Sensitive Hydrazine Electrochemical Biosensor Based on a Porous Chitosan–Carbon Nanofiber Nanocomposite Modified Electrode

Quantum dot-protein interface: Interaction of the CdS quantum dot with human hemoglobin for the study of the energy transfer process and binding mechanism along with detection of the unfolding of hemoglobin

In this study, the interaction of the human hemoglobin with cost effective and chemically fabricated CdS quantum dots (QDs) (average sizes ≈3nm) has been investigated. The semiconductor QDs showed maximum visible absorption at 445 nm with excitonic formation and band gap of ≈ 2.88 eV along with hexagonal crystalline phase. The binding of QDs-Hb occurs through corona formation to the ground sate complex formation. The life time of the heme pocket binding and reorganization were found to be t1 = 43 min and t2 = 642 min, respectively. The emission quenching of the Hb has been indicated large energy transfer between CdS QDs and Hb with tertiary deformation of Hb. The binding thermodynamics showed highly exothermic nature. The ultrafast decay during corona formation was studied from TCSPC. The results showed that the energy transfer efficiency increases with the increase of the QDs concentration and maximum ≈71.5 % energy transfer occurs and average ultrafast lifetime varies from 5.45 ns to1.51 ns. The deformation and unfolding of the secondary structure of Hb with changes of the α-helix (≈74 % to ≈51.07 %) and β-sheets (≈8.63 % to ≈10.25 %) have been observed from circular dichroism spectrum. The SAXS spectrum showed that the radius of gyration of CdS QDs-Hb bioconjugate increased (up to 23 ± 0.45 nm) with the increase of the concentration of QDs compare with pure Hb (11 ± 0.23 nm) and Hb becoming more unfolded.

Biocompatibility assessment of chemically modified GONRs with hemoglobin and histopathological studies for its toxicity evaluation

Transition metal-Schiff base complexes are found to be important for biomedical applications but have demerits of being homogeneous complexes, thus their synthesis on the surface of graphene oxide nanoribbons (GONRs), materials of specific interest, can be beneficial for preparing advanced graphene-based materials for biomedical applications. Of foremost importance is their safety and biocompatibility with biological systems. In this study, a transition metal-Schiff base complex has been synthesized on the surface of a GONR (Ni-S-GNR) using 3-aminopropyltriethoxysilane and pyridine-2-carbaldehyde and complexing nickel. This Ni-S-GNR was characterized well by various physicochemical techniques. The evaluation of biocompatibility of Ni-S-GNR with hemoglobin confirmed binding interactions and influence on the native structure of hemoglobin. It was found that there was alteration in the secondary and tertiary structures of hemoglobin. In addition, histopathological studies on the liver and kidney cells of rats revealed non-toxicity of Ni-S-GNR towards these cells. Overall, Ni-S-GNR was found to be compatible with protein as the native structure was not destroyed and was non-toxic to cells.

Biomass-Derived Carbon Materials in Heterogeneous Catalysis: A Step towards Sustainable Future

Biomass-derived carbons are emerging materials with a wide range of catalytic properties, such as large surface area and porosity, which make them ideal candidates to be used as heterogeneous catalysts and catalytic supports. Their unique physical and chemical properties, such as their tunable surface, chemical inertness, and hydrophobicity, along with being environmentally friendly and cost effective, give them an edge over other catalysts. The biomass-derived carbon materials are compatible with a wide range of reactions including organic transformations, electrocatalytic reactions, and photocatalytic reactions. This review discusses the uses of materials produced from biomass in the realm of heterogeneous catalysis, highlighting the different types of carbon materials derived from biomass that are potential catalysts, and the importance and unique properties of heterogeneous catalysts with different preparation methods are summarized. Furthermore, this review article presents the relevant work carried out in recent years where unique biomass-derived materials are used as heterogeneous catalysts and their contribution to the field of catalysis. The challenges and potential prospects of heterogeneous catalysis are also discussed.

Palladium-Nickel Electrocatalysts on Nitrogen-Doped Reduced Graphene Oxide Nanosheets for Direct Hydrazine/Hydrogen Peroxide Fuel Cells

In the present work, nitrogen-doped reduced graphene oxide-supported (NrGO) bimetallic Pd–Ni nanoparticles (NPs), fabricated by means of the electrochemical reduction method, are investigated as an anode electrocatalyst in direct hydrazine–hydrogen peroxide fuel cells (DHzHPFCs). The surface and structural characterization of the synthesized catalyst affirm the uniform deposition of NPs on the distorted NrGO. The electrochemical studies indicate that the hydrazine oxidation current density on Pd–Ni/NrGO is 1.81 times higher than that of Pd/NrGO. The onset potential of hydrazine oxidation on the bimetallic catalyst is also slightly more negative, i.e., the catalyst activity and stability are improved by Ni incorporation into the Pd network. Moreover, the Pd–Ni/NrGO catalyst has a large electrochemical surface area, a low activation energy value and a low resistance of charge transfer. Finally, a systematic investigation of DHzHPFC with Pd–Ni/NrGO as an anode and Pt/C as a cathode is performed; the open circuit voltage of 1.80 V and a supreme power density of 216.71 mW cm−2 is obtained for the synthesized catalyst at 60 °C. These results show that the Pd–Ni/NrGO nanocatalyst has great potential to serve as an effective and stable catalyst with low Pd content for application in DHzHPFCs.

An amperometric biosensor based on poly(L-aspartic acid), nanodiamond particles, carbon nanofiber, and ascorbate oxidase-modified glassy carbon electrode for the determination of L-ascorbic acid

An amperometric L-ascorbic acid biosensor utilizing ascorbate oxidase (AOx) immobilized onto poly(L-aspartic acid) (P(L-Asp)) film was fabricated on carbon nanofiber (CNF) and nanodiamond particle (ND)-modified glassy carbon electrode (GCE). Effects of AOx, ND, and CNF amounts were investigated by monitoring the response currents of the biosensor at different amounts of AOx, ND, and CNF. The electropolymerization step of L-aspartic acid on CNF-ND/GCE surface was also optimized. Scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) techniques were used to enlighten the modification steps of the biosensor. The effects of pH and applied potential were studied in detail to achieve the best analytical performance. Under optimized experimental conditions, the AOx/P(L-Asp)/ND-CNF/GCE biosensor showed a linear response to L-ascorbic acid in the range of 2.0 × 10^-7-1.8 × 10^-3 M with a detection limit of 1.0 × 10^-7 M and sensitivity of 105.0 μAmM^-1 cm^-2. The novel biosensing platform showed good reproducibility and selectivity. The strong interaction between AOx and the P(L-Asp)/ND-CNF matrix was revealed by the high repeatability (3.4%) and good operational stability. The AOx/P(L-Asp)/ND-CNF/GCE biosensor was successfully applied to the determination of L-ascorbic acid in vitamin C effervescent tablet and pharmaceutical powder containing ascorbic acid with good results, which makes it a promising approach for quantification of L-ascorbic acid. Graphical abstract.

Tailoring pore structures with optimal mesopores to remarkably promote DNA adsorption guiding the growth of active Mn3(PO4)2 toward sensitive superoxide biomimetic enzyme sensors

The great challenge in preparing a biomimetic enzyme sensor is to have sensitivity and selectivity equal to or better than its corresponding biological sensor. Porous electrodes possess a large surface area and are often used to greatly improve the sensor sensitivity. However, how to tailor the pore structure, especially the pore size distribution to further improve the sensitivity and selectivity of a biomimetic sensor, has not been investigated yet. The superoxide anion (O2˙-) plays essential roles in various biological processes and is of importance in clinical diagnosis and life science research. It is generally detected by the superoxide dismutase enzyme. Herein, we delicately tailor the pore structure of carbon nanofibers (CNFs) by pyrolysis to obtain an optimal mesopore structure for strong adsorption of DNA, followed by guiding the growth of Mn3(PO4)2 as a biomimetic enzyme toward highly sensitive detection of O2˙-. The Mn3(PO4)2-DNA/CNF sensor achieves the best sensitivity among the reported O2˙- sensors while possessing good selectivity. The enhancement mechanism is also investigated, indicating that the mesopore ratio of CNFs plays an essential role in the high sensitivity and selectivity due to their strong adsorption of DNA for guiding the growth of a large amount of uniform sensing components, Mn3(PO4)2, toward high sensitivity and selectivity. The biomimetic sensor was further used to in situ monitor O2˙- released from human keratinocyte cells and human malignant melanoma cells under drug stimulation, showing high sensitivity to real-time quantitative detection of O2˙-. This work provides a highly sensitive in situ real-time biomimetic O2˙- sensor for applications in biological research and diagnosis, while shedding light on the enhancement mechanism of the pore structure, especially the pore size distribution of a porous electrode for high performance sensing processes.

Catalyst for the degradation of 1,1-dimethylhydrazine and its by-product N-nitrosodimethylamine in propellant wastewater

A three-component metal catalyst was prepared and used in the process of catalytic wet peroxide oxidation (CWPO) for the degradation of unsymmetrical dimethylhydrazine (UDMH) in propellant wastewater with H₂O₂.