This review discusses recent advances in graphene-based Hg²⁺sensors with a focus on optical, electrochemical, and electronic sensing platforms.

Nitrate, the main form of dissolved nitrogen, is one of the key factors causing water eutrophication. Conventional detection methods are unsuitable for real-time and in situ monitoring of nitrates because they need chemical reagents for sensing and are time-consuming. Here we report a novel nitrate sensor based on a field-effect transistor (FET) device. With reduced graphene oxide (rGO) nanosheets as the FET channel material, the sensor uses benzyltriethylammonium chloride (TEBAC) as a capture probe which has been modified on the rGO surface. The rGO/TEBAC sensor exhibits an ultra-low detection limit of 1.1 μg L⁻¹ NO₃-N with a rapid response within 2–7 s, which is superior to that of most commonly used sensors and far lower than the threshold concentration of total nitrogen (0.3 mg L⁻¹) for water eutrophication. This simple and miniaturized sensor also shows high selectivity over other anions such as Cl⁻, SO₄ ²⁻ and CO₃ ²⁻. Our study provides a new strategy for rapid, sensitive, and selective detection of nitrates, which is promising for real-time and in situ water quality monitoring.

Per- and polyfluoroalkyl substances (PFASs) are an emerging group of persistent organic pollutants in aquatic environments with high levels of toxicity and bioaccumulation. The risks posed by PFASs to the environment and health have attracted increasing attention. To remove them from water, advanced oxidation processes (AOPs), with the merits of high efficiency and low cost, are mainly used. Photo/electrocatalytic heterogeneous AOPs, with the assistance of nanostructured catalysts and external energy in the form of light/electricity, have emerged as one of the most powerful techniques, overcoming the difficulty associated with defluorination and achieving the effective and complete degradation of PFASs in water. The structures of photo/electrocatalysts play a critical role in the production of reactive oxygen species, the electron transfer process, and the degradation pathway and its efficiency. Herein, to elucidate the structure–performance relationship, a review of photo/electrocatalysts for the enhanced degradation of PFASs in heterogeneous AOPs, organized according to their composition and nanostructure design, is provided. This review article is mainly focused on (1) the mechanisms and pathways of PFAS degradation by heterogeneous photo/electrocatalytic AOPs, and (2) the structural designs and modifications of photo/electrocatalysts for the enhanced degradation of PFASs by heterogeneous AOPs. Finally, the challenges and prospects for future research into photo/electrocatalysts of heterogeneous AOPs in the field of PFAS remediation are discussed.

Electronic sensors can detect nutrients such as nitrogen and phosphorus that are key indexes in evaluating water eutrophication.