## 2 Materials and Methods  
All solvents and reagents were obtained from the commercial sources and were used without further purification. Cetyltrimethylammonium chloride-stabilized gold nanotriangles (CTAC-stabilized Au NTs) were synthetized following a three-step (seed preparation, growth and shaping) procedure previously described in the literature [23]. Briefly, first Au seeds were synthesized by the standard CTAC/NaBH\({}_{4}\) procedure; then a \"growing solution\" (CTAC, HAuCl\({}_{4}\) and NaI onto Milli-Q water) and a \"shaping solution\" (CTAC, HAuCl\({}_{4}\) and NaI) were prepared. Ascorbic acid was added to both solutions and were manually stirred until they become colorless (AuIII\(\rightarrow\) AuI). Consequently, 250 uL of seeds were added to solution 1 and manually stirred. Right after, 3.2 mL of solution 1 were added to solution and left to react in the dark during 1 h at room temperature. Finally, to induce flocculation of Au NTs, cetyltrimethylammonium bromide (CTAB) was added until the desired concentration of CTAC+CTAB was reached. The solution was left overnight to flocculate the gold nanotriangles. Scanning electron microscope (SEM) JEOL 7001F with Oxford light elements, energy dispersive (EDX) detector and electron backscatter diffraction (EBSD) detector (JEOL, Tokyo, Japan) was used to characterize the size distribution and morphology of Au triangles. Transmission Electron Microscopy (TEM) measurements were carried out on a Transmission Electron Microscope Hitachi 8100 with ThermoNoran light elements EDX detector and digital image acquisition (Hitachi, Tokyo, Japan). UV-visible spectroscopic measurements of CTAC-stabilized Au NTs aqueous solutions were performed on a PerkinElmer Lambda 750 UV-visible spectrophotometer (PerkinElmer, Inc., Waltham, MA, USA), using a 1 cm path length quartz cuvette. The catalytic oxidation reactions of cyclohexane were performed in an Anton Paar Microwave 300 reactor (Anton Paar GmbH, Graz, Austria) fitted with a rotational system and an infra-red (IR) temperature detector, in G10 borosilicate glass tubes. In a typical experiment, were introduced in a 10 mL Pyrex tube a desired volume of Au NTs solution, 5.00 mmol of cyclohexane and 50 uL of nitromethane (as internal standard). The additive (if any) was added and the reaction started by adding TBHP (70% aqueous solution, 10.0 mmol) in one portion. The mixture was irradiated with 10 W and stirred (650 rpm) at the desired temperature (30-70 \({}^{\circ}\)C) and reaction time (1-6 h). After the reaction, the obtained mixture was cooled to room temperature and centrifuged. A sample (4 uL) was taken from the organic phase and analyzed by gas chromatography (GC) upon the addition of an excess of PPh\({}_{3}\) to reduce cyclohexyl hydroperoxide to cyclohexanol, following a method developed by [PERSON] [25; 26]. For the experiments using air as oxidant, atmospheric pressure was used, and the other reaction conditions are the same as the stated before. GC measurements were performed in a FISONS Instruments GC 8000 series gas chromatograph with a flame ionization (FID) detector and a capillary column (DB-WAX, column length: 30 m; internal diameter: 0.32 mm) and the Jasco-Borwin v. 1.50 software (Jasco, Tokyo, Japan) using helium as the carrier gas. The temperature of injection was 240 \({}^{\circ}\)C. The initial temperature was kept at 100 \({}^{\circ}\)C for 1 min, then increased 10 \({}^{\circ}\)C/min until 180 \({}^{\circ}\)C and maintained at this temperature for 1 min. GC-MS analyses were executed in a Perkin Elmer Clarus 600 C instrument (He as the carrier gas). The ionization voltage was 70 eV. GC was conducted in the temperature-programming mode, using an SGE BPX5 column (30 m \(\times\) 0.25 mm \(\times\) 0.25 \(\upmu\)m). All products formed were identified by comparison of their retention times confirmed with those of commercially available samples.