A review of molecular probes for nickel(II) ion sensing

Water contamination by nickel poses serious risks to human health and ecosystems, underscoring the need for simple and effective sensor-based detection methods. This critical review covers research reported between 2006 and 2024 and explores the relationship between molecular design, structural motifs, and the performance of colorimetric and fluorescent chemosensors for nickel(II) ions. The analysis classifies sensors into categories-including rhodamine, fluorescein, Schiff base, naphthyridine, azo, polymer, imidazole, nanoparticle-based, quinoline, coumarin, and calixarene systems-to elucidate structure-property relationships. Complementing this, a bibliometric analysis of the research landscape reveals a notably lower publication output for nickel sensors compared to those for other metal ions, identifies 'chemosensor' as the most frequent keyword, and highlights India's leading role in co-authorship networks. This review provides valuable insights to guide future research, emphasizing the need to overcome key challenges such as reliance on organic solvents and to advance the development of practical and field-deployable nickel-sensing technologies.