Indian researchers have synthesised a light-emitting nanoprobe that can detect minute traces of mercury in various water samples, bacteria and small fish1. The nanoprobe can also remove this toxic metal.

The nanoprobe, they say, is potentially useful for monitoring mercury levels in various fish, including edible ones that transport mercury to humans.

The fish without the nanoprobe (above) and a confocal microscope image (below) of its body parts after the injection of the nanoprobe revealing the presence of mercury. © Panda, S. et al.

Fossil fuel burning and various industries emit mercury into the environment, from where it accumulates in fish and other aquatic animals, ending up in humans. Existing techniques for detecting mercury are expensive and complex.

Scientists from the National Institute of Technology in Rourkela and Orissa University of Agriculture and Technology in Bhubaneswar, invented the nanoprobe using modified carbon quantum dots and iron oxide nanoparticles. They then tested the nanoprobe’s efficiency in monitoring mercury in different water samples and in fish.

The researchers, led by Biswaranjan Paital, found that the nanoprobe emitted a feeble green signal in the absence of mercury. However, the green signal became intense in the presence of mercury. The intensity of the signal increased with increasing mercury concentration.

The nanoprobe exhibited a negligible signal in the presence of various metal ions such as sodium, potassium, magnesium and calcium, indicating that it could selectively bind to mercury ions in a solution. Since the nanoprobe contains magnetic nanoparticles, a mercury-attached nanoprobe could be separated using an external magnet.

At high concentrations, the nanoprobe was non-toxic to bacteria, showing that it is biocompatible. It successfully monitored mercury levels in different fish organs such as gills, muscles, the liver and the brain. It also detected mercury levels in bacteria, and tap and river water samples.


1. Panda, S. et al. CQD@γ-Fe2O3 multifunctional nanoprobe for selective fluorescence sensing, detoxification and removal of Hg(II). Colloid. Surface. Physicochem. Eng. Aspect. 589, 124445 (2020)