• Home
  • Search Results
  • Mechanistic insight into the formation of cationic naked nanocrystals generated under equilibrium control.

Mechanistic insight into the formation of cationic naked nanocrystals generated under equilibrium control.

Journal of the American Chemical Society (2014-10-11)
Sean E Doris, Jared J Lynch, Changyi Li, Andrew W Wills, Jeffrey J Urban, Brett A Helms
ABSTRACT

Cationic naked nanocrystals (NCs) are useful building units for assembling hierarchical mesostructured materials. Until now, their preparation required strongly electrophilic reagents that irreversibly sever bonds between native organic ligands and the NC surface. Colloidal instabilities can occur during ligand stripping if exposed metal cations desorb from the surface. We hypothesized that cation desorption could be avoided were we able to stabilize the surface during ligand stripping via ion pairing. We were successful in this regard by carrying out ligand stripping under equilibrium control with Lewis acid-base adducts of BF3. To better understand the microscopic processes involved, we studied the reaction pathway in detail using in situ NMR experiments and electrospray ionization mass spectrometry. As predicted, we found that cationic NC surfaces are transiently stabilized post-stripping by physisorbed anionic species that arise from the reaction of BF3 with native ligands. This stabilization allows polar dispersants to reach the NC surface before cation desorption can occur. The mechanistic insights gained in this work provide a much-needed framework for understanding the interplay between NC surface chemistry and colloidal stability. These insights enabled the preparation of stable naked NC inks of desorption-susceptible NC compositions such as PbSe, which were easily assembled into new mesostructured films and polymer-nanocrystal composites with wide-ranging technological applications.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Nitric acid, puriss. p.a., reag. ISO, reag. Ph. Eur., for determinations with dithizone, ≥65%
Supelco
Nitric acid concentrate, 0.1 M HNO3 in water (0.1N), eluent concentrate for IC
Oleic acid, European Pharmacopoeia (EP) Reference Standard
Sigma-Aldrich
Toluene, suitable for HPLC, 99.9%
Sigma-Aldrich
Toluene, puriss. p.a., ACS reagent, reag. ISO, reag. Ph. Eur., ≥99.7% (GC)
Sigma-Aldrich
Toluene, ACS reagent, ≥99.5%
Sigma-Aldrich
Ethyl alcohol, Pure, 200 proof, ACS reagent, ≥99.5%
Sigma-Aldrich
Ethyl alcohol, Pure, 200 proof, meets USP testing specifications
Sigma-Aldrich
Ethyl alcohol, Pure, 200 proof, HPLC/spectrophotometric grade
Sigma-Aldrich
Nitric acid, ACS reagent, 70%
Sigma-Aldrich
Toluene, HPLC Plus, for HPLC, GC, and residue analysis, ≥99.9%
Sigma-Aldrich
Toluene, ACS reagent, ≥99.5%
Sigma-Aldrich
Toluene, ACS reagent, ≥99.5%
Sigma-Aldrich
Nitric acid, puriss. p.a., ≥65% (T)
Sigma-Aldrich
Nitric acid, puriss. p.a., 65.0-67.0%
Sigma-Aldrich
Toluene, Laboratory Reagent, ≥99.3%
Sigma-Aldrich
Ethanol, ACS reagent, prima fine spirit, without additive, F15 o1
Sigma-Aldrich
Nitric acid, red, fuming, HNO3 >90 %
Sigma-Aldrich
Ethyl alcohol, Pure, 200 proof, for molecular biology
Sigma-Aldrich
Ethyl alcohol, Pure, 190 proof, for molecular biology
Supelco
Toluene, Pharmaceutical Secondary Standard; Certified Reference Material
Sigma-Aldrich
Toluene, suitable for HPLC, ≥99.9%
Supelco
Oleic acid, Selectophore, ≥99.0%
Sigma-Aldrich
Oleic acid, natural, FCC
Sigma-Aldrich
Hexamethylphosphoramide, absolute, over molecular sieve (H2O ≤0.03%), ≥98.0% (GC)
Sigma-Aldrich
Oleic acid, suitable for cell culture, BioReagent
Supelco
Acetone solution, contains 20.0 % (v/v) acetonitrile, suitable for HPLC
Sigma-Aldrich
Nitric acid, ACS reagent, ≥90.0%
Sigma-Aldrich
Oleic acid, ≥99% (GC)
Sigma-Aldrich
Ethanol, anhydrous, denatured