Enhanced melanin fluorescence by stepwise three-photon excitation Journal Article
| Authors: | Kerimo, J.; Rajadhyaksha, M.; DiMarzio, C. A. |
| Article Title: | Enhanced melanin fluorescence by stepwise three-photon excitation |
| Abstract: | The fluorescence of eumelanin (from Sepia officinalis and black human hair) was activated and enhanced by almost three orders of magnitude by exposure to near-infrared radiation. No activation or enhanced emission was observed when the samples were heated up to 100°C. The near-infrared irradiation caused obvious changes to the eumelanin and could be seen by fluorescence and bright field imaging. The area of enhanced emission appeared to originate from a region with changes in the morphology of the eumelanin's granule and increased with exposure time. At least two different components with enhanced fluorescence were activated and could be distinguished by their excitation properties. One component could be excited efficiently with wavelengths in the visible region and exhibited linear absorption dependence with respect to the laser power level. The second component could be excited efficiently using near-infrared wavelengths by a nonlinear process and exhibited a third-order dependence on the excitation. The third-order dependence is explained by a step-wise excited-state absorption process since the same third-order dependence was present when either continuous wave or femtosecond pulsed laser, with similar average-power levels, was used. Eumelanin (from Sepia officinalis and black human hair) fluorescence was activated by near-infrared radiation and enhanced by almost three orders of magnitude. Two components with enhanced fluorescence were observed and could be distinguished by their excitation wavelength and laser power dependence. One was excited with wavelengths in the visible region and had linear absorption dependence (red color in the figure) and the other was excited in the near-infrared region with three photons (green color in the figure). The third-order dependence is due to a step-wise excited-state absorption process. © 2011 The Authors. |
| Keywords: | sepia officinalis; sepiidae |
| Journal Title: | Photochemistry and Photobiology |
| Volume: | 87 |
| Issue: | 5 |
| ISSN: | 0031-8655 |
| Publisher: | Wiley Blackwell |
| Date Published: | 2011-09-01 |
| Start Page: | 1042 |
| End Page: | 1049 |
| Language: | English |
| DOI: | 10.1111/j.1751-1097.2011.00949.x |
| PROVIDER: | scopus |
| PUBMED: | 21668873 |
| DOI/URL: | |
| Notes: | --- - "Export Date: 3 October 2011" - "CODEN: PHCBA" - "Source: Scopus" |
