Nonporous Silica Research Articles

Water adsorption on planar interfaces: Classical density functional study

• A new cDFT based on SAFT with an explicit account for dipole-dipole interactions was formulated. • Our model provides a good description of binodal, liquid-vapor surface tension, latent heat of vaporization, and wetting contact angles. • The energy distribution functions for non-porous silica and alumina were calculated. Theoretical modeling of water adsorption in micro- and mesoporous materials remains a challenging problem for physical chemistry and chemical engineering despite its great importance for industrial applications. Here, we present the theoretical study of bulk and inhomogeneous water within the classical density functional theory. Our model includes all important intermolecular interactions, such as dispersion, association, and dipole-dipole. We validated the model via comparison with existing literature experimental and computer simulation data. Among the others, the following water properties were compared: liquid-vapor binodal (T - ρ ), surface tension, latent heat of vaporization, wetting contact angle, and adsorption isotherms on nonporous silica and alumina. Our computational results demonstrate good agreement with the experimental literature data and show similar trends compared to the several commonly used water models (SPC/E, TIP4P, TIP4P/2005). Because the presented model can accurately describe the thermodynamic and interfacial properties of water then it can be of interest to the adsorption community. Also, the model may serve as a starting point for further works regarding porous adsorbents characterization employing classical density functional theory.

Non-porous silica support covalent organic frameworks as stationary phases for liquid chromatography.

A new strategy using non-porous silica (NPS) spheres as the support and covalent organic frameworks (COFs) as the porous functional shell for liquid chromatography was developed to ensure the independent effect of the COFs on the separation. As a proof of concept, NPS@TPB-DMTP was prepared for liquid chromatographic analysis using 1,3,5-tris(4-aminophenyl)benzene (TPB) and 2,5-dimethoxy-1,4-benzenedicarboxaldehyde (DMTP) as monomers by in situ polymerisation on the surface of NPS. It is a new way of developing COF-based stationary phases, which will be helpful in understanding what effect the COFs will have on separation.

Can We Form Mesoporous Zeolites by Steam Assisted Crystallization of MCM-41?

The possibility of crystallizing silicalite-1 (MFI) from the pore walls of as-synthesized MCM-41 via steam-assisted crystallization (SAC) was thoroughly investigated. A kinetic study was conducted through the impregnation of as-synthesized MCM-41 with the structure-directing agent tetrapropyl-ammonium hydroxide (TPAOH). Materials obtained after different SAC treatment times (1-288 h) were characterized by XRD, nitrogen physisorption at 77 K, TGA/DTA, and SEM. The achieved results allowed us to conclude that during SAC treatment, rapid destruction of the hexagonal mesophase occurs with the enlargement of mesopores, probably by their coalescence, until achieving non-porous amorphous silica. Only thereafter is the crystallization of the MFI phase evidenced through the development of micron-sized (>10 µm) MFI structured crystals. This study suggests the probable practical impossibility of even partial crystallization of the pore walls of mesoporous materials by SAC.

Directed Immobilization of PETase on Mesoporous Silica Enables Sustained Depolymerase Activity in Synthetic Wastewater Conditions.

Microplastic accumulation in terrestrial and aquatic environments is a growing environmental challenge. Biodegradation has shown promise as an intervention strategy for reducing the spread of microplastics. The wastewater treatment system is a key intervention point in microplastic biodegradation due to its pivotal role in the water cycle at the interface between human activity and the environmental. However, the best characterized microplastic degradation enzyme, PETase, lacks the stability to perform at scale in wastewater treatment. In this work, we show that genetic fusion of PETase to a silica binding peptide enables directed immobilization of the enzyme onto silica nanoparticles. PETase activity in simulated wastewater conditions is quantified by linear regression from time zero to the time of maximum fluorescence of a fluorescent oxidized product of PETase degradation of PET microfibers. Mesoporous silica is shown to be a superior support material to nonporous silica. The resulting biocatalytic nanomaterial has up to 2.5-fold enhanced stability and 6.2-fold increased activity compared to free enzyme in unbuffered, 40 °C simulated influent (ionic strength ∼15 mM). In unbuffered, 40 °C simulated effluent (ionic strength ∼700 μM), reaction velocity and overall catalytic activity were increased by the biocatalytic material 2.1-fold relative to free PETase. All reactions were performed in 0.2 mL volumes, and enzyme concentrations were normalized across both free and immobilized samples to 9 μg/mL. Site-directed mutagenesis is shown to be a complementary technique to directed immobilization, which may aid in optimization of the biomaterial for wastewater applications. PETase stabilization in application-relevant environments as shown here enables progress toward application of PETase for microplastic biodegradation in wastewater treatment.

Greater Plasma Protein Adsorption on Mesoporous Silica Nanoparticles Aggravates Atopic Dermatitis.

PurposeThe protein corona surrounding nanoparticles has attracted considerable attention as it induces subsequent inflammatory responses. Although mesoporous silica nanoparticles (MSN) are commonly used in medicines, cosmetics, and packaging, the inflammatory effects of the MSN protein corona on the cutaneous system have not been investigated till date.MethodsWe examined the greater plasma protein adsorption on MSN leads to serious inflammatory reactions in Dermatophagoides farinae extract (DFE)-induced mouse atopic dermatitis (AD)-like skin inflammation because of increased uptake by keratinocytes.ResultsWe compare the AD lesions induced by MSN and colloidal (non-porous) silica nanoparticles (CSN), which exhibit different pore architectures but similar dimensions and surface chemistry. MSN-corona treatment of severe skin inflammation in a DFE-induced in vivo AD model greatly increases mouse ear epidermal thickness and infiltration of immune cells compared with the CSN-corona treatment. Moreover, MSN-corona significantly increase AD-specific immunoglobulins, serum histamine, and Th1/Th2/Th17 cytokines in the ear and lymph nodes. MSN-corona induce more severe cutaneous inflammation than CSN by significantly decreasing claudin-1 expression.ConclusionThis study demonstrates the novel impact of the MSN protein corona in inducing inflammatory responses through claudin-1 downregulation and suggests useful clinical guidelines for MSN application in cosmetics and drug delivery systems.

Accelerated and simplified synthesis of magnetic mesoporous nanoparticles in a continuous multistep microfluidic system

Here a fully continuous flow strategy for the preparation of Fe3O4@nSiO2@mSiO2 nanocomposites starting from ferrous and ferric ions was established for the first time. The three synthetic steps for Fe3O4 core, nonporous silica middle shell and mesoporous silica outer shell were connected and integrated into a single flow sequence with a total residence time of approximately 3 min. Moreover, the multistep continuous flow system was simplified with smaller footprint and increased safety by feeding all the ammonia needed by the three synthetic steps only once at the starting point of the system. The final product Fe3O4@nSiO2@mSiO2 nanoparticles with a specific surface area 378 m2 g−1 and saturation magnetization 19.3 emu g−1 showed great potential as a catalyst support with easy and excellent recyclability. Proved to be capable of achieving fast and accurate parameter optimization, the uninterrupted continuous flow system proposed in this work holds great prospects to mediate multistep synthesis of complex nanoparticles with hierarchical structures in an efficient and controllable manner.

Effect of mesoporous silica@nano-bioactive glass complex particles on the durability of dentin bonding

This study introduced a process for synthesizing mesoporous silicon@nano-bioactive glass (nano-BAG) complex particles, and evaluated their effects on dentin bonding and remineralizing activity. Mesoporous and nonporous silica microspheres were coated with nano-BAG via a quick alkali-mediated sol–gel method at different pH values (4, 7, 9). The eight groups of particles were examined by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, nitrogen adsorption tests, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Inductively coupled plasma optical emission spectrometry (ICP-OES) was employed to record the cumulative release of Ca2+ at 7, 14, and 28 days. The ability to promote the formation of hydroxyapatite was assessed by mineralization tests. The CCK-8 cell counting kit was used to test the cytotoxicity. Microtensile bond strength (μTBS) tests nanoleakage and were carried out to evaluate the effects of a pretreatment using mesoporous or nonporous silica microspheres coated with nano-BAG. XRD and FTIR analyses confirmed that nano-BAG coated mesoporous silica and formed a relatively ordered mesoporous structure, whereas nonporous silica did not exhibit major structural changes. In N2 adsorption tests, the specific surface area and pore volume of mesoporous silica (927.04 m2/g; 0.77 cm3/g) were much larger than those of silica (10.76 m2/g; 0.04 cm3/g). Both SEM and TEM revealed a greater homogeneity and dispersity in mesoporous silica coated with nano-BAG at pH 4. This kind of particles maintained a high level of cumulative release of Ca2+ (178.29 ± 0.950 mg/L at 28 days), showed the strongest Ca and P signal intensity after being immersed in SBF for 28 days, and exhibited higher μTBS values (41.56 ± 3.110 MPa) and minimal nanoleakage. Cytotoxicity tests indicated a well-preserved cell viability in these particles. Nano-BAG-coated mesoporous silica particles, obtained at pH 4, provided a stable release of Ca2+ in body fluid, and showed a strong ability to promote the formation of hydroxyapatite. These features are beneficial for enhancing the resin–dentin bonding and reducing nanoleakage.

Reversible ionic liquids (RevILs) for the preparation of thermally stable SBA-15 supported gold nanoparticle catalysts

Reversible ionic liquids (RevILs) are ionic liquids that can be switched between molecular and ionic forms via two stimuli, and they can assist in the synthesis of colloidal gold nanoparticles. The RevIL-stabilized gold nanoparticles are deposited in the pores of SBA-15 mesoporous silica via incipient wetness without the functionalization of the SBA-15 surface. The location of nanoparticles inside the pores was confirmed by transmission electron microscopy technique and by a measured increase in the thermal stability of the nanoparticles in SBA-15 compared to non-porous silica. The porous gold catalysts are active in the selective oxidation of benzyl alcohol without calcination due to the absence of the ligands on the gold surface after deposition. Additionally, they are more active than the non-porous gold catalysts, indicating that the pore geometry enhances catalytic performance. Ultimately, the catalysts prepared by RevIL technique are thermally stable and active and show fine control over particle size.

Preparation of Ca doped wrinkled porous silica (Ca-WPS) for the improvement of apatite formation and mechanical properties of dental resins

The purpose of this work was to fabricate and characterize Ca doped wrinkled porous silica (Ca-WPS), and evaluate their effect on the mineralization and mechanical properties of resin composites as functional fillers. Ca-WPS were prepared by sol-gel method and characterized by scanning electron microscopy, transmission electron microscopy and N2 adsorption–desorption measurements. The mineralization properties of the prepared Ca-WPS particles and the resin composites with different amount of Ca-WPS were evaluated by simulated body fluid (SBF) immersion method. The mechanical properties (flexural strength, flexural modulus, compressive strength and microhardness) of the dental resins containing unimodal Ca-WPS fillers and bimodal Ca-WPS fillers with nonporous silica were evaluated by a universal testing machine. Results showed that after immersing in SBF for 5 d, apatite formed on the surface of Ca-WPS and composites containing Ca-WPS fillers, indicating the excellent mineralization property of the prepared Ca-WPS. The mechanical properties of the dental resins increase with the increase of the proportion of unimodal Ca-WPS fillers. The dental resins with bimodal Ca-WPS fillers showed better mechanical properties than the group with only nonporous fillers at the same filler loading (60 wt%). Among all the samples, the dental composites filled with bimodal fillers (mass ratio of Ca-WPS: nonporous silica = 10:50, total filler loading 60 wt%) exhibited the best mechanical performance. The flexural strength, flexural modulus, compressive strength and microhardness of these samples were 26.96%, 42.75%, 16.04% and 54.1% higher than the composites with solid silica particles alone, respectively. Thus, the prepared Ca-WPS could effectively improve the apatite formation and mechanical properties of resin composites.

高碳含量新型亚微米无孔二氧化硅材料的修饰方法及其在反相加压毛细管电色谱平台上的应用

亚微米无孔二氧化硅(NPS)材料具有小粒径及表面光滑形状规整等特点,是一种性能优异的色谱材料,但其存在比表面积小、修饰效率低的问题。针对此设计了一种具有高碳含量的修饰方法:以3-缩水甘油基氧基丙基三甲氧基硅烷(GPTS)作为硅烷偶联剂,聚乙烯亚胺(PEI)作为聚合物包覆层,并以硬脂酰氯修饰得到一种氨基包覆的具有C18碳链结构的新型亚微米无孔二氧化硅材料(C18-NH2-GPTS-SiO2)。利用元素分析、傅里叶变换红外光谱、Zeta电势等进行表征,证明C18-NH2-GPTS-SiO2固定相的成功制备。该修饰方法将NPS的碳含量从0.55%提高到了8.29%,解决了过往NPS材料采用十八烷基氯硅烷等传统C18修饰方法时碳含量较低的问题。此外,29Si固体核磁显示:NPS与多孔二氧化硅(PS)微球相比不仅存在孔结构与比表面积区别,且表面硅羟基种类也不同。16%的PS微球硅原子带有一个硅羟基(孤立硅羟基,Q3)、19%带有两个硅羟基(偕硅羟基,Q2);而NPS微球不存在偕硅羟基,仅有30%硅原子处于孤立硅羟基状态。实验发现NPS微球存在硅羟基数量低且缺少偕硅羟基的特点,导致NPS材料表面修饰活性低,难以通过简单一步反应获得高碳含量。采用不同疏水物质如苯系物、多环芳烃对色谱性能及保留机理进行研究,结果表明C18-NH2-GPTS-SiO2色谱柱符合反相作用机理。氨基的包覆改变硅球表面电性,提高了NPS材料运用于加压毛细管电色谱平台(pCEC)时的电渗流大小,施加+15 kv时,显示出良好的分离能力,证实了C18-NH2-GPTS-SiO2材料通过多步反应提高碳含量的修饰方法在pCEC平台上应用的优异性。

Cobalt oxide decorated porous silica particles: Structure and activity relationship in the catalytic oxidation of carbon monoxide

Porous (0.6–30 nm) and non-porous spherical silica nanoparticles are synthesized. These silicas with different morphologies are decorated with cobalt (2.9 wt%) using Co(NO3)2·6H2O as precursor. Co-SiO2 particles are studied by N2 sorption, TEM, XRD, XPS, FTIR and TPR-H2 methods. Specific surface area (SSA) of the prepared materials is 10–1200 m2/g. The main crystalline phase is identified as Co3O4. The activity of Co-SiO2 composites in the CO oxidation and preferential oxidation of CO (PROX) in a H2-rich gas mixture improves with increasing atomic ratios of Co/Si and Co3+/Co2+ on the silica surface. Catalysts with the large mesopores containing mainly Co2+ are the least active. Co-SiO2 composites based on synthetic opal grown by sedimentation of non-porous silica particles with the lowest SSA demonstrate the highest catalytic activity. The CO conversion reaches 100% at 150 °C in the absence of hydrogen, while in PROX the 90% conversion of CO is achieved at 170 °C. The large Co3O4 aggregates between non-porous spherical silica particles of opal are the most active and stable during CO-PROX reaction. The lower interaction of Co3O4 nanoparticles with this support promotes the stabilization of the oxidized state Co3+ and provides a higher yield of CO2 in CO-PROX reaction.

Concerted effect of boron and porosity on shear thickening behavior of hybrid mesoporous silica dispersions

In the present work, the influence of porosity and boron on shear thickening behavior of hybrid mesoporous silica has been studied. Three different levels of boron modification were performed by varying the molar composition of boric acid viz., 1.5 mmol, 2.5 mmol, and 3.5 mmol in a co-condensation approach. The incorporation of boron in mesoporous silica network was confirmed by various techniques such as Fourier transform infra-red (FTIR), and 11B solid- state nuclear magnetic resonance (NMR) spectroscopy. The morphology and particle size were confirmed by using scanning and transmission electron microscopy. To evaluate the effect of boron and porosity on the shear thickening behavior, dispersions were prepared from mesoporous boron- modified silica (MSiB), control mesoporous silica (MSi), non-porous boron-modified silica (SiB), and control non-porous silica (Si) in polyethylene glycol. The shear thickening behavior was studied using steady shear rheology. The dispersion prepared from different loadings of synthesized MSiB containing 1.5 mmol boron showed more than 16 times increase in viscosity (657.7 Pa.s) compared to that of MSi (39.2 Pa.s) at a fairly low volume fraction (φ = 0.15) of silica. It is expected that the highly ordered mesoporous architecture of hybrid silica has improved the interaction between the particle and the dispersing medium through hydrogen bonding. The porous morphology of the hybrid mesoporous silica as well as the incorporation of boron in the silica network favors the formation of a frictional contact network, and a transition from continuous shear thickening (CST) to discontinuous shear thickening (DST) behavior was observed. Therefore, silica prepared via incorporation of boron as well as porosity can be material of interest in variety of applications, for example, soft body armors, sporting goods, and shear thickening electrolytes for high impact resistant batteries.

Study on Occluding Dentinal Tubules with a Nanosilver-Loaded Silica System In Vitro.

The effects of most clinical treatments for dentin hypersensitivity are not long-lasting. To overcome the defects, the mesoporous silica nanoparticles and silver nanoparticles entered the field of oral materials. This study aimed to synthesize a novel, low-cytotoxic dentin desensitizer and investigate its occlusion effects on dentinal tubules. The biphasic stratification approach, a chemical reduction method, and the Stöber method were used to synthesize silver nanoparticle-loaded and nonporous silica-encapsulated mesoporous silica (Ag-MSNs@nSiO2), which was a noncrystalline structure with an average size of approximately 128 nm and a silver content of 3.506%. Atomic absorption spectrometry and the 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide cell viability assay showed that Ag-MSNs@nSiO2 slowly released silver ions and had nearly no cytotoxicity. An electron microscope was used to observe the blocking effects on the dentinal tubules of sensitive tooth disc models, which were randomly divided into the following four groups: a deionized water group, a 5.9 M silver nitrate solution group, an Ag-MSNs@nSiO2 group, and a Gluma desensitizer group. There were no significant differences in the relative area of open dentinal tubules between the Ag-MSNs@nSiO2 group and the Gluma desensitizer group (P > 0.05). Detection of protein structures showed that multilevel structures of bovine serum albumin in dentin tubules were significantly changed by silver ions from Ag-MSNs@nSiO2. These results suggest that nearly noncytotoxic Ag-MSNs@nSiO2 was successfully synthesized by a series of methods. Ag-MSNs@nSiO2 occluded dentin tubules immediately and effectively. Moreover, the blockage effects may be enhanced and maintained by continuous condensation of proteins in dentinal tubules.

Comparative study in use sodium silicate instead of NH4OH as an alkaline basic catalyst to gelation unmodified silica aerogel based on tetraethoxysilane (TEOS)

In the present work, nonporous hydrophilic unmodified silica aerogel was synthesized successfully by ambient drying with one step base catalyst by used silica organic initiator tetraethoxysilane (TEOS). Silica aerogel was prepared twice by sol-gel technique; the first one was the gelation that happened under the alkaline catalyst NH4OH, which has a toxic property and dangerous to human health. The second gelation under the effect of the safety inorganic base catalyst sodium silicate (water glass) that used as an inorganic low-cost and environmentally friendly initiator to silica, plays a role in increasing pH as a catalyst and as a new rare co-precursor mixing organic and inorganic silica precursors (TEOS+Na2SiO3). The impurities accompanying water glass and sodium residue were eliminated by a lot of washing. The volume ratio of the (TEOS: ethanol: H2O: base catalyst) fixed respectively at (5.6:50:10:0,01M). The gelation reaction time, the gel properties, it's quality and the amount of the reactant, the density, and the appearance all effect by the type of catalyst used. The comparative study of silica porous aerogel production properties diagnostic achieved by FTIR, XRF, BET, BJH, FESEM and thermal conductivity applied as insulation materials .

Correlation of Secondary Particle Number with the Debye-Hückel Parameter for Thickening Mesoporous Silica Shells Formed on Spherical Cores.

Mesoporous silica shells were formed on nonporous spherical silica cores during the sol–gel reaction to elucidate the mechanism for the generation of secondary particles that disturb the efficient growth of mesoporous shells on the cores. Sodium bromide (NaBr) was used as a typical electrolyte for the sol–gel reaction to increase the ionic strength of the reactant solution, which effectively suppressed the generation of secondary particles during the reaction wherein a uniform mesoporous shell was formed on the spherical core. The number of secondary particles (N2nd) generated at an ethanol/water weight ratio of 0.53 was plotted against the Debye–Hückel parameter κ to quantitatively understand the Debye screening effect on secondary particle generation. Parameter κa, where a is the average radius of the secondary particles finally obtained in the silica coating, expresses the trend in N2nd at different concentrations of ammonia and NaBr. N2nd was much lower than that expected theoretically from the variation of secondary particle sizes at a constant Debye–Hückel parameter. A similar correlation with κa was observed at the high and low ethanol/water weight ratios of 0.63 and 0.53, respectively, with different hydrolysis rate constants. The good correlation between N2nd and κa revealed that controlling the ionic strength of the silica coating is an effective approach to suppress the generation of secondary particles for designing mesoporous shells with thicknesses appropriate for their application as high-performance liquid chromatography column packing materials.

Inulin-Coated Iron Oxide Nanoparticles: A Theranostic Platform for Contrast-Enhanced MR Imaging of Acute Hepatic Failure.

The present study introduces a superparamagnetic nanocomposite, Fe-Si-In, as a T2 magnetic resonance imaging (MRI) contrast agent with a core of iron oxide nanoparticles and a nonporous silica inner shell/carboxymethyl inulin outer shell. Due to its core/shell properties, the structure characterization, biocompatibility, and performance in MRI, as well as its potential as a drug delivery system, were thoroughly evaluated. The results have shown that the synthesized nanocomposite possesses excellent biocompatibility and acceptable magnetization (Ms = 20 emu g-1). It also has the potential to be a nanocarrier for drug delivery purposes, as evidenced by the results of curcumin administration studies. The developed nanocomposite has shown excellent performance in MRI, while the in vitro relaxivity measurements reveal a stronger T2 relaxivity (r2 = 223.2 ms) compared to the commercial samples available in the market. Furthermore, the in vivo MRI studies demonstrate an excellent contrast between injured livers and normal ones in rats which again upholds the high performance of Fe-Si-In in MRI diagnostics.

The synthesis and nanostructure investigation of noble metal-based nanocomposite materials

The presented work follows the theme of applied chemistry toward nanomaterials and multiphase functional systems of practical importance. Structural studies of nanocomposite materials are important due to the correlation between physicochemical/structural properties and their application potential. In this work, we report the fabrication and structural characterization of nanocomposite materials constituting noble metal (plasmonic) nanoparticles (AgNP and AuNP) dispersed on selected types of nanostructured solid hosts (nonporous silica, microporous activated carbon, chitosan biopolymer, and ordered mesoporous silica). The ability to maintain a dispersed state of colloidal precursors throughout their deposition on solid hosts was assessed. The influence of the carrier role in the formation and stabilization of nanometallic phases was evaluated taking into account the physicochemical and textural properties of the support surfaces. The size and shape of nanoobjects, clustering effects, interfacial properties, and stability of the immobilized nanophase were implemented by analyzing relevant parameters of SAXS analysis. The dimensional characteristic of the scatterers was evaluated by volume-weighted particle size distribution Dv(R). The detailed overall shape and maximal particle dimension were described by the analysis of pair distance distribution functions (PDDFs). The radius of gyration (Rg) from PDDF and Guinier approximation was calculated for illustrating the dimension of scattered heterogeneities in the investigated solids. The asymptotic behavior of a scattering curve and Porod theory were applied for determining the diffusion and quality of the interfacial surfaces. The size and morphology of nanoparticles in colloidal precursor solutions have been defined as spherical and bimodal in size (~ 6 nm and 20 nm). It was observed that the spherical shape and dispersed state of nanoparticles were achieved for all systems after deposition. However, the morphology of their final form was conditioned by the solid matrices. The particle properties from SAXS were correlated with properties determined by TEM and low-temperature nitrogen sorption analysis. Obtained results suggest good compatibility and correctness of SAXS data reading of nanocomposite systems and can be successfully applied for quick, nondestructive, and effective evaluation of structural properties of complex systems.Graphical abstract

Organic dyes (acid red, fluorescein, methylene blue) and copper(II) adsorption on amino silica spherical particles with tailored surface hydrophobicity and porosity

Organic dyes are common constituents in wastewater and contribute to accumulation of persistent organic pollutants in the environment. Common dyes are aromatic compounds, bearing a variety of hydrophilic functional groups. Their interaction with solid surfaces can thus involve both van-der-Waals and hydrophobic interactions and electrostatic and/or hydrogen bonding. Aiming to tailor adsorbents with specific capacity for removal of dyes, silica microspheres were synthesized, combining aminopropyl functions as moderators of hydrophilic interaction and bridging aliphatic and aromatic functions as potential moderators of hydrophobic and π-stacking interactions. Two groups of samples were produced: non-porous silica spheres with amino or combined amino and hydrophobic residues; and porous polysilsesquioxane spheres incorporating aminopropyl components and organic bridges in the silica network. The hydrophilicity/hydrophobicity of the samples was studied by the absorption of water and benzene vapors. Bridged fragments, expected to promote the porosity of the samples, as well as hydrophobicity, did not contribute to the latter, because polysilsesquioxanes were bearing large numbers of residual silanol groups. Particles synthesized using tetraethoxysilane were up to 130 nm in size and held 1.6–1.8 mmol/g of amino groups, while, materials prepared from bridged silanes featured particle agglomerates up to 300 nm, 2.2–2.7 mmol/g amino groups content, and specific surface area of 540–620 m2/g. Interaction with Cu2+ was used to probe concentration and surface location of the amino functions, reaching 76–203 mg/g. Adsorption of anionic (acid red 88), neutral (fluorescein) and cationic (methylene blue) dyes was investigated revealing multiple interactions between the sorbent and sorbate. The dye sorption capacity values were 81–262 mg/g for acid red 88, 26–132 mg/g for fluorescein, and 55–146 mg/g for methylene blue. Produced silica microspheres have potential as high performance sorbents for the extraction of copper(II) ions and the dyes, and can act as fluorescent carriers after the dye adsorption.

Plasma ammonia synthesis over mesoporous silica SBA-15

Herein we demonstrate the synthesis of ammonia via atmospheric dielectric barrier discharge plasma discharge over silica. We evaluated the performance of three structural different silicas: non-porous silica, fumed-silica and mesoporous SBA-15 silica. The mesoporous SBA-15 sample resulted in an ammonia synthesis rate per gram of catalyst at least three times higher than that of the non-porous and fumed silica when employing a hydrogen rich gas feed. The hierarchical ordered pore size in the mesoporous range of SBA-15 allowed us to observe experimentally, the pore size effect in the plasma discharge. Specifically, the ammonia production is enhanced by the presence of mesopores that can effectively enable the discharge diffusion into the pore as predicted by theoretical calculations. The importance of the porous structure was confirmed by optical emission spectra which indicates a similarity on the relative intensity on the main plasma activated species in the gas phase such as N2 +, NH and for the three silicas employed in this work i.e. non-porous, fumed and mesoporous (SBA-15). However, the remarkable ammonia production when employing the SBA-15 shows that despite the similarities in the gas phase the main differences might be attributed to the diffusion of the plasma discharge into the pores.

Membrane Interactions of Virus-like Mesoporous Silica Nanoparticles.

In the present study, we investigated lipid membrane interactions of silica nanoparticles as carriers for the antimicrobial peptide LL-37 (LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES). In doing so, smooth mesoporous nanoparticles were compared to virus-like mesoporous nanoparticles, characterized by a "spiky" external surface, as well as to nonporous silica nanoparticles. For this, we employed a combination of neutron reflectometry, ellipsometry, dynamic light scattering, and ζ-potential measurements for studies of bacteria-mimicking bilayers formed by palmitoyloleoylphosphatidylcholine/palmitoyloleoylphosphatidylglycerol. The results show that nanoparticle topography strongly influences membrane binding and destabilization. We found that virus-like particles are able to destabilize such lipid membranes, whereas the corresponding smooth silica nanoparticles are not. This effect of particle spikes becomes further accentuated after loading of such particles with LL-37. Thus, peptide-loaded virus-like nanoparticles displayed more pronounced membrane disruption than either peptide-loaded smooth nanoparticles or free LL-37. The structural basis of this was clarified by neutron reflectometry, demonstrating that the virus-like nanoparticles induce trans-membrane defects and promote incorporation of LL-37 throughout both bilayer leaflets. The relevance of such effects of particle spikes for bacterial membrane rupture was further demonstrated by confocal microscopy and live/dead assays on Escherichia coli bacteria. Taken together, these findings demonstrate that topography influences the interaction of nanoparticles with bacteria-mimicking lipid bilayers, both in the absence and presence of antimicrobial peptides, as well as with bacteria. The results also identify virus-like mesoporous nanoparticles as being of interest in the design of nanoparticles as delivery systems for antimicrobial peptides.