Environmentally friendly cleaner water-soluble fluorescent carbon dots coated with chitosan: synthesis and its application for sensitivity determination of Cr(VI) ions

In the current work, novel environmentally friendly water-soluble fluorescent carbon dots coated with chitosan (CDs/CTS) were successively synthesized via a facile and green preparation procedure. The fluorescent carbon dots were prepared through a simple, convenient and one-step hydrothermal method in the presence of cellulose as a raw material. The CDs/CTS were connected together via intermolecular hydrogen bonds interaction and chemical bonds between hydroxyl and amino groups in the chitosan polymeric chains and hydroxyl groups of fluorescent carbon dots. This approach can be applied for milligram-scale preparation of these water-soluble particles. The CDs/CTS material showed blue fluorescence under UV exposure. The structure and morphology of as-prepared CDs/CTS were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. The as-prepared CDs/CTS exhibited excellent fluorescent property and good stability. The fluorescence of as-prepared CDs/CTS could be quenched by the Cr(VI) ions. The effects of environmental factors on the fluorescence intensity were investigated in detail, and the obtained results showed that the optimum conditions for the Cr(VI) ions determination were as follows: 1:3 of mass ratio of CDs/CTS, 9.5 of pH and 20 min of reaction time. Under optimized experimental conditions, a novel fluorescent probe was developed for the detection of Cr(VI) ions, which exhibited wide linear ranges (0–600 μmol/L) and excellent selectivity. The proposed method was directly applied for the determination of Cr(VI) ions in water and soil samples with satisfactory results.     

基于碳点-铕的比率荧光探针可视化检测四环素

结合四环素对碳点(CDs)的荧光猝灭及对铕离子(Eu ³⁺)的荧光增强作用, 建立了一种肉眼可辨的比率荧光分析方法用于水样中四环素残留的便捷检测. 通过优化CDs/Eu ³⁺比例、 溶液pH值等实验条件, 使检测体系对四环素的荧光响应呈现由蓝色→粉色→红色的颜色转变过程, 易于通过肉眼进行分辨和半定量分析. 实验结果表明, 2种荧光探针响应比(I₆₁₈/I₄₄₀)的对数值与四环素的浓度在20~100 nmol/L范围内呈线性关系, 方法的检出限为1 nmol/L. 将该方法应用于江水样品中四环素的加标检测, 获得了较好结果.     

碳量子点荧光猝灭法检测药物中的异鼠李素

以L-天冬氨酸为碳源,尿素为氮源,采用微波加热法制备荧光碳量子点(CDs),得到的CDs具有球形结构和单一分散性,平均粒径约为5 nm。红外光谱、X射线光电子能谱、紫外和荧光光谱的表征结果表明,合成的CDs具有较高的荧光稳定性,良好的水溶性和对异鼠李素(ISOR)高的选择性。在优化条件下,ISOR浓度在0.22～180 nmol/L范围内时与CDs荧光猝灭程度(I_(F_0)/I_F)呈良好的线性关系,检出限(LOD)为1.32 nmol/L,回收率为90.8%～107%。结果表明,该CDs可用于ISOR的快速、高效、灵敏检测。     

基于聚乙烯亚胺碳纳米点的桑色素比率型荧光探针

利用水热合成法制备了一种基于聚乙烯亚胺的荧光碳纳米点, 用光谱方法研究了其对桑色素的识别作用. 结果表明, 该碳纳米点对桑色素具有比率型荧光响应, 且响应速度快、 选择性和灵敏度高、 抗干扰能力强. 将桑色素加入到碳纳米点溶液中后, 碳纳米点自身的荧光(460 nm)立即被猝灭, 同时在555 nm处出现新的荧光发射峰并逐渐增强; 其新发射峰(555 nm)与原发射峰(460 nm)的强度比值在此过程中呈线性增加. 基于此, 在1.0×10^-6~4.0×10^-5 mol/L浓度范围内, 可实现对桑色素的检测, 该比率荧光响应非常灵敏, 检出限可达3.0×10^-8 mol/L. 另外, 该碳纳米点与常见金属离子、 氨基酸及其它具有类似桑色素结构的黄酮醇均不反应, 显示出对桑色素的高选择性. 该检测方法的荧光强度随桑色素浓度的增加而逐渐增强, 并伴随着由蓝色到黄色的荧光颜色变化, 可实现对桑色素的可视化检测; 同时该碳纳米点还可用于稀释胎牛血清中桑色素的定量检测.     

Detection of Sn(II) ions via quenching of the fluorescence of carbon nanodots

We report that fluorescent carbon nanodots (C-dots) can act as an optical probe for quantifying Sn(II) ions in aqueous solution. C-dots are synthesized by carbonization and surface oxidation of preformed sago starch nanoparticles. Their fluorescence is significantly quenched by Sn(II) ions, and the effect can be used to determine Sn(II) ions. The highest fluorescence intensity is obtained at a concentration of 1.75 mM of C-dots in aqueous solution. The probe is highly selective and hardly interfered by other ions. The quenching mechanism appears to be predominantly of the static (rather than dynamic) type. Under optimum conditions, there is a linear relationship between fluorescence intensity and Sn(II) ions concentration up to 4 mM, and with a detection limit of 0.36 μM.

Fluorescent carbon dots for sensitive determination and intracellular imaging of zinc(II) ion

We describe the preparation of carbon dots (CDs) from glucose that possess high stability, a quantum yield of 0.32, and low toxicity (according to an MTT assay). They were used, in combination with the fluorogenic zinc(II) probe quercetin to establish a fluorescence resonance energy transfer (FRET) system for the determination of Zn(II). The CDs are acting as the donor, and the quercetin-Zn(II) complex as the acceptor. This is possible because of the strong overlap between the fluorescence spectrum of CDs and the absorption spectrum of the complex. The method enables Zn(II) to be determined in the 2 to 100 μM concentration range, with a 2 μM detection limit. The method was applied to image the distribution of Zn(II) ions in HeLa cells.

Based on the fluorescence resonance energy transfer (FRET) between carbon dots and quercetin (QCT)-Zn²⁺, the fluorescence indicator was established, which displays high sensitivity and selectivity in the detection of Zn²⁺. The method was also applied to image the distribution of Zn(II) ions in HeLa cells.

     

Hybrid supraparticles of carbon dots/porphyrin for multifunctional tongue-mimic sensors

Supraparticles（SPs）, such as assembly of inorganic components with organic, have made tremendous attention in biochemical analysis, which represents a novel but challenging research orientation. Herein, a single-SPs multifunctional fluorescent sensor array has been developed for high-throughput detection of heavy metal ions in biofluids, which is based on an inorganic/organic hybrid SPs consisting of carbon dots（CDs） and an easily available porphyrin [5,10,15,20-tetra（4-carboxyphenyl）porphyrin（T...     

由蚕砂制备的碳量子点在不同激发、pH、金属离子、温度及极性环境下的荧光性质研究

碳量子点作为一种新兴的荧光纳米材料,具有粒径分布均匀、光稳定性好、激发-发射波长可调控、表面可修饰等优良的性质,兼具低毒性、生物相容性好等优点,在分析检测和生物成像等领域展现出广阔的应用前景。而蚕砂是家蚕的干燥粪便,简单易得。利用蚕砂作为碳量子点制备原料,采用微波合成的方法制备得到了一种平均水合粒径为4.86 nm,含氮、硫修饰的碳量子点材料,可作为针对激发波长、pH、金属离子浓度、温度及溶剂极性的变化有着显著响应特性的碳量子点型荧光探针。该探针的荧光最大发射波长随激发波长或pH的增加而红移;荧光强度随温度或pH的降低而增加;随着金属离子,特别是铜离子的加入而逐渐降低,并随着EDTA络离子的加入而逐渐回复。在多种溶剂中该探针均具有较好的溶解度,当换用不同极性的溶剂时,随着溶剂极性的增加荧光发射波长逐渐红移。荧光性质随多重环境参数变化为该碳量子点在未来的生物检测和成像领域提供了广阔的应用前景。     

Synthesis of carbon dots with a tunable photoluminescence and their applications for the detection of acetone and hydrogen peroxide

Carbon dots(CDs) with multi-color emissive properties and a high photoluminescent quantum yield(PLQY) have attracted great attention recently due to their potential applications in chemical,environmental,biological and photo-electronic fields.Solvent-dependent effect in photoluminescence provides a facial and effective approach to tune the emission of CDs.In this study,green emissive nitrogen-doped carbon dots(N-CDs) are synthesized from p-hydroquinone and ethylenediamine through a simple hydrothermal method.The as-prepared N-CDs possess a robust excitation-independent green luminescence and a high PLQY of up to 15.9%.Further spectroscopic characterization indicates that the high PLQY is achieved by the balance of nitrogen doping states and the surface passivation extent in CDs.The N-CDs also exhibit solvent-dependent multi-color emissive property and distinct PLQY in different solvents(the maximum can reach up to 25.3%).Furthermore,the as-prepared N-CDs are applied as fluorescence probes to detect acetone and H2O2 in water.This method has exhibited a low detection limit of acetone(less than 0.1 %) and a quick and linear response to the H_2O_2 with the concentration from 0 to 120 μmol/L.This work broadens the knowledge of applying CDs as probes in the bio and chemical sensing fields.     

酪氨酸微波水热法制备碳点及其在Fe3+检测和荧光标记方面的应用

以酪氨酸为原料,乙二胺为钝化剂,采用绿色、简便的微波辅助水热法制备了尺寸均一、分散性好的碳点.通过调节乙二胺的加入量可以在一定程度上对碳点尺寸进行调节.所得碳点可以通过改变激发波长实现蓝光到绿光的转变,且荧光强度随激发光波长的红移也保持了一定的强度.所得碳点对Fe³⁺具有很好的选择性猝灭,被用于检测Fe³⁺时检测限为0.82 nmol/L,检出限为2.98 nmol/L.所制备碳点具有良好的生物相容性和低细胞毒性,被用于标记AD293细胞时标记位置为细胞质.     

Comparative study for N and S doped carbon dots: Synthesis,characterization and applications for Fe probe and cellular imaging

A facile and eco-friendly approach to prepare nitrogen(N)- and sulfur(S)-doped carbon dots (CDs) by one step microwave-assisted pyrolysis of the precursors with dl-malic acid as carbon source, ethanolamine and ethane-sulfonic acid as N and S dopants, respectively, was reported. Through the extensive investigation on morphology, chemical structures and optical properties of the carbon dots, it was found that the obtained CDs exhibited good luminescence stability, high resistance to photo bleaching and favorite solubility. Compared with undoped CDs, adding the N or S dopant could give rise to a slightly smaller particle size and a long fluorescence lifetime of CDs. Moreover, the optimal N-CDs was successfully employed as good multicolor cell imaging probes due to its fine dispersion in water, excitation-dependent emission, excellent biocompatibility and low toxicity. Besides, such N-CDs showed a wide detection range and excellent accuracy as fluorescent probe for Fe³⁺ ions. This probe enabled the selective detection of Fe³⁺ ions with a linear range of 6.0–200 μM and a limit of detection of 0.80 μM.     

基于碳点的荧光纳米开关灵敏检测Cu(Ⅱ)离子和焦磷酸盐

利用羟基与氨基在高温条件下反应,不断聚合生成碳点（CDs）,该碳点可发射不依赖激发波长的明亮的红色荧光.将CDs作为目标敏感荧光团时,发现Cu²⁺可特异性猝灭碳点的荧光,而焦磷酸盐（PPi）可在一定程度上恢复上述体系的荧光.其中,Cu²⁺对CDs的荧光猝灭是由于Cu²⁺与CDs发生络合反应,从而发生静态猝灭过程;而加入PPi之后,由于它与CDs的结合能力更强,因此Cu²⁺离开CDs的表面,体系的荧光得以恢复.在此基础上构建了一种高选择性、高灵敏度的off-on荧光纳米开关传感体系,分别用于Cu²⁺和PPi的定量检测,检出限分别达2.14 μmol/L和1.85 μmol/L.该传感体系可应用于实际样品检测,拓宽了荧光CDs的传感应用,为其在生物体内目标分子的检测提供了可能性.     

Photoactivated Fluorescence Enhancement in F,N-Doped Carbon Dots with Piezochromic Behavior

Photoactivation in CdSe/ZnS quantum dots (QDs) on UV/Vis light exposure improves photoluminescence (PL) and photostability. However, it was not observed in fluorescent carbon quantum dots (CDs). Now, photoactivated fluorescence enhancement in fluorine and nitrogen co-doped carbon dots (F,N-doped CDs) is presented. At 1.0 atm, the fluorescence intensity of F,N-doped CDs increases with UV light irradiation (5 s–30 min), accompanied with a blue-shift of the fluorescence emission from 586 nm to 550 nm. F,N-doped CDs exhibit photoactivated fluorescence enhancement when exposed to UV under high pressure (0.1 GPa). F,N-doped CDs show reversible piezochromic behavior while applying increasing pressure (1.0 atm to 9.98 GPa), showing a pressure-triggered aggregation-induced emission in the range 1.0 atm–0.65 GPa. The photoactivated CDs with piezochromic fluorescence enhancement broadens the versatility of CDs from ambient to high-pressure conditions and enhances their anti-photobleaching.     

Eco friendly synthesis of fluorescent carbon dots for the sensitive detection of ferric ions and cell imaging

This study established a ferric ion (Fe³⁺) detection method as a result of the fluorescence quenching effect of Fe³⁺ on carbon dots (CDs). Specifically, we proposed, a green microwave synthesis route towards fluorescent CDs that requires only the brewer’s spent grain as starting materials. Transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectra and X-ray photoelectron spectroscopy were performed to investigate the CDs characteristic: morphology, size distribution, functional groups, and composition, respectively. The experimental results, which were run under optimal experimental conditions, indicated that the fluorescence intensity and concentration of Fe³⁺ were within the desired linear range (0.3–7 μM). The detection limit of this assay towards Fe³⁺ was 95 nM. The proposed method showed significant selectivity with respect to interfering ions. We evaluated the potential application of this method with tap water, lake water and fetal bovine serum as real samples. Additionally, the CDs could be served as superior bioimaging probes in Hela cells as a result of their excellent optical stability and good biocompatibility. In a word, the present study provides a new idea for CDs derived from the waste of agricultural products for detecting food or environmental contaminants and cell imaging.     

Photoactivated Fluorescence Enhancement in F,N‐Doped Carbon Dots with Piezochromic Behavior

Photoactivation in CdSe/ZnS quantum dots (QDs) on UV/Vis light exposure improves photoluminescence (PL) and photostability. However, it was not observed in fluorescent carbon quantum dots (CDs). Now, photoactivated fluorescence enhancement in fluorine and nitrogen co‐doped carbon dots (F,N‐doped CDs) is presented. At 1.0 atm, the fluorescence intensity of F,N‐doped CDs increases with UV light irradiation (5 s–30 min), accompanied with a blue‐shift of the fluorescence emission from 586 nm to 550 nm. F,N‐doped CDs exhibit photoactivated fluorescence enhancement when exposed to UV under high pressure (0.1 GPa). F,N‐doped CDs show reversible piezochromic behavior while applying increasing pressure (1.0 atm to 9.98 GPa), showing a pressure‐triggered aggregation‐induced emission in the range 1.0 atm–0.65 GPa. The photoactivated CDs with piezochromic fluorescence enhancement broadens the versatility of CDs from ambient to high‐pressure conditions and enhances their anti‐photobleaching.     

Synthesis of strongly fluorescent carbon quantum dots modified with polyamidoamine and a triethoxysilane as quenchable fluorescent probes for mercury(II)

This article reports on the synthesis of water dispersible carbon quantum dots (CDs) by a one-step hydrothermal method using polyamidoamine (PAMAM) and (3-aminopropyl)triethoxysilane (APTES) as a platform and passivant. The resulting CDs are highly uniform and finely dispersed. The synergistic effect between PAMAM and APTES on the surface of the CDs results in a fluorescence that is much brighter than that of CDs modified with either APTES or PAMAM only. The fluorescence of the co-modified CDs is quenched by Hg(II) ions at fairly low concentrations. Under the optimum conditions, the intensity of quenched fluorescence drops with Hg(II) concentration in the range from 0.2 nM to 10 μM, and the detection limit is 87 fM. The effect of potentially interfering cations on the fluorescence revealed a high selectivity for Hg²⁺. The fluorescent probe was applied to the determination of Hg(II) in (spiked) waters and milk and gave recoveries between 95.6 and 107 %, with relative standard deviation between 4.4 and 6.0 %.

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Graphical abstract Strongly fluorescent carbon quantum dots (CDs) modified with polyamidoamine (PAMAM) and 3-aminopropyltriethoxysilane (APTES) were synthesized by one-step hydrothermal strategy. The resulting co-modified CD s were used as fluorescent probe for sensitive and selective detection of Hg²⁺.

     

基于碳量子点光活性模拟酶性能灵敏检测焦磷酸根离子

利用简单的水热法合成了具有良好水溶性、优良光活性模拟酶性质的碳量子点(CDs),该量子点在可见光照(λ≥400 nm)下可以催化氧化辣根过氧化物酶(HRP)的特征底物3,3,5,5-四甲基联苯(TMB),生成与HRP催化氧化相同的产物。铜离子可与CDs发生配位作用,使CDs聚集光诱导模拟酶的活性降低;焦磷酸根(ppi)存在时,铜离子与ppi配位生成Cu~(2+)-ppi复合物,从而使CDs分散模拟酶活性恢复。利用这一现象建立了一种比色检测ppi的方法,在最佳条件下,检测信号与ppi的浓度之间存在良好的线性关系,其线性范围为1.0×10~(-6)~5.0×10~(-3)mol/L,检出限为2.5×10~(-7)mol/L。将该方法应用于健康人血浆中ppi的检测,ppi的回收率为97.4%~104.8%,研究表明该比色传感器可用于人血浆中ppi的检测。     

Rapid and Large‐Scale Production of Multi‐Fluorescence Carbon Dots by a Magnetic Hyperthermia Method

The intrinsic low yield of carbon dots (CDs) is a barrier that limits practical application. Now, a magnetic hyperthermia (MHT) method is used to synthesize fluorescent CDs on a large scale (up to 85 g) in one hour (yield ca. 60 %). The reaction process is intensified by MHT since the efficient heating system enhances the energy transfer. CDs with blue, green, and yellow luminescence are synthesized by using carbamide and citrate with three different cations (Zn²⁺, Na⁺, K⁺), respectively. The CDs exhibit bright fluorescence under UV light and show excellent monodispersity and solubility in water. The alternation of photoluminescence (PL) emissions of these CDs is probably due to the difference in particle sizes and surface state. A bar coating technique is used to construct large‐area emissive polymer/CDs films. CDs can insert themselves into the polymer chains by hydrogen bonding and electrostatic interactions. Wound healing efficiency can be enhanced by the Zn‐CDs/PCL nanofibrous scaffold.     

Rapid and Large-Scale Production of Multi-Fluorescence Carbon Dots by a Magnetic Hyperthermia Method

The intrinsic low yield of carbon dots (CDs) is a barrier that limits practical application. Now, a magnetic hyperthermia (MHT) method is used to synthesize fluorescent CDs on a large scale (up to 85 g) in one hour (yield ca. 60 %). The reaction process is intensified by MHT since the efficient heating system enhances the energy transfer. CDs with blue, green, and yellow luminescence are synthesized by using carbamide and citrate with three different cations (Zn²⁺, Na⁺, K⁺), respectively. The CDs exhibit bright fluorescence under UV light and show excellent monodispersity and solubility in water. The alternation of photoluminescence (PL) emissions of these CDs is probably due to the difference in particle sizes and surface state. A bar coating technique is used to construct large-area emissive polymer/CDs films. CDs can insert themselves into the polymer chains by hydrogen bonding and electrostatic interactions. Wound healing efficiency can be enhanced by the Zn-CDs/PCL nanofibrous scaffold.     

Carbon dots as a fluorescent probe for label-free detection of physiological potassium level in human serum and red blood cells

A unique photoluminescence carbon dots (CDs) with larger size were prepared by microwave-assisted method. Complex functional groups on the surface of the CDs facilitate the nanoparticles to form affinity with some metal ions. Taking advantage of the effective fluorescence quenching effect of K⁺, a highly sensitive CD-based fluorescence analytical system for label-free detection of K⁺ with limit of detection (LOD) 1.0 × 10⁻¹² M was established. The concentrations of potassium ion in biological samples such as human serum are usually found at millimolar levels or even higher. The proposed method begins with a substantial dilution of the sample to place the K⁺ concentration in the dynamic range for quantification, which covers 3 orders of magnitude. This offers some advantages: the detection of K⁺ only needs very small quantities of biological samples, and the dilution of samples such as serum may effectively eliminate the potential interferences that often originate from the background matrix. The determined potassium levels were satisfactory and closely comparable with the results given by the hospital, indicating that this fluorescent probe is applicable to detection of physiological potassium level with high accuracy. Compared with other relative biosensors requiring modified design, bio-molecular modification or/and sophisticated instruments, this CD-based sensor is very simple, cost-effective and easy detection, suggesting great potential applications for successively monitoring physiological potassium level and the change in biological system.