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A DNA-Encapsulated Silver Cluster and the Roles of Its Nucleobase Ligands
摘要： Silver clusters consisting of ~10 atoms are readily bound by and encapsulated within DNA strands to yield strong absorption and emission. The coordination environments, however, are poorly understood, so cluster adducts can only be empirically tuned. This work describes the C4AC4TC3G strand that templates a particular cluster adduct. Its sequence has three types of nucleobases with distinct roles – tracts of cytosines that collectively coordinate the cluster, thymine acting as a junction in the overall strand, and the adenine/guanine pair that exclusively forms the cluster. In relation to the native oligonucleotide, the DNA-silver cluster complex diffuses faster and is more compact, thus suggesting that the strands folds because of the cluster. The Ag10 6+ adduct emits with λex/λem = 490/540 nm, a 19% quantum yield, and a biexponential 1.1/2.1 ns lifetime. The electronic environment for the cluster is controlled by the heteroatoms in the adenine and guanine. Most significantly, the N7 and the N2 in the guanine change the fluorescence quantum yield by 60-fold and shift the fluorescence lifetime by ~3.8 ns. Thus, our studies discern distinct spectroscopic and structural roles for the nucleobase ligands in C4AC4TC3G, and these finding may help develop new DNA templates for other silver cluster adducts.
关键词： Nucleobase ligands,DNA,Silver clusters,Lifetime,Fluorescence,Quantum yield
更新于2025-09-23 15:21:21
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[IEEE 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Saint Petersburg, Russia (2018.10.22-2018.10.23)] 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Porous Silicon as a Material for Nanocomposites and the Effect of its Parameters on the Morphology of Silver Clusters
摘要： On the example of the por-Si/Ag composites it is demonstrated the ability to control the morphology of the guest material (Ag) by changing the parameters of the porous media (por-Si). Two groups of key parameters of porous materials important for creating composites based on them are discussed. Porous silicon was obtained by electrochemical anodic etching. The introducing Ag into the pores was performed by the cathodic electrochemical deposition. It is observed the increasing the anodizing time is leads to the noticeably changes of wetting angle of por-Si, and, in turn, significantly affects the morphology of Ag clusters. The growth mechanisms of Ag clusters on the por-Si surface and the fields of its potential application are discussed.
关键词： porous texture,surface properties,porous silicon composites,por-Si/Ag composites,electrochemical deposition,surface functionality,silver clusters
更新于2025-09-23 15:19:57
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A thirty-fold photoluminescence enhancement induced by secondary ligands in monolayer protected silver clusters
摘要： In this paper, we demonstrate that systematic replacement of the secondary ligand PPh3 leads to an enhancement in the near-infrared (NIR) photoluminescence (PL) of [Ag29(BDT)12(PPh3)4]3?. While the replacement of PPh3 with other monophosphines enhances luminescence slightly, the replacement with diphosphines of increasing chain length leads to a drastic PL enhancement, as high as 30 times compared to the parent cluster, [Ag29(BDT)12(PPh3)4]3?. Computational modeling suggests that the emission is a ligand to metal charge transfer (LMCT) which is affected by the nature of the secondary ligand. Control experiments with systematic replacement of the secondary ligand confirm its influence on the emission. The excited state dynamics shows this emission to be phosphorescent in nature which arises from the triplet excited state. This enhanced luminescence has been used to develop a prototypical O2 sensor. Moreover, a similar enhancement was also found for [Ag51(BDT)19(PPh3)3]3?. The work presents an easy approach to the PL enhancement of Ag clusters for various applications.
关键词： photoluminescence enhancement,phosphorescence,secondary ligands,silver clusters,O2 sensor
更新于2025-09-19 17:15:36
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Luminescent silver–lithium-zeolite phosphors for near-ultraviolet LED applications
摘要： Silver clusters (AgCLs) confined in zeolites show remarkable luminescence properties, displaying high photoluminescence quantum efficiencies combined with tunable visible light emission characteristics, making them highly promising phosphors in lighting devices. However, to date the lack of efficient near-ultraviolet (NUV) and blue excitable silver zeolites has hindered their use in remote LEDs. In this report, we show the utilization of Ag-zeolites in a NUV-LED device, displaying highly efficient green emission with an external quantum efficiency of 83% and a broad excitation range between 300 and 400 nm. This phosphor material was obtained by confining AgCLs in a dehydrated fully Li-exchanged Linde-type A (LTA) zeolite. The unique effect of Li+ ions and dehydration, on the luminescence properties of AgCLs, originates from the structural changes of both the zeolite framework, and the ligand coordinated tetrahedral Ag4 clusters, as observed by X-ray diffraction analysis and X-ray excited optical luminescence–X-ray absorption fine structure (XEOL-XAFS) method, respectively. Moreover, photophysical evidence showed long decay times for these samples in the order of 210 ms, responsible for the steady-state emission, which most likely originates from the decay of the triplet state with a charge transfer character of Ag4(O2) tetrahedral clusters surrounded by 6 lithium cations confined in the sodalite cages of LTA zeolites.
关键词： luminescence,NUV-LED,Silver clusters,quantum efficiency,phosphors,zeolites
更新于2025-09-16 10:30:52
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Synthesis of Plasmonic Photonic Crystal SiO2–Ag Nanostructures by Ion Beam Deposition of Silver Clusters onto Silica Microspheres
摘要： The synthesis of plasmonic photonic crystal SiO2–Ag nanostructures by deposition of silver nanoparticles is considered. The technique includes the physical sputtering of a silver target with a kiloelectronvolt argon ion beam onto silica microspheres obtained according to St?ber. The plasmon resonance effect is shown to be interrelated with the optical properties of nanostructured supports and the morphology of aggregate structures of silver nanoparticles (clusters).
关键词： silica microspheres,ion beam deposition,plasmonic photonic crystal,SiO2–Ag nanostructures,silver clusters
更新于2025-09-11 14:15:04