Rogier Brand

PhD Candidate

Employed since: September 2012
Phone: +31 6 22 73 63 61
E-mail: r.p.brand (at) uu.nl
Room: 4th floor study area

Research

Scanning Probe Microscopy (covering  all techniques in the range of Atomic Force Microscopy(AFM) [1] and Scanning Tunneling Microscopy (STM) [2]) has already become a very powerful analytical field for many research areas ranging from UHV low temperature surface science [3] to biological experiments [4].  AFM and its derivatives are however not very well explored in (heterogeneous) catalysis research. Combination of AFM and spectroscopic techniques, which could give more insight on for example the chemical nature of catalyst surfaces, could be one of the possibilities to change this.

In my research I will try to combine the benefits of AFM and Raman spectroscopy on thin layers of porous catalyst materials such as MOFs, ZIFs and in the end zeolites. Because Raman scattering often only yields very weak signals, signal enhancement is probably a vital point. This enhancement is induced by local (strong) electric fields which can be generated by the interaction of light with the electron cloud on the surface of nanoscaled noble metal surfaces (Au, Ag, Cu): a plasmonic effect. In this way the signal is predicted to be enhanced by a factor 103 till even 1014 [5]. When used in spectroscopy the technique is named after the effect: SERS (Surface Enhanced Raman Spectroscopy).

In so called Tip Enhanced Raman Spectroscopy (TERS) one makes use of this effect by coating the AFM-tip with one of the previously mentioned metals with nanoscaled corrugation. Because the enhanced Raman signal is a very local effect - in this case determined by the diameter of the tip apex (down to ~10 nm)- the spatial resolution of the Raman signal is also brought down well below the diffraction limit. Although this spatial resolution is certainly not higher than that of AFM on its own which has shown to be able to even distinguish bond orders of single atoms [6], the combination gives the possibility to monitor for example reactions by tracking the changes in for example morphology, phase (AFM) and/or the spectra (Raman) [7].

We investigate the possibilities to use the technique under in-situ conditions (e.g. for catalyzed reactions, or crystal growth of porous materials such as MOFs and ZIFs), which would yield a real extension into the field of heterogeneous catalysis.

Students that are interested in doing a bachelor’s or master’s thesis related to this research are very welcome to contact me.

[1] Atomic force microscope, Binnig, G., Quate, C. F., Gerber, C. Physical review letters 1986, 56 (9), 930–933 
[2] Surface studies by scanning tunneling microscopy, Binnig, G., Rohrer, H., Gerber, C., Weibel, E. Physical Review Letters 1982, 49 (1), 57–61
[3] Scanning Tunneling Microscopy in Surface Science, Bowker, M., Davies, P. R. (Eds.). (1st ed., p. 258).  2009, Weinheim: Wiley.
[4] AFM: A Nanotool in Membrane Biology†, Muller, D.J., Biochemistry 2008, 47 (31), 7986-7998
[5] (a) Surface Enhanced Raman Scattering Enhancement Factors: A Comprehensive Study, Blackie, E. J., Le Ru, E. C., Meyer, M., Etchegoin, P. G.,  J. Phys. Chem.  2007, 111 (37): 13794–13803. (b) Population Pumping of Excited Vibrational States by Spontaneous Surface-Enhanced Raman Scattering, K. Kneipp, Y. Wang, H. Kneipp, et al., Phys. Rev. Lett. 1996, 76, 2444-2447
[6] Bond-Order Discrimination by Atomic Force Microscopy, Gross, L., Mohn, F., Moll, N., et al., Science 2012, 337, 1326-1329
[7] Catalytic processes monitored at the nanoscale with tip-enhanced Raman spectroscopy, Schrojenstein Lantman, E., Deckert-Gaudig, T., Mank, A.J.G., Deckert, V. and Weckhuysen, B.M., Nature Nanotechnology 2012, 7 583-586