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Theoretical explanation of strong enhancement of alkali metal ion neutralization on Au nanoclusters
摘要： We present a theoretical study of alkali metal ion neutralization on gold nanoclusters. The experimental time-of-flight measurements show that neutral fraction of alkali metal ions scattered from flat Au surface is low (3%-15%), but it increases up to 50% for small Au clusters. Several possible explanations of alkali metal ions neutralization enhancement on nanoclusters have been proposed earlier, but they do not fully explain existing experimental data. We introduce alternative explanation of neutralization probability enhancement for small clusters. It is based on ion energy level shift due to interaction with image/induced charges, which significantly differs in the case of metallic nanocluster and in the case of flat continuous metallic surface. Another known mechanism is greater neutralization rate on positively charged edge atoms of Au nanocluster. The combination of two mechanisms and difference in atomic radii possibly explains greater neutralization probability enhancement for Na+ in comparison to Li+.
关键词： Resonant Charge Transfer,Low Energy Ion Scattering (LEIS),Alkali Metal Ions,Neutralization Effect
更新于2025-09-09 09:28:46
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Efficient improvement of 2.7μm luminescence of Er3+:oxyfluorideglass containing gallium by Yb3+ions codoping
摘要： Mid-infrared laser materials with low phonon energy have significant applications. However, the development of available glass systems for high-power laser gain medium have posed a great challenge. Therefore, we investigated the 2.7 μm spectroscopic properties of Er3+/Yb3+-codopedoxyfluoride glass containing gallium, which were prepared by typically melting and quenching methods. The 2.7 μm luminescence properties of the Er3+/Yb3+-codopedoxyfluoride glass containing gallium were recorded by a 980 nm laser diode. The Judd–Ofelt parameters, decay curves, emission cross section, energy transfer efficiency, and quantum efficiency were calculated. The maximum emission cross section of YbFGa-0.5 is 1.63×10?20 cm2 by 980 nm excitation. The energy transfer efficiency is calculated to be 77.8% for the YbFGa-0.5 glass around 2700 nm. The quantum efficiency at 1530 nm is 65.6%. The resulting reveals that the best doping concentration ratio of Er3+:Yb3+ ions is 1:0.5, and suggests an effective energy transfer from Yb3+ to Er3+ ions.
关键词： optical materials,rare-earth ions doped,optical spectroscopy,mid-infrared,energy transfer
更新于2025-09-09 09:28:46
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Synthesis of Novel Organic-Inorganic Hybrid Fluorescent Microspheres and Their Applications as Fe(III), Hg(II) and Biothiols Probes
摘要： Organic-inorganic hybrid fluorescent microspheres (OI-FMs) without typical fluorophores were prepared. Fluorescence quantum yield of OI-FMs is up to 0.7 after being heated in an oven at 120°C (named as OIFMs-120). Interestingly, OI-FMs-120 shows different detection performances in different solvents. It can be used for qualitative and quantitative detection of Fe3+ with a detection limit of 37.8 nM in absolute ethanol. While in aqueous solution, it can be applied as an ONOFF-ON fluorescent probe. Fluorescence of the probe is quenched by Hg2+and later recovered by biothiols. The detection limit are as low as 34.9 nM for Hg2+, 91.0 nM for Cys, 0.12 μM for Hcy and 0.13 μM for GSH in aqueous medium, respectively.
关键词： Biothiols,Heavy metal ions,Atypical fluorophores,Fluorescence sensor
更新于2025-09-09 09:28:46
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Design of Surface Acoustic Wave Sensors Functionalized with Bisphenol S Based Molecules for Lead Ions Detection
摘要： This study concerns the design of surface acoustic wave sensors functionalized with bisphenol S based molecules for lead ions detection. (4-hydroxyphenyl, 4′-benzyloxyphenyl) sulfone (M1), (4-hydroxyphenyl,4′-anthrylmethyloxyphenyl) sulfone (M2) and (4,4′-bis (anthrylmethyloxyphenyl)) sulfone (M3) were synthesized and then drop-coated on the SAWs sensing areas. Gravimetric results indicate that the limit of detection of the three sensors is in the picomolar range and that the M3/SAW sensor has the highest affinity towards lead ions compared to M1/SAW and M2/SAW. Density functional theory (DFT) calculations were investigated to support experimental results and to understand the nature of interactions involved between lead ions and the three synthetized molecules.
关键词： surface acoustic wave sensors,density functional theory calculations,lead ions
更新于2025-09-09 09:28:46
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Novel Approach for Modeling an Ionic Imprinted Polymer Based SAW Sensor with COMSOL Multiphysics
摘要： Modeling a Surface Acoustic Wave (SAW) sensor response as a chemosensor and not only as just an electronic transducer was performed with COMSOL Multiphysics. For this study, the SAW’s sensing area was functionalized with an ionic imprinted polymer (IIP), designed for the selective detection of lead ions. The idea consists in subdividing the IIP into elementary blocks whose physical properties can be modified separately. Three configurations have been envisaged: the IIP before and after lead ions extraction and the non-imprinted polymer (NIP). The generation of shear-horizontal waves on LiTaO3 piezoelectric substrate is confirmed by recording the displacement amplitude versus time, according to the three space directions. The sensors sensitivity is estimated from the delays induced by the incorporation of the lead ions in the IIP layer. To the best of our knowledge, this approach has never been presented in the literature.
关键词： SAW sensor,chemosensor,IIP after extraction,lead ions,ionic imprinted polymer (IIP),IIP before extraction,Non-imprinted polymer
更新于2025-09-09 09:28:46
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Distribution of Yb <sup>3+</sup> and Yb <sup>2+</sup> Ions along YbF <sub/>3</sub> -Doped BaF <sub/>2</sub> Crystals
摘要： BaF2 crystals doped with 0.05, 0.1, and 0.2 mol% YbF3 are grown using vertical Bridgman method. Transparent crystals, (cid:2)5–6 cm in length, (cid:2)10 mm in diameter, are obtained in vacuum using a shaped graphite furnace. The absorption spectra reveal the characteristic absorption bands of the Yb3+and Yb2+ ions in the as-grown crystals. The distribution of ytterbium ions along the crystals and the e?ective segregation coe?cient of the Yb3+ and Yb2+ ions in the BaF2 host are determined by using the optical absorption method. The crystals are cleaved from the bottom to the top into 10–17 slices of (cid:2)2 mm thickness. The optical absorption spectrum of every slice is recorded. The dopant distribution along the crystal is estimated studying the absorption spectrum of every slice. Two well-shaped and strong characteristic bands, 968 nm and 352 nm, respectively, are chosen. The Yb3+ and Yb2+ ions are not uniformly distributed along the BaF2 crystals. The calculated e?ective segregation coe?cients of the Yb3+ range from 0.7 to 0.84 and from 0.66 to 0.82 for Yb2+ ions.
关键词： segregation coefficient,ytterbium ions,optical properties,barium fluoride crystals
更新于2025-09-09 09:28:46
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Spectroscopic characterization of orthorhombic δ-BiB3O6 phase nonlinear single crystal doped with Pr3+ ions
摘要： The spectroscopic properties of 1at % Pr3+ doped δ-BiB3O6 (BIBO) single crystal were investigated. The absorption, emission and excitation spectra were studied at low (10 K) and at room temperature, with the emission and absorption spectra showing clear polarization dependence. The strongest observed luminescence band corresponds to the 1D2 → 3H4 transition at 610 nm. Energy levels of Pr3+ in δ-BIBO host were assigned on the basis of low temperature absorption and emission measurements. The number of crystal field levels derived implies that Pr3+ ions are located in one crystal site in the BIBO host. Decay time of the praseodymium 3P0 emission was unusually short and the 1D2 decay was non-exponential. The modified Judd-Ofelt intensity formalism was used to analyze the experimental data. The ?λ parameters, branching ratios and electric dipole transition probabilities were determined. The stimulated emission cross-sections σ for the 5D0 → 3HJ transitions were also evaluated in this system.
关键词： Pr3+ spectroscopic properties,Pr3+ luminescence,Pr3+ ions in borate hosts,δ-BiB3O6,Judd-Ofelt formalism
更新于2025-09-09 09:28:46
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Microwave Induced Center-Doping of Transition Metals Ions in Aqueous CdS NCs with Special Optical Properties
摘要： Under microwave irradiation, we systematically studied the formation of transition metal ions (TM), Ag+, Mn2+, Cu2+, Fe2+, Co2+ and Ni2+, doped CdS semiconductor nanocrystals in a pure water solution. The center-doping strategy is essential for achieving efficient internal-doping to improve the optical properties and stability of doped nanocrystals. The resulting TM doped nanocrystals have a high photoluminescence quantum yield (~ 60%) and an amazingly large range of the visible spectrum (480 ~ 650 nm). For Mn2+ doped CdS nanocrystals, significant high photoluminescence quantum yield, between 20% and 50% even at more than 600 nm, was achieved and there is potential for them to be directly used as a consummate toner for multicolor sensing and encoding without ligand exchange. Highly emissive-doped nanocrystals synthesized under designed conditions have been found to have excellent stability; samples could be stored for months without precipitation. In practice, this approach has great potential to promote the metal doping of various semiconductor nanocrystals to realize the specific advantages of doped nanocrystals in water solution.
关键词： transition metal ions,microwave,nanocrystals,doping,CdS
更新于2025-09-09 09:28:46
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Towards the lowest-energy limit for light ions identification with silicon pixel-type detectors
摘要： An in-beam test of two pixel-type silicon detectors of the TRACE detector project has been performed at Laboratori Nazionali di Legnaro (Italy). The aim was to investigate the lowest kinetic energy values at which isotopic identification of heavy-ion reactions products with mass A ～ 10 is possible, by using a single-layer silicon detector. Two separate read-out chains, analog and digital, were used, and the Pulse Shape Analysis technique was employed to obtain the particle identification matrices for the digitally processed data. The results confirmed the high capability of the Pulse Shape Analysis method which can be used for light ion identification, with performances similar to the analog approach. Separation in both charge and mass was obtained for Li and Be isotopes, however, the presence of a significant background from alpha particles severely limited the data analysis in the lower energy region. Due to this effect, the identification of the light products (7,6Li isotopes) could be possible down to ～ 24.5 MeV only, while the 9,7Be isotopes were separable down to ～ 29 MeV. This gives the value of < 4 MeV/nucleon as the lowest kinetic energy for light products identification by using the pixel-type detectors of the TRACE project, in the present experimental conditions.
关键词： isotopic identification,TRACE detector project,silicon detectors,light ions identification,Pulse Shape Analysis
更新于2025-09-09 09:28:46
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Improving the precision of frequency estimation via long-time coherences
摘要： In the last years several estimation strategies have been formulated to determine the value of an unknown parameter in the most precise way, taking into account the presence of noise. These strategies typically rely on the use of quantum entanglement between the sensing probes and they have been shown to be optimal in the asymptotic limit in the number of probes, as long as one performs measurements on shorter and shorter time scales. Here, we present a different approach to frequency estimation, which exploits quantum coherence in the state of each sensing particle in the long time limit and is obtained by properly engineering the environment. By means of a commonly used master equation, we show that our strategy can overcome the precision achievable with entanglement-based strategies for a finite number of probes. We discuss a possible implementation of the scheme in a realistic setup that uses trapped ions as quantum sensors.
关键词： quantum coherence,frequency estimation,trapped ions,quantum metrology
更新于2025-09-09 09:28:46