Ultrasensitive detection of saccharides using terahertz sensor based on metallic nano-slits

Enhancing Multi-Spectral Fingerprint Sensing for Trace Explosive Molecules with All-Silicon Metasurfaces

Spectroscopy is a powerful tool to identify the specific fingerprints of analytes in a label-free way. However, conventional sensing methods face unavoidable barriers in analyzing trace-amount target molecules due to the difficulties of enhancing the broadband molecular absorption. Here, we propose a sensing scheme to achieve strong fingerprint absorption based on the angular-scanning strategy on an all-silicon metasurface. By integrating the mid-infrared and terahertz sensing units into a single metasurface, the sensor can efficiently identify 2,4-DNT with high sensitivity. The results reveal that the fingerprint peak in the enhanced fingerprint spectrum is formed by the linked envelope. It exhibits a significant enhancement factor exceeding 64-fold in the terahertz region and more than 55-fold in the mid-infrared region. Particularly, the corresponding identification limit of 2,4-DNT is 1.32 µg cm-2, respectively. Our study will provide a novel research idea in identifying trace-amount explosives and advance practical applications of absorption spectroscopy enhancement identification in civil and military security industries.

Design and assembly of porous organic cages

Porous organic cages (POCs) represent a notable category of porous materials, showing remarkable material properties due to their inherent porosity. Unlike extended frameworks which are constructed by strong covalent or coordination bonds, POCs are composed of discrete molecular units held together by weak intermolecular forces. Their structure and chemical traits can be systematically tailored, making them suitable for a range of applications including gas storage and separation, molecular separation and recognition, catalysis, and proton and ion conduction. This review provides a comprehensive overview of POCs, covering their synthesis methods, structure and properties, computational approaches, and applications, serving as a primer for those who are new to the domain. A special emphasis is placed on the growing role of computational methods, highlighting how advanced data-driven techniques and automation are increasingly aiding the rapid exploration and understanding of POCs. We conclude by addressing the prevailing challenges and future prospects in the field.

A terahertz metasurface sensor with fingerprint enhancement in a wide spectrum band for thin film detection

Terahertz spectroscopy is a powerful tool to resolve molecular fingerprints by detecting their vibrational and rotational modes, and has great application potential in chemistry and biomedicine. However, the limited sensitivity and poor specificity restrict its applications in these areas, where trace amounts of analytes need to be identified effectively and accurately. Here, we propose a sensing scheme for enhancing molecular fingerprints based on angle-scanning of terahertz waves on an all-silicon metasurface. The metasurface consists of a periodic array of silicon cylinder dimers arranged in a square lattice. An ultrasharp guided mode resonance governed by bound states in the continuum can be excited by elaborately arranging the silicon cylinder dimers. By utilizing the angle-scanning strategy, two kinds of saccharides are successfully identified with extremely high sensitivity. Specifically, the detection limits for lactose and glucose are 1.53 μg cm^-2 and 1.54 μg cm^-2, respectively. Our study will provide a new idea for the detection of trace amounts of analytes, and promote the application of terahertz technology in chemistry and biomedicine.

Recent advances in the applications of porous organic cages

Porous organic cages (POCs) have emerged as a new sub-class of porous materials that stand out by virtue of their tunability, modularity, and processibility. Similar to other porous materials such...

Enhanced on-chip terahertz vibrational absorption spectroscopy using evanescent fields in silicon waveguide structures

In this study, we demonstrate on-chip terahertz absorption spectroscopy using dielectric waveguide structures. The structures' evanescent fields interact with the sample material surrounding the waveguide, enabling the absorption signature of the material to be captured. The ability of fabricated terahertz dielectric waveguide structures, based on the newly developed silicon-BCB-quartz platform, to capture the fingerprint of α-lactose powder (as an example material) at 532 GHz is examined. Enhancement of the spectroscopy sensitivity through techniques such as tapering the waveguide, confining the field in a slot dielectric waveguide, and increasing the interaction length using a spiral-shaped waveguide are investigated experimentally. The proposed on-chip spectroscopy structures outperform conventional and state-of-the-art approaches in terms of sensitivity and compactness.