Fluorescent nanoparticles for detection of heavy metals or formulation into paints and coatings

Tunable, non-toxic, water stable quantum dots with broad applications at industrial scale

Materials Sensors Environmental

Schematic of generic ligand-capped fluorescent nanoparticle showing the fluorescence mechanism where light (hν) excites an electron from the valence band (VB) to the conduction band (CB). The loss of energy from the excited electron results in the observed fluorescence.

Fluorescent nanoparticles and their subclass of quantum dots have been explored for many potential applications including high-efficiency solar panels, LEDs, flexible and brighter displays, advanced bioimaging, and biosensing techniques.

Most of these potential applications utilize nanoparticles that are unstable in environmental conditions thus requiring air and water sealed systems and careful treatment to avoid oxidation and deterioration. An additional problem with current nanoparticles is that they are made with toxic metals such as cadmium, selenium, lead, or tellurium. The combination of toxicity and instability limit potential nanoparticle uses outside of a laboratory environment.

Opening the door for broader uses of nanoparticles, 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.

These nanoparticles have potential in a number of naval applications particularly in the areas of biofouling and condition-based maintenance through the visible fluorescence detection of trace metals. In addition to the sensing applications, other uses of these nanoparticles include incorporation into coatings and paints for applications such as safety paint on rotor blades of helicopters to make them more visible at night or commercial applications such as enhanced visibility road signs.

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