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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.

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Energy diagram of the Er3+/Yb3+ codoped materials [24].
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f4-sensors-12-02414: Energy diagram of the Er3+/Yb3+ codoped materials [24].

Mentions: For example, in the system of NaYF4:Yb3+ (Figure 4) Er3+ UCNs, red, blue, and green light can be emitted through this process. The Yb3+ ion, with its excited state 2F5/2, has an energy comparable to 4I11/2 (Er3+), which can act as a sensitizer for Er3+ and transfer its energy to an unexcited Er3+ ion through the energy transfer process: 2F5/2 (Yb3+) + 4I15/2 (Er3+) → 2F7/2 (Yb3+) + 4I11/2 (Er3+). By further cross relaxation and phonon-assisted process, red emission (∼654 nm) can be emitted from 4F9/2 [2F5/2 (Yb3+) + 4I13/2 (Er3+) → 2F7/2 (Yb3+) + 4F9/2 (Er3+)]. The blue (∼408 nm) and green luminescence emissions (∼526 nm and ∼533 nm) are emitted from2H9/2 – 4I15/2 and 2H11/2 – 4I15/2 (also 4S3/2 − 4I15/2) via similar ways, respectively.


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

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

Energy diagram of the Er3+/Yb3+ codoped materials [24].
© Copyright Policy
Related In: Results  -  Collection

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

f4-sensors-12-02414: Energy diagram of the Er3+/Yb3+ codoped materials [24].
Mentions: For example, in the system of NaYF4:Yb3+ (Figure 4) Er3+ UCNs, red, blue, and green light can be emitted through this process. The Yb3+ ion, with its excited state 2F5/2, has an energy comparable to 4I11/2 (Er3+), which can act as a sensitizer for Er3+ and transfer its energy to an unexcited Er3+ ion through the energy transfer process: 2F5/2 (Yb3+) + 4I15/2 (Er3+) → 2F7/2 (Yb3+) + 4I11/2 (Er3+). By further cross relaxation and phonon-assisted process, red emission (∼654 nm) can be emitted from 4F9/2 [2F5/2 (Yb3+) + 4I13/2 (Er3+) → 2F7/2 (Yb3+) + 4F9/2 (Er3+)]. The blue (∼408 nm) and green luminescence emissions (∼526 nm and ∼533 nm) are emitted from2H9/2 – 4I15/2 and 2H11/2 – 4I15/2 (also 4S3/2 − 4I15/2) via similar ways, respectively.

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