Tailoring of cobalt phosphide anchored nitrogen and sulfur co-doped three dimensional graphene hybrid: Boosted electrocatalytic performance towards hydrogen evolution reaction

Tailored portable electrochemical sensor for dopamine detection in human fluids using heteroatom-doped three-dimensional g-C3N4 hornet nest structure

BACKGROUND

There is widespread interest in the design of portable electrochemical sensors for the selective monitoring of biomolecules. Dopamine (DA) is one of the neurotransmitter molecules that play a key role in the monitoring of some neuronal disorders such as Alzheimer's and Parkinson's diseases. Facile synthesis of the highly active surface interface to design a portable electrochemical sensor for the sensitive and selective monitoring of biomolecules (i.e., DA) in its resources such as human fluids is highly required.

RESULTS

The designed sensor is based on a three-dimensional phosphorous and sulfur resembling a g-C3N4 hornet's nest (3D-PS-doped CNHN). The morphological structure of 3D-PS-doped CNHN features multi-open gates and numerous vacant voids, presenting a novel design reminiscent of a hornet's nest. The outer surface exhibits a heterogeneous structure with a wave orientation and rough surface texture. Each gate structure takes on a hexagonal shape with a wall size of approximately 100 nm. These structural characteristics, including high surface area and hierarchical design, facilitate the diffusion of electrolytes and enhance the binding and high loading of DA molecules on both inner and outer surfaces. The multifunctional nature of g-C3N4, incorporating phosphorous and sulfur atoms, contributes to a versatile surface that improves DA binding. Additionally, the phosphate and sulfate groups' functionalities enhance sensing properties, thereby outlining selectivity. The resulting portable 3D-PS-doped CNHN sensor demonstrates high sensitivity with a low limit of detection (7.8 nM) and a broad linear range spanning from 10 to 500 nM.

SIGNIFICANCE

The portable DA sensor based on the 3D-PS-doped CNHN/SPCE exhibits excellent recovery of DA molecules in human fluids, such as human serum and urine samples, demonstrating high stability and good reproducibility. The designed portable DA sensor could find utility in the detection of DA in clinical samples, showcasing its potential for practical applications in medical settings.

Natural resource-derived NiO nanoparticles via aloe vera for high-performance symmetric supercapacitor

This investigation reported a one-step green synthesis of nickel oxide nanoparticles (NiO NPs) using aloe vera leaves extract solution for their application in a supercapacitor. This method used aloe vera leaves as a reducing agent, which is very simple and cost-effective. The synthesized NPs were thoroughly characterized using various techniques. The X-ray diffraction analysis unequivocally confirmed the crystalline nature; field emission scanning electron microscopy and transmission electron microscopy images showed different shapes and forms of an agglomerated cluster of synthesized NPs. The absorption spectra were recorded from UV visible spectroscopy, while Fourier transform infrared spectroscopy provided insights into the functional groups present. Electrochemical assessments were carried out via cyclic voltammetry, galvanostatic charging-discharging and electrochemical impedance spectroscopy. These experiments were performed using a 2 M KOH electrolyte within a 1.0 V potential window. Impressively, the single electrode displayed a remarkable specific capacitance of 462 F g-1 at a scan rate of 1 mV s-1 and 336 F g-1 at a current density of 0.76 A g-1. Further, a symmetric two-electrode device (NiO||NiO) has been successfully fabricated by employing a separator between the electrodes. The device exhibited an exceptional specific capacitance of approximately 239 F g-1, along with an energy density of 47.8 Wh kg-1 and a power density of 545 W kg-1 at 1 A g-1 current density within a 1.2 V potential window. The fabricated device also shows a retention capacity of 89% at 10 A g-1 after 2000 cycles with 114% of columbic efficiency. The present study underscores the effectiveness of the green synthesis approach in producing NiO NPs and establishes their potential as highly promising candidates for supercapacitor applications, showcasing both excellent electrochemical performance in a three-electrode system and remarkable stability in a practical two-electrode device. The results collectively highlight the efficacy of the green approach in producing NiO NPs, establishing its potential as a highly promising candidate for supercapacitor application.

An Enzyme-Free Sandwich Amperometry-Type Immunosensor Based on Au/Pt Nanoparticle-Functionalized Graphene for the Rapid Detection of Avian Influenza Virus H9 Subtype

Avian influenza virus H9 subtype (AIV H9) has contributed to enormous economic losses. Effective diagnosis is key to controlling the spread of AIV H9. In this study, a nonenzymatic highly electrocatalytic material was prepared using chitosan (Chi)-modified graphene sheet (GS)-functionalized Au/Pt nanoparticles (GS-Chi-Au/Pt), followed by the construction of a novel enzyme-free sandwich electrochemical immunosensor for the detection of AIV H9 using GS-Chi-Au/Pt and graphene-chitosan (GS-Chi) nanocomposites as a nonenzymatic highly electrocatalytic material and a substrate material to immobilize capture antibodies (avian influenza virus H9-monoclonal antibody, AIV H9/MAb), respectively. GS, which has a large specific surface area and many accessible active sites, permitted multiple Au/Pt nanoparticles to be attached to its surface, resulting in substantially improved conductivity and catalytic ability. Au/Pt nanoparticles can provide modified active sites for avian influenza virus H9-polyclonal antibody (AIV H9/PAb) immobilization as signal labels. Upon establishing the electrocatalytic activity of Au/Pt nanoparticles on graphene towards hydrogen peroxide (H₂O₂) reduction for signal amplification and optimizing the experimental parameters, we developed an AIV H9 electrochemical immunosensor, which showed a wide linear range from 10^1.37 EID₅₀ mL^-1 to 10^6.37 EID₅₀ mL^-1 and a detection limit of 10^0.82 EID₅₀ mL^-1. This sandwich electrochemical immunosensor also exhibited high selectivity, reproducibility and stability.

2D MXene Nanomaterials as Electrocatalysts for Hydrogen Evolution Reaction (HER): A Review

MXenes, a novel family of 2D transition metal carbide, nitride and carbonitride materials, have been gaining tremendous interest in recent days as potential electrocatalysts for various electrochemical reactions, including hydrogen evolution reaction (HER). MXenes are characterized by their etchable metal layers, excellent structural stability, versatility for heteroatoms doping, excellent electronic conductivity, unique surface functional groups and admirable surface area, suitable for the role of electrocatalyst/support in electrochemical reactions, such as HER. In this review article, we summarized recent developments in MXene-based electrocatalysts synthesis and HER performance in terms of the theoretical and experimental point of view. We systematically evaluated the superiority of the MXene-based catalysts over traditional Pt/C catalysts in terms of HER kinetics, Tafel slope, overpotential and stability, both in acidic and alkaline electrolytic environments. We also pointed out the motives behind the electro catalytic enhancements, the effect of synthesis conditions, heteroatom doping, the effect of surface terminations on the electrocatalytic active sites of various MXenes families. At the end, various possible approaches were recommended for a deeper understanding of the active sites and catalytic improvement of MXenes catalysts for HER.

Graphene-Based Electrochemical Sensors for Psychoactive Drugs

Sensors developed from nanomaterials are increasingly used in a variety of fields, from simple wearable or medical sensors to be used at home to monitor health, to more complicated sensors being used by border customs or aviation industries. In recent times, nanoparticle-based sensors have begun to revolutionize drug-detection techniques, mainly due to their affordability, ease of use and portability, compared to conventional chromatography techniques. Thin graphene layers provide a significantly high surface to weight ratio compared to other nanomaterials, a characteristic that has led to the design of more sensitive and reliable sensors. The exceptional properties of graphene coupled with its potential to be tuned to target specific molecules have made graphene-based sensors one of the most popular and well-researched sensing materials of the past two decades with applications in environmental monitoring, medical diagnostics, and industries. Here, we present a review of developments in the applications of graphene-based sensors in sensing drugs such as cocaine, morphine, methamphetamine, ketamine, tramadol and so forth in the past decade. We compare graphene sensors with other sensors developed from ultrathin two-dimensional materials, such as transition-metal dichalcogenides, hexagonal boron nitrate, and MXenes, to measure drugs directly and indirectly, in various samples.

Recent Progress in Graphene-Based Electrocatalysts for Hydrogen Evolution Reaction

Hydrogen is regarded as a key renewable energy source to meet future energy demands. Moreover, graphene and its derivatives have many advantages, including high electronic conductivity, controllable morphology, and eco-friendliness, etc., which show great promise for electrocatalytic splitting of water to produce hydrogen. This review article highlights recent advances in the synthesis and the applications of graphene-based supported electrocatalysts in hydrogen evolution reaction (HER). Herein, powder-based and self-supporting three-dimensional (3D) electrocatalysts with doped or undoped heteroatom graphene are highlighted. Quantum dot catalysts such as carbon quantum dots, graphene quantum dots, and fullerenes are also included. Different strategies to tune and improve the structural properties and performance of HER electrocatalysts by defect engineering through synthetic approaches are discussed. The relationship between each graphene-based HER electrocatalyst is highlighted. Apart from HER electrocatalysis, the latest advances in water electrolysis by bifunctional oxygen evolution reaction (OER) and HER performed by multi-doped graphene-based electrocatalysts are also considered. This comprehensive review identifies rational strategies to direct the design and synthesis of high-performance graphene-based electrocatalysts for green and sustainable applications.

Utilization of a double-cross-linked amino-functionalized three-dimensional graphene networks as a monolithic adsorbent for methyl orange removal: Equilibrium, kinetics, thermodynamics and artificial neural network modeling

Herein, it is aimed to develop a high-performance monolithic adsorbent to be utilized in methyl orange (MO) adsorption. Therefore, amino-functionalized three-dimensional graphene networks (3D-GN_f) fulfilling the requirements of reusability and high capacity have been fabricated via hydrothermal self-assembly approach followed by a double-crosslinking strategy. The potential utilization of 3D-GN_f as an adsorbent for removal MO has been assessed using both batch-adsorption studies and an artificial neural network (ANN) approach. Graphene oxide sheets have been amino-functionalized and cross-linked, by ethylenediamine (EDA) during hydrothermal treatment, following the glutaraldehyde has used as a double-crosslinking agent to facilitate the crosslinking of architecture. The successful fabrication of 3D-GN_f has been confirmed by field-emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR), Raman and X-ray photoelectron spectroscopy (XPS). Moreover, N₂ adsorption/desorption isotherms have revealed the high specific surface area (1015 m² g^-1) with high pore volume (1.054 cm³ g^-1) and hierarchical porous structure of 3D-GN_f. The effect of initial concentration, contact time, and temperature on adsorption capacity have been thoroughly studied, and the kinetics, isotherms, and thermodynamics of MO adsorption have been modelled. The MO adsorption has been well defined by the pseudo-second-order kinetic model and Langmuir isotherm model with a monolayer adsorption capacity of 270.27 mg g^-1 at 25 °C. The thermodynamic findings have revealed MO adsorption has occurred spontaneously with an endothermic process. The Levenberg-Marquardt backpropagation algorithm has been implemented to train the ANN model, which has used the activation functions of tansig and purelin functions at the hidden and output layers, respectively. An optimum ANN model with high-performance metrics (coefficient of determination, R² = 0.9995; mean squared error, MSE = 0.0008) composed of three hidden layers with 5 neurons in each layer was constructed to forecast MO adsorption. The findings have shown that experimental results are consistent with ANN-based data, implying that the suggested ANN model may be used to forecast cationic dye adsorption.

Porous carbon materials derived from discarded COVID-19 masks via microwave solvothermal method for lithium‑sulfur batteries

With the spread of COVID-19, disposable medical masks (DMMs) have become a significant source of new hazardous solid waste. Their proper disposal is not only beneficial to the safety of biological systems but also useful to achieve considerable economic value. The first step of this study was to investigate the chemical composition of DMMs. It is primarily composed of polypropylene, polyethylene terephthalate and iron, with fibrous polypropylene accounting for approximately 80% of the total weight. Then, DMMs were sulfonated and oxidised by the microwave-driven concentrated sulfuric acid within 8 min based on the fact that the concentrated sulfuric acid exhibits a good microwave absorption capacity. The co-doping of sulfur and oxygen was achieved while improving the thermal stability of DMMs. Subsequently, the self-activation pyrolysis of sulfonated and oxidised DMMs (P-SO@DMMs) was further realized in low-flow-rate argon. The specific surface area of P-SO@DMMs increased from 2.0 to 830.9 m²·g^-1. P-SO@DMMs sulfur cathodes have promising electrochemical properties because of their porous structures and the synergistic effect of sulfur and oxygen co-doping. The capacity of the samples irradiated by microwave for 10 min at 0.1, 0.2, 0.5, 1, 2 and 5 C were 1313.6, 1010.9, 816.5, 634.4, 513.4 and 453.1 mAh·g^-1, respectively, and after returning to 0.2 C and continuing the cycle for 50 revolutions, maintained 50.5% of the initial capacity. After 400 cycles, its capacity is 38.1% of the initial capacity at 0.5 C. It is slightly higher than the electrochemical performance of the sample treated by microwave for 8 min and significantly higher than the sample treated by 6 min. This work converts structurally complex, biohazardous DMMs into porous carbon with high specific surface area by clean and efficient microwave solvothermal and self-activating pyrolysis, which facilitates the development of carbon based materials at low cost and large scale.

Biosynthesis of Ag-Pt bimetallic nanoparticles using propolis extract: Antibacterial effects and catalytic activity on NaBH4 hydrolysis

The critical environmental issues of antibiotic resistance and renewable energies supply urge researching materials synthesis and catalyst activity on hydrogen production processes. Aiming to analyse the antibacterial effect of platinum-silver (Ag-Pt) nanoparticles (NPs) and the catalyst effect on NaBH₄ hydrolysis that can be used for hydrogen generation technology, in this work, Ag-Pt NPs were prepared using aqueous propolis extract. Various methods were used for the characterization (Uv-vis Spectroscopy, Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Atomic Force Microscopy (AFM) and X-ray diffraction Spectroscopy (XRD)). The antimicrobial activity of Ag-Pt bimetallic nanoparticles was evaluated in vitro by the microdilution method against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumoniae, Staphylococcus epidermidis, and Serratia marcescens. The results confirmed the antimicrobial activity of bimetallic NPs Ag-Pt concentrations of (25, 50, and 100 μg/ml). A concentration of 100 μg/ml showed low bacterial viability varying between 22.58% and 29.67% for the six tested bacteria. For the catalyst activity on NaBH₄ hydrolysis, the results showed high turnover factor (TOF) and low activation energy of 1208.57 h^-1 and 25.61 kJ/mol, respectively, with high hydrogen yield under low temperature. Synthesized Ag-Pt NPs can have great potential for biological and hydrogen storage applications.

Low-temperature synthesis of hetero-structures of magnetically separable iron oxide@Au-rGO nanocomposite for efficient degradation of organic dye under visible light irradiation

In the present study, Fe₃O₄@Au core-shell nanoparticles decorated on reduce graphene oxide (Fe₃O₄@Au/rGO) nanocomposite were synthesized using the reduction method by sodium citrate, Hummer's method, and hydrothermal method, respectively. The as-prepared nanostructures were characterized by X-ray diffraction (XRD), Energy Dispersive X-ray (EDX), transmission electron microscopy (TEM), scanning electron microscopy (SEM)to assess the surface features, crystallinity and morphological characteristics. These nanostructures were employed for photocatalytic degradation of crystal violet (CV), and amongst them, Fe₃O₄@Au/rGO nanocomposite offered the best results under the visible light irradiation and optimal conditions. The effect of the amount of nano-photocatalyst, initial CV concentration, the initial pH, temperature, stirring speed, and degradation time was evaluated individually. A 100% degradation was obtained after 1 min in the presence of 0.008 g nano-photocatalyst, and also 100% of degradation was achieved after 5 min in the presence of 0.005 g of the prepared nano-photocatalyst. After a few tests, its photocatalytic performance was retained, implying the superior stability of Fe₃O₄@Au/rGO nanocomposite. The kinetic study of photocatalytic degradation also indicated that the fit model for the kinetic reaction was the pseudo-second-order kinetic model. Finally, the photocatalytic degradation of real samples with synthesized nanocomposite showed promising results.

Green synthesis, characterization and bioactivity of biogenic zinc oxide nanoparticles

In this study, we tried to enlighten the structure of zinc oxide nanoparticles (ZnO NPs) obtained from Thymbra Spicata L. plant by using green synthesis method in various ways. Some properties of zinc oxide nanoparticles were determined by using the characterization methods that scanning electron microscopy (SEM), Energy Dispersive X-ray analysis (EDX), fouirer transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), ultraviolet visible spectroscopy (UV-Vis) spectroscopy methods. The detected Zn nanoparticle sizes were determined to be between 6.5 nm and 7.5 nm. In addition to these studies, we investigated the antimicrobial effects of zinc oxide nanoparticles obtained by green synthesis against some pathogens. According to the results, it was seen that zinc oxide nanoparticles formed zones with a diameter of 16.3 mm, 10.25 mm, 13 mm and 10.2 mm, respectively, against Bacillus subtilis ATCC 6633, Escherichia coli ATCC 25952, Pseudomonas aeruginosa ATCC 27853 bacteria and Candida albicans ATTC 90028 fungus, respectively. However, the radical quenching activity (DPPH) of the nanoparticles (Ts-ZnONP (79.67%)) was determined to be quite good compared to the positive control BHA. In addition, it is seen that the protective effect of ZnO NPs against DNA damage increases depending on the concentration. At a concentration of 100 mg/L, the DNA damage inhibitory effect was found to be maximum. In line with the comprehensive results, it was determined that the zinc oxide nanoparticles obtained with the green synthesis method have the potential of use in a wide variety of fields.

Hierarchical porous polystyrene-based activated carbon spheres for CO2 capture

It is rather essential to design porous carbon adsorbents with high CO2 capture performance for improving global warming and climate change. Activated carbon spheres with high specific surface area and hierarchical porous texture were prepared from polystyrene-based macroreticular resin spheres due to their low ash and mechanical stability by air pre-oxidization and steam activation. The as-prepared carbon spheres had a specific surface area of 1274.95 m2 g-1, total pore volume of 1.09 cm3 g-1 and micropore volume of 0.47 cm3 g-1. Moreover, these carbon spheres showed a hierarchical porous texture composed of ultrafine micropores (0.5-1 nm), micropores (1-2 nm), mesopores (10-50 nm) and macropores (50-100 nm). A CO2 adsorption capacity of 2.82 mmol g-1 for carbon spheres can be obtained at 30 °C and 1 atm. Further, after introducing nitrogen-containing functional groups by gaseous ammonia at 600 °C, these carbon spheres (NPSRCSs) exhibited a high CO2 adsorption capacity of 3.2 mmol g-1. In addition, excellent cyclic stability, low hygroscopicity and regenerability temperature suggested these carbon spheres were favorable for CO2 capture.

In situ electrochemical synthesis of graphene-poly(arginine) composite for p-nitrophenol monitoring

Para-Nitrophenol (p-nitrophenol) is a common industrial pollutant occurring widely in water bodies, yet actual monitoring methods are limited. Herein we proposed a fully electrochemically in situ synthesized graphene-polyarginine composite functionalized screen printed electrode, as a novel p-nitrophenol sensing platform. The electrode was characterized by morphologic, spectrometric and electrochemical techniques. p-nitrophenol in both pure aqueous solution and real water samples was tested. Results show a detection limit as low as the nanomolar level, and display a linear response and high selectivity in the range of 0.5-1250 μM. Molecular simulation reveals a detailed synergy between graphene and poly-arginine. The preferable orientation of nitrophenol molecules on the graphene interface in the presence of poly-arginine induces H- and ionic binding. This sensor is an ideal prototype for p-nitrophenol quantification in real waters.

Removal of metal ions using a new magnetic chitosan nano-bio-adsorbent; A powerful approach in water treatment

In this study, a magnetic chitosan/Al₂O₃/Fe₃O₄ (M-Cs) nanocomposite was developed by ethylenediaminetetraacetic acid (EDTA) functionalization to enhance its adsorption behavior for the removal of Cd(II), Cu(II) and Zn(II) metal ions from aqueous solution. The results revealed that the EDTA functionalization of M-Cs increased its adsorption capacity ~9.1, ~5.6 and ~14.3 times toward Cu, Cd and Zn ions. The maximum adsorption capacity followed the order of Cd(II) > Cu(II) > Zn(II) and the maximum adsorption efficiency was achieved at pH of 5.3 with the removal percentage of 99.98, 93.69 and 83.81 %, respectively, for the removal of Cu, Cd and Zn ions. The metal ions adsorption kinetic obeyed pseudo-second-order equation and the Langmuir isothermal was found the most fitted model for their adsorption isothermal experimental data. In addition, the thermodynamic study illustrated that the adsorption process was exothermic and spontaneous in nature.

3D nanoporous NiCoP as a highly efficient electrocatalyst for the hydrogen evolution reaction in alkaline electrolyte

3D nanoporous NiCoP properly inherits the dealloyed double-continuous nanoporous structure, enables fast charge transfer, and fully reflects its inherent activity.

Production of bioethanol from carrot pulp in the presence of Saccharomyces cerevisiae and beet molasses inoculum; A biomass based investigation

Nowadays, ethanol (ethyl alcohol, bioethanol) is one of the most commonly used liquid biofuels, playing a vital role in industrial development. There are some advanced technologies available to produce ethanol by fermentation of agricultural wastes, fruit wastes, municipal and industrial wastes. Herein, the dried carrot pulp as a source of raw material has been utilized for the production of bioethanol by using the yeast Saccharomyces cerevisiae and beet molasses inoculated at 28 °C for 72 h. The results have revealed that the highest amount of alcohol (10.3 ml (40.63 g/l)) has been obtained in a sample containing 50 ml of inoculum, 150 ml of water, and 10 g of dried waste. This study has proved the potential of dried carrot pulp to be converted into a value-added product such as ethanol.

Green and facile synthesis of nickel oxide-porous carbon composite as improved electrochemical electrodes for supercapacitor application from banana peel waste

Lithium-ion batteries and supercapacitors are examples of energy storage technologies that have a lot of promise in a variety of applications. Herein, NiO-porous carbon composites were prepared by a green and cost-effective facile synthesis route from banana peel waste materials. The surface morphology and chemical composition of the NiO-porous carbon composite were investigated using a scanning electron microscope (SEM) and energy dispersive x-ray analysis (EDX). The prepared samples were also described through Fourier transform infrared (FTIR) spectroscopy, x-ray powder diffraction (XRD), thermal gravimetric analysis (TGA), and surface area measurements. The electrochemical behavior of prepared materials was studied by cyclic voltammetry (CV), galvanostatic charge-discharge, and electrochemical impedance (EIS) to test their applicable suitability as supercapacitor electrode. PC-NiO (3) composite exhibits a remarkable specific capacitance of 811 F/g at a current density of 1 A/g. The specific capacitance of PC-NiO (3) is 5.3 times more than that of PC material at 1.0 A/g. Furthermore, the PC-NiO (3) composite material still exhibits a specific capacitance of 780 F/g at 5.0 A/g, high rate capability of 84.55% retention at a high current density of 10.0 A/g and superior cycle stability at 1000 cycles. Based on its high specific capacitance, the NiO-porous carbon nanocomposite is one of the most promising electrode materials for supercapacitors, according to the above results.

Highly sensitive detection of salvianic acid a drug by a novel electrochemical sensor based on HKUST-1 loaded on three-dimensional graphene-MWCNT composite

HKUST-1, a kind of metal-organic framework (MOF) composed by Cu²⁺ and trimesic acid, loaded on reduced graphene oxide and multi-walled carbon nanotubes nanocomposite [HKUST-1 @ (RGO-MWCNT)] was successfully synthesized by a facile and simple route. Then, a highly sensitive non-enzymatic salvianic acid A (SAA) electrochemical sensor was fabricated by modifying HKUST-1 @ (RGO-MWCNT) on a glassy carbon electrode, taking full advantage of the synergistic effect between the redox catalytic capacity of Cu²⁺ and the electrical conductivity of carbon materials. The sensor showed a low limit of detection of 0.081 μM, limit of quantitation of 0.27 μM, high sensitivity of 509.6 μA/mM and a good relationship between reduction peak current and concentration of SAA from 2 to 4600 μM. Meanwhile, the sensor had the advantages of repeatability and stability. Finally, it was used to detect SAA in real samples with noteworthy electroanalytical performance. In short, the sensor has considerable potential for the electroanalysis of SAA. Moreover, the study provides a promising composite of MOF and carbon materials with potential application in the analysis of effective components of herbaceous medicinal plants.

Three-dimensional porous reduced graphene oxide decorated with carbon quantum dots and platinum nanoparticles for highly selective determination of azo dye compound tartrazine

In this work, an electrochemical sensor for the azo dye compound tartrazine (TRT) determination was proposed. A screen-printed carbon electrode (SPCE) was modified by depositing three-dimensional porous reduced graphene oxide decorated with carbon quantum dots and platinum nanoparticles (Pt/CQDs@rGO/SPCE). The resulting amount of TRT was observed by differential pulse voltammetry. Under optimal conditions, the sensor exhibited two wide linearities ranging from 0.01 to 1.57 μM and 1.57-9.3 μM with the reliability coefficient of determination of 0.991 and 0.992, respectively. The detection limit (LOD) was also estimated to be 7.93 nM. Moreover, the Pt/CQDs@rGO/SPCE suggested high selectivity in the presence of several interfering agents and azo dye compounds that have a similar structure. Additionally, the Pt/CQDs@rGO/SPCE revealed superior recovery values of about 96.5-101.6% for candy, 99.7-103.5% for soft drinks, 96.0-101.2% for jelly powder, and 98.0-103.0% for water samples. Furthermore, the fabricated sensor exhibits excellent selectivity, stability, reproducibility, and repeatability, indicating a great perspective in the monitoring of TRT. Therefore, it can be speculated that the proposed electrode could be effectively applied to determine TRT in food samples.

Graphene and Graphene Oxide as a Support for Biomolecules in the Development of Biosensors

Graphene and graphene oxide have become the base of many advanced biosensors due to their exceptional characteristics. However, lack of some properties, such as inertness of graphene in organic solutions and non-electrical conductivity of graphene oxide, are their drawbacks in sensing applications. To compensate for these shortcomings, various methods of modifications have been developed to provide the appropriate properties required for biosensing. Efficient modification of graphene and graphene oxide facilitates the interaction of biomolecules with their surface, and the ultimate bioconjugate can be employed as the main sensing part of the biosensors. Graphene nanomaterials as transducers increase the signal response in various sensing applications. Their large surface area and perfect biocompatibility with lots of biomolecules provide the prerequisite of a stable biosensor, which is the immobilization of bioreceptor on transducer. Biosensor development has paramount importance in the field of environmental monitoring, security, defense, food safety standards, clinical sector, marine sector, biomedicine, and drug discovery. Biosensor applications are also prevalent in the plant biology sector to find the missing links required in the metabolic process. In this review, the importance of oxygen functional groups in functionalizing the graphene and graphene oxide and different types of functionalization will be explained. Moreover, immobilization of biomolecules (such as protein, peptide, DNA, aptamer) on graphene and graphene oxide and at the end, the application of these biomaterials in biosensors with different transducing mechanisms will be discussed.

Developing a simple box-behnken experimental design on the removal of doxorubicin anticancer drug using Fe3O4/graphene nanoribbons adsorbent

This paper aims to develop a Box-Behnken experimental design system to optimize the removal process of doxorubicin anticancer drugs. For this goal, Fe₃O₄/graphene nanoribbons was selected as adsorbent and removal of doxorubicin anticancer drug optimized using Box-Behnken experimental design with a selection of four effective factors. A three-level, four-factor Box-Behnken experimental design was used to assess the relationship between removal percentage as a dependent variable with adsorption weight (0.0015-0.01 mg), pH (3-9), temperature (15-45 °C) and time (1-15 min) as independent variables. Optimized condition by Behnken experimental design (pH = 7.36; time = 15 min; adsorbent weight = 0.01 mg and temperature = 29.26 °C) improved removal of doxorubicin anticancer drug about 99.2% in aqueous solution. The dynamic behavior, adsorption properties and mechanism of doxorubicin molecule on Fe₃O₄/graphene nanoribbon were investigated based on ab initio molecular dynamics (AIMD) simulations and density functional theory calculations with dispersion corrections. A closer inspection of the adsorption configurations and binding energies revealed that π-π interactions were the driving force when the doxorubicin molecule adsorbed on Fe₃O₄/graphene nanoribbon. The observed negative adsorption energy signifies a favourable and exothermic adsorption process of the various adsorbate-substrate systems. Besides, AIMD and phonon dispersion calculations confirm the dynamic stability of Fe₃O₄/graphene nanoribbon.

Doxorubicin Anticancer Drug Monitoring by ds-DNA-Based Electrochemical Biosensor in Clinical Samples

In this research, glassy carbon electrode (GCE) amplified with single-wall carbon nanotubes (SWCNTs) and ds-DNA was fabricated and utilized for voltammetric sensing of doxorubicin with a low detection limit. In this technique, the reduction in guanine signal of ds-DNA in the presence of doxorubicin (DOX) was chosen as an analytical factor. The molecular docking study revealed that the doxorubicin drug interacted with DNA through intercalation mode, which was in agreement with obtained experimental results. The DOX detection performance of ds-DNA/SWCNTs/GCE was assessed at a concentration range of 1.0 nM-20.0 µM. The detection limit was found to be 0.6 nM that was comparable and even better (in many cases) than that of previous electrochemical reported sensors. In the final step, the ds-DNA/SWCNTs/GCE showed powerful ability for determination of the DOX in injection samples with acceptable recovery data.

Evaluation of Peroxidase in Herbal Medicines Based on an Electrochemical Sensor

Peroxidases are species-specific. Differences in peroxidase can objectively reflect the genetics among species. The use of peroxidase to assist in species identification is relatively simple and effective. In this work, we proposed a graphene-modified electrode. This electrode can amplify the signal of electrocatalytic reduction of hydrogen peroxide. Since peroxidase can catalyze the reduction of hydrogen peroxide, this signal can be used as an indicator to demonstrate the content of peroxidase in different plant tissues. Twelve herbal medicines were selected for our study. The results show that this electrochemical-based detection technique was comparable to colorimetric method in terms of accuracy.

Sustainable electrode material for high-energy supercapacitor: biomass-derived graphene-like porous carbon with three-dimensional hierarchically ordered ion highways

Biomass-derived carbonaceous materials have been deemed to be one of the up-and-coming electrode materials for high-performance energy storage systems due to their cost-neutral abundant resources, sustainable nature, easy synthesis methods, and environmentally benign features. In this work, various graphene-like porous carbon networks (GPCs) with three-dimensional (3D) hierarchically ordered "ion highways" have been synthesized by the carbonization/activation of orange-peel wastes for use as an electrode material in high-energy supercapacitors. The porous structures and surface morphologies of the GPCs were rationally fine-tuned as a function of the activation agent ratio. The prepared GPCs offered superior specific surface area in addition to a 3D porous structure with a fine-tuned pore size distribution. The electrochemical behaviors of all the GPCs were evaluated in 6.0 M KOH aqueous electrolyte via a three-electrode electrochemical setup. Owing to their synergistic characteristics, including superior specific surface area (1150 m2 g-1), large pore volume, and fine-tuned 3D porous architecture, GPC-3.0 (synthesized with a KOH : GPC ratio of 3.0, by wt.) exhibited the best capacitive behavior amongst the studied GPCs. The 3D hierarchically ordered architecture acts like well-designed ion highways that boost electron transportation, thereby enhancing electrochemical energy storage. A coin-cell-type symmetrical supercapacitor based on GPC-3.0 was tested in both 1.0 M Na2SO4 (salt-in-water) and 12.0 m NaNO3 (water-in-salt) electrolytes. The supercapacitor cell based on the water-in-salt electrolyte offered a wide operating voltage of 2.3 V. The obtained energy density and power density values were comparable to those of commercial high-performance electrical double-layer capacitors. Such notable findings will shed light on next-generation high-rate electrochemical energy storage systems based on biomass-derived carbonaceous materials.