M.T. Parodi

Assembling thiolated gold nanoparticles in compact patterns: a transmission electron microscopy and scanning probe microscopy investigation

We present results from a study of the deposition of synthesized dodecanethiol capped gold clusters onto solid substrates investigated using Transmission Electron Microscopy (TEM) and Scanning Probe Microscopy (SPM). TEM imaging of films prepared onto carbon coated grids using the drop cast method from cluster solutions that have undergone an increasing number of selective size separation steps show the efficacy of the vapor transfer technique in narrowing down the particle size distribution. In order to assemble the gold clusters in compact patterns and investigate their organization using SPM, we have prepared 1,4-benzenedimethanethiol self-assembled films onto heteroepitaxial gold on mica to be used as a substrate. A comparison of results obtained on this substrate using gold cluster films prepared with the drop cast method and the Langmuir-Blodgett (LB) technique is made. In the case of LB films made from size-selected nanoparticles, we present room temperature scanning tunneling images of clusters arranged in compact patterns.

Deposition and Characterization of Langmuir-Blodgett Films of Monomeric and Polymeric Pyrrole Derivatives

Abstract In this Paper we report the deposition and characterization of Langmuir-Blodgett multilayers of pyrrole derivatives in monomeric and polymeric form. The influence of monolayer preparation and deposition conditions, the quality and reproducibility of the multilayers were studied by FTIR, Brewster angle and scanning force microscopy.

From Electrical Interactions Among Dipoles To Cellular Automata: A Model

In this paper we present how monolayers of electric dipoles can be modeled from a logic-functional point of view by a cellular automaton. The electrical interactions among dipoles are expressed by the torsional moment produced on each dipole, and the dipoles dynamics is computed taking into account a viscosity term. An updating law for the parameters of a cellular automaton is finally given and the convergence to stable states is also shown.

Investigation of the conductivity properties of Langmuir-Blodgett films of pyrrole derivatives

Abstract In this paper, we present conductivity measurements made on Langmuir-Blodgett (LB) polymeric films obtained from pyrrole derivatives (3-hexadecyl-pyrrole and mixtures 3-hexadecyl-pyrrole/pyrrole) and deposited onto interdigitated structures designed ad hoc for electrical measurements on planar structures. Step response and voltage vs. current characteristics are reported and discussed, with particular attention to linearity and stability; from these data, the resistivity values of both types of film are derived. The results show that monolayers obtained from the mixtures are by far more conductive (four orders of magnitude) than pure 3-hexadecyl-pyrrole (3HP) multilayers, and that their electrical behaviour can be easily related to a pure Ohmic behaviour, while the 3HP multilayers cannot be considered as pure Ohmic components.

On the preparation of Langmuir-Blodgett films of pyrrole derivatives

Abstract In this paper, we present a study of the preparation of Langmuir-Blodgett films of polymers obtained on a trough from mixtures made by pyrrole derivatives. In particular, the comparison between films obtained by different molar ratios of 3-hexadecyl-pyrrole to pure pyrrole is shown, in terms of the kinetics of the process and of the compressibility of the products obtained. Depending on the molar ratio in the composition of the mixtures, differences have been found in the structure of the co-polymer obtained and in the behaviour of the resulting film.

Dipole monolayers: a model for elementary information processors

A 2-D array of electric dipoles contacted by suitable electrodes is shown to offer paramount properties necessary for intelligent processing of information. On the basis of a simplified mechanism that models the interactions among the dipoles and between the dipoles and the external electrodes, the possibility of transforming the 2-D dipole array into an elementary molecular processor is explored.

SPM Investigation of Thiolated Gold Nanoparticle Patterns Deposited on Different Self-Assembled Substrates

We present the results of a Scanning Probe Microscopy (SPM) investigation of ordered nanosized metallo-organic structures. Our aim is to investigate the organization and stability of thiolated gold nanoparticles in a compact pattern when deposited onto gold substrates functionalized with self-assembled monolayers made from two molecules that differ essentially in their terminating group: 1,4-benzenedimethanethiol and 4-methylbenzylthiol.

Scanning probe characterization of Langmuir-Blodgett and self-assembled films of pyrrole derivatives

Abstract Atomic force microscopy was used to investigate the space molecular organization of Langmuir-Blodgett (LB) and self-assembled (SA) films of pyrrole derivatives on different substrates. The LB films were obtained from monomers of 3-hexadecyl-pyrrole (3HP); the polymerization of the film was performed directly at the air-subphase interface, and the films were collected on hydrophilic glass. Very homogeneous polymeric and monomeric LB films were collected on glass with a transfer rate near unity, the typical average roughness range was 0.9 ± 0.4 nm, and the quality of films was independent of the dipping speed. A functionalized molecule, 11-(3-pyrrolyl)undecyl mercaptane (3UPSH), was used to modify Ti and TiN electrodes by immersing the substrates in a solution containing the redox active molecule. The modification of the metal surfaces was proved by means of time of flight secondary ion mass spectrometry (TOF SIMS) and AFM characterization.

An experimental study on the structural and electrical properties of pyrrole derivatives Langmuir-Blodgett films

The electrical properties of conducting polymers can be efficiently exploited in the development of new smart gas-sensing devices. In this paper the authors describe the preparation of Langmuir-Blodgett (LB) polymeric films made from pyrrole monomers functionalized with alkyl chains of variable length. The structural and electrical properties of such films are investigated.

Surface modifications induced by scanning force microscopy on Langmuir-Blodgett films

One of the key points for the development of molecular manipulation based technologies is the availability of techniques capable to operate in such a dimensional range. The Scanning Probe Microscopes as well as the Langmuir-Blodgett film deposition technology have always been the best candidates for such a task. In this paper the authors present a method that allows one to obtain controlled surface modifications of cadmium arachidate Langmuir-Blodgett multilayers through Scanning Force Microscopy. Variable depth permanent ablations at the submicron scale have been produced as a function of applied force and scanning speed. In view of an organic microelectronics technology this technique can be envisaged as the organic analog of the microelectronics lithographic techniques.