Related Experiment Video
Updated: May 8, 2026

Synthesis of Monocyte-targeting Peptide Amphiphile Micelles for Imaging of Atherosclerosis
Published on: November 17, 2017
Two-photon absorption properties of chromophores in micelles: electrostatic interactions
Semere Bairu1, Guda Ramakrishna
1Department of Chemistry, Western Michigan University , Kalamazoo, Michigan 49008, United States.
Abstract:
Two-photon absorption (2PA) cross sections of neutral Coumarin 485 (C485) and anionic Coumarin 519 (C519(-)) solubilized in Triton X-100 (Tx-100, neutral), sodium dodecyl sulfate (SDS, anionic), and cetyltrimethylammonium bromide (CTAB, cationic) are reported. The objective of the study is to probe the influence of local electrostatic fields in micelles on the 2PA properties of chromophores. The 2PA measurements have shown that the cross sections of neutral C485 are unchanged in different micellar environments, although the local micropolarities of chromophores are different. On the other hand, the 2PA cross sections of C519(-) are unchanged or slightly decreased in Tx-100 and SDS micelles when compared to water while 100% increase in 2PA cross sections was observed for C519(-) in CTAB micelles. The enhancement in 2PA cross section is attributed to the electrostatic fields arising in the Stern layer of CTAB, where C519(-) is solubilized. The titration measurements have shown that the 2PA enhancement is due to the organized medium only and not because of the simple association of C519(-) and the quaternary ammonium group of CTAB. From the analysis, local electric field of 0.7 ± 0.3 MV/cm is estimated for the Stern layer of CTAB.
Related Concept Videos
Micelles
Intermolecular Forces
Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
Variables Affecting Phosphorescence and Fluorescence
Complexation Equilibria: The Chelate Effect
Interaction of EM Radiation with Matter: Spectroscopy

