Xia Zhou,Qian Zhao,Guangqiang Liu,Hongwen Zhang,Yue Li,Weiping Cai
A modified seed growth route was developed to fabricate the Au nanocrystals with high-density tips based on kinetically-controlled growth via adjusting the adding rate of Au seeds into growth solution. The obtained Au nanostructures were chestnut-like in morphology and about 100 nm in size. They were built of the radial [111]-oriented nanoneedles and were 30–50 nm in length. There were about 120–150 tips in each nanocrystal. The formation of chestnut-like Au nanocrystals is ascribed to surfactant-induced preferential growth of seeds along direction [111]. Importantly, the chestnut-like Au configuration displayed powerful surface enhanced Raman scattering (SERS) performance (enhance factor > 107), owing to the high density of tips. Further, such film was used as a SERS substrate for the detection of lindane (γ-666) molecules (the typical organochlorine pesticide). The detection limit was about 10 ppb, and the relationship between SERS intensityIand concentrationCof 666 accords with the double logarithm linear. This work presents a simple approach to Au nanocrystal with high-density tips, and provides a highly efficacious SERS-substrate for quantitative and trace recognition of toxic chlorinated pesticides.Keywords:kinetically-controlled seed growth;chestnut-like Au nanocrystals;high-density tips;SERS performances;chlorinated pesticide residues
Qian Zhao,Guangqiang Liu,Hongwen Zhang,Weiping Cai
A simple and cost-effective route to fabricating gold-coated glass nano-stings' arrays is presented for highly efficient surface enhanced Raman spectroscopy (SERS) chips via reactive ion etching of the glass slide covered with polystyrene (PS) colloidal monolayer and sputtering deposition of gold on it. The as-fabricated SERS chips consist of the nearly-hemispherical particles with submicron-size, which are hexagonally arranged into the ordered arrays. There are many short and long Au-coated glass nano-stings standing vertically on the hemispherical particles, showing high density tips (up to 7.0 × 103 μm−2). The formation of such gold-coated glass hierarchically structured array is attributed to the geometry of PS colloidal monolayer and the nanoscale roughness of glass slide's surface. Further, it has been demonstrated that such gold-coated glass array chip is highly SERS-active and can be utilized to detect trace organophosphorous toxicant with the limit below ppt level and good reproducibility in measurements. The intensity of the Raman peak shows the linear relation, in logarithmic scale, with the organophosphorous concentration from ppt to ppm level, exhibiting the possibility of quantitative detection in a large concentration range. This work has demonstrated the cost-effective method to fabricate the high performance SERS chips for trace detection of toxic molecules.
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