Used as a spin label in electron paramagnetic resonance (EPR) spectroscopy to study the dynamics, fluidity, and structure of biological membranes and lipid bilayers. Its nitroxide radical allows detection of molecular motion and environmental changes in membrane systems. Commonly applied in biophysical research to monitor phase transitions, lipid-protein interactions, and membrane permeability. Also utilized in polymer science to investigate microenvironment polarity and viscosity in soft materials.