Fluorescent probe for detection of Cu 2+ using core‐shell CdTe/ZnS quantum dots

Near‐infrared (NIR) core–shell CdSeTe/CdS quantum dots (QDs) modified with l‐cysteine were synthesized in aqueous solution. The QDs had a special NIR‐emitting spectrum, high fluorescence stability and low cytotoxicity. In addition, they exhibited an obvious fluorescence quenching when Cu2+ was present. An NIR nanosensor was prepared for rapidly, sensitively, and selectively determining Cu2+ in solution quantitatively and monitoring the changes in Cu2+ in cells with fluorescence imaging in a semiquantitative way. The linear relationship between the relative fluorescence intensity (F0/F) and the concentration of Cu2+ from 5.12 × 10−8 M to 2.56 × 10−5 M in solution was observed using an NIR fluorescence spectrophotometer with R2 equal to 0.9958. Moreover, in the experiment with the fluorescence microscope, F0/F versus the concentration of Cu2+ from 5.00 × 10−8 M to 7.68 × 10−6 M also showed a good linear relationship with R2 equal to 0.9817. Practical water sample ion detecting experiments had good accuracy and recovery rates. Cell experiments showed that the NIR imaging intensity of cells was inversely proportional to the concentration of copper ions, therefore NIR QDs have great potential for detection of metal ions in solution and in cells.

Section: Resultsmentioning

confidence: 99%

Assaying of Cu²⁺ with near‐infrared l‐cysteine‐capped CdSeTe/CdS quantum dots and its effect on cell imaging

Zhang

Huang

et al. 2021

“…It is well known that certain transition metal ions, such as Cu 2+ , Ag + , and Hg 2+ , etc. can induce the PL quenching of QDs and the possible PL quenching mechanism can be ascribed to the charge transfer between metal ions and QDs . These results indicate that common metal ions except for Cu 2+ , Ag + , and Hg 2+ have only a small effect on PL response of − OPhS‐QDs for pH.…”

Section: Resultsmentioning

confidence: 99%

Sodium 4‐mercaptophenolate capped CdSe/ZnS quantum dots as a fluorescent probe for pH detection in acidic aqueous media

Liu

Zhao

et al. 2017

Development of the fluorescent pH detection method is promising due to the sensitivity, easy operation, and low-cost, etc. However, traditional organic fluorophores have still some disadvantages such as the tedious preparation and purification as well as low photostability and water solubility, which limits the rapid detection application. Semiconductor quantum dots (QDs) have recently risen to prominence as an alternative for organic fluorophores in fluorescence analysis by virtue of their convenient synthesis and superior optical properties. In this study, we report on sodium 4-mercaptophenolate functionalized CdSe/ZnS QDs (denoted as OPhS-QDs), which can serve as a selective "on-off" fluorescence probe for aqueous media pH. OPhS-QDs exhibit strong fluorescence in near neutral medium. As a Lewis organic base, OPhS- moieties on QDs surface easily binds to proton under acidic conditions to yield 4-mercaptophenol capped QDs (i.e. HOPhS-QDs), which acts as an efficient hole trapper. As a result, the QDs photoluminescence (PL) is switched off. Under optimal conditions, the present probe exhibits a good linear relationship between fluorescence response and pH values in the pH range 3.0-5.2. Furthermore, the present probe exhibits a high selectivity for proton over other common cations and has been successfully used for pH detection in real water samples.

“…Water‐soluble MPA‐capped CdTe QDs were synthesized according to previous reports . Typically, under N 2 protection, 6.8 mg of tellurium powder and 20 mg of excess NaBH 4 were added to 3 ml of absolute ethanol.…”

Section: Methodsmentioning

confidence: 99%

Core–shell structured CdTe/CdS@SiO₂@CdTe@SiO₂ composite fluorescent spheres: Synthesis and application for Cd²⁺ detection

Liu

et al. 2016

Core-shell structured quantum dot (QD)-silica fluorescent nanoparticles have attracted a great deal of attention due to the excellent optical properties of QDs and the stability of silica. In this study, core-shell structured CdTe/CdS@SiO @CdTe@SiO fluorescent nanospheres were synthesized based on the Stöber method using multistep silica encapsulation. The second silica layer on the CdTe QDs maintained the optical stability of nanospheres and decreased adverse influences on the probe during subsequent processing. Red-emissive CdTe/CdS QDs (630 nm) were used as a built-in reference signal and green-emissive CdTe QDs (550 nm) were used as a responding probe. The fluorescence of CdTe QDs was greatly quenched by added S , owing to a S -induced change in the CdTe QDs surface state in the shell. Upon addition of Cd to the S -quenched CdTe/CdS@SiO @CdTe@SiO system, the responding signal at 550 nm was dramatically restored, whereas the emission at 630 nm remained almost unchanged; this response could be used as a ratiometric 'off-on' fluorescent probe for the detection of Cd . The sensing mechanism was suggested to be: the newly formed CdS-like cluster with a higher band gap facilitated exciton/hole recombination and effectively enhanced the fluorescence of the CdTe QDs. The proposed probe shows a highly sensitive and selective response to Cd and has potential application in the detection of Cd in environmental or biological samples.