碳量子点纳米材料在铅卤钙钛矿太阳能电池中的应用研究进展

碳量子点（CQDs）是一类粒径较小,光学性能显著,且电荷传输性能优异的类半导体纳米材料,在钙钛矿太阳能电池的性能调控和改善中得到广泛的应用。从CQDs纳米材料的合成、性能及应用出发,综述了CQDs纳米材料在钙钛矿太阳能光电器件中电子传输层、钙钛矿光吸收层和空穴传输层等方面的应用进展,并展望了该类材料调控钙钛矿太阳能器件性能的发展趋势。     

One‐Pot Green Synthesis of Nitrogen‐Doped Carbon Quantum Dots for Cell Nucleus Labeling and Copper(II) Detection

The doping of nitrogen into carbon quantum dots is vitally important for improved fluorescence performance. However, the synthesis of nitrogen‐doped carbon quantum dots (N‐CQDs) is usually conducted under strong acid and high temperature, which results in environmental pollution and energy consumption. Herein, the N‐CQDs were prepared by a mild one‐pot hydrothermal process. The hydrothermal reaction temperature was adjusted to control the particle size, nitrogen/carbon atomic ratio, and quantum yield. The products were water soluble with a narrow particle size distribution and good dispersion stability over a wide pH range. The N‐CQDs could penetrate into the HeLa cell nucleus without any further functionalization. Moreover, the fluorescence of N‐CQDs could be selectively quenched by Cu²⁺, which suggested applications for the detection of Cu²⁺ in human plasma.     

碳量子点的合成研究进展与展望

碳量子点(CQDs)呈现出的亲水性、低细胞毒性、化学及光稳定性等优异性质,使其在化学、生物医学、传感学及光电子学领域得到了广泛的关注与应用。本文重点介绍CQDs合成的最新进展,总结了宏观条件下CQDs合成的自上而下法(弧光放电、激光烧蚀、电化学等)与自下而上法(化学氧化、热分解、微波加热等),比较了不同合成方法中碳源的利用率、反应条件、产物的尺寸分布、荧光性能及应用,讨论了各种合成方法的成功之处与存在的问题。文中详细介绍了基于微反应器原理的反胶束法和模板法在CQDs尺寸可控合成领域的应用。微流控芯片技术在纳米材料合成中显现安全、高效、可控等优于宏观反应体系的优势,结合目前微流控芯片合成CQDs的研究进展,可以预期微流控芯片在不久的将来将会在CQDs的合成中得到更成功的应用。     

Selenium‐Doped Carbon Quantum Dots for Free‐Radical Scavenging

Heteroatom doping is an effective way to adjust the fluorescent properties of carbon quantum dots. However, selenium‐doped carbon dots have rarely been reported, even though selenium has unique chemical properties such as redox‐responsive properties owing to its special electronegativity. Herein, a facile and high‐output strategy to fabricate selenium‐doped carbon quantum dots (Se‐CQDs) with green fluorescence (quantum yield 7.6 %) is developed through the hydrothermal treatment of selenocystine under mild conditions. Selenium heteroatoms endow the Se‐CQDs with redox‐dependent reversible fluorescence. Furthermore, free radicals such as ^.OH can be effectively scavenged by the Se‐CQDs. Once Se‐CQDs are internalized into cells, harmful high levels of reactive oxygen species (ROS) in the cells are decreased. This property makes the Se‐CQDs capable of protecting biosystems from oxidative stress.     

Electrochemistry in Carbon‐based Quantum Dots

Electrochemistry belongs to an important branch of chemistry that deals with the chemical changes produced by electricity and the production of electricity by chemical changes. Therefore, it can not only act a powerful tool for materials synthesis, but also offer an effective platform for sensing and catalysis. As extraordinary zero‐dimensional materials, carbon‐based quantum dots (CQDs) have been attracting tremendous attention due to their excellent properties such as good chemical stability, environmental friendliness, nontoxicity and abundant resources. Compared with the traditional methods for the preparation of CQDs, electrochemical (EC) methods offer advantages of simple instrumentation, mild reaction conditions, low cost and mass production. In return, CQDs could provide cost‐effective, environmentally friendly, biocompatible, stable and easily‐functionalizable probes, modifiers and catalysts for EC sensing. However, no specific review has been presented to systematically summarize both aspects until now. In this review, the EC preparation methods of CQDs are critically discussed focusing on CQDs. We further emphasize the applications of CQDs in EC sensors, electrocatalysis, biofuel cells and EC flexible devices. This review will further the experimental and theoretical understanding of the challenges and future prospective in this field, open new directions on exploring new advanced CQDs in EC to meet the high demands in diverse applications.     

基于碳量子点的绿色合成及生物成像研究进展EI北大核心CSCD

碳量子点(CQDs)作为碳纳米材料家族成员之一,因其原材料广、成本低廉、较高的光致发光性能和良好的生物相容性,在研究和应用领域都受到了广泛的关注,是应用于生物成像的理想材料。CQDs的绿色合成是指采用环保型或无毒型原料,通过绿色合成方法,如炭化法、微波法、水热法等,合成具有荧光性能的无毒碳量子点,与传统的化学氧化、激光烧蚀、热解处理等方法相比,更加绿色环保、经济,其应用已成为研究热点。本文对碳量子点材料特性、绿色合成过程机理、绿色合成原料来源、合成方法,及其在癌细胞、微生物细胞等细胞成像方面的应用进行了综述,探讨了绿色合成CQDs的利弊问题,并提出了今后该研究领域面临的机遇与挑战。     

碳点的制备及荧光量子产率的测定 ——一个仪器分析综合实验

As a new type of nano-materials, carbon dots have unique optical properties and excellent chemical properties, such as easy preparation, low cost, high chemical stability and good biocompatibility. Three kinds of carbon dots were prepared by microwave, hydrothermal and pyrolysis methods, and characterized by infrared spectroscopy. The ultraviolet-visible absorption spectra and fluorescence spectra of the three carbon dots were measured and compared with those of small organic fluorescent molecules. The fluorescence quantum yield of three carbon dots was measured using quinine sulfate as standards. This experiment not only enables students to learn the preparation methods and the unique luminescent properties of carbon nanomaterials, but also enables students to have a deeper understanding of the structures, principles and applications of three kinds of molecular spectroscopy instruments based on the measurement of quantum yield. This experiment can be used as a comprehensive 10-hour instrumental analysis experiment for junior students majoring in chemistry, applied chemistry and material chemistry.     

Green process of biomass waste derived fluorescent carbon quantum dots for biological imaging in vitro and in vivo

In the context of the circular economy, the huge amounts of biomass waste should be converted into value-added materials and energy to diminish pollution, atmospheric CO₂ levels and costly waste disposal. Biological imaging usually uses expensive and toxic chemicals e.g., organic dyes, semiconductor quantum dots, calling for safer, greener, cheaper fluorescent probes for biological imaging in vitro and in vivo. In these regards, carbon quantum dots (CQDs)-based fluorescent probes using biomass waste as a precursor may have much higher potential. Here we transformed the biomass waste of peach leaves into value-added fluorescent CQDs through a low-cost and green one-step hydrothermal process. The obtained CQDs show excitation-dependent photoluminescence properties with a fluorescence lifetime of 5.96 ns and a quantum yield of 7.71% without any passivation. In addition, the CQDs have a fine size of 1.9 nm with good hydrophilicity and high fluorescent stability over pH 4.0–11.0 range. Fluorescence imaging of in vitro cell cultures and in vivo with zebrafish show that CQDs possess ultra-low toxicity and remarkable performance for biological imaging. Even when CQDs present at a concentration as high as 500 µg/mL, the organism can still maintain more than 90% activity both in vitro and in vivo, and present bright fluorescence. The cheaper, greener, ultra-low toxicity CQDs developed in this work is a potential candidate for biological imaging in vitro and in vivo.     

野酸枣氮掺杂荧光碳量子点高灵敏检测Hg2+

以天然产物野酸枣和色氨酸为原料,通过水热法一步合成量子产率为16.9%的氮掺杂荧光碳量子点。该碳量子点具有良好的水溶性和耐光性,在高盐环境中也呈现出了较高的稳定性。应用荧光光谱、透射电子显微镜(TEM)、傅里叶变换红外光谱(FTIR)和X射线光电子能谱(XPS)对碳量子点进行了表征。此外,Hg^2+能够有效地猝灭碳量子点的荧光,猝灭机理为电子转移的动态猝灭。基于此,可将碳量子点作为荧光探针检测Hg^2+。方法对Hg^2+的检测范围为1~50 nmol/L,检出限为0.26 nmol/L,能够应用于实际水样中Hg2+含量的测定。     

Facile Microwave‐Assisted Solid‐Phase Synthesis of Highly Fluorescent Nitrogen–Sulfur‐Codoped Carbon Quantum Dots for Cellular Imaging Applications

Carbon quantum dots (CQDs) have recently attracted significant attention for both their fundamental science and technological applications as a new class of fluorescent zero‐dimensional nanomaterials with a size below 10 nm. However, the reported methods of synthesis were generally less suitable for the large‐scale production of the CQDs with high‐fluorescent quantum yield (QY). In the paper, a novel one‐pot microwave‐assisted drying synthesis approach was presented to prepare CQDs with high QY of 61.3 % for the first time. The production yield of CQDs was 35±3 % in weight. The as‐prepared CQDs were characterized by various techniques such as TEM, AFM, XRD, XPS, FTIR spectroscopy, UV/Vis absorption spectroscopy, and fluorescence spectroscopy. The results showed that the high QY of CQDs was largely attributed to the dual doping of nitrogen and sulphur into CQDs. Such CQDs were then used as live‐cell imaging reagents due to their high QY, good water dispersibility, fine biocompatibility, high photostability, and low cytotoxicity.     

Electrochemical Synthesis of Carbon Nanodots Directly from Alcohols

Carbon nanodots (C‐dots) show great potential as an important material for biochemical sensing, energy conversion, photocatalysis, and optoelectronics because of their water solubility, chemical inertness, low toxicity, and photo‐ and electronic properties. Numerous methods have been proposed for the preparation of C‐dots. However, complex procedures and strong acid treatments are often required, and the as‐prepared C‐dots tend to be of low quality, and in particular, have a low efficiency for photoluminescence. Herein, a facile and general strategy involving the electrochemical carbonization of low‐molecular‐weight alcohols is proposed. As precursors, the alcohols transited into carbon‐containing particles after electrochemical carbonization under basic conditions. The resultant C‐dots exhibit excellent excitation‐ and size‐dependent fluorescence without the need for complicated purification and passivation procedures. The sizes of the as‐prepared C‐dots can be adjusted by varying the applied potential. High‐quality C‐dots are prepared successfully from different small molecular alcohols, suggesting that this research provides a new, highly universal method for the preparation of fluorescent C‐dots. In addition, luminescence microscopy of the C‐dots is demonstrated in human cancer cells. The results indicate that the as‐prepared C‐dots have low toxicity and can be used in imaging applications.     

碳量子点上转换材料的制备及其应用研究进展

碳量子点(CQD)具有化学惰性,生物相容性和低毒性等优势,可能在能源、生物医药等领域得到广泛的应用. CQD可通过表面被聚合物(例如PEG)钝化而表现出很强的光致发光特性.在生物成像,疾病检测和药物输送中使用表面钝化后的功能化生物分子更为有效.并且碳材料由于其优异的电化学性能还展现出在催化、电子器件等许多领域广泛的应用前景.我们将对近年来碳量子点发光材料的研究进行总结,并讨论碳量子点在能源、环境和其他一些领域的应用.     

Blood compatible heteratom-doped carbon dots for bio-imaging of human umbilical vein endothelial cells

Carbon dots have unique advantages in biological applications owing to their excellent optical prope rties.However,the biosafety evaluation of carbon dots has limitations owing to cytotoxicity in vitro,and the re is little pre-safety evaluation before in vivo and clinical applications.Whether the carbon dots are or not suitable for applications in vivo,evaluation analysis can be made based on hemolysis and changes in erythrocyte morphology.In this work,a green fluorescent N,S-doped carbon dots(N,S-CDs)were obtained by hydrothermal method,tobias acid,and m-phenylenediamine as precursors.N,S-CDs not only possessed excellent dispersibility,uniform particle size,high quantum yield(37.2%)and stable photoluminescence property but also retain their photostability and stro ng fluorescence intensity in the acid/alkaline solutions,different ionic strengths(NaCl)and under 365 nm UV illumination.Moreove r,the N,S-CDs displayed low cytotoxicity and high cellular uptake efficiency in human umbilical vein endothelial cells(HUVEC)and excellent blood compatibility to the erythrocyte.It is foreseeable that N,S-CDs could be further studied as a promising biological imaging agent in vivo.     

Room‐Temperature Solution‐Processed PbS Quantum Dot Solar Cells

Colloidal quantum dots (CQDs) are attractive absorber materials for high‐efficiency photovoltaics because of their facile solution processing, bandgap tunability due to quantum confinement effect, and multi‐exciton generation. To date, all published performance records for PbS CQDs solar cells have been based on the conventional hot‐injection synthesis method. This method usually requires relatively strict conditions such as high temperature and the utility of expensive source material (pyrophoric bis(trimethylsilyl) sulfide (TMS‐S)), limiting the potential for large‐scale and low‐cost synthesis of PbS CQDs. Here we report a facile room‐temperature synthetic method to produce high‐quality PbS CQDs through inexpensive ionic source materials including Pb(NO₃)₂ and Na₂S in the presence of triethanolamine (TEA) as the stabilizing ligand. The PbS CQDs were successfully prepared with an average particle size of about 5 nm. Solar cells based on the as‐synthesized PbS CQDs show a preliminary power conversion efficiency of 1.82%. This room‐temperature and low‐cost synthesis of PbS CQDs will further benefit the development of solution‐processed CQD solar cells.     

Metal-enhanced photoluminescence from carbon nanodots

In the last couple of years, carbon dots have emerged as a new novel luminescent particle for applications in fluorescence and microscopy in some ways analogous to quantum dots and silicon nanocrystals/particles. As with any fluorescent label or tag, absolute fluorescence intensity, brightness, and particle photostability are a primary concern. In this communication we subsequently show that similar to classical fluorophores, carbon dots located in the near-field, near to Plasmon supporting materials, show enhanced intensities and improved photostabilities.     

碳量子点的制备及其在能源与环境领域应用进展

碳量子点(carbon quantum dots,CQDs)作为碳纳米材料家族的新成员引起了科学家广泛关注和极大的研究兴趣。 CQDs具有优良的光学特性、生物相容性及微弱的细胞毒性,在生物医药、生物传感器及光电子设备、环境及能源等领域中具有重要的应用。 本文从CQDs的制备方法出发,介绍了近年来发展的新型制备方法,讨论了其优缺点以及对所得CQDs在组成、结构和性质等方面的影响;基于CQDs独特的光学及电化学性能,重点介绍了CQDs在环境与能源领域的应用。 此外,对CQDs研究过程中存在的若干挑战进行了分析,提出了未来发展的一些思考和建议,为拓展CQDs多方面应用提供重要参考。     

Control the size and surface chemistry of graphene for the rising fluorescent materials

Fluorescent graphene-based materials, labelled as a sort of fluorescent carbon-based nanomaterial, have drawn increasing attention in recent years. When the size and structure of graphene were controlled properly, photoluminescence was induced in graphene, resulting in the so-called fluorescent graphene (FG). FG has a size-, defect-, and wavelength-dependent luminescence emission, which is similar to traditional semiconductor-based quantum dots. Moreover, with excellent chemical stability, fine biocompatibility, low toxicity, up-conversion emission, pH-sensitivity and resistance to photobleaching, FG promises to offer substantial applications in numerous areas: bioimaging, photovoltaics, sensors, etc. Currently, research works have allowed FG to be produced by many approaches ranging from simple oxidation of graphene to cutting carbon sources and organic synthesis from small molecules. In this Feature Article, we summarize the reported fluorescent graphenes, with emphasis on their category, properties, synthesis and applications. Meanwhile, we give a perspective on their subsequent developments and compare the features of FG and other fluorescent carbon-based materials.     

中温煤沥青基碳量子点的制备与结构解析

以中温煤沥青为碳源，采用HNO₃预处理结合球磨过程及双氧水氧化刻蚀的方法制备沥青基荧光碳量子点，以CQDs的收率和荧光量子产率为目标，获得最优制备条件：反应时间6 h、H₂O₂加入量100 mL （c-CQDs），此时，CQDs收率和荧光量子产率分别为6.3%和11.2%，且尺寸均匀、粒径分布在4-14 nm。延长反应时间至8 h （a-CQDs），碳量子点团聚；H₂O₂用量增加至120 mL （b-CQDs）则导致碳量子点氧化过度，颗粒小且杂乱无章。对不同条件下所制备的CQDs进行XPS、红外光谱、热重、¹³C NMR、Raman和晶相分析，探究反应条件对CQDs结构的影响规律。结果表明，就碳含量而言，a-CQDs > b-CQDs > c-CQDs，氧元素含量则为b-CQDs > c-CQDs > a-CQDs。各CQDs结构中C主要以芳碳形式存在，c-CQDs的C=O、O-C=O含量最高，而b-CQDs的C-O含量最高，¹³C NMR分析发现CQDs中表征平均芳环尺寸大小的X_b约为0.5，相应地，其平均芳环数约为3。     

Deep Eutectic Solvent-assisted Synthesis of Nitrogen-doped Carbon Quantum Dots for Cell Imaging

Carbon quantum dots(CQDs) are widely used in fluorescence imaging due to their negligible toxicity, low-cost and excellent fluorescence properties. The fluorescence properties of CQDs are greatly affected by the synthesis method, passivation agent and reaction media. In this study, the nitrogen-doped CQDs(N-CQDs) were synthesized by a facile microwave-assisted method with citric acid(CA) as a carbon source and deep eutectic solvents as a N-dopant as well as the reaction solvent. After detailed characterizations, the as-prepared N-CQDs exhibited near spherical morphology with an average size of (2.64±0.55) nm. Besides, the abundant hydrophilic functional groups including hydroxyl, carboxyl, amine and quaternary ammonium were present on the surface of the N-CQDs. The N-CQDs displayed the excitation-dependent fluorescence feature under the excitation wavelength of 350-480 nm. Moreover, the N-CQDs could be efficiently uptaken by RAW264.7 cells and emitted bright green light. Meanwhile, the resultant N-CQDs showed the low cytotoxicity in living cells, suggesting the great potential in bio-imaging applications.