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Recently, nanoporous gold nanoparticles have attracted great interest due to their optical and catalytic properties. However, most reports on their fabrication are based on the dealloying method. Here, we report a new fabrication technique for hollow nanoporous gold nanoshells (NPGNSs) with high structural tunability by sintering chemically synthesized gold nanoparticles (AuNPs) on the surface of polymer colloid particles. Size reduction of the colloid template by plasma etching induces contact of the AuNPs on the colloid surface. Elimination of the capping layers of AuNPs by plasma etching facilitates sintering of the contacted AuNPs. Complete removal of the colloid template after AuNP sintering results in hollow NPGNSs. A combination of AuNPs and polymer colloid templates of different sizes can change the structure and optical properties of hollow NPGNSs. Furthermore, AuNPs of different shapes, such as gold nanorods with a high aspect ratio and spherical AuNPs, can be used to make hollow NPGNSs, which gives more flexibility in tuning their structures. Our proposed fabrication technique based on shrinkage of templates and sintering of nanoparticles can be a new platform to prepare hollow nanoporous metal structures having nanoscale overall sizes with high structural tunability. [ABSTRACT FROM AUTHOR]

Adsorption of organic cations of malachite green (MG) on an anionic microsphere surface was monitored in real time using a surface-specific second-harmonic generation (SHG) technique. This adsorption was found to consist of two processes of different timescales for all MG concentrations, which has not been considered in previous SHG experiments. The two-step adsorption can be well explained by our suggested model, which consists of an initial fast electrostatic alignment of weakly bound MG followed by slow non-electrostatic adsorption of MG on the surface of a microsphere. This study shows the importance of kinetics measurements in providing full understanding of adsorption of charged molecules on colloid surfaces. [ABSTRACT FROM AUTHOR]

An anionic conjugated polyelectrolyte based on polydiphenylacetylene showed a significant fluorescence turn-on response to positively-charged proteins through a conformational relaxation of its intramolecular stack structure. [ABSTRACT FROM AUTHOR]

A new design for light-emitting diodes (LEDs) with on-chip photocatalysts is presented for purification applications. An array of disk-shaped TiO 2 , with a diameter of several hundred nanometers, combined with SiO 2 pedestals was fabricated directly on the surface of an InGaN-based near-ultraviolet (UV) LED using a dry etching process. The high refractive-index contrast at the boundary and the circular shape can effectively confine the near-UV light generated from the LED through multiple internal reflections inside the TiO 2 nanodisks. Such a feature results in the enhancement of light absorption by the photocatalytic TiO 2 . The degradation of the organic dye malachite green was monitored as a model photocatalytic reaction. The proposed structure of LEDs with TiO 2 /SiO 2 nanodisk/pedestal array exhibited a photocatalytic activity that was three times higher than the activity of LEDs with a TiO 2 planar layer. The integration of photocatalytic materials with near-UV LEDs in a single system is promising for various purification applications, such as sterilization and disinfection., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)