The authors present a new method for deposition of thin nanocomposite films made of sol-gel-based Au nanoparticles using a single electrochem. step. Applying a neg. potential to an electrode (indium Sn oxide or stainless steel) immersed in a soln. of Au nanoparticles stabilized with N-[3-(trimethoxysilyl)propyl]ethylenediamine (EDAS) caused the redn. of the protic solvent, which altered the pH and therefore catalyzed the deposition. The nanocomposite thin films were characterized by various techniques: the morphol. and structure of the layers were examd. by high-resoln. SEM and at. force microscopy; their thickness was detd. by profilometry; and the permeability of the films was studied by electrochem. Homogeneous defect-free layers could be deposited only upon adding tetramethoxysilane (TMOS) to the deposition soln. Also, the applied potential, the ratio between the TMOS and the Au nanoparticles, and the type of the substrate significantly affected the aggregation and d. of the Au nanoparticles in the nanocomposite. Finally, by applying a pos. potential to the nanocomposite films the authors succeeded to electrochem. dissolve the embedded Au nanoparticles, forming holes and channels. The oxidn. treatment had a remarkable effect on the permeability of the film and exposed the electrode to faradic activity. This method seems to be of general applicability in templating of nanometer-sized objects in thin films. [on SciFinder(R)]
A review. The formation of thin coatings based on either self-assembled monolayers or polymeric films is discussed. These coatings are used to structure surfaces and control their phys. and chem. properties. Different examples are given from our work emphasizing the advantages of monolayers and polymeric films. Finally, different approaches, which benefit from both monolayers and polymeric films, are presented. [on SciFinder(R)]
Cellobiose dehydrogenase (CDH) is a fascinating extracellular fungal enzyme that consists of two domains, one carrying a flavin adenine dinucleotide (FAD) and the other a cytochrome-type heme b group as cofactors. The two domains are interconnected by a linker and electrons can shuttle from the FAD to the heme group by intramolecular electron transfer. Electron transfer between CDH and an electrode can occur by direct electron transfer (DET) and by mediated electron transfer (MET). This characteristic makes CDH an interesting candidate for integration in systems such as biosensors and biofuel cells. Moreover, it makes CDH an alternative for the reduction of metal ions through DET and MET. In this work we have explored the localized deposition of gold on Pd substrates by CDH through DET and MET. For this purpose we exploited the advantage of scanning electrochemical microscopy (SECM) as a patterning tool. We first demonstrated that gold nanoparticles can be formed in homogenous solution. Then we showed that Au nanoparticles can also be locally formed and deposited on surfaces through DET at low pH and by MET at neutral pH using benzoquinone/hydroquinone as mediator.[on SciFinder (R)]
Cellobiose dehydrogenase (CDH) is a fascinating extracellular fungal enzyme that consists of two domains, one carrying a FAD and the other a cytochrome-type heme b group as cofactors. The two domains are interconnected by a linker, and electrons can shuttle from the FAD to the heme group by intramol. electron transfer. Electron transfer between CDH and an electrode can occur by direct electron transfer (DET) and by mediated electron transfer (MET). This characteristic makes CDH an interesting candidate for integration in systems such as biosensors and biofuel cells. Moreover, it makes CDH an alternative for the redn. of metal ions through DET and MET. In this work we have explored the localized deposition of gold on Pd substrates by CDH through DET and MET. For this purpose we exploited the advantage of scanning electrochem. microscopy (SECM) as a patterning tool. We first demonstrated that gold nanoparticles can be formed in homogeneous soln. Then we showed that Au nanoparticles can also be locally formed and deposited on surfaces through DET at low pH and by MET at neutral pH using benzoquinone/hydroquinone as mediator. [on SciFinder(R)]
A new approach for assembling selective electrodes based on molecularly imprinted polymers (MIPs) is presented. The approach is based on the radical polymerization of a mixture of methacrylic acid (MAA) and ethyleneglycol dimethacrylate (EGDMA) in the presence of an initiator, benzoyl peroxide (BPO) and an activator, N,N’-dimethyl-p-toluidine (DMpT) at room temperature and atmospheric pressure. To form nanometric thin polymeric films the polymerization solution was spin-coated in the course of polymerization. The different physical and chemical parameters that affected the properties of the films, such as the spinning rate and the EGDMA:MAA ratio, were studied and optimized. A variety of techniques, e.g., rheoscopy, SEM, AFM, profilometry and electrochemistry, were used to characterize the films and the polymerization process. By optimizing the conditions very thin and reproducible films could be prepared and imprinted. The electrochemical behavior of the films showed that they were permeable to water-soluble electroactive species providing that either polyethylene glycol or template species were added to the polymerization mixture. Finally, we demonstrated that films imprinted with ferrocenylmethyl alcohol (Fc-MeOH) successfully extracted the imprinted species after their removal from MIPs.[on SciFinder (R)]
A new approach for assembling selective electrodes based on molecularly imprinted polymers (MIPs) is presented. The approach is based on the radical polymn. of a mixt. of methacrylic acid (MAA) and ethyleneglycol dimethacrylate (EGDMA) in the presence of an initiator, benzoyl peroxide (BPO) and an activator, N,N’-dimethyl-p-toluidine (DMpT) at room temp. and atm. pressure. To form nanometric thin polymeric films the polymn. soln. was spin-coated in the course of polymn. The different phys. and chem. parameters that affected the properties of the films, such as the spinning rate and the EGDMA:MAA ratio, were studied and optimized. A variety of techniques, e.g., rheoscopy, SEM, AFM, profilometry and electrochem., were used to characterize the films and the polymn. process. By optimizing the conditions very thin and reproducible films could be prepd. and imprinted. The electrochem. behavior of the films showed that they were permeable to water-sol. electroactive species providing that either polyethylene glycol or template species were added to the polymn. mixt. Finally, we demonstrated that films imprinted with ferrocenylmethyl alc. (Fc-MeOH) successfully extd. the imprinted species after their removal from MIPs. [on SciFinder(R)]
A novel method for a low-voltage electrodeposition of insulating oxide sol-gel thin films on complex conducting patterns is described. By this method gold meshes and printed chips were selectively coated with titania and zirconia thin films. This method solves a classical problem in the thin-films world: dip-coating, spin-coating, spraying without masks-all cannot be used for selective coating of a complex conductive pattern, because these methods do not differentiate between conducting vs non-conducting areas. The newly developed method provides an electrochem. pattern recognition, which solves this problem. [on SciFinder(R)]
The electrochem. deposition of org. nanoparticles on conducting surface, such as a coronary stents, in the absence of a polymeric matrix is demonstrated. A novel approach, whereby pH-responsive org. nanoparticles coagulate on a conducting surface as a result of applying pos. potential, has been studied. Specifically, latex nanoparticles stabilized by sodium oleate in aq. solns. were deposited by applying a pos. potential that oxidized the water and caused the decrease of pH on various conducting surfaces. It was found that the applied potential, its duration and the concn. of the dispersed nanoparticles govern the deposition characteristics of the coating. This generic approach allows coating objects with complex geometries with thickness ranging from nanometers to microns and therefore can be utilized for coating medical and other devices as well as for controlling drug release. [on SciFinder(R)]