The fabrication of multiple heterojunctions with tunable photocatalytic reactivity in full-range BiOBr-BiOI composites based on microstructure modulation and band structures is demonstrated. The multiple heterojunctions are constructed by precipitation at room temperature and characterized systematically. Photocatalytic experiments indicate that there are two types of heterostructures with distinct photocatalytic mechanisms, both of which can greatly enhance the visible-light photocatalytic performance for the decomposition of organic pollutants and generation of photocurrent. The large separation and inhibited recombination of electron-hole pairs rendered by the heterostructures are confirmed by electrochemical impedance spectra (EIS) and photoluminescence (PL). Reactive species trapping, nitroblue tetrazolium (NBT, detection agent of (•)O2(-)) transformation, and terephthalic acid photoluminescence (TA-PL) experiments verify the charge-transfer mechanism derived from the two types of heterostructures, as well as different enhancements of the photocatalytic activity. This article provides insights into heterostructure photocatalysis and describes a novel way to design and fabricate high-performance semiconductor composites.

A new series of alkaline beryllium borates NaBeB(3)O(6), alpha-KBe(2)B(3)O(7), beta-KBe(2)B(3)O(7), gamma-KBe(2)B(3)O(7), and RbBe(2)B(3)O(7) were synthesized by spontaneous crystallization with molten fluxes based on A(2)O-B(2)O(3) (A = Na, K, Rb) solvent. For KBe(2)B(3)O(7), three polymorphous phases were found and are referred to as alpha-, beta-, and gamma-KBe(2)B(3)O(7) relative to their crystallization temperature from high to low. All of the materials are noncentrosymmetric except alpha-KBe(2)B(3)O(7). NaBeB(3)O(6) and alpha-KBe(2)B(3)O(7) consist of a new anionic group [Be(2)B(3)O(11)](9-), which is similar to a naphthalene molecule that is rarely found in inorganic matter. beta-KBe(2)B(3)O(7), gamma-KBe(2)B(3)O(7), and RbBe(2)B(3)O(7) consist of 2D alveolate beryllium borate layers [Be(2)BO(5)](infinity), which are connected by strong covalent bonds. The UV-vis diffuse reflectance spectroscopy on powder samples indicated that the short-wavelength absorption edges of noncentrosymmetric materials are all below 200 nm. Second-harmonic generation (SHG) on powder samples was measured using the Kurtz and Perry technique, which indicated that NaBeB(3)O(6), beta-KBe(2)B(3)O(7), gamma-KBe(2)B(3)O(7), and RbBe(2)B(3)O(7) are all phase matchable materials, and their measured SHG coefficients were approximately 1.60, 0.75, 0.68, and 0.79 times as large as that of d(36) (KDP), respectively.

A new deep-UV nonlinear optical crystal, Na(2)CsBe(6)B(5)O(15), has been grown through spontaneous crystallization with a molten flux based on Na(2)O-Cs(2)O-B(2)O(3). Na(2)CsBe(6)B(5)O(15) contains two-dimensional alveolate beryllium borate layers [Be(2)BO(5)](∞) that are bridged via planar [BO(3)] groups. UV-vis diffuse reflectance analysis on a powder sample of Na(2)CsBe(6)B(5)O(15) indicates that the short-wavelength absorption edge of Na(2)CsBe(6)B(5)O(15) is below 200 nm. Second-harmonic generation (SHG) on the powder sample was measured with a 1064 nm laser using the Kurtz and Perry technique, which showed that Na(2)CsBe(6)B(5)O(15) is a phase-matchable material, and its measured SHG coefficient is ~1.17 times as large as the d(36) coefficient of potassium dihydrogen phosphate. The relatively larger SHG coefficient of Na(2)CsBe(6)B(5)O(15) originates from its shorter distance between the adjacent layers bridged via the small [BO(3)] groups.

The novel Ce and F codoped Bi2WO6 samples have been successfully obtained by a facile one-step hydrothermal reaction for the first time. They were characterized by X-ray diffraction patterns (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectra (DRS) and photoluminescence (PL) spectra. The presence of Ce3+, Ce4+, and F– dopants in Bi2WO6 was confirmed by XPS. The change of microstructure and optical band gap has also been observed after the doping of Ce and F. Under visible light, the as-synthesized plate-like F–Ce–Bi2WO6 sample exhibits a much better visible-light-responsive photocatalytic performance than pure Bi2WO6 for the degradation of RhB and photocurrent (PC) generation. The mechanism of high photcatalytic activity was also suggested on the basis of the PL spectra, electrochemical impedance spectra (EIS), and active species trapping measurements. The results indicated that the synergistic effect of the Ce and F dopants is responsible for the efficient separation and migration of photoinduced charge carriers, thus resulting in the remarkably improved photocatalytic activity.

The prospects of all known noncentrosymmetric alkali and/or alkaline earth beryllium borates for nonlinear optical (NLO) generation in the deep-ultraviolet (DUV) spectral region are evaluated by first-principles studies. It is shown that all these crystals possess large enough energy band gaps and relatively strong NLO responses that satisfy the requirement for DUV second-harmonic generation (SHG). However, the practical DUV SHG capabilities of these crystals are mostly limited by the phase-matching condition, as determined not only by the optical birefringence but also by the refractive-index dispersion that is explicitly emphasized for the first time in this work. Therefore, although the K 2 Be 2 BO 3 F family and NaBeB 3 O 6 both have a large birefringence, Δn ≈ 0.08, at a wavelength of 400 nm, the DUV SHG lasers can only be produced in the former but cannot be fulfilled in the latter due to its large refractive-index dispersion in the DUV region. The crystal structural features for large birefringence and the electronic structure origins for different refractive-index dispersion behaviors are discussed. The elucidation of the structure−property relationship presents a useful guide to the exploration of new NLO crystals that can be practically applied for DUV SHG. KEYWORDS: alkali and/or alkaline earth beryllium borates, deep ultraviolet nonlinear optical, phase-matching condition, birefringence, refractive-index dispersion T he demand for deep-ultraviolet (DUV, wavelength λ < 200 nm) coherent light becomes increasingly urgent, owing to its great application in many scientific and technical fields, such as in microcircuit photolithography, high density storage, laser micromachining, and high-precision scientific equipment. 1−5 Up to now, the most effective method to produce DUV lasers with high quality is from all-solid-state lasers using cascaded frequency conversion by DUV nonlinear optical (NLO) crystals. 6−9 The search for new NLO crystals for the DUV spectral region is one of the research hot spots in optoelectronic functional materials. 10−15 It is commonly accepted that the following conditions of optical properties are vital for the DUV NLO performance of a crystal: 16,17 (i) a short-wavelength absorption cutoff (λ cutoff ) of less than 200 nm (i.e., an energy band gap E g > 6.2 eV) for good optical transmission in the DUV region (also corresponding to a large laser damage threshold 18 ); (ii) a relatively large second-harmonic-generation (SHG) response (usually the effective SHG effect should be larger than that of KH 2 PO 4 (KDP, d 36 = 0.39 pm/V)) for a high NLO conversion efficiency, and (iii) a moderate birefringence (Δn should be larger than 0.075 but smaller than 0.11 at a wavelength of 400 nm) for the achievement of the phase-matching condition in the DUV region.For decades, the exploration of DUV NLO crystals has been focused on the noncentrosymmetric alkali and/or alkaline earth beryllium borates, 7−17 mainly due to their very short absorption edges and relatively large NLO effects. In the ...

A noncentrosymmetric nitrate Sr2(OH)3NO3 has been synthesized which is the first nitrate as a promising deep-UV nonlinear optical material.

Osteosarcoma is a malignant musculoskeletal tumor that has high-rate morbidity and mortality worldwide. Alginate oligosaccharide (AOS), a natural product, has antitumor activities and may have therapeutic effects in osteosarcoma, the molecular mechanisms of which remain unclear. AOS was prepared from alginate sodium using alginate lyase. The fractions of AOS were further isolated by size-exclusion chromatography and verified by electrospray ionization mass spectrometry (ESI-MS). Osteosarcoma patients were enrolled in the study and assigned into two groups: AOS (AG, oral administration of 10-mg AOS daily) and control groups (CG, placebo). Preoperative and postoperative clinical data were investigated and analyzed. Four different degrees of polymerizations (DPs) were isolated and denominated as DP2, DP3, DP4, and DP5. Among these polymers, only DP5 showed antitumor functions on osteosarcoma cells. Before surgery and the outcome of primary end point after surgery, no significant differences were observed for clinical data and tumor size between the AG and CG groups (P > 0.05). After 2-year therapy, the mean tumor volume was 214.6 ± 145.7 c.c. in AG and 467.2 ± 225.3 c.c in CG (P < 0.01). The rate of local recurrence was 44.9 and 68.7% in AG and CG, respectively (P < 0.01). AOS treatment resulted in the increase in serum levels of SOD, GSH, HDL-C, and reduction in the levels of interleukin-1 (IL-1) beta and IL-6; the ratios of AST/ALT; and triglycerides, total cholesterol (TC), low-density lipoprotein cholesterol LDL-C, and malondialdehyde (MDA) (P < 0.05). AOS reduces osteosarcoma progression, which is associated with improvement in antioxidant and anti-inflammatory capacities of patients, and may be used as a potential drug for osteosarcoma therapy.

We report detailed studies showing that the novel layered polysulfide compounds S x -LDH (S x 2–, polysulfides, x = 2, 4, 5; LDH, Mg–Al layered double hydroxides) can capture efficiently large quantities of mercury (Hg0) vapor. During the adsorption process, the interlayer polysulfides [S x ]2– react with Hg0 through their S–S bond to produce HgS. The structure of S x -LDH before and after Hg-adsorption was characterized with X-ray diffraction, vibration spectroscopy, and scanning electron microscopy. The presence of adsorbed Hg was verified by weight gain, inductively coupled plasma atomic emission spectroscopy and X-ray photoelectron spectroscopy. Despite their relatively low surface areas, the S2-LDH, S4-LDH, and S5-LDH samples show excellent Hg capture capacities of 4.9 × 105, 7.4 × 105, and 1.0 × 106 μg/g, respectively, corresponding to 50–100% adsorption rates by weight, highlighting the potential of these materials in natural gas purification. The Hg-capture efficiency and mechanism in S x -LDH are supported by control experiments with K2S4, S8, LDH-NO3-CoS4, and MgAl-NO3-LDH.