditions, pomegranate peel extract reacted with dilute AgNO3 solution to produce Ag/Ag+/Ag3+ nanoparticle composites. At pH = 8 and 10 mmol/L of AgNO3 concentration, the size of the achieved composites ranged between 15 and 35 nm with spherical shapes and good crystallinity. The bactericidal experiment indicated that the prepared Ag/Ag+/Ag3+ nanoparticles had strong antibacterial activity against gram positive bacteria and gram negative bacteria. FTIR analysis revealed that biological macromolecules with groups of sbnd NH2, sbnd OH, and others were distributed on the surface of the newly synthesized Ag/Ag+/Ag3+ nanoparticles. This provided a useful clue to further study the AgNP biosynthesis mechanism.

Facile fabrication of homogeneous 3D silver nanostructures on gold-supported polyaniline membranes as promising SERS substrates.

PubMed

Xu, Ping; Mack, Nathan H; Jeon, Sea-Ho; Doorn, Stephen K; Han, Xijiang; Wang, Hsing-Lin

2010-06-01

We report a facile synthesis of large-area homogeneous three-dimensional (3D) Ag nanostructures on Au-supported polyaniline (PANI) membranes through a direct chemical reduction of metal ions by PANI. The citric acid absorbed on the Au nuclei that are prefabricated on PANI membranes directs Ag nanoaprticles (AgNPs) to self-assemble into 3D Ag nanosheet structures. The fabricated hybrid metal nanostructures display uniform surface-enhanced Raman scattering (SERS) responses throughout the whole surface area, with an average enhancement factor of 10(6)-10(7). The nanocavities formed by the stereotypical stacking of these Ag nanosheets and the junctions and gaps between two neighboring AgNPs are believed to be responsible for the strong SERS response upon plasmon absorption. These homogeneous metal nanostructure decorated PANI membranes can be used as highly efficient SERS substrates for sensitive detection of chemical and biological analytes.

Pt@Ag and Pd@Ag core/shell nanoparticles for catalytic degradation of Congo red in aqueous solution.

PubMed

Salem, Mohamed A; Bakr, Eman A; El-Attar, Heba G

2018-01-05

Platinum/silver (Pt@Ag) and palladium/silver (Pd@Ag) core/shell NPs have been synthesized in two steps reaction using the citrate method. The progress of nanoparticle formation was followed by the UV/Vis spectroscopy. Transmission electron microscopy revealed spherical shaped core/shell nanoparticles with average particle diameter 32.17nm for Pt@Ag and 8.8nm for Pd@Ag. The core/shell NPs were further characterized by FT-IR and XRD. Reductive degradation of the Congo red dye was chosen to demonstrate the excellent catalytic activity of these core/shell nanostructures. The nanocatalysts act as electron mediators for the transfer of electrons from the reducing agent (NaBH 4 ) to the dye molecules. Effect of reaction parameters such as nanocatalyst dose, dye and NaBH 4 concentrations on the dye degradation was investigated. A comparison between the catalytic activities of both nanocatalysts was made to realize which of them the best in catalytic performance. Pd@Ag was the higher in catalytic activity over Pt@Ag. Such greater activity is originated from the smaller particle size and larger surface area. Pd@Ag nanocatalyst was catalytically stable through four subsequent reaction runs under the utilized reaction conditions. These findings can thus be considered as possible economical alternative for environmental safety against water pollution by dyes. Copyright © 2017. Published by Elsevier B.V.

pH-sensitive nanocarrier based on gold/silver core-shell nanoparticles decorated multi-walled carbon manotubes for tracing drug release in living cells.

PubMed

Chen, Peng; Wang, Zhuyuan; Zong, Shenfei; Zhu, Dan; Chen, Hui; Zhang, Yizhi; Wu, Lei; Cui, Yiping

2016-01-15

We fabricate a multifunctional nanocarrier based on multi-walled carbon nanotubes (MWCNTs) decorated with gold/silver core-shell nanoparticles (Au@Ag NPs) and fluorescein isothiocyanate (FITC) for tracking the intracellular drug release process. In the demonstrated nanocarrier, the Au@Ag NPs adsorbed on the surface of MWCNTs were labeled with the pH-dependent SERS reporter 4-Mercaptobenzoic acid (4MBA) for SERS based pH sensing. FITC was conjugated on MWCNTs to provide fluorescence signal for tracing the MWCNTs. Fluorescent doxorubicin (DOX) was used as the model drug which can be loaded onto MWCNTs via π-π stacking and released from the MWCNTs under acidic condition. By detecting the SERS spectrum of 4MBA, the pH value around the nanocarrier could be monitored. Besides, by tracing the fluorescence of FITC and DOX, we can also investigate the drug release process in cells. Experimental results show that the proposed nanocarrier retained a well pH-sensitive performance in living cells, and the DOX detached from MWCNTs inside the lysosomes and entered into the cytoplasm with the MWCNTs being left in lysosomes. To further investigate the drug release dynamics, 2-D color-gradient pH mapping were plotted, which were calculated from the SERS spectra of 4MBA. The detailed release process and carrier distribution have been recorded as environmental pH changes during cell endocytosis. Furthermore, we also confirmed that the proposed nanocarrier has a good biocompatibility. It indicates that the designed nanocarrier have a great potential in intraceable drug delivery, cancer cells imaging and pH monitoring. Copyright © 2015 Elsevier B.V. All rights reserved.

Decoration of gold nanoparticles on thin multiwall carbon nanotubes and their use as a glucose sensor

NASA Astrophysics Data System (ADS)

Gangwar, Rajesh K.; Dhumale, Vinayak A.; Date, Kalyani S.; Alegaonkar, Prashant; Sharma, Rishi B.; Datar, Suwarna

2016-03-01

Thin multiwall carbon nanotubes (MWCNTs) have been decorated with gold nanoparticles (Au NPs) with polyaniline (PANI) as an inter-linker by a simple wet chemical method. The synthesized AuNPs:MWCNT:PANI composite was studied with UV-vis, FTIR, Raman spectroscopy, x-ray diffractometer, transmission electron microscopy (TEM) and atomic force microscopy (AFM). Conducting AFM (C-AFM) images of the composite reveal the role played by the two components in electrochemical reactions. The size of the Au NPs was found to be 13 ± 2 nm in the composite as observed from TEM. The synthesized AuNPs:MWCNT:PANI composite was further drop casted onto a glassy carbon electrode (GCE) for electrocatalytic study. The resulting composite exhibits good electrocatalytic activity towards reduction of H2O2 and O2. A glucose biosensor was developed by immobilizing glucose oxidase into AuNPs:MWCNT:PANI composite film on GCE. The fabricated sensor demonstrates good linear response to glucose (i.e. R = 0.9975) in the range of 2 to 12 mM.

The effect of nanoparticles (NPs) on sorption and suspension stability of technology critical elements (TCEs) in soil/sand solutions.

NASA Astrophysics Data System (ADS)

Dror, I.; Stepka, Z.; Berkowitz, B.

2016-12-01

As a consequence of their growing use in a range of electronic and industrial applications, increasing amounts of technology critical elements (TCEs) are being released to the environment. Currently, little is known about their fate and potential environmental impact. We report here on the adsorption of TCEs on sand and soil in the presence of selected nanoparticles (NPs). TCEs were tested within three different mixtures containing (i) rare earth elements (REEs), (ii) Ge, Pd, Ru and Ir together with Mo, Sb, Sn and Ti, and (iii) In, Sc, Th, Y and Yb together with a variety of other metals. The NPs examined for their suspending properties were: Al2O3, SiO2, CeO2, ZnO, Ag, Au, carbon dots and montmorillonite. Each NP was examined with each TCE solution mixture separately and with added humic acid. A clear difference was observed between REEs (and In, Sc), and the other TCEs. All REEs (and In, Sc) completely adsorb on soil and sand. For sand and soil, the presence of most NPs, alone, does not increase TCE concentrations in solution. For sand, addition of humic acid, with or without NPs, yields approximately the same increase in TCE concentration in solution (>80%). For soil solutions, presence of both NPs and humic acid increases TCE concentrations up to 500% more than any other combination tested, yielding 20% of added TCE amount. The other TCEs tested (mixtures (ii) and (iii)) adsorb less strongly to soil and sand, and unlike the REEs no general trend can be identified. For Al2O3, SiO2, CeO2, ZnO, carbon dots and montmorillonite, the increased concentrations of TCEs in the presence of NPs and humic acid were similar. This indicates that the observed effect depends on the presence of NPs and their surface coating rather than on the type of NP. Ag and Au NPs, however, reduce adsorption of TCEs to sand even when humic acid is absent. For example, Ag NPs reduce adsorption of REEs by >90% and Au NPs by 10%. For REEs, increased solution concentrations are correlated

Activated Carbon Fibers "Thickly Overgrown" by Ag Nanohair Through Self-Assembly and Rapid Thermal Annealing

NASA Astrophysics Data System (ADS)

Yan, Xuefeng; Xu, Sijun; Wang, Qiang; Fan, Xuerong

2017-11-01

Anisotropic nanomaterial-modified carbon fibers attract increasing attention because of their superior properties over traditional ones. In this study, activated carbon fibers (ACFs) "thickly overgrown" by Ag nanohair were prepared through self-assembly and rapid thermal annealing. Viscose fibers with well-dispersed silver nanoparticles (AgNPs) on surfaces were first prepared through self-assembly of hyperbranched poly(amino-amine) (HBPAA)-capped AgNPs on viscose surfaces. HBPAA endowed the AgNP surfaces with negative charges and abundant amino groups, allowing AgNPs to monodispersively self-assemble to fiber surfaces. Ag nanohair-grown ACFs were prepared by sequential pre-oxidation and carbonization. Because the carbonization furnace was open-ended, ACFs are immediately transferrable to the outside of the furnace. Therefore, the Ag liquid adsorbed by ACF pores squeezed out to form Ag nanowires through thermal contraction. FESEM characterization indicated that Ag nanohairs stood on ACF surface and grew from ACF caps. XPS and XRD characterization showed that Ag successfully assembled to fiber surfaces and retained its metallic state even after high-temperature carbonization. TG analysis suggested that Ag nanohair-grown ACFs maintained their excellent thermal stabilities. Finally, the fabricated ACFs showed excellent and durable antibacterial activities, and the developed method may provide a potential strategy for preparing metal nanowire-grown ACFs.

Surface colonized silver nano particles over chitosan poly-electrolyte micro-spheres and their multi-functional behavior

NASA Astrophysics Data System (ADS)

Prakash, B.; Asha, S.; Nimrodh Ananth, A.; Vanithakumari, G.; Okram, G. S.; Jose, Sujin P.; Jothi Rajan, M. A.

2018-02-01

Chitosan/tripolyphosphate polyelectrolyte (TPP) microspheres, decorated and surface functionalized with silver nanoparticles (NPs) of average diameter of 15 nm, were synthesized following a simple two-step procedure. These Ag NP-functionalized polyelectrolyte microspheres (Ag-CSPMs) are found to be biocompatible and enhancing the reactive oxygen species in curcumin with excellent anti-bacterial activity for selected Gram-positive and negative bacterial strains, making them much attractive relative to bare surface counterparts; the well-stabilized silver NPs do not form any agglomerations on the surface of the chitosan microspheres. They also show excellent cytotoxic behavior towards MCF7 cell lines, showing a half-maximal inhibitory concentration (IC50) of 32 μg ml-1. Therefore, Ag-CSPMs exhibit multi-functional ability having potential towards theranostics applications.

Enhanced non-enzymatic glucose sensing based on copper nanoparticles decorated nitrogen-doped graphene.

PubMed

Jiang, Ding; Liu, Qian; Wang, Kun; Qian, Jing; Dong, Xiaoya; Yang, Zhenting; Du, Xiaojiao; Qiu, Baijing

2014-04-15

Copper nanoparticles (NPs) decorated nitrogen-doped graphene (Cu-N-G) was prepared by a facile thermal treatment, and further employed as a novel sensing material for fabricating the sensitive non-enzymatic glucose sensor. Compared with pure Cu NPs, the Cu-N-G showed enhanced electrocatalytic activity to glucose oxidation due to the integration of N-G, which exhibited the oxidation peak current of glucose ca. 23-fold higher than that of pure Cu NPs. The presented sensor showed excellent performances for glucose detection including wide linear range of 0.004-4.5 mM, low detection limit (1.3 μM, S/N=3), high sensitivity (48.13 μA mM(-1)), fast response time (<5 s), good selectivity to the general coexisted interferences, etc. Such properties would promote the potential application of the nitrogen-doped graphene as enhanced materials in fabricating sensors for chemical and biochemical analysis. © 2013 Published by Elsevier B.V.

Synthesis and visible-light-induced catalytic activity of Ag2S-coupled TiO2 nanoparticles and nanowires

NASA Astrophysics Data System (ADS)

Xie, Yi; Heo, Sung Hwan; Kim, Yong Nam; Yoo, Seung Hwa; Cho, Sung Oh

2010-01-01

We present the synthesis and visible-light-induced catalytic activity of Ag2S-coupled TiO2 nanoparticles (NPs) and TiO2 nanowires (NWs). Through a simple wet chemical process from a mixture of peroxo titanic acid (PTA) solution, thiourea and AgAc, a composite of Ag2S NPs and TiO2 NPs with sizes of less than 7 nm was formed. When the NP composite was further treated with NaOH solution followed by annealing at ambient conditions, a new nanocomposite material comprising Ag2S NPs on TiO2 NWs was created. Due to the coupling with such a low bandgap material as Ag2S, the TiO2 nanocomposites could have a visible-light absorption capability much higher than that of pure TiO2. As a result, the synthesized Ag2S/TiO2 nanocomposites exhibited much higher catalytic efficiency for the decomposition of methyl orange than commercial TiO2 (Degussa P25, Germany) under visible light.

Improved diode performance of Ag nanoparticle dispersed Er doped In2O3 film

NASA Astrophysics Data System (ADS)

Ghosh, Anupam; Dwivedi, Shyam Murli Manohar Dhar; Chakrabartty, Shubhro; Mondal, Aniruddha

2018-04-01

Ag nanoparticle(NP) dispersedEr doped In2O3 film was prepared by sol-gel method followed by thermal evaporation cum glancing angle deposition technique. The Schottky contact based devicecontaining Ag NPs shows ideality factor of ˜180 at 10 K and ˜5 at 300 K, which is lesser as compared to the device that does not contain Ag NPs. The lower ideality factor value all over the temperature range makes the diode more reliable.

High-performance antibacterial of montmorillonite decorated with silver nanoparticles using microwave-assisted method

NASA Astrophysics Data System (ADS)

Kheiralla, Zeinab Mohamed Hassan; Rushdy, Abeer Ahmed; Betiha, Mohamed Ahmed; Yakob, Naglaa Abdullah Nasif

2014-08-01

Syntheses of silver nanocomposites (AgNPs@MMT) were fabricated with different silver nanoparticles to montmorillonite clay (MMT) ratios using microwave-assisted synthesis method, and silver nitrate was used as the precursor of silver nanoparticles. The antibacterial activities of the nanocomposite were evaluated against Staphylococcus aureus and Pseudomonas aeruginosa bacteria by the disk diffusion and macrodilution broth techniques. The prepared nanocomposites were characterized by N2 adsorption-desorption isotherms, X-ray diffraction (XRD), field emission scanning electron microscope, high-resolution transmission electron microscope (HRTEM), X-ray fluorescence spectroscopy and Fourier transform infrared spectroscopy. The wide-angle XRD patterns and HRTEM images demonstrate that silver nanoparticles were fabricated on surface and within MMT channels. The diameters of the AgNPs were below 15 nm, as indicated by UV-Vis absorption, which effectively controlled by the pores of the MMT host. Data revealed that 5 % AgNP@MMT nanocomposite is much more effective than silver nitrate and shows strong antibacterial activities. The efficiency of antibiotics increased when combined with 5 % AgNP@MMT nanocomposite against both the tested strains. The increase in fold area was higher in case of P. aeruginosa than S. aureus. The highest percentage of fold increases was found for Sulfamethaxole/Trimethoprim and Oxacillin followed by Levofloxaci and Nalidixic acid against P.aeruginosa. On the other hand, Imipenem increases activity in presence of AgNP@MMT nanocomposite against S. aureus. Overall, the synergistic effect of antibiotics and nanoparticles clearly revealed that nanoparticles can be effectively used in combination with antibiotics in order to improve their efficiency against various pathogenic microbes. The suspensions of the synthesized nanocomposites were found to be stable over a long time without any sign of detachment of AgNPs.

Plasmon enhanced upconversion luminescence of NaYF4:Yb,Er@SiO2@Ag core-shell nanocomposites for cell imaging.

PubMed

Yuan, Peiyan; Lee, Yih Hong; Gnanasammandhan, Muthu Kumara; Guan, Zhenping; Zhang, Yong; Xu, Qing-Hua

2012-08-21

NaYF(4):Yb,Er@SiO(2)@Ag core-shell nanocomposites were prepared to investigate metal-enhanced upconversion luminescence. Two sizes (15 and 30 nm) of Ag nanoparticles were used. The emission intensity of the upconversion nanocrystals was found to be strongly modulated by the presence of Ag nanoparticles (NPs) on the outer shell layer of the nanocomposites. The extent of modulation depended on the separation distance between Ag NPs and upconversion nanocrystals. The optimum upconversion luminescence enhancement was observed at a separation distance of 10 nm for Ag NPs with two different sizes (15 and 30 nm). A maximum upconversion luminescence enhancement of 14.4-fold was observed when 15 nm Ag nanoparticles were used and 10.8-fold was observed when 30 nm Ag NPs were used. The separation distance dependent emission intensity is ascribed to the competition between energy transfer and enhanced radiative decay rates. The biocompatibility of the nanocomposites was significantly improved by surface modification with DNA. The biological imaging capabilities of these nanocomposites were demonstrated using B16F0 cells.

Silver nanoparticles coated with natural polysaccharides as models to study AgNP aggregation kinetics using UV-Visible spectrophotometry upon discharge in complex environments.

PubMed

Lodeiro, Pablo; Achterberg, Eric P; Pampín, Joaquín; Affatati, Alice; El-Shahawi, Mohammed S

2016-01-01

This study provides quantitative information on the aggregation and dissolution behaviour of silver nanoparticles (AgNPs) upon discharge in fresh and sea waters, represented here as NaCl solutions of increasing ionic strength (up to 1M) and natural fjord waters. Natural polysaccharides, sodium alginate (ALG) and gum Arabic (GA), were used as coatings to stabilize the AgNPs and the compounds acted as models to study AgNP aggregation kinetics. The DLVO theory was used to quantitatively describe the interactions between the AgNPs. The stability of AgNPs was established using UV-Visible spectrophotometry, including unique information collected during the first seconds of the aggregaton process. Alginate coating resulted in a moderate stabilization of AgNPs in terms of critical coagulation concentration (~82mM NaCl) and a low dissolution of <10% total Ag in NaCl solutions up to 1M. Gum Arabic coated AgNPs were more strongly stabilized, with ~7-30% size increase up to 77mM NaCl, but only when the silver ion content initially present in solution was low (<10% total Ag). The ALG and GA coated AgNPs showed a strongly enhanced stability in natural fjord waters (ca. 5h required to reduce the area of the surface plasmon resonance band (SPRB) by two fold) compared with NaCl at an equivalent ionic strength (1-2min period for a two fold SPRB reduction). This is ascribed to a stabilizing effect from dissolved organic matter present in natural fjord waters. Interestingly, for AgNP-GA solutions with 40% of total silver present as unreacted silver ions in the NP stock solution, fast aggregation kinetics were observed in NaCl solutions (SPRB area was reduced by ca. 50% within 40-150min), with even more rapid removal in fjord waters, attributed to the high amount of silver-chloride charged species, that interact with the NP coating and/or organic matter and reduce the NPs stabilization. Copyright © 2015 Elsevier B.V. All rights reserved.

Ag-graphene hybrid conductive ink for writing electronics.

PubMed

Xu, L Y; Yang, G Y; Jing, H Y; Wei, J; Han, Y D

2014-02-07

With the aim of preparing a method for the writing of electronics on paper by the use of common commercial rollerball pens loaded with conductive ink, hybrid conductive ink composed of Ag nanoparticles (15 wt%) and graphene-Ag composite nanosheets (0.15 wt%) formed by depositing Ag nanoparticles (∼10 nm) onto graphene sheets was prepared for the first time. Owing to the electrical pathway effect of graphene and the decreased contact resistance of graphene junctions by depositing Ag nanoparticles (NPs) onto graphene sheets, the concentration of Ag NPs was significantly reduced while maintaining high conductivity at a curing temperature of 100 ° C. A typical resistivity value measured was 1.9 × 10(-7) Ω m, which is 12 times the value for bulk silver. Even over thousands of bending cycles or rolling, the resistance values of writing tracks only increase slightly. The stability and flexibility of the writing circuits are good, demonstrating the promising future of this hybrid ink and direct writing method.

Preparation, characterization and antimicrobial efficiency of Ag/PDDA-diatomite nanocomposite.

PubMed

Panáček, Aleš; Balzerová, Anna; Prucek, Robert; Ranc, Václav; Večeřová, Renata; Husičková, Vendula; Pechoušek, Jiří; Filip, Jan; Zbořil, Radek; Kvítek, Libor

2013-10-01

Nanocomposites consisting of diatomaceous earth particles and silver nanoparticles (silver NPs) with high antimicrobial activity were prepared and characterized. For the purpose of nanocomposite preparation, silver NPs with an average size of 28nm prepared by modified Tollens process were used. Nanocomposites were prepared using poly(diallyldimethylammonium) chloride (PDDA) as an interlayer substance between diatomite and silver NPs which enables to change diatomite original negative surface charge to positive one. Due to strong electrostatic interactions between negatively charged silver NPs and positively charged PDDA-modified diatomite, Ag/PDDA-diatomite nanocomposites with a high content of silver (as high as 46.6mgAg/1g of diatomite) were prepared. Because of minimal release of silver NPs from prepared nanocomposites to aqueous media (<0.3mg Ag/1g of nanocomposite), the developed nanocomposites are regarded as a potential useful antimicrobial material with a long-term efficiency showing no risk to human health or environment. All the prepared nanocomposites exhibit a high bactericidal activity against Gram-negative and Gram-positive bacteria and fungicidal activity against yeasts at very low concentrations as low as 0.11g/L, corresponding to silver concentration of 5mg/L. Hence, the prepared nanocomposites constitute a promising candidate suitable for the microbial water treatment in environmental applications. Copyright © 2013 Elsevier B.V. All rights reserved.

Acetylene Gas-Sensing Properties of Layer-by-Layer Self-Assembled Ag-Decorated Tin Dioxide/Graphene Nanocomposite Film

PubMed Central

Jiang, Chuanxing; Yin, Nailiang; Yao, Yao; Shaymurat, Talgar; Zhou, Xiaoyan

2017-01-01

This paper demonstrates an acetylene gas sensor based on an Ag-decorated tin dioxide/reduced graphene oxide (Ag–SnO2/rGO) nanocomposite film, prepared by layer-by-layer (LbL) self-assembly technology. The as-prepared Ag–SnO2/rGO nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectrum. The acetylene sensing properties were investigated using different working temperatures and gas concentrations. An optimal temperature of 90 °C was determined, and the Ag–SnO2/rGO nanocomposite sensor exhibited excellent sensing behaviors towards acetylene, in terms of response, repeatability, stability and response/recovery characteristics, which were superior to the pure SnO2 and SnO2/rGO film sensors. The sensing mechanism of the Ag–SnO2/rGO sensor was attributed to the synergistic effect of the ternary nanomaterials, and the heterojunctions created at the interfaces between SnO2 and rGO. This work indicates that the Ag–SnO2/rGO nanocomposite is a good candidate for constructing a low-temperature acetylene sensor. PMID:28927021

Tannic Acid/Fe3+/Ag Nanofilm Exhibiting Superior Photodynamic and Physical Antibacterial Activity.

PubMed

Xu, Ziqiang; Wang, Xiuhua; Liu, Xiangmei; Cui, Zhenduo; Yang, Xianjin; Yeung, Kelvin Wai Kwok; Chung, Jonathan Chiyuen; Chu, Paul K; Wu, Shuilin

2017-11-15

Silver nanoparticles (AgNPs) enwrapped in the biologically safe tannic acid (TA)/Fe 3+ nanofilm are synthesized by an ultrafast, green, simple, and universal method. The physical antibacterial activity and photodynamic antibacterial therapy (PAT) efficacy of the TA/Fe 3+ /AgNPs nanofilm were investigated for the first time, which exhibited a strong physical antibacterial activity as well as great biocompatibility, through in vitro and in vivo studies. The results disclosed that this hybrid coating could possess high PAT capabilities upon irradiation under a visible light of 660 nm, which is longer than those of previously reported green and blue sensitization light, thus allowing deeper light penetration into biological tissues. Electron spin resonance (ESR) spectra proved that the PAT efficacy of the TA/Fe 3+ /AgNPs nanofilm was associated with the yields of singlet oxygen ( 1 O 2 ) under the irradiation of visible light (660 nm). A higher PAT efficiency of 100 and 94% against Escherichia coli and Staphylococcus aureus could be achieved within 20 min of illumination under 660 nm visible light, whereas the innate physical antibacterial activity of AgNPs could endow the implants with long-term prevention of bacterial infection. The mechanism of PAT may be associated with the formation of oxidative stress and oxidative damage to key biomolecules (proteins and lipids) in bacteria. Our results reveal that the synergistic action of both PAT and physical action of AgNPs in this hybrid nanofilm is an effective way to inactivate bacteria, with minimal side effects.

C. elegans-on-a-chip for in situ and in vivo Ag nanoparticles’ uptake and toxicity assay

NASA Astrophysics Data System (ADS)

Kim, Jin Ho; Lee, Seung Hwan; Cha, Yun Jeong; Hong, Sung Jin; Chung, Sang Kug; Park, Tai Hyun; Choi, Shin Sik

2017-01-01

Nanomaterials are extensively used in consumer products and medical applications, but little is known about their environmental and biological toxicities. Moreover, the toxicity analysis requires sophisticated instruments and labor-intensive experiments. Here we report a microfluidic chip incorporated with the nematode Caenorhabditis elegans that rapidly displays the changes in body growth and gene expression specifically responsive to the silver nanoparticles (AgNPs). C. elegans were cultured in microfluidic chambers in the presence or absence of AgNPs and were consequently transferred to wedge-shaped channels, which immobilized the animals, allowing the evaluation of parameters such as length, moving distance, and fluorescence from the reporter gene. The AgNPs reduced the length of C. elegans body, which was easily identified in the channel of chip. In addition, the decrease of body width enabled the worm to advance the longer distance compared to the animal without nanoparticles in a wedge-shaped channel. The transgenic marker DNA, mtl-2::gfp was highly expressed upon the uptake of AgNPs, resulting in green fluorescence emission. The comparative investigation using gold nanoparticles and heavy-metal ions indicated that these parameters are specific to AgNPs. These results demonstrate that C. elegans-on-a-chip has a great potential as a rapid and specific nanoparticle detection or nanotoxicity assessment system.

Multi-walled carbon nanotubes decorated by platinum catalyst nanoparticles--examination and microanalysis using scanning and transmission electron microscopies.

PubMed

Guinel, M J-F; Brodusch, N; Verde-Gómez, Y; Escobar-Morales, B; Gauvin, R

2013-10-01

Carbon nanotubes (CNTs) decorated with platinum (Pt) nanoparticles (NPs) have been characterized using a cold field-emission scanning electron microscope (SEM) and a high resolution field-emission transmission electron microscope (TEM). With this particular composite material, the complementary nature of the two instruments was demonstrated. Although the long CNTs were found to be mostly bent and defective in some parts, the nucleation of Pt occurred randomly and uniformly covered the CNTs. The NPs displayed a large variation in size, were sometimes defective with twins and stacking faults, and were found to be faceted with the presence of surface steps. The shape and size of the NPs and the presence of defects may have significant consequences on the activity of the Pt catalyst material. Also, thin layers of platinum oxide were identified on the surface of some NPs. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

Plasmon enhanced upconversion luminescence of NaYF4:Yb,Er@SiO2@Ag core-shell nanocomposites for cell imaging

NASA Astrophysics Data System (ADS)

Yuan, Peiyan; Lee, Yih Hong; Gnanasammandhan, Muthu Kumara; Guan, Zhenping; Zhang, Yong; Xu, Qing-Hua

2012-07-01

NaYF4:Yb,Er@SiO2@Ag core-shell nanocomposites were prepared to investigate metal-enhanced upconversion luminescence. Two sizes (15 and 30 nm) of Ag nanoparticles were used. The emission intensity of the upconversion nanocrystals was found to be strongly modulated by the presence of Ag nanoparticles (NPs) on the outer shell layer of the nanocomposites. The extent of modulation depended on the separation distance between Ag NPs and upconversion nanocrystals. The optimum upconversion luminescence enhancement was observed at a separation distance of 10 nm for Ag NPs with two different sizes (15 and 30 nm). A maximum upconversion luminescence enhancement of 14.4-fold was observed when 15 nm Ag nanoparticles were used and 10.8-fold was observed when 30 nm Ag NPs were used. The separation distance dependent emission intensity is ascribed to the competition between energy transfer and enhanced radiative decay rates. The biocompatibility of the nanocomposites was significantly improved by surface modification with DNA. The biological imaging capabilities of these nanocomposites were demonstrated using B16F0 cells.NaYF4:Yb,Er@SiO2@Ag core-shell nanocomposites were prepared to investigate metal-enhanced upconversion luminescence. Two sizes (15 and 30 nm) of Ag nanoparticles were used. The emission intensity of the upconversion nanocrystals was found to be strongly modulated by the presence of Ag nanoparticles (NPs) on the outer shell layer of the nanocomposites. The extent of modulation depended on the separation distance between Ag NPs and upconversion nanocrystals. The optimum upconversion luminescence enhancement was observed at a separation distance of 10 nm for Ag NPs with two different sizes (15 and 30 nm). A maximum upconversion luminescence enhancement of 14.4-fold was observed when 15 nm Ag nanoparticles were used and 10.8-fold was observed when 30 nm Ag NPs were used. The separation distance dependent emission intensity is ascribed to the competition between energy

Direct evidence and enhancement of surface plasmon resonance effect on Ag-loaded TiO2 nanotube arrays for photocatalytic CO2 reduction

NASA Astrophysics Data System (ADS)

Low, Jingxiang; Qiu, Shuoqi; Xu, Difa; Jiang, Chuanjia; Cheng, Bei

2018-03-01

Surface plasmon resonance (SPR) effect has been utilized in many solar conversion applications because of its ability to convert visible photons into "hot electron" energy. However, the direct evidence and enhancement of this unique effect are still great challenges, limiting its practical applications. Here we present the direct evidence and enhancement of SPR effect using TiO2 nanotube arrays (TNTAs) loaded with Ag nanoparticles (NPs) as a proof-of-concept example. Particularly, electrochemical deposition method is applied to deposit Ag NPs into the inner space of TNTAs for enhancing SPR effect of Ag NPs, as demonstrated by Raman and light absorption spectroscopies. This enhanced SPR effect is because multi-scattered light within TNTAs can be effectively utilized by Ag NPs in the inner space of TNTAs. Moreover, combining synchronous-illumination X-ray photoelectron and electrochemical impedance spectroscopy characterization, we confirm that the SPR effect of Ag NPs can enhance photocatalytic performance of TNTAs mainly from two aspects: (i) injection of "hot electrons" from Ag NPs to TNTAs and (ii) acceleration of charge carrier migration on the TNTAs through a unique near field effect. The direct evidence and enhancement of SPR effect open new perspectives in design of functional plasmonic nanomaterials with high solar conversion efficiency.

Chromatographic analysis of phytochemicals components present in mangifera indica leaves for the synthesis of silver nanoparticles by AgNO3 reduction

NASA Astrophysics Data System (ADS)

Martínez-Bernett, D.; Silva-Granados, A.; Correa-Torres, S. N.; Herrera, A.

2016-02-01

It was studied the green synthesis of silver nanoparticles (AgNPs) from the reduction of a silver nitrate solution (1 and 10mM) in the presence of an extract of mangifera indica leaves. Phytochemicals components present in extracts of mango leaves were determined using a GC-MS chromatograph. The results showed the presence of the phenolic compound pyrogallol (26.9% wt/5mL of extract) and oleic acid (29.1% wt/5mL of extract), which are useful for the reduction of the metallic salt AgNO3 and the stabilization of silver nanoparticles. The synthesized nanoparticles were characterized by UV visible spectroscopy (UV-vis), evidencing absorbances at wavelengths of 417nm (AgNPs-1) and 414nm (AgNPs- 10), which are characteristic peaks of this metallic nanoparticles. Scanning Electron Microscopy (SEM) was used to determine the size of the synthesized nanoparticles. A particle size of about 28±7nm was observed for the AgNPs-1 sample and 26±5nm for the AgNPs-10. This suggests the advantages of green chemistry to obtain silver nanoparticles with a narrow size distribution.

The utilization of SiNWs/AuNPs-modified indium tin oxide (ITO) in fabrication of electrochemical DNA sensor.

PubMed

Rashid, Jahwarhar Izuan Abdul; Yusof, Nor Azah; Abdullah, Jaafar; Hashim, Uda; Hajian, Reza

2014-12-01

This work describes the incorporation of SiNWs/AuNPs composite as a sensing material for DNA detection on indium tin-oxide (ITO) coated glass slide. The morphology of SiNWs/AuNPs composite as the modifier layer on ITO was studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The morphological studies clearly showed that SiNWs were successfully decorated with 20 nm-AuNPs using self-assembly monolayer (SAM) technique. The effective surface area for SiNWs/AuNPs-modified ITO enhanced about 10 times compared with bare ITO electrode. SiNWs/AuNPs nanocomposite was further explored as a matrix for DNA probe immobilization in detection of dengue virus as a bio-sensing model to evaluate its performance in electrochemical sensors. The hybridization of complementary DNA was monitored by differential pulse voltammetry (DPV) using methylene blue (MB) as the redox indicator. The fabricated biosensor was able to discriminate significantly complementary, non-complementary and single-base mismatch oligonucleotides. The electrochemical biosensor was sensitive to target DNA related to dengue virus in the range of 9.0-178.0 ng/ml with detection limit of 3.5 ng/ml. In addition, SiNWs/AuNPs-modified ITO, regenerated up to 8 times and its stability was up to 10 weeks at 4°C in silica gel. Copyright © 2014 Elsevier B.V. All rights reserved.

Different behaviors in the transformation of PATP adsorbed on Ag or Au nanoparticles investigated by surface-enhanced Raman spectroscopy - A study of the effects from laser energy and annealing

NASA Astrophysics Data System (ADS)

Xu, Jian-Fang; Luo, Shi-Yi; Liu, Guo-Kun

2015-05-01

In order to explore the key role of surface plasmon resonance (SPR) and active 3O2 for the chemical transformation to 4,4-dimercaptoazobenzene (DMAB) from p-aminothiophenol (PATP) adsorbed on Ag or Au NPs, we systematically investigated the laser wavelength and temperature dependent surface-enhanced Raman spectra of PATP capped Ag and Au NPs. DMAB can be easily observed at the 514.5 nm laser for Ag NPs but at the 632.8 nm laser for Au NPs, indicating that a suitable energy level is necessary for the formation of DMAB. The tendency is consistent with the wavelength dependent SPR properties of Ag or Au NPs accordingly. With the energy provided by annealing, the transformation of PATP to DMAB is much easier on Ag NPs at a lower temperature, and more DMAB can be observed at the same temperature, compared to the case of Au NPs under the same condition. It is mainly due to the active 3O2 on Ag surfaces could be more easily formed than that on Au surfaces.

Enhanced and Facet-specific Electrocatalytic Properties of Ag/Bi2Fe4O9 Composite Nanoparticles.

PubMed

Wang, Kai; Xu, Xiaoguang; Lu, Liying; Wang, Haicheng; Li, Yan; Wu, Yong; Miao, Jun; Zhang, Jin Zhong; Jiang, Yong

2018-04-18

Ag/Bi 2 Fe 4 O 9 nanoparticles (BFO NPs) have been synthesized using a two-step approach involving glycine combustion and visible light irradiation. Their structures were characterized in detail using X-ray diffraction, transmission electron microscope, scanning electron microscopy, and scanning transmission electron microscopy techniques. Their electrocatalytic properties were studied through enzymatic glucose detection with an amperometric biosensor. The Ag deposited on selective crystal facets of BFO NPs significantly enhanced their electrocatalytic activity. To gain insights into the origin of the enhanced electrocatalytic activities, we have carried out studies of Ag + reduction and Mn 2+ oxidation reaction at the {200} and {001} facets, respectively. The results suggest effective charge separation on the BFO NP surfaces, which is likely responsible for the enhanced electrocatalytic properties. Furthermore, enhanced ferromagnetism was observed after the Ag deposition on BFO NPs, which may be related to the improved electrocatalytic properties through spin-dependent charge transport. The facet-specific electrocatalytic properties are highly interesting and desired for chemical reactions. This study demonstrates that Ag/BFO NPs are potentially useful for electrocatalytic applications including biosensing and chemical synthesis with high product selectivity.

Synthesis of Ag and Au nanoparticles embedded in carbon film: Optical, crystalline and topography analysis

NASA Astrophysics Data System (ADS)

Gholamali, Hediyeh; Shafiekhani, Azizollah; Darabi, Elham; Elahi, Seyed Mohammad

2018-03-01

Atomic force microscopy (AFM) images give valuable information about surface roughness of thin films based on the results of power spectral density (PSD) through the fast Fourier transform (FFT) algorithms. In the present work, AFM data are studied for silver and gold nanoparticles (Ag NPs a-C: H and Au NPs a-C: H) embedded in amorphous hydrogenated carbon films and co-deposited on glass substrate via of RF-Sputtering and RF-Plasma Enhanced Chemical Vapor Deposition methods. Here, the working gas is acetylene and the targets are Ag and Au. While time and power are constant, the only variable parameter in this study is initial pressure. In addition, the crystalline structure of Ag NPs a-C: H and Au NPs a-C: H are studied using X-ray diffraction (XRD). UV-visible spectrophotometry will also investigate optical properties and localized surface plasmon resonance (LSPR) of samples.

A novel and facile synthesis of carbon quantum dots via salep hydrothermal treatment as the silver nanoparticles support: Application to electroanalytical determination of H2O2 in fetal bovine serum.

PubMed

Jahanbakhshi, Mojtaba; Habibi, Biuck

2016-07-15

A simple, low-cost, and green process was used for the synthesis of carbon quantum dots (CQDs) through the hydrothermal treatment of salep as a novel bio-polymeric carbon source in presence of only pure water. The silver nanoparticles (AgNPs) were embedded on the surface of CQDs by ultra-violate (UV) irradiation to the CQDs and silver nitrate mixture solution. The as-synthesized CQDs and AgNPs decorated CQDs nanohybrid (AgNPs/CQDs) were characterized by UV-vis and photoluminescence spectroscopy, Fourier transform-infrared spectroscopy, transmission electron microscopy, atomic force microcopy, X-ray diffraction, and field emission scanning electron microscopy. Then, the AgNPs/CQDs nanohybrid was casted on the glassy carbon electrode in order to prepare an amperometric hydrogen peroxide (H2O2) sensor. The electrochemical investigations show that the AgNPs/CQDs nanohybrid possesses an excellent performance toward the H2O2 reduction. In the optimum condition, the linear range of H2O2 determination was achieved from 0.2 to 27.0μM with high sensitivity (1.5μA/µM) and the limit of detection was obtained about 80nM (S/N=3). Finally, the prepared nanohybrid modified electrode was effectively applied to the H2O2 detection in the disinfected fetal bovine serum samples, and the recovery was obtained about 98%. The achieved results indicate that the AgNPs/CQDs nanohybrid with high reproducibility, repeatability, and stability has a favorable capability in electrochemical sensors improvement. Copyright © 2016 Elsevier B.V. All rights reserved.

Eco-friendly biosynthesis, anticancer drug loading and cytotoxic effect of capped Ag-nanoparticles against breast cancer

NASA Astrophysics Data System (ADS)

Naz, M.; Nasiri, N.; Ikram, M.; Nafees, M.; Qureshi, M. Z.; Ali, S.; Tricoli, A.

2017-11-01

The work aimed to prepare silver nanoparticles (Ag-NPs) from silver nitrate and various concentrations of the seed extract ( Setaria verticillata) by a green synthetic route. The chemical and physical properties of the resulting Ag-NPs were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectrometry and ultraviolet-visible (UV-Vis) spectrophotometry. Anticancer activity of Ag-NPs (5-20 nm) had dose-dependent cytotoxic effect against breast cancer (MCF7-FLV) cells. The in vitro toxicity was studied on adult earthworms (Lumbricina) resulting in statistically significant ( P < 0.05) inhibition. The prepared NPs were loaded with hydrophilic anticancer drugs (ACD), doxorubicin (DOX) and daunorubicin (DNR), for developing a novel drug delivery carrier having significant adsorption capacity and efficiency to remove the side effects of the medicines effective for leukemia chemotherapy.

Multi-Shaped Ag Nanoparticles in the Plasmonic Layer of Dye-Sensitized Solar Cells for Increased Power Conversion Efficiency.

PubMed

Song, Da Hyun; Kim, Ho-Sub; Suh, Jung Sang; Jun, Bong-Hyun; Rho, Won-Yeop

2017-06-04

The use of dye-sensitized solar cells (DSSCs) is widespread owing to their high power conversion efficiency (PCE) and low cost of manufacturing. We prepared multi-shaped Ag nanoparticles (NPs) and introduced them into DSSCs to further enhance their PCE. The maximum absorption wavelength of the multi-shaped Ag NPs is 420 nm, including the shoulder with a full width at half maximum (FWHM) of 121 nm. This is a broad absorption wavelength compared to spherical Ag NPs, which have a maximum absorption wavelength of 400 nm without the shoulder of 61 nm FWHM. Therefore, when multi-shaped Ag NPs with a broader plasmon-enhanced absorption were coated on a mesoporous TiO₂ layer on a layer-by-layer structure in DSSCs, the PCE increased from 8.44% to 10.22%, equivalent to an improvement of 21.09% compared to DSSCs without a plasmonic layer. To confirm the plasmon-enhanced effect on the composite film structure in DSSCs, the PCE of DSSCs based on the composite film structure with multi-shaped Ag NPs increased from 8.58% to 10.34%, equivalent to an improvement of 20.51% compared to DSSCs without a plasmonic layer. This concept can be applied to perovskite solar cells, hybrid solar cells, and other solar cells devices.

Graphene Oxide-Based Nanocomposites Decorated with Silver Nanoparticles as an Antibacterial Agent

NASA Astrophysics Data System (ADS)

Jaworski, Sławomir; Wierzbicki, Mateusz; Sawosz, Ewa; Jung, Anna; Gielerak, Grzegorz; Biernat, Joanna; Jaremek, Henryk; Łojkowski, Witold; Woźniak, Bartosz; Wojnarowicz, Jacek; Stobiński, Leszek; Małolepszy, Artur; Mazurkiewicz-Pawlicka, Marta; Łojkowski, Maciej; Kurantowicz, Natalia; Chwalibog, André

2018-04-01

One of the most promising methods against drug-resistant bacteria can be surface-modified materials with biocidal nanoparticles and nanocomposites. Herein, we present a nanocomposite with silver nanoparticles (Ag-NPs) on the surface of graphene oxide (GO) as a novel multifunctional antibacterial and antifungal material. Ultrasonic technologies have been used as an effective method of coating polyurethane foils. Toxicity on gram-negative bacteria ( Escherichia coli), gram-positive bacteria ( Staphylococcus aureus and Staphylococcus epidermidis), and pathogenic yeast ( Candida albicans) was evaluated by analysis of cell morphology, assessment of cell viability using the PrestoBlue assay, analysis of cell membrane integrity using the lactate dehydrogenase assay, and reactive oxygen species production. Compared to Ag-NPs and GO, which have been widely used as antibacterial agents, our nanocomposite shows much higher antimicrobial efficiency toward bacteria and yeast cells.

Graphene Oxide-Based Nanocomposites Decorated with Silver Nanoparticles as an Antibacterial Agent.

PubMed

Jaworski, Sławomir; Wierzbicki, Mateusz; Sawosz, Ewa; Jung, Anna; Gielerak, Grzegorz; Biernat, Joanna; Jaremek, Henryk; Łojkowski, Witold; Woźniak, Bartosz; Wojnarowicz, Jacek; Stobiński, Leszek; Małolepszy, Artur; Mazurkiewicz-Pawlicka, Marta; Łojkowski, Maciej; Kurantowicz, Natalia; Chwalibog, André

2018-04-23

One of the most promising methods against drug-resistant bacteria can be surface-modified materials with biocidal nanoparticles and nanocomposites. Herein, we present a nanocomposite with silver nanoparticles (Ag-NPs) on the surface of graphene oxide (GO) as a novel multifunctional antibacterial and antifungal material. Ultrasonic technologies have been used as an effective method of coating polyurethane foils. Toxicity on gram-negative bacteria (Escherichia coli), gram-positive bacteria (Staphylococcus aureus and Staphylococcus epidermidis), and pathogenic yeast (Candida albicans) was evaluated by analysis of cell morphology, assessment of cell viability using the PrestoBlue assay, analysis of cell membrane integrity using the lactate dehydrogenase assay, and reactive oxygen species production. Compared to Ag-NPs and GO, which have been widely used as antibacterial agents, our nanocomposite shows much higher antimicrobial efficiency toward bacteria and yeast cells.

Synthesis of β-AgVO3 nanowires decorated with Ag2CrO4, with improved visible light photocatalytic performance

NASA Astrophysics Data System (ADS)

Ouyang, Qi; Li, Zhonghua; Liu, Jiawen

2018-05-01

Silver chromate‑silver vanadate (Ag2CrO4/β-AgVO3) heterojunction composites are synthesized through a facile precipitation process. The Ag2CrO4/β-AgVO3 hybrids obtained exhibit better photocatalytic activity in degradation of RhB than both pure Ag2CrO4 and β-AgVO3 under visible light irradiation. The 20 wt% Ag2CrO4/β-AgVO3 heterojunction possesses the best photocatalytic ability for degrading RhB: 24.4 times that of pristine β-AgVO3 nanowires and 3.2 times that of individual Ag2CrO4 particles. The phase of the nanocomposites was analyzed using x-ray diffraction as well as x-ray photoelectron spectroscopy. Their morphology was observed via scanning electron microscopy and transmission electron microscopy. The improvement in photocatalytic performance is chiefly ascribed to the synergies between Ag2CrO4/β-AgVO3 heterostructure, which can enhance the light absorbance ability and also accelerate the separation and transfer of photoinduced electrons and holes under visible light irradiation; this is also confirmed by UV–vis diffuse reflection spectrometry and fluorescence emission spectra.

Ag/CuO nanoparticles prepared from a novel trinuclear compound [Cu(Imdz)4(Ag(CN)2)2] (Imdz = imidazole) by a pyrolysis display excellent antimicrobial activity

NASA Astrophysics Data System (ADS)

Adhikary, Jaydeep; Das, Balaram; Chatterjee, Sourav; Dash, Sandeep Kumar; Chattopadhyay, Sourav; Roy, Somenath; Chen, Jeng-Wei; Chattopadhyay, Tanmay

2016-06-01

One copper and two silver containing one hetero tri-nuclear precursor compound [Cu(Imdz)4(Ag(CN)2)2] (1) (Imdz = Imidazole) has been synthesized and characterized by single crystal X-ray diffraction. Simple pyrolysis of the complex at 550 °C for 4 h afforded Ag/CuO nanoparticles (NPs). The synthesized nanoparticles were characterized by ultraviolet-visible (UV-Vis), Fourier transform infrared (FT-IR), X-ray powder diffraction (XRPD), dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) and X-ray photo electron spectroscopy (XPS). Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) have been employed as model microbial species to study the anti-microbial activity of the synthesized NPs. The NPs showed potent anti-microbial activity evidenced from the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values. Very high level of cell uptake and then generation of reactive oxygen species (ROS) are the origin of such strong antimicrobial activity for the NPs. However, the cytotoxicity level of the NPs towards normal human cell is very low.

Thermal conductivity studies of novel nanofluids based on metallic silver decorated mesoporous silica nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tadjarodi, Azadeh, E-mail: tajarodi@iust.ac.ir; Zabihi, Fatemeh; Chemistry and Nanotechnology Laboratory, National Center for Laser Science and Technology, Tehran

2013-10-15

Graphical abstract: - Highlights: • Metallic silver was decorated in mSiO{sub 2} with grafted hemiaminal functional groups. • Synthesized nanoparticles were used for preparation of glycerol based nanofluids. • The effect of temperature, weight fraction of mSiO{sub 2} and concentration of silver nanoparticles on thermal conductivity of nanofluids was investigated. - Abstract: In the present study, the mesoporous structure of silica (mSiO{sub 2}) nanoparticles as well as hemiaminal grafted mSiO{sub 2} decorated by metallic silver (Ag/mSiO{sub 2}) has been used for the preparation of glycerol based nanofluids. Structural and morphological characterization of the synthesized products have been carried out usingmore » Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), UV–vis spectroscopy, inductively coupled plasma (ICP) and N{sub 2} adsorption–desorption isotherms. The thermal conductivity and viscosity of the nanofluids have been measured as a function of temperature for various weight fractions and silver concentrations of mSiO{sub 2} and Ag/mSiO{sub 2} nanoparticles, respectively. The results show that the thermal conductivity of the nanofluids increase up to 9.24% as the weight fraction of mSiO{sub 2} increases up to 4 wt%. Also, increasing the percent of the silver decorated mSiO{sub 2} (Ag/mSiO{sub 2}) up to 2.98% caused an enhancement in the thermal conductivity of the base fluid up to 10.95%. Furthermore, the results show that the nanofluids have Newtonian behavior in the tested temperature range for various concentrations of nanoparticles.« less

Direct electron transfer of Phanerochaete chrysosporium cellobiose dehydrogenase at platinum and palladium nanoparticles decorated carbon nanotubes modified electrodes.

PubMed

Bozorgzadeh, Somayyeh; Hamidi, Hassan; Ortiz, Roberto; Ludwig, Roland; Gorton, Lo

2015-10-07

In the present work, platinum and palladium nanoparticles (PtNPs and PdNPs) were decorated on the surface of multi-walled carbon nanotubes (MWCNTs) by a simple thermal decomposition method. The prepared nanohybrids, PtNPs-MWCNTs and PdNPs-MWCNTs, were cast on the surface of spectrographic graphite electrodes and then Phanerochaete chrysosporium cellobiose dehydrogenase (PcCDH) was adsorbed on the modified layer. Direct electron transfer between PcCDH and the nanostructured modified electrodes was studied using flow injection amperometry and cyclic voltammetry. The maximum current responses (Imax) and the apparent Michaelis-Menten constants (K) for the different PcCDH modified electrodes were calculated by fitting the data to the Michaelis-Menten equation and compared. The sensitivity towards lactose was 3.07 and 3.28 μA mM(-1) at the PcCDH/PtNPs-MWCNTs/SPGE and PcCDH/PdNPs-MWCNTs/SPGE electrodes, respectively, which were higher than those measured at the PcCDH/MWCNTs/SPGE (2.60 μA mM(-1)) and PcCDH/SPGE (0.92 μA mM(-1)). The modified electrodes were additionally tested as bioanodes for biofuel cell applications.

Collection Development "Budget Decorating": Decorating Cents

ERIC Educational Resources Information Center

Kumaran, Maha

2008-01-01

Home decorating is a popular idea these days as seen in the rise of cable television channels like TLC and HGTV (Home & Garden Television) and TV shows like "Trading Spaces, Take This House and Sell It, Design on a Dime, Decorating Cents," and many others. Throughout history, humans have always expressed the desire to personalize and beautify…

LSPR Tuning from 470 to 800 nm and Improved Stability of Au-Ag Nanoparticles Formed by Gold Deposition and Rebuilding in the Presence of Poly(styrenesulfonate).

PubMed

Cathcart, Nicole; Chen, Jennifer I L; Kitaev, Vladimir

2018-01-16

Stability and precise control over functional properties of metal nanoparticles remain a challenge for the realization of prospective applications. Our described process of shell formation and rebuilding can address both these challenges. Template silver nanoparticles (AgNPs) stabilized by poly(styrenesulfonate) are first transformed with gold deposition, after which the resulting shell rebuilds with the replaced silver. The shell formation and rebuilding are accompanied by large shifts in localized surface plasmon resonance (LSPR) peak position, which enables LSPR tuning in a range from 470 to 800 nm. Furthermore, chemical stability of Au-AgNPs is significantly improved compared to AgNPs due to gold stability. Silver templates of different shapes and sizes were demonstrated to transform to AuAg composite NPs to further extend the accessible LSPR range tuning. Stabilization of template AgNPs with poly(styrenesulfonate), in contrast to commonly used poly(vinylpyrrolidone), was found to be a key factor for shell rebuilding. The developed Au-AgNPs were shown to be advantageous for surface plasmon resonance (SPR) detection and surface-enhanced Raman spectroscopy (SERS) owing to their tunable LSPR and enhanced stability.

Broadband light absorption enhancement in dye-sensitized solar cells with Au-Ag alloy popcorn nanoparticles

NASA Astrophysics Data System (ADS)

Xu, Qi; Liu, Fang; Liu, Yuxiang; Cui, Kaiyu; Feng, Xue; Zhang, Wei; Huang, Yidong

2013-07-01

In this paper, we present an investigation on the use of Au-Ag alloy popcorn-shaped nanoparticles (NPs) to realise the broadband optical absorption enhancement of dye-sensitized solar cells (DSCs). Both simulation and experimental results indicate that compared with regular plasmonic NPs, such as nano-spheres, irregular popcorn-shaped alloy NPs exhibit absorption enhancement over a broad wavelength range due to the excitation of localized surface plasmons (LSPs) at different wavelengths. The power conversion efficiency (PCE) of DSCs is enhanced by 16% from 5.26% to 6.09% by incorporating 2.38 wt% Au-Ag alloy popcorn NPs. Moreover, by adding a scattering layer on the exterior of the counter electrode, the popcorn NPs demonstrate an even stronger ability to increase the PCE by 32% from 5.94% to 7.85%, which results from the more efficient excitation of the LSP mode on the popcorn NPs.

Broadband light absorption enhancement in dye-sensitized solar cells with Au-Ag alloy popcorn nanoparticles.

PubMed

Xu, Qi; Liu, Fang; Liu, Yuxiang; Cui, Kaiyu; Feng, Xue; Zhang, Wei; Huang, Yidong

2013-01-01

In this paper, we present an investigation on the use of Au-Ag alloy popcorn-shaped nanoparticles (NPs) to realise the broadband optical absorption enhancement of dye-sensitized solar cells (DSCs). Both simulation and experimental results indicate that compared with regular plasmonic NPs, such as nano-spheres, irregular popcorn-shaped alloy NPs exhibit absorption enhancement over a broad wavelength range due to the excitation of localized surface plasmons (LSPs) at different wavelengths. The power conversion efficiency (PCE) of DSCs is enhanced by 16% from 5.26% to 6.09% by incorporating 2.38 wt% Au-Ag alloy popcorn NPs. Moreover, by adding a scattering layer on the exterior of the counter electrode, the popcorn NPs demonstrate an even stronger ability to increase the PCE by 32% from 5.94% to 7.85%, which results from the more efficient excitation of the LSP mode on the popcorn NPs.

Broadband light absorption enhancement in dye-sensitized solar cells with Au-Ag alloy popcorn nanoparticles

PubMed Central

Xu, Qi; Liu, Fang; Liu, Yuxiang; Cui, Kaiyu; Feng, Xue; Zhang, Wei; Huang, Yidong

2013-01-01

In this paper, we present an investigation on the use of Au-Ag alloy popcorn-shaped nanoparticles (NPs) to realise the broadband optical absorption enhancement of dye-sensitized solar cells (DSCs). Both simulation and experimental results indicate that compared with regular plasmonic NPs, such as nano-spheres, irregular popcorn-shaped alloy NPs exhibit absorption enhancement over a broad wavelength range due to the excitation of localized surface plasmons (LSPs) at different wavelengths. The power conversion efficiency (PCE) of DSCs is enhanced by 16% from 5.26% to 6.09% by incorporating 2.38 wt% Au-Ag alloy popcorn NPs. Moreover, by adding a scattering layer on the exterior of the counter electrode, the popcorn NPs demonstrate an even stronger ability to increase the PCE by 32% from 5.94% to 7.85%, which results from the more efficient excitation of the LSP mode on the popcorn NPs. PMID:23817586

Mechanical, structural and thermal properties of Ag-Cu and ZnO reinforced polylactide nanocomposite films.

PubMed

Ahmed, Jasim; Arfat, Yasir Ali; Castro-Aguirre, Edgar; Auras, Rafael

2016-05-01

Plasticized polylactic acid (PLA) based nanocomposite films were prepared by incorporating polyethylene glycol (PEG) and two selected nanoparticles (NPs) [silver-copper (Ag-Cu) alloy (<100 nm) and zinc oxide (ZnO) (<50 and <100 nm)] through solvent casting method. Incorporation of Ag-Cu alloy into the PLA/PEG matrix increased the glass transition temperature (Tg) significantly. The crystallinity of the nanocomposites (NCs) was significantly influenced by NP incorporation as evidenced from differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis. The PLA nanocomposite reinforced with NPs exhibited much higher tensile strength than that of PLA/PEG blend. Melt rheology of NCs exhibited a shear-thinning behavior. The mechanical property drastically reduced with a loading of NPs, which is associated with degradation of PLA. SEM micrographs exhibited that both Ag-Cu alloy and ZnO NPs were dispersed well in the PLA film matrix. Copyright © 2016 Elsevier B.V. All rights reserved.

Adenosine diphosphate-decorated chitosan nanoparticles shorten blood clotting times, influencing the structures and varying the mechanical properties of the clots

PubMed Central

Chung, Tze-Wen; Lin, Pei-Yi; Wang, Shoei-Shen; Chen, Yen-Fung

2014-01-01

Chitosan nanoparticles (NPs) decorated with adenosine diphosphate (ADP) (ANPs) or fibrinogen (FNPs) were used to fabricate hemostatic NPs that can shorten blood clotting time and prevent severe local hemorrhage. The structure and mechanical properties of the blood clot induced with ANP (clot/ANP) or FNP (clot/FNP) were also investigated. The NPs, ANPs, and FNPs, which had particle sizes of 245.1±14.0, 251.0±9.8, and 326.5±14.5 nm and zeta potentials of 24.1±0.5, 20.6±1.9, and 15.3±1.5 mV (n=4), respectively, were fabricated by ionic gelation and then decorated with ADP and fibrinogen. The zeta potentials and Fourier transform infrared (FTIR) spectroscopy of the NPs confirmed that their surfaces were successfully coated with ADP and fibrinogen. The scanning electron microscope (SEM) micrographs of the structure of the clot induced with “undecorated” chitosan NPs (clot/NP), clot/ANP, and clot/FNP (at 0.05 wt%) were different, after citrated bloods had been recalcified by a calcium chloride solution containing NPs, ANPs, or FNPs. This indicated that many NPs adhered on the membrane surfaces of red blood cells, that ANPs induced many platelet aggregates, and that FNPs were incorporated into the fibrin network in the clots. Measurements of the blood clotting times (Tc) of blood clot/NPs, clot/ANPs, and clot/FNPs, based on 90% of ultimate frequency shifts measured on a quartz crystal microbalance (QCM), were significantly (P<0.05) (n=4) shorter than that of a clot induced by a phosphate-buffered solution (PBS) (clot/PBS) (63.6%±3.1%, 48.3%±6.2%, and 63.2%±4.7%, respectively). The ΔF2 values in the spectra of frequency shifts associated with the propagation of fibrin networks in the clot/ANPs and clot/FNPs were significantly lower than those of clot/PBS. Interestingly, texture profile analysis of the compressional properties showed significantly lower hardness and compressibility in clot/NPs and clot/ANPs (P<0.05 or better) (n=4) compared with clot/PBS and

Adenosine diphosphate-decorated chitosan nanoparticles shorten blood clotting times, influencing the structures and varying the mechanical properties of the clots.

PubMed

Chung, Tze-Wen; Lin, Pei-Yi; Wang, Shoei-Shen; Chen, Yen-Fung

2014-01-01

Chitosan nanoparticles (NPs) decorated with adenosine diphosphate (ADP) (ANPs) or fibrinogen (FNPs) were used to fabricate hemostatic NPs that can shorten blood clotting time and prevent severe local hemorrhage. The structure and mechanical properties of the blood clot induced with ANP (clot/ANP) or FNP (clot/FNP) were also investigated. The NPs, ANPs, and FNPs, which had particle sizes of 245.1 ± 14.0, 251.0 ± 9.8, and 326.5 ± 14.5 nm and zeta potentials of 24.1 ± 0.5, 20.6 ± 1.9, and 15.3 ± 1.5 mV (n=4), respectively, were fabricated by ionic gelation and then decorated with ADP and fibrinogen. The zeta potentials and Fourier transform infrared (FTIR) spectroscopy of the NPs confirmed that their surfaces were successfully coated with ADP and fibrinogen. The scanning electron microscope (SEM) micrographs of the structure of the clot induced with "undecorated" chitosan NPs (clot/NP), clot/ANP, and clot/FNP (at 0.05 wt%) were different, after citrated bloods had been recalcified by a calcium chloride solution containing NPs, ANPs, or FNPs. This indicated that many NPs adhered on the membrane surfaces of red blood cells, that ANPs induced many platelet aggregates, and that FNPs were incorporated into the fibrin network in the clots. Measurements of the blood clotting times (Tc) of blood clot/NPs, clot/ANPs, and clot/FNPs, based on 90% of ultimate frequency shifts measured on a quartz crystal microbalance (QCM), were significantly (P<0.05) (n=4) shorter than that of a clot induced by a phosphate-buffered solution (PBS) (clot/PBS) (63.6% ± 3.1%, 48.3% ± 6.2%, and 63.2% ± 4.7%, respectively). The ΔF2 values in the spectra of frequency shifts associated with the propagation of fibrin networks in the clot/ANPs and clot/FNPs were significantly lower than those of clot/PBS. Interestingly, texture profile analysis of the compressional properties showed significantly lower hardness and compressibility in clot/NPs and clot/ANPs (P<0.05 or better) (n=4) compared with

Enhancement of the optical, thermal and electrical properties of PEO/PAM:Li polymer electrolyte films doped with Ag nanoparticles

NASA Astrophysics Data System (ADS)

Morsi, M. A.; El-Khodary, Sherif A.; Rajeh, A.

2018-06-01

Both lithium bromide (LiBr) and biosynthesized silver nanoparticles (Ag NPs) with average size 2-30 nm have been incorporated into the polymeric matrix of polyethylene oxide and polyacrylamide (PEO/PAM) blend by the casting method. FT-IR analysis indicates the formation of hydrogen bond between the blend components. Also, LiBr and Ag NPs interact with the functional groups of PEO/PAM matrix. The results of XRD analysis depict the semi-crystalline nature of these polymer samples and the degree of crystallinity is decreased due to the addition process. The values of optical energy gap from UV-Vis. data are decreased from 3.55 eV for blend to 3.26 for the nanocomposite sample in the indirect transition. LiBr/Ag NPs assist the improvement of the thermal stability of the PEO/PAM blend, as evidenced by TGA and DTA techniques. Upon the addition of LiBr and Ag NPs, an improvement for the conductivity, dielectric permittivity (έ) and dielectric loss (ἕ) of PEO/PAM solid polymer electrolytes are observed. It's clear that the improvement of the electrical conductivity and dielectric parameters for PEO/PAM: Li+/Ag NPs polymer electrolyte system makes it as a promising candidate for solid-state Li battery applications.

Enhancement in volatile organic compound sensitivity of aged Ag nanoparticle aggregates by plasma exposure

NASA Astrophysics Data System (ADS)

Hosomi, Kei; Ozaki, Koichi; Nishiyama, Fumitaka; Takahiro, Katsumi

2018-01-01

Silver nanoparticles (Ag NPs) tarnish easily upon exposure to ambient air, and eventually lose their ability as a plasmonic sensor via weakened localized surface plasmon resonance (LSPR). We have demonstrated the enhancement in plasmonic sensitivity of tarnished Ag NP aggregates to vapors of volatile organic compounds (VOCs) such as ethanol and butanol by Ar plasma exposure. The response of Ag NP aggregates to the VOC vapors was examined by measuring the change in optical extinction spectra before and after exposure to the vapors. The sensitivity of Ag NP aggregates decreased gradually when stored in ambient air. The performance of tarnished Ag NPs for ethanol sensing was recovered by exposure to argon (Ar) plasma for 15 s. The reduction from oxidized Ag to metallic one was recognized, while morphological change was hardly noticeable after the plasma exposure. We conclude, therefore, that a compositional change rather than a morphological change occurred on Ag NP surfaces enhances the sensing ability of tarnished Ag NP aggregates to the VOC vapors.

Levofloxacin capped Ag-nanoparicles: A new highly selective sensor for cations under joint experimental and DFT investigation

NASA Astrophysics Data System (ADS)

Mondal Roy, Sutapa; Roy, Debesh Ranjan

2017-05-01

A very new and alternate function of an antibiotic drug levofloxacin (Lv), as a highly selective, colorimetric turn-OFF/turn-ON chemosensor for metal-ions Hg2+ and Fe3+, has been reported in this study. An extremely easy, very less time consuming, economical one-pot method of synthesis has been developed for the production of silver nanoparticles (AgNPs). The AgNPs that are stabilized and surface functionalized by Lv. Functionalization of AgNPs by antibiotic drug Lv has been thoroughly confirmed using FTIR spectrophotometry. Two carbonyl oxygen moieties, one belongs to the pyridine oxygen group and another one from the carboxylate oxygen group of Lv together form the binding site over the nanoparticle surface. The Lv-AgNPs system has shown naked eye detectable colour change, as well as significant change via both UV-Vis and fluorescence spectroscopy. The limits of detection (LODs) are predicted to be 6.86 × 10-8 M for Hg2+ and 2.52 × 10-9 M for Fe3+ using UV-Vis spectroscopy and 2.35 × 10-9 M for Fe3+ using fluorescence spectroscopy. UV-Vis spectroscopy, fluorescence spectroscopy, FTIR, TEM, DLS etc. have been used for the physico-chemical characterization of Lv-AgNPs system and the nanoparticle mediated sensing process. Detailed experimental and theoretical studies employing FTIR spectrophotometry and density functional theory (DFT) studies have been used for the elucidation of drug-nanoparticle based sensing mechanism. It is also demonstrated that the Lv-AgNPs system can show real time application using Test-Paper Kit to establish the drug-nanoparticle assembly as a potential colorimetric turn-OFF/turn-ON sensing system for Hg2+ and Fe3+ respectively.

Swift fabrication of Ag nanostructures using a colloidal solution of Holostemma ada-kodien (Apocynaceae) - Antibiofilm potential, insecticidal activity against mosquitoes and non-target impact on water bugs.

PubMed

Alyahya, Sami A; Govindarajan, Marimuthu; Alharbi, Naiyf S; Kadaikunnan, Shine; Khaled, Jamal M; Mothana, Ramzi A; Al-Anbr, Mohammed N; Vaseeharan, Baskaralingam; Ishwarya, Ramachandran; Yazhiniprabha, Mariappan; Benelli, Giovanni

2018-04-01

Recent research in entomology and parasitology focused on the efficacy of green fabricated nanomaterials as novel insecticides. In this study, we synthesized poly-dispersed and stable silver nanoparticles (AgNPs) using the leaf extract of Holostemma ada-kodien. The nanostructures were characterized by ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray, and X-ray diffraction analysis. The efficacy of H. ada-kodien leaf extract and AgNPs in vector control was evaluated against the mosquitoes Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus, which act as major vectors of important parasitic and arboviral diseases. AgNPs showed higher toxicity if compared to the H. ada-kodien leaf aqueous extract, LC 50 towards larvae of A. stephensi, A. aegypti, and C. quinquefasciatus were 12.18, 13.30, and 14.70 μg/mL, respectively. When the AgNPs were tested on non-target water bugs, Diplonychus indicus, the LC 50 value was 623.48 μg/mL. Furthermore, 100 μl/mL of AgNPs achieved significant antimicrobial activity against Bacillus pumilus, Enterococcus faecalis, Pseudomonas aeruginosa, Proteus vulgaris, and Candida albicans. Light and confocal laser scanning microscopy highlighted a major impact of the H. ada-kodien-synthesized AgNPs on the external topography and architecture of microbial biofilms, both on Gram-positive and Gram-negative bacteria. Overall, this study sheds light on the insecticidal and antibiofilm potential of H. ada-kodien-synthesized AgNPs, a potential green resource for the rapid synthesis of polydispersed and highly stable AgNPs. Copyright © 2018 Elsevier B.V. All rights reserved.

Synthesis, characterization, and evaluation of antibacterial effect of Ag nanoparticles against Escherichia coli O157:H7 and methicillin-resistant Staphylococcus aureus (MRSA)

PubMed Central

Paredes, Daissy; Ortiz, Claudia; Torres, Rodrigo

2014-01-01

Silver nanoparticles (AgNPs) have been shown great interest because of their potential antibacterial effect. Recently, this has been increased due to resistance in some pathogenic bacteria strains to conventional antibiotics, which has initiated new studies to search for more effective treatments against resistant microorganisms. For these reasons, AgNPs have become an important approach for applications in nanobiotechnology in the development of antibiotic treatment of different bacterial infections. This study was aimed at synthesizing AgNPs using cysteine as a reducer agent and cetyl-tri-methyl-ammonium bromide as a stabilizer in order to obtain more efficient treatment against the pathogen bacteria Escherichia coli O157:H7. These AgNPs were characterized through UV-Vis spectroscopy, transmission electron microscopy, and dynamic light scattering. From these analyses, formation of spherical nanoparticles with an average size of 55 nm was confirmed. Finally, minimal inhibitory concentration (MIC) and minimal bactericide concentration (MBC) of these AgNPs against pathogenic strains E. coli O157:H7 and methicillin-resistant Staphylococcus aureus (MRSA) were determined in both solid and liquid media. MIC and MBC values were around 0.25 μg/mL and 1 μg/mL, respectively. These parameters were comparable to those reported in the literature and were even more effective than other synthesized AgNPs. PMID:24729707

Enhanced photoelectrochemical and photocatalytic activity in visible-light-driven Ag/BiVO{sub 4} inverse opals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, Liang, E-mail: lfang@suda.edu.cn, E-mail: dawei.cao@tu-ilmenau.de; Nan, Feng; Yang, Ying

2016-02-29

BiVO{sub 4} photonic crystal inverse opals (io-BiVO{sub 4}) with highly dispersed Ag nanoparticles (NPs) were prepared by the nanosphere lithography method combining the pulsed current deposition method. The incorporation of the Ag NPs can significantly improve the photoelectrochemical and photocatalytic activity of BiVO{sub 4} inverse opals in the visible light region. The photocurrent density of the Ag/io-BiVO{sub 4} sample is 4.7 times higher than that of the disordered sample without the Ag NPs, while the enhancement factor of the corresponding kinetic constant in photocatalytic experiment is approximately 3. The improved photoelectrochemical and photocatalytic activity is benefited from two reasons: onemore » is the enhanced light harvesting owing to the coupling between the slow light and localized surface plasmon resonance effect; the other is the efficient separation of charge carriers due to the Schottky barriers.« less

Noble metal nanoparticle-decorated TiO2 nanobelts for enhanced photocatalysis

NASA Astrophysics Data System (ADS)

He, Haiyan; Yang, Ping; Jia, Changchao; Miao, Yanping; Zhao, Jie; Du, Yingying

2014-07-01

TiO2 nanobelts have been fabricated through a hydrothermal method and subsequently sulfuric-acid-corrosion-treated for a rough surface. Noble metal nanoparticles such as Ag and Au were deposited on the coarse surface of TiO2 nanobelts via a coprecipitation procedure. Ag-TiO2 nanobelts were prepared in ethanolic solution contained silver nitrate (AgNO3) and sodium hydroxide (NaOH). Au-TiO2 nanobelts were obtained in chloroauric acid (HAuCl4) using sodium borohydride (NaBH4) as the reductant. It is confirmed by the results of XRD patterns together with the SEM images that the composite of noble metal and TiO2 nanobelts were obtained successfully and the Ag or Au nanoparticles were well-dispersed on the TiO2 nanobelts. Moreover, the as-prepared Ag and Au nanoparticle-decorated TiO2 nanobelts represent an enhanced photocatalytic activity compared with pure TiO2 nanobelts, which is due to the fact that the Ag and Au nanoparticles on the surface of TiO2 nanobelts act as sinks for the photogenerated electrons and promote the separation of the electrons and holes.

Green synthesized gold nanoparticles decorated graphene oxide for sensitive determination of chloramphenicol in milk, powdered milk, honey and eye drops.

PubMed

Karthik, R; Govindasamy, Mani; Chen, Shen-Ming; Mani, Veerappan; Lou, Bih-Show; Devasenathipathy, Rajkumar; Hou, Yu-Shen; Elangovan, A

2016-08-01

A simple and rapid green synthesis using Bischofia javanica Blume leaves as reducing agent was developed for the preparation of gold nanoparticles (AuNPs). AuNPs decorated graphene oxide (AuNPs/GO) was prepared and employed for the sensitive amperometric determination of chloramphenicol. The green biosynthesis requires less than 40s to reduce gold salts to AuNPs. The formations of AuNPs and AuNPs/GO were evaluated by scanning electron and atomic force microscopies, UV-Visible and energy dispersive X-ray spectroscopies, X-ray diffraction studies, and electrochemical methods. AuNPs/GO composite film modified electrode was fabricated and shown excellent electrocatalytic ability towards chloramphenicol. Under optimal conditions, the amperometric sensing platform has delivered wide linear range of 1.5-2.95μM, low detection limit of 0.25μM and high sensitivity of 3.81μAμM(-1)cm(-2). The developed sensor exhibited good repeatability and reproducibility, anti-interference ability and long-term storage stability. Practical feasibility of the sensor has been demonstrated in food samples (milk, powdered milk and honey) and pharmaceutical sample (eye drops). The green synthesized AuNPs/GO composite has great potential for analysis of food samples in food safety measures. Copyright © 2016 Elsevier Inc. All rights reserved.

Silica decorated on porous activated carbon nanofiber composites for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Kim, So Yeun; Kim, Bo-Hye

2016-10-01

A hybrid of silica decorated on porous activated carbon nanofibers (ACNFs) is fabricated in the form of a web via electrospinning and an activation process as an electrode material for electrochemical capacitors in an organic electrolyte. The introduction of PhSiH3 (PS) into the polyacrylonitrile (PAN) solution induces a porous ACNF structure containing silica nanoparticles (NPs) via the spontaneous sol-gel process of PS by steam in the subsequent physical activation process. These inorganic-organic hybrid composites of porous ACNF containing silica NPs show superior specific capacitance and energy density in electrochemical tests, along with good rate capability and excellent cycle life in an organic electrolyte, which is attributed to the combination of ACNF's high surface area and silica's hydrophilicity. The electrochemical performance decreases with increasing PS concentration, and this trend is consistent with the specific surface area results, which reveal the rapid formation of a double layer.

Preparation of silver nanoparticles/graphene nanosheets as a catalyst for electrochemical oxidation of methanol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Kun; Miao, Peng; Tang, Yuguo, E-mail: tangyg@sibet.ac.cn

2014-02-03

In this report, silver nanoparticles (AgNPs) decorated graphene nanosheets have been prepared based on the reduction of Ag ions by hydroquinone, and their catalytic performance towards the electrochemical oxidation of methanol is investigated. The synthesis of the nano-composite is confirmed by transmission electron microscope measurements and UV-vis absorption spectra. Excellent electrocatalytic performance of the material is demonstrated by cyclic voltammograms. This material also contributes to the low peak potential of methanol oxidation compared with most of the other materials.

Bioaccumulation of Zn and Ag Nanoparticles in the Earthworms (Eisenia fetida)

NASA Astrophysics Data System (ADS)

Ha, Lee Seung; Sung-Dae, Kim; Yi, Yang Song; Byeong-Gweon, Lee

2014-05-01

Many studies are carried out to evaluate environmental effects of engineered nanoparticles (ENPs). Most of the previous studies primarily focused on the effects of nanoparticles into the aquatic environment and human. Model studies predict that ENPs released into environment would transferred primarily to the soil of the terrestrial environment. Despite this prediction, biogeochemical behavior of ENPs in soil environment as well as bioavailability of ENPs to soil-dwelling organisms such as earthworm, springtail, isopod and nematodes are poorly understood. The main goal of this study was to compare the bioaccumulation factor (BAFs) and subcellular partitioning of nanoparticles in the soil-dwelling earthworm (Eisenia fetida) from ENP (ZnO and Ag nanoparticles) or ionic metal (Zn2+, Ag+) contaminated soil. And the sequential extraction was also used to determine the mobility of metals in soil which could be used as to predict bioavailability and compare that with bioaccumulation factor. The radiotracer method was employed to trace the transfer of ENPs and ionic metal among different environmental media and animals. Radiolabeled 65ZnO, 110mAgNPs coated with PVP or citrate were synthesized in the laboratory and their chemical and biological behavior was compared to ionic 65Zn and 110mAg. The BAFs of Zn and Ag in the earthworms were determined after animals exposed to the contaminated soils. After the 7 days of elimination phase, subcellular partitioning of metals were also obtained. BAF for ZnO(0.06) was 31 times lower than that for Zn ion (1.86), suggesting that ZnO was less bioavailable than its ionic form from contaminated soil. On the other hands, BAFs for AgNPs coated with PVP (0.12) or with citrate (0.11) were comparable to those for Ag ion (0.17), indicating that Ag from contaminated soil was bioavailable in a similar rate regardless of chemical forms. The subcellular partitioning results showed that bioaccumulated Zn from Zn ion and ZnO contaminated soil were

Ultrasensitive luminol electrochemiluminescence for protein detection based on in situ generated hydrogen peroxide as coreactant with glucose oxidase anchored AuNPs@MWCNTs labeling.

PubMed

Cao, Yaling; Yuan, Ruo; Chai, Yaqin; Mao, Li; Niu, Huan; Liu, Huijing; Zhuo, Ying

2012-01-15

In this study, an ultrasensitive luminol electrochemiluminescence (ECL) immunosensor was constructed using carboxyl group functionalized multi-walled carbon nanotubes (MWCNTs) as platform and glucose oxidase (GOD) supported on Au nanoparticles (AuNPs) decorated MWCNTs (AuNPs@MWCNTs-GOD) as labels. Firstly, using poly(ethylenimine) (PEI) as linkage reagents, AuNPs@MWCNTs were prepared and introduced for binding of the secondary antibody (Ab(2)) and glucose oxidase (GOD) with high loading amount and good biological activity due to the improved surface area of AuNPs@MWCNTs and excellent biocompatibility of AuNPs. Then the GOD and Ab(2) labeled AuNPs@MWCNTs were linked to the electrode surface via sandwich immunoreactions. These localized GOD and AuNPs amplified luminol ECL signals dramatically, which was achieved by efficient catalysis of the GOD and AuNPs towards the oxidation of glucose to in situ generate improved amount of hydrogen peroxide (H(2)O(2)) as coreactant and the enhancement of AuNPs to the ECL reaction of luminol-H(2)O(2). The experimental results demonstrated that the proposed immunosensor exhibited sensitive and stable response for the detection of α-1-fetoprotein (AFP), ranging from 0.0001 to 80 ng mL(-1) with a limit of detection down to 0.03 pg mL(-1) (S/N=3). With excellent stability, sensitivity, selectivity and simplicity, the proposed luminol ECL immunosensor showed great potential in clinical applications. Copyright © 2011 Elsevier B.V. All rights reserved.

Antimicrobial and cell viability measurement of bovine serum albumin capped silver nanoparticles (Ag/BSA) loaded collagen immobilized poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) film.

PubMed

Bakare, Rotimi; Hawthrone, Samantha; Vails, Carmen; Gugssa, Ayele; Karim, Alamgir; Stubbs, John; Raghavan, Dharmaraj

2016-03-01

Bacterial infection of orthopedic devices has been a major concern in joint replacement procedures. Therefore, this study is aimed at formulating collagen immobilized poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) film loaded with bovine serum albumin capped silver nanoparticles (Ag/BSA NPs) to inhibit bacterial growth while retaining/promoting osteoblast cells viability. The nanoparticles loaded collagen immobilized PHBV film was characterized for its composition by X-ray Photoelectron Spectroscopy and Anodic Stripping Voltammetry. The extent of loading of Ag/BSA NPs on collagen immobilized PHBV film was found to depend on the chemistry of the functionalized PHBV film and the concentration of Ag/BSA NPs solution used for loading nanoparticles. Our results showed that more Ag/BSA NPs were loaded on higher molecular weight collagen immobilized PHEMA-g-PHBV film. Maximum loading of Ag/BSA NPs on collagen immobilized PHBV film was observed when 16ppm solution was used for adsorption studies. Colony forming unit and optical density measurements showed broad antimicrobial activity towards Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa at significantly lower concentration i.e., 0.19 and 0.31μg/disc, compared to gentamicin and sulfamethoxazole trimethoprim while MTT assay showed that released nanoparticles from Ag/BSA NPs loaded collagen immobilized PHBV film has no impact on MCTC3-E1 cells viability. Copyright © 2015 Elsevier Inc. All rights reserved.

Integrative assessment of the effects produced by Ag nanoparticles at different levels of biological complexity in Eisenia fetida maintained in two standard soils (OECD and LUFA 2.3).

PubMed

Garcia-Velasco, N; Peña-Cearra, A; Bilbao, E; Zaldibar, B; Soto, M

2017-08-01

There is a potential risk to increase the release of silver nanoparticles (Ag NPs) into the environment: For instance. in soils receiving sludge models estimate 0.007 mg Ag NPs kg -1 that will annually increase due to sludge or sludge incineration residues land-disposal. Thus, the concern about the hazards of nanosilver to soils and soil invertebrates is growing. Studies performed up to now have been focused in traditional endpoints, used limit range concentrations and employed different soil types that differ in physico-chemical characteristics. Presently, effects of Ag NPs have been measured at different levels of biological complexity in Eisenia fetida, exposed for 3 and 14 d to high but sublethal (50 mg Ag NPs kg -1 ) and close to modeled environmental concentrations (0.05 mg Ag NPs kg -1 ). Since characteristics of the exposure matrix may limit the response of the organisms to these concentrations, experiments were carried out in OECD and LUFA soils, the most used standard soils. High concentrations of Ag NPs increased catalase activity and DNA damage in OECD soils after 14 d while in LUFA 2.3 soils produced earlier effects (weight loss, decrease in cell viability and increase in catalase activity at day 3). At day 14, LUFA 2.3 (low clay and organic matter-OM-) could have provoked starvation of earthworms, masking Ag NPs toxicity. The concentration close to modeled environmental concentrations produced effects uniquely in LUFA 2.3 soil. Accurate physico-chemical characteristics of the standard soils are crucial to assess the toxicity exerted by Ag NPs in E. fetida since low clay and OM contents can be considered toxicity enhancers. Copyright © 2017 Elsevier Ltd. All rights reserved.

Invoking Direct Exciton-Plasmon Interactions by Catalytic Ag Deposition on Au Nanoparticles: Photoelectrochemical Bioanalysis with High Efficiency.

PubMed

Ma, Zheng-Yuan; Xu, Fei; Qin, Yu; Zhao, Wei-Wei; Xu, Jing-Juan; Chen, Hong-Yuan

2016-04-19

In this work, direct exciton-plasmon interactions (EPI) between CdS quantum dots (QDs) and Ag nanoparticles (NPs) were invoked ingeniously by catalytic Ag deposition on Au NPs for the stimulation of high efficient damping effect toward the excitonic responses in CdS QDs, on the basis of which a novel photoelectrochemical (PEC) bioanalytical format was achieved for sensitive microRNA detection. Specifically, upon the configurational change from the hairpin probe DNA to the "Y"-shaped ternary conjugate consisting of the original probe DNA, assistant DNA, and the target microRNA, the alkaline phosphatase (ALP) catalytic chemistry would then trigger the transition of the interparticle interplay from the CdS QDs-Au NPs to the CdS QDs-Ag NPs systems for the microRNA detection due to the dependence of the photocurrent quenching on the target concentration. This work not only provided a unique method for EPI generation among the PEC nanosystems but also offered a versatile and general protocol for future PEC bioanalysis development.

Investigation of imatinib loaded surface decorated biodegradable nanocarriers against glioblastoma cell lines: Intracellular uptake and cytotoxicity studies.

PubMed

Khan, Abrar M; Ahmad, Farhan Jalees; Panda, Amulya K; Talegaonkar, Sushama

2016-06-30

Overexpression of P-glycoprotein (P-gp) efflux transporter in glioma cells thwarts the build-up of therapeutic concentration of drugs usually resulting into poor therapeutic outcome. To surmount aforesaid challenge, Imatinib (IMM) loaded Poly-lactide-co-glycolic acid nanoparticles (IMM-PLGA-NPs) were developed and optimized by Box Behnken Design as a new treatment stratagem in malignant glioma. Optimized NPs were functionalized with Pluronic(®) P84, P-gp inhibitor (IMM-PLGA-P84-NPs) which showed size, PDI, zeta potential, drug loading, 182.63±13.56nm, 0.196±0.021, -15.2±1.49mV, 40.63±2.04μg/mg, respectively. Intracellular uptake study conducted on A172, U251MG and C6 glioma cells demonstrated significantly high uptake of IMM through NPs when compared with IMM solution (IMM-S), p<0.001. IMM-PLGA-P84-NPs showed better uptake in P-gp expressing cell line (U251MG and C6) while uncoated NPs showed higher uptake in non-P-gp expressing cell line (A-172). Cytotoxicity studies demonstrated significantly low IC50 for both IMM-PLGA-NPs and IMM-PLGA-P84-NPs when compared with IC50 of IMM-S. IMM-PLGA-P84-NPs showed a significantly low IC50 against P-gp overexpressing cell lines when compared with IC50 of IMM-PLGA-NPs. In contrary, IMM-PLGA-NPs showed lower IC50 against non P-gp expressing cell line. This study demonstrated the feasibility of targeting surface decorated NPs to multidrug resistant gliomas. However, to address its clinical utility extensive in vivo studies are required. Copyright © 2016 Elsevier B.V. All rights reserved.

Highly Stable Graphene-Based Nanocomposite (GO-PEI-Ag) with Broad-Spectrum, Long-Term Antimicrobial Activity and Antibiofilm Effects.

PubMed

Zhao, Rongtao; Kong, Wen; Sun, Mingxuan; Yang, Yi; Liu, Wanying; Lv, Min; Song, Shiping; Wang, Lihua; Song, Hongbin; Hao, Rongzhang

2018-05-30

Various silver nanoparticle (AgNP)-decorated graphene oxide (GO) nanocomposites (GO-Ag) have received increasing attention owing to their antimicrobial activity and biocompatibility; however, their aggregation in physiological solutions and the generally complex synthesis methods warrant improvement. This study aimed to synthesize a polyethyleneimine (PEI)-modified and AgNP-decorated GO nanocomposite (GO-PEI-Ag) through a facile approach through microwave irradiation without any extra reductants and surfactants; its antimicrobial activity was investigated on Gram-negative/-positive bacteria (including drug-resistant bacteria) and fungi. Compared with GO-Ag, GO-PEI-Ag acquired excellent stability in physiological solutions and electropositivity, showing substantially higher antimicrobial efficacy. Moreover, GO-PEI-Ag exhibited particularly excellent long-term effects, presenting no obvious decline in antimicrobial activity after 1 week storage in physiological saline and repeated use for three times and the lasting inhibition of bacterial growth in nutrient-rich culture medium. In contrast, GO-Ag exhibited a >60% decline in antimicrobial activity after storage. Importantly, GO-PEI-Ag effectively eliminated adhered bacteria, thereby preventing biofilm formation. The primary antimicrobial mechanisms of GO-PEI-Ag were evidenced as physical damage to the pathogen structure, causing cytoplasmic leakage. Hence, stable GO-PEI-Ag with robust, long-term antimicrobial activity holds promise in combating public-health threats posed by drug-resistant bacteria and biofilms.

Synthesis of Ag-ZnO with multiple rods (multipods) morphology and its application in the simultaneous photo-catalytic degradation of methyl orange and methylene blue.

PubMed

Arab Chamjangali, M; Bagherian, G; Javid, A; Boroumand, S; Farzaneh, N

2015-11-05

In this study, the photo-decolorization of a mixture of methylene blue (MB) and methyl orange (MO) was investigated using Ag-ZnO multipods. The photo-catalyst used, ZnO multipods, was successfully synthesized. The surface of ZnO microstructure was modified by deposition of different amounts of Ag nanoparticles (Ag NPs) using the photo-reduction method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis and atomic absorption spectroscopy. The photo-catalytic efficiency of Ag-ZnO is mainly controlled by the amount of Ag NPs deposited on the ZnO surface. The results obtained suggest that Ag-ZnO containing 6.5% Ag NPs, has the highest photo-catalytic performance in the simultaneous photo-degradation of dyes at a shorter time. Copyright © 2015 Elsevier B.V. All rights reserved.

Morphologically manipulated Ag/ZnO nanostructures as surface enhanced Raman scattering probes for explosives detection

NASA Astrophysics Data System (ADS)

Shaik, Ummar Pasha; Hamad, Syed; Ahamad Mohiddon, Md.; Soma, Venugopal Rao; Ghanashyam Krishna, M.

2016-03-01

The detection of secondary explosive molecules (e.g., ANTA, FOX-7, and CL-20) using Ag decorated ZnO nanostructures as surface enhanced Raman scattering (SERS) probes is demonstrated. ZnO nanostructures were grown on borosilicate glass substrates by rapid thermal oxidation of metallic Zn films at 500 °C. The oxide nanostructures, including nanosheets and nanowires, emerged over the surface of the Zn film leaving behind the metal residue. We demonstrate that SERS measurements with concentrations as low as 10 μM, of the three explosive molecules ANTA, FOX-7, and CL-20 over ZnO/Ag nanostructures, resulted in enhancement factors of ˜107, ˜107, and ˜104, respectively. These measurements validate the high sensitivity of detection of explosive molecules using Ag decorated ZnO nanostructures as SERS substrates. The Zn metal residue and conditions of annealing play an important role in determining the detection sensitivity.

The photovoltaic performance of Ag2S quantum dots-sensitized solar cells using plasmonic Au nanoparticles/TiO2 working electrodes

NASA Astrophysics Data System (ADS)

Badawi, Ali; Mostafa, Nasser Y.; Al-Hosiny, Najm M.; Merazga, Amar; Albaradi, Ateyyah M.; Abdel-Wahab, F.; Atta, A. A.

2018-06-01

The photovoltaic performance of silver sulfide (Ag2S) quantum dots-sensitized solar cells (QDSSCs) using different concentrations (0, 0.05, 0.1, 0.3 and 0.5 wt.%) of plasmonic Au nanoparticles (NPs)/titania (TiO2) electrodes has been investigated. Ag2S quantum dots (QDs) were adsorbed onto the Au NPs/titania electrodes using the successive ionic layer adsorption and reaction (SILAR) deposition technique. The morphological properties of the Au NPs and the prepared titania electrodes were characterized using transmission electron microscope (TEM) and scanning electron microscope (SEM), respectively. The energy-dispersive X-ray (EDX) spectra of the bare titania and Ag2S QDs-sensitized titania electrodes were recorded. The optical properties of the prepared Ag2S QDs-sensitized titania electrodes were measured using a UV-visible spectrophotometer. The estimated energy band gap of Ag2S QDs-sensitized titania electrodes is 1.96 eV. The photovoltaic performance of the assembled Ag2S QDSSCs was measured under 100 mW/cm2 solar illumination. The optimal photovoltaic parameters were obtained as follows: open circuit voltage Voc = 0.50 V, current density Jsc = 3.18 mA/cm2, fill factor (FF) = 0.35 and energy conversion efficiency η = 0.55% for 0.3 wt.% of Au NPs/titania electrode. These results are attributed to the enhancement in the absorption and decrease in the electron-hole pairs recombination rate. The open circuit voltage decay (OCVD) measurements of the assembled Ag2S QDSSCs were measured. The calculated electron lifetime (τ) in Ag2S QDSSCs with Au NPs/titania electrodes is at least one order of magnitude more than that with bare titania electrode. The cut-on-cut-off cycles of the solar illumination measurements show the rapid sensitivity and good reproducibility of the assembled Ag2S QDSSCs.

Facile synthesis of dispersed Ag nanoparticles on chitosan-TiO2 composites as recyclable nanocatalysts for 4-nitrophenol reduction

NASA Astrophysics Data System (ADS)

Xiao, Gang; Zhao, Yilin; Li, Linghui; Pratt, Jonathan O.; Su, Haijia; Tan, Tianwei

2018-04-01

This paper presents a facile, rapid, and controllable procedure for the recovery of trace Ag+ ions and in situ assembly of well dispersed Ag nanoparticles on chitosan-TiO2 composites through bioaffinity adsorption followed by photocatalytic reduction. The prepared Ag nanoparticles are proven to be efficient and recyclable nanocatalysts for the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4. Well dispersed quasi-spherical Ag NPs are synthesized in 20 min in the designed inner-irradiated photocatalytic system under a wide range of Ag+ concentrations (50-200 mg l-1), temperatures (10 °C-25 °C) conditions, and UV or visible light irradiation. The synthesized Ag NPs can catalyze the reduction of 4-nitrophenol by NaBH4 at 100% conversion in 120 min and preserve the catalytic activity in five successive cycles. This procedure for trace Ag+ ions recovery and Ag NPs assembly has the potential to be scaled up for the mass production of recyclable Ag nanocatalysts. The present work provides a green and efficient procedure for the conversion of hazardous 4-nitrophenol to industrially important 4-aminophenol and also sheds a light on designing scaled-up procedures for treating high volumes of wastewater with dilute heavy metals to produce recyclable metallic nanocatalysts in aqueous systems.

Cobalt/copper-decorated carbon nanofibers as novel non-precious electrocatalyst for methanol electrooxidation

PubMed Central

2014-01-01

In this study, Co/Cu-decorated carbon nanofibers are introduced as novel electrocatalyst for methanol oxidation. The introduced nanofibers have been prepared based on graphitization of poly(vinyl alcohol) which has high carbon content compared to many polymer precursors for carbon nanofiber synthesis. Typically, calcination in argon atmosphere of electrospun nanofibers composed of cobalt acetate tetrahydrate, copper acetate monohydrate, and poly(vinyl alcohol) leads to form carbon nanofibers decorated by CoCu nanoparticles. The graphitization of the poly(vinyl alcohol) has been enhanced due to presence of cobalt which acts as effective catalyst. The physicochemical characterization affirmed that the metallic nanoparticles are sheathed by thin crystalline graphite layer. Investigation of the electrocatalytic activity of the introduced nanofibers toward methanol oxidation indicates good performance, as the corresponding onset potential was small compared to many reported materials; 310 mV (vs. Ag/AgCl electrode) and a current density of 12 mA/cm2 was obtained. Moreover, due to the graphite shield, good stability was observed. Overall, the introduced study opens new avenue for cheap and stable transition metals-based nanostructures as non-precious catalysts for fuel cell applications. PMID:24387682

Ag nanoparticle-filled TiO2 nanotube arrays prepared by anodization and electrophoretic deposition for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Wei, Xing; Sugri Nbelayim, Pascal; Kawamura, Go; Muto, Hiroyuki; Matsuda, Atsunori

2017-03-01

A layer of TiO2 nanotube (TNT) arrays with a thickness of 13 μm is synthesized by a two-step anodic oxidation from Ti metal foil. Surface charged Ag nanoparticles (NPs) are prepared by chemical reduction. After a pretreatment of the TNT arrays by acetone vapor, Ag NP filled TNT arrays can be achieved by electrophoretic deposition (EPD). Effects of the applied voltage during EPD such as DC-AC difference, frequency and waveform are investigated by quantitative analysis using atomic absorption spectroscopy. The results show that the best EPD condition is using DC 2 V + AC 4 V and a square wave of 1 Hz as the applied voltage. Back illuminated dye-sensitized solar cells are fabricated from TNT arrays with and without Ag NPs. The efficiency increased from 3.70% to 5.01% by the deposition of Ag NPs.

Coherent-Interface-Assembled Ag2O-Anchored Nanofibrillated Cellulose Porous Aerogels for Radioactive Iodine Capture.

PubMed

Lu, Yun; Liu, Hongwei; Gao, Runan; Xiao, Shaoliang; Zhang, Ming; Yin, Yafang; Wang, Siqun; Li, Jian; Yang, Dongjiang

2016-10-26

Nanofibrillated cellulose (NFC) has received increasing attention in science and technology because of not only the availability of large amounts of cellulose in nature but also its unique structural and physical features. These high-aspect-ratio nanofibers have potential applications in water remediation and as a reinforcing scaffold in composites, coatings, and porous materials because of their fascinating properties. In this work, highly porous NFC aerogels were prepared based on tert-butanol freeze-drying of ultrasonically isolated bamboo NFC with 20-80 nm diameters. Then nonagglomerated 2-20-nm-diameter silver oxide (Ag 2 O) nanoparticles (NPs) were grown firmly onto the NFC scaffold with a high loading content of ∼500 wt % to fabricate Ag 2 O@NFC organic-inorganic composite aerogels (Ag 2 O@NFC). For the first time, the coherent interface and interaction mechanism between the cellulose I β nanofiber and Ag 2 O NPs are explored by high-resolution transmission electron microscopy and 3D electron tomography. Specifically, a strong hydrogen between Ag 2 O and NFC makes them grow together firmly along a coherent interface, where good lattice matching between specific crystal planes of Ag 2 O and NFC results in very small interfacial straining. The resulting Ag 2 O@NFC aerogels take full advantage of the properties of the 3D organic aerogel framework and inorganic NPs, such as large surface area, interconnected porous structures, and supreme mechanical properties. They open up a wide horizon for functional practical usage, for example, as a flexible superefficient adsorbent to capture I - ions from contaminated water and trap I 2 vapor for safe disposal, as presented in this work. The viable binding mode between many types of inorganic NPs and organic NFC established here highlights new ways to investigate cellulose-based functional nanocomposites.

A sensitive sandwich-type electrochemical aptasensor for thrombin detection based on platinum nanoparticles decorated carbon nanocages as signal labels.

PubMed

Gao, Fenglei; Du, Lili; Zhang, Yu; Zhou, Fuyi; Tang, Daoquan

2016-12-15

In this work, a novel and sensitive sandwich-type electrochemical aptasensor has been developed for thrombin detection based on platinum nanoparticles (Pt NPs) decorated carbon nanocages (CNCs) as signal tags. The morphological and compositional of the Pt NPs/CNCs were examined using transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. The results showed that the Pt NPs with about 3-5nm in diameter were well dispersed on the surface of CNCs. The thiolated aptamer was firstly immobilized on the gold electrode to capture the thrombin molecules, and then aptamer functionalized Pt NPs/CNCs nanocomposites were used to fabricate a sandwich sensing platform. Then, the high-content Pt NPs on carbon nanocages acting as hydrogen peroxide-mimicking enzyme catalyzed the reduction of H2O2, resulting in significant electrochemical signal amplification. Differential pulse voltammetry is employed to detect thrombin with different concentrations. Under optimized conditions, the approach provided a good linear response range from 0.05 pM to 20nM with a low detection limit of 10fM. This Pt NPs/CNCs-based aptasensor shows good precision, acceptable stability and reproducibility, which provided a promising strategy for electrochemical aptamer-based detection of other biomolecules. Copyright © 2016 Elsevier B.V. All rights reserved.

Comparison of antibacterial activities of Ag@TiO2 and Ag@SiO2 core-shell nanoparticles

NASA Astrophysics Data System (ADS)

Dhanalekshmi, K. I.; Meena, K. S.

2014-07-01

Core-shell type Ag@TiO2 nanoparticles were prepared by one pot simultaneous reduction of AgNO3 and hydrolysis of Ti (IV) isopropoxide and Ag@SiO2 core-shell nanoparticles were prepared by Stober's method. They were characterized by absorption, XRD, and HR-TEM techniques. XRD patterns show the presence of anatase form of TiO2 and amorphous form of SiO2 and the noble metal (Ag). High resolution transmission electron microscopy measurements revealed that their size is below 50 nm. The antibacterial properties of Ag@TiO2 and Ag@SiO2 core-shell nanoparticles against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were examined by the agar diffusion method. As a result E. coli and S. aureus were shown to be substantially inhibited by Ag@TiO2 and Ag@SiO2 core-shell nanoparticles. These results demonstrated that TiO2 and SiO2 supported on the surface of Ag NPs without aggregation was proved to have enhanced antibacterial activity.

Comparison of antibacterial activities of Ag@TiO2 and Ag@SiO2 core-shell nanoparticles.

PubMed

Dhanalekshmi, K I; Meena, K S

2014-07-15

Core-shell type Ag@TiO2 nanoparticles were prepared by one pot simultaneous reduction of AgNO3 and hydrolysis of Ti (IV) isopropoxide and Ag@SiO2 core-shell nanoparticles were prepared by Stober's method. They were characterized by absorption, XRD, and HR-TEM techniques. XRD patterns show the presence of anatase form of TiO2 and amorphous form of SiO2 and the noble metal (Ag). High resolution transmission electron microscopy measurements revealed that their size is below 50 nm. The antibacterial properties of Ag@TiO2 and Ag@SiO2 core-shell nanoparticles against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were examined by the agar diffusion method. As a result E. coli and S. aureus were shown to be substantially inhibited by Ag@TiO2 and Ag@SiO2 core-shell nanoparticles. These results demonstrated that TiO2 and SiO2 supported on the surface of Ag NPs without aggregation was proved to have enhanced antibacterial activity. Copyright © 2014 Elsevier B.V. All rights reserved.

A non-enzymatic amperometric hydrogen peroxide sensor based on iron nanoparticles decorated reduced graphene oxide nanocomposite.

PubMed

Amanulla, Baishnisha; Palanisamy, Selvakumar; Chen, Shen-Ming; Velusamy, Vijayalakshmi; Chiu, Te-Wei; Chen, Tse-Wei; Ramaraj, Sayee Kannan

2017-02-01

A simple and facile green process was used for the synthesis of iron nanoparticles (FeNPs) decorated reduced graphene oxide (rGO) nanocomposite by using Ipomoea pes-tigridis leaf extract as a reducing and stabilizing agent. The as-prepared rGO/FeNPs nanocomposite was characterized by transmission electron microscopy, X-ray spectroscopy and Fourier transform infrared spectroscopy. The nanocomposite was further modified on the glassy carbon electrode and used for non-enzymatic sensing of hydrogen peroxide (H 2 O 2 ). Cyclic voltammetry results reveal that rGO/FeNPs nanocomposite has excellent electro-reduction behavior to H 2 O 2 when compared to the response of FeNPs and rGO modified electrodes. Furthermore, the nanocomposite modified electrode shows 9 and 6 folds enhanced reduction current response to H 2 O 2 than that of rGO and FeNPs modified electrodes. Amperometric method was further used to quantify the H 2 O 2 using rGO/FeNPs nanocomposite, and the response was linear over the concentration ranging from 0.1μM to 2.15mM. The detection limit and sensitivity of the sensor were estimated as 0.056μM and 0.2085μAμM -1 cm -2 , respectively. The fabricated sensor also utilized for detection of H 2 O 2 in the presence of potentially active interfering species, and found high selectivity towards H 2 O 2 . Copyright © 2016 Elsevier Inc. All rights reserved.

ZnO-Ag core shell nanocomposite formed by green method using essential oil of wild ginger and their bactericidal and cytotoxic effects

NASA Astrophysics Data System (ADS)

Azizi, Susan; Mohamad, Rosfarizan; Rahim, Raha Abdul; Moghaddam, Amin Boroumand; Moniri, Mona; Ariff, Arbakariya; Saad, Wan Zuhainis; Namvab, Farideh

2016-10-01

In this paper, a novel green method for fabrication of zinc oxide-silver (ZnO-Ag) core-shell nanocomposite using essential oil of ginger (EO-G) is reported. The EO-G played two significant roles in the synthesis process: it could act as a reaction media for the formation of ZnO and reduce Ag+ to Ag0. The bioformed ZnO-Ag nanocomposite was compared with pure biosynthesized ZnO-NPs and characterized by UV-vis spectroscopy, TEM, EDX, XRD and FTIR. The characterization results confirmed that Ag-NPs had been embedded in ZnO hexagonal nanoparticles. Six Gram positive and negative pathogens were used to investigate the antibacterial effects of these samples. Ag-doping improves the bactericidal activity of ZnO-NPs. In vitro cytotoxicity studies on Vero cells, a dose dependent toxicity with non-toxic effect of concentration below 100 μg/mL was shown for ZnO-Ag nanocomposite. The biosynthesized ZnO-Ag nanocomposites were found to be comparable to those obtained from the conventional methods using hazardous materials which can be an excellent alternative for the synthesis of ZnO-Ag using biomass.

Modification of the internal surface of photonic crystal fibers with Ag and Au nanoparticles for application as sensor elements

NASA Astrophysics Data System (ADS)

Pidenko, Pavel S.; Borzov, Victor M.; Savenko, Olga A.; Skaptsov, Alexander A.; Skibina, Yulia S.; Goryacheva, Irina Yu.; Rusanova, Tatiana Yu.

2017-03-01

Photonic crystal fibers (PCFs) are one of the most promising materials for biosensors construction due to their unique optical properties. The modification of PCF by noble metal nanoparticles (NPs) provides the SPR and SERS signal detection where as the application amino group-containing compounds allows efficient binding of biomolecules. In this work the internal surface of glass hollow core photonic crystal fibers (HC-PCFs) has been modified Ag and Au nanoparticles using three different approaches. PCFs were treated by: 1) mixture of NPs and precursors for silanization (tetraethoxysilane (TEOS) and (3-aminopropyl)triethoxysilane (APTES)); 2) alternately deposition of polyelectrolytes and NPs, 3) mixture of chitosan with NPs. The shift of local maxima in the HC-PCF transmission spectrum has been selected as a signal for estimating the amount of NPs on the HC-PCF inner surface. The most efficient techniques were the chitosan application for Ag NPs and silanization for Au NPs. The obtaining PCFs could be useful for creating biosensitive elements.

The effect of TiO{sub 2} and Ag nanoparticles on reproduction and development of Drosophila melanogaster and CD-1 mice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Philbrook, Nicola A., E-mail: 3nap@queensu.ca; Department of Biomedical and Molecular Sciences, Botterell Hall, 5th Floor, Queen's University, 18 Stuart Street, Kingston, Ontario, Canada K7L 3N6; Winn, Louise M., E-mail: winnl@queensu.ca

2011-12-15

In the last two decades, nanoparticles (NPs) have found applications in a wide variety of consumer goods. Titanium dioxide (TiO{sub 2}) and silver (Ag) NPs are both found in cosmetics and foods, but their increasing use is of concern due to their ability to be taken up by biological systems. While there are some reports of TiO{sub 2} and Ag NPs affecting complex organisms, their effects on reproduction and development have been largely understudied. Here, the effects of orally administered TiO{sub 2} or Ag NPs on reproduction and development in two different model organisms were investigated. TiO{sub 2} NPs reducedmore » the developmental success of CD-1 mice after a single oral dose of 100 or 1000 mg/kg to dams, resulting in a statistically significant increase in fetal deformities and mortality. Similarly, TiO{sub 2} NP addition to food led to a significant progeny loss in the fruit fly, Drosophila, as shown by a decline in female fecundity. Ag NP administration resulted in an increase in the mortality of fetal mice. Similarly in Drosophila, Ag NP feeding led to a significant decrease in developmental success, but unlike TiO{sub 2} NP treatment, there was no decline in fecundity. The distinct response associated with each type of NP likely reflects differences in NP administration as well as the biology of the particular model. Taken together, however, this study warns that these common NPs could be detrimental to the reproductive and developmental health of both invertebrates and vertebrates.« less

Stress-dislocation interaction mechanism in low-temperature thermo-compression sintering of Ag NPs

NASA Astrophysics Data System (ADS)

Wang, Fuliang; Tang, Zikai; He, Hu

2018-04-01

The sintering of metal nanoparticles (NPs) has been widely studied in the field of nanotechnology, and low-temperature sintering has become the industry standard. In this study, a molecular dynamics (MD) model was established to study the sintering behaviour of silver NPs during low-temperature thermo-compression. Primarily, we studied the sintering process, in which the ratio of neck radius to particle radius (x/r) changes. Under a uniaxial pressure, the maximum ratio in the temperature range 420-425 K was 1. According to the change of x/r, the process can be broken down into three stages: the neck-formation stage, neck-growth stage, and neck-stability stage. In addition, the relationship between potential energy, internal stress, and dislocation density during sintering is discussed. The results showed that cycling internal stress played an important role in sintering. Under the uniaxial pressure, the stress-dislocation interaction was found to be the major mechanism for thermo-compression sintering because the plastic deformation product dislocation intensified the diffusion of atoms. Also, the displacement vector, the mean square displacement, and the changing crystal structure during sintering were studied.

Eco-friendly fabrication of Ag nanostructures using the seed extract of Pedalium murex, an ancient Indian medicinal plant: Histopathological effects on the Zika virus vector Aedes aegypti and inhibition of biofilm-forming pathogenic bacteria.

PubMed

Ishwarya, Ramachandran; Vaseeharan, Baskaralingam; Anuradha, Ramasamy; Rekha, Ravichandran; Govindarajan, Marimuthu; Alharbi, Naiyf S; Kadaikunnan, Shine; Khaled, Jamal M; Benelli, Giovanni

2017-09-01

The control of Zika virus mosquito vectors and well as the development of drugs in the fight against biofilm-forming microbial pathogens, are timely and important challenges in current bionanoscience. Here we focused on the eco-friendly fabrication of Ag nanostructures using the seed extract of Pedalium murex, an ancient Indian medicinal plant. Initial confirmation of Ag nanoparticles (AgNPs) production was showed by a color change from transparent to dark brown. The UV-Visible spectrum (476nm), X-ray diffraction peaks (101, 200, 220 and 311) and Fourier transform infrared spectroscopy shed light on the production of green-capped AgNPs. Morphological structure analysis using HR-TEM showed that the AgNPs were mostly hexagonal in shape with rough edges, and a size of 20-30nm. The larvicidal potential of P. murex seed extract and AgNPs fabricated using the P. murex seed extract (Pm-AgNPs) was tested on fourth instar mosquito larvae of the Zika virus vector Aedes aegypti. Maximum efficacy was achieved by Pm-AgNPs against Ae. aegypti after 24h (LC 50 34.88; LC 90 64.56mg/ml), if compared to the P. murex seed extract. Histopathological analyses showed severe damages to the hindgut and larval muscles in NPs-treated Ae. aegypti larvae. The sub-MIC concentrations of Pm-AgNPs exhibited significant anti-biofilm activity against Gram positive (Enterococcus faecalis, Staphylococcus aureus) and Gram negative (Shigella sonnei, Pseudomonas aeruginosa) bacterial pathogens, as showed by EPS and MTP assays. Light and CLSM microscopic studies highlighted a significant impact of P. murex seed extract and Pm-synthesized AgNPs on the surface topography and architecture of bacterial biofilm, both in Gram positive and Gram negative species. Overall, results reported here contribute to the development of reliable large-scale protocols for the green fabrication of effective mosquito larvicides and biofilm inhibitors. Copyright © 2017 Elsevier B.V. All rights reserved.

Investigation on the morphological and optical evolution of bimetallic Pd-Ag nanoparticles on sapphire (0001) by the systematic control of composition, annealing temperature and time.

PubMed

Pandey, Puran; Kunwar, Sundar; Sui, Mao; Bastola, Sushil; Lee, Jihoon

2017-01-01

Multi-metallic alloy nanoparticles (NPs) can offer additional opportunities for modifying the electronic, optical and catalytic properties by the control of composition, configuration and size of individual nanostructures that are consisted of more than single element. In this paper, the fabrication of bimetallic Pd-Ag NPs is systematically demonstrated via the solid state dewetting of bilayer thin films on c-plane sapphire by governing the temperature, time as well as composition. The composition of Pd-Ag bilayer remarkably affects the morphology of alloy nanostructures, in which the higher Ag composition, i.e. Pd0.25Ag0.75, leads to the enhanced dewetting of bilayers whereas the higher Pd composition (Pd0.75Ag0.25) hinders the dewetting. Depending on the annealing temperature, Pd-Ag alloy nanostructures evolve with a series of configurations, i.e. nucleation of voids, porous network, elongated nanoclusters and round alloy NPs. In addition, with the annealing time set, the gradual configuration transformation from the elongated to round alloy NPs as well as size reduction is demonstrated due to the enhanced diffusion and sublimation of Ag atoms. The evolution of various morphology of Pd-Ag nanostructures is described based on the surface diffusion and inter-diffusion of Pd and Ag adatoms along with the Ag sublimation, Rayleigh instability and energy minimization mechanism. The reflectance spectra of bimetallic Pd-Ag nanostructures exhibit various quadrupolar and dipolar resonance peaks, peak shifts and absorption dips owing to the surface plasmon resonance of nanostructures depending on the surface morphology. The intensity of reflectance spectra is gradually decreased along with the surface coverage and NP size evolution. The absorption dips are red-shifted towards the longer wavelength for the larger alloy NPs and vice-versa.

Investigation on the morphological and optical evolution of bimetallic Pd-Ag nanoparticles on sapphire (0001) by the systematic control of composition, annealing temperature and time

PubMed Central