Thiol-PEG3-phosphonic acid is widely used in surface modification and functionalization due to its unique combination of thiol, polyethylene glycol (PEG), and phosphonic acid groups. It is particularly valuable in creating self-assembled monolayers (SAMs) on metal oxides, such as titanium or iron oxide, where the phosphonic acid group provides strong anchoring. The PEG spacer enhances biocompatibility and reduces non-specific interactions, making it suitable for biomedical applications like biosensors and drug delivery systems. The thiol group allows for further conjugation with biomolecules, nanoparticles, or other functional groups, enabling precise control over surface properties. This compound is also employed in nanotechnology for stabilizing nanoparticles and improving their dispersion in aqueous solutions. Its multifunctional nature makes it a versatile tool in material science, biotechnology, and nanotechnology research.