Electrocatalytic oxidation of glucose on nanoporous gold membranes
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- Li, Q., Cui, S. & Yan, X. J Solid State Electrochem (2012) 16: 1099. doi:10.1007/s10008-011-1501-x
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With characteristic of structural integrity and high surface area, nanoporous gold (NPG) prepared by dealloying method is proposed to be a highly sensitive catalyst for glucose electrooxidation. It can be found that a-NPG which obtained by electrochemical corrosion method has the highest sensitivity for glucose electrooxidation among the three studied samples. Under alkaline conditions, the catalytic current density of a-NPG is over 1.5 times and 17 times higher than that of f-NPG (prepared by free corrosion) and poly-Au electrode, respectively. Using a-NPG sample for glucose detection, the obtained minimum sensible concentration are 413 nM in alkaline media and 1 μM in neutral solutions. The a-NPG electrode also shows stable recovery and reproducibility characteristics. These results indicate that NPG may work as an efficient electrode material for electrochemical sensors and a promising catalyst for alkaline glucose fuel cells.
KeywordsGlucose oxidationNanoporous goldElectrocatalysisDetectionNonenzymatic sensor
Electrocatalytic oxidation of glucose, as a key reaction in the fields of sensors [25, 29] and fuel cells [13, 19], has been widely investigated during the past decades. Nanomaterials with special surface structures and properties provide great opportunities for this oxidation reaction . Besides the widely used nanoparticles [30, 33, 34], the reported nanostructures also include porous materials [9, 15, 22]. Due to the three-dimensional and continuous pore channels, porous metallic materials possess excellent performances for catalysis, sensing, and biotechnology [6, 8, 10, 18]. Among various porous metallic materials, the nanoporous gold (NPG), a unique class of functional materials for catalytic applications [21, 27, 28], have been extensively studied since Au would not be self-poisoned [14, 24, 26], and its activity could be regenerated after removing the oxidation products on the surface [2, 3]. Although there are so many approaches to achieve this desired material [16, 17], the simple dealloying process  represents a facile method to fabricate NPG with extremely clean surface, which is a well-known significant factor for electrochemistry.
As have been proved in previous works, NPG shows superior activity toward a series of important electrochemical reaction including methanol oxidation [12, 32], formic acid oxidation , thus are regarded as promising electrocatalysts in glucose electrooxidation. Recently, Ma et al. prepared nanoporous Au–Ag alloy with different Ag content, and they found the existence of a tiny amount of silver can obviously enhanced catalytic activity for the electrooxidation of glucose . In this work, our interest is focused on the use of NPG membranes in glucose detection and further in nonenzymatic biosensors. Systematical studies demonstrate that NPG shows much higher electrocatalytic activity and sensitivity toward glucose oxidation in alkaline and neutral solutions than polycrystalline gold. Additionally, glucose detection under physiological condition is also monitored. The results indicate that NPG is a potential material to be used in nonenzymatic glucose biosensor.
Reagents and apparatus
All chemicals were of analytical grade and used as purchased without further purification. d-Glucose, NaOH, HNO3 (67%), Na2HPO4·12H2O, and NaH2PO4·2H2O were obtained from Sinopharm Chemical Reagent Co., Ltd. Ultra pure water (18.2 MΩ) was used throughout the experiments, and 0.1 M phosphate buffer solutions (PBS) were prepared with pH 7.4. Au/Ag alloy (50:50, wt.%) leaves with thickness of 100 nm (Sepp Leaf Products, New York) were used for NPG fabrication. The surface structure of NPG was observed use JSM-6700F SEM. All electrochemical measurements were performed at room temperature in a three-electrode electrochemical cell with a CHI 760C electrochemical workstation (Shanghai). Saturated calomel electrode (SCE) was selected as reference electrode in all electrochemical measurements and a pure Pt foil as the counter electrode. Both NaOH and PBS solutions were purged with high pure nitrogen (99.999%) for 20 min prior to measuring.
Preparation of NPG electrodes
NPG with 35-nm pore size was made by dealloying commercial 12-carat white gold (Au50Ag50 wt.%) membrane in concentrated (67%) nitric acid (free corrosion) for 30 min at 303 K (mark as f-NPG). The NPG with 12-nm pore size was obtained by electrochemical dealloying under anodic potential (600 mV) for 25 s at 303 K on a CHI 760C (mark as a-NPG). Subsequently, these two NPG samples were immediately transferred to ultra-pure water and repeatedly washed to remove Ag+ and NO3-. Then, the membranes were affixed onto a clean glassy carbon electrode and fixed with 2 μL dilute Nafion solution (0.5 wt.%). The as-prepared NPG electrodes were dried at room temperature before measuring.
Results and discussion
Surface structure of the NPG
Electrocatalytic properties of NPG for glucose oxidation in alkaline media
A detailed description of glucose oxidation peaks in Fig. 2
−0.6 ∼ −0.16 V
−0.15 ∼ 0.3 V
74.8 mA cm-2
−0.6 ∼ 0.1 V
−0.8 ∼ −0.5 V
−0.5 ∼ 0.3 V
831.2 mA cm-
−0.8 ∼ 0.1 V
−0.9 ∼ −0.5 V
−0.5 ∼ −0.24 V
1270.2 mA cm-2
−0.9 ∼ −0.01 V
Electrocatalytic properties of a-NPG for glucose oxidation in neutral media
The data of reproducibility on a-NPG electrodes
Current density, μA cm-2
NPG membranes, a type of porous nanostructures, were fabricated by dealloying and were studied for glucose electrooxidation and detection. Taking advantage of the smallest pore size and largest active surface area, a-NPG exhibits the best activity and sensitivity toward the reaction both in neutral and alkaline conditions. The detection results in neutral media also promised that a-NPG exhibited excellent anti-interference from AA, urea, and sucrose at normal physiological levels and reproducibility characteristics. The a-NPG is thus expected to be a promising electrocatalyst for application in the fields of glucose electrochemical sensors and fuel cells.
We thank Prof. Y. Ding and Houyi Ma for valuable discussions and sharing their nanomaterials and facilities.