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The article presents information on a study which reveals that introduction of thermosensitive polymers on to gold nanoparticles become responsive to temperature. Poly(N-isopropylacrylamide) (PPA) exhibits a low critical solution temperature (LCST) transition from 30 to 45 degree Celsius. The polymer is hydrophilic and soluble in water below the LCST, but becomes hydrophobic and forms a macroscopic coacervate phase above that temperature due to the fluctuation of hydrophobic interactions and hydrogen bonding. Conjugation with gold nanoparticles requires that the polymer should bear a thiol group at one terminus. Using S-benzyl dithiobenzoate as the reversible addition-fragmentation chain transfer, researchers prepared a PPA homopolymer terminated with thioester groups. Gold nanoparticles coated with thiol-terminated PPA show remarkable temperature sensitivity as manifested in their optical transmittance switching property at 600 nm.