IntroductionDendrimers [1] are highly branched macromolecules consisting of a multifunctional core, to which repeating units are sequentially covalently bonded to create a topologically regular structure. The resultant molecules present a well-defined number of terminal groups and a narrow molecular weight distribution that is truly monodisperse in most cases. Owing to their structural uniformity, dendrimers provide a valuable model for correlating the macromolecular structure to the technological function [2][3][4][5]. Thus, dendrimers have a wide range of applications, including drug delivery [6], catalysis, and sensors [7][8] in high-technology fields. The organization of dendrimers in monolayers results in materials that can be applied as devices [7][8][9][10] and scaffolds for posterior elaborations [11][12][13][14][15][16][17]. Moreover, stratumous-layered composites of a dendrimer and a linear polymer can be prepared by linking terminal groups of a dendrimer to functional groups of a polymer [12,13,16,[18][19][20].Double-layered hydroxides, also known as ionic clays, are important inorganic materials, and have deserved Progr Colloid Polym Sci (2004) Abstract Nanocomposites have been prepared through the intercalation of poly(amido amine) dendrimers with carboxylate terminals into hydrotalcite clays. The formation of nanocomposites by anion exchange during incubating at 70°C was investigated at various compositions with increasing dendrimer content in water and was assessed by Fourier transform IR absorption spectroscopy, X-ray diffraction, small-angle X-ray scattering, and elemental analysis. The dendrimer diffused into the clay galleries: the spacing between the clay layers (sheets) increased from its intrinsic value of 3.2 to 20-23 Å , and the mass fraction of the dendrimer in the composite was around 0.50 for mixing ratios (charge of clay to carboxylate of the dendrimer) higher than 1:2, indicating the saturated intercalation of the dendrimer in the clay. The dendrimers are densely packed with an ellipsoidal structure in the interlayer. At a mixing ratio of 1:8, there was excess adsorption of the dendrimer on the clay surface besides the intercalation and initial adsorption.

A hydrotalcite clay/dendrimer nanocomposite prepared by the ionic exchange process was adsorbed from suspension of the nanocomposite on a Langmuir monolayer of arachidic acid at the air/water interface, followed by compressing and transferring onto an arachidic acid monolayer Langmuir-Blodgett (LB) film on mica. For comparison, the hydrotalcite-adsorbed hybrid film was also prepared. The morphology of hydrotalcite and the nanocomposite studied by transmission electron microscopy indicated the layered structures with respectively 1.2 +/- 0.3 and 3.2 +/- 0.5 nm repeating distances. The hybrid Langmuir films displayed the occupied surface area of 0.24 nm2 for both hydrotalcite and the nanocomposite. The formation of hybrid Langmuir films was confirmed by Brewster angle microscopy. Atomic force microscopic images of hybrid LB films revealed the formation of plateau domains with the height difference of 6 nm for hydrotalcite and 12 nm for the nanocomposite and the presence of dendrimers adsorbed on the clay surface of the nanocomposite.

Low-energy platinum ions were implanted with 15 keV under normal incidence into synthesized conducting polymer films with the aim to improve film conductivity and to demonstrate the use of implanted platinum in a simple sensing design. Conductivity measurements, cyclic voltammetry, and Raman spectroscopy were performed on samples both before and following ion implantation. Results display an optimum fluence of ion implantation for which polypyrrole films implanted with 2 × 1016 at. cm–2 display and retain enhanced conductivity compared with nonimplanted samples. X-ray photoelectron spectroscopy (XPS) and scanning electron microscope–energy-dispersive X-ray spectroscopy (SEM-EDS) confirmed that implanted platinum is present mainly as Pt0 and indicated that the depth and amount of ion implantation are in agreement with a simulated implantation profile. Raman spectroscopy showed a surface-enhanced Raman spectroscopy (SERS) effect with platinum’s presence. The advantageous increase in conductivity can be rationalized by two chemical modifications to the polymer upon high-fluence implantation: (1) an increase in the number of charge carriers (dications) within the polymer and (2) the presence of elemental platinum metal and its synergistic effect on conductivity. A simple DNA sensor was constructed on the basis of polypyrrole/Pt0 films where Pt0 was able to serve as anchoring points for DNA attachment as well as an enhancer of the film’s conductivity. This enabled a DNA sensor capable of successful detection of cDNA, and a good discrimination of noncDNA, thus opening a way to direct electrochemical biosensing on the basis of ion implanted highly conducting polymer films.

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