Porous Silicon Bragg Reflector and 2D Gold-Polymer Nanograting: A Route Towards a Hybrid Optoplasmonic Platform

Fabrication of optoplasmonic particles through electroless deposition and the application in SERS-based screening of nodule-involved lung cancer

In this work, a core-satellite optoplasmonic particle containing a silica microsphere covered with gold nanoparticles (AuNPs) was developed through wet chemistry synthesis in aqueous phase. The electroless deposition and galvanic replacement were employed to anchor AuNPs onto silica sphere surface. The escalated as well as expanded electric field enhancement within the dielectric-metallic interface was analyzed through finite difference time domain (FDTD) simulation. The numerical models and the surface-enhancement Raman spectroscopy (SERS) measurements over blood serum both support that the equatorial plane is the preferred collecting plane for improved signal intensity and stability. The nanocomposite emerged lower relative standard deviation (RSD) in repetitive measurement compared to AuNPs. In practice, this hybrid structure was applied for lung cancer diagnosis based on serum SERS spectra analysis of the patients diagnosed with nodules. The prediction with the aid of principal component analysis (PCA) and support-vector machine (SVM) was attempted for the classification of healthy, benign and relatively malignant sample groups. The accuracy of distinguish benign samples from malignant ones reaches over 90%. These advantages make the structure a promising SERS substrate for the early screening of cancer based on the non-invasive biological samples.

Plasma Fabrication and SERS Functionality of Gold Crowned Silicon Submicrometer Pillars

Sequential plasma processes combined with specific lithographic methods allow for the fabrication of advanced material structures. In the present work, we used self-assembled colloidal monolayers as lithographic structures for the conformation of ordered Si submicrometer pillars by reactive ion etching. We explored different discharge conditions to optimize the Si pillar geometry. Selected structures were further decorated with gold by conventional sputtering, prior to colloidal monolayer lift-off. The resulting structures consist of a gold crown, that is, a cylindrical coating on the edge of the Si pillar and a cavity on top. We analysed the Au structures in terms of electronic properties by using X-ray absorption spectroscopy (XAS) prior to and after post-processing with thermal annealing at 300 °C and/or interaction with a gold etchant solution (KI). The angular dependent analysis of the plasmonic properties was studied with Fourier transformed UV-vis measurements. Certain conditions were selected to perform a surface enhanced Raman spectroscopy (SERS) evaluation of these platforms with two model dyes, prior to confirming the potential interest for a well-resolved analysis of filtered blood plasma.