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This study investigates the synthesis and characterization of graphene oxide (GO) and its reduced form, reduced graphene oxide (rGO), focusing on their structural, physicochemical and electrochemical properties. Graphene oxide was synthesized from graphite flakes using the modified Hummer’s method, and hydrothermal reduction with ascorbic acid, which was employed to convert GO into rGO, forming a two-dimensional structure with a high surface area. The structural transformations were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM), which revealed a significant reduction in interlayer spacing and restoration of the $s{p}^2$ hybridized carbon network in rGO, confirming the successful reduction of GO. Chemical modifications were characterized through Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy and X-ray photoelectron spectroscopy (XPS). These techniques demonstrated a marked decrease in oxygen-containing functional groups in rGO, indicating effective reduction and restoration of graphitic structure. Electrochemical studies using cyclic voltammetry demonstrated that rGO-modified carbon paste electrodes (rGO/MCPE) offer superior sensitivity and enhanced electron transfer efficiency. The effects of scan rate, concentration and pH were also evaluated, underscoring its potential for high-sensitivity detection applications. These findings highlight the potential applications of GO and rGO in electrochemical sensors, particularly for detecting biomolecules like serotonin, as well as in energy storage devices such as supercapacitors and batteries, where their high surface area and conductivity offer significant advantages.

This study aimed to investigate the synthesis of polyaniline (PANI) through electrochemical cyclic voltammetry at varying pH levels and its subsequent adsorption behavior towards Congo red. The products were analyzed using Fourier Transform-infrared spectroscopy (FTIR) and Scanning Electron Microscope (SEM). Results showed that acidic conditions led to faster synthesis rates and complete planes with intercalated flakes, while neutral and alkaline conditions resulted in mostly granular aggregates. PANI synthesized with the maximum adsorption capacity is 58.07mg/g. The interaction between PANI and Congo red occurred through protonation-induced positive charges and electrostatic attraction, as indicated by UV–Vis spectroscopy results. The adsorption process followed the Langmuir model and pseudo-second-order kinetic process, indicating a chemical adsorption process. This study emphasizes the significance of pH conditions in polyaniline synthesis and its potential application in dye removal processes.

CuCo₂O₄ nanoparticles were synthesized via facile hydrothermal route using oxalic as a precipitant, thermal decomposition of CuCo₂O₄ precursor at 400${}^{\circ }$C. The structural studies from X-ray diffraction (XRD), Fourier transform infrared spectrometer, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) disclose the predominant spinel crystal phase for copper cobaltite. The optical absorption spectra reveal two band gaps of 3.8eV and 4.4eV in the CuCo₂O₄ nanoparticles. The cyclic voltammetry (CV) was used to assess the electrochemical characteristics of the resulting product in an organic electrolyte at −1.5–1.5V under ambient conditions. On 22.4nm CuCo₂O₄ nanoparticles, a greater capacitance of 920F/g at a scan rate of 5mV/s was achieved.

Cyclic voltammetric measurements of Cu(II) and Ni(II) phthalocyanines with four 16-membered diazadithia macrocycles (1 and 2) and pentanuclear Ni(II) phthalocyanine bearing four Cu(II) ions in diazadithia macrocycles at the peripheral positions (3) have been carried out on platinum in DMSO and in aqueous medium 3 showed strong adsorption properties in DMSO and especially in aqueous medium, possibly as a result of the interaction between the copper ions in the four macrocycles and the platinum working electrode. Interestingly, the oxidation peak of 3 was split into two waves in aqueous medium. This behaviour is discussed in terms of disaggregation of the mixed valence species produced by the oxidation of aggregated species. A mechanism for both the oxidation of the complex and the splitting of the oxidation peak into two waves is suggested.

(Acetato)-1,8,15,22-tetra-n-heptylphthalocyaninatomanganese(III) (C₇H₁₅)₄PcMn-(OAc) (+structural isomers) (1) and the octa-n-heptyl-substituted (acetato)phthalocyaninatomanganese(III) complexes 1,4,8,11,15,18,22,25-(C₇H₁₅)₈PcMn(OAc) (2) and 2,3,9,10,16,17,23,24-(C₇H₁₅)₈PcMn(OAc) (3) have been synthesized and characterized by IR and UV-vis spectroscopy and elemental analysis. Electrochemical investigations of complexes 1 and 2 (CV, SEC) show similar electrochemical behaviour as the literature known compound (chloro)-2,9,16,23-tetra-tert-butylphthalocyaninatomanganese(III) (t-bu)₄PcMnCl (+structural isomers) (4).

Octakis(alkoxymethyl) cobalt phthalocyanines with relatively short side chains were synthesized which exhibited no thermotropic liquid crystalline behaviour. The final products as well as the intermediates have been characterized by proton magnetic resonance, infrared and electron spectra and elemental analysis. Cyclic voltammograms were measured for octakis(alkoxymethyl) cobalt phthalocyanines in order to examine their electron transfer properties. The electron transfer properties of octakis (alkoxymethyl) cobalt phthalocyanines depend on the kind and number of substituents and are due to the interaction between the phthalocyanine ring, the central metal which is influenced by the conjugated π electron current of the porphyrazine ring.

Improvement of electrical conductivity was attempted by polymerizing octacyanometallophthalocyanine (MPcOC; M≡Fe, Co) units into one-dimensional molecular complexes. The synthetic route to MPcOC was established by reacting tetracyanobenzene with a metal(II) acetate in sulfolane. Poly(μ-pyrazine)octacyanophthalocyaninatoiron(II) and -cobalt(II) were synthesized and their doping with lithium was carried out. The Fe(II) and Co(II) octacyanophthalocyanine complexes showed good electrical conductivities of the order of 10^-8-10^-4S cm^-1. The electrical conductivities of the lithium-doped complexes were improved by two or three orders of magnitude in comparison with the corresponding monomeric and polymeric complexes.

Cyclic voltammetry of octakis(hydroxyethylthio)-substituted phthalocyanines with 2H (H₂OHETPc), Zn(II) (Zn^IIOHETPc(−2)) and Co(II) (Co^II(OHETPc(−2)) in the phthalocyanine core has been investigated in dimethylsulfoxide (DMSO), and some of the results were evaluated together with their absorption spectra in the visible range. The redox processes due to both aggregated and non-aggregated species were observed on the voltammograms of phthalocyanines with Zn(II). The effect of chloride ion on the cyclic voltammetry of Co^IIOHETPc(−2) has been investigated in the DMSO/ClO₄⁻ couple. The comparison of cyclic voltammetry for Co^IIOHETPc in the absence and presence of chloride ion showed that chloride ion does not bind to either Co(II) or Co(I) but does bind very strongly to Co(III). The detailed electrochemistry of Co^IIOHETPc(−2) was investigated in terms of the Co(I)/Co(II) and Co(II)/Co(III) redox couples, and various equilibria related to the species coordinated to Co(II) and Co(III) in the phthalocyanine core.

A number of octaphenoxyphthalocyaninato silicon complexes containing a variety of axial ligands, represented by (OPh)₈PcSi(X)₂ (where X = chloro3, hydroxy 4, (4-carboxybenzene) acetato 5, isonicatinato 6, propionato 7, nitrophenoxy 8 and dimethylaminoxy 9) have been synthesized using a convenient route starting with the 4,5-diphenoxy-1,2-dicyanobenzene. ¹H NMR and UV/vis spectra, and the cyclic voltammetry of the complexes are reported. The complexes are obtained in high yield and are soluble in many organic solvents. Cyclic voltammetry revealed two reduction couples and one oxidation couple for these complexes. Analysis of the cyclic voltammograms showed that compounds 6 and 8 were easier to oxidize and more difficult to reduce than the rest. Also cyclic voltammetry data suggested that electron transfer was not governed only by diffusion.

In this investigation, SnO₂ nanoparticles are prepared through environmental benign method using Nelumbo nucifera (lotus leaf) leaves extract as a reducing agent without any other reagents. The phase formation and the morphology of the as-synthesized SnO₂ nanoparticles are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The nanoparticle size is obtained using selected area diffraction patterns of transmission electron microscope (TEM). The synthesized material modified glassy carbon electrode (GCE) is used for electrochemical detection of the dopamine (DA). In cyclic voltammetry (CV), the modified GCE shows effective electrochemical sensing performance than the bare GCE electrode. The limit of detection (LOD) and limit of quantification (LOQ) of DA were calculated by differential pulse voltammetry (DPV). Aforementioned material has high sensitivity and selectivity towards DA oxidation through electrochemical sensing.

A boron-doped diamond (BDD) thin film was synthesized using the hot filament chemical vapor deposition (HFCVD) method. The surface shape, growth rate, bonding structure, and electrochemical properties of the BDD thin films were estimated through scanning electron microscopy (SEM), Raman spectroscopy, and cyclic voltammetry. As the boron doping concentration increased, the growth rate and crystal size of the diamond thin film decreased. Through Raman analysis, it was confirmed that the 1332 cm${}^{-1}$ peak of diamond gradually became less intense, and peaks were generated at 480 cm${}^{-1}$ and 1220 cm${}^{-1}$ due to the bonding of boron to carbon. Cyclic voltammetry analysis of the BDD thin film showed a large potential window with a width of approximately 2.8 V. The highest applied voltage (2 V) versus response current (0.02 A) was obtained at a B/C ratio of 2000 ppm.

Polypyrrole (PPy) films have been successfully electrodeposited on stainless steel substrates in aqueous solution. In this work, three systems of electrolytes were studied: oxalic acid, dodecylbenzenesulfonic acid (DBSA) and a mixture of oxalic acid and DBSA. A combination of XPS and TOF–SIMS revealed the formation of an iron oxalate layer at the interface between the oxalic acid-doped PPy (PPy(Ox)) and stainless steel and a thin layer of DBSA was observed at the interface between DBSA-doped PPy (PPy(DBSA)) and stainless steel. Similar to the PPy(Ox) system, an iron oxalate was also present at the co-doped PPy/stainless steel interface. Cyclic voltammetry indicated that an iron oxalate layer initially formed at the surface of the stainless steel when the co-doping system was used. The adhesion strength and corrosion performance of the PPy coating on stainless steel were evaluated by lap shear tests and an anodic potentiodynamic polarization technique, respectively. The co-doped PPy-coated stainless steel exhibited the best adhesion and a significant shift of corrosion potential to the positive direction. This finding opens the possibility for the co-doped PPy coating to be deployed as a strongly adherent corrosion inhibitor by using a simple one-step electropolymerization process.

The kinetics of formation of self-assembled monolayers on gold generated by the adsorption of 1-octanethiol and 1,8-octanedithiol were explored by electrochemistry measurement. The time dependence of capacitance and surface coverage supported that the adsorption of thiols typically processed with a two-step adsorption consisted of a fast initial adsorption and a slowly following reorganization. From the function of surface coverage versus time, one could get rate constants of adsorption of thiols, and the adsorption process was demonstrated to follow a diffusion-controlled Langmuir model. A comparison of the adsorption rates for different concentration between 1-octanethiol and 1,8-octanedithiol revealed that their adsorption processes were almost identical and independent on the concentration, inferring that only one sulfur atom contributed to the self-assembly of dithiol molecule.

Surface functional modification of NiTi electrode with noble Pt and Pd metal has been successfully carried out by simple and cost effective electro-spark deposition technique (ESD). Thin-film X-ray diffraction (TF-XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and cyclic voltammetry (CV) have been carried out in order to investigate the structure, morphology, chemical composition and electrochemical behavior of the modified electrode surface. The modified Pt/NiTi and Pd/NiTi electrode surface exhibit a circular splash pattern with a tiny amount of Pt ($\sim$5.30 at.% Pt) and Pd ($\sim$5.71 at.% Pd) existence. The electrochemical results demonstrate that the Pt/NiTi and Pd/NiTi electrode possess an improved electro-catalytic activities toward methanol (MeOH), ethanol (EtOH) and ethylene glycol (EG) oxidation in alkaline media in comparison with the bare NiTi electrode. In acidic environments, the Pt/NiTi electrode exhibits even much better catalytic activities than the pure Pt sheet electrode due to the bi-functional mechanism. In the same way, the electro-catalytic activity of the modified Pd/NiTi electrode is also slightly larger than that of the pure Pd sheet electrode in alkaline environment. The electro-spark surface modification approach is rapid and environmentally-benign, being attractive to widen the application of traditional surface modification technique in the field of material surface/interface design and functionalization.

The electrodeposition of Ni–nano-Cr₂O₃ composite coatings was studied in electrolyte containing different contents of Cr₂O₃ nanoparticles (Cr₂O₃ NPs) on mild steel surfaces. Some techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness, the potentiodynamic polarization curves (Tafel) and electrochemical impedance spectroscopy (EIS) were used to compare pure Ni coatings and Ni–nano-Cr₂O₃ composite coatings. The results show that the incorporation of Cr₂O₃ NPs resulted in an increase of hardness and corrosion resistance, and the maximum microhardness of Ni-nano-Cr₂O₃ composite coatings reaches about 495 HV. The coatings exhibit an active-passive transition and relatively large impedance values. Moreover, the effect of Cr₂O₃ NPs on Ni electrocrystallization is also investigated by cyclic voltammetry (CV) and EIS spectroscopy, which demonstrates that the nature of Ni-based composite coatings changes attributes to Cr₂O₃ NPs by offering more nucleation sites and less charge transfer resistance.

The deposition of Ni–Fe thin layers in boric acid and ionic liquid ([BuMePyr][Tf₂N]) baths were successfully prepared. The obtained materials have been characterized by X-ray diffraction (XRD), Energy Dispersive X-ray spectroscopy (EDX) and SEM. Meanwhile, these materials were carried out by chronoamperometry or chronopotentiometry by varying the intensity of the current and the deposition potential. The results indicate that the coatings of Ni–Fe alloys were successfully obtained by electroplating on the copper substrates, and the alloys composition shows irregular behavior with polarization. The nickel content in the samples is in the range of 55–90%, but the iron content ranges from 10–30%, when potential deposits were varied from $-$2V to $-$4V vs Ni electrode. The results also showed that the thin layers are monophased; they contain the Ni₃Fe phase. Further, SEM images of Ni–Fe alloys show the different shapes of particles.

We report here the development of MnO₂ nanostructure electrode for electrochemical energy storage application. MnO₂ nanoparticles synthesized by a facile and efficient precipitation approach have been investigated for supercapacitor application. The structures and morphologies of MnO₂ nanoparticles were systematically studied using X-ray diffraction, Raman spectroscopy and transmission electron microscopy. The synthesized nanoparticles are observed spherical in shape with uniform size distribution. The electrochemical properties were studied in two-electrode configuration by cyclic voltammetry process. A specific capacitance of 52.8F/g has been obtained for MnO₂ nanoparticles at scan rate of 100mV/s. The electrode is able to deliver a power density of 0.66kW/kg and energy density of 1.8Wh/kg.

Inspired by nature, Metal-N₄-complexes have been utilized as potential models to catalyze the sluggish oxygen reduction reaction (ORR) at cathode in fuel cells. Herein, we designed and synthesized dibenzo-N₄-[14]annulene metal complexes of Fe^II and Co^II metal ions and their nanocomposites with carbon black and characterized by various techniques. Computational and spectroscopic results suggested that the prepared complexes have saddle octahedral geometry. Further, the electrocatalytic activity of prepared nanocomposites towards ORR was investigated by using cyclic and linear sweep voltammetric techniques. The results exhibited that these nanocomposites are significantly ORR active; however, Fe-nanocomposite showed high ORR activity as compared to Co-composite. Theoretical studies indicated that the HOMO of Fe-complex was very near to the antibonding LUMO orbitals of dioxygen as compared to Co-complex, endowing high ORR activity.

Macrocyclic compounds have got recognition in modern science and technologies because of their potential applications in energy, catalysis, material science, biochemistry, and pharmaceutical. The most interesting feature of macrocyclic complexes is their adjustable macrocyclic cavity which opens many possibilities for the development of various important fields. Herein, we synthesized two MN₄-macrocyclic complexes (M = Fe(III) and Ni(II) by using template method, and characterized by employing multiple techniques like molar conductance, FTIR, UV–Vis and mass spectra. On the basis of characterization results, a saddle shaped octahedral geometry can be attributed to theses complexes. The “saddle shape” geometry of these complexes is due to the steric repulsions between the benzenoid and amidic moieties on the macrocyclic framework as suggested by theoretical investigations. Further, the electrochemical investigations carried out using cyclic voltammetry in methanol at the Pt electrode indicated that the unusual oxidation state of metal ion could stabilize the macrocyclic framework of the complex. Moreover, these complexes were also evaluated for their antibacterial activities against several pathogens using Gentamycin as standard drug. The results suggested that these complexes did have significant antimicrobial activity.

Proper selection of bath additives is critical to the plating rate, phosphorus content and corrosion resistance of the nickel–phosphorus (Ni–P) alloy deposits. In this work, electroless Ni–P alloy deposition from an acidic bath using sodium hypophosphite as the reducing agent at relatively low temperatures (30°C and 60°C) was carried out in the presence and absence of urea additives. The effects of different concentrations of urea on plating rate and phosphorus content of the Ni–P deposits were studied. The results showed that the plating rate and the phosphorus content of the Ni–P deposits were largely dependent on the concentration of urea in the bath. The corrosion resistance of the Ni–P deposits was evaluated in aerated 3.5 wt.% sodium chloride (NaCl) solution using potentiodynamic polarization curves. It was found that the corrosion resistance of the deposits obtained from the bath solution containing 1 g/L of urea was the highest. In addition, cyclic voltammetry techniques were used to study the mechanism of electroless Ni–P alloy deposition in the bath. The results revealed that the addition of urea to the bath promoted the concentrations of adsorbed atomic hydrogen and sodium hypophosphite on mild steel surface, which markedly increased the phosphorus content of the Ni–P deposits. This work offers a new way that highlights the relation between the urea additives and phosphorus content.