溶剂热法合成橙-绿双波段荧光碳点

荧光碳点具有激发波长依赖的独特性质,有望基于此制备检测溶液pH值的荧光探针。以柠檬酸和尿素为原料、N,N-二甲基甲酰胺为溶剂,采用一步溶剂热法在200℃下保温12 h制备了一种新型的具有橙-绿双波段荧光发射性能的水溶性碳点。采用透射电子显微镜、X射线衍射、拉曼光谱、傅里叶变换红外光谱和X射线光电子能谱等方法对荧光碳点的组成和形貌进行了表征,还通过荧光发射光谱和紫外-可见吸收光谱对其光学性能进行了研究。结果表明,制备的碳点粒径为2.7~4.3 nm,表面带有大量含氧官能团,具有良好的水分散性。在440 nm和540 nm波长光激发下分别呈现绿色(500 nm)和橙色(590 nm)双波段荧光发射。合成的荧光碳点发光性能对pH值具有敏感性:在强碱性溶液中,590 nm的荧光强度比水溶液中提高了6.71倍,同时吸收峰的蓝移使得自然光下其溶液颜色发生了明显改变,具有强碱性指示剂的作用;在pH值为2~6的酸性溶液中,500 nm与590 nm发光峰强度比与pH值之间呈现良好的线性关系,展现了作为pH值比率荧光探针的应用潜力。     

pH响应型碳点的荧光机制和生物医学应用

碳点(CDs)作为一种新型的零维碳基纳米材料,由于其优异的荧光性质、良好的生物兼容性、低细胞毒性以及丰富的表面官能团等性质,在荧光传感和生物医学领域具有巨大的应用潜力。特别是针对肿瘤弱酸性的微环境特点,设计pH响应型碳点来实现对肿瘤的特异性治疗将尤为重要。本文对近年来基于pH响应型碳点的研究工作进行了系统的调研,综述了pH响应型碳点的荧光机制及其在pH传感、生物成像及癌症治疗等生物医学领域的应用,并对pH响应型碳点目前面临的主要挑战以及未来发展的方向进行了展望。     

CdSe/ZnS量子点在倏逝波光纤pH传感中的应用

将新型量子点荧光传感技术与光纤倏逝波传感技术相结合,发展了一种基于量子点荧光效应并结合倏逝波传导进行溶液酸碱度检测的新型传感技术,具有灵敏度高、检测速度快、便于微环境检测、可实现远程探测、实时监测和原位分析等特点。详细介绍了用于倏逝波传感的锥柱组合型光纤荧光探头的制备方法,量子点在光纤探头表面的修饰流程,光谱与强度两种光纤pH传感平台的建立,并分别从响应范围、线性度、重复性和稳定性等方面对CdSe/ZnS量子点应用于光纤pH传感进行了评价。结果表明,在pH值为2~12的范围内,CdSe/ZnS量子点的荧光光谱信号的峰位在强酸和强碱的情况下都会产生红移,且红移量随pH值的变化呈线性关系,其量子点荧光强度信号随pH值的减小呈线性降低关系,通过在强酸和强碱下交替测试的实验表明其具有较好的重复性,利用荧光强度传感平台进行实时监测的实验表明其具有较好的稳定性。因此,将CdSe/ZnS量子点用于倏逝波光纤pH传感具有可行性,在生物化学、环境监测、医学临床、食品安全等领域的pH值测量方面有着广泛的应用前景。     

生物质碳量子点的绿色制备及对Cu2+的检测

向日葵作为我国主要的油料作物之一,其秸秆是天然的纤维素材料,具有绿色无毒,成本低廉的优势,是制备生物质碳量子点的理想材料之一。近年来,由于含铜农药和化学肥料的不规范使用,大量含铜污染物被排放导致农田土壤和水环境中的铜含量远高于环境背景值。因此,迫切需要开发出一种选择性好、灵敏性强且对环境友好的Cu²⁺检测方法。碳量子点(CDs)是一种粒径小于10 nm的准球形荧光碳纳米材料,因其表面含有丰富的极性官能团,具有良好的水溶性而被广泛研究。与传统的半导体量子点(CdSe, CdTe)相比,CDs具有合成原料广泛、生物相容性好等优点。主要应用于生物成像、光催化、光电转化以及传感检测等领域。然而目前用于碳化合成CDs的前驱体大多为昂贵的化学品,且合成过程复杂污染环境,限制了CDs的大规模生产与应用。开发出一种生态友好,简单、廉价的CDs合成方法是很有意义的。本研究以废弃的向日葵秸秆为碳源,采用简便的水热法合成生物质碳量子点(S-CDs)作为荧光探针,用于检测识别Cu²⁺。通过对S-CDs的一系列光学性质分析与表征,鉴定出其表面官能团主要包括O—H, N...     

Cyclodextrin Functionalized Carbon Dots Using IFE and FRET Dual Mechanism for Sequential Detection of Morin and Al3+

Carbon dots (CDs) are emerging photoluminescent materials with excellent optical properties. However, the lack of active sites in primitive CDs has limited their development applications. Herein, functionalized carbon dots (Z-CDs) are successfully prepared by surface modification of CDs with mono (6-amino-6-deoxy) cyclodextrin (β-CD). The introduction of β-CD increases the spatial potential resistance between CDs, which effectively reduces the self-quenching effect. Moreover, the conjugated domains of Z-CDs are expanded, which improves the optical properties with a quantum yield of 48.74%. Z-CDs are able to be used in the sequential detection of morin and Al³⁺, and the fluorescence mechanisms are confirmed to be internal filtration effect and fluorescence resonance energy transfer, respectively. The limits of detection are 0.817 and 0.231 × 10⁻⁶ m . This study not only provides an idea to solve the problem of self-quenching of CDs but also enriches the detection means of flavonoids and ions, which is expected to be applied to biosensing and environmental monitoring.     

基于碳点“开关”型荧光探针在组氨酸检测中的研究

研究并构建了一种基于荧光碳点(carbon dots, CDs)的新型“开关”探针,利用CDs荧光强度的变化进行痕量组氨酸(histidine, His)的检测。在pH 7.6的溶液中,钌(Ru)能与CDs通过静电吸引作用形成弱的基态化合物,导致CDs的荧光猝灭,此时体系处于“关闭”状态。而His与Ru有更强的亲和力,故向体系中加入 His后,Ru从CDs表面竞争中下来,CDs的荧光得到恢复,此时体系被“打开”。考察了pH、缓冲溶液、反应时间、温度等因素对体系的影响,并初步讨论了Ru对CDs荧光的猝灭类型,得出了Ru对CDs荧光的猝灭属于静态猝灭的结论。实验结果表明,在pH 7.6的溶液中,在20～25 ℃条件下,体系在10 min 内反应完成。His的浓度与碳点荧光的恢复程度呈良好的线性关系,其线性范围为：6.5～219.3×10-6 mol·L-1,检出限为：2.15×10-6 mol·L-1。将方法应用于实际样品氨基酸注射液中组氨酸含量的测定,其RSD≤2.07%,回收率在95.7%～102.4%之间。将具有优良光学特性的CDs应用于构建“开关”型荧光探针,不但拓宽了CDs的应用范围,为一些重要物质的检测提供了参考。     

One step synthesis of ultra-high quantum yield fluorescent carbon dots for “on-off-on” detection of Hg2+ and biothiols

In this paper, the carbon dots (CDs) with strong blue fluorescence were synthesized through hydrothermal method, which using folic acid, ammonium citrate and ethylenediamine as precursors. The prepared CDs with a high absolute quantum yield of 81.94% and showed excellent stability in high concentration salt solution and different pH conditions. With the addition of Hg²⁺, the signal of CDs was selectively quenched. At the same time, the CDs-Hg²⁺ system could be recovered after the introduction of biothiols. Moreover, the fluorescence of CDs showed a good linear relationship with Hg²⁺ (1–15 µM), and the detection limit as low as 0.08 µM. In addition, the prepared CDs with low toxicity could be used to detect Hg²⁺ in living cells and actual water samples.

     

One-pot synthesis of carbon dots co-doped with N and S: high quantum yield governed by molecular state and fluorescence detection of Ag+

Fluorescent carbon-based nanoparticles, called chronically as carbon dots (CDs), were synthesised from citric acid (CA) and 2-Aminothiophenol (2AT) via an N and S co-doped hydrothermal method. After a series of micro-structural characterisation, N and S elements could be sufficiently doped by means of the heteroatom in the CDs solution. The as-prepared CDs solution showed blue colour fluorescence with the highest QY of 78.6%, and study on the UV–visible and PL spectra further revealed that the outstanding fluorescence of as-prepared CDs mainly originates from the generated molecular fluorophores instead of the surface state. Owing to the strong fluorescence, the as-prepared CDs can be used as a sensing probe for the detection of Ag⁺ with high sensitivity and selectivity. However, the changes of fluorescence intensity exhibited the complex nature of the quenching mechanism due to the –SH and –NH₂ groups on the fringes of carbonaceous cores or molecular fluorophores to aggregate into another fluorescent cores with the assistance of Ag⁺ ions, which promises a new approach for efficient detection of Ag⁺ for the application in industrial pollutants.

This figure shows citric acid (CA) and 2-Aminothiophenol (2AT) via an N and S co-doped hydrothermal method to prepare CDs with blue colour fluorescence and the highest QY of 78.6%. Owing to the excellent fluorescence, the as-prepared CDs can be used as a sensing probe for the detection of Ag⁺ with high sensitivity and selectivity, and the changes of fluorescence intensity exhibited the complex nature of the quenching mechanism due to the –SH and –NH₂ groups on the fringes of carbonaceous cores or molecular fluorophores to aggregate into another fluorescent cores with the assistance of Ag⁺ ions, which promises a new approach for efficient detection of Ag⁺ for the application in industrial pollutants.     

以醇溶剂为碳源制备碳点的荧光性能

以乙二醇和丙三醇为碳源,用一元醇（异丙醇和乙醇）为对比,通过溶剂热法制备得到碳点。通过傅里叶红外光谱、紫外-可见吸收光谱和激发光谱对所制得的碳点进行表征和分析,探讨了不同碳源对碳点的表面官能团、荧光性能等的影响,从而分析其荧光的发光机理。结果表明：乙二醇与丙三醇制备的碳点含有C=C键和C=O键,均在365 nm光激发后在450 nm处有荧光峰;而一元醇是由C-OH基团中的孤对电子产生荧光,碳源分子中羟基含量对碳点的荧光性能有很大影响,羟基含量越高,越容易形成双键结构。     

Nitrogen-doped carbon dots embedded in a SiO<Subscript>2</Subscript> monolith for solid-state fluorescent detection of Cu<Superscript>2+</Superscript> ions

We describe the simple fabrication of SiO₂ sol-gel monoliths embedding highly luminescent carbon nanodots (CDs) sensitive to metal ions. The pristine CDs we synthesize display an intense dual emission consisting in two fluorescence bands in the green and violet region, and we demonstrate that this photoluminescence is substantially unchanged when the dots are incorporated in the SiO₂ matrix. The emission of these CDs is quenched by interactions with Cu²⁺ ions, which can be used to detect these ions with a detection limit of 1 μM. The chromophores remain accessible to diffusing Cu²⁺ ions even after embedding CDs in the sol-gel monolith, where their detection capabilities are preserved. Such a result provides the proof-of-principle of a new sensing scheme, where CDs are exploited as active sensing centers of metal transition ions within a solid-state device. The different interaction mechanisms of CDs with copper, in liquid and solid phase, are analyzed in detail and discussed in terms of different accessibility of their chromophores when the dots are incorporated in the SiO₂ matrix.     

壳聚糖基聚合物碳点荧光材料合成及其自组装载药应用

荧光碳点具有化学稳定性好、毒性小、可表面功能化等优点,引起了人们极大的兴趣。近年来,由高分子多糖合成的聚合物碳点成为另一研究热点。本文通过水热法合成了一种壳聚糖基荧光聚合物碳点材料（P（CS-g-mPEG-CA）CDs）,并用于载药研究。基于壳聚糖和聚乙二醇既是碳点的碳源也是碳点的钝化试剂,本文选择壳聚糖接枝聚乙二醇单甲醚和柠檬酸衍生物作为聚合物碳点的碳源,以提高聚合碳点的量子产率。另外,聚合物碳点还可以保留聚乙二醇与壳聚糖分子结构,为其在载药方面的应用提供有利条件。采用红外光谱、紫外光谱、X射线衍射、光电子能谱、透射电子显微镜和光致发光光谱对P（CS-g-mPEG-CA）CDs进行了结构表征以及pH值稳定性的测试。结果表明,所合成的P（CS-g-mPEG-CA）CDs具有较高的荧光量子产率（66.81%）、较长的荧光寿命（15.247 ns）、良好的pH稳定性。以阿霉素为模型药物,利用该聚合物碳点进行了负载研究,结果表明,当聚乙二醇单甲醚取代度为11.9%时,聚合物碳点的载药量最高为51.3%,最大药物释放率为28.7%,此外,药物的装载和释放可以通过mPEG的接枝率进行控制。采用MTT法评价了聚合物的碳点对鼻咽癌细胞（CNE-2）的毒性作用。研究表明,空白聚合物碳点无明显细胞毒性,CNE-2细胞存活率随着载药胶束的增加而降低,说明载药胶束对CNE-2细胞有较强的抑制作用。可见该P（CS-g-mPEG-CA）CDs在荧光标记、药物递送、荧光示踪系统和控制释放方面,具有一定的应用前景。     

壳聚糖碳点的水热法制备及其对金属离子的选择性研究

以壳聚糖为碳源通过水热法合成碳点,对影响碳点荧光强度的水热温度、水热时间和壳聚糖质量分数进行考察。通过紫外分光光度计、荧光分光光度计、原子力显微、Fourier红外光谱仪、X-ray光电子能谱、X射线衍射仪对壳聚糖碳点的光学性质、化学结构、晶体结构、形貌结构等进行表征分析。结果表明,在水热温度200℃、水热时间9 h、壳聚糖质量分数2%的条件下制备得到的壳聚糖碳点量子产率为32.86%。碳点呈现出主要尺寸为3～10 nm的球形颗粒状,且在波长335 nm激发下,发射峰位于410 nm(蓝)。对金属离子的选择性研究分析表明,Fe~(3+)对碳点溶液的荧光猝灭效应最显著,说明碳点对Fe~(3+)具有较好敏感性和高选择性,且荧光猝灭效率对Fe~(3+)浓度在0～100μmol/L范围内呈现线性响应,因此有望将碳点作为荧光探针应用于Fe~(3+)的检测表征。     

以固态法一步合成的荧光碳点为探针测定人体尿液中阿霉素

以柠檬酸和尿素为碳源和氮源,采用固态法一步合成出量子产率高达23%的荧光碳点。表征结果表明,所合成的荧光碳点为平均粒径为3~4 nm的球形,表面富含羟基、羧基和胺基等基团。此外,碳点的XRD谱图显示出无定型碳的特征峰。以所制备的碳点为荧光探针,基于碳点和阿霉素之间的共振能量转移而猝灭碳点的荧光,建立了阿霉素定量分析新方法。实验中考察了溶液的pH值和孵化时间的影响。在最佳实验条件下,阿霉素浓度在0.67~16.67 μg·mL-1范围之间与碳点的荧光猝灭值ΔF呈良好的线性关系(R2=0.995),检出限为0.22 μg·mL-1,回收率为83.0%～89.2%,相对标准偏差小于2.5%(n=5)。尿样中常见物质对测定干扰较小,显示出所建立的方法具有较好的选择性。     

Facile Synthesis of Mg2+‐Doped Carbon Dots as Novel Biomaterial Inducing Cell Osteoblastic Differentiation

Carbon dots (CDs), as an emerging fluorescent nanomaterial with low toxicity, has been widely applied in various bio‐related fields. However, investigations on their capabilities in guiding osteogenic differentiation are rarely seen, which has great significance in osteoporosis therapy and bone regeneration. Herein, for the first time, a new kind of Mg²⁺‐doped CDs is facilely synthesized through a one‐step hydrothermal method from metal gluconate salts. The CDs can serve as nanocarrier of Mg²⁺ ions entering into cells, and the bioessential metal ions subsequently stimulate osteoblastic differentiation by improving alkaline phosphatase (ALP) activity and upregulation related mRNA expression. Noteworthy, the raw material has almost negligible performance on osteoblastic differentiation compared to Mg‐CDs, which is due to the ultrasmall sizes of CDs and the efficient uptake by cells. Moreover, benefitting from the fluorescence properties, Mg‐CDs can also be applied as cell labeling agents. This work proposes a new strategy to synthesize multifunctional metal ion‐doped CDs, which might had great potential in serving as promising nanodrugs for bone loss therapy.     

Influence of sulfur doping on the molecular fluorophore and synergistic effect for citric acid carbon dots

In citric acid-based carbon dots, molecular fluorophore contributes greatly to the fluorescence emission. In this paper,the nitrogen and sulfur co-doped carbon dots(N,S-CDs) were prepared, and an independent sulfur source is selected to achieve the doping controllability. The influence of sulfur doping on the molecular fluorophore was systematically studied.The introduction of sulfur atoms may promote the formation of molecular fluorophore due to the increased nitrogen content in CDs. The addition surface states containing sulfur were produced, and S element exists as –SO_3, and –SO_4 groups.Appreciate ratio of nitrogen and sulfur sources can improve the fluorescence emission. The photoluminescence quantum yields(PLQY) is increased from 56.4% of the single N-doping CDs to 63.4% of double-doping CDs, which ascribes to the synergistic effect of molecular fluorophores and surface states. The sensitivity of fluorescence to p H response and various metal ions was also explored.     

Fluorescent Carbon Dots as Cost-Effective and Facile Probes for Caffeic Acid Sensing via a Fluorescence Quenching Process

Caffeic acid (CA), a familiar color stabilizing reagent, has aroused general concern due to its uncontrolled addition, and thus the detection of CA is increasingly important. In our report, the bright carbon dots (CDs) were prepared via hydrothermal treatment with urea and citric acid act as raw material and their characteristics were discussed through X-ray diffraction (XRD), transmission electron microscopy (TEM) and so on. Impressively, the strong emission of the as-prepared CDs (Quantum Yield: 24.3%) decreased sharply upon a full reaction with the added CA. Hence, we first present an improved strategy for determining CA based upon the quenching of the strong emission of CDs. In this strategy, 0.79–100.0 µmol L^??1 caffeic acid could be simply detected, and a detection limit of 0.24 µmol L^??1 was allowed. Additionally, CA in red wine samples can be successfully detected by this method and the exploration of the quenching mechanism of the CA-CDs system was done.     

Green Synthetic Approach for Synthesis of Fluorescent Carbon Dots for Lisinopril Drug Delivery System and their Confirmations in the Cells

In this work, highly luminescent carbon dots (CDs) were synthesized by the hydrothermal method at 170 °C for 12 h using pasteurized milk as a carbon source. The prepared CDs exhibited bright blue fluorescence under UV light illumination at 365 nm. The CDs show fluorescence life time of ~4.89 ns at excitation wavelength of 370 nm. The effect of different solvents on the fluorescence property of CDs was also investigated. The lisinopril (Lis)-loaded CDs were fabricated by self-assembly of lisinopril on the surfaces of CDs, which were characterized by UV-visible and FT-IR spectroscopic techniques. The controlled release of lisinopril from the Lis-CDs was realized at pH values of 5.2, 6.2 and 7.4, respectively. The results of the cytotoxicity and confocal laser scanning microscopic images indicate that the Lis-CDs were successfully uptaken by HeLa cells without apparent cytotoxicity. The synthesized CDs show great potential as drug vehicles with good biocompatibility, sustained release of lisinopril from CDs, indicating that the CDs can act as a promising drug delivery system for therapeutic delivery and/or bioimaging applications.     

A solvent-governed surface state strategy for rational synthesis of N and S co-doped carbon dots with multicolour fluorescence

ABSTRACT

Multicolour emissive carbon dots (CDs) are widely investigated by virtue of their merits on fluorescent properties. Method on heteroatom doping assisted with various solvents has been proved efficient in achieving multiple-colour-emissive CDs, especially long-wavelength emission. Herein, a synthesis of multicolour-emissive CDs by controlled surface function is reported. By tuning the thermal-pyrolysis temperature and molar ratio of reactants, optimal emission of the resulted CDs gradually shifts from blue to yellow light with the assistance of different solvents. According to the emissive relationship dependent on excitation, fluorescence lifetimes, and FT-IR of these CDs, the different surface states participated with S and N elements on the surface of carbogenic core govern fluorescent colours of the CDs. In terms of the applications, blue CDs (B-CDs) exhibits high sensitivity for ion detections of Ag⁺ and Fe³⁺, which is further illustrated to have different quenching mechanisms each other because that these ions have the affinity interaction with different surface groups of the CDs. Moreover, blue and yellow CDs solutions are mixed with PVP water solution to fabricate white-light CDs/PVP film, which exhibits stable fluorescence with a CIE coordinate of (0.32, 0.33) and endows these CDs as potentially fluorescent nanomaterial in the solid state lighting field.     

Introduction to the Performance and Mechanism of Various Photocatalytic Materials Compounded with Carbon Dots

With their unique optical and electronic properties, carbon dots (CDs) are showing great momentum in many fields such as biosensing, imaging, drug delivery, and photocatalysis. Due to their efficient light harvesting, extraordinary upconversion photoluminescence, and excellent photoinduced electron transfer capabilities, the combination of CDs with photocatalytic materials will promote light absorption resulting in increased generation of electron-hole pairs and faster photogenerated electron transfer, effectively suppressing the rate of electron-hole pair complexation and thus improving photocatalytic activity. In this paper, the mechanism of CDs photocatalysis and various photocatalytic materials such as TiO₂, Bi-based, CdS, and g-C₃N₄ complexed with CDs are reviewed. It is hoped that research into CDs in the field of photocatalysis will be advanced and that CDs will be used more widely in environmental and energy applications.     

碳点与曙红B间的荧光共振能量转移效应测定培氟沙星

通过构建碳点（CDs,供体）和曙红B（EB,受体）间的荧光共振能量转移（FRET）体系,建立了一种灵敏且具有选择性的检测培氟沙星（PEFL）含量的新方法。以紫叶草为碳源,采用热解法制备了荧光碳点（CDs）,其在水中分散性较好、稳定性较高、量子产率为3.7%。利用高分辨电子显微镜（HRTEM）、X射线电子衍射仪（XRD）和傅里叶变换红外光谱仪（FTIR）等手段对碳点进行了形貌和结构表征,结果表明,所制得的碳点为无定形态,其表面含有羟基（-OH）和羧基（-COOH）等活性基团。利用能量转移Frster理论,确定CDs和EB之间发生了荧光共振能量转移,从而在CDs和EB之间构建了荧光共振能量转移体系。并考察了影响荧光共振能量转移效应测定培氟沙星的重要因素,如反应介质和酸度、反应时间、供体和受体的浓度和盐效应等。结果表明,在pH 3.0的磷酸盐（PBS）缓冲溶液中,以340 nm为激发波长,碳点将能量转移给曙红B,使得曙红B的荧光信号增强。加入培氟沙星之后,由于培氟沙星与碳点之间相互作用,从而使得碳点的荧光显著增强。并且在优化的实验条件下,培氟沙星的浓度在0.0168~6.71 μg·mL-1范围内与体系的荧光强度改变值（ΔF）之间有较好的线性关系,检出限为0.072 5 ng·mL-1（3s/k,n=11）。一些常见的阳离子（如Fe3+,Al3+,Ca2+,Zn2+,Cr3+,Co2+,Cu2+,Mn2+等）、阴离子（如Cl-,NO-₃,I-,S2-,SCN-,SO2-₄,Br-,NO-₂,IO-₃,F-,ClO-₃,SO2-₃等）和药物（异烟肼,抗坏血酸和肝素钠）及三聚氰胺均不影响培氟沙星含量的测定。将该方法用于甲磺酸培氟沙星胶囊和片剂中PEFL含量的测定,回收率为100.4%~105.1%,相对标准偏差（RSD,n=5）均不大于2.5%,表明该方法可用于甲磺酸培氟沙星药物中培氟沙星的实际检测。该方法具有灵敏度高、选择性好等优点。