Three-photon luminescence

Recently, Wong and coworkers reported an emissive Tb(III) complex [Tb(L73)(N03)3] (Tb-73, Figure 13.34) based on a ligand of 7V-[2-(bis 2-[(3-methoxybenzoyl)amino]-ethyl amino)ethyl]-3-methoxybenzamide) (L73) as a three-photon luminescence probe with low cytotoxicity [109]. The three-photon process of Tb-73 under excitation at a femtosecond 800 nm laser was confirmed by a power dependence experiment. The three-photon absorption cross section of Tb-73 is around 1.9 GM. Furthermore, the interaction of three selected cells with Tb-73 over different durations of time (from 0 to 60 min and 24 h) was investigated. As shown in Figure 13.34, intracellular luminescence increased as the exposure time increased. At an exposure time of 60 min, more than 95% of the cells under 800 nm excitation exhibited green luminescence, as was observed in the cytoplasmic foci around the cell nucleus. 

Gold nanorods exhibit intense two-photon luminescence. Two-photon imaging of tissue phantoms treated with 50 x 15 nm gold nanorods functionalized with EGFR antibodies increased intensity by three orders of magnitude compared with cellular autofluorescence with 760 nm excitation [48]. 

Law G-L, Wong K-L, Kwok W-M, Wong W-T (2007) Tanner P A (2007) Terbium luminescence sensitized through three-photon excitation in a self-assembled unlinked antenna. J Phys Chem B 111 10858-10861... 

The LaOBr host has low phonon energy, which indicates that LaOBrEr " may have high luminescent efficiency [14]. Under excitation into the " In/2 level of Er ions by 980-nm laser, the two- and three-photon upconversion luminescence of... 

Typically, the optimization of sunlight harvesting in PV devices by means of spectral managing coatings can be performed via three different luminescence processes upconversion (UC), downconversion (DC) (or quantum-cutting (QC)) and downshifting (DS) (see Figure 11.1). As a mle of thumb, UC layers are placed at the rear of the PV cell so as to collect transmitted photons, while DC and DS layers are placed on the front surface. 

Eliseeva S. V., G. Aubbck, F. van Mourik, A. Cannizo, B. Song, E. Deiters, A.-S. Chauvin, M. Chergui, J.-C. G. Btinzli. Multiphoton-excited Luminescent Lanthanide Bioprobes Two- and Three-photon Cross Sections of Dipicolinates Derivatives and Binuclear Helicates, J. Phys. Chem. B, 114, 2932-2937 (2010). 

Figure 5.9 From left to right structure of water soluble tris-dipicolinate complexes (Ln = Tb or Eu), three photon excited (lex = S00nm) luminescence, variation of the luminescence intensity with the incident laser power for a two (right, top) or three (right, bottom) photon excitation (Zex = 532 or 800 nm respectively) In linear or log scale, respectively (between parenthesis is indicated the experimental determination of the multi-photon absorption)...

It was not possible to determine quantitatively the two-photon cross-seclion of the [Tb(DPA)3] because of its low efficiency and because the use of ns-pulsed laser induced important error in the ct2pa determination. Using a fs Ti Sa laser as source and an integration sphere, Btinzli et al. [62] determined the three-photon cross-section by comparison of the 3PA and 1 PA luminescence. This absolute method does not require any standard and the [Pg.208]

The morphological dependence of the antenna effect was quantitatively studied by the comparison of the three focal isomers of benzene-cored 4th-genera-tion dendrimers [7]. The energy of the photon absorbed by the dendron subunits must be dissipated either through radiative (luminescence) or nonradia-... 

Figure 1.9 The energy-level and transition schemes and possible luminescence spectra of a three-level ideal phosphor (a) the absorption spectrum (b, c) emission spectra under excitation with light of photon energies hvi and /iV2, respectively (d, e) Excitation spectra monitoring emission energies at /i( V2 — vi) and at /i vi, respectively. Arrows mark the absorption/emission transitions involved in each spectrum. Eixed indicates that the excitation or emission monochromator is fixed at the energy (wavelength) corresponding to this transition.

Another possible solution that has been under development for three decades is to use a pulsed laser and time-resolved detection to allow the Raman photons to be discriminated from the broad luminescence background. The Raman interaction time is virtually instantaneous (less than 1 picosecond), whereas luminescence emission is statistically relatively slow, with minimum hundreds of picoseconds elapsing between electronic excitation and radiative decay. If we illuminate a sample with a very short (= 1 ps) laser pulse, all of the Raman... 

Luminescence spectroscopy involves three related optical methods fluorescence, phosphorescence, and chemiluminescene. These methods utilize excited molecules of an analyte to give a species whose emission spectrum can provide information about the molecule. In fluorescence, atoms can be excited to a higher energy level by the absorption of photons of radiation. Some features of luminescence methods are increased sensitivity (in the order of three magnitudes smaller than absorption spectroscopy), larger linear range of concentration, and method selectivity (Parsons 1982). 

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