quarta-feira, 8 de setembro de 2010

Nova variante do teste de Oddy envolvendo o uso de nanopartículas

A seguinte tese de mestrado está livremente disponível aqui:

Laura Moussa, Nanoscience and Nanotechnology Applied to Art Conservation: Improved Oddy Test Using Silver Nanoparticle Sensor, Pittsburgh, The Carnegie Mellon University, 2007.


Damage to metal artifacts from the materials used for display and storage cases is of great concern to art museums. The current technology used, the “three in one” Oddy Test, tests for the suitability of these construction materials by placing silver, copper, and lead metal coupons in one container along with the material at 60°C and 100 % relative humidity. After a 28-day period the metal coupons are assessed for any visual changes. There are many shortcomings to this simple test. It is time consuming, irreproducible, slow, hard to evaluate and most importantly gives no quantitation. A new way to test for the suitability of these materials using a silver nanoparticle sensor is described here. Two types of silver nanoparticle shapes, spherical and triangular, were self-assembled using polyethylenimine (PEI) onto a glass coverslip to produce two different sensors. The spherical nanoparticle sensor gave a yellow color and when evaluated for its sensitivity to hydrogen sulfide gas changed colors from yellow to colorless. The triangular nanoparticle sensor gave a blue color and when evaluated for its sensitivity to hydrogen sulfide gas changed colors from blue to colorless. Color changes were followed through UV-Vis spectrophotometry, which showed a decrease in absorption of the initial characteristic peak after exposure to hydrogen sulfide. Kinetic studies were performed on the spherical and triangular nanoparticles, and the reaction rates were determined to be first-order with k = 0.0002 for the triangular nanoparticles and k = 0.0001 for the spherical nanoparticles. When compared to the Oddy Test, both the spherical and triangular silver nanoparticle sensors reacted fully by showing the characteristic color change before the 28-day period of the test. The nanoparticle sensor will allow for high sensitivity, easy evaluation, and quantitative analysis for corrosive gases that would react with silver.