Preparation and characterization of cellulose-chitosan/β-FeOOH composite hydrogels for adsorption and photocatalytic degradation of methyl orange

Biopolymer-based hydrogels have received great attention in wastewater treatment due to their excellent properties, e.g., high adsorption capacity, fast kinetics, reusability and ease of operation. In the present work, cellulose-chitosan/β-FeOOH composite hydrogels were prepared via co-dissolution and regeneration process as well as hydrothermal in situ synthesis of β-FeOOH. Effect of β-FeOOH loading on the properties of the composite hydrogels and the removal efficiency of methyl orange (MO) was investigated. Results showed that β-FeOOH was uniformly loaded onto the hydrogel framework, and the nanoporous structure of composite hydrogels could increase not only the effective contact area between β-FeOOH and the pollutants but also the active sites. Moreover, the increased β-FeOOH loading led to the enhanced MO removal rate under light conditions. When the loading time was extended from 6 h to 9 h, the MO removal rate increased by 21%, which can be mainly due to the photocatalytic degradation. In addition, MO removal rate reached 97.75% within 40 min under optimal conditions and attained 80.81% after five repetitions. The trapping experiment and EPR results indicated that the main active species were hydrogel radicals and holes. Consequently, this work provides an effective preparation approach for cellulose-chitosan/β-FeOOH composite hydrogel with high adsorption and photocatalytic degradation, which would hold great promise for wastewater treatment applications.

Toehold Strand Displacement-Mediated Exponential HCR for Highly Sensitive and Specific Analysis of miRNA in Living Cells

As an important disease biomarker, the development of sensitive detection strategies for miRNA, especially intracellular miRNA imaging strategies, is helpful for early diagnosis of diseases, pathological research, and drug development. Hybridization chain reaction (HCR) is widely used for miRNA imaging analysis because of its high specificity and lack of biological enzymes. However, the classic HCR reaction exhibits linear amplification with low efficiency, limiting its use for the rapid analysis of trace miRNA in living cells. To address this problem, we proposed a toehold-mediated exponential HCR (TEHCR) to achieve highly sensitive and efficient imaging of miRNA in living cells using β-FeOOH nanoparticles as transfection vectors. The detection limit of TEHCR was as low as 92.7 fM, which was 8.8 × 103 times lower compared to traditional HCR, and it can effectively distinguish single-base mismatch with high specificity. The TEHCR can also effectively distinguish the different expression levels of miRNA in cancer cells and normal cells. Furthermore, TEHCR can be used to construct OR logic gates for dual miRNA analysis without the need for additional probes, demonstrating high flexibility. This method is expected to play an important role in clinical miRNA-related disease diagnosis and drug development as well as to promote the development of logic gates.

Electrospun Functional Nanofiber Membrane for Antibiotic Removal in Water: Review

As a new kind of water pollutant, antibiotics have encouraged researchers to develop new treatment technologies. Electrospun fiber membrane shows excellent benefits in antibiotic removal in water due to its advantages of large specific surface area, high porosity, good connectivity, easy surface modification and new functions. This review introduces the four aspects of electrospinning technology, namely, initial development history, working principle, influencing factors and process types. The preparation technologies of electrospun functional fiber membranes are then summarized. Finally, recent studies about antibiotic removal by electrospun functional fiber membrane are reviewed from three aspects, namely, adsorption, photocatalysis and biodegradation. Future research demand is also recommended.

β-FeOOH/Fe-TiO2 heterojunctions on Ti for bacteria inactivation under light irradiation and biosealing

Intraosseous transcutaneous implants transferring mechanical stress directly from the skeleton to a prosthesis are an area of biological mechanics. However, bacterial invasion and weak biosealing with skin tissue usually induce implant failure. In this paper, composite coatings consisting of β-FeOOH as an outer layer and Fe-TiO₂ as an inner layer were prepared on Ti via micro-arc oxidation and hydrothermal treatment (HT). The surface microstructures and optical absorption properties of the coatings were observed, the production of reactive oxygen species (ROS) was measured, Staphylococcus aureus (S. aureus) and fibroblast behaviors were studied in vitro, and bacteria inactivation and skin tissue responses on different surfaces were evaluated in vivo. The results show that Fe³⁺ was doped into TiO₂ and β-FeOOH nanoparticles were gradually deposited on TiO₂ during HT treatment, forming β-FeOOH/Fe-TiO₂ heterojunctions. The light absorption of the composite coatings shifted to the longer wavelength region because of a narrowed TiO₂ bandgap and the formation of heterojunctions. Under light irradiation, photoinduced electrons and holes on the heterojunctions were separated efficiently. Via optimizing the amount of Fe³⁺ in TiO₂, ROS that formed at the heterojunctions after light irradiation for 10 min could kill 80% of S. aureus compared with pure Ti in vitro, but they did not affect fibroblast behavior, including proliferation and phenotyping. In vivo, the optimized β-FeOOH/Fe-TiO₂ heterojunctions, upon light irradiation, could inhibit bacterial infection, suppress an inflammatory response, and promote integration with skin tissue. Such results provide a new perspective suggesting the potential application of β-FeOOH/Fe-TiO₂ heterojunctions in percutaneous Ti implants, especially in infected cases.

Hierarchically Stabilized PAN/β-FeOOH Nanofibrous Membrane for Efficient Water Purification with Excellent Antifouling Performance and Robust Solvent Resistance

Filtration membranes, with good antifouling performance and robust solvent resistance (e.g., organic solvents or highly acidic/alkaline/saline solvents), that can effectively purify complex polluted water systems are especially demanded in practice but present a challenge to be conquered. Herein, a simple method has been demonstrated to address the obstacles, applying the stabilized polyacrylonitrile (SPAN) nanofiber/β-FeOOH nanorod composite membrane as a model. In this work, simply stabilizing PAN nanofibers in air can achieve robust solvent resistance against organic solvents and strong inorganic acidic/alkaline/saline solutions. Hydrophilic β-FeOOH nanorods were anchored onto SPAN nanofibers of our electrospun membrane and achieve superhydrophilicity (0°)/underwater superoleophobicity (>155°) for various oils. More importantly, the SPAN/β-FeOOH nanofibrous membrane exhibits robust mechanical strength (274 MPa of Young's modulus), excellent chemical stability, fast separation flux (2532-10146 L m^-2 h^-1), and satisfying removal ratio (>98.2%) against insoluble oils and soluble cationic dyes. In addition, good photocatalytic activity against organic pollutants provides our membranes with excellent flux restorability and a long-term use capacity. These outstanding performances endow our membrane with a great potential application in purifying polluted aquatic systems in worldly harsh conditions.

Highly self-diffused Sn doping in α-Fe2O3 nanorod photoanodes initiated from β-FeOOH nanorod/FTO by hydrogen treatment for solar water oxidation

In this study, we present an advanced strategy of low-temperature hydrogen annealing combined with high- temperature quenching in air for activating α-Fe₂O₃ nanorod photoanodes to boost the photoelectrochemical performance. We report that various low-temperature annealing conditions (340, 360, 380, and 400 °C) under hydrogen gas flow convert β-FeOOH into magnetite (Fe₃O₄) as well as introduce Sn⁴⁺ diffusion from FTO substrates to its surface. Furthermore, high-temperature quenching (800 °C) resulted in the phase change of magnetite (Fe₃O₄) into hematite (α-Fe₂O₃) and self Sn⁴⁺ doping into the hematite lattice. Thus, the hydrogen-assisted thermally activated hematite photoanode achieved a photocurrent density of 1.35 mA cm^-2 at 1.23 V vs. RHE and 1.91 mA cm^-2 at 1.4 V vs. RHE, which is 70% and 80% higher than that of directly quenched hematite at 800 °C. These combined two step strategies provide new insight into high Sn-self doping for α-Fe₂O₃ photoanodes and allow for further development of more efficient solar water oxidation systems.

Functionalized biochar-supported magnetic MnFe2O4 nanocomposite for the removal of Pb(ii) and Cd(ii)

In this study, a novel magnetic biochar-MnFe2O4 nanocomposite (BC/FM) was prepared using low-cost corn straw and MnFe2O4 by sol-gel/pyrolyzing route using egg white, which has abundant functional groups (-NH2 and -COOH). Following that, its composition, morphology and structure was characterized by various techniques including SEM-EDX, BET, XRD, and VSM. Batch experiment of the adsorption for Pb(ii) and Cd(ii) including influence of pH, kinetics, isotherm and thermodynamics was also studied. The results demonstrated that biochar could effectively support MnFe2O4, which displayed high dispersion on the surface of the biochar and possessed abundant functional groups and high surface area contributing to superior performance on Pb(ii) and Cd(ii) removal. Therein, MnFe2O4 with high magnetism is convenient for separating the magnetic BC/FM from an aqueous medium. Adsorption experiment results indicate that Pb(ii) and Cd(ii) removal by BC/FM was closely related to pH with the best value of pH 5.0, and the process reached equilibrium in 2 h. The adsorption process is well-described by the pseudo-second-order kinetic model and Sips (Freundlich-Langmuir) model. Thermodynamic studies suggest that the adsorption process is spontaneous and exothermic. The maximum experimental adsorption capacity of BC/FM is 154.94 and 127.83 mg g-1 for Pb(ii) and Cd(ii), respectively, in single-solute system, which is higher than that of some of the other adsorbents of biochar or biochar-based composites. In bi-solute system, the preferential adsorption order of BC/FM for the two metals is Pb(ii) prior to Cd(ii). Finally, FTIR and XPS analysis verified that the main mechanism of Pb(ii) and Cd(ii) removal by BC/FM is by forming Pb/Cd-O or complexation of carboxyl and hydroxyl and ion exchange. Therefore, the prepared magnetic BC/FM composite, as an excellent adsorbent, exhibited potential applications for the removal of Pb(ii) and Cd(ii) from wastewater.

Synthesis and characterization of a novel antibacterial material containing poly(sulfobetaine) using reverse atom transfer radical polymerization

A novel antibacterial agent was synthesized using 2-(dimethylamino)ethyl methacrylate (DM) and sodium 3-chloro-2-hydroxypropane sulfonate (CHPS). It was characterized by Fourier transform infrared spectroscopy (FTIR), NMR Spectroscopy (¹H NMR), and X-ray photoelectron spectroscopy (XPS). This new agent DMCHPS was then grafted onto a polyurethane (PU) substrate via surface-initiated reverse atom transfer radical polymerization (SI-RATRP). The modified PU was characterized by FTIR and XPS. The hydrophilic properties of the PU surface before and after the incorporation of DMCHPS were determined by static contact angle (SCA) measurements. The results showed that the hydrophilicity of the PU surface after the modification was remarkably improved. MIC tests and bacterial adhesion confirmed that modified PU has good antibacterial properties. Protein adsorption experiments show that the material has a certain ability to resist pollution. Furthermore, the high survival rate of HEK293 human embryonic kidney cells shows that the modified PU has a potential use as a medicinal material.

A novel antibacterial agent was synthesized using 2-(dimethylamino)ethyl methacrylate (DM) and sodium 3-chloro-2-hydroxypropane sulfonate (CHPS).

Effective Construction of High-quality Iron Oxy-hydroxides and Co-doped Iron Oxy-hydroxides Nanostructures: Towards the Promising Oxygen Evolution Reaction Application

Rational design of high efficient and low cost electrocatalysts for oxygen evolution reaction (OER) plays an important role in water splitting. Herein, a general gelatin-assisted wet chemistry method is employed to fabricate well-defined iron oxy-hydroxides and transitional metal doped iron oxy-hydroxides nanomaterials, which show good catalytic performances for OER. Specifically, the Co-doped iron oxy-hydroxides (Co_0.54Fe_0.46OOH) show the excellent electrocatalytic performance for OER with an onset potential of 1.52 V, tafel slope of 47 mV/dec and outstanding stability. The ultrahigh oxygen evolution activity and strong durability, with superior performance in comparison to the pure iron oxy-hydroxide (FeOOH) catalysts, originate from the branch structure of Co_0.54Fe_0.46OOH on its surface so as to provide many active edge sites, enhanced mass/charge transport capability, easy release oxygen gas bubbles, and strong structural stability, which are advantageous for OER. Meanwhile, Co-doping in FeOOH nanostructures constitutes a desirable four-electron pathway for reversible oxygen evolution and reduction, which is potentially useful for rechargeable metal−air batteries, regenerative fuel cells, and other important clean energy devices. This work may provide a new insight into constructing the promising water oxidation catalysts for practical clean energy application.

In situ dual-functional water purification with simultaneous oil removal and visible light catalysis

Dual purification of both oily wastewater and dye-polluted water for enhancing the use of freshwater is an urgent task. We report herein, the facile synthesis of inorganic semiconductor nanomaterials anchored mesh for in situ dual-functional water purification. This resultant mesh combines the excellent capacity of oil removal and the advantage of photocatalytic performance for dye degradation under visible light irradiation at the same time. In addition, the mesh was easily regenerated and remained unaltered in photocatalytic performance over five successive dye degradation cycles. Given the innovative integration of special wettability and photocatalytic activity of such a semiconductor material under visible light for dual elimination of various pollutants from water, we anticipate that this approach will provide a promising pathway for versatile applications in oily wastewater treatment, water purification and so on.

Gelatin assisted wet chemistry synthesis of high quality β-FeOOH nanorods anchored on graphene nanosheets with superior lithium-ion battery application

High quality β-FeOOH nanorods anchored on graphene nanosheets to form β-FeOOH/rGO hybrid nanostructures were synthesized by using a gelatin assisted wet chemistry strategy.

CoFe2O4 nanoparticles synthesized with natural templates

CoFe₂O₄ nanoparticles with high magnetic coercivity were synthesized using natural templates.

Synthesis of high quality CuO nanoflakes and CuO–Au nanohybrids for superior visible light photocatalytic behavior

High-quality CuO nanoflakes and CuO–Au nanohybrids are synthesized by a facile wet chemistry strategy. Compared with pure CuO nanoflakes, CuO–Au nanohybrids exhibit superior visible light-driven photocatalytic performance and have a higher photocurrent density (46 mA cm⁻²).