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1.
Intense green‐emitting Li(Gd,Y)F4:Yb,Er/LiGdF4 core/shell (C/S) upconversion nanophosphors (UCNPs) with a tetragonal bipyramidal morphology are synthesized. The morphology and UC luminescence of the Li(Gd,Y)F4:Yb,Er UCNPs are significantly affected by the Li precursors, and bright UC green‐emitting Li(Gd,Y)F4:Yb,Er UCNPs with a tetragonal bipyramidal shape, i.e., UC tetragonal bipyramids (UCTBs), are synthesized using LiOH·H2O as a Li precursor. A LiGdF4 shell is grown on the Li(Gd,Y)F4:Yb,Er UCTBs, and the C/S UCNPs exhibit 4.7 times higher luminescence intensity than core UCTBs. The C/S UCNPs show a high absolute UC quantum yield of 4.6% under excitation with 980 nm near infrared (NIR) light, and the UC luminescence from the C/S UCNPs is stable under continuous irradiation with the 980 nm NIR laser for 1 h. The hydrophobic surfaces of the as‐synthesized C/S UCNPs are modified to hydrophilic surfaces by using poly(acrylic acid) (PAA) for bioimaging applications. They are applied to human cervical adenocarcinoma (HeLa) cell imaging and SK‐MEL‐2 melanoma cell imaging and in vivo imaging, including subcutaneous and intramuscular imaging, and UC luminescence images with high signal‐to‐noise ratio are obtained. Furthermore, sentinel‐lymph‐node imaging is successfully conducted with the PAA‐capped Li(Gd,Y)F4:Yb,Er/LiGdF4 C/S UCNPs under illumination with NIR light.  相似文献   

2.
A series of Gd3+ doping hollow upconversion nanoparticles NaYF4:Yb,Gd,Tm (h‐UNCP) are prepared successfully. The hollow NaYF4:Yb,Gd,Tm possess excellent upconversion luminescence (UCL) and large longitudinal relativity (r1 = 128.3 mm ?1 s?1), which can be potentially used for UCL/magnetic resonance imaging (MRI) dual mode imaging. On the basis of the optimal h‐UCNP, doxorubicin hydrochloride (DOX) and methotrexate (MTX) are used as drug models to prepare a dual drug carrier. After the encapsulation of DOX on the h‐UCNP, chitosan (CS) is further wrapped and then used to load MTX to obtain a dual drug carrier h‐UCNPs/DOX/CS/MTX. The pH responsive release of DOX and MTX is discussed. The MTX release climbs from 33% to 100% by regulating the pH from 5.8 to 7.4. The DOX release is different at different pH conditions. The synergistic effect of DOX and MTX on the cancer cells is confirmed by cell viability. The h‐UCNPs/DOX/CS/MTX are tracked by cells UCL imaging and vivo MRI imaging. The excellent performance of UCL imaging and positive MRI images demonstrates that h‐UCNPs/DOX/CS/MTX can be used for UCL/MRI dual mode imaging. All the results show the potential application of h‐UCNPs/DOX/CS/MTX in pH responsive release and UCL/MRI dual imaging.  相似文献   

3.
There is a great challenge to overcome the limitation of tissue penetration depth, while maximizing the benefit of light‐triggered biochemical cascades in a well‐defined mode simultaneously. Here, a new method of near‐infrared (NIR) light‐triggered release of nitric oxide (NO) by developing upconversion nanoparticles (UCNPs)‐based conjugate chemistry is reported. As the key nanotransducer in the design, core–shell‐structured UCNPs are encapsulated with a layer of SiO2 and then covalently linked with a potent NO‐releasing donor (S‐nitroso‐N‐acetyl‐dl ‐penicillamine, SNAP). It is featured with highly localized breakage of chemical bonds of SNAP molecules by NIR–UV upconversion, enabling simultaneous NO release in a light dosage‐dependent manner. The biological effects of NO releasing are demonstrated by cellular imaging and inhibition of platelet aggregation from blood samples. This work provides a flexible and robust platform to generate cell‐signaling gas molecules trigged by NIR laser with deep tissue penetration.  相似文献   

4.
《Current Applied Physics》2020,20(10):1150-1155
In the present work, lysine modified NaY0.78Er0.02Yb0.2F4 upconversion nanoparticles (UCNPs, positively charged) and lysine modified ZnSe:Mn2+ quantum dots (QDs, positively charged) are attached onto the surface of citrate reduced gold nanoparticles (AuNPs, negatively charged). The gold nanoparticles not only entangle the QDs and the UCNPs, through electrostatic interaction, but also tune the optical properties of UCNPs through the effect of surface plasmon resonance. The hybrid nanostructure gives green emission both through photoluminescence (under UV excitation) and through photon upconversion (under IR light excitation) process. The colour tuning is observed through variation in the size of QDs and through plasmonic effect of gold nanoparticles. In both the cases, the colour of emission gradually changes from green to red. The colour tunability and bi-modal photon conversion property of this material could be useful for its application in the field of bio-imaging and solar energy harvesting.  相似文献   

5.
The efficiency of upconversion fluorescence for Er3+ and Yb3+ codoped into NaYF4 powder crystals is investigated. The dependence of Er3+ green (540 nm) and red (660 nm) upconversion fluorescence intensities on laser excitation intensity and the ratio of the green and red fluorescence intensities respectively under 355‐nm and 936‐nm excitations have been measured and analyzed in terms of radiative and nonradiative relaxation mechanisms. It is shown that the intensity of both the green and red upconversion fluorescence bands is affected at high pumping intensities by a low‐lying state acting as a bottleneck, with the red fluorescence less affected than the green. In addition to two‐photon, two‐step excitation and energy transfer processes, nonlinear optical coupling mechanisms of avalanche processes appear responsible for reducing the bottleneck saturation of the red upconversion fluorescence.  相似文献   

6.
In the present report, bare CdO and CdO/MnO2 core/shell nanostructures of various cores and different shell sizes were synthesized using co‐precipitation method. The phase, size, shape and structural details of the bare CdO and CdO/MnO2 nanostructures were investigated by X‐ray diffraction, transmission electron microscopy (TEM), and Raman spectroscopy measurements. TEM micrographs confirm the formation of core/shell nanostructures. The presence of CdO (core) and MnO2 (shell) crystal phases was determined by analyzing the Raman data of bare CdO and CdO/MnO2 core/shell nanostructures. The Raman spectra of bare CdO nanostructures contain one broad intense convoluted envelop of three bands in the spectral range of 200–500 cm−1 and a weaker band located at ~940 cm−1. The intensity of these two Raman bands is decreased with the increase of shell size and disappeared completely for the shell size 5.3 ± 1 nm. Further, two new Raman bands appeared at ~451 and ~665 cm−1 for the shell size 1.3 ± 0.1 nm. These two Raman bands are assigned to the deformation of Mn–O–Mn and Mn–O stretching modes of MnO2. The intensity of these two Raman bands is enhanced with the increase of shell size and attains a maximum value for the shell size 5.3 ± 1 nm. The disappearance of characteristics Raman bands of CdO phase and the appearance of characteristics Raman bands corresponding to MnO2 phase for nanostructures of shell size 5.3 ± 1 nm authenticate the presence of CdO as core and MnO2 as shell in the core/shell nanostructures. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

7.
Fluorescently labeled nanoparticles are widely used to investigate nanoparticle cell interactions by fluorescence microscopy. Owing to limited lateral and axial resolution, nanostructures (<100 nm) cannot be resolved by conventional light micro­scopy techniques. Especially after uptake into cells, a common fate of the fluorescence label and the particle core cannot be taken for granted. In this study, a correlative approach is presented to image fluorescently labeled gold nanoparticles inside whole cells by correlative light and electron microscopy (CLEM). This approach allows for detection of the fluorescently labeled particle shell as well as for the gold core in one sample. In this setup, A549 cells are exposed to 8 nm Atto 647N‐labeled gold nanoparticles (3.3 × 109 particles mL?1, 0.02 μg Au mL?1) for 5 h and are subsequently imaged by confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM). Eight fluorescence signals located at different intracellular positions are further analyzed by TEM. Five of the eight fluorescence spots are correlated with isolated or agglomerated gold nanoparticles. Three fluorescence signals could not be related to the presence of gold, indicating a loss of the particle shell.  相似文献   

8.
In this paper, we report a simple and sensitive fluorescent biosensor for the quantitative analysis of silver ions (Ag+) by using NaYF4:Yb3+, Tm3+ upconversion nanoparticles (UCNPs). Ag+ could oxidize o-phenylenediamine (OPD) to the oxidized OPD (oxOPD) directly. The fluorescence of UCNPs can be significantly quenched by oxOPD through inner filter effects (IFE). Under the optimized conditions, the Ag+ concentration is proportional to the changes of the fluorescence intensity of UCNPs. The proposed method shows high selectivity and Ag+ could be quantitatively detected in the range of 0 to 0.5 mM with a low detection limit of 33 nM for Ag+. The selectivity and sensitivity of the detection can also be satisfactory. More importantly, this method has potential in practical application to detect Ag+ in real samples without interference.  相似文献   

9.
3D vertically aligned carbon nanotubes (CNTs)/NiCo2O4 core/shell structures are successfully synthesized as binder‐free anode materials for Li‐ion batteries (LIBs) via a facile electrochemical deposition method followed by subsequent annealing in air. The vertically aligned CNTs/NiCo2O4 core/shell structures are used as binder‐free anode materials for LIBs and exhibit high and stable reversible capacity (1147.6 mAhg?1 at 100 mAg?1), excellent rate capability (712.9 mAh g?1 at 1000 mAg?1), and good cycle stability (no capacity fading over 200 cycles). The improved performance of these LIBs is attributed to the unique 3D vertically aligned CNTs/NiCo2O4 core/shell structures, which support high electron conductivity, fast ion/electron transport in the electrode and at the electrolyte/electrode interface, and accommodate the volume change during cycling. Furthermore, the synthetic strategy presented can be easily extended to fabricate other metal oxides with a controlled core/shell structure, which may be a promising electrode material for high‐performance LIBs.  相似文献   

10.
As one promising anode material with high theoretical capacity, metallic tin has attracted much research interest in the field of lithium‐ion batteries. Here, two types of tin/carbon (Sn@C) core–shell nanostructures with inner buffering voids are fabricated from SnO2 hollow nanospheres via a facile chemical vapor deposition (CVD) method. The crystallinity and surface topography of SnO2 hollow nanospheres are found to affect the morphology of resultant Sn@C materials. Sn@C yolk–shell nanospheres and core–sheath nanowires are obtained from the as‐prepared SnO2 and high‐temperature annealed SnO2 nanospheres, respectively. The unique Sn@C nanostructures can mitigate the agglomeration/pulverization of Sn nanoparticles and electrical disconnection from the current collector caused by the large volume change during the lithium alloying/dealloying process. Both Sn@C yolk–shell and core–sheath nanostructures show stable cycling performance up to 500 cycles with specific capacities of ca. 430 and 520 mA h g?1, respectively.  相似文献   

11.
A new upconversion nanocrystal phase Yb2Mo4O15:Er is developed by using a facile aqueous‐precipitation procedure combined with thermal annealing. Nanocrystals of Yb2Mo4O15 are exclusively synthesized, with particle sizes ranging from 1 to 20 nm. The optical properties are characterized and a high upconversion quantum yield is determined to be ≈1.3% at room temperature, under excitation of ≈500 mW cm?2 IR (975 nm). To the best of our knowledge, this is the first work concerning the synthesis of nanocrystalline Yb2Mo4O15 and the characterization of its upconversion properties, which possesses the potential to be utilized in bio‐probing and thin‐film optoelectronic device applications.  相似文献   

12.
LD抽运Nd:YVO4晶体中的上转换及其影响   总被引:9,自引:0,他引:9       下载免费PDF全文
对激光二极管抽运下Nd:YVO4晶体中的上转换发光做了测量与分析,发现对应4G7/2能级向下跃迁的上转换发光的主导机制为能量传递上转换.接着,对上转换对LD抽运Nd:YVO4激光器运转的影响进行了理论分析,并特别讨论了上转换对热效应的影响. 关键词: 上转换 固体激光器 热效应  相似文献   

13.
To investigate the upconversion emission,this paper synthesizes Tm3+ and Yb3+ codoped Y2O3 nanoparticles,and then coats them with TiO2 shells for different coating times.The spectral results of TiO2 coated nanoparticles indicate that upconversion emission intensities have respectively been enhanced 3.2,5.4,and 2.2 times for coating times of 30,60 and 90 min at an excitation power density of 3.21×102 W.cm 2,in comparison with the emission intensity of non-coated nanoparticles.Therefore it can be concluded that the intense upconversion emission of Y2O3:Tm3+,Yb3+ nanoparticles can be achieved by coating the particle surfaces with a shell of specific thickness.  相似文献   

14.
Gao  Chao  Song  Zhiqian  Li  Yingxue  Han  Yingdong  Wei  Tian 《Journal of fluorescence》2022,32(5):1679-1684

It is widely recognized that a proper way of adjusting fluorescence color is meaningful for pushing forward upconversion materials to be utilized in anti-counterfeiting, display and solid-state lightning applications. Traditional routes that apply different host materials and/or doping categories to adjust fluorescence color have shown large color region tunability yet have to rely on complex synthesis process accompanied with time and raw material consumption. In this work, in order to get a wide luminous color gamut without depending on reciprocating synthesis, we desinged and provided a high-sensitizer-concentration upconversion crystals, hexagonal NaLuF4:Yb3+/Er3+ (50/2 mol%), whose red-to-green emission intensity ratio can be conveniently tuned from 2.69 to 4.96 by simply modulating excitation power densities. The promoted three-photon-population progress of red emission achieved by using an intensive excitation laser is considered to be responsible for the facile upconversion modulation. The results may provide new ideas for emission color control that based on external parameters in identical host and the greatly amplified excitation power-sensitivity of NaLuF4:Yb3+/Er3+ (50/2 mol%) is highly potential for fluorescence anti-fake and colorful display applications.

  相似文献   

15.
Abstract

The internal kinetics of NO2 as well as the kinetics of crossover between CH3F and NO3 were studied in mixtures of these polyatomics and rare gases.

Subsequent to excitation of the CH3F to v 3=1 by the P(20) line of a 9.6μ Q-switch CO2 laser, fluorescence of NO2 at 6.12μ from v 3=1 was monitored.

The equilibration rate of the stretching modes in NO2 was determined to be 46 ± 10 msec?1 torr?1 while the rate of stretches-bend equilibration was measured as 15 ± 3 msec?1 torr?1. The rate of crossover from excited CH3F to NO2 in high rare gas dilution was measured as 90 ± 20 msec?1 torr?1 and the reverse rate as 285 ± 60 msec?1 torr?1.

Comparison to other triatomic systems as well as other experiments with mixtures of polyatomics are made and implications of laser “photochemistry” of NO2 reactions are discussed.  相似文献   

16.
A distinct enhancement of upconversion luminescence from core to core/shell (C/S) structure under low flux near infrared (NIR) excitation at 976 nm has been achieved in lanthanide (Er3+, Yb3+)-doped NaYF4 core with undoped NaYF4 shell nanoparticles (NP). A green chemistry approach has been taken to synthesize monodisperse monophasic C/S NP with the core (~20 nm) and shell (~5 nm) crystallizing into cubic phase. Hydrophobic C/S NP have been further made hydrophilic by coating a transparent SHMP layer without affecting luminescence. C/S (NaYF4: Er, Yb/NaYF4) NP integrated dye-sensitized solar cell indicated 11.9% enhancement in overall conversion efficiency under AM 1.5 conditions, due to NIR–visible spectrum modification by fluorescent NPs. The results indicate great potential of such upconverting C/S nanophosphor in solar cell applications.  相似文献   

17.
Ultraviolet and visible upconversion properties of Er3+ in YAlO3 were investigated following 652.2 nm excitation of the multiples 4F9/2. The luminescence and excitation spectra were recorded. Ultraviolet (326-342 and 354-359 nm), violet (405-420 nm), blue (436-442 nm) and green (525-575 nm) upconversion and infrared downconversion luminescence were simultaneously observed. The intense green luminescence corresponds to the emissions from the thermal coupled 4S3/2 and 2H11/2 bands and 2G9/2 level. Energy transfer upconversion processes were proposed to explain the upconversion phenomena. The luminescence kinetics was discussed in detail by the analyses of fluorescence decay curves.  相似文献   

18.
Wang  Zirui  Song  Qiusheng  Zhu  Lin  Zhao  Chengyan  Ma  Haihong 《Journal of fluorescence》2022,32(2):771-782

In the present study, a novel composite nanogel based on fluorescence resonance energy transfer (FRET) and its application for photodynamic therapy is reported. First of all, nanoparticles of silica doped with Nile Red (NR) were prepared by Stöber method, then they were decorated by γ-methacryloxypropyltrimethoxysilane (MPS) to prepare MPS decorated NR@SiO2 nanoparticles, and finally they were copolymerized with N-isopropylacrylamide (NIPAm) and Pyropheophorbide-a (Ppa) by free radical copolymerization, and composite nanogel of NR@SiO2/PNIPAm-co-Ppa was fabricated. The microstructure of the as-prepared nanogel was characterized by Fourier transform infrared spectrum (FTIR), photoluminescence (PL), UV–Visible spectrophotometer (UV–Vis), dynamic light scattering (DLS) and transmission electron microscopy (TEM). PL spectrum indicated that, under irradiation of visible light source, energy can be transferred from NR to Ppa. UV–Vis spectrum demonstrated that aggregation of Ppa is prevented efficiently and Ppa exists as “monomer” state in the composite nanogel. Under irradiation of laser, singlet oxygen (1O2) can be produced efficiently by excited nanogel. The in vitro cytotoxicity test showed that HeLa cells can be killed by the composite nanogel.

  相似文献   

19.
Electrochemical splitting of water is an efficient way to produce clean energy for energy storage and conversion devices. Herein, 3D hierarchical NiCo2O4@NiO@Ni core/shell nanocone arrays (NAs) are reported on Ni foam for stable overall water splitting with high efficiency. The architecture and composition of the 3D catalysts are particularly tuned. The outstanding structural and component features of the as‐prepared 3D catalysts are characterized by the vertically grown NiCo2O4 nanocone/NiO nanosheet core/shell structure and Ni decorated 3D‐conductive networks, which largely prompt the catalytic performance. The hybrid catalyst with core/shell nanocone array structures exhibits superior bifuncational activities for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with an overpotential of 240 and 120 mV at a current density of 10 mA cm?2, respectively. The Tafel slope of the optimal 3D electrode is about 43 and 58 mV dec?1 in an alkaline electrolyte for OER and HER, respectively. An alkaline electrolyzer constructed by two symmetric NiCo2O4@NiO@Ni electrodes delivers splendid activity toward overall water splitting with a current of 10 mA cm?2 at only ≈1.60 V and almost no deactivation after 10 h. This work provides a promising strategy to design ternary core/shell electrodes as high performance Janus catalysts for overall water splitting.  相似文献   

20.
In the present work, gold nanocluster (GNC) induced by bovine serum albumin (BSA) was synthesized as a novel fluorescence probe to detect nitrite (NO2 ?) sensitively and selectively. The fluorescence of GNC was found to be quenched effectively by NO2 ?. Under the optimum conditions, it was found that the change of fluorescence intensity was proportional with the concentration of NO2 ? in the linear range of 0.1–50 μM (R?=?0.9990), with a detection limit (S/N?=?3) of 30 nM. The absorption spectroscopy, circular dichroism (CD), and X-ray photoelectron spectroscopy (XPS) studies were employed to discuss the quenching mechanism. In addition, the present approach was successfully applied in real water samples.  相似文献   

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