• Applied Chemistry for Engineering
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• v.32 no.2
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• pp.125-131
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• 2021

Semiconductor-based photocatalysts can only be activated with ultraviolet or visible light due to their intrinsic bandgap, and they cannot use the energy in the near-infrared region, which accounts for about 50% of solar energy. Therefore, in order to improve the performance of the semiconductor photocatalyst, it is necessary to utilize more solar energy in a broad band ranging from ultraviolet to near-infrared. Combining upconversion nanoparticles with semiconductor photocatalysts for near-infrared absorption have thus been reported. Upconversion nanoparticles can sequentially absorb multiple near-infrared photons and convert them into ultraviolet or visible to activate photocatalysts. In addition, by coupling the semiconductor photocatalyst and the upconversion nanoparticles with the plasmonic metal nanoparticles, the photocatalytic activity can be further improved. This review summarizes the recent studies on improving the photocatalytic performance with near-infrared absorption by using upconversion nanoparticles.

• Ceramist
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• v.21 no.3
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• pp.270-282
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• 2018

The increasing importance of biomedical imaging technology has led to the development of a variety of luminescent materials, including molecular fluorophores, fluorescent proteins, and quantum dots. Owing to their inherent disadvantages, such as insufficient chemical stability and limited biocompatability, their utilization has been limited with imaging only under highly optimized and controlled conditions. Recently, a new class of luminescent nanoparticles, upconversion nanoparticles (UCNPs), have been emerging as a practically useful nanoprobe for various bioimaging applications. The detailed synthesis, functionalization, properties and in-vitro / in-vivo applications of the UCNPs are introduced and discussed in this Review.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.420.2-420.2
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• 2016

Various fields have been paid attention to upconversion nanoparticles (UCNPs) because of its unique optical properties. Moreover, to use the UC luminescent techniques through cell images for identified apoptosis/necrosis of cancer cells have been performed. They have been studied for a versatile biomedical application such as a biosensing tool, or delivery of active forms of medicines inside living cells. UCNPs have distinctive characteristics such as photoluminescence, special emission, low background fluorescence signal and good colloidal stability, which have many advantages compared with the organic dyes and quantum dots. UCNPs have not only a great potential for imaging (UC luminescence) but also therapies (photo-thermal therapy, PTT and photo-dynamic therapy, PDT) in cancer diagnostics. Therefore, we report the enhancement of upconversion red emission in NaYF4:Yb3+,Er3+ nanoparticles, synthesized via solid-state method with the thermal decomposition of trifluoroacetate as precursors and organic solvent at a high boiling point. The UCNPs have an emission in the field of near infrared wavelength, cubic shape and nano-size in length. In this study, we will further investigate it for cancer therapy with NIR optical detection onto the solid substrate.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.34 no.5
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• pp.187-193
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• 2024

Lanthanide-doped upconversion nanoparticles (UCNPs) are capable of converting low energy near-infrared photons into relatively high energy visible and ultraviolet photon. Their unique optical properties have a broad range of applications such as volumetric display, security labelling and deep-tissue imaging. Herein, the optically active hexagonal phased NaYF₄:Nd³⁺, Yb³⁺@NaYF₄:Yb³⁺, Tm³⁺ core-shell nanoparticles were synthesized via facile co-precipitation method which can show upconversion luminescence upon 745 nm laser excitation. This is accomplished by taking advantages of the large absorption cross-section of Nd³⁺ ions between 720 to 760 nm plus efficient spatial energy transfer and migration which starts from Nd³⁺ ions to Yb³⁺ ions and Tm³⁺ ions. Also, the formation of inert NaYF₄ shell significantly enhance the upconversion efficiency. The core-shell-shell UCNPs were characterized with X-ray diffraction (XRD) patterns, scanning electron microscope (SEM), transmission electron microscope (TEM), absorbance, and photoluminescence spectra.

• Medical Lasers
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• v.10 no.1
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• pp.7-14
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• 2021

In cancer therapy, it is often desirable to use precision medicine that involves treatments of high specificity. One such treatment is the use of photo-triggered theranostic nanoparticles. These nanoparticles make it possible to visualize and treat tumors specifically in a controlled manner with a single injection. Several novel and powerful photo-triggered theranostic nanoparticles have been developed. These range from small organic dyes, semiconducting and biopolymers, to inorganic nanomaterials such as iron-oxide or gold nanoparticles, carbon nanotubes, and upconversion nanoparticles. Using photo-triggered theranostic nanoparticles and localized irradiation, complete tumor ablation can be achieved without causing significant toxicity to normal tissue. Given the great advances and promising future of theranostic nanoparticles, this review highlights the progress that has been made in the past couple of years, the current challenges faced and offers a future perspective.

• Applied Chemistry for Engineering
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• v.29 no.2
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• pp.138-146
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• 2018

Photodynamic therapy (PDT) is a great potential approach for the localized tumor removal with fewer metastatic potentials and side effects in treating the disease. In the treatment process, a photosensitizer (PS) that absorbs a light energy to generate reactive oxygen is essential. In general, a visible light is used as a light source of PDT, so that side effects from the light source are inevitable. For this reason, upconversion nanoparticles (UCNPs) using near-infrared (NIR) as an excitation source are attracting attention in the field of disease diagnosis and treatment. UCNPs have the low cytotoxicity and phototoxicity, and also advantages such as deep tissue penetration and low background autofluorescence. For PDT, UCNPs should be combined with a PS which absorbs the light energy from UCNPs and transfers it to the surrounding oxygen to produce reactive oxygen. In addition, the therapeutic efficacy can be improved by modifying nanoparticle surfaces, adding anti-cancer drugs, or combining with photothermal therapy (PTT). In this review, we summarize the recent research to improve the efficiency of PDT using UCNPs.

• Journal of Powder Materials
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• v.25 no.2
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• pp.170-177
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• 2018

Colloidally synthesized luminescent nanocrystals (NCs) have attracted tremendous attention due to their unique nanoscale optical and electronic properties. The emission properties of these NCs can be precisely tuned by controlling their size, shape, and composition as well as by introducing appropriate dopant impurities. Nowadays, these NCs are actively utilized for various applications such as optoelectronic devices including light emitting diodes (LEDs), lasers, and solar cells, and bio-medical applications such as imaging agents and bio-sensors. In this review, we classify luminescent nanomaterials into quantum dots (QDs), upconversion nanoparticles (UCNPs), and perovskite NCs and present their intrinsic emission mechanism. Furthermore, the recently emerging issues of efficiency, toxicity, and durability in these materials are discussed for better understanding of industry demands. As well, the future outlook will be offered for researchers to guide the direction of future research.