Ultraviolet and Visible Absorption Spectroscopy

Ultraviolet and visible (UV-Vis) absorption spectroscopy is the measurement of the attenuation of a beam of light after it passes through a sample or after reflection from a sample surface. This article uses the term UV-Vis spectroscopy to include a variety of absorption, transmittance, and reflectance measurements in the ultraviolet (UV), visible, and near-infrared (NIR) spectral regions. These measurements can be at a single wavelength or over an extended spectral range. This article provides an overview of the technique and does not attempt to provide a comprehensive review of the many applications of UV-Vis spectroscopy in materials research. In this regard, many of the references were chosen to illustrate the diversity of applications rather than to comprehensively survey the uses of UV-Vis spectroscopy. A unifying theme is that most of the measurements discussed in this article can be performed with simple benchtop spectrometers and commercially available sampling accessories. The UV-Vis spectral range is approximately 190 to 900 nm. This definition originates from the working range of a typical commercial UV-Vis spectrometer. This article includes the use of UV-Vis-NIR instruments because of the importance of characterizing the NIR properties of materials for lasers, amplifiers, and low-loss optical fibers for fiber-optic communications and other applications. Wavelength and energy ranges of the UV-Vis and related spectral regions are summarized. Ultraviolet-visible spectroscopy is one of the more ubiquitous analytical and characterization techniques in science. There is a linear relationship between absorbance and absorber concentration, which makes UV-Vis spectroscopy especially attractive for making quantitative measurements. Ultraviolet and visible photons are energetic enough to promote electrons to higher energy states in molecules and materials. UV-Vis spectroscopy is useful to the exploration of the electronic properties of materials and materials precursors in basic research and in the development of applied materials. Materials that can be characterized by UV-Vis spectroscopy include semiconductors for electronics, lasers, and detectors; transparent or partially transparent optical components; solid-state laser hosts; optical fibers, waveguides, and amplifiers for communication; and materials for solar energy conversion. The UV-Vis range also spans the range of human visual acuity of approximately 400 to 750 nm, making UV-Vis spectroscopy useful in characterizing the absorption, transmission, and reflectivity of a variety of technologically important materials, such as pigments, coatings, windows, and filters. The use of UV-Vis spectroscopy in materials research can be divided into two main categories: (1) quantitative measurements of an analyte in the gas, liquid, or solid phase and (2) characterization of the optical and electronic properties of a material. Keywords: ultraviolet spectroscopy; visible absorption spectroscopy; materials properties; related techniques; competitive techniques; principles; material characterization; quantitative analysis; components; single-beam spectrometer; dual-beam spectrometer; array detector spectrometer; method automation; sample preperation; data analysis; specimen modification; problems