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An electrochemiluminescent immunosensor is constructed for the detection of diethylstilbestro (DES) on the basis of amplified quenching of electrochemiluminescence (ECL) from CdTe nanocrystal (NC)/reduced graphene oxide (rGO) composite films by antibody (Ab) against DES-modified SiO2 nanoparticles (Ab@SiO2). In this immunosensing system, CdTe NC/rGO composite films act as solid supporters for both DES and ECL emitters, which generate a 100-fold stronger ECL emission than CdTe NC films because the presence of rGO can lower the potential barrier, facilitate charge transfer, suppress nonradiative Auger recombination, and make the electron trap states fill more efficiently. On the composite films, the immobilized ovalbumin-modified DES (OVA-DES) competes with free target DES to bind Ab@SiO2. As a result, the number of formed OVA-DES-Ab@SiO2 immunocomplexes is inversely related to that of target DES. Using an ECL quenching maximum at blank as a calculation benchmark, the ECL intensity increment of the immunosensor and the concentration of target DES show a linear range of 0.002–2 ng/mL (R2 = 0.996) with a detection limit of 0.001 ng/mL (signal/noise = 3). This immunosensor, of good selectivity and stability, was used to detect beef samples, with recoveries at a scope of 93.2%–105.0%. [ABSTRACT FROM AUTHOR]

We report a study on anion exchange reaction of CdTe nanocrystals with S 2− in aqueous solution under ambient condition. We found that the optical properties of CdTe nanocrystals can be well tuned by controlling the reaction conditions, in which the reaction temperature is crucially important. At low reaction temperature, the product nanocrystals showed blue-shifts in both absorption and PL spectra, while the photoluminescence quantum yield (PLQY) was significantly enhanced. When anion exchanges were carried out at higher reaction temperature, on the other hand, obvious red shifts in absorption and PL spectra accompanied by a fast increase followed by gradual decrease in PLQY were observed. On variation of S 2− concentration, it was found that the overall kinetics of Te 2− for S 2− exchanges depends also on [S 2− ] when anion exchanges were performed at higher temperature. A possible mechanism for anion exchanges in CdTe NCs was proposed. [ABSTRACT FROM AUTHOR]

We report an efficient way to improve the photoluminescence (PL) of water-soluble CdTe nanocrystals (NCs) by irradiating the NCs in the presence of pyridine. Under illumination, continuous increases in PL of CdTe NCs were observed. The maximum quantum yield reached up to 41% was obtained, showing five times higher than that of the as prepared parent CdTe NCs. While keeping the illuminated CdTe NCs in dark, further increase in PL quantum yield to over 60% was observed. PL decay measurements revealed that the PL enhancement is associated with the increase of the average lifetime of CdTe NCs. The effects of light wavelength and intensity, pyridine derivatives as well as oxygen on the PL of CdTe NCs were investigated, and a competition mechanism between photodegradation and surface passivation of CdTe NCs induced by illumination and pyridine was suggested. [ABSTRACT FROM AUTHOR]

In this research MPA capped CdTe nanocrystals with sizes around 2.7–3.5 nm were grown in aqueous solution. The process was performed through the reaction of NaHTe with MPA and CdCl 2 solution in high temperature. The synthesis was carried out in two different states of standard and modified forms. In the modified synthesis, the hydrazine hydrate material was added to the MPA plus CdCl 2 solution before injection. The evolution of the nanocrystals size and PL quantum yield was monitored during the heating time for the growth. The results demonstrated that for the standard synthesis the growth rate was slow. The CdTe nanocrystals with high PL quantum yields were achieved in more than 10 h of heating. In contrast for the modified synthesis the growth rate was considerably higher. In this state a band edge emission with PL quantum yield of about 26% was achieved for the MPA capped CdTe nanocrystals in just 2 h of the heating process. [ABSTRACT FROM AUTHOR]

CdTe quantum dots capped with thioglycolic acid (TGA) display a strong turn-on fluorescence response if exposed to solutions of cysteine (Cys). In order to exploit this effect, a molecularly imprinted polymer (MIP) for Cys was covalently linked to the QDs via allyl mercaptan. The resulting nanomaterials (QDs, MIP-coated QDs, and nonimprint-coated QDs) were characterized by FTIR and scanning electron microscopy. The adsorption of Cys was studied in phosphate buffer (pH 7.4) with respect to equilibration times (5, 15, and 40 min, respectively), binding constants [2.98, 2.42, and 0.96 (×10 M)], and Langmuir isotherms (R = 0.9995, 0.9999, and 0.9983) in the Cys concentration range between 3.33 μM to 500 μM. The method has a detection limit of 0.85 μM (3σ, blank, for n = 10). The selectivity of the MIP-coated QDs for Cys over 19 other amino acids is similar to that of bare QDs, but MIP-QDs afford better recoveries of Cys from solutions also containing bovine serum albumin (90 %) and fetal bovine serum (97 %), respectively, when compared to the recoveries that are obtained with bare (non-imprinted) QDs (135 % and 120 %). This is probably due to the fact that the outer MIP shell largely reduces protein wrapping, dot aggregation, and matrix inclusion. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Ordered rutile TiO2 nanorod arrays are prepared on fluorine doped transparent conductive glass (FTO) by hydrothermal method. CdTe-coated TiO2 core-shell nanorod arrays(CdTe/TiO2 ) are fabricated by electrodepositing CdTe nanoparticles on the TiO2 nanorods array. A composite structure of poly(3-hexylthiophene) (P3HT) coated CdTe/TiO2 core-shell nanorod arrays(P3 HT/CdTe/TiO2 ) is formed after P3HT in chlorobenzene solution is spin-coated onto the CdTe/TiO2 core-shell nanorod arrays. The hybrid solar cell is wade with the P3HT/CdTe/TiO2 core-shell nanorod array composite nanostructure film and Au film sputtered on the composite film. The energy conversion efficiency is up to 0. 91 % by using the designed hybrid solar cell. [ABSTRACT FROM AUTHOR]

A colloidal suspension method is used to obtain CdTe nanocrystals modified with thioglycolic acid in aqueous solutions of ethylene glycol. Their photoluminescence spectrum is shifted to shorter wavelengths relative to that of CdTe nanocrystals synthesized in water. It is found that the ethylene glycol molecules participate in the stabilization of the nanocrystals and passivation of surface defects, with an optimum concentration of 10% ethylene glycol in the reactive mixture for production of stably dispersed CdTe. It is difficult to observe plasmon effects in these nanoparticles when Ag nanoparticles are present because cadmium iodide is used as a precursor salt, which leads to the appearance of I, an oxidant for Ag nanoparticles, in the solution. When a protective polyelectrolyte intermediate layer of thickness ~11.7 nm is deposited on a colloidal silver substrate, the photoluminescence intensity of the CdTe nanoparticles increases by a factor of 1.7. The chemical features of these nanoparticle solutions cause their luminescence characteristics to be highly sensitive to the presence of Ag nanoparticles in the solution. Changes in the position and intensity of the photoluminescence peak are observed for concentrations of Ag nanoparticles in the solution as low as 10 mol/l. [ABSTRACT FROM AUTHOR]

One of the strategies to tune current-voltage behaviors in organic diodes is to combine field-induced charge transfer processes with schottky barrier. According to this principle, a rectifying diode with hysteresis effect was fabricated utilizing a hybrid of electroactive polystyrene derivative covalently tethered with electron-donor carbazole moieties and electrostatic linked with electron-acceptor CdTe nanocrystals. Current-voltage characteristics show an electrical switching behavior with some hysteresis is only observed under a negative bias, with three orders of On/Off current ratio. The hybrid material based rectifier exhibits a rectification ratio of six and its maximum rectified output current is about 5 × 10 A. The asymmetric switching is interpreted as the result of both field induced charge transfer and schottky barrier, capable of reducing the misreading of cross-bar memory. Meanwhile, chemical doping of CdTe nanocrystals instead of physical blend favor their uniform dispersion in matrix and stable operation of device. [ABSTRACT FROM AUTHOR]

Abstract: A series of positively charged polystyrene (PS) nanosphere emulsions were prepared by copolymerization of quaternary ammonium chloride cationic monomer with styrene via emulsifier-free emulsion polymerization. The average diameter of the nanospheres was tuned in the range of 35–100nm by adjusting the recipe. The PS nanospheres were used as carriers of aqueous CdTe nanocrystals (NCs) by adsorbing them on the surface through static interaction. After attached to the nanospheres, NCs’ stability against pH change and UV light irradiation was enhanced. The CdTe–PS composite nanospheres were blended with compatible poly (vinyl alcohol) (PVA) matrix to prepare fluorescent thin film by spin coating. CdTe–PS nanospheres had homogenous distribution in the thin film and their light scattering performance was largely reduced after solvent evaporated, as a result, the composite thin film was highly transparent. In the meantime, the immobilization effect of PS nanospheres prevented NCs from aggregation, thus they preserved original high fluorescence without fluorescence resonance energy transfer. The CdTe–PS/PVA composite solution has potential applications in light emitting devices by inkjet printing. [Copyright &y& Elsevier]

In this paper, we have reported a mixing alkali medium method for the preparation of highly emissive CdTe quantum dots (QDs). The pH of the reaction medium was tuned by varying the ratio of ammonia and sodium hydroxide, and the photoluminescence quantum yield of the as-prepared CdTe QDs was greatly enhanced compared to the traditional single alkali source method. Due to the good photoluminescence, the as-prepared CdTe QDs possess high potential in cell imaging. [ABSTRACT FROM AUTHOR]

An analysis of physical mechanisms responsible for the influence of stabilizer type and ambient material on CdTe nanocrystal growth rate and passivation effectiveness of surface dangling bonds has been carried out. The possibility to change properties of nanocrystals by changing the stabilizer type has been shown. [ABSTRACT FROM AUTHOR]

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 (3 б) 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. [ABSTRACT FROM AUTHOR]

Abstract: The interactions of lysozyme and calf thymus DNA (ctDNA) or thioglycolic acid (TGA) modified CdTe nanoparticles in aqueous solution have been studied by resonance light-scattering (RLS) spectroscopy. At pH 7.2 Britton–Robinson (BR) buffer solution and pH 7.4 phosphate buffered saline (PBS), the RLS signals of ctDNA and TGA modified CdTe nanoparticles were greatly enhanced by lysozyme in the region of 220–750nm characterized by the peak around 306 and 353nm, respectively. Under optimal conditions, the increase of RLS intensity of the two systems is proportional to the concentration of lysozyme. The linear range is 0.1–25μg/ml for the lysozyme–ctDNA system, and 0.2–10.7μg/ml for the lysozyme–TGA modified CdTe nanoparticles system. The detection limit is 0.041μg/ml for the lysozyme–ctDNA system, and 0.083μg/ml for the lysozyme–TGA modified CdTe nanoparticles system, respectively. Meanwhile lysozyme can also be used as a probe to determine the ctDNA. The increase of RLS intensity of the system is also proportional to the concentration of ctDNA. The linear range is 0.078–13μg/ml. The detection limit is 0.024μg/ml. Three kinds of samples were analyzed with satisfactory results. [Copyright &y& Elsevier]

Abstract: This paper described a novel assay of enzyme based on the measurement of enhanced resonance light-scattering (RLS) signals resulting from the electrostatic and coordination interaction of functionalized CdTe nanoparticles with enzyme. The CdTe nanoparticles which were modified with 3-mercaptocarboxylic acid (MPA) have abundant carboxylic groups ( the nanoparticles are water-soluble, stable and biocompatible. At pH 8.3 phosphate buffered saline (PBS), the RLS signals of functionalized nano-CdTe are greatly enhanced by bromelain and papain in the region of 220–800nm characterized by the peak around 318–314nm, respectively. The optimization conditions of the reaction were also examined and selected. Under the selected conditions, the enhanced RLS intensity is linearly proportional to the concentration of bromelain and papain. The liner range is (0.09–0.9)×10−6 mol/L for bromelain and (0.048–0.702)×10−6 mol/L for papain. The influences of some foreign substances were also examined. This method can be applied to the determination of enzyme. [Copyright &y& Elsevier]