Ag nanocluster functionalized glasses for efficient photonic conversion in light sources, solar cells and flexible screen monitors

Tunable Visible Light and Energy Transfer Mechanism in Tm3+ and Silver Nanoclusters within Co-Doped GeO2-PbO Glasses

This study introduces a novel method for producing Ag nanoclusters (NCs) within GeO2-PbO glasses doped with Tm3+ ions. Sample preparation involved the melt-quenching method, employing adequate heat treatment to facilitate Ag NC formation. Absorption spectroscopy confirmed trivalent rare-earth ion incorporation. Ag NC identification and the amorphous structure were observed using transmission electron microscopy. A tunable visible emission from blue to the yellow region was observed. The energy transfer mechanism from Ag NCs to Tm3+ ions was demonstrated by enhanced 800 nm emission under 380 and 400 nm excitations, mainly for samples with a higher concentration of Ag NCs; moreover, the long lifetime decrease of Ag NCs at 600 nm (excited at 380 and 400 nm) and the lifetime increase of Tm3+ ions at 800 nm (excitation of 405 nm) corroborated the energy transfer between those species. Therefore, we attribute this energy transfer mechanism to the decay processes from S1→T1 and T1→S0 levels of Ag NCs to the 3H4 level of Tm3+ ions serving as the primary path of energy transfer in this system. GeO2-PbO glasses demonstrated potential as materials to host Ag NCs with applications for photonics as solar cell coatings, wideband light sources, and continuous-wave tunable lasers in the visible spectrum, among others.

Structural water molecules dominated p band intermediate states as a unified model for the origin on the photoluminescence emission of noble metal nanoclusters: from monolayer protected clusters to cage confined nanoclusters

In the past several decades, noble metal nanoclusters (NMNCs) have been developed as an emerging class of luminescent materials due to their superior photo-stability and biocompatibility, but their luminous quantum yield is relatively low and the physical origin of the bright photoluminescence (PL) of NMNCs remain elusive, which limited their practical application. As the well-defined structure and composition of NMNCs have been determined, in this mini-review, the effect of each component (metal core, ligand shell and interfacial water) on their PL properties and corresponded working mechanism were comprehensively introduced, and a model that structural water molecules dominated p band intermediate state was proposed to give a unified understanding on the PL mechanism of NMNCs and a further perspective to the future developments of NMNCs by revisiting the development of our studies on the PL mechanism of NMNCs in the past decade.

Silver Nanoclusters Tunable Visible Emission and Energy Transfer to Yb3+ Ions in Co-Doped GeO2-PbO Glasses for Photonic Applications

This work investigates the optical properties of Yb³⁺ ions doped GeO₂-PbO glasses containing Ag nanoclusters (NCs), produced by the melt-quenching technique. The lack in the literature regarding the energy transfer (ET) between these species in these glasses motivated the present work. Tunable visible emission occurs from blue to orange depending on the Yb³⁺ concentration which affects the size of the Ag NCs, as observed by transmission electron microscopy. The ET mechanism from Ag NCs to Yb³⁺ ions (²F_7/2 → ²F_5/2) was attributed to the S₁→T₁ decay (spin-forbidden electronic transition between singlet-triplet states) and was corroborated by fast and slow lifetime decrease (at 550 nm) of Ag NCs and photoluminescence (PL) growth at 980 nm, for excitations at 355 and 405 nm. The sample with the highest Yb³⁺ concentration exhibits the highest PL growth under 355 nm excitation, whereas at 410 nm it is the sample with the lowest concentration. The restriction of Yb³⁺ ions to the growth of NCs is responsible for these effects. Thus, higher Yb³⁺ concentration forms smaller Ag NCs, whose excitation at 355 nm leads to more efficient ET to Yb³⁺ ions compared to 410 nm. These findings have potential applications in the visible to near-infrared regions, such as tunable CW laser sources and photovoltaic devices.

Nanodiamond-promoted white light emission in Eu, Dy, and Cu-containing phosphate glass: quantitative analysis and colorimetric study

A thorough analysis of glass containing Eu₂ O₃ and Dy₂ O₃ , or Eu₂ O₃ , Dy₂ O₃ , and CuO melted together with nanodiamond powder was pursued based on measurements of optical absorption, photoluminescence (PL) emission and excitation spectra, and colorimetry. Nanodiamond facilitated the stabilization of Cu⁺ and Eu²⁺ ions with blue-emitting characteristics that, along with yellow-emitting Dy³⁺ and red-emitting Eu³⁺ led to the white light-emitting glass. Novel intensity notations implemented in intensity-based spectral ratios, and difference intensity correlation analysis were proposed for the assessment of PL properties. The chromaticity and correlated colour temperature of the emission were ultimately investigated as a two-parametric problem based on: (1) the different ionic components; and (2) the various excitation wavelengths employed. The optical analysis approach adds to the characterization methods to further fundamental understanding and provide helpful analytical tools for designing materials for tunable white light-emitting devices.

Thermal-Driven Formation of Silver Clusters Inside Na/Li FAUY Zeolites for Formaldehyde Detection

In this research, the LiY zeolite was firstly synthesized by using NaY as the parent zeolite; thereafter, the LiYAg and NaYAg zeolites created for formaldehyde gas detection were prepared with further Ag⁺-Li⁺/Na⁺ exchange and a mild thermal treatment at 300 °C to promote the formation of luminescent Ag CLs. The spectra experimental results indicated that Ag CLs showed stronger and blue-shifted emissions in LiYAg compared with in NaYAg, and the emission intensity of Ag CLs in both zeolites monotonously decreased when exposed to increasing formaldehyde gas content. Moreover, the linear dependence of the Ag CLs' emission intensity variation on formaldehyde content indicated a reliable method for fast and sensitive formaldehyde detection. According to the XPS, UV-vis absorption, and N₂ adsorption-desorption isotherm studies, the formaldehyde-gas-induced luminescence quenching of Ag CLs is due to the formation of Ag₂O and Ag NPs, in which the higher content of Ag⁺/Ag⁰ redox couples in LiYAg and larger surface area of NaYAg benefit the precise detection of formaldehyde gas in low- and high-content ranges, respectively. Furthermore, the blue-shifted peak position and widened FWHM of Ag CLs can also be used for the indication of formaldehyde gas and the detection limit of NaYAg and LiYAg, which both meet with the standards of the WHO and OSHA.

Ag Nanocluster-Enhanced Scintillation Properties of Borophosphate Glasses Doped with CsPbBr3 Quantum Dots

A novel and effective method to improve scintillation properties of glass-ceramics, such as intensity enhancement and decay-time shortening, is reported in this work. Compared with crystal scintillators, glass scintillators always have the problems of low efficiency and long decay; how to solve them has always been a scientific puzzle in the field of scintillation glass-ceramics. The plasma enhancement effect can be predicted to solve the above problems. Ag⁺ ions were diffused into glasses by ion exchange, and then Ag nanoparticles and CsPbBr₃ quantum dots were formed by heat treatment. The structure of the CsPbBr₃ perovskite consists of a series of shared corner PbBr₆ octahedra with Cs ions occupying the cuboctahedral cavities. By using Ag and the plasma resonance effect, the photoluminescence intensity of CsPbBr₃ quantum dot glasses was enhanced by 3 times, its radioluminescence intensity increased by 6.25 times, and its decay time was reduced by a factor of more than one. Moreover, the mechanism of photoluminescence and radioluminescence enhanced by Ag and plasma was discussed based on the experimental results and finite-difference time-domain method. We concluded that the increase in radioluminescence intensity was related to plasma enhancements and the energy exchange between Ag nanoclusters and CsPbBr₃ quantum dots. Doping Ag is a valid means to improve the scintillation luminescence of CsPbBr₃ quantum dot glasses, which can be applied in the field of scintillation.

Atomic-scale detection of individual lead clusters confined in Linde Type A zeolites

Structural analysis of metal clusters confined in nanoporous materials is typically performed by X-ray-driven techniques. Although X-ray analysis has proved its strength in the characterization of metal clusters, it provides averaged structural information. Therefore, we here present an alternative workflow for bringing the characterization of confined metal clusters towards the local scale. This workflow is based on the combination of aberration-corrected transmission electron microscopy (TEM), TEM image simulations, and powder X-ray diffraction (XRD) with advanced statistical techniques. In this manner, we were able to characterize the clustering of Pb atoms in Linde Type A (LTA) zeolites with Pb loadings as low as 5 wt%. Moreover, individual Pb clusters could be directly detected. The proposed methodology thus enables a local-scale characterization of confined metal clusters in zeolites. This is important for further elucidation of the connection between the structure and the physicochemical properties of such systems.

Silver in the Center Enhances Room-Temperature Phosphorescence of a Platinum Sub-nanocluster by 18 Times

There has been controversy surrounding the roles of the metal core (metal-metal interaction) and the shell (metal-ligand interaction) in photoluminescence of ligand-protected metal nanoclusters. We have discovered aggregation-induced room-temperature phosphorescence of a platinum-thiolate complex and its silver ion inclusion complex (a silver-doped platinum sub-nanocluster). The inclusion of silver ion boosted the photoluminescent quantum yield by 18 times. Photophysical measurements indicate that the rate of nonradiative decay was slower for the silver-doped platinum sub-nanocluster. DFT calculations showed that the LUMO, which had the main contribution from Ag s-orbital and Pt d-orbitals, played a critical role in suppressing the structural distortion at the excited state. This work will hopefully stimulate more research on designing strategies based on molecular orbitals of atomicity-precise luminescent multimetallic nanoclusters.

Coefficient effect of rare earth and metal ions in phosphor combined glass materials for a wide color gamut display

The surface plasmon resonance (SPR) of metal nanostructures is known to affect the optical properties of solid luminescent materials. Ag nanoparticles were first used to obtain a wider color gamut in rare-earth-doped phosphor-in-glass for application as color filters for white light emitting diodes. The existence of Ag nanocrystallites at nanometer scale and the independent integrity of the phosphor luminescence center in the amorphous glass environment were demonstrated. Using UV-Vis spectroscopy, the localized SPR absorption band was observed at 480 nm, and the optical properties of the nanostructures were found to be dependent on the annealing temperature. Hence, an expansion of the color gamut from 79.07% to 93.31% was realized by the coefficient effect of Nd³⁺ active ions and Ag nanoparticles. These results suggest that Nd³⁺-ion-co-doped phosphor-in-glass modified by Ag nanoparticles could be potentially applied as a novel optical material with a wide color gamut.

Re-examining the electronic structure of fluorescent tetra-silver clusters in zeolites

In the present study, we have examined the electronic structures related to the fluorescence properties of small Ag42+ complexes encapsulated in zeolites. We find that interaction between Ag42+ and coordinated water molecules, which was previously proposed to be the origin of fluorescence, may not be a sufficient condition by itself. Refinement of the previously used all-silicon-cage model to include framework Al atoms leads to an asymmetric environment, and this alters the electronic structure in favor of fluorescence. We have further examined the substitution of the H2O ligands by NH3, H2S, PH3, CO and CS. Among these systems, Ag42+ binds most strongly to NH3 but the energetics for the H2S and PH3 complexes is also reasonable. The energy of the fluorescent light is related to the energy of the lowest-energy triplet state, and these energies for the H2O, NH3, H2S and PH3 systems span the range of ∼2-3 eV, i.e., roughly the visible range. Thus, the use of different ligands appears to be an attractive means for tailoring the luminescence properties.

Fluorochromic polymeric elastomer film containing copper nanoclusters in response to multistimuli

Smart chromic elastomers exhibiting multistimuli responsiveness are of interest with regard to the development of sensors, optical data storage, and smart wearable devices. We report a new design of Cu nanoclusters (Cu NCs) containing polymeric elastomer film, showing reversible fluorescence ON/OFF when subjected to organic solvents (e.g. ethanol, methanol and tetrahydrofuran), and heating/cooling cycles at temperatures lower than 80 °C. Different from the solvato-responsiveness of Cu NCs in solution state, organic solvents increase nonradiative decay and quench fluorescence emission in the solid polymer matrix. It is deduced that lower temperatures (<80 °C) increase reversible nonradiative decay, while higher temperatures (>80 °C) trigger an irreversible change of the aggregation state of Cu NCs in the elastomer film. A strong oxidizer (e.g. H₂O₂) irreversibly quenches the fluorescence emission and changes its color (under sunlight) from light green to blue, by oxidizing Cu NCs to Cu²⁺ ions. This Cu NC-containing elastomer film illustrates a new pathway to the fabrication of multi-responsive smart optical materials, particularly for potential applications in optical data storage (e.g. thermo-printing), and multistimuli-responsive elastomeric sensors integrated into wearable devices.

Simultaneous energy transfer from molecular-like silver nanoclusters to Sm3+/Ln3+ (Ln = Eu or Tb) in glass under UV excitation

Molecular-like silver nanoclusters (ML-Ag NCs) with size dependent tunable luminescence properties and high-quantum yield has been explored as a new type of sensitizer for rare earth (RE) ions in glasses recently. In this research, the borosilicate glasses containing ML-Ag NCs and RE³⁺ (RE = Sm, Eu, Tb) ions were prepared with melt-quenching method. The absorption, TEM and steady spectra measurements indicated that compare with Sm³⁺ and Tb³⁺, the introduction of Eu³⁺ can more effectively promote the formation of luminescent ML-Ag NCs and their further aggregation. Besides the predictable efficient energy transfer from ML-Ag NCs to a single type of RE³⁺ ion in the codoped glasses, the simultaneously sensitization of Sm³⁺/Eu³⁺ and Sm³⁺/Tb³⁺ couples by ML-Ag NCs were further realized in the tri-doped glasses. Benefited from the excitation wavelength dependence of energy transfer from ML-Ag NCs to Sm³⁺/Eu³⁺ and Sm³⁺/Tb³⁺ couples and excitation efficiency on ML-Ag NCs and RE³⁺ ions, the tri-doped glasses exhibit broad tunable emission simply by changing the excitation wavelength, and the white light emission was achieved in GAgSmEu under UV excitation.

Towards operando computational modeling in heterogeneous catalysis

An increased synergy between experimental and theoretical investigations in heterogeneous catalysis has become apparent during the last decade. Experimental work has extended from ultra-high vacuum and low temperature towards operando conditions. These developments have motivated the computational community to move from standard descriptive computational models, based on inspection of the potential energy surface at 0 K and low reactant concentrations (0 K/UHV model), to more realistic conditions. The transition from 0 K/UHV to operando models has been backed by significant developments in computer hardware and software over the past few decades. New methodological developments, designed to overcome part of the gap between 0 K/UHV and operando conditions, include (i) global optimization techniques, (ii) ab initio constrained thermodynamics, (iii) biased molecular dynamics, (iv) microkinetic models of reaction networks and (v) machine learning approaches. The importance of the transition is highlighted by discussing how the molecular level picture of catalytic sites and the associated reaction mechanisms changes when the chemical environment, pressure and temperature effects are correctly accounted for in molecular simulations. It is the purpose of this review to discuss each method on an equal footing, and to draw connections between methods, particularly where they may be applied in combination.

Origin of the bright photoluminescence of few-atom silver clusters confined in LTA zeolites

Silver (Ag) clusters confined in matrices possess remarkable luminescence properties, but little is known about their structural and electronic properties. We characterized the bright green luminescence of Ag clusters confined in partially exchanged Ag–Linde Type A (LTA) zeolites by means of a combination of x-ray excited optical luminescence-extended x-ray absorption fine structure, time-dependent–density functional theory calculations, and time-resolved spectroscopy. A mixture of tetrahedral Ag4(H2O)x2+(x= 2 andx= 4) clusters occupies the center of a fraction of the sodalite cages. Their optical properties originate from a confined two-electron superatom quantum system with hybridized Ag and water O orbitals delocalized over the cluster. Upon excitation, one electron of the s-type highest occupied molecular orbital is promoted to the p-type lowest unoccupied molecular orbitals and relaxes through enhanced intersystem crossing into long-lived triplet states.

Synthesis of fluorescent conjugated polymer nanoparticles and their immobilization on a substrate for white light emission

Fluorescent conjugated polymers (CPs) for blue, green, and red emission were polymerized via the Suzuki coupling reaction.

White light and multicolor emission tuning in Ag nanocluster doped fluorophosphate glasses

The emission properties of Ag NCs dispersed in a fluorophosphate glass have been studied. White light is generated under UV excitation due to the presence of a variety of Ag NCs with different sizes, emitting in the blue, green and red regions.

Highly luminescent silver nanocluster-doped fluorophosphate glasses for microfabrication of 3D waveguides

Highly photoluminescent glasses were prepared by embedding silver nanoclusters (Ag NCs) in a fluorophosphate matrix using a melt-quenching method.

Synthesis of water-soluble and highly fluorescent gold nanoclusters for Fe3+ sensing in living cells using fluorescence imaging

Gold nanoclusters are used as excellent scaffolds for the development of chemical and biological sensors due to their outstanding physical and chemical properties.

Tuning the energetics and tailoring the optical properties of silver clusters confined in zeolites

The integration of metal atoms and clusters in well-defined dielectric cavities is a powerful strategy to impart new properties to them that depend on the size and geometry of the confined space as well as on metal-host electrostatic interactions. Here, we unravel the dependence of the electronic properties of metal clusters on space confinement by studying the ionization potential of silver clusters embedded in four different zeolite environments over a range of silver concentrations. Extensive characterization reveals a strong influence of silver loading and host environment on the cluster ionization potential, which is also correlated to the cluster's optical and structural properties. Through fine-tuning of the zeolite host environment, we demonstrate photoluminescence quantum yields approaching unity. This work extends our understanding of structure-property relationships of small metal clusters and applies this understanding to develop highly photoluminescent materials with potential applications in optoelectronics and bioimaging.

Gold Nanocluster and Quantum Dot Complex in Protein for Biofriendly White-Light-Emitting Material

We report the synthesis of a biofriendly highly luminescent white-light-emitting nanocomposite. The composite consisted of Au nanoclusters and ZnQ2 complex (on the surface of ZnS quantum dots) embedded in protein. The combination of red, green, and blue luminescence from clusters, complex, and protein, respectively, led to white light generation.

Visible emission from Ag(+) exchanged SOD zeolites

Broad visible emissions dominant at green or red have been observed for the thermally-treated Ag(+) exchanged SOD zeolites, determined by the Ag(+) loading contents and the excitation wavelengths. Contrary to the notable reversible green/red dominant emission evolution in the Ag(+) exchanged LTA zeolites upon hydration/dehydration in air (or water vapor)/vacuum, emission spectra of the Ag(+) exchanged SOD zeolites are insensitive to the environmental change. This is most probably due to the difficult H2O permeation in SOD zeolites in comparison with LTA zeolites. By combining the environment dependent emission spectra of the Ag(+) exchanged LTA and SOD zeolites, we proposed the following emission mechanisms for Ag(+) exchanged LTA and SOD zeolites: the green emission is due to the transition from ligand-to-metal (framework O(2-)→ Ag(+)) charge transfer state to the ground state and the red emission is due to the transition from the metal-metal (Ag(+)-Ag(+)) charge transfer state to the ground state. The insensitive environment dependent emission characteristics of Ag(+) exchanged SOD zeolites may have potential applications as robust phosphors.

Direct oxidative esterification of alcohols and hydration of nitriles catalyzed by a reusable silver nanoparticle grafted onto mesoporous polymelamine formaldehyde (AgNPs@mPMF)

Oxidative esterification and hydration of nitriles are catalyzed by a newly synthesized AgNPs@mPMF. The catalyst is well characterized and reusable.