On the Sintering Behavior of Nb2O5 and Ta2O5 Mixed Oxide Powders

A mixed oxide system consisting of Nb₂O₅ and Ta₂O_5, was subjected to annealing in air/hydrogen up to 950 °C for 1–4 h to study its sintering behavior. The thermogravimetric–differential scanning calorimetry (TGA–DSC) thermograms indicated the formation of multiple endothermic peaks at temperatures higher than 925 °C. Subsequently, a 30% Ta₂O₅ and 70% Nb₂O₅ (mol%) pellet resulted in good sintering behavior at both 900 and 950 °C. The scanning electron microscope (SEM) images corroborated these observations with necking and particle coarsening. The sintered pellets contained a 20.4 and 20.8% mixed oxide (Nb₄Ta₂O₁₅) phase, along with Ta₂O₅ and Nb₂O₅, at both 900 and 950 °C, indicating the possibility of the formation of a solid solution phase. In situ high-temperature X-ray diffraction (XRD) scans also confirmed the formation of the ternary oxide phase at 6 and 19.8% at 890 and 950 °C, respectively. The Hume–Rothery rules could explain the good sintering behavior of the Ta₂O₅ and Nb₂O₅ mixed oxides. An oxide composition of 30% Ta₂O₅ and 70% Nb₂O₅ (mol%) and a sintering temperature of 950 °C appeared adequate for fabricating well-sintered oxide precursors for subsequent electrochemical polarization studies in fused salts.

Detection of a Double-Stranded MGMT Gene Using Electrochemically Reduced Graphene Oxide (ErGO) Electrodes Decorated with AuNPs and Peptide Nucleic Acids (PNA)

The ability to detect double-stranded DNA (dsDNA) as a biomarker without denaturing it to single-stranded DNA (ss-DNA) continues to be a major challenge. In this work, we report a sandwich biosensor for the detection of the ds-methylated MGMT gene, a potential biomarker for brain tumors and breast cancer. The purpose of this biosensor is to achieve simultaneous recognition of the gene sequence, as well as the presence of methylation. The biosensor is based on reduced graphene oxide (rGO) electrodes decorated with gold nanoparticles (AuNPs) and uses Peptide Nucleic Acid (PNA) that binds to the ds-MGMT gene. The reduction of GO was performed in two ways: electrochemically (ErGO) and thermally (TrGO). XPS and Raman spectroscopy, as well as voltammetry techniques, showed that the ErGO was more efficiently reduced, had a higher C/O ratio, showed a smaller crystallite size of the sp2 lattice, and was more stable during measurement. It was also revealed that the electro-deposition of the AuNPs was more successful on the ErGO surface due to the higher At% of Au on the ErGO electrode. Therefore, the ErGO/AuNPs electrode was used to develop biosensors to detect the ds-MGMT gene. PNA, which acts as a bio-recognition element, was used to form a self-assembled monolayer (SAM) on the ErGO/AuNPs surface via the amine-AuNPs interaction, recognizing the ds-MGMT gene sequence by its invasion of the double-stranded DNA and the formation of a triple helix. The methylation was then detected using biotinylated-anti-5mC, which was then measured using the amperometric technique. The selectivity study showed that the proposed biosensor was able to distinguish between blank, non-methylated, non-complementary, and target dsDNA spiked in mouse plasma. The LOD was calculated to be 0.86 pM with a wide linear range of 1 pM to 50 µM. To the best of our knowledge, this is the first report on using PNA to detect ds-methylated DNA. This sandwich design can be modified to detect other methylated genes, making it a promising platform to detect ds-methylated biomarkers.

Diverse physical functionalities of rare-earth hexacyanidometallate frameworks and their molecular analogues

The combination of rare-earth metal complexes and hexacyanidometallates of transition metals is a fruitful pathway for achieving functional materials exhibiting a wide scope of mechanical, magnetic, optical, and electrochemical properties.

A flexible rGO electrode: a new platform for the direct voltammetric detection of salicylic acid

Flexible sensors are of considerable interest for the development of wearable smart miniature devices. This work reported a flexible electrochemical platform based on reduced graphene oxide (rGO) for the detection of salicylic acid (SA). The free-standing and flexible rGO electrode was prepared via a simple extruded process. Dynamic mechanical deformation and bending studies illustrated the resilience and compliance of the flexible electrode against extreme mechanical deformations. Quantitative analysis of SA was performed by using differential pulse voltammetry (DPV) with this flexible rGO electrode. Linearity ranges for SA were obtained from 1.0 × 10^-10 M to 1.0 × 10^-5 M with the detection limit of 2.3 × 10^-11 M (S/N = 3). This strategy provided a new insight into the design and application of flexible electrodes. It will extend the applications of rGO in sensing, bio-electronics and lab-on-chip devices.

The electrochemical applications of rare earth-based nanomaterials

This review presents a general description of the synthesis and electrochemical properties of rare earth-based nanomaterials and their electrochemical applications.

An electrochemical bifunctional sensor for the detection of nitrite and hydrogen peroxide based on layer-by-layer multilayer films of cationic phthalocyanine cobalt(ii) and carbon nanotubes

Binder-free multilayer films composed of phthalocyanine and carbon nanotubes were constructed by the layer-by-layer electrostatic assembly and applied for the electrochemical detection of NO₂⁻ and H₂O₂.