Prevalent intrinsic emission from nonaromatic amino acids and poly(amino acids)

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All experiments were conducted at room temperature unless specified. Though some concentrated nonaromatic amino acids are nonemissive at room temperature, they do become emissive when frozen by liquid nitrogen (Figure S1). And some relatively weakly emissive crystals (i.e. L-Leu, D-Leu, and D-Met) get more emissive upon cooling to 77 K (Figure S7)

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Tested with the detector at nanosecond scale

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CCDC 1542778 contains the supplementary crystallographic data for L-Ile. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif

Previously, glutathione was reported to be nonluminescent (see Ref. [8]), our results, however, show it can be emissive under proper conditions. Detailed results will be reported later