The NaHSe solution in EtOH was diluted by water and the cotton socks were immersed in it to upload selenium
via the mechanisms illustrated in
Scheme 1b (
Fig. 1a). After then, they were washed by water and dried by airing. Inductively coupled plasma-mass spectrometry (ICP-MS) analysis indicated that the selenized material contained
ca. 0.15% of Se (weight content). Scanning electron microscope (SEM) was used to investigate the micro-morphologies of the materials. It was found that the selenization process did not destroy the surface structures of the materials, as the morphologies observed in the SEM images of the selenized and unselenized sock were similar (
Figs. 1d and e
vs. 1b and
c). Fourier transform infrared (FT-IR) analysis was employed to characterize the functional groups of the materials (
Fig. 1f). In the IR spectrum of unselenized cotton sock (
Fig. 1f, blue line), the characterization peaks of cellulose can be observed nearing the 708 cm
−1 wave number position. The peaks at 1058 cm
−1, 1431 cm
−1 and 2902 cm
−1 attribute to the C-O-C, C-O-H and the CH
2 and CH stretching vibrations, respectively. The above peaks did not change after selenization (
Fig. 1f, red line
vs. blue line). The stretching vibration of O-H is reflected by the absorption peak at 3297 cm
−1. The signal moved to 3339 cm
−1 after selenization due to the interaction of the introduced selenium groups, which affected the hydroxyl by weakening the hydrogen bonds of the materials (
Fig. 1f, red line
vs. blue line). Generally, the FT-IR spectrum of selenized sock did not change much, verifying that the selenization process did not cause significant damage to the functional groups of the cellulose of cotton socks. In the X-ray diffraction (XRD) pattern of unselenized sock (
Fig. 1g, black line), the signal peaks at 2
θ = 14.5
o, 16.6
o, 22.5
o and 34.4
o are the typical crystallization peaks of natural cellulose attributing the facets of (
110), (110), (200) and (040) respectively and these results are in accordance to the structures of the materials [
17]. The selenization process damaged the crystal structures of the materials, as being reflected by the weakened diffraction peaks in the XRD pattern of selenized sock (
Fig. 1g, red line
vs. black line). However, tension tests showed that the mechanical properties of the materials did not change much after selenization (for details see Supporting information).