Graphene-like sheets supported Fe-Co layered double hydroxides nanoflakes as an efficient electrocatalyst for both hydrogen and oxygen evolution reaction, A green investigation.

Herein, a nanohybrid material containing graphene-like sheets (GS) and Fe-Co layered double hydroxides nanoflakes (LDHs) was synthesized via simple two-step processes and named Fe-Co LDHs/GS. The Fe-Co LDHs/GS nanohybrid was characterized by various techniques. Fe-Co LDHs nanoflakes were grown on GS in Fe-Co LDHs/GS nanohybrid. The electrochemical surface area of Fe-Co LDHs/GS nanohybrid was obtained 0.05 cm2 based on the Randles-Sevcik equation. The Fe-Co LDHs/GS nanohybrid was applied as an electrocatalyst of HER and OER in a 1.0 M KOH. The electrochemical performance of Fe-Co LDHs/GS nanohybrid was surveyed by several electrochemical methods, and long-term electrochemical stability. The onset potential, overpotential at 10 mA cm-1 current density, and Tafel slope for the Fe-Co LDHs/GS nanohybrid were obtained -0.33 V, -0.43 V (vs. RHE), and 122 mV dec-1, respectively. The Fe-Co LDHs/GS nanohybrid has long-term stability over 35 h in alkaline media toward HER. Furthermore, the onset potential, overpotential at 10 mA/cm, and Tafel slope for the Fe-Co LDHs/GS nanohybrid were obtained as 1.52 V, 1.60 V (vs. RHE), and 44 mV dec-1, respectively. The Fe-Co LDHs/GS nanohybrid has long-term durability over 10 h in alkaline media toward OER.

Green application of trimetallic nickel-cobalt-molybdenum nanocomposites on 3D graphene oxide as a powerful electrocatalyst for hydrogen evolution reaction.

In-situ designing of multiple metals electrocatalysts with high active sites and performance is the main challenge for hydrogen evolution reaction (HER). So in this work, 3D-rGO was easily obtained from 2D-graphene by a simple one-step hydrothermal method to create the interspace sites and active surface area. The Ni-Co-Mo tri-metallic@3D-rGO was synthesized and fully characterized by different techniques, e.g., FT-IR, XRD, Raman, FE-SEM, TEM, EDS, mapping, ICP-OES, AFM, voltammetry, and electrochemical impedance spectroscopy. According to the FE-SEM and TEM images, the Ni-Co-Mo tri-metallic@3D-rGO has a crumpled-formed structure. The as-prepared nanocomposite has high HER performance with a low potential of -0.11 (vs. RHE) to deliver 10 mA cm-2 and Tafel slope of 68 mV dec-1 for Pt and -0.25 V (vs. RHE) to deliver 10 mA cm-2 and Tafel slope of 110 mV dec-1 for graphite counter electrode. Furthermore, the 3D structure illustrates high long-term durability in the HER process for 1000 continuous cycles and 12 h operation at -0.42 V (vs. RHE) for Pt and graphite counter electrode. It's noticeable HER performance has the synergetic effect between 3D-rGO and tri-metallic structure with high porosity and electrical conductivity, enhancing HER kinetic.

A novel aptasensor based on 3D-reduced graphene oxide modified gold nanoparticles for determination of arsenite.

In this study, a sensitive aptasensor based on three-dimensional reduced graphene oxide-modified gold nanoparticles (3D-rGO/AuNPs) was fabricated for the determination of arsenite (As(III)). The 3D-rGO/AuNPs was fully characterized with various techniques. The 5'-thiolate aptamer was first self-assembled on a glassy carbon electrode (GCE) that it's modified with 3D-rGO/AuNPs via Au-S covalent bonding. In the presence of As(III), the G-quadruplex interaction was formed between a single-stranded DNA and the target, which produced a hindrance for electron transfer. Consequently, the electrochemical impedance spectroscopy signals of a GCE modified with 3D-rGO/AuNPs was increased. In order to improve the response of the designing aptasensor, the effect of the various parameters was optimized. Under the optimal conditions, the aptasensor has an extraordinarily low detection limit of 1.4 × 10-7 ng mL-1 toward As(III) with a dynamic range of 3.8 × 10-7 3.0 × 10-4 ng mL-1. The 3D-rGO/AuNPs aptasensor displayed superior selectivity and reproducibility with an acceptable recovery for determination of As(III) in real water samples.

Experimental and theoretical investigation effect of flavonols antioxidants on DNA damage.

A new electrochemical biosensor was developed to demonstrate the effect of Acridine Orange (AO) on DNA damage. Then, the biosensor was used to check the inhibitors effect of three flavonols antioxidants (myricetin, fisetin and kaempferol) on DNA damage. Acridine Orange (AO) was used as a damaging agent because it shows a high affinity to nucleic acid and stretch of the double helical structure of DNA. Decreasing on the oxidation signals of adenine and guanine (in the DNA) in the presence of AO were used as probes to study the antioxidants power, using DNA-modified screen printed graphene electrode (DNA/SPGE). The results of our study showed that the DNA-biosensor could be suitable biosensor to investigate the inhibitors ability of the flavonols antioxidants on the DNA damage. The linear dependency was detected in the two regions in the ranges of 1.0-15.0 and 15.0-500.0 pmol L(-1). The detection limit was found 0.5 pmol L(-1) and 0.6 pmol L(-1) for guanine and adenine, respectively. To confirm the electrochemical results, Uv-Vis and fluorescence spectroscopic methods were used too. Finally molecular dynamic (MD) simulation was performed on the structure of DNA in a water box to study any interaction between the antioxidant, AO and DNA.