Label‐Free Fluorometric Detection of Adulterant Malachite Green Using Carbon Dots Derived from the Medicinal Plant Source Ocimum tenuiflorum

Abstract

Food adulteration is an alarming concern in developing countries causing an increased rate of cancer incidents. This study aims to address this concern by detecting adulteration in green vegetables. A facile green one-step and cost-effective strategy to synthesize carbon quantum dots derived from a herbal source has been utilized to design a fluorescence-based sensor for detecting malachite green (MG), a toxic carcinogenic dye, commonly used as an adulterant to give a fresh green look to green vegetables. The leaf-extract of Ocimum tenuiflorum has been used to synthesize highly photostable carbon dots for detecting MG with a limit of detection (LOD) as low as 18 nM. Further, this principle has been utilized to design a prototype calorimetric sensor. The mechanism of the interaction between malachite green and carbon dots has been probed using DFT by employing the SMD solvation model. In addition, CQDs also possess strong antioxidant activity and minimal cytotoxicity enabling their utilization in many biological and sensing applications. This shows the versatility of these easily scalable carbon dots.

Understanding the In Situ Mechanistic Control of Plant‐Derived Carbon Quantum Dots on the Synthesis of Gold Nanoparticles

“…The time‐resolved fluorescence decay curves showed an average lifetime of 3 ns (2.914 ns for E200; 3.055 ns for W200) when fitted into a tri‐exponential function (R 2 =0.999) for all the CQDs hinting at similar energy exchanges and rapid radiative recombination caused due to similar functional groups and carbon core of CQDs (Figure S3). This is in tandem with most carbon dot fluorescence lifetimes reported …”

“…This also may be attributed to the π‐π* or n‐π* electronic transitions of carbon, nitrogen and oxygen double bonds. The absorbance spectra of both ECQDs and WCQDs show absorbance peak maxima in the 200–350 nm range that is typical of plant‐derived CQDs emitting blue fluorescence . It is also to be noted that the solvent largely contributes to the absorbance peak shifts even though the starting material is the same.…”

Recent advances of biomass carbon dots on syntheses, characterization, luminescence mechanism, and sensing applications

“…Using potato starch [ 21 ] as carbon source, CQDs with abundant oxygen groups were synthesized by ultrasonic method, the particle size and QY were 3–5 nm and 10%, respectively. At the same time, green tea, [ 22 ] ocimum tenuiflorum, [ 23 ] and cyanobacteria, [ 24 ] etc. were also used as carbon source to synthesize carbon dots.…”

Sweet Corn (Zea mays L. var. rugosa) Derived Fluorescent Carbon Quantum Dots for Selective Detection of Hydrogen Sulfide and Bioimaging Applications

“…The broad peak centered at 3293 and 3057 cm −1 was attributed to the stretching vibration of –OH or NH 2 and C=O groups, respectively . Besides, a pair of peaks at 1527 and 1388 cm −1 were assigned to the asymmetric and symmetric stretching modes of C−O−C, respectively.…”