In situ liquid cell crystallization and imaging of thiamethoxam by helium ion microscopy

Abstract

Pest insect control is an essential component for crop protection and public health. Neonicotinoids are a relatively new class of insecticides developed in the last four decades. Thiamethoxam, a member of the neonicotinoid class, has shown outstanding potency for crop protection against a variety of piercing-sucking pests. However, its use in industrial-volume packing and transportation is complicated by crystallization dynamics. In this work, a helium ion microscope (HIM) with a Protochips liquid cell was utilized to crystallize and image thiamethoxam in situ. The results of the study illustrate the growth and morphology of the thiamethoxam crystals at different He+ exposure doses, which is markedly different from what has been typically observed. Energy-dispersive x-ray spectroscopy results confirm the presence of the thiamethoxam on the liquid cell membrane. This imaging study illustrates the HIM ability to image and induce the crystallization in soft materials in liquid environments, and attempts to shed light onto the key processes involved in liquid imaging.