In the present work, we report a practical fabrication method of gold-aluminium substrates for surface enhanced Raman spectroscopy. A commercial aluminium-foil was used to fabricate SERS substrates by depositing gold nanocuboids and faceted particles onto their surfaces using the drop-drying method. The gold nanoparticles were characterized by ultraviolet-visible spectroscopy, while the size and morphology were determined by field emission scanning electron microscopy. The performance of the substrates was investigated using Rhodamine 6G in a water solution where a volume of 3 μl was placed on the surfaces of the SERS substrates, and the Raman spectra were immediately acquired using diode laser excitation at 785 nm. The estimated analytical enhancement factor of the gold-aluminium substrates was 1.8 × 106, using a solution of Rhodamine 6G with a concentration of 1 × 109 (0.4796 ppb). We show that our SERS substrates can be easily fabricated, and that they are reproducible and have suitable surface uniformity, thus allowing one to analyse Rhodamine 6G not only as a dry sample, but also in a solution.
We report a simple preparation of surface enhanced Raman spectroscopy (SERS) substrates with gold concave nanocubes of different sizes, deposited onto aluminum slides. The SERS substrates were characterized using 4-Aminothiophenol. Resulting in that the substrate prepared with 55 nm nanocubes exhibits the higher analytical enhancement factor (AEF), 1.5 × 106. Moreover, the SERS substrates’ performance was also evaluated for thiram detection using a series of water and tomato juice samples spiked with the pesticide. Our results show that the excellent performance of the substrate allows the detection of thiram with high sensitivity. The substrates were able to detect thiram with a limit of detection of 7 ppm and 14 ppm, respectively, in water and tomato juice. Our preliminary results open the possibility of using our methodology to detect diverse pollutants of interest.
Aluminum is the most common metal element found in earth, one of its crystalline forms is the pseudoboehmite, used mainly as catalyst [1]. There are many chemical reactions to synthesize pseudoboehmite, most of them include heat treatment and result in a powder [2,3]. While in other works high purity Al plates are necessary to growth pseudoboehmite on its surface; in this work, easily available aluminum alloy 6063 (Al-6063) plates were employed to synthesize pseudoboehmite/aluminum, resulting in a low-cost functionalized substrate for the analysis of nanoparticles by Scanning Electron Microscopy (SEM) [3].Al-6063 is a very common and cheap alloy used widely in machine shops. The plates were worked in a grinding machine using 25µm alumina oxide, followed by Brasso metal polisher on a clean cotton fabric. The cotton fabric was replaced until a mirror like ending was obtained. To eliminate the residues of the metal polisher, they were rinsed with acetone and alcohol under sonication for 15min.An electropolish solution was prepared by mixing perchloric acid (Aldrich, 70%) and ethanol (Aldrich, 99.8%) (4:1), this solution was kept at 4C by an ice bath. The Al-6063 plates were immersed in the perchloric acid solution at 25V and 2.5A for 40s. The plates were then rinsed with Milli-Q water, followed by immersion in sodium hydroxide (1.5M, Aldrich) and nitric acid (1.4M, Aldrich) solutions, rinsed again with water, immersed into boiling water for two minutes and finally blow dried with cleaned air.The formation of a pseudoboehmite layer over the Al-6063 was confirmed by X-ray diffraction according to ICDD 00-021-1307 card (XRD, D2 Phaser Bruker, with a Bragg-Brentano geometry and Cu-kα radiation (λ=1.5418Å) and using the following scan: step size = 0.02°, t = 5s, 10° ≤ 2θ ≤ 80°) (Fig. 1A). The hydroxyl groups available in the surface allow the functionalization by immersing the plates in a 20mM (3-Mercaptopropyl)trimethoxysilane (MPTS, Aldrich) methanolic solution (Aldrich) for 15h. In order to eliminate the unbounded MPTS molecules, the plates were rinsed with deionized water and dried in an oven at 120C for 10 min.These functionalized Al-6063 plates allowed a uniform deposit of gold nanoparticles by drop casting (Fig. 1B). As an example, concave gold nanocubes (CGNC) were synthesized in a seed mediated growth method [4,5] and concentrated 40x by centrifugation (1100g). Next, a 3µL nanocubes solution drop was placed on the functionalized Al-6063 plates and left to dry at room temperature. To ensure that the surfactant of the nanoparticles was removed, samples were plasma cleaned (Femto low-pressure plasma system, Diener) for 10min under nitrogen flow. SEM images (JEOL, JSM-7800F, operating in gentle beam mode at 15kV and 3mm working distance) show the mesoporous surface due to the pseudoboehmite and the attached CGNC (Fig. 1C). The functionalized surface of the Al plates allowed the homogeneous deposit of the CGNC (Fig. 1D).Here we have demonstrated that by using a low-cost Al-6063 plates it was possible to synthesize ...
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