Glassy carbon electrode modified with poly(methyl orange) as an electrochemical platform for the determination of 4-nitrophenol at nanomolar levels

Krishnan Giribabu,Yuvaraj Haldorai,Muruganantham Rethinasabapathy,장성찬,Ranganathan Suresh,조완섭,한영규,노창현,허윤석,Vengidusamy Narayanan 한국물리학회 2017 Current Applied Physics Vol.17 No.8

In this study, poly(methyl orange) (PMO) was synthesized by electrodeposition onto a glassy carbon electrode (GCE), and the resulting structure was examined for the determination of 4-nitrophenol (4-NP). Cyclic voltammetry revealed that the PMO-modified GCE (PMO/GCE) exhibited excellent electrocatalytic activity for the oxidation of 4-NP in a 0.5-M phosphate buffer solution. In contrast, the bare GCE showed no oxidation peak. Interestingly, PMO/GCE exhibited an oxidation peak at approximate 0.93 V, and the background current was higher than that of the bare GCE. Furthermore, the developed electrochemical sensor exhibited a linear relationship with the 4-NP concentration from 600 nM to 10 mM, and the limit of detection was 170 nM (signal/noise ¼ 3). The sensor demonstrated excellent selectivity, good stability, and reproducibility. It was applied to the determination of 4-NP in water samples by the standard addition method and gave recoveries of 99.2e100.9%.

Electrochemical determination of chloramphenicol using a glassy carbon electrode modified with dendrite-like Fe₃O₄ nanoparticles

Krishnan Giribabu,Sung-Chan Jang,Yuvaraj Haldorai,Muruganantham Rethinasabapathy,Seo Yeong Oh,Arunkumar Rengaraj,Young-Kyu Han 한국탄소학회 2017 Carbon Letters Vol.23 No.-

In this study, magnetite (Fe3O4) nanoparticles were electrochemically synthesized in an aqueous electrolyte at a given potential of -1.3 V for 180 s. Scanning electron microscopy revealed that dendrite-like Fe3O4 nanoparticles with a mean size of < 80 nm were electrodeposited on a glassy carbon electrode (GCE). The Fe3O4/GCE was utilized for sensing chloramphenicol (CAP) by cyclic voltammetry and square wave voltammetry. A reduction peak of CAP at the Fe3O4/GCE was observed at 0.62 V, whereas the uncoated GCE exhibited a very small response compared to that of the Fe3O4/GCE. The electrocatalytic ability of Fe3O4 was mainly attributed to the formation of Fe(VI) during the anodic scan, and its reduction to Fe(III) on the cathodic scan facilitated the sensing of CAP. The effects of pH and scan rate were measured to determine the optimum conditions at which the Fe3O4/GCE exhibited the highest sensitivity with a lower detection limit. The reduction current for CAP was proportional to its concentration under optimized conditions in a range of 0.09-47 μM with a correlation coefficient of 0.9919 and a limit of detection of 0.09 μM (S/N=3). Moreover, the fabricated sensor exhibited anti-interference ability towards 4-nitrophenol, thiamphenicol, and 4-nitrobenzamide. The developed electrochemical sensor is a cost effective, reliable, and straightforward approach for the electrochemical determination of CAP in real time applications.

Sensing of picric acid with a glassy carbon electrode modified with CuS nanoparticles deposited on nitrogen-doped reduced graphene oxide

Giribabu, Krishnan,Oh, Seo Yeong,Suresh, Ranganathan,Kumar, Sivakumar Praveen,Manigandan, Ramadoss,Munusamy, Settu,Gnanamoorthy, Govindhan,Kim, Jun Yeong,Huh, Yun Suk,Narayanan, Vengidusamy Springer-Verlag 2016 Mikrochimica acta Vol.183 No.8

<P>We describe the preparation of a nanohybrid consisting of nitrogen doped reduced graphene oxide and CuS nanoparticles (N-rGO/CuS) by in-situ microwave irradiation at weight ratios of 25/75, 50/50, and 75/25. The resulting nanohybrids were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, FTIR, spectroscopy, scanning electron and transmission electron microscopy, electrochemically by cyclic voltammetry and electrochemical impedance analysis. It is shown that the CuS nanoparticles are evenly decorated onto the N-rGO surface. The nanohybrids was placed on glassy carbon electrode (GCE) where they showed electro-reductive activity towards picric acid, typically at working voltages between -0.2 and -0.8 V (vs. SCE). Effects of pH value and scan rate were evaluated, and it is shown that two electrons are involved in electro-reduction. The detection limits of the GCE modified with various N-rGO/CuS hybrids (with 25/75, 50/50, and 75/25 wt%) are 6.2, 3.2, and 0.069 mu M respectively. The method demonstrates its applicability in sensing of picric acid with good reproducibility.</P>

A spick-and-span approach to the immobilization of horseradish peroxidase on Au nanospheres incorporated with a methionine/graphene biomatrix for the determination of endocrine disruptor bisphenol A

Vilian, A.T. Ezhil,Giribabu, Krishnan,Choe, Sang Rak,Muruganantham, Rethinasabapathy,Lee, Hoomin,Roh, Changhyun,Huh, Yun Suk,Han, Young-Kyu Elsevier Sequoia 2017 Sensors and actuators. B Chemical Vol.251 No.-

<P><B>Abstract</B></P> <P>In the present study, we employ a straightforward, benign strategy to prepare thiol-functionalized reduced graphene oxide (S-RGO) using methionine as the sulphur source and reducing agent. The immobilization of horseradish peroxidase (HRP) over the AuNPs/S-RGO was developed by incorporating AuNPs on the S-RGO surface. The fabricated HRP/AuNPs/S-RGO electrode exhibits a remarkable decrease in the overpotential and a significantly increased oxidation peak current of bisphenol A (BPA) compared with the bare glassy carbon electrode (GCE) and AuNPs/S-RGO electrode. The biosensor shows an excellent amperometric analytical performance with a low detection limit of 2.6×10<SUP>−12</SUP> M and a linear range from 2.0×10<SUP>−11</SUP> to 1.18×10<SUP>−9</SUP> M, with the response time <2s for BPA. From the results, the apparent Michaelis-Menten constant was calculated as 8.14nM. The HRP/AuNPs/S-RGO biosensor exhibited faster response, adequate storage stability, inexpensive, simple fabrication with disposability, satisfactory reproducibility and repeatability, and outstanding selectivity. Finally, the constructed biosensor was utilized successfully for detecting BPA in tomato juice and milk samples with acceptable results.</P> <P><B>Highlights</B></P> <P> <UL> <LI> HRP/AuNPs/S-RGO biocomposite has been prepared to determine bisphenol A. </LI> <LI> The AuNPs/S-RGO is a promising platform for HRP immobilization. </LI> <LI> The biosensor exhibits excellent stability, reproducibility and high selectivity. </LI> <LI> It exhibits LOD of 2.6×10<SUP>−12</SUP> in a wide linear range from 2.0×10<SUP>−11</SUP> to 1.18×10<SUP>−9</SUP> M. </LI> <LI> It detects bisphenol A in real samples such as tomato juice and milk. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

AgNWs-PANI nanocomposite based electrochemical sensor for detection of 4-nitrophenol

Zhang, Chao,Govindaraju, Saravanan,Giribabu, Krishnan,Huh, Yun Suk,Yun, Kyusik Elsevier 2017 Sensors and actuators. B, Chemical Vol.252 No.-

<P><B>Abstract</B></P> <P>Silver Nanowire-Polyaniline (AgNWs-PANI) composite modified glassy carbon electrode (GCE) was fabricated for the sensitive electrochemical determination of 4-nitrophenol (4-NP). AgNWs-PANI composite was synthesized in two steps process. The synthesized AgNWs-PANI was characterized by UV–vis, FTIR, SEM and TEM analysis. The electrochemical reduction determination of 4-NP under optimized conditions exhibited a reduction peak at −0.77V with higher current response compared with bare GCE and AgNWs modified glassy carbon electrode (AgNWs/GCE). Effect of pH and scan rate was investigated to examine the proton transfer number, electron transfer number, electron transfer coefficient and standard rate constant of electrode. Under optimized condition, the reduction peak current and the concentration of 4-NP exhibits the linear relation with the concentration range from 0.6–32μM, and the limit of detection was determined to be 52nM (S/N=3). Although, AgNWs-PANI/GCE were applied to detect the determination the 4-NP in real water samples at the recover ranging from 97.0–101.5%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Silver Nanowire-Polyaniline (AgNWs-PANI) composite were synthesized. </LI> <LI> Physico-chemical characterization was analyzed. </LI> <LI> Electrochemical sensor was done. </LI> <LI> Lower limit of detection was determined to be 52nM. </LI> </UL> </P>

Pd nanospheres decorated reduced graphene oxide with multi-functions: Highly efficient catalytic reduction and ultrasensitive sensing of hazardous 4-nitrophenol pollutant

Vilian, A.T. Ezhil,Choe, Sang Rak,Giribabu, Krishnan,Jang, Sung-Chan,Roh, Changhyun,Huh, Yun Suk,Han, Young-Kyu Elsevier 2017 Journal of hazardous materials Vol.333 No.-

<P><B>Abstract</B></P> <P>We illustrate a facile approach for in situ synthesis of Pd-gum arabic/reduced graphene oxide (Pd-GA/RGO) using GA as the reducing agent, which favors the instantaneous reduction of both Pd ions and GO into Pd nanoparticles (NPs) and RGO. From the morphological analysis of Pd-GA/RGO, we observed highly dispersed spherical 5nm Pd NPs decorated over RGO. The as-synthesized Pd-GA/RGO composite was employed for the catalytic reduction and the electrochemical detection of 4-nitrophenol (4-NP), respectively. The catalytic reduction of 4-NP was highly pronounced for Pd-GA/RGO (5min) when compared to Pd NPs (140min) and Pd/RGO (36min). This enhanced catalytic activity was attributed to the synergistic effect of Pd NPs and the presence of various functional groups of GA. Significantly, the fabricated sensor offered a low detection limit (9fM) with a wider linear range (2–80 pM) and long-term stability. The simple construction technique, high sensitivity, and long-term stability with acceptable accuracy in wastewater samples were the main advantages of the developed sensor. The results indicated that the as-prepared Pd-GA/RGO exhibited better sensing ability than the other graphene-based modified electrodes. Therefore, the proposed sensor can be employed as a more convenient sensing platform for environmental and industrial pollutants.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pd-GA/RGO catalysts were successfully synthesized by a simple chemical reduction method. </LI> <LI> Pd-GA/RGO catalysts show excellent fast catalytic activity (5min) towards the reduction of 4-NP to 4-AP. </LI> <LI> The developed sensor showed a wide linear range of 2–80pM with a low detection limit of 9fM. </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>[DISPLAY OMISSION]</P>

Plasmonic-based biosensor for highly sensitive detection of noroviral proteins

Seo Yeong OH,Nam Su HEO,Myung Yi RYU,Hye Jin HWANG,Krishnan GIRIBABU,Jong Pil PARK,Yun Suk HUH 한국생물공학회 2016 한국생물공학회 학술대회 Vol.2016 No.10

Visible-light-driven dynamic cancer therapy and imaging using graphitic carbon nitride nanoparticles

Heo, Nam Su,Lee, Sun Uk,Rethinasabapathy, Muruganantham,Lee, Eun Zoo,Cho, Hye-Jin,Oh, Seo Yeong,Choe, Sang Rak,Kim, Yeonho,Hong, Won G,Krishnan, Giribabu,Hong, Won Hi,Jeon, Tae-Joon,Jun, Young-Si,Kim, Elsevier 2018 Materials Science and Engineering C Vol.90 No.-

<P><B>Abstract</B></P> <P>Organic graphitic carbon nitride nanoparticles (NP-g-CN), less than 30 nm in size, were synthesized and evaluated for photodynamic therapy (PDT) and cell imaging applications. NP-g-CN particles were prepared through an intercalation process using a rod-like melamine-cyanuric acid adduct (MCA) as the molecular precursor and a eutectic mixture of LiCl-KCl (45:55 wt%) as the reaction medium for polycondensation. The nano-dimensional NP-g-CN penetrated the malignant tumor cells with minimal hindrance and effectively generated reactive oxygen species (ROS) under visible light irradiation, which could ablate cancer cells. When excited by visible light irradiation (<I>λ</I> > 420 nm), NP-g-CN introduced to HeLa and cos-7 cells generated a significant amount of ROS and killed the cancerous cells selectively. The cytotoxicity of NP-g-CN was manipulated by altering the light irradiation and the BP-g-CN caused more damage to the cancer cells than normal cells at low concentrations. As a potential non-toxic organic nanomaterial, the synthesized NP-g-CN are biocompatible with less cytotoxicity than toxic inorganic materials. The combined effects of the high efficacy of ROS generation under visible light irradiation, low toxicity, and bio-compatibility highlight the potential of NP-g-CN for PDT and imaging without further modification.</P> <P><B>Highlights</B></P> <P> <UL> <LI> NP-g-CN are metal free non-toxic organic matter. </LI> <LI> Bulk-g-CN are breakdown into uniform NP-g-CN through intercalation of LiCl. </LI> <LI> NP-g-CN has high efficacy to generate ROS under visible light irradiation </LI> <LI> NP-g-CN is biocompatible, selectively kills cancer cells and less toxic to normal cells. </LI> <LI> Being organic, NP-g-CN avoids the potential toxicity from heavy metal in humans. </LI> <LI> NP-g-CN can be used for both photodynamic therapy (PDT) and imaging applications. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>