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The electron-withdrawing capability of metal nanocrystals and the photosensitization effect of atomically precise metal NCs are synergistically harnessed to finely mediate the charge transfer pathways.

Transition metal chalcogenide quantum dots (TMC QDs) represent promising light-harvesting antennas because of their fascinating physicochemical properties including quantum confinement effect and suitable energy band structures. However, TMC QDs generally suffer from poor photoactivities and photostability due to deficiency of active sites and ultrafast recombination rate of photoinduced charge carriers. Here, we demonstrate how to rationally arouse the charge transfer kinetic of TMC QDs by close monolayered graphene (GR) encapsulation via a ligand-dominated layer-by-layer (LbL) assembly utilizing oppositely charged TMC QDs and GR nanosheets as the building blocks. The assembly units were spontaneously and intimately integrated in an alternate integration mode, thereby resulting in the multilayered three-dimensional (3D) TMC QDs/GR ensembles. It was unveiled that multifarious photoactivities of TMC QDs/GR nanocomposites toward versatile photoredox organic catalysis including photocatalytic aromatic alcohols oxidation to aldehydes and nitroaromatics reduction to amino derivatives under visible light irradiation are conspicuously boosted because of spatially multilayered monolayered GR encapsulation which are superior to those of TMC QDs counterparts. The substantially enhanced photoactivities of TMC QDs/GR nanocomposites arise from reasons including improved light absorption and enhanced charge separation efficacy because of GR encapsulation together with unique stacking mode between TMC QDs and GR endowed by LbL assembly. Our work would provide a promising and efficacious route to smartly accelerate the charge transfer kinetic of TMC QDs for solar energy conversion.

Atomically precise metal nanoclusters (NCs)-based photocatalytic systems have garnered enormous attention owing to the fascinating merits including unique physicochemical properties, quantum confin...

Directional and high-efficiency charge transport to the target active sites of photocatalyst is central to boost the solar energy conversion but is retarded by the sluggish charge transfer kinetics and deficiency of active sites. Here, we report the elaborate design of cascade unidirectional charge transfer channel over spatially multilayered CdS@CdTe@MoS2 dual core-shell ternary heterostructures by partial transformation of CdS to CdTe interim layer followed by seamless encapsulation with an ultrathin MoS2 layer. The suitable energy-level alignment and unique coaxial multilayered assembly mode among the building blocks accelerate the interfacial charge separation and transport, endowing the CdS@CdTe@MoS2 heterostructures with conspicuously enhanced visible-light-driven photocatalytic hydrogen generation performances along with good photostability. The integrated roles of ultrathin CdTe intermediate layer in passivating the defect sites of CdS NWs framework, mediating the unidirectional charge transfer cascade and prolonging the charge lifetime, were ascertained. Besides, the crucial role of the outermost MoS2 layer as the metal-free cocatalyst in enriching the surface active sites for hydrogen evolution was also determined. Our work would provide new alternatives for finely tuning the charge flow toward promising solar-to-hydrogen conversion efficiency.

Finely tuning the charge transfer constitutes a central challenge in photocatalysis, yet exquisite control of the directional charge transfer to the target reactive sites is hindered by the rapid charge recombination. Herein, dual separated charge transport channels were fabricated in a one-dimensional transition-metal chalcogenide (TMC)-based system via an elaborate layer-by-layer (LbL) self-assembly approach, for which oppositely charged metal-ion-coordinated branched polyethylenimine (BPEI) and MoS2 quantum dots (QDs) were alternately integrated to fabricate the multilayered TMC@(BPEI/MoS2 QDs)n heterostructures with controllable interfaces. Photocatalytic hydrogen generation performances of such ternary heterostructures under visible light irradiation were evaluated, which unravels that the BPEI layer not only behaves as "molecule glue" to enable the electrostatic LbL assembly with MoS2 QDs in an alternate stacking fashion on the TMC frameworks but also acts as a unidirectional hole-transfer channel. More significantly, transition-metal ions (Fe2+, Co2+, Ni2+, Cu2+, and Zn2+) coordinated on the outmost BPEI layer are able to function as interfacial electron transfer mediators for accelerating the interfacial cascade electron transport efficiency. These simultaneously constructed dual high-speed electron and hole-transfer channels are beneficial for boosting the charge separation and enhancing the photocatalytic hydrogen evolution performances.

Unidirectional and smooth charge transfer to the reactive sites plays an imperative role in boosting the solar-to-hydrogen conversion efficiency of photoelectrochemical (PEC) cells but suffers from sluggish charge transfer kinetics. Herein, as a proof-of-concept demonstration, high-speed spatially separated electron and hole transfer channels were simultaneously constructed in an integrated multilayered heterostructured photoanode via an efficient electrostatic layer-by-layer (LbL) assembly strategy, wherein a tailor-made positively charged polymer of branched polyethylenimine (BPEI) and negatively charged MoS2 quantum dot (QD) building blocks were intimately and alternately integrated on the hierarchically ordered TiO2 nanotube array (TNTA) framework in a unique “face-to-face” stacking fashion. The periodically alternately stacked ultra-thin BPEI layer in the ternary multilayered photoanode serves as a directional hole transport channel and the MoS2 QD layer functions as a cascade electron transfer channel, which synergistically contribute to the considerably enhanced separation and prolonged lifetime of charge carriers, endowing the multilayered TNTAs/(BPEI–MoS2 QDs)n photoanodes with markedly enhanced PEC water dissociation performances with respect to the single and binary counterparts under simulated solar light irradiation. Moreover, the essential role of the assembly unit was clarified. Our work would afford a new frontier to intelligently mediate the photoinduced charge flow by rationally constructing the unidirectional charge transport channels in semiconductor-based photoelectrodes for solar energy conversion.

High-resolution images of human brain are critical for monitoring the neurological conditions in a portable and safe manner. Sound speed mapping of brain tissues provides unique information for such a purpose. In addition, it is particularly important for building digital human acoustic models, which form a reference for future ultrasound research. Conventional ultrasound modalities can hardly image the human brain at high spatial resolution inside the skull due to the strong impedance contrast between hard tissue and soft tissue. We carry out numerical experiments to demonstrate that the time-domain waveform inversion technique, originating from the geophysics community, is promising to deliver quantitative images of human brains within the skull at a sub-millimeter level by using ultra-sound signals. The successful implementation of such an approach to brain imaging requires the following items: signals of sub-megahertz frequencies transmitting across the inside of skull, an accurate numerical wave equation solver simulating the wave propagation, and well-designed inversion schemes to reconstruct the physical parameters of targeted model based on the optimization theory. Here we propose an innovative modality of multiscale deconvolutional waveform inversion that improves ultrasound imaging resolution, by evaluating the similarity between synthetic data and observed data through using limited length Wiener filter. We implement the proposed approach to iteratively update the parametric models of the human brain. The quantitative imaging method paves the way for building the accurate acoustic brain model to diagnose associated diseases, in a potentially more portable, more dynamic and safer way than magnetic resonance imaging and x-ray computed tomography.

Metal–semiconductor heterostructures have been arousing enduring interest on account of the pivotal roles of metal nanocrystals (NCs) as interfacial Schottky junction-induced charge flow mediators ...

Semiconductor quantum dots (QDs) have garnered tremendous attention by virtue of their substantial light-harvesting and conversion efficiencies, large number of active sites, unique quantum size co...

Metal/semiconductor heterostructures have been arousing persistent interest on account of prominent roles of metal nanocrystals (NCs) in modulating charge transfer in photocatalysis. It has been ge...

Glutathione-protected Aux nanoclusters uniformly and intimately embedded at the interface of CdSe QDs and graphene were in situ self-transformed to Au nanocrystals (NCs) via a facile thermal reduction strategy. The inlaid Au NPs substantially accelerate the interfacial directional charge transfer toward multifarious photoreduction catalysis under visible light irradiation.

Recent years have witnessed an explosive investigation on the construction of graphene (GR)–semiconductor composite photocatalysts, but the specific correlation of the interface integration mode between GR and a semiconductor with the interfacial charge transfer characteristics is yet to be clearly clarified. To this end, a facile, green and surface linker-triggered self-assembly has been designed to construct GR-encapsulated antimony sulfide nanorod (Sb2S3 NRs–GR) ensembles, wherein tartaric acid-capped intrinsically negatively charged Sb2S3 NRs and surface-modified positively charged GR nanosheets were utilized as the building blocks. It was unveiled that the exquisitely designed interface configuration afforded by the intimate encapsulation of Sb2S3 NRs with GR via an electrostatic/hydrogen interaction is beneficial for fully harnessing the structural merits of GR in boosting light absorption, increasing the specific surface area and accelerating the interfacial electron transfer kinetics. Thus, the lifetimes of the photogenerated charge carriers were synergistically prolonged over Sb2S3, resulting in the considerably enhanced visible-light-responsive photoredox performances of the Sb2S3–GR nanocomposites toward the photoreduction of heavy metal ions and mineralization of organic pollutants compared with the blank Sb2S3 and nanocomposite counterpart without a finely tuned interface. More importantly, the crucial role of interface configuration between GR and the Sb2S3 NRs in dictating the interfacial charge transfer efficiency was substantiated. In addition, the predominant active species in the photoredox catalysis were determined and the corresponding photocatalytic mechanism was elucidated. Our work sheds light on mediating the interfacial charge transfer via rational interface configuration modulation toward substantial solar energy conversion.

Photoinduced charge separation and transfer have been deemed the core factors affecting the efficiency of photoelectrocatalysis; precisely modulating the spatial migration of photo-induced charge carriers to the ideal reaction sites is of paramount importance for boosting the solar conversion efficiency of photoelectrochemical (PEC) cells. In this work, a combinatorial strategy has been developed to progressively construct highly efficient charge transport channels on the quintessential electrochemically anodized one-dimensional semiconductor framework (TiO2 nanotube arrays, TNTAs) by in situ annealing-induced intrinsic ultrathin carbon encapsulation. Antimony sulfide (Sb2S3) nanocrystals were subsequently attached to the interior and exterior surfaces of the carbon-encapsulated TNTA (C–TNTA) substrate forming a well-defined ternary photoanode (C–Sb2S3–TNTA) capable of triggering smooth and cascade electron transfer. Cooperativity stemming from intrinsic carbon encapsulation on the surface for fast electron transport in conjunction with Sb2S3 photosensitization for substantial visible light harvesting endows the C–Sb2S3–TNTA heterostructure with markedly enhanced solar-powered PEC water dissociation performances, conspicuously exceeding its single and binary counterparts. Furthermore, a hole transport pathway was further constructed by site-selective incorporation of an oxygen evolving catalyst (Co-Pi) in the ternary system via a photo-assisted electrodeposition or electrodeposition approach, which contributes to more enhanced separation efficiency and prolonged lifetime of photo-induced charge carriers together with improved photostability. It is expected that our work would afford a new frontier to intelligently mediate the spatial directional flow of photogenerated charge carriers and rationally construct efficient charge transport channels on the semiconductor-based photoelectrodes for high-efficiency solar energy harvesting and conversion.

Interfacial charge separation and transfer enduringly constitutes a core issue, which dictates the efficiency of a photocatalytic reaction. However, the exquisite modulation of directional charge transfer to ideal reaction sites remains challenging in terms of the fast recombination rates of photoinduced charge carriers and the difficulty in constructing spatially separated high-speed charge transfer channels. Herein, we demonstrate the general construction of metal/metal chalcogenide heterostructures by a facile, green, universal, scalable and simple yet efficient electrostatic self-assembly strategy, wherein tailor-made positively charged 4-dimethylaminopyridine (DMAP)-capped metal nanocrystals (NCs, Au, Pd) were spontaneously and intimately tethered on negatively charged one-dimensional (1D) transition metal chalcogenides (TMC: CdS, CdIn2S4, ZnIn2S4, and Zn0.5Cd0.5S) initiated by a surface linker (DMAP) to fabricate well-defined heterostructured photocatalysts. Moreover, the interface configurations between the metal NCs and TMC matrices were finely designed by ligand engineering to afford controllable charge transfer pathways. Intriguingly, this tunable charge flow endows the metal NC/TMC heterostructures with markedly enhanced and versatile photoredox performance toward the anaerobic-selective photoreduction of aromatic nitro compounds, photocatalytic hydrogen generation, and photocatalytic selective oxidation of aromatic alcohols under visible light irradiation, in which metal NCs play imperative roles in efficiently capturing Schottky-junction-driven electrons from the TMC substrates without the interference of the hierarchically branched ligand capped on the metal NCs. Our studysheds light on the rational modulation of interfacial charge flow in photoredox catalysis for substantial solar energy conversion.

Recent years have witnessed a rise in the construction of transition metal chalcogenide (TMS)-based heterostructured photocatalysts in terms of their excellent light absorption and suitable energy level alignment. Nevertheless, controllable modulation of photoinduced charge separation/transfer toward target active sites for photoredox catalysis still constitutes an enduringly challenging issue. Herein, tailor-made negatively charged mercaptoacetic acid (MAA)-capped CdX@MAA (X = Se, Te, S) quantum dot (QD) and positively charged ultra-thin branched poly-ethyleneimine (BPEI) layer building blocks were alternately assembled on the hierarchically ordered TiO2 nanotube array (NP-TNTA) framework for general electrostatic layer-by-layer (LbL) assembly of spatially multilayered NP-TNTAs/(BPEI/CdX QDs)n (X = Se, Te, S) photoanodes. The ultra-thin BPEI polymer layer integrated in-between the interface of CdX QDs functions as a cascade hole transfer channel for efficiently extracting the holes photoexcited over neighboring CdX QD layers, and simultaneously, alternately deposited CdX QD layers serve as an efficacious photosensitizer for constructing directional electron flow channels. The unique integration mode and intimate interfacial interaction endowed by LbL assembly render the well-defined NP-TNTAs/(BPEI/CdX QDs)n multilayered heterostructures a high-efficiency photoanode toward photoelectrochemical (PEC) water splitting under both simulated solar and visible light irradiation, greatly outperforming the single and binary counterparts on account of in situ generation of two spatially separated charge transfer channels, ultimately synergistically boosting the separation efficiency and prolonging the lifetime of charge carriers. Our work would open up new frontiers for strategically mediating the interfacial charge transfer and advancing rational construction of heterostructured photocatalysts for solar energy conversion.

The purpose of this study was to identify independent prognostic factors for breast cancer patients with T1-2 tumors and 1-3 positive lymph nodes, and discuss the role of postmastectomy radiotherapy(PMRT) in these patients.Between January 2005 and December 2015, the data on 840 eligible patients with breast cancer were retrospectively reviewed. Of these patients, 368 women received PMRT and 472 did not. The endpoints were locoregional recurrence (LRR) and distant metastasis (DM).With a median follow-up of 62.0 months, multivariate analysis identified the following independent risk factors for increased LRR: tumor size ≥ 4 cm (HR: 2.994, 95% CI: 1.190-7.535, P = 0.020), ER- and PR-negative tumor (HR: 2.540, 95% CI: 1.165-5.537, P = 0.019), preoperative high neutrophil-to-lymphocyte ratio (NLR) (HR: 4.716, 95% CI: 1.776-12.528, P = 0.002)and low neutrophil-to-monocyte ratio (NMR) (HR: 0.231, 95% CI: 0.084-0.633, P = 0.004). And independent risk factors for increased DM: ER- and PR-negative tumor (HR: 2.540, 95% CI: 1.880-5.625, P = 0.000), high NLR (HR: 2.693, 95% CI: 1.426-5.084, P = 0.002) and low NMR (HR: 0.460, 95% CI: 0.257-0.824, P = 0.009). The high-risk patients (≥ 2 risk factors) had worse LRRFS and DFS than low-risk patients (0-1 risk factor) (all, P 0.05). In the subgroup analysis, both low- and high-risk patients received PMRT had better LRRFS and DFS than those who without PMRT (all, P 0.05), and the high-risk patients received PMRT had similar 5-year rates of LRRFS and DFS than low-risk patients who without PMRT (94.5 vs. 94.3%, P = 0.402; 83.4 vs.87.4%, P = 0.877, respectively).Tumor size, ER/PR status, preoperative NLR and NMR were independent predictors of risk of recurrence. PMRT could improve locoregional control even in low-risk subgroup of breast cancer patients with T1-2 tumors and 1-3 positive lymph nodes significantly.

Tunable and efficacious modulation of photo-induced charge carrier separation and transfer in photoelectrochemical (PEC) cell for solar water splitting constitute a central challenge. Herein, high-efficiency plasmon-induced hot carriers transfer channel has been rationally and progressively constructed by judicious layer-by-layer assembly of graphene quantum dots (GQDs) and plasmonic metal nanocrystals (Ag NCs) on the one-dimensional semiconductor (TiO2 nanorods arrays, TiO2 NRs) framework, resulting in a well-defined spatially multilayered photoanode. The unique and alternate integration of GQDs with Ag NCs on the TiO2 NRs is closely associated with charge transfer behaviors. It was unveiled that Ag NCs in situ integrated in the multilayered film enable hot electron generation, and simultaneously play a crucial role in finely relaying electron transfer from GQDs to TiO2. This gives rise to significantly enhanced solar-powered PEC water splitting performances of TiO2 NRs@Ag@GQDs ternary multilayered heterostructure, which far surpasses the corresponding binary and single counterparts. Consequently, intrinsic correlation of metal NCs with GQDs in terms of charge transport was for the first time clarified.

In order to evaluate the reliability of the deck system of concrete bridge reasonably, multi-index multilevel reliability assessment model of the bridge deck system was set up based on the ...

Bauxite residue disposal areas (BRDA) appear to result in the heavy metal pollution of the farm fields surrounding them. In total, 194 topsoil samples were collected from the fields surrounding a BRDA in Guangxi in order to comprehensively understand the pollutant characteristics. These characteristics and their ecological risks were assessed by the Nemerow and Harkanson indices, whilst the sources and correlations of eight heavy metals (V, Cr, Ni, Cu, Zn, As, Pb, and Co) were analyzed by means of the spatial interpolation method, correlation analysis, and principal component analysis (PCA). The results demonstrated that the surrounding fields were seriously polluted by heavy metals. Ninety-two percent of samples were polluted, including 36% that showed serious pollution, and As was the dominant contaminant. The ecological risk results showed that the risks of the surrounding fields were medium, and As was responsible for 68% of this. Spatial interpolation suggested that concentrations of heavy metals in the northeastward and southwestward areas were higher, however the southeastward areas were lower. Multivariate statistics indicated that the possible source of As contaminant was different to those of V, Ni, Zn, Pb, and Co; As was primarily influenced by anthropogenic contamination, including atmospheric sedimentation, and agricultural fertilization. Cr was affected by both soil parent material and atmospheric sedimentation, whereas V, Ni, Zn, Pb, And Co levels were mainly affected by soil parent material.

Recently, environmental protection becomes increasingly crucial throughout the whole world and the great concern should be focused on how to handle the relationship between human beings and nature. About two hundred years ago, Henry David Thoreau already made a creative and elementary experiment in the woods—returning to nature. Thoreau recorded his daily life there in Walden that is considered as a representative book in exploring the relationship between human beings and nature. It is considered that moderation plays an important role in Thoreauvian returning to nature and it is necessary to reaffirm the principles of Thoreauvian moderation—self-sufficiency and self-discipline, which can provide profound inspirations for modern environment-oriented life. Thoreauvian paradigm of moderation can help more people to keep it internalized.

Concurrent engineering has been used in many OEMs in order to face up to the fierce competition situation. Modular development teams develop common modules which are applied in the same platform-based variants and its product family in order to save design costs and reduce development time. The R&D department should construct a concurrent engineering team to quicken the pace of new product development and to ensure product quality by means of open-loop and close-loop cycle, and frame a platform to frequent communication and quick decision for the concurrent engineering team.