Photoinduced high-quality ultrathin SiO2 film from hybrid nanosheet at room temperature
ABSTRACT The paper describes a flexible approach to building up high-quality ultrathin SiO2 films under deep UV light irradiation at room temperature. The ultrathin hybrid nanosheet possessing polyoctahedral silsesquioxane (POSS) has been designed to prepare densely packed ultrathin POSS films by the Langmuir-Blodgett (LB) technique. The LB technique enables POSS to have a multilayered structure with nanoscale precision. The films' hardness and modulus changed considerably from 0.1 and 2.6 GPa to 1.7 and 32.2 GPa, respectively, after deep UV light irradiation. Subsequent FTIR measurements revealed that the organic components were removed completely and that the POSS cage structure turned to an Si-O-Si network structure. X-ray photon spectroscopy also confirmed high-quality SiO2 formation with no suboxides.
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ABSTRACT: Porous polymer films are necessary for dissolved gas sensor applications that combine high sensitivity with selectivity. This report describes a greatly enhanced dissolved oxygen sensor system consisting of amphiphilic acrylamide-based polymers: poly(N-(1H, 1H-pentadecafluorooctyl)-methacrylamide) (pC7F15MAA) and poly(N-dodecylacrylamide-co-5- [4-(2-methacryloyloxyethoxy-carbonyl)phenyl]-10,15,20-triphenylporphinato platinum(II)) (p(DDA/PtTPP)). The nanoparticle formation capability ensures both superhydrophobicity with a water contact angle greater than 160° and gas permeability so that molecular oxygen enters the film from water. The film was prepared by casting a mixed solution of pC7F15MAA and p(DDA/PtTPP) with AK-225 and acetic acid onto a solid substrate. The film has a porous structure comprising nanoparticle assemblies with diameters of several hundred nanometers. The film shows exceptional performance as the oxygen sensitivity reaches 126: the intensity ratio at two oxygen concentrations (I0/I40) respectively corresponding to dissolved oxygen concentration 0 and 40 (mg L(-1)). Understanding and controlling porous nanostructures are expected to provide opportunities for making selective penetration/separation of molecules occurring at the superhydrophobic surface.ACS Applied Materials & Interfaces 02/2015; DOI:10.1021/am509147h · 5.90 Impact Factor
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ABSTRACT: We propose a room-temperature and ambient-pressure fabrication process of SiO2 nanofilms on flexible poly(ethylene terephthalate) (PET) substrates. Polymer Langmuir–Blodgett (LB) films containing silsesquioxane units (p(DDA/SQ22)) are successfully photo-oxidized into SiO2 nanofilms without PET degradation by UV-ozone treatment. Thicknesses of the obtained SiO2 nanofilms are tuned by 0.4 nm per monolayer, indicating that this method affords SiO2 nanofilms with a precisely controlled thickness. Photo-oxidized SiO2 nanofilms have good transparency and high electric resistance (ca. 10−9 S cm−1) even on flexible PET substrates. The resulting SiO2 nanofilms also serve as a protecting layer for PET substrates against photo-oxidizing degradation. Thus, PET films retain optical transparency even after UV-ozone treatment. Results of an investigation of the photo-oxidization mechanism reveal that UV-ozone induced conversion from silsesquioxane to SiO2 comprises two photochemical reaction processes: (1) decomposition of organic moieties in p(DDA/SQ22) LB films and (2) subsequent photo-oxidation of residual silsesquioxane units. The time constant of the second reaction strongly depends on the initial film thickness. This sequential and thickness-dependent conversion indicates that the conversion is controlled by the diffusion of extrinsic oxygen sources into the films. The results show that this method is promising for the coating of transparent insulating SiO2 layers for flexible optoelectronic device applications.12/2014; 3(6). DOI:10.1039/C4TC02131B
Article: Porphyrin-POSS molecular hybrids.[Show abstract] [Hide abstract]
ABSTRACT: Porphyrin-POSS hybrid: Porphyrin-POSS molecular hybrid composites (see scheme; POSS = polyhedral oligomeric silsesquioxanes) were synthesized and structurally characterized, allowing the realization of truly homogenous dispersion of basic functional building blocks between organic and inorganic components at the molecular level. These materials allow the optimization of aggregation/association behavior and thus the functional optical properties of the porphyrinato zinc compounds.Chemistry - A European Journal 09/2013; 19(38):12613-8. DOI:10.1002/chem.201301875 · 5.70 Impact Factor