A Library of Selenourea Precursors to PbSe Nanocrystals with Size Distributions near the Homogeneous Limit

Abstract

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.

Ligand-Induced Shape Transformation of PbSe Nanocrystals

“…As Grisorio et al claimed, it can be the result from the use of Pb(oleate) 2 -hydrate in their advanced synthesis procedure for PbS nanocrystals. 26 We also remark that we did not observe hydroxide and oleic acid signals for the NCs synthesized with the method developed by Campos et al 27 …”

Identifying reactive organo-selenium precursors in the synthesis of CdSe nanoplatelets

“…Recently, substituted thio and selenourea precursors with tailored reactivity were used to improve PbS and PbSe quantum dots. 19,20 Libraries of bis(acyl) selenide or sulfide precursors could similarly allow for tailored reactivity. In contrast to substituted thio or selenourea, bis(acyl) chalcogenides yield only carbonyl byproducts after reaction with cadmium carboxylates.…”

Fused 1,2,3‐Thiaselenazoles Synthesized from 1,2,3‐Dithiazoles through Selective Chalcogen Exchange

“…At about 90–100 °C, a vigorous reaction occurs that features gas evolution and precipitation of elemental Se, which is most likely to be oxidation of DMF or TMU by SeO 2 —a well‐known oxidant for organic compounds (the formal stoichiometry for DMF is 4C 3 H 7 NO+17SeO 2 →12CO 2 +14H 2 O+2N 2 +17Se). Neither the known species Me 2 N−CH=Se (DMF) or (Me 2 N) 2 C=Se (TMU) nor any other Se‐containing species were detected in the reaction mixture by 1 H, 13 C, or 77 Se NMR spectroscopy. When specially prepared Me 2 N−CH=Se was reacted with 1 under the conditions shown in Scheme , the target 2 did not form (according to 77 Se NMR spectroscopy) but starting material 1 was completely consumed.…”

“…12CO 2 + +14H 2 O+ +2N 2 + +17Se). Neither the known speciesM e 2 NÀ CH=Se [23] (DMF) or (Me 2 N) 2 C=Se [24] (TMU) nor any other Se-containing speciesw ere detected in the reaction mixture by 1 H, 13 C, or 77 Se NMR spectroscopy.W hen specially prepared Me 2 NÀ CH=Se [23] was reacted with 1 under the conditions showni n Scheme 2, the target 2 did not form (according to 77 Se NMR spectroscopy) but startingm aterial 1 wasc ompletely consumed. Furthermore, no Se-containing derivatives were detected by 77 Se NMRs pectroscopy in the range d Se = 160-1900 ppm.…”