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Interfacing green synthesized flake like-ZnO onto TiO <sub/>2</sub> as a bilayer electron extraction for efficient perovskite solar cells
摘要： To improve the performance of the PSCs, it is essential to prevent the carrier recombination losses at the interfaces of the transparent metal oxide electrode/electron transport layer (ETL) / active absorber perovskite layer. This present work reports about the green synthesis approach used for the preparation of flake like-ZnO nanostructure (GF-ZnO NSs), naturally extracted from the leaf of Albizia Amara - as a reducing cum capping agent. Herein, we have introduced the above prepared an n-type GF-ZnO NSs material as efficient electron transport interfacial layer (bi-ETL) at the ETL/perovskite junction in the fabricated perovskite solar cells (PSCs). The structure of the fabricated PSC device as follow: Glass/ITO/bi-ETL (c-TiO2/GF-ZnO NSs)/CH3NH3PbI3-xClx/Spiro-MeOTAD/Au. A comparative study has also been made by deploying electron transport materials such as c-TiO2 and GF-ZnO NSs separately. From this, it has been found that the bi-ETL perovskite solar cell devices achieved a maximum power conversion efficiency (PCE) of 7.83% with open-circuit voltage (VOC) of 0.728 V, short circuit current density (JSC) of 20.46 mA/cm2 and a fill factor (FF) of 52.61% compared to that of the chemically reduced ZnO based devices. Whereas, the c-TiO2, GF-ZnO NSs and the chemically reduced CR-ZnO based ETL based devices achieved a PCE of 4.84%, 5.82% and 6.81% respectively. The obtained better performance of the bi-ETL based devices is ascribed to the enhanced carrier extraction and the reduced recombination losses at the interface between the ETL and the active perovskite layer.
关键词： bilayer electron extraction,green synthesis,Perovskite solar cells,Interfacial layer,ZnO nanostructure,Albizia Amara leaf extract
更新于2025-09-23 15:19:57
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Controlled synthesis of ultrathin MoS <sub/>2</sub> nanoflowers for highly enhanced NO <sub/>2</sub> sensing at room temperature
摘要： Fabrication of a high-performance room-temperature (RT) gas sensor is important for the future integration of sensors into smart, portable and Internet-of-Things (IoT)-based devices. Herein, we developed a NO2 gas sensor based on ultrathin MoS2 nanoflowers with high sensitivity at RT. The MoS2 flower-like nanostructures were synthesised via a simple hydrothermal method with different growth times of 24, 36, 48, and 60 h. The synthesised MoS2 nanoflowers were subsequently characterised by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, energy-dispersive X-ray spectroscopy and transmission electron microscopy. The petal-like nanosheets in pure MoS2 agglomerated to form a flower-like structure with Raman vibrational modes at 378 and 403 cm?1 and crystallisation in the hexagonal phase. The specific surface areas of the MoS2 grown at different times were measured by using the Brunauer–Emmett–Teller method. The largest specific surface area of 56.57 m2 g?1 was obtained for the MoS2 nanoflowers grown for 48 h. This sample also possessed the smallest activation energy of 0.08 eV. The gas-sensing characteristics of sensors based on the synthesised MoS2 nanostructures were investigated using oxidising and reducing gases, such as NO2, SO2, H2, CH4, CO and NH3, at different concentrations and at working temperatures ranging from RT to 150 °C. The sensor based on the MoS2 nanoflowers grown for 48 h showed a high gas response of 67.4% and high selectivity to 10 ppm NO2 at RT. This finding can be ascribed to the synergistic effects of largest specific surface area, smallest crystallite size and lowest activation energy of the MoS2-48 h sample among the samples. The sensors also exhibited a relative humidity-independent sensing characteristic at RT and a low detection limit of 84 ppb, thereby allowing their practical application to portable IoT-based devices.
关键词： gas sensing,room temperature,hydrothermal synthesis,MoS2 nanoflowers,NO2 gas sensor
更新于2025-09-23 15:19:57
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Ultrathin two-dimensional conjugated metala??organic framework single-crystalline nanosheets enabled by surfactant-assisted synthesis
摘要： Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) have recently emerged for potential applications in (opto-)electronics, chemiresistive sensing, and energy storage and conversion, due to their excellent electrical conductivity, abundant active sites, and intrinsic porous structures. However, developing ultrathin 2D c-MOF nanosheets (NSs) for facile solution-processing and integration into devices remains a great challenge, mostly due to unscalable synthesis, low yield, limited lateral size and low crystallinity. Here, we report a surfactant-assisted solution synthesis toward ultrathin 2D c-MOF NSs, including HHB-Cu (HHB=hexahydroxybenzene), HHB-Ni and HHTP-Cu (HHTP=2,3,6,7,10,11-hexahydroxytriphenylene). For the first time, we achieve single-crystalline HHB-Cu(Ni) NSs featured with a thickness of 4-5 nm (~8-10 layers) and a lateral size of 0.25-0.65 μm2, as well as single-crystalline HHTP-Cu NSs with a thickness of ~5.1±2.6 nm (~10 layers) and a lateral size of 0.002-0.02 μm2. Benefiting from the ultrathin feature, the synthetic NSs allow fast ion diffusion and high utilization of active sites. As a proof of concept, when serving as a cathode material for Li-ion storage, HHB-Cu NSs deliver a remarkable rate capability (charge within 3 min) and long-term cycling stability (90% capacity retention after 1000 cycles), superior to the corresponding bulk materials and other reported MOF cathodes.
关键词： Li-ion batteries,Two-dimensional conjugated metal-organic frameworks,electrochemical performance,surfactant-assisted synthesis,ultrathin nanosheets
更新于2025-09-23 15:19:57
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Controlled synthesis and upconversion luminescence properties of Yb3+/Er3+ co-doped Bi2O3 nanospheres for optical and X-ray computed tomography imaging
摘要： Bi2O3 nanospheres co-doped with Yb3t/Er3t upconverting ions pair have been successfully synthesized via a facile hydrothermal method followed by a heat treatment. The resulting Bi2O3:Yb3t,Er3t nanospheres show a monodisperse spherical morphology with narrow size distribution (~180 nm) and display intense upconversion luminescence under 980 nm laser excitation. It is found that the crystal structure, morphology and upconversion luminescence properties of nanospheres have a direct relationship with the doping concentration of Yb3t and the subsequent calcination temperature. These Bi2O3:Yb3t,Er3t nanospheres can be prepared in large quantities and can be easily modified with a layer of biocompatible polyethyleneimine (PEI) molecules. The yielded nanospheres could not only maintain uniform size and morphological characteristics, but also show good water dispersibility and biocompatibility. Remarkably, these Bi2O3:Yb3t,Er3t upconversion nanophosphors could also act as an effective contrast agent for X-ray computed tomography (CT) imaging, which show higher contrast efficacy than commercial iodine-based contrast agent. The proposed facile synthetic route and inexpensive matrix materials pave the way for broad use of these Bi2O3:Yb3t,Er3t nanospheres as ideal dual-mode bio-imaging probes in biomedical field.
关键词： Hydrothermal synthesis,CT imaging,Bi2O3,Upconversion luminescence,Nanophosphors
更新于2025-09-23 15:19:57
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Photo-chemically derived Plasmonic Semiconductor Nanocrystals as Optical Switch for Ultrafast Photonics
摘要： Establishing new photonic material with large optical nonlinearity in the near-infrared regime is significant for ultrafast optical science and devices. In this paper, we developed a facile photochemical approach to fabricate covellite CuS plasmonic nanocrystals (NCs) with high chemical stability and strong oxidation resistance under ambient conditions. The photo-chemically derived CuS NCs possess strong absorption in the visible-to-near-infrared optical range caused by the localized surface plasmon resonance effect (LSPR). We further demonstrate superior saturable absorption behavior of CuS NCs with large modulation depth and high damage threshold. By using CuS as an optical switch, a highly-stable mode-locked pulsed laser operating in the telecommunication band with signal-to-noise ratio over 70 dB and pulse duration of 1.57 ps has been achieved. Our results suggest that the photochemical method is an effective technique to fabricate plasmonic NCs, which can be developed as an excellent candidate for ultrafast photonic devices in the visible-to-near-infrared region.
关键词： Optical switch,CuS nanocrystals,Photochemical synthesis,Ultrafast photonics,Plasmonic semiconductor nanocrystals
更新于2025-09-23 15:19:57
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Controlled Hydrogenation of Alkynes on Photogenerated Palladium Nanoparticles
摘要： A palladium nanoparticles–bisacyl-phosphine oxide composite (PdNPs@BAPO) was prepared by treatment of Pd(OAc)2 under UV irradiation using bis(mesitylcarbonyl)(phenyl)phosphine oxide as a photoinitiator (eq. 1). PdNPs@BAPO catalyzed the controlled hydrogenation of alkynes under H2 to give the corresponding (Z)-alkenes in up to 99% yield and up to 99:1 Z/E selectivity (eq. 2; 18 examples).
关键词： palladium catalysis,hydrogenation,nanoparticles,alkynes,alkenes,light-mediated synthesis
更新于2025-09-23 15:19:57
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Aqueous synthesis of L-cysteine-modified cobalt-doped zinc selenide/zinc sulfide quantum dots with enhanced fluorescence
摘要： Cobalt-doped zinc selenide/zinc sulfide quantum dots have been successfully synthesized directly in aqueous solution by using L-cysteine as the modifier. The optical properties and structures of the as-prepared quantum dots have been characterized through transmission electron microscopy, X-ray powder diffraction, infrared spectrum, energy dispersive X-ray spectrum, ultraviolet-visible spectrum, and fluorescence spectrum. The results show that cobalt-doped zinc selenide/zinc sulfide quantum dots are spherical particles with a diameter around 2.8 nm, have good dispersity and have a cubic zinc blende structure. The effects of several synthesis conditions on the fluorescence properties of the as-prepared quantum dots are surveyed and the optimum synthesis conditions are found to be as follows: reaction solution pH of 10.0; molar ratio of L-cysteine to hydrogen selenide ions to zinc ions of 1.6:0.15:1; doping content of cobalt ions of 2%; molar ratio of shell (zinc sulfide) to core (cobalt-doped zinc selenide) of 1.5:1. The fluorescence quantum yield of the as-prepared quantum dots increases from 6.4% to 19% via doping with cobalt ions and the epitaxial growth of zinc sulfide shell. The L-cysteine modified on the surface of cobalt-doped zinc selenide/zinc sulfide quantum dots renders the quantum dots water-soluble and bioconjugation capable. The L-cysteine-modified cobalt-doped zinc selenide/zinc sulfide quantum dots will have potential applications in biological fluorescence analysis.
关键词： ZnSe:Co/ZnS,L-cysteine,Fluorescence,synthesis
更新于2025-09-23 15:19:57
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[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - A Frequency Hopping Communication System Using Directly Modulated Laser Based Optical Heterodyne Technique
摘要： This paper proposes a Frequency Hopping (FH) communication system with a novel frequency synthesis method. Considering that the existing frequency synthesis methods are inevitably limited by the electronic device bandwidth, a combination of directly modulated laser (DML) and optical heterodyne technique is proposed as a hopping frequency source. The principle of the method is presented and a dual frequency hopping system in E band is carried out through simulation to veri?ed the feasibility of the proposed method. This frequency synthesis method supports high radio frequency, ultra-wideband and high hopping speed.
关键词： Directly Modulated Laser,E band,Optical Heterodyne Technique,Frequency Hopping,Frequency Synthesis
更新于2025-09-23 15:19:57
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Morphology control and luminescence properties of red-emitting BaSiF6:Eu3+ hexagonal nanorod phosphors for WLEDs
摘要： To promote the development of solid-state lighting industry, exploring excellent inorganic phosphors has been always a scientific and applied hot issue. Herein, a series of efficient red BaSiF6:Eu3+ hexagonal nanorod phosphors with varied size and morphology were successfully prepared through a hydrothermal route. The reaction time, dosage of surfactant and solvent play an important role in the formation of the nanorod structures. The corresponding formation mechanism was discussed and revealed. The effects of surfactant, reaction time and solvent on photoluminescence properties of the as-prepared BaSiF6:Eu3+ nanorod phosphors were investigated in detail. Under excitation at 394 nm, all samples emit bright red light due to the typical Eu3+ 4f-4f transitions. Comparing the luminescence intensity of samples with different size of nanorods, it is found that the length of the nanorod is about 10–20 μm, the luminescence intensity of the sample is 3–5 times of the initial intensity of the nanorod sample that the length is around 30–40 μm. Moreover, when adding ethylene glycol as a solvent, the luminescence intensity of samples with different morphology increases with the increase of the reaction time. Importantly, as the temperature rising to 150 °C, the integrated intensity of the as-prepared sample still could obtain more than 95% of the intensity at room temperature, indicating the phosphors show excellent thermal stability. Thus, the as-prepared BaSiF6:Eu3+ nanorod phosphor is a potential red-emitting phosphor for white light-emitting diodes (WLEDs).
关键词： BaSiF6:Eu3+,luminescence properties,hydrothermal synthesis,thermal stability,WLEDs,hexagonal nanorod phosphors
更新于2025-09-23 15:19:57
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Investigation of Microwave Irradiation Procedure for Synthesizing CdSe Quantum Dots
摘要： In recent years, microwave heating techniques for quantum dot (QD) synthesis have come to supplement the typical hot-injection methods. In addition to increasing control and replicability, microwave synthesis can be up-scaled to industry standards, an advantage that increases its lucrativeness. This study depicts a strategy to take a hot-injection procedure for cadmium selenide (CdSe) QD synthesis that is safe enough for undergraduate research labs and adapt it to an easier, more energy-efficient microwave synthesis method. Additionally, this study details successes in synthesizing these QDs, along with some challenges, limitations, and peculiarities. For future users of this method, it is recommended to keep holding temperatures between 170°C and 240°C to achieve the highest monodispersity of CdSe QDs while also avoiding confounding effects, such as wide-spectrum photoluminescence and bulk CdSe precipitation.
关键词： microwave synthesis,photoluminescence,hot-injection method,quantum dots,CdSe
更新于2025-09-23 15:19:57