Detection of low concentration oxygen containing functional groups on activated carbon fiber surfaces through fluorescent labeling

Covalent fluorescent labeling of surface species (FLOSS) was used to detect relatively low concentrations of surface functional groups (OH, COOH and CHO) on activated carbon fiber surfaces. The chromophores were attached to the surface through a reaction specific to each type of surface functional group. FLOSS indicated the presence of 8.7×1011 COOHgroups/cm2 and 1.3×1012 CHOgroups/cm2 on the ACF 25 fiber surface. Neither the infrared spectrum nor the X-ray photoelectron spectrum showed evidence of the existence of those low concentration groups. The concentration of OH groups on the fiber surface was lower than the detection limit (∼1010/cm2) of FLOSS under the present conditions. The FLOSS results for CHO and COOH groups were compared with the concentrations determined by Boehm titration (3.11×1013/cm2 for CHO and 1.05×1013/cm2 for COOH). The limited accessibility of the ACF surface to relatively large chromophores is one of the main reasons for the discrepancy between these two methods. FLOSS detects only exposed functional groups as opposed to functional groups hidden in small pores. This apparent limitation, however, highlights the surface sensitivity and specificity of FLOSS technique.

表面物种的共价荧光标记（FLOSS）被用于检测活性炭纤维表面相对低浓度的表面官能团（羟基、羧基和醛基）。发色团通过针对每种表面官能团类型的特异性反应连接到表面。FLOSS表明在ACF 25纤维表面存在8.7×10¹¹个羧基/平方厘米和1.3×10¹²个醛基/平方厘米。红外光谱和X射线光电子能谱都没有显示出这些低浓度基团存在的证据。在当前条件下，纤维表面羟基的浓度低于FLOSS的检测限（约10¹⁰/平方厘米）。将醛基和羧基的FLOSS结果与通过博姆滴定法测定的浓度（醛基为3.11×10¹³/平方厘米，羧基为1.05×10¹³/平方厘米）进行了比较。活性炭纤维表面对相对较大发色团的可及性有限是这两种方法之间存在差异的主要原因之一。FLOSS仅检测暴露的官能团，而不检测隐藏在小孔中的官能团。然而，这种明显的局限性突出了FLOSS技术的表面敏感性和特异性。