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Synthesis of Inorganic-Organic 2D CdSe Slab-Diamine Quantum Nets
摘要： Porous semiconductors attract great interest due to their unique structural characteristics of high surface area as well as their intrinsic optical and electronic properties. In this study, synthesis of inorganic–organic 2D CdSe slabs-diaminooctane (DAO) porous quantum net structures is demonstrated. It is found that the hybrid 2D CdSe-DAO lamellar structures are disintegrated into porous net structures, maintaining an ultrathin thickness of ≈1 nm in CdSe slabs. Furthermore, the CdSe slabs in quantum nets show the highly shifted excitonic transition in the absorption spectrum, demonstrating their strongly confined electronic structures. The possible formation mechanism of this porous structure is investigated with the control experiments of the synthesis using n-alkyldiamines with various hydrocarbon chain lengths and ligand exchange of DAO with oleylamine. It is suggested that a strong van der Waals interaction among long chain DAO may exert strong tensile stress on the CdSe slabs, eventually disintegrating slabs. The thermal decomposition of CdSe-DAO quantum nets is further studied to form well-defined CdSe nanorods. It is believed that the current CdSe-DAO quantum nets will offer a new type of porous semiconductors nanostructures under a strong quantum-confinement regime, which can be applied to various technological areas of catalysts, electronics, and optoelectronics.
关键词： quantum nets,porous materials,semiconductor nanocrystals,CdSe,2D materials
更新于2025-09-23 15:23:52
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Electron–hole correlations govern Auger recombination in nanostructures
摘要： The fast nonradiative decay of multiexcitonic states via Auger recombination is a fundamental process affecting a variety of applications based on semiconductor nanostructures. From a theoretical perspective, the description of Auger recombination in confined semiconductor nanostructures is a challenging task due to the large number of valance electrons and exponentially growing number of excited excitonic and biexcitonic states that are coupled by the Coulomb interaction. These challenges have restricted the treatment of Auger recombination to simple, noninteracting electron–hole models. Herein we present a novel approach for calculating Auger recombination lifetimes in confined nanostructures having thousands to tens of thousands of electrons, explicitly including electron–hole interactions. We demonstrate that the inclusion of electron–hole correlations are imperative to capture the correct scaling of the Auger recombination lifetime with the size and shape of the nanostructure. In addition, correlation effects are required to obtain quantitatively accurate lifetimes even for systems smaller than the exciton Bohr radius. Neglecting such correlations can result in lifetimes that are 2 orders of magnitude too long. We establish the utility of the new approach for CdSe quantum dots of varying sizes and for CdSe nanorods of varying diameters and lengths. Our new approach is the first theoretical method to postdict the experimentally known “universal volume scaling law” for quantum dots and makes novel predictions for the scaling of the Auger recombination lifetimes in nanorods.
关键词： semiconductor nanocrystals,quantum dots,excitons,auger recombination,biexcitons,nanorods
更新于2025-09-23 15:21:21
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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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Composition and size controlled I-V-VI semiconductor nanocrystals
摘要： Non-isovalent ternary and quaternary semiconductors (i.e., having two or more cations with different valence) have unique structural and electronic properties that are leveraged in photovoltaic, thermoelectric, and phase-change memory devices. Making these complex semiconductors in the form of colloidal nanocrystals imparts size-dependent properties and solution processability. Here, we present results on I‐V‐VI group colloidal nanocrystals. We focus on achieving sub-10 nm sizes for a wide range of I-V-VI selenide nanocrystals, including AgSbSe2, AgSb2Se3, CuSbSe2, Cu3SbSe4, AgBiSe2, and CuBiSe2. To highlight one possible application for these I-V-VI colloidal nanomaterials, we analyze the optical absorption and show that through composition and size control, this class of materials offers bandgaps in the mid- to near-IR. Absorption coefficients of AgSbSe2, CuSbSe2, and Cu3SbSe4 nanocrystals are on par with or higher than the well-studied PbS nanocrystals highlighting their potential for devices such as solar cells, (mid-)infrared photodetectors, and near-infrared bio-imaging systems.
关键词： solar cells,optical absorption,bio-imaging systems,colloidal nanocrystals,infrared photodetectors,mid- to near-IR,I-V-VI semiconductor nanocrystals,bandgaps
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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Properties, fabrication and applications of plasmonic semiconductor nanocrystals
摘要： In semiconductor nanocrystals (NCs), a new regime has been opened in the plasmonic field since the discovery of localized surface plasmon resonances (LSPRs). LSPRs that lead to near-field enhancement, scattering, and resonant absorption around the NC can be tuned in the range from the visible to the near-infrared (NIR) region across a wide optical spectrum by synthetically varying the doping level, and post synthetically via electrochemical control, photochemical control, and chemical oxidation and reduction. In this review, we will focus on the three widely explored and interrelated examples and their manipulation methods of LSPR of (1) hydrogen molybdenum bronze (HxMoO3?y) NCs, (2) hydrogen tungsten bronze (HxWO3?y) NCs, and (3) oxygen vacancy doped molybdenum tungsten oxide (MoxW1?xO3?y) NCs. Finally, a brief outlook on the applications of these plasmonic NCs is presented.
关键词： hydrogen molybdenum bronze,localized surface plasmon resonances,hydrogen tungsten bronze,plasmonic semiconductor nanocrystals,molybdenum tungsten oxide
更新于2025-09-23 15:19:57
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Nanoshell quantum dots: Quantum confinement beyond the exciton Bohr radius
摘要： Nanoshell quantum dots (QDs) represent a novel class of colloidal semiconductor nanocrystals (NCs), which supports tunable optoelectronic properties over the extended range of particle sizes. Traditionally, the ability to control the bandgap of colloidal semiconductor NCs is limited to small-size nanostructures, where photoinduced charges are confined by Coulomb interactions. A notorious drawback of such a restricted size range concerns the fact that assemblies of smaller nanoparticles tend to exhibit a greater density of interfacial and surface defects. This presents a potential problem for device applications of semiconductor NCs where the charge transport across nanoparticle films is important, as in the case of solar cells, field-effect transistors, and photoelectrochemical devices. The morphology of nanoshell QDs addresses this issue by enabling the quantum-confinement in the shell layer, where two-dimensional excitons can exist, regardless of the total particle size. Such a geometry exhibits one of the lowest surface-to-volume ratios among existing QD architectures and, therefore, could potentially lead to improved charge-transport and multi-exciton characteristics. The expected benefits of the nanoshell architecture were recently demonstrated by a number of reports on the CdSbulk/CdSe nanoshell model system, showing an improved photoconductivity of solids and increased lifetime of multi-exciton populations. Along these lines, this perspective will summarize the recent work on CdSbulk/CdSe nanoshell colloids and discuss the possibility of employing other nanoshell semiconductor combinations in light-harvesting and lasing applications.
关键词： Optoelectronic properties,Nanoshell quantum dots,CdSbulk/CdSe nanoshell,Colloidal semiconductor nanocrystals,Quantum confinement
更新于2025-09-23 15:19:57
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Robust Polymer Matrix Based on Isobutylene (Co)Polymers for Efficient Encapsulation of Colloidal Semiconductor Nanocrystals
摘要： We introduce new oxygen- and moisture-proof polymer matrices based on polyisobutylene (PIB) and its block copolymer with styrene (poly(styrene-block-isobutylene-block-styrene), PSt-b-PIB-b-PSt) for encapsulation of colloidal semiconductor nanocrystals. In order to prepare transparent and processable composites, we developed a special procedure of the nanocrystal surface engineering including ligand exchange of parental organic ligands to inorganic species followed by attachment of specially designed short-chain PIB functionalized with amino-group (PIB-NH2). The latter provides excellent compatibility of the particles with the polymer matrices. As colloidal nanocrystals, we chose CdSe nanoplatelets (NPLs), since they possess a large surface and thus are very sensitive to the environment, in particular in terms of their limited photostability. The encapsulation strategy is quite general and can be applied to a wide variety of semiconductor nanocrystals, as demonstrated on the example of PbS quantum dots. All obtained composites exhibited excellent photostability being tested in a focus of a powerful white-light source, as well as exceptional chemical stability in a strongly acidic media. We compared these properties of the new composites with those of widely used polyacrylate based materials, demonstrating the superiority of the former. The developed composites are of particular interest for application in optoelectronic devices, such as color-conversion light emitting diodes (LEDs), laser diodes, luminescent solar concentrators, etc.
关键词： photoluminescence,nanocrystals-in-polymer composites,lead sulfide quantum dots,semiconductor nanocrystals,isobutylene (co)polymers,cadmium selenide nanoplatelets,photostability,chemical stability
更新于2025-09-19 17:15:36
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Tailored Photoluminescence Properties of Ag(In,Ga)Se <sub/>2</sub> Quantum Dots for Near-Infrared in vivo Imaging
摘要： Multinary semiconductor quantum dots (QDs) that have less toxicity and show near-infrared light responsivity have attracted much attention for in vivo bioimaging. In this study, we controlled the optical properties of Ag-In-Se QDs by modulating the non-stoichiometry and the degree of Ga3+ doping. Precise tuning of the Ag/In ratio of Ag-In-Se QDs enabled a sharp band-edge emission to emerge without broad defect-site emission. Ga3+ doping into Ag-In-Se (AIGSe) QDs enlarged their energy gap, resulting in a blue shift of band-edge PL peak from from 890 to 630 nm. The band-edge PL intensity was remarkably enlarged by surface coating with a thin GaSx shell followed by treatment with trioctylphosphine, the highest PL yield being 38% for the PL peak at 800 nm. Thus-obtained QDs were successfully used as near-IR PL probes for three-dimensional in vivo bio-imaging in which the wavelengths of excitation and detection lights could be selected in the first biological window and then the signals were clearly detected from AIGSe@GaSx core-shell QDs injected into biological tissues by ca. 5 mm in depth.
关键词： I-III-VI2 semiconductor,Quantum dots,Semiconductor nanocrystals,Band-edge emission,Biological imaging,Near-IR photoluminescence
更新于2025-09-19 17:13:59
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Luminescent Down‐Conversion Semiconductor Quantum Dots and Aligned Quantum Rods for Liquid Crystal Displays
摘要： Herein, emerging applications of luminescent semiconductor nanocrystals are addressed, such as quantum dots and quantum rods as down-conversion materials used in liquid crystal displays (LCD). Their precisely tunable emission wavelengths and narrow emission bandwidths offer high color purity resulting in a wide color gamut with vivid colors for LCDs. Anisotropic materials, such as quantum rods, have the additional advantage of polarized emission, which can bring a significant improvement to the efficiency of LCD displays. The basic optical properties of these nanomaterials are considered, with a focus on quantum rods, and the challenges and progress in their assembly are discussed. Different techniques for quantum rod alignment are introduced such as shear-oriented, electric field and magnetic field assisted assembly, mechanical rubbing, stretching, and electrospinning. The photoalignment approach allows for an easy arrangement of quantum rods in-plane, and the implications of this method to patterning are considered. Different configurations of LCDs utilizing semiconductor quantum dots and quantum rods as down-conversion layers are also presented, and the potential applications that are enabled by the wide range of emerging materials are highlighted.
关键词： quantum dots,liquid crystal displays,photoalignment,quantum rods,luminescent semiconductor nanocrystals,down-conversion materials,polarized emission
更新于2025-09-19 17:13:59