The Experts below are selected from a list of 34515 Experts worldwide ranked by ideXlab platform
Xinxin Zhang - One of the best experts on this subject based on the ideXlab platform.
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determining the surface tension of two dimensional Nanosheets by a low rate advancing contact angle measurement
Langmuir, 2019Co-Authors: Xinru Zhang, Zeyi Jiang, Hao Yuan, Yang Wang, Xinxin ZhangAbstract:Because of their atomic thinness, two-dimensional (2D) Nanosheets need be bound to a substrate or be dispersed in material in various applications. The surface tension (ST) of a 2D nanosheet is critical for analyzing the physicochemical interactions between 2D Nanosheets and other materials. To date, the determination of the ST of 2D Nanosheets has relied mainly on the contact angle (CA) method. However, because of the difficulty in measuring the thermodynamically significant Young?s CA, which is the only meaningful CA that can be used to determine the ST, significant differences exist in reported STs of 2D Nanosheets. In this study, we obtained such unique Young?s CAs on graphene, boron nitride, molybdenum disulfide, and tungsten disulfide Nanosheets by a low-rate advancing contact angle measurement using a rigorously designed experimental setup. By interpreting the CA with Neumann?s equation of state, we determined the STs of these four Nanosheets to be 29.7 ? 0.6, 30.9 ? 0.7, 27.8 ? 0.7, and 29.1 ? 0.8...
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determining the surface tension of two dimensional Nanosheets by a low rate advancing contact angle measurement
Langmuir, 2019Co-Authors: Xinru Zhang, Zeyi Jiang, Hao Yuan, Yang Wang, Xinzhi Cai, Kairu Jin, Yan Jia, Limei Cao, Xinxin ZhangAbstract:Because of their atomic thinness, two-dimensional (2D) Nanosheets need be bound to a substrate or be dispersed in material in various applications. The surface tension (ST) of a 2D nanosheet is cri...
Xinru Zhang - One of the best experts on this subject based on the ideXlab platform.
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determining the surface tension of two dimensional Nanosheets by a low rate advancing contact angle measurement
Langmuir, 2019Co-Authors: Xinru Zhang, Zeyi Jiang, Hao Yuan, Yang Wang, Xinxin ZhangAbstract:Because of their atomic thinness, two-dimensional (2D) Nanosheets need be bound to a substrate or be dispersed in material in various applications. The surface tension (ST) of a 2D nanosheet is critical for analyzing the physicochemical interactions between 2D Nanosheets and other materials. To date, the determination of the ST of 2D Nanosheets has relied mainly on the contact angle (CA) method. However, because of the difficulty in measuring the thermodynamically significant Young?s CA, which is the only meaningful CA that can be used to determine the ST, significant differences exist in reported STs of 2D Nanosheets. In this study, we obtained such unique Young?s CAs on graphene, boron nitride, molybdenum disulfide, and tungsten disulfide Nanosheets by a low-rate advancing contact angle measurement using a rigorously designed experimental setup. By interpreting the CA with Neumann?s equation of state, we determined the STs of these four Nanosheets to be 29.7 ? 0.6, 30.9 ? 0.7, 27.8 ? 0.7, and 29.1 ? 0.8...
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determining the surface tension of two dimensional Nanosheets by a low rate advancing contact angle measurement
Langmuir, 2019Co-Authors: Xinru Zhang, Zeyi Jiang, Hao Yuan, Yang Wang, Xinzhi Cai, Kairu Jin, Yan Jia, Limei Cao, Xinxin ZhangAbstract:Because of their atomic thinness, two-dimensional (2D) Nanosheets need be bound to a substrate or be dispersed in material in various applications. The surface tension (ST) of a 2D nanosheet is cri...
Xidong Wang - One of the best experts on this subject based on the ideXlab platform.
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electrodeposition of hierarchical zno nanorod nanosheet structures and their applications in dye sensitized solar cells
ACS Applied Materials & Interfaces, 2011Co-Authors: Xidong WangAbstract:We present a two-step electrochemical deposition process to synthesize hierarchical zinc oxide (ZnO) nanorod-nanosheet structures on indium tin oxide (ITO) substrate, which involves electrodeposition of ZnO nanosheet arrays on the conductive glass substrate, followed by electrochemical growth of secondary ZnO nanorods on the backbone of the primary ZnO Nanosheets. The formation mechanism of the hierarchical nanostructure is discussed. It is demonstrated that annealing treatment of the primary Nanosheets synthesized by the first-step deposition process plays a key role in synthesizing the hierarchical nanostructure. Photovoltaic properties of dye-sensitized solar cells (DSSCs) based on hierarchical ZnO nanostructures are investigated. The hierarchical ZnO nanorod-nanosheet DSSC exhibits improved device performance compared to the DSSC constructed using photoelectrode of bare ZnO nanosheet arrays. The improvement can be attributed to the enhanced dye loading, which is caused by the enlargement of internal s...
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electrodeposition of hierarchical zno nanorod nanosheet structures and their applications in dye sensitized solar cells
ACS Applied Materials & Interfaces, 2011Co-Authors: Jianhang Qiu, Min Guo, Xidong WangAbstract:We present a two-step electrochemical deposition process to synthesize hierarchical zinc oxide (ZnO) nanorod-nanosheet structures on indium tin oxide (ITO) substrate, which involves electrodeposition of ZnO nanosheet arrays on the conductive glass substrate, followed by electrochemical growth of secondary ZnO nanorods on the backbone of the primary ZnO Nanosheets. The formation mechanism of the hierarchical nanostructure is discussed. It is demonstrated that annealing treatment of the primary Nanosheets synthesized by the first-step deposition process plays a key role in synthesizing the hierarchical nanostructure. Photovoltaic properties of dye-sensitized solar cells (DSSCs) based on hierarchical ZnO nanostructures are investigated. The hierarchical ZnO nanorod-nanosheet DSSC exhibits improved device performance compared to the DSSC constructed using photoelectrode of bare ZnO nanosheet arrays. The improvement can be attributed to the enhanced dye loading, which is caused by the enlargement of internal surface area within the nanostructure photoelectrode. Furthermore, we perform a parametric study to determine the optimum geometric dimensions of the hierarchical ZnO nanorod-nanosheet photoelectrode through adjusting the preparation conditions of the first- and second-step deposition process. By utilizing a hierarchical nanostructure photoelectrode with film thickness of about 7 μm, the DSSC with an open-circuit voltage of 0.74 V and an overall power conversion efficiency of 3.12% is successfully obtained.
Jonathan N Coleman - One of the best experts on this subject based on the ideXlab platform.
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spectroscopic metrics allow in situ measurement of mean size and thickness of liquid exfoliated few layer graphene Nanosheets
Nanoscale, 2016Co-Authors: Claudia Backes, Damien Hanlon, Keith R Paton, Shengjun Yuan, M I Katsnelson, James Houston, Ronan J Smith, David Mccloskey, J F Donegan, Jonathan N ColemanAbstract:Liquid phase exfoliation is a powerful and scalable technique to produce defect-free mono- and few-layer graphene. However, samples are typically polydisperse and control over size and thickness is challenging. Notably, high throughput techniques to measure size and thickness are lacking. In this work, we have measured the extinction, absorption, scattering and Raman spectra for liquid phase exfoliated graphene Nanosheets of various lateral sizes (90 ≤ 〈L〉 ≤ 810 nm) and thicknesses (2.7 ≤ 〈N〉 ≤ 10.4). We found all spectra to show well-defined dependences on nanosheet dimensions. Measurements of extinction and absorption spectra of nanosheet dispersions showed both peak position and spectral shape to vary with nanosheet thickness in a manner consistent with theoretical calculations. This allows the development of empirical metrics to extract the mean thickness of liquid dispersed Nanosheets from an extinction (or absorption) spectrum. While the scattering spectra depended on nanosheet length, poor signal to noise ratios made the resultant length metric unreliable. By analyzing Raman spectra measured on graphene nanosheet networks, we found both the D/G intensity ratio and the width of the G-band to scale with mean nanosheet length allowing us to establish quantitative relationships. In addition, we elucidate the variation of 2D/G band intensities and 2D-band shape with the mean nanosheet thickness, allowing us to establish quantitative metrics for mean nanosheet thickness from Raman spectra.
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large scale production of size controlled mos2 Nanosheets by shear exfoliation
Chemistry of Materials, 2015Co-Authors: Eswaraiah Varrla, Claudia Backes, Zahra Gholamvand, Andrew Harvey, Keith R Paton, Joe Mccauley, Jonathan N ColemanAbstract:In order to fulfill their potential for applications, it will be necessary to develop large-scale production methods for two-dimensional (2D) inorganic Nanosheets. Here we demonstrate the large-scale shear-exfoliation of molybdenum disulfide Nanosheets in aqueous surfactant solution using a kitchen blender. Using standard procedures, we measure how the MoS2 concentration and production rate scale with processing parameters. However, we also use recently developed methods based on optical spectroscopy to simultaneously measure both nanosheet lateral size and thickness, allowing us to also study the dependence of nanosheet dimensions on processing parameters. We found the nanosheet concentration and production rates to depend sensitively on the mixing parameters (the MoS2 concentration, Ci; the mixing time, t; the liquid volume, V; and the rotor speed, N). By optimizing mixing parameters, we achieved concentrations and production rates as high as 0.4 mg/mL and 1.3 mg/min, respectively. Conversely, the nanos...
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Measuring the lateral size of liquid-exfoliated Nanosheets with dynamic light scattering
Nanotechnology, 2013Co-Authors: Mustafa Lotya, Aliaksandra Rakovich, John F. Donegan, Jonathan N ColemanAbstract:We have developed an in situ method to estimate the lateral size of exfoliated Nanosheets dispersed in a liquid. Using standard liquid exfoliation and size-selection techniques, we prepared a range of dispersions of graphene, MoS2 and WS2 Nanosheets with different mean lateral sizes. The mean nanosheet length was measured using transmission electron microscopy (TEM) to vary from ∼40 nm to ∼1 μm. These dispersions were characterized using a standard dynamic light scattering (DLS) instrument. We found a well-defined correlation between the peak of the particle size distribution as outputted by the DLS instrument and the nanosheet length as measured by TEM. This correlation is consistent with the DLS instrument outputting the radius of a sphere with volume equal to the mean nanosheet volume. This correlation allows the mean nanosheet length to be extracted from DLS data.
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preparation of high concentration dispersions of exfoliated mos2 with increased flake size
Chemistry of Materials, 2012Co-Authors: Arlene Oneill, Umar Khan, Jonathan N ColemanAbstract:Solvent exfoliation of inorganic layered compounds is likely to be important for a range of applications. However, this method generally gives dispersions of small Nanosheets at low concentrations. Here we describe methods, based on sonication of powdered MoS2 in the solvent N-methyl-pyrrolidone, to prepare dispersions with significantly increased lateral nanosheet size and dispersed concentration. We find the concentration to scale linearly with starting MoS2 mass allowing the definition of a yield. This yield can be increased to ∼40% by controlling the sonication time, resulting in concentrations as high as 40 mg/mL. We find the nanosheet size to increase initially with sonication time reaching ∼700 nm (for a concentration of ∼7.5 mg/mL). At longer sonication times the Nanosheets size falls off due to sonication induced scission. The Nanosheets produced by such methods are relatively thin and have no observable defects. We can separate the dispersed Nanosheets by size using controlled centrifugation. Th...
Yang Wang - One of the best experts on this subject based on the ideXlab platform.
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determining the surface tension of two dimensional Nanosheets by a low rate advancing contact angle measurement
Langmuir, 2019Co-Authors: Xinru Zhang, Zeyi Jiang, Hao Yuan, Yang Wang, Xinxin ZhangAbstract:Because of their atomic thinness, two-dimensional (2D) Nanosheets need be bound to a substrate or be dispersed in material in various applications. The surface tension (ST) of a 2D nanosheet is critical for analyzing the physicochemical interactions between 2D Nanosheets and other materials. To date, the determination of the ST of 2D Nanosheets has relied mainly on the contact angle (CA) method. However, because of the difficulty in measuring the thermodynamically significant Young?s CA, which is the only meaningful CA that can be used to determine the ST, significant differences exist in reported STs of 2D Nanosheets. In this study, we obtained such unique Young?s CAs on graphene, boron nitride, molybdenum disulfide, and tungsten disulfide Nanosheets by a low-rate advancing contact angle measurement using a rigorously designed experimental setup. By interpreting the CA with Neumann?s equation of state, we determined the STs of these four Nanosheets to be 29.7 ? 0.6, 30.9 ? 0.7, 27.8 ? 0.7, and 29.1 ? 0.8...
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determining the surface tension of two dimensional Nanosheets by a low rate advancing contact angle measurement
Langmuir, 2019Co-Authors: Xinru Zhang, Zeyi Jiang, Hao Yuan, Yang Wang, Xinzhi Cai, Kairu Jin, Yan Jia, Limei Cao, Xinxin ZhangAbstract:Because of their atomic thinness, two-dimensional (2D) Nanosheets need be bound to a substrate or be dispersed in material in various applications. The surface tension (ST) of a 2D nanosheet is cri...
