Fiber sampling technique and counting protocol development for carbon nanotubes

项目摘要 本项目的目标是开发一种新的纤维取样方法。目前用于机载的方法 碳纳米管(CNT)的采样采用了微米级的石棉采样。为了实现我们的目标 为此，我们将研究不同碳纳米管的表面性质和有助于提高效率的采样过滤器，开发一种 新的图像分析协议与我们的算法，使用新开发的纳米颗粒(NP)等速扩散 采样器，模拟和阐明了颗粒行为，提出了一种适合于碳纳米管采样的新方法。 负担：在被指定为潜在的碳纳米管后，接触空气中的碳纳米管一直是最令人担忧的问题 人类致癌物质。碳纳米管对健康的潜在影响与石棉纤维有一些相似之处。 在动物模型中。预计到2030年，全球碳纳米管市场规模将达到1032亿美元，年增长率为16.3%。 用于石棉的纤维取样方法是对碳纳米管纤维取样的推荐方法。碳纳米管 含有直径为石棉纤维的十分之一到百分之一的单独纤维。NIOSH 方法7402被发现对于鉴定几个非常细的CNT纤维是非常具有挑战性和耗时的 在电子显微镜下的栅格样本上。这一挑战提出的问题包括，数字和 通过7402方法采集的碳纳米管纤维的尺寸代表了空气中的尺寸，无论这些尺寸是 受取样和粗加工方法的影响，以及如何接触到细小纤维 可以适当地量化，以评估相关的健康影响，当该方法尚未对CNT进行验证时。 需要：一种新的采样细纤维的方法和技术，以1)有效地收集采样空气中的纤维 无损失，2)直接分析采集的纤维，只需对样品进行最小的处理，3)易于计数 获得纤维的浓度和尺寸，这将解决曝光测量不准确的问题 以及样品分析的显著时间要求。当用于碳纳米管时，收集效率和 必须对采样和分析的性能进行评估。设计一种新的采样基板是至关重要的 因为目前使用的用于收集石棉的混合纤维素酯(MCE)过滤器可能不适合 收集碳纳米管。收集在MCE过滤器上的纤维需要被处理以转移到栅格进行分析， 细小的纤维可能会结块或丢失。一种可有效采集纤维的新采样方法及基板 直接分析将防止收集的纤维在传输过程中丢失或变化。 影响：使用碳纳米管、石棉和玻璃纤维等纤维材料的广泛应用 核动力站可以使用开发的方案和方法来有效地量化暴露水平 纤维/颗粒浓度。此信息可能会将碳纳米管的当前测量指标从质量更改为 浓度与纤维/颗粒数浓度之比。使用更精确的计数可以确定暴露的特征 浓度非常低，很难测量质量浓度并提供相关关联 低于当前碳纳米管质量量化极限的测量对健康的影响。

PROJECT ABSTRACT The goal of this project is to develop a new method for fiber sampling. The method currently used for airborne sampling of carbon nanotubes (CNTs) is adapted from micrometer-scale asbestos sampling. To achieve our goal, we will study surface properties of different CNTs and sampling filters contributing to efficiency, develop a novel image analysis protocol with our algorithms, use a newly developed nanoparticle (NP) isokinetic diffusion sampler, simulate and elucidate the particle behavior, and produce a new method suitable to CNTs sampling. Burden: Exposure to airborne CNTs has been of highest concern following their designation as a potential human carcinogen. The potential health effects of CNTs have shown some similarity to those of asbestos fibers in animal models. CNTs global market is projected to reach $103.2 billion by 2030 with 16.3% annual growth. The fiber sampling method used for asbestos has been a recommended method for sampling CNT fibers. CNTs contain individual fibers with diameters that are one tenth to one hundredth that of asbestos fibers. The NIOSH Methods 7402 was found to be very challenging and time consuming for identifying a few very fine CNT fibers on a grid sample under electron microscopy. Questions raised by this challenge include whether the number and size of CNT fibers collected by 7402 method are representative of those in the air, whether these sizes are affected by the sampling and extensive processing required by the method, and how the exposure to fine fibers can be quantified properly to evaluate associated health effects when this method is not yet validated for CNT. Need: A new method and technique for sampling fine fibers to 1) collect fibers efficiently in the sampled air without loss, 2) directly analyze the collected fibers with minimal processing of the sample, and 3) easily count the fibers to obtain the concentration and size, which will resolve the lack of accuracy of exposure measurements and the significant time requirement of sample analysis. When used for CNTs, the collection efficiency and performance of sampling and analysis must be evaluated. It is critical to design a new sampling substrate because the currently used mixed cellulose ester (MCE) filter for collecting asbestos may not be suitable for collecting CNTs. The fibers collected on the MCE filter need to be processed for transfer to a grid for analysis, small fibers can be agglomerated or lost. A new sampling method and substrate that can effectively collect fibers to be analyzed directly will prevent the loss or change of collected fibers through the transfer process. Impact: The wide range of applications that use fiber materials such as CNTs, asbestos and fiberglass and other NPs can employ the developed protocol and method to effectively quantify the exposure level in terms of fiber/particle concentration. This information may change the current measurement metric for CNTs from mass concentration to fiber/particle number concentration. Using more precise counting can characterize the exposure concentration at a very low and difficult to measure mass concentration and provide associations to related health effects for a measurement below the current limit of mass quantification for CNTs.