Glassy carbon electrode modified with graphene oxide and gold nanoparticles for ascorbic acid detection

Glassy carbon electrodes modified with graphene oxide (GO), gold nanoparticles (AuNP) and methylene blue (MB) were produced by drop casting method for ascorbic acid (AA) determination. Nafion was used as a polymeric immobilizing matrix. The GCE/GO-AuNP-MB-Nafion and GCE/GO-AuNP-Nafion electrodes were characterized by using cyclic voltammetry and electrochemical impedance spectroscopy to investigate electrocatalytic effect, stability and reproductibility. After optimization, the analytical parameters of the modified electrodes were determined by amperometry. The limit of detection for ascorbic acid at GCE/GO-AuNP-Nafion modified electrode was 2.4 µM and the linear domain from 5 to 50 µM. The electrodes showed significant electrocatalytic effect with good stability and reproductibility

Electrochemical Detection of Lead Ions with Ordered Mesoporous Silica–Modified Glassy Carbon Electrodes

The development of methods for lead ion determination in various biological and environmental samples is both necessary and challenging. In this context, considering the properties of both SBA-15 and MCM-41 mesoporous materials and the role of NH2-functional groups grafted on the silica surface (SBA-15-NH2 and MCM-41-NH2), the aim of the study was to investigate the electrochemical detection of Pb2+ by means of silica-modified glassy carbon electrodes (GCEs). The square wave anodic stripping voltammetry (SWASV) was used to characterize the modified electrodes with four different samples of ordered mesoporous silica (OMS) powders, mentioned above. Additionally, scanning electron microscopy (SEM) was used to characterize these modifiers. Pb2+ exhibits a well-defined oxidation peak (around − 0.5 V vs. Ag/AgCl/KClsat) and high peak current at either bare or OMS-modified glassy carbon electrodes, but the best response was recorded in the case of GC/SBA-15-NH2-modified electrode in 0.1 M acetate buffer. The performance of the prepared electrodes is highlighted by good analytical parameters (satisfies the requirements of low cost and rapid results), which recommends them to be used for real sample analysis

Role of pH and temperature on silica network formation and calcium incorporation into sol–gel derived bioactive glasses

Bioactive glasses and inorganic/organic hybrids have great potential as implant materials. Bioactive glasses can bond to bone through the formation of a bone-like hydroxycarbonate apatite (HCA) layer and stimulate bone growth via their dissolution products. The brittle nature of these glasses can be combined with the toughness of a biodegradable polymer by forming a hybrid through the sol–gel process. However, for polymer incorporation, lower temperatures and milder pH conditions are required rather than the current method which uses pH 2 were mesoporous. This indicates a difference in gel formation about the isoelectric point of silicic acid, which was confirmed by 29Si solid state NMR. When immersed in simulated body fluid (SBF), the glasses stabilised at 600 °C were more porous, yet had a slower ion release rate than the gels dried at 40 °C. All gels and glasses formed an HCA layer in SBF; however, calcium was only incorporated into the silica network after stabilisation at 600 °C and thus a new way of incorporating calcium at low temperatures must still be found. This work is an important foundation for hybrid synthesis as raising the pH of the sol–gel process from pH < 1 to pH 5.5 was found to have no adverse effects on silica network formation and thus polymer can be incorporated into the sol–gel process at milder pH conditions without the concern of acid catalysed polymer degradation by chain scission