Electrochemical Techniques for the Detection of Heavy Metals

The present chapter emphases on the approach of electrochemical sensor of metallic oxide nanocomposites to sense/detect heavy metal ions. Several methods have been incorporated with modified electrode for the sensing/detection of heavy metal ions. Among these methods square wave anodic stripping voltammetry method and differential normal pulse voltammetry method have been tested and being recommended for the individual analysis as well as simultaneous analysis of heavy metal ions by various researchers. We also endorse the said methods as the best choice for sensing of heavy metal ions however the material phase (plane) is also of specific importance in this regard. We suggest that these methods may be practiced by chemical industries the main sources of heavy metal ions waste. Furthermore, the statistical approach for the detection limit (3σ method) has been illustrated in the last paragraph of this unit

Facile Synthesis of Highly Dispersed Co₃O₄ Nanoparticles on Expanded, Thin Black Phosphorus for a ppb-Level NO_<i>x</i> Gas Sensor

Expanded few-layer black phosphorus nanosheets (FL-BP NSs) were functionalized by branched polyethylenimine (PEI) using a simple noncovalent assembly to form air-stable overlayers (BP-PEI), and a Co₃O₄@BP-PEI composite was designed and synthesized using a hydrothermal method. The size of the highly dispersed Co₃O₄ nanoparticles (NPs) on the FL-BP NSs can be controlled. The BP-C5 (190 °C for 5 h) sensor, with 4–6 nm Co₃O₄ NPs on the FL-BP NSs, exhibited an ultrahigh sensitivity of 8.38 and a fast response of 0.67 s to 100 ppm of NO_<i>x</i> at room temperature in air, which is 4 times faster than the response of the FL-BP NS sensor, and the lower detection limit reached 10 ppb. This study points to a promising method for tuning properties of BP-based composites by forming air-stable overlayers and highly dispersed metal oxide NPs for use in high-performance gas sensors