A critical review on the metal sensing capabilities of optically active nanomaterials: Limiting factors, mechanism, and performance evaluation

Nanomaterials have been the subject of intense and extensive research in developing various optical sensing tools due to their light dependent remarkable structural and functional attributes. In this review, we conducted a comprehensive and critical assessment of the optical sensing methods (e.g., colorimetry and fluorometry) using various types of nanomaterials (e.g., metal organic frameworks, metal nanoparticles, carbon nanomaterials, quantum dots, chiral molecules, and polymers). Special emphasis was placed on explaining key factors that govern their sensing capabilities, sensing mechanisms, and practical applications toward optical sensing of diverse metal species. Some recent case studies elaborating on the detection of toxic and heavy metal species are described in depth. The discussion is also extended to assess the reliability of nanomaterial-based optical sensing approaches with respect to their performance along with the major challenges and constraints in this research field.