Grafting Route Research Articles

Oxidative dehydrogenation of propane with nitrous oxide over Fe-ZSM-5 prepared by grafting: Characterization and performance

Iron-zeolites with well-defined extra-framework iron species were prepared via organometallic chemistry grafting route, i.e. the surface reaction between ferrocene and Brønsted acid sites in zeolites, and the calcined iron-zeolites were studied as catalysts for N2O-mediated oxidative dehydrogenation of propane to propylene. The framework structures of zeolite hosts and the calcination temperatures showed great impact on the catalytic performances. Fe-ZSM-5 calcined at 1073K exhibited the highest activity for N2O-mediated propane oxidative dehydrogenation and a maximal initial propylene yield of ca. 30% can be obtained at a reaction temperature of 748K (after time-on-stream of 15min). A transformation of iron sites in Fe-ZSM-5 upon high-temperature calcination was well established based on the spectroscopic characterization results from UV–vis, H2-TPR, EPR and FTIR of NO adsorption. According to the correlation between catalytic activity and iron sites, extra-framework Fe–O–Al species are proposed to be the preferred active sites for N2O-mediated oxidative dehydrogenation of propane.

Synthesis and characterization of degraded gelatin grafted poly(ɛ-caprolactone) copolymers

Hydrophilic degraded gelatin was modified with hydrophobic poly(ɛ-caprolactone) (PCL) via a chemical grafting route. Firstly, PCL with one hydroxyl end group was prepared by the ring-opening polymerization of ɛ-caprolactone (ɛ-CL) with tin (II) 2-ethylhexanoate as catalyst and n-butyl alcohol as initiator. Secondly, the PCL reacted with isophorone diisocyanate (IPDI) to prepare PCL with isocyanate functional group (PCL-NCO). Hydroxylamine was used to degrade gelatin by the cleavage between asparagine and glycine residues of gelatin. PCL-NCO reacted with the hydroxyl/amino groups of degraded gelatin in a homogeneous system and yielded the PCL modified gelatin copolymers. The gelatin grafted PCL copolymers were measured by means of XRD, FTIR, DSC and 1H NMR. The results confirmed the conjugation of PCL onto gelatin chains. The PCL modified gelatin can be used as biomaterials owing to their biocompatibility and biodegradation.

Effect of Sn surface states on the photocatalytic activity of anatase TiO2

The influence of surface Sn-doping on the photocatalytic properties of anatase TiO2 has been investigated in samples prepared by a grafting route using Sn(IV) tert-butoxide as Sn precursor. The grafting procedure leads to the formation of isolated Sn(IV) sites on the surface of anatase TiO2 powders as gauged by structural characterisation based on XRD, Raman spectroscopy and XAS. Studies of the surface reduction based on TPR experiments and XPS provide the conditions for a selective reduction of surface Sn(IV) to the divalent oxidation state. Electronic structure characterisation based on valence band XPS and DRS shows that there is a slight widening of the band gap upon Sn(IV)-grafting, but Sn(II) related states emerge at the top of the main valence band upon reduction at temperatures up to 350°C, and this induces visible light absorption. Grafting of TiO2 with Sn(IV) increases the formation rate of OH radicals on the surface of the material. Reduction of the Sn(IV)-grafted TiO2 to form surface Sn(II) brings about substantial increase of the photocatalytic efficiency for the methylene blue degradation under irradiation with λ≥320nm compared with Sn(IV)-grafted and pure anatase TiO2. This observation is explained based on a surface hole trapping by the Sn(II)-related surface states which lie above the top of the main valence band and can therefore act as trapping sites for holes produced under photoexcitation.

Preparation and CO2 adsorption of diamine modified montmorillonite via exfoliation grafting route

In this paper, diamine modified montmorillonite was prepared by water aided exfoliation/grafting method. The materials were characterized by elemental analysis (EA), X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectrometer (DRIFTS), automated surface area and porosity analyser (ASAP 2420) and thermogravimetric analysis (TGA). Adsorption of carbon dioxide on modified montmorillonite was investigated by isothermal CO2 adsorption, temperature ramp CO2 adsorption, regeneration screening test with adsorption/desorption cycles, and multiple cyclic test. The maximum adsorption capacity for modified montmorillonite is 2.4mmolg−1 at 100°C. In a 15% CO2 in N2 mixture, the material achieves a maximum adsorption capacity of 1.8mmolg−1, which is 75% of its maximum capacity in pure CO2. The optimum adsorption and desorption temperature are found to be 80 and 160°C, respectively, by regeneration testing. The long term performance was also studied in pure CO2, 15% CO2 in N2 and 15% CO2 in N2 with 1000ppm SO2. The material is stable in pure CO2 and 15% CO2 in N2, while the adsorption capacity drops dramatically with the presence of SO2. In order to understand the kinetics of CO2 adsorption, four kinetics models were evaluated, with the Avrami equation providing the best experimental-simulation fit.

Effect of surface properties of mesoporous silica on adsorption of mesoionic compound molsidomine

Abstract

Fabrication of VMn@mesoporous silica for epoxidation of cyclohexene

Vanadium-manganese containing mesoporous silica (VMnS) was prepared by an in situ grafting route by varying the wt% of vanadium and manganese. The materials were characterized by SXRD, BET-surface area, pore size distribution, SEM, EDAX-semiquantitative analysis, XPS, TPR, DRUV-vis, FTIR. The modification of silanol groups were evidenced from the characterization results. The activity of the catalysts was evaluated for cyclohexene epoxidation reaction. VMnS (2:2) showed highest conversion of 75% with selectivity 94%. Interestingly, only side product 2-cyclohexene-1-one (5%) was produced over the same catalyst.

Facile and tunable functionalization of carbon nanotube electrodes with ferrocene by covalent coupling and π-stacking interactions and their relevance to glucose bio-sensing

Ferrocene derivatives were π-stacked or covalently grafted onto a film of carbon nanotubes (CNTs) in order to determine the most effective method to immobilize redox centres on those high-surface area electrodes for sensors or catalytic applications. The immobilization of the ferrocene moiety via π–π interactions was done with a new ferrocene derivative bearing a pyrene group. The covalent grafting on the film of CNTs was achieved in two steps via the electroreduction of an aminoethylbenzenediazonium salt followed by post-functionalization with an activated ester derivative of ferrocene. Cyclic voltammetry and XPS measurements showed respectively that, in our conditions, the covalent grafting route gave more redox centres fixed on CNTs than the π-stacking one and the probes are located differently on the electrodes. In the first case, the high specific area of the CNTs electrodes resulted in a 32-fold increase of the amount of immobilized redox species with respect to its projected plane surface. Finally, a preliminary activity test of our π-stacked and covalently functionalized electrodes on glucose sensing was realized.

New photoinitiating systems designed for polymer/inorganic hybrid nanocoatings

Conventional UV-curable formulations consist of photoinitiators, multifunctional monomers and oligomers, reactive diluents, pigments, and additives. While photoinitiators are the key components of the formulations and responsible for the absorption of light and relevant performances (e.g., cure speed, high-percent conversion, etc.), the final properties of the cured coating are governed by the other high-volume components. With recent advances in the use of nanomaterials like metals, metal oxides, and silicates in coatings, it is now possible to prepare nanocoatings with enhanced physical, chemical, and biological properties. This is due, in part, to the difference in surface area per unit of volume at the nanoscale. Nanocoatings are usually prepared by UV irradiation of formulations containing dispersed nanoparticles. However, the homogeneous dispersion of these nanoparticles is a key challenge due to their easy agglomeration arising from their high surface-free energy. It is often difficult to obtain well-dispersed formulations providing good transmission of light for a complete cure. In this article, we report several synthetic methodologies for the preparation of epoxy and (meth)acrylate-based nanocoatings containing clay or metal nanoparticles. In the former case, photolysis of intercalated photoinitiator within the layers of montmorillonite clay in the presence of monomers resulted in the in situ formation of exfoliated structures. For the preparation of metal nanocoatings, the formation of silver or gold nanoparticles and crosslinking are accomplished simultaneously by photoinduced electron transfer and polymerization processes. The nanoparticles are homogenously distributed in the network without macroscopic agglomeration. Applicability to both free radical and cationic systems is demonstrated. Moreover, a novel photochemical route for grafting from the self-assembled monolayers on gold is presented.

Treatment of rat spinal cord injury with autologous activated Schwann cells via different grafting routes

Objective To explore the curative effect of autologous activated Schwann cells (AASCs) in rat spinal cord injury (SCI) via different grafting routes. Methods Saphenous nerve of the adult Wistar rat was ligated for one week to activate Schwann cells. And then AASCs were cultured, passaged, purified and identified in vitro. Sixty Wistar rats were all made into SCI model at T10 and then divided into three groups randomly. One week after injury, AASCs were transplanted into the SCI rats via three different routes [group Ⅰ: tail vein; group Ⅱ: intrathecal (subarachnoid route); group Ⅲ: intraspinal cord]. BBB score was carried out to evaluate the functional recovery of the injured rats at weekly interval postinjury. Three months later, corticospinal tract (CST) was labeled by 10% BDA. Two weeks after labeling, the rats were sacrificed and then their injured spinal cord tissues were take out to carry out 10 μm fast frozen section, which was then followed by Cy3 fluorescent probe staining, NF200 and HE staining. Results AASCs passed over 4 stable passages and expressed S-100 antigen in vitro. The difference among groups could be considered sig-nificant in BBB score on the 5th week postinjury. HE staining showed that the injured cavity was evidently smaller in group Ⅲ compared with other two groups. Statistical difference also existed among groups by com-paring the percentage of positive response areas in NF200 staining. 10%BDA stain demonstrated that more regenerated axons passed through the injured cavity in group Ⅲ when compared with other two groups, which was also confirmed by immunohistochemistry stain. Conclusion The amount of grafted AASCs can be guaranteed effectively in injured epicenter via the grafting route of intraspinal cord. AASCs promote the repair after SCI by secreting multiple kinds of neurotrophic factors and bridge injured axons for regrowth. Key words: Schwann cells; Spinal cord injuries; Nerve growth factors; Axon

Optimising catalytic properties of supported sulfonic acid catalysts

Siliceous mesoporous molecular sieves (SBA-15) have been functionalised with propylsulfonic acid groups by both co-condensing 3-mercaptopropyltrimethoxysilane with the solid at the synthesis (sol–gel) stage and by grafting the same compound to pre-prepared SBA-15, followed, in both cases, by oxidation to sulfonic acid. The acidic and catalytic properties of the supported sulfonic acids prepared in the two ways have been compared, using ammonia adsorption calorimetry and the benzylation reaction between benzyl alcohol and toluene. Using a combination of X-ray photoelectron spectroscopy and other analytical techniques, the level of functionalisation and the extent of subsequent oxidation of tethered thiol to sulfonic acid, both in the bulk and close to the surface of SBA-15 particles, have been assessed. The research shows that the co-condensing route leads to higher levels of functionalisation than the grafting route. The extent of oxidation of added thiol to acid groups is similar using the two routes, about 70% near the surface and only 50% in the bulk. Comparison is made with polymer supported sulfonic acid catalysts, Amberlysts 15 and 35, and Nafion. Nafion shows the highest acid strength and the highest specific catalytic activity of all materials studied. Amongst the other materials, average acid strengths are broadly similar but there appears to be a relationship between the concentration of acid sites on the catalysts and their specific activity in the benzylation reaction. A model is proposed to explain this, in which clustering of sulfonic acid groups, even to a small extent, leads to disproportionately enhanced catalytic activity.

Intraspinal cord graft of autologous activated Schwann cells efficiently promotes axonal regeneration and functional recovery after rat's spinal cord injury

Basic research in spinal cord injury (SCI) has made great strides in recent years, and some new insights and strategies have been applied in promoting effective axonal regrowth and sprouting. However, a relatively safe and efficient transplantation technique remains undetermined. This study, therefore, was aimed to address a question of how to graft Schwann cells to achieve the best possible therapeutic effects. To clarify the issue, the rats were subjected to spinal cord injury at T10. Autologous activated Schwann cells (AASCs) were obtained by prior ligation of saphenous nerve and subsequently isolated and purified in vitro and then grafted into spinal cord-injured rats via three different routes (group I: intravenous, group II: intrathecal and group III: intraspinal cord). Neurologic function was serially evaluated by Basso, Beattie, Bresnahan locomotor rating scale and footprint analysis. We also evaluated the migration of the transplanted cells at 2 weeks after transplantation. Using biotinylated dextran amine (BDA) anterograde tracing, we demonstrated that more regenerative axons of corticospinal tract (CST) surrounding the injured cavity in group III than those in the other two groups, and we also confirmed it further by quantitative analysis. The microenvironment surrounding the injured spinal cord has been improved to the greatest extent in group III, as determined by immunohistological staining. Relatively complete myelin sheaths and more neurofilaments in axons were found in groups II and III than those in group I under electron microscopy. The results showed that intraspinal cord injection of AASCs promoted recovery of hindlimb locomotor function of injured rats more efficiently than the other grafting routes. In addition, intact myelin sheaths and sufficient neurofilaments in axons were not adequate for full functional recovery after SCI, suggesting that reestablishment of normal synaptic connection is indispensable. The findings in this study strongly suggest that transplantation of AASCs directly into the spinal cord may be one of the promising candidates for potential scaffold for injured spinal cord, and such strategy of transplantation of AASCs could be hopeful to treat patients with SCI.

Thermal stability of octadecylsilane hybrid silicas prepared by grafting and sol–gel methods

Hybrid silicas bearing octadecylsilane groups were prepared by grafting and sol–gel (SG) methods. The effect of the preparative route on the thermal stability was evaluated by means of thermal gravimetric analysis (TGA), infrared emission spectroscopy (IRES) and, complementary, by 13C solid-state nuclear magnetic resonance ( 13C NMR) and matrix assisted laser deionization time of flight mass spectroscopy (MALDI-TOF-MS). Silicas prepared by the grafting route seem to be slightly more stable than those produced by the sol–gel method. This behavior seems to be associated to the preparative route, since grafting affords a liquid-like conformation, while in the case of sol–gel a highly organized crystalline chain conformation was observed.

Influence of carbon nanotube grafting on chemo-electrical properties of Conductive Polymer nanoComposites

ABSTRACTNew unique abilities towards solvents' vapor of electrically Conductive Polymer nanoComposites (CPCs) have made it a subject, holding the attention of research groups. The direct conversion from chemical information into an electrical signal can take advantage of existing low power microelectronics and sensing technology such as detection of toxic vapor; environmental monitoring in chemical industry and quality control in food processing, beverage and perfume industry. Conductive Polymer nanoComposite (CPC) is a heterogeneous system consisting of insulated polymer matrices and conductive nanofillers. In this paper we have investigated a new route for CNT grafting via ring opening polymerization of e-caprolactone. The influence of this treatment on chemo-electrical properties of the so-called CPC based sensor was investigated in this work.

Carbon coating via an alkyl phosphonic acid grafting route: Application on TiO 2

In the Li-ion battery the electronic conductivity is usually enhanced mixing carbon (black or graphite) with the active cathode material during the electrode preparation. The electronic conductivity is achieved in the system via the percolation of particles. From this point of view, an individual carbon coating of each active material particle is an interesting alternative to enhance conductivity. In this paper, we present a two steps original coating route based on anchoring phenyl phosphonic acid on the surface of anatase TiO 2 and followed by thermal treatment under inert atmosphere. Conductivity tests and galvanostatic measurements at different C-rate have been performed to show the effectiveness of this carbon coating upon lithium insertion.

Vibrational study on styrene functionalized porous silicon: A method for determining the relative yield of different grafting routes

A new semi-quantitative method providing the relative efficiency of three different organic functionalization reactions onto porous silicon has been set up, based on infrared absorption data. Compared to previously reported techniques, it enables a direct titration of the grafted molecules. We demonstrated that grafting of Si-styrenyl moieties by ethylaluminium dichloride mediated hydrosilylation of phenylacetylene leads to higher yields than organometallic addition onto either hydrogenated or brominated silicon.

Photophysical Properties of [60]Fullerenes and Phthalocyanines Embedded in Ordered Mesoporous Silica Films Annealed at Various Temperatures

The photophysical properties of fullerene and/or phthalocyanine dyes embedded in ordered mesoporous silica films and the influence of annealing temperature on the nature of the immobilized dye molecules has been investigated using photoluminescence (PL) and diffuse reflectance (DR) studies. The PL and DR studies show that fullerene (C60) and/or zinc phthalocyanine (ZnPc) molecules incorporated into transparent mesoporous silica films, via either sol-gel or grafting routes, exist predominantly in monomeric form. Careful choice of annealing temperature, between 25 and 225 degrees C, can further enhance monomeric dispersion. For C60-containing films, monomeric dispersion of fullerene was observed for annealing temperatures up to 175 degrees C for sol-gel derived films and 225 degrees C for grafted films. Both sol-gel and grafted ZnPc-containing films showed evidence of monodispersed phthalocyanine for annealing temperatures up to 225 degrees C. In general, annealing temperatures in the range 125-175 degrees C were found to yield optimal monodispersion of the dye molecules. When both C60 and ZnPc were incorporated into the silica films, no evidence of interaction between the dyes, i.e., charge-transfer transitions or the formation of fullerene/phthalocyanine charge-transfer complexes, was observed. This suggests that embedded fullerene and phthalocyanine molecules may be used for the preparation of solid-state optical limiters, based on reverse saturable absorption, where monomeric dispersion of the dye molecules is important.

Grafting of 1-alkynes to hydrogen-terminated (100)silicon surfaces

Hydrogen-terminated, atomically flat, 1×1 (un)reconstructed, (100)-oriented, silicon surfaces have been functionalized with 1-octyne and then studied via X-ray photoelectron spectroscopy. The C 1s signal shows that the addition of the hydrocarbon chain occurs through the formation of environmentally stable Si-C bonds, in agreement with hydrosilation as the major grafting route.

Ultrastable Mesoporous Aluminosilicates by Grafting Routes

Ultrastable Mesoporous Aluminosilicates by Grafting Routes

Ultrastable Mesoporous Aluminosilicates by Grafting Routes

Ultrastable Mesoporous Aluminosilicates by Grafting Routes

Ultrastable Mesoporous Aluminosilicates by Grafting Routes

A combination of postsynthesis grafting and hydrothermal treatment offers an excellent route for the synthesis of ultrastable mesoporous aluminosilicates with enhanced acidity and catalytic activity. The stability observed (>150 h in boiling water; 4 h at 1000 degrees C) is, for mesoporous silicates, remarkable. Unusually the hydrothermal treatment is beneficial with respect to the use of the stable aluminosilicates as solid acid catalysts.