Physical Chemistry and Applied Spectroscopy

2020

• Spectroscopic insights into high defect tolerance Zn:CuInSe₂ quantum-dot-sensitized solar cells

2019

• Harshini Mukundan selected as AAAS IF/THEN Ambassador
• Rapid detection of bacteremia in human blood
• Chemistry research featured by DOE BES
• More stable light comes from intentionally squashed quantum dots

The automatic force microscope (AFM) research community has developed a universe of distinct imaging techniques that provide extremely high resolution material contrast. Among these, automatic force microscope infrared spectroscopy (AFM-IR) is the first technique that provides chemical characterization for large classes of samples and can enable the analysis of chemical contrast in the nanometer (nm) spatial regime.

AFM-IR works by illuminating a sample with pulses of infrared radiation, then using the oscillating tip of an AFM to detect the absorbed radiation. Specifically, infrared light, if absorbed by the sample, causes a rapid thermal expansion directly under the AFM tip. This, in turn, alters the resonant oscillation of the AFM cantilever.

An AFM-IR absorption spectrum is created by using a tunable, monochromatic infrared light source and measuring the cantilever oscillation amplitude as a function of the wavelength. The resulting spectrum has the same peak centers, widths and relative intensities as far field infrared absorption, so that the spectra can be compared to traditional spectral libraries.

A variety of imaging modalities are available, including traditional AFM, point nm-scale sampling infrared spectra, AFM-IR imaging using contrast at different frequencies, and full AFM-IR hyperspectral imaging.