Ultraviolet (UV) irradiation is an effective bacterial inactivation technique with broad applications in environmental disinfection. However, biomedical applications are limited due to the low selectivity, undesired inactivation of beneficial bacteria and damage of healthy tissue. New approaches are needed for the protection of biological cells from UV radiation for the development of controlled treatment and improved biosensors. Aluminum plasmonics offers attractive opportunities for the control of light-matter interactions in the UV range, which have not yet been explored in microbiology. Here, we investigate the effects of aluminum nanoparticles (Al NPs) prepared by sonication of aluminum foil on the UVC inactivation of E. coli bacteria and demonstrate a new radiation protection mechanism via plasmonic nanoshielding. We observe direct interaction of the bacterial cells with Al NPs and elucidate the nanoshielding mechanism via UV plasmonic resonance and nanotailing effects. Concentration and wavelength dependence studies reveal the role and range of control parameters for regulating the radiation dosage to achieve effective UVC protection. Our results provide a step towards developing improved radiation-based bacterial treatments.

Drought stress disrupts the balance of macro- and micronutrients and affects the yield of agriculturally and economically significant plants. Rapid detection of stress-induced changes of relative content of elements such as sodium (Na), potassium (K), calcium (Ca) and iron (Fe) in the field may allow farmers and crop growers to counter the effects of plant stress and to increase their crop return. Unfortunately, the analytical methods currently available are time-consuming, expensive and involve elaborate sample preparation such as acid digestion which hinders routine daily monitoring of crop health on a field scale. We report application of an alternative method for rapid detection of drought stress in plants using femtosecond laser-induced breakdown spectroscopy (LIBS). We demonstrate daily monitoring of relative content of Na, K, Ca and Fe in decorative indoor (gardenia) and cultivated outdoor (wheat) plant species under various degrees of drought stress. The observed differences in spectral and temporal responses indicate different mechanisms of drought resistance. We identify spectroscopic markers of drought stress which allow for distinguishing mild environmental and severe drought stress in wheat and may be used for remote field-scale estimation of plant stress resistance and health.

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