Although considerable progress has been made in direct synthesis gas (syngas) conversion to light olefins (C2(=)-C4(=)) via Fischer-Tropsch synthesis (FTS), the wide product distribution remains a challenge, with a theoretical limit of only 58% for C2-C4 hydrocarbons. We present a process that reaches C2(=)-C4(=) selectivity as high as 80% and C2-C4 94% at carbon monoxide (CO) conversion of 17%. This is enabled by a bifunctional catalyst affording two types of active sites with complementary properties. The partially reduced oxide surface (ZnCrO(x)) activates CO and H2, and C-C coupling is subsequently manipulated within the confined acidic pores of zeolites. No obvious deactivation is observed within 110 hours. Furthermore, this composite catalyst and the process may allow use of coal- and biomass-derived syngas with a low H2/CO ratio.

Engineering robust protein production and purification of correctly folded biotherapeutic proteins in cell-based systems is often challenging due to the requirements for maintaining complex cellular networks for cell viability and the need to develop associated downstream processes that reproducibly yield biopharmaceutical products with high product quality. Here, we present an alternative Escherichia coli-based open cell-free synthesis (OCFS) system that is optimized for predictable high-yield protein synthesis and folding at any scale with straightforward downstream purification processes. We describe how the linear scalability of OCFS allows rapid process optimization of parameters affecting extract activation, gene sequence optimization, and redox folding conditions for disulfide bond formation at microliter scales. Efficient and predictable high-level protein production can then be achieved using batch processes in standard bioreactors. We show how a fully bioactive protein produced by OCFS from optimized frozen extract can be purified directly using a streamlined purification process that yields a biologically active cytokine, human granulocyte-macrophage colony-stimulating factor, produced at titers of 700 mg/L in 10 h. These results represent a milestone for in vitro protein synthesis, with potential for the cGMP production of disulfide-bonded biotherapeutic proteins. Biotechnol. Bioeng. 2011; 108:1570–1578. © 2011 Wiley Periodicals, Inc.

Improving the catalytic selectivity of Pd catalysts is of key importance for various industrial processes and remains a challenge so far. Given the unique properties of single-atom catalysts, isolating contiguous Pd atoms into a single-Pd site with another metal to form intermetallic structures is an effective way to endow Pd with high catalytic selectivity and to stabilize the single site with the intermetallic structures. Based on density functional theory modeling, we demonstrate that the (110) surface of Pm3̅m PdIn with single-atom Pd sites shows high selectivity for semihydrogenation of acetylene, whereas the (111) surface of P4/mmm PdIn with Pd trimer sites shows low selectivity. This idea has been further validated by experimental results that intermetallic PdIn nanocrystals mainly exposing the (110) surface exhibit much higher selectivity for acetylene hydrogenation than PdIn nanocrystals mainly exposing the (111) surface (92% vs 21% ethylene selectivity at 90 °C). This work provides insight for rational design of bimetallic metal catalysts with specific catalytic properties.

Nanocrystals prepared in organic media can be easily self-assembled into close-packed hexagonal monolayers on solvent evaporation for various applications. However, they usually rely on the use of organometallic precursors that are soluble in organic solvents. Herein we report a general protocol to transfer metal ions from an aqueous solution to an organic medium, which involves mixing the aqueous solution of metal ions with an ethanolic solution of dodecylamine (DDA), and extracting the coordinating compounds formed between the metal ions and DDA into toluene. This approach could be applied towards transferring a wide variety of transition-metal ions with an efficiency of >95%, and enables the synthesis of a variety of metallic and semiconductor nanocrystals to be carried out in an organic medium using relatively inexpensive water-soluble metal salts as starting materials. This protocol could be easily extended to synthesize a variety of heterogeneous semiconductor/noble-metal hybrids and to nanocomposites with multiple functionalities.

The key of syngas (a mixture of CO and H2) chemistry lies in controlled dissociative activation of CO and C–C coupling. We demonstrate here that a bifunctional catalyst of partially reducible manganese oxide in combination with SAPO-34 catalyzes the selective formation of light olefins, which validates the generality of the OX-ZEO (oxide-zeolite) concept for syngas conversion. Results from in situ ambient-pressure X-ray photoelectron spectroscopy, infrared spectroscopy, and temperature-programmed surface reactions reveal the critical role of oxygen vacancies on the oxide surface, where CO dissociates and is converted into surface carbonate and carbon species. They are converted to CO2 and CH x in the presence of H2. The limited C–C coupling and hydrogenation activities of MnO enable the reaction selectivity to be controlled by the confined pores of SAPO-34. Thus, a selectivity of light olefins up to 80% is achieved, far beyond the limitation of Anderson–Shultz–Flory distribution. These findings open up possibilities to explore other active metal oxides for more efficient syngas conversion.

As nanoparticle syntheses in aqueous and organic systems have their own merits and drawbacks, specific applications may call for the transfer of newly formed nanoparticles from a polar to a non-polar environment (or vice versa) after synthesis. This critical review focuses on the application of phase transfer in nanoparticle synthesis, and features core-shell structures in bimetallic nanoparticles, replacement reactions in organic media, and catalytic properties of various nanostructures. It also describes the reversible organic and aqueous phase transfer of semiconductor and metallic nanoparticles for biological applications, and the use of phase transfer in depositing noble metals on semiconductor nanoparticles (258 references).

Core-shell Au-Pt nanoparticles with intimate contact of Pt and Au were prepared by a displacement reaction without formation of monometallic Au nanoparticles. The Au-Pt nanoparticles were dispersed on carbon (Au@Pt/C) and were used to catalyze methanol electrooxidation in acidic solutions at room temperature. The core-shell nanostructure was confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy, and specific catalytic activities were evaluated by CO anodic stripping voltammetry in 0.5 M H(2)SO(4) and by cyclic voltammetry in 1 M CH(3)OH + 0.5 M H(2)SO(4). The Au@Pt/C catalyst demonstrated enhanced specific activity in methanol electrooxidation and showed multiple CO stripping peaks which were all negatively shifted with respect to a similarly prepared Ag@Pt/C catalyst. The activity enhancement is attributed to the presence of Au underneath a very thin Pt shell where electron exchange between Au and Pt had promoted the formation of active oxygen species on Pt, which facilitated the removal of inhibiting CO-like reaction intermediates.

Besides the more conventional hybrid nanomaterials, for example, core-shell, [1][2][3][4] alloy, [5][6][7] and bimetallic heterostructures, [8][9][10][11] there has been increasing interest devoted towards the development of semiconductor-metal nanocomposites that consist of different classes of materials with coherent interfaces. This type of nanostructure combines materials with distinctly different physical and chemical properties to yield a unique hybrid nanosystem with multifunctional capabilities and tunable or enhanced properties that may not be attainable otherwise. [12] The early studies of semiconductor-metal nanocomposites involved different metals (e.g. gold, silver, and platinum) deposited on or doped in TiO 2 powders for photocatalytic applications. [13][14][15][16][17][18][19] In these structures, the metal domain induces the charge equilibrium in photoexcited TiO 2 nanocrystals, thus affecting the energetics of the nanocomposites by shifting the Fermi level to more negative potentials. The shift in Fermi level is indicative of improved charge separation in TiO 2 -metal systems and is effective towards enhancing the efficiency of photocatalysis. [20,21] In 2004, Banin and co-workers made a breakthrough in semiconductor-metal nanocomposites.[22] They demonstrated a solution synthesis for nanohybrids by the selective growth of gold tips on the apexes of hexagonal-phase CdSe nanorods at room temperature. The novel nanostructures displayed modified optical properties arising from the strong coupling between the gold and semiconductor components. The gold tips showed increased conductivity and selective chemical affinity for forming self-assembled chains of rods. The architecture of these nanostructures was qualitatively similar to bifunctional molecules such as dithiols, which provide twosided chemical connectivity for self-assembly and for electrical devices and contacting points for colloidal nanorods and tetrapods. These researchers later reported the synthesis of asymmetric semiconductor-metal heterostructures in which gold was grown on one side of CdSe nanocrystalline rods and dots. Theoretical modeling and experimental analysis showed that the one-sided nanocomposites were transformed from the two-sided architectures through a ripening process. [23] Subsequently, various approaches were developed for the synthesis of semiconductor-metal nanocomposites (e.g. ZnO-Ag, [24,25] CdS-Au, [26,27] InAs-Au, [28] TiO 2 -Co, [29] PbSAu, [30][31][32][33][34] Ag 2 S-Au, [35] and semiconductor-Pt systems [36][37][38][39] ) by anisotropic growth of metals on semiconductors through reduction, physical deposition, or photochemistry.We recently presented a general protocol for transferring the transition-metal ions from water to an organic medium using an ethanol-mediated method, which was extended to synthesize a wide variety of heterogeneous semiconductornoble-metal nanocomposites. [40] In another study, we synthesized three different types of semiconductor-Au nanocomposites (CdS-Au, CdSe-Au, and PbS-Au), which d...