1、一步水热法合成超低电荷转移阻抗的碳材料及其葡萄糖检测性能研究（英文） 胡博韬 刘仁材 陈靖容 赵湛 张淑真 康沛伦 College of Materials Science and Opti-Electronic Technology,University of Chinese Academy of Sciences School of Electronic,Electrical and Communication Engineering,University of Chinese Academy of Sciences State Key Lab of Transducer Technolo
2、gy,Institute of Electronics,Chinese Academy of Sciences Department of Electric Engineering,I-Shou University Cardiovascular Surgery,Department of Surgery,Kaohsiung Veterans General Hospital 摘 要： 水热碳材料具有较好的水溶性, 但是通常表现为绝缘性, 因此提高水热碳材料的导电性仍然是一个重大挑战.化学掺杂已经被证实能够显著提高碳材料的导电性, 但目前尚没有一种简单且绿色的方法制备高灵敏度水热碳基的电化学传
3、感器.本文在水热反应体系中用 L-半胱氨酸和葡萄糖合成了超低电子转移阻抗的氮硫掺杂碳材料, 随后分析了材料的形貌、结构和电化学性质.氮硫掺杂碳修饰电极电子转移阻抗 (46) 大约是非掺杂碳修饰电极 (476) 的 1/10.氮硫掺杂碳材料制备的葡萄糖传感器具有较宽线性范围 (502500mol L -1) , 低的检测限 (1.77mol L -1, S/N=3) 和高的灵敏度 (0.0554A cm -2mol L -1) .GCE/NS-C/GOx/nafion 电极的米氏常数为 0.769 mmol L-1, 表明 NS-C 负载的葡萄糖氧化酶 (GOx) 对葡萄糖具有较高亲和力.本研究
4、提出以水热法合成具有高电导性的碳材料, 并应用于高性能的葡萄糖传感器.作者简介：Jen-Tsai Liu , Jen-Tsai Liu is an associate professor at the University of Chinese Academy of Sciences. He received his bachelor degree in 2002 and master degree in 2004 from I-Shou University, and his PhD in 2010 in chemical and materials engineering from Cen
5、tral University, Taiwan. His current research has been mainly focused on biosensors and bioelectrics.作者简介：Ching-Jung Chen , Ching-Jung Chen is an associate professor at the University of Chinese Academy of Sciences. She received his bachelor degree in 2002 and master degree in 2004 from I-Shou Univ
6、ersity, and her PhD in 2010 in electrical engineering from Central University, Taiwan. Her current research has been mainly focused on biosensors, bioelectrics and biomaterials.作者简介：Botao Hu received his bachelor degree from Anhui Normal University. He is now a master candidate at the University of
7、Chinese Academy of Sciences (UCAS) and his research is focused on the carbon materials.收稿日期：28 June 2017基金：supported by the National Basic Research Program of China (973 Program, 2014CB931900) Ultra-low charge transfer resistance carbons by onepot hydrothermal method for glucose sensingBotao Hu Jen-
8、Tsai Liu Ching-Jung Chen Zhan Zhao Shwu Jen Chang Pei-Leun Kang College of Materials Science and Opti-Electronic Technology, University of Chinese Academy of Sciences; School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences; Department of Electric En
9、gineering, I-Shou University; Cardiovascular Surgery, Department of Surgery, Kaohsiung Veterans General Hospital; Abstract： Hydrothermal carbon (HTC) is typically welldispersed, but it remains a great challenge for HTC to become conductive. Co-doping with heteroatoms has been confirmed to be an effe
10、ctive strategy to significantly promote the electrical conductivity of carbon. Moreover, there is no simple and green method to construct sensitive HTC based electrochemical biosensors until now. In this paper, N and S dualdoped carbon (NS-C) with ultra-low charge transfer resistance is easily synth
11、esized from L-cysteine and glucose in a hydrothermal reaction system. The morphology, structural properties and electrochemical properties of the as-prepared NS-C are analyzed. In comparison with the undoped hydrothermal (UC) modified glassy carbon electrode (GCE) , the charge transfer resistance of
12、 UC (476 ) is ten times the value of NSC (46 ) . The developed biosensor shows a better performance to detect glucose in a wide concentration range (502500mol L -1) with the detection limit of 1.77 mol L -1 (S/N=3) and a high sensitivity (0.0554 A cm -2mol -1 L) . The apparent Michaelis-Menten const
13、ant value of GCE/NS-C/GOx/nafion modified electrode is 0.769 mmol L-1, indicating a high affinity of glucose oxidase to glucose. These results demonstrate that the hydrothermal method is an effective way for preparing high electrical conductivity carbon with excellent performances in biosensor appli
14、cation.Keyword： hydrothermal method; glucose biosensor; charge transfer resistance; heteroatom doped carbon; electrochemical behavior; Received： 28 June 2017INTRODUCTIONCarbon has many advantages such as abundant source and fine chemical stability.Carbon materials have attracted increasing attention
15、 because of its remarkable electronic1, optical2, mechanical3and catalytic4, 5properties.These characteristics make it one of the most common electrode materials applied in electrochemical sensing platforms6, 7.Carbon based electrochemical biosensors have been extensively used in many hot fields suc
16、h as environmental analysis, food industry and clinical testing because of their unique electrochemical properties7.Recently, many investigations have been focused on finding a simple, green and low toxic process to synthesize carbon materials with excellent electrical properties.The chemical vapor
17、deposition (CVD) method8, template method9, arc discharge method10and high temperature pyrolysis method11to produce carbon materials normally rely on very harsh and multistep processes, and a large consumption of energy and many chemical sources.By comparison, hydrothermal synthetic approach is a gr
18、een12, non-toxic, cheap and sustainable way to obtain carbon materials from biomass13, 14.The hydrothermal carbon (HTC) products synthesized in comparatively mild condition are mostly disordered amorphous carbon, resulting in poor conductivity14, 15and large electron transfer resistance.Although man
19、y researches have been focused on the field of fluorescence because of abundant functional groups on the carbon surface2, a few studies have used HTC to fabricate electrochemical sensors.For example, graphene-multiwalled carbon nanotubes composite (G-MWCNTs) 16was prepared by an in situ hydrothermal
20、 process and the molecularly imprinted polymer and G-MWCNTs modified glassy carbon electrode (GCE) was investigated for rutin sensing.The linear response range was 0.011.0mol Land the detection limit was 0.005mol Lat a signal-to-noise ratio of 3.The hydrothermal method was also used for synthesis of
21、 graphene quantum dots (GQD) .The response of the developed biosensor to glucose was observed in the range of 51270mol L, and the detection limit was calculated to be 1.73mol Lwith a sensitivity of 0.085A cmmolL17.By contrast with graphene nanosheets modified GCE electrode18and acetylene black modif
22、ied GCE electrode19, the HTC based electrodes have less unbound electron, larger transfer resistance in the electrochemical impedance spectra and result in poor sensitivity when applied in biosensors20.Thus, enhancing electron transfer of HTC is one of the most important issues.In the previous studi
23、es, researchers have attempted to improve the electrical conductivity of carbon materials by chemical doping2126and increased crystallized graphene structure27, such as using H2SO4to strip off O and H from the COH, CH, and C=O groups, to form the electro-conductive graphite structure;however, the ef
24、fect is limited.Several studies have shown that doping carbon materials with heteroatoms (nitrogen, boron, sulfur and phosphorous) is a promising way to further improve the electrical conductivity2126, such as doping nitrogen into carbon to form pyridine-N, pyrroleN and graphitic-N structure.These d
25、onating electron structures can form enhanced-bonding to promote electron transfer28, 29which is advantageous for enhancing electrochemical sensing performances30.Wang et al.31reported a glucose sensor based on N-doped graphene (N-G) by using nitrogen plasma treatment of graphene, and the results sh
26、owed that the N-doped graphene modified glucose oxidase (GOx) electrode displayed a high electrocatalytic activity for reduction of H2O2with high sensitivity and selectivity for glucose sensing.Ji et al.32obtained N-doped carbon dots synthesised from polyacrylamide.The N-doped carbon dots showed str
27、ong electrocatalysis to the reduction of O2and the N-doped carbon dots based biosensor responded efficiently to glucose at the concentration range of 1 to 12 mmol Lwith a detection limit of0.25 mmol L.Similar to nitrogen, sulfur doping can also improve electron conductivity22, 33.N and S co-doping h
28、as been confirmed to be an effective strategy to significantly promote the electrocatalytic activity of carbon.Chen et al.22synthesized N and S dual-doped graphene (NS-G) using a simple two-step solvothermal method.The dualdoping of N and S in carbon not only modulated its electrical properties, but
29、 also introduced active sites by the doping heteroatoms34.Comparing GOx/N-G/GCE with GOx/NS-G/GCE, the latter showed a lower detect limit, a wider detection range, and a higher sensitivity towards glucose detection.Tian et al.35used a one-step and low cost microwave-assisted solvothermal approach to
30、 synthesize NS-G (N:6.8 at.%, S:2.1 at.%) .The NS-G was then evaluated as an electrocatalyst for H2O2reduction and exhibited a higher electrochemical performance than its undoped or mono-doped counterparts due to the synergistic effect of N, S co-doping.But solvothermal synthesis involves organic so
31、lvents, and it is not suitable for fabricating biocompatible electrodes for enzyme immobilization36.The procedure of hydrothermal method, however, is green and non-toxic, making it a better choice for fabricating biocompatible electrodes.Considering the aforementioned merits, we proposed a simple an
32、d green one-step hydrothermal method to synthesize N and S dual-doped carbon by using glucose as the sustainable precursor and L-cysteine as the N/S source.To explore the structural and surface properties of NS-C, the morphology, crystal and chemical structure characterizations were carried out.The
33、electrochemical behaviors of the NS-C modified electrodes were further characterized by cyclic voltammograms (CV) , chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) .The electrochemical performance of the NS-C modified electrode was compared with undoped carbon (UC) , and the
34、NS-C as a GOx platform was examined as a sensitive glucose biosensor.EXPERIMENTAL SECTIONChemicals and reagentsGlucose oxidase was obtained from Sigma Chemical (USA) , and the solution was prepared in 0.1 mol Lphosphate buffer solution (PBS) with p H 7.4 and stored at 4C before use.Glucose, concentr
35、ated sulfuric acid (H2SO4) , sodium hydroxide, K3Fe (CN) 6, K4Fe (CN) 6and L-cysteine were purchased from Beijing Chemical Reagent Co., Ltd.Deionized water (18.2 Mcm) was obtained from an Explorer Series ultrapure water purification system (Explorer Technic Co., Ltd., China) .All other chemical reag
36、ents were analytical grade and used without purification.Synthesis of NS-CN and S dual-doped carbon was prepared through a onestep hydrothermal method by using glucose, L-cysteine and sulfuric acid (Fig.1a) .L-cysteine acts as a functionalization agent to provide the source for N and S doping.Fig.1a
37、 shows pyridinc-N, pyrrolic-N, and graphitic-N in the carbon structure.The amine and thiol group of L-cysteine can react with the aldehyde group of the glucose.These so-called Maillard reactions play a major role in the incorporation of heteroatoms during HTC28, 29.Briefly, 1.5 g of glucose and 0.4
38、g of L-cysteine or its derivative were dissolved in 10 g of double distilled H2O, followed by the introduction of 10 m L of concentrated sulfuric acid (H2SO4) .The mixture was then treated by the hydrothermal method in Teflon-lined stainless-steel autoclave (50 m L) .The autoclave was placed in a pr
39、eheated furnace at 180C for 5 h, after which it was allowed to cool down to room temperature.The brown/black solid product was collected by filtration and neutralized with sodium hydroxide.The samples were washed several times by water and ethanol, and dried at 70C overnight for further characteriza
40、tion.Figure 1 Schematic representation of the synthesis route of NS-C (a) and the GCE/NS-C/GOx/nafion modified electrode and the mechanism of the oxidation of glucose (b) , catalyzed by GOx and mediated byFe (CN) 6. 下载原图Preparation of NS-C/GOx modified GCEThe GCE (3 mm in diameter) was polished with
41、 polishing paper and alumina/water slurry.Then it was rinsed with double distilled water and ethanol.5L of NS-C solution (5 mg m L) was cast on the surface of GCE and dried at60C to obtain a homogeneous NS-C film.Then 5L of GOx suspension (0.5 mg m L) was cast onto the NS-C/GCE surface to prepare th
42、e NS-C/GOx modified GCE.Finally, 5L nafion solutions (0.5 mg m L) was cast onto the electrode surface and dried at ambient temperature to produce the GCE/NS-C/GOx/nafion.The electrode was stored at 4C when not in use.Surface morphology and composition analysisThe morphologies of the as-prepared samp
43、les were studied by scanning electron microscopy (SEM, Hitachi S-4800, Japan) and transmission electron microscopy (TEM, Tecnai G2T20, USA) .The phase identification of the sample was characterized by X-ray diffraction (XRD, Persee XD-3, China) .The XRD equipped with Cu Kradiation source was in the
44、range from 1060 (the scan speed is 2min) .The chemical status of elements were investigated by X-ray photoelectron spectroscopy (XPS, Thermo ESCALAB 250Xi, USA) , which used Mg Kradiation as the exciting source.Further structural information of carbon materials was obtained from Raman spectroscopy (
45、Renishaw in Via plus, UK) .Electrochemical measurementsNS-C as a GOx platform for the construction of GOxbased glucose biosensor is illustrated by Fig.1b.The electrochemical experiments were carried out using an electrochemical analyser (CHI660E, Shanghai) at room temperature.The three-electrode sys
46、tem is composed of reference electrode, auxiliary electrode and working electrode, in which Ag/Ag Cl electrode as the reference electrode, platinum wire as the auxiliary electrode and the prepared electrode as the working electrode.The electrochemical behaviors of the modified electrodes were furthe
47、r investigated by CV, EIS and CA.The basic study of electrode modification was carried out using CV at a scan rate of 50 m V swith a potential range of0.8 to+0.8 V.EIS was performed in 0.1 mol LKCl solution containing 5 mmol LK3Fe (CN) 6/K4Fe (CN) 6 (1:1) as a supporting electrolyte at its open circ
48、uit potential with a frequency range from 1.010to 1.010Hz.The alternating current voltage was 5 m V.CA was used for the measurement of different concentrations of glucose solution.The initial potential was 0.3 V, each with a duration time of 50 s.Figure 2 Images of the NS-C solid products (a) and af
49、ter dispersed in water (b) , SEM of solid products after hydrothermally treated pure glucose (c) , TEM (d) and HRTEM (e) of NS-C, and XRD patterns of HTC and NS-C (f) . 下载原图RESULTS AND DISCUSSIONMorphologies and structures of NS-CA photograph of the black solid products is shown in Fig.2a, and the yield of solid products is 48%.The solid products could be dispersed in distilled water and result in the black suspension (Fig.2b) .Fig.2c sh
