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Optical Engineering

Effects of sodium chloride on the properties of chlorophyll a submonolayer adsorbed onto hydrophobic and hydrophilic surfaces using broadband spectroscopy with single-mode integrated optical waveguides
Author(s): Rodrigo S. Wiederkehr; Sergio B. Mendes; Geoffrey C. Hoops
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Paper Abstract

In this work, we experimentally investigated the effects of sodium chloride on the molar absorptivity and surface density of a submonolayer of chlorophyll a adsorbed onto hydrophilic and hydrophobic solid/liquid interfaces. Those investigations were made possible by a broadband spectroscopic platform based on single-mode, integrated optical waveguides, which allows for extremely sensitive spectroscopic detection of analytes immobilized at submonolayer levels. Chlorophyll a with a constant bulk concentration (1.4 μM) was dissolved in phosphate buffer solutions (7 mM) of neutral pH, but with different sodium chloride concentrations. For a buffer solution of 1 mM of sodium chloride, the measured surface density of chlorophyll a was 0.209 pmol/cm2 for a hydrophilic and 0.125 pmol/cm2 for a hydrophobic surface. For a phosphate buffer solution of 10 mM of sodium chloride, the measured surface density of chlorophyll a was 0.528 pmol/cm2 for a hydrophilic and 0.337 pmol/cm2 for a hydrophobic surface. Additionally, a hypsochromic shift of the Soret band was observed for the adsorbed pigment in correlation with an increase in buffer ionic strength. The adsorption of chlorophyll a onto different surfaces can play an important role to elucidate several processes found in nature and provide a rationale for bio-inspired new material technologies.

Paper Details

Date Published: 1 July 2011
PDF: 9 pages
Opt. Eng. 50(7) 071109 doi: 10.1117/1.3564421
Published in: Optical Engineering Volume 50, Issue 7
Show Author Affiliations
Rodrigo S. Wiederkehr, Univ. of Louisville (United States)
Sergio B. Mendes, Univ. of Louisville (United States)
Geoffrey C. Hoops, Butler Univ. (United States)

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