Development and Characterisation of High Surface Energy Microstructured Sol-gel Coatings for Sensing Applications

Investigations on the Impact of a Series of Alkoxysilane Precursors on the Structure, Morphology and Wettability of an Established Zirconium-Modified Hybrid Anticorrosion Sol–Gel Coating

“…To properly identify the impact of the chemical alterations and curing processes on the structure of the materials, the FTIR spectra (800-1250 cm −1 ) of all materials were recorded (Figure 4). All spectra displayed the characteristic vibrations of Si-O-C (810 and 1170 cm −1 ), Si-OH (840 cm −1 ), Si-O-Si (880 and 1000-1100 cm −1 ) and Si-O-Zr (940 cm −1 ) in the reference materials [29][30][31]. The large band located in the 1000-1100 cm −1 spectral range was safely assigned to the asymmetric siloxane vibrations, where in this region, the four superimposed bands located at 1010, 1030, 1055 and 1090 cm −1 were identified in purely inorganic silicate materials [29][30][31].…”

“…All spectra displayed the characteristic vibrations of Si-O-C (810 and 1170 cm −1 ), Si-OH (840 cm −1 ), Si-O-Si (880 and 1000-1100 cm −1 ) and Si-O-Zr (940 cm −1 ) in the reference materials [29][30][31]. The large band located in the 1000-1100 cm −1 spectral range was safely assigned to the asymmetric siloxane vibrations, where in this region, the four superimposed bands located at 1010, 1030, 1055 and 1090 cm −1 were identified in purely inorganic silicate materials [29][30][31]. Those bands were also identified in similar hybrid sol-gel materials prepared from combinations of zirconium complexes and single or multiple hybrid alkoxysilanes, including MAPTMS and TEOS [32], GPTMS [33], GPTMS and TEOS [34], octlytrimethoxysilane [35], VTES and methyltrimethoxysilane [36].…”

“…These studies fully support our above assignments. The band located at 1090 cm −1 was attributed to the stretching vibration of the Si-O-Si groups located at the interface between tetrahedral and octahedral units (called silicon The band located at 1090 cm −1 was attributed to the stretching vibration of the Si-O-Si groups located at the interface between tetrahedral and octahedral units (called silicon apical oxide units), whereas the other three bands at 1010, 1030 and 1055 cm −1 were safely assigned to stretching vibrations of siloxane bonds within symmetrical tetrahedral units [29][30][31]. Thus, the observed vibration located at 1090 cm −1 (Figure 4) represents the formation of high-energy siloxane bonds originating from the aggregation of nanostructures of different sizes and possibly different densities, while bands located at 1010, 1030 and 1055 cm −1 represent siloxane bonds within networks of lower connectivity.…”

“…Gels 2024, 10, x FOR PEER REVIEW 7 of 18 apical oxide units), whereas the other three bands at 1010, 1030 and 1055 cm −1 were safely assigned to stretching vibrations of siloxane bonds within symmetrical tetrahedral units [29][30][31]. Thus, the observed vibration located at 1090 cm −1 (Figure 4) represents the formation of high-energy siloxane bonds originating from the aggregation of nanostructures of different sizes and possibly different densities, while bands located at 1010, 1030 and 1055 cm −1 represent siloxane bonds within networks of lower connectivity.…”

“…Gels 2024, 10, x FOR PEER REVIEW 9 of 18 2.5. 29 Si-NMR 29 Si-NMR spectra of the pure functional alkoxysilanes were initially recorded to characterise the purity and chemical shifts before the reaction with the reference sol-gel material, as shown in Figure 6A. A well-defined and sharp single peak was easily observed at −42.6, −82.5, −59.5, −45.4 and −42.4 ppm for MAPTMS, TEOS, VTES, APTES and GPTMS, respectively.…”