Co-condensation Method Research Articles

Features of aminopropyl modified mesoporous silica nanoparticles. Implications on the active targeting capability

Aminopropyl modified mesoporous SiO2 nanoparticles, MCM-41 type, have been synthesized by the co-condensation method from tetraethylorthosilicate (TEOS) and aminopropyltriethoxysilane (APTES). By means of modifying TEOS/APTES ratio we have carried out an in-depth characterization of the nanoparticles as a function of APTES content. Surface charge and nanoparticles morphology were strongly influenced by the amount of APTES and particles changed from hexagonal to bean-like morphology insofar APTES increased. Besides, the porous structure was also affected, showing a contraction of the lattice parameter and pore size, while increasing the wall thickness. These results bring about new insights about the nanoparticles formation during the co-condensation process. The model proposed herein considers that different interactions stablished between TEOS and APTES with the structure directing agent have consequences on pore size, wall thickness and particle morphology. Finally, APTES is an excellent linker to covalently attach active targeting agents such as folate groups. We have hypothesized that APTES could also play a role in the biological behavior of the nanoparticles. So, the internalization efficiency of the nanoparticles has been tested with cancerous LNCaP and non-cancerous preosteoblast-like MC3T3-E1 cells. The results indicate a cooperative effect between aminopropylsilane presence and folic acid, only for the cancerous LNCaP cell line.

Carbon Self-Doped Carbon Nitride Nanosheets with Enhanced Visible-Light Photocatalytic Hydrogen Production

In this study, we prepared carbon self-doped carbon nitride nanosheets through a glucose synergic co-condensation method. In the carbon self-doped structure, the N atoms in the triazine rings were substituted by C atoms, resulting in enhanced visible-light photocatalytic hydrogen production, which is three-times higher than that of bulk carbon nitride. The enhanced photocatalytic hydrogen production was attributed to the higher charge-carrier transfer rate and widened light absorption range of the carbon nitride nanosheets after carbon self-doping. Thus, this work highlights the importance of carbon self-doping for improving the photocatalytic performance. Meanwhile, it provides a feasible method for the preparation of carbon self-doped carbon nitride without destroying the 2D conjugated backbone structures.

Carboxylic acid Functionalized Cage-Type Mesoporous Silica FDU-12 as Support for Controlled Synthesis of Platinum Nanoparticles and Their Catalytic Applications.

Carboxylic acid functionalized 3D cage-type mesoporous silica FDU-12 with high surface area and pore volume was synthesized by a one-pot co-condensation method and used as support to synthesize Pt nanoparticles (NPs). The uniformly distributed COOH groups in the cage can control the growth of Pt NPs with high dispersion (Pt@CF-12). Pt@CF-12 was used as catalyst for the hydrolysis of ammonia borane to generate H2 and for the reduction of 4-nitrophenol to 4-aminophenol. The catalyst exhibits higher catalytic activity (H2 generation rate of 17.8 L min-1 ) and lower activation energy of 30.67 kJ mol-1 compared with other Pt-based silica catalysts due to the small size of the Pt NPs (3.5 nm) and cage-type porous structure of the support, which allowed easy diffusion of reactants. Pt@CF-12 has excellent durability, since the support prevented NP aggregation and leaching of NPs during catalysis. Pt@CF-12 can convert 93 % of 4-nitrophenol to 4-aminophenol within 10 min.

Efficient grafting of polypropylene onto silica nanoparticles and the properties of PP/PP-g-SiO2 nanocomposites

Grafting polyolefin chains onto the surface of silica nanoparticles to form satisfactory polyolefin/silica nanocomposites still remains a challenge, even after the complicated functionalization of the polyolefin chains and surface modification of the silica. In this study, an efficient route for the preparation of polypropylene-grafted nanosilica (PP-g-SiO2) masterbatch was presented through the reactive melt blending of maleic-anhydride-grafted polypropylene (PP-MAH) and amino-functionalized silica (SN-NH2) synthesized by the co-condensation method. The amount of grafted PP chains could achieve to 80.8 wt%. And PP-g-SiO2 exhibited fine dispersion in PP matrix. The shear and extension rheology results of PP/PP-g-SiO2 nanocomposites showed that melt strength of PP could be enhanced remarkably by incorporation of PP-g-SiO2 masterbatch, which revealed the strong interactions between PP-g-SiO2 and PP matrix. These findings provide a facile way to prepare polyolefin-grafted nanosilica, while expanding the potential applications of nanosilica in polyolefin nanocomposites.

Preparation and analytical application of novel thiol-functionalized solid extraction matrices: From mesoporous silica to hybrid monolithic capillary column

A comprehensively comparative study of thiol-functionalized mesoporous silica and organic-inorganic hybrid monolithic column was reported, aiming at the separation and enrichment of inorganic arsenic. Thiol-functionalized mesoporous silica was synthesized based on the one-step co-condensation method. At the same time, a novel thiol-functionalized organic-inorganic hybrid monolithic column was synthesized using an unconventional ternary weak basic solvent system via one-step sol-gel process. The approach to prepare monolithic column through mild condition remarkably improved delamination phenomenon of thiol-functionalized hybrid monolithic column easily caused by conventional methods. As(III) can be selectively uptaken by the hybrid monolithic column and homemade syringe-based solid phase extraction device containing mesoporous silica through chelation in a wide range of pH, while As(V) cannot, and then the captured As(III) was eluted by 3% HNO3 (v/v) with 0.01 mol L−1 KIO3. Under the optimized conditions, the extraction recoveries were 91–102% and 93–103% for mesoporous silica and monolithic column, respectively. Although both two materials were ideal solid matrices for the removal and speciation analysis of As(III) in environmental waters, the monolith-based solid phase microextration protocol was more fast and reagent-saving than the other, which endued monolithic columns with more application prospects for trace elemental analysis and speciation. Even so, the exploration of mesoporous silica could efficiently pilot the synthesis of monolithic columns.

Amino‐Functionalized Multilayer Core–Shell Mesoporous Organosilica Nanospheres for Cr(VI) Removal

AbstractDeveloping low‐cost and highly efficient adsorbents for the removal of toxic heavy metal ions is the subject of intensive research with the increasingly stringent water pollution control standards. In this paper, three types of amino‐functionalized multilayer core–shell mesoporous organosilica nanospheres (MCMONs) are synthesized using an indirect cocondensation method for Cr(VI) removal applications. Results show that amino groups are successfully immobilized on the nanospheres and these amino‐functionalized MCMONs exhibit unique organic–inorganic multilayer core–shell structures. When used as adsorbent for Cr(VI) removal, the N‐(3‐trimethoxysilylpropyl)diethylenetriamine functionalized MCMONs exhibit a maximum adsorption capacity of 279.92 mg g−1 at initial Cr(VI) concentration of 150 mg L−1. This is about 20% greater than the highest Cr(VI) adsorption capacity previously reported for other core–shell silica‐based adsorbents, demonstrating the great potential of MCMONs in Cr(VI) removal applications.

Synthesis of halogen doped graphite carbon nitride nanorods with outstanding photocatalytic H2O2 production ability via saturated NH4X (X = Cl, Br) solution-hydrothermal post-treatment

Doping is a very effective method to promote the photocatalytic performance of graphitic carbon nitride (g-C3N4) based catalyst. However, the traditional co-condensation method causes the large particle size, small surface area and low separation rate of electrons-holes. In this work, halogen doped g-C3N4 nanorods with outstanding photocatalytic H2O2 production ability were prepared via saturated NH4X (X = Cl, Br) solution-hydrothermal post-treatment. XRD, N2 adsorption, UV–Vis, SEM, XPS, EPR, EIS and PL were used to characterize the obtained catalysts. Saturated salt solution-hydrothermal post-treatment changed the morphology and surface area of as-prepared g-C3N4 catalyst, as well as doped the halogen atoms into g-C3N4 lattice simultaneously. Br doped g-C3N4 catalyst displayed higher photocatalytic H2O2 production ability than that of Cl doped g-C3N4 catalyst. Compared with traditional co-condensation method, the catalyst prepared via saturated salt solution-hydrothermal post-treatment exhibited larger surface area, more effective separation rate and higher photocatalytic H2O2 production ability. This work can provide a new strategy for doping heteroatoms into g-C3N4 based catalyst.

Synthesis of Nano-Zinc Oxide Loaded on Mesoporous Silica by Coordination Effect and Its Photocatalytic Degradation Property of Methyl Orange.

Salicylaldimine-modified mesoporous silica (Sal-MCM-3 and Sal-MCM-9) was prepared through a co-condensation method with different amounts of added salicylaldimine. With the coordination from the salicylaldimine, zinc ions were impregnated on Sal-MCM-3 and Sal-MCM-9. Then, Zn-Sal-MCM-3 and Zn-Sal-MCM-9 were calcined to obtain nano-zinc oxide loaded on mesoporous silica (ZnO-MCM-3 and ZnO-MCM-9). The material structures were systematically studied by Fourier transform infrared spectroscopy (FTIR), N2 adsorption/desorption measurements, X-ray powder diffraction (XRD), zeta potential, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet diffused reflectance spectrum (UV-vis DRS), and thermogravimetry (TGA). Methyl orange (MO) was used to investigate the photocatalysis behavior of ZnO-MCM-3 and ZnO-MCM-9. The results confirmed that nano ZnO was loaded in the channels as well as the outside surface of mesoporous silica (MCM-41). The modification of salicylaldimine helped MCM-41 to load more nano ZnO on MCM-41. When the modification amount of salicylaldimine was one-ninth and one-third of the mass of the silicon source, respectively, the load of nano ZnO on ZnO-MCM-9 and ZnO-MCM-3 had atomic concentrations of 1.27 and 2.03, respectively. ZnO loaded on ZnO-MCM-9 had a wurtzite structure, while ZnO loaded on ZnO-MCM-3 was not in the same crystalline group. The blocking effect caused by nano ZnO in the channels reduced the orderliness of MCM-41. The photodegradation of MO can be divided in two processes, which are mainly controlled by the surface areas of ZnO-MCM and the loading amount of nano ZnO, respectively. The pseudo-first-order model was more suitable for the photodegradation process.

Sulphated Al-MCM-41: A simple, efficient and recyclable catalyst for synthesis of substituted aryl ketones/olefins via alcohols addition to alkynes and coupling with styrenes

A series of sulphate modified Al-MCM-41 acid catalysts are synthesized following impregnation and co-condensation methods The physico-chemical characterizations of all the samples are done by XRD, FT-IR, TGA/DTA, TPD, N2 adsorption and desorption study, SEM, HRTEM and EDAX etc. The structural advantages of Al-MCM-41 such as large specific surface area, wide pore size and pore volume and Bronsted and Lewis acid sites favor the coupling reaction. The catalysts endorsed the direct addition of alcohols to alkynes as well as their coupling with styrenes. The various combinations of alcohols with alkynes and styrenes are compatible with diverse functional groups to synthesize a substituted aryl ketones, as well as olefins with good to excellent yields. Additionally, the approach is advantageous in terms using alcohols, discounting the pre-functionalization and generation of waste by-products. Used precursors, alkynes and styrenes, are valuable since they are stable and found in many biologically active compounds. This current research work provides supplements to CC bond formation methodologies as a single step with atom economy and recyclable approach under mild and environmentally benign conditions.

Synthesis of ferrocenylazobenzene-functionalized MCM-41 via direct co-condensation method

Ferrocenylazobenzene-functionalized mesoporous MCM-41 material (Fc-Az-M14), was synthesized directly through co-condensation of 4-triethoxysilyl-3′-ferrocenylazobenzene (TEFA) and tetraethyl orthosilicate (TEOS), under basic conditions, using cetyltrimethylammmonium bromide (CTAB) as structure-directing agent. The template was removed through solvent extraction, to yield the ferrocenylazobenzene-containing ordered mesoporous organosilicas Fc-Az-M41. The prepared material was characterized by nitrogen adsorption, X-ray diffraction (XRD), solid state 29Si MAS NMR and 13C CP-MAS NMR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Thermogravimetric analysis (TGA) and diffuse reflectance UV-Vis spectroscopy (DR UV). The results showed that Fc-Az-M41 had an ordered two-dimensional hexagonal mesostructure, high BET surface area and pore volume. The pore diameter, BET surface area, and pore volume of the extracted material were 3.8 nm, 1070 m2/g and 0.80 cm3/g, respectively. The mean pore diameters of MCM-41 clearly decreased by ca. 0.65 nm upon incorporation of Fc-Az groups. UV-Vis spectrum of Fc-Az-M41 was determined by a diffuse reflectance method after UV irradiation. The presence of the azobenzene chromophores in this material can be clearly observed in the DR UV-Vis spectra of surfactant-free Fc-Az-M41. This spectra shows that the framework of this material is formed predominantly by trans isomer, and the π-π* and the n-π* absorption bands were affected by metal-to-ligand charge transfer (MLCT).

Direct synthesis of magnesium doped mesoporous silica: Their catalytic activity in Knoevenagel Condensation

Mesoporous magnesium silicate has been synthesized by co-condensation method using unconventional source of magnesium, namely magnesium ethoxide, in the presence of supramolecular assembly of a mixture of surfactants. Three different samples have been synthesized with magnesium to silicon ratio of 1:100, 1:50 and 1:10. The samples produced had high surface area and uniform pore size distribution and the loading of magnesium in each case was in conformity with the amount of magnesium introduced in the reaction gel during the syntheses of the respective samples. The nanostructures of the materials have been characterized by powder X-ray diffraction, transmission electron microscopy and nitrogen adsorption-desorption studies. The insertion of magnesium into the silica framework has been confirmed by UV-visible spectroscopy whereas the magnesium content of the samples has been estimated by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Catalytic studies revealed high activity of these magnesium-doped mesoporous silica in Knoevenagel condensation of benzaldehyde, 1-naphthaldehyde and 2-hydroxy naphthaldehyde with ethyl cyanoacetate. Knoevenagel reaction takes place in presence of a base and in this case the alkaline earth metal sites act as those basic centres. Such high catalytic efficiency cannot be achieved over basic sites in conventional microporous zeolites due to space constraint. The catalysts were found to be reusable for up to three reaction cycles and their efficiency can be attributed to the improved mass transfer rate which arises due to the presence of mesopores. Hot filtration test carried out for a representative reaction further established the heterogeneity of the catalytic reaction.

Decontamination of radionuclides by functionalized mesoporous silica under gamma irradiation.

Schiff base functionalized mesoporous silica (SA-SBA-15) was synthesized by the co-condensation method to remove the radioactive corrosion products from contaminated water coming from nuclear installations. SA-SBA-15 nanoparticles were first irradiated in a solid powder form and then applied to remove Cu(ii), Ni(ii), and Co(ii) from their aqueous mixture in the range from 0 to 1000 Gy of gamma irradiation. The FTIR, TGA, zeta potential, XRD, BET, TEM, and CHN analysis results revealed the stability of a ligand support material, mesopore ordering and the functional groups. The structural and functional group endurance under our studied gamma irradiation makes SA-SBA-15 a potential adsorbent for routine decontamination and decommissioning activities as well as in radioactively contaminated emergency scenarios. Furthermore, the adsorbent-metal complexation followed the Irving–Williams order (Cu(ii) > Ni(ii) > Co(ii)) and showed a higher selectivity for Cu(ii) with removal capacity up to 99.76 ± 0.01%, thus suggesting its applicability to separate Cu(ii) from other metal ions.

An ion imprinted amino-functionalized mesoporous sorbent for the selective minicolumn preconcentration of cadmium ions and determination by GFAAS

An amino-functionalized mesoporous sorbent with double imprinting of Cd(ii) and surfactant micelles was prepared via the sol–gel co-condensation method.

Supported choline hydroxide (ionic liquid) on mesoporous silica as heterogeneous catalyst for Knoevenagel condensation reactions

In this work hybrid mesoporous SBA-15 and mesoporous silica microspheres functionalized with choline hydroxide ionic liquid have been prepared. A two-step process inspired by the industrial production of choline hydroxide has been developed to synthesize the hybrid SBA-15 material with choline hydroxide ionic liquid (Chol-SBA-15) and the hybrid SBA-15 material with choline hydroxide ionic liquid and hexamethyldisilizane as capping agent (Chol-HMDS-SBA-15). For the preparation of hybrid mesoporous silica microspheres (Chol-MSMs), a co-condensation method has been employed with an ionic liquid prepared by reaction of 3-(glycidyloxypropyl)trimethoxysilane and trimethylamine in aqueous media. The synthesized materials have been fully characterized by elemental analysis, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), N2 adsorption-desorption, transmission electron microscopy (TEM) and 13C CP/MAS NMR spectroscopy. These materials have been tested successfully as catalysts in Knoevenagel condensation of benzaldehyde with RCH2C≡N (R = CN (malononitrile), CO2Et (ethyl cyanoacetate)). The catalyst Chol-MSMs showed high catalytic activity, 99% of conversion and 99% of selectivity towards ethyl 2-cyano-3-phenylacrylate in 2 h of reaction and using ethanol as solvent. In addition, their reusability without loss of activity has been demonstrated.

Preparation of cyclic carbonate via cycloaddition of CO2 on epoxide using amine-functionalized SAPO-34 as catalyst

Amine-functionalized chabazite (CHA) type silicoaluminophosphate (SAPO-34) materials were prepared under hydrothermal conditions by a direct co-condensation method. Different concentrations of an organo-amine (3-aminopropyltrimethoxysilane) were incorporated into the CHA-type framework under hydrothermal conditions. The crystalline structures of the organoamine modified SAPO-34 materials with different concentrations of amine functionalities were confirmed by powder XRD. The morphology of the materials was confirmed by SEM, FE-SEM, and TEM analysis. The successful incorporation of amine-functionalities into the wall of SAPO-34 framework was confirmed by 29Si and 13C magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The acidity and basicity of the materials was studied by NH3 and CO2 temperature programmed desorption (TPD). The resultant amine-functionalized SAPO-34 materials were utilized for the cyclo-addition of CO2 to epoxide in liquid phase medium. The organoamine-modified SAPO-34 acted as a bi-functional (acidic and basic) catalyst. The incorporated amine sites played a crucial role in CO2 activation on the surface, while the acidic sites of the SAPO-34 framework accelerated the epoxide ring opening. Thus, the amine-functionalized SAPO-34 prepared as described in this work can be an effective catalyst for the activation and utilization of CO2 in cyclic carbonate synthesis from epoxides (98%) conversion of epichlorohydrin with 96% selectivity toward cyclic carbonate.

One-step synthesis, characterization and oxidative desulfurization of 12-tungstophosphoric heteropolyanions immobilized on amino functionalized SBA-15

Keggin-type 12-tungstophosphoric [PW12O40]3− heteropolyanions were successfully immobilized onto mesoporous material surface of SBA-15 functionalized using the (3-aminopropyl)triethoxysilane (APTES) synthesized by one-pot co-condensation method, also called one-step synthesis. The synthesized PW−-NH3+-SBA-15 catalyst was characterized by XRD, N2 adsorption–desorption, FT-IR, TGA, SEM, TEM, EDS, XPS methods. The results indicated that ordered hexagonal mesostructure for SBA-15 support was still maintained after being functionalized with amine groups, while the specific surface area of SBA-15 was decreased. The active species of phosphotungstic acid H3PW12O40 (HPW) retained its Keggin structure of the heteropolyanions on the amine-modified SBA-15. The PW−–+H3N–SBA–15 catalyst exhibited a high catalytic activity for oxidative desulfurization process of sulfur-containing model fuel. The dibenzothiophene (DBT) conversion of almost 100% was achieved with reaction conditions of 40 mg of catalyst dosage, 2 mL of hydrogen peroxide, 90 °C of reaction temperature, and 120 min of reaction time.

Tailored hybrid materials for biodiesel production: Tunning the base type, support and preparation method for the best catalytic performance

Hybrid materials were prepared by the functionalization of mesoporous silica MCM-41 with 1,5,7-triazabicyclo [4.4.0] dec-5-ene (TBD) and 3-aminoquinuclidine (3AQ) by the co-condensation method, resulting in the heterogeneous catalysts MCM-41-TBD, MCM-41-3AQ. Silica gel was also functionalized with TBD and 3AQ using post-synthetic method upon the reaction with 3-chloro-propyl-triethoxy-silane and then, undergoing nucleophilic substitution with TBD or 3AQ, resulting in SG-TBD and SG-3 AQ, respectively. The successful anchoring of the organic bases on the silica supports has been shown by 29Si MAS/NMR and elemental analysis (CNH). The ordered structure of the MCM-41 support was damaged upon base functionalization. The heterogeneous catalysts were tested in the transesterification of soybean oil to produce biodiesel. MCM-41-TBD catalyst converted 100% of the soybean oil to biodiesel within 2h at 70°C, whereas the other catalysts required more severe reaction conditions to achieve conversion in the range of 24–98%. The catalysts based on grafted TBD, regardless of the type of silica used, were more active than those based on 3AQ, because of the higher basicity of the former amine. The MCM-41-TBD presented slower deactivation rate, upon reuse, compared with the same material prepared by post-synthetic methods The possible explanation is related with the higher incorporation of the base on the silica support by the co-condensation synthetic method as well as its more uniform distribution on the catalyst surface.

Ion-Imprinted Mesoporous Silica for Selective Removal of Uranium from Highly Acidic and Radioactive Effluent.

It is strategically important to recycle uranium from radioactive liquid wastes for future uranium supply of nuclear energy. However, it is still a challenge to adsorb uranium selectively from highly acidic and radioactive waste. In this paper, we report a novel strategy for effective uranium removal from highly acidic and radioactive media by surface ion-imprinted mesoporous silica sorbent. The sorbent was successfully synthesized by a co-condensation method with uranyl as the template ion and diethylphosphatoethyltriethoxysilane as the functional ligands. The pseudo-second-order model and Langmuir model showed better correlation with the sorption kinetic and isotherm data, and the sorption equilibrium could be reached within 40 min, the maximum adsorption capacity from Langmuir model was 80 mg/g in 1 mol/L nitric acid (HNO3) solution at 298.15 K. The sorbent showed faster kinetics and higher selectivity toward uranium over other ions compared with nonimprinted mesoporous and other previous sorbents. Furthermore, the ion-imprinted materials exhibited remarkable radioresistance stability and could be regenerated efficiently after five cycles. This work may provide a new approach for highly efficient sorption of uranium from strong HNO3 and radioactive media.

Performance of methylphenyl hydrogen-containing silicone oils for LED encapsulation

ABSTRACTThree-dimensional light-emitting diodes (LEDs) are the preferred light source for bulb lamps due to their 360° illumination. Addition curing silicone resins have usually been used to encapsulate LEDs. LED-filament encapsulation needs silicone resins having high thermal performance and thixotropy. Herein, a low refractive index and highly anti-thermal aging silicone oil was synthesized by hydrolysis and co-condensation method, and used to prepare an encapsulation material for high-power LED-filament. The cured silicone materials were characterized by thermogravimetric analysis (TGA) and thermal aging test under 180°C and 250°C. The results demonstrated that the thermal stability of the cured silicone resins with short-chain phenyl silicone as a crosslinker was higher than that with long-chain methyl silicone oil crosslinker. Owing to the excellent thermal stability, appropriate hardness, high transparency and photoelectric efficiency, this LED encapsulation material is a promising candidate for high-power LED package.

Effect of Silica Base Catalyst on Transformation of Methanol to Hydrocarbon

Five different types of silica catalyst (SBA-15, SBA-15-PO3H2, and three different Si/Al ratio of commercial zeolites (30, 80 and 280) were used to study the transformation of methanol to hydrocarbon (MTH). The aim of this study was to investigate the effect of pore diameter and acidity in the structure of silica catalysts on the process performances in terms of methanol conversion and hydrocarbon selectivity. The mesoporous silica catalysts were prepared by co-condensation method. The catalysts samples were characterized by GC-MS, XRD, BET, and NH3-TPD techniques. The catalytic performance of synthesized and commercial catalysts for MTH process was evaluated using a homemade fixed bed reactor at temperature (300°C). It was found that the liquid hydrocarbon product provided by zeolite catalysts is aromatic hydrocarbons-rich. High Si/Al zeolites with larger pore size lead to higher selectivity and yield to paraffins (C1-C7). In contrast to commercial zeolite catalyst, SBA-15 and its modification with phosphorus species showed no conversion under studied condition. These results indicate that both pore diameter and acidity influence the product distribution in methanol to hydrocarbon process.