Investigating the Effects of Primary Amine Linkers with Different Carbon Chain Lengths on the Acid Dissociation Constant (pKa) for Covalently Immobilized Anthraquinone at the Electrode Surface Using Linear and Non-Linear Fittings

Abstract

The caption for Fig. 1, on page H880, failed to note the use of statistical analysis. The corrected figure and caption appear as follows.

Hexanediamine Monolayer Electrografted at Glassy Carbon Electrodes Enhances Oxygen Reduction Reaction in Aqueous Neutral Media

“…The polishing and electrografting procedures followed the steps that have been reported previously. 3,12 The electrochemical attachment of Boc-HDA linker to the electrode surface was performed by electrochemical oxidation in 15 mM N-Boc-1,6-hexanediamine solution in acetonitrile containing 0.1 M TBATFB as the supporting electrolyte. The electrode potential was swept from 0.0 to 2.0 V vs. Ag/AgCl for 7 cycles at 50 mV s −1 .…”

“…1,2 Electrografting of primary amine linkers is a widely used technique for electrode modification to covalently immobilize redox molecules or biomolecules onto the electrode surface. [3][4][5] The electrochemical attachment of primary amines at carbon electrodes is an efficient method since a strong carbon-nitrogen bond is formed during the one-electron oxidation of the amine. 6,7 Electrografting has received increasing attention due to its potential application in the development of electrochemical devices, given that uniform and highly stable organic monolayers can be formed.…”

Comparative Proton Coupled Electron Transfer at Glassy Carbon and Boron‐Doped Diamond Electrodes

“…From previous studies, anthraquinone, and its‐closely related aqueous soluble counterpart anthraquinone‐2‐sulfonate, are known to have two acid dissociation constants ( K a ) values [23,24] . However, in the case of immobilised anthraquinone, since the second K a value is very small, [24] the first dissociation constant, K a1 , can be determined from a non‐linear fitting of midpoint potential of the anthraquinone oxidation and reduction as a function of pH using Eq. : [24,46,47] $$$\vcenter{\openup.5em\halign{$\displaystyle{#}$\cr E{_{{\rm mid}}}=E{_{0}}+{{RT} \over {{\rm{2}}F}}\ln (\left[ {{\rm{H}}^ + } \right]^2 + K_{{\rm{a}}1} \left[ {{\rm{H}}^ + } \right])\hfill\cr}}$$$ …”

“…[23,24] However, in the case of immobilised anthraquinone, since the second K a value is very small, [24] the first dissociation constant, K a1 , can be determined from a non-linear fitting of midpoint potential of the anthraquinone oxidation and reduction as a function of pH using Eq. ( 4): [24,46,47]…”

“…[53,54] In these works, the authors propose that shifts in pK a upon immobilisation arise from the differences in the hydrophobicity or hydrophilicity of different interfaces, which are either facilitating or impeding the formation of the solvation shell near the surface. [54] In most scenarios, a shift to more basic pK a values is observed, [10,24,55] with examples of shifts to more acidic pK a values seldomly reported. For example, Saby et al [19] and Abiman et al [53] immobilised benzoic acid (4carboxyphenyl) on the surface of GC electrodes.…”