{"id":151156,"date":"2014-05-20T18:02:31","date_gmt":"2014-05-20T21:02:31","guid":{"rendered":"http:\/\/revistapesquisa.fapesp.br\/?p=151156"},"modified":"2014-06-23T09:24:38","modified_gmt":"2014-06-23T12:24:38","slug":"extra-gold-makes-slower-reactions","status":"publish","type":"post","link":"https:\/\/revistapesquisa.fapesp.br\/en\/extra-gold-makes-slower-reactions\/","title":{"rendered":"Extra gold makes for slower reactions"},"content":{"rendered":"<div id=\"attachment_151157\" style=\"max-width: 300px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-151157\" alt=\"Electron microscopy images showing gold (red) and silver nanoparticles (green)\" src=\"http:\/\/revistapesquisa.fapesp.br\/wp-content\/uploads\/2014\/06\/Tecno_ouro-e-prata.jpg\" width=\"290\" height=\"282\" srcset=\"https:\/\/revistapesquisa.fapesp.br\/wp-content\/uploads\/2014\/06\/Tecno_ouro-e-prata.jpg 290w, https:\/\/revistapesquisa.fapesp.br\/wp-content\/uploads\/2014\/06\/Tecno_ouro-e-prata-120x117.jpg 120w, https:\/\/revistapesquisa.fapesp.br\/wp-content\/uploads\/2014\/06\/Tecno_ouro-e-prata-250x243.jpg 250w\" sizes=\"auto, (max-width: 290px) 100vw, 290px\" \/><p class=\"wp-caption-text\"><span class=\"media-credits-inline\">university of MANCHESTER <\/span>Electron microscopy images showing gold (red) and silver nanoparticles (green)<span class=\"media-credits\">university of MANCHESTER <\/span><\/p><\/div>\n<p>Pedro Henrique Cury Camargo, chemist at the USP Chemistry Institute, has discovered that catalyst materials made of gold and silver nanoparticles become less efficient as the proportion of gold in their composition increases. Catalysts are substances that accelerate chemical reactions, and some of them have industrial applications. Taken separately, gold is a stronger catalyst than silver. \u201cBecause of this, it was believed that catalytic activity would increase proportionally to the amount of gold,\u201d Camargo explains. \u201cBut surprisingly, we observed the opposite effect.\u201d To arrive at this result, the chemist synthesized nanostructures with different compositions, gradually increasing the proportion of gold up to a 34% gold, 66% silver alloy. At this ratio, the bimetallic nanostructures exhibited the lowest catalytic activity. The highest was observed at 18% gold to 82% silver. To understand why, Camargo sought collaboration with researcher Sarah Haigh from the University of Manchester, in England. \u201cUsing spectroscopy techniques in association with high-resolution electron microscopy, we were able to 3D-map the relative distribution of elements in the bimetallic nanoparticles,\u201d he explains. The two researchers discovered that when the proportion of gold increases, this element moves toward the center of the nanoparticles, leaving silver on the surface \u2013 the most important region for catalysis to occur. But silver is a weaker catalyst, and therefore the bimetallic compound becomes less efficient. \u201cWhen gold content is lowered to 18%, the surface will be occupied by a mix of the two metals, with a slightly higher proportion of gold,\u201d Camargo explains. \u201cSo the nanostructures with this exact proportion are the most efficient.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"Catalyst becomes less efficient as the proportion of gold increases","protected":false},"author":475,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[168],"tags":[259,249],"coauthors":[785],"class_list":["post-151156","post","type-post","status-publish","format-standard","hentry","category-technoscience","tag-chemistry","tag-nanotechnology"],"acf":[],"_links":{"self":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/151156","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/users\/475"}],"replies":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/comments?post=151156"}],"version-history":[{"count":0,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/151156\/revisions"}],"wp:attachment":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media?parent=151156"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/categories?post=151156"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/tags?post=151156"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/coauthors?post=151156"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}