## 1 Introduction  
Surface-enhanced Raman spectroscopy (SERS) technology has attracted widespread attention since its discovery in 1974 [1]. Comparing to the normal Raman scattering process, SERS is capable of enhancing Raman scattering of analytes by up to a million times or more [2]. It has the potential to provide a very fast and sensitive method of detecting chemicals and biomolecules, which is useful for applications that require fast and highly sensitive detection [3; 4]. For example, [PERSON] [5] et al. used a SERS probe for intracellular imaging, SERS signals were strong enough and could be detected even from inside cells. SERS can also be employed to study weak interaction between protein and alizarin [6]. Many SERS substrates use colloidal clusters of noble metal nanoparticles or noble metals with a rough surface to enhance SERS signals. For example, [PERSON] [7] et al. used silver nanoparticles, tri-iron tetroxide, and carbon cores to form multilayered microsphere particles SERS substrate to detect pentachlorophenol (PCP), diethylhexyl phthalate (DEHP), and trinitrotoluene (TNT). In 2014, Au-Ag-S substrate developed by [PERSON] et al. [8] was used for surface-enhanced Raman detection and photocatalytic degradation of DEHP and DEHA. [PERSON] et al. [9] developed an alloy of gold and silver nanoparticles urchin shape (hollow Au-Ag alloy nanourchins, HAAA-NUs) as a SERS active substrate to detect \(10^{-15}\) mol/L of DEHP. Most of these studies focus on achieving large enhancement factors, but fail to address the uniformity and reproducibility of these substrates. Due to the random distribution of nanoparticles on the substrate, the interparticle gap size is difficult to control. Therefore, it is difficult to uniformly control the generation of hot spots, resulting in large signal intensity variations, which is detrimental to quantitative analysis. Some researchers have tried to use linker molecules to control the distance between colloidal nanoparticles. For example, [PERSON] [10] et al. made silver nanoparticle array tethered to a silver film using an appropriate tethering linker such as a dithiol or diamine. However, these linker molecules usually require a dedicated environment (some pH levels or temperatures) to serve the desired purpose, which limits their applications. In addition, linker molecules can block the analyte and prevent it from attaching to the plasmonic surface, which results in a low SERS signal of the analyte. Furthermore, it is possible for the linker molecules to introduce background noise, making the desired SERS signal difficult to measure. The lack of uniform, reproducible and low-cost SERS active substrates suitable for quantitative analysis remains a major obstacle to the widespread use of SERS for routine analysis [11]. Many research efforts have focused on the development of bottom-up and top-down approaches for the manufacture of controllable and reproducible metal nanostructures for SERS applications [12]. These approaches include: anodic aluminum oxide (AAO) templates assist techniques, lithographic techniques, and oblique angle deposition (OAD) technique. For the metal nanoparticle arrays created using AAO templates, [PERSON] et al. [13] used electroless deposition and adjusted the pH and temperature of the gold plating bath to control the plating rate to achieve the desired particle size and interparticle gap. [PERSON] [14] used densely packed nanowires fabricated from AAO templates. Nevertheless, these approaches require sacrificing the AAO template each time to produce an ordered gold nanoparticle array, which results in increased time and cost expense. For the lithographic techniques, [PERSON] et al. [15] uses block copolymer micellar nanolithography to create seeds for chemical growth of uniform Ag nanoparticle arrays. However, controlling seeds growth at the same rate is not easy, which makes it difficult to obtain a large-sized uniform Ag nanoparticle array.