RESUMEN
Construction of a fast, easy and sensitive neurotransmitters-based sensor could provide a promising way for the diagnosis of neurological diseases, leading to the discovery of more effective treatment methods. The current work is directed to develop for the first time a flexible Surface-Enhanced Raman Spectroscopy (SERS) based neurotransmitters sensor by using the ultrasonic-assisted fabrication of a new set of epoxy resin (EPR) nanocomposites based on graphene nanosheets (GNS) using the casting technique. The perspicuous epoxy resin was reinforced by the variable loading of GNS giving the general formula GNS/EPR1-5. The designed products have been fabricated in situ while the perspicuous epoxy resin was formed. The expected nanocomposites have been fabricated using 3%, 5%, 10%, 15% and 20% GNS loading was applied for such fabrication process. The chemical, physical and morphological properties of the prepared nanocomposites were investigated by using Fourier transforms infrared spectroscopy, X-ray diffraction, Thermogravimetric analysis, Differential Thermal gravimetry, and field emission scanning electron microscopy methods. The GNS/EPR1-5 nanocomposites were decorated with a layer of gold nanoparticles (Au NPs/GNS/EPR) to create surface-enhanced Raman scattering hot points. The wettability of the Au NPs/GNS/EPR was investigated in comparison with the different nanocomposites and the bare epoxy. Au NPs/GNS/EPR was used as a SERS-active surface for detecting different concentrations of dopamine with a limit of detection of 3.3 µM. Our sensor showed the capability to detect low concentrations of dopamine either in a buffer system or in human serum as a real sample.
RESUMEN
The present study is aimed to fabricate composite materials containing epoxy resin (EPYR) reinforced by mixed carbon-based nano-fillers in the form of graphene nano-platelet (GNP) and multi-walled carbon nanotube (MWCNT) using the dissolution casting technique with the help of ultrasonic assistance. The pure epoxy resin was reinforced by variable loading of mixed GNP/MWCNT in situ, and the epoxy resin is denoted as EPYR/GNP/MWCNT2-30. The numbers 2-30 corresponded to the final mass ratio of the nano-fillers. The designed products were reinforced by variable percentages of GNP/MWCNTs. XRD, FT-IR, thermal analyses, FE-SEM, TEM and electrical conductivity were utilized as identification techniques to confirm the structures of these composite materials. An excellent evidence for the composite formation was given by XRD diffraction patterns and FT-IR spectroscopy. The introduced amounts of mixed nano-fillers showed significant effects on the thermal, conducting and coating behaviors of pure EPYR. Pure EPYR and EPYR/GNP/MWCNT20,30 showed higher thermal stabilities than other materials in the range of 400-410 °C. EPYR/GNP/MWCNT20 also showed remarkable increase in the thermal stability compared to other materials. T 10 represents the temperatures at which 10% weight losses are examined. Pure EPYR and its related EPYR/GNP/MWCNT2-30 displayed similar thermal stabilities at T 10 temperature (330 ± 4 °C). The morphological features were examined by SEM and TEM; these features showed that the nanocomposite components were extremely compatible. The in situ electrical conductivity values showed noticeable enhancement for the formulations of EPYR/GNP/MWCNT2-10. Moreover, the coating performance of EPYR was tested by water uptake experiments and electrochemical impedance; both tests proved that the mixed GNP/MWCNT nano-fillers remarkably improved the pure EPYR coating due to the ionic charge transfer resistance and elevated barrier behaviour. The coating resistance variations values (CRv) of EPYR/GNP/MWCNT10 were the highest among the measured composition values, closely followed by those of EPYR/GNP/MWCNT20 and EPYR/GNP/MWCNT30.
RESUMEN
Nanocrystalline Tb4O7 was fabricated by the calcination of its precursor, which was prepared by the precipitation method using NaOH as a precipitant. The phase changes accompanying the thermal treatment of the terbium parent were monitored using X-ray diffractometry (XRD) and thermogravimetry (TGA). The Calcination was performed over the temperature range of 300-700 degrees C. The texture of the produced nanocrystalline Tb4O7 samples was investigated using field-emission scanning electron microscopy (FE-SEM) and nitrogen adsorption measurements at -196 degrees C. Transmission electron microscopy (TEM) was used to determine the crystallite size of the obtained Tb4O7. The obtained results reveal that Tb4O7 with crystallites that measured 6-12 nm was formed at 400 degrees C. The crystallite size increased to 15-29 nm for the sample calcined at 700 degrees C. The electrical conductance properties of the different calcined samples were investigated over the temperature range of 150-500 degrees C. The electrical conductivity was observed to increase with the calcination temperature.
