Babar Dipak Gorakh, Sonkar Sumit Kumar, Tripathi Kumud Malika, Sarkar Sabyasachi
J Nanosci Nanotechnol. 2014 Mar;14(3):2334-42. doi: 10.1166/jnn.2014.8487.
A low cost synthesis of multicolor fluorescent carbon dots (C-dots) from edible sugars is described here. Common sugars like dextrose, lactose or maltose in aqueous medium gets dehydrated using phosphorus pentoxide (P2O5). The reaction is facile and completed within few minutes to form insoluble carbon (C-dots) mostly having the graphitic (G-band, Raman) sp2 hybridized carbon atoms (C-atoms). This insoluble carbon on oxidative treatment with nitric acid produced disordered sp3 (D-band retaining G-band, Raman) hybridized C-atoms, originated from the graphitic pool with sp2 hybridized C-atoms. This high density assimilation of self passivated "surfacial defects" become emissive during electronic transitions. Surfacial defects due to high degree of electrophilic carboxylation create the water soluble version of multicolor fluorescent C-dots as "water soluble fluorescent carbon dots" (wsFCDs). wsFCDs being itself self-passivated imposes the tunable multicolor emission throughout the visible spectrum without having any external coating and surface passivation and could be used as multicolor fluorescent probe especially in the emerging field of optical bio-imaging.
本文介绍了一种从食用糖低成本合成多色荧光碳点（C点）的方法。在水性介质中，葡萄糖、乳糖或麦芽糖等常见糖类使用五氧化二磷（P2O5）进行脱水。该反应很容易进行，几分钟内即可完成，形成大部分具有石墨化（G带，拉曼）sp2杂化碳原子（C原子）的不溶性碳（C点）。这种不溶性碳用硝酸进行氧化处理后，产生了无序的sp3（保留G带的D带，拉曼）杂化C原子，这些C原子源自具有sp2杂化C原子的石墨池。这种高密度的自钝化“表面缺陷”在电子跃迁过程中会发光。由于高度亲电羧化导致的表面缺陷产生了多色荧光C点的水溶性形式，即“水溶性荧光碳点”（wsFCDs）。wsFCDs本身具有自钝化作用，无需任何外部涂层和表面钝化即可在整个可见光谱范围内实现可调谐的多色发射，并且可用作多色荧光探针，特别是在新兴的光学生物成像领域。
