Surface coordination chemistry of germanium nanocrystals synthesized by microwave-assisted reduction in oleylamine

Smock, Sara R.; Tabatabaei, Katayoon; Williams, Travis J.; Kauzlarich, Susan M.; Brutchey, Richard L.

doi:10.1039/c9nr09233a

Cited by 12 publications

(21 citation statements)

References 36 publications

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“…The peak near 2.89 ppm is attributed to the α protons, which are deshielded by the terminal amine group, causing the peak to shift from the expected position at 2.6 ppm. , Peaks for the alkyl chain and terminal methyl groups are found at 1.24 and 0.85 ppm, respectively, and are broadened relative to those of the free ligand. Peak shifting and broadening indicate a ligand–surface interaction and have been attributed to poor solvation of the ligand shell, slow rotation of bound ligands, and heterogeneous particle size. − In free OAm, the chemical shift from the amine proton is found at 1.05 ppm, but it is not observed for OAm-capped Ge NCs; this is consistent with previous observations for amine ligands on the surface of Ge and ZnO NCs and may be attributed to rapid exchange of the acidic proton or broadening due to close proximity to the NC surface. ,,, Peaks at 2.33 and 1.52 ppm are attributed to toluene and water impurities in the NMR solvent, respectively …”

Section: Resultssupporting

confidence: 85%

“…The surface ligand capping was characterized to consist of a mixture of weaker L-type oleylamine ligands and stronger X-type oleylamide ligands. It was recently demonstrated that OAm binds to the surface of Ge NCs as an X-type oleylamide ligand (Ge–NHR bonding), but physiosorbed OAm may also be present . Upon introduction of undecenethiol to the OAm-capped Ge NCs, thiol binding as an X-type thiolate ligand was observed.…”

Section: Resultsmentioning

confidence: 99%

“…It was recently demonstrated that OAm binds to the surface of Ge NCs as an X-type oleylamide ligand (Ge−NHR bonding), but physiosorbed OAm may also be present. 26 Upon introduction of undecenethiol to the OAm-capped Ge NCs, thiol binding as an X-type thiolate ligand was observed. There was no observed loss of OAm; thus, it was concluded that the thiol occupies uncoordinated surface sites rather than displaces OAm.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

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Diorganyl Dichalcogenides as Surface Capping Ligands for Germanium Nanocrystals

Newton

Tabatabaei

et al. 2020

Organometallics

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Indirect ligand exchange methods have been demonstrated to replace the oleylamine capping with dodecanethiol for germanium nanocrystals (Ge NCs). In these methods, hydrazine is employed to effectively remove the oleylamine ligand before the NCs are passivated by microwave-assisted heating with dodecanethiol. In this work, octadecanethiol passivation is accomplished by the in situ reaction of dioctadecyl disulfide with diphenylphosphine. 1H NMR and FTIR are used to characterize the surface ligand capping and the effectiveness of ligand exchange. Thiol passivation is achieved either by an exchange reaction at room temperature or by using microwave-assisted heating. Indirect and direct ligand exchange methods are demonstrated to be effective. The microwave-assisted reaction of GeI2 with dioctadecyl disulfide also achieves thiol passivation without interfering in the formation of Ge NCs. Additional experiments study the effects of nanoparticle synthesis temperature, solvent, and ligand concentration on the exchange of oleylamine for octadecanethiol ligands.

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Section: Resultssupporting

confidence: 85%

Section: Resultsmentioning

confidence: 99%

Section: ■ Experimental Sectionmentioning

confidence: 99%

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Diorganyl Dichalcogenides as Surface Capping Ligands for Germanium Nanocrystals

Newton

Tabatabaei

et al. 2020

Organometallics

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“…Two distinct fractions of both weakly physisorbed and strongly covalent X-type bonded OAm on the Ge surface were resolved by exchange reactions with different functional groups (amines/ammonium, thiols, and carboxylic acids). It was shown that their fraction ratio directly correlates with the reaction temperature . The broadening of NMR peaks and the chemical shifts slightly downfield compared to unbounded ligands are characteristic for nanomaterials. , The 31 P NMR signal at −32.2 ppm compared to −30.6 ppm of free TOP confirms the binding of TOP on the Ge NCs surface.…”

Section: Resultsmentioning

confidence: 87%

“…1 H and 31 P NMR were performed on OAm/TOP and DDT-capped Sb-doped Ge NCs (Figures , ). The absence of a vinylic proton peak between 5 and 6 ppm indicates the complete removal of OAm ligands through hydrazine treatment. , Recently, we reported a detailed solution NMR study on OAm-capped Ge NCs synthesized at different temperatures to determine the binding mode of this native primary amine on the Ge surface . Two distinct fractions of both weakly physisorbed and strongly covalent X-type bonded OAm on the Ge surface were resolved by exchange reactions with different functional groups (amines/ammonium, thiols, and carboxylic acids).…”

Section: Resultsmentioning

confidence: 99%

Structural Insights on Microwave-Synthesized Antimony-Doped Germanium Nanocrystals

Tabatabaei

Sully

et al. 2021

ACS Nano

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Doped and alloyed germanium nanocrystals (Ge NCs) are potential candidates for a variety of applications such as photovoltaics and near IR detectors. Recently, bismuth (Bi) as an n-type group 15 element was shown to be successfully and kinetically doped into Ge NCs through a microwave-assisted solution-based synthesis, although Bi is thermodynamically insoluble in bulk crystalline Ge. To expand the composition manipulation of Ge NCs, another more common n-type group 15 element for semiconductors, antimony (Sb), is investigated. Oleylamine (OAm)- and OAm/trioctylphosphine (TOP)-capped Sb-doped Ge NCs have been synthesized by the microwave-assisted solution reaction of GeI2 with SbI3. Passivating the Ge surface with a binary ligand system of OAm/TOP results in formation of consistently larger NCs compared to OAm alone. The TOP coordination on the Ge surface is confirmed by 31P NMR and SEM-EDS. The lattice parameter of Ge NCs increases with increasing Sb concentration (0.00–2.0 mol %), consistent with incorporation of Sb. An increase in the NC diameter with higher content of SbI3 in the reaction is shown by TEM. XPS and EDS confirm the presence of Sb before and after removal of surface ligands with hydrazine and recapping the Ge NC surface with dodecanethiol (DDT). EXAFS analysis suggests that Sb resides within the NCs on highly distorted sites next to a Ge vacancy as well as on the crystallite surface. High Urbach energies obtained from photothermal deflection spectroscopy (PDS) of the films prepared from pristine Ge NC and Sb-doped Ge NCs indicate high levels of disorder, in agreement with EXAFS data. Electrical measurements on TiO2–NC electron- and hole-only devices show an increase in hole conduction, suggesting that the Sb-vacancy defects are behaving as a p-type dopant in the Ge NCs, consistent with the vacancy model derived from the EXAFS results.

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Characterization of Germanium Nanoparticles from Arylgermanium Trihydrides

Schmid,

Bitschnau,

Finšgar

et al. 2024

Chemistry A European J

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Germanium is a promising basis for nanomaterials due to its low toxicity and valuable optical and electronic properties. However, germanium nanomaterials have seen little research compared to other group 14 elements due to unpredictable chemical behavior and high costs. Here, we report the dehydrocoupling of o‐tolylgermanium trihydride to amorphous nanoparticles. The reaction is facilitated through reflux at 162 °C and can be accelerated with an amine base catalyst. Through cleavage of both H2 and toluene, new Ge‐Ge bonds form. This results in nanoparticles consisting of crosslinked germanium with o‐tolyl termination. The particles are 2‐6 nm in size and have masses above approximately 3500 Da. The organic substituents are promising for further functionalization. Combined with strong absorption up to 600 nm and moderate solubility and air stability, there are numerous possibilities for future applications.

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Surface coordination chemistry of germanium nanocrystals synthesized by microwave-assisted reduction in oleylamine

Abstract: Comprehensive solution NMR experiments reveal the binding modes of the native ligands to Ge nanocrystals synthesized via microwave-assisted reduction in oleylamine.

Cited by 12 publications

References 36 publications

Diorganyl Dichalcogenides as Surface Capping Ligands for Germanium Nanocrystals

Diorganyl Dichalcogenides as Surface Capping Ligands for Germanium Nanocrystals

Structural Insights on Microwave-Synthesized Antimony-Doped Germanium Nanocrystals

Characterization of Germanium Nanoparticles from Arylgermanium Trihydrides

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