油溶性CdSe量子点荧光探针直接检测农药水胺硫磷

基于农药水胺硫磷对油溶性CdSe量子点荧光猝灭的现象,建立了一种简单、快速、直接检测农药水胺硫磷的新方法。在最佳实验条件下,油溶性CdSe量子点的荧光猝灭程度与水胺硫磷浓度在2.30×10-7～1.09×10-5 mol·L-1范围内呈较好的线性关系,相关系数为0.999 9,对水胺硫磷的检出限为1.1×10-7 mol·L-1。本法已成功用于大米和小麦面粉样品中水胺硫磷农药残留的检测,加入回收率在93.3%～105.0%之间,结果满意。结合紫外-可见吸收光谱及时间分辨荧光光谱,探讨了水胺硫磷对油溶性CdSe量子点荧光猝灭的机理。研究结果表明,水胺硫磷能有效改变油溶性CdSe量子点的表面状态,增大了表面缺陷和非辐射重组的发生,从而使油溶性CdSe量子点的荧光猝灭。     

基于石墨烯量子点的荧光探针应用于抗坏血酸检测的研究

基于石墨烯量子点(GQDs)的荧光性能建立了一种非标记荧光方法,用于灵敏和选择性测定抗坏血酸(AA)。GQDs溶液在紫外光激发下发出很强的蓝色荧光,当向溶液中加入AA后,GQDs溶液的荧光被猝灭。猝灭机理可能为在弱酸性介质中,AA与GQDs发生氧化还原反应,AA转移电子给GQDs。荧光猝灭强度与AA浓度在5.0×10~(-6)~7.5×10~(-5)mol/L范围内呈良好的线性关系,检出限低至1.0×10~(-6)mol/L。该体系成本低、操作简单,并且在多种可能干扰的物质存在下对AA表现出很高的选择性。本方法应用于生物样品中AA的检测,回收率在95.2%~115.3%之间。     

Surface Molecular Imprinting on Silica-Coated CdTe Quantum Dots for Selective and Sensitive Fluorescence Detection of p-aminophenol in Water

In this paper, a selective and sensitive sensor for the determination of p-aminophenol (PAP) was developed by grafting molecularly imprinted polymers (MIPs) on the surface of silica-coated CdTe quantum dots (CdTe@SiO₂@MIPs). The obtained CdTe@SiO₂@MIPs were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and fluorescence spectroscopy. The fluorescence intensity of CdTe@SiO₂@MIPs was more strongly quenched by PAP than that of the structural analogues of PAP. Under the optimal conditions, the fluorescence intensity of the CdTe@SiO₂@MIPs decreased sensitively with the increase of PAP concentration in the range of 0.05–50 μM. The limit of detection was 0.02 μM (3σ/K _sv). The sensor was successfully used to determine PAP in tap and lake water samples, and the average recoveries of PAP at various spiking levels ranged from 97.33 % to 103.3 % with relative standard deviations below 20 %.     

Selective Determination of Atropine Using poly Dopamine-Coated Molecularly Imprinted Mn-Doped ZnS Quantum Dots

In this study, a selective method for the determination of atropine in pharmaceutical formulations was proposed. L-cysteine capped Mn-doped ZnS quantum dots (QDs) were prepared in an in-situ method using sodium thiosulfate precursor and characterized by spectrofluorometer, Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM) and X-ray diffractometer (XRD). Dopamine hydrochloride was used as a precursor for preparation of poly dopamine-coated molecularly imprinted Mn-doped ZnS quantum dots. Finally, these prepared molecularly imprinted Mn-doped ZnS quantum dots were used for determination of atropine in pharmaceutical formulations. The obtained linear range for determination of atropine was in the range of 2 × 10^?8 – 7 × 10^?6 M, with a correlation coefficient (R²) of 0.9889; and the detection limit (S/N = 3) was 3.2 nM.     

氧化锌量子点浅施主能级增强绿色光致发光光谱的实验证明

利用溶胶-凝胶法制备了粒径在5 nm左右的氧化锌量子点,通过测量氧化锌量子点光致发光光谱、吸收光谱以及荧光寿命得到氧化锌量子点绿光光谱可分为两种且对应不同发光机理。较高能量的绿光光谱是电子由导带底跃迁至氧空穴辐射产生的,而较低能量的则归因于电子由浅施主能级跃迁到氧空位,这种浅施主能级能够增强绿光发射且激发光能量稍小于带隙时绿光光谱相对强度达到最大。其次,实验得到氧化锌量子点的蓝光光谱是由于激发电子从锌间隙能级跃迁至价带产生。该研究提出并分析了氧化锌量子点绿光光谱的两种发光机制,可为其在光学方面的应用提供参考。     

The Fluorescence Bioassay Platforms on Quantum Dots Nanoparticles

In this paper, we present the optical properties and the platforms on fluorescent quantum dots for biological labeling, biomedical engineering and biosensor in molecular imaging. Quantum dots possess several properties that make them very attractive for fluorescent tagging: broad excitation spectrum, narrow emission spectrum, precise tunability of their emission peak, longer fluorescence lifetime than organic fluorophores and negligible photobleaching. We describe how to take such advantages of quantum dots to develop the technology and employ it to build assay platforms. Finally, ultrasensitivity, multicolor, and multiplexing of the technology of semiconductor quantum dots open up promising and interesting possibilities for bioassay platform.     

以花生碳量子点为探针基于其荧光猝灭-恢复测定多巴胺的研究

碳量子点(CQDs)是一种新型的荧光碳纳米功能材料,其良好的生物相容性和优异的光学性能引起了人们的广泛关注。选用富含蛋白质、脂肪和碳水化合物的花生仁(Peanut,PN)及水为原料,无需添加任何其他试剂,在水热反应釜中于190℃反应20 h,可一步合成绿色发光CQDs。透射电镜(TEM)结果显示,所制备的花生碳量子点(PN-CQDs)的粒径大约在10 nm左右,分布较为均匀;X射线衍射谱(XRD)和傅里叶变换红外光谱(FTIR)显示PN-CQDs晶型为无定型碳,表面富含-OH、-COOH、含氮官能团等亲水性基团,具有良好的水溶性。紫外-可见光谱(UV-Vis)和荧光发射光谱(FL)表明, PN-CQDs在275 nm处有一明显的吸收峰,为CQDs紫外特征吸收峰;该PN-CQDs具有激发波长依赖性,荧光发射峰的位置随激发波长的变化而移动;当激发波长λex为326 nm时,发射波长λem为408 nm处的荧光强度最大, PN-CQDs发出蓝色的荧光。以硫酸奎宁为参照物,利用参比法测得PN-CQDs的荧光量子产率φ为5.0%。基于该PN-CQDs良好的发光特性,以其为探针,构建了"关-开"型荧光体系用于多巴胺(Dopamine,DA)的高灵敏度检测。研究表明,在pH 3.80的HAc-NaAc缓冲介质中, Ce(Ⅳ)存在下, PN-CQDs与Ce(Ⅳ)之间的电子转移反应和Ce(Ⅳ)与该PN-CQDs表面基团结合使PN-CQDs发生的聚集作用共同导致PN-CQDs在λex/λem=326 nm/408 nm处的荧光发生猝灭,荧光信号"关闭";当加入DA后, DA与结合于PN-CQDs表面的强氧化性Ce(Ⅳ)发生反应,从而将Ce(Ⅳ)从PN-CQDs表面移除, PN-CQDs的荧光得以恢复,荧光信号重新"打开"。在优化的实验条件下, DA浓度与PN-CQDs在λex/λem=326/408 nm处的荧光恢复值ΔF呈良好线性关系,线性范围为2.5×10-7~1.0×10-5mol·L^-1,决定系数R2为0.997 6,检出限为9.0×10-8mol·L^-1。探讨了体系的荧光"猝灭-恢复"机理,对PN-CQDs和PN-CQDs-Ce(Ⅳ)体系进行了荧光寿命拟合,其加权平均荧光寿命分别为6.02与5.15 ns, Ce(Ⅳ)对PN-CQDs荧光猝灭类型为动态猝灭;反应中生成的Ce(Ⅲ)于λex/λem=251/350 nm处的荧光对DA的测定无影响。该方法灵敏、简便、快速,应用于实际样品中DA的测定,加标回收率(平均值±SD)在97.5%±1.3%~103%±1.5%之间,结果满意。该研究提供了一种新的DA荧光检测方法,实现了对DA的准确测定。     

Synthesis of AS1411-Aptamer-Conjugated CdTe Quantum Dots with High Fluorescence Strength for Probe Labeling Tumor Cells

In this paper, we report microwave-assisted, one-stage synthesis of high-quality functionalized water-soluble cadmium telluride (CdTe) quantum dots (QDs). By selecting sodium tellurite as the Te source, cadmium chloride as the Cd source, mercaptosuccinic acid (MSA) as the capping agent, and a borate-acetic acid buffer solution with a pH range of 5–8, CdTe nanocrystals with four colors (blue to orange) were conveniently prepared at 100 °C under microwave irradiation in less than one hour (reaction time: 10–60 min). The influence of parameters such as the pH, Cd:Te molar ratio, and reaction time on the emission range and quantum yield percentage (QY%) was investigated. The structures and compositions of the prepared CdTe QDs were characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, selective area electron diffraction, and X-ray powder diffraction experiments. The formation mechanism of the QDs is discussed in this paper. Furthermore, AS1141-aptamer-conjugated CdTe QDs in the U87MG glioblastoma cell line were assessed with a fluorescence microscope. The obtained results showed that the best conditions for obtaining a high QY of approximately 87 % are a pH of 6, a Cd:Te molar ratio of 5:1, and a 30-min reaction time at 100 °C under microwave irradiation. The results showed that AS1141-aptamer-conjugated CdTe QDs could enter tumor cells efficiently. It could be concluded that a facile high-fluorescence-strength QD conjugated with a DNA aptamer, AS1411, which can recognize the extracellular matrix protein nucleolin, can specifically target U87MG human glioblastoma cells. The qualified AS1411-aptamer-conjugated QDs prepared in this study showed excellent capabilities as nanoprobes for cancer targeting and molecular imaging.     

Studies on Interaction of CdTe Quantum Dots with Bovine Serum Albumin Using Fluorescence Correlation Spectroscopy

Luminescent quantum dots (QDs) have widely used in some biological and biomedical fields due to their unique and fascinating optical properties, meanwhile the interaction of QDs with biomolecules recently attract increasing attention. In this paper, we employed fluorescence correlation spectroscopy (FCS) to investigate the nonspecific interaction between CdTe QDs and bovine serum albumin (BSA) as a model, and evaluate their stoichiometric ratio and association constant. Our results documented that BSA was able to bind to CdTe QDs and form the QD–BSA complex by a 1:1 stoichiometric ratio. The association constant evaluated is 1.06 ± 0.14 × 10⁷ M⁻¹ in 0.01 M phosphate buffer (pH = 7.4). Furthermore, we found that QD–BSA complex dissociated with increase of ion strength, and we speculated that the interaction of CdTe QDs with BSA was mainly attributed to electrostatic attraction. Our preliminary results demonstrate that fluorescence correlation spectroscopy is an effective tool for investigation of the interaction between quantum dots (or nanoparticles) and biomolecules.     

CdTe量子点作荧光探针检测微量铅的方法研究

研究了用表面修饰的CdTe量子点作荧光探针检测水相中的微量铅离子。以巯基丙酸为稳定剂,在水相中合成了CdTe量子点。基于Pb2+对CdTe量子点有显著的荧光猝灭作用,用CdTe量子点作荧光探针,建立了水相中微量Pb2+的定量检测方法。研究结果表明:在优化的实验条件下,当Pb2+浓度在1.0×10-8～1.0×10-6 mol.L-1范围内时,量子点的荧光猝灭强度(ΔF)与Pb2+的浓度之间有良好的线性关系,线性相关系数为0.997 2,计算此方法的检出限为9.3×10-10 mol.L-1,相对标准偏差为5.9%,回收率为86%～110%。同时研究了常见金属离子的干扰作用,结果表明所建立的方法具有很好的选择性。     

CdTe量子点荧光猝灭法测定钴

以CdTe量子点作为荧光探针,基于荧光猝灭法对钴(Ⅱ)进行了定量检测,考察了缓冲溶液体系、量子点浓度、反应时间等多种因素的影响。实验结果表明,在pH8.0的0.2mol/LNa2HPO4-NaH2PO4缓冲液中,反应时间为10min,钴(Ⅱ)浓度为1.6×10-5—20×10-5mol/L范围时,其线性回归方程为F0/F=1.45+0.096Q(10-5mol/L),检出限为3×10-7mol/L。该方法检测范围宽,灵敏度高,为钴的测定提供了新的方法。     

Investigation of Novel Quantum Dots/Proteins/Cellulose Bioconjugate Using NSOM and Fluorescence

We investigated the engineered bioconjugate of cadmium selenide core/zinc sulfide shell, (CdSe)ZnS, quantum dots (QDs) with genetically modified proteins using fluorescence spectroscopy, near-field scanning optical microscopy (NSOM) and spectroscopy (NSOS). The protein polymer was allowed to self-assemble to the bacterial microcrystalline cellulose surface through the cellulosic binding domain. Results from the sample containing the QDs/protein/cellulose assemblies suggest that QDs were arrayed along the cellulose surface. The spectroscopic change of spectroscopic properties of the QDs upon bioconjugation, indicating the interaction among the immobilized QDs and between the constructed protein and QDs.     

Low-Cost UV-IR Dual Band Detector Using Nonporous ZnO Film Sensitized by PbS Quantum Dots

A low-cost photoconductive dual-band detector was prepared using a nanoporous ZnO film sensitized by PbS quantum dots （QDs）. At room temperature the device shows a UV response in the wavelength range of 200-400 nm with a 370 nm peak responsivity of 4.0×105 V/W and a vis-NIR response from 500 to 1400 nm with a 700 nm peak responsivity of 5.4×105 V/W. By increasing the size of the PbS QD, the response can be extended up to 2.9 μm. It is suggested that the UV response is a result of interband absorption of UV radiation by ZnO and the IR response comes from the absorption of PbS QDs.     

Fluorescent Recognition of Potassium and Calcium Ions Using Functionalised CdSe / ZnS Quantum Dots

Schiff base receptor 1a has been synthesised and attached to the surface of preformed CdSe/ZnS Quantum Dots (QDs) to form QD-conjugate 2a. While 1a was determined to be selective for Mg²⁺, 2a demonstrated selectivity for both K⁺ and Ca²⁺ when tested against a range of physiologically and environmentally relevant cations by changes in the fluorescence spectra. Thus, the nanoparticle surface functions as a scaffold for the organisation of receptors enabling semi-selective binding. The fluorescence response was shown to be linear between 15–50?μM for K⁺ and 2–35?μM for Ca²⁺. It was also demonstrated that 2a could measure both K⁺ and / or Ca²⁺ in solutions containing both ions.     

Fluorescence Lymph Node Mapping in Living Mice Using Quantum Dots and a Compression Technique

The lymphatic system is essential in oncology and immunology, and in vivo fluorescence imaging plays a major role in assessing the lymphatic drainage. We investigated non–invasive fluorescence lymph node mapping in mice with special reference to the assessment of deep abdominal lymph nodes. Quantum dots were injected subcutaneously into the rear footpads of mice, and the time course of the fluorescent signal was assessed. Visualization of abdominal lymph nodes was compared with and without compression of the abdomen with transparent, colorless tape at injection doses of 1, 5, and 20 pmol. Popliteal, sacral, iliac, and renal lymph nodes were delineated by non–invasive imaging. Lymph node signals increased up to 3 h after injection. Compression of the abdomen markedly improved the visualization of the iliac nodes, which were invisible at 5 pmol without compression and visible at 1 pmol with compression. Fluorescence lymph node mapping using quantum dots allowed the visualization of deep abdominal lymph nodes in addition to superficial nodes in intact mice, with the aid of a simple compression technique.     

1-氨基萘印迹聚合物分子识别特性的光谱学研究

采用分子自组装印迹技术合成了一种对1-氨基萘有高度选择性的分子印迹聚合物新材料。应用紫外光谱、红外光谱、X射线光电子能谱和1H核磁共振波谱等研究了印迹聚合物的结合位点和识别机理。结果表明模板分子与功能单体通过氢键作用形成1:1型配合物,配合物的稳定常数K=5.537×104L/mol。1-氨基萘分子氨基上的氮原子是质子接受体,功能单体甲基丙烯酸分子羧基上的氢原子是氢键的质子给予体,是与1-氨基萘形成氢键作用的选择性识别位点。利用平衡吸附试验研究了印迹聚合物的结合特性,表明印迹聚合物对1-氨基萘分子具有特异的识别性能。     

基于碳量子点荧光恢复的三聚氰胺测定方法

在碳量子点溶液中加入汞离子,量子点的荧光被猝灭,加入三聚氰胺后荧光恢复。据此,建立了基于碳量子点荧光恢复测定三聚氰胺的新方法并应用于实际样品的分析。研究结果表明,在汞离子和碳量子点浓度之比为15∶10000且碳量子点浓度为4.0 g/L、pH值为7.5的实验条件下,方法的线性范围为3.0~60.0mg/L,检出限(3σ/k)为2.2 mg/L。方法应用于实际样品测定时,其回收率为95%~103%。     

Time-Resolved Fluorescence Spectroscopy Study on the Photophysical Behavior of Quantum Dots

Room-temperature time-resolved luminescence measurements on single CdSe/ZnS quantum dots (QDs) are presented. Fluorescence emission spectra were recorded over periods of up to 30 minutes with a time resolution as small as 6 ms. For QDs in ambient air, a clear 30–40 nm blue shift in the emission wavelength is observed, before the luminescence stops after about 2–3 minutes because of photobleaching. In a nitrogen atmosphere, the blue shift is absent while photobleaching occurs after much longer times (i.e., 10–15 minutes). These observations are explained by photoinduced oxidation. The CdSe surface is oxidized during illumination in the presence of oxygen. This effectively results in shrinkage of the CdSe core diameter by almost 1 nm and consequently in a blue shift. The faster fading of the luminescence in air suggests that photoinduced oxidation results in the formation of non-radiative recombination centers at the CdSe/CdSeO_x interface. In a nitrogen atmosphere, photoinduced oxidation is prevented by the absence of oxygen. Additionally, a higher initial light output for CdSe/ZnS QDs in air is observed. This can be explained by a fast reduction of the lifetime of the long-lived defect states of CdSe QDs by oxygen.     

微波水热法制备Gd3+掺杂的碳量子点型高性能磁共振-荧光双模态分子影像探针

以同时提供钆源和碳源的钆喷酸单葡甲胺为前驱体,利用微波作为加热手段实现分子水平上的搅拌,达到低温、短时间内制得均匀的小粒度Gd³⁺掺杂碳量子点(Gd³⁺/CQDs-MH)的目的。当前驱体在250 ℃下微波水热反应45 min时,获得的Gd³⁺/CQDs-MH表现出较高的量子产率和极强的磁共振性能,避免了传统加热方式对碳量子点的发光能力和弛豫性能极难同时提高的矛盾。该条件下合成出尺寸约1.0 nm的碳量子点,其荧光量子产率为11.0%,Gd³⁺的掺杂质量分数达16.9%,纵向弛豫性能高达4 545.3 mmol^-1·L·s^-1 ([Gd³⁺]=0.01 mmol·L^-1)。并且,该碳量子点对HeLa细胞无明显毒性,有望用作高弛豫性能和高发光性能的磁共振-荧光双模态探针。