Molecular recognition has been described as the “ultimate” form of sensing and plays a fundamental role in biological processes. There is a move towards biomimetic recognition elements to overcome inherent problems of natural receptors such as limited stability, high-cost, and variation in response. In recent years, several alternatives have emerged which have found their first commercial applications. In this review, we focus on molecularly imprinted polymers (MIPs) since they present an attractive alternative due to recent breakthroughs in polymer science and nanotechnology. For example, innovative solid-phase synthesis methods can produce MIPs with sometimes greater affinities than natural receptors. Although industry and environmental agencies require sensors for continuous monitoring, the regulatory barrier for employing MIP-based sensors is still low for environmental applications. Despite this, there are currently no sensors in this area, which is likely due to low profitability and the need for new legislation to promote the development of MIP-based sensors for pollutant and heavy metal monitoring. The increased demand for point-of-use devices and home testing kits is driving an exponential growth in biosensor production, leading to an expected market value of over GPB 25 billion by 2023. A key requirement of point-of-use devices is portability, since the test must be conducted at “the time and place” to pinpoint sources of contamination in food and/or water samples. Therefore, this review will focus on MIP-based sensors for monitoring pollutants and heavy metals by critically evaluating relevant literature sources from 1993 to 2022.

The electrochemical synthesis of nickel–cobalt (Ni–Co) layered double hydroxides (LDHs) on a nickel-coated graphite support for water splitting applications was investigated. Three different electrochemical approaches, namely, cyclic voltammetry (CV), chronoamperometry (CA), and chronopotentiometry (CP), were employed for evaluating the electrodeposition of Ni–Co LDHs. The graphite support was initially coated with a thin layer of Ni by applying 50 mA cm⁻² constant current density for 120 s. Raman spectroscopy results confirmed the intercalation of nitrates, evidenced by the characteristic Raman bands at 1033 cm⁻¹ (ν₁) and 1329 cm⁻¹ (ν₃). These characteristic bands were indicative of nitrate intercalation, a key feature of LDHs, further supporting the classification of the synthesized material as NiCo LDHs on a nickel-coated graphite support. It was observed that the electrochemical routes used for the synthesis influenced the morphology, composition, and electrochemical behavior of the obtained Ni–Co LDHs. Moreover, atomic force microscopy (AFM) measurements revealed distinct nanoscale surface characteristics associated with the synthesis methods, with the Ni–Co LDH synthesized via the CV route exhibiting higher surface heterogeneity than that synthesized via the constant potential method (CA), resulting in a more textured surface. These findings were further supported by roughness average (Ra) values, where CV-synthesized Ni–Co LDH displayed the highest R_a of 221 nm, indicating a more extensive active surface area. The electrochemical performance, both for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), were correlated with these surface variations. This study provides valuable insights into the electrochemical experimental parameters for the synthesis of Ni–Co LDHs and their potential application in water splitting processes.

In this paper, the surface of mild steel is modified with 4-carboxyphenyl diazonium and subsequently, the corrosion behaviour of the modified surface is scrutinized in hydrochloric and sulfuric acid solutions. The diazonium salt was synthesized in situ either in 0.5 M HCl or 0.25 M H₂SO₄ through the reaction between 4-aminobenzoic acid and sodium nitrite. The surface of mild steel was modified with the obtained diazonium salt with or without the need for electrochemical assistance. Electrochemical impedance spectroscopy (EIS) measurements show that a spontaneously grafted mild steel surface has a better corrosion inhibition efficiency (86%) in 0.5 M HCl. Scanning electron microscopy reveals that the protective film formed on the surface of mild steel exposed to 0.5 M HCl containing the diazonium salt looks more consistent and uniform compared to the surface exposed to 0.25 M H₂SO₄. Optimized diazonium structure and the separation energy calculated using density functional theory correlate with the good corrosion inhibition obtained experimentally.