Morphological and Structural Properties of Amino-Functionalized Fumed Nanosilica and Its Comparison with Nanoparticles Obtained by Modified Stöber Method.

In industry, silica nanoparticles (NPs) are obtained by the fuming and the precipitation method. Fumed silica NPs are commonly used in the preparation of nanocomposites because they have an extremely low bulk density (160-190 kg/m3), large surface area (50-600 m2/g), and nonporous surface, which promotes strong physical contact between the NPs and the organic phase. Fumed silica has fewer silanol groups (Si-OH) on its surface than the silica prepared by the Stöber method. However, the number of -OH groups on the fumed silica surface can be increased by pretreating them with sodium hydroxide (NaOH) before further surface modification. In this study, the effectiveness of the NaOH pretreatment was evaluated on commercial fumed silica NPs with a surface area of 200 m2/g. The number of surface -OH groups was estimated by potentiometric titration. The pretreated fumed NPs, and the precipitated NPs (prepared by the Stöber method) were modified with 3-aminopropyltriethoxysilane (APTES) to obtain A200S and nSiO2-APTES, respectively. The NPs were characterized using electron dispersive scanning (EDS), scanning electron microscopy (SEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), BET (Brunauer-Emmett-Teller) analysis, and ζ-potential. XRD confirmed the presence of the organo-functional group on the surface of both NPs. After the amino-functionalization, the ζ-potential values of the nSiO2 and A200 changed from -35.5 mV and -14.4 mV to +26.2 mV and +11.76 mV, respectively. Consequently, we have successfully synthesized functionalized NPs with interesting, specific surface area and porosity (pore volume and size), which can be attractive materials for chemical and energy industries.

New Nanohybrid Based on Hydrolyzed Polyacrylamide and Silica Nanoparticles: Morphological, Structural and Thermal Properties.

In this study, a set of advanced characterization techniques were used to evaluate the morphological, structural, and thermal properties of a novel molecular hybrid based on silica nanoparticles/hydrolyzed polyacrylamide (CSNH-PC1), which was efficiently obtained using a two-step synthetic pathway. The morphology of the nanohybrid CSNH-PC1 was determined using scanning electron microscopy (SEM), dynamic light scattering (DLS), and nanotracking analysis (NTA) techniques. The presence of C, N, O, and Si atoms in the nanohybrid structure was verified using electron dispersive scanning (EDS). Moreover, the corresponding structural analysis was complemented using powder X-ray diffraction (XRD) and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FT-IR). The covalent bond between APTES-functionalized SiO2 nanoparticles (nSiO2-APTES), and the hydrolyzed polyacrylamide (HPAM) chain (MW ≈ 20.106 Da) was confirmed with high-resolution X-ray spectroscopy (XPS). Finally, the thermal properties of the nanohybrid were evaluated by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results showed that the CSNH-PC1 has a spherical morphology, with sizes between 420-480 nm and higher thermal resistance compared to HPAM polymers without modification, with a glass transition temperature of 360 °C. The integration of these advanced characterization techniques implemented here shows promising results for the study and evaluation of new nanomaterials with multiple applications.