An intrinsic internal standard substrate of Au@PS-b-P4VP for rapid quantification by surface enhanced Raman scattering†
Reliable quantification by surface enhanced Raman scattering (SERS) highly depends on the development of a reproducible substrate with excellent anti-interference capability. In this work, an intrinsic internal standard (IS) SERS substrate based on a diblock copolymer, polystyrene-block-poly-4-vinylpyridine (PS-b-P4VP), as a template was developed by a modified block copolymer lithography (BCL) technique of reserving the diblock copolymer template. This substrate generated a stable vibration peak at 1066 cm−1 attributed to poly(4-vinylpyridine) (P4VP) which could be used as an intrinsic IS for precise SERS quantification. A series of characterization results showed that the diblock copolymer template endowed this substrate with homogeneous distribution of Au nanoparticles, excellent stability and reproducibility. A minor relative standard deviation (RSDs) of SERS responses at 1066 cm−1 was measured and calculated to be 4.3% from ten different substrates in the same batch, which suggested good substrate-to-substrate reproducibility of this substrate. Finally, this intrinsic IS substrate was successfully applied for the rapid quantification of a trace banned dye, chrysoidine, in food samples with complicated matrices by SERS. It was proved that chrysoidine could be found and quantified to be 0.50 and 0.41 mg L−1 in a positive dried bean curd stick and chilli powder sample respectively with good recoveries by this substrate coupled with SERS. The development of intrinsic IS substrates would benefit rapid and accurate quantification of trace targets in complex samples coupled with SERS analysis.