共查询到20条相似文献,搜索用时 187 毫秒
1.
Jie Chang Yanhui Ning Suli Wu Wenbin Niu Shufen Zhang 《Advanced functional materials》2013,23(47):5910-5915
TiO2/NaYF4:Yb3+,Er3+ nano‐heterostructures are prepared in situ on the TiO2 photoanode of dye‐sensitized solar cells (DSCs). Transmission electron microscopy (TEM) and high‐resolution (HR)‐TEM confirm the formation of TiO2/NaYF4:Yb3+,Er3+ nano‐heterostructures. The up‐converted fluorescence spectrum of the photoanode containing the nano‐heterostructure confirms electron injection from NaYF4:Yb3+,Er3+ to the condution band (CB) of TiO2. When using a photoanode containing the nano‐heterostructure in a DSC, the overall efficiency (η) of the device is 17% higher than that of a device without the up‐conversion nanoparticles (UCNPs) and 13% higher than that of a device containing mixed TiO2 and UCNPs. Nano‐heterostructures of TiO2/NaYF4:Yb3+,Tm3+ and TiO2/NaYF4:Yb3+,Ho3+ can also be prepared in situ on TiO2 photoanodes. The overall efficiency of the device containing TiO2/NaYF4:Yb3+,Ho3+ nano‐heterostructures is 15% higher than the control device without UCNPs. When nano‐heterostructures of TiO2/NaYF4:Yb3+,Tm3+ are used, the open‐circuit voltage (Voc) and the short‐circuit current density (Jsc) are all slightly decreased. The effect of the different UCNPs results from the different energy levels of Er3+, Tm3+, and Ho3+. These results demonstrate that utilizing the UCNPs with the apporpriate energy levels can lead to effective electron injection from the UCNPs to the CB of TiO2, effectively improving the photocurrent and overall efficiency of DSCs while using NIR light. 相似文献
2.
A New Single 808 nm NIR Light‐Induced Imaging‐Guided Multifunctional Cancer Therapy Platform
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Fei He Guixin Yang Piaoping Yang Yuxiu Yu Ruichan Lv Chunxia Li Yunlu Dai Shili Gai Jun Lin 《Advanced functional materials》2015,25(25):3966-3976
The NIR light‐induced imaging‐guided cancer therapy is a promising route in the targeting cancer therapy field. However, up to now, the existing single‐modality light‐induced imaging effects are not enough to meet the higher diagnosis requirement. Thus, the multifunctional cancer therapy platform with multimode light‐induced imaging effects is highly desirable. In this work, captopril stabilized‐Au nanoclusters Au25(Capt)18?(Au25) are assembled into the mesoporous silica shell coating outside of Nd3+‐sensitized upconversion nanoparticles (UCNPs) for the first time. The newly formed Au25 shell exhibits considerable photothermal effects, bringing about the photothermal imaging and photoacoustic imaging properties, which couple with the upconversion luminescence imaging. More importantly, the three light‐induced imaging effects can be simultaneously achieved by exciting with a single NIR light (808 nm), which is also the triggering factor for the photothermal and photodynamic cancer therapy. Besides, the nanoparticles can also present the magnetic resonance and computer tomography imaging effects due to the Gd3+ and Yb3+ ions in the UCNPs. Furthermore, due to the photodynamic and the photothermal effects, the nanoparticles possess efficient in vivo tumor growth inhibition under the single irradiation of 808 nm light. The multifunctional cancer therapy platform with multimode imaging effects realizes a true sense of light‐induced imaging‐guided cancer therapy. 相似文献
3.
Jingning Shan Mruthunjaya Uddi Nan Yao Yiguang Ju 《Advanced functional materials》2010,20(20):3530-3537
Size‐dependent Raman spectra of the hexagonal (β)‐phase Yb3+,Er3+ codoped NaYF4 nanophosphors and dynamic probing of the upconversion luminescence (UCL) are reported. Raman scattering results show the normal red shifts of Raman peaks but anomalous line narrowing with decreasing the particle sizes. The phonon confinement effects are believed to be dominated by the surface vibrational energies in affecting UCL. Dynamic decay data are then applied to quantitatively verify the surface effects and size‐dependent UCL. Dynamic probing is shown to be an efficient tool to both qualitatively and quantitatively characterize the upconversion nanophorphors (UCNPs) that have no “quantum efficiency.” The findings are relevant to the engineering of the nanostructures of the UCNPs for the applications of the bioimaging and photodynamic therapy. 相似文献
4.
Cypate‐Conjugated Porous Upconversion Nanocomposites for Programmed Delivery of Heat Shock Protein 70 Small Interfering RNA for Gene Silencing and Photothermal Ablation
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Lu Wang Chang Gao Keyin Liu Yuxin Liu Liyi Ma Lidong Liu Xiaoxia Du Jing Zhou 《Advanced functional materials》2016,26(20):3480-3489
Synergistic therapy is an accepted method of enhancing the efficacy of cancer therapies. In this study, cypate‐conjugated porous NaLuF4 doped with Yb3+, Er3+, and Gd3+ is synthesized and its potential for upconversion luminescence/magnetic resonance dual‐modality molecular imaging for guiding oncotherapy is tested. Loading cypate‐conjugated upconversion nanoparticles (UCNP‐cy) with small interfering RNA gene against heat shock protein 70 (UCNP‐cy‐siRNA) enhances the cell damage. UCNP‐cy‐siRNA exhibits remarkable antitumor efficacy in vivo as a result of the synergistic effects of gene silencing and photothermal therapy, with low drug dose and minimal side effects. This result thus provides an explicit strategy for developing next‐generation multifunctional nanoplatforms for multimodal imaging‐guided synergistic oncotherapy. 相似文献
5.
Fiorenzo Vetrone Rafik Naccache Venkataramanan Mahalingam Christopher G. Morgan John A. Capobianco 《Advanced functional materials》2009,19(18):2924-2929
Nanoparticles of NaGdF4 doped with trivalent erbium (Er3+) and ytterbium (Yb3+) are prepared by a modified thermal decomposition synthesis from trifluoroacetate precursors in 1‐octadecene and oleic acid. The nanoparticles emit visible upconverted luminescence on excitation with near‐infrared light. To minimize quenching of this luminescence by surface defects and surface‐associated ligands, the nanoparticles are coated with a shell of NaGdF4. The intensity of the upconversion luminescence is compared for nanoparticles that were coated with an undoped shell (inert shell) and similar particles coated with a Yb3+‐doped shell (active shell). Luminescence is also measured for nanoparticles lacking the shell (core only), and doped with Yb3+ at levels corresponding to the doped and undoped core/shell materials respectively. Upconversion luminescence was more intense for the core/shell materials than for the uncoated nanoparticles, and is greatest for the materials having the “active” doped shell. Increasing the Yb3+ concentration in the “core‐only” nanoparticles decreases the upconversion luminescence intensity. The processes responsible for the upconversion are presented and the potential advantages of “active‐core”/“active‐shell” nanoparticles are discussed. 相似文献
6.
Zhiyao Hou Chunxia Li Ping'an Ma Ziyong Cheng Xuejiao Li Xiao Zhang Yunlu Dai Dongmei Yang Hongzhou Lian Jun Lin 《Advanced functional materials》2012,22(13):2713-2722
Up‐conversion (UC) luminescent and porous NaYF4:Yb3+, Er3+@SiO2 nanocomposite fibers are prepared by electrospinning process. The biocompatibility test on L929 fibrolast cells reveals low cytotoxicity of the fibers. The obtained fibers can be used as anti‐cancer drug delivery host carriers for investigation of the drug storage/release properties. Doxorubicin hydrochloride (DOX), a typical anticancer drug, is introduced into NaYF4:Yb3+, Er3+@SiO2 nanocomposite fibers (denoted as DOX‐NaYF4:Yb3+, Er3+@SiO2). The release properties of the drug carrier system are examined and the in vitro cytotoxicity and cell uptake behavior of these NaYF4:Yb3+, Er3+@SiO2 for HeLa cells are evaluated. The release of DOX from NaYF4:Yb3+, Er3+@SiO2 exhibits sustained, pH‐sensitive release patterns and the DOX‐NaYF4:Yb3+, Er3+@SiO2 show similar cytotoxicity as the free DOX on HeLa cells. Confocal microscopy observations show that the composites can be effectively taken up by HeLa cells. Furthermore, the fibers show near‐infrared UC luminescence and are successfully applied in bioimaging of HeLa cells. The results indicate the promise of using NaYF4:Yb3+, Er3+@SiO2 nanocomposite fibers as multi‐functional drug carriers for drug delivery and cell imaging. 相似文献
7.
Zhiyao Hou Chunxia Li Pingan Ma Guogang Li Ziyong Cheng Chong Peng Dongmei Yang Piaoping Yang Jun Lin 《Advanced functional materials》2011,21(12):2356-2365
Up‐conversion (UC) luminescent porous silica fibers decorated with NaYF4:Yb3+, Er3+ nanocrystals (NCs) (denoted as NaYF4:Yb3+, Er3+@silica fiber) are prepared by the electrospinning process using cationic surfactant P123 as a template. Monodisperse and hydrophobic oleic acid capped β‐NaYF4: Yb3+, Er3+ NCs are prepared by thermal decomposition methodology. Then, these NCs are transferred into aqueous solution by employing cetyltrimethylammonium bromide (CTAB) as secondary surfactant. The water‐dispersible β‐NaYF4:Yb3+, Er3+ NCs are dispersed into precursor electrospinning solution containing P123 and tetraethyl orthosilicate (TEOS), followed by preparation of precursor fibers via electrospinning. Finally, porous α‐NaYF4:Yb3+, Er3+@silica fiber nanocomposites are obtained after annealing the precursor fibers containing β‐NaYF4:Yb3+, Er3+ at 550 °C. The as‐prepared α‐NaYF4:Yb3+, Er3+@silica fiber possesses porous structure and UC luminescence properties simultaneously. Furthermore, the obtained nanocomposites can be used as a drug delivery host carrier and drug storage/release properties are investigated, using ibuprofen (IBU) as a model drug. The results indicate that the IBU–loaded α‐NaYF4:Yb3+, Er3+@silica fiber nanocomposites show UC emission of Er3+ under 980 nm NIR laser excitation and a controlled release property for IBU. Meanwhile, the UC emission intensity of IBU–α‐NaYF4:Yb3+, Er3+@silica fiber system varies with the released amount of IBU. 相似文献
8.
Highly Emissive Nd3+‐Sensitized Multilayered Upconversion Nanoparticles for Efficient 795 nm Operated Photodynamic Therapy
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Photodynamic therapy (PDT) is a noninvasive and site‐specific therapeutic technique for the clinical treatment of various of superficial diseases. In order to tuning the operation wavelength and improve the tissue penetration of PDT, rare‐earth doped upconversion nanoparticles (UCNPs) with strong anti‐stokes emission are introduced in PDT recently. However, the conventional Yb3+‐sensitized UCNPs are excited at 980 nm which is overlapped with the absorption of water, thus resulting in strong overheating effect. Herein, a convenient but effective design to obtain highly emissive 795 nm excited Nd3+‐sensitized UCNPs (NaYF4:Yb,Er@NaYF4:Yb0.1Nd0.4@NaYF4) is reported, which provides about six times enhanced upconversion luminescence, comparing with traditional UCNPs (NaYF4:Yb,Er@NaYF4). A colloidal stable and non‐leaking PDT nanoplatform is fabricated later through a highly PEGylated mesoporous silica layer with covalently linked photosensitizer (Rose Bengal derivative). With as‐prepared Nd3+‐sensitized UCNPs, the nanoplatform can produce singlet oxygen more effective than traditional UCNPs. Significant higher penetration depth and lower overheating are demonstrated as well. All these features make as‐prepared nanocomposites excellent platform for PDT treatment. In addition, the nanoplatform with uniform size, high surface area, and excellent colloidal stability can be extended for other biomedical applications, such as imaging probes, biosensors, and drug delivery vehicles. 相似文献
9.
Remarkable NIR Enhancement of Multifunctional Nanoprobes for In Vivo Trimodal Bioimaging and Upconversion Optical/T2‐Weighted MRI‐Guided Small Tumor Diagnosis
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Zhigao Yi Xiaolong Li Zhenluan Xue Xiao Liang Wei Lu Hao Peng Hongrong Liu Songjun Zeng Jianhua Hao 《Advanced functional materials》2015,25(46):7119-7129
Effective nanoprobes and contrast agents are urgently sought for early‐stage cancer diagnosis. Upconversion nanoparticles (UCNPs) are considerable alternatives for bioimaging, cancer diagnosis, and therapy. Yb3+/Tm3+ co‐doping brings both emission and excitation wavelengths into the near‐infrared (NIR) region, which is known as “optical transmission window” and ideally suitable for bioimaging. Here, NIR emission intensity is remarkably enhanced by 113 times with the increase of Yb3+ concentration from 20% to 98% in polyethylene glycol (PEG) modified NaYF4:Yb3+/Tm3+ UCNPs. PEG‐UCNPs‐5 (98% Yb3+) can act as excellent nanoprobes and contrast agents for trimodal upconversion (UC) optical/CT/T2‐weighted magnetic resonance imaging (MRI). In addition, the enhanced detection of lung in vivo long‐lasting tracking, as well as possible clearance mechanism and excretion routes of PEG‐UCNPs‐5 have been demonstrated. More significantly, a small tumor down to 4 mm is detected in vivo via intravenous injection of these nanoprobes under both UC optical and T2‐weighted MRI modalities. PEG‐UCNPs‐5 can emerge as bioprobes for multi‐modal bioimaging, disease diagnosis, and therapy, especially the early‐stage tumor diagnosis. 相似文献
10.
Single Ho3+‐Doped Upconversion Nanoparticles for High‐Performance T2‐Weighted Brain Tumor Diagnosis and MR/UCL/CT Multimodal Imaging
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Dalong Ni Wenbo Bu Shengjian Zhang Xiangpeng Zheng Ming Li Huaiyong Xing Qingfeng Xiao Yanyan Liu Yanqing Hua Liangping Zhou Weijun Peng Kuaile Zhao Jianlin Shi 《Advanced functional materials》2014,24(42):6613-6620
Multimodal bio‐imaging has attracted great attention for early and accurate diagnosis of tumors, which, however, suffers from the intractable issues such as complicated multi‐step syntheses for composite nanostructures and interferences among different modalities like fluorescence quenching by MRI contrast agents (e.g., magnetic iron oxide NPs). Herein, the first example of T2‐weighted MR imaging of Ho3+‐doped upconversion nanoparticles (UCNPs) is presented, which, very attractively, could also be simultaneously used for upconversion luminesence (UCL) and CT imaging, thus enabling high performance multi‐modal MRI/UCL/CT imagings in single UCNPs. The new finding of T2‐MRI contrast enhancement by integrated sensitizer (Yb3+) and activator (Ho3+) in UCNPs favors accurate MR diagnosis of brain tumor and provides a new strategy for acquiring T2‐MRI/optical imaging without fluorescence quenching. Unlike other multi‐phased composite nanostructures for multimodality imaging, this Ho3+‐doped UCNPs are featured with simplicity of synthesis and highly efficient multimodal MRI/UCL/CT imaging without fluorescence quenching, thus simplify nanostructure and probe preparation and enable win–win multimodality imaging. 相似文献
11.
Helmut Schäfer Pavel Ptacek Henning Eickmeier Markus Haase 《Advanced functional materials》2009,19(19):3091-3097
Nanocrystals of NaYF4 doped with Yb3+ and Er3+ are synthesized in oleylamine using Y2(CO3)3, Yb2(CO3)3, Er2(CO3)3, Na2CO3, and NH4F as precursors. In contrast to other starting materials normally used for such syntheses, these precursors react even at room temperature to form hexagonal‐phase (β‐phase) NaYF4:Er,Yb nanoparticles. Cubic‐phase (α‐phase) NaYF4:Yb,Er particles are formed only at elevated temperatures (>250 °C). The formation of the cubic phase at high temperatures can be suppressed by replacing pure oleylamine with oleic acid/oleylamine mixtures. Under optimized reaction conditions, particles with an average particle size of about 7 nm are generated in 84% yield. Heat treatment (30 min, 280 °C) of the particles significantly increases the luminescence efficiency. A transparent solution of the heat‐treated, nanometer‐sized phosphor in toluene shows intense visible light emission upon excitation in the near infrared. 相似文献
12.
Rajiv Kumar Marcin Nyk Tymish Y. Ohulchanskyy Christopher A. Flask Paras N. Prasad 《Advanced functional materials》2009,19(6):853-859
Here, novel nanoprobes for combined optical and magnetic resonance (MR) bioimaging are reported. Fluoride (NaYF4) nanocrystals (20–30 nm size) co‐doped with the rare earth ions Gd3+ and Er3+/Yb3+/Eu3+ are synthesized and dispersed in water. An efficient up‐ and downconverted photoluminescence from the rare‐earth ions (Er3+ and Yb3+ or Eu3+) doped into fluoride nanomatrix allows optical imaging modality for the nanoprobes. Upconversion nanophosphors (UCNPs) show nearly quadratic dependence of the photoluminescence intensity on the excitation light power, confirming a two‐photon induced process and allowing two‐photon imaging with UCNPs with low power continuous wave laser diodes due to the sequential nature of the two‐photon process. Furthermore, both UCNPs and downconversion nanophosphors (DCNPs) are modified with biorecognition biomolecules such as anti‐claudin‐4 and anti‐mesothelin, and show in vitro targeted delivery to cancer cells using confocal microscopy. The possibility of using nanoprobes for optical imaging in vivo is also demonstrated. It is also shown that Gd3+ co‐doped within the nanophosphors imparts strong T1 (Spin‐lattice relaxation time) and T2 (spin‐spin relaxation time) for high contrast MR imaging. Thus, nanoprobes based on fluoride nanophosphors doped with rare earth ions are shown to provide the dual modality of optical and magnetic resonance imaging. 相似文献
13.
Nanocrystalline Ln3+‐doped YF3 phosphors have been synthesized via a facile sonochemistry‐assisted hydrothermal route. YF3 nanoparticles are demonstrated to be a good host material for different lanthanides. Varying the dopants leads to different optical properties. In particular, the feasibility of inducing red, green, and especially blue emission in the Yb3+/Er3+ co‐doped YF3 sample by up‐conversion excitation in the near‐infrared region is demonstrated. Such unusually strong 411 nm blue up‐conversion emission has seldom been reported in other Yb3+/Er3+‐doped systems. The up‐conversion mechanisms have been analyzed. 相似文献
14.
Plasmonic Dual‐Enhancement and Precise Color Tuning of Gold Nanorod@SiO2 Coupled Core–Shell–Shell Upconversion Nanocrystals
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Fengwen Kang Jijun He Tianying Sun Zhi Yong Bao Feng Wang Dang Yuan Lei 《Advanced functional materials》2017,27(36)
The last decade has witnessed the remarkable research progress of lanthanide‐doped upconversion nanocrystals (UCNCs) at the forefront of promising applications. However, the future development and application of UCNCs are constrained greatly by their underlying shortcomings such as significant nonradiative processes, low quantum efficiency, and single emission colors. Here a hybrid plasmonic upconversion nanostructure consisting of a GNR@SiO2 coupled with NaGdF4:Yb3+,Nd3+@NaGdF4:Yb3+,Er3+@NaGdF4 core–shell–shell UCNCs is rationally designed and fabricated, which exhibits strongly enhanced UC fluorescence (up to 20 folds) and flexibly tunable UC colors. The experimental findings show that controlling the SiO2 spacer thickness enables readily manipulating the intensity ratio of the Er3+ red, green, and blue emissions, thereby allowing us to achieve the emission color tuning from pale yellow to green upon excitation at 808 nm. Electrodynamic simulations reveal that the tunable UC colors are due to the interplay of plasmon‐mediated simultaneous excitation and emission enhancements in the Er3+ green emission yet only excitation enhancement in the blue and red emissions. The results not only provide an upfront experimental design for constructing hybrid plasmonic UC nanostructures with high efficiency and color tunability, but also deepen the understanding of the interaction mechanism between the Er3+ emissions and plasmon resonances in such complex hybrid nanostructure. 相似文献
15.
Helmut Schäfer Pavel Ptacek Otmane Zerzouf Markus Haase 《Advanced functional materials》2008,18(19):2913-2918
KYF4/Yb3+, Er3+ nanocrystals with a mean diameter of approximately 13 nm were synthesized at 200 °C in the high boiling organic solvent N‐(2‐hydroxyethyl)ethylenediamine (HEEDA). The particles crystallize in the cubic phase known from α‐NaYF4 and form transparent colloidal solutions in tetraethylene glycol (TEG) or propanol. Solutions containing 1 wt % of the nanocrystals in TEG display visible upconversion emission upon continuous wave (CW) excitation at 978 nm. Growing undoped KYF4 on the surface of the KYF4/Yb3+, Er3+ nanocrystals increases the upconversion efficiency by more than a factor of 20. The XRD data of these particles, display a slight increase in the mean particle size from 13 to 15.5 nm, indicating that only a part of the subsequently added KYF4 shell material is deposited onto the particle surface. Nevertheless the performed surface modification obviously leads to core/shell structured particles. 相似文献
16.
Jingning Shan Stephanie J. Budijono Guohong Hu Nan Yao Yibin Kang Yiguang Ju Robert K. Prud'homme 《Advanced functional materials》2011,21(13):2488-2495
The utilization of upconverting nanophosphors (UCNP) for photodynamic therapy (PDT) has gained significant interests due to its ability to convert deep‐penetrating near‐infra red (NIR) light (i.e., 978 nm) to visible light. Previous attempts to co‐localize UCNPs with photosensitizers suffer from low photosensitizer loading and problems with nanoparticle aggregation. Here, the preparation of a novel composite nanoparticle formulation comprising 100 nm β?NaYF4:Yb3+,Er3+ UCNPs, and meso‐tetraphenyl porphine (TPP) photosensitizer, stabilized by biocompatible poly(ethylene glycol‐block‐(dl )lactic acid) block copolymers (PEG‐b‐PLA) is presented. A photosensitizer loading of 10 wt% with respect to UCNP crystal was achieved via the Flash NanoPrecipitation (FNP) process. A sterically stabilizing PEG layer on the composite nanoparticle surface prevents nanoparticle aggregation and ensures nanoparticle stability in water, PBS buffer, and culture medium containing serum proteins, resulting in nanoparticle suitable for in vivo applications. Based on in vitro studies utilizing HeLa cervical cancer cell lines, the composite nanoparticles are shown to exhibit low dark toxicity and efficient cancer cell‐killing activity upon NIR excitation. Exposure with 134 W cm?2 of 978 nm light for 45 min resulted in 75% HeLa cell death. This is the first quantification of the cell‐killing capabilities of the UCNP/TPP composite nanoparticles formulated for photodynamic therapy. 相似文献
17.
Tao Liang Qirong Wang Zhen Li Peipei Wang Junjie Wu Miaomiao Zuo Zhihong Liu 《Advanced functional materials》2020,30(16)
Although upconversion nanoparticles (UCNPs) have drawn increasing attention for their unique photophysical characteristics, they suffer from a bottleneck of low luminescence efficiency due to the poor absorption coefficient of Ln3+. Dye sensitization has provided thousands‐fold enhancement of upconversion luminescence (UCL) in organic solvents because of the remarkably improved light absorption ability, but the sensitization of UCL in aqueous phase is only less than 20 folds by far, with unknown restrictive factors. Herein, the aggregation‐caused quenching (ACQ) of dyes is revealed as the most important reason limiting dye sensitization in aqueous phase, and the problem is circumvented through delicately modulating the physical properties of dyes and their assembly manner with UCNPs. By further alleviating energy back transfer (EBT) from Ln3+ to dyes, more than 600‐fold enhancement of UCL is achieved in aqueous phase. The as‐obtained dyes modified UCNPs show good biocompatibility and high signal contrast when applied for deep in vivo imaging. 相似文献
18.
Nikhil Chander Atif F. Khan Vamsi K. Komarala Santa Chawla Viresh Dutta 《Progress in Photovoltaics: Research and Applications》2016,24(5):692-703
Upconverting NaYF4:Yb3+,Er3+/NaYF4 core‐shell (CS) nanoparticles (NPs) were synthesized by thermal decomposition of lanthanide trifluoroacetate precursors and mixed with TiO2 NPs to fabricate dye‐sensitized solar cells (DSSCs). The CS geometry effectively prevents the capture of electrons because of the surface states and improves photo‐emission. The as‐synthesized CS NPs show upconversion (UC) luminescence, converting near infrared (NIR) light into visible light (450–700 nm), making the photon absorption by the ruthenium‐based dyes (which have little or no absorption in the NIR region) possible. The champion DSSCs fabricated using CS UC NPs (average size = 25 nm) show enhancements of ~12.5% (sensitized with black/N749 dye) and of ~5.5% (sensitized with N719 dye) in overall power conversion efficiency under AM 1.5G illumination. This variation in the enhancement of the DSSC efficiencies for black and N719 dyes is attributed to the difference in the extinction coefficient and the absorption wavelength range of dyes. Incident photon‐to‐current conversion efficiency measurements also evidently showed the photocurrent enhancement in the NIR region of the spectrum because of the UC effect. The results prove that the augmentation in efficiency is primarily due to NIR to visible spectrum modification by the fluorescent UC NPs. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
19.
Y2O2S luminophors doped with Er3+ and Yb3+ ions are produced by means of solid-phase synthesis and deposited onto standard AL123A infrared light-emitting diodes. When excited with 940 nm radiation from a light-emitting diode, the structures exhibit intense visible up-conversion luminescence. A maximal brightness of 2340 cd/m2 of green and red up-conversion luminescence at corresponding wavelengths around 550 and 600 nm is observed for the Y2O2S compound doped with 2 at % Er3+ ions and 6 at % Yb3+ ions. The ratio of the intensity of green (or red) up-conversion luminescence to the intensity of infrared Stokes luminescence increases with increasing applied voltage. The efficiency of visible emission of the light-emitting diode structures is η = 1.2 lm/W at an applied voltage of 1.5 V. 相似文献
20.
3D Micromolding of Arrayed Waveguide Gratings on Upconversion Luminescent Layers for Flexible Transparent Displays without Mirrors,Electrodes, and Electric Circuits
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Satoshi Watanabe Takeo Asanuma Takafumi Sasahara Hiroshi Hyodo Mutsuyoshi Matsumoto Kohei Soga 《Advanced functional materials》2015,25(28):4390-4396
A new technique for the fabrication of arrayed waveguide gratings on upconversion luminescent layers for flexible transparent displays is reported. Ho3+‐ and Yb3+‐codoped NaYF4 nanoparticles are synthesized by hydrothermal techniques. Transparent films consisting of two transparent polymers on the NaYF4 nanoparticle films exhibit mechanical flexibility and high transparence in visible region. Patterned NaYF4 nanoparticle films are fabricated by calcination‐free micromolding in capillaries. Arrayed waveguide gratings consisting of the two transparent polymers are formed on the patterned NaYF4 nanoparticle films by micromolding in capillaries. Green and red luminescence is observed from the upconversion luminescent layers of the NaYF4 nanoparticle films in the arrayed waveguide gratings under excitation at 980 nm laser light. Arrayed waveguide gratings on the upconversion luminescent layers are fabricated with Er3+‐doped NaYF4 nanoparticles which can convert two photons at 850 and 1500 nm into single photon at 550 nm. These results demonstrate that flexible transparent displays can be fabricated by constructing arrayed waveguide gratings on upconversion luminescent layers, which can operate in nonprojection mode without mirrors, transparent electrodes, and electric circuits. 相似文献