Bio-liquid interfaces, Graphene, Mass spectrometry imaging (MSI), Time-of-flight medium energy ion scattering (ToF-MEIS), Electrical double layer (EDL)
Detailed compositional and structural characterization of bio-liquid interfaces is required to understand interfacial phenomena in electrochemical, colloidal, and biological systems. However, nanoscale analytical techniques based on accelerated electrons and ions operate in an ultra-high vacuum environment, which impedes their application to bio-liquid interfaces and presents a great challenge for analysis in solution environment. Recently, single layer graphene techniques have enabled electron microscopy imaging of materials and cells in solution. Here I propose an innovative method of probing bio-liquid interfaces using single graphene layer for various techniques such as mass spectrometric imaging of wet cells and tissues with time-of-flight secondary ion mass spectrometry (ToF-SIMS) and atmospheric pressure mass spectrometric (AP-MS) imaging technology, and time-of-flight medium energy ion scattering (ToF-MEIS) for the structural analysis of electrical double layer (EDL) between electrode and electrolyte solution. The analysis of bio-liquid interface using single graphene layer and ultrahigh vacuum-based micro/nanoscale characterization techniques will facilitate the acquisition of detailed intrinsic interfacial compositional and structural information of cell membranes, nano and bio materials in ambient solution environments for better understanding and control of interfaces for various researches of basic biology, biomedical science, electrochemistry, and material science.
Table Of Contents
I. INTRODUCTION 1 II. Mass Spectrometry Imaging of Biological Samples using Graphene 3 1 ToF-SIMS Imaging of Untreated Wet Cell Membranes 3 1.1 Introduction 3 1.2 Materials and methods 5 1.2.1 Preparing fixed cells and graphene covered untreated wet cells for ToF-SIMS imaging 5 1.2.2 Fabrication of cell culture media reservoir 6 1.2.3 Instrumentation and experimental details 8 1.2.4 Ab-initio molecular dynamics (AIMD) simulation 8 1.3 Results and discussions 9 1.3.1 ToF-SIMS imaging of graphene covered untreated wet cells 9 1.3.2 Secondary ion sputtering through single-layer graphene 13 1.4 Conclusions 16 2 ToF-SIMS Imaging of Fixed Cell Membranes using Graphene-cover and Air-plasma Treatment 18 2.1 Introduction 18 2.2 Materials and methods 19 2.2.1 Time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging 20 2.2.2 Cell culture 20 2.2.3 Chemical fixation and air-plasma treatment 21 2.2.4 Graphene transfer on cells and air-plasma treatment 21 2.2.5 Cellular sample characterization 22 2.3 Results and discussions 23 2.3.1 Synergy between graphene preserving cell morphology and air-plasma treatment cleaning cell surface enhances ToF-SIMS imaging 23 2.3.2 ToF-SIMS imaging improvement of neurons cells and skin cells 25 2.3.3 Effect of air-plasma treatment on graphene-covered cells 27 2.3.4 Effect of air-plasma treatment on ToF-SIMS imaging of graphene-removed cells 30 2.4 Conclusions 32 3 Atmospheric Pressure Mass Spectrometric Imaging of a Live Hippocampal Tissue 33 3.1 Introduction 33 3.2 Materials and methods 34 3.2.1 Materials 34 3.2.2 Preparation of single and multiple graphene layers on glass substrate 34 3.2.3 Mouse hippocampal tissue preparation 35 3.2.4 Instrumental setup for AP-MS imaging system 36 3.2.5 Instruments for Raman and Helium Ion Microscopy (HIM) 39 3.3 Results and discussions 39 3.3.1 Preparation and characterization of graphene coated glass substrate 39 3.3.2 Graphene layer dependence on the desorption efficiency with transmission-mode CW laser 40 3.3.3 Desorption characteristics (Graphene coated glass vs AuNPs) 42 3.3.4 High spatial resolution mass spectrometric imaging of live hippocampal tissue 44 3.3.5 Graphene-coated slide substrate for a highly reproducible MS imaging 47 3.4 Conclusions 48 III. Electrical Double Layer at Solid-Electrolyte Interface with ToF-MEIS 50 4 Structural Characterization of Electrical Double Layer using ToF-MEIS and Graphene Liquid Chamber 50 4.1 Introduction 50 4.2 Materials and methods 51 4.2.1 Graphene capping for liquid samples 51 4.2.2 Instrumentation and experimental details. 52 4.3 Results and discussions 53 4.3.1 EDL of KI solution on CuOx/Graphene 53 4.3.2 EDL of KI solution on carboxylated Fe3O4 nanoparticles 54 4.4 Conclusions 56 IV. Conclusions 58 REFERENCES 59