An ultra-sensitive and stable electrochemical sensor with an expanded working range via in situ assembly of 3-D structures based on MXene/GnR nanohybrids

Abstract

In this study, a multidisciplinary approach was taken to develop an ultrasensitive, mechanically strong, and environmentally stable volatile analytes sensor that can be incorporated into portable devices to provide on-demand data. On the nanoscale, nanohybrids consisting of MXene and graphene nanoribbons (GnRs) were prepared to benefit from MXene's abundant active functional sites and GnRs' facile orientation and bridging capability to form a robust active and conductive network. On the microscale, a novel in situ, electrostatic attraction-assisted fabrication method consisting of coaxial electrospinning and simultaneous electrospraying was developed to in situ decorate the cetrimonium bromide (CTAB)-functionalized styrene–butadiene–styrene (SBS) fibers with electronegative nanohybrids. The formation of the 3-D in situ assembled network increased the number of active sites by 148% and 125% compared to those of neat SBS and conventionally coated SBS membranes. This structural innovation, along with the formation of the 3-D conductive network formed in the X, Y, and Z directions (12.21 S m⁻¹, 11.75 S m⁻¹, and 10 S m⁻¹, respectively) expanded the working range to 40 ppb–6000 ppm. The hybridization of the active network helped increase the population of MXene's active groups during the thermal reduction of GOnRs to GnRs in the presence of MXene and modulated the narrow bandgap of MXene which enhanced the ammonia gas sensing performance by almost 9 fold. The sensors showed excellent flexibility, mechanical properties, and environmental stability by maintaining ideal responsiveness to relative humidity (RH) changes, even under severe external bending/stretching.