Mohammad Shamsuddin Ahmed

Reductive determination of hydrogen peroxide with MWCNTs-Pd nanoparticles on a modified glassy carbon electrode

This paper introduces the use of multi walled carbon nanotubes (MWCNTs) with palladium (Pd) nanoparticles in the electrocatalytic reduction of hydrogen peroxide (H(2)O(2)). We have developed and characterized a biosensor for H(2)O(2) based on Nafion(®) coated MWCNTs-Pd nanoparticles on a glassy carbon electrode (GCE). The Nafion(®)/MWCNTs-Pd/GCE electrode was easily prepared in a rapid and simple procedure, and its application improves sensitive determination of H(2)O(2). Characterization of the MWCNTs-Pd nanoparticle film was performed with transmission electron microscopy (TEM), Raman, and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) and amperometry (at an applied potential of -0.2V) measurements were used to study and optimize performance of the resulting peroxide biosensor. The proposed H(2)O(2) biosensor exhibited a wide linear range from 1.0 μM to 10 mM and a low detection limit of 0.3 μM (S/N=3), with a fast response time within 10s. Therefore, this biosensor could be a good candidate for H(2)O(2) analysis.

High catalytic activity of electrochemically reduced graphene composite toward electrochemical sensing of Orange II

Orange II, an azo dye, is sometimes illegally used as a red dye in food products despite its adverse health effects if consumed. Therefore, the determination of low concentrations of Orange II is an important target. An Orange II sensor was prepared using electrochemically reduced graphene oxide grafted with 5-amino-1,3,4-thiadiazole-2-thiol-Pt nanoparticles (denoted as ERGO-ATDT-Pt) onto a glassy carbon electrode (GCE) and investigated for Orange II detection in 0.1M acetate buffer solution (ABS at pH 4.5) with prominent reversible redox peaks. A wide linear range of 1×10(-)(8)-6×10(-)(7)M with a low detection limit of 3.4×10(-)(10)M (s/n=3) was found for Orange II detection. This developed ERGO-ATDT-Pt/GCE sensor showed good selectivity, excellent stability and better response to the real sample analysis with excellent recovery.

Different length linkages of graphene modified with metal nanoparticles for oxygen reduction in acidic media

This paper reports the chemical synthesis and experimental characterization of various graphene oxide (GO)-supported platinum (Pt) and palladium (Pd) nanoparticle (NP) catalysts. To investigate the relationship between the linker length and the catalytic activities of the metal-decorated GO catalysts, six samples were prepared with three different linker molecules, HS(CH2)2SH, HS(CH2)3SH and HS(CH2)4SH (denoted as GO-l-NPs), and two different metal NPs, Pt and Pd. All GO-l-NP catalysts were tested in oxygen reduction reaction (ORR) using electrochemical techniques such as cyclic voltammetry (CV) and rotating ring disk electrode (RRDE) hydrodynamic voltammetry to quantitatively obtain the ORR kinetic constants and the reaction mechanisms on a glassy carbon electrode (GCE) in 0.5 M H2SO4 solution. All GO-l-NPs/GCE electrodes showed significantly improved ORR activity and mechanisms. GO-l-NPs were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). The results showed that Pt and Pd were successfully attached onto the GO surface. A more positive potential catalytic ORR was observed in the modified GO-l-NPs with longer chain linker lengths in both cases.

A novel δ-MnO2 with carbon nanotubes nanocomposite as an enzyme-free sensor for hydrogen peroxide electrosensing

We have reported the synthesis and application of a δ-MnO2 with carbon nanotubes (δ-MnO2/CNTs) nanocomposite as an enzyme-free sensor for the detection of H2O2 through an electroreduction reaction, where δ-MnO2 serves as the catalytic center and CNTs as the highly conductive base material. The δ-MnO2/CNTs nanocomposite was synthesized via a simple and single-step hydrothermal process in alkaline solution without using any surfactants or templates. The electrochemical properties of the δ-MnO2/CNTs on a glassy carbon electrode were investigated by cyclic voltammetry, and amperometry. It was found that, under optimized conditions, the sensor fabricated electrode provides linear amperometric responses for H2O2 in a large concentration range from 0.05 to 22 mM and a detection limit of 1 μM with a comparatively high sensitivity of 243.9 μA mM−1 cm−2. In addition, the δ-MnO2/CNTs modified GCE exhibits excellent selectivity, and good reproducibility for H2O2 detection. It is promising that the proposed H2O2 sensor can be used as an effective tool to measure the H2O2 in practical samples.

New Approach for Porous Chitosan?Graphene Matrix Preparation through Enhanced Amidation for Synergic Detection of Dopamine and Uric Acid

Amide-functionalized materials have emerged as promising nonprecious catalysts for electrochemical sensing and catalysis. The covalent immobilization of chitosan (CS) onto graphene sheet (GS) (denoted as CS–GS) has been done via higher degree of amidation reaction to develop an electrochemical sensing matrix for simultaneous determination of dopamine (DA) and uric acid (UA). The enhanced amidation between CS and GS has not been reported previously. However, electrochemical results have revealed that the CS–GS enhances the electrocatalytic performance in terms of the oxidation potential and peak current due to the higher degree of amide functionalization compared to that of CS/GS, which has a lower amidation. Differential pulse voltammetry-based studies have indicated that the CS–GS matrix works at a lower detection limit (0.14 and 0.17 μM) (S/N = 3) and over a longer linear range (1–700 and 1–800 μM), with a comparatively higher sensitivity (2.5 and 2.0 μA μM–1 cm–2), for DA and UA, respectively. In addition, the CS–GS matrix demonstrates good selectivity toward the detection of DA and UA in the presence of a 10-fold higher concentration of AA and glucose. The as-prepared three-dimensional porous CS–GS also endows selective determination toward DA and UA in various real samples.

Ultra-fast and highly sensitive enzyme-free glucose biosensing on a nickel–nickel oxide core–shell electrode

Correction for ‘Ultra-fast and highly sensitive enzyme-free glucose biosensing on a nickel–nickel oxide core–shell electrode’ by Halima Begum et al., RSC Adv., 2017, 7, 3554–3562.

3D graphene preparation via covalent amide functionalization for efficient metal-free electrocatalysis in oxygen reduction

3D and porous reduced graphene oxide (rGO) catalysts have been prepared with sp3-hybridized 1,4-diaminobutane (sp3-DABu, rGO-sp3-rGO) and sp2-hybridized 1,4-diaminobenzene (sp2-DABe, rGO-sp2-rGO) through a covalent amidation and have employed as a metal-free electrocatalyst for oxygen reduction reaction (ORR) in alkaline media. Both compounds have used as a junction between functionalized rGO layers to improve electrical conductivity and impart electrocatalytic activity to the ORR resulting from the interlayer charge transfer. The successful amidation and the subsequent reduction in the process of catalyst preparation have confirmed by X-ray photoelectron spectroscopy. A hierarchical porous structure is also confirmed by surface morphological analysis. Specific surface area and thermal stability have increased after successful the amidation by sp3-DABu. The investigated ORR mechanism reveals that both functionalized rGO is better ORR active than nonfunctionalized rGO due to pyridinic-like N content and rGO-sp3-rGO is better ORR active than rGO-sp2-rGO due to higher pyridinic-like N content and π-electron interaction-free interlayer charge transfer. Thus, the rGO-sp3-rGO has proven as an efficient metal-free electrocatalyst with better electrocatalytic activity, stability, and tolerance to the crossover effect than the commercially available Pt/C for ORR.

Highly Efficient Dual Active Palladium Nanonetwork Electrocatalyst for Ethanol Oxidation and Hydrogen Evolution

Tunable palladium nanonetwork (PdNN) has been developed for catalyzing ethanol oxidation reaction (EOR) and hydrogen evolution reaction (HER) in alkaline electrolyte. 3D PdNN is regarded as a dual active electrocatalyst for both EOR and HER for energy conversion application. The PdNN has been synthesized by the simple chemical route with the assistance of zinc precursor and a surfactant (i.e., cetyltrimethylammonium bromide, CTAB). The thickness of the network can be tuned by simply adjusting the concentration of CTAB. Both EOR and HER have been performed in an alkaline electrolyte, and characterized by different voltammetric methods. The 3D PdNN has shown 2.2-fold higher electrochemical surface area than the commercially available Pt/C including other tested catalysts with minimal Pd loading. As a result, it provides a higher density of EOR and HER active sites and facilitated the electron transport. For example, it shows 2.6-fold higher mass activity with significantly lower CO2 production for EOR and the similar overpotential (110 mV @ 10 mA cm-2) for HER compared to Pt/C with better reaction kinetics for both reactions. Thus, the PdNN is proved as an efficient electrocatalyst with better electrocatalytic activity and stability than state-of-the-art Pt/C for both EOR and HER because of the crystalline, monodispersed, and support-free porous nanonetwork.

Development of Highly Active Bifunctional Electrocatalyst Using Co 3 O 4 on Carbon Nanotubes for Oxygen Reduction and Oxygen Evolution

Replacement of precious platinum catalyst with efficient and cheap bifunctional alternatives would be significantly beneficial for electrocatalytic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) and the application of these catalysts in fuel cells is highly crucial. Despite numerous studies on electrocatalysts, the development of bifunctional electrocatalysts with comparatively better activity and low cost remains a big challenge. In this paper, we report a nanomaterial consisting of nanocactus-shaped Co3O4 grown on carbon nanotubes (Co3O4/CNTs) and employed as a bifunctional electrocatalyst for the simultaneous catalysis on ORR, and OER. The Co3O4/CNTs exhibit superior catalytic activity toward ORR and OER with the smallest potential difference (0.72 V) between the