UV Spectroscopy

Ultraviolet (UV) spectroscopy is a analytic technique based on the absorption of light in the UV region of the electromagnetic spectrum, specifically between 200–400 nm. Organic compounds, biomolecules and nanomaterials are among the many different structures analyzed both qualitatively and quantitatively using this method. Due to its high sensitivity and ability to perform fast analysis, UV spectroscopy is a fundamental characterization tool in chemistry, biotechnology, environment science and nanotechnology such as.

Basic Principles

UV spectroscopy relies on the excitation of π electrons and nonbonding electron pairs in molecules to higher energy levels upon absorption of high-energy UV light. Particularly, π→π* transitions (in aromatic structures with conjugated bonds) and n→π* transitions (in groups containing heteroatoms) are observable in this region. The intensity and wavelength of these transitions provide direct information information about the chemical structure of the molecule.

Lambert-Beer Law:

A = ε ⋅ c ⋅ l

A = ε ⋅ c ⋅ l

This law enables the quantitative determination of a substance’s concentration in solution by measuring its absorbance.

Applications

Chemistry and Materials Science

• Used for purification and identification of organic compounds.
• Allows determination of conjugation degree, bonding structure and isomer differentiation.

Biology and Biochemistry

• DNA and RNA exhibit characteristic absorbance at 260 nm, while proteins absorb at 280 nm.
• Enzyme kinetics, protein folding and denaturation processes are analyzed using UV spectroscopy.

Environmental Science

• Phenolic compounds, pesticides and organic pollutants in drinking water can be detected using UV methods.
• UV photodegradation processes are evaluated for environmental remediation.

The Role of UV Spectroscopy in Nanotechnology

1. Optical Characterization of Nanoparticles

Metal nanoparticles (e.g., Ag, Au) exhibit surface plasmon resonance (SPR) in the UV region. The size, shape and distribution of particles can be determined based on the position and intensity of absorbance peaks in the UV-spectrum.

Example: Gold nanoparticles are known to show an SPR peak between 520–540 nm.

2. Activity Analysis of Photocatalysts

Particularly UV-active nanomaterials such as TiO₂ and ZnO can degrade organic pollutants under UV light. These photodegradation processes can be monitored over time by observing changes in the UV spectrum.

🔬 Application example: Monitoring the performance of TiO₂-based photocatalysts used in dye removal, water water purification and air purifiers.

3. Biosensors and Biomedical Applications

The interaction of DNA and protein-coated nanoparticles with target molecules can be tracked via UV spectroscopy through changes in absorbance. Drug loading and release behavior in drug delivery systems are also analyzed using this method.

DNA absorbance changes at 260 nm; protein absorbance changes at 280 nm can indicate binding or structural alterations.

Advantages and Limitations

Advantages:

• Provides fast and simple measurements.
• Non-destructive; does not damage the sample.
• Allows analysis with small sample volumes.
• Delivers both quantitative and qualitative information.

Limitations:

• Only UV-active groups can be analyzed.
• Some solvents (particularly aromatic ones) may interfere with the spectrum.
• Light scattering (especially with nanoparticles) can distort the signal.