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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
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Synchrotron infrared nanospectroscopy on a graphene chip
摘要： A recurring goal in biology and biomedicine research is to access the biochemistry of biological processes in liquids that represent the environmental conditions of living organisms. These demands are becoming even more specific as microscopy techniques are fast evolving to the era of single cells analysis. In the modality of chemical probes, synchrotron infrared spectroscopy (μ-FTIR) is a technique that is extremely sensitive to vibrational response of materials, however, the classical optical limits prevent the technique to access the biochemistry of specimens in the subcellular level. In addition, due to the intricate environmental requirements and strong infrared absorption of water, μ-FTIR of bioprocess in liquids remains highly challenging. In phase with those challenges, on-chip liquid cells emerge as a versatile alternative to control the water thickness while providing a biocompatible chemical environment for analytical analyzes. In this work we report the development of a liquid platform specially designed for nanoscale infrared analysis of biomaterials in wet environments. A key advantage of our designed platform is the use of graphene as the optical window that interfaces wet and dry environments in the liquid cell. By combining near-field optical microscopy and synchrotron infrared radiation, we measure nanoscale fingerprint IR absorbance of a variety of liquids often used in biological studies. Further, we demonstrate the feasibility of the platform for the chemical analysis of protein clusters immersed in water with a clear view of the proteins secondary structure signatures. The simplicity of the proposed platform combined to the high quality of our data make our findings a template for future microfluidic devices targeting dynamical nanoscale-resolved chemical analysis.
关键词： nanoscale chemical analysis,biomaterials,synchrotron infrared nanospectroscopy,graphene chip,liquid cell
更新于2025-09-11 14:15:04