In this study, three-dimensional (3D) polyacrylamide microstructures containing gold nanorods (AuNRs) were fabricated by two-photon polymerization (TPP) using Rose Bengal (RB) as the photoinitiator. To retain AuNRs in the 3D polymer microstructures, the laser wavelength was chosen for two-photon RB absorption for improved TPP efficiency, but not for enhancing the longitudinal plasmon resonance of AuNRs which may result in photothermal damage of AuNRs. After TPP processing, the laser wavelength was tuned for the longitudinal plasmon resonance and the laser power was increased to beyond the damage threshold of the AuNRs for reshaping the AuNRs into gold nanospheres. As a result, AuNRs in designated positions of the fabricated 3D microstructures can be achieved. Two-photon luminescence from the doped AuNRs can also act as contrast agent for the visualization of 3D polymer microstructures.
[Show abstract][Hide abstract] ABSTRACT: The two-photon excited fluorescence (TPEF) increments of two dyes via bovine serum albumin (BSA) microstructures
fabricated by the two-photon crosslinking technique were investigated. One is Rose Bengal (RB) with a high nonradiative decay rate, while the other is Eosin Y with a low non-radiative decay rate. Experimental results demonstrate that the quantum yield and lifetime of RB are both augmented via crosslinked BSA microstructures. Compared with theoretical analysis, this result indicates that the non-radiative decay rate of RB is decreased; hence, the quenched effect induced by BSA solution is suppressed. However, the fluorescence lifetime of Eosin Y is acutely abated despite the augmented quantum yield for the two-photon crosslinking processing from BSA solution. This result deduces that the radiative decay rate increased. Furthermore, the increased TPEF intensity and lifetime of RB correlated with the concentration of fabricated crosslinked BSA microstructures through pulse selection of the employed femtosecond laser is demonstrated and capable of developing a zone-plate-like BSA microstructure.
"where δ is the cross section of TPA of a fluorescence species, η2 the quantum efficiency of two-photon excited fluorescence (TPEF), λ the excitation wavelength, τ the excitation pulse width at full-width at half maximum, and F the time-averaged TPEF photon count. In TPA spectrum measurement experiment, it was found that the excitation wavelength corresponding to the maximum value of the relative TPA of the RB was between 710 and 720 nm . Therefore, a fabrication laser wavelength of around 715 nm was adopted. "
[Show abstract][Hide abstract] ABSTRACT: In this study, three-dimensional (3D) crosslinked bovine serum albumin
(BSA) microstructures containing gold nanorods (AuNRs) at different
absorption wavelengths were fabricated via multiphoton excited
photochemistry using rose Bengal (RB) as the photoactivator. After the
processing, a higher laser power, greater than the threshold of the AuNR
photothermal damage at the matched wavelength for the longitudinal
plasmon resonance of AuNR, is adopted to reshape the AuNRs into gold
nanospheres at the designed positions of the 3D structure. As a result,
3D BSA microstructures containing different color AuNRs at the designed
positions can be successfully fabricated. The AuNRs-doped BSA multicolor
microstructures not only can be applied in biomedical scaffolds with
plasmonic properties such as two-photon luminescence imaging and
photothermal therapy but also can be a specific 3D biomaterial
microdevice for plasmonic field.
Proceedings of SPIE - The International Society for Optical Engineering 02/2012; 8234:37-. DOI:10.1117/12.914044 · 0.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We investigated the plasmonic resonance enhanced two-photon photopolymerization (PETPP) using the isolated chemical synthesized gold nanorods for fabrication of polymer/metal nanocomposites. The isolated gold nanorods with the plasmonic resonance band around 750 nm covered by photoresist were irradiated by a femtosecond laser with the wavelength of 780 nm. The PETPP trigged by the plasmonic resonance enhancement of gold nanorods was localized only in the distance smaller than 30 nm from the surface of gold nanorods, which matched the distance of plasmonic resonant enhanced field of the gold nanorod. The shapes of obtained polymer/gold nanocomposites were changed from the “dumbbell” to the “ellipsoid” with the increase of laser irradiating intensity used for PETPP. This study would provide a potential method for fabricating the plasmonic nanomaterials and nanostructures of polymer/metal nanocomposites, which could be expected to be applied in the emerging fields such as nanophotonics, nanobiosensor, nanolithography.
Applied Physics A 03/2012; 106(4). DOI:10.1007/s00339-012-6768-y · 1.70 Impact Factor
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