Synthesis and Electrochemical Sensing Toward Heavy Metals of Bunch-like Bismuth Nanostructures
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Large-scale bunch-like bismuth (Bi) nanostructures were the first time to be synthesized via two-step electrochemical deposition. The growth mechanism of the nanostructures was discussed. Such a designed bunch-like Bi electrode has high sensitivity to detect the heavy metal ions due to its unique three-dimensional structures and strong ability of adsorbing the heavy metal ions. The bunch-like Bi electrode’s detection of heavy metals was statically performed using anodic stripping voltammetry (ASV). The detection in the Pb(II) concentration range of 2.5–50 μg/l was also performed. Based on the experimental results, this bunch-like Bi electrode can be considered as an interesting alternative to common mercury electrodes and bismuth film electrodes for possible use in electrochemical studies and electroanalytical applications.
KeywordsBismuth Nanostructure Electrochemical deposition
Mercury electrode has gained wide acceptance for the electrochemical stripping analysis of heavy metal. However, the toxicity of mercury and its difficulties in handling, storage, and disposal may severely restrict its use as an electrode material [1, 2, 3, 4, 5]. Recently, a bismuth electrode as a favorable replacement for a mercury electrode has been introduced, because of behavior similar to the mercury electrode and the environmentally friendly nature of bismuth [6, 7, 8, 9, 10].
To date, the research of the bismuth electrode mainly focused on the bismuth film electrodes (BiFEs) [11, 12, 13, 14, 15, 16]. However, the three-dimensional nanostructures with large specific surface area and high surface free energy, which is superior to the film in the chemical sensor applications, have aroused much attention in recent years. In addition, electrochemistry offers convenient and elegant techniques for the fabrication of nanostructures [17, 18]. The properties of these nanostructures can be controlled by their electrochemical potential, a variable that is not available in vacuum or in air. Therefore, a three-dimensional ordered bismuth electrode formatted via the electrochemistry method should be an ideal electrode for effectively improving the properties of detecting heavy metal ions.
Herein, a new self-organized morphology of Bi (the bunch-like Bismuth) is the first time to be prepared by a two-step template synthesis using electrodeposition. The growth habits and growth mechanism of this electrode were discussed. On account of the unique structure, this morphology of bismuth has been at the first time studied as an electrode, which has a good performance to detecting the heavy metal ions.
The electrolyte solution contained 20 g/l BiCl3, 50 g/l tartaric acid, 95 g/l glycerol, and 70 g/l NaCl at room temperature. The pH of the solution was strictly controlled at a value of 2 by the addition of nitric acid. Stock solution of 0.01 M Pb2+, Cd2+, Hg2+, Cu2+ was prepared by dissolving Pb(NO3)2, Cd(NO3)2, Cu(NO3)2, HgCl2(Shanghai Reagent Corporation, China) in deionized water and then diluted to various concentrations of working solutions. 0.2 M HAc-NaAc buffer solutions (pH: 4.4) were used as the supporting electrolyte for heavy metal determination.
All electrochemical experiments were performed with a CHI660C (Chen Hua Shanghai, China) workstation at room temperature, employing a three electrode system consisting of a saturated calomel electrode (SCE) reference electrode, an alumina/Au composite working electrode (with diameter of 4.0 mm), and a Pt wire counter electrode. Mesh-like thin Au layer only covering the surface of the membrane and still leaving the pores open was sputtered on one planar surface side of the AAO template to make the surface electrically conductive, and a Cu wire was connected to the Au layer with Ag paint. The Au side and edges of the alumina template were then insulated with clear nail polish to ensure the electrodeposition could only occur on the other side of the AAO.
Preparation and Analytical Procedure
A potential of −1.5 V was applied between cathode and anode. The pulse time was 0.4 ms and the time between pulses was 0.8 ms. After deposition of 40 min, the nano bismuth electrode array was fabricated. Step 2: a potential of −2.5 V was applied, the bunch-like Bi microstructures were fabricated, respectively. SWASV was performed under the following conditions:Edep, −1.1 V for 60 s;Esw, 25 mV;Estep, 5 mV;f, 50 Hz; scan range, −1.2–0 V.
Results and Discussion
In summary, we have successfully fabricated a single-crystalline bunch-like Bi nanostructure using a two-step electrodeposition in anodic alumina membranes for the first time. We have demonstrated that the stripping voltammetric performance of this bunch-like bismuth electrode compares favorably with that of common mercury-based electrodes. The higher sensitivity of the bunch-like bismuth electrodes makes it suitable for detecting metals more sensitive than other bismuth electrode.
The authors acknowledge the financial support from the Chinese National Key Basic Research Special Found (Grant No. 2006CB921704), the NSF of China (Grant No. 60976014), and the Key Basic Research Project of Scientific and Technology Committee of Shanghai (Grant No. 09DJ1400200).
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