Low-cost and Fast Wet-based Technique to Generate Nanostructured Organic Materials Layers and its Application to Chemiresistive Gas-sensing Devices

Nanostructured P3HT as a Promising Sensing Element for Real-Time, Dynamic Detection of Gaseous Acetone

“…Previous studies showed that P3HT nanofibers (NF)-based CRs exposed to acetone have very fast response times and nearly perfect baseline recovery [18,19]. These results were obtained in a qualitative way, i.e., by blowing acetone vapors onto the sensing layer, in an open environment, realizing in this way a dynamic interaction between the analyte and the sensing surface.…”

“…Preliminary tests carried out on P3HT NF sensors able to detect gaseous acetone evidenced how by applying a remarkably low bias of 0.5 V, devices were characterized by currents in the order of tens of nA, and by a noise (derived from the standard deviation of the baseline signal) about four orders of magnitude lower [18,19]. In order to make a more quantitative assessment of these parameters in conditions as similar as possible to those found in breath exhalation, a P3HT NF-based sensor was placed in the flow-injection analysis test chamber.…”

“…Since P3HT is hydrophobic, a swelling effect due to water absorption is ruled out as a possible cause of the sensor response to water. The saturation of the P3HT NF sensor upon injection of 10 mL of water vapor is likely due to the fact that the water has a much longer response decay time than the acetone [18,19]. Therefore, by the time that the last injected water vapor is arriving on the sensor (with a 10 mL injection the total injection time is about 5.5 s, close to the 5.8 s needed to completely fill the chamber in the considered flow conditions), the first arrived water vapor is still adsorbed on the P3HT surface, originating signal saturation phenomena.…”

“…Interdigitated Au electrodes onto SiO 2 /Si substrates, consisting of identical fingers having 10 μm width and gap, were fabricated at the Trieste CNR-IOM premises using standard lithographic techniques. P3HT nanofibers were grown directly on these substrates according to the procedure described in previous works [18,19,39]. In more detail, 2 μL of a solution composed by 1 mg of P3HT (99% HT, Rieke Metals, Lincoln, NE, USA), 1 mL of CHCl 3 (spectroscopic grade, Sigma Aldrich, St. Louis, MO, USA) and 0.9 g of para -dichlorobenzene (98%, Sigma Aldrich, Saint Louis, MO, USA, spectroscopic grade) were drop cast onto the interdigitated gold electrodes.…”

“…Also SPs-based sensors usually suffer from slow response (average response times ranging around tens of seconds in the best cases [11,12,15,16,17]) and little reversibility, with overall performances similar to those of their ICPs-based counterparts. To the knowledge of the authors, the only works reporting gas-sensing performances from SP-based chemiresistors with response time below one minute and satisfactory reproducibility are based on self-assembled nanofibers of P3HT (head-to-tail, regioregular poly(3-hexylthiophene), a well-known semi-conducting polymer), that demonstrated recovery times below one second and nearly perfect reversibility upon exposure to gaseous H 2 O, NH 3 , acetone [18,19], even though the measurements were carried out only at a qualitative level. This performance in terms of rapidity of response was much higher than that of previously reported thin films-based sensors based on the same polymer [13,14,15,16].…”