The Experts below are selected from a list of 3597 Experts worldwide ranked by ideXlab platform
Zhengbo Chen - One of the best experts on this subject based on the ideXlab platform.
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Determining Alkaline Phosphatase Based on Core–Shell Gold@silver Nanocubes by Single-Particle Dark-Field Images
ACS Sustainable Chemistry & Engineering, 2020Co-Authors: Qingyun Liu, Zhengbo ChenAbstract:We develop a rapid and ulsensitive colorimetric method for alkaline phosphatase (ALP) activity based on Dark-Field Microscope. In the presence of ALP, the ALP will hydrolyze L-ascorbic acid 2-phosp...
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Optical aptasensing of mercury(II) by using salt-induced and exonuclease I-induced gold nanoparticle aggregation under Dark-Field Microscope observation
Mikrochimica acta, 2019Co-Authors: Qingyun Liu, Zhengbo ChenAbstract:An optical method for determination of Hg(II) is described that exploits the aggregation of gold nanoparticles (AuNPs) under Dark-Field Microscope (DFM) observation. This assay is based on the use of a Hg(II)-specific aptamer, AuNPs modified with complementary DNA strands, and exonuclease I (Exo I). In the absence of Hg(II), the added dsDNA prevents salt-induced aggregation of the green-colored AuNPs. If Hg(II) is added, the aptamer will capture it to form T-Hg(II)-T pairs, and the complementary strand is digested by Exo I. On addition of a solution of NaCl, the AuNPs will aggregate. This is accompanied by a color change from green to orange/red) in the Dark-Field image. By calculating the intensity of the orange/red dots in the Dark-Field image, concentration of Hg(II) can be accurately determined. The limit of detection is as low as 36 fM, and response is a linear in the 83 fM to 8.3 μM Hg(II) concentration range.
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Single particle-based colorimetric assay of pyrophosphate ions and pyrophosphatase with Dark-Field Microscope
Sensors and Actuators B: Chemical, 2019Co-Authors: Caiyun Kong, Qingyun Liu, Zhengbo ChenAbstract:Abstract We propose a sensitive colorimetric method for the detection of P2O74− and pyrophosphatase (PPase). Without Na4P2O7 and PPase, under the catalysis of gold nanoparticles (AuNPs), Cu(II) can be reduced to Cu by nicotinamide adenine dinucleotide (NADH), leading to the Cu-coating onto the surfaces of AuNPs, accompanied by the color change from green to red under the Dark-Field Microscope observation. While in the presence of Na4P2O7, the formation of Au@Cu NPs is suppressed due to the strong complexation reaction between Cu(II) and Na4P2O7. Thus, the NPs exhibit uniform green color in the Dark-Field image. By quantitatively counting the integrated optical density (IOD) of red dots in the Dark-Field images, P2O74− concentration can be accurately determined. A linear logarithmic dependence on P2O74− concentrations from 0.1 nM to 10 mM with a limit of detection (LOD) of 0.0324 nM was obtained. The addition of PPase to the Na4P2O7-triggered dispersed AuNPs restores the formation of Au@Cu NPs owing to the hydrolysis of Na4P2O7 into sodium phosphate under the catalysis of PPase, resulting in reliable quantification of color change of NPs from red to green in the Dark-Field images. The LOD is as low as 0.0007 U/mL with a linear dynamic range of 0.005–10 U/mL.
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Aggregation-to-Deaggregation" Colorimetric Signal Amplification Strategy for Ag+ Detection at the Femtomolar Level with Dark-Field Microscope Observation.
Analytical chemistry, 2018Co-Authors: Caiyun Kong, Qingyun Liu, Zhengbo ChenAbstract:Robust but ultrasensitive aptasensors with an ability to detect lower concentrations of heavy metal ions enable the detection of serious environmental and health issues. We herein develop a label-free aptasensor for ultrasensitive detection of the silver ion (Ag+) utilizing gold nanoparticle (AuNP) intensity measurement methodology by Dark-Field microscopy, which is based on target Ag+ and exonuclease III (Exo III)-dependent DNA cleavage recycling amplification. In the presence of target Ag+, thymine (T) bases at two termini of hairpin DNA bind with Ag+ through C–Ag+–C coordination to form a DNA duplex, Exo III can recognize the blunt 3′ end of the DNA duplex and digest it from the 3′ end to the 5′ direction. The released target Ag+ then binds with another hairpin DNA via C–Ag+–C pairs. After many cycles of the digestion of the DNA duplex by Exo III, numerous remaining single-stranded DNA (ssDNA) are generated. These ssDNA are absorbed on the surface of AuNPs, enhancing the repulsion force between AuNPs, ...
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aggregation to deaggregation colorimetric signal amplification strategy for ag detection at the femtomolar level with Dark Field Microscope observation
Analytical Chemistry, 2018Co-Authors: Caiyun Kong, Qingyun Liu, Zhengbo ChenAbstract:Robust but ultrasensitive aptasensors with an ability to detect lower concentrations of heavy metal ions enable the detection of serious environmental and health issues. We herein develop a label-free aptasensor for ultrasensitive detection of the silver ion (Ag+) utilizing gold nanoparticle (AuNP) intensity measurement methodology by Dark-Field microscopy, which is based on target Ag+ and exonuclease III (Exo III)-dependent DNA cleavage recycling amplification. In the presence of target Ag+, thymine (T) bases at two termini of hairpin DNA bind with Ag+ through C–Ag+–C coordination to form a DNA duplex, Exo III can recognize the blunt 3′ end of the DNA duplex and digest it from the 3′ end to the 5′ direction. The released target Ag+ then binds with another hairpin DNA via C–Ag+–C pairs. After many cycles of the digestion of the DNA duplex by Exo III, numerous remaining single-stranded DNA (ssDNA) are generated. These ssDNA are absorbed on the surface of AuNPs, enhancing the repulsion force between AuNPs, ...
Alexis Deschamps - One of the best experts on this subject based on the ideXlab platform.
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Size distribution and volume fraction of T1 phase precipitates from TEM images: Direct measurements and related correction
Micron, 2015Co-Authors: Thomas Dorin, Patricia Donnadieu, Jean-marc Chaix, Williams Lefebvre, Frédéric De Geuser, Alexis DeschampsAbstract:Transmission Electron Microscopy (TEM) can be used to measure the size distribution and volume fraction of fine scale precipitates in metallic systems. However, such measurements suffer from a number of artefacts that need to be accounted for, related to the finite thickness of the TEM foil and to the projected observation in two dimensions of the microstructure. We present a correction procedure to describe the 3D distribution of disc-like particles and apply this method to the plate-like T-1 precipitates in an Al-Li-Cu alloy in two ageing conditions showing different particle morphologies. The precipitates were imaged in a High-Angular Annular Dark Field Microscope (HAADF-STEM). The corrected size distribution is further used to determine the precipitate volume fraction. Atom probe tomography (APT) is finally utilised as an alternative way to measure the precipitate volume fraction and test the validity of the electron microscopy results. (C) 2015 Elsevier Ltd. All rights reserved.
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Size distribution and volume fraction of T1 phase precipitates from TEM images: Direct measurements and related correction
Micron (Oxford England : 1993), 2015Co-Authors: Thomas Dorin, Patricia Donnadieu, Jean-marc Chaix, Williams Lefebvre, Frédéric De Geuser, Alexis DeschampsAbstract:Transmission Electron Microscopy (TEM) can be used to measure the size distribution and volume fraction of fine scale precipitates in metallic systems. However, such measurements suffer from a number of artefacts that need to be accounted for, related to the finite thickness of the TEM foil and to the projected observation in two dimensions of the microstructure. We present a correction procedure to describe the 3D distribution of disc-like particles and apply this method to the plate-like T1 precipitates in an Al-Li-Cu alloy in two ageing conditions showing different particle morphologies. The precipitates were imaged in a High-Angular Annular Dark Field Microscope (HAADF-STEM). The corrected size distribution is further used to determine the precipitate volume fraction. Atom probe tomography (APT) is finally utilised as an alternative way to measure the precipitate volume fraction and test the validity of the electron microscopy results.
Qingyun Liu - One of the best experts on this subject based on the ideXlab platform.
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Determining Alkaline Phosphatase Based on Core–Shell Gold@silver Nanocubes by Single-Particle Dark-Field Images
ACS Sustainable Chemistry & Engineering, 2020Co-Authors: Qingyun Liu, Zhengbo ChenAbstract:We develop a rapid and ulsensitive colorimetric method for alkaline phosphatase (ALP) activity based on Dark-Field Microscope. In the presence of ALP, the ALP will hydrolyze L-ascorbic acid 2-phosp...
-
Optical aptasensing of mercury(II) by using salt-induced and exonuclease I-induced gold nanoparticle aggregation under Dark-Field Microscope observation
Mikrochimica acta, 2019Co-Authors: Qingyun Liu, Zhengbo ChenAbstract:An optical method for determination of Hg(II) is described that exploits the aggregation of gold nanoparticles (AuNPs) under Dark-Field Microscope (DFM) observation. This assay is based on the use of a Hg(II)-specific aptamer, AuNPs modified with complementary DNA strands, and exonuclease I (Exo I). In the absence of Hg(II), the added dsDNA prevents salt-induced aggregation of the green-colored AuNPs. If Hg(II) is added, the aptamer will capture it to form T-Hg(II)-T pairs, and the complementary strand is digested by Exo I. On addition of a solution of NaCl, the AuNPs will aggregate. This is accompanied by a color change from green to orange/red) in the Dark-Field image. By calculating the intensity of the orange/red dots in the Dark-Field image, concentration of Hg(II) can be accurately determined. The limit of detection is as low as 36 fM, and response is a linear in the 83 fM to 8.3 μM Hg(II) concentration range.
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Single particle-based colorimetric assay of pyrophosphate ions and pyrophosphatase with Dark-Field Microscope
Sensors and Actuators B: Chemical, 2019Co-Authors: Caiyun Kong, Qingyun Liu, Zhengbo ChenAbstract:Abstract We propose a sensitive colorimetric method for the detection of P2O74− and pyrophosphatase (PPase). Without Na4P2O7 and PPase, under the catalysis of gold nanoparticles (AuNPs), Cu(II) can be reduced to Cu by nicotinamide adenine dinucleotide (NADH), leading to the Cu-coating onto the surfaces of AuNPs, accompanied by the color change from green to red under the Dark-Field Microscope observation. While in the presence of Na4P2O7, the formation of Au@Cu NPs is suppressed due to the strong complexation reaction between Cu(II) and Na4P2O7. Thus, the NPs exhibit uniform green color in the Dark-Field image. By quantitatively counting the integrated optical density (IOD) of red dots in the Dark-Field images, P2O74− concentration can be accurately determined. A linear logarithmic dependence on P2O74− concentrations from 0.1 nM to 10 mM with a limit of detection (LOD) of 0.0324 nM was obtained. The addition of PPase to the Na4P2O7-triggered dispersed AuNPs restores the formation of Au@Cu NPs owing to the hydrolysis of Na4P2O7 into sodium phosphate under the catalysis of PPase, resulting in reliable quantification of color change of NPs from red to green in the Dark-Field images. The LOD is as low as 0.0007 U/mL with a linear dynamic range of 0.005–10 U/mL.
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Aggregation-to-Deaggregation" Colorimetric Signal Amplification Strategy for Ag+ Detection at the Femtomolar Level with Dark-Field Microscope Observation.
Analytical chemistry, 2018Co-Authors: Caiyun Kong, Qingyun Liu, Zhengbo ChenAbstract:Robust but ultrasensitive aptasensors with an ability to detect lower concentrations of heavy metal ions enable the detection of serious environmental and health issues. We herein develop a label-free aptasensor for ultrasensitive detection of the silver ion (Ag+) utilizing gold nanoparticle (AuNP) intensity measurement methodology by Dark-Field microscopy, which is based on target Ag+ and exonuclease III (Exo III)-dependent DNA cleavage recycling amplification. In the presence of target Ag+, thymine (T) bases at two termini of hairpin DNA bind with Ag+ through C–Ag+–C coordination to form a DNA duplex, Exo III can recognize the blunt 3′ end of the DNA duplex and digest it from the 3′ end to the 5′ direction. The released target Ag+ then binds with another hairpin DNA via C–Ag+–C pairs. After many cycles of the digestion of the DNA duplex by Exo III, numerous remaining single-stranded DNA (ssDNA) are generated. These ssDNA are absorbed on the surface of AuNPs, enhancing the repulsion force between AuNPs, ...
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aggregation to deaggregation colorimetric signal amplification strategy for ag detection at the femtomolar level with Dark Field Microscope observation
Analytical Chemistry, 2018Co-Authors: Caiyun Kong, Qingyun Liu, Zhengbo ChenAbstract:Robust but ultrasensitive aptasensors with an ability to detect lower concentrations of heavy metal ions enable the detection of serious environmental and health issues. We herein develop a label-free aptasensor for ultrasensitive detection of the silver ion (Ag+) utilizing gold nanoparticle (AuNP) intensity measurement methodology by Dark-Field microscopy, which is based on target Ag+ and exonuclease III (Exo III)-dependent DNA cleavage recycling amplification. In the presence of target Ag+, thymine (T) bases at two termini of hairpin DNA bind with Ag+ through C–Ag+–C coordination to form a DNA duplex, Exo III can recognize the blunt 3′ end of the DNA duplex and digest it from the 3′ end to the 5′ direction. The released target Ag+ then binds with another hairpin DNA via C–Ag+–C pairs. After many cycles of the digestion of the DNA duplex by Exo III, numerous remaining single-stranded DNA (ssDNA) are generated. These ssDNA are absorbed on the surface of AuNPs, enhancing the repulsion force between AuNPs, ...
Thomas Dorin - One of the best experts on this subject based on the ideXlab platform.
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Size distribution and volume fraction of T1 phase precipitates from TEM images: Direct measurements and related correction
Micron, 2015Co-Authors: Thomas Dorin, Patricia Donnadieu, Jean-marc Chaix, Williams Lefebvre, Frédéric De Geuser, Alexis DeschampsAbstract:Transmission Electron Microscopy (TEM) can be used to measure the size distribution and volume fraction of fine scale precipitates in metallic systems. However, such measurements suffer from a number of artefacts that need to be accounted for, related to the finite thickness of the TEM foil and to the projected observation in two dimensions of the microstructure. We present a correction procedure to describe the 3D distribution of disc-like particles and apply this method to the plate-like T-1 precipitates in an Al-Li-Cu alloy in two ageing conditions showing different particle morphologies. The precipitates were imaged in a High-Angular Annular Dark Field Microscope (HAADF-STEM). The corrected size distribution is further used to determine the precipitate volume fraction. Atom probe tomography (APT) is finally utilised as an alternative way to measure the precipitate volume fraction and test the validity of the electron microscopy results. (C) 2015 Elsevier Ltd. All rights reserved.
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Size distribution and volume fraction of T1 phase precipitates from TEM images: Direct measurements and related correction
Micron (Oxford England : 1993), 2015Co-Authors: Thomas Dorin, Patricia Donnadieu, Jean-marc Chaix, Williams Lefebvre, Frédéric De Geuser, Alexis DeschampsAbstract:Transmission Electron Microscopy (TEM) can be used to measure the size distribution and volume fraction of fine scale precipitates in metallic systems. However, such measurements suffer from a number of artefacts that need to be accounted for, related to the finite thickness of the TEM foil and to the projected observation in two dimensions of the microstructure. We present a correction procedure to describe the 3D distribution of disc-like particles and apply this method to the plate-like T1 precipitates in an Al-Li-Cu alloy in two ageing conditions showing different particle morphologies. The precipitates were imaged in a High-Angular Annular Dark Field Microscope (HAADF-STEM). The corrected size distribution is further used to determine the precipitate volume fraction. Atom probe tomography (APT) is finally utilised as an alternative way to measure the precipitate volume fraction and test the validity of the electron microscopy results.
Patricia Donnadieu - One of the best experts on this subject based on the ideXlab platform.
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Size distribution and volume fraction of T1 phase precipitates from TEM images: Direct measurements and related correction
Micron, 2015Co-Authors: Thomas Dorin, Patricia Donnadieu, Jean-marc Chaix, Williams Lefebvre, Frédéric De Geuser, Alexis DeschampsAbstract:Transmission Electron Microscopy (TEM) can be used to measure the size distribution and volume fraction of fine scale precipitates in metallic systems. However, such measurements suffer from a number of artefacts that need to be accounted for, related to the finite thickness of the TEM foil and to the projected observation in two dimensions of the microstructure. We present a correction procedure to describe the 3D distribution of disc-like particles and apply this method to the plate-like T-1 precipitates in an Al-Li-Cu alloy in two ageing conditions showing different particle morphologies. The precipitates were imaged in a High-Angular Annular Dark Field Microscope (HAADF-STEM). The corrected size distribution is further used to determine the precipitate volume fraction. Atom probe tomography (APT) is finally utilised as an alternative way to measure the precipitate volume fraction and test the validity of the electron microscopy results. (C) 2015 Elsevier Ltd. All rights reserved.
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Size distribution and volume fraction of T1 phase precipitates from TEM images: Direct measurements and related correction
Micron (Oxford England : 1993), 2015Co-Authors: Thomas Dorin, Patricia Donnadieu, Jean-marc Chaix, Williams Lefebvre, Frédéric De Geuser, Alexis DeschampsAbstract:Transmission Electron Microscopy (TEM) can be used to measure the size distribution and volume fraction of fine scale precipitates in metallic systems. However, such measurements suffer from a number of artefacts that need to be accounted for, related to the finite thickness of the TEM foil and to the projected observation in two dimensions of the microstructure. We present a correction procedure to describe the 3D distribution of disc-like particles and apply this method to the plate-like T1 precipitates in an Al-Li-Cu alloy in two ageing conditions showing different particle morphologies. The precipitates were imaged in a High-Angular Annular Dark Field Microscope (HAADF-STEM). The corrected size distribution is further used to determine the precipitate volume fraction. Atom probe tomography (APT) is finally utilised as an alternative way to measure the precipitate volume fraction and test the validity of the electron microscopy results.
