Developing Label-free Imaging Techniques to Study Biological and Energy Conversion Processes

Obtaining in situ characteristics of Lithium metal batteries (LMBs) is extremely important for understanding basic surface reactions involved in solid electrolyte interphase (SEI) formation, lithium nucleation/plating and thus overall cycling performance improvement of the battery cell. This thesis demonstrates a new characterization technique based on a principle that is completely different from the conventional EC detection technologies, plasmonic-based electrochemical imaging (PECI). It images local reactions (both faradaic and non-faradaic) without using a scanning microelectrode. Utilizing the reflectivity from surface plasmon resonance (SPR), PECI is fast and non-invasive, and its signal is proportional to incident light intensity, thus does not decrease with the area of interest. SEI layer formation dynamics as well as its correlation with the afterwards lithium plating and nucleation have been successfully characterized in the form of spatial resolved electrochemical current images at various fixed potentials and local cyclic voltammetry methods are developed and demonstrated with real samples. Fast imaging rate (up to 106 frames per second) with 0.2×3μm spatial resolution have been achieved in both tradition electrolyte (1M LiPF6 in EC/DMC) and engineered electrolyte systems, including highly concentrated electrolyte (4M LiFSI in DME) , and additive added electrolytes. An advanced localized high concentration electrolyte composed of 1M LiTFSI in 1,2 DME-TTE have also been characterized in support of the discovery of advanced ether-based electrolyte performances. This dissertation also describes a related but different research project that develops a facile method to test the possibility of metal plasmon induced by intrinsic lithium on non-plasmon surfaces. A third project of this dissertation is to develop a method to provide local insights on oxygen evolution reaction electrocatalyst design and material discovery using total internal reflection. The last part constitutes the expansion of conventional microscope to single cell impedance and cancer metabolism screening. Different phases of cell-substrate adhesion were successfully extracted via a conductive polymer (PEDOT:PSS) and using HeLa cell line. Using a facile imaging method, the metabolic pathway switch has also been observed in the HeLa cell line in the presence of glucose transporter inhibitor and drug dosage for 14 hours.