A promising, environmentally safe method for inactivating fungal spores of Penicillium digitatum, a difficult-to-inactivate food spoilage microorganism, was developed using a high-density nonequilibrium atmospheric pressure plasma (NEAPP). The NEAPP employing Ar gas had a high electron density on the order of ${10}^{15}{\text{cm}}^{-3}$ . The spores were successfully and rapidly inactivated using the NEAPP, with a decimal reduction time in spores (D value) of 1.7 min. The contributions of ozone and UV radiation on the inactivation of the spores were evaluated and concluded to be not dominant, which was fundamentally different from the conventional sterilizations.

We demonstrate the monitoring of plant nutrients in leaves of Citrus unshiu and Rhododendron obtusum using low-energy (<1 mJ) laser-induced breakdown spectroscopy. The raw plant leaf was successfully ablated without desiccation before laser irradiation, by applying metallic colloidal particles to the leaf surface. The emission intensity with the metallic particles was larger than that without the particles. This result indicates an improvement of the sensitivity and the detection limit of laser-induced breakdown spectroscopy. The emission enhancement was caused by localized surface plasmon resonance and was dependent on the size and material of metallic particles.

The effectiveness of atomic and excited molecular oxygen species at inactivating Penicillium digitatum spores was quantitatively investigated by measuring these species and evaluating the spore inactivation rate. To avoid the effects of ultraviolet light and charged species, a non-equilibrium atmospheric-pressure radical source, which supplies only neutral radicals, was employed. Ground-state atomic oxygen (O(³P_j)) and excited molecular oxygen (O₂(¹Δ_g)) species were measured using vacuum ultraviolet absorption spectroscopy. The inactivation rate of spores was evaluated using the colony count method. The lifetimes of O(³P_j) and O₂(¹Δ_g) in an argon gas ambient at atmospheric pressure were found to be about 0.5 ms and much more than tens of ms, and their spore inactivation rates were about 10⁻¹⁷ cm³ s⁻¹ and much lower than 10⁻²¹ cm³ s⁻¹, respectively.