Synergetic Sensing Effect of Sodium Carboxymethyl Cellulose and Bismuth on Cadmium Detection by Differential Pulse Anodic Stripping Voltammetry.

In the present work, a novel electrochemical sensor was developed for the detection of trace cadmium with high sensitivity and selectivity in an easy and eco-friendly way. Firstly, a glassy carbon electrode (GCE) was modified with nontoxic sodium carboxymethyl cellulose (CMC) by a simple drop-casting method, which was applied to detect cadmium by differential pulse anodic stripping voltammetry (DPASV) in a solution containing both target cadmium and eco-friendly bismuth ions, based on a quick electro-codeposition of these two metal ions on the surface of the modified electrode (CMC-GCE). Investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FT-IR), both CMC (with good film-forming ability) and bismuth (with well-defined stripping signal) were found to be well complexed with target cadmium, leading to vital signal amplification for cadmium detection at a sub-nanomolar level. Under the optimal conditions, the proposed sensor exhibited a good linear stripping signal response to cadmium (Ⅱ) ion, in a concentration range of 0.001 µmol/L-1 µmol/L with a limit of detection of 0.75 nmol/L (S/N = 3). Meanwhile, the results demonstrate that this novel electrochemical sensor has excellent sensitivity and reproducibility, which can be used as a promising detection technique for testing natural samples such as tap water.

A high performance Pb(II) electrochemical sensor based on spherical CuS nanoparticle anchored g-C3N4.

A new electrochemical sensor has been constructed for ultra-sensitive detection of lead ions (Pb2+) by square wave anodic stripping voltammetry (SWASV), based on the copper sulfide/graphitic carbon nitride nanocomposite modified glassy carbon electrode (CuS/g-C3N4/GCE). First, spherical CuS nanoparticles with good electrical conductivity were anchored on layered g-C3N4 with high coordination activity, affording an excellent electrode modifier CuS/g-C3N4 nanocomposite. Then, the performance of the CuS/g-C3N4/GCE and its electrochemical response to Pb2+ were thoroughly studied, and the sensing mechanism was investigated. On the one hand, the CuS/g-C3N4 nanocomposite has greatly improved the electron transportation and electrode performance through functional complementarity - CuS endows g-C3N4 with a good electrical conductivity and a large active specific surface area, while g-C3N4 endows CuS with high dispersibility and strong adsorption. On the other hand, the CuS/g-C3N4 modifier has effectively promoted the deposition of trace Pb2+ from the solution onto the electrode surface by means of synergistic enrichment (crucial for amplification of detection signals) - g-C3N4 can coordinate with Pb2+ by its large number of conjugated triazine heterocyclic rings in its molecular framework, while CuS can adsorb Pb2+ due to its inherent size effect of nanomaterials. The proposed sensor can efficiently detect Pb2+ in the concentration range of 0.050-5.000 µM with a limit of detection (LOD) as low as 4.00 nM, and can be well applied for the detection of trace Pb2+ in actual tea samples.