Generation of Clusters with Laser Desorption Ionization (LDI) and Matrix Assisted or LDI with
   Quadrupole Ion Trap Time-of-Flight Mass Spectrometric characterization of Inorganic Materials

                                          Mayuri Ausekar


Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5/A14, 625 00 Brno, Czech
                                             Republic


                       PhD thesis supervisor: Prof. RNDr. Josef Havel, DrSc.


Mass spectrometry has extensive applications in science and especially MALDI for the analysis of
bio-molecules. On the other hand, it can also be applied to inorganic materials. The aim of this
work was to study the use of LDI QIT TOFMS for characterization of various nanomaterials,
chalcogenide glasses, etc.    Several examples will be discussed.

   Chalcogenide glasses As[2]Ch[3] (Ch = S, Se, and Te) were ablated with laser and mass spectra
were recorded in both positive and negative ion modes. Up to 102 As[m]Ch[n] clusters were
identified: 10 unary (S[p]^+/– and As[m]^+/–) and 34 binary (As[m]S[p]^+/–) species for As[2]S[3]
glass; 2 unary (Se[q]^+/–) and 26 binary (As[m]Se[q]^+/–) species in case of As[2]Se[3] glass; 7
unary (Te[r]^+/–) and 23 binary (As[m]Te[r]^+/–) species for As[2]Te[3] material. The clusters
results from the fragmentation of glass structure. A novel approach was developed to diminish the
fragmentation of chalcogenide glasses and 45 new high mass clusters were observed when using
polymers such as polyvinyl pyrrolidine (PVP), polyethylene glycol and/or Parafilm [1].

   The same procedure as used for glasses was used to study formation of W[x]O[y]^+●/-● clusters
generated in gas phase via laser ablation of solid WO[3]. The LDI produced (WO[3])[n]^+●/-● (n =
1-7) clusters while in MALDI when nano-diamonds (NDs), graphene oxide (GO), or fullerene (C[60])
were used as matrices, higher mass clusters (WO[3])[n]^-● (n =1-19) were detected. Carbonaceous
materials (nano-diamonds, fullerene, and graphene oxide) were for the first time used as matrices
for the generation of (WO[3])[n]^+●/-● clusters^ in the gas phase. In MALDI new high mass clusters
(WO[3])[n]^-● (n = 12-19) were detected [2].

   Another work deals with synthesis of magnetic Co-Au nanocomposite. It was then examined as LDI
and MALDI matrices. Synthetized Co-Au nanomaterial was characterized by MS and it might have
various applications for drug delivery, magnetic therapy, hypothermia treatment, etc. [3,4].

   Concluding, LDI with TOF MS detection was shown to be a useful technique for the
characterization of various inorganic materials. The knowledge of the clusters stoichiometry is
helpful for elucidation of the materials structures.


References

[1] R. Mawale, M. Ausekar, L. Prokeš, V. Nazabal, E. Baudet, T. Halenkovič, M. Bouška, M. Alberti,
P. Němec, J. Havel. Laser desorption ionization of As[2]Ch[3] (Ch = S, Se, and Te) chalcogenides
using quadrupole ion trap time-of-flight mass spectrometry: A comparative study. J. Am. Soc. Mass
spectrom. 2017, 28, 2569-2579.

[2] M. Ausekar, R. Mawale, P. Pazdera, J. Havel. Matrix assisted and/or laser desorption ionization
quadrupole ion trap time-of-flight mass spectrometry of WO[3 ]clusters formation in gas phase.
Nanodiamonds, fullerene and graphene oxide matrices. J. Am. Soc. Mass spectrom. 2018, 29, 581-587.

[3] A. Mayoral, D. Llamosa, Y. Huttel. A novel Co@Au structure formed in bimettalic core@shell
nanoparticles. Chem. Commun. 2015, 51, 8442-844.

[4] M. Ausekar, in preparation.