Monodisperse Silver Nanoparticles Research Articles

Efficient surface modification of carbon nanotubes for fabricating high performance CNT based hybrid nanostructures

Carbon nanotubes (CNTs) were chemically modified to achieve strong binding strength with the attached functional components as well as good dispersability and nanoparticle size-uniformity. An efficient multi-oxidation process was developed to create porous out layer with many nanoscale defects on the surface of CNTs for metallic nanoparticle close attachment and bond sufficient oxygen-containing groups, which assisted the dispersion of CNTs in the aqueous solution. The surface modified CNTs have advantages of strong binding capability, large surface area, high mechanical strength and good dispersability, which show great potential as building blocks for hybrid nanomaterials. Monodispersed silver nanoparticles with an average size of 3 nm were formed from inside the created nanoscale defects on the surface of CNTs without any obvious agglomerations. The fabricated hybrid exhibited much enhanced anti-bacterial performance compared to commercial silver nanoparticles due to the combined anti-bacterial effects of CNTs and silver nanoparticles. With these superior properties, the developed surface modification process could be widely used for improving the performances of many CNT based hybrid nanomaterials in diverse applications.

Rapid Synthesis of Silver Nanoparticles by Microwave-Polyol Method with the Assistance of Latex Copolymer

Highly stable and monodispersed silver nanoparticles with uniform morphology have been successfully prepared by microwave (MW) irradiation within a few seconds from the mixture of silver nitrate, ethanol and latex copolymer. The aqueous emulsion of latex copolymer acts as both reducing and stabilizing agent. To the best of our knowledge, it was the first time that the effect of MW irradiation time and latex concentration on the silver nanoparticle preparation and properties was analyzed. The formation of silver nanoparticles was confirmed by Ultraviolet–visible spectroscopy and transmission electron microscopy (TEM). The UV–Vis spectra are marked by the characteristic surface plasmon absorption band in the range 410–420 nm. From TEM images, silver nanoparticles were observed to be spherical with sizes ranging from 4 to 10 nm. Electron diffraction patterns on selected area, indicated that the silver nanoparticles are crystalline with face centered cubic structure.

Green synthesis and antimicrobial activity of monodisperse silver nanoparticles synthesized using Ginkgo Biloba leaf extract

Various parts of plants can be used as a raw material for the synthesis of nanoparticles, which is eco-friendly way and does not involve any harmful chemicals. In this project, Ginkgo biloba leaf, an abundantly available medicinal plant in China, was for the first time adopted as a reducing and stabilizing agent to synthesize smaller sized and stable silver nanoparticles (AgNPs). To improve the quality of AgNPs, the reduction was accelerated by changing the concentrations of initial Ag+ (0.02, 0.04, 0.06 and 0.08 mol/L) of the reaction mixture consisting of silver nitrate solution (AgNO3) and Ginkgo biloba leaf extract. At pH=8 and lower AgNO3 concentration (0.02 mol/L), a colloid consisting of well-dispersed spherical nanoparticles was obtained. The synthesized nanocrystals were successfully characterized by UV–vis and XRD. TEM images revealed the size of the spherical AgNPs ranged between 10–16 nm. FTIR analysis revealed that biological macromolecules with groups of NH2, OH, and others were distributed on the surface of the nanoparticles. The biosynthesized AgNPs exhibited good antibacterial activities against gram-negative bacteria and gram-positive bacteria. Compared to traditional chemical methods, Ginkgo biloba leaf extract provides an easy green synthetical way. It is anticipated that the biosynthesized AgNPs can be used in areas such as cosmetics, foods and medical applications.

One-pot facile green synthesis of biocidal silver nanoparticles

The plant root extract mediated green synthesis method produces monodispersed spherical shape silver nanoparticles (AgNPs) with a size range of 15–30 nm as analyzed by atomic force and transmission electron microscopy. The material showed potent antibacterial and antifungal properties. Synthesized AgNPs display a characteristic surface plasmon resonance peak at 420 nm in UV–Vis spectroscopy. X-ray diffractometer analysis revealed the crystalline and face-centered cubic geometry of in situ prepared AgNPs. Agar well diffusion and a colony forming unit assay demonstrated the potent biocidal activity of AgNPs against Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Klebsiella pneumoniae, Pseudomonas diminuta and Mycobacterium smegmatis. Intriguingly, the phytosynthesized AgNPs exhibited activity against pathogenic fungi, namely Trichophyton rubrum, Aspergillus versicolor and Candida albicans. Scanning electron microscopy observations indicated morphological changes in the bacterial cells incubated with silver nanoparticles. The genomic DNA isolated from the bacteria was incubated with an increasing concentration of AgNPs and the replication fidelity of 16S rDNA was observed by performing 18 and 35 cycles PCR. The replication efficiency of small (600 bp) and large (1500 bp) DNA fragments in the presence of AgNPs were compromised in a dose-dependent manner. The results suggest that the Thalictrum foliolosum root extract mediated synthesis of AgNPs could be used as a promising antimicrobial agent against clinical pathogens.

Antibacterial activity and nanocomposite properties of monodispersed silver nanoparticles synthesized by the microwave method

Abstract Monodispersed colloidal silver nanoparticles (Ag-NPs) were synthesized by a simple and rapid microwave method. A precursor, AgNO3, was reduced by ethylene glycol (EG) and N,N-dimethylformamide (DMF) in the presence of polyvinylpyrrolidone (PVP) as a stabilizer or capping agent. It was found that the concentration of AgNO3 significantly affected Ag-NPs particle sizes. The particle sizes decreased when the concentration decreased from 0.1 to 0.05 and 0.01 M, which corresponded to narrow size distribution of the particle diameters of approximately 60 to 80, 30 to 40 and 10 to 20 nm. The spherical-shaped monodispersed Ag-NPs were obtained by using a volume ratio of EG to DMF of 2.75 : 2.25, microwave power of 400 W and heating time of 2 min. The volume ratio of EG to DMF and the microwave power influenced the uniformity of the Ag-NPs shape and size, while the heating time had no effect. For antibacterial application, 60–80 and 10–20 nm Ag-NPs showed good disinfection ability against Escherichia coli (ATCC 25922) at the minimum inhibitory concentrations (MIC) of 32 and 16 µg × ml−1, respectively. In addition, the electrical resistance of the nanocomposites of DMF-loaded Ag-NPs (20–50 nm) without PVP on single-walled carbon nanotubes and polyethylene terephthalate (PET) was measured. As a result, it is obvious that the Ag-NPs help to increase the electrical conductivity of the nanocomposites as the electrical resistance of the Ag-NPs nanocomposites was 4.68 kΩ × cm−2 compared to that of the nanocomposites without Ag-NPs of 8.76 kΩ × cm−2.

Microwave synthesis Ag/reduced graphene oxide composites and enhanced antibacterial performance

A series of water-soluble silver/reduced graphene oxide (Ag/rGO) composites were prepared with rGO as a carrier. The obtained composites were characterised by energy-dispersive X-ray spectrometer (EDS), TEM, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analyses (TGA). TEM images demonstrated that well monodispersed silver nanoparticles (Ag NPs) precipitate on the rGO sheets. X-ray photoelectron spectroscopy showed that graphene oxide (GO) had been reduced to rGO in our hybrid. The antibacterial properties of Ag/rGO composites were investigated by bacteriostatic curve, and the experiments showed that the antibacterial properties of Ag/rGO antimicrobial materials were enhanced, which exhibited a superior antibacterial activity towards Escherichia coli (E. coli) because of the synergistic effect of rGO and Ag NPs. These results indicated that Ag/rGO composites attached to hierarchal hybrid supports can lead to compact and powerful antibacterial devices for chemical-free disinfection devices of the future.

In-situ reduction of monodisperse nanosilver on hierarchical wrinkled mesoporous silica with radial pore channels and its antibacterial performance

Monodisperse silver nanoparticles (Ag NPs) were facilely loaded on the inner and outer surface of hierarchical wrinkled mesoporous silica (WMSs) via an in situ chemical reduction, and the antibacterial capacity of the obtained nanocomposite was investigated in detail. Typical sulfydryl-functionalized wrinkled mesoporous silica nanoparticle with radical pore channels was firstly prepared through sol-gel technique with cetyltrimethylammonium bromide (CTAB) as the templating surfactant. After sulfonation of the as-prepared WMSs, Ag+ ions were then densely locked up on the inner and outer surface of WMSs via electrostatic interactions. Well distributed Ag NPs (ca. 3–5nm) on WMSs without any agglomeration were finally obtained via a simple in situ reduction reaction with sodium borohydride. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) test indicated that the obtained products can achieve durable and much better antibacterial performance both against Gram-negative bacterium Escherichia coli (E. coli) and Gram-positive bacterium Staphylococcus aureus (S. aureus) comparing to pure colloidal silver nanoparticles, which rendered them as favorable candidate for the development of effective antibacterial agents.

Influence of antibiotic adsorption on biocidal activities of silver nanoparticles.

Excessive use of antibiotics has posed two major challenges in public healthcare. One of them is associated with the development of multi-drug resistance while the other one is linked to side effects. In the present investigation, the authors report an innovative approach to tackle the challenges of multi-drug resistance and acute toxicity of antibiotics by using antibiotics adsorbed metal nanoparticles. Monodisperse silver nanoparticles (SNPs) have been synthesised by two-step process. In the first step, SNPs were prepared by chemical reduction of AgNO3 with oleylamine and in the second step, oleylamine capped SNPs were phase-transferred into an aqueous medium by ligand exchange. Antibiotics - tetracycline and kanamycin were further adsorbed on the surface of SNPs. Antibacterial activities of SNPs and antibiotic adsorbed SNPs have been investigated on gram-positive (Staphylococcus aureus, Bacillus megaterium, Bacillus subtilis), and gram-negative (Proteus vulgaris, Shigella sonnei, Pseudomonas fluorescens) bacterial strains. Synergistic effect of SNPs on antibacterial activities of tetracycline and kanamycin has been observed. Biocidal activity of tetracycline is improved by 0-346% when adsorbed on SNPs; while for kanamycin, the improvement is 110-289%. This synergistic effect of SNPs on biocidal activities of antibiotics may be helpful in reducing their effective dosages.

Synthesis of transparent dispersion of monodispersed silver nanoparticles with excellent conductive performance using high-gravity technology

Transparent dispersion of silver nanoparticles (Ag-NPs) is important for transparent conductive coatings to fabricate the printed electronic devices such as flexible displays and solar cells. However, it is still great challenge to produce the transparent dispersion of Ag-NPs in large scale. In this work, we synthesize the transparent dispersion of monodispersed Ag-NPs with excellent conductive performance by a high-gravity strategy using rotating packed bed (RPB) reactor, which is easy to realize the large scale production. Based on the nano-dispersion, the transparent conductive films are further fabricated. The as-synthesized Ag-NPs are monodispersed in liquid medium with the average diameter about 7nm. Compared with stirred tank reactor (STR), the Ag-NPs in transparent dispersions prepared by RPB have a smaller average diameter, a narrower particle size distribution (PSD) and better stability. The transparent conductive films with continuous percolated network structure exhibit excellent transparency and conductive properties. The visible transmittance of the films with a sheet resistance of 98.1 Ω/□ and 12.7 Ω/□ can reach 91% and 85% respectively. It is expected that the high-gravity technology would provide a promising strategy for the large-scale preparation of transparent silver dispersion for fabricating transparent electric devices.

Silver Nanoparticles Exhibit the Dose-Dependent Anti-Proliferative Effect against Human Squamous Carcinoma Cells Attenuated in the Presence of Berberine.

The biological activity of nanosize silver particles towards oral epithelium-derived carcinoma seems to be still underinvestigated. We evaluated the influence of low doses of nanosize scale silver particles on the proliferation and viability of malignant oral epithelial keratinocytes in vitro, alone and in conjunction with the plant alkaloid berberine. Cells of human tongue squamous carcinoma SCC-25 (ATCC CRL-1628), cultivated with the mixture of Dulbecco's modified Eagle’s medium, were exposed to silver nanoparticles alone (AgNPs, concentrations from 0.31 to 10 μg/mL) and to a combination of AgNPs with berberine chloride (BER, 1/2 IC50 concentration) during 24 h and 48 h. The cytotoxic activity of AgNPs with diameters of 10 nm ± 4 nm was measured by 3-(4,5-dimethyl-2-thiazyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Cell cycle analysis was performed by treating cells with propidium iodide followed by flow-activated cell sorting. RT-QPCR reaction was used to assess expression of anti-apoptotic proteins Bcl-2 and pro-apoptotic protein Bcl-2-associated X protein Bax genes expression. Monodisperse silver nanoparticles at a concentration of 10 μg/mL arrested SCC-25 cells cycle after 48 h at the G0/G1 phase in a dose- and time-dependent manner through disruption G0/G1 checkpoint, with increase of Bax/Bcl-2 ratio gene expression. AgNPs exhibit cytotoxic effects on SCC-25 malignant oral epithelial keratinocytes, which is diminished when combined with BER. The AgNPs concentration required to inhibit the growth of carcinoma cells by 50% (IC50) after 48 h was estimated at 5.19 μg/mL. AgNPs combined with BER increased the expression of Bcl-2 while decreasing the ratio of Bax/Bcl-2 in SCC-25 cells. Silver particles at low doses therefore reduce the proliferation and viability of oral squamous cell carcinoma cells. SCC-25 cells are susceptible to damage from AgNPs-induced stress, which can be regulated by the natural alkaloid berberine, suggesting that nanoparticles may be potentially used in a chemoprevention/chemotherapy by augmentation of action of standard anti-cancer drugs.

Green synthesis and characterization of monodispersed silver nanoparticles obtained using oak fruit bark extract and their antibacterial activity

Green synthesis of silver nanoparticles (Ag NPs) has been achieved using oak fruit bark extract as a reducing, capping and stabilizing agent. The biosynthesized Ag NPs were characterized using various techniques. UV–visible spectrum of prepared silver colloidal solution showed absorption maximum at 433 nm. X‐ray diffraction and transmission electron microscopy analysis revealed that Ag NPs have a face‐centred cubic structure being spherical in shape with an average particle size of 20–25 nm. The toxicity of the Ag NPs was tested on bacterial species such as Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Escherichia coli by comparison based on diameter of inhibition zone in disc diffusion tests and minimum inhibitory concentration and minimum bactericidal concentration of NPs dispersed in liquid cultures. The antimicrobial activity of Ag NPs was greater towards Gram‐positive bacteria (S. aureus and B. subtilis) compared to Gram‐negative bacteria as determined using standard Kirby–Bauer disc diffusion assay and serial dilution. Copyright © 2016 John Wiley & Sons, Ltd.

Asperical silver nanoparticles by thermal decomposition of a single-source-precursor

The synthesis and characterization of silver(I) 2-phenyl-3,6,9-trioxadecanoate (3) is described. Thermal decomposition of 3 at 100–165°C in a long-chained amine resulted in the formation of monodisperse silver nanoparticles with sizes of about 7–10nm. By variation of the reaction conditions aspherical silver nanoparticles with hexagonal contours could be obtained, which is a novelity for silver nanoparticles prepared by thermal decompositon.

Light-scattering Characteristics of Metal Nanoparticles on a Single Bacterial Cell.

Metal nanoparticles express unique light-scattering characteristics based on the localized surface plasmon resonance, which depends on the metal species, particle size, and aggregation state of the nanoparticles. Therefore, we focused on the light-scattering characteristics of metal nanoparticles, such as silver, gold, and copper oxide, adsorbed on a bacterium. Monodisperse silver nanoparticles expressed the strongest scattered light among them, and showed various colors of scattered light. Although a monodisperse gold nanoparticle produced monochromatic light (green color), the color of the scattered light strongly depended on the aggregation state of the nanoparticles on a bacterium. On the other hand, copper oxide nanoparticles expressed monochromatic light (blue color), regardless of their aggregation states on a bacterium. We examined details concerning the light-scattering characteristics of metal nanoparticles, and discussed the possibility of their applications to bacterial cell imaging.

Sodium Alginate Mediated Route for the Synthesis of Monodisperse Silver Nanoparticles Using Glucose as Reducing Agents

A simple and environmentally friendly method was developed for preparing colloidal silver nanoparticles in aqueous solutions using silver nitrate, sodium alginate and glucose as silver precursor, capping agents and reducing agents, respectively. The formation of silver nanoparticles was observed by the change of color from colorless to yellow. The silver nanoparticles were characterized by transmission electron microscopy (TEM), UV-visible spectroscopy (UV-vis) and X-ray diffraction (XRD). The TEM images show that the particles are small, well dispersed and spherical in shape with a narrow distribution from 3 nm to 12 nm. The XRD demonstrates that the obtained metallic nanoparticles are single crystalline silver nanoparticles. The effects of the reaction time, the reaction temperature and the concentration of silver ion and reducing agent on the particle size were investigated by the UV-vis spectra. The present process is an excellent candidate for the preparation of silver nanoparticles because it is simple, free-pollutant, inexpensive and easy to perform. The method may be extended to other noble metals, such as Au, Pd and Pt, for medicinal, industrial and technological applications.

In-situ immobilization of silver nanoparticles on ZSM-5 type zeolite by catechol redox chemistry, a green catalyst for A3-coupling reaction

For the first time in literature, we used a mussel-inspired surface chemistry for the production of propargylamines by the immobilization of silver nanoparticles (AgNPs) on the surface of mesoporous ZSM-5 zeolite. The ZSM-5 zeolite has a large surface area with a porous structure and provides a sufficient reaction space for monodisperse silver nanoparticles, resulting in high catalytic activity for the production of propargylamines with a shorter reaction time. The catalyst was recovered easily and could be used for three cycles without any significant loss in catalytic activity. N2 adsorption/desorption, ICP-AES, XRD, XPS, FE-SEM, TEM and FT-IR experiments were carried out to characterize the heterogeneous catalysts of this study.

Green microfluidic synthesis of monodisperse silver nanoparticles via genetic algorithm optimization

A scalable and green procedure for the microfluidic flow synthesis of monodisperse silver nanoparticles is reported.

Impact electrochemistry on screen-printed electrodes for the detection of monodispersed silver nanoparticles of sizes 10-107 nm.

Impact electrochemistry provides a useful alternative technique for the detection of silver nanoparticles in solutions. The combined use of impact electrochemistry on screen-printed electrodes (SPEs) for the successful detection of silver nanoparticles provides an avenue for future on-site, point-of-care detection devices to be made for environmental, medicinal and biological uses. Here we discuss the use of screen-printed electrodes for the detection of well-defined monodispersed silver nanoparticles of sizes 10, 20, 40, 80, and 107 nm.

The interaction of fluorescent Pyronin Y molecules with monodisperse silver nanoparticles in chloroform

The interaction of fluorescent Pyronin Y (PyY) molecules with monodisperse silver nanoparticles (Ag NPs) in chloroform was studied by using UV–Vis, steady-state and time-resolved fluorescence spectroscopies. Monodisperse Ag NPs were synthesized by using a surfactant assisted organic solution phase protocol comprising the tandem thermal decomposition and reduction of silver (I) acetate in oleic acid and oleylamine at 180 °C. The average particle size of Ag NPs was determined to be ∼3 nm by transmission electron microcopy (TEM) and their X-ray diffraction (XRD) pattern revealed the face centered cubic crystal phase. Afterward, PyY and monodisperse Ag NPs were interacted in chloroform via sonication at various time periods. The obtained spectroscopic results revealed that the photophysical properties of PyY molecules were dramatically changed after their interaction with Ag NPs in chloroform. It was determined that the amount of Ag NPs and PyY has the major effects on the photophysical properties of the dye.

Green Synthesis and Antimicrobial Activity of Monodispersed Silver Nanoparticles Synthesized Using Lemon Extract

A simple, environmentally benign green synthesis of silver nanoparticles was achieved using lemon fruit extract (Citrus lemon). The synthesized silver nanoparticles were characterized using UV-Vis spectroscopy, infrared spectroscopy, powder X-ray diffraction, and transmission electron microscopy. The predominantly spherical monodispersed 2–10 nm sized silver nanoparticles were obtained for the first time using lemon extract. The antimicrobial activity of silver nanoparticles was also explored. Lemon extract–mediated synthesis is cost efficient, eco-friendly and an easy alternative to conventional methods of silver nanoparticles synthesis.

Green synthesis of silver nanoparticles: Another honor for the yeast model Saccharomyces cerevisiae

Background and Purpose:Microorganism-based synthesis of nanostructures has recently been noted as a green method for the sustainable development of nanotechnology. Nowadays, there have been numerous studies on the emerging resistant pathogenic bacteria and fungal isolates, the probable inability of bacteria and fungi to develop resistance against silver nanoparticles’ (SNPs) antibacterial, antifungal, antiviral and, particularly antibacterial activities. In this study, we aim to use the yeast Saccharomyces cerevisiae model for synthesis of SNPs and to investigate its antifungal activity against some isolates of Candida albicans.Materials and Methods:A standard strain of S. cerevisiae was grown in liquid medium containing mineral salt; then, it was exposed to 2 mM AgNO3. The reduction of Ag+ ions to metal nanoparticles was virtually investigated by tracing the color of the solution, which turned into reddish-brown after 72 hours. Further characterization of synthesized SNPs was performed afterwards. In addition, antifungal activity of synthesized SNPs was evaluated against fluconazole-susceptible and fluconazole-resistant isolates of Candida albicans. Results:The UV-vis spectra demonstrated a broad peak centering at 410 nm, which is associated with the particle sizes much less than 70 nm. The results of TEM demonstrated fairly uniform, spherical and small in size particles with almost 83.6% ranging between 5 and 20 nm. The zeta potential of SNPs was negative and equal to -25.0 (minus 25) mv suggesting that there was not much aggregation. Silver nanoparticles synthesized by S. cerevisiae, showed antifungal activity against fluconazole-susceptible and fluconazole-resistant Candida albicans isolates, and exhibited MIC90 values of 2 and 4 μg/ml, respectively.Conclusion:The yeast S. cerevisiae model demonstrated the potential for extracellular synthesis of fairly monodisperse silver nanoparticles.