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

Alex Belianinov, Alison Pawlicki, Matt Burch, Songkil Kim, Anton Ievlev, Jeff Fowler, and Olga Ovchinnikova, 2018

Image courtesy of Protochips

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.

Impact Statement

A significant challenge in the application the commonly used pest control family of neonicotiniods is the stability of the colloidal particles in solution, both for shelf life and delivery concentration. The crystallization process of the neonicotinoid, thiamethoxam was observed in-situ in a liquid environment using a helium ion microscope, demonstrating that the soft materials can be effectively imaged in liquid using helium ion microscopy.