EDITORIAL (Hot topic : new developments on nanomaterials for electrochemical applications)

Nanomaterials and their composites (various forms) (both inorganic and organic) are still evolving and encouraging scientist community to explore their various possibilities and applications in developing Science and technology. In this era, we are experiencing and realizing a vital role of Nanotechnology as we are seeing in smart phones, millimeter sized storage devices, micro devices, digital voice/telecommunications etc. All these developments are possible because of small matters so called “Nanoparticles”. In the same way, electrochemistry is undertaking a big role in all areas of science and engineering. For ex; Electroanalytical methods have potential advantages in (bio) chemical sensing and biomedical science. Cyclic voltammetry is a classical tool to investigate and derive the reaction mechanisms of electroactive inorganic and organic materials. This special issue of article will address the recent developments of nanomaterials and their applications in the electrochemical solid-state science. In the first article, Prof. Subramaniam et al. reported about graphene and its charge storage performance. His group found that graphene enhanced charge storage performance in the Electrochemical Double Layer Capacitors (EDLC). Secondly, Karthick et al. developed a reliable method for the green synthesis of gold nanoparticles (Au- NPs) using a medicinally valued Adhatoda vasica Nees. It is a rapid and eco-friendly method which may help researchers to synthesize Au-NPs covered with bioactive compounds and is expected to have potential applications in biomedical science. Thirdly, Felix et al. have successfully synthesized IrO2 and demonstrated it as an effective anodic electrocatalyst for the oxygen evolution reaction (OER) in solid polymer electrolyte. In the fourth article, Arockiasamy et al. deposited titanium nitride (TiN)/nickel (Ni) composite by plasma assisted metal-organic chemical vapor deposition (PAMOCVD) using organo-metallic and metal-organic complexes. They proposed that Ni/TiN composite is useful to create super hard coatings. Lastly, Sundramoorthy et al. have proposed a conducting redox-polymer coated sensor for the detection of reduced form of nicotinamide adenine dinucleotide in physiological condition with lower detection limit. This new electrode system may be useful for real-sample analysis. We kindly appreciate all of the contributors for their timely support and co-operation. We hope our articles will be useful for academic and industrial researchers

In vitro and in vivo characterization of mineralized hydroxyapatite/polycaprolactone-graphene oxide based bioactive multifunctional coating on Ti alloy for bone implant applications

Hydroxyapatite (HAP) is a form of naturally occurring calcium apatite present in bone and tooth enamel. It is an important biomaterial with diverse biomedical applications such as a surface coating for metallic orthopedic implants. Synthesized pristine HAP has poor mechanical properties, inferior wear resistance and has limits for directly used in bone tissue engineering applications. To address these limitations, we synthesized a suitable orthopedic implant hybrid material (M-HAP/PCL/GO) by using positively charged calcium ions of mineralized HAP (M-HAP) combined with Polycaprolactone-negatively charged graphene oxide (PCL-GO). The successfully synthesized M-HAP/PCL/GO composite was comprehensively characterized by Fourier-transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). The micro-hardness technique was used to determine the mechanical strength of M-HAP (315 ± 4 Hv), M-HAP/GO (370 ± 3 Hv) and M-HAP/PCL/GO (455 ± 5 Hv). M-HAP/PCL/GO was also tested for its anti-bactericidal impact against Staphylococcus aureus and Escherichia coli. MG63 osteoblast cells cultured on the M-HAP/PCL/GO composite (10 mg/mL) coated sample, displayed outstanding viability after 3 and 5 days of incubation at pH 7.4, which indicated that the composite is suitable material for bone implants and induces the cell proliferation. It was also tested in vivo in Wistar rats and was observably beneficial bone formation within 28 days post-implant operation. These tests proved that the M-HAP/PCL/GO composite can be considered as a prospective candidate for future bone implant applications. Keywords: Polycaprolactone, Graphene oxide, Hydroxyapatite, Bone implants, Antibacterial activity, MG63 osteoblasts cells, Surface coatin

Electroanalysis of nickel ions released in artificial saliva from three orthodontic arch wires: Stainless Steel (SS), NiTi, and CuNiTi

Background: Nickel titanium wires are superior for first alignment because they have exceptional shape memory and super-elasticity. Increased concerns have been raised about the high rate of nickel (Ni) allergy and the growing usage of dental biomaterials that contain Ni. Aim: The aim of the study was to analyze and evaluate the rate of nickel release from different types of orthodontic arch wires. Materials and methods: A set of arch wires of nickel titanium (NiTi), SS and Cu-NiTi were immersed in artificial saliva for three days and analyzed after three days. The amount of Ni ions released from the sample were evaluated using electrochemical techniques such as Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and polarization (Tafel) plot. Results: The EIS and Tafel graph confirmed the s-NiTi, s-CuNiTi showed an excellent corrosion resistance than the s-SS. From all the above measurements, we can conclude that the saliva can affect the corrosion resistance property of the SS, NiTi, CuNiTi day by day. Conclusion: From this study it was concluded that the saliva can affect the corrosion resistance property of the SS, NiTi, CuNiTi day by day, and there was nickel ion release but at a very negligible rate

Disposable redox polymer coated screen-printed carbon electrode for NADH sensing

Electrochemical behavior of electro-generated poly-pyronin B (PyB) film was reported at a screen-printed carbon electrode (SPCE). The poly(PyB) modified SPCE showed excellent redox activity in neutral and alkaline media. Surface topography of poly(PyB) film modified electrode was analyzed by using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Poly(PyB) film coated electrode was characterized by electrochemical impedance spectroscopy (EIS), UV–visible absorption spectroscopy (UV–vis) and cyclic voltammetry (CV). The poly(PyB) modified electrode showed electrocatalytic response to the reduced form of nicotinamide adenine dinucleotide (NADH) in physiological condition, and was used for the detection of NADH with high selectivity. The anodic peak current was linearly related to concentrations of NADH over the range from 1x10-5 M to 5.2x10-4 M, and the detection limit was 5x10-7 M (S/N = 3)

Electrochemical detection of uric acid on exfoliated nanosheets of graphitic-like carbon nitride (g-C3N4) based sensor

A highly sensitive, selective and stable electrochemical sensor for detection of uric acid (UA) in aqueous solution has been successfully developed by deposition of exfoliated graphitic-like carbon nitride (g-C3N4) nanosheets on glassy carbon electrode (GCE). The synthesized g-C3N4 was confirmed by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and Raman spectroscopies. Field-emission scanning electron microscopy (FE-SEM) and High-resolution transmission electron microscopy (HR-TEM) were used to investigate the crystalline structure of g-C3N4. The elemental composition was characterized by energy-dispersive X-ray spectroscopy (EDXS). Compared to bare GCE, exfoliated g-C3N4 nanosheets (NS) modified GCE exhibited higher catalytic current for UA electro-oxidation at reduced over potential in 0.1 M phosphate buffered saline solution (PBS), which is essential to discriminate interfering analytes. g-C3N4 NS modified GCE showed a linear relationship between the electrochemical signal and the UA concentration from 100 to 1000 μM with fast response by differential pulse voltammetry (DPV). The common interferent molecules such as dopamine, ascorbic acid, folic acid, paracetamol, lactic acid, oxalic acid, cysteine, and ciprofloxacin were tested in 0.1 M PBS for the g-C3N4 NS modified GCE. It was found that these molecules did not affect the oxidation current of UA when they co-existed in the same buffer solution. Moreover, the modified sensor probe was tested for UA in urine samples with satisfactory recovery values. The proposed sensor offers high accuracy, sensitivity, simple fabrication and low cost. We suggest that g-C3N4 NS based sensor can be useful for UA analysis in medical, environmental, food and industrial applications.Published versio

Highly Selective Mercury Detection at Partially Oxidized Graphene/Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) Nanocomposite Film Modified Electrode

Partially oxidized graphene flakes (po-Gr) were obtained from graphite electrode by an electrochemical exfoliation method. As-produced po-Gr flakes were dispersed in water with the assistance of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS). The po-Gr flakes and the po-Gr/PEDOT:PSS nanocomposite (po-Gr/PEDOT:PSS) were characterized by Raman spectroscopy, Fourier transform-infrared spectroscopy (FT-IR), UV-Vis spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). In addition, we demonstrated the potential use of po-Gr/PEDOT:PSS electrode in electrochemical detection of mercury ions (Hg2+) in water samples. The presence of po-Gr sheets in PEDOT:PSS film greatly enhanced the electrochemical response for Hg2+. Cyclic voltammetry measurements showed a well-defined Hg2+ redox peaks with a cathodic peak at 0.23 V, and an anodic peak at 0.42 V. Using differential pulse stripping voltammetry, detection of Hg2+ was achieved in the range of 0.2 to 14 µM (R2 = 0.991), with a limit of detection (LOD) of 0.19 µM for Hg2+. The electrode performed satisfactorily for sensitive and selective detection of Hg2+ in real samples, and the po-Gr/PEDOT:PSS film remains stable on the electrode surface for repeated use. Therefore, our method is potentially suitable for routine Hg2+ sensing in environmental water samples

Upcycling of surgical facemasks into carbon based thin film electrode for supercapacitor technology

Abstract Polypropylene (PP), a commonly used plastic, is used for making the outer layers of a surgical face mask. In 2020, around 3 billion surgical face masks were disposed into the environment, causing a huge threat to wildlife, aquatic life, and ecosystems. In this work, we have reported the sulfonation technique for stabilizing the surgical face masks and their conversion into carbon nanoparticles for application as a supercapacitor electrode. The electrode is fabricated by preparing a slurry paste of carbon nanoparticles and pasting it on a conductive wearable fabric. To investigate the performance of the carbon thin film electrode, electrochemical techniques are employed. The Cyclic Voltammetry (CV) analysis performed at different scan rates in a 6 molar KOH electrolyte reveals that the carbon thin film acts as a positive electrode. At 4 A g−1, the electrode shows a specific capacitance of 366.22 F g−1 and 100% retention of specific capacitance for 8000 cycles. A two-electrode asymmetric device is fabricated using carbon thin film as the positive electrode, NiO thin film as the negative electrode, and a KOH separator between two electrodes. The device shows a specific capacitance of 113.73 F g−1 at 1.3 A g−1 and glows a red LED for 6 min. This work is a step towards upcycling the waste produced from surgical face masks used during the COVID-19 pandemic and its application for energy storage

Biocompatible MXene (Ti3C2Tx) Immobilized with Flavin Adenine Dinucleotide as an Electrochemical Transducer for Hydrogen Peroxide Detection in Ovarian Cancer Cell Lines

Flavin adenine dinucleotide (FAD) is a coenzyme and acts as a redox cofactor in metabolic process. Owing to such problems as poor electron transfer properties, unfavorable adsorption, and lack of stability on rigid electrodes, the bio-electrochemical applications of FAD have been limited. Herein, a novel fabrication method was developed for the immobilization process using 2D MXene (Ti3C2Tx), which enhanced the redox property of FAD and improved the electro-catalytic reduction of hydrogen peroxide (H2O2) in neutral medium. The FAD-immobilized Ti3C2Tx electrode (FAD/Ti3C2Tx) was studied by UV-Visible and Raman spectroscopies, which confirmed the successful adsorption of FAD on the Ti3C2Tx surface. The surface morphology and the elemental composition of Ti3C2Tx were investigated by high resolution transmission electron microscopy and the energy dispersive X-ray analysis. The redox property of the FAD/Ti3C2Tx modified glassy carbon electrode (FAD/Ti3C2Tx/GCE) was highly dependent on pH and exhibited a stable redox peak at −0.455 V in neutral medium. Higher amounts of FAD molecules were loaded onto the 2D MXene (Ti3C2Tx)-modified electrode, which was two times higher than the values in the reported work, and the surface coverage (ᴦFAD) was 0.8 × 10−10 mol/cm2. The FAD/Ti3C2Tx modified sensor showed the electrocatalytic reduction of H2O2 at −0.47 V, which was 130 mV lower than the bare electrode. The FAD/Ti3C2Tx/GCE sensor showed a linear detection of H2O2 from 5 nM to 2 µM. The optimization of FAD deposition, amount of Ti3C2Tx loading, effect of pH and the interference study with common biochemicals such as glucose, lactose, dopamine (DA), potassium chloride (KCl), ascorbic acid (AA), amino acids, uric acid (UA), oxalic acid (OA), sodium chloride (NaCl) and acetaminophen (PA) have been carried out. The FAD/Ti3C2Tx/GCE showed high selectivity and reproducibility. Finally, the FAD/Ti3C2Tx modified electrode was successfully applied to detect H2O2 in ovarian cancer cell lines

Development of Electrochemical Sensor Using Iron (III) Phthalocyanine/Gold Nanoparticle/Graphene Hybrid Film for Highly Selective Determination of Nicotine in Human Salivary Samples

Nicotine is the one of the major addictive substances; the overdose of nicotine (NIC) consumption causes increasing heart rate, blood pressure, stroke, lung cancer, and respiratory illnesses. In this study, we have developed a precise and sensitive electrochemical sensor for nicotine detection in saliva samples. It was built on a glassy carbon electrode (GCE) modified with graphene (Gr), iron (III) phthalocyanine-4,4′,4″,4′′′-tetrasulfonic acid (Fe(III)Pc), and gold nanoparticles (AuNPs/Fe(III)Pc/Gr/GCE). The AuNPs/Fe(III)Pc/Gr nanocomposite was prepared and characterized by using FE-SEM, EDX, and E-mapping techniques to confirm the composite formation as well as the even distribution of elements. Furthermore, the newly prepared AuNPs/Fe(III)Pc/Gr/GCE-nanocomposite-based sensor was used to detect the nicotine in phosphate-buffered solution (0.1 M PBS, pH 7.4). The AuNPs/Fe(III)Pc/Gr/GCE-based sensor offered a linear response against NIC from 0.5 to 27 µM with a limit of detection (LOD) of 17 nM using the amperometry (i–t curve) technique. This electrochemical sensor demonstrated astounding selectivity and sensitivity during NIC detection in the presence of common interfering molecules in 0.1 M PBS. Moreover, the effect of pH on NIC electro-oxidation was studied, which indicated that PBS with pH 7.4 was the best medium for NIC determination. Finally, the AuNPs/Fe(III)Pc/Gr/GCE sensor was used to accurately determine NIC concentration in human saliva samples, and the recovery percentages were also calculated

Reduced Graphene Oxide-Poly(3,4-ethylenedioxythiophene) Polystyrenesulfonate Based Dual-Selective Sensor for Iron in Different Oxidation States

A dual-selective sensor platform for detection of iron in ferrous (Fe²⁺) and ferric (Fe³⁺) oxidation states was developed. Upon dispersing reduced graphene oxide (rGO) sheets into poly­(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) polymer, we deposited a hybrid film of rGO-PEDOT:PSS onto a glassy carbon electrode (GCE) surface. Effective intercalation of rGO sheets in PEDOT:PSS film was observed by Raman spectroscopy, UV–vis-NIR spectroscopy, and scanning electron microscopy. The rGO-PEDOT:PSS/GCE sensor showed high electrocatalytic activity for Fe²⁺/Fe³⁺ redox reaction. Using amperometry with controlled applied potential, we demonstrated selective detection of both Fe²⁺ and Fe³⁺ with rGO-PEDOT:PSS/GCE. The sensor responded linearly to Fe²⁺ from 20–833 μM (at 0.6 V) and Fe³⁺ from 1–833 μM (at 0.4 V) in 0.5 M KCl + 0.05 M HCl. The presence of several common metal and organic interferents such as Cu²⁺, Co²⁺, Ag⁺, Pb²⁺, Cd²⁺, Zn²⁺, Mn²⁺, Ni²⁺, Hg²⁺, l-glycine, l-cysteine, l-tyrosine, glucose, KCN, guanine, uric acid, xanthan, salicylate, tartrazine, and naphthol yellow did not affect the selective detection of Fe²⁺ and Fe³⁺. In addition, detection of Fe²⁺ and Fe³⁺ ions in a red wine sample and iron supplement tablets were performed with satisfactory results. The sensor was also useful in determining oxidation kinetics of Fe²⁺ using hydrogen peroxide and measuring Fe³⁺ by differential pulse voltammetry. Thus, rGO/PEDOT:PSS hybrid film based electrode we developed can serve as a practical sensor for detecting iron in its different oxidation states in real samples for different applications