Simultaneous Electrochemical Sensing of Ultra-Trace Multiple Heavy Metals Using Metal–Organic Frameworks-Graphene Oxide Nanocomposite-Modified Electrodes
Md Humayun Kabir, Maksudul M. Alam, Rashomi Mathanan, E. M. Ford, Charles C. Chusuei, Jacob A. Wolvington, Kanyon Demonbreun, William Ghann, Jamal Uddin, Mohammed Muzibur Rahman, Meser M. Ali
Abstract
High Resolution Image Download MS PowerPoint Slide The relentless pace of industrialization has significantly exacerbated environmental pollution, with heavy-metal ions (HMIs) emerging as some of the most persistent and toxic pollutants in natural ecosystems. Growing concerns over environmental pollution have created a need for advanced sensing technologies that offer superior sensing sensitivity, selectivity, and reliability. This work reports the development of an electrochemical sensor based on a UiO-66-NH 2 (Zr) metal–organic framework (MOF)/graphene oxide (GO) nanocomposite for the simultaneous detection of HMIs in aqueous environments. Using one-pot hydrothermal synthesis, MOFs and conductive GO materials were integrated into a single nanostructure via in situ growth of the UiO-66-NH 2 (Zr) MOF on the GO matrix, resulting in the formation of a stable MOF/GO nanocomposite with enhanced conductivity and increased number of effective reaction sites. The amino groups (−NH 2 ) on UiO-66-NH 2 (Zr) porous materials serve as adsorption sites to capture HMIs. The morphological, structural, and electrochemical properties of the UiO-66-NH 2 (Zr)-GO nanocomposite were examined by using scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS), powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Differential pulse anodic stripping voltammetry (DPASV) was subsequently employed for the detection of heavy-metal ions over nanomolar to micromolar concentration ranges using a UiO-66-NH 2 (Zr)-GO-modified glassy carbon (GC) electrode. The electrochemical sensor developed in this study was successfully utilized for the selective and concurrent detection of multiple HMIs, namely, copper ion (Cu 2+ ), cadmium ion (Cd 2+ ), and lead ion (Pb 2+ ) in electrolyte solution. The sensor demonstrated achieving high selectivity and sensitivity (1.30 μA μM –1 for Cu 2+, 0.50 μA μM –1 for Cd 2+, and 12.38 μA μM –1 for Pb 2+ ) with low limit of detection (LOD) (0.59 ng/mL for Cu 2+, 0.84 ng/mL for Cd 2+, and 2.9 ng/mL for Pb 2+ ), and observed ≥85% reproducibility. The sensor demonstrated excellent long-term stability and operated effectively within a temperature range of 283–313 K, enabling the simultaneous detection of multiple heavy-metal ions from small sample volumes. The developed electrochemical method can equally be employed to detect HMIs at trace (parts-per-billion (ppb)) levels in diverse environmental matrices such as lake, river, tap water, river sediments, and wastewater.