Theoretical study on efficient HF gas sensing by functionalized, decorated, and doped nanocone strategy.

Hydrogen fluoride (HF) is a highly dangerous and corrosive gas that can cause severe burns and respiratory damage. The density functional theory method (DFT) used to study the interaction between the HF gas and the surface of a carbon nanocone (CNC) doped with gallium atom as a chemical sensor. The results showed that CNC wasn't a good candidate to sense the HF gas and consequently its electrical properties are changed insignificant. To improve the properties of the CNC, several strategies were tried: functionalizing by pyridinol (Pyr) and pyridinol oxide (PyrO), decorated with metals (M = B, Al, and Ga), and doped with element of third group (M = B, Al, and Ga). The obtained data demonstrated that the promising results were obtained by doping the CNC with Ga atom. After full optimization, we achieved one stable configuration between the HF gas and CNC-Ga structure (S15 configuration) with Eads = -19.86 kcal/mol. The electronic properties of the CNC-Ga structure is sensible changed after the HF molecule is adsorbed. According to calculated the energy gap between HOMO and LUMO orbitals of S15 configuration are increased which could be applied a chemical signal. Eventually, one could propose that the CNC-Ga has the ability to act as a Φ-type sensor based on its physical adsorption energy and quick recovery time and doped with gallium atom is a promising strategy.

Simultaneous determination of Pb2+ and Hg2+ at food specimens by a Melamine-based covalent organic framework modified glassy carbon electrode.

Heavy metals determination is of great importance. In this respect, a recently synthesized melamine-based covalent organic framework (Schiff base network1 (SNW1)) was used in this research as a novel modifier to alter a glassy carbon electrode for the simultaneous anodic stripping square wave voltammetric measurement of Pb2+ and Hg2+ ions. At first, the complexation of SNW1 with Pb2+ and Hg2+ ions were evaluated by density functional theory calculations. Afterward, the modified electrode was characterized by various techniques including Fourier-transform infrared spectroscopy, Scanning electron microscopy, energy dispersive X-ray analysis, cyclic voltammetry, and electrochemical impedance spectroscopy. Then, all of the effective experimental factors including pH, supporting electrolyte type, and instrumental parameters were optimized. Under optimized conditions (pH = 2.0, deposition time = 150 S, accumulation potential = -1000 (mV), pulse amplitude = 40 mV, frequency = 50 Hz, and voltage step = 7 mV) the designed sensor showed a linear response over the concentration ranges of 0.01-0.3 and 0.05-0.3 µmol/L for Pb2+ and Hg2+ respectively with a detection limit of 0.00072 and 0.01211 µmol/L. In the end, the designed electrochemical sensor was successfully employed for simultaneous measurement of Pb2+ and Hg2+ at different edible samples.

Ultra-trace levels voltammetric determination of Pb2+ in the presence of Bi3+ at food samples by a Fe3O4@Schiff base Network1 modified glassy carbon electrode.

In this research, a highly sensitive electrochemical sensor was developed for the square wave anodic stripping voltammetric determination of Pb2+ at ultra-trace levels. A Glassy carbon electrode was modified with an in-situ electroplated bismuth film and the nanocomposite of a recently synthesized melamine based covalent organic framework (schiff base network1 (SNW1)) and Fe3O4 nanoparticles (Fe3O4@SNW1). The obtained results exhibit clearly that combination of Fe3O4@SNW1 and in-situ electroplated bismuth film enhances the sensitivity of the modified electrode towards Pb2+ remarkably. A Plackett-Burman design was implemented for screening experimental factors to specify the significant variables influencing the sensitivity of the electroanalytical method. Afterward, the effective factors were optimized using Box-Behnken design (BBD). Under optimized conditions, the proposed electrode showed a linear response towards Pb2+ in the concentration range of 0.003-0.3 µmol L-1 with the detection limit of 0.95 nmol L-1. The selectivity of the fabricated electrode towards different ionic species were checked out and no serious interference was observed. At the end, the application of the designed sensor in the determination of Pb2+ at 10 different edible specimens were investigated and the obtained recovery values were in the range of (95.56-106.64%) indicating the successful performance of the designed sensor.