Sensitive and label-free shell isolated Ag NPs@Si architecture based SERS active substrate: FDTD analysis and in-situ cellular DNA detection

Abstract

In recent years there has been increasing interest to elicit the molecular dynamics at the single-cell level. In this purview, we report the fabrication of SiO2 capped silver nanoparticles (Ag NPs) on silicon (Si) substrate to understand and divulge the fingerprint of cellular DNA by a label-free method. For the in-situ label free identification thin layer of SiO2 deposited on Ag NPs@Si by e-beam evaporation method which forbids the surface degradation of NPs in culture medium. The hot spots generation in the metal-dielectric nano junction assembly from aggregates of identical and non-identical Ag NPs have been evaluated by Finite-Difference Time-Domain simulation method. The coverage of non-identical Ag NPs with a various layer thickness of SiO2 is shown to be the greatest hotspot rather than an identical particle, and appropriate non-identical NPs are validated with experimental evidence at different excitation wavelengths. The SERS efficiency of analyte molecule Rhodamine 6G is evaluated and the enhancement factor of 107 with the low detection limit up to 10−10 M concentration is achieved. The SiO2-Ag NPs@Si substrate could be an ideal platform for the detection of DNA at cellular level.