Advances in Heavy Metal Sensing: Utilizing Immobilized Chromogenic Reagents, Nanomaterials Perovskite and Nanonzymes.

Heavy metal pollution is a major environmental and health problem due to the toxicity and persistence of metals such as lead, mercury, cadmium, and arsenic in water, soil, and air. Advances in sensor technology have significantly improved the detection and quantification of heavy metals, providing real-time monitoring and mitigation tools. This review explores recent developments in heavy metal detection, focusing on innovative uses of immobilized chromogenic reagents, nanomaterials, perovskites, and nanozymes. Immobilized chromogenic reagents, with their high specificity and visual detection capabilities, provide cost effective solutions for heavy metal detection. Techniques to improve their stability and sensitivity, including surface modifications and hybrid materials, are discussed. Nanomaterials, including quantum dots, metal-organic frameworks, and carbon-based nanostructures, have emerged as versatile platforms due to their unique physicochemical properties. These materials enable highly sensitive and selective sensing mechanisms, such as fluorescence quenching and electrochemical sensing. Perovskites, a class of materials known for their tunable optoelectronic properties, have shown great promise in the optical and electrochemical detection of heavy metals. Despite challenges related to stability and environmental safety, their potential for low-cost and scalable applications is remarkable. Nanozymes, synthetic enzyme mimics, offer robust and catalytic sensing capabilities, particularly in colorimetric and electrochemical analyses. Their superior stability and reusability compared to natural enzymes make them ideal candidates for environmental monitoring. This review provides a comparative analysis of these techniques, highlighting their strengths, limitations, and real-world applicability. Emerging trends include hybrid systems that combine the benefits of multiple approaches. The discussion concludes by addressing current challenges and providing perspectives on future directions for advancing heavy metal detection technologies to improve environmental health and safety. Integrating chromogenic reagents with perovskite materials represents a promising direction for developing robust, sensitive, and easy-to-use sensors for health and environmental safety monitoring.