Self-Healing Conjugated Microporous Polyanilines for Effective and Continuous Catalytic Detoxification of 4-Nitrophenol to 4-Aminophenol

Detoxification of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with high efficiency and dynamic performance is challenging for a polymeric catalyst. Herein, a series of conjugated microporous polyanilines (CMPAs), capable of efficiently catalytically reducing 4-NP, were synthesized based on the Buchwald-Hartwig cross-coupling reaction mechanism. By adjusting the types of linkers and the molar ratios of linker to core, CMPAs with different Brunauer-Emmett-Teller (BET) specific surface areas and reduction degrees were obtained and used as the catalysts in reducing 4-NP. The ultrahigh catalytic reduction efficiency (K = 141.32 s-1 g-1, kapp = 0.00353 s-1) was achieved when using CMPA-3-0.7 as the catalyst (prepared with 4,4'-diaminodiphenylamine as the linker and a 0.7:1 molar ratio of linker to core). The catalytic reduction performance exhibited a strong correlation with the reduction degree and BET specific surface area of CMPAs. Furthermore, they also exhibit excellent cycling stability and dynamic performance. The coexistence of a microporous structure and high BET specific surface area endowed CMPAs with an increased number of catalytic active centers. The reversible redox transformation of CMPAs in the presence of NaBH4 and air enabled self-healing (the oxidation units in CMPAs were reduced to reduction units by NaBH4, and the newly generated reduction unit in CMPAs was subsequently oxidized to its original state by the O2 in the air), leading to the reduction reaction of 4-NP proceeded continuously and stably. The aforementioned factors resulted in the high efficiency of CMPAs for reducing 4-NP to 4-AP, enhancing the practical application prospects of CMPAs in the detoxification of 4-NP wastewater.

Impact of calcium ions at physiological concentrations on the adsorption behavior of proteins on silica nanoparticles

The adsorption of proteins on nanoparticles (NPs) largely decides the fate and bioeffects of NPs in vivo. However, bio-fluids are too complicated to directly study in them to reveal related mechanisms, and current studies on model systems often ignore some important biological factors, such as metal ions. Herein, we evaluate the effect of Ca2+ at physiological concentrations on the protein adsorption on negatively-charged silica NP (SNP50). It is found that Ca2+, as well as Mg2+ and several transition metal ions, significantly enhances the adsorption of negatively-charged proteins on SNP50. Moreover, the Ca2+-induced enhancement of protein adsorption leads to the reduced uptake of SNP50 by HeLa cells. A double-chelating mechanism is proposed for the enhanced adsorption of negatively-charged proteins by multivalent metal ions that can form 6 (or more) coordinate bonds, where the metal ions are chelated by both the surface groups of NPs and the surface residues of the adsorbed proteins. This mechanism is consistent with all experimental evidences from metal ions-induced changes of physicochemical properties of NPs to protein adsorption isotherms, and is validated with several model proteins as well as complicated serum. The findings highlight the importance of investigating the influences of physiological factors on the interaction between proteins and NPs.

Synthesis of micron-sized magnetic agarose beads chelated with nickel ions towards the affinity-based separation of histidine-tagged/rich proteins

Developing high-performance magnetic particles for the effective separation and purification of target proteins has become an important topic in the area of biomedical research. In this work, a simple and novel strategy was proposed for fabricating magnetic Fe3O4@agarose-iminodiacetic acid-Ni microspheres (MAIN), which can efficiently and selectively isolate histidine-tagged/rich proteins (His-proteins). Based on the thermoreversible sol-gel transition of agarose, basic magnetic agarose microspheres were prepared through the inverse emulsion method, in which the emulsion contained agarose and amine-modified Fe3O4 nanoparticles. The size of the emulsion was controlled by the emulsification of a high-speed shear machine, which improved the specific surface area of MAIN. Subsequently, the amine-modified Fe3O4 nanoparticles were covalently crosslinked with agarose through epichlorohydrin, which could avoid leakage of the magnetic source during use and increase the stability of MAIN. The microsized MAIN exhibited a clearly visible spherical core-shell structure with a diameter range from 3.4 μm to 9.8 μm, and excellent suspension ability in aqueous solution. The maximum adsorption capacity of MAIN for histidine-rich bovine hemoglobin was 1069.2 mg g-1 at 35 °C, which was higher than those of commercialized and most reported magnetic agarose microspheres/nanoparticles. The MAIN showed excellent adsorption ability and selectivity toward His-proteins in a mixture of histidine-rich bovine serum albumin (BSA) and histidine-poor lysozyme (LYZ). When the amount of LYZ was 5-fold higher than that of BSA, the recovery of BSA reached 75.0%. To prove its practicability, MAIN was successfully employed for the enrichment of histidine-tagged RSV-F0 from the cell culture medium supernatant. According to the optimized conditions, MAIN could enrich approximately 0.1 mg of RSV-F0 from 1 mL of complex biological sample. Therefore, we believe that the novel MAIN could be applicable for efficient separation and purification of His-proteins from complex biological systems.

Reactive Template-Engaged Synthesis of NiSx/MoS2 Nanosheets Decorated on Hollow and Porous Carbon Microtubes with Optimal Electronic Modulation toward High-Performance Enzyme-like Performance

As a promising cost-effective nanozyme, MoS₂ nanosheets (NSs) have been considered as a good candidate for the enzyme-like catalysis. However, their catalytic activity is still restricted by the insufficient active sites and poor conductivity, and thus, the comprehensive performances are still unsatisfactory. To address these issues, herein, we design and fabricate an intelligent tubular nanostructure of hierarchical hollow nanotubes, which are assembled by NiS_x/MoS₂ NSs encapsulated into N-doped carbon microtubes (NiS_x/MoS₂@NCMTs). The N-doped carbon microtubes (NCMTs) serve as a conductive skeleton, integrating with NiS_x/MoS₂ NSs and ensuring their well-distribution, thereby maximally exposing more active sites. Additionally, the tube-like structure is favorable for increasing the mass transfusion to ensure their excellent catalytic performance. Profiting from their component and structural advantages, the obtained NiS_x/MoS₂@NCMTs exhibit a surprisingly enhanced enzyme-like activity. Based on these, a facile colorimetric sensing platform to detect H₂O₂ and GSH has been developed. This proposed approach can be expected to synthesize a series of tubular heterostructured MoS₂-based composites, which will be widely applied in catalysis, energy storage, disease diagnosis, etc.

Rational design, synthesis, and applications of carbon-assisted dispersive Ni-based composites

Herein, we review recent developments in the rational design and engineering of various carbon-assisted dispersive nickel-based composites, and boosted properties for protein adsorption and nitroaromatics reduction.

Facile fabrication of ultrafine CoNi alloy nanoparticles supported on hexagonal N-doped carbon/Al2O3 nanosheets for efficient protein adsorption and catalysis

C–CoNi/@Al2O3 nanosheets were well constructed with CoAl-LDH nanosheets as a precursor, and exhibited excellent performance as both a catalyst and an adsorbent.

Controllable Compositions and Structures of FexOy@SiO2@C-Ni Hybrids with a Silica Layer as a Mineral Redox Buffer

Mineral redox buffer is a vital concept in geology that can be applied to modulate hybrid compositions and generate nanostructures with expected morphology. Here, via combining a dual coating of an inorganic silica and organic resorcinol-formaldehyde-Ni²⁺ (RF-Ni²⁺) layer on α-Fe₂O₃ spindles with a subsequent calcination process, core-shell Fe_xO_y@SiO₂@C-Ni composites with multicompositional structures were fabricated as efficient catalysts for 4-nitrophenol (4-NP) reduction. Notably, the silica layer as a redox buffer between hematite cores and the RF-Ni²⁺ shell played a crucial role in modulating the compositions and structures of the Fe_xO_y@SiO₂@C-Ni. Without the silica layer, Fe₃O₄-Ni/C composites with Ni nanoparticles trapped into the Fe₃O₄ cores were generated. Moreover, a significant impact of the calcination temperature on morphologies and compositions of the Fe_xO_y@SiO₂@C-Ni catalysts along with their catalytic performances has been verified. As a result, the catalyst annealed at 500 °C exhibited a high magnetic property and optimized morphology with high-density small nickel nanoparticles (∼11.6 nm), showing remarkably enhanced catalytic activity compared to the Fe₃O₄-Ni/C composites and excellent recyclability with a high conservation of about 92%. Furthermore, this synthetic strategy shows significant potential to modulate the nanostructures and phases of other multivalent metal oxide nanocomposites.

Integration with MoO3 microrods as precursors for hierarchical polyaniline microtubes and composites for anionic dye removal in water treatment

PANI microtubes were well constructed with MoO₃ microrods as a sacrificing template, and exhibited excellent performance for dye removal. Moreover, the PANI microtubes can be a good support to synthesize multifunctional PANI-based composites.

Carbon-supported Ni and MoO2 nanoparticles with Fe3O4 cores as a protein adsorbent

Here we have fabricated hierarchical structures of Fe₃O₄@MoO₂∩C–Ni and Fe₃O₄@C∩MoO₂–Ni composites using two different synthetic strategies, which can be used for histidine-rich protein separation.