Search

The manipulation and understanding of molecular transport across functionalized nanopores will take us closer to mimicking biological membranes and thus to design high-performance permselective separation systems. In this work, Surface-initiated atom transfer radical polymerization (SI-ATRP) of (2-methacryloyloxy)-ethyltrimethylammonium chloride (METAC) was performed on both mesoporous silica and mesoporous titania thin films. Pores were proven to be filled using ellipsometry and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Furthermore, the employed method leads to a polymer overlayer, whose thickness could be discriminated using a double-layer ellipsometry model. Cyclic voltammetry experiments reveal that the transport of electrochemically active probes is affected by the PMETAC presence, both due to the polymer overlayer and the confined charge of the pore-tethered PMETAC. A more detailed study demonstrates that ion permeability depends on the combined role of the inorganic scaffolds' (titania and silica) surface chemistry and the steric and charge exclusion properties of the polyelectrolyte. Interestingly, highly charged negative walls with positively charged polymers may resemble zwitterionic polymer behavior in confined environments. [ABSTRACT FROM AUTHOR]

The sensory-motor interaction is a hallmark of living systems. However, developing inanimate systems with "recognize and attack" abilities remains challenging. On the other hand, controlling the inter-droplet dynamics on surfaces is key in microengineering and biomedical applications. We show here that a pair of droplets can become intelligently interactive (chemospecific stimulus-response inter-droplet autonomous operation) when placed on a nanoporous thin film surface. We find an attacker-victim-like non-reciprocal interaction between spatially separated droplets leading to an only-in-one shape instability that triggers a drop projection to selectively couple, resembling cellular phenomenologies such as pseudopod emission and phagocytic-like functions. The nanopore-driven underlying communication and associated chemical activity are the main physical ingredients behind the observed behavior. Our results reveal that basic features found in many living cell types can emerge from a simple two-droplet framework. This work is a promising step towards the design of microfluidic smart robotics and for origin-of-life protocell models. While a hallmark of living systems, developing sensory-motor interactions in inanimate systems remains challenging. Here, authors show that nanoporous surfaces can be used to create stimuli-responsive droplet interplay with shape transformation and complex behaviours reminiscent of living cell actions. [ABSTRACT FROM AUTHOR]

Mesoporous TiO2 thin films have been extensively studied and applied in the construction of a wide variety of devices. To this end, it is critical to obtain detailed structural information regarding film formation and processing. However, there is still a lack of information about their chemical identity during thermal treatment, in which a transition from a hybrid mesostructure to a mesoporous matrix occurs. In this work, we present the FTIR characterization of three different mesoporous TiO2 films, templated with Brij 58, Pluronic F127 and Pluronic P123. The FTIR spectra were followed in situ from the sol deposition, through the thermal treatments until reaching 400 °C, using a high temperature cell. A detailed analysis taking into account all of the sol's components and all the spectral regions in the range 3600–650 cm−1 was performed. The results obtained were compared with thermal analysis, coupled with mass spectrometry analysis of the released species. By this means, all the stages of the processing (solvent evaporation, template elimination and precursors condensation) were identified, and we were able to determine which chemical species are present at every treatment step. The results presented here can be useful when choosing processing conditions adapted for the final application of the TiO2 films. Highlights: Thermal evolution of mesoporous TiO2 with three different templates was assessed by FTIR analysis. Temperatures at which each processing stage occurs were determined. The three templated systems studied present equivalent behavior. Thermal analysis and mass spectrometry confirm and complement the FTIR results. [ABSTRACT FROM AUTHOR]

Rational design and elaborate modular construction of interfacial architectures in which molecular transport is mediated by responsive/adaptive nanostructures has become a growing and fertile field of research in supramolecular materials chemistry. This work presents, for the first time, the use of PNIPAM-capped mesoporous silica thin films as thermosensitive cation-selective mesochannels. Thus far, this feature has only been observed in thermosensitive biological channels. The interfacial architecture created here accomplishes its specific functions through the concerted or simultaneous action of spatially addressed subunits with temperature response and ion exclusion capabilities. The thermo-perm-selectivity effect stems from the synergistic interplay between the pH-dependent electrostatic characteristics of the silica scaffold and the thermo-controlled steric effects introduced by the capping brush layer. It is hoped that the 'nanoarchitectonic' approach presented here will provide new routes toward the generation of heterosupramolecular nanosystems displaying addressable transport properties similar to those encountered in biological ion channels. [ABSTRACT FROM AUTHOR]

A novel composite material based on metal nanoparticles (NP) and mesoporous thin films (MPTF), more specifically bilayers of MPTF with a submonolayer of NP deposited between them is introduced. By controlling the deposition conditions, it is possible to build a variety of multilayers including MPTF with different compositions (TiO2, SiO2) and pore sizes (templated with cetyltrimethylammonium bromide, F127, Brij 58) and NP of different characteristics and sizes (Au spheres, Au decorated SiO2). By means of 2D small angle X-ray scattering, transmission electron microscopy, UV-vis spectroscopy, and ellipsometric porosimetry it is demonstrated that NP and MPTF retain their structure and properties within the new material. Importantly, the NP remain accessible for further reactions, a feature that is established by Au overgrowth. Interestingly, the extent of Au growth depends on the mesoporous size and the position of the MPTF with respect to the NP. This new architecture allows the NP to be in direct contact with two different chemical environments and, as a consequence, opens up the possibility to control identity and size of the molecules that can reach them. Thus, the obtained materials may be applied in the development of highly specific sensors and catalysts, in which spatial position plays a fundamental role. [ABSTRACT FROM AUTHOR]

In this paper, we report the complete synthesis and characterization procedures to generate highly organized and oriented mesoporous titania thin films, using poly(ethylene oxide) (PEO)-based templates. Controlled conditions in the deposition, postsynthesis, and thermal treatment steps allow one to tailor the final mesostructure (2D hexagonal, p6m, or 3D cubic, Im3m). Various techniques were used to determine the time evolution of the mesostructure. Spectroscopic techniques (UV/vis, [sup 17]O NMR) and EXAFS/XANES have been used to follow the chemical changes in the Ti(IV) environment. Crossing these techniques spanning all ranges permits a complete description of the chemistry all the way from solution to the mesostructured metal oxide. A critical discussion on all important chemical and processing parameters is provided; the understanding of these features is essential for a rational design and the reproducible construction of mesoporous materials. [ABSTRACT FROM AUTHOR]

We showed for the first time how to tailor the permselectivity of mesoporous thin films by changing the electrostatic environment of the nanopores through the covalent functionalization with polyelectrolyte brushes. [ABSTRACT FROM AUTHOR]

Abstract: The thermal stability of anatase TiO2 mesoporous thin films has been considerably increased up to 800°C by substituting a fraction of Ti cations by Nb. Mesoporous mixed oxide films Ti1−x Nb x O2, with x =Nb/(Nb+Ti) ranging from 0 to 1, and homogeneous crystalline walls have been successfully prepared from chloride precursors and non-ionic block copolymer templates. They all exhibit a uniaxially distorted Im3m bcc mesostructure with the a lattice parameter ranging from 14 to 19nm. Films have been characterised by simultaneous in situ SAXS and WAXS investigations during thermal treatment. Transmission electron microscopy and UV–visible ellipsometry were used to confirm the structure, the porosity and the good optical quality. A high porosity of 40% (pore size estimated at 7nm) was maintained for the 10% Nb-doped films above the temperature of crystallisation and a bandgap of 3.40eV has been measured after annealing at 500°C. [Copyright &y& Elsevier]