Search

This paper reports a facile carbonization method of a biopolymer to synthesize reduced graphene oxide with excellent electrochemical properties for use as a supercapacitor electrode. Oil palm lignin is used as the biopolymer-based graphene precursor, and a carbon dioxide laser is used to carbonize the material via lithography. Using Raman Spectroscopy, the characterization of the resultant graphene (OP-LSG) revealed D, G, and 2D peaks corresponding to multilayer graphene. Scanning Electron Microscopy of OP-LSG revealed three-dimensional particle-like fibrous and porous nanostructures with an enhanced surface area. In a three-electrode setup in ferrocyanide electrolyte, cyclic voltammetry showed the electrode coated with OP-LSG achieving a specific capacitance as high as 108.044 mF/cm² at a scan rate of 0.01 V/s. The galvanostatic charge-discharge of OP-LSG revealed energy and power density values of 15 µWh/cm² and 597 µW/cm² at a scan rate of 0.01 V/s. The OP-LSG electrode retained 97.5% of its initial capacitance after 1000 charge-discharge cycles.

Current collectors and electrolyte pairs are frequently overlooked in the development of supercapacitors. In electrode design and sealed packaging, the mechanical and chemical properties of the electrolyte must be retained while maintaining the integrity of microelectrodes and current collectors of the microsupercapacitors. In this research, the physical and electrochemical response of copper (Cu) and 316 stainless steel current collector (SS) for lignin-derived laser scribed graphene (L-LSG) microsupercapacitor with K2SO4 (K+) and H2SO4 (H+) as an electrolyte medium was studied. XPS results confirmed a passivation layer on a copper electrode before and after the electrochemical reaction involving H2SO4 as the electrolyte medium of the highly porous L-LSG structure with six pairs of microelectrodes and graphene current collectors. Analysis of the CV and GCD curves shows that the SS/K+ pair is the most suited for an L-LSG microsupercapacitor, with an areal capacitance and energy density of 22.22 mFcm−2 and 0.00153 mWhcm−2, respectively at 0.08 mAcm−2.

Acid extract of Solanum tuberosum was tested as corrosion inhibitor for mild steel in 1 M HCl and H2SO4 media using different techniques: Weight loss (in different temperatures viz., 303, 313 and 323 K), Potentiodynamic polarization, Electrochemical Impedance Spectroscopy (EIS) and SEM techniques. The studies reveal that the plant extract act as good inhibitors in both the acid media and better in H2SO4 medium. Tafel polarization method indicated that the plant extract behaves as mixed mode inhibitor. Double layer capacitance and charge transfer resistance values derived from Nyquist plots obtained from AC impedance studies give supporting evidence for the anticorrosive effects of these plants. The inhibitive effect may be attributed to the adsorption of the inhibitor on the surface of MS following Temkin adsorption isotherm. Increase of inhibition efficiency with increase of temperature along with Ea values serve as proof for chemisorption. SEM studies provide the confirmatory evidence for the protection of MS by the green inhibitor. The study reveals the potential of the plantextract for combatingcorrosionwhich maybedue to the adsorption of alkaloids and other phytoconstituents.

This study aims to determine the performance of a commercial corrosion inhibitor (mixture of ethanediol, 2-butoxy ethanol, and fatty acid amine) in inhibiting weldment corrosion. The inhibitor's effect on parent metals (PM), heat affected zone (HAZ), and weld metal (WM) has been investigated on the corrosion behaviour of X65-welded structures in brine solution (10 m/s) using submerged jet impingement (SJI) flow loops. The results show that inhibitors can reduce the corrosion rate by 10 times to 0.36 mm/y for WM. Linear polarization resistance and electrochemical impedance spectroscopy (EIS) show that the WM exhibited the highest corrosion rate.

Aircraft fuel with a maximum freezing point of – 47 °C can be obtained from converting low quality hydrocarbons (linear chain) into high quality hydrocarbons (branched chain) through a hydroisomerization reaction. This research aims to study platinum concentrations impregnated on Zeolite Socony Mobile-48-γ-Al2O3 and reaction temperature on the hydroisomerization of n-dodecane. Catalyst with 0.5 wt% platinum operated at 300 °C had the highest conversion, whereas the highest select ivity into iso-dodecane was shown by catalyst with 0.3 wt% platinum with a reaction temperature of 300 °C.

Abstract Tuberculosis (TB), caused by Mycobacterium tuberculosis (M. tuberculosis), requires a high level of attention and is one of the most infectious diseases in the air. Present methods of diagnosing TB remain ineffective owing to their low sensitivity and time consumption. In this study, we produced a green graphene nanofiber laser biosensor (LSG-NF) decorated with oil palm lignin-based synthetic silver nanoparticles (AgNPs). The resulting composite morphology was observed by field-emission scanning electron microscopy and transmission electron microscopy, which revealed the effective adaptation of the AgNPs to the LSG-NF surface. The successful attachment of AgNPs and LSG-NFs was also evident from X-ray diffraction and Raman spectroscopy studies. In order to verify the sensing efficiency, a selective DNA sample captured on AgNPs was investigated for specific binding with M.tb target DNA through selective hybridisation and mismatch analysis. Electrochemical impedance studies further confirmed sensitive detection of up to 1 fM, where a detection limit of 10−15 M was obtained by estimating the signal-to-noise ratio (S/N = 3:1) as 3σ. Successful DNA immobilisation and hybridisation was confirmed by the detection of phosphorus and nitrogen peaks based on X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. The stability and repeatability of the analysis were high. This approach provides an affordable potential sensing system for the determination of M. tuberculosis biomarker and thus provides a new direction in medical diagnosis.

The inhibiting effect of Gum Arabic-nanoparticles (GA-NPs) to control the corrosion of reinforced concrete that exposed to carbon dioxide environment for 180 days has been investigated. The steel reinforcement of concrete in presence and absence of GA-NPs were examined using various standard techniques. The physical/surface changes of steel reinforcement was screened using weight loss measurement, electrochemical impedance spectroscopy (EIS), atomic force microscopy and scanning electron microscopy (SEM). In addition, the carbonation resistance of concrete as well screened using visual inspection (carbonation depth), concrete alkalinity (pH), thermogravimetric analysis (TGA), SEM, energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The GA-NPs inhibitor size was also confirmed by transmission electron microscopy (TEM). The results obtained revealed that incorporation of 3% GA-NPs inhibitor into concrete inhibited the corrosion process via adsorption of inhibitor molecules over the steel reinforcement surface resulting of a protective layer formation. Thus, the inhibition efficiency was found to increase up-to 94.5% with decreasing corrosion rate up-to 0.57 × 10−3 mm/year. Besides, the results also make evident the presence of GA-NPs inhibitor, ascribed to the consumption of calcium hydroxide, and reduced the Ca/Si to 3.72% and 0.69% respectively. Hence, C-S-H gel was developed and pH was increased by 9.27% and 12.5, respectively. It can be concluded that green GA-NPs have significant corrosion inhibition potential and improve the carbonation resistance of the concrete matrix to acquire durable reinforced concrete structures.

In this study we have reported sodium tartrate (ST) and Zn2+ as the potential mixed corrosion inhibitors for copper corrosion in drinking water, by using electrochemical impedance and polarization techniques. The results of potentio-dynamic polarization indicated that sodium tartrate could be used as mixed type inhibitor with Zn2+. ST was found to be 92% effective for slowing down both the anodic and cathodic reaction rates. It was additionally found that ST could coat the surface of copper to prevent it from conducting electricity. As the inhibitor concentration increased, the stability of the formed protective layer was also improved. The results obtained from studies like SEM, EDAX, AFM, and water contact angle clearly indicated the development of a barrier by inducing the lotus effect on copper surface. The water contact angle measurement results suggested that the coating formed in the presence of inhibitor was superhydrophobic, and the surface was homogeneous. [ABSTRACT FROM AUTHOR]

In this study we have reported sodium tartrate (ST) and Zn2+ as the potential mixed corrosion inhibitors for copper corrosion in drinking water, by using electrochemical impedance and polarization techniques. The results of potentio-dynamic polarization indicated that sodium tartrate could be used as mixed type inhibitor with Zn2+. ST was found to be 92% effective for slowing down both the anodic and cathodic reaction rates. It was additionally found that ST could coat the surface of copper to prevent it from conducting electricity. As the inhibitor concentration increased, the stability of the formed protective layer was also improved. The results obtained from studies like SEM, EDAX, AFM, and water contact angle clearly indicated the development of a barrier by inducing the lotus effect on copper surface. The water contact angle measurement results suggested that the coating formed in the presence of inhibitor was superhydrophobic, and the surface was homogeneous.

In this work, the mixture of trisodium cittrate and Zn2+ was used as binary (hetero type) inhibitor for corrosion inhibition of copper metal in potable water. The binary inhibitor system (Zn2+ and trisodium citrate) was used to form hydrophobic surfaces on copper submerged in potable water. Water contact angle (WCA) was found to be 155°4° when the inhibitor was present, whereas it was 84°2° when there was no inhibitor. These observations suggested the development of superhydrophobic layer on the surface of copper in drinkable water. Electrochemical impedance spectroscopy (EIS – AC mode), and potentiodynamic polarization (DC mode) experiments conveyed that the copper surface could be protected by utilizing the mixture of trisodium citrate and Zn2+ in potable water. The morphological studies including SEM (coupled with EDX), AFM, and WCA were evidenced the formulation of a hetero-type inhibitor for the corrosion inhibition of copper in potable water. In this study, the decline in the double-layer capacitance and the rise in the charge transfer resistance were due to the adsorption of inhibitor confirming the development of protective layer, which EIS, SEM, EDX, AFM, and WCA studies also supported. Thus, there was a synergism observed between TSC and Zn2+, and the formulation consisting of TSC and Zn2+ provided 83% of inhibition efficiency (IEp). So, it was suggested that the approach reported in this study could be a simple method for obtaining the superhydrophobic copper surface.

Lactic acid bacteria (LAB) can produce γ-aminobutyric acid (GABA) with antioxidant properties and sedative effects when it binds to the GABA receptor in the human brain. LAB can also produce bacteriocin-like inhibitory substances (BLIS) with antimicrobial capabilities during carbohydrate fermentation. GABA and BLIS are natural compounds with potential health benefits and food preservation properties. Lactobacillus brevis C23 was co-cultured with three different LABs as inducers, which produced the highest GABA content and BLIS activity. They were cultured in various plant-based media to obtain an edible and better-tasting final product over commercially available media like MRS broth. A coconut-based medium with additives was optimized using response surface methodology (RSM) to increase GABA and BLIS production. The optimized medium for maximum GABA production (3.22 ± 0.01 mg/mL) and BLIS activity (84.40 ± 0.44%) was a 5.5% coconut medium containing 0.23% glucose, 1.44% Tween 20, 0.48% L-glutamic acid, and 0.02% pyridoxine. Due to the presence of GABA, the cell-free supernatant (CFS) as a postbiotic showed higher antioxidant activity than other food preservatives like nisin and potassium sorbate. Finally, microbiological tests on food samples showed that the postbiotic was more effective than other preservatives at combating the growth of LAB, molds and coliform bacteria, making it a possible food preservative.

Biopolymers are an attractive green alternative to conventional polymers, owing to their excellent biocompatibility and biodegradability. However, their amorphous and nonconductive nature limits their potential as active biosensor material/substrate. To enhance their bio-analytical performance, biopolymers are combined with conductive materials to improve their physical and chemical characteristics. We review the main advances in the field of electrochemical biosensors, specifically the structure, approach, and application of biopolymers, as well as their conjugation with conductive nanoparticles, polymers and metal oxides in green-based noninvasive analytical biosensors. In addition, we reviewed signal measurement, substrate bio-functionality, biochemical reaction, sensitivity, and limit of detection (LOD) of different biopolymers on various transducers. To date, pectin biopolymer, when conjugated with either gold nanoparticles, polypyrrole, reduced graphene oxide, or multiwall carbon nanotubes forming nanocomposites on glass carbon electrode transducer, tends to give the best LOD, highest sensitivity and can detect multiple analytes/targets. This review will spur new possibilities for the use of biosensors for medical diagnostic tests.

For the past decades, several cancer biomarkers have been exploited for rapid and accurate prognosis or diagnosis purposes. In this review, the optical biosensor is targeted for carcinoembryonic antigen (CEA) detection. The CEA level is a prominent parameter currently used in clinical cases for the prognosis of cancer-related diseases. Many nanomaterial-based biosensors are invented as alternatives for the commonly used enzyme-linked immunosorbent assays (ELISA) immunoassay method in CEA detection as the traditional approach. But they possess certain drawbacks such as tedious procedure, high technical demand, and costly. Nevertheless, the effort appears to be wasted as none of them are being actualised. Generally, the sensor function was carried out by converting bio-signals generated upon the interface of the receptor into light signals. These sensors were popular due to specific advantages such as sensitivity, being free from chemical and electromagnetic interferences, wide dynamic range, and being easy to be monitored. The features of PoC diagnostics are discussed and associated to the various applications of colorimetric-based and chemiluminescent-based biosensors. The roles of nanomaterials in each application were also summarised by comparing the modification, incubation period, lowest detection limit (LOD) and linear range of detection amount. The challenges and future perspectives were highlighted as well at the end of the review., (© 2022 Wiley-VCH GmbH.)