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Highly sensitive non-enzymatic glucose sensor based on porous NiCo2O4 nanowires grown on nickel foam
Materials Letters 256 (2019) 126603
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/mlblue
Highly sensitive non-enzymatic glucose sensor based on porous NiCo2O4 nanowires grown on nickel foam Qi Guo a, Wen Zeng a,⇑, Yanqiong Li b a b
College of Materials Science and Engineering, Chongqing University, Chongqing, China School of Electronic and Electrical Engineering, Chongqing University of Arts and Sciences, Chongqing, China
a r t i c l e
i n f o
Article history: Received 16 July 2019 Received in revised form 10 August 2019 Accepted 29 August 2019 Available online 30 August 2019 Keywords: Non-enzymatic electrochemical glucose NiCo2O4 Electronic property Semiconductor Functional
a b s t r a c t In this work, we have triumphantly synthesized porous NiCo2O4 nanowires array on nickel foam (NiCo2O4 NWs/NF) via a facile hydrothermal method. Benefiting from its great one-dimensional porous nanowires architecture along with synergistic interactions between NiCo2O4 arrays and Ni foam, the NiCo2O4 NWs/ NF-based sensor exhibited enhanced glucose sensing performance. The sensitivity could reach up to 5916 lA mM 1 cm 2, meanwhile, the linear range was 1 lM–3.987 mM with a low detection limit (LOD) of 0.94 lM (S/N = 3). Furthermore, it displayed good selectivity. These results inspire that the porous NiCo2O4 nanowires will be a promising candidate for non-enzymatic glucose sensors. Ó 2019 Elsevier B.V. All rights reserved.
1. Introduction Recently, various metals and their oxides, boasting eminent electrocatalytic properties, low cost and high time-efficiency, have been extensively investigated for glucose sensing applications [1]. Among these materials, cobalt acid nickel (NiCo2O4) is deemed as a promising candidate by reason of their low-cost, good catalytic activity and prominent electrical conductivity (at least two orders of magnitude higher than those of single NiO and Co3O4) [2]. Additionally, the structure and morphology of NiCo2O4 are of vital importance to the performance of the glucose sensor. Diverse morphologies of the NiCo2O4-based nanomaterials have been reported, such as nanorods [3], nanospheres [4], nanowires [5] and nanosheets [6]. However, these above mentioned nanomaterials are prone to trigger self-aggregation or structural collapse, thus weakening electrocatalytic performance [7]. Nickel foam (NF) has been extensively used as conductive substrate on account of its large electrochemical active surface area and three-dimensional (3D) interconnected character [8]. Therefore, the direct growth of NiCo2O4 porous nanowires on the surface of NF can not only prevent agglomeration and structural collapse but also improve its electrical conductivity, which is an efficient approach to obtain satisfying non-enzymatic glucose sensing performance. So far, there
⇑ Corresponding author. E-mail address: [email protected] (W. Zeng). https://doi.org/10.1016/j.matlet.2019.126603 0167-577X/Ó 2019 Elsevier B.V. All rights reserved.
are a few reports about the application of NiCo2O4 NWs/NF in glucose sensing. Herein, porous NiCo2O4 nanowire arrays have been successfully synthesized on nickel foam via a facile hydrothermal method. The glucose sensing enhancement, in addition to the synergistic effects between Co and Ni elements of NiCo2O4 bimetallic oxide, can be ascribed to one-dimensional porous architecture offering abundant transport pathways and plentiful active sites.
2. Experimental A piece of Ni foam (2 4 cm2) was firstly sonicated in 2 M HCl, absolute ethanol and deionized water for 15 min, respectively. Then, 5 mmol Co(NO3)26H2O, 2.5 mmol Ni(NO3)26H2O, 4.5 mmol urea and 2 mmol cetyl trimethyl ammonium bromide (CTAB) were dissolved in 30 mL distilled water and magnetically stirred for 30 min at a constant temperature of 45 °C to obtain a homogeneous solution. Subsequently, the mixture was transferred into a 30 mL Teflon-lined autoclave, and the cleaned Ni foam was immersed into the solution. The autoclave was maintained at 120 °C for 6 h. After cooling to the room temperature naturally, the nickel foam was rinsed with ethanol and distilled water several times, followed by drying in vacuum at 60 °C for 8 h. Finally, the as-synthesized precursor was annealed at 350 °C for 2 h with a heating rate of 2 °C min 1 in air. The X-ray diffraction (XRD) patterns were obtained by a Rigaku D/Max-1200X X-ray diffraction. Morphologies and the element
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Q. Guo et al. / Materials Letters 256 (2019) 126603
distribution were investigated by field emission scanning electron microscope (FESEM, JEOL JSM-7800F) equipped with an energy dispersive X-ray spectrum (EDS) analyzer and transmission electron micrographs (TEM, Tecnai G2 F20). The cyclic voltammetry (CV) and amperometry (i-t) were performed under three-electrode system in 0.1 M aqueous NaOH solution at room temperature. The asprepared NF loaded with NiCo2O4 arrays (1 2 cm2), an Ag/AgCl electrode and a Pt plate were used as the working electrode, reference electrode and counter electrode, respectively. 3. Results and discussion The XRD patterns of NiCo2O4 arrays on nickel foam are displayed in Fig. 1a. The sharp diffraction peaks at 18.9°, 31.1°, 36.7°, 44.6°, 55.4°, 59.1° and 65.0° are well assigned to the (1 1 1), (2 2 0), (3 1 1), (4 0 0), (4 2 2), (5 1 1) and (4 4 0) planes of NiCo2O4 (JCPDS 20-0781). Two strong peaks at 44.5° and 52.1° can be corresponded to the Ni foam. The energy dispersive spectrometry (EDS) elemental mapping images confirm the presence and homogenous distribution of Ni, Co and O, as depicted in Fig. 1b. The results further corroborate the formation of spinel
NiCo2O4. The SEM and TEM were employed to identify the morphology of as-synthesized NiCo2O4 nanowires. Fig. 1c reveals the SEM image of NiCo2O4 nanowires grown on Ni foam. Surface of the nickel foam substrate is uniformly covered by NiCo2O4 nanowires. Fig. 1d exhibits a typical TEM image of NiCo2O4 nanowire scratched from the Ni foam by ultrasonication. The well-defined nanowires consist of a great deal of interconnected nanoparticles, which demonstrates the porous structure of the NiCo2O4 nanowires. Meanwhile, the nanowire morphology suggests its diameter is about 80 nm. Fig. 2a exhibits the cyclic voltammograms of NiCo2O4 NWs/NF in the absence and presence of 1 mM glucose in 0.1 M aqueous NaOH at a scan rate of 10 mV s 1. Obviously, a significant increase in the current response can be observed after the addition of 1 mM glucose, resulting from the excellent catalytic activity of NiCo2O4 NWs/NF towards glucose. Fig. 2b presents the CV curves of NiCo2O4 NWs/NF under different scan rates (5–50 mV s 1) in 0.1 M NaOH solution. With the increase of the scanning rate, both the anodic and cathodic peak current increase. Moreover, both the anodic and cathodic peak current maintain good linear relationship with the square root of the scanning rate, as shown in Fig. 2c. This
Fig. 1. (a) XRD patterns of NiCo2O4 NWs/NF. (b) Element mapping images of the NiCo2O4 NWs/NF. (c) SEM image of NiCo2O4 NWs/NF. (d) TEM image of NiCo2O4 nanowire.
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Q. Guo et al. / Materials Letters 256 (2019) 126603
Fig. 2. CVs of NiCo2O4 NWs/NF in 0.1 M NaOH (a) absence and presence of glucose and (b) at different scan rates. (c) Linear relationship between the anodic/cathodic peak currents and the square root of scanning rate (v1/2). (d) The amperometric response of NiCo2O4 NWs/NF to the successive injection of glucose into 0.1 M NaOH solution at 0.45 V; the inset showed the enlarged response from the black rectangle. (e) Calibration curve between current response and glucose concentration. (f) Amperometric responses to the sequential addition of 1 mM glucose and 0.1 mM different interferents (UA, AA, Fructose and Sucrose); Potential: 0.45 V.
Table 1 Performance comparison of NiCo2O4 NWs/NF with other glucose sensors based on NiCo2O4-based materials. Electrode
Sensitivity (lA mM
Hierarchical NiCo2O4 hollow nanorods Porous NiCo2O4 hollow nanospheres Urchin-like NiCo2O4 Co3O4/NiCo2O4 DSNCs@G NiCo2O4 nanorods NiCo2O4/rGO NiCo2O4 NW/Ni foam
1685 1917 72.4 304 4710 2082 5916
1
cm
2
)
result indicates that the redox reaction of the NiCo2O4 NWs/NF is a diffusion controlled process [1]. Chronoamperometry was employed to further investigate the nonenzymatic glucose sensing performance of NiCo2O4 NWs/NF sensor. Fig. 2d shows the current-time curve, which was recorded by successive adding different concentrations of glucose into 0.1 M NaOH at a working potential of 0.45 V. A well-defined and stable staircase curve occurred with the successive addition of glucose. Fig. 2e displays the calibration curve between the current density and glucose concentration. The fabricated NiCo2O4 NWs/NF glucose sensor manifests a wide linear range of 1 lM–3.987 mM with a high sensitivity of 5916 lA mM 1 cm 2 (R23 = 0.99044). Moreover, the limit of detection (LOD) for glucose was estimated to be 0.94 lM (S/N = 3). The catalytic performance of the enzyme-free glucose sensor has been compared with other reported NiCo2O4based glucose sensors, as illustrated in Table 1. Obviously, the as-prepared sensor in this paper displays enhanced sensing performance, such as excellent sensitivity, wide linear range and low detection limit. The enhanced sensing performance may attribute to the following factors. Firstly, the synergistic effects between cobalt and nickel elements of NiCo2O4 bimetallic oxide improve the conductivity of the materials. Secondly, the onedimensional porous NiCo2O4 nanowire arrays offer abundant transport pathways for ions and plentiful active sites for redox reaction, so that the glucose sensor has excellent electrocatalytic sensing performance. Thirdly, the NiCo2O4 nanowires directly
Linear range (mM)
Detection limit (lM)
Reference
0.0003–1.0 0.01–2.24 0.37–2.0 0.01–3.52 0.001–0.88 0.04–1.28 0.001–3.987
0.16 0.6 0.37 0.384 0.063 0.7 0.94
[3] [4] [5] [9] [10] [11] This work
grown on the Ni foam without additional conductive or binders agents can reduce the system resistance, favoring the enhancement of electrochemical performance. In this work, the selectivity of our sensor was investigated by employing amperometry. It is universally acknowledged that the concentration of glucose in the blood is about 30 times higher than other interfering substance such as uric acid (UA), ascorbic acid (AA), fructose and sucrose. Thus, the anti-interfering test of the sensor was conducted in 0.1 M NaOH by the consecutive addition of 1 mM glucose and 0.1 mM other interferences at 0.45 V. As can be seen from Fig. 2f, the current response witnessed a significant increase after adding glucose, while little current response is noticed upon the addition of various interfering species [12–14]. The results of the test manifest that the NiCo2O4 NWs/NF sensor possesses satisfactory selectivity towards glucose detection.
4. Conclusions In summary, this work presents a one-step facile hydrothermal method for the synthesis of NiCo2O4 NWs/NF, which is used to prepare non-enzymatic sensor towards glucose. The electrochemical testing results manifest that the sensor has good sensitivity (5916 lA mM 1 cm 2), relatively wide linear detection range (1 lM–3.987 mM) and low detection limit (0.94 lM). Besides, it possesses excellent selectivity towards glucose. Therefore, it can
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Q. Guo et al. / Materials Letters 256 (2019) 126603
be deemed as a promising material for enzyme-free glucose sensing. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. References [1] H. Xu, C. Xia, S. Wang, et al., Sens. Actuators B: Chem. 267 (2018) 93–103.
[2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14]
C. Yuan, H.B. Wu, Y. Xie, et al., Angew. Chem. 53 (2014) 1488–1504. J. Yang, M. Cho, Y. Lee, et al., Biosens. Bioelectron. 75 (2016) 15–22. W. Huang, Y. Cao, Y. Chen, et al., Appl. Surf. Sci. 396 (2017) 804–811. Z. Qin, Q. Cheng, Y. Lu, et al., Appl. Phys. A 123 (2017) 492–510. S. Cui, J. Zhang, Y. Ding, et al., Sci. China Mater. 60 (2017) 766–776. G. Ma, M. Yang, C. Li, et al., Electrochim. Acta 220 (2016) 545–553. P. Arul, S.A. John, et al., Electrochim. Acta 306 (2019) 254–263. B. Xue, K. Li, L. Feng, et al., Electrochim. Acta 239 (2017) 36–44. M. Saraf, K. Natarajan, S.M. Mobin, et al., New J. Chem. 41 (2017) 9299–9313. B. Wang, Y. Cao, Y. Chen, et al., Nanotechnology 28 (2017) 025501. Y. Zhang, W. Zeng, Y. Li, Ceram. Int. 45 (2019) 6043–6050. Y. Zhang, W. Zeng, Y. Li, Mater. Lett. 241 (2019) 223–226. J. Wang, Q. Zhou, W. Zeng, Appl. Surf. Sci. 479 (2019) 185–197.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/mlblue
Highly sensitive non-enzymatic glucose sensor based on porous NiCo2O4 nanowires grown on nickel foam Qi Guo a, Wen Zeng a,⇑, Yanqiong Li b a b
College of Materials Science and Engineering, Chongqing University, Chongqing, China School of Electronic and Electrical Engineering, Chongqing University of Arts and Sciences, Chongqing, China
a r t i c l e
i n f o
Article history: Received 16 July 2019 Received in revised form 10 August 2019 Accepted 29 August 2019 Available online 30 August 2019 Keywords: Non-enzymatic electrochemical glucose NiCo2O4 Electronic property Semiconductor Functional
a b s t r a c t In this work, we have triumphantly synthesized porous NiCo2O4 nanowires array on nickel foam (NiCo2O4 NWs/NF) via a facile hydrothermal method. Benefiting from its great one-dimensional porous nanowires architecture along with synergistic interactions between NiCo2O4 arrays and Ni foam, the NiCo2O4 NWs/ NF-based sensor exhibited enhanced glucose sensing performance. The sensitivity could reach up to 5916 lA mM 1 cm 2, meanwhile, the linear range was 1 lM–3.987 mM with a low detection limit (LOD) of 0.94 lM (S/N = 3). Furthermore, it displayed good selectivity. These results inspire that the porous NiCo2O4 nanowires will be a promising candidate for non-enzymatic glucose sensors. Ó 2019 Elsevier B.V. All rights reserved.
1. Introduction Recently, various metals and their oxides, boasting eminent electrocatalytic properties, low cost and high time-efficiency, have been extensively investigated for glucose sensing applications [1]. Among these materials, cobalt acid nickel (NiCo2O4) is deemed as a promising candidate by reason of their low-cost, good catalytic activity and prominent electrical conductivity (at least two orders of magnitude higher than those of single NiO and Co3O4) [2]. Additionally, the structure and morphology of NiCo2O4 are of vital importance to the performance of the glucose sensor. Diverse morphologies of the NiCo2O4-based nanomaterials have been reported, such as nanorods [3], nanospheres [4], nanowires [5] and nanosheets [6]. However, these above mentioned nanomaterials are prone to trigger self-aggregation or structural collapse, thus weakening electrocatalytic performance [7]. Nickel foam (NF) has been extensively used as conductive substrate on account of its large electrochemical active surface area and three-dimensional (3D) interconnected character [8]. Therefore, the direct growth of NiCo2O4 porous nanowires on the surface of NF can not only prevent agglomeration and structural collapse but also improve its electrical conductivity, which is an efficient approach to obtain satisfying non-enzymatic glucose sensing performance. So far, there
⇑ Corresponding author. E-mail address: [email protected] (W. Zeng). https://doi.org/10.1016/j.matlet.2019.126603 0167-577X/Ó 2019 Elsevier B.V. All rights reserved.
are a few reports about the application of NiCo2O4 NWs/NF in glucose sensing. Herein, porous NiCo2O4 nanowire arrays have been successfully synthesized on nickel foam via a facile hydrothermal method. The glucose sensing enhancement, in addition to the synergistic effects between Co and Ni elements of NiCo2O4 bimetallic oxide, can be ascribed to one-dimensional porous architecture offering abundant transport pathways and plentiful active sites.
2. Experimental A piece of Ni foam (2 4 cm2) was firstly sonicated in 2 M HCl, absolute ethanol and deionized water for 15 min, respectively. Then, 5 mmol Co(NO3)26H2O, 2.5 mmol Ni(NO3)26H2O, 4.5 mmol urea and 2 mmol cetyl trimethyl ammonium bromide (CTAB) were dissolved in 30 mL distilled water and magnetically stirred for 30 min at a constant temperature of 45 °C to obtain a homogeneous solution. Subsequently, the mixture was transferred into a 30 mL Teflon-lined autoclave, and the cleaned Ni foam was immersed into the solution. The autoclave was maintained at 120 °C for 6 h. After cooling to the room temperature naturally, the nickel foam was rinsed with ethanol and distilled water several times, followed by drying in vacuum at 60 °C for 8 h. Finally, the as-synthesized precursor was annealed at 350 °C for 2 h with a heating rate of 2 °C min 1 in air. The X-ray diffraction (XRD) patterns were obtained by a Rigaku D/Max-1200X X-ray diffraction. Morphologies and the element
2
Q. Guo et al. / Materials Letters 256 (2019) 126603
distribution were investigated by field emission scanning electron microscope (FESEM, JEOL JSM-7800F) equipped with an energy dispersive X-ray spectrum (EDS) analyzer and transmission electron micrographs (TEM, Tecnai G2 F20). The cyclic voltammetry (CV) and amperometry (i-t) were performed under three-electrode system in 0.1 M aqueous NaOH solution at room temperature. The asprepared NF loaded with NiCo2O4 arrays (1 2 cm2), an Ag/AgCl electrode and a Pt plate were used as the working electrode, reference electrode and counter electrode, respectively. 3. Results and discussion The XRD patterns of NiCo2O4 arrays on nickel foam are displayed in Fig. 1a. The sharp diffraction peaks at 18.9°, 31.1°, 36.7°, 44.6°, 55.4°, 59.1° and 65.0° are well assigned to the (1 1 1), (2 2 0), (3 1 1), (4 0 0), (4 2 2), (5 1 1) and (4 4 0) planes of NiCo2O4 (JCPDS 20-0781). Two strong peaks at 44.5° and 52.1° can be corresponded to the Ni foam. The energy dispersive spectrometry (EDS) elemental mapping images confirm the presence and homogenous distribution of Ni, Co and O, as depicted in Fig. 1b. The results further corroborate the formation of spinel
NiCo2O4. The SEM and TEM were employed to identify the morphology of as-synthesized NiCo2O4 nanowires. Fig. 1c reveals the SEM image of NiCo2O4 nanowires grown on Ni foam. Surface of the nickel foam substrate is uniformly covered by NiCo2O4 nanowires. Fig. 1d exhibits a typical TEM image of NiCo2O4 nanowire scratched from the Ni foam by ultrasonication. The well-defined nanowires consist of a great deal of interconnected nanoparticles, which demonstrates the porous structure of the NiCo2O4 nanowires. Meanwhile, the nanowire morphology suggests its diameter is about 80 nm. Fig. 2a exhibits the cyclic voltammograms of NiCo2O4 NWs/NF in the absence and presence of 1 mM glucose in 0.1 M aqueous NaOH at a scan rate of 10 mV s 1. Obviously, a significant increase in the current response can be observed after the addition of 1 mM glucose, resulting from the excellent catalytic activity of NiCo2O4 NWs/NF towards glucose. Fig. 2b presents the CV curves of NiCo2O4 NWs/NF under different scan rates (5–50 mV s 1) in 0.1 M NaOH solution. With the increase of the scanning rate, both the anodic and cathodic peak current increase. Moreover, both the anodic and cathodic peak current maintain good linear relationship with the square root of the scanning rate, as shown in Fig. 2c. This
Fig. 1. (a) XRD patterns of NiCo2O4 NWs/NF. (b) Element mapping images of the NiCo2O4 NWs/NF. (c) SEM image of NiCo2O4 NWs/NF. (d) TEM image of NiCo2O4 nanowire.
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Q. Guo et al. / Materials Letters 256 (2019) 126603
Fig. 2. CVs of NiCo2O4 NWs/NF in 0.1 M NaOH (a) absence and presence of glucose and (b) at different scan rates. (c) Linear relationship between the anodic/cathodic peak currents and the square root of scanning rate (v1/2). (d) The amperometric response of NiCo2O4 NWs/NF to the successive injection of glucose into 0.1 M NaOH solution at 0.45 V; the inset showed the enlarged response from the black rectangle. (e) Calibration curve between current response and glucose concentration. (f) Amperometric responses to the sequential addition of 1 mM glucose and 0.1 mM different interferents (UA, AA, Fructose and Sucrose); Potential: 0.45 V.
Table 1 Performance comparison of NiCo2O4 NWs/NF with other glucose sensors based on NiCo2O4-based materials. Electrode
Sensitivity (lA mM
Hierarchical NiCo2O4 hollow nanorods Porous NiCo2O4 hollow nanospheres Urchin-like NiCo2O4 Co3O4/NiCo2O4 DSNCs@G NiCo2O4 nanorods NiCo2O4/rGO NiCo2O4 NW/Ni foam
1685 1917 72.4 304 4710 2082 5916
1
cm
2
)
result indicates that the redox reaction of the NiCo2O4 NWs/NF is a diffusion controlled process [1]. Chronoamperometry was employed to further investigate the nonenzymatic glucose sensing performance of NiCo2O4 NWs/NF sensor. Fig. 2d shows the current-time curve, which was recorded by successive adding different concentrations of glucose into 0.1 M NaOH at a working potential of 0.45 V. A well-defined and stable staircase curve occurred with the successive addition of glucose. Fig. 2e displays the calibration curve between the current density and glucose concentration. The fabricated NiCo2O4 NWs/NF glucose sensor manifests a wide linear range of 1 lM–3.987 mM with a high sensitivity of 5916 lA mM 1 cm 2 (R23 = 0.99044). Moreover, the limit of detection (LOD) for glucose was estimated to be 0.94 lM (S/N = 3). The catalytic performance of the enzyme-free glucose sensor has been compared with other reported NiCo2O4based glucose sensors, as illustrated in Table 1. Obviously, the as-prepared sensor in this paper displays enhanced sensing performance, such as excellent sensitivity, wide linear range and low detection limit. The enhanced sensing performance may attribute to the following factors. Firstly, the synergistic effects between cobalt and nickel elements of NiCo2O4 bimetallic oxide improve the conductivity of the materials. Secondly, the onedimensional porous NiCo2O4 nanowire arrays offer abundant transport pathways for ions and plentiful active sites for redox reaction, so that the glucose sensor has excellent electrocatalytic sensing performance. Thirdly, the NiCo2O4 nanowires directly
Linear range (mM)
Detection limit (lM)
Reference
0.0003–1.0 0.01–2.24 0.37–2.0 0.01–3.52 0.001–0.88 0.04–1.28 0.001–3.987
0.16 0.6 0.37 0.384 0.063 0.7 0.94
[3] [4] [5] [9] [10] [11] This work
grown on the Ni foam without additional conductive or binders agents can reduce the system resistance, favoring the enhancement of electrochemical performance. In this work, the selectivity of our sensor was investigated by employing amperometry. It is universally acknowledged that the concentration of glucose in the blood is about 30 times higher than other interfering substance such as uric acid (UA), ascorbic acid (AA), fructose and sucrose. Thus, the anti-interfering test of the sensor was conducted in 0.1 M NaOH by the consecutive addition of 1 mM glucose and 0.1 mM other interferences at 0.45 V. As can be seen from Fig. 2f, the current response witnessed a significant increase after adding glucose, while little current response is noticed upon the addition of various interfering species [12–14]. The results of the test manifest that the NiCo2O4 NWs/NF sensor possesses satisfactory selectivity towards glucose detection.
4. Conclusions In summary, this work presents a one-step facile hydrothermal method for the synthesis of NiCo2O4 NWs/NF, which is used to prepare non-enzymatic sensor towards glucose. The electrochemical testing results manifest that the sensor has good sensitivity (5916 lA mM 1 cm 2), relatively wide linear detection range (1 lM–3.987 mM) and low detection limit (0.94 lM). Besides, it possesses excellent selectivity towards glucose. Therefore, it can
4
Q. Guo et al. / Materials Letters 256 (2019) 126603
be deemed as a promising material for enzyme-free glucose sensing. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. References [1] H. Xu, C. Xia, S. Wang, et al., Sens. Actuators B: Chem. 267 (2018) 93–103.
[2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14]
C. Yuan, H.B. Wu, Y. Xie, et al., Angew. Chem. 53 (2014) 1488–1504. J. Yang, M. Cho, Y. Lee, et al., Biosens. Bioelectron. 75 (2016) 15–22. W. Huang, Y. Cao, Y. Chen, et al., Appl. Surf. Sci. 396 (2017) 804–811. Z. Qin, Q. Cheng, Y. Lu, et al., Appl. Phys. A 123 (2017) 492–510. S. Cui, J. Zhang, Y. Ding, et al., Sci. China Mater. 60 (2017) 766–776. G. Ma, M. Yang, C. Li, et al., Electrochim. Acta 220 (2016) 545–553. P. Arul, S.A. John, et al., Electrochim. Acta 306 (2019) 254–263. B. Xue, K. Li, L. Feng, et al., Electrochim. Acta 239 (2017) 36–44. M. Saraf, K. Natarajan, S.M. Mobin, et al., New J. Chem. 41 (2017) 9299–9313. B. Wang, Y. Cao, Y. Chen, et al., Nanotechnology 28 (2017) 025501. Y. Zhang, W. Zeng, Y. Li, Ceram. Int. 45 (2019) 6043–6050. Y. Zhang, W. Zeng, Y. Li, Mater. Lett. 241 (2019) 223–226. J. Wang, Q. Zhou, W. Zeng, Appl. Surf. Sci. 479 (2019) 185–197.