Surface Plasmon Resonance Absorption Peak Research Articles

Green synthesis of silver nanoparticles using cranberry powder aqueous extract: characterization and antimicrobial properties.

BackgroundThe growing threat of microbial resistance against traditional antibiotics has prompted the development of several antimicrobial nanoparticles (NPs), including silver NPs (AgNPs). In this article, a simple and eco-friendly method for the synthesis of AgNPs using the cranberry powder aqueous extract is reported.Materials and methodsCranberry powder aqueous extracts (0.2%, 0.5%, and 0.8% w/v) were allowed to interact for 24 hours with a silver nitrate solution (10 mM) at 30°C at a ratio of 1:10. The formation of AgNPs was confirmed by ultraviolet-visible spectroscopy and their concentrations were determined using atomic absorption spectroscopy. The prepared NPs were evaluated by transmission electron microscopy, measurement of ζ-potential, and Fourier-transform infrared spectroscopy. The in vitro antimicrobial properties of AgNPs were then investigated against several microbial strains. Finally, in vivo appraisal of both wound-healing and antimicrobial properties of either plain AgNPs (prepared using 0.2% extract) or AgNP-Pluronic F-127 gel was conducted in a rat model after induction of a Staphylococcus aureus ATCC 6538P wound infection.ResultsThe formation of AgNPs was confirmed by ultraviolet-visible spectroscopy, where a surface-plasmon resonance absorption peak was observed between 432 and 438 nm. Both size and concentration of the formed AgNPs increased with increasing concentration of the extracts. The developed NPs were stable, almost spherical, and polydisperse, with a size range of 1.4–8.6 nm. The negative ζ-potential values, as well as Fourier-transform infrared spectroscopy analysis, indicated the presence of a capping agent adsorbed onto the surface of the particles. In vitro antimicrobial evaluation revealed a size-dependent activity of the AgNPs against the tested organisms. Finally, AgNPs prepared using 0.2% extract exhibited a substantial in vivo healing potential for full-thickness excision wounds in rats.ConclusionAgNPs were successfully synthesized from a silver nitrate solution through a simple green route, using cranberry powder aqueous extract as a reducing as well as capping agent.

Linear Optical Properties of Gold Colloid

Gold colloid was prepared by reducing HAuCl 4 ·4H 2 O with Na 3 C 6 H 5 O 7 ·2H 2 O. The morphology, size of gold nanoparticles and the optical property of colloid were characterized by transmission electron microscope and UV-Vis spectrophotometer, respectively. It shows that the gold nanoparticles are in the shape of spheres with diameters less than 8 nm, and the surface plasmon resonance absorption peak is located at about 438 nm. As the volume fraction of gold particles increases, the intensity of absorption peak strengthens. The optical property of gold colloid was analyzed by Maxwell-Garnett (MG) effective medium theory in the company of Drude dispersion model. The results show that the matrix dielectric constant is a main factor, which influences the optical property of gold colloid. DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9558

Surface plasmon enhanced third-order optical nonlinearity of silver nanocubes

We present the linear and nonlinear optical properties of Ag nanocubes. The surface plasmon resonance absorption peak shows a red shift with increasing cube size. The nonlinear absorption and nonlinear refraction were measured by using Z-scan technique. The Ag nanocubes with the edge size of 60 nm show the largest third-order optical nonlinearity, which is supported by the largest field enhancement factor through the FDTD simulations. In the wavelength range from 720 nm to 920 nm, the one-photon and two-photon figures of merit, W and T satisfy the demand of W > 1 and T < 1, which implies it is a promising candidate for the optical switching devices.

The Surface Plasmon Resonance Absorption of Indium Tin Oxide Nanoparticles and its Control

Indium tin oxide (ITO) nanoparticles (NPs) were prepared by a coprecipitation process from a mixed solution consisting of indium chloride and tin chloride. The surface plasmon resonance (SPR) absorption was studied under different calcinate atmospheres. The characteristics of the optical properties, especially the absorption of near-infrared (NIR) region was recorded by the UV-Vis-NIR absorption spectroscopy. The results show that the SPR absorption peak appears at 2500 nm under an oxidizing atmosphere (air) or at 1300 nm under a reducing atmosphere (a gas mixture of Ar and 5 vol% H2) when calcinated under a single atmosphere. There is no change in the plasmon frequency with the variance of calcinate temperatures and therefore no change in the free carrier concentration. However, when calcinated first at 600 °C under an oxidizing atmosphere and then reheated under a reducing atmosphere at different temperature, the SPR absorption peaks of the ITO NPs are at the range of from 1200 nm to 1430 nm, undergoing a blue shift as the reducing process temperature increases. The SPR absorption of the prepared ITO NPs is easily controlled by calcinate temperature under a process of calcination first under an oxidizing atmosphere and followed by under a reducing atmosphere.

Effect of laser fluence on the characteristics of Al nanoparticles produced by laser ablation in deionized water

We have studied the effects of the laser fluence on the characteristics of Al nanoparticles produced by pulsed laser ablation of Al plate in deionized water without using surfactant. Five samples of aluminum nanoparticles were synthesized by nanosecond pulsed laser ablation of a high purity aluminum plate in distilled water at five different fluences in the range of 1–3 J/cm2. There is threshold fluence of the laser at which absorption of laser energy by water rises significantly. Absorption of the laser energy by water leads to increase oxygen atoms in the ablation medium and formation of aluminum oxide nanoparticles. By increasing the laser fluence below the threshold magnitude size of produced nanoparticles increase while by increasing the laser fluence above the threshold magnitude size of produced nanoparticles decrease. The UV-Visible-NIR absorption spectra of nanoparticles exhibit surface plasmon resonance absorption peak in the ultraviolet region. TEM and SEM micrographs are used to characterize the produced nanoparticles. The production rate of nanoparticles is increased with increasing the laser fluence.

Gold nanorod as saturable absorber for Q-switched Yb-doped fiber laser

We reported on the generation of Q-switched pulse in an Yb-doped fiber laser by using a filmy polyvinyl alcohol (PVA)-based gold nanorods (GNRs) saturable absorber (SA). The GNRs are synthesized through seed-mediated method whose longitudinal surface plasmon resonance (SPR) absorption peak is located at 1038nm. The modulation depth of the GNRs SA is ∼4.06%. By gradually increasing the pump power from 62mW to 128mW, the repetition rate of Q-switched pulse increases from 8.78kHz to 20.78kHz and the pulse duration decreases from 9.43μs to 3.65μs. In addition, the dual-wavelength switchable Q-switched operation was also observed. The obtained results further expand the applications of GNRs SA to the field of Q-switched pulsed fiber lasers at 1.0μm waveband.

Synthesis, characterization and antimicrobial activity of carboxymethyl dextrane stabilized silver nanoparticles

Silver nanoparticles (AgNPs–CMD) were synthesized from aqueous solution of silver nitrate (AgNO3) and carboxymethyl dextrane (CMD) in mole ratio 1:1 and 1:2. The characterization of AgNPs–CMD was performed by ultraviolet–visible (UV–VIS) spectroscopy, gel permeation chromatography (GPC), scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and antimicrobial activity. The formation of AgNPs–CMD was screened by color changes of the reaction mixture to yellow, by measuring the surface plasmon resonance absorption peak in UV–VIS region at 420nm. The GPC chromatography measurement confirmed the formation of AgNPs–CMD. The SEM microscopy was used for size and shape of AgNPs–CMD nanoparticles determination. The presence of elemental silver and crystalline structure of AgNPs–CMD were confirmed by XRD analyses. The possible functional group of CMD responsible for the reduction and stabilization of AgNPs were determinated by FT-IR spectroscopy. The AgNPs–CMD showed strong antibacterial activity against Bacillus lutea, Bacillus aureus, Bacillus cereus, Enterococus fecalis, Pseudomonas aeruginosa, Klebsiella pneumoniae and antifungal activity against Aspergillus spp., Penicillum spp., and Candida albicans.

Preparation and Characterization of Hydrocolloid Stabilized Silver Nanoparticles

Silver nanoparticles (AgNPs) are of considerable interest for medical application due to their antimicrobial activity. However, only a limited number of natural polymers have been reported as colloidal stabilizers for AgNPs. This study aimed to synthesize AgNPs using hydrocolloids, alginate and carrageenan, as stabilizers. Hydrocolloid-capped AgNPs were synthesized by two methods: M1, a reductive sodium borohydride (NaBH4) method, and M2, a microwave assisted reduction method. The synthesized AgNPs were characterized for surface plasmon resonance (SPR), size, surface charge and morphology. From the results, AgNPs stabilized by alginate (al-AgNPs) and carrageenan (ca-AgNPs) were able to be synthesized by methods M1 and M2. The SPR absorption peak around 400 nm of AgNPs represented the formation of rather spherical particles. The AgNPs formed by method M1were narrower in size distribution than that of AgNPs formed by method M2. Laser doppler electrophoresis (LDE) showed negative surface charges of al-AgNPs and ca-AgNPs because the anionic hydrocolloid polymers consist of carboxylic acid (alginate) and sulfate (carrageenan). Conclusively, AgNPs can be successfully formed and stabilized by alginate and carrageenan. Hydrocolloid-capped AgNPs are stable due to the electrostatic repulsion and steric stabilization of such polymers.

Controllable synthesis and characterization of Fe3O4/Au composite nanoparticles

Abstract Fe3O4/Au composite nanoparticles (GoldMag NPs) have received considerable attention because of their advantageous properties arisen from both individual Au and Fe3O4 nanoparticles. Many efforts have been devoted to the synthesis of these composite nanoparticles. Herein, GoldMag NPs were reported to be synthesized by two-step method. Fe3O4 nanoparticles were prepared by co-precipitation and modified by the citric acid, and then citric acid-coated Fe3O4 nanoparticles were used as seeds in sodium citrate solution to reduce the HAuCl4. The size of obtained nanoparticles was geared from 25 to 300 nm by controlling the concentration of reactants. The GoldMag NPs were characterized by UV–vis spectrometer, dynamic light scattering (DLS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). The GoldMag NPs showed good superparamagnetism at room temperature and were well dispersed in water with surface plasmon resonance absorption peak varied from 538 nm to 570 nm.

Plasmonic properties of Au/SiO2 nanoparticles: effect of gold size and silica dielectric layer thickness

Metallic nanoparticles with plasmonic properties have extensive potential applications in biodiagnostics and sensing, bioimaging and solar cells, but a comprehensive theoretical and experimental investigation of the phenomenon is far from being complete. In this manuscript, about 30, 40 and 50 nm Au nanoparticles were synthesised by Frens method, and Au/SiO2 nanoparticles were obtained by a modified Stöber method; the thickness of SiO2 layer were adjusted from 15 to 45 nm. The effect of Au size and SiO2 dielectric layer thickness on the plasmonic properties of Au/SiO2 nanoparticles were numerically simulated by 3D comsol and were experimentally studied by UV-vis absorption spectra. UV-vis absorption spectra showed that the increase in Au particle size or SiO2 thickness resulted in a red shift of the surface plasmon resonance absorption peak of Au/SiO2 nanoparticles, which is consistent with the simulation results by 3D comsol. Thicker SiO2 layer and smaller Au nanoparticles led to the decrease of electric field.

A new silver nanorod SPR probe for detection of trace benzoyl peroxide.

The stable silver nanorod (AgNR) sol in red was prepared by the two-step procedure of NaBH4-H2O2 and citrate heating reduction. The AgNR had a transverse and a longitudinal surface plasmon resonance (SPR) absorption peak at 338 nm and 480 nm. Meanwhile, two transverse and longitudinal SPR Rayleigh scattering (SPR-RS) peaks at 340 nm and 500 nm were observed firstly using common fluorescence spectrometer. The SPR absorption, RS, surface enhanced Raman scattering (SERS) and electron microscope technology were used to study the formation mechanism of red silver nanorods and the SERS enhancement mechanism of nano-aggregation. The AgNR-BPO SPR absorption and AgNR-NaCl-BPO SPR-RS analytical systems were studied to develop two new simple, rapid, and low-cost SPR methods for the detection of trace BPO.

Xe ion irradiation-induced polycrystallization of Ag nanoparticles embedded in SiO_2 and related optical absorption property

The Xe ion irradiation-induced structural modifications of implantation-synthesized Ag NPs were explored in this paper. Our results clearly show that Xe ion irradiation could induce transformation of crystalline Ag NPs into polycrystalline ones with various shapes. The modified Ag NPs exhibit a notable shoulder absorption band around 550 nm besides the surface plasmon resonance (SPR) peak located at about 400 nm. Reduction of the electron mean-free-path and interaction between crystallites in the formed polycrystalline NPs have been proposed to interpret the appearance of the shoulder absorption band. Moreover, our results also show that subsequent thermal annealing at 400 °C for 1h can restore polycrystalline Ag NPs to crystalline ones with spherical shape, which are nearly aligned around the end of the Ag ion range, and contribute a much narrower SPR absorption peak at 400 nm.

High temperature optical sensing of gas and temperature using Au-nanoparticle incorporated oxides

Au-nanoparticle incorporated metal oxide based sensing layers show significant promise for high temperature optical sensing applications at temperatures approaching 800°C or even higher depending upon the base oxide material. Several Au-nanoparticle incorporated oxide systems were synthesized and investigated here, namely TiO2, ZrO2, and Yttria-Stabilized Zirconia (YSZ). Gas (CO, H2, and O2) and temperature sensing responses were observed at wavelengths near the localized surface plasmon resonance (LSPR) absorption peak of the Au nanoparticles and addition of 1% O2 content to a N2 baseline gas stream resulted in significantly enhanced recovery kinetics for H2 sensing. TiO2 films with a relatively small bandgap as compared to ZrO2 and YSZ enabled band-edge monitoring yielding a strong temperature sensing response with minimal cross-correlation to changes in gas composition. Testing of the films in high H2-level gas streams demonstrated that monotonic responses to H2 up to 98% H2 by volume in 2% O2 balance N2 gas streams could be achieved by interrogation at wavelengths shorter than the transmittance minimum associated with the Au LSPR absorption peak. These results collectively demonstrate the importance of careful wavelength selection or broadband wavelength interrogation to minimize cross-correlation between composition and temperature and to optimize the gas sensing response in high temperature gas streams. Although the tested films were stable in the presence of simple gas mixtures (N2, H2, CO, O2) used for gas and temperature sensing experiments, a preliminary study of film stability in a contaminated (H2S-containing) high temperature fuel gas stream relevant for solid oxide fuel cell applications was also carried out and yielded two important conclusions deserving further investigation: (1) enhanced microstructural stability of Au nanoparticle incorporated TiO2 due to grain boundary pinning and (2) significant mass loss of Au with an associated reduction in LSPR absorption.

Autocatalytic Oxidization of Nanosilver and Its Application to Spectral Analysis

The stable yellow nanosilver (AgNP) and blue nanosilver (AgNPB) sols were prepared by the NaBH4 procedure. The new nanocatalytic reaction of AgNP-NaCl-H2O2 was investigated by surface plasmon resonance (SPR) absorption, resonance Rayleigh scattering (RRS), surface-enhanced Raman scattering (SERS) and scanning electron microscope (SEM) techniques. The autocatalytic oxidization of Ag on AgNP surface by H2O2 was observed firstly and the AgNP/AgCl nanoparticles were characterized. The [Ag+] from AgNP is different to the Ag+ from AgNO3 that adsorb on the AgNP surface. An autocatalytic oxidization mechanism was proposed to explain experimental phenomena. The relationship between the SPR absorption peaks and the RRS peaks of AgNPB was studied, and three characteristic RRS peaks called as out-of-plane quadrupole, out-of-plane dipole and in-plane dipole RRS peaks were observed firstly. Using AgNP as nanoprobe, a simple, sensitive and selective RRS method was developed for assay of H2O2 in the range of 2.0 × 10−8-8.0 × 10−5 mol/L.

Effect of Laser Pulse Energy on the Characteristics of Cu Nanoparticles Produced by Laser Ablation Method in Acetone

The effect of laser fluence on the characteristics of Cu nanoparticles, prepared by laser ablation method, is investigated experimentally. 1–6 nm Cu nanoparticles were synthesized by the pulsed laser ablation of a high purity copper bulk in acetone. Effect of laser fluence on the size, morphology and structure of produced nanoparticles has been studied. Pulses of a Q-switched Nd:YAG laser of 1,064 nm wavelengths at 7 ns pulse width at different fluences was employed to irradiate the Cu target in acetone. The UV–Vis–NIR absorption spectra of nanoparticles exhibit surface plasmon resonance absorption peak in the visible region. TEM and SEM micrographs indicate that with increasing the laser fluence the average size of spherical Cu nanoparticles is decreased and only the sample which is produced with the highest fluence shows exceptional behavior. It is found that Cu nanoparticles exhibit photoluminescence emission with single peak due to its interband transition.

Modifications in structure and optical property of Cu nanoparticles in SiO2 by post heavy ion irradiation

The implantation-synthesized Cu nanoparticles (NPs) in silica were irradiated with 500keV Xe and Ar ions, respectively. After Xe ion irradiation at a fluence of 2×1016/cm2, the average diameter of Cu NPs was increased from 7.3 to 8.5nm, and especially, Cu NPs with a diameter of 11–14nm were formed beyond the projected range of Cu ions and nearly aligned at the same depth, which presented a higher volume fraction. As a result, the Cu surface plasmon resonance (SPR) absorption peak was enhanced. However, if Xe ion fluence was less than 1×1016/cm2, no clear variation of the Cu SPR absorption peak could be found. Further, it was also revealed that Xe ion irradiation caused the Cu SPR absorption peak to more drastically change than Ar ion irradiation at the same ion fluence. The underlying processes for the above findings were discussed and tentatively proposed.

Synthesis of nanoparticles in SiO2 by implantation of Cu and Zn ions and their thermal stability in oxygen atmoshphere

Cu nanoparticles (NPs) embedded in silica were synthesized by implantation of 45 keV Cu ions at a fluence of 1.01017 cm-2, and then subjected to post irradiation with 50 keV Zn ions at fluences of 0.51017 cm-2 and 1.01017 cm-2, respectively. Zn post ion implantation induced modifications in structures, optical absorption properties of Cu NPs as well as their thermal stability in oxygen ambient have been investigated in detail. Results clearly show that Cu-Zn alloy NPs could be formed in the Cu pre-implanted silica followed by Zn ion irradiation at a fluence of 0.51017 cm-2, which causes an unique surface plasmon resonance (SPR) absorption peak at about 516 nm. Subsequent annealing in oxygen atmosphere results in the decomposition of Cu-Zn alloy NPs, at 450 ℃, and thus, ZnO and Cu NPs appear in the substrate. Further increase of annealing temperature to 550 ℃ could transform all the Zn and Cu into ZnO and CuO. Moreover, results also demonstrate that introduction of Zn into SiO2 substrate could effectively suppress the oxidation of Cu NPs, meanwhile, the existence of Cu could promote thermal diffusion of Zn towards substrate surface, which enhances the oxidation of Zn. The underlying mechanism has been discussed.

Morphology and absorption properties control of silver nanoparticles deposited on two types of sol–gel spherical silica substrates

In this work, the size, distribution, morphology and optical absorption properties of silver nanoparticles are regulated by controlling the type of spherical silica substrate. Two different types of SiO2 microparticles with unmodified and amino-functionalized surface are used as a matrix for Ag nanocrystals deposition. In both cases, silver ions are located on the substrate surface and then are thermally reduced to metallic silver, however, modification of silica spheres with –NH2 groups enables the accomplishment of Ag ions reduction at considerably lower temperatures. Controlled surface functionalization of silica substrate clearly affects the morphology and optical absorption properties of obtained silver nanoparticles. Amine functional groups have a significant influence on the silica dense coverage by Ag nanoparticles. Dense packing of nano-sized metallic silver particles causes red shifting and broadening of surface plasmon resonance (SPR) absorption peak compared to sparse nanoparticles distribution. The size of obtained Ag nanocrystals is ranged from 3nm to 20nm depending on the selected silica substrate as well as silver concentration.

Spectroscopic study of gold nanoparticle formation through high intensity laser irradiation of solution

A spectroscopic study of the gold nanoparticle (NP) formation by high-intensity femtosecond laser irradiation of a gold ion solution was reported. The effect of varying energy density of the laser on the formation of gold NPs was also investigated. The surface plasmon resonance (SPR) peak of the gold nanocolloid in real-time UV-visible absorption spectra during laser irradiation showed a distinctive progress; the SPR absorption peak intensity increased after a certain irradiation time, reached a maximum and then gradually decreased. During this absorption variation, at the same time, the peak wavelength changed from 530 to 507 nm. According to an empirical equation derived from a large volume of experimental data, the estimated mean size of the gold NPs varied from 43.4 to 3.2 nm during the laser irradiation. The mean size of gold NPs formed at specific irradiation times by transmission electron microscopy showed the similar trend as that obtained in the spectroscopic analysis. From these observations, the formation mechanism of gold NPs during laser irradiation was considered to have two steps. The first is a reduction of gold ions by reactive species produced through a non-linear reaction during high intensity laser irradiation of the solution; the second is the laser fragmentation of produced gold particles into smaller pieces. The gold nanocolloid produced after the fragmentation by excess irradiation showed high stability for at least a week without the addition of any dispersant because of the negative charge on the surface of the nanoparticles probably due to the surface oxidation of gold nanoparticles. A higher laser intensity resulted in a higher efficiency of gold NPs fabrication, which was attributed to a larger effective volume of the reaction.

A highly sensitive non-aggregation colorimetric sensor for the determination of I− based on its catalytic effect on Fe3+ etching gold nanorods

I− could accelerate the selective etching along longitudinal direction of gold nanorods (AuNRs) induced by Fe3+ in HCl medium, which decreased the aspect ratio (length/width) of AuNRs, and thus the longitudinal surface plasmon resonance (LSPR) absorption peaks of AuNRs blue shifted (Δλ=λ0−λ), the corresponding absorbance decreased (ΔA=A0−A), and the color of the solution obviously changed. Therefore, a non-aggregation AuNRs colorimetric sensor for the detection of I− was developed. The proposed colorimetric sensor is responsive, simple, selective and sensitive with the limit of quantization (LOQ) of 8.8×10−8M. The highly accurate sensor has been used to determine the content of I− in table salt samples with the results consistent with those obtained by inductively coupled plasma-mass spectroscopy (ICP-MS). Moreover, the morphological changes of AuNRs during the etching procedure were characterized by high resolution transmission electron microscopy (HRTEM) and the sensing mechanism for I− detection was also discussed.