Surface Of Mesoporous Silica Research Articles

Design of self-healing nanocomposite hydrogels and the application to the detection of human exercise and ascorbic acid in sweat

Hydrogel sensors have broad application prospects in human motion monitoring and sweat composition detection. However, hydrogel-based sensors are faced with challenges such as low accuracy and poor mechanical properties of analytes detection. Based on mussel-inspired chemistry, we synthesized mesoporous silica@polydopamine-Au (MPS@PDA-Au) nanomaterials and designed a self-healing nanocomposite hydrogel to monitor human movement and ascorbic acid detection in sweat. Mesoporous silica (MPS) possess orderly mesoporous structure. Dopamine (DA) polymerized on the surface of MPS to generate polydopamine (PDA), forming the composite material MPS@PDA-Au. This composite was then embedded into polyvinyl alcohol (PVA) hydrogels through a simple freeze-thaw cycle process. The hydrogels have achieved excellent deformable ability (508.6%), self-healing property (90.5%) and mechanical strength (2.9 MPa). The PVA/MPS@PDA-Au hydrogel sensors had the characteristics of fast response time (123.2 ms), wide strain sensing range (0–500%), excellent fatigue resistance and stability in human detection. The detection range of ascorbic acid (AA) in sweat was wide (8.0 μmol/L-100.0 μmol/L) and the detection limit was low (3.3 μmol/L). Therefore, these hydrogel sensors have outstanding application prospects in human motion monitoring and sweat composition detection.

Construction and Evaluation of Paclitaxel Mn-Doped Dendritic Mesoporous Silica Coated with N-Succinyl Chitosan

Mesoporous silica, as a drug carrier, has become the new research focus in the field of nanodrug delivery system in recent years. In this study, Mn-doped mesoporous silicas are synthesized by template and in-situ doping method and physically characterized. The drug-loading performance of silica and its impact on drug release are studied. The Mn-doped mesoporous silicas show dendritic morphology (MDMS) with a loose wrinkle structure on the surface and a large number of pores. MDMS is used as a carrier to solve the problem of low water solubility of paclitaxel. In order to avoid leakage during drug transportation, the surface of Mn-doped mesoporous silica loaded with paclitaxel is coated with N-succinyl chitosan to construct a new type of nanodrug delivery system (MDMS-PTX-NSC). Compared to MDMS, MDMS-PTX-NSC shows an increase in particle size and smooth surface. The dissolution characteristics of manganese ions and swelling behavior of N-succinyl chitosan make MDMS-PTX-NSC delivery system exhibit a good pH-responsive release. And MDMS-PTX-NSC release curve can be well fitted by Ritger-Peppas equation. The cytotoxicity test shows that the MDMS-PTX-NSC has significant biocompatibility and enhanced cytotoxicity, which reveals that the MDMS-PTX-NSC is a promising nanodrug delivery system.

Mesoporous silica supported ionic liquid materials with high efficacy for CO2 adsorption studies

CO2 capture from industrial processes and power plants, contribute to curbing global warming and advancing sustainability efforts. This study involves the design and synthesis of novel mesoporous silica supported ionic liquid based adsorbents for carbon dioxide capture. Utilization of MSILs delves into the efficiency and mechanisms of CO2 adsorption, offering insights for sustainable carbon capture technologies in combating greenhouse gas emissions. 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium ethyl sulfate and 1-ethyl-3-methylimidazolium methylsulfate ionic liquids were anchored on the surface of mesoporous silica which then led to highly efficient adsorbent material. Simple, efficient and cost saving methodology was performed to synthesize such highly efficient CO2 adsorbent materials. In addition, we theoretically predicted the favorable interaction mechanism of chosen molecular entities for CO2 adsorption using density functional theory (DFT) analysis. Theoretical results depict the strong interaction of molecular entities with CO2 gas molecules which is clearly evident from the experimental findings.

Synthesis of Mesoporous Silica Using the Sol-Gel Approach: Adjusting Architecture and Composition for Novel Applications.

The sol-gel chemistry of silica has long been used for manipulating the size, shape, and microstructure of mesoporous silica particles. This manipulation is performed in mild conditions through controlling the hydrolysis and condensation of silicon alkoxide. Compared to amorphous silica particles, the preparation of mesoporous silica, such as MCM-41, using the sol-gel approach offers several unique advantages in the fields of catalysis, medicament, and environment, due to its ordered mesoporous structure, high specific surface area, large pore volume, and easily functionalized surface. In this review, our primary focus is on the latest research related to the manipulation of mesoporous silica architectures using the sol-gel approach. We summarize various structures, including hollow, yolk-shell, multi-shelled hollow, Janus, nanotubular, and 2D membrane structures. Additionally, we survey sol-gel strategies involving the introduction of various functional elements onto the surface of mesoporous silica to enhance its performance. Furthermore, we outline the prospects and challenges associated with mesoporous silica featuring different structures and functions in promising applications, such as high-performance catalysis, biomedicine, wastewater treatment, and CO2 capture.

Histidine-modified pillar[5]arene-functionalized mesoporous silica materials for highly selective enantioseparation

Chiral enantiomers, especially the enantiomers of chiral drugs often exhibit different pharmacological activity, metabolism and toxicity, thus it is of great research significance to scientifically and reasonably develop single chiral drugs with low toxicity and high efficiency. Among them, high performance liquid chromatographic techniques based on chiral stationary phases (CSPs) has become one of the most attractive methods used to evaluate the enantiomeric purity of single-enantiomers compound of pharmacological relevance. In this work, pillar[5]arene functionalized with L- and D-histidine, respectively, were modified on the surface of mesoporous silica as novel chiral stationary phases called L/DHis-BP5-Sil. Notably, L/D-histidine had the characteristics of low steric hindrance and easy derivatization. Although the π-π interaction of imidazole group was weaker than that of benzene ring, the benzene ring bonding imidazole-conjugated ring in the structure produced better enantioseparation effect. The results showed that L/DHis-BP5-Sil can separate a variety of complex structural enantiomers with excellent reproducibility, thermal stability and separation performance. Hence, the unique advantage of the highly selective separation of L/DHis-BP5-Sil provides new insights into the enantioseparation field.

NMR Relaxation Dispersion of Liquids Adsorbed on Modified Surfaces of SBA-15 Mesoporous Silica

NMR Relaxation Dispersion of Liquids Adsorbed on Modified Surfaces of SBA-15 Mesoporous Silica

Mesoporous silica nanoparticles as a drug delivery mechanism.

Research in intelligent drug delivery systems within the field of biomedicine promises to enhance drug efficacy at disease sites and reduce associated side effects. Mesoporous silica nanoparticles (MSNs), characterized by their large specific surface area, appropriate pore size, and excellent biocompatibility, have garnered significant attention as one of the most effective carriers for drug delivery. The hydroxyl groups on their surface are active functional groups, facilitating easy functionalization. The installation of controllable molecular machines on the surface of mesoporous silica to construct nanovalves represents a crucial advancement in developing intelligent drug delivery systems (DDSs) and addressing the issue of premature drug release. In this review, we compile several notable and illustrative examples of MSNs and discuss their varied applications in DDSs. These applications span regulated and progressive drug release mechanisms. MSNs hold the potential to enhance drug solubility, improve drug stability, and mitigate drug toxicity, attributable to their ease of functionalization. Furthermore, intelligent hybrid nanomaterials are being developed, featuring programmable properties that react to a broad spectrum of stimuli, including light, pH, enzymes, and redox triggers, through the use of molecular and supramolecular switches.

Ethylene trimerization using half‐sandwich titanium‐based catalysts supported on mesoporous silica modified with ionic liquids

Linear alpha olefins (LAOs) are produced industrially via ethylene oligomerization using catalytic methods. The cost‐effective separation process has sparked significant interest in the selective oligomerization of ethylene to produce alpha‐olefins, including 1‐hexene (1‐C6), in multi‐product commercial processes. In addition, the utilization of immobilized catalysts is crucial because of their reduced environmental impact, ease of catalyst separation, recyclability, and transportability. Furthermore, the use of immobilized catalysts simplifies the purification process, making it easier to isolate pure products. In the present study, mesoporous silica (MS) was first modified with ionic liquids (ILs) consisting BF4− and Br− counter‐anions to prepare IL‐BF4@MS and IL‐Br@MS, respectively. Then 12 catalysts were synthesized through immobilization of the half‐sandwich catalysts with different bridges on the surface of MS, IL‐Br@MS, and IL‐BF4@MS and characterized by BET, TGA, and SEM–EDX‐Mapping analyses. UV–Visible spectroscopy showed a tetrahedral structure for the synthesized complexes. The activity and selectivity of the catalysts for the production of 1‐hexene were studied under specific conditions, including an ethylene pressure of 8 bar, a temperature of 40 °C, and an Al/Ti ratio of 1:2000. The C1‐IL‐BF4@MS immobilized catalyst with cyclohexane middle bridge immobilized on MS modified with IL‐BF4 revealed the highest activity (1199 kg 1‐C6 molTi−1·h−1) at a catalyst concentration of 1.5 μmol. The lowest activity (138 kg 1‐C molTi−1·h−1) was obtained for both C3@MS and C4@MS catalysts.

Covalent bonding of N-hydroxyphthalimide on mesoporous silica for catalytic aerobic oxidation of p-xylene at atmospheric pressure.

The surface of SBA-15 mesoporous silica was modified by N-hydroxyphthalimide (NHPI) moieties acting as immobilized active species for aerobic oxidation of alkylaromatic hydrocarbons. The incorporation was carried out by four original approaches: the grafting-from and grafting-onto techniques, using the presence of surface silanols enabling the formation of particularly stable O-Si-C bonds between the silica support and the organic modifier. The strategies involving the Heck coupling led to the formation of NHPI groups separated from the SiO2 surface by a vinyl linker, while one of the developed modification paths based on the grafting of an appropriate organosilane coupling agent resulted in the active phase devoid of this structural element. The successful course of the synthesis was verified by FTIR and 1H NMR measurements. Furthermore, the formed materials were examined in terms of their chemical composition (elemental analysis, thermal analysis), structure of surface groups (13C NMR, XPS), porosity (low-temperature N2 adsorption), and tested as catalysts in the aerobic oxidation of p-xylene at atmospheric pressure. The highest conversion and selectivity to p-toluic acid were achieved using the catalyst with enhanced availability of non-hydrolyzed NHPI groups in the pore system. The catalytic stability of the material was additionally confirmed in several subsequent reaction cycles.

Optimizing the method for removing MSNs templates using an ionic liquid ([C4mim]Cl)

The key step in preparing mesoporous silica is to remove the organic template agent, and the most common method used to achieve this goal is high-temperature calcination. However, this method has many disadvantages, one of which is that it reduces the silanol density on the surface of mesoporous silica, which affects its subsequent modification. Ionic liquids (ILs) are often used as extractants. In this work, the 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) IL is considered, and the effects of its concentration, reaction temperature, and reaction time as well as HCl concentration on the extraction rate and silanol density were investigated using an IL extraction template agent (cetyl trimethyl ammonium bromide (CTAB)). The results show that an IL concentration of 10%, a reaction temperature of 120 °C, a reaction time of 12 h, and an HCl concentration of 1% are the best reaction parameters; with these parameters, the extraction rate and the silanol density were found to be 93.19% and 2.23%, respectively. The silanol density of mesoporous silica treated by calcination is only 0.81%. A higher silanol density provides more reaction sites, so that the modified mesoporous silica treated with the IL can be loaded with more Zn ions.

Grafting and controlled release of antimicrobial peptides from mesoporous silica.

The grafting of antimicrobial peptides onto mesoporous silica particles and their controlled release using a green light-responsive linker, which enables tunable release-concentration-time profiles, is presented. The mesoporous silica surface is functionalized with antimicrobial peptides employing sequential functionalization steps, including the grafting of 3-[(2-propynylcarbamate)propyl]triethoxysilane (PPTEOS) as anchor, boron-dipyrromethene (BODIPY) as photosensitive linker, and C14R peptides as antimicrobial agents. Characterization using scanning electron microscopy (SEM), transmission electron microscopy (TEM), attenuated total reflectance infrared (ATR-IR) spectroscopy, and thermogravimetric analysis (TGA) validate the successful fabrication and functionalization of mesoporous silica. The ester-1,2,3-triazole-BODIPY demonstrates high sensitivity to green light and enables C14R antimicrobial peptide release with adjusted concentration-time profiles. Under the applied conditions up to 64 μg mL-1 were released within 40 minutes. The antimicrobial activity of the released C14R on Escherichia coli. BL21(DE3) is demonstrated. Overall, the use of the photosensitive linker not only provides a promising avenue for controlling the release of biomolecules and therapeutics but also opens up opportunities for the development of materials for targeted release in wound dressings, for example.

Synthesis and characterization of mesoporous silica supported metallosalphen-azobenzene complexes: efficient photochromic heterogeneous catalysts for the oxidation of cyclohexane to produce KA oil.

The oxidation of cyclohexane to produce KA oil (cyclohexanone and cyclohexanol) is important industrially but faces challenges such as low cyclohexane conversion at high KA oil selectivity, and difficult catalyst recyclability. This work reports the synthesis and evaluation of new heterogeneous catalysts consisting of Co(ii), Mn(ii), Ni(ii) and Cu(ii) salphen-azobenzene complexes [ML1] immobilized on amino-functionalized mesoporous silica (SBA-15, MCM-41, MCM-48) through coordination bonding. In the first step, the salphen-azobenzene ligand was synthesized and complexed with Co, Mn, Ni and Cu metal ions. In the second step, aminopropyltriethoxysilane (APTES) was grafted onto the surface of different types of commercial mesoporous silica. The immobilization of [ML1] onto the mesoporous silica surface and the thermal stability of the obtained materials were confirmed using different characterization techniques such as FT-IR, powder XRD, SEM, TEM, BET, and TGA. The obtained results revealed high dispersion of [ML1] through the silica surface. The catalytic activity of the prepared materials Silica-N-ML1 was evaluated on the cyclohexane oxidation to produce KA oil using various oxidants. The cis-trans isomerization of the azobenzene upon UV irradiation was found to affect the catalytic performance of Silica-N-ML1. The cis isomer of SBA-15-N-CoL1 exhibited the highest cyclohexane conversion (93%) and KA selectivity (92%) under mild conditions (60 °C, 6 h) using m-CPBA as oxidant. Moreover, The SBA-15-N-CoL1 showed high stability during four successive cycles.

Stabilisation of molecular TiO4 species on the pore surface of mesoporous silica for photocatalytic H2 evolution.

Although molecular tetrahedral Ti-oxo species exhibit unique electronic and photochemical properties due to their discrete energy levels, which are different from those of anatase and rutile, such Ti-oxo species are generally unstable and readily transformed to amorphous/crystalline TiO2 (bulk phases, nanoparticles and clusters) via hydrolysis and condensation. Here, molecular Ti-oxo species were immobilised within mesoporous silica SBA-15 by grafting titanium(IV) oxyacetylacetonate using the surface silanol groups of SBA-15 as a scaffold, followed by chemical etching with dilute hydrochloric acid to form molecular TiO4 species. These Ti species mainly exist as isolated tetrahedrally coordinated structures, as was confirmed by diffuse reflectance UV-vis and Raman spectroscopy. The SBA-15-immobilised molecular TiO4 exhibited higher photocatalytic activity for H2 evolution from an aqueous methanol solution than conventional Ti-incorporated mesoporous silica (Ti-MCM-41) and reference TiO2 (P25).

Metallic Cation-Mediated Entrapment of Nucleic Acids on Mesoporous Silica Surface: Application in Castration-Resistant Prostate Cancer

Metallic Cation-Mediated Entrapment of Nucleic Acids on Mesoporous Silica Surface: Application in Castration-Resistant Prostate Cancer

Preparation and Characterization of a Novel Additive for Elastomeric Polymer from Oligoisoprene Modified Mesoporous Silica

This manuscript presents a novel instant additive for elastomeric polymers, specifically focusing on the modification of synthesized mesoporous silica using carbonyl telechelic natural rubber (CTNR). The surface of mesoporous silica particles was modified using a two-step approach. In the first step, a strategy involving the grafting of 3-aminopropyltriethoxysilane (APTES) onto the silica particles was employed. Subsequently, in the second step, a Schiff's base reaction was carried out between the aldehyde functional group of CTNR and the amines on the modified silica surface. The grafting percentage achieved through this process was determined to be 4.70%. This novel instant additive has the potential to enhance the properties and performance of elastomeric polymers by leveraging the unique characteristics of CTNR and the mesoporous silica surface. Further investigations and applications of this additive can contribute to advancements in the field of elastomeric polymer materials.

Natural Rubber/Hexagonal Mesoporous Silica Nanocomposites as Efficient Adsorbents for the Selective Adsorption of (-)-Epigallocatechin Gallate and Caffeine from Green Tea.

(-)-Epigallocatechin gallate (EGCG) is a bioactive component of green tea that provides many health benefits. However, excessive intake of green tea may cause adverse effects of caffeine (CAF) since green tea (30-50 mg) has half the CAF content of coffee (80-100 mg). In this work, for enhancing the health benefits of green tea, natural rubber/hexagonal mesoporous silica (NR/HMS) nanocomposites with tunable textural properties were synthesized using different amine template sizes and applied as selective adsorbents to separate EGCG and CAF from green tea. The resulting adsorbents exhibited a wormhole-like silica framework, high specific surface area (528-578 m2 g-1), large pore volume (0.76-1.45 cm3 g-1), and hydrophobicity. The NR/HMS materials adsorbed EGCG more than CAF; the selectivity coefficient of EGCG adsorption was 3.6 times that of CAF adsorption. The EGCG adsorption capacity of the NR/HMS series was correlated with their pore size and surface hydrophobicity. Adsorption behavior was well described by a pseudo-second-order kinetic model, indicating that adsorption involved H-bonding interactions between the silanol groups of the mesoporous silica surfaces and the hydroxyl groups of EGCG and the carbonyl group of CAF. As for desorption, EGCG was more easily removed than CAF from the NR/HMS surface using an aqueous solution of ethanol. Moreover, the NR/HMS materials could be reused for EGCG adsorption at least three times. The results suggest the potential use of NR/HMS nanocomposites as selective adsorbents for the enrichment of EGCG in green tea. In addition, it could be applied as an adsorbent in the filter to reduce the CAF content in green tea by up to 81.92%.

Atomic insights into the heterogeneity and the interface interactions of nanoconfined aqueous electrolyte solution

The structure and properties of nanoconfined electrolyte (nano electrolyte) solutions are important subjects in biochemistry, electrochemistry, separation science, etc. In the present work, neutron scattering and data driven reverse Monte Carlo were employed to quantitatively reveal the microstructure of aqueous CaCl2 solution in mesoporous silica MCM-41 at the atomic level. The electrolyte solution distributes in-homogeneously in the pores of mesoporous silica along the radial direction, which can be divided into the core, the transition, and the interface regions. The hydrogen bond structure of water in nano electrolytes is strengthened in the core region, analogous to that of nano water confined in nanochannels, and the ion association was enhanced in the transition region. The structure of the solution in the interface region was analogous to the bulk electrolyte solution under high pressure because of the confinement and interface effects. When the package ratio of nano electrolyte solution is insufficient, small amount of solution quasi-monolayer adsorb on the internal surface of mesoporous silica, the majority solution preferentially forms clusters with different sizes to adhere to the wetted interface. The anomalous hydrogen-bonding structure and ion association found in the present work improve our understanding of nanoconfined electrolyte solutions.

Organically modified mesoporous silica as a performance additive in tubular quenched polypropylene films

Mesoporous silica nanoparticles were synthesized by base-catalyzed hydrolysis of tetraethyl orthosilicate in the water-acetone medium. For surface modification of mesoporous silica, commercially available silane, 3-(trimethoxysilyl)propyl methacrylate was reacted with mono-thioglycerol via 2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl (TEMPO) aided thiol-ene reaction, and the obtained silane was incorporated on the surface of neat mesoporous silica to graft extended alkyl chains terminating in hydroxyl groups. The prepared MSNs were characterized by thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), nitrogen adsorption-desorption analysis, scanning electron microscopy, and dynamic light scattering. These MSNs were compared to conventionally used commercial silica as an additive in tubular quenched polypropylene films (TQPP) for their anti-blocking, thermal, mechanical, optical, and barrier properties. Organic modification of MSNs decreased the blocking force in TQPP films. The mechanical properties including % elongation and tensile strength increased for TQPP films with mesoporous silica, while it decreased for films containing commercial silica. Both modified and unmodified MSNs decreased haze and enhanced gloss in TQPP films, showing improved optical properties as compared to commercial silica particles. In TQPP film with modified MSNs, a reduced value of the water contact angle was obtained, indicating better wettability of the surface of the TQPP film.

Temperature dependence of aggregation behavior and dye adsorption of poly(N-isopropylacrylamide) hydrogel/mesoporous silica composites

This study aimed to synthesize mesoporous silica (MS) with various amounts of poly(N-isopropylacrylamide) (PNIPAM) hydrogel using two procedures and investigate the influence of the PNIPAM hydrogel on the aggregation performance of the synthesized PNIPAM hydrogel/MS composite at temperatures above the lower critical solution temperature (LCST) of PNIPAM (i.e., 32 °C) and adsorption behavior of the composite below the LCST. To rapidly recover an MS adsorbent from water, we synthesized the MS coated with hydrogel composed of PNIPAM as a temperature-responsive polymer and N, N′-methylenebisacrylamide (BIS) as a cross-linker. We characterized our samples using ultraviolet-visible spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption and desorption experiment, and thermogravimetric analysis (TG). Using TG, we found that the amount of immobilized PNIPAM hydrogel could vary from 6.6 to 57.5 wt% by changing the amount of BIS and the immobilization procedure. The XRD patterns revealed that the PNIPAM hydrogel coating had slight influence on the MS structure. The higher the amount of PNIPAM hydrogel in the composite, the faster the turbidity rate decreased based on the turbidity measurement of the supernatant solution during the PNIPAM hydrogel/MS composite sedimentation test in water at 50 °C. The coating by PNIPAM hydrogel of the MS surface only slightly affected the amount of methyl orange adsorbed at 30 °C.

Construction of Dual-Channel Water Transport in Mesoporous Silica Low Humidity Sensors to Achieve High Sensitivity.

In this paper, strong hydrophilic poly(ionic liquid)s (PILs) are selectively grafted on different positions (mesoporous channels and outer surface) of mesoporous silica via thiol-ene click chemical reaction. The purposes of selective grafting are on the one hand, to explore the differences of adsorption and transportation of water molecules in mesoporous channels and on the outer surface, and on the other hand, to combine the two approaches (intra-pore grafting and external surface grafting) to reasonably design SiO2 @PILs low humidity sensing film with synergetic function to achieve high sensitivity. The results of low relativehumidity （RH）sensing test show that the sensing performance of humidity sensor based on mesoporous silica grafted with PILs in the channels is better than that of humidity sensor based on mesoporous silica grafted with PILs on the outer surface. Compared with water molecules transport single channel, the construction of dual-channel water transport significantly improves the sensitivity of the low humidity sensor, and the response of the sensor is up to 4112% in the range of 7-33% RH. Moreover, the existence of micropores and the formation of dual-channel water transport affect the adsorption/desorption behaviors of the sensor under different humidity ranges, especially below 11% RH.