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oe1(光电查) - 科学论文

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出版时间
  • 2018
研究主题
  • Signal-to-Noise Ratio (SNR)
  • Infinite Gain Multiple Feedback (IGMF)
  • Visible Light Communications (VLC)
  • LED
  • Trans-Impedance Amplifier (TIA)
应用领域
  • Optoelectronic Information Science and Engineering
机构单位
  • University of Northumbria
  • University of Huddersfield
221 条数据
?? 中文（中国） ▾

  • Luminescence properties of novel red-emitting phosphors Ba3B6Si2O16: Eu3+ for near-UV excited LED

    摘要： A novel Eu3+ doped Ba3B6Si2O16 red-emitting phosphor was synthesized by a high temperature solid state reaction and its luminescence properties were investigated. All the phosphors are pure phase of triclinic Ba3B6Si2O16 in structure. Under 393 nm excitation, Ba3B6Si2O16: Eu3+ phosphor exhibits intense red emissions due to the characteristic f–f transitions of Eu3+ with the strongest emission peaks at 613 nm. The optimum doping concentration of Eu3+ is 0.09 and the corresponding critical distance is estimated to be 23.9 ?. The emission intensity decreases with increase of Eu3+ ion concentration(x>0.09) due to dipole-dipole interactions among Eu3+. Ba3B6Si2O16: Eu3+ phosphor exhibits high color purity (92%), good thermal stability (the activation energy of 0.2121 eV) and high quantum efficiency (36.5 %) with CIE chromaticity coordinates of (0.6460, 0.3534). These results indicate that Ba3B6Si2O16: Eu3+ phosphor can be anticipated as a red emitting phosphor for near-UV pumped white LEDs.

    关键词： luminescence property,Eu3+ ions,phosphors

    更新于2025-09-23 15:19:57

  • Synthesis of highly fluorescent and water soluble graphene quantum dots for detection of heavy metal ions in aqueous media

    摘要： Fluorescent graphene quantum dots (GQDs) are nanomaterials which possess unique properties that show great potential in different applications. In this work, GQDs were synthesized using graphene oxide (GO) as precursor via thermal treatment at high temperature. The obtained GQDs were highly fluorescent and were suitable for the determination of heavy metal ions. X-ray diffraction, FTIR spectroscopy, and UV visible spectroscopy confirm the formation of GQDs. TEM images show that formed GQDs have size ranging from 2 to 10 nm. Emission profile of aqueous GQDs was taken by exciting GQDs at different wavelength. The intensity of GQDs remains the same for 4–5 months. Furthermore, as prepared, GQDs were used for selective recognition of Fe3+, Pb+2, and Cr3+ from the bunch of different metal ions in aqueous media. Lower limit of detection obtained for Fe3+, Cr3+ and Pb2+ using GQDs were 50, 100 and 100 nM, respectively, which indicates that the GQDs can be utilized as a promising material for sensing of the heavy metal ions.

    关键词： GQDs,Lead and chromium ions,Iron,Fluorescence

    更新于2025-09-23 15:19:57

  • Binary synergetic ions reduce defect density in ambient air processed perovskite solar cells

    摘要： At present, significant research efforts are being concentrated on enhancing the performance and stability of perovskite solar cells (PSC) by lowering defect traps. In this study, NH4+ and SCN- binary ions as additive were incorporated into perovskite precursor to control the crystal growth. Our best performance based on the devices fabricated under fully open air condition was improved from 15.67 to 18.75%, boosting by 20%. The stability results display that devices containing additive maintained ~90% of the initial efficiency for 400 h in ambient air with a humidity of 30%. We first study the fundamentals of defect properties and carrier recombination kinetics behind the multifaceted role of mixed NH4+ and SCN- ions. Compared to using a single active specie as additive, mixed-ions devices exhibit effective bifacial trap passivation as well as lowered defect density in not only perovskite bulk material but also interfaces significantly, leading to facilitated electron transport. Our work can manifest a simple ambient air based approach by the mixed binary ions as additives in order to potentially promote the commercial prospects of PSCs.

    关键词： Ambient air process,Performance and stability,Defect density,Binary synergetic ions,Perovskite solar cell

    更新于2025-09-23 15:19:57

  • Luminescent Sulfur Quantum Dots for Colorimetric Discrimination of Multiple Metal Ions.

    摘要： The classical chemistry of sodium thiosulphate was applied to synthesize luminescent Sdots where elemental sulfur produced in situ was etched with NaOH. This method notably reduces the synthesis time of Sdots in comparison to the previously reported etching technique of bulk sulfur. The as-synthesized Sdots exhibited excitation dependent photoluminescence with a QY of 2.5 %, photostabality under UV light irradiation, excellent dispersibility in aqueous medium and also the stability even after several weeks. Notably, no emission was observed due to the oxidation of PEG-400 during the course of reaction. The Sdots was then employed as a dual function probe for the sensing of metal ions. Using fluorimetric method, Sdots showed preferential selectivity towards the Co2+ metal ions. However, a single probe Sdots can colorimetrically distinguish multiple metal ions such as Co2+, Cr6+ and Pb2+ by displaying color change on the immediate addition of analytes. Furthermore, the color change of Sdots is demonstrated with the help of hue images and hue spectra (or histogram) that will help in the development of Sdots based portable device. The present study contributes to the further advancement of this emerging field as a promising single-element nanomaterial an alternative to luminescent metallic nanomaterials.

    关键词： Colorimetric Discrimination,Photoluminescence,Hue,Sodium Thiosulphate,Sdots,Metal Ions

    更新于2025-09-23 15:19:57

  • Synthesis and photoluminescence properties of a new blue-light-excitable red phosphor Ca2LaTaO6:Eu3+ for white LEDs

    摘要： In this paper, a series of Eu3+-activated double-perovskite Ca2LaTaO6 (abbreviated as CLT:xEu3+; x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8) red-emitting phosphors have been successfully synthesized via the conventional high-temperature solid-state reaction method. These samples were characterized by X-ray diffraction, Rietveld refinement, field-emission scanning electron microscope, elemental mapping, energy-dispersive spectrum, room-temperature photoluminescence, decay lifetimes, quantum efficiency, CIE color coordinates, and temperature-dependent emission spectra. Interestingly, under blue excitation into the 7F0→5D2 transition of Eu3+ at 466 nm, the CLT:xEu3+ phosphors could emit bright red light corresponding to the 5D0→7FJ (J = 1, 2, 3, 4) transitions. Their luminescence properties have been investigated as a function of the Eu3+ ions concentration. It was found that the CLT:0.4Eu3+ sample exhibited the strongest emission intensity, and the concentration quenching effect was caused by the dipole-dipole interaction among Eu3+ activators. Impressively, the emission intensity of the as-prepared CLT:0.4Eu3+ phosphors was about 4.3 times higher than the commercial Y2O3:Eu3+ red phosphors. Moreover, the CLT:0.4Eu3+ sample had excellent CIE color coordinates of (0.665, 0.334) and supereminent color purity of 95.3%. Notably, the study on temperature-dependent emission spectra of the CLT:0.4Eu3+ sample revealed its good thermal stability and color stability at high temperatures. These excellent photoluminescence properties of CLT:0.4Eu3+ phosphors indicated their promising application potential in white light-emitting diodes as blue-light-excitable red phosphors.

    关键词： Ca2LaTaO6,White LEDs,Red-emitting phosphors,Eu3+ ions,Double-perovskite,Photoluminescence

    更新于2025-09-23 15:19:57

  • Ionization and acceleration of multiply charged gold ions in solid film irradiated by high intensity laser

    摘要： In this paper, we present the mechanisms of ionization of a thin gold ?lm irradiated by a high-intensity, short-pulse laser in the range of I ? 1020(cid:2)22 W=cm2 and the associated acceleration of multiply charged gold ions. A numerical one-dimensional simulation using an extended particle-in-cell code, which includes atomic and collisional relaxation processes, indicates that two types of acceleration, hole-boring radiation pressure acceleration (RPA) and target normal sheath acceleration (TNSA), contribute to the generation of highly charged ions with kinetic energies on the order of 10 MeV/u. In each acceleration, a longitudinal electrostatic ?eld excited by different mechanisms dominantly ionizes atoms to higher charge states and accelerates them to the vacuum region from the rear surface, which is opposite the front surface irradiated by the laser ?eld. The ?eld ionization process dominantly ionizes high energy ions to the high charge state, while a large number of ions with energy <1 MeV=u are ionized by an electron impact ionization process. In TNSA, a multiply charged ion generated at the rear surface is accelerated to the maximum energy although the ion with the highest charge state is generated at the front surface in RPA. However, the existence of contamination, such as water vapor, suppresses the ion energy of TNSA to less than that of RPA since the sheath ?eld readily accelerates the protons and oxygen prior to the acceleration of the gold ions. Our derived theoretical scaling describes the maximum ion energy for each charge state in the cases with and without contamination using the relationship between the longitudinal electrostatic ?eld pro?le near the rear surface and the classical tunnel ?eld ionization model.

    关键词： acceleration,multiply charged gold ions,RPA,TNSA,high-intensity laser,ionization,solid film

    更新于2025-09-23 15:19:57

  • A reaction-and-assembly approach using monoamine zinc porphyrin for highly stable large-area perovskite solar cells

    摘要： Inhibiting the irreversible escape of organic cations and iodide species in perovskite films is crucial for the fabrication of efficient and stable perovskite solar cells (PSCs). Here, we develop a reaction-and-assembly approach using monoamine zinc porphyrin (ZnP) to modify methylammonium (MA+) lead iodide perovskite film. The amine group in ZnP reacts with MA+ and I? ions to yield monoammonium zinc porphyrin (ZnP-H+I?). The resultant films show no escape of iodide when immersed in ether solutions. Measurements from space-charge limited currents and transient photoluminescence indicate the modified films have reduced density of defects. These results suggest the formed ZnP-H+I? is bound on the surface and grain boundary of perovskite film to retard migrations of ions. DFT calculations also show that the energy alignment between ZnP-H+ and perovskite facilitates the electron transfer and reduces charge recombination at the perovskite grains. Furthermore, post-treating the ZnP-doped film with ZnP again results in the formation of a one dimension zig-zag coordination polymer on the surface of the perovskite film. The single crystal structure of ZnP shows the polymer layer is formed through the coordination interaction between the Zn(II) metal center and a neighboring monoamine. The polymer facilitates the interfacial charge transfer, and reduces the escape of organic cations and iodide species in perovskite films, thereby keeping the excellent cell performance (20.0%) and further realizing the ion encapsulation. Finally, the modified PSCs retain over 90% of its original efficiency over 2,000 h at 85 °C or AM 1.5 G continuous illumination, or over 6,000 h in 45% humidity without encapsulation. This work affords a new strategy to achieve the efficient ions immobilization and encapsulation by in situ reaction and coordination assembly of mono-amine zinc porphyrin.

    关键词： monoamine porphyrin,perovskite solar cells,ions immobilization,reaction-and-assembly

    更新于2025-09-23 15:19:57

  • Dynamic characteristics of multi-charged ions emitted from nanosecond laser produced molybdenum plasmas

    摘要： Diagnostics of plasma-wall interaction processes provide important information for nuclear fusion devices. Elucidation of the charge state distribution and temporal evolution of the multi-charged ions is essential to improve laser ablation-based diagnostics of the plasma-wall interaction processes. Molybdenum is a material of interest in fusion and has been used as the plasma-facing material of the first wall in the EAST tokamak. In this work, the dynamic characteristics of multi-charged ions emitted from a molybdenum plasma produced by a Q-switched Nd:YAG nanosecond laser (wavelength 1064 nm, pulse width 7 ns) were studied using time of flight mass spectroscopy under a pressure of 6×10-4 Pa. The charge state distribution and temporal evolution of the multi-charged ions at various laser power densities from 0.85 GW/cm2 to 7.9 GW/cm2 were systematically investigated. This power density range is commensurate to that used in LIBS and LIAS diagnostics of the plasma-wall interaction process in EAST tokamaks.The ion charge state was found to increase with laser power density and the observed maximum charge state was up to seven at the highest laser power density used in these experiments. The higher charged ions had greater velocities indicating that separation took place between the different charged ions during the plasma expansion process. The origin of multi-charged ions is attributed to step-wise ionization due to plasma shielding from strong laser absorption in the plasma and the reduction of the ablation rate with increase in laser power density. The velocities between these multi-charged ions were related to the acceleration of the transient plasma sheath during the laser interaction with the target and plasma.

    关键词： molybdenum plasma,plasma-wall interaction,time of flight mass spectroscopy,multi-charged ions,laser ablation

    更新于2025-09-23 15:19:57

  • Engineering efficient upconverting nanothermometers using Eu <sup>3+</sup> ions

    摘要： Upconversion nanothermometry combines the possibility of optically sensing temperatures in very small areas, such as microfluidic channels or on microelectronic chips, with a simple detection setup in the visible spectral range and reduced heat transfer after near-infrared (NIR) excitation. We propose a ratiometric strategy based on Eu3+ ion luminescence activated through upconversion processes. Yb3+ ions act as a sensitizer in the NIR region (980 nm), and energy is transferred to Tm3+ ions that in turn excite Eu3+ ions whose luminescence is shown to be thermally sensitive. Tridoped SrF2:Yb3+,Tm3+,Eu3+ nanoparticles (average size of 17 nm) show a relative thermal sensitivity of 1.1% K-1 at 25.0 °C, in the range of the best ones reported to date for Ln3+-based nanothermometers based on upconversion emission. The present nanoparticle design allows us to exploit upconversion of lanthanide ions that otherwise cannot be directly excited upon NIR excitation and that may provide operational wavelengths with a highly stable read out to fill the spectral gaps currently existing in upconversion-based nanothermometry.

    关键词： nanothermometry,nanoparticles,upconversion,ratiometric strategy,lanthanide ions,Eu3+

    更新于2025-09-19 17:15:36

  • Self-agglomerated crystalline needles harnessing ESIPT and AIEE features for the ‘turn-on’ fluorescence detection of Al <sup>3+</sup> ions

    摘要： We report the synthesis of probe 2 for the fluorescence "turn-on" detection of Al3+ ions in CH3OH. Probe 2 has been designed via utilizing the aggregation-induced emission properties of the tetraphenylethylene unit, with further enhancement from Schiff base units for the ESIPT phenomenon. Probe 2 exhibits emission at 548 nm (lex = 360 nm), with a large Stokes shift of 188 nm, indicating the ESIPT phenomenon. Probe 2 also exhibits emission enhancement via increasing the H2O ratio up to 70–90% H2O/THF (v/v) and altering the spherical morphology to needle shapes. Probe 2 has been found to be highly selective and sensitive towards Al3+ ions over other metal ions in pure CH3OH using absorption and emission spectroscopy. FESEM analysis revealed that the size of probe 2 increases upon the addition of Al3+ ions. Thus, the fluorescence "turn-on" behaviour of probe 2(cid:2)Al3+ is due to metal-induced aggregation.

    关键词： fluorescence detection,ESIPT,Al3+ ions,AIEE,aggregation-induced emission

    更新于2025-09-19 17:15:36