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Journal of Self-Assembly and Molecular Electronics

Baoquan Ding, National Center for Nanoscience and Technology, China
Peter Fojan, Aalborg University, Denmark
Leonid Gurevich, Aalborg University, Denmark

ISSN: 2245-4551 (Print Version),

ISSN: 2245-8824 (Online Version)
Vol: 5   Issue: Continuos Article Publication

Published In:   2017

Publication Frequency: Continuous Article Publication

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Characterization of Emergence of the Coulomb Blockade in a Pearl-Like DNA-AuNP Assembly

Kosti Tapio and J. Jussi Toppari

University of Jyvaskyla, Department of Physics, Nanoscience Center, P.O. Box 35, FI-40014 University of Jyv¨askyl¨a, Finland

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Abstract: Due to its superior self-assembly properties and vast functionalization possibilities DNA has long been one of the most promising candidates for fabrication of nanoscale electrical components using molecular building blocks. There exist already many demonstrations on optical devices based on organizing metallic nanoparticles (NP) viaDNAself-assembly, but despite the promises only few DNAbased electrical devices or studies have been realized so far. Here we study the gold NP conjugated and metallized DNA TX-tilestructure, which we recently showed to exhibit the room temperature Coulomb blockade, the pre-requisition for a single electron transistor. The properties of the obtained Coulomb blockade are further characterized via the differential conductance measurements at temperatures ranging from 4.2 K to 10.2 K. The results show sharp blockade plateaus with varying threshold voltages, which yields further evidence of a gating effect by background charges. This strongly indicates that the DNA-NP assembly functions as a single electron transistor. Also, the additional growth of gold NPs and electrodes via chemical gold deposition process, needed to achieve the Coulomb blockade, is studied here in more details, yielding more insight to the process, and thus helping to realize better control of it.

Keywords: DNA, gold nanoparticles, metallization, single electron transistor, differential conductance.

Electrospinning of Core-Shell Fibers for Drug Release Systems

Dennis Pedersbæk, Magnus Tudsborg Frantzen and Peter Fojan

Department of Physics and Nanotechnology, Aalborg University Skjernvej 4A, 9220 Aalborg Ø, Denmark

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Abstract: Electrospinning is a promising method for the fabrication of fibers used for drug release system, due the ease of operation of the electrospinning process and the high surface to volume ratio, high loading capacity and high encapsulation efficiency of the obtained fibers. In this study release of tetracycline hydrochloride (TCH) from both monolithic and core-shell electrospun fibers of poly-lactic acid (PLA), poly--caprolactone (PCL) and their blend were studied. It was found that the drug release from the fibers depended on their composition. Core-shell fibers were designed with PCL and TCH in the core and with blends (PCL/PLA) of varying composition in the shell. A varying initial burst release was observed when the composition of the shell was varied. This illustrates that the burst release might be tunable which can be advantageous for many applications.

Keywords: Electrospinning, core-shell fibers, drug release, burst release, poly, caprolactone, poly-lactic acid.

Influence of Film Morphology on Transient Photocurrent Pulse Shape in Organic Thin Films: A Monte Carlo Study

S. Raj Mohan1, Manoranjan P. Singh2,3 and M. P. Joshi1,3

1Laser Materials Processing Division, Raja Ramanna Centre for Advanced Technology, Indore, India, 452 013
2Theory and Simulation Lab, Raja Ramanna Centre for Advanced Technology, Indore, India, 452 013
3Homi Bhabha National Institute, Anushaktinagar, Mumbai, Maharashtra, India, 400 094

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Abstract: The influence of film morphology on the broadening of the time-of-flight transient photo-current pulse is investigated using Monte Carlo simulation. Simulation of the time-of-flight transient photo-current pulse shape is carried out for homogeneous and inhomogeneous organic thin films by varying the overall energetic disorder. In homogeneous system, the value of the tail broadening parameter (W) of the photocurrent pulse is found to decrease upon decreasing the energetic disorder, which can be attributed to the variation in the non-thermal field assisted diffusion. Interestingly, in the case of inhomogeneous system, upon decreasing the overall energetic disorder of the system the value of W initially attains a maximum value before it starts decreasing. This observation is explained in terms of the morphology dependent carrier diffusion. This study asserts the importance of the influence of the morphology dependent carrier diffusion on the charge transport in disordered systems and the related experimental measurements.

Keywords: Film Morphology, Polycrystalline organic thin films, Charge transport, Time of flight photoconductivity, Tail broadening, Diffusion.

River Publishers: Journal of Self-Assembly and Molecular Electronics