Nano Fourier Transform Infrared Spectrometer Nano FTIR

A major research challenge in modern chemistry is how to achieve non-destructive chemical composition identification of materials at the nanoscale. Some existing high-resolution imaging technologies, such as electron microscopy or scanning probe microscopy, can to some extent solve this problem to a limited extent, but the chemical sensitivity of these technologies themselves is too low to meet the requirements of modern chemical nanoanalysis. On the other hand, infrared spectroscopy has high chemical sensitivity, but its spatial resolution is limited by the diffraction limit of half a wavelength, which can only reach the micrometer level, and therefore cannot be used for nanoscale chemical identification. The nano FTIR nano Fourier transform infrared spectroscopy developed by the German company Neaspec using its unique scattering based near-field optical technology makes nanoscale chemical identification and imaging possible. This technology combines the high spatial resolution of atomic force microscopy with the high chemical sensitivity of Fourier transform infrared spectroscopy, enabling chemical resolution of almost all materials at the nanoscale. Therefore, the nano new era of modern chemical analysis began from then on. The scattering near-field technology of neaspec company detects the backscattered light when scanning the sample surface with an interferometric probe tip, and simultaneously obtains the intensity and phase signals of the near-field signal. When using a wide wave infrared laser to irradiate the AFM tip, the infrared spectrum within the 10nm region below the tip can be obtained, namely nano FTIR

The nano FTIR spectrum is highly consistent with the standard FTIR spectrum:

Without using any model correction, the molecular fingerprint characteristics reflected in the near-field absorption spectra obtained by the nano FTIR Fourier transform infrared spectrometer are highly consistent with those obtained using traditional FTIR spectrometers (as shown in the figure below). This is of great significance in both basic research and practical applications, as researchers can compare the nano FTIR spectra with data from widely established traditional FTIR spectral databases, thereby achieving fast and accurate material chemical analysis at the nanoscale. The combination of high sensitivity to chemical composition and ultra-high spatial resolution makes nano FTIR a unique tool for nanoanalysis.

Main technical parameter configuration:

• Reflective AFM needle tip illumination
• Standard spectral resolution: 6.4/cm-1
• Background free detection technology protected by patents
• Optimization based Fourier Transform Spectrometer
• Collection rate: Up to 3 spectra /s
• A detection module optimized for high-performance near-field spectroscopic microscopy
• Upgradable spectral resolution: 3.2/cm-1
• Suitable detection range: visible, infrared (0.5-20 µ m)
• Including replaceable beam splitter base
• Suitable for synchrotron radiation infrared light source NEW!!!

Application Cases

Study on the Penetration Behavior of Single Virus Membrane

In recent years, influenza viruses have been used as prototypes for enveloped viruses to study the process of virus entry into host cells. Hemagglutinin (HA) in IFV is the main surface glycoprotein embedded in the IFV envelope. HA is responsible for the connection between IFV and host cell receptors, and participates in mediating membrane fusion during virus entry. Numerous studies have established a recognized model for the fusion mechanism between targets and viral membranes. This model suggests that pores can only be formed when the target and virus membrane undergo membrane fusion, thereby mediating virus cell membrane permeation behavior. However, other reports have also observed the rupture of the target and viral membrane before fusion occurs. In addition, studies on adenovirus proteins and host cells have shown that the host cell membrane may be disrupted and enter the virus without membrane fusion. On the other hand, the viral envelope and the target host cell membrane have different chemical compositions or structures, and the requirements for forming pores in each membrane are different. Therefore, the rupture of the target host or viral membrane may also be independently induced.

In summary, there is still some controversy regarding the mechanism of virus cell membrane permeation behavior. Clarifying the complex fusion mechanism between individual viruses and host cells can provide favorable information for designing antiviral compounds. However, conventional virus fusion assays are a collective response to membrane fusion events and cannot directly and quantitatively study subtle, especially complex fusion details at the nanoscale. Therefore, they cannot directly quantify some fusion details that can be obtained by studying individual viruses, nanoscale surface glycoproteins, and lipid envelopes. For example, the chemical and structural changes in the virus membrane and host cell membrane caused by viral infection at the molecular level can be detected through molecular specific infrared spectroscopy technology. However, the size of individual viruses, surface glycoproteins, and lipid envelopes is smaller than the diffraction limit of infrared light, which limits the infrared spectroscopic study of individual viruses. Therefore, it is crucial to find a tool that can provide nano high spatial resolution while also detecting mechanical and chemical properties (molecular specific infrared spectroscopy) and environmental influences, enabling the study of virus membrane fusion processes at the single virus level.

Researchers Sampath Gamage and Yohannes Abate from the University of Georgia and Georgia State University in the United States used nano FTIR&neaSNOM to study the structural changes of a single prototype enveloped influenza virus X31 in different pH environments. At the same time, the effectiveness of antiviral compound (compound 136) in preventing virus membrane damage during changes in environmental pH was quantitatively evaluated, providing a new mechanism for inhibiting virus entry into cells.

Detailed information reading: Application topic | Nano FTIR&neaSNOM technology helps scientists achieve research progress on single virus membrane permeation behavior

reference: [1] Sampath Gamage, Yohannes Abate et al.， Probing structural changes in single enveloped virus particles using nano-infrared spectroscopic imaging， PLOS ONE.

Chemical identification of nanoscale pollutants

The nano FTIR Fourier transform infrared spectrometer can be applied to the chemical identification of pollutants in nanoscale samples. The cross-sectional AFM imaging image of Si surface covered with PMMA film is shown in the following figure. The AFM phase image shows the presence of a 100nm sized pollutant at the interface between Si sheet and PMMA film, but its chemical composition cannot be determined from this image. The infrared spectrum obtained using nano FTIR at the center of the pollutant clearly reveals the chemical composition of the pollutant. By comparing the absorption spectra obtained from nano FTIR with those in the standard FTIR database, it can be determined that the pollutant is PDMS particles.

AFM surface morphology image (left), a small pollutant can be observed between the Si substrate (dark area B) and the PMMA film (A). In the mechanical phase image (middle), the contrast change proves that the pollutant is different from other substances in the substrate and film. Compare the nano FTIR absorption spectra of points A and B (right) with the standard infrared spectroscopy database to obtain the chemical composition information of each component The collection time for each spectral line is 7 minutes, and the spectral resolution is 13 cm-1 （'Nano-FTIR absorption spectroscopy of molecular fingerprints at 20 nm spatial resolution.,”,F. Huth, A. Govyadinov, S. Amarie, W. Nuansing, F. Keilmann, R. Hillenbrand,）Nanoletters 12, p. 3973 (2012)）

Study on phonon polaritons in two-dimensional boron nitride crystals

Van der Waals crystal is a thin layer crystal composed of weak van der Waals forces between layers, similar to the single atomic layer of graphene in graphite blocks. This type of crystal has special properties such as superconductivity, ferromagnetism, and luminescence.

S. Dai et al. used Neaspec's Nano FTIR spectroscopy system to investigate phonon polaritons (a type of photon optical phonon coupling) in thin boron nitride crystals of different thicknesses. The results indicate that the propagation phenomenon of polarized waves exists on the surface of boron nitride crystals, and the wavelength of polarized waves varies with the thickness of boron nitride crystals. The analysis results can also obtain the dispersion characteristics of surface phonon polaritons. These experimental data can be well matched with the theoretical model. Compared with graphene, the loss factor of boron nitride crystals is much smaller, so the propagation distance of surface acoustic waves in boron nitride crystals is relatively larger.

reference: S.Dai; et.al. Tunable Phonon Polaritons in Atomically Thin van der Waals Crystals of Boron Nitride. Science 2014, 343, 1125-1129.

Phase distribution during the charging and discharging process of lithium batteries

I. T. Lucas et al. conducted a detailed study on the phase distribution of lithium iron phosphate during the charging and discharging process of lithium batteries using Neaspec's nano Fourier transform infrared spectroscopy (nano FTIR) technology. Based on the study of infrared absorption spectra of positive electrode materials at different stages of charge and discharge, the experimental results directly prove that the positive electrode material partially delithiated during the intermediate process of charge and discharge simultaneously exists in two phases: lithium iron phosphate and iron phosphate. By establishing and analyzing a three-dimensional tomographic imaging model, the "shell core structure" model consisting of a shell composed of iron phosphate surrounding a core composed of lithium iron phosphate is most suitable for explaining the results obtained from this experiment. Analysis shows that during the process of lithium removal, the lithium iron phosphate in the core gradually decreases until it eventually disappears.

reference: I. T. Lucas ; et. al. IR Near-Field Spectroscopy and Imaging of Single LixFePO4 Microcrystals. Nano Letters 2015, 15, 1-7.