Navy

Detection of heavy metals by means of fluorescence change detectable by the naked eye

Tunable, non-toxic, water stable quantum dots for in-field detection of heavy metals

Materials Sensors Environmental

Cotton pads with (a) QD alone, (b) QD with 1 ppm copper added, and (c) QD with 1 ppm dichromate added. Dichromate completely quenched the fluorescence. The left side shows the cotton pads illuminated under a UV light, while the right side shows the luminosity histogram of each pad

The ability to identify heavy metal contamination in a variety of water sources, quickly and inexpensively, would greatly help in many situations.  Many pollution problems could be mitigated if an easy, in-situ analytical method existed to indicate the presence of contaminated water.

Currently, the state of the art technique for metal detection in water is inductively coupled plasma-mass spectrometry – a laboratory centric method.

Navy researchers have developed a simple, easily scaled process for producing fluorescent nanoparticles, including quantum dots that are relatively non-toxic and environmentally stable in both air and water. These nanoparticles are made from more benign metals such as zinc, silver, indium, and copper. The interaction between the nanoparticles and a target analyte (particularly metal ions, both cations, and anions) are used for sensing applications and they are ideally suited for testing in a non-laboratory environment. The technology encompasses several methods of detection including shifting of the wavelength of fluorescence, an enhancement of fluorescence, or quenching of fluorescence when a specific target element or molecule is present.

Analytes of environmental interest such as Cu2+, Hg2+, and Cr6+ have been detected in concentrations as low as ~1ppm.

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