As compared with epitaxial semiconductor devices, two-dimensional (2D) heterostructures offer alternative facile platforms for many optoelectronic devices. Among them, photovoltaic based photodetectors can give fast response, while the photogate devices can lead to high responsivity. Here, we report a 2D photogate photodiode, which combines the benefits of 2D black phosphorus/MoS2 photodiodes with the emerging potential of perovskite, to achieve both fast response and high responsivity. This device architecture is constructed based on the fast photovoltaic operation together with the high-gain photogating effect. Under reverse bias condition, the device exhibits high responsivity (11 A/W), impressive detectivity (1.3 × 1012 Jones), fast response (150/240 μs), and low dark current (3 × 10–11 A). All these results are already much better in nearly all aspects of performance than the previously reported 2D photodiodes operating in reverse bias, achieving the optimal balance between all figure-of-merits. Importantly, with a zero bias, the device can also yield high detectivity (3 × 1011 Jones), ultrahigh light on/off ratio (3 × 107), and extremely high external quantum efficiency (80%). This device architecture thus has a promise for high-efficiency photodetection and photovoltaic energy conversion.

Two-dimensional (2D) Ruddlesden-Popper perovskites are currently drawing significant attention as highly-stable photoactive materials for optoelectronic applications. However, the insulating nature of organic ammonium layers in 2D perovskites results in poor charge transport and limited performance. Here, we demonstrate that Al 2 O 3 /2D perovskite heterostructure can be utilized as photoactive dielectric for high-performance MoS 2 phototransistors. The type-II band alignment in 2D perovskites facilitates effective spatial separation of photo-generated carriers, thus achieving ultrahigh photoresponsivity of >10 8 A/ W at 457 nm and >10 6 A/W at 1064 nm. Meanwhile, the hysteresis loops induced by ionic migration in perovskite and charge trapping in Al 2 O 3 can neutralize with each other, leading to low-voltage phototransistors with negligible hysteresis and improved bias stress stability. More importantly, the recombination of photo-generated carriers in 2D perovskites depends on the external biasing field. With an appropriate gate bias, the devices exhibit wavelengthdependent constant photoresponsivity of 10 3-10 8 A/W regardless of incident light intensity.

We have developed semiconducting polymer nanoparticle-based photosensitizers for O2mapping and enhanced the PDT effect by using fluorescence resonance energy transfer.

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Temperature plays an important part in many biochemical processes. Accurate diagnosis and proper treatment usually depend on precise measurement of temperature. In this work, a dual-emissive phosphorescent polymer temperature probe, composed of iridium(III) complexes as temperature sensitive unit with phosphorescence lifetime of ∼500 ns and europium(III) complexes as reference unit with lifetime of ∼400 μs, has been rationally designed and synthesized. Upon the increase of the temperature, the luminescence intensity from the iridium(III) complexes is enhanced, while that from the europium(III) complexes remains unchanged, which makes it possible for the ratiometric detection of temperature. Furthermore, the polymer also displays a significant change in emission lifetime accompanied by the temperature variation. By utilizing the laser scanning confocal microscope and time-resolved luminescence imaging systems, ratiometric and time-resolved luminescence imaging in Hela cells and zebrafish have been carried out. Notably, the intensity ratio and long-lifetime-based imaging can offer higher sensitivity, decrease the detection limit, and minimize the background interference from biosamples.

A scalable and low-cost strategy is developed to fabricate a novel CuS/SiO-based nanotherapeutic agent for dual-model imaging-guided photothermal/photodynamic combined therapy. In this design, mesoporous silica nanoparticles (MSNs) with CuS bundled in the channel are obtained in aqueous solution via in situ growth route for the first time. Furthermore, to achieve a more efficient therapy, photosensitizer (complex Ir-2) and bovine serum albumin are sequentially assembled via layer-by-layer method. The as-prepared complex Ir-2 presents a remarkably high O generation (Φ = 1.3) under light illumination to offer effective photodynamic cell killing, and MSN/CuS exhibits high photothermal conversion efficiency (η = 31.7%) under illumination by 808 nm light to offer hyperthermia tumor ablation. In vitro and in vivo analyses show that the as-obtained nanotherapeutic agents exhibit excellent performance in tumor therapy even under irradiation with low power because of the high yield of O combined with the high photothermal conversion efficiency. Additionally, the nanotherapeutic agents are readily visualized in vivo via near-infrared fluorescence and thermal imaging. More importantly, based on the strategy of in situ growth and layer-by-layer assembly developed in this study, the development of other "all-in-one" multifunctional theranostic platform with high efficiency can be predictable.

To eliminate the time-consuming oil-gas separation process in online dissolved gas detection of power transformer, fiber Bragg grating (FBG) based hydrogen sensor is proposed to be installed into the power transformer oil directly. In the sensor design, the FBG cladding is side-polished with residual thickness of 20 µm and sputtered with palladium/silver. Since side-polished cladding is very sensitive to curvature strain induced by palladium in the presence of dissolved hydrogen, the proposed sensor is much more sensitive than the untreated FBG hydrogen sensor. Measurements prove that the sensitivity is as high as 0.477 (pm/(µL/L)), about 11.4 times higher than the conventional FBG hydrogen sensor. Furthermore, repeatability and short term stability have been investigated. The performances satisfy the actual need of monitoring dissolved hydrogen concentration in power transformer oil.