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Upconversion nanomaterials: synthesis, mechanism, and applications in sensing.

Chen J, Zhao JX - Sensors (Basel) (2012)

Bottom Line: Over the past decade, high-quality rare earth-doped upconversion nanoparticles have been successfully synthesized with the rapid development of nanotechnology and are becoming more prominent in biological sciences.The synthesis methods are usually phase-based processes, such as thermal decomposition, hydrothermal reaction, and ionic liquids-based synthesis.In this review, the synthesis of upconversion nanoparticles and the mechanisms of upconversion process will be discussed, followed by their applications in different areas, especially in the biological field for biosensing.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of North Dakota, Grand Forks, ND 58202, USA. jiao.chen@my.und.edu

ABSTRACT
Upconversion is an optical process that involves the conversion of lower-energy photons into higher-energy photons. It has been extensively studied since mid-1960s and widely applied in optical devices. Over the past decade, high-quality rare earth-doped upconversion nanoparticles have been successfully synthesized with the rapid development of nanotechnology and are becoming more prominent in biological sciences. The synthesis methods are usually phase-based processes, such as thermal decomposition, hydrothermal reaction, and ionic liquids-based synthesis. The main difference between upconversion nanoparticles and other nanomaterials is that they can emit visible light under near infrared irradiation. The near infrared irradiation leads to low autofluorescence, less scattering and absorption, and deep penetration in biological samples. In this review, the synthesis of upconversion nanoparticles and the mechanisms of upconversion process will be discussed, followed by their applications in different areas, especially in the biological field for biosensing.

Show MeSH
Energy transfer processes between two ions: (a) resonant non-radiative transfer; (b) phonon-assisted non-radiative transfer. (S: sensitizer ions, A: activator ions) [1].
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f3-sensors-12-02414: Energy transfer processes between two ions: (a) resonant non-radiative transfer; (b) phonon-assisted non-radiative transfer. (S: sensitizer ions, A: activator ions) [1].

Mentions: ETU is by far the most efficient upconversion process in RE doped nanomaterials and it is independent of the pump power. In the process of ETU, two situations, resonant non-radiative transfer and phonon-assisted non-radiative transfer in two-ion-involved system, will be mainly discussed (Figure 3) [1]. When the excited energies of sensitizer (S) and activator (A) are nearly equal and the distance between them is near enough, energy can be transferred from S to A, exciting A from its ground state to excited state before S emits photons. In phonon-assisted non-radiative transfer, an energy mismatch exists between S and A ions, so phonon assistance is necessary to have the energy transfer process.


Upconversion nanomaterials: synthesis, mechanism, and applications in sensing.

Chen J, Zhao JX - Sensors (Basel) (2012)

Energy transfer processes between two ions: (a) resonant non-radiative transfer; (b) phonon-assisted non-radiative transfer. (S: sensitizer ions, A: activator ions) [1].
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3376553&req=5

f3-sensors-12-02414: Energy transfer processes between two ions: (a) resonant non-radiative transfer; (b) phonon-assisted non-radiative transfer. (S: sensitizer ions, A: activator ions) [1].
Mentions: ETU is by far the most efficient upconversion process in RE doped nanomaterials and it is independent of the pump power. In the process of ETU, two situations, resonant non-radiative transfer and phonon-assisted non-radiative transfer in two-ion-involved system, will be mainly discussed (Figure 3) [1]. When the excited energies of sensitizer (S) and activator (A) are nearly equal and the distance between them is near enough, energy can be transferred from S to A, exciting A from its ground state to excited state before S emits photons. In phonon-assisted non-radiative transfer, an energy mismatch exists between S and A ions, so phonon assistance is necessary to have the energy transfer process.

Bottom Line: Over the past decade, high-quality rare earth-doped upconversion nanoparticles have been successfully synthesized with the rapid development of nanotechnology and are becoming more prominent in biological sciences.The synthesis methods are usually phase-based processes, such as thermal decomposition, hydrothermal reaction, and ionic liquids-based synthesis.In this review, the synthesis of upconversion nanoparticles and the mechanisms of upconversion process will be discussed, followed by their applications in different areas, especially in the biological field for biosensing.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of North Dakota, Grand Forks, ND 58202, USA. jiao.chen@my.und.edu

ABSTRACT
Upconversion is an optical process that involves the conversion of lower-energy photons into higher-energy photons. It has been extensively studied since mid-1960s and widely applied in optical devices. Over the past decade, high-quality rare earth-doped upconversion nanoparticles have been successfully synthesized with the rapid development of nanotechnology and are becoming more prominent in biological sciences. The synthesis methods are usually phase-based processes, such as thermal decomposition, hydrothermal reaction, and ionic liquids-based synthesis. The main difference between upconversion nanoparticles and other nanomaterials is that they can emit visible light under near infrared irradiation. The near infrared irradiation leads to low autofluorescence, less scattering and absorption, and deep penetration in biological samples. In this review, the synthesis of upconversion nanoparticles and the mechanisms of upconversion process will be discussed, followed by their applications in different areas, especially in the biological field for biosensing.

Show MeSH