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Functionalized nanogaps embedded in nanopores show a strong potential for enhancing the detection of biomolecules, their length, type, and sequence. This detection is strongly dependent on the features of the target biomolecules, as well as the characteristics of the sensing device. In this work, through quantum-mechanical calculations, we elaborate on representative such aspects for the specific case of DNA detection and read-out. These aspects include the influence of single DNA nucleotide rotation within the nanogap and the current-voltage (I-V) characteristics of the nanogap. The results unveil a distinct variation in the electronic current across the functionalized device for the four natural DNA nucleotides with the applied voltage. These also underline the asymmetric response of the rotating nucleotides on this applied voltage and the respective variation in the rectification ratio of the device. The electronic tunneling current across the nanogap can be further enhanced through the proper choice of an applied bias voltage. We were able to correlate the enhancement of this current to the nucleotide rotation dynamics and a shift of the electronic transmission peaks towards the Fermi level. This nucleotide specific shift further reveals the sensitivity of the device in reading-out the identity of the DNA nucleotides for all different configurations in the nanogap. We underline the important information that can be obtained from both the I-V curves and the rectification characteristics of the nanogap device in view of accurately reading-out the DNA information. We show that tuning the applied bias can enhance this detection and discuss the implications in view of novel functionalized nanopore sequencers., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

We report on the specific interaction of a small diamond-like molecule, known as diamondoid, with single amino-acids forming nano/bio molecular complexes. Using time-dependent density-functional theory calculations we have studied two different relative configurations of three prototypical amino acids, phenylalanine, tyrosine, and tryptophan, with the diamondoid. The optical and charge-transfer properties of these complexes exhibit amino acid and topology specific features which can be directly utilized for in the direction of novel biomolecule detection schemes., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The possibility of distinguishing between DNA nucleobases of different sizes is manifested here through quantum-mechanical simulations. By using derivatives of small, modified diamond clusters, known as diamondoids, it is possible to separate the pyrimidines (cytosine and thymine) from the larger purines (adenine and guanine), according to the collective electronic and binding properties of these DNA nucleobases and the diamondoid. The latter acts as a probe with which these properties can be examined in detail. Short single-stranded DNA is built up from single nucleobases to reveal the effect of each DNA unit on the sensing abilities of the diamondoid probe. Several ways of orienting the nucleobases, nucleosides, nucleotides, and short single-stranded DNA are investigated; these lead to quite different electronic properties and may or may not enhance the possibility of separating the DNA nucleobases. For the optimum orientation, that is, one that promotes stronger hydrogen bonding of the diamondoid to the short DNA strand, it is found that the electronic band gaps of a purine strand lie in a completely different range to the band gaps of a pyrimidine strand. This difference can be over 1 eV, which is measurable and shows the potential of using diamondoids and their derivatives in biosensing devices., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)