1：Experimental Design and Method Selection:

A direct-current atmospheric pressure plasma (APP) setup was used for one-step synthesis of AuNP/CNT hybrids in aqueous solution at room temperature, without reducing agents or surfactants. The design rationale was to leverage plasma-liquid interactions for rapid, green synthesis.

2：Sample Selection and Data Sources:

Carboxyl (-COOH) and hydroxyl (-OH) functionalized multiwall carbon nanotubes (CNTs) were purchased from Cheap Tubes Inc. HAuCl4 solutions (2.5 μM, 0.1 mM, 0.2 mM) were prepared from chloroauric acid trihydrate. Deionized water (18.2 MΩ·cm) was used.

3：5 μM, 1 mM, 2 mM) were prepared from chloroauric acid trihydrate. Deionized water (2 MΩ·cm) was used. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: APP setup with graphite anode and stainless-steel capillary cathode, helium gas supply, sonicator, centrifuge, UV-Vis spectrometer (Cary 60, Agilent), TEM (Philips Tecnai F20D), ζ-potential analyzer (Omni, Brookhaven), XPS system (Kratos Axis Ultra), Raman spectrometer (LabRAM 300, Horiba), diode laser (B4-852-1500-15C, Sheaumann), IR temperature sensor (CSL-CF2, Micro-Epsilon).

4：Experimental Procedures and Operational Workflow:

CNTs were dispersed in water, sonicated, centrifuged, and supernatant collected. HAuCl4 was added to CNT dispersions, settled for 0.5 hour, then treated with APP (2 kV, 5 mA, 10 min). Samples were characterized using UV-Vis, TEM, ζ-potential, XPS, Raman spectroscopy, and photothermal tests with laser irradiation.

5：5 hour, then treated with APP (2 kV, 5 mA, 10 min). Samples were characterized using UV-Vis, TEM, ζ-potential, XPS, Raman spectroscopy, and photothermal tests with laser irradiation. Data Analysis Methods:

5. Data Analysis Methods: TEM images analyzed with ImageJ for particle size distribution (Gaussian fit). XPS data analyzed with CasaXPS software. UV-Vis and Raman spectra interpreted for plasmonic and scattering effects. Photothermal data averaged from three measurements.