- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Exploring the surface chemistry of cesium lead halide perovskite nanocrystals
摘要： Colloidal nanocrystals (NCs) of cesium lead halide perovskites (CsPbX3, X = Cl, Br or I) are emerging as an exciting class of optoelectronic materials, but the retention of their colloidal and structural integrity during isolation, purification and handling still represents a critical issue. The impelling questions concerning their intrinsic chemical instability are connected to the dynamic nature of the bonding between the inorganic surface and the long-chain capping ligands. However, the key aspects of CsPbX3's surface chemistry that directly impact their stability remain elusive. In this contribution, we provide an in-depth investigation of the surface properties of differently composed CsPbX3 NCs, prepared by traditional hot-injection methods. The study, mainly relying on solution NMR spectroscopy, is backed up by elemental analysis as well as morphological, structural and optical investigations. We ascertained that the nature of the ligand adsorption/desorption processes at the NC surface is dependent on its elemental composition, thus explaining the origin of the instability afflicting CsPbI3 NCs. We also evaluated the effect of NC purification as well as of the degradation pathways involving the organic shell on the surface chemistry of CsPbX3 NCs. This study paves the way for new post-functionalization strategies for this promising class of nanomaterials.
关键词： surface chemistry,colloidal stability,degradation pathways,cesium lead halide perovskite nanocrystals,purification,ligand adsorption/desorption,NMR spectroscopy
更新于2025-09-19 17:15:36
-
Design of Chalcopyrite-type CuFeSe2 Nanocrystals: Microstructure, Magnetism, Photoluminescence and Sensing performances
摘要： Most of reported I-III-VI2 type chalcopyrites have been developed as indispensible materials for potential application in photovoltaic solar cells, magnetism or thermoeletrics. The exploration of its photoluminescence potentials has been very limited and the chemical sensing using fluorescence to signal a recognition event is realized by way of CuFeSe2 nanocrystals. A novel solution-based synthesis strategy has been developed for the preparation of CuFeSe2 quantum dots (QDs) via oleylamine and dodecanethiol as precursors. QDs possess an intense blue luminescence at 431 nm and excitation-dependent features are recorded. The nanocrystals exhibit transformation from ferromagnetism to paramagnetism state between 4K and 298K. Another distinct advantage of the quantum dots will be the signaling pathway in response to external analytes. It gives rise to a rapid and selective assay of Cr2O7 2- through an “on-off” switching process. A linear equation can be obtained in the range from 0 to 47.5 μM and the detection limit has been determined to be 0.46 μM. This cost-effective method will pave the way for the efficient synthesis of ternary chalcopyrites and provide suitable chemical routes for sensing purposes.
关键词： Optical sensor,Nanocrystals,Magnetic,CuFeSe2
更新于2025-09-19 17:15:36
-
Thermoelectric Properties of (100) Oriented Silicon and Nickel Silicide Nanocomposite Films Grown on Si on Insulator and Si on Quartz Glass Substrates
摘要： We have grown (100) oriented composite films of Si and Ni silicide nanocrystals (Ni–Si NC film) on substrates of Si on insulator (SOI) and Si on quartz glass (SOQ). Owing to improvement of carrier transport properties and reduction of the thermal conductivity in the oriented films, they have higher dimensionless figures of merit, ZT of 0.22–0.42 for p-type Ni–Si NC film and 0.08–0.13 for n-type Ni–Si NC film than that of bulk Si (ZT < 0.01) at 30°C. The ZT values of p-type and n-type Ni–Si NC films were increased to 0.65 and 0.40 at 500°C, respectively.
关键词： silicon based thermoelectric materials,nanocomposite films,nickel silicide nanocrystals,silicon nanostructures,phonon scattering
更新于2025-09-19 17:15:36
-
Facet-Dependent Optical Properties of Semiconductor Nanocrystals
摘要： Recent observations of facet-dependent electrical conductivity and photocatalytic activity of various semiconductor crystals are presented. Then, the discovery of facet-dependent surface plasmon resonance absorption of metal–Cu2O core–shell nanocrystals with tunable sizes and shapes is discussed. The Cu2O shells also exhibit a facet-specific optical absorption feature. The facet-dependent electrical conductivity, photocatalytic activity, and optical properties are related phenomena, resulting from the presence of an ultrathin surface layer with different band structures and thus varying degrees of band bending for the {100}, {110}, and {111} faces of Cu2O to absorb light of somewhat different wavelengths. Recently, it is shown that the light absorption and photoluminescence properties of pure Cu2O cubes, octahedra, and rhombic dodecahedra also display size and facet effects because of their tunable band gaps. A modified band diagram of Cu2O can be constructed to incorporate these optical effects. Literature also provides examples of facet-dependent optical behaviors of semiconductor nanostructures, indicating that optical properties of nanoscale semiconductor materials are intrinsically facet-dependent. Some applications of semiconductor optical size and facet effects are considered.
关键词： surface band bending,semiconductors,facet-dependent properties,cuprous oxide,nanocrystals
更新于2025-09-19 17:15:36
-
Shape-control of CeF <sub/>3</sub> nanocrystals by doping polyoxometalates: syntheses, characterization and tunable photoluminescence
摘要： A series of CeF3 nanocrystals with uniform morphologies have been synthesized by introducing various polyoxometalates as dopants and shape modifiers. The results indicate that the shape and photoluminescence of the CeF3 nanocrystals could be finely tuned by changing the component and amount of the polyoxometalates.
关键词： doping,CeF3 nanocrystals,photoluminescence,shape-control,polyoxometalates
更新于2025-09-19 17:15:36
-
Solid-State Encapsulation and Color Tuning in Films of Cesium Lead Halide Perovskite Nanocrystals for White Light Generation
摘要： Perovskite nanocrystals (PNCs) are highly demanding nanomaterials for solid-state lighting applications. A challenge for their exploitation in practical applications is the insufficient ambient and water stability associated with their ionic nature. Here we report a novel route for solid-state encapsulation of films of perovskite nanocrystals (PNCs) through vapor-phase deposition of a thin and hydrophobic layer of fluoroalkyltrichlorosilanes (FAS). High quality nanoscale crystals of CsPbBr3 were synthesized with well-established colloidal methods and coated on solid substrates. The films of PNCs were then subjected to vapor of FAS for short durations of time (<60 s) in ambient atmosphere resulting in deposition of a thin (< 20 nm) hydrophobic layer. Besides providing a barrier for water and humidity, the vapor-phase deposition of FAS was accompanied with the blue-shift of the emission wavelength of the PNCs. The color shift results from the exchange of Br with Cl anions, which emerge during the self-hydrolysis of the silane molecules. Throughout this process, we demonstrate the enhanced water stability of the films of PNCs and fine tunability of the wavelength in films from 516 nm to 488 nm. The fabrication of a white light emitting diode and tunability of the color coordinates with the duration of the FAS deposition was demonstrated. The rapid, scalable, and inexpensive solid-state encapsulation approach shows great promise for films of halide perovskites.
关键词： perovskite nanocrystals,vapor-phase deposition,trichlorosilane,colloidal optoelectronics
更新于2025-09-19 17:15:36
-
Amplified spontaneous emission (ASE) and laser effects in ?2-LiYF4: Ce, Tb micro- and nanocrystals
摘要： β-NaYF4 crystals family are interesting materials and have potential for various applications. Here we present our research regarding amplified spontaneous emission (ASE) and laser effects of three materials: LiY0.7 F4: (Ce0.2 Tb0.1), NaY0.5 F4: (Ce0.4 Tb0.1) and LiLuY0.7 F4: (Ce0.2 Tb0.1), prepared by hydrothermal synthesis method. The luminescent active ion is Tb3+. β- LiY0.7 F4: (Ce0.2 Tb0.1) crystals with a hexagonal plate shape have ASE threshold at 400 mW/cm2, excitation with λex = 365 nm and a laser threshold at 490 J for a doped PMMA rod with a length of 25 mm. Laser line was observed at 542 nm.
关键词： β-LiYF4: Ce, Tb micro- and nanocrystals,Laser effect,Amplified spontaneous emission (ASE),Hydrothermal growth
更新于2025-09-19 17:13:59
-
Low-Cost RoHS Compliant Solution Processed Photovoltaics enabled by Ambient Condition Synthesis of AgBiS2 Nanocrystals
摘要： Two major challenges exist before colloidal nanocrystal solar cells can take their place in the market: So far these devices are based on Pb/Cd containing nanocrystals and secondly the synthesis of these nanocrystals takes place in inert atmosphere at elevated temperatures due to the use of air-sensitive chemicals. In this report, a room-temperature, ambient-air synthesis for non-toxic AgBiS2 nanocrystals is presented. As this method utilizes stable precursors, the need for the use of a protective environment is eliminated, enabling the large-scale production of AgBiS2 nanocrystals. The production cost of AgBiS2 NCs at room temperature and under ambient conditions reduces by ~ 60 % compared to prior reports based on hot injection and the solar cells made of these nanocrystals yield a promising power conversion efficiency (PCE) of 5.5 %, the highest reported to date for a colloidal nanocrystal material free of Pb or Cd synthesized at room temperature and under ambient conditions.
关键词： semiconductors,room temperature,non-toxic,solar cells,nanocrystals
更新于2025-09-19 17:13:59
-
CdSe@CdS Dot@Platelet Nanocrystals: Controlled Epitaxy, Mono-Exponential Decay of Two-Dimensional Exciton, and Non-Blinking Photoluminescence of Single Nanocrystal
摘要： Wurtzite CdSe@CdS dot@platelet nanocrystals—a dot-shaped CdSe nanocrystal encased within an epitaxially-grown CdS nanoplatelet—are controllably synthesized with nearly monodisperse size/shape distribution and outstanding photoluminescence (PL) properties. The excellent size/shape control with their lateral to thickness dimension ratio up to 3 to 1 is achieved by systematically studying the synthetic parameters, which results in a simple, tunable yet reproducible epitaxy scheme. This special type of core/shell nanocrystals possess two-dimensional emission dipole with the ab plane of the wurtzite structure. While their near-unity PL quantum yield and mono-exponential PL decay dynamics are at the same level of the-state-of-art CdSe/CdS core/shell nanocrystals in dot shape, CdSe@CdS dot@platelet nanocrystals possess ~2 orders of magnitude lower probability for initiating PL blinking at single-nanocrystal level than the dot-shaped counterparts do.
关键词： dot@platelet nanocrystals,non-blinking,photoluminescence,CdSe@CdS,epitaxy
更新于2025-09-19 17:13:59
-
High-speed colour-converting photodetector with all-inorganic CsPbBr3 perovskite nanocrystals for ultraviolet light communication
摘要： Optical wireless communication (OWC) using the ultra-broad spectrum of the visible-to-ultraviolet (UV) wavelength region remains a vital field of research for mitigating the saturated bandwidth of radio-frequency (RF) communication. However, the lack of an efficient UV photodetection methodology hinders the development of UV-based communication. The key technological impediment is related to the low UV-photon absorption in existing silicon photodetectors, which offer low-cost and mature platforms. To address this technology gap, we report a hybrid Si-based photodetection scheme by incorporating CsPbBr3 perovskite nanocrystals (NCs) with a high photoluminescence quantum yield (PLQY) and a fast photoluminescence (PL) decay time as a UV-to-visible colour-converting layer for high-speed solar-blind UV communication. The facile formation of drop-cast CsPbBr3 perovskite NCs leads to a high PLQY of up to ~73% and strong absorption in the UV region. With the addition of the NC layer, a nearly threefold improvement in the responsivity and an increase of ~25% in the external quantum efficiency (EQE) of the solar-blind region compared to a commercial silicon-based photodetector were observed. Moreover, time-resolved photoluminescence measurements demonstrated a decay time of 4.5 ns under a 372-nm UV excitation source, thus elucidating the potential of this layer as a fast colour-converting layer. A high data rate of up to 34 Mbps in solar-blind communication was achieved using the hybrid CsPbBr3–silicon photodetection scheme in conjunction with a 278-nm UVC light-emitting diode (LED). These findings demonstrate the feasibility of an integrated high-speed photoreceiver design of a composition-tuneable perovskite-based phosphor and a low-cost silicon-based photodetector for UV communication.
关键词： CsPbBr3 perovskite nanocrystals,Silicon-based photodetector,UV photodetection,Solar-blind UV communication,Optical wireless communication
更新于2025-09-19 17:13:59