UV-VIS spectroscopy is a powerful analytical technique widely used in chemistry, physics, biology, and other scientific disciplines to study the interaction of molecules with ultraviolet (UV) and visible (VIS) light. It provides valuable information about the electronic structure and properties of molecules, helping researchers understand their composition, concentration, and behavior.

The electromagnetic spectrum consists of a range of wavelengths, from short gamma rays and X-rays to long radio waves. Within this spectrum, the UV and VIS regions span wavelengths from approximately 10 nanometers (nm) to 700 nm. UV light has shorter wavelengths and higher energy than visible light, which has longer wavelengths and lower energy.

UV-VIS spectroscopy involves the absorption, transmission, or reflection of UV or visible light by a sample under investigation. When a sample is exposed to light within the UV-VIS range, certain molecules within the sample can absorb specific wavelengths of light. The absorption occurs due to the excitation of electrons from lower energy states to higher energy states within the molecules.

The absorption of light by a sample is dependent on the molecular structure, electronic transitions, and concentration of the absorbing species. UV-VIS spectroscopy is particularly useful for studying conjugated systems, chromophores, and transition metal complexes. It can provide insights into the presence and concentration of substances such as organic compounds, inorganic ions, transition metals, and biological molecules.

The working principle of UV-VIS spectroscopy involves passing a beam of UV or visible light through the sample and measuring the intensity of the transmitted or absorbed light. A spectrophotometer is commonly used in UV-VIS spectroscopy to generate the light beam, split it into different wavelengths, and detect the intensity of the transmitted or absorbed light. The resulting data is often displayed as a UV-VIS absorption spectrum, which shows the absorbance or transmittance of light as a function of wavelength.

UV-VIS spectroscopy offers numerous applications in scientific research and practical fields. It is frequently employed in chemical analysis to determine the concentration of a substance in a solution, characterize the purity of compounds, and investigate chemical reactions. In biological and pharmaceutical sciences, UV-VIS spectroscopy aids in the quantification of biomolecules, drug analysis, and the study of molecular interactions.

Furthermore, UV-VIS spectroscopy is crucial in environmental analysis, including monitoring water quality, analyzing air pollutants, and assessing the presence of harmful substances. It also plays a role in materials science, where it helps study the electronic properties and optical behavior of materials, such as semiconductors and nanoparticles.