Nano-FTIR absorption and far-field FTIR (ATR modality) spectra measured on the same polymer sample show great agreement.

The subsequent Fourier transform of this interferogram returns the near-field spectra of the sample. Recording the backscattered signal while translating the reference mirror yields an interferogram. The sample stage is placed into one arm of a conventional Michelson interferometer, while a mirror on a piezo stage is placed into another, reference arm. Nano-FTIR detects the tip-scattered light interferometrically. Thus by detecting tip scattering, one can obtain information about the sample. A sample, brought into this near field, interacts with the tip electromagnetically and modifies the tip (back)scattering in the process. The tip greatly enhances the illuminating IR light in the nanoscopic volume around its apex, creating a strong near field. Nano-FTIR is based on s-SNOM, where the infrared beam from a light source is focused onto a sharp, typically metalized AFM tip and the backscattering is detected. Principles of near-field probing: the sample is analyzed via scattering from a sharp, externally illuminated probe Nano-FTIR is complementary to tip-enhanced Raman spectroscopy (TERS), SNOM, AFM-IR and other scanning probe methods that are capable of performing vibrational analysis. Nano-FTIR can be utilized from THz to visible spectral rangeР’В (and not only in infrared as its name suggests) depending on the application requirements and availability of broadband sources. It uses an AFM operated in noncontact mode that is intrinsically nondestructive and sufficiently gentle to be suitable for soft-matter and biological sample investigations. Nano-FTIR does not require special sample preparation and is typically performed under ambient conditions. Р”Р‡or organic compounds, polymers, biological and other soft matter, nano-FTIR spectra can be directly compared to the standard FTIR databases, which allows for a straightforward chemical identification and characterization. Nanoscale chemical identification with nano-FTIR: local spectroscopy performed by nano-FTIR allowed for chemical identification of a nanoscale contaminant РІР‚вЂњ a Polydimethylsiloxane (PDMS) particle РІР‚вЂњ adjacent to a Poly(methyl methacrylate) (PMMA) film. A spatial resolution of 10Р’В nm to 20Р’В nm is routinely achieved. Recording infrared spectra as a function of position can be used for nanoscale mapping of the sample chemical composition, performing a local ultrafast IR spectroscopy and analyzing the nanoscale intermolecular coupling, among others. The detection of a single molecular complex and the sensitivity to a single monolayer has been shown. Nano-FTIR is capable of performing infrared (IR) spectroscopy of materials in ultrasmall quantities and with nanoscale spatial resolution. The use of broadband infrared sources enables the acquisition of continuous spectra, which is a distinctive feature of nano-FTIR compared to s-SNOM. complete spectrum at every pixel of the scanned area) with nanoscale spatial resolution determined by the tip apex size. Scanning the tip allows for performing hyperspectral imaging (i.e. In nano-FTIR, the sample stage is placed in one of the interferometer arms, which allows for recording both amplitude and phase of the detected light (unlike conventional FTIR that normally does not yield phase information).

A typical nano-FTIR setup thus consists of an atomic force microscope, a broadband infrared light source used for tip illumination, and a Michelson interferometer acting as Fourier transform spectrometer.

As s-SNOM, nano-FTIR is based on atomic-force microscopy (AFM), where a sharp tip is illuminated by an external light source and the tip-scattered light (typically back-scattered) is detected as a function of tip position. Nano-FTIR ( nanoscale Fourier transform infrared spectroscopy, also known as scattering-type scanning near-field optical spectroscopy) is a scanning probe technique that can be considered as a combination of two techniques: Fourier transform infrared spectroscopy (FTIR) and scattering-type scanning near-field optical microscopy (s-SNOM). The schematic representation of a nano-FTIR system with a broadband infrared source.

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