Greatly enhanced upconversion luminescence was demonstrated by integrating the core−shell upconversion nanorods with the Ag nanogratings. Both the Ag nanogratings and upconversion nanorods were fabricated/synthesized in a facile, cost-effective, high-throughput way. Experimental results showed that the upconversion luminescence intensity of Er 3+ in the core−shell upconversion nanorods can be well tuned and enhanced by changing the shell thickness and the period of the Ag nanograting. The underlying physical mechanism for the upconversion luminescence enhancement was attributed to the plasmonically enhanced near infrared broadband absorption of the periodic Ag nanograting and the localized surface plasmon resonance of Ag nanocrystals. The maximum enhanced factors of 523 nm, 544 nm (green emission), and 658 nm (red emission) of Er 3+ ions excited at 980 nm are 3.8-, 5.5-, and 4.6-folds, respectively. Our fabrication approach and results suggest that such a simple integration is potentially useful for biosensing/imaging and anti-counterfeiting applications.
Over the past decades, considerable development and improvement can be observed in the area of the ion‐sensitive field‐effect transistor (ISFET) for biosensing applications. The mature semiconductor industry provides a solid foundation for the commercialization of the ISFET‐based sensors and extensive research has been conducted to improve the performance of ISFET, with a special research focus on the materials, device structures, and readout topologies. In this review, the basic theories and mechanisms of ISFET are first introduced. Research on ISFET gate materials is reviewed, followed by a summary of typical gate structures and signal readout methods for the ISFET sensing system. After that, a variety of biosensing applications including ions, deoxyribonucleic acid, proteins, and microbes are presented. Finally, the prospects and challenges of the ISFET‐based biosensors are discussed.
We propose and numerically demonstrate a microfluidenabled spinselective chiral metasurface with tunable circular dichroism. The chiral metasurface consists of periodic array of gammadionlike multilayer nanostructures. With the help of microfluidic technology, fine tuning of circular dichroism from the chiral metasurface can be achieved. Numerical results show that a broad tuning range of 40 nm can be achieved, while the circular dichroism only shows a slight decrease. Such a proposed device could be potentially useful for chirality detection, polarimetric imaging, and spincommunications.
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