Photoluminescence Of Ag Research Articles

Two-photon absorption induced optical limiting action of Ag-doped lanthanum molybdate decorated reduced graphene oxide nanocomposites

In this research, we aimed to investigate the linear and non-linear optical properties of Ag-La2(MoO4)3@RGO nanocomposites. For this purpose, Graphene Oxide (GO) was synthesized by Modified Hummer’s method after which GO was chemically reduced to Reduced graphene oxide (RGO). The nanocomposite Ag-doped La2(MoO4)3 is prepared by a simple and facile co-precipitation method. The prepared nanocomposite was characterized by Fourier transform infrared (FTIR), Ultraviolet-Visible (UV-Vis) absorption, X-ray diffraction (XRD), Scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDX). XRD and EDX analysis indicated the reduction of GO and successful synthesis of Ag-doped La2(MoO4)3 nanocomposite. FESEM images portray the presence of thin layers of graphene sheets and Ag-doped La2(MoO4)3 on the sheets of reduced graphene oxide. Ground state absorption studies show that the reduction of graphene oxide causes a hypsochromic shift in the absorption maxima of the graphene layers. The photoluminescence of Ag- La2(MoO4)3@RGO demonstrates the utmost emission in the UV range caused by the valence band and conduction band's direct transitions in the band gap region. Z-scan method using Nd: YAG laser exposes that both nanocomposite and specific counterparts hold reverse saturable absorption behaviour. The source of optical limiting action is attributed to the excited state absorption process, emerging from the influence of the plasmon resonance state of Ag nanoparticles. Strong nonlinear absorption and lower onset limiting threshold make the Ag-La2(MoO4)3@RGO nanocomposite desirable material for laser safety devices.

Preparation and photoluminescence of Ag+ and / or Sm3+-doped polyphosphate phosphors

A series of novel phosphors such as Ba2Mg(PO4)2: Ag+ (BMPO: xAg), Ba2Mg(PO4)2: Sm3+ (BMPO: ySm) and Ba2Mg(PO4)2: Ag+, Sm3+ (BMPO: 1%Ag, ySm) were prepared by solid-state reaction method. Phase structure and luminescent properties of Ba2Mg(PO4)2 were explored. It is shown that, under the excitation of 278 nm DUV light, a broadband emission peak centered at 400 nm was obtained in BMPO: xAg at room temperature, which is attributed to the emission of the Ag+-Ag+ pairs. The optimum doping concentration of Ag+ in Ba2Mg(PO4)2 is 1 mol.%. And the main emission peaks of Ba2Mg(PO4)2: ySm are located at 564 nm, 600 nm and 645 nm, respectively, which are ascribed to the 4G5/2→6Hj (j = 5/2, 7/2, 9/2) transitions of Sm3+. In BMPO: 1%Ag, ySm, Ag+ can enhance the emission intensity of BMPO: ySm effectively via an energy transfer and/or absorptions with Sm3+.

Facilitating Hotspot Alignment in Tip-Enhanced Raman Spectroscopy via the Silver Photoluminescence of the Probe.

A tip-enhanced Raman spectroscopy (TERS) system based on an atomic force microscope (AFM) and radially polarized laser beam was developed. A TERS probe with plasmon resonance wavelength matching the excitation wavelength was prepared with the help of dark-field micrographs. The intrinsic photoluminescence (PL) from the silver (Ag)-coated TERS probe induced by localized surface plasmon resonance contains information about the near-field enhanced electromagnetic field intensity of the probe. Therefore, we used the intensity change of Ag PL to evaluate the stability of the Ag-coated probe during TERS experiments. Tracking the Ag PL of the TERS probe was helpful to detect probe damage and hotspot alignment. Our setup was successfully used for the TERS imaging of single-walled carbon nanotubes, which demonstrated that the Ag PL of the TERS probe is a good criterion to assist in the hotspot alignment procedure required for TERS experiments. This method lowers the risk of contamination and damage of the precious TERS probe, making it worthwhile for wide adoption in TERS experiments.

Photoluminescence of Ag+ and Agn+m in co-doped Pr3+/Yb3+ fluorophosphate glasses: tuning visible emission and energy transfer to Pr3+/Yb3+ ions through excitation in different silver species

Here, we report the luminescence properties of Yb3+/Pr3+ dual-doped fluorophosphate glasses containing silver clusters. Through the solubility of silver into the glass system as function of its initial concentration, charged species characterized as Ag+ and Ag m n+ were formed and identified according to their absorption and emission spectral responses. By changing the transition metal concentration, multi-energy transfer mechanisms were observed between silver and Yb3+/Pr3+ co-doped glasses. The stabilization of silver species seems to be detrimental to the radiative processes of the rare earth ions under excitation at 444 nm (Pr3+3H4 → 3P0 absorption line). In other words, the main visible emissions of Pr3+ and the NIR emission of Yb3+ decrease with increment of Ag concentration. However, energy transfer occurs for large spectral range by the excitation of the silver species. In consequence, the visible and NIR emission could be activate in a broadband from ultraviolet to the blue part of the spectral region. These two observations highlight the competitive absorption processes and probabilities between the cationic elements and the interest to use the transition metal species as sensitizers to excite the rare earth elements.

Photoluminescence of Cu(I)(PPh3)2(8-quinolinolate)

The complex Cu(I)(PPh3)2(oxinate) with oxine=8-quinolinole is luminescent under ambient conditions. In the solid state it shows an emission which originates from the lowest-energy oxinate ILCT state. It consists of a fluorescence and a phosphorescence. In solution saturated with argon, a single broad emission band appears which seems to be composed of a more intense fluorescence and a much weaker phosphorescence at longer wavelength. If this solution is saturated with air, the complete emission band becomes less intense. This is quite surprising, since the oxinate ILCT fluorescence of other oxinate complexes is not quenched by oxygen. It is conceivable that the fluorescence largely consists of a delayed fluorescence. When the emitting triplet is depopulated by a thermally activated transition to the fluorescent singlet, both emissions, the delayed fluorescence and the phosphorescence, may undergo a luminescence quenching. For a simple comparison, the photoluminescence of Ag(PPh3)2(oxinate) was also briefly examined. The absorption and emission spectra of this silver complex in solution at r.t. resemble those of the copper complex.