Although humic acids (HAs) from peat exhibit various therapeutic properties, there is little information available concerning their physicochemical and antioxidant properties. To address this issue, nine different types of peat, including oligotrophic, mesotrophic, and minerotrophic peat samples, were used for isolation of HA fractions by basic (HAb) and pyrophosphate (HAp) extractions. Physical parameters of the HAs were analyzed by UV-Vis, fluorescent, infrared (IR), and electron paramagnetic resonance (EPR) spectroscopy. Average M_r of the fractions ranged from 17.2 to 39.7 kDa, while their humification index (HIX) varied from 0.49 to 1.21. HAp fractions had a higher content of aromatic structures compared to HAb fractions. Moreover, HAp fractions had a significantly higher content of phenolic OH groups (3.6 ± 0.5 mmol/g) versus HAb (3.1 ± 0.5 mmol/g). All HA fractions exhibited antioxidant activity in radical scavenging and electrochemical assays, and their EPR signal had a single line with g = 2.0035, which is consistent with semiquinone type radicals. Furthermore, the HIX was found to be important in determining the number of semiquinone-type free radicals in the HA structures. Overall, these data provide a molecular basis to explain at least part of the beneficial therapeutic properties of peat-derived HAs.

We have studied monolayer (ML) and submonolayer InAs insertions (1–0.08 ML) in a GaAs matrix by photoluminescence, photoluminescence excitation, and optical-reflectance spectroscopy. Linewidths of heavy-hole and light-hole exciton peaks as narrow as 0.15 meV are observed. A surprisingly high exciton oscillator strength, its weak dependence on the average thickness of the InAs layer, and the pronounced anisotropy and splitting of heavy- and light-hole exciton peaks are all revealed in the optical studies and are attributed to the formation of ordered arrays of InAs wirelike islands. Furthermore, from photoluminescence and reflectance-anisotropy measurements, we confirm that the wire arrays are elongated along the [011¯] direction.