Abstract
Oblique angle deposition (OAD) is a simple, low cost, effective, and maskless nanofabrication process. It can offer a reliable method for the mass fabrication of uniform metal nanorods which can be used as the surface-enhanced Raman scattering (SERS) substrate with an excellent enhancing performance. Up to now, Ag nanorods SERS substrates have been extensively studied. However, Ag is chemically active and easy to oxidize under atmospheric conditions. Comparatively, Au is chemically stable and has better biocompatibility than Ag. In this paper, we in detail, studied the electromechanical (EM) field distribution simulation, fabrication, and application of Au nanorods (AuNRs) on trace detection of methamphetamine. According to the finite-difference time-domain (FDTD) calculation results, the maximum EM intensity can be obtained with the length of AuNRs to be 800 nm and the tilting angle of AuNRs to be 71° respectively. The aligned Au nanorod array substrate was fabricated by the OAD process. The two key process parameters, deposition angle, and deposition rate were optimized by experiments, which were 86° and 2 Å/s, respectively. Using 1,2-bis (4-pyridyl) ethylene (BPE) as the probe molecule, the limit of detection (LOD) was characterized to be 10−11 M. The AuNRs were also used to detect methamphetamine. The LOD can be down to M (i.e., 14.92 pg/ml), which meet the requirements of the on-site rapid detection of the methamphetamine in human urine (500 ng/ml).
Highlights
Surface-enhanced Raman scattering (SERS) has been widely used as a powerful tool for ultrasensitive chemical analysis [1] and bioanalysis [2]
This is better than the limit of detection (LOD) of the commercial colloidal gold test paper, i.e., 10−6 M
finite-difference time-domain (FDTD) software was utilized to visualize the electromagnetic characteristic of the Au nanorods (AuNRs)
Summary
Surface-enhanced Raman scattering (SERS) has been widely used as a powerful tool for ultrasensitive chemical analysis [1] and bioanalysis [2]. The metal nanoparticle solution may fail due to long-term storage or vibration These will result in a non-uniform and non-stable SERS performance and make it difficult for quantitative analysis using the SERS technique. Sensors 2019, 19, 3742 nanostructures, which is inherited from the advantages of the fabrication process These will lead to a better SERS performance; the solid-state SERS substrate has a long shelf life (1 year at least) [7]. Many of previous methods proposed were complex, high cost, and time consuming, which made it difficult for mass production [9]. OAD is a very promising SERS substrate fabrication method that features the advantages of easy implementation, more control, low cost, less time consuming, and suitable for mass production
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