Core-shell Magnetic Nanoparticles Research Articles

Novel magnetic bimetallic AuCu catalyst for reduction of nitroarenes and degradation of organic dyes.

Herein, core-shell magnetic nanoparticles are modified with imidazolium-tagged phosphine and propylene glycol moieties and used for the stabilization of bimetallic AuCu nanoparticles. The structure and morphology of the prepared material are identified with SEM, TEM, XRD, XPS, atomic absorption spectroscopy, Fourier translation infrared spectroscopy, and a vibrating sample magnetometer. This hydrophilic magnetic bimetallic catalyst is applied in the reduction of toxic nitroarenes and reductive degradation of hazardous organic dyes such as methyl orange (MO), methyl red (MR), and rhodamine B (RhB), as well as in the degradation of tetracycline (TC). This magnetic AuCu catalyst indicated superior activity in all three mentioned reactions in comparison with its single metal Au and Cu analogs. This catalyst is recycled for 17 consecutive runs in the reduction of 4-nitrophenol to 4-aminophenol without a significant decrease in catalytic activity and recycled catalyst is characterized.

Enhancing biocatalyst performance through immobilization of lipase (Eversa® Transform 2.0) on hybrid amine-epoxy core-shell magnetic nanoparticles

Magnetic nanoparticles were functionalized with polyethylenimine (PEI) and activated with epoxy. This support was used to immobilize Lipase (Eversa® Transform 2.0) (EVS), optimization using the Taguchi method. XRF, SEM, TEM, XRD, FTIR, TGA, and VSM performed the characterizations. The optimal conditions were immobilization yield (I.Y.) of 95.04 ± 0.79 %, time of 15 h, ionic load of 95 mM, protein load of 5 mg/g, and temperature of 25 °C. The maximum loading capacity was 25 mg/g, and its stability in 60 days of storage showed a negligible loss of only 9.53 % of its activity. The biocatalyst demonstrated better stability at varying temperatures than free EVS, maintaining 28 % of its activity at 70 °C. It was feasible to esterify free fatty acids (FFA) from babassu oil with the best reaction of 97.91 % and ten cycles having an efficiency above 50 %. The esterification of produced biolubricant was confirmed by NMR, and it displayed kinematic viscosity and density of 6.052 mm2/s and 0.832 g/cm3, respectively, at 40 °C. The in-silico study showed a binding affinity of −5.8 kcal/mol between EVS and oleic acid, suggesting a stable substrate-lipase combination suitable for esterification.

Development of magnetic La doped Al2O3 core-shell nanoparticle loaded hydrogel for selective recovery of fluoride from aquatic medium

The selective removal of pollutants from water bodies is regarded as a conciliation between the rapid expansion of industrial activities and need of clean water for sustainability. Fluoride is one such geogenic pollutant, and various materials have already been reported. Developing an efficient field employable material is however a challenge. Herein, we report the synthesis and competencies of strategically designed magnetic La-doped Al2O3 core-shell nanoparticle loaded polymeric nanohybrid as a benchmark fluoride sorbent. A facile synthesis strategy involved fabrication of Fe3O4 magnetic core followed by growth of La doped Al2O3 shell using sol-gel method. Doping of La2O3 into Al2O3 structure was optimised (6%), resulting in Fe3O4-Al0.94 La0.06O1.5 core-shell particles which provided exceptional fluoride affinity. The obtained magnetic Fe3O4-Al0.94La0.06O1.5 core-shell nanoparticles were then loaded (22%) into alginate to form cross-linked hydrogel beads (Fe3O4-Al0.94 La0.06 O1.5-Ca-ALG). These prepared hydrogel beads were characterised and utilized for selective recovery of fluoride under different ambient conditions. Driving forces for enhanced fluoride uptake by La doped Al2O3 were investigated and explained with the help of both experimental observation and theoretical simulation. Density functional theory calculations indicated significant expansion in the cell volume of Al2O3 due to La doping which favoured the fluoride sorption. The calculated defect formation energy for the incorporation of F into Al2O3 was found to decrease in the presence of La. XPS analysis suggested direct interaction of fluoride with Al, forming Al-F bond and breaking Al-O bond. Different vital parameters for uptake were optimised. Also, kinetics, isotherm and diffusion models were evaluated. Developed hydrogel beads attained record sorption capacity of 132.3mgg-1 for fluoride. Overall, excellent stability, no leaching of constituents, effectiveness for selective fluoride recovery from groundwater, brand it a perfect epitome of sustainable water treatment application.

Production and immobilization of pectinases from Penicillium crustosum in magnetic core-shell nanostructures for juice clarification

Global market of food enzymes is held by pectinases, mostly sourced from filamentous fungi via submerged fermentation. Given the one-time use nature of enzymes to clarify juices and wines, there is a crucial need to explore alternatives for enzyme immobilization, enabling their reuse in food applications. In this research, an isolated fungal strain (Penicillium crustosum OR889307) was evaluated as a new potential pectinase producer in submerged fermentation. Additionally, the enzyme was immobilized in magnetic core-shell nanostructures for juice clarification. Findings revealed that Penicillium crustosum exhibited enzymatic activities higher than other Penicillium species, and pectinase production was enhanced with lemon peel as a cosubstrate in submerged fermentation. The enzyme production (548.93 U/mL) was optimized by response surface methodology, determining the optimal conditions at 35 °C and pH 6.0. Subsequently, the enzyme was covalently immobilized on synthesized magnetic core-shell nanoparticles. The immobilized enzyme exhibited superior stability at higher temperatures (50 °C) and acidic conditions (pH 4.5). Finally, the immobilized pectinases decreased 30 % the orange juice turbidity and maintained 84 % of the enzymatic activity after five consecutive cycles. In conclusion, Penicillium crustosum is a proven pectinase producer and these enzymes immobilized on functionalized nanoparticles improve the stability and reusability of pectinase for juice clarification.

Quantitative detection of chloramphenicol residue in fish based on SERS aptasensor coupled with magnetic separation

Chloramphenicol (CAP) is a widely used antibiotic in aquaculture. However, its improper use and the resulting residues in fish have become a significant concern for human health. Conventional methods for quantifying CAP are complex and expensive, leading to the need for more efficient and sensitive techniques. In this study, both CAP aptamer and sulfhydryl (SH) complementary DNA strand (SH-cDNA) were bound to gold and silver core–shell nanoparticles (Ag@Au CSNPs) and core–shell magnetic nanoparticles (Fe3O4@Au MNPs) via Au-S covalent bonding and were used as SERS signal probes and capture probes, respectively. The principle of aptamer competitive recognition was applied to achieve the quantitative detection of CAP in fish. The capture probe and the signal probe generated strong signals by complementary hybridization in the absence of CAP in the detection system. In the presence of CAP, the CAP aptamer bonded to the CAP, and the signal probe was separated from the capture probe, resulting in a linear decrease in SERS signal intensity. Consequently, there was a strong inverse relationship between SERS intensity and the logarithm of CAP concentration, ranging from 10-5 to 10-1 µg·mL−1 (R2 = 0.9974). The limit of detection (LOD) was as low as 16 pg·mL−1. The established method exhibited strong selectivity, anti-interference, reproducibility, and stability.

Novel core–shell and recyclable gas hydrate promoter for efficient solidified natural gas storage

The storage and transportation of gases, including hydrogen, methane, and carbon dioxide in the form of gas hydrates, have recently garnered considerable attention. The practical implementation of gas hydrates crucially depends on the development of efficient and reusable promoters. In this study, novel core–shell magnetic nanoparticles (CSNs) developed as recyclable promoter to enhance gas uptake. Hydrate formation experiments indicated that the storage capacity can reach up to 132.7 ± 1.4 v/v and 160.6 ± 2.5 v/v in CSNs and CSNs + SDS solutions, respectively. Compared to pure water and SDS solution, the initial methane consumption rate (0.5972 mol/h) of CSNs increased by 12.2 times and 1.08 times at 3000 ppm, respectively. CSNs exhibited favorable characteristics in terms of cycling ability and preventing foam formation during repeated methane hydrate formation and dissociation experiments. Furthermore, the combination of CSNs and SDS resulted in a 72 % reduction in hydrate nucleation induction time and a 58.3 % decrease in foam formation ability compared to the sole use of SDS. In comparison to pure water, the addition of CSNs increased the onset temperature of hydrate formation by 4 °C and reduced the driving force required for methane hydrate formation. Additionally, molecular dynamics simulation studies revealed that CSNs effectively improved the amount of the ordered water structure, hydrate cage formation, and the growth state of methane hydrates. These properties make CSNs promising for potential use in the storage and transportation of gas, considering the economic and environmental advantages associated with the use of promoters.

Schiff Base Complex of Copper Immobilized on Core-Shell Magnetic Nanoparticles Catalyzed One-Pot Syntheses of Polyhydroquinoline Derivatives under Mild Conditions Supported by a DFT Study.

We synthesized a stable and reusable Schiff base complex of copper immobilized on core-shell magnetic nanoparticles [Cu(II)-SB/GPTMS@SiO2@Fe3O4] with simple, efficient, and available materials. A variety of characterization analyses including Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA), X-ray diffraction (XRD), vibrating-sample magnetometry (VSM), energy-dispersive X-ray spectrometry (EDX), and inductively coupled plasma (ICP) confirm that our synthesized nanocatalyst was obtained. The particle size distribution from the TEM image was obtained in the range of 42-55 nm. The existence of cupric species (Cu2+) in the catalyst was determined with XPS analysis and clearly indicated two peaks at 933.7 and 953.7 eV for Cu 2p3/2 and Cu 2p1/2, respectively. BET results showed that our catalyst synthesized with a mesoporous structure and with a specific area of 48.82 m2 g-1. After detailed characterization, the resulting nanocatalyst exhibited excellent catalytic performance for the explored catalytic reactions in the one-pot synthesis of polyhydroquinoline derivatives by the Hantzsch reaction of dimedone, ethyl acetoacetate, ammonium acetate, and various aldehydes under sustainable and mild conditions. The corresponding products 5a-l are achieved in yields of 88-97%. Additionally, density functional theory (DFT) calculations were carried out to investigate the electrostatic potential root (ESP), natural bond orbital (NBO), and molecular orbitals (MOs), drawing the reaction mechanism using the total energy of the reactant and product and the study of structural parameters.

Upscale Synthesis of Magnetic Mesoporous Silica Nanoparticles and Application to Metal Ion Separation: Nanosafety Evaluation.

The synthesis of core-shell magnetic mesoporous nanoparticles (MMSNs) through a phase transfer process is usually performed at the 100-250 mg scale. At the gram scale, nanoparticles without cores or with multicore systems are observed. Iron oxide core nanoparticles (IO) were synthesized through a thermal decomposition procedure of α-FeO(OH) in oleic acid. A phase transfer from chloroform to water was then performed in order to wrap the IO nanoparticles with a mesoporous silica shell through the sol-gel procedure. MMSNs were then functionalized with DTPA (diethylenetriaminepentacetic acid) and used for the separation of metal ions. Their toxicity was evaluated. The phase transfer procedure was crucial to obtaining MMSNs on a large scale. Three synthesis parameters were rigorously controlled: temperature, time and glassware. The homogeneous dispersion of MMSNs on the gram scale was successfully obtained. After functionalization with DTPA, the MMSN-DTPAs were shown to have a strong affinity for Ni ions. Furthermore, toxicity was evaluated in cells, zebrafish and seahorse cell metabolic assays, and the nanoparticles were found to be nontoxic. We developed a method of preparing MMSNs at the gram scale. After functionalization with DTPA, the nanoparticles were efficient in metal ion removal and separation; furthermore, no toxicity was noticed up to 125 µg mL-1 in zebrafish.

The core-shell structure of nitrogen-doped carbon coated Fe3O4 decorated MXene for broadband and efficient microwave absorption

In recent years, MXene has gained widespread attention in the field of microwave absorption (MA) due to its unique two-dimensional layered structure, excellent electrical conductivity, and chemically active surface. However, the MA mechanism of MXene is limited to dielectric loss alone, which poses a challenge in meeting the performance requirements of new absorbers. Therefore, to enhance the performance of MXene in MA, this paper successfully prepared Fe3O4/NC@MXene (FNCM) composites by modifying core-shell magnetic nanoparticles of nitrogen-doped carbon coated Fe3O4 (Fe3O4/NC) on MXene. By adjusting the dose of Fe3O4/PDA precursor, the impedance matching is further optimized. FNCM-2 demonstrates superior MA performance with a thickness of 2mm, achieving a minimum reflection loss (RLmin) of −54.41 dB and an effective absorption bandwidth (EAB) of 7.32 GHz. Meanwhile, the RLmin of the FNCM-1 sample at a thickness of 2 mm can reach −55.65 dB. The remarkable improvement in MA performance can be attributed to the synergistic effect of dielectric and magnetic losses, which optimizes impedance matching. This study is expected to provide insights for the development of efficient and broadband MXene-based MA materials.

Synthesis of core-shell magnetic mesoporous silica nanoparticles to disperse amine functionalities for post-combustion carbon dioxide capture

BackgroundPost-combustion capture technology appears a suitable approach to reduce the emission of CO2 by power plants. The use of solid sorbents would permit to overcome the limitations of the well-established liquid amine-based absorption process. In particular, mesoporous silica materials have been proposed as suitable sorbents especially if functionalized with amines. MethodsThe properties of as-synthesized (by using dodecylamine as synthesis amine) and calcined hexagonal mesoporous silica (HMS), impregnated or not with tetraethylenepentamine (TEPA), were studied. Magnetite (Fe3O4) nanoparticles were specifically used to obtain HMS core-shell nanoparticles in order to investigate the effect of the magnetite core on CO2 uptake capability. CO2 uptake measurements were carried out on all HMS and core-shell particles. Furthermore, Transmission Electron Microscopy (TEM) images, Fourier Transform Infrared (FTIR) spectra and N2 adsorption/desorption measurements allowed analyzing some important properties of the sorbent particles, such as particle aggregation, incorporation and dispersion of amines, surface area, pore volume and pore size distribution. Significant FindingsThe best performance in terms of chemical CO2 uptake was obtained on core-shell material, calcined and impregnated with TEPA (about 89 mg/g), but also the as prepared core-shell sample impregnated with TEPA seems promising since the synthesis dodecylamine sites can be activated during the impregnation process.

Synthesis and Characterization of Core-Shell Mesoporous Iron oxide Magnetic Nanoparticles using Modified Co-Precipitation Method

In recent era, development of nanotechnology is an art of delivery of drug by improving its compatibility, effectiveness and efficacy. Among all nanoparticles, magnetic nanoparticles play a predominant role to shows their targeted drug delivery using a magnetic field, also helps to diagnose the diseases like cancer. The present study included preparation of four different mesoporous nanoparticles using the Pluronic block copolymer P123 as a surfactant template, then insert iron oxides using co-precipitation method. The resulted formed mesoporous magnetic nanoparticles are examined for structural characters by using FTIR, XRD, HRSEM and Elemental Mapping techniques. The results of X-ray diffraction (XRD) showed that the formed composites conserved ordered mesoporous structure after the formation of iron oxide nanoparticles in the pores. FTIR results indicated that the surface contains silanol group and Fe–O on the surface of the materials at 1060 cm-1 and 1020 cm-1 peaks respectively. Scanning electron microscopy (SEM) results showed that all mesoporous magnetic nanoparticles within the range of size from 50 to 100nm also possessed a regular spherical shape. These particles possessed high surface area, high pore volume and showed magnetic response sufficient for drug targeting in the presence of an external magnetic field. Elemental mapping data indicated about the percentage of all elements present in the mesoporous materials. We concluded that all four types of magnetic nanoparticles are structurally arranged in their structure with sufficient percentage of elements on their particle surface along with good size range. Further loading of drug into all types of magnetic nanoparticles decides the loading efficiency, stability and drug release nature.

A Novel pH-Responsive Iron Oxide Core-Shell Magnetic Mesoporous Silica Nanoparticle (M-MSN) System Encapsulating Doxorubicin (DOX) and Glucose Oxidase (Gox) for Pancreatic Cancer Treatment.

This study developed a pancreatic cancer targeted drug delivery system that responds to changes in acidity. The system was based on iron oxide core-shell magnetic mesoporous silica nanoparticles (M-MSNs) to treat pancreatic cancer through combined chemotherapy and starvation therapy. Glucose oxidase (Gox) was coupled to the cancer cell surface to reduce glucose availability for cancer cells, exacerbating the heterogeneity of the tumor microenvironment. Reduced pH accelerated the depolymerization of pH-sensitive polydopamine (PDA), thereby controlling the spatial distribution of Gox and release of doxorubicin (DOX) within tumor cells. Characterization results showed the successful synthesis of DG@M-MSN-PDA-PEG-FA (DG@NPs) with a diameter of 66.02 ± 3.6 nm. In vitro data indicated DG@NPs were highly effective and stable with good cellular uptake shown by confocal laser scanning microscopy (CLSM). DG@NPs exhibited high cytotoxicity and induced apoptosis. Additionally, in vivo experiments confirmed DG@NPs effectively inhibited tumor growth in nude mice with good biosafety. The combination of starvation therapy and chemotherapy facilitated drug release, suggesting DG@NPs as a novel drug delivery system for pancreatic cancer treatment. This study successfully constructed a doxorubicin release system responsive to acidity changes for targeted delivery in pancreatic cancer, providing a new strategy for combination therapy.

Studies on the extraction performance of phorate by aptamer-functionalized magnetic nanoparticles in plasma samples

Abstract Phorate, a highly toxic organophosphorus pesticide, poses significant risks due to its efficiency, versatility, and affordability. Therefore, studying pretreatment and detection methods for phorate in complex samples is crucial. In this study, we synthesized core-shell phorate aptamer-functionalized magnetic nanoparticles using solvothermal and self-assembly techniques. Subsequently, we developed a magnetic dispersive solid-phase extraction and detection method to identifying phorate in plasma samples. Under optimal conditions, we achieved quantitation of phorate within a range of 2–700 ng·mL−1 using gas chromatography-mass spectrometry. The detection limit (S/N = 3) was 0.46 ng·mL−1, and the intraday and interday relative standard deviation were 3.4% and 4.1%, respectively. In addition, the material exhibited excellent specificity, an enrichment capacity (EF = 416), and reusability (≥15). During phorate extraction from real plasma samples, spiked recoveries ranged from 86.1% to 101.7%. These results demonstrate that our method offers superior extraction efficiency and detection capability for phorate in plasma samples.

Efficient Hapten-Specific Biopanning Strategy Based on the Fe3O4@ENR-Functionalized Core-Shell Magnetic Nanoparticles.

The biopanning of target-specific phages is one of the most critical steps in the preparation of single-domain antibodies. In the traditional biopanning of haptens, the nonspecific binding of library phages to macromolecular proteins is one of the most challenging problems in preparing single-domain antibodies. In this research, Fe3O4@ENR-functionalized core-shell magnetic nanoparticles (FMNPs) were silylated and aminated by tetraethyl orthosilicate and (3-aminopropyl)triethoxysilane, and target enrofloxacin was coupled onto the surface by the carbodiimide method. The magnetic nanoparticles were characterized by Fourier transform infrared spectroscopy, particle size distribution, zeta potential, transmission electron microscopy observation, and indirect enzyme-linked immunosorbent assay (ELISA). A biopanning strategy based on Fe3O4@ENR FMNPs was then established to solve the problem in the traditional solid-phase biopanning process. The results showed that a considerable number of enrofloxacin (ENR)-positive phages were screened by only one round of biopanning. Finally, two ENR-specific shark-derived single-domain genes were identified and validated by monoclonal phage ELISA, gene sequencing, and biolayer interferometry technology. Our study provides a new biopanning strategy based on Fe3O4@ENR FMNPs for efficiently providing phages specific to haptens.

Cobalt Ferrite Nanoparticles Capped with Perchloric Acid for Life-Science Application

Among the modern oncological therapies, one of the most promising is based on tumor hyperthermia with magnetic nanoparticles resulting from the crystallization of iron and cobalt oxides. We synthesized core–shell magnetic nanoparticles of perchlorate-CoxFe3−xO4 (x = 0; 0.5; 1.0) via the co-precipitation method and stabilized them in aqueous suspensions. Fine granulation of the dispersed ferrophase was revealed by Transmission Electron Microscopy and Dynamical Light Scattering, with FTIR data detailing the surface-interaction phenomena. X-ray diffractometry revealed specific crystallization features of inverse spinel lattice, providing crystallite size and lattice parameters dependent on the cobalt content. The results of the Vibrating Sample Magnetometry investigations indicated that cobalt doping has reduced the magnetic core size and increased the nanoparticle dimension, which could be the result of crystallization defects at the nanoparticle surface related to the presence of cobalt ions. A mathematical model was applied with a focus on the quantitative description of the temperature distribution around magnetic nanoparticles. Further development of our research will consider new cobalt ferrite nanoparticles with new cobalt contents and different organic coatings to contribute to their biocompatibility and stability in aqueous suspensions, as required by administration in living organisms.

SO3H-Functionalized Epoxy-Immobilized Fe3O4 Core-Shell Magnetic Nanoparticles as an Efficient, Reusable, and Eco-Friendly Catalyst for the Sustainable and Green Synthesis of Pyran and Pyrrolidinone Derivatives.

A SO3H-functionalized epoxy-immobilized Fe3O4 core-shell magnetic nanocatalyst was prepared through a simple three-step procedure, and it was identified by various analyses such as Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), differential thermal gravity (DTG), Brunauer-Emmett-Teller (BET) analysis, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), vibration sample magnetometry (VSM), and powder X-ray diffraction (PXRD). BET analysis showed that the as-prepared nanocatalyst was synthesized with a mesoporous structure and high specific area (35.45 m2 g-1). The TEM image clearly showed that the particle size distribution was in the range of 47-65 nm. The designed magnetic nanocatalyst was used successfully in the synthesis of pyran derivatives via the reaction of dimedone, malononitrile, and various aromatic aldehydes and synthesis of pyrrolidinone derivatives via the reaction of various aromatic aldehydes, aniline, and diethyl acetylenedicarboxylate. The nanocatalyst was simply isolated from the reaction mixture utilizing an external magnet and reused several times according to the model reactions without significant loss in its efficiency.

Magnetically Stimulable Graphene Oxide/Polypropylene Nanocomposites.

Core-shell magnetic air-stable nanoparticles have attracted increasing interest in recent years. Attaining a satisfactory distribution of magnetic nanoparticles (MNPs) in polymeric matrices is difficult due to magnetically induced aggregation, and supporting the MNPs on a nonmagnetic core-shell is a well-established strategy. In order to obtain magnetically active polypropylene (PP) nanocomposites by melt mixing, the thermal reduction of graphene oxides (TrGO) at two different temperatures (600 and 1000 °C) was carried out, and, subsequently, metallic nanoparticles (Co or Ni) were dispersed on them. The XRD patterns of the nanoparticles show the characteristic peaks of the graphene, Co, and Ni nanoparticles, where the estimated sizes of Ni and Co were 3.59 and 4.25 nm, respectively. The Raman spectroscopy presents typical D and G bands of graphene materials as well as the corresponding peaks of Ni and Co nanoparticles. Elemental and surface area studies show that the carbon content and surface area increase with thermal reduction, as expected, following a reduction in the surface area by the support of MNPs. Atomic absorption spectroscopy demonstrates about 9-12 wt % metallic nanoparticles supported on the TrGO surface, showing that the reduction of GO at two different temperatures has no significant effect on the support of metallic nanoparticles. Fourier transform infrared (FT-IR) spectroscopy shows that the addition of a filler does not alter the chemical structure of the polymer. Scanning electron microscopy of the fracture interface of the samples demonstrates consistent dispersion of the filler in the polymer. The TGA analysis shows that, with the incorporation of the filler, the initial (Tonset) and maximum (Tmax) degradation temperatures of the PP nanocomposites increase up to 34 and 19 °C, respectively. The DSC results present an improvement in the crystallization temperature and percent crystallinity. The filler addition slightly enhances the elastic modulus of the nanocomposites. The results of the water contact angle confirm that the prepared nanocomposites are hydrophilic. Importantly, the diamagnetic matrix is transformed into a ferromagnetic one with the addition of the magnetic filler.

A fluorescent magnetic core–shell nanosensor for detection of copper ions in natural waters

A nanosensor based on magnetic core–shell nanoparticles functionalized with rhodamine derivative, N-(3-carboxy)acryloyl rhodamine B hydrazide (RhBCARB), using (3-aminopropyl)triethoxysilane (APTES) as a linker, has been synthesized for detection of Cu(II) ions in water. The magnetic nanoparticle and the modified rhodamine were fully characterized, showing a strong orange emission sensitive to Cu(II) ions. The sensor shows a linear response from 10 to 90 µg L−1, detection limit of 3 µg L−1 and no interference of Ni(II), Co(II), Cd(II), Zn(II), Pb(II), Hg(II) and Fe(II) ions. The nanosensor performance is similar to those described in the literature, being a viable option for the determination of Cu(II) ions in natural waters. In addition, the magnetic sensor can be easily removed from the reaction medium with the aid of a magnet and its signal recovered in acidic solution, allowing its reuse in subsequent analysis.

Fe3O4@Au Core–Shell Magnetic Nanoparticles for the Rapid Analysis of E. coli O157:H7 in an Electrochemical Immunoassay

Escherichia coli (E. coli) O157:H7 is a pathogenic bacterium that causes serious toxic effects in the human gastrointestinal tract. In this paper, a method for its effective analytical control in a milk sample was developed. To perform rapid (1 h) and accurate analysis, monodisperse Fe3O4@Au magnetic nanoparticles were synthesized and used in an electrochemical sandwich-type magnetic immunoassay. Screen-printed carbon electrodes (SPCE) were used as transducers, and electrochemical detection was performed by chronoamperometry using a secondary horseradish peroxidase-labeled antibody and 3,3',5,5'-tetramethylbenzidine. This magnetic assay was used to determine the E. coli O157:H7 strain in the linear range from 20 to 2 × 106 CFU/mL, with a limit of detection of 20 CFU/mL. The selectivity of the assay was tested using Listeria monocytogenes p60 protein, and the applicability of the assay was assessed by analyzing a commercial milk sample, demonstrating the usefulness of the synthesized nanoparticles in the developed magnetic immunoassay.

Near-infrared magnetic core-shell nanoparticles based on lanthanide metal-organic frameworks as a ratiometric felodipine sensing platform

Felodipine is an effective drug to treat hypertension, but its abuse can cause bardycardia. It is significant to develop highly sensitive detection platform for felodipine to enable the efficient treatment of hypertension diseases. In this work, to highly efficiently detect felodipine, multi-emission near-infrared (NIR) hierarchical magnetic core-shell lanthanide-MOF nanoparticles, namely Nd-MOF@Yb-MOF@SiO2@Fe3O4 (NIR-1), has been synthesized by layer-by-layer (LBL) method. LBL method can adjust the optical properties of NIR-1 and expose more active sites to improve sensitivity in detection process. NIR-1 has near-infrared luminescence emission, which can efficiently avoid the interference of autofluorescence in biological tissues. Photo-luminescent (PL) experiments also reveal that NIR-1 could be used as a near-infrared ratiometric luminescent sensor for felodipine detection with high selectivity and sensitivity, the low of detection limit (LOD) is 6.39 nM in felodipine detection, which is also performed using real biological samples. In addition, NIR-1 can be used as a ratiometric thermometer could also be applied in the temperature sensing from 293 K to 343 K. Finally, detection mechanisms for felodipine and temperature sensing performance based on near-infrared (NIR) emission were also investigated and discussed in detail.