Department of Materials and Environmental Chemistry, Stockholm University, 10691, Stockholm, Sweden.
Nanoscale. 2017 Jun 8;9(22):7419-7428. doi: 10.1039/c7nr01566f.
TEMPO (2,2,6,6-tetramethylpiperidine-1-oxylradical)-mediated oxidation nanofibers (TOCNF), as a biocompatible and bioactive material, have opened up a new application of nanocellulose for the removal of water contaminants. This development demands extremely sensitive and accurate methods to understand the surface interactions between water pollutants and TOCNF. In this report, we investigated the adsorption of metal ions on TOCNF surfaces using experimental techniques atthe nano and molecular scales with Cu(ii) as the target pollutant in both aqueous and dry forms. Imaging with in situ atomic force microscopy (AFM), together with a study of the physiochemical properties of TOCNF caused by adsorption with Cu(ii) in liquid, were conducted using the PeakForce Quantitative NanoMechanics (PF-QNM) mode at the nano scale. The average adhesion force between the tip and the target single TOCNF almost tripled after adsorption with Cu(ii) from 50 pN to 140 pN. The stiffness of the TOCNF was also enhanced because the Cu(ii) bound to the carboxylate groups and hardened the fiber. AFM topography, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) mapping and X-ray photoelectron spectroscopy (XPS) indicated that the TOCNF were covered by copper nanolayers and/or nanoparticles after adsorption. The changes in the molecular structure caused by the adsorption were demonstrated by Raman and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). This methodology will be of great assistance to gain qualitative and quantitative information on the adsorption process and interaction between charged entities in aqueous medium.
TEMPO（2,2,6,6-四甲基哌啶-1-氧自由基）介导的氧化纳米纤维（TOCNF）作为一种生物相容性和生物活性材料，为纳米纤维素去除水中污染物开辟了新的应用。这一发展需要极其敏感和准确的方法来了解水中污染物与 TOCNF 之间的表面相互作用。在本报告中，我们使用纳米和分子尺度的实验技术研究了金属离子在 TOCNF 表面的吸附，以 Cu(ii)为目标污染物，分别在水相和干燥相中进行。使用原位原子力显微镜（AFM）进行成像，并结合在液体中吸附 Cu(ii)对 TOCNF 物理化学性质的研究，在纳米尺度上使用 PeakForce Quantitative NanoMechanics（PF-QNM）模式进行。在吸附 Cu(ii)后，针尖与目标单根 TOCNF 之间的平均粘附力从 50 pN 增加到 140 pN，几乎增加了两倍。由于 Cu(ii)与羧酸盐基团结合并使纤维变硬，因此 TOCNF 的刚度也得到了增强。AFM 形貌、扫描电子显微镜-能量色散 X 射线光谱（SEM-EDS）映射和 X 射线光电子能谱（XPS）表明，在吸附后 TOCNF 被铜纳米层和/或纳米颗粒覆盖。吸附引起的分子结构变化通过拉曼和衰减全反射-傅里叶变换红外光谱（ATR-FTIR）得到证明。这种方法将有助于获取关于带电实体在水介质中吸附过程和相互作用的定性和定量信息。
