Improved colorimetric detection of 2,4,6‑trinitrotoluene through γ-cyclodextrin complexation

Simple and convenient detection of 2,4,6‑trinitrotoluene (TNT) explosive is of great importance for public security and environmental protection. Herein we report the fabrication of a supramolecular visual colorimetric assay for TNT based on γ-cyclodextrin (γ-CD) molecular container. The hydrophobic cavity of γ-CD can encapsulate the hydrophobic TNT molecular because the molecular size of TNT is smaller than that of γ-CD. The γ-CD-TNT inclusion complex can react with NaOH to generate colored Meisenheimer complexes with enhanced absorption capacity, enabling highly sensitive colorimetric detection of TNT. Under optimal experimental parameters, the present visual colorimetric method displays a linear dynamic range of 0–200 μM with a detection limit of 0.8 μM, which shows 2-fold enhancement in the sensitivity compared with the γ-CD-free detection system. When the TNT concentration reaches 10 μM, it is discernible by the naked eye. Moreover, this assay is highly selective to TNT and applied for real water and soil samples. The spiked recoveries vary from 91.5% to 100%, demonstrating the potential practical applications.