Electrochemically Modified Carbon Composite Electrode Using Diazonium Salt

Abstract

Carbon composite thermoplastic electrodes (TPEs) were fabricated using graphite, thermoplastic binder and solvent. TPEs were used due to their outstanding properties such as high conductivity, good electron transfer kinetics, inexpensive, easy patterning and reusability. TPEs were modified with aryl diazonium salts using p-nitroaniline for the first time. An in-situ modification method based on diazonium ion synthesis was developed for thermoplastic electrodes. A mixture of aryl amine, p-toluenesulfonic acid, and sodium nitrite in aquous phase was prepared and grinded together in order to synthesize diazonium salts. A color change (from green to yellow) of the synthesized paste occurred upon reaction, which indicated diazonium ion formation. 4-nitroaniline was used to synthesize and graft diazonium ion. In-situ generated nitrophenyl monodiazonium cations were electrochemically reduced to aminophenyl groups on the surface of the thermoplastic electrode. The presence of aminophenyl groups on the surface of the electrode was confirmed via electrochemistry. After electrochemical reduction in aqueous acidic media, the electrochemical behavior of a 4-aminophenyl modified thermoplastic electrode was investigated in the presence of ferricyanide. Characteristic peaks were obtained due to the formation of grafted groups on the electrode surface by cyclic voltammetry. The reduction of the 4-aminophenyl resulted in the product of amino groups at about -0.4 V versus Ag/AgCl reference electrode. A scan rate study was performed by modified TPEs and a linear dependence of the anodic peak current was observed up to 100 mV/s indicating that the electroactive species were grafted at the TPE surface. Furthermore, incubation time of synthesized diazonium salt on the electrode surface was optimized and found as 5 min. 

Keywords

• Diazonium
• Solid-phase synthesis
• Thermoplastic electrode

Diazonyum Tuzu Kullanılarak Elektrokimyasal Olarak Modifiye Edilmiş Karbon Kompozit Elektrot

Öz

Karbon kompozit termoplastik elektrotlar (TPE'ler), grafit, termoplastik bağlayıcı ve çözücü kullanılarak üretilmiştir. TPE'ler, yüksek iletkenlik, iyi elektron transfer kinetiği, düşük maliyetli olma, kolay şekil verilebilme ve tekrar kullanılabilirlik gibi üstün özellikleri nedeniyle kullanılmıştır. TPE'ler, ilk kez p-nitroanilin kullanılarak aril diazonyum tuzları ile modifiye edilmiştir. Termoplastik elektrotlar için diazonyum iyon sentezine dayanan bir modifikasyon yöntemi geliştirilmiştir. Sulu fazda bir aril amin, p-tolüensülfonik asit ve sodyum nitrit karışımı hazırlanmış ve diazonyum tuzunun sentezlenmesi için birlikte öğütülmüştür. Reaksiyon sonucunda diazonyum iyonu oluşumunun göstergesi olarak pastanın rengi yeşil renkten sarı renge dönüşmüştür. Diazonyum iyonunun sentezlenmesi ve graf edilmesi için 4-nitroanilin kullanılmıştır. Termoplastik elektrot yüzeyinde üretilen nitrofenil monodiazonyum katyonları elektrokimyasal olarak aminofenil gruplarına indirgenmiştir. Elektrotun yüzeyindeki aminofenil gruplarının varlığı elektrokimyasal yolla doğrulanmıştır. Sulu asidik ortamdaki elektrokimyasal indirgeme işleminden sonra, 4-aminofenil ile modifiye edilen termoplastik elektrotun elektrokimyasal davranışı ferrisiyanür varlığında araştırılmıştır. Dönüşümlü voltametri ile elektrot yüzeyinde graf edilen grupların oluşması nedeniyle karakteristik pikler elde edilmiştir. Ag/AgCl referans elektrota karşı yaklaşık -0,4 V'de 4-aminofenilin indirgenerek amino grupları oluşmuştur. Modifiye edilen TPE'ler ile tarama hızı testi yapılarak anodik pik akımın 100 mV/s'ye kadar lineer bir davranış gösterdiği gözlemlenmiştir. Bu da elektroaktif türlerin TPE yüzeyine graf edildiğini göstermiştir. Ayrıca, sentezlenmiş diazonyum tuzunun elektrot yüzeyi üzerindeki inkübasyon süresi optimize edilmiştir ve optimum inkübasyon süresi 5 dakika olarak bulunmuştur.

Anahtar Kelimeler

• diazonyum
• termoplastik elektrot
• katı faz sentezi

Kaynakça

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