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Carbon dots (C-dots) were facilely fabricated via a hydrothermal method and fully characterized. Our study shows that the as-synthesized C-dots are nontoxic, negatively charged spherical particles (average diameter 4.7 nm) with excellent water dispersion ability. Furthermore, the C-dots have a rich presence of surface functionalities such as hydroxyls and carboxyls as well as amines. The significance of the C-dots as highly efficient photocatalysts for rhodamine B (RhB) and methylene blue (MB) degradation was explored. The C-dots demonstrate excellent photocatalytic activity, achieving 100% of RhB and MB degradation within 170 min. The degradation rate constants for RhB and MB were 1.8 × 10−2 and 2.4 × 10−2 min−1, respectively. The photocatalytic degradation performances of the C-dots are comparable to those metal-based photocatalysts and generally better than previously reported C-dots photocatalysts. Collectively considering the excellent photocatalytic activity toward organic dye degradation, as well as the fact that they are facilely synthesized with no need of further doping, compositing, and tedious purification and separation, the C-dots fabricated in this work are demonstrated to be a promising alternative for pollutant degradation and environment protection.

With increasingly stringent environmental regulations, the removal of nitrogen-containing compounds (NCCs) from gasoline fuel has become a more and more important research subject. In this work, we have successfully synthesized TiO2/α-Fe2O3 heterogeneous photocatalysts with different mass ratios of TiO2 vs. α-Fe2O3. Taking photocatalytic denitrification of typical alkali NCCs, pyridine, in gasoline fuel under visible light irradiation (λ ≥ 420 nm) as the model reaction, the TiO2/α-Fe2O3 hybrids have exhibited enhanced photocatalytic activity compared with pure TiO2 and α-Fe2O3, giving a pyridine removal ratio of ∼100% after irradiation for 240 min. The improved photocatalytic performance can be attributed to the integrative effect of the enhanced light absorption intensity and more efficient separation of photogenerated electron-hole pairs. Importantly, this type of heterogeneous photocatalysts can be easily separate in the reaction medium by an external magnetic field that is very important for industrial purpose. In addition, major reaction intermediates have been identified by the liquid chromatograph-mass spectrometer (HPLC-MS) and a tentative photocatalytic denitrification mechanism has been proposed.

A nonlinear optical crystal cadmium borate chlorine (Cd(BO)Cl) has been successfully grown through a spontaneous crystallization method. Cd(BO)Cl crystallizes in the noncentrosymmetric space group Cm with isolated BO and distorted CdOCl (n = 4, 5, 7; m = 0, 1, 2) polyhedra. Powder second harmonic generation (SHG) measurements on polycrystalline Cd(BO)Cl indicated that the title compound is phase-matchable in the visible region and exhibits a large SHG response of about 5 × KHPO (KDP). Further optical characterization suggested that the compound has a wide transparent region ranging from UV to near IR with a UV cutoff edge at about 295 nm. In addition, first-principles electronic structure calculations revealed that the macroscopic SHG coefficients of Cd(BO)Cl originate from the cooperative effects of the BO groups with asymmetric π-delocalization, the d cation Cd with the polar displacement and the Cl anions.

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This study investigated the chemical nature of impurity iron species and photoactive sites in the commercially available HZSM-5 zeolites with different Si/Al ratios. The samples were characterized by X-ray fluorescence spectroscopy, atomic absorption spectroscopy, X-ray absorption near-edge structure spectroscopy, extended X-ray absorption fine structure spectroscopy, electron paramagnetic resonance spectroscopy, UV Raman spectroscopy, and photocatalytic degradation of ethylene. The results revealed that the photocatalytic activity of the HZSM-5 originated from the isolated tetrahedrally coordinated iron−oxo species present in the zeolite framework. The formation of such active isolated iron−oxo species was strongly influenced by the chemical compositions (e.g., Si/Al ratio, and iron content) and the preparation methods of zeolite. This could explain the difference in photoactivity of the different types of HZSM-5 and FeZSM-5 zeolites. Possible mechanisms of the photocatalysis on the zeolites were also discussed.