Responsive core–shell microgels: Synthesis,characterization, and possible applications

Core–shell microgels are of increasing interest as smart carriers of catalysts, as sensors, or as building blocks for colloidal superstructures. In the context of colloidal assemblies, photonic applications are probably the most promising ones. This progress report presents and discusses the most recent results in this area focusing on the last 2–3 years, and also gives some background information. In addition, potential perspectives of this area will be outlined. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1073–1083     

Nanoassemblies with light‐responsive size and density from linear flexible polyelectrolytes

This study presents electrostatically self‐assembled nanoparticles from linear flexible polyelectrolytes (poly(diallyldimethylammonium chloride or quarternized poly(4‐vinylpyridine)) and an ionic photo‐isomerizable azo dye (Acid Yellow 38) that can change their size upon UV‐light irradiation. Assemblies with narrow size distribution are stable in aqueous solution. For samples with under‐stoichiometric dye load, UV‐light exposure triggers a size decrease, e.g. from a hydrodynamic radius of R_h = 94 nm to R_h = 62 nm for an Ay38‐PDADMAC sample with a charge ratio of l_charge = 0.7. Size changes are caused by trans‐cis isomerization of the dye, accompanied by a change in hydrophilicity, binding enthalpy and entropy. Assemblies are characterized by static and dynamic light scattering, atomic force microscopy, UV–vis spectroscopy and isothermal titration calorimetry. Zeta potential measurements give insight into the electrostatic stabilization and size‐control of the ionic nano‐assemblies, revealing a master curve of effective surface charge density versus hydrodynamic radius. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys., 2013     

Vibrational spectroscopic study of poly(dimethylsiloxane)-ZnO nanocomposites

A series of poly(dimethylsiloxane)-zinc oxide (PDMS-ZnO) nanocomposites having different concentrations of ZnO nanoparticles (0, 1, 5, 10 and 20 wt%) have been prepared. Raman and FTIR-ATR spectroscopic analysis was performed in order to determine the interaction between the ZnO nanoparticles and PDMS polymer matrix. Density functional theory (DFT) using the (B3-LYP)/6-311++G(2df,2p) method was used to investigate the vibrational spectra of PDMS. A complete vibrational assignment is supported by the normal coordinate analysis, calculated Raman activities as well as IR intensities.The presence of ZnO nanoparticles in PDMS gives rise to significant differences in relative intensities of the characteristic vibrational bands with respect to the cross-linked polymer. The changes in relative intensities of Raman bands, as well as swelling measurements, were used to explain the effect of ZnO nanoparticles on the cross-linked structure of PDMS nanocomposites. It is established that ZnO nanoparticles influence the cross-linking density of the polymer matrix.     

Development of a test strip based on DNA-functionalized gold nanoparticles for rapid detection of mercury(II) ions

A rapid,sensitive,selective and reliable strip assay based on DNA-functionalized gold nanoparticles for Hg²⁺ detection has been developed,with a detection limit 5 nmol/L.The measurement principle was based on thymine-Hg²⁺-thymine(T-Hg²⁺-T) coordination chemistry and streptavidin-biotin interaction.The major advantages of this assay are that results can be read visually without any instrument in less than 10 min and that it does not require any sample pretreatment.