Synthesis of Palladium, ZnFe2O4 Functionalized Reduced Graphene Oxide Nanocomposites as H2O2 Detector

CCH-Pd complex anchored on ZrFe2O4 nanoparticles as a novel magnetic catalytic for C-C coupling reactions

In the present work, Palladium nanoparticles were supported on Cinchonine functionalized ZrFe2O4 MNPs. The structure, morphology, and physicochemical properties of the particles were characterized through different analytical techniques, including fourier transformed infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), inductively coupled plasma (ICP), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), energy dispersive X-ray spectroscopy (EDS) and vibrating sample magnetometer (VSM) techniques. Moreover, it was obtained as an efficient catalyst for Hiyama and Suzuki reactions under green conditions with good to excellent yields. This method has the advantages of simple methodology, high yields, easy work-up, greener conditions, and short reaction times. This catalyst was reused four times in C-C coupling reaction without loss of its catalytic activity. The reused catalyst was characterized by ICP and FT-IR techniques. Heterogeneity and stability of ZrFe2O4@SiO2-S-CCH-Pd were studied by hot filtration test and ICP analysis.

Voltammetric determination of hydrogen peroxide at decorated palladium nanoparticles/poly 1,5-diaminonaphthalene modified carbon-paste electrode

In this work, palladium nanoparticles (PdNPs)/p1,5-DAN/ carbon paste electrode (CPE) and p1,5-DAN/CPE sensors have been developed for determination of hydrogen peroxide. Both sensors showed a highly sensitive and selective electrochemical behaviour, which were derived from a large specific area of poly 1,5 DAN and super excellent electroconductibility of PdNPs. PdNPs/p1,5-DAN/CPE exhibited excellent performance over p1,5-DAN/CPE. Thus, it was used for detecting hydrogen peroxide (H2O2) with linear ranges of 0.1 to 250 µM and 0.2 to 300 µM as well as detection limits (S/N = 3) of 1.0 and 5.0 nM for square wave voltammetry (SWV) and cyclic voltammetry (C.V) techniques, respectively. The modified CPE has good reproducibility, adequate catalytic activity, simple synthesis and stability of peak response during H2O2 oxidation on long run that exceeds many probes. Both reproducibility and stability for H2O2 detection are attributable to the PdNPs immobilized on the surface of p1,5-DAN/CPE. The modified CPE was used for determining H2O2 in real specimens with good stability, sensitivity, and reproducibility.

Laccase-Conjugated Nanostructured ZnFe2O4/rGO-Modified Electrode-Based Interfaces for Electrochemical Impedance Monitoring of Adrenaline: A Promising Biosensor for Management of Neurodegenerative Disorders

A propitious biosensor for adrenaline (AD) detection in bovine serum albumin (BSA) real samples, which can be used for diagnosis and treatment of neurodegenerative disorders, is reported here. The biosensor consists of a La/ZF/rGO/ITO bioelectrode, which is fabricated by electrophoretic deposition of zinc ferrite/reduced graphene oxide (ZF/rGO) nanohybrid followed by drop casting of laccase (La) enzymes. The material characterization and electrochemical studies revealed that the ZF/rGO nanohybrid enhanced the electroactive surface and facilitated direct electron transfer between the electrode and electrolyte interface, resulting in enhanced electrocatalytic performance. The cyclic voltammetry and electrochemical impedance spectroscopy results asserted that the ZF/rGO nanohybrid decreased the charge-transfer resistance (Rct) and increased the surface adsorption, leading to a high diffusion coefficient (D) of 0.192 cm2/s. The biosensor exhibited a high sensitivity of 0.71 Ω/μM cm2, a good linear range (0.1 to 140 μM with R2 = 0.98), and a low limit of detection (LOD) is 12.5 μM, demonstrating the synergic effect of ZF and rGO in the La/ZF/rGO/ITO bioelectrode with AD. The biosensor also exhibited high selectivity and stability (55 days) in the presence of interfering substances and in BSA samples, with a recovery percentage close to 100 ± 5% RSD, indicating its potential biosensing applications for real-world applications in disease diagnostics, monitoring, and treatment.

Facile preparation of a cost-effective platform based on ZnFe2O4 nanomaterials for electrochemical cell detection

Circulating tumor cells (CTCs) are important tumor markers that indicate early metastasis, tumor recurrence, and treatment efficacy. To identify and separate these cells from the blood, new nanomaterials need to be developed. The present study explored the potential application of ZnFe₂O₄ magnetic nanoparticles in capturing CTCs with cell surface markers. Folic acid was coupled to L-cysteine-capped ZnFe₂O₄ nanoparticles (ZC) to provide binding sites on ZnFe₂O₄ nanoparticles for the recognition of folate bioreceptors, which are highly expressed in MCF-7 breast cancer cells. The cytotoxicity of ZnFe₂O₄ nanoparticles and ZC against MCF-7 was analyzed with the MTT assay. After 24 h of incubation, there were IC50 values of 702.6 and 805.5 µg/mL for ZnFe₂O₄ and ZC, respectively. However, after 48 h of incubation, IC50 values of ZnFe₂O₄ and ZC were reduced to 267.3 and 389.7 µg/mL, respectively. The cell quantification was conducted with magnetically collected cells placed on a glassy carbon electrode, and the differential pulse voltammetry (DPV) responses were analyzed. This cost-effective ZnFe₂O₄-based biosensing platform allowed cancer cell detection with a limit of detection of 3 cells/mL, ranging from 25 to 10⁴ cells/mL. In future, these functionalized zinc ferrites may be used in electrochemical cell detection and targeted cancer therapy.

A versatile switchable dual-modal colorimetric and photoelectrochemical biosensing strategy via light-controlled sway of a signal-output transverter

A design criterion to construct a versatile dual-modal colorimetric and PEC biosensing platform for switching the corresponding mode freely is proposed via integration of a natural enzyme, light-activated nanozyme and light-controlled swayable signal-output transverter. A switchable dual-modal platform toward DNA analysis is developed as a proof of concept.

Hard template synthesis of 2D porous Co3O4 nanosheets with graphene oxide for H2O2 sensing

In this work, we used graphene oxide (GO) as a template that was removed by calcination to finally successfully prepare Co₃O₄ with 2D porous nanostructure. The results show that 2D porous structure Co₃O₄ nanosheets were only prepared at pH = 2. After electrochemical tests, the as-prepared Co₃O₄ nanosheets showed electrochemical properties that are highly suitable for H₂O₂ detection, such as high current response, short response time (less than 3 s), wide linear range (0.388-44.156 mM), low limit of detection (2.33 μM) and high sensitivity (0.0891 mA mM^-1 cm^-2). These excellent properties are mainly due to GO, as a 2D template, which connects Co₃O₄ nanoparticles to each other on a 2D plane, preventing the agglomeration of Co₃O₄ nanoparticles. The abundant pores between Co₃O₄ nanoparticles can greatly increase the reaction between the nanoparticles and H₂O₂ molecules.

Graphene and Perovskite-Based Nanocomposite for Both Electrochemical and Gas Sensor Applications: An Overview

Perovskite and graphene-based nanocomposites have attracted much attention and been proven as promising candidates for both gas (H₂S and NH₃) and electrochemical (H₂O₂, CH₃OH and glucose) sensor applications. In this review, the development of portable sensor devices on the sensitivity, selectivity, cost effectiveness, and electrode stability of chemical and electrochemical applications is summarized. The authors are mainly focused on the common analytes in gas sensors such as hydrogen sulfide, ammonia, and electrochemical sensors including non-enzymatic glucose, hydrazine, dopamine, and hydrogen peroxide. Finally, the article also addressed the stability of composite performance and outlined recent strategies for future sensor perspectives.

Size-controllable synthesis of zinc ferrite/reduced graphene oxide aerogels: efficient electrochemical sensing of p-nitrophenol

In this study, a nonaqueous method for the synthesis of size-controlled highly crystalline zinc ferrite/reduced graphene oxide (ZFO/rGO) aerogel was provided by using benzyl alcohol as the medium. In our findings, benzyl alcohol was introduced not only as the solvent, but the structure-directing agent and strong reducing agent during the nucleation and growth of ZnFe₂O₄ nanoparticles (NPs). The characterization analysis indicated that ZnFe₂O₄ NPs were immobilized on the multilayer rGO with a controllable size of 12 nm. Moreover, the 3D ZFO/rGO aerogel shows excellent electrochemical property as a facile electrochemical sensor for the detection of p-nitrophenol (p-NP). The ZFO/rGO electrochemical sensing offers the advantages of wide linear range (1-500 μmol l^-1), excellent sensitivity (23.985 mA mM^-1 cm^-2), good stability and selectivity (<8.8%). In addition, the possible reaction mechanism of 3D ZFO/rGO aerogel was explained during the detection process under acidic condition. Significantly, our results not only provided insight into the possible reaction mechanism of 3D ZFO/rGO nanocomposite, but proposed the way for the synthesis of highly crystalline materials through a benzyl alcohol-mediated method.

Magnetic, Pseudocapacitive, and H2O2-Electrosensing Properties of Self-Assembled Superparamagnetic Co0.3Zn0.7Fe2O4 with Enhanced Saturation Magnetization

The present work explores the structural, microstructural, optical, magnetic, and hyperfine properties of Co0.3Zn0.7Fe2O4 microspheres, which have been synthesized by a novel template-free solvothermal method. Powder X-ray diffraction, electron microscopic, and Fourier transform infrared spectroscopic techniques were employed to thoroughly investigate the structural and microstructural properties of Co0.3Zn0.7Fe2O4 microspheres. The results revealed that the microspheres (average diameter ∼121 nm) have been formed by self-assembly of nanoparticles with an average particle size of ∼12 nm. UV-vis diffuse reflectance spectroscopic and photoluminescence studies have been performed to study the optical properties of the sample. The studies indicate that Co0.3Zn0.7Fe2O4 microspheres exhibit a lower band gap value and enhanced PL intensity compared to their nanoparticle counterpart. The outcomes of dc magnetic measurement and Mössbauer spectroscopic study confirm that the sample is ferrimagnetic in nature. The values of saturation magnetization are 76 and 116 emu g-1 at 300 and 5 K, respectively, which are substantially larger than its nanosized counterpart. The infield Mössbauer spectroscopic study and Rietveld analysis of the PXRD pattern reveal that Fe3+ ions have migrated from [B] to (A) sites resulting in the cation distribution: (Zn2+ 0.46Fe3+ 0.54)A[Zn2+ 0.24Co2+ 0.3Fe3+ 1.46]BO4. Comparison of electrochemical performance of the Co0.3Zn0.7Fe2O4 microspheres to that of the Co0.3Zn0.7Fe2O4 nanoparticles reveals that the former displays greater specific capacitance (149.13 F g-1) than the latter (80.06 F g-1) due to its self-assembled porous structure. Moreover, it was found that Co0.3Zn0.7Fe2O4 microspheres possess a better electrochemical response toward H2O2 sensing than Co0.3Zn0.7Fe2O4 nanoparticles in a wide linear range.

A review on graphene-based nanocomposites for electrochemical and fluorescent biosensors

Biosensors with high sensitivity, selectivity and a low limit of detection, reaching nano/picomolar concentrations of biomolecules, are important to the medical sciences and healthcare industry for evaluating physiological and metabolic parameters.

Application of pyrite and chalcopyrite as sensor electrode for amperometric detection and measurement of hydrogen peroxide

The sensing performance of solid-state amperometric sensors based on natural sulfide minerals, i.e., pyrite and chalcopyrite, has been characterized for the detection and measurement of hydrogen peroxide (H₂O₂) in aqueous medium.