CdTe nanocrystals sensitized chemiluminescence and the analytical application

It was found that the mixing of CdTe semiconductor nanocrystals (NCs) with luminol in the presence of KMnO₄ can induce a great sensitized effect on chemiluminescence (CL) emission. When the concentration of luminol, KMnO₄ and NaOH were fixed at 1 μM, 1 μM and 0.05 M, respectively, the most excellent performance can be obtained for the CdTe NCs sensitized CL. By means of CL and photoluminescence spectra, we suppose the enhanced CL signals resulted from the accelerated luminol CL induced by the oxidized species of CdTe NCs. Based on the finding, using thioglycolic acid-capped CdTe NCs as label and immunoglobulin G (IgG) as a model analyte, a CL immunoassay protocol for IgG content detection was developed. The strong inhibition effect of phenol compounds on luminol-KMnO₄-CdTe NCs CL system was also observed. All these findings demonstrated the possibility of semiconductor nanocrystals induced chemiluminescence to be utilized for more practical applications.     

CdTe nanocrystals-enhanced chemiluminescence from peroxynitrous acid-carbonate and its application to the direct determination of nitrite

It was found that CdTe semiconductor nanocrystals (NCs) can induce a great sensitized effect on chemiluminescence (CL) emission from peroxynitrous acid (ONOOH)-Na(2)CO(3) system. CL spectra, fluorescence (FL) spectra, and the quenching effect of reactive oxygen species were used to investigate the CL reaction mechanism. The CL intensity was proportional to the concentration of nitrite in the range from 0.05 to 50μM. The detection limit (S/N=3) was 0.024μM and the relative standard deviation (RSD) for five repeated measurements of 0.5μM nitrite was 4.2%. This method has been successfully applied to determine nitrite in well water samples with recoveries of 94.0-100.5%. This was the first work for direct (not inhibition effect) determination of analytes using semiconductor NCs-based CL sensor.     

CdTe纳米棒-过氧化氢化学发光体系的研究

在水相中合成了以巯基乙酸和L-半胱氨酸为稳定剂的CdTe纳米棒。研究发现在碱性溶液中H2O2能直接氧化CdTe纳米棒产生强烈的化学发光,化学发光的强度与CdTe纳米棒尺寸大小相关,且一些表面活性剂能强烈敏化该反应。     

Luminescence 3D-ordered porous materials composed of CdSe and CdTe nanocrystals

The luminescence porous materials of CdTe or CdSe nanocrystals (NCs) were prepared by filling the corresponding NCs into the voids of colloidal crystal by co-deposition of polymer beads and NCs. After removing the beads with tetrahydrofuran (THF), the 3D-ordered porous materials of CdTe (or CdSe) NCs were obtained. The wavelength of maximum photoluminescence of the NCs porous material shows obvious red shift compared with their aqueous dispersion. Under the excitation of high-energy electron the porous materials of CdTe and CdSe NCs will emit photons that can be collected to form a cathode luminescence (CL) image.     

Electrostatic and covalent interactions in CdTe nanocrystalline assemblies

This paper focuses on the interactions between cysteamine-stabilized CdTe nanocrystals [CdTe(CA) NCs] and thioglycolic-acid-stabilized CdTe nanocrystals [CdTe(TGA) NCs]. These interactions were examined by the absorption, continuous, and time-resolved photoluminescence (PL) spectra of the electrostatically mixed and the covalently linked NCs assemblies comprised of the oppositely surface charged CdTe(CA) and CdTe(TGA) NCs and by a comparison with those of the corresponding pristine NCs. The CdTe(CA)-CdTe(TGA) coupling is dictated by the surfactant spacer, ranging between 0.93 and 1.14 nm and by electrostatic and covalent interactions, enabling a F?rster resonance energy transfer (FRET) process among the NCs. The results revealed an excellent spectral overlap between the emission of the CdTe(TGA) NCs and the absorption of the CdTe(CA) NCs as well as a PL spectral red shift on the formation of electrostatic and covalent interactions. Furthermore, the measurements showed a lifetime ranging between 1.2 and 3 ns for the electrostatically mixed and the covalently linked assemblies, shorter than those of the pristine CdTe(CA) NCs and CdTe(TGA) NCs, both of which measured as approximately 5.5 ns. When CdTe(TGA) NCs performed as the most efficient donors, FRET rates of 10(10)-10(11) s(-1) were calculated for the electrostatically mixed NCs or covalently linked NCs.     

Sensitized chemiluminescence of CdTe quantum-dots on Ce(IV)-sulfite and its analytical applications

Water-soluble CdTe quantum-dots (QDs) of different sizes capped with thioglycolic acid (TGA) were synthesized via a microwave-assisted method. It was found that CdTe QDs, as a kind of sensitizer, could enhance the chemiluminescence (CL) emission from the redox reaction of SO3(2-) with Ce(IV) in acidic medium. In combination with the flow injection technique, the effects of reactant concentrations, the sizes of CdTe QDs, some organic compounds, and several electron transfer proteins on the CL emission were investigated in detail. The sensitized CL displayed the size-dependent effect and increased along with increasing the QDs sizes. Organic compounds containing OH, NH2, or SH groups, and some electron transfer proteins such as cytochrome c, hemoglobin and myoglobin, which readily interact with CdTe QDs, were observed to inhibit the CL signal of the Ce(IV)-SO3(2-)-CdTe QDs system, which made it applicable for the determination of such compounds and proteins. The CL enhancement mechanism was also discussed briefly on the basis of the photoluminescence (PL) and CL spectra. This work is not only of importance for gaining a better understanding of the unique optical and physical chemistry properties of semiconductor nanocrystals but also of great potential to find applications in many fields such as luminescence devices, bioanalysis, and multicolor labeling probes.     

Stable Water‐dispersed CdTe Nanocrystals Dependent on Stoichiometric Ratio of Cd to Te Precursor

The improved properties of CdTe nanocrystals (NCs) synthesized by hydrothermal method were introduced. The experimental results indicated that the NCs properties could be dramatically influenced by means of changing Cd‐to‐Te molar ratio (the molar ratio of CdCl₂ and NaHTe in the precursor) of the MPA‐capped CdTe NCs. With the increase of the ratio from 2:1 to 10:1, the formation time of near‐infrared‐emitting CdTe NCs was shortened. In particular, high Cd‐to‐Te molar ratio brought about MPA‐capped CdTe NCs of superior radical oxidation‐resistance and photostability. As a result, the optimum ratio was found to be 8:1 or 10:1 in the study in order to efficiently attain stable, water‐dispersed CdTe NCs.     

Special characteristics of fluorescence and resonance Rayleigh scattering for cadmium telluride nanocrystal aqueous solution and its interactions with aminoglycoside antibiotics

CdTe nanocrystals (CdTe NCs) were achieved by reaction of CdCl₂ with KHTe solution and were capped with sodium mercaptoacetate. The product was detected by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive spectroscopy (EDS), fluorescence spectra, ultraviolet-visible spectra and X-ray diffraction (XRD). The CdTe NCs are of cubic structure and the average size is about 5 nm. The fluorescence quantum yield of CdTe NCs aqueous solution increased from 37% to 97% after 20 d under room light. The maximum λ _em of fluorescence changed from 543 nm to 510 nm and the blue shift was 33 nm. CdTe NCs aqueous solution can be steady for at least 10 months at 4 in° a refrigerator. The resonance Rayleigh scattering (RRS) of CdTe NCs in the aqueous solution was investigated. The maximum scattering peak was located at about 554 nm. The interactions of CdTe NCs with amikacin sulfate (AS) and micronomicin sulfate (MS) were investigated respectively. The effects of AS and MS on fluorescence and RRS of CdTe NCs were analyzed. It was found that AS and MS quenched the photoluminescence of CdTe NCs and enhanced RRS of CdTe NCs. Under optimum conditions, there are linear relationships between quenching intensity (F ₀-F), intensity of RRS (I-I ₀) and concentration of AS and MS. The detection limits (3б) of AS and MS are respectively 3.4 ng·mL⁻¹ and 2.6 ng·mL⁻¹ by the fluorescence quenching method, and 15.2 ng·mL⁻¹ and 14.0 ng·mL⁻¹ by the RRS method. The methods have high sensitivity, thus CdTe NCs may be used as fluorescence probes and RRS probes for the detection of aminoglycoside antibiotics. Supported by the National Natural Science Foundation of China (Grant No. 20475045)     

Synthesis of CdTe/SiO_2 Composites and Their Fluorescence Properties

Thioglycolic acid(TGA)-stabilized CdTe nanocrystals(NCs) were prepared with sodium tellurite as tellurium source,which avoids the cumbersome processes associated with H2Te or NaHTe sources.Fluorescent CdTe/SiO2 composites were synthesized by a sol-gel method without the exchange of surface ligands.The phase structure of CdTe NCs was investigated by X-ray diffractometry.For comparison,some characterizations were done for both the CdTe NCs and the composites.CdTe NCs and CdTe/SiO2 composites were characterize...     

Preparation of monodisperse CdTe nanocrystals-SiO2 microspheres without ligands exchange

Fluorescent CdTe-SiO₂ composite microspheres were prepared by a sol–gel method without the exchange of surface ligands for the first time. We loaded CdTe nanocrystals (NCs) into the matrix of silica microspheres during the formation of composite spheres. In contrast to CdTe NCs in aqueous solutions, CdTe NCs in the composite microspheres revealed better stability while their fluorescence properties were retained due to the confined effects of silica matrix. In addition, we also investigated the dependency of properties of these composite spheres on such important synthesis factors as pH value, concentration and stabilizers during experiment procedure in details.     

Metal‐Enhanced Fluorescence of CdTe Nanocrystals in Aqueous Solution

Metal‐enhanced fluorescence of semiconductor nanocrystals (NCs) is investigated. There is very little attention paid to the metal‐enhanced fluorescence in aqueous solution, which has great potential applications in bioscience. In this work, we directly observe metal‐enhanced fluorescence of CdTe NC solution by simply mixing CdTe NCs and Au nanoparticles, both of which are negatively charged. In order to study this kind of photoluminescence enhancement in aqueous solutions, we propose a calibration method, which takes into account the light attenuation in solutions. After consideration of the light weakening in transmission, the maximal PL enhancement is about 3 times as large as the ones without Au NPs. Some factors related to the enhanced magnitude of fluorescence, for instance, the concentration and the molar feed ratio of CdTe NCs and Au NPs, are studied in detail. Furthermore, the decreased lifetimes of CdTe NCs induced by Au NPs are also obtained, which are in accord with the enhancement of the photoluminescence.     

Chemiluminescence of CdTe quantum dots using K3Fe(CN)6 as oxidant and its capping ligand-dependent effect

Water-soluble CdTe quantum dots (QDs) capped with three different thioalkyl acids (mercaptoacetic acid, cysteine and glutathione) were synthesized in aqueous solution. In basic media, K₃Fe(CN)₆ could directly oxidize the water-soluble CdTe QDs to produce strong CL emission. It was found that the CL intensity depended on the capping ligand and size of CdTe QDs. CL spectra and fluorescence spectra of the system were measured to investigate the CL reaction mechanism. Moreover, the effects of 17 metal ions on the CL system were carefully investigated. Ca²⁺, Co²⁺, Mn²⁺, Hg²⁺, Mg²⁺, Cu²⁺, Ni²⁺, Cr³⁺ and Fe³⁺ could markedly inhibit the CL signal of the K₃Fe(CN)₆–CdTe QDs system, which makes it applicable for the detection of such ions. This work is of importance for gaining a better understanding of the unique optical and physical chemistry properties of QDs, and it is also helpful to find more practical applications of QDs.     

水相中CdTe纳米晶的制备及其光学性质

用不同稳定剂(巯基乙酸(TGA)、巯基丙酸(MPA)、L-半胱氨酸(L-Cys)、3-巯基-1,2-丙二醇(TG))在水相中制备了CdTe纳米晶, 并用透射电子显微镜(TEM)、X射线光电子能谱(XPS)和X射线粉末衍射(XRD)等技术对其进行了表征. 研究了不同水相合成条件对CdTe纳米晶光学性质的影响, 结果表明, n(Cd):n(Te)、溶液pH值、回流时间以及稳定剂的性质, 对纳米晶的光学性质具有显著影响. 制得的CdTe纳米晶发射峰窄且对称(半高全宽达38 nm), 用不同稳定剂制备的纳米晶发光量子效率有所不同, 用不同的激发波长对纳米晶进行激发时, 发射峰并未表现出明显的移动.     

Interaction of CdTe nanocrystals with thiol-containing amino acids at different pH: a fluorimetric study

3-Mercaptopropionic acid (MPA)-capped CdTe nanocrystals (NCs) were synthesized in aqueous medium, and their interaction with cysteine (Cys) and homocysteine (Hcy) was studied by steady-state and time-resolved fluorescence spectra at different pH. At 6.4?<?pH?<?8.0, the fluorescence of CdTe NCs can be effectively enhanced by Cys and Hcy. While pH?>?9.6, only Cys quenches the fluorescence of the CdTe NCs, no fluorescence changes are observed for Hcy. Mechanism study shows that these pH manipulating fluorescence responses can be attributed to the following two reasons: first, both the thiol–thiolate equilibrium of Cys (Hcy) and the number of undercoordinated NCs surface sites capped with dual coordinated ligands are strong pH-dependent; second, different thiol-containing amino acids, with different redox energy level, can lead to distinguishable fluorescence responses of NCs. Based on these unique fluorescence responses, the possibilities of developing a sensitive detecting technique for Cys/Hcy and Cys through pH modulation can be explored.     

Synthesis of Aqueous CdTe Nanocrystals with High Efficient Blue‐Green Emission of Exciton

As one of the most popular nanocrystals (NCs), aqueous CdTe NCs have very weak green emission under conventional synthesis conditions. In this work, we report the first example of blue‐emitting CdTe NCs directly synthesized in aqueous solution by slowing down the growth rate after nucleation. The key for the synthesis is the optimization of NC growth conditions, namely pH range of 7.5 to 8.5, TGA/Cd ratio of 3.6, Cd/Te ratio of 10, and Te concentration of 2×10^?5 mol/L, to get a slow growth rate after nucleation. The as‐prepared blue‐emitting CdTe NCs have small size (as small as 1.9 nm) and bright emission [with 4% photoluminescence quantum yield (PL QY) at 486 nm and 17% PLQY at 500 nm]. Transmission electron microscopy (TEM) images of the as‐prepared CdTe show monodispersed NCs which exhibit cubic zinc blend structure. Moreover, time‐resolved PL decay and X‐ray photoelectron spectroscopy (XPS) results show the as‐prepared NCs have better surface modification by ligand, which makes these luminescent small CdTe NCs have higher photoluminescence quantum yield, compared with NCs synthesized under conventional conditions.     

A new determining method of copper(<Emphasis Type="Bold">II</Emphasis>) ions at ng ml<Superscript>−1</Superscript> levels based on quenching of the water-soluble nanocrystals fluorescence

CdTe nanocrystals (NCs) were prepared and modified in aqueous solution by using 3-mercaptopropionic acid (MPA). Compared with previous fluorescent sensors based on organic fluorophores, these NCs have the following merits. First, they are sensitive and the synthetic procedure is simple; second, they have narrow, tunable, symmetric emission spectra and are photochemically stable. The applicability of these NCs to the determination of Cu(II) ions was studied successfully. Maximum fluorescence intensity was produced at pH 7.8, with excitation and emission wavelengths at 365 and 532 nm, respectively. Under optimal conditions, linear relationships were found between the relative fluorescence intensity and the concentration of Cu(II) ions in the range 0–256 ng ml^–1 and the limit of detection was 0.19 ng ml^–1. This method was applied to determine real samples successfully. In addition, the quenching mechanism is also described.     

Enhanced chemiluminescence from reactions between CdTe/CdS/ZnS quantum dots and periodate

A novel chemiluminescence (CL) performance of CdTe/CdS/ZnS quantum dots (QDs) with periodate (KIO₄) was studied. Effects of concentration and pH on the CL system were investigated. Electron spin resonance (ESR) and the effects of radical scavenger analysis were employed for identification of intermediate species. The CL spectra for this system showed only one maximum emission peak centered around 620 nm, which was similar with photoluminescence (PL) spectra of CdTe/CdS/ZnS QDs. The CL of CdTe/CdS/ZnS QDs was induced by direct chemical oxidation and the possible mechanism could be explained by radiative recombination of injected holes and electrons. This investigation not only provided new sight into the optical characteristics of CdTe/CdS/ZnS QDs, but also broadened their potential optical utilizations.     

Facile synthesis of nanocrystal encoded fluorescent silica microspheres

Monodisperse CdTe composite microspheres with a spherical shape were prepared using organosilane chemicals in aqueous solution. CdTe nanocrystals (NCs) were loaded into the matrix of silica microspheres during the formation of composite microspheres. Detailed characterization of the CdTe composite microspheres by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and spectrofluorimeter was performed to elucidate the morphology and fluorescence of the composite microspheres. In contrast to CdTe NCs in aqueous solution, CdTe NCs in the composite microspheres revealed high stability and fluorescence due to the confined effects of silica matrix. In addition, multicolored CdTe QDs were encoded into the microspheres at precise ratios.     

(Yb3+, Mn2+) Co-doped CdTe nanocrystals with enhanced quantum yields and red-shift emission

We prepared the nanocrystals (NCs) of CdTe, CdTe:Yb, and CdTe:Yb, Mn vis water phase synthesis and examined their structural, morphological, and optical properties. All NCs have a particle diameter of about 2–4 nm, and the monodispersed, uniform spherical, cubic structure of the CdTe NC remains largely unchanged after the doping with Yb and Mn. According to the X-ray diffraction results, the CdTe, CdTe:Yb, and CdTe:Yb, Mn NCs all have a cubic structure, and the diffraction peak of CdTe:Yb NC is at a lower 2θ angle compared with that of the CdTe NC. With the CdTe NC as the reference, the UV–Vis absorption of the CdTe:Yb and the CdTe:Yb, Mn NCs exhibits a blueshift and a redshift, and the emission of CdTe:Yb and CdTe:Yb, Mn has a blueshift of about 12 nm and a redshift of about 73 nm, respectively. The CdTe:Yb, Mn NCs have higher quantum yields than the CdTe:Yb NC, and the quantum yield is the highest when CdTe is doped with 1:1 Mn²⁺/Yb³⁺. In addition, both the CdTe:Yb and CdTe:Yb, Mn NCs have a shorter fluorescence lifetime than the CdTe NC.     

CdTe纳米晶与蛋白相互作用研究

当半导体纳米晶的直径小于其电子的玻尔直径时 ,半导体纳米晶对电子具有量子限域效应 ,其发光波长与纳米晶的尺寸相关 .与有机荧光分子相比 ,荧光半导体纳米晶具有以下优点 :(1 )其激发谱在吸收阈值以上几乎是连续的 ,利于多波长激发 ;(2 )高强荧光发射 ,谱峰窄 ,峰形对称 ;(3 )发射波长随着粒径的增大而有规律地红移 ,只需改变粒径即可获得多色发光 ;(4)纳米晶的发光稳定性好 ,不易被光分解和漂白 .因此 ,半导体纳米晶作为新一代荧光生物标记物已有研究[1～ 6] .荧光生物标记要求使用水溶性的纳米粒子 ,水相合成半导体纳米晶操作简便、重复…