Peptide-functionalized semiconductor surfaces: strong surface electronic effects from minor alterations to backbone composition

Semiconductor surface electronic properties are shown to be sensitive to subtle changes in the backbone composition of surface-bound dipeptide ligands.</p

Surface Termination Control in Chemically Deposited PbS Films: Nucleation and Growth on GaAs(111)A and GaAs(111)B

This study addresses the question of whether chemically deposited PbS thin films grown on GaAs(111) are affected by the oppositely terminated substrate surfaces, gallium terminated GaAs(111)A and arsenic terminated GaAs(111)B. The differences in PbS film deposition pathway in both cases of substrate surface termination were investigated using X-ray photoelectron spectroscopy (XPS), Raman scattering, and contact potential difference (CPD) measurements. The morphology, microstructure, and crystallographic orientation of the films were studied using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. XPS and CPD measurements indicated that PbS films deposited on oppositely terminated GaAs(111) surfaces possessed corresponding surface terminations, with PbS(111)B obtained on GaAs(111)B and PbS(111)A on GaAs(111)A. Subsequently, different surface oxides were detected by XPS on A and B terminated PbS(111), with lead oxide obtained on PbS(111)A and PbSO3 obtained on PbS(111)B. Moreover, CPD measurements revealed that PbS(111)A shows a 40 mV smaller work function than PbS(111)B surfaces, therefore emphasizing the importance of polarity and surface termination control for heterojunction based electronic devices

Filling the Green Gap of a Megadalton Photosystem I Complex by Conjugation of Organic Dyes

Photosynthesis is Nature’s major process for converting solar into chemical energy. One of the key players in this process is the multiprotein complex photosystem I (PSI) that through absorption of incident photons enables electron transfer, which makes this protein attractive for applications in bioinspired photoactive hybrid materials. However, the efficiency of PSI is still limited by its poor absorption in the green part of the solar spectrum. Inspired by the existence of natural phycobilisome light-harvesting antennae, we have widened the absorption spectrum of PSI by covalent attachment of synthetic dyes to the protein backbone. Steady-state and time-resolved photoluminescence reveal that energy transfer occurs from these dyes to PSI. It is shown by oxygen-consumption measurements that subsequent charge generation is substantially enhanced under broad and narrow band excitation. Ultimately, surface photovoltage (SPV) experiments prove the enhanced activity of dye-modified PSI even in the solid state