Espinoza Vanessa B, Bachilo Sergei M, Zheng Yu, Htoon Han, Weisman R Bruce
Department of Chemistry and the Smalley-Curl Institute, Rice University, Houston, Texas 77005, United States.
Center for Integrated Nanotechnologies, Materials, Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
ACS Nano. 2025 Jan 21;19(2):2497-2506. doi: 10.1021/acsnano.4c13605. Epub 2025 Jan 8.
The reaction of aqueous suspensions of single-wall carbon nanotubes (SWCNTs) with UV-excited sodium hypochlorite has previously been reported to be an efficient route for doping nanotubes with oxygen atoms. We have investigated how this reaction system is affected by pH level, dissolved O content, and radical scavengers and traps. Products were characterized with near-IR fluorescence, Raman, and XPS spectroscopy. The reaction is greatly accelerated by removal of dissolved O and strongly suppressed by TEMPO, a radical trap. Alcohols added as radical scavengers alter the reaction efficiency and the product peak emission wavelengths. Photofunctionalization with 300 nm irradiation is substantially less efficient at pH levels low enough to protonate the OCl ion to HOCl. We deduce that in mildly treated high pH samples, the main product is sp hybridized O-doped adducts formed by reaction of SWCNTs with atomic oxygen in its P (ground) level. By contrast, treatment under low pH conditions leads to sp hybridized SWCNT adducts formed by the addition of secondary radicals from reactions of OH and Cl. There is also evidence for additional photoreactions of product species under stronger irradiation. Researchers using photoexcited hypochlorite for SWCNT functionalization should be alert to the range of products and the sensitivity to reaction conditions in this system.
据报道，单壁碳纳米管（SWCNT）水悬浮液与紫外线激发的次氯酸钠反应是用氧原子掺杂纳米管的有效途径。我们研究了该反应体系如何受到pH值、溶解氧含量以及自由基清除剂和捕获剂的影响。用近红外荧光、拉曼光谱和XPS光谱对产物进行了表征。去除溶解氧可大大加速反应，而自由基捕获剂TEMPO则强烈抑制反应。作为自由基清除剂添加的醇会改变反应效率和产物的峰值发射波长。在pH值低到足以使OCl离子质子化为HOCl的情况下，300nm辐照的光功能化效率大大降低。我们推断，在轻度处理的高pH值样品中，主要产物是SWCNT与处于P（基态）的原子氧反应形成的sp杂化O掺杂加合物。相比之下，在低pH条件下处理会导致由OH和Cl反应产生的次级自由基加成形成的sp杂化SWCNT加合物。也有证据表明在更强的辐照下产物物种会发生额外的光反应。使用光激发次氯酸盐对SWCNT进行功能化的研究人员应注意该体系中产物的范围以及对反应条件的敏感性。
