Polysulfide Chalcogels with Ion-Exchange Properties and Highly Efficient Mercury Vapor Sorption

We report the synthesis of metal–chalcogenide aerogels from Pt²⁺ and polysulfide clusters ([S_<i>x</i>]^2–, <i>x</i> = 3–6). The cross-linking reaction of these ionic building blocks in formamide solution results in spontaneous gelation and eventually forms a monolithic dark brown gel. The wet gel is transformed into a highly porous aerogel by solvent exchanging and subsequent supercritical drying with CO₂. The resulting platinum polysulfide aerogels possess a highly porous and amorphous structure with an intact polysulfide backbone. These chalcogels feature an anionic network that is charged balanced with potassium cations, and hosts highly accessible S–S bonding sites, which allows for reversible cation exchange and mercury vapor capture that is superior to any known material

CsHgInS₃: a New Quaternary Semiconductor for γ‑ray Detection

The new layered compound CsHgInS₃ was synthesized using solid state and flux synthesis techniques. The compound is a semiconductor and shows promising properties for X-ray and γ-ray detection. It features a layered structure that crystallizes in the monoclinic space group <i>C</i>2/<i>c</i> with cell parameters: <i>a</i> = 11.2499(7) Ǻ, <i>b</i> = 11.2565(6) Ǻ, <i>c</i> = 22.146(1) Ǻ, β = 97.30(5)°, <i>V</i> = 2781.8(4) Ǻ³, and <i>Z</i> = 8. CsHgInS₃ is isostructural to Rb₂Cu₂Sn₂S₆, where the Hg, In, and Cs atoms occupy the Cu, Sn, and Rb sites, respectively. Large single crystals with dimension up to 5 mm were grown with a vertical Bridgman method as well as a horizontal traveling heater method. CsHgInS₃ has a γ-ray attenuation length comparable to commercial Cd_1–<i>x</i>Zn_<i>x</i>Te and a band gap value of 2.30 eV. The electrical resistivity of CsHgInS₃ is anisotropic with values of 98 GΩ cm and 0.33 GΩ cm perpendicular and parallel to the (001) plane, respectively. The mobility-lifetime product (<i>μτ</i>) of electrons and holes estimated from photoconductivity measurements on the as-grown crystals were (<i>μτ</i>)_e = 3.6 × 10^–5 cm² V^–1 and (<i>μτ</i>)_h = 2.9 × 10^–5 cm² V^–1, respectively. Electronic structure calculations at the Density Functional Theory level were performed based on the refined crystal structure of CsHgInS₃ and show a direct gap with the conduction band near the Fermi level being highly dispersive, suggesting a relatively small carrier effective mass for electrons

CsCdInQ₃ (Q = Se, Te): New Photoconductive Compounds As Potential Materials for Hard Radiation Detection

Two new compounds CsCdInQ₃ (Q = Se, Te) have been synthesized using a polychalcogenide flux. CsCdInQ₃ (Q = Se, Te) crystals are promising candidates for X-ray and γ-ray detection. The compounds crystallize in the monoclinic <i>C</i>2/<i>c</i> space group with a layered structure, which is related to the CsInQ₂ (Q = Se, Te) ternary compounds. The cell parameters are: <i>a</i> = 11.708(2) Å, <i>b</i> = 11.712(2) Å, <i>c</i> = 23.051(5) Å, β = 97.28(3)° for CsCdInSe₃ and <i>a</i> = 12.523(3) Å, <i>b</i> = 12.517(3) Å, <i>c</i> = 24.441(5) Å, β = 97.38(3)° for CsCdInTe₃. Both the Se and Te analogues are wide-band-gap semiconductors with optical band gaps of 2.4 and 1.78 eV for CsCdInSe₃ and CsCdInTe₃, respectively. High-purity polycrystalline raw material for crystal growth was synthesized by the vapor transfer method for CsCdInQ₃. Large single crystals up to 1 cm have been grown using the vertical Bridgman method and exhibit photoconductive response. The electrical resistivity of the crystals is highly anisotropic. The electronic structure calculation within the density functional theory (DFT) framework indicates a small effective mass for the carriers. Photoconductivity measurements on the as grown CsCdInQ₃ crystals gives high carrier mobility-lifetime (μτ) products comparable to other detector materials such as α-HgI₂, PbI₂, and Cd_<i>x</i>Zn_1–<i>x</i>Te (CZT)