Ultrathin films of 2-ferrocenyl-1,3-dithiolane and 2-ferrocenyl-1,3-dithiane (Fcs), which are chemically inert at ambient conditions, are studied on the basal plane of highly oriented pyrolytic graphite (HOPG) using atomic force microscopy (AFM) and scanning tunneling microscopy (STM). Films are prepared by drop-casting using Fcs dissolved in different solvents. Films prepared from methanol and dichloromethane show structural polymorphs on HOPG, while those prepared from ethanol, acetone, and dimethylformamide show an exclusive selection of one of the polymorphs. The selection of growth patterns of Fcs shows interesting correlation to the bulk solubility of molecules in the corresponding solvents and the solvent boiling point. The growth of Fcs at the submonolayer coverage is templated by the surface symmetry, and the molecular level packing on the surface is understood using high-resolution AFM, STM, and the bulk crystal packing of the molecules.
The solvothermal reaction of Zn(NO)·6HO and a linear dicarboxylate ligand HL, in the presence of urotropine in N,N'-dimethylformamide (DMF), gives rise to a new porous two-dimensional (2D) coordination network, {[Zn(L)(urotropine)]·2DMF·3HO} (1), with hxl topology. Interestingly, framework 1 exhibits excellent emission properties owing to the presence of naphthalene moiety in the linker HL, that can be efficiently suppressed by subtle quantity of nitro explosives in aqueous medium. Furthermore, presence of urotropine molecules bound to the metal centers, 1 is found to be an excellent heterogeneous catalyst meant for atom-economical C-C bond-forming Baylis-Hillman reactions. Additionally, crystals of 1 undergo complete transmetalation with Cu(II) to afford isostructural 1. Moreover, the 2D framework of 1 allows replacement of urotropine molecules by 4,4'-azopyridine (azp) linker resulting in a three-dimensional (3D) metal-organic framework, {[Zn(L)(azp)]·4DMF 2HO} (2). The 1→2 transformation takes place in single-crystal-to-single crystal manner supported by powder X-ray diffraction, atomic force microscopy, high-resolution transmission electron microscopy, and morphological studies. Remarkably, during this 2D→3D transformation, the original trinuclear [Zn(COO)] secondary building unit changes to a mononuclear node, which is unprecedented.
various microfluidic devices have been routinely employed. However, in these approaches, there is either a high chance of damaging the cells while detaching the adherent cells from the surfaces, or isolation of individual cells from the adherent cell culture is not at all possible. Table 1 lists the drawbacks and challenges associated with these cell sorting techniques. Recently, atomic force microscope (AFM) has emerged as a significant tool to study microorganisms and mammalian cells in real time. This is due to its compatibility with the physiological conditions of the cells. [3] AFM allows the bioimaging of cells with various degrees of resolution, from whole cells [4] down to individual molecules. [5] Using force-curve based imaging, Alsteens et al. revealed single bacteriophages extruding from the surface of bacteria, [6] whereas our group was able to image nanostructures termed microvilli on the surface of T cells. [7] With the introduction of high-speed AFMs, Yamashita et al. were able to follow the diffusion of single molecules on the surface of living bacterial cells in real time. [8] Valuable biophysical and structural information can be achieved down to a single-cell level by means of high-resolution imaging and force spectroscopy. [9] In force spectroscopy experiments using AFM, a cell is directly attached to the cantilever apex with a biocompatible glue (e.g., polydopamine (PDA)). However, since the cell is irreversibly bound to the AFM probe, each functionalized cantilever can be utilized with only one cell for manipulation. It is, therefore, challenging to perform serial and rapid measurement of a reasonable number of cells; this makes it a time-consuming and elaborate process to address a statistical distribution. For injecting biomolecules such as dyes, enzymes or nanoparticles into single living cells, various approaches such as nano-fountain probes, [10] nanoneedles, [11] and carbon nanotubes [12] have been used. However, these approaches lack precise handling for local dispensing of fluid and are limited to the handling of very small volumes (on the order of attoliters (aLs) up to 50 femtoliters (fLs)). Moreover, using these approaches, a relatively long period of time is required to perform intracellular injection. With the advancement of technologies, it has become relatively easier to address these problems in a more controlled manner. Conventional AFM has been integrated with microfluidics to overcome these limitations. [13] This bioanalytical tool is known as a fluidic force microscope or FluidFM, which was This review describes the potential of FluidFM technology and its implementation in studying the interface between a single cell (prokaryote or eukaryote) and a surface or a surrounding area. A combination of microfluidics with conventional atomic force microscope (AFM) makes this platform efficient to address challenges associated with various biomolecular systems and biophysical activities down to single-cell levels. Upon regulating the pressure through a microchanneled cantilever v...
Ferrocenyl-Alkyl-Protected Sugar (Fc-Sug) and Ferrocenyl-Oxo-Alkyl-Protected Sugar (Fc-Oxo-Sug) were deposited on the basal plane of Highly Oriented Pyrolytic Graphite (HOPG) using a drop-casting method. Ultrathin films of these molecules were investigated using Atomic Force Microscopy to understand the growth at low coverage. Both molecules are forming highly ordered one-dimensional molecular islands, which are growing from a dimer building block. The dimer and interdimer interactions (along the length of islands) are stabilized by −C2O···H–C hydrogen bonding. Unlike for Fc-Sug, the islands of Fc-Oxo-Sug are extended to tens of micrometers, and the growth is only limited by terrace edges or other islands on the surface. This exceptional growth of islands is understood in terms of an additional −CO···H–C– hydrogen bonding leading to stronger interdimer interactions along the length of the islands compared to Fc-Sug.
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