NaYF4 Upconversion Research Articles

Laser Transfer of Upconversion Nanoparticles

A method of the transfer of NaYF4:Yb3+Tm3+/NaYF4 upconversion core/shell nanoparticles with an average size of 30 nm via laser-induced forward transfer is proposed. The method provides a high spatial resolution by creating a “sandwich” structure on the donor substrate: for reliable fixation, nanoparticles are located between gold layers 50 and 20 nm thick. The transfer of upconversion nanoparticles is implemented by focusing nanosecond laser radiation into a 30-μm-diameter spot and at optimal pulse energies of 8.5–25 μJ. It has been shown that, despite large temperature, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta T > 1000{\\kern 1pt} $$\\end{document} K, and pressure, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta P > 150{\\kern 1pt} $$\\end{document} MPa, fluctuations upconversion nanoparticles fully retain their photoluminescent characteristics.

Optimization of the structure, morphology and luminescent properties of NaYF4 upconversion nanoparticles

We designed and constructed rare earth doped upconversion nanoparticles β-Na(Y0.78Yb0.18Er0.04)F4, sensitizing layer encapsulated β-Na(Y0.9Er0.1)F4@β-NaYbF4 and inert layer encapsulated β-Na(Y0.9Er0.1)F4@β-NaYbF4@β-NaYF4. Compared with the mononuclear material, the luminescence intensity of the particles encapsulated with double shells in the three main bands of blue, green and red emissions increased by 346, 22, and 54 times respectively. While improving the upconversion luminescence performance, the underlying reasons for this improvement were analyzed in detail. The effects of shell coating on the fluorescence lifetime, thermal stability and energy level transition are discussed. On this basis, the composite film material was constructed by combining the shell coating strategy and the plasma resonance interaction strategy, which further improved the upconversion efficiency. In addition, by combining performance optimized upconversion particles with information coding, we explored its potential as an anti-counterfeiting material.

Layer-by-layer assembly of NaYF4:Yb3+/Er3+ UCNPs@Cystein and UCNPs@Cys-Ab as hybrid bio-optical sensors for E. coli bacteria

An innovative bio-optical Layer-by-Layer sensor was developed for the detection of Escherichia coli (E. coli) bacteria. This groundbreaking sensor utilizes upconversion NaYF4:Yb3+/Er3+ nanoparticles (UCNPs) that have been modified with cysteine (UCNPs@Cys) and E. coli antibodies (UCNPs@Cys-Ab). The optical sensing system employed Layer-by-Layer (LbL) films of UCNPs, harnessing the emission of rare earth nanoparticles to detect the presence or absence of E. coli. The incorporation of Ab into the UCNPs@Cys nanoparticle was confirmed through SEM-EDS imaging, resulting in the formation of aggregated UCNPs@Cys-Ab microparticles with an approximate diameter of 2 μm. To further analyze the sensing capability, Principal Component Analysis (PCA) was employed to examine the differences between the UCNPs@Cys and UCNPs@Cys-Ab sensors. The results indicated that the incorporation of antibodies to the optical system significantly enhanced sensor sensitivity. This improvement was evident in the expanded detection range, which spanned from 2 × 103–106 CFU/mL, and the remarkably low limit of detection (LOD) value of 34 CFU/mL. These findings highlight the extensive potential of the UCNPs@Cys-Ab as a sensor. Furthermore, it was demonstrated the sensor's enhanced sensitivity and broad detection range make it an invaluable tool for ensuring the well-being of communities by enabling effective management of potential E. coli contamination.

Temoporfin-Conjugated Upconversion Nanoparticles for NIR-Induced Photodynamic Therapy: Studies with Pancreatic Adenocarcinoma Cells In Vitro and In Vivo.

Upconverting nanoparticles are interesting materials that have the potential for use in many applications ranging from solar energy harvesting to biosensing, light-triggered drug delivery, and photodynamic therapy (PDT). One of the main requirements for the particles is their surface modification, in our case using poly(methyl vinyl ether-alt-maleic acid) (PMVEMA) and temoporfin (THPC) photosensitizer to ensure the colloidal and chemical stability of the particles in aqueous media and the formation of singlet oxygen after NIR irradiation, respectively. Codoping of Fe2+, Yb3+, and Er3+ ions in the NaYF4 host induced upconversion emission of particles in the red region, which is dominant for achieving direct excitation of THPC. Novel monodisperse PMVEMA-coated upconversion NaYF4:Yb3+,Er3+,Fe2+ nanoparticles (UCNPs) with chemically bonded THPC were found to efficiently transfer energy and generate singlet oxygen. The cytotoxicity of the UCNPs was determined in the human pancreatic adenocarcinoma cell lines Capan-2, PANC-01, and PA-TU-8902. In vitro data demonstrated enhanced uptake of UCNP@PMVEMA-THPC particles by rat INS-1E insulinoma cells, followed by significant cell destruction after excitation with a 980 nm laser. Intratumoral administration of these nanoconjugates into a mouse model of human pancreatic adenocarcinoma caused extensive necrosis at the tumor site, followed by tumor suppression after NIR-induced PDT. In vitro and in vivo results thus suggest that this nanoconjugate is a promising candidate for NIR-induced PDT of cancer.

Understanding the effect of Mn2+ on Yb3+/Er3+ co-doped NaYF4 upconversion and obtaining the optimal combination of these tridoping

In this work, we investigated in detail the upconversion properties of several types of nanoparticles, including NaYF4:5%Yb3+/30%Mn2+, NaYF4:40%Mn2+/x%Yb3+ (x% = 1, 5, 10, 20, 30, and 40), NaYF4:2%Er3+/x%Mn2+ (x% = 20, 30, 40, 50, 60, and 70), NaYF4:40%Mn2+/x%Er3+ (x% = 1, 2, 5, and 10), and NaYF4:40%Mn2+/1%Yb3+/x%Er3+ (x% = 0, 2, 5, and 10). We studied their upconversion emission under 980 nm excitation in both pulsed and continuous wave modes at different synthesis temperatures. The nanoparticles were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), and photoluminescence (PL) spectroscopy. The doping of Yb3+ and Mn2+ ions resulted in the nanoparticles assuming cubic and hexagonal crystal structures. The emission intensity increased (106.4 (a.u.*103) to 334.4(a.u.*103)) with increasing synthesis temperature from 120 to 140 °C, while a sharp decrease was observed when the synthesis temperature was increased to 200 °C. The gradual decrease in peak intensity with increasing Mn2+ concentration from 20 to 70% was attributed to energy transfer from Mn2+ to Yb3+. In NaYF4:Mn2+/Yb3+/Er3+ UCNPs, increasing the Er3+ concentration from 0 to 10% led to the disappearance of the blue, orange, and green emission bands. The intense upconversion luminescence pattern with high spatial resolution indicates excellent potential for applications in displays, biological sensors, photodetectors, and solar energy converters.

Template-free hydrothermal preparation of IR-blue light upconverting NaYF4: Yb, Eu phosphors

Highly efficient IR-blue light up-converting NaYF4: Yb3+, Eu2+ phosphors have been prepared by a template-free hydrothermal method under mild and reductive experimental conditions. It has been demonstrated that for a fixed reaction time and temperature (150°C/4h), the α→β NaYF4 conversion can be accurately controlled by modifying the F/Y ratio. UC emission spectroscopy reveals that IR-blue light emission efficiency is greatly improved when β-NaYF4 phase predominates. Under the experimental conditions set in this work, reaching full α→β conversion just by increasing fluoride content entails the co-crystallization of the secondary phase YF3 1.5NH3, but far from causing a detrimental effect on the optical properties, it has been found that the samples where both β-NaYF4 and YF3 1.5NH3 phases coexist, exhibit outstanding optical properties.

Red emission upconversion of NaYF4: Yb3+/Er3+ nanoparticles: Rapid preparation via single-mode focused microwave method and their application in cell imaging

The red emission of upconversion nanoparticles (UCNPs) is located in an “optical window” range of the biological tissue, which has a promising prospect in biology application. In this work, novel red-emitting NaYF4:Yb3+/Er3+ UCNPs with CH3COO− modifications were synthesized by single-mode focused microwave method. The morphology, structure, and luminescence properties of as-prepared UCNPs were characterized. The results showed that single-mode focused microwave method was an effective approach to prepare hydrophilic and strongly red emission UCNPs within a drastically reduced reaction time (only 10 min) compared to the traditional methods. Importantly, we also demonstrated that the CH3COO− modified NaYF4:Yb3+/Er3+ UCNPs could be successfully applied for in vitro imaging of HeLa cells. This work not only provides a rapidly synthetic methodology for the preparation of red-emitting UCNPs but also offers an effective material for cancer cell imaging.

Intense green upconversion in core-shell structured NaYF4:Er,Yb@SiO2 microparticles for anti-counterfeiting printing

Rare-earth-doped NaYF4 nanoparticles are considered crucial upconversion luminescent materials with many applications, including anti-counterfeiting printing, biological imaging, and optical information storage. This work presents progress in obtaining hydrophilic pigments based on NaYF4:Er,Yb@SiO2 nanoparticles, and their utilization in water-based ink printing for anti-counterfeiting applications. Coating NaYF4:Yb/Er microparticles with SiO2 shells can provide several benefits for printing purposes, such as improved stability, dispersion, and ease of printing. The hydrophilic core-shell structured β-NaYF4:Er, Yb@SiO2 microparticles were successfully prepared using the hydrothermal synthesis and sol-gel Stober method. The obtained microparticles were characterized by Scanning Electron Microscopy, X-ray diffraction, and Energy-dispersive X-ray spectroscopy. Such characterizations confirm that the Er3+ and Yb3+ ions are incorporated in NaYF4 cores, the NaYF4:Er, Yb cores are in hundreds of nanometer sizes, and the NaYF4:Er, Yb microparticles are coated by a silica layer of 50 nm thick. Both NaYF4:Er, Yb and NaYF4:Er, Yb@SiO2 behave as up-conversion luminescent microparticles for both green and red emissions. The CIE chromaticity coordinates indicate that both the nanoparticles have their greenish color under excitation at 980 nm. Although decorating the NaYF4:Er, Yb nanoparticles with the SiO2 shell decreases luminescent intensity (by a factor of 2), this step is still necessary to achieve hydrophilic surfaces for preparing water-based printing inks. Using the synthesized NaYF4:Er, Yb@SiO2 as a pigment, a new water-based ink formula was created based on Polyamide as a polymer matrix. The obtained ink is printable on paper and on transparent and flexible Polyethylene substrate. The printed patterns with a height of 2 cm and a width of 2.5 cm were observed clearly under the irradiation of a 980 nm LED. Their durability in terms of sharpness and color was also assessed after six months.

The effect of Er3+ concentration on the kinetics of multiband upconversion in NaYF4:Yb/Er microcrystals.

In Yb-Er co-doped upconversion (UC) nanomaterials, upconversion luminescence (UCL) can be modulated to generate multiband UCL emissions by changing the concentration of activator Er3+. Nonetheless, the effect of the Er3+ concentrations on the kinetics of these emissions is still unknown. We here study the single β-NaYF4:Yb3+/Er3+ microcrystal (MC) doped with different Er3+ concentrations by nanosecond time-resolved spectroscopy. Interestingly, different Er3+ doping concentrations exhibit different UCL emission bands and UCL response rates. At low Er3+ doping concentrations (1mol%), multiband emission in β-NaYF4:Yb3+/Er3+ (20/1mol%) MCs could not be observed and the response rate of UCL was slow (5-10μs) in β-NaYF4:Yb3+/Er3+. Increasing the Er3+ doping concentration to 10mol% can shorten the distance between Yb3+ ions and Er3+ ions, which promotes the energy transfer between them. β-NaYF4:Yb3+/Er3+ (20/10mol%) can achieve obvious multiband UCL and a quick response rate (0.3µs). However, a further increase in the Er doping concentration (80mol%) makes MCs limited by the CR process and cannot achieve the four-photon UC process (4F5/2 → 2K13/2 and 2H9/2 → 2D5/2). Therefore, the result shows that changing the Er3+ doping concentration could control the energy flow between the different energy levels in Er3+, which could affect the response time and UCL emission of the Yb/Er doped rare earth materials. Our work can facilitate the development of fast-response optoelectronics, optical-sensing, and display industries.

Single up-conversion nanocrystal as a local temperature probe of electrically heated silver nanowire.

Luminescence thermometry is a powerful technique for monitoring temperature in a sensitive, remote (through light), and minimally invasive manner. Up to now, many macroscopic and microscopic luminescence temperature probes exploiting different temperature sensing schemes have been investigated, with the majority of the studies using aggregates of nanothermometers. This work presents isolated single up-converting NaYF4:Er3+/Yb3+ nanocrystals as functional temperature indicators operating in a standard confocal microscopy configuration. More specifically, the nanocrystals were used to monitor the temperature of a single silver nanowire, whose temperature was controlled electrically via the Joule process. We demonstrate that individual nanocrystals placed near the nanowire can precisely determine the temperature distribution in its surroundings. These results, which combine nanoscopic heat generation with temperature readout using isolated nanocrystals, represent an essential step for the application of isolated single nanoprobes for luminescence thermometry at the nanoscale.

Rapid determination of serum amyloid A using an upconversion luminescent lateral flow immunochromatographic strip.

The early diagnosis and real-time prognosis of cardiovascular diseases (CVDs) at the bedside are important. However, real-time detection of myocardial infarction involves the use of large-scale instrumentation and long test times. Herein, a simple, rapid and sensitive lateral flow immunochromatographic strip (LFIS) based on Yb/Er co-doped NaYF4 upconversion nanoparticles (UCNPs) was demonstrated for use in the detection of myocardial infarction. First, through heavy Yb/Er doping and an inert NaYF4 shell coating on the nanoparticles, the surface-related luminescence quenching effect of UCNPs was eliminated to enhance the upconversion luminescence. Second, through uniform coating of a SiO2 layer on the UCNPs, the biological affinity was improved to couple UCNPs and antibody proteins. Finally, through modification and activation with a specific antibody protein (serum amyloid A (SAA)), the UCNPs exhibited intense upconversion luminescence and high specificity when applied as a lateral flow immunochromatographic strip (LFIS). The developed UC-LFIS was highly sensitive (0.1 μg mL-1) and specific for detecting SAA in only 10 μL of serum. The UC-LFIS holds great potential for the early diagnosis and prognosis of CVDs.

Preparation of upconversion NaYF4:Yb/Tm@NaYF4:Yb-Cit-CD for doxorubicin detection

Doxorubicin hydrochloride (DOX), an anthraquinone-based antibiotic, is widely used in human tumors treatment. However, the residues of DOX in body would pose a threat to the health of heart and liver. Herein, a photochemical sensor NaYF4:Yb/Tm@NaYF4:Yb-Cit-CD (UCNPs) for detecting DOX has been developed in this paper. The fluorescence emission spectrum of UCNPs under 980 nm laser excitation has a wide range overlap with UV–vis absorption spectrum of DOX. Therefore, the fluorescence emission of UCNPs at 480 nm can be quenched by DOX. The UCNPs sensor has displayed a linear range of 0.05–20 μg/mL with a detection limit (LOD) of 0.005 μg/mL for DOX. Furthermore, the results of recovery for DOX in human serum samples is 98.68–104.20% and in accord with those obtained by HPLC and UV–vis.

NaYF4 upconversion crystals with red light emission by low Er3+ concentration doping

In the work, a range of Er3+-sensitized NaYF4 upconversion (UC) particles doped with Tm3+ and Ho3+ are successfully prepared by hydrothermal process. The UC crystals appear two green emission peaks at 529 and 541 nm and a remarkable red emission peak at 655 nm under 980 and 1532 nm irradiations. Here, Tm3+ and Ho3+ serve as trapping centers, which confine the excitation energy efficiently to promote the red UC emission and improve the red to green ratio. UC mechanisms in the Er3+/Tm3+ co-doped and Er3+/Ho3+ co-doped NaYF4 crystals are discussed at length based on the UC luminescence spectroscopy. Unlike the traditional sensitization with high Er3+ concentration doping to obtain red light, the red UC luminescence is acquired by low Er3+ concentration doping, which can effectively avoid concentration quenching caused by high Er3+ concentration doping. Furthermore, NaYF4:Er3+, Tm3+ crystals exhibit stronger red UC emission compared with NaYF4:Er3+, Ho3+ counterparts. Er3+-sensitized NaYF4 crystals doped with Tm3+ and Ho3+ ions generate pure red light more efficaciously under 1532 nm excitation than under 980 nm excitation. The phosphors emitting brilliant red UC emission have the potential applications in solid state lasers and biological imaging.

Natural and Synthetic Polymer Scaffolds Comprising Upconversion Nanoparticles as a Bioimaging Platform for Tissue Engineering.

Modern biocompatible materials of both natural and synthetic origin, in combination with advanced techniques for their processing and functionalization, provide the basis for tissue engineering constructs (TECs) for the effective replacement of specific body defects and guided tissue regeneration. Here we describe TECs fabricated using electrospinning and 3D printing techniques on a base of synthetic (polylactic-co-glycolic acids, PLGA) and natural (collagen, COL, and hyaluronic acid, HA) polymers impregnated with core/shell β-NaYF4:Yb3+,Er3+/NaYF4 upconversion nanoparticles (UCNPs) for in vitro control of the tissue/scaffold interaction. Polymeric structures impregnated with core/shell β-NaYF4:Yb3+,Er3+/NaYF4 nanoparticles were visualized with high optical contrast using laser irradiation at 976 nm. We found that the photoluminescence spectra of impregnated scaffolds differ from the spectrum of free UCNPs that could be used to control the scaffold microenvironment, polymer biodegradation, and cargo release. We proved the absence of UCNP-impregnated scaffold cytotoxicity and demonstrated their high efficiency for cell attachment, proliferation, and colonization. We also modified the COL-based scaffold fabrication technology to increase their tensile strength and structural stability within the living body. The proposed approach is a technological platform for “smart scaffold” development and fabrication based on bioresorbable polymer structures impregnated with UCNPs, providing the desired photoluminescent, biochemical, and mechanical properties for intravital visualization and monitoring of their behavior and tissue/scaffold interaction in real time.

Upconversion boosting pollutants degradation efficiency in wide-spectrum responsive photocatalysts

Recently, the composite photocatalysts coupled with upconversion materials have received widespread attention due to higher utilization efficiency of solar energy in a wide-spectrum range. Novel heterojunction photocatalysts of CoWO4@NaYF4:Yb3+,Er3+ were designed and developed herein. The structural characterization, morphology and elemental composition analysis demonstrated that heterojunctions between CoWO4 and NaYF4:Yb3+,Er3+ were indeed formed in the composite photocatalysts. Moreover, CoWO4@NaYF4:Yb3+,Er3+ heterojunction photocatalysts exhibited higher pollutants degradation efficiency. Especially, a great enhancement of +87% on the photocatalytic activity was achieved in the heterojunction photocatalyst of 60CoWO4–NaYF4:Yb3+,Er3+ compared with pure CoWO4. The dominant radicals generated from the heterojunction photocatalysts were confirmed as the photo-generated holes (h+) and hydroxyl radicals (⋅OH) through the radical species trapping experiments and fluorescence detection, which is fully in line with the expected band structure characteristics of CoWO4. Eventually, an underlying mechanism was proposed that the enhanced photocatalytic activity should be attributed to the wide-spectrum responsive features of CoWO4@NaYF4:Yb3+,Er3+ heterojunction photocatalysts. Within the heterostructures, CoWO4 photocatalyst can absorb both the UV–Vis light due to its narrow bandgap and the Near-Infrared energy through the upconversion NaYF4:Yb3+,Er3+, thereby utilizing solar energy more efficiently in a wide-spectrum range for photocatalytic reactions.

Dual‐Functional Nonmetallic Plasmonic Hybrids with Three‐Order Enhanced Upconversion Emission and Photothermal Bio‐Therapy

AbstractPlasmonic semiconductor nanoparticles (NPs) with wide‐range tailorable localized surface plasmon resonance (LSPR) hold exciting prospects on optical signal amplification. In this work, by precisely controlling oxygen vacancies around W atoms, plasmonic bismuth tungstate Bi2WO6 (BWO) nanosheets are constructed to enhance emission of Yb3+/Er3+ co‐doped NaYF4 upconversion nanoparticles (UCNPs). In the optimal conditions, the UCNPs/BWO‐2 hybrids exhibit over three‐order (1260‐fold) enhancement selectively on the 520 nm emission owing to the strong LSPR‐induced electrical field and photothermal effect. Moreover, it is found that the highly efficient emission of UCNPs/BWO‐2 allows it to act as a thermometer to monitor the real‐time local temperature with high absolute sensitivity of 5.8 × 10−3 K−1 in wide temperature range (up to 990 K). For proof‐of‐concept, the dual functions of plasmonic UCNPs/BWO‐2 hybrids on bioimaging and photothermal therapy for cancer cells are demonstrated that can be completely killed within 5 min under 980 nm irradiation. As far as it is known, this work reaches a new level on UCNPs emission enhancement by plasmonic semiconductor, exceeding most plasmonic metals.

Construction of NaYF4: Yb, Ho/B, N-GQDs nanocomposites for double anti-counterfeiting fluorescence ink

Fluorescent nanomaterials with multiple anti-counterfeiting play a vital role in economic and social fields in our daily lives. In this work, a hybridized composite of boron and nitrogen co-doped graphene quantum dots (B, N-GQDs) and lanthanide-doped up-conversion NaYF4 was prepare for a double anti-counterfeiting application. The composite was obtained by one-pot hydrothermal method and it was commixed with glycerol in a ratio of 4 : 1 to prepare a fluorescence ink, which exhibited independent blue and green fluorescence emissions under ultraviolet light and near-infrared laser excitation. Therefore, it had a considerable application in confidential communications, logo designing and file encryptions.

The influence of Ce3+ codoping on upconversion in nanocrystalline NaYF4:Yb3+,Tm3+

Usually, to obtain multicolor upconversion in lanthanides, materials with different codopants, different size, chemical composition or compositional architecture are required. However, designing a material whose emission color can be tuned in-situ by an external stimulus, such as temperature, excitation pulse duration or photoexcitation density, is of great interest for many applications, but still remains a challenge. The possible solution for this issue can be achieved by intentional codoping the luminescent materials with optically active ions which can disturb or compete with other energy transfer processes, and in consequence lead to changes in relative emission intensity, thus the dominant emission color. Here we synthesized and investigated colloidal luminescent Yb3+ and Tm3+ doped NaYF4 nanoparticles which were codoped with optically active Ce3+ ions, whose relative emission intensity ratios between 1D2→3F4 (at 450 nm), 1G4→3H6 (at 475 nm), 1G4→3F4 (at 650 nm), and 3H4→3H6 (at 800 nm) were significantly dependent from external stimulus – namely temperature and/or excitation pulse length. Our results shows two fold increase in 450/800, 470/800 and 650/800 luminescence intensity bands ratios (LIR) only after incorporation of Ce3+ ions to the material, and even three-fold increase in those LIR after changing the excitation conditions (i.e. pulse width). Moreover, temperature dependent luminescence properties revealed relative sensitivity of 4%/K for the 450/800 and 470/800 bands ratio and almost 5.5%/K for the 650/800 band ratio close to 0 °C. By switching to physiological range of temperatures, the thermal sensitivity decreased to around 2%/K for the 450/800 and 470/800 bands ratio and to over 2.5%/K for 650/800 bands ratio, which should be considered as significant values and suitable for temperature sensing in practical applications. It is worth noting that the thermal sensitivity values can be further enhanced by applying different excitation pulse width. The proposed materials allows to tune its emissions as well as thermal properties by changing the dopant concentration or more importantly also in situ, through excitation scheme modifications.

Novel Fluorescent Probe Based on Rare-Earth Doped Upconversion Nanomaterials and Its Applications in Early Cancer Detection.

In this paper, a novel rare-earth-doped upconverted nanomaterial NaYF4:Yb,Tm fluorescent probe is reported, which can detect cancer-related specific miRNAs in low abundance. The detection is based on an upconversion of nanomaterials NaYF4:Yb,Tm, with emissions at 345, 362, 450, 477, 646, and 802 nm, upon excitation at 980 nm. The optimal Yb3+:Tm3+ doping ratio is 40:1, in which the NaYF4:Yb,Tm nanomaterials have the strongest fluorescence. The NaYF4:Yb, Tm nanoparticles were coated with carboxylation or carboxylated protein, in order to improve their water solubility and biocompatibility. The two commonly expressed proteins, miRNA-155 and miRNA-150, were detected by the designed fluorescent probe. The results showed that the probes can distinguish miRNA-155 well from partial and complete base mismatch miRNA-155, and can effectively distinguish miRNA-155 and miRNA-150. The preliminary results indicate that these upconverted nanomaterials have good potential for protein detection in disease diagnosis, including early cancer detection.

Optical ammonia sensor based on Yb3+, Er3+, Tm3+ co-doped NaYF4 up-conversion material/phenol red composites

In this paper, optical ammonia sensor based on Yb3+, Er3+, Tm3+ co-doped NaYF4 up-conversion material/phenol red composites was proposed. Phenol red and Yb3+, Er3+, Tm3+ co-doped NaYF4 were mixed thoroughly and transferred into PE conical shell to form ammonia sensitive unit. The epoxy resin was coated onto two end sides of PE conical shell to fix ammonia sensitive composite. The absorption intensity of up-conversion luminescence located at 663 nm will be affect by the concentration of ammonia attribute to the reaction between ammonia and phenol red. The detected intensity near 663 nm decreases exponentially with the increasing ammonia concentration. The water absorption of epoxy resin benefit for the detection of ammonia. The signal wavelength will not be affected by the background visible light due to the 980 nm wavelength of excitation is far from the signal wavelength. The response time and recover time of the sensor also were measured and discussed.