New SiO2/Caffeic Acid Hybrid Materials: Synthesis, Spectroscopic Characterization, and Bioactivity

Abstract

The sol–gel route represents a valuable technique to obtain functional materials, in which organic and inorganic members are closely connected. Herein, four hybrid materials, containing caffeic acid entrapped in a silica matrix at 5, 10, 15, and 20 wt.%, were synthesized and characterized through Fourier-Transform Infrared (FT-IR) and Ultraviolet-Visible (UV–Vis) spectroscopy. FT-IR analysis was also performed to evaluate the ability to induce the hydroxyapatite nucleation. Despite some structural changes occurring on the phenol molecular skeleton, hybrid materials showed scavenging properties vs. 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and 2,2′-azinobis-(3-ethylbenzothiazolin-6-sulfonic acid) radical cation (ABTS•+), which was dependent on the tested dose and on the caffeic acid wt.%. The SiO2/caffeic acid materials are proposed as valuable antibacterial agents against Escherichia coli and Enterococcus faecalis.

Biopolymer-Based Hybrids as Effective Admixtures for Cement Composites

“…In addition, subsequent bands reveal typical vibrations characteristic for silica: Si-O group (ν s : 1200 cm −1 ; ν as : 1102 cm −1 ), Si-OH group (ν as : 992 cm −1 , ν s : 865 cm −1 ) and Si-O group (δ: 512 cm −1 ), where ν s and ν as are symmetrical and asymmetrical stretching vibrations and δ-bending vibrations, respectively. The obtained absorption maxima data are consistent with the course of the silica spectrum, which were included in previous publications [33,[36][37][38].…”

Wear Resistant Nanocomposites Based on Biomedical Grade UHMWPE Paraffin Oil and Carbon Nano-Filler: Preliminary Biocompatibility and Antibacterial Activity Investigation

“…In addition, the P−O bond of the phosphate group appears at 1122 and 1111 cm −1 [39]. Furthermore, only in this spectrum, the typical peaks of the polymer are not very intense, which is probably because the material's surface is In Figure 3, the spectra of all materials are reported, in which it is possible to observe the peaks at 3429 and 1647 cm −1 that correspond to the −OH groups [34,35]. Comparing all materials, in the spectra of UHMWPE with paraffin oil and with 1.0 wt % of carbon nano-filler (curve d), the typical bands of the hydroxyapatite layer are clearly visible.…”

“…The materials were soaked in simulated body fluid (SBF) for 21 days, and after this exposure time, the formation of the hydroxyapatite on the surfaces of all samples was detected by ATR/FTIR. In Figure 3, the spectra of all materials are reported, in which it is possible to observe the peaks at 3429 and 1647 cm −1 that correspond to the −OH groups [34,35]. Comparing all materials, in the spectra of UHMWPE with paraffin oil and with 1.0 wt % of carbon nano-filler (curve d), the typical bands of the hydroxyapatite layer are clearly visible.…”

The effect of high energy milling and high thermal treatment on the structure and thermal decomposition of minerals from natural CaO-SiO2-P2O5 ceramic system

“…The SiO 2 group shows the absorption bands for all investigated samples at ~514, ~687, ~775, ~795, ~1092 cm − 1 , and ~1872 cm − 1 , assigned as Si-O in quartz [33][34][35][36]. The Si-O symmetric (ν 1 ) and asymmetric (ν 3 ) stretching vibrations are presented at 798− 800 cm − 1 and 1085− 1092 cm − 1 .…”