Journal of Semiconductors, Volume. 46, Issue 3, 032101(2025)
Fabrication and application of SiNWs based PANI:MOxheterostructures for human respiratory monitoring
Fig. 1. (Color online) Schematic representation of randomly aligned vertical SiNWs using MACE.
Fig. 2. (Color online) Representation of structural schemes considered for respiratory sensing mechanism, i.e., (a) SiNWs with PANI, (b) SiNWs with MOxparticles and (c) SiNWs coated with hybrid PANI:MOxnanocomposite. (d) A schematic representation of structure with metal contacts.
Fig. 3. (Color online) Room temperature Raman spectra of WO3 and TiO2 nanopowder. The respetive peaks are marked for both WO3 and TiO2, respectively. In (b) the dotted line represents the Raman modes of anatase TiO2 whereas the solid line represents rutile TiO2.
Fig. 4. (Color online) Room temperature Raman spectra of SiNWs structure coated with PANI, PANI:WO3, and PANI:TiO2. The Raman peaks are marked for PANI and that for WO3 and TiO2, respectively .
Fig. 5. (Color online) XRD diffractogram for (a) polyaniline (b) WO3 nanopowder and TiO2 nanopowder. The green indicated lines in (b) and (c) represent the standard tabulated position of WO3 and anatase (a-TiO2) and the red indicated line in (c) represents the standard tabulated position for rutile(r)-TiO2, according to JCPDS no. 98-007-1692, 00-021-1272, and 00-021-1276, respectively.
Fig. 6. (Color online) Reciprocal space map of (a) SiNWs and (b) SiNWs with PANI along (004) crystallographic plane.
Fig. 7. (Color online) SEM microgrpahs. (a) and (b) cross-sectional and top-view of SiNWs structures obtained by MACE, (c) top-view of SiNWs coated with PANI, (d) and (e) cross-sectional and top-view of SiNWs coated with PANI:TiO2, (f) top-view of SiNWs coated with PANI:WO3, along with a magnified image showing the presence of NWs, (g) and (h) cross-sectional and top-view of SiNWs spin-coated with WO3, respectively. The scale bars are provided along with each figure.
Fig. 8. (Color online) A schematic illustration of SiNWs sensing mechanism based on the bundling with NW−NW junction, demonstrating the modulation in potential barrier in air and during exposure to oxidizing and reducing analyte, respectively.
Fig. 9. (Color online) Respiratory sensing for three different breathing patterns i.e., (a)−(c) normal, rapid, and deep breathing, respectively, using SiNWs structures decorated with PANI and PANI:MOx, respectively. The highlighted regions represent the exhaling and inhaling stimulus characteristics.
Fig. 10. (Color online) Schematic illustration of p−n junction formation in (a) hybrid p-type PANI encapsulating n-type MOxnanoparticles. The figure demonstrate the depletion layer width alteration in air and in presence of oxidizing or reducing agent. (b) Potential band alignment and charge transfer in p-type SiNWs coated with hybrid of p-PANI:n-WO3. (c) Energy band with p−n junction formed between p-type SiNWs spin coated with n-type MOxnanoparticles.
Fig. 11. (Color online) (a) Room temperature plot of dR/dt for SiNWs structure with and without hybrid PANI:WO3 deposition, respectively. The inset shows the resistance vs time plot of SiNWs with arrow representing a drift in baseline. (b) Plot for room temperature change in resistance as a function of time under varying breathing stimulus using SiNWs structures decorated with (top) PANI:WO3 using electroless deposition and (bottom) WO3 nanoparticles using spin-coating, respectively. The insets show magnified pattern under rapid breathing.
Fig. 12. (Color online) Response of the structure (SiNWs/ PANI: WO3) after shelving for more than two-months.
Fig. 13. (Color online) (a) Photograph of data acquisition electronics, utilizing an oscilloscope, assisted with Arduino microcontroller board (not shown here). (b) 3D printed mask with an outer cover for mounting sample and an inner grid which can be integrated with course filter for damage protection. (c) Sample before mounting with size ~10 × 10 mm2. (d) Circuit diagram of breath sensor.
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Muhammad Taha Sultan, Anca Dumitru, Elham Fakhri, Rachel Brophy, Snorri Thorgeir Ingvarsson, Andrei Manolescu, Halldor Gudfinur Svavarsson. Fabrication and application of SiNWs based PANI:MOxheterostructures for human respiratory monitoring[J]. Journal of Semiconductors, 2025, 46(3): 032101
Category: Research Articles
Received: Sep. 18, 2024
Accepted: --
Published Online: Apr. 27, 2025
The Author Email: Muhammad Taha Sultan (MTSultan)