The ongoing race of biomedical applications has given momentum to the development of graphene quantum dots (GQDs). GQDs are zero-dimensional fluorescent carbon-nanomaterials, with a pronounced quantum confinement effect, and abundant edge states and functional groups. Despite their potential applications, mass-scale synthesis of single crystalline graphene quantum dots (GQDs) with high quantum yields derived via a direct green synthesis approach from bio-wastes is a major challenge. Hitherto, green extract (i.e. sugarcane molasses) driven single crystalline sulphur-doped GQDs (S-GQDs) with a longer decay time, high quantum yield, and excellent biocompatibility have remained unexplored in the bioimaging arena. At the same time, this agro-industrial waste has value in terms of both products and byproducts i.e. zero waste generation resulting in reduced human footprint on the environment. For the first time, we present a facile, large-scale, one-step, economical, template- and catalyst-free synthesis of sustainable, highly crystalline S-GQDs via a hydrothermal route from second generation (2G) bio-wastes. Mechanistic insight into the formation of S-GQDs from their precursor was obtained using powder X-ray diffraction patterns (PXRD). S-GQDs directly obtained from bio-wastes without surface passivation showed the highest quantum yield (QY) ∼ 47% obtained to date. The wide and symmetric emission spectrum of these S-GQDs is instrumental for sensitive detection as labelling nanoprobes. Moreover, their non-toxic behavior, in vitro and in vivo, has a future in quick point-of-care screening and real-time bioimaging. Thus, the as-synthesized bio-waste derived S-GQDs accomplished the purpose of an advanced environmentally friendly and sustainable material which is non-toxic, viable, safe, and cheap. This unprecedented work advances the synthesis of high-quality S-GQDs from bio-waste, which provides a breakthrough in the bioimaging field.

中文翻译：

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可持续合成单晶硫掺杂石墨烯量子点的生物成像及后续应用

生物医学应用的不断发展为石墨烯量子点（GQD）的发展提供了动力。GQD是零维荧光碳纳米材料，具有显着的量子约束效应，并具有丰富的边缘态和官能团。尽管具有潜在的应用前景，但通过直接绿色合成方法从生物废物中获得高量子产率的单晶石墨烯量子点（GQD）的大规模合成仍是一项重大挑战。迄今为止，绿色提取物（即甘蔗糖蜜）驱动的单晶硫掺杂GQD（S-GQDs）具有更长的衰减时间，高量子产率和出色的生物相容性，在生物成像领域尚未得到开发。同时，这种农业工业废物在产品和副产品方面都具有价值，即废物产生量为零，从而减少了人类对环境的足迹。首次，我们提出了一种通过以下途径轻松，大规模，一步一步，经济，无模板和无催化剂地合成可持续的高度结晶的S-GQD的方法来自第二代（2G）生物废物的热液路线。使用粉末X射线衍射图谱（PXRD），可以深入了解由S-GQD的前体形成的机理。没有表面钝化的直接从生物废物中获得的S-GQD表现出迄今为止最高的量子产率（QY）〜47％。这些S-GQD的宽且对称的发射光谱有助于进行敏感检测，如标记纳米探针。此外，它们在体外和体内的无毒行为，在快速即时筛查和实时生物成像方面具有广阔的前景。因此，合成后的生物废物衍生的S-GQD达到了一种无毒，可行，安全且廉价的先进的环境友好和可持续材料的目的。这项史无前例的工作推动了由生物废物合成高质量S-GQD的发展，这为生物成像领域提供了突破。