Light Absorption

A UV-vis-NIR spectrophotometer is a non-destructive technique that measures the absorbance, transmittance and/or reflectance of light by a material.

Our instrument covers a broad range of wavelengths from 190 nm in the UV all the way through the visible and into the near-infrared up to 2500 nm with the fitted integrating sphere accessory. The wavelengths that interact with a material can tell us about its composition, the amount or concentration of a component and optical properties. In addition, the integrating sphere enables the measurement of total, diffuse and specular reflectance.

The technique has applications across several areas:

  • Concentration in solutions: A core usage of UV-vis is the determination of an unknown concentration of a compound in solution. First a calibration plot is made with known concentrations of the material of interest, then comparisons are made with unknowns. This can be used to determine the presence of certain compounds in solutions, products of reactions, consumption of reactants, degradation and so on.
  • Colour identification: Using spectra obtained in the visible light region (400 – 780 nm) the colour can be determined according to various industry standards. Image shown is a chromati city diagram for CIR 1976 colour space, one of several calculations available.
  • Efficiency of optical surfaces: The diffuse and specular reflectance of surface can easily be measured using the integrating sphere, so that surface scattering can be quantified. Schematic shows some examples of common reflection types.
  • Semiconductor band gaps: The calculation of Tauc plots from spectra can be used to measure band gaps in semiconductors.
  • Nanoparticles and plasmons: Nanoparticles and nanostructures with dimensions at or less than the wavelength of light interact with light in different ways that can be characterised using UV-vis spectroscopy. Image shows a representation of a light wave passing over a silver nanoparticle, inducing oscillation of charge across it. Depending on size and shape, certain wavelengths will be absorbed.

For more information or to discuss your testing requirement, please contact Dr Wayne Lam at wayne.lam@brunel.ac.uk

You can return to our main Commercial Services page to see what else we have that could support your requirements.