Modification of AuNRs with PNIPAm or PEG

A general procedure for the modification of CTAB-stabilized AuNRs with thiol-functionalized PEG derivates is as follows: as-synthesized AuNR (20 mL) were centrifuged at 6000 rpm for 30 min. The supernatant was removed, and the AuNRs were redispersed in deionized water. A solution of HS-PNIPAm (M_w = 45 kDa) or HS-PEG-OH (M_w = 3 kDa, 32 mg in 4 mL EtOH) was added, and the reaction mixture was sonicated for 30 min at 60 °C and further 3.5 h at 20 °C.⁴¹ Successively, the mixture was extracted 4 times with CHCl₃ (∼20 mL), washed by centrifugation (3× 6000 rpm for 30 min at room temperature), and finally redispersed in deionized water to yield AuNR–PNIPAm or −PEG hybrids (20 mL).