awen Hu

A new insight into PAM/graphene-based adsorption of water-soluble aromatic pollutants

Graphene materials have been extensively verified as a good adsorbent for tackling wastewater containing various aromatic pollutants; however, little attention has been paid to understanding the graphene-based adsorption mechanism. Here, a systematic work is performed to prepare a series of graphene oxide (GO)-incorporated polyacrylamide hydrogels, with a three-dimensional (3D) monolithic structure, followed by in situ conversion of GO to reduced graphene oxide. Such a method not only enables the prevention of irreversible aggregation of graphene sheets during the in situ reduction, but also facilitates the clarification of the relationship between the structure and adsorption properties of the graphene materials. This work presents two kinds of graphene-based 3D monolithic adsorbents for either selective separation of the cationic aromatic pollutant from anionic one or uptake both of them for the total purification purpose. More importantly, we effectively unravel that the sp2-conjugated carbon network of the graphene materials plays a pivotal role in purifying the aromatic organic pollutants through π–π stacking interactions that outstrip electrostatic attraction interactions. Therefore, the present work is expected to provide an impetus toward exploration of high-performance graphene-based materials for various applications, especially environmental remediation, on the basis of effectively impeding self-aggregation of graphene sheets and judiciously modulating their intrinsic structure.

A mini review of the synthesis of poly-1,2,3-triazole-based functional materials

As a class of nitrogenous heterocyclic compounds, poly-1,2,3-triazole-based functional materials have recently attracted growing attention across many important scientific areas such as the synthesis of drugs and functional materials. There is therefore an urgent need to perform a review study of such an important class of materials for summarizing the state-of-the-art contributions and for clarifying the direction of the most recent advances (mostly in 2016). Herein, from the perspective of raw material selection and synthetic processes, we conduct a mini review study of the most recent new findings, including technologies and strategies, on the synthesis of macromolecular 1,2,3-triazole-based functional materials, such as various state-of-the-art approaches based on click chemistry and optimization of synthetic conditions like selection of raw materials, control of their concentrations, and selective utilization of different active groups. This mini review also briefly introduces the progress of using poly-1,2,3-triazole-based materials for a broad range of applications including molecular recognition, chemical sensing, drug chemistry, bio-chemistry, and conducting materials, etc.

Improving Visible Light-Absorptivity and Photoelectric Conversion Efficiency of a TiO2 Nanotube Anode Film by Sensitization with Bi2O3 Nanoparticles

This study presents a novel visible light-active TiO2 nanotube anode film by sensitization with Bi2O3 nanoparticles. The uniform incorporation of Bi2O3 contributes to largely enhancing the solar light absorption and photoelectric conversion efficiency of TiO2 nanotubes. Due to the energy level difference between Bi2O3 and TiO2, the built-in electric field is suggested to be formed in the Bi2O3 sensitized TiO2 hybrid, which effectively separates the photo-generated electron-hole pairs and hence improves the photocatalytic activity. It is also found that the photoelectric conversion efficiency of Bi2O3 sensitized TiO2 nanotubes is not in direct proportion with the content of the sensitizer, Bi2O3, which should be carefully controlled to realize excellent photoelectrical properties. With a narrower energy band gap relative to TiO2, the sensitizer Bi2O3 can efficiently harvest the solar energy to generate electrons and holes, while TiO2 collects and transports the charge carriers. The new-type visible light-sensitive photocatalyst presented in this paper will shed light on sensitizing many other wide-band-gap semiconductors for improving solar photocatalysis, and on understanding the visible light-driven photocatalysis through narrow-band-gap semiconductor coupling.

Using biochemical system to improve cinnabar dissolution.

In order to evaluate the leaching of cinnabar, a chemobiological reactor system with Acidithiobacillus ferrooxidans for cinnabar dissolution was investigated. The results demonstrated cinnabar dissolution had relation to bioprocess of A. ferrooxidans and iron concentration tightly. The optimal dilution rate and iron concentration were 0.4/h and 2-3 g/L in chemobiological reactor. The process may be contributed to the indirect catalyzing of ferric iron generated with A. ferrooxidans and direct adherence oxidation function. This research shows the new microbiological technique may be a feasible and economical method in application.

Rapid and sensitive detection of trace malachite green and its metabolite in aquatic products using molecularly imprinted polymer-coated wooden-tip electrospray ionization mass spectrometry

In this study, a molecularly imprinted polymer-coated wooden-tip (MIPCWT) electrospray ionization mass spectrometry (ESI-MS) method was developed for rapid and sensitive detection of trace malachite green (MG) and its metabolite in aquatic products. Such a method was realized by applying a silicone-modified acrylate molecularly imprinted emulsion (SMAMIE) onto the surface of wooden tips to specially design a MIPCWT solid-phase micro-extraction (SPME) probe for selective enrichment of MG and its metabolite from aquatic products. Subsequently, a high voltage and some spray solvent were applied to the MIPCWT SPME probe, and ESI was induced for direct MS analysis under ambient and open-air conditions. The MIPCWT-SPME probe exhibits a high enriching capacity of approximately 1500–2000 fold toward MG and leucomalachite green (LMG), with detection limit reaching 0.01 μg L−1. In addition, a good linearity is obtained for both MG and LMG, with correlation coefficient values (R2) of no less than 0.998. The present method was successfully applied to analyze MG and LMG in real-life tap water, river water and fish samples, and good recoveries in the range of 93–103%, 92–108% and 106–113%, respectively, were found. All of these demonstrated that our developed MIPCWT-ESI-MS method holds great potential for rapid, direct, sensitive, and reliable detection and analysis of trace veterinary drug residues in aquatic products.

Combining Pickering Emulsion Polymerization with Molecular Imprinting to Prepare Polymer Microspheres for Selective Solid-Phase Extraction of Malachite Green

Malachite green (MG) is currently posing a carcinogenic threat to the safety of human lives; therefore, it is highly desirable to develop an effective method for fast trace detection of MG. Herein, for the first time, this paper presents a systematic study on polymer microspheres, being prepared by combined Pickering emulsion polymerization and molecular imprinting, to detect and purify MG. The microspheres, molecularly imprinted with MG, show enhanced adsorption selectivity to MG, despite a somewhat lowered adsorption capacity, as compared to the counterpart without molecular imprinting. Structural features and adsorption performance of these microspheres are elucidated by different characterizations and kinetic and thermodynamic analyses. The surface of the molecularly imprinted polymer microspheres (M-PMs) exhibits regular pores of uniform pore size distribution, endowing M-PMs with impressive adsorption selectivity to MG. In contrast, the microspheres without molecular imprinting show a larger average particle diameter and an uneven porous surface (with roughness and a large pore size), causing a lower adsorption selectivity to MG despite a higher adsorption capacity. Various adsorption conditions are investigated, such as pH and initial concentration of the solution with MG, for optimizing the adsorption performance of M-PMs in selectively tackling MG. The adsorption kinetics and thermodynamics are deeply discussed and analyzed, so as to provide a full picture of the adsorption behaviors of the polymer microspheres with and without the molecular imprinting. Significantly, M-PMs show promising solid-phase extraction column applications for recovering MG in a continuous extraction manner.

Sealing Holes of an Anodic Aluminum Oxide Alloy by Nanotitania for Enhanced Corrosion Resistance

This study aims to explore an effective, novel, and environmentally friendly method that overcomes the limitations and shortcomings existing in the traditional approaches for sealing holes on aluminum alloy. Herein, the holesealing treatment of an Anodic Aluminum Oxide (AAO) alloy film using two types of titanium sources with a high stability in aqueous electrolytes, that is, ammonium fluorotitanate and titanium potassium oxalate, to electrically deposit nanotitania on the film surface was investigated. The nanotitania deposited electrochemically for hole sealing has the advantages of the high physiochemical stability, low cost, and non-toxicity, which can thus readily improve the corrosion resistance of the sealed AAO in an environmentally friendly manner. Such sealed AAO can also result in a UV-shielding performance due to the commonly-known UV absorption properties of nanotitania. The hole sealing effect is also compared between the two systems involving the two types of titanium sources at different concentrations, voltages and time. The optimization of the preparation conditions is achieved by means of weight loss measurements. Potentiodynamic scan and electrochemical impedance spectroscopy results reveal that the hole-sealed sample-based on ammonium fluorotitanate shows a higher corrosion resistance as compared to the one based on titanium potassium oxalate. Significantly, the optimal conditions for the hole sealing of the aluminum alloy are evidenced to be the concentration of ammonium fluorotitanate of 0.1 mol/L, AC voltage of 3 V, and time of 900 s.

Core-shell-core heterostructural engineering of Y 2 O 3 :Eu 3+ /MCM-41/YVO 4 :Eu 3+ for enhanced red emission and tunable, broadened-band response to excitation

For the first time, a hierarchical phosphor Y2O3:Eu3+/MCM-41/YVO4:Eu3+, with a core–shell-core heterostructure, is presented in this study. Synergistically bridging the phosphors Y2O3:Eu3+ (as an inner core) and YVO4:Eu3+ (as an outer core) by amorphous SiO2, i.e., MCM-41 (with ordered mesoporous channels) leads to the generation of the core–shell-core heterostructure with enhanced red emission and tunable, broadened-band response to excitation. The novel structure of the core–shell-core hierarchical material is clarified through various characterization methods including X-ray diffraction analysis, transmission electron microscopy, selected-area electron diffraction and N2 adsorption–desorption measurements. Significantly, through temperature-dependent fluorescence investigation, it is found that our core–shell phosphor (Y2O3:Eu3+/MCM-41) exhibits impressive fluorescence stability against temperature variation (27–227 °C) due to the protective effect resulting from MCM-41. By contrast, lowered stability can be noted for the core–shell-core phosphor (Y2O3:Eu3+/MCM-41/YVO4:Eu3+), especially when the temperature is higher than 100 °C, owing to the outer core (YVO4:Eu3+ nanoparticles) that is directly exposed to heat. Such a kind of luminescent materials holds substantial promise for labeling the organisms that are vulnerable to short-wavelength UV light irradiation. Additionally, potential intelligent systems can be expected to be designed on the basis of the fluorescence mutation as triggered by the temperature of 100 °C.

Functionalization of Molecularly Imprinted Polymer Microspheres for the Highly Selective Removal of Contaminants from Aqueous Solutions and the Analysis of Food-Grade Fish Samples

The proliferation of pollution in aquatic environments has become a growing concern and calls for the development of novel adsorbents capable of selectively removing notorious and recalcitrant pollutants from these ecosystems. Herein, a general strategy was developed for the synthesis and functionalization of molecularly imprinted polymer microspheres (MIPs) that could be optimized to possess a significant adsorption selectivity to an organic pollutant in aqueous media, in addition to a high adsorption capacity. Considering that the molecular imprinting alone was far from satisfactory to produce a high-performance MIPs-based adsorbent, further structural engineering and surface functionalization were performed in this study. Although the more carboxyl groups on the surfaces of the MIPs enhanced the adsorption rate and capacity toward an organic pollutant through electrostatic interactions, they did not strengthen the adsorption selectivity in a proportional manner. Through a systematic study, the optimized sample exhibiting both impressive selectivity and capacity for the adsorption of the organic pollutant was found to possess a small particle size, a high specific surface area, a large total pore volume, and an appropriate amount of surface carboxyl groups. While the pseudo-second-order kinetic model was found to better describe the process of the adsorption onto the surface of MIPs as compared to the pseudo-first-order kinetic model, neither Langmuir nor Freundlich isothermal model could be used to well fit the isothermal adsorption data. Increased temperature facilitated the adsorption of the organic pollutant onto the MIPs, as an endothermic process. Furthermore, the optimized MIPs were also successfully employed as a stationary phase for the fabrication of a molecularly imprinted solid phase extraction column, with which purchased food-grade fish samples were effectively examined.