Showing papers in "Journal of the American Chemical Society in 2012"
TL;DR: A new composite material consisting of TiO(2) nanocrystals grown in the presence of a layered MoS(2)/graphene hybrid as a high-performance photocatalyst for H( 2) evolution without noble metals is reported.
Abstract: The production of H2 by photocatalytic water splitting has attracted a lot attention as a clean and renewable solar H2 generation system. Despite tremendous efforts, the present great challenge in materials science is to develop highly active photocatalysts for splitting of water at low cost. Here we report a new composite material consisting of TiO2 nanocrystals grown in the presence of a layered MoS2/graphene hybrid as a high-performance photocatalyst for H2 evolution. This composite material was prepared by a two-step simple hydrothermal process using sodium molybdate, thiourea, and graphene oxide as precursors of the MoS2/graphene hybrid and tetrabutylorthotitanate as the titanium precursor. Even without a noble-metal cocatalyst, the TiO2/MoS2/graphene composite reaches a high H2 production rate of 165.3 μmol h–1 when the content of the MoS2/graphene cocatalyst is 0.5 wt % and the content of graphene in this cocatalyst is 5.0 wt %, and the apparent quantum efficiency reaches 9.7% at 365 nm. This unusu...
2,201 citations
TL;DR: It is found that Fe(3)O(4)/N-GAs show a more positive onset potential, higher cathodic density, lower H(2)O-2) yield, and higher electron transfer number for the ORR in alkaline media than Fe( 3)O (4) NPs supported on N-doped carbon black or N- doped graphene sheets, highlighting the importance of the 3D macropores and high specific surface area of the GA support for
Abstract: Three-dimensional (3D) N-doped graphene aerogel (N-GA)-supported Fe3O4 nanoparticles (Fe3O4/N-GAs) as efficient cathode catalysts for the oxygen reduction reaction (ORR) are reported. The graphene hybrids exhibit an interconnected macroporous framework of graphene sheets with uniform dispersion of Fe3O4 nanoparticles (NPs). In studying the effects of the carbon support on the Fe3O4 NPs for the ORR, we found that Fe3O4/N-GAs show a more positive onset potential, higher cathodic density, lower H2O2 yield, and higher electron transfer number for the ORR in alkaline media than Fe3O4 NPs supported on N-doped carbon black or N-doped graphene sheets, highlighting the importance of the 3D macropores and high specific surface area of the GA support for improving the ORR performance. Furthermore, Fe3O4/N-GAs show better durability than the commercial Pt/C catalyst.
1,952 citations
TL;DR: The simple mesoscopic CH(3)NH( 3)PbI(3)/TiO(2) heterojunction solar cell shows impressive photovoltaic performance, with short-circuit photocurrent J(sc)= 16.1 mA/cm(2), open-circuits photovvoltage V(oc) = 0.631 V, and a fill factor FF =0.57.
Abstract: We report for the first time on a hole conductor-free mesoscopic methylammonium lead iodide (CH3NH3PbI3) perovskite/TiO2 heterojunction solar cell, produced by deposition of perovskite nanoparticles from a solution of CH3NH3I and PbI2 in γ-butyrolactone on a 400 nm thick film of TiO2 (anatase) nanosheets exposing (001) facets. A gold film was evaporated on top of the CH3NH3PbI3 as a back contact. Importantly, the CH3NH3PbI3 nanoparticles assume here simultaneously the roles of both light harvester and hole conductor, rendering superfluous the use of an additional hole transporting material. The simple mesoscopic CH3NH3PbI3/TiO2 heterojunction solar cell shows impressive photovoltaic performance, with short-circuit photocurrent Jsc= 16.1 mA/cm2, open-circuit photovoltage Voc = 0.631 V, and a fill factor FF = 0.57, corresponding to a light to electric power conversion efficiency (PCE) of 5.5% under standard AM 1.5 solar light of 1000 W/m2 intensity. At a lower light intensity of 100W/m2, a PCE of 7.3% was m...
1,799 citations
TL;DR: A simple electrochemical approach to luminescent and electrocatalytically active nitrogen-doped GQDs (N-GQDs) with oxygen-rich functional groups is reported, which allows them to be used for biomedical imaging and other optoelectronic applications.
Abstract: Graphene quantum dots (GQDs) represent a new class of quantum dots with unique properties. Doping GQDs with heteroatoms provides an attractive means of effectively tuning their intrinsic properties and exploiting new phenomena for advanced device applications. Herein we report a simple electrochemical approach to luminescent and electrocatalytically active nitrogen-doped GQDs (N-GQDs) with oxygen-rich functional groups. Unlike their N-free counterparts, the newly produced N-GQDs with a N/C atomic ratio of ca. 4.3% emit blue luminescence and possess an electrocatalytic activity comparable to that of a commercially available Pt/C catalyst for the oxygen reduction reaction (ORR) in an alkaline medium. In addition to their use as metal-free ORR catalysts in fuel cells, the superior luminescence characteristic of N-GQDs allows them to be used for biomedical imaging and other optoelectronic applications.
1,796 citations
TL;DR: Modified Cu electrodes were prepared by annealing Cu foil in air and electrochemically reducing the resulting Cu(2)O layers, which resulted in electrodes whose activities were indistinguishable from those of polycrystalline Cu and a higher level of activity than all previously reported metal electrodes evaluated under comparable conditions.
Abstract: Modified Cu electrodes were prepared by annealing Cu foil in air and electrochemically reducing the resulting Cu2O layers. The CO2 reduction activities of these electrodes exhibited a strong dependence on the initial thickness of the Cu2O layer. Thin Cu2O layers formed by annealing at 130 °C resulted in electrodes whose activities were indistinguishable from those of polycrystalline Cu. In contrast, Cu2O layers formed at 500 °C that were ≥ ∼3 μm thick resulted in electrodes that exhibited large roughness factors and required 0.5 V less overpotential than polycrystalline Cu to reduce CO2 at a higher rate than H2O. The combination of these features resulted in CO2 reduction geometric current densities >1 mA/cm2 at overpotentials <0.4 V, a higher level of activity than all previously reported metal electrodes evaluated under comparable conditions. Moreover, the activity of the modified electrodes was stable over the course of several hours, whereas a polycrystalline Cu electrode exhibited deactivation within...
1,619 citations
TL;DR: The exceptional properties, including good electronic conductivity, fast Li diffusion, low operating voltage, and high theoretical Li storage capacity, make Ti(3)C(2) MXene a promising anode material for Li ion batteries.
Abstract: Density functional theory (DFT) computations were performed to investigate the electronic properties and Li storage capability of Ti3C2, one representative MXene (M represents transition metals, and X is either C or/and N) material, and its fluorinated and hydroxylated derivatives. The Ti3C2 monolayer acts as a magnetic metal, while its derived Ti3C2F2 and Ti3C2(OH)2 in their stable conformations are semiconductors with small band gaps. Li adsorption forms a strong Coulomb interaction with Ti3C2-based hosts but well preserves its structural integrity. The bare Ti3C2 monolayer exhibits a low barrier for Li diffusion and high Li storage capacity (up to Ti3C2Li2 stoichiometry). The surface functionalization of F and OH blocks Li transport and decreases Li storage capacity, which should be avoided in experiments. The exceptional properties, including good electronic conductivity, fast Li diffusion, low operating voltage, and high theoretical Li storage capacity, make Ti3C2 MXene a promising anode material for...
1,609 citations
TL;DR: This study establishes principles for the rational design of clinically useful nanomaterials by investigating the role of size and surface chemistry in mediating serum protein adsorption to gold nanoparticles and their subsequent uptake by macrophages.
Abstract: Delivery and toxicity are critical issues facing nanomedicine research. Currently, there is limited understanding and connection between the physicochemical properties of a nanomaterial and its interactions with a physiological system. As a result, it remains unclear how to optimally synthesize and chemically modify nanomaterials for in vivo applications. It has been suggested that the physicochemical properties of a nanomaterial after synthesis, known as its “synthetic identity”, are not what a cell encounters in vivo. Adsorption of blood components and interactions with phagocytes can modify the size, aggregation state, and interfacial composition of a nanomaterial, giving it a distinct “biological identity”. Here, we investigate the role of size and surface chemistry in mediating serum protein adsorption to gold nanoparticles and their subsequent uptake by macrophages. Using label-free liquid chromatography tandem mass spectrometry, we find that over 70 different serum proteins are heterogeneously adso...
1,588 citations
TL;DR: It is shown that the problem of sulfur loss can be effectively diminished by controlling the sulfur as smaller allotropes in the confined space of a conductive microporous carbon matrix.
Abstract: The lithium–sulfur battery holds a high theoretical energy density, 4–5 times that of today’s lithium-ion batteries, yet its applications have been hindered by poor electronic conductivity of the sulfur cathode and, most importantly, the rapid fading of its capacity due to the formation of soluble polysulfide intermediates (Li2Sn, n = 4–8). Despite numerous efforts concerning this issue, combatting sulfur loss remains one of the greatest challenges. Here we show that this problem can be effectively diminished by controlling the sulfur as smaller allotropes. Metastable small sulfur molecules of S2–4 were synthesized in the confined space of a conductive microporous carbon matrix. The confined S2–4 as a new cathode material can totally avoid the unfavorable transition between the commonly used large S8 and S42–. Li–S batteries based on this concept exhibit unprecedented electrochemical behavior with high specific capacity, good cycling stability, and superior rate capability, which promise a practicable bat...
1,443 citations
TL;DR: It is demonstrated that black TiO(2) nanoparticles obtained through a one-step reduction/crystallization process exhibit a bandgap of only 1.85 eV, which matches well with visible light absorption.
Abstract: The increasing need for new materials capable of solar fuel generation is central in the development of a green energy economy. In this contribution, we demonstrate that black TiO2 nanoparticles obtained through a one-step reduction/crystallization process exhibit a bandgap of only 1.85 eV, which matches well with visible light absorption. The electronic structure of black TiO2 nanoparticles is determined by the unique crystalline and defective core/disordered shell morphology. We introduce new insights that will be useful for the design of nanostructured photocatalysts for energy applications.
1,403 citations
TL;DR: It is demonstrated computationally that by shifting from phenyl groups to "space efficient" acetylene moieties as linker expansion units, the hypothetical maximum surface area for a MOF material is substantially greater than previously envisioned.
Abstract: We have synthesized, characterized, and computationally simulated/validated the behavior of two new metal–organic framework (MOF) materials displaying the highest experimental Brunauer–Emmett–Teller (BET) surface areas of any porous materials reported to date (∼7000 m2/g). Key to evacuating the initially solvent-filled materials without pore collapse, and thereby accessing the ultrahigh areas, is the use of a supercritical CO2 activation technique. Additionally, we demonstrate computationally that by shifting from phenyl groups to “space efficient” acetylene moieties as linker expansion units, the hypothetical maximum surface area for a MOF material is substantially greater than previously envisioned (∼14600 m2/g (or greater) versus ∼10500 m2/g).
1,393 citations
TL;DR: Electrokinetic studies indicate that the improved catalysis is linked to dramatically increased stabilization of the CO(2)(•-) intermediate on the surfaces of the oxide-derived Au electrodes.
Abstract: Carbon dioxide reduction is an essential component of many prospective technologies for the renewable synthesis of carbon-containing fuels. Known catalysts for this reaction generally suffer from low energetic efficiency, poor product selectivity, and rapid deactivation. We show that the reduction of thick Au oxide films results in the formation of Au nanoparticles (“oxide-derived Au”) that exhibit highly selective CO2 reduction to CO in water at overpotentials as low as 140 mV and retain their activity for at least 8 h. Under identical conditions, polycrystalline Au electrodes and several other nanostructured Au electrodes prepared via alternative methods require at least 200 mV of additional overpotential to attain comparable CO2 reduction activity and rapidly lose their activity. Electrokinetic studies indicate that the improved catalysis is linked to dramatically increased stabilization of the CO2•– intermediate on the surfaces of the oxide-derived Au electrodes.
TL;DR: In this article, a chemical approach to immobilize sulfur and lithium polysulfides via the reactive functional groups on graphene oxide was proposed, which obtains a uniform and thin (˜tens of nanometers) sulfur coating.
Abstract: The loss of sulfur cathode material as a result of polysulfide dissolution causes significant capacity fading in rechargeable lithium/sulfur cells. Embodiments of the invention use a chemical approach to immobilize sulfur and lithium polysulfides via the reactive functional groups on graphene oxide. This approach obtains a uniform and thin (˜tens of nanometers) sulfur coating on graphene oxide sheets by a chemical reaction-deposition strategy and a subsequent low temperature thermal treatment process. Strong interaction between graphene oxide and sulfur or polysulfides demonstrate lithium/sulfur cells with a high reversible capacity of 950-1400 mAh g −1 , and stable cycling for more than 50 deep cycles at 0.1 C.
TL;DR: The high OER activity and simple synthesis make these Ni-based catalyst thin films useful for incorporating with semiconductor photoelectrodes for direct solar-driven water splitting or in high-surface-area electrodes for water electrolysis.
Abstract: Water oxidation is a critical step in water splitting to make hydrogen fuel. We report the solution synthesis, structural/compositional characterization, and oxygen evolution reaction (OER) electrocatalytic properties of ∼2–3 nm thick films of NiOx, CoOx, NiyCo1–yOx, Ni0.9Fe0.1Ox, IrOx, MnOx, and FeOx. The thin-film geometry enables the use of quartz crystal microgravimetry, voltammetry, and steady-state Tafel measurements to study the electrocatalytic activity and electrochemical properties of the oxides. Ni0.9Fe0.1Ox was found to be the most active water oxidation catalyst in basic media, passing 10 mA cm–2 at an overpotential of 336 mV with a Tafel slope of 30 mV dec–1 with oxygen evolution reaction (OER) activity roughly an order of magnitude higher than IrOx control films and similar to the best known OER catalysts in basic media. The high activity is attributed to the in situ formation of layered Ni0.9Fe0.1OOH oxyhydroxide species with nearly every Ni atom electrochemically active. In contrast to pr...
TL;DR: BiOCl single-crystalline nanosheets with exposed {001} and {010} facets were selectively synthesized via a facile hydrothermal route and exhibited higher activity for direct semiconductor photoexcitation pollutant degradation under UV light, but the counterpart with exposed} facets possessed superior activity for indirect dye photosensitization degradation under visible light.
Abstract: BiOCl single-crystalline nanosheets with exposed {001} and {010} facets were selectively synthesized via a facile hydrothermal route. The resulting BiOCl single-crystalline nanosheets with exposed {001} facets exhibited higher activity for direct semiconductor photoexcitation pollutant degradation under UV light, but the counterpart with exposed {010} facets possessed superior activity for indirect dye photosensitization degradation under visible light.
TL;DR: Strong luminescence emission by the mechanism of aggregation-induced emission (AIE) is reported of Au(I)-thiolate complexes, and the synthetic strategy was extended to other thiolate ligands with added functionalities (in the form of custom-designed peptides).
Abstract: A fundamental understanding of the luminescence of Au–thiolate nanoclusters (NCs), such as the origin of emission and the size effect in luminescence, is pivotal to the development of efficient synthesis routes for highly luminescent Au NCs. This paper reports an interesting finding of Au(I)–thiolate complexes: strong luminescence emission by the mechanism of aggregation-induced emission (AIE). The AIE property of the complexes was then used to develop a simple one-pot synthesis of highly luminescent Au–thiolate NCs with a quantum yield of ∼15%. Our key strategy was to induce the controlled aggregation of Au(I)–thiolate complexes on in situ generated Au(0) cores to form Au(0)@Au(I)–thiolate core–shell NCs where strong luminescence was generated by the AIE of Au(I)–thiolate complexes on the NC surface. We were able to extend the synthetic strategy to other thiolate ligands with added functionalities (in the form of custom-designed peptides). The discovery (e.g., identifying the source of emission and the s...
TL;DR: Two new chemically stable [acid and base] 2D crystalline covalent organic frameworks (COFs) were synthesized using combined reversible and irreversible organic reactions and showed strong resistance toward acid and boiling water and exceptional stability in base.
Abstract: Two new chemically stable [acid and base] 2D crystalline covalent organic frameworks (COFs) (TpPa-1 and TpPa-2) were synthesized using combined reversible and irreversible organic reactions. Syntheses of these COFs were done by the Schiff base reactions of 1,3,5-triformylphloroglucinol (Tp) with p-phenylenediamine (Pa-1) and 2,5-dimethyl-p-phenylenediamine (Pa-2), respectively, in 1:1 mesitylene/dioxane. The expected enol–imine (OH) form underwent irreversible proton tautomerism, and only the keto–enamine form was observed. Because of the irreversible nature of the total reaction and the absence of an imine bond in the system, TpPa-1 and TpPa-2 showed strong resistance toward acid (9 N HCl) and boiling water. Moreover, TpPa-2 showed exceptional stability in base (9 N NaOH) as well.
TL;DR: TADF has been characterized for a carbazole/sulfone derivative in both solutions and doped films and a pure blue organic light emitting diode (OLED) based on this compound demonstrates a very high external quantum efficiency (EQE) of nearly 10% at low current density.
Abstract: Efficient thermally activated delayed fluorescence (TADF) has been characterized for a carbazole/sulfone derivative in both solutions and doped films. A pure blue organic light emitting diode (OLED) based on this compound demonstrates a very high external quantum efficiency (EQE) of nearly 10% at low current density. Because TADF only occurs in a bipolar system where donor and acceptor centered 3ππ* states are close to or higher than the triplet intramolecular charge transfer (3CT) state, control of the π-conjugation length of both donor and acceptor is considered to be as important as breaking the π-conjugation between them in blue TADF material design.
TL;DR: Electrochemical and X-ray near-edge structure (XANES) investigations revealed that the nucleation and growth method for forming inorganic-nanocarbon hybrids results in covalent coupling between spinel oxide nanoparticles and N-doped reduced graphene oxide (N-rmGO) sheets.
Abstract: Through direct nanoparticle nucleation and growth on nitrogen doped, reduced graphene oxide sheets and cation substitution of spinel Co3O4 nanoparticles, a manganese–cobalt spinel MnCo2O4/graphene hybrid was developed as a highly efficient electrocatalyst for oxygen reduction reaction (ORR) in alkaline conditions Electrochemical and X-ray near-edge structure (XANES) investigations revealed that the nucleation and growth method for forming inorganic–nanocarbon hybrids results in covalent coupling between spinel oxide nanoparticles and N-doped reduced graphene oxide (N-rmGO) sheets Carbon K-edge and nitrogen K-edge XANES showed strongly perturbed C–O and C–N bonding in the N-rmGO sheet, suggesting the formation of C–O–metal and C–N–metal bonds between N-doped graphene oxide and spinel oxide nanoparticles Co L-edge and Mn L-edge XANES suggested substitution of Co3+ sites by Mn3+, which increased the activity of the catalytic sites in the hybrid materials, further boosting the ORR activity compared with th
TL;DR: RET from a plasmonic metal to a semiconductor is a viable and efficient mechanism that can be used to guide the design of photocatalysts, photovoltaics, and other optoelectronic devices.
Abstract: Plasmonic metal nanostructures have been incorporated into semiconductors to enhance the solar-light harvesting and the energy-conversion efficiency. So far the mechanism of energy transfer from the plasmonic metal to semiconductors remains unclear. Herein the underlying plasmonic energy-transfer mechanism is unambiguously determined in Au@SiO2@Cu2O sandwich nanostructures by transient-absorption and photocatalysis action spectrum measurement. The gold core converts the energy of incident photons into localized surface plasmon resonance oscillations and transfers the plasmonic energy to the Cu2O semiconductor shell via resonant energy transfer (RET). RET generates electron–hole pairs in the semiconductor by the dipole–dipole interaction between the plasmonic metal (donor) and semiconductor (acceptor), which greatly enhances the visible-light photocatalytic activity as compared to the semiconductor alone. RET from a plasmonic metal to a semiconductor is a viable and efficient mechanism that can be used to ...
TL;DR: 3D GA-based mesoporous carbons and metal oxide hybrids can be successfully constructed via a nanocasting technology and manifests outstanding specific capacitance (226 F g(-1), high rate capability, and excellent cycling stability when it is applied in electrochemical capacitors.
Abstract: Three-dimensional graphene-based frameworks (3D-GFs) with hierarchical macro- and meso-porous structures are presented. The interconnected macropores are derived from hydrothermally assembled 3D graphene aerogels (GAs), while the mesopores are generated by the silica networks uniformly grown on the surface of graphene. The resulting 3D-GFs exhibit narrow mesopore size distribution (2–3.5 nm), high surface area, and low mass density. These intriguing features render 3D-GFs a promising template for creating various 3D porous materials. Specifically, 3D GA-based mesoporous carbons (GA-MC) and metal oxide hybrids (GA-Co3O4, GA-RuO2) can be successfully constructed via a nanocasting technology. Benefiting from the integration of meso- and macroporous structures, 3D GA-MC manifests outstanding specific capacitance (226 F g–1), high rate capability, and excellent cycling stability (no capacitance loss after 5000 cycles) when it is applied in electrochemical capacitors.
TL;DR: The performance characteristics of mmen-Mg(2)(dobpdc) indicate it to be an exceptional new adsorbent for CO(2) capture, comparing favorably with both amine-grafted silicas and aqueous amine solutions.
Abstract: Two new metal–organic frameworks, M2(dobpdc) (M = Zn (1), Mg (2); dobpdc4– = 4,4′-dioxido-3,3′-biphenyldicarboxylate), adopting an expanded MOF-74 structure type, were synthesized via solvothermal and microwave methods. Coordinatively unsaturated Mg2+ cations lining the 18.4-A-diameter channels of 2 were functionalized with N,N′-dimethylethylenediamine (mmen) to afford Mg2(dobpdc)(mmen)1.6(H2O)0.4 (mmen-Mg2(dobpdc)). This compound displays an exceptional capacity for CO2 adsorption at low pressures, taking up 2.0 mmol/g (8.1 wt %) at 0.39 mbar and 25 °C, conditions relevant to removal of CO2 from air, and 3.14 mmol/g (12.1 wt %) at 0.15 bar and 40 °C, conditions relevant to CO2 capture from flue gas. Dynamic gas adsorption/desorption cycling experiments demonstrate that mmen-Mg2(dobpdc) can be regenerated upon repeated exposures to simulated air and flue gas mixtures, with cycling capacities of 1.05 mmol/g (4.4 wt %) after 1 h of exposure to flowing 390 ppm CO2 in simulated air at 25 °C and 2.52 mmol/g (9...
TL;DR: A luminescent mixed lanthanide metal-organic framework approach has been realized to explore luminescence thermometers that is not only more robust, reliable, and instantaneous but also has higher sensitivity than the parent MOF Tb-DMBDC based on one emission at a wide range from 10 to 300 K.
Abstract: A luminescent mixed lanthanide metal–organic framework approach has been realized to explore luminescent thermometers. The targeted self-referencing luminescent thermometer Eu0.0069Tb0.9931-DMBDC (DMBDC = 2, 5-dimethoxy-1, 4-benzenedicarboxylate) based on two emissions of Tb3+ at 545 nm and Eu3+ at 613 nm is not only more robust, reliable, and instantaneous but also has higher sensitivity than the parent MOF Tb-DMBDC based on one emission at a wide range from 10 to 300 K.
TL;DR: Fe(2)O(3) microboxes with hierarchically structured shells have been synthesized simply by annealing Prussian blue microcubes and demonstrated a scalable synthesis of anisotropic hollow structures with various shell architectures.
Abstract: Fe2O3 microboxes with hierarchically structured shells have been synthesized simply by annealing Prussian blue (PB) microcubes. By utilizing simultaneous oxidative decomposition of PB microcubes and crystal growth of iron oxide shells, we have demonstrated a scalable synthesis of anisotropic hollow structures with various shell architectures. When evaluated as an anode material for lithium ion batteries, the Fe2O3 microboxes with a well-defined hollow structure and hierarchical shell manifested high specific capacity (∼950 mA h g–1 at 200 mA g–1) and excellent cycling performance.
TL;DR: To make Quantum Dot Sensitized Solar Cells competitive, it is necessary to achieve power conversion efficiencies comparable to other emerging solar cell technologies, and employing Mn(2+) doping of CdS has now succeeded in significantly improving QDSC performance.
Abstract: To make Quantum Dot Sensitized Solar Cells (QDSC) competitive, it is necessary to achieve power conversion efficiencies comparable to other emerging solar cell technologies. By employing Mn2+ doping of CdS, we have now succeeded in significantly improving QDSC performance. QDSC constructed with Mn-doped-CdS/CdSe deposited on mesoscopic TiO2 film as photoanode, Cu2S/Graphene Oxide composite electrode, and sulfide/polysulfide electrolyte deliver power conversion efficiency of 5.4%.
TL;DR: TAT peptide has been employed to conjugate onto mesoporous silica nanoparticles (MSNs-TAT) with high payload for nuclear-targeted drug delivery for the first time, and may provide an effective strategy for the design and development of cell-nuclear-targeting drug delivery.
Abstract: Most present nanodrug delivery systems have been developed to target cancer cells but rarely nuclei. However, nuclear-targeted drug delivery is expected to kill cancer cells more directly and efficiently. In this work, TAT peptide has been employed to conjugate onto mesoporous silica nanoparticles (MSNs-TAT) with high payload for nuclear-targeted drug delivery for the first time. Monodispersed MSNs-TAT of varied particle sizes have been synthesized to investigate the effects of particle size and TAT conjugation on the nuclear membrane penetrability of MSNs. MSNs-TAT with a diameter of 50 nm or smaller can efficiently target the nucleus and deliver the active anticancer drug doxorubicin (DOX) into the targeted nucleus, killing these cancer cells with much enhanced efficiencies. This study may provide an effective strategy for the design and development of cell-nuclear-targeted drug delivery.
TL;DR: It is evidenced that a competition takes place at the end of the discharge of the Sb/Na cell between the formation of the hexagonal and the cubic polymorphs of Na(3)Sb, the last being described in the literature as unstable at atmospheric pressure.
Abstract: Pure micrometric antimony can be successfully used as negative electrode material in Na-ion batteries, sustaining a capacity close to 600 mAh g–1 at a high rate with a Coulombic efficiency of 99 over 160 cycles, an extremely high capacity compared to any other compound tested against both Li and Na. The reaction mechanism with Na does not simply go through the alloying mechanism observed for Li where the intermediate species are those expected from the phase diagram. In the case of Na, the intermediate phases are mostly amorphous and could not be precisely identified. Surprisingly, we evidenced that a competition takes place at the end of the discharge of the Sb/Na cell between the formation of the hexagonal and the cubic polymorphs of Na3Sb, the last being described in the literature as unstable at atmospheric pressure and only synthesized under high pressure (1–9 GPa). In addition, fluoroethylene carbonate added to the electrolyte combined with an appropriate electrode formulation based on carboxymethyl...
TL;DR: The results show that the addition of pyridine-functionalized graphene changes the crystallization process of iron-porphyrin in the MOF, increases its porosity, and enhances the electrochemical charge transfer rate of Iron-porPHyrin.
Abstract: Pyridine-functionalized graphene (reduced graphene oxide) can be used as a building block in the assembly of metal organic framework (MOF). By reacting the pyridine-functionalized graphene with iron–porphyrin, a graphene–metalloporphyrin MOF with enhanced catalytic activity for oxygen reduction reactions (ORR) is synthesized. The structure and electrochemical property of the hybrid MOF are investigated as a function of the weight percentage of the functionalized graphene added to the iron–porphyrin framework. The results show that the addition of pyridine-functionalized graphene changes the crystallization process of iron–porphyrin in the MOF, increases its porosity, and enhances the electrochemical charge transfer rate of iron–porphyrin. The graphene–metalloporphyrin hybrid shows facile 4-electron ORR and can be used as a promising Pt-free cathode in alkaline Direct Methanol Fuel Cell.
TL;DR: The results implicate the participation of SnO(x) in the CO(2) reduction pathway on Sn electrodes and suggest that metal/metal oxide composite materials are promising catalysts for sustainable fuel synthesis.
Abstract: The importance of tin oxide (SnOx) to the efficiency of CO2 reduction on Sn was evaluated by comparing the activity of Sn electrodes that had been subjected to different pre-electrolysis treatments. In aqueous NaHCO3 solution saturated with CO2, a Sn electrode with a native SnOx layer exhibited potential-dependent CO2 reduction activity consistent with previously reported activity. In contrast, an electrode etched to expose fresh Sn0 surface exhibited higher overall current densities but almost exclusive H2 evolution over the entire 0.5 V range of potentials examined. Subsequently, a thin-film catalyst was prepared by simultaneous electrodeposition of Sn0 and SnOx on a Ti electrode. This catalyst exhibited up to 8-fold higher partial current density and 4-fold higher faradaic efficiency for CO2 reduction than a Sn electrode with a native SnOx layer. Our results implicate the participation of SnOx in the CO2 reduction pathway on Sn electrodes and suggest that metal/metal oxide composite materials are promi...
TL;DR: The resultant POMC with a small amount of P doping is demonstrated as a metal-free electrode with excellent electrocatalytic activity for oxygen reduction reaction (ORR), coupled with much enhanced stability and alcohol tolerance compared to those of platinum via four-electron pathway in alkaline medium.
Abstract: Phosphorus-doped ordered mesoporous carbons (POMCs) with different lengths were synthesized using a metal-free nanocasting method of SBA-15 mesoporous silica with different sizes as template and triphenylphosphine and phenol as phosphorus and carbon sources, respectively. The resultant POMC with a small amount of P doping is demonstrated as a metal-free electrode with excellent electrocatalytic activity for oxygen reduction reaction (ORR), coupled with much enhanced stability and alcohol tolerance compared to those of platinum via four-electron pathway in alkaline medium. Interestingly, the POMC with short channel length is found to have superior electrochemical performances compared to those with longer sizes.
TL;DR: The nonaqueous surfactant-assisted synthesis of highly uniform anatase TiO(2) NCs with tailorable morphology in the 10-100 nm size regime is reported, prepared through a seeded growth technique and the data suggest that the {101} facets of anatase are more active than the {001}.
Abstract: Control over faceting in nanocrystals (NCs) is pivotal for many applications, but most notably when investigating catalytic reactions which occur on the surfaces of nanostructures. Anatase titanium dioxide (TiO2) is one of the most studied photocatalysts, but the shape dependence of its activity has not yet been satisfactorily investigated and many questions still remain unanswered. We report the nonaqueous surfactant-assisted synthesis of highly uniform anatase TiO2 NCs with tailorable morphology in the 10–100 nm size regime, prepared through a seeded growth technique. Introduction of titanium(IV) fluoride (TiF4) preferentially exposes the {001} facet of anatase through in situ release of hydrofluoric acid (HF), allowing for the formation of uniform anatase NCs based on the truncated tetragonal bipyramidal geometry. A method is described to engineer the percentage of {001} and {101} facets through the choice of cosurfactant and titanium precursor. X-ray diffraction studies are performed in conjunction wi...