Investigation on acid functionalization of double-walled carbon nanotubes of different lengths on the development of amperometric sensors

Highly Sensitive Humidity Sensors Based on Polyethylene Oxide/CuO/Multi Walled Carbon Nanotubes Composite Nanofibers

Polymer composites are favorite materials for sensing applications due to their low cost and easy fabrication. In the current study, composite nanofibers consisting of polyethylene oxide (PEO), oxidized multi-walled carbon nanotubes (MWCNT) and copper oxide (CuO) nanoparticles with 1% and 3% of fillers (i.e., PEO–CuO–MWCNT: 1%, and PEO–CuO–MWCNT: 3%) were successfully developed through electrospinning for humidity sensing applications. The composite nanofibers were characterized by FTIR, XRD, SEM and EDX analysis. Firstly, they were loaded on an interdigitated electrode (IDE), and then the humidity sensing efficiency was investigated through a digital LCR meter (E4980) at different frequencies (100 Hz–1 MHz), as well as the percentage of relative humidity (RH). The results indicated that the composite nanofibers containing 1% and 3% MWCNT, combined with CuO in PEO polymer matrix, showed potent resistive and capacitive response along with high sensitivity to humidity at room temperature in an RH range of 30–90%. More specifically, the PEO–CuO–MWCNT: 1% nanocomposite displayed a resistive rapid response time within 3 s and a long recovery time of 22 s, while the PEO–CuO–MWCNT: 3% one exhibited 20 s and 11 s between the same RH range, respectively.

Electrochemical detection of methyl parathion via a novel biosensor tailored on highly biocompatible electrochemically reduced graphene oxide-chitosan-hemoglobin coatings

A quick electrochemical sensing tool by utilizing novel bioelectrode based on redox active protein hemoglobin (Hb) has been offered here for the determination of methylparathion (MP). The bioelectrode has been designed by immobilizing Hb on electrochemically reduced graphene oxide-chitosan (ERGO-CS/Hb/FTO) based biocompatible coatings. Fourier transform-infrared analyses (FTIR), field emission scanning electron microscopy (FESEM), UV-visible and electrochemical characterization reveal the successful grafting of ERGO-CS/Hb/FTO. A detailed impedimetric analysis shows low charge transfer resistance (R_CT) and solution resistance (Rs) for the fabricated biosensor, thus pointing towards improved electrochemical performance and sensitivity. In-depth elucidation of redox analysis has been presented in terms of surface concentration of redox moiety (2.92 × 10^-9 mol cm^-2) and heterogeneous electron transfer rate constant (0.0032 s^-1) which indicate enhanced surface coverage and better charge transfer properties of the proposed electrochemical biosensor. The sensor is equipped with a low limit of detection of 79.77 nM and a high sensitivity of 45.77 Acm^-2 μM^-1 with excellent reproducibility. The modified biosensor also offered its credibility towards detection of MP in vegetable samples with recovery (%) ranging from 94% to 101%. The designed biosensor hereby, evolves as a promising approach for the recognition of MP.