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The flow of Mask R-CNN model for processing digital polymerase chain reaction (dPCR) fluorescence images.

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The complexity of lithography methods and other methods utilizing chiral templates to produce three-dimensional structures restricts further research on chiral plasmonics. Herein, a plasmonic nanostructure with a strong chiroptical response and enhanced near-fields generated on a large and highly ordered achiral tapered nanopore anodic aluminum oxide template is proposed and fabricated via a low-cost and efficient glancing angle deposition method. The plasmonic chiral conic nanoshell metallic nanostructure (CCNM), which is composed of three nanoshells of different heights, is obtained by varying the incidence and orientation angles of deposition to achieve symmetry breaking. Such a conic nanoshell nanostructure can couple incident light into the nanostructure, thus reducing the reflection and localizing the electromagnetic energy inside the nanoshell. The experimental circular dichroism spectra of the CCNM in the visible range shows that the chiroptical response is amplified with an increased height difference of the three nanoshells and period of the nanopore. The dissymmetry factor of the CCNM is up to 0.45, which results from the helix-like electron oscillation characteristics on the surface of the three nanoshells. The simulation result shows that the enhancement of the chiral near-fields of the CCNM reaches 155 times with respect to the circularly polarized light due to the small angle between electric and magnetic fields. The chiral signal is enhanced by about 2 orders of magnitude using the CCNM to detect chiral molecules. This study offers a concise and large-area regular method for fabricating plasmonic chiral nanostructures with a tunable chiroptical response and provides an effective and convenient idea to control the chiral near-fields for sensitive biomolecule detection.

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Real-time observation of small volumes helps to understand phenomena ranging from reaction kinetics to cellular heterogeneity. However, highthroughput real-time monitoring systems based on droplets are rarely reported due to droplet motion and coalescence. Herein, a thermosetting oil is developed as a continuous phase to solve these problems through transforming into elastic solid after droplet generation. The thermosetting oil consists of silicon oil, nonionic surfactant, vinyl silicone oil, hydrosilicone oil, and Pt catalyst. Using Pt as the catalyst, the polymerization of this mixture can be accomplished in 72 min and 37 s at 37 and 95 °C, respectively, based on the hydrosilation of vinyl silicone oil and hydrosilicone oil without other inducers (e.g., UV, Ca 2+ ). Droplet-based real-time monitoring of digital polymerase chain reaction (PCR) and cell culture is successfully achieved using this thermosetting oil, demonstrating that droplets motion and coalescence can be eliminated by the crosslinking material without the influence on bioreactions. In addition, the PCR products can be totally recovered from microcapsules created by this oil for further analysis. Thus, the newly developed oil allows real-timely monitoring individual droplets in a high-throughput manner, as well as has potential for other bioreactions and cell-based assays.

The designed superhydrophobic−superhydrophilic hybrid surface (SSHS) with highly ordered tip-capped nanopore arrays can be used as an intelligent and fast platform to realize different analyte solutions with different concentrations to be detected at the same time by surfaceenhanced Raman spectroscopy. This surface is fabricated in a large area by a facile and low-cost method of programmed multistep anodization of aluminum and pore widening process followed by selective chemical modification. The highly ordered tip-capped nanopore arrays can induce the highly sensitive and reproducible Raman signal, whose enhanced factor for rhodamine 6G (R6G) at 1358 cm −1 is 4.46 × 10 6 . The superhydrophobic− superhydrophilic hybrid property can realize the homogeneous distribution of the concentrated analyte in a droplet at the fixed place, which can avoid the diffusion-limit problem and further enhance the Raman signal. Surface-enhanced Raman spectroscopy of dried droplets with different concentrations of R6G or thiram is tested on SSHS, which show good reproducibility. The detection limits of R6G and thiram on SSHS are 10 −10 and 10 −7 M in 50 μL droplets, respectively. Due to the industrial compatibility of the fabrication technique, this smart surface has the potential to evolve into a general platform to develop various advanced chemical and biological sensors.

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