A surface-enhanced Raman scattering strategy for detection of peanut allergen Ara h 1 using a bipyramid-shaped gold nanocrystal substrate with an improved synthesis

Abstract

Branched and star-shaped gold nanocrystals have received significant attention owing to their unique optical and electronic properties, but most gold nanocrystals have zero-dimensional shape with varying numbers of branches coming from a quasi-spherical core. Here, we reported an improved method for synthesis of branched gold nanocrystals through the use of a sodium dodecylbenzene sulfonate (SDBS) additive. The introduction of SDBS allows reduction of hexadecyltrimethylammonium bromide to 0.05 M, accelerates the growth rate of gold seeds and improves the side growth over twin boundaries. This leads to formation of five elongated branches with the highest point of each branch bisecting the branch into two halves. The resulting bipyramid-shaped gold nanocrystals (BPGNs) offer excellent monodispersion and thus a morphology separation process for BPGNs is not necessary before use. The hybridization of target DNA with probe DNA will result in a sensitive SERS response. The SERS intensity linearly decreases with the increase of target DNA concentration in the range from 10⁻¹⁴ to 10⁻⁸ M. The detection limit was 3.3 × 10⁻¹⁵ M (N/S = 3). The analytical method provides significant advantages of sensitivity, selectivity and repeatability compared with other SERS methods using gold nanoparticles, gold nanorods and star-shaped gold nanocrystals, and it has been successfully applied to detect peanut allergen Ara h 1 in food samples.