Silver in the linings The bacterium Shewanella oneidensis is well known to use extracellular electron sinks, metal oxides and ions in nature or electrodes when cultured in a fuel cell, to power the catabolism of organic material. However, the power density of microbial fuel cells has been limited by various factors that are mostly related to connecting the microbes to the anode. Cao et al . found that a reduced graphene oxide–silver nanoparticle anode circumvents some of these issues, providing a substantial increase in current and power density (see the Perspective by Gaffney and Minteer). Electron microscopy revealed silver nanoparticles embedded or attached to the outer cell membrane, possibly facilitating electron transfer from internal electron carriers to the anode. —MAF

A solid-state thermoelectric device is attractive for diverse technological areas such as cooling, power generation and waste heat recovery with unique advantages of quiet operation, zero hazardous emissions, and long lifetime. With the rapid growth of flexible electronics and miniature sensors, the low-cost flexible thermoelectric energy harvester is highly desired as a potential power supply. Herein, a flexible thermoelectric copper selenide (Cu Se) thin film, consisting of earth-abundant elements, is reported. The thin film is fabricated by a low-cost and scalable spin coating process using ink solution with a truly soluble precursor. The Cu Se thin film exhibits a power factor of 0.62 mW/(m K ) at 684 K on rigid Al O substrate and 0.46 mW/(m K ) at 664 K on flexible polyimide substrate, which is much higher than the values obtained from other solution processed Cu Se thin films (<0.1 mW/(m K )) and among the highest values reported in all flexible thermoelectric films to date (≈0.5 mW/(m K )). Additionally, the fabricated thin film shows great promise to be integrated with the flexible electronic devices, with negligible performance change after 1000 bending cycles. Together, the study demonstrates a low-cost and scalable pathway to high-performance flexible thin film thermoelectric devices from relatively earth-abundant elements.

The development of future sustainable energy technologies relies critically on our understanding of electrocatalytic reactions occurring at the electrode–electrolyte interfaces, and the identification of key reaction promoters and inhibitors. Here we present a systematic in situ nanoelectronic measurement of anionic surface adsorptions (sulfates, halides, and cyanides) on ultrathin platinum nanowires during active electrochemical processes, probing their competitive adsorption behavior with oxygenated species and correlating them to the electrokinetics of the oxygen reduction reaction (ORR). The competitive anionic adsorption features obtained from our studies provide fundamental insight into the surface poisoning of Pt-catalyzed ORR kinetics by various anionic species. Particularly, the unique nanoelectronic approach enables highly sensitive characterization of anionic adsorption and opens an efficient pathway to address the practical poisoning issue (at trace level contaminations) from a fundamental perspective. Through the identified nanoelectronic indicators, we further demonstrate that rationally designed competitive anionic adsorption may provide improved poisoning resistance, leading to performance (activity and lifetime) enhancement of energy conversion devices.

The electrical conductivity measured in Shewanella and Geobacter spp. is an intriguing physical property that is the fundamental basis for possible extracellular electron transport (EET) pathways. There is considerable debate regarding the origins of the electrical conductivity reported in these microbial cellular structures, which is essential for deciphering the EET mechanism. Here, we report systematic on-chip nanoelectronic investigations of both Shewanella and Geobacter spp. under physiological conditions to elucidate the complex basis of electrical conductivity of both individual microbial cells and biofilms. Concurrent electrical and electrochemical measurements of living Shewanella at both few-cell and the biofilm levels indicate that the apparent electrical conductivity can be traced to electrochemical-based electron transfer at the cell/electrode interface. We further show that similar results and conclusions apply to the Geobacter spp. Taken together, our study offers important insights into previously proposed physical models regarding microbial conductivities as well as EET pathways for Shewanella and Geobacter spp.

A low-cost, non-toxic, environmentally friendly, and solution-processed new oxide-based semiconducting material (Sn 1Àx Co x O 2 ) was developed as an absorption material for all oxide solar cell fabrication in this work. The newly developed n-type cobalt-doped tin oxide (n-Sn 1Àx Co x O 2 ) nanoparticles and p-type copper oxide (p-Cu 2 O) nanostructures were successfully synthesized via a lowtemperature solution process. Combined with the use of non-vacuum spray and hot-press processes, the n-Sn 1Àx Co x O 2 /p-Cu 2 O heterojunction solar cells exhibit low-cost and large-scale fabrication advantages. The highest power conversion efficiency (PCE) of 1.2% can be obtained from the solar cells with n-Sn 0.86 Co 0.14 O 2 /p-Cu 2 O, under AM 1.5 illumination, a noteworthy improvement in solutionprocessed all-oxide-based nanostructures heterojunction solar cells.Responding to the threats of global warming and climate change urges the development of environmentally friendly and low-cost solar cell technologies. 1,2 In addition, it is critical to develop earth-abundant absorption materials for solar cell applications. Currently, the mainstream PV market is dominated by crystalline silicon-based solar cells. 3 Although crystalline silicon-based solar cells provide high efficiency advantages, the cost due to vacuum process and limitation on large-scale production still make it hard to compete with the electricity cost of fossil energy. [3][4][5][6][7] Consequently, in addition to the demands of low-cost, and earth-abundant/non-toxic materials, a non-vacuum and large-scale process for solar cell fabrication is needed for sustainable power generation. 8,9 In order to provide solutions for low-cost and large-scale applications, spray and solution processes for new absorber layers were developed to replace vacuumbased technologies. [8][9][10] The non-vacuum technologies for solar cell fabrications, such as organics, dye-sensitized and oxide-based solar cells, are very attractive because of their potential applications on inexpensive oxide-based solar cells with minimal energy input. [10][11][12] Recently, Cu 2 O, SnO 2 , TiO 2 , CuO, ZnO, AZO and other oxide semiconducting materials were developed for low-cost and large-scale applications.