Gas sensing properties of platinum derivatives of single-walled carbon nanotubes: A DFT analysis.

The limitations of intrinsic carbon nanotube (CNT) based devices to examine toxic gases motivate us to investigate novel sensors which can possibly overcome sensitivity problems. Pt-CNT assemblies (with Pt deposited externally as well as internally Pt-doped ones) interacting with NO(2) and NH(3) are studied and compared with unmodified CNTs. DFT calculations show that Pt can enhance adsorption and charge transfer processes to a very large degree. Incoming gas molecules cause changes in the electronic structure and charge distribution of the Pt-substituted CNTs that are both larger and more far-reaching than in their unmodified counterparts. Their relatively high stability is unaffected by the complexation with NO(2) and NH(3). CNTs with defective surface were also investigated. The sensing performance of Pt-doped CNT is found to be superior to defected CNTs.

Structure and electronic properties of "DNA-gold-nanotube" systems: a quantum chemical analysis.

The development of novel DNA sensors is a crucial issue in the diagnosis of pathogenic and genetic diseases. We have used density functional theory (DFT) to investigate the performance of hybrid DNA sensors consisting of a gold atom (Au) deposited on two types of single-walled carbon nanotubes: armchair SWCNT(8,0)/Au and zigzag SWCNT(5,5)/Au and compared these with bare Au. We also chose adenine:thymine (A:T) as a Watson-Crick base pair of the DNA double helix. In the recognition probe, SWCNT/Au/A, adenine is immobilized on the SWCNT/Au supporter via its active N7 anchor point. After thymine hybridization (SWCNT/Au/A:T), the overall modulations compared with the original systems. Due to the complimentary functions of gold, which acts as a powerful electron withdrawing and transmitting group and of the SWNCTs, which act as electron collecting centers, respectively, the hybrid systems, "SWNCTs/Au", were found to exhibit more stability and sensitivity than the Au center alone. The changes in the HOMO-LUMO band gaps and in the atomic partial charges upon binding of thymine were rather small, but the change of the overall dipole moment was considerably larger in SWCNT/Au/A than it was in Au/A alone. The overall results suggest that the "SWCNTs/gold" system is a potential candidate for a nanostructure-based DNA sensor.