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Dmitri V. Talapin

Publications and source records attributed to Dmitri V. Talapin.

21 records · Page 2Linked to original sources

CdS nanoparticles capped with 1-substituted 5-thiotetrazoles: Synthesis, characterization, and thermolysis of the surfactant

We propose a new type of surfactants, namely, tetrazole derivatives which can be controllably removed from the nanoparticle surface. Tetrazoles are a peculiar class of heterocyclic compounds. The presence of four nitrogen atoms in the tetrazole ring determines their interesting physical and chemical properties. Tetrazoles show high thermal stability below 200C while decomposing at higher temperature with formation of gaseous products and no or very little solid residue. Moreover, the tetrazole group is known as an important ligand in coordination chemistry. Its donor nitrogen atoms can bind to various metal ions leading to stable complexes with diverse coordination modes of the heteroring. We report the synthesis of CdS NPs capped with 1-R-5-thiotetrazoles using two different synthetic schemes: solution-phase and solventless single precursor approaches. In both synthetic procedures cadmium thiotetrazolates were used as cadmium precursors and sources of surfactant.

cond-mat.mtrl-sci↗

Spin-dependent exciton quenching and intrinsic spin coherence in CdSe/CdS nanocrystals

Large surface to volume ratios of semiconductor nanocrystals cause susceptibility to charge trapping, which can modify luminescence yields and induce single-particle blinking. Optical spectroscopies cannot differentiate between bulk and surface traps in contrast to spin-resonance techniques, which in principle avail chemical information on such trap sites. Magnetic resonance detection via spin-controlled photoluminescence enables the direct observation of interactions between emissive excitons and trapped charges. This approach allows the discrimination of two functionally different trap states in CdSe/CdS nanocrystals underlying the fluorescence quenching and thus blinking mechanisms: a spin-dependent Auger process in charged particles; and a charge-separated state pair process, which leaves the particle neutral. The paramagnetic trap centers offer control of energy transfer from the wide-gap CdS to the narrow-gap CdSe, i.e. light harvesting within the heterostructure. Coherent spin motion within the trap states of the CdS arms of nanocrystal tetrapods is reflected by spatially remote luminescence from CdSe cores with surprisingly long coherence times of >300 ns at 3.5 K.

cond-mat.mes-hall↗

Temperature-tuning of near-infrared monodisperse quantum dot solids at 1.5 um for controllable Forster energy transfer

We present the first time-resolved cryogenic observations of Forster energy transfer in large, monodisperse lead sulphide quantum dots with ground state transitions near 1.5 um (0.83 eV), in environments from 160 K to room temperature. The observed temperature-dependent dipole-dipole transfer rate occurs in the range of (30-50 ns)^(-1), measured with our confocal single-photon counting setup at 1.5 um wavelengths. By temperature-tuning the dots, 94% efficiency of resonant energy transfer can be achieved for donor dots. The resonant transfer rates match well with proposed theoretical models.

physics.optics↗