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Plasmon-enhanced upconversion photoluminescence: mechanism and application
摘要： The enhanced local electromagnetic field (EM) excited on the noble metallic nanostructure exhibits potential application in various areas, particularly in surface-enhanced spectroscopy (SES). Resonant coupling of SPs to luminous centers can strongly moderate the emission spectra properties, including the angular distribution, the intensity, the speed of radiative decay, and even the spectrum radiation polarization, or so-called plasmon-enhanced fluorescence (PEF). Due to the low efficiency of emission and small absorption section of rare earth ions, plasmon-enhanced upconversion photoluminescence(PUCPL) has attracted increasing attention recently. In this review, we focus on recent advanced reports on PUCPL. First, the mechanism of the conventional upconversion process and related reports will be introduced. We will then demonstrate that the introduction of plasmonic nanostructure, including nonperiodic and periodic metallic nanostructures, has a critical effect on upconversion nanoparticles(UCNPs). The recent advances in plasmon-enhanced fluorescence with metallic tip configuration are also noted. Finally, the recent applications of PUCPL are introduced. As a result, the combination of a rare-earth luminescent center with plasmonic nanostructure can largely expand the application of upconversion materials.
关键词： surface-enhanced spectroscopy,mechanism,plasmonic nanostructure,Plasmon-enhanced upconversion photoluminescence,application,rare earth ions
更新于2025-09-10 09:29:36
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Using optical tweezers to construct an upconversion luminescent resonance energy transfer analytical platform
摘要： We report a new upconversion nanoparticles (UCNPs) based luminescent resonance energy transfer (LRET) analytical platform by making use of optical tweezers technology. The LRET model is designed by simultaneously conjugating Yb3+ and Er3+ co-doped UCNPs (as the donors) and tetramethyl rhodamine (TAMRA) molecules (as the acceptors) on microspheres to fabricate complex microspheres. Upon a single complex microsphere entering the three-dimensional potential well formed with a tightly focused 980 nm Guassian-shaped laser beam, it is optically trapped and concurrently the upconversion emission is excited, whereby the donor signals are transferred to the acceptors. As a proof-of-concept investigation, microRNA-21 sequences are selected as the targets, by which the distance between the two perfectly matched luminophors is controlled to several nanometers via nucleic acid hybridization. Without the involvement of luminescence amplification strategies, the proposed single microsphere based LRET method shows highly competitive sensitivity with a limit of detection down to 114 fM and satisfactory specificity towards microRNAs detection. Moreover, its practical working ability is demonstrated by credibly quantifying the absolute contents of miRNA-21 sequences in three cancer cell lines and even tracing the targets in as few as 100 cancer cells. Thus, this favorable analytical methodology provides an alternative for bioassays and holds certain potential in biomedical applications.
关键词： microRNA detection,Upconversion nanoparticle (UCNPs),Luminescent resonance energy transfer (LRET),Optical tweezers
更新于2025-09-10 09:29:36
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Over 1000-fold enhancement of upconversion luminescence using water-dispersible metal-insulator-metal nanostructures
摘要： Rare-earth activated upconversion nanoparticles (UCNPs) are receiving renewed attention for use in bioimaging due to their exceptional photostability and low cytotoxicity. Often, these nanoparticles are attached to plasmonic nanostructures to enhance their photoluminescence (PL) emission. However, current wet-chemistry techniques suffer from large inhomogeneity and thus low enhancement is achieved. In this paper, we report lithographically fabricated metal-insulator-metal (MIM) nanostructures that show over 1000-fold enhancement of their PL. We demonstrate the potential for bioimaging applications by dispersing the MIMs into water and imaging bladder cancer cells with them. To our knowledge, our results represent one and two orders of magnitude improvement, respectively, over the best lithographically fabricated structures and colloidal systems in the literature. The large enhancement will allow for bioimaging and therapeutics using lower particle densities or lower excitation power densities, thus increasing the sensitivity and efficacy of such procedures while decreasing potential side effects.
关键词： upconversion nanoparticles,plasmonic enhancement,bioimaging,photoluminescence,metal-insulator-metal nanostructures
更新于2025-09-10 09:29:36
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Solving the oxygen sensitivity of sensitized photon upconversion in life science applications
摘要： The conversion of low-energy light into high-energy light, also known as upconversion, can be exploited in life science applications such as bioimaging and phototherapy. Sensitized triplet–triplet annihilation upconversion (sTTA-UC) is one type of upconversion in which a photosensitizer is excited using a low-energy light and then transfers energy to an annihilator that emits at much higher energy. Changing the molecular components enables the fine-tuning of excitation and emission wavelengths. sTTA-UC is an appealing approach because it results in high upconversion efficiencies. However, its sensitivity to the presence of dioxygen in living cells and biological tissues is problematic. In this Review , the essential requirements of sTTA-UC for bio-nanodevices and life science applications are outlined before discussing the different ways to circumvent the dioxygen sensitivity of sTTA-UC.
关键词： phototherapy,dioxygen sensitivity,sensitized triplet–triplet annihilation upconversion,bioimaging,upconversion
更新于2025-09-09 09:28:46
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Morphological evolution of upconversion nanoparticles and their biomedical signal generation
摘要： Advancements in the fabrication of upconversion nanoparticles (UCNPs) for synthetic control can enable a broad range of applications in biomedical systems. Herein, we experimentally verified the role of the hydrothermal reaction (HR) time in the synthesis of NaYF4:20%Yb3+/3%Er3+ UCNPs on their morphological evolution and phase transformation at different temperatures. Characterizations of the as-prepared UCNPs were conducted using X-ray diffraction (XRD), electron microscopy and spectroscopy, and thermogravimetric and upconversion (UC) luminescence analysis. We demonstrated that determining the optimal HR time, also referred to here as the threshold time, can produce particles with good homogeneity, hexagonal phase, and UC luminescence efficiency. Subsequently, the polymer coated UCNPs maintained their original particle size distribution and luminescence properties, and showed improved dispersibility in a variety of solvents, cellular nontoxicity, in vitro bioimaging, and biocompatibility as compared to the bare UCNP. Besides this, polyacrylic acid conjugated UCNPs (UCNP@PAA) also revealed the strong anticancer effect by conjugating with doxorubicin (DOX) as compared to the free DOX. Based on these findings, we suggest that these particles will be useful in drug-delivery systems and as in vivo bioimaging agents synchronously.
关键词： phase transformation,morphological evolution,biomedical applications,hydrothermal reaction,upconversion nanoparticles
更新于2025-09-09 09:28:46
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Effect of Hf <sup>4+</sup> doping on structure and enhancement of upconversion luminescence in Yb:Tm:LiNbO <sub/>3</sub> crystals
摘要： A series of Yb:Tm:LiNbO3 crystals doped with x mol% Hf4+ ions (x = 2, 4, and 6) were grown by the Czochralski method. The dopant occupancy and defect structure of Hf:Yb:Tm:LiNbO3 crystals were investigated by x-ray diffraction and infrared transmission spectra. The influence of Hf4+ ions concentration on UV–VIS–NIR absorption spectra of Hf:Yb:Tm:LiNbO3 crystals was discussed. The upconversion luminescence of Hf:Yb:Tm:LiNbO3 crystals was obtained under 980 nm excitation. Strong emissions were observed at 475 nm in the blue wavelength range and 651 nm in the red wavelength range. Remarkably, enhancement of the red and blue upconversion luminescence was achieved by tridoping Hf4+ ions.
关键词： crystal structure,Hf:Yb:Tm:LiNbO3 crystals,upconversion luminescence
更新于2025-09-09 09:28:46
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Optical investigation of Er3+ and Er3+/Yb3+ doped zinc-tellurite glass for solid-state lighting and optical thermometry
摘要： Er3+ and Er3+/Yb3+ doped zinc tellurite (ZnO/TeO2) glasses were prepared using melt quenching technique. Spectroscopic properties of the glasses were studied by absorption spectroscopy, luminescence spectroscopy, and color chromaticity coordinates (CIE-1931) measurements. Upconverted-emission intensities and the CIE-1931 coordinates were strongly affected by the presence of Yb3+ ion, as well as the excitation power density of 975 nm laser light. Effect of temperature on green upconverted-emissions from two thermally coupled 2H11/2 and 4S3/2 levels of Er3+ ions were measured and fluorescence intensity ratio technique was applied to investigate the temperature sensing properties. High sensitivity and short response time properties make ZnO/TeO2 glasses a very good candidate for non-contact optical temperature sensor applications. The maximum sensitivity of the glasses doped with Er3+ and Er3+/Yb3+ were found to be 72×10-4 K-1 and 120×10-4 K-1 at 429 K, respectively which are much higher than previously reported temperature sensors based on Er3+ ion doped materials. Hence, Er3+/Yb3+ doped zinc-tellurite glass can be more suitable than that of doped with Er3+ ions only for color tunable solid-state lighting and non-contact optical thermometry applications.
关键词： Solid-state lighting,non-contact optical thermometry,fluorescence intensity ratio (FIR),zinc-tellurite glass,upconversion
更新于2025-09-09 09:28:46
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Future prospects of fluoride based upconversion nanoparticles for emerging applications in biomedical and energy harvesting
摘要： Rare earth doped/codoped phosphors have been extensively studied for different types of applications based on their intense luminescence features. For this, researchers have tried to choose the inorganic host matrices having both a low phonon cut-off frequency and a high refractive index. Many articles have been published on oxide based phosphor materials, but due to their high cut-off phonon frequency, use of these materials is restricted for optical based applications. This is why additional research has been carried out on fluoride based host materials because of their low phonon frequencies, low composition degradation, and high quantum efficiency. In this paper, the authors review the rare earth fluoride based host nano- and micromaterials for different applications and discuss possible mechanisms.
关键词： biomedical applications,fluoride based upconversion nanoparticles,energy harvesting,luminescence,rare earth doped phosphors
更新于2025-09-09 09:28:46
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Enhanced Red Emission in Er <sup>3+</sup> -Sensitized NaLuF <sub/>4</sub> Upconversion Crystals via Energy Trapping
摘要： Luminescence e?ciency of trivalent lanthanide-doped upconversion (UC) materials is signi?cantly limited by luminescence concentration quenching. In this work, red UC emission is dramatically enhanced in Er3+-sensitized NaLuF4 UC crystals through energy trapping under multiple excitation wavelengths. Cross-relaxation quenching and the energy migration to internal lattice defects are simultaneously suppressed by con?ning the excitation energy in the Er3+ activator after introducing the Tm3+ or Ho3+ energy trapping center. The enhanced red UC emission (Er3+: 660 nm) mainly comes from the e?ective excitation energy con?nement by Tm3+ and Ho3+ trapping centers through an easy energy transfer between Er3+ and Tm3+/Ho3+: 4I11/2 (Er3+) → 3H5 (Tm3+) → 4I13/2 (Er3+) and 4I11/2 (Er3+) → 5I6 (Ho3+) → 4I13/2 (Er3+). It is found that the con?ning e?ciency of excitation energy in Er3+-sensitized NaLuF4 crystals is higher than that in Yb3+/Er3+ cosensitized NaLuF4 crystals, and the luminescence e?ciency of Er3+-sensitized NaLuF4 crystals is much higher than that of Er3+-based host sensitization UC crystals (NaErF4). Moreover, Er3+-sensitized UC particles can be e?ciently excited by three di?erent wavelengths (808, 980, and 1532 nm), indicating huge advantages for applications in bioimaging, anticounterfeiting, and solar cells.
关键词： energy trapping,anticounterfeiting,NaLuF4,Er3+-sensitized,solar cells,bioimaging,upconversion,luminescence
更新于2025-09-09 09:28:46
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Simultaneous detection of 2, 4-dichlorophenoxyacetic acid and fenitrothion through lanthanide doped β-NaYF4 upconversion nanoparticles with different emitting light colors
摘要： A real-time, on-site rapid and sensitive detection method of low-molecular chemical pollutants was developed by an immunochromatographic strip based on the competitive reaction between the pesticide antigens and polyclonal antibody labeled with upconversion nanoparticles (UCNPs) bio-probes. Two polyclonal antibodies of 2, 4-D and fenitrothion were labeled by β-NaYF4:Yb, Er (green phosphors) and β-NaY(Gd)F4:Yb, Er (red phosphors) UCNPs respectively and dropped to the conjugation pads on the immunochromatographic strip. The competitors of fenitrothion-OVA and 2, 4-D-OVA were immobilized onto a nitrocellulose membrane to form two test lines T1 and T2, respectively. Meanwhile, the goat anti-rabbit IgG was built onto a nitrocellulose membrane to form control lines (C). The detection limits of 2, 4-D and fenitrothion are 5 ng/mL and 12 ng/mL respectively by using the UCNPs-based immunochromatographic strip. The demonstrated results indicated that two di?erent emitting colors UCNPs have great superiority as luminescent bio-probes for simultaneous detection of low-molecular pesticide residues.
关键词： Multi-component detection,2,4-D,Fenitrothion,Immunochromatography,Upconversion nanoparticles
更新于2025-09-09 09:28:46