AcknowledgementThis work was supported by project “Centre for MaterialsResearch at FCH BUT” No. CZ.1.05/2.1.00/01.0012 from EuropeanRegional Development Fund (ERFD) and by the project “Excel-lent young researcher at BUT” No. CZ.1.07./2.3.00/30.0039. Authorskindly thank to Dr. Tomas Opravil (Brno University of Technology,Czech Republic) for collection of spent coffee grounds.