Holographic monitoring of transportation effects on canvas paintings

Digital holographic speckle pattern interferometry is used to locate areas at risk of deterioration in paintings due to vibration

Photon-induced formation of CdS nanocrystals in selected areas of polymer matrices

We demonstrate light-induced formation of semiconductor quantum dots in TOPAS (R) polymer matrix with very high control of their size and their spatial localization. Irradiation with UV laser pulses of polymer films embedding Cd thiolate precursors results in the formation of cadmium sulfide nanocrystals well confined in the irradiation area, through a macroscopically nondestructive procedure for the host matrix. With increasing number of laser pulses, we accomplish the formation of nanoparticles with gradually increasing dimensions, resulting in the dynamic change of the spectra emitted by the formed nanocomposite areas. The findings are supported by x-ray diffraction and transmission electron microscopy measurements. (C) 2007 American Institute of Physic

Controlling the reversible wetting capability of smart photochromic-polymer surfaces by micro patterning

We demonstrate the wetting behavior control of polymer surfaces doped with photochromic molecules by modifying the surface patterning features introduced by soft molding lithography. Such surfaces enhance their hydrophilicity upon UV irradiation due to conversion of the non-polar spiropyran dopant molecules to their polar merocyanine isomers. The process is reversed upon visible light irradiation. By changing the topological parameters of the introduced pattern, one achieves surface tuning from hydrophobic to hydrophilic situations. The difference for the contact angles between UV- and green-irradiated surfaces may become significantly higher than for the flat surfaces, for the specific patterning parameters analyzed

Comparison between laser-induced nucleation of ZnS and CdS nanocrystals directly into polymer matrices

The nucleation of two kinds of crystalline nanoparticles, zinc sulfide (ZnS), and cadmium sulfide (CdS), is achieved directly into specific sites of polymer matrices after their irradiation with UV laser pulses. The starting samples consist of polymers doped with precursors of Zn or Cd thiolate that are proved to decompose after the absorption of UV light, resulting into the nanoparticles formation. The growth of the crystalline nanostructures is followed throughout the irradiation of the samples with successive incident pulses, by different methods, such as transmission electron microscopy, atomic force microscopy, confocal microscopy, and X-ray diffraction. Special attention is paid to the difference of the formation pathways of the two kinds of nanoparticles studied, because the Cd thiolate precursor exhibits much higher absorption efficiency than the Zn thiolate one, at the applied UV wavelength. Indeed, CdS nanoparticles become evident after the very first incident UV pulses, whereas the formation of ZnS nanocrystals requires rather prolonged irradiation, always through a macroscopically nondestructive procedure for the polymer matrix. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineer

Studying transportation effects on canvas paintings by full field digital holographic techniques

Digital holographic speckle pattern interferometry (DHSPI) is a tool that retrieves the mechanical reaction of a work of art after a shock or vibration, perhaps as a result of mishandling. It provides a method for the assessment of the impact of transportation and reliable risk analysis. In order to assess the effect of handling and transportation on canvas paintings, an investigation was conducted at Bern University of Applied Sciences, University of the Arts, Conservation and Restoration employing DHSPI. Samples of canvas were used for a series of measurements simulating transportation vibrations. The surface deformation topology of the samples was studied with DHSPI in order to acquire information about all the alterations caused on the canvas samples by the vibration ‘fatigue’ (i.e. the repeated deformation due to vibration). Crack maps, provided by analysis of the DHSPI measurements, illustrate the crack growth with time. Risk areas, located before any vibration loading, also proved to be those most likely to develop cracks. The tests of the transportation of canvas paintings have been successful in detecting cracks and areas with defects, and also in monitoring their propagation with high precision