Functional materials displaying tunable emission and long-lived luminescence have recently emerged as a powerful tool for applications in information encryption, organic electronics and bioelectronics. Herein, we present a design strategy to achieve color-tunable ultralong organic room temperature phosphorescence (UOP) in polymers through radical multicomponent cross-linked copolymerization. Our experiments reveal that by changing the excitation wavelength from 254 to 370 nm, these polymers display multicolor luminescence spanning from blue to yellow with a long-lived lifetime of 1.2 s and a maximum phosphorescence quantum yield of 37.5% under ambient conditions. Moreover, we explore the application of these polymers in multilevel information encryption based on the color-tunable UOP property. This strategy paves the way for the development of multicolor bio-labels and smart luminescent materials with long-lived emission at room temperature.

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All-in-fiber optofluidics is an analytical tool that provides enhanced sensing performance with simplified analyzing system design. Currently, its advance is limited either by complicated liquid manipulation and light injection configuration or by low sensitivity resulting from inadequate light-matter interaction. In this work, we design and fabricate a side-channel photonic crystal fiber (SC-PCF) and exploit its versatile sensing capabilities in in-line optofluidic configurations. The built-in microfluidic channel of the SC-PCF enables strong light-matter interaction and easy lateral access of liquid samples in these analytical systems. In addition, the sensing performance of the SC-PCF is demonstrated with methylene blue for absorptive molecular detection and with human cardiac troponin T protein by utilizing a Sagnac interferometry configuration for ultra-sensitive and specific biomolecular specimen detection. Owing to the features of great flexibility and compactness, high-sensitivity to the analyte variation, and efficient liquid manipulation/replacement, the demonstrated SC-PCF offers a generic solution to be adapted to various fiber-waveguide sensors to detect a wide range of analytes in real time, especially for applications from environmental monitoring to biological diagnosis.

We propose and study an optical microfiber coupler (OMC) sensor working near the turning point of effective group index difference between the even supermode and odd supermode to achieve high refractive index (RI) sensitivity. Theoretical calculations reveal that infinite sensitivity can be obtained when the measured RI is close to the turning point value. This diameter-dependent turning point corresponds to the condition that the effective group index difference equals zero. To validate our proposed sensing mechanism, we experimentally demonstrate an ultrahigh sensitivity of 39541.7 nm/RIU at a low ambient RI of 1.3334 based on an OMC with the diameter of 1.4 lm. An even higher sensitivity can be achieved by carrying out the measurements at RI closer to the turning point. The resulting ultrasensitive RI sensing platform offers a substantial impact on a variety of applications from high performance trace analyte detection to small molecule sensing.

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Controlled fragmentation of graphene is achieved by harnessing the necking process of the thermoplastic polymers. We have pushed the necking phenomenon to become a versatile and lithography-free fabrication tool to precisely ''cut'' graphene into ordered submicron ribbons on a large scale. The fabricated graphene ribbons have higher reactivity due to the numerous graphene edges formed, which can serve as an exceptional platform for the study of graphene edge chemistry. Furthermore, this method can be applied to various atomic-thin layered materials.

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We demonstrate an azimuthally polarized radial emission with zero-angular-momentum from a CdSe/CdZnS/ZnS quantum dots (QDs) fiber laser. This fiber laser is realized by axially pumping the QDs doped gain plug infiltrated in the hollow cavity of a multilayer photonic bandgap fiber. The cylindrically symmetric radial emission is registered as a perfect ring-shaped pattern in the far field. The lasing threshold is measured to be ~238 µJ/pulse and the quality factor (Q-factor) is calculated to be ~4000. The unique radial emission from the resulting QDs fiber laser offers a fundamental solution for the development of omnidirectional displays and light sources for biomedical analysis and phototherapy with minimal invasion.