Electrochemical determination of dopamine based on electrospun CeO2/Au composite nanofibers

SERS Resolving of the Significance of Acetate on the Enhanced Catalytic Activity of Nanozymes

Understanding the structure-activity correlation and reaction mechanism of the catalytic process in an acetic acid-sodium acetate (HAc-NaAc) buffer environment is crucial for the design of efficient nanozymes. Here, we first reported a lattice restructuration of Au-LaNiO_3-δ nanofibers (NFs) after acidification with the HAc-NaAc buffer to show a significantly enhanced oxidase-like property. Surface-enhanced Raman spectroscopy (SERS) and density functional theory (DFT) calculation confirm the direct evidence for the formation of specific enhanced intermediate O-O species after acidification, indicating that the insertion of the carboxyl group in the A-Au/LaNiO_3-δ NFs plays crucial roles in both producing vacancies in HAc-NaAc solution from its dissociation during the catalytic process and the protection of the vacancies, which can be directly interacted with oxygen in the environment to produce O-O species, realizing the enhanced oxidation of substrate molecules. The insertion of the carboxyl group increased the oxidase-like catalytic activity by 2.38 times and the SERS activity by 5.27 times. This strategy offers a way to construct an efficient nanozyme-linked immunosorbent assay system for the diagnosis of cancer through the highly sensitive SERS identification of exosomes.

Electrochemical assays for determination of H2O2 and prostate-specific antigen based on a nanocomposite consisting of CeO2 nanoparticle-decorated MnO2 nanospheres

A nanocomposite consisting of CeO₂ nanoparticle-decorated MnO₂ nanospheres (CeO₂@MnO₂) was synthesized for the first time via a hydrothermal method. CeO₂@MnO₂ was exploited to construct an electrochemical assays for detecting H₂O₂ and prostate-specific antigen (PSA) with square wave voltammetry (SWV). The electrochemical results proved that CeO₂@MnO₂ owned a better electrocatalytic effect towards H₂O₂ reduction than pure MnO₂ NS and CeO₂ NP due to the synergistic effect between MnO₂ NS and CeO₂ NP. Under optimized conditions, CeO₂@MnO₂-based assay can be applied to detect H₂O₂ in the range 1 to 3.0 × 10³ μmol L^-1. The label-free electrochemical immunoassay based on CeO₂@MnO₂ displayed linearly with concentrations of PSA from 0.005 to 50.0 ng mL^-1. The electrochemical assays also possessed acceptable sensitivity, selectivity, and stability. The study showed that CeO₂@MnO₂ hold great potential as a biosensing platform and the clinical determination of tumor markers in human serum. Graphical abstract A nanocomposite consisting of CeO₂ nanoparticles decorated MnO₂ nanospheres (CeO₂ @MnO₂) was firstly synthesized via a hydrothermal method. CeO₂@MnO₂ was firstly exploited to construct electrochemical assays for detecting H2O₂ and prostate-specific antigen (PSA) with square wave voltammetry (SWV), respectively. The electrochemical results proved that CeO₂@MnO₂ owned better electrocatalysis towards H₂O₂ reduction than pure MnO₂ NS and CeO₂ NP due to the synergistic effect between MnO₂ NS and CeO₂ NP. Under optimized conditions, CeO₂@MnO₂ based assay relative to the H₂O₂ system can be applied to detect H₂O₂ with range from 1 to 3.0 × 10³ μmol L^-1. The label-free electrochemical immunoassay based on CeO₂@MnO₂ relative to the H₂O₂ system displayed linearly with concentrations of PSA from 0.005 to 50.0 ng mL^-1. The electrochemical assays also possessed acceptable sensitivity, selectivity and stability. The study showed that CeO₂@MnO₂ hold great potential for biosensing platform and the clinic determination of tumor markers in human serum.

Platelet-structured strontium titanate perovskite decorated on graphene oxide as a nanocatalyst for electrochemical determination of neurotransmitter dopamine

In this work, we synthesized strontium titanate (SrTiO₃) by a simple co-precipitation technique and decorated it with graphene oxide (SrTiO₃/GO) for the effective determination of neurotransmitter agent dopamine (DA).

Rational design and facile synthesis of binary metal sulfides VS2-SnS2 hybrid with functionalized multiwalled carbon nanotube for the selective detection of neurotransmitter dopamine

In this work, we report a sensitive and selective electrochemical sensor for the detection of dopamine (DA) neurotransmitter based on VS₂-SnS₂/f-MWCNT hybrids. Herein, the binary metal sulfide (VS₂-SnS₂) was synthesized via single step hydrothermal route and hybrids with f-MWCNT via the ultrasonication process. The as-prepared VS₂-SnS₂/f-MWCNT hybrids were characterized through the FESEM, EDX and elemental mapping, TEM, XPS, Raman and XRD techniques. The electrochemical performance and catalytic activity of the modified electrodes were probed using electrochemical impedance spectra (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Interestingly, DPV results exhibits an appreciable linear range from 0.025 to 1017 μM and LOD of 0.008 μM. The selectivity study was performed to prove the high selectivity of the VS₂-SnS₂/f-MWCNT hybrids modified electrode. Furthermore, the practical applicability of the DA sensor was scrutinized in human serum sample and rat brain sample.

Facile, low-temperature synthesis of tungsten carbide (WC) flakes for the sensitive and selective electrocatalytic detection of dopamine in biological samples

Transition metal carbides have shown potential for use in electrochemical applications due to their excellent electronic conductivity, stability and electrocatalysis.

In Situ Vapor Polymerization of Poly(3,4-ethylenedioxythiophene) Coated SnO₂-Fe₂O₃ Continuous Electrospun Nanotubes for Rapid Detection of Iodide Ions

In this work poly(3,4-ethylenedioxythiophene) (PEDOT) coated SnO₂-Fe₂O₃ continuous nanotubes with a uniform core–shell structure have been demonstrated for rapid sensitive detection of iodide ions. The SnO₂-Fe₂O₃ nanotubes were firstly fabricated via an electrospinning technique and following calcination process. An in situ polymerization approach was then performed to coat a uniform PEDOT shell on the surface of as-prepared SnO₂-Fe₂O₃ nanotubes by vapor phase polymerization, using Fe₂O₃ on the surface of nanotubes as an oxidant in an acidic condition. The resultant PEDOT@SnO₂-Fe₂O₃ core-shell nanotubes exhibit a fast response time (~4 s) toward iodide ion detection and a linear current response ranging from 10 to 100 μM, with a detection limit of 1.5 μM and sensitivity of 70 μA/mM/cm². The facile fabrication process and high sensing performance of this study can promote a wide range of potential applications in human health monitoring and biosensing systems.

Catalytic activity of biomimetic model of cytochrome P450 in oxidation of dopamine

The introduction of electron-withdrawing group into porphyrin molecule as cytochrome P450 model can tune the energy level and have an effect on the electronic structure. In this work, linking with the strong electron-withdrawing fluorine atoms, a starburst dendritic molecule, 5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H-porphyrin iron (III) chloride (FeTFPP), containing a saddle-shaped porphyrin as the central core and four pentafluorophenyl rings as the peripheral functional groups was successfully synthesized. Subsequently, the macrocyclic conjugate polymer film of FeTFPP was achieved via a low-cost electrochemical method and exploited as an efficient mimetic enzyme. Furthermore, a biomimetic sensor was constructed by the poly(FeTFPP) film and graphene (rGO) sheet (rGO-poly(FeTFPP)) for selective and sensitive detection of dopamine (DA). Here, the FeTFPP polymer performs three functions: electrochemical recognition (owing to the hydrogen bonding between the strongly electronegative fluorine atoms and DA), biomimetic microenvironment (owing to interaction between porphyrin core and DA), electrocatalysis (owing to remarkable catalytic ability of iron (III) ion). Under optimum conditions, the response to DA was linear in the concentration range between 0.05 to 300μM, and the detection limit was 0.023μM. In addition, we applied the rGO-poly(FeTFPP) film to detect DA in real samples and the results implied its feasibility for practical application. As a result, it is believed that the rGO-poly(FeTFPP) film is one of the promising biomimetic catalysts for electrocatalysis and relevant fields.

Synthesis of bifunctional reduced graphene oxide/CuS/Au composite nanosheets for in situ monitoring of a peroxidase-like catalytic reaction by surface-enhanced Raman spectroscopy

In this work, we have demonstrated the synthesis of bifunctional reduced graphene oxide/CuS/Au composite nanosheets for in situ monitoring of peroxidase-like catalytic reaction by surface-enhanced Raman spectroscopy.

Electrospun polyamide 6/poly(allylamine hydrochloride) nanofibers functionalized with carbon nanotubes for electrochemical detection of dopamine

The use of nanomaterials as an electroactive medium has improved the performance of bio/chemical sensors, particularly when synergy is reached upon combining distinct materials. In this paper, we report on a novel architecture comprising electrospun polyamide 6/poly(allylamine hydrochloride) (PA6/PAH) nanofibers functionalized with multiwalled carbon nanotubes, used to detect the neurotransmitter dopamine (DA). Miscibility of PA6 and PAH was sufficient to form a single phase material, as indicated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), leading to nanofibers with no beads onto which the nanotubes could adsorb strongly. Differential pulse voltammetry was employed with indium tin oxide (ITO) electrodes coated with the functionalized nanofibers for the selective electrochemical detection of dopamine (DA), with no interference from uric acid (UA) and ascorbic acid (AA) that are normally present in biological fluids. The response was linear for a DA concentration range from 1 to 70 μmol L(-1), with detection limit of 0.15 μmol L(-1) (S/N = 3). The concepts behind the novel architecture to modify electrodes can be potentially harnessed in other electrochemical sensors and biosensors.

Simultaneous electrochemical detection of dopamine and ascorbic acid using an iron oxide/reduced graphene oxide modified glassy carbon electrode

The fabrication of an electrochemical sensor based on an iron oxide/graphene modified glassy carbon electrode (Fe₃O₄/rGO/GCE) and its simultaneous detection of dopamine (DA) and ascorbic acid (AA) is described here. The Fe₃O₄/rGO nanocomposite was synthesized via a simple, one step in-situ wet chemical method and characterized by different techniques. The presence of Fe₃O₄ nanoparticles on the surface of rGO sheets was confirmed by FESEM and TEM images. The electrochemical behavior of Fe₃O₄/rGO/GCE towards electrocatalytic oxidation of DA was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) analysis. The electrochemical studies revealed that the Fe₃O₄/rGO/GCE dramatically increased the current response against the DA, due to the synergistic effect emerged between Fe₃O₄ and rGO. This implies that Fe₃O₄/rGO/GCE could exhibit excellent electrocatalytic activity and remarkable electron transfer kinetics towards the oxidation of DA. Moreover, the modified sensor electrode portrayed sensitivity and selectivity for simultaneous determination of AA and DA. The observed DPVs response linearly depends on AA and DA concentration in the range of 1–9 mM and 0.5–100 μM, with correlation coefficients of 0.995 and 0.996, respectively. The detection limit of (S/N = 3) was found to be 0.42 and 0.12 μM for AA and DA, respectively.

Electrospun carbon nanofibers decorated with Ag-Pt bimetallic nanoparticles for selective detection of dopamine

Electrospun nanoporous carbon nanofibers (pCNFs) decorated with Ag-Pt bimetallic nanoparticles have been successfully synthesized by combining template carbonization and seed-growth reduction approach. Porous-structured polyacrylonitrile (PAN) nanofibers (pPAN) were first prepared by electrospinning PAN/polyvinylpyrrolidone (PVP) blend solution, followed by subsequent water extraction and heat treatment to obtain pCNFs. Ag-Pt/pCNFs were then obtained by using pCNFs as support for bimetallic nanoparticle loading. Thus, the obtained Ag-Pt/pCNFs were used to modify glassy carbon electrode (GCE) for selective detection of dopamine (DA) in the presence of uric acid (UA) and ascorbic acid (AA). This novel sensor exhibits fast amperometric response and high sensitivity toward DA with a wide linear concentration range of 10-500 μM and a low detection limit of 0.11 μM (S/N = 3), wherein the interference of UA and AA can be eliminated effectively.

Enhanced catalytic and dopamine sensing properties of electrochemically reduced conducting polymer nanocomposite doped with pure graphene oxide

Significantly enhanced catalytic activity of a nanocomposite composed of conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) doped with graphene oxide (GO) was achieved through a simple electrochemical reduction process. The nanocomposite (PEDOT/GO) was electrodeposited on an electrode and followed by electrochemical reduction, and the obtained reduced nanocomposite (PEDOT/RGO) modified electrode exhibited lowered electrochemical impedance and excellent electrocatalytic activity towards the oxidation of dopamine. Based on the excellent catalytic property of PEDOT/RGO, an electrochemical sensor capable of sensitive and selective detection of DA was developed. The fabricated sensor can detect DA in a wide linear range from 0.1 to 175μM, with a detection limit of 39nM, and it is free from common interferences such as uric acid and ascorbic acid.

Nanosheet-based 3D hierarchical ZnO structure decorated with Au nanoparticles for enhanced electrochemical detection of dopamine

A novel sensor based on well-dispersed Au nanoparticles on a nanosheet-based three-dimensionally hierarchical ZnO matrix was fabricated to sensitively detect DA.

Differential pulse voltammetry detection of dopamine and ascorbic acid by permselective silica mesochannels vertically attached to the electrode surface

Silica mesochannels vertically aligned on the electrode surface have been employed for permselective detection of dopamine and ascorbic acid.