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Layered MoS2 defect-driven in-situ synthesis of plasmonic gold nanocrystals visualizes the planar size and interfacial diversity
摘要： Current defect theories significantly guide broadband research progresses, whereas the recognition of defect status remains challenging. Herein, MoS2 defect type, density and exposed state are visually identified with a reagent indicator of HAuCl4. Mo-terminated defects spontaneously reduce [AuCl4]- anions, and oxidized Mo species are dissociated. Consequently, MoS2 edges guide the epitaxial branch of Au nanocrystals (NCs), followed with sequential growths at their planar defects. The size-evolution processes of LaMer growth and planar packages of aggregative growth of Au/MoS2 nanoseeds result in the occupation of Au atomic layers on heterostructures. Consequently, shell-core hybrids are presented with localized surface plasmon resonance characteristics. The mechanism is systematically explored via the discriminated performance of plasmonic characteristics of Au nanostructures on semiconducting MoS2 substrates. With plasmonic identification, defect-associated size and interfacial diversities of MoS2 are visually information-rich. Tunable morphologies and synergistic optical characteristics of plasmonic semiconductor heterostructures inspire many more applications through the edge and planar defects intrinsic in layered MoS2.
关键词： heterostructures,gold nanocrystals,defect,MoS2,plasmonic
更新于2025-09-23 15:21:01
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Binary Superlattices of Infrared Plasmonic and Excitonic Nanocrystals
摘要： Self-assembled superlattices of nanocrystals offer exceptional control over the coupling between nanocrystals, similar to how solid-state crystals tailor the bonding between atoms. By assembling nanocrystals of different properties (e.g., plasmonic, excitonic, dielectric, or magnetic), we can form a wealth of binary superlattice metamaterials with new functionalities. Here, we introduce infrared plasmonic Cu2?xS nanocrystals to the limited library of materials that have been successfully incorporated into binary superlattices. We are the first to create a variety of binary superlattices with large excitonic (PbS) nanocrystals and small plasmonic (Cu2?xS) nanocrystals, both resonant in the infrared. Then, by controlling the surface chemistry of large Cu2?xS nanocrystals, we produced structurally analogous superlattices of large Cu2?xS and small PbS nanocrystals. Transmission electron microscopy (TEM) and grazing-incidence small-angle X-ray scattering (GISAXS) were used to characterize both types of superlattices. Furthermore, our unique surface modification of the large Cu2?xS nanocrystals also prevented them from chemically quenching the photoluminescence of the PbS nanocrystals, which occurred when the PbS nanocrystals were mixed with unmodified Cu2?xS nanocrystals. These synthetic achievements create a set of binary superlattices that can be used to understand how infrared plasmonic and excitonic nanocrystals couple in a variety of symmetries and stoichiometries.
关键词： infrared quantum dots,nanocrystals,self-assembly,supracrystal,metamaterial,binary superlattice,grazing-incidence small-angle X-ray scattering (GISAXS)
更新于2025-09-23 15:21:01
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Enhancing the performance of LARP-synthesized CsPbBr <sub/>3</sub> nanocrystal LEDs by employing a dual hole injection layer
摘要： Lead halide perovskites have been considered promising materials for optoelectronic applications owing to their superior properties. CsPbBr3 nanocrystals (NCs) with a narrow particle size distribution and a narrow emission spectrum are synthesized by ligand-assisted re-precipitation (LARP), a low-cost and facile process. In inverted CsPbBr3 NC LEDs, a dual hole injection layer (HIL) of 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN)/MoO3 is introduced to enhance hole injection and transport, because HAT-CN can extract electrons easily from the hole transport layer and leave a large number of holes there. The current and power efficiencies of the optimized device with a dual HIL are 1.5- and 1.8-fold higher than those of the single HIL device. It is believed that the dual HAT-CN/MoO3 HIL effectively promotes hole injection and has promise for application in many other devices.
关键词： Ligand-assisted re-precipitation,Optoelectronic applications,Lead halide perovskites,CsPbBr3 nanocrystals,Dual hole injection layer,HAT-CN/MoO3
更新于2025-09-23 15:21:01
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Self-assembled monolayer film of concave star-shaped Au nanocrystals as highly efficient SERS substrates
摘要： In this work, various geometries of Au nanocrystals with sharp tips including decahedra, concave star, and spindle were synthesized through Ag underpotential deposition-dominated growth approach based on utilizing a novel type of Au nanoseed (i.e., pentatwinned Au nanospheres). These as-prepared Au nanocrystals exhibited a broad localized surface plasmon resonance (LSPR) tunability from visible to near-infrared region. Furthermore, we fabricated the monolayer film based on Au nanocrystals with different morphologies through liquid/liquid interface self-assembly technique, which displayed strong shape-dependent surface enhanced Raman scatting (SERS) performance. More significantly, concave star-shaped Au nanocrystals with ten sharp tips endowed them with 12-fold higher SERS enhancements than Au nanospheres, which was in line with the simulation results by finite difference time domain (FDTD) method. Our study provides a novel route for fabrication of Au nanocrystals with diversified structures, and the efficient SERS substrates have great prospect for the applications in ultrasensitive chemical and biological sensing.
关键词： Au nanocrystals,SERS,Self-assembly,LSPR,Underpotential deposition
更新于2025-09-23 15:21:01
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Morphological and optoelectronic investigations of CsPbBr3 nanocrystals chelating diphenylammonium halide ligands via low temperature synthesis
摘要： In this study, the low temperature method was adopted to synthesize all-inorganic cesium lead bromide CsPbBr3 nanocrystals (NCs) as the active layer in light-emitting devices. In order to improve film-forming and optoelectronic properties of CsPbBr3 NCs, a surface ligand diphenylammonium bromide (DPABr) was added from 0 to 0.15 mole fraction in proportion to the amount of oleylamine. The experimental results showed that introducing 0.1 mole fraction of DPABr in CsPbBr3 NCs brought the best performance. The SEM and AFM results revealed that smooth and pinhole-free films of CsPbBr3 NCs were formed by introducing DPABr with a low surface roughness of 4.6 nm. The introduced bromide ions can passivate the surface vacancies of CsPbBr3 NCs and improve photoluminescence quantum yield (PLQY) from 38% to 72% compared with the pristine CsPbBr3 NCs. Moreover, shorter and π electron-rich phenyl groups help to increase carrier injection into nanocrystalline core, preventing carriers from being hindered by oleic acid and oleylamine with longer alkyl chains. Therefore, the conductivity of the resulting CsPbBr3 NCs was augmented. The maximum brightness and current efficiency of the optimized device based on CsPbBr3 NCs with 0.1 mole fraction of DPABr were enhanced 2.3- and 3.3-fold, respectively, relative to the pristine one.
关键词： perovskite nanocrystals,low temperature method,photoluminescence quantum yield,surface passivation,diphenylammonium bromide
更新于2025-09-23 15:21:01
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Surface passivation enabled-structural engineering of I-III-VI <sub/>2</sub> nanocrystal photocatalysts
摘要： Cation exchange has evolved into a powerful tactic for synthesis of semiconductor nanocrystals (NCs) that are not readily accessible otherwise. Here we have investigated the In3+-for-Cu+ cation exchange in the dodecahedral-shaped Cu7S4 NCs and found that surface passivation, either caused by excess guest cations or ligand molecules, can be exploited to engineer the structural properties of the NCs. By monitoring the parallel reactions carried out under systematically varied conditions, together with the positron annihilation spectroscopy investigation, we have demonstrated that the key element accounting for the observed surface passivation is associated with the copper vacant sites on the surface of Cu7S4 NCs. The reduction in In3+/Cu+ ratio and the presence of strong-binding ligands could enhance the density of surface copper vacancies and boost cation exchange reaction, which therefore alters the competition between the in-di?usion of In3+ and out-di?usion of Cu+ ions. Such capability to control the inter-di?usion balance in cation exchange (and the accompanying Kirkendall e?ect) enables the creation of a series of CuInS2 (and Cu7S4@CuInS2) NCs with various exotic structures, which show di?erent photocatalytic abilities in singlet oxygen generation. This study can not only add more structural complexity and diversity to the semiconductor NCs achievable by cation exchange, but also presents an important guideline for establishing a unifying mechanistic understanding of the reaction kinetics in cation exchange process.
关键词： cation exchange,Kirkendall effect,semiconductor nanocrystals,photocatalysis,surface passivation
更新于2025-09-23 15:21:01
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Solutiona??Processed, Selfa??Powered Broadband CH <sub/>3</sub> NH <sub/>3</sub> PbI <sub/>3</sub> Photodetectors Driven by Asymmetric Electrodes
摘要： In general, the fabrication of high-performance, self-powered broadband photodetectors based on traditional semiconducting thin films is tedious and costly. Here, in this paper a high-performance, solution-processed, and self-powered CH3NH3PbI3 (MAPbI3) nanocrystal based photodetector ITO/MAPbI3/Ag is presented, and it shows broadband photoresponse from the visible to the near-infrared wavelength region. The pronounced enhanced performance of the photodetector is due to taking the advantage of the built-in electric field induced by the work function difference of two electrodes. The optimized photodetector shows a responsivity of 4.9 and 1.42 A W?1 with a specific detectivity of 7.6 × 1013 and 1.77 × 1013 Jones under 19 μW cm?2 white light illumination and 26 μW cm?2 808 nm illumination at zero bias, respectively. Therefore, such a concept of simple device geometry and feasible technique will open up a new and promising avenue for the fabrication of self-powered photodetectors and the development of imaging devices.
关键词： ligand-assisted reprecipitation (LARP),CH3NH3PbI3 nanocrystals,broadband photodetectors,photocurrent imaging
更新于2025-09-23 15:21:01
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Electrogenerated Chemiluminescence and Spectroelectrochemistry Characteristics of Blue Photoluminescence Perovskite Quantum Dots
摘要： Lead-based perovskite MAPbX3 (MA= CH3NH3, X=Cl and Br) has shown great potential benefits to advance modern optoelectronics and clean energy harvesting devices. Poor structural stability is one of the major challenges of MAPbX3 perovskite materials to overcome to achieve desired device performance. Here we present the electrochemical stability study of CH3NH3PbCl1.08Br1.92 quantum dots (QDs) by electrogenerated chemiluminescence (ECL) and photoluminescence (PL) spectroelectrochemistry methods. Electrochemical anodization of pristine MAPbX3 QD film results in the disproportionate loss of methylammonium and halide ions (X=Cl and Br). ECL efficiency and stability of perovskite QDs in the presence of co-reactant tripropyl amine (TPrA) can be greatly improved after being incorporated into a polystyrene (PS) matrix. Mass spectrum and X-ray photoelectron spectroscopy (XPS) measurements are used to provide chemical composition variation details of QDs, responsible for the ECL and PL characteristics (e.g., wavelength redshift) of perovskite QDs in an electrochemical cell.
关键词： quantum dots (QDs),Perovskite,Blue light emission,nanocrystals,polystyrene (PS),electrogenerated chemiluminescence (ECL),photoluminescence (PL)
更新于2025-09-23 15:21:01
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Facile Exchange of Tightly Bonded L-Type Oleylamine and Diphenylphosphine Ligands on Copper Indium Diselenide Nanocrystals Mediated by Molecular Iodine
摘要： Copper indium diselenide (CuInSe2) nanocrystals are a prototypical I-III-VI semiconductor quantum dot material, typically synthesized in oleylamine (OLAm) as a solvent and capping ligand, often with the addition of diphenylphosphine (DPP) to improve the reaction yield. Using 1H NMR spectroscopy, we study the association of OLAm and DPP on CuInSe2 nanocrystals and find that they both behave as tightly bonded L-type ligands. There is no observable desorption of OLAm or DPP when a toluene-d8 dispersion is heated to 100 oC, and no ligand exchange occurs when the nanocrystals are exposed to other L-type species like trioctylphosphine (TOP), or octadecanethiol (ODT), which can bind as either X-type or L-type. Molecular iodine (I2), however, is found to readily displace both OLAm and DPP from the nanocrystal surface and facilitate efficient and complete ligand exchange with either TOP or ODT, and appears to behave as a Lewis Acidic Z-type ligand. We also find that the X-type ligand, stearic acid (StAc), does not bond to the CuInSe2 nanocrystals under any circumstances.
关键词： L-type ligands,molecular iodine,ligand exchange,CuInSe2 nanocrystals,Z-type ligands
更新于2025-09-23 15:21:01
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Application of perovskite nanocrystals (NCs)/quantum dots (QDs) in solar cells
摘要： Since it was first reported in 2014, colloidal halide perovskite (CHP) nanocrystals (NCs)/quantum dots (QDs) have been quickly applied in photovoltaic devices, and useful results have been obtained due to their excellent optoelectronic properties. In this review, we aim to summarize the progresses in this field up to now, and propose solutions to the development bottlenecks. Generally, we will first introduce crystal/electronic structures, optoelectronic properties and stabilities, and the synthesis methods of CHP NCs/QDs, followed by their applications in solar cell as active layer, interfacial layer, additive and energy transfer layer. Finally, we will briefly discuss the stability challenges for CHP NCs/QDs, and make a simple prospect for the possible directions of CHP NCs/QDs in future solar cell applications.
关键词： Quantum dots,Ligand,Passivation,Doping,Solar cell,Nanocrystals
更新于2025-09-23 15:21:01