Tin(IV) Chalcogenide Complexes: Single Source Precursors for SnS, SnSe and SnTe Nanoparticle Synthesis

Single source precursor route to nanometric tin chalcogenides

Low-temperature solution phase synthesis of nanomaterials using designed molecular precursors enjoys tremendous advantages over traditional high-temperature solid-state synthesis. These include atomic-level control over stoichiometry, homogeneous elemental dispersion and uniformly distributed nanoparticles. For exploiting these advantages, however, rationally designed molecular complexes having certain properties are usually required. We report here the synthesis and complete characterization of new molecular precursors containing direct Sn-E bonds (E = S or Se), which undergo facile decomposition under different conditions (solid/solution phase, thermal/microwave heating, single/mixed solvents, varying temperatures, etc.) to afford phase-pure or mixed-phase tin chalcogenide nanoflakes with defined ratios.

Low temperature CVD of thermoelectric SnTe thin films from the single source precursor, [nBu3Sn(TenBu)]

This work has demonstrated that the single source precursor [nBu3Sn(TenBu)], bearing n-butyl groups and containing the necessary 1 : 1 Sn : Te ratio, facilitates growth of continuous, stoichiometric SnTe thin films. This single source CVD precursor allows film growth at significantly lower temperatures (355-434 °C at 0.01-0.05 Torr) than required for CVD from SnTe powder. This could be advantageous for controlling the surface states in topological insulators. The temperature-dependent thermoelectric performance of these films has been determined, revealing them to be p-type semiconductors with peak Seebeck coefficient and power factor values of 78 μV K-1 and 8.3 μW K-2 cm-1, respectively, at 615 K; comparing favourably with data from bulk SnTe. Further, we have demonstrated that the precursor facilitates area selective growth of SnTe onto the TiN regions of SiO2/TiN patterned substrates, which is expected to be beneficial for the fabrication of micro-thermoelectric generators.

The Frontiers of Nanomaterials (SnS, PbS and CuS) for Dye-Sensitized Solar Cell Applications: An Exciting New Infrared Material

To date, extensive studies have been done on solar cells on how to harness the unpleasant climatic condition for the binary benefits of renewable energy sources and potential energy solutions. Photovoltaic (PV) is considered as, not only as the future of humanity's source of green energy, but also as a reliable solution to the energy crisis due to its sustainability, abundance, easy fabrication, cost-friendly and environmentally hazard-free nature. PV is grouped into first, second and third-generation cells. Dye-sensitized solar cells (DSSCs), classified as third-generation PV, have gained more ground in recent times. This is linked to their transparency, high efficiency, shape, being cost-friendly and flexibility of colour. However, further improvement of DSSCs by quantum dot sensitized solar cells (QDSSCs) has increased their efficiency through the use of semiconducting materials, such as quantum dots (QDs), as sensitizers. This has paved way for the fabrication of semiconducting QDs to replace the ideal DSSCs with quantum dot sensitized solar cells (QDSSCs). Moreover, there are no absolute photosensitizers that can cover all the infrared spectrum, the infusion of QD metal sulphides with better absorption could serve as a breakthrough. Metal sulphides, such as PbS, SnS and CuS QDs could be used as photosensitizers due to their strong near infrared (NIR) absorption properties. A few great dependable and reproducible routes to synthesize better QD size have attained much ground in the past and of late. The injection of these QD materials, which display (NIR) absorption with localized surface plasmon resonances (SPR), due to self-doped p-type carriers and photocatalytic activity could enhance the performance of the solar cell. This review will be focused on QDs in solar cell applications, the recent advances in the synthesis method, their stability, and long term prospects of QDSSCs efficiency.

Isolation of a Diylide-Stabilized Stannylene and Germylene: Enhanced Donor Strength through Coplanar Lone Pair Alignment

The preparation of the first stable diylide‐substituted stannylene and germylene (Y₂E, with E=Ge, Sn and Y=[PPh₃‐C‐SO₂Tol]⁻) is reported. The synthesis is easily accomplished in one step from the sulfonyl‐substituted metalated ylide YNa and the corresponding ECl₂ precursors. Y₂Ge and Y₂Sn exhibit unusual structures in the solid state and in solution, in which the three adjacent lone pairs in the C‐E‐C linkage are arranged coplanar to each other. As shown by DFT studies, this bonding situation is preferred over the typical π‐donation from the ligands into the empty p‐orbital at the metal due to the strong anion‐stabilizing ability of the sulfonyl groups in the ylide backbone and their additional coordination to the metal. The alignment of the three lone pairs leads to a remarkable boost of the HOMO energy and thus of the donor strengths of the tetrylenes. Hence, Y₂Ge and Y₂Sn become stronger donors than their diamino or diaryl congeners and comparable to cyclic alkyl(amino)carbenes. First reactivity studies confirm the high reactivity of Y₂Ge and Y₂Sn, which for example undergo an intramolecular C−H activation reaction via metal–ligand cooperation.

Effect of Temperature and Capping Agents on Structural and Optical Properties of Tin Sulphide Nanocrystals

SnS nanocrystals were synthesized using bis(phenylpiperazine dithiocarbamate)tin(II) in oleic acid (OA) and octadecylamine (ODA) at three different temperatures (150, 190, and 230°C). XRD diffraction pattern confirms that OASnS and ODASnS nanoparticles are in the orthorhombic phase and the type of capping agent used affects the crystallinity. Transmission electron microscopy (TEM) images shows spherically shaped nanocrystals for oleic acid capped SnS (OASnS) while octadecylamine (ODASnS) are cubic. Monodispersed SnS of size range 10.67–17.74 nm was obtained at 150°C for OASnS while the biggest-sized nanocrystals were obtained at 230°C for ODASnS. Temperature and capping agents tuned the crystallite sizes and shapes of the as-prepared nanocrystals. Electron dispersive X-ray spectroscopy indicates the formation of tin sulphide with the presence of Sn and S peaks in the nanocrystals. Flowery and agglomerated spherical-like morphology were observed for ODASnS and OASnS nanocrystals, respectively, using a SEM (scanning electron microscope). Direct electronic band gaps of the synthesized SnS nanocrystals are 1.71–1.95 eV and 1.93–2.81 eV for OASnS and ODASnS nanocrystals, respectively.

Chlorogermylenes and -stannylenes stabilized by diimidosulfinate ligands: synthesis, structures, and reactivity

The reaction of the lithium salt of N,N'-di-tert-butyldiimidosulfinate ([PhS(N^tBu)₂]Li) having a phenyl group on the sulphur atom with ECl₂·(dioxane) (E = Ge, Sn) afforded the corresponding chlorogermylene [PhS(N^tBu)₂]GeCl 1 and -stannylene [PhS(N^tBu)₂]SnCl 2, respectively. In contrast, treatment of the N,N'-bis(trimethylsilyl)diimidosulfinate ion ([PhS(NSiMe₃)₂]^-) with ECl₂·(dioxane) resulted in the unexpected formations of six-membered 1,3-bis(chlorogermylene) [PhS(NSiMe₃)₂(η¹-η¹-GeCl)₂[μ-NSPh(NHSiMe₃)] 7 and -stannylene [PhS(NSiMe₃)₂(η¹-η¹-SnCl)₂[μ-NSPh(NHSiMe₃)] 8. The structures of these chlorometallylene derivatives were fully characterized on the basis of their NMR spectroscopic data and X-ray diffraction. In the crystalline states of 1 and 2, the diimidosulfinate ligands chelate to the metal centre to form slightly hinged four-membered EN₂S rings. On the other hand, X-ray analyses of 7 and 8 revealed that the central six-membered E₂N₃S rings adopt a distorted boat-conformation, and one diimidosulfinate ligand coordinates to the metal centre in a bridging monodentate μ-η¹-η¹-fashion. As the reactivity of 1 and 2, the oxidation of 1 with elemental chalcogen (S₈ or Se) afforded the corresponding tetra-coordinated germanium compounds [PhS(N^tBu)₂]Ge([double bond, length as m-dash]Ch)Cl 3 (Ch[double bond, length as m-dash]S) and 4 (Ch[double bond, length as m-dash]Se). In sharp contrast, the reactions of 2 with elemental chalcogen resulted in the formation of four-membered Sn₂Ch₂ ring compounds, 1,3,2,4-dichalcogenadistannetanes {(PhS(N^tBu)₂)SnCl(μ-Ch)}₂5 (Ch[double bond, length as m-dash]S) and 6 (Ch[double bond, length as m-dash]Se).