Reversible regulation of CdTe quantum dots fluorescence intensity based on Prussian blue with high anti-fatigue performance

A fluorescence switching device with excellent anti-fatigue performance based on the electrochromic material Prussian blue and fluorophore CdTe quantum dots was realized. The fluorescence switching device ultimately demonstrated a high fluorescence contrast, short response time and superior anti-fatigue property. Notably, the fluorescence contrast remains unchanged after 133 cycles.

A "Turn-On" Fluorescence Copper Biosensor Based on DNA Cleavage-Dependent Graphene Oxide-dsDNA-CdTe Quantum Dots Complex

A novel “turn-on” fluorescent copper biosensor is developed successfully based on the graphene oxide (GO)-dsDNA-CdTe quantum dots (QDs) complex via chemical crosslink method. The optical and structure properties of GO-dsDNA-CdTe QDs complex are studied by fluorescence (FL) spectra and transmission electron microscopy (TEM) in detail. It is demonstrated that the fluorescence quenching of CdTe QDs is a process of fluorescence resonance energy transfer (FRET) due to the essential surface and quenching properties of two-dimensional GO. Copper ions induce the catalytic reaction of DNA chain and irreversibly break at the cleavage site, which will cause the G-quadruplex formation, moreover further result in the CdTe QDs separated from GO and restored its fluorescence. Therefore, a significant recovery effect on the fluorescence of the GO-dsDNA-CdTe QDs complex is observed in the presence of copper ions. The fluorescence responses are concentration-dependent and can be well described by a linear equation. Compared with other metal ions, the sensor performs good selectivity for copper ions.

Electrophoretic study of peptide-mediated quantum dot-human immunoglobulin bioconjugation

The bioconjugation of quantum dots (QDs) is a key process in their application for bioanalysis as well as imaging. The coupling of QDs with biologically active molecules such as peptides, nucleic acids, and/or antibodies enables their fluorescent labeling, and therefore, selective and sensitive tracking during the bioanalytical process, however, the efficiency of the labeling and preservation of the biological activity of the bioconjugate have to be considered. In this study, a new approach of the bioconjugation of CdTe-QDs and human immunoglobulin employing a small peptide is described. The heptapeptide (HWRGWVC) was synthesized and characterized by mass spectrometry, liquid chromatography, and capillary electrophoresis. Moreover, the peptide was used as a capping agent for QDs synthesis. The CdTe-QDs were synthesized by microwave synthesis (600 W, 20 min) using 3.2 mM CdCl2 and 0.8 mM Na2TeO3. The bioconjugation of QDs capped by this peptide with immunoglobulin was investigated by capillary electrophoresis and magnetic immunoextraction coupled with electrochemical detection by differential pulse voltammetry. Furthermore, the applicability of prepared bioconjugates for fluorescent immunodetection was verified using immobilized goat antihuman IgG antibody.

One-pot noninjection route to CdS quantum dots via hydrothermal synthesis

Water-dispersible CdS quantum dots (QDs) emitting from 510 to 650 nm were synthesized in a simple one-pot noninjection hydrothermal route using cadmium chloride, thiourea, and 3-mercaptopropionic acid (MPA) as starting materials. All these chemicals were loaded at room temperature in a Teflon sealed tube and the reaction mixture heated at 100 °C. The effects of CdCl(2)/thiourea/MPA feed molar ratios, pH, and concentrations of precursors affecting the growth of the CdS QDs, was monitored via the temporal evolution of the optical properties of the CdS nanocrystals. High concentration of precursors and high MPA/Cd feed molar ratios were found to lead to an increase in the diameter of the resulting CdS nanocrystals and of the trap state emission of the dots. The combination of moderate pH value, low concentration of precursors and slow growth rate plays the crucial role in the good optical properties of the obtained CdS nanocrystals. The highest photoluminescence achieved for CdS@MPA QDs of average size 3.5 nm was 20%. As prepared colloids show rather narrow particle size distribution, although all reactants were mixed at room temperature. CdS@MPA QDs were characterized by UV-vis and photoluminescence spectroscopy, powder X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectrometry and MALDI TOF mass spectrometry. This noninjection one-pot approach features easy handling and large-scale production with excellent synthetic reproducibility. Surface passivation of CdS@MPA cores by a wider bandgap material, ZnS, led to enhanced luminescence intensity. CdS@MPA and CdS/ZnS@MPA QDs exhibit high photochemical stability and hold a good potential to be applied in optoelectronic devices and biological applications.