Geldenhuys Genna-Leigh, Mason Yvonne, Dragan George C, Zimmermann Ralf, Forbes Patricia
Department of Chemistry, University of Pretoria, Lynnwood Road, Hatfield, Pretoria 0001, South Africa.
Processing Laboratory, Impala Platinum Limited, 123 Bethlehem Drive, Rustenburg 0299, South Africa.
ACS Omega. 2021 Sep 13;6(38):24765-24776. doi: 10.1021/acsomega.1c03595. eCollection 2021 Sep 28.
Volatile and semivolatile organic compounds in ambient air and occupational settings are of great concern due to their associated adverse human health and environmental impacts. Novel graphene wool samplers have been developed and tested to overcome limitations of commercially available sorbents that can only be used once and typically require solvent extraction. Graphene wool (GW) was synthesized by non-catalytic chemical vapor deposition with optimized conditions, resulting in a novel fibrous graphene wool that is very easy to manage and less rigid than other forms of graphene, lending itself to a wide range of potential applications. Here, the air pollutant sampling capabilities of the GW were of interest. The optimal packing weight of GW inside a glass tube (length 178 mm, i.d. 4 mm, o.d. 6 mm) was investigated by the adsorption of vaporized alkane standards on the GW, using a condensation aerosol generator in a temperature-controlled chamber and subsequent detection using a flame ionization detector. The optimized GW packing density was found to be 0.19 mg mm at a flow rate of 500 mL min, which provided a gas collection efficiency of >90% for octane, decane, and hexadecane. The humidity uptake of the sampler is less than 1% (m/m) for ambient humidities <70%. Breakthrough studies showed the favorable adsorption of polar molecules, which is attributed to the defective nature of the graphene and the inhomogeneous coating of the graphene layers on the quartz wool, suggesting that the polar versus non-polar uptake potential of the GW can be tuned by varying the graphene layering on the quartz wool substrate during synthesis. Oxidized domains at the irregular edges of the graphene layers, due to a broken, non-pristine sp carbon network, allow for adsorption of polar molecules. The GW was applied and used in a combustion sampling campaign where the samplers proved to be comparable to frequently used polydimethylsiloxane sorbents in terms of sampling and thermal desorption of non-polar semivolatile organic compounds. The total alkane concentrations detected after thermal desorption of GW and PDMS samplers were found to be 17.96 ± 13.27 and 18.30 ± 16.42 μg m, respectively; thus, the difference in the alkane sampling concentration between the two sorbent systems was negligible. GW provides a new, exciting possibility for the monitoring of organic air pollutants with numerous advantages, including high sampling efficiencies, simple and cost-effective synthesis of the thermally stable GW, solvent-free and environmentally friendly analysis, and, importantly, the reusability of samplers.
由于挥发性和半挥发性有机化合物对人类健康和环境具有不利影响，因此环境空气和职业环境中的这些化合物备受关注。已开发并测试了新型石墨烯棉采样器，以克服市售吸附剂的局限性，这些吸附剂只能使用一次，通常需要溶剂萃取。通过非催化化学气相沉积在优化条件下合成了石墨烯棉（GW），得到了一种新型纤维状石墨烯棉，它易于处理，比其他形式的石墨烯刚性更小，具有广泛的潜在应用。在此，GW对空气污染物的采样能力受到关注。通过在温度控制室内使用冷凝气溶胶发生器将汽化的烷烃标准物吸附在GW上，并随后使用火焰离子化检测器进行检测，研究了玻璃管（长度178毫米，内径4毫米，外径6毫米）内GW的最佳填充重量。发现在流速为500毫升/分钟时，优化后的GW填充密度为0.19毫克/毫米，这为辛烷、癸烷和十六烷提供了>90%的气体收集效率。对于环境湿度<70%，采样器的湿度吸收小于1%（质量/质量）。穿透研究表明极性分子具有良好的吸附性，这归因于石墨烯的缺陷性质以及石墨烯层在石英棉上的不均匀涂层，这表明可以通过在合成过程中改变石英棉基材上的石墨烯层数来调节GW对极性与非极性物质的吸收潜力。由于石墨烯层不规则边缘处的sp碳网络断裂且不完整，形成了氧化区域，从而允许极性分子的吸附。GW被应用于一次燃烧采样活动中，在该活动中，就非极性半挥发性有机化合物的采样和热解吸而言，采样器被证明与常用的聚二甲基硅氧烷吸附剂相当。GW和PDMS采样器热解吸后检测到的总烷烃浓度分别为17.96±13.27和18.30±16.42微克/立方米；因此，两种吸附剂系统之间的烷烃采样浓度差异可忽略不计。GW为监测有机空气污染物提供了一种令人兴奋的新可能性，具有许多优点，包括高采样效率、热稳定的GW合成简单且经济高效、无溶剂且环保分析，以及重要的是采样器可重复使用。
