Biomedical Engineering Reference
In-Depth Information
Photoluminescence spectra relative to the
4
I
13/2
-
4
I
15/2
transition of
Er
3+
ions for Er
3+
activated SiC/SiO
2
nanocomposite pyrolyzed at 1200
3.16
8
C
for 1 h and doped with (a) 1Nmol%, (b) 2 mol%, (c) 3 mol% and (d)
4 mol% Er
3+
. The emission spectra were obtained using a diode laser
operating at 980 nm as a pump beam.
14
independent of the erbium content, at least for Er
3+
concentration up to
4 mol% (Fig. 3.16). This effect suggests that the SiCO network is flexible
enough to accommodate Er
3+
without appreciable matrix strains. The
luminescence spectra do not show evidence of crystalline environment for
the Er
3+
ion, suggesting that at least the majority of erbium ions are
accommodated in the glass. The arrow in Fig. 3.17(a) shows the excitation
wavelength (980 nm) used to obtain the luminescence spectra shown in Fig.
3.16. The UV edge shifts to longer wavelengths with respect to pure silica
glasses with an increase
in annealing temperature,
resulting in a
corresponding decrease in the electronic bandgap energy.
Since the 1990s, the use of fluorescent nanoparticles as indicators in
biological applications such as imaging and sensing has dramatically
increased. These applications require that the fluorescent nanoparticles are
monodisperse, bright, photostable and amenable to further surface
modification for the conjugation of biomolecules and/or fluorophores.
Aslan et al.
35
developed core-shell (silver core-silica shell) (Fig. 3.18)
nanoparticles with various shell thicknesses featuring a variety of
fluorophores to show the versatility of the core-shell architecture. They
demonstrated their applicability for two platform technologies: metal-
enhanced fluorescence and single nanoparticle sensing. They also developed
three different fluorescent probes: an organic fluorophore (Rh800), a doped
lanthanide probe (non-covalently linked) and another organic fluorophore
(Alexa 647) covalently linked to the silica shell. When compared with the
control sample fluorescent nanoparticles (nanobubbles), fluorescent nano-
particles with core-shell architecture yielded up to 20-fold (with Rh800)
