Coupled chemical reactions in dynamic nanometric confinement: IX. Etched tracks with membranes made of calcium carbonate

Abstract

In the recent papers of this series the formation and characterisation of Ag₂O and LiF membranes within etched swift heavy ion tracks in thin polymer foils by the ‘Coupled Chemical Reaction’ (CCR) approach was described. Such membrane-containing etched tracks were shown to be useful to create enzyme-clad biosensors of optimum efficiency. Some planned biosensors of higher complexity would, however, require the re-dissolution of the membranes after the enzyme deposition step, without affecting the enzyme’s performance. To accomplish this, we looked for membrane materials that could, on the one hand, be easily produced by the CCR strategy, but on the other hand, be also easily re-dissolved thereafter in a bio-friendly way. As we think that earth alkali carbonates would fulfil these requirements (they dissolve already in very weak organic acids), we studied here the formation of membranes of Calcium carbonate. Interestingly it turned out that their membrane formation mechanism differs somewhat from that of the previously studied systems. Their basic ‘fingerprints’ are stable capacitive current responses – rather than the ‘quiet phases’ during else highly agitated spiky Ohmic current responses, as was observed for the earlier studied membrane materials Ag₂O and LiF.

KEYWORDS:

• Chemistry
• etching
• ions
• nanostruct
• polymers
• swift heavy ions

Acknowledgement

D.F. is grateful to the Universidad Autónoma Metropolitana-Iztapalapa, Mexico City, for the guest professorship in the frame of the Cathedra ‘Alonso Fernandez.’ We are further obliged to Dr. P. Apel from JINR Dubna, Russia for providing us with the examined ion-irradiated polymer foils. Thanks also to Dr. Trautmann from GSI and Prof. G.Szenes from Eoetvoes University for providing many of the other samples.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1 Whenever the conductance of the examined foil exceeds that of the measuring circuit, no more information about the track radius or shape can be derived any longer (if in such a case, more information is still required, the circuit’s specifications have to be modified accordingly). In such a case, the current remains virtually constant with time. However, in the case of Fig. 1d, the observed marginal current changes after ∼ 7000 s indicate that this saturation of the recorded electronic signal is not yet reached, i.e. that the measured results are not an artefact of wrongly adjusted circuit specifications but do reflect reality.

2 Though this small current component exhibits a positive phase shift like inductive currents do, one can definitely exclude that the measured currents really stem from inductivities as there are none of importance in the measuring system. We therefore rather think that these after-runner currents rather reflect some time-delayed charge carrier migration via a trapping-detrapping mechanism, with the radiochemical reaction products in the tracks acting as transient traps for the migrating charge carriers (ions). For more information on this topic of positive phase shifts during track etching, please consult also Ref. (22).

Additional information

Funding

The project was supported by the Grant Agency of the Czech Republic (P108-12G-108) and the Nuclear Physics Institute, Řež near Prague.