Intense Surface Plasmon Resonance Research Articles

Modulation of inner filter effect of non-conjugated silver nanoparticles on blue emitting ZnS quantum dots for the quantitation of betahistine.

A simple, reliable and efficient fluorescent probe has been developed for the detection and quantitation of betahistine using inner filter effect (IFE) of silver nanoparticles (AgNPs) on zinc sulphide (ZnS) quantum dots. The synthesized ZnS exhibited blue emission at 403nm which was quenched upon mixing with AgNPs due to intensive localized surface plasmon resonance (LSPR) absorption at 401nm. The presence of IFE was confirmed by UV-Visible and fluorescence spectroscopy, dynamic light scattering and transmission electron microscopy. Addition of betahistine caused aggregation of AgNPs as visualized by the change in colour of nano-suspension. The reduced absorption at LSPR resulted in inhibition of IFE leading to higher fluorescence intensities in the presence of betahistine. Parameters such as pH, incubation time and concentration of AgNPs were suitably optimized. The fluorescence signal (I-I0/I0) responded linearly for betahistine in the concentration range from 0.1 to 10μM under the optimized experimental conditions. Due to the aggregation of AgNPs, a simple colorimetric approach was also studied for quantitation of betahistine in the range 1.0-20μM. The limit of detection for fluorescence measurement and colorimetric approach was 0.02μM and 0.23μM, respectively. Further, the proposed method exhibited excellent selectivity towards betahistine in presence of several cations, biomolecules such as glucose, uric acid, creatinine, amino acids and several anti-vertigo medications. The method was applied to quantify betahistine from pharmaceutical products and results obtained were in good agreement with the claimed values. The proposed sensor can serve a low cost, selective, sensitive and a precise tool for routine quantitation of betahistine.

Photo‐Dissociation of CO2 over Plasmonic RuO2 Nanoparticles

AbstractThe synthesis, characterisation and application of RuO2 nanoparticles through a facile hydrothermal preparation technique is described. The prepared solid is extensively characterised and shown to have a narrow size distribution (1.6–3.2 nm) and exhibit an intense surface plasmon resonance giving rise to an absorption band peaking at λ=424 nm. This material is applied in gas‐phase artificial photosynthesis reactions, and interestingly, the only products observed are CO and O2 (at a constant 2 : 1 ratio). Even though this RuO2 catalyst is unable to perform the water‐splitting step of the artificial photosynthesis reaction, it is active in the CO2 photo‐decomposition reaction (ΔG(298.15 K)=64.41 Kcal mol−1), and thus it may be a convenient catalyst for downstream production of methanol or hydrocarbons from a CO2 feedstock.

Phytosynthesis of silver nanoparticles using rhizome extract of Alpinia officinarum and their photocatalytic removal of dye under UV and visible light irradiation

Silver nanoparticles (AgNPs) were successfully synthesized using rhizome extract of Alpinia officinarum (AO) through an eco-friendly green route. The prepared silver nanoparticles (AO-AgNPs) were characterized by a relevant intense surface plasmon resonance (SPR) band at 468 nm measured by UV–vis spectrophotometry. The SPR peaks clearly indicate the formation of silver nanoparticles. The crystalline nature of AgNPs was examined by X-ray diffraction (XRD), and field emission transmission electron microscopy (FE-TEM) analysis showed their shape to be hexagonal with some agglomeration generating different shapes. Fourier transform infrared spectroscopy (FTIR) was employed to determine the functional groups and capping agents of the synthesized silver nanoparticles. A comparison study investigated the photodegradation activity of synthesized AO-AgNPs on malachite green (MG) and methylene blue (MB) dyes under UV and visible light irradiation. The comparative study results revealed that the biosynthesized AO-AgNPs are a potential biomaterial for use as an effective catalyst to remedy environmental pollution.

Surface plasmon resonance sensor based on D-shaped Hi-Bi photonic crystal fiber

A surface plasmon resonance (SPR) refractive index (RI) sensor based on a D-shaped Hi-Bi photonic crystal fiber (PCF) is investigated with finite element method. Through changing the asymmetry of the fiber core along x- and y- axis, it is found that the Hi-Bi structure can greatly enhance the plasmon resonance at near-infrared wavelength, thus effectively reducing the FWHM. Benefiting from this, the designed sensor can provide higher FOM than other works previously reported. In addition, from the design and optimization of sensor structure and material, it is found that compared with the refractive index of the material, the structure has little influence on the sensitivity of the sensor, but can effectively improve the resonance intensity of SPR, which has certain guiding significance for the design and optimization of such PCF SPR sensors in the future.

Synthesis and characterization of 3-(p-tolyl)-2,3-dihydropyrazolo[3,4-b]indole-1(4H)-carbothioamide functionalized gold nanoparticles for the CIEL∗a∗b∗/Yxy colorimetric detection of Cr(VI)

In this study we present a simple colorimetric assay that was used to develop a gold nanoparticles (AuNPs) enabled optical sensor. The colorimetric sensor was fabricated using the ligand 3-(p-tolyl)-2,3-dihydropyrazolo[3,4-b]indole-1(4H)-carbothiomide (TRPIDA_CH3) which was synthesized through the multicomponent reaction of toluidine, thio-semi-carbazide and indole. The synthesized ligand was fully characterized by 1H NMR, 13C NMR, 2D NMR, TOF-MS and elemental analysis. Spherical gold nanoparticles depicted two well-separated surface plasmon resonance (SPR) peaks that were observed at 520 nm and 645 nm. The addition of Cr (VI) into TRPIDA_CH3-AuNPs solution resulted in a decrease of SPR intensity at 520 nm whilst there was an increase in intensity at 645 nm. ImageJ software was used to measure the CIEL∗a∗b∗/Yxy colour dynamics between the reaction of TRPIDA_CH3-AuNPs and Cr(VI). The chromaticity diagram of gold nanoparticle complex with TRPIDA_CH3 correlated with the colour change as observed from RGB values after addition of different concentration of the chromium standards. Furthermore, recoveries for both tap and river water, after spiked with chromium, ranged from 72 to 101% with a limit of detection and limit of quantification of 0.14 and 0.47 μM, respectively. Seven interfering ions, viz., Cr, Cu, Fe, Ni, Zn, Pb and Mn were investigated: low detection limits were observed suggesting minimum interference with the desired analyte occurred. This colorimetric assay is simple and demonstrates high selectivity to Cr (VI) over other heavy interfering metal ions that were tested.

A new and facile nanosilver SPR colored method for ultratrace arsenic based on aptamer regulation of Au-doped carbon dot catalytic amplification.

Here, Au-doped carbon dots (CDAu) nanosols with good stability were prepared by hydrothermal reaction method. We found that CDAu can efficiently catalyze the nanoreaction of reducing AgNO3 by glucose, and at 420nm，the reaction products of yellow spherical silver nanosol exhibit an intense surface plasmon resonance (SPR) absorption peak. The nucleic acid aptamers (Apt) can be adsorbed on the surface of carbon dots, so that their catalytic activity was suppressed, the nanosilvers were reduced, the solution color becomes lighter, and the Abs value was weakened. When As3+ was added, it forms a stable conjugate with the Apt, releases free carbon dots, restored its catalytic activity, and the color and Abs signals enhanced linearly. Based on the Apt regulation and the catalytic amplification effect of CDAu on AgNO3-glucose, a new extremely sensitive SPR spectrophotometric method for the determination of arsenic ion content of 0.025-0.75μg/L was established, and the detection limit of As3+ is 0.01μg/L.

Tunable distributed SPR sensors with symmetrical structures excited by planar waveguides

Measurement ranges of the traditional surface plasmon resonance (SPR) sensors, which use intensity detection method and are excited by waveguides, are limited by the equivalent refractive index of the excited waveguide, not only makes it non-adjustable but also difficult to realize multi-range detection. To solve the above problems, tunable distributed SPR sensors with symmetrical structures excited by planar waveguides are designed. By studying several metrics of a metal-medium-metal SPR sensing structure exited by a planar waveguide, the influence of a metallic material’s thickness, and the medium thickness between the gold films on the measurement characteristics, are accordingly optimized to design the detection system. Double attenuation peaks can be generated under certain conditions, which embodies distributed sensing characteristics. Here, changing the resonance condition by changing the thickness of the measured medium between the metal films makes the measured refractive index range tunable. The planar waveguide with the Fermi refractive index distribution is prepared and the symmetrical sensing structures are arranged longitudinally alongside the direction of light propagation to achieve multiple attenuation peaks, and thus distributed sensing in different measured ranges is realized. The structure of different medium thicknesses excited by planar waveguides is used to test the honey solution with refractive indices varying between 1.33299 and 1.53246 in exciting the surface plasma waves with double attenuation peaks. For any refractive index range, the linear correlation coefficients are all above 0.99232, which demonstrates that the refractive index detection can be carried out within multiple ranges. This result constitutes a theoretical and practical basis for tunable distributed online measurement of the intensity SPR sensors.

Interaction of polyphenols and Ag on the surface plasmon resonance absorption and resonance Rayleigh scattering spectra

Polyphenols are a kind of vital biologically active substances in fruits and vegetables. In this study, with the reductive ability in the alkaline solution, eight polyphenols[(-)-Epigallocatechin gallate (EGCG), (-)-Epigallocatechin (EGC), (-)-Epicatechin gallate (ECG), (-)-Epicatechin (EC), (-)-Gallocatechin gallate (GCG), (-)-Gallocatechin (GC), (+)-Catechin (C) and Gallic acid (GA)] could produce silver nanoparticles(AgNPs) with [Ag(NH3)2]+. It was found that the AgNPs had intense surface plasmon resonance bands at 415 nm and RRS spectra signals at 450 nm, which were linearly related to the concentration of polyphenols. It was used for the spectrophotometric and RRS spectra determination of the former eight polyphenols with low detection limits. The developed method was applied for the determination of polyphenols in tea and products.

ECO-FRIENDLY SYNTHESIS OF SILVER NANOPARTICLES BY USING GREEN METHOD: IMPROVED INTERACTION AND APPLICATION IN VITRO AND IN VIVO.

The present study was aimed to biosynthesis of silver nanoparticles by using rhaminolipid produced from local isolate Pseudomonas aeruginosa as reducing and stabilizing agent. Silver nanoparticles (AgNPs) synthesized by green method have shown several applications such as biomedical, anticancer, bio sensing, catalysis etc. Characterization study of purified bioemulsifier using thin layer chromatography (TLC) was demonstrated that the biosurfactant contains mono, and di- rhamnolipid with Rf values of 0.86 and 0.36 respectively. Optimization results of biosynthesis silver nanoparticles were revealed that an increasing in intensity of Surface Plasmon Resonance (SPR) bands of nanoparticles with shifting at wavelength (400 nm). Also optimum synthesis of AgNPs was at pH 5, Temperature 40℃, reaction time 5 minutes with concentration of rhaminolipid as reducing agents (2×10-3w/v) and Silver ion concentration (6×10-3 mol/L). The result of X-ray diffraction was indicated that the size of silver nanoparticles observed was 38 nm and show relatively stable peak at -23.2 mV. Finally, the minimum inhibitory concentration of Ag NPs against human pathogenic bacteria obtained at concentration (1mg/ml) for both gram negative and gram-positive bacteria. The results of anti-inflammatory effects of Ag NPs obviously, cleared that the infection of test animals treated with AgNPs were completely healed after 6 days of treatment, while the animals treated with fucidin (as control) not exhibited any healing in the infection.

Sodium gluconate capped silver nanoparticles as a highly sensitive and selective colorimetric probe for the naked eye sensing of creatinine in human serum and urine

A highly selective and fast analytical assay using sodium gluconate -capped Ag nanoparticles (GA@AgNPs) was developed for the determination of creatinine by UV–Vis spectrophotometric detection. By adding creatinine to the GA@AgNPs solution, the extinction intensity of the surface plasmon resonance (SPR) band of the corresponding UV–Vis spectrum of GA@AgNPs at 393 nm reduced and meanwhile a new absorption peak appeared at 560 nm gradually with increasing creatinine concentratin. Induced aggregation of GA@AgNPs by creatinine, accompanied with color changes from yellow to red, can be directly observed by the nacked eye in five minutes. The extinction spectra ratio of A560/A393 was used for the colorimetric determination of creatinine. Effective parameters on the absorption intensity such as the sample pH, the type and buffer concentration, ionic strength and AgNPs concentration were optimized. Under the optimal conditions, a linear relationship between the SPR intensity ratio of A560/A393 values and creatinine concentrations is obtained over the range of 0.3–50 nM with a correlation coefficient of 0.9763 and a limit of detection of 0.2 nM. The relative standard deviation (RSD%) for five measurements of creatinine solution at 1 nM was 4.0%, exhibiting good repeatability. The results indicate that the developed probe can be successfully used for the determination of creatinine in serum and urine samples with satisfactory results.

Photodegradation of Methylene Blue Dye Using Nanocomposites of Copper Sulfide Doped with Fe/Cd/Zr as Nanophotocatalyst

Objectives: To characterize and to know the nature of the synthesized products and identify the photocatalytic response of the hybrid nanocomposites was investigated by the decolourization of (MB) dye under natural Sunlight radiation. Methods/statistical analysis: We report fabrication of mesoporous nanocomposites (Fe–CuS, Cd–CuS, Zr–CuS) with uniform nanostructures via a hydrothermal method employing copper nitrate trihydrate (Cu (NO3).3H2O), Thiourea (Tu,Sc(NH2)2, Iron trinitrate (Fe(No3)3), (Cd(No3)3) and (Zr(No3)3) as starting materials with cationic surfactant cetyltrimethylammonium bromide (CTAB) as stabilizer/ size controller and ethylene glycol as solvent at 130˚C temperature. The products were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy TEM, and UV-Vis spectrum (UV) analysis. Findings: X-ray diffraction (XRD) spectra confirmed the Fe doped copper sulfide nanocomposites are crystalline in nature with the hexagonal CuS phase. XRD pattern showed Fe doped spherical structure of CuS with a grain size of 21 nm. An intense surface Plasmon resonance between 250–300 nm in the UV–Vis spectrum clearly reveals the formation of Fe doped copper sulfide nanocomposites. The XRD pattern of Cd incorporated CuS shows crystallite nature and crystallinity increases with the addition of cadmium on CuS. The observed results show that Zr is homogeneously dispersed on CuS and well separated from one another. The XRD results confirm the presence of well-dispersed cubic ZrS2 on the covellite CuS surface. Photo reactivity of copper sulfide nanoparticles as undoped and doped with ferrous, cadmium and Zirconium were studied in the decolorization of methylene blue under natural sunlight. The concentration of dopants and concentration of dye are variables that influence the photoreactivity of nanocatalysts. Application/improvements: The prepared nanoparticles CuS, Fe–CuS, Cd–CuS and Zr–CuS show the most degradation efficiency. The optimum dosage of the photocatalyst was 120 mg/L. In the optimized conditions, the degradation efficiency was 86–95% for methylene blue in irradiation time of 150 min.Keywords: Nanophotocatalyst, Copper Sulfide, Methylene Blue, Photodegradation.

GREEN SYNTHESIS OF SILVER NANOPARTICLES AND THEIR CATALYTIC APPLICATION FOR THE DEGRADATION OF ORGANIC POLLUTANTS

A simple and rapid method of green synthesis of silver nanoparticles (AgNPs) was developed using aqueous extract of grape pomas (GP) obtained from by plasma-chemical extraction technique, and their catalitic potential was investigated. With this aim, the plasma-chemical obteained aqueous solutions of grape pomace and AgNO3 (0.25-6.0 mM) were mixed (1:1 v/v), and heated for 10 mim. The synthesized GP-AgNPs were characterized by UV-visible spectroscopy, AFM, DSL analyses. The synthesized AgNPs showed an intense surface plasmon resonance band at 405-420 nm. The AgNPs were in highly uniform shape (everage size 20 nm). The role of pH in the green synthesis of silver nanoparticles (AgNPs) is investigated. The presence of silver nanoparticles with sun light was proven very effective for degradation of organic dyes. The reaction kinetics was found to be pseudo first order with respect to the dye concentration. The outcomes of the current study confirmed that the synthesized AgNPs had an awesome guarantee for application in catalysis and wastewater treatmen.

The Use of Spectral Ellipsometry and Raman Spectroscopy in Screening Diagnostics of Colorectal Cancer

Diagnostic pilot monitoring of the groups of healthy patients and patients with colorectal cancer (CRC) at different stages of the disease was carried out using Raman spectroscopy (RS) and measuring the state of polarized light near the conditions of observation of surface plasmon resonance (SPR). The reaction of the blood serum antigens with antibodies to serum M2 pyruvate kinase (M2-PK) nears the conditions of observation of SPR was used for diagnosing; for this, the Ellipse-SPEC spectral ellipsometric complex created at the Rzhanov Institute of Semiconductor Physics (Siberian Branch, Russian Academy of Sciences) and having a high sensitivity, accuracy, and nondestructive nature of the effect on the studied sample, was used in the work. The peak intensities at 1005, 1157, and 1520 cm–1 in Raman spectra in CRC patients as compared with healthy individuals (as well as the intensity of surface plasmon resonance) were significantly lower, correlating with the stage of the disease and the presence of metastases; this allows to consider these optical methods for studying the blood serum as promising diagnostic approaches in diagnosis CRC, including in the early stages of the disease.

Synergetic antibacterial and anticarcinogenic effects of Annona squamosa leaf extract mediated silver nano particles

The present investigation deals with the antibiotic potentiation and antitumor activity of green processed Ag NPs. Silver nanoparticles were prepared using Annona squamosa (AS) leaf extract as a potent bio-reducer and stabilizer. An intense surface plasmon resonance (SPR) band around 430 nm indicates the formation of well-stabilized silver nano particles, which was conformed from UV–Visible spectroscopy. TEM analysis manifests the formation of crystalline AS-Ag NPs through assorted functional groups in a size range of 7–8 nm. The antibacterial activity along with the combinatorial potential of AS-Ag NPs was assessed with neomycin against five wound/burn infection inducing skin isolates such as S. aureus, B. subtilis, E. faecium, P. aeruginosa and E. coli. The combinatorial analysis revealed synergetic pharmacodynamic interaction between nanoparticles and antibiotic with all the tested bacteria. Besides, AS-Ag NPs cytotoxicity was tested on mammalian cells (HEK-293) and cancerous cells (HeLa) with a fact-finding that AS-Ag NPs possess selective nature to target and kill foreign cells with a biocompatibility towards mammalian cells. Thus, our findings encourage nano green synthesis as an exploiting nano-medicine, owing to their effective cancer therapy and antibiotic potentiating capability by overcoming biocompatibility limitations of conventional therapeutics.

Eco-Friendly Green Synthesis of Silver Nanoparticles from Egyptian Honey: Evaluating its Antibacterial Activities

THIS RESEARCH article describes a strong approach for the green synthesis of silver nanoparticles (AgNPs) that employs a local black seed honey (BSH). Honey was chosen as the eco-friendly reducing and stabilizing agent replacing most reported reducing agents which represent highly biological risk to the society and environment. Honey reduced silver ions into AgNPs after 20min in a stirred reaction mixture. Nanoparticles of different sizes were obtained, and the solution turned black over time. The antibacterial activity of AgNPs was investigated against eight pathogenic bacterial strains; five Gram-negative and three Gram-positive. AgNPs were potentially effective against the Gram-negative more than Gram-positive bacterial strains. E. coli and P. aeruginosa were the highly susceptible strains with 6.3μg/ml minimum inhibitory concentrations (MICs). The AgNPs were characterized by perform UV-visible spectroscopy, fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) imaging. The colloid obtained at a pH of 9 was found to be spherical in shape and was distributed with a certain amount of agglomeration. An intense surface plasmon resonance band at 400nm in the UV-visible spectrum clearly revealed the formation of AgNPs after 72hr. TEM showed spherically shaped AgNPs, and the sizes of the nanoparticles ranged from 25-70nm. AgNPs had broad spectrum antibacterial property thus it can be explored further for medical and therapeutic applications.

Improvement of amperometric laccase biosensor using enzyme-immobilized gold nanoparticles coupling with ureasil polymer as a host matrix

Synthesis of gold nanoparticles (Au-NPs) was performed using method of an inorganic chemical reduction. The synthesized Au-NPs showed an intensive surface plasmon resonance band at 525 nm that is typical for corresponding Au-NPs reported in literature. The structural and morphology characterizations of the obtained Au-NPs were carried out using SEM, AFM, TEM, and X-ray spectral analysis. The possibility of usage of Au-NPs as a carrier for covalent immobilization of commercial laccase and the combination of the obtained bio-Au-NPs with ureasil polymers as host matrixes for formation of bio-nanocomposite films was studied. The prospect of using the obtained bio-nanocomposite films in biosensor technologies in order to improve the bioanalytical characteristics of sensory elements has been proved.

Phase Separation in Liquid Metal Nanoparticles

Nanoparticles produced from gallium-based liquid metal alloys have been explored for developing applications in the fields of electronics, catalysis, and biomedicine. Nonetheless, physical properties, such as phase behavior at micro-/nanosize scale, are still significantly underexplored for such nanoparticles. Here, we conduct an in situ investigation of phase behavior for gallium-based liquid metal nanoparticles and discover the unprecedented coexistence of solid particles in spherical liquid metal shells without the support of a crystalline substrate. The particles can also transform into solid Janus nanoparticles after temperature cycling. In addition, we investigate the optical properties of the nanoparticles before and after phase separation using in situ electron energy-loss spectroscopy. Most importantly, we discover that increasing the content of indium within the nanoparticle can stabilize the solid-core/liquid-shell structure at room temperature. This study provides a foundation to engineer liquid metal nanoparticles for developing new applications in nanoscale optical platforms and shape-configurable transformers.Although various electronic, chemical, and biomedical applications have been demonstrated for nanoparticles made from gallium-based liquid metal alloys, fundamental physical properties such as phase behavior of such nanoparticles are still significantly underexplored. Here, Tang and coworkers present the in situ investigation of phase separation in binary and ternary spherical liquid metal nanoparticles upon cooling, and demonstrate the coexistence of solid core/liquid shell without the support of a crystalline substrate. This study provides insight into engineering such nanoparticles for the development of new applications.Despite gallium-based liquid metal alloys attracting extensive attention for various applications, their phase behavior at the nanoscale is still underexplored. Understanding the impact of phase separation in nanoparticles can be extremely useful for developing new structures and exploring suitable applications. Here, we report on the investigation of phase behavior for spherical nanoparticles made from gallium-based liquid metal alloys upon cooling. We discover the thermally stable coexistence of solid cores in spherical liquid metal shells without the support of a crystalline substrate at room temperature. Given the unique properties of liquid metal, together with the facile process for producing core-shell and Janus nanoparticles, this work will encourage further investigation of the properties of such nanoparticles for developing applications in the fields of electronics, catalysis, nanomedicine, and beyond.

Robust one-pot synthesis of citrate-stabilized Au@CeO2 hybrid nanocrystals with different thickness and dimensionality

Well-defined colloidal Au@CeO2 hybrid nanocrystals (NCs) comprising different core/shell morphologies have been synthesized via a novel and simple one-pot aqueous approach. The method allows producing hybrid morphologies composed by an active and accessible Au core coated by a porous CeO2 shell with varying shell thickness and dimensionality by simply adjusting the Au3+/Ce3+ precursor ratio. These hybrid NCs are highly monodisperse and well-dispersed in water, showing intense surface plasmon resonance bands that offer unique opportunities for advanced material applications, such as plasmonics and catalysis.

Dual Activities of Nano Silver Embedded Reduced Graphene Oxide Using Clove Leaf Extracts: Hg2+ Sensing and Catalytic Degradation

AbstractSilver nanoparticles embedded reduced graphene oxide (rGO−Ag) nanocomposites are synthesized by green technique using clove leaf aqueous extract as reducing agent. The surface plasmon resonance (SPR) peak of silver nanoparticles (Ag NPs) at 410 nm in rGO−Ag nanocomposites is analysed by UV–visible spectroscopy. The intensity of surface plasmon resonance (SPR) peak of Ag NPs in rGO−Ag nanocomposites is decreased with addition of Hg2+ ion at small interval of time. This is due to the occurrence of redox reaction between Ag(0) and Hg2+ and also for the formation Ag/Hg amalgam. The lower limit of detection (LOD) of rGO−Ag nanocomposites for Hg2+ ion is found to be 9.5 nM. Moreover, the rGO−Ag nanocomposites may be used as catalyst for degradation of methylene blue (MB) by sodium borohydride (NaBH4) at ambient temperature. The adsorption efficiency of methylene blue is increased due to hydrogen bonding and electrostatic interaction along with π–π stacking between the catalyst and the dye molecules. The methylene blue is degraded within a small time due to large surface area and more number of active sites of rGO−Ag nanocomposites. The as‐synthesized nanocomposite is a potential hybrid material having dual activity as Hg2+ sensing and catalytic behaviour in degradation of methylene blue.

Improved stability of gold nanoparticles on the optical fiber and their application to refractive index sensor based on localized surface plasmon resonance

A simple method for firmly immobilizing gold (Au) nanoparticles on optical fibers without using any binding molecules, via an Au capping process based on seed-mediated growth which controls the size of Au nanoparticles (AuNPs), was investigated. Changes in the size of AuNPs in relation to the growth times of these particles in aqueous chloroauric acid solution were examined. Connectivity between AuNPs and the optical fiber surface was analyzed using a spectrometer and a field emission scanning electron microscope. Because of advantages gained via this immobilization method, the fiber-optic based localized surface plasmon resonance sensor demonstrated higher stability and an improved refractive index sensitivity. The sensing performance of the sensor was studied using the antibody-antigen model. Changes in localized surface plasmon resonance intensity were highly correlated to antigen concentrations. Based on these results, we tested our sensor's ability to detect thyroglobulin (Tg) in the sera of patients, by comparing our results with those obtained via currently used clinical techniques.