Regulating the Fluorescence Emission of CdSe Quantum Dots Based on the Surface Ligand Exchange with MAA

Abstract

Cadmium selenide (CdSe) quantum dots (QDs) is a promising semiconductor and fluorescence nanocrystal with quantum size effect. To address the problem of fluorescence emission during the process of the ligand transformation of colloidal cluster CdSe QDs from nonpolar organic solvents to polar inorganic aqueous solutions, the surface ligand exchange with mercapto acetic acid (MAA) was proposed. It was attributed to the Cd‐O bond breaking and the Cd‐S bond formation. The intensity and wavelength of fluorescence emission spectra could be adjusted by controlling the concentration of MAA. The photoluminescence (PL) spectra and UV‐Vis absorption spectra of colloidal cluster CdSe QDs indicated that the electronic properties of the interface varied with the exchange of the surface ligands. Moreover, the band‐edge emission quenching occurred and the maximum redshift of the PL spectrum could reach 28 nm. The enhancement of the deep trap emission peaks of CdSe QDs appeared in 600‐900 nm region, and the maximum blue shift of the defect peak in PL spectrum could reach 80 nm with the increase concentration of MAA. The absorption spectra and PL spectra on the surface of porous alumina thin film were used to further analyze the charge separation and capture of charge carriers. This novel organic‐inorganic ligand exchange method provides an effective strategy for regulating fluorescence and electron transfer, which could be used on biological, solar cells or other practical applications.

Top-down produced CdSe quantum dots as an ultrasensitive SERS platform for the detection of uric acid

“…Obviously, it confirmed a defect-free single crystallinity with intrinsic lattice spacings of 2.2, 3.3, and 3.5 Å, corresponding to the (220), (311), and (111) crystal planes of the CdSe microstructure, respectively. 22 It was demonstrated that the crystal structure of the CdSe QDs was in agreement with that of the powders, which had no observable change in the preparation process. The corresponding fast Fourier transform (FFT) image (insert of Fig.…”

“…High-resolution transmission electron microscopy (HRTEM) images were also collected to further observe the microstructure of CdSe QDs, and the images could be more distinctly reflected in Fig.1cand Fig.S2 (ESI †). Obviously, it confirmed a defect-free single crystallinity with intrinsic lattice spacings of 2.2, 3.3, and 3.5 Å, corresponding to the (220), (311), and (111) crystal planes of the CdSe microstructure, respectively 22. It was demonstrated that the crystal structure of the CdSe QDs was in agreement with that of the powders, which had no observable change in the preparation process.…”

Luminescence Enhancement, Encapsulation, and Patterning of Quantum Dots Toward Display Applications

“…For QDs with a fixed size, ligands and other reagent species can also affect their emission properties. [72] When exposed to light, an intensity change or wavelength shift can occur, which is attributed to photoactivation, photoelectrification, or photoneutralization. [73][74][75] The energy transfer process can also be utilized to modulate the emission of QDs by constructing a QD-dye system.…”

“…[84] By using a rational design, the performance of QDs can be improved. [72,133] As an example, alkyl phosphate (TDPA)-coated CsPbBr 3 QD powders were developed, which retained high photoluminescence quantum yield (PLQY, 68%) and narrow band emission (FHWM ≈22 nm), as well as high stability in water and high-temperature atmospheres. [106] The alkyl phosphate matrix prevents agglomeration and fluorescence quenching, leading to a high PLQY.…”

Discussions of Fluorescence in Selenium Chemistry: Recently Reported Probes, Particles, and a Clearer Biological Knowledge

“…The process of organic–inorganic ligand exchange works by way of electron transfer; Cd–O scission and Cd–S formation were involved. Band edge emission was monitored and the maximum red shift found in this case was 28 nm [ 134 ].…”