Colorimetric magnetic microspheres as chemosensor for Cu(2+) prepared from adamantane-modified rhodamine and β-cyclodextrin-modified Fe3O4@SiO2 via host-guest interaction

Click Chemoselective Probe with a Photoswitchable Handle for Highly Sensitive Determination of Steroid Hormones in Food Samples

Residues of endocrine disrupting steroid hormones in food might cause various diseases like cardiovascular diseases and breast and prostate cancers. Monitoring steroid hormone levels plays a vital role in ensuring food safety and exploring the pathogenic mechanism of steroid hormone-related diseases. Based on the Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click reaction, a novel chemoselective probe, Azo-N3, which contains a reactive site N3, an imidazolium salt-based MS tag, and an azobenzene-based photoswitchable handle, was designed and synthesized to label ethynyl-bearing steroid hormones. The probe Azo-N3 was applied for the highly selective and sensitive detection of four ethynyl-bearing steroid hormones in food samples (milk, egg, and pork) by using ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The ionization efficiency of the labeled analytes could be increased by 6-105-fold, and such a labeled method exhibited satisfactory detection limits (0.04-0.2 μg/L), recovery (80.6-122.4%), and precision (RSDs% lower than 6.9%). Interestingly, the efficient immobilization of the probe Azo-N3 onto α-cyclodextrin (α-CD)-modified magnetic particles to construct a solid supported chemoselective probe Fe3O4-CD-Azo-N3 and UV light-controlled release of the labeled analytes from a magnetic support can be achieved by taking advantage of the photoswitched host-guest inclusion between the azobenzene unit and α-CD. The potential applications of Fe3O4-CD-Azo-N3 for labeling, capturing, and the photocontrolled release of the labeled steroid hormones were fully investigated by mass spectrometry imaging analysis. This work not only provides a sensitive and accurate method to detect steroid hormones in food but also opens a new avenue in designing solid supported chemoselective probes.

Magnetic Core-Shell Nanoparticles Using Molecularly Imprinted Polymers for Zearalenone Determination

This paper describes the synthesis of novel molecularly imprinted magnetic nano-beads for the selective extraction (MISPE) of zearalenone mycotoxin in river and tap waters and further analysis by high-performance liquid chromatography (HPLC) with fluorescence detection (FLD). A semi-covalent imprinting approach was achieved for the synthesis of the molecularly imprinted polymers (MIP). The nanoparticles were prepared by covering the starting Fe3O4 material with a first layer of tetraethyl orthosilicate (TEOS) and then with a second layer using cyclododecyl 2-hydroxy-4-(3-triethoxysilylpropylcarbamoyloxy) benzoate. The last was used with a dual role, template and functional monomer after the extraction of the template molecule. The material was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopies (FT-IR). The solid phase extraction was optimized in all the steps: loading, washing and elution. The optimal conditions allowed the determination of zearalenone in trace levels of 12.5, 25 and 50 µg L-1 without significant differences between the fortified and found level concentrations.

A novel chemosensor for the distinguishable detections of Cu2+ and Hg2+ by off-on fluorescence and ratiometric UV-visible absorption

A novel dual-functional chemosensor, derived from the conjugation of rhodamine B with a quinoline derivative (RHQ), was firstly synthesized with high efficiency and cost-effectiveness for the distinguishable detections of Cu²⁺ and Hg²⁺ via ring-opening and ring-forming mechanism. The chemosensor exhibits highly selective and distinguishable responses for Cu²⁺ and Hg²⁺ in CH₃CN-H₂O (4:1, v/v) with off-on fluorescence and ratiometric ultraviolet-visible (UV-Vis) absorption changes. Additionally, Cu²⁺ is identified by opening a rhodamine spirocycle with a UV-Vis absorption band, at around 560 nm and fluorescence turn-on. Interestingly, Hg²⁺ is discerned by opening the rhodamine spirocycle and by generating a new special cycle for the quinoline unit. Resultantly, there were two UV-Vis absorption bands at around 365 nm and 560 nm, which were accompanied by fluorescence turn-on. Moreover, the chemosensor can quantitatively detect Cu²⁺ and Hg²⁺ by off-on fluorescence and ratiometric UV-Vis absorption changes, respectively. Furthermore, the chemosensor with low cytotoxicity could be successfully administered to monitor Cu²⁺ and Hg²⁺ in living cells. This work may pay the way for the development of dual-functional chemosensor for quantificationally detecting metal ions in environmental and biological systems.

An in situ and rapid self-healing strategy enabling a stretchable nanocomposite with extremely durable and highly sensitive sensing features

Progress toward the development of wearable electromechanical sensors with durable and reliable sensing performance is critical for emerging wearable integrated electronic applications. However, it remains a long-standing challenge to realize mechanically stretchable sensing materials with extremely durable and high-performing sensing ability due to the fundamental dilemma lying in the sensing mechanism. In this work, we proposed an in situ and rapid self-healing strategy through nano-confining a dynamic host-guest supramolecular polymer network in a graphene-based multilevel nanocomposite matrix to fabricate a mechanically stretchable and structurally healable sensing nanocomposite which is provided with intriguing sensing durability and sensitivity simultaneously. When repeatedly stretching and releasing the nanocomposite sensing film, the fast association kinetics of cyclodextrin and adamantane host-guest inclusion complexes and good polymer chain dynamics in the supramolecular polymer network endowed by the nanoconfinement effect enable autonomous and rapid repair of the micro-cracks in situ generated in the sensing material. As a result, our strain sensing devices can achieve an extremely high durability and retain stable sensing performance even after over 100 000 stretching-releasing cycles at large strain of 50%. Moreover, the brittle nature originated from the inorganically dominated structure in conjunction with the thermodynamically stable host-guest interactions and dynamic hydrogen bonds inside the multilevel nanocomposite allow the sensing material to exhibit an ultrahigh gauge factor over 1500 with a large working strain of 58%. This work presents a reliable approach for the construction of ultradurable and high-performing wearable electronics.

Synthesis of mesoporous magnetic MnFe2O4@CS-SiO2 microsphere and its adsorption performance of Zn2+ and MB studies

Because of its superior physical and chemical properties, MnFe₂O₄ is regarded as one of the best magnetic material alternatives for Fe₃O₄. However, MnFe₂O₄ alone cannot remove heavy metal ions and dyes. Here, we report on a new mesoporous magnetic MnFe₂O₄@CS-SiO₂ microsphere material that was synthesised via the hydrothermal method to remove Zn²⁺ and methylene blue (MB) in simulated textile wastewater. The composite was characterised using a vibrating sample magnetometer, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and a Brunauer-Emmett Teller analysis. The pH, adsorbent dosage, initial adsorbate concentration, and reaction time effects on the removal of Zn²⁺ and MB were studied under different conditions, and a possible removal mechanism was proposed and discussed. The experimental results show that the suitable pH range for MB adsorption was extremely wide, and the adsorption equilibrium can be reached within 30 min. In addition, the prepared material has excellent stability. With an excellent removal efficiency as high as 56.1% and 93.86% for Zn²⁺ and MB, respectively, after five consecutive cycles and a superior adsorption capacity compared with other materials, the prepared composite in this paper proved to be a promising and effective magnetic adsorbent for the removal of Zn²⁺ and MB from textile wastewater.

Hairy Fluorescent Nanospheres Based on Polyelectrolyte Brush for Highly Sensitive Determination of Cu(II)

Currently, it is an ongoing challenge to develop fluorescent nanosphere detectors that are uniform, non-toxic, stable and bearing a large number of functional groups on the surface for further applications in a variety of fields. Here, we have synthesized hairy nanospheres (HNs) with different particle sizes and a content range of carboxyl groups from 4 mmol/g to 9 mmol/g. Based on this, hairy fluorescent nanospheres (HFNs) were prepared by the traditional coupling method (TCM) or adsorption-induced coupling method (ACM). By comparison, it was found that high brightness HFNs are fabricated based on HNs with poly (acrylic acid) brushes on the surface via ACM. The fluorescence intensity of hairy fluorescent nanospheres could be controlled by tuning the content of 5-aminofluorescein (5-AF) or the carboxyl groups of HNs easily. The carboxyl content of the HFNs could be as high as 8 mmol/g for further applications. The obtained HFNs are used for the detection of heavy metal ions in environmental pollution. Among various other metal ions, the response to Cu (II) is more obvious. We demonstrated that HFNs can serve as a selective probe and for the separation and determination of Cu(II) ions with a linear range of 0-0.5 μM and a low detection limit of 64 nM.

Experimental and Theoretical Studies on a Simple S-S-Bridged Dimeric Schiff Base: Selective Chromo-Fluorogenic Chemosensor for Nanomolar Detection of Fe2+ & Al3+ Ions and Its Varied Applications

A simple S-S (disulfide)-bridged dimeric Schiff base probe, L, has been designed, synthesized, and successfully characterized for the specific recognition of Al3+ and Fe2+ ions as fluorometric and colorimetric "turn-on" responses in a dimethylformamide (DMF)-H2O solvent mixture, respectively. The probe L and each metal ion bind through a 1:1 complex stoichiometry, and the plausible sensing mechanism is proposed based on the inhibition of the photoinduced electron transfer process (PET). The reversible chemosensor L showed high sensitivity toward Al3+ and Fe2+ ions, which was analyzed by fluorescence and UV-vis spectroscopy techniques up to nanomolar detection limits, 38.26 × 10-9 and 17.54 × 10-9 M, respectively. These experimental details were advocated by density functional theory (DFT) calculations. The practical utility of the chemosensor L was further demonstrated in electrochemical sensing, in vitro antimicrobial activity, molecular logic gate function, and quantification of the trace amount of Al3+ and Fe2+ ions in real water samples.

Novel porous magnetic nanospheres functionalized by β-cyclodextrin polymer and its application in organic pollutants from aqueous solution

Magnetic β-cyclodextrin (β-CD) porous polymer nanospheres (P-MCD) was fabricated by one-pot solvent thermal method using β-CD immobilized Fe₃O₄ magnetic nanoparticles with tetrafluoroterephthalonitrile as the monomer. Compared with the β-CD polymerization method reported in the literature,_ENREF_1 the synthetic route is effective and simple, thereby overcoming the harsh conditions that require nitrogen protection and always maintain anhydrous and oxygen-free. Moreover, the immobilization of β-CD on magnetic nanoparticles is combined with the cross-linking polymerization of the cross-linker, leading to a good synergistic effect on the removal of contaminants. Meanwhile, the dispersibility of the magnetic carrier enhances the dispersion of the β-CD porous polymer in the aqueous phase, and improves the inclusion adsorption performance and the adsorption process. P-MCD exhibited superior adsorption capacity and fast kinetics to MB. The maximum adsorption capacity of MB for P-MCD was 305.8 mg g ^-1, which is more than β-CD modified Fe₃O₄ magnetic nanoparticles (Fe₃O₄@β-CD). Moreover, the material had a short equilibrium time (5 min) for MB, high recovery and good recyclability (the adsorption efficiency was still above 86% after five repeated uses).

Preparation of prolinamide with adamantane for aldol reaction catalysis in brine and separation using a poly(AN-MA-β-CD) nanofibrous film via host-guest interaction

Prolinamides with double-H potential were prepared and employed as organocatalysts in asymmetric aldol reactions. The catalyst with adamantane showed improved catalytic activity, which was further enhanced by using brine as the solvent. A series of aldol reactions in brine at 0 °C provided good yields (up to 98%) with high diastereoselectivities (>99 : 1) and enantioselectivities (>99%). The prepared catalyst was adsorbed by a nanofibrous film of poly(AN-MA-β-CD) via host-guest interaction in the reaction system. The catalyst was separated from the film by applying ultrasound, with a total recovery of 96.2%. The catalyst was reused up to five times without a significant change in diastereoselectivity and enantioselectivity.

An efficient proline-based homogeneous organocatalyst with recyclability

A homogeneous organocatalyst for asymmetric reduction of imines can be reused for several cycles through a self-assembly method using MNPs.

Fabrication of Stable and Regenerable Amine Functionalized Magnetic Nanoparticles as a Potential Material for Pt(IV) Recovery from Acidic Solutions

MnFe₂O₄@SiO₂-NH₂ magnetic nanocomposite (AFMNC) adsorbent with a particle size of ∼50 nm was successfully synthesized using a facile approach. The as-prepared composite particles showed a fast binding of Pt(IV) with easy magnetic solid-liquid separation. The kinetic data were fitted to both pseudo-first and second-order rate models, indicating that AFMNC exhibited a much higher rate of Pt(IV) binding (0.125 g mg^-1 min^-1) compared to that of commercial ion-exchange resin Amberjet 4200 (0.0002 g mg^-1 min^-1). The equilibrium adsorption data were fitted to the Langmuir isotherm model with a relatively high sorption capacity of 380 mg/g. Scanning transmission electron microscopy analysis demonstrated the presence of platinum chloride after sorption on AFMNC, suggesting an adsorbate-adsorbent anion-exchange interaction. In addition, due to its magnetic characteristics, AFMNC can be easily separated from the aqueous medium after the sorption process. The novel nanocomposite may facilitate recovery of Pt(IV) from waste solutions.

A colorimetric sensor based on thiourea–polyvinyl alcohol microspheres for the selective recognition of Hg2+ and Cu2+

A novel colorimetric sensor was proposed, and the sensor can be used to monitor Hg²⁺ and Cu²⁺ ions.

Plasma polyacrylic acid and hollow TiO2 spheres modified with rhodamine B for sensitive electrochemical sensing Cu(ii)

A rhodamine B-modified nanocomposite-based electrochemical sensor was fabricated for selectively and sensitively detecting Cu(ii) in environmental fields.

Synthesis of graphene oxide decorated with core@double-shell nanoparticles and application for Cr(vi) removal

A novel graphene oxide composite, namely Fe₃O₄@SiO₂@ chitosan/GO nanocomposite (MSCG) was synthesized for decontamination of Cr(vi) from aqueous solution.