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Liquid Phase Studies of Nanomaterials
摘要： Liquid cell transmission electron microscopy (LCTEM) is a relatively new technique enabling researchers to study dynamic phenomena in materials sciences, life sciences and electrochemistry. LCTEM has proved to be a remarkable tool for observing colloidal nanoparticle syntheses at fairly high temporal and spatial resolutions offered by transmission electron microscopy (TEM). Though the idea of observing syntheses in their native media is not new, a practical approach has only been made possible through massive improvements in microfabrication technology to fabricate liquid cells.[1] The idea is to use thin window materials such as SiN membranes (50 nm or less) to encapsulate tens of cubic nanometers of liquid in a stable thin profile suitable forTEM imaging considering the vacuum environment of the microscope (Fig. 1).
关键词： Radiolysis,Nanoparticles,Electron beam irradiation,Solvent,Liquid cell TEM
更新于2025-09-23 15:21:21
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Liquid-Cell Scanning Transmission Electron Microscopy and Fluorescence Correlation Spectroscopy of DNA-Directed Gold Nanoparticle Assemblies
摘要： In the use of solution-based 3D nanoarchitectures for optics, drug delivery, and cancer treatment, the precise nanoparticle architecture morphologies, architecture sizes, interparticle distances, and the assembly stability are all critical to their functionality. 3D nanoparticle architectures in solution are difficult to characterize, as few techniques can provide individualized information on interparticle spacing (defined by linkage molecule), nanoparticle assembly size, morphology, and identification of false aggregation. Bulk characterization techniques, including small angle x-ray scattering, can provide architecture sizes, though they are unable to precisely measure differences within interparticle spacings for individual architectures and can falsely measure assemblies caused by non-linkage grouped nanoparticles. Two solution-based characterization techniques were used to determine which assembly type and linkage length would produce the fastest assembly rate for large DNA-directed gold nanoparticle assemblies. In-situ liquid-cell scanning transmission electron microscopy (STEM), measured interparticle spacings between DNA-functionalized nanoparticles, and fluorescence correlation spectroscopy provided the bulk volume fraction of large and small assemblies for nanoparticle architectures that were assembled using two different types: (1) the hybrid assemblies join two complementary single-stranded DNA linkages, and (2) the bridged assemblies are comprised of single-stranded DNA (bridging component) that is double the length of two different complementary single-stranded DNA-functionalized gold nanoparticles (Fig. 1). Assembly times were tested at 24-hour intervals over 3 days. Statistics derived from the in-situ liquid-cell STEM images provided data for interparticle distance measurements, which identified the fraction of nanoparticles within the images acquired that were at the expected double-stranded DNA-binding distance of the linkages (varied in three distances for each of the two different architectures). In general, longer linkage lengths assembled in the shortest amount of time. The bridged assemblies formed fewer large architectures at 24-hours but ultimately assembled a greater fraction of nanoparticles, which was due to the longer functionalized DNA lengths for individual nanoparticles. Fluorescence correlation spectroscopy provided a bulk average of the gold nanoparticle assembly sizes over time, which supported the conclusions drawn from the in-situ liquid-cell STEM data. The microscopy provided sub-2 nanometer precision in the interparticle distances between gold nanoparticles in a solution environment. This coupled microscopy and spectroscopy characterization approach can provide more detailed information than bulk characterization methods.
关键词： gold,nanoparticle,DNA,FCS,assembly,liquid-cell TEM
更新于2025-09-23 15:21:21