Electrochemical Sensor for Sensitive Determination of Capsaicin Using Pd Decorated Reduced Graphene Oxide

In this work, the reduced graphene oxide functionalized with poly dimethyl diallyl ammonium chloride (PDDA) modified palladium nanoparticles (PDDA‐rGO/Pd) had been facile synthesized and used as the sensing layer for sensitive determination of capsaicin. The prepared composite was characterized by transmission electron microscopy, UV‐visible absorption spectroscopy. The image demonstrated that Pd nanoparticles were uniformly distributed on the graphene surface. The electrochemical properties of the prepared sensor were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results showed that the nanocomposite exhibits attractive electrocatalytic activity towards the oxidation of capsaicin. This attributed to the synergistic action of the excellent properties of Pd nanoparticles and graphene nanosheets. Under optimized conditions, the electrochemical sensor possessed a dynamic linear range from 0.32 μM to 64 μM with a detection limit of 0.10 μM (S/N=3) for capsaicin detection. Moreover, the cost‐effective and simple fabrication procedure, good reproducibility and stability as well as acceptable accuracy for capsaicin determination in actual samples are also the main advantages of this method, which might have broad application in other amide alkaloid detection.     

二氧化锆/石墨烯复合材料对亚硝酸盐的电化学传感研究

制备了一种二氧化锆/还原氧化石墨烯(ZrO2NPs/rGO)复合材料修饰电极的亚硝酸盐电化学传感器,并成功用于亚硝酸盐的检测.采用循环伏安法和电流-时间曲线考察了修饰电极的电化学行为.实验结果表明,ZrO2NPs/rGO复合材料修饰电极对亚硝酸盐具有良好的电流响应.在最优实验条件下,电流-时间曲线中的电流响应信号与亚硝酸盐浓度在3.0×10Symbolm@@_7～1.0×10Symbolm@@_6 mol/L和1.0×10Symbolm@@_6～6.0×10Symbolm@@_6 mol/L的范围内呈良好的线性关系,检测限为1.0×10Symbolm@@_7 mol/L(S/N 3).该传感器灵敏性高、稳定性和重现性好.使用此传感器检测实际样品香肠中的亚硝酸盐的回收率为93.7％～110.4％,相对标准偏差为1.6％～2.1％.     

Electrochemical Sensor‐Based Ruthenium Nanoparticles on Reduced Graphene Oxide for the Simultaneous Determination of Ethinylestradiol and Amoxicillin

The composite material of reduced graphene and Ru nanoparticles (rGO/RuNP) was obtained by electrochemical oxidation of ruthenium nanoparticles immobilised on the glassy carbon electrode (GCE) surface and used for simultaneous electroanalysis of drugs. There are many discussions in the scientific community about the decrease in therapeutic efficacy of contraceptives when associated with antibiotics. The antibiotic effect of the antagonist can increase the contraceptive excretion levels in urine, indicating a reduction in the body and thus a decrease in the desired effect. Using the DPV technique, it was possible to quantify ethinylestradiol (EE2) and amoxicillin (AMX) with a linear response range, 5.50x10⁻⁸ – 1.20x10⁻⁶ mol L⁻¹, and LOD, 2.04 nmol L⁻¹ and 1.63 nmol L⁻¹, respectively. The results for the electrochemical behaviour of EE2 and AMX using GCE/rGO/RuNP were compared with GCE/rGO and GCE. The GCE/rGO/RuNP showed greater stability and separation anodic peak currents, suitable for the quantification of organic molecules in samples of environmental interest, as well as clinical and food samples.     

基于还原石墨烯/纳米银复合材料的电化学传感器测定双酚A

石墨烯特有的褶皱层状结构以及银纳米粒子良好的催化性能,使其在电化学方面具有良好的应用潜能.本研究以柠檬酸钠为还原剂,通过水热反应原位制备出还原石墨烯/纳米银复合材料(rGO/AgNPs),用于修饰玻碳电极,研究了双酚A的电化学行为.循环伏安法(CV)和方波伏安法(SWV)的实验结果表明,双酚A可以在rGO/AgNPs修饰电极表面发生快速的氧化还原反应,基于此实现了对双酚A的高灵敏检测.在最优条件下,双酚A的氧化峰电流与其浓度在0.1~40.0μmol/L范围内呈良好的线性关系(r2=0.996),检出限为50.7 nmol/L(S/N=3).将其用于实际环境和塑料样品中双酚A的检测,回收率为91.7%~102.9%.     

基于银纳米粒子/氧化石墨烯复合薄膜制备TNP电化学传感器

利用改进的Hummers法制备了氧化石墨烯(GO),以葡萄糖为还原剂直接在GO表面沉积银纳米粒子(AgNPs)得到性能稳定的AgNPs/GO纳米复合材料;基于该纳米复合材料修饰电极构建了一种新型的2,4,6-三硝基苯酚(TNP)电化学传感器。采用原子力显微镜(AFM)、扫描电镜(SEM)、透射电镜(TEM)、紫外可见光谱(UV-Vis)和交流阻抗(EIS)等多种方法对纳米复合薄膜进行了表征;并研究了TNP在复合薄膜修饰电极上的电化学行为和动力学性质。结果表明,AgNPs/GO对TNP有较强的电催化活性,在复合薄膜修饰电极出现一灵敏的氧化峰和3个还原峰;利用氧化峰可对TNP进行定量分析。同时整个电极过程明显不可逆,电极反应受到吸附步骤控制;复合膜电极表面覆盖度为5.617×10-8mol.cm-2,在所研究电位下的速率常数为9.745×10-5cm.s-1。在pH 6.8的磷酸缓冲液中,当富集电位为-0.70 V,富集时间为60 s;TNP氧化峰电流与其浓度在5.0×10-9~1.0×10-7mol.L-1范围内成良好线性关系,相关系数为0.995 8,检出限可达1.0×10-9mol.L-1。所制备的电化学传感器稳定性和选择性较好;用于实际水样中TNP的现场快速检测,加标回收率在97.6%~103.9%之间。     

基于银纳米粒子/氧化石墨烯复合薄膜制备TNP电化学传感器

利用改进的Hummers法制备了氧化石墨烯(GO), 以葡萄糖为还原剂直接在GO表面沉积银纳米粒子(AgNPs)得到性能稳定的AgNPs/GO纳米复合材料;基于该纳米复合材料修饰电极构建了一种新型的2, 4, 6-三硝基苯酚(TNP)电化学传感器。采用原子力显微镜(AFM)、扫描电镜(SEM)、透射电镜(TEM)、紫外可见光谱(UV-Vis)和交流阻抗(EIS)等多种方法对纳米复合薄膜进行了表征;并研究了TNP在复合薄膜修饰电极上的电化学行为和动力学性质。结果表明, AgNPs/GO对TNP有较强的电催化活性, 在复合薄膜修饰电极出现一灵敏的氧化峰和3个还原峰;利用氧化峰可对TNP进行定量分析。同时整个电极过程明显不可逆, 电极反应受到吸附步骤控制;复合膜电极表面覆盖度为5.617×10^-8 mol·cm^-2, 在所研究电位下的速率常数为9.745×10^-5 cm·s^-1。在pH 6.8的磷酸缓冲液中, 当富集电位为-0.70 V, 富集时间为60 s;TNP氧化峰电流与其浓度在5.0×10^-9~1.0×10^-7 mol·L^-1范围内成良好线性关系, 相关系数为0.995 8, 检出限可达1.0×10^-9 mol·L^-1。所制备的电化学传感器稳定性和选择性较好;用于实际水样中TNP的现场快速检测, 加标回收率在 97.6%~103.9%之间。     

DNA Induced FePt Bimetallic Nanoparticles on Reduced Graphene Oxide for Electrochemical Determination of Dopamine

FePt bimetallic nanoparticles were formed on reduced graphene oxide(rGO) with the help of double-stranded DNA(dsDNA) via a simple and universal route to obtain a FePt/DNA-rGO composite. The FePt nanoparticles with an average size of about 5 nm were well dispersed on rGO. FePt/DNA-rGO modified glassy carbon electrode(GCE) exhibited excellent electrocatalytic activity for the oxidation of dopamine(DA) with a detection limit of 100 nmol/L(S/N = 3). In addition, the FePt/DNA-rGO based electrochemical sensor showed an excellent selectivity for DA in the presence of ascorbic acid(AA), uric acid(UA) and other interference reagents. The as-prepared electrochemical biosensor shows great promise in the application of clinical diagnostics.     

Prussian Blue Nanoparticles Self Assembling on Electrochemically Reduced Graphene Oxide Modified GC Electrode for Sensitive Hydrogen Peroxide Detection

A facile, fast, and convenient route was suggested for the fabrication of Prussian blue nano particles (PBNPs) assembled on reduced graphene oxide (RGO) modified glassy carbon electrode (PBNPs|RGO|GCE). RGO was electrodeposited on the surface of GCE and the prepared RGO|GCE was immersed into a ferric‐hexacyanoferrate(III) solution and PBNPs were assembled on the RGO|GCE for a certain period of time. The PBNPs film thickness can be easily controlled by adjusting the assembling duration. The developed PBNPs|RGO|GCE was successfully used for determining hydrogen peroxide, with a linear response over the concentration range 0.5‐400 μM, a good accuracy and precision, detection limit 0.44 μM, and sensitivity 1168 mA M^?1 cm^?2.     

还原氧化石墨烯/TiO2复合材料在钠离子电池中的电化学性能

二氧化钛(TiO₂)作为有前景的钠离子电池负极材料, 具有良好的循环稳定性, 但由于其导电率较低, 而导致容量和倍率性能不佳限制了其实际应用. 本文采用喷雾干燥技术制备了氧化石墨烯/纳米TiO₂复合材料(GO/TiO₂), 通过热处理获得还原氧化石墨烯/TiO₂复合材料(RGO/TiO₂). 电化学测试结果表明, 还原氧化石墨烯改性的RGO/TiO₂复合材料的电化学性能得到显著提升, RGO含量为4.0%(w)的RGO/TiO₂复合材料在各种电流密度下的可逆容量分别为183.7 mAh·g^-1 (20 mA·g^-1), 153.7 mAh·g^-1 (100 mA·g^-1)和114.4 mAh·g^-1 (600mA·g^-1), 而纯TiO₂的比容量仅为93.6 mAh·g^-1 (20 mA·g^-1), 69.6 mAh·g^-1 (100 mA·g^-1)和26.5 mAh·g^-1 (600mA·g^-1). 4.0%(w) RGO/TiO₂复合材料体现了良好的循环稳定性, 在100 mA·g^-1电流密度下充放电循环350个周期后, 比容量仍然保持146.7 mAh·g^-1. 同等条件下, 纯TiO₂电极比容量只有68.8 mAh·g^-1. RGO包覆改性极大提高了TiO₂在钠离子电池中的电化学嵌钠/脱钠性能. RGO包覆改性技术在改进钠离子电池材料性能中将有很好的应用前景.     

Selective and Simultaneous Determination of Dihydroxybenzene Isomers Based on Green Synthesized Gold Nanoparticles Decorated Reduced Graphene Oxide

In the present study, we report the simultaneous electrochemical determination of hydroquinone (HQ), catechol (CC) and resorcinol (RC) at gold nanoparticles (Au‐NPs) decorated reduced graphene oxide (RGO) modified electrode. An enhanced and well defined peak current response with a better peak separation of HQ, CC and RC is observed at RGO/Au‐NPs composite than that of RGO and Au‐NPs modified electrodes. The fabricated modified electrode shows a wide linear response in the concentration range of 3–90 µM, 3–300 µM and 15–150 µM for HQ, CC and RC, respectively. The detection limit of HQ, CC and RC is found as 0.15 µM, 0.12 µM and 0.78 µM, respectively.     

基于中空多孔金纳米/石墨烯复合纳米材料的葡萄糖氧化酶直接电化学及其生物传感研究

采用溶液相牺牲模板法制备中空多孔金纳米粒子（HPAuNPs）,并将该材料与还原氧化石墨烯（rGO）复合,用于葡萄糖氧化酶（GOx）在玻碳电极（GCE）表面的有效固定,构建GOx/HPAuNPs/rGO/GCE传感界面。利用扫描和透射电镜、X射线光电子能谱、X射线衍射谱、红外光谱及电化学等方法对材料的形貌与结构,GOx的固定化过程,以及传感器的直接电化学和电催化性能进行表征。结果表明,HPAuNPs和rGO的协同作用能有效促进GOx与电极之间的直接电子转移（DET）。基于GOx/HPAuNPs/rGO/GCE对葡萄糖的良好电催化性能,该方法有效实现了对葡萄糖的高灵敏度检测,其电流响应的线性范围为0.05～7.0 mmol/L,检出限（S/N=3）为16μmol/L。该传感器具有良好的选择性、重现性及稳定性,对实际样品血清中血糖的测定结果令人满意,回收率为98.0%～103%,相对标准偏差不大于5.0%。     

Octahedral Cuprous Oxide Decorated Flexible Reduced Graphene Oxide Paper for Food Sensing Application

This work presents a simple method to fabricate an octahedral cuprous oxide (Cu₂O) decorated two-dimensional (2D) flexible rGOP electrode with filtration and electrodeposition strategies. The characteristic of the Cu₂O/rGOP electrodes was recorded by SEM, EDX, XPS, XRD, and Raman spectroscopy. The results clearly showed that Cu₂O was successfully electrodeposited on the surface of rGOP by controlling the electrodeposition potential without the introduction of any template or surfactant. The electrochemical characterizations of the Cu₂O/rGOP exhibited high electrocatalytic activity toward the reduction of H₂O₂. The linear detection range for the Cu₂O/rGOP flexible sensor was 5.0 μM to 5.5 mM, with a limit of detection of 1.27 μΜ. Subsequently, the developed flexible rGOP sensor was extended for H₂O₂ detection in milk samples for avoiding milk spoilage_. Such judicial preparation of rGOP as a sensing device will certainly pave the way for various other sensing applications including environmental and biomedical applications.     

Electrochemical Detection of Alloxan on Reduced Graphene Oxide Modified Glassy Carbon Electrode

Alloxan is a toxic reagent that strongly induces the diabetes by destroying insulin‐producing β‐cells in the pancreas of living organisms. The reduction product of alloxan is dialuric acid, which is responsible for the intracellular generation of ROS to enhance the stress in living cells to cause kidney disease or diabetic nephropathy. Herein, we studied for the first time the electrochemical properties of alloxan on reduced graphene oxide modified glassy carbon electrode (rGO/GCE) in 0.1 M phosphate buffer solution (PBS) at pH 7. The obtained results were compared with graphene oxide modified GCE (GO/GCE) and bare GCE surfaces. The modified rGO/GCE showed well defined redox couple with 10 fold increase in both reduction as well as oxidation peak current for alloxan than that of GO/GCE and bare GCE. Differential pulse voltammetry (DPV) technique shows the linear increase in both oxidation and reduction peak current of alloxan in the range of 30 μM to 3 mM with LOD of 1.2 μM. An amperometric signal of alloxan is also increases with respect to each addition of 50 μM of alloxan on rGO/GCE at constant potential of ?0.05 V. The linear range of alloxan is observed between 50 μM to 750 μM (S/N=3). This kind of rGO/GCE surface is more suitable platform or sensor matrix for estimating unknown concentration of alloxan molecule in the real biological systems.     

Protein‐Directed In Situ Synthesis of Gold Nanoparticles on Reduced Graphene Oxide Modified Electrode for Nonenzymatic Glucose Sensing

A novel nonenzymatic glucose sensor was developed based on well‐dispersed gold nanoparticles, which were in situ grown under direction of protein on a reduced graphene oxide modified electrode. This electrode exhibited high electrocatalytic activity towards glucose oxidation without use of any enzyme or mediator. In application for the amperometric detection of glucose, a wide linear range of 0.02–16.6 mM, low detection limit of 5 µM and good selectivity were obtained. The attractive analytical performances of the proposed glucose sensor, coupled with the facile preparation method, provide a promising electrochemical platform for the development of effective nonenzymatic sensors.     

Highly Sensitive Electrochemical Hydrogen Peroxide Sensor Based on Iron Oxide‐Reduced Graphene Oxide‐Chitosan Modified with DNA‐Celestine Blue

The present study describes a novel and very sensitive electrochemical assay for determination of hydrogen peroxide (H₂O₂) based on synergistic effects of reduced graphene oxide‐ magnetic iron oxide nanocomposite (rGO‐Fe₃O₄) and celestine blue (CB) for electrochemical reduction of H₂O₂. rGO‐Fe₃O₄ nanocomposite was synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X‐ray diffraction (XRD), electrochemical impedance spectroscopy and cyclic voltammetry. Chitosan (Chit) was used for immobilization of amino‐terminated single‐stranded DNA (ss‐DNA) molecules via a glutaraldehyde (GA) to the surface of rGO‐Fe₃O₄. The MTT (3‐(4,5‐Dim ethylt hiazol‐2‐yl)‐2,5‐diphenylt etrazolium bromide) results confirmed the biocompatibility of nanocomposite. Experimental parameters affecting the ss‐DNA molecules immobilization were optimized. Finally, by accumulation of the CB on the surface of the rGO‐Fe₃O₄‐Chit/ssDNA, very sensitive amperometric H₂O₂ sensor was fabricated. The electrocatalytic activity of the rGO‐Fe₃O₄‐Chit/DNA‐CB electrode toward H₂O₂ reduction was found to be very efficient, yielding very low detection limit (DL) of 42 nM and a sensitivity of 8.51 μA/μM. Result shows that complex matrices of the human serum samples did not interfere with the fabricated sensor. The developed sensor provided significant advantages in terms of low detection limit, high stability and good reproducibility for detection of H₂O₂ in comparison with recently reported electrochemical H₂O₂ sensors.     

Electrochemical Synthesis of β‐Cyclodextrin Functionalized Silver Nanoparticles and Reduced Graphene Oxide Composite for the Determination of Hydrazine

β‐cyclodextrin (β‐CD) functionalized silver nanoparticles (AgNPs) and reduced graphene oxide (RGO) via one step electrochemical potentiodyanamic method has been prepared. Scanning electron microscopy, Energy‐Dispersive X‐ray spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry were used to study the role of β‐CD on preparation of AgNPs and RGO. RGO/β‐CD/AgNPs modified GCE showed good electrochemical activity towards electro‐oxidation of hydrazine in terms of decreasing the over potential and increasing the peak current. The kinetic parameters such as electron transfer coefficient (α) and diffusion coefficient (Do) of the modified electrode towards hydrazine were determined to be 0.66 and 0.97×10^?6 cm² s^?1, respectively. The LOD of our sensor was many folds lower than that of recommended concentration of hydrazine in drinking water by United States Environmental Protection Agency and World Health Organization. The sensor exhibited a wide linear range from 0.08 to 1110 µM and a very low detection limit (LOD) of 1.4 nM. In addition, the sensor selectively determined hydrazine even in the presence of common interferents.     

Magnetite Nanorods Stabilized by Polyaniline/Reduced Graphene Oxide as a Sensing Platform for Selective and Sensitive Non‐enzymatic Hydrogen Peroxide Detection

In this study, magnetite nanorods stabilized on polyaniline/reduced graphene oxide (Fe₃O₄@PANI/rGO) was synthesized via a wet‐reflux strategy. The possible formation of Fe₃O₄@PANI/rGO was morphologically and structurally verified by field emission scanning electron microscopy (FE‐SEM), Fourier transform infrared (FT‐IR) spectroscopy, Raman spectroscopy, X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). Furthermore, the thermal stability of Fe₃O₄@PANI/rGO was measured by a thermogravimetric analyzer (TGA); the composite had good thermal stability owing to the ceramic nature of Fe₃O₄. The Fe₃O₄@PANI/rGO has been applied as a potential sensing platform for electrochemical detection of hydrogen peroxide (H₂O₂). By the combined efforts of extended active surface area, active carbon support, more catalytic active sites and high electrical conductivity, the Fe₃O₄@PANI/rGO exhibited an improved performance toward the non‐enzymatic detection of H₂O₂ in 0.5 M KOH with a fast response time (5 s), high sensitivity (223.7 μA mM^?1 cm^?2), low limit of detection (4.45 μM) and wide linear range (100 μM–1.5 mM). Furthermore, the fabricated sensor exhibited excellent recovery rates (94.2–104.0 %) during real sample analysis.     

聚吡咯/氧化石墨烯层状复合材料的制备及其在超级电容器中的应用(英文)

通过将吡咯单体在低温下与氧化石墨烯进行原位聚合,获得聚吡咯/石墨烯(Ppy/CRGO)复合材料.采用场发射电子显微镜(FESEM)、红外(FT-IR)和热重分析(TGA)对复合物的表面形貌、结构进行表征.FESEM结果表明,通过控制氧化石墨烯(GO)和吡咯单体的质量比例,可以对复合物的层状和厚度进行调控.FT-IR和TGA结果表明,聚吡咯(Ppy)是通过化学键合的方式与氧化石墨烯复合在一起.通过机械冷压法将粉末状Ppy/CRGO复合物压成圆片电极,并探讨了石墨烯和聚吡咯复合比例、反应时间、烘干温度和孔隙率等因素对Ppy/CRGO复合物电极的电学和电化学性能的影响.结果表明,Ppy与CRGO质量比为10∶1所制得的Ppy/CRGO复合物的电容量为421 F·g-1,通过在电极中引入孔隙,电容量能进一步提升为509 F·g-1.     

氮掺杂还原氧化石墨烯负载铂催化剂的制备及甲醇电氧化性能

采用高温热解聚苯胺修饰的氧化石墨烯（PANI-GO）,得到了氮掺杂的还原氧化石墨烯碳材料（N-RGO）,以其负载Pt 制备了Pt/N-RGO纳米结构电催化剂. 采用透射电镜（TEM）、X射线光电子能谱（XPS）、X 射线衍射（XRD）谱及拉曼光谱等技术对N-RGO和Pt/N-RGO的形貌及结构进行了表征,用循环伏安、计时电流等电化学技术研究了Pt/N-RGO电极催化剂对CO溶出反应和甲醇电氧化反应的催化性能. 结果表明：高温热解PANIGO可同时实现GO的还原及其氮掺杂的过程,氮掺杂引起还原氧化石墨烯碳材料表面缺陷结构和导电性的增加;与相应的未掺杂氮样品Pt/RGO相比较,Pt/N-RGO样品上Pt 颗粒的分散更均匀,显示出更强的抗CO毒化能力和更高的甲醇电氧化催化活性及稳定性.     

Highly Selective and Sensitive Voltammetric Sensor Based on Ruthenium Nanoparticle Anchored Calix[4]amidocrown‐5 Functionalized Reduced Graphene Oxide: Simultaneous Determination of Quercetin,Morin and Rutin in Grape Wine

In this report, ruthenium nanoparticles (RuNPs) and calix[4]amidocrown‐5 (C4A5) were synthesized and grafted onto the surface of reduced graphene oxide (RGO) nanocomposite (RuNPs/C4A5/RGO). The morphologies of the nanocomposites were characterized by transmission electron microscope, scanning electron microscope, atomic force microscope, electrochemical impedance spectroscopy and x‐ray photoelectron spectroscopy. The electrochemical experiments were performed by cyclic voltammetry, electrochemical impedance spectroscopy and square wave voltammetry. The simultaneous determination of quercetin, rutin and morin was performed on glassy carbon electrode modified with RuNPs/C4A5/RGO (RuNPs/C4A5/RGO/GCE). The linearity ranges and the detection limits of QR, RT and MR were 1.0×10^?10–1.0×10^?8 M and 2.0×10^?11 M respectively.