Summary Fungal–mineral interactions can produce large amounts of biogenic nano‐size (~ 1–100 nm) minerals, yet their influence on fungal physiology and growth remains largely unexplored. Using Trichoderma guizhouense NJAU4742 and magnetite (Mt) as a model fungus and mineral system, we have shown for the first time that biogenic Mt nanoparticles formed during fungal–mineral cultivation exhibit intrinsic peroxidase‐like activity. Specifically, the average peroxidase‐like activity of Mt nanoparticles after 72 h cultivation was ~ 2.4 times higher than that of the original Mt. Evidence from high resolution X‐ray photoelectron spectroscopy analyses indicated that the unique properties of magnetite nanoparticles largely stemmed from their high proportion of surface non‐lattice oxygen, through occupying surface oxygen‐vacant sites, rather than Fe redox chemistry, which challenges conventional Fenton reaction theories that assume iron to be the sole redox‐active centre. Nanoscale secondary ion mass spectrometry with a resolution down to 50 nm demonstrated that a thin (< 1 μm) oxygen‐film was present on the surface of fungal hyphae. Furthermore, synchrotron radiation‐based micro‐FTIR spectra revealed that surface oxygen groups corresponded mainly to organic OH, mineral OH and carbonyl groups. Together, these findings highlight an important, but unrecognized, catalytic activity of mineral nanoparticles produced by fungal–mineral interactions and contribute substantially to our understanding of mineral nanoparticles in natural ecosystems.
Currently used dielectric spectroscopy methods for measuring soil water contents are highly susceptible to their electrical conductivities. Some of the existing methods are double-plate capacitance sensors. A novel technique based on the use of fringing field sensors for the content detection is presented in our work, which is able to perform real-time capacitance measurements, and process recorded data to obtain the given parameters of interest. A modulated circuit and data acquisition system are designed to meet practical application requirements, and high sensitivity of the proposed sensor to parameter variation was demonstrated based on the experimental data. An approximately linear dependency is observed between water content and measurement voltage when the proportion of water content in the soil sample is below 24% (gravimetric water content), which implies a wide-ranging application of such a technique for real-time measurements of various soil water content under field working conditions where conventional instruments are unavailable.
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