Facile fabrication of a novel 3D graphene framework/Bi nanoparticle film for ultrasensitive electrochemical assays of heavy metal ions

In this work, a novel 3D graphene framework/Bi nanoparticle (GF/BiNP) film was fabricated with a facile preparation route. 3D graphene framework with porous structures was electrochemically reduced and in situ assembled on the electrode, and BiNPs with tunable morphologies were highly dispersed on the framework by a chemical reduction. Newly-designed 3D GF/BiNP film possessed a significantly large active area, fast electron transfer ability, high mass transfer efficiency, and excellent structure stability and binding strength on electrode. To demonstrate its superior ability, electrochemical sensors for the assay of heavy metal ions were constructed. As a result, a simultaneous assay of Pb²⁺ and Cd²⁺ with ultralow detection limits (0.02 μg L⁻¹ of Pb²⁺ and 0.05 μg L⁻¹ of Cd²⁺, S/N = 3) and a wide linear range from 1 to 120 μg L⁻¹ was achieved. Meanwhile, a separate analysis of Zn²⁺ was performed to get optimum responses, in which a low detection limit of 4.0 μg L⁻¹ (S/N = 3) with a linear range from 40 to 300 μg L⁻¹ was observed, confirming the versatility of the GF/BiNP film in the detection of heavy metal ions. Moreover, excellent repeatability, reproducibility and stability, and reliable assays in real water samples were realized with constructed sensors. Due to its convenient preparation, favorable structures and excellent properties, prepared 3D GF/BiNP film will find great potential for advanced applications in environment, biomedicine and energy systems. - Highlights: • A novel 3D graphene framework/Bi nanoparticle (GF/BiNP) film is prepared. • Porous graphene framework is in situ assembled on the electrode. • BiNPs with tunable morphologies are highly dispersed on the framework. • Newly-designed 3D GF/BiNP film possesses excellent properties. • Sensitive electrochemical sensors for Pb²⁺, Cd²⁺ and Zn²⁺ are constructed.