Position Of Surface Plasmon Resonance Band Research Articles

Insights into the role of ionic surfactants on the morphology of gold and gold@silver nanoparticles

Cyanidin-3, 5-di-O-glycoside (anthocyanin) was extracted from the red rose flower petals in an aqueous media. Anthocyanin was used as reductant to the preparation of gold nanoparticles with cationic and anionic surfactants. UV–visible absorption spectroscope, transmission electron microscope, scanning electron microscope, and energy dispersive X-ray spectroscope were employed to determine absorption bands of anthocyanin, surface Plasmon resonance (SPR) band, and morphology of the gold and gold@silver nanoparticles. Anthocyanin exhibited two absorption peaks at 284 and 518 nm, and one shoulder at 328 nm in the UV–visible spectrum. The intensity of these peaks decreases with time after the addition of HAuCl4. The color and the position of SPR band of gold nanoparticles depend on the concentration of gold salt with and without cetyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS). The anionic and cationic head groups of SDS and CTAB micelles have significant impact of the morphology of gold nanoparticles. Seedless co-reduction method was used for the synthesis of gold@silver nanoparticles. TEM images clearly indicate the formation of bimetallic gold@silver core-shell nanoparticles. The antioxidant power of AuNPs and gold@silver nanoparticles were tested in terms of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity as a function of different concentrations of nanoparticles.

Effect of Gold Nanoparticles on the Crystallization and Optical Properties of Glass in ZnO-MgO-Al2O3-SiO2 System

Gold nanoparticles precipitated in transparent glass-ceramics could pave the way for the development of multifunctional materials that are in demand in modern photonics and optics. In this work, we explored the effect of gold nanoparticles on the crystallization, microstructure, and optical properties of ZnO-MgO-Al2O3-SiO2 glass containing TiO2 and ZrO2 as nucleating agents. X-ray diffraction, transmission electron microscopy, Raman, and optical spectroscopy were used for the study. We showed that gold nanoparticles have no effect on the formation of gahnite nanocrystals during the glass heat treatments, while optical properties of the glass-ceramics are strongly dependent on the gold addition. A computational model was developed to predict optical properties of glass during the crystallization, and the possibility for adjusting the localized surface plasmon resonance band position with the heat treatment temperature was shown.

Role of ionic surfactants on the nucleation and growth of silver nanoparticles

Sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) were used as stabilizers for the preparation of silver nanoparticles (AgNPs) by the reduction of silver nitrate with proanthocyanidines (Pas). UV–visible spectra shows that the surface Plasmon resonance (SPR) intensity of AgNPs increases and decreases with increasing SDS and became constant at higher concentration. CTAB has no effect on the nucleation of AgNPs due to the insolubility of Pas. The position of SPR band (λmax = from 438 to 476 nm) depends on the concentration of Pas and a red shift of 38 nm was observed in absence of externally added SDS. The micellar pseudo phase proposed by Menger and Portnoy, modified by Bunton was used to determine the rate constants in micellar media. The Ag+ ions were formed complex with negative head group (OSO3−) of SDS electrostatically. Raman scattering spectroscopy, transmission electron microscopy, and scanning electron microscopy were used to discuss the capping action of SDS. Zeta potential of SDS-capped AgNPs was negative and resulting sols were stable for many months.

Citrus sinensis peel waste assisted synthesis of AgNPs: effect of surfactant on the nucleation and morphology

Silver nanoparticles (AgNPs) were synthesized by using Citrus sinensis peel waste extract. Optical images and UV-visible spectroscopy reveals the appearance of yellow to brown-red color and surface plasmon resonance (SPR) band at 400–480 nm, respectively, due to the formation of AgNPs. The stable perfect transparent silver sols were formed in presence of cetyltrimethylammonium bromide (CTAB). The brownish precipitates appeared with sodium dodecyl sulphate (SDS) after 3 h. The nucleation, position of SPR band and intensity depends on the head group nature of cationic and anionic micelles of SDS and CTAB. The as-prepared AgNPs were characterized using conventional techniques such as Fourier-transform infra-red, energy dispersed X-ray detector, scanning electron microscope, transmission electron microscope, and X-ray diffractometer. Zeta potential of CTAB-AgNPs was calculated and found to be stable for ca. 1 week. Molar concentration (3.3 × 10−4 mol/L) and aggregation number (607,339.917) of DPE-AgNPs were calculated. Ascorbic acid, citric acid and total reducing sugars were estimated in dry and fresh peel extract. Gram positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria shows excellent antibacterial activities toward DPE-AgNPs.

Rose cyanidin 3,5-di-O-glucoside-assisted gold nanoparticles, their antiradical and photocatalytic activities

Cyanidin 3,5-di-O-glucoside anthocyanin was extracted from red rose flower petals and used as reducing and capping agent for the green synthesis of anisotropic gold nanoparticles (Au NPs). Transmission electron microscope (TEM) images indicated that the Au NPs have large number of small spheres of gold. Surface plasmon resonance band position strongly depended on the [HAuCl4] and [anthocyanin]. Cationic surfactant distinctly changed the shape, size, number of NPs, and size distribution of Au nanodisks at room temperature. Conventional techniques were used to the estimate the antiradical and antimicrobial activities of the cyanidin 3,5-di-O-glucoside anthocyanin and gold NPs. The 2,2-diphenyl-l-picrylhydrazyl nitrogen radical (DPPH·), two bacteria strains (Staphylococcus aureus and Escherichia coli), and two yeast strains (Candida albicans ATCC 10231 and Candida parapsilosis ATCC 22019) were used to determine the antioxidant and antimicrobial properties of CTAB-capped gold NPs. Eosin yellow photocatalytic degradation followed apparent first-order kinetics with activation energies of 54.4 kJ/mol and 39.5 kJ/mol, respectively, for oxidative and sunlight catalyzed paths. The photocatalytic rates drastically inhibited with scavengers, demonstrating that the reactive radical oxygen species (HO· and O2−·), holes (h+) and electrons (e−) played major role in the degradation.

Structural and physical characteristics of Au2O3‐doped sodium antimonate glasses – Part I

AbstractNa2O‐Sb2O3 glasses doped with different concentrations of Au2O3 were prepared by melt quenching technique and later were heat treated at 800°C for 6 hours. Structural analysis by XRD, XPS, SEM, EDS, and DSC techniques indicated that the samples are embedded with multiple crystallites composed of Sb3+, Sb5+, Au3+ ions, and Au0 metallic particles. These studies have further demonstrated a gradual increasing fraction of Au0 metallic particles with increasing Au2O3 concentration. IR spectral studies suggested increasing the degree of polymerization of the glass network (due to increasing concentration of Sb5+ ions that participate in the glass network with SbVO4 structural units) with rise in the concentration of Au2O3. Optical absorption spectra of the titled samples have exhibited a broad absorption band at about 530 nm predicted due to the surface plasmon resonance (SPR) and exhibited a spectral red shift with increasing intensity with increase in Au2O3 content. Photoluminescence (PL) spectra of the samples recorded (at λexc = corresponding SPR band position) exhibited an emission peak at about 580 nm (identified as being due to interband transition between sp and d bands of gold particles). Overall, the analysis of these results has confirmed increasing concentration of Au metallic particles with increase in Au2O3 content in the titled material. Finally, it is predicted that the presence of higher concentration of gold particles in the polymerized antimonate glass network makes the materials useful for designing different nano dimensional optoelectronic devices.

Tracking the effect of binder length on colloidal stability and bioconjugation of gold nanoparticles

Understanding the organization of self-assembled monolayers (SAMs) on gold nanoparticles (AuNPs) as protective coatings is a key role of biological applications of nanomaterials. Here, we report the influence on the stability of the surface coverage of three mercaptocarboxylic lingands onto AuNPs, mercaptopropanoic acid (MPA), mercaptoundecanoic acid (MUA) and mercaptopropionic acid (MHA) under different conditions. In addition, we optimized a bioconjugation route using bovine serum protein (BSA) as a protein model. AuNPs and successful binding of ligands and BSA on the AuNPs were analyzed by UV–Vis, TEM, FTIR, RAMAN, DLS and zeta potential. The size of as-synthesized AuNPs was 18 ± 1,2 nm with surface plasmon resonance (SPR) peak at 522 nm. The magnitude of the bathochromic shift of AuNPs with MPA, MUA and MHA was determined by UV–Vis and the SPR band position of AuNP shifts to 1.5, 3 and 5 nm longer. Moreover, the data show the influence of chain length on colloidal stability and covalent and non-covalent coupling steps with nanomaterials. We demonstrate a method for quantitative determination of the coatings on gold nanoparticles and open new perspectives in understanding the influence of monolayer thickness on the generation of nanobioconjugates for biological applications.

Engineered Au Core@Prussian Blue Analogous Shell Nanoheterostructures: Their Magnetic and Optical Properties.

We report a new approach for the synthesis of multifunctional Au core@Prussian Blue analogous (PBA) shell nanoheterostructures that involves PBA shell growth on the surface of cyanide-stabilized gold nanoparticles. It permits the assembly of Au@KNiII [FeII (CN)6 ] core@shell and Au@KNiII [FeII (CN)6 ]@KNiII [CrIII (CN)6 ] core@shell@shell heterostructures with well-defined and size-controlled gold cores and PBA shells. These heterostructures exhibit tunable size- and shape-dependent magnetic and optical properties: (i) the surface plasmon resonance band position and intensity mainly depend on the PBA shell thickness, and (ii) the magnetic properties (the transition temperature, the coercivity, and magnetic regime) depend in a complex manner on the thickness as well as the particular morphology of the magnetic shell.

Effect of anionic surfactants on the surface plasmon resonance band of silver nanoparticles: Determination of critical micelle concentration

We have utilized surface plasmon resonance (SPR) band sensitivity to surfactant concentration to investigate the critical micelle concentration (cmc) of AOT and SDS. The process is based on an in situ formation of silver nanoparticles (AgNPs) through the reduction of silver ions (Ag+) by diethylene triamine (DETA) at room temperature. The shift of the SPR band position (λmax) at cmc can be observed with the naked eye in the form of a color change from brown to red for SDS and from brown to yellow for AOT.

Enhancement of a whispering gallery mode microtoroid resonator by plasmonic triangular gold nanoprism for label-free biosensor applications

Whispering gallery mode microresonators coupled to plasmonic nanoparticles have shown great promise for ultra-sensitive and label-free biological sensing. We analyze a whispering gallery mode microtoroid biosensor with a triangular gold nanoprism bound to its surface. We choose triangular nanoprism because of its capability of considerable enhancement of electromagnetic field at the tips and because its localized surface plasmon resonance band position is readily tunable. The local electric field enhancement at different points of plasmonic triangular gold nanoprism is calculated and the effect of rounded tip is investigated. This field enhancement permits the detection and characterization of some large protein molecules. We have studied the detection of single bovine serum albumin protein using our hybrid microcavity.

Deposition of Ag and Au–Ag alloy nanoparticle films by spray pyrolysis technique with tuned plasmonic properties

Abstract Silver (Ag) and gold–silver (Au–Ag) alloy nanoparticle films have been prepared on the transparent substrates using a simple inexpensive spray pyrolysis technique. The surface plasmon resonance (SPR) properties of Ag films were investigated by varying spray solution volume. Also, the tunability of SPR properties using an electric field to the nozzle was demonstrated in this work. The reduced full width at half maximum and blue shift in the SPR band position were observed with ΔλFW ∼ 35 nm and ΔλP ∼ 30 nm at the applied voltage of 2 kV. The extinction spectra of alloy nanoparticle films show only one plasmon absorption it is concluded that mixing of gold and silver precursors leads to a homogeneous formation of alloy nanoparticles. The maximum of the SPR band tuned continuously from λmax ∼ 414–525 nm with increasing gold content. The SEM observations show the variable size and spherical structure of nanoparticle films.

Deposition of gold nanoparticle films using spray pyrolysis technique: Tunability of SPR band by electric field

AbstractGold nanoparticle films are prepared using a simple inexpensive spray pyrolysis technique. X‐ray as well as TEM diffraction patterns revealed pure cubic structure. The effect of gold nanoparticle concentration on surface plasmon resonance (SPR) band position and bandwidth are investigated for varying spray solution volume. The tunability of SPR band position and bandwidth using an electric field, by applying a voltage (up to 2000 V) to the nozzle, has been demonstrated. The reduced full width at half maximum and blue shift in the SPR band position are observed with ΔλFW ∼ 55 nm and ΔλP ∼ 40 nm for the applied voltage of 2 kV. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Surface plasmon resonance of Ag organosols: Experimental and theoretical investigations

The aim of this paper is to investigate and compare the changes in surface plasmon resonance (SPR) of silver (Ag) hydrosol and organosols obtained by experimental and theoretical approaches. Silver nanoparticles (Ag NPs) of 5 ? 1.5 nm in diameter were prepared in water by reduction of silver nitrate with sodium borohydride. Nanoparticles were subsequently transferred into different organic solvents (chloroform, hexane, toluene, 1,2-dichlorobenzene) using oleylamine as a transfer agent. These solvents were chosen because of the differences in their refractive indices. Using UV-Vis absorption spectrophotometry and transmission electron microscopy (TEM), we confirmed that there were no shape and size changes of the nanoparticles upon the transfer to the organic phase. The absorption spectra of the obtained Ag organosols showed only changes in the position of SPR band depending on dielectric property of the used solvent. To analyze these changes, absorption spectra were modelled using Mie theory for small spherical particles. The experimental and theoretical resonance values were compared with those predicted by Drude model and its limitations in the analysis of absorption behavior of Ag NPs in organic solvents were briefly discussed.

Enhancement of ZnO light emission via coupling with localized surface plasmon of Ag island film

Enhancement of the light emission of ZnO films was observed by coupling through localized surface plasmons. By sputtering Ag islands onto ZnO films, their band gap emission coming through the Ag island films was enhanced by threefolds, while the defect emission was quenched. The enhancement was found to be mainly dependent on the sputtering time of the Ag islands, which is related to the island size. Furthermore, the relative spectral position between the ZnO emission band and the localized surface plasmon resonance bands of Ag islands was found to be decisive for the enhancement or quenching of photoluminescence, indicating that the emission intensity of ZnO films can be controlled by the Ag island size and the localized surface plasmon resonance band position.