Surface Plasmon Resonance Of Ag Nanoparticles Research Articles

Enhanced non-linear optical properties of Eu3+ activated glasses by embedding silver nanoparticles

Tri-positive lanthanide ion (Eu3+) activated glasses doped with different concentrations of silver (Ag0) nanoparticles obtained using thermal reducing agent were fabricated by applying the method of melt quench. The formation of Ag0 nanoparticles in glasses was revealed by the surface plasmon resonance (SPR) peak in the absorption spectra. Transmission electron microscopic measurements confirmed the presence of spherically shaped Ag0 nanoparticles of different size distribution. The absorption spectra showed a red–shift of the SPR peak with an increase in AgNO3 concentration occurring through Ostwald's ripening process because of the growth of particle size (as evidenced from microscope images). The non-linear optical (NLO) and optical limiting measurements were performed in the near infrared spectral region and femtosecond pulse excitation. The non-linear parameters were found to increase as the AgNO3 concentration increased to 0.6 mol %, however, the parameters subsequently decreased at higher doping level. The optical limiting threshold values demonstrated a reverse trend. The increase in non-linear optical properties regarding Ag nanoparticles concentration attributed to the enhancement of polarizabilities of glasses that occurred through local field stimulated by SPR of Ag nanoparticles when exposed to laser radiation of high energy. The increase in NLO coefficients (particularly the non-linear absorption coefficient) and the decrease in optical limiting threshold values with AgNO3 concentration (up to 0.6 mol %) indicated that these glasses containing 0.6 mol % AgNO3 are useful for the construction of the power optical limiters that function at the infrared region in the femtosecond pulse regime.

Synthesis of Ag–Carbon–TiO2 composite tubes and their antibacterial and organic degradation properties

Ag–Carbon–TiO2 composite tubes were prepared by using polystyrene/AgNO3 composite fibers as a sacrifice template and a co-pyrolysis process. The Ag–Carbon–TiO2 tubes were characterized by SEM, TEM, X-ray diffraction, Raman spectrum, XPS, and UV–vis spectrum. The results showed that the Ag–Carbon–TiO2 tubes possessed uniform tubular structure with amorphous carbon, graphitic carbon, and Ag nanoparticles (AgNPs) distributing uniformly in TiO2. The Ag–Carbon–TiO2 tubes were confirmed high UV–vis light utilization and photocatalytic degradation efficiency to Rhodamine B due to the carbon doping, the surface plasmon resonance of AgNPs and the tubular structure, and the degradation of Rhodamine B reached 90% in 6 h. Meanwhile, they showed an excellent antibacterial effect on staphylococcus aureus, and the fatality rate of Ag–Carbon–TiO2 tubes to staphylococcus aureus reached 99.9% in 24 h when its concentration was higher than 4 mg/ml. The co-pyrolysis process could repress the AgNPs to grow to be large particles, which could be a key for the excellent antibacterial property. The research showed a promising strategy for preparing Ag–Carbon–TiO2 composite tubes by co-pyrolysis of PS composite electrospinning fibers, indicating their potential application in wastewater treatment and antibacterial materials.

Enhancement of Signal Intensity for Inverse Photoelectron Spectroscopy by Surface Plasmon Resonance of Ag Nanoparticles

Information concerning the unoccupied states of condensed matter is of great relevance to its electronic, optical and chemical properties. These unoccupied states can be directly examined by inverse photoelectron spectroscopy (IPES), which is often regarded as the time-inversion process of photoelectron spectroscopy. The fundamental drawback of IPES is its low signal intensity. Other spectroscopic intensities are enhanced by surface plasmon resonance (SPR), so the intensity of the IPES signal may also be enhanced by SPR. This was, however, impossible because the photon energy involved in conventional IPES exceeds 9 eV and is much higher than the SPR energy of existing materials. In 2012, we developed low-energy IPES (LEIPS), in which the photon energy is <5 eV, which can then be matched with the SPR energy. We demonstrate a five-fold enhancement of the LEIPS signal from a prototypical organic semiconductor, copper phthalocyanine (CuPc), by SPR of Ag nanoparticles.

Optical detection of CO gas by the surface-plasmon resonance of Ag nanoparticles and nanoclusters synthesized on a hydrogenated amorphous carbon (a-C:H) film

Ag nanoparticles were deposited on a hydrogenate amorphous carbon (a-C:H) thin film as a host by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) for various deposition times. We observed that as the sputtering time increases, the particle shape of the deposited nanostructures changes to a cluster shape. AFM images show that the accumulation of the nanoparticles on each other leads to the vertical growth of the nanoclusters. According to X-ray diffraction patterns, the crystalline structure is formed for the nanocluster shape. The Fourier-transform infrared (FTIR) spectroscopy showed that bonds are formed between Ag ions and free hands of carbons on the surface of the a-C:H film. The peak related to carbide structures is seen around 2100cm^-1. UV-Vis spectroscopy demonstrates that the formation of Ag nanoclusters leads to the appearance of a sharp plasmonic peak, shifted towards longer wavelengths. The plasmonic peak of Ag was used for detecting CO gas in the ambient air. The adhesion of CO molecules to the Ag particles makes a significant change in the plasmonic peak. In the presence of CO gas flow, the localized surface plasmon resonance (LSPR) of Ag nanoclusters moves to a longer wavelength (red-shift) and the LSPR intensity increases. The sample with a nanocluster structure is a better adsorber for CO molecules due to its larger specific surface area.

Enhancement of the YAG:Ce,Yb down-conversion emission by plasmon resonance in Ag nanoparticles

Silver (Ag) plasmonic structures on the surface of Сe and Yb co-doped yttrium aluminium garnet fluorescent epitaxial films were prepared by the magnetron sputtering technique. The nucleation and growth of Ag nanoparticles (NPs) were controlled by a thermal annealing process. Annealing of the samples at T ≥ 350 °C results in growth of Ag NPs size. A broad absorption band peaking in the range from 440 to 550 nm was observed due to the dipole mode of the surface plasmon resonance (SPR) of Ag NPs. Photoluminescence emission and excitation spectra were measured for samples having different concentrations, sizes and shapes of Ag particles. Plasmon-enhanced Ce3+ luminescence was observed for samples with particles bigger than 50 nm. On the other hand luminescence quenching was observed for samples with high Ag concentration and smaller NPs size. Presented luminescence results suggest that there are two competitive effects, namely enhancement and quenching, affecting the luminescence in the presence of Ag NPs. The enhancement of Ce3+ luminescence is mainly attributed to local field effect i.e. the SPR of Ag NPs causes an intensified electromagnetic field around them, resulting in enhanced optical transitions of Ce3+ ions in the vicinity of Ag NPs. The quenching effect, in the presence of Ag NPs, suggests an energy transfer from Ce3+ ions directly to them. The competition between the plasmonic enhancement and the quenching effect is discussed for samples with different nanoparticles concentrations and sizes.

Localized Surface-Plasmon Resonance of Ag Nanoparticles Produced by Laser Dewetting to Improve the Performance of a Sensitized TiO 2 Solar Cell

본 논문에서는 레이저 dewetting에 의해 형성된 은 나노입자들의 국소 표면플라즈몬 공명이 감응형 $TiO_2$ 태양전지의 전류밀도 및 효율 향상에 유용하게 이용될 수 있음을 보여준다. 전도성 유리기판 위에 증착된 은 박막을 펄스 레이저 조사에 의해 나노입자로 변환시킨 후 이 기판을 사용하여 감응형 $TiO_2$ 태양...

Near-infrared light photocatalytic ability for degradation of tetracycline using carbon dots modified Ag/AgBr nanocomposites

Abstract Ever-increasing environmental concerns have stimulated great progresses in photocatalytic technology in collection with the environmental remediation and solar energy utilization. In this study, carbon dots (CDs)/Ag/AgBr nanocomposites were prepared via a facile precipitation-photoreduction method. Moreover, CDs/Ag/AgBr nanocomposites show a strong absorbance in the full solar spectrum due to the interaction of Ag nanoparticles (Ag-NPs) and CDs. Meanwhile, compared with pristine AgBr and Ag/AgBr nanoparticles, a dramatic enhancement in the degradation of tetracycline under near-infrared light irradiation is observed over the CDs/Ag/AgBr nanocomposites. Significantly, the extraordinary photocatalytic performance is attributed to the extended absorption in the full spectrum, effective charge separation, and synergistic enhancement induced by surface plasmon resonance of Ag-NPs and the photogenerated change transfer properties of CDs in the complex nanocomposites.

Enhanced Raman scattering and photocatalytic activity of TiO2 films with embedded Ag nanoparticles deposited by magnetron sputtering

Nanoaprticles(Nps)-Ag/TiO2 multilayer films with different working pressures of Ag and inserted SiO2 shell layers between Ag and TiO2 were prepared by alternate magnetron sputtering. The formation of Ag nanoparticles embedded in TiO2 matrix was confirmed by the XRD and TEM results. The optical absorption peaks assigned to the surface plasmon resonance (SPR) of Ag nanoparticles were observed in the wavelength range of 550–750 nm. With increasing working pressure of Ag, the SPR peaks show blue-shift due to the decreasing Ag Nps size and increasing spacing between them. Compared with the pure TiO2 film, the Nps-Ag/TiO2 and Nps-Ag/SiO2/TiO2 film show significantly enhanced Raman scattering due to the strong local field induced by the SPR of Ag nanoparticles, and the enhanced photocatalytic activity of Nps-Ag/TiO2 film is related with the improved charge separation by the embedded Ag nanoparticles.

Enhancing the Surface-State Emission in Trap-Rich CdS Nanocrystals by Silver Nanoparticles

It is well known that surface plasmon resonance (SPR) can selectively enhance the photoluminescence (PL) from nearby chromophores with a single emission peak at an appropriate distance. Here, we combine white light-emitting CdS quantum dot nanocrystals containing band-edge and surface-state emissions simultaneously with Ag nanoparticles and study the interaction between them. It is found that the surface-state emission is always enhanced while the band-edge emission quenched regardless of the SPR wavelength of Ag nanoparticles. This phenomenon reveals that the SPR of Ag nanoparticles is not enhancing the emission from a wavelength-matched state. We propose that the surface plasmon of Ag nanoparticles is first excited by the energy of the band-edge emission and then the excited energetic electrons transfer to the surface-state of CdS. Through this energy transfer process, the surface-state emission is enhanced and band-edge emission quenched. This investigation can not only deliver understanding of the complicated interaction between metallic nanoparticles and nearby multi-emission-peak contained chromophores, but it also has potential applications in tuning the color temperature of white light-emitting materials.

Ag nanoparticles enhanced 2 um luminescences of Ho3+/Tm3+ codoped bismuth germanate glasses

The Ho3+/Tm3+ codoped bismuth germanate glasses containing Ag nanoparticles (NPs) are synthesized by a chemical reduction method based on the conventional melting-quenching technique. The effect of concentration of Ag NPs on the 2 um emission is studied. The absorption band related to the surface plasmon resonance (SPR) of the Ag NPs is located in a range from 500 to 900 nm. Transmission electron microscopic image clearly reveals homogeneously dispersed Ag NPs with the sizes ranging from 5 to 10 nm. The luminescence spectra in a range of 1.7-2.3 um are collected. With the addition mass fraction of the AgCl up to 0.3%, the intensity of emission band of Ho3+ ions, centered at 2.03 um, is increased by 10 folds. The enhancement of 2 um luminescence is attributed to the enhanced local field induced by SPR of Ag NPs. The calculated absorption cross section and emission cross section are 0.491 10-20 cm-2 and 1.0310-20 cm-2, respectively. When the gain coefficient p=0.2, the positive gain would be realised.

Photocatalytic Activity of Vis-Responsive Ag-Nanoparticles/TiO2 Composite Thin Films Fabricated by Molecular Precursor Method (MPM)

The Ag-nanoparticles (Ag-NP)/TiO2 composite thin films with various amounts of Ag (10 mol% ≤ n ≤ 80 mol%) were examined as a potential photocatalyst by decoloration reaction of methylene blue (MB) in an aqueous solution. These composite thin films of ca. 100 nm thickness were fabricated by the MPM at 600 °C in air. The decoloration rates monitored by the absorption intensity of the MB solution indicated that the composite thin films of Ag with an amount less than 40 mol% are not effective under vis-irradiation, though they can work as a photocatalyst under UV-irradiation. Further, the UV-sensitivity of the composite thin films gradually decreased to almost half the level of that of the TiO2 thin film fabricated under the identical conditions when the Ag amount increased from 10 to 40 mol%. Contrarily, the composite thin films of Ag content larger than 50 mol% showed the vis-responsive activity, whose level was slightly lower than the decreased UV-sensitivity. Diffuse reflectance spectra suggested that the vis-responsive activity of the composite thin films is due to the conductivity, localized surface plasmon resonance and surface plasmon resonance of Ag-NP. It was also elucidated that the vis-responsive level of the composite thin films corresponds to their electrical conductivity that depends on the Ag content.

Spectroscopic studies of Er3+ doped Ge-Ga-S glass containing silver nanoparticles

Abstract The spectroscopic characteristics of an erbium-doped Ga 10 Ge 25 S 65 (GGS) glass containing silver were studied and compared with that of an erbium-doped GGS glass without silver. The optical absorption spectra revealed the surface plasmon resonance (SPR) related characteristic of silver nanoparticles (NPs) around 490 nm. Enhancement of Er 3+ luminescence was observed for a broad excitation wavelength region, and the largest enhancement was observed for the excitation at 488 nm, which is near the peak of SPR of silver NPs in GGS glass and in resonance with Er 3+ ions. For the excitation at 405 nm, enhancement of luminescence from both GGS host and Er 3+ ions was observed. A smaller enhancement was observed for a two-step upconversion luminescence excited at 801 nm. The observed enhancement of Er 3+ luminescence is mainly attributed to the local field effects: the SPR of Ag NPs causes an intensified electromagnetic field around NPs, resulting in enhanced optical transitions of Er 3+ ions in the vicinity.