An electrochemically reduced graphene oxide sample, ERGO_0.8v, was prepared by electrochemical reduction of graphene oxide （GO） at -0.8 V, which shows unique electrocatalytic activity toward tetracycline （TTC） det...An electrochemically reduced graphene oxide sample, ERGO_0.8v, was prepared by electrochemical reduction of graphene oxide （GO） at -0.8 V, which shows unique electrocatalytic activity toward tetracycline （TTC） detection compared to the ERGO-12v （GO applied to a negative potential of-1.2 V）, GO, chemically reduced GO （CRGO）-modified glassy carbon electrode （GC） and bare GC electrodes. The redox peaks of TTC on an ERGO-0.8v-modifled glass carbon electrode （GC/ERGO-0.8v） were within 0-0.5 V in a pH 3.0 buffer solution with the oxidation peak current correlating well with TTC concentration over a wide range from 0.1 to 160 mg/L Physical characterizations with Fourier transform infrared （FT-IR）, Raman, and X-ray photoelectron spectroscopies （XPS） demonstrated that the oxygen-containing functional groups on GO diminished after the electrochemical reduction at -0.8 V, yet still existed in large amounts, and the defect density changed as new sp2 domains were formed. These changes demonstrated that this adjustment in the number of oxygen-containing groups might be the main factor affecting the electrocatalytic behavior of ERGO. Additionally, the defect density and sp2 domains also exert a profound influence on this behavior. A possible mechanism for the TTC redox reaction at the GC/ERGO-0.8v electrode is also presented. This work suggests that the electrochemical reduction is an effective method to establish new catalytic activities of GO by setting appropriate parameters.展开更多
Enzymeless hydrogen peroxide （H2O2） detection with high sensitivity and excellent selectivity is desirable for clinical diagnosis. Herein, one-dimensional Co3O4 nanowires have been successfully constructed on reduce...Enzymeless hydrogen peroxide （H2O2） detection with high sensitivity and excellent selectivity is desirable for clinical diagnosis. Herein, one-dimensional Co3O4 nanowires have been successfully constructed on reduced graphene oxide （rGO） via a simple hydrothermal procedure and subsequent thermal treatment. These Co3O4 nanowires, assembled by small nanoparticles, are interlaced with one another and make a spider web-like structure on rGO. The formation of Co3O4-rGO hybrids is attributed to the structure-directing and anchoring roles of DDA and GO, respectively. The resulting structure possesses abundant active sites, the oriented transmission of electrons, and unimpeded pathways for matter diffusion, which endows the Co3O4-rGO hybrids with excellent electrocatalytic performance. As a result, the obtained Co3O4-rGO hybrids can serve as an efficient electrochemical catalyst for H2O2 oxidation and high sensitivity detection. Under physiological conditions, the oxidation current of H2O2 varies linearly with respect to its concentration from 0.015 to 0.675 mM with a sensitivity of 1.14 mA.mM^-1.cm^-2 and a low detection limit of 2.4 μM. Furthermore, the low potential （-0.19 V） and the good selectivity make Co3O4-rGO hybrids suitable for monitoring H2O2 generated by liver cancer HepG2 cells. Therefore, it is promising as a non-enzymatic sensor to achieve real-time quantitative detection of H2O2 in biological applications.展开更多
Herein, we present the electrochemical co-deposition of Al3+/graphene composites directly from an aqueous mixture containing graphene oxide (GO) and Al3+. The obtained Al3+/graphene composites with good electrochemica...Herein, we present the electrochemical co-deposition of Al3+/graphene composites directly from an aqueous mixture containing graphene oxide (GO) and Al3+. The obtained Al3+/graphene composites with good electrochemical activity were regarded as an appropriate immobilization platform for double-stranded DNA (dsDNA). The nontoxic redox probe xanthurenic acid (XA) was successfully applied to recognize single-stranded DNA and dsDNA. We illustrated that the scission of dsDNA caused by GO combining with some metal ions could be detected by monitoring the electrochemical signals of XA.展开更多
In this paper, composite film based on polyvinylpyrrolidone(PVP)/graphene oxide(GO) was fabricated by spray method on AT-cut 9.986 MHz quartz crystal microbalance(QCM) for NH_3 sensing. The thin films were characteriz...In this paper, composite film based on polyvinylpyrrolidone(PVP)/graphene oxide(GO) was fabricated by spray method on AT-cut 9.986 MHz quartz crystal microbalance(QCM) for NH_3 sensing. The thin films were characterized by scanning electron microscope(SEM), Fourier transform infrared spectroscopy(FTIR) and ultraviolet-visible spectroscopy(UV-VIS) to investigate the morphologies and the composition contents, respectively. The experimental results reveal that PVP/GO based sensor holds higher sensitivity, larger responsiveness and smaller baseline drift than those based on pure PVP at room temperature. Besides, the prepared sensor exhibits greater response to NH_3 than other gases such as CO, CO_2 and NO_2 at the same concentration. The good linearity, reproducibility and stability demonstrate the practicability of PVP/GO hybrid film in detecting NH_3.展开更多
The aim of this paper is to investigate the damage cracking characteristics of rock and soil aggregate(RSA)by X-ray computed tomography(CT)under uniaxial compressive loading.The mean CT value for the region of interes...The aim of this paper is to investigate the damage cracking characteristics of rock and soil aggregate(RSA)by X-ray computed tomography(CT)under uniaxial compressive loading.The mean CT value for the region of interest(ROI)is used to analyze the cracking characteristics.Also,the mathematical morphology method based on the image threshold segmentation is used to obtain characteristic parameters of cracks to describe the cracking evolution of RSA.Results show that the elastic mismatch between rock blocks and soil matrix is the primary reason for RSA cracking.The mean CT value for the RSA specimen,rock block inclusions,and their adjacent soil regions decreases with the increasing stress level.However,it is more sensitive for block inclusions than soil regions.Using the image segmentation method,length,area and mean width of cracks obey to power function distribution.Crack statistical characteristics are closely related to the rock block’s distribution and morphology.These results may be useful to reveal the mesoscopic cracking mechanism,establish meso-damage evolution equation,and constitutive relation for RSA.展开更多
The demand for simple and rapid bioassays in ecotoxicological evaluations is of paramount importance in order to speed up environmental monitoring programs.In this study we performed bioassays with lettuce seeds and t...The demand for simple and rapid bioassays in ecotoxicological evaluations is of paramount importance in order to speed up environmental monitoring programs.In this study we performed bioassays with lettuce seeds and two species of terrestrial isopods (Armadillidium vulgare and Porcellio dilatatus) for the ecotoxicological assessment of a landfarming soil from a petrochemical complex area.The solubilized content of test soil demonstrated a concentration-response type toxic effect on seed germination rate,and a delay on germination,but showed toxic effect on seedlings wet weight only at the highest concentration.Toxic effects were also observed in mortality rate and avoidance behavior of the two woodlice species.These results demonstrated the sensitiveness of the organisms studied,and highlighted the possibility to use these bioassays in environmental monitoring programs in areas contaminated with fossil fuels.展开更多
We have developed a multiplexed DNA detection method based on graphene oxide （GO） and molecular beacons （MBs） by synchronous fluorescence analysis, demonstrated it by an oligonucleotide sequence of wild-type HBV ...We have developed a multiplexed DNA detection method based on graphene oxide （GO） and molecular beacons （MBs） by synchronous fluorescence analysis, demonstrated it by an oligonucleotide sequence of wild-type HBV （T1） and a re- verse-transcription oligonucleotide sequence of the RNA fragment of HIV （T2） as a model system. In the absence of targets DNA, FAM-tagged free MB probes （PHBv） and ROX-tagged free MB probes （PHIv） are adsorbed on GO via π-π interactions between DNA nucleobases and nucleosides, and the π-rich GO brings the fluorophores of MB and GO into close proximity. And then, the fluorescence of fluorophores is quenched by GO. But in the presence of targets DNA, PHBV and PHW hybridize with their targets DNA resulting in the formation of double-stranded DNA （dsDNA）, causing the separation of PHBV and PHW from the surface of GO and the recovery of the fluorescence of fluorophores （FAM and ROX） simultaneously. The simultane- ous detection of T1 and T2 can be realized by measuring fluorescence signals of FAM and ROX, respectively. Under the op- timum conditions, the fluorescence intensities of two dyes all exhibit good linear dependence on their target DNA concentra- tion in the range of 5×10-11-5×10 9 M. The detection limit of T1 is 3×10-11 M （3σ）, and that of T2 is 2×10-11 M. Compared with other methods for DNA detection based on GO, the proposed method has some advantages including higher selectivity and shorter analytical time.展开更多
Graphene has the advantages of high electrical conductivity,high heat conductivity,and low noise,which makes it a potential option for integrated circuits interconnection and nanoelectrodes.In this paper,we present a ...Graphene has the advantages of high electrical conductivity,high heat conductivity,and low noise,which makes it a potential option for integrated circuits interconnection and nanoelectrodes.In this paper,we present a novel fabrication method for graphene nanoeletrodes with nanogap.First,graphene grown by chemical vapor deposition(CVD)is assembled to a chip with microelectrodes.Second,an atomic force microscopy(AFM)based mechanical cutting method is developed to cut the graphene into nanoribbons and nanoeletrodes with nanogap.Then the electronic property of a single nanodot is characterized using the garphene nanoelectrodes,demonstrating the effectiveness of the graphene nanoelectrodes.The fabricated graphene nanoeletrode pairs can be used as probes to detect single molecule in micro-environment,and show an attractive prospect for future molecular electronics applications.展开更多
基金supported by the National Natural Science Foundation of China(21007033)the Fundamental Research Funds of Shandong University(2015JC017)~~
文摘An electrochemically reduced graphene oxide sample, ERGO_0.8v, was prepared by electrochemical reduction of graphene oxide （GO） at -0.8 V, which shows unique electrocatalytic activity toward tetracycline （TTC） detection compared to the ERGO-12v （GO applied to a negative potential of-1.2 V）, GO, chemically reduced GO （CRGO）-modified glassy carbon electrode （GC） and bare GC electrodes. The redox peaks of TTC on an ERGO-0.8v-modifled glass carbon electrode （GC/ERGO-0.8v） were within 0-0.5 V in a pH 3.0 buffer solution with the oxidation peak current correlating well with TTC concentration over a wide range from 0.1 to 160 mg/L Physical characterizations with Fourier transform infrared （FT-IR）, Raman, and X-ray photoelectron spectroscopies （XPS） demonstrated that the oxygen-containing functional groups on GO diminished after the electrochemical reduction at -0.8 V, yet still existed in large amounts, and the defect density changed as new sp2 domains were formed. These changes demonstrated that this adjustment in the number of oxygen-containing groups might be the main factor affecting the electrocatalytic behavior of ERGO. Additionally, the defect density and sp2 domains also exert a profound influence on this behavior. A possible mechanism for the TTC redox reaction at the GC/ERGO-0.8v electrode is also presented. This work suggests that the electrochemical reduction is an effective method to establish new catalytic activities of GO by setting appropriate parameters.
文摘Enzymeless hydrogen peroxide （H2O2） detection with high sensitivity and excellent selectivity is desirable for clinical diagnosis. Herein, one-dimensional Co3O4 nanowires have been successfully constructed on reduced graphene oxide （rGO） via a simple hydrothermal procedure and subsequent thermal treatment. These Co3O4 nanowires, assembled by small nanoparticles, are interlaced with one another and make a spider web-like structure on rGO. The formation of Co3O4-rGO hybrids is attributed to the structure-directing and anchoring roles of DDA and GO, respectively. The resulting structure possesses abundant active sites, the oriented transmission of electrons, and unimpeded pathways for matter diffusion, which endows the Co3O4-rGO hybrids with excellent electrocatalytic performance. As a result, the obtained Co3O4-rGO hybrids can serve as an efficient electrochemical catalyst for H2O2 oxidation and high sensitivity detection. Under physiological conditions, the oxidation current of H2O2 varies linearly with respect to its concentration from 0.015 to 0.675 mM with a sensitivity of 1.14 mA.mM^-1.cm^-2 and a low detection limit of 2.4 μM. Furthermore, the low potential （-0.19 V） and the good selectivity make Co3O4-rGO hybrids suitable for monitoring H2O2 generated by liver cancer HepG2 cells. Therefore, it is promising as a non-enzymatic sensor to achieve real-time quantitative detection of H2O2 in biological applications.
基金the National Natural Science Foundation of China (20975057, and 21275084)Doctoral Foundation of the Ministry of Education of China (20113719130001)+1 种基金Outstanding Adult-Young Scientific Research Encouraging Foundation of Shandong Province (No. BS2012CL013)Scientific and Technical Development Project of Qingdao (12-1-4-3-(23)-jch)
文摘Herein, we present the electrochemical co-deposition of Al3+/graphene composites directly from an aqueous mixture containing graphene oxide (GO) and Al3+. The obtained Al3+/graphene composites with good electrochemical activity were regarded as an appropriate immobilization platform for double-stranded DNA (dsDNA). The nontoxic redox probe xanthurenic acid (XA) was successfully applied to recognize single-stranded DNA and dsDNA. We illustrated that the scission of dsDNA caused by GO combining with some metal ions could be detected by monitoring the electrochemical signals of XA.
基金supported by the Funds for Creative Research Groups of China(Grant No.61421002)the National Natural Science Foundation of China(Grant No.61571097)
文摘In this paper, composite film based on polyvinylpyrrolidone(PVP)/graphene oxide(GO) was fabricated by spray method on AT-cut 9.986 MHz quartz crystal microbalance(QCM) for NH_3 sensing. The thin films were characterized by scanning electron microscope(SEM), Fourier transform infrared spectroscopy(FTIR) and ultraviolet-visible spectroscopy(UV-VIS) to investigate the morphologies and the composition contents, respectively. The experimental results reveal that PVP/GO based sensor holds higher sensitivity, larger responsiveness and smaller baseline drift than those based on pure PVP at room temperature. Besides, the prepared sensor exhibits greater response to NH_3 than other gases such as CO, CO_2 and NO_2 at the same concentration. The good linearity, reproducibility and stability demonstrate the practicability of PVP/GO hybrid film in detecting NH_3.
基金supported by the National Natural Science Foundation of China(Grants Nos.41227901,41027001,and 41027001)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grants Nos.XDB10030000,XDB10030300 and XDB10050400)
文摘The aim of this paper is to investigate the damage cracking characteristics of rock and soil aggregate(RSA)by X-ray computed tomography(CT)under uniaxial compressive loading.The mean CT value for the region of interest(ROI)is used to analyze the cracking characteristics.Also,the mathematical morphology method based on the image threshold segmentation is used to obtain characteristic parameters of cracks to describe the cracking evolution of RSA.Results show that the elastic mismatch between rock blocks and soil matrix is the primary reason for RSA cracking.The mean CT value for the RSA specimen,rock block inclusions,and their adjacent soil regions decreases with the increasing stress level.However,it is more sensitive for block inclusions than soil regions.Using the image segmentation method,length,area and mean width of cracks obey to power function distribution.Crack statistical characteristics are closely related to the rock block’s distribution and morphology.These results may be useful to reveal the mesoscopic cracking mechanism,establish meso-damage evolution equation,and constitutive relation for RSA.
基金Supported by Brazil National Petroleum Agency and Petrobras(No.PRH-ANP/MME/MCT 27)
文摘The demand for simple and rapid bioassays in ecotoxicological evaluations is of paramount importance in order to speed up environmental monitoring programs.In this study we performed bioassays with lettuce seeds and two species of terrestrial isopods (Armadillidium vulgare and Porcellio dilatatus) for the ecotoxicological assessment of a landfarming soil from a petrochemical complex area.The solubilized content of test soil demonstrated a concentration-response type toxic effect on seed germination rate,and a delay on germination,but showed toxic effect on seedlings wet weight only at the highest concentration.Toxic effects were also observed in mortality rate and avoidance behavior of the two woodlice species.These results demonstrated the sensitiveness of the organisms studied,and highlighted the possibility to use these bioassays in environmental monitoring programs in areas contaminated with fossil fuels.
文摘We have developed a multiplexed DNA detection method based on graphene oxide （GO） and molecular beacons （MBs） by synchronous fluorescence analysis, demonstrated it by an oligonucleotide sequence of wild-type HBV （T1） and a re- verse-transcription oligonucleotide sequence of the RNA fragment of HIV （T2） as a model system. In the absence of targets DNA, FAM-tagged free MB probes （PHBv） and ROX-tagged free MB probes （PHIv） are adsorbed on GO via π-π interactions between DNA nucleobases and nucleosides, and the π-rich GO brings the fluorophores of MB and GO into close proximity. And then, the fluorescence of fluorophores is quenched by GO. But in the presence of targets DNA, PHBV and PHW hybridize with their targets DNA resulting in the formation of double-stranded DNA （dsDNA）, causing the separation of PHBV and PHW from the surface of GO and the recovery of the fluorescence of fluorophores （FAM and ROX） simultaneously. The simultane- ous detection of T1 and T2 can be realized by measuring fluorescence signals of FAM and ROX, respectively. Under the op- timum conditions, the fluorescence intensities of two dyes all exhibit good linear dependence on their target DNA concentra- tion in the range of 5×10-11-5×10 9 M. The detection limit of T1 is 3×10-11 M （3σ）, and that of T2 is 2×10-11 M. Compared with other methods for DNA detection based on GO, the proposed method has some advantages including higher selectivity and shorter analytical time.
基金supported by the National Natural Science Foundation of China(Grant Nos.61106109,61304251)the CAS/SAFEA Internaional Partnership Program for Creative Research Teams
文摘Graphene has the advantages of high electrical conductivity,high heat conductivity,and low noise,which makes it a potential option for integrated circuits interconnection and nanoelectrodes.In this paper,we present a novel fabrication method for graphene nanoeletrodes with nanogap.First,graphene grown by chemical vapor deposition(CVD)is assembled to a chip with microelectrodes.Second,an atomic force microscopy(AFM)based mechanical cutting method is developed to cut the graphene into nanoribbons and nanoeletrodes with nanogap.Then the electronic property of a single nanodot is characterized using the garphene nanoelectrodes,demonstrating the effectiveness of the graphene nanoelectrodes.The fabricated graphene nanoeletrode pairs can be used as probes to detect single molecule in micro-environment,and show an attractive prospect for future molecular electronics applications.
