Experimental and theoretical investigations of the ligand structure of water-soluble CdTe nanocrystals

Abstract

The unique optical properties, such as size-tunable absorption and emission, caused semiconductor nanocrystals to attract a great deal of interest for recent technological developments. For the evaluation of semiconductor nanocrystals as new materials for various applications like optoelectronic devices, knowledge of the structure-property relationships is indispensable, but still presents a challenge. Here, we address these challenges for thioglycolic acid-capped CdTe nanocrystals with a focus on the quantification of thiol ligands, identification of the ligand shell structure and their influence on the optical properties of these nanocrystals. We present the use of a simple analytical technique, the Ellman's test, and ICP-OES analysis for the study of the surface chemistry of these nanomaterials. Together with theoretical calculations, the results of these studies show the strong influence of the amount of Cd-thiolates present in the ligand shell on the concentration-dependent emission properties, thereby providing the basis for a better understanding of the chemical nature of the NC-ligand interface. In this context, the present work contributes to the establishment of a clearer picture and better control of the surface chemistry, which will provide the basis for the design of highly emitting nanocrystals and the prediction of their applicability.

Highly Stabilized Quantum Dot Ink for Efficient Infrared Light Absorbing Solar Cells

“…To examine such hypothesis, the Zeta potential of PbS-PbX 2 and PbS-AI QD ink was measured, the result of which reveals that the PbS-AI QD ink was more neutral than that of PbS-PbX 2 QD ink system. [33,35,36] Meanwhile, the solvent propylene carbonate has a higher dielectronic constant (ε = 65.1) compared with that of butylamine (ε = 4.92), which would contribute to decreasing the potential energy of the QDs and thus increasing their stability. Second, the solvent butylamine applied for the PbS-PbX 2 ink is characterized by a high Lewis basicity (pK BHX = 2.21) with the tendency to solvate cations and could result in resolving or precipitation the ink.…”

Quantification of Anisotropy-Related Uncertainties in Relative Photoluminescence Quantum Yield Measurements of Nanomaterials – Semiconductor Quantum Dots and Rods

“…For nanocrystalline materials like semiconductor quantum dots and rods, the size of PL presents also a criterion for particle quality, i.e., the passivation of surface defects. [10,12,13] Although for accurate PL measurements, the use of polarizers set to magic angle conditions (excitation polarizer set to 0 ∘ , emission polarizer set to 54.7 ∘ ) has been recommended, [9,14] the emission spectra and PL values of many emitters are still often measured without Unauthenticated Download Date | 5/11/18 8:59 AM polarizers, even for systems that could reveal a partly or even strongly polarized emission.…”

5‐(2‐Mercaptoethyl)‐1H‐tetrazole: Facile Synthesis and Application for the Preparation of Water Soluble Nanocrystals and Their Gels

“…It is well known that complexes containing five‐membered chelate rings are significantly more stable than complexes with six‐membered chelate rings . Cadmium–thiolate complexes that are present in the ligand shell, significantly affect the optical properties of the quantum dots, as reported for the colloidal synthesis of NCs in the presence of thioglycolic acid . Moreover, the six‐membered chelate complex can more easily undergo hydrolysis under reflux, increasing the amount of sulfur in the NCs, which can be seen in the selected area electron diffraction pattern (Figure S7).…”

“…[24] Cadmium-thiolate complexest hat are present in the ligand shell, significantly affect the optical properties of the quantum dots, as reported for the colloidal synthesis of NCs in the presence of thioglycolic acid. [25] Moreover,t he six-membered chelate complex can more easily undergoh ydrolysis under reflux, increasing the amount of sulfur in the NCs, which can be seen in the selected area electron diffraction pattern ( Figure S7). This may be the reason for such as trong QE enhancement, as was discussed in previous studies.…”