Surface-enhanced vibrational Raman spectroscopy of C60 and C70 on rough silver surfaces

The observation of the surface-enhanced vibrational Raman spectra of vapor-deposited C₆₀ and C₇₀ on rough silver films is reported. Both near-monolayer and multilayer films of pure C₆₀ and of C₆₀/C₇₀ mixtures are studied. The films are obtained by evaporating fullerene samples at temperatures of 683–875 K in ultra-high vacuum. Mixed fullerene samples were greatly enriched in C₇₀ by making use of the slightly different vapor pressures of the two major components at the low end of this temperature range. The spectra contain all the lines of the normal Raman spectra as well as several additional lines caused by a reduction in the stringency of the normal Raman selection rules. These results demonstrate the potential of this technique for detecting small quantities of fullerenes and obtaining their vibrational spectra.     

Reaction of trans-[Pt(H)2(PCy3)2] with C60 reductive elimination of H2 and formation of [Pt(PCy3)2(η-C60)]

Reaction of trans-[Pt(H)₂(PCy₃)₂], 1, with [60]fullerene at room temperature affords [Pt(PCy₃)₂(η²-C₆₀)], 2, in nearly quantitative yield. The most probable reaction pattern is the insertion of a fullerene 6,6 junction onto a Pt-H bond yielding an η¹ alkyl derivative which, after hydrogen extrusion, gives 2. On the other hand, addition of 1 to different electron-deficient olefins, such as dimethyl maleate and fumarate, furnishes mixtures of both η¹ metal—alkyl and η² metal—olefin derivatives. If tetrachloroethylene is used as 2π component, trans-[PtCl(H)(PCy₃)₂] forms exclusively.     

Enhanced‐fluidity liquid chromatography using mixed‐mode hydrophilic interaction liquid chromatography/strong cation‐exchange retention mechanisms

The potential of enhanced‐fluidity liquid chromatography, a subcritical chromatography technique, in mixed‐mode hydrophilic interaction/strong cation‐exchange separations is explored, using amino acids as analytes. The enhanced‐fluidity liquid mobile phases were prepared by adding liquefied CO₂ to methanol/water mixtures, which increases the diffusivity and decreases the viscosity of the mixture. The addition of CO₂ to methanol/water mixtures resulted in increased retention of the more polar amino acids. The “optimized” chromatographic performance (achieving baseline resolution of all amino acids in the shortest amount of time) of these methanol/water/CO₂ mixtures was compared to traditional acetonitrile/water and methanol/water liquid chromatography mobile phases. Methanol/water/CO₂ mixtures offered higher efficiencies and resolution of the ten amino acids relative to the methanol/water mobile phase, and decreased the required isocratic separation time by a factor of two relative to the acetonitrile/water mobile phase. Large differences in selectivity were also observed between the enhanced‐fluidity and traditional liquid mobile phases. A retention mechanism study was completed, that revealed the enhanced‐fluidity mobile phase separation was governed by a mixed‐mode retention mechanism of hydrophilic interaction/strong cation‐exchange. On the other hand, separations with acetonitrile/water and methanol/water mobile phases were strongly governed by only one retention mechanism, either hydrophilic interaction or strong cation exchange, respectively.     

Semiempirical molecular dynamics studies of C60/C70 fullerene oxides: C60O, C60O2 and C70O

The spectral analysis indicates that all isomers of C₆₀O, C₇₀O and C₆₀O₂ have an epoxide-like structure (an oxygen atom bridging across a C–C bond). According to the geometrical structure analysis, there are two isomers of fullerene monoxide C₆₀O (the 5,6 bond and the 6,6 bond), eight isomers of fullerene monoxide C₇₀O and eight isomers of fullerene dioxide C₆₀O₂. In order to simulate the real reaction conditions at 300 K, the calculation of the different isomers of C₆₀O, C₆₀O₂ and C₇₀O fullerene oxides was carried out using the semiempirical molecular dynamics method with two different approaches: (a) consideration of the geometries and thermodynamic stabilities, and (b) consideration of the ozonolysis mechanism. According to the semiempirical molecular dynamic calculation analysis, the probable product of this ozonolysis reaction is C₆₀O with oxygen bridging over the 6–6 bond (C_2v). The most probable product in this reaction contains oxygen bridging across in the upper part of C₇₀ (6–6 bond in C₇₀O-2 or C₇₀O-4) an epoxide-like structure. C₆₀O₂-1, C₆₀O₂-3 and C₆₀O₂-5 are the most probable products for the fullerene dioxides. All of these reaction products are consistent with the experimental results. It is confirmed that the calculation results with the semiempirical molecular dynamics method are close to the experimental work. The semiempirical molecular dynamics method can offer both the reaction temperature effect by molecular dynamics and electronic structure, dipole moment by quantum chemistry calculation.     

Evaluation of Raman spectroscopy to detect fullerenes in geological materials

Fullerene C(60) was determined repeatedly from a few types of carbonaceous matter from geological environments. Detailed investigation of structural aspects of pure carbonaceous matrices as well as of their experimental mixtures with fullerene C(60) permits better understanding of the occurrence mode of fullerenes inside the network of natural samples. However, it appears that Raman microspectrometry is not competitive in the case of investigated current geological carbonaceous matrices with added fullerenes, when the concentration of fullerene C(60) is 100 ppm or lower. In such a situation, C(60) is highly dispersed and careful interpretation of the results of Raman microspectrometry does not permit us to obtain valuable quantitative structural data. Obtained sensitivity for detecting C(60) in investigated matrices was only 1%. Analytical reasons for these results are discussed.     

Thermal Reactions of Fullerene C60 with Iron(III) Acetylacetonate

Thermal reaction of solid mixtures of fullerene C₆₀ with iron(III) acetylacetonate proceeds in the combustion mode; the composition and characteristics of the reaction products are governed by the Fe : C₆₀ ratio in the initial mixture. The magnetization of iron-fullerene complexes was measured.     

Polylactide microspheres prepared by premix membrane emulsification—Effects of solvent removal rate

Polylactide microspheres were prepared by pre-mix membrane emulsification and subsequent extraction of solvent in a coagulation bath, and ultimately to the gas phase. The polymer was dissolved in dichloromethane and emulsified with water or water–methanol mixtures by repeated passage through a glass membrane. During and after emulsification, the droplets are exposed to a bath consisting of a mixture of water and methanol. Transfer of dichloromethane takes place into the bath and (subsequently) to the gas phase. Compared to water, the solubility of dichloromethane is increased when using water–methanol mixtures; the continuous phase can quickly dissolve a significant amount of the solvent, while transfer to the gas phase is strongly enhanced as well. This was observed experimentally and by computer simulation, using a combined model based on the Maxwell–Stefan theory for non-ideal, multi-component mass transfer.

With increasing methanol concentration, the size and span of the microspheres became smaller, and was approximately 1 μm at 30% methanol. The surface morphology of these particles was solid and smooth, whereas holes were observed in those prepared in pure water. At methanol concentrations higher than 30%, the size of the microspheres increased again. This is probably due to the swelling of the particles because of the high in-diffusion of methanol which increases the porosity of the particles. Our main conclusion is that particles of defined size and size distribution can be produced by simply adjusting the non-solvent composition of the pre-mix.     

亚临界和超临界二氧化碳-甲醇混合气相及液相区中甲醇核磁弛豫速率比较研究

用核磁共振氢谱测量了不同温度（293.15和308.15 K）及压力高达25 MPa下二氧化碳-甲醇混合气相（超临界）及液相区（亚临界）中甲醇（羟基及甲基）的纵向弛豫时间T_1,exp。本工作的目的是考察近临界区二氧化碳-甲醇混合物的压力、温度及组成对甲醇弛豫速率的影响,揭示混合物不同相区（气相及液相区）中自旋-晶格弛豫（SLR）过程的机理。此外,还对比研究了等温条件下超临界和亚临界混合气相及液相区中甲醇的SLR速率1/T_1,exp随混合物密度的变化规律。研究发现,在本工作所涉及的温度及压力区间,对于纯甲醇或液相区其SLR过程是以偶极-偶极（DD）作用机理为主导,而在气相区SLR过程则是以自旋-转动（SR）作用机理占优势,也即,超临界和亚临界二氧化碳-甲醇混合物的SLR过程在不同相区有不同的作用机理控制。由于甲醇的SLR弛豫速率1/T_1,exp是由甲醇分子间及分子内的DD作用和SR作用三部分共同决定的,所以研究超临界和亚临界二氧化碳-甲醇混合物的SLR弛豫速率随压力、浓度及温度的变化规律有助于提供更多该混合物不同相态区分子间相互作用的动态学信息。     

铈源对甲醇水蒸气重整制氢CuO/CeO2催化剂的影响

采用沉淀法合成了CeO_2载体,再经浸渍法负载活性组分得到CuO/CeO_2催化材料,探究了铈源(Ce(NO_3)_3·6H_2O、Ce Cl_3·6H_2O、Ce(NH_4)_2(NO_3)_6、Ce(SO_4)_2·4H_2O)对CuO/CeO_2催化性能的影响。通过采用XRD、SEM、N_2O滴定、BET和H_2-TPR等表征手段对催化材料的结构和性质研究发现,四种铈源合成的CuO/CeO_2催化材料在Cu比表面积、还原性能以及活性组分和载体间的相互作用方面存在着明显差别。其中,由Ce(NO_3)_3·6H_2O合成的CuO/CeO_2催化材料的Cu比表面积较大,CuO还原温度较低,CeO_2载体与CuO之间相互作用较强,在甲醇水蒸气重整反应过程中,表现出较佳的催化活性,在反应温度为553 K,水醇比n(H_2O)/n(MeOH)为1.2,甲醇水蒸气气体空速(GHSV)为1760 h~(-1)时,甲醇的转化率为100%,重整气中CO摩尔含量为0.84%。     

载体焙烧气氛对甲醇水蒸气重整制氢CuO/CeO2催化剂的影响

采用沉淀法和浸渍法制备了具有氧空位的CeO₂纳米材料和甲醇水蒸气重整制氢CuO/CeO₂催化剂,探索不同焙烧气氛对CeO₂纳米材料结构、性质和甲醇水蒸气重整制氢性能的影响。采用SEM、XRD、BET、H₂-TPR、N₂O滴定和XPS等手段对催化剂进行了表征。结果表明,CuO/CeO₂催化剂的催化活性与催化剂的Cu比表面积大小、Cu-Ce的相互作用强弱、表面缺陷和表面氧空位的多少有关。其中,在氢气气氛下焙烧所得的CeO₂负载CuO后的CuO/CeO₂-H催化剂催化活性最佳。在反应温度为250℃,水醇物质的量比为1.2时,甲醇气体空速为800 h^-1,甲醇转化率达到了100%,重整尾气中CO含量为0.87%。     

Single-stage plasma-arc synthesis of metallo-endofullerences

Single-stage plasma-arc synthesis of metallo-endofullerences of the types C₆₀Pd, C₆₀Ni, and C₆₀Cr, whose content in a mixture of extracted fullerenes was 0.05 to 0.15 wt %, was performed. The effect of introduction of these metals into the reaction plasma on the total yield of fullerenes and on the fraction composition of the fullerene mixture was studied. The fullerene mixtures were analyzed by mass spectrometry and liquid chromatography.     

Molecular simulation study on adsorption of methanol/water mixtures in mesoporous silicas modified pore surface silylation

Two types of molecular simulation techniques have been utilized to investigate adsorption of methanol/water mixtures in a mesoporous silica with a hydrophobic pore surface: the NVT-ensemble Molecular Dynamics method with the melt-quench algorithm for modeling a fully-silylated mesoporous silica and the μVT-ensemble Orientaional-Biased Monte Carlo method for calculating adsorption isotherms. Adsorption isotherms of methanol and water at 333 K are calculated for an equi-relative-pressure mixture (each component has the same relative pressure which is defined as the ratio of the partial pressure to the saturation pressure of the pure gas) together with pure gases. In the case of the pure gas, water hardly adsorb even at elevated pressures, while the adsorption isotherm for methanol shows the condensable adsorption. On the other hand, in the case of the mixture, water molecules are substantially adsorbed along with methanol molecules, showing an isotherm representing the condensation mechanism. In addition, it is found that the separation factor of methanol to water is the highest in the case of monolayer adsorption from a liquid mixture.     

Hydrogen-bonding between pyrimidine and water: a vibrational spectroscopic analysis

We present an experimental and a theoretical study on hydrogen-bonding between pyrimidine and water as the H-donor. The degree of hydrogen-bonding in this binary system varies with mixture composition. This was monitored experimentally by polarization-resolved linear Raman spectroscopy with the pyrimidine ring breathing mode nu1 as a marker band. A subsequent quantitative line shape analysis of the isotropic Raman intensity for 24 pyrimidine/water mixtures clearly revealed a splitting into three spectral components upon dilution with water. The two additional peaks have been assigned to distinct groups of hydrogen-bonded species that differ in the number of pyrimidine nitrogen atoms (N) involved in hydrogen-bonding to water hydrogen atoms (H). From the integrated Raman intensities for "free" and "hydrogen-bonded" pyrimidine, a concentration profile for these species was established. Our assignments and interpretations are supported by quantum mechanical calculations of structures and by vibrational spectra for pyrimidine and 10 pyrimidine/water complexes with increasing water content. Also, accurate structure-spectra correlations for different cluster subgroups have been determined; within each particular cluster subgroup the water content varies, and a perfect negative correlation between NH hydrogen-bond distances and nu1 wavenumbers was observed.     

Statistical mixture design selective extraction of compounds with antioxidant activity and total polyphenol content from Trichilia catigua

Statistical design mixtures of water, methanol, acetone and ethanol were used to extract material from Trichilia catigua (Meliaceae) barks to study the effects of different solvents and their mixtures on its yield, total polyphenol content and antioxidant activity. The experimental results and their response surface models showed that quaternary mixtures with approximately equal proportions of all four solvents provided the highest yields, total polyphenol contents and antioxidant activities of the crude extracts followed by ternary design mixtures. Principal component and hierarchical clustering analysis of the HPLC–DAD spectra of the chromatographic peaks of 1:1:1:1 water–methanol–acetone–ethanol mixture extracts indicate the presence of cinchonains, gallic acid derivatives, natural polyphenols, flavanoids, catechins, and epicatechins.     

Doping of C60 fullerene peapods with lithium vapor: Raman spectroscopic and spectroelectrochemical studies

Raman spectroscopy and in situ Raman spectroelectrochemistry have been applied to the study of the lithium vapor doping of C60@SWCNTs (peapods; SWCNT=single-walled carbon nanotube). A strong degree of doping was proven by the disappearance of the radial breathing mode (RBM) of the SWCNTs and by the attenuation of the tangential (TG) band intensity by two orders of magnitude. The lithium doping causes a downshift of the Ag(2) mode of the intratubular C60 by 27 cm(-1) and changes the resonance condition of the encapsulated fullerene. In contrast to potassium vapor doping, the strong downshift of the TG band was not observed for lithium doping. The peapods treated with lithium vapor remained partially doped even when they were exposed to humid air. This was reflected by a reduction in the intensity of the nanotube and the fullerene modes and by the change in the shape of the RBM band compared with that of the undoped sample. The Ag(2) mode of the intratubular fullerene was not resolved after contact of the lithium-doped sample with water. Lithium insertion into the interior of a peapod and its strong interaction with the intratubular fullerene is suggested to be responsible for the air-insensitive residual doping. This residual doping was confirmed by in situ spectroelectrochemical measurements. The TG band of the lithium-doped peapods did not undergo an upshift during the anodic doping, which points to the formation of a stable exohedral metallofullerene peapod.     

Clustering dynamics in water/methanol mixtures: a nuclear magnetic resonance study at 205 k<T<295 k

Proton nuclear magnetic resonance (1H NMR) experiments have been performed to measure the spin-lattice, T1, and spin-spin, T2, relaxation times of the three functional groups in water/methanol mixtures at different methanol molar fractions (XMeOH=0, 0.04, 0.1, 0.24, 0.5, 1) as a function of temperature in the range 205 K相似文献   

Synthesis of two A-B-C type conjugated amphiphilic triblock fullerene derivatives and their application in organic solar cells

Two A-B-C type conjugated amphiphilic triblock fullerene derivatives C60-2 HMTPB and C60-2 EHTPB were obtained in multi steps synthesis with three different blocks,and the amphiphilic diblock molecular C60-4 TPB was also preferred as a reference.When as modifying layer on zinc oxide(ZnO),the three fullerene derivatives can all reduce the work function of ZnO via modulation of the interfacial dipoles and lead a better electrical coupling.As introducing treatment of toluene,the obvious self-assembly of fullerene derivatives were observed,which were supported by X-ray diffraction and contact angle of water measurement.Base on PTB7-Th:PC71 BM system,the inverted organic solar cells devices with structure of ITO/ZnO/fullerene derivatives/PTB7-Th:PC71BM/Mo03/Al got power conversion efficiencies of 8.62%,8.83%and 9.00%for C60-4 TPB,C60-2 HMTPB and C60-2 EHTPB,respectively,compared 8.13%of devices with bare ZnO.The result of conjugated amphiphilic triblock fullerene derivatives provides a straightforward approaching by simultaneously modulating the morphology and interfacial work function of ZnO,which can also lead high performance in optoelectronic devices.     

Ionic Liquid for in situ Vis/NIR and Raman Spectroelectrochemistry: Doping of Carbon Nanostructures

1-butyl-3-methylimidazolium tetrafluoroborate (an ionic liquid) is an advantageous electrolyte for the study of charge-transfer reactions at single-walled carbon nanotubes (SWCNTs) and fullerene peapods (C₆₀@SWCNT). Compared to traditional electrolyte solutions, this medium offers a broader window of electrochemical potentials to be applied, and favorable optical properties for in situ Vis/NIR and Raman spectroelectrochemistry of nano-carbon species. The electrochemistry of both nanotubes and peapods is dominated by their capacitive double-layer charging. Vis/NIR spectroelectrochemistry confirms the charging-induced bleaching of transitions between Van Hove singularities. At high positive potentials, new optical transitions were activated in partly filled valence band. The bleaching of optical transitions is mirrored by the quenching of resonance Raman scattering in the region of tube-related modes. The Raman frequency of the tangential displacement mode of SWCNT shifts to blue upon both anodic and cathodic charging in the ionic liquid. The Raman modes of intratubular C₆₀ exhibit a considerable intensity increase upon anodic doping of peapods.     

Density and surface tension of binary mixtures of 1-ethyl-3-methylimdazolium nitrate with alcohols

New experimental data of densities and surface tensions are presented for the binary mixtures of the ionic liquid 1-ethyl-3- methyl imidazolium nitrate（[EMIM]NO₃） with methanol and ethanol.Measurements were performed at 298.15 K and atmospheric pressure,covering the whole composition range.Excess molar volumes V^E and the surface tension deviations Sy have been determined.For the excess molar volumes of binary mixture,there is a region of negative V^E at low IL mole fraction,passing through a minimum and then V^E increases and becomes positive,showing maximum at higher IL mole fraction.It is shown that the surface tension deviations Sy of[EMIM]NO₃ + methanol system are positive but those of[EMIM]NO₃ + ethanol system are negative over the entire mole fraction range.     

甲醇水蒸气重整制氢CuO/CeO2-ZrO2/SiC整体催化剂的研究

采用浸渍法和溶胶凝胶法制备了CuO/CeO₂-ZrO₂/SiC整体催化剂，并将其用于甲醇水蒸气重整制氢反应中。结果表明，与CuO/CeO₂-ZrO₂颗粒催化剂相比，CuO/CeO₂-ZrO₂/SiC整体催化剂催化活性较好，产氢速率较快且重整气中CO体积分数较低。进一步探究了涂层涂覆量和CuO负载量对催化性能的影响，结果表明，当CeO₂-ZrO₂复合氧化物涂层涂覆量在15%±1%，CuO负载量为5%±1%时，催化性能较好；当反应温度为340℃，水醇物质的量比为1.2，甲醇水蒸气气体空速为4840 h^-1时，甲醇转化率为86.0%，产氢速率为1490.0 L/（m³·s），重整气中CO体积分数为1.55%。最后通过单因素实验法探究了甲醇水蒸气气体空速、水醇物质的量比和反应温度对反应的影响。结果表明，随着气体空速变大，甲醇转化率下降，产氢速率上升，重整气中CO体积分数下降。随着水醇物质的量比增加，甲醇转化率先上升后下降，产氢速率先上升后下降，重整气中CO体积分数下降。随着反应温度的升高，甲醇转化率、产氢速率和重整气中CO体积分数均上升。