Detection and analysis of spin signal in spin-labeled poly(l-lysine).

In this paper, the authors present the study of spin-labeled poly(l-lysine) biological molecules (polypeptides) using electron paramagnetic resonance, atomic force microscopy, and electron spin noise-scanning tunneling microscopy. In the presented studies, the authors were able to obtain the information about the local distribution of the spin signal emission, and they registered the spectra for the selected area with nanometer resolution. The preparation method of spin-labeled biopolymer, experimental setup, and the procedure of calibration are also described in detail.

Electronic transport properties of individual 4,4'-bis(mercaptoalkyl)-biphenyl derivatives measured in STM-based break junctions.

Electronic transport measurements of single, systematically varied 4,4'-bis(mercaptoalkyl)-biphenyl derivatives (MABP) are performed in a controlled test-device. The molecules are composed of a central biphenyl unit (BP) carrying two mercaptoalkyl substituents with different chain lengths (m, n = number of CH(2)-units), in the para-position of the BP unit. The total length of both spacers is m + n = 10. The molecular conductance of these individual MABPs deposited on Au (111) substrates is studied using STM-based break junctions. It is shown that the molecular conductance depends on the relative position of the BP unit within the molecule. In the case of the symmetric derivative 5BP5 a value of 0.07 +/- 0.01 nS is obtained, while for 1BP9 the molecular conductance is doubled and a value of 0.17 +/- 0.03 nS results. This relatively high value of conductance for the single Au(tip)-1BP9-Au(substrate) junction is attributed to an increased coupling of the BP unit to the adjacent electrode, i.e. the STM-tip or the Au-substrate. We address the role of the specific contact situation (-S-Au) and of the position of the electrically active molecular moiety and thus come to a deeper understanding of the electronic transport properties of 4,4'-bis(mercaptoalkyl)biphenyl derivatives.