Ba 2 AsGaSe 5 : A New Quaternary Selenide with the Novel [AsGaSe 5 ] 4– Cluster and Interesting Photocatalytic PropertiesInorganic Chemistry


Chao Li, Xiaoshuang Li, Hongwei Huang, Jiyong Yao, Yicheng Wu
Physical and Theoretical Chemistry / Inorganic Chemistry


Ba2AsGaSe5: A New Quaternary Selenide with the Novel [AsGaSe5] 4−

Cluster and Interesting Photocatalytic Properties

Chao Li,†,‡,§ Xiaoshuang Li,†,‡,§ Hongwei Huang,∥ Jiyong Yao,*,†,‡ and Yicheng Wu†,‡ †Center for Crystal Research and Development and ‡Key Laboratory of Functional Crystals and Laser Technology, Technical

Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China §University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China ∥Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes, National Laboratory of Mineral Materials,

School of Materials Science and Technology, China University of Geosciences, Beijing 100083, People’s Republic of China *S Supporting Information

ABSTRACT: The new zero-dimensional selenide

Ba2AsGaSe5 was synthesized via a solid-state reaction at 900 °C. It belongs to the orthorhombic space group Pnma with a = 12.632(3) Å, b = 8.9726(18) Å, c = 9.2029(18) Å, and Z = 4.

In the structure, the As atom adopts trigonal-pyramidal coordination owing to the stereochemically active 4s2 lone pair electrons and the Ga atom is tetrahedrally coordinated with four Se atoms. The AsSe3 trigonal pyramids share edges with GaSe4 tetrahedra to form novel [AsGaSe5] 4− clusters, which are further separated from each other by Ba2+ cations.

The optical band gap was determined as 1.39 eV according to

UV−vis−NIR diffuse reflectance spectroscopy. Interestingly, the photocatalytic behavior investigated by decomposing rhodamine B indicates that the compound displays a 6.5 times higher photocatalytic activity than does P25. ■ INTRODUCTION

Low-dimensional structures are of great interest due to their intriguing structures and important electrical, optical, and magnetic properties.1−10 From a structural point of view, lowdimensional structures result from the coexistence and separation of several building units with different bonding nature (covalent, ionic, or van der Waals) in one compound.

The interplay of these different bonding units gives the materials unique properties. For instance, the LnFeOPn (Ln = rare-earth metal; Pn = P, As) oxypnictinide superconductors contain alternately stacked ionic Ln2O2 layers and covalent

Fe2Pn2 layers. 11 The electron or hole doping is achieved by varying the elements in the Ln2O2 layers, which may induce further change in the electronic structure of the Fe2Pn2 layer,. the main structural unit for the superconducting performance, thus significantly influencing the superconducting behavior.

Similarly, in the p-type transparent conducting material

LnCuOTe (Ln = La, Ce, Nd)12 and BaCuQF (Q = S, Se),13 the hole conduction is realized via the covalent Cu2Q2 layers, which form the valence band maximum, whereas the large band gap and the high transparent quality are maintained through the ionic Ln2O2 or Ba2F2 layers confining the Cu−S bonds in the

CuS layers.

In comparison with the large number of two-dimensional (2D) and one-dimensional (1D) structures, the number of zero-dimensional (0D), e.g. “molecular”, inorganic compounds is much smaller. Furthermore, inorganic 0D compounds, often synthesized via high-temperature solid-state reactions, contain anions with simple structures, such as the [BO3] 3− triangles in

Na3BO3 14 and Ca4LnO(BO3)3 (Ln = rare-earth metal), 15 the [AsS3] 3− trigonal pyramids in Pr4As2S9, 16 the [GeCl3] − trigonal pyramids in CsGeCl3, 17 the tetrahedral [WS4] 2− in A2WS4 (A =

Cs, Rb)18 and [MSe4] 5− in Ba5M2Se8 (M = Al, Ga), 19 the [Ga2S7] 8− anion (two tetrahedra with a common corner) in

Ba4Ga2S7, 20 the [U2I10] 2− anion (two octahedra with a common edge) in [Ta7(Se2)14][U2I10]2, 21 and the [B3O6] 3− anion (three triangles with three common corners) in the commercial NLO crystal β-BaB2O4 (BBO). 22 In recently years, many interesting and more complex anions have been discovered as a result of the development of the synthesis methods.23 For example, the novel uranyl sulfide Na2Ba2(UO2)S4 24 comprises isolated centrosymmetric [(UO2)S4] 6− anions that are surrounded by

Na+ and Ba2+ cations and Cs5[U2(μ-S2)2Cl8]I 25 contains the [U2(μ-S2)2Cl8] 4− anion with two US4Cl4 square antiprisms sharing two common S2 2− anions, while Cs5P5Se12 26 contains [P5Se12] 5− anions featuring an octahedrally coordinated P3+ cation surrounded by two ethane-like [P2Se6] 4− units and exhibits a second harmonic generation response.

In the search for new As-containing chalcogenides, we discovered a 0D quaternary selenide, namely Ba2AsGaSe5, through a solid-state reaction.27 It displays discrete unpreceReceived: July 4, 2015

Article © XXXX American Chemical Society A DOI: 10.1021/acs.inorgchem.5b01501

Inorg. Chem. XXXX, XXX, XXX−XXX dented [AsGaSe5] 4− anions consisting of edge-shared GaSe4 tetrahedra and AsSe3 trigonal pyramids. Furthermore, inspired by the research that many compounds containing cations with electron lone pairs demonstrate excellent photocatalytic activities,28−30 we studied the photocatalytic performance of

Ba2AsGaSe5. Interestingly, the compound exhibits a photocatalytic activity to RhB about 6.5 times that of P25. ■ EXPERIMENTAL SECTION

Syntheses. All elements, including Ba (3N), As (4N), Ga (5N), and Se (6N), were obtained from Sinopharm Chemical Reagent Co.,

Ltd., and used without further purification. BaSe, As2Se3, and Ga2Se3 were first synthesized by traditional solid-state reactions of the elements in sealed silica tubes at temperatures of 620, 450, and 980 °C, respectively.

Crystal Growth of Ba2AsGaSe5. A mixture of 0.5 mmol of BaSe, 0.125 mmol of As2Se3, and 0.125 mmol of Ga2Se3 was ground in a glovebox and loaded into a fused-silica tube. The tube was then evacuated to a high vacuum of 10−3 Pa atmosphere and sealed.

Afterward, the sample was heated in a resistance furnace to 900 °C in 15 h and kept at that temperature for 48 h. After the reaction, the sample was slowly cooled at 3 °C/h to 350 °C, and then the furnace was shut off. The resultant air-stable chip black crystals were manually selected for structure characterization. Elemental analysis of the crystals was performed on an EDX-equipped Hitachi S-4800 SEM instrument, and the results showed that the crystals consisted of