Functionalized CdTe Quantum Dots Research Articles

Stepwise Chemical Reaction Strategy for Highly Sensitive Electrochemiluminescent Detection of Dopamine

A stepwise chemical reaction strategy based on the specific recognition of boronic acid to diol, and N-hydroxysuccinimide (NHS) ester to amine group, was designed to construct a "signal on" electrochemiluminescence (ECL) platform for highly sensitive detection of dopamine. A boronic acid-functionalized pyrene probe was synthesized and was self-assembled on the sidewalls of carbon nanotubes via π-π stacking interactions as capture probes on a glassy carbon electrode. Meanwhile, 3,3'-dithiodipropionic acid di(N-hydroxysuccinimide ester) (DSP)-functionalized CdTe quantum dots (QDs) were designed as signal probes and characterized with transmission electron microscopy and spectroscopic techniques. Upon stepwise chemical reaction of dopamine with boronic acid and then DSP-QDs, the QDs were captured on the electrode as ECL emitters for signal readout, leading to an ultralow background signal. By using O2 as an endogenous coreactant, the "signal on" ECL method was employed to quantify the concentration of dopamine from 50 pM to 10 nM with a detection limit of 26 pM. Moreover, the stepwise chemical reaction-based biosensor showed high specificity against cerebral interference and was successfully applied in the detection of dopamine in cerebrospinal fluid samples. The stepwise chemical reaction strategy should be a new concept for the design of highly selective analytical methods for the detection of small biomolecules.

Highly luminescent chitosan-l-cysteine functionalized CdTe quantum dots film: Synthesis and characterization

The present work describes synthesis of water soluble l-cysteine-functionalized CdTe quantum dots (QDs) with size tunable emission at different time intervals for chitosan based film. The characterization of the synthesized CdTe QDs–chitosan film was made by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA) and scanning electron microscope (SEM). The optical property of CdTe QDs–chitosan film was determined by UV–vis and photo-luminescence (PL) spectroscopy whereas their antibacterial activity was screened for Gram positive (Staphylococcus aureus) as well as Gram negative (Pseudomonas aurigionasa and Escherichia coli) bacteria by disc diffusion method. The loss of tunable light emission effect of QDs as well as the positive result of antibacterial study reveals that the synthesized QDs based chitosan film is a promising candidate for wide range of biomedical applications.

Supramolecular self-assembly and photophysical properties of pillar[5]arene-stabilized CdTe quantum dots mediated by viologens

Carboxylatopillar[5]arene (CP[5]A) functionalized CdTe quantum dots (CP[5]A@QDs) were synthesized via a ligand-exchange method and shown to be very stable in basic aqueous solutions. Significantly, CP[5]As can be modified on the surfaces of QDs to stabilize the photochemical properties of CdTe nanocrystals and serve as bridges to induce the formation of an aggregated supramolecular network upon the addition of bridged methyl viologen guest molecules.

Improved sensing performance from methionine capped CdTe and CdTe/ZnS quantum dots for the detection of trace amounts of explosive chemicals in liquid media

Water soluble methionine functionalized CdTe quantum dots (QDs) and CdTe/ZnS core–shell QD samples have been prepared by a reflux condensation method and have been used to detect explosive chemicals, such as dinitrotoluene (DNT), nitrotoluene (NT) and nitrobenzene (NB) in liquid media. Meisenheimer complex formation between the QD surface attached methionine and aromatic explosive molecules has helped to detect them selectively via a fluorescent quenching process. Fluorescence quenching occurred because of the transfer of excited electrons from QD to the explosive molecules. Depending upon the number of nitro groups present on the explosive molecule, the quenching efficiency of different analytes varied. Due to surface passivation and inductive effects, the methionine capped CdTe/ZnS core–shell quantum dot sample resulted in the maximum quenching constant.

Novel synthesis of β-cyclodextrin functionalized CdTe quantum dots as luminescent probes

A novel, inexpensive procedure for the preparation of highly fluorescent and water-soluble CdTe quantum dots (QDs) using β-cyclodextrin (β-CD) as surface-coating agents was fabricated through the substitution reaction at the C-6 position of mono-6-deoxy-6-(p-tolylsulfonyl)-cyclodextrin (6-TsO-β-CD) by the NH2 of (3-aminopropyl)triethoxysilane-coated CdTe QDs (APTES/CdTe QDs) under mild conditions. X-ray powder diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), ultraviolet and visible (UV–vis) spectrophotometer, and fluorescence (FL) spectrophotometer were used to characterize the obtained nanoparticles, which proved that the CdTe QDs have been effectively modified by β-CD. The quantum yields (QYs) of CdTe QDs, APTES/CdTe QDs and β-CD/APTES/CdTe QDs in water comparative to Rhodamine 6G were about 17%, 12%, and 9%, respectively. A pair of isomer o,p′-DDT and p,p′-DDT was chosen as the template molecules to evaluate the molecular recognition properties of β-CD/APTES/CdTe QDs. The results revealed that β-CD/APTES/CdTe QDs simultaneously possessed unique optical properties of QDs and excellent molecules recognition ability of β-CD through combining their individual distinct advantages.

A novel β-Cyclodextrin-QDs optical biosensor for the determination of amantadine and its application in cell imaging

In this paper, a novel optical biosensor for amantadine (AD) determination has been constructed successfully based on the fluorescence resonance energy transfer (FRET) between water-soluble β-Cyclodextrin (β-CD)-functionalized CdTe quantum dots (QDs) and Rhodamine B (RB). RB could enter the cavity of β-CD by hydrophobic interaction, and the process of FRET between QDs and RB occurred. However, the process of FRET was switched off with the addition of AD, due to its larger hydrophobic association constant with β-CD than that of RB. The fluorescence intensity of CdTe QDs (donor) would increase gradually with the increasing concentration of AD, which shown a good linear relationship in the range of 1×10−5–1.6×10−4mol/L with a correlation coefficient R2=0.998. We also obtained a satisfactory result using this spectrophotometric method for the determination of AD in pharmaceutical formulation. Furthermore, β-CD-functionalized CdTe QDs with AD in the cavity were incubated with target HepG2 cells and could be observed in the cytoplasm of cells. The β-CD-functionalized CdTe QDs could act as a visible biomarker for AD in cancer cells fluorescence imaging, which presents a potential application in biomedical field.

CdTe quantum dots functionalized with 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide as luminescent nanoprobe for the sensitive recognition of bromide ion

A novel bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) has been developed. Fluorescence quenching of the QDs by 4AT was observed. The functionalized QDs-4AT nanoprobe allowed a highly sensitive determination of bromide ion via analyte-induced change in the photoluminescence (fluorescence recovery) of the modified QDs. A detection limit of 0.6nM of bromide ion was obtained, while the interfering effect of other inorganic cations and anions was investigated to examine the selectivity of the nanoprobe. The linear range was between 0.01 and 0.13μM. Combined fluorescence lifetime and electron paramagnetic resonance measurements confirmed electron transfer processes between bromide ion and QDs-4AT.

Highly Fluorescent Fluoride-Responsive Hydrogels Embedded with CdTe Quantum Dots

Functionalized CdTe quantum dots (QDs) synthesized via ion exchange demonstrated a selective response toward fluoride in aqueous solutions based on a rapid sol-gel transition that was visible to the naked eye. The fluoride-induced hydrogel exhibited excellent fluorescent performance because of the incorporation of QDs. As a result, this highly fluorescent fluoride-induced hydrogel may pave a new way to sense fluoride using a visible sol-gel transition.

A nanoprobe for nonprotein thiols based on assembling of QDs and 4-amino-2,2,6,6-tetramethylpiperidine oxide

A new fluorescent nanoprobe, 4-amino-2,2,6,6-tetramethylpiperidine oxide (AT)-functionalized CdTe quantum dots (QDs–AT), was synthesized, for selective detection of nonprotein thiols based on electron transfer (ET). In the presence of nonprotein thiols, the nitroxide radicals in QDs–AT were converted to hydroxylamines, resulting in the fluorescence recovery of the quenched QDs. The detection mechanism of the probe was investigated using Rh-Se-2 probe. The nanoprobe has high sensitivity toward glutathione (GSH) with a detection limit of 7.1 × 10 −8 M. The fluorescent imaging of living cells showed that QDs–AT could distinguish the concentration differences of GSH in HL-7702 and HepG2 cells.

Electrochemiluminescence quenching by CdTe quantum dots through energy scavenging for ultrasensitive detection of antigen

Efficient electrochemiluminescence (ECL) quenching was achieved by functionalized CdTe quantum dots (QDs) through ECL energy scavenging, based on which ultrasensitive antigen detection could be realized.