Search results for "Benzene"

Polyoxometalate-based metal-organic frameworks for boosting electrochemical capacitor performance

2019

Abstract Polyoxometalate-based metal-organic frameworks (POMOFs) possess promising applications as capacitors. Herein, we report the syntheses, structures and electrochemical properties of five copper-containing POMOFs: [CuI4H2(btx)5(PW12O40)2]·2H2O (1), [CuIICuI3(H2O)2(btx)5(PWVI10WV2O40)]·2H2O (2), [CuI6(btx)6(PWVI9WV3O40)]·2H2O (3), [CuI4H2(btx)5(PMo12O40)2]·2H2O (4) and [CuIICuI3(btx)5(SiMoVI11MoVO40)]·4H2O (5) (btx = 1,4-bis(triazol-1-ylmethyl) benzene) with potential applications as capacitors. Compounds 1–3 contain the same Keggin-type polyoxometalate (POM) although with different oxidation states, allowing the analysis of the effect of the electronic population on the capacitance pe…

Inhomogeneity of gel and microsyneresis in porous styrene‐divinylbenzene copolymers

1985

The porosity of styrene-divinylbenzene copolymers prepared by suspension copolymerisation of the monomers carried out in the presence of inert diluent changes due to solvent pretreatment is investigated. The changes seem to reflect the inhomogeneity of copolymer gel. Various portions of it are transferred from the rubber-like into the glassy state at different stages of either swelling solvent exchange or the drying process. A microsyneresis, i.e. a local collapse of loosely crosslinked gel portions not followed by a shrinkage of the whole system, leads to the porosity changes.

2014

NanosizedCeO2powders were synthesized via hydrothermal method with different types of surfactants (polyethylene glycol (PEG), cetyltrimethylammonium bromide (CTAB), and sodium dodecylbenzenesulfonate (SDBS)). X-ray diffraction, Raman spectroscopy, and transmission electron microscopy were utilized to characterize the phase structures and morphologies of the products. The sample with CTAB as surfactant (CeO2-C) has the largest specific surface area and the smallest particle size among these three samples. The humidity sensor fabricated byCeO2-C shows higher performance than those usedCeO2-P andCeO2-S. The impedance of theCeO2-C sensor decreases by about five orders of magnitude with relative…

Photoresponsive Halogen-Bonded Liquid Crystals: The Role of Aromatic Fluorine Substitution

2019

A new strategy for controlling the liquid crystalline and photophysical properties of supramolecular mesogens assembled via halogen bonding is reported. Changing the degree of fluorination at the halogen-bond donor of the supramolecular liquid crystal allows for the fine-tuning of the halogen bond strength and thereby provides control over the temperature range of the mesophase. At least three fluorine atoms have to be present to ensure efficient polarization of the halogen-bond donor and the formation of a mesophase. In addition, it was found that stilbazole acceptors are superior to their azopyridine counterparts in promoting stable liquid crystalline phases. The halogen-bond-driven supra…

Series of charge transfer complexes obtained as crystals in a confined environment

2021

A series of charge transfer complexes (CTCs) were successfully formed by solvent free processing techniques, using the 1,2,4,5-tetracyano benzene (TCNB) as πA molecule and a series of p-dihydroquinones (H2Qs) as πD counterparts. Additionally to the classical co-evaporation techniques, we obtained CTCs in less than an hour, in a very simple confined environment, between two 100 μm – spaced glass plates. A systematical study by Raman spectroscopy on crystals highlighted the CTCs formation. Moreover, three new crystalline structures were obtained, namely TCNB-H2Q that crystallizes in columns connected to each other by H-bonds, while with the methoxy- and dimethoxy-H2Qs the CTC forms crystals w…

Photo-switching in a hybrid material made of magnetic layered double hydroxides intercalated with azobenzene molecules.

2014

Financial support from the EU (Projects HINTS FP7-263104-2 and SpinMol Advanced Grant ERC-2009-AdG-20090325), the Spanish Ministerio de Economia y Competitividad (Projects with FEDER cofinancing MAT 2009-14528-C02-01, MAT2011-22785, MAT2012-38567-C02-01, CTQ-2011-26507, Consolider-Ingenio in Molecular Nanoscience CSD2007-00010, Consolider-Ingenio 2010-Multicat CSD2009-00050, and Severo Ochoa Program SEV-2012-0267), Generalitat Valenciana (PROMETEO and ISIC-Nano programs), and VLC/Campus Microcluster "Functional Nanomaterials and Nanodevices" is gratefully acknowledged. C. M. G. thanks the Spanish MINECO for a Ramon y Cajal Fellowship (RYC-2012-10894). We also acknowledge P. Atienzar and J. …

MOF-Mediated Synthesis of Supported Fe-Doped Pd Nanoparticles under Mild Conditions for Magnetically Recoverable Catalysis**

2020

Metal–organic framework (MOF)-driven synthesis is considered as a promising alternative for the development of new catalytic materials with well-designed active sites. This synthetic approach is used here to gradually transform a new bimetallic MOF, with Pd and Fe as the metal components, by the in situ generation of aniline under mild conditions. This methodology results in a compositionally homogeneous nanocomposite formed by Fe-doped Pd nanoparticles that, in turn, are supported on iron oxide-doped carbon. The nanocomposite has been fully characterized by several techniques such as IR and Raman spectroscopy, TEM, XPS, and XAS. The performance of this nanocomposite as an heterogeneous cat…

Photoresponsive anisotropic and isotropic gels of semicarbazide-azobenzene organogelators: the use of magnetic polymer colloids to detect gel-sol tra…

2020

Photoinduced gel-sol transformation of semicarbazide-azobenzene-based organogels containing entrapped organic solvents (isotropic gel) and liquid-crystalline material (anisotropic gel) has been studied. Thin films (4 µm) of gel materials were used to study the gel-sol transformation, as thicker films possess high absorbance due to the relatively high concentration of the gelator molecules. Photoinduced trans-cis isomerization of the azobenzene units causes destruction of the gel structure, and the consequent change in viscosity has been investigated employing magnetic polymer colloids. In the gel state the movement of the colloids is restricted due to their entrapment within the gel fibers …

Wavelength-Selective Softening of Hydrogel Networks.

2021

Photoresponsive hydrogels hold key potential in advanced biomedical applications including tissue engineering, regenerative medicine, and drug delivery, as well as intricately engineered functions such as biosensing, soft robotics, and bioelectronics. Herein, the wavelength-dependent degradation of bio-orthogonal poly(ethylene glycol) hydrogels is reported, using three selective activation levels. Specifically, three chromophores are exploited, that is, ortho-nitrobenzene, dimethyl aminobenzene, and bimane, each absorbing light at different wavelengths. By examining their photochemical action plots, the wavelength-dependent reactivity of the photocleavable moieties is determined. The wavele…

Photoalignment and Surface-Relief-Grating Formation are Efficiently Combined in Low-Molecular-Weight Halogen-Bonded Complexes

2012

It is demonstrated that halogen bonding can be used to construct low-molecular-weight supramolecular complexes with unique light-responsive properties. In particular, halogen bonding drives the formation of a photoresponsive liquid-crystalline complex between a non-mesogenic halogen bond-donor molecule incorporating an azo group, and a non-mesogenic alkoxystilbazole moiety, acting as a halogen bond-acceptor. Upon irradiation with polarized light, the complex exhibits a high degree of photoinduced anisotropy (order parameter of molecular alignment > 0.5). Moreover, efficient photoinduced surface-relief-grating (SRG) formation occurs upon irradiation with a light interference pattern, with…