2024 Volume 92 Issue 4 Pages 047001
Eectrochemical glucose sensors is crucial for both environmental and human health, requiring rational nanoarchitectures with high electrochemical performance for glucose oxidation. Ni(OH)2/Ni(DMG)2 composite nanotubes were synthesized by etching nickel-dimethylglyoxime (DMG) nanorods with OH−, using Ni(DMG)2 as a partially sacrificial template. The optimal Ni(OH)2/Ni(DMG)2 nonenzymatic glucose sensor was evaluated on both conventional and portable electrochemical workstations, showing high sensitivity and a low detection limit. The optimal Ni(OH)2/Ni(DMG)2 glucose sensors integrated into smartphones demonstrated a low detection limit of 3.3 µM (M = mol L−1), a wide linear range (10 µM–8 mM), and a sensitivity of 262.80 µA mM−1 cm−2 for glucose detection. The sensors also exhibited favorable stability and reproducibility, along with preferable resistance to interference in the presence of uric acid, gluconate, proline, NaCl, valine, and lysine. Moreover, the portable sensor also demonstrated satisfactory glucose recovery (97.25–104 %) in serum samples, indicating its potential for future applications in real samples analysis.
The advancement of highly selective and sensitive detection of biomarkers has consistently held significant importance for the sustainability of both the environment and human life. Glucose not only serves as the fundamental energy source for the human body but also constitutes the primary components of our foods. Excessive consumption of sugar in individuals’ diets has been associated with various chronic health issues, especially diabetes, resulting in metabolic disorders and, in some cases, mortality.1 Therefore, the prompt and dependable detection of glucose holds significant technological and scientific importance in both industrial analytical (such as food, beverage, and fermentation manufacturing areas,) and healthcare applications, which can not only control glucose intake, but also monitor blood glucose levels.2–4
Numerous techniques have been adopted for detecting and measuring glucose, such as electrochemical method,5,6 colorimetry,7 chromatography8 and fluorescence spectroscopy.9 Based on the advantages of rapid response and high accuracy, currently commercially available glucose sensors are mainly electrochemically enzymatic based sensors. However, the current electrochemical glucose sensors also suffer from inherent defects of the enzyme catalyst, which is poor stability, high cost and vulnerability to environment (such as temperature, humidity, and pH).3,10 As glucose can be directly oxidized on inorganic catalyst, noble-metal or transition metal have attracted more and more attention in non-enzymatic glucose sensing. Because noble metals are expensive and scarce, limiting their commercial applications, transition metals (such as Ni,11 Co,12 and Cu13) are regarded as more promising catalysts for glucose sensing application.
In theory, Ni demonstrates superior potential as an electrocatalyst for glucose detection because of its high catalytic activity for glucose oxidation by the redox pair of Ni2+/Ni3+.14 Ni(OH)2, known for its high specific capacitance and exceptional electrocatalytic activity, is regarded as a highly promising catalyst for electrocatalytic oxidation of glucose.15 Nevertheless, the limited application range of Ni(OH)2 has resulted from its drawbacks, including low surface area, low conductivity, and poor cycle stability. To address these limitations, studies have demonstrated that diverse morphology Ni(OH)2 or loading Ni(OH)2 nanoparticles onto compatible supports to create a composite may bring more effective contact areas and boost electron transport rate.16,17 Metal organic frameworks (MOFs) have garnered growing interest in the field of glucose sensing applications due to their good physical and chemical properties, which is originated from their special structure consisting metal nodes (metal ions or metal clusters) self-assemble with organic ligands through coordination bonds. Moreover, they can also serve as precursors and/or templates for the production of other metal nanocomposites exhibiting varied structures and morphologies, intended for applications in electrocatalysis.5,18–20 Due to its sensitivity and stability, diamethyglyoxime (DMG) is widely employed as a ligand to coordinate nickel ions, leading to the formation of nickel-dimethyglyoxime complexes. Moreover, the adsorption of the ligand on the electrode surface can markedly increase the electrochemical reactivity of Ni ions. The catalytic activity of Ni(DMG)2 complex for the electro-oxidation of molecule (such as methanol, ethanol and nitrophenols) in alkaline solution has been recently documented.21–23 Nevertheless, there is no existing report on the utilization of Ni(DMG)2 as an electrocatalyst for glucose oxidation, and even less information is available regarding the application of Ni(OH)2/Ni(DMG)2 complexes as glucose sensing catalysts.
In this work, we present novel Ni(OH)2/Ni(DMG)2 composite nanotubes and showcase their remarkable electrochemical glucose-sensing capability. Such a composite was designed by in situ growing Ni(OH)2 nanoparticles on Ni(DMG)2 nanorods (NRs), wherein the NRs acted as a partially sacrificed template to form Ni(OH)2 and with the remaining part transforming into Ni(DMG)2 nanotubes. The advantageous tubular structures in Ni(OH)2/Ni(DMG)2 serve to expand the specific surface area and enrich the active sites. Additionally, these structures prevent aggregation of Ni(OH)2 nanoparticles, leading to more ion diffusion paths, shortened electron transmission distances, and a further improvement in electrocatalytic performance. Ni(OH)2/Ni(DMG)2 composite nanotubes exhibit an efficient and sensitive non-enzymatic glucose sensing performance, thanks to the favorable synergistic effect between two materials.
Ni(DMG)2 NRs were prepared by addition of an alcoholic solution of dimethylglyoxime to an aqueous solution of (Ni(CH3COO)2·4H2O). Initially, solution A was obtained by dissolving 1.114 g dimethylglyoxime into ethanol (64 mL). Concurrently, solution B was prepared by dissolving 0.487 g (Ni(CH3COO)2·4H2O) into 32 mL deionized water. Then, solution A was added into solution B with constant stirring, and the resulting mixture was stirred for an extra 20 minutes. The precipitate was subjected to centrifugation at 4000 rpm for 5 min, followed by multiple washes with water and ethanol. Ultimately, Ni(DMG)2 NRs products were acquired through drying it at 65 °C for 24 h.
2.2 Fabrication of Ni(OH)2/Ni(DMG)2 composite nanotubesThe Ni(OH)2/Ni(DMG)2 composite nanotubes were obtained through hydrothermally treating Ni(DMG)2 NRs in an alkaline solution. Initially, the Ni(DMG)2 NRs were dissolved in 15 ml of 3.3 M (M = mol L−1) NaOH solution. Subsequently, the resulting mixtures were transferred to a Teflon-lined stainless autoclave. Various samples undergo hydrothermal treatment at 100 °C for varying durations as required. The final products of Ni(OH)2/Ni(DMG)2 composite nanotubes were obtained through the separation of precipitates, followed by washing with water and ethanol, and drying at 80 °C for 10 hours. The labeling of the samples as Ni(OH)2/Ni(DMG)2-1, Ni(OH)2/Ni(DMG)2-3, Ni(OH)2/Ni(DMG)2-5, and Ni(OH)2/Ni(DMG)2-10 corresponded to hydrothermal treatment times of 1 h, 3 h, 5 h, and 10 h, respectively.
2.3 Apparatus and measurementsThe X-ray diffractometer (XRD, Thermo ARL SCINTAG X’TRA, CuKα radiation) was used to analyze the crystallinity and composition of the materials. The Scanning Electron Microscope (SEM, Thermo Fisher Scientific Apreo S HiVAac) and Transmission Electron Microscope (TEM, JEOL 200CX) were employed to analyze the morphologies and microstructures of the materials. Energy Dispersive X-ray Spectroscopy (EDS, JEOL 200CX) was utilized to detect the distribution of elements on the surface of composite nanotubes.
The CHI instrument (CHI-630D workstation) and a portable electrochemical workstation (HY-1550) were utilized for conducting the electrochemical measurements. The three-electrode system was selected in the test with Pt, Ag/AgCl (Saturated KCl), and modified glassy carbon electrode (GCE, 5 mm in diameter), respectively, as counter, reference, and working electrodes and 0.1 M NaOH as supporting electrolyte. The GCE, previously polished with 0.3 µm alumina, was coated with a 10 µL catalyst solution for the working electrode preparation. The catalyst solution was derived by dissolving 10 mg catalyst into a 10 mL anhydrous ethanol solution containing 10 µL Nafion reagent. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA) techniques were employed to assess the electrochemical performance of the electrode. The ZAHNER Zennium electrochemical workstation was used to perform the EIS test in 0.1 M KCl electrolyte containing 5 mM K4[Fe(CN)6]/K3[Fe(CN)6], employing an AC amplitude of 5 mV and a frequency range of 0.1 Hz to 100 kHz.
Figure 1 provides a schematic representation of the fabrication process for Ni(OH)2/Ni(DMG)2 composite nanotubes. Briefly, Ni(DMG)2 NRs were firstly formed in aqueous solution with the coordination of diamethyglyoxime (DMG) to Ni2+. Then, Ni(DMG)2 NRs were hydrothermally treated in alkaline solution resulting in Ni(OH)2 nanoparticles generating on Ni(DMG)2 NRs surface. With the continuously OH− etching more and more Ni(OH)2 were formed accompanied by the depletion of Ni(DMG)2. Meanwhile, Ni(DMG)2 NRs can also be transformed into the hollow tubular structure. Figure 2 displays the ball-and-stick model of Ni(DMG)2 and the evolution in XRD patterns of Ni(DMG)2 with the hydrothermally treated time in alkaline. It can be observed that all the diffraction lines of Ni(DMG)2 were indexed in the orthorhombic structure, in agreement with previous reports.24,25 Moreover, the highly crystalline structure of Ni(DMG)2 is evident from the sharp diffraction patterns, revealing a preferentially exposed (1 1 0) plane at 2θ of 9.9°, which may indicate that the Ni(DMG)2 nanorods grow along the [1 1 0] direction of the crystals. It is evident that upon the treatment with OH-, the XRD patterns revealed a gradual emergence of distinct diffraction peaks corresponding to Ni(OH)2. The diffraction peaks appearing at 2θ of 19.26 (0 0 1), 33.06 (1 0 0), 38.54 (1 0 1), 52.10 (1 0 2), 59.05 (1 1 0), and 62.73 (1 1 1) match well with the reflection planes of the hexagonal phase of Ni(OH)2 (JCPDS, No. 14-0117). Based on the diffraction intensity of Ni(OH)2 and Ni(DMG)2, it is evident that the content of Ni(OH)2 gradually increases over hydrothermal treated time. Moreover, there is very little Ni(DMG)2 phase in Ni(OH)2/Ni(DMG)2 composite nanotubes after 10 h hydrothermal treatment.
The schematic illustration of the fabrication process for Ni(OH)2/Ni(DMG)2 composite nanotubes.
The ball-and-stick model of Ni(DMG)2 (a) and the XRD patterns of Ni(OH)2/Ni(DMG)2 composite nanotubes treated with various times (b).
Figure 3 presents SEM images of Ni(DMG)2 NRs and Ni(OH)2/Ni(DMG)2 composite nanotubes. Obviously, Ni(DMG)2 NRs displays a typical nanorod morphology with relatively high aspect ratio (length/diameter) (Fig. 3a). Upon alkali treatment, the rods undergo a reduction in length with the longer the treatment time, the shorter the tube length (Figs. 3b to 3f). Moreover, a tubular structure gradually appears as the length of Ni(DMG)2 nanorods becomes shorter (marked with a yellow circle in Fig. 3b). The typical tubular structure of Ni(OH)2/Ni(DMG)2-5 was showed in Fig. 3e, which displays the distinctly open top with the tube diameter less than 500 nm. The tubular structures of Ni(OH)2/Ni(DMG)2-5 were further confirmed through TEM images as shown in Fig. 4, which provide clear evidence to support the exclusive formation of hollow nanotubes with wall thickness less than 50 nm (Fig. 4b). Figure 4c shows the HAADF-STEM image and the corresponding EDS mapping images of Ni(OH)2/Ni(DMG)2-5. The uniform distribution of C, Ni, N, and O elements across the entire hollow tubular structures indicates the successful formation of Ni(OH)2/Ni(DMG)2 composite nanotubes.
SEM images of Ni(DMG)2 NRs (a), Ni(OH)2/Ni(DMG)2-1 (b), Ni(OH)2/Ni(DMG)2-3 (c), Ni(OH)2/Ni(DMG)2-5 (d and e), Ni(OH)2/Ni(DMG)2-10 (f).
TEM images (a, b) and the HAADF-STEM image and corresponding EDS mapping images (c) of Ni(OH)2/Ni(DMG)2-5.
The chemical composition and valence state of Ni(OH)2/Ni(DMG)2-5 were analyzed through XPS. The characteristic peaks of C, Ni, N, and O elements observed in the XPS survey spectra of Ni(OH)2/Ni(DMG)2-5 (Fig. 5a) are in accordance with the results from EDS analysis. The C 1s spectrum is showed in Fig. 5b, presenting typical sp2 C–C bonds in Ni(DMG)2 with binding energy at 285.78 eV. The peak at 288.27 eV belongs to C=O bonds, which may attribute to CO2 absorption, while the peak at 284.8 eV is designated for adventitious carbon.26 The presence of Ni2+ in Ni(OH)2/Ni(DMG)2-5 is indicated by the Ni 2p (Fig. 5c), which shows Ni 2p3/2 and Ni 2p1/2 peaks at 854.5 eV and 871.7 eV, along with their corresponding satellite peaks.27,28 N 1s spectrum (Fig. 5d) displays two peaks at 400.08 eV and 403.05 eV, corresponding to C=N (pyrrolic-type N) bonds and its satellite peaks, respectively.26 The O 1s spectrum in Fig. 5e exhibits two peaks at 532.32 eV and 531.17 eV, which can be attributed to OH groups in Ni(DMG)2 and adsorbed oxygen in water. Then XPS results further confirm the successful formation of the Ni(OH)2/Ni(DMG)2 composite nanotubes.
Survey XPS spectra of Ni(OH)2/Ni(DMG)2-5 (a), and C1s (b), Ni 2p (c), N 1s (d), O 1s (e) spectrum.
The initial assessment of the electrochemical properties of Ni(OH)2/Ni(DMG)2 composite materials was conducted through CVs (scan rate, 50 mV s−1) in a 0.1 M NaOH, as depicted in Fig. 6a. Each CV curve displays a set of redox peaks that align with the redox mechanism from Ni2+ to Ni3+, a process explicable through Eq. 1.
| \begin{align} &\text{Ni(OH)$_{2}$/Ni(DMG)$_{2}$} + \text{2OH$^{-}$}\notag\\ &\quad\to \text{NiOOH/Ni(OH)(DMG)$_{2}$} + \text{H$_{2}$O} + \text{2e$^{-}$} \end{align} | (1) |
Additionally, the peak intensity shows a gradual rise with the prolonged duration of hydrothermal treatment, followed by a decline after 5 h. Evidently, Ni(OH)2/Ni(DMG)2-5 presented the highest anodic current intensity, suggesting the appropriate ratio of Ni(OH)2 and Ni(DMG)2 is beneficial to the electrochemical properties. Furthermore, the evaluation of the electrochemically active surface area (ECSA) was conducted to gain deeper insights into the excellent electrocatalytic performance of Ni(OH)2/Ni(DMG)2-5 nanotubes. ECSA was estimated by measuring CVs in a non-Faradaic region at different scan rates ranging from 10 to 150 mV s−1 (Figs. S1a–S1e). The ECSA was determined using the equation ECSA = Cdl/Cs, where Cdl represents the double layer capacitance calculated from the slope of the plot of capacitive current versus scan rates (Fig. S1f), and Cs is the specific capacitance (0.040 mF cm−2). The Cdl and ECSA values of the prepared electrodes are provided in Table S1. The results indicate that as the hydrothermal treatment time increases, the ECSA of Ni(OH)2/Ni(DMG)2 nanotubes gradually increases, reaching a maximum at Ni(OH)2/Ni(DMG)2-5 (3.6825 m2/g), beyond which it starts to decrease. Hence, although prolonging the hydrothermal treatment time may increase the specific surface area of Ni(OH)2/Ni(DMG)2 nanotubes, as indicated by the reduction in tubular length in SEM images, it does not necessarily lead to an increase in their ECSA. Thus, the synergistic effect of the tubular structure and optimal Ni(OH)2 and Ni(DMG)2 ratio enhances the number of electroactive sites on the electrode surface and facilitates the penetration of electrolyte ions during catalytic processes.
(a) CVs of Ni(DMG)2 NRs and series of Ni(OH)2/Ni(DMG)2 in 0.1 M NaOH; (b) CVs of Ni(DMG)2 NRs and Ni(OH)2/Ni(DMG)2-5 in 0.1 M NaOH in presence and absence of 1 mM glucose; (c) CVs of Ni(OH)2/Ni(DMG)2-5 in presence of different amount of glucose and (d) the corresponding linear plot of glucose concentration vs. anodic current.
Figure 6b displays the CVs for Ni(OH)2/Ni(DMG)2-5 in the presence and absence of glucose. Peak current intensities exhibited a significant increase to 1 mM glucose, indicating the excellent catalytic characteristics of Ni(OH)2/Ni(DMG)2-5 in facilitating glucose oxidation. CVs of Ni(OH)2/Ni(DMG)2-5 in presence of glucose with various concentration of 0–3 mM are presented in Fig. 6c. The increasing concentration of glucose is clearly associated with a rise in current response, indicating good responsiveness of Ni(OH)2/Ni(DMG)2-5 to varying amounts of glucose. Additionally, there is a good linear correlation between the anodic current and glucose concentration (Fig. 6d), indicating the potential of Ni(OH)2/Ni(DMG)2-5 as promising non-enzymatic catalysts for glucose sensing applications. Obviously, the inclusion of glucose results in a shift of the anodic peak potential towards a more positive value, possibly due to diffusion limitations at the electrode surface. The description of the electrooxidation of glucose at Ni(OH)2/Ni(DMG)2 composite nanotubes can be illustrated in Fig. 7, along with the Eqs. 1 and 2.
| \begin{equation} \text{Ni$^{3+}$} + \text{C$_{6}$H$_{12}$O$_{6}$}\to \text{Ni$^{2+}$} + \text{C$_{6}$H$_{10}$O$_{6}$} \end{equation} | (2) |
Firstly, Ni2+ in Ni(OH)2 or Ni(DMG)2 underwent oxidation to form highly oxidative Ni3+ under the anodic potential. Subsequently, glucose oxidation to gluconolactone occurred through Ni3+ species on the electrode surface, leading to the transformation of Ni3+ species into Ni2+.
The mechanism of Ni(OH)2/Ni(DMG)2 electrode catalyzed oxidation of glucose.
Figure 8a displays the CVs of Ni(OH)2/Ni(DMG)2-5 under different scan rates (υ) with 1.0 mM glucose in 0.1 M NaOH. It can be observed that the anodic currents (Ipa) of Ni(OH)2/Ni(DMG)2-5 rise as the scan rate increases, and concurrently, their oxidation peak potentials gradually shift towards positive values. Moreover, the diffusion-controlled process is indicated by the linear increase of both Ipa and Ipc with the square root of the scan rate (υ1/2) within the 5–200 mV s−1 range (Fig. 8b), as described by the linear equations Ipa (mA) = 0.0608 υ1/2 (mV s−1)1/2 − 0.09956 (R2 = 0.9964) and Ipc (mA) = −0.03061 υ1/2 (mV s−1)1/2 + 0.080187 (R2 = 0.99615).
(a) CVs of Ni(OH)2/Ni(DMG)2-5 in 0.1 M NaOH containing 0.5 mM glucose with various scan rate (5–200 mV/s) and (b) the linear plots of the square root of the scan rate vs. anodic and cathodic current; (c) EIS of Ni(OH)2/Ni(DMG)2 composite nanotubes and Ni(DMG)2-5 NRs in 0.1 M NaCl containing 5 mM K4[Fe(CN)6]/K3[Fe(CN)6] with an AC amplitude of 5 mV and a frequency of 0.1 Hz–100 kHz (the inset on the left is the enlarged EIS in high frequency and insert on the right is the corresponding equivalent circuit); (d) The amperometric response curves of Ni(OH)2/Ni(DMG)2-5 with applied potential from 0.45 V to 0.65 V.
Figure 8c shows the electrochemical impedance spectroscopy (EIS) for Ni(OH)2/Ni(DMG)2 composite nanotubes and Ni(DMG)2 NRs electrodes in 0.1 M NaCl containing 5 mM K4[Fe(CN)6]/K3[Fe(CN)6], in order to further investigate the electrochemical behavior of the modified electrodes. All Nyquist plots exhibit a semicircle in the high-frequency region and a straight line in the low-frequency region. These correspond to the charge transfer-controlled process and the diffusion-controlled process, respectively. The appropriate equivalent circuit obtained by fitting the measured EIS is depicted in insert of Fig. 8c, and the corresponding parameters are listed in Table S2. This model comprises the ohmic resistance of the electrolyte (Rs), a double layer capacitance (CPE), the charge-transfer resistance (Rct), and the Warburg impedance (Zw). The Rct of Ni(OH)2/Ni(DMG)2-5 (2.16 × 103 Ω) is markedly lower than the Rct of Ni(DMG)2 NRs (6.46 × 103 Ω). The improved overall conductivity of Ni(OH)2/Ni(DMG)2-5, along with the increased release of surface active sites from their tubular structures, may account for the improved electrochemical performance for glucose sensing applications.
A real-time amperometric investigation is conducted to examine the detection sensitivity of Ni(OH)2/Ni(DMG)2-5. Figure 8d illustrates how current response of Ni(OH)2/Ni(DMG)2-5 changes with varying potentials during stepwise addition of glucose. The amperometric current response shows a gradual increase as the applied potential increases. Given the likelihood of increased noise currents at higher voltages, the optimal potential for amperometric detection of glucose was chosen to be 0.60 V, in accordance with the previously mentioned CV results.
Figure 9a illustrates the amperometric I-t responses of Ni(DMG)2 NRs and series of Ni(OH)2/Ni(DMG)2 materials at 0.60 V upon the incremental introduction of glucose into the 0.1 M NaOH with continuous stirring. After injecting a certain amount of glucose into the NaOH alkaline solution, each electrode promptly exhibited a response, and a subsequent change in current towards a stable state was observed following each addition. Moreover, the Ni(OH)2/Ni(DMG)2-5 displayed the highest current response among all the materials, which may result from the quick absorption and activation of glucose on Ni(OH)2/Ni(DMG)2-5 nanocomposite’s surface. Figure 9b illustrates the linear relationship between current and glucose concentration for Ni(OH)2/Ni(DMG)2-5. A good linear relationship between glucose concentration (1–8000 µM) and current density can be achieved on Ni(OH)2/Ni(DMG)2-5 with the fitting equation of I (mA) = 0.0473c (mM) + 0.00647 (R2 = 0.996). The detection limit was estimated to be 0.33 µM (S/N = 3) and the sensitivity is about 240.91 µA mM−1 cm−2, suggesting the good sensing performance of Ni(OH)2/Ni(DMG)2-5 for glucose detection. Furthermore, glucose sensing performance of Ni(OH)2/Ni(DMG)2-5 has been compared to that of previously reported nonenzymatic sensors (Table 1), revealing its potential as a promising electrocatalytic material for glucose sensors. The selectivity of Ni(OH)2/Ni(DMG)2-5 was also assessed through measuring I-t curves while introducing glucose and a specific quantity of interferences into a NaOH (0.1 M) solution. Figure 9c illustrates that Ni(OH)2/Ni(DMG)2-5 exhibited noteworthy current signals in the presence of 0.5 mM glucose, whereas the introduction of 0.1 mM interferences resulted in only negligible responses. Ni(OH)2/Ni(DMG)2-5 exhibits valuable selectivity due to the fact that the glucose concentration in a physiological environment is over 30 times greater than that of interfering species. The feasibility of the Ni(OH)2/Ni(DMG)2-5 sensor was assessed by employing amperometric methods to measure the glucose concentration in serum samples. Figure 9d displays the I-t curves, illustrating the progressive addition of glucose and serum samples to the analytical solution. The serum glucose concentration was determined by comparing the current responses of a serum sample with those of a standard glucose solution. The calculated recoveries fall within an acceptable range (Table 2), indicating the potential suitability of Ni(OH)2/Ni(DMG)2-5 for analyzing real serum samples.
(a) Amperometric response of Ni(DMG)2 NRs and series Ni(OH)2/Ni(DMG)2 to successive addition glucose in 0.1 M NaOH solution at 0.60 V; (b) the Plot of linear relationship between current density and glucose concentration for Ni(OH)2/Ni(DMG)2-5; (c) Current response of Ni(OH)2/Ni(DMG)2-5 to successive addition of glucose and interferences in 0.1 M NaOH solution; (d) the typical I-t curves of Ni(OH)2/Ni(DMG)2-5 with the addition of glucose and serum samples into the analytical solution.
| Electrode materials |
Linear range (µM) |
Detection limit (µM) |
Sensitivity (µA mM−1 cm−2) |
References |
|---|---|---|---|---|
| CoFe PB | 100–8200 | 67 | 18.69 | 29 |
| Cu@Pani/MoS2 | 100–11000 | 1.78 | 69.82 | 30 |
| MXene/NiCo-LDH | 2–4096 | 0.53 | 64.75 | 31 |
| Tremella-like CoS | 5–1000 | 1.5 | 139.35 | 32 |
| Pt/Ni@rGO | 20–5000 | 6.3 | 117.92 | 33 |
| Pd–Ni@f-MWCNT | 10–1400 | 0.026 | 71 | 34 |
| CoMn2O4@Ni(OH)2 | 8.5–1830.5 | 0.264 | 0.00646 | 28 |
| Ni(OH)2/Ni(DGM)2-5 | 1–8000 | 0.35 | 240.91 | This work |
| Detection Instrument |
Added (µM) |
Found (µM) |
Recovery (%) |
RDS% (N = 3) |
|---|---|---|---|---|
| CHI-630D Workstation |
10 | 10.00 | 100.02 | 2.62 |
| 20 | 20.41 | 102.06 | 0.218 | |
| Portable Workstation |
10 | 10.07 | 100.65 | 1.20 |
| 20 | 20.52 | 102.60 | 2.98 |
The amperometric I-t response was also recorded to assess the performance of the glucose sensing device based on smartphones. As shown in Fig. 10a, the device built on smartphone technology comprises a microelectrochemical workstation, smartphone, and corresponding electrodes. Additionally, an App serves as the interactive interface connecting users to the system. Figure 10b displays the typical I-t curves of Ni(OH)2/Ni(DMG)2-5 at 0.60 V on this device with the sequential incorporation of glucose. Insets are the corresponding linear plots illustrating the current response against glucose concentration. The addition of glucose also results in a swift current response, leading promptly to a steady state. Furthermore, the Ni(OH)2/Ni(DMG)2-5 electrode exhibits a linear response behavior within the range of 10 to 8000 µM, accompanied by a correlation coefficient of 0.998. The sensitivity is determined to be approximately 262.80 µA mM−1 cm−2, with the estimated LOD of 3.3 µM (S/N = 3). The investigation of anti-interference capabilities of Ni(OH)2/Ni(DMG)2-5 electrodes with a smartphone device involves recording I-t curves sequentially with the introduction of glucose, uric acid, glusate, proline, NaCl, valine, lysine, and glucose. As depicted in Fig. 10c, Ni(OH)2/Ni(DMG)2-5 exhibited satisfactory anti-interference capability. Figure 10d illustrates the typical I-t curves on the smartphone-based glucose sensing device by adding standard glucose solutions and serum samples into 0.1 M NaOH. The outcomes derived from the sensor based on a smartphone were additionally compared with the results from the sensor based on the CHI potentiostat (Table 2). The smartphone-based sensors yielded recoveries ranging from 100.65 % to 102.60 %, and the %RSD values ranged from 1.20 % to 2.98 %, closely matching the results obtained from the CHI potentiostat-based sensor. The findings indicated that the glucose sensing device based on smartphones is feasibly favorable for determining glucose levels in serum samples.
(a) The photo of the smartphone-based glucose sensing system (inset is the sideview of the electrodes system); (b) Amperometric response of Ni(OH)2/Ni(DMG)2-5 to successive addition glucose in 0.1 M NaOH solution at 0.60 V (insert is the linear plot current density vs. glucose concentration); (c) Current response of Ni(OH)2/Ni(DMG)2-5 to successive addition of glucose and interferences in 0.1 M NaOH solution; (d) the typical I-t curves of Ni(OH)2/Ni(DMG)2-5 with the addition of glucose and serum samples into the analytical solution.
To delve deeper into the evaluation of the nonenzymatic glucose sensor’s performance, the reproducibility and stability of Ni(OH)2/Ni(DMG)2-5 were also evaluated. Figure S2a illustrates the measurement of current responses for 1 mM glucose on Ni(OH)2/Ni(DMG)2-5 using six different electrodes, all demonstrating similar current responses. The calculated RSD is 2.9 %, affirming the sensors’ excellent reproducibility. Figure S2b illustrates the continuous measurement of the current response of a single Ni(OH)2/Ni(DMG)2-5 electrode to 1 mM glucose over a period of 6 consecutive days. The findings reveal that the glucose sensor maintains 91.3 % of its initial value after 6 days, indicating excellent stability.
In summary, the composite nanotubes of Ni(OH)2/Ni(DMG)2 were generated through hydrothermal treatment of Ni(DMG)2 nanorods in an alkaline solution. As the processing time of Ni(DMG)2 NRs increases, the proportion of Ni(OH)2 gradually rises in Ni(OH)2/Ni(DMG)2 composites. The Ni(OH)2/Ni(DMG)2-5 sensor exhibits excellent glucose sensing performance due to the advantages of high surface area, enriched active sites, and shortened electron transmission distances. Smartphone based portable sensors utilizing Ni(OH)2/Ni(DMG)2-5 electrodes showed reliable glucose sensing capabilities, featuring a broad linear range (10 µM–8 mM), high sensitivity (262.80 µA mM−1 cm−2), and a low detection limit (3.3 µM), comparable to traditional electrochemical workstation-based sensors. The portable sensor exhibited good specificity for detecting glucose in presence of other interference components. The sensor is additionally utilized to detect glucose in serum samples, demonstrating promising potential for the analysis of actual samples.
This work was financially supported by Zhejiang Province Natural Science of China (No. LY22B060009).
The data that support the findings of this study are openly available under the terms of the designated Creative Commons License in J-STAGE Data at https://doi.org/10.50892/data.electrochemistry.25345795.
Chengqi Feng: Investigation (Lead), Writing – original draft (Lead)
Zhiyuan Chen: Data curation (Equal), Investigation (Supporting)
Haoyong Yin: Supervision (Lead), Writing – review & editing (Lead)
Jianying Gong: Data curation (Equal), Resources (Supporting)
Hui Wang: Methodology (Equal), Visualization (Equal)
Cancan Wang: Data curation (Supporting), Investigation (Supporting)
Ling Wang: Conceptualization (Equal), Supervision (Supporting), Validation (Equal)
The authors declare no conflict of interest in the manuscript.
Natural Science Foundation of Zhejiang Province: LY22B060009
H. Yin: ECSJ Active Member
