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Showing papers in "Journal of the American Chemical Society in 2010"


Journal ArticleDOI
TL;DR: This work develops an approach to detect noncovalent interactions in real space, based on the electron density and its derivatives, which provides a rich representation of van der Waals interactions, hydrogen bonds, and steric repulsion in small molecules, molecular complexes, and solids.
Abstract: Molecular structure does not easily identify the intricate noncovalent interactions that govern many areas of biology and chemistry, including design of new materials and drugs. We develop an approach to detect noncovalent interactions in real space, based on the electron density and its derivatives. Our approach reveals the underlying chemistry that compliments the covalent structure. It provides a rich representation of van der Waals interactions, hydrogen bonds, and steric repulsion in small molecules, molecular complexes, and solids. Most importantly, the method, requiring only knowledge of the atomic coordinates, is efficient and applicable to large systems, such as proteins or DNA. Across these applications, a view of nonbonded interactions emerges as continuous surfaces rather than close contacts between atom pairs, offering rich insight into the design of new and improved ligands.

5,731 citations


Journal ArticleDOI
TL;DR: In this article, the authors developed two-step solution-phase reactions to form hybrid materials of Mn(3)O(4) nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications.
Abstract: We developed two-step solution-phase reactions to form hybrid materials of Mn(3)O(4) nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Selective growth of Mn(3)O(4) nanoparticles on RGO sheets, in contrast to free particle growth in solution, allowed for the electrically insulating Mn(3)O(4) nanoparticles to be wired up to a current collector through the underlying conducting graphene network. The Mn(3)O(4) nanoparticles formed on RGO show a high specific capacity up to ∼900 mAh/g, near their theoretical capacity, with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn(3)O(4) nanoparticles grown atop. The Mn(3)O(4)/RGO hybrid could be a promising candidate material for a high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for the design and synthesis of battery electrodes based on highly insulating materials.

1,810 citations


Journal ArticleDOI
TL;DR: The homogeneous substitution of sulfur for lattice nitrogen and a concomitant quantum confinement effect are identified as the cause of this unique electronic structure and the excellent photoreactivity of C(3)N(4-x)S(x), which may shed light on general doping strategies for designing potentially efficient photocatalysts.
Abstract: Electronic structure intrinsically controls the light absorbance, redox potential, charge-carrier mobility, and consequently, photoreactivity of semiconductor photocatalysts. The conventional approach of modifying the electronic structure of a semiconductor photocatalyst for a wider absorption range by anion doping operates at the cost of reduced redox potentials and/or charge-carrier mobility, so that its photoreactivity is usually limited and some important reactions may not occur at all. Here, we report sulfur-doped graphitic C(3)N(4) (C(3)N(4-x)S(x)) with a unique electronic structure that displays an increased valence bandwidth in combination with an elevated conduction band minimum and a slightly reduced absorbance. The C(3)N(4-x)S(x) shows a photoreactivity of H(2) evolution 7.2 and 8.0 times higher than C(3)N(4) under lambda > 300 and 420 nm, respectively. More strikingly, the complete oxidation process of phenol under lambda > 400 nm can occur for sulfur-doped C(3)N(4), which is impossible for C(3)N(4) even under lambda > 300 nm. The homogeneous substitution of sulfur for lattice nitrogen and a concomitant quantum confinement effect are identified as the cause of this unique electronic structure and, consequently, the excellent photoreactivity of C(3)N(4-x)S(x). The results acquired may shed light on general doping strategies for designing potentially efficient photocatalysts.

1,762 citations


Journal ArticleDOI
TL;DR: Ni(OH)2 nanocrystals grown on graphene sheets with various degrees of oxidation are investigated as electrochemical pseudocapacitor materials for potential energy storage applications in this paper, where they exhibit a high specific capacitance of ∼1335 F/g at a charge and discharge current density of 2.8 A/g and ∼953 F/m at 45.7 A/m with excellent cycling ability.
Abstract: Ni(OH)2 nanocrystals grown on graphene sheets with various degrees of oxidation are investigated as electrochemical pseudocapacitor materials for potential energy storage applications. Single-crystalline Ni(OH)2 hexagonal nanoplates directly grown on lightly oxidized, electrically conducting graphene sheets (GS) exhibit a high specific capacitance of ∼1335 F/g at a charge and discharge current density of 2.8 A/g and ∼953 F/g at 45.7 A/g with excellent cycling ability. The high specific capacitance and remarkable rate capability are promising for applications in supercapacitors with both high energy and power densities. A simple physical mixture of pre-synthesized Ni(OH)2 nanoplates and graphene sheets shows lower specific capacitance, highlighting the importance of direct growth of nanomaterials on graphene to impart intimate interactions and efficient charge transport between the active nanomaterials and the conducting graphene network. Single-crystalline Ni(OH)2 nanoplates directly grown on graphene she...

1,751 citations


Journal ArticleDOI
TL;DR: It is reported that GO is an amphiphile with hydrophilic edges and a more hydrophobic basal plane, and the ease of its conversion to chemically modified graphene could enable new opportunities in solution processing of functional materials.
Abstract: Graphite oxide sheet, now called graphene oxide (GO), is the product of chemical exfoliation of graphite and has been known for more than a century. GO has been largely viewed as hydrophilic, presumably due to its excellent colloidal stability in water. Here we report that GO is an amphiphile with hydrophilic edges and a more hydrophobic basal plane. GO can act like a surfactant, as measured by its ability to adsorb on interfaces and lower the surface or interfacial tension. Since the degree of ionization of the edge −COOH groups is affected by pH, GO’s amphiphilicity can be tuned by pH. In addition, size-dependent amphiphilicity of GO sheets is observed. Since each GO sheet is a single molecule as well as a colloidal particle, the molecule−colloid duality makes it behave like both a molecular and a colloidal surfactant. For example, GO is capable of creating highly stable Pickering emulsions of organic solvents like solid particles. It can also act as a molecular dispersing agent to process insoluble mat...

1,572 citations


Journal ArticleDOI
TL;DR: Physical and chemical characterization of the nanostructured Mn oxide bifunctional catalyst reveals an oxidation state of Mn(III), akin to one of the most commonly observed Mn oxidation states found in the OEC.
Abstract: There is a growing interest in oxygen electrochemistry as conversions between O(2) and H(2)O play an important role in a variety of renewable energy technologies. The goal of this work is to develop active bifunctional catalyst materials for water oxidation and oxygen reduction. Drawing inspiration from a cubane-like CaMn(4)O(x), the biological catalyst found in the oxygen evolving center (OEC) in photosystem II, nanostructured manganese oxide surfaces were investigated for these reactions. Thin films of nanostructured manganese oxide were found to be active for both oxygen reduction and water oxidation, with similar overall oxygen electrode activity to the best known precious metal nanoparticle catalysts: platinum, ruthenium, and iridium. Physical and chemical characterization of the nanostructured Mn oxide bifunctional catalyst reveals an oxidation state of Mn(III), akin to one of the most commonly observed Mn oxidation states found in the OEC.

1,400 citations


Journal ArticleDOI
TL;DR: This work shows that the high surface density of exposed TiO(2) (001) facets leads to fast lithium insertion/deinsertion processes in batteries that mimic features seen in high-power electrochemical capacitors.
Abstract: Synthesis of nanocrystals with exposed high-energy facets is a well-known challenge in many fields of science and technology. The higher reactivity of these facets simultaneously makes them desirable catalysts for sluggish chemical reactions and leads to their small populations in an equilibrated crystal. Using anatase TiO2 as an example, we demonstrate a facile approach for creating high-surface-area stable nanosheets comprising nearly 100% exposed (001) facets. Our approach relies on spontaneous assembly of the nanosheets into three-dimensional hierarchical spheres, which stabilizes them from collapse. We show that the high surface density of exposed TiO2 (001) facets leads to fast lithium insertion/deinsertion processes in batteries that mimic features seen in high-power electrochemical capacitors.

1,206 citations


Journal ArticleDOI
TL;DR: A new soluble C(60) derivative, indene-C( 60) bisadduct (ICBA), with a LUMO energy level 0.17 eV higher than that of PCBM is synthesized and indicates that ICBA is an alternative high-performance acceptor and could be widely used in high- performance PSCs.
Abstract: Polymer solar cells (PSCs) are commonly composed of a blend film of a conjugated polymer donor and a soluble C60 derivative acceptor sandwiched between an ITO anode and a low-workfunction metal cathode. Poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) are the most widely used donor and acceptor materials, respectively. However, the low LUMO energy level of PCBM limits the open circuit voltage (Voc) of the P3HT-based PSCs to ca. 0.6 V. Here we synthesized a new soluble C60 derivative, indene−C60 bisadduct (ICBA), with a LUMO energy level 0.17 eV higher than that of PCBM. The PSC based on P3HT with ICBA as acceptor shows a higher Voc of 0.84 V and higher power conversion efficiency (PCE) of 5.44% under the illumination of AM1.5, 100 mW/cm2, while the PSC based on P3HT/PCBM displays a Voc of 0.58 V and PCE of 3.88% under the same experimental conditions. The results indicate that ICBA is an alternative high-performance acceptor and could be widely used in high-performance ...

1,147 citations


Journal ArticleDOI
TL;DR: PtAu nanoparticles were shown to strongly enhance the kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable Li-O(2) cells, found to exhibit the highest round-trip efficiency reported to date.
Abstract: PtAu nanoparticles (NPs) were shown to strongly enhance the kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable Li−O2 cells. Li−O2 cells with PtAu/C were found to exhibit the highest round-trip efficiency reported to date. During ORR via xLi+ + O2 + xe− → LixO2, the discharge voltage with PtAu/C was considerably higher than that of pure carbon and comparable to that of Au/C. During OER via LixO2 → xLi+ + O2 + xe−, the charge voltages with PtAu/C fell in the range from 3.4 to 3.8 VLi, which is slightly lower than obtained with Pt. It is hypothesized that PtAu NPs exhibit bifunctional catalytic activity, having surface Au and Pt atoms primarily responsible for ORR and OER kinetics in Li−O2 cells, respectively.

1,134 citations


Journal ArticleDOI
TL;DR: The UV-vis spectra show that the Ti(3+) here extends the photoresponse of TiO(2) from the UV to the visible light region, which leads to high visible-light photocatalytic activity for the generation of hydrogen gas from water.
Abstract: Through a facile one-step combustion method, partially reduced TiO2 has been synthesized. Electron paramagnetic resonance (EPR) spectra confirm the presence of Ti3+ in the bulk of an as-prepared sample. The UV−vis spectra show that the Ti3+ here extends the photoresponse of TiO2 from the UV to the visible light region, which leads to high visible-light photocatalytic activity for the generation of hydrogen gas from water. It is worth noting that the Ti3+ sites in the sample are highly stable in air or water under irradiation and the photocatalyst can be repeatedly used without degradation in the activity.

1,120 citations


Journal ArticleDOI
TL;DR: A "structural doping" strategy was reported, in which phosphorus heteroatoms were doped into g-C(3)N(4) via carbon sites by polycondensation of the mixture of the carbon nitride precursors and phosphorus source (specifically from 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid).
Abstract: As a new kind of polymeric semiconductors, graphitic carbon nitride (g-C3N4) and its incompletely condensed precursors are stable up to 550 °C in air and have shown promising photovoltaic applications. However, for practical applications, their efficiency, limited e.g. by band gap absorption, needs further improvement. Here we report a “structural doping” strategy, in which phosphorus heteroatoms were doped into g-C3N4 via carbon sites by polycondensation of the mixture of the carbon nitride precursors and phosphorus source (specifically from 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid). Most of the structural features of g-C3N4 were well retained after doping, but electronic features had been seriously altered, which provided not only a much better electrical (dark) conductivity up to 4 orders of magnitude but also an improvement in photocurrent generation by a factor of up to 5. In addition to being active layers in solar cells, such phosphorus-containing scaffolds and materials are als...

Journal ArticleDOI
TL;DR: It is found that blood plasma-derived coronas are sufficiently long-lived that they, rather than the nanomaterial surface, are likely to be what the cell sees, when interacting with a nanoparticle dispersed in a biological medium.
Abstract: What the biological cell, organ, or barrier actually “sees” when interacting with a nanoparticle dispersed in a biological medium likely matters more than the bare material properties of the particle itself. Typically the bare surface of the particle is covered by several biomolecules, including a select group of proteins drawn from the biological medium. Here, we apply several different methodologies, in a time-resolved manner, to follow the lifetime of such biomolecular “coronas” both in situ and isolated from the excess plasma. We find that such particle−biomolecule complexes can be physically isolated from the surrounding medium and studied in some detail, without altering their structure. For several nanomaterial types, we find that blood plasma-derived coronas are sufficiently long-lived that they, rather than the nanomaterial surface, are likely to be what the cell sees. From fundamental science to regulatory safety, current efforts to classify the biological impacts of nanomaterials (currently acc...

Journal ArticleDOI
TL;DR: The synthesis of ultra-low-density three-dimensional macroassemblies of graphene sheets that exhibit high electrical conductivities and large internal surface areas are reported, making these materials viable candidates for use in energy storage, catalysis, and sensing applications.
Abstract: We report the synthesis of ultra-low-density three-dimensional macroassemblies of graphene sheets that exhibit high electrical conductivities and large internal surface areas. These materials are prepared as monolithic solids from suspensions of single-layer graphene oxide in which organic sol−gel chemistry is used to cross-link the individual sheets. The resulting gels are supercritically dried and then thermally reduced to yield graphene aerogels with densities approaching 10 mg/cm3. In contrast to methods that utilize physical cross-links between GO, this approach provides covalent carbon bonding between the graphene sheets. These graphene aerogels exhibit an improvement in bulk electrical conductivity of more than 2 orders of magnitude (∼1 × 102 S/m) compared to graphene assemblies with physical cross-links alone (∼5 × 10−1 S/m). The graphene aerogels also possess large surface areas (584 m2/g) and pore volumes (2.96 cm3/g), making these materials viable candidates for use in energy storage, catalysis...

Journal ArticleDOI
TL;DR: These electrokinetic studies suggest a mechanism involving a rapid, one electron, one proton equilibrium between Co(III)-OH and Co(IV)-O in which a phosphate species is the proton acceptor, followed by a chemical turnover-limiting process involving oxygen-oxygen bond coupling.
Abstract: The mechanism of the oxygen evolution reaction (OER) by catalysts prepared by electrodepositions from Co2+ solutions in phosphate electrolytes (Co-Pi) was studied at neutral pH by electrokinetic and 18O isotope experiments. Low-potential electrodepositions enabled the controlled preparation of ultrathin Co-Pi catalyst films (<100 nm) that could be studied kinetically in the absence of mass transport and charge transport limitations to the OER. The Co-Pi catalysts exhibit a Tafel slope approximately equal to 2.3 × RT/F for the production of oxygen from water in neutral solutions. The electrochemical rate law exhibits an inverse first order dependence on proton activity and a zeroth order dependence on phosphate for [Pi] ≥ 0.03 M. In the absence of phosphate buffer, the Tafel slope is increased ∼3-fold and the overall activity is greatly diminished. Together, these electrokinetic studies suggest a mechanism involving a rapid, one electron, one proton equilibrium between CoIII−OH and CoIV−O in which a phosph...

Journal ArticleDOI
TL;DR: The dramatic delivery, protection, and sensing capabilities of GO-nS in living cells indicate that graphene oxide could be a robust candidate for many biological fields, such as DNA and protein analysis, gene and drug delivering, and intracellular tracking.
Abstract: Graphene has shown fascinating applications in bionanotechnology, including DNA sensing, protein assays, and drug delivery. However, exploration of graphene with intracellular monitoring and in situ molecular probing is still at an early stage. In this regard, we have designed an aptamer-carboxyfluorescein (FAM)/graphene oxide nanosheet (GO-nS) nanocomplex to investigate its ability for molecular probing in living cells. Results demonstrate that uptake of aptamer-FAM/GO-nS nanocomplex and cellular target monitoring were realized successfully. The dramatic delivery, protection, and sensing capabilities of GO-nS in living cells indicate that graphene oxide could be a robust candidate for many biological fields, such as DNA and protein analysis, gene and drug delivering, and intracellular tracking.

Journal ArticleDOI
TL;DR: Dye-sensitized solar cells with cobalt-based mediators with efficiencies surpassing the record for DSCs with iodide-free electrolytes were developed by selecting a suitable combination of a cobalt polypyridine complex and an organic sensitizer.
Abstract: Dye-sensitized solar cells (DSCs) with cobalt-based mediators with efficiencies surpassing the record for DSCs with iodide-free electrolytes were developed by selecting a suitable combination of a cobalt polypyridine complex and an organic sensitizer. The effect of the steric properties of two triphenylamine-based organic sensitizers and a series of cobalt polypyridine redox mediators on the overall device performance in DSCs as well as on transport and recombination processes in these devices was compared. The recombination and mass-transport limitations that, previously, have been found to limit the performance of these mediators were avoided by matching the properties of the dye and the cobalt redox mediator. Organic dyes with higher extinction coefficients than the standard ruthenium sensitizers were employed in DSCs in combination with outer-sphere redox mediators, enabling thinner TiO2 films to be used. Recombination was reduced further by introducing insulating butoxyl chains on the dye rather than...

Journal ArticleDOI
TL;DR: The surface chemistry and the surface structure at the atomic level are key factors in tuning the adsorption selectivity and, consequently, photocatalytic selectivity of HTS toward azo dyes.
Abstract: A fluoride mediated self-transformation method is proposed for the synthesis of hollow TiO2 microspheres (HTS) composed of anatase polyhedra with exposed ca. 20% {001} facets. Importantly, HTS exhibit tunable photocatalytic selectivity in decomposing azo dyes in water. The fluorinated HTS show preferential decomposition of methyl orange (MO) in comparison to methylene blue (MB). In contrast, the surface-modified HTS by either NaOH washing or calcinations at 600 °C favor decomposition of MB over MO. The surface chemistry and the surface structure at the atomic level are key factors in tuning the adsorption selectivity and, consequently, photocatalytic selectivity of HTS toward azo dyes.

Journal ArticleDOI
TL;DR: A ZIF-8 thin film-based Fabry-Pérot device has been fabricated as a selective sensor for chemical vapors and gases as well as a series of ZIF -8 thin films grown on silicon substrates.
Abstract: A ZIF-8 thin film-based Fabry−Perot device has been fabricated as a selective sensor for chemical vapors and gases. The preparation of the ZIF-8 thin film and a series of ZIF-8 thin films of various thicknesses grown on silicon substrates are presented.

Journal ArticleDOI
TL;DR: The total structure of Au(38)(SC(2)H(4)Ph)(24) nanoparticles determined by single crystal X-ray crystallography is reported, which is based upon a face-fused Au(23) biicosahedral core and capped by three monomeric Au(SR)(2) staples at the waist of the Au( 23) rod.
Abstract: We report the total structure of Au38(SC2H4Ph)24 nanoparticles determined by single crystal X-ray crystallography. This nanoparticle is based upon a face-fused Au23 biicosahedral core, which is further capped by three monomeric Au(SR)2 staples at the waist of the Au23 rod and six dimeric staples with three on the top icosahedron and other three on the bottom icosahedron. The six Au2(SR)3 staples are arranged in a staggered configuration, and the Au38S24 framework has a C3 rotation axis.

Journal ArticleDOI
TL;DR: By tuning the composition of the CZTS nanocrystals and developing a robust film coating method, a total area efficiency as high as 7.2% under AM 1.5 illumination and light soaking has been achieved.
Abstract: Earth abundant copper-zinc-tin-chalcogenide (CZTSSe) is an important class of material for the development of low cost and sustainable thin film solar cells. The fabrication of CZTSSe solar cells by selenization of CZTS nanocrystals is presented. By tuning the composition of the CZTS nanocrystals and developing a robust film coating method, a total area efficiency as high as 7.2% under AM 1.5 illumination and light soaking has been achieved.

Journal ArticleDOI
TL;DR: The effect of the alkyl groups on the structural order and orientation of the polymer backbone is correlated using grazing incidence X-ray scattering analysis and it is demonstrated how fine-tuning of these parameters can improve the power conversion efficiency.
Abstract: The correlation between the nature of alkyl substituents on N-alkylthieno[3,4-c]pyrrole-4,6-dione (TPD)-based polymers and solar cell device performance has been investigated. After adjusting device parameters, these TPD-based polymers used with PC61BM provided photovoltaic responses ranging from 4.0% to 6.8%, depending on the size and shape of the alkyl solubilizing groups. Further, we have correlated the effect of the alkyl groups on the structural order and orientation of the polymer backbone using grazing incidence X-ray scattering analysis, and we have demonstrated how fine-tuning of these parameters can improve the power conversion efficiency.

Journal ArticleDOI
TL;DR: The fabrication of multifunctional microspheres which possess a core of nonporous silica-protected magnetite particles, transition layer of active gold nanoparticles, and an outer shell of ordered mesoporous silica with perpendicularly aligned pore channels makes the microsphere to be a novel stable and approachable catalyst system for various catalytic industry processes.
Abstract: The precise control of the size, morphology, surface chemistry, and assembly process of each component is important to construction of integrated functional nanocomposites. We report here the fabrication of multifunctional microspheres which possess a core of nonporous silica-protected magnetite particles, transition layer of active gold nanoparticles, and an outer shell of ordered mesoporous silica with perpendicularly aligned pore channels. The well-designed microspheres have high magnetization (18.6 emu/g), large surface area (236 m(2)/g), highly open mesopores (approximately 2.2 nm), and stably confined but accessible Au nanoparticles and, as a result, show high performance in catalytic reduction of 4-nitrophenol (with conversion of 95% in 12 min), styrene epoxidation with high conversion (72%) and selectivity (80%), especially convenient magnetic separability, long life and good reusability. The unique nanostructure makes the microsphere to be a novel stable and approachable catalyst system for various catalytic industry processes.

Journal ArticleDOI
TL;DR: The synthesis and structure of Co(2)(ad)(2)(CO(2)CH(3))( 2) x 2 DMF x 0.5 H(1)O (bio-MOF-11) is described, and its carbon dioxide adsorption properties were evaluated.
Abstract: The synthesis and structure of Co2(ad)2(CO2CH3)2·2DMF·0.5H2O (bio-MOF-11) is described. Pyrimidine and amino groups of adeninate (ad) decorate the pores of the framework. The porosity of this material was studied, and its CO2 and H2 adsorption properties were evaluated. bio-MOF-11 exhibits a high heat of adsorption for CO2 (∼45 kJ/mol), a high CO2 capacity (∼6 mmol/g, 273 K), and exceptional selectivity for CO2 over N2 at 273 K (81:1) and 298 K (75:1).

Journal ArticleDOI
TL;DR: Mesoporous hematite photoelectodes prepared by a solution-based colloidal method which yield water-splitting photocurrents of 0.56 mA cm(-2) under standard conditions and a considerable change in the absorption coefficient and onset properties, critical aspects for hematites as a solar energy converter, as a function of the sintering temperature are revealed.
Abstract: Sustainable hydrogen production through photoelectrochemical water splitting using hematite (α-Fe2O3) is a promising approach for the chemical storage of solar energy, but is complicated by the material’s nonoptimal optoelectronic properties. Nanostructuring approaches have been shown to increase the performance of hematite, but the ideal nanostructure giving high efficiencies for all absorbed light wavelengths remains elusive. Here, we report for the first time mesoporous hematite photoelectodes prepared by a solution-based colloidal method which yield water-splitting photocurrents of 0.56 mA cm−2 under standard conditions (AM 1.5G 100 mW cm−2, 1.23 V vs reversible hydrogen electrode, RHE) and over 1.0 mA cm−2 before the dark current onset (1.55 V vs RHE). The sintering temperature is found to increase the average particle size, and have a drastic effect on the photoactivity. X-ray photoelectron spectroscopy and magnetic measurements using a SQUID magnetometer link this effect to the diffusion and incorp...

Journal ArticleDOI
TL;DR: The synthesized novel ZIF-8 membranes displayed unprecedented high CO( 2) permeances and relatively high separation indexes for equimolar mixtures of CO(2) and CH(4) and the presence of small, highly crystalline, microporous crystals led to continuous thin membranes.
Abstract: ZIF-8 membranes, a type of zeolite imidazolate framework, were synthesized by secondary seeded growth on tubular α-Al2O3 porous supports. The presence of small, highly crystalline, microporous crystals with narrow particle size distribution led to continuous thin membranes. The synthesized novel ZIF-8 membranes displayed unprecedented high CO2 permeances and relatively high separation indexes for equimolar mixtures of CO2 and CH4.

Journal ArticleDOI
TL;DR: Mesoporous carbon nitride polymer can function as a metal-free photocatalyst to activate O(2) for the selective oxidation of benzyl alcohols with visible light, avoiding the cost, toxicity, and purification problems associated with corresponding transition-metal systems.
Abstract: Mesoporous carbon nitride (mpg-C3N4) polymer can function as a metal-free photocatalyst to activate O2 for the selective oxidation of benzyl alcohols with visible light, avoiding the cost, toxicity, and purification problems associated with corresponding transition-metal systems. By combining the surface basicity and semiconductor functions of mpg-C3N4, the photocatalytic system can realize a high catalytic selectivity to generate benzaldehyde. The metal-free photocatalytic system also selectively converts other alcohol substrates to their corresponding aldehydes/ketones, demonstrating a potential pathway of accessing traditional mild radical chemistry with nitroxyl radicals.

Journal ArticleDOI
TL;DR: C cyanostilbene-based highly luminescent molecular sheets which exhibit two-color fluorescence switching in response to pressure, temperature, and solvent vapor are reported, which provides a novel concept of rewritable fluorescent optical recording media.
Abstract: Color tuning and switching of the solid-state luminescence of organic materials are attractive subjects for both the fundamental research and practical applications such as optical recording. We report herein cyanostilbene-based highly luminescent molecular sheets which exhibit two-color fluorescence switching in response to pressure, temperature, and solvent vapor. The origin for the multistimuli luminescence switching is the two-directional shear-sliding capability of molecular sheets, which are formed via intermolecular multiple C−H···N and C−H···O hydrogen bonds. The resulting two distinctive crystal phases are promoted by different modes of local dipole coupling, which cause a substantial alternation of π−π overlap. These changes can be directly correlated with the subsequent intermolecular excitonic and excimeric coupling in both phases, as demonstrated by an in-depth theory-assisted spectroscopic and structural study. Finally, we have prepared a first device demonstrator for rewritable fluorescent ...

Journal ArticleDOI
TL;DR: Graphene oxide can be reduced and decorated by bovine serum albumin at suitable pH and temperature and are ideal templates for highly efficient assembly of a variety of nanoparticles with dramatically different compositions, sizes, shapes, and properties.
Abstract: Graphene oxide (GO) can be reduced and decorated by bovine serum albumin (BSA) at suitable pH and temperature. The resulting bioconjugates between BSA and GO or reduced GO are ideal templates for highly efficient assembly of a variety of nanoparticles with dramatically different compositions, sizes, shapes, and properties. This methodology offers a great chance for investigations on the structure−performance relationship of hybrid nanomaterials toward combinatorial material design aiming at special functions and applications.

Journal ArticleDOI
TL;DR: A auxiliary-directed, palladium-catalyzed beta-arylation and alkylation of sp(3) and sp(2) C-H bonds in carboxylic acid derivatives can be developed and some functional group tolerance is observed and amino- and hydroxy-acid derivativesCan be functionalized.
Abstract: We have developed a method for auxiliary-directed, palladium-catalyzed β-arylation and alkylation of sp3 and sp2 C−H bonds in carboxylic acid derivatives. The method employs a carboxylic acid 2-methylthioaniline- or 8-aminoquinoline amide substrate, aryl or alkyl iodide coupling partner, palladium acetate catalyst, and an inorganic base. By employing 2-methylthioaniline auxiliary, selective monoarylation of primary sp3 C−H bonds can be achieved. If arylation of secondary sp3 C−H bonds is desired, 8-aminoquinoline auxiliary may be used. For alkylation of sp3 and sp2 C−H bonds, 8-aminoquinoline auxiliary affords the best results. Some functional group tolerance is observed and amino- and hydroxy-acid derivatives can be functionalized. Preliminary mechanistic studies have been performed. A palladacycle intermediate has been isolated, characterized by X-ray crystallography, and its reactions have been studied.

Journal ArticleDOI
TL;DR: A new low-band-gap thieno[3,4-c]pyrrole-4,6-dione-based copolymer, PBDTTPD, has been designed and synthesized and demonstrated a power conversion efficiency of 5.5% in a bulk-heterojunction photovoltaic device having an active area of 1.0 cm(2).
Abstract: A new low-band-gap thieno[3,4-c]pyrrole-4,6-dione-based copolymer, PBDTTPD, has been designed and synthesized PBDTTPD is soluble in chloroform or o-dichlorobenzene upon heating and shows a broad absorption in the visible region The HOMO and LUMO energy levels were estimated to be at −556 and −375 eV, respectively These electrochemical measurements fit well with an optical bandgap of 18 eV When blended with PC71BM, this polymer demonstrated a power conversion efficiency of 55% in a bulk-heterojunction photovoltaic device having an active area of 10 cm2