Raman / Raman Spectroscopy & Microscopy

Raman spectroscopy is a non-destructive vibrational technique based on the inelastic scattering of light. A vibration is Raman active if the polarizability attributed to the vibrating entity is modified during the vibration. As such, Raman is complementary to infrared spectroscopy and can be employed on (mostly solid and liquid) samples without sample preparation.

Raman spectra are generated by exciting the sample with monochromatic radiation by means of UV, VIS or NIR lasers, masking the elastically scattered radiation and recording the inelastically scattered phonons in the so-called Stokes and anti-Stokes ranges with appropriate high sensitivity detectors. Scattering is typically measured at 90o or 180o from the exciting line. Dispersive instruments are employed with visible (or UV) excitations. Low energy excitation (e.g. 1064 nm) can benefit from Fourier transform designs. Different excitation lines are needed to avoid unwanted luminescence phenomena, or to tune resonance or surface plasmon enhancements.

Similar to infrared (albeit with different "selection rules") the Raman spectrum is a structural fingerprint of each chemical compound, which can differentiate it from other compounds of either the same composition but different crystal structure (polymorph) or different composition. Quantitative applications are also possible but require the control of the scattering geometry or the use or internal standards.

Tool

(1) Horriba LabRAM HR Evolution dispersive confocal Raman microscope with open plan design
Spectrometer: Fully achromatic UV ready open plan @ fd up to 50 mm
Laser lines: 514.5 nm nm @ max 50 mW (single mode air cooled Argon Ion), 785 nm @ max 200 mW (single mode Solid State)
Detector: CCD, Peltier cooled, 1024 x 2056
Gratings: 600, 1800 grooves/mm
Spectral range: 200 - 1050 nm
Spectral resolution: 0.6 cm-1FWHM (laser @ 585 nm) 1800 grooves/mm grating)
Spatial resolution: 0.5 nm lateral, 2 nm axial (×100 lens 514.5 nm Laser line)
Stages: motorized xyz stage with 2kgr load capacity with 100 nm step
Analysis Software: Lab Spec 6.0

(2) Renishaw RM1000 dispersive confocal Raman microscope
Laser line: 532 nm (DPSS single longitudinal mode, 200mW)
Detector: CCD, Peltier cooled
Gratings: 1800 grooves/mm
Spectral range: 100 - 4000 cm-1
Spectral resolution: ca. 1.0 cm-1 typical
Area of analysis (laser spot): ~1 μm  diameter with ×100 lens
Analysis Chamber: xyz stage
Analysis Software: WiRE 1.3

(3) JASCO RFT-6000 Fourier-transform (FT) Raman spectrometer
Laser line: 1064 nm Nd YAG laser (600 mW)
Detector: InGaAs
Spectral range: ca. 150 to 3600 cm-1
Beam splitter: Si/CaF2
Spectral resolution: variable, 2.0 cm-1 typical
Area of analysis (laser spot): ~20 μm  diameter
Analysis Chamber: Enclosure with xyz stage with 2D mapping capability and easy switching from macro to micro mode and vv
Analysis Software: Spectra Manager

Additional Tools

(a) 10x, 50x and 100x achromatic objectives, 50x Ultra Long Working Distance (10mm) achromatic objective na 0.75
(b) Polariser Analyser set (visible to IR region) for polarisation studies
(c) Fulham Mechanical stage (Tension-Compression-Bending-Shear) for on stage/ under Microscope with 5 N, 50N, 20N, 1000N load cells, monotonic / fatigue loading @ 5Hz
(d) Tension, Bending, Cantilever beam fixtures for static/ step testing under microscope
(e) Peltier heater/ cooler (independent or in combination with Fulham stage), -80 to 120 °C
(f) Heating stage RT to 300 °C

Applications

Raman spectroscopy and microscopy. Fundamental aspects, often coupled with infrared spectroscopy.
Examples: (a) Molecular fingerprint identification (composition, crystal structure), short- and medium-range order (nano- and meso-scale) modification studies in solids. (b) Orientation studies via polarised Raman microscopy. (c) Crystallisation studies, phase change monitoring as a function of the thermal/ electrical/stress field. (d) Temperature dependence of vibrational modes, phase transitions. (e) Depth profiling by confocal data acquisition with 2 μm resolution. (f) Mapping with sub μm spatial resolution. (g) Study of structural heterogeneities. (h) 2D and 3D imaging at the frequency plane as a functions of spectral properties (intensities and relative intensities, FWHM, absolute and relative frequency shifts). (i) Identification of defects. (j) Mapping of internal stresses OD at submicron resolution (relative to spot size), 1D (ie. following a trajectory in space), 2D or 3D.

Sample Specifications

Solid blocks, pellets, powder, films, liquids in capillary.
Sample maximum dimensions: ca. 50 × 50 × 30 (height) mm3
Sample maximum dimensions for Horriba LabRAM HR Evolution: No restrictions due to the Open plan microscope design. Maximum dimension at the optical axis (z) 150mm, no restrictions perpendicular to the focal plane (xy).

Additional Information

(microRaman) Dr. Alkiviadis Paipetis, paipetis@uoi.gr
(FT-Raman) Dr. Michael Karakassides, mkarakas@uoi.gr

Tool

(1) RENISHAW inVia Reflex dispersive confocal Raman microscope
Laser lines: 457.9, 488.0, 514.5, 632.8, 785 nm
Detector: CCD, Peltier cooled
Gratings: 1200, 2400, 3000 grooves/mm
Spectral range: (a) 130 - 3500 cm-1 typical for all laser lines, (b) 15 - 600 cm-1 (for 488.0, 514.5, 632.8 nm using special setup), (c) 5 - 4000 cm-1 for 514.5 nm.
Spectral resolution: ca. 1.0 cm-1 typical
Area of analysis (laser spot): ~1.5 μm diameter with ×100 lens
Analysis Chamber: Enclosure with xyz motorized stage with 2D mapping and depth profiling capability (a few tens of microns per direction)
Analysis Software: WiRE 3.4

(2) BRUKER RFS 100 Fourier-transform (FT) Raman spectrometer.
Laser line: 1064 nm Nd YAG laser
Detector: InGaAs
Spectral range: ca. 80 to 3500 cm-1 (Stokes) and -500 to -80 cm-1 (anti-Stokes)
Spectral resolution: variable, 2.0 cm-1 typical
Area of analysis (laser spot): ~300 μm diameter
Analysis Chamber: Enclosure with 1D motorized stage
Analysis Software: OPUS 4.0

Additional Tools

(a) 5x, 20x, 50x and 100x achromatic objectives, 50x Long Working Distance (7mm) achromatic objective N.A. 0.50
(b) Polariser / Analyser set (457 - 785 nm) for polarisation studies.
(c) Cooling/heating stage (Linkam FTIR 600) operating from -193 (liquid N2) to 300°C (without water cooling circuit).

Applications

Raman spectroscopy and microscopy. Fundamental aspects, often coupled with infrared spectroscopy.
Examples: (a) Molecular fingerprint identification (composition, crystal structure), short- and medium-range order (nano- and meso-scale) modification studies in solids. (b) Orientation studies. (c) Depth profiling by confocal data acquisition. (d) Mapping with μm spatial resolution. (e) Study of structural heterogeneities, Identification of defects. (f) Temperature dependence of vibrational modes, phase transitions.

Sample Specifications

Solid blocks, pellets, powder, films, liquids in capillary.
Sample maximum dimensions: ca. 50 × 50 × 30 (height) mm3

Additional Information

(microRaman) Dr. Dimitrios Palles, dpalles@eie.gr
(FT-Raman) Dr. Vassilis Gionis, vgionis@eie.gr

Tool

(1) Jobin Yvon T-64000 triple micro Raman (ISA-Horiba group) with triple monochromator (low frequency Raman spectra e.g. down to ~5 cm-1) and single spectrograph configurations.
Laser lines/ sources: 632.8 nm, 514.5 and 488 nm
Detector: Spectraview-2DTM liquid N2-cooled CCD detector
Spectra range: 5-3500cm-1
Resolution: better than 1.0cm-1
Area of analysis (laser spot): ~1.5μm (diameter) depending on the laser line
Software: LabSpec 5.93
Accessories: Heating & Cooling microscope stage – Linkam THMS 600/720 (77 – 900 K). Home-made optical furnaces (ambient – 1200 K)
Alternative measurement: Macro (bulk measurements involving conventional lenses) and micro-Raman (measurements with almost light diffraction limit spatial resolution (i.e. ~λ/2, where λ the excitation wavelength).

(2) UV-Vis HR-800 Labram spectrometer of Jobin Yvon–Horiba
Laser line/source: 441.6 nm, 325 nm line (air-cooled HeCd laser of Kimmon Electric Co.)
Detector: Spectraview 2D liquid N2 - cooled CCD detector
Spectra range: 130-4000cm-1
Resolution: ca 1.0cm-1
Area of analysis (laser spot): ~1.5μm (diameter) depending the laser line
Software: LabSpec 5.93
Accessories: Heating & Cooling microscope stage – Linkam THMS 600/720 (77 – 900 K). Home-made optical furnaces (ambient – 1200 K)

(3) Bruker FT-Raman FRA-106/S attached to an EQUINOX 55 spectrometer
Laser line/source: R510 diode pumped Nd:YAG polarized laser at 1,064 nm
Detector: High sensitivity liquid N2-cooled Ge
Spectral range: ca. 80 to 3500 cm-1
Accessories: Home-made optical furnaces (ambient-473K)

(4) Custom made Dilor Super Head of Jobin Yvon– Horiba excited with the linearly polarized light of a solid state Nd:YAG laser, doubled frequency at 532 nm.

Additional Tools

Polarization measurements for estimation of sample’s anisotropy (e.g. segmental orientation in stretched polymers)

Applications

Applications involve in-situ and ex-situ characterization of materials at molecular level as a function of temperature, composition as well as under controlled environment and illumination. Carbon based composite materials (applications on gas separation as well as water purification membranes), sensors (temperature, pH, oxygen etc.), solar cell devices and associated materials, biodegradable as well as typical polymeric materials used as food packaging (laboratory and industrial samples), multifunctional materials used in textiles, nanoparticles and molecular release studies in specific environments, drug delivery materials, ionic liquids and molten salts, . In addition Surface Enhanced Raman Spectroscopy based on controlled colloidal as well as solid state substrates is applied for the identification and quantification of molecular species at extremely low concentrations, while polarization measurements may be applied in order to monitor and quantify segmental orientation in macromolecular systems.

Sample Specifications

Samples could be of any form (solids, liquids or gases). For measurements using the microscope: sample dimensions should be less than ~10 cm (z-axis) and ~30 cm (x-, y-axis), maximum working distance 1.1 mm. For macro measurements: sample dimensions have no restrictions (sufficient positioning of large samples may require support from contact person), maximum working distance 12 cm.

Additional Information

Dr. George Voyiatzis, gvog@iceht.forth.gr

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