Synergy of Two Intermolecular Hydrogen Bonds Promotes Highly Sensitive and Selective Room-Temperature Dimethyl Methylphosphonate Sensing: A Case of rGO-Based Gas Sensors

Sensing of volatile pollutants on reduced graphene oxide-polypyrrole composite: DFT investigation

Air pollutants generated from volatile toxic chemicals pose significant public health concerns. Density functional theory (DFT) computations were used in this research to explore the efficiency and mechanism of harmful gas sensing over the reduced graphene oxide-polypyrrole (rGO-PPy) composite. Volatile molecule sensing was investigated for the NH3, H2CO, CH3OH, and C2H5OH gas molecules over three PPy orientations on the rGO substrate. Results showed that PPy orientation over rGO plays a crucial role in the sensing efficiency of the investigated gas molecules. The rGO-PPy composite, with PPy in a vertical orientation, demonstrated higher stability and enhanced sensing than other orientations. The results indicate that the strong hydrogen bonding of NH3 and CH3OH with both PPy and rGO significantly enhanced the sensing of these gas molecules on rGO by influencing the charge transfer with adsorption energy values of - 0.84 and - 0.92 eV, respectively. The lack of a direct hydrogen bonding with rGO and the weak hydrogen bonding with PPy caused a weak adsorption of H2CO and C2H5OH over rGO as indicated by the adsorption energy values of - 0.60 and - 0.78 eV, respectively. Selectivity analysis for the NH3 and C2H5OH gas molecules showed that NH3 can maintain hydrogen bonding with PPy in the presence of C2H5OH while C2H5OH cannot sustain this interaction. This study highlights the importance of the structural and electronic properties of the rGO-PPy composite in volatile pollutant sensing, providing insights for designing high-performance gas sensors.

Potentiometric sensing of ibuprofen over ferric oxide doped chitosan grafted polypyrrole-based electrode

The present work demonstrates the correlation between structure, properties, and self-sensing protocols of in situ prepared ferric oxide doped grafted copolymer composite, comprised of ferric oxide, chitosan, and polypyrrole (α-Fe2O3-en-CHIT-g-PPy) for residual ibuprofen present in natural and artificial samples. The chemical structure, morphology, functionality, and physio-mechanical properties of the composite were determined by Fourier transform infrared spectrometer (FT-IR), Raman spectra, X-ray diffraction (XRD), Scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), Two probe method, and standard ASTM techniques to explore sensing nature. The results confirm the evolution of axially aligned structure against 110 planes of α-Fe2O3 and chemically functionalized expanded polymer matrix during in-situ chemical polymerization of pyrrole, with better porosity, interactivity, and improved electrical conductivity i.e. 7.32 × 10-3 S cm-1. Further, a thin film of prepared composite coated on an ITO glass plate was explored for potentiometric sensing of ibuprofen (IBU) present in artificial and natural samples without the use of any additional energy sources. The observed sensing parameters are the sensing ranging 0.5 μM to 100.0 μM, sensitivity 2.5081 mV μM-1 cm-2, response time 50 s, recovery time 10 s, and stability for 60 days. The sensing mechanism of the IBU sensor and effective charge transfer in the electrode was also discussed based on changes in IR spectra of the electrode recorded before and after sensing due to surface oxidation of IBU due to the presence of iron and doping effect of iron oxide in the composite.