Metallic nanocube ensembles exhibit tunable localized surface plasmon resonance to induce the light manipulation at the subwavelength scale. Nevertheless, precisely control anisotropic metallic nanocube ensembles with relative spatial directionality remains a challenge. Here, we report a DNA origami based nanoprinting (DOBNP) strategy to transfer the essential DNA strands with predefined sequences and positions to the surface of the gold nanocubes (AuNCs). These DNA strands ensured the specific linkages between AuNCs and gold nanoparticles (AuNPs) that generating the stereo‐controlled AuNC‐AuNP nanostructures (AANs) with controlled geometry and composition. By anchoring the single dye molecule in hot spot regions, the dramatic enhanced electromagnetic field aroused stronger surface enhanced Raman scattering (SERS) signal amplification. Our approach opens the opportunity for the fabrication of stereo‐controlled metal nanostructures for designing highly sensitive photonic devices.
Magnetic core gold shell nanostructures which integrate both SERS activity and superparamagnetism are widely utilized in SERS-based detection as SERS substrates, sample separation and preconcentration operators, as well as external magnetic field controlled directional carrier. However, most of the reported gold shells coated on the magnetic cores had smooth surfaces rather than branched nanostructures with enhanced SERS activity. Here, a novel type of Fe3O4-Au core-shell nanoparticles with branched gold shell was prepared by a seed-mediated method together with the shape induction agent AgNO3, and their growth process and mechanism, properties, as well as morphologically controlled synthesis were also investigated. The branched gold coated magnetic nanoparticles (B-GMNPs) with improved SERS performance were further utilized to build superparamagnetic and SERS-active capturers by assembling tetrahedral DNA onto their surfaces for sandwich-structured detection of cancer-related biomarker miRNA-21. The experimental results indicate that highly sensitive and specific detections can be obtained by the proposed SERS sensing system including B-GMNPs and tetrahedral DNA, and the limit of detection (LOD) of miRNA-21 in serum is 623 amol L −1 . These B-GMNPs can be used as good SERS substrates with the functions of external magnetic field controlled sample separation and directional enrichment for effective SERS-based biochemical sensing and detections.
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