High precision attachment of silver nanoparticles on AFM tips by dielectrophoresis.

AFM tips are modified with silver nanoparticles using an AC electrical field. The used technique works with sub-micron precision and also does not require chemical modification of the tip. Based on the electrical parameters applied in the process, particle density and particle position on the apex of the tip can be adjusted. The feasibility of the method is proven by subsequent tip-enhanced Raman spectroscopy (TERS) measurements using the fabricated tips as a measurement probe. Since this modification process itself does not require any lithographic processing, the technique can be easily adapted to modify AFM tips with a variety of nanostructures with pre-defined properties, while being parallelizable for a potential commercial application.

Producing high-strength liquor from mesophilic batch acidification of chicken manure.

This report describes the results from anaerobic batch acidification of chicken manure as a mono-substrate studied under mesophilic conditions. The manure was diluted with tap water to prevent methane formation during acidification and to improve mixing conditions by reducing fluid viscosity; no anaerobic digester sludge has been added as an inoculum. Highest acidification rates were measured at concentrations of 10 gVS L⁻¹ and 20 gVS L⁻¹; the pH value remained high (pH 6.9-7.9) throughout the test duration and unexpected fast methane formation was observed in every single batch. At substrate concentrations of 10 gVS L⁻¹ there was a remarkable methane formation representing a value of 82% of the respective biochemical methane potential of chicken manure. Increasing substrate concentrations did not supress methane formation but impaired acid production. Consequently, the liquor cannot be stored over longer periods but should immediately be used in a digestion process.