Elucidating Facet-Dependent Photocatalytic Activities of Metastable CdS and Au@CdS Core-Shell Nanocrystals.

Controlling the crystal facets of semiconductor nanocrystals (NCs) has been proven as an effective approach to tune their physicochemical properties. However, the study on facet-engineering of metastable zinc blende CdS (zb-CdS) and its heterostructures is still not fully explored. In this study, the zb-CdS and Au@zb-CdS core-shell NCs with tunable terminating facets are controllably synthesized, and their photocatalytic performance for water splitting are evaluated. It is found that the {111} facets of the zb-CdS NCs display higher intrinsic activity than the {100} counterparts, which originates from these surfaces being much more efficient, facilitating electron transition to enhance the adsorption ability and the dissociation of the adsorbed water, as revealed by theoretical calculations. Moreover, the Au@zb-CdS core-shell NCs exhibit better photocatalytic performance than the zb-CdS NCs terminated with the same facets under visible light irradiation (≥400 nm), which is mainly ascribed to the accelerated electron separation at the interface, as demonstrated by femtosecond transient absorption (fs-TA) spectroscopy. Importantly, the quantum yield of plasmon-induced hot electron transfer quantified by fs-TA in the Au@zb-CdS core-shell octahedrons can be reached as high as 1.2% under 615 nm excitation, which is higher than that of the Au@zb-CdS core-shell cubes. This work unravels the face-dependent photocatalytic performance of the metastable semiconductor NCs via a combination of experiments and theoretical calculations, providing the understanding of the underlying mechanism of these photocatalysts.

A Multistate Thermoresponsive Smart Window Based on a Multifunctional Luminescent Solar Concentrator.

Conventional luminescent solar concentrators (LSCs) usually only have the ability to absorb solar energy and convert it to electricity but are not able to regulate the transmitted light. Herein, a multistate thermoresponsive smart window (SW) based on LSC has been fabricated, in which the stimuli-responsive host layer consists of polydimethylsiloxane (PDMS) and ethylene glycol solution (EGS) microdroplets stacking with LSC layer-based on near-infrared (NIR) CuInSe2-xSx/ZnS core/shell quantum dots (QDs) and PDMS matrix. As-synthesized CISSe/ZnS QDs with broad NIR absorption in LSC exhibit controllable emission spectra over 833-1088 nm and high photoluminescence (PL) quantum yield from 45 to 83%. Coupling with Si solar cells as a reference, optimized LSC-SW devices with dimensions of 5 × 5 × 0.9 cm3 exhibit higher power conversion efficiency (PCE) of 1.19-1.36% with increased temperature from 0 to 50 °C than those of sole LSC and SW devices. The corresponding visible light transmissions are regulated from 75.1 to 48.1% accordingly. The improvement of PCEs in an opaque state is mainly due to enhanced absorption of QDs originating from rescattered photons from the EGS/PDMS layer, leading to more emitted photons reaching photovoltaics. This work is expected to bring up new opportunities for applications in greenhouses, building facades, and energy-efficient smart windows.

Accessible Tetrathiafulvalene Moieties in a 3D Covalent Organic Framework for Enhanced Near-Infrared Photo-Thermal Conversion and Photo-Electrical Response.

Redox-active tetrathiafulvalene (TTF)-based covalent organic frameworks (COFs) exhibit distinctive electrochemical and photoelectrical properties, but their prevalent two-dimensional (2D) structure with densely packed TTF moieties limits the accessibility of redox center and constrains their potential applications. To overcome this challenge, an 8-connected TTF linker (TTF-8CHO) is designed as a new building block for the construction of three-dimensional (3D) COFs. This approach led to the successful synthesis of a 3D COF with the bcu topology, designated as TTF-8CHO-COF. In comparison to its 2D counterpart employing a 4-connected TTF linker, the 3D COF design enhances access to redox sites, facilitating controlled oxidation by I2 or Au3+ to tune physical properties. When irradiated with a 0.7 W cm-2 808 nm laser, the oxidized 3D COF samples ( I X - ${\mathrm{I}}_{\mathrm{X}}^{-}$ @TTF-8CHO-COF and Au NPs@TTF-8CHO-COF) demonstrated rapid temperature increases of 239.3 and 146.1 °C, respectively, which surpassed those of pristine 3D COF (65.6 °C) and the 2D COF counterpart (6.4 °C increment after I2 treatment). Furthermore, the oxidation of the 3D COF heightened its photoelectrical responsiveness under 808 nm laser irradiation. This augmentation in photothermal and photoelectrical response can be attributed to the higher concentration of TTF·+ radicals generated through the oxidation of well-exposed TTF moieties.

Visible-Light-Driven Selective Hydrogenation of Nitrostyrene over Layered Ternary Sulfide Nanostructures.

Selective hydrogenation of nitrostyrenes is a great challenge due to the competitive activation of the nitro groups (─NO2 ) and carbon-carbon (C═C) double bonds. Photocatalysis has emerged as an alternative to thermocatalysis for the selective hydrogenation reaction, bypassing the precious metal costs and harsh conditions. Herein, two crystalline phases of layered ternary sulfide Cu2 WS4 , that is, body-centered tetragonal I-Cu2 WS4 nanosheets and primitive tetragonal P-Cu2 WS4 nanoflowers, are controlled synthesized by adjusting the capping agents. Remarkably, these nanostructures show visible-light-driven photocatalytic performance for selective hydrogenation of 3-nitrostyrene under mild conditions. In detail, the I-Cu2 WS4 nanosheets show excellent conversion of 3-nitrostyrene (99.9%) and high selectivity for 3-vinylaniline (98.7%) with the assistance of Na2 S as a hole scavenger. They also can achieve good hydrogenation selectivity to 3-ethylnitrobenzene (88.5%) with conversion as high as 96.3% by using N2 H4 as a proton source. Mechanism studies reveal that the photogenerated electrons and in situ generated protons from water participate in the former hydrogenation pathway, while the latter requires the photogenerated holes and in situ generated reactive oxygen species to activate the N2 H4 to form cis-N2 H2 for further reduction. The present work expands the rational synthesis of ternary sulfide nanostructures and their potential application for solar-energy-driven organic transformations.

Halide Ions Regulating the Morphologies of PbS and Au@PbS Core-Shell Nanocrystals: Synthesis, Self-Assembly, and Electrical Transport Properties.

The geometry and surface state of nanocrystals (NCs) strongly affect their physiochemical properties, self-assembly behaviors, and potential applications, but there is still a lack of a facile method to regulate the exposed facets of the NCs, especially metal@semiconductor core-shell NCs. Herein, we present a reproducible approach for tuning the morphology of PbS NCs from nanocubes to nano-octahedrons by introducing lead halides as precursors. Excitingly, the method can be easily extended to the synthesis of metal@PbS core-shell NCs with single-crystalline shells and specific exposed facets. In addition, the halide passivation layers on the NCs are found to greatly improve their antioxidant ability. Therefore, the Cl-passivated NCs can self-assemble into atomic-coupled monolayer films via oriented attachment under ambient conditions, which exhibit enhanced electrical conductivities compared with uncoupled counterparts. The precise synthesis of nanocrystals with tunable shapes and the construction of self-assembled films provide a way to expand their application in high-performance optoelectronic devices.

Versatile synthesis of nano-icosapods via cation exchange for effective photocatalytic conversion of biomass-relevant alcohols.

Branched metal chalcogenide nanostructures with well-defined composition and configuration are appealing photocatalysts for solar-driven organic transformations. However, precise design and controlled synthesis of such nanostructures still remain a great challenge. Herein, we report the construction of a variety of highly symmetrical metal sulfides and heterostructured icosapods based on them, in which twenty branches were radially grown in spatially ordered arrangement, with a high degree of structure homogeneity. Impressively, the as-obtained CdS-PdxS icosapods manifest a significantly improved photocatalytic activity for the selective oxidation of biomass-relevant alcohols into corresponding aldehydes coupled with H2 evolution under visible-light irradiation (>420 nm), and the apparent quantum yield of the benzyl alcohol reforming can be achieved as high as 31.4% at 420 nm. The photoreforming process over the CdS-PdxS icosapods is found to be directly triggered by the photogenerated electrons and holes without participation of radicals. The enhanced photocatalytic performance is attributed to the fast charge separation and abundant active sites originating from the well-defined configuration and spatial organization of the components in the branched heterostructures.

Epitaxial growth of highly symmetrical branched noble metal-semiconductor heterostructures with efficient plasmon-induced hot-electron transfer.

Epitaxial growth is one of the most commonly used strategies to precisely tailor heterostructures with well-defined compositions, morphologies, crystal phases, and interfaces for various applications. However, as epitaxial growth requires a small interfacial lattice mismatch between the components, it remains a challenge for the epitaxial synthesis of heterostructures constructed by materials with large lattice mismatch and/or different chemical bonding, especially the noble metal-semiconductor heterostructures. Here, we develop a noble metal-seeded epitaxial growth strategy to prepare highly symmetrical noble metal-semiconductor branched heterostructures with desired spatial configurations, i.e., twenty CdS (or CdSe) nanorods epitaxially grown on twenty exposed (111) facets of Ag icosahedral nanocrystal, albeit a large lattice mismatch (more than 40%). Importantly, a high quantum yield (QY) of plasmon-induced hot-electron transferred from Ag to CdS was observed in epitaxial Ag-CdS icosapods (18.1%). This work demonstrates that epitaxial growth can be achieved in heterostructures composed of materials with large lattice mismatches. The constructed epitaxial noble metal-semiconductor interfaces could be an ideal platform for investigating the role of interfaces in various physicochemical processes.

Directly Imaging Dynamic Electronic Coupling during Electrochemical Oxidation of Single Silver Nanoparticles.

The electronic coupling between a metal electrode and single nano-entities is of unfading significance which impacts the heterogeneous electron transfer. Herein, we demonstrated a simple optical technique for directly imaging the transient interfacial electronic coupling events during electrochemical oxidation of single Ag nanoparticles on Au electrode. The electronic coupling brings out a dramatic dip behavior of bright field imaging traces, and is conductive to cross the energy barrier of oxidation for single silver nanoparticles. This dip behavior is further verified by in situ vis-transmission spectroscopy, and the heterogeneity of the Au-Ag electronic coupling down to single-nanoparticle level is uncovered by unifying the morphology and size of individual silver nanoparticles. These results suggest the interfacial electronic coupling facilitates electron transfer of single nanoparticles, and provide important insight into understanding detailed mechanism of nanoelectrochemistry.

Ultrasensitive detection of local acoustic vibrations at room temperature by plasmon-enhanced single-molecule fluorescence.

Sensitive detection of local acoustic vibrations at the nanometer scale has promising potential applications involving miniaturized devices in many areas, such as geological exploration, military reconnaissance, and ultrasound imaging. However, sensitive detection of weak acoustic signals with high spatial resolution at room temperature has become a major challenge. Here, we report a nanometer-scale system for acoustic detection with a single molecule as a probe based on minute variations of its distance to the surface of a plasmonic gold nanorod. This system can extract the frequency and amplitude of acoustic vibrations with experimental and theoretical sensitivities of 10 pm Hz-1/2 and 10 fm Hz-1/2, respectively. This approach provides a strategy for the optical detection of acoustic waves based on molecular spectroscopy without electromagnetic interference. Moreover, such a small nano-acoustic detector with 40-nm size can be employed to monitor acoustic vibrations or read out the quantum states of nanomechanical devices.

Direct synthesis of Au-Ag nanoframes by galvanic replacement via a continuous concaving process.

Controlled synthesis of noble-metal nanoframes is of great interest due to their promising applications in plasmonics and catalysis. However, the synthesis is largely limited to a multiple-step approach involving selective deposition followed by selective etching. Here we report a facile and general strategy to synthesize Au-Ag nanoframes based on a direct galvanic replacement reaction between Ag nanoparticles and a gold(I) complex, sodium aurothiosulfate, without an extra etching process. The formation of Au-Ag nanoframes in our approach undergoes a continuous concaving and hollowing-out process from Ag templates, which is related to selective Au deposition and the Kirkendall effect. As a proof-of-concept, it was shown that Au-Ag nanoframes with different dimensions can be prepared from the corresponding Ag nanocolloids using our strategy. The prepared wire-like Au-Ag nanoframes show superior single-particle surface-enhanced Raman scattering due to the linear narrow nanogaps within the nanoframes. We believe this study signifies a new approach by mediating galvanic replacement to prepare noble-metal nanoframes with precise controllability, which may enable a variety of applications in plasmonics and catalysis.

Nonblinking Colloidal Quantum Dots via Efficient Multiexciton Emission.

Nonblinking colloidal quantum dots (QDs) are significant to their applications as single-photon sources or light-emitting materials. Herein, a simple heat-up method was developed to synthesize high-qualityWZ-CdSe/CdS core-shell colloidal QDs, which achieved a near-unity photoluminescence quantum yield (PLQY). It was found that the blinking behavior of such QDs was completely suppressed at high excitation intensities, and ultra-stable PL emission was observed. For this reason, a systematic investigation was conducted, revealing that the complete blinking suppression was attributed mainly to the efficient multiexciton emission at high excitation intensities. Such high-quality QDs with nonblinking behaviors and nearly ideal PL properties at high excitation intensities have massive potential applications in various robust conditions, including QD display screens, single-particle tracks, and single-photon sources.

Simple Synthesis of Red Iridium(III) Complexes with Sulfur-Contained Four-Membered Ancillary Ligands for OLEDs.

Phosphorescent iridium(III) complexes have been widely researched for the fabrication of efficient organic light-emitting diodes (OLEDs). In this work, three red Ir(III) complexes named Ir-1, Ir-2, and Ir-3, with Ir-S-C-S four-membered framework rings, were synthesized efficiently at room temperature within 5 min using sulfur-containing ancillary ligands with electron-donating groups of 9,10-dihydro-9,9-dimethylacridine, phenoxazine, and phenothiazine, respectively. Due to the same main ligand of 4-(4-(trifluoromethyl)phenyl)quinazoline, all Ir(III) complexes showed similar photoluminescence emissions at 622, 619, and 622 nm with phosphorescence quantum yields of 35.4%, 50.4%, and 52.8%, respectively. OLEDs employing these complexes as emitters with the structure of ITO (indium tin oxide)/HAT-CN (dipyra-zino[2,3-f,2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile, 5 nm)/TAPC (4,4'-cyclohexylidenebis[N,N-bis-(4-methylphenyl)aniline], 40 nm)/TCTA (4,4″,4″-tris(carbazol-9-yl)triphenylamine, 10 nm)/Ir(III) complex (10 wt%): 2,6DCzPPy (2,6-bis-(3-(carbazol-9-yl)phenyl)pyridine, 10 nm)/TmPyPB (1,3,5-tri(mpyrid-3-yl-phenyl)benzene, 50 nm)/LiF (1 nm)/Al (100 nm) achieved good performance. In particular, the device based on complex Ir-3 with the phenothiazine unit showed the best performance with a maximum brightness of 22,480 cd m-2, a maximum current efficiency of 23.71 cd A-1, and a maximum external quantum efficiency of 18.1%. The research results suggest the Ir(III) complexes with a four-membered ring Ir-S-C-S backbone provide ideas for the rapid preparation of Ir(III) complexes for OLEDs.

Preparation of CdSy Se1- y -MoS2 Heterostructures via Cation Exchange of Pre-Epitaxially Synthesized Cu2- χ Sy Se1- y -MoS2 for Photocatalytic Hydrogen Evolution.

Construction of 2D transition metal dichalcogenide (TMD)-based epitaxial heterostructures with different compositions is important for various promising applications, including electronics, photonics, and catalysis. However, the rational design and controlled synthesis of such kind of heterostructures still remain challenge, especially for those consisting of layered TMDs and other non-layered materials. Here, a facile one-pot, wet-chemical method is reported to synthesize Cu2- χ Sy Se1- y -MoS2 heterostructures in which two types of different epitaxial configurations, i.e., vertical and lateral epitaxies, coexist. The chalcogen ratio (S/Se) in Cu2- χ Sy Se1- y and the loading amount of MoS2 in the heterostructures can be tuned. Impressively, the obtained Cu2- χ Sy Se1- y -MoS2 heterostructures can be transformed to CdSy Se1- y -MoS2 without morphological change via cation exchange. As a proof-of-concept application, the obtained CdSy Se1- y -MoS2 heterostructures with controllable compositions are used as photocatalysts, exhibiting distinctive catalytic activities toward the photocatalytic hydrogen evolution under visible light irradiation. The method paves the way for the synthesis of different TMD-based lateral epitaxial heterostructures with unique properties for various applications.

Rational Synthesis of 1D Hyperbranched Heterostructures with Enhanced Optoelectronic Performance.

One-dimensional (1D) hyperbranched heterostructures (HBHSs) with abundant interfaces are rendered with various interfacial phenomena and functionalities. However, the rational synthesis of 1D HBHSs with desired spatial architecture and specific interface remains a great challenge. Here, we report a seeded growth method for controlled synthesis of two extraordinary types of HBHSs, in which high-intensity of CdS branches selectively grow on 1D nanowire (NW) trunks with different growth behaviors. The composition of the HBHSs can be further tuned by combining with cation exchange method, which enriches the variety of the HBHSs. The optoelectronic devices based on a single HBHS were fabricated and exhibit a better photoresponse performance compared with that of a single NW trunk. This advance provides a strategy for the controlled synthesis HBHSs with complex morphology and offers a platform for exploring their applications for photo harvesting and conversion.

Tanshinone IIA Suppresses Hypoxia-induced Apoptosis in Medial Vestibular Nucleus Cells Via a Skp2/BKCa Axis.

BACKGROUND: The aim of the present study was to investigate the protective effects of Tanshinone IIA (Tan IIA) on hypoxia-induced injury in the medial vestibular nucleus (MVN) cells. METHODS: An in vitro hypoxia model was established using MVN cells exposed to hypoxia. The hypoxia-induced cell damage was confirmed by assessing cell viability, apoptosis and expression of apoptosis-associated proteins. Oxidative stress and related indicators were also measured following hypoxia modeling and Tan IIA treatment, and the genes potentially involved in the response were predicted using multiple GEO datasets. RESULTS: The results of the present study showed that Tan IIA significantly increased cell viability, decreased cell apoptosis and decreased the ratio of Bax/Bcl-2 in hypoxia treated cells. In addition, hypoxia treatment increased oxidative stress in MVN cells, and treatment with Tan IIA reduced the oxidative stress. The expression of SPhase Kinase Associated Protein 2 (SKP2) was upregulated in hypoxia treated cells, and Tan IIA treatment reduced the expression of SKP2. Mechanistically, SKP2 interacted with large-conductance Ca2+-activated K+ channels (BKCa), regulating its expression, and BKCa knockdown alleviated the protective effects of Tan IIA on hypoxia induced cell apoptosis. CONCLUSION: The results of the present study suggested that Tan IIA had a protective effect on hypoxia-induced cell damage through its anti-apoptotic and anti-oxidative activity via an SKP2/BKCa axis. These findings suggest that Tan IIA may be a potential therapeutic for the treatment of hypoxia-induced vertigo.

Synthesis of Palladium-Based Crystalline@Amorphous Core-Shell Nanoplates for Highly Efficient Ethanol Oxidation.

Phase engineering of nanomaterials (PEN) offers a promising route to rationally tune the physicochemical properties of nanomaterials and further enhance their performance in various applications. However, it remains a great challenge to construct well-defined crystalline@amorphous core-shell heterostructured nanomaterials with the same chemical components. Herein, the synthesis of binary (Pd-P) crystalline@amorphous heterostructured nanoplates using Cu3- χ P nanoplates as templates, via cation exchange, is reported. The obtained nanoplate possesses a crystalline core and an amorphous shell with the same elemental components, referred to as c-Pd-P@a-Pd-P. Moreover, the obtained c-Pd-P@a-Pd-P nanoplates can serve as templates to be further alloyed with Ni, forming ternary (Pd-Ni-P) crystalline@amorphous heterostructured nanoplates, referred to as c-Pd-Ni-P@a-Pd-Ni-P. The atomic content of Ni in the c-Pd-Ni-P@a-Pd-Ni-P nanoplates can be tuned in the range from 9.47 to 38.61 at%. When used as a catalyst, the c-Pd-Ni-P@a-Pd-Ni-P nanoplates with 9.47 at% Ni exhibit excellent electrocatalytic activity toward ethanol oxidation, showing a high mass current density up to 3.05 A mgPd -1 , which is 4.5 times that of the commercial Pd/C catalyst (0.68 A mgPd -1 ).

Selective Epitaxial Growth of Oriented Hierarchical Metal-Organic Framework Heterostructures.

Metal-organic framework (MOF) heterostructures have shown promising applications in gas adsorption, gas separation, catalysis, and energy, arising from the synergistic effect of each component. However, owing to the difficulty in controlling the size, shape, nucleation, and growth of MOFs, it remains a great challenge to construct MOF heterostructures with precisely controlled orientation, morphology, dimensionality, and spatial distribution of each component. Here, we report a seeded epitaxial growth method to prepare a series of hierarchical MOF heterostructures by engineering the structures, sizes, dimensionalities, morphologies, and lattice parameters of both MOF seeds and the secondary MOFs. In these heterostructures, PCN-222 (also known as MOF-545) nanorods selectively grow along the major axis of the ellipsoid-like PCN-608 nanoparticles, on the two end facets of the hexagonal prism-like NU-1000 nanorods, and on the two basal planes of the hexagonal PCN-134 nanoplates, while Zr-BTB nanosheets selectively grow on the six edge facets of PCN-134 nanoplates. The selective epitaxial growth of MOFs opens the way to synthesize different hierarchical heterostructures with tunable architectures and dimensionalities, which could process various promising applications.

Ag@MoS2 Core-Shell Heterostructure as SERS Platform to Reveal the Hydrogen Evolution Active Sites of Single-Layer MoS2.

Understanding the reaction mechanism for the catalytic process is essential to the rational design and synthesis of highly efficient catalysts. MoS2 has been reported to be an efficient catalyst toward the electrochemical hydrogen evolution reaction (HER), but it still lacks direct experimental evidence to reveal the mechanism for MoS2-catalyzed electrochemical HER process at the atomic level. In this work, we develop a wet-chemical synthetic method to prepare the single-layer MoS2-coated polyhedral Ag core-shell heterostructure (Ag@MoS2) with tunable sizes as efficient catalysts for the electrochemical HER. The Ag@MoS2 core-shell heterostructures are used as ideal platforms for the real-time surface-enhanced Raman spectroscopy (SERS) study owing to the strong electromagnetic field generated in the plasmonic Ag core. The in situ SERS results provide solid Raman spectroscopic evidence proving the S-H bonding formation on the MoS2 surface during the HER process, suggesting that the S atom of MoS2 is the catalytic active site for the electrochemical HER. It paves the way on the design and synthesis of heterostructures for exploring their catalytic mechanism at atomic level based on the in situ SERS measurement.

Identification of molecular mechanism underlying therapeutic effect of tanshinone IIA in the treatment of hypoxic vestibular vertigo via the NO/cGMP/BKCa signaling pathway.

This study aimed to investigate the molecular mechanisms underlying the effect of Tashinone IIA (Tan) on the treatment of ischemic vertigo. Sprague-Dawley (SD) male rats were divided into a SHAM group, a MODEL group, a MODEL+PBS group, a MODEL+Tan (10 mg/kg) group, a MODEL+Tan (20 mg/kg) group, a MODEL+Tan (40 mg/kg) group and a MODEL+Tan (80 mg/kg) group. The escape latency was observed among different groups of rats, while the production of NO/cGMP and the expression of BKCa were measured in vivo and in vitro by H&E staining, Western Blot and IHC assays. While the rats with ischemic vertigo showed prolonged escape latency, the treatment by Tan (40 mg/kg and up) shortened the escape latency in rats with ischemic vertigo. Moreover, the reduced production of NO/cGMP and expression of BKCa protein in the MODEL group were increased by a certain extent upon the treatment of 40 mg/kg or 80 mg/kg Tan. H&E staining of MVN neuron cells collected from different rat groups also validated the positive effects of Tan on the repair of damaged MVN neuron cells. Moreover, the above results were also validated in vitro, as the cells treated with 5 ug/ml and 10 ug/ml Tan increased the levels of NO/cGMP production and BKCa protein expression. At a certain dose, Tan could increase the production of NO and cGMP as well as the expression of BKCa, which would subsequently aid the treatment of ischemic vertigo.

Publisher Correction: Unusual 4H-phase twinned noble metal nanokites.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.