Strain engineered biocompatible h-WO₃ nanofibers based highly selective and sensitive chemiresistive platform for...

In this work, we demonstrate a simple, low-cost biocompatible 1D-WO₃ electrospun nanofibers based strain-induced high-performance chemiresistive catechol sensor. WO₃ nanofibers were synthesized using e-spinning, annealed and drop-casted on to flexible PET substrate. X-Ray Diffraction (XRD) studies confirm the formation of Hexagonal phase-WO₃ and Raman spectroscopy proved the presence of O-W-O bending modes. Field emission scanning electron microscopy (FESEM) images displayed the random orientation of dense WO₃ nanofibers on PET substrate. Hall measurements confirmed the formation of n-type WO₃ nanofibers with carrier density of 10¹⁹ cm^-3. The sensor responded to a broad dynamic range of catechol concentrations from 1 μM to 100 μM with sensitivity of 51.29 μM^-1 cm^-2 and limit of detection of 0.52 μM which are better than previously reported catechol sensors. Interestingly, upon application of compressive strain to the flexible sensor, a remarkable increase in sensitivity to 88.34 μM^-1 cm^-2 was observed with further reduction of the limit of detection to 42 nM. Upon subjecting the sensor to strain ranging from 3.14% to 47.6%, an increase in sensitivity to catechol was observed due to the increase in the exposed surface area of interconnected WO₃ nanofibers which enhances the active sites for catechol oxidation by enhancing the tunneling current. The sensor could detect catechol in simulated blood samples with excellent selectivity against AA, UA, Na⁺, Ca⁺, hydroquinone and glucose.