Marco Rolandi

A polysaccharide bioprotonic field-effect transistor.

In nature, electrical signalling occurs with ions and protons, rather than electrons. Artificial devices that can control and monitor ionic and protonic currents are thus an ideal means for interfacing with biological systems. Here we report the first demonstration of a biopolymer protonic field-effect transistor with proton-transparent PdH(x) contacts. In maleic-chitosan nanofibres, the flow of protonic current is turned on or off by an electrostatic potential applied to a gate electrode. The protons move along the hydrated maleic-chitosan hydrogen-bond network with a mobility of ~4.9×10(-3) cm(2) V(-1) s(-1). This study introduces a new class of biocompatible solid-state devices, which can control and monitor the flow of protonic current. This represents a step towards bionanoprotonics.

A Facile and Patternable Method for the Surface Modification of Carbon Nanotube Forests Using Perfluoroarylazides

A facile patterning method for the functionalization of vertically aligned carbon nanotubes is described. Modification of the surface of nanotube forests with hydrophilic, hydrophobic, or polymerizable small molecules was achieved via UV-triggered attachment of perfluoroarylazides. Multiple functionalizations of the tube surface can be achieved. Macro- and micropatterning of forest substrates were demonstrated. Superhydrophobic surfaces containing superhydrophilic regions were prepared.

Aharonov-bohm interference and beating in single-walled carbon-nanotube interferometers

Relatively low magnetic fields applied parallel to the axis of a chiral single-walled carbon nanotube are found causing large modulations to the p channel or valence band conductance of the nanotube in the Fabry-Perot interference regime. Beating in the Aharonov-Bohm type of interference between two field-induced nondegenerate subbands of spiraling electrons is responsible for the observed modulation with a pseudoperiod much smaller than that needed to reach the flux quantum Phi0 = h/e through the nanotube cross section. We show that single-walled nanotubes represent the smallest cylinders exhibiting the Aharonov-Bohm effect with rich interference and beating phenomena arising from well-defined molecular orbitals reflective of the nanotube chirality.

A Biomimetic Composite from Solution Self-Assembly of Chitin Nanofibers in a Silk Fibroin Matrix

A chitin nanofiber-silk biomimetic nanocomposite with enhanced mechanical properties is self-assembled from solution to yield ultrafine chitin nanofibers embedded in a silk matrix.

Chitin Nanofiber Transparent Paper for Flexible Green Electronics

A transparent paper made of chitin nanofibers (ChNF) is introduced and its utilization as a substrate for flexible organic light-emitting diodes is demonstrated. Given its promising macroscopic properties, biofriendly characteristics, and availability of the raw material, the utilization of the ChNF transparent paper as a structural platform for flexible green electronics is envisaged.

Two-terminal protonic devices with synaptic-like short-term depression and device memory.

Two-terminal protonic devices with PdHx proton conducting contacts and a Nafion channel achieve 25 ms spiking, short term depression, and low-energy memory switching.

A facile bottom-up route to self-assembled biogenic chitin nanofibers

A facile bottom-up strategy affords cytocompatible self-assembled biogenic chitin nanofibers with diameter control. Ultrafine (3 nm) nanofibers are easily obtained from drying a chitin/hexafluoro 2-propanol solution, and larger (10 nm) nanofibers are precipitated from LiCl/N,N-dimethylacetamide upon addition of water.

H+-type and OH−-type biological protonic semiconductors and complementary devices

Proton conduction is essential in biological systems. Oxidative phosphorylation in mitochondria, proton pumping in bacteriorhodopsin, and uncoupling membrane potentials by the antibiotic Gramicidin are examples. In these systems, H+ hop along chains of hydrogen bonds between water molecules and hydrophilic residues – proton wires. These wires also support the transport of OH− as proton holes. Discriminating between H+ and OH− transport has been elusive. Here, H+ and OH− transport is achieved in polysaccharide- based proton wires and devices. A H+- OH− junction with rectifying behaviour and H+-type and OH−-type complementary field effect transistors are demonstrated. We describe these devices with a model that relates H+ and OH− to electron and hole transport in semiconductors. In turn, the model developed for these devices may provide additional insights into proton conduction in biological systems.

Self-assembled chitin nanofibers and applications.

Self-assembled natural biomaterials offer a variety of ready-made nanostructures available for basic science research and technological applications. Most natural structural materials are made of self-assembled nanofibers with diameters in the nanometer range. Among these materials, chitin is the second most abundant polysaccharide after cellulose and is part of the exoskeleton or arthropods and mollusk shells. Chitin has several desirable properties as a biomaterial including mechanical strength, chemical and thermal stability, and biocompatibility. However, chitin insolubility in most organic solvents has somewhat limited its use. In this research highlight, we describe recent developments in producing biogenic chitin nanofibers using self-assembly from a solution of squid pen β-chitin in hexafluoroisopropanol. With this solution based assembly, we have demonstrated chitin-silk composite self-assembly, chitin nanofiber fabrication across length-scales, and manufacturing of chitin nanofiber substrates for tissue engineering.

Self-assembled chitin nanofiber templates for artificial neural networks

Self-assembled chitin nanofibers were applied as a biomimetic extracellular matrix for the attachment of primary neuronsin vitro. Chitin nanofiber surfaces were deacetylated to form 4 nm and 12 nm diameter chitosan nanofibers that were coupled with poly-D-lysine (PDL) to examine combinatory effects and structurally analyzed by atomic force microscopy. The chitosan substrates were then employed for mouse cortical neuron cultures to examine their capabilities to support cell attachment, neurite coverage and survival. The 4 nm chitosan nanofibers improved single cortical neuron attachment compared to the 12 nm chitosan fibers and bare glass substrates, illustrating the improved adhesive properties of the surface. Importantly, the 4 nm chitosan nanofibers with PDL supported 37.9% neuron viability compared to only 13.5% on traditional PDL surfaces after a 7-day culture period, illustrating significantly improved long-term cell viability. The nanofibrillar chitosan surface could provide an alternative substrate for in vitroprimary neuron cultures to serve as artificial neural networks for diagnostics and therapeutics.