An unusual electrochemical oxidation of phenothiazine dye to phenothiazine-bi-1,4-quinone derivative (a donor-acceptor type molecular hybrid) on MWCNT surface and its cysteine electrocatalytic oxidation function

Shanmugam, Ramasamy; Barathi, Palani; Zen, Jyh‐Myng; Kumar, Annamalai Senthil

doi:10.1016/j.electacta.2015.11.032

Cited by 20 publications

(13 citation statements)

References 60 publications

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“…The tethered nature of the Car-HQ, its surface orientation, and partial protonation of the N-atom of Car-HQ are likely the influencing parameters for the observation 34 . Similar kind of Non-Nernstian observation was previously reported with various proton-coupled electron transfer systems such as Hemoglobin(Hb)/Nafion/MWCNT modified electrode (− 50.9 mV pH −1 ) 35 and redox-active quinolone-quinones on MWCNT modified electrode (− 54 mV pH −1 ) 36 . Indeed, the E pa versus pH linearity is found to be highly suitable to extend for practical applications.…”

Section: Resultssupporting

confidence: 82%

A prototype device of microliter volume voltammetric pH sensor based on carbazole–quinone redox-probe tethered MWCNT modified three-in-one screen-printed electrode

Srinivas

Ashokkumar

Kamaraj

et al. 2021

Sci Rep

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As an alternate for the conventional glass-based pH sensor which is associated with problems like fragile nature, alkaline error, and potential drift, the development of a new redox-sensitive pH probe-modified electrode that could show potential, current-drift and surface-fouling free voltammetric pH sensing is a demanding research interest, recently. Herein, we report a substituted carbazole-quinone (Car-HQ) based new redox-active pH-sensitive probe that contains benzyl and bromo-substituents, immobilized multiwalled carbon nanotube modified glassy carbon (GCE/MWCNT@Car-HQ) and screen-printed three-in-one (SPE/MWCNT@Car-HQ) electrodes for selective, surface-fouling free pH sensor application. This new system showed a well-defined surface-confined redox peak at an apparent standard electrode potential, Eo′ = − 0.160 V versus Ag/AgCl with surface-excess value, Γ = 47 n mol cm−2 in pH 7 phosphate buffer solution. When tested with various electroactive chemicals and biochemicals such as cysteine, hydrazine, NADH, uric acid, and ascorbic acid, MWCNT@Car-HQ showed an unaltered redox-peak potential and current values without mediated oxidation/reduction behavior unlike the conventional hydroquinone, anthraquinone and other redox mediators based voltammetry sensors with serious electrocatalytic effects and in turn potential and current drifts. A strong π–π interaction, nitrogen-atom assisted surface orientation and C–C bond formation on the graphitic structure of MWCNT are the plausible reasons for stable and selective voltammetric pH sensing application of MWCNT@Car-HQ system. Using a programed/in-built three-in-one screen printed compatible potentiostat system, voltammetric pH sensing of 3 μL sample of urine, saliva, and orange juice samples with pH values comparable to that of milliliter volume-based pH-glass electrode measurements has been demonstrated.

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Section: Resultssupporting

confidence: 82%

A prototype device of microliter volume voltammetric pH sensor based on carbazole–quinone redox-probe tethered MWCNT modified three-in-one screen-printed electrode

Srinivas

Ashokkumar

Kamaraj

et al. 2021

Sci Rep

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“…With increase in the scan rate, E 1/2 shifted to higher potentials, which may indicate kinetically controlled redox process of the present system. 33 Effect of solution pH on the CV responses of GCE/MWCNT*@Car-Qn electrode showed a linear shift of E 1/2 to negative values with a slope, ∂E pa /∂pH = −59 ± 3 mV pH −1 (Figure 2C). This behavior confirms Nernstian-type pH dependence (proton-coupled electron-transfer reaction) of the MWCNT*@Car-Qn redox system.…”

Section: Resultsmentioning

confidence: 88%

“…To find out the position, we resorted to the methodology used in our earlier work dealing with a similar situation to decide ortho-or para-quinone position in the oxidation products of catechol 41 and pyrene. 33 It has been shown the that copper ion does not form a complex with 1,4quinone isomer (para compound) but readily forms with 1,2quinone isomer (ortho compound), and the {copper-1,2-quinone} complex so formed, selectively mediates electrocatalytic H 2 O 2 reduction at −0.1 V versus Ag/AgCl in pH 7 PBS (Scheme 1H). CV responses of GCE/MWCNT*@Car-Qn treated with Cu 2+ showed no redox peak at −0.1 V versus Ag/AgCl in pH 7 PBS and also failed to show any mediation of H 2 O 2 reduction in 100 μM H 2 O 2 containing pH 7 PBS (data not enclosed) (Scheme 1G).…”

Section: Resultsmentioning

confidence: 91%

“…A double logarithmic plot of the anodic peak current (i pa ) versus scan rate (v) is linear with the slope, ∂log(i pa )/∂log(v), ∼1 (Figure 2B, curve a), indicating that the A2/C2 redox process is surface confined electron-transfer in nature. 33 The anodic and cathodic peak potentials of A2/C2, E pa and E pc , respectively, yielded an halfwave potential, E 1/2 ((E pa + E pc )/2), of 215 mV at the lowest scan rate 5 mV s −1 . With increase in the scan rate, E 1/2 shifted to higher potentials, which may indicate kinetically controlled redox process of the present system.…”

Section: Resultsmentioning

confidence: 95%

“…In continuation of these studies, to understand how the structural features of the substrate molecule control which benzene ring should get oxidized, phenathiozene, an heteroatom-substituted anthracene analogue with two benzene rings fused symmetrically to two sides of a 6-membered ring with NH and S occupying para positions has been studied on MWCNT in pH 7 phosphate buffer solution (PBS) recently. 33 Phenathiozene-bi-1,4-quinone has been found to be the end product, suggesting that the planar nature of the phenathiozene molecule allowed its three hexagonal rings to strongly bind with the hexagonal rings of the MWCNT, which enabled oxidation of the two symmetrical benzene rings of it to phenathiozene-bi-1,4-quinone. Following this observation, it is intriguing to ask if a substrate molecule with an incompatible (with respect to MWCNT hexagonal benzene ring structure) 5-membered ring with two benzene rings symmetrically present on either side of it is used: what would happenwhether it would allow oxidation of both the benzene rings or only one benzene ring?…”

Section: Introductionmentioning

confidence: 99%

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Regioselective Electrochemical Oxidation of One of the Identical Benzene Rings of Carbazole to 1,4-Quinone on the MWCNT Surface and Its Electrocatalytic Activity

Gayathri¹,

Pillai

Kumar³

2019

J. Phys. Chem. C

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Carbazole-1,4-quinone is a key structural unit of naturally occurring carbazole-quinone alkaloids, for instance, 3-methyl carbazole-1,4-quinone (Murrayaquinone), that are widely used in pharmaceutics and medicine. These compounds are generally synthesized from tetrahydro ketone derivatives by multistep synthetic routes. Until now, there is no direct method reported for the partial oxidation of carbazole to carbazole-1,4-quinone by chemical, biochemical, or electrochemical reaction routes. Literature survey on the oxidation of carbazole and its derivatives suggests that polymeric or oligomeric forms are the sole products, but not, monomeric carbazole-1,4-quinone. Herein, we report a simple electrochemical oxidation of surface-confined carbazole to a highly redox active carbazole-mono-1,4-quinone, where only one of the identical benzene rings of carbazole gets selectively oxidized, on a cathodically activated multiwalled carbon nanotube (MWCNT) surface anchored to a glassy carbon electrode (GCE/MWCNT*@Car-Qn; * = cathodically activated, Car-Qn = carbazole-1,4-quinone) in pH 7 phosphate buffer solution, unlike the time consuming conventional multistep synthetic routes. The GCE/MWCNT*@Car-Qn showed a well-defined surface-confined peak at E 1/2 = 215 ± 5 mV versus Ag/AgCl with a Nertisan pH dependence in character. This new hybrid system showed efficient electrocatalytic oxidation and sensing of hydrazine in a neutral pH solution. No such electrochemical features were noticed for carbazole on the GCE surface. Collective physico-chemical (scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, HRMS, and NMR) and electrochemical characterizations of the MWCNT*@Car-Qn formation process revealed that in situ formed H2O2 at cathodic potentials and iron impurity in MWCNT, forming electro-Fenton species, are responsible for the selective electrochemical oxidation of carbazole to carbazole-1,4-quinone on the MWCNT surface.

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D–A Structured High‐Performance Photothermal/Photodynamic Thionin‐Synthetic Melanin Nanoparticles for Rapid Bactericidal and Wound Healing Effects

Liu

Cheng

et al. 2023

Adv Healthcare Materials

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Synthesized melanin nanoparticles (SMNPs) are used as advanced photothermal materials. However, their internal structures are complex and disordered, and tuning the photothermal performance of nanoparticles is still a hot spot of concern. This article presents thionin (Th)‐doped SMNPs, namely Th‐SMNPs, which are the first SMNPs formed using the one‐pot polymerization of Th with Levodopa. Th can undergo Michael addition and Schiff base reaction between indole dihydroxy/indolequinone and their oligomers to form donor–acceptor pairs in the structure to modulate the photothermal performance of SMNPs. Structural and spectroscopic analyses and density functional theory simulations further confirm the existence of the donor–acceptor structure. Th‐SMNPs exhibit excellent total photothermal efficiency (34.49%) in the near‐infrared region (808 nm), which is a 60% improvement compared to SMNPs. This allows Th‐SMNPs to exhibit excellent photothermal performance at low power 808 nm laser irradiation. Meanwhile, Th not only enhances the photothermal properties of SMNPs, but also imparts photodynamic effects to SMNPs. Th‐SMNPs can produce 1O2 under 660 nm laser irradiation. A dual‐function photothermal and photodynamic textile named Th‐SMNPs@cotton is constructed based on Th‐SMNPs, which can act as a rapid photothermal/photodynamic sterilization and is promising for wound healing treatment of bacterial infections under low‐power dual laser irradiation.

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An unusual electrochemical oxidation of phenothiazine dye to phenothiazine-bi-1,4-quinone derivative (a donor-acceptor type molecular hybrid) on MWCNT surface and its cysteine electrocatalytic oxidation function

Cited by 20 publications

References 60 publications

A prototype device of microliter volume voltammetric pH sensor based on carbazole–quinone redox-probe tethered MWCNT modified three-in-one screen-printed electrode

A prototype device of microliter volume voltammetric pH sensor based on carbazole–quinone redox-probe tethered MWCNT modified three-in-one screen-printed electrode

Regioselective Electrochemical Oxidation of One of the Identical Benzene Rings of Carbazole to 1,4-Quinone on the MWCNT Surface and Its Electrocatalytic Activity

D–A Structured High‐Performance Photothermal/Photodynamic Thionin‐Synthetic Melanin Nanoparticles for Rapid Bactericidal and Wound Healing Effects

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