*2.2. Preparation of Au-TNR Hybrid Nanoparticles*

Au-TNR hybrid nanoparticles were prepared through a modified Turkevich method. The corresponding procedure is described as follows: heat treatment of TNR powder was carried out by ultrasonically dispersing the powder in deionized water for 30 min. Then, the white TNR suspension was stirred using a magnetic stirrer at ~25 ◦C for 30 min, after which 1 mM HAuCl4·3H2O was dissolved in the TNR solution under constant stirring. After the solution was heated to 300 ◦C, 38.8 mM of sodium citrate (>99.0%, Sigma-Aldrich) solution was dissolved in the TNR solution. To ensure a complete reaction, the suspension was stirred until its color changed from white to purple. The purple suspension was sequentially cooled to room temperature, centrifuged at 8500 rpm, and washed several times with deionized water. Finally, Au-TNR hybrid nanoparticles were obtained without agglomeration by freeze-drying.
