Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 9, Issue 38, Pages 32896-32906Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.7b09884
Keywords
dielectric microsphere; PDMS film; microsphere-enhanced Raman spectroscopy; surface-enhanced Raman spectroscopy; flexible Raman enhancer
Funding
- National Natural Science Foundation of China [11674018, 11504012]
- Beijing Nova Program [Z171100001117101]
- Beijing Municipal Commission of Education [KM20150005013]
- Young Talent program of Beijing Municipal Commission of Education
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Dielectric microspheres with extraordinary micro scale optical properties, such as photonic nanojets, optical whispering-gallery modes (WGMs), and directional antennas, have drawn interest in many research fields. Microsphere-enhanced Raman spectroscopy (MERS) is an alternative approach for enhanced Raman detection by dielectric microstructures. Unfortunately, fabrication of microsphere monolayer arrays is the major challenge of MERS for practical applications on various specimen surfaces. Here we report a microsphere-embedded film (MF) by immersing a highly refractive micro sphere monolayer array in the poly(dimethylsiloxane) (PDMS) film as a flexible MERS sensing platform for one-to three-dimensional (1D to 3D) specimen surfaces. The directional antennas and wave-guided whispering-gallery modes (WG-WGMs) contribute to the majority of Raman enhancement by the MFs. Moreover, the MF can be coupled with surface-enhanced Raman spectroscopy (SERS) to provide an extra >10-fold enhancement. The limit of detection is therefore improved for sensing of crystal violet (CV) and Sudan I molecules in aqueous solutions at concentrations down to 10-7 M. A hybrid dual-layer microsphere enhancer, constructed by depositing a MF onto a microsphere monolayer array, is also demonstrated, wherein the WG-WGMs become dominant and boost the enhancement ratio >50-fold. The present work opens up new opportunities for design of cost-effective and flexible MERS sensing platforms as individual or associated techniques toward practical applications in ultrasensitive Raman detection.
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