Soft Report - Dipartimento di Fisica - Sapienza

Instrumentations and Methods for NanotechnologyOur interests on instrumentation development,applied to the characterization of mechanical andoptical properties of thin film devices, focusparticularly on two main topics: quartz crystalsmicrobalance and near field optical microscopy.Standard quartz crystal microbalance (QCM) isrouting technique applied to the measure of massdeposited on quartz resonator plate by measuringthe frequency shift. We developed a new QCMdevice with improved time resolution, which allows afull characterization of the mechanical properties(elasticity and viscosity) of the molecular filmdeposited on the electrode. In such instrumentboth the frequency shift and the quality factor Q ofthe resonator are acquired in real time, withresolution of tens of millisecond in time and sub-Hzin frequency. We are currently applying suchtechnique on the study of fast light inducedvariation of viscoelastic properties in photosensitivepolymeric films. In such materials illumination canplay a role equivalent to the temperature[1] withalso the possibility to quench the material optically.With our technique we are able to monitor the fastdynamics taking place during and following thequenching process and aging process as function oftemperature/illumination history.The new QCM devices are applied also to scanningnear field optical microscopy SNOM for an accurateand fast tip sample servo distance control. We alsodeveloped, for SNOM, contrast mechanisms suitablefor molecular axis determination in optical dichroism,birefringence or fluorescence measurements onnanoscale with applications on nanowriting inpolymeric liquid crystals [2].Currently developed technique of the formation ofnanocapsules had attracted a great attention ofresearch groups due to its obvious applicationperspectives. The technique is based on the selfassemblingof polymeric shells on the spherical (orother shape) precursors by means of electrostaticinteractions or by control-precipitation method.When the shell is formed, it was proven to bepossible to remove the precursor varying thecomposition of the solvent (in the most of cases – pHvariation resulted in the solubility of the precursornuclei). Thus, nanocapsules are formed. Animportant feature of these capsules is the smartnature of the shell changing its properties as aresponse of the environmental condition variations.Several applications, such as biosensors, magneticmedia, etc., demand patterned organization of layersof capsules on solid surfaces. We have developedtwo methods of patterning. The first one is based onthe electron beam treatment of capsule layers,deposited by solution casting on solid surfaces [3].Optical microscopy image of resulting patternedlayer, composed by two different types of capsules(hollow capsules and those with gold in the core) isshown in Fig. The method was applied for theformation of layers of magnetic capsules [4].Second method implies self-assembling of capsuleaggregates on the specially prepared solid surfaceswith difference in the hydrophilic/hydrophobicproperties [5]. During assembly, capsules attachthemselves onto hydrophilic areas of the support. Inthe case of hydrophobic coatings with differentdegree of hydrophobicity, capsules form rings on thesurface.References[1] P. Camorani, M.P. Fontana Phys. Rev. E 73,011703 (2006) L. Cristofolini, M.P. Fontana -Philosophical Magazine B84, 1537, (2004). L.Cristofolini, M.P. Fontana T. Berzina, P. Camorani -Mol. Cryst. Liq. Cryst. 398, 11 (2003).[2] P. Camorani, L. Cristofolini , G. Galli, M. P.Fontana Mol. Crystal Liq. Crystal. 375, (2002) 175-184 and P.Camorani, M.Labardi , M. Allegrini - Mol.Crystal Liq. Crystal. 372, (2001) 365-372[3] T. Berzina, S. Erokhina, D. Shchukin, G.Sukhorukov, and V. Erokhin, Macromolecules, 36,6493 (2003).[4] S. Erokhina, T. Berzina, L. Cristofolini, D.Shchukin, G. Sukhorukov, L. Musa, V. Erokhin, andM.P. Fontana, J. Magnetism Magn. Mater., 272-276,1353 (2004).[5] V. Troitsky, T. Berzina, D. Shchukin, G.Sukhorukov, V. Erokhin, and M.P. Fontana, Colloidsand Surfaces A, 245, 163 (2004).Fig. 1. Two-step electron beam patterning of layer ofhollow and gold containing nano-engineeredpolymeric capsules.AuthorsT. Berzina, P. Camorani, L. Cristofolini, S. Erokhina,V. Erokhin, and M.P. FontanaUniversity of Parma and CRS SOFT CNR-INFM.57SOFT Scientific Report 2004-06