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Tunable Emission of Bluish Zn-Cu-Ga-S Quantum Dots by Mn Doping and their Electroluminescence
摘要： Based on bluish-emitting double-shelled quantum dots (QDs) of Zn?Cu?Ga?S (ZCGS)/ZnS/ZnS, Mn doping into ZCGS host with different Mn/Cu concentrations is implemented via surface adsorption and lattice diffusion. The resulting double-shelled Mn-doped ZCGS (ZCGS:Mn) QDs exhibit a distinct Mn2+ 4T1?6A1 emission as a consequence of effective lattice incorporation simultaneously with host intragap states-involving emissions of free-to-bound and donor-acceptor pair (DAP) recombinations. The relative contribution of Mn emission in the overall photoluminescence (PL) is consistently proportional to its concentration, resulting in tunable PL from bluish, white, to reddish white. Regardless of Mn doping and its concentration all QDs possess high PL quantum yield (QY) levels of 74?79%. Those undoped and doped QDs are then employed as an emitting layer (EML) of all-solution-processed QD-light-emitting diodes (QLEDs) with hybrid charge transport layers and their electroluminescence (EL) is compared. When compared to undoped QDs, doped analogues give rise to a huge spectral disparity of EL versus PL, specifically showing a near-complete quenching of Mn2+ EL. This unexpected observation is rationalized primarily by considering unbalanced carrier injection to QD EML on the basis of energetic alignment of the present QLED and rapid trapping of holes injected at intragap states of QDs.
关键词： Tunable emission,Electroluminescence,Emission quenching,Zn?Cu?Ga?S quantum dots,Mn doping
更新于2025-11-20 15:33:11
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Robust CsPbX <sub/>3</sub> (X = Cl, Br, and I) perovskite quantum dot embedded glasses: nanocrystallization, improved stability and visible full-spectral tunable emissions
摘要： Currently, all inorganic perovskite quantum dots (QDs) of cesium lead halides (CsPbX3, X = Cl, Br, and I) have been mainly fabricated using wet chemical methods. Unfortunately, applications of perovskite QDs have been limited due to their poor stability. In the present work, the in situ growth of whole-family CsPbX3 (X = Cl, Br, and I) perovskite QDs in Zn–P–B–Sb based oxide glass via a glass crystallization strategy is reported. The as-prepared CsPbX3 QDs@glass nanocomposites exhibit typical excitonic recombination emissions and superior chemical stability benefited from the protection of the robust inorganic glass matrix. Through modifying the molar ratio of halide sources in glass, multi-color tunable emissions in the entire visible spectral range of 400–750 nm are achieved. As a result, light-emitting diode devices can be constructed by coupling blue-emissive CsPbBrCl2, green-emissive CsPbBr3 and red-emissive CsPbBr0.5I2.5 QDs@glass powders with a commercial ultraviolet chip, yielding bright white light luminescence with excellent optoelectronic performance.
关键词： stability,light-emitting diodes,tunable emissions,glass crystallization,perovskite quantum dots
更新于2025-11-20 15:33:11
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Saponification Precipitation Method of CsPbBr3 Nanocrystals with Blue-Green Tunable Emission
摘要： We report on a new synthesis process for halide perovskite nanoplatelets and nanoplates that switches the production process of the cesium precursor from a fatty acid/cesium salt reaction to a cesium base/fatty acid ester reaction, thus enabling the reaction to occur in ambient conditions in minutes instead of hours. The saponification precipitation process reported here, as a result, does not require a vacuum oven or inert reaction environment in obtaining the cesium precursor, or any part of the reaction. Furthermore, the process creates a hygroscopic byproduct that results in a self-drying synthesis. The obtained perovskite nanocrystals exhibit a blue-green tunable emission that occurs via quantum confinement effect, phase, and morphology change. The consequence of these physical processes is that the band gap is highly tunable with temperature and the resulting nanocrystals show remarkable optical properties, while greatly simplifying the production of halide perovskite nanoplatelets and nanoplates.
关键词： Blue-Green Tunable Emission,Saponification Precipitation Method,Hybrid Materials,Magnetic,CsPbBr3 Nanocrystals,Plasmonics,Optical
更新于2025-11-19 16:46:39
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A widely tunable bandpass filter adopting novel fully tunable resonators
摘要： A widely tunable bandpass filter adopting a novel fully tunable resonator is proposed in this letter. The fully tunable resonator is mainly consisted of an open ring, a frequency tuning structure, and a coupling tuning structure. Adopting the fully resonators, the center frequency, the input/output external Q value, and the coupling coefficients can be tuned at the same time. And the tuning range of a tunable filter adopting the novel fully tunable resonators can be expanded. The fully tunable resonators can be combined to achieve more excellent suppression performance. A widely tunable bandpass filter consisted of five fully tunable resonators with 86.5% frequency tuning range is designed, fabricated, and measured. The simulated results are in good agreement with the measured ones.
关键词： widely tunable filter,coupling tuning structure,open ring,fully tunable resonators,more excellent suppression
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE Conference on Antenna Measurements & Applications (CAMA) - Va?ster?s (2018.9.3-2018.9.6)] 2018 IEEE Conference on Antenna Measurements & Applications (CAMA) - Overview On Functional Materials for Frequency Tunable Antennas
摘要： We report the integration of different kind of materials with improved and adapted properties within antenna designs. In this framework, an overview of three frequency tunable antennas will be presented. Two of them are based on radiating slot elements integrating a Ba2/3Sr1/3TiO3 (BST)-based tunable capacitance and therefore present a continuous tunability for the first one while the second one is integrating a VO2-based switch for a discrete tuning. The third design presented in this paper propose a frequency reconfigurable composite GeTe-metal patch antenna operating at the millimeter-waves (24-30 GHz) whose resonant frequency can be tuned and repeatedly changed upon the application of successive laser pulses.
关键词： Frequency tunable antenna,VO2 switches,BST tunable capacitance,Phase Change Materials
更新于2025-09-23 15:23:52
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Gold Nanorod-Coated Capillaries for the SERS-Based Detection of Thiram
摘要： Surface enhanced Raman scattering (SERS)-based capillary system is a promising route towards fast, real-time and in-situ detection using a facile sampling process. Here, we demonstrate for the first time resonance-tunable SERS-active capillaries with high sensitivity, reproducibility and stability. The strong signal consistency independent of measurement spots or storage time supports the long-term storage and signal tracking of analytes in practical use. The capillaries were successfully applied to the in-situ detection of pesticide residues, and the sampling process provides operation conveniency compared to conventional methods. These results indicate that our SERS-active capillaries have great potentials in fast in-situ detection for many practical applications.
关键词： surface enhanced Raman scattering,stability,thiram detection,gold nanorod,capillary tube,tunable plasmon resonance
更新于2025-09-23 15:23:52
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Tunable photoluminescence properties and energy transfer of Ca5(BO3)3F: Tb3+/Eu3+ phosphors for solid state lighting
摘要： A series of Ca5(BO3)3F: Tb3+/Eu3+ phosphors have been prepared via solid-state reaction. Phase purity and crystal structure of as-prepared samples are confirmed by X-ray diffraction measurements. The emission intensity of Ca5(BO3)3F: Tb3+ with Li+, Na+, K+ as charge compensators are remarkably enhanced, and the sample in presence of Na+ exhibits the strongest emission intensity. The emission spectra and fluorescence decays confirm the presence of efficient energy transfers from Tb3+ to Eu3+ in Ca5(BO3)3F: Tb3+/Eu3+ phosphors. The energy transfer mechanism between Tb3+ and Eu3+ has been proven to be resonant type via the electric dipole-dipole interaction. The thermal quenching temperature T50 obtained from the temperature-dependent emission spectra is 478 K, demonstrating a high thermal stability of the as-obtained Ca5(BO3)3F: Tb3+/Eu3+ phosphors. Moreover, by increasing the molar ratio of Eu3+ to Tb3+, the emission colors of Ca5(BO3)3F: Tb3+/Eu3+ phosphors can be tuned from green to orange, and then to red. These results demonstrate that the as-obtained Ca5(BO3)3F: Tb3+/Eu3+ phosphors may have potential applications in solid-state lighting fields.
关键词： Energy transfer,Ca5(BO3)3F,Phosphors,Tunable luminescence,Solid-state reaction
更新于2025-09-23 15:23:52
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In-band phase deviation minimization method for wideband tunable phase shifter
摘要： This article provides a novel approach to analyze and design wideband tunable reflection-type phase shifter (RTPS) with low in-band phase deviation (IBPD) error. The proposed RTPS consists of coupled lines where through and coupled ports are terminated with varactor diodes. The coupled lines can minimize the parasitic elements of varactor diode to achieve high phase shift range (PSR). In addition, the measured frequency-dependent capacitance of varactor diode was used in the analytical analysis to obtain minimum IBPD error and high PSR. For experimental demonstration, phase shifter was fabricated at the center frequency of 2.5 GHz. The measured results show that the fabricated circuit achieved 126.85° PSR with ±6.48° IBPD error for 500 MHz bandwidth (BW). In addition, the measured maximum insertion loss variation and input/output return losses are within ±0.34 dB and higher than 16.85 dB within 500 MHz BW, respectively.
关键词： varactor diode,coupled line,low in-band phase deviation error,wideband tunable reflection-type phase shifter
更新于2025-09-23 15:23:52
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Cesium lead halide perovskite nanocrystals for ultraviolet and blue light blocking
摘要： Direct exposure to ultraviolet (UV) light is closely related to various harmful effects [1-3], ranging from skin injures to cancer originated from DNA damage. Recent years, some studies reported that blue light are also detrimental to humans [4,5], for example, the blue light could cause photochemical lesions to human retinal within the intensity range of the natural light [6]. Furthermore, blue light is responsible for the solar retinitis and may play a role in age-related macular degeneration. Importantly, the harmful effects of blue lights generated from the electronic display devices should also be careful [7]. Thus, the development of new UV and blue light shielding materials has been received much attention [8]. In the past few years, there has been an increased awareness of the importance to develop UV shielding materials. A variety of materials have been used to prevent UV lesions. Organic molecules like avobenzone or oxybenzone have been used as a UV absorber for many years, but the self-degradation limits their usage time. Inorganic materials such as zinc oxide (ZnO) and titanium oxide (TiO2) have been used intensively for UV shielding [9-12]. However, photocatalytic properties and self-degradations of the ZnO and TiO2 based absorbers also hindered their applications [13,14]. Other materials, e.g., graphene oxide-poly(vinyl alcohol) composite film and lanthanide complex functionalized cellulose nanopaper were also reported for UV shielding [15,16]. Whereas, the excellent UV-filtering capability of these films was obtained by sacrificing the visible light transmittance. Therefore, fabricating UV and blue light blocking materials with good photostability and high transparency to the rest of visible light still remains a challenge and is urgently needed to be developed. Recently, because of the outstanding performance in photovoltaic applications, lead halide perovskite APbX3 (where A = CH3NH3+, (NH2)2CH+ and Cs+, X = Cl?, Br? and I?) has become the most noticeable materials [17-22]. These perovskite nanocrystals exhibit intriguing features [23], such as easy tunable band gap, sharp optical absorption edges and high quantum efficiency with narrow emission spectra. These nanocrystals have been studied extensively for various optical applications, especially light emitting diodes and lasers [24-27]. Post modification of perovskite nanocrystals by anion exchange enables the absorbance band gap tuned from ultraviolet to near infrared spectra [28,29]. In addition, the perovskite nanocrystals show large absorption range, which offers the great potential for UV and blue light shielding applications. Although the tunable absorption-band edge of perovskite nanocrystals has already been realized, there have not been reports on developing UV and blue light blocking material with tunable absorption-band edge. Herein, we aim to the development of a simple and easy way to fabricate UV and blue light blocking material by mixing pervoskite nanocrystals and ethyl cellulose (EC). In this study, EC was used as a host material for the CsPb(Cl/Br)3 pervoskite nanocrystals. By tuning the ratio of Br to Cl, the blocked wavelength range could be easily controlled. Using the sharp absorption edges, the material possesses excellent light blocking ability in the range of 200-460 nm and maintains high transparency (95%) to visible light in the range beyond blue light.
关键词： UV blocking,Cesium lead halide nanocrystals,Blue light blocking,Tunable adsorption edge,Perovskite nanocrystals
更新于2025-09-23 15:23:52
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Electrically tuned microwave CP cross slot patch antenna using liquid crystal technology
摘要： The rapid progress in material science and electronic technology is great possibility in designing reconfigurable wireless devices which are frequency tunable, flexible and consume low energy. In this paper, the anisotropic propriety of a new liquid crystal mixture 'GT3-23001' in their nematic phase are exploited for designing tunable circular polarized cross slot patch antenna for WLAN applications. Reconfiguration of frequency response is controlled through an electrical external command. The proposed reconfigurable antenna based on liquid crystal satisfies a continuous frequency tuning of 15.83% with a global bandwidth of around 467.92 MHz (19.5%). to validate this novel mixture of liquid crystal, the simulated results are compared with the measured data and a good agreement is noticed.
关键词： liquid crystal mixture,Material science,tunable patch,circular polarized,reconfigurable,frequency tuning
更新于2025-09-23 15:23:52