Flexible, Label-Free DNA Sensor Using Platinum Oxide as the Sensing Element

Platinum oxide thin film (100 nm) deposited using an optimized reactive ion sputtering process revealed p-type semiconducting behavior with a band-gap of 1.5 eV, resistivity of <inline-formula> <tex-math notation="LaTeX">$0.16~\Omega $ </tex-math></inline-formula>-m, and activation energy of 0.22 eV. XPS spectra indicated the presence of PtO phase (32%) along with PtO₂ phase (68%). The XRD spectra indicated the formation of <inline-formula> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>-PtO₂ phase. arrays of simple, two terminal sensors were fabricated on transparent, flexible, and acetate substrates with platinum oxide thin film forming the active layer (8.0 mm <inline-formula> <tex-math notation="LaTeX">$\times 60~\mu \text{m}$ </tex-math></inline-formula>) for DNA detection. The sensor operated on the principle of conductance change resulting from the change in charge carrier density due to attachment of DNA to the platinum oxide surface. The DNA attachment onto platinum oxide was experimentally verified by performing Fourier transform infrared spectroscopy and optical fluorescence measurements. The binding constant of DNA to platinum oxide was found to be 7.35 pM for every percentage increase in fluorescence intensity. The sensor arrays showed a DNA concentration-dependent current change that was linear over a large dynamic range and sensitivity down to 0.5 nM. The label-free platinum oxide DNA sensors showed reproducibility with a coefficient of variation of less than 10%.