不同参数多壁碳纳米管的拉曼光谱研究

拉曼光谱是进行碳材料结构与性质研究的有力手段,为了研究多壁碳纳米管(MWCNT)的管径和长度对其拉曼光学性质的影响,本研究对一系列不同管径和长度的多壁碳纳米管进行拉曼光谱的测试和分析。研究发现: 与高取向的石墨相比,多壁碳纳米管一阶拉曼光谱的G峰中心和D峰中心都会向低波数发生不同程度的红移;MWCNT两个主要特征峰(G峰和D峰)峰强在其他条件相同的情况下,与MWCNT的管径成正比,与长度成反比;G峰的频移与MWCNT的管径和长度两个因素密切相关,与管径成反比关系(这与单壁碳纳米管的径向呼吸模有着一致的结果),与管长成正比关系,而D 峰的频移受MWCNT的管径和长度的影响很弱,并对此现象进行了初步分析。在此基础上,我们以MWCNT的长径比为横坐标,G峰频移为纵坐标作图,进行线性拟合,得到了G峰频移与长径比成一定的线性递增关系。采用同样的分析方法,我们将G峰和D峰强度分别对MWCNT的长径比作图,进行线性拟合,得到了G峰和D峰强度分别与MWCNT的长径比成一定的线性递减关系。     

水溶液中硫酸根离子的拉曼光谱定量分析

拉曼光谱因其具有无损、非接触以及原位的技术优势被广泛应用于科学研究领域。但是,当前拉曼光谱主要应用于定性研究,即根据拉曼波数偏移进行物质分子的鉴别,相比之下,拉曼光谱定量分析则明显不足。因此,有必要进一步开展拉曼光谱定量方面的研究。根据拉曼光谱原理分析可知,拉曼光谱定量研究应当根据相对强度比进行,也就是在定量化过程中需要选择一个参考系,可以分为内标法和外标法。拉曼光谱定量可以根据被测分子与该参考系的拉曼强度比值进行,通过这个方法可以消除测试条件的影响。对水溶液而言,可将液态水的OH伸缩振动作为内标,进行拉曼光谱定量分析。本文研究了Na₂SO₄-H₂O,K₂SO₄-H₂O以及NaCl-Na₂SO₄-H₂O体系的拉曼光谱特征。通过将水分子的OH伸缩振动（2 750~3 900 cm-1附近）拟合为两个高斯谱峰,并以I_SO2-4/I_W为参数来确定溶液中的硫酸根离子浓度,其中I_SO2-4为硫酸根离子的特征峰强度,I_W为水的两个高斯谱峰强度之和。实验结果表明,水溶液中SO2-₄浓度与拉曼强度比I_SO2-4/I_W之间有较好的线性关系,其中,R2=0.997 73,符合定量要求。据此,本文应用拉曼光谱定量分析,建立了一种相对快速、准确测量水溶液中SO2-₄浓度的方法。     

不同煤级煤的Raman谱特征及与XRD结构参数的关系

11种Cdaf在57.58%～94.01%的不同变质程度煤的拉曼光谱实验表明不同变质程度煤的拉曼光谱一级模都存在两个明显的振动峰,分别为较为宽缓的D峰(1 340～1 380 cm-1)和相对较为尖锐的G峰(1 580～1 600 cm-1)。将800～1 800 cm-1范围的谱图拟合为两个洛仑兹峰,每个峰的峰位置,峰强度以及半峰宽等拉曼参数与碳含量的相关关系分析结果显示：D峰位置和G峰位置随碳含量的增加分别向低波数和高波数区域移动;两峰的峰位差随碳含量的增加而增加;两峰的半峰宽FWHM-D,FWHM-G及两峰强度比I_D/I_G在碳含量75％～94％范围内与碳含量线性相关。发现XRD分析获得的d002和L_c与拉曼谱中的G峰位置及半峰宽存在着良好的相关性。与X射线衍射得到的晶粒尺寸L_a值相关性分析表明用Cancado公式和KW公式对L_a进行估算均是不合理的。     

掺钽钨青铜的制备及光学性能

以TaCl₅和Na₂WO₄为原料,采用水热法在170 ℃制备性能良好的掺钽钨青铜(Ta_<i>xWO₃)纳米线。利用Ｘ射线衍射技术(XRD)、扫描电镜(SEM)、紫外可见漫反射光谱(UV-Vis)及拉曼光谱(Raman)等分析手段,对该材料的结构、形貌及光谱性能进行表征。XRD结果表明：Ta_xWO₃纳米材料为六方相结构氧化钨,当Ta_xWO₃中Ta/W摩尔比小于0.04时,晶胞参数随着掺杂量的增大而逐渐增大,当掺杂量达到大于0.04后保持基本不变。UV-Vis光谱表明,随着钽掺杂量的增大,紫外吸收峰发生红移,即能隙逐渐减小。Raman光谱显示：随钽掺杂量的增大,Raman峰位逐渐向低波数方向移动,同时振动峰逐渐宽化,进一步证明了钽掺杂对氧化钨结构的影响。光催化降解罗丹明B的实验显示,制备的Ta_xWO₃具有较高的光催化活性。     

甲状腺癌转移性淋巴结的红外光谱研究

联合运用衰减全反射(attenuated total reflectance,ATR)探头与FTIR光谱仪,测定了新鲜离体的甲状腺癌转移性颈部淋巴结20枚和非转移性淋巴结69枚的FTIR光谱,比较两组光谱13个谱带的峰位及相对峰强等28个指标,找出甲状腺癌转移性淋巴结光谱的特征。与非转移性淋巴结相比,转移性淋巴结光谱中与蛋白、脂质、糖类、核酸相关的谱带均发生了明显的变化,具体如下：(1)与蛋白质相关的谱带的相对峰强I_{3 280}/I1 460(P=0.029),I_{1 640}/I_{1 460}(P=0.019),I_{1 546}/I_{1 460}(P=0.004)均显著升高;(2)脂类相关的相对峰强I_{1 743}/I_{1 460}显著降低(P=0.026),而I_{1 400}/I_{14 60}则明显增高(P=0.001);(3)与糖类相关的1 165与1 120 cm-1处峰位P_{1 165}(P=0.019),P_{1 120}(P=0.000)发生明显蓝移(向高波数移动),相对峰强I1 165/I_{1 460}显著降低(P=0.006);(4)与核酸相关的1 085 cm-1处峰位P_{1 085}发生明显地红移(向低波数移动)(P=0.029);(5)其他指认未明的谱带的相对峰强I_{1 303}/I_{1 460}(P=0.008),I_{1 303}/I1 240(P=0.039)均明显升高。与非转移性淋巴结光谱相比较,甲癌转移的淋巴结光谱在多个谱带的峰位或相对峰强方面存在显著的差异。FTIR可应用于术中甲状腺癌转移性淋巴结的探测。     

非晶碳薄膜振动拉曼光谱的第一性原理研究

采用基于第一性原理的赝势平面波方法,对3个不同密度(2.6,2.9和3.2 g·cm-3)非晶碳结构的振动态密度和振动拉曼光谱进行了研究。结构模型由快速“液体-淬火”方法模拟得到,振动频率和本征模由线性响应理论决定,拉曼耦合张量由有限电场方法计算。计算结果表明：当密度从2.6增加到3.2 g·cm-3时,sp3碳含量从50%增加到84.4%,G峰向高频区偏移,D峰和G峰的强度之比I_D/I_G减小,T峰向低频区偏移且T峰和G峰的强度之比I_T/I_G增大。该结果与实验结果显示出很好的一致性。依据原子振动的分析结果证实：拉曼光谱的G峰和D峰均来自于sp2碳原子的振动贡献,且G峰是由任何成对的sp2碳原子的伸缩振动产生的,T峰来自于sp3杂化碳原子的振动贡献,G峰和T峰峰位随结构的色散是由键长变化导致的。     

傅里叶变换红外光谱实时监测乳腺癌细胞化疗反应性的研究

应用傅里叶变换红外光谱技术监测乳腺癌细胞株MCF-7在化疗药物5氟尿嘧啶(5-FU)干预过程中相应的红外光谱变化,验证其与药物作用的时间和剂量相关性。对数据结果整理发现,在时间相关性方面,随药物作用时间的延长,乳腺癌细胞株MCF-7对脂类的利用率下降,细胞中脂类含量增加,同时肿瘤细胞分裂增殖受阻,细胞内DNA和RNA的含量降低,实验中观察到,48 h内,乳腺癌细胞MCF-7的红外光谱中代表脂类变化的峰强比I_{2 920}/I_{1 460}逐渐升高,I_{1 400}/I_{1 460}逐渐降低,代表细胞内核酸变化的峰强比I_{1 080}/I_{1 550},I_{1 240}/I_{1 550}逐渐降低;在剂量相关性方面,癌细胞红外光谱中峰强比I_{1 640}/I_{1 550}较正常升高,实验中观察到峰强比I_{1 640}/I_{1 550}随药物浓度的增加而呈现逐渐降低的趋势。以上这些变化与乳腺癌细胞在化疗药物干预过程中的生物学改变相符,可作为FTIR实时监测乳腺癌细胞化疗反应性的参考指标。     

硼碳氮纳米管的拉曼光谱研究

对不同温度和不同催化条件下用高温热解法制备的硼碳氮(BCN)纳米管的拉曼光谱进行了分析。随着制备温度的升高,拉曼光谱中D带和G带的强度比I_D/I_G由小变大,而后又变小,说明存在一个最佳温度,在该温度下生成的BCN纳米管中B、N元素掺杂浓度最大。不同催化剂对BCN纳米管的拉曼光谱也有影响,当以钴/二茂铁和镍/二茂铁为催化剂时的I_D/I_G值比以钴、镍和钴/镍为催化剂时大,说明这时的B、N的掺杂浓度较高,纳米管的质量较好,这与透射电子显微镜观察结果一致。     

显微红外光谱法研究豚鼠膝关节软骨下骨的增龄性改变

应用显微FTIR技术原位分析雌性Hartley豚鼠随月龄增加胫骨关节软骨下骨的化学变化。红外光谱测定三种月龄(1月、2月和3月)豚鼠软骨下3个不同吸收颜色的骨小梁区(a,b,c)和中央骨髓区(d)。结果显示：(1)随月龄增加,骨小梁总面积增加,与正常骨小梁谱图相似的a区减少,d区波形有逐渐向a区发展的趋势。(2)2月龄和3月龄的b和c区AmideⅢ红移以c区红移显著并且变成肩峰,代表核酸和多糖的吸收峰峰强是a区的7倍。(3)三种月龄的c区均出现了β型糖苷键吸收峰。(4)I_AmideⅠ/I_AmideⅡ在2月b区最大,3月各区最小,I_AmideⅢ/I_AmideⅡ 在 2月、3月由a到c依次降低,I_νsPO-₂/I_AmideⅡ在2月、3月的b和c区较相应a区高7倍以上。结果符合骨关节炎不同阶段软骨下骨的组织结构及化学组成的变化规律。初步研究表明,显微光谱成像技术结合FTIR可原位分析不同区域的软骨下骨小梁和骨髓的分子组成,为骨关节炎软骨下骨组织病理学的分子水平研究提供了可靠信息。     

PAN基碳纤维在石墨化过程中的拉曼光谱

采用激光拉曼光谱研究了PAN基碳纤维在石墨化(2 000～3 000 ℃)过程中的结构变化;比较了石墨化前后纤维表面和断面拉曼光谱特征。结果表明：高温石墨化后,碳纤维的一级拉曼光谱有3个峰(D,G和D′),表征碳纤维结构有序程度的拉曼参数主要有D和G峰的半高宽(FWHM)、G峰的拉曼位移和D与G峰的积分强度比R(I_D/I_G)。随着热处理温度的提高,D和G峰的半高宽、G峰的拉曼位移和R值均逐渐减小,即使经过3 000 ℃高温处理后,D峰仍然存在,R值为0.19,说明纤维中仍存在无序结构。另外,R值与纤维中石墨微晶的基面宽度L_a成反比,石墨化后纤维取向性的增加使得表面和断面的拉曼光谱有明显的差异。因此,可利用激光拉曼光谱来定量表征碳纤维的石墨化程度和取向。     

Growth of multiwalled carbon nanotube arrays by chemical vapour deposition over iron catalyst and the effect of growth parameters

Multiwalled carbon nanotube (CNT) arrays were grown by catalytic thermal decomposition of acetylene, over Fe-catalyst deposited on Si-wafer in the temperature range 700-750 °C. The growth parameters were optimized to obtain dense arrays of multiwalled CNTs of uniform diameter. The vertical cross-section of the grown nanotube arrays reveals a quasi-vertical alignment of the nanotubes. The effect of varying the thickness of the catalyst layer and the effect of increasing the growth duration on the morphology and distribution of the grown nanotubes were studied. A scotch-tape test to check the strength of adhesion of the grown CNTs to the Si-substrate surface reveals a strong adhesion between the grown nanotubes and the substrate surface. Transmission electron microscopy analysis of the grown CNTs shows that the grown CNTs are multiwalled nanotubes with a bamboo structure, and follow the base-growth mechanism.     

RF-PECVD掺溴非晶碳氢膜的Raman光谱分析

在室温条件下,以溴乙烷为单体、氢气为载气,用13.56 MHz射频等离子体化学气相淀积方法(RF-PECVD)在硅片衬底上生长了掺溴非晶碳氢薄膜(a-C:Br:H).通过对其进行Raman光谱分析,研究了工作气压对薄膜结构的影响.结果显示:随着气体工作压力从20 Pa下降至5 Pa,样品D峰强度增强,I_D/I_G值逐步由1.18增加至1.36,G峰的位置向高频轻微移动;与此同时,薄膜生长方式逐步转为低能态形式生长,薄膜中sp~2C逐步由链式结构向环式结构转化.     

Detailed profiling of CNTs arrays along the growth window in a floating catalyst reactor

We report a detailed longitudinal and depth profiles of multi-wall carbon nanotubes (CNTs) arrays synthesized using xylene and ferrocene in a floating catalyst reactor. Point to point analyses of the CNTs grown in a “growth window” with CNTs arrays longer than 0.5 mm were performed using optical microscopy, Raman spectroscopy, FESEM, high-resolution TGA/DTA, and TEM techniques. The heights of the CNTs arrays show a maximum at a mid point of the growth window, while a reverse trend of minimum is observed for iron-to-CNTs atomic ratios. The ratio of amorphous carbon to CNTs sharply increases along the growth window and from the bottom to top of CNTs arrays. The CNTs diameter also increases along the growth window, due to deposition of the amorphous carbon, which can be almost removed by temperature programmed oxidation up to around 500 °C. A base growth mechanism, the variations of catalyst content, residence time and temperature profile along the growth window, the adsorption and decomposition of polycyclic aromatic hydrocarbons to amorphous carbon, and a limited diffusion of hydrocarbon species through the arrays covered by excessive amorphous carbon may explain the results.     

Smallest carbon nanotube is 3 a in diameter

Previous energetic considerations have led to the belief that carbon nanotubes (CNTs) of 4 A in diameter are the smallest stable CNTs. Using high-resolution transmission electron microscopy, we find that a stable 3 A CNT can be grown inside a multiwalled carbon nanotube. Density functional calculations indicate that the 3 A CNT is the armchair CNT(2,2) with a radial breathing mode at 787 cm(-1). Each end can be capped by half of a C12 cage (hexagonal prism) containing tetragons.     

Memristor effect on bundles of vertically aligned carbon nanotubes tested by scanning tunnel microscopy

We report on the results of experimental study of an array of vertically aligned carbon nanotubes (VA CNTs) by scanning tunnel microscopy (STM). It is shown that upon the application of an external electric field to the STM probe/VA CNT system, individual VA CNTs are combined into bundles whose diameter depends on the radius of the tip of the STM probe. The memristor effect in VA CNTs is detected. For the VA CNT array under investigation, the resistivity ratio in the low- and high-resistance states at a voltage of 180 mV is 28. The results can be used in the development of structures and technological processes for designing nanoelectronics devices based on VA CNT arrays, including elements of ultrahigh-access memory cells for vacuum microelectronics devices.     

Effect of carbon nanotubes dispersion on morphology, internal structure and thermal stability of electrospun poly(vinyl alcohol)/carbon nanotubes nanofibers

The current work reports the effect of multi walled carbon nanotubes and single walled carbon nanotubes dispersion on morphological, structural and thermal degradation of electrospun poly(vinyl alcohol) (PVA)/carbon nanotubes (CNTs) dispersed in sodium dodecyl sulfate (SDS) (PVA/CNTs–SDS) composites nanofibers. (PVA/CNTs–SDS) nanocomposites fibers were elaborated using the traditional electrospinning process to disperse and align CNTs into the fibers, especially for low CNTs loading fraction: 0.3 and 0.7 wt%. The morphology of the electrospun fibers was studied using the scanning electronic microscopy. The average diameter of the fibers changes significantly after the incorporation of the CNTs in the PVA. Furthermore, Fourier transform infrared spectroscopy elucidated the effect of CNTs on the crystallization of the PVA which was confirmed by X-ray diffraction analysis. Thermogravimetric analysis showed that the thermal stability of the composite fibers depends on the loading fraction and on the type of carbon nanotubes.     

Sulfur impregnation of multi‐walled carbon nanotubes via SF6/NH3 plasma exposure

Plasma treatments are established methods to functionalise carbon nanotubes (CNTs) and modify their surface structure. This paper presents a mild glow‐discharge plasma treatment of aligned arrays of multi‐walled carbon nanotubes employing sulfur hexafluoride (SF₆), ammonia (NH₃), and their mixtures as process gases. For the latter, sulfur was detected at the tip and sidewalls of the nanotubes via energy‐dispersive X‐ray spectroscopy, while electron microscopy served as method to verify the structural integrity of the CNTs after the plasma treatment. This approach provides the basis for an easy and quick alternative to existing sulfur functionalisation methods of MWCNTs. Furthermore, the proposed method can conveniently be applied to carbon nanotube arrays on substrate while preserving their structure and alignment.

SEM‐EDX map of SF₆/NH₃ plasma‐treated multi‐walled carbon nanotubes on substrate. Green, yellow and red correspond to silicon, carbon and sulfur signals, respectively.     

Electron field emission properties of highly dense carbon nanotube arrays

In this paper, we have studied field emission properties of highly dense arrays of multi-walled carbon nanotubes (CNTs) used as cathodes in diode-type field emission devices with a phosphor screen. For the high-density CNT emitters it is demonstrated that the emission sites are located on the CNT-cathode edges, which is direct experimental evidence of the ‘edge effect’. The results of computer simulations (using ‘ANSYS Electromagnetic’ software) are presented to confirm the experimental data and to analyze the effect of patterning on the electric field distribution for high-density CNT arrays. It is shown that selective-area removal of nanotubes in the arrays leads to the formation of additional edges characterized by the high field enhancement factor and enhanced emission from the CNT cathodes. In addition, scanning probe microscopy techniques are employed to examine surface properties of the high-density CNT arrays. For CNT arrays of ‘short’ nanotubes, the work function distribution over the sample surface is detected using a scanning Kelvin microscopy method.     

碳纳米管阵列、捆束的三步升温工艺制备及其形貌与结构

使用结构简单的单温炉设备，通过三步升温热解二茂铁、三聚氰氨混合物方法，在二氧化硅、多晶陶瓷基底上分别合成了碳纳米管阵列、碳纳米管捆束.使用扫描电子显微镜、透射电子显微镜、电子能量损失谱和x射线光电子能谱对合成样品进行了结构和成分分析.结果显示：两种基底上合成的纳米管均为多壁纯碳管；生长于光滑二氧化硅表面的碳纳米管具有高度取向性和一致的外径，长度为10—40μm.碳纳米管采取催化剂顶端生长模式并展示出类杯状形貌；生长于粗糙多晶陶瓷表面的碳纳米管捆束随机取向，碳纳米管直径为15—80nm，长度在几百微米，展示 关键词： 碳纳米管 热解法 三步升温工艺