Research Group of
Denis Gebauer

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12.01.2015

Faraday Discussions article available online "High-resolution insights into the early stages of silver nucleation and growth"

 

Abstract. Nucleation and growth of silver nanoparticles has already been investigated with various experimental and computational tools, however, owing to inherent problems associated with the analytical characterization of nucleation processes, there is a generic lack of experimental data regarding the earliest precursors and smallest Ag(0) clusters. Here, we address this problem by the application of Synthetic Boundary Crystallization Ultracentrifugation, utilizing a multiwavelength detector for the first time, complemented by a specialized Titration Assay. These techniques shed new light on silver nanoparticle precursors existing in the pre-nucleation regime and the initially nucleated ensemble of nanoclusters. For the first time, we present experimental data of UV-vis spectra for fractionated silver clusters. These allow for unsurpassed insights into the sequence of nucleation and early growth species as well as their optical properties. [Faraday Discussions (2015), DOI: 10.1039/C4FD00269E]

 

 


 

01.11.2014

Grazyna Durak has joined the team as a postdoctoral researcher. Welcome!

 

Grazyna's project is a collaboration with Thomas Böttcher.

 

 


 

09.10.2014

Nanoscale article available online "New Insights into the Early Stages of Silica-Controlled Barium Carbonate Crystallisation"

 

Abstract. Recent work has demonstrated that the dynamic interplay between silica and carbonate during co-precipitation can result in the self-assembly of unusual, highly complex crystal architectures with morphologies and textures resembling those typically displayed by biogenic minerals. These so-called biomorphs were shown to be composed of uniform elongated carbonate nanoparticles that are arranged according to a specific order over mesoscopic scales. In the present study, we have investigated the circumstances leading to the continuous formation and stabilisation of such well-defined nanometric building units in these inorganic systems. For this purpose, in-situ potentiometric titration measurements were carried out in order to monitor and quantify the influence of silica on both the nucleation and early growth stages of barium carbonate crystallisation in alkaline media at constant pH. Complementarily, the nature and composition of particles occurring at different times in samples under various conditions were characterised ex situ by means of high-resolution electron microscopy and elemental analysis. The collected data clearly evidence that added silica affects carbonate crystallisation from the very beginning on (i.e. already prior to, during, and shortly after nucleation), eventually arresting growth at the nanoscale by cementation of BaCO3 particles within a siliceous matrix. Our findings thus shed novel light on the fundamental processes driving bottom-up self-organisation in silica-carbonate materials and, for the first time, provide a direct experimental proof that silicate species are responsible for the miniaturisation of carbonate crystals during growth of biomorphs, hence confirming previously discussed theoretical models for their formation mechanism. [Nanoscale (2014), DOI: 10.1039/C4NR05436A]

 

 


 

01.10.2014

Yu-Chieh Huang has joined the team as a PhD student. Welcome!

 

 


 

19.09.2014

Bingqiang Lu has joined the team as a postdoctoral researcher. Welcome!

 

 


 

24.07.2014

Denis Gebauer has been elected as a new member of the executive board of the Graduate School Chemistry.

 

 


 

04.02.2014

Denis Gebauer has been promoted to a Research Fellow (5-year fellowship) of the Zukunftskolleg of the University of Konstanz.

 

 


 

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