Carbon nanomaterials, including graphene, graphite and carbon nanotubes (Figure 1), carry unique physical and thermal properties that make them key elements in industries as wide-ranging as battery manufacturing, construction and sports equipment.
由于这些材料越来越亚博网站下载多地用于制造环境中,因此需要直接,安全和全面的特征方法的需求。拉曼光谱法是碳纳米材料表征的宝贵工具,因为其速度,选择性和能力非破坏性测量样品。亚博网站下载
图片来源:B&W Tek
通常,碳材料的拉曼光谱相对简单,但它们还可以根据峰位置,形状和相对强度亚博网站下载披露有关内部微晶结构的大量信息。
拉曼光谱石墨烯基材料亚博网站下载可以以三个主要峰为特征:G波段,D波段和2D波段。G波段发生在1580厘米左右-1和constitutes the graphene in-plane bending motion of the sp2杂交碳原子。G频段在石墨烯中非常锋利,显示出高质量的属性,信号表达了高结晶度。
图1。碳同素体的结构。图片来源:B&W Tek
G波段的位置也对石墨烯层的数量有反应,但不受激光激发的影响。D波段可以被视为在石墨烯样品中的疾病量度。
乐队代表SP的环呼吸模式2杂交碳原子。为了在石墨烯谱中检测到D波段,石墨烯中必须有故障或模式接近边缘。
我n clean, unspoiled graphene, the D-band cannot be seen. The D-band demonstrates dispersive behavior, meaning that it demonstrates a sensitive response to the laser excitation used in the experiment. The 2D band is an overtone of the D-band, but contrary to the D-band, it does not need to be close to a defect for it to activate.
2D频段的峰形可以用于识别层厚度。像D波段一样,2D频段也具有分散性,因此它会通过不同的激光激发稍微改变。
实验
一个我 - 拉曼®Prime 532Hsystem(BWS475-532H-HT) was employed for each measurement of graphene-based materials. The system is comprised of 532 nm laser, which is the laser wavelength typically selected when conducting Raman measurements of carbon.
表格1。用于测量碳材料的配置。亚博网站下载资料来源:B&W Tek
。 |
。 |
System model |
我 - 拉曼®Prime 532H |
激光波长 |
532nm |
配件 |
探针持有人BAC150B 视频显微镜BAC151C-532(可选) SWCNT的电子级探测升级(可选) |
软件 |
BWSpec® |
这我 - 拉曼Prime is a low-noise, high-signal throughput and fully incorporated Raman system with an integrated tablet computer. To support the fiber optic probe, a probe holder (BAC150B) was acquired for all measurements.
为了使原本的3B级激光器安全用于制造地板,可以使用外壳系统(BAC152C)使其与1类激光相等。通常使用的激光功率约为34兆瓦,获取时间范围为30-90秒。
碳纳米材料的拉曼光谱亚博网站下载
D波段构成了石墨烯样品中的混乱程度,而G波段表示结构阶的水平。因此,D和G波段强度的比率(我d/我G)计算的可以用作确定石墨烯样品质量的半定量参数。
这我d/我G在样本中,与结构障碍相连。这个我d/我Gparameter typifies a quick quality-control parameter that can be employed as a Pass/Fail test in manufacturing settings.
某些碳纳米材料的拉曼光谱如图2所示。原始石墨烯(红色光谱)仅包含G波段和二亚博网站下载波段。D波段不存在。另外,2D频段的强度与G波段的强度之比(我2d/我G) ≈2.
图2。石墨烯(红色),碳纳米管(黑色),石墨(绿色)和碳黑色(蓝色)的拉曼光谱。图片来源:B&W Tek
石墨(绿色光谱)的光谱通过扩大和不对称的2D带区分,并区分我2d/我G明显较低。从石墨烯卷起的碳纳米管(黑色光谱)中的光谱显示出适度分裂的G波段。1
G波段分为两个退化模式(g+和g-)通过单壁碳纳米管(SWCNT)的曲率。碳黑色(蓝色光谱)具有最小的结构顺序,显示出强大的D波段,因此很高我d/我G。
我t should be noted that if a laser different from the 532 nm laser is used for these measurements, the D-band and 2D band’s position will slightly change due to their dispersive nature.
确定我d/我G
我nstructions for calculating我d/我Gwith Raman spectroscopy are detailed in ASTM E3220-20 Standard Guide for Characterization of Graphene Flakes.2Spectra should be baseline corrected before identifying peak intensity.
For the spectra in Figure 3, a baseline removal algorithm was applied to the data in the BWSpec software. The peak intensities of the D-bands and G-bands of the spectra are calculated after baseline removal.
图3。碳纳米纤维(A,B)和碳黑粉(C-F)的拉曼光谱。插入物显示了应用于所有数据的基线校正的示例。所有光谱都是手动偏移以澄清的。注意:尖峰达到〜1550厘米-1和〜2300厘米-1are attributed to atmospheric oxygen and nitrogen, respectively. Image Credit: B&W Tek
随后,我d/我G然后可以计算。可以对BWSPEC软件进行编程以报告我d/我G,确定我d/我G源自收集的光谱。为了易于报告,可以将计算导出到表格。表2显示了该软件生成的表的类型。
表2。Measured我d, IG,并计算我d/ 我G来自BWSPEC软件。资料来源:B&W Tek
我n Figure 3, the nanofiber spectra are marked by intense D-bands at around 1350 cm-1以及G波段中的许多不对称。这我d/我G频谱(a)的高度特别高,表明该纳米纤维样品中存在相当多的结构障碍。
来自碳黑色样品的光谱由宽的D波段和G带确定,这表明样品内的结晶度极低。这我d/我G针对碳黑色样品测量的均高于0.5,通过样品结构表示结构障碍。
这个我d/我Gcan be employed as a rapid quality-control test of manufactured graphene, graphite, carbon black powder and carbon nanotubes, either as an offline or at-line measurement.
结论
拉曼光谱法已经揭示了自己是碳纳米材料表征的宝贵技术。亚博网站下载碳光谱是相对碱性的,通常以三个峰为特征。
峰强度,形状和位置披露了有关样品内部结晶度的信息。D波段的强度与G波段强度的比率是样品结构障碍的普通指标。研究人员和制造商可以使用我d/我G样品以表征碳纳米材料。亚博网站下载
参考
- A. C.法拉利。固态通信。143,47–57(2007)。
- ASTM E3220-20,石墨烯薄片的标准指南,ASTM International,West Conshohocken,宾夕法尼亚州,2020年,www.astm.org
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