Abstract
In this study, hexagonal boron nitride nanosheets enriched with hydroxyl groups (h-BN-OH) were successfully grafted on the surface of cellulose fibers after the simple and effective exfoliation and oxidation of bulk h-BN. OH groups of h-BN-OH and the ones presented on the surface of cellulose fibers interacted via hydrogen bonding. Both spectroscopic (FT-IR, XRD) and microscopic (TEM, SEM, and atomic force microscopy (AFM)) methods results proved the successful functionalization of the cellulose fibers with the nanomaterial. Modified cellulose fibers were used to prepare paper sheets samples with different concentrations of the nanomaterial (1 wt %, 2 wt %, and 3 wt %). All the samples were tested for the antibacterial properties via the colony forming unit method and exhibited good performance against both Gram-negative (E. coli) and Gram-positive (S. epidermidis) model bacteria. Additionally, the influence of the volume of working bacterial suspension on the antibacterial efficiency of the obtained materials was examined. The results showed significantly better antibacterial performance when the volume of bacterial suspension was reduced. Mechanical properties of the paper samples with and without nanofiller were also characterized. Tensile strength, tearing strength, and bursting strength of the paper samples containing only 2 wt % of the nanofiller were improved by 60%, 61%, and 118% in comparison to the control paper samples, respectively. Furthermore, the nanofiller improved the thermal properties of the composite paper—the heat release rate decreased by up to 11.6%. Therefore, the composite paper can be further explored in a wide range of antibacterial materials, such as packaging or paper coatings
Highlights
Cellulose is one of the most abundant biopolymer on the earth: it is the main constituent of plant cell walls and is synthesized by algae, fungi, and some bacteria [1,2]
The desired amount of h-BN-OH corresponding to 1 wt %, 2 wt %, and 3 wt % of nanofiller per 1 g of dry cellulose fibers was added to the suspension and the mixture was stirred for 1 h, allowing h-BN-OH to bond to cellulose fibers via -OH bonds
Paper sheets prepared from modified cellulose fibers presented strong antibacterial performance against both Gram-negative (E. coli) and Gram-positive (S. epidermidis) bacteria in comparison to raw cellulose paper
Summary
Cellulose is one of the most abundant biopolymer on the earth: it is the main constituent of plant cell walls and is synthesized by algae, fungi, and some bacteria [1,2]. The broad band near 3400 cm-1 is SEM micrographs of the raw and functionalized cellulose fibers are presented in Figure 4C,D, respectively. The presence of the nanomaterial on the surface of cellulose fibers even after the milling process proves that interaction between h-BN-OH and cellulose is sufficiently strong for the industrial paper manufacturing in which high water pressure is involved. The most intense peaks of pristine and functionalized cellulose fibers are observed at 3422 cm−1 and 3426 cm−1, respectively These broad bands are characteristic for O-H stretching vibrations. The results show that the antibacterial performance of functionalized cellulose samples against S. epidermidis was weaker in comparison to E. coli, when the volume of bacterial solution was larger (Figure 8A,C). The results indicate that exfoliated and oxidized boron nitride nanosheets boost flame retardancy of composite cellulose paper. The final product was dried in an oven at 90 ◦C for 12 h
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