J.-P. Douliez, N. Martin, A. Perro and L. Béven
Building artificial cells through a bottom‐up approach is a remarkable challenge. All‐in‐water emulsion droplets, including coacervate droplets, are promising compartments, mainly because they can spontaneously sequester chemicals. These all‐in‐water emulsion droplets are expected to be suitable compartments as artificial cells.
J. Kalecki, M. Cieplak, M. Dąbrowski, W. Lisowski, A. Kuhn, P. Sindhu Sharma
Homogenous nanostructuration of molecularly imprinted polymer (MIP) films for follicle-stimulating hormone (FSH) sensing was achieved by using optimized colloidal crystals as a hard mold. Introduction of heating step after assembling colloidal crystals of silica beads promoted their adhesion. Thus precise assembling of beads was not disturbed during further multistep of surface imprinting, and crack free hexagonal packing was maintained. SEM imaging confirmed hexagonal packing of silica colloidal crystals as well as homogenous nanostructurization in MIP films. FSH immobilization over silica beads and later its derivatization with electroactive functional monomers was confirmed by XPS analysis. The nanostructured molecular recognition films prepared in this way were combined with an electrochemical transducer in order to design a capacitive impedimetry (CI) based chemosensing system. It was tested for the determination of FSH in the range from 0.1 fM to 100 pM in 10 mM MES buffer (pH = 4.2). The detection limit of the chemosensor was 0.1 fM showing a high selectivity with respect to common protein interferences as well as other protein hormones of the gonadotropin family.
S. Assavapanumat, M. Ketkaew, A. Kuhn, C.Wattanakit
J. Am.Chem.Soc. 141 (2019) 18870 (Front Cover)
see also CNRS press release
The enantioselective synthesis of chiral compounds is of crucial importance for a wide range of potential applications, especially in cosmetic and pharmaceutical industries. Recently, chiral imprinted mesoporous platinum films, produced by the electrodeposition of the metal, in the simultaneous presence of a lyotropic liquid crystalline phase of non-ionic surfactants as mesoporogens and chiral templates, have been applied as electrocatalysts and selective stationary phases for the asymmetric synthesis and separation of chiral compounds, respectively. However, platinum is an expensive metal and therefore it is mandatory to explore the possibility to apply this concept also to other metals. In this contribution, we propose mesoporous chiral imprinted nickel as an alternative cheap and earth-abundant metal. The designed surface layers not only demonstrate electrochemical discrimination between two enantiomers, but most importantly, also allow stereospecific electroreduction of a prochiral compound, with very significant enantioselectivity of up to 80% ee. These results open up very promising perspectives for the development of low cost non-noble metal matrices for the synthesis of chiral compounds.
C. Wattanakit, A. Kuhn
The concept of encoding molecular information in bulk metals has been proposed over the past decade. The structure of various types of molecules has been imprinted, including also enantiomers. Typically, to encode metals with chiral information, several approaches, based on chemical and electrochemical concepts, can be used. In this minireview we discuss recent achievements with respect to the development of such materials, including the entrapment of chiral biomolecules in metals, the chiral imprinting of metals, as well as the combination of imprinting with nanostructuring. The features and potential applications of these designer materials, such as chirooptical properties, enantioselective adsorption and separation as well as their use for asymmetric synthesis will be presented. This will illustrate that the development of molecularly encoded metal structures opens up very interesting perspectives, especially in the frame of chiral technologies.
Gold microelectrodes decorated with nanotips were developed for spectroelectrochemical experiments. These new dual probes were fabricated by combining fabrication processes of scanning near-field optical microscopy with photolithography. A nanotip array was produced at the surface of a coherent optical fiber bundle by a wet chemical etching step. The resulting nanostructured surface was sputter-coated with a thin gold layer. This gold film conferred plasmonic properties to the sharp nanotips and served as well as the electrode material to enable electrochemical reactions. A photolithographic process was used to define on the bundle surface nanotips-decorated microelectrodes with tunable dimensions (radii ranging between 20 μm and 3.5 μm) individually or in an array format. The resulting microelectrodes with a regular nanotip pattern were characterized first by cyclic voltammetry. Numerical simulation was used to assess the electrochemical properties of these platforms and the influences of the recessed geometry and of the nanotips. Approach curves were recorded in negative and positive feedback modes of scanning electrochemical microscopy (SECM) on insulating and conducting substrates. Finally, spatially resolved Raman imaging allowed us to detect a mercaptobenzoic acid monolayer adsorbed on the microelectrode surface, demonstrating a surface-enhanced Raman scattering (SERS) effect induced by the gold-coated nanotips with a typical enhancement factor of ∼7 × 104. Such an approach introduces a reproducible method to fabricate promising SERS-active platforms with microelectrode behavior for SECM experiments.
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