Nanocomposite approaches for enhancing the DC and photoconductivity of DNA films.

Enhanced DC conductivity and photoconductivity of cationic carbazole tethered deoxyribonucleic acid (Cz-DNA) in film devices is achieved by incorporating mobility enhancers. An anthracene-based organic semiconductor (namely 4HPA-Ant) and the inorganic semiconductor cadmium sulfide (CdS) multipod nanocrystal (NC) were used as the mobility enhancers. Space charge limited current (SCLC) experiments show that hole mobility in CdS:Cz-DNA composite film is improved significantly, by about an order of magnitude, compared to the Cz-DNA film. Similarly, the DC conductivity of the composite film is slightly enhanced by 4HPA-Ant. The photoconductivity is also improved in the Cz-DNA composite, with both 4HPA-Ant and CdS multipod NCs. The enhancement in photocurrent is by more than an order of magnitude, as demonstrated by current-voltage (I-V) characterization using DNA composite photodetectors.

Filterless optical oxygen sensor based on a CMOS buried double junction photodiode.

We present a custom CMOS IC with a buried double junction (BDJ) photodiode to detect and process the optical signal, eliminating the need for any off-chip optical filters. The on-chip signal processing circuitry improves the desired signal extraction from the optical background noise. Since the IC is manufactured using standard commercial fabrication processes with no post-processing necessary, the system can ultimately be low cost to fabricate. Additionally, because of the CMOS integration, it will consume little power when operating, and even less during stand-by.

Enhanced performance from a hybrid quenchometric deoxyribonucleic acid (DNA) silica xerogel gaseous oxygen sensing platform.

A complex of salmon milt deoxyribonucleic acid (DNA) and the cationic surfactant cetyltrimethylammonium (CTMA) forms an organic-soluble biomaterial that can be readily incorporated within an organically modified silane-based xerogel. The photoluminescence (PL) intensity and excited-state luminescence lifetime of tris(4,7'-diphenyl-1,10'-phenanathroline) ruthenium(II) [(Ru(dpp)3](2+), a common O2 responsive luminophore, increases in the presence of DNA-CTMA within the xerogel. The increase in the [Ru(dpp)3](2+)excited-state lifetime in the presence of DNA-CTMA arises from DNA intercalation that attenuates one or more non-radiative processes, leading to an increase in the [Ru(dpp)3](2+) excited-state lifetime. Prospects for the use of these materials in an oxygen sensor are demonstrated.