Mayuri Pinapeddavari, Kumar Annamalai Senthil
Environmental and Analytical Chemistry Division, School of Advanced Sciences, Vellore Institute of Technology University, Vellore 632 014, India.
Langmuir. 2015 Jun 2;31(21):5945-51. doi: 10.1021/acs.langmuir.5b00491. Epub 2015 May 21.
The derivatization of an intrinsic iron impurity in a carbon nanotube (CNT-*Fe, *Fe-intrinsic, and redox-active iron impurity) as a functional molecular system has been challenging to realize. There are certain limitations on the derivatization of such iron impurities such as low concentration and limited accessibility. Herein, we report an in situ electroassisted derivatization of an intrinsic and redox-active iron impurity in a multiwalled carbon nanotube (MWCNT-*Fe, *Fe, 2.1 wt %) as MWCNT-*Fe(bpy)3(2+), where Fe(bpy)3(2+) = iron(II)tris(2,2'-bipyridine) complex and bpy = 2,2'-bipyridine. The hybrid complex was prepared by the electrochemical treatment of a 2,2'-bipyridine ligand adsorbed {MWCNT-*Fe + Nafion} modified glassy carbon electrode in pH 7 phosphate buffer solution. This new MWCNT-*Fe(bpy)3(2+) hybrid electrode showed well-defined, stable redox at E1/2 = 830 mV with a peak-to-peak separation (ΔEp) of 72 mV in a neutral pH solution. This is quite different from an ex situ Nafion-Fe(bpy)3(2+) complex system that showed an unstable response at neutral pH. This in situ approach can allow the redox-active iron impurity in the CNTs to be quantified using the current signal of the Fe(bpy)3(2+) hybrid system. This MWCNT-*Fe(bpy)3(2+) hybrid modified electrode was further used as an electrochemical detector for selective and separation-less flow injection analysis of DNA's purine bases, adenine and guanine, without interference from pyrimidine bases, cytosine, and thymine at different oxidative detection potentials of 1 V (for adenine and guanine) and 0.7 V vs Ag/AgCl (for guanine) using the pH 7 phosphate buffer solution as a carrier system.
将碳纳米管中的固有铁杂质（碳纳米管 - 铁、固有铁以及氧化还原活性铁杂质）衍生化为功能性分子体系一直难以实现。此类铁杂质的衍生化存在一定局限性，比如浓度低且可及性有限。在此，我们报道了在多壁碳纳米管（MWCNT - 铁，铁含量2.1 wt%）中原位电辅助将固有且具有氧化还原活性的铁杂质衍生化为MWCNT - Fe(bpy)₃²⁺，其中Fe(bpy)₃²⁺ = 铁（II）三（2,2'-联吡啶）配合物，bpy = 2,2'-联吡啶。通过在pH 7磷酸盐缓冲溶液中对吸附有2,2'-联吡啶配体的{MWCNT - 铁 + 全氟磺酸离子交换膜}修饰玻碳电极进行电化学处理，制备了这种杂化配合物。这种新型的MWCNT - Fe(bpy)₃²⁺杂化电极在中性pH溶液中，在E₁/₂ = 830 mV处显示出明确、稳定的氧化还原峰，峰 - 峰间距（ΔEp）为72 mV。这与非原位全氟磺酸离子交换膜 - Fe(bpy)₃²⁺配合物体系截然不同，后者在中性pH下显示出不稳定的响应。这种原位方法能够利用Fe(bpy)₃²⁺杂化体系的电流信号对碳纳米管中具有氧化还原活性的铁杂质进行定量分析。这种MWCNT - Fe(bpy)₃²⁺杂化修饰电极还被进一步用作电化学检测器，用于对DNA的嘌呤碱基腺嘌呤和鸟嘌呤进行选择性且无需分离的流动注射分析，在1 V（针对腺嘌呤和鸟嘌呤）以及相对于Ag/AgCl为0.7 V（针对鸟嘌呤）的不同氧化检测电位下，以pH 7磷酸盐缓冲溶液作为载体体系，不受嘧啶碱基胞嘧啶和胸腺嘧啶的干扰。
