Surface Si OH Research Articles

PdCl2-FeCl3-imidazolium ionic liquid immobilized SBA-15 for boosting heterogeneous Wacker oxidation of styrene

PdCl2-FeCl3-imidazolium ionic liquid immobilized SBA-15 (SIL-PdFe) was prepared via chloropropyltriethoxysilane grafting with the surface Si-OH and N-methyl imidazole with C-Cl bond, followed by PdCl2 and FeCl3 coordinating to imidazolium ring. The SIL-PdFe was used as a heterogeneous catalyst for solvent-free Wacker oxidation of styrene with H2O2 oxidant, exhibiting high catalytic performance with styrene conversion of 95.4% and 87.7 % selectivity (54.2% acetophenone and 33.5% benzaldehyde). The catalyst can be easily recovered and effectively reused without a significant loss in the activity and selectivity. The quenching experiments by adding tert-butanol (TBA), 1,4-benzoquinone (p-BQ) and furfural alcohol (FA) in the reaction system were conducted to identify kind of the reactive O species produced by the catalyst activating H2O2 and the reaction mechanism of the Wacker oxidation was then proposed.

Sensitive quantification of the surface Si–OH group in MQ silicone resins by benzoylation and GPC−UV analysis

The content of the Si–OH group markedly affects the physical and chemical properties of MQ silicone resin (MQ) and its secondary processing products. However, current methods for the determination of the Si–OH group are still unsatisfactory due to their insensitivity and inaccuracy. Herein, an accurate analytical method has been developed for the determination of the active Si–OH group in MQ based on benzoylation and GPC–UV analysis. The UV-insensitive Si–OH group in MQ was converted to a UV-sensitive benzoyl group by the benzoylation with p-methoxy benzoyl chloride, which greatly improved its detection sensitivity. The interference of water was also excluded by the introduction of GPC separation. The effect of several derivatization parameters was investigated and optimized, and complete benzoylation of the Si–OH group in MQ was achieved under the optimized experimental parameters. Good linearity was obtained in a range of 0.425–42.5 μg/g for the content of the Si–OH group in MQ, with a correlation coefficient greater than 0.999. Reasonable reproducibility was also obtained, with the intraday RSD (N = 3) of 1.78 % and the interday RSD (3 days) of 3.98 %, respectively. This method has been successfully applied for the determination of the active Si–OH group in several commercial MQs.

(Invited) Bonding Strength of Cu-Cu Hybrid Bonding for 3D Integration Process

Introduction Cu-Cu hybrid bonding is a significant technology in the manufacture of 3D stacked semiconductor devices and is indispensable for the integration of 3D heterogeneous stacked packages.1 A process is used to thin the bonded semiconductor during 3D stacking integration, but delamination can occur when the bonding strength of the bonded interface is insufficient.Therefore, the bonding strength is a key factor in the 3D stacked integration process, and mechanisms for improving the strength have been thoroughly investigated. Cu-Cu hybrid bonding strength During Cu-Cu hybrid bonding, the bonding strength between bonded wafers, which is a crucial factor, is complicated to describe because of the various materials contained in the bonding interface. Because the bonding interface includes not only Cu/Cu and dielectric/dielectric films, but also Cu/dielectrics as a result of the misalignment of Cu pads, the strength of the Cu-Cu hybrid bond needs to comprehensively account for these interfaces. We investigated the relationship between the bonding strength and amount of misalignment using patterned Si substrates that were bonded after intentionally being aligned with an offset and thermally annealed.Although the bonding strength before annealing was confirmed to decrease lineally depending on the amount of misalignment, the wafers showed a different behavior after annealing in the region where the amount of misalignment was low. Simulation calculations elucidated the behavior of the overall bonding strength. When a Cu pad with a large recess contacted the opposing Cu pad, an uneven amount of pressure was generated between their contact surfaces because of the thermal expansion produced by the annealing. An area with very low pressure was also found between the surfaces, and extremely little or no diffusion occurred in this area.2 This phenomenon was not observed in a case where the amount of recess was small in both the experiments and simulation calculations, which showed linear relationships dependent on the misalignment after annealing.This study determined the misalignment dependence of the bonding strength after annealing considering the recess of the Cu pad, and an integrated model of the comprehensive bonding strength that included three interfaces involved in the Cu-Cu hybrid bonding could be presented. Improvement of bonding strength between dielectric films We are also continuing to study ways to improve the bonding strength of the interface between the dielectrics films that exist in the interfaces of a Cu-Cu hybrid bond. Elucidating the mechanism of strength generation would offer a guideline to improve the bonding strength.The dielectric films are bonded using a dehydration condensation reaction on the plasma-activated surface by thermal annealing. This bonding process has been widely studied from the perspective of the amount of surface Si-OH by considering the activation method and condition, type of dielectrics, and flatness of the surface. Because few investigations have considered factors other than the bonding interfaces, we focused on the influence of the H2O contained in the dielectric film to be bonded and investigated the relationship between the amount of H2O in the film and the bonding strength.The deposition conditions of the dielectric films produced using Plasma Enhanced Chemical Vapor Deposition (PE-CVD) were varied to prepare five types of films that contained various amounts of H2O. After CMP treatment of each film, the surface roughness and amount of Si-OH were measured, and it was confirmed that there was no significant difference. When the bonding strength was obtained by bonding using these films and plotted against the amount of H2O, it was found that the bonding strength was dependent on the amount of H2O. In addition, after being bonded and annealed, it was confirmed that the expansion of the dielectric film depended on the amount of H2O, as seen in cross-sectional STEM images of the interface.An investigation of the mechanism for this phenomenon suggested that the bonding strength was increased by filling the gap in the bonding interface through the expansion of the film. This study suggested that filling up the gap in the interface would be one approach for improving the bonding strength.These results offer a deep understanding of the mechanism for the bonding strength of Cu-Cu hybrid bonds and will contribute to the development of 3D stacking technology in the future.

Siliplant1 B-domain precipitates silica spheres, aggregates, or gel, depending on Si-precursor to peptide ratios

Silica is extensively deposited by plants, however, only little is known about the molecular control over this process. Siliplant1 is the only known plant protein to precipitate biosilica. The protein contains seven repeats made of three domains. One of the domains exhibits a conserved sequence, which catalyzes silica precipitation in vitro. Here, silica was synthesized by the activity of a peptide carrying this conserved sequence. Infrared spectroscopy and thermal gravimetric analyses showed that the peptide was bound to the mineral. Scanning electron microscopy showed that silica-peptide particles of 22 ± 4 nm aggregated to spherical structures of 200–300 nm when the ratio of silicic acid to the peptide was below 183:1 molecules. When the ratio was about 183:1, similar particles aggregated into irregular structures, and silica gel formed at higher ratios. Solid-state NMR spectra indicated that the irregular aggregates were richer in Si-O-Si bonds as well as disordered peptide. Our results suggest that the peptide catalyzed the condensation of silicic acid and the formation of ∼20 nm particles, which aggregated into spheres. Excess of the peptide stabilized surface Si-OH groups that prevented spontaneous Si-O-Si bonding between aggregates. Under Si concentrations relevant to plant sap, the peptide and possibly Siliplant1, could catalyze nucleation of silica particles that aggregate into spherical aggregates.

Tuning the 1O2 Oxidation of a Phenol at the Air/Solid Interface of a Nanoparticle: Hydrophobic Surface Increases Oxophilicity.

Although silica surfaces have been used in organic oxidations for the production of peroxides, studies of airborne singlet oxygen at interfaces are limited and have not found widespread advantages. Here, with prenyl phenol-coated silica and delivery of singlet oxygen (1O2) through the gas phase, we uncover significant selectivity for dihydrofuran formation over allylic hydroperoxide formation. The hydrophobic particle causes prenyl phenol to produce an iso-hydroperoxide intermediate with an internally protonated oxygen atom, which leads to dihydrofuran formation as well as O atom transfer. In contrast, hydrophilic particles cause prenyl phenol to produce allylic hydroperoxide, due to phenol OH hydrogen bonding with SiOH surface groups. Mechanistic insight is provided by air/nanoparticle interfaces coated with the prenyl phenol, in which product yield was 6-fold greater on the hydrophobic nanoparticles compared to the hydrophilic nanoparticles and total rate constants (ASI-kT) of 1O2 were 13-fold greater on the hydrophobic vs hydrophilic nanoparticles. A slope intersection method was also developed that uses the airborne 1O2 lifetime (τairborne) and surface-associated 1O2 lifetime (τsurf) to quantitate 1O2 transitioning from volatile to non-volatile and surface boundary (surface···1O2). Further mechanistic insights on the selectivity of the reaction of prenyl phenol with 1O2 was provided by density functional theory calculations.

Molecular Dynamics Study on the Reaction of RDX Molecule with Si Substrate.

RDX is widely used in various explosion situations, and there are many studies on its detonation performance, safety, preparation, etc. Research on preparation of β-RDX is mainly conducted by experiments. In recent years, part of the research points to the use of substrate as a medium to produce β-RDX faster. Based on this guidance, our work aims to theoretically solve the physical and chemical processes that RDX may experience in the production process through numerical simulation. In this work, molecular dynamics simulation is set up for the interaction between RDX and a Si clean surface and a Si hydroxyl saturated surface separately, and a higher precision simulation is set up to verify the reliability of the results. NCI analysis is also used to guess the possible phase transition mechanism in the simulation results. In the simulation process, a 7 × 7 Si clean surface, a 3 × 3 Si clean surface, and a 7 × 7 Si-OH surface are set, and each surface adsorbs one α-RDX. The semiempirical Gfn1-xtb method is used for the 7 × 7 surface, and the DFT method is used for the 3 × 3 surface. The calculation results confirmed by high-precision results show that RDX molecules will react with the dangling bonds on the Si surface. Three conformations of RDX were found on the hydroxyl saturated surface of Si. The isosurface generated by the NCI method is used to analyze the reasons for the formation of these conformations.

Continuous-flow synthesis of amphiphilic rhodamine B-polymethylsilsesquioxane fluorescent microspheres for micro-PIV analysis

• Rhodamine B- polymethylsilsesquioxane fluorescent microspheres were prepared. • Synthetic process was performed in a one-step continuous-flow microreaction system. • The hydrophilic and hydrophobic RhB-PMSQ microspheres were synthesized. • Amphiphilic RhB-PMSQ particles were used as tracer particles for micro-PIV analysis. Tracer particle is a key element in the micro-PIV flow field measurements. The oil-dispersible tracer particles are mainly obtained by post modification, resulting in relatively poor uniformity and dispersibility. In this work, we developed a molecular-level amphiphilic tracer particle, i.e., rhodamine B-polymethylsilsesquioxane (RhB-PMSQ) fluorescent microspheres. The RhB-PMSQ microspheres were synthesized in a continuous-flow microreaction system with the aqueous solution of NH 4 OH and RhB as the continuous phase and methyltrimethoxysilane (MTMS) as the dispersed phase. The microreaction system consisted of a T -junction micromixer, a capillary reactor for MTMS hydrolysis, and a millimeter-scale tubular reactor for condensation reaction. By controlling the condensation degree of surface Si-OH groups, the hydrophilic and hydrophobic RhB-PMSQ microspheres could be synthesized with the same reaction system, and they could be uniformly dispersed in the aqueous phase and oil phase, respectively. The density, pore structure, and fluorescence property of the RhB-PMSQ microspheres were investigated in detail. The RhB-PMSQ microspheres were employed as the tracer particles of water and liquid paraffin, and the two-phase velocity profiles were measured via micro-PIV technique in a step T -junction microchannel. The micro-PIV results indicated that amphiphilic RhB-PMSQ microspheres could serve as the tracer particles for the flow field measurement both of aqueous phase and oil phase.

Study chemical reaction of –Si–OH surface layer by solid and ionic form to surface quality when polishing with chemical–mechanical slurry

The yttrium aluminium garnet (YAG) and sapphire materials are commonly used in laser and optical devices. Producing an ultra-precise surface quality is necessary for the application in optical devices. However, YAG and sapphire materials belong to difficult-to-machine materials with high brittleness and hardness. Therefore, ensuring the main criterion of producing a quality surface in the nanometre form with the ability to remove the material when finishing this material is challenging. Eliminating machining residues using chemical–mechanical slurry (CMS) is essential in creating ultra-precise components in optical devices. Based on this feature, this work investigates the efficiency of the CMS polishing process by comparing the surface reaction modes with the ionic and solid reaction modes when polishing YAG and sapphire materials. The study procedures aim to clarify the polishing performance corresponding to these two reaction types. Experimental analyses show the balance between CMS polishing technology’s mechanical and chemical effects with the ionic reaction model that can be generated. Results also show that the ionic surface reaction modes give more uniform material removal than the solid reaction on YAG and sapphire crystal surfaces. Therefore, when polished by CMS technology with ionic surface reaction modes, the surface quality is better than solid reaction. In the CMS polishing with ionic responses, adding more Na2SiO3–5H2O content to the CMS is necessary if the chemical reaction is weak. This process will facilitate the –Si–OH components to be more distributed on the workpiece’s surface, thereby improving reaction speed and correcting the balance between mechanical and chemical in polishing by CMS. This balance action results in an ultra-smooth YAG crystal surface without scratches, with a roughness obtained in the nanometre form (Ra = 1.031 nm) after polishing by CMS-2.

Surface acidity of colloidal silica and its correlation with sapphire surface polishing

Colloidal silica occupies the field of polishing solution application of chemical mechanical polishing (CMP). Si-OH groups dominate the surface of colloidal silica nanoparticles, and their chemical nature, acidity, is a determining factor for CMP. However, due to the delicate nature, very vulnerable to self-condensation at elevated temperatures, of colloidal silica nanoparticles, traditional techniques used for characterizing powder samples are limited to gaining true insights into the chemical reactivity of these Si-OH groups without disturbing the surface chemistry, which hinders the deep exploration of the essential mechanism of CMP on silica. In this manuscript, low-field nuclear magnetic resonance (LF NMR) and freeze-drying-programmed temperature desorption (TPD) techniques were, for the first time, combined to investigate the true acidity of the surface Si-OH groups in colloidal silica with minimized perturbance from sample preparations. The results from both characterization methodologies complemented each other, and are in good agreement about the surface structure and acidity of the surface Si-OH groups on colloidal silica. The results demonstrate that the acidity of Si-OH hydroxyl groups on the surface of silica-soluble nanoparticles spreads in a very broad range from very weak, medium-strong, to very strong. CMP performance of sapphire substrates by using colloidal silica strongly correlates with the acidic nature of surface Si-OH groups at the acidic polishing condition. The stronger acidity of surface Si-OH groups, the higher material removal rates in sapphire polishing through the chemical bonding of deprotonated Si-O- functional surface of colloidal silica with hydrolyzed sapphire Al-OH surface. Therefore, when a large number of Si-O- active centers in the basic environment attack the sapphire Al-OH sites, the rate of the chemical reaction is accelerated.

Connecting Thermodynamics of Alkali Ion Exchange on the Quartz (101) Surface with Density Functional Theory Calculations.

Periodic plane-wave density functional theory (DFT) calculations were performed on the α-quartz (SiO2) (101) surface to model exchange of adsorbed Li+ and either Na+, K+, or Rb+ in inner- and outer-sphere adsorbed, and aqueous configurations, which are charge-balanced with 2 Cl-. SiO- or SiOH groups represented the adsorption surface sites. The SiO- models included 58 H2O and 2 H3O+ molecules to approximate an aqueous environment, whereas the SiOH models had 59 H2O and 1 H3O+ molecules. The goal of this work is to calculate the heats of exchange for these alkali ions and to compare the results with those measured by flow microcalorimetry to ascertain the most probable mechanisms for these cations exchanging on the α-quartz (101) surface. Energy minimizations of each alkali ion adsorbed as outer-sphere complexes on SiOH surface sites, and as inner- and outer-sphere complexes on SiO- surface sites, were used to determine the energy of exchange (ΔEex) with Li+ for comparison with experimentally determined ΔHex values. Here, we present a novel method for calculating ΔEex using the difference in energies of geometry-optimized end member models. The aqueous and surface structures produced are similar to those observed experimentally. Although the trend for the calculated ΔEex values is consistent with those from the heats of exchange measured experimentally, the magnitude of our modeled ΔEex results is significantly larger than select experimental data from the literature [Peng, L. Zeta-Potentials and Enthalpy Changes in the Process of Electrostatic Self-Assembly of Cations on Silica Surface. Powder Technol. 2009, 193(1), 46-49]; we discuss the reasons for this discrepancy herein. The relative energy differences of the various configurations modeled have implications for the measurements of the surface charge via potentiometric titrations due to the more active role of alkali cations in quartz surface chemistry that have been previously considered as inert background electrolytes.

Olefin-Surface Interactions: A Key Activity Parameter in Silica-Supported Olefin Metathesis Catalysts.

Molecularly defined and classical heterogeneous Mo-based metathesis catalysts are shown to display distinct and unexpected reactivity patterns for the metathesis of long-chain α-olefins at low temperatures (<100 °C). Catalysts based on supported Mo oxo species, whether prepared via wet impregnation or surface organometallic chemistry (SOMC), exhibit strong activity dependencies on the α-olefin chain length, with slower reaction rates for longer substrate chain lengths. In contrast, molecular and supported Mo alkylidenes are highly active and do not display such dramatic dependence on the chain length. State-of-the-art two-dimensional (2D) solid-state nuclear magnetic resonance (NMR) spectroscopy analyses of postmetathesis catalysts, complemented by Fourier transform infrared (FT-IR) spectroscopy and molecular dynamics calculations, evidence that the activity decrease observed for supported Mo oxo catalysts relates to the strong adsorption of internal olefin metathesis products because of interactions with surface Si–OH groups. Overall, this study shows that in addition to the nature and the number of active sites, the metathesis rates and the overall catalytic performance depend on product desorption, even in the liquid phase with nonpolar substrates. This study further highlights the role of the support and active site composition and dynamics on activity as well as the need for considering adsorption in catalyst design.

Synthesis of Amphiphilic Silica with High Exposure of Surface Groups and Its Utilization in Efficient Removal of Organic Dyes from Aqueous Solution

AbstractAmphiphilic silica is synthesized with the simultaneous introduction of two kinds of polar and weakly polar organic groups on its surface using a one‐step reverse‐phase microemulsion method. The obtained materials present as nanospheres with a size of ≈100 nm. A high percentage (≈80%) of silicon species can be exposed and the amount of surface SiOH increased by above 50% with the introduction of organic groups. Plenty of groups, including polar groups (3‐aminopropyl and hydroxyl) and weakly polar group (n‐propyl) coexisting on the surface, enable the material to show amphiphilicity. This amphiphilic material can show an excellent property for the removal of various organic dyes from the aqueous solution, and the maximum adsorption capacity of Congo Red, Acid Blue 25, Reactive Blue 19, and Reactive Black 5 can reach 2453.1, 1157.7, 964.6, and 916.9 mg g−1, respectively. Good reusability is also realized for the present amphiphilic material, which can be reused for at least three times. The reported work provides a successful example to prove that the surface hydrophilicity and lipophilicity can be simultaneously improved just through a simple introduction of certain organic groups, and then realize efficient removal of dyes from the polluted water.

Polyol-pretreated SBA-16 supported Ni-Fe bimetallic catalyst applied in CO methanation at low temperature

• Polyols were used to pretreat the mesoporous silica molecular sieve SBA-16 to adjust the surface groups. • Bimetallic Ni-Fe catalysts with polyol-pretreated support were obtained. • The mechanism of how the polyols influence the surface SiOH groups and thus the metal particles distribution was figured out. • Catalysts with polyol-pretreated support lowered the minimum temperature for CO complete conversion to 230 °C from 290 °C. Polyols were used to pretreat the mesoporous silica molecular sieve SBA-16 and thus supported bimetallic Ni-Fe catalyst was prepared in order to address the low activity of CO methanation at lower temperature. The characterization of the pretreated support and catalysts indicated that the residual polyols release heat during combustion, which could provide energy for the decomposition of metal precursors, lowering the decomposition temperature and reducing the metal particle size. More importantly, the pretreatment of support with polyols could increase the isolated silicon hydroxyl, and strengthen the metal-support interaction, thus obtaining smaller metal particles. The smaller metal particles promoted the dissociation of reactant gas, as a result, Ni-Fe bimetallic catalyst with polyol-pretreated support could lower the minimum temperature for CO complete conversion from 290 °C to 230 °C while keeping CH 4 selectivity above 90%. Catalysts with polyol-pretreated support provide a new possibility for low-temperature CO methanation technology.

Fischer-Tropsch to olefins over Co2C-based catalysts: Effect of thermal pretreatment of SiO2 support

SiO2 supported Co2C-based catalysts were used for Fischer-Tropsch to olefins (FTO), and the effect of thermal pretreatment of SiO2 support under different temperatures on the Co2C morphology and catalytic performance was investigated. It was found that the interaction between cobalt and support was weakened when SiO2 was pretreated at high temperature (990 °C) due to the decreased content of surface SiOH groups. The relative weak interaction between cobalt and support benefited the formation of cobalt manganese composite oxide after calcination and reduction, and thus promoted the generation of Co2C nanoprisms with promising FTO performance. In contrast, for the SiO2 support pretreated at 350 °C or 650 °C, the strong interaction between cobalt and support led to phase separation of cobalt and manganese. As a result, only Co2C nanospheres were generated which displayed low activity and high methane selectivity.

The chemistry of spin-coated rhodium-ferrocenyl complexes supported on silanol-capped silicon wafers

A series of rhodium β-diketonato complexes [Rh(FcCOCHCOR)(CO)2] and [Rh(FcCOCHCOR)(CO)(PPh3)] with R = CF3, CH3, Ph = C6H5 and Fc (ferrocenyl = FeII(C5H5)(C5H4)) were spin-coated on two-dimensional silanol-functionalised silicon wafers. Chemical reactions were observed that do not occur in ethanol solutions. Si-OH fragments on the wafers substituted ligands and oxidatively added to the Rh(I) centres. A multitude of different surface species could be identified with X-ray photoelectron spectroscopy (XPS). These included the parent spin-coated rhodium(I) complexes and rhodium(I) species that resulted from β-diketonato displacement from parent rhodium complexes by surface silanol OH’s to generate [wafer-(O)2-Rh-(CO)2]⊝ and [wafer-(O)2-Rh-(CO)(PPh3)]⊝ units. Several RhIII surface species that inter alia resulted from oxidative addition of surface Si-OH groups to surface-coordinated RhI core atoms were also identified. Efficacy of β-diketonato ligand substitution by the silanol surfaces is a kinetically driven process and can be related to the rate of solution-phase β-diketonato substitution by 1,10-phenanthroline from parent [Rh(FcCOCHCOR)(CO)2] and [Rh(FcCOCHCOR)(CO)(PPh3)] complexes. The binding energies of the RhI and RhIII 3d5/2 photoelectron lines were found to be functions of Gordy scale R-group electronegativities and they are also linearly related to electrochemically determined RhI oxidation potentials.

Template-free synthesis of hybrid silica nanoparticle with functionalized mesostructure for efficient methylene blue removal

A simple one-pot synthesis process for functionalized mesostructured silica nanoparticles (MSNP) is reported. The novel process demonstrated the possibility to achieve MSNP with a surface area up to 501 m2.g−1 using a phosphonate based nonsilane precursor such as N, N´-bis[4,6-bis(diethylphosphono)-1,3,5-triazin-yl]-1,2-diaminoethane (ED). MSNP obtained by using 20 mol% of ED achieved a surface area of 80 m2.g−1 and increasing the ED content to 30 mol% resulted in a surface area of 501 m2.g−1. Zeta potential of novel MSNPs (−65.5 and 70.0 mV) were much higher than the nanoparticle (NP) prepared from only TEOS (−49 mV), indicating the presence of a large number of –SiOH and phosphonic acid surface functional groups, as confirmed by Fourier-transform infrared spectroscopy (FT-IR) and Nuclear magnetic resonance (NMR) analysis. The functionalized MSNPs were used as an adsorbent for the removal of cationic pollutants like methylene blue (MB). The MSNP with the highest porosity displayed favorable MB adsorption behavior with ~380 mg.g−1 of MB adsorption capacity. Facile regeneration in an acidic medium (~pH 4.5) with easy recyclability (10 cycles) confirmed the practical applicability of this novel functionalized MSNPs.

Template-Free Synthesis of Hybrid Silica Nanoparticle With Functionalized Mesostructure for Efficient Methylene Blue Removal

A simple one-pot synthesis process for functionalized mesostructured silica nanoparticles (MSNP) is reported. The novel process demonstrated the possibility to achieve MSNP with a surface area up to 501 m2.g−1 using a phosphonate based nonsilane precursor such as N, N´-bis[4,6- bis(diethylphosphono)-1,3,5-triazin-yl]-1,2-diaminoethane (ED). MSNP obtained by using 20 mol% of ED achieved a surface area of 80 m2.g−1 and increasing the ED content to 30 mol% resulted in a surface area of 501 m2.g−1. Zeta potential of novel MSNPs (-65.5 and -70.0 mV) were much higher than the nanoparticle (NP) prepared from only TEOS (-49 mV), indicating the presence of a large number of –SiOH and phosphonic acid surface functional groups, as confirmed by Fouriertransform infrared spectroscopy (FT-IR) and Nuclear magnetic resonance (NMR) analysis. The functionalized MSNPs were used as an adsorbent for the removal of cationic pollutants like methylene blue (MB). The MSNP with the highest porosity displayed favorable MB adsorption behavior with ~380 mg.g−1 of MB adsorption capacity. Facile regeneration in an acidic medium (~pH 4.5) with easy recyclability (10 cycles) confirmed the practical applicability of this novel functionalized MSNPs.

Synthesis of hyaluronated poly(exo-7-oxabicyclo[2.2.1]hept-5-en-2,3-dicarboxylic anhydride) brushes via a combination of surface-initiated ring-opening metathesis polymerization and thiol-ene click reaction

Well-defined hyaluronated poly(exo-7-oxabicyclo[2.2.1]hept-5-en-2,3-dicarboxylic anhydride) [poly(EHDA)-HA] brushes on the hydroxyl-terminated silicon (Si–OH) surface were prepared through the combination of surface-initiated ring-opening metathesis polymerization (ROMP) and thiol-ene click reaction. This process was realized in four successive steps: (i) formation of self-assembled monolayer of (3-aminopropyl) triethoxysilane on the Si–OH surface (Si-APTES), (ii) bonding of EHDA monomer to the Si-APTES surface, (iii) synthesis of poly(EHDA) brushes via surface-initiated ROMP and (iv) coupling of thiolated hyaluronic acid (Th-HA) to poly(EHDA) chains via thiol-ene click reaction. Surface wettability, surface morphology and chemical compositions of poly(EHDA)-HA brushes were characterized by contact angle measurements, atomic force, microscopy and X-ray photoelectron spectroscopy, respectively. Grafting density (σ, chains nm−2) and average distance between grafting points (D, nm) of the poly(EHDA) brushes were measured to be 0.50 chains nm−2 and 1.65 nm, independent of the [catalyst]/[monomer] ratios, which indicated that high grafting was created on the silicon substrate. However, low amounts of HA molecules were bonded to poly(EHDA) chains due to the high volume of Th-HA chains creating some steric hindrances. Biocompatible property of the poly(EHDA)-HA brushes are useful candidate for making advanced biological devices to control the behavior of biomolecules on surfaces.

Accessibility and strength of H-acceptor hydroxyls of ordered mesoporous silicas probed by pyridine donor

Ordered mesoporous silica (OMS) is an important and useful material for a variety of applications, including catalysis, adsorption, sensing and controlled drug delivery. The surface chemistry and the silanol groups on OMS pores are key properties for the potential modification and application of this material. This research aimed to synthesize (using standard protocols) and differentiate the accessibility and strength of the H-acceptor Si–OH from FDU-12, SBA-16, MCM-41 and SBA-15 by pyridine (Py) donor, where the first two have cubic pore structures and the last two have hexagonal pore structures. Donor–acceptor properties were assessed by calculation of the surface Si–OH densities by thermogravimetry (TG), H2O-TPD/MS, and 29Si MAS and CP/MAS NMR. The nature of the Si–OH groups on these materials was determined to be hydrogen-bonding sites using FT-IR spectroscopy of Py adsorption. The reactivity of these silanol groups was probed by Py-TG and slurry microcalorimetry of Py adsorption in cyclohexane. Differences in accessibility and reactivity were discussed considering the total potential sites on the surface (nOH) versus the actual sites that can react with the Py molecule (nPy). By using microcalorimetry, it was possible to quantitatively distinguish the strength of the sites: The acidity order was approximately the same as the relative amount of silanol groups (Si–OH) and Py on the surface of the OMS materials (αPy): FDU-12 > MCM-41 ≥ SBA-16 > SBA-15.

Study of the Microstructure of Amorphous Silica Nanostructures Using High-Resolution Electron Microscopy, Electron Energy Loss Spectroscopy, X-ray Powder Diffraction, and Electron Pair Distribution Function.

Silica has many industrial (i.e., glass formers) and scientific applications. The understanding and prediction of the interesting properties of such materials are dependent on the knowledge of detailed atomic structures. In this work, amorphous silica subjected to an accelerated alkali silica reaction (ASR) was recorded at different time intervals so as to follow the evolution of the structure by means of high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), and electron pair distribution function (e-PDF), combined with X-ray powder diffraction (XRPD). An increase in the size of the amorphous silica nanostructures and nanopores was observed by HRTEM, which was accompanied by the possible formation of Si–OH surface species. All of the studied samples were found to be amorphous, as observed by HRTEM, a fact that was also confirmed by XRPD and e-PDF analysis. A broad diffuse peak observed in the XRPD pattern showed a shift toward higher angles following the higher reaction times of the ASR-treated material. A comparison of the EELS spectra revealed varying spectral features in the peak edges with different reaction times due to the interaction evolution between oxygen and the silicon and OH ions. Solid-state nuclear magnetic resonance (NMR) was also used to elucidate the silica nanostructures.