A comprehensive review of theoretical approaches to simulate plasmonic-active metallic nano-arrangements is given. Further, various fabrication methods based on bottom-up, self-organization and top-down techniques are introduced. Here, analytical approaches are discussed to investigate the optical properties of isotropic and non-magnetic spherical or spheroidal particles. Furthermore, numerical methods are introduced to research complex shaped structures. A huge variety of fabrication methods are reviewed, e.g. bottom-up preparation strategies for plasmonic nanostructures to generate metal colloids and core-shell particles as well as complex-shaped structures, self-organization as well as template-based methods and finally, top-down processes, e.g. electron beam lithography and its variants as well as nanoimprinting. The review article is aimed at beginners in the field of surface enhanced spectroscopy (SES) techniques and readers who have a general interest in theoretical modelling of plasmonic substrates for SES applications as well as in the fabrication of the desired structures based on methods of the current state of the art.

Considering both the potential effects on human health and the need for knowledge of food composition, quantitative detection of synthetic dyes in foodstuffs and beverages is an important issue. For the first time, we report a fast quantitative analysis of the food and drink colorant azorubine (E 122) in different types of beverages using surface-enhanced Raman scattering (SERS) without any sample preparation. Seven commercially available sweet drinks (including two negative controls) with high levels of complexity (sugar/artificial sweetener, ethanol content, etc.) were tested. Highly uniform Au "film over nanospheres" (FON) substrates together with use of Raman signal from silicon support as internal intensity standard enabled us to quantitatively determine the concentration of azorubine in each drink. SERS spectral analysis provided sufficient sensitivity (0.5-500 mg L(-1)) and determined azorubine concentration closely correlated with those obtained by a standard HPLC technique. The analysis was direct without the need for any pretreatment of the drinks or Au surface. Our SERS approach is a simple and rapid (35 min) prescan method, which can be easily implemented for a field application and for preliminary testing of food samples.

Gold plasmonic nanostructures with high sensitivity and spectral reproducibility are key components of molecular sensors based on surface‐enhanced Raman scattering (SERS). In this paper, we report a “bottom‐up” fabrication of gold “film over nanosphere” (FON) substrates for SERS sensing on the basis of very small (107 nm in diameter) polystyrene spheres coated with 20 nm of gold. To obtain close‐packed spheres in a large scale area, the self‐assembly at the water–air interface was found to be very efficient. Sensitivity and reproducibility of the AuFON substrates were tested using various molecular probes: 5,10,15,20‐tetrakis(1‐methyl‐4‐pyridyl)porphyrin, p‐aminothiophenol, and benzocaine. Relative standard deviation of SERS signal was found to be less than 20% confirming good spectral reproducibility especially using a 100× objective. Then, we demonstrated sensitive SERS detection of other biologically important molecules adsorbed on our AuFON substrates: thiolated‐polyA, protoporphyrin IX, and two alkaloids (nicotine and strychnine). Estimated limits of detection were 8.2 × 10−7 and 4.5 × 10−7 M (in order of 100 ng.ml−1) incubation concentration for strychnine and nicotine, respectively. Therefore, we conclude that the 20‐nm gold film deposited on polystyrene spheres of 107 nm in diameter provided both good spectral reproducibility and sensitivity. Their implementation into the SERS‐active system will enable to bring about new quantitative and analytical SERS applications.