Light absorption engineering of a hybrid (Sn3S72−)n based semiconductor – from violet to red light absorption

Abstract

The crystalline two-dimensional thiostannate Sn3S7(trenH)2 [tren = tris(2-aminoethyl)amine] consists of negatively charged (Sn3S72−)n polymeric sheets with trenH+ molecular species embedded in-between. The semiconducting compound is a violet light absorber with a band gap of 3.0 eV. In this study the compound was synthesized and functionalized by introducing the cationic dyes Methylene Blue (MB) or Safranin T (ST) into the crystal structure by ion exchange. Dye capacities up to approximately 45 mg/g were obtained, leading to major changes of the light absorption properties of the dye stained material. Light absorption was observed in the entire visible light region from red to violet, the red light absorption becoming more substantial with increasing dye content. The ion exchange reaction was followed in detail by variation of solvent, temperature and dye concentration. Time-resolved studies show that the ion exchange follows pseudo-second order kinetics and a Langmuir adsorption mechanism. The pristine and dye stained compounds were characterized by powder X-ray diffraction and scanning electron microscopy revealing that the honeycomb hexagonal pore structure of the host material was maintained by performing the ion exchange in the polar organic solvent acetonitrile, while reactions in water caused a break-down of the long-range ordered structure.

The structure-directing amine changes everything: structures and optical properties of two-dimensional thiostannates

“…Pienack et al refer to the cation as trenH + suggesting a protonated amine (Pienack et al, 2012). We have recently investigated the nature of the cation in tren-SnS-1 by solid-state 13 C NMR spectroscopy confirming it to be mainly trenH + in addition to a minor fraction of another compound, probably formed by decomposition (Hvid et al, 2017). By applying the solvent-masking procedure SQUEEZE (Spek, 2003) to the single-crystal diffraction data, the total solvent accessible void was estimated to be 2005 Å 3 per unit cell out of the unit cell volume of 2923 Å 3 .…”

“…The electron count in the voids was estimated to be 578 electrons per unit cell. While each trenH + contains 82 electrons (corresponding to 7.0 trenH + per unit cell), the trenH + content is underestimated by one trenH + per cell compared with the formal stoichiometry of (trenH) 2 Sn 3 S 7 (Table 1) as suggested by Pienack et al (2012) and Hvid et al (2017). Alternatively, the underestimated trenH + either supports the finding of a low concentration of a cationic decomposition product (Hvid et al, 2017) in the compound or that some cations are protonated at two sites.…”

“…À0.59 † Estimated composition according to results byPienack et al (2012) andHvid et al (2017). By applying SQUEEZE (Spek, 2003), a non-described electron density of 578 electrons per unit cell resulted, corresponding to seven trenH + molecules per unit cell.…”

Alkylammonium thiostannate inorganic/organic hybrids as high-performance photocatalysts with a decoupled adsorption–photodegradation mechanism

“…Meanwhile, it has been reported that organic cationic dyes, such as Methylene Blue (MB) or Safranin T (ST), have been introduced into the crystalline structure of 2D thiostannate (trenH) 2 Sn 3 S 7 (tren ¼ tris(2-aminoethyl)amine) by ion exchange with an adsorption capacity of 45 mg g À1 . 29 This revealed that the oleophility of the interlayered alkylammonium would be favourable to enhance the adsorption of organic contaminants and, replacing shorter chain alkylammonium with longer chain alkylammonium in the hybrid should be reasonable to enhance this adsorption. Furthermore, if the hybrid possesses an ion-exchange and photocatalytic ability at the same time, the organic pollutants could be further thoroughly degraded in an environmental-friendly way.…”

Directed Dehydration as Synthetic Tool for Generation of a New Na4SnS4 Polymorph: Crystal Structure, Na+ Conductivity, and Influence of Sb‐Substitution

“…Thiostannates with metal cations as counter ions were mainly synthesized using the molten‐flux approach, [13, 14] or via high‐temperature syntheses [15–19] . Thiostannates with protonated amine molecules, transition metal cations, or transition metal complexes as counter ions compensating the negative charge of the [Sn x S y ] n − anions were mostly prepared under solvothermal conditions [9, 20–35] . Applying suitable precursors, the preparation of thiostannates at room temperature was also reported [36–41] .…”