The key operating characteristics of biofuel cells, high energy density and low power delivery, make them ideal power choices for military, industrial, and niche wireless sensor network applications. There is virtually universal demand for higher energy power supplies for wireless sensors to enable longer operation, more frequent data capture, and higher bandwidth sensing techniques such as video. Advanced biofuel cell technology has been demonstrated for such applications that is capable of 2 -4Â increase in energy density compared to incumbent batteries of a similar size.

We report a rectangular charge density wave (CDW) phase in strained 1T-VSe2 thin films synthesized by molecular beam epitaxy on c-sapphire substrates. The observed CDW structure exhibits an unconventional rectangular 4a×√3a periodicity, as opposed to the previously reported hexagonal 4a×4a structure in bulk crystals and exfoliated thin layered samples. Tunneling spectroscopy shows a strong modulation of the local density of states of the same 4a×√3a CDW periodicity and an energy gap of 2ΔCDW = (9.1 ± 0.1) meV. The CDW energy gap evolves into a full gap at temperatures below 500 mK, indicating a transition to an insulating phase at ultra-low temperatures. First-principles calculations confirm the stability of both 4a×4a and 4a×√3a structures arising from soft modes in the phonon dispersion. The unconventional structure becomes preferred in the presence of strain, in agreement with experimental findings.

Although biofuel cell research has progressed over the past decade, there were still problems with employing enzymes at air-breathing cathodes, because enzymes need to remain hydrated and most enzyme reactions occur in solution and not in gas phase. This research details an approach to the development of an air-breathing biocathode employing direct electron transfer. This laccase biocathode is studied in two different fuel cell configurations: a proton exchange membrane hydrogen/air fuel cell and a direct methanol fuel cell (DMFC) with an anion exchange membrane. The laccase from the Rhus vernificera biocathode with an enzyme loading of 0.224mg/cm2 provides fuel crossover tolerance and provides a high operational current density of 50.0mA/cm2 and a maximum power density of 8.5mW/cm2 in a 40% methanol DMFC. The laccase biocathode shows a lifetime of 290 h in a DMFC. The hydrogen/air fuel cell provides a stable current for a total of 350 discontinuous hours when operated for 8 h daily.

Improving the power conversion efficiency of photovoltaic (PV) devices is challenging because the generation, separation and collection of electron-hole pairs are strongly dependent on details of the nanoscale chemical composition and defects which are often poorly known. In this work, two novel scanning probe nano-spectroscopy techniques, direct-transmission near-field scanning optical microscopy (dt-NSOM) and photothermal induced resonance (PTIR), are implemented to probe the distribution of defects and the bandgap variation in thin lamellae extracted from polycrystalline CdTe PV devices. dt-NSOM provides high-contrast spatially-resolved maps of light transmitted through the sample at selected wavelengths. PTIR provides absorption maps and spectra over a broad spectral range, from visible to mid-infrared. Results show variation of the bandgap through the CdTe thickness and from grain to grain that is spatially uncorrelated with the distributions of shallow and deep defects.