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A plasmon-enhanced pyroelectric membrane was applied to control the current flow in a graphene transistor for light detection. The graphene transistor was built on a free-standing, 15-μm-thick PVDF membrane, which was doped using gold nanorods to facilitate its optical absorption. Under the resonant condition, the device exhibited a responsivity of 0.79 μA/mW. 

Exosomes have been considered as high-quality biomarkers for disease diagnosis, as they are secreted by cells into extracellular environments as nanovesicles with rich and unique molecular information, and can be isolated and enriched from clinical samples. However, most existing exosome assays, to date, require time-consuming isolation and purification procedures; the detection specificity and sensitivity are also in need of improvement for the realization of exosome-based disease diagnostics. This paper reports a unique exosome assay technology that enables completing both magnetic nanoparticle (MNP)-based exosome extraction and high-sensitivity photonic crystal (PC)-based label-free exosome detection in a single miniature vessel within one hour, while providing an improved sensitivity and selectivity. High specificity of the assay to membrane antigens is realized by functionalizing both the MNPs and the PC with specific antibodies. A low limit of detection on the order of 10 7 exosome particles per milliliter (volume) is achieved because the conjugated MNP–exosome nanocomplexes offer a larger index change on the PC surface, compared to the exosomes alone without using MNPs. Briefly, the single-step exosome assay involves (i) forming specific MNP–exosome nanocomplexes to enrich exosomes from complex samples directly on the PC surface at the bottom of the vessel, with a >500 enrichment factor, and (ii) subsequently, performing in situ quantification of the nanocomplexes using the PC biosensor. The present exosome assay method is validated in analyzing multiple membrane proteins of exosomes derived from murine macrophage cells with high selectivity and sensitivity, while requiring only about one hour. This assay technology will provide great potential for exosome-based disease diagnostics. 

Abstract Pyroelectric detectors are often broadband and require external filters for wavelength‐specific applications. This paper reports a tunable, narrowband, and lightweight pyroelectric infrared detector built upon a flexible membrane of As₂S₃−Ag−P(VDF‐TrFE) with subwavelength grating, which is capable of both on‐chip filtering and photopyroelectric energy conversion. The top surface of this hybrid membrane is a corrugated As₂S₃−Ag film contributing to narrowband light absorption in the near‐infrared (NIR) regime, and the bottom part is a polyvinylidene fluoride‐trifluoroethylene (PVDF‐TrFE) membrane for the conversion of the absorbed light to an electrical signal. Uniquely, applying a bias voltage to the PVDF‐TrFE membrane enables the tuning of the device's absorption and pyroelectric characteristics owing to the piezoelectrically induced mechanical bending. The resonator exhibited a resonant absorption coefficient of 80% and a full‐width‐half‐maximum of 15 nm within the NIR, a responsivity of 1.4 mV mW⁻¹, and an equivalent noise power of 13 µW Hz^−1/2at 1560 nm. By applying a 15‐V bias to the PVDF‐TrFE membrane, the absorption coefficient decreased to 18% due to the change in the grating period and incident angle. The narrowband and tunable features of the As₂S₃−Ag−P(VDF‐TrFE) pyroelectric detector will benefit a variety of potential applications in sensors, optical spectroscopy, and imaging. 

Abstract This work presents a low‐cost, large‐scale nanofabrication approach that combines imprint lithography and silver doping (IL‐SD) to pattern chalcogenide glass (ChG) films for realizing IR devices. The IL‐SD method involves controled photodoping of silver (Ag) atoms into ChG films and selective removing of undoped ChG. For photodoping of Ag, an Ag‐coated elastomer stamp is brought in contact with the ChG film and exposed to ultraviolet light, and subsequently, the Ag atoms are photo‐dissolved into the ChG film following the nanopatterns on the elastomer stamp. Due to the high wet‐etching selectivity of the undoped ChG to Ag‐doped one, the ChG film can be precisely patterned with a spatial resolution on the order of a few tens of nanometers. Also, by controling the lateral diffusion of Ag atoms during ultraviolet exposure, it is possible to adjust the size of the final patterns formed in the ChG film. As an application demonstration of the IL‐SD process, the As₂S₃‐based near‐infrared photonic crystals (PhCs) in the wavelength range and flexible midinfrared PhCs are formed, and their optical resonances are investigated. The IL‐SD process enables the low‐cost fabrication of ChG nanostructures on different substrate materials and gives a great promise to realize various IR devices.