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Abstract We directly measure the electric dipole of InN quantum dots (QDs) grown on In-rich InGaN layers by Kelvin probe force microscopy. This significantly advances the understanding of the superior catalytic performance of InN/InGaN QDs in ion- and biosensing and in photoelectrochemical hydrogen generation by water splitting and the understanding of the important third-generation InGaN semiconductor surface in general. The positive surface photovoltage (SPV) gives an outward QD dipole with dipole potential of the order of 150 mV, in agreement with previous calculations. After HCl-etching, to complement the determination of the electric dipole, a giant negative SPV of −2.4 V, significantly larger than the InGaN bandgap energy, is discovered. This giant SPV is assigned to a large inward electric dipole, associated with the appearance of holes, matching the original QD lateral size and density. Such surprising result points towards unique photovoltaic effects and photosensitivity.

We present a basic, comprehensive study of the electrocatalytic activity of epitaxial InN/InGaN quantum dots (QDs) by cyclic voltammetry, electrochemical impedance spectroscopy, linear sweep voltammetry and capacitance-voltage measurements, using the ferro/ferricyanide redox probe. Key is the direct proof of the dependence of the catalytic activity on the QD structural properties and of the existence and overall tunability of high positive surface charge on the QDs being in origin of the catalytic activity together with the zero-dimensional electronic properties. This fundamental assessment paves the way to fine-tuning the artificial QD structure as efficient catalyst to further boost the performance of biosensors and photoanodes for solar hydrogen generation. Keywords: Quantum dots, InN, InGaN, Catalysis

The cost of dairy manure treatment and bedding material purchase increases the operating cost of the dairy farm. Membrane-covered aerobic fermentation system has been widely used for dealing with dairy manure and recycling the final product as bedding material. However, the microbial safety in each processing step is still uncertain. To better understand the bacterial community dynamics during the whole bedding conversion process, a full-chain and large-scale experiment including 16-day membrane-covered aerobic fermentation and 11-day bedding material application was conducted. The results showed that the pile temperatures in the fermentation stage rapidly increased to 80°C and maintained >50°C for more than 11 days and the use of fermentation product as bedding material provided cows with a stable and comfortable bedding environment. The Chao1 and Shannon index decreased at the end of the fermentation stage and remained stable in the application stage, indicating that membrane-covered aerobic fermentation effectively killed some pathogenic bacteria and guaranteed both the maturity and stability of the final product. The dominant bacteria in the fermentation stage were Acinetobacter, Thermus, and Rhodothermus at genus level. Seven common potential pathogens of mastitis (Staphylococcus, Enterococcus, Serratia, Pseudomonas, Corynebacterium, Mycobacterium, and Bacillus) were found at the end of fermentation stage but the relative abundance was low (0.0025%-0.2727%). The dominant bacteria in the application stage mainly included Acinetobacter, Pseudomonas, and Flavobacterium at the genus level. The relative abundance of Pseudomonas increased in the application stage, which was a reminder to the dairy farm to pay attention to the disinfection and timely replacement of bedding material to prevent the occurrence of dairy mastitis. The results of this study contributed deep understanding of the microorganism-driven bedding conversion process and provide practical guidance and cautions for the bedding materials application. [ABSTRACT FROM AUTHOR]

We demonstrate an all-solid-state potentiometric sensor constructed from solid-state InN/InGaN sensing- and reference electrodes with the epitaxial InN/InGaN layers directly grown on Si substrates. The sensor, evaluated in KCl aqueous solution, exhibits super-Nernstian sensitivity of −78 mV/decade with good linearity for concentrations of 0.01–1 M, which is the physiologically relevant range. Good stability and re-usability are demonstrated by a long-time drift below 0.2 mV h−1 and standard deviation of 8 mV for repeated measurements over 10 d. These properties fulfil the requirements for compact, robust and highly sensitive all-solid-state sensors and sensor arrays. [ABSTRACT FROM AUTHOR]

We introduce cyclic voltammetry (CV) with dissolved, chemically stable electrolytes as a sensitive, non-destructive and fast method for the analysis of the surface morphology of InGaN epitaxial layers and nanostructures grown on silicon. The surface area is probed by the electric double layer capacitance (EDLC) formed upon attachment of ions in solution under close-to-equilibrium conditions. The dynamics of the measured EDLC as a function of scan rate characterizes the nano-scale surface morphology. The dynamics of the measured EDLC follows a power law dependence on the scan rate. The exponent clearly correlates with the RMS surface roughness at the nano/atomic scale deduced from atomic force microscopy. CV is thus complementary to other established methods for the morphological analysis of epitaxial layers in general. [ABSTRACT FROM AUTHOR]