Upconversion Fluorescence Intensity Research Articles

Fiber Optical Temperature Sensor Based on 980nm Excitation of CaWO4: Yb3+, Er3+ with Up-conversion Fluorescence Intensity Ratio

The Yb3+, Er3+ co-doped calcium tungstate materials were prepared. The temperature-sensitive fiber optic probes made from CaWO4:Yb3+, Er3+ were prepared by the high-temperature solid-phase sintering method. The XRD lattice structure of CaWO4: Yb3+, Er3+ was tested. The fluorescence spectra of the probe under 980nm excitation were tested, and the variable temperature profile of the probe was analyzed to derive its two-photon absorption process. The temperature characteristics of the up-conversion fluorescence intensity ratio (FIR) of the probe in the temperature range of 303-673K were investigated, and the results showed that this optical fiber probe can be used as a fiber optic temperature sensor with a linearity of 5.8% and a temperature measurement return difference of only 1.5%; it was found that the temperature characteristic curve of FIR of this fiber optic probe was reproducible. These properties show that CaWO4: Yb3+, Er3+ is feasible to be made into a fiber optic sensor.

Background-free and signal-amplified upconversion fluorescent biosensing platform for sensitive detection of CYFRA21-1

Accurate and ultrasensitive detection of cytokeratin 19 fragment (CYFRA21-1) is of vital importance for screening and diagnosis of potential lung cancer patient. In this paper, surface-modified upconversion nanomaterials (UCNPs) capable of aggregation by atom transfer radical polymerization (ATRP) were used as luminescent materials for the first time to achieve signal-stable, low-biological background, and sensitive detection of CYFRA21-1. Upconversion nanomaterials (UCNPs) feature extremely low biological background signals and narrow emission peaks, making them ideal sensor luminescent materials. The combination of UCNPs and ATRP not only improves sensitivity, but also reduces biological background interference for detecting CYFRA21-1. The target CYFRA21-1 was captured by specific binding of the antigen and the antibody. Subsequently, the end of the sandwich structure with the initiator reacts with monomers modified on UCNPs. Then, massive UCNPs are aggregated by ATRP that amplify the detection signal exponentially. Under optimal conditions, a linear calibration plot of the logarithm of CYFRA21-1 concentration versus the upconversion fluorescence intensity was obtained in the range of 1 pg/mL to 100 μg/mL with a detection limit of 38.7 fg/mL. The proposed upconversion fluorescent platform can distinguish the analogues of the target with excellent selectivity. Besides, the precision and accuracy of the developed upconversion fluorescent platform were verified by clinical methods. As an enhanced upconversion fluorescent platform of CYFRA21-1, it is expected to be useful in screening potential patients with NSCLC and provides a promising solution for the high-performance detection of other tumor markers.

Synthesis and surface modification of ultrasmall monodisperse NaYF4:Yb3+/Tm3+ upconversion nanoparticles

The emerging upconversion nanoparticles (UCNP) have gained substantial consideration in the field of bioanalytical as well as diagnostic applications. Therefore, great progress has been made in the synthesis and surface modification of luminescent UCNPs over the last two decades. In this paper, we have reported monodispersed and high luminescent upconversion nanoparticles NaYF4: 20%Yb3+, 2%Tm3+ have been synthesized using a solvothermal method, followed by a coating of the NaYF4 shell with a thin layer of SiO2 on the surface to afford the core-shell NaYF4:Yb3+, Tm3+@SiO2 nanoparticles (NP@SiO2). The prepared nanoparticles were of strong upconversion fluorescent emission intensity, hexagonal phase, and with an average size of about 8 ± 1 nm, which have been characterized by luminescence spectroscopy, powder X-ray diffraction (P-XRD), Dynamic light scattering (DLS), and Transmission electron microscopy (TEM). The results indicate that the NP@SiO2 can be used for the conjugation of fluorescent probes for various biomolecules and can find applications in cancer cell imaging and disease diagnosis.

Magnetic modification of lanthanide-based upconversion nanocrystals for fingerprint information recognition

The development of new magnetic fluorescent materials is of great significance for identification and criminal investigation. Since the photosensitive elements used in conventional cameras have exhibited the highest quantum efficiency in the range of 500–700 nm, lanthanide-based upconversion nanoparticles (UCNPs) with main emission peaks at 507–533 nm, 533–568 nm and 637–683 nm are suitable for constructing magnetic fluorescent materials. In this work, we demonstrate a type of magnetic upconversion nanoparticle (MUCNP) of NaGdF<sub>4</sub>:Yb,Er-Fe<sub>3</sub>O<sub>4</sub> by a ligand-linked method. After optimizing the reaction parameters, the composite particles possess remarkable magnetic properties and upconversion fluorescence intensity and achieve high contrast for latent fingerprint recognition on various substrates. The combination of upconversion luminescence and magnetism contributes to good fingerprint recognition sensitivity and universality.

A novel ADA-coated UCNPs@NB sensing platform combined with nucleic acid amplification for rapid detection of Escherichia coli

In this study, we reported a novel sensing platform based on fluorescence quenching composed of alendronic acid (ADA) coated upconversion nanoparticles (UCNPs) and Nile Blue (NB) combined with polymerase chain reaction (PCR) for rapid, sensitive, and specific detection of Escherichia coli (E. coli). As a fluorescence acceptor, NB has a broad absorption band and can quench upconversion fluorescence intensity at 544 nm and 658 nm based on IFE. PCR is a double-stranded DNA (dsDNA) amplification technique with high specificity. The NB-dsDNA complex can be formed by intercalation of NB between base pairs and groove of dsDNA, leading to upconversion fluorescence recovery. The ADA-coated UCNPs@NB sensing platform achieved to detect E. coli in 1.5 h, with a lower limit of detection (33 CFU mL−1). In addition, the sensitivity of the ADA@UCNPs-NB fluorescence sensor under different PCR cycle numbers was discussed. The results showed that the proposed sensor could effectively shorten the assay time (1.0 h) while maintaining excellent sensitivity. This study demonstrated a rapid and sensitive analytical method for detecting E. coli in chicken, providing a reference for constructing PCR fluorescence sensors.

Enhanced dual-wavelength up-conversion luminescence and temperature sensitivity of NaYF4:Yb3+, Er3+ phosphors by Bi3+ introducing

The up-conversion composite fluoride phosphor BixNayYzF3x + y+3z +3z+3m+3n: Er3+m, Yb3+n were synthesized using the optimized low-temperature combustion synthesis (LCS) method. The optimal formula was determined by step-by-step orthogonal experiments. The effects of the introduction of Bi3+ ions on phase formation and fluorescence intensity were systematically studied. The results indicate that introducing 10 mol% Bi3+ ions can substantially strengthen the dual-wavelength up-conversion fluorescence intensity of the sample. Then the temperature sensitivity of the sample is calculated, indicating that the sample has good temperature sensitivity and can be used as an effective material for temperature sensors. X-ray diffraction and scanning electron microscopy (SEM) were used to analyze the phase composition and morphology of the phosphor. The product exhibits characteristic emission of Er3+ ions under the excitation of 1550 nm ＆ 980 nm dual-wavelength, and its luminescence mechanism was studied. This work provides new ideas for studying photothermal dual response up-conversion fluoride phosphors under excitation at 1550 nm & 980 nm.

Novel upconversion fluorescence sensor for the detection and imaging of procyanidins in foods by NaYF4:Yb/Tm@NaYF4:Yb-Cit-CD

In this paper, a β-cyclodextrin (CD)-modified citric acid (Cit)-stabilized blue-emitting upconversion nanocomposite NaYF4:Yb/Tm@NaYF4:Yb-Cit-CD (abbreviated as Y/Yb/Tm@Y/Yb-Cit-CD) has been prepared. Under 980 nm laser excitation, the fluorophore Y/Yb/Tm@Y/Yb of the nanocomposite emits blue fluorescence, and the spectral peak is approximately 482 nm. The emission spectrum partly overlaps with the absorption spectrum of procyanidins, which will lead to the upconversion fluorescence intensity of Y/Yb/Tm@Y/Yb decreasing by the fluorescence resonance energy transfer between Y/Yb/Tm@Y/Yb and procyanidins. Thus, the Y/Yb/Tm@Y/Yb-Cit-CD nanocomposite can be used as an upconversion fluorescence probe to detect procyanidins. The quantitative analysis of procyanidins has displayed a linear range of 0.1–1000 μM, with a detection limit of 0.06718 μM (S/N = 3). Furthermore, this probe has shown potential for detection of procyanidins in biological samples and upconversion luminescence imaging analysis in vivo.

Optical fiber temperature sensor based on the upconversion fluorescence intensity ratio of NaYF4:Er3+ excited by a 1525-nm laser

Remote and accurate temperature measurements in severe environments are of great importance. A 1525-nm wavelength located in the C band of optical fiber communication is used as a pumping light source for NaYF4:Er3+ phosphor possessing high upconversion efficiency. The upconversion luminescence characteristics were demonstrated in the temperature range of 160-400 K. Based on the thermal coupling energy level theory, the temperature measurement principle of the fluorescence intensity ratio is analyzed. The energy gap between the 2H11/2 and 4S3/2 energy levels of the Er3+ ions is approximately 787cm-1, which is appropriate for a temperature sensor. The experimental results indicated that its maximum temperature sensitivity was 0.00335K-1. The proposed optical fiber temperature sensor indicates good hysteresis and repeatability and has potential applications in resisting electromagnetic interference and remote temperature sensing.

Optical Detection of Ammonia in Water Using Integrated Up-Conversion Fluorescence in a Fiberized Microsphere

A novel optical sensor for ammonia concentration in water is demonstrated using up-conversion (UC) fluorescence intensity ratio (FIR). The sensor element consists of (i) an Er3+-Yb3+ co-doped tellurite glass microsphere integrated inside a section of suspended tri-core hollow fiber (STCHF) and (ii) the pH indicator phenol red. When 980 nm pump is coupled into the microsphere, the Er3+ ions produce green and red UC emissions. Exposure to ammonia results in a strong increase in the 560 nm absorption of the phenol red, which acts as a filter for the green emission, while the red emission is unaffected. A simple linear relation between the FIR and the ammonia aqueous concentration has been established.

Preparation, crystallization kinetics, and optical temperature sensing properties of Er3+-Yb3+ co-doped fluorosilicate glass-ceramics containing ZnAl2O4 crystals

Er3+-Yb3+ co-doped glass-ceramics were fabricated by the conventional melt-quenching method and subsequent heat treatment. The precipitation of ZnAl2O4 microcrystals with spinel structure was confirmed by the XRD pattern and SEM photographs. Raman spectra show that the glass-ceramics have lower maximum phonon energy compared with the glass matrix. Under the excitation of 378 nm Xenon lamp and 980 nm laser, different degrees of enhancement in the visible, NIR, and up-conversion fluorescence intensity attributed to the transitions of Er3+ ions in glass-ceramics, can be observed by emission spectra. Finally, according to the fluorescence intensity ratio between the transition from the thermal coupling energy level 2H11/2 and 4S3/2 to the ground state 4I15/2, the optical temperature sensing properties of glass-ceramics were evaluated, and the maximum absolute sensitivity Sa-max of 0.006 K−1 can be obtained at 404 K. These results indicate that the Er3+-Yb3+ co-doped ZnAl2O4 glass-ceramics may be utilized as a potential high-sensitivity up-conversion optical temperature sensing material.

1550nm Infrared Laser Heating NaYF4:Er3+ Nanoparticle In Isolated Pig Liver and Up-conversion Fluorescence Intensity Ratio Temperature Measurement

Hyperthermia is an important means of cancer treatment which is called “tumor green therapy”. The clinical heat therapy heating sources include ultrasound, microwave, alternating magnetic field, infrared laser. However, it is still difficult to accurately measure the temperature of tumor hyperthermia and the dose of hyperthermia. Here, NaYF4:Er3+ nanoparticles were injected into a small part of isolated pig liver, and heated it with 1550nm infrared laser. At the same time, the laser excited the NaYF4:Er3+ nanoparticles to generate up-conversion green fluorescence. The fluorescence intensity ratio was used to measure the temperature of the heating part in real time.

Tricolor flag-shaped nanobelt array and derivant 3D structures display concurrent conductive anisotropy, up-conversion fluorescence and magnetism

Unique-structured [NaYF4:Yb3+,Tm3+/polymethylmethacrylate (PMMA)]//[polyaniline (PANI)/PMMA]//[CoFe2O4/PMMA] fluorescent-conductive-magnetic tricolor flag-shaped nanobelt and array (marked as FCM-TNA) are innovatively designed and constructed by using tri-axial parallel electrospinning. Partition of three independent functional zones is microscopically realized in the tricolor flag-shaped nanobelt to avoid harmful mutual influences among three functions via confining luminescent, conductive and magnetic substances into their own domains, and thus achieving superior fluorescent-conductive-magnetic trifunction. Tricolor flag-shaped nanobelt used as building unit ensures excellent fluorescence, anisotropic conduction and magnetism of FCM-TNA. FCM-TNA emits blue fluorescence upon 980-nm laser excitation. Conductance ratio of conductive direction to insulating direction in FCM-TNA reaches 2.54 × 108 when the mass percentage of PANI to PMMA is settled at 70%, achieving high conductive anisotropy. By adjusting the contents of NaYF4:Yb3+,Tm3+ NPs, PANI and CoFe2O4 NPs, FCM-TNA exhibits tunable up-conversion fluorescence intensity, conductive anisotropy and magnetism. The formative mechanisms of tricolor flag-shaped nanobelt and FCM-TNA are advanced, and construction technologies are also established. Furthermore, neoteric 3D tubes and 3D + 2D complete banner-typed structures with similar multi-functionalities are derived from the FCM-TNA by using different construction strategies. The new design philosophy and technique can provide support for the design and construction of other new multifunctional anisotropic conductive materials in the future.

Sensitive Ho3+,Yb3+ co-doped mixed sesquioxide single crystal fibers thermometry based on upconversion luminescence

Mixed sesquioxide crystals (R2O3, R = Lu, Y or Sc, where R is occupied by two different elements) have drawn an increasing attention due to their outstanding physical and chemical properties. In this work, we have grown Ho3+,Yb3+ co-doped mixed sesquioxide LuYO3 and LuScO3 single crystal fibers (SCFs) in centimeter-length by laser heated pedestal growth (LHPG) method for optical temperature sensing. Both mixed sesquioxide SCFs yield strong green emission (5F4,5S2→5I8) and weak red emission (5F5→5I8) under the excitation of 980 nm laser. Their upconversion (UC) levels are not thermally coupled levels (NTCL). Importantly, these mixed sesquioxide SCFs show a good temperature sensitivity in the temperature range of 298–748 K. Using UC fluorescence intensity ratio (FIR) method, the calculated maximum values of absolute sensitivity of Ho,Yb:LuYO3 and Ho,Yb:LuScO3 are 0.1603 (at 303 K) and 0.0886 K−1 (at 300 K), respectively. These features indicate that our grown mixed sesquioxides show a great potential for high-sensitivity temperature sensing applications. Furthermore, the presented mixed sesquioxide SCFs are excellent candidates for the high-integrated temperature sensor.

Upconversion Thermometry Using Yb3+/Er3+ Co-Doped KY3F10 Nanoparticles

We report high-sensitivity luminescence thermometry using Yb3+/Er3+ co-doped KY3F10 core and core–shell upconverting nanoparticles. The highest thermal sensitivities of 1.510 ± 0.015%·K–1 (300 K) and 1.245 ± 0.013%·K–1 (316 K) and temperature uncertainty of 0.11 K were achieved by tuning the excitation wavelength to 975 nm to be in-resonant with optical transitions of the Yb3+ ion. The high-resolution Yb3+ excitation spectra were recorded by observing the Er3+, 4S3/2, 4F9/2 → 4I15/2 upconversion fluorescence, with the highest fluorescence yield obtained at 10 254 cm–1 (975 nm) for both nanoparticles. This coincides with the ground-state absorption maximum at 297 K. However, at 10 K, the Yb3+ upconversion excitation spectra also exhibit excited-state absorption peaks. The Yb3+ absorption spectra for the core and core–shell nanoparticles are dominated by single-ion centers (of C4v symmetry). Resonant excitation of the core and core–shell nanoparticles is observed to yield a 5-fold enhancement in Er3+ upconversion fluorescence intensity in comparison to excitation at 980 nm, increasing the fluorescence intensity ratio and the thermal sensitivity of a KY3F10 nanothermometer operating at the physiological temperatures.

Laser Ablation in Liquid Synthesis and Optical Temperature Sensing of YGdO3:Er3+ Nanoparticles

YGdO3:Er3+ nanoparticles were successfully synthesized by pulsed laser ablation in liquid method. The structural and morphological properties of the product are investigated by X-Ray diffraction and transmission electron microscopy. The upconversion photoluminescence properties were investigated in detail. Obvious stark splitting phenomena were observed in the green and red emission bands. The decay behaviors of three emission bands were studied. Based on thermal coupled energy level related upconversion fluorescence intensity ratio, the temperature sensing properties of product were studied. Linear function has beenused to reveal the relationship between fluorescence intensity ratio and temperature. Using stark sublevels related emission bands, sensitivity of the temperature sensor was successfully enhanced. These results suggest the YGdO3:Er3+ nanoparticles prepared via pulsed laser ablation in liquid are promising luminescent materials for optical thermometry.

Improvement of luminescence properties of NaYF4 :Yb3+ /Er3+ upconversion materials by a cross-relaxation mechanism based on co-doped Ho3+ ion concentrations.

NaYF4 :Yb3+ /Er3+ /Ho3+ nanophosphors were successfully synthesized using a solvothermal method and with various concentrations of Ho3+ ions. The crystal structure, grain size, morphology, and luminescence properties were analyzed by X-ray diffraction, field-emission scanning electron microscopy, and photoluminescence measurements. All samples were crystallized as a cubic structure; it was confirmed that all samples exhibited strong green emission and weak red emission generated at a particular level of the activated ions. The strongest upconversion fluorescence intensity was observed in the Ho3+ and Er3+ ions co-doped NaYF4 materials with a Ho3+ ion concentration of 0.005 mol. Only the green fluorescence intensity at the 542 nm centre increased strongly due to the 4 S3/2 →4 I15/2 energy transfer. This increase in upconversion fluorescence intensity at a selected wavelength was described as a cross-relaxation mechanism due to the addition of Ho3+ ions.

A Fluorescent Sensor for Daunorubicin Determination Using 808 nm-excited Upconversion Nanoparticles

Daunorubicin is a common antineoplastic agent used for the treatment of lymphoma and acute leukemia. Here, we report an 808 nm-excited, citric acid coated, core–shell upconversion fluorescent sensor for daunorubicin (DAU) detection in aqueous solutions. The designed Nd3+ doped core–shell structure significantly raises the upconversion fluorescence intensity, while the presence of citric acid ligands helps to reduce the surface quenching effect exerted by water and improve the dispersibility. The upconversion fluorescence of nanoparticles is efficiently quenched in the presence of DAU via a fluorescence resonance energy transfer mechanism. The dynamic quenching constant was 1.58 × 104 M−1. The fluorescence intensity ratio showed a good linear response to DAU concentration in the range of 0.1 μM to 70 μM with a detection limit of 0.06 μM. The sensing method was simple, rapid, and low-cost and was further applied to determine the levels of DAU in urine with spike recoveries from 97.3% to 101.5%. The proposed fluorescent sensor holds great potential for in vivo imaging and detection of DAU.

Double Stopband Bilayer Photonic Crystal Based Upconversion Fluorescence PSA Sensor

Precise detection on tumor markers is significant for the early diagnosis on cancer. Upconversion fluorescence probes are ideal for tumor marker sensing, but still subject to bottleneck problems of low emission efficiency/strength. In this work, a novel bilayer of poly(methyl methacrylate) opal photonic crystal (PMMA OPC) with double photonic stop bands was fabricated to match the excitation field and emission field of the upconversion nanoparticles (UCNPs) at the same time, and greatly enhance their upconversion fluorescence intensity. Herein, NaYF4:Yb3+,Er3+ UCNPs and NaYF4:Yb3+,Er3+@NaYF4:Yb3+,Nd3+ UCNPs with a core-shell structure were employed as a core, which could be excited by 980 nm and 808 nm light, respectively. With the optimized geometry structure, the upconversion emission intensity was enhanced over 150 folds under the excitation of both 808 nm and 980 nm laser. Through the NaYF4/OPC biochip and florescence resonant energy transfer (FRET) sensing strategy, the lowest detection limit of 0.01 ng/mL with good linear relationship was obtained ranging from 0.1 ng/mL to 10 ng/mL. The power density of the pumping light was as low as 1.7 W/cm2. This enhanced upconversion tumor marker biochip sensor provides a promising and powerful tool for facile early diagnosis on cancer markers.

Precise Control of Copper-Localized Surface Plasmon Resonance in the Near Infrared Region for Enhancement of Up-Conversion Luminescence

The surface plasmon resonance of copper in the near infrared region provides a novel method for enhancement of up-conversion luminescence compared to using gold and silver, as the former grants significant cost savings. In this study, we made a flat Cu film covered TiO2 to enhance the up-conversion fluorescence intensity. The results show that the deposition of copper/TiO2 dioxide nanocomposite film prepared via spin-coating has no effect on the structure of NaGdF4:Er3+, Yb3+. The absorption wavelength of the copper film moved from the original visible wavelength (~600 nm) range to the infrared wavelength after covering TiO2, and most obviously, the copper film covered two layers of TiO2 by about 16 nm; the peak of the absorption appeared at 835 nm due to the enhanced excitation field. The behavior of the nanocomposite film with NaGdF4:Er3+ and Yb3+ under 980 nm excitation was investigated; it provides a novel way for studying mental-enhanced fluorescence. Besides, the peaks of the fluorescence spectrum show different emissions at 542 nm and 660 nm, respectively. The copper nanoparticles-covered TiO2 layer can obviously enhance the fluorescence intensity, and the maximum enhancement factors of emission of NaGdF4:Er3+ and Yb3+ nanoparticles are 3.1 and 1.9 on the nanocomposite film, respectively.

Studies on the influence of structure units on the state of ytterbium ions in TeO2-based glasses

Abstract