专业英语写作作业.docx

1、专业英语写作作业Non-enzymatic Detection of Glucose based on Dendrite-like gold nanostructuresAbstractDendrite-like gold nanostructures (DGNs) were directly electrodeposited onto the surface of a glassy carbon electrode (GCE) via the potentiostatic method without any templates, surfactants, or stabilizers. T

2、he effects of the deposition time, potential and the concentration of precursor solution on the evolution of the nanostructure and on the electrocatalytic activity of the DGNs were systematically investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electr

3、ochemical methods including cyclic voltammetry, linear voltammetry and chronoamperometry. The results confirmed that DGNs have good electrocatalytic activity towards the electro-oxidation of glucose in a neutral phosphate buffer solution (PBS, pH 7.4). A non-enzymatic glucose sensor fabricated with

4、the DGNs as an electrocatalyst showed a quick response (less than 2 s), a low detection limit (0.05 mM), a wide and valuable linear range (0.1 - 25 mM), a high sensitivity (190.7 A cm-2 mM-1) and good repeatability and stability. In addition, the commonly interfering species, such as ascorbic acid (

5、AA), uric acid (UA), and 4-acetaminophen (AP), did not cause obvious interference because of the use of a low detection potential (0.15 V vs. Ag/AgCl). This work demonstrates a simple and an effective sensing platform for the non-enzymatic detection of glucose. Keywords： Dendrite-like gold nanostruc

6、tures; Electrodeposition; Glassy carbon electrode; Glucose oxidation; Non-enzymatic glucose sensor 1. IntroductionGlucose sensors have been extensively studied over the past twenty years because of their applications in the prevention and treatment of diabetes mellitus, from which millions of people

7、 suffer 1. Therefore, there has been an increasing demand for the development of inexpensive glucose sensors that have high selectivity, sensitivity, and good stability 2, 3. Most studies are based on glucose oxidase (GOx) bound to electrode transducers, in which hydrogen peroxide is produced from t

8、he oxidation of glucose and can be amperometrically detected to be stoichiometrically related to glucose levels. Although enzymatic detection shows a high sensitivity and a great selectivity, the sensitivity to the environment and the instability are the primary difficulties to overcome. In addition

9、, the oxidation of H2O2 usually requires a relatively high positive potential (usually over + 0.6 V vs. SCE) 4, 5. Many other electroactive species that commonly coexist in biological uids, such as ascorbic acid (AA), uric acid (UA), and 4-acetamidophenol (AP), can also be oxidized at such high pote

10、ntials, and their electrochemical signals thus severely affect the selectivity of the biosensors 6.To overcome these problems, many attempts have been devoted to develop non-enzymatic glucose biosensor using noble metal nanomaterials to substitute the enzyme as electrocatalyst. The majority of these

11、 sensors rely on the current response of glucose oxidation directly at the surface of the nanomaterials modified electrode. Thus the non-enzymatic biosensor exhibited much higher stability for a long period and resistance ability to the environmental factors than the glucose biosensor using enzyme 7

12、, 8. To date, a large amount of metals and oxide nanoparticles, such as Pd 1, 6, Pt 9-13, Au 2, 14-19, CuxO 3, 20 and CeO2 21, have been implemented in electrochemical catalytic reactions. Among these materials, non-enzymatic biosensors using Cu nanomaterials as electrocatalyst for glucose sensing,

13、an alkaline solution environment is usually required. Although Pt nanomaterials show high catalytic properties in neutral buffers to glucose molecules, their intrinsic activities are normally suppressed because they are easily poisoned by intermediates and products generated during the experimental

14、processes 22. Au as a potential candidate has attracted much attention for the unique properties of its nanostructures, such as good conductivity, useful electrocatalytic activity, and biocompatibility 23, 24. Moreover, nanosized gold structures exhibit superior poison resistivity toward the electro

15、-oxidation of glucose due to their large surface-to-volume ratio and the presence of highly active binding sites on the surface of the particles 25. Therefore, using Au nanostructure material as a catalyst would be expected to meet the need of non-enzymatic detection of glucose.Many methods have bee

16、n used to obtain gold nanostructures, such as self-assembly with polymers 26-28, seed-mediated growth 29-32 and thermal-driven attachment 33. However, the application of surfactants, bridging agents and organic solutions in the reactions might reduce the electrocatalytic activity of Au nanoparticles

17、 due to blocking of the active sites. So challenges still exist in the preparation of Au nanostructures with a clean surface and a high catalytic ability. On the other hand, dendrite-like gold nanostructures (DGNs) have received considerable interests for their larger specific surface area and the e

18、xtensive applications in super hydrophobic property, diverse catalytic fields, such as electro-oxidation of ethanol and glucose 19, 24. It is well known that electrodes with increased specific surface areas can provide improved performance for kinetically controlled reactions, such as glucose oxidat

19、ion. However, the influence of the specific surface area on diffusion-controlled reactions is tiny, for example, most interference (AA and UA) oxidation on the electrodes. Thus, fabricating electrodes with high surface areas is a promising method to increase the electrochemical response of glucose w

20、hile limit the impact of interferences reactions 12, 22. This means that dendrite-like gold nanostructures with larger surface area will lead to a higher sensitivity for glucose detection, as well as a better selectivity. However, to our knowledge, a systematic study on the non-enzymatic detection o

21、f glucose using DGNs has not been reported. In this work, the dendrite-like gold nanostructures was fabricated by a potentiostatic method which is very simple and clean. The obtained DGNs with extremely increased specific surface area displayed a high catalytic activity in the oxidation of glucose.

22、Moreover, the normal interferences that coexist in physiological conditions, such as AA, UA, and AP, can be effectively avoided due to the high specific surface area and the lower detection potential. The influence of the electrodepositing conditions, such as the deposition time, deposition potentia

23、l and the concentration of precursor solution, was also investigated to find out the impact factors on the morphology of the gold nanostructures and the catalytic performance in the oxidation of glucose. It is interestingly found that the catalyst material of DGNs generated under the optimized elect

24、rodepositing conditions shows a rapid response and high sensitivity towards the catalytic oxidation of glucose. 2. Experimental Section2.1. Materials HAuCl43H2O was purchased from Aldrich Co., Ltd. Ascorbic acid (AA), uric acid (UA), 4-acetaminophen (AP), glucose, absolute alcohol, Na2HPO412H2O, NaH

25、2PO43H2O, concentrated sulfuric acid (H2SO4) and KCl were obtained from the Sinopharm Chemical Regent Co. Ltd. All the chemicals were of analytical grade. A phosphate buffer solution (PBS, 0.1 M, pH 7.4) was prepared from Na2HPO412H2O and NaH2PO43H2O. Solutions of glucose, AA, UA and AP were prepare

26、d using PBS. Rod-shaped glassy carbon electrodes (GCE, 3 mm in diameter) were obtained from the Gaoss Union Instrument Company, Wuhan, China, and bulk gold electrode (2.0 mm in diameter) was ordered from BAS. Co. Ltd. Both of the electrodes were polished sequentially with slurries of 0.3 and 0.05 m

27、alumina to create a mirror finish, and then they washed sequentially in pure water, ethanol and pure water while sonicating for 1 min in each. After washing, the electrodes were thoroughly rinsed with pure water and dried with nitrogen gas. In all the procedures, the pure water we used was prepared

28、with a Kertone Ultrapure Water System P60-CY (Kertone Water Treatment Co.Ltd, resistivity 18 M.cm). Additionally, all the experimental measurements were carried out at room temperature.2.2. ApparatusesThe size and morphology of the Au nanostructures deposited on the glassy carbon electrode surfaces

29、were characterized with scanning electron microscopy (SEM) and transmission electron microscopy (TEM; FEI TECNAI20, USA). All the electrochemical measurements were carried out with a 550 electrochemical workstation (Gaoss Union Instrument Company, Wuhan, China) in a conventional three-electrode cell

30、. For SEM characterization, we used a removable glassy carbon electrode that could be directly examined under the scanning electron microscope. For TEM characterization, the dendrite-like gold nanostructures were first scraped from the GC electrode and then dispersed in pure water with sonication fo

31、r 1 hour. Subsequently, 10 L of the suspension was casted on a copper mesh, and dried under ambient conditions, and finally transferred into the microscope for observation.2.3. Procedures for preparing the DGN-modified GC electrodeDirect electrodeposition of the DGNs onto the GC electrode surface wa

32、s carried out via a potentiostatic method 19, 34, 35. First, the precursor solution was prepared by dissolving a predetermined amount of HAuCl43H2O into a 0.1 M KCl solution. Then, the treated GC electrode was immersed into the electrolyte solution and used as the working electrode. A clean platinum

33、 wire and a Ag/AgCl electrode were used as the counter and reference electrodes, respectively. Finally, the electrodeposition was performed under potentiostatic mode. The resulting electrodes were thoroughly rinsed several times with pure water. In this work, we systematically investigated the effects of the elect