Síntese de vidros borofosfato: uso como materiais antimicrobianos e crescimento de nanopartículas de cobre em catalisadores esféricos

Abstract

The study focuses on the synthesis and application of moisture-resistant borophosphate glasses, incorporating biocompatible ions such as calcium (Ca), magnesium (Mg), zinc (Zn), and copper (Cu). A melt-quenching method was used at 1050°C for one hour, applying a DOE 23 experimental design that considered three variables: the molar percentage of Ca-Mg oxides (10, 12.5, and 15 %), the addition of CuO (3, 6, and 9 %), and the ratio of KH2PO4 to H3BO3 (P/B) with values of 1, 1.5, and 2. Glasses without CuO were also synthesized. The moisture absorption profle was determined in a closed system with 75 % relative humidity, fnding that the glasses with a P/B of 1 showed the best chemical stability against water, while an increase in phosphate led to hydrolysis in the glasses with P/B of 1.5 and 2. X-ray diffraction (XRD) analysis indicated that the borophosphate glass matrices with P/B of 1 and 1.5 were amorphous, while for P/B of 2 there was a tendency towards crystallization. After a thermal treatment with H2(g) fow, characteristic peaks of copper nanoparticles (CuNPs) were identifed. Infrared spectroscopy (FTIR) confrmed the formation of P – O – P and B – O bonds, evidencing Q1 and Q2 structures. Scanning electron microscopy (SEM) showed a porous surface on the catalysts. The glasses (CaMg10Cu9) with a P/B of 1 exhibited the best chemical stability and were mixed with residual glass to create glass spheres through encapsulation. The growth of CuNPs was achieved by thermal treatment at 430°C in a hydrogen atmosphere, resulting in CuNPs on the surface of the spheres (CuNPs@VBPs), applicable as heterogeneous catalysts. The kinetic effect was demonstrated with different concentrations of reagents and the effect of the amount of catalysts, with the possibility of determining the activation energy, which was 29.0158 kJ·mol−1. Additionally, the antibacterial effect of the copper-free glass matrices in powder form was evaluated using the agar diffusion method against Staphylococcus aureus and Escherichia coli. The results showed a greater antibacterial effect against gram-positive bacteria, with a halo of ≈ 35 mm for the glasses with P/B of 1 and ≈ 30 mm for P/B of 2, while for E. coli, the halo was ≈ 21 mm. This work highlights the use of residual glasses as a support to obtain stable catalysts with self-supported nanoparticles and the application of borophosphate glasses doped with biocompatible ions as potential antibacterial materials.