Functionalized cadmium sulfide quantum dots as fluorescence probe for silver ion determination

CdS quantum dots (QDs) modified with l-cysteine has been prepared by one step. They are water-soluble and biocompatible. To improve CdS QDs stability and interaction between silver ion and functionalized CdS QDs in aqueous solution, some amounts of fresh l-cysteine were added to functionalized CdS solution. Based on the characteristic fluorescence enhancement of CdS QDs at 545 nm by silver ions in the presence of some amounts of fresh l-cysteine, simultaneously, a gradual red shift of fluorescence emission bands of CdS QDs from 545 to 558 nm was observed. A simple, rapid, sensitive and specific detection method for silver ion was proposed. Under optimum conditions, the fluorescence intensity of CdS QDs is linearly proportional to silver concentration from 2.0 × 10⁻⁸ to 1.0 × 10⁻⁶ mol/L with a detection limit of 5.0 × 10⁻⁹ mol/L. In comparison with single organic fluorophores, functionalized CdS quantum dots are brighter, more stable against photobleaching, and don’t suffer from blinking. Furthermore, owing to the fluorescence enhancement effect of CdS QDs by silver ion, the proposed method showed lower detection blank and higher sensitivity. Possible fluorescence enhancement mechanism was also studied.     

Amiloride-modulated phosphorescence turn-off/on method for the detection of abasic site-containing dsRNA based on uridine triphosphate-capped Mn-doped ZnS quantum dots

RNA plays a crucial role in biochemical processes. RNAs with abasic sites (AP-RNA), as one of RNA lesions, will cause serious negative consequences. Efficient and sensitive detection of AP-RNA deserves but does not receive enough attention. Water-soluble uridine triphosphate (UTP)-capped Mn-doped ZnS quantum dots (QDs), which have excellent room-temperature phosphorescence (RTP) properties, were prepared by wet-chemical method. The UTP on the surface of QDs could form a precipitation complex with amiloride (AMI) to quench the RTP. Meanwhile, abasic double-stranded RNA (AP-dsRNA) with a high affinity to AMI could dissociate AMI from the surface of UTP-QDs, resulting in RTP recovery. In this process, a highly sensitive and selective RTP-detection system for AP-dsRNA was constructed with AMI as the modulation factor and UTP-QDs as the luminescence matrix. RTP was turned off and on for the determination of AP-dsRNA, and the interference of background fluorescence and scattered light was effectively avoided during complex formation and aggregation. Steric hindrance of the conformation of AP-dsRNA provided efficient selectivity. The detection limit for AP-dsRNA was 0.86 nM, the relative standard deviation was 2.1%, and the recovery of biological samples with AP-dsRNA addition ranged from 95% to 103% at optimal conditions. The system is expected to provide new methods for environmental monitoring, early disease screening, and evaluation of gene editing efficiency.     

Mn-doped ZnS quantum dots for the determination of acetone by phosphorescence attenuation

Quantum dot (QD) nanoparticles (NPs) are increasingly used as highly valuable fluorescent biomarkers and as sensitive (bio)chemical probes. Interestingly, if certain metal impurities are incorporated during the NPs synthesis, phosphorescent QDs with analytical potential can be obtained.     

CdTe量子点荧光探针测定氯霉素含量的研究

在水溶液体系中制备出了具有高质量荧光性能,巯基乙酸(TGA)修饰的CdTe量子点(QDs),基于量子点与氯霉素混合后发生荧光猝灭作用,建立CdTe量子点作为荧光探针测定氯霉素的新方法。在Tris-HCl缓冲液(pH 7.00,0.10 mol·L-1)中,反应时间为10min时,氯霉素浓度在10～70μg·mL-1范围内与CdTe量子点的荧光猝灭程度呈良好的线性关系,相关系数为0.9981,检出限为0.799μg.mL-1。方法简便快速,灵敏度高,可用于实际样品中氯霉素的检测。     

Mn,B, N co-doped graphene quantum dots for fluorescence sensing and biological imaging

The fluorescent and quantum yield (QY) of graphene quantum dots has been improved in recent years by doped atoms, which have good application prospects in fluorescence sensors and biological imaging. Here, a one-step hydrothermal synthesis method was used to synthesize manganese ions bonded with boron and nitrogen-doped graphene quantum dots (Mn-BN-GQDs). Compared with the boron and nitrogen co-doping graphene quantum dots (BN-GQDs), the fluorescence properties and quantum yield of Mn-BN-GQDs are significantly improved. Meanwhile, Mn-BN-GQDs exhibit low toxicity and good fluorescence imaging in living cells and has high selectivity to Fe³⁺ ions. Therefore, this experiment design Mn-BN-GQDs as a fluorescence sensor to detect Fe³⁺ ions, providing strong evidence for the advanced high sensitivity, selectivity and wide detection range of the Mn-BN-GQDs as a fluorescence sensor. These results indicate a dual linear relationship with good linear relationships in the 10–100 μM and 100–800 μM ranges, and limit of detection are 0.78 μM and 9.08 μM, respectively. Cellular imaging results demonstrate that Mn-BN-GQDs can be used as fluorescence sensors in biological imaging. Mn-BN-GQDs can be used for fluorescence sensing in biological imaging in combination with low toxicity, QY and quantum dot lifetime.     

Optical applications of quantum dots in biological system

This review presents a simple introduction on the unique properties and general synthesis of quantum dots (QDs) in which we lay emphasis on the optical applications in the biological system. The detection of biological molecules such as DNA, protein and enzyme, the cell-based analysis and in vivo animal imaging are mainly discussed.     

Mn-doped ZnS quantum dots/methyl violet nanohybrids for room temperature phosphorescence sensing of DNA

Mn-doped ZnS quantum dots/methyl violet nanohybrids were explored to develop a novel room temperature phosphorescence (RTP) sensor for the detection of DNA. Methyl violet (MV) as the electron acceptors was adsorbed on the surface of the quantum dots (QDs) to quench the RTP of the Mn-doped ZnS QDs through an electron-transfer process under excitation. The addition of DNA recovered the RTP signal of the Mn-doped ZnS QDs due to the binding of MV with DNA and the removal of MV from the surface of the Mn-doped Z...     

A novel fluorescent assay for edaravone with aqueous functional CdSe quantum dots

Aqueous thiol-capped CdSe QDs with a narrow, symmetric emission were prepared under a low temperature. Based on the fluorescence enhancement of thiol-stabilized CdSe quantum dots (QDs) caused by edaravone, a simple, rapid and specific quantitative method was proposed to the edaravone determination. The concentration dependence of fluorescence intensity followed the binding of edaravone to surface of the thiol-capped CdSe QDs was effectively described by a modified Langmuir-type binding isotherm. Factors affecting the fluorescence detection for edaravone with thiol-stabilized CdSe QDs were studied, such as the effect of pH, reaction time, the concentration of CdSe QDs and so on. Under the optimal conditions, the calibration plot of C/(I − I₀) with concentration of edaravone was linear in the range of (1.45–17.42) μg/mL (0.008–0.1 μmol/L) with correlation coefficient of 0.998. The limit of detection (LOD) (3σ/κ) was 0.15 μg/mL (0.0009 μmol/mL). Possible interaction mechanism was discussed.     

CdTe quantum dots as a highly selective probe for prion protein detection: colorimetric qualitative, semi-quantitative and quantitative detection

CdTe quantum dots (QDs) were used as a highly selective probe for the detection of prion protein. Orange-emitting precipitates appeared within 30 s of the addition of recombination prion protein (rPrP) to a solution of green-emitting CdTe QDs. This allowed colorimetric qualitative and semi-quantitative detection of rPrP. The decrease in fluorescence intensity of the supernatant could be used for quantitative detection of rPrP. The fluorescence intensity of the supernatant was inversely proportional to the rPrP concentration from 8 to 200 nmol L⁻¹ (R² = 0.9897). Transmission electron microscopy results showed that fibrils existed in the precipitates and these were partly transformed to amyloid plaques after the addition of rPrP.     

Highly luminescent water-dispersed silicon quantum dots for fluorometric determination of oxytetracycline in milk samples

A fluorescent probe based on silicon quantum dots (SiQDs) was developed for the selective and sensitive detection of oxytetracycline (OTC) via the inner filter effect (IFE). The water-soluble fluorescent SiQD was synthesized based on the reaction of 3-Aminopropyltriethoxysilane (APTES) and sodium citrate as precursors by the one-pot hydrothermal process. The strong fluorescence emission of quantum dots (QDs) was obtained at 440 nm when excited at 350 nm and OTC had a broad absorption band between 200 and 400 nm. The excitation spectrum of SiQDs was completely overlapped with the absorption spectrum of OTC. The light at an excitation wavelength of QDs absorbed by OTC caused a decrease in fluorescence intensity with an increase in the concentration of OTC. Under optimal conditions, the linear concentration range was 0.92–9.2 µg mL1 with a detection limit (LOD; S/N = 3) of 0.19 µg mL ^-1 . The proposed method was applied to the determination of OTC in milk samples and satisfactory recoveries (98.8–100.5%) with low RSD % values (0.93–2.31%) were achieved. This simple, selective, sensitive, rapid, and cheap method can be used as a promising tool for OTC analysis in food safety.     

基于头孢他啶测定的CQDs内标型比率荧光探针的构建

以天然生物质蒲公英为碳源,加入乙二胺,通过一步水热法合成氨基化蒲公英碳量子点(DE-CQDs).该DE-CQDs可与罗丹明6G(Rh6G)通过静电吸附作用形成具有特征双发射信号的DE-CQDs/Rh6G复合物.单一激发波长343 nm下,BR缓冲溶液pH 3.0时,复合物DE-CQDs/Rh6G于425 nm和550 ...     

L-Cysteine-coated CdSe/CdS core-shell quantum dots as selective fluorescence probe for copper(II) determination

Quantum dots (QDs) or semiconductor nanocrystals have been receiving great interest in the last few years. In this paper, L-cysteine-coated CdSe/CdS core-shell QDs (λ_em = 585 nm) have been prepared, which have excellent water-solubility. The full width at half maximum (FWHM) of the photoluminescence of these nanocrystals is very narrow (about 30 nm), and the quantum yield (QY) is 15% relative to Rhodamine 6G in ethanol (QY = 95%). With excess free L-cysteine in the solution, the fluorescence intensity of L-cysteine-coated CdSe/CdS QDs showed improved stability. It was found that the fluorescence of L-cysteine-capped CdSe/CdS QDs could be quenched only by copper (II) ions and was insensitive to other physiologically important cations, such as Ca²⁺, Mg²⁺, Zn²⁺, Al³⁺, Fe³⁺, Mn²⁺ and Ni²⁺ etc. Based on this finding, the quantitative analysis of Cu²⁺ with L-cysteine-capped CdSe/CdS QDs has been established. The linear range was from 1.0 × 10^− 8 to 2.0 × 10^− 7 mol L^− 1 and the limit of detection (LOD) was 3.0 × 10^− 9 mol L^− 1 (S/N = 3). The proposed method has first been applied to the determination of Cu²⁺ in vegetable samples with recoveries of 99.6–105.8%.     

氮掺杂鸡毛碳点荧光关开探针用于测定百草枯

以鸡毛和乙二胺为碳源和氮源,通过一步水热法合成强荧光性能的氮掺杂碳量子点(N-CQDs),并优化其制备和掺杂条件.该碳量子点具有良好的光学、结构性质和稳定性,平均粒径7.89 nm,荧光量子产率为14％.最大激发波长为320 nm,最大发射波长为386 nm.Hg2+存在条件下N-CQDs溶液的荧光被碎灭(关),添加百...     

Determination of abscisic acid based on the fluorescent quenching of quantum dots

The quenching mechanism of the fluorescence of quantum dots by abscisic acid has been systematically investigated.The quenching constant KSV = 5.1 × 1011 / M was obtained under the optimized condition.On the basis of that,a very sensitive method for the determination of abscisic acid has been developed.The linear equation was F0/F = 0.9309 + 0.5072 C(pmol/L) and its linear range was 0.2-3.0 pmol/L with a correlation coefficient of 0.9939.The limit of detection was 0.09 pmol/L.     

Visible light induced photoelectrochemical biosensing based on oxygen-sensitive quantum dots

A visible light induced photoelectrochemical biosensing platform based on oxygen-sensitive near-infrared quantum dots (NIR QDs) was developed for detection of glucose. The NIR QDs were synthesized in an aqueous solution, and characterized with scanning electron microscopy and X-ray photoelectron spectroscopy. The as-prepared NIR QDs were employed to construct oxygen-sensitive photoelectrochemical biosensor on a fluorine-doped tin oxide (FTO) electrode. The oxygen dependency of the photocurrent was investigated at as-prepared electrode, which demonstrated the signal of photocurrent is suppressed with the decreasing of oxygen. Coupling with the consumption of oxygen during enzymatic reaction, a photoelectrochemical strategy was proposed for the detection of substrate. Using glucose oxidase (GOx) as a model enzyme, that is, GOx was covalently attached to the surface of CdTe QDs, the resulting biosensor showed the sensitive response to glucose. Under the irradiation of visible light of a wavelength at 505 nm, the proposed photoelectrochemical method could detect glucose ranging from 0.1 mM to 11 mM with a detection limit of 0.04 mM. The photoelectrochemical biosensor showed a good performance with high upper detection limit, acceptable stability and accuracy, providing an alternative method for monitoring biomolecules and extending the application of near-infrared QDs.     

A novel method for iodate determination using cadmium sulfide quantum dots as fluorescence probes

We have developed a novel method for the determination of iodate based on the carboxymethyl cellulose-capped CdS quantum dots (QDs). Factors affecting the iodate detection were investigated, and the optimum conditions were determined. Under the optimum conditions, the relative fluorescence intensity of CdS quantum dots was linearly proportional to IO₃⁻ over a concentration range from 1.0 × 10⁻⁸ to 1.0 × 10⁻⁵ mol L⁻¹ with a correlation coefficient of 0.9987 and a detection limit of 6.0 nmol L⁻¹. Iodide, being oxidized by bromine to form iodate, was detected indirectly. The method was successfully applied to the determination of iodate and total amount of iodine in table salt samples. The related mechanism was also discussed.     

水溶性CdSe量子点的合成及其作为荧光探针对大肠杆菌的快速检测

采用水相法以谷胱甘肽为稳定剂合成高稳定性的CdSe量子点,利用化学偶联剂的作用使得量子点表面基团与菌体之间的成功结合,对偶联的条件进行了优化.基于荧光分析法建立了一种快速简便的大肠杆菌检测定量分析方法.研究结果表明:合成的量子点具有稳定、荧光性能良好等突出优点.通过偶联剂量子点能与大肠杆菌结合,其荧光强度与大肠杆菌浓度...     

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.     

硫鸟嘌呤修饰的Mn:ZnS QDs磷光探针检测铂(Ⅲ)

通过水相合成法制备了硫鸟嘌呤(TG)修饰的锰掺杂硫化锌量子点(TG-Mn:ZnS QDs)。加入Pt⁴⁺后,Pt⁴⁺会与硫鸟嘌呤上的氮原子结合形成N-Pt⁴⁺配位结构附着在TG-Mn:ZnS QDs的表面,随着Pt⁴⁺浓度的增加,TG-Mn:ZnS QDs-Pt⁴⁺体系发生电子转移而导致磷光逐渐被猝灭,基于此构建了检测Pt⁴⁺的磷光探针。实验中考察了p H、时间对Pt⁴⁺猝灭TG-Mn:ZnS QDs磷光强度的影响。在最佳实验条件下,Pt⁴⁺浓度在0.06～2.4μg/mL范围内与TG-Mn:ZnS QDs的磷光强度呈良好的线性关系y=0.0884x+0.2319,R²=0.991,方法检出限(3σ/n)为1.3μg/mL。该磷光探针适用于实际样品中Pt⁴⁺含量的测定。     

Preparation and recognition performance of ratio-fluorescent probe based on sulfadiazine imprinted polymersEI北大核心CSCD

A novel ratio-fluorescent probe based on molecular imprinting polymer ( MIP) for the detection of sulfadiazine was prepared by using nitrogen-doped carbon quantum dots (N-CQDs) as the fluorescence response signal, silica-embedded cadmium telluride quantum dots ( CdTe QDs) as the fluorescence reference signal, sulfadiazine ( SDZ) as template molecule, acrylamide as functional monomer, N, N-methyl bisacrylamide as crosslinking agent and 2,2-Azobisisobutyronitrile as initiator. The results showed that the probe has a core-shell structure and fluorescence sensitive to SDZ, by the characterization of scanning electron microscopy, transmission electron microscopy, and fluorescence spectrophotometer. Under the wavelength of 360 nm, the ratio-fluorescent signal of probe showed a linear response with SDZ concentration in the range of 0-100 μmol / L with the detection limit of 11 nmol / L. Also, the ratio-fluorescent probe was applied to the detection of SDZ with a recovery of 92. 0%-95. 1% and relative standard deviation (RSD) of 3. 6% in real water samples. © 2022, Youke Publishing Co.,Ltd. All rights reserved.