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Nonradiative Energy Transfer in a??Colloidal Quantum Dot Nanoclustera??Dyea?? Hybrid Nanostructures: Computer Experiment
摘要： A computer model of nonradiative electronic excitation energy transfer from nanoclusters of colloidal quantum dots of cadmium selenide to the meso-tetra(3-pyridyl)porphyrin molecule in hybrid nanostructures nanocluster–dye has been constructed and analyzed. The model uses the experimental luminescence and absorption spectra of quantum dots and the dye, takes into account heterogeneity of the properties of quantum dots in nanoclusters and the different location of the dye in the hybrid structure. It has been shown that, in the ideal case, due to such energy transfer, the intensity of the luminescent signal of the dye can be increased by five orders of magnitude. However, this value is significantly reduced due to nonluminescent particles, the presence of a protective ligand shell, a large size distribution of the particles, and the non-optimal geometric structure of the hybrid system.
关键词： porphyrin dye,colloidal quantum dots,F?rster resonance energy transfer,hybrid systems,cadmium selenide,computer simulation
更新于2025-09-19 17:13:59
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Interfacial Capillarya??Forcea??Driven Selfa??Assembly of Monolayer Colloidal Crystals for Supersensitive Plasmonic Sensors
摘要： Colloidal lithography technology based on monolayer colloidal crystals (MCCs) is considered as an outstanding candidate for fabricating large-area patterned functional nanostructures and devices. Although many efforts have been devoted to achieve various novel applicatons, the quality of MCCs, a key factor for the controllability and reproducibility of the patterned nanostructures, is often overlooked. In this work, an interfacial capillary-force-driven self-assembly strategy (ICFDS) is designed to realize a high-quality and highly-ordered hexagonal monolayer MCCs array by resorting the capillary effect of the interfacial water film at substrate surface as well as controlling the zeta potential of the polystyrene particles. Compared with the conventional self-assembly method, this approach can realize the reself-assembly process on the substrate surface with few colloidal aggregates, vacancy, and crystal boundary defects. Furthermore, various typical large-scale nanostructure arrays are achieved by combining reactive ion etching, metal-assisted chemical etching, and so forth. Specifically, benefiting from the as-fabricated high-quality 2D hexagonal colloidal crystals, the surface plasmon resonance (SPR) sensors achieve an excellent refractive index sensitivity value of 3497 nm RIU?1, which is competent for detecting bovine serum albumin with an ultralow concentration of 10?8 m. This work opens a window to prepare high-quality MCCs for more potential applications.
关键词： colloidal lithography,plasmonic sensors,monoloidal colloidal self-assembly,nanostructure arrays,interfacial capillary force
更新于2025-09-16 10:30:52
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Improving indistinguishability of single photons from colloidal quantum dots using nanocavities
摘要： Colloidal quantum dots have garnered active research interest as quantum emitters due to their robust synthesis process and straightforward integration with nanophotonic platforms. However, obtaining indistinguishable photons from the colloidal quantum dots at room temperature is fundamentally challenging because they suffer from an extremely large dephasing rate. Here we propose an experimentally feasible method of obtaining indistinguishable single photons from an incoherently pumped solution-processed colloidal quantum dot coupled to a system of nanocavities. We show that by coupling a colloidal quantum dot to a pair of silicon nitride cavities, we can obtain comparable performance of a single photon source from colloidal quantum dots as other leading quantum emitters like defect centers and self-assembled quantum dots.
关键词： Colloidal quantum dots,Nanocavities,Indistinguishable single photon source
更新于2025-09-16 10:30:52
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Spatial Collection in Colloidal Quantum Dot Solar Cells
摘要： In thin-film photovoltaic (PV) research and development, it is of interest to determine where the chief losses are occurring within the active layer. Herein, a method is developed and presented by which the spatial distribution of charge collection, operando, is ascertained, and its application in colloidal quantum dot (CQD) solar cells is demonstrated at a wide range of relevant bias conditions. A systematic computational method that relies only on knowledge of measured optical parameters and bias-dependent external quantum efficiency spectra is implemented. It is found that, in CQD PV devices, the region near the thiol-treated hole-transport layer suffers from low collection efficiency, as a result of bad band alignment at this interface. The active layer is not fully depleted at short-circuit conditions, and this accounts for the limited short-circuit current of these CQD solar cells. The high collection efficiency outside of the depleted region agrees with a diffusion length on the order of hundreds of nanometers. The method provides a quantitative tool to study the operating principles and the physical origins of losses in CQD solar cells, and can be deployed in thin-film solar cell device architectures based on perovskites, organics, CQDs, and combinations of these materials.
关键词： colloidal quantum dots,Gaussian regularization least-squares,spatial collection efficiency,photovoltaics
更新于2025-09-16 10:30:52
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Photons and charges from colloidal doped semiconductor quantum dots
摘要： The utility of colloidal semiconductor quantum dots as a source of photons and charge carriers for photonic and photovoltaic applications has created a large field of research focused on tailoring and broadening their functionality beyond what an exciton can provide. One approach towards expanding the range of characteristics of photons and charge carriers from quantum dots is through doping impurity ions (e.g. Mn2+, Cu+, and Yb3+) in the host quantum dots. In addition to the progress in synthesis enabling fine control of the structure of the doped quantum dots, a mechanistic understanding of the underlying processes correlated with the structure has been crucial in revealing the full potential of the doped quantum dots as the source of photons and charge carriers. In this review, we discuss the recent progress made in gaining microscopic understanding of the photophysical pathways that give rise to unique dopant-related luminescence and the generation of energetic hot electrons via exciton-to-hot electron upconversion.
关键词： doping impurity ions,charge carriers,photons,hot electrons,colloidal semiconductor quantum dots,photophysical pathways
更新于2025-09-16 10:30:52
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Solution-processed P3HT:PbS based NIR Photodetector with FET Configuration
摘要： A near-infrared (NIR) solution-processed photodetector based on a mixture of PbS colloidal quantum dots (CQDs) and Poly(3-hexylthiophene) (P3HT) was presented. In a reverse field-effect transistor (FET) device configuration Au(S,D)/P3HT:PbS/PMMA/Al(G), uniform-sized and well-dispersed PbS CQDs were employed as NIR absorbing materials in the active layer. Meanwhile, the poly(methyl methacrylate) (PMMA) dielectric layer could be seen as an encapsulation to enhance the device stability. Herein, High “on/off” current ratio (Ion/Ioff) of 104 was obtained in dark, and the maximum photosensitivity (P) of 947 was gotten under 200 mW/cm2 980 nm illumination. When the irradiance reduced to 0.1 mW/cm2, the responsivity (R) and detectivity (D?) of the NIR photodetector reached 9.4 mA/W and 2.5×1011 Jones, respectively. Therefore, the P3HT:PbS hybrid FET-based NIR photodetector had shown both relatively high electrical and detecting performance, which provided an experimental foundation and method for the next fabrication of medical infrared detectors and sensors.
关键词： PbS colloidal quantum dots (CQDs),Near-infrared (NIR) photodetector,Poly(3-hexylthiophene) (P3HT),Field-effect transistor (FET)
更新于2025-09-16 10:30:52
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Resonant waveguide grating based assays for colloidal aggregate detection and promiscuity characterization in natural products
摘要： Small molecules, including natural compounds, in aqueous buffer that self-associate into colloidal aggregates is the main cause of false results in the early stage of drug discovery. Here we reported resonant waveguide grating (RWG) based assays to identify natural compound aggregation and characterize its influence on membrane receptors in living cells. We first applied a cell-free aggregation assay to determine compound critical aggregation concentration (CAC) values. Then we characterized the aggregators' influence on membrane receptors using three types of dynamic mass redistribution (DMR) assays. Results showed that colloidal aggregates may cause false activity in DMR desensitization assays; some of the false activities can be implied by the large response in DMR agonism assays and can further be identified by DMR antagonism assays. Furthermore, the aggregation mechanism was confirmed by addition of 0.025% tween-80, with cell signals attenuated and potency decreased. Finally, these observations were used for aggregate examination and promiscuity investigation of a traditional herbal medicine, Rhodiola rosea, which ultimately led to the revealing of the true target and reduced the risk of a bioactivity tracking process at the very first stage. This study highlights that the RWG based assays can be used as practical tools to distinguish between real and false hits to provide reliable results in the early stage of drug discovery.
关键词： natural products,drug discovery,colloidal aggregate detection,resonant waveguide grating,false results
更新于2025-09-16 10:30:52
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A quantitative analysis of memory effects in the viscously coupled dynamics of optically trapped Brownian particles
摘要： We provide a quantitative description of the memory e?ects existing in the apparently random Markovian dynamics of a pair of optically trapped colloidal microparticles in water. The particles are trapped in very close proximity to each other such that the resultant hydrodynamic interactions lead to non-Markovian signatures manifested by the double exponential auto-correlation function for the Brownian motion of each particle. In connection with the memory e?ects, we quantify the storage of energy in terms of various system parameters and demonstrate that a pair of Markovian particles – confined in individual optical traps in a viscous fluid – can be described in the framework of a single Brownian particle in a viscoelastic medium. We define and quantify the equivalent storage and loss moduli of the two-particle system, and show experimentally that the memory effects are maximized at a certain trap stiffness ratio, and reduce with increasing particle separation. The technique can be generally used to determine the effective viscoelastic parameters of any such fluid–particle systems, and can thus help understand the interactions between active particles mediated by simple or complex fluids.
关键词： memory effects,non-Markovian signatures,hydrodynamic interactions,viscoelastic medium,optically trapped colloidal microparticles
更新于2025-09-16 10:30:52
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Micropatterning and defect engineering of colloidal photonic crystals <i>via</i> laser direct writing
摘要： Micropatterning and defect engineering of colloidal photonic crystals (CPCs) play a significant role in the functionality of photonic crystals as they are crucial for optical chip integration, microcavity lasing, chemical sensing, etc. However, obstacles have arisen in recent years especially due to the lack of a general, cost-effective and versatile strategy to make these functional structures in one step. Traditional micro-/nanofabrication techniques may work for one structure but fail for another and the fabrication process is mostly complicated, which potentially incurs reproducibility issues. Here, point defects, waveguides and micropatterns with variable feature sizes (4B500 nm) can be easily created in polystyrene (PS)/SiO2 CPC films via laser direct writing, which is based on selective photodegradation of PS beads. By applying different laser powers or irradiation times, different coloured micropatterns and images with high resolution can be generated, which has great implications for image displays and anti-counterfeiting.
关键词： photodegradation,Micropatterning,colloidal photonic crystals,anti-counterfeiting,defect engineering,laser direct writing,image displays
更新于2025-09-16 10:30:52
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Observation of a phonon bottleneck in copper-doped colloidal quantum dots
摘要： Hot electrons can dramatically improve the efficiency of solar cells and sensitize energetically-demanding photochemical reactions. Efficient hot electron devices have been hindered by sub-picosecond intraband cooling of hot electrons in typical semiconductors via electron-phonon scattering. Semiconductor quantum dots were predicted to exhibit a "phonon bottleneck" for hot electron relaxation as their quantum-confined electrons would couple very inefficiently to phonons. However, typical cadmium selenide dots still exhibit sub-picosecond hot electron cooling, bypassing the phonon bottleneck possibly via an Auger-like process whereby the excessive energy of the hot electron is transferred to the hole. Here we demonstrate this cooling mechanism can be suppressed in copper-doped cadmium selenide colloidal quantum dots due to femtosecond hole capturing by copper-dopants. As a result, we observe a lifetime of ~8.6 picosecond for 1Pe hot electrons which is more than 30-fold longer than that in same-sized, undoped dots (~0.25 picosecond).
关键词： phonon bottleneck,electron-phonon scattering,hot electrons,colloidal quantum dots,copper-doped
更新于2025-09-16 10:30:52