Preparation of nitrogen doped TiO2 nanofibers by near field electrospinning (NFES) technique for NO2 sensing

Parallel arrays of well aligned crack-free N-doped and undoped TiO2 nanofibers (3–4 mm long, 300–500 nm diameter) have been deposited by near field electrospinning (NFES) technique on Si3N4 substrates with interdigitated Pt electrodes and annealed at 400 °C for 1 h. Anatase TiO2 with crystallites’ size of approximately 12 nm have been prepared and characterized by XRD, SEM, TEM and XPS techniques. Experimental measurements have been conducted through an ad hoc analog integrated resistive sensor interface, based on an oscillating circuit, fabricated in a 0.35 μm standard CMOS technology. Gas response to NO2 in the range 1–10 ppm and 100–300 °C operating temperature (OT) has shown best practical sensor sensitivity (S = RG/RA) at a relatively low OT (150 °C) and detection limits down to 1 ppm gas. Nitrogen doping at N:Ti 1:1 atomic ratio has been proposed in order to decrease the intrinsic resistance of TiO2, thus enabling better signal to noise ratio of the electrical response.