Upconverting Nanoparticles (UCNPs) List
Upconverting nanoparticles (UCNPs) are new nanomaterials with low toxicity, stability and long luminescence life. Upconverting nanoparticles (UCNPs) are composed of substrates and rare earth ions. The substrates usually can be oxides, fluoride, oxyhalide and the others. After absorbing two or more low energy photons, upconverting nanoparticles (UCNPs) will radiate a high energy photon, and this phenomenon is known as upconversion luminescence. The biggest characteristic of upconverting nanoparticles (UCNPs) is that the photon energy absorbed is lower than the photon energy emitted. This process is against Stokes law, so it is also called "anti-Stokes luminescence". The luminous mechanisms of upconverting nanoparticles (UCNPs) mainly include excited state absorption (ESA), energy transfer upconversion (ETU) and cooperative sensitization upconversion (CSU).
Applications:
- Tumor diagnosis and treatment field: Stimulated by near-infrared light (NIR), upconverting nanoparticles (UCNPs) can transfer long wave radiation into short wave radiation, which has the advantages of reducing spontaneous fluorescence background interference, high tissue penetration ability and excellent optical stability. Therefore, upconverting nanoparticles (UCNPs) are highly favored in the field of tumor treatment. The applications of upconverting nanoparticles (UCNPs) in tumor diagnosis and treatment field mainly focuses on photodynamic therapy, photothermal therapy, chemical combination therapy, integration of diagnosis and treatment guided by multi-mode imaging and in vitro diagnosis.
Figure 1. An example of upconversion nanoparticles (UCNPs) applied in tumor diagnosis and treatment field.
- Fluorescent probe field: Fluorescent probes have important applications in the detection field. Upconverting nanoparticles (UCNPs) can be designed as fluorescence probes based on the principle of fluorescence resonance energy transfer (FRET), which can be used to detect a variety of ions and molecules.
- Fluorescence imaging field: With the advantages of high resolution, sensitivity and speed, fluorescence imaging plays an increasingly important role in biomedicine. Upconverting nanoparticles (UCNPs) have the superiority of high light stability, narrow emission spectrum, high chemical stability, which can be used as fluorescent markers. Moreover, upconverting nanoparticles (UCNPs) can completely eliminate the spontaneous background fluorescence and obtain ultra-high image contrast.
Figure 2. An example of upconverting nanoparticles (UCNPs) applied in fluorescence imaging field.
- The others: Upconverting nanoparticles (UCNPs) also have important applications in other fields. For example, upconverting nanoparticles (UCNPs) have a large specific surface area and abundant modifiable characteristics and can be used as drug delivery carriers. In addition, upconverting nanoparticles (UCNPs) can also be applied as biosensors.
Classification:
According to the type of transition metals used for doping, upconverting nanoparticles (UCNPs) can be divided into transition metals upconverting nanoparticles (UCNPs), lanthanide metals upconverting nanoparticles (UCNPs) and actinide metals upconverting nanoparticles (UCNPs). Among them, the trivalent lanthanide metal ions are the most commonly doped ions due to their multiple metastable energy states, and the lanthanide metal upconverting nanoparticles (UCNPs) is also the most widely used nanomaterial.
References
- Cen Y, Deng W J, Yang Y, et al. A Core-Shell-Shell Multifunctional Nanoplatform for Intracellular Tumor-Related mRNAs Imaging and Near-Infrared Light Triggered Photodynamic-Photothermal Synergistic Therapy.[J]. Analytical Chemistry, 2017:10321.
- Min Y, Li J, Liu F, et al. Recent Advance of Biological Molecular Imaging Based on Lanthanide-Doped Upconversion-Luminescent Nanomaterials[J]. Nanomaterials, 2014, 4(1):129-154.
