In situ recrystallisation of a coordination polymer with hemilabile linkers

The variable coordination pattern of a hemilabile phosphazene ligand equipped with six pendent olefin groups facilitates the in situ recrystallisation of a silver(I) complex from an amorphous precipitate into a 1D coordination polymer and its subsequent isomerisation to a 3D coordination network.     

In situ vibrational spectroscopy of conducting polymer electrodes

The application of in situ Fourier transform infrared spectroscopy for the study of electrochemical redox reactions of conducting polymers is described. The experimental setup of two different methods, external reflection absorption spectroscopy and attenuated total reflection spectroscopy, is shown. The results of spectroelectrochemical investigations of the reactions of polyaniline in different electrolyte solutions are discussed.     

In situ preparation of highly fluorescent dyes upon photoirradiation

Photoswitchable or photoactivatable fluorescent dyes are potentially applicable to ultrahigh density optical memory media as well as super-resolution fluorescence imaging when the dyes are highly fluorescent and have large absorption coefficients. Here, we report on highly fluorescent photochromic dyes, which are initially nonluminous in solution under irradiation with visible light but activated to emit green or red fluorescence upon irradiation with ultraviolet (UV) light. The dyes 5a-9a are sulfone derivatives of 1,2-bis(2-ethyl-6-phenyl(or thienyl)-1-benzothiophen-3-yl)perfluorocyclopentene. It was found that substitution of phenyl or thiophene rings at 6 and 6' positions of the benzothiophene-1,1-dioxide groups is effective to increase the fluorescence quantum yields of the closed-ring isomers over 0.7 and absorption coefficients over 4 × 10(4) M(-1) cm(-1). The phenyl-substituted derivatives 5a-7a undergo photocyclization reactions to produce yellow closed-ring isomers 5b-7b, which emit brilliant green fluorescence at around 550 nm (Φ(F) = 0.87-0.88) under irradiation with 488 nm light. Any absorption intensity change of the closed-ring isomers was not observed even after 100 h storage in the dark at 80 °C. The closed-ring isomers slowly returned to the initial open-ring isomers upon irradiation with visible (λ > 480 nm) light. The ring-opening quantum yields (Φ(C→O)) were measured to be (1.6-4.0) × 10(-4). When the phenyl substituents are replaced with thiophene rings, such as compounds 8a and 9a, the absorption bands of the closed-ring isomers shift to longer than 500 nm. The closed-ring isomers exhibit brilliant red fluorescences at around 620 nm (Φ(F) = 0.61-0.78) under irradiation with 532 nm light. The ring-opening reactions are very slow (Φ(C→O) < 1 × 10(-5)). The fluorescence lifetimes of these sulfone derivatives were measured to be around 2-3 ns, which is much longer than the value of the closed-ring isomer of 1,2-bis(2-methyl-1-benzothiophen-3-yl)perfluorocyclopentene (τ(F) = 4 and 22 ps). The closed-ring isomer 8b in 1,4-dioxane exhibits excellent fatigue resistant property under irradiation with visible light (λ > 440 nm) superior to the stability of Rhodamine 101 in ethanol.     

Enzymatic synthesis and bioactivity of estradiol derivative conjugates with different amino acids

A series of N-protected amino acid-estradiol derivative conjugates have been synthesized by coupling of 17β-aminoestra-1,3,5 (10)-trien-3-ol (1) or 17β-hydrazonoestra-1,3,5 (10)-trien-3-ol (2) with different amino acids via the catalysis of subtilisin Carlsberg in organic solvent. Various factors, including the structure of amino acid residue, different N-protecting groups of amino acids, different esters of carboxyl group and water content of the reaction media that influence the efficiency of enzymatic reactions were systematically studied. In vitro biological activity studies revealed that the binding interactions between estradiol derivative conjugates and estrogen receptor can be affected by the properties of the conjugated amino acid, but the effects of the change in binding properties did not result in changes in biological activities in both MCF-7 and HeLa cell lines.     

In situ thermo-optical studies of polymer:fullerene blend films

Optical properties of a blend thin film (1:1 wt) of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) exposed to a stepwise heating and cooling, have been reported and compared with the properties of pure PCBM and P3HT films. The UV–Vis(T) absorption measurements were performed in situ, during annealing and cooling runs, at the precisely defined temperatures, in a range of 20–210 °C. It was demonstrated that this new method allows to observe the changes of absorption coefficient spectra and absorption edge parameters: the energy gap (E_G) and the Urbach energy (E_U), connected with the length of conjugation and structural disorder of thin film, respectively. Several stages, during annealing/cooling runs, were distinguished for the P3HT:PCBM blend film and related to the following processes, as an increase of P3HT crystallinity in the blend, the orderly stacking of polymer chains, thermally induced structural defects and the phase separation, caused by an aggregation of PCBM in the polymer matrix. These changes were also observed on the P3HT:PCBM film surface, by means to the microscopic studies.     

In situ preparation and surface modification of magnesium hydroxide nanoparticles

Hydrophobic magnesium hydroxide (Mg(OH)₂) nanoparticles were successfully synthesized via a one-step solution precipitation method with octadecyl dihydrogen phosphate (n-C₁₈H₃₇OPO₃H₂, ODP) as a surface modifier. The ODP was used to control the growth of crystal in the c direction (direction perpendicular to the layers) and to modify the surface property of the Mg(OH)₂ particles produced from the precipitation. Measurements of relative contact angle and active ratio indicated that Mg(OH)₂ samples were hydrophobic. The samples were characterized by using field emission scanning electron microscope (SEM), X-ray diffraction (XRD), infrared analysis (IR). The mechanism of influence of ODP on the surface property and morphology of Mg(OH)₂ was discussed. Furthermore, from the results of the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) tests, it was confirmed that small amount of magnesium alkyl phosphate on the surface of Mg(OH)₂ particles enhanced the thermal stability of the low density polyethylene(LDPE)/Mg(OH)₂.     

In situ GISAXS investigation of gold sputtering onto a polymer template

Microphase-separation structures in mixed diblock-triblock copolymer thin films are used for the incorporation of gold atoms inside the polymer matrix via sputtering of gold. Polystyrene (PS) spheres are arranged in a liquidlike type with a well defined nearest neighbor distance inside a polyisoprene matrix acting as a template for directing the gold atoms. Sputtering conditions are selected with a very low sputtering rate to avoid clustering in the atmosphere so that gold reaches the polymer surface in its atomic state. Due to the mobility of the gold atoms and the selective interaction with the PS parts of the microphase separation structure, gold is accumulated inside the polymer film in the PS spheres, as probed in situ with grazing incidence small-angle X-ray scattering (GISAXS). Nominally 4.3 A of gold is deposited, which by diffusion is spread out vertically over a thickness of 280 nm. UV-vis spectroscopy reveals a small blue shift for the gold sputtered polymer film. Atomic force microscopy proves the absence of gold clusters on the film surface. For low sputtering rate, GISAXS proves good sensitivity for gold migration inside the polymer film and opens new possibilities for studying polymer-metal interaction.     

In situ spectroscopic ellipsometry of pH-responsive polymer brushes on gold substrates

The dynamic and reversible switching behaviour of polyelectrolyte brushes of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) toward changes of the pH value was studied by in situ VIS-spectroscopic ellipsometry (SE). For this, PDMAEMA brushes with three different molecular weights were synthesized via the “grafting from” method using surface initiated atom transfer radical polymerization. In detail, the applicability of different SE data modelling to describe the optical properties of the different brush layers in the swollen and collapsed state was investigated. Especially for the PDMAEMA brushes with a high molecular weight, an improved optical modelling of the experimental data could be achieved and revealed an exponential distribution of the PDMAEMA fraction in the brush layer.

In situ determination of glass transition temperatures in thin polymer films

A method for determining the glass transition temperature T_g of waveguiding NLO-films is presented. This enables for the first time monitoring of the T_g of NLO-films on device substrates in situ. T_g is shown to follow from the temperature dependencies of the refractive index n(T) or the thickness d_f(T) of thin films.     

In situ growth of polymer electrolytes on lithium ion electrode surfaces

Polyacrylonitrile (PAN) films were grown on glassy carbon, nickel foam and MnO₂ substrates by cathodic electropolymerisation of acrylonitrile in acetonitrile with tetrabutylammonium perchlorate (TBAP) as the supporting electrolyte. The electronic barrier properties of the films were confirmed by impedance spectroscopy of carbon |PAN| Hg cells while the ionic resistance of the films varied from 200 kΩ cm² in the dry state to 1.4 Ω cm² when plasticised with 1 M LiPF₆ in propylene carbonate. A galvanic cell was prepared by successive electrodepositions of MnO₂ and PAN on a carbon substrate, using liquid lithium amalgam as the top contact. The cell showed a stable open circuit potential and behaved normally under the galvanostatic intermittent titration technique (GITT).     

In situ film characterization of thermally treated microstructured conducting polymer films

Based on a low‐cost fabrication routine microstructured conducting polymer films of poly (dioctylfluorene‐co‐benzothiadiazole) (F8BT) are prepared without any heat treatment or vacuum steps. The influence of thermal annealing at temperatures below the glass transition temperature of F8BT on such microstructured channel structures is investigated. In the applied structuring routine, a F8BT film is spin coated on a channel‐type hard master structure and afterwards floated on a flat support. Thereby, the properties of the final polymeric structures, for example channel width and height, can be tuned by simply varying the polymer concentration in solution and using the same master structure. With in situ grazing incidence small angle X‐ray scattering and imaging ellipsometry the installed channel structure and the influence of thermal treatment are probed. A complex interplay between a macroscopic polymer flow (reduced channel heights) and a molecular rearrangement (formation of mesoscopic crystallites) takes place during thermal annealing. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

In situ preparation of oxide-based supported catalysts by solution combustion synthesis

The oxide-based supported catalysts with high specific surface area (>200 m(2)/g) were produced in one step through combination of the impregnation and solution combustion synthesis approaches. As a model system, iron oxide was selected, which was loaded on different porous supports including alpha-Al(2)O(3), gamma-Al(2)O(3), and ZrO(2), as well as activated alumina. It was shown that for the former three cases the specific surface areas of the supported catalysts are about or below the surface areas of the support. However, for the activated Al(2)O(3) this characteristic significantly increases compared to that of the support. It was demonstrated that the developed approach may be used to produce different types of oxide-based supported catalysts, including perovskites.     

In situ preparation of Al-containing PVDF ultrafiltration membrane via sol-gel process

Recently, inorganic nanoparticles blended within polymeric membranes have shown improved antifouling performance in wastewater treatment. However, agglomeration of nanoparticles remains as one of the major obstacles for generating a uniform surface. In this study, a new method for in situ preparation of Al-containing PVDF ultrafiltration membranes to improve the dispersion of nanoparticles is reported. The strategy of this method is to combine sol-gel process with traditional immersion precipitation process. Al sol was synthesized by the addition of anionic exchange resin in N,N-dimethylformamide (DMF) solvent containing aluminum chloride. Homogeneous Al-containing PVDF casting solution was then obtained by dissolving PVDF polymer in the Al sol. The membrane formation mechanism was investigated by precipitation kinetics and morphology. Results indicate that the addition of Al species can accelerate phase inversion of casting solution. Scanning electron microscopic images show that a typical transition from sponge-like structure to finger-like structure occurred with increasing Al species content. The existence and dispersion states of Al species in the resultant membrane matrix were further examined by transmission electron microscope and X-ray photoelectron spectrometer. The results indicate the Al species nanoparticles were well dispersed throughout PVDF matrix. Dynamic BSA fouling resistance experiments demonstrate the Al-containing PVDF membranes possess improved separation performances over the pure PVDF membranes.     

"Three-dimensional hybridization" with polyvalent DNA-gold nanoparticle conjugates

We have determined the minimum number of base pairings necessary to stabilize DNA-Au NP aggregates as a function of salt concentration for particles between 15 and 150 nm in diameter. Significantly, we find that sequences containing a single base pair interaction are capable of effecting hybridization between 150 nm DNA-Au NPs. While traditional DNA hybridization involves two strands interacting in one dimension (1D, Z), we propose that hybridization in the context of an aggregate of polyvalent DNA-Au NP conjugates occurs in three dimensions (many oligonucleotides oriented perpendicular to the X, Y plane engage in base pairing), making nanoparticle assembly possible with three or fewer base pairings per DNA strand. These studies enabled us to compare the stability of duplex DNA free in solution and bound to the nanoparticle surface. We estimate that 4-8, 6-19, or 8-33 additional DNA bases must be added to free duplex DNA to achieve melting temperatures equivalent to hybridized systems formed from 15, 60, or 150 nm DNA-Au NPs, respectively. In addition, we estimate that the equilibrium binding constant (K(eq)) for 15 nm DNA-Au NPs (3 base pairs) is approximately 3 orders of magnitude higher than the K(eq) for the corresponding nanoparticle free system.     

In situ preparation of hetero-polymers/clay nanocomposites by CUAAC click chemistry

A series of polymer/clay nanocomposites containing mechanistically two different polymers, poly(ethylene glycol) (PEG) and poly(epsilon caprolactone) (PCL), were prepared by simultaneous copper(I)-catalyzed alkyne-azide cycloaddition click reactions. Both clickable polymers, PEG-Alkyne and PCL-Alkyne, were simultaneously clicked on to azide-functional montmorillonite (MMT-N₃) nanoclay to get corresponding PEG-PCL/MMT nanocomposites. The chemical structures of the resulting nanocomposites were verified by following azide and silicone-oxygen bands using FT-IR and characteristic bands of PEG and PCL segments using ¹H-NMR spectroscopy. The combined XRD and TEM analysis confirmed that all PEG-PCL/MMT nanocomposites had partially exfoliated/intercalated morphologies. In addition, the increase of MMT-N₃ loading not only improved the onset and maximum degradation temperatures of the nanocomposites but also their char yields. Furthermore, the incorporation of MMT-N₃ in the polymer matrix did not significantly influence the crystallization behavior of both PEG and PCL segments.     

In situ preparation of a highly active N-heterocyclic carbene-coordinated olefin metathesis catalyst

Highly active N-heterocyclic carbene-coordinated catalysts may be synthesized and used in situ, without requiring prior isolation of the catalyst. Activation of this in situ catalyst with ethereal HCl dramatically reduces the reaction times required for high conversions. A variety of alpha,beta-unsaturated carbonyl-containing substrates participate readily in cross and ring-closing metathesis reactions using this preparation.     

去氢吴茱萸碱的制备及其生物活性研究进展

去氢吴茱萸碱是中药吴茱萸中的吲哚喹唑啉类生物碱,具有抗阿尔茨海默症、抗肿瘤、抗炎及抗菌等多种生物活性,具有巨大的开发潜力及应用价值。本文对去氢吴茱萸碱的提取分离、合成和生物活性的研究进展进行了综述,并对该化合物及其衍生物的研究方向及应用进行展望,以期为去氢吴茱萸碱及其衍生物的进一步开发利用提供参考。     

In situ XAFS studies of Au particle formation by photoreduction in polymer solutions

Formation mechanisms of metal particles (gold (Au) particles) in an aqueous ethanol solution of HAuCl4 with poly(N-vinyl-2-pyrrolidone) (PVP) by the photoreduction method were investigated by UV-vis, transmission electron microscopy (TEM), and in situ and ex situ X-ray absorption fine structure (XAFS) analysis. The average diameters of the dilute and concentrated Au particles in PVP solution are estimated from TEM to be 106 A and 925 A, respectively. XAFS analysis was carried out to elucidate the reduction process of AuCl4- ionic species to metallic Au particles for the Au-L3 edge of the colloidal dispersions of the concentrated Au solutions. In the photoreduction process, the reduction of AuCl2- species to Au0 atoms is a slower process than that of AuCl4- to AuCl2-, and the reduction of AuCl2- to Au0 atoms and the association of Au0 atoms to form seed Au particles (particle diameter between 5.5 and 30 A) concurrently proceeds in the short-duration photoirradiation. In addition, in the long-duration photoirradiation, the slow progression of Au particle growth occurs with the association of Au0-Au0 metallic bonds, resulting in the formation of larger Au particles (particle diameter larger than 500 A).     

In situ rapid versatile method for the preparation of zirconium metal-organic framework filters

The development of the rapid preparation of highly stable metal-organic framework(MOF)-based devices provides the possibility of meeting the increasing demands of MOF in industrial applications.However,MOFs experience poor processability and stable high-valence-metal(Ⅳ)-based MOFs favor forming either thermodynamically stable metal hydroxides or oxides during their growth and nucleation,which hinders their practical applications.Herein,we present a versatile deep eutectic solvent(DES)-assisted h...