Long Kong

β-Cyclodextrin stabilized magnetic Fe3S4 nanoparticles for efficient removal of Pb(II)

In this study, magnetic β-cyclodextrin stabilized Fe3S4 nanoparticles (CD-Fe3S4) were fabricated via a facile one-step route. The as-prepared CD-Fe3S4 exhibited a high Pb(II) adsorption capacity of 256 mg g−1, and it also showed a surprisingly efficient adsorption toward Zn(II), Cd(II), and Cu(II). XRD, FTIR and XPS analyses suggested that the mechanisms governing Pb(II) removal by CD-Fe3S4 were precipitation (formation of galena) and surface adsorption. Additionally, the magnetic properties of the synthesized Fe3S4 nanoparticles allow fast separation of sorbents from water. The sorption kinetic data were well-described by a pseudo-second-order model, whereas the adsorption isotherms followed a Langmuir isotherm model. Our experimental results proved that the β-cyclodextrin stabilized Fe3S4 could be a promising candidate for the removal of Pb(II) from water via simultaneously taking advantage of its magnetic properties and high affinity for heavy metals.

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.

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

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.

Optimized synthesis of CuInS2/ZnS:Al–TiO2 nanocomposites for 1,3-dichloropropene photodegradation

A novel and improved protocol was developed to prepare CuInS2/ZnS:Al-sensitized TiO2 (CIS/ZnS:Al–TiO2) nanocomposites for 1,3-dichloropropene (1,3-D) photodegradation. Response surface methodology was employed to model and optimize the operational parameters of this protocol. The CIS/ZnS:Al quantum dot (QDs) content, ZnS:Al coating time, and TGA/TiO2 molar ratio were chosen as independent variables at three levels by using the Box–Behnken design; their combined effects on the 1,3-D degradation efficiency were investigated. The synthesized CIS/ZnS:Al QDs and CIS/ZnS:Al–TiO2 nanocomposites were characterized by their photoluminescence intensity, UV-vis absorption spectra, X-ray diffraction, and transmission electron microscopy. Based on the experimental results, an empirical expression was established and subsequently applied to predict the 1,3-D degradation efficiency with the prepared photocatalysts. The predicted degradation efficiencies matched well with the experimental values (R2, 0.9874). The ANOVA results showed that the significance of the parameters was ZnS:Al coating time > QDs content > TGA/TiO2 molar ratio. The 3D response surface plots indicated that the optimum synthesis parameters were a CIS/ZnS:Al QDs content of 23%, a coating time of 418 min, and a molar ratio of 1.6. The 1,3-D degradation efficiency with the optimized photocatalyst reached 92% under an irradiation time of 5 h. The photodegradation kinetics of 1,3-D was well fitted with a pseudo-first-order kinetic equation. The experimental design and theoretical prediction methods in this work are of great significance in the design and development of high-performance CIS/ZnS:Al–TiO2 nanocomposites.

Postsynthesis Phase Transformation for CsPbBr3/Rb4PbBr6 Core/Shell Nanocrystals with Exceptional Photostability

Lead halide perovskite nanocrystals (NCs) as promising optoelectronic materials are intensively researched. However, instability is one of the biggest challenges needed to overcome before fulfill their practical applications. To improve their stability, we present a postsynthetic controlled phase transformation of CsPbBr3 toward CsPbBr3/Rb4PbBr6 core/shell structure triggered by rubidium oleate treatment. The resulting core/shell NCs show exceptional photostability both in solution and on-chip. The solution of CsPbBr3/Rb4PbBr6 NCs can remain over 90% of the initial emission photoluminescence quantum yields after 42 h of intense light-emitting diodes illumination (450 nm, 175 mW/cm2), which is even better than the conventional CdSe/CdS quantum dots whose emission drop to 50% after 18 h under the same condition. We believe that the exceptional photostability should be resulted from the protection of the robust Rb4PbBr6 shell on CsPbBr3 NCs.

Synthesis of novel magnetic sulfur-doped Fe 3 O 4 nanoparticles for efficient removal of Pb(II)

In this work, we report the synthesis of magnetic sulfur-doped Fe3O4 nanoparticles (Fe3O4:S NPs) with a novel simple strategy, which includes low temperature multicomponent mixing and high temperature sintering. The prepared Fe3O4:S NPs exhibit a much better adsorption performance towards Pb(II) than bare Fe3O4 nanoparticles. FTIR, XPS, and XRD analyses suggested that the removal mechanisms of Pb(II) by Fe3O4:S NPs were associated with the process of precipitation (formation of PbS), hydrolysis, and surface adsorption. The kinetic studies showed that the adsorption data were described well by a pseudo second-order kinetic model, and the adsorption isotherms could be presented by Freundlich isotherm model. Moreover, the adsorption was not significantly affected by the coexisting ions, and the adsorbent could be easily separated from water by an external magnetic field after Pb(II) adsorption. Thus, Fe3O4:S NPs are supposed to be a good adsorbents for Pb(II) ions in environmental remediation.