The Experts below are selected from a list of 9 Experts worldwide ranked by ideXlab platform
Prashant K. Jain - One of the best experts on this subject based on the ideXlab platform.
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Nanoscale optical Imaging in Chemistry.
Chemical Society reviews, 2020Co-Authors: Andrew J. Wilson, Dinumol Devasia, Prashant K. JainAbstract:Single-molecule-level measurements are bringing about a revolution in our understanding of chemical and biochemical processes. Conventional measurements are performed on large ensembles of molecules. Such ensemble-averaged measurements mask molecular-level dynamics and static and dynamic fluctuations in reactivity, which are vital to a holistic understanding of chemical reactions. Watching reactions on the single-molecule level provides access to this otherwise hidden information. Sub-diffraction-limited spatial resolution fluorescence Imaging methods, which have been successful in the field of biophysics, have been applied to study chemical processes on single-nanoparticle and single-molecule levels, bringing us new mechanistic insights into physiochemical processes. However, the scope of chemical processes that can be studied using fluorescence Imaging is considerably limited; the chemical reaction has to be designed such that it involves fluorophores or fluorogenic probes. in this article, we review optical Imaging modalities alternative to fluorescence Imaging, which expand greatly the range of chemical processes that can be probed with nanoscale or even single-molecule resolution. First, we show that the luminosity, wavelength, and intermittency of solid-state photoluminescence (PL) can be used to probe chemical transformations on the single-nanoparticle-level. Next, we highlight case studies where localized surface plasmon resonance (LSPR) scattering is used for tracking solid-state, interfacial, and near-field-driven chemical reactions occurring in individual nanoscale locations. Third, we explore the utility of surface- and tip-enhanced Raman scattering to monitor individual bond-dissociation and bond-formation events occurring locally in chemical reactions on surfaces. Each example has yielded some new understanding about molecular mechanisms or location-to-location heterogeneity in chemical activity. The review finishes with new and complementary tools that are expected to further enhance the scope of knowledge attainable through nanometer-scale resolution chemical Imaging.
Andrew J. Wilson - One of the best experts on this subject based on the ideXlab platform.
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Nanoscale optical Imaging in Chemistry.
Chemical Society reviews, 2020Co-Authors: Andrew J. Wilson, Dinumol Devasia, Prashant K. JainAbstract:Single-molecule-level measurements are bringing about a revolution in our understanding of chemical and biochemical processes. Conventional measurements are performed on large ensembles of molecules. Such ensemble-averaged measurements mask molecular-level dynamics and static and dynamic fluctuations in reactivity, which are vital to a holistic understanding of chemical reactions. Watching reactions on the single-molecule level provides access to this otherwise hidden information. Sub-diffraction-limited spatial resolution fluorescence Imaging methods, which have been successful in the field of biophysics, have been applied to study chemical processes on single-nanoparticle and single-molecule levels, bringing us new mechanistic insights into physiochemical processes. However, the scope of chemical processes that can be studied using fluorescence Imaging is considerably limited; the chemical reaction has to be designed such that it involves fluorophores or fluorogenic probes. in this article, we review optical Imaging modalities alternative to fluorescence Imaging, which expand greatly the range of chemical processes that can be probed with nanoscale or even single-molecule resolution. First, we show that the luminosity, wavelength, and intermittency of solid-state photoluminescence (PL) can be used to probe chemical transformations on the single-nanoparticle-level. Next, we highlight case studies where localized surface plasmon resonance (LSPR) scattering is used for tracking solid-state, interfacial, and near-field-driven chemical reactions occurring in individual nanoscale locations. Third, we explore the utility of surface- and tip-enhanced Raman scattering to monitor individual bond-dissociation and bond-formation events occurring locally in chemical reactions on surfaces. Each example has yielded some new understanding about molecular mechanisms or location-to-location heterogeneity in chemical activity. The review finishes with new and complementary tools that are expected to further enhance the scope of knowledge attainable through nanometer-scale resolution chemical Imaging.
Dinumol Devasia - One of the best experts on this subject based on the ideXlab platform.
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Nanoscale optical Imaging in Chemistry.
Chemical Society reviews, 2020Co-Authors: Andrew J. Wilson, Dinumol Devasia, Prashant K. JainAbstract:Single-molecule-level measurements are bringing about a revolution in our understanding of chemical and biochemical processes. Conventional measurements are performed on large ensembles of molecules. Such ensemble-averaged measurements mask molecular-level dynamics and static and dynamic fluctuations in reactivity, which are vital to a holistic understanding of chemical reactions. Watching reactions on the single-molecule level provides access to this otherwise hidden information. Sub-diffraction-limited spatial resolution fluorescence Imaging methods, which have been successful in the field of biophysics, have been applied to study chemical processes on single-nanoparticle and single-molecule levels, bringing us new mechanistic insights into physiochemical processes. However, the scope of chemical processes that can be studied using fluorescence Imaging is considerably limited; the chemical reaction has to be designed such that it involves fluorophores or fluorogenic probes. in this article, we review optical Imaging modalities alternative to fluorescence Imaging, which expand greatly the range of chemical processes that can be probed with nanoscale or even single-molecule resolution. First, we show that the luminosity, wavelength, and intermittency of solid-state photoluminescence (PL) can be used to probe chemical transformations on the single-nanoparticle-level. Next, we highlight case studies where localized surface plasmon resonance (LSPR) scattering is used for tracking solid-state, interfacial, and near-field-driven chemical reactions occurring in individual nanoscale locations. Third, we explore the utility of surface- and tip-enhanced Raman scattering to monitor individual bond-dissociation and bond-formation events occurring locally in chemical reactions on surfaces. Each example has yielded some new understanding about molecular mechanisms or location-to-location heterogeneity in chemical activity. The review finishes with new and complementary tools that are expected to further enhance the scope of knowledge attainable through nanometer-scale resolution chemical Imaging.
Charles M Lieber - One of the best experts on this subject based on the ideXlab platform.
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direct growth of single walled carbon nanotube scanning probe microscopy tips
Journal of the American Chemical Society, 1999Co-Authors: Jason H Hafner, Chin Li Cheung, Charles M LieberAbstract:Herein, we report the first growth of single-walled carbon nanotubes (SWNTs) directly from conventional atomic force microscopy (AFM) cantilever assemblies to create very highresolution tips for scanning probe microscopies. Metal catalysts were deposited onto the pyramids of microfabricated AFM tips and chemical vapor deposition (CVD) was used to synthesize carbon nanotubes. Scanning and transmission electron microscopies show that nanotubes grow along the surface and reproducibly protrude from the tip apex in the optimal orientation for Imaging, and that single SWNT, small SWNT bundle, or very small diameter multi-walled nanotube (MWNT) tips can be controllably made. AFM measurements demonstrate that these new nanotube tips are mechanically robust and can image with very high resolution. We believe that this straightforward growth method will make nanotube tips broadly accessible, and moreover, that the molecular size diameters of these SWNT tips creates unique opportunities for Imaging in Chemistry and biology. Carbon nanotubes are ideal structures for the tips used in scanning probe microscopies, such as AFM, since they (i) have intrinsically small diameters, which are comparable to molecules in the case of SWNTs, (ii) have high aspect ratios, (iii) can buckle elastically, and (iv) can be selectively modified at their ends with organic and biological species to create functional probes.1-6 Mechanical methods have been used to attach nanotube bundles in the fabrication of tips, although we believe that this timeconsuming approach has limited the development of nanotube tips.1-6 To overcome these limitations we have been exploring the direct catalytic growth of nanotubes from conventional tips and recently showed that individual MWNTs could be grown by CVD from the ends of Si tips with controlled orientation.7 in this first example of the direct growth of nanotube probes, we utilized selective etching of commercial tips to create nanopores, deposited catalyst within these pores, and used the pores to help orient the nanotubes in an ideal direction for Imaging.7 Our present work extends this initial demonstration in two important ways: we show that (1) the pore etching step can be eliminated by using “surface growth” and (2) SWNT tips can be readily prepared by controlling the CVD growth conditions. Our overall strategy for the growth of SWNT tips is outlined in Figure 1. in this approach, catalyst is first deposited onto the pyramidal tip of a commercial cantilever assembly, and then CVD is used to grow the SWNT probe. The basis for this approach is our observation that SWNTs and small diameter MWNTs prefer to grow along a surface (due to the attractive nanotube-surface interaction8), and therefore, will generally bend to stay in contact rather than grow out from the surface when they encounter an edge. Nanotubes prepared from catalyst deposited on a pyramidal AFM tip will grow along the surfaces until they reach the pyramid edges, then some will be directed toward the tip apex along the edges. At the pyramid end the nanotubes will protrude straight from the apex (vs bending) to create an ideal tip, because the strain energy cost of bending the nanotube is not compensated by nanotube-surface interactions. We find that this approach is extremely robust and works readily with a wide range of catalysts. Well-defined SWNT tips are formed reproducibly after CVD growth with ethylene using electrophoretically deposited supported Fe-Mo9 and colloidal Fe-oxide10 catalysts.11,12 Representative electron microscopy images of a nanotube tip produced from the supported Fe-Mo catalyst after 3 min growth in 1:200:300 C2H4:H2:Ar at 800 °C are shown in Figure 2.12 These conditions were specifically chosen to favor the growth of SWNTs and very small diameter MWNTs (<10 nm), and it should be noted that well-defined changes in the ratio of C2H4:H2:Ar can be used to tune nanotube tips from SWNTs to large MWNTs.9 Fieldemission scanning electron microscopy (FE-SEM) images demonstrate that nanotube tips prepared in this way protrude from
Mitsuhiro Murayama - One of the best experts on this subject based on the ideXlab platform.
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ultra fast electron microscopic Imaging of single molecules with a direct electron detection camera and noise reduction
Microscopy and Microanalysis, 2020Co-Authors: Joshua Stuckner, Toshiki Shimizu, Koji Harano, Eiichi Nakamura, Mitsuhiro MurayamaAbstract:Time-resolved Imaging of molecules and materials made of light elements is an emerging field of transmission electron microscopy (TEM), and the recent development of direct electron detection cameras, capable of taking as many as 1,600 fps, has potentially broadened the scope of the time-resolved TEM Imaging in Chemistry and nanotechnology. However, such a high frame rate reduces electron dose per frame, lowers the signal-to-noise ratio (SNR), and renders the molecular images practically invisible. Here, we examined image noise reduction to take the best advantage of fast cameras and concluded that the Chambolle total variation denoising algorithm is the method of choice, as illustrated for Imaging of a molecule in the 1D hollow space of a carbon nanotube with ~1 ms time resolution. Through the systematic comparison of the performance of multiple denoising algorithms, we found that the Chambolle algorithm improves the SNR by more than an order of magnitude when applied to TEM images taken at a low electron dose as required for Imaging at around 1,000 fps. Open-source code and a standalone application to apply Chambolle denoising to TEM images and video frames are available for download.
