Origin of luminescence enhancement and quenching of europium complex in solution phase containing Ag nanoparticles

Tm3+ Ion Blue Emission Quenching by Pd2+ Ions in Barium Phosphate Glasses: Fundamental Analysis toward Sensing Applications

The quenching effect of Pd²⁺ ions on the blue emission from Tm³⁺ was investigated for the first time using barium phosphate glass as model matrix. Glasses containing fixed Tm₂O₃ at 0.5 mol % and PdO up to 0.3 mol % (added relative to P₂O₅) were prepared by melting and first characterized for basic structural properties by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and Raman spectroscopy. Thermal properties were then evaluated by differential scanning calorimetry (DSC). The focus was thereafter on evaluating the optical properties by absorption and photoluminescence (PL) spectroscopy with decay kinetics assessment. XRD confirmed the amorphous nature of the glasses synthesized. The vibrational spectroscopy assessment consistently exhibited the IR- and Raman-active bands characteristic of phosphate glasses, showing no significant variation with PdO codoping. The DSC analysis revealed all glasses possessed high thermal stability assessed by the differences (ΔT = T_g - T_x ≥ 154 °C) between glass transition temperatures (T_g) and onset of crystallization (T_x). A tendency of the T_g values to increase with PdO contents was however exhibited. In addition, specific enthalpies of crystallization showed magnitudes decreasing with increasing PdO concentration, thus suggesting crystallization suppression by Pd²⁺. Concerning the optical properties, it was observed that codoping the glasses with PdO (0.1-0.3 mol %) led to the development of the visible Pd²⁺ d-d absorption band (peak ≈415-410 nm). In addition, drastic PL quenching of the Tm³⁺ blue emission around 452 nm (¹D₂ → ³F₄ transition) was induced by Pd²⁺. Analyzing PL decay curves obtained by exciting Tm³⁺ ions at 359 nm while monitoring 452 nm emission revealed decreased ¹D₂ state lifetimes. Thus, a potential of Tm³⁺ for analytical sensing of Pd²⁺ in various matrices was suggested. Ultimately determining quenching constants from the PL data and based on the comparison of results from emission intensity and decay rates, likely Tm³⁺ → Pd²⁺ energy transfer processes underlying the PL quenching were proposed.

Modulated Luminescence of Lanthanide Materials by Local Surface Plasmon Resonance Effect

Lanthanide materials have great applications in optical communication, biological fluorescence imaging, laser, and so on, due to their narrow emission bandwidths, large Stokes' shifts, long emission lifetimes, and excellent photo-stability. However, the photon absorption cross-section of lanthanide ions is generally small, and the luminescence efficiency is relatively low. The effective improvement of the lanthanide-doped materials has been a challenge in the implementation of many applications. The local surface plasmon resonance (LSPR) effect of plasmonic nanoparticles (NPs) can improve the luminescence in different aspects: excitation enhancement induced by enhanced local field, emission enhancement induced by increased radiative decay, and quenching induced by increased non-radiative decay. In addition, plasmonic NPs can also regulate the energy transfer between two close lanthanide ions. In this review, the properties of the nanocomposite systems of lanthanide material and plasmonic NPs are presented, respectively. The mechanism of lanthanide materials regulated by plasmonic NPs and the scientific and technological discoveries of the luminescence technology are elaborated. Due to the large gap between the reported enhancement and the theoretical enhancement, some new strategies applied in lanthanide materials and related development in the plasmonic enhancing luminescence are presented.

Pd2+-induced quenching of the UV emission from Gd3+ ions in phosphate glass

This paper reports on the influence of Pd²⁺ ions on the ultraviolet emission from Gd³⁺, investigated in barium phosphate glass as model matrix. The glasses were prepared by the melting technique and characterized by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, optical absorption, and photoluminescence (PL) spectroscopy including decay kinetics assessment. The XRD data confirmed the amorphous nature of the glasses, whereas FT-IR spectra indicated the basic structural features of PO₄ tetrahedra. The optical absorption analysis showed that addition of PdO up to 0.3 mol% lead to significant growth of the visible Pd²⁺ d-d absorption band around 415 nm, with ultimately some decrease in the optical band gap energies assessed through Tauc plots. Further, significant PL quenching of Gd³⁺ ions emission around 312 nm was observed with increasing PdO contents, alongside increased decay rates for the ⁶P_7/2 emitting state in Gd³⁺. An analysis of quenching constants was ultimately performed comparing results from emission intensity with the decay rates. It is suggested that a Gd³⁺ → Pd²⁺ excitation transfer and/or absorption competition lead the quenching process with a contribution from a channel depopulating the ⁶P_7/2 metastable state.

Advances in Ultrasonic Spray Pyrolysis Processing of Noble Metal Nanoparticles-Review

In the field of synthesis and processing of noble metal nanoparticles, the study of the bottom-up method, called Ultrasonic Spray Pyrolysis (USP), is becoming increasingly important. This review analyses briefly the features of USP, to underline the physical, chemical and technological characteristics for producing nanoparticles and nanoparticle composites with Au and Ag. The main aim is to understand USP parameters, which are responsible for nanoparticle formation. There are two nanoparticle formation mechanisms in USP: Droplet-To-Particle (DTP) and Gas-To-Particle (GTP). This review shows how the USP process is able to produce Au, Ag/TiO2, Au/TiO2, Au/Fe2O3 and Ag/(Y0.95 Eu0.05)2O3 nanoparticles, and presents the mechanisms of formation for a particular type of nanoparticle. Namely, the presented Au and Ag nanoparticles are intended for use in nanomedicine, sensing applications, electrochemical devices and catalysis, in order to benefit from their properties, which cannot be achieved with identical bulk materials. The development of new noble metal nanoparticles with USP is a constant goal in Nanotechnology, with the objective to obtain increasingly predictable final properties of nanoparticles.

Recent Advances in the Optimization of Organic Light-Emitting Diodes with Metal-Containing Nanomaterials

Metal-containing nanomaterials have attracted widespread attention in recent years due to their physicochemical, light-scattering and plasmonic properties. By introducing different kinds and different structures of metal-containing nanomaterials into organic light-emitting diodes (OLEDs), the optical properties of the devices can be tailored, which can effectively improve the luminous efficiency of OLEDs. In this review, the fundamental knowledge of OLEDs and metallic nanomaterials were firstly introduced. Then we overviewed the recent development of the optimization of OLEDs through introducing different kinds of metal-containing nanomaterials.

Efficacy improvement in polymer LEDs via silver-nanoparticle doping in the emissive layer

The coupling of surface plasmons and excitons in the emissive layer (EML) can improve the performance of polymer light-emitting diodes (PLEDs). Silver nanoparticles (Ag-NPs) with a decahedron structure are prepared by the chemical reduction and photochemical methods and doped directly into the EML after the phase-transfer process. The surface plasmon resonance effect of Ag-NPs, which makes full use of quenched excitons and increases the efficiency of excitons in the EML in a PLED, enhances the current efficacy by a factor of 75 relative to that of the undoped reference device (from 0.22 to 16.64 cd/A). These results demonstrate that Ag-NPs can assist in simple and low-cost fabrication of high-performance polymer optoelectronic devices.

A novel photo-responsive europium(III) complex for advanced anti-counterfeiting and encryption

A novel europium(iii) complex simultaneously exhibiting photocolorimetric and photofluorometric behavior was obtained. Multiple distinguishable identities can be obtained and reversibly modulated using light as external stimuli. With this novel photo-responsive complex, double encryption and advanced anti-counterfeiting were realized.

Influence of Ag nanoparticles on the luminescence dynamics of Dy3+ ions in glass: the "plasmonic diluent" effect

This work demonstrates that metallic nanoparticles (NPs) embedded in rare-earth (RE) co-doped dielectrics are able to produce an effect analogous to a reduction in the effective concentration of the luminescent RE ions in the matrix, herein coined the "plasmonic diluent" effect. This has been revealed explicitly for Dy(3+) and Ag NP co-doped aluminophosphate glasses, which were investigated using optical absorption and photoluminescence (PL) spectroscopy with emphasis on the influence of plasmonic NPs on the luminescence decay dynamics of Dy(3+) ions. The glasses were prepared using the melt-quenching technique, where the precipitation of Ag NPs was subsequently induced by heat treatment (HT). The development of the surface plasmon resonance (SPR) band of Ag NPs at around 410 nm resulted in the quenching of Dy(3+) emission for the (4)F9/2 → (6)H15/2, (6)H13/2 transitions (484, 574 nm) under resonant excitation of (6)H15/2 → (4)I15/2 transition at 450 nm. The decay of the (4)F9/2 excited state was monitored at 574 nm (away from SPR) under excitation at 450 nm (within SPR), where the PL dynamics indicated the presence of two populations of Dy(3+) ions in the glasses, in connection with slow (τs) and fast (τf) lifetime components. A tendency of the decay times to increase gradually with HT holding time was observed as the volume fraction of the plasmonic Ag particles increased. The data are interpreted in terms of an ion-to-particle excitation energy transfer operating via surface plasmons in the nanoscale metal. This produces a Dy(3+) deactivation effect analogous to a lowering in the effective concentration of emitting Dy(3+) ions in the matrix, i.e., the metal NPs play a role as a "plasmonic diluent" in the glass system with respect to the luminescent RE ions.

Localized surface plasmon enhanced cathodoluminescence from Eu3+-doped phosphor near the nanoscaled silver particles

We elucidate that the luminescence from Eu3+-doped phosphor excited by the electron collision can be modified on location near the metallic nanoparticles. The Eu3+-doped phosphor was fabricated on the nanoscaled Ag particles ranging of 5 nm to 30 nm diameter. As a result of the cathodoluminescence measurements, the phosphor films on the Ag particles showed up to twofold more than that of an isolated phosphor film. Enhanced cathodoluminescence originated from the resonant coupling between the localized surface plasmon of Ag nanoparticles and radiating energy of the phosphor. Cathodoluminescent phosphor for high luminous display devices can be addressed by locating phosphor near the surface of metallic nanoparticles.

Optical properties of silver nanoprisms and their influences on fluorescence of europium complex

The optical properties of truncated triangular silver nanoprisms and their influences on the fluorescence of europium complex Eu(TTFA)(3) were investigated in theory and experiment separately. In theory, we found that the fluorescence of Eu ions would be greatly enhanced by these nanoprisms, the enhancement factor of the fluorescence depended on the concentrations of nanoprisms. They were verified in the experiment. The influence of silver nanoprisms on the radiative and nonradiative decay rates of Eu ions were also deduced, and found that the silver nanoprisms greatly reduced the energy loss caused by the nonradiative decay.