Noninvasive and sensitive thermometry is crucial to human health monitoring and applications in disease diagnosis. Despite recent advances in optical temperature detection, the construction of sensitive wearable temperature sensors remains a considerable challenge. Here, a flexible and biocompatible optical temperature sensor is developed by combining plasmonic semiconductor W 18 O 49 enhanced upconversion emission (UCNPs/ WO) with flexible poly(lactic acid) (PLA)-based optical fibers. The UCNPs/WO offers highly thermal-sensitive and obviously enhanced dual-wavelength emissions for ratiometric temperature sensing. The PLA polymer endows the sensor with excellent lighttransmitting ability for laser excitation and emission collection and high biocompatibility. The fabricated UCNPs/WO-PLA sensor exhibits stable and rapid temperature response in the range 298− 368 K, with a high relative sensitivity of 1.53% K −1 and detection limit as low as ±0.4 K. More importantly, this proposed sensor is demonstrated to possess dual function on real-time detection for physiological thermal changes and heat release, exhibiting great potential in wearable health monitoring and biotherapy applications.
Highly sensitive detection of refractive index (RI) is essential for the analysis of the bio-microenvironment and basic cellular reactions. To achieve this, optic-fiber RI sensors based on localized surface plasmon resonance (LSPR) have been widely used for their flexibility and high sensitivity. However, the current optic-fiber RI sensors are mainly fabricated using glass, which makes them face the challenges in biocompatibility and biosafety. In this work, a RI sensor with high sensitivity is fabricated using metal-nanostructure-decorated spider silk. The spider silk, which is directly dragged from Araneus ventricosus, is natural protein-based biopolymer with low attenuation, good biocompatibility and biodegradability, large RI, great flexibility, and easy functionalization. Hence, the spider silk can be an ideal alternative to glass for sensing in biological environments with a wide RI range. Different kinds of metal nanostructures, such as gold nanorods (GNRs), gold nanobipyramids (GNBP), and Ag@GNRs, are decorated on the surface of the spider silk utilizing the surface viscidity of the silk. By directing a beam of white light into the spider silk, the LSPR of the metal nanostructures was excited and a highly sensitive RI sensing (the highest sensitivity of 1746 nm per refractive index was achieved on the GNBP-decorated spider silk) was obtained. This work may pave a new way to precise and sensitive biosensing and bioanalysis.
Optical manipulation of metal nanowires offers a promising route to building optoelectronic nanosystems, which remains a challenge because of their strong absorption or scattering properties. Here, precise optical manipulation of a single Ag nanowire, including capture, translation, rotation, immobilization, and release, was readily achieved within a large operation range of 100 μm by a single unpolarized Gaussian beam based on an optical scattering force. Besides, the optical forces and torques exerted on the Ag nanowires under different conditions were quantitatively analyzed and calculated by simulation to give insight into the manipulation mechanism. This proposed scattering-force-based optical manipulation method also has great position and orientation stability with a capture stiffness of 1.2 pN/μm and an orientation standard deviation of 0.3°. More surprisingly, it is independent of both laser polarization and the metal material, shape, and size and is a universal and promising strategy for the manipulation and assembly of nontransparent structures in mesoscopic/Mie sizes.
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