Sizing Curve, Absorption Coefficient, Surface Chemistry, and Aliphatic Chain Structure of PbTe Nanocrystals

Abstract

For colloidal semiconductor nanocrystals (NCs), the knowledge of the chemical structure and the size-dependent optical properties is of crucial importance, both from a practical and fundamental perspective. Here, we report the basic properties of PbTe NCs in order to complement the already existing knowledge on PbS and PbSe NCs. The band gap versus NC diameter (sizing) curve was determined by combining transmission electron microscopy with absorption spectroscopy; the energy of the primary optical absorption follows 1/d dependence with the diameter. The lead content of the NCs was determined with inductive coupled plasma optical emission spectrometry and the relative tellurium content with energy-dispersive X-ray spectroscopy. Combining these results yields a relation for the intrinsic absorption coefficient, which is independent of the NC size at 3.1 eV. The PbTe NCs are stabilized by Pb(oleate)2, but different from PbS NCs, oleate is predominantly bound in a chelating bidentate coordination. Besides that, we analyzed the structure of the aliphatic chains on all lead chalcogenide NCs and showed that the aliphatic chains are partly crystalline near the core and more liquid-like at the solvent side.

A Facile Chemical Synthesis of PbTe Nanostructures at Room Temperature

“…FTIR transmittance bands are summarized in Table 3 . The FTIR spectra of sample well matched with those reported earlier [ 54 , 60 , 61 , 62 , 63 ].…”

“…The bands around 1107 cm −1 to 1409 cm −1 might originate from –C–N stretching, –CH 2 scissoring mode of vibration, and –OH bending mode. The bands between 781–907 cm −1 reveal vibrations of ternary amines with –CH 2 rocking modes [ 54 , 60 , 61 ].…”

“…FTIR spectra of the sample A5 show that the strong absorption bands at 1572 cm −1 , 1270 cm −1 , and 1385 cm −1 are attributed to stretching vibrations of the carboxylate groups in the film. Various bands at 2980 cm −1 , 2882 cm −1 , and 2776 cm −1 are due to –CH stretching vibrations present in the structure of the PbTe [ 60 ]. The FTIR spectrum of the PbTe sample prepared by chemical precipitation at room temperature for 288 h of sample A5, indicates the presence of the bond of Pb–Te.…”

The dynamic surface chemistry of colloidal metal chalcogenide quantum dots

“…This constraint in the synthetic procedures permits to reduce the complexity of the investigated systems. We remark that, despite controversies on the presence of hydroxyl anions at the PbE QD surface, 9,12,21,22 only one oleate ligand per excess Pb atom is commonly found in PbE QDs, 4,7,9,12 whereas Cd-(oleate) 2 is expected to be at the surface of CdE QDs. 5,20 Therefore, the X species in QDs with the chemical formula [ME] n (MX 2 ) mÀn generally refers to anionic ligands.…”

“…13 Markedly narrower resonances are, instead, commonly observed for PbE QDs in CDCl 3 (Dn z 10 Hz for the vinylene protons of small PbS QDs). 22,28,29 Such an evident discrepancy highlights substantial differences between CdE and PbE QDs, which may be related to the inorganic core composition and to the ligand interactions with the QD surface that contribute heterogeneous broadening to the spectral line width. The reliability of measured line width values is corroborated by batch to batch reproducibility of the NMR spectra of PbS QDs in toluene-d8, as shown in Fig.…”