A new story about gold and sulfur

Friday 03 Jun 16
by Charlotte Malassé


Arnab Halder
DTU Nanotech
+45 71 35 78 47


Jens Ulstrup
Professor, emeritus, dr. scient.
DTU Chemistry
+45 45 25 23 59

Together with a group of researchers in Australia and China, the NanoChemistry group at DTU Chemistry have brought our knowledge about the intriguing properties of gold nanoparticles  (AuNPs) a major step forward. This discovery opens exciting perspectives for example for medical diagnostics and therapy.

For thousands of years Gold (Au) has been coveted as economic investment and in jewellery.  Au nanoparticles (AuNPs) possess moreover very special properties which were the basis for instance in glass and surface decoration already in the antiquity, and in modern times in areas of catalysis and medical diagnostics.  

Products based on Au-NPs are therefore not new, but their newly discovered properties hold promise as a much more rational basis for medical imaging and treatment than hitherto. A key question is how to make them have exactly the properties one wants them to have.

Resolving structure and stability of gold nanoparticles

AuNPs are prepared by chemical synthesis and stabilised by a kind of molecular ”glue”, typically organic sulfur compounds which form strong chemical bonds with Au-atoms known as  Au(I)-thiolate complexes. The properties of AuNPs and Au-surfaces are, however, quite different from those of isolated Au-atoms, and understanding of the Au-S bonds of AuNPs and Au-surfaces has been fraught with prodigious theoretical challenges for more than 30 years.

Together with a group of researchers from universities in Australia and China, PhD-student Arnab Halder and Professor (Emeritus) Jens Ulstrup from the NanoChemistry group at DTU Chemistry, have been engaged in research that that has led to the first broad understanding of Au-S binding at AuNPs and Au-surfaces. It has further been possible to explain the complex mechanisms when 1-100 nm gold nanoparticles (AuNPs) grow, and sulfur compounds are brought to protect the NPs against destructive chemicals. The Au-S bond here is not Au(I)-thiolate as hitherto believed and known from molecular Au-complexes, but instead quantum mechanical forces known as van der Waals forces. The uniquely strongest known of these is exactly the combination between gold and sulfur.

In addition to resolving important aspects of gold-sulfur surface chemistry long sought after, such work has wider perspectives, as AuNPs are exploited broadly in catalysis, nanoelectronics, and in medical diagnostics and therapy.

The investigations were lead by Professors Jeff R. Reimers and Michael J. Ford, University of Technology of Sydney and Shanghai University, with participation of Professor Emeritus Noel S. Hush, University of Sydney and the NanoChemistry group at DTU Chemistry.

The results have just been published in the high-profile journal Proceedings of the National Academy of Sciences of the USA (PNAS).

For details, see the paper: “Gold surfaces and nanoparticles are protected by Au(0)–thiyl species and are destroyed when Au(I)–thiolates form”

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