Laboratory Description

SISSI-Bio offline Instruments

Fourier Transform infrared spectroscopy (FTIR spectroscopy) may be performed at SISSI-Bio Offline by exploiting a large variety of interferometric systems and associated accessories. The VERTEX 70v (see Figure 1) is an in-vacuum interferometer that may operate in the Mid (MIR) and Fir (FIR) regimes, by using single point DTGS/MCT and bolometric detection schemes respectively. A special technology capable to cover the FIR and MIR in a single scan, named Bruker FM, is also available. Conventional transmission measurements may be done and accessories are available for Single reflection Attenuated Total Reflection, ATR (Platinum by Bruker, Miracle by PIKE Miracle and G-ATR by Harrick Scientific), 25-reflection ATR (25-reflections by Harrick scientific), Infrared Reflection Absorption Spectroscopy accessory (A513/Q Variable angle reflection accessory by Bruker). Diamond compression cells (2 mm culet) and a diamond anvil cell (800 µm culet) are available.
The laboratory is also equipped with the ALPHA II (See Figure 2) compact interferometer by Bruker (PRP@CERIC*). Conceived for being portable and easy to use, the ALPHA II system is equipped for ATR and reflection non-contact measurements, particularly useful for surface analysis of bulky samples.
An additional VERTEX 70 interferometer is also available.

Figure 1 VERTEX 70v interferometer coupled with Hyperion 3000 microscope

Figure 2 ALPHA II at SISSI-Bio OFF-line



SISSI-Bio OFF-line features two FTIR microscopes, for correlating the morphological features of a sample with its local chemistry in the MIR. The Hyperion 3000 Vis/IR microscope (see Figure 1), coupled with the vertex 70v microscope, is equipped with a single point MCT detector for single point measurements and hyperspectral mapping. It also mounts a bidimensional Focal Plane Array (FPA) detector for hyperspectral imaging (64X64 pixels). Transmission, reflection, Grazing incidence and micro-ATR sampling modalities are possible (15X, 36X objectives; micro-ATR objective; grazing incidence (GIR) objective). In addition, a FTIR-600 Linkam cell devoted to dedicated T-dependent studies (-195°C-600°C) may be exploited.
A new Bruker Hyperion II microscope coupled with the INVENIO-II interferometer (see Figure 3) has been recently installed (PRP@CERIC*). With respect to the Hyperion 3000 microscope, the Hyperion II mounts a larger FPA detector (128x128 pixels) for faster imaging of larger areas. The system is also devoted to IR tomography measurements (See Figure 3).


Figure 3 Hyperion II microscopes coupled with INVENIO-II interferometer
 

A microscopy endstation for vibrational hyperspectral mapping and imaging with sub-micrometer lateral resolution is available (see Figure 4). The former experimental station is based on the so-called optical photothermal infrared (O-PTIR) microscopy, also known as Midinfrared photothermal (MIP) microscopy (PRP@CERIC*). The O-PTIR approach may be summarized as an IR-pump/visible probe approach. It works by illuminating a sample with pulsed IR radiation, from a tunable IR quantum cascade laser (QCL). When IR light excites molecular bonds within a sample, a portion of the energy absorbed and dissipated in the sample results in localized heating that, in turn, causes a reduction of the index of refraction of the IR-heated regions. An optical probe beam, i.e. a green-laser, detects the IR-induced changes that alter the intensity and angular distribution of probe light reflected, scattered, and/or transmitted by the sample. O-PTIR microscopy is diffraction limited. However, despite conventional IR microscopes, the aforementioned limit is imposed but the probing visible laser. Considering that visible light wavelengths are on average 1 order of magnitude shorted than Mid-IR wavelengths, the achievable lateral resolution is about a factor 10 better, allowing to switch from the micron to the sub-micron scale.
In addition, O-PTIR supports simultaneous Raman microscopy: sample scattered light may be separated by a dichroic mirror: elastic scattered light is exploited for probing IR sample absorption, whereas inelastic scattered light is sent to a Raman spectrometer for the generation of Raman spectra. As such, the IR and Raman measurements are obtained at the same time, same location, and same spatial resolution. In addition, fluorescence microscopy is also combined within the same instrument.
For more details on the technique and application, the reader may refer to the following recent paper: Craig B. Prater, Mustafa Kansiz, Ji-Xin Cheng; A tutorial on optical photothermal infrared (O-PTIR) microscopy. APL Photonics 1 September 2024; 9 (9): 091101. https://doi.org/10.1063/5.0219983


Figure 4 O-PTIR microscope for IR-Raman-FL microscopy and imaging
  

At SISSI-Bio OFF-line, users may also perform vibrational analysis at the nanoscale exploiting the possibility offered by the near-field NeaSNOM microscope, by Attocube GmbH (see Figure 5). The equipment is suitable for surface analysis by IR scattering-type scanning near field optical microscopy (IR s-SNOM) in the 670-1800 cm^-1 spectral with a DFG laser source (nano-FTIR module) and Photo Thermal Expansion imaging feature AFM-IR modality of the instrument (NIM module) with a QCL laser source.


Figure 5 NeaSNOM microscope. NIM and nano-FTIR module may be seen on the left and the right respectively.

*under the  PNRR (National Recovery and Resilience Plan) project Pathogen Readiness Platform for CERIC-ERIC upgrade (PRP@CERIC), under Mission 4 “Education and Research”, Component 2 “From Research to Enterprise”, Investment Line 3.1 “Fund for the creation of an integrated system of research and innovation infrastructures”,” funded by the European Union – Next Generation EU".