Phosphorescence of conjugated poly-<Emphasis Type="Italic">para</Emphasis>-phenylene polymers sensitized by an organometallic complex with a heavy metal atom

We investigated phosphorescence of conjugated poly-para-phenylene polymers sensitized by a dimethylamino derivative of benzyl (DMAB) and a methyl derivative of tri(2-phenylpyridyl)iridium(III) [Ir(meppy)₃]. We found that adding both compounds to the polymer quenches the fluorescence of the polymer and increases its phosphorescence. Although the effectiveness of fluorescence quenching of the polymer is the same, a higher intensity and decay rate of phosphorescence quenching are observed for the polymer activated by the organometallic complex. The results are interpreted in the framework of the model of a remote resonance-enhanced effect of an external heavy atom. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 447–452, July–August, 2007.     

Phosphorescence of pi-conjugated oligomers and polymers

We observed phosphorescence from a ladder-type poly-(para-phenylene) and an analogous oligomer containing five phenylene rings. The spectra are similar to the intrinsic fluorescence spectra and bear out a singlet-triplet splitting of 5000 cm(-1) (polymer) and 6800 cm(-1) (oligomer). Phosphorescence decay of the polymer occurs on a 10-100-micros scale obeying a power law and suggestive of nonradiative quenching, while that of the oligomer is asymptotically exponential with an intrinsic decay time of approximately 250 ms. The polymer also exhibits delayed fluorescence. It originates from delayed recombination of geminate electron-hole pairs rather than from triplet-triplet annihilation.     

利用磷光敏化改善聚合物白光OLED性能

基于新型聚合物白光材料PF-DTFO制备了一种聚合物白光发光二极管(PWOLED),通过在聚合物发光层中掺杂蓝光磷光染料FIrpic,利用磷光敏化发光原理,改善器件电致发光性能。在敏化PWOLED中,掺杂的FIrpic染料作为给体将产生的三重态能量传递给白光聚合物的长波发射基团,进一步提高了长波基团的发光强度,改善了白光光谱,使基色更平衡并且光谱更稳定。驱动电压从8 V增加到16 V时,器件电致发光光谱基本不变,色坐标仅从(0.33,0.38)移动至(0.32,0.38)。敏化后的器件发光效率相对于未掺杂器件提高了38%。     

Femtosecond laser-induced long-lasting phosphorescence in Pr^3＋-doped ZnO-B2O3-SiO2 glass

This paper studies the phenomenon of long-lasting phosphorescence induced by a femtosecond laser in Pr3 -doped ZnO-B2O3-SiO2 glass. With the glass irradiated by a focused femtosecond laser for a short time, the emission of strong reddish long-lasting phosphorescence from the irradiated part of the glass can be observed. The emission peaks are located at 495 and 603 nm in wavelength, showing that the long-lasting phosphorescence originates from the emission of Pr^3 . The intensity of the phosphorescence decreases in inverse proportion to time after the removal of the laser. By analysing the absorption and electron spin resonance spectra of the glass, we find that colour-centres are induced in the glass matrix after the irradiation of the femtosecond laser. A possible mechanism has been provided to account for the generation of long-lasting phosphorescence.     

Annihilation kinetics for triplet excitations in organic glasses

The results of investigations of delayed luminescence decay are presented for disordered phenanthrene in the microsecond, millisecond, and second time ranges. At liquid nitrogen temperature, the highly non-exponential decay of both the phosphorescence and the annihilation delayed fluorescence is observed. This character of decay is caused by the relaxation of the electron-excitation energy in the system of energy-disordered centers when a quantity kT is much less than the width of the distribution for the excited-state energy. At the same time, the analysis of the time dependence for the triplet-triplet-annihilation rate exhibits two time intervals in which different kinetics is observed for the triplet excitations annihilation. In the microsecond range, the classical relationship between the phosphorescence and the delayed fluorescence takes place for the system under investigation; i.e., the triplet-triplet-annihilation rate is constant. At large times, the reaction-rate time dependence is described by the power law characteristic of inhomogeneous and low-dimensional systems. When the temperature increases, a transition to the classical behavior is observed throughout the entire time interval.     

Kinetics of Triplet-Triplet Annihilation in Organic Glasses

In the present paper, the results of the investigation of the decay kinetics of delayed luminescence of organic glasses are presented. A strong deviation of the decay of both phosphorescence and annihilation delayed fluorescence from the exponential law is observed. This effect is shown to be due to the relaxation process of electronic excitation energy in the system with large energetic disorder. At the same time, the presence of two time intervals in which the rate coefficient for triplet-triplet annihilation (TTA) reaction shows different dependence on time is observed. On a short time scale the classical behavior is observed, i.e., the reaction is well described by the second-order equation with a time-independent rate coefficient. At the limit of long times, we have strong dependence of rate coefficient on time, i.e., the electronic excitation energy transport is dispersive. It is shown that behavior observed for the rate coefficient for TTA reaction is due to the relaxation process (on short time scale) and the equilibrium energy migration (in long time limit).     

Characteristic features of carbazole phosphorescence quenching by benzophenone molecules in toluene at 77 K

We have studied the characteristic features of carbazole phosphorescence quenching by benzophenone in toluene at 77 K. We have shown that the decrease in the relative phosphorescence intensity for carbazole (energy donor) by a greater factor than we see for the relative change in its decay time is due to the fact that a change in the phosphorescence decay time occurs only for carbazole molecules participating in triplet-triplet energy transfer, while the substantial decrease in the phosphorescence intensity for carbazole with no change in the phosphorescence decay time is connected with quenching of its singlet states. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 554–556, July–August, 2006.     

The Influence of Human Serum Albumin on The Photogeneration of Singlet Oxygen by meso-Tetra(4-Sulfonatophenyl)Porphyrin. An Infrared Phosphorescence Study

meso-Tetra(4-sulfonatophenyl)porphyrin (TPPS₄) is a water soluble photosensitizer, which is currently clinically tested as a PDT drug. In our contribution, we present IR spectral- and time-resolved phosphorescence data reflecting the influence of human serum albumin (HSA) on singlet oxygen photogeneration by TPPS₄. IR emission of TPPS₄ was studied in samples containing various concentrations of HSA in phosphate buffer. The observed changes in spectral and temporal behaviour of TPPS₄ and singlet oxygen phosphorescence caused by the addition of HSA are equivalent to the effect of nitrogen purging of HSA-free solutions of TPPS₄. The main feature induced by addition of HSA appears to be the occurrence of a long-lived (tens of microseconds) photosensitizer phosphorescence at 900 nm besides ordinary short-lived (≈2 μs) one at 820 nm. It is accompanied by presence of a long-lived component of singlet oxygen emission with lifetime roughly corresponding to that of the long photosensitizer phosphorescence component. Moreover, the quantum yield of singlet oxygen phosphorescence decreases with increasing HSA concentration, while total quantum yield of TPPS₄ phosphorescence rises. These facts are explained by a shielding effect of HSA on bound molecules of TPPS₄ against quenching by oxygen which is analogous to oxygen removal by nitrogen purging.     

On the temperature dependence of the phosphorescence of CaF2 : Mn phosphor in different atmospheres

The temperature dependence inthe region of 24–150°C of the phosphorescence of CaF₂ : Mn phosphor in the atmospheres of nitrogen gas, vacuum and moisture-saturated air were studied. A decay formula was found to adequately describe the rate of decay of the trapped electrons — which is assumed to be proportional to the amount of phosphorescence observed — in thermal traps. In nitrogen gas and vacuum the decay constants of the trapped electrons are dependent only on the storage temperature and not on the storage atmosphere of the phosphor. A slight effect of water on the rate of decay of the trapped electrons was also observed.     

钻石中硼受主电荷转移引发磷光的直接证据

受主元素硼与不带电荷的替位硼进行电荷重组会导致钻石发出磷光,但Ⅱb型钻石硼含量较高,难以为电荷重组与磷光的相关性提供直接证据。作者针对一粒在常光环境下近无色的钻石,利用DiamondViewTM的深紫外强光源照射样品,使之产生蓝绿色磷光,结合前人研究,推断该类型磷光与含硼元素有关。采集样品红外光谱,在磷光消退前,谱图呈现2 803 cm-1吸收峰,磷光消失后采集的红外谱图不显示2 803 cm-1峰。这一实验中受主硼在紫外光激发下失去电子,成为不带电荷的替位硼原子(B0),B0浓度升高超过红外光谱检测限,红外光谱识别到B0的存在,即引发2 803 cm-1吸收峰。处于激发态的电子返回基态与亚稳态的B0结合过程释放出光子产生磷光。该实验首次直接证实了硼受主与无电荷替位硼之间的电荷重组转移会引发钻石磷光。     

Investigation on the improvement of red phosphorescence in CaTiO3:Pr3+ nanoparticles

Red phosphorescence in nanosized CaTiO₃:Pr³⁺ phosphors has been investigated by measuring the spectra of emission and excitation, as well as the charging and decay processes. The emission intensity and the persistent time have been improved. More energy traps have been observed in nanoparticles compared to the bulk powders. The integral emission intensity from the nanoparticles is remarkably greater than that from the bulk. A phosphorescence recombination mechanism through tunneling in nanoparticles is discussed.     

一种独立于激发光脉冲参量的磷光寿命测量方法

脉冲法磷光寿命测量中，激发光脉冲参量（脉冲宽度和形状）、用于磷光强度衰减分析的起始时刻的选取是影响寿命计算准确度的关键因素。以线性时不变系统理论为依据，探讨了磷光强度衰减特性与激发光脉冲参量之间的关系，发现对于有限宽度的激发光，激发光脉冲消失之后的磷光强度衰减特性独立于激发光脉冲参量；选取激发光脉冲消失时刻作为磷光强度衰减分析的起始时刻，可获得准确的寿命计算。利用磷光探针氧卟啉（Oxy-PhorR2）标准试样做了针对性实验，实验结果验证了理论的正确性。     

VUV excitation of benzene : C6H6 and C6D6 fluorescence and phosphorescence in argon and nitrogen matrices

Benzene isolated in argon or nitrogen matrix at about 5 K has been irradiated with photons of 6 eV (206.2 nm), 8.4 eV (147 nm), and 10 eV (123.6 nm) energy. In every case phosphorescence and fluorescence have been observed from the vibrationally relaxed states. The phosphorescence emission is still observed after the extinction of the excitation during the warming up as a thermoluminescence. The phosphorescence versus fluorescence ratio increases when passing from a nitrogen matrix to an argon matrix and as the photon energy increases. The main conclusion is that, in the condensed phase, the electronic relaxation processes leading to the emitting states are not as fast as usually assumed.     

Phosphorescence properties of sol–gel derived ruby measured as functions of temperature and Cr<Superscript>3+</Superscript> content

A novel approach for the contactless measurement of surface temperatures is to evaluate the temperature dependent phosphorescence properties of chromium doped aluminium oxide (ruby) coatings, such as phosphorescence intensity, spectral distribution, or the phosphorescence lifetime. However, these properties are also affected by the chromium content in the films. In the present study the phosphorescence lifetimes were studied for the first time as a function of the chromium content. We use a simple sol–gel depositing technique for the preparation of precisely doped ruby coatings in Si(100) substrates. These coatings (Cr-to-Al-ratios y between 0% and 6.8 at. %) are well suited for studying the influence of the chromium concentration on the phosphorescence properties: at room temperature (294 K), the phosphorescence intensity is strongly affected by the chromium doping (maximum at y∼1–1.5%) while the spectrum shifts only slightly with varying chromium content. The phosphorescence lifetime τ at 294 K remains constant with varying Cr³⁺ content below y∼1.1%, and decreases strongly above y∼1.1%. Thus, ruby doped with y∼1% seems to be most promising as a temperature sensor because it shows the highest phosphorescence intensity and a low variance in the phosphorescence lifetimes. Due to the latter property the temperature evaluation from τ is less affected by imprecise doping. The phosphorescence lifetimes of several sol–gel ruby coatings (y=1.1%) on Si(100) substrates were measured as a function of the temperature to be between 2.7 ms at 294 K and 4 μs at 833 K. PACS 07.20.Dt; 78.55.-m; 78.66.-w     

Phosphorescence of Poly(Methylphenyl)Silane Films

In the 5–100 K temperature range, the photoluminescence spectra of poly(methylphenyl)silane (PMPS) and polystyrene films doped with acetophenone, propiophenone, benzophenone, diphenyl, and naphthalene, as well as the thermostimulated luminescence spectra of neat PMPS films, have been investigated. It has been shown that the PMPS film phosphorescence spectrum consists of a structureless band with a maximum near 450 nm, and the literature structural phosphorescence spectrum of this polymer may belong to an uncontrolled impurity or a defect with chromophore groups of acetophenone.     

Is Phosphorescence Lifetime an Indicator of Angiogenesis in Cortical Sarcoma?

In this paper, the oxygen dependent phosphorescence quenching method is proposed to study the correlation between the phosphorescence lifetime and microvessel density in tumors. In the implementation, the S180 transplanted tumor in the mouse is used for the collection of the time-resolved phosphorescence, the tumor microvessel density is measured by immunohistochemical examination of FVIII, the correlation between microvessel density and phosphorescence lifetime is analyzed by multiple regression method. The results show the phosphorescence decay constant measured in tumors is enlarged in the tumor progression. Furthermore, the relative total microvessel area is positively correlative with the phosphorescence lifetime, which is estimated by a two dimension regression equation. It is concluded phosphorescence lifetime is a valuable indicator of angiogenesis during the tumor development.     

静电纺丝纳米ZrO_2:Ti纤维的制备与发光性质的研究

通过静电纺丝和高温煅烧相结合的方法制备了一维钛掺杂氧化锆的纳米纤维。复合纤维在1 000℃煅烧后,由于模板剂、聚乙烯吡咯烷酮(PVP)在高温下的分解,纤维直径大大减小,扫描电镜观察最终得到直径100 nm左右的单斜相纤维。利用稳态光谱和时间分辨光谱技术室温下研究了纤维的光致发光性质。结果表明发射主峰在467 nm的宽带,在350 nm处有一个小肩峰。两种不同的发光行为可以通过ZrO2∶Ti纳米纤维中存在的两种情况的氧空穴作为电子俘获中心来解释。一种由电荷补偿产生的氧空位,俘获电子,产生467 nm处Ti参与的发光现象。另外一种ZrO2表面缺陷导致的氧空穴,对应于350 nm的发光现象,没有发现长余辉现象。测得的激发态寿命短于体材料而长于普通的纳米晶,可能是由于一维纳米结构的独特性质导致的。     

Long lasting phosphorescence of Eu2+-activated MO-B2O3 glasses

In this letter, Eu 2+ -activated MO-B 2 O 3 (M=Ca, Sr, and Ba) glasses are prepared in reductive atmosphere and their long lasting phosphorescence properties are studied. The intensity of the phosphorescence for the glasses is Sr>Ca>Ba. The light-induced electron paramagnetic resonance signal is observed after the irradiation of an ultraviolet lamp, which is due to the electron trapped by oxygen vacancy. The energy depth of the glasses is calculated using Hoogenstraaten’s method.     

Role of Acids in Producing Ultrabright,Dual-Emissive Carbon Dots and their Urea/Biuret Composites with Ultralong Afterglow

Since 2015, m-phenylenediamines (mPD) have become a popular carbon source for the synthesis of carbonized polymer dots (CPDs). However, their exact fluorescence mechanism is still obscure. To elucidate this, inorganic acids that are carbon-free are chosen as additives for a comparative study. It is found that the green fluorescence quantum yield (nearly 80%), photostability, and reaction yield (over 90%) can be enhanced by introduction of most of inorganic acids with moderate amount. Besides, green-blue dual emission is observed in acid-assisted groups. UV-vis absorption, Fourier-transform infrared spectroscopy, and surface-enhanced Raman scattering results indicate that the green fluorescence center is composed of quinoid rings, whereas the blue fluorophore contains benzenoid rings. Moreover, room-temperature afterglow with lifetime up to 1.25 s is observed exclusively in acid-assisted CPDs composites with urea/biuret. The blue chromophore is proposed to be the origin of the triplet level that induces the long afterglow. This work provides an in-depth understanding on the macromolecular structures of CPDs derived from phenylenediamines, and contributes a new line of thought to the origin of phosphorescence in N-doped carbon dots.     

Properties of low-temperature spectral relaxation of eosin phosphorescence in a glycerol-water mixture

The low-temperature dynamics of the Stokes shift of the instantaneous phosphorescence spectra of eosin in 94% glycerol-water solution is studied upon pulsed excitation. At temperatures T<T _tg , where T _g =183–187 K is the glass transition temperature of the solution, the blue shift of the instantaneous phosphorescence spectra is observed. In the vicinity of T _g , the spectral dynamics undergoes inversion, and the red shift of the instantaneous spectra is observed at temperatures between 188 and 210 K, which is caused by freezing out the orientation mobility of the solvent molecules in the first solvate shells of the chromophore molecule. In the temperature range from 230 to 273 K, the enhancement effect was observed at the initial parts of phosphorescence kinetic curves, which is probably explained by cooperative phenomena in the solvent.