Di-ureasil Matrix Research Articles

Easily processable multimodal spectral converters based on metal oxide/organic—inorganic hybrid nanocomposites

This manuscript reports the synthesis and characterization of the first organic–inorganic hybrid material exhibiting efficient multimodal spectral converting properties. The nanocomposite, made of Er3+, Yb3+ codoped zirconia nanoparticles (NPs) entrapped in a di-ureasil d–U(600) hybrid matrix, is prepared by an easy two-step sol-gel synthesis leading to homogeneous and transparent materials that can be very easily processed as monolith or film. Extensive structural characterization reveals that zirconia nanocrystals of 10–20 nm in size are efficiently dispersed into the hybrid matrix and that the local structure of the di-ureasil is not affected by the presence of the NPs. A significant enhancement in the refractive index of the di-ureasil matrix with the incorporation of the ZrO2 nanocrystals is observed. The optical study demonstrates that luminescent properties of both constituents are perfectly preserved in the final hybrid. Thus, the material displays a white-light photoluminescence from the di-ureasil component upon excitation at UV/visible radiation and also intense green and red emissions from the Er3+- and Yb3+-doped NPs after NIR excitation. The dynamics of the optical processes were also studied as a function of the lanthanide content and the thickness of the films. Our results indicate that these luminescent hybrids represent a low-cost, environmentally friendly, size-controlled, easily processed and chemically stable alternative material to be used in light harvesting devices such as luminescent solar concentrators, optical fibres and sensors. Furthermore, this synthetic approach can be extended to a wide variety of luminescent NPs entrapped in hybrid matrices, thus leading to multifunctional and versatile materials for efficient tuneable nonlinear optical nanodevices.

Influence of Cd 2+ /S 2− molar ratio and of different capping environments in the optical properties of CdS nanoparticles incorporated within a hybrid diureasil matrix

Abstract The incorporation of CdS nanoparticles (NPs), as prepared through colloidal methods using reverse micelles, within diureasil hybrid organic–inorganic sol–gel matrices was investigated. Several experimental conditions, namely the influence of capping agent 3-mercaptopropyltrimethoxysilane (MPTMS) or the use of tetraethoxysilane (TEOS), were studied in order to assure the preservation of the original optical properties of colloidal CdS NPs after the incorporation of the NPs within the solid diureasil hybrid matrix. The diureasil matrix is based on a siliceous network cross linked through urea bonds to poly(oxyethylene)/poly(oxypropylene) (PEO/PPO) chains. The influence of the Cd2+/S2− molar ratio of the NPs in the stability and dispersion of the NPs within the diureasil matrix was also investigated. The obtained CdS doped hybrid matrix was characterized by absorption, steady-state and time-resolved photoluminescence (PL) spectroscopy and by transmission electron microscopy (TEM). The stability of the CdS NPs within the hybrid matrix showed to be dependent on the Cd2+/S2− molar ratio used in the synthesis of the NPs. The use of MPTMS proved to be crucial in the preservation of the original optical properties of the colloidal CdS NPs after the incorporation of the NPs within the hybrid matrix. The effect of MPTMS was in turn influenced by the Cd2+/S2− molar ratio employed in the synthesis of the CdS NPs. The use of MPTMS was less effective when Cd2+/S2− molar ratio equal to 0.5 was used. In the absence of MPTMS or TEOS larger NPs size distribution and clustering of the CdS NPs were obtained after the transfer of the NPs into the hybrid matrix.

Synthesis and characterization of organic–inorganic hybrid materials prepared by sol–gel and containing CdS nanoparticles prepared by a colloidal method using poly(N-vinyl-2-pyrrolidone)

This paper describes the synthesis and characterization of CdS nanoparticles (NPs) stabilized with poly(N-vinyl-2-pyrrolidone) and their further immobilization on a hybrid organic–inorganic matrix produced by the sol–gel process. The production of the hybrid matrix doped with CdS NPs was carried out in two steps. In the first step a precursor, designated diureasil precursor, was synthesized from the reaction between the terminal amine groups of α,ω-diamine-poly(oxyethylene-co-oxypropylene) and the isocyanate group of 3-isocyanatopropyltriethoxysilane. The next step involved the hydrolysis and condensation reactions of ethoxy groups attached to silicon, this step resulting in the formation of a crosslinked siliceous network linked through urea bonds to a poly(oxyethylene)/poly(oxypropylene) chain. The NPs were added to the diureasil precursor before the gelation process to allow a homogeneous dispersion of the NPs within the matrix. The developed method allowed the transfer of colloidal NPs to a solid matrix without the need of exchange the capping agents or the solvent. The materials were characterized by absorption, steady-state photoluminescence spectroscopy and by TEM. The results obtained showed the presence of CdS NPs with quantum size effect dispersed within the diureasil matrix. The obtained nanocomposites show a high transparency in the visible range accounting for the good dispersion of the NPs within the matrix. The TEM analysis confirmed that the NPs are uniformly dispersed within the diureasil matrix.

A new highly conductive organic-inorganic solid polymer electrolyte based on a di-ureasil matrix doped with lithium perchlorate

A new hybrid organic-inorganic polymer electrolyte based on poly(propylene glycol) tolylene 2,4-diisocyanate terminated (PPGTDI), poly(propylene glycol)-block–poly(ethylene glycol)-block-poly(propylene glycol) bis(2-aminopropyl ether) (ED2000) and 3-isocyanatepropyltriethoxysilane (ICPTES) has been synthesized and characterized. A maximum ionic conductivity value of 1.0 × 10−4 S cm−1 at 30 °C and 1.1 × 10−3 S cm−1 at 80 °C is achieved for the hybrid electrolyte with a [O]/[Li] ratio of 32. The conductivity mechanism changes from Arrhenius to Vogel-Tamman-Fulcher (VTF) behavior with the increase in temperature from 20 to 80 °C. The present hybrid electrolyte system offers a remarkable improvement in ionic conductivity by at least one order of magnitude higher than the previously reported organic-inorganic electrolytes. The 7Li NMR (nuclear magnetic resonance) results reveal that there exists a strong correlation between the dynamic properties of the charge carriers and the polymer matrix. Two Li+ local environments are identified, for the first time, in such a di-ureasil based polymer electrolyte. The electrochemical stability window is found to be in the range of 4.6–5.0 V, which ensures that the present hybrid electrolyte is a potential polymer electrolyte for solid-state rechargeable lithium ion batteries.

Real time random laser properties of Rhodamine-doped di-ureasil hybrids

This investigation explores, for the first time, the random laser behavior of ground powder obtained from organic-inorganic hybrid materials based on Rhodamine 6G incorporated into a di-ureasil matrix. The experimental results, both in the spectral and temporal domains, obtained by pumping with picosecond laser pulses, show the existence of efficient random laser emission in this system. Finally, the random laser performance is compared with the one of other Rhodamine-doped solid state silica compounds.

Er3+-Based Diureasil Organic−Inorganic Hybrids

Erbium-doped organic−inorganic hybrids derived from different carboxylic acids (acetic, formic, and valeric) solvolysis have been prepared and characterized. The hybrid matrix (named as diureasil) is composed of a siliceous network grafted to both ends of a polymer chain containing about 8.5 oxyethylene units. Er3+ ions have been incorporated as erbium triflate salt, Er(CF3SO3)3, with n = 5, 10, and 20, where n denotes the ratio of (OCH2CH2) moieties of the hybrid organic counterpart per Er3+ ion. Characterization techniques include X-ray absorption (EXAFS) at the Er LIII-edge, Fourier transform infrared spectroscopy (FT-IR) and photoluminescence. FT-IR studies reveal that both free and coordinated triflate ions exist in the hybrids, independently of the carboxylic acid used. Moreover, the “amide I” and “amide II” infrared spectral regions are deeply affected suggesting that the Er3+ ions interact with the carbonyl groups of the diureasil matrix. EXAFS results show that the Er3+ first coordination shell is composed by 10−11 oxygen atoms at an average distance of 2.30−2.32 Å. The Ωλ (λ = 2,4,6) intensity parameters were evaluated from absorption measurements together with the Er3+ 4I13/2 state radiative lifetime (τRAD) and the peak emission cross section (σEM). Values obtained were Ω2 = 12.3 × 10−20 cm2, Ω4 = 5.56 × 10−20 cm2 and Ω6 = 3.56 × 10−20 cm2, τRAD = 3.6 ms and σEM(1537 nm) = 1.0 × 10−20 cm2. The host characteristic broad emission band in the visible and the Er3+ emission at 1.5 μm were discerned. Bandwidth of ∼78 nm is observed for the latter emission which, together with the Ωλ, τRAD, and σEM spectroscopic parameters, denote the potential application of these hybrids in optical amplification devices.

Preparation of hybrid organic–inorganic materials based on a di-ureasil matrix doped with lithium bis(trifluoromethanesulfonyl)imide

In this presentation we describe the preparation of solvent-free solid polymer electrolytes (SPEs) by the sol–gel route with the incorporation of controlled quantities of lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) into the host matrix. The host framework of these xerogels, designated as di-ureasils and represented by d-U(900), contains oxyethylene oligomers with about 15 repeat units bonded at each end to a siliceous backbone through urea bridging links. Electrolytes were characterized by ionic conductivity measurements, cyclic voltammetry at a gold microelectrode and thermal analysis. The results obtained reveal that these hybrid materials are completely amorphous and exhibit appropriate electrochemical characteristics for a variety of applications.

Optically functional nanocomposites with poly(oxyethylene)-based di-ureasils and mesoporous MCM-41

Di-urea cross-linked poly(oxyethylene) (POE)/siloxane hybrid structure (di-ureasil) was incorporated into the hexagonal array of one-dimensional channels of mesoporous silica MCM-41. X-ray diffraction, nitrogen adsorption–desorption, Fourier transform mid-infrared spectroscopy, 29Si and 13C nuclear magnetic resonance, transmission electron microscopy and photoluminescence results demonstrate the interaction (covalent grafting and impregnation) between the di-ureasil structure and the silanol groups of the MCM-41 channels, preserving their integrity. The composites are photoluminescent displaying the intrinsic green emission of MCM-41 superposed to the blue and purplish-blue di-ureasil components. Time-resolved spectroscopy provides further support from energy transfer between the mesopourous silica and the di-ureasil matrix.