Valeria Casuscelli

Hydrophobin Vmh2–glucose complexes self-assemble in nanometric biofilms

Hydrophobins are small proteins secreted by fungi, which self-assemble into amphipathic membranes at air–liquid or liquid–solid interfaces. The physical and chemical properties of some hydrophobins, both in solution and as a biofilm, are affected by poly or oligosaccharides. We have studied the interaction between glucose and the hydrophobin Vmh2 from Pleurotus ostreatus by spectroscopic ellipsometry (SE), atomic force microscopy (AFM) and water contact angle (WCA). We have found that Vmh2–glucose complexes forms a chemically stable biofilm, obtained by drop deposition on silicon, 1.6 nm thick and containing 35 per cent of glucose, quantified by SE. AFM highlighted the presence of nanometric rodlet-like aggregates (average height, width and length being equal to 3.6, 23.8 and 40 nm, respectively) on the biofilm surface, slightly different from those obtained in the absence of glucose (4.11, 23.9 and 64 nm). The wettability of a silicon surface, covered by the organic layer of Vmh2–glucose, strongly changed: WCA decreased from 90° down to 17°.

Steps farther towards micro-nano-mole integration via the multispacer patterning technique

The production of memories with bit density of the order of 1011 cm−2 (projected to be possible within the current silicon technology in 2020 AD) seems now possible by exploiting the hybrid crossbar architecture. This new paradigm (that assigns to silicon the functions of power supply, addressing, sensing and writing, and to reprogrammable molecules the function of memory) requires the solution of a number of new problems not considered yet in integrated-circuit processing. In particular, the most advanced example of hybrid crossbars (Green J E et al 2007 Nature 445 414) does not yet consider the problems of hardware demultiplexing (the connection of wire arrays with a sublithographic pitch of 30 nm to lithographic contacts with pitch 90 nm), the covalent linkage of the functional molecules to the crossbar, and their insertion at the end of process. In this paper it is shown that the multispacer patterning technique (Cerofolini G F et al 2005 Nanotechnology 16 1040) can be adapated to solve all these problems.

Water-gated organic transistors on polyethylene naphthalate films

Water-gated organic transistors have been successfully exploited as potentiometric transducers in a variety of sensing applications. The device response does not depend exclusively on the intrinsic properties of the active materials, as the substrate and the device interfaces play a central role. It is therefore important to fine-tune the choice of materials and layout in order to optimize the final device performance. Here, polyethylene naphthalate (PEN) has been chosen as the reference substrate to fabricate and test flexible transistors as bioelectronic transducers in liquid. PEN is a biocompatible substrate that fulfills the requirements for both bio-applications and micro-fabrication technology. Three different semiconducting or conducting polymer thin films employing pentacene, poly(3-hexylthiophene) or poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) were compared in terms of transconductance, potentiometric sensitivity and response time. The different results allow us to identify material properties crucial for the optimization of organic transistor-based transducers operating in water.

Short Communication: Synthesis of Polymer-Embedded Metal Clusters by Thermolysis of Mercaptides—Polymer Blends

Small conductive solid phases (metals and semiconductors) behave much different from ordinary bulk materials, because of surface and confinement effects. As a result, novel optical, magnetic, catalytic, and electronic properties become available. These new properties can be used to provide polymers of special functionalities and the resulting nanocomposite materials can be exploited for a number of functional applications in many technological fields (e.g., linear and nonlinear optics, magnetic data-storage, sensors). The research activity in this area is very promising and it is mainly devoted to development of chemical routes for the preparation of these systems, which allows one to achieve polymer-embedded particles of different shape, size, and spatial organization (the properties of nanoscale metals and semiconductors are size-dependent and consequently they can be finely tuned by controlling the morphology). There is also a strong interest for polymetallic particles (e.g., core/shell clusters), nano...