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Analytical Chemistry

AFM Coupled With Mass Spec Plots Properties Of Materials With A Single Platform

Chemical Mapping: New analytical tool boasts high resolution under ambient conditions

by Matt Davenport
May 11, 2015 | A version of this story appeared in Volume 93, Issue 19

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Credit: ORNL/DOE
A hybrid AFM-mass spec method maps topography (left), elasticity (middle), and chemistry (right) of the same 100-µm × 100-µm area of a polystyrene-poly(2-vinylpyridine) blend.
Three squares showing different views of the same surface.
Credit: ORNL/DOE
A hybrid AFM-mass spec method maps topography (left), elasticity (middle), and chemistry (right) of the same 100-µm × 100-µm area of a polystyrene-poly(2-vinylpyridine) blend.

Researchers at Oak Ridge National Laboratory have developed an instrument capable of probing a surface’s physical and chemical properties with unprecedented resolution under ambient conditions (ACS Nano 2015, DOI: 10.1021/acsnano.5b00659). Working in collaboration with Anasys Instruments, a company focused on nanoscale analytics, the team coupled atomic force microscopy and mass spectrometry in a single platform. Researchers have developed similar instruments in the past, but they have struggled to marry AFM’s spatial precision with mass spec’s chemical sensitivity outside a vacuum chamber, explains team leader Olga S. Ovchinnikova. The new platform uses an AFM tip, about 30 nm in diameter, to probe the topography and elasticity of the surface moving beneath it. The teensy tips also locally heat samples, to up to 1,000 °C, vaporizing surface molecules. A stainless steel tube directly above the AFM tip collects liberated molecules and feeds them to a mass spectrometer. This efficient harvesting helped the team map physical and chemical data on polymers, tissue, and bacteria to single pixels smaller than a square micrometer, Ovchinnikova says.

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