Interim Layer Research Articles

Photocarrier relay modulating solar CO2-to-Syngas conversion

Solar-driven syngas generation by CO2 reduction provides a sustainable strategy to produce renewable fossil fuels. Nevertheless, this promising approach often suffers from tough CO2 activation, sluggish reaction kinetics and complex selectivity. Herein, we exquisitely constructed spatially directional charge transport channel over two-dimensional transition metal chalcogenide (TMC)-based heterostructure via a facile and universal electrostatic self-assembly method. Tailor-made positively charged non-conjugated insulating polymer of poly(diallyl-dimethyl-ammonium chloride) (PDDA) and negatively charged graphene oxide (GO) precursor as building blocks are controllably anchored on the TMC substrate, by which ultrathin PDDA layer is intercalated at the interface of GO and TMC. We ascertain that, in this customized sandwiched heterostructures, PDDA interim layer functions as an electron-relaying mediator, whilst graphene (GR) obtained from in-situ GO reduction during the photocatalytic reaction serves as a terminal electron-trapping reservoir, synergistically facilitating the spatially vectorial charge separation/migration over TMC, thus endowing the TMC/PDDA/GR heterostructures with conspicuously enhanced visible-light-driven photoactivity toward CO2-to-syngas conversion. Our work would inspire judicious ideas for finely modulating charge transfer over polymer-mediated photosystems and benefit our fundamental understanding of solar CO2 conversion.

Photocarrier tunneling triggering CO2 photocatalysis.

Solar CO2 reduction to renewable hydrocarbon fuels offers a promising pathway to carbon neutrality, but it is retarded by tough CO2 activation, complicated mechanisms, sluggish charge transport kinetics, and a scarcity of strategies for precise tuning of charge transport pathways. Herein, we first conceptually design a novel insulating polymer-mediated electron-tunneling artificial photosystem via progressive interface configuration regulation, wherein tailor-made Ag@citrate nanocrystals (NCs) are controllably self-assembled on transition metal chalcogenides (TMCs) assisted by an ultrathin insulating polymer interim layer, i.e., poly(allylamine hydrochloride) (PAH). In this multilayered nano-architecture, a solid ultra-thin insulating PAH interim layer serves as an unexpected charge tunneling mediator to stimulate smooth electron transfer from the TMC substrate to the terminal electron reservoirs of Ag@citrate NCs, engendering the tandem charge transfer route and significantly boosting the visible-light-driven photocatalytic CO2-to-syngas conversion performances. Furthermore, we have ascertained that such TMC-insulating polymer-metal NC tunneling photosystems are universal. This study would spark new inspiration for unleashing the long-term neglected charge tunneling capability of insulating polymers and diversifying non-conjugated polymer-based artificial photosystems for solar-to-fuel energy conversion.

Solar CO2 Reduction Enabled by Cascade Hole Migration.

Solar-powered photocatalytic conversion of CO2 to hydrocarbon fuels represents an emerging approach to solving the greenhouse effect. However, low charge separation efficiency, deficiency of surface catalytic active sites, and sluggish charge-transfer kinetics, together with the complicated reaction pathway, concurrently hinder the CO2 reduction. Herein, we show the rational construction of transition metal chalcogenides (TMCs) heterostructure CO2 reduction photosystems, wherein the TMC substrate is tightly integrated with amorphous oxygen-containing cobalt sulfide (CoSOH) by a solid non-conjugated polymer, i.e., poly(vinyl alcohol) (PVA), to customize the unidirectional charge-transfer pathway. In this well-defined multilayered nanoarchitecture, the PVA interim layer intercalated between TMCs and CoSOH acts as a hole-relaying mediator and meanwhile boosts CO2 adsorption capacity, while CoSOH functions as a terminal hole-collecting reservoir, stimulating the charge transport kinetics and boosting the charge separation over TMCs. This peculiar interface configuration and charge transport characteristics endow TMC/PVA/CoSOH heterostructures with significantly enhanced visible-light-driven photoactivity and CO2 conversion. Based on the intermediates probed during the photocatalytic CO2 reduction reaction, the photocatalytic mechanism was determined. Our work would inspire sparkling ideas to mediate the charge transfer over semiconductor for solar carbon neutral conversion.

Electron Tunneling Fosters Solar-to-Hydrogen Energy Conversion.

Transition-metal chalcogenide quantum dots (TMCs QDs) exhibit emerging potential in the field of solar energy conversion due to large absorption coefficients for light harvesting, quantum size effect, and abundant active sites. However, fine-tuning the photoinduced charge carrier over TMCs QDs to manipulate the directional charge-transfer pathway remains challenging, considering their ultrashort charge lifetime and slow charge-transfer kinetics. To this end, herein, MoSx/PDDA/TMCs QDs heterostructures were exquisitely designed by a simple and green electrostatic self-assembly strategy under ambient conditions, wherein tailor-made negatively charged TMCs QDs stabilized by mercaptoacetic acid (MAA) were precisely self-assembled on the positively charged polydiallyl dimethylammonium chloride (PDDA)-modified MoSx nanoflowers (NFs), forming a well-defined three-dimensional heterostructured nanoarchitecture. As an electron trapping agent, an MoSx NFs cocatalyst benefits the unidirectional electron transfer from TMCs QDs to the ideal active centers on the MoSx NFs surface by tunneling the ultrathin insulating polymer interim layer, thereby boosting the charge separation efficiency and endowing self-assembled MoSx/PDDA/TMCs QDs heterostructures with considerably increased photocatalytic hydrogen evolution activity (1.96 mmol·g-1·h-1) and admirable stability under visible light irradiation. Our work will provide new insights into smart regulation of directional charge transfer over TMCs QDs-based photosystems for solar energy conversion.

Robust and Stable Atomically Precise Metal Nanoclusters Mediated Solar Water Splitting.

Atomically precise metal nanoclusters (NCs) represent an emerging sector of light-harvesting antennas by virtue of peculiar atomic stacking fashion, quantum confinement effect, and molecular-like discrete energy band structure. Nevertheless, precise control of charge carriers over metal NCs has yet to be achieved by the short carrier lifetime and intrinsic instability of metal NCs, which renders the complexity of metal NCs-based photosystems with photoredox mechanisms remaining elusive. Herein, fine tuning of charge migration over metal NCs is demonstrated by constructing directional charge transfer channels in multilayered heterostructure enabled by a facile layer-by-layer (LbL) assembly approach, wherein oppositely charged branched poly-ethylenimine (BPEI) and glutathione (GSH)-capped gold NCs [Aux NCs, Au25 (GSH)18 NCs] are alternately deposited on the metal oxide (MOs: TiO2 , WO3 , Fe2 O3 ) substrates. TheAux (Au25 ) NCs layer serves as light-harvesting antennas for engendering charge carriers, andBPEI interim layer uniformly intercalated at the interface of Aux NCs layer constitutes the tandem hole transport channel for motivating the charge transfer cascade, resulting in the considerably enhanced photoelectrochemical water oxidation performances. Besides, poor photo-stability of Aux NCs is surmounted by stimulating the hole transfer kinetics process.

Ag nanoparticles interlayered Fe3O4/Ag/m(TiO2-ZrO2) magnetic photocatalysts with enhanced stability and photocatalytic performance for Cr(Ⅵ) reduction

A sandwich structured Fe3O4/Ag/m(TiO2-ZrO2) magnetic nanosphere with Ag nanoparticles as an interim layer was fabricated with in situ deposition of Ag nanoparticles onto Fe3O4 nanospheres and subsequent coating an outmost shell of mesoporous TiO2-ZrO2. As compared to Fe3O4/m(TiO2-ZrO2)/Ag with Ag nanoparticles as the outmost layer, unique Fe3O4/Ag/m(TiO2-ZrO2) sandwich nanospheres possess higher efficient charge migration and larger specific surface area disclosed by the BET and photoelectrochemical characterizations, so they present improved photocatalytic activity toward Cr(VI) reduction. In addition, they have high thermal stability because mesoporous TiO2-ZrO2 outmost shell could protect the interim Ag nanoparticles from damage and agglomeration at high temperature. Results showed reduction efficiency of Cr(VI) of Fe3O4/Ag/m(TiO2-ZrO2) reached 98.4 % in 30 min, as 1.6 times as that of Fe3O4/m(TiO2-ZrO2)/Ag. The Fe3O4/Ag/m(TiO2-ZrO2) still obtained 91.3 % and 87.9 % reduction ratio after calcination at 500 ℃ and recycling 5 times, respectively. The photocatalytic mechanism was also revealed by scavenger experiments and ERP analysis. This work provided a good example for further design and preparation of magnetic photocatalysts with high performance for the remediation of heavy metal pollutants.

Unleashing non-conjugated polymers as charge relay mediators.

The core factors affecting the efficiency of photocatalysis are predominantly centered on controllable modulation of anisotropic spatial charge separation/transfer and regulating vectorial charge transport pathways in photoredox catalysis, yet it still meets with limited success. Herein, we first conceptually demonstrate the rational design of unidirectional cascade charge transfer channels over transition metal chalcogenide nanosheets (TMC NSs: ZnIn2S4, CdS, CdIn2S4, and In2S3), which is synergistically enabled by a solid-state non-conjugated polymer, i.e., poly(diallyldimethyl ammonium chloride) (PDDA), and MXene quantum dots (MQDs). In such elaborately designed photosystems, an ultrathin PDDA layer functions as an intermediate charge transport mediator to relay the directional electron transfer from TMC NSs to MQDs that serve as the ultimate electron traps, resulting in a considerably boosted charge separation/migration efficiency. The suitable energy level alignment between TMC NSs and MQDs, concurrent electron-withdrawing capabilities of the ultrathin PDDA interim layer and MQDs, and the charge transport cascade endow the self-assembled TMC/PDDA/MQD heterostructured photosystems with conspicuously improved photoactivities toward anaerobic selective reduction of nitroaromatics to amino derivatives and photocatalytic hydrogen evolution under visible light irradiation. Furthermore, we ascertain that this concept of constructing a charge transfer cascade in such TMC-insulating polymer-MQD photosystems is universal. Our work would afford novel insights into smart design of spatial vectorial charge transport pathways by precise interface modulation via non-conjugated polymers for solar energy conversion.

Polymer‐Mediated Electron Tunneling Towards Solar Water Oxidation

AbstractExploiting emerging artificial photosystems with regulated vectorial charge transfer pathways is retarded by the difficulties in precise interface modulation at the nanoscale level, deficiency of suitable assembly methodologies, and ultra‐short charge lifetime. Herein, it is first conceptually demonstrated the general design of transition metal chalcogenides quantum dots (TMCs QDs)‐insulating polymer‐metal oxides (MOs) electron‐tunneling photosystems, wherein TMCs QDs are controllably layer‐by‐layer self‐assembled on the MOs substrates assisted by an ultrathin insulating polymer interim layer. It is ascertained that electrons photoexcited over TMCs QDs in spatially highly ordered MOs/(TMCs QDs/polymer)n multilayered heterostructures can be unidirectionally extracted and tunneled to the MOs substrates across the intermediate insulating polymer layer by engendering the tandem charge transfer to accelerate the interfacial charge migration kinetics, thereby triggering the significantly boosted net efficiency of solar‐driven photoelectrochemical water oxidation. This study would spark new inspirations for designing novel electron‐tunneling photosystems for fine carrier modulation towards solar energy harvesting and conversion.

Intercalating ultrathin polymer interim layer for charge transfer cascade towards solar-powered selective organic transformation

Transition metal chalcogenide quantum dots (TMCs QDs) constitute a crucial sector of semiconductors on account of large absorption coefficient for light harvesting, peculiar quantum confinement effect, and abundant active sites stemming from ultra-small size. However, elaborate and tunable modulation of anisotropic photoinduced charge carriers over TMCs QDs represents an enduring challenge in terms of sluggish charge transfer kinetic and ultra-short charge lifetime compared with nanoparticulate counterparts, thereby rendering maneuvering charge transfer of TMCs QDs a tough issue. We herein conceptually unlock the unanticipated charge transport capability of solid-state non-conductive poly(diallyl dimethylammonium chloride) (PDDA) for constructing cascade charge transfer pathway over self-assembled wide bandgap semiconductors (WBS)/PDDA/TMCs QDs multilayered heterostructures, by which unidirectional and accelerated electron transfer from TMCs QDs to WBS support mediums was spontaneously activated, markedly boosting the charge separation/migration efficiency. The integrated roles of such ultrathin insulating PDDA intermediate layer as simultaneous surface charge modifying agent and interfacial charge transfer mediator have been evidenced to be universal. The unexpected electron-withdrawing capability of ultrathin PDDA layer endows WBS (SnO2, TiO2)@PDDA@TMCs (CdSe, CdS) QDs heterostructures with significantly enhanced net efficiency of photoactivities toward selective anaerobic reduction of nitroaromatics to amino derivatives under visible light irradiation. Our work would feature a promising scope for rational design of multifarious novel insulating polymers-based photosystems for solar energy conversion.

Partially Self-Transformed Transition-Metal Chalcogenide Interim Layer: Motivating Charge Transport Cascade for Solar Hydrogen Evolution.

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.

Analysis of the Stiffness Ratio at the Interim Layer of Frame-Supported Multi-Ribbed Lightweight Walls under Low-Reversed Cyclic Loading

By conducting low-reversed cyclic loading tests, this paper explores the load-bearing performance of frame-supported multi-ribbed lightweight wall structures. The finite-element software (OpenSees) is used to simulate the process with the shear wall width (at the frame-supported layer) and different hole opening approaches (for multi-ribbed lightweight walls) as variables. The conclusions reflect the influence of the stiffness ratio at the interim layer on the load-bearing performance of the structure. On this basis, the paper identifies the preferable numerical range for engineering design, which provides a solid foundation for the theoretical advancement of the structures in this study.

Fabrication & Microstructure of TiB<sub>2</sub>+TiC Duplex Particulates Reinforced Carbon Steel Matrix Surface Composite

This paper presents a novel fabrication process that combines SHS with V-EPC (vacuum expandable pattern casting) and microstructural features of TiB2+TiC duplex particulates reinforced surface composite with carbon steel matrix. Macro structural observation shows that the surface composite is dense and there are no obvious defects. Microstructural investigation demonstrates that the composite from surface to core is consisted of three different layers, i.e., the top surface compound layer, the interim transitional layer and the bottom carbon steel matrix. A large amount of fine TiB2 and TiC duplex particles are evenly distributed in the composite matrix, while the concentration are significantly decreased and non-uniform distribution increased for these particles in the interim layer.

Achieve high-quality GaN films on La0.3Sr1.7AlTaO6 (LSAT) substrates by low-temperature molecular beam epitaxy

The growth of c-plane GaN films on La0.3Sr1.7AlTaO6 (LSAT) (111) substrates has been carried out by molecular beam epitaxy (MBE) at various substrate temperatures. GaN grown at 750 °C shows poor crystallinity with an up to 8 nm thick interim layer between LSAT and GaN, mainly due to the severe interfacial reaction between the substrate and the film. On the contrary, an atomically abrupt interface has been observed when GaN was grown at a lower temperature of 500 °C. This low-temperature grown GaN exhibits high crystallinity with a very smooth surface and strong band-edge emission, which we attribute to the well-controlled oxygen atom evaporation from LSAT substrate surface thanks to the low temperature growth. On the one hand, it avoids the severe interfacial reaction that takes place in the case of high-temperature epitaxial growth; on the other hand, it conserves the crystalline structure of the substrate surface, and consequently takes good advantage of the small lattice mismatch between GaN and LSAT. Considering the advantages of LSAT over sapphire, and the device-ready film quality of GaN achieved on LSAT, this work exhibits a promising future for high-performance light emitting diodes on this unconventional substrate.

Ti4+‐Immobilized Magnetic Composite Microspheres for Highly Selective Enrichment of Phosphopeptides

AbstractArchitectural design is essential to achieve ideal chemical and biological properties of nanomaterials. In this article, a novel route to fabricate high‐quality magnetic composite microspheres composed of a high‐magnetic‐response magnetic colloid nanocrystal cluster (MCNC) core, a poly(methylacrylic acid) (PMAA) interim layer, and a Ti4+‐immobilized poly(ethylene glycol methacrylate phosphate) (PEGMP) shell via two‐step distillation–precipitation polymerization is presented. The unique as‐synthesized MCNC@PMAA@PEGMP‐Ti4+ composite microsphere is investigated for its applicability for selective enrichment of phosphopeptides from complex biological samples. The experiment results demonstrate that, by taking advantage of the pure phosphate–Ti4+ interface and high Ti4+ loading amount, the MCNC@PMAA@PEGMP‐Ti4+ composite microsphere possesses remarkable selectivity for phosphopeptides even at a very low molar ratio of phosphopeptides/nonphosphopeptides (1:500). The extreme sensitivity, excellent recovery of phosphopeptides, and high magnetic susceptibility are also proven. These outstanding features demonstrate that the MCNC@PMAA@PEGMP‐Ti4+ composite microspheres have great benefit for the pretreatment before mass spectrometric analysis of phosphopeptides. Furthermore, the performance of the approach in selective enrichment of phosphopeptides from drinking milk and human serum gives powerful evidence for its high selectivity and effectiveness in identifying the low‐abundant phosphopeptides from complicated biological samples.

Ligand-free strategy for ultrafast and highly selective enrichment of glycopeptides using Ag-coated magnetic nanoarchitectures

Selective enrichment of glycopeptides from complicated biological samples is essential for MS-based glycoproteomics, but still remains a great challenge. In this study, we report an unprecedented ligand-free strategy for the selective enrichment of glycopeptides by simply utilizing the multivalent interaction between glycopeptides and silver nanoparticles (Ag-NPs) coated magnetic nanoarchitectures. The composite microspheres were deliberately designed to be constructed with a high-magnetic-response magnetic colloid nanocrystal cluster (MCNC) core, a poly(methacrylic acid) (PMAA) interim layer and a Ag-NPs functional shell with high coverage. Taking advantage of the reversible interaction of glycans with Ag-NPs and the high magnetic susceptibility of the magnetite core, the MCNC@PMAA@Ag-NPs microspheres possess remarkable selectivity for glycopeptides even at a low molar ratio of glycopeptides/non-glycopeptides (1:100) with a very rapid enrichment speed (only 1 min needed) and a simple operation procedure using magnetic separation. Applying this approach, we identified 127 unique glycopeptides mapped to 51 different glycoproteins from only 1 μL rat serum samples. These results clearly demonstrated that the MCNC@PMAA@Ag-NPs have great potential for purifying and identifying the low-abundant glycopeptides in complex biological samples.

New Reactive Compatibilizer B Preparation and its Application in Polystyrene Ether/Nylon 66 Alloy

A new type compatibilizer-boric acid ester with carboxylic acid functional groups (refered as B) was synthesized and used in PPO/PA66 alloys. The PPO/PA66 alloys were produced by melting blending. The micromorphological and mechanical properties of PPO/PA66 blends with different contents of the compatibilizer were studied by transmission electron microscope (TEM), scanning electron microscope (SEM) and mechanical test. The effects of the compatibilizer B on the mechanical property and morphology of PPO/PA alloy were discussed. The results showed that, the compatibilizer B can also improve the mechanical property, besides showing good effect on the compatibility improvement for PPO/PA blends; it (B) acts as a compatibilizer for the blends by forming interim layer with dispersed phase PPO and continuous phase PA. The compatibilization of PPO and PA66 alloy was due to the chemical reaction between carboxyl group and amine group.

Synthesis of Au–CdS Core–Shell Hetero‐Nanorods with Efficient Exciton–Plasmon Interactions

AbstractThe synthesis of large lattice mismatch metal‐semiconductor core–shell hetero‐nanostructures remains challenging, and thus the corresponding optical properties are seldom discussed. Here, we report the gold‐nanorod‐seeded growth of Au–CdS core–shell hetero‐nanorods by employing Ag2S as an interim layer that favors CdS shell formation through a cation‐exchange process, and the subsequent CdS growth, which can form complete core–shell structures with controllable shell thickness. Exciton–plasmon interactions observed in the Au–CdS nanorods induce shell thickness‐tailored and red‐shifted longitudinal surface plasmon resonance and quenched CdS luminescence under ultraviolet light excitation. Furthermore, the Au–CdS nanorods demonstrate an enhanced and plasmon‐governed two‐photon luminescence under near‐infrared pulsed laser excitation. The approach has potential for the preparation of other metal‐semiconductor hetero‐nanomaterials with complete core–shell structures, and these Au–CdS nanorods may open up intriguing new possibilities at the interface of optics and electronics.

Reduced magnetic hyperfine field at the surface of α-Fe 2 O 3 and FeBO 3 single crystals

The surface magnetic ordering of an α-57Fe2O3 and 57FeBO3 single crystal was studied by Depth Selective Conversion Electron Mossbauer Spectroscopy (DCEMS). The depth selective Mossbauer data of 57FeBO3 up to the Neel temperature (T N = 348.35 K) reveal the coexistence of the canted antiferromagnetic bulk phase and a magnetic surface phase that shows time relaxation. Both phases are separated by a wall (interim layer) and the thickness of the magnetic surface layer increases as the crystal is heated to T N.

THE TRANSMISSION MECHANISM OF FIBER-OPTIC FACEPLATE (I)

An elementary fiber in fiber-optic faceplate serves as a channel for transferring the optical information. The propagation characteristics of an elementary fiber hasagreat effect on the transfer of the maximum information content. A physical model of an elementary fiber with the diffused type, a 3-layer structure fiber, is set up. The concept of the is introduced, and the eigenequation of guided-mode transmission and interim-layer mode transmission has also been deduced. The expressions of transmissive efficiency and crosstalk are defined. According to some low-order modes, in different cases of diffusion and structural design parameters, the transmissive efficiency is calculated. Results show that the existence of the diffused interim layer is the main factor that affects the efficient transmission in fiber and causes crosstalk.