Prevalent Room-Temperature Phosphorescence in Natural Nuts

Room-temperature phosphorescence (RTP) has extensive applications in various fields such as data encryption, chemical sensing, optoelectronic displaying, and time-resolved bioimaging, yet most materials are fossil fuel-based. Recently, an increasing interest has emerged with respect to natural organic RTP. However, the cases are rare and the structure-property relationships remain poorly understood. Here, natural nuts with prevalent RTP characters were unveiled with comprehensive elucidation on the molecular origins, representing an alternative reservoir of sustainable and clean RTP materials. The nuts generally show seconds-long afterglow at ambient conditions, relying heavily on excitation wavelengths and nut composition. RTP of intrinsic nutrients including aromatic vitamins, aromatic nucleobases, and aromatic amino acids dispersed in nonaromatic natural media at low contents (as low as the ppm level) covers the entire RTP spectra of nuts, spanning <400 to >700 nm. Different aromatic nutrients require varied excitation energies and are capable of showing distinct RTP colors. Thus, biomatrices and diverse aromatic nutrients should rationalize excitation-dependent broad-band nut RTP synergistically, both of which should not be overlooked. Furthermore, nut RTP can be facilely modulated by trace polyaromatic phosphors, facilitating color-tunable 3D afterglow for multilevel information storage. This work considerably expands the scope of natural RTP based on abundant sources and provides new insights into the underlying mechanism, opening a broad avenue for applying sustainable luminescent materials that can be produced at a large scale and low cost.