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Geobacter sulfurreducensis of interest for the highest efficiency of power generation and extremely long extracellular electron transfer (EET) between the bacterium and electrodes. Despite more than 15 years of intensive molecular biological research, there is still no clear answer which molecules are responsible for these processes. In the present work, we look at the problem from another (atomic) perspective and identify the location and shape of the compounds that are known to be conductive, particularly those containing Fe atoms. By using highly sophisticated energy dispersive X-ray spectroscopy combined with high-angle annular dark-field transmission electron microscopy enabling detection, identification, and localization of chemical compounds on the surface at nearly atomic spatial resolution, we analyze Fe spatial distribution within the G. sulfurreducenscommunity. We discover the presence of small Fe-containing particles on the surface of the bacterium cells. The size of the particles (diameter 5.6 nm) is highly reproducible and comparable with the size of a single protein. The particles cover about 2% of the cell surface, which is similar to that expected for molecular conductors responsible for electron transfer through the bacterium cell wall. We find that G. sulfurreducensfilaments (“bacterial molecular wires”) also contain Fe atoms in their bundles. We observe that the bacterium enable changing the distance between the Fe-containing bundles in the filaments from separated to attached (the latter is needed for the efficient electron transfer between the Fe-containing particles), depending on the bacterium metabolic activity and attachment to extracellular substrates. These results are consistent with the recently published research about the role of Fe atoms in protein molecular conductance (Phys. Chem. Chem. Phys., 2018, 20, 14072−14081) and show what type of Fe-containing particles are involved in the bacterial extracellular communication. They can be used for the design and construction of artificial biomolecular wires and bioinorganic interfaces.

Antibacterial copper–hydroxyapatite (Cu–HA) composite coatings on titanium were synthesized using a novel process consisting of two consecutive electrochemical reactions. In the first stage, HA nanocrystals were grown on titanium using the cathodic electrolytic synthesis. The HA-coated titanium was then used as the cathode in a second reaction stage to electrochemically reduce Cu2+ions in solution to metallic Cu nanoparticles. Reaction conditions were found that result in nanoscale Cu particles growing on the surface of the HA crystals. The two-stage synthesis allows facile control of copper content in the HA coatings. Antibacterial activity was measured by culturing Escherichia coli(Gram-negative) and Staphylococcus aureus(Gram-positive) in the presence of coatings having varying copper contents. The coatings displayed copper concentration-dependent antibacterial activity against both types of bacteria, likely due to the slow release of copper ions from the coatings. The observation of antibacterial activity from a relatively low loading of copper on the bioactive HA support suggests that multifunctional implant coatings can be developed to supplement or supplant prophylactic antibiotics used in implant surgery that are responsible for creating resistant bacteria strains.

Fast recombination of photogenerated charge carriers in titanium dioxide (TiO2) remains a challenging issue, limiting the photocatalytic activity. This study demonstrates increased photocatalytic performance of TiO2nanoparticles supported on electrically polarized hydroxyapatite (HA) films. Dense and thermally stable yttrium and fluorine co-doped HA films with giant internal polarization were synthesized as photocatalyst supports. TiO2nanoparticles deposited on the support were then used to catalyze the photochemical reduction of aqueous silver ions to produce silver nanoparticles. It was found that significantly more silver nanoparticles were produced on polarized HA supports than on depolarized HA supports. In addition, the photodegradation of methyl orange with TiO2nanoparticles on polarized HA supports was found to be much faster than with TiO2nanoparticles on depolarized HA supports. It is proposed that separation of photogenerated electrons and holes in TiO nanoparticles is promoted by the internal polarization of the HA support, and consequently, the recombination of charge carriers is mitigated. The results imply that materials with large internal polarization can be used in strategies for enhancing quantum efficiency of photocatalysts.

A new approach to enhancing proton conductivity of ceramics is demonstrated by aligning proton conductive pathways and eliminating resistive grain boundaries. Hydroxyapatite (HAP) membranes are synthesized by multistage crystallization onto palladium. The synthesis involves three steps: electrochemical deposition of HAP seeds, secondary hydrothermal crystallization onto the seed layer to promote c‐axis growth normal to the substrate, and tertiary hydrothermal crystallization to promote a‐axis growth to fill the gaps between the aligned crystals. The c‐axis alignment with crystal domains spanning the membrane thickness significantly enhances proton conduction since protons are primarily transported along the c‐axes of HAP crystals. The novel HAP membranes display proton conductivity almost four orders of magnitude higher than traditional sintered HAP ceramics. The HAP membranes on palladium hydrogen membrane substrates hold promise for use in intermediate‐temperature fuel cells, chemical sensors, and other devices. The synthesis approach presented may also be applied to other ion‐conducting membrane materials to enhance transport properties.

Novel rod-shaped calcite crystals are formed by precipitation from cetyltrimethylammonium bromide (CTAB)/1-pentanol/cyclohexane microemulsions containing calcium chloride and ammonium carbonate. The calcium carbonate initially precipitates as hexagon-shaped vaterite crystals. The vaterite crystals transform to unusual rod-shaped calcite crystals over several days. The rod-shaped calcite crystals are prismatic, with the longest crystal axis displaying (110) crystal faces. A possible mechanism of crystal growth is discussed. The elongated shape of the crystals facilitates the assembly into hierarchical structures and can allow the crystals to be used as templates for fabricating advanced materials.

A double conjugate addition sequence anneals heterocyclic rings onto a 2-alkyl quinone monoketal intermediate. This operation, reminiscent of a Barco annulation, proceeds in excellent overall yield. The new chemistry offers interesting opportunities in alkaloid synthesis.

An efficient method to oxidize an olefin to the less substituted carbonyl compound is described. This new methodology utilizes borane dimethyl sulfide followed by tetrapropylammonium perruthenate N-methylmorpholine N-oxide to oxidize the resulting alkylborane.

•The performance of two liquid cooling designs for lithium-ion battery packs was investigated.•The effects of channel number, hole diameter, mass flow rate and inlet locations are investigated.•This study shows the maximum temperature difference of the CCHS is significantly less than the MCC.•Considering maximum temperature and temperature uniformity, the MCC design provides superior performance to the CCHS.

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The Pd‐catalyzed aerobic alcohol oxidations developed on a small scale are translated into a scalable flow‐based process.

The inside cover image showns a side view of a hydroxyapatite membrane with aligned crystal domains synthesized as described by Liu et al. on page 3941. The microstructure of the membrane is engineered to promote proton transport through orientation of the proton conducting paths. These novel structures have significantly higher proton conductivity than traditional hydroxyapatite ceramics and may offer improved performance in intermediate temperature fuel cells.

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