Controlled growth of silver on gold triangular nanoprisms: Improved surface enhanced Raman scattering for ultrasensitive detection of cancer biomarker

The precise design and synthesis of Au and Ag composite nanomaterials can provide them with richer plasmonic modes, resulting in enhanced optical properties. Here, a novel strategy was demonstrated to control the selective deposition of Ag at different positions of Au triangular nanoprisms (Au TNPs). 1,4-benzenedithiol (BDT) was selectively absorbed in different positions of Au TNPs which made Ag selectively deposited on Au TNPs. A series of Ag islands-Au TNPs including 3AgNPs islands-Au@Ag TNPs, 3AgNPs islands-Au TNPs, 2AgNPs islands-Au TNPs and 1AgNPs island-Au TNPs were obtained. We found that Surface enhanced Raman scattering (SERS) activity was closely associated with the position of Ag deposition under the same volume of AgNO₃. It has strongest SERS activity when Ag deposit on the surface, edges and corners of Au TNPs which corresponding to 3AgNPs islands-Au@Ag TNPs with a high enhancement factor of 5.50 × 10⁷. Raman reporter molecules were embedded between Au core, Ag shell and Ag islands which enhanced the stability, making them ideal candidates for Raman tag-based applications. We used it as SERS probes to realize the ultra-sensitive detection of Cyfra21-1, with a low limit of detection of 2.84 × 10⁻¹⁴ g/L and a wide linear range of 1.00 × 10⁻¹³–1.00 × 10⁻¹ g/L.