Journal
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
Volume 5, Issue 21, Pages 3909-3913Publisher
AMER CHEMICAL SOC
DOI: 10.1021/jz502058y
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Funding
- National Science Foundation NSF CAREER Award [CBET-1351281]
- Directorate For Engineering
- Div Of Chem, Bioeng, Env, & Transp Sys [1351281] Funding Source: National Science Foundation
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Quantum dots (Qps) are semiconductor nanocrystallites with multiple size-dependent quantum-confined states that are being explored for utilizing broadband radiation. While DNA has been used for the self-assembly of nanocrystals, it has not been investigated for the formation of simultaneous conduction pathways for transporting multiple energy charges or excitons. These exciton shelves can be formed by coupling the conduction band, valence band, and hot-carrier states in QDs with different HOMO-LUMO levels of DNA nudeobases, resulting from varying degrees of conjugation in the nudeobases. Here we present studies on the electronic density of states in four naturally occurring nudeobases (guanine, thymine, cytosine, and adenine), which energetically couple to quantized states in semiconductor QDs. Using scanning tunneling spectroscopy of single nanopartide-DNA constructs, we demonstrate composite DOS of chemically coupled DNA oligonudeotides and cadmium chalcogenide QDs (CdS, CdSe, CdTe). While perfectly aligned CdTe QD-DNA states lead to exciton shelves for multiple energy charge transport, mismatched energy levels in CdSe QD-DNA introduce intrabandgap states that can lead to charge trapping and recombination. Although further investigations are required to study the rates of charge transfer, recombination, and back-electron transfer, these results can have important implications for the development of a new class of nanobioelectronics and biological transducers.
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