Phosphonate-functionalized three-dimensional gold nanocomposite as a sensitive interface for facile electrochemical stripping detection of trace copper(II) ions

• Nano-branched gold with interconnected hierarchical porous structure is prepared.
• Functional monolayer of less densely packed 3-mercaptopropylphosphonic acid is built.
• Designed sensing interface exhibits excellent performance to trace Cu(II) detection.
• Proposed protocol gives insight for design of 3D nanostructure with specific sensing.

In biological systems, specific status of the essential transition metal ions in body fluids is of clinical significance for sustaining normal, healthy individual. In this work, we demonstrate an efficient and controllable phosphonate-functionalized interface, self-assembled on the surface of three-dimensional nanoporous gold electrode, that responds to trace copper(II) ions in aqueous solution with appropriate sensitivity and stability, when combined with facile differential pulse anodic stripping voltammetry (DPASV), thus offering the opportunity to probe physiological and pathological condition of cellular metals with spatial fidelity. The structural morphology and electrochemical properties of the as-prepared phosphonate-functionalized three-dimensional (3D) gold electrodes were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), dynamic contact angle analysis and cyclic voltammetry. The results indicated that, by use of cost-effective materials of short-chain MPPA (3-mercaptopropylphosphonic acid), the derived less densely packed self-assembled monolayers (SAMs), with evenly-spread terminal –PO3H2 functionality at intermediate surface coverage unlike its long-chain counterparts, exhibited great performance for trace analysis of heavy metal ions of copper(II) in aqueous environment. Incorporated with 3D gold substrate, possessing highly interconnected hierarchical porous structure beneficial for mass transport, a linear dynamic range from 0.05 to 350 μM to the detection of copper ions, was obtained under the optimized conditions with a relatively low detection limits. The proposed sensing interface using phosphonic moieties as functional group holds promise to generally estimate metal accumulation, trafficking, and function or toxicity in living systems.

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