Dimethyl Dihydroacridines as Photocatalysts in Organocatalyzed Atom Transfer Radical Polymerization of Acrylate Monomers

Development of photocatalysts (PCs) with diverse properties has been essential in the advancement of organocatalyzed atom transfer radical polymerization (O‐ATRP). Dimethyl dihydroacridines are presented here as a new family of organic PCs, for the first time enabling controlled polymerization of challenging acrylate monomers by O‐ATRP. Structure–property relationships for seven PCs are established, demonstrating tunable photochemical and electrochemical properties, and accessing a strongly oxidizing ²PC^.+ intermediate for efficient deactivation. In O‐ATRP, the combination of PC, implementation of continuous‐flow reactors, and promotion of deactivation through addition of LiBr are critical to producing well‐defined acrylate polymers with dispersities as low as 1.12. The utility of this approach is established through demonstration of the oxygen‐tolerance of the system and application to diverse acrylate monomers, including the synthesis of well‐defined di‐ and triblock copolymers.     

Analytical approach for characterization of cadmium-induced thiol peptides—a case study using <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis>

Phytochelatins (PC) were described earlier to play a role in metal detoxification in Chlamydomonas reinhardtii but were not clearly identified. The focus of this case study was to identify PC synthesized by C. reinhardtii exposed to Cd. Only low intracellular concentrations of cadmium (85 nmol g⁻¹ fresh weight) were sufficient to cause significant changes in thiol peptide pools. Thus, results showed a progressive decline of the glutathione content, accompanied by an induction of phytochelatins. Not only canonic phytochelatins but for the first time also the iso-phytochelatins CysPC _n and PC₂Ala were identified in this unicellular green alga using electrospray ionization quadrupole time-of-flight tandem mass spectrometry. Additionally, CysPC _n desGly, PC _n desGly, CysPC _n Glu, and PC₂Glu were found throughout MS analysis. Also, low abundant PCs could be detected due to the high sample preconcentration combined with little sample amounts (0.3 μL min⁻¹) necessary for electrospray. Identified PCs had a maximum number of 5 γ-glutamyl cysteine (γ-GluCys) units. Thiol peptides of higher molecular masses suggesting PC _n with n > 5 could be identified as intermolecular oxidation products of smaller PCs. Thiols may easily be oxidized. Therefore, PCs were reduced prior to MS analysis. Dithiothreitol and tris(2-carboxyethyl) phosphine were compared concerning their reduction effort.      

Synthesis of Soluble Quinacridone Photocatalysts for the Homogeneous Oxidation of Thioethers

Evaluation of quinacridone (QA) derivatives as homogeneous metal-free photocatalysts is here presented. QA derivatives were synthetized and systematically characterized, measuring their ground state and excited state redox potentials in dichloromethane (DCM) and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), in order to understand how structural modifications influenced their photocatalytic properties. In particular, the effect of dicyanomethylene and nitro EWG groups was investigated, in order to develop a photocatalyst capable of promoting oxidative processes in the presence of molecular oxygen. Among the analyzed derivatives, 2,9-dinitro-N,N′-dibutylquinacridone (DNDBQA) was the one with the highest excited state reduction potential (E_red*=1.60 V in HFIP vs SCE), while N,N’-dibutylquinacridone (DBQA) showed valuable excited state redox potentials (E_red*=1.29 V; E_ox*=−1.28 V in HFIP vs SCE), making it suitable for bimodal applications in oxidative and reductive photocatalytic processes. Afterwards, the synthetized QA derivatives were examined as photocatalysts to promote the selective aerobic oxidation of thioether to sulfoxide. Promising results in thioanisole oxidation were achieved with all the QA derivatives tested as photocatalysts, in terms of yield and selectivity. Remarkably, DBQA showed the best performances, catalyzing the reaction in only 20 minutes, using 0.5 % of the photocatalyst, and showing excellent performances in the oxidation of several thioether derivatives.     

Protective Effects and Mechanisms of Procyanidins on Parkinson’s Disease In Vivo and In Vitro

This research assessed the molecular mechanism of procyanidins (PCs) against neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and its metabolite 1-methyl-4-phenylpyridinium (MPP⁺) induced Parkinson’s disease (PD) models. In vitro, PC12 cells were incubated with PCs or deprenyl for 24 h, and then exposed to 1.5 mM MPP⁺ for 24 h. In vivo, zebrafish larvae (AB strain) 3 days post-fertilization (dpf) were incubated with deprenyl or PCs in 400 μM MPTP for 4 days. Compared with MPP⁺/MPTP alone, PCs significantly improved antioxidant activities (e.g., glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), catalase (CAT)), and decreased levels of reactive oxygen species (ROS) and malondialdehyde (MDA). Furthermore, PCs significantly increased nuclear Nrf2 accumulation in PC12 cells and raised the expression of NQO1, HO-1, GCLM, and GCLC in both PC12 cells and zebrafish compared to MPP⁺/MPTP alone. The current study shows that PCs have neuroprotective effects, activate the nuclear factor-erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway and alleviate oxidative damage in MPP⁺/MPTP-induced PD models.     

The Chemistry of Vanadium bis-Phenolate NHC Complexes in Three Oxidation States

Twenty-one vanadium bis-phenolate benzimidazolylidene complexes, spanning three oxidation states, have been investigated. Special emphasis is placed on their salt metathesis reactivity and the accessibility of the +IV oxidation state by reductive or oxidative routes, starting from vanadium(V) or vanadium(III) respectively. While the reductive route is highly dependent on the reducing agent and starting material used, the oxidative route gives clean access to vanadium(IV) dihalide complexes. The low-valent vanadium(III) complexes are excellent precursors for salt metathesis reactions which lead to the isolation of a rare vanadium(III) NHC alkyl complex. All new complexes have been characterized by (paramagnetic) ¹H NMR and ⁵¹V NMR, UV–VIS, IR and EPR spectroscopy as well as elemental analysis. Cyclic voltammetry has been performed in selected cases to study the influence of imido or phenolate supporting ligands towards the redox-potential of the vanadium(V/IV) redox couple compared to the parent oxo-chlorido complex A .     

Rapid and simple UPLC-MS/MS method for precise phytochelatin quantification in alga extracts

Quantitative phytochelatin (PC) analysis is, due to oxidation sensitivity of the PCs, matrix effects, and time consuming sample preparation, still a challenging analytical task. In this study, a rapid, simple, and sensitive method for precise determination of native PCs in crude extracts of the green alga Chlamydomonas reinhardtii was developed. Algae were exposed 48 h to 70 μM Cd. Coupling of ultra performance liquid chromatography and electrospray ionization tandem mass spectrometry with multi-reaction mode transitions for detection permitted the required short-time, high-resolution separation and detection specificity. Thus, under optimized chromatographic conditions, 10 thiol peptides were baseline-separated within 7 min. Relative detection limits in the nanomolar range in microliter sample volumes were achieved (corresponding to absolute detection limits at femtomol level). Next to glutathione (GSH), the most abundant cadmium-induced PCs in C. reinhardtii, namely CysGSH, PC₂, PC₃, CysPC₂, and CysPC₃, were quantified with high reproducibility at concentrations between 15 and 198 nmol g^?1 fresh weight. The biological variation of PC synthesis of nine independently grown alga cultures was determined to be on average 13.7%.

Identification of in vivo nitrosylated phytochelatins in Arabidopsis thaliana cells by liquid chromatography-direct electrospray-linear ion trap-mass spectrometry

Reversed-phase liquid chromatography (RPLC) and electrospray (ESI)-linear ion trap (LIT) mass spectrometry was applied to the direct characterization of in vivo S-nitrosylated (SNO) phytochelatins (PCs) expressed in cadmium-stressed Arabidopsis thaliana cells. Cys-nitrosylation is under discussion as in vivo redox-based post-translational modification of proteins and peptides in plants in which the –NO group is involved as signal molecule in different biological functions. The gas-phase ion chemistry of in vivo and in vitro generated SNO-PC_s was compared with the aim of evaluating NO binding stability and improving MS knowledge about peptide nitrosation. Using RPLC separation and ESI-LIT-MS, mono-nitrosylated PCs were identified in in vivo cadmium treated A. thaliana cells without derivatization. The in vivo binding of the NO group to PC₂, PC₃ and PC₄ resulted to occur selectively on only one cystein residue. The fragmentation pathway energies of the in vitro GSNO-generated NO-PCs with respect to the in vivo NO-PCs were investigated, suggesting the presence of a different internal stability for these molecules. By carrying out MS² experiments on these quasi-symmetric peptides, the different stability degree of the NO group was demonstrated to be correlated with the PC chain length. In addition, the data obtained highlight a putative role of the adjacent Glu/Cys motif in the gas-phase stability of the NO-containing molecule.     

Electrochemical characterization of small organic hole-transport molecules based on the triphenylamine unit

A series of substituted triphenylamine-containing organic compounds are synthesized and their hole-transport properties are examined by electrochemical and spectroelectrochemical methods. Several substituted tirphenylamines exhibited irreversible electron-transfer reactions both in the oxidative and reductive scan. On the other hand, the cyclic voltammograms of the p-phenylenediamine series are well defined. N,N^′-bis(4-nitrophenyl)-N,N^′-diphenyl-1,4-phenylenediamine (NPD) exhibited two reversible oxidation redox couples at +1.00 and +1.28 V vs. Ag/AgCl in dichloromethane solution. There is one reversible reduction redox couple at −1.12 V and one irreversible wave with E_p,c at −1.87 V. Cyano-substituted p-phenylenediamine (CPD) exhibited similar oxidation redox couples. Amino-substituted p-phenylenediamine (APD) is easier to oxidize than NPD and CPD. APD exhibits two reversible oxidation redox couples at +0.40 and +0.70 V and two extra irreversible oxidation waves at +1.26 and +1.52 V. Optically transparent thin-layer electrode (OTTLE) coupled with UV/Vis/NIR spectroscopy was used to examine the oxidation products of the above reactions. The electrogenerated cation and dication of the substituted p-phenylenediamine are very stable in the spectroelectrochemical studies. Oxidation of the compound APD exhibited a distinguished absorption pattern, which is different from those of compound NPD and compound CPD.     

Electron-Poor Acridones and Acridiniums as Super Photooxidants in Molecular Photoelectrochemistry by Unusual Mechanisms

Electron-deficient acridones and in situ generated acridinium salts are reported as potent, closed-shell photooxidants that undergo surprising mechanisms. When bridging acyclic triarylamine catalysts with a carbonyl group (acridones), this completely diverts their behavior away from open-shell, radical cationic, ‘beyond diffusion’ photocatalysis to closed-shell, neutral, diffusion-controlled photocatalysis. Brønsted acid activation of acridones dramatically increases excited state oxidation power (by +0.8 V). Upon reduction of protonated acridones, they transform to electron-deficient acridinium salts as even more potent photooxidants (*E_1/2=+2.56–3.05 V vs SCE). These oxidize even electron-deficient arenes where conventional acridinium salt photooxidants have thusfar been limited to electron-rich arenes. Surprisingly, upon photoexcitation these electron-deficient acridinium salts appear to undergo two electron reductive quenching to form acridinide anions, spectroscopically-detected as their protonated forms. This new behaviour is partly enabled by a catalyst preassembly with the arene, and contrasts to conventional SET reductive quenching of acridinium salts. Critically, this study illustrates how redox active chromophoric molecules initially considered photocatalysts can transform during the reaction to catalytically active species with completely different redox and spectroscopic properties.     

6,7-dialkoxy-2,3-diphenylquinoxaline based conjugated polymers for solar cells with high open-circuit voltage

6,7-Dialkoxy-2,3-diphenylquinoxaline based narrow band gap conjugated polymers, poly[2,7-(9-octyl-9H-carbazole)-alt-5,5-(5,8-di-2-thinenyl-(6,7-dialkoxy-2,3-diphenylquinoxaline))] (PCDTQ) and poly[2,7-(9,9-dioctylfluorene)-alt-5,5-(5,8-di-2-thinenyl-(6,7-dialkoxy-2,3-diphenylquinoxaline))] (PFDTQ), have been synthesized by Suzuki polycondensation. Their optical, electrochemical, transport and photovoltaic properties have been investigated in detail. Hole mobilities of PCDTQ and PFDTQ films spin coated from 1,2-dichlorobenzene (DCB) solutions are 1.0 × 10-4 and 4.1 × 10-4 cm2V-1s-1, respectively. Polymer solar cells were fabricated with the as-synthesized polymers as the donor and PC61BM and PC71BM as the acceptor. Devices based on PCDTQ:PC71BM (1:3) and PFDTQ:PC71BM (1:3) fabricated from DCB solutions demonstrated a power conversion efficiency (PCE) of 2.5% with a Voc of 0.95 V and a PCE of 2.5% with a Voc of 0.98 V, respectively, indicating they are promising donor materials.     

Prediction of Redox Potentials and Isomer Distribution Yields for Reductive Dechlorination of Chlorobenzenes

Abstract

Gibbs free energies of reductive dechlorination processes of chlorobenzenes are calculated from thermodynamic data. The results are utilized to predict redox potentials and isomer distribution yields.

The model predicts a standard redox potential of 0.680 V for the reduction of hexachlorobenzene to pentachlorobenzene, tapering off to 0.535 V for the reduction of monochlorobenzene to benzene. It is shown that under anaerobic conditions, reductive dechlorination is more likely to occur, while aerobic conditions favour the formation of chlorophenols.

An isomer distribution yield is predicted for each of the reductive dechlorination processes of chlorobenzenes. Predicted yields correspond to experimental values within 10%. The model includes a possibility to establish a temperature dependence of the relative isomer yields.     

Sensitized photo-redox reaction: VII. The Synthesis,FAB mass spectrum,stationary absorption,emission, transient absorption spectra,redox potential of dihydroxy-tin (IV)-mesoporphyrin dimethyl ester and its sensitized photo-reduction of methyl viologen

In DMSO/water (4:1), photolysis of the dihydroxy-Sn (IV)-mesoporphyrin dimethyl ester (SnP)/methyl viologen (MV²⁺)/ethylene diamine tetraacetic acid (EDTA) ternary system produces methyl viologen cation radical with a quantum yield of 0.67, much higher than that of systems with other metal complexes of mesoporphyrin dimethyl ester. Neither EDTA nor MV²⁺ quenches the stationary fluorescence of SnP, implying that the reaction does not take place at the singlet state. With flash photolysis we obtain the T-T absorption spectrum of SnP (λ_max 440 nm). By following the decay of this absorption, the triplet life time of SnP is estimated to be 41 μs. The life time is related to the concentration of either MV²⁺ or EDTA. Good linear relationships are obtained by plotting τ₀τ vs. the concentration of MV²⁺ or EDTA (Stern-Volmer plot), from which we determine the quenching constants: _kq(MV²⁺) =5.5 × 10⁷ mol^?1, s^?1; k_q (EDTA) =2.7 × 10⁷ mol^?1, s^?1. The data suggests that upon photolysis of the above ternary system, both oxidative quenching and reductive quenching of the triplet state of the sensitizer are occurring. From the measured phosphorescence spectrum (λ_max 704 nm) and the ground state redox, potentials (E^red_1/2?-0.84V, E^ox_1/2?+1.43 V, vs. Ag/AgCl, KCl (sat.)), we obtain the redox potential of triplet SnP to be E(P⁺/P*_T)?-0.33 V, E(P*_T+/P^?)?+0.92 V. Matching this data with the redox potential of MV²⁺ and EDTA, we establish the fact that during the photolysis of the SnP/MV²⁺/EDTA ternary system, both oxidative and reductive quenching are thermodynamically favorable processes. This is also the reason why the SnP sensitized reaction is much more efficient relative to other mesoporphyrin derivatives.     

Oxidative versus reductive additions: A 13C NMR study of H2, HX (X = Cl,Br, OR I), and Cl2 additions to some iridium(I) complexes

The ¹³C NMR spectra of a number of iridium complexes and of their adducts with H₂, HX, and Cl₂ (X = Cl, Br, I) are used to estimate the redox character of these additions. Rather than having the oxidative character expected, H₂ addition seems to be reductive. HX and Cl₂ additions are oxidative. Some of these complexes appear to have Lewis acid, rather than the expected Lewis base character.     

Rhodium complexes of PCNHCP: Oxidative addition of dichloromethane and catalytic hydrosilylation of alkynes affording (E)-alkenylsilanes

New rhodium complexes of PC^NHCP have been synthesized by using the silver transfer reagent, [Ag₃(PC^NHCP)₂Cl]Cl₂ (2). In the reaction between 2 and [Rh(COD)Cl]₂ in dichloromethane, the presumably formed nucleophilic Rh^I(PC^NHCP)Cl intermediate (A), undergoes a C–Cl bond activation of CH₂Cl₂ giving cis,mer-Rh^III(PC^NHCP)(CH₂Cl)Cl₂ (3) as the final product. Attempts to isolate A affords the oxidative degradation product of mer-Rh^III(PC^NHCP)Cl₃ complex (4). In contrast, the rhodium(I) center in Rh(PC^NHCP)(CO)Cl (5) is stabilized by the π-back bonding of CO ligand; a robust complex is, therefore, obtained. The solid-state structures of 2 and 3 were determined by X-ray diffraction. Complexes 3–5 are catalyst precursors for efficient, chemoselective hydrosilylation of alkynes. For the reaction between phenylacetylene and dimethylphenylsilane, a rapid hydrosilylation occurs, producing isomers of alkenylsilanes; then a slow isomerization pathway converts (Z)-alkenylsilane to its (E)-isomer. For 3, under catalytic condition, a facile reductive elimination of dichloromethane giving A is anticipated. The similarity in reactivity and selectivity between 3, 4 and 5 suggests the involvement of A as the active species in a common catalytic cycle.     

柱前衍生高效液相色谱-荧光检测法测定水稻中7种巯基化合物

建立了水稻中半胱氨酸(Cys)、谷胱甘肽(GSH)和植物螯合肽(phytochelatin, PC:PC₂、PC₃、PC₄、PC₅、PC₆)7种巯基化合物的柱前衍生高效液相色谱-荧光检测分析方法.样品经0.1%三氟乙酸(TFA)(含6.3 mmol/L二乙烯三胺五乙酸(DTPA))超声提取,然后以单溴二胺(mBrB)为衍生剂在pH 8.0的4-羟乙基哌嗪丙磺酸(HEPPS)缓冲溶液中衍生化.采用的色谱分离柱为Agilent Eclipse plus C_l8柱,流动相为0.1%TFA(pH 2.5)和100%乙腈(ACN),梯度洗脱,流速为0.8 mL/min.荧光检测的激发波长和发射波长分别为380 nm和470 nm.结果表明,7种巯基化合物在0.7~100.0 mg/L范围内,峰面积与质量浓度之间的线性关系良好(r²≥0.9991);检出限为0.03~0.20 mg/L;加标回收率为89.26%~99.42%,相对标准偏差为2.05%~5.87%.该方法准确、灵敏度高、重现性好,为水稻中巯基化合物的研究提供了检测手段.     

Biosynthesis of Cd-bound phytochelatins by <Emphasis Type="Italic">Phaeodactylum tricornutum</Emphasis> and their speciation by size-exclusion chromatography and ion-pair chromatography coupled to ICP–MS

Cd-bound phytochelatins (Cd–PCs) have been synthesised by incubation of Phaeodactylum tricornutum cell cultures with Cd and purified by size-exclusion chromatography–UV–Vis. These complexes, which were identified in previous work, have now been used as model substances to develop and optimise ion-pair chromatography (IPC) coupled to inductively coupled plasma–mass spectrometry (ICP–MS) for analysis of Cd–PCs. Subsequent analysis of samples taken from Silene vulgaris plants cultivated under heavy metal stress conditions revealed Cd signals but no Cd–PC signals. By use of isotopically enriched ¹¹⁶Cd–PCs the sample preparation steps were verified to determine the stability of the analytes. We observed species transformation between Cd–PCs and other unidentified Cd complexes. Consequently, the kinetic and thermodynamic lability of Cd–PCs are decisive factors in their detection.     

New 5-Octyl-thieno[3,4-c]pyrrole-4,6-dione Based Polymers: Synthesis and Photovoltaic Properties

Two donor-acceptor conjugated polymers, namely poly{4,8-bis(5-(2-ethylhexyl) thiophen-2-yl)benzo[1,2-b:4,5-b']difuran-alt-5-octyl-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione}(PBDFTTPD) and poly{4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b: 4,5-b']dithiophene-alt-5-octyl-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione}(PBDTTTPD), were synthesized by Stille coupling polymerization reactions. Their structures were verified by ¹H-NMR and elemental analysis, the molecular weights were determined by gel permeation chromatography and the thermal properties were investigated by thermogravimetric analysis. The polymer films exhibited broad absorption bands. The hole mobility of PBDFTTPD:PC₇₁BM(1:2, w/w) blend reached up to 5.5 × 10^?2 cm² v^?1 s^?1 by the space-charge-current method. Preliminary photovoltaic cells based on the device structure of ITO/PEDOT:PSS/PBDFTTPD:PC₇₁BM(1:2, w/w)/Ca/Al showed a power conversion efficiency of 2.32% with an open-circuit voltage of 0.90 V and a short circuit current of 4.40 mA cm^?2.     

Organometallic Iridium(III) Complex Sensitized Ternary Hybrid Photocatalyst for CO2 to CO Conversion

A series of heteroleptic iridium(III) complexes functionalized with two phosphonic acid (−PO₃H₂) groups ( ^dfppy IrP , ^ppy IrP , ^btp IrP , and ^piq IrP ) were prepared and anchored onto rhenium(I) catalyst (ReP)-loaded TiO₂ particles (TiO₂/ReP) to build up a new IrP -sensitized TiO₂ photocatalyst system ( IrP /TiO₂/ReP). The photosensitizing behavior of the IrP series was examined within the IrP /TiO₂/ReP platform for the photocatalytic conversion of CO₂ into CO. The four IrP -based ternary hybrids showed increased conversion activity and durability than that of the corresponding homo- ( IrP +ReP) and heterogeneous ( IrP +TiO₂/ReP) mixed systems. Among the four IrP /TiO₂/ReP photocatalysts, the low-energy-light (>500 nm) activated ^piq IrP immobilized ternary system ( ^piq IrP /TiO₂/ReP) exhibited the most durable conversion activity, giving a turnover number of ≥730 for 170 h. A similar kinetic feature observed through time-resolved photoluminescence measurements of both ^btp IrP /TiO₂ and TiO₂-free ^btp IrP films suggests that the net electron flow in the ternary hybrid proceeds dominantly through a reductive quenching mechanism, unlike the oxidative quenching route of typical dye/TiO₂-based photolysis.     

Sterically constrained tricyclic phosphine: redox behaviour,reductive and oxidative cleavage of P–C bonds,generation of a dilithium phosphaindole as a promising synthon in phosphine chemistry

The redox behaviour of sterically constrained tricyclic phosphine 3a was investigated by spectroelectrochemistry. The data suggested a highly negative reduction potential with the reversible formation of a dianionic species. Accordingly, 3a reacted with two equivalents of Li/naphthalene by reductive cleavage of a P–C bond of one of the PC₄ heterocycles. The resulting dilithium compound 5 represents a phosphaindole derivative with annulated aromatic C₆ and PC₄ rings. It is an interesting starting material for the synthesis of new heterocyclic molecules, as was shown by treatment with Me₂SiCl₂ and PhPCl₂. The structures of the products (6 and 7) formally reflect ring expansion by insertion of silylen or phosphinidene fragments into a P–C bond of 3a. Treatment of 3a with H₂O₂ did not result in the usually observed transfer of a single O atom to phosphorus, but oxidative cleavage of a strained PC₄ ring afforded a bicyclic phosphinic acid, R₂PO₂H.

Sterically constrained tricyclic phosphines with annulated five- and six-membered rings show fascinating chemical and redox reactivity as indicated by sophisticated in situ UV-vis CV and multi-pulse chronoamperometry.     

Preparation of cobalt-tetraphenylporphyrin/reduced graphene oxide nanocomposite and its application on hydrogen peroxide biosensor

A novel cobalt-tetraphenylporphyrin/reduced graphene oxide (CoTPP/RGO) nanocomposite was prepared by a π–π stacking interaction and characterized by ultraviolet–visible absorption spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS). The CoTPP/RGO nanocomposite exhibited high electrocatalytic activity both for oxidation and reduction of H₂O₂. The current response was linear to H₂O₂ concentration with the concentration range from 1.0 × 10⁻⁷ to 2.4 × 10⁻³ mol L⁻¹ (R = 0.998) at the reductive potential of −0.20 V and from 1.0 × 10⁻⁷ to 4.6 × 10⁻⁴ mol L⁻¹ (R = 0.996) at the oxidative potential of +0.50 V. The H₂O₂ biosensor showed good anti-interfering ability towards oxidative interferences at the oxidative potential of +0.50 V and good anti-interfering ability towards reductive interferences at the reductive potential of −0.20 V.