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Temperature modulation of concentration quenching in lanthanide-doped nanoparticles for enhanced upconversion luminescence

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Nano Research 2018年第4期11卷 2104-2115页

作者： Luoyuan Li Ningjiu Zhao Limin Fu Jing Zhou xicheng ai Jianping Zhang Department of Chemistry Renmin University of China Beijing 100872 China State Key Laboratory of Molecular Reaction Dynamics Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian 116023 China Department of Chemistry Capital Normal University Beijing 100048 China

The doping concentration of lanthanide ions is important for manipulating the luminescence properties of upconversion nanoparticles （UCNPs）. However, the serious concentration quenching in highly doped UCNPs remains a vital restriction for further enhanced upconversion luminescence （UCL）. Herein, we examined the effect of temperature on the concentration quenching of rare-earth UCNPs, an issue that has been overlooked, and we show that it is significant for biomedical or optical applications of UCNPs. In this work, we prepared a series of UCNPs by doping Er3. luminescent centers at different concentrations in a NaLuF4：Yb3＋ matrix. At room temperature （298 K）, steady-state photoluminescence （PL） spectroscopy showed substantial concentration quenching of the Er~ emission with increasing doping concentrations. However, the concentration quenching effect was no longer effective at lower temperatures. Kinetic curves obtained from time-resolved PL spectroscopy further showed that the concen- tration quenching dynamics were vitally altered in the cryogenic temperature region, i.e., below 160 K. Our work on the temperature-switchable concentration quenching mechanism may shed light on improving UCL properties, promoting their practical applications.

关键词： upconversionluminescence lanthanide-doped nanoparticle temperature modulation concentration quenching energy transfer

Ultrafast isomerization dynamics of retinal in bacteriorhodopsin as revealed by femtosecond absorption spectroscopy

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Chinese Science Bulletin 2008年第13期53卷 1972-1977页

作者： WU YiShi ZHONG Sheng ai xicheng HU KunSheng ZHANG JianPing Slate Key Laboratory for Structural Chemistry of Unstable and Stable Species Institute of Chemistry Chinese Academy of Sciences Beijing 100190 China Institute of Biophysics the Chinese Academy of Sciences Beijing 100101 China Department of Chemistry Renmin University of China Beijing 100872 China

A femtosecond (fs) broad-band absorption apparatus was used to measure the early photoisomeriza-tion process of bacteriorhodopsin’s (BR) photocycle to reveal the character of the important interme-diate of J625 and to obtain a deeper understanding of the role of photoisomerization in BR photocycle. Two time constants of 0.5 ps (95%) and 2.0 ps (5%) were brought out by global fitting on thirty curves in the near-infrared region. We suggest that the first time constant results from the decay of I460 interme-diate,and the longer component might be associated with BR isomer. The global analysis over 450,540,630,710 and 870 nm traces identified two time constants,～0.5 and～3 ps. The slower component can be extracted from the processes of both J625→BR568 (540 nm) and J625→K590 (630 nm),suggesting J-in-termediate takes a partial cis configuration. The obvious negative feature in early delay time of 700―780 nm regions was attributed to the radiative transition (stimulated emission) from the Franck-Condon active configuration along the isomerization potential surface of all-trans-retinal.

关键词：光致异构化受激发射球状配件噬菌调理素

Influence of nanostructure on the device performance and charge recombination dynamics of P3HT:PCBM solar cells

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Chinese Science Bulletin 2012年第26期57卷 3436-3441页

作者： LI Dan XING YaDong YUE He ZHANG JianPing ai xicheng Department of Chemistry Renmin University of ChinaBeijing 100872China

In this paper,we investigated the recombination dynamics of photogenerated charge carriers in a poly(3-hexylthiophene)(P3HT):[6,6]-phenyl-C 61-butyric acid methyl ester(PC 61 BM) blend system with donor-acceptor ratio of 1:1 before and after solvent annealing *** technique of transient photocurrent and photovoltage measurements were used,and charge carriers were photogenerated by a 7 ns laser pulse at room temperature(298 K).In transient photocurrent measurement,we observed some differences in the saturation extracted charge in P3HT:PCBM solar cells with different power *** addition,the bimolecular recombination coefficient is found to be 3.5×10-13 cm 3 s-1 for annealed devices,while 9.5×10-12 cm3 s-1 for as-cast *** the transient photovoltage measurement,we found that the photovoltage decay can be fitted by power-law equation at long time *** exponent parameter is 2.6 for annealed devices,which can be described as trap-free bimolecular recombination;is 1.76 for as-cast device due to the trap-limited bimolecular *** experimental results indicate that the nanomorphology of active layer indeed have influence on charge carriers dynamics in P3HT:PCBM blend systems.

关键词：退火设备太阳能电池电荷载体重组蛋白动力学结构体瞬态光电流纳米

Interactions between meso-tetrakis(4-(N-methylpyridiumyl))porphyrin TMPyP4 and DNA G-quadruplex of telomeric repeated sequence TTAGGG

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Science China Chemistry 2008年第5期51卷 452-456页

作者： ZHANG HuiJuan WANG XueFei WANG Peng PANG SiPing ai xicheng ZHANG JianPing School of Life Science&Technology Beijing Institute of TechnologyBeijing 100081China Department of Chemistry Renmin University of ChinaBeijing 100872China Institute of Chemistry Chinese Academy of SciencesBeijing 100080China

The binding properties between meso-tetrakis(4-(N-methylpyridiumyl))porphyrin (TMPyP4) and the parallel DNA G-quadruplex (G4) of telomeric repeated sequence 5′-TTAGGG-3′ have been characterized by means of circular dichroism,steady-state absorption,steady-state fluorescence and picosecond time-resolved fluorescence spectroscopies. The binding constant and the saturated binding number were determined as 1.29×106 (mol/L)-1 and 3,respectively,according to steady-state absorption spec-troscopy. Based on the findings by the use of time-resolved fluorescence spectroscopic technique,it is deduced that TMPyP4 binds to a DNA G-quadruplex with both the thread-intercalating and end-stacking modes and at the saturated binding state,one TMPyP4 molecule intercalates into the intervals of G-tetrads while the other two stack to the ends of the DNA G-quadruplex.

关键词： TMPyP4 DNA G-quadruplex spectroscopic technique binding mode

Spectroscopic investigation on the telomeric DNA base sequence repeat

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Chinese Science Bulletin 2002年第2期47卷 108-111页

作者： Sichuan Xu xicheng ai Zhaoyong Sun Qiyuan Zhang Xingkang Zhang Chinese Acad Sci Inst Chem State Key Lab Struct Chem Unstable & Stable Speci Ctr Mol Sci Beijing 100080 Peoples R China

Telomeres are protein-DNA complexes at the terminals of linear chromosomes, which protect chromoso-mal integrity and maintain cellular replicative capacity. From single-cell organisms to advanced animals and plants, structures and functions of telomeres are both very conser-vative. In cells of human and vertebral animals, telomeric DNA base sequences all are (TTAGGG)n. In the present work, we have obtained absorption and fluorescence spectra measured from seven synthesized oligonucleotides to simu-late the telomeric DNA system and calculated their relative fluorescence quantum yields on which not only telomeric DNA characteristics are predicted but also possibly the shortened telomeric sequences during cell division are im-plied. Oligonucleotide 5’- TTAGGGTTAGGG holds a low relative fluorescence quantum yield and remarkable excitation energy innerconversion, which tallies with the telomeric sequence of (TTAGGG)n. This result shows that telomeric DNA has a strong non-radiative or innerconvertible capabil-

关键词： DNA telomere oligonucleotide fluorescence quantum yield.

Trans-membrane controlling of an amphiphilic metalloporphyrin

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Chinese Science Bulletin 2000年第12期45卷 1082-1085页

作者： ZHANG Yunhong MA Chen CHANG Hailong LI Qianshu FENG Juan ai xicheng School of Chemical Engineering and Materials Science Beijing Institute of TechnologyBeijing 100081China Institute of Chemistry Chinese Academy of SciencesBeijing 100080China

In order to perform a transfer process of the porphyrin moiety across membrane media, an amphiphilic porphyrin 5,10,15-tri(4-hydroxyphenyl)-20-(4-hexadecyloxy-phenyl) porphyrin (P1) and its metalloporphyrin (P1Zn) were selected to be solubilized in cetyltrimethyl ammonium bromide (CTAB) micellar solutions. By taking advantage of the microenvironment sensitivity of their Soret band, UV-Vis spectra were used to study the dependence of location of the porphyrins in CTAB micellar media on the bulk pH value or the salt concentration of bulk solutions. The red shift of the Soret band, the decrease of its absorbance and the increase of the full width at half-maximum (FWHM) of P1Zn and P1 with pH titration process from neutral to weak basicity were attributed to the transfer process of the porphyrin moiety from the inner core to the outer surface of the micelles. In the pH sensitive area of the Soret band of P1Zn and P1, the blue shift of the Soret band, the increase of its absorbance and decrease of FWHM

关键词： amphiphilic porphyrin micelle trans-membrane.

Mechanism of intram olecular charge transfer in DNA helix as probed by the use of the fluorescent 2-aminopurine

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Science China Chemistry 2004年第5期47卷 367-372页

作者： ZHANG Huijuan WANG Peng WANG Xuefei FENG Juan XU Sichuan ai xicheng ZHANG Xingkang ZHANG Jianping State Key Laboratory for Structural Chemistry of Unstable and Stable Species Institute of Chemistry Chinese Academy of SciencesBeijing 100080 China

As a structural analogue of adenine, 2-aminopurine (2Ap) is often used as a fluorescent probe to study the intramolecular charge transfer reaction in DNA. We have designed and synthesized a series of model DNA helix with the variation in the distance between the 2Ap probe and the GGG sequence, and have investigated, by means of picosecond time-resolved fluorescence spectroscopy, the effect of the length of the bridge (consisting of a number of inosines, I) separating the electron donor (???GGG???) and the acceptor (2Ap) on the charge transfer dynamics. The fluorescence dynamics of 2Ap exhibited three exponential decay components, the one with a time constant of a few hundred picoseconds is assigned to the intramolecular charge transfer from GGG to 2Ap. Within 2.4 nm of the donor-acceptor separation, the rate of charge transfer decreased exponentially upon increasing the separation, from which the decay factor β is determined to be 1.3 nrrf-1. Beyond 2.4 nm, however, the rate started toincrease, this abnormal behavior of charge transfer is interpreted in terms of the match of elec- tronic energies between the l-bridge and the donor/acceptor couple.

关键词： 2-aminopurine(2Ap) DNA charge transfer time-resolved fluorescence spectroscopy.

Effects of different aggregation forms of LHC Ⅱ from Bryopsis corticulans on the excited state properties of Chl a

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Chinese Science Bulletin 2006年第12期51卷 1444-1451页

作者： ZUO Ping CHEN Hui WU Yishi SHEN Shihua WANG Peng ai xicheng ZHANG Jianping LI Liangbi KUANG Tingyun State Key Laboratory for Structural Chemistry of Stable and Unstable Species Institute of Chemistry Chinese Academy of Sciences Beijing 100080 China Key Laboratory of Photosynthesis and Environmental Molecular Physiology Institute of Botany Chinese Academy of Sciences Beijing 100093 China

Steady-state and time-resolved fluo- rescence spectroscopies have been used to study the excited state properties of Chl a in different ag- gregation forms of light-harvesting complex II (LHC II) from an intertidal green alga, Bryopsis corticulans, i.e. LHC II monomer, trimer and oligomer. When either Chl a or Chl b was selectively excited, the observed decrease in Chl a fluorescence in the oligomer is proved to be caused mainly by the fast fluorescence quenching among Chl a molecules, rather than by the decrease in Chl b-to-Chl a singlet excitation transfer efficiency. Analyses of the picosecond time-resolved fluorescence kinetics identified two exponential de- cay components in all of the three forms of LHC II: a longer-lived component (4.1―4.7 ns) originating from fluorescence emission of Chl a, and a shorter-lived one (135―540 ps) from the rapid equilibration of singlet excitation among Chl a molecules. The time constant of excitation equilibration is 135 ps in oli- gomer, 520 ps in trimer and 540 ps in monomer. These results imply that LHC II in oligomer form is inherently able to quench Chl a excitation, a mecha- nism which may be related to the photoprotection of PS II via changing the degree of LHC II aggregation in Bryopsis corticulans.

关键词： LHC Ⅱ 聚集形式 Chl a 荧光光捕获化合物能量转变

Study on time-resolved fluorescence dynamics of cyanine dye sensitizing AgBr

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Science China(Physics,Mechanics & Astronomy) 2008年第3期51卷 243-250页

作者： YANG ShaoPeng FAN ShanShan LI ChunLei FAN GuoZhi MENG Tao LI XiaoWei FU GuangSheng ai xicheng ZHAO XiaoHui YE JianPing WANG LingXuan College of Physics Science&Technology Hebei UniversityBaoding 071002China Institute of Chemistry Chinese Academy of SciencesBeijing 100080China

The fluorescence spectra of three different dyes adsorbed on the tabular and cubic AgBr microcrystals are obtained by the picosecond time-resolved streak camera technique. The dependence of the ultrafast electron transferring from dye-aggre-gates to the conduction band of AgBr and the efficiency of spectral sensitization on different kinds of dyes with different concentrations is analyzed. Further more,the microcosmic mechanism of the sensitization process is discussed. It is found that the fluorescence decay curves are fitted very well by the double exponential func-tion,consisting of a slow component and a fast one with large amplitude. We con-sider this fast one mainly attributable to the electron transfer from dye J-aggre-gates to the conduction band of AgBr.

关键词： spectral sensitization electron transfer rate Streak Camera AgBr