Chemistry Reference
In-Depth Information
3.2.2.2 Upconversion nanoparticles
Fluorescent lanthanide-doped nanoparticles, which possess
upconversion characteristics, have gained popularity as a class
of fluorescent labels recently. Upconversion occurs when two
or more photons of lower energy are absorbed, followed by the
emission of a photon of higher energy. Upconversion mechanisms
include energy transfer upconversion, excited state absorption,
and photon avalanche [11]. The phenomenon of upconversion was
first noticed in the 1960s in bulk materials. Only in the past decade,
there has been a lot of focus on developing lanthanide upconversion
nanomaterials. A review by Feng
. provides a clear picture on the
mechanisms of upconversion and also gives the selection criteria for
the host material and lanthanide dopants, which are necessary for
the synthesis of lanthanide upconversion nanomaterials [5].
et al
Table 3.1
Comparison of different classes of fluorescent nanoparticles
Organic dye-doped
nanoparticles
Quantum
dots (QDs)
Upconversion
nanoparticles
(UCNs)
Size
50-500 nm
2-10 nm
50-200 nm
Autofluorescence High
High
Low
Light penetration
depth
Medium/High
Medium/High High
Photodamage Medium/Low
Medium/Low Low
Cytotoxicity
Medium
High/Medium Low
Biocompatibility Good
Good
Good
Photostability Low
High
High
Excitation
wavelength
UV/Vis/NIR
UV/NIR
NIR
Cost
Low
High
Low
Excitation
Radiation
toxicity
Medium/Low
Medium/Low Low
Multiplexing
assays
N/A
Good
Good
Note
: Adapted from [12], reprinted with permission from the Royal Society Publishing,
© 2010.
