Siloxane based Organic-Inorganic Hybrid Polymers and their Applications for Nanostructured Optical/Photonic Components

We have studied the preparation of organic-inorganic hybrid polymer precursors  by  sol-gel  technique  and  their  utilization  for  nanostructured  optical components for photonic applications. The gel polymer precursors were prepared from  siloxane  modified  by  polymerizable  acrylate  groups,  which  can  be processed  further  by  photopolymerization  process.  Molecular  structure characterizations by means of the FTIR measurements indicate the conversion of C=C  bonds  into  C-C  bonds  after  photopolymerization.  This  bond  co nversion produces  high  cross-linking  between  the  organic  and  inorganic  moieties, resulting  in  thermally  stable and chemically resistant thin polymer layer which provide  unique  advantages  of  this  material  for  particular  optical/photonic applications.  By  employing  laser  interference  technique,  gratings  with periodicity between 400-1000 nm have been successfully fabricated. Application of  those  sub-micron  periodicity  of  grating  structure  as  active  elements  in optically  pumped  polymer  laser  system  and  Surface Plasmon Resonance  (SPR) based  measurement  system  have  been  also  explored.  The  experimental  results therefore  also  show  the  potential  applications  of  this  hybrid  polymer  as  a building material for micro/nano-photonics components.

Low-frequency Raman study of the ferroelectric phase transition in a layered CuCl4-based organic-inorganic hybrid

The ferroelectric phase transition at TC = 340 K in (C6H5CH2CH2NH3)2CuCl4 is studied by means of temperature-dependent low-frequency Raman scattering, focusing on the coupling of a low-energy librational mode to the order parameter of the transition. Analysis of the symmetry and characteristics of this mode links the dipolar order to the tilt angle of the organic cations. The thermal evolution of the Raman spectrum demonstrates the displacive component of the phase transition in combinationwith order-disorder phenomena and the importance of the organic-inorganic interplay to the physical properties of the compound. The ferroelectric properties investigated here can be generalized to the family of layered organic-inorganic hybrids.

Siloxane Based Organic-Inorganic Hybrid Polymers and Their Applications for Nanostructured Optical/Photonic Components

We have studied the preparation of organic-inorganic hybrid polymer precursors by sol-gel technique and their utilization for nanostructured optical components for photonic applications. The gel polymer precursors were prepared from siloxane modified by polymerizable acrylate groups, which can be processed further by photopolymerization process. Molecular structure characterizations by means of the FTIR measurements indicate the conversion of C=C bonds into C-C bonds after photopolymerization. This bond co nversion produces high cross-linking between the organic and inorganic moieties, resulting in thermally stable and chemically resistant thin polymer layer which provide unique advantages of this material for particular optical/photonic applications. By employing laser interference technique, gratings with periodicity between 400-1000 nm have been successfully fabricated. Application of those sub-micron periodicity of grating structure as active elements in optically pumped polymer laser system and Surface Plasmon Resonance (SPR) based measurement system have been also explored. The experimental results therefore also show the potential applications of this hybrid polymer as a building material for micro/nano-photonics components

Oxidized colloidal h-BN nanoscrolls: Spectroscopic study of the phase transformation upon scrolling process

In comparison to carbon nanostructures, hexagonal boron nitride (hBN) nanostructures show better biocompatibility and lower cytotoxicity. However, research studies on hBN nanostructures for biomedical applications are still in an early stage, which limits the current knowledge about this group of materials, particularly their functionalization. Herein, we report a simple and scalable two-step method for the simultaneous synthesis and functionalization of hBN nanosheets (NSHs) and nanoscrolls (NSCs). The first step is conventional chemical exfoliation under alkaline conditions to weaken the interlayer interactions. The second step is exposure to low-frequency ultrasonic irradiation to obtain partially oxidized NSHs and NSCs. The successful formation of both NSHs and NSCs is confirmed using electron microscopy. The effective incorporation of O atoms into hBN nanostructures was confirmed through (i) the changes in the optical bandgaps deduced from UV–vis absorption, and (ii) the decrease in B atoms bonded to three N atoms and the increase in the BNxOy component observed using high-resolution XPS. Raman spectroscopy was used to analyze the evolution of the active phonon modes upon further exposure to irradiation, and showed a phase transition from sp2 to a mixture of sp2–sp3 bondings at the occurrence of the shape transformation from NSHs to NSCs.R. Miranti thanks to Research Council of Norway for the financial support under FRINATEK Project Nr. 275139. M.S. Qayyum thanks NTNU NanoLab support through the Norwegian Micro- and Nano-Fabrication Facility, NorFab, (Grant No. 245963/F50).Peer reviewe

Super-coercive electric field hysteresis in ferroelectric plastic crystal tetramethylammonium bromotrichloroferrate(III)

Ionic plastic crystals are part of an emerging class of hybrid organic–inorganic ferroelectrics. The combination of low dielectric constants (100 pC N−1) and low temperature synthesis make ferroelectric plastic crystals strong candidates for sensing and energy harvesting applications so more research of the electrical properties, such as dielectric loss and super-coercive hysteresis is needed. Tetramethylammonium bromotrichloroferrate(III) was studied as a prototypical material and a non-centrosymmetric orthorhombic Amm2 structure was confirmed by X-ray diffraction at room temperature. The relative permittivity was below 20 at high frequencies (105 Hz) but high dielectric losses at frequencies 80 to 30 kV cm−1 and 0.046 to 0.017% respectively between 100 and 0.1 Hz. At 100 Hz the material exhibited a strong asymmetric hysteresis that was reversible depending on the electric field direction. The observed behavior was consistent with a defect pinning model of ferroelectric switching behavior and thus some likely point defect species were proposed and thought to result from solution non-stoichiometry or residual moisture and solvent

Photoinduced Charge Transfer in Hybrid Systems of CuInS2 Nanocrystals and Conductive Polymer

© 2015 American Chemical Society. Colloidal CuInS2 nanocrystals are a promising alternative to toxic cadmium or lead chalcogenide nanocrystals that are widely studied as absorbing material in hybrid solar cells. Photovoltaic devices with colloidal CuInS2 nanoparticles suffer, however, still from low performance. The present study focuses on a detailed investigation of charge transfer as an elemental process involved in the energy conversion process. Therefore, the excited state properties and the process of charge transfer in CuInS2 (CIS) nanocrystal/polymer composites were studied by applying quasi-steady-state photoinduced absorption (PIA) and steady-state photoluminescence (PL) as well as time-resolved photoluminescence (PL) spectroscopy. The excited state dynamics of our systems was studied using time-correlated single photon counting. We examined two different composites, namely, CuInS2 nanocrystals combined with either poly(3-hexylthiophene) (P3HT) or poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT). Optical absorption and emission spectra of these hybrid material systems exhibit luminescence quenching and polaronic photoinduced absorption indicating photoinduced charge transfer. By systematic variations of the composition of the films, the material ratios favoring efficient charge transfer were determined.status: publishe

Siloxane based Organic-Inorganic Hybrid Polymers and their Applications for Nanostructured Optical/Photonic Components

We have studied the preparation of organic-inorganic hybrid polymer precursors by sol-gel technique and their utilization for nanostructured optical components for photonic applications. The gel polymer precursors were prepared from siloxane modified by polymerizable acrylate groups, which can be processed further by photopolymerization process. Molecular structure characterizations by means of the FTIR measurements indicate the conversion of C=C bonds into C-C bonds after photopolymerization. This bond conversion produces high cross-linking between the organic and inorganic moieties, resulting in thermally stable and chemically resistant thin polymer layer which provide unique advantages of this material for particular optical/photonic applications. By employing laser interference technique, gratings with periodicity between 400-1000 nm have been successfully fabricated. Application of those sub-micron periodicity of grating structure as active elements in optically pumped polymer laser system and Surface Plasmon Resonance (SPR) based measurement system have been also explored. The experimental results therefore also show the potential applications of this hybrid polymer as a building material for micro/nano-photonics components

In situ synthesis of epoxy nanocomposites with hierarchical surface-modified SiO2 clusters

Polymer nanocomposites are often produced using in situ approaches where an inorganic filler (as the dispersed phase) is synthesized directly in an organic matrix. Such an approach generally leads to improved dispersion and reduced agglomeration of the filler material. Epoxy-based nanocomposites have demonstrated promising properties for application as high-voltage insulation materials. In this work, a sol–gel based method has been adapted to synthesize surface-functionalized SiO2 in situ in epoxy. The synthesized SiO2 moieties were dispersed in clusters of 10–80 nm, and formed chemical bonds with the epoxy monomers via a silane coupling agent. Raman spectra show the formation of four-membered D1 rings, which may be part of a cage-like structure similar to that of polyhedral oligomeric silsesquioxanes (POSS). SAXS measurements indicate that the SiO2 clusters consist of a hierarchical structure with an increasing fractal dimension with increasing SiO2 content. The nanocomposites displayed improved thermal stability, while the glass transition behavior varied depending on the structure and content of the SiO2 moieties. While the relative permittivity showed no significant changes from that of pure epoxy, the onset of the dielectric relaxation changed with the SiO2 structure and content, similar to the behavior observed for the glass transition

Siloxane based Organic-Inorganic Hybrid Polymers and their Applications for Nanostructured Optical/Photonic Components

We have studied the preparation of organic-inorganic hybrid polymer precursors  by  sol-gel  technique  and  their  utilization  for  nanostructured  optical components for photonic applications. The gel polymer precursors were prepared from  siloxane  modified  by  polymerizable  acrylate  groups,  which  can  be processed  further  by  photopolymerization  process.  Molecular  structure characterizations by means of the FTIR measurements indicate the conversion of C=C  bonds  into  C-C  bonds  after  photopolymerization.  This  bond  co nversion produces  high  cross-linking  between  the  organic  and  inorganic  moieties, resulting  in  thermally  stable and chemically resistant thin polymer layer which provide  unique  advantages  of  this  material  for  particular  optical/photonic applications.  By  employing  laser  interference  technique,  gratings  with periodicity between 400-1000 nm have been successfully fabricated. Application of  those  sub-micron  periodicity  of  grating  structure  as  active  elements  in optically  pumped  polymer  laser  system  and  Surface Plasmon Resonance  (SPR) based  measurement  system  have  been  also  explored.  The  experimental  results therefore  also  show  the  potential  applications  of  this  hybrid  polymer  as  a building material for micro/nano-photonics components.