Preparation of Pt–CeO2/MWNT nano-composites by reverse micellar method for methanol oxidation

We report the preparation of Pt–CeO₂ nanoparticles on the multi-walled carbon nanotubes (MWNTs) by a reverse micellar method. Transmission electron microscopy (TEM) analysis indicated that well-dispersed small Pt–CeO₂ nanoparticles were formed on the MWCNTs. X-ray diffraction (XRD) analysis confirmed the formation of the Pt–CeO₂ nanoparticles on the MWNTs. Cyclic voltammetry (CV) results demonstrated that the Pt–CeO₂/MWNT exhibited a higher methanol oxidation than did the Pt/MWNT catalyst. The CO stripping test showed that CeO₂ can make CO stripped at a lower potential, which is helpful for CO and methanol electro-oxidation.     

Sonocatalytic injury of cancer cells attached on the surface of a nickel–titanium dioxide alloy plate

The present study demonstrates ultrasound-induced cell injury using a nickel–titanium dioxide (Ni–TiO₂) alloy plate as a sonocatalyst and a cell culture surface. Ultrasound irradiation of cell-free Ni–TiO₂ alloy plates with 1 MHz ultrasound at 0.5 W/cm² for 30 s led to an increased generation of hydroxyl (OH) radicals compared to nickel–titanium (Ni–Ti) control alloy plates with and without ultrasound irradiation. When human breast cancer cells (MCF-7 cells) cultured on the Ni–TiO₂ alloy plates were irradiated with 1 MHz ultrasound at 0.5 W/cm² for 30 s and then incubated for 48 h, cell density on the alloy plate was reduced to approximately 50% of the controls on the Ni–Ti alloy plates with and without ultrasound irradiation. These results indicate the injury of MCF-7 cells following sonocatalytic OH radical generation by Ni–TiO₂. Further experiments demonstrated cell shrinkage and chromatin condensation after ultrasound irradiation of MCF-7 cells attached on the Ni–TiO₂ alloy plates, indicating induction of apoptosis.     

Near-infrared quantum cutting in Yb3+ ion doped strontium vanadate

The materials Sr_3−x(VO₄)_2:xYb were successfully synthesized by co-precipitation method varying the concentration of Yb³⁺ ions from 0 to 0.06 mol. It was characterize by powder X-ray powder diffraction (XRD) and surface morphology was studied by scanning electronic microscope (SEM). The photoluminescence (PL) properties were studied by spectrophotometers in near infra red (NIR) and ultra violet visible (UV–VIS) region. The Yb³⁺ ion doped tristrontium vanadate (Sr₃(VO₄)₂) phosphors that can convert a photon of UV region (349 nm) into photons of NIR region (978, 996 and 1026 nm). Hence this phosphor could be used as a quantum cutting (QC) luminescent convertor in front of crystalline silicon solar cell (c-Si) panels to reduce thermalization loss due to spectral mismatch of the solar cells. The theoretical value of quantum efficiency (QE) was calculated from steady time decay measurement and the maximum efficiency approached up to 144.43%. The Sr_(3−x) (VO₄)_2:xYb can be potentiality used for betterment of photovoltaic (PV) technology.     

Light scattering of nanocrystalline TiO2 film used in dye-sensitized solar cells

This paper studies the light scattering and adsorption of nanocrystalline TiO2 porous films used in dye-sensitized solar cells composed of anatase and/or rutile particles by using an optical four-flux radiative transfer model. These light properties are difficult to measure directly on the functioning solar cells and they can not be calculated easily from the first-principle computational or quantitative theoretical evaluations. These simulation results indicate that the light scattering of 1 25 nm TiO2 particles is negligible, but it is effective in the range of 80 and 180 nm. A suitable mixture of small particles （10 nm radius）, which are resulted in a large effective surface, and of larger particles （150 nm radius）, which are effective light scatterers, have the potential to enhance solar absorption significantly. The futile crystals have a larger refractive index and thus the light harvest of the mixtures of such larger rutile and relatively small anatase particles is improved in comparison with that of pure anatase films. The light absorption of the 10μm double-layered films is also examined. A maximal light absorption of double-layered film is gotten when the thickness of the first layer of 10 urn-sized anatase particles is comparable to that of the second larger rutile layer.     

Social behavior of bacteria: from physics to complex organization

I describe how bacteria develop complex colonial patterns by utilizing intricate communication capabilities, such as quorum sensing, chemotactic signaling and exchange of genetic information (plasmids) Bacteria do not store genetically all the information required for generating the patterns for all possible environments. Instead, additional information is cooperatively generated as required for the colonial organization to proceed. Each bacterium is, by itself, a biotic autonomous system with its own internal cellular informatics capabilities (storage, processing and assessments of information). These afford the cell certain plasticity to select its response to biochemical messages it receives, including self-alteration and broadcasting messages to initiate alterations in other bacteria. Hence, new features can collectively emerge during self-organization from the intra-cellular level to the whole colony. Collectively bacteria store information, perform decision make decisions (e.g. to sporulate) and even learn from past experience (e.g. exposure to antibiotics)-features we begin to associate with bacterial social behavior and even rudimentary intelligence. I also take Schrdinger’s’ “feeding on negative entropy” criteria further and propose that, in addition organisms have to extract latent information embedded in the environment. By latent information we refer to the non-arbitrary spatio-temporal patterns of regularities and variations that characterize the environmental dynamics. In other words, bacteria must be able to sense the environment and perform internal information processing for thriving on latent information embedded in the complexity of their environment. I then propose that by acting together, bacteria can perform this most elementary cognitive function more efficiently as can be illustrated by their cooperative behavior.     

基于超短脉冲的癌细胞荧光光谱

研究用于癌症诊断与治疗的光敏剂血卟啉(hematoporphyrin derivative,HPD)的超快光动力学过程。采用超短脉冲激光光谱技术和皮秒时间相关单光子计数系统,测量经血卟啉培养的活体癌细胞与正常细胞的荧光光谱、荧光寿命特性及荧光峰值强度随时间的变化,观测到:癌细胞样品在645nm处具有特征发射光谱峰;癌细胞与正常细胞样品荧光寿命的快成分分别为150,300ps;癌细胞与正常细胞的荧光峰值强度经12h分别衰减10%和55%。对测量所得的荧光光谱曲线及时间分辨荧光衰减曲线分析,计算出:在癌细胞内部血卟啉浓度增大了约2个数量级;癌细胞与正常细胞的荧光寿命分别为824,1798ps;血卟啉在癌细胞与正常细胞样品中滞留时间分别为17,6d。测量结果确认了荧光光谱技术诊断与治疗癌症的可行性,并对发展超短脉冲激光光谱技术早期诊断与治疗癌症具有重要的指导意义和临床应用价值。     

V掺杂ZnO透明导电薄膜研究

本文分别采用磁控溅射技术与基于密度泛函理论的平面波赝势方法两种方式, 对高价态差元素V掺杂ZnO薄膜进行研究. 实验研究结果表明: V的掺入并未改变ZnO的生长方式, 所制备的薄膜都呈(002)择优生长; 随着衬底温度增加, VZO薄膜的结晶质量逐步改善, 当衬底温度超过280 ℃时薄膜的结晶质量恶化; 在280 ℃时获得的VZO薄膜电阻率最低3.8×10^-3 Ω·m, 500-2000 nm平均透过率高于85%. 理论模拟结果表明: V以替位形式掺入ZnO六角纤锌矿晶格结构中, 费米能级进入导带, 材料表现出n 型半导体的特性, 导电电子主要由V 3d及O 2p电子轨道提供. 理论计算结果与实验结果的一致性, 表明VZO薄膜具有作为高效Si基薄膜太阳电池透明导电薄膜的应用潜力.     

氧族元素对D-A和D-π-A共聚物光吸收谱红移的第一性原理研究

D-A型共聚物作为有机聚合物太阳能电池的电子给体材料近年来引起广泛关注. 本文以苯并二噻吩(BDT)为电子给体单元, 苯并噻二唑(BT)为电子受体单元来模拟D-A共聚体; 并用噻吩环作为π桥, 构造出D-π-A(PBDT-DTBX, X = O, S, Se, Te)结构. 采用第一性原理的密度泛函理论, 系统地计算相应的电子结构和光吸收谱. 比较不同氧族元素和噻吩π-键桥对聚合物光吸收谱的影响. 研究结果表明: D-A共聚体中当X位元素以O, S, Se, T_e 替换时, 其体系的最高占有分子轨道(HOMO)能级变化不大, 最低未占有分子轨道(LUMO)能级逐渐靠近费米能级, 带隙逐渐减小. 在可见光区有两个较强的吸收峰, 随着X位元素原子序数增大, 位于4.0 eV左右的光吸收峰位基本不变, 另一光吸收峰强度明显增大并发生红移. 与D-A结构相比, D-π-A结构的带隙均有所减小, 其中X为Te时带隙最小; 光吸收峰强度随着氧族元素原子序数的增大也明显增大并发生红移. 通过比较光吸收系数和相应态密度, 结果表明, 4.0 eV 左右的光吸收峰主要是BDT单元的贡献, 氧族元素的改变主要影响519.4-703.9 nm范围的光吸收.     

十二烷二酸修饰TiO_2电子传输层改善钙钛矿太阳电池的电流特性

在经典的平面异质结钙钛矿太阳电池中,TiO_2致密层的电子传输性能一直是获得优异光伏性能的决定性因素之一.相较于spriro-OMe TAD等常见的空穴传输材料优异的空穴传输能力,作为电子传输材料的TiO_2的导电性较弱,无法形成良好的电荷匹配.为了解决这个问题,我们使用自组装的十二烷二酸(DDDA)单分子层来修饰TiO_2致密层的表面,TiO_2致密层的导电性能得到大幅提升,并且其能带结构得到优化,促进了电子传输,降低了电子积聚和载流子复合,使得电池的短路电流密度(JSC)从修饰前的20.34 mA·cm~(-2)提升至修饰后的23.28 mA·cm~(-2),进而使得电池在标准测量条件下的光电能量转换效率从14.17%提升至15.92%.同时还发现,通过DDDA修饰TiO_2致密层,所制备的器件的光稳定性显著提升,器件未封装暴露在AM 1.5光强100 mW·cm~(-2)的模拟太阳光下超过720 min,保持初始效率的71%以上且趋于稳定.