Characterization of PbS Nanocrystals

PbS nanocrystals (0.5 g) were dissolved in d₆-benzene (2 mL) and TMEDA (3 mL) was added. After stirring for 10 minutes, acetonitrile (5 mL) was added and the nanocrystals separated by centrifugation. The clear supernatant was collected and dried under vacuum for 5 hours. d₆-benzene (0.6 ml) was added to dissolve the residue and the solution was analyzed with ¹H NMR spectroscopy. Infrared absorption spectroscopy was performed using diffuse reflectance geometry as a mixture with KBr. Energy dispersive X-ray spectroscopy was conducted on a film drop-cast on a highly ordered pyrolitic graphite substrate using a Cold Field Emission Hitachi 4700 Scanning Electron Microscope. ¹H NMR (C₆D₆, 500 MHz): δ = 0.91 (t, 6H, −CH₃), 1.281.6 (b, 44H, −CH₂), 1.84 (m, 4H, β-CH₂), 1.94 (s, 4H, −NCH₂), 2.09 (m, 8H, −C=CCH₂), 2.24 (s, 12H, −N(CH₃)₂), 2.52 (t, 4H, α-CH₂), 5.49 (m, 4H, −CH=CH), 9.3 (b, −NH). FT-IR (Diamond ATR): ν = 1384 cm⁻¹ (s CO₂ assym), 1560 cm⁻¹ (s CO₂ sym), 1720 cm⁻¹ (w COOH), 2920 cm⁻¹ (s C-H).