Surface Of CdTe QDs Research Articles

Design of smartphone platform by ratiometric fluorescent for visual detection of silver ions

In this work, a smartphone platform based on ratiometric fluorescence signals was reported, which can achieve fast, sensitive, and on-site visual detection of silver ions. The ratiometric fluorescent probe was constructed with fluorescein isothiocyanate (FITC) and telluride quantum dots (CdTe QDs) through electrostatic interaction. Silver ions will interact with -SH on the surface of CdTe QDs, which can cause the decrease of the fluorescence intensity at 680 nm, while the fluorescence of FITC at 522 nm remains unchanged. It displays the obvious color changes from orange-red to light yellow to green. Based on the changes, the portable smartphone platform was used to identify the RGB values of the system. Then, an analysis model was established according to the variation of RGB values for the visual analysis of Ag+. Under the best experimental conditions, the detection limit of Ag+ by fluorescence spectrometer analysis can be as low as 3.65 nM, the linear range was 12.50 nM to 500 nM. Additionally, the linear range of smartphone platform was 0.125–12.5 μM, and the detection limit was 40 nM. Therefore, visual on-site analysis of Ag+ in environmental water samples can be achieved by capturing the obvious color changes of the system on a smartphone platform.

Immobilization of catalytic sites on quantum dots by ligand bridging for photocatalytic CO2 reduction.

Harvesting solar energy to convert carbon dioxide (CO2) into fossil fuels shows great promise to solve the current global problems of energy crisis and climate change. To achieve this goal, it is desirable to develop efficient catalysts with visible light response to cater for the solar spectrum. CdTe QDs are ideal candidates for absorbing visible light, but it is difficult to directly perform CO2 reduction due to the lack of effective catalytic sites. Herein, we report a strategy for the activation of mercaptopropionic acid (MPA)-capped CdTe QDs for visible-light-driven CO2 reduction, in which iron ions (Fe2+) are immobilized onto CdTe QDs using l-cysteine as a bridging ligand (CdTe-b-Fe). This ligand bridging strategy can immobilize Fe2+ ions on the surface of CdTe QDs as catalytic sites, and these catalytic sites can be conveniently adjusted by directly adding different types or numbers of metal ions. In addition to effectively immobilizing catalytic sites, the bridging ligands can also provide a pathway for electron transport between CdTe QDs and the catalytic sites. The CdTe-b-Fe QD system based on the ligand bridging strategy exhibits excellent catalytic properties: the yield of CH4/CO (two products together) is 126 μmol g-1 h-1, and the selectivity for carbon-based products approaches 98%. This work presents a facile strategy for immobilizing catalytic sites on QDs and provides a platform for designing efficient visible-light driven catalysts for CO2 reduction.

Fluorescence enhancement of CdTe quantum dots by HBcAb-HRP for sensitive detection of H2O2 in human serum

A simple, high selective, ultra-sensitive and stable biosensor based on hepatitis B core antibody labeled with horseradish peroxidase (HBcAb-HRP) induced fluorescent enhancement of CdTe QDs for recognition of H2O2 have been constructed. In this assay, sulfurs in HBcAb-HRP, which possess a strong affinity towards Cd2+, can improve greatly the recombination fluorescence of CdTe QDs by creating more radiative centers at CdTe/Cd-SR complex. Then, H2O2 oxidizes Cd-S bonds in CdTe QDs to organic disulfide product (RS-SR), causing thioglycolic acid (TGA) and HBcAb-HRP detach from surface of CdTe QDs and thus leading to fluorescence quenching. Just with the addition of HBcAb-HRP, sensitivity of the new biosensor has been improved by near one order of magnitude as compared with CdTe QDs probe. Detection limit of HBcAb-HRP-CdTe QDs biosensor for determination of H2O2 was 6.9×10−8mol L−1 (3σ/slope), and the excellent linear range was 1.0×10−7~1.5×10−4molL−1. By using sodium diethyldithiocarbamate (DDTC) and NH4OH as masking agents of Ag+, Hg2+ and Cu2+, H2O2 can be selectively detected in coexistence with Ag+, Hg2+ and Cu2+, and the biosensor has been used to detect H2O2 in human serum with satisfactory results. The superior properties of this biosensor showed great potential usage in more chemical and biological researches.

Visible quantum-dot-based targeted siRNA delivery for HIF-1α gene silencing

In the present paper, we synthesized cadmium (Cd) telluride (Te) quantum dots (CdTe QDs) by a hydrothermal method using three different ligands as stabilizers: N-acetyl-L-cysteine (NAC), cysteamine hydrochloride (CA), or 2-(dimethylamino) ethanethiol hydrochloride (DMAE). The results demonstrated that CA-coated CdTe QDs had a higher zeta potential (positive) compared with the NAC- and DMAE-coated CdTe QDs. Furthermore, CA-coated CdTe QDs had greater ability to bind siRNA and greater uptake by human gastric cancer cells (SGC-7901). The release of siRNA from the surface of CdTe QDs was induced by high concentrations of reduced glutathione (GSH). mRNA and protein levels of HIF-1α in SGC-7901 cells were significantly reduced after being treated with the complex of CA-coated CdTe QDs and HIF-1α siRNA under strictly anerobic conditions. In addition, CA-coated CdTe QDs displayed excellent optical properties, good morphology, and low toxicity to normal cells.

A novel carboxymethyl chitosan–quantum dot-based intracellular probe for Zn2+ ion sensing in prostate cancer cells

In this paper, we fabricated novel carboxymethyl chitosan-coated CdTe quantum dots (CMC–CdTe QDs) via the electrostatic interaction between amino groups in the carboxymethyl chitosan polymeric chains and carboxyl groups of the CdTe QDs. Carboxymethyl chitosan on the surface of CdTe QDs had strong binding ability with Zn2+, resulting in the obvious enhancement of the photoluminescence of CdTe QDs. The photoluminescence intensity of CMC–CdTe QDs probe was proportional to the concentration of Zn2+ in the range of 5.0×10−6 to 5.0×10−3moll−1. The detection limit for Zn2+ was 4.5×10−6 moll−1. The experimental results indicate that the CMC–CdTe QDs possess favorable cell compatibility, good sensitivity and selectivity for intracellular Zn2+ sensing, and are promising candidates for cellular imaging and sensing in prostate cancer cells. The present study also provides an approach for the further development of nanoprobes dedicated to intracellular sensing.

Encodable multiple-fluorescence CdTe@carbon nanoparticles from nanocrystal/colloidal crystal guest–host ensembles

We report herein the controllable generation of encodable multi-fluorescence CdTe@carbon nanoparticles (CdTe@C NPs) via the pyrolysis of quantum dot/photonic crystal (QD/PC) guest–host ensembles. The precursors of CdTe/poly(styrene-co-glycidylmethacrylate) (PS-co-PGMA) QD/PC guest–host ensembles were initially formed via the assembly of epoxy groups of PCs and carboxyl groups on the surface of CdTe QDs, followed by a pyrolysis process to generate CdTe@C NPs. The as-prepared CdTe@C NPs not only integrate the optical properties for both the carbon and CdTe QD constituents, but also enable an impressive enhancement of the fluorescence lifetime for CdTe QDs. The multifarious fluorescent spectra coding for CdTe@C NPs was further generated through regulating the embedded sizes or concentrations of CdTe QDs and the excitation wavelength, and their applications in DNA detection and luminescent patterns were achieved.

Fabrication of Fe(CN)63− Functionalized PDDA/CdTe Layer‐by‐layer Film with Good Electron Transfer Ability

Abstract(PDDA/CdTe)n layer‐by‐layer (LBL) film immobilized with Fe(CN)63− was fabricated on the gold electrode. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to investigate the electrochemical properties of this film. The peak current of the immobilized Fe(CN)63− increased as the number of the bilayers increased and was proportional to the scan rate. Compared with pure (PDDA/CdTe)n and (PDDA/PSS)n LBL film, Fe(CN)63− immobilized (PDDA/CdTe)n LBL film had good electron transfer ability. The immobility of Fe(CN)63− into the film was attributed to its interaction with Cd2+ on the surface of CdTe QDs. Fe(CN)63− also can interact with other metal ions, which would make Fe(CN)63− release from the film. The concentrations of metal ions will affect the CV response of Fe(CN)63− immobilized LBL film. It has provided a novel prototype of device or sensor for quantitative detection of metal ions.