Electrodeposition of Gold on Fluorine-Doped Tin Oxide: Characterization and Application for Catalytic Oxidation of Nitrite

Rahman, Md. Mahbubur,Li, Xiao-Bo,Lopa, Nasrin Siraj,Lee, Jae-Joon Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.7

Sub-micrometer size gold particles were electrodeposited on a transparent fluorine-doped tin oxide (FTO) from acetonitrile solution containing $AuCl_4{^-}$ and tetramethylammonium tetraflouroborate (TMATFB) for detecting $NO_2{^-}$. A series of two-electron ($2e^-$) and one-electron ($1e^-$) reductions of the $AuCl_4{^-}-AuCl_2{^-}-Au$ redox systems were observed at FTO and a highly stable and homogeneous distribution of Au on FTO (Au/FTO) was obtained by stepping the potential from 0 to -0.55 V (vs. Ag/$Ag^+$). The Au/FTO electrode exhibited sufficiently high catalytic activity toward the oxidation of $NO_2{^-}$ with a detection limit (S/N = 3) and sensitivity of 2.95 ${\mu}M$ and 223.4 ${\mu}A{\cdot}cm^{-2}{\cdot}mM^{-1}$, respectively, under optimal conditions. It exhibited an interference-free signal for $NO_2{^-}$ detection with excellent recoveries from real samples.

A non-absorbing organic redox couple for sensitization-based solar cells with metal-free polymer counter electrode

Rahman, Md. Mahbubur,Wang, Jia,Nath, Narayan Chandra Deb,Lee, Jae-Joon Elsevier 2018 ELECTROCHIMICA ACTA Vol.286 No.-

<P><B>Abstract</B></P> <P>An organo-sulfur compound, 5-methylthio-1,3,4-thiadiazole-2-thiol and its oxidized dimer 5-methylthio-1,3,4-thiadiazolium disulfide dication are used as a novel and universal redox couple in both dye-sensitized and quantum-dot sensitized solar cells, in conjunction with a conducting poly(3,4-ethylenedioxythiophene) counter electrode. The 5-methylthio-1,3,4-thiadiazole-2-thiol/5-methylthio-1,3,4-thiadiazolium disulfide dication redox couple is low-cost and easily processable, and exhibits non-absorption of visible light, showing improved redox behavior at an electrochemically deposited poly(3,4-ethylenedioxythiophene) counter electrode. Its redox potential is <I>ca.</I> 60 mV negatively and <I>ca.</I> 170 mV (<I>vs.</I> normal hydrogen electrode) positively positioned than those of iodide/tri-iodide and polysulfide electrolytes, respectively. The maximum power conversion efficiency of (3.55 and 1.20) % is obtained in dye and quantum-dot sensitized solar cells, respectively, sensitized by 5-[[4-[4-(2, 2-Diphenylethenyl) phenyl]-1,2,3,3a,4,8b hexahydrocyclopent [b] indol-7-yl] methylene]-2-(3-octyl-4-oxo-2-thioxo-5-thiazolid dye and CdS-quantum dot, respectively, together with the optimized poly(3,4-ethylenedioxythiophene) counter electrode. These results clearly outperform the performance of identical dye and quantum-dot sensitized solar cells with Pt and Cu<SUB>2</SUB>S-counter electrodes. Thus, this new redox couple and poly(3,4-ethylenedioxythiophene) counter electrode pair is expected to offer a promising and universal alternative to the conventional iodide/tri-iodide and polysulfide electrolytes for sensitization-based solar cells.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel non-absorbing organosulfur redox couple MTDT/MTDD<SUP>2+</SUP> was developed for DSSCs and QDSSCs. </LI> <LI> The MTDT/MTDD<SUP>2+</SUP> and PEDOT-CE conjugate outperformed the performance of identical DSSCs and QDSSCs with Pt and Cu<SUB>2</SUB>S-CEs. </LI> <LI> PEDOT was deposited on FTO by electrochemical method. </LI> <LI> Improved PCEs of (3.55 and 1.20) % were attained in DSSCs and QDSSCs, respectively. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Nigella sativa seed extract attenuates the fatigue induced by exhaustive swimming in rats

Rahman, Mahbubur,Yang, Dong Kwon,Kim, Gi-Beum,Lee, Sei-Jin,Kim, Shang-Jin Spandidos Publications 2017 Biomedical reports Vol.6 No.4

Effect of Titanium Nanorods in the Photoelectrode on the Efficiency of Dye Sensitized Solar Cells

Rahman, Md. Mahbubur,Kim, Hyun-Yong,Jeon, Young-Deok,Jung, In-Soo,Noh, Kwang-Mo,Lee, Jae-Joon Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.9

The effect of $TiO_2$ nanorods (TNR) and nanoparticles (TNP) composite photoelectrodes and the role of TNR to enhance the energy conversion efficiency in dye-sensitized solar cells (DSSCs) was investigated. The 5% TNR content into the TNP photoelectrode significantly increased the short-circuit current density ($J_{sc}$) and the open-circuit potential ($V_{oc}$) with the overall energy conversion efficiency enhancement of 13.6% compared to the pure TNP photoelectrode. From the photochemical and impedemetric analysis, the increased $J_{sc}$ and $V_{oc}$ for the 5% TNR/TNP composite photoelectrode was attributed to the scattering effect of TNR, reduced electron diffusion path and the suppression of charge recombination between the composite photoelectrode and electrolyte or dye.

Label-Free DNA Hybridization Detection by Poly(Thionine)-Gold Nanocomposite on Indium Tin Oxide Electrode

Rahman, Md. Mahbubur,Lopa, Nasrin Siraj,Kim, Young Jun,Choi, Dong-Kug,Lee, Jae-Joon The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.5

<P>A simple and label-free electrochemical DNA hybridization sensor was developed based on a poly(thionine)/gold nanoparticle composite-modified indium tin oxide (PTH/GNPs/ITO) electrode. The PTH/GNPs/ITO electrode was prepared by the electrode position of GNPs on ITO followed by the electropolymerization of thionine (TH). Probe DNA (pDNA) was immobilized on this substrate via covalent linkage between the -NH2 group of PTH and the PO43- group at the 5' end of pDNA. The immobilized single-strand pDNA increased the stiffness of the PTH film and decreased the PTH oxidation current, whereas the current was reduced to a greater extent after the formation of double-strand DNA by the hybridization of target complementary DNA (cDNA). The pDNA/PTH/GNPs/ITO sensor exhibited excellent stability, and selectivity to discriminate DNA base pair mismatches. The semi-log plot of the [cDNA] vs. oxidation current of PTH was linear in the concentration range of 1 mu M - 1 fM with the detection limit (S/N = 3) and sensitivity of ca. 0.3 fM and ca. 2.0 mu A . cm(-2) . fM(-1), respectively. (C) 2016 The Electrochemical Society. All rights reserved.</P>

Simultaneous Determination of Ranitidine and Metronidazole at Poly(thionine) Modified Anodized Glassy Carbon Electrode

Rahman, Md. Mahbubur,Li, Xiao-Bo,Jeon, Young-Deok,Lee, Ho-Joon,Lee, Soo Jae,Lee, Jae-Joon The Korean Electrochemical Society 2012 Journal of electrochemical science and technology Vol.3 No.2

A simple and sensitive electrochemical sensor for simultaneous and quantitative detection of ranitidine (RT) and metronidazole (MT) was developed, based on a poly(thionine)-modified anodized glassy carbon electrode (PTH/GCE). The modified electrode showed the excellent electrocatalytic activity towards the reduction of both RT and MT in 0.1M phosphate buffer solution (PBS, pH 7.0). The peak-to-peak separations (${\Delta}E_p$) for the simultaneous detection of RT and MT between the two reduction waves in CV and DPV were increased significantly from ca. 100 mV at anodized GCE, to ca. 550 mV at the PTH/GCE. The reduction peak currents of RT and MT were linear over the range from 35 to $500{\mu}M$ in the presence of 200 and $150{\mu}M$ of RT and MT, respectively. The sensor showed the sensitivity of 0.58 and $0.78{\mu}A/cm^2/{\mu}M$ with the detection limits (S/N = 3) of 1.5 and $0.96{\mu}M$, respectively for RT and MT.

Electrochemical Dopamine Sensors Based on Graphene

Rahman, Md. Mahbubur,Lee, Jae-Joon The Korean Electrochemical Society 2019 Journal of electrochemical science and technology Vol.10 No.2

The large surface area and the high electrical conductivity of graphene (GP) allow it to act as an "electron wire" between the redox center of biomolecules and an electrode surface. The faster electron transfer kinetics and excellent catalytic activity of GP facilitate the accurate and selective electrochemical detection of biomolecules. This mini-review provides an overview of the recent developments and progress of GP, functionalized or doped GP, and GP-composites based sensors for the selective and interference-free detection of dopamine (DA). The electrochemical principles and future perspective and challenges of DA sensors were also discussed based on GP.

Effect of the TiO₂ Nanotubes in the Photoelectrode on Efficiency of Dye-sensitized Solar Cell

Rahman, Md. Mahbubur,Son, Hyun-Seok,Lim, Sung-Su,Chung, Kyung-Ho,Lee, Jae-Joon The Korean Electrochemical Society 2011 Journal of electrochemical science and technology Vol.2 No.2

The effect of $TiO_2$ nanotube (TNT) and nanoparticle (TNP) composite photoelectrode and the role of TNT to enhance the photo conversion efficiency in dye-sensitized solar cell (DSSC) have investigated in this study. Results demonstrated that the increase of the TNT content (1-15 %) into the electron collecting TNP film increases the open-circuit potential ($V_{oc}$) and short circuit current density ($J_{sc}$). Based on the impedance analysis, the increased $V_{oc}$ was attributed to the suppressed recombination between electrode and electrolyte or dye. Photochemical analysis revealed that the increased Jsc with the increased TNT content was due to the scattering effect and the reduced electron diffusion path of TNT. The highest $J_{sc}$ (12.6 mA/$cm^2$), Voc (711 mV) and conversion efficiency (5.9%) were obtained in the composite photoelectrode with 15% TNT. However, $J_{sc}$ and $V_{oc}$ was decreased for the case of 20% TNT, which results from the significant reduction of adsorbed dye amount and the poor attachment of the film on the fluorine-doped tin oxide (FTO). Therefore, application of this composite photoelectrode is expected to be a promising approach to improve the energy conversion efficiency of DSSC.

Highly sensitive and simultaneous detection of dopamine and uric acid at graphene nanoplatelet-modified fluorine-doped tin oxide electrode in the presence of ascorbic acid

Rahman, Md. Mahbubur,Lopa, Nasrin Siraj,Ju, Myung Jong,Lee, Jae-Joon Elsevier 2017 Journal of Electroanalytical Chemistry Vol.792 No.-

<P><B>Abstract</B></P> <P>We developed a graphene nanoplatelet-modified fluorine-doped tin oxide electrode (GNP/FTO) for the simultaneous detection of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA) and investigated the interaction mechanisms of DA, UA, and AA with GNPs considering their charging states at different pH values. Owing to the unique structure and properties originating from the oxygen and nitrogen functional groups at the edges, GNPs showed high electrocatalytic activity for the electrochemical oxidations of AA, DA, and UA with peak-to-peak potential separations (Δ<I>E</I> <SUB> <I>P</I> </SUB>) between AA-DA and DA-UA of <I>ca</I>. 0.23 and 0.17V, respectively. These values are sufficiently high to allow the simultaneous detection of DA and UA without interference from AA. The highly sensitive and stable GNP/FTO sensor showed sensitivities of <I>ca</I>. 0.15±0.004 and 0.14±0.007μA/μM, respectively, with detection limits of <I>ca</I>. 0.22±0.009 and 0.28±0.009μM, respectively, for DA and UA. The sensor could detect DA and UA concentrations in human serum samples with excellent recoveries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> FTO was modified with graphene nanoplatelets (GNPs) by the e-spray method. </LI> <LI> Dopamine and uric acid were simultaneously detected with GNP/FTO without interference from ascorbic acid. </LI> <LI> Sensor allows low detection limits of 0.22 and 0.28μM for dopamine and uric acid, respectively. </LI> <LI> Sensor shows good stability and recoveries from human serum samples. </LI> <LI> The interaction mechanisms between dopamine, uric acid, and ascorbic acid with GNPs were discussed and verified. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Relationships between blood Mg2+ and energy metabolites/enzymes after acute exhaustive swimming exercise in rats.

Rahman, Md Mahbubur,Lee, Sei-Jin,Mun, A-Reum,Adam, Gareeballah Osman,Park, Ra-Mi,Kim, Gi-Beum,Kang, Hyung-Sub,Kim, Jin-Shang,Kim, Shang-Jin,Kim, Sung-Zoo Humana Press 2014 Biological trace element research Vol.161 No.1

<P>Magnesium (Mg) plays a central role in neuronal activity, cardiac excitability, neuromuscular transmission, muscular contraction, vasomotor tone, and blood pressure, all of which are significantly related to physical performance. To date, the available data about detection of blood total Mg (tMg; free-ionized, protein-bound, and anion-complex forms) are inconsistent, and there is limited information on blood free-ionized Mg (Mg(2+)) in relation to physical exercise. The aim of this study was to determine the biochemical changes related to energy metabolism after acute exhaustive swimming exercise (AESE) in rats in an attempt to correlate the role of blood Mg(2+) with metabolites/enzymes related to energy production. After AESE, blood Mg(2+), tMg, K(+), partial pressure of carbon dioxide, lactate, total protein (T-PRO), high-density lipoprotein (HDL), creatinine (CRE), blood urea nitrogen (BUN), uric acid (UA), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alanine phosphatase (ALP), lactate dehydrogenase (LDH), and creatinine kinase (CK) were significantly increased, whereas pH, partial pressure of oxygen, oxygen saturation, the Mg(2+)/tMg and Ca(2+)/Mg(2+) ratios, HCO3 (-), glucose, triglyceride (TG), and low-density lipoprotein (LDL) were significantly decreased. During AESE, lactate, T-PRO, albumin, AST, ALP, LDH, CK, CRE, BUN, and UA showed significant positive correlations with changes in blood Mg(2+), while glucose, TG, and LDL correlated to Mg(2+) in a negative manner. In conclusion, AESE induced increases in both blood Mg(2+) and tMg, accompanied by changes in blood metabolites and enzymes related to energy metabolism due to increased metabolic demands and mechanical damages.</P>