New near-IR two-photon absorbing fluorene derivatives : synthesis and nonlinear optical characterization

Keywords

Fluorene, Photoabsorption

Abstract

The quest for organic materials exhibiting high nonlinear (NLO) absorptivities has increased dramatically over the past several years. Specifically, the nonlinear process of two-photon absorption is the subject of intense interest in the chemistry, photonics, and biophotonics communities. Two-photon absorption (TP A) can be defined as the simultaneous absorption of two photons via virtual states in a medium. The process requires high peak power, which is available from pulsed lasers. Several current and emerging technologies exploit the two-photon absorption phenomenon, including optical power limiting materials, two-photon fluorescence imaging, photodynamic cancer therapy, and two-photon microfabrication. The two-photon process considered here involves the simultaneous absorption of two photons, either degenerate or nondegenerate, at wavelengths well beyond the linear absorption spectrum of a particular molecule. Unfortunately, the criteria for the design of molecules with large TP A cross-sections, o, have not been well developed, impeding the full potential of TP A-based applications. Herein, the synthesis and characterization of new near-IR TPA dyes are presented. The synthetic methodology developed facilitates the systematic preparation of derivatives with varying electronic character. The dyes employ fluorene as a thermally and photochemically stable n-conjugated system from which the 2, 7 and 9-postions can be readily functionalized. Nondegenerate, TP A spectra of select dyes were obtained using a recently developed "NLO spectrometer". Their respective o values, a . measurement of the efficiency of the TP A process, are reported. Finally, comparisons of the nonlinear data have generated preliminary trends of the TP A process as a function of wavelength and chemical structure.

Notes

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Graduation Date

1999

Semester

Fall

Advisor

Belfield, Kevin

Degree

Master of Science (M.S.)

College

College of Arts and Sciences

Department

Chemistry

Format

PDF

Pages

103 p.

Language

English

Length of Campus-only Access

None

Access Status

Masters Thesis (Open Access)

Identifier

DP0028706

Subjects

Arts and Sciences -- Dissertations, Academic; Dissertations, Academic -- Arts and Sciences

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