Multiphoton luminescence

Gold nanoparticles have large second- and third-order nonlinear susceptibilities and are therefore a promising class of nonlinear optical materials.214 We will briefly discuss several nonlinear optical processes from metal nanoparticles, such as multiphoton luminescence, hyper-Rayleigh scattering, and multiharmonic generation. 

Rare Earth Complexes as Multiphoton Luminescence Probes for Bioimaging... 

Figure 13.13 Plasmonics laser nanoablation of cancer cells (MDA-MB-468) labeled with 80nm gold nanoparticles functionalized with anti-EGFR antibodies, (a) Nanoparticles in red, imaged at 850nm wavelength through multiphoton luminescence, and cell membrane-impermeable dye (lOkDa FITC-...

Through scattering and bright multiphoton luminescence, nanoparticles can additionally double as image contrast agents... 

Farrer, R.A., Butterfield, F.L., Chen, V.W. and Fourkas, J.T. (2005) Highly efficient multiphoton-absorption-induced luminescence from gold nanoparticles. Nano Letters, 5, 1139-1142. 

See also Luminescent dendrimers antibacterial, 26 799 biocompatibility studies of, 26 800-801 in catalysis, 26 805-806 in cell targeting, 26 797-798 as chelators, 26 806-807 core and interior shells of, 26 789 cytotoxicity of, 26 800-801 in drug delivery, 26 792-795 in gene transfection, 26 791-792 as imaging agents, 26 795-797 luminescent, 26 801-804 medical applications of, 26 791-801 micelle-mimetic behavior of, 26 789 multiphoton applications of, 26 803-804... 

The red PL band of PS can not only be excited by above bandgap photons, but also by an intense IR (1064 nm) pulse [Di6]. Such a thermostimulated luminescence is known for the case of glasses. This observation was attributed to PS having about 100 times the third-order nonlinear optical susceptibility of bulk Si, as discussed in Section 7.3. Multiphoton excitation of the red PL band by resonant pumping of the vibrational modes of surface groups like Si-O [Di4] or Si-H [Ch8] provided evidence for excitation modes that involve the porous skeleton surface. 

Extension to the use of multi-photon induced luminescence lanthanide-based bioprobes adds new possibilities and challenges to the field. However, there are even fewer examples of multiphoton lanthanide bioprobes because achieving acceptable quantum yields is fairly difficult in view of the numerous nonradiative deactivation pathways created by a wealth of vibrations, including high energy oscillators located far from the emitting lanthanide ion. 

Here, we will give an overview on the work on NIR labels and probes based on lanthanide ions. The emphasis will be on the NIR luminescent ions (Yb , Nd ", Er ", Pr ", Ho ", Tm " ), which may be incorporated in complexes that can be excited by ultraviolet, visible or possibly NIR light. Alternatively, multiphoton excitation and lanthanide-based upconversion make possible the use of NIR... 

Studies of lanthanide complexes under such multiphoton excitation are rare [24, 76-78], and further work is necessary to identify complexes that have a suitable response towards multiphoton excitation under biological conditions. We note that multiphoton-excited luminescence, which involves the simultaneous absorption of several photons, is different from the upconversion luminescence for lanthanide-doped phosphors described earlier in this chapter, which is based on the sequential absorption of photons. 

Not surprisingly, multiphoton excitation of the luminescence of lanthanide complexes has mainly been applied to Eu and Tb complexes, yielding NIR excitation of visible luminescence. Multiphoton excitation of NIR luminescent complexes has been pioneered [79] and seems a viable option, giving rise to NIR excitation of NIR luminescence, of particular interest for luminescence detection in biological media, since both the NIR excitation light and the NIR emitted light propagate well in these materials. 

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