Synthesis and Characterization of Silica–Polymer Nanocomposites Functionalized with Piperazine for the Synthesis of β-Nitro Alcohols

Abstract  

In order to compare the activity and selectivity for the synthesis of β-nitro alcohols, piperazine was functionalized directly and after surface modification into the ordered mesoporous SBA-15 framework. The materials were characterized by powder X-ray diffraction, N₂-adsorption–desorption isotherm, FT-IR, SS-NMR and scanning electron microscopy. The catalyst synthesized via surface modification under solvent free conditions showed very high activity and selectivity of β-nitro alcohols compared to the one synthesized by direct functionalization of SBA-15. Finally the possible reaction pathways were explained mechanistically.     

Selective Delivery of Doxorubicin to EGFR+ Cancer Cells by Cetuximab–DNA Conjugates

Doxorubicin is a hydrophobic anticancer drug that has poor selectivity, due to the lack of active targeting capability. Here, learning lessons from the success of antibody–drug conjugates, we have designed a new doxorubicin delivery system without conjugating doxorubicin to antibody directly. In this setup, cetuximab, an antibody that targets the epidermal growth factor receptor (EGFR) in cancer cells, was conjugated to a single-stranded DNA with a carefully designed sequence in a site-selective manner by using the DNA-templated protein conjugation (DTPC) method. The DNA duplex in the conjugates serves as a carrier of doxorubicin through noncovalent intercalation, and cetuximab functions as the targeting agent; this could drastically decrease systemic toxicity and potentially avoid under- or overdosing. The size of conjugates loaded with doxorubicin was about 8.77 or 16.61 nm when characterized by dynamic light scattering and atomic force microscopy, respectively. In vitro cytotoxicity and selective cancer cell killing was investigated against two EGFR⁺ cell lines (KB and MDA-MB-231) and one EGFR⁻ cell line (NIH-3T3). Cytotoxicity and flow cytometry data showed that doxorubicin loaded in cetuximab–DNA conjugates was more potent in terms of cell cytotoxicity than free doxorubicin in EGFR-overexpressed cell lines, thus suggesting that the conjugates were more selectively and easily taken up into cells, followed by rapid release of doxorubicin from the system into the cytoplasm from endosomes.     

Mesoporous Silica Functionalized by Cyclam–Metal Groups: Spectroscopic Studies and Numerical Modeling

Mesoporous silica functionalized by cyclam–metal molecules were investigated by spectroscopic methods including Raman, IR, UV–VIS absorption and EPR technique. To analyse quantitatively the physical features, numerical models were developed using the density functional theory method. Thus, the construction of molecular geometries and their optimisation analysis were achieved on the cyclam–metal molecules in vacuum as well as constrained by the host mesoporous silica matrixes. In this context and with regard to the paramagnetic nature of the metals chelated by cyclam molecules, EPR technique allows probing the metal environments which can be compared to theoretical results inferred from numerical models. The vibrational and optical properties were exhaustively investigated and the assignment of the main features was quantitatively discussed thanks to the carried out numerical analyses. The developed approach point out the possibility to define a targeted application of such functional materials based on the possibility to fine tune the absorption features in a wide wavelength range by stabilizing defined configurations of the cyclam–metal groups.     

Mesoporous Silica–Zirconia Systems for Catalytic Applications

In this study synthesis and characterization of solid acid catalysts with definite textural properties (high surface area, narrow pore size dimension, ordered structure) are described. In particular sulphated zirconia (SZ) has been introduced on three ordered mesoporous silica, MCM-41, MCM-48 and SBA-15, in order to study the influence of silica supports on textural and chemical–physical properties of final catalysts. The correlation between the catalytic behavior of SZ supported samples and their textural and chemical physical properties was studied in the liquid-phase acylation of anisole with benzoic anhydride.     

Luminescent Organic–Inorganic Hybrids of Functionalized Mesoporous Silica SBA-15 by Thio-Salicylidene Schiff Base

Novel organic–inorganic mesoporous luminescent hybrid material N,N′-bis(salicylidene)-thiocarbohydrazide (BSTC-SBA-15) has been obtained by co-condensation of tetraethyl orthosilicate and the organosilane in the presence of Pluronic P123 surfactant as a template. N,N′-bis(salicylidene)-thiocarbohydrazide (BSTC) grafted to the coupling agent 3-(triethoxysilyl)-propyl isocyanate (TESPIC) was used as the precursor for the preparation of mesoporous materials. In addition, for comparison, SBA-15 doped with organic ligand BSTC was also synthesized, denoted as BSTC/SBA-15. This organic–inorganic hybrid material was well-characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy (HRTEM), and photoluminescence spectra, which reveals that they all have high surface area, uniformity in the mesostructure. The resulting materials (BSTC-SBA-15 and BSTC/SBA-15) exhibit regular uniform microstructures, and no phase separation happened for the organic and the inorganic compounds was covalently linked through Si–O bonds via a self-assemble process. Furthermore, the two materials have different luminescence range: BSTC/SBA-15 presents the strong dominant green luminescence, while BSTC-functionalized material BSTC-SBA-15 shows the dominant blue emission.     

Promoted Hydroformylation of Formaldehyde By Electronic Metal–Support Interactions in N-Group Functionalized Silica Supported Rhodium Catalyst

Catalysis Letters - The influence of surface modification of SiO2 carrier by grafting method and its effects for Rh supporting was investigated on formaldehyde hydroformylation reaction. The...     

Confined Iron Nanoparticles on Mesoporous Ordered Silica for Fischer–Tropsch Synthesis

Iron oxide particles were deposited in an ordered mesoporous material (SBA-15) with the aim of studying its behavior in the catalytic hydrogenation of CO (Fischer–Tropsch Synthesis). Bulk iron oxide, and iron supported on porous silica with different textural properties (Aerosil^®-200) were used for comparison. The characterization of the materials showed that in the Fe@SBA-15 material, iron nanoparticles were confined inside the mesopores of the SBA-15 support (pore diameter ~?8 nm), and Fe@Aerosil^®-200 material also presented iron oxide nanoparticles highly dispersed on the material. In situ Synchrotron radiation XRD studies were performed in order to study the evolution of iron phases in the Fe@SBA-15 and the bulk iron oxide under hydrogen and hydrogen/carbon monoxide conditions. DFT calculations were performed on bare Fe(100) and a Fe₁₆ cluster in CO activation and C_xH_y hydrogenation. Catalytic microactivity tests, performed at conversions of ~?6–8%, showed important differences in the selectivity of the materials. Higher selectivity to methane and light hydrocarbons were observed in the supported catalysts (Fe@SBA-15 and Fe@Aerosil^®-200) than in bulk Fe catalyst. Moreover, the supported catalysts showed selectivity to ethylene (Fe@SBA-15) and propylene (Fe@Aerosil^®-200), products that were not observed in the bulk iron catalyst. On the other hand, bulk iron showed a major selectivity to higher hydrocarbons (C₅–C₉) and oxygenates.

     

Sol–Gel Assisted Preparation of Chromia–Silica Catalysts for Non-Oxidative Dehydrogenation of Propane

Preparation of continuous silica gel in the presence of dissolved Cr(NO₃)₃ leads to a hard high surface area (710 m²/g) microporous xerogel. Formation of the gel in the pore structure of mesoporous Pore-Expanded MCM-41 (PE-MCM-41) and macroporous commercial Cab–O–Sil silica results in retention of the mesoporous structure in the case of PE-MCM-41, and the formation of a powder with a broad pore size distribution in the case of Cab–O–Sil silica. Comparison of the catalytic activities in non-oxidative dehydrogenation of propane revealed a linear correlation of the initial conversion with the surface area for all three samples. The sample prepared from PE-MCM-41 through a sol–gel assisted procedure was the most active, particularly with respect to the catalysts prepared by simple wet impregnation with chromium nitrate.     

Pd(II)/Pd(0) Anchored on Magnetic Organic–Inorganic Hybrid Mesoporous Silica Nanoparticles: A Nanocatalyst for Suzuki–Miyaura and Heck–Mizoroki Coupling Reactions

Journal of Inorganic and Organometallic Polymers and Materials - 3-Chloropropyltrimethoxysilane (CPTMS) was grafted on the surface of silica coated Fe3O4 core (Fe3O4@MCM-41) and then condensed with...     

Magnetic Zinc Ferrite–Alginic Biopolymer Composite: As an Alternative Adsorbent for the Removal of Dyes in Single and Ternary Dye System

Recently, magnetic bio-composites as adsorbent are widely being explored in waste water treatment because of their exceptional properties like high adsorption capacity, selectivity and cost-effective nature. In the present study, a novel recyclable magnetic composite containing magnetic zinc ferrite and alginate in alginic form (ZnFN–Alg) was developed. Various techniques like Fourier Transform-Infra Red, X-ray diffraction, transmission electron microscope with energy dispersive spectra, Brunauer–Emmett–Teller, thermo gravimetric-differential thermal analysis and Point Zero Charge (pH_zpc) were used to characterize the surface morphology of magnetic composite. The magnetic composite was used as adsorbent to remove congo red, crystal violet and brilliant green dyes in single and ternary systems. The kinetic studies data was best fitted to Lagergren pseudo second order whereas mechanism of adsorption was described by intra particle diffusion model in single as well as ternary systems. The adsorption equilibrium data was best fitted to Langmuir isotherm among various adsorption isotherm models. Thermodynamic studies confirmed that the adsorption process was spontaneous in nature. The regeneration ability of ZnFN–Alg composite was studied individually in single and ternary dye systems for seven cycles and showed significant results. It was concluded that magnetic ZnFN–Alg can serve as suitable alternative for the removal of dyes in single and ternary systems.     

One-Pot Synthesis of Spiro[chromeno[2,3-c]pyrazole-4,3′-indoline]-diones Using Sulfonic Acid Functionalized Nanoporous Silica SBA-Pr-SO3H and Study of Their Antimicrobial Properties

A novel and clean one-pot synthesis of spiro[chromeno[2,3-c]pyrazole-4,3′-indoline]-2′,5(6H)-diones via cyclocondensation reaction of isatins, 1,3-cyclohexadiones, and pyrazolone in aqueous media using SBA-Pr-SO₃H (sulfonic acid-functionalized mesoporous silica) as an efficient heterogeneous solid acid catalyst was reported. The antimicrobial activities of synthesized compounds have been tested.     

Theoretical Analysis of d–d Transitions for the Reduced Cr/Silica System

The utilisation of high CO₂ content natural gas, such as that found at Natuna island in Indonesia, using methane dry reforming with carbon dioxide to synthesis gas is demonstrated. Highly active catalysts employed for coke-free, stable dry reforming include alumina-supported nickel, either as-prepared or doped with tungsten oxide or calcium oxide, and the supported group VIII metals. No deactivation was observed for the duration of any of the experiments (>70 h), and the methane conversion and product distributions were close to those predicted from thermodynamic equilibrium calculations. It is calculated that the application of dry reforming to the Natuna field alone, combined with known gas-to-liquids (GTL) technology, could provide liquid fuel to Indonesia for almost 18 years.     

CuI Immobilized on Tricationic Ionic Liquid Anchored on Functionalized Magnetic Hydrotalcite (Fe3O4/HT-TIL-CuI) as a Novel,Magnetic and Efficient Nanocatalyst for Ullmann-Type C–N Coupling Reaction

One of the most important reactions in organic synthesis is Ullmann-type C–N coupling reaction which has been used for preparation of numerous biologically active compounds. In this work, CuI immobilized on tricationic ionic liquid anchored on functionalized magnetic hydrotalcite (Fe₃O₄/HT-TIL-CuI) has been successfully prepared and fully characterized by different techniques, including fourier-transform infrared spectroscopy, vibrating sample magnetometer, thermo gravimetric analysis, transmission electron microscopy, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, elemental mapping, zeta potential, X-ray diffraction, temperature programmed desorption of ammonia (NH₃-TPD), temperature-programmed reduction and inductively coupled plasma. The results showed that the as-prepared nanocatalyst possesses plate-like morphology with approximate size of 50 nm and superparamagnetic behavior. Also, total acidity and total hydrogen consumption of the nanocatalyst were measured to be 8.5 and 1.41 mmol g^?1, respectively. This nanocatalyst exhibited favorable performance for C–N coupling reaction among a variety of aryl halides and N(H)-heterocycles (benzimidazoles, pyrazoles and triazoles) in the presence of 2.5 mol% of nanocatalyst without any additives under air atmosphere revealing high yields in all cases. Besides, it is noted that in the present system the desired product can be easily and quickly isolated and nanocatalyst also recovered magnetically from the reaction mixture employing a permanent magnet for at least six consecutive trials without a discernible decrease in catalytic activity which makes the proposed methodology appropriate for industrial. The findings demonstrated the advantages of the present method as no need for neutral atmosphere, appropriate times, recyclability of the catalyst, broad substrate scope, minimization of chemical waste, simple purification of products, easy workup process, and high yields.

     

Titanium–Silica Catalysts for the Production of Fully Epoxidised Fatty Acid Methyl Esters

Grafted titanium-containing mesoporous silica catalysts were used in the selective epoxidation of C-18 unsaturated fatty acid methyl esters (FAMEs). High yields in mono- and diepoxide derivatives were obtained under acid-free reaction conditions with TBHP as oxidant. Ti-MCM-41 showed the best performance in terms of activity over the three FAMEs. Easy separation of the desired products and recycling of the catalyst were demonstrated.     

Slow-Release of Curcumin Induced by Core–Shell Mesoporous Silica Nanoparticles (MSNs) Modified MIL-100(Fe) Composite

As a biocompatible porous material, bio-MOF is a very promising material as a carrier for hydrophobic drugs, including curcumin. However, the stability of bio-MOF against water and humidity still needs to be improved; therefore, surface modifications are required. This study aims to modify the MIL-100(Fe)-based bio-MOF through core–shell architecture by employing mesoporous silica nanoparticles (MSNs or SiO₂) for improving the stability and performance of MIL-100(Fe) to provide a slow-release feature of curcumin. The composites were synthesized via sonochemistry-assisted or mechanochemistry-assisted green protocol to form core–shell structure of MIL-100(Fe)@SiO₂ (Composite-1) or SiO₂@MIL-100(Fe) (Composite-2). Structural, textural, and morphological analyses, including XRD, FTIR, SEM, TEM, and N₂ adsorption–desorption, are discussed in this study to evaluate the composite formation. BET surface area of the MIL-100(Fe) decreased from 1197.45 m²/g to 565.63 and 823.70 m²/g after forming composite-1 and composite-2 with SiO₂. The loading capacity, however, just increased slightly up to 97.89% after the modification. The presence of SiO₂ as shell (composite-1) protects the MIL-100(Fe) from degradation under the acidic condition at pH 5.8 and can maintain the slow-release of curcumin. In contrast, the presence of SiO₂ as core (composite-2) induces the sustained release due to faster degradation of MIL-100(Fe) in acidic condition. Both composites serve as a model for either sustained release or delayed release drug delivery systems.