Tuned optical properties of in-situ synthesized m-nitroaniline doped Ag/PVA nano-composites

Meta-nitroaniline (m-NA) doped silver/poly(vinylalcohol) (Ag/PVA) nanocomposites are prepared via in-situ reduction of silver salt by employing hydrazine hydrate (HH) in order to study the effect of the NLO active m-NA on the optical properties of nanoparticles of silver in the colloidal as well as self supported film form. Reduction of silver salt in aqueous alcoholic PVA with HH is done first followed by doping of the reaction mixture with m-NA. The UV-Visible absorption spectra show peak at about 400 nm for Ag nanoparticles due to surface plasmon resonance phenomenon, which gets blue shifted with the change in m-NA concentration. The Second Harmonic Generation (SHG) studies show improvement in intensity with increasing m-NA concentration up to a saturation point (approximately 2.52 wt% with respect to PVA). Further increase in m-NA concentration leads to decrease in SHG intensity. The solutions and the films are characterized by photoluminescence (PL), FTIR spectroscopy, XRD, SEM, TEM, and thermal analysis. m-NA doped composites showed better PL efficiency. SEM of the nanocomposite film shows uniform distribution of particles within the film. The particle size as shown by TEM is found to be less than 10 nm.     

Photocatalytic degradation of methyl red dye by silica nanoparticles

Silica nanoparticles (SiO2 NPs) were found to be photocatalytically active for degradation of methyl red dye (MR). The SiO2 NPs and SiO2 NPs doped with silver (and or) gold nanoparticles were prepared. From the transmission electron microscopy (TEM) images the particle size and particle morphology of catalysts were monitored. Moreover, SiO2 NPs doped with silver and gold ions were used as a photocatalyst for degradation of MR. The rate of photocatalytic degradation of MR was found to be increased in the order of SiO2 NPs, SiO2 NPs coated with gold nanoparticles (Au NPs) and silver nanoparticles (Ag NPs), SiO2 NPs coated with Ag NPs, SiO2 NPs coated with Au NPs, Ag+-doped SiO2 NPs, and Au3+-doped SiO2 NPs. The kinetic and mechanism of photocatalytic reaction were studied and accorded well with experimental results.     

Fabrication of Ag nanoparticles dispersed in PVA nanowire mats by microwave irradiation and electro-spinning

In this study, the antimicrobial substance, silver nanoparticles (Ag NPs) loaded in poly (vinyl alcohol) (PVA) nanowire mats were fabricated by conjugation of the electro-spinning method and the microwave-assisted process. The best PVA nanowire mats were fabricated by through control of electro-spinning conditions, which were applied for fabrication of Ag NPs loaded in PVA nanowires. PVA was used not only as a carrier for loading of Ag NPs but also as a reduction agent with which the Ag⁺ ion was already reduced to a large number of Ag NPs by irradiation with a microwave. Ag NPs were synthesized inside the PVA solution depending on the time of microwave irradiation — whether for 60 s or 90 s. Size distribution of Ag NPs was 5–10 nm in diameter for 60 s; and 10–20 nm in diameter for 90 s of irradiation. Presence of Ag NPs acquired through microwave assisted irradiation was confirmed by X-ray diffraction profiles (XRD). Microstructure, particle size distribution, and morphology of both the nanowire mats and the Ag particles were investigated using SEM and TEM techniques. The effect of Ag-NPs on the PVA mechanical property of nano-fibrous mats was investigated according to tensile strength. Antibacterial activity of PVA loaded Ag NPs at different irradiation times was tested on Gram-positive bacteria, Staphylococcus aureus Gram-negative bacteria, and Escherichia coli.     

Synthesis and optical absorption property of ordered macroporous titania film doped with Ag nanoparticles

Ordered macroporous anatase titania films doped with Ag nanoparticles (NPs) were synthesized by infiltrating titania sol into the interstitial voids of polystyrene colloidal sphere templates, removing the templates, immersing the films in a silver nitrate solution, and subsequently reducing in hydrogen atmosphere. Ag NPs were distributed uniformly within the macropores of the anatase titania film. Both the macroporous titania films doped with Ag NPs and those without doping have a blue-shift compared with that of the sol–gel derived titania film. Except for the plasma resonance absorption of Ag NPs, the macroporous titania film doped with Ag NPs also has a red-shift compared with the undoped sample. The macroporous titania film doped with Ag NPs have potential applications in the fields of optics, gas sensors, and catalysis.     

Absence of exchange interaction between localized magnetic moments and conduction-electrons in magnetic ions diluted in Ag-nanoparticles

The Electron Spin Resonance (ESR) of diluted magnetic ions (MI) of Er3+, Yb3+ and Mn2+ in Ag nanoparticles (NPs) is reported. Monodisperse samples of Ag NPs doped with these MI were synthesized by reducing silver nitrate and MI-oxides. This simple method can be extended to all rare-earths. The measurements of the g-values and hyperfine splittings indicates that the MI are located at cubic sites in the Ag:MI NPs. The ESR spectra show that there is no g-shift and Korringa-relaxation due to the exchange interaction between the MI and the conduction electrons, suggesting that the exchange interaction is absent in the Ag:MI NPs. Thus, the nature of this interaction needs to be reexamined at the nanoscale range.     

Synthesis,structural and optical properties of Ag doped ZnO nanoparticles with enhanced photocatalytic properties by photo degradation of organic dyes

In present paper chemical route based synthesis of Ag doped ZnO nanoparticles (NPs) by co-precipitation method is reported to develop ZnO NPs for photo catalytic application. XRD confirms the structural purity of ZnO NPs. FESEM and TEM study reveals the surface and ultra structure morphology of NPs. EDAX study confirms the purity and homogeneity of NPs. The Ag/ZnO NPs with different weight percentage of Ag relative to ZnO were applied under visible light irradiation for evaluating heterogeneous photo catalytic degradation of methylene blue (MB) and Brilliant blue (BB) respectively. The presence of Ag in ZnO enhance MB and BB dye degradation effectiveness from 96.78 to 98.66 and 82.15 to 97.36% for pure ZnO and maximum Ag doped ZnO (x?=?0.1) respectively. In comparison of MB and BB final degradation ability, MB dyes have more effective photo catalytic efficiency towards different oxidizing species to degradation process.     

Electrospun polyvinyl alcohol/chitosan composite nanofibers involving Au nanoparticles and their in vitro release properties

Au nanoparticles (Au NPs) containing polyvinyl alcohol (PVA)/chitosan (CS) composite nanofibers were successfully prepared by a simple and effective method called electrospinning. Au NPs were firstly synthesized under a mild condition with CS as the reducing agent and stabilizer, followed by being mixed with PVA solution and then the resulting fibers were fabricated. The research indicated that Au NPs were indeed doped into the as-prepared fibers and the composite fibers well preserved Au NPs' unique optical characteristics. Additionally, with the adjustment of the weight ratios between PVA and CS, the diameter distribution and the morphology of the nanofibers were largely changed. In vitro drug release experiments demonstrated that the drug release rate can be conveniently controlled by changing the crosslink time.     

Reflectivity spectra and colors of porous anodic aluminum oxide containing silver nanoparticles by plasmonic absorption

The reflectivity spectra and color of porous anodic aluminum oxide (AAO) nanostructures containing the assembly of silver (Ag) nanoparticles (NPs) with a diameter of -10 nm were investigated. The Ag NPs were assembled inside the pores of AAO with a diameter of -60 nm by dip-coating process during which Ag NPs adsorbed on the surface of AAO and driven inside the pores by capillary force upon the evaporation of solvent. The reflectivity spectra and associated colors of AAO with Ag NPs were determined by the plasmonic absorption of light by Ag NPs. Even with the monolayer coverage of Ag NPs in the pores of AAO, the reflectivity is significantly reduced specifically at -465 nm wavelength by a strong plasmonic absorption, resulting in its golden color. Aggregating Ag NPs by post-annealing at 300 and 400 degrees C changed the color to pink due to the red-shift of absorption. These results are indicative of potential color-engineering of NPs/AAO platform by wavelength-selective reduction of reflected light intensity and using it in direct optical read-out of change of surface and morphology conditions.     

Localized surface plasmon resonance of single silver nanoparticles studied by dark-field optical microscopy and spectroscopy

Localized surface plasmon resonance (LSPR) of Ag nanoparticles (NPs) with different shapes and disk-shaped Ag NP pairs with varying interparticle distance is studied using dark-field optical microscopy and spectroscopy (DFOMS). Disk-, square-, and triangular-shaped Ag NPs were fabricated on indium tin oxide-coated glass substrates by electron beam lithography. The LSPR spectra collected from single Ag NPs within 5×5 arrays using DFOMS exhibited pronounced redshifts as the NP shape changed from disk to square and to triangular. The shape-dependent experimental LSPR spectra are in good agreement with simulations using the discrete dipole approximation model, although there are small deviations in the peak wavelengths for square- and triangular-shaped NPs. The LSPR spectra of disk-shaped Ag NP pairs with varying interparticle distances were acquired from five different locations across the pair axis. It was clearly observed that the LSPR wavelength redshifts as the interparticle distance decreases, indicating a strong interaction when two Ag NPs are close to each other.     

A Novel one-step synthesis of Ag-doped ZnO nanoparticles for high performance photo-catalytic applications

In this report, pure and silver (Ag) doped zinc oxide (ZnO) nanoparticles with various concentrations of silver (5 and 10 wt%) was successfully synthesized by a novel and one step microwave irradiation method. Powder X-ray diffraction results indicates that all of the as-synthesized samples including the highest Ag (10 wt%) doping have a hexagonal wurtzite type structure and average crystalline size was found to be 28, 21 and 16 nm for pure and Ag doped ZnO respectively. Spherical shaped morphology with an average diameter of around 32–13 nm was observed by Transmission electron microscope analysis. UV–Vis spectra revealed that, Ag doped samples exhibits a red shift in the absorption band edge with increasing Ag dopant concentration. The photocatalytic degradation of methyl violet (MV), phenol and rhodamine B (RHB) was investigated by using Ag-ZnO catalyst under UV light irradiation. The result showed that the photocatalytic property was significantly improved by Ag doping. The improved photocatalytic mechanism by Ag doping was also discussed. The samples were further characterized by photoluminescence spectra and Fourier Transform Infrared Spectra (FTIR) analysis.     

Structural and optical properties of Ag doped tungsten oxide (WO<Subscript>3</Subscript>) by microwave-assisted chemical route

The present study explores, the pure and silver (Ag) doped WO₃ nanoparticles synthesized by microwave irradiation method. Powder X-ray diffraction results reveal that the WO₃ doped with Ag concentration from 0 to 10 wt% crystallizes in monoclinic structure. TEM analysis shows both pristine and silver doped WO₃ nanoparticles. They are having spherical morphology with a average size from 30 to 40 nm. Scanning electron microscopy studies depicts that both the pristine and Ag doped WO₃ form in spherical shaped morphology with an average diameter of 40–30 nm, which is in proper agreement with the average crystallite sizes calculated by Scherrer’s formula. A considerable red shift in the absorbing band edge and a decrease in the band gap energy from 3.00 to 2.85 eV for Ag doped samples were observed by using UV–DRS spectra analysis. The defects in crystal and oxygen deficiencies were analyzed by photoluminescence spectra analysis.     

Interaction of silver nanoparticles with an environmentally beneficial bacterium, Pseudomonas chlororaphis

This study explores the potential antimicrobial mechanisms of commercial silver nanoparticles (Ag NPs) in the environmental bacterium, Pseudomonas chlororaphis O6. The 10nm size NPs aggregated in water, as demonstrated by atomic force microscopy. Solubility of the NPs at 10mg/L was 0.28 mg/L (pH 6) and 2.3mg/L (pH 7); release from 10mg/L bulk Ag was below detection. The NPs eliminated cell culturability at 3mg/L, whereas no effect was observed at 10mg/L bulk Ag. Zeta potential measurements revealed that the NPs were negatively charged; unlike Ag ions, their addition to the negatively charged cells did not change cell charge at pH 6, but showed a trend to reduce cell charge at pH 7. Isolated extracellular polymeric substances (EPS) from PcO6 was polydisperse, with negative charge that was neutralized by Ag ions, but not by the NPs. Addition of EPS eliminated Ag NP's toxicity in cells lacking EPS. Intracellular accumulation of OH was not detected in NP-treated cells; however, the use of scavengers suggested the NPs caused extracellular H(2)O(2) production. No evidence was found for loss of membrane integrity upon treatment with the NPs. Our findings indicate that growth of environmental bacteria could be impaired by Ag NPs, depending on the extent of EPS production.     

Structural phase analysis,band gap tuning and fluorescence properties of Co doped TiO2 nanoparticles

This paper reports on structural and optical properties of Co (0, 3, 5 & 7 mol%) doped TiO₂ (titania) nanoparticles (NPs) synthesized by employing acid modified sol–gel method. The crystalline phase of the pure and doped NPs was observed with X-ray diffraction (XRD) followed by Raman scattering technique. Field emission scanning electron microscope and transmission electron microscopy give the morphological details. Fourier transform infrared spectra indicate the bonding interactions of Co ions with the titania lattice framework. Optical studies were attained with UV–visible absorption and fluorescence emission spectroscopy. XRD analysis reveals that all prepared samples have pure anatase phase with tetragonal symmetry devoid of any other secondary phase. The average crystallite size of all samples was calculated using Scherrer’s formula and was found to vary from 8 to 10 nm with doping concentration of Co. The Raman spectroscopy further confirmed the formation of TiO₂ in anatase structure in both pure and Co doped TiO₂ NPs. The most intense Raman active E_g peak of TiO₂ NPs shifted to higher energy on doping. Both UV–visible and fluorescence spectra show a blue shift in their absorption and band edge emission subsequently on increasing with Co percentage in titania host matrix, wherever there is an indication of quantum confinement effect with widening of band gap on decreasing in NPs size. There is also a possibility of strong Coulomb interaction effect on the optical processes involving the Co ions. However, the intensities of different emission spectra are not the same but decrease profoundly for doping samples due to concentration quenching effect.     

铈掺杂氧化铜纳米颗粒的制备及其抗菌性能研究

采用水热法制备了铈离子掺杂的氧化铜纳米颗粒(Ce-CuO NPs)。FESEM图像显示掺杂氧化铜为球形和近球形颗粒;XRD图谱表明,当掺杂量低于10%时,图谱中只出现了单斜结构的CuO衍射峰,当掺杂量增加至15%时,形成了CeO2独立相;ICP分析表明,铈元素的掺杂对CuO NPs中铜离子的释放具有促进作用。铈掺杂氧化铜纳米颗粒的抗菌测试结果显示,其对革兰氏阳性菌金黄色葡萄球菌(S.aureus)的抗菌能力,较革兰氏阴性菌大肠杆菌(E.coli)更为显著;其中,5% Ce-CuO NPs在0.05 mg/mL的低浓度下表现出最佳的抗菌效果。Cu^2+与细菌细胞表面的结合在抑制细菌生长的过程中起到重要作用。     

Zephyranthes candida flower extract mediated green synthesis of silver nanoparticles for biological applications

The development of biologically active nanoparticles (NPs) has played a prominent role in medicinal, pharmaceuticals and bio-nanotechnology fields. Phytosynthesis is a simple, reproducible, and effective method to produce highly stable metal nanoparticles. In this present work, silver (Ag) nano particles (NPs) were produced using Zephyranthes candida (Z. candida) flower extract as a sustainable, cost-effective, and non-hazardous stabilizing agent. In the view of X-ray diffraction (XRD) analysis, the face centred cubic structure of Ag NPs was revealed. From the UV–Vis spectral analysis, the formations of Ag NPs were further confirmed through surface plasmon resonance (SPR) at the highest absorbance (λ_max) of 418 nm. FT-IR represents the spectra that reveal the presence of diverse functional groups along with their vibrational modes present in Ag NPs and Z.candida flower extract. SEM and TEM denote the formation of spherical morphology of Ag NPs. Furthermore, EDX and XPS spectra confirmed the purity of the prepared Ag NPs. Finally, the biological studies such as anti-inflammatory, anti-diabetic, anti-oxidant, anticancer confirm the bioactivity of the synthesized Zephyranthes Candida mediated Ag NPs.     

Type I collagen-templated assembly of silver nanoparticles and their application in surface-enhanced Raman scattering

Silver nanoparticles (Ag NPs) are one of the active substrates that are employed extensively in surface-enhanced Raman scattering (SERS), and aggregations of Ag NPs play an important role in enhancing the Raman signals. In this paper, we fabricated two kinds of SERS-active substrates utilizing the electrostatic adsorption and superior assembly properties of type I collagen. These were collagen-Ag NP aggregation films and nanoporous Ag films. Two probe molecules, 4-aminothiophenol (4-ATP) and methylene blue (MB), were studied on these substrates. These substrates showed reproducible SERS intensities with relative standard deviations (RSDs) of 8-10% and 11-14%, respectively, while the RSDs of the traditional thick Ag films were 12-28%. Also, the intensities for the 4-ATP spectrum on the collagen-templated nanoporous Ag film were approximately one order higher than those on the DNA-templated Ag?film.     

Photocatalytic and antibacterial properties of a TiO2/nylon-6 electrospun nanocomposite mat containing silver nanoparticles

Silver-impregnated TiO(2)/nylon-6 nanocomposite mats exhibit excellent characteristics as a filter media with good photocatalytic and antibacterial properties and durability for repeated use. Silver nanoparticles (NPs) were successfully embedded in electrospun TiO(2)/nylon-6 composite nanofibers through the photocatalytic reduction of silver nitrate solution under UV-light irradiation. TiO(2) NPs present in nylon-6 solution were able to cause the formation of a high aspect ratio spider-wave-like structure during electrospinning and facilitated the UV photoreduction of AgNO(3) to Ag. TEM images, UV-visible and XRD spectra confirmed that monodisperse Ag NPs (approximately 4 nm in size) were deposited selectively upon the TiO(2) NPs of the prepared nanocomposite mat. The antibacterial property of a TiO(2)/nylon-6 composite mat loaded with Ag NPs was tested against Escherichia coli, and the photoactive property was tested against methylene blue. All of the results showed that TiO(2)/nylon-6 nanocomposite mats loaded with Ag NPs are more effective than composite mats without Ag NPs. The prepared material has potential as an economically friendly photocatalyst and water filter media because it allows the NPs to be reused.     

Influence of organic polymers as capping agent on structural and optical properties of ZnS:Mn2+ and CdS nanocrystals

We have synthesized the luminescent ZnS:Mn2+ and bare CdS nanocrystals by employing polyvinyl alcohol (PVA), citric acid (CA) and biotin as organic capping agents by chemical co-precipitation route. The synthesized materials were characterized by X-ray diffraction, small angle X-ray scattering and transmission electron microscopy for the structural analysis, while UV-Visible spectroscopy and photoluminescence (PL) for optical properties. The results show that all the three organic polymers have the same effect and are capable of controlling the growth of the nanoclusters. From UV-Visible absorption spectra, it was observed that different capping agents do not affect the band gap of ZnS:Mn2+ system as well, while capping effect clearly observed on PL properties of ZnS:Mn2+ system. We have observed a novel result that capping with biotin show excellent photoluminescence as compared to capping of PVA and CA on ZnS:Mn2+ -systems. On the other hand, the annealing of these systems leads to degradation of luminescence intensity.     

Studies on antimicrobial and wound healing applications of gauze coated with CHX–Ag hybrid NPs

In this study, chlorhexidine (CHX)–silver (Ag) hybrid nanoparticles (NPs) coated gauze was developed, and their bactericidal effect and in vivo wound healing capacities were tested. A new method was developed to synthesise the NPs, wherein Ag nitrate mixed with sodium (Na) metaphosphate and reduced using Na borohydride. Finally, CHX digluconate was added to form the hybrid NPs. To study the antibacterial efficacy of particles, the minimal inhibition concentration and biofilm degradation capacity against Gram‐positive and Gram‐negative bacteria was studied using Escherichia coli and Staphylococcus aureus. The results indicated that the NP inhibited biofilm formation and was bactericidal as well. The gauze was doped with NPs, and its wound healing property was evaluated using mice model. Results indicated that the wound healing process was fastened by using the NPs gauze doped with NPs without the administration of antibiotics.Inspec keywords: nanomedicine, nanoparticles, wounds, silver, cellular biophysics, biomedical materials, nanofabrication, microorganisms, antibacterial activityOther keywords: NPs gauze, antimicrobial wound healing applications, hybrid NPs, chlorhexidine–silver hybrid nanoparticles, CHX, coated gauze, bactericidal effect, minimal inhibition concentration, biofilm degradation capacity, Gram‐negative bacteria, wound healing property, wound healing process, in vivo wound healing capacities, Staphylococcus aureus, Escherichia coli, antibiotics administration, Na borohydride, Ag nitrate mixing, sodium metaphosphate, CHX digluconate, NP inhibited biofilm formation, Ag     

Thermoelectric characteristics of nanocomposites made of HgSe and Ag nanoparticles for flexible thermoelectric devices

We synthesized thermoelectric nanocomposites by mixing HgSe nanoparticles (NPs) and Ag NPs in a solution and investigated the thermoelectric properties of the nanocomposite thin films on flexible plastic substrates.The X-ray diffraction patterns and the X-ray photoelectron spectra of the nanocomposites demonstrate that cation-exchange reactions occurred spontaneously in the mixed solution of HgSe and Ag NPs and that the HgSe NPs were completely converted to Ag2Se when the Ag NP content was 20 vol.％.The maximum power factor and the thermoelectric figure of merit were obtained as 75 FμW/mK2 and 0.043 at 300 K,respectively,when the Ag NP content was 10 vol.％,which is 100 times higher than that of HgSe NP thin films.In addition,the mechanical stability of the thermoelectric nanocomposite film was confirmed through repeated bending tests.