Materials Science and Engineering C 52 (2015) 219–224
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Fabrication of a nonenzymatic glucose sensor using Pd-nanoparticles decorated ionic liquid derived fibrillated mesoporous carbon Behzad Haghighi a,b,⁎, Babak Karimi a, Mojtaba Tavahodi a, Hesam Behzadneia a a b
College of Chemistry, Institute for Advanced Studies in Basic Sciences, P.O. Box 45195-1159, Gava Zang, Zanjan, Iran Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran
a r t i c l e
i n f o
Article history: Received 10 December 2014 Received in revised form 2 February 2015 Accepted 23 March 2015 Available online 25 March 2015 Keywords: Pd nanoparticles Ionic liquid derived fibrillated mesoporous carbon materials Nonenzymatic sensor Glucose
a b s t r a c t A novel nonenzymatic sensor was developed for glucose detection by the use of ionic liquid derived fibrillated mesoporous carbon (IFMC) decorated with palladium nanoparticles (PdNPs). PdNPs were uniformly decorated on IFMC and then the prepared nano-hybrid material (Pd@IFMC) was drop cast on the surface of a glassy carbon electrode to fabricate a glucose sensor. The prepared Pd@IFMC showed excellent electrocatalytic activity towards glucose oxidation. An oxidation peak at about +0.40 V vs. Ag|AgCl|KClsat was observed for glucose on the fabricated sensor in alkaline solution. The oxidation peak current intensity was linear towards glucose in the concentration range between 1 and 55 mM (R2 = 0.9958) with a detection limit of 0.2 mM. The relative standard deviation (RSD) for repetitive measurements (n = 6) of 5 mM of glucose was of 5.3%. The fabricated sensor showed a number of great features such as ease of fabrication, wide linear range, excellent reproducibility, satisfactory operational stability and outstanding resistance towards interfering species such as ascorbic acid, uric acid, dopamine, fructose and chloride. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Diabetes mellitus is a group of metabolic diseases characterized by evaluated blood glucose levels which occurs if the body either does not produce enough insulin or does not respond appropriately to the produced insulin or both. Almost, 380 million people around the world suffer from diabetes [1] and monitoring of their blood glucose levels several times daily is needed to confirm whether the treatments are working efficiently. Therefore, fast and reliable determination of glucose is of considerable importance in clinical diagnostics and in many other areas such as food industry, biotechnology and fuel cells [2–4]. Glucose biosensors account for approximately 85% of the current world biosensor market although, they suffer from many drawbacks such as the chemical instabilities originated from the nature of enzyme, high cost of enzymes and difficult immobilization procedure [2–4]. So, the design and fabrication of nonenzymatic glucose sensor seems to be a promising alternative to overcome the mentioned drawbacks ascribed to the enzyme-based biosensors. In the electrochemical based nonenzymatic glucose sensors, the current response of glucose oxidation at the electrode surface is directly measured and the catalytic activity of the electrode material towards glucose oxidation influences the ⁎ Corresponding author at: College of Chemistry, Institute for Advanced Studies in Basic Sciences, P.O. Box 45195-1159, Gava Zang, Zanjan, Iran. E-mail address: [email protected] (B. Haghighi).
http://dx.doi.org/10.1016/j.msec.2015.03.045 0928-4931/© 2015 Elsevier B.V. All rights reserved.
performance of the sensor [5,6]. Different nanomaterials such as Ni nanoparticle-loaded carbon nanofiber (NiCFP) [7], PtPd nanoparticles/ onion-like mesoporous carbon [8], Pd nanoparticle-graphene [5], Pd-nanoparticle carbon nanotubes [9], Au@Pd core–shell nanoparticles– ionic liquids composite [10] and metal oxide nanoparticles [11–14] have been employed for electrode modification and fabrication of nonenzymatic glucose sensor. The most important disadvantages reported for the nonenzymatic glucose sensors are high cost, low sensitivity, narrow linear range and poor selectivity due to surface poisoning from adsorbed intermediate products and/or some interferences normally found in foods and biological samples. Therefore, the fabrication of a cheap, selective and reliable nonenzymatic glucose sensor is still widely demanded. Nowadays, nano-scale carbon-based materials including single walled carbon nanotubes (SWCNTs) [15], multi walled carbon nanotubes (MWCNTs) [16], carbon nanofibers [17], graphene [18–20] and ordered mesoporous carbon (OMC) [12,21] have attracted considerable attention because of their excellent properties. Innovative characteristic such as well-ordered pore structure, narrow pore size distribution, admirable chemical stability, large surface area and excellent conductivity are ascribed to the ordered mesoporous carbons [22,23]. Also, it is well documented that the nanostructures of OMCs and their electronic properties depend on the carbon source and the synthetic conditions [24,25]. Recently, Karimi et al. described novel protocols for the synthesis of ionic liquid derived fibrillated mesoporous carbon (IFMC) and Pd nanoparticles decorated IFMC (Pd@IFMC) [23,26] using ionic liquid as the carbon source. It has also been shown that the resulting fibrillated
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mesoporous carbons had superior electrical conductivity and mechanical properties. Carbonous materials have been widely used as a support or template for the formation of linear metal and metal oxide NPs assemblies due to their large chemically active surface and high stability. The prepared nanohybrid materials which are often referred as “decorated” carbonous materials are a new class of nanohybrid materials with the integrated properties of two components and show interesting properties such as electrochemical, mechanical and catalytic properties that are not available to the respective components alone [27–29]. It seems that the synergic effect of the decorated nanohybrid materials as a result of direct attachment of metal or metal oxide NPs on carbonous materials is responsible for those interesting properties. In the present work, Pd nanoparticles decorated IFMC (Pd@IFMC) was utilized to modify the surface of a glassy carbon electrode (GCE) by simple drop casting. The prepared sensor, GCE/Pd@IFMC/Nafion, showed excellent electrocatalytic activity towards glucose oxidation in an alkaline solution. The course of sensor fabrication was optimized and the analytical features of the prepared nonenzymatic glucose sensor (GCE/Pd@IFMC/Nafion) were evaluated. The prepared glucose sensor presented excellent sensitivity, high selectivity, good stability and fast amperometric response towards glucose detection which are promising characteristics for a typical nonenzymatic electrochemical glucose sensor.
hydrogen sulfate (MPIHS) was used as carbon source. Ionic liquid derived fibrillated mesoporous carbon (IFMC) was prepared based on the method reported previously [23] by the use of SBA-15 and MPIHS. Pd nanoparticles decorated ionic liquid derived fibrillated mesoporous carbon (Pd@IFMC) was prepared based on the method reported previously [24,26]. 2.4. Fabrication of GCE/Pd@IFMC/Nafion The surface of a glassy carbon electrode (GCE) was polished with alumina paste (0.3 and then 0.1 μm, Struers, Copenhagen, Denmark) to obtain a mirror finish and then sonicated in water–ethanol solution for 5 min to detach adsorbed alumina particles. One milligram of Pd@ IFMC was well-dispersed in 1 mL of DMF with ultrasonic agitation for 30 min. 5 μL of Pd@IFMC suspension (1 mg mL− 1) was cast on the surface of the polished GCE and dried in an oven at 60 °C to prepare a GCE modified with Pd@IFMC (GCE/Pd@IFMC). Finally, 3 μL of an aqueous solution of Nafion (0.25%) was dropped on the surface of GCE/Pd@IFMC. The fabricated glucose sensor, GCE/Pd@IFMC/Nafion, was dried at room temperature for 15 min and stored at 4 °C when not in use. 3. Results and discussion 3.1. Characterization of Pd@IFMC
2. Experimental 2.1. Chemicals and reagents All chemicals were of analytical reagent grade and utilized without further purification. Palladium (II) acetate (Pd(CH3COO)2), 1methylimidazole, tetraethoxysilane (TEOS), dimethylformamide (DMF), KOH, KCl, K4[Fe(CN)6] and K3[Fe(CN)6] were obtained from Merck (Darmstadt, Germany). D-(+)-Glucose (97%) and Pluronic P123 (EO20PO70EO20) were obtained from Sigma-Aldrich (St. Louis, MO, USA). Nafion perfluorinated ion-exchange (5% solution in 90% light alcohol) was obtained from Fluka (Buchs, Switzerland). A stock solution of glucose (1 M) was prepared using doubly distilled water and stored at 4 °C when not in use. The glucose stock solution was allowed to mutarotate at room temperature for at least 24 h before use. Standard working solutions of glucose were prepared freshly by diluting its stock solution with 0.15 M NaOH solution. Double distilled water was used in all experiments.
Bundles of well-ordered array of carbon nanofibers with a uniform distribution of Pd nanoparticles with an average diameter of about 5 nm on their surface (Fig. S1), a characteristic reported previously [23], were clearly observed in the HRTEM images of the prepared Pd@ IFMC. Cyclic voltammograms (CVs) of GCE/Nafion, GCE/IFMC/Nafion and GCE/Pd@IFMC/Nafion were recorded in a 0.15 M NaOH solution at a scan rate of 100 mV s− 1 to confirm the presence of Pd nanoparticles on the surface of IFMC (Fig. 1). Four redox phenomena were observed for GCE/Pd@IFMC/Nafion in the alkaline solution and no significant redox reactions for the other investigated electrodes. The anodic peak which appeared at a potential of about 0.2 V, started at about 0 V, was related to the Pd hydroxide formation and the increase of anodic current at the potential more positive than +0.45 V was attributed to Pd oxide formation. The produced Pd oxide stabilized at the potential more positive than 0.6 V. A single cathodic peak at a potential of about − 0.41, started at about − 0.20 V, was ascribed to the reduction of dissolved oxygen in the solution. The oxidation and reduction peaks at about −0.67
2.2. Apparatus Amperometric and cyclic voltammetric investigations were performed by the use of an Autolab potentiostat–galvanostat model PGSTAT30 (Eco Chemie, Utrecht, The Netherlands) with a conventional three-electrode set-up, in which a GCE/Pd@IFMC/Nafion, a platinum rod and an Ag|AgCl|KClsat served as working, auxiliary and reference electrodes, respectively. Electrochemical impedance spectroscopy (EIS) experiments were performed by the use of a Zahner Zennium couple (1:1, 5.0 mM) was used as the redox workstation. Fe(CN)3−/4− 6 probe and an oscillation potential of 10 mV was applied over a frequency range of 100 kHz to 0.1 Hz. The output EIS signal was acquired with the Thales z (Zennium release) software. A Metrohm 691 pH meter was used for pH adjustments. High-resolution transmission electron microscopy was performed on a JEOL HRTEM 3000F (Company, Japan). All measurements were performed at room temperature. 2.3. Synthesis of Pd@IFMC Mesoporous silica material (Santa Barbara Material No. 15, SBA15) was synthesized based on the method described by Stucky et al. [30] and used as template. 1-Methyl-3-phenethyl-1H-imidazolium
Fig. 1. Cyclic voltammograms obtained for GCE/Nafion (dotted line), GCE/IFMC/Nafion (dashed line) and GCE/Pd@IFMC/Nafion (solid line) in a 0.15 M NaOH solution at the scan rate of 100 mV s−1.
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and − 0.70 can be assigned to redox reactions of oxygen-containing groups at the IFMC surface, respectively [5,9,17]. Electrochemical impedance spectroscopy (EIS) experiments were also carried out to explore the effect of modification process on the interfacial property of the modified electrodes. Nyquist plots obtained for GCE/Pd@IFMC/Nafion, GCE/IFMC/Nafion and GCE/Nafion in the presence of 5 mM of Fe(CN)36 −/4 − (1:1 ratio in 0.1 M KCl) as the redox probe (Fig. S2). The charge-transfer resistance (Rct) values for at GCE/Pd@IFMC/Nafion, GCE/IFMC/Nafion and GCE/Nafion were about 5, 35 and 300 Ω, respectively. As obvious, the Rct value decreased significantly by modification of GCE with IFMC. Moreover, further decoration of IFMC with Pd nanoparticles caused a significant decrease in the Rct value of the modified electrode. The obtained results indicate that the decorated IFMC with Pd-NPs is an excellent electric conducting material which can be used for electroanalytical purposes.
3.2. Electrocatalytic oxidation of glucose at GCE/Pd@IFMC/Nafion Cyclic voltammetry was performed in 0.15 M NaOH solution in the absence and presence of 20 mM of glucose to investigate the electrocatalytic activity of the prepared modified glassy carbon electrodes towards glucose oxidation. Typical CVs obtained for GCE/Nafion, GCE/IFMC/Nafion and GCE/Pd@IFMC/Nafion at the scan rate of 100 mV s−1 are shown in Fig. 2. As obvious, no remarkable electrochemical activity was observed for glucose at GCE/Nafion, GCE/IFMC/Nafion (Fig. 2, inset) but glucose oxidized at GCE/Pd@IFMC/Nafion with a complex electrochemical behavior similar to that reported previously by Chen et al. [9]. Two anodic peaks at potentials of about − 0.09 and 0.49 V were recorded for glucose at GCE/Pd@IFMC/Nafion during the scan of potential in the positive direction. The first peak was ascribed to the electroadsorption of glucose followed by incomplete oxidization of glucose and consequently formation of intermediates on the electrode surface which poisoned the immobilized Pd nanoparticles. As reported previously [9], the accumulation of intermediates blocked further electroadsorption of glucose on the electrode surface and declined the anodic peak current intensity as the electrochemical reaction continued. The generation of Pd(OH)x species was started at the potentials more positive than 0.28 V. These species, oxidized Pd nanoparticles, oxidized the adsorbed poisoning intermediates and became clean and accessible for direct oxidation of glucose. Therefore, the second anodic peak that appeared at about 0.49 V was attributed to the direct oxidation of glucose on the oxidized Pd nanoparticles. On the basis of the previously reported mechanisms for glucose oxidation [5]
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and our finding in this study, a possible catalytic mechanism for glucose oxidation at GCE/Pd@IFMC/Nafion is proposed as the following: −
−
Pd þ OH →PdOH þ e
ð1Þ
PdOH þ Glucose→Pd þ Glucolactone:
ð2Þ
During the scan of potential in the negative direction, the oxidized Pd nanoparticles started to reduce at a potential of about 0.0 V. The scan of potential to a more negative value caused the activity of more Pd nanoparticles recovered and became available for the oxidation of glucose. As a result, a catalytic anodic peak was observed at a potential of about −0.40 V in the potential range between −0.30 and −0.60 V. The observed catalytic anodic peak was attributed to the electroadsorption and oxidation of glucose at the surface of renewed Pd nanoparticles. As shown in Fig. 3, the mentioned catalytic anodic peak at a potential of about −0.40 V was only observed at the high concentrations of glucose (N 4 mM) but not lower, similar to that reported previously by Chen et al. [9]. Also, cyclic voltammetry was performed using GCE/Pd@IFMC/Nafion in 0.15 M NaOH solution containing 2 mM of glucose at different scan rates. The anodic peak current intensities due to the incomplete and direct oxidation of glucose at potentials of about −0.09 and +0.49 V, respectively were proportional to the scan rates (Fig. S3). A good linearity was obtained between the anodic peak currents and scan rates in the range between 10 and 500 mV s−1 for both potentials, indicating the presence of surface-controlled redox processes at the electrode surface. As mentioned in the main text and shown in Eq. (1), the presence of OH− and consequently the formation of Pd(OH)x was essential for electrocatalytic oxidation of glucose. The observation of no electrocatalytic peak for oxidation of glucose at GCE/Pd@IFMC/Nafion in 0.5 M H2SO4 verified the mentioned fact. So, hydrodynamic amperometric studies were performed to explore the effect of NaOH concentration and applied potential on the response of proposed sensor towards 5 mM of glucose. As shown in Fig. 4A, with increasing the concentration of NaOH the current signal intensity of the sensor increased and reached a maximum at about 0.15 M NaOH and then decreased. It seems that with the increase of OH−, more Pd(OH)x can be formed and consequently higher electrocatalytic activity can be observed, but electroadsorption of glucose anions followed by their electrocatalytic oxidation can be blocked with too much OH−. Also, the results showed (Fig. 4B) that the amperometric response of the sensor passed over a maximum at a potential of about 0.40 V with increasing the applied potential from 0.20 to 0.60 V vs. Ag|AgCl|KClsat. So, 0.15 M NaOH and applied potential of 0.40 V were selected for subsequent experiments.
f e
d c b a
Fig. 2. Cyclic voltammograms obtained in the absence and presence of 20 mM of glucose in a 0.15 M NaOH using GCE/Nafion (a, b), GCE/IFMC/Nafion (c, d) and GCE/Pd@IFMC/Nafion (e, f) at the scan rate of 100 mV s−1. Inset: Magnified cyclic voltammograms obtained for GCE/Nafion (a, b) and GCE/IFMC/Nafion (c, d).
Fig. 3. Cyclic voltammograms obtained for GCE/Pd@IFMC/Nafion in the presence of different concentrations of glucose from 0 (dashed line), 2 to 16 mM with an increment of 2 mM (from inner to outer) in a 0.15 M NaOH at the scan rate of 100 mV s−1.
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A
B 0.6 V
0.25 M 0.20 M
0.5 V
0.15 M
0.4 V
0.10 M
0.3 V
0.05 M
0.2 V
Fig. 4. Steady-state current-time responses of GCE/Pd@IFMC/Nafion towards 5 mM of glucose (A) in NaOH solution with different concentrations at the applied potential of +0.40 V and (B) in 0.15 M NaOH solution at different applied potentials.
3.3. Analytical performance of GCE/Pd@IFMC/Nafion towards glucose Fig. 5 illustrates hydrodynamic amperometric responses of GCE/Pd@ IFMC/Nafion to successive addition of glucose under optimized experimental conditions. A well-defined and stable hydrodynamic amperometric response was recorded for glucose less than 2 s at the potential of 0.40 V and 0.15 M NaOH. The calibration equation for glucose determination was linear in the concentration range between 1 and 55 mM with a correlation coefficient (R2) of 0.9958. The detection limit was found to be 0.2 mM (S/N = 3). The relative standard deviation (RSD) for repetitive measurements (n = 6) of 5 mM of glucose was 5.3%. The fabrication reproducibility for five GCE/Pd@IFMC/Nafion prepared and used in different days for determination of 5 mM glucose was about 6.1%. The electroanalytical features of the proposed nonenzymatic glucose sensor are summarized in Table 1 and compared with the other reported nonenzymatic glucose sensors prepared using different modification strategies. As obvious from Table 1, the proposed nonenzymatic glucose sensor presented a wide linear range and it is very suitable to
diagnose diabetes, considering blood sugar levels in diabetic and nondiabetic people. It seems that the increase of electrode surface area because of the presence of IFMC and deposition of Pd NPs on IFMC created abundant active sites for the electrocatalytic oxidation of glucose. Moreover, high electrical conductivity provided by IFMC together with the sensitizing effect of Pd@IFMC towards glucose oxidation as a result of direct attachment of Pd NPs on the surface of IFMC were the main reasons to observe wide linear range and fast response time for glucose detection. The operational stability of the fabricated sensor was examined by monitoring of its current response towards repetitive measurements of 5 mM of glucose for six times in each day over twelve days. The response of the proposed sensor gradually decreased to almost 90% of its initial value after twelve days (Fig. S4). To evaluate the selectivity of proposed glucose sensor, the effect of the presence of some easily oxidizable species such as dopamine (DP), ascorbic acid (AA) and uric acid (UA) which usually co-exist with glucose in human serum on glucose detection was studied. Considering normal blood glucose level (4–7 mM) and AA, UA and DP levels (about
Table 1 Electroanalytical features of the proposed nonenzymatic glucose sensor GCE/Pd@IFMC/ Nafion and some reported nonenzymatic glucose sensors prepared using different modification strategies.
5 mM
1 mM
Fig. 5. Hydrodynamic amperometric responses of GCE/Pd@IFMC/Nafion in 0.15 M NaOH solution towards successive additions of glucose at the applied potential of +0.40 V. Inset: Plot of amperometric responses of the sensor versus glucose concentration.
Electrode material
Response Potential (V) LR time (s)
Cu/Gr Pt-CuO/rGO NiO/MFs CuO/SWCNTs Gr/PdNPs Ni/MWCNTs CuONPs/CNFs Pt-CuO/rGO NiO-Pt/ERGO Pt/MWNTs/Gr Pd/IFMC
b2 b3 N/A b2 9 b2 5 b3 2.5 N/A b2
0.5 0.6 0.5 0.45 0.4 0.6 0.5 0.6 0.6 0.4 0.4
DL (μM) Ref.
Up to 4.5 mM 0.5 Up to 12 mM 0.01 1–270 μM 0.03 0.05–1800 μM 0.05 10 μM–5 mM 1 3.2 μM–17.5 mM 0.89 0. 5 μM–11.1 0.2 0.5 μM–12 mM 0.01 2 μM–5.66 mM 0.20 1–7 mM 387 1–55 mM 200
[31] [32] [11] [13] [5] [6] [14] [32] [33] [34] This work
Gr, graphene; rGO, reduced graphene oxide; MFs, microfibers; SWCNTs, single wall carbon nanotube; MWCNTs, multi wall carbon nanotubes; CNFs, carbon nanofibers; ERGO, electrochemically reduced graphene oxide.
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0.1 mM), a series of solutions containing 5.0 mM of glucose, 0.5 mM of potent interfering compounds and 0.15 M NaOH were prepared. The amperometric responses of the prepared test solutions were recorded and compared with that obtained for the uncontaminated glucose solution (5 mM). A 5% error criterion was adopted. AA, DP and UA increased the amperometric response of 5 mM of glucose for 4.7, 5.1 and 8.9%, respectively (Fig. S5). Also, the effect of the presence of chloride ion and fructose on amperometric response of the sensor towards 5 mM of glucose was studied in 0.15 M NaOH. Chloride ion and fructose at concentrations of about 0.2 M and 0.5 mM, respectively altered the amperometric response of the sensor for about less than 5.0%. It seems that the sulfonic groups of Nafion layer repel chloride ion, ascorbate, urate and deprotonated form of DP from the electrode surface and prevent their unwanted electrochemical reactions, leading to have an improved selectivity. Moreover, Nafion layer prohibits the adsorption of redox intermediate products on the electrode surface and reduces the poisoning of electrode, leading to observe highly stable response. 3.4. Real sample analysis To examine the applicability of the proposed glucose sensor, it was employed for the determination of glucose in normal human serum. Blood sample was centrifuged for 20 min at 12,000 rpm to separate out the serum. 50 μL of human serum was mixed with 10 mL of 0.15 M NaOH and then analyzed using the proposed sensor at + 0.40 V. The concentration of glucose in serum was determined and compared with that determined in local hospital. The concentration of glucose in human serum was determined to be 6.68 mM. The recovery of the analysis was about 96.3%, considering the value determined by a local hospital (6.93 mM). Also, the reliability of the proposed glucose sensor was evaluated using standard addition method with the spiking of specific amounts of glucose (0, 1.0, 2.0, 3.0 and 4.0 mM) to the normal human serum. The recovery for each measurement was calculated by comparing the results obtained in the absence and presence of specific amounts of glucose. The obtained average recovery for the spiked samples was 95%. 4. Conclusions A nonenzymatic glucose sensor was fabricated by the use of Pd nanoparticles (PdNPs) decorated ionic liquid derived fibrillated mesoporous carbon (IFMC). Deposition of PdNPs on IFMC surface led to the formation of many active sites for direct glucose oxidation. The fabricated sensor exhibited high electrocatalytic ability towards glucose oxidation in alkaline solution. The prepared sensor showed high sensitivity towards glucose even in the presence of chloride ion, wide range of linearity and low detection limit. The obtained results clearly indicated that the proposed sensor is highly specific towards glucose even in the presence of easily oxidizable and nonoxidizable interfering compounds that normally exist in food and biological samples. Acknowledgment The authors acknowledge the Institute for Advanced Studies in Basic Sciences (IASBS, grant number G2014IASBS119) for financial support. Appendix A. Supplementary data Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.msec.2015.03.045. References [1] Y. Shi, F.B. Hu, The global implications of diabetes and cancer, Lancet 383 (2014) 1947–1948.
223
[2] G. Wang, X. He, L. Wang, A. Gu, Y. Huang, B. Fang, B. Geng, X. Zhang, Non-enzymatic electrochemical sensing of glucose, Microchim. Acta 180 (2013) 161–186. [3] C. Chen, Q. Xie, D. Yang, H. Xiao, Y. Fu, Y. Tan, S. Yao, Recent advances in electrochemical glucose biosensors: a review, RSC Adv. 3 (2013) 4473–4491. [4] J. Wang, Electrochemical glucose biosensors, Chem. Rev. 108 (2007) 814–825. [5] L.-M. Lu, H.-B. Li, F. Qu, X.-B. Zhang, G.-L. Shen, R.-Q. Yu, In situ synthesis of palladium nanoparticle–graphene nanohybrids and their application in nonenzymatic glucose biosensors, Biosens. Bioelectron. 26 (2011) 3500–3504. [6] A. Sun, J. Zheng, Q. Sheng, A highly sensitive non-enzymatic glucose sensor based on nickel and multi-walled carbon nanotubes nanohybrid films fabricated by one-step co-electrodeposition in ionic liquids, Electrochim. Acta 65 (2012) 64–69. [7] Y. Liu, H. Teng, H. Hou, T. You, Nonenzymatic glucose sensor based on renewable electrospun Ni nanoparticle-loaded carbon nanofiber paste electrode, Biosens. Bioelectron. 24 (2009) 3329–3334. [8] X. Bo, J. Bai, L. Yang, L. Guo, The nanocomposite of PtPd nanoparticles/onion-like mesoporous carbon vesicle for nonenzymatic amperometric sensing of glucose, Sensors Actuators B Chem. 157 (2011) 662–668. [9] X.-m. Chen, Z.-j. Lin, D.-J. Chen, T.-t. Jia, Z.-m. Cai, X.-r. Wang, X. Chen, G.-n. Chen, M. Oyama, Nonenzymatic amperometric sensing of glucose by using palladium nanoparticles supported on functional carbon nanotubes, Biosens. Bioelectron. 25 (2010) 1803–1808. [10] X. Chen, H. Pan, H. Liu, M. Du, Nonenzymatic glucose sensor based on flower-shaped Au@Pd core–shell nanoparticles–ionic liquids composite film modified glassy carbon electrodes, Electrochim. Acta 56 (2010) 636–643. [11] F. Cao, S. Guo, H. Ma, D. Shan, S. Yang, J. Gong, Nickel oxide microfibers immobilized onto electrode by electrospinning and calcination for nonenzymatic glucose sensor and effect of calcination temperature on the performance, Biosens. Bioelectron. 26 (2011) 2756–2760. [12] L. Luo, F. Li, L. Zhu, Y. Ding, Z. Zhang, D. Deng, B. Lu, Nonenzymatic glucose sensor based on nickel(II)oxide/ordered mesoporous carbon modified glassy carbon electrode, Colloids Surf. B Biointerfaces 102 (2013) 307–311. [13] N. Quoc Dung, D. Patil, H. Jung, D. Kim, A high-performance nonenzymatic glucose sensor made of CuO-SWCNT nanocomposites, Biosens. Bioelectron. 42 (2013) 280–286. [14] J. Zhang, X. Zhu, H. Dong, X. Zhang, W. Wang, Z. Chen, In situ growth cupric oxide nanoparticles on carbon nanofibers for sensitive nonenzymatic sensing of glucose, Electrochim. Acta 105 (2013) 433–438. [15] C.B. Jacobs, M.J. Peairs, B.J. Venton, Review: carbon nanotube based electrochemical sensors for biomolecules, Anal. Chim. Acta 662 (2010) 105–127. [16] C. Gao, Z. Guo, J.-H. Liu, X.-J. Huang, The new age of carbon nanotubes: an updated review of functionalized carbon nanotubes in electrochemical sensors, Nanoscale 4 (2012) 1948–1963. [17] G. Hu, F. Nitze, H.R. Barzegar, T. Sharifi, A. Mikołajczuk, C.-W. Tai, A. Borodzinski, T. Wågberg, Palladium nanocrystals supported on helical carbon nanofibers for highly efficient electro-oxidation of formic acid, methanol and ethanol in alkaline electrolytes, J. Power Sources 209 (2012) 236–242. [18] J. Gunho, C. Minhyeok, L. Sangchul, P. Woojin, K. Yung Ho, L. Takhee, The application of graphene as electrodes in electrical and optical devices, Nanotechnology 23 (2012) 112001. [19] Y. Shao, J. Wang, H. Wu, J. Liu, I.A. Aksay, Y. Lin, Graphene based electrochemical sensors and biosensors: a review, Electroanalysis 22 (2010) 1027–1036. [20] Y. Liu, X. Dong, P. Chen, Biological and chemical sensors based on graphene materials, Chem. Soc. Rev. 41 (2012) 2283–2307. [21] A. Vu, X. Li, J. Phillips, A. Han, W.H. Smyrl, P. Bühlmann, A. Stein, Three-dimensionally ordered mesoporous (3DOm) carbon materials as electrodes for electrochemical double-layer capacitors with ionic liquid electrolytes, Chem. Mater. 25 (2013) 4137–4148. [22] H. Wang, B. Qi, B. Lu, X. Bo, L. Guo, Comparative study on the electrocatalytic activities of ordered mesoporous carbons and graphene, Electrochim. Acta 56 (2011) 3042–3048. [23] B. Karimi, H. Behzadnia, M. Rafiee, H. Vali, Electrochemical performance of a novel ionic liquid derived mesoporous carbon, Chem. Commun. 48 (2012) 2776–2778. [24] J. Jin, S. Tanaka, Y. Egashira, N. Nishiyama, KOH activation of ordered mesoporous carbons prepared by a soft-templating method and their enhanced electrochemical properties, Carbon 48 (2010) 1985–1989. [25] R.J. Bowling, R.T. Packard, R.L. McCreery, Activation of highly ordered pyrolytic graphite for heterogeneous electron transfer: relationship between electrochemical performance and carbon microstructure, J. Am. Chem. Soc. 111 (1989) 1217–1223. [26] B. Karimi, H. Behzadnia, M. Bostina, H. Vali, A nano-fibrillated mesoporous carbon as an effective support for palladium nanoparticles in the aerobic oxidation of alcohols “on pure water”, Chem. Eur. J. 18 (2012) 8634–8640. [27] B. Haghighi, S. Bozorgzadeh, Fabrication of a highly sensitive electrochemiluminescence lactate biosensor using ZnO nanoparticles decorated multiwalled carbon nanotubes, Talanta 85 (2011) 2189–2193. [28] B. Haghighi, S. Bozorgzadeh, L. Gorton, Fabrication of a novel electrochemiluminescence glucose biosensor using Au nanoparticles decorated multiwalled carbon nanotubes, Sensors Actuators B Chem. 155 (2011) 577–583. [29] B. Haghighi, S. Bozorgzadeh, Enhanced electrochemiluminescence from luminol at multi-walled carbon nanotubes decorated with palladium nanoparticles: a novel route for the fabrication of an oxygen sensor and a glucose biosensor, Anal. Chim. Acta 697 (2011) 90–97. [30] D. Zhao, Q. Huo, J. Feng, B.F. Chmelka, G.D. Stucky, Nonionic triblock and star diblock copolymer and oligomeric surfactant syntheses of highly ordered,
224
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hydrothermally stable, mesoporous silica structures, J. Am. Chem. Soc. 120 (1998) 6024–6036. [31] J. Luo, S. Jiang, H. Zhang, J. Jiang, X. Liu, A novel non-enzymatic glucose sensor based on Cu nanoparticle modified graphene sheets electrode, Anal. Chim. Acta 709 (2012) 47–53. [32] K. Dhara, J. Stanley, T. Ramachandran, B.G. Nair, T.G. Satheesh Babu, Pt-CuO nanoparticles decorated reduced graphene oxide for the fabrication of highly sensitive nonenzymatic disposable glucose sensor, Sensors Actuators B Chem. 195 (2014) 197–205.
[33] M. Li, X. Bo, Z. Mu, Y. Zhang, L. Guo, Electrodeposition of nickel oxide and platinum nanoparticles on electrochemically reduced graphene oxide film as a nonenzymatic glucose sensor, Sensors Actuators B Chem. 192 (2014) 261–268. [34] S. Badhulika, R.K. Paul, Rajesh, T. Terse, A. Mulchandani, Nonenzymatic glucose sensor based on platinum nanoflowers decorated multiwalled carbon nanotubes-graphene hybrid electrode, Electroanalysis 26 (2014) 103–108.
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Materials Science and Engineering C journal homepage: www.elsevier.com/locate/msec
Fabrication of a nonenzymatic glucose sensor using Pd-nanoparticles decorated ionic liquid derived fibrillated mesoporous carbon Behzad Haghighi a,b,⁎, Babak Karimi a, Mojtaba Tavahodi a, Hesam Behzadneia a a b
College of Chemistry, Institute for Advanced Studies in Basic Sciences, P.O. Box 45195-1159, Gava Zang, Zanjan, Iran Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran
a r t i c l e
i n f o
Article history: Received 10 December 2014 Received in revised form 2 February 2015 Accepted 23 March 2015 Available online 25 March 2015 Keywords: Pd nanoparticles Ionic liquid derived fibrillated mesoporous carbon materials Nonenzymatic sensor Glucose
a b s t r a c t A novel nonenzymatic sensor was developed for glucose detection by the use of ionic liquid derived fibrillated mesoporous carbon (IFMC) decorated with palladium nanoparticles (PdNPs). PdNPs were uniformly decorated on IFMC and then the prepared nano-hybrid material (Pd@IFMC) was drop cast on the surface of a glassy carbon electrode to fabricate a glucose sensor. The prepared Pd@IFMC showed excellent electrocatalytic activity towards glucose oxidation. An oxidation peak at about +0.40 V vs. Ag|AgCl|KClsat was observed for glucose on the fabricated sensor in alkaline solution. The oxidation peak current intensity was linear towards glucose in the concentration range between 1 and 55 mM (R2 = 0.9958) with a detection limit of 0.2 mM. The relative standard deviation (RSD) for repetitive measurements (n = 6) of 5 mM of glucose was of 5.3%. The fabricated sensor showed a number of great features such as ease of fabrication, wide linear range, excellent reproducibility, satisfactory operational stability and outstanding resistance towards interfering species such as ascorbic acid, uric acid, dopamine, fructose and chloride. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Diabetes mellitus is a group of metabolic diseases characterized by evaluated blood glucose levels which occurs if the body either does not produce enough insulin or does not respond appropriately to the produced insulin or both. Almost, 380 million people around the world suffer from diabetes [1] and monitoring of their blood glucose levels several times daily is needed to confirm whether the treatments are working efficiently. Therefore, fast and reliable determination of glucose is of considerable importance in clinical diagnostics and in many other areas such as food industry, biotechnology and fuel cells [2–4]. Glucose biosensors account for approximately 85% of the current world biosensor market although, they suffer from many drawbacks such as the chemical instabilities originated from the nature of enzyme, high cost of enzymes and difficult immobilization procedure [2–4]. So, the design and fabrication of nonenzymatic glucose sensor seems to be a promising alternative to overcome the mentioned drawbacks ascribed to the enzyme-based biosensors. In the electrochemical based nonenzymatic glucose sensors, the current response of glucose oxidation at the electrode surface is directly measured and the catalytic activity of the electrode material towards glucose oxidation influences the ⁎ Corresponding author at: College of Chemistry, Institute for Advanced Studies in Basic Sciences, P.O. Box 45195-1159, Gava Zang, Zanjan, Iran. E-mail address: [email protected] (B. Haghighi).
http://dx.doi.org/10.1016/j.msec.2015.03.045 0928-4931/© 2015 Elsevier B.V. All rights reserved.
performance of the sensor [5,6]. Different nanomaterials such as Ni nanoparticle-loaded carbon nanofiber (NiCFP) [7], PtPd nanoparticles/ onion-like mesoporous carbon [8], Pd nanoparticle-graphene [5], Pd-nanoparticle carbon nanotubes [9], Au@Pd core–shell nanoparticles– ionic liquids composite [10] and metal oxide nanoparticles [11–14] have been employed for electrode modification and fabrication of nonenzymatic glucose sensor. The most important disadvantages reported for the nonenzymatic glucose sensors are high cost, low sensitivity, narrow linear range and poor selectivity due to surface poisoning from adsorbed intermediate products and/or some interferences normally found in foods and biological samples. Therefore, the fabrication of a cheap, selective and reliable nonenzymatic glucose sensor is still widely demanded. Nowadays, nano-scale carbon-based materials including single walled carbon nanotubes (SWCNTs) [15], multi walled carbon nanotubes (MWCNTs) [16], carbon nanofibers [17], graphene [18–20] and ordered mesoporous carbon (OMC) [12,21] have attracted considerable attention because of their excellent properties. Innovative characteristic such as well-ordered pore structure, narrow pore size distribution, admirable chemical stability, large surface area and excellent conductivity are ascribed to the ordered mesoporous carbons [22,23]. Also, it is well documented that the nanostructures of OMCs and their electronic properties depend on the carbon source and the synthetic conditions [24,25]. Recently, Karimi et al. described novel protocols for the synthesis of ionic liquid derived fibrillated mesoporous carbon (IFMC) and Pd nanoparticles decorated IFMC (Pd@IFMC) [23,26] using ionic liquid as the carbon source. It has also been shown that the resulting fibrillated
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mesoporous carbons had superior electrical conductivity and mechanical properties. Carbonous materials have been widely used as a support or template for the formation of linear metal and metal oxide NPs assemblies due to their large chemically active surface and high stability. The prepared nanohybrid materials which are often referred as “decorated” carbonous materials are a new class of nanohybrid materials with the integrated properties of two components and show interesting properties such as electrochemical, mechanical and catalytic properties that are not available to the respective components alone [27–29]. It seems that the synergic effect of the decorated nanohybrid materials as a result of direct attachment of metal or metal oxide NPs on carbonous materials is responsible for those interesting properties. In the present work, Pd nanoparticles decorated IFMC (Pd@IFMC) was utilized to modify the surface of a glassy carbon electrode (GCE) by simple drop casting. The prepared sensor, GCE/Pd@IFMC/Nafion, showed excellent electrocatalytic activity towards glucose oxidation in an alkaline solution. The course of sensor fabrication was optimized and the analytical features of the prepared nonenzymatic glucose sensor (GCE/Pd@IFMC/Nafion) were evaluated. The prepared glucose sensor presented excellent sensitivity, high selectivity, good stability and fast amperometric response towards glucose detection which are promising characteristics for a typical nonenzymatic electrochemical glucose sensor.
hydrogen sulfate (MPIHS) was used as carbon source. Ionic liquid derived fibrillated mesoporous carbon (IFMC) was prepared based on the method reported previously [23] by the use of SBA-15 and MPIHS. Pd nanoparticles decorated ionic liquid derived fibrillated mesoporous carbon (Pd@IFMC) was prepared based on the method reported previously [24,26]. 2.4. Fabrication of GCE/Pd@IFMC/Nafion The surface of a glassy carbon electrode (GCE) was polished with alumina paste (0.3 and then 0.1 μm, Struers, Copenhagen, Denmark) to obtain a mirror finish and then sonicated in water–ethanol solution for 5 min to detach adsorbed alumina particles. One milligram of Pd@ IFMC was well-dispersed in 1 mL of DMF with ultrasonic agitation for 30 min. 5 μL of Pd@IFMC suspension (1 mg mL− 1) was cast on the surface of the polished GCE and dried in an oven at 60 °C to prepare a GCE modified with Pd@IFMC (GCE/Pd@IFMC). Finally, 3 μL of an aqueous solution of Nafion (0.25%) was dropped on the surface of GCE/Pd@IFMC. The fabricated glucose sensor, GCE/Pd@IFMC/Nafion, was dried at room temperature for 15 min and stored at 4 °C when not in use. 3. Results and discussion 3.1. Characterization of Pd@IFMC
2. Experimental 2.1. Chemicals and reagents All chemicals were of analytical reagent grade and utilized without further purification. Palladium (II) acetate (Pd(CH3COO)2), 1methylimidazole, tetraethoxysilane (TEOS), dimethylformamide (DMF), KOH, KCl, K4[Fe(CN)6] and K3[Fe(CN)6] were obtained from Merck (Darmstadt, Germany). D-(+)-Glucose (97%) and Pluronic P123 (EO20PO70EO20) were obtained from Sigma-Aldrich (St. Louis, MO, USA). Nafion perfluorinated ion-exchange (5% solution in 90% light alcohol) was obtained from Fluka (Buchs, Switzerland). A stock solution of glucose (1 M) was prepared using doubly distilled water and stored at 4 °C when not in use. The glucose stock solution was allowed to mutarotate at room temperature for at least 24 h before use. Standard working solutions of glucose were prepared freshly by diluting its stock solution with 0.15 M NaOH solution. Double distilled water was used in all experiments.
Bundles of well-ordered array of carbon nanofibers with a uniform distribution of Pd nanoparticles with an average diameter of about 5 nm on their surface (Fig. S1), a characteristic reported previously [23], were clearly observed in the HRTEM images of the prepared Pd@ IFMC. Cyclic voltammograms (CVs) of GCE/Nafion, GCE/IFMC/Nafion and GCE/Pd@IFMC/Nafion were recorded in a 0.15 M NaOH solution at a scan rate of 100 mV s− 1 to confirm the presence of Pd nanoparticles on the surface of IFMC (Fig. 1). Four redox phenomena were observed for GCE/Pd@IFMC/Nafion in the alkaline solution and no significant redox reactions for the other investigated electrodes. The anodic peak which appeared at a potential of about 0.2 V, started at about 0 V, was related to the Pd hydroxide formation and the increase of anodic current at the potential more positive than +0.45 V was attributed to Pd oxide formation. The produced Pd oxide stabilized at the potential more positive than 0.6 V. A single cathodic peak at a potential of about − 0.41, started at about − 0.20 V, was ascribed to the reduction of dissolved oxygen in the solution. The oxidation and reduction peaks at about −0.67
2.2. Apparatus Amperometric and cyclic voltammetric investigations were performed by the use of an Autolab potentiostat–galvanostat model PGSTAT30 (Eco Chemie, Utrecht, The Netherlands) with a conventional three-electrode set-up, in which a GCE/Pd@IFMC/Nafion, a platinum rod and an Ag|AgCl|KClsat served as working, auxiliary and reference electrodes, respectively. Electrochemical impedance spectroscopy (EIS) experiments were performed by the use of a Zahner Zennium couple (1:1, 5.0 mM) was used as the redox workstation. Fe(CN)3−/4− 6 probe and an oscillation potential of 10 mV was applied over a frequency range of 100 kHz to 0.1 Hz. The output EIS signal was acquired with the Thales z (Zennium release) software. A Metrohm 691 pH meter was used for pH adjustments. High-resolution transmission electron microscopy was performed on a JEOL HRTEM 3000F (Company, Japan). All measurements were performed at room temperature. 2.3. Synthesis of Pd@IFMC Mesoporous silica material (Santa Barbara Material No. 15, SBA15) was synthesized based on the method described by Stucky et al. [30] and used as template. 1-Methyl-3-phenethyl-1H-imidazolium
Fig. 1. Cyclic voltammograms obtained for GCE/Nafion (dotted line), GCE/IFMC/Nafion (dashed line) and GCE/Pd@IFMC/Nafion (solid line) in a 0.15 M NaOH solution at the scan rate of 100 mV s−1.
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and − 0.70 can be assigned to redox reactions of oxygen-containing groups at the IFMC surface, respectively [5,9,17]. Electrochemical impedance spectroscopy (EIS) experiments were also carried out to explore the effect of modification process on the interfacial property of the modified electrodes. Nyquist plots obtained for GCE/Pd@IFMC/Nafion, GCE/IFMC/Nafion and GCE/Nafion in the presence of 5 mM of Fe(CN)36 −/4 − (1:1 ratio in 0.1 M KCl) as the redox probe (Fig. S2). The charge-transfer resistance (Rct) values for at GCE/Pd@IFMC/Nafion, GCE/IFMC/Nafion and GCE/Nafion were about 5, 35 and 300 Ω, respectively. As obvious, the Rct value decreased significantly by modification of GCE with IFMC. Moreover, further decoration of IFMC with Pd nanoparticles caused a significant decrease in the Rct value of the modified electrode. The obtained results indicate that the decorated IFMC with Pd-NPs is an excellent electric conducting material which can be used for electroanalytical purposes.
3.2. Electrocatalytic oxidation of glucose at GCE/Pd@IFMC/Nafion Cyclic voltammetry was performed in 0.15 M NaOH solution in the absence and presence of 20 mM of glucose to investigate the electrocatalytic activity of the prepared modified glassy carbon electrodes towards glucose oxidation. Typical CVs obtained for GCE/Nafion, GCE/IFMC/Nafion and GCE/Pd@IFMC/Nafion at the scan rate of 100 mV s−1 are shown in Fig. 2. As obvious, no remarkable electrochemical activity was observed for glucose at GCE/Nafion, GCE/IFMC/Nafion (Fig. 2, inset) but glucose oxidized at GCE/Pd@IFMC/Nafion with a complex electrochemical behavior similar to that reported previously by Chen et al. [9]. Two anodic peaks at potentials of about − 0.09 and 0.49 V were recorded for glucose at GCE/Pd@IFMC/Nafion during the scan of potential in the positive direction. The first peak was ascribed to the electroadsorption of glucose followed by incomplete oxidization of glucose and consequently formation of intermediates on the electrode surface which poisoned the immobilized Pd nanoparticles. As reported previously [9], the accumulation of intermediates blocked further electroadsorption of glucose on the electrode surface and declined the anodic peak current intensity as the electrochemical reaction continued. The generation of Pd(OH)x species was started at the potentials more positive than 0.28 V. These species, oxidized Pd nanoparticles, oxidized the adsorbed poisoning intermediates and became clean and accessible for direct oxidation of glucose. Therefore, the second anodic peak that appeared at about 0.49 V was attributed to the direct oxidation of glucose on the oxidized Pd nanoparticles. On the basis of the previously reported mechanisms for glucose oxidation [5]
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and our finding in this study, a possible catalytic mechanism for glucose oxidation at GCE/Pd@IFMC/Nafion is proposed as the following: −
−
Pd þ OH →PdOH þ e
ð1Þ
PdOH þ Glucose→Pd þ Glucolactone:
ð2Þ
During the scan of potential in the negative direction, the oxidized Pd nanoparticles started to reduce at a potential of about 0.0 V. The scan of potential to a more negative value caused the activity of more Pd nanoparticles recovered and became available for the oxidation of glucose. As a result, a catalytic anodic peak was observed at a potential of about −0.40 V in the potential range between −0.30 and −0.60 V. The observed catalytic anodic peak was attributed to the electroadsorption and oxidation of glucose at the surface of renewed Pd nanoparticles. As shown in Fig. 3, the mentioned catalytic anodic peak at a potential of about −0.40 V was only observed at the high concentrations of glucose (N 4 mM) but not lower, similar to that reported previously by Chen et al. [9]. Also, cyclic voltammetry was performed using GCE/Pd@IFMC/Nafion in 0.15 M NaOH solution containing 2 mM of glucose at different scan rates. The anodic peak current intensities due to the incomplete and direct oxidation of glucose at potentials of about −0.09 and +0.49 V, respectively were proportional to the scan rates (Fig. S3). A good linearity was obtained between the anodic peak currents and scan rates in the range between 10 and 500 mV s−1 for both potentials, indicating the presence of surface-controlled redox processes at the electrode surface. As mentioned in the main text and shown in Eq. (1), the presence of OH− and consequently the formation of Pd(OH)x was essential for electrocatalytic oxidation of glucose. The observation of no electrocatalytic peak for oxidation of glucose at GCE/Pd@IFMC/Nafion in 0.5 M H2SO4 verified the mentioned fact. So, hydrodynamic amperometric studies were performed to explore the effect of NaOH concentration and applied potential on the response of proposed sensor towards 5 mM of glucose. As shown in Fig. 4A, with increasing the concentration of NaOH the current signal intensity of the sensor increased and reached a maximum at about 0.15 M NaOH and then decreased. It seems that with the increase of OH−, more Pd(OH)x can be formed and consequently higher electrocatalytic activity can be observed, but electroadsorption of glucose anions followed by their electrocatalytic oxidation can be blocked with too much OH−. Also, the results showed (Fig. 4B) that the amperometric response of the sensor passed over a maximum at a potential of about 0.40 V with increasing the applied potential from 0.20 to 0.60 V vs. Ag|AgCl|KClsat. So, 0.15 M NaOH and applied potential of 0.40 V were selected for subsequent experiments.
f e
d c b a
Fig. 2. Cyclic voltammograms obtained in the absence and presence of 20 mM of glucose in a 0.15 M NaOH using GCE/Nafion (a, b), GCE/IFMC/Nafion (c, d) and GCE/Pd@IFMC/Nafion (e, f) at the scan rate of 100 mV s−1. Inset: Magnified cyclic voltammograms obtained for GCE/Nafion (a, b) and GCE/IFMC/Nafion (c, d).
Fig. 3. Cyclic voltammograms obtained for GCE/Pd@IFMC/Nafion in the presence of different concentrations of glucose from 0 (dashed line), 2 to 16 mM with an increment of 2 mM (from inner to outer) in a 0.15 M NaOH at the scan rate of 100 mV s−1.
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A
B 0.6 V
0.25 M 0.20 M
0.5 V
0.15 M
0.4 V
0.10 M
0.3 V
0.05 M
0.2 V
Fig. 4. Steady-state current-time responses of GCE/Pd@IFMC/Nafion towards 5 mM of glucose (A) in NaOH solution with different concentrations at the applied potential of +0.40 V and (B) in 0.15 M NaOH solution at different applied potentials.
3.3. Analytical performance of GCE/Pd@IFMC/Nafion towards glucose Fig. 5 illustrates hydrodynamic amperometric responses of GCE/Pd@ IFMC/Nafion to successive addition of glucose under optimized experimental conditions. A well-defined and stable hydrodynamic amperometric response was recorded for glucose less than 2 s at the potential of 0.40 V and 0.15 M NaOH. The calibration equation for glucose determination was linear in the concentration range between 1 and 55 mM with a correlation coefficient (R2) of 0.9958. The detection limit was found to be 0.2 mM (S/N = 3). The relative standard deviation (RSD) for repetitive measurements (n = 6) of 5 mM of glucose was 5.3%. The fabrication reproducibility for five GCE/Pd@IFMC/Nafion prepared and used in different days for determination of 5 mM glucose was about 6.1%. The electroanalytical features of the proposed nonenzymatic glucose sensor are summarized in Table 1 and compared with the other reported nonenzymatic glucose sensors prepared using different modification strategies. As obvious from Table 1, the proposed nonenzymatic glucose sensor presented a wide linear range and it is very suitable to
diagnose diabetes, considering blood sugar levels in diabetic and nondiabetic people. It seems that the increase of electrode surface area because of the presence of IFMC and deposition of Pd NPs on IFMC created abundant active sites for the electrocatalytic oxidation of glucose. Moreover, high electrical conductivity provided by IFMC together with the sensitizing effect of Pd@IFMC towards glucose oxidation as a result of direct attachment of Pd NPs on the surface of IFMC were the main reasons to observe wide linear range and fast response time for glucose detection. The operational stability of the fabricated sensor was examined by monitoring of its current response towards repetitive measurements of 5 mM of glucose for six times in each day over twelve days. The response of the proposed sensor gradually decreased to almost 90% of its initial value after twelve days (Fig. S4). To evaluate the selectivity of proposed glucose sensor, the effect of the presence of some easily oxidizable species such as dopamine (DP), ascorbic acid (AA) and uric acid (UA) which usually co-exist with glucose in human serum on glucose detection was studied. Considering normal blood glucose level (4–7 mM) and AA, UA and DP levels (about
Table 1 Electroanalytical features of the proposed nonenzymatic glucose sensor GCE/Pd@IFMC/ Nafion and some reported nonenzymatic glucose sensors prepared using different modification strategies.
5 mM
1 mM
Fig. 5. Hydrodynamic amperometric responses of GCE/Pd@IFMC/Nafion in 0.15 M NaOH solution towards successive additions of glucose at the applied potential of +0.40 V. Inset: Plot of amperometric responses of the sensor versus glucose concentration.
Electrode material
Response Potential (V) LR time (s)
Cu/Gr Pt-CuO/rGO NiO/MFs CuO/SWCNTs Gr/PdNPs Ni/MWCNTs CuONPs/CNFs Pt-CuO/rGO NiO-Pt/ERGO Pt/MWNTs/Gr Pd/IFMC
b2 b3 N/A b2 9 b2 5 b3 2.5 N/A b2
0.5 0.6 0.5 0.45 0.4 0.6 0.5 0.6 0.6 0.4 0.4
DL (μM) Ref.
Up to 4.5 mM 0.5 Up to 12 mM 0.01 1–270 μM 0.03 0.05–1800 μM 0.05 10 μM–5 mM 1 3.2 μM–17.5 mM 0.89 0. 5 μM–11.1 0.2 0.5 μM–12 mM 0.01 2 μM–5.66 mM 0.20 1–7 mM 387 1–55 mM 200
[31] [32] [11] [13] [5] [6] [14] [32] [33] [34] This work
Gr, graphene; rGO, reduced graphene oxide; MFs, microfibers; SWCNTs, single wall carbon nanotube; MWCNTs, multi wall carbon nanotubes; CNFs, carbon nanofibers; ERGO, electrochemically reduced graphene oxide.
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0.1 mM), a series of solutions containing 5.0 mM of glucose, 0.5 mM of potent interfering compounds and 0.15 M NaOH were prepared. The amperometric responses of the prepared test solutions were recorded and compared with that obtained for the uncontaminated glucose solution (5 mM). A 5% error criterion was adopted. AA, DP and UA increased the amperometric response of 5 mM of glucose for 4.7, 5.1 and 8.9%, respectively (Fig. S5). Also, the effect of the presence of chloride ion and fructose on amperometric response of the sensor towards 5 mM of glucose was studied in 0.15 M NaOH. Chloride ion and fructose at concentrations of about 0.2 M and 0.5 mM, respectively altered the amperometric response of the sensor for about less than 5.0%. It seems that the sulfonic groups of Nafion layer repel chloride ion, ascorbate, urate and deprotonated form of DP from the electrode surface and prevent their unwanted electrochemical reactions, leading to have an improved selectivity. Moreover, Nafion layer prohibits the adsorption of redox intermediate products on the electrode surface and reduces the poisoning of electrode, leading to observe highly stable response. 3.4. Real sample analysis To examine the applicability of the proposed glucose sensor, it was employed for the determination of glucose in normal human serum. Blood sample was centrifuged for 20 min at 12,000 rpm to separate out the serum. 50 μL of human serum was mixed with 10 mL of 0.15 M NaOH and then analyzed using the proposed sensor at + 0.40 V. The concentration of glucose in serum was determined and compared with that determined in local hospital. The concentration of glucose in human serum was determined to be 6.68 mM. The recovery of the analysis was about 96.3%, considering the value determined by a local hospital (6.93 mM). Also, the reliability of the proposed glucose sensor was evaluated using standard addition method with the spiking of specific amounts of glucose (0, 1.0, 2.0, 3.0 and 4.0 mM) to the normal human serum. The recovery for each measurement was calculated by comparing the results obtained in the absence and presence of specific amounts of glucose. The obtained average recovery for the spiked samples was 95%. 4. Conclusions A nonenzymatic glucose sensor was fabricated by the use of Pd nanoparticles (PdNPs) decorated ionic liquid derived fibrillated mesoporous carbon (IFMC). Deposition of PdNPs on IFMC surface led to the formation of many active sites for direct glucose oxidation. The fabricated sensor exhibited high electrocatalytic ability towards glucose oxidation in alkaline solution. The prepared sensor showed high sensitivity towards glucose even in the presence of chloride ion, wide range of linearity and low detection limit. The obtained results clearly indicated that the proposed sensor is highly specific towards glucose even in the presence of easily oxidizable and nonoxidizable interfering compounds that normally exist in food and biological samples. Acknowledgment The authors acknowledge the Institute for Advanced Studies in Basic Sciences (IASBS, grant number G2014IASBS119) for financial support. Appendix A. Supplementary data Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.msec.2015.03.045. References [1] Y. Shi, F.B. Hu, The global implications of diabetes and cancer, Lancet 383 (2014) 1947–1948.
223
[2] G. Wang, X. He, L. Wang, A. Gu, Y. Huang, B. Fang, B. Geng, X. Zhang, Non-enzymatic electrochemical sensing of glucose, Microchim. Acta 180 (2013) 161–186. [3] C. Chen, Q. Xie, D. Yang, H. Xiao, Y. Fu, Y. Tan, S. Yao, Recent advances in electrochemical glucose biosensors: a review, RSC Adv. 3 (2013) 4473–4491. [4] J. Wang, Electrochemical glucose biosensors, Chem. Rev. 108 (2007) 814–825. [5] L.-M. Lu, H.-B. Li, F. Qu, X.-B. Zhang, G.-L. Shen, R.-Q. Yu, In situ synthesis of palladium nanoparticle–graphene nanohybrids and their application in nonenzymatic glucose biosensors, Biosens. Bioelectron. 26 (2011) 3500–3504. [6] A. Sun, J. Zheng, Q. Sheng, A highly sensitive non-enzymatic glucose sensor based on nickel and multi-walled carbon nanotubes nanohybrid films fabricated by one-step co-electrodeposition in ionic liquids, Electrochim. Acta 65 (2012) 64–69. [7] Y. Liu, H. Teng, H. Hou, T. You, Nonenzymatic glucose sensor based on renewable electrospun Ni nanoparticle-loaded carbon nanofiber paste electrode, Biosens. Bioelectron. 24 (2009) 3329–3334. [8] X. Bo, J. Bai, L. Yang, L. Guo, The nanocomposite of PtPd nanoparticles/onion-like mesoporous carbon vesicle for nonenzymatic amperometric sensing of glucose, Sensors Actuators B Chem. 157 (2011) 662–668. [9] X.-m. Chen, Z.-j. Lin, D.-J. Chen, T.-t. Jia, Z.-m. Cai, X.-r. Wang, X. Chen, G.-n. Chen, M. Oyama, Nonenzymatic amperometric sensing of glucose by using palladium nanoparticles supported on functional carbon nanotubes, Biosens. Bioelectron. 25 (2010) 1803–1808. [10] X. Chen, H. Pan, H. Liu, M. Du, Nonenzymatic glucose sensor based on flower-shaped Au@Pd core–shell nanoparticles–ionic liquids composite film modified glassy carbon electrodes, Electrochim. Acta 56 (2010) 636–643. [11] F. Cao, S. Guo, H. Ma, D. Shan, S. Yang, J. Gong, Nickel oxide microfibers immobilized onto electrode by electrospinning and calcination for nonenzymatic glucose sensor and effect of calcination temperature on the performance, Biosens. Bioelectron. 26 (2011) 2756–2760. [12] L. Luo, F. Li, L. Zhu, Y. Ding, Z. Zhang, D. Deng, B. Lu, Nonenzymatic glucose sensor based on nickel(II)oxide/ordered mesoporous carbon modified glassy carbon electrode, Colloids Surf. B Biointerfaces 102 (2013) 307–311. [13] N. Quoc Dung, D. Patil, H. Jung, D. Kim, A high-performance nonenzymatic glucose sensor made of CuO-SWCNT nanocomposites, Biosens. Bioelectron. 42 (2013) 280–286. [14] J. Zhang, X. Zhu, H. Dong, X. Zhang, W. Wang, Z. Chen, In situ growth cupric oxide nanoparticles on carbon nanofibers for sensitive nonenzymatic sensing of glucose, Electrochim. Acta 105 (2013) 433–438. [15] C.B. Jacobs, M.J. Peairs, B.J. Venton, Review: carbon nanotube based electrochemical sensors for biomolecules, Anal. Chim. Acta 662 (2010) 105–127. [16] C. Gao, Z. Guo, J.-H. Liu, X.-J. Huang, The new age of carbon nanotubes: an updated review of functionalized carbon nanotubes in electrochemical sensors, Nanoscale 4 (2012) 1948–1963. [17] G. Hu, F. Nitze, H.R. Barzegar, T. Sharifi, A. Mikołajczuk, C.-W. Tai, A. Borodzinski, T. Wågberg, Palladium nanocrystals supported on helical carbon nanofibers for highly efficient electro-oxidation of formic acid, methanol and ethanol in alkaline electrolytes, J. Power Sources 209 (2012) 236–242. [18] J. Gunho, C. Minhyeok, L. Sangchul, P. Woojin, K. Yung Ho, L. Takhee, The application of graphene as electrodes in electrical and optical devices, Nanotechnology 23 (2012) 112001. [19] Y. Shao, J. Wang, H. Wu, J. Liu, I.A. Aksay, Y. Lin, Graphene based electrochemical sensors and biosensors: a review, Electroanalysis 22 (2010) 1027–1036. [20] Y. Liu, X. Dong, P. Chen, Biological and chemical sensors based on graphene materials, Chem. Soc. Rev. 41 (2012) 2283–2307. [21] A. Vu, X. Li, J. Phillips, A. Han, W.H. Smyrl, P. Bühlmann, A. Stein, Three-dimensionally ordered mesoporous (3DOm) carbon materials as electrodes for electrochemical double-layer capacitors with ionic liquid electrolytes, Chem. Mater. 25 (2013) 4137–4148. [22] H. Wang, B. Qi, B. Lu, X. Bo, L. Guo, Comparative study on the electrocatalytic activities of ordered mesoporous carbons and graphene, Electrochim. Acta 56 (2011) 3042–3048. [23] B. Karimi, H. Behzadnia, M. Rafiee, H. Vali, Electrochemical performance of a novel ionic liquid derived mesoporous carbon, Chem. Commun. 48 (2012) 2776–2778. [24] J. Jin, S. Tanaka, Y. Egashira, N. Nishiyama, KOH activation of ordered mesoporous carbons prepared by a soft-templating method and their enhanced electrochemical properties, Carbon 48 (2010) 1985–1989. [25] R.J. Bowling, R.T. Packard, R.L. McCreery, Activation of highly ordered pyrolytic graphite for heterogeneous electron transfer: relationship between electrochemical performance and carbon microstructure, J. Am. Chem. Soc. 111 (1989) 1217–1223. [26] B. Karimi, H. Behzadnia, M. Bostina, H. Vali, A nano-fibrillated mesoporous carbon as an effective support for palladium nanoparticles in the aerobic oxidation of alcohols “on pure water”, Chem. Eur. J. 18 (2012) 8634–8640. [27] B. Haghighi, S. Bozorgzadeh, Fabrication of a highly sensitive electrochemiluminescence lactate biosensor using ZnO nanoparticles decorated multiwalled carbon nanotubes, Talanta 85 (2011) 2189–2193. [28] B. Haghighi, S. Bozorgzadeh, L. Gorton, Fabrication of a novel electrochemiluminescence glucose biosensor using Au nanoparticles decorated multiwalled carbon nanotubes, Sensors Actuators B Chem. 155 (2011) 577–583. [29] B. Haghighi, S. Bozorgzadeh, Enhanced electrochemiluminescence from luminol at multi-walled carbon nanotubes decorated with palladium nanoparticles: a novel route for the fabrication of an oxygen sensor and a glucose biosensor, Anal. Chim. Acta 697 (2011) 90–97. [30] D. Zhao, Q. Huo, J. Feng, B.F. Chmelka, G.D. Stucky, Nonionic triblock and star diblock copolymer and oligomeric surfactant syntheses of highly ordered,
224
B. Haghighi et al. / Materials Science and Engineering C 52 (2015) 219–224
hydrothermally stable, mesoporous silica structures, J. Am. Chem. Soc. 120 (1998) 6024–6036. [31] J. Luo, S. Jiang, H. Zhang, J. Jiang, X. Liu, A novel non-enzymatic glucose sensor based on Cu nanoparticle modified graphene sheets electrode, Anal. Chim. Acta 709 (2012) 47–53. [32] K. Dhara, J. Stanley, T. Ramachandran, B.G. Nair, T.G. Satheesh Babu, Pt-CuO nanoparticles decorated reduced graphene oxide for the fabrication of highly sensitive nonenzymatic disposable glucose sensor, Sensors Actuators B Chem. 195 (2014) 197–205.
[33] M. Li, X. Bo, Z. Mu, Y. Zhang, L. Guo, Electrodeposition of nickel oxide and platinum nanoparticles on electrochemically reduced graphene oxide film as a nonenzymatic glucose sensor, Sensors Actuators B Chem. 192 (2014) 261–268. [34] S. Badhulika, R.K. Paul, Rajesh, T. Terse, A. Mulchandani, Nonenzymatic glucose sensor based on platinum nanoflowers decorated multiwalled carbon nanotubes-graphene hybrid electrode, Electroanalysis 26 (2014) 103–108.
