From rational design of organometallic precursors to optimized synthesis of core/shell Ge/GeO₂nanoparticles

Abstract

The synthesis of germanium nanoparticles has been carried out, thanks to the design of novel aminoiminate germanium(II) precursors: (ATI)GeZ (with Z = OMe, NPh2, and ATI = N,N'-diisopropyl-aminotroponiminate) and (Am)2Ge (Am = N,N'-bis(trimethylsilyl)phenyl amidinate). These complexes were fully characterized by spectroscopic techniques as well as single crystal X-ray diffraction. The thermolysis of both complexes yielded NPs which display similar features that are a Ge/GeO2 core/shell structure with a mean diameter close to 5 nm with a narrow size distribution (<15%). Whereas the high temperatures (>300 °C) classically reported in the literature for the preparation of germanium-based NPs were necessary for thermolysis of the complexes (ATI)GeZ, the use of amidinate-based precursors allows the preparation at an unprecedented low temperature (160 °C) for the thermolytic route. As suggested by a mechanistic study, the lower reactivity of (ATI)GeZ (for which the concomitant use of high temperature and acidic reagent is required) was explained in terms of lower ring strain compared to the case of (Am)2Ge.

Chiral nematic porous germania and germanium/carbon films

“…4d) shows two peaks at 29.9 eV and 31.8 eV attributed to GeO and GeO 2 , respectively. 70 The data indicate that most of GeO 2 was generated in Ge-N during calcination under N 2 in accordance with the PXRD results and the formation of some GeO may be caused by reducing GeO 2 by carbon. These results confirm that the GeO 2 /CNC composites were converted to the hexagonal GeO 2 /C under pure N 2 , and to the diamond Ge/C under H 2 /N 2 by a complete reduction of Ge 4+ to Ge 0 during calcination.…”

“…29 Both Ge-N and Ge-H have amorphous carbon derived from CNCs under pyrolysis and this was further confirmed by Raman spectroscopy (Fig. 70 The data indicate that most of GeO 2 was generated in Ge-N during calcination under N 2 in accordance with the PXRD results and the formation of some GeO may be caused by reducing GeO 2 by carbon. 29 IR spectra (Fig.…”

Highly Dynamic Ligand Binding and Light Absorption Coefficient of Cesium Lead Bromide Perovskite Nanocrystals

“…To gain more insight in the dynamics of stabilization, the diffusion coefficient D of a molecule is a helpful parameter as the diffusion coefficient of a bound ligand is equal to the diffusion coefficient of the total object (NC plus ligand shell). The diffusion coefficient can be obtained from Diffusion Ordered NMR Spectroscopy (DOSY) and can be related to the size of the molecule via the Stokes–Einstein equation with f the friction coefficient, k B the Boltzmann constant, and T the absolute temperature: For spherical particles, the friction coefficient is f = 6πη r s (η the solvent’s viscosity, r s the solvodynamic radius of the object/molecule) and this expression was already repeatedly used to calculate the solvodynamic radius of NCs from DOSY data. ,,− For non-spherical NCs, the friction coefficient needs adjusting , and the general expression is f = 6πη C with C the so-called capacity of the object . Although there is no previous account of DOSY NMR on cubic NCs, Hubbard and Douglas calculated the capacity of arbitrary shaped objects.…”

“…For spherical particles, the friction coefficient is f = 6πηr s (η the solvent's viscosity, r s the solvodynamic radius of the object/molecule) and this expression was already repeatedly used to calculate the solvodynamic radius of NCs from DOSY data. 26,32,[39][40][41] For non-spherical NCs, the friction coefficient needs adjusting 42,43 and the general expression is f = 6πηC with C the socalled capacity of the object. 44 Although there is no previous account of DOSY NMR on cubic NCs, Hubbard 44 and Douglas 45 However, 166 µm 2 /s corresponds to a cube edge length of 3.7 nm, clearly smaller than expected, as the NCs measure 8.4 nm in TEM.…”

Single-Crystalline Germanium Nanocrystals via a Two-Step Microwave-Assisted Colloidal Synthesis from GeI4

“…A low-temperature synthesis of Ge NCs was also recently reported for the thermolysis of a bis(amidinato)germylene(II) complex and suggests that these species might be present in the reaction mixture after the initial heat treatment. 33 To the best of our knowledge, this is the first example of high-quality colloidal Ge NCs being prepared at a temperature lower than 200 °C in organic solvent media without any additional reducing agents and suggests further research to determine whether small Ge-contained molecular clusters may be participating in this reaction as is noted for other semiconductor nanoparticle growth, such as the case of InP. 34 Figure 6 displays Ge NCs synthesized at different temperatures with the corresponding size histograms shown in SI, Figure S7.…”