Fundamentals of Nanopipette Probes and Applications with Electrospray and Electrochemical Microscopy (FEM Simulations) to Study Nanoscale Systems.

다국어 초록 (Multilingual Abstract)

Nanoscale measurements to study heterogeneity in chemical and biological systems are essential to identify and understand the underlying processes, which cannot be observed from ensemble measurements. Nanopipettes, glass capillaries pulled to nanoscale size tip openings, provide an interesting tool for studies of such heterogeneity at small length scales. Work presented here details fundamentals of electrospray (ES) mass spectrometry (MS) analysis through nanometer-sized emitters. Determination of ES flow rates during self-aspirated ES from nanopipettes and effect of emitter geometry and solution conductivity are described. The debate on whether native structures of protein and protein complexes are preserved during ES from nanometer emitters is addressed. With the understanding of the fundamental nature of ES, new methods for the study of local chemistry and single nanoparticles are developed. Simultaneous liquid extraction and chemical analysis nanopipette probe design is proposed for local chemical analysis. ES deposition from nanopipettes to obtain single, isolated particles for single entity electrochemistry (SEE) measurements is described. Fast detection of ES from nanopipettes with 70-100 nm orifice is developed to detect single particle (26 nm and 60 nm diameter) translocation through the emitter tip during ES. Furthermore, finite element method (FEM) simulation studies to inform experimental studies of nanoscale electrochemical systems where nanopipettes are used as probes are discussed. Studies of electrocatalysis of nanoparticles, heterogeneous surface charge at the mineral-air interface, and local electric field determinations were performed through simulations to support experimental results.