No abstract

The influence of iron oxide nanoparticles decorating the external surface of multiwall carbon nanotubes (MWCNTs) on the amperometric sensing of glucose in solution is investigated. Oxidized nanotubes are decorated with iron oxide nanoparticles and then glucose oxidase is chemically bound to the MWCNTs for glucose sensing within physiological levels. MWCNTs which are only oxidized (without decorating nanoparticles) are used as reference. The results of the electrochemical characterizations consistently show that the presence of iron oxide nanoparticles decorating the surface of MWCNTs enhance the amperometric response and the sensitivity to increments in glucose concentration, when compared to non-decorated MWCNTs. The biosensor containing iron oxide decorated nanoparticles showed an amperometric sensitivity of 4.75 µA/mMcm 2 and an average response time of 6.6 s.

Sol-gel synthesis is used to obtain coatings that can modify the surfaces of metals to avoid corrosion or to enhance the biocompatibility and bioactivity of metals and their alloys that are of biomedical interest. Anticorrosion coatings composed of smart coatings and self-healing coatings will be described. TiO 2 , hydroxyapatite, bioglass, and hybrid coatings synthetized by sol-gel technology will be briefly introduced with regard to their role in surface-modifying metals for biomedical purposes. Finally, although there are other approaches to surface-modifying metals for either anticorrosion or biomedical purposes, sol-gel methods have several advantages in controlling surface chemistry composition and functionality.

Hybrid membranes with three different thicknesses, PMDS_C1, PMDS_C2, and PMDS_C3 (0.21 ± 0.03 mm, 0.31 ± 0.05 mm, and 0.48 ± 0.07 mm), were synthesized by the sol–gel method using polydimethylsiloxane, hydroxy-terminated, and cyanopropyltriethoxysilane. The presence of cyano, methyl, and silicon-methyl groups was confirmed by FTIR analysis. Contact angle analysis revealed the membranes’ hydrophilic nature. Solvent resistance tests conducted under vortex and ultrasonic treatments (45 and 60 min) demonstrated a preference order of acetonitrile > methanol > water. Furthermore, the membranes exhibited stability over 48 h when exposed to different pH conditions (1, 3, 6, and 9), with negligible mass losses below 1%. The thermogravimetric analysis showed that the material was stable until 400 °C. Finally, the sorption analysis showed its capacity to detect furfural, 2-furylmethylketone, 5-methylfurfural, and 2-methyl 2-furoate. The thicker membrane was able to adsorb and slightly desorb a higher concentration of furanic compounds due to its high polarity provided by the addition of the cyano groups. The results indicated that the membranes may be suitable for sorbent materials in extracting and enriching organic compounds.

Multiwalled Carbon Nanotubes (MWCNTs) were used as a support of amperometric enzymatic biosensors of guaiacol. The structural quality of MWCNTs was determined for Raman Spectra and DRX analysis. MWCNTs were decorated with iron oxide nanoparticles (36 w/w%), which were observed by FE-SEM, and were confirmed by with EDX, and TGA analysis. Laccase enzyme (aspergillus sp.) was immobilized on the surface of MWCNTs (oxidized and decorated with iron oxide nanoparticles) confirmed by XPS analysis and used to amperometric detection of guaiacol. The material obtained was deposited on the active surface of glassy carbon electrode (GCE) and was carried out using a typical three-electrode system with saturated calomel electrode as a reference and a graphite rod as a counter-electrode. The results confirm the potential use of bioelectrode Lac/MWCNTs/GCE and Lac/Fe3O4/MWCNTs/GCE for the guaiacol detection in low concentrations. Amperometric sensitivities and detection limits of Lac/Fe3O4/MWCNTs/GCE bioelectrode (110.186 μA mMcm−2 and 34.301 nM for reduction current respectively) showed better results than Lac/MWCNTs/GCE bioelectrode in a linear range 0–0.066 μM of guaiacol.