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Silver cloud

An unexpected silver cloud

Sample of silver tungstate: nanometric particle cloud circles around the material

CDMFSample of silver tungstate: nanometric particle cloud circles around the materialCDMF

Studies on the chemical compound silver tungstate – a semiconductor with potential applications in fiber optics, photocatalysis (using light to accelerate the rate of a reaction) and sensors – have led to unprecedented findings by the research group headed by Professor Elson Longo of the Chemistry Institute at the São Paulo State University (Unesp) in Araraquara, São Paulo State.  After studying the compound in 2013 and observing a spontaneous growth of silver filaments with potential antibacterial and antifungal properties (see Pesquisa FAPESP Issue nº 212), the researcher’s team discovered a cloud of nanometric silver particles circling around these filaments (Scientific Reports, March 16, 2016).  “This is a new finding in scientific literature,” says Longo.  “The cloud appears when the electron beam of a transmission electron microscope hits the filaments.  Our work builds on existing knowledge about interactions between electrons and silver tungstate.”  The nanoparticles in the cloud are 1.5 to 2 nanometers in diameter, and they coalesce like water to form bigger and bigger droplets.  At the end of the process, more metallic silver is deposited onto the tungstate.  Longo coordinates the Functional Materials Development Center (CDMF), one of FAPESP’s Research, Innovation and Dissemination Centers (CEPID).