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Abstract Surface‐enhanced Raman scattering (SERS) sensing in microfluidic devices, namely optofluidic‐SERS, suffers an intrinsic tradeoff between mass transport and hot spot density, both of which are required for ultrasensitive detection. To overcome this compromise, photonic crystal‐enhanced plasmonic mesocapsules are synthesized, utilizing diatom biosilica decorated with in‐situ growth silver nanoparticles (Ag NPs). In the optofluidic‐SERS testing of this study, 100× higher enhancement factors and more than 1,000× better detection limit are achieved compared with traditional colloidal Ag NPs, the improvement of which is attributed to unique properties of the mesocapsules. First, the porous diatom biosilica frustules serve as carrier capsules for high density Ag NPs that form high density plasmonic hot‐spots. Second, the submicron‐pores embedded in the frustule walls not only create a large surface‐to‐volume ratio allowing for effective analyte capture, but also enhance the local optical field through the photonic crystal effect. Last, the mesocapsules provide effective mixing with analytes as they are flowing inside the microfluidic channel. The reported mesocapsules achieve single molecule detection of Rhodamine 6G in microfluidic devices and are further utilized to detect 1 × 10−9mof benzene and chlorobenzene compounds in tap water with near real‐time response, which successfully overcomes the constraint of traditional optofluidic sensing.
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Silica Nanowire Growth on Coscinodiscus Species Diatom Frustules via Vapor–Liquid–Solid Process
Abstract Diatom frustules are a type of porous silicon dioxide microparticle that has long been used in applications ranging from biomedical sensors to dye‐sensitized solar cells. The favorable material properties, enormous surface area, and enhanced light scattering capacity support the promise of diatom frustules as candidates for next generation biomedical devices and energy applications. In this study, the vapor–liquid–solid (VLS) method is employed to incorporate silica nanowires on the surface of diatom frustules. Compared to the original frustule structures, the frustule–nanowire composite material's surface area increases over 3‐fold, and the light scattering ability increases by 10%. By varying the gold catalyst thickness during the VLS process, tuning of the resultant nanowire length/density is achieved. Through material characterization, it is determined that both float growth and root growth processes jointly result in the growth of the silica nanowires. From a thermodynamics point of view, the preferential growth of the silica nanowires on frustules is found to have resulted from the enormous partial surface area of gold nanoparticles on the diatom frustules. The frustule–nanowire composite materials have potential applications in the development of novel biomedical sensing devices and may greatly enhance next generation solar cell performance.
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- Award ID(s):
- 1762739
- PAR ID:
- 10078232
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Small
- Volume:
- 14
- Issue:
- 47
- ISSN:
- 1613-6810
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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