# Pt-Based Nanostructures for Observing Genuine SERS Spectra of _p_-Aminothiophenol (PATP) Molecules
## 1 Introduction  
Nanomaterials can exhibit unique properties due to the size effects, when compared to their bulk conterparts [1; 2; 3; 4; 5]. Among various nanostructures, the hollow nanostructure has attracted significant attention owing to its high surface area [6], low density, and potential applications in a series of technologies, such as catalysis [7], optical detection [8; 9; 10; 11], and photothermal therapy [12]. Therefore, it is of interest to explore hollow-structured nanomaterials in the hope of disclosing their important physical properties.  
One of the most significant physical properties of nanostructures is their optical/plasmonic properties [13; 14], which is characterized by their strong interaction with resonant photons through the excitation of surface plasmon resonance (SPR). The SPR effect can be utilized in the analytical technique of surface enhanced Raman scattering (SERS) [15; 16; 17; 18]. Current accepted knowledge suggests that noble metals (Au, Ag, and Cu) are the best materials as SERS substrates, with high enhancement factors [19], and therefore they have been widely applied in Raman detection since the discovery of SERS in 1970s [20]. During the past decades, many efforts have been made to break the limitation of substrate specificity and to expand SERS applications to other metals, especially the transition metals Pd and Pt, which are widely used in catalysis [15; 21; 22]. Recently, it was reported that bimetallic/multiple metallic nanomaterials display novel properties distinct from the pure Pd or Pt element nanostructures [23; 24; 25; 26; 27; 28].  
Unique physical properties benefiting from the synergistic effect of magnetic material (Ni, Co, Fe) alloying were observed in Pt-based bimetallic nanomaterials, such as good electrical, catalytic, and stability characteristics [29; 30].  
SERS spectra of 4-aminothiophenol (PATP) molecules adsorbed on a SERS substrate surface have been widely investigated. In previous work, bands seen at 1140, 1390, and 1432 cm\({}^{-1}\) have been ascribed to the b2 mode, which is selectively enhanced by the chemical enhancement effect [31; 32; 33]. It has been confirmed that these peaks come from 4,4\({}^{\prime}\)-dimercaptoazobenzene (DMAB) molecules due to the dimerisation reaction from PATP to DMAB by surface catalysis, making the observation of SERS spectrum of PATP molecules a challenge [31]. In this work, we attempt to observe the genuine SERS spectrum of PATP with a novel substrate. By one-pot wet chemical method using water solution at room temperature, Pt-based hollow nanostructures were synthesised. Because of the highly damping optical response of the metal, these Pt-based hollow nanostructures exhibited weak dimerising effects with PATP molecules [34]. The genuine SERS spectra of PATP was able to be seen, where the vibrational bands at 1140, 1390 and 1432 cm\({}^{-1}\) from DMAB molecules were absent from observation. Furthermore, the SERS spectra remained consistent with the Raman spectra of PATP powder under laser illumination for more than 2000 s, during the experimental measurement process.