Shouqiang Huang

Enhancing the Stability of CH3NH3PbBr3 Quantum Dots by Embedding in Silica Spheres Derived from Tetramethyl Orthosilicate in “Waterless” Toluene

Methylammonium lead halide perovskites suffer from poor stability because of their high sensitivity to moisture. Inorganic material coatings of SiO2 are preferred for coupling with perovskites to improve their stability, whereas the conventional SiO2 formation method is unsuitable because it requires water. Here, a simple SiO2 generation method based on the high hydrolysis rate of tetramethyl orthosilicate in analytical-grade toluene was developed to avoid the addition of water and catalyst. As a result, SiO2-encapsulated CH3NH3PbBr3 quantum dots (MAPB-QDs/SiO2) were fabricated without decreasing the quantum yield. Photostability tests indicated that the MAPB-QDs/SiO2 samples were markedly more stable than the unencapsulated MAPB-QDs. The photoluminescence (PL) of the MAPB-QDs/SiO2 powders was maintained at 94.10% after 470 nm LED illumination for 7 h, which was much higher than the remnant PL (38.36%) of the pure MAPB-QD sample under a relative humidity of 60%. Similar test results were observed when the MAPB-QDs/SiO2 powders were incorporated into the poly(methyl methacrylate) films. The enhanced photostability is ascribed to the SiO2 barriers protecting the MAPB-QDs from degradation.

Adsorption and Fenton-like degradation of naphthalene dye intermediate on sewage sludge derived porous carbon

A sewage sludge derived porous carbon (SC), which was prepared by physicochemical activation and carbonization (600°C), was applied for the adsorption and degradation of 1-diazo-2-naphthol-4-sulfonic acid (1,2,4-Acid) in the presence of H(2)O(2) and the performance was compared to that of pure Fe(3)O(4) magnetic nanoparticles (MNPs). The prepared SC showed mesoporous structure with magnetic property, which made it favorable for solid-liquid separation application. Further experiments revealed that SC had a higher adsorption capacity and degradation efficiency of 1,2,4-Acid than bare Fe(3)O(4). The Langmuir and Freundlich model fitted the isotherm data and illustrated that the equilibrium adsorption amount of 1,2,4-Acid onto SC (95.1 mg g(-1)) was quadruple as large as that on Fe(3)O(4) (26.4 mg g(-1)). The subsequent degradation experiments were conducted at conditions (pH 5.0 in the presence of 15 mM H(2)O(2)) with regard to 1,2,4-Acid degradation efficiency and metal ions leach. The 120 mins treatment in SC/H(2)O(2) system achieved 94% of 1,2,4-Acid (from 150 mg L(-1) after adsorption equilibrium to 9 mg L(-1)) and 48.1% TOC reduction, far higher than the efficiency of 46% and 24.3% by using Fe(3)O(4) MNPs. Further analysis evidenced the co-catalytic effect of iron, carbon, silicon and aluminum, which existed in large quantities in sludge derived SC. The carbonaceous phase along with silica contributes to an increase in the dispersion of catalytic centers and an adsorbent to concentrate organic pollutant whereas the iron oxide as well as alumina provides the catalytic centers for a Haber-Weiss initiated reactions.

Near-infrared photocatalyst of Er3+/Yb3+ codoped (CaF2@TiO2) nanoparticles with active-core/active-shell structure

A novel near-infrared (NIR) photocatalyst of Er3+/Yb3+-(CaF2@TiO2) was synthesized with optically active centers (Er3+/Yb3+) presented both in the CaF2 cores and TiO2 shells, and the corresponding upconversion luminescence properties increased greatly, which was helpful for the organic dye solution removal efficiency under NIR irradiation.

Morphology Evolution and Degradation of CsPbBr3 Nanocrystals under Blue Light-Emitting Diode Illumination

Under illumination of light-emitting diode (LED) or sunlight, the green color of all-inorganic CsPbBr3 perovskite nanocrystals (CPB-NCs) often quickly changes to yellow, followed by large photoluminescence (PL) loss. To figure out what is happening on CPB-NCs during the color change process, the morphology, structure, and PL evolutions are systematically investigated by varying the influence factors of illumination, moisture, oxygen, and temperature. We find that the yellow color is mainly originated from the large CPB crystals formed in the illumination process. With maximized isolation of oxygen for the sandwiched film or the uncovered film stored in nitrogen, the color change can be dramatically slowed down whether there is water vapor or not. Under dark condition, the PL emissions are not significantly influenced by the varied relative humidity (RH) levels and temperatures up to 60 °C. Under the precondition of oxygen or air, color change and PL loss become more obvious when increasing the illumination power or RH level, and the large-sized cubic CPB crystals are further evolved into the oval-shaped crystals. We confirm that oxygen is the crucial factor to drive the color change, which has the strong synergistic effect with the illumination and moisture for the degradation of the CPB film. Meanwhile, the surface decomposition and the increased charge trap states occurred in the formed large CPB crystals play important roles for the PL loss.

Heavy metal recovery from electroplating wastewater by synthesis of mixed-Fe3O4@SiO2/metal oxide magnetite photocatalysts

Heavy metal recovery is a promising way to reduce the pollution from electroplating wastewater (EPW), and magnetite photocatalysts of mixed-ferrite (M-Fe3O4)@SiO2/metal oxides have been prepared to reuse heavy metals from simulated-EPW (S-EPW) and real-EPW (R-EPW). In this work, four pure magnetite photocatalysts M-Fe3O4@SiO2/ZnO, M-Fe3O4@SiO2/CuO, M-Fe3O4@SiO2/Fe2O3, and M-Fe3O4@SiO2/NiO were synthesized via a simple precipitation reaction, where the M-Fe3O4@SiO2 core–shell nanoparticles served as the magnetic cores and supports for the metal oxides. The structures, morphologies, and magnetic properties of these magnetite photocatalysts were characterized, and then the photocatalytic performances of the pure and complex magnetite photocatalysts (M-Fe3O4@SiO2 supported single and mixed-metal oxides) were tested and compared using methyl orange (MO) degradation experiments. It was found that M-Fe3O4@SiO2/ZnO had the best photocatalytic performance of the pure magnetite photocatalysts, with a MO removal rate of 91.5%, followed by 37.4% for M-Fe3O4@SiO2/NiO, 19.0% for M-Fe3O4@SiO2/Fe2O3, and 17.6% for M-Fe3O4@SiO2/CuO. The removal rates were 17.4% and 13.2% for the complex magnetite photocatalysts prepared from S-EPW and R-EPW, respectively. More than 98% of the heavy metals can be recovered from EPW through the simultaneous synthesis of the magnetite photocatalysts.

Upconversion assisted BiOI/ZnWO4:Er3+, Tm3+, Yb3+ heterostructures with enhanced visible and near-infrared photocatalytic activities

Photocatalytic activities of near-infrared (NIR) photocatalysts can be improved by the formation of heterostructures, and an efficient semiconductor upconversion agent of ZnWO4:Er3+, Tm3+, Yb3+ (ZWOETY) was applied to synthesize the BiOI/ZWOETY (BOI/ZWOETY) composite with a p–n heterostructure. BOI/ZWOETY displays a flower-like structure, and ZWOETY nanoparticles are found to be dispersed homogeneously throughout the BOI surfaces, which is beneficial for the NIR light harvesting. Due to the upconversion luminescence properties of ZWOETY, NIR light can be upconverted to a wide range of light emissions, including red (658 nm), green (526 and 550 nm), blue (483 nm), violet (410 nm), and UV (367 and 380 nm) light, and all these upconversion emissions can be absorbed by BOI for photocatalysis. Under visible and NIR light irradiation, BOI/ZWOETY shows better photocatalytic activities in the degradation of methyl orange (MO) and salicylic acid (SA), compared to pure BOI and BOI/ZWO. The generation of holes contributes to the MO and SA decomposition greatly, and the upconversion properties and the highly efficient separation of electron–hole pairs are responsible for the enhanced photocatalytic activities in BOI/ZWOETY.

Preparation of sewage sludge based activated carbon by using Fenton's reagent and their use in 2-naphthol adsorption.

In this study, Fentons reagents (H2O2/Fe(2+)) are used to activate raw sewage sludge for the preparation of the sludge based activated carbon. The effect of the amount of hydrogen peroxide addition on carbons chemical composition, texture properties, surface chemistry and morphology are investigated. Choosing an appropriate H2O2 dosage (5 v%) (equivalent to 70.7 mM/(g VS)), it is possible to obtain a comparatively highly porous materials with SBET and the total pore volume being 321 m(2)/g and 0.414 cm(3)/g, respectively. Continuously increasing the oxidant ratio resulted in a decreased SBET value. Further adsorption experiments by using 2-naphthol as model pollutant revealed that the adoption followed a pseudo-second-order kinetics better than pseudo-first-order. The calculated adsorption capacity is 111.9 mg/g on the carbon with 5% H2O2 pretreatment while this value is just 51.5mg/g on carbons without any pretreatment.

Conversion of invisible metal-organic frameworks to luminescent perovskite nanocrystals for confidential information encryption and decryption

Traditional smart fluorescent materials, which have been attracting increasing interest for security protection, are usually visible under either ambient or UV light, making them adverse to the potential application of confidential information protection. Herein, we report an approach to realize confidential information protection and storage based on the conversion of lead-based metal-organic frameworks (MOFs) to luminescent perovskite nanocrystals (NCs). Owing to the invisible and controlled printable characteristics of lead-based MOFs, confidential information can be recorded and encrypted by MOF patterns, which cannot be read through common decryption methods. Through our conversion strategy, highly luminescent perovskite NCs can be formed quickly and simply by using a halide salt trigger that reacts with the MOF, thus promoting effective information decryption. Finally, through polar solvents impregnation and halide salt conversion, the luminescence of the perovskite NCs can be quenched and recovered, leading to reversible on/off switching of the luminescence signal for multiple information encryption and decryption processes.Materials with switchable fluorescence possess great potential for information encryption applications, but systems where the off state is invisible are lacking. Here the authors print patterns of colourless metal organic frameworks and reversibly transform these inks into fluorescent perovskite nanocrystals

An efficient near infrared photocatalyst of Er3+/Tm3+/Yb3+ tridoped (CaWO4@(TiO2/CaF2)) with multi-stage CaF2 nanocrystal formation

The formation process of CaF2 is critical for the improvement of upconversion properties of the CaF2 based upconversion photocatalysts, and for this purpose a near-infrared (NIR) photocatalyst of Er3+/Tm3+/Yb3+ tridoped (CaWO4@(TiO2/CaF2)) (ETY-CTC) was synthesized. CaF2 nanocrystals are converted from CaWO4 precursors in a multi-stage process, and the remaining CaWO4 microspheres are wrapped in CaF2 and TiO2 nanocrystals to form the heterostructure of the photocatalyst. CaF2 is found to connect with TiO2 nanocrystals, instead of being coated by TiO2, resulting in a higher upconversion luminescence efficiency of ETY-CTC than that of pure Er3+/Tm3+/Yb3+ tridoped (CaWO4@CaF2). ETY-CTC possesses higher photocatalytic activities compared to Er3+/Tm3+/Yb3+ tridoped (CaWO4@TiO2) under NIR and UV-vis-NIR light irradiations, since more ˙OH and O2˙− radicals, and higher electron–hole separation efficiency are obtained in the ETY-CTC system. The multi-stage formation of luminescence agents can be an attractive method for the synthesis of NIR photocatalysts with enhanced upconversion properties and photocatalytic activities.

Efficient removal of Pb(II) from water using magnetic Fe3S4/reduced graphene oxide composites

Nanostructured metal sulfides hold great promise for adsorption and catalysis applications, but it remains challenging for them to achieve highly efficient decontamination and facile separation of heavy metal ions from water. Herein, Fe3S4/reduced graphene oxide composites (Fe3S4/rGO) were successfully prepared and utilized for the removal of Pb(II) from water. Uniform Fe3O4 nanoparticles were firstly dispersed on the rGO, and employed as sacrificial materials for a facile sulfuration approach. This gave rise to the fabrication of Fe3S4 nanoparticles (Fe3S4 NPs) with an average size of 14.3 nm. The resultant Fe3S4/rGO presented an evidently greater adsorption capacity (285.71 mg g−1) and advantages in driving fast adsorption of Pb(II) in comparison with Fe3O4/rGO (106.27 mg g−1). A remarkable selectivity for Pb(II) was achieved in the presence of coexisting cations and anions, and the addition of humic acid promoted the removal of Pb(II) by Fe3S4/rGO. The enhanced performance of Fe3S4/rGO was mostly facilitated by synergetic contributions of the strong and selective Pb–S interactions between Pb(II) and small Fe3S4 NPs associated with the surface adsorption. Remarkably, a single treatment of smelting wastewater with Fe3S4/rGO effectively reduced Pb(II) concentration below the drinking water standard that is recommended by the U.S. Environmental Protection Agency, along with a surprisingly high removal efficiency toward arsenic (96.18%). However, Fe3O4/rGO merely exhibited a low removal rate of 29.59% for Pb(II). The efficient removal performance of Fe3S4/rGO exhibited its great potential in the remediation of heavy metal polluted water via simultaneously taking advantage of magnetic properties and a high affinity for heavy metals.