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The first NLO-active metal iodate-phosphates, namely, Cd2(IO3)(PO4) and Cd1.62Mg0.38(IO3)(PO4) (1 and 2), with three types of NLO groups, have been reported. 1 and 2 are isostructural and the structure of 1 features a 3D network formed by the Cd4(IO3)8/4(PO4)6/3 groups. 1 and 2 with strong SHG signals of 4 × and 3.5 × KH2PO4 are promising SHG materials in the visible region. [ABSTRACT FROM AUTHOR]

Through systematic experiments, two novel mercury iodate sulfates, namely, Hg2(IO3)2(SO4)(H2O) and Hg2(IO3)2(SO4) were obtained. They crystallize in monoclinic space group C2 and C2/c, respectively. Hg2(IO3)2(SO4)(H2O) exhibits the [Hg(IO3)]+ polar cationic layer inherited from Hg(IO3)2 and the three‐dimensional (3D) framework inherited from HgSO4. This enables Hg2(IO3)2(SO4)(H2O) to generate a strong second harmonic generation (SHG) response of 6 times that of KH2PO4 (KDP). The structure of Hg2(IO3)2(SO4) is very similar to that of Hg2(IO3)2(SO4)(H2O), and they can be transformed into each other. Hg2(IO3)2(SO4)(H2O) shows a large optical band gap of 3.98 eV and a high dehydration temperature of 250 °C. This study indicates that by reasonable design, the introduction of multiple functional groups into a compound may combine their advantages to achieve good overall optical performance. [ABSTRACT FROM AUTHOR]

This paper comprehensively reviews 63 selenite compounds with bandgaps above 4.2 eV in four major categories. The focus is on their structures, optical properties, and design strategies, offering valuable insights for the future development of UV selenites. [Display omitted] • This article provides the first comprehensive review of UV selenite materials. • The article emphasizes the classification, structure, optical property, and design strategy of UV selenite. • We have summarized UV selenites' distribution by space group, symmetry, chemical composition, and optical properties. • We have offered guidance for UV selenites development, encompassing synthesis, design strategies, and so on. Nonlinear optical materials and birefringent materials are essential components of modern industrial technology. Selenites, owing to the unique stereochemical activity of the lone pair electrons, have a history spanning several decades as both linear and nonlinear optical materials. Up to now (January 16, 2024), nearly 1100 selenite materials have been discovered, some of which exhibit strong second-harmonic generation effects or large birefringence. With the strategic layout of nations and the rapid advancement of modern industrial technology, the demands on the transparency range of linear and nonlinear optical crystals have become increasingly stringent. Crystals transparent only in the visible spectrum are no longer adequate to meet current requirements. Selenites, which have a long history in the field, seem to have encountered a bottleneck in their recent development, primarily due to an excessive focus on their applications in the visible and near-infrared regions while neglecting their potential uses in the ultraviolet (UV) window. To explore new development directions of selenites, our research group is actively investigating their application as UV optical materials. Through a fluorination control strategy, we successfully synthesized a UV nonlinear optical crystal Y 3 F(SeO 3) 4 and a birefringent crystal CaYF(SeO 3) 2 , thereby developing the application of selenites in the UV region. Additionally, we found that some previously reported selenites with band gaps larger than 4.2 eV have not received sufficient attention from researchers, and their potential application in the UV region have been overlooked. To further promote the research progress of UV selenite materials, this paper comprehensively summarizes the reported selenite materials with bandgaps larger than 4.2 eV, totaling 63 compounds across 6 crystal systems and 19 space groups. We provide a detailed analysis of their structures, optical properties, and design strategies. These materials can be classified into four categories based on different anionic groups: simple selenites, fluoride selenites, selenites with tetrahedral groups, and other selenite compounds. Through a comprehensive review of UV selenites, we have identified ions or groups conducive to expanding the band gaps of selenites, proposed several reliable design methods for UV selenites, and offered useful suggestions for the development of UV selenites. Despite having a long history, selenite systems still hold significant untapped potential for further exploration. We hope this review provides valuable guidance and insights for the future development of inorganic selenites. [ABSTRACT FROM AUTHOR]

Exploration of new types of borates is important because of their promising applications in diverse fields. Two new boroselenites, namely, M(B(SeO3)3)H2O (M = Al, Ga), which represent the first IIIA metal boroselenite, were synthesized by hydrothermal reactions. M(B(SeO3)3)H2O (M = Al, Ga) possesses a unique sandwich like double-layer structure formed by two 2D [MSe2O8]5− layers interconnected by 1D [BSeO5]3− chains. More interestingly, both compounds display large band gaps (4.86/4.79 eV) and moderate birefringences (Δn = 0.063/0.064 at 1064 nm) based on density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

A new noncentrosymmetric iron-iodate-fluoride Ba2[FeF4(IO3)2]IO3 was ingeniously obtained based on the centrosymmetric Ba[FeF4(IO3)] through chemical tailoring. Ba2[FeF4(IO3)2]IO3 exhibits a strong phase-matchable second-harmonic generation effect, a large band gap, and a wide mid-infrared transparent window. The chemical tailoring design based on oxide-fluoride anions affords a feasible approach to design nonlinear optical materials. [ABSTRACT FROM AUTHOR]

An organic–inorganic hybrid polyiodate, namely, [o‐C5H4NHOH]2[I7O18(OH)]⋅3 H2O (I), featuring a novel branched polyiodate chain has been obtained by evaporation method. [o‐C5H4NHOH]2[I7O18(OH)]⋅3 H2O (I) crystalizes in the polar space group Ia and features an [I7O18(OH)]∞2- branched polyiodate chain in which [I3O9]3− trimers are grafted on the same side of the one‐dimensional (1D) chain based on [I4O11(OH)]3− tetramers. The asymmetric organic amine groups are beneficial to the polymerization of iodate groups and inducing the formation of the non‐centrosymmetric (NCS) structure. Compound I exhibits a rather large Second‐Harmonic‐ Generation (SHG) signal of 8.5×KH2PO4 (KDP) upon 1064 nm laser radiation, a moderate band gap of 3.90 eV and a high laser‐induced‐damage‐threshold (LIDT) of 182.34 MW cm−2, hence it is a promising new SHG material. The relationship between the structures of the organic amine groups and the overall structures has been also analyzed. [ABSTRACT FROM AUTHOR]

Two UV inorganic yttrium selenite optical materials, namely, Y(HSeO 3)(SeO 3)(H 2 O)·(H 2 O) (1) and Y 2 (SeO 3) 2 (SeO 4)(H 2 O) 2 ·(H 2 O) 0.75 (2), have been synthesized successfully by hydrothermal reactions. Of these, Y 2 (SeO 3) 2 (SeO 4)(H 2 O) 2 ·(H 2 O) 0.75 (2) is a new mixed valent selenium oxide containing Se(IV) and Se(VI) cations simultaneously. Y(HSeO 3)(SeO 3)(H 2 O)·(H 2 O) (1) shows a 3D structure composed of 2D yttrium selenite layers linked by O−H···O bonds. Y 2 (SeO 3) 2 (SeO 4)(H 2 O) 2 ·(H 2 O) 0.75 (2) exhibits a 3D structure composed of 2D yttrium selenite layers connected by SeO 4 tetrahedron. Y(HSeO 3)(SeO 3)(H 2 O)·(H 2 O) (1) crystallized in a chiral space group P 2 1 2 1 2 1 and could display a moderate SHG intensity about 0.7 times of the commercial KH 2 PO 4 (KDP). Its powder laser damage threshold quantity was estimated to be 120.2 MW/cm2, which is about 46.2 times that of AGS (2.6 MW/cm2). UV–vis–NIR spectra reflectance spectra showed that these solids are wide band gap compounds with Eg of 5.5 and 5.1 eV respectively. Theoretical calculations disclosed that Y(HSeO 3)(SeO 3)(H 2 O)·(H 2 O) (1) is an indirect band gap structures and its bandgaps is determined by O and Se atoms. [Display omitted] • Y(HSeO 3)(SeO 3)(H 2 O)•(H 2 O) is a UV NLO material in pure selenite compounds with balanced properties. • Y(HSeO 3)(SeO 3)(H 2 O)•(H 2 O) exhibits a moderate SHG intensity, wide band gap, large LIDT and moderate birefringence. • Y 2 (SeO 3) 2 (SeO 4)(H 2 O) 2 •(H 2 O) 0.75 is a new mixed valent selenium oxide containing Se(IV) and Se(VI) cations simultaneously. [ABSTRACT FROM AUTHOR]

Two mixed‐metal gallium iodate fluorides, namely, α‐ and β‐Ba2[GaF4(IO3)2](IO3) (1 and 2), have been designed by the aliovalent substitutions of α‐ and β‐Ba2[VO2F2(IO3)2](IO3) (3 and 4) involving one cationic and two anionic sites. Both 1 and 2 display large second‐harmonic generation responses (≈6×KH2PO4 (KDP)), large energy band gaps (4.61 and 4.35 eV), wide transmittance ranges (≈0.27–12.5 μm), and high relevant laser‐induced damage thresholds (29.7× and 28.3×AgGaS2, respectively), which indicates that 1 and 2 are potential second‐order nonlinear optical materials in the ultraviolet to mid‐infrared. Our studies propose that three‐site aliovalent substitution is a facile route for the discovery of good NLO materials. Trading places: Two new nonlinear optical materials, α‐ and β‐Ba2[GaF4(IO3)2](IO3) (1 and 2), were designed via three‐site aliovalent substitution of VO4F2 in α‐ and β‐Ba2[VO2F2(IO3)2](IO3) by GaO2F4. The new materials display large second‐harmonic generation responses (≈6×KH2PO4 (KDP)), wide energy band gaps (4.61 and 4.35 eV), and high laser damage thresholds (29.7× and 28.3× relative to that of AgGaS2). [ABSTRACT FROM AUTHOR]

Based on the structure related to the high-temperature superconductor yttrium-barium-copper oxide, two novel high-efficiency visible light photocatalysts were created in this study. The yttrium-barium oxide (YBO) semiconductors Y 2 Ba 3 O 6 (YB3O) and Y 2 Ba 4 O 7 (YB4O) were prepared by a copper-free solid-phase sintering method. They were applied for the effective treatment of dye-containing wastewater by photocatalysis under visible light irradiation. The degradation efficiency of methylene blue (MB) reached more than 95% within 10 min. Stable visible light degradation of methyl orange (MO) was achieved in the presence of YB3O and YB4O. The electron spin resonance technique and active substance capture technique confirmed the presence of superoxide radicals (·O 2 −), hydroxyl radicals (·OH) and holes (h VB +) under visible light illumination. UV–Vis diffuse reflectance spectroscopy analysis showed that the direct optical band gaps of YB3O and YB4O were 2.550 eV and 2.583 eV, respectively, which resulted in their high visible absorption at 486.27 nm and 480.06 nm. After five cycles, the recoveries of YB3O and YB4O reached 67.15% and 72.98%. Therefore, YB3O and YB4O are considered as powerful semiconductor catalysts for the photocatalytic degradation of organic dyes in wastewater. • Synthesis of yttrium -barium oxide (YBO) visible light catalyst. • Y 2 Ba 3 O 6 (YB3O) and Y 2 Ba 4 O 7 (YB4O) show a forbidden band width of 2.550 eV and 2.583 eV respectively. • The effective degradation of methylene blue was achieved within 10 min under visible light. • The mineralization of the total organic carbon in the degraded solutions of both dyes reached close to 80%. [ABSTRACT FROM AUTHOR]

• W vacancies containing Bi 2 WO 6 was prepared by a facile hydrothermal method. • V W -Bi 2 WO 6 was highly effective for pollutants removal under visible light. • More reductive photoelectrons were produced to accelerate surface reaction kinetics. • More holes were separated by surface W vacancies to directly degrade pollutants. • The interaction between pollutants and V W -Bi 2 WO 6 at interface was enhanced. W vacancies containing Bi 2 WO 6 (V W -Bi 2 WO 6) was synthesized by a reductant-involved hydrothermal process. The photoactivity of Bi 2 WO 6 was enhanced by 3.3 times and the TOC removal rate increased from 38.3% to 64.7% after the introduction of surface W vacancies. Positron annihilation spectrometry (PAS), XPS, Raman spectra and other characterization results indicated that W vacancies existed on the catalyst surface. The surface W vacancies were proved to widen the band gap and negatively shift CB edge to produce more O 2 •− and photoexcited holes at catalyst surface, as confirmed by ESR and radicals trapping experiments. Further, according to the results of pyridine adsorbed FTIR and Zeta potentials, the enhanced interaction between pollutants and V W -Bi 2 WO 6 was confirmed. As a result, the active species produced at surface were able to be accelerated to directly react with organic pollutants, leading to the highly efficient degradation and mineralization of pollutants in water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two novel yttrium-barium oxide photocatalysts, YBO, were discovered based on YBCO. • The energy band, density of states and charge density difference of YB3O and YB4O were analyzed and compared. • Electron spin polarization enables efficient separation of photogenerated carriers generated by YBO. • YB3O and YB4O had good semiconductor properties and photocatalytic potentials. Novel semiconductor photocatalysts are currently a hot research topic. We are inspired by the phenomenon that high-temperature superconductors can achieve superconductivity only under certain conditions (e.g., liquid nitrogen temperature). Here, based on the analysis of the energy band structure of the high-temperature superconductor YBCO (YBa 2 Cu 3 O 7-x , YBCO), two new yttrium barium oxide (YBO) semiconductor materials, Y 2 Ba 3 O 6 (YB3O) and Y 2 Ba 4 O 7 (YB4O), are reported in this study. According to first-principles calculations, we find that YB4O and YB3O have stable formation energies, as well as forbidden band gaps, which are suitable for the visible light response. In addition, YB4O possesses a larger effective mass difference of carrier and stronger electron delocalization in various directions than that of YB3O, while YB3O possesses a larger light absorption threshold than that of YB4O. These two innovative yttrium-barium oxide materials show strong semiconducting properties and have great potential as photocatalysts. [ABSTRACT FROM AUTHOR]