Showing papers by "Dong Wang published in 2014"
TL;DR: By utilizing the synergistic effect of poly-dopamine (PD) with functional groups and graphene oxide (GO) with a high surface area, a series of sub-nano thick PD layer coated GO (PD/GO) composites were fabricated by a well-controlled self-polymerization of dopamine via catechol chemistry and used for effectively decontaminating wastewater.
Abstract: By utilizing the synergistic effect of poly-dopamine (PD) with functional groups and graphene oxide (GO) with a high surface area, a series of sub-nano thick PD layer coated GO (PD/GO) composites were fabricated by a well-controlled self-polymerization of dopamine via catechol chemistry and used for effectively decontaminating wastewater. The obtained PD/GO could selectively adsorb the dyes containing an Eschenmoser structure and showed an extremely high adsorption capacity up to 2.1 g g−1, which represents the highest value among dye adsorptions reported so far. The adsorption mechanism was investigated by FTIR analysis, solution pH effect, and some control experiments. It was concluded that the adsorption process was based on the Eschenmoser salt assisted 1,4-Michael addition reaction between the ortho position of the catechol phenolic hydroxyl group of PD and Eschenmoser groups in the dyes. The adsorption isotherms were explored according to the Langmuir and Freundlich models respectively, and matched well with the Langmuir model. The thermodynamic parameters (ΔH, ΔG, ΔS, and E) were also calculated, which suggested an exothermic and spontaneous adsorption process. In addition, PD/GO exhibited an improved adsorption capacity for heavy metal ions (53.6 mg g−1 for Pb2+, 24.4 mg g−1 for Cu2+, 33.3 mg g−1 for Cd2+, and 15.2 mg g−1 for Hg2+, respectively) than pure PD and GO. Our results indicate the effectiveness of the synergistic effect of individual components on designing new functional composites with high performance.
229 citations
TL;DR: The recent development of the bottom-up synthesis methods of 2D sCOFs, such as thermodynamic equilibrium control methods, growth-kinetics control Methods, and surface-assisted covalent polymerization methods, are reviewed.
Abstract: Two-dimensional (2D) nanomaterials, such as graphene and transition metal chalcogenides, show many interesting dimension-related materials properties. Inspired by the development of 2D inorganic nanomaterials, single-layered covalent organic frameworks (sCOFs), featuring atom-thick sheets and crystalline extended organic structures with covalently bonded building blocks, have attracted great attention in recent years. With their unique graphene-like topological structure and the merit of structural diversity, sCOFs promise to possess novel and designable properties. However, the synthesis of sCOFs with well-defined structures remains a great challenge. Herein, the recent development of the bottom-up synthesis methods of 2D sCOFs, such as thermodynamic equilibrium control methods, growth-kinetics control methods, and surface-assisted covalent polymerization methods, are reviewed. Finally, some of the critical properties and application prospects of these materials are outlined.
192 citations
TL;DR: In this review, the recent progress in fabricating bioinspired materials with the emphasis on mimicking the structure from one to three dimensions is summarized with a focus on the relationship between the structural characters and the corresponding functions.
Abstract: The surprising properties of biomaterials are the results of billions of years of evolution. Generally, biomaterials are assembled under mild conditions with very limited supply of constituents available for living organism, and their amazing properties largely result from the sophisticated hierarchical structures. Following the biomimetic principles to prepare manmade materials has drawn great research interests in materials science and engineering. In this review, we summarize the recent progress in fabricating bioinspired materials with the emphasis on mimicking the structure from one to three dimensions. Selected examples are described with a focus on the relationship between the structural characters and the corresponding functions. For one-dimensional materials, spider fibers, polar bear hair, multichannel plant roots and so on have been involved. Natural structure color and color shifting surfaces, and the antifouling, antireflective coatings of biomaterials are chosen as the typical examples of the two-dimensional biomimicking. The outstanding protection performance, and the stimuli responsive and self-healing functions of biomaterials based on the sophisticated hierarchical bulk structures are the emphases of the three-dimensional mimicking. Finally, a summary and outlook are given.
185 citations
TL;DR: In this paper, a new sequential-vapourdeposition method is demonstrated for the growth of high quality CH3NH3PbI3 perovskite films.
Abstract: A new sequential-vapour-deposition method is demonstrated for the growth of high-quality CH3NH3PbI3 perovskite films. This has enabled the all-vapour, low-temperature fabrication of hole-conductor-free planar perovskite solar cells consisting of only a CH3NH3PbI3/C60 bi-layer sandwiched between two electrical contacts, with a power conversion efficiency of 5.4%.
127 citations
TL;DR: It is reported that importin 8 (IPO8), a member of the karyopherin β (also named the protein import receptor importin β) family, plays a critical role in mediating the cytoplasm-to-nucleus transport of mature miRNAs.
115 citations
TL;DR: In this paper, a new type of intrinsic microporosity copolymer derived from 2,3,8,9-tetrahydroxy-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine (THTB) and 5,5′, 6,6,6)-tetramethylspirobisindane (TTSBI) copolymers were synthesized and their properties for CO2 separation were investigated.
99 citations
TL;DR: An in situ single nanowire atomic force microscopy (AFM) method is used to investigate the interface electrochemistry of silicon nanowires (SiNW) electrode and a mixture-packing structural model was proposed for the SEI film on SiNW anode.
Abstract: Silicon nanowires (SiNWs) have attracted great attention as promising anode materials for lithium ion batteries (LIBs) on account of their high capacity and improved cyclability compared with bulk silicon. The interface behavior, especially the solid electrolyte interphase (SEI), plays a significant role in the performance and stability of the electrodes. We report herein an in situ single nanowire atomic force microscopy (AFM) method to investigate the interface electrochemistry of silicon nanowire (SiNW) electrode. The morphology and Young’s modulus of the individual SiNW anode surface during the SEI growth were quantitatively tracked. Three distinct stages of the SEI formation on the SiNW anode were observed. On the basis of the potential-dependent morphology and Young’s modulus evolution of SEI, a mixture-packing structural model was proposed for the SEI film on SiNW anode.
98 citations
TL;DR: This work presents a type of polymer-free anisotropic lamellar hydrogels composed of 100-nm-thick water layers sandwiched by two bilayer membranes of a self-assembled nonionic surfactant, hexadecylglyceryl maleate, and detects the optical and electrical properties on a single gold membrane.
Abstract: Hydrogels are generally thought to be formed by nano- to micrometre-scale fibres or polymer chains, either physically branched or entangled with each other to trap water. Although there are also anisotropic hydrogels with apparently ordered structures, they are essentially polymer fibre/discrete polymer chains-based network without exception. Here we present a type of polymer-free anisotropic lamellar hydrogels composed of 100-nm-thick water layers sandwiched by two bilayer membranes of a self-assembled nonionic surfactant, hexadecylglyceryl maleate. The hydrogels appear iridescent as a result of Bragg's reflection of visible light from the periodic lamellar plane. The particular lamellar hydrogel with extremely wide water spacing was used as a soft two-dimensional template to synthesize single-crystalline nanosheets in the confined two-dimensional space. As a consequence, flexible, ultrathin and large area single-crystalline gold membranes with atomically flat surface were produced in the hydrogel. The optical and electrical properties were detected on a single gold membrane.
93 citations
TL;DR: In this paper, the authors demonstrate that an innovative approach by applying mixed lead salts (PbI2 + PbCl2) to facilitate reproducible fabrication of compact perovskite thin film.
Abstract: Methylammonium lead trihalide perovskites are attracting intensive interest due to its high photovoltaic performance, low cost and one-step solution processability. Since the morphology of the perovskite thin films play the central role on the cell performance, a plethora of methods have been developed to fabricate uniform perovskite film. Herein, we demonstrate that an innovative approach by applying mixed lead salts (PbI2 + PbCl2) to facilitate reproducible fabrication of compact perovskite thin film. It is proposed that rapid reaction kinetics of PbI2 with MAI enables preformation of perovskite within the intermidiate film matrix, working as homogeneously located domains for squential growth of the PbCl2-derived perovskite. The as-prepared perovskite film exhibited a overall textured crystal morphology and superior compactness, which enables excellent light absorption and long-time preservation of photogenerated charge carriers and therefore exhibits 11% efficiency in planar-structured solar cells. The annealing testing shows the film also possesses very stable morphology upon long-time heating, indicative of the insensitivity of our new protocol to the preparation condition and also the promising thermal stability of its based solar cells. The simplicity of the one-step solution-processing and the high morphology stability of the as-prepared perovskite film endow this mixing lead salts method with feasibility of the large-scale fabrication.
77 citations
TL;DR: This study highlights the important roles of monomer structure and reaction temperature in the design and synthesis of covalent bond connected functional nanoporous networks and shows how surface diffusion of monomers and the molecule-substrate interaction is tunable by reaction temperature.
Abstract: With graphene-like topology and designable functional moieties, single-layered covalent organic frameworks (sCOFs) have attracted enormous interest for both fundamental research and application prospects. As the growth of sCOFs involves the assembly and reaction of precursors in a spatial defined manner, it is of great importance to understand the kinetics of sCOFs formation. Although several large families of sCOFs and bulk COF materials based on different coupling reactions have been reported, the synthesis of isomeric sCOFs by exchanging the coupling reaction moieties on precursors has been barely explored. Herein, a series of isomeric sCOFs based on Schiff-base reaction is designed to understand the effect of monomer structure on the growth kinetics of sCOFs. The distinctly different local packing motifs in the mixed assemblies for the two isomeric routes closely resemble to those in the assemblies of monomers, which affect the structural evolution process for highly ordered imine-linked sCOFs. In addition, surface diffusion of monomers and the molecule-substrate interaction, which is tunable by reaction temperature, also play an important role in structural evolutions. This study highlights the important roles of monomer structure and reaction temperature in the design and synthesis of covalent bond connected functional nanoporous networks.
53 citations
TL;DR: It is demonstrated that an electric field applied between an STM tip and a substrate triggered the formation of a bilayer structure at the solid-liquid interface that was transformed into a monolayer kagome structure by changing the polarity of the electric field.
Abstract: The construction of a spatially defined assembly of molecular building blocks, especially in the vertical direction, presents a great challenge for surface molecular engineering. Herein, we demonstrate that an electric field applied between an STM tip and a substrate triggered the formation of a bilayer structure at the solid–liquid interface. In contrast to the typical high electric-field strength (109 V m−1) used to induce structural transitions in supramolecular assemblies, a mild electric field (105 V m−1) triggered the formation of a bilayer structure of a polar molecule on top of a nanoporous network of trimesic acid on graphite. The bilayer structure was transformed into a monolayer kagome structure by changing the polarity of the electric field. This tailored formation and large-scale phase transformation of a molecular assembly in the perpendicular dimension by a mild electric field opens perspectives for the manipulation of surface molecular nanoarchitectures.
TL;DR: A facile protocol is developed for the direct observation and characterization of a single particle electrode during the lithium ion battery operation by using in situ AFM and the SEI formation on the LiNi0.5Mn1.5O4 particle cathode surface is found to be highly related to the exposed planes.
TL;DR: Evidence is provided indicating that Argonaute 2 (Ago2) plays a role in stabilizing miRNAs and facilitating the packaging of secreted mi RNAs into MVs, and Ago2 in origin cell-secreted MVs (but not in recipient cells) directs the function ofsecreted miRN as well as exogenous miR-16.
Abstract: MicroRNAs (miRNAs) secreted by cells into microvesicles (MVs) form a novel class of signal molecules that mediate intercellular communication. However, several fundamental aspects of secreted miRNAs remain unknown, particularly the mechanism that governs the function or fate of exogenous miRNAs in recipient cells. In the present study, we provide evidence indicating that Argonaute 2 (Ago2) plays a role in stabilizing miRNAs and facilitating the packaging of secreted miRNAs into MVs. More importantly, Ago2 in origin cell-secreted MVs (but not in recipient cells) directs the function of secreted miRNAs. First, Ago2 overexpression clearly increased the level of miR-16 in cells transfected with a miR-16 mimic by protecting the miRNAs from degradation in lysosomes. Second, Ago2 overexpression increased the level of miR-16 in cell-secreted MVs, suggesting that Ago2 may facilitate the packaging of secreted miRNAs into MVs. Third, exogenous miR-16 delivered by MVs within the origin cells significantly reduced the Bcl2 protein level in recipient cells, and miR-16 and Bcl2 mRNA were physically associated with exogenous HA-tagged Ago2 (HA-Ago2). Finally, the effect of MV-delivered miR-16 on the production of the Bcl2 protein in recipient cells was not abolished by knocking down Ago2 in the recipient cells.
TL;DR: A novel uniform amorphous carbon-coated SnO2 nanocrystal (NCs) for use in lithium-ion batteries is formed by utilizing bovine serum albumin as both the ligand and carbon source and two stable interfaces built between the active material and the buffer layer and the binder provide a stable matrix for active materials.
Abstract: A novel uniform amorphous carbon-coated SnO2 nanocrystal (NCs) for use in lithium-ion batteries is formed by utilizing bovine serum albumin (BSA) as both the ligand and carbon source. The SnO2 -carbon composite is then coated by a controlled thickness of polydopamine (PD) layer through in situ polymerization of dopamine. The PD-coated SnO2 -carbon composite is finally mixed with polyacrylic acid (PAA) which is used as binder to accomplish a whole anode system. A crosslink reaction is built between PAA and PD through formation of amide bonds to produce a robust network in the anode system. As a result, the designed electrode exhibits improved reversible capacity of 648 mAh/g at a current density of 100 mA/g after 100 cycles, and an enhanced rate performance of 875, 745, 639, and 523 mAh/g at current densities of 50, 100, 250, and 500 mA/g, respectively. FTIR spectra confirm the formation of crosslink reaction and the stability of the robust network during long-term cycling. The great improvement of capacity and rate performance achieved in this anode system is attributed to two stable interfaces built between the active material (SnO2 -carbon composite) and the buffer layer (PD) and between the buffer layer and the binder (PAA), which effectively diminish the volume change of SnO2 during charge/discharge process and provide a stable matrix for active materials.
TL;DR: The formation of a distinct patterned superlattice of guest molecules is reported by selective trapping of guest molecule into the honeycomb network of trimesic acid (TMA).
Abstract: The ordered array of nanovoids in nanoporous networks, such as honeycomb, Kagome, and square, provides a molecular template for the accommodation of “guest molecules”. Compared with the commonly studied guest molecules featuring high symmetry evenly incorporated into the template, guest molecules featuring lower symmetry are rare to report. Herein, we report the formation of a distinct patterned superlattice of guest molecules by selective trapping of guest molecules into the honeycomb network of trimesic acid (TMA). Two distinct surface patterns have been achieved by the guest inclusion induced adaptive reconstruction of a 2D molecular nanoporous network. The honeycomb networks can synergetically tune the arrangement upon inclusion of the guest molecules with different core size but similar peripherals groups, resulting in a trihexagonal Kagome or triangular patterns.
TL;DR: A three-step growth method for high-quality mono-layer, bi-layer and tri-layer graphene with coverage ~90% at atmospheric pressure is reported, of great importance for the large scale production of graphene with defined thickness.
TL;DR: Theoretical simulation indicates that the electrode potential-activated, one-electron transfer from Fe(C60Me5)Cp to the electrode leads to the change of the delocalization character of the frontier orbital in the molecule, which is responsible for the STM image contrast change, beneficial for understanding the structure and property of single electron donor-acceptor dyads.
Abstract: The electron donor–acceptor dyads are an emerging class of materials showing important applications in nonlinear optics, dye-sensitized solar cells, and molecular electronics. Investigation of their structure and electron transfer at the molecular level provides insights into the structure–property relationship and can benefit the design and preparation of electron donor–acceptor dyad materials. Herein, the interface adstructure and electron transfer of buckyferrocene Fe(C60Me5)Cp, a typical electron donor–acceptor dyad, is directly probed using in situ electrochemical scanning tunneling microscopy (STM) combined with theoretical simulations. It is found that the adsorption geometry and assembled structure of Fe(C60Me5)Cp is significantly affected by the electrochemical environments. In 0.1 M HClO4 solution, Fe(C60Me5)Cp forms well-ordered monolayers and multilayers on Au(111) surfaces with molecular dimer as the building block. In 0.1 M NaClO4 solution, typical six-fold symmetric close-packed monolayer w...
TL;DR: The properties of miRNA-based biomarkers suggest they could be used as novel, minimally invasive and stable DILI biomarkers, and the main advantages and challenges of miRNAs as novel DILi biomarkers are discussed.
Abstract: Drug-induced liver injury (DILI) is a leading cause of acute liver failure, and a major reason for the recall of marketed drugs. Detection of potential liver injury is a challenge for clinical management and preclinical drug safety studies, as well as a great obstacle to the development of new, effective and safe drugs. Currently, serum levels of alanine and aspartate aminotransferases are the gold standard for evaluating liver injury. However, these levels are assessed by nonspecific, insensitive, and non-predictive tests, and often result in false-positive results. Therefore, there is an urgent need for better DILI biomarkers to guide risk assessment and patient management. The discovery of microRNAs (miRNAs) as a new class of gene expression regulators has triggered an explosion of research, particularly on the measurement of miRNAs in various body fluids as biomarkers for many human diseases. The properties of miRNA-based biomarkers, such as tissue specificity and high stability and sensitivity, suggest they could be used as novel, minimally invasive and stable DILI biomarkers. In the current review, we summarize recent progress concerning the role of miRNAs in diagnosing and monitoring both clinical and preclinical DILI, and discuss the main advantages and challenges of miRNAs as novel DILI biomarkers.
TL;DR: An efficient cooperative biscinchona alkaloid and Lewis acid catalytic system was developed in the enantioselective α-alkylation of 2-oxindoles with (3-indolyl)(phenyl)methanols to provide (2- oxindole)-linker-indole derivatives in good yields and with high enantiOSElectivities.
Abstract: An efficient cooperative biscinchona alkaloid and Lewis acid catalytic system was developed in the enantioselective α-alkylation of 2-oxindoles with (3-indolyl)(phenyl)methanols to provide (2-oxindole)-linker-indole derivatives in good yields (70–83%) with high enantioselectivities (81%–92%).
TL;DR: The present work provides a feasible way to fabricate hybrid multilayers on the electrode surface via electrostatic interaction, which has great significance for the design of molecular nanodevices.
Abstract: Hybrid bilayers consisting of 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) and meso-tetra(4-pyridyl)porphine (TPyP) have been successfully constructed on Au(111) and investigated by electrochemical scanning tunneling microscopy (ECSTM). Under the guidance of the electrostatic interaction between negatively charged sulfonate groups and positively charged pyridyl groups, the underlying HPTS arrays act as templates for the deposition of cationic TPyPs, forming two types of TPyP/HPTS complex bilayers. The present work provides a feasible way to fabricate hybrid multilayers on the electrode surface via electrostatic interaction, which has great significance for the design of molecular nanodevices.
TL;DR: The bulk synthesis of free-standing polymeric nanosheets via spatially confined polymerization from an elaborate 2D supramolecular system composed of two liquid-crystalline lamellar bilayer membranes of a self-assembled nonionic surfactant--dodecylglyceryl itaconate (DGI)--sandwiched by a water layer is reported.
Abstract: Polymeric nanosheets organized by molecular building blocks bearing specifically oriented reactive groups provide abundant and versatile strategies for tailoring structure and chemical functionality periodically over extended length scales that complement graphene. Here we report the bulk synthesis of free-standing polymeric nanosheets via spatially confined polymerization from an elaborate 2D supramolecular system composed of two liquid-crystalline lamellar bilayer membranes of a self-assembled nonionic surfactant--dodecylglyceryl itaconate (DGI)--sandwiched by a water layer. By employing a covalent polymerization on the lamellar bilayer membranes, single-bilayer-thick (4.2 nm), and large area (greater than 100 μm(2)) polymeric nanosheets of bilayer membranes are achieved. The polymeric nanosheets could serve as a well-defined 2D platform for post-functionalization for producing advanced hybrid materials by introducing the reactions on the hydroxyl groups at the head of DGI on the outer surfaces.
TL;DR: In this paper, a facile way to fabricate robust free-standing BCP thin films with perpendicularly orientated microdomains on a CVD-grown monolayer graphene support is reported.
Abstract: A facile way to fabricate robust free-standing BCP thin films with perpendicularly orientated microdomains on a CVD-grown monolayer graphene support is reported. Graphene acts as both the neutral surface to control the assembly of the BCP film and the support of the thin film to provide high mechanical strength. The free-standing BCP films with the nanopattern can be used as a substrate-independent template to facilitate BCP nano-lithography.
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TL;DR: In this article, the dependences of high harmonic micro-bunching in the high gain harmonic generation (HGHG), echo-enabled harmonic generation and phase-merging enhanced harmonic generator (PEHG) schemes on the electron energy spread distribution are studied.
Abstract: The beam energy spread at the entrance of undulator system is of paramount importance for efficient density modulation in high-gain seeded free-electron lasers (FELs). In this paper, the dependences of high harmonic micro-bunching in the high-gain harmonic generation (HGHG), echo-enabled harmonic generation (EEHG) and phase-merging enhanced harmonic generation (PEHG) schemes on the electron energy spread distribution are studied. Theoretical investigations and multi-dimensional numerical simulations are applied to the cases of uniform and saddle beam energy distributions and compared to a traditional Gaussian distribution. It shows that the uniform and saddle electron energy distributions significantly enhance the performance of HGHG-FELs, while they almost have no influence on EEHG and PEHG schemes. A numerical example demonstrates that, with about 84keV RMS uniform and/or saddle slice energy spread, the 30th harmonic radiation can be directly generated by a single-stage seeding scheme for a soft x-ray FEL facility.
TL;DR: In this paper, the adsorption structures of three thiophene derivatives and one pyrrole derivative on Au(1.1) have been investigated by scanning tunneling microscopy (STM) and cyclic voltammetry in 0.1 M HClO 4.
TL;DR: Measurements of the conductivity of the dimeric 1,4-benzenedithiol (BDT) junction are reported using the scanning tunneling microscopy (STM)-based current-displacement I(s) method, finding the conductance to be almost two orders of magnitude lower than that of the monomer BDT junction.
Abstract: Understanding the electron transport between single molecules connected through weak interaction is of great importance for molecular electronics. In this paper, we report measurements of the conductivity of the dimeric 1,4-benzenedithiol (BDT) junction using the scanning tunneling microscopy (STM)-based current-displacement I(s) method. The conductance was measured to be 6.14×10(-6) G0 , a value almost two orders of magnitude lower than that of the monomer BDT junction. In control experiments, the probability of junction formation decreased with the presence of tris(2-chloroethyl) phosphate (TCEP), a reducing reagent for the disulfide bond. According to theoretical computations, the dihedral angle of the SS bond tends to take a perpendicular conformation. This non-conjugated structure localizes the electron distribution and accounts for the low conductivity of the disulfide linkage.
TL;DR: Experimental results prove the effectiveness of the blind band elimination method based on an improved layout of CCD in spacecraft jitter estimation.
Abstract: We propose a blind spot elimination method based on an improved layout of CCD
in spacecraft jitter estimation. At least three CCDs are required and designed with
two pairs of overlapping area and one non-overlapping pair. The two number of lines
in space of overlapping pairs are made coprime to minimize the number of common
blind spots. The third non-overlapping pair is arranged with the space less than the
quotient of the least line frequency and bandwidth. It is used to eliminate the
aliasing blind frequencies of the first two overlapping pairs. Experimental results
prove the effectiveness of the blind band elimination.
01 Jun 2014
TL;DR: In this article, a modified feed-forward calibration method based on the Prandtl-Ishlinskii (PI) model was proposed to reduce the intrinsic hysteresis nonlinearity weakens the accuracy of the observation and manipulation of AFM.
Abstract: Atomic force microscopy (AFM) has been widely applied in the field of science and technology because it can observe and manipulate at the nanometer scale. The piezoelectric is a regular choice for the actuator of AFM because of its high resolution and fast response. However, the intrinsic hysteresis nonlinearity weakens the accuracy of the observation and manipulation of AFM. Aiming at the hysteresis problem of the piezoelectric actuators in AFM, a modified feedforward calibration method based on the Prandtl-Ishlinskii (PI) model was proposed. By the means of identify the parameters of inverse model directly, the modified method simplify the obtaining procedure for the PI inverse model. The restriction to obtain the inverse model was removed, and the computational complexity was decreased. Experiments validate that the method is effective in reducing errors due to hysteresis, and improving AFM image quality.