Nanotube coating helps shrink mass spectrometers

Tue, 03/25/2014 - 11:52am
Elizabeth K. Gardner, Purdue Univ.

A carbon nanotube-coated paper triangle placed on an ionization source charged by a small battery is held in front of a mass spectrometer. Researchers at Purdue Univ. and the Indian Institute of Technology Madras studied the use of carbon nanotubes to advance ambient ionization techniques. Image: Purdue Univ./Courtesy of Thalappil PradeepNanotechnology is advancing tools likened to Star Trek's "tricorder" that perform on-the-spot chemical analysis for a range of applications including medical testing, explosives detection and food safety.


A team of researchers from Purdue Univ. and the Indian Institute of Technology Madras performed the study, which is detailed in a designated "very important paper" by Angewandte Chemie.

"This is a big step in our efforts to create miniature, handheld mass spectrometers for the field," said R. Graham Cooks, a distinguished prof. of chemistry. "The dramatic decrease in power required means a reduction in battery size and cost to perform the experiments. The entire system is becoming lighter and cheaper, which brings it that much closer to being viable for easy, widespread use."

Cooks and Thalappil Pradeep, a prof. of chemistry at the Indian Institute of Technology Madras, Chennai, led the research.


The National Science Foundation-funded study used an analysis technique developed by Cooks and his colleagues called PaperSpray ionization. The technique relies on a sample obtained by wiping an object or placing a drop of liquid on paper wet with a solvent to capture residues from the object's surface. A small triangle is then cut from the paper and placed on a special attachment of the mass spectrometer where voltage is applied. The voltage creates an electric field that turns the mixture of solvent and residues into fine droplets containing ionized molecules that pop off and are vacuumed into the mass spectrometer for analysis. The mass spectrometer then identifies the sample's ionized molecules by their mass.


"The trick was to isolate these tiny, nanoscale antennae and keep them from bundling together because individual nanotubes must project out of the paper," he said. "The carbon nanotubes work well and can be dispersed in water and applied on suitable substrates."



"Under these conditions, the analysis is nearly noise free and a sharp, clear signal of the sample is delivered," he said. "We don't know why this is – why background molecules that surround us in the air or from within the equipment aren't being ionized and entering into the analysis. It's a puzzling, but pleasant surprise."


"It is a very soft method," Cooks said. "Fragile molecules and complexes are able to hold together here when they otherwise wouldn't. This could lead to other potential applications."


Source: Purdue Univ.


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