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Electrocatalytic activity of C-dots for highly sensitive detection of Uric acid
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 14 (2019) 545–552
www.materialstoday.com/proceedings
ICRAMC_2018
Electrocatalytic activity of C-dots for highly sensitive detection of Uric acid T. Dhanasekaran1, A. Padmanaban1, G. Gnanamoorthy1, S. Praveen Kumar1, A. Stephen2, and V. Narayanan1* 1
Department of Inorganic Chemistry, Guindy Campus, University of Madras, Chennai-600 025 2 Department of Nuclear Physics, Guindy Campus, University of Madras, Chennai-600025
Abstract Over the past decades, carbon based materials used as many applications, particularly, medicine, biosensors, catalysis and so on. The high potential C-dots (CDs) were synthesized via simple microwave irradiation method. As synthesized C-dots were characterized using many of the techniques, such as XRD, FT-IR, DRS UV vis spectroscopy. The CDs surface was analyzed using FESEM microscopy. Further the objective of the synthesized CDs was catalytic sensing of Uric Acid (UA). The CDs modified electrode gives better result than bare electrode. The electrochemical station comprises three electrode systems, calomel electrode as a reference electrode, platinum electrode as counter electrode and glassy carbon electrode (GCE) as a working electrode. The CDs modified electrode gives the sensing of 10-4M UA oxidation peak at 0.51 V at 50 mV scan rate using pH 7 buffer solution. © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference On Recent Advances In Material Chemistry. Keywords:CDs, modified GCE, Uric acid sensing.
1. Introduction In recent years, carbon dots (CDs), as one kind of carbon nanoparticle, are attracting great interest owing to their low toxicity, low cost, biocompatibility, and excellent photoluminescence. CDs are usually composed of nano-sized ____________ * Corresponding author. Tel.: +91-9444299226; fax: 91-44-22300488. E-mail address:[email protected] 2214-7853© 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of 2nd International Conference On Recent Advances In Material Chemistry.
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T. Dhanasekaran et al. / Materials Today: Proceedings 14 (2019) 545–552
sp2 hybridized graphitic cores and carbonyl surface moieties, and they can be widely used in the field of biochemical sensing, environment photocatalytic technology, drug carriers [1-3]. The development of novel nanosensors for highly sensitive, rapid, and specific bioanalysis is of vital importance for disease diagnosis, medicine research, food safety and environmental monitoring. Carbon dots (C dots) have emerged as a biocompatible and environmentfriendly nanomaterial and have been successfully synthesized via many approaches [4, 5].
Besides, the
hydrophilicity of the surface functional groups such as carboxylic and alcoholic groups further offers the basis for easy conjugation with affinity ligands. The C dots have strong absorption in the visible range and are highly fluorescent, and the energy can be coupled with many conventional semiconductors through charge injection. Carbon nanodots (C-dots) which comprise quasispherical nanoparticles with sizes below 10 nm are becoming both an important class of imaging probes and a versatile platform for developing high-performance nanosensors, due to their fascinating properties such as aqueous solubility, tunable surface functionalities, non-blinking, excellent biocompatibility and cell membrane permeability [6,7]. Surface functionalization of C-dots is paving the way towards quantitative detection, highly efficient fluorescent imaging, and real-time tracking of targets. Electrochemical biosensing applications have been increasingly established for continuous observing in environmental and health care applications. Like devices contain a biological sensing element connected to a transducer that converts the exact bio recognition event to an electrical signal. The main key steps in the fabrication of biosensors consist of the effective immobilization of biomolecules onto the transducer surface [8]. The intentions are to find an immobilization method that keeps the enzyme activity, increases its stability, and offers accessibility toward substrate. Various immobilization methods have been recognized for electrochemical biosensor applications, such as bio affinity attachment, self-assembled multilayers, mixing in carbon composites, and entrapment within polymeric and inorganic environments. In purine metabolism, Uric acid (UA) is the primary end product and UA is one of the powerful indicators because it can be used as a warning sign of kidney diseases observing UA in the blood or urine [9]. Many of the disease such as gout, hyperuricemia, Lesch-Nyan syndrome, cardiovascular, leukemia, pneumonia and chronic renal disease affect from unusual UA level in a human body [10]. The determination of uric acid is executed by oxidation of enzymatically generated H2O2 at the sensing electrode. The intensive on parameters such as simplicity, sensitivity, low detection limit and low cost, none of them has been able to implement uric acid sensing for in vivo applications [11].The present study, C-dots was synthesized by simple microwave irradiation method. The XRD pattern given the formation of C-dots and FT-IR reveals the functional groups present in C-dots. FESEM microscope analyzed the formation of C-dots are spherical shape. The active C-dots are casting on the GCE electrode it gives the good result for sensing of UA at 50 mV scan rate using pH 7.
T. Dhanasekaran et al. / Materials Today: Proceedings 14 (2019) 545–552
547
1.1Chemicals Chitosan was purchased from Sigma Aldrich chemicals. Acetic acid, Ethanol and Acetone were bringing from LOBA chemicals without distillation. 1.2Synthesis of C-dots 2 g of chitosan was dissolved in 18 ml of 2% acetic acid with vigorous stirring at room temperature for 40 min. the mixed solution was heated by the microwave with the power of 750W (MCR-3 microwave chemical reactor) for 20 minutes, following the products were cooled to room temperature and dissolved by 50 ml ultrapure water. In this way, the original CDs aqueous solution was obtained. After being placed for 24 hrs, the solution was purified by a 0.22 μm filter membrane. The filtered CDs were first dried at 60 °C in a constant and then 80 °C in a vacuum drying oven. 1.3 Electrochemical experiment Cyclic voltammetry methods were utilized to examine the electrochemical sensing properties of
C-dots
towards Uric Acid (UA). All electrochemical sensing experiments were carried out using a CHI 1103A electrochemical station connected to a PC. The electrochemical experiments were carried out in 0.2 M phosphate buffer solution (PBS), pH 7 in a conventional three-electrode system using the bare and modified GCE as the working electrode. Platinum wire and saturated calomel electrode (SCE) were used as the counter electrode and reference electrode respectively. For cyclic voltammetric measurements, the sensors were immersed in 60 mL of 0.2 M PBS containing 10-4M UA, applying the potential in the range of 0.2 V to +1.2 V. All measurements were carried out at room temperature (25 °C). 1.4 Preparation of modified electrode 2 mg of the C-dots sample was dispersed in 5 ml acetone and the solution was sonication for 30 min. Then the dispersed solution was coated on the GCE surface using drop casting method and dried. Before and after each cycling, the modified GCE was washed with double distilled water and activated again with the same procedure [12]. 2. Result and Discussion 2.1 X-ray diffraction analyses The crystal phase and purity of the sample was determined from XRD pattern. As synthesized C-dots was successfully analyzed using XRD. The peak at 2θ = 26.5 and 42.5 was confirms the formation of C-dots [13]. The cell parameters is a=2.45Å, b= 4.25Å and c=6.69Å and forms as an orthorhombic structure. The d-spacing value is 3.348Å. These evidences clearly tell the formation of C-dots.
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Figure. 1 XRD pattern of synthesized C-dots
2.2 Fourier Transform Infra-red spectroscopy The FT-IR was used to determine the presence of functional groups as synthesized samples. From the Fig. 2the broad peak at 3442 cm-1 was corresponds to stretching of water molecules and the bending mode of vibration appears at 1638 cm-1. The sharp peaks appears around 3000-2800 cm-1 is respect to the C=H stretching for the precursor of chitosan. The stretching of N-H vibration mode shows around at 1476-1300 cm-1 because of the presence of amine group. The broad shoulder peak appears at 1055 cm-1 is due to the C-OH stretching vibrations. The aliphatic groups can have CH2 vibrations, these C-H modes are displays at 800-600 cm-1[14].
Figure. 2 The FT-IR spectrum of synthesized C-dots.
2.3 Diffuse Reflectance UV-Vis Spectroscopy From Fig. 3 the DRS-UV vis spectroscopy techniques gives the remarkable excitation values of the corresponding C-dots. The broad peak at 380 nm reveals the π-π conjugation of the chitosan precursors. The highly amorphous phase of the C-dots was shows in the DRS spectroscopy.
T. Dhanasekaran et al. / Materials Today: Proceedings 14 (2019) 545–552
549
Figure. 3 DRS UV vis spectroscopy of as synthesized C-dots
2.4 Field Emission Scanning Electron Microscopy The morphology of the synthesized sample was wisely analyzed from FESEM. The high and low magnification images shows that the C-dots were looks like sphere morphology with the formation of randomly. From this FESEM images the average particle size was determined. The particle size is ~ 15 nm.
Figure. 4.FESEM image of sphere shape C-dots.
3. Electrochemical Activity 3.1 Sensing of Uric acid Fig.5.Shows the cyclic voltammogram in presence of 10-4 M uric acid for bare GCE and modified Cdots/GCE nano sphere at 50mV/s scan rate. The initial potential range was +0.2 to +1.2 Vin pH 7.The oxidation of UA gives the peak at 0.51 V and 0.58 V for bare GCE and C-dots@GCE respectively in pH 7 buffer solution [15]. The C-dots modified GCE to exhibit the enormous current at 4.53 μA. The UA oxidation proceeds 2e-, 2H+ system to lead to an unstablediimine species. After the water molecules can attack the diimine for stepwise to form iminealcohol and the uric acid-4,5 diol. Fig. 5 shows the higher potential shift than the bare GCE, it denotes that Cdots@GCE shows the better catalytic activity on the surface of GCE.
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T. Dhanasekaran et al. / Materials Today: Proceedings 14 (2019) 545–552
Figure. 5 cyclic voltammogram of 0.001 M uric acid at 50 mV/s in pH7 for bareGCE and modified C-dots GCE
3.2 Effect of pH on the oxidation of UA The pH effect of 10-4M uric acid in was analyzed using cyclic voltammogram at scan rate 50mV/s. Fig. 6 indicates the pH response of the UA using pH7, pH9 and pH 10. Among the different pH solutions the UA was gives the good result for pH7. Hence the neutral pH has better sensing ability against the UA.
Figure. 6 pH effect of 0.001 M uric acid using pH 7 , pH 9 and pH 10
3.3 Effect of Scan rate Fig. 7(a) shows the effect of scan rate on the electrooxidation of 0.001 M uric acid at C-dots@GCE was investigated to study the kinetics of the electrode reaction. The cyclic voltammetry response of pH7 at 0.001 M UA with the scan rate of 30-175 mV/s. From the fig. shows the gradually increasing with increase the scan rate without any potential shift. Fig. 7(b) shows the double logarithmic plot of log (ν) vs log (Ipa), from this the slope value was found to be 0.65 (R2=0.9988) which is similar to that the electron transfer process is adsorption controlled.From this, it is clearthat the electrooxidation of 10-4M uric acid at C-dots@GCE involves twoelectron and three proton transfer process which is consistentwith the Laviron equation [16].
T. Dhanasekaran et al. / Materials Today: Proceedings 14 (2019) 545–552
551
Figure. 7. (a) Scan rate of C-dots at 30-175 mV and (b) Plot of log of scan rate versus log I pa .
4. Summary The facile method for synthesis of C-dots via simple hydrothermal and followed by characterized using primary techniques such as, XRD, FT-IR, DRS-UV vis spectroscopy and the surface morphology of the as synthesized C-dots were analyzed using FESEM microscope. The active C-dots were modified on GCE for sensing of uric acid. The modified GCE shows the better results than bare GCE. The uric acid oxidation occurs at 0.58 V in 50 mV/s using pH 7. Further the C-dots was proceeds pH effect and scan rate effect, from these analyses gives the 2e-, 2H+ system and adsorption controlled process. Among theanalytical methods, electrochemical method has a number of advantages, including simple, cost effective and high sensitive. Acknowledgement The author (T.D) acknowledges for Prof. M. Sathiyendiran,School of Chemistry, Hyderabad Central University for UGC-NRC program and Dept. of Inorganic chemistry, University of Madras, for Instrumentation facility. References 1.
Q. Ma and X. Su, Analyst, 136 (2011) 4883-4893.
2.
B. De, B. Voitb and N. Karak, RSC Adv., 4 (2014) 58453-58459.
3.
V. Biju, Chem. Soc. Rev., 43 (2014) 744-764.
4.
A. Prasannan and T. Imae, Ind. Eng. Chem. Res. 52 (2013) 15673-15678.
5.
H. Xu, X. Yang, G. Li, C. Zhao, X. Liao, J. Agric. Food Chem. 63 (2015) 6707-6714
6.
A. Kundu, J. Lee, B. Park, C. Ray, K. VijayaSankar, W. S. Kim, S. H. Lee, Il-Joo Cho, S. C. Jun, J. Colloid and Inter. Sci., 513 (2018) 505514.
7.
H. Nie, M. Li, Q. Li, S. Liang, Y. Tan, L. Sheng, W. Shi, and S. Xiao-An Zhang, Chem. Mater., 26 (2014) 3104-3112.
8.
C. Ge, J. Zou, M. Yan, H. Bi, Mater. Lett., 137 (2014) 41-44.
9.
R. Suresh, K. Giribabu, R. Manigandan, A. Stephen and V. Narayanan, RSC Adv., 4 (2014) 17146-17155.
10. H. Beitollahi, F. G. Nejad and S. Shakeri, Anal. Methods, 9 (2017) 5541-5549.
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11. M. Taei, F. Hasanpour, S. Habibollahi, L. Shahidi, J. Electroanal. Chem. 789 (2017) 140- 147. 12. T. Dhanasekaran, A. Padmanaban, G. Gnanamoorthy, R. Manigandan, S. Praveen Kumar, A. Stephen, P. Selvam, M. Subaraja, and V. Narayanan, Chem.Select 2 (2017) 11717-11726. 13. Z. Bo, H. Maimaiti, Z. De-Dong, X. Bo, W. Ming, J. Photochem. Photobiol. A: Chem. 345 (2017) 54-62. 14. W. Zhou, J. Zhuang, W. Li, C. Hu, B. Lei, and Y. Liu, J. Mater. Chem. C, 5 (2017) 8014-8021. 15. S. B. Khoo and F. Chen, Anal. Chem. 74 (2002) 5734-5741. 16. T. Dhanasekaran, A. Padmanaban, R. Manigandan, S. Praveen Kumar, A. Stephen, V. Narayanan. J Mater Sci: Mater Electron 28 (2017) 12726-12740.
ScienceDirect Materials Today: Proceedings 14 (2019) 545–552
www.materialstoday.com/proceedings
ICRAMC_2018
Electrocatalytic activity of C-dots for highly sensitive detection of Uric acid T. Dhanasekaran1, A. Padmanaban1, G. Gnanamoorthy1, S. Praveen Kumar1, A. Stephen2, and V. Narayanan1* 1
Department of Inorganic Chemistry, Guindy Campus, University of Madras, Chennai-600 025 2 Department of Nuclear Physics, Guindy Campus, University of Madras, Chennai-600025
Abstract Over the past decades, carbon based materials used as many applications, particularly, medicine, biosensors, catalysis and so on. The high potential C-dots (CDs) were synthesized via simple microwave irradiation method. As synthesized C-dots were characterized using many of the techniques, such as XRD, FT-IR, DRS UV vis spectroscopy. The CDs surface was analyzed using FESEM microscopy. Further the objective of the synthesized CDs was catalytic sensing of Uric Acid (UA). The CDs modified electrode gives better result than bare electrode. The electrochemical station comprises three electrode systems, calomel electrode as a reference electrode, platinum electrode as counter electrode and glassy carbon electrode (GCE) as a working electrode. The CDs modified electrode gives the sensing of 10-4M UA oxidation peak at 0.51 V at 50 mV scan rate using pH 7 buffer solution. © 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference On Recent Advances In Material Chemistry. Keywords:CDs, modified GCE, Uric acid sensing.
1. Introduction In recent years, carbon dots (CDs), as one kind of carbon nanoparticle, are attracting great interest owing to their low toxicity, low cost, biocompatibility, and excellent photoluminescence. CDs are usually composed of nano-sized ____________ * Corresponding author. Tel.: +91-9444299226; fax: 91-44-22300488. E-mail address:[email protected] 2214-7853© 2019 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of 2nd International Conference On Recent Advances In Material Chemistry.
546
T. Dhanasekaran et al. / Materials Today: Proceedings 14 (2019) 545–552
sp2 hybridized graphitic cores and carbonyl surface moieties, and they can be widely used in the field of biochemical sensing, environment photocatalytic technology, drug carriers [1-3]. The development of novel nanosensors for highly sensitive, rapid, and specific bioanalysis is of vital importance for disease diagnosis, medicine research, food safety and environmental monitoring. Carbon dots (C dots) have emerged as a biocompatible and environmentfriendly nanomaterial and have been successfully synthesized via many approaches [4, 5].
Besides, the
hydrophilicity of the surface functional groups such as carboxylic and alcoholic groups further offers the basis for easy conjugation with affinity ligands. The C dots have strong absorption in the visible range and are highly fluorescent, and the energy can be coupled with many conventional semiconductors through charge injection. Carbon nanodots (C-dots) which comprise quasispherical nanoparticles with sizes below 10 nm are becoming both an important class of imaging probes and a versatile platform for developing high-performance nanosensors, due to their fascinating properties such as aqueous solubility, tunable surface functionalities, non-blinking, excellent biocompatibility and cell membrane permeability [6,7]. Surface functionalization of C-dots is paving the way towards quantitative detection, highly efficient fluorescent imaging, and real-time tracking of targets. Electrochemical biosensing applications have been increasingly established for continuous observing in environmental and health care applications. Like devices contain a biological sensing element connected to a transducer that converts the exact bio recognition event to an electrical signal. The main key steps in the fabrication of biosensors consist of the effective immobilization of biomolecules onto the transducer surface [8]. The intentions are to find an immobilization method that keeps the enzyme activity, increases its stability, and offers accessibility toward substrate. Various immobilization methods have been recognized for electrochemical biosensor applications, such as bio affinity attachment, self-assembled multilayers, mixing in carbon composites, and entrapment within polymeric and inorganic environments. In purine metabolism, Uric acid (UA) is the primary end product and UA is one of the powerful indicators because it can be used as a warning sign of kidney diseases observing UA in the blood or urine [9]. Many of the disease such as gout, hyperuricemia, Lesch-Nyan syndrome, cardiovascular, leukemia, pneumonia and chronic renal disease affect from unusual UA level in a human body [10]. The determination of uric acid is executed by oxidation of enzymatically generated H2O2 at the sensing electrode. The intensive on parameters such as simplicity, sensitivity, low detection limit and low cost, none of them has been able to implement uric acid sensing for in vivo applications [11].The present study, C-dots was synthesized by simple microwave irradiation method. The XRD pattern given the formation of C-dots and FT-IR reveals the functional groups present in C-dots. FESEM microscope analyzed the formation of C-dots are spherical shape. The active C-dots are casting on the GCE electrode it gives the good result for sensing of UA at 50 mV scan rate using pH 7.
T. Dhanasekaran et al. / Materials Today: Proceedings 14 (2019) 545–552
547
1.1Chemicals Chitosan was purchased from Sigma Aldrich chemicals. Acetic acid, Ethanol and Acetone were bringing from LOBA chemicals without distillation. 1.2Synthesis of C-dots 2 g of chitosan was dissolved in 18 ml of 2% acetic acid with vigorous stirring at room temperature for 40 min. the mixed solution was heated by the microwave with the power of 750W (MCR-3 microwave chemical reactor) for 20 minutes, following the products were cooled to room temperature and dissolved by 50 ml ultrapure water. In this way, the original CDs aqueous solution was obtained. After being placed for 24 hrs, the solution was purified by a 0.22 μm filter membrane. The filtered CDs were first dried at 60 °C in a constant and then 80 °C in a vacuum drying oven. 1.3 Electrochemical experiment Cyclic voltammetry methods were utilized to examine the electrochemical sensing properties of
C-dots
towards Uric Acid (UA). All electrochemical sensing experiments were carried out using a CHI 1103A electrochemical station connected to a PC. The electrochemical experiments were carried out in 0.2 M phosphate buffer solution (PBS), pH 7 in a conventional three-electrode system using the bare and modified GCE as the working electrode. Platinum wire and saturated calomel electrode (SCE) were used as the counter electrode and reference electrode respectively. For cyclic voltammetric measurements, the sensors were immersed in 60 mL of 0.2 M PBS containing 10-4M UA, applying the potential in the range of 0.2 V to +1.2 V. All measurements were carried out at room temperature (25 °C). 1.4 Preparation of modified electrode 2 mg of the C-dots sample was dispersed in 5 ml acetone and the solution was sonication for 30 min. Then the dispersed solution was coated on the GCE surface using drop casting method and dried. Before and after each cycling, the modified GCE was washed with double distilled water and activated again with the same procedure [12]. 2. Result and Discussion 2.1 X-ray diffraction analyses The crystal phase and purity of the sample was determined from XRD pattern. As synthesized C-dots was successfully analyzed using XRD. The peak at 2θ = 26.5 and 42.5 was confirms the formation of C-dots [13]. The cell parameters is a=2.45Å, b= 4.25Å and c=6.69Å and forms as an orthorhombic structure. The d-spacing value is 3.348Å. These evidences clearly tell the formation of C-dots.
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Figure. 1 XRD pattern of synthesized C-dots
2.2 Fourier Transform Infra-red spectroscopy The FT-IR was used to determine the presence of functional groups as synthesized samples. From the Fig. 2the broad peak at 3442 cm-1 was corresponds to stretching of water molecules and the bending mode of vibration appears at 1638 cm-1. The sharp peaks appears around 3000-2800 cm-1 is respect to the C=H stretching for the precursor of chitosan. The stretching of N-H vibration mode shows around at 1476-1300 cm-1 because of the presence of amine group. The broad shoulder peak appears at 1055 cm-1 is due to the C-OH stretching vibrations. The aliphatic groups can have CH2 vibrations, these C-H modes are displays at 800-600 cm-1[14].
Figure. 2 The FT-IR spectrum of synthesized C-dots.
2.3 Diffuse Reflectance UV-Vis Spectroscopy From Fig. 3 the DRS-UV vis spectroscopy techniques gives the remarkable excitation values of the corresponding C-dots. The broad peak at 380 nm reveals the π-π conjugation of the chitosan precursors. The highly amorphous phase of the C-dots was shows in the DRS spectroscopy.
T. Dhanasekaran et al. / Materials Today: Proceedings 14 (2019) 545–552
549
Figure. 3 DRS UV vis spectroscopy of as synthesized C-dots
2.4 Field Emission Scanning Electron Microscopy The morphology of the synthesized sample was wisely analyzed from FESEM. The high and low magnification images shows that the C-dots were looks like sphere morphology with the formation of randomly. From this FESEM images the average particle size was determined. The particle size is ~ 15 nm.
Figure. 4.FESEM image of sphere shape C-dots.
3. Electrochemical Activity 3.1 Sensing of Uric acid Fig.5.Shows the cyclic voltammogram in presence of 10-4 M uric acid for bare GCE and modified Cdots/GCE nano sphere at 50mV/s scan rate. The initial potential range was +0.2 to +1.2 Vin pH 7.The oxidation of UA gives the peak at 0.51 V and 0.58 V for bare GCE and C-dots@GCE respectively in pH 7 buffer solution [15]. The C-dots modified GCE to exhibit the enormous current at 4.53 μA. The UA oxidation proceeds 2e-, 2H+ system to lead to an unstablediimine species. After the water molecules can attack the diimine for stepwise to form iminealcohol and the uric acid-4,5 diol. Fig. 5 shows the higher potential shift than the bare GCE, it denotes that Cdots@GCE shows the better catalytic activity on the surface of GCE.
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T. Dhanasekaran et al. / Materials Today: Proceedings 14 (2019) 545–552
Figure. 5 cyclic voltammogram of 0.001 M uric acid at 50 mV/s in pH7 for bareGCE and modified C-dots GCE
3.2 Effect of pH on the oxidation of UA The pH effect of 10-4M uric acid in was analyzed using cyclic voltammogram at scan rate 50mV/s. Fig. 6 indicates the pH response of the UA using pH7, pH9 and pH 10. Among the different pH solutions the UA was gives the good result for pH7. Hence the neutral pH has better sensing ability against the UA.
Figure. 6 pH effect of 0.001 M uric acid using pH 7 , pH 9 and pH 10
3.3 Effect of Scan rate Fig. 7(a) shows the effect of scan rate on the electrooxidation of 0.001 M uric acid at C-dots@GCE was investigated to study the kinetics of the electrode reaction. The cyclic voltammetry response of pH7 at 0.001 M UA with the scan rate of 30-175 mV/s. From the fig. shows the gradually increasing with increase the scan rate without any potential shift. Fig. 7(b) shows the double logarithmic plot of log (ν) vs log (Ipa), from this the slope value was found to be 0.65 (R2=0.9988) which is similar to that the electron transfer process is adsorption controlled.From this, it is clearthat the electrooxidation of 10-4M uric acid at C-dots@GCE involves twoelectron and three proton transfer process which is consistentwith the Laviron equation [16].
T. Dhanasekaran et al. / Materials Today: Proceedings 14 (2019) 545–552
551
Figure. 7. (a) Scan rate of C-dots at 30-175 mV and (b) Plot of log of scan rate versus log I pa .
4. Summary The facile method for synthesis of C-dots via simple hydrothermal and followed by characterized using primary techniques such as, XRD, FT-IR, DRS-UV vis spectroscopy and the surface morphology of the as synthesized C-dots were analyzed using FESEM microscope. The active C-dots were modified on GCE for sensing of uric acid. The modified GCE shows the better results than bare GCE. The uric acid oxidation occurs at 0.58 V in 50 mV/s using pH 7. Further the C-dots was proceeds pH effect and scan rate effect, from these analyses gives the 2e-, 2H+ system and adsorption controlled process. Among theanalytical methods, electrochemical method has a number of advantages, including simple, cost effective and high sensitive. Acknowledgement The author (T.D) acknowledges for Prof. M. Sathiyendiran,School of Chemistry, Hyderabad Central University for UGC-NRC program and Dept. of Inorganic chemistry, University of Madras, for Instrumentation facility. References 1.
Q. Ma and X. Su, Analyst, 136 (2011) 4883-4893.
2.
B. De, B. Voitb and N. Karak, RSC Adv., 4 (2014) 58453-58459.
3.
V. Biju, Chem. Soc. Rev., 43 (2014) 744-764.
4.
A. Prasannan and T. Imae, Ind. Eng. Chem. Res. 52 (2013) 15673-15678.
5.
H. Xu, X. Yang, G. Li, C. Zhao, X. Liao, J. Agric. Food Chem. 63 (2015) 6707-6714
6.
A. Kundu, J. Lee, B. Park, C. Ray, K. VijayaSankar, W. S. Kim, S. H. Lee, Il-Joo Cho, S. C. Jun, J. Colloid and Inter. Sci., 513 (2018) 505514.
7.
H. Nie, M. Li, Q. Li, S. Liang, Y. Tan, L. Sheng, W. Shi, and S. Xiao-An Zhang, Chem. Mater., 26 (2014) 3104-3112.
8.
C. Ge, J. Zou, M. Yan, H. Bi, Mater. Lett., 137 (2014) 41-44.
9.
R. Suresh, K. Giribabu, R. Manigandan, A. Stephen and V. Narayanan, RSC Adv., 4 (2014) 17146-17155.
10. H. Beitollahi, F. G. Nejad and S. Shakeri, Anal. Methods, 9 (2017) 5541-5549.
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T. Dhanasekaran et al. / Materials Today: Proceedings 14 (2019) 545–552
11. M. Taei, F. Hasanpour, S. Habibollahi, L. Shahidi, J. Electroanal. Chem. 789 (2017) 140- 147. 12. T. Dhanasekaran, A. Padmanaban, G. Gnanamoorthy, R. Manigandan, S. Praveen Kumar, A. Stephen, P. Selvam, M. Subaraja, and V. Narayanan, Chem.Select 2 (2017) 11717-11726. 13. Z. Bo, H. Maimaiti, Z. De-Dong, X. Bo, W. Ming, J. Photochem. Photobiol. A: Chem. 345 (2017) 54-62. 14. W. Zhou, J. Zhuang, W. Li, C. Hu, B. Lei, and Y. Liu, J. Mater. Chem. C, 5 (2017) 8014-8021. 15. S. B. Khoo and F. Chen, Anal. Chem. 74 (2002) 5734-5741. 16. T. Dhanasekaran, A. Padmanaban, R. Manigandan, S. Praveen Kumar, A. Stephen, V. Narayanan. J Mater Sci: Mater Electron 28 (2017) 12726-12740.