Electrografting of carboxyphenyl thin layer onto gold for DNA and enzyme immobilization

Ethanol vs. water: influence of the terminal functional group of the alkyl chain and environment of the self-assembly process on electron transport through the thiol layer

Self-assembly of alkanethiol chains on metallic surfaces is a spontaneous process which leads to the formation of highly ordered layers. However, the organization of the thiol chains on the surface strongly depends on the intermolecular interactions between the terminal groups in the chain. The solution environment also plays an important role. In this paper we present the effect of solution solvent (water and ethanol) and the presence of various hydrophilic terminal groups (–OH, –NH₂ and –COOH) on the quality and electrochemical properties of the formed alkanethiol layers. In the studies we applied voltammetry, atomic force microscopy and quartz crystal microbalance to characterize the morphology, packing density and ability to electron exchange through the thiol layer. The blocking properties of the formed SAMs expressed as the electron-transfer rate constant as well as their organization have been examined using a model electrochemical probe, Fe(CN)₆³⁻. With the increase in the polarity of the terminal functional group the regularity of the thiol layer decreased.

The organization of the thiol chains on the surface strongly depends on the intermolecular interactions between the terminal groups in the chain and the solution environment.

Selective and sensitive electrochemical device for direct VB2 determination in real products

The developed by us electrochemical device for vitamin B₂ (VB₂; riboflavin) determination, without preconcentration step, in real products exhibits high sensitivity, selectivity, stability and low detection limit compared to those described in the literature. The determination procedure was based on the monitoring of the reduction current signal of VB₂ bound with dsDNA anchored to the electrode surface through intermediary - carboxyphenyl layer. The application of such intermediary layer formed during electroreduction of appropriate diazonium salt at CV peak potential guarantees high efficiency of hybridization process and thus fully available places for VB₂ interaction. Moreover, such intermediary layer provides good electrical contact, what is very important in the case of electrochemical sensors. The analytical range of work of the proposed VB₂ sensor was between 0.08-1µM (30-377μgL^-1) of riboflavin concentration. The obtained detection (LOD) and quantification limits (LOQ) were 24±2 and 55±5μgL^-1, respectively. The proposed VB₂ detection method was used for determination of riboflavin content in commercially available dietary supplements and yolk of hen egg samples. The accuracy of the obtained data was proved using comparison with an independent method (HPLC FLD).