Chicago (AFP) - The Scottish-born winner of the Nobel Prize for Chemistry took a jab Wednesday at US presidential candidate Donald Trump, who has bragged that he was "smart" to avoid paying taxes.

"I am not very smart. The IRS (Internal Revenue Service) will run off with a third of it," said Northwestern University professor Fraser Stoddart, referring to his portion of the eight million Swedish kronor (around $933,000 or 832,000 euros) award, which he shares with Jean-Pierre Sauvage of France and Bernard Feringa of the Netherlands.

"Did you all get that? I'm not very smart," Stoddart added, to laughter and applause during a champagne-fueled press conference to celebrate the Nobel win.

Trump, the Republican nominee for US president, has refused to release his tax returns.

In the first presidential debate on September 26 Democratic nominee Hillary Clinton suggested that Trump is hiding "something terrible," and suggested that he had not paid any federal income tax.

Trump's answer: "That makes me smart."

Days later, the New York Times published a bombshell based on a leaked copy of his 1995 tax documents, showing he declared a loss of nearly $1 billion, and could likely have avoided paying taxes for almost two decades.

Stoddart, who said he has lived in the United States for 20 years, did not press any deeper into politics, but said he wants to use whatever is left of his prize money to help others.

"One of the things that drives academia in this country is philanthropy," said Stoddart.

"What I want to do, of course, is give back."

Stoddart listed a number of his favorite universities as potential recipients, including his alma mater, the University of Edinburgh, the University of California Los Angeles, Northwestern University, and the universities of Birmingham, Sheffield, Cambridge, Durham and Imperial College.

Stoddart, Sauvage and Feringa won for developing the world's smallest molecular machines, which may some day have uses in cancer treatment, robotics and prosthetics.

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Stoddart described their work as "a fundamental advance in chemistry" that will take some time before it translates into real-life applications.

He also urged young people to press on with their goals, even if they face detractors and doubts.

"Through the early years you take some criticism because people don't understand why you are doing what you are doing," he said.

"But that eventually ebbs away and then the recognition starts to come."