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2.
The photoluminescence of silver nanoparticles glasses obtained by ionic exchange and annealing is investigated for various
ionic exchange times. These glasses are prepared by immersion of silicate glass samples in a molten salt bath of molar concentration
10% AgNO 3 in NaNO 3 at T = 320 °C. Scanning electron microscopy measurement in electron diffraction scattering (EDS) configuration confirms the silver
presence in the various glasses, and the UV/visible absorption gives the evolution of the spectra after ionic exchange and
plasmon resonance apparition after annealing. After annealing at 450 °C, both diagnostics inform us about the particles’ formation
and the silver rediffusion. Silver nanoparticle growth after annealing prior leads to photoluminescence exaltation and quenching
for the longest exchange samples. Subsequently, we propose potential mechanisms of the nanoparticle formation with an initial
depolymerization of the silicate network during the ionic exchange and repolymerization during annealing. 相似文献
3.
Spectroscopic study of photoluminescence (PL) enhancement due to the coupling of the light emitters in InGaN/GaN multiple quantum wells (MQWs) with the localized surface plasmon (LSP) resonance on silver (Ag) nanoparticles ( NPs) is performed using the confocal microscopy and scanning near-field optical microscopy (SNOM) techniques. The paper is focused on revealing the emission enhancement due to coupling with a single metal nanoparticle. The enhancement is confirmed by time-resolved study of differential transmission (DT). The enhancement suppression caused by potential fluctuations due to the variations of indium content and quantum well (QW) width is also studied. A strong photoexcitation intensity dependence of the emission enhancement due to spectral runaway of the MQW emission from the resonance as carrier density increases is observed both in spatially integrated spectra and in the vicinity of a single nanoparticle. 相似文献
4.
The oxidation reaction of luminol with AgNO 3 can produce chemiluminescence (CL) in the presence of silver nanoparticles (NPs) in alkaline solution. Based on the studies of UV‐vis absorption spectra, photoluminescence (PL) spectra and CL spectra, a CL enhancement mechanism is proposed. The CL emission spectrum of the luminol–AgNO 3–Ag NPs system indicated that the luminophore was still 3‐aminophthalate. On injection of silver nanoparticles into the mixture of luminol and AgNO 3, they catalysed the reduction of AgNO 3 by luminol. The product luminol radicals reacted with the dissolved oxygen, to produce a strong CL emission. As a result, the CL intensity was substantially increased. Moreover, the influences of 18 amino acids, e.g. cystine, tyrosine and asparagine, and 25 organic compounds, including gallic acid, tannic acid and hydroquinone, on the luminol–AgNO 3–Ag NPs CL system were studied by a flow‐injection procedure, which led to an effective method for detecting these compounds. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
5.
The optical response of a new graphene-like material Si2BN’s nanostructures and some kinds of hybrid structures formed by Si2BN and metal nanoparticles was studied by using time-dependent density functional theory (TDDFT). We found that the periodic structures of Si2BN have wider absorption ranges than graphene. When the impulse excitation polarizes in different directions (armchair-edge direction and zigzag-edge direction), the absorption spectra of Si2BN nanostructures would be different (optical anisotropy). And in the hybrid structures, the increase of metal nanoparticles’ number brings the absorption intensity strengthening and red shift, which means a stronger ability of localized surface plasmon tuning. Also, the different metal nanoparticles were used to form the hybrid structures; they show an obviously different property as well. In addition, in the kinds of situations mentioned above, the plasmons were produced in visible region. This investigation provides an improved understanding of the plasmon enhancement effect in graphene-like photoelectric devices. 相似文献
6.
TiO 2 nanotube arrays (TiO 2 NTs) were fabricated by anodic oxidation and then Ag nanoparticles (Ag NPs) were assembled in TiO 2 NTs (Ag/TiO 2 NTs) by microwave-assisted chemical reduction. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence spectrum (PL), UV–vis absorption spectrum (UV–vis), and Raman spectrum, respectively. The results showed that Ag NPs were well dispersed on the surface of TiO 2 NTs with metallic state. The surface plasmon resonance (SPR) effect of Ag NPs could extend the visible light response and enhance the absorption capacity of TiO 2. Furthermore, Ag NPs could also restrain the recombination of photo-generated electron–hole pairs of TiO 2 NTs efficiently. The methylene blue photodegradation experiment proved that the SPR phenomenon had an effect on photoreaction enhancement. The results of photocatalytic water splitting indicated that Ag/TiO 2 NTs samples had better photocatalytic performance than pure TiO 2 NTs. The corresponding hydrogen evolution rate of Ag/TiO 2 NTs prepared with 0.002 M AgNO 3 solution was 3.3 times as that of pure TiO 2 NTs in the test condition. Additionally, the mechanism of catalyst activity enhanced by SPR effect was proposed. 相似文献
7.
In transparent conducting oxide films, tuning of plasmonic resonance is directly controlled by free electron concentration and thus by activated dopants. In this study, large area AlxInyZn1-x-yO thin films at various concentrations were prepared by spray coating using water as a solvent. The effect of Al/In dopant ratio on the structural, electrical, optical, and plasmonic properties was investigated. Tuning of optical response to a well-defined plasmon resonance is correlated to the above properties of AlxInyZn1-x-yO films. Theoretical fitting based on the Drude-Lorentz (D-L) theory was utilized for extracting the dielectric spectra and cross-over wavelength (ωc). The studies revealed plasmonic properties in NIR for the films with Al/In ratios of A5I5, A2.5I7.5, and A0I10, indicating In as the most activated dopant. Surface plasmon mode simulated using the extracted permittivity values showed the influence of mobility of these films on the broadening of the dip. The minimum plasmonic loss suggests the suitability as an alternative plasmonic material in the near infrared. 相似文献
8.
A highly sensitive dual-core photonic crystal fiber based on a surface plasmon resonance (PCF-SPR) biosensor with a silver-graphene layer is described. The silver layer with a graphene coating not only prevents oxidation of the silver layer but also can improve the silver sensing performance due to the large surface-to-volume ratio of graphene. The dual-core PCF-SPR biosensor is numerically analyzed by the finite-element method (FEM). An average spectral sensitivity of 4350 nm/refractive index unit (RIU) in the sensing range between 1.39 and 1.42 and maximum spectral sensitivity of 10,000 nm/RIU in the sensing range between 1.43 and 1.46 are obtained, corresponding to a high resolution of 1 × 10−6 RIU as a biosensor. Our analysis shows that the optical spectra of the PCF-SPR biosensor can be optimized by varying the structural parameters of the structure, suggesting promising applications in biological and biochemical detection. 相似文献
9.
There is increasing interest in tuning the physical properties of semiconductor nanostructures using metal nanoparticles. In this work, ZnO nanosphere covered with Ag nanoparticles were synthesized using gamma–radiation-assisted method. The amount of deposited Ag nanoparticles is controlled by changing irradiation dose in the range of 30–100 kGy in order to tune the semiconductor–metal interaction. The successful deposition of Ag on the ZnO nanoparticles is examined by analyzing the morphology, microstructure, optical, and magnetic properties of ZnO/Ag nanoparticles through field emission scanning electron (FESEM), microscopy X-ray diffraction spectra, UV-visible absorption, photoluminescence measurement, and vibrating sample magnetometer. FESEM and elemental mapping results confirmed that Ag nanoparticles have been concentrated at the surface of spherical ZnO particles. Moreover, formation of pure metallic Ag nanoparticles has been confirmed by XRD analysis. UV-visible absorption spectra of obtained ZnO/Ag showed two combined peaks, a weak peak at the shoulder around 360 nm corresponds to ZnO and a sharp absorption at 420 nm refers to spherical Ag nanoparticles. Obtained results from photoluminescence revealed that the near-band-edge emission and defect-related visible emission bands of ZnO could be enhanced dramatically at the same time by deposition of Ag nanoparticles, which was ascribed to localized surface plasmon–exciton coupling and surface plasmon scattering. Controlling the semiconductor and metal coupling effect is interesting because of its application in highly efficient optoelectronic devices and biosensor. 相似文献
10.
In this article, we investigate the plasmon-dielectric spectral interaction in the Ag/InSe and Al/InSe thin-film interfaces. The mechanism is explored by means of optical absorbance and reflectance at terahertz frequencies and by the impedance spectroscopy at gigahertz frequencies. It was observed that the interfacing of the InSe with Ag and Al metals with a film thickness of 250 nm causes an energy band gap shift that suits the production of thin-film optoelectronic devices. The reflectance and dielectric constant and optical conductivity spectral analysis of these devices displayed the properties of wireless band stop filters at 390 THz. The physical parameters which are computed from the conductivity spectra revealed higher mobility of charge carriers at the Al/InSe interface over that of Ag/InSe. The respective electron-bounded plasmon frequencies are found to be 2.61 and 2.13 GHz. On the other hand, the impedance spectral analysis displayed a microwave resonator feature with series resonance peak position at 1.68 GHz for the Al/InSe/Ag interface. In addition, the temperature-dependent impedance spectra, which were recorded in the temperature range of 300–420 K, revealed no significant effect of temperature on the wave trapping properties of the Al/InSe/Ag interface. The sensitivity of the interfaces to terahertz and gigahertz frequencies nominates it as laser light/microwave traps, which are used in fibers and communications. 相似文献
11.
Ag-loaded TiO 2 (Ag/TiO 2) nanocomposites were prepared by microwave-assisted chemical reduction method using tetrabutyl titanate as the Ti source. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N 2 adsorption–desorption isotherms, UV–vis absorption spectrum, X-ray photoelectron spectrum, photoluminescence spectrum, and Raman scattering spectrum, respectively. Results revealed that Ag nanoparticles (NPs) were successfully deposited on TiO 2 by reduction of Ag +, and the visible light absorption and Raman scattering of TiO 2 were enhanced by Ag NPs based on its surface plasmon resonance effect. Besides, Ag NPs could also effectively restrain the recombination of photogenerated electrons and holes with a longer luminescence life time. In addition, photocatalytic reduction of CO 2 with H 2O on the composites was conducted to obtain methanol. Experimental results indicated that Ag-loaded TiO 2 had better photocatalytic activity than pure TiO 2 due to the synergistic effect between UV light excitation and surface plasmon resonance enhancement, and 2.5 % Ag/TiO 2 exhibited the best activity; the corresponding energy efficiency was about 0.5 % and methanol yield was 405.2 μmol/g-cat, which was 9.4 times higher than that of pure TiO 2. Additionally, an excitation enhancement synergistic mechanism was proposed to explain the experimental results of photocatalytic reduction of CO 2 under different reaction conditions. 相似文献
12.
In this paper, we have inspected the optical characteristics of one-dimensional periodic structure (1DPS) of TiO2 and MgF2 dielectric materials with defect layer of liquid crystal (LC) sandwiched with two silver layers, i.e., (TiO2|MgF2)3|Ag|LC|Ag|(TiO2/MgF2)3 using transfer matrix method (TMM). The optical tunable properties of considered periodic structures investigated at different incident angles and temperatures for TE and TM modes. Our study shows that absorption peak of 1DPS varies with incident angle and temperature. The defect layer (Ag-LC-Ag), sandwiched LC within two metallic (Ag) layers, exhibits the surface plasmon waves at the metal LC interfaces. The effect of surface plasmon waves can be better understand through the optical sensing property of such defect periodic structure. The detailed study concludes that such a type of one-dimensional periodic structure (1DPS) may be useful to design a tunable sensor and monochromatic filter. 相似文献
13.
The magnetic/metallic nanocomposites are special intelligent materials and find many applications in photonics, magneto-optical devices, and biosensors. This paper introduces the synthesis and performance of Fe3O4/Ag ferrofluids using a facile one-step modified co-precipitation method. The nanocomposites were characterized using X-ray diffraction, scanning electron microscopy, XPS, and Fourier transform infrared spectra for structure, morphology, and component investigation, respectively. The viscosity, stability, magnetic, and magneto-optical properties of the ferrofluids were measured through the vibrating sample magnetometer, Faraday rotation optical bench, and viscosity tester. Fe3O4/Ag-based ferrofluids demonstrated good stability (did not agglomerate for 120 h), big magnetic field-dependent-viscosity, surface plasmon resonance effect, superpagamagnetic nature, and improved Faraday effect; these characters are good for MO sensing application. The Verdet constant of ferrofluids at 633 nm increased from 5.66 to 8.53 × 10−2 deg/G cm after Ag coating on Fe3O4. 相似文献
14.
We demonstrate the optical response of metal nanoparticles and their interaction with organic-inorganic perovskite (methyl ammonia lead halide (CH3NH3PbI3)) environment using discrete dipole approximation (DDA) simulation technique. Important optical properties like absorption, scattering, and electric field calculations for metal nanoparticle using different geometry have been analyzed. The metal nanoparticles embedded in the perovskite media strongly support surface plasmon resonances (SPRs). The plasmonic interaction of metal nanoparticles with perovskite matrix is a strong function of MNP’s shape, size, and surrounding environment that can manipulate the optical properties considerably. The cylindrical shape of MNPs embedded in perovskite environment supports the SPR which is highly tunable to subwavelength range of 400–800 nm. Wide range of particle sizes has been selected for Ag, Au, and Al spherical and cylindrical nanostructures surrounded by perovskite matrix for simulation. The chosen hybrid material and anisotropy of structure together make a complex function for resonance shape and width. Among all MNPs, 70-nm spherical silver nanoparticle (NP) and cylindrical Ag NP having diameter of 50 nm and length of 70 nm (aspect ratio 1.4) generate strong electric field intensity that facilitates increased photon absorption. The plasmonic perovskite interaction plays an important role to improve the absorption of photon inside the thin film perovskite environment that may be applicable to photovoltaics and photonics. 相似文献
15.
Diamagnetic TeO2-PbO-B2O3 glasses were melt-quenching fabricated and characterized for Fe3O4/Ag nanoparticles doping through radio-frequency sputtering and thermal treatment techniques. The surface plasmon resonance influenced structure, composition, optical, and magneto optical properties of Fe3O4/Ag doped glasses were investigated through XRD, SEM, XPS analysis, and Faraday rotation measurement. The optimized sputtering and thermal conditions Fe3O4 and Ag nanoparticles were obtained. Under the optimized conditions, a great enhancement of Faraday rotation, thermal property, and big UV cutoff red-shift due to the excited surface plasma’s resonance effect was achieved in diamagnetic glass. 相似文献
16.
Au/Ag core/shell nanoparticles are fabricated by laser-ablating Ag plates in Au colloid solution. The absorption band is found to blue shift with increasing ablation time. Mie theory calculations show that the shift is caused by the increase of the Ag shell thickness. The average Ag shell thickness can be determined from the measured absorption peak. Using the plasmon hybridization approach, we show that the absorption band around 510 nm originates from an anti-bonding mode ω ?+ caused by the interaction between a bonding Ag shell mode ω ?? and Au sphere mode ω S-Au. The blue shift of the ω ?+ mode with the increase of Ag shell thickness is also well predicted by the hybridization theory. 相似文献
17.
We report a new concept of tuning plasmonic colors of two-dimensional crystalline silver nanoparticle sheets with layer-by-layer structures. The multilayered crystalline sheets fabricated by the Langmuir–Schaefer method keep the localized surface plasmon resonance bands at the same position ( λ max?=?465 nm) on quartz, while they change their colors drastically on metal substrates depending on the number of layers (one to five layers). The response of the absorption spectra was absolutely nonlinear, with maximum absorption for two or three layers. The obtained results were well reproduced by the finite difference time domain simulation. The simulation confirmed that these plasmonic colors originate not only from near-field coupling of plasmon resonance but also far-field nano-optics of the multilayered silver nanoparticle sheets. 相似文献
18.
The present work reports an investigation of surface plasmon resonance (SPR) of silver nanoparticles in SiO 2–TiO 2 hosts. The surface plasmon resonance of silver nanoparticles was observed in the wavelength range 300–400 nm. Numerical calculation of SPR of silver nanoparticles with spherical morphology was done on the basis of discrete dipole approximation (DDA) method. The observed fluorescence spectrum fits well with the theoretically calculated one. The luminescence enhancement is attributed to the strong local electric field which increases the exciting and emitting photons coupled to SPR. An effort has been made to study the surface plasmon mediated excitation energy transfer (EET) between two spherical metal nanoparticles. The van der Waals (vdW) energy between plasmonic silver nanoparticles in the present hosts has been estimated. 相似文献
19.
Here, we report for the first time the synthesis of bismuth-coated silver nanoparticles in dichroic bismuth glass nanocomposites
by a novel and simple one-step melt quench technique without using any external reducing agent. The metallic silver nanoparticles
(Ag NPs) were generated first, and subsequently, metallic bismuth was deposited on the Ag NPs and formed a thick layer. The
reduction of Bi 3+ to Bi o and subsequently its deposition on the Ag NPs (which were formed earlier than Bi o) in the K 2O–Bi 2O 3–B 2O 3 (KBB) glass system have been explained by their standard reduction potentials. The UV–vis absorption spectra show a prominent
surface plasmon resonance (SPR) absorption band at 575 nm at lower concentrations (up to 0.01 wt%); three bands at 569, 624
and 780 nm at medium concentration (0.02–0.03 wt%); and two weak bands at 619 and 817 nm at highest concentration (0.06 wt%)
of silver. They have been explained by the electrodynamics theories. TEM images reveal the conversion of spheroidal (5–15 nm)
to hexagonal (10–35 nm) shaped Ag NPs with the increase in concentration of silver (up to 0.06 wt%). SAED pattern confirms
the crystalline planes of rhombohedral bismuth and cubic silver. Thermal treatment at 360 °C, which is the glass transformation
temperature ( T
g) of the sample containing lower concentration of silver (0.007 wt%), shows red-shifted SPR band due to increase in size of
NPs. Whereas the sample containing higher concentration (0.06 wt%) of silver under similar treatment exhibited changes in
SPR spectral profile happened due to conversion to spherical NPs from hexagonal shape and reduction in size (10–20 nm) of
NPs after heat treatment for 65 h. HRTEM images corroborate the different orientations of the NPs. FESEM images reveal hexagonal
disk like structure having different orientations. Dichroic nature of the nanocomposites has been explained with the size
and shape of Ag nanoparticles. We believe that this work will create new avenues in the area of nanometal–glass hybrid nanocomposites
and the materials have significant applications in the field of optoelectronics and nanophotonics. 相似文献
20.
The optical properties of a novel nanostructure consisting of a hexagonal array of aligned vertically three-layered metal-dielectric-metal nanodisks on a silver film are theoretically studied through the finite-difference time-domain method. The novel nanostructure exhibits three obvious optical transmission bands due to the excitation of subradiant plasmon modes, superradiant plasmon modes, and Fano resonances. Surface plasmon polaritons of the underlying Ag film also play a significant role on these three optical transmission bands via coupling with localized surface plasmons of nanodisk pairs. Moreover, the nanostructure also exhibits a good tunability of optical response by modifying the sizes of cylinders, the thickness of underlying metal film, and the dielectric constant of middle layer. These results demonstrate the nanostructure with great advantages in optical sensors and filters. 相似文献
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