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In this work, we synthesized an iridium(III) complex and studied its selective ability to interact with a specific G-quadruplex DNA sequence (GTGGGTAGGGCGGGTTGG). Results showed that the iridium(III) complex exhibits high selectivity for the G-quadruplex DNA and could be used as an efficient electrochemiluminescence (ECL) probe in a switch-on assay format for the detection of double-stranded DNA (dsDNA). To construct the assay, a hairpin-structured capture probe (CP) which was modified by thiol at its 3′ end and contained the G-quadruplex sequence at its 5′ end was firstly immobilized on a gold electrode. Upon the specific recognition of the dsDNA sequence with the corresponding CP, the hairpin structure of the CP was opened to free G-quadruplex sequence, forming the G-quadruplex structure with the assistance of K+. Then, the iridium(III) complex was able to specifically interact with the G-quadruplex to produce an obvious ECL signal that was proportional to the dsDNA concentration. Notably, this iridium(III) complex/G-quadruplex-based strategy was universal and was not limited to the analysis of DNA using specific sequences, thus opening a new avenue for the application of the G-quadruplex-selective iridium(III) complex in the field of ECL. [ABSTRACT FROM AUTHOR]

A versatile nanocomposite was simply prepared based upon the electrostatic adsorption of positively charged gold nanoparticles with negatively charged graphene oxide (nano-gold@GO), and utilized as a novel fluorescence quenching platform for ultrasensitive detection of adenosine triphosphate (ATP). In the designed system, DNA-stabilized Ag nanoclusters (DNA/AgNCs) were used as fluorescent probes, DNA duplex was formed in the presence of ATP, and they can electrostatically adsorb onto the surface of nano-gold@GO to quench the fluorescence signal. Upon the addition of exonuclease III (Exo III), the DNA duplex would be hydrolyzed into DNA fragments and resulted in the recovery of the fluorescence signals due to the diffusion of AgNCs away from nano-gold@GO. Based on these, sensitive detection of ATP was realized with a detection range of 5.0 pM–20 nM. Notably, a good recovery in the range of 94–104% was obtained when detecting ATP in human serum samples, indicating a promising application value in early disease diagnosis. [ABSTRACT FROM AUTHOR]

A photoactive difluoroborate-based conjugated organic polymer (B-COP) with A3B2-type donor-acceptor arrays in the polymer framework was synthesized by direct polycondensation and exhibited amorphous structure, high thermal and photophysical stability. The B-COP was shown to be a highly efficient heterogeneous photocatalyst for a wide range of photocatalytic transformations, including the oxidative coupling of primary amine and cross-dehydrogenative coupling reactions between tetrahydroisoquinolines and nucleophiles such as nitromethane, nitroethane, acetone and phenylethyl ketone. [ABSTRACT FROM AUTHOR]

The hydrothermal crystallization of zeolite IM-5 was investigated under rotating (denoted as IM-5-R) and static (denoted as IM-5-S) synthesis conditions. Mo-modified catalysts (Mo-IM-5-R and Mo-IM-5-S) were prepared for the methane non-oxidative aromatization. The physical properties and acidities of the samples were characterized by XRD, SEM, BET and IR spectroscopy. Compared with Mo-IM-5-S, the Mo-IM-5-R catalyst showed both a higher conversion of methane and higher selectivity to benzene in methane aromatization. A higher catalytic activity of Mo-IM-5-R may be attributed to the preferable textural properties and acidities of zeolite IM-5-R. Moreover, the catalyst prepared by the physical mixing method exhibited lower initial activity, but better stability for methane aromatization than that prepared by the impregnation method. [ABSTRACT FROM AUTHOR]

Encapsulation of tetraazamacrocyclic complexes of Co(II), Cu(II) and V(IV) into zeolite-Y has been accomplished, and the resulting materials were used as heterogeneous catalysts for aerobic oxidation of styrene. The materials were prepared by a ship-in-a-bottle method, in which the transition metal cations were first ion-exchanged into zeolite-Y and then reacted with ethylenediamine, followed by acetylacetone. The pure tetraazamacrocyclic complexes were characterized by FTIR, solid UV-Vis and elemental analysis. The structural integrity throughout the immobilization procedure, the successful immobilization of the macrocyclic complexes, and the loadings of metal ions and macrocyclic ligands were determined by characterization techniques such as FTIR, diffuse reflection UV-Vis, inductively coupled plasma atomic emission spectroscopy, scanning electron microscopy, TG/DTA and powder X-ray diffraction. Compared with their homogeneous analogues, the catalytic properties of the encapsulated macrocyclic complexes in the oxidation of styrene with air were investigated. The immobilized complexes proved to be active catalysts and could be reused without significant loss in activity. [ABSTRACT FROM AUTHOR]

Keggin-type phosphomolybdic acids with molybdenum partially substituted by vanadium and protons completely substituted by tellurium have been prepared, characterized and tested as catalysts in the partial oxidation of isobutane into methacrolein (MAL) and methacrylic acid (MAA). Characterization results showed that the structures of TePMoVO (x = 1-3) with Mo partially substituted by V can basically be preserved, while the XRD pattern of TePMoO was different from HPMoO. It is found that Te element induced a positive effect on the selectivity to MAL with slightly negative effect on the activity and selectivity to MAA. [ABSTRACT FROM AUTHOR]

A novel zeolite material denoted as ITQ-2-like was synthesized by treating MCM-22 precursor with HO and characterized by various physicochemical techniques (X-ray powder diffraction, transmission electron microscopy, thermogravimetric-differential thermal analyses, Fourier transform infrared spectroscopy and nitrogen adsorption-desorption). It was found that not only the organic template could be completely removed but also the morphology and topology structure of MCM-22 precursor was well preserved after HO treatment. Novel zeolite material ITQ-2-like presented relatively ordered cascaded layers in a face-to-face orientation along the c-axis and exhibited different physicochemical properties in comparison with ITQ-2 and MCM-22 prepared from the same precursor. Moreover, the catalytic behaviour and pore roles of three kinds of Mo-containing catalysts of ITQ-2-like, MCM-22 and ITQ-2 were investigated in the reaction of methane aromatization. [ABSTRACT FROM AUTHOR]

Super-microporouos silicon material with high hydrothermal stability denoted as MCM-41-T has been prepared from mesoporous MCM-41 by high temperature treatment. The structural and chemical property of MCM-41-T has been characterized by X-ray diffraction, transmission electron microscopy, N adsorption-desorption, infrared spectroscopy and Si MAS NMR. The characteristic results show that Si-OH groups are forced to condense by high temperature treatment, and the pore size of MCM-41-T is around 1.5 nm in the super-microporous range. Compared with the original material MCM-41, the hydrothermal stability of MCM-41-T has been significantly enhanced. [ABSTRACT FROM AUTHOR]

Two samples of aminopropyl-functionalized silica (APS) have been prepared by grafting an organosilane precursor 3-aminopropyl-triethoxysilane onto the SBA-15 in ethanol or toluene. Aminopropyl-functionalized silica-E (sample grafted in ethanol) and APS-T (sample grafted in toluene) were evaluated in carbon-carbon bond forming reactions such as the Knoevenagel condensation and the Claisen-Schmidt condensation. It has been found that the sample grafted in ethanol displayed better catalytic properties than the sample grafted in toluene. The surface silanol groups, which were proven to be more numerous in samples grafted in ethanol compared to those grafted in toluene, were found to be responsible for the enhanced catalytic activity in carbon-carbon bond forming reactions. [ABSTRACT FROM AUTHOR]

Hydrogenated amorphous silicon (a-Si:H) films were deposited by reactive facing target sputtering (FTS) technique with a mixture of Ar and H reaction gas. Fourier transform infrared (FTIR) absorption, Raman scattering and ultraviolet-visible optical absorption are used to investigate the microstructure and optical properties of the deposited films. The decrease of the concentration of bonded hydrogen, especially that of (Si-H) with increasing substrate temperature ( Ts), was observed in FTIR spectra, suggesting the atomic density increases and the concentration of microvoids decrease in a-Si:H films. The increase of both the short range order and the intermediate range order of amorphous network for a-Si:H films were verified by Raman scattering spectra, in which increasing Ts decreasing the band width of TO and the scattering intensity ratio I / I were obtained. All above results clarify the effect of increasing Ts on the microstructure amelioration for a-Si:H films. The reduction of disordered domains is correlated with the film growing process, where the increased surface diffusion mobility and etching of weak bonds is induced by increasing Ts. Furthermore, analysis of optical absorption indicates that the films with a lower optical band gap and a narrower band edge can be obtained by this FTS technique. [ABSTRACT FROM AUTHOR]

ITQ-13, a tridirectional medium-pore zeolite containing 9- and 10-member-ring pores, has been successfully synthesized by a hydrothermal method. The catalytic performance of Mo-ITQ-13 is worse than with Mo-ZSM-5 in the methane aromatization reaction. It has been shown that 9-member-ring channels favor coke and are a disadvantage in methane non-oxidative aromatization. [ABSTRACT FROM AUTHOR]

Using zeolite MCM-22 as source and cetyltrimethylammonium bromide (CTAB) as template, mesoporous material denoted as M-MCM-22 with enhanced acidity has been synthesized and characterized by XPD, FT-IR, N2 adsorption–desorption, 27Al-MAS NMR, IR spectra of pyridine adsorption, and NH3-TPD techniques, etc. The catalytic performance of M-MCM-22 was tested in alkylation of phenol with tert-butanol, indicating that M-MCM-22 showed highly and steadily catalytic properties. The highest conversion of phenol could be achieved at 418 K, while the highest selectivity to 2, 4-di-TBP was obtained at 398 K. It is found that high temperature is advantageous to form 4-TBP, whereas low weight hourly space velocity (WHSV/h−1) is helpful for both conversion of phenol and selectivity to 2,4-DTBP. It is also shown that high ratio of tert-butanol/phenol is beneficial for obtaining high conversion of phenol and selectivity to 2,4-di-TBP. [ABSTRACT FROM AUTHOR]

An electrochemical method is described for ultrasensitive determination of protein tyrosine kinase-7 (PTK7). It is based on (a) the use of positively charged gold nanoparticles (AuNPs) and negatively charged graphene oxide (GO), and (b) of toehold-mediated strand displacement amplification. A hairpin probe 2 (HP2) containing the sgc8 aptamer was used to modify a glassy carbon electrode (GCE). Its hairpin structure is opened in the presence of PTK7 to form the PTK7-HP2 complex. The exposed part of HP2 partly hybridizes with hairpin probe 1 (HP1) that was immobilizing on the AuNPs and GO modified GCE. On addition of the hairpin probe 3 that was labeled with the redox probe Methylene Blue (MB-HP3), toehold-mediated strand displacement occurs due to complementary hybridization of HP1 with MB-HP3. This causes the release of PTK7-HP2 into the solution and makes it available for the next reaction. Under optimal conditions, PTK7 can be quantified by voltammetry (typically performed at −0.18 V) with a detection limit of 1.8 fM. The assay possesses high selectivity for PTK7 due to the employment of the aptamer. It was successfully applied to the determination of PTK7 in the debris of malignant melanoma A375 cells. [ABSTRACT FROM AUTHOR]

The authors describe a method for detection of Hg2+ by using positively charged gold nanoparticles ((+)AuNPs) as a quencher of the fluorescence of DNA-capped silver nanoclusters (DNA-AgNCs) which are negatively charged. In the presence of Hg2+, a DNA duplex is formed through T-Hg2+-T coordination chemistry. The duplex can be digested by exonuclease III to form smaller DNA fragments. This leads to the release of the AgNCs and the recovery of fluorescence, best measured at excitation/emission wavelengths of 460/530 nm. The (+)AuNPs and Hg2+ are also released and can be reused for target recycling signal amplification. Based on these findings, a method is worked out for the determination of Hg2+ that works in the 5.0 pM to 10 nM concentration range and has a detection limit as low as 2.3 pM. It is highly selective because of the highly specific formation of T-Hg2+-T bonds. [ABSTRACT FROM AUTHOR]