Chiral Graphene Quantum Dots
Chiral Graphene Quantum Dots
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DOI：
10.1021/acsnano.5b06369
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发表时间：
2016-02-01
期刊：
影响因子：
17.1
通讯作者：
Kotov, Nicholas A.
中科院分区：
文献类型：
--
作者：
Suzuki, Nozomu;Wang, Yichun;Kotov, Nicholas A.
金属和半导体的手性纳米结构作为偏振光电子器件的组成部分吸引了广泛的兴趣。与纳米技术的其他领域类似，石墨烯基材料可以极大地丰富与手性纳米结构的光学和电子性质相关的物理和化学现象，并促进其在生物学以及其他领域的应用。在这里，我们报告说，共价连接的L/D-半胱氨酸部分的石墨烯量子点（GQD）的边缘导致其螺旋屈曲由于手性相互作用在“拥挤”的边缘。GQD的圆二色性（CD）光谱显示在约100 nm处的谱带。210-220和250-265 nm，其对于半胱氨酸边缘配体的不同手性改变其符号。在210-220 nm处的高能手性峰对应于涉及氨基酸手性中心和石墨烯边缘原子的杂化分子轨道。不同的实验和建模数据，包括密度泛函理论计算的CD光谱与GQD异构体的概率分布，表明在250-265 nm的带起源于三维扭曲的石墨烯片，可以归因于手性激子跃迁。正、负低能CD带分别对应于GQD的左、右螺旋度。肝HepG 2细胞暴露于L/D-GQD揭示了它们的一般生物相容性和立体异构体毒性的显著差异。分子动力学模拟表明，D-GQD具有比L-GQD更强的在细胞膜内积累的倾向。用生物分子修饰的GQD中纳米级手性的出现预计是柔性纳米材料片的一般立体化学现象。
Chiral nanostructures from metals and semiconductors attract wide interest as components for polarization-enabled optoelectronic devices. Similarly to other fields of nanotechnology, graphene-based materials can greatly enrich physical and chemical phenomena associated with optical and electronic properties of chiral nanostructures and facilitate their applications in biology as well as other areas. Here, we report that covalent attachment of L/D-cysteine moieties to the edges of graphene quantum dots (GQDs) leads to their helical buckling due to chiral interactions at the "crowded" edges. Circular dichroism (CD) spectra of the GQDs revealed bands at ca. 210-220 and 250-265 nm that changed their signs for different chirality of the cysteine edge ligands. The high-energy chiroptical peaks at 210-220 nm correspond to the hybridized molecular orbitals involving the chiral center of amino acids and atoms of graphene edges. Diverse experimental and modeling data, including density functional theory calculations of CD spectra with probabilistic distribution of GQD isomers, indicate that the band at 250-265 nm originates from the three-dimensional twisting of the graphene sheet and can be attributed to the chiral excitonic transitions. The positive and negative low-energy CD bands correspond to the left and right helicity of GQDs, respectively. Exposure of liver HepG2 cells to L/D-GQDs reveals their general biocompatibility and a noticeable difference in the toxicity of the stereoisomers. Molecular dynamics simulations demonstrated that D-GQDs have a stronger tendency to accumulate within the cellular membrane than L-GQDs. Emergence of nanoscale chirality in GQDs decorated with biomolecules is expected to be a general stereochemical phenomenon for flexible sheets of nanomaterials.