Nanoarray Structures for Artificial Photosynthesis.

Conversion and storage of solar energy into fuels and chemicals by artificial photosynthesis has been considered as one of the promising methods to address the global energy crisis. However, it is still far from the practical applications on a large scale. Nanoarray structures that combine the advantages of nanosize and array alignment have demonstrated great potential to improve solar energy conversion efficiency, stability, and selectivity. This article provides a comprehensive review on the utilization of nanoarray structures in artificial photosynthesis of renewable fuels and high value-added chemicals. First, basic principles of solar energy conversion and superiorities of using nanoarray structures in this field are described. Recent research progress on nanoarray structures in both abiotic and abiotic-biotic hybrid systems is then outlined, highlighting contributions to light absorption, charge transport and transfer, and catalytic reactions (including kinetics and selectivity). Finally, conclusions and outlooks on future research directions of nanoarray structures for artificial photosynthesis are presented.

A scalable approach to topographically mediated antimicrobial surfaces based on diamond.

Bio-inspired Topographically Mediated Surfaces (TMSs) based on high aspect ratio nanostructures have recently been attracting significant attention due to their pronounced antimicrobial properties by mechanically disrupting cellular processes. However, scalability of such surfaces is often greatly limited, as most of them rely on micro/nanoscale fabrication techniques. In this report, a cost-effective, scalable, and versatile approach of utilizing diamond nanotechnology for producing TMSs, and using them for limiting the spread of emerging infectious diseases, is introduced. Specifically, diamond-based nanostructured coatings are synthesized in a single-step fabrication process with a densely packed, needle- or spike-like morphology. The antimicrobial proprieties of the diamond nanospike surface are qualitatively and quantitatively analyzed and compared to other surfaces including copper, silicon, and even other diamond surfaces without the nanostructuring. This surface is found to have superior biocidal activity, which is confirmed via scanning electron microscopy images showing definite and widespread destruction of E. coli cells on the diamond nanospike surface. Consistent antimicrobial behavior is also observed on a sample prepared seven years prior to testing date.

Improving the Water Oxidation Efficiency with a Light-Induced Electric Field in Nanograting Photoanodes.

Severe charge recombination in solar water-splitting devices significantly limits their performance. To address this issue, we design a frustum of a cone nanograting configuration by taking the hematite and Au-based thin-film photoanode as a model system, which greatly improves the photoelectrochemical water oxidation activity, affording an approximately 10-fold increase in the photocurrent density at 1.23 V versus the reversible hydrogen electrode compared to the planar counterpart. The surface plasmon polariton-induced electric field in hematite plays a dominant role in efficiency enhancement by facilitating charge separation, thus dramatically increasing the incident photon-to-current efficiency (IPCE) by more than 2 orders of magnitude in the near band gap of hematite. And the relatively weak electric field caused by light scattering in the nanograting structure is responsible for the approximate maximum 20-fold increase in IPCE within a broadband wavelength range. Our scalable strategy can be generalized to other solar energy conversion systems.

Low-Temperature and Fast Kinetics for CO2 Sorption Using Li6WO6 Nanowires.

In this paper, lithium hexaoxotungstate (Li6WO6) nanowires were synthesized via facile solid-state reaction and were tested for CO2 capture applications at both low (<100 °C) and high temperatures (>700 °C). Under dry conditions, the nanowire materials were able to capture CO2 with a weight increment of 12% in only 60 s at an operating temperature of 710 °C. By contrast, under humidified ambience, Li6WO6 nanowires capture CO2 with weight increment of 7.6% at temperatures as low as 30-40 °C within a time-scale of 1 min. It was observed that the CO2 chemisorption in Li6WO6 is favored in the oxygen ambience at higher temperatures and in the presence of water vapor at lower temperatures. Nanowire morphology favors the swift lithium supply to the surface of lithium-rich Li6WO6, thereby enhancing the reaction kinetics and lowering time scales for high capacity adsorption. Overall, high chemisorption capacities, superfast reaction kinetics, wide range of operating temperatures, and reasonably good recyclability make 1-D Li6WO6 materials highly suitable for various CO2 capture applications.

A new nanowire-based lithium hexaoxotungstate anode for lithium-ion batteries.

This study reports one dimensional lithium hexaoxotungstate (Li6WO6), with a diameter in the range of 200-500 nm, as a novel anode material for lithium-ion batteries. The electrochemical performance of lithium hexaoxotungstate was investigated and a discharge capacity of 705 mA h g-1 was achieved after 50 cycles, along with an excellent rate capability. The 1D morphology of the material is believed to provide excellent transport properties, resulting in a high rate capability. The remarkable electrochemical performance of the Li6WO6 nanowires indicates that this new class of anode holds a lot of promise for future deployment in energy storage devices.

Antibacterial Carbon-Based Nanomaterials.

The emergence and global spread of bacterial resistance to currently available antibiotics underscore the urgent need for new alternative antibacterial agents. Recent studies on the application of nanomaterials as antibacterial agents have demonstrated their great potential for management of infectious diseases. Among these antibacterial nanomaterials, carbon-based nanomaterials (CNMs) have attracted much attention due to their unique physicochemical properties and relatively higher biosafety. Here, a comprehensive review of the recent research progress on antibacterial CNMs is provided, starting with a brief description of the different kinds of CNMs with respect to their physicochemical characteristics. Then, a detailed introduction to the various mechanisms underlying antibacterial activity in these materials is given, including physical/mechanical damage, oxidative stress, photothermal/photocatalytic effect, lipid extraction, inhibition of bacterial metabolism, isolation by wrapping, and the synergistic effect when CNMs are used in combination with other antibacterial materials, followed by a summary of the influence of the physicochemical properties of CNMs on their antibacterial activity. Finally, the current challenges and an outlook for the development of more effective and safer antibacterial CNMs are discussed.