Michael Campos

We report a tunable library of N,N,N′-trisubstituted selenourea precursors and their reaction with lead oleate at 60–150 °C to form carboxylate-terminated PbSe nanocrystals in quantitative yields. Single exponential conversion kinetics can be tailored over 4 orders of magnitude by adjusting the selenourea structure. The wide range of conversion reactivity allows the extent of nucleation ([nanocrystal] = 4.6–56.7 μM) and the size following complete precursor conversion (d = 1.7–6.6 nm) to be… Mehr zeigen

We report a tunable library of N,N,N′-trisubstituted selenourea precursors and their reaction with lead oleate at 60–150 °C to form carboxylate-terminated PbSe nanocrystals in quantitative yields. Single exponential conversion kinetics can be tailored over 4 orders of magnitude by adjusting the selenourea structure. The wide range of conversion reactivity allows the extent of nucleation ([nanocrystal] = 4.6–56.7 μM) and the size following complete precursor conversion (d = 1.7–6.6 nm) to be controlled. Narrow size distributions (σ = 0.5–2%) are obtained whose spectral line widths are dominated (73–83%) by the intrinsic single particle spectral broadening, as observed using spectral hole burning measurements. The intrinsic broadening decreases with increasing size (fwhm = 320–65 meV, d = 1.6–4.4 nm) that derives from exciton fine structure and exciton–phonon coupling rather than broadening caused by the size distribution. Weniger anzeigen

The surfaces of cadmium telluride (CdTe) crystal grains play an important, yet poorly understood role in CdTe solar cell efficiency. In order to study this issue, we have developed a scalable synthesis of colloidal CdTe nanocrystals from cadmium bis(phenyltellurolate) and cadmium carboxylate (Cd(O2CR)2) complexes. Using solution chemical techniques, we demonstrate that the binding of surface ligands to CdTe is particularly weak, enabling controlled study of solution-processed CdTe solar cells… Mehr zeigen

The surfaces of cadmium telluride (CdTe) crystal grains play an important, yet poorly understood role in CdTe solar cell efficiency. In order to study this issue, we have developed a scalable synthesis of colloidal CdTe nanocrystals from cadmium bis(phenyltellurolate) and cadmium carboxylate (Cd(O2CR)2) complexes. Using solution chemical techniques, we demonstrate that the binding of surface ligands to CdTe is particularly weak, enabling controlled study of solution-processed CdTe solar cells free from organic contaminants. Weniger anzeigen

Controlling the size of colloidal nanocrystals is essential to optimizing their performance in optoelectronic devices, catalysis, and imaging applications. Traditional synthetic methods control size by terminating the growth, an approach that limits the reaction yield and causes batch-to-batch variability. Herein we report a library of thioureas whose substitution pattern tunes their conversion reactivity over more than five orders of magnitude and demonstrate that faster thiourea conversion… Mehr zeigen

Controlling the size of colloidal nanocrystals is essential to optimizing their performance in optoelectronic devices, catalysis, and imaging applications. Traditional synthetic methods control size by terminating the growth, an approach that limits the reaction yield and causes batch-to-batch variability. Herein we report a library of thioureas whose substitution pattern tunes their conversion reactivity over more than five orders of magnitude and demonstrate that faster thiourea conversion kinetics increases the extent of crystal nucleation. Tunable kinetics thereby allows the nanocrystal concentration to be adjusted and a desired crystal size to be prepared at full conversion. Controlled precursor reactivity and quantitative conversion improve the batch-to-batch consistency of the final nanocrystal size at industrially relevant reaction scales.

Featured in:
“Economical routes to colloidal nanocrystals” Science, 2015, 348, 1211-1212.
“New synthesis heralds low-cost quantum dots” Chemistry World, RSC, June 12th, 2015. Weniger anzeigen

This study describes the effect of titanium precursor and surface density in determining the resulting oxide surface species. We also introduce a tool for determining the number of fluid-accessible Ti sites, and demonstrate the usefulness of the technique through a structure-insensitive photo-oxidation.