Spectroscopic Characterization
Spectroscopic Characterization
Spectroscopic Characterization
Spectroscopic techniques have in common the obtaining of a characteristic spectrum of the sample, based on fundamental properties and resulting from the interaction of an energy source (laser, infrared light, X-rays, UV-Vis light, etc.) with the sample. From spectroscopic techniques it is possible to obtain qualitative and in some cases also quantitative information about the chemical composition of the sample. Applications that use light as an energy source, such as photocatalysis or specialized optical applications, require these techniques for the fundamental characterization of nanomaterials.

In this technique, a monochromatic beam of light is incident on the sample. The Raman spectrum is the result of inelastic scattering that occurs in 1 out of every 106 incident photons and is analyzed in a CCD detector. The spectrum provides information on the vibrational energies of the chemical bonds, obtaining the vibrational fingerprint characteristic of the compounds that are part of the sample. This technique is indispensable for the study of carbon nanomaterials, nanotubes and graphene. The Raman signal is usually weak and the use of plasmonic nanoparticles produces a signal increase of several orders of magnitude between 104 and 108, this technique is known as Raman spectroscopy SERS (Surface Enhance Raman Scattering).

INMA has a WITec Alpha 300 (spectral resolution 2 cm-1) equipped with a confocal microscope, 4 lasers (488, 532, 633, 785nm) and their corresponding detectors. In addition, there is also a fiber coupled to a pressurized system for monitoring chemical reactions in-situ.

INMA researchers working in the field of Raman SERS sensors, for the detection and identification of compounds in trace concentrations, have portable Raman equipment. Raman BWTEK i-Raman® Pro (spectral resolution 6 cm-1) and Serstech 100 Indicator (spectral resolution 10cm-1) using a 785nm laser.

Contact person: Antonio Monzón (amonzon@unizar.es)

Infrared spectroscopy FITIR an infrared beam is incident on the sample and this energy is absorbed by the sample due to the vibration of the chemical bonds, the result is a spectral fingerprint characteristic of the compounds that are part of the sample. This spectral technique is widely used for the identification of organic compounds, polymers and the study of the functionalization of nanomaterials.

The Bruker Vertex 70 FTIR instrument can perform measurements in different configurations, Transmission, Attenuated Total Reflectance, ATR and DRIFT Diffuse Reflectance. A catalytic chamber accessory is also available for in-situ evolution of reactions and a microscope for obtaining compositional maps. There is the possibility of working with a TGS or a liquid nitrogen-cooled CdTe detector.

 Contact Person: Silvia Irusta (sirusta@unizar.es

X-ray photoelectron spectroscopy (XPS) is a quantitative technique primarily used to study the chemical composition of the surface of a material. It is one of the most powerful techniques for the study of surfaces, interfaces and thin films. It is based on shining a focused beam of X-rays on a surface and analyzing the electrons extracted by photoelectric effect, whose kinetic energies are characteristic of the atoms from which they originate and their chemical environment.

This technique is routinely used in the characterization of polymers, alloys, semiconductors, minerals, inks, glasses, paper, wood, bones, biomaterials… and in the study of surface processes/effects such as segregation, diffusion, adsorption, absorption/desorption, corrosion, degradation, adhesion, welding, contamination, cleaning, coating, functionalization, etc. The equipment available at LMA for XPS analysis of the Kratos brand are the AXIS Supra and AXIS UltraDLD.

 More information: LMA 

UV-Vis-NIR spectroscopy is a basic technique in laboratories dedicated to the preparation and characterization of materials. The spectra obtained in the most common configuration are the result of the absorption of incident light by the sample, as a consequence of electronic transitions between quantized levels.

In the case of molecular materials, the absorption bands are generally broad and this quantitative technique is used, among other purposes, to measure the concentration of chemical species (dyes, for example) in solution.

The analysis of the spectra of materials with a certain content of absorbing impurities (ions, chromophores, etc.) makes it possible, for example, to study the influence of the environment or the interactions between the absorbing species.

In the case of plasmonic nanomaterials, the surface plasmon resonance (SPR) is characteristic of the size and shape of the nanoparticles. 

This technique is especially useful for the characterization of photocatalysts, solar cells and, in general, nanomaterials for advanced optical applications.

Several research groups at INMA have UV-Vis equipment available for routine measurements in liquids in transmission configuration. There is also more specific equipment in which it is possible to extend the UV-Vis-NIR measurement range between 175-3200 nm, with different accessories for measurements of solids and surfaces both in transmission and diffuse reflectance and specular reflectance at fixed and variable angles.

 Contact: infraestructurasinma@…

The incident UV light excites the electrons of the molecules, causing radiation emission, conventionally of lower energy, and quantized so it is characteristic of each molecule. This technique is conventionally employed when fluorophore molecules are used as markers in biological samples. The technique is also used for the characterization of nanomaterials with up-conversion properties with applications in photocatalysis and biomedicine. In this case, the light emitted by the material is of higher energy than the incident light.

At INMA there is a fluorimeter capable of 200-800 nm excitation and 200-900 nm emission. Sample holder for liquid cell and sample holder for frontal detection films.

Contact person: Javier Galbán (jgalban@unizar.es)

Mössbauer spectrometer, with CEMS option (conversion electron Mossbauer spectroscopy).

In addition to the features common to Mossbauer spectroscopy, CEMS allows the measurement of very small sample quantities, including nanometric ones.) It has temperature control down to liquid nitrogen on a routine basis.

Contact person: Javier Rubín (jrubin@unizar.es)

Instrument for the precise determination of the spectral response of photovoltaic cells and photodetectors and their photon conversion efficiency (300 – 2500 nm) to electric current. The PVE300 is equipped with silicon and germanium detectors, monochromator and dual halogen and xenon light source.

Contact person: María Bernechea / Emilio Juárez
(mbernechea@unizar.es / ejjuarezperez@unizar.es)

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