title: AC electrical characterisation and insight to charge transfer mechanisms in DNA molecular wires through temperature and UV effects.
abstract: In this study, AC characterisation of DNA molecular wires, effects of frequency, temperature and UV irradiation on their conductivity is presented. λ-DNA molecular wires suspended between high aspect-ratio electrodes exhibit highly frequency-dependent conductivity that approaches metal-like behaviour at high frequencies (∼MHz). Detailed temperature dependence experiments were performed that traced the impedance response of λ-DNA until its denaturation. UV irradiation experiments where conductivity was lost at higher and longer UV exposures helped to establish that it is indeed λ-DNA molecular wires that generate conductivity. The subsequent renaturation of λ-DNA resulted in the recovery of current conduction, providing yet another proof of the conducting DNA molecular wire bridge. The temperature results also revealed hysteretic and bi-modal impedance responses that could make DNA a candidate for nanoelectronics components like thermal transistors and switches. Further, these experiments shed light on the charge transfer mechanism in DNA. At higher temperatures, the expected increase in thermal-induced charge hopping may account for the decrease in impedance supporting the 'charge hopping mechanism' theory. UV light, on the other hand, causes damage to GC base-pairs and phosphate groups reducing the path available both for hopping and short-range tunneling mechanisms, and hence increasing impedance--this again supporting both the 'charge hopping' and 'tunneling' mechanism theories.
authors.affiliation: MEMS Research Lab, Department of Mechanical Engineering, College of Engineering, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-1323, USA. kassegne@mail.sdsu.edu.
authors.forename: Sam
authors.initials: S
authors.lastname: Kassegne
authors.affiliation: MEMS Research Lab, Department of Mechanical Engineering, College of Engineering, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-1323, USA.
authors.forename: Denni
authors.initials: D
authors.lastname: Wibowo
authors.affiliation: MEMS Research Lab, Department of Mechanical Engineering, College of Engineering, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-1323, USA.
authors.forename: James
authors.initials: J
authors.lastname: Chi
authors.affiliation: MEMS Research Lab, Department of Mechanical Engineering, College of Engineering, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-1323, USA.
authors.forename: Varsha
authors.initials: V
authors.lastname: Ramesh
authors.affiliation: MEMS Research Lab, Department of Mechanical Engineering, College of Engineering, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-1323, USA.
authors.forename: Alaleh
authors.initials: A
authors.lastname: Narenji
authors.affiliation: MEMS Research Lab, Department of Mechanical Engineering, College of Engineering, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-1323, USA.
authors.forename: Ajit
authors.initials: A
authors.lastname: Khosla
authors.affiliation: Department of Biology, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA.
authors.forename: John
authors.initials: J
authors.lastname: Mokili
mesh_terms: D010582:Bacteriophage lambda; D004247:DNA / Q000737:chemistry*; D004553:Electric Conductivity; D055615:Electrical Equipment and Supplies; D004566:Electrodes; D036103:Nanotechnology; D012822:Silicon Dioxide / Q000737:chemistry; D013696:Temperature; D014466:Ultraviolet Rays
chemical_list: D012822:Silicon Dioxide; D004247:DNA