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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 of the design of the versatile photosensitizer based on UCNs [78].
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f9-sensors-12-02414: Schematic of the design of the versatile photosensitizer based on UCNs [78].

Mentions: UCN satisfies all the requirements due to its deeper penetration (capable of converting NIR light into visible light), lower toxicity, higher stability, and easier surface modification. UCNs used in PDT are usually pre-coated with a shell, which has the functions of: (1) doping matrix for photosensitizers; (2) specific target on tumor cells; and (3) UCNs stabilization. The NaYF4:Yb/Er UCN is one of the most common used UCN in PDT due to its high UC efficiency [19,75–77]. Zhang and co-workers first demonstrated a novel design for PDT based on UCNs for the treatment of bladder cancer cells (Figure 9) [78]. UCNs were coated with a layer of mesoporous silica shell, in which the photosensitizers were doped. An antibody, which had specific antigens that were expressed on the target cell’s surface, was covalently attached on the surface of the silica shell. Due to the spectra overlap between photosensitizers’ absorbance and UCNs’ emission, the photosensitizer-doped UCNs can generate 1O2 under NIR irradiation and further kill the target cells. The generation of 1O2 is usually indicated by the quenching phenomenon of ABDA or ADPA.


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

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

Schematic of the design of the versatile photosensitizer based on UCNs [78].
© Copyright Policy
Related In: Results  -  Collection

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

f9-sensors-12-02414: Schematic of the design of the versatile photosensitizer based on UCNs [78].
Mentions: UCN satisfies all the requirements due to its deeper penetration (capable of converting NIR light into visible light), lower toxicity, higher stability, and easier surface modification. UCNs used in PDT are usually pre-coated with a shell, which has the functions of: (1) doping matrix for photosensitizers; (2) specific target on tumor cells; and (3) UCNs stabilization. The NaYF4:Yb/Er UCN is one of the most common used UCN in PDT due to its high UC efficiency [19,75–77]. Zhang and co-workers first demonstrated a novel design for PDT based on UCNs for the treatment of bladder cancer cells (Figure 9) [78]. UCNs were coated with a layer of mesoporous silica shell, in which the photosensitizers were doped. An antibody, which had specific antigens that were expressed on the target cell’s surface, was covalently attached on the surface of the silica shell. Due to the spectra overlap between photosensitizers’ absorbance and UCNs’ emission, the photosensitizer-doped UCNs can generate 1O2 under NIR irradiation and further kill the target cells. The generation of 1O2 is usually indicated by the quenching phenomenon of ABDA or ADPA.

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