Channels Of Mesoporous Silica Research Articles

N-coordinated Ag sites on ordered mesoporous carbons for highly efficient electrolytic production of H2O2 in acidic electrolyte

N-coordinated Ag (Ag-Nx) sites embedded in ordered mesoporous carbon (Ag-Nx/C) were prepared by pyrolyzation of Ag-2, 2-bipyridine complexes in the confined channels of mesoporous SBA-15 silica. This nanocasting method allowed high dispersion state of Ag-Nx sites on carbons with ordered mesoporous channels and higher specific surface area. Ag-Nx/C was found to be very active electrocatalyst for two-electron oxygen reduction reaction (2e- ORR) in 0.1 M HClO4 acidic electrolyte. The bulk electrolytic production for hydrogen peroxides (H2O2) could be achieved with a high production rate of 1.67 mol h−1 gcat−1 together with high electrolysis Faraday efficiency of about 93%. Ag-Nx/C also revealed better acid-resistant durability during H2O2 electrolysis production. This work provided an efficient and durable Ag-Nx/C electrocatalyst for electrolytic H2O2 production in acids.

Stabilizing cubic γ-Ga2O3:Cr3+ spinel nanocrystals by size confinement into mesoporous silica nanoreactor channels

Mesoporous silica channels of different sizes are used to stabilize γ-Ga2O3:Cr3+ spinel nanocrystals with phase stability up to 1000 °C. Their optical properties are deeply investigated.

A Double-Chamber "Dandelion" Appearance Sequential Drug Delivery System for Synergistic Treatment of Malignant Tumors.

IntroductionDuring the combined treatment of tumors, the non-interfering transportation of drugs with different solubilities and the controllable sequential release are the main challenges. Here, we reported a double-chamber “Dandelion” -like sequential drug delivery system to realize the sequential release of different drugs for treating malignant tumors synergistically.MethodsAfter synthesizing mesoporous silica nanoparticles (MSN) by template method, a hydrophilic chemotherapy drug doxorubicin (DOX) was loaded into the channels of mesoporous silica (MSN) and locked with polydopamine (PDA) coating. Next, β-cyclodextrin (β-CDs) was decorated on PDA by Michael addition reaction, and the hydrophobic photosensitizer chlorin e6 (Ce6) was encapsulated into the hydrophobic chambers of β-CDs. Finally, AS1411 was modified on the surface of PDA and obtained DOX@MSN@PDA-β-CD/Ce6-AS1411 nanoparticles (DMPCCA) through which orthogonal loading and effective controlled release of different drugs were realized.ResultsUnder the sequential irradiations of 808 nm and 660 nm near-infrared (NIR) laser, PDA promoted the extensive release of Ce6 firstly while playing the effect of photothermal therapy (PTT), further to achieve the effect of photodynamic therapy (PDT) of Ce6. Meanwhile, the rapid release of DOX loaded in MSN channels showed a time lag of about 5 h after Ce6 release, through which it maximized the chemotherapeutic effect. Besides, the present drug loading nano-platform combined passive tumor-targeting effect given by EPR and active tumor-targeting effect endowed by AS1411 realized PTT-PDT-chemotherapy triple mode synergistic combination.ConclusionWe offer a general solution to address the key limitations for the delivery and sequential release of different drugs with different solubilities.

Fabrication of Dimensional and Structural Controlled Open Pore, Mesoporous Silica Topographies on a Substrate.

Open pore mesoporous silica (MPS) thin films and channels were prepared on a substrate surface. The pore dimension, thickness and ordering of the MPS thin films were controlled by using different concentrations of the precursor and molecular weight of the pluronics. Spectroscopic and microscopic techniques were utilized to determine the alignment and ordering of the pores. Further, MPS channels on a substrate surface were fabricated using commercial available lithographic etch masks followed by an inductively coupled plasma (ICP) etch. Attempts were made to shrink the channel dimension by using a block copolymer (BCP) hard mask methodology. In this regard, polystyrene-b-poly(ethylene oxide) (PS-b-PEO) block copolymer (BCP) thin film forming perpendicularly oriented PEO cylinders in a PS matrix after microphase separation through solvent annealing was used as a structural template. An insitu hard mask methodology was applied which selectively incorporate the metal ions into the PEO microdomains followed by UV/Ozone treatment to generate the iron oxide hard mask nanopatterns. The aspect ratio of the MPS nanochannels can be varied by altering etching time without altering their shape. The MPS nanochannels exhibited good coverage across the entire substrate and allowed direct access to the pore structures.

A simple and universal strategy for construction and application of silica-based flame-retardant nanostructure

Inorganic-organic nanocomposites present excellent comprehensive performance due to the combination of the advantages of inorganic, organic, and nanotechnology. However, the preparation methods are usually complex and inefficient, especially not universal. Here, a simple and universal strategy was designed for preparing silica-based nanocomposite flame retardants . Mesoporous silica (m-SiO 2 ) was used to load ethylenediamine tetra(methylene phosphonic acid) (EDTMPA). Above the melting point of EDTMPA, molten EDTMPA enters into the mesoporous channels of m-SiO 2 by means of capillary force . After cooling, EDTMPA is fixed in the mesoporous cavity to form a flame retardant nanostructure containing silicon, phosphorus, and nitrogen (SiP). The whole process of mesoporous silica-loaded organic flame retardant is simple and green. Adding 3 phr SiP2 into epoxy (EP) resin can reduce the peak heat release rate , total smoke production, and peak CO production by 44.3%, 30.4%, and 45.5%, respectively. Besides, it shows good mechanical properties compared with the EP composites with physically blended m-SiO 2 and EDTMPA. These excellent performances are attributed to the combined effect of EDTMPA and m-SiO 2 as well as the nanoscale effect . This strategy provides a simple, efficient, and general method to prepare nanocomposites by loading molten organic compounds into m-SiO 2 . • A new universal strategy for preparing silica-based nanocomposite is developed. • Molten organic flame retardant was loaded into the channels of mesoporous silica. • A novel flame retardant containing silica, phosphorus, and nitrogen was obtained. • The flame retardant has better comprehensive properties than comparative samples. • The process of mesoporous silica-loaded organic flame retardant is simple and green.

Temperature and Tumor Microenvironment Dual Responsive Mesoporous Magnetic Nanospheres for Magnetothermal Effect-Induced Cancer Theranostics

Temperature and Tumor Microenvironment Dual Responsive Mesoporous Magnetic Nanospheres for Magnetothermal Effect-Induced Cancer Theranostics

Chirality Transfer from Chiral Mesoporous Silica to Perovskite CsPbBr 3 Nanocrystals: The Role of Chiral Confinement

Chirality Transfer from Chiral Mesoporous Silica to Perovskite CsPbBr ₃ Nanocrystals: The Role of Chiral Confinement

Getting closer to the intrinsic properties of Ni2+salen polymer semiconductors accessed by chain isolation inside silica nanochannels

The scientific problem aimed to be solved by our research is to improve the charge transport of Ni2+salen polymer semiconductors by isolation of individual chains inside mesoporous silica channels capable of ensuring the suppression of interchain interactions that cause the charge carrier trapping in the continuous polymer films.

Structure and dynamics of water confined in cylindrical nanopores with varying hydrophobicity.

We report a detailed study of the main structural and dynamical features of water confined in model Lennard–Jones nanopores with tunable hydrophobicity and finite length ( Å). The generic model of cylindrical confinement used is able to reproduce the wetting features of a large class of technologically and biologically relevant systems spanning from crystalline nanoporous materials, to mesoporous silica and ion channels. The aim of this work is to discuss the influence of parameters such as wall hydrophobicity, temperature, and pore size on the structural and dynamical features of confined water. Our simulation campaign confirmed the existence of a core domain in which water displays bulk-like structural features even in extreme ( Å) confinement, while dynamical properties were shown to depend non-trivially on the size and hydrophobicity of the pores.This article is part of the theme issue ‘Progress in mesoscale methods for fluid dynamics simulation’.

Structural designing of Zn2SiO4:Mn nanocrystals by co-doping of alkali metal ions in mesoporous silica channels for enhanced emission efficiency with short decay time.

High purity Zn2SiO4:Mn crystals were synthesized by impregnating a precursor solution into mesoporous silica followed by sintering process. The effects of doping alkali metal ions (Li+, Na+, K+) on the structural, morphological and photoluminescence properties were investigated. Formation of single phase α-Zn2SiO4:Mn crystals was confirmed from X-ray diffraction. The crystal size was significantly decreased from 54 nm to 35 nm with increasing molar concentration of alkali metal ion dopants in Zn2SiO4:Mn. Zn2SiO4:Mn crystals co-doped with alkali metal ions showed stronger emission and faster decay times compared to the un-doped Zn2SiO4:Mn phosphor. The highest emission quantum yields (EQEs) of 68.3% at λexc 254 and 3.8% at λexc 425 nm were obtained for the K+ ion doped samples with Mn2+ : K+ ratio of ∼1 : 1. With alkali metal ions (Li+, Na+, K+) co-doping, the decay time of Zn2SiO4:Mn crystals was shortened to ∼4 ms, whereas the emission intensity was elevated, with respect to un-doped Zn2SiO4:Mn crystals. Zn2SiO4:Mn crystal growth in silica pores together with selective doping with alkali metal ions paves a way forward to shorten the phosphor response time, without compromising emission efficiency.

Preparation and characterisation of silica-based nanoparticles for cisplatin release on cancer brain cells.

In the present work, the preparation, characterisation, and efficiency of two different silica nanostructures as release vehicles of Cisplatin are reported. The 1-hexadeciltrimethyl-ammonium bromide templating agent was used to obtain mesoporous silica nanoparticles which were later loaded with Cisplatin. While sol-gel silica was very fast prepared using an excess of acetic acid during the hydrolysis-condensation reactions of tetraethylorthosilicate and at the same time the Cisplatin was added. Several physicochemical techniques including spectroscopies, electronic microscopy, X-ray diffraction, N2 adsorption-desorption were used to characterise the silica nanostructures. An in vitro Cisplatin release test was carried out using artificial cerebrospinal fluid. Finally, the toxicity of all silica nanostructures was tested using the C6 cancer cell line. The spectroscopic results showed the suitable stabilisation of Cisplatin into the two different silica nanostructures. A large surface area was obtained for the mesoporous silica nanoparticles, while low areas were obtained in the silica nanoparticles. Cisplatin was released faster from mesoporous silica channels than from inside of aggregates nanoparticles silica. Cisplatin alone, as well as, cisplatin released from both silica nanostructures exerted a toxic effect on cancer cells. In contrast, both silica structures without the drug did not exert any toxic effect.

A Supported Bismuth Halide Perovskite Photocatalyst for Selective Aliphatic and Aromatic C-H Bond Activation.

Direct selective oxidation of hydrocarbons to oxygenates by O2 is challenging. Catalysts are limited by the low activity and narrow application scope, and the main focus is on active C−H bonds at benzylic positions. In this work, stable, lead‐free, Cs3Bi2Br9 halide perovskites are integrated within the pore channels of mesoporous SBA‐15 silica and demonstrate their photocatalytic potentials for C−H bond activation. The composite photocatalysts can effectively oxidize hydrocarbons (C5 to C16 including aromatic and aliphatic alkanes) with a conversion rate up to 32900 μmol gcat −1 h−1 and excellent selectivity (>99 %) towards aldehydes and ketones under visible‐light irradiation. Isotopic labeling, in situ spectroscopic studies, and DFT calculations reveal that well‐dispersed small perovskite nanoparticles (2–5 nm) possess enhanced electron–hole separation and a close contact with hydrocarbons that facilitates C(sp3)−H bond activation by photoinduced charges.

Amino acid–intercalated layered double hydroxide core @ ordered porous silica shell as drug carriers: Design and applications

Abstract

Hydroxyapatite incorporation into MCM-41 and study of ibuprofen drug release

In this study, the mesoporous silica/hydroxyapatite (MCM/HA) was successfully synthesized by a simple one-step method as a controlled drug delivery system. The characterization of mesoporous materials was carried out by X-ray diffraction (XRD), transmission electron microscopy (HRTEM), Fourier-transform infrared spectroscopy (XRF), N2 adsorption/desorption analysis, and ultraviolet spectroscopy. Furthermore, ibuprofen (IBU) drug storage capacities and release rate were studied at in vitro conditions. The XRD and HRTEM results showed the formation of hydroxyapatite nanocrystals into mesoporous silica channels. The BET results indicated that the formation of hydroxyapatite into meso-channels leads to decrease in MCM-41 surface area and pore volume. In addition, the ibuprofen loading and release results showed that adsorption and release behavior of ibuprofen were extremely depended on the interaction of the MCM-41 surface groups and ibuprofen and carrier structural properties in the presence of hydroxyapatite crystals.

Antioxidant Activity of Natural Compounds Supported on Mesoporous Silica

The preparation of new composites and their antioxidant properties are reported in this study. Eugenol, vanillin and cinnamaldehyde were supported on silica material, through a microwave assisted process. N2 adsorption/desorption analysis, XRD, SAXS, TEM, FTIR and XPS were used to characterize these materials. The results proved that these compounds were successfully anchored into the channels of mesoporous silica and that the ordered mesoporous structure of inorganic material was well preserved. The antioxidant activities of composites were evaluated by the phosphomolybdene method and results showed that they have a marked antioxidant activity better than free antioxidants.

N‐heterocyclic carbene–palladium(II) complex supported on magnetic mesoporous silica for Heck cross‐coupling reaction

Magnetic mesoporous silica was prepared via embedding magnetite nanoparticles between channels of mesoporous silica (SBA‐15). The prepared composite (Fe3O4@SiO2‐SBA) was then reacted with 3‐chloropropyltriethoxysilane, sodium imidazolide and 2‐bromopyridine to give 3‐(pyridin‐2‐yl)‐1H‐imidazol‐3‐iumpropyl‐functionalized Fe3O4@SiO2‐SBA as a supported pincer ligand for Pd(II). The functionalized magnetic mesoporous silica was further reacted with [PdCl2(SMe2)2] to produce a supported N‐heterocyclic carbene–Pd(II) complex. The obtained catalyst was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray analysis, vibrating sample magnetometry, Brunauer–Emmett–Teller surface area measurement and X‐ray diffraction. The amount of the loaded complex was 80.3 mg g−1, as calculated through thermogravimetric analysis. The formation of the ordered mesoporous structure of SBA‐15 was confirmed using low‐angle X‐ray diffraction and transmission electron microscopy. Also, X‐ray photoelectron spectroscopy confirmed the presence of the Pd(II) complex on the magnetic support. The prepared magnetic catalyst was then effectively used in the coupling reaction of olefins with aryl halides, i.e. the Heck reaction, in the presence of a base. The reaction parameters, such as solvent, base, temperature, amount of catalyst and reactant ratio, were optimized by choosing the coupling reaction of 1‐bromonaphthalene and styrene as a model Heck reaction. N‐Methylpyrrolidone as solvent, 0.25 mol% catalyst, K2CO3 as base, reaction temperature of 120°C and ultrasonication of the catalyst for 10 min before use provided the best conditions for the Heck cross‐coupling reaction. The best results were observed for aryl bromides and iodides while aryl chlorides were found to be less reactive. The catalyst exhibited noticeable stability and reusability.

Acid-redox bifunctional Fe/Al-AMS catalyst: Simultaneously oriented introducing Fe2O3 in the channels and Al in the framework of AMS and its enhanced catalytic performance

For the silica-supported catalysts, the acid-free property and weak interaction between metal active centers and silica cause great limitations in their catalytic applications. In this work, a modified metal-assisted templating method was designed for simultaneously introducing different metal sites into two different locations to obtain a novel bifunctional catalyst, in which the acid sites are produced by incorporating Al species in the framework and the redox sites are brought by encapsulating Fe2O3 in the channels of anionic surfactant-templated mesoporous silica (AMS), respectively. The functionalized Fe-APTES micelles establish a critical effect between the surfactant head groups and silica species by counterion-mediated interaction, and the adjustable pH value makes the co-hydrolysis of Al species and silica resource. The results show that Fe2O3 are highly dispersed in the channels with a strong interaction, and the framework Al species produce large amount of weak Lewis acid sites. The reaction of phenol hydroxylation was proceeded under the condition of phenol/H2O2 = 1:2 (molar ratio), reaction temperature 30 °C, reaction time 4 h. For this reaction, the redox active sites and acid sites in Fe/Al-AMS catalysts are both effective. In specific, the well-dispersed Fe2O3 in the confined channels will provide more exposed active sites, and more importantly, by replacement of toxic mineral acids, a large amount of surface acid groups stimulates and adsorbs more hydroxyl radicals, leading to the improvement of catalytic activity, also for the selectivity of hydroquinone. Compared with the reference catalysts, by the synergic effect of the metal active centers and surface acid groups, 3Fe/Al-AMS catalyst displays the best catalytic performance (Conv. 46.6%, CAT Select. 49.9%, HQ Select. 33.3%) and stability in the phenol hydroxylation reaction. This oriented introduction pathway of multiple metals in different locations of silica reveals new vision in the development of multi-functional catalysts for other catalytic applications.

Ternary-Responsive Drug Delivery with Activatable Dual Mode Contrast-Enhanced in Vivo Imaging.

Designing a smart nanotheranostic system has recently attracted tremendous attention and is highly desirable for realizing targeted cancer therapy and early diagnosis. Herein we report the fabrication of smart nanotheranostic system using multiresponsive gatekeeping protocol of mesoporous silica nanoparticles (MSN). Acid, oxidative stress and redox sensitive manganese oxide (MnO x) coated superparamagnetic iron oxide nanoparticle (SPION) were employed as nanolids to regulate the camptothecin drug release from the channels of mesoporous silica and achieve responsive dual-mode MRI contrast. The nonvehicle showed high magnetization and T2 contrast in magnetic resonance imaging (MRI) due to the significant density of SPION onto the surface of MSN, and at the same time the MnO x shell degradation release Mn2+ which enhanced the T1MRI visualization. The efficacy of responsive drug delivery system was investigated on pancreatic cancer cells and tumor-bearing mice, and results reinforced that MnO x-SPION@MSN@CPT nonvehicle is efficacious against cancer cells. We envision that our unique and multiresponsive nanoplatform may find applications in effective delivering of imaging and therapeutic agents to wide range of diseases besides cancer.

CoMo Hydrotreating Catalysts Supported on Al2O3, SiO2 and SBA-15 Prepared from Single Co2Mo10-Heteropolyacid: In Search of Self-Promotion Effect

CoMo hydrotreating catalysts with varied metal loading (1–4 Mo at nm− 2) based on Co2Mo10 heteropolyacid (HPA) and different supports (γ-Al2O3, SBA-15, SiO2) were prepared by incipient wetness impregnation. The catalysts were characterized by N2 physisorption, high resolution transmission electron microscopy (HRTEM), Raman and X-ray photoelectron spectroscopy (XPS). Catalytic activity was evaluated in co-hydrotreating (HDT) of the model feed containing dibenzothiophene (DBT) and naphthalene. The catalytic properties of CoMo catalysts were shown to depend on the morphological characteristics of CoMoS species, its promotion degree, and metal loading. The sulfidation degree of the initial precursor and effective cobalt amount in the CoMoS species increased with the Mo loading increase from 1 to 4 at nm− 2 in all studied catalysts. The DBT conversion maximum was achieved over CoMo/Al2O3 and CoMo/SBA-15 with 4 Mo at nm− 2. CoMo/SBA-15 catalysts had higher TOF numbers both in DBT HDS and in naphthalene hydrogenation (HYD) at the surface concentration of Mo same as in the other samples. These results can be attributed to optimal morphology of sulfide particles and the Co/Mo promotion degree due to a more suitable interaction between the active phase and support in mesoporous silica channels.

Controllable integration of ultrasmall noble metal nanoparticles into mesoporous silica matrixes by a self-assembly method.

Noble metal nanoparticles smaller than 2 nm were immobilized inside the channels of mesoporous silica via a self-assembly method using cetyltrimethylammonium chloride as a structural directing agent. This general approach can be used for integration of various precious metals into mesoporous silica matrixes of ∼30 nm to achieve better matter utilisation and higher catalytic activity.