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oe1(光电查) - 科学论文

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出版时间
  • 2018
研究主题
  • ac-dc difference
  • Thermal transfer standard
  • inductive voltage
  • uncertainty budget
  • pulse-driven ac Josephson voltage standard
应用领域
  • Measurement and Control Technology and Instruments
机构单位
  • National Institute of Metrology
1183 条数据
?? 中文（中国） ▾

  • Role of Yb3+ ion on the evaluation of energy transfer and cross-relaxation processes in Gd2Ce2O7: Yb3+, Er3+ phosphors

    摘要： Energy transfer (ET) and cross-relaxation (CR) processes play significant roles in regulating emitting colors and intensity of upconversion (UC) materials. Calculating the coefficients in ET and CR processes can provide visual descriptions for evaluating the UC luminescence properties. Here, we find that those ET and CR processes are responsible for the color-tunable properties in Gd2Ce2O7: Yb3+, Er3+ phosphors. By solving the rate equation, mathematical expressions are established to calculate the ET and CR coefficients based on the experimental UC spectra and lifetimes. The results are benefit to evaluate the efficiencies of ET and CR processes in quantization in different Yb3+ ion concentrations doped samples. The coefficients of ET process arise from 1.05 to 7.93 × 1017 cm3s?1 while those of CR process increase from 2.69 to 72.01 × 1017 cm3s?1 with increasing the Yb3+ ion concentration, which suggest that the CR and ET processes are efficient in Gd2Ce2O7 host. Furthermore, potential temperature sensing properties are also evaluated according to the fluorescence intensity ratio of 2H11/2 and 4S3/2 levels and the maximal sensitivity (S) is achieved about 0.00337 K?1 at 503 K. This work provides an insight into the evaluation of those UC processes and reveals the capacity in color-tunable and temperature sensing aspects.

    关键词： Upconversion,Mathematical expression,Cross-relaxation,Temperature sensing,Energy transfer

    更新于2025-11-14 17:03:37

  • Determination of cholic acid in body fluids by β?cyclodextrin-modified N-doped carbon dot fluorescent probes

    摘要： An easy, dependable, and sensitive cholic acid activity experiment was designed based on β?cyclodextrin-modi?ed carbon dot (β?CD-CD) nanoprobes with speci?c host–guest recognizing ability and photoelectron transfer capability. The β?CD-CD nanoprobes were characterized by infrared, ultraviolet-visible, and ?uorescence spectroscopy and transmission electron microscopy. The ?uorescence of the probes under optimized conditions linearly responded to cholic acid concentration from 0 to 650 μmol·L?1 with a detection limit of 25 nmol·L?1. The probes also performed well in detecting cholic acid in serum and urine samples with an average recovery rate of 97.1%–103.4%. Thus, this study provides a reliable, rapid, and easy method of cholic acid detection in body ?uids that can be potentially applied in medical studies.

    关键词： Host–guest recognition,β?cyclodextrin,Cholic acid,Photoinduced electron transfer,Carbon dots

    更新于2025-11-14 17:03:37

  • Competing photochemical reactions of bis-naphthols and their photoinduced antiproliferative activity

    摘要： Photophysical properties and photochemical reactivity for a series of bis-naphthols 4a-4e and bis-anthrols 5a and 5e were investigated by preparative irradiations in CH3OH, fluorescence spectroscopy and laser flash photolysis (LFP). Methanolysis taking place via photodehydration (bis-naphthols ΦR = 0.04-0.05) is in competition with symmetry breaking charge separation (SB-CS). The SB-CS gives rise to radical ions that were for 4a and 4e detected by LFP. Photodehydration gives quinone methides (QMs) that were also detected by LFP (λmax = 350 nm, τ ≈ 1-2 ms). In the aqueous solvent, excited state proton transfer (ESPT) competes with the above mentioned processes, giving rise to naphtholates, but the process is inefficient and can only be observed in the buffered aqueous solution at pH >7. Since the dehydration of bis-naphthols delivers QMs, their potential antiproliferative activity was investigated by MTT test on three human cancer cell lines (NCI-H1299, lung carcinoma; MCF-7, breast adenocarcinoma; and SUM159, pleomorphic breast carcinoma). Cells were treated with 4 or 5 with or without irradiation (350 nm). An enhancement of the activity (up to 10-fold) was observed upon irradiation, which may be associated to the QM formation. However, these QMs do not cross-link DNA. The activity is most likely associated to the alkylation of proteins present in the cell cytoplasm, as evidenced by photoinduced alkylation of bovine and human serum albumins by 4a.

    关键词： quinone methides,bis-anthrols,excited state proton transfer,protein alkylation,bis-naphthols,antiproliferative activity,photodehydration,symmetry breaking charge separation

    更新于2025-11-14 15:32:45

  • Tricolor- and White Light–Emitting Ce <sup>3+</sup> /Tb <sup>3+</sup> /Mn <sup>2+</sup> -Coactivated Li <sub/>2</sub> Ca <sub/>4</sub> Si <sub/>4</sub> O <sub/>13</sub> Phosphor via Energy Transfer

    摘要： Single-component tunable Li2Ca4Si4O13:Ce3+,Tb3+,Mn2+ phosphors were successfully synthesized at 950 °C. Li2Ca4Si4O13:Ce3+,Tb3+ exhibits two luminescence peaking at 430 and 550 nm, which originated from the allowed 5d → 4f transition of the Ce3+ ion and the 5D4 → 7FJ (J = 6, 5, 4, 3) transition of the Tb3+ ion, respectively. Moreover, by codoping Ce3+ ions in the Li2Ca4Si4O13:Mn2+ system, yellow-red emission from the forbidden transition of Mn2+ could be enhanced. Under UV excitation, dual energy transfers (ETs), namely, Ce3+ → Mn2+ and Ce3+ → Tb3+, are present in the Li2Ca4Si4O13:Ce3+,Tb3+,Mn2+ system. The ET process was confirmed by the overlap of the excitation spectra, variations in the emission spectra, ET efficiency, and decay times of phosphors. In addition, quantum yields and CIE chromatic coordinates are presented. The emission color of these phosphors can be tuned precisely from blue to green via ET of Ce3+ → Tb3+ and from blue to yellow via ET of Ce3+ → Mn2+. White light can also be achieved upon excitation of UV light by properly tuning the relative composition of Tb3+/Mn2+. This result indicates that the developed phosphor may be regarded as a good tunable emitting phosphor for UV light-emitting diodes.

    关键词： phosphor,energy transfer,Mn2+,Tb3+,Li2Ca4Si4O13,Ce3+,white light-emitting diodes

    更新于2025-11-14 15:29:11

  • Mechanofluorochromism based on BOPIM complexes: The effect of substituents and regulation of the direction of the emission color changes

    摘要： Novel boron 2-(2′-pyridyl)imidazole (BOPIM) complexes T1, T2 and T3 with different substituents (including bromo, tert-butyl and methoxyl) on the benzene ring of BOPIM dyes have been designed and synthesized, and their optical properties in both solution and the solid state were investigated and compared. The three compounds exhibited typical intramolecular charge transfer (ICT) characteristics. Solvent-dependent UV-vis absorption, fluorescence emission spectra and quantum chemical calculation indicated a molecular push-pull electronic structure. Their ICT degrees increased with the sequence of T1 < T2 < T3. The analysis of the X-ray crystal structure revealed the twisted molecular conformation of BOPIM dyes. Furthermore, they showed remarkable reversible mechanofluorochromic (MFC) features under mechanical force. It was found that the MFC activities could be tuned easily by changing the substituents on the BOPIM dyes. T1 exhibited emission color change from bright green to yellowish green with a spectral red-shift of only 22 nm under mechanical stimuli, whereas T2 and T3 gave the large spectral red-shifts of 36 and 30 nm. Electronic and steric effects of the substitutes were proved playing significant roles in regulating the ICT effect and intermolecular interactions. More importantly, the remarkable effect of substituents on the MFC behaviors of BOPIM dyes will provide an effective way to obtain novel high-contrast MFC dyes.

    关键词： Mechanofluorochromism,Substituent effect,Intramolecular charge transfer,Solid-state fluorescence,BOPIM complexes

    更新于2025-11-14 15:26:12

  • Erbium-to-dysprosium energy-transfer mechanism and visible luminescence in lead-cadmium-fluorogermanate glass excited at 405?nm

    摘要： Erbium-to-dysprosium energy-transfer and visible luminescence in the blue, green, yellow, red, and NIR is reported in PbGeO3:PbF2:CdF2 glass under 405 nm excitation. Absorption and excitation spectra were examined in the UV-VIS-IR spectral region. Emission showed a decrease in the Er3+ emissions around 520 and 545 nm when Dy3+ was added to the host matrix, while the Dy3+ emission around 576 nm (4F9/2 – 6H13/2) increased concomitantly. The recorded lifetime for Er3+ emissions also decreased, as Dy3+ concentration was increased for fixed Er3+ content. No similar behavior was observed when Er3+ concentration varied, confirming a one-way Er3+-to-Dy3+ energy transfer mechanism.

    关键词： glass,energy-transfer,visible-light,rare-earth

    更新于2025-11-14 15:25:21

  • Glutaraldehyde non-conjugated chitosan polymer fluorophores for selective determination of picric acid via fluorescence resonance energy transfer strategy

    摘要： Water-dispersed glutaraldehyde (GA) non-conjugated chitosan polymer fluorophores (GCPF) with quantum yield of 16 % is synthesized by stirring chitosan and GA for 6 h at room temperature in the present work. It is a facile and mild method and fluorescent GCPF can be stabled for two months. Owing to the spectral overlap of fluorescent spectrum of GCPF and absorption spectrum of picric acid (PA), a novel sensitive fluorescent method using fluorescent GCPF for PA detection from 10 nM to 50 μM via fluorescence resonance energy transfer (FRET) strategy is established. The distance between donor of GCPF and acceptor of PA (R0 value) is calculated to be 3.5 nm. FRET method using fluorescent GCPF possesses high sensitivity (LOD of 2.8 nM), and selectivity and fast response within 2 min. Moreover, fluorescent GCPF is also utilized in visual analysis of PA using cotton swabs. Fluorescence quenching effect can be observed by eyes irradiated with 365 nm ultraviolet light at cotton swabs and using GCPF solid on quartz glasses, which paves an effect and wide way for the application of fluorescent GCPF in our daily life.

    关键词： Glutaraldehyde non-conjugated chitosan polymer fluorophores (GCPF),picric acid (PA),fluorescence resonance energy transfer (FRET),glutaraldehyde (GA),chitosan

    更新于2025-11-14 15:23:50

  • A new disordered langbeinite-type compound, K <sub/>2</sub> Tb <sub/>1.5</sub> Ta <sub/>0.5</sub> P <sub/>3</sub> O <sub/>12</sub> , and Eu <sup>3+</sup> -doped multicolour light-emitting properties

    摘要： For the first time, a new langbeinite-type phosphate, namely potassium terbium tantalum tris(phosphate), K2Tb1.5Ta0.5(PO4)3, has been prepared successfully using a high-temperature flux method and has been structurally characterized by single-crystal X-ray diffraction. The results show that its structure can be described as a three-dimensional open framework of [Tb1.5Ta0.5(PO4)3] interconnected by K+ ions. The TbIII and TaV cations in the structure are disordered and occupy the same crystallographic sites. The IR spectrum, the UV–Vis spectrum, the morphology and the Eu3+-activated photoluminescence spectroscopic properties were studied. A series of Eu3+-doped phosphors, i.e. K2Tb1.5–xTa0.5(PO4)3:xEu3+ (x = 0.01, 0.03, 0.05, 0.07, 0.10), were prepared via a solid-state reaction and the photoluminescence properties were studied. The results show that under near-UV excitation, the luminescence colour can be tuned from green through yellow to red by simply adjusting the Eu3+ concentration from 0 to 0.1, because of the efficient Tb3+→Eu3+ energy-transfer mechanism.

    关键词： photoluminescence,Langbeinite-type phosphate,crystal structure,energy-transfer mechanism,multicolour light

    更新于2025-11-14 15:23:50

  • Quenched Sandwich-type Photoelectrochemical Aptasensor forProtein Detection based on Exciton Energy Transfer

    摘要： This work proposes a quenched photoelectrochemical sensing method for highly selective and sensitive detection of protein via Energy Transfer (ET) effect between the AuNPs and CdS:Mn quantum dots. This detection was performed on a sandwich-type aptamer sensing interface. Chitosan modified CdS:Mn/TiO2/ITO electrode was used to immobilize capture DNA (S1) via -CONH- bond. In the presence of target protein, AuNPs labeled DNA (AuNPs-S2) was further bonded to the protein to fabricate sandwich sensing platform, which forced the AuNPs away from the electrode surface. In this state, the photocurrent was greatly depressed, mainly due to two factors: (a) the ET effect produced by interparticle distance between CdS:Mn and AuNPs; (b) the steric hindrance of AuNPs-S2 partly obstructs the diffusion of the electron donor. The photocurrent decreased with the increasing concentration of the target protein. Using thrombin as a target, this sensitized method showed a detectable range of 0.1 pM to 8 nM and a detection limit of 30 fM. It possessed high selectivity and good stability for detection of thrombin. This method is extremely flexible and can be extended to varieties of protein targets.

    关键词： CdS:Mn,Photoelectrochemical aptasensor,Thrombin,Energy transfer,AuNPs

    更新于2025-11-14 15:15:56

  • Study of the photoresponse of a titanium anode coated with solution-processed fullerene-containing metal porphyrin/phthalocyanine films

    摘要： The present paper deals with the recent studies on the preparation of porphyrin-based donor-acceptor complexes capable of photoinduced electron transfer for solution-processed organic solar cells. Here the synthesis and chemical structure of (octakis(3,5-di-tert-butylphenoxy)phthalocyaninato) cobalt(II) (1) and (2,3,7,8,12,18-hexamethyl,13,17-diethyl,5-(2-pyridyl)porphinato) manganese(III) chloride (2) are performed and self-assembly in toluene solution of 1 and 1′-N-methyl-2′-(pyridin-4-yl)pyrrolidino[3′,4′:1,2][60]fullerene (PyC60) were discussed in more details. The structure of the obtained dyad 1-PyC60 is con?rmed by means of chemical thermodynamics/kinetics, UV–vis, IR, 1H NMR spectroscopy. Photoelectrochemical studies of the phthalocyanine-fullerene dyad and its precursors were carried out by voltammetry and amperometry methods. A comparative analysis of the photoelectrochemical characteristics obtained in this paper and these for recent described cobalt(II)/manganese(III) porphyrin/phthalocyanine-fullerene dyads are introduced from which ideas for the future design of high performance organic solar cells will be developed.

    关键词： donor-acceptor complexes,organic solar cells,phthalocyanine,photoinduced electron transfer,fullerene,porphyrin

    更新于2025-11-14 15:14:40