Post-grafting Method Research Articles

Ionic Liquid [Bmim]OH Grafted Catalyst for Cycloaddition of Carbon Dioxide

An ionic liquid 1-butyl-3-methylimidazolium hydroxide ([Bmim]OH) was grafted on silica gel by post-grafting method. Such grafted ionic liquids (GILs) which were verified by means of FTIR, element analysis N2adsorption-desorption and TG could be used as highly effective heterogeneous catalysts toward propylene carbonate synthesis through cycloaddition of carbon dioxide with propylene oxide under solventless and mild conditions.

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Various types of MOFs (metal-organic frameworks) were prepared via hydrothermal and post-grafting methods and applied as catalysts for the synthesis of jasminaldehyde, one of the representative perfume intermediates, by Aldol condensation of benzaldehyde with heptanal. Although both acid and base sites could catalyze the reaction, the catalytic performance was strongly dependent on the physical properties as well as the nature of functionalization on MOFs. While the use of sulfonated MOF catalysts led to decrease of jasminaldehyde selectivity regardless of MOFs used, the selectivity change was found to rely on the MOF types in the case of the amine-functionalization. Among the catalysts tested, MIL-101 shows the best catalytic per- formance, which may suggest that MIL-101 has suitable acid properties to promote the Aldol condensation and the large pore of MIL-101 is also advantageous to alleviate the diffusion problem of bulky products.

Adsorption Behavior of Phenol in Aqueous Solution on MCM-41 Grafted by Different Functional Groups

Four types of organo-functionalized mesoporous silicas were synthesized by post-grafting method, and characterized by powder X-ray diffraction, nitrogen adsorption/desorption and fourier transform infrared spectroscopy. In addition, adsorption behaviors of the prepared material modified with different functional groups were studied by adsorption of phenol in aqueous solution. When the concentration of phenol was 800 mg/L, the equilibrium adsorption capacity of N-aminoethyl-γ-aminopropyl-MCM-41, aminopropyl-MCM-41, mercaptopropyl-MCM-41 and propyl-MCM-41 was respectively as 2.5 times, 2.2 times, 1.9 times, and 1.7 times as that of MCM-41. It was due to the introduction of organo-functional groups, changing the polarity of the channel surface, and increasing the hydrophobic properties. N-aminoethyl-γ-aminopropyl and aminopropyl groups could generate acid-base interactions with phenol, therefore, their adsorption capacity increased much more. Besides, the pH value of the solution could significantly affect the adsorption amount of phenol on samples. The result showed that with the increase of pH, the adsorption amount of phenol increased at first, and then decreased. The maximum adsorption amount of all the prepared materials occurred at about pH value of 6.

Synthesis and characterization of mesoporous composite silica monolith

Coumarin4 (Cou4) was loaded into mesoporous silicon SBA-15 monolith channels by a simple postgrafting method at room temperature. The obtained Cou4/SBA-15 composite monolith was compared with the blank SBA-15 monolith. The investigation of X-ray diffraction, transmission electron microscopy (TEM), UV–vis and photoluminescence (PL) reveals the existence of cou4 in the channels of SBA-15 monolith. In addition, a red-shift and strong fluorescence in PL spectrum was observed from the composite monolith compared with that of Cou4 in C2H5OH solution. This is good for the new application of optical materials.

Functionalization with amine-containing organosilane of mesoporous silica MCM-41 and MCM-48 obtained at room temperature

Functionalized ordered MCM-41 and MCM-48 materials have been obtained by a post-grafting method using 3-aminopropyltrimethoxysilane (APS) as modifying agent. The dependence of APS concentration, and reaction time on average pore size, grafted APS content, pore volume, superficial area, and morphology was studied. The modified silicas were characterized by powder X-ray diffraction (XRD), infrared spectroscopy (FT-IR), transmission electron microscope (TEM) and nitrogen adsorption–desorption experiments. MCM-41 appeared to be more prone to pore blockage than MCM-48 in the grafting procedure. According to the TEM results, no morphological changes were observed in the modified MCM-41 and MCM-48 silicas by comparing with bare silicas. These amine-grafted silicas could have potential application to be used as adsorbents of CO2 in the natural gas sweetening process or as fillers in the preparation of mixed matrix membranes.

Optical performance of mesostructured composite silica film loaded with organic dye

A mesoporous composite silica film loaded with organic dye has been successfully synthesized by a solgel reaction process and a simple postgrafting method at room temperature. The composite film was characterized by x-ray diffraction, transmission electron microscopy, UV-Vis, photoluminescence (PL) spectra, and laser performance, and the results confirmed the existence of dyes in the channels of the silica film. A blue-shift and fluorescence property in the PL spectrum was observed from the composite film compared with that of dye molecules in C₂H₅OH solution. The spectrum narrowing phenomena has been observed when the composite film is pumped at λp=355 nm by a Nd:YAG pulsed laser. A narrower, higher peak was observed in emission spectra from the mesostructured composite silica film compared with the PL spectrum of dye in C₂H₅OH solution. There is a substantial reduction in the full width at half-maximum of the emitting light, which results in peaks with linewidths of 26 nm or more. This collapse of the emission spectrum is one of the signatures of the presence of amplified spontaneous emission.

Synthesis and characterization of lysine-modified SBA-15 and its selective adsorption of scandium from a solution of rare earth elements

A novel lysine-functionalized mesoporous material was synthesized using a facile two-step post-grafting method, selectively adsorbing scandium from aqueous solution.

Preparation, characterization, and highly effective mercury adsorption ofl-cysteine-functionalized mesoporous silica

A novel L-cysteine-functionalized mesoporous SBA-15 (SH-SBA-15) material was synthesized by an easy two-step post-grafting method of L-cysteine using poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) as a template under acidic conditions. The material maintained its well-ordered mesostructure after two-step modification as confirmed by powder X-ray diffraction and transmission electron microscopy analyses. X-ray photoelectron spectroscopy and 13C cross-polarization/magic angle spinning NMR revealed that L-cysteine was successfully introduced into SBA-15. The material showed excellent mercury adsorption capacity (429 mg g−1) at room temperature and mercury uptake time (<5 min). Adsorption isotherms and uptake kinetics were also investigated. Equilibrium data were found to be represented better by the Freundlich isotherm model than the Langmuir one. The pseudo-second-order kinetics model best described the kinetic adsorption process of Hg(II) ions onto SH-SBA-15. Moreover, the material possessed high selectivity for mercury and can be easily eluted with 5% thiourea in 1 mol L−1 aqueous HCl.

Removal of uranium(vi) from aqueous solution using iminodiacetic acid derivative functionalized SBA-15 as adsorbents

Three different functional SBA-15 were prepared by a post-grafting method using three iminodiacetic acid derivatives of ethylenediaminetriacetic acid (ED3A), diethylenetriaminetetraacetic acid (DT4A), and 1,2-cyclohexylenedinitrilotriacetic acid (CyD3A), which were used as adsorbents for removal of uranium(vi) from aqueous solution. These materials were characterized by FT-IR, NMR, TEM, nitrogen adsorption/desorption experiments, and elemental analysis. The effect of pH, ionic strength, contact time, solid-liquid ratio, initial metal ion concentration, temperature, and coexisting ions on uranium(vi) sorption behaviors of the functionalized SBA-15 was studied. Typical sorption isotherms (Langmuir and Freundlich) were determined for the sorption process, and the maximum sorption capacity was calculated. The influence of functional groups on uranium(vi) sorption was also discussed. As a result, compared with other current U(vi) sorbents (granite, kaolin, attapulgite), SBA-15-1,2-cyclohexylenedinitrilotriacetic acid (SBA-15-CyD3A) possessed good selective sorption properties, which had potential application in separation of uranium(vi).

Surface functionalization of SBA-15 nanorods for anticancer drug delivery

SBA-15 nanorods with high surface area (1010m2g−1) were functionalized by post grafting method with three different alkoxysilanes including (3-aminopropyl) triethoxysilane (APTES), 3-[bis(2-hydroxyethyl)amino] propyl triethoxysilane (HAPS) and 3-[2-(2-aminoethylamino) ethylamino] propyl trimethoxysilane (AEPS). The prepared materials were used as nanocarriers for an anticancer drug (gemcitabine). The obtained samples were characterized by SAXS, elemental analysis, TGA, N2 adsorption/desorption, SEM, TEM, FTIR and UV spectroscopies. The adsorption and release properties of all samples were investigated. It was found that the surface functionalization increases the interaction between the carrier and gemcitabine and results in the loading enhancement of the drug. In addition, the adsorption of gemcitabine on the modified mesoporous matrix depends on the type and the amount of alkoxysilanes groups. The maximum content of the deposited drug in the modified SBA-15 nanorods is close to 22wt.%. The rate of the drug release from the modified samples containing NH2 groups on their surfaces is pH dependent.

Chemical Functionalization of Carbon Supported Metal Nanoparticles by Ionic Conductive Polymer via the “Grafting From” Method

Platinum nanoparticles (Pt-NPs) supported on carbon powder are prepared via a water-in-oil microemulsion method and modified by a disulfide aryl initiator either by a postgrafting method or by a one pot in situ “grafting from” method. It is shown that the grafting of the disulfide derivation initiator is quantitative from 2 to 10 wt %, independently on the method. ATRP of sodium styrene sulfonate (SSNa) has then been performed from the initiator molecules grafted on the surface of the Pt-NPs supported on an electron conductive porous substrate and electrochemical measurements are performed. Although the polymerization reaction was not total (60%), derivatization of the Pt-NPs-initiator/C with different polymerization densities and polymer molecular weights are obtained. Electrodes fabricated from such nanocomposites shows enhanced performances toward the oxygen reduction reaction. Higher activity is obtained with lower polymerization density and higher polymer molecular weight. The enhancement of activity is attributed to the difference in hydrophilic character between the polymer skeleton (which could favor oxygen transport toward active sites) and the pendant sulfonic acid groups (which favor the proton transport toward the active sites).

Role of 3-aminopropyltriethoxysilane in the preparation of mesoporous silica nanoparticles for ibuprofen delivery: Effect on physicochemical properties

The development of mesoporous silica nanoparticle-based platforms for a controlled drug delivery was studied. Mesoporous silica nanoparticles (MSN) was synthesized and modified with 3-aminopropyltriethoxysilane (APTES) using co-condensation (MSNco) and post-grafting (MSNpost) methods. X-ray diffraction (XRD) and transmission electron microscopy (TEM) data confirmed the formation of ordered mesostructured silica nanoparticles. The performance of MSNs was then tested on an ibuprofen immobilization and release. The results revealed that unmodified MSN demonstrated the best immobilization rate and capacity of ibuprofen (98%), MSNpost exhibited higher ibuprofen adsorption (78%) as compared to MSNco (71%), suggesting the modification method is not the dominant factor for the adsorption studied. In fact, according to the FT-IR results, the silanol groups density was found to be the contributing factor that affected the adsorption. The in vitro drug release was also investigated with simulated biological fluids. In 20h, MSNco showed the fastest release of ibuprofen (100%), followed by MSN (50%) and MSNpost (38%). Both pore size and amine groups influenced the rate of the release process. From the results, MSN and MSNpost is suggested to have suitable features for slow drug release which provides constant release over a defined period to avoid repeated administration. While MSNco could be best employed as a fast release system that provides initial burst of drug release to achieve rapid and maximum relief.

Preparation, characterization and luminescent properties of dense nano‐silica hybrids loaded with 1,8‐naphthalic anhydride

Novel luminescent dense nano-silica hybrid materials (DNSS) modified with different amounts of (3-aminopropyl)triethoxysilane (APTES) and 1,8-naphthalic anhydride (NA) were successfully synthesized via two steps combined with post-grafting methods. Powder X-ray diffraction (XRD), N2-sorption analysis, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), photoluminescence (PL) spectroscopy and elemental analysis, as well as time-resolved decays were employed to characterize the resultant hybrid materials. The results revealed that luminescent organic molecules had been successfully loaded onto the amine-modified surface of nano-silica spheres. In addition, their fluorescence intensity and characteristic peak of emission spectra changed with increasing amount of APTES and NA additive. In particular, the characteristic peak showed a red shift from 390 to 450 nm, however, this was inconsistent with results calculated on the basis of the elemental analysis data, most probably because of the dispersion behaviors of NA molecules from the aggregating to the monolayer state. These observations demonstrated the existence of a quantum confinement effectiveness of NA-DNSS samples, and therefore a possible mechanism was put forward.

Synthesis of VTES/SBA-15 Prepared by Post-Grafting: XRD Characteristics on the Effect of Calcination Properties

Functionalization of Santa Barbara Amorphous-15 (SBA-15) with vinyltriethoxysilane (VTES) via post-grafting method has been synthesized with the effect of calcination time span and temperature range. X-ray powder diffraction has been a means to evident the incorporation of VTES functional groups and to characterize the peak diffraction pattern. The samples of parent SBA-15 have been treated in different calcination temperature and time, ranging from 400°C to 800°C and 2 hr to 8 hr, respectively. The XRD results show that two dimensionalp6mmof high order hexagonal mesoscopic structure of VTES/SBA-15 could not be retained at higher temperature of calcination than 700°C. However, the higher time spans of calcination up to 8 hrs preserve the long-range order of functionalized SBA-15.

A novel Fe3+ ions chemosensor by covalent coupling fluorene onto the mono, di- and tri-ammonium functionalized nanoporous silica type SBA-15

Fluorene functionalized mesoporous silica (FM-SBA-15, FD-SBA-15 and FT-SBA-15) were prepared the post synthesis grafting method of SBA-15. The grafting of fluorene in nanochannels of SBA-15 was performed in two steps: (i) attachment of the 3-aminopropyltriethoxysilane, [1-(2-aminoethyl)-3-aminopropyl]trimethoxysilane and 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane on SBA-15, then (ii) covalent linkage of fluorene. The obtained material was characterized by SAXS, N2 adsorption–desorption, FT-IR spectroscopy, Raman spectroscopy and thermogravimetric analysis that indicate the successful immobilization of fluorene on the surface of mesoporous silica. The sensing ability of FM-SBA-15, FD-SBA-15 and FT-SBA-15 was studied by addition of the cations Fe3+, Mg2+, Cr3+, Co2+, Ni2+ Cu2+, Hg2+ and Zn2+ to water suspensions of the assayed solid. Of all the cations tested addition of Fe3+ ion to a suspension of these materials resulted in the largest decrease in the fluorescence intensity but addition of Mg2+, Cr3+, Co2+, Ni2+, Cu2+, Hg2+ and Zn2+ did not quench the fluorescence of FM-SBA-15, FD-SBA-15 and FT-SBA-15. A good linearity between the fluorescence intensity of the prepared materials and the concentration of Fe3+ ion is constructed, which enables these materials as a fluorescence chemo sensor for detecting the Fe3+ ion with a suitable detection limit.

Synthesis of highly loaded and well dispersed CuO/SBA-15 via an ultrasonic post-grafting method and its application as a catalyst for the direct hydroxylation of benzene to phenol

A novel ultrasonic post-grafting method has been developed to obtain highly-loaded and well-dispersed CuO nanoclusters inside the channels of mesoporous silica (SBA-15). Trimethylchlorosilane (TMCS) and 3-aminopropyltriethoxysilane (APTES) were used as modification surfactants, and copper nitrate solution was used as the precursor. The samples were characterized by FT-IR, XRD, SAXRD, ICP-AES, BET, HRTEM, TPR and XPS, which illustrated that the CuO clusters were well-dispersed in very small sizes. The hydroxylation of benzene to phenol in a one-step liquid-phase process using CuO/SBA-15 as the catalyst was evaluated. High conversion (28%) and selectivity (95%) were achieved with a 13.4wt.% copper grafted on SBA-15. Furthermore, the catalyst was shown to have the ability to be recycled up to five times without a significant loss of conversion or selectivity.

A Selective Functionalized Mesoporous Silica-Supported Rh Catalyst for Effective 1-Octene Hydroformylation

Through different functionalization methods, three kinds of Rh-immobilized mesoporous silicas have successfully been prepared to investigate catalytic behavior, including yield and the linear/branched ratio of aldehyde (L/B) in 1-octene hydroformylation. A conventional post grafting method and two kinds of selective bifunctionalized methods for modification of the mesoporous silica have been applied for this purpose. A relatively high L/B (> 2.0) was effectively achieved using Rh-immobilized inner pores in the MCM-41 support due to the confinement effects of the Rh complex in the nanospace. Moreover, the Rh-immobilized MCM-41 catalyst, passivated with trimethylchlorosilane (TMCS) only on the external surface, showed fairly good yields of the aldehyde (> 40%).

Thermal decomposition behaviors and kinetic properties of 1,8-naphthalic anhydride loaded dense nano-silica hybrids

A certain amount of (3-aminopropyl)triethoxysilane (APTES) and various capacity of 1,8-naphthalic anhydride (NA) were employed to modify and then graft onto the surface of the dense nano-silica spheres (DNSS) via a post-grafting method, and thereby, a novel luminescent density nano-silica hybrid materials have been successfully synthesized. Meanwhile, the structures and properties of obtained hybrid DNSS were characterized by XRD, TEM, N2 sorption, FT-IR, and TG analysis. Furthermore, the thermal stability of before and after modification were demonstrated by using both Kissinger methods and Ozawa–Flynn–Wall methods. Particularly, the thermal decomposition behaviors of amino-modified groups and NA-grafted organic molecules were emphasized based on the TG and DTG analysis and then the related mechanism was put forward according to Coats and Redfern methods. Finally, as a comparison, the obtained results and the proposed decomposition mechanism of hybrid DNSS with non-pores were discussed with that of mesopores silicas in details.

Green graft process for preparation of functional mesoporous silica materials

This study presents a green post-grafting method to prepare functional mesoporous silica materials. In the functionalisation stage, potassium iodide was applied as catalyst, and ecofriendly ethanol was used as solvent. The optimal molecular ratio of the reagent was n (potassium iodide)/n (3-chloropropyltriethoxysilane)/n (2-mercaptobenzothiazole) = 1·5∶1∶1·5. The reaction could be completed after reflux for 12 h at 90°C. The resulting materials were characterised by scanning electron microscopy, X-ray diffraction, nitrogen adsorption–desorption, Fourier transform infrared spectroscopy and elemental analysis. The results indicate that the large pore (the maximal size is ∼8·62 nm) functional mesoporous silica could be prepared by our improved graft method, which has a high efficiency of 50·63%. The functional mesoporous silica was applied to adsorb trace amount of heavy metal ions [Hg(II), Pb(II) and Cd(II)]. The materials exhibit large adsorption capacity and excellent regeneration ability.

Preparation of Boronic Acid-Functionalized Mesoporous Nanomaterial and Its Application in Enrichment of Glycopeptides

A boronic acid-functionalized mesoporous nanomaterial was prepared by using a two-step post-grafting method. Firstly, the 3-glycidyloxypropyltrimethoxysilane (GLYMO) and 3-aminophenylboronic acid monohydrate (APB) were re- acted in oxyhydrogen sodium solution (pH 9.18) to prepare boronic-acid bonded GLYMO (denoted as GLYMO-APB). Sec- ondly, the MCM-41 was added into the prepared GLYMO-APB solution to prepare the final product of boronic acid func- tionalized MCM-41 (denoted as MCM-41-GLYMO-APB). This as-prepared material was characterized by FT-IR and the results showed that the boronic acid groups were successfully grafted to MCM-41. Glycopeptides can be enriched with high selectivity and high efficiency based on the formation of a cyclic diester between boronic hydroxyl and cis-diol on the glycan chain. The conditions of enriching glycopeptides in mixed digests of standard proteins by MCM-41-GLYMO-APB were compared and optimized. The incubation time, incubation solutions, washing ways and eluents used in the enrichment of glycopeptides were investigated. When using the ammonium bicarbonate buffer (100 mmol/L, pH 8.0) as the incubation so- lution and incubated for 1 h, the maximum number of enriched glycopeptides from horseradish peroxidase (HRP) digests could be obtained. After enrichment, washing the prepared material with the incubation solution twice for 5 min, nonglyco- peptides interference can be in a large extent removed. The enriched glycopeptides binding to the surface of MCM-41-GLYMO-APB could be released when using 1% trifluoroacetic acid containing 2,5-dihydroxybenzoic acid as the eluent, the operating steps could be simplified when using this optimized eluent because there was no need of adding the MALDI matrix solution afterwards. Therefore, this optimized protocol provided a reference for the glycopeptide enrichment with boronic acid-functionalized materials, and it also laid the foundation for the research of utilizing boronic acid-based chemical method to the glycopeptide enrichment in biological samples. Meanwhile, the highly ordered hexagonal cylindrical mesoporous structure of MCM-41-GLYMO-APB provided the possibility of being used for the research of glycopeptidome in biological samples. Keywords glycoproteins; boronic acid-functionalized mesoporous nanomaterial; enrichment; mass spectrometry