Heavy-metal pollution is a foremost concern, as excessive heavy metals produce environmental contamination, and the accumulative effects of heavy metals pose a major hazard to human health. There is an urgent need for a fast, sensitive and effective method for detecting heavy metal cations in the environment. In recent years, using Quartz Crystal Microbalance (QCM) technique, significant progress was achieved in quantitative analysis by providing a new approach for determination of chemical content analysis. The objective aim of this review is to assess the research development of QCM applications in detection of heavy metal cations in natural water (or aqueous solution) and reflect the challenges and forthcoming point of view for QCM-based sensors for heavy-metal ions. A brief outline about the basic measurement methodologies and analytical techniques is given. To illustrate applications of the QCM techniques, the influence of the structural transformation resulting from polymer, macrocyclic ‘calixarenes’ and nanostructural coating on sensation will be discussed. Lastly, we summarise fields of applications and future forecast for the utilisation of functionalised QCM surface as a chemical sensor to study the interaction of heavy metal ions with calixarenes.

High levels of metallic ions, particularly heavy metals, can cause serious damage not only to public health but to the whole ecosystem. Therefore, rapid and precise detection and monitoring of heavy metals have become vital. The detection of heavy metals in water using conventional monitoring approaches based on physicochemical and analytical procedures, e.g., inductively coupled plasma combined with atomic absorption spectroscopy, X-ray fluorescence, instrumental neutron activation analysis, etc., has been immensely utilized. However, the sophisticated sample preparation and evaluation procedures for most of the mentioned methods are time- and labor-intensive, and economically more favorable detection approaches, e.g., sensors and lab-on-a-chip techniques, are being developed. Chemical sensors (electrochemical, optical, and piezogravimetric) with different sensing platforms (nanostructures, biological, polymeric, and macrocyclic) have been considered to be the most promising ones, owing to their strong adsorption of target elements, fast electron transfer kinetics, and biocompatibility, which are very apt for sensing applications. The combination of electrochemical, optical, and piezogravimetric techniques with nanomaterials has enhanced the sensitivity, limit of detection, and robustness of the chemosensors. Following this perspective, this review highlights surface modification platforms of sensors that enhance the detection properties (sensitivity, selectivity, limit of detection, and linear range) of the proposed devices, including nanostructures, biological networks, polymers, and macrocycles with a special emphasis on calixarenes/resorcinarenes oligomers. The capabilities, limitations, and prospect assessments of the covered techniques in detection and monitoring have been highlighted.

A flow type quartz crystal microbalance with impedance analysis capability (QCM‐I) chemical sensor was tested for heavy metal (HM) ions detection in aqueous solutions. The sensor development is based upon the complexing ability of the functionalized AT‐cut quartz resonator gold surface, by calixresorcinarenes, towards the HM ions. These calixresorcinarenes coated QCM sensors were tested for selectively adsorbing HM ions, such as copper, lead, mercury, and cadmium, from solution over a wide range of concentration (5‐1000 ppm) through complexation with functional groups in the coating layers. QCM‐Calix based chemosensors, C‐dec‐9‐en‐1‐ylcalix[4]resorcinarene (ionophore I), C‐undecylcalix[4]resorcinarene (ionophore II), C‐dec‐9‐enylcalix[4]resorcinarene‐O‐(S‐)‐α‐methylbenzylamine (ionophore III) and C‐dec‐9‐enylcalix[4]resorcinarene‐O‐(R+)‐α‐methylbenzylamine (ionophore IV), were synthesized and immobilized to detect HM ions of Pb²⁺, Cd²⁺, Hg²⁺, and Cu²⁺ in aqueous solutions. Using the impedance analysis, which facilitates a complete description of the acoustic loading of the crystal surface, the full width at half maximum of the QCM resonance peak (FWHM) values are obtained from the impedance spectra. FWHM variations revealed the effectiveness of the proposed ionophores in detecting HM at different levels. Sensitivities and wide linear relationships between HM concentration and FWHM were interpreted. Detection limits of (0.32, 0.57, 0.37, 0.89 ppm) and (1.63, 0.18, 0.76, 0.2 ppm) were determined for ionophore I and II, for Cd²⁺, Cu²⁺, Hg²⁺ and Pb²⁺ ions, respectively. Ionophore (I) showed binding preferences towards Cd²⁺ ions where ionophore (II) produced similar selectivity toward Cu²⁺ and Pb²⁺ ions. Ionophores III and IV were used for the assessment of ▵FWHM values to comprehend the detection affinities of the ionophores toward HM ions.