量子点比率荧光探针研究进展

量子点(QDs)是一种纳米发光粒子,具有优异的发光性能,在太阳能利用、荧光检测等方面具有广阔的应用前景。QDs与另一荧光团复合可构建比率荧光探针,实现可视化检测目标物并且提高了检测灵敏度。本文主要对QDs比率荧光探针的种类、构建方法和应用领域的研究进展进行综述,并对其中的不足进行分析,以期为研发具有优异性能的比率荧光探针提供借鉴。     

基于双发射碳量子点的比率型荧光探针检测阿司匹林

以间苯二胺和酒石酸为原料,通过一步水热法合成了在单一激发波长下具有双发射特性的碳量子点(CQDs)。利用透射电镜(TEM)、傅里叶变换红外光谱(FTIR)、 X射线光电子能谱(XPS)、紫外-可见吸收光谱(UV-vis)和荧光光谱对其结构和光学性质进行了表征。当激发波长为390 nm时,该CQDs在440和502 nm处有2个发射峰。阿司匹林能够使502 nm处的发射峰荧光强度增加,而440 nm处的发射峰强度基本不变,基于此,构建了一种CQDs比率型荧光探针检测阿司匹林的新方法。阿司匹林浓度在0.5～160μmol/L范围内与CQDs的2个发射峰的荧光强度比(F₅₀₂/F₄₄₀)呈良好的线性关系,检出限低至0.062μmol/L。该方法成功用于药品中阿司匹林的检测。     

荧光探针在羧酸酯酶检测中的研究进展

羧酸酯酶(CES)属于丝氨酸酯酶超家族,它们位于多种组织的内质网和胞质,参与药物、环境毒物和前致癌物的代谢激活或发挥解毒作用。为进一步了解CES生理学和药理学的作用,研发出一种能够在细胞、组织和有机体水平上实时准确监测CES的方法非常有必要。荧光探针具有高选择性、高灵敏度、快速检测、比色明显、操作简便、实时成像等优势,作为一种灵敏的检测手段,被广泛应用于生物检测、光学成像等领域。本文主要对近5年来用于CES检测的荧光探针研究进展进行总结。     

半导体荧光量子点标记技术

生命体系中化学、生物信息的活体、原位、实时、动态和高灵敏获取,是当前生命科学研究中迫切需要解决的关键问题之一,发展相关的新技术与新方法至关重要。半导体荧光量子点因其优异的荧光特性可望在解决此类难题中发挥重要作用而日益受到关注。本文将根据我们课题组多年来的研究工作经验,就半导体荧光量子点标记技术的相关基础问题、在生物医学领域中的应用以及发展前景等做简要评述。     

用于生物标记的半导体量子点研究

半导体量子点的独特光学性质使之成为理想的荧光探针材料,在生物医学领域具有广阔的应用前景.本文评述了目前量子点合成、表面修饰、结合生物分子的方法,以及半导体量子点在生物标记应用中相对于传统有机染料的优点.     

石墨烯量子点-金纳米簇比率荧光传感器用于海水pH检测

表层海洋pH正以约每年0.002的速度下降,这种变化将会对地球的化学循环和气候变化的物理化学参数产生潜在的影响。为了准确了解海洋的酸化程度,本文建立了一种快速准确检测海水pH的方法。采用柠檬酸热解法合成石墨烯量子点（GQDs）,以谷胱甘肽（GSH）为模板合成金纳米簇（GSH-AuNCs）,将GQDs和GSH-AuNCs结合制成GQDs-AuNCs比率荧光传感器,用于海水pH的检测。在酸性条件下,由于GSH-AuNCs表面的羧基发生质子化,GSH-AuNCs分子之间的静电斥力减弱因而发生聚集,荧光强度随之降低。在碱性条件下,GSH-AuNCs表面的羧基脱质子化,GSH-AuNCs分子之间的静电斥力增强,荧光强度也随之增强。在pH 2～11范围内,GQDs-AuNCs比率荧光探针的荧光强度比值(I₅₆₅/I₄₄₀)与pH之间呈线性相关。将该方法用于海水的pH检测,得到较好的实验结果。     

基于三羧酸异构体的二维锌配位聚合物对硝基苯的荧光传感

在水热条件下,以2个异构体5-((3-羧基苯氧基)亚甲基)间苯二甲酸(3-H₃CIA)、5-((4-羧基苯氧基)亚甲基)间苯二甲酸(4-H₃CIA)和3-双(咪唑-1-甲基)苯(3-bibz)为原料,合成了2种二维锌(Ⅱ)配位聚合物(CPs)：[Zn₄(3-CIA)₂(OH)₂(3-bibz)₂](1)和[Zn₂(4-CIA)(OH)(3-bibz)]·H₂O (2),采用单晶X射线衍射、红外光谱、热重、粉末X射线衍射技术进行了表征。结构分析表明,由于2个异构体的配位方式不同,CP 1为基于四核单元的二维网结构,而2则为基于三核单元的二维网络结构。CP 1和2对有机溶剂的荧光传感测试表明,其荧光对水中的硝基苯都表现为完全猝灭现象,检出限分别为0.248和0.309 μmol·L^-1。理论计算表明,1和2对硝基苯传感机理主要可归因于光诱导电子转移(PET)效应。     

量子点在生物化学传感中的应用研究进展

综述了荧光量子点在生物化学传感中的研究应用进展,重点介绍离子、酶以及糖类的传感,并展望了其发展趋势和应用前景。     

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.     

Near-Infrared-II Semiconducting Polymer Dots for Deep-tissue Fluorescence Imaging

Fluorescence imaging, particularly in the NIR-II region (1000–1700 nm), has become an unprecedented tool for deep-tissue in vivo imaging. Among the fluorescent nanoprobes, semiconducting polymer nanoparticles (Pdots) appear to be a promising agent because of their tunable optical and photophysical properties, ultrahigh brightness, minimal autofluorescence, narrow-size distribution, and low cytotoxicity. This review elucidates the recent advances in Pdots for deep-tissue fluorescence imaging and the facing future translation to clinical use.     

A Single‐Wavelength‐Emitting Ratiometric Probe Based on Phototriggered Fluorescence Switching of Graphene Quantum Dots

Ratiometric fluorescent probes are of great importance in research, because a built‐in correction for environmental effects can be provided to reduce background interference. However, the traditional ratiometric fluorescent probes require two luminescent materials with different emission bands. Herein a novel ratiometric probe based on a single‐wavelength‐emitting material is reported. The probe works by regulating the luminescent property of graphene quantum dots with UV illumination as activator. The ratiometric sensor shows high sensitivity and specificity for iron ions. Moreover, the ratiometric sensor was successfully employed to monitor ferritin levels in Sprague Dawley rats with chemical‐induced acute liver damage. The proposed single‐wavelength ratiometric fluorescent probe may greatly broaden the applicability of ratiometric sensors in diagnostic devices, medical applications, and analytical chemistry.     

Highly Fluorescent Semiconducting Polymer Dots for Biology and Medicine

In recent years, semiconducting polymer nanoparticles have attracted considerable attention because of their outstanding characteristics as fluorescent probes. These nanoparticles, which primarily consist of π‐conjugated polymers and are called polymer dots (Pdots) when they exhibit small particle size and high brightness, have demonstrated utility in a wide range of applications such as fluorescence imaging and biosensing. In this review, we summarize recent findings of the photophysical properties of Pdots which speak to the merits of these entities as fluorescent labels. This review also highlights the surface functionalization and biomolecular conjugation of Pdots, and their applications in cellular labeling, in vivo imaging, single‐particle tracking, biosensing, and drug delivery. We discuss the relationship between the physical properties and performance, and evaluate the merits and limitations of the Pdot probes for certain imaging tasks and fluorescence assays. We also tackle the current challenges of Pdots and share our perspective on the future directions of the field.     

Fluorination Enhances NIR-II Fluorescence of Polymer Dots for Quantitative Brain Tumor Imaging

Here, we describe a fluorination strategy for semiconducting polymers for the development of highly bright second near-infrared region (NIR-II) probes. Tetrafluorination yielded a fluorescence QY of 3.2 % for the polymer dots (Pdots), over a 3-fold enhancement compared to non-fluorinated counterparts. The fluorescence enhancement was attributable to a nanoscale fluorous effect in the Pdots that maintained the molecular planarity and minimized the structure distortion between the excited state and ground state, thus reducing the nonradiative relaxations. By performing through-skull and through-scalp imaging of the brain vasculature of live mice, we quantitatively analyzed the vascular morphology of transgenic brain tumors in terms of the vessel lengths, vessel branches, and vessel symmetry, which showed statistically significant differences from the wild type animals. The bright NIR-II Pdots obtained through fluorination chemistry provide insightful information for precise diagnosis of the malignancy of the brain tumor.     

Water‐Soluble Polymer Functionalized CdTe/ZnS Quantum Dots: A Facile Ratiometric Fluorescent Probe for Sensitive and Selective Detection of Nitroaromatic Explosives

A ratiometric fluorescent probe based on dual luminescence QD/CPL for selective sensing of the nitroaromatic explosive picric acid (PA) was constructed. The observed ratiometric fluorescence intensity change allows the quantitative detection of PA with a detection limit of 9 nM .     

Boron Doped Carbon Dots with Unusually High Photoluminescence Quantum Yield for Ratiometric Intracellular pH Sensing

Herein we report that boron doping in carbon dots results in increased photoluminescence (PL) quantum yield, which could be used for ratiometric intracellular pH sensing in cancer cell lines. Using a mixture of citric acid monohydrate, thiourea, and boric acid, microwave-assisted synthesis of boron doped blue emitting carbon dots (B-Cdots) with an average size of 3.5±1.0 nm was achieved. For B-Cdots, the maximum quantum yield (QY) was observed to be 25.8 % (11.1 % (w/w) H₃BO₃ input concentration), whereas, the same was calculated to be 16.9 % and 11.4 % for Cdots (synthesized from citric acid monohydrate and thiourea only) and P-Cdots (phosphorus doped carbon dots; synthesized using citric acid monohydrate, thiourea and phosphoric acid) (11.1 % (w/w) H₃PO₄ input concentration), respectively. The observed luminescence efficiencies as obtained from steady state and time-resolved photoluminescence measurements suggest an alternative emission mechanism due to boron/phosphorus doping in carbon dots. We furthermore demonstrated facile composite formation using B-Cdots and another carbon dots with orange emission in presence of polyvinyl alcohol (PVA), resulting in white light emission (0.31, 0.32; λ_ex 380 nm). The white light emitting composite enabled ratiometric pH sensing in the aqueous medium and showed favorable uptake properties by cancerous cells for intracellular pH sensing as well.     

超小尺寸聚焦硫量子点荧光传感探针的制备及传感应用

采用简单的组装-裂变法和透析后处理技术相结合的方法,制备了一种超小尺寸聚焦的荧光硫量子点(SQDs).采用透射电子显微镜(TEM)、X射线能谱(EDX)、紫外-可见吸收光谱(UV-Vis)和荧光光谱对所制备的SQDs进行了表征.结果表明,平均粒径为2.2 nm的SQDs在水溶液中具有非激发波长依赖特性和光学稳定性.并且...     

Fabrication of a Ratiometric Fluorescence Sensor Based on Carbon Dots as Both Luminophores and Nanozymes for the Sensitive Detection of Hydrogen Peroxide

The construction of novel fluorescent nanozymes is highly desirable for providing new strategies for nanozyme-based sensing systems. Herein, a novel ratiometric fluorescence sensing platform was constructed based on carbon dots (CDs) as both luminophores and nanozymes, which could realize the sensitive detection of hydrogen peroxide (H₂O₂). CDs with peroxidase-mimicking activity were prepared with a one-step hydrothermal method using L-histidine as an inexpensive precursor. CDs had bright blue fluorescence. Due to the pseudo-peroxidase activity, CDs catalyzed the oxidation of o-phenylenediamine (OPD) with H₂O₂ to generate 2,3-diaminophenolazine (DAP). The fluorescence resonance energy transfer (FRET) between CDs and DAP resulted in a decrease in the fluorescence of CDs and an increase in the fluorescence of DAP, leading to a ratiometric fluorescence system. The free radical trapping experiment was used to investigate the reactive oxygen radicals (ROS) in the catalytic process of CD nanozymes. The enzymatic parameters of CD nanozymes, including the Michaelis constant (K_m) and the maximum initial reaction velocities (V_max), were investigated. A good affinity for both OPD and H₂O₂ substrates was proven. Based on the FRET between CDs and OPD, a ratiometric fluorescence analysis of H₂O₂ was achieved and results ranged from 1 to 20 μM and 20 to 200 μM with a low limit of detection (LOD, 0.42 μM). The detection of H₂O₂ in milk was also achieved.     

Fluorescence and Sensing Applications of Graphene Oxide and Graphene Quantum Dots: A Review

Graphene oxide and graphene quantum dots are attractive fluorophores that are inexpensive, nontoxic, photostable, water‐soluble, biocompatible, and environmentally friendly. They find extensive applications in fluorescent biosensors and chemosensors, in which they serve as either fluorophores or quenchers. As fluorophores, they display tunable photoluminescence emission and the “giant red‐edge effect”. As quenchers, they exhibit a remarkable quenching efficiency through either electron transfer or Förster resonance energy transfer (FRET) process. In this review, the origin of fluorescence and the mechanism of excitation wavelength‐dependent fluorescence of graphene oxide and graphene quantum dots are discussed. Sensor design strategies based on graphene oxide and graphene quantum dots are presented. The applications of these sensors in health care, the environment, agriculture, and food safety are highlighted.