Activated Carbons from Hydrochars Prepared in Milk.

Hydrothermal carbonization converts organics in aqueous suspension to a mixture of liquid components and carbon-rich solids (hydrochars), which in turn can be processed into activated carbons. We investigated whether milk could be used as a medium for hydrothermal carbonization, and found that hydrochars prepared from milk, with or without an added fibrous biomass, contained more carbon (particularly aliphatic carbon), less oxygen, and more mineral components than those prepared from fibrous biomass in water. Activated carbons produced from hydrochars generated in milk had lower specific surface areas and CO2 capacities than those from hydrochars formed in water; however, these differences disappeared upon normalizing to the combustible mass of the solid. Thus, in the context of N2 and CO2 uptake on activated carbons, the primary effect of using milk rather than water to form the hydrochar precursor was to contribute inorganic mass that adsorbed little CO2. Nevertheless, some of the activated carbons generated from hydrochars formed in milk had specific CO2 uptake capacities in the normal range for activated carbons prepared by activation in CO2 (here, up to 1.6 mmol g-1 CO2 at 15 kPa and 0 °C). Thus, hydrothermal carbonization could be used to convert waste milk to hydrochars and activated carbons.

Spray pyrolysis of CuIn(S,Se)2 solar cells with 5.9% efficiency: a method to prevent Mo oxidation in ambient atmosphere.

Direct spray pyrolysis to form CuInS2 (CIS) on molybdenum substrate in ambient environment has been a challenge because of the ease of Mo oxidation at low temperatures. MoO2 formation affects the wettability of precursor solution during spray pyrolysis, which degrades the uniformity of CIS film and acts as a resistive layer for carrier transport. In this paper, Mo oxidation was prevented by using excess sulfur in the precursor solution under a gradual heating and spray process. A thin precursor layer was initially deposited as a barrier layer to prevent oxygen adsorption on Mo surface before the temperature was increased further to form polycrystalline CuInS2. The CuIn(S,Se)2 (CISSe) device fabricated from selenization of the spray-pyrolyzed CIS film exhibited a power conversion efficiency (PCE) of 5.9%. The simple spray method proposed here can be used to deposit a variety of Cu-based chalcopyrite precursor to produce high-quality thin film solar cells.

Microlandscaping on a graphene oxide film via localized decoration of Ag nanoparticles.

A direct and facile method for micro-landscaping of Ag nanoparticles on reduced graphene oxide (rGO) is presented. This method employs a focused laser beam to achieve local reduction of Ag(+) ions to Ag NPs by laser irradiation on a GO film that is submerged in AgNO3 solution. Using this method, the Ag nanoparticles can be directly anchored on a rGO film, creating a microlandscape of Ag nanoparticles on the rGO film. In addition, varying the intensity of the laser beam can control the shapes, sizes and distributions of Ag nanoparticles. The resulting hybrid materials exhibit surface enhanced Raman scattering of up to 16 times depending on the size and number density of silver nanoparticles. In addition, the hybrid Ag-rGO material shows superior photoresponse when compared to rGO.

Controllable unzipping for intramolecular junctions of graphene nanoribbons and single-walled carbon nanotubes.

Graphene is often regarded as one of the most promising candidates for future nanoelectronics. As an indispensable component in graphene-based electronics, the formation of junctions with other materials not only provides utility functions and reliable connexions, but can also improve or alter the properties of pristine graphene, opening up possibilities for new applications. Here we demonstrate an intramolecular junction produced by the controllable unzipping of single-walled carbon nanotubes, which combines a graphene nanoribbon and single-walled carbon nanotube in a one-dimensional nanostructure. This junction shows a strong gate-dependent rectifying behaviour. As applications, we demonstrate the use of the junction in prototype directionally dependent field-effect transistors, logic gates and high-performance photodetectors, indicating its potential in future graphene-based electronics and optoelectronics.

CoOOH nanosheet electrodes: Simple fabrication for sensitive electrochemical sensing of hydrogen peroxide and hydrazine.

Cobalt oxyhydroxide, CoOOH, nanosheets were prepared via a surface alkaline treatment of cobalt foil at room temperature without using templates and catalysts. The morphology, chemical composition and structures of the nanosheets were characterized by XRD, FTIR and Raman spectroscopy, FESEM and TEM. These oriented and nanostructured arrays can be used directly as electrodes, thus simplifying the electrode fabrication process, as well as offering advantages such as enhanced electrode-electrolyte contact area, minimum diffusion resistance and direct active material-current collector connection for fast electron transport. The electrode was used as an electrochemical sensor towards non-enzymatic detection of hydrogen peroxide and hydrazine in alkaline solution. The amperometric detection of H(2)O(2) and N(2)H(4) was carried out at low potential (0V and 0.1V). At 0.1V, the amperometric signals are linearly proportional to H(2)O(2) concentration up to 1.6mM (R(2)=0.995), showing a detection limit (S/N=3) of 40µM and a high sensitivity of 99µA mM(-1)cm(-2). For N(2)H(4), the amperometric signals are linearly proportional to concentration up to 1.2mM (R(2)=0.99), showing a detection limit (S/N=3) of 20µM and a high sensitivity of 155µA mM(-1)cm(-2) at 0.1V.