Surface Plasmon Resonance Of Silver Nanoparticles Research Articles

Antibacterial, antioxidant and photocatalytic activity of novel Rubus ellipticus leaf mediated silver nanoparticles

Nanotechnology is an emerging field of science that has significant applications in applied sciences. In this study, silver nanoparticles (SNPs) were synthesized utilizing the leaf filtrate of Rubus ellipticus. SNPs were characterized using UV–visible spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction patterns to determine their morphology and chemical composition. The surface plasmon resonance of SNPs revealed a peak at 415 nm. The synthesized SNPs were mainly spherical crystals with an average size of 21.43 nm. When compared to plant extract and positive controls (AgNO3 and penicillin), SNPs demonstrated significant bactericidal activity against all the tested bacteria (gram-positive and gram-negative). The most effective bactericidal activity was found against Pseudomonas aeruginosa, with a minimum inhibitory concentration of 1.25 µg/mL. In addition, a dose-dependent antioxidant activity of SNPs was found against the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical with an average IC50 value of 72.84 µg/mL. The photocatalytic activity of Methylene blue (MB) dye decomposition under sunlight was studied. The results showed that MB degraded by 98 % after 150 min in the sun. Overall, the findings of this study indicate that R. ellipticus biosynthesized SNPs may have bactericidal and photocatalytic effects.

Synthesis and photoluminescence of silver and europium codoped germinate tellurite oxyfluoride glasses

Germinate tellurite oxyfluoride glasses of composition TeO2-GeO2-WO3-Li2O3-EuF3-AgCl (TGEUAC) were synthesized by melt quenching and heat-treated for the growth of silver nanoparticles (AgNPs). The presence of surface Plasmon resonance (SPR) absorption band of silver species with Eu3+ ions absorptions peaks for differently heat-treated glass samples were measured by the absorption spectrum. The green, red and deep- red photoluminescence intensity variation of Eu3+ ions under the influence of AgNPs has been observed. Maximum three-fold enhancement of TGEUAC-6 sample for green, red and mainly deep- red emission of Eu3+ caused by SPR of silver nanoparticles has also been observed. On the other hand, emission quenching of after long heat-treated of other samples was attributed to back energy transfer from Eu3+ ions to silver species or local field saturation. The emission intensities characterized through the CIE diagram and energy transfer mechanism of the Ag NPs to Eu3+ ions in glasses are discussed for potential application of optical devices.

Ag nanoparticles induced luminescence enhancement of Eu3+ doped phosphate glasses

Abstract Sodium phosphate glasses co-doped with Eu3+/Ag NPs were prepared by the melt quenching method. A thermal annealing process is proposed to control the aggregation and growth of Ag NPs. The amorphous nature is confirmed by the x-ray diffraction patterns for all the glasses. TEM picture analyses revealed the presence of silver nanoparticles of almost spherical shape and various sizes inside the glass matrix depending on the annealing time. The absorption spectra revealed seven absorption peaks of Eu3+ions in addition to the surface Plasmon resonance (SPR) band of Ag NPs centered at 400 nm. The luminescence properties of Eu3+ doped phosphate glass containing silver nanoparticles (NPs) are investigated. The observed enhancement of the photoluminescence and the PL lifetime relative to 5D0 → 7F2 transitions are explained not only by the energy transfer ions, but NPs to Eu3+ ions but also by the enhancement of local field effect LFE induced by SPR of silver NPs. Based on the emission spectra, Judd Offelt (JO) parameters (Ω2 and Ω4), spontaneous emission probabilities, the radiative lifetime, luminescence branching factors, the quantum yield of luminescence and the stimulated cross-section emissions for 5D0→7F2 transition are calculated. The fluorescence quantum efficiencies are found to be enhanced with the increase of heat treatment until it attains 85% for the sample PAZE20. The results indicated that the heat-treated glass for 20 h has a good prospect as a gain medium applied for 615 nm broadband and high-gain europium-doped fiber amplifiers.

Microwave-assisted synthesis of silver nanoparticles from Origanum majorana and Citrus sinensis leaf and their antibacterial activity: a green chemistry approach

Silver nanoparticles (SNPs) play important role in the field of optics and electronics and also as a novel antibacterial agents. Here, we report a simple and green method for the biosynthesis of SNPs using aqueous leaf extract of Origanum majorana and Citrus sinensis as a novel bio source of cost-effective, non-hazardous reducing, and stabilizing agents. A 3 mM solution of silver nitrate was prepared. Five milliliter aqueous leaf extract was slowly added to 20 ml silver salt solution (3 mM) with constant stirring. No noticeable color change was observed. The solution was then heated in domestic microwave for variable time intervals. The intense brown colored solution was obtained on 1 min heating with O. majorana and 5 min heating with C. sinensis extract. The intense brown color indicated the formation of SNPs. The antibacterial activity of synthesized SNPs was investigated. SNPs were rapidly synthesized using aqueous leaf extract of O. majorana and C. sinensis on microwave irradiation. Formation of SNPs was confirmed by the change in color from yellowish green to brown and absorption maximum around ~420 and 410 nm due to surface plasmon resonance of SNPs. They were also characterized by other physical–chemical techniques like Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope coupled with X-ray energy dispersive spectroscopy, and high-resolution transmission electron microscopy. TEM analysis showed the presence of feather-shaped NPs in O. majorana and spherical as well as cubical-shaped NPs in C. sinensis-mediated SNPs. The synthesized SNPs showed significance antibacterial activity against two human pathogenic strains. The SNPs were synthesized using leaf extract of plants. This synthesis method is nontoxic, eco-friendly, and a low-cost technology for the large-scale production. The SNPs can be used as a new generation of antibacterial agents.

A new simple method for determining the critical micelle concentration of surfactants using surface plasmon resonance of silver nanoparticles

A new and simple determination method for critical micelle concentration (CMC) has been developed based on surface plasmon resonance (SPR) technique. In the current work, the CMCs for sodium dodecyl sulfate (SDS), cetyl trimethyl ammonium bromide (CTAB), and Triton X-100 (TX-100) were determined in aqueous media by SPR of silver nanoparticles (AgNPs). The variation of the absorbance of AgNPs in respect of bulk water is a consequence of the micelles formation from the surfactants monomer, here, SDS, CTAB, and TX-100. Under the optimal experimental conditions, CMCs for SDS, CTAB, and TX-100 using SPR technique were 8.6 × 10−3, 9.1 × 10−4, and 2.6 × 10-4 mol L−1, respectively. The potential application of SPR technique for the CMC determination has been demonstrated in this work. Comparing to the other CMC determination methods, this SPR method is universal, sensitive, and nonadditive; it can be used for the direct measurements of CMC without adding any dyes or fluorescent probes. CMC values of various surfactants including SDS, CTAB, and TX-100 determined by this method are in agreement with those determined by the other methods. The results obtained by our simple method have comparable accuracy with those obtained from more elaborate experiments.

Development of antibacterial cellulosic fabric via clean impregnation of silver nanoparticles

In the present study, we investigate single bath fabrication and impregnation of silver nanoparticles (SNPs) on enzymatic pretreated cotton fabric by using starch both as reducing as well as stabilizing agent under the autoclave conditions of 103.42 kPa, 121 °C for 15 min. The SNPs were characterized using UV–visible (UV–vis) spectroscopy, zetasizer nano and transmission electron microscopy. The UV–vis absorption spectra showed typical absorption peaks at ∼420 nm corresponding to the surface plasmon resonance of SNPs. The hydrodynamic diameter of SNPs was as smaller as 20 nm with their respective zeta potential of −43.20 mV. Both scanning electron and atomic force microscopic analyses revealed that the surface of the treated cotton fabric was rougher than that of untreated fabric, and the SNPs were present on the surface of the treated fabric. Silver mapping and elemental analysis of the treated cotton fabric using energy dispersive X-ray spectroscopy confirmed the presence of SNPs in a homogeneous distribution. The textile properties of the fabric including wettability, whiteness, tensile strength and antibacterial activity were measured by using the standard methods. The SNPs impregnated cotton fabrics showed good durable antibacterial activity against Escherichia coli and Staphylococcus aureus strains.

Nano-silver enhanced luminescence of Eu3+-doped lead tellurite glass

Eu3+-doped lead sodium tellurite glasses containing silver nanoparticles (NPs) were synthesized by melt-quenching technique and annealed for different time intervals at above the glass transition temperature. The glasses were characterized by UV–Vis–IR absorption, photoluminescence spectroscopy and transmission electron microscope imaging. Four absorption peaks of Eu3+ ion were observed due to transitions from ground state to different excited states in 400–600nm region. The surface plasmon resonance (SPR) peak of silver NPs was probed at 632nm. Five emission lines were recorded at 568, 587, 614, 650 and 704nm which were intensified in the order of ∼1.9 times for heat-treated samples containing silver NPs. The average size of NPs was estimated to be ∼10nm. Different mechanisms for interaction of light with metal and luminescent ions are discussed. Such enhancements are attributed to the strong local electric field induced by SPR of silver NPs as the major factor, and energy transfer from surface of silver NP to Eu3+ ion. The glasses show promising properties for optical applications.

Biosynthesis of silver nanoparticles by marine bacterium, Idiomarina sp. PR58-8

Metal-tolerant microorganisms have been exploited in recent years to synthesize nanoparticles due to their potential to offer better size control through peptide binding and compartmentalization. In this paper, we report the intracellular synthesis of silver nanoparticles (SNPs) by the highly silver-tolerant marine bacterium, Idiomarina sp. PR58-8 on exposure to 5 mM silver nitrate. SNPs were characterized by UV-visible spectrophotometry, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). UV-visible absorption scan of a 48 h culture exposed to 5 mM silver nitrate revealed a broad peak at 450 nm indicative of the surface plasmon resonance of SNPs. XRD analysis confirmed the presence of elemental silver and the crystallite size was calculated to be 25 nm using Scherrer formula. The average particle size as per TEM analysis was found to be 26 nm. Metal stress is known to induce the production of non-protein thiols (NP–SHs) which sequester metal ions. In this study, the production of NP–SHs was followed from 6–48 h, wherein it was observed that the NP–SH levels in the silver-exposed culture were consistently higher (261% on an average) than in the unexposed culture.

Localized surface plasmon resonance effect on photo-induced alignment of films composed of silver nanoparticles and azopolymers with cyano or methyl substitutes on azobenzene moieties

In this paper, we report the localized surface plasmon resonance of silver nanoparticles on the photo-induced alignment properties of azopolymers. Two series of azopolymer films doped with silver nanoparticles (SNPs) were prepared with different contents of SNPs, in which two side chain azopolymers, with cyano group (AzoCN) and methyl group (AzoCH 3) as substitutes, respectively, were designed and synthesized because of the different interaction between SNPs and each kind of substitute. Tapping-mode atomic force microscope imaging was used to characterize the distribution of SNPs in azopolymer films, from which it was found that in AzoCN film SNPs were almost uniformly distributed, whereas in AzoCH 3 film several decades of single SNP aggregated into a cluster. Photo-induced alignment of azopolymer films doped with SNPs was performed under irradiation of linearly polarized light at 442 nm. The experimental results reveal that there is an obvious difference in photo-induced alignment behavior between two series of azopolymer films. For AzoCN, the alignment rate decreased with the increase of SNPs concentration, and when the SNPs' concentration achieved 0.24% the ratio of alignment rate reached the minimum, about 77% of that of the undoped sample. For AzoCH 3, the alignment rate increased along with the increase of the content of SNPs, showing that the alignment rate, at least for “fast” process, could be enhanced by doping SNPs. This phenomenon resulted from localized surface plasmon resonance of SNPs and was also found to be affected by the chemical structure and the condensed state of azopolymers doped with SNPs.

Size-dependent surface-plasmon-enhanced photoluminescence from silver nanoparticles embedded in silica

The size dependence of the photoluminescence spectra from silver nanoparticles embedded in a silica host medium was observed. The quantum yield of the photoluminescence increased when the size of the nanoparticles was decreased. The quantum yield for 8 nm silver nanoparticle was estimated to be on the order of ${10}^{\ensuremath{-}2}$ which is ${10}^{8}$ times higher than the one observed for bulk silver. The two photoluminescence bands observed from silver nanoparticles were rationalized as the radiative electron interband transitions and radiative decay of the surface plasmons in silver nanoparticles. The strong local electric field induced by the surface-plasmon resonance in silver nanoparticles enhances the exciting and emitted photons and increases the quantum yield of the photoluminescence.

Study of Tb-doped Li2O-LaF3-Al2O3-SiO2 Glasses Containing Silver Nanoparticles

AbstractTb-doped Li2O-LaF3-Al2O3-SiO2 (LLAS) glasses containing silver were fabricated using melt-quenching technique. Silver nanoparticles (NPs) in glass matrix were confirmed by optical absorption and X-ray diffraction (XRD). The nucleation of silver NPs was controlled by heat-treatment. A broad absorption band peaked at about 420 nm was observed due to surface plasmon resonance (SPR) of the silver NPs. This SPR absorption of silver NPs increases with the time of heat-treatment. Photoluminescence (PL) emission and excitation spectra were measured on Tb-doped LLAS glasses with and without silver NPs. Strong Tb3+ luminescence was observed. For excitation at 325 nm, luminescence of Tb3+ ions increases for the glass containing silver NPs compared to that in the glass without silver NPs. After further heat-treatment at 520 °C for 5 hours, Tb3+ luminescence decreased. Our luminescence results suggest that there are two competitive effects, enhancement and quenching effects, acting on Tb3+ luminescence in the glass containing silver NPs. The enhancement of Tb3+ luminescence is attributed to local field effects due to the excitation of SPR of silver NPs. The quenching effect in the presence of Ag NPs suggests an energy transfer from Tb3+ ions to silver NPs exists, which may provide an additional non-radiative relaxation pathway for the excited Tb3+ ions.

Morphology and surface-plasmon resonance of silver nanoparticles sandwiched between Si3N4 and BN layers

Nanocermet trilayered thin films consisting of silver nanoclusters sandwiched between two dielectric layers (the buffer and the cap) have been synthesized by ion-beam sputtering with an alternate deposition of the metal and the dielectric species. The influence of the amount of silver, the nature of the buffer and the cap (BN or Si3N4), and a time delay before the cap deposition on clusters morphology and repartition have been investigated by transmission electron microscopy. It has been observed that the clusters display truncated ellipsoidal shapes in which the height to diameter ratio H∕D decreases as the amount of deposited silver increases. For a given amount of silver, this ratio is lower in the case of a Si3N4 cap, whatever the nature of the buffer. Two explanations are proposed to account for this “cap effect” on clusters morphology: the first one is based on a calculation of the H∕D minimizing the surface free energy of the clusters embedded between the buffer and the cap; the second one holds on the shape relaxation of the coalesced nonequilibrium clusters towards their equilibrium shape with the buffer, this process occurring until clusters are fully covered with the cap. Because of the higher deposition rate of Si3N4 compared to BN, a Si3N4 cap would allow a less efficient reshaping and consequently lead to flatter clusters. This explanation is supported by the temporal evolution of clusters morphology and repartition observed during the time delay before deposition of the cap. The evolution of the spectral position of the surface-plasmon resonance (SPR) of the trilayers as a function of their structure has also been investigated by optical transmittance measurements. The influence of cluster morphology, as well as the nature of the buffer and the cap on the SPR spectral position are discussed.