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Heavily doped Semiconductor Colloidal Nanocrystals as Ultra-Broadband Switches for Near Infrared and Mid-Infrared Pulse Lasers
摘要： Heavily self-doped semiconductors can be designed to use for advanced photonics due to both fabrication and functional advantages. Ultrafast response, strong optical nonlinearity, broadband wavelength range and accessibility of integration are major challenges for ultrafast all-optical photonics operating in infrared wavelength range. Here, solution-processed Cu1.8Se semiconductor nanocrystals (NCs) demonstrate ultrafast response (about 360~520 fs), strong optical nonlinearity (as large as -1.4×103 cm GW-1) and broadband (from 800 to 3000 nm) nonlinear optical absorption in the near-infrared and mid-infrared wavelength range. The ultrafast response and larger optical nonlinearity may be triggered by the plasma ground-state bleaching in the strong surface electromagnetic filed. Stable Q-switched lasers in Er-doped fiber laser, Tm-doped fiber laser and Ho/Pr co-doped ZBLAN fiber laser are operated, respectively. These findings indicate that Cu1.8Se NCs are prospective nonlinear materials for ultrafast response and broadband pulse laser.
关键词： semiconductor nanocrystals,ultrafast photonics,optical modulation,superbroadband,nonlinear optical
更新于2025-09-16 10:30:52
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Stronger Reductive Environment in Solvothermal Synthesis Leads to Improved Ga Doping Efficiency in ZnO Nanocrystals and Enhanced Plasmonic Absorption
摘要： The key parameter for degenerated semiconductor oxide plasmonic nanocrystals is the doping level. Hydrothermal and solvothermal approaches are considered to be less effective toward achieving high concentration of aliovalent donor dopants in a host oxide when compared to other synthesis methods that use long chain hydrocarbon solvents, fatty acids, and fatty amines as precursors. Because of this, although they have several advantages such as sustainability, ease of use, relatively inexpensive reagents and apparatus, and reduced environmental impact, they are excluded from the list of potential synthesis methods. Herein, an effective Zn2+ substitution with aliovalent Ga3+ in the ZnO host lattice is demonstrated, and it is achieved by increasing the reductive power of the solvothermal synthesis conditions by either solvent substitution or the addition of reducing agents. This increase results in an increased oxidation affinity of the medium. This in turn promotes Ga3+ incorporation into the ZnO lattice, by skewing the reaction equilibrium toward oxygen evolution.
关键词： plasmonic resonance,semiconductor nanocrystals,gallium-doped zinc oxide,degenerated oxide semiconductor nanocrystals
更新于2025-09-11 14:15:04
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Evaluating glucose and mannose profiles in Candida species using quantum dots conjugated with Cramoll lectin as fluorescent nanoprobes
摘要： Glycoconjugates found on cell walls of Candida species are fundamental for their pathogenicity. Laborious techniques have been employed to investigate the sugar composition of these microorganisms. Herein, we prepared a nanotool, based on the fluorescence of quantum dots (QDs) combined with the specificity of Cramoll lectin, to evaluate glucose/mannose profiles on three Candida species. The QDs-Cramoll conjugates presented specificity and bright fluorescence emission. The lectin preserved its biological activity after the conjugation process mediated by adsorption interactions. The labeling of Candida species was analyzed by fluorescence microscopy and quantified by flow cytometry. Morphological analyses of yeasts labeled with QDs-Cramoll conjugates indicated that C. glabrata (2.7 μm) was smaller when compared to C. albicans (4.0 μm) and C. parapsilosis sensu stricto (3.8 μm). Also, C. parapsilosis population was heterogeneous, presenting rod-shaped blastoconidia. More than 90% of cells of the three species were labeled by conjugates. Inhibition and saturation assays indicated that C. parapsilosis had a higher content of exposed glucose/mannose than the other two species. Therefore, QDs-Cramoll conjugates demonstrated to be effective fluorescent nanoprobes for evaluation of glucose/mannose constitution on the cell walls of fungal species frequently involved in candidiasis.
关键词： Candida,Cratylia mollis,Bioconjugation,Semiconductor nanocrystals,Lectin
更新于2025-09-11 14:15:04
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Wavelength-Tunable Band-Edge Photoluminescence of Nonstoichiometric Ag–In–S Nanoparticles via Ga <sup>3+</sup> Doping
摘要： The nonstoichiometry of I?III?VI semiconductor nanoparticles, especially the ratio of group I to group III elements, has been utilized to control their physicochemical properties. We report the solution-phase synthesis of non-stoichiometric Ag?In?S and Ag?In?Ga?S nanoparticles and results of the investigation of their photoluminescence (PL) properties in relation to their chemical compositions. While stoichiometric AgInS2 nanoparticles simply exhibited only a broad PL band originating from defect sites in the particles, a narrow band edge PL peak newly appeared with a decrease in the Ag fraction in the nonstoichiometric Ag?In?S nanoparticles. The relative PL intensity of this band edge emission with respect to the defect-site emission was optimal at a Ag/(Ag + In) value of ca. 0.4. The peak wavelength of the band edge emission was tunable from 610 to 500 nm by increased doping with Ga3+ into Ag?In?S nanoparticles due to an increase of the energy gap. Furthermore, surface coating of Ga3+-doped Ag?In?S nanoparticles, that is, Ag?In?Ga?S nanoparticles, with a GaSx shell drastically and selectively suppressed the broad defect-site PL peak and, at the same time, led to an increase in the PL quantum yield (QY) of the band edge emission peak. The optimal PL QY was 28% for Ag?In?Ga?S@GaSx core?shell particles, with green band-edge emission at 530 nm and a full width at half-maximum of 181 meV (41 nm). The observed wavelength tunability of the band-edge PL peak will facilitate possible use of these toxic-element-free I?III?VI-based nanoparticles in a wide area of applications.
关键词： band-edge photoluminescence,multinary semiconductor,quantum dots,nonstoichiometry,I?III?VI2 semiconductor,visible photoluminescence,wavelength tunability,semiconductor nanocrystals
更新于2025-09-10 09:29:36
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Synthesis of ultra-narrow PbTe nanorods with extremely strong quantum confinement
摘要： Monodisperse, high-quality, ultra-narrow PbTe nanorods were synthesized for the first time in a one-pot, hot-injection reaction using trans-2-decenoic acid as the agents for lead precursors and tris(diethylamino)phosphine as the telluride precursors. High monomer reactivity, rapid nucleation and fast growth rate derived from the new precursors led to the anisotropic growth of PbTe nanocrystals at low reaction temperatures (< 150 oC). In addition, the aspect ratio of PbTe nanorods could be largely adjusted from 4 to 15 by tuning the Pb to Te precursor molar ratio and reaction temperatures. Moreover, the synthesized ultra-narrow PbTe nanorods exhibited extremely strong quantum confinement and presented unique optical properties. We revealed that the diameter and length of PbTe nanorods could significantly affect their optical properties, which potentially offer them new opportunities in the application of optoelectronic and thermoelectric devices and make them desired subjects for multiple exciton generation and other fundamental physics studies.
关键词： optical properties,PbTe nanorods,Colloidal semiconductor nanocrystals
更新于2025-09-10 09:29:36
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14.2: <i>Invited Paper:</i> Quantum Yield Measurement Using Organic Dyes as References for Semiconductor Nanocrystals
摘要： A method of using series of organic dyes as reference to measure the quantum yield efficiency (QY) for semiconductor nanocrystals (Quantum Dots, QDs) in solution state is reported. In the proposed method, the sensitivity of the fluorescence spectrophotometer on wavelength as well as the excitation power intensity is considered to improve the accuracy.
关键词： Semiconductor Nanocrystals,Quantum Dots,QDs,Quantum Yield Efficiency Measurment
更新于2025-09-09 09:28:46
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Number series of atoms, interatomic bonds and interface bonds defining zinc-blende nanocrystals as function of size, shape and surface orientation: Analytic tools to interpret solid state spectroscopy data
摘要： Semiconductor nanocrystals (NCs) experience stress and charge transfer by embedding materials or ligands and impurity atoms. In return, the environment of NCs experiences a NC stress response which may lead to matrix deformation and propagated strain. Up to now, there is no universal gauge to evaluate the stress impact on NCs and their response as a function of NC size dNC. I deduce geometrical number series as analytical tools to obtain the number of NC atoms NNC(dNC[i]), bonds between NC atoms Nbnd(dNC[i]) and interface bonds NIF(dNC[i]) for seven high symmetry zinc-blende (zb) NCs with low-index faceting: {001} cubes, {111} octahedra, {110} dodecahedra, {001}-{111} pyramids, {111} tetrahedra, {111}-{001} quatrodecahedra and {001}-{111} quadrodecahedra. The fundamental insights into NC structures revealed here allow for major advancements in data interpretation and understanding of zb- and diamond-lattice based nanomaterials. The analytical number series can serve as a standard procedure for stress evaluation in solid state spectroscopy due to their deterministic nature, easy use and general applicability over a wide range of spectroscopy methods as well as NC sizes, forms and materials.
关键词： solid state spectroscopy,analytical number series,semiconductor nanocrystals,zinc-blende nanocrystals,stress evaluation
更新于2025-09-04 15:30:14
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The Quantum Efficiency of Charge Transfer Competing Against Non-Exponential Processes: The Case of Electron Transfer from CdS Nanorods to Hydrogenase
摘要： Photoexcited charge transfer from semiconductor nanocrystals to charge acceptors is a key step for photon energy conversion in semiconductor nanocrystal-based light-harvesting systems. Charge transfer competes against relaxation processes within the nanocrystals, and this competition determines the quantum efficiency of charge transfer. The quantum efficiency is a critical design element in photochemistry, but in nanocrystal–acceptor systems its extraction from experimental data is complicated by sample heterogeneity and intrinsically non-exponential excited-state decay pathways. In this manuscript, we systematically explore these complexities using TA spectroscopy over a broad range of timescales to probe electron transfer from CdS nanorods to the redox enzyme hydrogenase. To analyze the experimental data, we build a model that quantifies the quantum efficiency of charge transfer in the face of competing, potentially non-exponential, relaxation processes. Our approach can be applied to calculate the efficiency of charge or energy transfer in any donor–acceptor system that exhibits non-exponential donor decay and any ensemble distribution in the number of acceptors provided that donor relaxation and charge transfer can be described as independent, parallel decay pathways. We apply this analysis to our experimental system and unveil the connections between particle morphology and quantum efficiency. Our model predicts a finite quantum efficiency even when the mean recombination time diverges, as it does in CdS nanostructures with spatially separated electron–hole pairs that recombine with power-law dynamics. We contrast our approach to the widely-used expressions for the quantum efficiency based on average lifetimes, which for our system overestimate the quantum efficiency. The approach developed here is straightforward to implement and should be applicable to a wide range of systems.
关键词： electron transfer,quantum efficiency,semiconductor nanocrystals,non-exponential processes,charge transfer,hydrogenase,CdS nanorods
更新于2025-09-04 15:30:14
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In-doped As2Se3 thin films studied by Raman and X-ray photoelectron spectroscopies
摘要： Amorphous In-doped As2Se3 films with nominal indium contents x up to 7 at. % were prepared by thermal evaporation. Atomic force microscopy studies confirm the uniform film structure with a surface roughness near 5 nm, noticeably higher than for similarly prepared undoped As2Se3 film. X-ray photoelectron spectroscopy (XPS) studies enabled the chemical composition of the films to be examined. As follows from the XPS data, the In content in the film strongly decreases with the film depth. For films with x ≥ 2 at.%, Raman features attributed to transverse and longitudinal optical phonons of InAs are revealed in the Raman spectra as an evidence for the formation of InAs nanocrystallites in the As2Se3:In film under laser illumination.
关键词： X-ray photoelectron spectroscopy,amorphous,film,Raman scattering,atomic force microscopy,semiconductor nanocrystals
更新于2025-09-04 15:30:14