Heptamethine Cyanine Dyes with Ultra-Efficient Excited-State Nonradiative Decay for Synergistic Photothermal Immunotherapy

Organic dyes in the excited singlet state (S₁) decay via intersystem crossing (ISC) to the triplet state, radiative dissipation as fluorescence, or nonradiative decay for thermal deactivation. Although many studies are conducted to improve ISC and fluorescence efficiency, few have optimized S₁ decay via thermal deactivation, which is crucial for designing photothermal agents. A strategy for inhibiting radiative decay and ISC by introducing electron withdraw groups (EWGs) into the meso position of heptamethine cyanines (Cy7) is reported here, which allows S₁ energy decay via nonradiative relaxation. The decrease in the electron density of Cy7 caused by EWGs improved the photostability, which is important for biological applications because conventional cyanine dyes are easily photobleached. The EWG substitutes acted as efficient rotation groups with low-energy barriers, narrowing the energy gap between S₁ and the ground state and considerably improving the photothermal conversion efficiency (PCE). The PCE of CF₃cy with the strongest EWG is increased up to 83%. Liposome is used as a carrier to improve the biocompatibility and tumor retention of CF₃cy, which is combined with the toll-like receptor agonist resiquimod (R848) for synergistic photothermal immunotherapy against both primary and distant tumors and elicits a long-lasting immunological memory effect.     

Gain measurements on uniformly excited HF/DF TEA lasers

The gain of a uniformly excited HF/DF TEA laser was measured to be 76 dB/m for HF and 39 dB/m for DF. The gain is followed by an absorption which decays with10-50mus time constants attributed to V-T and V-R relaxation processes, Limited measurements on the HCl system show similar absorption that persists for about 50 ms, limiting the pulse repetition rate.     

Photophysics of Conjugated Oligoelectrolytes Relevant to Two-Photon Fluorescence-Lifetime Imaging Microscopy

Conjugated oligoelectrolytes (COEs) comprise a class of cell-membrane intercalating molecules that serve as effective optical reporters. However, little is known about the photophysical properties of COEs in biological environments such as buffers, cell membranes, and intracellular organelles, which is critical to optimize performance. Herein, how COE self-assembly depends on the dielectric environment (polarity and ion content) is explored based on the representative molecule 6-ring phenylenevinylene (PV) conjugated oligoelectrolyte (COE-S6), and its optical properties within mammalian cells are subsequently studied. Two-photon fluorescence lifetime imaging microscopy (FLIM), confocal laser scanning microscopy, and optical properties in solutions are brought together to obtain information about the location, accumulation, and characteristics of the local surroundings. FLIM imaging lifetime phasor plots, decays, and fluorescence spectra on stained mammalian cells provide evidence of successful COE-S6 internalization via endocytosis. The fluorescence lifetime of COE-S6 is identical when in A549 mammalian cells and in giant unilamellar vesicle model membranes, thereby providing a correlation between living system and artificial constructs.     

准二维强耦合激子能量的温度依赖性

采用线性组合算符法和LLP变分法研究了晶格热振动和极化子效应对量子阱中激子与界面光学(IO)声子强耦合又与体纵光学(LO)声子弱、中耦合体系的基态和激发态的影响,推导出作为量子阱宽和温度函数的激子基态能量的移动和第一内部激发态能量的移动的表达式,以AgCl/AgBr/AgCl量子阱为例进行了数值计算.结果表明,由激子IO声子强耦合所产生的激子基态能量移动和第一内部激发态能量移动随温度的升高而增大,而由激子-LO声子弱、中耦合所产生的激子基态能量移动和第一内部激发态能量移动随温度的升高而减小.     

Exciton–Exciton Annihilation in Thermally Activated Delayed Fluorescence Emitter

Recent studies have demonstrated that in thermally activated delayed fluorescence (TADF) materials, efficient reverse intersystem crossing occurs from nonradiative triplet exited states to radiative singlet excited states due to a small singlet–triplet energy gap. This reverse intersystem crossing significantly influences exciton annihilation processes and external quantum efficiency roll‐off in TADF based organic light‐emitting diodes (OLEDs). In this work, a comprehensive exciton quenching model is developed for a TADF system to determine singlet–singlet, singlet–triplet, and triplet–triplet annihilation rate constants. A well‐known TADF molecule, 3‐(9,9‐dimethylacridin‐10(9H)‐yl)‐9H‐xanthen‐9‐one (ACRXTN), is studied under intensity‐dependent optical and electrical pulse excitation. The model shows singlet–singlet annihilation dominates under optically excited decays, whereas singlet–triplet annihilation and triplet–triplet annihilation have strong contribution in electroluminescence decays under electrical pulse excitation. Furthermore, the efficiency roll‐off characteristics of ACRXTN OLEDs at steady state is investigated through simulation. Finally, singlet and triplet diffusion length are calculated from annihilation rate constants.     

Comparison of four-wave mixing techniques for studying orientational relaxation

Three four-wave mixing techniques for measuring orientational relaxation of molecules in solution using time-separated pulses are compared both theoretically and experimentally. This comparison is shown to be greatly facilitated by modifying the conventional third-order response functions to incorporate a portion due to the slowly varying reorientation of the transition dipoles. Ordinary Bragg diffraction of a probe field, in which a transient grating formed by excitation pulses of the same polarization is probed with parallel and perpendicular polarizations, has the advantage of yielding both the time dependence and the magnitude of the induced anisotropy. However, the accompanying acoustic grating interferes with the polarization-sensitive excited state concentration grating unless the probe wavelength falls within a very strong absorption band. The acoustic grating can be eliminated by using perpendicularly polarized pumping pulses (the "crossed grating" configuration). Polarization spectroscopy in which the generated field is collinear with the probe gives the same anisotropy decay kinetics as the crossed grating, but is more sensitive to interference from background birefringence. These three methods, together with time-resolved fluorescence polarization, have been used to examine rotational dynamics in the ground and excited states of rhodamine 6G, 9-aminoacridine, and benzophenone.     

无线通信系统中时频域联合的机会频谱接入算法

该文讨论一个多信道的无线通信系统,信道建模为慢衰落瑞利信道。根据信道信噪比,将信道质量划分多个状态,每个状态对应一个最大传输速率。此类系统中,发送节点一般已知信道状态的部分信息,并可以通过逐信道探测的方法获取实时的信道状态信息(Channel State Information,CSI)。而探测过程会消耗可以用于真正数据包(DATA)的时间。通过分析基于最优停止时间理论的机会频谱接入算法的局限性,该文提出了时频域联合的机会频谱接入算法,仿真分析证明在不同条件下本算法性能优越。     

原子和腔场衰减对耦合腔系统中几何量子失谐的影响

本文考虑原子和腔场存在衰减的情况,研究了耦合腔系统中两子系统间的几何量子失谐.在原子和腔场衰减系数相等的特殊情况下,通过解薛定谔方程,给出了系统态矢演化规律.采用数值计算方法,讨论了原子和腔场衰减对两子系统间几何量子失谐的影响.研究结果表明:两原子间、两腔场间、以及原子和腔场之间的几何量子失谐都呈现出振幅衰减式振荡,直...     

SF_6-UF_6-H_2体系激光光敏反应中红外荧光的研究

研究了由10.6μm P(24)支线脉冲CO_2激光引发SF_6UF_6-H_2体系红外光敏反应中产生的红外荧光。当体系的组成和激光频率都不变时,由HF产生的荧光信号强度与激光的能量密度呈线性关系,改变体系中UF_6的分压,红外荧光信号的强度和时间特性都发生比较明显的变化。此外,由SF_6-UF_6H_2。体系红外光敏反应的动力学讨论了上述红外荧光的一些特性。     

The perylene derivative BASF-241 solution as a new tunable dyelaser in the visible

Basic optical properties of the perylene derivative BASF-241 solution in chloroform relevant to its application as a dye laser were measured. The fluorescence spectrum, excited by frequency-doubled (532-nm) Nd:YAG laser pulses, shows three pronounced peaks centered at 540, 580, and 630 nm, with a Stokes shift and mirror image in relation to the absorption spectrum. The quantum yield was about a unity, with a lifetime of 5.0±0.5 ns. Addition of trichloroacetic acid (CCl₃COOH) causes a red shift of absorption and fluorescence spectra by about 750 cm^-1-L/mol. In a cavity consisting of a ~100% reflecting back mirror and an 8% reflecting output coupler, lasing was obtained at 577 nm, with a threshold of ~10 μJ/pulse. Using a grating, a tuning range of almost 20 nm was obtained, centered at the 0-1 fluorescence emission peaks     

Rb+(Ar,N2)混合蒸气中5P3/2能级有效辐射率的计算和测量

计算和测量了Rb (Ar,N2)混合蒸气中Rb(5P3/2)共振能级的有效辐射率。使用单模半导体激光器(抽运激光)将Rb原子激发至5P3/2态,另一调谐到5P3/2→7S1/2的单模激光束(检测激光)与抽运光束反平行通过样品池,并在池的径向平行移动,通过检测激光束的吸收测定了激发态原子密度及其空间分布。由于辐射陷获存在,有效辐射率为自然辐射率与透射因子(发射的光子在探测区域内没有被吸收的平均概率)的乘积。5P3/2原子密度及其空间分布结合5P3/2←5S1/2跃迁线的碰撞增宽计算了透射因子,从而得到了不同Ar或N2气压下,RbD2线的有效辐射率。对5P3/2-Ar系统,在不同气压下测得的D2线强度比值与有效辐射率计算值的比值相符。对于5P3/2-N2系统,研究了电子态向振动态的碰撞转移,得到了转移截面。     

四路频分复用荧光共焦显微探测系统实验研究

报道了采用全息聚合物分散液晶(H-PDLC)布拉格光栅阵列斩波调制的四通道频分复用荧光共焦显微探测系统的实验研究。通过高衍射率H-PDLC布拉格光栅将单束激光分成四束激发光并进行不同频率的载频调制,将激发光聚焦到生物样品上产生荧光信号并采集后,再通过傅里叶变换、滤波和解调,最后将采集到的信号还原成四路荧光信号强度随时间变化的曲线。实验搭建了激发光中心波长为405 nm的四路频分复用荧光探测系统,并成功探测到鼠神经海马细胞样品中激发的四点荧光信号的图像以及强度变化信息。     

Dynamics of longitudinal and transverse modes along the junction plane in GaAlAs stripe lasers

Observations of the transient excitation of higher order transverse modes along the junction plane in DH GaAlAs stripe lasers during subnanosecond pulse modulation is reported. These modes are strongly excited at the onset of the light pulse, they decay during 200 ps, and reappear after 400-600 ps. The width of the longitudinal mode spectrum decays from 40 to 10 Å during 0.5-1 ns.     

The First Inert and Photostable Encapsulated Lanthanide(III) Complexes Based on Dendritic 9,10‐Diphenylanthracene Ligands: Synthesis,Strong Near‐Infrared Emission Enhancement,and Photophysical Studies

A series of inert and photostable encapsulated lanthanide(III) complexes—based on dendritic anthracene ligands—is shown for the first time to exhibit strong near‐IR emission bands via efficient energy transfer from the excited states of the peripheral antenna to the Ln³⁺ ions (Er³⁺, Yb³⁺, and Nd³⁺). A significant decrease in the fluorescence of the anthracene ligand is accompanied by a strong increase in the near‐IR emission of the Ln³⁺ ions. The near‐IR emission intensities of Ln³⁺ ions in the encapsulated Ln³⁺–dendrimer complexes are dramatically enhanced on increasing the generation number (n) of dendrons, owing to site‐isolation and light‐harvesting effects. Furthermore, a first attempt is made to distinguish between the site‐isolation and light‐harvesting effects in the present complexes. Photophysical studies indicate the sensitization of Ln³⁺ luminescence by energy transfer through the excited singlet state of the anthracene ligands, and the energy‐transfer efficiency between the dendritic anthracene ligands and the Ln³⁺ ion is evaluated to be in the range of 90 to 97 %. Their energy‐transfer efficiency is in good agreement with the result that the biexponential decays contain a radiative decay of anthracene units (< ca. 10 %) and an energy‐transfer component (> ca. 90 %) from the excited state of anthracene ligands to the Ln³⁺ ions. Time‐resolved luminescence spectra show monoexponential decays with a lifetime of 2 μs for the Er³⁺ ion 11 μs for the Yb³⁺ ion and 0.7 μs for the Nd³⁺ ion in thin films, and calculated intrinsic quantum yields of the Ln³⁺ ions are in the range of ca. 0.025 to 0.55 %.     

双光子Jaynes-Cummings模型中运动原子与光场的纠缠特性

用量子信息理论研究具有原子运动的双光子Jaynes-Cummings模型中运动原子与光场的纠缠特性.结果表明:当运动原子的场模结构参数p取值较小时,系统的纠缠度不具有周期振荡特性,在p取值较大时,系统的纠缠度有明显的周期振荡特性,且振荡周期是原子静止情况下的2倍;在运动原子处于基态或激发态时,系统处于消纠缠状态,当运动原子处在相干叠加态时,原子才与场发生纠缠.     

Aggregation-Induced Emission in a Flexible Phosphine Oxide and its Zn(II) Complexes—A Simple Approach to Blue Luminescent Materials

Easily accessible blue-emitting materials are in the focus of ongoing research, as they still lack the efficiency and lifetime of their red and green counterparts. The new multidentate phosphine oxide ligands and two respective ZnCl₂ complexes presented here combine a straightforward synthesis with high yields and show interesting luminescent properties. The free ligand exhibits blue luminescence in the crystalline state, but not in amorphous films or diluted solution. In contrast, the Zn(II) complexes shows intense blue luminescence in the crystalline state as well as in amorphous thin films and in solution. Fluorescence lifetime imaging microscopy measurements show luminescence lifetimes of 3–6 ns indicative of fluorescence. By combining the experimental data with quantum chemical calculations, we propose a model where the conformation of the molecule is restricted, either via the crystal environment, aggregation, or the steric fixation by the coordinating central atom, blocking the nonradiative relaxation from the excited into the ground electronic state. However, this nonradiative relaxation is still possible in the gas phase via elongation of a P C bond. These results may provide a general mechanism to explain the luminescence properties in a whole class of organic phosphine oxides.     

Automated analysis of fluorescence lifetime imaging microscopy (FLIM) data based on the Laguerre deconvolution method

In fluorescence lifetime imaging microscopy (FLIM), fluorescence time decay at each pixel of the imaged sample are measured. Every recorded fluorescence decay corresponds to the time convolution of the instrument response with the intrinsic fluorescence impulse response function (IRF), from which the sample fluorescence lifetime is determined. To estimate the IRF, the instrument response thus needs to be deconvolved from the recorded fluorescence decay. We have recently introduced a novel FLIM time-deconvolution method based on the linear expansion of the fluorescence decays on an orthonormal Laguerre basis. Since this method allows simultaneous estimation of the IRFs at all pixels, it performs at least two orders of magnitude faster than standard algorithms. In its original implementation, however, the Laguerre basis, determined by the Laguerre parameter α, is selected using a heuristic approach. Here, we present an automated implementation, whereby the Laguerre parameter α is treated as a free parameter within a nonlinear least squares optimization scheme. The new implementation combines the unmatched inherent computational speed of the Laguerre deconvolution method with a systematic model selection approach. This method will thus facilitate applications of FLIM requiring automatic estimation of the spatial distribution of fluorescence lifetimes, such as in in vivo tissue FLIM imaging.     

利用量子比特间交换衰减实现无退纠缠的量子信息传输

在量子信息传输过程中,环境的作用会导致退相干与退纠缠。利用不同类型量子比特的优点,构成杂化量子比特系统是克服退相干效应,实现量子信息传输的一个有效方案。本文指出：将耦合量子比特之间信息交换过程中存在的能量损耗(量子比特间的交换衰减),与外部环境的退相干效应有机的结合起来,可以实现无退纠缠效应的量子信息传输。给出了实现无退纠缠效应信息传输,交换衰减率与退相干时间匹配的约束关系。     

单模辐射场与两个二能级原子相互作用过程中的熵特性

在大失谐条件下，研究了一位于能量损耗腔中两个二能级原子与单模辐射场相互作用系统中，原子-光场系统线性熵、原子线性熵和光场线性熵的时间演化特性，讨论了两原子的初始状态、腔场衰减常数以及光场的平均光子数对各线性熵的影响。结果表明：当两原子均处于激发态或基态时，各线性熵始终为零；而当两原子初始均处于激发态与基态的相干叠加态时，腔场损耗使得系统演化为混合态，原子线性熵和光场线性熵作振幅逐渐减小的周期振荡。     

Investigation of carrier relaxation dynamics in single CdSe/ZnSe self-organized quantum dot by time-resolved micro-photoluminescence

We have investigated carrier relaxation dynamics in single CdSe/ZnSe quantum dot (QD) by time-resolved micro-photoluminescence (PL). The discrete sharp lines, originated from individual QD states, exhibit various rise and decay time constants. The decay times of the sharp lines from ground states and excited states are estimated to be 700≈800 psec and 400≈500 psec, respectively, and the rise times of the ground states become longer compared with those of the excited states. There results are in contrast to successive change of the rise and decay times observed in time-resolved macro-PL with varying the detection wave-length. The quasi-continuum higher states with much shorter decay times are clearly observed over the discrete states of the QDs.