Enzymatic catalysis in living cells enables the in-situ detection of cellular metabolites in single cells, which could contribute to early diagnosis of diseases. In this study, enzyme is packaged in amorphous metal-organic frameworks (MOFs) via a one-pot co-precipitation process under ambient conditions, exhibiting 5–20 times higher apparent activity than when the enzyme is encapsulated in corresponding crystalline MOFs. Molecular simulation and cryo-electron tomography (Cryo-ET) combined with other techniques demonstrate that the mesopores generated in this disordered and fuzzy structure endow the packaged enzyme with high enzyme activity. The highly active glucose oxidase delivered by the amorphous MOF nanoparticles allows the noninvasive and facile measurement of glucose in single living cells, which can be used to distinguish between cancerous and normal cells.

In order to increase the response speed of the InSe-based photodetector with high photoresponsivity, Graphene is used as the transparent electrodes to modify the difference of the work function between the electrodes and the InSe. As expected, the response speed of InSe/graphene photodetectors is down to 120 μs, which is about 40 times faster than that of our InSe/metal device. And it can also be tuned by the back-gate voltage from 310 μs down to 100 μs. With high response speed, the photoresponsivity can reach as high as 60 AW -1 simultaneously. Meanwhile the InSe/graphene photodetectors possess a broad spectral range at 400-1000 nm. The design of 2D crystal/graphene electrical contacts could be important for high performance optoelectronic devices.

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A critical challenge for the integration of optoelectronics is that photodetectors have relatively poor sensitivities at the nanometer scale. Generally, a large electrodes spacing in photodetectors is required to absorb sufficient light to maintain high photoresponsivity and reduce the dark current. However, this will limit the optoelectronic integration density. Through spatially resolved photocurrent investigation, we find that the photocurrent in metal-semiconductor-metal (MSM) photodetectors based on layered GaSe is mainly generated from the region close to the metal-GaSe interface with higher electrical potential. The photoresponsivity monotonically increases with shrinking the spacing distance before the direct tunneling happens, which was significantly enhanced up to 5,000 AW−1 for the bottom Ti/Au contacted device. It is more than 1,700-fold improvement over the previously reported results. The response time of the Ti/Au contacted devices is about 10–20 ms and reduced down to 270 μs for the devices with single layer graphene as metallic electrodes. A theoretical model has been developed to well explain the photoresponsivity for these two types of device configurations. Our findings realize reducing the size and improving the performance of 2D semiconductor based MSM photodetectors simultaneously, which could pave the way for future high density integration of optoelectronics with high performances.

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