A green preparation of nitrogen doped graphene using urine for oxygen reduction in alkaline fuel cells.

Ahmed, Mohammad Shamsuddin,You, Jung-Min,Han, Hyoung Soon,Jeong, Dae-Cheol,Jeon, Seungwon American Scientific Publishers 2014 Journal of Nanoscience and Nanotechnology Vol.14 No.8

<P>A simple, eco-friendly and efficient harmless chemical approach has been developed for the simultaneous nitrogen (N) doping and reduction of graphene oxide (GO) by cost free human urine using simple refluxing. Large-scale preparation of graphene has been hindered largely by several issues, such as highly toxic reducing agents that are harmful to human health and environment, complicated reduction process and costly chemicals. Human urine is a natural precursor of urea with no cost. In this process, the NH3 has acted as not only reducing but also doping agent that produced via thermal decomposition of urea, while the N doping level of ~11.1 at% is achieved. For the first time we have used urine as a reductant and doping agent in such a high class chemical technology. The simultaneous reduction and N-doping of GO using urine (denoted as UNG) have confirmed by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and UV-vis spectroscopy. The resultant UNG has demonstrated to show remarkable electrocatalytic activity toward oxygen reduction reaction (ORR) with better fuel selectivity, and stability than that of the commercially available 20 wt% Pt/C electrode using cyclic voltammetry (CV) and chronoamperometry.</P>

Graphene Supported Silver Nanocrystals Preparation for Efficient Oxygen Reduction in Alkaline Fuel Cells

Ahmed, Mohammad Shamsuddin,Lee, Dong-Weon,Kim, Young-Bae The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.10

<P>The silver nanocrystals (AgNCs) anchored on graphene oxide (GO) catalysts have been synthesized by a facile chemical reduction and nontemplate method using ascorbic acid (AA) as reducing agent and have successfully employed as a cathode catalyst for oxygen reduction reaction (ORR) in direct alkaline fuel cells (DAFCs). The morphological characterizations demonstrate that the AgNCs have crystalline form and grafted onto reduced graphene oxide (AgNCs/rGO_AA). Comparatively better dispersion and higher population of AgNCs have observed on AA treated AgNCs/rGO than NaBH4 which is known as conventional reducing agent. The electrochemical catalysis in 0.1 M KOH electrolyte has demonstrated that the AgNCs/rGO_AA has an excellent electrocatalytic activity for ORR in alkaline media compared to the other tested electrodes. Particularly, it shows 40% higher mass activity with large specific activity against 20 wt% Pt/C with faster electron transfer rate per O-2. Moreover, the reaction kinetic parameters have confirmed that the ORR at AgNCs/rGO_AA catalyst not only follows a 4e(-) process with lowering H2O2 formation but also proceeds on with good stability and fuel selectivity in DAFCs. (C) The Author(s) 2016. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.</P>

Amide-functionalized graphene with 1,4-diaminobutane as efficient metal-free and porous electrocatalyst for oxygen reduction

Ahmed, Mohammad Shamsuddin,Kim, Young-Bae Elsevier 2017 Carbon Vol.111 No.-

<P>A porous graphene catalyst was prepared with 1,4-diaminobutane (DAB) through amide functionalization and was used as a metal-free electrocatalyst for oxygen reduction reaction (ORR) in alkaline fuel cells. DAB was used as a junction among functionalized graphene layers to impart electrocatalytic activity for the ORR resultant from the interlayer charge transfer. The successful amidation and subsequent reduction in the process of catalyst preparation were confirmed using X-ray photoelectron spectroscopy. A hierarchical porous structure was also confirmed through the surface morphological analysis. The Brunauer-Emmett-Teller specific surface area and thermal stability increased by 2.6- and 1.5-fold, respectively, after successful amide functionalization. The as-prepared catalyst was proved an efficient metal-free electrocatalyst with better electrocatalytic activity, stability, and tolerance to the crossover effect than commercially available Pt/C for ORR by a direct four-electron involved pathway. These results indicate that the amide-functionalized graphene metal-free catalyst reported in this study is a promising alternative to traditional noble metal-based ORR catalysts. (C) 2016 Elsevier Ltd. All rights reserved.</P>

Novel Silver(I) Ion Selective PVC Membrane Electrode Based on the Schiff Base (N²E,N^2'E)-N²,N^2'-Bis(Thiophen-2-ylmethylene)-1,1'-Binaphthyl-2,2'-Diamine

Jeong, Eunseon,Ahmed, Mohammad Shamsuddin,Jeong, Hae-Sang,Lee, Eun-Hee,Jeon, Seung-Won Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.3

A potentiometric sensor based on the Schiff base $(N^2E,N^{2'}E)-N^2,N^{2'}$-bis(thiophen-2-ylmethylene)-1,1'-binaphthl-2,2'-diamine has been synthesized and explored as an ionophore PVC-based membrane sensor selective for the silver ($Ag^+$) ion. Potentiometric investigations indicate a high affinity of this receptor for the silver ion. Seven membranes have been fabricated with different compositions, with the best performance shown by the membrane with an ionophore composition (w/w) of: 1.0 mg, PVC: 33.0 mg, DOA: 66.0 mg in 1.0 mL THF. The sensor worked well within a wide concentration range of $1.0{\times}10^{-2}$ to $1.0{\times}10^{-7}$ M, at pH 5, at room temperature (slope 57.4 mV/dec.), and with a rapid response time of 9 s; the sensor also showed good selectivity towards the silver ion over a huge number of interfering cations, with the highest selectivity coefficient for $Hg^{2+}$ at -3.7. Thus far, the best lower detection limit was $4.0{\times}10^{-8}$ M.

Electrodeposited Palladium Nanotubes on Nanoclusters Mosaic Basement for Electrooxidation of Hydrazine

Begum, Halima,Ahmed, Mohammad Shamsuddin,Jeon, Seungwon American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.7

<P>A series of electrochemically deposited palladium nanotubes (e-PdNTs) on nanoclusters (e-PdNCs) mosaic basement have been prepared with variation of cycle number and scan rate through a facile electrochemical deposition method using cyclic voltammetry (CV) technique in 20 mM HCl solution and have been used as an anode electrocatalyst for hydrazine (N2H4) oxidation reaction. The morphology and structure of the self-formed e-PdNTs catalysts have characterized by scanning electron microscopy. As observed, the size and amount of e-PdNTs increased with the increasing of cycle number and decreased with respect to the increasing of scan rate. The overall experimental parameters have determined that the superior and direct electrocatalytic N2H4 oxidation obtained with lowering NH3 formation upon 6 cycles deposited e-PdNTs at 50 mV s(-1) scan rate in 0.1 M KOH solution than that of other prepared e-PdNTs and Pd/C in respect to the onset potential, current intensity and durability. The lower detection limit (3.6 mu M) and the linear range of N2H4 (up to 14 mM) have also been determined on e-PdNTs via amperometry for further sensor application.</P>

Determination of Dopamine by Dual Doped Graphene-Fe₂O₃ in Presence of Ascorbic Acid

Yasmin, Sabina,Ahmed, Mohammad Shamsuddin,Jeon, Seungwon The Electrochemical Society 2015 Journal of the Electrochemical Society Vol.162 No.14

<P>Both nitrogen and sulfur dual doped graphene supported Fe2O3 (NSG-Fe2O3) have been prepared by hydrothermal methods and subsequently utilized for the electrochemical determination of dopamine (DA) in presence of ascorbic acid (AA). The NSG-Fe2O3 has been characterized via transmission electron microscopy (TEM) and X-ray photoelectron spectroscopic (XPS). The electrochemical detection of DA was measured through the cyclic voltammetry, differential pulse voltammetry, and amperometric techniques in a 0.1 M phosphate buffer solution (PBS) at pH 7.4. Interferences have been investigated in presence of AA, glucose, serotonin, N2H4, and uric acid. The NSG-Fe(2)O(3)has shown good analytical performance for DA with comparatively better sensitivity (29.1 mu A mM(-1)), long linear detection range (0.3-210 mu M) and detection limit (0.035 mu M) (S/N = 3). The catalytic rate constant for DA detection has been calculated as 9.6 x 10(4) M-1 s(-1) with a good diffusion coefficient of 3.5 x 10(-4) cm(2) s(-1). The electrooxidation of DA may enhances by fast proton acceptance and/or electron donation due to higher electron density for excess loan pair electron that provided from N and S dual-doped graphene sheets. (C) The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. All rights reserved.</P>

Poly-Cobalt[tetrakis(<i>o</i>-aminophenyl)porphyrin] Nanowire and Single-Walled Carbon Nanotube for the Analysis of Hydrogen Peroxide

Jeong, Haesang,Ahmed, Mohammad Shamsuddin,Jeon, Seungwon American Scientific Publishers 2011 Journal of Nanoscience and Nanotechnology Vol.11 No.2

<P>Nanowires of poly-cobalt[tetrakis(o-aminophenyl)porphyrin] (PCoTAPPNW) were fabricated by electrochemical polymerization by the cyclic voltammetric method in anodic aluminum oxide membranes. A glassy carbon electrode (GCE) modified by PCoTAPPNW and single-walled carbon nanotubes (SWNT) without any binder was investigated with voltammetric methods in phosphate buffer saline (PBS) at pH 7.4. The PCoTAPPNW + SWNT/GCE exhibited strongly enhanced voltammetric and amperometric sensitivity towards hydrogen peroxide (H2O2), which shortened the response time (< 5 seconds), showed detection limit of 1.0 microM and enhanced the sensitivity for H2O2 detection with 194 microA mM(-1) cm(-2). The PCoTAPPNW + SWNT/GCE can be used to monitor H2O2 at very low concentration in physiological pH as an efficient electrochemical H2O2 sensor.</P>

Potential enhancement of antibacterial activity of graphene oxide-silver nanocomposite by introducing C₂ carbon chain linkage

Yun, Hyosuk,Ahmed, Mohammad Shamsuddin,Lee, Kyungmi,Jeon, Seungwon,Lee, Chul Won Elsevier 2016 APPLIED SURFACE SCIENCE - Vol.360 No.2

<P><B>Abstract</B></P> <P>Various carbon chain linkages were introduced during the process of synthesizing silver-nanoparticles (AgNPs)-decorated graphene nanocomposites [referred to as GO-<I>C</I> <SUB> <I>x</I> </SUB>-Ag where, HS-(CH<SUB>2</SUB>)<SUB> <I>x</I> </SUB>-SH= <I>C</I> <SUB> <I>x</I> </SUB> and <I>x</I> =0, 2, or 4] to evaluate antibacterial properties. The nano-structures of GO-<I>C</I> <SUB> <I>x</I> </SUB>-Ag were characterized using TEM and XPS, revealing that GO-<I>C</I> <SUB> <I>2</I> </SUB>-Ag comprises well-dispersed and smaller AgNPs anchored onto the surface of graphene sheets than the GO-<I>C</I> <SUB> <I>0</I> </SUB>-Ag and GO-<I>C</I> <SUB> <I>4</I> </SUB>-Ag. The antibacterial activities of those nanocomposites were assessed using paper-disk diffusion and minimal inhibitory concentration (MIC) methods against Gram-negative and Gram-positive bacteria. The results showed that carbon chain linkers enhanced the antibacterial activity against Gram-negative <I>Salmonella typhimurium</I> and <I>Pseudomonas aeruginosa</I> and Gram-positive <I>Staphylococcus aureus</I>. In particular, GO-<I>C</I> <SUB> <I>2</I> </SUB>-Ag showed higher antibacterial activity than GO-<I>C</I> <SUB> <I>0</I> </SUB>-Ag and GO-<I>C</I> <SUB> <I>4</I> </SUB>-Ag due to nearly eight times higher reactive oxygen species (ROS) formation which determined by fluorescence-based ROS detection experiment. Also, LC-inductively coupled plasma mass spectrometer (LC-ICP-MS) demonstrated that the Ag release from GO-<I>C</I> <SUB> <I>x</I> </SUB>-Ag was insignificant (0.03%). However, the higher ROS formation from GO-<I>C</I> <SUB> <I>2</I> </SUB>-Ag was facilitated by higher dispersion, smaller size, and well attachment of AgNPs with AgO species onto graphene sheets. These results suggest that the medium length carbon chain linkers in between Ag and GO can be utilized to improve antibacterial activity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We introduce various carbon chain linkages during the synthesis of AgNPs-decorated GO. </LI> <LI> GO-<I>C</I> <SUB> <I>2</I> </SUB>-Ag comprises well-dispersed and smaller AgNPs on the surface of GO. </LI> <LI> GO-<I>C</I> <SUB> <I>2</I> </SUB>-Ag has a higher antibacterial activity than GO-<I>C</I> <SUB> <I>0</I> </SUB>-Ag and GO-<I>C</I> <SUB> <I>4</I> </SUB>-Ag. </LI> <LI> The high antibacterial activity of GO-<I>C</I> <SUB> <I>2</I> </SUB>-Ag is facilitated by increased ROS formation. </LI> </UL> </P>

Various Carbon Chain Containing Linkages Grafted Graphene with Silver Nanoparticles Electrocatalysts for Oxygen Reduction Reaction

Lee, Kyungmi,Ahmed, Mohammad Shamsuddin,Jeon, Seungwon The Electrochemical Society 2015 Journal of the Electrochemical Society Vol.162 No.1

<P>In this study, we have synthesized an efficient catalyst by various carbon chain containing linkers grafted graphene with silver nanoparticles (AgNPs)-decorated GO-S-(CH<SUB>2</SUB>)<I><SUB>x</SUB></I>-SH (where <I>x</I> = 2, 3, 4 and denoted as GO-<I>C<SUB>x</SUB></I>-Ag) for oxygen reduction reaction (ORR). The structural and morphological properties have investigated <I>via</I> several instrumental methods. Among those catalysts, the GO-<I>C<SUB>2</SUB></I>-Ag has showed an excellent electrocatalytic performance by cyclic voltammetry (CV) and hydrodynamic techniques for ORR in alkaline media. Hydrodynamic voltammetry reveals that the GO-<I>C<SUB>2</SUB></I>-Ag modified electrode has catalyzed effectively at higher potential. The overall electrocatalytic results showed that the GO-<I>C<SUB>2</SUB></I>-Ag has better activity toward ORR and demonstrated nearly four electron transfer pathway into H<SUB>2</SUB>O due to much grafting of linker molecule and smaller size of AgNPs. The value of transferred electron number (<I>n</I>) and other kinetic parameters have demonstrated that the GO-<I>C<SUB>2</SUB></I>-Ag is highly facilitated than that of GO-Ag and other GO-<I>C<SUB>x</SUB></I>-Ag to electrocatalytic oxygen reduction.</P>

Nitrogen-Doped Graphene Supported Cobalt Oxide Nanocomposite as High Performance Electrocatalyst for Oxygen Reduction Reaction

Yasmin, Sabina,Ahmed, Mohammad Shamsuddin,Jeon, Seungwon American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.6

<P>Nitrogen doped reduced graphene oxide-supported cobalt oxide catalyst has been synthesized by a simple one step chemical reduction method (denoted as NrGO-Co3O4) for electrocatalytic oxygen reduction reaction (ORR). This material has been characterized by various instrumental methods. The morphological analysis shows the Co3O4 nanocomposites are well set on to the reduced graphene oxide with better dispersion. The X-ray photoelectron spectroscopy (XPS) shows electrochemical reduction has been done successfully with the increasing C/O ratio. Also, the Raman data reveals that the Co is presents with the oxidized form. The electrocatalytic activities have been verified using cyclic voltammetry (CV) and hydrodynamic voltammetry techniques in 0.1 M KOH electrolyte. The as prepared catalyst has shown more positively shifted onset and half wave potential (-0.091 V and -0.276 vs. Ag/AgCl) and high cathodic current density 2.57 mA cm(-2) and high methanol, ethanol crossover tolerance than Pt/C. It is the introduction of strongly bonded cobalt nanocomposite into the network of NrGO that modulate the electronic properties of the NrGO-Co3O4, resulting in the superb electrocatalytic performance. The reaction kinetics have confirmed that the ORR at NrGO-Co3O4 catalyst follows a four electron transfer reaction process.</P>