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Plasmonic nanoshells have been acknowledged as efficient nanomaterials for laser desorption/ionization mass spectrometry (LDI-MS) detection of a wide range of small molecules, whereas their applications in mass spectrometry imaging (MSI) are less developed. In this work, we constructed and optimized SiO 2 @Au nanoshells with tailor-made shell structures and compositions for high-sensitivity LDI-MS analysis and a wide range of MSI applications. Owing to the synergistic effects of plasmonic shells with nanoscale roughness and specific crevice space for the selective trapping of small molecules and cations, SiO 2 @Au core−shell nanoparticles exhibit superior performance for the detection of a vast diversity of small molecules, including amino acids, oligosaccharides, dyestuff and drugs, peptides, nucleosides, and poly(ethylene glycols). Compared with organic matrices, this method affords a high reduction in matrix interference, higher analyte coverage, lower detection limits ranging from fmol to pmol, and good repeatability with relative standard deviation (RSD) below 5%. Due to the nanoscale size and homogeneous deposition of SiO 2 @Au nanoshells, the spatial distribution of various smallmolecule metabolites can be visualized in strawberry tissues at a pixel size of 100 μm without imaging artifacts. More valuably, the universality of SiO 2 @Au-assisted LDI-MSI is further demonstrated for mapping the lipid distribution within the whole-body tissues of zebrafish (Danio rerio), honeybees (Apis cerana), and mouse brain tissues in a spatially resolved manner at pixel sizes of 55, 30, and 50 μm, respectively. These results facilitate the expansion of the abilities of plasmonic core−shell nanoparticles in real-case MSI applications. Taken together, the results indicate that the SiO 2 @Au nanoshells are expected to be promising and efficient nanomaterials with superior DI efficiency and imaging capabilities, especially in the environmental science and life science fields.

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The effects of exogenous melatonin on the growth, chlorophyll fluorescence parameters and related components of distribution of heat dissipation in tomato seedlings under Ca (NO3) 2 stress were studied in this experiment. The results showed that calcium nitrate stress inhibited the growth of tomato seedlings, reduced Y (II), Fv’/Fm’, qP and ETR, and produced photoinhibition on tomato seedlings. Spraying exogenous melatonin could increase the growth of tomato seedlings under calcium nitrate stress. Melatonin regulated qP and ETR under calcium nitrate stress, reduced the ratio of Y(NPQ), Y(NO), and increased the ratio of Y(II). Further analysis of NPQ and its three components, which including qE, qT and qI, showed that NPQ and its three components were significantly increased in the stress treatment group, while melatonin could inhibit the increase. Thus, it indicated that exogenous melatonin could effectively alleviate the growth of tomato seedlings under calcium nitrate stress, maintain the reasonable distribution of light energy, and protect the photosystem II from light damage caused by excess light energy.