# Pt-Based Nanostructures for Observing Genuine SERS Spectra of _p_-Aminothiophenol (PATP) Molecules
## 3 Results  
The morphology of the as-prepared products was investigated by SEM at different magnifications. A typical low-magnification SEM image, as seen in in Figure 1a, shows that the sample can be prepared in uniform large quantities. The Pt-based hollow nanostructure size is about 300 nm, as shown in Figure 1c,d. It demonstrates that the Pt-based hollow nanostructure surface is rough, indicating that the sample has a high surface area to volume ratio. This feature is very important for enhancing the substrate SERS activity, especially for the Pt substrate, which has low SERS activity, to allow the acquisition of high quality SERS spectra. The SERS and catalysing property of as-prepared Pt hollow nanostructures will be described later. The EDS data (Figure S1a) shows that the main signal peaks are ascribed to the elements Co and Pt, and reveals that the atomic ratio of Co to Pt is nearly 30:70. The XRD data of samples is shown in Figure S1b, which represents a good match with the face-centered cubic (fcc) structure of CoPt, according to the Bragg reflections data [35; 36]. The TEM image shown in Figure 2a displays a single Pt-based nanostructure, in which a hollow core can be deduced from the distinct color contrast. The size of the Pt-based hollow nanostructure is about 300 nm, in agreement with the SEM image in Figure 1d. In Figure 2b, the hollow structure was more evident given the bright colour contrast. To investigate the elemental distribution of the Pt-based hollow nanostructures, the TEM-EELs Co mapped image of the Pt-based hollow nanostructure is shown in Figure 2c. Because the EELs spectroscopy is not sensitive to the Pt element, and no EELs Pt  
Figure 1: Scanning electron microscope (SEM) images of Pt-based hollow nanostructures. Scale bars in (**a**–**d**) indicate the images proceed from from low to high magnification. map could be collected. The EELs spectrum of Co is shown in Figure S2. The corresponding selected area electron diffraction (SAED) pattern taken from the area shown in Figure 2a, demonstrates a typical polycrystalline fcc structure with lattice parameter a = 0.38 nm. It is in good agreement with the obtained XRD data, and the lattice fringes of CoPt which were measured to be 0.22 and 0.19 nm, corresponding to the (111) and (200) planes, respectively. High-resolution TEM (HR-TEM) images of the Pt-based hollow nanostructures are shown in Figure S3 for additional support. The genuine SERS spectrum of the 10\({}^{-4}\) mol/L PATP molecules [37] adsorbed on the Pt-based hollow nanostructure surfaces under a laser wavelength of 532 nm is shown in Figure 3a. The emission spectrum of the Pt nanostructure powder was observed with a Raman spectrometer, using a 504 nm wavelength excitation laser as shown in Figure S4. In the SERS spectrum, the band at 1580 cm\({}^{-1}\) is assigned to the C=C stretching vibration of the benzenyl ring mode and the band at 1080 cm\({}^{-1}\) is attributed to the C-S stretching mode. The band at 1180 cm\({}^{-1}\) corresponds to the C-H deformation mode [31]. And it can be calculated that the EF factor is approximately \(1\times 10^{6}\), and the detailed analysis method can be seen in the Supporting Information (Figure S5). In addition, the high power of the laser on the focal spot can result in the thermal effects. This is known to promote the PATP dimerising to DMAB. However, as shown in Figure 3a, the vibrational peaks of DMAB at 1140, 1390, and 1432 cm  
Figure 2: (**a**) Transmission electron microscope (TEM) image of a single Pt-based hollow nanostructure. (**b**) TEM image of a single Pt-based hollow nanostructure with enhance color contrast. (**c**) TEM-EELs mapping of Co element in the Pt-based hollow nanostructure. (**d**) The corresponding selected area electron diffraction (SAED) image of Pt-based hollow nanostructure. were not observed in the SERS spectrum. This demonstrated that the SERS signal could be attributed to the PATP monomer, instead of DMAB dimerising from two PATP molecules.