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•Arrays of glassy carbon nanoelectrodes are prepared by nanoimprinting lithography.•They are designed to operate under total overlap diffusion conditions.•They provide high Faradaic ...signals and low capacitive current.•Achievable potential window is extended with respect to noble metal arrays.•Highly reversible responses are detected for oxidase and reductase redox mediators.
In the present study, the preparation and electrochemical application of perfectly ordered arrays of glassy carbon nanoelectrodes (GC-NEAs) is presented. After careful morphological characterization, we examined the voltammetric behaviour on GC-NEAs of some redox mediators commonly used in enzymatic electrochemical biosensors. GC-NEAs were fabricated by using nanoimprint lithography to generate ordered arrays of nanoholes, with average radius of 145 nm, onto a polycarbonate thin film deposited on a glassy carbon plate. The redox mediators examined were (ferrocenylmethyl)trimethylammonium (FA+) as typical redox mediator for oxidase enzymes and Azure A and B as examples of mediators used for reductase enzymes. The voltammetric signals recorded indicate that the here prepared GC-NEAs operate under total overlap diffusion conditions, with an accessible potential window significantly wider than the one typical of arrays of gold nanoelectrodes. Interestingly, the electrochemical behaviour of the GC-NEAs perfectly fits with what expected on the basis of the geometrical features of the array demonstrating the role of these parameters in ruling the contribution of capacitive and faradic currents of the array which reflect in improved detection capabilities.
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The development of new safe inorganic UV filters to effectively protect the skin from ultraviolet (UV) radiation effects is an emerging issue. Bismuth titanate-based UV filters ...embedded into mesoporous silica nanoparticles (MSN) represent a new class of inorganic sunscreens, with excellent UVA and UVB shielding properties. In addition, the presence of bismuth ions promotes a self-sealing process, allowing (i) the entrapment of the active phases in the deepest core of the system and (ii) the formation of an external glassy silica layer with a consequent suppression of the photocatalytic activity.
In this work, aimed at studying in detail the self-sealing mechanism and accessing the role of bismuth ions in the formation of the system, a series of samples impregnated with a different amount of bismuth were investigated. The self-sealing process already occurs at the lowest content of bismuth and the mechanism is demonstrated to be triggered by the ability of Bi to work as a low-melting point agent for silica. Finally, a sunscreen formulation containing the new UV filter was prepared and the Sun Protection Factor (SPF), the pH and the viscosity were measured, demonstrating the potential of the proposed material for large-scale applications.
A synthesis of variably functionalized thiol-protected palladium nanoparticles (Pd-NPs) is presented. The nanoparticle syntheses are performed in acetone–water or tetrahydrofuran–water solutions, ...without making use of either phase-transfer agents or complex purification procedures of the as-synthesized nanoparticles. Small and mostly monodisperse thiol-protected Pd nanoparticles (Pd-NPs ∼ 2 nm) have been prepared with 11-mercaptoundecanoic acid (MUA), 9-mercapto-1-nonanol (MN), 1-dodecanethiol (DT), or mixtures thereof, and a simple scale-up synthesis is also proposed. The role of PdII-thiolate species as metal precursors in the stage of nanoparticle synthesis and the influence of the reaction parameters on the final Pd-NPs size and size distribution are discussed. The formation of mixed-monolayer protected nanoparticles is achieved, with the final monolayer composition dictated by the thiols, initial molar ratio. Overall, the procedure presented here allows the preparation of functionalized nanoparticles with a high density of functional groups at the edge of the monolayer, with no need of place-exchange reactions. Specific postfunctionalization procedures conducted at the acid groups of the MUA-Pd monolayer are reported so as to widen the potential applicability of these amphiphilic nanoparticle precursors with respect to different applications in the field of material science. Finally, the successful use and the easy recycling/reuse of the Pd-NPs in a model Suzuki cross-coupling reaction are presented.
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Palladium-bismuth nanoparticles were supported into strongly basic anion-exchange resin of gel-type and tested as catalysts for the selective oxidation of glycerol with molecular ...oxygen at atmospheric pressure. Detailed study of the precursors preparation and reduction were undertaken. The catalyst 3%Pd-1%Bi where the bismuth was deposited on the palladium particles (3.4nm) exhibited at 95% glycerol conversion more than 63% yield toward glyceric acid and tartronic acid after 3h of reaction. The catalyst maintains practically similar catalytic performance as in fresh state for at least five consecutive catalytic cycles without extra catalyst treatment and reactivation.
Silver−poly(acrylate) clusters have been synthesized in water by reduction of AgNO3 in the presence of poly(acrylates) of different molecular weights through two different methods, NaBH4 reduction ...and UV exposure. The structure of the clusters and the effect of the synthesis parameters on the size and polydispersity of the particles were evaluated by means of small-angle X-ray scattering (SAXS) and confirmed by UV−visible absorption and transmission electron microscopy (TEM). The results clearly show that the reduction method and the polymer chain length play key roles in the achievement of few-nanometer-sized nanoparticles. The effect of the pH was also investigated. The nanoparticle dispersions were then used to functionalize cotton, wool, and polyester samples in order to obtain antimicrobial textiles for biomedical applications. The antimicrobial activity of the as-treated samples has been tested against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Candida albicans.
In this work we study the surface enhanced Raman scattering (SERS) produced by hierarchical nanostructures obtained by coupling different anisotropic nanomaterial of two SERS active metals, namely Ag ...nanostars (AgNSs) and Au nanowires (AuNWs). Ag nanostars (AgNSs) are prepared, by a two-step one-pot synthesis by reduction of AgNO3 with hydroxylamine, trisodium citrate and NaOH. AuNWs are obtained by electroless templated synthesis in track-etched polycarbonate membranes with following etching of the template. The two precursors are bound together by bridging with the bifunctional cysteamine molecule, obtaining AgNS@AuNW hierarchical structures. Benzenethiol (BT) is adsorbed on the nanostructured material and used as SERS probe to study the amplification of Raman signals. Experimental results indicate significantly larger Raman enhancement when BT is adsorbed onto the AgNS@AuNW in comparison to AuNWs alone or decorated with quasi-spherical silver nanoparticles obtaining AgNP@AuNW. Digital simulations performed by the boundary element method agree with the experimental findings, showing higher number of hot spots and significantly higher SERS enhancements for AgNS@AuNW versus AuNWs or AgNSs or AgNP@AuNW.
Mechanical forces control the function of organisms and mediate the interaction between biological systems and their environments. Knowledge of these forces will increase the understanding of ...biological processes and can support the development of novel diagnostic and therapeutic procedures. Although techniques like atomic force microscopy and droplet insertion method allow measuring forces over a broad range of values, they are invasive and lack versatility. A promising way to overcome these hurdles is luminescent nanomanometry. Quantum dots (QDs) specifically have optical properties that depend on their size because of the quantum confinement, which makes them responsive to applied forces. Yet, a fine understanding of how fundamental parameters affect the response to applied stress is required before a QD family can be credibly proposed as luminescent nanomanometers. Here, a thorough study is conducted on how size and stoichiometry affect the nanomanometry performance of CuInS2 QDs. The studied QDs feature pressure‐dependent photoluminescence in the red/near‐infrared range, which can enable the measurement of mechanical forces in the range of physiological relevance in a remote and minimally invasive way. It is shown that tuning size and stoichiometry can simultaneously enhance the CuInS2 QDs’ brightness and response to applied pressure, thus providing guidelines for better luminescent nanomanometers.
The performance of CuInS2 quantum dots as luminescent nanomanometers can be tuned by finely adjusting their size and stoichiometry. Control over these two parameters allows to maximize simultaneously sensitivity to mechanical pressure and brightness of the quantum dots. These observations provide indications for the design of CuInS2‐based nanomanometers with improved sensing performance.
The sulfur poisoning of carbon-supported bimetallic Pd–Au systems was investigated. Catalytic activity results for benzaldehyde hydrogenation clearly show that gold addition improves catalyst ...resistance to sulfur poisoning with respect to the monometallic Pd-based sample. Samples were characterized by pulse-flow CO chemisorption and XRD in order to correlate the structural properties with the resistance to sulfur poisoning. Gold addition prevents the progressive transformation of Pd in Pd4S in the presence of sulfur compounds by hindering the availability of ensembles of four Pd atoms in the correct geometrical configuration.
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