Synthesis of Cysteine-Capped Zn_xCd_1-xSe Alloyed Quantum Dots Emitting in the Blue−Green Spectral Range

Abstract

Alloyed ZnxCd1-xSe quantum dots (QDs) have been successfully prepared at low temperatures by reacting a mixture of Cd(ClO4)2 and Zn(ClO4)2 with NaHSe using cysteine as a surface-stabilizing agent. The photoluminescence (PL) spectra of the alloyed QDs are determined on the basis of the Zn2+/Cd2+ molar ratio, reaction pH, intrinsic Zn2+and Cd2+ reactivities toward NaHSe, concentration of NaHSe, and the kind of thiols. A systematic blue shift in emission wavelength of the alloyed QDs was found with the increase in the Zn mole fraction. This result provides clear evidence of the formation of ZnxCd1-xSe QDs by the simultaneous reaction of Zn2+ and Cd2+ with NaHSe, rather than the formation of separate CdSe and ZnSe nanocrystals or core-shell structure CdSe/ZnSe nanocrystals. The size and inner structure of these QDs are also corroborated by using high-resolution transmission electron microscopy and X-ray powder diffraction. To further understand the formation mechanism, the growth kinetics of Zn0.99Cd0.01Se was studied by measuring the PL spectra at different growth intervals. The results demonstrated that, in the initial stage of growth, Zn0.99Cd0.01Se has a structure with a Cd-rich core and a Zn-rich shell. The post-preparative irradiation of these QDs improved their PL properties, resulting in stronger emission.

Synthesis and spectroscopic studies of chiral CdSe quantum dots

“…[22][23][24] Thiol group containing amino acids have proved to be excellent stabilisers, with L-cysteine becoming one of the popular surface capping molecules for CdX (X ¼ S, Se, and Te) nanoparticles. 18,[25][26][27][28][29][30][31] In addition this use of stereospecific chiral stabilising molecules opened another avenue of interest in the area of quantum dot research, as chirality is a key factor in biological and biochemical interactions. Due to their unique photophysical properties, we believe that chiral QDs have a range of potential applications in photonics and biochemistry.…”

Formation of 3-mercaptopropionic acid-Zn Cd1−Se quantum dots with tunable band gap

“…where QY is the quantum yield, F is the integrated emission intensity, A is the absorbance of the corresponding sample, n is the refractive index of the solvent, n u = 1.333 (the refractive index of water at 298 K), n s = 1.096 (the refractive index of alcohol at 298 K), and the subscripts refer to the reference fluorophore with a known QY (Rhodamine B, 65%) [17].…”

“…Liu and Yu [16] prepared three sizes of CdTe QDs by using tiopronin, thioglycolic acid, and glutathione as capping reagents. Tseng and coworkers [17] successfully synthesized thiolcapped Zn x Cd 1−x Se QDs with three different thiol ligands, and cysteine-capped Zn x Cd 1−x Se QDs showed single emission and a high quantum yield (QY) of 13% because the ligand provides good surface passivation.…”

Application of Gold Nanoparticles to Spectrophotometric Sensing of Hydrophilic Anions Based on Molecular Recognition by Urea Derivative

“…30,31 Thus, we have designed a bifunctional GNP covered with both PhUET and L-cysteine, a typical hydrophilic thiol, which has been used to prepare water-soluble GNP, 44 gold nanorod, 45 and quantum dots. 46,47 We measured the absorption spectra of the resulting GNP (PhU-Cys-GNP) in water upon the addition of several anions. Figure 5a provides the absorption-spectral changes of the PhU-Cys-GNP in water upon the addition of H2PO4 -.…”