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81.
Krause KM Vick DW Malac M Brett MJ 《Langmuir : the ACS journal of surfaces and colloids》2010,26(22):17558-17567
The high surface area, large aspect ratio, and porous nature of nanorod arrays make them excellent foundation materials for many devices. Of the many synthesis techniques for forming nanorods, glancing angle deposition (GLAD) offers one of the more straightforward and flexible methods for ensuring control of alignment, porosity, and architecture of the nanorods. Here we demonstrate the first use of a dual-beam (focused ion beam (FIB) combined with scanning electron microscopy (SEM)) instrument to section and image the internal morphology of a nanorod array fabricated using the GLAD technique. We have used the FIB-SEM to reconstruct the 3D composition of TiO(2) nanorods, allowing us to visualize for the first time the core structures of many potential devices. We have also been able to probe the relationship between critical parameters such as diameter (w(act)), internanorod spacing (ν(act)), center-to-center spacing (c(act)), and nanorod population density (d(act)) and the depth of the nanocolumn (t) for a single homogeneous structure. A continuous data set was obtained from a single 5-μm-thick GLAD film, avoiding the artifacts arising from the analysis of the top surfaces of multiple samples of varying thicknesses. An analysis of the acquired sectioned data has allowed us to determine that the critical nanocolumn parameters follow a power-law scaling trend with w(act) = 9.4t(0.35) nm, ν(act) = 15.2t(0.25) nm, c(act) = 24.8t(0.31) nm, and d(act) = 3402t(-0.65) columns μm(-2). Using the FIB/SEM images acquired for the TiO(2) nanorods, we have also investigated the evolution of individual nanocolumns and have observed that bifurcation and branching play a significant role in the extinction or survival of these nanorods. These findings will allow for the optimization of nanorod properties for device applications. Also, the FIB sectioning and reconstruction process developed here will permit for the investigation of nanorod arrays formed from a range of synthesis techniques and materials. 相似文献
82.
Michael E. Kurczy Paul D. Piehowsky David Willingham Kathleen A. Molyneaux Michael L. Heien Nicholas Winograd Andrew G. Ewing 《Journal of the American Society for Mass Spectrometry》2010,21(5):833-836
A C60+ cluster ion projectile is employed for sputter cleaning biological surfaces to reveal spatio-chemical information obscured
by contamination overlayers. This protocol is used as a supplemental sample preparation method for time of flight secondary
ion mass spectrometry (ToF-SIMS) imaging of frozen and freeze-dried biological materials. Following the removal of nanometers
of material from the surface using sputter cleaning, a frozen-patterned cholesterol film and a freeze-dried tissue sample
were analyzed using ToF-SIMS imaging. In both experiments, the chemical information was maintained after the sputter dose,
due to the minimal chemical damage caused by C60+ bombardment. The damage to the surface produced by freeze-drying the tissue sample was found to have a greater effect on
the loss of cholesterol signal than the sputter-induced damage. In addition to maintaining the chemical information, sputtering
is not found to alter the spatial distribution of molecules on the surface. This approach removes artifacts that might obscure
the surface chemistry of the sample and are common to many biological sample preparation schemes for ToF-SIMS imaging. 相似文献
83.
84.
Structural Chemistry - In the current study, the energetics of fractionally (and indeed arbitrary non-integer) charged species is explicitly discussed for the enhanced understanding of aromaticity... 相似文献
85.
Simon G. Bott Alan P. Marchand L. Kathleen Talafuse D. Rajagopal 《Journal of chemical crystallography》1995,25(9):543-547
The structure consists of two acetyl-substituted PCU cages linked by a diyne fragment. The conformation about the linker is midway between staggered and eclipsed, and the acetyl groups are somewhat distorted due to the proximity to the bulky cage units. 相似文献
86.
A divergent synthesis of (-)-4-epi-shikimic acid was developed. This route features a one-pot zinc-mediated reductive ring opening of an arabinofuranose followed by a Barbier reaction and culminates in a ring-closing metathesis. Functionalization of (-)-4-epi-shikimic acid via conjugate addition of a thiol occurs in high diastereoselectivity to afford a product with the features of fucosylated glycans. 相似文献
87.
Christine N. Morrison Kathleen E. Prosser Ryjul W. Stokes Anna Cordes Nils Metzler-Nolte Seth M. Cohen 《Chemical science》2022,13(32):9450
Correction for ‘Expanding medicinal chemistry into 3D space: metallofragments as 3D scaffolds for fragment-based drug discovery’ by Christine N. Morrison et al., Chem. Sci., 2020, 11, 1216–1225, https://doi.org/10.1039/C9SC05586J.The authors regret that in the original article, inhibitory values reported for some metallofragments were incorrect. Unfortunately, DMSO stock solutions of reportedly active ferrocene-based metallofragments were found to decompose in the presence of light, which resulted in inaccurate inhibition values. The authors maintain that the core conclusions of the paper are accurate and the utility of three-dimensional metal complexes for fragment-based drug discovery has merit.In the original article, ‘class A’ metallofragments are comprised of ferrocene derivatives (Fig. 1). Some of these ferrocene fragments (specifically those containing carbonyl groups) are reported as broadly inhibiting several protein targets. It was noted in our original report that the ferrocene scaffold was likely promiscuous due to its lipophilicity and potential redox activity, but that it might still serve as a useful metallofragment for fragment-based drug discovery (FBDD) campaigns. However, re-evaluation of these compounds against the influenza endonuclease (PAN) failed to reproduce our original inhibition results for the class A metallofragments using freshly prepared stocks, indicating a problem with the materials used in the original study.Open in a separate windowFig. 1Chemical structures of class A metallofragments.Several compounds from class A were originally reported as having near complete (100%) inhibition against PAN endonuclease at an inhibitor concentration of 200 μM (and2).2). However, when re-evaluated under identical conditions, using freshly prepared DMSO stock solutions, inhibition was only observed with one fragment of this class (A22, Fig. 1), with the previously reported highly active fragments (A4, A7–A21, Compound A1 A2 A3 A4 A5 A7 A8 A9 A10 A11 Reported 12 ± 6 <1 <1 45 ± 14 8 ± 7 103 ± 5 103 ± 4 53 ± 5 46 ± 7 90 ± 5 Corrected 3 ± 10 n.d. 18 ± 3 6 ± 3 21 ± 5 9 ± 3 10 ± 5 4 ± 2 16 ± 4 10 ± 7