Electrochemical reactions of catechol, methylcatechol and dopamine at tetrahedral amorphous carbon (ta-C) thin film electrodes

The electrochemical reactions of dopamine, catechol and methylcatechol were investigated at tetrahedral amorphous carbon (ta-C) thin film electrodes. In order to better understand the reaction mechanisms of these molecules, cyclic voltammetry with varying scan rates was carried out at different pH values in H2SO4 and PBS solutions. The results were compared to the same redox reactions taking place at glassy carbon (GC) electrodes. All three catechols exhibited quasi-reversible behavior with sluggish electron transfer kinetics at the ta-C electrode. At neutral and alkaline pH, rapid coupled homogeneous reactions followed the oxidation of the catechols to the corresponding o-quinones and led to significant deterioration of the electrode response. At acidic pH, the extent of deterioration was considerably lower. All the redox reactions showed significantly faster electron transfer kinetics at the GC electrode and it was less susceptible toward surface passivation. An EC mechanism was observed for the oxidation of dopamine at both ta-C and GC electrodes and the formation of polydopamine was suspected to cause the passivation of the electrodes.

Hādhihi Taqrīrāt rāʼiqah wa-taḥqīqāt fāʼiqah

nammaqahā Muḥammad al-Azharī najl al-Ḥasan al-ʻAdawī al-Ḥamzāwī. Washshaḥa bihā ḥawāshī Muḥammad al-Ḥifnī ʻalá Sharḥ al-Risālah al-waḍʻīyah al-ʻAḍudīyah / li-Abī al-Qāsim al-Samarqandī wa-bi-hāmishihā al-ḥawāshī al-madhkūrah maʻa al-sharḥ al-madhkūr.

Sharḥ Ashkāl al-taʼsīs

[Mūsá ibn Muḥammad Qāḍīʹzādah].

Taʼrikh-i emeniyye

Mullā Mūsá ibn Mullā ʻĪsá Sayrāmī nīng taʼlīfī.

al- Taʻrībāt al-shāfiyah li-murīd al-jughrāfiyah

Rifāʻah Badawī Rāfiʻ al-Ṭahṭāwī.

al- Sawāniḥ al-jāzimah fī al-taʻārīf al-lāzimah

li-muʼallifihā Muḥammad ʻAlī ibn Ḥusayn.

Kitāb Taḥrīr al-Uṣūl li-Ūqlīdis

min taʼlīf Khūjah Naṣīr al-Dīn al-Ṭūsī.

Kashf al-qināʻ fī taḍmīn al-ṣunnāʻ

[al-Ḥasan ibn Raḥḥāl al-Tadlāwī].

Kitāb Shams al-taḥqīq wa-ʻurwat ahl al-tawfīq

lil-Imām Aḥmad ibn Sharqāwī. Wa-yalīhā kitāb Naṣīḥat al-dhākirīn wa-irghām al-mukābirīn / lil-Ustādh al-madhkūr. Muṭarrizan hāmishahā bi-al-risālah al-musammāh bi-al-Asinnah al-faʻʻālah fī akbād man ankara ʻalá al-ustādh marartu ʻalá al-jalālah / lil-ʻAllāmah al-Muḥaqqiq Mawlānā al-Shaykh Muḥammad al-Miṣrī al-Jirjāwī.

al- Nuṣḥ al-khāliṣ li-kāffat al-Muslimīn bi-al-tawassul ilayhi taʻālá bi-aṣfiyāʼihi al-muqarrabīn

Abī ʻĪsá Sayyid al-Mahdī ibn Sayyid Muḥammad al-Wazzānī.

Hādhā kitāb Kurūm ʻarāyis al-tahānī sharḥ Ṣalawāt Ibn Mashīsh al-Dānī / taʼlīf al-Imām al-Fāḍil al-Ṣūfī al-Humām al-Shaykh Muṣṭafá al-Bakrī al-Ṣiddīqī al-Khalwatī : manuscript, 1840

Author's own abridgement of his longer commentary on Moroccan sufi Ibn Mashīsh's prayer book known as Ṣalawāt. Longer version is titled: Rawḍāt al-ʻarshīyah fī al-kalām ʻala al-Ṣalawāt al-Mashīshīyah.

Risālah fī al-ʻamal bi-rubʻ al-dāyirah al-ālah al-maʻrūfah / taʼlīf al-Shaykh al-Imām al-ʻAllāmah ʻIzz al-Dīn ʻAbd al-ʻAzīz ibn Muḥammad al-Wafāʼī al-Muwaqqit bi-Jāmiʻ al-Muʼayyad : manuscript, 1673

Unbound.

Hādhihi taʻlīqah laṭīfah fī-mā yataʻallaq bi-qawl al-Nabīy ṣallá Allāhu ʻalayhi wa-sallam "ḥubbiba ilayya min dunyākum al-nisāʼ wa-al-ṭīb wa-juʻilat qurrat ʻaynī fī al-ṣalāt" / taʼlīf al-Shaykh al-Imām al-Ālim al-Allāmah wa-al-baḥr al-fahhāmah Shaykh al-Islām wa-al-muslimīn ʻumdat al-fuqahāʼ wa-al-muḥaddithīn Sayyidī Abū al-Suʻūd ibn Tāj al-Dīn ibn Muḥammad ibn Aḥmad ibn Zakī al-Dīn al-Khazrajī al-Shāfiʻī : manuscript, 1685

Written in one column, 15 lines per page, in black rubricated in red. Title written in green and red ink.

Kitāb al-Arbaʻīn ʻan arbaʻīn min arbaʻīn li-arbaʻīn fī arbaʻīn / taʼlīf al-Imām al-Ḥāfiẓ Muḥaddith al-Shām Nāṣir al-Sunnah afḍal al-Mutaʼakhkhirīn awḥad al-ʻUlamāʼ ʻAlī ibn al-Ḥasan ibn Hibat Allāh ibn ʻAbd Allāh ibn al-Ḥusayn ibn ʻAsākir al-Dimashqī al-Shāfiʻī : manuscript, 1287

Written in one column, from 17 to 23 lines per page, in black.

Kitāb Laṭāʼif akhbār al-uwal fī-man taṣarrafa fī Miṣr min al-duwal / taʼlīf sayyidinā wa-mawlānā al-ʻālim al-ʻallāmah Muḥammad ibn ʻAbd al-Muʻṭī ibn Abī al-Fatḥ ibn Aḥmad ibn ʻAbd al-Ghanī ibn ʻAlī al-Isḥāqī al-Shāfiʻī : manuscript, 1733

بسم الله الرحمن الرحيم فهو حبي اكفي الحمد لله الملك العزيز في ملكه واقتذاره الذي ملك الوجود يقوته واوجد بارادته واختياره... :Incipit