Huan Yang,Xinbing Jiang,Manman Zhang,Ben Q Li,Jiajie Wang,Yiping Han
We report a structure of silicon eccentric shell particles array, fabricated by the SiO2 particles monolayer array assisted deposition of amorphous Si, for high-efficiency light confinement. The SiO2 particles monolayer array is tailored to regulate its interparticle distance, followed by silicon film deposition to obtain silicon eccentric shell arrays with positive and negative off-center distance e. We studied the Mie resonances of silicon solid sphere, concentric shell, eccentric shell and observed that the eccentric shell with positive off-center e supports superior light confinement because of the enhanced Mie magnetic resonances. Spectroscopic measurements and finite difference time domain simulations were conducted to examine the optical performance of the eccentric shell particles array. Results show that the Mie magnetic resonance wavelength can be easily regulated by the size of the inner void of the silicon shell to realize tunable enhanced light confinement. It was found silicon shell with D = 460/520 nm offered high enhanced light absorption efficiency at wavelength of λ = 830 nm, almost beyond the bandgap of the amorphous silicon.
Junjie Wang,Chunxiang Xu,Milan Lei,Yi Ma,Xiaoxuan Wang,Ru Wang,Jianli Sun,Ru Wang
The detection of cardiac markers with high sensitivity and specificity is exceedingly essential for the early diagnosis and warning of cardiovascular disease. In this work, we developed a microcavity-based sandwich immune chip to realize the ultrasensitive detection of cardiac troponin I (cTnI) and creatine kinase isoenzyme MB (CK-MB) by surface-enhanced Raman spectroscopy (SERS) method. Herein, polystyrene microspheres modified with gold nanoparticles (Au NPs) were fixed on the substrate via polydopamine, which was used as an immune capture chip. 5,5′-Dithio bis-(2-nitrobenzoic acid) (DTNB) and 4-mercaptobenzoic acid (4MBA) labelled Au NPs served as immune signal probes for cTnI and CK-MB, respectively. Light confinement effect of polystyrene (PS) microcavities and localized surface plasmon resonance (LSPR) near the Au NPs synergistically strengthened the electromagnetic field and promoted the interaction between light and matter, which enhanced SERS performance with an enhancement factor of 1.95 × 10 12 for SERS sensing. The immunoassay results demonstrated the sensitive quantitative detection with the limit of detection (LOD) of 3.16 pg/mL and 4.27 pg/mL for cTnI and CK-MB, separately. The method also had good specificity, reproducibility and stability. It could be expected that our proposed microcavity-based SERS chip immunoassay technique would be considered as an effective diagnostic tool for ultrasensitive detection of cardiac biomarkers.
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