Calcined ZnTi-Layered Double Hydroxide Intercalated with H3 PW12 O40 with Efficiently Photocatalytic and Adsorption Performances

Wastewater treatment is of great significance to environmental remediation. The exploration of efficient and stable methods for wastewater treatment is still a challenging issue. Herein, a heterojunction material with photocatalysis and adsorption properties has been designed to remove the complex pollutants from wastewater. The heterojunction material (ZnO/TiO₂ -PW₁₂ , PW₁₂ =[PW₁₂ O₄₀ ]^3- ) was synthesized by calcining the ZnTi-layered double hydroxide (ZnTi-LDH) intercalated with the Keggin-type polyoxometalate H₃ PW₁₂ O₄₀ . In the construction of ZnO/TiO₂ -PW₁₂ it was found that the polyanionic PW₁₂ remained unchanged in the process of forming the proposed heterojunction. The photochemical properties verify that heterojunction synergistic with PW₁₂ facilitated the separation of photoproduced electron-hole pairs and thus suppressed the recombination. Therefore, ZnO/TiO₂ -PW₁₂ exhibits excellent photocatalytic property, and the efficiency of Cr(VI) photoreduction reached more than 90 % in the first 3 min. Furthermore, the electrostatic force between the PW₁₂ and cationic dyes makes ZnO/TiO₂ -PW₁₂ having an outstanding adsorption performance for cationic dyes, such as rhodamine B, crystal violet and methyl blue. Such heterojunction material combined with polyoxometalate puts forward new insights for the design of functional materials for water treatment with low cost and high efficiency.

CO2-Responsive Spherical Polyelectrolyte Brush with Multi-Stimulation for Reversible Protein Immobilization and Release

Multi-responsive materials have received extensive interest in many areas due to their smart characteristics. This paper presents rationally designed multi-responsive spherical polyelectolyte brushes composed of a solid polystyrene (PS) core and a poly (2-(dimethylamino) ethyl methacrylate) (PDMAEMA) shell synthesized by photoemulsion polymerization. Based on dynamic light scattering, Zeta potential, turbidity measurements, isothermal titration calorimetry, and UV-vis spectroscopy, PS-PDMAEMA works as a good potential adsorbent for bovine serum albumin (BSA) for which the maximum adsorption capability could reach up to 5190mg g−1. Moreover, the immobilization and release of protein on the polymer brush could be adjusted with different triggers, including the pH, ionic strength, and temperature. Furthermore, the green gas triggers, CO2 and N2, could be employed in the BSA@ PS-PDMAEMA system by easily bubbling over many cycles without any salt accumulation. The main reason for the observed actions is the brushes could be switched alternately between extended and collapsed states with different stimulations. Upon comparing the circular dichroism spectra of original and released BSA after many cycles of adsorption and release, it’s clear that the protein can retain its initial biological activity after release from the PS-PDMAEMA. This work provides an effective and green way to immobilize and release proteins in biotechnology.

Ultrabright dye-loaded spherical polyelectrolyte brushes and their fundamental structure-fluorescence tuning principles

Ultrabright fluorescent particles (UFPs) have attracted increasing attention because of their outstanding signal amplification functions. However, there is still an urgent demand for designing novel UFPs with new components or structures as the existing ones can not satisfy the practical requirements due to their inherent disadvantages. Here we propose a novel ultrabright fluorescent particle platform by doping dyes of 5-aminofluorescein (5-AF) into silica core-based spherical poly (acrylic acid) brushes (SiO₂@PAA@5-AF) and discuss their fundamental structure-fluorescence tuning principles. A series of brushes with different polymer chain lengths are successfully synthesized and then loaded with 5-AF through chemical binding. The high loading amount, suitable density or distribution, and enhanced quantum yield (QY) of 5-AF due to the amide bond formation with PAA chains on brushes are concluded as the three major reasons for the ultrabrightness of SiO₂@PAA@5-AF. Therefore, a 2350 ± 445 times brighter brush particle in comparison to a single quantum dot (QD) is realized, and a 2.1 ± 0.4 times fluorescence improvement of a brush vs. a QD normalized by volume is also achieved when taking the hydrodynamic diameter into consideration (∼300 nm vs. ∼30 nm). Moreover, the excellent tolerance stabilities in normally applied environments and outstanding label effects to form 4-plexed encoded beads are demonstrated as well. The results in this work strongly indicate a promising potential of SiO₂@PAA@5-AF as an ultrabright and stable signal amplification tool for biomedical related sensing, labeling, and biodetection.

Electrospun Polyacrylonitrile Nanofibrous Membranes for Point-of-Use Water and Air Cleaning

Novel electrospun polyacrylonitrile (PAN) nanofibrous membranes were prepared by using heat-press lamination under various conditions. The air permeability and the burst-pressure tests were run to select the membranes for point-of-use air and water cleaning. Membrane characterization was performed by using scanning electron microscopy, contact angle, and average pore size measurements. Selected membranes were used for both air dust filtration and cross-flow water filtration tests. Air dust filter results indicated that electrospun PAN nanofibrous membranes showed very high air-dust filtration efficiency of more than 99.99 % in between PM0.3 and PM2.5, whereas cross-flow filtration test showed very high water permeability over 600 L/(m2hbar) after 6 h of operation. Combining their excellent efficiency and water permeability, these membranes offer an ideal solution to filter both air and water pollutants.

Eosin Y sensitized BiPO4 nanorods for bi-functionally enhanced visible-light-driven photocatalysis

Eosin Y sensitized BiPO₄ nanorods enhanced the degradation efficiency of MB and 2,4-DCP compared to pristine BiPO₄ by 46.7 and 10.5 fold with a 100% mineralization rate.

Selective Adsorption and Separation of Organic Dyes by Poly(acrylic acid) Hydrogels Formed with Spherical Polymer Brushes and Chitosan

Direct discharge of industry organic dyes has caused serious environmental pollution. In this study, a series of double network poly(acrylic acid) (PAA) hydrogels were fabricated with spherical polymer brushes (SPBs) and chitosan (CS) as crosslinker. Neutral spherical polyelectrolyte brushes of polystyrene–poly-N-isopropylacrylamide (PNIPAM@PS) in which poly(N-isopropylacrylamide) (PNIPAM) arms were grafted on polystyrene (PS) nanospheres, were employed as macro-crosslinkers. The innumerable hydrogen bonds both between the highly entangled PAA chains and between PNIPAM and the PAA chains composed the first network of the hydrogels. The electrostatic interactions between CS and the PAA chains formed the second network of the hydrogels. These double network hydrogels, named PNIPAM@PS/CS/PAA, achieve good compressive performance and a low swell ratio because of their compact structure through plentiful hydrogen bonding and electrostatic interactions. The hydrogel could absorb cationic dyes from water with high separation efficiency and selectivity due to the electrostatic interaction between the carboxy groups and dye molecules. The adsorption process fitted a pseudo-second-order kinetic model and Langmuir isotherm model very well. Moreover, the hydrogel can separate cationic dyes from mixed dye solutions through electrostatic interactions. After being loaded with silver nanoparticles, the obtained silver@hydrogel exhibited a good capacity for the photocatalytic degradation towards different dyes. The hydrogels are promising for dye-containing wastewater treatment.