Graphene-carbon 2D heterostructures with hierarchically-porous P,N-doped layered architecture for capacitive deionization.

Exploring a new-family of carbon-based desalinators to optimize their performances beyond the current commercial benchmark is of significance for the development of practically useful capacitive deionization (CDI) materials. Here, we have fabricated a hierarchically porous N,P-doped carbon-graphene 2D heterostructure (denoted NPC/rGO) by using metal-organic framework (MOF)-nanoparticle-driven assembly on graphene oxide (GO) nanosheets followed by stepwise pyrolysis and phosphorization procedures. The resulting NPC/rGO-based CDI desalinator exhibits ultrahigh deionization performance with a salt adsorption capacity of 39.34 mg g-1 in a 1000 mg L-1 NaCl solution at 1.2 V over 30 min with good cycling stability over 50 cycles. The excellent performance is attributed to the high specific surface area, high conductivity, favorable meso-/microporous structure together with nitrogen and phosphorus heteroatom co-doping, all of which are beneficial for the accommodation of ions and charge transport during the CDI process. More importantly, NPC/rGO exhibits a state-of-the-art CDI performance compared to the commercial benchmark and most of the previously reported carbon materials, highlighting the significance of the MOF nanoparticle-driven assembly strategy and graphene-carbon 2D heterostructures for CDI applications.

Effects of air pollution control devices on volatile organic compounds reduction in coal-fired power plants.

Air pollution control devices (APCDs) have been fitted to many coal-fired power plants to decrease the impacts of pollutants generated during coal combustion. APCDs remove conventional pollutants but also decrease volatile organic compound (VOC) emissions. In this study, flue gas samples were collected from different points in seven typical coal-fired power and two industrial boilers, and the VOC concentrations in the flue gas samples were determined by gas chromatography-mass spectrometry (GC-MS). Selective catalytic reduction (SCR) systems and electrostatic precipitators (ESP) can synergistically remove VOCs, the mean removal rate of VOCs by ESP was 42% ± 9%. This was caused by the catalyst in SCR systems and the condensation process in the ESP. Wet flue gas desulfurization (WFGD) affected different VOCs in different ways, increasing the halogenated hydrocarbons and aromatic hydrocarbons concentrations but decreasing the oxygenated VOCs concentrations by 12%. Wet electrostatic precipitators (WESP) increased VOC emissions. By calculating Ozone formation potential (OFP), aromatic hydrocarbons are important contributors to ozone production. The emission factor of the power plant was 0.69 g/GJ, and the Chinese annual emission was about 1.2 × 104 t. VOCs emissions in different regions were affected by factors such as the economy and population. VOC emissions can be decreased by using the most appropriate unit load and improving the VOC removal efficiencies of the APCDs.

Direct Z-scheme CuInS2/Bi2MoO6 heterostructure for enhanced photocatalytic degradation of tetracycline under visible light.

The construction of direct Z-scheme heterojunctions with high photocatalytic degradation ability is a theme of importance in both environmental and materials sciences, but still retains many unresolved challenges. In this article, we report the construction of Z-scheme CuInS2/Bi2MoO6 heterostructure by in-situ hydrothermal reactions, demonstrating superior photocatalytic activity towards the degradation of tetracycline under visible light, compared to their individual components: that is to say 8 and 2.5 times those of CuInS2 and Bi2MoO6, respectively. The photocatalytic performance of CuInS2/Bi2MoO6 heterostructure is mainly ascribed to the effective charge transfer at the interface through the construction of a direct Z-scheme heterojunction, combined with a ternary sulfide semiconductor absorbing light in the useful region of the solar spectrum. This photocatalyst provides new insights on the fundamental aspects governing the mechanisms responsible for multicomponent photodegradation, while constituting already a promising candidate for practical environmental applications.

Rational tailoring of the electronic structure for the SrxNaTayO3 semiconductor: Insights into its enhanced photoactivity and optical property.

NaTaO3 (NTO), as a popular photocatalyst with the prominent redox ability, largely straddles across the conduction band minimum (CBM) and valence band maximum (VBM) edge over Fermi level. Pristine NTO exhibits the poor light-harvesting ability and the rapid recombination of electron-hole pairs. We proposed an effective method to improve the photocatalytic property of NTO (ABO3-type) by substituting B site with Sr. The SrxNaTayO3 (SNTO) exhibited the boosted photocatalytic activity toward tetracycline oxidation under solar light irradiation. The rate constant for S0.5NTO (molar ratio of Sr: Ta = 1 : 2) was 5.1 times higher than the pure NTO. DFT results indicated that the Sr 3d orbital combining the O 2p and Ta 5d hybrid orbitals, widened the VB of SNTO. The band gap was narrowed from 3.86 to 2.82 eV after Sr substitution, which enhanced its light-harvesting ability. The VBM moved upward for 1.42 V and the CBM moved upward for 0.38 V. The shifts of the CBM and VBM, together with the more stretched Ta-O-Ta configuration, highly facilitated the electron-hole pair separation in SNTO. These electronic structure changes accounted for the significant photocatalytic performance enhancement of NaTaO3 via Sr substitution for B-site-Ta.

The precursor-guided hydrothermal synthesis of CuBi2O4/WO3 heterostructure with enhanced photoactivity under simulated solar light irradiation and mechanism insight.

Z-scheme heterojunction can efficiently suppress the electron-holes recombination and promote the charges transfer rate, which result in the high photocatalytic performance. Herein, a flower-flake-sphere like CuBi2O4/WO3 hybrid photocatalyst was fabricated via a precursor-guided hydrothermal method. The morphology, structure, composition, chemical and electronic properties of the as-prepared samples were systematically investigated by multiple techniques (XRD, FT-IR, SEM, TEM, XPS, UV-vis, BET, PL, ESR. etc.). Particularly, the 60 wt% CuBi2O4/WO3 nanocomposite exhibited the highest photocatalytic activity for tetracycline (20 mg/L) degradation under simulated solar light irradiation. The rate constant was 0.0179 min-1, which was almost 8 times and 4.5 times higher than that of bulk WO3 and CuBi2O4, respectively. The experimental results confirmed that CuBi2O4 made a direct Z-scheme heterojunction by band alignment with WO3, which are conducive to the efficient charges separation and prolonged carriers lifetime. According to the quenching experiments, •OH and •O2- were testified to be the predominant active species. The electrons accumulated in the CuBi2O4 negative CB and the holes in the WO3 positive VB made significant contribution to the strong redox ability of the CuBi2O4/WO3 nanocomposite. This work provides some deep insights into the design of band-alignment-based Z-scheme heterostuctures, which is also applicable to other catalytic system.

Construction of novel Ag/HKUST-1/g-C3N4 towards enhanced photocatalytic activity for the degradation of pollutants under visible light.

A novel Ag/metal-organic framework/graphitic carbon nitride (Ag/HKUST-1/g-C3N4, AHC) photocatalyst was prepared via an in situ growth strategy and photo-deposition technique for environmental remediation. The as-obtained samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption isotherm measurement, UV-vis diffuse reflection spectroscopy (UV-vis DRS), and photoluminescence (PL) spectroscopy. The results indicated that the hybrids have large surface area, mesoporous structure and enhanced visible-light absorption. The as-prepared hybrid samples exhibited considerable improvement in photocatalytic activity and stability for rhodamine B (RhB) degradation under visible light irradiation (λ > 420 nm). In addition, they also have good adsorption properties. Compared to the pure g-C3N4 and Ag/g-C3N4, the 5% AHC photocatalyst showed superior photocatalytic activity. Moreover, 5% AHC exhibits good photocatalytic activity even after four cycles. Additionally, the active species trapping and electron spin resonance (ESR) experiments indicated that h+ and ·OH were the main active species.

Influence of super-hydrophobic silicone rubber substrate on the growth and differentiation of human lens epithelial cells.

Materials with low cell adhesion are advantageous for production of replacement intraocular lens (IOL) to prevent posterior capsular opacification (PCO). We evaluated the feasibility of compression molding for manufacture of silicone rubber with super-hydrophobic surface and low cell infiltrative characteristics compared to ordinary hydrophobic silicone rubber. Silicone specimens with complex surface topology (super-hydrophobic) or smooth surfaces (hydrophobic) were manufactured by vacuum deforming and molding. Contact angle, microscopic surface structure, and transparency were evaluated. Super-hydrophobic and smooth samples were compared for effects on proliferation, adhesion, and morphology of human lens epithelial cells (hLECs). Epithelial-mesenchymal transition (EMT) was examined by immunofluorescence expression of fibronectin (Fn), Alpha-smooth muscle actin (α-SMA), and vimentin. The surface contact angle of super-hydrophobic silicone was greater than that of smooth silicone (153.8° vs. 116°). The super-hydrophobic surface exhibited a micron-scale palisade structure under scanning electron microscopy (unit length, width, and height of 80, 25, and 25 µm, respectively). However, cell number per 50 × microscopic field on super-hydrophobic surfaces was markedly reduced 24 and 72 h post-seeding compared to smooth surfaces (p < 0.01). Cells were cuboidal or spherical after 72h on super-hydrophobic surfaces, and exhibited numerous surface microvilli with fluff-base polarity, while cells on smooth surfaces exhibited morphological characteristics of EMT. Expression levels of the α-SMA and vimentin were reduced on super-hydrophobic surfaces compared to smooth surfaces. Super-hydrophobic silicon inhibits proliferation, adhesion, and EMT of hLECs, properties that may prevent fibrosis following cataract surgery.

Comparison of the photocatalytic performance of TiO2/AC and TiO2/CNT nanocomposites for methyl orange photodegradation.

To enhance the photocatalytic degradation efficiency of TiO2 on methyl orange (MO) removal, TiO2/AC (activated carbon) and TiO2/CNT (carbon nanotube) composites were synthesized. The prepared catalysts were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The photocatalytic performance of the obtained composites were investigated by the degradation of MO under UV irradiation (254 nm, 365 nm). The results revealed that the prepared nanocomposite showed higher MO degradation efficiency than pure nano-TiO2. Additionally, batch experiments of influencing factors, including H2O2 dosage, metal dopants, inorganic anions, chloride ion concentration and ultraviolet wavelength on the MO removal efficiency were also conducted. The results demonstrated that metal dopant and the presence of H2O2 significantly enhanced MO removal efficiency.

Synthesis of ZnWO4/Ag3PO4 p-n heterojunction photocatalyst and enhanced visible-light photocatalytic applications.

The ZnWO4/Ag3PO4 nanocomposites synthesized by simple precipitation processes were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis diffuse reflectance spectra. The results indicated that the ZnWO4 nanorods dispersed well on the surface of Ag3PO4 particles and ball-and-rod structure p-n heterojunctions were successfully fabricated. In subsequent degradation experiments of methyl orange (MO), ZnWO4/Ag3PO4 composites showed the highest photocatalytic activity compared to pure Ag3PO4 and ZnWO4, due to the presence of ZnWO4/Ag3PO4 heterojunctions, which could separate and transfer the electron-hole pairs generated by visible light and enhance the photocatalytic performance of the catalysts. The band gap structure and degradation mechanism of the enhanced photocatalytic materials are also discussed in this article. In conclusion, the ZnWO4/Ag3PO4 composite is a promising and excellent photocatalyst for the degradation of dye wastewater under visible light irradiation.

Study on highly enhanced photocatalytic tetracycline degradation of type â ¡ AgI/CuBi2O4 and Z-scheme AgBr/CuBi2O4 heterojunction photocatalysts.

Removal of antibiotics from aqueous solutions by photocatalysis is an advanced technology for environmental remediation. Herein, we have fabricated a series of AgX (X = I, Br)/CuBi2O4 composites through an in-situ precipitation method. The photocatalytic activity of the obtained photocatalysts was measured by the degradation of tetracycline (TC) under visible light irradiation (λ > 420 nm). All the AgX (X = I, Br)/CuBi2O4 composites exhibit much higher photocatalytic activity than that of pure CuBi2O4. The enhanced photocatalytic activity is mainly attributed to the efficient interfacial charge separation and migration in the AgX (X = I, Br)/CuBi2O4 heterojunctions. Meanwhile, AgX (X = I, Br)/CuBi2O4 heterojunctions display excellent photocatalytic stability, and the photocatalytic degradation rates were not obvious decreased even after five successive cycles. Based on the energy band structure, the radicals trapping and electronic spin resonance (ESR) experiments, the Z-scheme mechanism of AgBr/CuBi2O4 and type II mechanism of AgI/CuBi2O4 heterojunction photocatalysts were tentatively discussed, respectively.

N,S co-doped carbon dots as a stable bio-imaging probe for detection of intracellular temperature and tetracycline.

Stable bioimaging with nanomaterials in living cells has been a great challenge and of great importance for understanding intracellular events and elucidating various biological phenomena. Herein, we demonstrate that N,S co-doped carbon dots (N,S-CDs) produced by one-pot reflux treatment of C3N3S3 with ethane diamine at a relatively low temperature (80 °C) exhibit a high fluorescence quantum yield of about 30.4%, favorable biocompatibility, low-toxicity, strong resistance to photobleaching and good stability. The N,S-CDs as an effective temperature indicator exhibit good temperature-dependent fluorescence with a sensational linear response from 20 to 80 °C. In addition, the obtained N,S-CDs facilitate high selectivity detection of tetracycline (TC) with a detection limit as low as 3 × 10-10 M and a wide linear range from 1.39 × 10-5 to 1.39 × 10-9 M. More importantly, the N,S-CDs display an unambiguous bioimaging ability in the detection of intracellular temperature and TC with satisfactory results.

Microwave-assisted in situ synthesis of reduced graphene oxide-BiVO4 composite photocatalysts and their enhanced photocatalytic performance for the degradation of ciprofloxacin.

To improve the photodegradation efficiency for ciprofloxacin (CIP), a new-type microwave-assisted in situ growth method is developed for the preparation of reduced graphene oxide (RGO) -BiVO4 composite photocatalysts. The as-produced RGO-BiVO4 composite photocatalysts show extremely high enhancement of CIP degradation ratio over the pure BiVO4 photocatalyst under visible light. Specially, the 2 wt% RGO-BiVO4 composite photocatalyst exhibits the highest CIP degradation ratio (68.2%) in 60 min, which is over 3 times than that (22.7%) of the pure BiVO4 particles. The enhancement of photocatalytic activities of RGO-BiVO4 photocatalysts can be attributed to the effective separation of electron-hole pairs rather than the improvement of light absorption.