Photothermal FT-IR Spectroscopy: A Step towards FT-IR Microscopy at a Resolution Better Than the Diffraction Limit

Abstract

We have used a miniaturized Wollaston wire resistive thermometer as a probe to record infrared absorption spectra of polymeric samples by detecting photothermally induced temperature fluctuations at the sample surface. This method opens the way to absorption Fourier transform infrared spectroscopy/microscopy with a spatial resolution that is no longer diffraction limited, but is determined instead by the size of the contact between probe and sample. At present, this is on the order of a few hundred nanometers. The thermal probe, of a type used in scanning thermal microscopy and microthermal analysis, allows us to detect the photothermal response of a specimen exposed to the beam of a Fourier transform infrared spectrometer and heated thereby. The signal from this probe measures the resulting temperature fluctuations, and thus provides an interferogram which replaces the interferogram normally obtained by means of direct detection of the IR transmitted by a sample.

Vibrational spectroscopic mapping and imaging of tissues and cells

“…An emerging technique for obtaining maps with a spatial resolution of well below the diffraction limit is photothermal micro-spectroscopy (PTMS), alternatively known as PTTF (photothermal temperature fluctuation) (Hammiche et al 1999;Pollock and Smith 2002). This technique combines FTIR and atomic force microscopy (AFM) using scanning thermal microscopy.…”

Nanoscale optical imaging by atomic force infrared microscopy

“…Scattering near-field microscopy (SNIM) is based on the detection of scattered light from an oscillating antenna i.e. an AFM cantilever tip to enable optical imaging with high lateral resolution [19][20][21][22][23][24][25]. This method uses a vibrating metallic AFM cantilever tip, which periodically and locally modifies the electromagnetic field distribution of the excitation laser which has been focused to a diffraction limited spot size.…”

“…Albeit with this limitation in recovering IR absorption information, SNIM IR imaging has been applied to image a number of systems with a spatial resolution of tens of nm [22]. SNIM has been applied to image functional materials such as insulator-to-metal transition in vanadium dioxide thin films [23]. This studied probed directly percolative insulator metal transition with temperature.…”

Near-field antennas integrated with scanning probes for THz to visible microscopy: scale modeling and limitations on performance

“…Although recent developments have stimulated great interest [1]- [4], the wealth of spectroscopic information available in this regime has thus remained untapped except in collective (far-field) measurements, such as Fourier-transform infrared spectroscopy (FTIR), which is a mainstay of chemical analysis.…”

“…A few groups [25], [26] have adapted this technique to probe samples at the 10.6-m (CO laser) wavelength since it readily accommodates conventional SPM tips, which serve double duty as scattering probes and topography sensors. groups have used total internal reflection tips [27] or heated tips as black body sources for local FTIR spectra [4].…”