NONLINEAR OPTICAL STUDIES OF POTENTIAL-SENSITIVE DYES BY HAOWEN LI Submitted in partial fulfillment of the requirements For the degree of Doctor of Philosophy Thesis Advisor: Professor Kenneth D. Singer Department of Physics CASE WESTERN RESERVE UNIVERSITY MAY, 2007 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the dissertation of ______________________________________________________ candidate for the Ph.D. degree *. (signed)_______________________________________________ (chair of the committee) ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ (date) _______________________ *We also certify that written approval has been obtained for any proprietary material contained therein. To AMZ and my parents Table of Contents Table of Contents...........................................................................................................1 List of Tables .................................................................................................................3 List of Figures................................................................................................................4 List of Figures................................................................................................................4 Acknowledgements........................................................................................................7 Acknowledgements........................................................................................................7 Abstract..........................................................................................................................8 Chapter 1: Introduction................................................................................................10 1.1 A brief introduction to membrane potential.......................................................10 1.2 Mechanisms of potential-sensitive dyes ............................................................12 1.3 Styryl potential-sensitive dye applications ........................................................15 1.4 Overview of this thesis.......................................................................................18 References................................................................................................................21 Chapter 2: Nonlinear optical theory for potential-sensitive dyes ................................26 2.1 Macroscopic susceptibility.................................................................................26 2.2 Microscopic susceptibility .................................................................................30 2.2.1 Early models ...............................................................................................31 2.2.2 Quantum mechanical calculation................................................................33 2.2.3 Two-level model .........................................................................................35 2.3 Relationship between microscopic and macroscopic optical nonlinearities......39 2.3.1 Oriented gas model .....................................................................................40 2.3.2 In Langmuir-Blodgett films ........................................................................42 2.4 Measurement Techniques [38]...........................................................................44 References................................................................................................................46 Chapter 3: Spectroscopic studies and the first hyperpolarizability of di-8-ANEPPS..50 3.1 A brief introduction to styryl dyes.....................................................................51 3.2 Spectroscopic studies of di-8-ANEPPS.............................................................52 3.2.1 Materials and methods ................................................................................53 3.2.2 Results.........................................................................................................55 3.2.3 Discussion...................................................................................................57 3.3 The first hyperpolarizability of di-8-ANEPPS ..................................................63 3.3.1 Introduction.................................................................................................63 3.3.2 Experiment and Results ..............................................................................65 3.3.3 Discussion...................................................................................................71 3.4 Conclusion .........................................................................................................73 Appendix..............................................................................................................74 References................................................................................................................76 Chapter 4: Solvent effects on the non-linear optical response of a potentiometric biological imaging dye.................................................................................................79 4.1 Introduction........................................................................................................80 4.2 Methods and Theory ..........................................................................................82 4.3 Experimental......................................................................................................88 4.4 Results and discussion .......................................................................................90 1 4.5 Conclusions......................................................................................................101 Appendix................................................................................................................102 References..............................................................................................................104 Chapter 5: Applications of potential-sensitive dyes ..................................................108 5.1 Introduction................................................................................................108 5.2 Langmuir-Blodgett films ...........................................................................110 5.2.1 Film Deposition ........................................................................................110 5.2.2 Film characterization ...............................................................................112 5.2.2.1 π – A Isotherm ..................................................................................112 5.2.2.2 UV-VIS Absorption measurements ...................................................114 5.2.2.3 Second harmonic generation (SHG) .................................................115 5.2.3 Conclusion ................................................................................................117 5.3 Near-field Scanning optical microscopy.........................................................118 5.3.1 History of near-field scanning optical microcopy ....................................118 5.3.2 AlphaSNOM from WiTec..................................................................120 5.3.3 Samples....................................................................................................122 5.3.4 Latex projection pattern imaging............................................................123 5.3.5 T-cell imaging..........................................................................................125 5.3.5.1 Comparison between confocal microsocopy and NSOM................125 5.3.5.2 Single T-cell NSOM imaging ............................................................127 5.3.6 Conclusion ...............................................................................................127 5.4 Future studies of potential-sensitive dye applications ...................................129 References..............................................................................................................131 Bibliography ..............................................................................................................135 2 List of Tables Table 3-1 Solution properties. F is the polarity, ε the dielectric constant, and n the refractive index. Data for mixtures are calculated from algebraic sum of the cosolvent fractions using ε and n of chloroform as 4.81 and 1.4458, respectivelya. ...................54 3 List of Figures Figure 1.1 Electrostatic potential profiles across a phospholipid bilayer..............12 Figure 1.2 Generalized structure of styryl dyes. The structure shown is the primary contributor to the ground state, where the positive charge concentrates in the pyridine ring. One double bond could be replaced by two double bonds; the phenyl ring could be replaced by a naphthalene ring ....................................................................................14 Figure 2.1 Typical organic molecules for nonlinear optical effects. The electron donor group (D) is connected to the electron acceptor group (A) through a π electron system. The π electron system can be those containing benzene analogs or stilbene analogs. R1 and R2 are usually carbon or nitrogen. (Adapted from reference [6] )....31 2 22 Figure