Titanium dioxide nanoreactor

The titanium dioxide nanoparticles crystallize in a polymer network at room temperature.

The titanium dioxide nanoparticles crystallize in a polymer network at room temperature.

Tiny particles of titanium dioxide are found as key ingredients in wall paints, sunscreens, and toothpaste; they act as reflectors of light or as abrasives. However with decreasing particle size and a corresponding change in their surface-to-volume ratio, their properties change so that crystalline titanium dioxide nanoparticles acquire catalytic ability: Activated by the UV component in sunlight, they break down toxins or catalyze other relevant reactions.

Now, Dr. Katja Henzler and a team of chemists at the Helmholtz Centre Berlin have developed a synthesis to produce nanoparticles at room temperature in a polymer network. Their analysis, conducted at BESSY II, Berlin's synchrotron radiation source, has revealed the crystalline structure of the nanoparticles. This represents a major step forward in the usage of polymeric nanoreactors since, until recently, the nanoparticles had to be thoroughly heated to get them to crystallize. The last synthesis step can be spared due to the special environment inside the PNIPAM network.

The Henzler team's polymeric nanoreactors consist of a polystyrene core surrounded by a network of PNIPAM chains. A titanium compound was added to an ethanolic solution of the polymer colloids, which did trigger the formation of small titanium dioxide particles within the PNIPAM network. The BESSY II experiments showed that the chemists were able to control the speed of these processes while at the same time affecting the quality of the nanocrystals that had formed.

Using the novel combination of x-ray microscopy and spectroscopy (NEXAFS-TXM, U41-SGM) at BESSY II, Henzler and the microscopy team were able to show that the nanoparticles are homogeneously distributed over the polymeric nanoreactors. The researchers examined their samples in a cryogenic aqueous environment, which prevents artifact formation due to sample drying. Their analysis showed that the nanoparticles have a crystalline structure. "The nanocrystals have a tetragonal anatase structure and this crystalline structure is a key to their catalytic performance. Additionally, our new analytic method allows us to control the quality of the synthesized particles so that we can optimize them for relevant applications," says Katja Henzler. 


Nano Letters, 2013, 13 (2), pp 824–828;

DOI: 10.1021/nl3046798



You might also be interested in

  • 40 years of research with synchrotron light in Berlin
    40 years of research with synchrotron light in Berlin
    Press release _ Berlin, 14 September: For decades, science in Berlin has been an important driver of innovation and progress. Creative, talented people from all over the world come together here and develop new ideas from which we all benefit as a society. Many discoveries – from fundamental insights to marketable products – are made by doing research with synchrotron light. Researchers have had access to this intense light in Berlin for 40 years. It inspires many scientific disciplines and is an advantage for Germany.

  • New road towards spin-polarised currents
    Science Highlight
    New road towards spin-polarised currents
    The transition metal dichalcogenide (TMD) series are a family of promising candidate materials for spintronics. A study at lightsource BESSY II has unveiled that in one of those materials even simple linear polarised light is sufficient to selectively manipulate spins of different orientations. This result provides an entirely new route for the generation of spin-polarised currents and is a milestone for the development of spintronic and opto-spintronic devices.
  • BESSY II resumes operation after a long shutdown
    BESSY II resumes operation after a long shutdown
    On 30 August, BESSY II ligth source will resume user operation: the research centre will then welcome guest researchers from all over the world and support them in their various experiments. The 14-week  shutdown was the longest in BESSY II history. Among other works, the main supply was completely renewed. The successful completion of the work was celebrated with all those involved.