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反应型转光剂制备及其与聚乙烯接枝研究
No full text有机染料类转光剂制备的转光棚膜相较稀土类具有透光性好等优点，但是存在转光剂与聚乙烯等常用基材相容性低导致喷霜等问题，因此需要对有机染料和基材分别进行改性。本论文以制备耐迁移的有机染料类转光膜为目的，合成了两种反应型转光剂N-烯丙基-4-甲氧基-1,8-萘酰亚胺(MOANI)和N, N’-二烯丙基-1,6,7,12-四(4-叔丁基苯氧基)-苝-3,4,9,10-四甲酰二亚胺(DAPBI)，并采用预辐照与熔融接枝联用技术，将两种反应型转光剂接枝到了线性低密度聚乙烯(LLDPE)上，发展了接枝率的测定及转光膜耐迁移性的测试方法，最终制备出了比常规掺混转光膜耐迁移性能更高的荧光有机染料类转光膜。 首先，以4-氯-1,8-萘二甲酸酐为原料通过一锅法一步制得了MOANI；以N,N’-二正丁基-1,6,7,12-四(4-叔丁基苯氧基)-苝-3,4,9,10-四甲酰二亚胺为原料，经水解、烯丙基化，两步制得DAPBI。采用质谱，红外光谱，核磁共振证明了两种产物的组成结构。采用紫外可见及荧光分光光度法测试了产物在溶液中的吸收及发射光谱，两种光谱证明MOANI及DAPBI可以作为转光剂。 随后，将MOANI及DAPBI分别与预辐照的线性低密度聚乙烯进行熔融接枝，纯化后，采用紫外可见、荧光、红外光谱法以及氢核磁共振波谱法对接枝物的结构进行了表征，结果证明MOANI及DAPBI已经分别接枝到了LLDPE分子链上。通过紫外可见分光光度法建立了一套接枝率(GD)的测定方法，测定了两种接枝聚合物的接枝率并计算了接枝效率(GE)，并用其研究了初始单体浓度、反应温度、反应时间三种因素对GD及GE的影响。结果表明，两种单体的接枝率均随这三种因素的增加而增加，但初始单体浓度对MOANI接枝率的影响最大，反应温度对DAPBI的影响最大；相同反应温度及时间的条件下，MOANI的初始单体浓度在1.5wt%时接枝效率最大，DAPBI在0.3wt%时GE最大。对两种接枝物的流变性能、热学性能和样品表面性质的研究表明：1. pi-LLDPE在熔融状态下会发生分子链交联，从而产生长支链，而两种单体的接枝会减少交联过程的发生；2. 接枝上的单体起到了异相成核剂的作用；3. 纯化后的接枝聚合物在与共混物相同荧光性能的条件下不会发生喷霜现象。 最后，为了更贴近工业生产的实际，我们通过预辐照与反应挤出接枝连用技术及色母粒技术制备了一系列浓度未经纯化的接枝聚合物，并研究了它们吹塑成膜后的紫外耐候性能和迁移析出性能。一、紫外耐候性能的研究：我们将紫外耐候试验仪不同时间老化后的样品用荧光分光光度计及万能拉力机测试，得到了老化条件下薄膜的荧光衰减性质及力学老化性质。研究表明：1.接枝上的单体减小了荧光的衰减速率；2.MOANI起到了紫外线吸收剂的作用，但DAPBI却起到了光敏剂的作用。二、薄膜转光效果的评价：我们以氙灯为光源，通过光谱验证仪对所有薄膜样品的透过光谱进行了研究，研究表明：未经纯化的LLDPE-g-MOANI膜起到了紫外转蓝作用，增强了聚乙烯薄膜在400~500nm间的透过光强，初始MOANI浓度为0.15 wt%的膜在该范围内透过光强与300~750nm总透过光强的积分相较LLDPE增加了2.5%；未纯化LLDPE-g-DAPBI膜起到了黄绿转橙红的作用，增强了聚乙烯薄膜在600~750nm间的透过光强，初始DAPBI浓度为0.09 wt%的膜在该范围内透过光强与300~750nm总透过光强的积分比较LLDPE增加了1.7%，此外其红光/远红光量比相较LLDPE膜增加了0.033。三、迁移析出性能的研究：结合转光膜实际使用的特点，我们用流滴膜的测试装置——加速流滴仪结合荧光分光光度计测定了两种接枝聚合物薄膜因单体迁移析出造成的荧光衰减性质。经60℃加速诱导，22天后，初始单体浓度为0.15wt%的未纯化LLDPE-g-MOANI膜（所用1wt%色母粒GD=0.17wt%）的蓝色荧光占初始强度的百分数为64.5%，而对比的同初始浓度的共混膜只有41.6%；相同条件下，47天后，含有流滴剂且初始单体浓度为0.13wt%未纯化LLDPE-g-DAPBI膜（所用1wt%色母粒GD=0.10wt%）的红色荧光占初始强度的百分数为58.4%，而对比的同初始浓度的共混膜只有42.0%。结果表明：接枝上的单体抑制了未接枝单体的迁移析出过程。此外通过复配我们发现，两种接枝物的复配更能延缓未接枝单体的迁移渗出过程。As one kind of light-converting agents, fluorescent organic dyes are widely used, because they are molecular dispersion in the polymer than rare earth type light-converting agents. Unfortunately, fluorescent organic dyes lack an affinity for aliphatic hydrocarbons, consequently migrate to the surface of polyolefins and even crystallize on the surface, so the dyes or polyethylene need to be modified. In this work, we synthesized two polymerisable light-converting agents, 4-methoxy-N-allyl-1,8-naph -thalimide (MOANI) and N,N'-diallyl-1,6,7,12-tetra(4-tert-butylphenoxy)-perylene-3,4, 9,10-tetracarboxylic bisimide (DAPBI), grafted them onto linear low density polyethylene (LLDPE) with the pre-irradiation and melt grafting joint technology and finally the two modified LLDPEs showed the potential application in long-term light-converting films. Firstly, MOANI was synthesized from 4-chloro-1,8-naphthalic anhydride through using a one-pot method. DAPBI was synthesized from N,N'-di-n-butyl-1,6,7,12-tetra(4 -tert-butylphenoxy)-perylene-3,4,9,10-tetracarboxylic bisimide through using hydrolyzation and allylation reaction successively. The chemical structures of products were proved through using MS, FTIR and NMR. The absorption and emission spectra were obtained through using UV/vis spectrometer and fluorospectrometer, and they prove that MOANI and DAPBI can be as light-converting agents. Secondly, MOANI and DAPBI were respectively grafted onto pre-irradiated linear low density polyethylene (LLDPE) with a melt reactive mixing process, and charactered spectral, thermo and rheological properties of two grafting polymers (LLDPE-g-MOANI, LLDPE-g-DAPBI) obtained in mixer after purification. By comparing UV/vis, fluorescence, FTIR, 1HNMR spectra of the LLDPE, two grafting polymers and two polymerisable light-converting agents, it was proved that MOANI and DAPBI were grafted on LLDPE. The grafting degree (GD) of MOANI or DAPBI in LLDPE-g-MOANI or LLDPE-g-DAPBI was determined by UV/Vis spectra and relevant grafting efficiency (GE) was also calculated. The effects of monomer concentration, chamber temperature and reaction time on GD and GE were systematically studied. The results show that GDs of MOANI and DAPBI increased with increasing initial monomer concentration, chamber temperature and reaction time. However, the initial monomer concentration and chamber temperature are the main processing parameters for controlling the GD to MOANI and DAPBI, respectively. In the same chamber temperature and reaction time, the highest GE of MOANI was reached in 1.5wt% of initial monomer concentration of MOANI, but in 0.3wt% of initial monomer concentration of DAPBI. The rheological behaviors of LLDPE-g-MOANI and LLDPE-g-DAPBI suggest that the crosslinking of LLDPE can be inhibited effectively by graft of MOANI and DAPBI. The grafted monomer acts as a nucleation agent, which improves the crystallization rates of LLDPE molecular chains. Surface morphologies of LLDPE-g-MOANI and LLDPE-g-DAPBI demonstrating the grafted monomer are difficult to migrate to the surface of the films. Finally, accelerated migration and UV weathering of blown films of unpurified LLDPE-g-MOANI and LLDPE-g-DAPBI obtained in extruder were tested in order to close to actual industrial production. Mechanical properties of unpurified LLDPE-g-MOANI films as function of UV weathering period mean that MOANI acts as the role of ultraviolet absorber and inhibited the aging process of LLDPE. But for unpurified LLDPE-g-DAPBI films, DAPBI acts as the role of sensitizer and accelerated the aging process of LLDPE. The test results of spectrograph suggest that unpurified LLDPE-g-MOANI and LLDPE-g-DAPBI films can increase light intensity of blue-violet light and orange-red light compared with LLDPE film, respectively. Besides, the intensity ratio of red and far-red light of unpurified LLDPE-g-DAPBI film with 0.09 wt% DAPBI initial concentration increased by 0.033, compared with LLDPE film. The test results of accelerated migration and UV weathering indicate that migration processes of the free MOANI or DAPBI in unpurified LLDPE-g-MOANI or LLDPE-g-DAPBI films were delayed effectively by the grafted MOANI or DAPBI in these films. Through blown films of mixture of unpurified LLDPE-g-MOANI and LLDPE-g-DAPBI, migration processes of the free MOANI or DAPBI were delayed further, compared with unpurified LLDPE-g-MOANI or LLDPE-g-DAPBI with same MOANI or DAPBI initial concentration
钛/铝配合物催化剂下二氧化碳共聚物的合成
No full text钛/铝配合物催化剂下二氧化碳共聚物的合成 摘要 学生：王勇（高分子化学与物理） 导师：王佛松 院士 王献红 研究员 二氧化碳储量丰富，价格低廉，是一种理想的C1资源，以二氧化碳为原料合成大宗小分子化合物已有很多工业化案例。二氧化碳和环氧化合物的共聚反应是少有的能够净消耗二氧化碳的反应过程，同时能够生成生物可降解塑料，有望成为传统的非降解聚烯烃塑料的替代品，解决日益严重的白色污染问题。因此二氧化碳和环氧化物共聚也具有很好的工业化潜力。目前钴系配合物(Salen)Co(III)X为代表的催化体系已经显示了很高的催化活性和产物选择性，但是Co是一种有毒金属，在各种行业标准被被严格限制使用，尤其是作为生物降解塑料使用必须满足可堆肥的前提，但Co系催化剂在产品中可能的残余是该催化体系的一个瓶颈问题，影响了其工业化应用。但是从学术研究的角度来分析，钴系催化剂的设计理念和催化机理的研究为新催化体系的研发具有很大的借鉴价值。本文正是以Co系催化剂的设计理念为基础，以环境友好型金属为催化中心代替钴，发展钛系催化剂和双官能卟啉铝催化剂，探索其对二氧化碳和环氧化合物的共聚反应的催化行为。所取得的主要结果如下： 1．根据(Salen)Co(III)X体系催化二氧化碳和环氧化合物共聚的机理，在Salen配体的衍生物Salalen上引入活泼氢，用强碱拔去活泼氢使Salalen能够提供-3价配位环境，合成了与(Salen)Co(III)X结构类似的四价钛配合物 (Salalen)Ti(IV)Cl。在季铵盐类助催化剂[PPN]Cl作用下，能够催化二氧化碳和环氧环己烷（CHO）共聚，得到完全交替结构的共聚物，同时显示出活性聚合的特征。但是作为钛的最高氧化态，四价钛形成的Ti-O键极性较弱，阻碍了二氧化碳和环氧环己烷共聚合的链增长反应，在70oC和4.0MPa下反应的TOF仅为24h-1，且反应温度升高会导致大量环状碳酸酯副产物的生成 2．为增强Ti-O键的极性，合成了三价钛为中心金属的配合物(Salen)Ti(III)Cl，在70 oC和4.0 MPa下催化二氧化碳和环氧环己烷的共聚反应， TOF达到84h-1。同时发现 (Salen)Ti(III)Cl有良好的热稳定性，高温下依然保持高的产物选择性，在120oC和4.0MPa下的TOF高达577h-1，且没有环状碳酸酯副产物生成，并且聚合物为完全交替结构。 3．以季铵盐双官能团卟啉铝催化体系为基础，将大位阻有机碱1,5,7-三氮杂双环[4,4,0-癸-5-烯]（TBD）引入到卟啉铝，合成了有机碱双官能团卟啉铝配合物，用于催化二氧化碳和环氧丙烷（PO）的共聚反应。与双官能团季铵盐卟啉铝催化剂相比，有机碱双官能团卟啉铝铝催化体系有更高的催化活性和产物选择性。在90oC和3.0MPa下TOF高达1400h-1，聚合物的选择性89%。 4．引入不对称卟啉配体，合成了官能度为1，2，4的双官能团卟啉铝配合物，分别研究了官能度对有机碱双官能团卟啉铝体系和季铵盐双官能团卟啉铝体系催化性能的影响。发现随着官能度增加，有机碱双官能团卟啉铝催化活性升高，产物选择性保持不变，而季铵盐双官能团卟啉铝催化活性升高，产物选择性逐渐降低。Copolymerization of CO2 and Epoxides under Titanium or Aluminum Complex Catalyst Abstract Yong Wang (Polymer Chemistry and Physics) Directed by: Professor Fosong Wang Professor Xianhong Wang The utilization of CO2 as C1 resource has attracted extensive attention because it is inexpensive, rich and renewable carbon resource. Selective transformation of CO2 into biodegradable polycarbonates by alternating copolymerization with epoxides is an important green polymerization process, having great potentiality in industrialization. Such a reaction not only provides a net CO2 consuming process benefitting the environment, but also produces biodegradable polymers as possible solution to the white pollution problem due to the overuse of non-biodegradable. Among all the catalyst system ever developed till now, (Salen)Co(III)X displayed most ideal features like high catalytic activity and excellent polymer selectivity, as well as producing polymer with strict alternating structure and high molecular weight, however, the toxic feature of cobalt keeps it away from industry application, since the cobalt residue in biodegradable plastics is not acceptable, especially for the soil compostable requirement in which the toxic cobalt is strictly limited. In this thesis, environment-friendly catalyst based on titanium and aluminum complexes were designed and synthesized, inspired by the mechanistic understanding and designing strategy in (Salen)Co(III)X system. The main results are presented as follows. 1. Based on the mechanism understanding of (Salen)Co(III)X system, tetravalent titanium complexes were prepared from salen ligand (salen-H2= N, N-bis(3, 5-di-tert-butylsalicylidene)-1,2-benzenediamine) and its half saturated form salalen, and used as catalysts in combination with bis(triphenylphosphino)iminium chloride ([PPN]Cl) for coupling reaction of CO2 and cyclohexene oxide (CHO). Salen titanium complex (Salen)Ti(IV)Cl2 showed moderate activity producing unique cis-isomer of cyclic carbonate with high conversion up to 100% in 8h, however, it could not catalyze the copolymerization reaction. While salalen titanium complex (Salalen)Ti(IV)Cl was effective for the copolymerization of CO2 and CHO, where only one chain grew on Ti during chain propagation reaction, yielding completely alternating copolymer with -OH and -Cl as terminal groups. 2. In order to strengthen the polarity of Ti-O bond to accelerate the rate of chain propagation reaction, trivalent titanium complex combining salen ligand (salen-H2=N,N-bis(3,5-di-tert-butylsalicylidene)-1,2-benzenediamine) was synthesized, and used as catalyst for copolymerization of CO2 and cyclohexene (CHO). In combination with onium salt [PPN]Cl, (Salen)Ti(III)Cl, trivalent titanium complex showed impressive activity and selectivity, yielding completely alternating copolymer without the formation of cyclohexene carbonate (CHC), with turnover frequency (TOF) of 557 h-1 at 120 oC, which was more than 10 times higher than that from (Salalen)Ti(IV)Cl, and approaching that from the toxic Cr complex. In addition to the biocompatibility of Ti, thermally robust character resulting from the reducibility of trivalent Ti was industry desirable. 3. Bifunctional aluminum prophyrin complex bearing steric Lewis base 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) on the ligand framework was prepared, and used as catalyst for the copolymerization of CO2 and propylene oxide (PO). It displayed superior catalytic activity and selectivity compared to its quaternary ammonium salt analog, a TOF of 1,400 h-1 was achieved a t 90 oC under 3.0 MPa. 4. Asymmetric porphyrin ligand was designed, and bifunctional aluminum porphyrin with functionality of 1, 2 and 4 were synthesized. As for bifunctional aluminum porphyrin anchored with steric Lewis base, the catalytic activity increased with the increase of functionality, while the selectivity maintained almost the same, while the quaternary ammonium salts analogs showe
稀土单分子磁体的设计、合成及其磁性研究
No full text本学位论文围绕如何提升稀土化合物的单分子磁体性质这一核心问题进行了深入、系统的研究。主要内容分为四个部分，涵盖了单核、双核及四核稀土单分子磁体的磁性调控。对于单核稀土单分子磁体，主要探索了低配位稀土化合物的磁性，发现了第一个赤道配位的Er单分子磁体。在Dy2化合物中通过配体的调整及构筑单元组装等方法有效增强了稀土离子的轴向性及磁相互作用，成功地提高了化合物的单分子磁体性质。对于更加复杂的Dy4化合物，我们通过配位阴离子的调节，实现了化合物中反铁磁到铁磁相互作用的转变并极大提高了有效能垒。这些研究成果为设计、合成新的稀土单分子磁体提供重要的依据。具体内容分为以下四个方面： 1. 从晶体结构、静态及动态磁学性质、理论计算等方面对一系列低配位稀土化合物（1-7）的单分子磁体性质进行了深入的研究。其中，三配位化合物（1, 2）具有明显的赤道类型晶体场，而在其他化合物（3-7）中，负电荷同样集中在稀土离子的赤道位置，这为探索赤道类型晶体场对稀土单分子磁体行为的影响创造了有利条件。研究结果表明，三配位ErIII配合物1是第一个赤道类型的稀土单分子磁体，并且随赤道类型晶体场的减弱，Er化合物的单分子磁体性质减弱，而DyIII化合物的单分子磁体性质则显著增强，这与静电排斥模型的预测完全一致，从头计算进一步支持了以上实验结果。然而，对于一系列DyIII化合物静电势的计算也启示我们在设计稀土单分子磁体时并不能简单地考虑晶体场类型即静电排斥模型，同时也应该注意到分子本身的对称性。 2. 围绕配位构型对Dy2单分子磁体弛豫行为的影响，我们设计了类似于皮考林酰腙配体的西弗碱配体H3L1和尾端弯曲的8-羟基喹啉酰腙配体H2L2。将两个新配体与稀土盐反应，分别得到了一个醇氧桥连的带有呼啦圈构型的Dy2化合物8及一个配体交叉且呼啦圈构型遭到明显破坏的Dy2化合物9，并对他们进行了磁学表征。化合物8中，强磁相互作用及强单离子各向异性两者结合，有效抑制了低温区的量子隧穿，表现出较强的单分子磁体行为。与此相反，由于轴向配位环境的破坏，在化合物9中没有观察到单分子磁体行为。 3. 利用多齿salen型西弗碱配体H2L3合成了一系列3d-4f配合物（10-13），通过实验条件的控制，实现了[DyM]（M = ZnII，CuII）单元的连接。在[DyZn]2分子中，两个[DyZn]构筑单元的连接明显改变了DyIII离子周围的配位构型，进而有效增强了DyIII离子的单轴各向异性，并且CO32-离子的连接促使Dy离子之间呈现了明显的铁磁相互作用。结果，与[DyZn]化合物相比，[DyZn]2化合物的单分子磁体行为显著提升。这是一个通过构筑单元的组装实现单分子磁体行为提升的范例，对新型分子磁性材料的设计具有重要的指导意义。 4. 通过salen型西弗碱配体合成了三个平面Dy4（14-16）及一个Dy2Ba2（17）配合物，四个分子都呈现了中心对称的双缺角立方烷结构。尽管14-16结构极为相似，然而配位阴离子的变化却造成了分子内磁相互作用由反铁磁到铁磁的转变，严重影响了配合物的弛豫行为。相比其他两个化合物，有SCN-配位的Dy4分子展示了更加清晰的双弛豫过程，有效能垒也得到了极大提高。由于该系列化合物结构类似，我们不能简单地将双弛豫过程归因于分子中存在的两个不同金属中心，其实，磁相互作用的调整也可能对弛豫动态学产生重要影响。The thesis focuses on how to enhance the magnetic properties of lanthanide single molecule magnets (SMMs), and can be divided into four main parts, containing the modulations of SMM properties in mono-, bi-, and tetranuclear lanthanide complexes, where some significant breakthroughs were obtained. Herein, the magnetic properties of low-coordinate lanthanide complexes were explored firstly, leading to the discovery of the first equatorially-coordinated Er-based SMM. Furthermore, the axial anisotropies and intramolecular magnetic interactions in Dy2 complexes were improved effectively through the elaborate choice of bridging ligand or the linking of building units, resulting in their enhanced SMM behaviors. Remarkably, in more complicated Dy4 complexes, the intramolecular magnetic interactions change from antiferromagnetic to ferromagnetic as a result of the changes of coordinate anions, which further leads to the observation of two-step relaxation and the obvious improvement of effective barriers. The above results serve as the important avenues to improve SMM properties. More details are as follows： 1. We have investigated the magnetic anisotropy and relaxation dynamics of low-coordinate lanthanide complexes (1-7) through a combined experimental, ab initio and electrostatic potential study. Herein, the almost perfect equatorial crystal field occurs in three coordinate complexes (1, 2),while in other complexes ligands with negative charges are still concentrated in the equatorial positions of lanthanide ions, which enables us to explore the effects of equatorially shaped crystal field on the magnetic performances of theses complexes. Therefore, the three coordinate Er complex behaves as the first equatorially coordinated mononuclear Er SMM. In contrast, SMM behaviors are weakened gradually with the changing coordination geometries from triangle to tetrahedron and trigonal bipyramid in Er-based complex due to the breaking of equatorially coordinating crystal field, and reversely the obvious SMM behavior occurs in five-coordinateDy complex. Significantly, the results of theoretical calculations rationalized the change of SMM behavior originating from the equatorially coordinating crystal field. Nevertheless, the comparison of electrostatic potential maps for three Dy-based complexes revealed that one should simultaneously take a look at both the shape of the crystal field and molecular symmetry to tune the magnetic properties of a SMM. 2. Two novel Dy2 compounds (8 and 9) have been assembled from different types of ligands (H3L1 and H2L2), where H3L1 resembles the previous picolinoylhydrazone ligand, while a bended end is present in H2L2. Compound 8 with H3L1 represents the rare alkoxide-O bridged Dy2 complex and displays the hula hoop-like coordination geometry around each DyIII ion, thus leading to the typical SMM behavior combined with the strong ferromagnetic interactions between DyIII ions. The distorted coordination geometry around DyIII ion and much weaker interactions were observed in compound 9 due to the introduction of bent H2L2, thus resulting in the disappearance of SMM behavior 3. The reactions between a salen ligand (H2L3) and different metal salts lead to the formation of four 3d-4f [MDy] and [MDy]2 (M = Zn/Cu) compounds (10-13), where the [MDy]2 can be considered as resulting from the assembly of two [MDy] building blocks. The [ZnDy]2 compound (11) demonstrates typical single molecule magnet (SMM) behavior, which should originate from the high axial anisotropy of Dy ions correlating to the change of coordination geometry and enhanced ferromagnetic interactions between Dy ions via the coupling of two [DyZn] units. The result suggests the positive effects of coupling blocking units to enhance their SMM behavior, presenting a promising strategy for constructing efficient heterometallic SMMs. 4. Three planar Dy4 (14-16) and one Dy2Ba2 (17) SMMs have been assembled using a multidentate salen-type ligand. Althoug
The structure and function of cell membranes examined by atomic force microscopy and single-molecule force spectroscopy
No full textThe cell membrane is one of the most complicated biological complexes, and long-term fierce debates regarding the cell membrane persist because of technical hurdles. With the rapid development of nanotechnology and single-molecule techniques, our understanding of cell membranes has substantially increased. Atomic force microscopy (AFM) has provided several unprecedented advances (e.g., high resolution, three-dimensional and in situ measurements) in the study of cell membranes and has been used to systematically dissect the membrane structure in situ from both sides of membranes; as a result, novel models of cell membranes have recently been proposed. This review summarizes the new progress regarding membrane structure using in situ AFM and single-molecule force spectroscopy (SMFS), which may shed light on the study of the structure and functions of cell membranes
Lanthanide Ion Codoped Emitters for Tailoring Emission Trajectory and Temperature Sensing
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Unlocking the energy capabilities of micron-sized LiFePO4
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Individual Surface-Engineered Microorganisms as Robust Pickering Interfacial Biocatalysts for Resistance-Minimized Phase-Transfer Bioconversion
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Trivalent Titanium Salen Complex: Thermally Robust and Highly Active Catalyst for Copolymerization of CO2 and Cyclohexene Oxide
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How to split a G-quadruplex for DNA detection: new insight into the formation of DNA split G-quadruplex
No full textHere, we get a new insight into the formation of a split G-quadruplex from the viewpoints of the split mode and guanine base number. An unusual result is that the split mode 4 : 8 performed best in six split modes, including the frequently used mode 1 : 3 and 2 : 2 in the split G-quadruplex enhanced fluorescence assay. Circular dichroism spectra verified the conclusion. The application of the split G-quadruplex based assay in DNA detection was performed on the point mutations of the JAK2 V617F and HBB genes. A multi-target analysis method based on a pool of G-segments split from T30695 (GGGTGGGTGGGTGGGT) by the magic "law of 4 : 8" was established
Growth of lanthanide-doped LiGdF4 nanoparticles induced by LiLuF4 core as tri-modal imaging bioprobes
No full textMultimodal imaging can compensate for the deficiencies and incorporate the advantages of individual imaging modalities. In this paper, we demonstrated the synthesis of core-shell nanocomposites LiLuF4@LiGdF4:Yb,Er/Tm constituted of tetragonal LiLuF4 nanoparticles as core and Yb,Er/Tm-codoped LiGdF4 as shell. LiLuF4@LiGdF4:Yb,Er/Tm nanoparticles display brighter upconversion luminescence (UCL) than NaGdE4:Yb,Er/Tm nanoparticles with the same size under continuous-wave excitation at 980 nm. The active shell layer of LiGdF4:Yb,Er/Tm not only provide the UCL center, but also serve as magnetic resonance (MR) imaging contrast agent. To further improve the UCL intensity, the inert LiGdF4 shell was coated on the LiLuF4@LiGdF4:Yb,Er/Tm nanoparticles. Furthermore, LiLuF4@LiGdF4:Yb,Tm@LiGdF4 nanoparticles have been successfully applied to UCL/X-ray computed tomography (CT)/MR tri-modal imaging on the modal of tumor-bearing mice. (C) 2015 Elsevier Ltd. All rights reserved