In this communication, the novel nonlinear optical crystal material Cd(4)BiO(BO(3))(3) with 3-chromophore asymmetric structures of CdO(n), BiO(6), and BO(3) groups has been prepared by a flux method, and the single crystal structure has been determined with the space group Cm. It is the largest NLO coefficient for Cd(4)BiO(BO(3))(3) among borate systems, and the strong NLO response originates from cooperation effects of the 3-chromophore asymmetric structures composed of the polar displacement of d(10) Cd(2+) ion, stereochemically active lone pair of Bi(3+), and pi-delocalization of BO(3). These evidence are provided in view of evaluations of calculated density of states and electron-density difference maps. The experimental measurements show that the features of a large SHG effect, phase-match, and high thermal stability will be favorable in industrial production and applications for Cd(4)BiO(BO(3))(3).

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Two new mid-infrared transparency compounds, centric Ba(2)BiGaS(5) (1) and acentric Ba(2)BiInS(5) (2), were synthesized from a high-temperature solid-state reaction in evacuated closed silica tubes. Their crystal structures were determined by a single crystal X-ray diffraction method at 293 K. The results of crystal structure solution indicate that compound 1 crystallizes in the centrosymmetric space group Pnma with trans- (1)(∞)[BiGaS(5)](4-) chain structure, while compound 2 crystallizes in the noncentrosymmetric polar space group Cmc2(1) with cis- (1)(∞)[BiInS(5)](4-) chain structure. Two types of lone-pair electrons alignment fashions within (1)(∞)[BiMS(5)](4-) chains result in destructive (for 1) or constructive (for 2) dipole moments, as illustrated in the crystal structures and the partial electron density maps based on the first-principles electronic structure computations. Powder second-harmonic generation (SHG) experiments with a 2.05 μm pumping laser show that the SHG efficiency of the polar compound 2 is approximately 0.8 times that of KTiOPO(4) (KTP) reference. Furthermore, SHG signal intensity measurements using different size particles of powder samples indicate that compound 2 can also achieve type I phase-matching, which makes the compound promising for practical applications.

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It is important to reduce the recombination of electrons and holes and enhance charge transfer through fine controlled interfaces for advanced catalyst design. In this work, graphene oxide (GO) was composited with graphitic-C3N4 (g-C3N4) and BiOI forming GO/g-C3N4 and GO/BiOI heterostructural interfaces, respectively. GO, which has a work function between the conducting bands of g-C3N4 and BiOI, is used as a buffer material to enhance electron transfer from g-C3N4 to BiOI through the GO/g-C3N4 and GO/BiOI interfaces. The increased photocurrent and reduced photoluminescence indicate efficient reduction of electron and hole recombination under the successful heterostructure design. Accordingly, the introduction of GO as a charge transfer buffer material has largely enhanced the photocatalytic performance of the composite. Thus, introducing charge transfer buffer materials for photocatalytic performance enhancement has proved to be a new strategy for advanced photocatalyst design.

Cadmium sulfide (CdS), is one of the superior visible-light-driven photocatalysts, and has a prosperous and practical future in hydrogen (H2) production from water splitting for addressing environmental problems, such as environmental contamination and energy shortage. But the inherent serious drawback of photocorrision always limits its photocatalytic performance. Here, we fabricated a layered nanojunction to enhance the H2 generation of the surface-fluorinated TiO2/CdS–diethylenetriamine (F–TiO2/CdS–DETA) system. The loading of F–TiO2 nanosheets (NSs) with exposed {001} facets on inorganic–organic CdS–DETA nanobelts (NBs) greatly improves the interfacial contact. The layered nanojunction structure efficiently inhibits the charge carriers’ recombination and enhances the H2 production stability of CdS. At an optimal ratio of 30%F–TiO2, the F–TiO2/CdS–DETA composite exhibits the highest H2 production rate of 8342.86 μmol h–1 g–1, which is 6.6 times and 1.7 times as high as that of CdS nanoparticles and CdS–DETA NBs, respectively. The apparent quantum yield of the H2 evolution system reaches 24.9% at 420 nm with a Pt cocatalyst. More importantly, the surface of the F–TiO2 nanosheets enriches a large amount of trapping centers of photogenerated holes, which can thus efficiently promote the charge carriers’ separation and enhance the photocatalytic H2 evolution of CdS–DETA. Also, the effective charges transfer route of F–TiO2/CdS–DETA is also demonstrated by a photoluminescence test and photocurrent response. This work provides an ideal model for the design of stable and efficient H2 production photocatalysts.

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