Nanoparticles Sense Ultralow Levels Of Toxic Ions | Chemical & Engineering News
Volume 90 Issue 38 | p. 27 | Concentrates
Issue Date: September 17, 2012

Nanoparticles Sense Ultralow Levels Of Toxic Ions

Sensor coated with tiny, striped particles can detect as few as 600 methylmercury cations per mL of water
Department: Science & Technology
News Channels: Nano SCENE, Materials SCENE, Environmental SCENE, Analytical SCENE
Keywords: water analysis, pollution, heavy metals, methylmercury, nanoparticles, sensors
[+]Enlarge
IT’S A TRAP
When coated onto a sensor surface, patterned nanoparticles (red and yellow) capture methylmercury (green), increasing conductance across the device.
Credit: Adapted from Nat. Mater.
A new electronic sensor traps methylmercury cations (green) inside the molecular bristles on its nanoparticles. The particles are coated in alternating rows of hexanethiol (red) and alkanethiols tipped with three units of ethyleneglycol (yellow). The sensor registers the cations via an increase in conductance across its surface.
 
IT’S A TRAP
When coated onto a sensor surface, patterned nanoparticles (red and yellow) capture methylmercury (green), increasing conductance across the device.
Credit: Adapted from Nat. Mater.
[+]Enlarge
FIELDWORK
Grzybowski, Stellacci, and coworkers tested their striped nanoparticle sensors on water from Lake Michigan.
Credit: Thomas Hermans
Photo shows a new electronic sensor, made by coating patterned nanoparticles onto a glass substrate, measures ultralow concentrations of methylmercury in water. The group that developed it tested the device on water from Lake Michigan (in background).
 
FIELDWORK
Grzybowski, Stellacci, and coworkers tested their striped nanoparticle sensors on water from Lake Michigan.
Credit: Thomas Hermans

An electronic sensor coated with patterned nanoparticles can detect concentrations of the toxic ion methylmercury down to attomolar (10–18 M) levels in water (Nat. Mater., DOI: 10.1038/nmat3406). This detection limit—about 600 methylmercury cations per mL of solution—is far below what other analytical methods, such as atomic fluorescence spectroscopy, can achieve, according to the research team that designed the sensor. To fabricate the device, Bartosz A. Grzybowski of Northwestern University; Francesco Stellacci of the Swiss Federal Institute of Technology, Lausanne; and colleagues produced gold nanoparticles covered with alternating rows of short and long molecular bristles: n-hexanethiols and n-hexanethiols tipped with polyethylene glycol units. The team cast a film of the particles onto a glass substrate between two electrodes. When dipped into water containing methyl­mercury, the particles selectively trap the cations among their bristles. After the sensors are dried, the researchers measure this capture via an increase in conductance across the films. The researchers tested their sensors on water from Lake Michigan and on fish collected in Everglades National Park. The methylmercury levels determined from the sensor data agreed within error to published values for the lake and values measured by the U.S. Geological Survey for the fish.

 
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