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A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT
AbstractThe conductivity of DNA covalently bonded to a gold surface was studied by means of the STM technique. Various single-and double-stranded 32-nucleotide-long DNA sequences were measured under ambient conditions so as to provide a better understanding of the complex process of chargecarrier transport in natural as well as chemically modified DNA molecules. The investigations focused on the role of several features of DNA structure, namely the role of the negative charge at the backbone phosphate group and the related complex effects of counterions, and of the stacking interactions between the bases in Watson-Crick and other types of base pairs. The measurements have indicated that the best conductor is DNA in its biologically most relevant double-stranded form with Watson-Crick base pairs and charged phosphates equilibrated with counterions and water. All the studied modifications, including DNA with non-Watson-Crick base pairs, the abasic form, and especially the form with phosphate charges eliminated by chemical modifications, lower the conductivity of natural DNA.
The authors report on a biopolymeric material made of deoxyribonucleic acid ͑DNA͒ complexed with the cationic surfactant cetyltrimethyl-ammonium ͑CTMA͒ and doped with the photochromic disperse red 1 dye ͑DR1͒ for dynamic holographic recording. The molar ratio of the DNA-CTMA to the dye is about 5:1. They have found that the photochromic properties of DR1 in the DNA-CTMA matrix are favorably modified in speed of response with respect to conventional polymeric matrices. Dynamic holographic gratings which were inscribed in DR1:DNA-CTMA films are characterized by switching times within a 1-10 ms range. An excellent reversibility of the recording process is reported.
We investigate the possible application of a modified deoxyribonucleic acid (DNA)-dye system for dynamic processing of optical information, e.g., optical correlation. The system consists of a biopolymeric matrix made of DNA substituted with the cationic surfactant molecule cetyltrimethyl-ammonium chloride (CTMA) and doped with a photochromic Disperse Red 1 dye. Fast dynamics (millisecond range of rise and fall times) of output correlation signal formation was measured in a joint Fourier transform optical correlator experimental setup. Full reversibility of the correlation signal and reproducibility were observed even after long-time exposures.
Time-resolved terahertz spectroscopy and combination of quantum chemistry modeling and molecular dynamics simulations were used for the determination of charge carrier mobility in poly[methyl(phenyl)silylene]. Using time-resolved THz spectroscopy we established the on-chain charge carrier drift mobility in PMPSi as 0.02 cm(2) V(-1) s(-1). This value is low due to the formation of polarons: the hole is self-trapped in a potential formed by local chain distortion and the transient THz conductivity spectra show signatures of its oscillations within this potential well. This view is supported by the agreement between experimental and calculated values of the on-chain charge carrier mobility.
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