A simple hydrogen peroxide biosensor based on a novel electro-magnetic poly(p-phenylenediamine)@Fe3O4 nanocomposite

Electrochemical Detection of Bisphenol A Based on Gold Nanoparticles/Multi-Walled Carbon Nanotubes: Applications on Glassy Carbon and Screen Printed Electrodes

Bisphenol A (BPA) has been classified as an endocrine-disrupting substance that may cause adverse effects on human health and the environment. The development of simple and sensitive electrochemical biosensors is crucial for the rapid and effective quantitative determination of BPA. This work presents a study on electrochemical sensors utilizing gold nanoparticle-modified multi-walled carbon nanotubes (CNT/AuNPs). Glassy carbon electrodes (GCEs) and screen-printed electrodes (SPEs) were conveniently modified and used for BPA detection. AuNPs were electrodeposited onto the CNT-modified electrodes using the galvanostatic method. The electrodes were properly modified and characterized by using Raman spectroscopy, cyclic voltammetry (CV), and electrochemical impedance analysis (EIS). The electrochemical response of the sensors was studied using differential pulse voltammetry (DPV) and constant potential amperometry (CPA) for modified GCE and SPE electrodes, respectively, and the main analytical parameters were studied and optimized. Problems encountered with the use of GCEs, such as sensor degradation and high limit of detection (LOD), were overcome by using modified SPEs and a flow injection device for the measurements. Under this approach, an LOD as low as 5 nM (S/N = 3) was achieved and presented a linear range up to 20 μM. Finally, our investigation addressed interference, reproducibility, and reusability aspects, successfully identifying BPA in both spiked and authentic samples, including commercial and tap waters. These findings underscore the practical applicability of our method for accurate BPA detection in real-world scenarios. Notably, the integration of SPEs and a flow injection device facilitated simplified automation, offering an exceptionally efficient and reliable solution for precise BPA detection in water analysis laboratories.

Antibiotic photocatalysis and antimicrobial activity of low-cost multifunctional Fe3O4@HAp nanocomposites

Water contamination by multiple pollutants is a serious environmental issue originating from the many diverse sources of pollution. It has worsened with the appearance of new contaminants, named emerging micropollutants, such as drug residues which are considered a potential threat to human health and/or ecosystems. These require prior treatment before release into the environment. Simultaneous adsorption and photocatalysis as well as solid-liquid separation are promising technologies for water treatment. In order to obtain low cost photoactive nanocomposites, porous and magnetic Fe3O4-hydroxyapatite (wFeHAp) nanocomposites were prepared by soft chemistry from the dissociation of natural phosphate into Ca2+ and H3PO4 precursors, further neutralized by ammonia in the presence of preformed Fe3O4 particles. The magnetic nanocomposites were characterized and examined as effective antibacterial agents. Fe3O4 association with apatite modifies the surface properties of the wFeHAp nanocomposite materials, yielding efficient antimicrobial activity for S. aureus, B. subtilis, E. coli and K. pneumoniae strains. The photocatalytic removal of ciprofloxacin (CPF) and oxytetracyclin (OXT) antibiotics in water was also evaluated. The wFeHAp nanocomposites adsorbed and degraded the selected antibiotics successfully. Toxicity evaluation of the treated water after photodegradation using the four strains demonstrates the absence of toxic by-products at the end of the reaction. Therefore, Fe3O4@HAp nanoparticles are valuable for antimicrobial and photocatalysis applications.

Hydrogen Peroxide Electrochemical Sensor Based on Ag/Cu Bimetallic Nanoparticles Modified on Polypyrrole

Due to the strong oxidizing properties of H2O2, excessive discharge of H2O2 will cause great harm to the environment. Moreover, H2O2 is also an energetic material used as fuel, with specific attention given to its safety. Therefore, it is of great importance to explore and prepare good sensitive materials for the detection of H2O2 with a low detection limit and high selectivity. In this work, a kind of hydrogen peroxide electrochemical sensor has been fabricated. That is, polypyrrole (PPy) has been electropolymerized on the glass carbon electrode (GCE), and then Ag and Cu nanoparticles are modified together on the surface of polypyrrole by electrodeposition. SEM analysis shows that Cu and Ag nanoparticles are uniformly deposited on the surface of PPy. Electrochemical characterization results display that the sensor has a good response to H2O2 with two linear intervals. The first linear range is 0.1-1 mM (R2 = 0.9978, S = 265.06 μA/ (mM × cm2)), and the detection limit is 0.027 μM (S/N = 3). The second linear range is 1-35 mM (R2 = 0.9969, 445.78 μA/ (mM × cm2)), corresponding to 0.063 μM of detection limit (S/N = 3). The sensor reveals good reproducibility (σ = 2.104), repeatability (σ = 2.027), anti-interference, and stability. The recoveries of the electrode are 99.84-103.00% (for 0.1-1 mM of linear range) and 98.65-104.80% (for 1-35 mM linear range). Furthermore, the costs of the hydrogen peroxide electrochemical sensor proposed in this work are reduced largely by using non-precious metals without degradation of the sensing performance of H2O2. This study provides a facile way to develop nanocomposite electrochemical sensors.

Electroconductive bioplatform based on dextrin for the immobilization of hemoglobin: Application for electrochemical monitoring of H2O2

A novel biodegradable dextrin-based nanocomposite, involving polypyrrole (PPy) and hydrophilic dextrin (Dex) (PPy@Dex) was prepared using in-situ radical chemical polymerization technique. The obtained PPy@Dex bionanocomposite was fully characterized by FT-IR, XRD, FESEM, and DSC methods. The exceptional properties such as biocompatibility, high surface area, the proper functional group on the surface, and outstanding electrical conductivity of synthesized bionanocomposite made it a superior candidate over biomolecules immobilization. Electrochemical observations revealed that the PPy@Dex-coated glassy carbon electrode (GCE) demonstrated improved performance, making it a suitable substrate for immobilizing hemoglobin (Hb) and constructing an efficient biosensor. The resulting biosensor, named Hb-PPy@Dex/GCE, exhibited high activity in the reduction of hydrogen peroxide (H2O2). Amperometric examinations demonstrated an extensive linear range from 2 to 350 μM for Hb-PPy@Dex/GCE. The detection limit of the proposed approach was calculated to be 0.54 μM, following the S/N = 3 protocol.

A novel electrochemical immunosensor that amplifies Poly(o-phenylenediamine) signal by pH-driven cascade reaction used for alpha-foetoprotein detection

The present protocol develops an electrochemical immunosensor with poly(o-phenylene diamine) attached gold nanoparticles (PPD@Au NPs) as the immune platform, polydopamine-loaded cobalt ions (Co²⁺-PDA) as the immune probe, and K₂S₂O₈ as the signal amplifying substance with pH-driven cascade reaction. The application of conventional immunosensors often leads to easy leakage of the current signal and increases the impedance due to assembly. However, this new immunosensor offers the following advantages: (1) The signal substance PPD is modified on the electrode surface, effectively reducing the signal loss and leakage of the immunosensor; (2) The pH response reduces the impedance of the immunosensor while destroying the Co²⁺-PDA secondary antibody label; (3) The pH response releases a small amount of Co²⁺, leading to SO₄^-· generation by K₂S₂O₈ through a cascade reaction, further amplifying the PPD response current signal; (4) The pH response generates excess Co²⁺ and the by-product PDA fragments can consume the SO₄^-· generated by K₂S₂O₈, so that the final response signal decreases with the increasing antigen concentration. The experimental results showed that the immunosensor exhibited good selectivity, long-term stability, and reproducibility for AFP detection in the range of 1 pg/mL-100 ng/mL, with a detection limit of 0.214 pg/mL. Interestingly, it is expected to be used for detecting AFP in actual blood samples.

Preparation nanocapsules chitosan modified with selenium extracted from the Lactobacillus acidophilus and their anticancer properties

This study synthesized new modified imaging nanocapsules (NCs) of gallium@deferoxamine/folic acid/chitosan/polyaniline/polyvinyl alcohol (Ga@DFA/FA/CS/PANI/PVA) containing Morus nigra extract by selenium nanoparticles prepared from Lactobacillus acidophilus. Se nanoparticles were then deposited on (Ga@DFA/FA/CS/PANI/PVA) using the impregnation method. The modified contrast agents were further mixed with M. nigra extract, and their antibacterial activities were investigated by applying them on L929 cell lines. The influence of variable factors including surfactant, solvent, aqueous phase, pH, buffer, minimum Inhibitory concentration (MIC), minimum bactericidal concentration (MBC), cytotoxicity on cancer cells., antibiotic, antibiogram, release and loading, stirring effect, the concentration of nanoparticle, olive oil, and thermotical methods was investigated. The structure and morphology of the synthesized contrast agents were characterized by zeta potential sizer analysis (ZPS), X-Ray diffraction (XRD), Fourier-transform infrared (FT-IR), energy dispersive X-ray (EDX), ultraviolet-visible (UV-Vis) spectra, and scanning electron microscope (SEM). The experimental section was conducted and monitored by response surface methods (RSM) and MTT, MIC, MBC, and cancer cytotoxic conversion assay. Antibiogram testing of NCs on Pseudomonas aeruginosa bacteria was successful, and MIC = 2 factor was obtained with less harmful effect.

Surface-coated magnetic nanostructured materials for robust bio-catalysis and biomedical applications-A review

BACKGROUND

Enzymes based bio-catalysis has wide range of applications in various chemical and biological processes. Thus, the process of enzymes immobilization on suitable support to obtain highly active and stable bio-catalysts has great potential in industrial applications. Particularly, surface-modified magnetic nanomaterials have garnered a special interest as versatile platforms for biomolecules/enzyme immobilization.

AIM OF REVIEW

This review spotlights recent progress in the immobilization of various enzymes onto surface-coated multifunctional magnetic nanostructured materials and their derived nano-constructs for multiple applications. Conclusive remarks, technical challenges, and insightful opinions on this field of research which are helpful to expand the application prospects of these materials are also given with suitable examples.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Nanostructured materials, including surface-coated magnetic nanoparticles have recently gained immense significance as suitable support materials for enzyme immobilization, due to their large surface area, unique functionalities, and high chemical and mechanical stability. Besides, magnetic nanoparticles are less expensive and offers great potential in industrial applications due to their easy recovery and separation form their enzyme conjugates with an external magnetic field. Magnetic nanoparticles based biocatalytic systems offer a wide-working temperature, pH range, increased storage and thermal stabilities. So far, several studies have documented the application of a variety of surface modification and functionalization techniques to circumvent the aggregation and oxidation of magnetic nanoparticles. Surface engineering of magnetic nanoparticles (MNPs) helps to improve the dispersion stability, enhance mechanical and physicochemical properties, upgrade the surface activity and also increases enzyme immobilization capabilities and biocompatibility of the materials. However, several challenges still need to be addressed, such as controlled synthesis of MNPs and clinical aspects of these materials require consistent research from multidisciplinary scientists to realize its practical applications.

Electroconductive and photoactive poly(phenylenediamine)s with antioxidant and antimicrobial activities for potential photothermal therapy

In recent years, polyaniline derivatives such as poly(phenylenediamine)s have attracted the attention of researchers due to their better solubility, good optical and electrical properties. In the current work, poly(ortho- phenylenediamine)...

Determination of Salicylic Acid Using a Highly Sensitive and New Electroanalytical Sensor

Background:

A drug sensor (salicylic acid, in this case) was designed and made up of this research. The senor was made by modification of paste electrode (MPE) with CuO-SWCNTs and 1-hexyl-3-methylimidazolium chloride (HMICl). The MPE/CuO-SWCNTs/HMICl showed catalytic activity for the oxidation signal of salicylic acid in phosphate buffer solution.

Methods:

Electrochemical methods were used as a powerful strategy for the determination of salicylic acid in pharmaceutical samples. Aiming at this goal, carbon paste electrode was amplified with conductive materials and used as a working electrode.

Results:

The MPE/CuO-SWCNTs/HMICl was used for the determination of salicylic acid in the concentration range of 1.0 nM – 230 µM using differential pulse voltammetric (DPV) method. At pH=7.0, as optimum condition, the MPE/CuOSWCNTs/HMICl displayed a high-quality ability for the determination of salicylic acid in urine, pharmaceutical serum, and water samples.

Conclusion:

The MPE/CuO-SWCNTs/HMICl was successfully used as a new and high performance working electrode for the determination of salicylic acid at a nanomolar level and in real samples.

Properties and Recent Advantages of N,N’-dialkylimidazolium-ion Liquids Application in Electrochemistry

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N,Nʹ-dialkylimidazolium-ion liquids is one of the important ionic liquids with a wide range of application as conductive electrolyte and in electrochemistry. The modified electrodes create a new view in fabrication of electroanalytical sensors. Many modifiers have beeen suggested for modification of electroanalytical sensor since many years ago. Over these years, ionic liquids and especially room temperature ionic liquids have attracted more attention due to their wide range of electrochemical windows and high electrical conductivity. N,Nʹ-dialkylimidazolium-ion liquids are one of the main important ionic liquids suggested for modification of bare electrodes and especially carbon paste electrodes. Although many review articles have reported onthe use of ionic liquids in electrochemical sensors, no review article has been specifically introduced so far on the review of the advantages of N,Nʹ-dialkylimidazolium ionic liquid. Therefore, in this review paper we focused on the introduction of recent advantages of N,Nʹ-dialkyl imidazolium ionic liquid in electrochemistry.

Stimuli-responsive transdermal microneedle patches

Microneedle (MN) patches consisting of miniature needles have emerged as a promising tool to perforate the stratum corneum and translocate biomolecules into the dermis in a minimally invasive manner. Stimuli-responsive MN patches represent emerging drug delivery systems that release cargos on-demand as a response to internal or external triggers. In this review, a variety of stimuli-responsive MN patches for controlled drug release are introduced, covering the mechanisms of action toward different indications. Future opportunities and challenges with respect to clinical translation are also discussed.

Quantitative measurements of free and immobilized RgDAAO Michaelis-Menten constant using an electrochemical assay reveal the impact of covalent cross-linking on substrate specificity

Challenges facing enzyme-based electrochemical sensors include substrate specificity, batch to batch reproducibility, and lack of quantitative metrics related to the effect of enzyme immobilization. We present a quick, simple, and general approach for measuring the effect of immobilization and cross-linking on enzyme activity and substrate specificity. The method can be generalized for electrochemical biosensors using an enzyme that releases hydrogen peroxide during its catalytic cycle. Using as proof of concept RgDAAO-based electrochemical biosensors, we found that the Michaelis-Menten constant (K_m) decreases post immobilization, hinting at alterations in the enzyme kinetic properties and thus substrate specificity. We confirm the decrease in K_m electrochemically by characterizing the substrate specificity of the immobilized RgDAAO using chronoamperometry. Our results demonstrate that enzyme immobilization affects enzyme substrate specificity and this must be carefully evaluated during biosensor development.

Hierarchical structure in poly(N-vinyl carbazole)/Fe3O4 nanocomposites and the relevant magnetic coercivity

In this study, we report the dependence of the nanoparticle dispersion on the zero-conversion initiator efficiency in the nanocomposites formed by poly(N-vinyl carbazole) (PNVK) and acrylic acid-modified iron oxide (AA-Fe₃O₄) nanoparticles via free radical solution polymerization of the precursor solution, that is, a thorough mixture of 28.5 wt% AA-Fe₃O₄ nanoparticles and the N-vinyl carbazole (NVK) monomer with the solvent dimethylformamide and azobisisobutyronitrile as an initiator. Here three different types of the dispersion state of AA-Fe₃O₄ nanoparticles in the PNVK matrix have been distinguished by a combined approach of transmission electron microscopy and small-angle X-ray scattering coupled with real-space models of the nanoparticle assemblies. When the polymerization proceeded with a higher zero-conversion initiator efficiency (f°) by pre-polymerization at 115 °C, the generation of a large amount of free radicals could efficiently induce the dominant surface-initiated polymerization of the NVK monomer with the vinyl groups of tethered acrylic acids; in this case, the constitution of "shorter multiple grafted PNVK chains" threaded AA-Fe₃O₄ nanoparticles to form particle branches and the branches were joined together from branching points along each branch, thereby forming the network structure. However, once the polymerization was conducted at a lower f° by pre-polymerization at 75 °C, a significant reduction in the generation of free radicals likely greatly reduced the efficiency in the occurrence of surface-initiated polymerization at particle surfaces; nevertheless, the self-polymerization of the NVK monomer could still take place to induce a local demixing between the polymerizing longer PNVK chains and AA-Fe₃O₄ nanoparticles via the attractive depletion mechanism, thus locally leading to the formation of small aggregates. While if the f° was controlled to be intermediate by polymerization at 100 °C, an optimal balance between the rates of the surface-initiated polymerization and the self-polymerization induced a collective construction built from the network and aggregate structures, exhibiting the structural characteristics of large aggregates. Furthermore, the magnetic coercivity of PNVK/AA-Fe₃O₄ nanocomposites was found to depend on the dispersion state of the AA-Fe₃O₄ nanoparticles, presenting a tendency towards enhanced coercivity as the dispersion state changed from large aggregates to small aggregates to network structure.

Synthesis of Au–Cu Alloy Nanoparticles as Peroxidase Mimetics for H2O2 and Glucose Colorimetric Detection

The detection of hydrogen peroxide (H2O2) is essential in many research fields, including medical diagnosis, food safety, and environmental monitoring. In this context, Au-based bimetallic alloy nanomaterials have attracted increasing attention as an alternative to enzymes due to their superior catalytic activity. In this study, we report a coreduction synthesis of gold–copper (Au–Cu) alloy nanoparticles in aqueous phase. By controlling the amount of Au and Cu precursors, the Au/Cu molar ratio of the nanoparticles can be tuned from 1/0.1 to 1/2. The synthesized Au–Cu alloy nanoparticles show good peroxidase-like catalytic activity and high selectivity for the H2O2-mediated oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB, colorless) to TMB oxide (blue). The Au–Cu nanoparticles with an Au/Cu molar ratio of 1/2 exhibit high catalytic activity in the H2O2 colorimetric detection, with a limit of detection of 0.141 μM in the linear range of 1–10 μM and a correlation coefficient R2 = 0.991. Furthermore, the Au–Cu alloy nanoparticles can also efficiently detect glucose in the presence of glucose oxidase (GOx), and the detection limit is as low as 0.26 μM.

Functionalized gold nanoparticles: promising and efficient diagnostic and therapeutic tools for HIV/AIDS

Functionalized gold nanoparticles are recognized as promising vehicles in the diagnosis and treatment of human immunodeficiency virus (HIV) owing to their excellent biocompatibility with biomolecules (like DNA or RNA), their potential for multivalency and their unique optical and structural properties. In this context, this review article focuses on the diverse detection abilities and delivery and uptake methodologies of HIV by targeting genes and proteins using gold nanoparticles on the basis of different shapes and sizes in order to promote its effective expression. In addition, recent trends in gold nanoparticle mediated HIV detection, delivery and uptake and treatment are highlighted considering their cytotoxic effects on healthy human cells.

Hybrid conjugated polymer/magnetic nanoparticle composite nanofibers through cooperative non-covalent interactions

Hybrid organic-inorganic composites possessing both electronic and magnetic properties are promising materials for a wide range of applications. Controlled and ordered arrangement of the organic and inorganic components is key for synergistic cooperation toward desired functions. In this work, we report the self-assemblies of core-shell composite nanofibers from conjugated block copolymers and magnetic nanoparticles through the cooperation of orthogonal non-covalent interactions. We show that well-defined core-shell conjugated polymer nanofibers can be obtained through solvent induced self-assembly and polymer crystallization, while hydroxy and pyridine functional groups located at the shell of nanofibers can immobilize magnetic nanoparticles via hydrogen bonding and coordination interactions. These precisely arranged nanostructures possess electronic properties intrinsic to the polymers and are simultaneously responsive to external magnetic fields. We applied these composite nanofibers in organic solar cells and found that these non-covalent interactions led to controlled thin film morphologies containing uniformly dispersed nanoparticles, although high loadings of these inorganic components negatively impact device performance. Our methodology is general and can be utilized to control the spatial distribution of functionalized organic/inorganic building blocks, and the magnetic responsiveness and optoelectronic activities of these nanostructures may lead to new opportunities in energy and electronic applications.

Magneto-Optical Characteristics of Streptavidin-Coated Fe3O4@Au Core-Shell Nanoparticles for Potential Applications on Biomedical Assays

Recently, gold-coated magnetic nanoparticles have drawn the interest of researchers due to their unique magneto-plasmonic characteristics. Previous research has found that the magneto-optical Faraday effect of gold-coated magnetic nanoparticles can be effectively enhanced because of the surface plasmon resonance of the gold shell. Furthermore, gold-coated magnetic nanoparticles are ideal for biomedical applications because of their high stability and biocompatibility. In this work, we synthesized Fe₃O₄@Au core-shell nanoparticles and coated streptavidin (STA) on the surface. Streptavidin is a protein which can selectively bind to biotin with a strong affinity. STA is widely used in biotechnology research including enzyme-linked immunosorbent assay (ELISA), time-resolved immunofluorescence (TRFIA), biosensors, and targeted pharmaceuticals. The Faraday magneto-optical characteristics of the biofunctionalized Fe₃O₄@Au nanoparticles were measured and studied. We showed that the streptavidin-coated Fe₃O₄@Au nanoparticles still possessed the enhanced magneto-optical Faraday effect. As a result, the possibility of using biofunctionalized Fe₃O₄@Au nanoparticles for magneto-optical biomedical assays should be explored.

Synthesis and utilization of Co3O4 doped carbon nanofiber for fabrication of hemoglobin-based electrochemical sensor

In this paper cobalt oxide (Co₃O₄) nanoparticles were mixed with polyacrylonitrile to prepare Co₃O₄ doped carbon nanofiber (CNF) composite by electrospinning and carbonization, which was further used to modify on carbon ionic liquid electrode (CILE). Hemoglobin (Hb) was immobilized on Co₃O₄-CNF/CILE surface with Nafion acted as the protective film to fabricate an electrochemical biosensor (Nafion/Hb/Co₃O₄-CNF/CILE). Electrochemical behavior of Hb on the electrode was investigated with a pair of quasi-reversible redox peak appeared on cyclic voltammogram and electrochemical parameters were calculated. Moreover, this biosensor had good analytical capabilities for electrocatalytic reduction of different substrates including trichloroacetic acid, potassium bromate and sodium nitrite with wider detection range from 40.0 to 260.0 mmol L^-1, 0.1 to 48.0 mmol L^-1 and 1.0 to 12.0 mmol L^-1 by cyclic voltammetry, respectively. The proposed method showed excellent anti-interferences ability with good selectivity and was successful used for quantitative detection of real samples, which displayed the potential applications to develop into a new analytical device.

Optical-Based (Bio) Sensing Systems Using Magnetic Nanoparticles

In recent years, various reports related to sensing application research have suggested that combining the synergistic impacts of optical, electrical or magnetic properties in a single technique can lead to a new multitasking platform. Owing to their unique features of the magnetic moment, biocompatibility, ease of surface modification, chemical stability, high surface area, high mass transference, magnetic nanoparticles have found a wide range of applications in various fields, especially in sensing systems. The present review is comprehensive information about magnetic nanoparticles utilized in the optical sensing platform, broadly categorized into four types: surface plasmon resonance (SPR), surface-enhanced Raman spectroscopy (SERS), fluorescence spectroscopy and near-infrared spectroscopy and imaging (NIRS) that are commonly used in various (bio) analytical applications. The review also includes some conclusions on the state of the art in this field and future aspects.

Microwave-assisted synthesis of Pd3Ag nanocomposite via nature polysaccharide applied to glucose detection

In this work, a green strategy is performed to fabricate Pd₃Ag nanoparticles (NPs) using plant-extracted polysaccharide (Lilium brownie polysaccharide, LBP). As-obtained Pd₃Ag nanocomposite (Pd₃Ag-LBP/C) is surveyed including transmission election microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and powder X-ray diffraction (XRD). The result of glucose detection application shows that the Pd₃Ag-LBP/C glassy carbon electrode (GCE) exhibits good stability and sensitivity. It can completely cover the normal blood glucose concentration (3-8 mM) with high sensitivity of 77.20 μA mM^-1 cm^-2. This work undoubtedly has positive effects on green synthesis development. It not only proves the practicability of building nanomaterials by polysaccharide, but also offers an environmentally friendly way for fabricating other nanomaterials.

Surface Modification of Magnetic Iron Oxide Nanoparticles

Functionalized iron oxide nanoparticles (IONPs) are of great interest due to wide range applications, especially in nanomedicine. However, they face challenges preventing their further applications such as rapid agglomeration, oxidation, etc. Appropriate surface modification of IONPs can conquer these barriers with improved physicochemical properties. This review summarizes recent advances in the surface modification of IONPs with small organic molecules, polymers and inorganic materials. The preparation methods, mechanisms and applications of surface-modified IONPs with different materials are discussed. Finally, the technical barriers of IONPs and their limitations in practical applications are pointed out, and the development trends and prospects are discussed.

Voltammetric aptasensor for bisphenol A based on the use of a MWCNT/Fe3O4@gold nanocomposite

The present study describes an electrochemical aptamer-based method for the determination of bisphenol A (BPA). It is making use of gold nanoparticles (AuNPs) immobilized on a conjugate between multiwalled carbon nanotubes and thiol-functionalized magnetic nanoparticles (MWCNT/Fe₃O₄-SH) that are modified with an aptamer. The nanocomposite was characterized by Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, elemental mapping analysis and energy dispersive X-ray diffraction. The aptasensor, typically operated at 0.20 V (vs. Ag/AgCl), has a linear response in the 0.1 to 8 nM BPA concentration range, a low detection limit (0.03 nM), and high sensitivity (86.43 μA nM^-1 cm^-2). Voltammetric experiments were performed by using the hexacyanoferrate redox system as an electrochemical probe. The results indicate that the presence of AuNPs, magnetic nanoparticles and MWCNTs results a synergistic electrochemical augmentation. The method is highly selective, sensitive, efficient and environmentally friendly. The method was successfully applied to the determination of BPA in spiked real samples. Graphical abstract Aptasensor fabricated by MWCNT/Fe₃O₄-SH@Au nanocomposite and anti-BPA aptamer. The conformation of aptamer change after BPA binding, triggering a decrease in the electron transfer of Fe(CN)₆^3-/^4- on the electrode surface. The observed decline was detectable as a function of BPA concentration.

A novel nonenzymatic hydrogen peroxide amperometric sensor based on Pd@CeO2-NH2 nanocomposites modified glassy carbon electrode

Herein, (3-aminopropyl)triethoxysilane functionalized cerium (IV) oxide (CeO₂-NH₂) supported Pd nanoparticles were synthesized. The nanocomposites were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and High-resolution transmission electron microscopy (HRTEM). The Pd@CeO₂-NH₂ showed better electrocatalytic response to the reduction of H₂O₂ than CeO₂-NH₂. The fabricated sensor exhibited two linear responses to the reduction of H₂O₂. The first one was from 0.001 to 3.276 mM with 0.47 μM of a limit of detection (LOD) (S/N = 3) and excellent sensitivity of 440.72 μA mM^-1 cm^-2 and the second one was from 3.276 to 17.500 mM with the sensitivity of 852.65 μA mM^-1 cm^-2 in the optimum conductions. Also, the sensor exhibited 91% of electrocatalytic activity toward H₂O₂ after having been used for 30 days and the reproducibility was also satisfactory. The sensor response to H₂O₂ was not affected by ascorbic acid, fructose, glycine, dopamine, arginine, mannose, glucose, uric acid, Mg⁺², Ca⁺², and phenylalanine at the studied potential. Also, the fabricated sensor was used to determine H₂O₂ in milk samples. The results show that the constructed sensor can be a promising devise for the determination of H₂O₂ in real samples.