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A series of novel dual-responsive BN-embedded phenacenes were designed and synthesized, via N-directed borylation of donor–acceptor–donor (D–A–D) precursors as the key step. Their crystal structures, and photophysical and electrical properties were systematically studied, which were found to be highly dependent on the incorporated BN units and fused aromatic rings with varied electron density. For the first time, mechanochromic luminescent (MCL) properties of BN-embedded phenacenes were realized, which are regulated jointly by inter- and intra-molecular effects at the molecular level. In the solid state, their emission colors can be tuned reversibly by external force, and interestingly, they exhibit an unusual hypochromic shift after grinding. Furthermore, in solution, these BN-containing phenacenes enable colorimetric and fluorometric detection of fluoride ions with high selectivity and a low detection limit of down to 1.8 × 10−8 M. The dual-responsive properties of these compounds highlight the widespread applications of BN containing conjugated materials in optical sensors. [ABSTRACT FROM AUTHOR]

The preparation and application of fiber catalysts have attracted much attention. However, research on the effect of the micro-environment of fiber catalysts on the catalytic activities though of special importance is limited. In this work, a novel strategy for the synthesis of phosphoric acid-functionalized polyacrylonitrile fibers with a polarity tunable surface micro-environment by hydrophobic groups for one-pot C–C and C–N bond formation reactions is reported. The special hydrophobic surface micro-environment of the fiber catalysts is proven to promote the catalytic activities impressively in cyclocondensation of β-ketoesters with 2-aminobenzamides, the Knoevenagel condensation as well as the multi-component Biginelli reactions in green solvents. Both the surface synergy of the catalytic sites and hydrophobic auxiliary groups (benzyl or n-butyl) in the surface of fiber catalysts and interface acceleration in reaction medium play an important role in the highly efficient promotion of catalytic activity. Thereby a surface synergistic mechanism is proposed to explain the micro-environment effect. In addition, the fiber catalysts could be simply separated from the reaction system using tweezers and directly used in the next cycle without further treatment. Importantly, even after 10 reaction cycles in water or ethanol, there is no significant loss in their catalytic activity. The results indicate that the phosphoric acid functionalized fibers show green and sustainable potential for industrial production. [ABSTRACT FROM AUTHOR]

To understand the mechanism of the photocatalytic direct synthesis of 1,1-diethoxyethane (DEE) from ethanol is vital for enhancing the reaction efficiency. Based on photocatalytic data of different phase TiO2 and F–TiO2 catalysts, radical trapping data, and GC-MS data, we proposed a photocatalytic mechanism for the preparation of both DEE in neat ethanol and 2,3-butanediol (2,3-BD) in ethanol–H2O using photocatalytic methods. In neat ethanol, hydroxyl isn’t involved in the catalytic cyclic process but hydroxyl has an indirect site-holding effect, thus leading to more hydroxyl groups with higher activity. In ethanol–H2O, although the strong oxidant ṖOH radical is involved, fewer OH groups lead to higher selectivity of 2,3-BD. The interaction of the reactant/solvent with the surface group of the catalyst is important in the activity and selectivity of photocatalytic reactions. This finding gives fundamental insight into the role of TiO2 surface hydroxyl in the photocatalytic dehydrogenation process of alcohols and opens a promising path to obtaining both high selectivity and high conversion in TiO2-based photocatalytic activity. [ABSTRACT FROM AUTHOR]

A thiadiazole-functionalized polyacrylonitrile fiber (DPTD-PANPF) qualitative colorimetric sensor was prepared for the first time, and its absorption properties were investigated in detail. The obtained sensor exhibits excellent chelating selectivity towards Ag+ without interference by other co-existing ions (Pb2+, Hg2+, Cd2+, Zn2+, and Cu2+) and generates a remarkable visual color change from yellow to red-brown over a wide pH range from 3 to 12. The DPTD-PANPF for Ag+ has a naked-eye detection limit of 11 ppb (only one in ten thousand of that of the small molecule DPTD) and a much higher saturation absorption capacity of 149 mg g−1. Moreover, the fiber can be repeatedly used more than 50 times. In summary, this fiber sensor possesses the advantages of excellent selectivity, lower detection limit, outstanding absorption capacity and reusability to detect and remove Ag+ from water. [ABSTRACT FROM AUTHOR]

Three chiral pyrrolidine functionalized polyacrylonitrile fiber catalysts have been designed, prepared, and evaluated for their catalytic performance in asymmetric Michael addition of ketones to nitrostyrenes in water. With the optimized catalysts and conditions in hand, their reaction scope for nitrostyrenes was explored. Then the fiber catalysts were further applied to a packed-bed reactor for continuous-flow Michael addition. Based on the fact that organic solvent can inhibit the catalytic activity, a novel microenvironment catalytic mechanism is proposed. [ABSTRACT FROM AUTHOR]

A series of polyacrylonitrile fiber-supported quaternary ammonium salts (PANF-QAS) were prepared and applied to the catalytic reduction of aldehydes, ketones, azides, and benzyl halides in water using NaBH4 as the reducing reagent in a highly efficient, economic, and environmentally benign way. The structure–activity relationships were investigated, which showed that the catalysts made up of quaternary ammonium salts with longer alkyl chains, larger cationic radii and better lipophilicity speed up the reduction reaction to afford the products in excellent yield. Moreover, the optimized catalyst can be applied to the reduction of 1-naphthaldehyde in a continuous flow process with outstanding reactivity and recyclability. [ABSTRACT FROM AUTHOR]

A facet-dependent photo-deactivation mechanism of Cu2O was verified and reported, which is caused by the facet-dependent charge carrier transport. During irradiation, the {100} and {110} crystal facets are selectively corroded by the photo-generated holes, while the {111} facets are comparatively stable. [ABSTRACT FROM AUTHOR]

A colorimetric Hg2+ sensor based on the porphyrin-functionalized polyacrylonitrile fiber (CTAPP–PANAF) was prepared and investigated. This functional fiber sensor shows excellent selectivity and sensitivity towards Hg2+ over other common metal ions (Pb2+, Ba2+, Cd2+, Ag+, Zn2+, Cu2+, Ni2+, Co2+, Fe3+, Mn2+, Cr3+, Ca2+, Al3+ and Mg2+). Upon the addition of Hg2+, a remarkable visual color change from red-brown to dark-green and significant detectable changes in the FTIR, UV and FL spectra of CTAPP–PANAF were observed. The naked-eye detection limit is as low as 20 ppb (1 × 10−7 mol L−1), which is below the maximum contamination level of 50 ppb for mercury containing wastewater in China. This functional fiber sensor also exhibits excellent reusability and recyclability and can be repeatedly used more than 50 times. The Hg2+ complexed sensor can be easily separated from the aqueous solution by simple filtration and reversed back by treating with dilute HCl. Furthermore, real water sample testing confirms the practical application of CTAPP–PANAF. In a word, the fiber sensor possesses the advantages of simplicity, rapidity, and reusability as well as high selectivity and sensitivity. [ABSTRACT FROM AUTHOR]

Polymer composite flexible films with high dielectric constant are highly desirable in electronic and electrical industry. Higher loading of the ceramic fillers is usually needed in order to realize high dielectric constant. However, such composites exhibit low breakdown strength and poor mechanical and processing properties. In this work, by incorporating high aspect ratio surface-hydroxylated Ba0.6Sr0.4TiO3 nanotubes (BST NT) prepared via electrospinning into a polyvinylidene-fluoride (PVDF) matrix, PVDF nanocomposite flexible films with high dielectric constant have been successfully obtained. The nanocomposite containing 10 vol% BST NT-OH has a dielectric constant of 48.2 at 1 kHz, which is 6.1 times higher than that of the pure PVDF (7.9). The dielectric properties of the composites are closely related to the combined effects of the surface modification, large aspect ratio, high surface area and paraelectric polarization behavior of the BST NT. [ABSTRACT FROM AUTHOR]

A novel class of fiber supported ionic liquids (FSILs) was first used to catalyze fructose dehydration to 5-hydroxymethylfurfural (HMF) and exhibited excellent catalytic activity in terms of 86.2% and 84.7% HMF yield at 100 °C for 30 min in DMSO and 45 min in a mixed-aqueous system respectively, as well as the ability to be very easily recycled, with superior catalytic activity and stability even after 10 cycles. The procedures can be scaled up and the formed HMF can be easily obtained by simple distillation, and the solvent can be recycled. The fiber catalytic process is much better than that via acid resins and silica supported ionic liquid nanoparticles in yields and recyclability, and its extremely simple separation operation and low catalyst dosage as well as selectivity are significantly superior to the single ionic liquid catalysis and liquid–liquid biphasic system of ionic liquid catalysis. This is the first report on the application of the inexpensive and readily available polypropylene fiber (PPF) as a new support for ionic liquids, and the prominent features of PPF and the remarkable performance of FSILs are very attractive to the chemical industry. [ABSTRACT FROM AUTHOR]

A series of new fiber catalysts has been synthesized by aminating a commercially available polyacrylonitrile fiber with polyamines such as diethylenetriamine and triethylenetetramine. These fiber catalysts can efficiently catalyze the Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate in water (yields: 95–98%). The triethylenetetramine aminated fiber catalyst was used to catalyze the condensations of a wide range of aromatic aldehydes and active methylene compounds and in each case, this catalyst performed well with yields higher than 93%. This fiber catalyst also exhibited excellent reusability (up to 21 times) and photostability. [ABSTRACT FROM AUTHOR]

A new fiber catalyst for Knoevenagel condensation has been prepared by aminating a commercially available polyacrylonitrile fiber with N,N-dimethyl-1,3-propanediamine. The fiber catalyst was characterized by elemental analysis, X-ray powder diffraction spectra (XRD), scanning electron microscopy (SEM) and Fourier-transfer infrared spectroscopy (FTIR). The Knoevenagel condensation proceeded smoothly in the presence of the fiber catalyst and the products were obtained in excellent yields. This catalyst is applicable to a wide range of aromatic aldehydes. Moreover, the reaction can be easily carried out in different solvents of varying polarities. The newly developed fiber catalyst was also found to exhibit excellent recyclability and reusability (up to 10 times) without any additional treatment. [ABSTRACT FROM AUTHOR]

To understand the mechanism of the photocatalytic direct synthesis of 1,1-diethoxyethane (DEE) from ethanol is vital for enhancing the reaction efficiency. Based on photocatalytic data of different phase TiO 2 and F-TiO 2 catalysts, radical trapping data, and GC-MS data, we proposed a photocatalytic mechanism for the preparation of both DEE in neat ethanol and 2,3-butanediol (2,3-BD) in ethanol-H 2 O using photocatalytic methods. In neat ethanol, hydroxyl isn't involved in the catalytic cyclic process but hydroxyl has an indirect site-holding effect, thus leading to more hydroxyl groups with higher activity. In ethanol-H 2 O, although the strong oxidant ˙OH radical is involved, fewer OH groups lead to higher selectivity of 2,3-BD. The interaction of the reactant/solvent with the surface group of the catalyst is important in the activity and selectivity of photocatalytic reactions. This finding gives fundamental insight into the role of TiO 2 surface hydroxyl in the photocatalytic dehydrogenation process of alcohols and opens a promising path to obtaining both high selectivity and high conversion in TiO 2 -based photocatalytic activity.

A facet-dependent photo-deactivation mechanism of Cu2O was verified and reported, which is caused by the facet-dependent charge carrier transport. During irradiation, the {100} and {110} crystal facets are selectively corroded by the photo-generated holes, while the {111} facets are comparatively stable.

The title compound is an "off-on" rhodamine probe. It exhibits strong pH dependence and responds to protons. The optimized geometries and energies calculation of the protonation were determined at the B3LYP level using DFT. The theoretical results are in good agreement with the single crystal analysis and the spectral results.

Potential energy surfaces of the imine-ene reaction between methanimine and propene have been calculated using restricted and unrestricted density functional theory at the B3LYP level. The results show that a concerted mechanism with an exo configuration for lone pair electrons transition structure is more favourable for the intermolecular bare imine-ene reaction. In addition, the C-C bond formation and the migration of the propene α-hydrogen occur simultaneously. The promoting effect of seventeen Lewis acids was also studied. When a Lewis acid is used as a promoter, the corresponding activation and reaction energies decline greatly compared to those of the bare imine-ene reaction. A good correlation (R(2) > 0.9) was found between the activation barriers and the polar character of the transition states. Lewis acids and electron-withdrawing substituents on methanimine were proven to facilitate the imine-ene reaction, whereas electron-donating groups, conjugated groups or a bulky group hinders the reaction. The steric factor is the most unfavourable. The reactivity indices defined by the conceptual density functional theory were also studied and there is a good correlation between the activation barrier and electrophilicity. Frontier molecular orbital theory gives a good explanation for the above results.

Two novel tweezer-like 25,27-dihydroxy-26,28-bis(phenylthiaethoxy)calix[4]arenes 6 and 7 were synthesized by the reaction of 25,27-dihydroxy-26,28-bis(bromoethoxy)calix[4]arenes 3 and 4 for the evaluation of their ion-selectivity in ion-selective electrodes (ISEs). X-ray structural analysis indicated that calix[4]arene 7 is in an interesting infinite linear aggregate via self-inclusion. For investigation of the influences of substitutes on the behavior of the ISEs, the halogen substituted aryl analogues of 25,27-dihydroxy-26,28-bis(arylthiaethoxy)calix[4]arenes 8-12 were also synthesized and their ISE performances were evaluated under the same conditions. ISEs based on 6-12 as neutral ionophores were prepared, and their selectivity coefficients for Ag+ (log KAg,M(pot)) were investigated against other alkali metal, alkaline-earth metal, lead, ammonium ions and some transition metal ions using the fixed interference method (FIM). These ISEs showed excellent Ag+ selectivity over most of the interfering cations examined, except for Hg2+ having relative smaller interference (log KAg,Hg(pot) < or = 2.1). The 19F NMR spectra of 9 and 9.AgClO4 were recorded for investigation the fluorine environments in the complex. The 19F NMR spectra strongly suggested that the fluorine atoms on ionophore 9 participated in ligation with silver cation.