| The quest for miniaturization of electronic devices has caused a surge in research to find bottom-up alternatives for electronic circuit design and from this need, molecular electronics has emerged as a new field of study. For the development of "molecular-wire", it is very important to understand the flow of charge through molecular bridge systems that can be used to manipulate the flow of charge through these systems. Charge transfer (CT) through chiral organic molecules has been investigated by photoelectrochemistry through chiral molecular bridges. The study showed that the charge transfer through a chiral molecular bridge has a preference for circularly polarized light whose sense of rotation is either left or right. CT study through single stranded (ss) and double stranded (ds) peptide nucleic acid (PNA) films have been performed also. CT studies through PNA films show that at short distance the CT exponentially falls of with increasing distance, which is consistent with a super-exchange mediated tunneling mechanism, but at longer distance the decay is shallow, indicating that the CT follows a different mechanism called "hopping" mechanism. The experimentally determined mechanism switchover point from tunneling to hopping has been found to be in good agreement with a tight-binding model proposed earlier. Further, it has been found that CT through PNA is primarily controlled by nucleobases and CT can be manipulated by changing nucleobase or nucleobase pair sequence. |
