Reversible Modification of CdSe−CdS/ZnS Quantum Dot Fluorescence by Surrounding Ca Ions
نویسندگان
چکیده
It has been known for a long time that the fluorescence intensity of colloidal quantum dots (QDs) becomes modified when free ions are added to the QD solution. The consequences of removing free ions from the QD solution, however, have not been closely investigated. In this work we studied fluorescence from 3-mercaptopropionic acid (3-MPA) coated CdSe−CdS/ZnS core−multishell QDs when free Ca ions were added to and subsequently removed from the QD solution. It was found that QD fluorescence intensity was reduced when Ca ions were added to the QD solution, while the wavelength of the QD fluorescence peak remained unchanged. QD fluorescence recovered when the concentration of free Ca ions in the QD solution was reduced by adding Ca chelator (ethylene glycol tetraacetic acid, EGTA). It was further observed that the time of single QD fluorescence at on-state and QD fluorescence lifetimes were also reduced after adding Ca and then recovered when EGTA was added. Theoretical study shows that a free Ca ion can attach stably to the system of [QD + surface ligand], attract the photoexcited electron, and repel the photoexcited hole inside the QD core, leading to the reduction of the radiative recombination between the electron and hole, thereafter decreasing the QD fluorescence intensity, on-state time, and fluorescence lifetimes, as observed experimentally. To the best of our knowledge, this is a first study to show that the changes of QD optical properties are reversible under the influence of Ca ions. We further estimated the equilibrium association constant pKa of our QDs with Ca , which is much larger than QDs with Mg, Na, and K, indicating the feasibility of developing a QD-based Ca sensor.
منابع مشابه
The Study of Metal Sulfide as Efficient Counter Electrodes on the Performances of CdS/CdSe/ZnS-co-sensitized Hierarchical TiO2 Sphere Quantum Dot Solar Cells
The effects of using different counter electrode metal sulfides on the performances of solar cells made with CdS/CdSe/ZnS quantum dots co-sensitized onto hierarchical TiO2 spheres (HTSs) used as photo-electrode are reported. The HTS in the QDSSCs is composed of an assembly of numerous TiO2 spheres made by the solvolthermal method. The photoelectrical performance of HTS/CdS/CdSe/ZnS coupled to C...
متن کاملPhotothermal Spectroscopic Characterization in CdSe/ZnS and CdSe/CdS Quantum Dots: A Review and New Applications
متن کامل
CdSeS/ZnS alloyed nanocrystal lifetime and blinking studies under electrochemical control.
Alloyed CdSeS nanocrystals allow tuning between the CdSe and CdS band edges while remaining relatively small. The CdSeS cores also lead to a reduced electron confinement energy and a slower biexciton decay rate compared to CdSe cores of similar sizes. A ZnS shell synthesis procedure allows stable CdSeS/ZnS colloidal quantum dots (QDs) suitable for single dot imaging. These are compared to CdSe/...
متن کاملPurification non-aqueous solution of quantum dots CdSe- CdS-ZnS from excess organic substance-stabilizer by use PE- HD membrane
Recently, a new simple method for the purification of CdSe-CdS-ZnS quantum dots by using membrane filtration, the filtration process, successfully separated the oleic acid from quantum dots through membranes purification after synthesis; purification of quantum dots is a very significant part of post synthetical treatment that determines the properties of the material. We explore the possibilit...
متن کاملCopper-Doped CdSe/ZnS Quantum Dots: Controllable Photoactivated Copper(I) Cation Storage and Release Vectors for Catalysis**
The first photoactivated doped quantum dot vector for metal-ion release has been developed. A facile method for doping copper(I) cations within ZnS quantum dot shells was achieved through the use of metal-dithiocarbamates, with Cu(+) ions elucidated by X-ray photoelectron spectroscopy. Photoexcitation of the quantum dots has been shown to release Cu(+) ions, which was employed as an effective c...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2014