Polymorphic Architectures of Graphene Quantum Dots

A systematic strategy for designing structured nanomaterials is demonstrated through self‐assembly of graphene quantum dots. The approach reveals that graphene derivatives at the nanoscale assemble into various architectures of nanocrystals in a binary solution system. The shapes of the nanocrystals continue to evolve in terms of the intimate association of organic molecules with the dispersion medium, obtaining a high index faceted superlattice. This facile synthetic process provides a versatile strategy for designing particles to new structured materials systems, exploiting the crystallization of layered graphitic carbon structures within single crystals.     

Graphene Quantum Dots for Optical Bioimaging

Graphene quantum dots (GQDs) have shown great potential in bioimaging applications due to their excellent biocompatibility, low cytotoxicity, feasibility for surface functionalization, physiological stability, and tunable fluorescence properties. This Review first introduces the intriguing optical properties of GQDs that are suitable for biological imaging, and is followed by the GQDs' synthetic strategies. The emergent and latest development methods for tuning GQDs' optical properties are further described in detail. The recent advanced applications of GQDs in vitro, particularly in cell imaging, targeted imaging, and theranostic nanoplatform fabrication, are included. The applications of GQDs for in vivo bioimaging are also covered. Finally, the Review is concluded with the challenges and prospectives that face this nascent yet exciting field.     

From Graphite to Graphene Oxide and Graphene Oxide Quantum Dots

Many methods have been reported for synthesizing graphene oxide (GO) and graphene oxide quantum dots (GOQDs) where a tedious operational procedure and long reaction time are generally required. Herein, a facile one‐pot solvothermal method that allows selective synthesis of pure GO and pure GOQDs, respectively is demonstrated. What is more, the final product of either GO or differently sized GOQDs can be easily controlled by adjusting the reaction temperatures or reactant ratios, which is also feasible when enlarged to gram scale. The 2.5 nm GOQDs show excellent photoluminescence that can be utilized for bioimaging or distinctive detection of Eu³⁺ and Tb³⁺ from their respective mixtures with other rare earth and/or transition metal ions, at sub‐ppm level.     

石墨烯量子点的制备及其生物应用

石墨烯量子点(GQDs)作为石墨烯材料的衍生物, 在兼顾了石墨烯优良特性的同时, 又依靠量子限域效应和边界效应而具备了光致发光(PL)等石墨烯所不具备的性质, 而且在细胞毒性、生物相容性等方面也有更好的表现。近年来, GQDs的制备方法日趋多样化, 通常将其分为Top-down和Bottom-up两种方法。随着GQDs在生物医学领域应用的不断深化, 对其形貌和尺寸控制也提出了更高的要求, 因此本文对Bottom-up法等一些有希望精确控制GQDs形貌和尺寸的方法进行了重点介绍, 并对各种方法的优缺点进行了对比。目前GQDs的生物应用主要包括生物成像、生物传感器、药物输运和抗菌剂等, 本文对其各种应用分别进行了介绍, 并结合各种应用对GQDs的要求给出了制备方法的建议。文章最后还指出了GQDs研究中存在的问题及发展方向。     

Enzymatic Degradation of Graphene Quantum Dots by Human Peroxidases

Carbon‐based nanomaterials have demonstrated to be potent candidates for biomedical applications. Recently, graphene quantum dots (GQDs) have emerged as an attractive tool for bioimaging, biosensing, and therapy. Hence, studying their biodegradability in living systems is essential to speed up the translation toward real clinical innovations. Here, the enzymatic degradation of GQDs using human myeloperoxidase and eosinophil peroxidase is investigated. Transmission electron microscopy, fluorescence, and Raman spectroscopy are used to evaluate the biodegradation of GQDs. Signs of degradation by both enzymes are observed already after a few hours of incubation with each enzyme, being more evident after a couple of days of treatment. Molecular dynamics simulations show intimate interactions between the enzymes and the GQDs. The conformation of both peroxidases is slightly altered to favor the interactions, while the GQD sheets distort a little to adapt to the surface of the enzymes. The biodegradability of the GQDs ensures their real potential in the practical biomedical applications.     

含氮石墨烯量子点的制备及其光学性质研究

采用水热法一步合成了含氮石墨烯量子点(NGQDs), 通过原子力显微镜(AFM)、透射电镜(TEM)、X射线光电子能谱(XPS)等对NGQDs的形貌和组成进行表征, 并进一步通过紫外-可见光谱(UV-Vis)、荧光光谱(PL)等手段研究了NGQDs的光学性质。AFM和TEM分析结果表明, NGQDs尺寸约为8.9 nm、厚度为0.6 ~2.0 nm (即1~3个碳原子层)。XPS分析结果表明NGQDs中氮含量约为17%, 且氮元素主要以“吡咯N”形式存在。光谱学实验表明, NGQDs的激发光谱与吸收光谱基本一致, 且其发射光谱与激发波长之间不存在依赖关系。此外, NGQDs的量子产率为~18%, 并随着含氮量的增加而增加, 且其荧光寿命衰变曲线可以被拟合成很好的双指数衰变曲线(τ₁=2.93 ns, τ₂=9.00 ns), 表明NGQDs有两种发色源, 即边缘富有含氧官能团的sp²碳簇和含氮五元环-吡咯环。     

石墨烯量子点/CdS/CdSe共敏化太阳能电池

以三维锐钛矿TiO₂微球为上层光散射层材料, 以商业纳米TiO₂为下层连接材料, 采用刮刀法制备了一种新颖的双层TiO₂薄膜, 并应用于量子点敏化太阳能电池(QDSSC)。其中, 石墨烯量子点(GQDs)采用滴液法引入, CdS/CdSe量子点采用连续离子层吸附法(SILAR)制备。采用场发射扫描电镜、透射电镜、X射线衍射、紫外-可见漫反射光谱及荧光光谱对样品进行表征。实验还制备了CdS/CdSe量子点敏化及石墨烯量子点/CdS/CdSe共敏化太阳能电池, 并研究了石墨烯量子点及CdS不同敏化周期及对电池性能影响。研究结果表明, 石墨烯量子点及CdS不同敏化周期对薄膜的光学性质、电子传输及载流子复合均有较大影响。优选条件下, TiO₂/QGDs/CdS(4)/CdSe电池的光电转换效率为1.24%, 光电流密度为9.47 mA/cm², 显著高于TiO₂/CdS(4)/CdSe电池的这些参数(0.59%与6.22 mA/cm²)。这主要是由于TiO₂表层吸附石墨烯量子点后增强了电子的传输, 减少了载流子的复合。     

石墨烯量子点在分离膜材料中的应用研究进展

在传统分离膜中引入纳米材料,有望解决选择性与渗透性之间存在的Trade-off效应、膜污染、化学稳定性等关键共性技术难题.零维石墨烯量子点(GQDs)纳米材料具有尺寸小、比表面积大、亲水性强等突出优点,在分离膜材料领域具有潜在的应用前景.本文归纳了基于界面聚合、相转化、表面改性等常规制膜方法,将GQDs或改性GQDs引入活性层(表层)、中间层或支撑层(亚层)等膜基质中,实现调控与优化分离膜结构与性能的最新研究进展.探讨了GQDs与改性GQDs对界面聚合"反应-扩散"过程、铸膜液热力学与相转化动力学过程以及层状膜层间距的影响机制,并阐述了引入GQDs或改性GQDs赋予分离膜抑菌、自清洁、荧光检测等新功能的原因.最后,展望了基于GQDs开发新型膜材料所面临的机遇和挑战.     

Glowing Graphene Quantum Dots and Carbon Dots: Properties,Syntheses, and Biological Applications

The emerging graphene quantum dots (GQDs) and carbon dots (C‐dots) have gained tremendous attention for their enormous potentials for biomedical applications, owing to their unique and tunable photoluminescence properties, exceptional physicochemical properties, high photostability, biocompatibility, and small size. This article aims to update the latest results in this rapidly evolving field and to provide critical insights to inspire more exciting developments. We comparatively review the properties and synthesis methods of these carbon nanodots and place emphasis on their biological (both fundamental and theranostic) applications.     

石墨烯量子点在生物医学中的研究进展

石墨烯量子点是石墨烯超家族的衍生物,与高维度石墨烯相比,具有良好的生物相容性,较低的细胞毒性及较好的化学修饰性。自发现以来,石墨烯量子点的应用领域被逐渐地拓宽。其中石墨烯量子点的生物应用主要包括生物成像、生物传感器、药物运输、基因载体、抗菌抗病毒及肿瘤的光动力治疗研究等。主要介绍了近几年有关石墨烯量子点生物相容性及其在生物医学研究的进展,并对其发展前景进行了展望。     

石墨烯量子点/纤维素复合气凝胶材料的制备及其吸附性能研究

目的以石墨烯量子点为填充材料,纤维素为基体,制备石墨烯量子点/纤维素复合气凝胶。方法以原生木浆纤维为原料,氯化锌溶液为溶剂来溶解纤维素,以无水硫酸钠为成孔剂,石墨烯量子点为填充材料,经水洗固化、低温冷冻干燥制备纤维素气凝胶复合材料。利用扫描电镜、X射线衍射、红外光谱、吸附实验等研究气凝胶的微观结构和对甲基蓝的吸附性能。结果制备的气凝胶材料具有三维多孔结构,大孔较多,密度低,纤维素气凝胶的密度为0.113 g/cm^3,吸附率为5.85%;复合气凝胶的密度为0.116 g/cm^3,吸附率为11.22%。结论石墨烯量子点的加入改善了纤维素气凝胶对甲基蓝的吸附效果。     

Memristive Devices with Highly Repeatable Analog States Boosted by Graphene Quantum Dots

Memristive devices, having a huge potential as artificial synapses for low‐power neural networks, have received tremendous attention recently. Despite great achievements in demonstration of plasticity and learning functions, little progress has been made in the repeatable analog resistance states of memristive devices, which is, however, crucial for achieving controllable synaptic behavior. The controllable behavior of synapse is highly desired in building neural networks as it helps reduce training epochs and diminish error probability. Fundamentally, the poor repeatability of analog resistance states is closely associated with the random formation of conductive filaments, which consists of oxygen vacancies. In this work, graphene quantum dots (GQDs) are introduced into memristive devices. By virtue of the abundant oxygen anions released from GQDs, the GQDs can serve as nano oxygen‐reservoirs and enhance the localization of filament formation. As a result, analog resistance states with highly tight distribution are achieved with nearly 85% reduction in variations. In addition the insertion of GQDs can alter the energy band alignment and boost the tunneling current, which leads to significant reduction in both switching voltages and their distribution variations. This work may pave the way for achieving artificial neural networks with accurate and efficient learning capability.     

Specific Oxygenated Groups Enriched Graphene Quantum Dots as Highly Efficient Enzyme Mimics

Significant progress is achieved for the utilization of graphene quantum dots as enzyme mimics in various biomedical fields recently. Although promising, the biocatalytic performance is far from satisfactory. Here, the rational design and synthesis of specific oxygenated groups enriched graphene quantum dots (o‐GQDs) via a facile oxidation reflux route is reported. These well‐prepared o‐GQDs with uniform size exhibit an ultrahigh peroxidase‐like activity in a wide range of pH values, and their superior performance is verified by using glucose detection as a typical model. Compared with classical nanozymes, these o‐GQDs show multiple times higher enzymatic activity. It is believed that the super facile synthesis strategy can greatly facilitate the practical use of o‐GQDs as enzyme mimics in the future.