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Probing the Role of Nickle Dopant in Aqueous Colloidal ZnS Nanocrystals for Efficient Solar-Driven CO2 Reduction
摘要： Photocatalytic CO2 reduction reaction (CO2RR) on a heterogeneous catalyst offers the possibility for CO2 abatement and emerges as a promising avenue for renewable carbonaceous fuels production at ambient temperature and pressure using solar light as the sole energy input. Here, we report a newly aqueous colloidal comprised of monodispersed Ni-doped ZnS (ZnS:Ni) nanocrystals as excellent visible-light-responsive photocatalysts for CO2RR into formate. The wavelength-dependent quantum yield shows a significant contribution of Ni doping for visible light absorption. A high selectivity (>95%) of HCOOH production and a remarkable quantum efficiency of 59.1% at 340 nm and 5.6 % at 420 nm are obtained over ZnS:Ni (0.1 %) colloidal nanocrystals modified by Cd2+. The abundant sulfur vacancies and extended visible light absorption of the constructed colloidal ZnS:Ni nanocrystals contribute to the prominent performance for CO2RR. However, excessive doping of Ni does not guarantee an increase of photocatalytic CO2RR due to a diminish of sulfur vacancy. The regulation of sulfur vacancies by Ni doping and their interplay on photocatalytic CO2RR activity are presented and discussed. This work provides an in-depth insight of the role of dopant on vacancy modulation in photocatalyst beyond light absorption and a guidance for design of the potential photocatalyst for CO2RR.
关键词： CO2 reduction,vacancy,photocatalysis,doping,ZnS
更新于2025-11-19 16:51:07
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S, N-codoped Oil-soluble Fluorescent Carbon Dots for High Color-rendering WLED
摘要： Carbon dots (CDs) have attracted widespread attention in light-emitting-diode (LED) applications owing to their environmental friendliness, easy processing and unique optical properties. For the practical use of CDs in LEDs, the controllable synthesis of high performance oil-soluble carbon dots are still in urgent demand. In this study, S, N-codoped oil-soluble carbon dots (S, N-OCDs) with average size of 3.38 nm were prepared by solvothermal reaction of acetone, dimethyl trithiocarbonate (DMTTC) and nitric acid. Characterization results reveal that both the conjugated aromatic π systems from aldol condensation and highly active free radicals from DMTTC essentially dominate the development of this yellow-green emitting S, N-OCDs which possess high carbonization, quantum yield (21.08 %) and oil-solubility. Furthermore, a white light-emitting-diode (WLED) was fabricated through mixing the obtained S, N-OCDs and epoxy and drop-casting the mixure on the surface of gallium nitride (GaN) based blue chips. The as-prepared WLED showed excellent color rendering properties (CCT of 5389 K, CIE coordinates of (0.33,0.30), CRI of 88.38).
关键词： oil-soluble carbon dots,color rendering index,WLED,heteroatom doping
更新于2025-11-19 16:46:39
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One-step Aqueous Synthesis of Zn-based Quantum Dots as Potential Generators of Reactive Oxygen Species
摘要： The actual incorporation of dopant species into the ZnS Quantum Dots (QDs) host lattice will induce structural defects evidenced by a red shift in the corresponding exciton. The doping should create new intermediate energetic levels between the valence and conduction bands of the ZnS and affect the electron-hole recombination. These trap states would favour the energy transfer processes involved with the generation of cytotoxic radicals, so-called Reactive Oxygen Species, opening the possibility to apply these nanomaterials in cancer research. Any synthesis approach should consider the direct formation of the QDs in biocompatible medium. Accordingly, the present work addresses the microwave-assisted aqueous synthesis of pure and doped ZnS QDs. As-synthesized quantum dots were fully characterized on a structural, morphological and optical viewpoint. UV-Vis analyzes evidenced the excitonic peaks at approximately 310 nm, 314 nm and 315 nm for ZnS, Cu-ZnS and Mn-ZnS, respectively, Cu/Zn and Mn/Zn molar ratio was 0.05%. This indicates the actual incorporation of the dopant species into the host lattice. In addition, the Photoluminescence spectrum of non-doped ZnS nanoparticles showed a high emission peak that was red shifted when Mn2+ or Cu2+ were added during the synthesis process. The main emission peak of non-doped ZnS, Cu-doped ZnS and Mn-doped ZnS were observed at 438 nm, 487 nm and 521 nm, respectively. Forthcoming work will address the capacity of pure and Cu-, Mn-ZnS quantum dots to generate cytotoxic Reactive Oxygen Species for cancer treatment applications.
关键词： Cancer research,ZnS Quantum Dots,Doping,Microwave-assisted synthesis,Reactive Oxygen Species
更新于2025-11-19 16:46:39
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Electrochemical capacitance-voltage profiling of nonuniformly doped GaAs heterostructures with SQWs and MQWs for LED applications
摘要： Light-emitting heterostructures with single and multiple GaAs/InGaAs quantum wells have been investigated by means of electrochemical capacitance-voltage (ECV) profiling. Capacitance-voltage characteristics were measured; concentration profiles of free charge carriers over the heterostructure depth as well as the intensity of quantum well filling by charge carriers were obtained. In heterostructures with a single quantum well (QW) we considered limitations of capacitance techniques for undoped QW profiling, which is situated near the metallurgic border of the p–n –junction. We made a detailed consideration of phenomena related to Debye smearing and we developed and analyzed the dependence of the space charge region width on the doping. Special attention was paid to investigation of the “blind” area. This was inspired by the practical problem from capacitance spectroscopy of semiconductors, when the researcher poses the task of obtaining a free charge carrier depth distribution profile as deep as possible in the space charge region, i.e. where the intensity of the electric field is maximum. Generally, the active QW of a LED heterostructure is placed deep in the space charge region, so reaching these regions is extremely important for practical problems. We present an evolution of capacitance-voltage characteristics during ECV profiling of nonuniformly doped p – n– heterostructures. For a heterostructure with multiple quantum wells we registered a response from 6 QWs.
关键词： capacitance-voltage profiling,heterostructure,quantum well,nonuniform doping,Electrochemical capacitance-voltage profiling,quantum dot,light-emitting diodes
更新于2025-11-14 17:28:48
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Defect dipole evolution and its impact on the ferroelectric properties of Fe-doped KTN single crystals
摘要： The ferroelectric and piezoelectric properties of doped potassium tantalum niobate crystals with different Fe doping amounts and the adjustability of the properties are investigated. The hysteresis loops and current density curves show that the defect dipoles have an obvious effect on domain reorientation, and the effect decreases with increasing doping amount. The ferroelectric and piezoelectric properties can be adjusted via the defect dipoles, and the adjustability is reduced with increasing doping amount. A change of the doping amount leads to defect dipole structure evolution in the crystals, in which the defect dipoles transform from a polar structure to a nonpolar structure, which is the reason for the transition of the domain reorientation determined by the defect dipoles. This result has proved that introducing defects is an effective way to improve and regulate perovskite properties, and the doping amount is one of the important factors controlling the defect dipoles.
关键词： Ferroelectric,domain orientation mechanism,defect dipoles,doping behavior
更新于2025-11-14 17:28:48
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Influence of aging on electrocaloric effect in Li+ doped BaTiO3 ceramics
摘要： Aging creates significant changes in the properties of the ferroelectric materials such as dielectric and piezoelectric properties. However, the influence of aging on the electrocaloric effect (ECE) has not yet been investigated. In this work, we investigate the effect of the aging on the ECE in acceptor (Li+) doped BaTiO3 ceramics. We observe that aging induced defect polarization (PD) reduces the saturation polarization of the doped samples until Tc=115 oC. Above that temperature PD loses its effectiveness and material behaves like a fresh sample. Suppression of polarization below TC due to aging effect results in a sharper slope change in the temperature dependence of electrical polarization in aged samples which causes an increase in the electrocaloric temperature change of Li+ doped BaTiO3 ceramics up to 23 % at TC. Above a critical Li doping amount, both negative and positive electrocaloric effect are observed in the same sample.
关键词： Aging,BaTiO3,Li-doping,Electrocaloric effect,Defect dipoles
更新于2025-11-14 17:28:48
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Luminescence properties in relation to controllable morphologies of Ba <sub/>3</sub> [Ge <sub/>2</sub> B <sub/>7</sub> O <sub/>16</sub> (OH) <sub/>2</sub> ](OH)(H <sub/>2</sub> O):Eu <sup>3+</sup> and its thermal conversion product Ba <sub/>3</sub> Ge <sub/>2</sub> B <sub/>6</sub> O <sub/>16</sub> :Eu <sup>3+</sup>
摘要： Luminescence properties in relation to controllable morphologies of Ba3[Ge2B7O16(OH)2](OH)(H2O):Eu3+ and its thermal conversion product Ba3Ge2B6O16:Eu3+ were investigated. Three types of morphologies of Eu3+-doped Ba3[Ge2B7O16(OH)2](OH)(H2O) phosphors were obtained via hydrothermal reactions by different kinds of raw materials. In addition, Ba3Ge2B6O16:Eu3+ phosphors were obtained by calcining the precursor Ba3[Ge2B7O16(OH)2](OH)(H2O):Eu3+. The structure and morphology of the obtained samples were characterized by XRD, EDS, FT-IR, TG-DTA, SEM and HRTEM. Herein, the effects of the synthesis parameters, including the reaction temperature, boron sources and the dosage, doping of rare earth on the photoluminescence (PL) properties of Ba3[Ge2B7O16(OH)2](OH)(H2O) were investigated in detail. The lifetime and absolute quantum yield (QY) of different morphologies of Ba3[Ge2B7O16(OH)2](OH)(H2O):Eu3+ were also measured. The PL properties of the Ba3Ge2B6O16:Eu3+ phosphor prepared by the precursor calcination method compared with those prepared by the high-temperature solid-state method are discussed.
关键词： Morphologies,Eu3+ doping,Hydrothermal,Borogermanates,Phosphors,Luminescence
更新于2025-11-14 17:04:02
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Simultaneous enhancement of red upconversion luminescence and CT contrast of NaGdF <sub/>4</sub> :Yb,Er nanoparticles <i>via</i> Lu <sup>3+</sup> doping
摘要： To date, lanthanide-doped upconversion nanoparticles (UCNPs) have been widely reported as a promising CT contrast agent because they have high atomic numbers and big X-ray attenuation coefficient values. However, it is still a challenge to fabricate a simple multimodal imaging probe with improved image quality for early cancer diagnosis in clinical medicine. Herein, ultra-small, uniform and monodisperse β-NaGdF4:Yb,Er,X% Lu (X = 0, 1, 2.5, 4, 6, 7.5) UCNPs were prepared through a solvothermal method with high-level modulation of both the phase and morphology. Meanwhile, a remarkably enhanced red upconversion luminescence (UCL) in the β-NaGdF4:Yb,Er,X% Lu NPs was successfully realized via Lu3+ doping. It is found that as the content of Lu3+ increases from 0 to 7.5 mol%, the UCL intensity of the red emission first increases and then decreases, with the optimum doping content of Lu3+ ions of 2.5 mol%. The red UCL enhancement is ascribed to the change of the Yb–Er interionic distance controlling the Yb–Er energy transfer rate and the distortion of the local environment of Er3+ ions influencing the 4f–4f transition rates of Er3+ ions, which has been further confirmed by the experimental check of the crystallographic phase and by photoluminescence spectroscopy employing Eu3+ as the structural probe, respectively. More importantly, after being modified with the HS-PEG2000-NH2 ligand, the NH2-PEGylated-NaGdF4:Yb,Er,X% Lu NPs exhibited low cytotoxicity, high biocompatibility, and remarkably enhanced contrast performance in in vitro UCL and in vivo CT imaging. On the basis of our findings, the as-obtained functionalized UCNPs could be considered as a promising versatile dual-mode imaging probe for bioimaging, tumor diagnosis, and cancer therapy.
关键词： red luminescence enhancement,Lu3+ doping,upconversion nanoparticles,multimodal imaging,CT contrast
更新于2025-11-14 17:04:02
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Ultrathin, Core–Shell Structured SiO <sub/>2</sub> Coated Mn <sup>2+</sup> ‐Doped Perovskite Quantum Dots for Bright White Light‐Emitting Diodes
摘要： All-inorganic semiconductor perovskite quantum dots (QDs) with outstanding optoelectronic properties have already been extensively investigated and implemented in various applications. However, great challenges exist for the fabrication of nanodevices including toxicity, fast anion-exchange reactions, and unsatisfactory stability. Here, the ultrathin, core–shell structured SiO2 coated Mn2+ doped CsPbX3 (X = Br, Cl) QDs are prepared via one facile reverse microemulsion method at room temperature. By incorporation of a multibranched capping ligand of trioctylphosphine oxide, it is found that the breakage of the CsPbMnX3 core QDs contributed from the hydrolysis of silane could be effectively blocked. The thickness of silica shell can be well-controlled within 2 nm, which gives the CsPbMnX3@SiO2 QDs a high quantum yield of 50.5% and improves thermostability and water resistance. Moreover, the mixture of CsPbBr3 QDs with green emission and CsPbMnX3@SiO2 QDs with yellow emission presents no ion exchange effect and provides white light emission. As a result, a white light-emitting diode (LED) is successfully prepared by the combination of a blue on-chip LED device and the above perovskite mixture. The as-prepared white LED displays a high luminous efficiency of 68.4 lm W?1 and a high color-rendering index of Ra = 91, demonstrating their broad future applications in solid-state lighting fields.
关键词： quantum dots,white light-emitting diodes,core–shells,Mn2+-doping,SiO2-coating
更新于2025-11-14 15:32:45
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High-Performance Photoresistors Based on Perovskite Thin Film with a High PbI2 Doping Level
摘要： We prepared high-performance photoresistors based on CH3NH3PbI3 ?lms with a high PbI2 doping level. The role of PbI2 in CH3NH3PbI3 perovskite thin ?lm was systematically investigated using scanning electron microscopy, X-ray diffraction, time-resolved photoluminescence spectroscopy, and photoconductive atomic force microscope. Laterally-structured photodetectors have been fabricated based on CH3NH3PbI3 perovskite thin ?lms deposited using precursor solution with various CH3NH3I:PbI2 ratios. Remarkably, the introduction of a suitable amount of PbI2 can signi?cantly improve the performance and stability of perovskite-based photoresistors, optoelectronic devices with ultrahigh photo-sensitivity, high current on/off ratio, fast photo response speed, and retarded decay. Speci?cally, a highest responsivity of 7.8 A/W and a speci?c detectivity of 2.1 × 1013 Jones with a rise time of 0.86 ms and a decay time of 1.5 ms have been achieved. In addition, the local dependence of photocurrent generation in perovskite thin ?lms was revealed by photoconductive atomic force microscopy, which provides direct evidence that the presence of PbI2 can effectively passivate the grain boundaries of CH3NH3PbI3 and assist the photocurrent transport more effectively.
关键词： grain boundary passivation,PC-AFM,photoresistor,high PbI2 doping content
更新于2025-11-14 15:28:36