Thermally Induced Depolarization of the Photoluminescence of Carbon Nanodots in a Colloidal Matrix

The effect of temperature on fluorescence polarization in a colloidal system of carbon nanodots in glycerol under linearly polarized excitation is investigated for the first time. It is found that the experimentally obtained temperature dependence of the degree of linear polarization of fluorescence can be described by the Levshin–Perrin equation, taking into account the rotational diffusion of luminescent particles (fluorophores) in the liquid matrix. The fluorophore size determined in the context of the Levshin–Perrin model is significantly smaller than the size of carbon nanodots. This discrepancy gives evidence that small atomic groups responsible for nanodot luminescence are characterized by high segmental mobility with a large amplitude of motion with respect to the nanodot core.     

TP-LIF技术测量甲烷-空气火焰中CO的相对浓度分布

 阐述了双光子激光诱导荧光(TP-LIF)技术的原理及线性模型，利用双光子过程激励CO分子B¹∑+←←X¹∑＋(0,0)带Q支的跃迁(约230 nm)，分析了B¹∑+→A¹Π荧光带的荧光光谱特性，探讨了激光功率密度、激光波长及火焰温度等因素对测量的影响，并给出甲烷-空气火焰在一定燃烧条件下CO分子浓度随火焰位置及高度的变化关系。实验结果表明，利用TP-LIF技术测量CO的浓度分布，其时空分辨率及探测灵敏度都很高。当激光功率密度较强时，TP-LIF信号和激光能量成线性关系，而且由于光电离速率的增强，大大降低了碰撞猝灭速率等环境因素对信号测量造成的影响，该特性对实验标定及定量测量都非常有帮助。     

多元散射校正在荧光谱分析中的应用研究

针对废水中氨基酸荧光分析过程中光谱数据去噪声处理过程,提出了基于多元散射校正思想建立相对荧光强度与浓度关系模型的方法,建立了荧光测量中多波段波谱系列线性模型。研究结果表明,实验数据进行线性拟合,色氨酸呈现出良好线性关系,通过多元散射校正方法进行光谱数据处理,有效降低了散射及测量环境噪声的影响,提高了光谱数据的信噪比,校正后数据更加准确的表征了色氨酸相对荧光强度与浓度数据之间的线性相关性。建立的多波段波谱系列线性模型为现场检测仪器研制过程中滤波片的选择及混合溶液的在线解析提供了理论依据。     

水体的温度变化对测定溶解有机物浓度的影响

用激光诱导荧光(LIF)方法研究了水体的温度变化对溶解有机物(DOM)发射荧光强度的影响。随着温度的增加,DOM的荧光强度和水的拉曼散射强度不断降低。在20～75 ℃范围之内,对归一化荧光强度与温度关系曲线进行线性拟合,计算出归一化荧光强度随温度升高的变化梯度平均值为-5.24×10-4 ℃-1,根据归一化荧光强度与浓度的关系,给出了所测DOM的浓度随着温度升高的平均下降速率为-3.45×10-3 (mg·L-1)·℃-1。因此,在这一温度范围内测量时,假设归一化荧光强度不变,则温度变化将引起DOM浓度最大为8.45%的相对变化。     

典型食品果汁中百菌清农药残留荧光检测建模研究

利用荧光分光光度计对典型食品果汁(苹果汁和桃汁)与百菌清混合体系进行了荧光光谱检测,发现在352 nm处有明显百菌清药物特征峰。对混合体系的荧光发射光谱和其导数光谱进行回归分析建模,得到果汁中百菌清浓度和荧光强度之间的预测模型函数。在两种光谱模式下所建指数预测模型函数相关系数都高于0.99,优于线性模型函数;针对两种果汁,原始光谱模式下所建指数模型函数平均回收率分别为101%和100%,线性模型平均回收率分别为110%和118%;导数光谱模式下,两种果汁中百菌清指数函数预测模型平均回收率分别为101%和102%,而线性模型平均回收率分别为109%和120%。研究结果表明可以通过荧光光谱法直接实现果汁中百菌清残留检测,且指数函数预测模型优于线性模型,同时表明在果汁-百菌清混合体系的农药残留定量预测中,导数荧光光谱方法并无显著优势,可直接选用荧光原始光谱建模分析。     

Optical properties of Coumarin 314 doped sol-gel silica rods

Silica rods containing Coumarin 314 have been fabricated by the sol-gel method and their optical properties have been investigated under a linear Xenon flashlamp excitation. The fluorescence spectra of Coumarin 314 peaked at 508 nm in sol-gel silica while they peaked at 476 nm in ethanol. The fluorescence spectra of Coumarin 314 doped sol-gel silica rods were measured as function of heat treatment temperature. As heat treatment temperature of the rods increases, the fluorescence spectra band becomes somewhat broader. The photodegration of Coumarin 314 doped sol-gel silica rods was also studied under linear Xenon flashlamp excitation. The bulk transmission losses of the rods immersed in water were measured to be 0.51–0.57%/cm.     

温度对矿井老空水激光诱导荧光光谱的影响

煤矿井下突水水源的快速判别对煤矿安全生产意义非常重大,激光荧光技术用于煤矿突水水源的识别打破了传统水化学方法耗时长的不足。矿井老空水是最常见也是危害最大的水源类型,而温度是影响物质特性的重要因素之一,研究激光诱导荧光检测老空水的温度特性有助于快速准确识别矿井突水水源,该研究具有重要的学术意义和实用价值。采用405 nm蓝紫光半导体激光器作为光源,设定激光器功率为120 mW,产生的激光经UV/Vis石英光纤由荧光探头照射待测水样,待测水样受激光激发产生荧光由荧光探头采集,通过石英光纤传输至光谱仪。以2017年3月在淮南市张集煤矿采集的老空水作为研究对象,首先过滤掉水样中的悬浮颗粒,随后将其放置在烧杯中,使用冰块使样品温度降低至5.0 ℃,随后放入恒温水浴锅中,使用铁架台固定荧光探头使其位于液面下1 cm处。在荧光光谱采集过程中,样品始终放置在恒温水浴锅中,通过水浴锅控制样品在10.0～60.0 ℃温度范围内获取荧光光谱,并讨论了温度变化对老空水激光诱导荧光光谱谱图、波峰位置及峰值、温度系数、谱图面积的影响。研究结果表明：随着温度升高,加速了分子运动,增加了分子间碰撞的概率,使得非辐射跃迁增加,老空水的荧光效率下降,荧光强度减弱,荧光光谱整体呈衰减变化主要集中在400～700 nm波段;老空水荧光光谱的两个波峰所对应的波长保持不变,并未随着温度变化发生漂移,两个波峰处(472和493 nm)荧光强度减弱最明显,同时荧光强度减弱与温度升高存在较好的线性关系,荧光强度和温度在472 nm处拟合相关系数r2为0.91,在493 nm处的拟合相关系数r2为0.963 36;472 nm处的温度系数在20.0 ℃时达到最小值0.34%,493 nm处的温度系数在20 ℃时达到最小值0.81%,两处的温度系数均在20.0 ℃时达到最低值即荧光光谱在20.0 ℃附近最稳定;温度升高,老空水在荧光光谱在400～700 nm波段与温度轴包围的面积逐渐减小,400～700 nm波段谱图所对应的面积与温度的拟合相关系数r2为0.975 39即面积的减小与温度的升高有良好的线性关系。通过研究矿井老空水的温度特性,矿井老空水的激光诱导荧光光谱在20 ℃最稳定,在该温度条件下采用激光诱导荧光技术进行矿井水源的识别效果最佳,同时利用老空水波峰以及面积与温度的线性关系进行温度补偿可以进一步提升利用LIF技术进行矿井突水水源识别的灵敏度和精度,该研究对实现矿井老空水的快速、准确判别具有重要意义。     

荧光光谱法检测水质COD时温度、浊度、pH的影响分析

以COD标准液为研究对象,基于特定激发波长下的荧光发射光谱数据,采用化学计量学算法对水质COD进行了检测,分析了水的温度、浊度和pH的变化对发射光谱的影响,并对相关参数的影响进行了补偿校正。在此基础上建立了多参量共同作用时对水质COD预测模型的补偿校正方法。首先采用荧光光谱法对浓度范围为1～55 mg·L-1水质化学需氧量(COD)标准溶液进行三维荧光光谱的采集,去除散射峰以后采用基于蚁群算法优化的偏最小二乘法(ACO-iPLS)对不同激发波长(Ex=255～285 nm,间隔为5 nm)下的荧光发射光谱(Em=275～450nm)数据进行特征提取并采用基于粒子群优化的最小二乘支持向量机算法(PSO-LSSVM)进行预测模型的建立。结果表明,不同激发波长下的荧光发射光谱数据模型的检验集决定系数R2_p在0.961 8～0.998 1范围内,当采用波长为Ex=270 nm的激发光作用时所激发出的荧光发射光谱数据所建模型的效果最优,其检验集决定系数R2_p=0.998 1,预测均方根误差RMSEP=0.348 3 mg·L-1。其次,对温度、浊度、pH对荧光光谱法检测水质COD的影响进行了分析,并给出了相应的补偿模型。结果表明,温度和浊度在检测水质COD时对荧光光谱的影响不可忽略,但通过建立补偿模型可以对其影响进行有效的补偿校正,温度补偿后荧光数据模型的整体平均偏差Bias=0.130 6 mg·L-1,经浊度补偿后可以很好的校正浊度变化对荧光光谱法检测水质COD的影响,而pH范围在4～12.3内变化时对荧光光谱的影响相对较小,因此可忽略。最后,结合单一影响因素的分析结果,对荧光光谱法检测水质COD时水体的多种环境因素(温度、浊度、pH)共同作用的影响进行了分析。实验结果表明,忽略pH影响后,可以采用对温度和浊度同时补偿的方法对二者的影响进行有效的校正。该结果可为水质参数光学传感器在调试过程中抑制环境因素的影响提供参考。     

Ludwig-Soret effect in a linear temperature field: Theory and experiments for steady state distributions

The Ludwig-Soret effect, also known as thermal diffusion, describes the separation of mixtures in the presence of a temperature gradient. Here, a solution to the nonlinear differential equation that describes the motion of components of a binary mixture in a linear temperature field is given for long times, when the distribution of the components in space becomes time independent. A new experimental method based on the use of a scanning confocal microscope to monitor the spatial distribution of fluorescence from fluorescein labelled nanoparticles in water in a linear temperature field is described.     

Probing quantum-mechanical level repulsion in disordered systems by means of time-resolved selectively excited resonance fluorescence

We argue that the time-resolved spectrum of selectively-excited resonance fluorescence at low temperature provides a tool for probing the quantum-mechanical level repulsion in the Lifshits tail of the electronic density of states in a wide variety of disordered materials. The technique, based on detecting the fast growth of a fluorescence peak that is redshifted relative to the excitation frequency, is demonstrated explicitly by simulations on linear Frenkel exciton chains.     

3-Pentanone LIF at elevated temperatures and pressures: measurements and modeling

The objective of this study is to investigate 3-pentanone fluorescence experiments in a constant volume vessel at high temperature and high pressure to underline the influent parameters in conditions close to those encountered in internal combustion engines. To obtain quantitative analysis, measured fluorescence signals must be corrected by considering the influence of preponderant parameters such as temperature, pressure and gas composition. Quantitative dependences of fluorescence on thermodynamic parameters are measured and compared with the predictions of a photophysical model, which combines the effects of temperature, pressure, excitation wavelength on fluorescence quantum yield. The increase of 3-pentanone fluorescence with pressure is due to the vibrational relaxation of energy levels. The fluorescence decreases with increasing temperature, except at low temperature where the fluorescence increase is due to an activation of intersystem crossing between triplet toward singlet levels. The influences of thermodynamic parameters are based on an increase of the non-radiative decay rate with the vibrational energy level of excited electronic state and the important collisions to remove the excess vibrational energy. Experimental and calculated results show a satisfactory agreement. PACS 33.20; 33.50; 34.90     

血清自体荧光光谱联合肿瘤标志物群在肺癌诊断中的价值

血清自体荧光光谱可以反映血清中癌细胞在代谢过程中发生的异常改变而导致的血清中荧光物质的成分、含量及微环境的变化,可作为癌症辅助诊断的一种新方法。利用荧光光谱分析技术,探讨了肺癌、肺良性疾病以及正常人血清的荧光光谱的异同,建立了血清荧光光谱检测的方法。同时联合肿瘤标志物群CEA, NSE, SCC-Ag, CYFRA21-1和p16甲基化,并运用人工神经网络技术和Fisher线性判别分析法分别建立了肺癌的诊断预测模型,并用ROC判别法对其预测结果进行比较。结果表明,荧光光谱联合肿瘤标志物建立的人工神经网络模型的预测效果优于单纯的荧光光谱神经网络模型,判别效果优于Fisher线性判别分析。     

Analysis of fluorescence quenching of pyronin B and pyronin Y by molecular oxygen in aqueous solution

The fluorescence quenching of pyronin B and pyronin Y molecules by molecular oxygen in aqueous solution was studied by using steady-state and time-resolved fluorescence and UV-Vis absorption spectroscopy techniques. In order to understand the quenching mechanism, fluorescence decays, absorption and fluorescence spectra of the probes were recorded as a function of the oxygen concentration and temperature. The quenching was found to be appreciable and shows positive deviation in the Stern-Volmer representation obtained from the fluorescence intensity ratio. Fluorescence quenching constants (k_q) were calculated from the τ_o/τ vs. [Q] plots having linear correlation and compared with calculated diffusion-controlled rate constants (k_diff) values. Experimental results were in good agreement with the simultaneous dynamic and static quenching model.     

Stable Fluorescence of Green‐Emitting Carbon Nanodots as a Potential Nanothermometer in Biological Media

Temperature measurement in biology and medical diagnostics is of great importance. Herein, a novel carbon nanodot (CND) based fluorescent nanothermometry device for spatially resolved temperature measurements is demonstrated. The fluorescence CNDs are prepared by a simple one‐pot solvothermal method using sucrose as carbon source. Resultant CNDs show stable green fluorescence at 520 nm with high quantum yield (≈6%). The fluorescence of resultant CNDs exhibits a reversible linear response to temperature in a wide range of 20–85 °C. Moreover, the temperature resolution better than 0.5 °C and high sensitive variation of ≈1.3% °C^?1 are observed in a broad physiological temperature range of 20–40 °C. Therefore, the as‐prepared CNDs possess high water solubility, stable fluorescence, small size, and good biocompatibility, which make them promising candidate for thermometry and cell imaging in biological media.     

基于荧光光谱技术的菜籽油氧化状态智能评价

菜籽油在加工及贮藏过程中，易受氧气、温度、光照等因素的影响，产生氧化酸败现象。为准确判断油脂氧化程度，实现不同氧化模式下菜籽油品质的快速判别，采用三维同步荧光光谱技术结合平行因子分析法及BP神经网络法建立菜籽油氧化状态的智能评价模型。以冷榨菜籽油为原料，将样品分别置于常温、Schaal烘箱、高温模式中氧化处理，期间采集菜籽油的三维同步荧光光谱数据及理化指标，当理化指标超出国标限定范围时，停止采集数据。结果表明，菜籽油中荧光物质在不同氧化模式中的演变规律呈显著差异，氧化温度对菜籽油荧光光谱有明显影响。常温氧化350 d与第1 d相比，菜籽油的特征荧光峰位置无变化，仅在激发波长Ex为620和660 nm附近荧光峰强度发生微弱变化；Schaal烘箱氧化26 d后，在激发波长Ex为620和660 nm附近荧光峰强度显著减弱，且在激发波长Ex为350～450 nm之间有新的荧光峰生成；高温氧化48 h后，Ex为620和660 nm处荧光峰消失，在Ex为400～550 nm处产生显著荧光峰，相对Schaal烘箱氧化，荧光波长发生一定程度红移，这是由于高温氧化过程中油脂氧化生成的物质稳定性较差引起的。利用平行因子分析法对三维同步荧光光谱数据进行分解获取有效的二维荧光光谱数据，当组分数为6，Δλ=60 nm时激发波长的载荷值最大，不同样品间差异最显著。选定Δλ=60 nm波段的二维荧光光谱数据用于智能评价，作为BP神经网络模型的输入值，以极性组分作为模型输出值，分别对菜籽油三种氧化模式数据建模训练。实验结果表明，三种氧化模式对应的训练集、验证集、测试集模型相关系数r均能达到0.9以上，其中常温氧化模式中验证集及测试集模型的相关系数r为1，输出值与目标值较接近，模型的预测效果较好；综合三种氧化模式数据建模，对应训练集、验证集、测试集模型的相关系数分别为0.999，0.913和0.988，均方误差均较小，说明该模型能准确判断菜籽油的不同氧化状态。因此，三维同步荧光光谱技术结合平行因子分析法、BP神经网络法建立快速检测模型能实现菜籽油不同氧化状态的判别，为菜籽油的氧化程度的评价提供新方法，同时为其他食用油的品质评价提供参考。     

Determination of Iron(III) by Room Temperature Ionic Liquids/Surfactant Sensitized Fluorescence Quenching Method

A new method for the determination of iron (III) has been described. The analytical procedure was based on the fluorescence quenching of salicylfluorone (SAF) by iron (III) and the fluorescence quenching value (ΔF) could be increased in the medium of room temperature ionic liquids (RTILs) (1-ethyl-3-methylimidazolium ethyl sulfate)/SDS (sodium dodecyl sulfate). The main factors influencing the fluorescence quenching (ΔF) were investigated in detail. Under the optimal conditions, the linear equation was [Formula: see text](c:μg·mL(-1), r?=?0.9936). The linear range of calibration curve was 0.2-1.1 μg·mL(-1) and the detection limit was 8.3 ng·mL(-1). The preliminary sensitized mechanism was discussed with distribution coefficient and fluorescence quantum yield in different media. The method has been applied to the determination of Fe (III) in water samples with satisfactory results.     

咔唑类化合物的光致发光特性

聚二氯磷腈（PDCP）与N-（6-羟基己基）咔唑发生亲核取代,得到了热稳定性良好（约290 ℃）、玻璃化温度较低（约36 ℃）的光电导材料聚双（6-咔唑基己氧基）磷腈。稳态荧光光谱表明,N-（6-羟基己基）咔唑和聚双（6-咔唑基己氧基）磷腈的荧光发射最大波长分别在410 nm和393 nm,其荧光强度相比于咔唑的最大波长420 nm依次减弱并发生蓝移;瞬态荧光光谱表明聚磷腈的线型主链结构和孤立的d-p杂化轨道体系导致其空间位阻增大,破坏了原有的共轭体系,使聚双（6-咔唑基己氧基）磷腈在不同发射波长下的荧光寿命普遍减小。     

Laser-induced spectral broadening and hole-burning in rare earth doped crystals and coherent optical spectroscopy for frequency upconversion

The excitation spectra for linear fluorescence and for frequency upconversion are recorded in Er³⁺ doped crystal Er:YAG. An excitation induced spectral broadening and hole-burning are shown to appear at the resonant frequency of the linear fluorescence excitation spectrum, where the upconversion is simultaneously enhanced. Rate equation analysis is applied to model the optical pumping processes in the crystal. We present evidence that the induced resonance broadening and hole-burning are the result of excitation competition between the linear absorption and the excited state absorption. Femtosecond pulse pairs are applied to excite the linear and nonlinear frequency conversion, resulting in coherent controlled branching ratio between the linear and nonlinear frequency conversion. The experimental reasults are in good agreement with the numerical evaluation based on optical Bloch equation. PACS 78.47.+p; 42.65.Re; 78.20.Ci     

β-环糊精增敏荧光光谱法对柔红霉素的定量测定

采用荧光光谱法对β-环糊精（β-CD）与柔红霉素（DNR）包结物溶液进行表征。研究了β-CD与DNR之间的超分子包结作用机理,讨论了时间、温度和β-CD浓度对包结反应的影响,建立了新的定量检测微量DNR的方法。研究结果表明,DNR本身具有天然荧光,与β-CD形成1：1的超分子包结络合物后,荧光强度增大,β-CD对DNR有较强的荧光增敏作用。在25℃,pH7.0时,包结常数K=1.26×106L/mol。β-CD增敏荧光定量测定DNR的线性回归方程为y=1.78×107x＋312.76,相关系数为r=0.9953,检测下限为3.77×10-6mol/L。     

Energy transfer in europium doped yttrium vanadate crystals

The absorption, fluorescence and excitation spectra and fluorescence lifetimes were obtained at temperatures from 8 K to room temperature, for single crystals of yttrium vanadate doped with several concentrations of europium. A model is proposed to explain the luminescence properties of YVO₄ crystals based on transitions within the VO^3-₄ ion. The host sensitized energy transfer in YVO₄: Eu³⁺ is explained by amodel based on thermally activated exciton migration. The model predicts the observed temperature and concentration dependences for the fluorescence intensities and lifetimes. The diffusion coefficient, diffusion length, exciton hopping time and trapping rate are determined and compared with similar data obtained on other systems.