Magnetic Nanospheres Research Articles

Hierarchical micro- and mesoporous metal–organic framework-based magnetic nanospheres for the nontargeted analysis of chemical hazards in vegetables

H-MOF6@Fe3O4 nanospheres for complete removal of phytochromes through size selectivity to realize nontargeted analysis of chemical hazards in vegetables.

Hydrogen Sensing of Heterostructured Magnetic Nanospheres With Different Fe to Zn Molar Ratio

This article describes the fabrication of Zinc Ferrite-Zinc oxide (ZFO-ZnO) heterostructure devices and the various sensing schemes that can be exploited using the same. A solvothermal approach has been used for the synthesis of ZFO-ZnO heterostructures having different compositions. The investigation of magnetic and electric properties is performed by varying the ratio of Zn $^{2+}$ and Fe $^{3+}$ ions. These heterostructures show enhanced magnetization with (i) an increase in the concentration of Fe $^{3+}$ ions and (ii) exposure to hydrogen (H $_2$ ) gas. These fine molar ratio adjustments in magnetism are engineered to obtain desirable sensing properties. We fabricated several two-terminal devices for the study of multiple sensing schemes. These devices demonstrated a linear current-voltage characteristic, with enhanced electrical resistance when the Fe $^{3+}$ ion concentration is reduced. Keywords- Magnetic analysis, Zinc Ferrite-Zinc oxide, sensors, room temperature, heterostructures, tunability and nanotechnology

A lithium ion-imprinted adsorbent using magnetic carbon nanospheres as a support for the selective recovery of lithium ions

A magnetic carbon-based lithium ion-imprinted material (Li+-IIP-Fe3O4@C) with a high Li+ adsorption selectivity was designed and prepared by a surface ion imprinting method, using magnetic carbon nanospheres (Fe3O4@C) as the carrier and 2-hydroxymethyl-12-crown-4 as the adsorption unit. First, Fe3O4@C was silanized by γ-methacryloxypropyltrimethoxysilane to obtain Si-Fe3O4@C which was then functionalized with methacrylic acid (MAA), followed by polymerization to obtain PMAA-Fe3O4@C with a regular morphology and a high degree of MAA grafting. Finally, 2-hydroxymethyl-12-crown-4 was grafted onto the surface of PMAA-Fe3O4@C in the presence of LiClO4 under catalysis by p-toluenesulfonic acid. This was cross-linked by ethylene glycol dimethacrylate and eluted by a HNO3 solution to obtain Li+-IIP-Fe3O4@C. The kinetic adsorption and isothermal adsorption results for this material show that the adsorption of Li+ conforms to a pseudo-second-order kinetic model and has Langmuir isotherms. The maximum adsorption capacity of Li+-IIP-Fe3O4@C for Li+ is 22.26 mg g-1 at 25°C. The selection factors of Li+ against Na+, K+ and Mg2+ are 8.06, 5.72, and 2.75, respectively. The Li+ adsorption capacity of Li+-IIP-Fe3O4@C decreases by only 8.8% after six adsorption-desorption cycles, demonstrating an excellent regeneration capability and making it very useful for lithium recovery.

Magnetic Nanostructure-Loaded Bicontinuous Nanospheres Support Multicargo Intracellular Delivery and Oxidation-Responsive Morphological Transitions.

Magnetic nanostructures (MNS) have a wide range of biological applications due to their biocompatibility, superparamagnetic properties, and customizable composition that includes iron oxide (Fe3O4), Zn2+, and Mn2+. However, several challenges to the biomedical usage of MNS must still be addressed, such as formulation stability, inability to encapsulate therapeutic payloads, and variable clearance rates in vivo. Here, we enhance the utility of MNS during controlled delivery applications via encapsulation within polymeric bicontinuous nanospheres (BCNs) composed of poly(ethylene glycol)-block-poly(propylene sulfide) (PEG-b-PPS) copolymers. PEG-b-PPS BCNs have demonstrated versatile encapsulation and delivery capabilities for both hydrophilic and hydrophobic payloads due to their unique and highly organized cubic phase nanoarchitecture. MNS-embedded BCNs (MBCNs) were thus coloaded with physicochemically diverse molecular payloads using the technique of flash nanoprecipitation and characterized in terms of their structure and in vivo biodistribution following intravenous administration. Retention of the internal aqueous channels and cubic architecture of MBCNs were verified using cryogenic transmission electron microscopy and small-angle X-ray scattering, respectively. MBCNs demonstrated improvement in magnetic resonance imaging (MRI) contrast enhancement (r2 relaxivity) as compared to free MNS, which in combination with scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy evidenced the clustering and continued access to water of MNS following encapsulation. Furthermore, MBCNs were found to be noncytotoxic and able to deliver their hydrophilic and hydrophobic small-molecule payloads both in vitro and in vivo. Finally, the oxidation sensitivity of the hydrophobic PPS block allowed MBCNs to undergo a unique, triggerable transition in morphology into MNS-bearing micellar nanocarriers. In summary, MBCNs are an attractive platform for the delivery of molecular and nanoscale payloads for diverse on-demand and sustained drug delivery applications.

Effect of Varying Expression of EpCAM on the Efficiency of CTCs Detection by SERS-Based Immunomagnetic Optofluidic Device

Simple SummaryIn this work we present a magnetically supported SERS-based immunoassay based on solid SERS-active support for the detection of circulating tumor cells. The SERS response in our optofluidic device was correlated with the level of EpCAM expression. The level of EpCAM cell expression in four cell lines with relatively high (human metastatic prostate adenocarcinoma cells (LNCaP)), medium (human metastatic prostate adenocarcinoma cells (LNCaP)), weak (human metastatic prostate adenocarcinoma cells (LNCaP)), and no EpCAM expressions (cervical cancer cells (HeLa) has been estimated using Western Blot method supported by immunochemistry and correlated with responses of immunomagnetic SERS-based analysis. The capture efficiency of developed assay was investigated in metastatic lung cancer patients. The assay demonstrates the capability to detect circulating tumor cells from blood samples over a broad linear range (from 1 to 100 cells/mL) reflecting clinically relevant amount of CTCs depending on the stage of metastasis, age, applied therapy.The circulating tumor cells (CTCs) isolation and characterization has a great potential for non-invasive biopsy. In the present research, the surface–enhanced Raman spectroscopy (SERS)-based assay utilizing magnetic nanoparticles and solid SERS-active support integrated in the external field assisted microfluidic device was designed for efficient isolation of CTCs from blood samples. Magnetic nanospheres (Fe2O3) were coated with SERS-active metal and then modified with p-mercaptobenzoic acid (p-MBA) which works simultaneously as a Raman reporter and linker to an antiepithelial-cell-adhesion-molecule (anti-EpCAM) antibodies. The newly developed laser-induced SERS-active silicon substrate with a very strong enhancement factor (up to 108) and high stability and reproducibility provide the additional extra-enhancement in the sandwich plasmonic configuration of immune assay which finally leads to increase the efficiency of detection. The sensitive immune recognition of cancer cells is assisted by the introducing of the controllable external magnetic field into the microfluidic chip. Moreover, the integration of the SERS-active platform and p-MBA-labeled immuno-Ag@Fe2O3 nanostructures with microfluidic device offers less sample and analytes demand, precise operation, increase reproducibly of spectral responses, and enables miniaturization and portability of the presented approach. In this work, we have also investigated the effect of varying expression of the EpCAM established by the Western Blot method supported by immunochemistry on the efficiency of CTCs’ detection with the developed SERS method. We used four target cancer cell lines with relatively high (human metastatic prostate adenocarcinoma cells (LNCaP)), medium (human metastatic prostate adenocarcinoma cells (LNCaP)), weak (human metastatic prostate adenocarcinoma cells (LNCaP)), and no EpCAM expressions (cervical cancer cells (HeLa)) to estimate the limits of detection based on constructed calibration curves. Finally, blood samples from lung cancer patients were used to validate the efficiency of the developed method in clinical trials.

Synthesis and application of magnetic@layered double hydroxide as an anti-inflammatory drugs nanocarrier

BackgroundMagnetic nanocomposites with a core–shell nanostructure have huge applications in different sciences especially in the release of the drugs, because of their exclusive physical and chemical properties. In this research, magnetic@layered double hydroxide multicore@shell nanostructure was synthesized by the facile experiment and is used as novel drug nanocarrier.MethodsMagnetic nanospheres were synthesized by a facile one-step solvothermal route, and then, layered double hydroxide nanoflakes were prepared on the magnetic nanospheres by coprecipitation experiment. The synthesized nanostructures were characterized by FTIR, XRD, SEM, VSM, and TEM, respectively. After intercalation with Ibuprofen and Diclofenac as anti-inflammatory drugs and using exchange anion experiment, the basal spacing of synthesized layered double hydroxides was compared with brucite nanosheets from 0.48 nm to 2.62 nm and 2.22 nm, respectively.ResultsThe results indicated that Ibuprofen and Diclofenac were successfully intercalated into the interlay space of LDHs via bridging bidentate interaction. In addition, in-vitro drug release experiments in pH 7.4, phosphate-buffered saline (PBS) showed constant release profiles with Ibuprofen and Diclofenac as model drugs with different lipophilicity, water solubility, size, and steric effect.ConclusionThe Fe3O4@LDH-ibuprofen and Fe3O4@LDH-diclofenac had the advantage of the strong interaction between the carboxyl groups with higher trivalent cations by bridging bidentate, clarity, and high thermal stability. It is confirmed that Fe3O4@LDH multicore-shell nanostructure may have potential application for constant drug delivery.

Magnetic mesoporous silica nanospheres with dual probe & release fluorescent functionality

The combination of different nanomaterials through step-by-step synthesis procedures has turned into a promising alternative to fabricate high-quality nanosystems in order to satisfy the increasingly demanding requirements of the biomedical field. In this work, we report a detailed study on the synthesis and characterization of a complex nanosystem composed of nanoparticles with a single magnetic nanoparticle core and a shell of dense and mesoporous silica arranged in layers. The procedure designed to fabricate these systems lead us to the formation of a dispersion of non-agglomerated spherical nanoparticles of nearly 100 nm. The structural characterization performed over the final samples confirmed both the prevalence of single-core systems and the presence of the mesoporous silica shell in the outer layer. The performance of the nanosystem in a specific technological application was tested by sequentially loading two different fluorescents molecules by covalent and non-covalent bonding strategies. Due to the distinct loading strategies, the resulting nanosystem presented a magnetically-assisted probe & release functionality as analyzed in a magnetophoretic experiment.

Effective enrichment and detection of trace polybrominated diphenyl ethers in water samples based on magnetic covalent organic framework nanospheres coupled with chromatography-mass spectrometry

Novel core shell structured magnetic covalent organic frameworks were synthesized at room temperature and first applied in water samples for the enrichment of trace polybrominated diphenyl ethers (PBDEs) through magnetic solid-phase extraction. The prepared materials were characterized through transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometer and X-ray photoelectron spectroscopy. During adsorption, the parameters affecting extraction and desorption efficiency were further optimized. Combined gas chromatography and mass spectrometry (GC/MS) revealed that high enrichment factors (275–292), low limits of detection (0.12–0.38 ng·L−1), wide linear ranges (0.5–1000 ng·L−1), and good reproducibility (intra-day 1.40%–4.31% and inter-day 5.14%–9.12%) were obtained under optimal conditions. The method successfully detected PBDEs in different water samples.

Magnetic mesoporous carbon nanospheres from renewable plant phenol for efficient hexavalent chromium removal

Abstract Magnetic mesoporous carbon composites are promising adsorbents for water purification. However, the sustainable synthesis of such mesoporous carbon nanospheres with controllable structures and compositions using renewable biomass as a carbon source is still a great challenge. Herein, mesoporous carbon nanospheres have been successfully synthesized via direct pyrolysis of iron-phenolic coordination polymers. Such coordination polymers are fabricated using plant phenol as a renewable carbon source and iron ions as a metal source. The resultant magnetic mesoporous carbon nanospheres show large pore size (6.7 nm), high specific surface area (512.3 m2/g), excellent performance for Cr(VI) removal with a high adsorption capacity (336.7 mg/g), fast adsorption rate (1.60 × 10−3 mg g−1 min−1) and easy magnetic separation property. In the adsorption process, Cr(VI) is first trapped on the surface of magnetic mesoporous carbon nanospheres via electrostatic interaction. Then part of the adsorbed Cr(VI) is reduced to low-toxic Cr(III) by α-Fe/Fe3C nanoparticles dispersed in carbon nanospheres. This work provides an efficient synthesis strategy for magnetic mesoporous carbon nanospheres using plant polyphenol as a carbon source, which could be used in environmental science, energy storage and catalysis.

Hybrid Polydopamine/Ag Shell-Encapsulated Magnetic Fe3O4 Nanosphere with High Antibacterial Activity

The bacteria, which usually contaminate water environment, often cause terrible infectious diseases thus seriously threaten people’s health. To meet the increasing requirement of the public health care, an easily separable nanomaterial with sustainable anti-bacteria performance is required. This work reports a Fe3O4@PDA/Ag/PDA core-shell nanosphere in which the Ag nanocrystals immobilized on the magnetic carrier are protected by an external polydopamine (PDA) layer. The magnetic hybrid nanospheres are constructed by a tunable coating method and the particle parameters can be effectively controlled by the experimental condition. The antibacterial potential of the nanospheres is evaluable by using the Staphylococcus aureus and Escherichia coli as the models. The results indicate the Fe3O4@PDA/Ag/PDA core-shell nanospheres have a high antibacterial performance by measuring the minimum inhibitory concentration and the minimum bactericidal concentration. Finally, the product is expected to have a sustainable activity because the protecting PDA layer reduce the releasing rate of the Ag+ ions and the materials can be magnetically recovered from the media after the disinfection procedure.

Highly Sensitive Fluorescence-Linked Immunosorbent Assay for the Determination of Human IgG in Serum Using Quantum Dot Nanobeads and Magnetic Fe3O4 Nanospheres.

The aim of this study is to establish a new method with high sensitivity, accuracy, and stability for the determination of human IgG and then expand it to analyze severe acute respiratory syndrome corona virus 2 (SARS-CoV-2)-specific IgM and IgG, which is of great significance for the screening and diagnosis of COVID-19. In this study, the magnetic Fe3O4 nanospheres coupled with mouse antihuman IgG (Ab1IgG) were used as an immune capture probe (Fe3O4@Ab1IgG) to capture and separate the target, and rabbit antihuman IgG (Ab2IgG) coupled with highly luminescent quantum dot nanobeads (QBs) as a fluorescence detection probe (QBs@Ab2IgG) was used to realize high sensitivity detection. After the formation of a sandwich immunocomplex, the fluorescence intensity of the precipitate after magnetic separation was measured at the excitation wavelength of 370 nm. Under optimal conditions, a wide linear range varying from 0.005 to 40 ng·mL–1 was obtained for the detection of human IgG with a lower limit of detection at 4 pg·mL–1 (S/N = 3). The recoveries of intra- and interassays were 90.0–101.9 and 96.0–106.6%, respectively, and the relative standard deviations were 6.3–10.2 and 2.6–10.5%, respectively. Furthermore, the proposed method was successfully demonstrated to detect human IgG in serum samples, and the detection results were not statistically different (P > 0.05) from commercial enzyme-linked immunosorbent assay kits. This method is sensitive, fast, and accurate, which could be expanded to detect the specific IgM and IgG antibodies against SARS-CoV-2.

A Nanosensor for Naked-Eye Identification and Adsorption of Cadmium Ion Based on Core-Shell Magnetic Nanospheres.

Fe3O4@SiO2 nanospheres with a core–shell structure were synthesized and functionalized with bis(2-pyridylmethyl)amine (BPMA). The photoresponses of the as-obtained Fe3O4@SiO2-BPMA for Cr3+, Cd2+, Hg2+ and Pb2+ ions were evaluated through irradiation with a 352 nm ultraviolet lamp, and Fe3O4@SiO2-BPMA exhibited remarkable fluorescence enhancement toward the Cd2+ ion. The adsorption experiments revealed that Fe3O4@SiO2-BPMA had rapid and effective adsorption toward the Cd2+ ion. The adsorption reaction was mostly complete within 30 min, the adsorption efficiency reached 99.3%, and the saturated adsorption amount was 342.5 mg/g based on Langmuir linear fitting. Moreover, Fe3O4@SiO2-BPMA displayed superparamagnetic properties with the saturated magnetization of 20.1 emu/g, and its strong magnetic sensitivity made separation simple and feasible. Our efforts in this work provide a potential magnetic functionalized nanosensor for naked-eye identification and adsorption toward the Cd2+ ion.

Iron Oxide Mediated Photothermal Therapy in the Second Biological Window: A Comparative Study between Magnetite/Maghemite Nanospheres and Nanoflowers

The photothermal use of iron oxide magnetic nanoparticles (NPs) is becoming more and more popular and documented. Herein, we compared the photothermal (PT) therapy potential versus magnetic hyperthermia (MHT) modality of magnetic nanospheres, largely used in the biomedical field and magnetic multicore nanoflowers known among the best nanoheaters. The NPs were imaged using transmission electron microscopy and their optical properties characterized by UV-Vis-NIR-I-II before oxidation (magnetite) and after oxidation to maghemite. The efficiency of all NPs in MHT and PT in the preferred second near-infrared (NIR-II) biological window was carried out in water and in cancer cells. We show that, in water, magnetite nanoflowers are the most efficient nanoheaters for both modalities. Moreover, PT appears much more efficient than MHT at low NP dose, whatever the NP. In the cellular environment, for PT, efficiency was totally conserved, with magnetite nanoflowers as the best performers compared to MHT, which was totally lost. Finally, cell uptake was significantly increased for the nanoflowers compared to the nanospheres. Finally, the antitumor therapy was investigated for all NPs at the same dose delivered to the cancer cells and at reasonable laser power density (0.3 W/cm2), which showed almost total cell death for magnetite nanoflowers.

Electrochemical assay for detection of circulating tumor cells based on LiFePO4 as electrochemical probe

In this study, we reported an electrochemical assay for detecting circulating tumor cells (CTCs) in whole blood. Breast cancer cell MCF-7 was chosen as a model for study. Fe3O4 magnetic nanospheres (MNs) modified with anti-epithelial cell adhesion molecule (EpCAM) antibody were utilized to capture MCF-7 from samples and gold nanoparticles modified LiFePO4 (LiFePO4/Au) particles were chosen as electrochemical label. Aptamer can be linked onto LiFePO4/Au via Au-S bond, and then the LiFePO4/Au-aptamer complex can specifically bind to the MUC1 protein that is over-expressed on the cell surface of MCF-7. Electrochemical signals are generated by the reaction of phosphate in LiFePO4 with molybdate to form redox molybdophosphate. The utilization of LiFePO4 for signal probe may expand the application of LiFePO4 in biosensing fields.

Heterogeneous Fenton-like magnetic nanosphere coated with vanadium oxide quantum dots for enhanced organic dyes decolorization

The conventional Fenton reaction has played a vital role in the degradation of pollutants. However, this reaction is prone to forming iron mud, which causes secondary pollution. Additionally, most of the Fenton systems are in homogeneous forms and suffer from intrinsically short lifetimes, hydroxyl radicals that have short diffusion distances (OH) and non-recyclability. Herein, using magnetic composites (Fe3O4@SiO2) as the carrier and vanadium oxide quantum dots (VOxQDs) as the catalyst, we developed a renewable, heterogeneous, magnetic Fenton-like system for dye degradation in polluted wastewater. The VOxQDs of less than 10 nm showed large specific surface areas, enhanced surface-exposed active atoms, and low toxicity, which are favourable for developing an efficient Fenton-like system. In addition, owing to the electrostatic adsorption between the as-prepared catalyst and the dye molecules, the distance for OH sterilization and decolorization can be significantly reduced, overcoming the shortcomings of the short oxidation distance of OH. Accordingly, the degradation of dyes can be achieved in five seconds. Furthermore, the catalysts can be effectively separated and recycled based on their magnetic features, while the secondary pollution from both the catalysts and the incompletely degraded dye molecules into the environment can be avoided. In addition, the Fe3O4@SiO2 is able to maintain a superior morphology, and the composite material (VOxQDs/Fe3O4@SiO2) maintains more than 90% of the degradation effects even after eight repeated tests.

Surface morphology-controllable magnetic covalent organic frameworks: A novel electrocatalyst for simultaneously high-performance detection of p-nitrophenol and o-nitrophenol

Covalent organic frameworks (COFs) have attracted tremendous interest due to their promising applications, including electrocatalysis originating from their unique structural features. However, it remains a challenge to prepare COFs for p-nitrophenol (PNP) and o-nitrophenol (ONP) electrocatalysis because it is quite difficult to manipulate their dimension, composition, and morphology with abundant active sites. Here, a facile ambient temperature synthesis of unique Fe3O4-based magnetic COFs nanosphere (Fe3O4@AT-COFs) with different surface morphologic structure is reported, which exhibits higher surface area, good water dispersity, long-term stability, excellent electrical conductivity and pre-concentration effect. The prepared Fe3O4@AT-COF-based electrochemical sensor is then directly employed for the simultaneous detection of PNP and ONP with a wide linear detection range of 10–3000 μM and low detection limits (LOD) of 0.2361 μM and 0.6568 μM, respectively. Meanwhile, the Fe3O4@AT-COF can be also well-applied in lake and tap water for monitoring PNP and ONP with outstanding sensitivity and reliability, which is expect to be a high-efficient electrocatalyst with great promise for signal amplification of electrochemical sensing.

High-throughput screening of bisphenols using magnetic covalent organic frameworks as a SELDI-TOF-MS probe.

Core-shell structured magnetic covalent organic framework (Fe3O4@COF) nanospheres were rapidly synthesized at room temperature using the monodisperse Fe3O4 nanoparticles (NPs) as magnetic core and benzene-1,3,5-tricarbaldehyde (BTA) and 3,3'-dihydroxybenzidine (DHBD) as two building blocks (denoted as Fe3O4@BTA-DHBD), respectively. They can serve as a mass spectrometry probe for rapid and high-throughput screening of bisphenols (BPs) from pharmaceuticals and personal care products (PPCPs) by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS). The Fe3O4@BTA-DHBD nanospheres showed some superior features involving average pore size distribution (2.82nm), high magnetization values (42.5emug-1), high specific surface area (82.96m2g-1), and good chemical/thermal stability. It was used as both ideal adsorbent for enrichment of BPs and new substrate to assist ionization in SELDI-TOF-MS. The method exhibited good linearity in the range 0.05-4000ngmL-1 with correlation coefficients (r) higher than 0.9920. Lowlimits of detection (LODs) (500pgmL-1 for bisphenol A (BPA), 2pgmL-1 for bisphenol B (BPB), 28pgmL-1 for bisphenol C (BPC), 60pgmL-1 for bisphenol F (BPF), 33pgmL-1 for bisphenol AF (BPAF), 200pgmL-1 for bisphenol BP (BPBP), 10pgmL-1 for bisphenol S (BPS), 90pgmL-1 for tetrabromobisphenol A (BPA(Br)4), and 380pgmL-1 for tetrabromobisphenol S (BPS(Br)4)) and good recoveries (80.6-115%) of BPs in PPCPs were achieved. The relative standard deviations (RSDs) of spot-to-spot (n = 10) and sample-to-sample (n = 5) were in the ranges 5-11% and 5-12%, respectively. The dual-function platform was successfully applied to the quantitative determination of BPs in PPCPs. It not only expanded the scope of the application of COFs but also provided an alternative strategy for the determination of hazardous compounds in PPCPs. Graphical abstract Schematic representation of the synthesis of core-shell structured magnetic covalent organic framework nanospheres (Fe3O4@COFs) and its application in the analysis of bisphenols by using Fe3O4@BTA-DHBD nanospheres as a MS probe based on surface-enhanced laser desorption/ionization time-of-flight mass spectrometry.

Facile synthesis of Au nanoparticle-coated Fe3O4 magnetic composite nanospheres and their application in SERS detection of malachite green.

A facile method for synthesizing Au nanoparticle-coated Fe3O4 magnetic composite nanospheres (Fe3O4@Au MCS) via seed-mediated growth and iterative reduction is reported. The nanospheres were then successfully used to detect malachite green (MG) residues in water bodies via surface-enhanced Raman scattering (SERS) technique. Fe3O4@Au MCS has excellent optical properties and superparamagnetism; it can be dispersed into the solution to fully adsorb target molecules and then collected with a magnet to increase the molecular density and the number of SERS hot spots. Magnetic enrichment was superior to conventional detection method. The limit of detection for MG was 10-7 M and the enhancement factor was 1.1 × 105. The logarithm of the SERS intensity of the characteristic peak at 1618 cm-1 exhibited a linear relationship with the logarithm of the MG concentration over the range of 10-3- 10-7 M, with a correlation coefficient of 0.966. The Fe3O4@Au MCS had good uniformity of SERS signals, with a 18.59% relative standard deviation for the SERS intensity. MG detection in aquaculture water conformed with the established quantitative regulations. The SERS spectrum calculated with density function theory for MG adsorbed on Fe3O4@Au MCS was very close to the experimental spectrum, which verified enhancement by the substrate. Overall, Fe3O4@Au MCS enabled ultrasensitive, quantitative SERS detection of MG.

Magnetic surface molecularly imprinted polymer for selective adsorption of quinoline from coking wastewater

Quinoline, a refractory organic pollutant in coking wastewater, will harm human health and the environment if discharged directly. However, if recycled, it has considerable economic value. To realise the efficient and selective adsorption of quinoline from coking wastewater, a novel magnetic surface molecularly imprinted polymer (SMIP/MCNSs) was prepared for the specific removal and recycling of quinoline, using magnetic carbon nanospheres (MCNSs) as a carrier, quinoline as a template molecule, and acrylamide (AAm) as a functional monomer. The key preparation conditions were systematically optimised. The structure, morphology, and adsorption behaviours of SMIP/MCNSs were investigated in detail. With an imprinted layer thickness of approximately 9 nm, SMIP/MCNSs exhibits favourable magnetic responsivity, good adsorption performance, and reusability. Owing to the existence of imprinted cavities, for an initial quinoline concentration of 50 mg L-1, a high adsorption capacity qe (76.63 mg g−1) and high partition coefficient PC (0.847 mg g−1 μM−1) for SMIP/MCNSs are obtained. Competitive adsorption experiments revealed that SMIP/MCNSs possesses a greater affinity towards quinoline than towards other analogues, indicating its high quinoline selectivity. Moreover, SMIP/MCNSs shows a particular binding property for quinoline in real coking wastewater. Therefore, SMIP/MCNSs shows promise for the selective removal and enrichment recovery of quinoline in wastewater.

Degradation of Sesame Oil Phenolics Using Magnetic Immobilized Laccase

Phenolic compounds exhibit toxic effects and there are still many challenges to find an efficient way for degradation and removal of phenol especially from food. In the present study, magnetically immobilized laccase was prepared and applied as an efficient heterogeneous biocatalyst for biodegradation of phenol from sesame oil. Laccase was attached covalently to magnetic Fe3O4 nanospheres and nanorods, and the characteristics of the immobilized enzyme were studied. The magnetic supports were analyzed by scanning electron microscopy, X-ray diffraction, vibrating sample magnetometry, and Fourier-transform infrared spectroscopy. Storage stability analysis of immobilized enzyme showed that more than 70% of initial activity was kept after 15 days at 4 °C. More than 70% phenol degradation was achieved and a 60% decrease in the activity of immobilized laccase was observed after 20 independent cycles. The development of enzyme immobilization techniques on magnetic supports may expand the potential applications of heterogeneous biocatalysts in food industries.