Functionalization of TiO2 sol-gel derived films for cell confinement

The neuroscience field has increased enormously over the last decades, achieving the possible real application of neuronal cultures not only for reproducing neural architectures resembling in vivo tissues, but also for the development of functional devices. In this context, surface patterning for cell confinement is crucial, and new active materials together with new protocols for preparing substrates suitable for confining cells, guiding their processes in the desired configuration are extremely appreciated. Here, TiO₂ sol-gel derived films were selected as proof-of-concept materials to grow neurons in suitable confined configurations, taking advantage of the biocompatible properties of modified TiO₂ substrates. TiO₂ sol-gel derived films were made compatible with the growth of neurons thanks to a stable and controlled poly-lysine coating, obtained by silanization chemistry and streptavidin-biotin interactions. Moreover, a spotting protocol, here described and optimized, allowed the simple preparation of arrays of neurons, where cell adhesion was guided in specific areas and the neurites development driven in the desired arrangement. The resulting arrays were successfully tested for the growth and differentiation of neurons, demonstrating the possible adhesion of cells in specific areas of the film, therefore paving the way to applications such as the direct growth of excitable cells nearby electrodes of devices, with an evident enhancement of cell-electrodes communication.

3D structure reconstruction of nanoengineered polymeric capsules using Coherent X-Ray diffraction imaging

Nanoengineered polymeric capsules (NPCs) are smart objects that can be filled in with some desired chemical substance. They are considered among the most versatile tools in biology, pharmacy, medicine etc. Most often they have been used as containers for drug delivery. Main tools for studying their structure are electron (SEM, TEM) and fluorescence microscopies. In the case of electron microscopies, the main peculiarity was connected to the necessity of dried samples usage. In the case of fluorescence microscopy, the possible resolution is restricted by diffraction limits. The natural environment of the NPCs is liquid medium. In this paper we have developed a method of NPCs' structure investigation in liquid medium using coherent X-ray diffraction imaging (CXDI). The main points of this article are summarized as:•The procedure of NPCs' synthesis using layer-by-layer technique including gold nanoparticles;•Coherent X-ray diffraction imaging of the samples in liquid medium;•Imaging of objects without freezing of the sample.

Charge-separation enhancement in inverted polymer solar cells by molecular-level triple heterojunction: NiO-np:P3HT:PCBM

Hole collection and transport are crucial physical processes in bulk-heterojunction (BHJ) solar cells, which represent major bottlenecks due to their limitations in power conversion efficiency (PCE). Hence, a more efficient alternative is needed to accept and transport holes to the collection electrode in BHJ solar cells. Here, we bring both electron and hole collection centres close to the point of exciton generation by infiltrating P3HT poly(3-hexylthiophene):PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) blend into a highly porous interconnected p-type NiO-nanoparticle (NiO-np) network, through solvent-assisted grafting. In this study, a hybrid polymer solar cell is demonstrated with a P3HT:PCBM:NiO-np triple-heterojunction active layer which showed greatly improved rectification behaviour, long electron lifetime and generated higher PCE of 4% under AM 1.5 solar illumination with a 75% increase in PCE with respect to the P3HT:PCBM device. The optimum NiO-np amount and active-layer thickness were found to be 2% and 250 nm, respectively.

A hybrid living/organic electrochemical transistor based on the Physarum polycephalum cell endowed with both sensing and memristive properties

A hybrid bio-organic electrochemical transistor was developed by interfacing an organic semiconductor, poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate), with the Physarum polycephalum cell. The system shows unprecedented performances since it could be operated both as a transistor, in a three-terminal configuration, and as a memristive device in a two terminal configuration mode. This is quite a remarkable achievement since, in the transistor mode, it can be used as a very sensitive bio-sensor directly monitoring biochemical processes occurring in the cell, while, as a memristive device, it represents one of the very first examples of a bio-hybrid system demonstrating such a property. Our system combines memory and sensing in the same system, possibly interfacing unconventional computing. The system was studied by a full electrical characterization using a series of different gate electrodes, namely made of Ag, Au and Pt, which typically show different operation modes in organic electrochemical transistors. Our experiment demonstrates that a remarkable sensing capability could potentially be implemented. We envisage that this system could be classified as a Bio-Organic Sensing/Memristive Device (BOSMD), where the dual functionality allows merging of the sensing and memory properties, paving the way to new and unexplored opportunities in bioelectronics.

Real-time monitoring of self-assembling worm-like micelle formation by organic transistors

OECT (Fig. a) for monitoring micelle formation in a spherical (red points – Fig. b) and a wormlike (blue points – Fig. b) regime solutions.

ZnO nanowires-C microfiber hybrid nanosensor for liquefied petroleum gas detection

Zinc oxide nanowires are integrated onto carbon microfibers using a two-step approach which includes electrochemical deposition of zinc and its thermal oxidation. Such nano-on-micro hybrid architecture is then used as resistive gas sensor. Some properties like mechanical flexibility, low cost and large-area fabrication make this design appealing for different applications. The huge surface-to-volume ratio of such structure comes from being structured at both microscale and nanoscale (ZnO nanowires and C microfiber) and leads to a strong and rapid response/recovery times when it is used as a gas sensor. The fabrication process of the ZnO-microC device is very simple and doesn't involve any expensive lithographic step. The sensors show excellent liquefied petroleum gas sensing properties, with very fast response on gas exposure (about 3 s) and very good reversibility (less than 2%). In addition, the carbon microfiber substrate allows the use of the ZnO-microC sensor also in applications where flexibility is required (for example integrated in fabric).

Hyperthermal molecular beam deposition of highly ordered organic thin films

We use a seeded supersonic molecular beam to control the kinetic energy of pentacene (C22H14) during deposition and growth on Ag(111). Highly ordered thin films are grown at low substrate temperatures (approximately 200 K) at kinetic energies of a few electron volts, as shown by low energy He diffraction and x-ray reflectivity spectra. In contrast, deposition of thermal molecules yields only amorphous films. Growth at room or higher temperature substrates yields films of poorer quality irrespective of the depositing beam energy. We find that after the first wetting layer is completed, a new ordered phase is formed, whose in-plane lattice spacings match one of the bulk crystal planes. The high quality of the films can be interpreted as the result of local annealing induced by the impact of the impinging high-energy molecules.

SF6 scattering from graphite surfaces: comparison of effects induced by thermal and laser controlled vibrational excitation

We report scattering experiments of multiphoton vibrationally excited SF6 molecules from graphite surfaces demonstrating ro-vibrational excitation in the collision. The beam scattering experiments were carried out at different initial kinematic conditions and as a function of the surface temperature. The energy transfer depends both on the initial state of the molecule and on the momentum transferred as well as on the temperature of the surface. The role of surface atomic corrugation is evidenced.