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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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Schematic illustration of the growth stages of α-NaYF4:Yb3+, Er3+ nanocrystals via a delayed nucleation pathway [27].
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f5-sensors-12-02414: Schematic illustration of the growth stages of α-NaYF4:Yb3+, Er3+ nanocrystals via a delayed nucleation pathway [27].

Mentions: Thermal decomposition, which gives well shaped particles, with good size control, after a relatively short reaction time, is one of the most popular methods. It usually involves dissolving organic precursors in high-boiling organic solvents with the assistance of surfactants. The commonly used organic precursors are trifluoroacetate compounds, and the surfactants typically have polar capping groups and long hydrocarbon chains, such as oleic acid (OA), omeylamine (OM), and 1-octadecence (ODE). Mai et al. [27] systematically investigated the growth mechanism of nanocrystals and pointed out that the trifluoroaetate precursors in hot surfactant solutions went through a unique delayed nucleation pathway. The synthesis reaction was separated as four stages including nucleation in a delayed time, particle growth by monomer supply, size shrinkage by dissolution, and aggregation. Figure 5 illustrates the synthesis steps of α-NaYF4:Yb3+, Er3+ UCNs and by varying the reaction time, concentration of reagents, and reaction temperature, various sizes and shapes of NaYF4:Yb3+, Er3+ UCNs can be obtained.


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

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

Schematic illustration of the growth stages of α-NaYF4:Yb3+, Er3+ nanocrystals via a delayed nucleation pathway [27].
© Copyright Policy
Related In: Results  -  Collection

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

f5-sensors-12-02414: Schematic illustration of the growth stages of α-NaYF4:Yb3+, Er3+ nanocrystals via a delayed nucleation pathway [27].
Mentions: Thermal decomposition, which gives well shaped particles, with good size control, after a relatively short reaction time, is one of the most popular methods. It usually involves dissolving organic precursors in high-boiling organic solvents with the assistance of surfactants. The commonly used organic precursors are trifluoroacetate compounds, and the surfactants typically have polar capping groups and long hydrocarbon chains, such as oleic acid (OA), omeylamine (OM), and 1-octadecence (ODE). Mai et al. [27] systematically investigated the growth mechanism of nanocrystals and pointed out that the trifluoroaetate precursors in hot surfactant solutions went through a unique delayed nucleation pathway. The synthesis reaction was separated as four stages including nucleation in a delayed time, particle growth by monomer supply, size shrinkage by dissolution, and aggregation. Figure 5 illustrates the synthesis steps of α-NaYF4:Yb3+, Er3+ UCNs and by varying the reaction time, concentration of reagents, and reaction temperature, various sizes and shapes of NaYF4:Yb3+, Er3+ UCNs can be obtained.

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