11 February 2015

Jos van Rijssel wins LUM Young Scientist Award for innovative applications

Jos van Rijssel

Former Doctoral Candidate and Post-Doc Jos van Rijssel (Physical and Colloidal Chemistry; Chemistry) was presented with the LUM Young Scientist Award for his innovative application of an industrial colloidal stability analyzer. The Berlin-based firm LUM is the international market leader in the field of these instruments. The award includes a prize of € 1,000. Thanks to Van Rijssel’s research, the stability analyzer can now be used to measure the magnitude of the interactions between quantum dots in a solution. This is exciting, because the alternative techniques for measuring these interactions are much more complex and expensive.

Semi-conducting nanoparticles called quantum dots are becoming more common due to their use in LED lighting and in biomedical research as fluorescent labels for molecules and cells. In the preparation process, it is vital to know their interactions with one another in an apolar solution, because this determines whether they can be distributed throughout the fluid in a stable manner, and how they can form structures through self-assembly.

Alternative route

Van Rijssel was able to determine their interactions by using X-ray diffusion techniques and quantitative cryogenic electron microscopes, building on the pioneering work at Physical and Colloidal Chemistry by his predecessor Mark Klokkenburg. Although this method was successful, it relied on complex and expensive equipment, and both methods had their own intrinsic limitations. He therefore studied an alternative route using osmotic state comparisons.

Centrifuge

For this, Van Rijssel needed the equilibrium profiles for the concentration of colloidal quantum dots in a solution. An equilibrium profile is obtained by spinning a solution in a centrifuge for a specific amount of time. Unfortunately, the RPMs common in scientific analytical ultra-centrifuges is much to high for use with quantum dots. Van Rijssel therefore used a centrifuge that is used to determine the stability, and therefore the expiration date, of colloidal products such as paint or mayonnaise.

Results show positive correlation

After weeks of centrifuging, he was able to achieve a equilibrium profile that resembles the barometric equilibrium profile of air at 7 km altitude, which is one-third the pressure of air at sea level. From this equilibrium profile, Van Rijssel was able to derive the osmotic state comparison, and therefore the interaction between two quantum dots in the a-polar solution. The results of these methods positively correlate to those of the other two techniques studied.

Jos van Rijssel

Jos van Rijssel studied Chemistry at Utrecht University, and earned his PhD. in December 2013 with his dissertation ‘Colloidal interaction of quantum dots in apolar liquids’. His Promotor was Prof. Albert Philipse, and his Co-promotor was Dr. Ben Erné. Since then, he has continued his research as a Post-Doc.