Bio-inspired V 2 O 5 -polymer hybrid films were prepared following a one-step self-organization procedure based on liquid crystal formation of organic and inorganic components. These materials were previously reported to exhibit advantageous mechanical properties, comparable to biomaterials, such as human bone and dentin. Here, we show that these hybrid films prepared via a fast and simple synthesis procedure have an additional function as an electrochromic material, exhibiting a long-term cycle stability under alternating potentials. The structures were found to remain intact without visible changes after more than hundred switching cycles and storing the devices for several weeks. Consequently, this multifunctional V 2 O 5 -polymer hybrid system shows great promise for various technical applications.Organic-inorganic biomaterials, such as bone and nacre, consist of high, stiff and brittle, mineral fractions, which are embedded in a so organic matrix.1,2 These materials exhibit a pronounced hierarchical structure and a controlled coupling at the interface between organic and inorganic components. These structural characteristics contribute to their outstanding mechanical properties, combining both high stiffness and toughness.3-6 Very recently, we developed a biomimetic fabrication concept for the synthesis of organic-inorganic composites based on liquid crystal (LC) formation of organic and inorganic components.7 The LC 'gluing' polymer used was a statistical polyoxazoline with pendant cholesteryl and carboxyl side chains, enabling the polymer, on the one hand, to form chiral-nematic lyotropic phases on the length scale of several hundreds of micrometers upon shearing, and on the other hand, to selectively bind to nanoparticle faces via electrostatic interactions or hydrogen bridges.7,8 The inorganic nanoparticles, Laponite 7 and vanadium pentoxide (V 2 O 5 ), 8 are anisotropic in shape and consequently, were also able to form LC phases. V 2 O 5 -LC polymer composites structured on six hierarchical levels exhibiting a well-dened nanostructure and a hierarchical structuring on the length scale of several hundreds of micrometers were fabricated via this one-step selforganization process.8 Long-range orientation of the polymeric lyotropic phase was induced by rotational shearing by means of a shear cell. Remarkably, these materials exhibit advantageous mechanical properties, comparable to mechanical properties of natural hierarchically structured organic-inorganic composites like human bone and dentin (data obtained by nanoindentation; a video visualizing the bending performance of the composite is available in the ESI †).8 In this study, we investigated these materials regarding their electrochromic performance, a second feature of this composite system, besides mechanical reinforcement.Electrochromism of thin lms of transition-metal oxides, such as tungsten oxide (WO 3 ) or V 2 O 5 , have been previously studied. Upon cation intercalation (reduction) of the metal oxide, a change in absorbance in the visib...

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Electrochemical immunosensors enable rapid analyte quantification in small sample volumes, and have been demonstrated to provide high sensitivity and selectivity, simple miniaturization, and easy sensor production strategies. As a point-of-care (POC) format, user-friendliness is equally important and most often not combinable with high sensitivity. As such, we demonstrate here that a sequence of metal oxidation and reduction, followed by stripping via differential pulse voltammetry (DPV), provides lowest limits of detection within a 2-min automatic measurement. In exchanging gold nanoparticles (AuNPs), which dominate in the development of POC sensors, with silver nanoparticles (AgNPs), not only better sensitivity was obtained, but more importantly, the assay protocol could be simplified to match POC requirements. Specifically, we studied both nanoparticles as reporter labels in a sandwich immunoassay with the blood protein biomarker NT-proBNP. For both kinds of nanoparticles, the dose-response curves easily covered the ng∙mL−1 range. The mean standard deviation of all measurements of 17% (n ≥ 4) and a limit of detection of 26 ng∙mL−1 were achieved using AuNPs, but their detection requires addition of HCl, which is impossible in a POC format. In contrast, since AgNPs are electrochemically less stable, they enabled a simplified assay protocol and provided even lower LODs of 4.0 ng∙mL−1 in buffer and 4.7 ng∙mL−1 in human serum while maintaining the same or even better assay reliability, storage stability, and easy antibody immobilization protocols. Thus, in direct comparison, AgNPs clearly outperform AuNPs in desirable POC electrochemical assays and should gain much more attention in the future development of such biosensors.

Silver nanoparticles (AgNPs) have long been overshadowed by gold NPs’ success in sensor and point-of-care (POC) applications. However, their unique physical, (electro)chemical, and optical properties make them excellently suited for such use, as long as their inherent higher instability toward oxidation is controlled. Recent advances in this field provide novel strategies that demonstrate that the AgNPs’ inherent capabilities improve sensor performance and enable the specific detection of analytes at low concentrations. We provide an overview of these advances by focusing on the nanosized Ag (in the range of 1-100 nm) properties with emphasis on optical and electrochemical biosensors. Furthermore, we critically assess their potential for point-of-care sensors discussing advantages as well as limitations for each detection technique. We can conclude that, indeed, strategies using AgNP are ready for sensitive POC applications; however, research focusing on the simplification of assay procedures is direly needed for AgNPs to make the successful jump into actual applications. Graphical abstract

Bearing multiple functionalities dramatically increases nanomaterial capabilities to enhance analytical assays by improving sensitivity, selectivity, sample preparation, or signal read-out strategies. Magnetic properties are especially desirable for nanoparticles and nanovesicles...

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