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Self-assembled InAs/InGaAsP/InP quantum dots: Intraband relaxation impacted by ultrathin GaP sublayer
摘要： The influence of an ultrathin GaP (or GaAs) sublayer on the nonradiative intraband relaxation in InAs/InGaAsP/InP quantum dots (QDs) is investigated. It is found that, based on our studies, the QDs with some heights (e.g., 1.5 nm) and GaP sublayer thicknesses (e.g., 1.03 monolayers) present the first excited state (ES) with higher state degeneracy with respect to ground state (GS), which suggests that the Auger relaxation is triggered more easily. We also find that the energy difference of the ES and GS decreases with increasing sublayer thickness, which suggests that the electron–phonon interaction is affected. This work further presents a study of intraband relaxation for an InAs/InP QD with a GaP or GaAs sublayer. It is found that there is a critical thickness of the GaP sublayer: When the sublayer is less than the critical thickness, the intraband relaxation is only determined by one-longitudinal optical (LO) phonon or two-LO phonons, which is dependent on QD heights. However, with the GaAs sublayer, QDs do not have the above feature. This finding may be helpful for designing and optimizing high-speed QD devices.
关键词： quantum dots,electron–phonon interaction,InAs/InGaAsP/InP,intraband relaxation,GaP sublayer
更新于2025-09-23 15:21:01
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Chirality Inversion on the Carbon Dot Surface via Covalent Surface Conjugation of Cyclic α-Amino Acid Capping Agents
摘要： Manipulating the chiroptical properties at the nanoscale is of great importance in stereoselective reactions, enantioseparation, self-assembly, and biological phenomena. In recent years, carbon dots have garnered great attention because of their favorable properties such as tunable fluorescence, high biocompatibility, and facile, scalable synthetic procedures. Herein, we report for the first time the unusual behavior of cyclic amino acids on the surface of carbon dots prepared via microwave-based carbonization. Various amino acids were introduced on the surface of carbon dots via EDC/NHS conjugation at room temperature. Circular dichroism results revealed that although most of the surface conjugated amino acids can preserve their chirality on negatively charged, “bare” carbon dots, the “handedness” of cyclic α-amino acids can be flipped when covalently attached on carbon dots. Moreover, these chiroptical carbon dots were found to interact with the cellular membrane or its mimic in a highly selective manner due to their acquired asymmetric selectivity. A comprehensive inhibitor study was conducted to investigate the pathway of cellular trafficking of these carbon dots. Overall, it was concluded that the chirality of the amino acid on the surface of carbon dots could regulate many of the cellular processes.
关键词： cyclic amino acids,chiroptical properties,chirality inversion,carbon dots,cellular interaction
更新于2025-09-23 15:21:01
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Graphene Foam: Hole-Flake Network for Uniaxial Supercompression and Recovery Behavior
摘要： We employed the coarse-grained molecular dynamics simulation method to systematically study the uniaxial supercompression and recovery behavior of multi-porous graphene foam, in which a mesoscopic three-dimensional network with hole-graphene flakes was proposed. The network model not only considers the physical cross-links and interlayer van der Waals interactions, but also introduces a hole in the flake to approach the imperfection of pristine graphene and the hierarchical porous configuration of real foam material. We first recreated a typical two-stage supercompression stress?strain relationship and the corresponding time-dependent recovery as well as a U-type nominal Poisson ratio. Then the recovery unloading at different strains and multicycle compression?uncompression were both conducted; the initial elastic moduli in the multicycles were found to be the same, and a multilevel residual strain was disclosed. Importantly, the residual strain is not exactly the plastic one, part of which can resurrect in the subsequent loading?unloading?holding. The mesoscopic mechanism of viscoelastic and residual deformation for the recovery can be attributed to the van der Waals repulsion and mechanical interlocking among the hole-flakes; interestingly, the local tensile stress was observed in the virial stress distribution. Particularly, an abnormal turning point in the length-time curve for the mean bead-bond length was captured during the supercompression. After the point, the length abnormally increases for different size ratios of the hole to the flake, which is in line with the mesostructure evolution. The finding may provide a mesoscopic criterion for the supercompression of graphene foam related materials.
关键词： supercompression,strain history,recovery behavior,mesoscale,van der Waals interaction,viscoelastoplasticity,graphene foam,coarse-grained molecular dynamics
更新于2025-09-23 15:21:01
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Whirling spins with a ferroelectric
摘要： Ferroelectric polarization enables the emergence and control of magnetic skyrmions at an oxide interface. Controlling magnetism with an electric field is a burgeoning scientific challenge with significant technological implications. The reduced power required to electrically manipulate magnetization opens up exciting prospects for functional devices with unprecedented performance. Ferroelectric materials are especially suitable because they possess spontaneous electric polarization, switchable by an applied electric field. A ferroelectric interfaced with a thin-film ferromagnet has already been shown to modify the electronic structure of the ferromagnet near the interface, allowing control of properties such as the interfacial magnetization and magnetic order via ferroelectric polarization. Now, writing in Nature Materials, Lingfei Wang and colleagues put a new spin on ferroelectric-controlled nanoscale magnetism. They demonstrate a strategy for creating and manipulating magnetic nanoscale vortices, so-called skyrmions, using intrinsic ferroelectric polarization at oxide interfaces.
关键词： oxide interface,ferroelectric polarization,skyrmions,nanoscale magnetism,Dzyaloshinskii–Moriya interaction
更新于2025-09-23 15:21:01
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Nonlinear Analysis Methods Applied on Grid-Connected Photovoltaic (PV) Systems Driven by Power Electronic Converters
摘要： A novel method of analysis is deployed in detail on the basis of nonlinear systems theory with aim to design suitable controllers with guaranteed stability for grid-connected photovoltaic (PV) systems driven by power converters. By this method, all the system nonlinearities are taken into account to allow a reliable analysis in a wide range of operation and to avoid instabilities that as shown in the paper can be occurred by inappropriate design. To this end, firstly a detailed accurate nonlinear dynamic model is presented for the PV system by including a cascade-mode control scheme. Then, taking into account the closed-loop system and incorporating the concept of input-to-state stability (ISS), a rigorous novel stability analysis is developed which achieves to prove asymptotic stability of the desired equilibrium point. A multi-step process is deployed in which the control loops operating in cascade-mode are involved. However, since the cascaded-mode control scheme and analysis is based on the time-scale separation principle, a systematic tuning method is conducted for the accurate gain selection of both inner-loop and outer-loop controllers which is based on the construction of suitable Lyapunov functions. To further validate the overall analysis, experimental results are carried out.
关键词： nonlinear analysis,grid-interaction,Photovoltaic systems,stability,power converter control design
更新于2025-09-23 15:21:01
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[ACM Press the 2018 ACM Symposium - Warsaw, Poland (2018.06.14-2018.06.17)] Proceedings of the 2018 ACM Symposium on Eye Tracking Research & Applications - ETRA '18 - Hands-free web browsing
摘要： Hands-free browsers provide an effective tool for Web interaction and accessibility, overcoming the need for conventional input sources. Current approaches to hands-free interaction are primarily categorized in either voice or gaze-based modality. In this work, we investigate how these two modalities could be integrated to provide a better hands-free experience for end-users. We demonstrate a multimodal browsing approach combining eye gaze and voice inputs for optimized interaction, and to suffice user preferences with unimodal benefits. The initial assessment with five participants indicates improved performance for the multimodal prototype in comparison to single modalities for hands-free Web browsing.
关键词： voice input,Web accessibility,speech commands,multimodal interfaces,eye tracking,Hands-free interaction
更新于2025-09-23 15:21:01
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Modulation of donor alkyl terminal chains with shifting branching point leads to optimized morphology and efficient all-small-molecule organic solar cells
摘要： Terminal group modification is one of the most influential factors for small molecular donors compared with their polymer counterparts, resulting in an opportunity to optimize the morphology of all-small-molecule organic solar cells (ASM-OSCs). In this manuscript, we report three novel small molecular donors with branching points at the 1-, 2-, and 3-positions in alkyl terminal chains, called BSCl-C1, BSCl-C2 and BSCl-C3, respectively. Using IDIC-4Cl as acceptor, the subtle branching position shift achieves a dramatic disparity in photovoltaic parameters, as indicated by the short circuit current (Jsc) changing from 4.90 mA cm?2 to 20.1 mA cm?2 to 14.2 mA cm?2 and the fill factor varying from 33.9% to 71.3% to 67.0% for BSCl-C1, BSCl-C2, and BSCl-C3, respectively. The best device performance of 12.4% is obtained by the BSCl-C2:IDIC-4Cl system, which not only ranks among the top values reported to date, but also exhibits low energy loss in systems that use IDIC as acceptors. The notable device performance based on BSCl-C2 is attributed to the optimized phase morphology caused by the strong molecular crystallinity and suitable intermolecular interaction with IDIC-4Cl. These results demonstrate that suitably tuning the branching position of terminal groups could promote the high performance of ASM-OSCs.
关键词： branching point,phase morphology,crystallinity,intermolecular interaction,all-small-molecule
更新于2025-09-23 15:21:01
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Highly Efficient Energy Transfer from Water Soluble Zinc Silver Indium Sulphide Quantum Dot to Organic J-Aggregates
摘要： The present work has been carried out with an aim to design and develop an efficient light harvesting inorganic-organic hybrid nanoscale material by employing less toxic, environment friendly inorganic substance and also to understand the mechanism of inter-particle electronic interaction between the inorganic and organic components of the nanomaterial. Specifically, the inorganic-organic hybrid associate has been made by integrating water soluble semiconductor QDs (Zinc-silver-indium-sulfide (ZAIS)) and organic J-aggregates of a cyanine dye (S2165). The fabrication of present nano-hybrid system has been achieved via electrostatically driven self-assembly of organic dyes over ZAIS QDs. The interaction between QD and J-aggregates have been investigated by steady state and time resolved fluorescence measurements. Zeta potential measurements have also been performed to understand the role of electrostatic interaction and thermodynamic feasibility of the association process. The investigations have revealed that energy transfer (ET) process between QD and J-aggregates mediated through dipole-dipole mechanism. Interestingly, data analysis based on F?rster theory has further revealed that the ET from QD to J-aggregates is very high indicating efficient electronic coupling between the inorganic QD and the organic J-aggregates. Zeta potential measurements and thermodynamic calculations have demonstrated that the interaction between QD and organic dye is electrostatically driven and the association of organic dyes over QD is thermodynamically feasible. The outcome of the present study is expected to be helpful in designing efficient nanoscale light harvesting devices. Additionally, fluorescence microscopy and toxicity studies on the QDs have also shown its suitability for biological applications.
关键词： energy transfer,fluorescence microscopy,electrostatic interaction,J-aggregates,inorganic-organic hybrid,toxicity studies,quantum dots
更新于2025-09-23 15:21:01
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Increasing the efficiency of material removal using dual laser micromachining
摘要： A continuous wave melting laser combined with a nanosecond ejection laser has been shown to improve the material removal efficiency by a factor of 2 to 8 compared with laser ablation processes reported in the literature. The decrease in the energy required for the combined lasers is primarily due to the optimisation of the irradiation time in the melting process, which is responsible for the majority of the total energy. For the laser used in this study, the optimal interaction time corresponding to the highest melting efficiency was found at 9-ms melting time, and this value is compared with results derived from a one-dimensional heating model. Metallurgical images of only melting and the produced hole after introducing the ejection pulse for the most efficient melting were presented as evidence of melt ejection. The results show that approximately 90% of the melt pool is ejected with little redeposited material at the periphery of the hole.
关键词： Beam-matter interaction,Short pulsed lasers,Laser material processing,Laser melting
更新于2025-09-23 15:21:01
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Diarylethene moiety as an enthalpy-entropy switch: photoisomerizable stapled peptides for modulating p53/MDM2 interaction
摘要： Analogs of the known inhibitor (peptide pDI) of the p53/MDM2 protein–protein interaction are reported, which are stapled by linkers bearing a photoisomerizable diarylethene moiety. The corresponding photoisomers possess significantly different affinities to the p53-interacting domain of the human MDM2. Apparent dissociation constants are in the picomolar-to-low nanomolar range for those isomers with diarylethene in the 'open' configuration, but up to eight times larger for the corresponding 'closed' isomers. Spectroscopic, structural, and computational studies showed that the stapling linkers of the peptides contribute to their binding. Calorimetry revealed that the binding of the 'closed' isomers is mostly enthalpy-driven, whereas the 'open' photoforms bind to the protein stronger due to their increased binding entropy. The results suggest that conformational dynamics of the protein-peptide complexes may explain the differences in the thermodynamic profiles of the binding.
关键词： Photoisomerizable stapled peptides,Thermodynamic profiles,p53/MDM2 interaction,Diarylethene,Conformational dynamics
更新于2025-09-23 15:21:01