Preparation,Marriage Chemistry and Applications of Graphene Quantum Dots–Nanocellulose Composite: A Brief Review

Graphene quantum dots (GQDs) are zero-dimensional carbon-based materials, while nanocellulose is a nanomaterial that can be derived from naturally occurring cellulose polymers or renewable biomass resources. The unique geometrical, biocompatible and biodegradable properties of both these remarkable nanomaterials have caught the attention of the scientific community in terms of fundamental research aimed at advancing technology. This study reviews the preparation, marriage chemistry and applications of GQDs–nanocellulose composites. The preparation of these composites can be achieved via rapid and simple solution mixing containing known concentration of nanomaterial with a pre-defined composition ratio in a neutral pH medium. They can also be incorporated into other matrices or drop-casted onto substrates, depending on the intended application. Additionally, combining GQDs and nanocellulose has proven to impart new hybrid nanomaterials with excellent performance as well as surface functionality and, therefore, a plethora of applications. Potential applications for GQDs–nanocellulose composites include sensing or, for analytical purposes, injectable 3D printing materials, supercapacitors and light-emitting diodes. This review unlocks windows of research opportunities for GQDs–nanocellulose composites and pave the way for the synthesis and application of more innovative hybrid nanomaterials.     

量子点在法庭科学手印显现中的研究进展

随着纳米技术的进步,纳米颗粒正在被逐步应用到法庭科学领域的手印检验之中。近年来,半导体量子点因其良好的荧光特性而备受国内外法庭科学家的推崇,但大多数半导体量子点具有毒性,且会对环境造成污染,这些问题制约了半导体量子点在法庭科学领域中的应用。与传统有机染料和金属内核的半导体量子点相比,碳量子点具有毒性低、污染小、生物相容性优异的特点,现已应用于医学、生物、化学等多个领域。本文综述了半导体量子点在手印显现中的应用,介绍了碳量子点的研究进展,并指出碳量子点显现手印是今后法庭科学领域的重要研究方向。     

发光碳量子点的合成、性质和应用

基于碳量子点具有良好的水溶性、化学惰性、低毒性、易于功能化和抗光漂白性等优异性能,碳量子点和其它的碳纳米材料（如富勒烯、碳纳米管和石墨烯等）同样引起了研究者广泛的关注。 碳量子点可以通过很多较为廉价的一步法进行大规模的制备,包括化学氧化法、超声法、微波法和激光烧蚀法等。 本文主要介绍了不同碳量子点的合成方法,以及依赖于碳量子点尺寸和波长等性质的发光性能,并且讨论了碳量子点在生物成像、光催化、能量转换/储存、光电子、光限幅和传感器等方面的应用。     

碳点的高性能化和功能化改性:方法、特性与展望

碳点作为一种新型碳纳米材料,由于其出色的光学性能、低毒性、良好的生物相容性和易修饰性而被广泛应用于各个领域。为了满足不同领域的需求,几种用以调控碳点光学性能的方法已被提出,例如杂原子掺杂、半导体量子点掺杂、聚合物钝化和改性以及主-客体构建。其中,杂原子掺杂是通过单原子或多原子引入电子给体或受体改变其相邻碳原子的电子密度来增加荧光强度;半导体量子点也可与碳点进行复合提升电子分离效率而起到荧光增强的效果;就聚合物改性而言,聚合物不仅可以对碳点表面实施钝化和功能化,而且其固态(或固化)薄膜可以提供紧密的空间促进碳点表面的辐射跃迁起到荧光增强的效果。此外,由碳点-染料和多孔材料-碳点构成的两种主要的主-客体结构中,前者不仅对碳点的荧光发射强度有着促进的作用,更使得碳点具备了显著的红/近红外荧光发射性能,后者对固态发光碳点不仅提供了可能性和设计的灵活性,且为打开碳点新的应用领域提供了机会。本文将围绕四种碳点功能化的方法逐步展开讨论,并介绍相应碳点的光学性能、发光机理和潜在应用;论述功能化碳点的研究现状,并展望功能化碳点的研究方向。     

基于碳量子点的稳定高效全色随机激光

以本征态发光的高量子产率的碳量子点为激光增益介质,Au-Ag双金属多孔纳米线为散射颗粒,在纳秒激光的脉冲下,首次实现了基于碳量子点的全色随机激光.其中,蓝、绿、红三基色的发射半峰宽分别为2.5、1.9、2.3 nm,阈值分别为0.27、0.21、0.58 MW/cm².激光照射60 min后,随机激光体系依然能保持良好的稳定性.将蓝、绿、红三色碳量子点以一定比例混合后,在高于阈值的泵浦功率下,首次实现了基于碳量子点的白光激光,为下一代的激光显示技术提供了新的可能.     

基于聚乙烯醇聚合物点制备荧光纳米复合材料

近年来, 由于聚合物点(PDs)具有良好的荧光性质和光收集能力, 受到了人们广泛的关注, 应用在生物成像和检测等领域. 然而, 目前报道的聚合物点大多数是指共轭聚合物经过组装、固定形成的, 因此聚合物点保持着形成之前的共轭聚合物的相关性质, 且具有更好的稳定性和进一步功能化的能力. 本文中我们研究的聚合物点是指从非共轭线性聚合物为原料而制备的聚合物点, 这类聚合物包括聚环氧乙烯, 多糖等. 聚合物点不仅包含使其具有荧光的碳化中心, 还具有外围的聚合物链结构. 因此, 可以拓展应用聚合物点的聚合物特性. 我们利用PDs的荧光中心和外围的聚合物链双功能性质, 详细研究了基于PDs制备功能性纳米复合材料体系. 首先, 我们原位制备了聚乙烯醇/PDs纳米复合膜材料(PDs是直接通过聚乙烯醇可控碳化而产生的). 复合材料不仅保持了PDs的荧光特性, 还保持了聚乙烯醇易加工的特性, 如可以制备成纳米复合膜材料, PDs含量可以根据需要调控: 0, 20%, 40%, 60%, 80%, 100%. 纳米复合膜材料在不同激发光下具有多颜色发光性质. 进一步的, 我们验证了PDs水溶液可以和很多其他水溶性聚合物, 石墨烯量子点或半导体量子点实现共混, 从而制备双功能性纳米复合材料.     

Polymer carbon dots—a highlight reviewing their unique structure,bright emission and probable photoluminescence mechanism

In recent years, a novel fluorescent material, carbon dots (CDs), is becoming a hot topic. Recent research works found that some types of CDs with high quantum yield are mainly composed of polymer structures or polymer/carbon hybrid structures rather than the pure carbon/graphite structure. These types of CDs, named as polymer carbon dots (PCDs) here, are drawing growing interests due to the designed hybrid structure and functional integration. Typically, PCDs are nano-sized particles possessing abundant polymer structures with low carbonization degree, prepared from the monomers or non-conjugated polymers by condensation, crosslinking, assembling, or slightly carbonization processes. In this highlight, we bring up the new concept of PCDs and discuss the relationships among non-conjugated polymer, PCDs and CDs, demonstrating that the possible fluorescence mechanism of PCDs is inferred as crosslink enhanced emission effect. Furthermore, the structure, properties, and synthetic methods of the reported typical PCDs were summarized and prospected. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 610–615     

Light scattering sensing detection of pathogens based on the molecular recognition of immunoglobulin with cell wall-associated protein A

In this contribution, we report a rapid optical detection method of pathogens using Staphylococcus aureus (S. aureus) as the model analyte based on the molecular recognition of immunoglobulin with cell wall-associated Protein A (SpA). It was found that the molecular recognition of human immunoglobulin (IgG) with protein A on the cell wall of S. aureus on glass slide sensing area could result in strong surface enhanced light scattering (SELS) signals, and the SELS intensity (ΔI) increases proportionally with the concentration of S. aureus over the range of 2.5 × 10⁵-1.0 × 10⁸ CFU mL⁻¹ with right angle light scattering (RALS) signals detection mode. In order to identify the solid support based molecular recognition between IgG with SpA, we also employed water-soluble CdS quantum dots (CdS-QDs) as a fluorescent marker for IgG by immobilizing the IgG onto the surfaces of CdS-QDs through covalent binding in order to generate recognition probes for SpA on the cell wall of S. aureus. Consequently, the fluorescent method also showed that the detection for pathogens with solid supports is reliable based on the molecular recognition of IgG with SpA.     

荧光可调控的碳量子点的电化学制备及性质研究

采用循环伏安法（Cyclic Voltammetry,CV）在碱性条件下电解石墨棒,得到水溶性的荧光碳量子点. 通过透射电子显微镜（TEM）、拉曼光谱（Raman spectrum）、原子力显微镜（AFM）对所制备的碳量子点进行形貌及结构表征,发现该碳量子点由1～4层石墨烯片层堆积形成,粒径在19 nm左右,厚度在1 nm左右. 通过荧光光谱（PL）、紫外可见吸收光谱（UV-vis）、傅里叶变换红外光谱（FTIR）、X射线光电子能谱（XPS）对所制备的碳量子点进行性质测定,发现该碳量子点在400和525 nm处有两个荧光发射峰,且通过控制扫描周数可以调节两个发射峰的相对强度,从而调控碳量子点的荧光颜色：随着扫描周数的增加,400 nm处发射峰的相对强度逐渐减小,而525 nm处发射峰的相对强度逐渐增大,两个荧光发射峰分别与碳量子点的π-π共轭体系和含氧官能团的n-π共轭体系有关.     

Fabrication of N-CQDs@W18O49 heterojunction with enhanced charge separation and photocatalytic performance under full-spectrum light irradiation

Increasing the charge separation and the utilization efficiency of sunlight are essential factors in a photocatalytic process. In this study, we prepared crystalline N-CQDs@W₁₈O₄₉ heterostructures, through the in situ growth of W₁₈O₄₉ nanocrystals on nitrogen-doped carbon quantum dots (N-CQDs). N-CQDs@W₁₈O₄₉ nanocomposites showed high activity in the photodegradation of ciprofloxacin (CIP) and methyl orange (MO). The photodegradation activity of the optimized N-CQDs@W₁₈O₄₉-5 sample was four times higher than that of W₁₈O₄₉ under ultraviolet-visible (UV–vis) light irradiation. The photodegradation activity of N-CQDs@W₁₈O₄₉-5 sample was two times higher than that of W₁₈O₄₉ under near-infrared (NIR) light irradiation. The enhanced photosensitivity of the nanocomposites was attributed to the promotion of charge separation by N-CQDs and the local surface plasmon resonance (LSPR) effect of W₁₈O₄₉ under NIR light irradiation. This work provides a promising approach for designing and manufacturing photocatalysts with full-spectral responsiveness and improved charge separation.     

Amphiphilic egg-derived carbon dots: rapid plasma fabrication, pyrolysis process, and multicolor printing patterns

How do you like your eggs? Amphiphilic carbon dots (CDs) with intense blue fluorescence have been produced from chicken eggs by treatment with plasma. They are used as effective "fluorescent carbon inks" for multicolor luminescent inkjet and silk-screen printing.     

Mesoporous Silica Particles Integrated with All‐Inorganic CsPbBr3 Perovskite Quantum‐Dot Nanocomposites (MP‐PQDs) with High Stability and Wide Color Gamut Used for Backlight Display

All‐inorganic CsPbX₃ (X=I, Br, Cl) perovskite quantum dots (PQDs) have been investigated because of their optical properties, such as tunable wavelength, narrow band, and high quantum efficiency. These features have been used in light emitting diode (LED) devices. LED on‐chip fabrication uses mixed green and red quantum dots with silicone gel. However, the ion‐exchange effect widens the narrow emission spectrum. Quantum dots cannot be mixed because of anion exchange. We address this issue with a mesoporous PQD nanocomposite that can prevent ion exchange and increase stability. We mixed green quantum‐dot‐containing mesoporous silica nanocomposites with red PQDs, which can prevent the anion‐exchange effect and increase thermal and photo stability. We applied the new PQD‐based LEDs for backlight displays. We also used PQDs in an on‐chip LED device. Our white LED device for backlight display passed through a color filter with an NTSC value of 113 % and Rec. 2020 of 85 %.