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Temperature Dependence of Desorbed Ions and Neutrals and Ionization Mechanism of Matrix-Assisted Laser Desorption/Ionization
摘要： Two separate temperature-dependent experiments were performed to investigate the ionization mechanism of ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI) of matrix 2,5-dihydroxybenzoic acid (2,5-DHB). First, the angular resolved intensity and velocity distributions of neutrals desorbed from the 2,5-DHB solid sample through UV laser (355 nm) pulse irradiation were measured using a rotating quadrupole mass spectrometer. Second, the desorbed neutrals, at an angle normal to the surface, and the desorbed ions were simultaneously detected for each laser shot using the quadrupole mass spectrometer, respectively. Both experiments were conducted at two initial temperatures: 100 and 300 K. The measurements from these two experiments were used to calculate the initial temperature dependence of the ion-to-neutral ratio. The results closely agreed with the predictions of the temperature-dependent ion-to-neutral ratio using the thermal model, indicating that thermally induced proton transfer is the dominant reaction that generates initial ions of 2,5-DHB in UV-MALDI.
关键词： temperature dependence,desorbed neutrals,MALDI,ionization mechanism,thermal model,desorbed ions,ion-to-neutral ratio,2,5-DHB
更新于2025-09-19 17:13:59
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Carbon multicharged ion generation from laser-spark ion source
摘要： Multicharged carbon ions are generated by using a laser-assisted spark-discharge ion source. A Q-switched Nd:YAG laser pulse (1064 nm, 7 ns, ≤ 4.5 × 109 W/cm2) focused onto the surface of a glassy carbon target results in its ablation. The spark-discharge (～1.2 J energy, ～1 μs duration) is initiated along the direction of the plume propagation between the target surface and a grounded mesh that is parallel to the target surface. Ions emitted from the laser-spark plasma are detected by their time-of-flight using a Faraday cup. The ion energy-to-charge ratio is analyzed by a three-mesh retarding field analyzer. In one set of experiments, the laser plasma is generated by target ablation using a 50 mJ laser pulse. In another set of experiments, ～1.2 J spark-discharge energy is coupled to the expanding plasma to increase the plasma density and temperature that results in the generation of carbon multicharged ions up to C6+. A delay-generator is used to control the time delay between the laser pulse and the thyratron trigger. Ion generation from a laser pulse when a high DC voltage is applied to the target is compared to that when a spark-discharge with an equivalent pulsed voltage is applied to the target. The laser-coupled spark-discharge (7 kV peak voltage, 810 A peak current) increases the maximum detected ion charge state from C4+ to C6+, accompanied by an increase in the ion yield by a factor of ～6 compared to applying 7.0 kV DC voltage to the target.
关键词： carbon multicharged ions,plasma,ion generation,spark-discharge,laser-spark ion source
更新于2025-09-19 17:13:59
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Radiation hardness investigation of heterojunction solar cell structures with TCO antireflection films
摘要： Phosphorus doped silicon carbide film as emitter in heterojunction structure was deposited on p-type Si(100) wafers at various deposition conditions by means of PECVD technology using silane (SiH4), methane (CH4), hydrogen (H2) and phosphine (PH3, 2 vol.% in H2) gas as precursors. ITO or IZO film was RF magnetron sputtered on top of the different P doped a-SiC:H(n) film. Irradiation of structures with Xe ions to total fluency 5x1011 cm-2 was performed at room temperature. Influence of phosphorus concentration and type of transparent conducting oxide was investigated. A deeper insight on the impact of irradiation on the electrophysical properties of sample was obtained by the analysis of complex impedance spectra.
关键词： Xe ions irradiation,RF magnetron sputtering,TCO antireflection films,radiation hardness,impedance spectra,heterojunction solar cell,PECVD
更新于2025-09-19 17:13:59
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Neoteric Mn <sup>2+</sup> ‐activated Cs <sub/>3</sub> Cu <sub/>2</sub> I <sub/>5</sub> dazzling yellow‐emitting phosphors for white‐LED
摘要： Neoteric Mn2+‐activated Cs3Cu2I5 yellow‐emitting halides were achieved by the simple solid‐state reaction route. The near‐ultraviolet light was the suitable excitation lighting source for the resultant halides. The resultant halides exhibited bright yellow emission under the excitation of 378 nm and the optimum dopant content was 11 mol%. The multipole‐multipole interaction contributed to the concentration quenching mechanism and the critical distance was 28.65 ?. The thermal resistance of the prepared compounds was identified by the temperature‐dependent emission spectra. Ultimately, the designed light‐emitting diode showed bright white light with satisfied color rendering index, proper color coordinate, and suitable correlated color temperature. These results indicated that the prepared yellow‐emitting halides were suitable for indoor illumination.
关键词： white‐LED,phosphors,Mn2+ ions,luminescence
更新于2025-09-19 17:13:59
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Cu2+-mediated Fluorescence Switching of Graphene Quantum Dots for Highly Selective Detection of Glutathione
摘要： As a short peptide containing active thiol group, glutathione (GSH) participates in many cellular reactions, so it is of great significance to detect cellular GSH. In this work, amino-rich graphene quantum dots (GQDs) were synthesized, which could coordinate with copper ions (Cu2+) and yield aggregation-induced fluorescence quenching. However, GSH owns stronger coordination ability with Cu2+, so that GSH could promote the dissociation of Cu2+ from the surface of GQDs, and then led to the fluorescence recovery of GQDs. In BR buffer medium at pH 6.8, GSH was able to gradually recover the fluorescence of GQDs (1 μg/mL) that was quenched by Cu2+ (250 μmol/L), which could be finished within 20 min. Additionally, the recovery degree of fluorescence was linear to the concentration of GSH in the range of 20─500 μmol/L with a detection limit of 3.4 μmol/L. This method was applicable to the detection of GSH in cell lysate by the switchable function of Cu2+ to improve the selectivity.
关键词： Graphene quantum dots,Fluorescence switching,Copper ions,Glutathione
更新于2025-09-19 17:13:59
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Improved photovoltaic performance of dye-sensitized solar cells by Au-ion implantation of titania film electrodes
摘要： Plasmonic metal nanoparticles are known to work as light-harvesting antennae and to enhance photocurrents of photovoltaic cells. Therefore, in this work, the effect of gold (Au) ions distribution on the efficiency of dye sensitized solar cells (DSSCs) has been investigated. Thin films of TiO2 have been deposited on FTO glass substrates by the doctor tape method. Au ions were then implanted on these films with different fluence rates (i.e., 2 × 1014, 4 × 1014 and 6 × 1014 ions/cm2). XRD results confirmed that TiO2 is present in the anatase phase up to a 4 × 104 ions/cm2 fluence rate. At a 6 × 1014 ions/cm2 fluence rate, one peak of rutile is obtained which confirmed that the film has mixed phases of TiO2. UV results show that dye is adsorbed into all photoanodes. Maximum dye absorption is seen at a fluence rate of 4 × 1014 ions/cm2. The energy conversion efficiency of DSSC is highly dependent on the fluence rate of Au. At a fluence rate of 4 × 1014 ions/cm2, the cell has a high short circuit current density (JSC) of 7.21 mA/cm2, resulting in a high efficiency (×) of 2.92%. Impedance spectroscopy shows that the cell formed by Au ions fluence rate of 4 × 1014 ions/cm2 has a low recombination rate of electron/hole pairs.
关键词： Impedance spectroscopy,Ions implantation,Au,TiO2,Dye-sensitized solar cells
更新于2025-09-19 17:13:59
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Ratiometric fluorometric determination of silver(I) by using blue-emitting silicon- and nitrogen-doped carbon quantum dots and red-emitting N-acetyl-L-cysteine-capped CdTe quantum dots
摘要： A ratiometric fluorometric assay for silver(I) is described. The method makes use of a dually emitting quantum dot hybrid, which is composed of (a) blue-fluorescent silicon- and nitrogen-doped carbon quantum dots (CQDs), and (b) of red-emitting CdTe quantum dots (QDs) capped with N-acetyl-L-cysteine. The red-emitting CdTe QDs undergo strong and specific quenching by Ag(I), whereas the blue-emitting N,Si-CQDs are not quenched. The two kinds of QDs are mixed and used as a ratiometric fluorescent probe. A linear relationship is found between the log of intensities [(I608/I441)0/(I608/I441)] and the concentration of Ag(I) in the range from 5.0–1000 nM, and the limit of detection (at S/N = 3) is 1.7 nM. Possible interferents (including 17 general metal ions, 12 anions and fulvic acid) do not interfere with the determination. The assay was successfully used for the determination of Ag(I) in surface water and wastewater samples. The fluorescence quenching mechanism of the ratiometric assay system was also discussed in detailed.
关键词： Fluorescence quenching mechanism,Surface water,Nitrogen-doped carbon dots,Silver ions,Silicon-doped carbon dots,Wastewaters,3-Aminopropyltriethoxysilane functionalized carbon dots,Quenching efficiency,Dual-emission quantum dots hybrid,Fluorescent probe
更新于2025-09-19 17:13:59
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One-pot synthesis of N, S co-doped photoluminescent carbon quantum dots for Hg2+ ion detection
摘要： N and S co-doped carbon quantum dots (N, S-CQDs) with a high fluorescence quantum yield (12.6%) were synthesized by a one-pot hydrothermal method. Results indicate that the N, S-CQDs have a small particle size and an amorphous structure, exhibiting unique surface states and excitation wavelength-independent fluorescent properties. Co-doping of N and S increases the electron-transfer rate and improves the coordination interaction between the N, S-CQDs and Hg2+ ions. The N, S-CQDs show a high sensitivity and selectivity in detecting Hg2+ ions even for a lake water sample. They are promising fluorescence probes for environmental monitoring.
关键词： Hg2+ ions detection,Co-doped,L-cysteine,Photoluminescent,Carbon quantum dots
更新于2025-09-19 17:13:59
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A Fluorescence Probe for Metal Ions Based on Black Phosphorus Quantum Dots
摘要： Fluorescence method for detecting metal ions has advantages of fast detection speed, simple operation, and low price over the conventional methods. Black phosphorus quantum dots (BP QDs) have high photoluminescence quantum yield and modifiable surface, which have great potential in the field of fluorescent probes. In this study, high quality BP QDs are prepared by pyrolysis method and are first time used as trace metal ion probes in both organic solutions and aqueous solutions. The detection limits of Hg2+ and Cu2+ in the aqueous solution are 5.3 × 10?9 m and 1.6 × 10?6 m, respectively. In addition, the detection limits of Cu2+ in the organic solution are 16 × 10?6 m. The fluorescence quenching mechanism based on the calculation of the electronic structure and adsorption energy of BP QDs after adsorption of metal ions is further explained. The results provide a new promising fluorescence probe for trace metal ions without the help of organic molecules.
关键词： electron transfer,fluorescence,black phosphorus,metal ions
更新于2025-09-19 17:13:59
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Efficient green-emitting Ca2GdZr2Al3O12:Ce3+,Tb3+ phosphors for near-UV-pumped high-CRI warm-white LEDs
摘要： In this work, we reported novel efficient Ce3+/Tb3+ co-doped Ca2GdZr2Al3O12 (CGZA) green-emitting phosphors by traditional solid state method. The phase purity, crystal structure, morphology, photoluminescence properties, internal quantum efficiencies (IQEs), and thermal stability of the samples were systematically investigated. The obtained results revealed that there was an obvious spectral overlap between the emission spectrum of Ce3+ singly doped CGZA phosphors and excitation spectrum of Tb3+ singly doped CGZA phosphors, and efficient energy transfer from Ce3+ to Tb3+ ions existed in Ce3+ and Tb3+ co-doped CGZA phosphors. The Ce3+→Tb3+ energy transfer mechanism was ascribed to the dipole-dipole interaction. The CGZA:Ce3+,Tb3+ phosphors exhibited a broad excitation spectrum in the wavelength range of 370-470 nm with a maximum at 408 nm corresponding to the spin-allowed 4f-5d transition of Ce3+ ions. Upon near-ultraviolet (near-UV) excitation at 408 nm, the composition-optimized CGZA:0.02Ce3+,0.8Tb3+ sample showed intense sharp narrow-line emissions at 485, 543, 591, 629, 643, 663, and 679 nm due to the 5D4→7FJ (J = 6-0) transitions of Tb3+ ions, along with a good IQE of 51%. Lastly, a white LED device was fabricated by using as-prepared CGZA:0.02Ce3+,0.8Tb3+ green phosphors, commercial BaMgAl10O17:Eu2+ blue phosphors, and CaAlSiN3:Eu2+ red phosphors, and under 300 mA driven current it gave bright warm-white light with a low correlated color temperature of 3969 K and a high color rendering index (Ra = 91.2). Our work provides a new perspective for the design and fabrication of efficient color conversion materials toward near-UV LED-based warm-white LEDs.
关键词： Garnet,Ce3+ ions,White LEDs,Phosphors,Tb3+ ions,Photoluminescence
更新于2025-09-16 10:30:52