Laser Ablation Synthesis of Gold Selenides by using a Mass Spectrometer as a Synthesizer: Laser Desorption Ionization Time-of-Flight Mass Spectrometry

Laser ablation synthesis of tellurium carbides using tellurium with nanodiamond nanocomposite

RATIONALE

Carbides, including tellurium carbides (TeC), play crucial roles in diverse applications, but TeC synthesis has not been described in the literature. Laser ablation synthesis (LAS) coupled with mass spectrometry was used here for in situ TeC clusters synthesis and identification of the reaction products to better understand TeC formation.

METHODS

Laser desorption ionization time-of-flight mass spectrometry (LDI-TOFMS) was used to generate the TeC clusters and determine their stoichiometry via computer modeling of isotopic patterns.

RESULTS

A simple one-pot procedure was developed for Te-nanodiamond nanocomposite preparation. A suspension of fine-powdered Te was mixed with a suspension of nanodiamonds (both in acetonitrile), and the resulting precipitated nanocomposite was suitable for the synthesis of TemC_n clusters using LDI. Various unary and binary clusters were formed. The stoichiometry of the novel TemC_n clusters, determined via computer modeling of isotopic patterns, is reported here for the first time.

CONCLUSIONS

The Te-nanodiamond composite was found to be the most suitable precursor for the generation of TemC_n clusters. In total, 35 binary TemC_n clusters were identified, when several of them were not obtained using commercial TeC material.

Gallium selenide clusters generated via laser desorption ionisation quadrupole ion trap time-of-flight mass spectrometry

RATIONALE

Gallium selenide thin films important for electronics and phase-change materials are prepared via pulsed laser deposition (PLD); however, there are no studies concerning the analysis of gallium selenide clusters formed in the gas phase. Laser desorption ionisation (LDI) combined with time-of-flight mass spectrometry (TOF-MS) has great potential to generate charged Ga_m Se_n clusters, to analyse them and thus to develop new materials.

METHODS

LDI of Ga-Se mixtures using a pulsed laser (337 nm nitrogen) was used to generate gallium-selenide clusters. Mass spectra were recorded (in positive and negative ion mode) on a TOF mass spectrometer equipped with a quadrupole ion trap and reflectron mass analyser.

RESULTS

Ga-Se mixtures were found to be suitable for laser ablation synthesis (LAS) of gallium selenide clusters, although their composition was strongly dependent on the laser energy. The effect of laser energy on the stoichiometry of the generated clusters was established. In total, over 100 gallium selenide Ga_m Se_n clusters were generated and identified from Ga-Se mixtures. LDI of Ga₂ Se₃ crystals showed almost the same clusters up to m/z 1000 with lower intensities, whereas no clusters from Ga₂ Se₃ were observed above m/z 1000.

CONCLUSIONS

A family of over 100 gallium selenide clusters, generated and identified for the first time, shows rich and complex chemistry. Some of the clusters represent new compounds that have the potential to be used in the development of advanced materials.

Laser Ablation Generation of Antimony Selenide Clusters: Laser Desorption Ionization (LDI) Quadrupole Ion Trap Time of Flight Mass Spectrometry

The binary system Sb-Se was studied via laser ablation using antimony-selenium mixtures made from powdered elements in various ratios generating new Sb_mSe_n clusters. The results show that in addition to Sb_m⁺ (m = 1-8) and Se_n⁺ (n = 2-9) clusters, a series of Sb_mSe_n⁺ clusters such as SbSe_1-8⁺, Sb₂Se_1-6⁺, Sb₃Se_1-5⁺, Sb₄Se_1-3⁺, and Sb₅Se_1,2⁺ is generated. In addition, some low intensity oxidized clusters like Se₆O₂⁺, Se₇O₂⁺, and SbSe_2-6O₅⁺ and partially hydroxylated clusters (SbSeO₂H₇⁺, SbSe₅O₄H⁺) are also formed. In total, 24 new antimony selenide clusters were generated. The knowledge gained can contribute to the elucidation of the structure of Sb_mSe_n glasses. Graphical Abstract.

Colloidal and Deposited Products of the Interaction of Tetrachloroauric Acid with Hydrogen Selenide and Hydrogen Sulfide in Aqueous Solutions

The reactions of aqueous gold complexes with H2Se and H2S are important for transportation and deposition of gold in nature and for synthesis of AuSe-based nanomaterials but are scantily understood. Here, we explored species formed at different proportions of HAuCl4, H2Se and H2S at room temperature using in situ UV-vis spectroscopy, dynamic light scattering (DLS), zeta-potential measurement and ex situ Transmission electron microscopy (TEM), electron diffraction, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Metal gold colloids arose at the molar ratios H2Se(H2S)/HAuCl4 less than 2. At higher ratios, pre-nucleation “dense liquid” species having the hydrodynamic diameter of 20–40 nm, zeta potential −40 mV to −50 mV, and the indirect band gap less than 1 eV derived from the UV-vis spectra grow into submicrometer droplets over several hours, followed by fractional nucleation in the interior and coagulation of disordered gold chalcogenide. XPS found only one Au+ site (Au 4f7/2 at 85.4 eV) in deposited AuSe, surface layers of which partially decomposed yielding Au0 nanoparticles capped with elemental selenium. The liquid species became less dense, the gap approached 2 eV, and gold chalcogenide destabilized towards the decomposition with increasing H2S content. Therefore, the reactions proceed via the non-classical mechanism involving “dense droplets” of supersaturated solution and produce AuSe1−xSx/Au nanocomposites.

Chalcogen-atom transfer and exchange reactions of NHC-stabilized heavier silaacylium ions

Heavier analogues of silaacylium ions 2-4 ([m-TerSiE(NHC)₂]Cl; m-Ter = 2,6-Mes₂C₆H₃; Mes = 2,4,6-Me₃C₆H₂; 2 (E = S), 3 (E = Se), 4 (E = Te)) were synthesized by the reaction of the NHC-stabilized silyliumylidene cation 1 with elemental chalcogens. Fascinating regeneration of 1 from the reaction of 2-4 with AuI was achieved, as successful recovery of a parent Si(ii) species from a silachalcogen Si(iv) compound. Furthermore, unique chalcogen exchange reactions from 4 → 3 → 2 were observed in line with the calculated silicon-chalcogen bond energies.