卟啉钯敏化剂构效性质与三线态-三线态湮灭上转换性能研究

上转换发光是一种将长波长的激发光转化为短波长发射的反斯托克斯发光现象,三线态-三线态湮灭上转换（TTA-UC）能够在较低密度能量下被激发,且上转换量子产率高,因此获得研究者们广泛关注。关于敏化剂分子结构与上转换发光性能相关性的研究一直是TTA-UC研究领域的重要热点,选择两种代表性的卟啉钯光敏剂[PdOEP-八乙基卟啉钯(Ⅱ)和PdBrTPP-四溴苯基卟啉钯(Ⅱ)]与蒽衍生物9,10-(4-羟甲基)苯基蒽p-DHMPA发光剂组合上转换体系作为研究模型,通过一系列合成工作获得材料分子后,进一步比较两种敏化剂的光谱性质与体系最终上转换性能之间关系。通过细致研究敏化剂和发光剂的荧光发射和寿命等光谱性质对敏化剂系间窜越,三线态-三线态能量转移及三线态-三线态湮灭等能量传递过程的影响后,发现在532 nm处的摩尔吸光系数PdBrTPP (10.8 cm-1·mmol-1)大于PdOEP (3.0 cm-1·mmol-1);三线态寿命PdBrTPP (173.13 μs)大于PdOEP (109.21 μs)。但与p-DHMPA配对时光敏剂与发光剂的三线态能级差ΔE_TT,PdOEP (0.140 eV)却高于PdBrTPP (0.062 eV),通过Stern-Volmer方程得到Stern-Volmer猝灭常数K_SV和双分子猝灭常数k_q值也是PdOEP略高,最终表现出上转换阈值PdOEP/p-DHMPA (22.40 mW·cm-2)小于PdBrTPP/p-DHMPA (29.78 mW·cm-2),上转换发光效率Φ_UC,PdOEP/p-DHMPA (28.3％)大于PdBrTPP/p-DHMPA (26.8％)。因此,卟啉钯敏化剂的构效对三重态湮灭上转换发光效率影响最为重要的决定因素是敏化剂三线态高低。对于不同的敏化剂,在分子主体结构、摩尔吸光系数与三线态寿命等光谱参数差别不大的情况下,敏化剂的三线态能级越高,就将会具有更大的上转换发光效率。然而如果以总上转换能力指标来评价,PdBrTPP的共轭结构能够提升其在激发波长处吸收更多光子的能力,具有比PdOEP更高的摩尔吸光系数,造成其总上转换能力η比PdOEP高3.4倍。因此从上转换总效能指标来评价,通过敏化剂分子设计调控其在激发光波长处的摩尔吸光系数也不失为一种简单易行的方法。     

光敏聚合中含二苯酮基高聚物的引发作用

合成了多种不同分子量和不同二苯酮侧基含量的高分子敏化剂PVB,从紫外吸收光谱及发射光谱的测定结果表明,PVB基本保持小分子二苯酮(BP)的光化学特性。采用PVB与叔胺组成光敏引发体系引发MMA光聚合时,聚合速度(R_ο)与小分子相比增加二倍以上。而且R_p随PVB分子中二苯酮基含量的增加而增加,当PVB分子量提高时引发聚合能力加强,这和高分子敏化剂分子链中高效率的能量传递以及色基的密集分布特性有关。     

Preparation and luminescence properties of SrTiO3:Pr,Al phosphor from the glycolate method

Spherical SrTiO₃:Pr³⁺,Al³⁺ phosphor with high crystallinity and uniform particle size distribution was formed from the glycolate precursor. The glycolate precursor was obtained by heating the mixed solution of metallic nitrates and titanium oxychloride in ethylene glycol up to 200 °C. The thermal decomposition of the glycolate precursor proceeded through three major stages, i.e., (i) evolution of glycols (∼200 °C), (ii) decomposition of glycolate precursor, and (iii) decomposition of strontium carbonate and crystallization of SrTiO₃:Pr³⁺,Al³⁺ phosphor.SrTiO₃:Pr³⁺,Al³⁺ phosphor exhibited a strong red emission, peaking at about 617 nm. SrTiO₃:Pr³⁺,Al³⁺ phosphor obtained from the glycolate complex has higher luminescent properties than the conventional solid state reaction and the Pechini method in terms of photoluminescence (PL) and cathodoluminescence (CL). High crystallinity, low residual carbon content and small grain size with uniform shape would enhance the luminescence intensity of phosphor by the glycolate method due to high surface area per unit volume and low organic content compared with the Pechini method. Also, Al³⁺ ion is more effective than Ga³⁺ ion to enhance PL intensity of SrTiO₃:Pr³⁺,Al³⁺ phosphor because of smaller Al³⁺ ion radius. Therefore, the glycolate method has been demonstrated to be a convenient and unique process for the production of muticomponent oxide with smaller grain size and higher crystallinity compared with the conventional mixed oxide reaction and the polymer precursor method.     

Photodynamic Therapy: Past,Present and Future

Though we crossed many milestones in the field of medicine and health care in eradicating some deadly diseases over the past decades, cancer remained a challenge taking the lives of millions of people and having adverse effects on the quality of life of survivors. Chemotherapy and radiotherapy, the two existing major treatment modalities, have severe side effects and patients undergoing these treatments experience unbearable pain. Consequently, clinicians and researchers are working for the alternate treatment regimens, which can provide complete cure with minimum or no side effects. To this end, the present review highlights the major advances and future promises of photodynamic therapy, an emerging and promising therapeutic modality for combating cancer. We delve on various important aspects of photodynamic therapy including principle, mechanism of action, brief history and development of photosensitizers from first generation to the existing third generation, delivery strategies, development or suppression of immunity, combination therapy and future prospects.     

The sensitizing effect of acrylates on radiation vulcanization of natural rubber latex

The sensitizing effect of acrylates on radiation vulcanization of natural rubber latex was studied. The results indicate that Gc value of crosslinking (Gc) will be higher at the same radiation dose when a sensitizer exists, and Gc value decreases with the increase of radiation dose (D) conforming to the formula Gc=KD^-α, where K and α are constants depending on sensitizers. The more sensitizers added, the greater the Gc value. However, the viscosity of the natural rubber latex also increases rapidly along with the increase of sensitizers added.Some sensitizers, such as TMPTA, can decrease the optimum dose from about 200 kGy to approximately 20 kGy according to our experiment. The tensile strength of the film can reach round 20 MPa. Other physical properties are comparable to those of unsensitized.     

两种主体材料中Ir(ppy)3和Rubrene的能量传递特性

OLED技术被认为是最有可能取代液晶显示的全新技术,而OLED中的有机电致磷光器件是近年来的研究热点.有机电致磷光器件的发光层往往采用主客体掺杂体系,主客体分子内的能量传递是磷光发光体分子被激发的主要途径,因此选择吸收能量和传递能量好的主体材料是改进有机电致磷光器件性能的主要途径之一.文章分别以PVK和CBP作为主体材料,以磷光材料Ir(PPY)3和荧光材料Rubrene作为掺杂剂,制备了不同配比的器件,研究了主体材料和掺杂剂之间的能量传递特性.结果发现,这两种主体材料分别通过Ir(ppy)3向Rubrene传递能量是主要的能量传递机制,而且CBP作为主体时能量传递比PVK更充分.另外掺入Ir(ppy)3后的器件比不掺Ir(ppy)3的器件在相同电压下的光功率明显增强.当我们增加Ir(PPY)3的浓度时,相同电压下的光功率下降,浓度猝灭效应增强.     

稀土碘氧化物的制备和X-射线分析

用改进的助熔剂法制备了十五个稀土元素(Ⅲ)的碘氧化物。通过化学和X光衍射分析方法确定这些化合物组成为LnOI,并计算了它们的晶胞参数。对Eu(Ⅲ)的碘氧化物异常现象进行了讨论。     

A STUDY ON RADIATION CROSSLINKING OFPOLYDIMETHYLSILOXANE （PDMS） RUBBER LATEX

Polydimethylsiloxane (PDMS) rubber latex with two sorts of sensitizers, trimethylol propane tri-methacrylate (TMPTMA) and diethylene glycol di-acrylate (DEGDA), was irradiated with y-rays and electron beams in various conditions. The radiation crosslinking reaction of PDMS occurs in the inner phase of the latex and is relatively isolated from the water phase. Therefore the oxygen and the radicals produced by the radiolysis reaction of water almost have no effect on the crosslinking reaction of polymer. The experimental data correspond with the Charlesby-Pinner relationship in the main. The gelation doses, degree of crosslinking and degradation as well as G values of crosslinking were calculated. From them, the sensitization coefficients were derived to offer a quantitative measurement of the enhancing effect of sensitizer on the radiation crosslinking.     

Application of Novel Calix[4]arene Metal-free Sensitizers in Dye-sensitized Photoelectrochemical Cells for Water Splitting

A series of novel calix[4]arene metal-free dyes, featuring macrocyclic structure and unique conical conformation, has been introduced into photoanode-based dye-sensitized electrochemical cell system as photosensitizers. The electrochemical properties of the corresponding sensitized photoanodes were systematically studied in the absence/presence of water oxidation catalyst(WOC). Furthermore, the visible-light-driven overall water-splitting reactions were conducted by fully assembled devices, obtaining a performance trend of Calix-3 > Calix-2 > Calix-1. The corresponding device of Calix-3 exhibited the best photoactivity, giving an initial photocurrent density of ca. 300 μA/cm², an IPEC peak value of ca. 9.0% at 365 nm and a wide photo-respond band up to ca. 620 nm. The best performance of Calix-3 can be attributed to its most effective light-harvesting ability, best ICT transition property, highest oxidation potential and thus best ability of activating WOC. This work offers an inspiration for the application of new-type effective metal-free sensitizers in photocatalytic water-splitting device.     

Photochemical synthesis of copper nanoparticles incorporated in poly(vinyl pyrrolidone)

The effect of the presence of poly(vinyl pyrrolidone) (PVP) on the copper nanoparticle formation, obtained by UV irradiation of ethanol solution of Cu(acac)₂ (acac = 2,4-pentanedionato), was investigated. At 254 nm, in conditions of light completely absorbed by complex, the PVP exhibited protective and stabilizing effects, as shown by the formation of a colloidal copper solution and by a block of the heterogeneous process, which leads to thin film formation on the quartz walls. The colloidal solution was tested for several months by plasmon position and it was found that it remained unaltered in inert atmosphere, but returned to the starting complex on contact with air. The PVP ability to control the particle size was investigated by carrying out photoreduction sensitized by Hacac at 254 and 300 nm, in the presence of PVP concentration varying from 0 to 0.2 M. In this range it was possible to obtain copper nanoparticles of dimensions decreasing from 30 to 4 nm. Besides this, the PVP (0.005–0.05 M) role as sensitizer was investigated by irradiating solutions of Cu(acac)₂ at 300 nm which is an inactive wavelength for copper reduction by direct light absorption. It was found that the PVP was an efficient sensitizer of the copper photoreduction. The nanoparticles were characterized by plasmon band, Trasmission Electron Microscope (TEM) as well as Dynamic Light Scattering (DSL) analysis. The overall results evidence the advantages of the PVP use in the nanoparticle copper formation through the photochemical technique such as the exclusive formation of colloidal copper, their size control, stable colloidal solution and complete return to the starting complex.