Peptide adhesion on semiconductors is quantitatively investigated by atomic force microscopy. A selected 12-mer peptide is reproducibly found to adhere to various III−V and group-IV semiconductor surfaces in a substrate-specific way. The observed succession Al 0.98 Ga 0.02 As, Si, Ge, InP, GaP, GaAs in terms of increasing peptide adhesion coefficients is qualitatively explained by the substrate electronegativity and the acidity of the amino acid side chains. It is shown that peptide adhesion is strongly dependent on the amino acid sequence.

We are thankful to Simon Mitternacht for helpful discussions regarding the peptide model and C. Dammann for peptide synthesis and purification. MB thanks the DFG (German Science * To whom correspondence should be addressed Foundation) and the Wenner-Gren Foundation (Sweden) for research fellowships, and the German-Israel "Umbrella" program for support. MB, AI, and WJ are grateful for support by the German-Swedish DAAD-STINT Personnel Exchange Programme. This work is also partially funded by the DFG under Grant Nos. JA 483/24-1/2/3, the Leipzig Graduate School of Excellence "BuildMoNa", TR 67 A4, and the German-French DFH-UFA PhD College under Grant No. CDFA-02-07. Supercomputer time at the John von Neumann Institute for Computing (NIC), Forschungszentrum Jülich, is acknowledged (Grant Nos. hlz11 and jiff39).

Peptide adhesion on semiconductor surfaces is quantitatively investigated by atomic force microscopy. The selected peptides are shown to cluster at the surface, with the larger, higher, and softer clusters appearing on the surfaces with lower peptide adhesion. Average cluster diameters vary from 40 nm on GaAs (100) to 300 nm on Si (100). Direct adhesion of the peptides to the surface competes with forming molecular aggregates that offer an overall reduced surface contact.

We report the electrically pumped emission of midinfrared (MIR) radiation from bipolar quantum-dot lasers during near-infrared lasing. The MIR spectrum exhibits a peak at 16 μm and is dominantly TM polarized. The MIR intensity exhibits a superlinear dependence on the injection; a maximum MIR power of 0.1 μW per facet was realized. Such a device is also modeled theoretically, and conditions for MIR lasing are predicted.

No abstract