Constructing an eco-friendly and ratiometric fluorescent sensor for highly efficient detection of mercury ion in environmental samples

Fast and eco-friendly synthesis of carbon dots from pinecone for highly effective detection of 2,4,6-trinitrophenol in environmental samples

2,4,6-Trinitrophenol (TNP) has high explosive risks and biological toxicity, and there has been considerable concern over the determination of TNP. In the present work, fluorescent carbon dots (CDs) stemmed from a green carbon source of pinecone by the facile hydrothermal approach. A novel environment- friendly fluorescent probe was developed to efficiently detect TNP by using the obtained CDs with remarkable fluorescence stability. The fluorescent CDs exhibited obvious excitation dependence with the highest peaks for excitation and emission occurring at 321 and 411 nm, respectively. The fluorescence intensity is significantly reduced by TNP owing to the inner filter effect with the CDs. The probe exhibited good linearity with TNP concentrations in the range of 0.025-20 μg mL-1, and the limit of detection was as low as 8.5 ng mL-1. Additionally, the probe proved successful in sensing TNP quantitatively in actual environmental samples with satisfied recoveries of 95.6-99.6%. The developed fluorescent probe offered an environment-friendly, efficient, rapid, and reliable platform for detecting trace TNP in the environmental field.Highlights Novel carbon dots were synthesised from green precursors of pineal powder.The highly effective quenching process was put down to the inner filter effect.The as-constructed fluorescent probe was successfully utilised for sensing 2,4,6-trinitrophenol in environmental samples.The proposed method was simple, rapid, efficient, economical, and eco-friendly.

A new Eosin Y-based 'turnon' fluorescent sensor for ratiometric sensing of toxic mercury ion (Hg2+) offering unaided eye detection and its antibacterial activity

A unique fluorescent molecule (ND-S) was obtained from Eosin Y in two simple yet high yielding steps (1). ND-S has special metal ion sensing ability, such that it can selectively detect toxic Hg2+ present in very low concentration in aqueous solutions in the presence of other competing metal ions. The host-guest complexation is ratiometric and is associated with significant increase in fluorescence during the process. Isothermal titration calorimetry (ITC) experiments provided thermodynamic parameters related to interaction between ND-S and Hg2+. Using inductively coupled plasma mass spectrometry (ICP-MS), the Hg2+(aq) removal efficiency of ND-S was estimated to be 99.88%. Appreciable limit of detection (LOD = 7.4 nM) was observed. Other competing ions did not interfere with the sensing of Hg2+ by ND-S. The effects of external stimuli (temperature and pH) were studied. Besides, the complex (ND-M), formed by 1:1 coordination of ND-S and Hg2+ was found to be effective against the survival of Gram-positive bacteria (S. aureus and B. subtilis) with a high selectivity index. Moreover, bacterial cell death mechanism was studied systematically. Overall, we have shown the transformation of a toxic species (Hg2+), extracted from polluted water by a biocompatible sensor (ND-S), into an effective and potent antibacterial agent (ND-M).