Fabrication of Cu−CeO2 Coated Multiwall Carbon Nanotube Composite Electrode for Simultaneous Determination of Guanine and Adenine

An electrochemical sensor for purine base detection with ZIF-8-derived hollow N-doped carbon dodecahedron and AuNPs as electrocatalysts

In this paper, a novel electrochemical sensor was constructed for the detection of purine bases. Ultrafine carbide nanocrystals confined within porous nitrogen-doped carbon dodecahedrons (PNCD) were synthesized by adding molybdate to ZIF-8 followed by annealing. With MoC-based PNCDs (MC-PNCDs) as the carrier, gold nanoparticles (AuNPs) were deposited on the electrode surface via potentiostatic deposition as the promoter of electron transfer, forming a AuNPs/MC-PNCDs/activated glassy carbon electrode (AGCE) sensor. MC-PNCDs had a large specific surface area, which combined with the excellent electrocatalytic activity of AuNPs, synergistically improved the electrocatalytic activity. The morphology and structure of the electrode surface modifier were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray photoelectron spectroscopy, infrared spectroscopy, X-ray diffraction, nitrogen adsorption-desorption analysis, and electrochemical characterization. Under the optimal conditions, the linear detection range of guanine (G) and adenine (A) was 0.5-160.0 μM, and the detection limits (S/N=3) were 72.1 and 69.6 nM, respectively. AuNPs/MC-PNCDs/AGCE was successfully constructed, and was used to simultaneously detect G and A with high sensitivity and selectivity. Moreover, the sensor was successfully used to detect G and A in herring sperm DNA samples.

A Micro Electrochemical Sensor for Multi-Analyte Detection Based on Oxygenated Graphene Modified Screen-Printed Electrode

Electrode interfaces with both antibiofouling properties and electrocatalytic activity can promote the practical application of nonenzymatic electrochemical sensors in biological fluids. Compared with graphene, graphene oxide (GO) possesses unique properties such as superior solubility (hydrophilicity) in water, negative charge, and abundant oxygenated groups (oxo functionalities) in the plane and edge sites, which play an essential role in electrocatalysis and functionalization. In this work, a micro electrochemical sensor consisting of GO-modified screen-printed electrode and PDMS micro-cell was designed to achieve multi-analyte detection with excellent selectivity and anti-biofouling properties by electrochemically tuning the oxygen-containing functional species, hydrophilicity/hydrophobicity, and electrical conductivity. In particular, the presented electrodes demonstrated the potential in the analysis of biological samples in which electrodes often suffer from serious biofouling. The interaction of proteins with electrodes as well as uric acid was investigated and discussed.

Simultaneous electrochemical detection of guanine and adenine using reduced graphene oxide decorated with AuPt nanoclusters

A rapid and sensitive electrochemical sensing platform is reported based on bimetallic gold-platinum nanoclusters (AuPtNCs) dispersed on reduced graphene oxide (rGO) for the simultaneous detection of guanine and adenine using square wave voltammetry (SWV). The synthesis of AuPtNCs-rGO nanocomposite was achieved by a simultaneous reduction of graphene oxide (GO) and metal ions (Au³⁺ and Pt⁴⁺) in an aqueous solution. The developed AuPtNCs-rGO electrochemical sensor with the optimized 50:50 bimetallic (Au:Pt) nanoclusters exhibited an outstanding electrocatalytic performance towards the simultaneous oxidation of guanine and adenine without the aid of any enzymes or mediators in physiological pH. The electrochemical sensor platform showed low detection limits of 60 nM and 100 nM (S/N = 3) for guanine and adenine, respectively, with high sensitivity and an extensive linear range from 1.0 μM to 0.2 mM for both guanine and adenine. The interference from the most common electrochemically active interferents, including ascorbic acid, uric acid, and dopamine, was almost negligible. The simultaneous sensing of guanine and adenine in denatured Salmon Sperm DNA sample was successfully achieved using the proposed platform, showing that the AuPtNCs-rGO nanocomposite could provide auspicious clinical diagnosis and biomedical applications.

A copper-based metal–organic framework/graphene nanocomposite for the sensitive and stable electrochemical detection of DNA bases

A simple and easy-operation electrode modification strategy was proposed using Cu-MOF/GO nanohybrids for physiologists and pathologists for the feasible and reliable simultaneous electrochemical detections of DNA bases, namely guanine and adenine.

Fabrication of carbon nanotube-polylactic acid composite electrode by melt compounding for capillary electrophoretic determination of tectoridin and irigenin in Belamcandae Rhizoma

A sensitive detection electrode based on the composite of carbon nanotubes (CNTs) and polylactic acid (PLA) was fabricated for measuring the bioactive constituents in Belamcandae Rhizoma by capillary electrophoresis (CE). The composite was facilely fabricated by packing a blend of CNTs and melted PLA into a fused silica capillary under heat. The prepared CNT-PLA composite was characterized by scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry. The results indicated that PLA bound electrically conductive CNTs to form a well-dispersed composite network for electrochemical sensing. The electrode was employed to the off-line detection of tectoridin and irigenin in Belamcandae Rhizoma to demonstrate its performance in capillary electrophoresis. At a separation voltage of 12 kV, the two isoflavones were well separated and detected within 8 min in a 40-cm fused silica capillary in a borate buffer at pH 9.8. The detection limits for tectoridin and irigenin were measured to be 0.24 and 0.21 μM, respectively.

Synthesis of MnCo2O4 nanoparticles as modifiers for simultaneous determination of Pb(II) and Cd(II)

The porous spinel oxide nanoparticles, MnCo₂O₄, were synthesized by citrate gel combustion technique. Morphology, crystallinity and Co/Mn content of modified electrode was characterized and determined by Fourier transform infra-red spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction pattern analysis (XRD), simultaneous thermogravimetry and differential thermal analysis (TG/DTA). Nanoparticles were used for modification of glassy carbon electrode (GCE) and new sensor was applied for simultaneous determination of Pb(II) and Cd(II) ions in water samples with the linear sweep anodic stripping voltammetry (LSASV).The factors such as pH, deposition potential and deposition time are optimized. Under optimal conditions the wide linear concentration range from 0.05 to 40 μmol/dm³was obtained for Pb(II), with limit of detection (LOD) of 8.06 nmol/dm³ and two linear concentration ranges were obtained for Cd(II), from 0.05 to 1.6 μmol/dm³ and from 1.6 to 40 μmol/dm³, with calculated LOD of 7.02 nmol/dm³. The selectivity of the new sensor was investigated in the presence of interfering ions. The sensor is stable and it gave reproducible results. The new sensor was succesfully applied on determination of heavy metals in natural waters.