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Guiding analytes to the sensing area is an indispensable step in a sensing system. Most of the sensing systems apply a passive sensing method, which waits for the analytes to diffuse towards the sensor. However, passive sensing methods limit the detection of analytes to a picomolar range on micro/nanosensors for a practical time scale. Therefore, active sensing methods need to be used to improve the detection limit in which the analytes are forced to concentrate on the sensors. In this article, we have demonstrated the manufacturing of nanogap-rich structures for active chemical sensing. Nanogap-rich structures are manufactured from metallic nanoparticles through an optothermally generated microbubble (OGMB) which is a laser-induced micron-sized bubble. The OGMB induces a strong convective flow that helps to deposit metallic nanoparticles to form nanogap-rich structures on a solid surface. In addition, the OGMB is used to guide and concentrate analytes towards the nanogap-rich structures for the active sensing of analytes. An active sensing method can improve the detection limit of chemical substances by an order of magnitude compared to a passive sensing method. The microbubble assisted manufacturing of nanogap-rich structures together with an active analyte sensing method paves a new way for advanced chemical and bio-sensing applications.
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Large‐Scale Sub‐1‐nm Random Gaps Approaching the Quantum Upper Limit for Quantitative Chemical Sensing
Abstract Metallic nanostructures with nanogap features can confine electromagnetic fields into extremely small volumes. In particular, as the gap size is scaled down to sub‐nanometer regime, the quantum effects for localized field enhancement reveal the ultimate capability for light–matter interaction. Although the enhancement factor approaching the quantum upper limit has been reported, the grand challenge for surface‐enhanced vibrational spectroscopic sensing remains in the inherent randomness, preventing uniformly distributed localized fields over large areas. Herein, a strategy to fabricate high‐density random metallic nanopatterns with accurately controlled nanogaps, defined by atomic‐layer‐deposition and self‐assembled‐monolayer processes, is reported. As the gap size approaches the quantum regime of ≈0.78 nm, its potential for quantitative sensing, based on a record‐high uniformity with the relative standard deviation of 4.3% over a large area of 22 mm × 60 mm, is demonstrated. This superior feature paves the way towards more affordable and quantitative sensing using quantum‐limit‐approaching nanogap structures.
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- Award ID(s):
- 1807463
- PAR ID:
- 10454482
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Optical Materials
- Volume:
- 8
- Issue:
- 24
- ISSN:
- 2195-1071
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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