Aggregation studies of the water-soluble gadofullerene magnetic resonance imaging contrast agent: [Gd@C82O6(OH)16(NHCH2CH2COOH)8]x

The aggregation behavior of the newly synthesized gadofullerene magnetic resonance imaging (MRI) contrast agent, i.e., Gd@C(82)O(6)(OH)(16)(NHCH(2)CH(2)COOH)(8) (abbreviated as AAD-EMF), was studied in detail by dynamic light scattering, scanning electron microscopy, T(1)-weighted magnetic resonance, and atomic force microscopy. It was revealed that the AAD-EMF aggregation in aqueous solution is pH-dependent. At pH 2, the AAD-EMF first self-assemble to form ca. 30 nm small clusters, and then dozens of the small clusters further aggregate to form large grapelike particles. At pH 7, the aggregates are also ca. 30 nm small clusters, but they are hard to further aggregate except for forming some cluster dimers or trimers, so AAD-EMF aggregates have a narrow size distribution by this time. At pH 9, the AAD-EMF aggregations cover a large range of continuous hydrodynamic diameters from 30 to 2000 nm. On the basis of the above observations, the aggregating mechanism of AAD-EMF under different pH values was proposed by concurrently considering the hydrogen-bonding effect and the dipolar interactions between AAD-EMF.     

Vibrational Characterization and Molecular Electronic Investigations of 2-acetyl-5-methylfuran using FT-IR,FT-Raman,UV–VIS,NMR, and DFT Methods

Spectroscopic (FT-IR, FT-Raman, UV–vis, and NMR) techniques have been extensively used for structural elucidation of compounds along with the study of geometrical and vibrational properties. Herein, 2-acetyl-5-methylfuran, a derivative of furan, was experimentally characterized and analyzed in details using FT-IR, FT-Raman, UV–vis, and ¹H NMR spectroscopic techniques conducted in different solvents. The experimentally analyzed spectral results were carefully compared with theoretical values obtained using density functional theory (DFT) calculations at the B3LYP/6–311?+?+?G (d, p) method to support, validate, and provide more insights on the structural characterizations of the titled compound. The correlated experimental and theoretical structural vibrational assignments along with their potential energy distributions (PEDs) and all the spectroscopic spectral investigations of the titled structure were observed to be in good agreements with calculated results.

     

Fluvio-mechanical resetting of the Al and Ti centres in quartz

ESR dating of fluvial terraces is usually based on the assumption of sunlight resetting of the Al centres in quartz. Very long bleaching times (months of sunlight exposure) are required to reset this centre to a stable, non-zero ESR intensity. Considering that highly light sensitive optically stimulated luminescence (OSL) analyses of fluvial samples often indicate partial bleaching, ESR dating should be extremely difficult. Two samples were analysed, a fluvial sediment from a Chinese river terrace and an Australian granite. Using a Höhnle sunlight simulator, the Ti centres of both samples were completely bleached within 1 to 65 h, while the Al centre required extreme bleaching times to reach stable residual intensities (∼1000 h). As an alternative to light resetting, tumbler experiments were carried out to simulate fluvial action. The samples were treated under OSL sample preparation conditions. After relatively short tumbling times, corresponding to a few km of fluvial transport, both Al- and Ti-centres were partially reset. In a granite sample, the tumbling reduced the intensity of the Al centre more effectively than light exposure.     

富勒烯结构Si60的从头算研究

采用量子化学从头算方法, 系统地研究了Si60-Ih及其各种降低对称性后的扭曲构型的稳定性. 找到了5个低能量低对称性(对称性分别为T, Ci, C1, CS和C2) Si60的稳定结构. 分析计算结果表明, 典型的低能量Si60结构对应着一些硅原子凸出球外和一些硅原子凹进球内, 部分Si原子间的成键呈sp3杂化方式.     

C60的产生与石墨晶面的关联（I）

Ｃ_（６０）的产生与石墨晶面的关联（Ｉ）谢兆雄，刘朝阳，林逢辰，王春儒，郑兰荪（厦门大学化学系固体表面物理化学国家重点实验室厦门，３６１００５）关键词Ｃ_（６０），激光溅射，石墨晶面Ｓｍａｌｌａｙ等［１］曾以激光在超声分子束喷口的喉道处蒸发石墨得到了Ｃ...     

银-四氰基对苯二醌二甲烷纳米线阵列的制备及其场发射性能

采用多孔氧化铝模板法, 通过四氰基对苯二醌二甲烷(TCNQ)与金属Ag的化学反应, 制备了银-四氰基对苯二醌二甲烷(AgTCNQ)纳米线阵列. AgTCNQ的直径由多孔氧化铝模板的内孔直径决定, 而其长度则可由反应时间与多孔氧化铝膜模板的厚度来控制. 所制备的AgTCNQ纳米线阵列表面光滑, 直径均一, 具有良好的场发射特性.     

Ultraviolet Photoelectron Spectroscopy of Fullerenes C60 and C70:A Model Study

Geometrical optimizations of two fullerenes, C₆₀ and C₇₀, have been performed by means of density-functional theory techniques. Based on the Gelius model, ultraviolet photoelectron spectra (UPS) of C₆₀ and C₇₀ have been simulated. We have shown how the different local arrangements of carbon atoms of C₇₀ are responsible for the spectra. Our calculated spectra are in good agreement with the experimental counterparts.     

Theoretical investigation of the formation mechanism of metallofullerene Y@C82

The formation mechanism of metallofullerene Y@C82 was investigated by ab initio calculations with two theoretical models. The first model is a traditional Y@C80 + C2 "fullerene-road" growing mechanism, in which the Y@C82 is assumed to form by combining Y@C80 and C2 fragments, and the second model involves formation by an unclosed C76 and a C6Y fragment. The calculated results showed that the second mechanism is much more energetically favorable.     

Size effect of encaged clusters on the exohedral chemistry of endohedral fullerenes: a case study on the pyrrolidino reaction of ScxGd3-xN@C80 (x = 0-3)

We report a combined experimental and theoretical investigation on the regiochemistry of a series of TNT endohedral fullerenes ScxGd3-xN@C80 (x = 0-3) in 1,3-dipolar cycloadditions, which demonstrates that the regioselectivity of the TNT-based endohedral fullerenes ScxGd3-xN@C80 (x = 0-3) in the exohedral cycloadditions depends remarkably on the size of the encaged cluster.     

Preparation and characterization of two new water-soluble endohedral metallofullerenes as magnetic resonance imaging contrast agents

Two new water-soluble Gd-containing endohedral metallofullerenes [ScxGd3-xN@C80OmOHn (x = 1, 2; m approximately 12; n approximately 26)] were synthesized in a simple one-step reaction and characterized by Fourier transform (FT)-IR as well as X-ray photoelectron spectroscopy (XPS). Their observed longitudinal relaxivities (R1) for water protons are 20.7 and 17.6 mM(-1) s(-1), respectively, which are significantly higher than that of the commercial magnetic resonance imaging (MRI) contrast agent (Gd-DTPA, 3.2 mM(-1) s(-1)). These results indicate these trimetallic nitride endohedral fullerenols are potential next-generation high-efficiency MRI contrast agents.