TITLE PAGE CHIRAL INDUCED SPIN SELECTIVITY EFFECT: FUNDAMENTAL STUDIES AND APPLICATIONS by Supriya Ghosh B.Sc., University of Calcutta, 2010 M.Sc., IIT Bombay, 2012 M.Sc., University of Alberta, 2015 Submitted to the Graduate Faculty of the Dietrich School of Arts and Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Pittsburgh 2021 COMMITTE E PAGE UNIVERSITY OF PITTSBURGH DIETRICH SCHOOL OF ARTS AND SCIENCES This dissertation was presented by Supriya Ghosh It was defended on April 5, 2021 and approved by Dr. Haitao Liu, Professor, Department of Chemistry Dr. Sean Garrett-Roe, Associate Professor, Department of Chemistry Dr. Andrew Gellman, Professor, Chemical Engineering, Carnegie Mellon University Dissertation Advisor: Dr. David Waldeck, Professor, Department of Chemistry ii Copyright © by Supriya Ghosh 2021 iii ABST RACT CHIRAL INDUCED SPIN SELECTIVITY EFFECT: FUNDAMENTAL STUDIES AND APPLICATIONS Supriya Ghosh, PhD University of Pittsburgh, 2021 Since the discovery, chiral induced spin selectivity effect or CISS effect, which refers to the preferential transmission of electron of one spin over another through a chiral molecule/material, has generated significant interest due to its versatile application in different branches of science. Over the years, a large number of theoretical and experimental studies have been performed to understand the mechanism for the CISS effect and also to utilize the effect in different fields of science; such as memory devices, electrocatalytic experiments, chiral separations etc. In this dissertation, fundamental studies of chiral molecules at ferromagnetic interfaces are investigated through surface potential and magnetic measurements. Experiments are also done to study the spin filtering properties of chiral thin films and explore their electrocatalytic activity. In the first study chiral molecule induced magnetization of the superparamagnetic particles was shown. This experiment shows a novel method to create a ferromagnetic domain of 10 nm size from superparamagnetic particles using CISS. In the second study, spin dependent charge penetration into chiral molecules from a ferromagnetic substrate is presented by measuring surface potential using Kelvin probe method. In the third study, spin dependent electron transmission through chiral cobalt oxide thin films was performed by using magnetic conductive AFM and magnetoresistance measurements. In the fourth study the electrocatalytic efficiency for water splitting was studied using chiral and magnetic thin cobalt oxide film. The finding of these iv studies serve to advance the CISS field and may help in developing new CISS based spintronics device and electrocatalysts. v TABLE OF CONTENTS PREFACE ................................................................................................................................. xxvi 1.0 INTRODUCTION................................................................................................................... 1 1.1 CHIRAL INDUCED SPIN SELECTIVITY EFFECT (CISS EFFECT) ................... 1 1.2 BASIC PRINCIPLE AND UNDERSTANDING OF CISS EFFECT ......................... 2 1.2.1 Measurements Methods and Detection Thereof ..................................................4 1.2.1.1 Photoemission Study ................................................................................. 4 1.2.1.2 Magnetic Conductive Probe AFM ........................................................... 5 1.2.1.3 Magnetoresistance Measurements .......................................................... 6 1.2.1.4 Electrochemistry ....................................................................................... 7 1.2.1.5 Hall Device ................................................................................................. 8 1.2.2 Timeline of Initial Experiments and Findings .....................................................9 1.2.3 Spin Polarization Through Different Chiral Material ......................................11 1.3 MAGNETIC AND THE CHIRAL INDUCED SPIN SELECTIVITY EFFECT .... 13 1.3.1 Size Dependent Magnetic Properties ..................................................................13 1.3.1.1 Magnetic Measurement .......................................................................... 18 1.3.2 Magnetism Induced by Proximity of Chiral Molecules ....................................20 1.3.3 CISS Based Memory Devices ..............................................................................21 1.4 IMPORTANCE OF SPIN IN CHEMICAL REACTION ......................................... 24 1.4.1 Basic Principles and Some Examples .................................................................25 1.4.2 Spin Control Using the CISS Effect ....................................................................26 1.4.3 OER and Mechanism ...........................................................................................27 vi 1.4.3.1 Basic of Oxygen Evolution Reaction ..................................................... 27 1.4.3.2 Oxygen Evolution Reactions Mechanisms ............................................ 28 1.4.4 Spin Control in Water Splitting ..........................................................................30 1.4.4.1 Control Spin with Magnetic Field ......................................................... 30 1.4.4.2 Control Spin with Chirality ................................................................... 31 1.5 DISSERTATION OUTLINE ........................................................................................ 33 1.6 REFERENCES .............................................................................................................. 34 2.0 SINGLE DOMAIN 10 nm FERROMAGNETISM IMPRINTED ON SUPERPARAMAGNETIC NANOPARTICLES USING CHIRAL MOLECULES ................................................................................................................... 41 2.1 INTRODUCTION ......................................................................................................... 42 2.2 RESULTS AND DISCUSSION .................................................................................... 45 2.2.1 Sample Preparation ..............................................................................................45 2.2.2 SQUID Measurement ...........................................................................................47 2.2.3 Magnetic Force Microscopy (M-AFM) Measurement ......................................49 2.2.4 Mechanism of Magnetization Imprinting ..........................................................51 2.3 SUMMARY .................................................................................................................... 53 2.4 REFERENCES .............................................................................................................. 54 3.0 EFFECT OF CHIRAL MOLECULES ON THE ELECTRON’S SPIN WAVEFUNCTION AT INTERFACES .......................................................................... 56 3.1 INTRODUCTION ......................................................................................................... 57 3.2 RESULTS ....................................................................................................................... 60 3.3 A MODEL ...................................................................................................................... 66 vii 3.4 SUMMARY .................................................................................................................... 70 3.5 REFERENCES .............................................................................................................. 71 4.0 SPIN POLARIZATION STUDY OF PURE AND DOPED CHIRAL OXIDE THIN FILM FOR SPINTRONICS BASED DEVICES WITHOUT A PERMANENT FERROMAGNET .................................................................................. 75 4.1 INTRODUCTION ......................................................................................................... 75 4.2 RESULTS ....................................................................................................................... 78 4.2.1 Cobalt Oxide Thin Film and Chirality ...............................................................78 4.2.2 Magnetic Conductive Atomic Force Microscopy ..............................................79 4.2.3 Spin Valve Based Magnetoresistance Device .....................................................82 4.2.4 Spin Polarization with Mn Doped Cobalt Oxide Film ......................................83 4.3 CONCLUSION .............................................................................................................. 85 4.4 EXPERIMENTAL METHODS ................................................................................... 86 4.4.1 Thin Chiral Cobalt Oxide Thin Film Deposition ...............................................86 4.4.2 Magnetic Conductive AFM .................................................................................87 4.4.3 Magnetoresistance Device ....................................................................................88 4.5 REFERENCES .............................................................................................................. 88 5.0 INCREASING THE EFFICIENCY OF WATER SPLITTING THROUGH SPIN POLARIZATION USING COBALT OXIDE THIN FILM CATALYSTS ................ 92 5.1 INTRODUCTION ......................................................................................................... 93 5.2 RESULTS