Electrochemical Detection of 4‐Chlorophenol Using Glassy Carbon Electrodes Modified with Thulium Double‐Decker Phthalocyanine Salts

Abstract

This paper presents newly developed electrochemical sensors based on green and blue lanthanide double‐decker phthalocyanines (LnPc2), with the green LnPc2 derivative referred to as 2 a while the blue counterpart is designated 2 b. The modified glassy carbon electrode (GCE) based on the blue LnPc2 complex is referred to as 2 b‐GCE while that which is based on the green LnPc2 complex is named 2 a‐GCE. The oxidation of 4‐chlorophenol is extensively investigated and found to differ from one modified electrode to the next. Interestingly, the electrode modified with blue LnPc2 complex (2 b‐GCE) showed lower peak potential 0.88 V vs Ag|AgCl and higher catalytic current of 593 μA compared to that based on the green LnPc2 counterpart (2 b‐GCE) which exhibited ∼ 1.05 V vs Ag|AgCl and 65 μA, respectively. Remarkable differences in Tafel slopes were also found to be complimented by high rate constants in the order: 2 b‐GCE>2 a‐GCE. The lowest limit of detection (LOD) was found for 2 b‐GCE at 4.16 ×10−8 M in comparison to that for 2 a‐GCE at 6.14 ×10−6 M. When investigating the electrochemical behavior, it was found that the first one‐electron oxidation minus the first one‐electron reduction differences were very low at 0.36 V and 0.55 V vs Ag|AgCl for 2 b and 2 a, respectively. Such values are comparable to the literature values for lutetium bisphthalocyanines.

Tunable construction of electrochemical sensors for chlorophenol detection

“…[46][47][48][49][50][51][52] Currently, most of the electrolytes used in this field are phosphate or sodium acetateacetic acid buffer solution. [53][54][55][56][57][58][59] The reference electrode offers a constant potential so as to control and adjust the working electrode potential accurately, which facilitates the quantitative analysis of the electrochemical system. In electrochemical sensors, the Ag/AgCl electrode and saturated calomel electrode (SCE) are the most commonly used reference electrodes.…”

“…6d, Sekhosana et al modified GCE surfaces with a thulium double-decker phthalocyanine (TmPcs), which possesses great electrocatalytic activity. 53 The surface modification resulted in the enhancement of the LSV response towards 4-CP, with a LOD of 0.0416 mM. 53 Metallophthalocyanines can also form a bimetallic system suitable for surface modification of electrodes.…”

“…53 The surface modification resulted in the enhancement of the LSV response towards 4-CP, with a LOD of 0.0416 mM. 53 Metallophthalocyanines can also form a bimetallic system suitable for surface modification of electrodes. 96 Makinde et al 96 reported on an Au electrode modified with cobalt binuclear phthalocyanine (CoBiPc) bearing thio substituents for binding to gold.…”

Lanthanide–tetrapyrrole complexes: synthesis, redox chemistry, photophysical properties, and photonic applications

“…The blue form stands for [(Pc 2À )Tm III (Pc 2À )] À (i.e., both the HOMO and LUMO are fully filled), with its overall charge compensated by a hexadecyltrimethylammonium cation, and responds better to oxidizing analytes, while the green form [(Pc À1 )Tm III (Pc 2À )] with one electron hole prefers reducing analytes. The authors discovered that the blue-GCE demonstrated a lower peak potential of 0.88 V vs. Ag|AgCl, a higher catalytic current of 593 mA, and apparent sensitivity towards the presence of 4-chlorophenol with a lowest detection limit of 4.16 Â 10 À8 M. 354 6.1.4 Temperature. Temperature-dependent lanthanide luminescence is a well-known physical phenomenon that can be exploited for thermosensing.…”

Analytical Detection and Electrocatalysis of Paracetamol in Aqueous Media Using Rare‐Earth Double‐Decker Phthalocyaninato Chelates as Electrochemically Active Materials

“…Such simpler LnPc 2 complexes have not been used as an electrochemical sensor for PA before and are reported for the first time in this manuscript. LnPc 2 complexes are superior electrochemically active materials and exhibit small first oxidation minus first reduction difference [32][33][34][35][36][37][38][39] which depicts the effective electron transfer compared to lanthanidebased monophthalocyaninato counterparts, [39] hence their application in electronics and electrochemistry and as ambipolar organic field-effect transistors. LnPc 2 complexes whose electrocatalytic behavior is investigated herein are highly soluble in nonpolar solvents due to the tert-butyl bearing substituents, hence the employment of dichloromethane as a solvent when modifying the surface of GCE.…”