Synthesis and characterization of tetra-ganciclovir cobalt (II) phthalocyanine for electroanalytical applications of AA/DA/UA

Graphene derivative-based ink advances inkjet printing technology for fabrication of electrochemical sensors and biosensors

The field of biosensing would significantly benefit from a disruptive technology enabling flexible manufacturing of uniform electrodes. Inkjet printing holds promise for this, although realizing full electrode manufacturing with this technology remains challenging. We introduce a nitrogen-doped carboxylated graphene ink (NGA-ink) compatible with commercially available printing technologies. The water-based and additive-free NGA-ink was utilized to produce fully inkjet-printed electrodes (IPEs), which demonstrated successful electrochemical detection of the important neurotransmitter dopamine. The cost-effectiveness of NGA-ink combined with a total cost per electrode of $0.10 renders it a practical solution for customized electrode manufacturing. Furthermore, the high carboxyl group content of NGA-ink (13 wt%) presents opportunities for biomolecule immobilization, paving the way for the development of advanced state-of-the-art biosensors. This study highlights the potential of NGA inkjet-printed electrodes in revolutionizing sensor technology, offering an affordable, scalable alternative to conventional electrochemical systems.

Co4+ in porous ZIF-67-derives intercalating-bridging adsorption of 2-reaction sites for simultaneous 2-electron transfer toward sensitive detection of uric acid

Metal-organic frameworks (MOFs) have been used to detect uric acid (UA), but still very challenging to achieve a low detection limit due to the low inferior conductivity of MOFs. Herein, three different N-doped ZIF-67-derived carbons were synthesized for the first time by one-step co-pyrolysis of 2-methylimidazole with cobalt nitrate (CN), cobalt acetate (CA) or cobalt chloride (CC) toward UA sensing. Afterwards, the cobalt nitrate-derived Co particle (Co/CN) supported by N-doped ZIF-67-derived carbon displays extremely low detection limit and high sensitivity for UA, outperformed all reported MOFs-based UA sensors. More interestingly, it was discovered that the high valence Co4+ within the Co/CN sample produced in high-acidic environment can intercalate in the frame for a bridge adsorption between two reaction sites, which boosted simultaneous 2-electron transfer, while Co3+ only allows an end-adsorption structure for one-electron transfer being the rate determining step. Furthermore, the bridge adsorption mode of UA on Co4+ -based catalyst was also verified by theoretical DFT calculations and XPS experiment. This work holds great promise for a selective and sensitive UA sensor for practical bioscience and clinic diagnostic applications while shedding lights in fundamental research for innovative designs and developments of high-sensitive electrochemical sensors.

Novel nickel(II) phthalocyanine/reduced graphene oxide: an electrochemical sensing platform for analysis of hydroquinone and chloramphenicol in environmental samples

Novel tetra-2-(biphenyl-4-yl)-1,3-benzoxazol-carboxamide nickel(II) phthalocyanine (NiTBPBXCAPc) and rGO were confirmed using FT-IR, UV-vis, XRD, TGA and Raman spectra. The NiTBPBXCAPc and rGO nanocomposite has been developed to detect hydroquinone (HQN) and chloramphenicol (CPC). NiTBPBXCAPc has been examined using cyclic voltammetry (CV), linear sweep voltammetry (LSV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) analysis. The simultaneous CV analysis of HQN and CPC demonstrated the ability of NiTBPBXCAPc@rGO/GCE to execute simultaneous redox reactions. The voltammetric and amperometric limit of detection for HQN and CPC was determined to be 4.5 and 3.5 nM respectively, with a sensitivity of 0.446 and 0.416 μA M-1 cm-2. The amperometric LOD was observed to be 5 and 4 nM with a sensitivity of 0.235 and 0.288 μA M-1 cm-2. Additionally, the NiTBPBXCAPc@rGO/GC electrode is also used for real sample analysis with outstanding recovery. The long-term storage stability, reusability, and real-world sample analysis of the NiTBPBXCAPc@rGO/GC electrode demonstrated its use in environmental analysis.

Electrochemical energy storage in an organic supercapacitor via a non-electrochemical proton charge assembly

Contrary to conventional beliefs, we show how a functional ligand that does not exhibit any redox activity elevates the charge storage capability of an electric double layer via a proton charge assembly. Compared to an unsubstituted ligand, a non-redox active carboxy ligand demonstrated nearly a 4-fold increase in charge storage, impressive capacitive retention even at a rate of 900C, and approximately a 2-fold decrease in leakage currents with an enhancement in energy density up to approximately 70% via a non-electrochemical route of proton charge assembly. Generalizability of these findings is presented with various non-redox active functional units that can undergo proton charge assembly in the ligand. This demonstration of non-redox active functional units enriching supercapacitive charge storage via proton charge assembly contributes to the rational design of ligands for energy storage applications.

A novel MWCNT-encapsulated (2-aminoethyl)piperazine-decorated zinc(II) phthalocyanine composite: development of an electrochemical sensor for detecting the antipsychotic drug promazine in environmental samples

A nanocomposite of (2-aminoethyl)piperazine ligand substituted with zinc(II) tetra carboxylic acid phthalocyanine (ZnTEPZCAPC) and MWCNTs was constructed and employed to develop an electrochemical sensor with outstanding sensitivity and a low detection limit. The macrocyclic complex ZnTEPZCAPC was first synthesized and then employed for the electrochemical determination of the antipsychotic drug promazine (PMZ). The as-prepared ZnTEPZCAPC and MWCNT nanocomposite was characterized using different techniques, such as Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), UV-visible spectroscopy (UV-Vis), field emission scanning electron microscopy (FE-SEM), and thermogravimetric analysis (TGA). Further, the prepared ZnTEPZCAPC@MWCNT nanocomposites were modified on a glassy carbon electrode (GCE) surface, and the electrochemical activity was investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry (CA) tests in pH 7.0 phosphate buffer solution (PBS) in the potential window of 0.0-1 V. The ZnTEPZCAPC@MWCNTs displayed a superior electrochemical performance because of their high electrochemical active surface area (0.453 cm2), good conductivity, and a synergetic effect. The developed electrochemical sensor exhibited a broad linear range of 0.05-635 μM and the lowest detection limit of 0.0125 nM, as well as excellent sensitivity, repeatability, and reproducibility. Finally, the fabricated sensor was successively used for the real-time detection of PMZ in environmental and biological samples and displayed feasible recoveries.

Novel decorated aluminium(iii) phthalocyanine complex with the application of MWCNTs on electrodes: electrochemical non-enzymatic oxidation and reduction of glucose and hydrogen peroxide

In this study, we performed the physicochemical and electrochemical characterization of a decorated macrocyclic aluminium(iii) phthalocyanine complex (AlTMQNCAPc). Subsequently, the AlTMQNCAPc@MWCNT/GC electrode was used for the electrochemical detection of glucose and hydrogen peroxide (H₂O₂) by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry (CA). Moreover, the limit of detection, linear range, and sensitivity for glucose and H₂O₂ were investigated (CV: 2.5 nM L^-1 and 25 nM L^-1, 50-500 μM, 0.052 and 0.072 μA μmol cm^-2; DPV: 3.1 nM L^-1 and 18 nM L^-1, 50-500 μM, 0.062 and 0.066 μA μmol cm^-2 and CA: 10 nM L^-1 and 20 nM L^-1, 50-500 μM, 0.098 and 0.07 μA μmol cm^-2, respectively). In addition, the AlTMQNCAPc@MWCNT/GC electrode showed good selectivity for the detection of glucose and H₂O₂ in the presence of common interfering substances, such as AA, DA, UA, glycine, l-cysteine, nitrite, Pb(ii), Cd(ii), Cu(ii), Co(ii), Hg(ii), Zn(ii), and glucose. For the detection of glucose and H₂O₂, the kinetic parameters, including the electron transfer coefficient and catalytic reaction rate constant, were also established. Finally, for usage in practical applications, the modified electrode was employed to achieve the quantitative detection of glucose and H₂O₂ in human urine and commercial samples of 3% H₂O₂, respectively.

Unusual Ligand Assistance in Molecular Electrocatalysis via Interfacial Proton Charge Assembly

We show that the ability of the ligand to reorganize the electric double layer (EDL) often dominates the electrocatalysis contrary to their inductive effect in the spectrochemical series, leading to counterintuitive electrocatalysis. With water oxidation and chlorine evolution as the probe reactions, the same catalytic entity with carboxy functionalized ligand exhibited surprisingly higher electrochemical activity in comparison to the aggressively electron-withdrawing nitro functionalized ligands, which is contrary to their actual location in the spectrochemical series. Spectroscopic and electrochemical analyses suggest the enrichment of catalytically active species in the carboxy substituted ligand via proton charge assembly in the EDL that in turn enhances the kinetics of the overall electrochemical process. This demonstration of less obvious ligands becoming indispensable in electrocatalysis suggests a blind designing of ligands solely based on their inductive effect should be reconsidered as it will prevent the utilization of the maximum potential of the molecule in electrocatalysis.

Electrochemical, Ultrasensitive, and Selective Detection of Nitrite and H2O2: Novel Macrostructured Phthalocyanine with Composite MWCNTs on a Modified GCE

In the current study, the synthesis of tetra-4-(2-methoxyphenoxy) carboxamide cobalt(II) amide-bridged phthalocyanine (CoTMePhCAPc) is described, as well as its characterization by Fourier transform infrared (FT-IR), UV-visible, and mass spectroscopy; powder X-ray diffraction (PXRD); thermogravimetric analysis (TGA); scanning electron microscopy (SEM); and electrochemistry. Sensing of nitrite (NO₂^-) and hydrogen peroxide (H₂O₂) simultaneously was done on CoTMePhCAPc with the composite multiwalled carbon nanotube (MWCNT)-modified glassy carbon electrode (CoTMePhCAPc/MWCNT/GCE) in the range of linear absorption (NO₂^- and H₂O₂: CV 50-750, differential pulse voltammetry (DPV) 50-750, CA 50-500 nmol L^-1), lower detection limit (NO₂^- and H₂O₂: CV 10.5 and 12.5, DPV 10.5 and 11.2, CA 6.0 and 5.5 nmol L^-1), and sensitivity (NO₂^- and H₂O₂: CV 0.379 and 0.529, DPV 0.043 and 0.049, CA 0.033 and 0.040 μA nM^-1 cm^-2). The composite electrode exhibits improved electrocatalytic behavior compared to modified electrodes for nitrite and H₂O₂. The CoTMePhCAPc/MWCNT/GCE sensor displays good selectivity even in the presence of an excess of interfering metal ions and biomolecules at the applied potentials of +400 mV (nitrite) and -400 mV (H₂O₂). Moreover, the fabricated sensor was studied with various phosphate-buffered saline (PBS) (pH 5-9) electrolyte solutions. The unknown H₂O₂ concentration in blood samples and apple juice and nitrite concentration in drinking water and butter leaf lettuce were all measured using the usual addition method. Docking analysis clearly indicates that the ligand shows excellent inhibition activity toward the three subjected protein molecules.

Electrochemical fabrication of Co(OH)2 nanoparticles decorated carbon cloth for non-enzymatic glucose and uric acid detection

Cobalt hydroxide nanoparticles (Co(OH)₂ NPs) were uniformly deposited on flexible carbon cloth substrate (Co(OH)₂@CC) rapidly by a facile one-step electrodeposition, which can act as an enzyme-free glucose and uric acid sensor in an alkaline electrolyte. Compositional and morphological characterization were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), which confirmed the deposited nanospheres were Co(OH)₂ nanoparticles (NPs). The electrochemical oxidation of glucose and uric acid at Co(OH)₂@CC electrode was investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry methods. The results revealed a remarkable electrocatalytic activity toward the single and simultaneous determination of glucose and uric acid at about 0.6 V and 0.3 V (vs. Ag/AgCl), respectively, which is attributed to a noticeable synergy effect between Co(OH)₂ NPs and CC with good repeatability, satisfactory reproducibility, considerable long-term stability, superior selectivity, outstanding sensitivity, and wide linear detection range from 1 uM to 2 mM and 25 nM to 1.5 uM for glucose and UA, respectively. The detection limits were 0.36 nM for UA and 0.24 μM for glucose (S/N = 3). Finally, the Co(OH)₂@CC electrode was utilized for glucose and uric acid determination in human blood samples and satisfying results were obtained. The relative standard derivations (RSDs) for glucose and UA were in the range 6 to 14% and 0 to 3%, respectively. The recovery ranges for glucose an UA were 97 to 103% and 95 and 101%, respectively. These features make the novel Co(OH)₂@CC sensor developed by a low-cost, efficient, and eco-friendly preparation method a potentially practical candidate for application to biosensors.

Novel Schiff base iron(ii) phthalocyanine with composite MWCNTs on modified GCE: electrochemical sensor development for paracetamol

Paracetamol is one of the most commonly consumed medicines to deal with minor pain, body ache, headache, fever etc. It can also be used for getting temporary relief from arthritis pain.

Novel Schiff base cobalt(ii) phthalocyanine with appliance of MWCNTs on GCE: enhanced electrocatalytic activity behaviour of α-amino acids

A novel tetra-4-{(E)-[(8-aminonaphthalen-1-yl)imino]methyl}-2-methoxyphenol Co(ii) phthalocyanine (CoTANImMMPPc) was synthesized using a precursor protocol and characterized via electroanalytical and spectroscopic techniques. The FT-IR spectra of the synthesized compounds showed significant peaks corresponding to the functional groups of the precursors and phthalocyanine (Pc) compound. The mass and NMR spectra confirmed the formation of the target precursor compounds. A film of CoTANImMMPPc was deposited on the surface of an electrode and applied for the detection and monitoring of l-alanine and l-arginine. The cyclic voltammetric studies of l-alanine and l-arginine using the (CoTANImMMPPc/MWCNTs/GC) electrode showed a linear response in the range of 50–500 nM and the limit of detection was found to be 1.5 and 1.2 nM, respectively. Differential pulse voltammetry and chronoamperometry showed that the catalytic response for l-alanine and l-arginine is in the range of 50–500 nM with an LoD of 1.8 and 2.3 nM, respectively. The oxidation-active CoTANImMMPPc film significantly enhanced the current response in the chronoamperometric method and displayed a selective and sensitive response towards l-alanine and l-arginine in the presence of various other bio-molecules. The developed electrode showed good working stability and was applied for the analysis of real samples, which yielded satisfactory results. Therefore, CoTANImMMPPc-MWCNTs/GCE shows good analytical performance, is economical and produced via a simple synthetic method and can be applied as a sensor for the detection of l-alanine and l-arginine.

A novel CoTANImMMPPc complex was synthesized using a precursor protocol and characterized via electroanalytical and spectroscopic techniques with enhanced electrocatalytic behaviour of α-amino acids.

Phthalocyanine Modified Electrodes in Electrochemical Analysis

Phthalocyanines are aromatic or macrocyclic organic compounds and attract great attention due to their numerous properties. They have many high-tech applications in different areas of the industry such as dyestuffs, thermal printing screens, photovoltaic solar cells, membrane catalytic reactors, semiconductor materials and gas sensors. In the last decade, electrochemical sensor studies have accelerated with the catalytic lighting. It plays a dominant role in the development and implementation of new generation sensors. The aim of this study is to review the electrochemical methods based on electrode modification with phthalocyanines and to shed light on new application areas of phthalocyanines. The focal point was based on the sensor applications of phthalocyanines in the determination of drugs, pesticides, organic materials and metals etc. by electrochemical methods. Experimental conditions and some validation parameters of the sensor applications such as metal phthalocyanine types, indicator electrodes, selectivity, working ranges, detection limits, and analytical applications were discussed. Consequently, this is the first review dealing with the applications of phthalocyanines in electrochemical sensors for the sensitive determination of analytes in a variety of matrices.

Novel garnished cobalt(ii) phthalocyanine with MWCNTs on modified GCE: sensitive and reliable electrochemical investigation of paracetamol and dopamine

The synthesized CoTBPCAPc was confirmed by physico-electrochemical analysis, is thermally stable, and has good yield. CoTBPCAPc/MWCNTs/GCE detects PA and its toxic degradation product DA at different potentials, simultaneously and with excellent analytical performance.