By Dr. Matthew Fielden, Marketing Manager, KSV Instruments Ltd, KSV Instruments Ltd. - Solutions for surface and interface preparation and analysis
SubscribeThe Dissipative Quartz Crystal Microbalance (QCM) is a highly sensitive tool for characterising surface specific behaviour, such as adsorption, adsorbed layer thickness and viscoelastic properties in a wide range of applications.
From specific biological interactions on analyte-immobilised surfaces, to characterisation of fouling in industrial processes, the dissipative QCM from KSV is an ideal solution.
Now, the introduction of simple screw-in ellipsometry and electrochemistry modules for the standard window cell, shed new light on dynamic processes, by enabling simultaneous measurement on the same surface using different techniques.
QCM Z-500 with Window Cell
Ellipsometry Module
The strength of the simultaneous ellipsometric measurement lies in the fact that QCM provides the "wet" mass (surface-coupled solvent is included), while ellipsometry provides the "dry" mass (the solvent is "invisible").
The combination therefore allows, for example, the determination of water-content of surface hydrogels (Figure 1). The evolution of film viscoelasticity and thickness is clearly also accessible from the QCM measurements.
The ability to measure simultaneously has the dual advantage of saving you time, and removing the uncertainty of comparing the same measurements done on separate occasions.
Simultaneous dissipative QCM and ellipsometry measurement of adsorption of polyelectrolyte multilayers (PEL) of poly-L-lysine / poly-L-glutamic acid to titanium dioxide, illustrating that the layer consists of about 80% water.
Simultaneous electrochemical measurements allow the determination of mass-change during standard voltammetric cycling (Figure 2). The overlap of DF at the different overtones (Figure 3) shows that the change in mass is occurring in a rigid layer. In both of the above cases, the QCM also follows the evolution of the viscoelasticity and thickness of the surface layer.
Simultaneous measurement of mass and current change during potential sweeps for dissolution and deposition of copper on gold in 10 mM CuSO4in 0.1 M H2 SO4.
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