Showed Surface Plasmon Resonance Research Articles

Green synthesis of silver nanoparticles using leaves extract of Skimmia laureola: Characterization and antibacterial activity

In the present study, silver nanoparticles (AgNPs) were synthesized by using aqueous leaves extract of Skimmia laureola at room temperature. The color change in reaction mixture (pale yellow to dark brown) was observed during synthesis process. Biosynthesized silver nanoparticles showed surface Plasmon resonance at around 460nm. The spherical and hexagonal shapes and crystalline nature of silver nanoparticles were confirmed by SEM and XRD analysis. The bioactive chemicals constituent of leaf extract of S. laureola such as tritepenoids, skimmidiol and coumarins, were mainly involved in the synthesis of silver nanoparticles. Furthermore, antibacterial potential of aqueous extract of S. laureola leaf and biosynthesized silver nanoparticles found to be potent agent against tested human pathogens and it is suitable nanomaterial for biomedical application.

Fabrication and Photocatalytic Properties of TiO2/Reduced Graphene Oxide/Ag Nanocomposites with UV/Vis Response

AbstractNovel one‐dimensional TiO2 nanofibers/reduced graphene oxide/Ag nanoparticles (TiO2/rGO/Ag) nanocomposite photocatalysts with UV/Vis response properties were fabricated by wrapping rGO sheets around TiO2 nanofibers and then loading Ag nanoparticles onto the surfaces of TiO2/rGO. The prepared samples were characterized by scanning electron microscopy, high‐resolution transmission electron microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, Raman spectroscopy, and UV/Vis diffuse reflectance spectroscopy. The photocatalytic activities of the samples were evaluated by photocatalytic degradation of an aqueous solution of rhodamine B (RhB) under UV/Vis light irradiation. The results showed that the introduction of rGO and Ag greatly improved the photocatalytic activity of the TiO2 nanofibers, and this enhancement was attributed to the hybridization of rGO possessing specific electronic effects and Ag nanoparticles showing surface plasmon resonance effects. As a consequence, extension of the absorption spectrum to the visible region and efficient restriction of the recombination of photogenerated carriers were achieved.

Green synthesis of gold nanoparticles using Pogestemon benghalensis (B) O. Ktz. leaf extract and studies of their photocatalytic activity in degradation of methylene blue

Biosynthesis of gold nanoparticles has been accomplished via reduction of aqueous chloroauric acid solution with the leaf extract of Pogestemon benghalensis (B) O. Ktz., as both reductant and stabilizer. The synthesized nanoparticles were characterized by UV–visible, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) studies. The UV–visible spectrum of the synthesized gold nanoparticles showed surface plasmon resonance (SPR) around 555nm after 12h. The powder XRD pattern furnished evidence for the formation of face-centered cubic structure of gold having average crystallite size 13.07nm. The shapes of synthesized gold nanoparticles are mostly spherical and triangular with sizes 10–50nm. The photocatalytic degradation of methylene blue dye was monitored spectrophotometrically using gold nanoparticles as catalyst under visible light illumination.

Biosynthesis, Characterization, and Antifungal Activity of the Silver Nanoparticles Against Pathogenic Candida species

Alcoholic extract of tulsi leaves was used as a reducing and stabilizing agent for the synthesis of silver nanoparticles (AgNPs). The use of plant extract for the synthesis of nanoparticles is cost-effective, single step, and an ecofriendly process. The biosynthesized AgNPs were characterized using UV-Vis, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) analysis. The AgNPs formed show surface plasmon resonance at 430 nm. They have a smooth surface with an average diameter of 2–7 nm. Their crystalline nature was confirmed by the XRD. The antifungal activity of the AgNPs was evaluated for opportunistic human fungal pathogens Candida albicans, Candida glabrata, and Candida tropicalis. The antifungal effect was determined by minimum inhibitory concentration (MIC), minimum fungicidal concentration (MFC), and disk diffusion assay. Further, to assess the pathogenicity, proteinase and phospholipase assays were performed. TEM analysis of treated Candida cells reveals that the AgNPs may be exerting antifungal activity by disrupting the cell membrane structure and integrity. Cytotoxicity of AgNPs was checked by performing hemolytic assay against human erythrocytes. At MIC values, AgNPs caused only 5.6 % lysis in RBCs which was very low in comparison to conventional antifungal agents. Hence, biosynthesized AgNPs using plant extracts have immense antifungal potential and can be used in the management of fungal infections. Further studies have to be done to understand their mode of action.

Particle placement and sheet topological control in the fabrication of Ag-hexaniobate nanocomposites.

Synthetic methods are demonstrated that allow for the fabrication of Ag-hexaniobate nanocomposites with directed nanoparticle (NP) placement and nanosheet morphological control. The solvothermal treatment of exfoliated nanosheets (NSs) in the presence of Ag NPs leads to a high yield of Ag nanocomposites. This approach is quite flexible and, with control of time and temperature, can be used to produce nanocomposites with specific architectures; Ag NPs can be attached to nanosheets, attached to the surfaces of nanoscrolls, or at higher temperatures, captured within nanoscrolls to form nanopeapod (NPP) structures. The decorated nanosheets and nanoscrolls show surface plasmon resonance (SPR) maxima similar to that of free Ag NPs, while the Ag NPPs exhibit a red shift of about 10 nm.

Plasmonic Switching in Au-Functionalized GaN Nanowires in the Realm of Surface Plasmon Polariton Propagation: a Single Nanowire Switching Device

Photoresponse of Au nanoparticle functionalized semiconducting GaN (Au-GaN) nanowires is reported for an optical switching using 532 excitation. Wide band gap GaN nanowires are grown by catalyst-assisted chemical vapor deposition technique and functionalized with Au in the chemical route. Au-GaN nanowires show surface plasmon resonance (SPR) mode of Au nanoclusters around 550 nm along with characteristic band for GaN around 365 nm. An optical switching is observed for Au-GaN nanowires with a sub-band gap excitation of 532 nm suggesting possible role of surface plasmon polariton-assisted transport of electron in the system. The role of band conduction is ruled out in the absence of optical switching using 325-nm excitation which is higher in energy that the reported band gap of GaN ∼3.4 eV (365 nm) at room temperature. A finite amount of interband contribution of Au plays an important role along with the interparticle separation. The switching device is also successfully tested for a single GaN nanowire functionalized with Au nanoclusters. A resistivity value of 0.05 Ω-cm is measured for surface plasmon polariton-assisted electrical transport of carrier in the single GaN nanowire.

Synthesis of silver nanoparticles using medicinal Zizyphus xylopyrus bark extract

In the present paper, biosynthesis of silver nanoparticles using Zizyphus xylopyrus bark extract is reported. Z. xylopyrus bark extract is efficiently used for the biosynthesis of silver nanoparticles. UV-Visible spec- troscopy showed surface plasmon resonance peaks in the range 413-420 nm confirming the formation of silver nanoparticles. Different factors affecting the synthesis of silver nanoparticles like methodology for the preparation of extract, concentration of silver nitrate solution used for biosynthesis and initial pH of the reaction mixture were studied. The extract prepared with 10 mM AgNO3 solution by reflux extraction method at optimum initial pH of 11, resulted in higher conversion of silver ions to silver nanoparticles as compared with those prepared by open heating or ultrasonication. SEM analysis showed that the biosynthesized nanoparticles are spherical in nature and ranged from 60 to 70 nm in size. EDX suggested that the silver nanoparticles must be capped by the organic com- ponents present in the plant extract. This simple process for the biosynthesis of silver nanoparticles using aqueous extract of Z. xylopyrus is a green technology without the usage of hazardous and toxic solvents and chemicals and hence is environment friendly. The process has several advantages with reference to cost, compatibility for its application in medical and drug delivery, as well as for large-scale commercial production.

Phytolatex synthesized gold nanoparticles as novel agent to enhance sun protection factor of commercial sunscreens.

To study the potential of phytolatex (latex of Jatropha gossypifolia) fabricated gold nanoparticles as promising candidate in sunscreen formulations for enhancement in sun protection factor. In this study, plant latex was used as reducing and capping agent to synthesize gold nanoparticles. Latex fabricated gold nanoparticles were characterized by different analytical techniques such as UV-Vis spectroscopy, Fourier transforms infrared spectroscopy, dynamic light scattering, zeta potential, transmission electron microscopy and X-ray diffraction. Potential of sunscreen preparations containing gold nanoparticles to protect skin from UV radiation was investigated by in vitro sun protection factor analysis. Transmission electron microscopy and UV-Vis spectroscopy techniques were used to get insight into mechanism by which AuNPs enhance sun protection factor of sunscreen. Monodisperse gold nanoparticles were synthesized using plant latex without need of hazardous chemical reducing and capping agents. Gold nanoparticles showed surface plasmon resonance peak at 550nm in UV-Vis spectroscopic study. Gold nanoparticles were spherical and triangular in shape with size range of 30-50nm. The zeta potential of gold nanoparticles was found to be -9.39±0.19 mV. XRD analysis confirmed face-centred cubic (fcc) structure of gold nanoparticles. Incorporation of latex synthesized gold nanoparticles (2 and 4 [% w/w]) into commercial sunscreens increased the sun protection factor from 2.43±0.74 to 24.11±0.46% than sunscreen devoid of gold nanoparticles. From UV-Vis absorption spectroscopy and TEM analysis, it was observed that gold nanoparticles enhance the sun protection factor of commercial sunscreens due to reflection and scattering of UV radiation. Phytolatex synthesized gold nanoparticle is novel agent to enhance sun protection factor of commercial sunscreens. Gold nanoparticles aggregation in commercial sunscreen was the main factor behind SPF enhancement. This study showed that gold nanoparticles are potent alternative to traditionally used hazardous titanium dioxide and zinc oxide nanoparticles in sunscreen.

Antibacterial activity of silver nanoparticle-coated fabric and leather against odor and skin infection causing bacteria.

We present a simple, eco-friendly synthesis of silver and gold nanoparticles using a natural polymer pine gum solution as the reducing and capping agent. The pine gum solution was combined with silver nitrate (AgNO3) or a chloroauric acid (HAuCl4) solution to produce silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs), respectively. The reaction process was simple; formation of the nanoparticles was achieved by autoclaving the silver and gold ions with the pine gum. UV-Vis spectra showed surface plasmon resonance (SPR) for silver and gold nanoparticles at 432 and 539 nm, respectively. The elemental forms of AgNPs and AuNPs were confirmed by energy-dispersive X-ray spectroscopy (EDX). Fourier transform infrared spectroscopy (FTIR) showed the biomolecules present in the pine gum, AgNPs, and AuNPs. Transmission electron microscopy (TEM) images showed the shape and size of AgNPs and AuNPs. The crystalline nature of synthesized AgNPs and AuNPs was confirmed by X-ray crystallography [X-ray diffraction (XRD)]. Application of synthesized AgNPs onto cotton fabrics and leather, in order to evaluate their antibacterial properties against odor- or skin infection-causing bacteria, is also discussed. Among the four tested bacteria, AgNP-coated cotton fabric and leather samples displayed excellent antibacterial activity against Brevibacterium linens.

Preparation of Ag nanoparticles loaded TiO2 nanoplate arrays on activated carbon fibers with enhanced photocatalytic activity

Ag loaded TiO2 nanoplate array which grew on activated carbon fiber (ACF) was prepared in the present work. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–Vis diffuse reflectance spectra (DRS). The photocatalytic degradation of methylene blue (MB) was used to investigate the activity of the synthesized samples. Under both UV and visible light irradiation, the Ag loaded samples showed enhanced photocatalytic activity. Besides, the effect of the deposition dosage of Ag nanoparticles on the photocatalytic activity was also investigated. Under UV light irradiation, the Ag nanoparticles acted as electron traps, which enhanced electron–hole separation efficiency of TiO2. Under visible light irradiation, the Ag nanoparticles showed surface plasmon resonance, which induced the visible light responsive photocatalytic activity for the obtained samples.

Biosynthesis of silver nanoparticles using Bacillus subtilis EWP-46 cell-free extract and evaluation of its antibacterial activity

This study highlights the ability of nitrate-reducing Bacillus subtilis EWP-46 cell-free extract used for preparation of silver nanoparticles (AgNPs) by reduction of silver ions into nano silver. The production of AgNPs was optimized with several parameters such as hydrogen ion concentration, temperature, silver ion (Ag(+) ion) and time. The maximum AgNPs production was achieved at pH 10.0, temperature 60 °C, 1.0 mM Ag(+) ion and 720 min. The UV-Vis spectrum showed surface plasmon resonance peak at 420 nm, energy-dispersive X-ray spectroscopy (SEM-EDX) spectra showed the presence of element silver in pure form. Atomic force microscopy (AFM) and transmission electron microscopy images illustrated the nanoparticle size, shape, and average particle size ranging from 10 to 20 nm. Fourier transform infrared spectroscopy provided the evidence for the presence of biomolecules responsible for the reduction of silver ion, and X-ray diffraction analysis confirmed that the obtained nanoparticles were in crystalline form. SDS-PAGE was performed to identify the proteins and its molecular mass in the purified nitrate reductase from the cell-free extract. In addition, the minimum inhibitory concentration and minimum bactericidal concentration of AgNPs were investigated against gram-negative (Pseudomonas fluorescens) and gram-positive (Staphylococcus aureus) bacteria.

Metallic nanoparticles functionalizing carbon nanotube networks for gas sensing applications

We report the fabrication of carbon nanotube (CNT) based gas sensors functionalized with different metallic nanoparticles (NPs) (Au, Pd, Ag) with exceptionally high responses towards four test gases (NH3, CO2, CO and ethanol). The CNT networks were fabricated through a low cost spray deposition process while the NPs were deposited by a thermal evaporation process. CNT based gas sensors functionalized with Au with a nominal thickness of 1.0 nm showed superior response towards NH3, CO and ethanol. The sensors’ normalized responses reached 92%, 22% and 32% with concentrations of 100 ppm, 50 ppm and 100 ppm for NH3, CO and ethanol respectively. CNT based gas sensors functionalized with Pd with a nominal thickness of 1.5 nm showed the best performance with CO2. The normalized response reached 3%, 6%, 12% and 17% with concentrations of 500 ppm, 1000 ppm, 2500 ppm and 5000 ppm of CO2 respectively. We also investigated the morphological and optical changes that occur to the NPs upon thermal treatment. Functionalization of CNT films deposited on glass with Au and Ag showed surface plasmon resonance effects that are dependent on the nominal thickness of the functionalization layer.

Facile production of ZnS quantum dot nanoparticles by Saccharomyces cerevisiae MTCC 2918

Microbial synthesis of nanoparticles is a green route towards ecofriendly measures to overcome the toxicity and non-applicability of nanomaterials in clinical uses obtained by conventional physical and chemical approaches. Nanoparticles in the quantum regime have remarkable characteristics with excellent applicability in bioimaging. Yeasts have been commercially exploited for several industrial applications. ZnS nanoparticles as semiconductor quantum dots have mostly been synthesized by bacterial species. Here in, we have attempted to produce ZnS nanoparticles in quantum regime by Saccharomyces cerevisiae MTCC 2918 fungus and characterize its size and spectroscopic properties. Intracellular ZnS nanoparticles were produced by a facile procedure and freeze thaw extraction using 1mM zinc sulfate. The ZnS nanoparticles showed surface plasmon resonance band at 302.57nm. The ZnS nanoparticles were in low yield and in the size range of 30–40nm. Powder XRD analysis revealed that the nanoparticles were in the sphalerite phase. Photoluminescence spectra excited at 280nm and 325nm revealed quantum confinement effects. This suggests that yeasts have inherent sulfate metabolizing systems and are capable fungal sources to assimilate sulfate. Further insights are required to identify the transport/reducing processes that may have caused the synthesis of ZnS nanoparticles such as an oxidoreductase enzyme-mediated mechanism.

High power laser coupling to carbon nano-tubes and ion Coulomb explosion

Linear and non linear interaction of laser with an array of carbon nanotubes is investigated. The ac conductivity of nanotubes, due to uneven response of free electrons in them to axial and transverse fields, is a tensor. The propagation constant for p-polarization shows resonance at a specific frequency that varies with the direction of laser propagation. It also shows surface plasmon resonance at ω=ωp/2, where ωp is the plasma frequency of free electrons inside a nanotube, assumed to be uniform plasma cylinder. The attenuation constant is also resonantly enhanced around these frequencies. At large laser amplitude, the nanotubes behave as thin plasma rods. As the electrons get heated, the nanotubes undergo hydrodynamic expansion. At an instant when plasma frequency reaches ωp=2ω, the electron temperature rises rapidly and then saturates. For a Gaussian laser beam, the heating rate is maximum on the laser axis and falls off with the distance r from the axis. When the excursion of the electrons Δ is comparable or larger than the radius of the nanotube rc, the nanotubes undergo ion Coulomb explosion. The distribution function of ions turns out to be a monotonically decreasing function of energy.

Synthesis, characterization and SERS activity of biosynthesized silver nanoparticles

Silver nanoparticles were rapidly synthesized using Moringa oleifera flower extract as the reducing agent shows surface plasmon resonance peak at 439nm. The size and shape of the nanoparticles controlled by varying the concentration of M. oleifera flower extract in the reaction medium. The synthesized silver nanoparticles were well-dispersed spherical nanoparticles with the average size of 14nm. The retinoic acid present in M. oleifera flower extract used as reducing agent and proteins was responsible for capping of the bioreduced silver nanoparticles. The obtained nanoparticle shows size-dependent SERS activity. The SERS spectrum indicates that the pyridine adsorbed on the silver surface in a stand-on orientation via its nitrogen lone pair electrons.

Green Synthesis of Gold and Silver Nanoparticles UsingAverrhoa bilimbiFruit Extract

We report on rapid one-step green synthesis of gold and silver nanoparticles using fruit extract ofAverrhoa bilimbi Linn. UV-Vis absorption spectroscopy was used to monitor the quantitative formation of gold and silver nanoparticles. The characteristics of the obtained gold and silver nanoparticles were studied using UV-Vis absorption spectroscopy (UV/Vis), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and Energy-dispersive spectroscopy (EDX). UV/Vis spectrum showed Surface Plasmon Resonance (SPR) for both gold and silver nanoparticles at 540 and 420 nm. The EDX spectrum of the solution containing gold and silver nanoparticles confirmed the presence of elemental gold and silver signals. The average diameter of the prepared nanoparticles in solution was about 50–150 nm. Synthesized particles were either hexagonal or rhomboidal in shape. This synthesis approach of gold and silver nanoparticles is cost effective and can be widely used in biological systems. The effect of fruit extract and metal ion concentration was also studied.

Surfactant-mediated low-temperature synthesis of phase pure multiply twinned copper nanoparticles under non-inert condition via thermal decomposition of copper malonate

Multiply twinned phase pure copper nanoparticles were successfully synthesized without any inert gas protection via a low-temperature thermal decomposition of a new precursor copper malonate, [CuCH2C2O4]·2H2O in the presence of surfactant stabilizers oleylamine (C18H35NH2) and triphenylphosphine ((C6H5)3P). The synthesized nanoparticles were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), FT-IR and UV–vis spectroscopy. Freshly prepared copper nanoparticles showed surface plasmon resonance (SPR) around 574nm. TEM studies revealed a five-fold multiply twinned morphology of decahedral shape for the copper nanoparticles. Powder XRD pattern furnished evidence for a face-centered cubic crystal structure of pure metallic copper having an average crystallite size of about 35nm.

Surface enhanced absorption and transmission from dye coated gold nanoparticles in thin films

Absorption spectra of gold nanoisland thin film and the composite film of gold having thin coating of Methylene Blue and Rh6G dyes have been studied. Thin gold nanoisland film shows surface plasmon resonance (SPR) peak in the visible wavelength range, which shifts to near infrared with an increase in the thickness of the film. It was found that thin film of gold consists of nanoparticles of different size and shape, particularly nanorods of noncylindrical shapes. A linear relation was found between SPR peak wavelength and the aspect ratio of the nanoparticles in gold thin film. Effective medium refractive index of the gold film is estimated to be ~2.5, which decreases with an increase in film thickness. The coating of dyes on gold films splits the SPR peak with an enhanced absorption. Enhancement in absorption of composite film is maximal when the dye absorption peak coincides with the SPR peak; otherwise enhancement in transmission is observed for all the wavelength range. Absorption amplitude of composite film peaks increase with an increase in the gold film thickness, which tend toward saturation for film thickness of ≥6 nm. A correlation shows that absorption spectra can be described by the Maxwell Garnett theory, when the gold nanoparticles have a nearly spherical shape for very thin film (≤6 nm).

One-pot synthesis of PVA-capped silver nanoparticles their characterization and biomedical application

The rapid one-pot synthesis of silver nanoparticles (SNPs) at room temperature by using hydrazine hydrate as reducing agent and polyvinyl alcohol as stabilizing agent is reported. The SNPs were characterized with UV-visible (UV-Vis) spectroscopy, x-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The synthesized silver nanoparticle shows surface plasmon resonance at 410 nm. The XRD reveals face-centered cubic (FCC) structure of SNPs. FE-SEM, AFM and TEM show that nanoparticles have spherical morphology with diameters in the range of 10–60 nm. The antimicrobial activity of synthesized hybrid material against strains of four different bacteria (Bacillus cereus, Escherichia coli, Staphylococus aureus, Proteus vulgaris), that are commonly found in hospitals has been studied. The results indicate that such particles have potential applications in biotechnology and biomedical science.

Green synthesis and characterization of gold nanoparticles using extract of anti-tumor potent Crocus sativus

In the present study, we have explored anti-tumor potent Crocus sativus (saffron) as a reducing agent for one pot size controlled green synthesis of gold nanoparticles (AuNps) at ambient conditions. The nanoparticles were characterized using UV–vis, scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and FTIR analysis. The prepared AuNPs showed surface Plasmon resonance centered at 549 nm with average particle size of 15±5 nm. Stable, spherical and triangular crystalline AuNPs with well-defined dimensions were synthesized using anti-tumor potent Crocus sativus (saffron). Crystalline nature of the nanoparticles is confirmed from the HR-TEM, SAED and SEM images, and XRD patterns. From the FTIR spectra it is found that the biomolecules are responsible for capping in gold nanoparticles.