Precursor Mediated Synthesis of Nanostructured Silicas: From Precursor-Surfactant Ion Pairs to Structured Materials

Imidazolium-Containing Hybrid Organic-Inorganic Materials for the Conversion of CO2: Unveiling the Key Role of the Ionic Template

A straightforward synthesis of a series of hybrid organic-inorganic materials (HOIMs) containing imidazolium moieties was achieved. The preparation of the imidazolium acetate precursor was performed in a single-step procedure using the Debus-Radziszewski reaction. The as-synthesized alkoxysilane was employed in combination with tetraethyl orthosilicate to generate an HOIM presenting a high specific surface area. Two different structure-directing agents (SDAs), an anionic (sodium dodecyl sulfate (SDS)) or a cationic (cetyltrimethylammonium bromide) surfactant, were used to investigate the role played by the SDA on the distribution of the imidazolium-based active sites within the silica structure. After the synthesis, the acetate ion was replaced with Cl- and Br- via a simple acid treatment. This procedure favors also the removal of the surfactant, thus releasing the porosity of the solids. The HOIMs synthesized were fully characterized via low-angle X-ray diffraction, N2 physisorption, transmission electron microscopy, 13C and 29Si MAS NMR, combustion chemical analysis, X-ray photoelectron spectroscopy, and CO2 physisorption to assess their physicochemical and structural features, as well as the successful incorporation of imidazolium salts. Their catalytic activity in the conversion of CO2 was tested over different epoxides to produce the corresponding cyclic carbonates. The key role of the SDS (anionic surfactant) as a templating agent was proved. The best material was stable under the selected reaction conditions, reusable over multiple cycles, and active on a series of different epoxides, thus proving its versatility.

Mesoporous TiO2-based architectures as promising sensing materials towards next-generation biosensing applications

In the past two decades, mesoporous TiO2 has emerged as a promising material for biosensing applications. In particular, mesoporous TiO2 materials with uniform, well-organized pores and high surface areas typically exhibit superior biosensing performance, which includes high sensitivity, broad linear response, low detection limit, good reproducibility, and high specificity. Therefore, the development of biosensors based on mesoporous TiO2 has significantly intensified in recent years. In this review, the expansion and advancement of mesoporous TiO2-based biosensors for glucose detection, hydrogen peroxide detection, alpha-fetoprotein detection, immobilization of enzymes, proteins, and bacteria, cholesterol detection, pancreatic cancer detection, detection of DNA damage, kanamycin detection, hypoxanthine detection, and dichlorvos detection are summarized. Finally, the future perspective and research outlook on the utilization of mesoporous TiO2-based biosensors for the practical diagnosis of diseases and detection of hazardous substances are also given.

Sol-gel process: the inorganic approach in protein imprinting

Proteins play a central role in the signal transmission in living systems since they are able to recognize specific biomolecules acting as cellular receptors, antibodies or enzymes, being themselves recognized by other proteins in protein/protein interactions, or displaying epitopes suitable for antibody binding. In this context, the specific recognition of a given protein unlocks a range of interesting applications in diagnosis and in targeted therapies. Obviously, this role is already fulfilled by antibodies with unquestionable success. However, the design of synthetic artificial systems able to endorse this role is still challenging with a special interest to overcome limitations of antibodies, in particular their production and their stability. Molecular Imprinted Polymers (MIPs) are attractive recognition systems which could be an alternative for the specific capture of proteins in complex biological fluids. MIPs can be considered as biomimetic receptors or antibody mimics displaying artificial paratopes. However, MIPs of proteins remains a challenge due to their large size and conformational flexibility, their complex chemical nature with multiple recognition sites and their low solubility in most organic solvents. Classical MIP synthesis conditions result in large polymeric cavities and unspecific binding sites on the surface. In this review, the potential of the sol-gel process as inorganic polymerization strategy to overcome the drawbacks of protein imprinting is highlighted. Thanks to the mild and biocompatible experimental conditions required and the use of water as a solvent, the inorganic polymerization approach better suited to proteins than organic polymerization. Through numerous examples and applications of MIPs, we proposed a critical evaluation of the parameters that must be carefully controlled to achieve sol-gel protein imprinting (SGPI), including the choice of the monomers taking part in the polymerization.

Fundamentals and recent progress relating to the fabrication, functionalization and characterization of mesostructured materials using diverse synthetic methodologies

Since 1990 and the invention of the very first generation of ordered mesoporous silica materials, several innovative methodologies have been applied to synthesize, characterize, and modify silica/non-silica mesoporous materials. The growth of the mesoporous materials field has generated significant environmental and economic advantages compared to various other industrial developments. According to the literature, there are several key synthesis approaches and parameters that can affect the structural, textural and morphological characteristics of mesoporous materials. To date, huge attempts have been made to maximize the activities and selectivities of these materials through either the in situ or post-synthesis functionalization of the large interior surface areas and internal mesostructured frameworks in the presence of specific organic/inorganic components. However, the main challenge is to provide good control over the incorporation and distribution of multiple guest components within the mesostructured hosts. Mesostructured materials have received great attention for various applications, such as being used in electronics, medicine, photocatalysis, catalyst supports, catalysis, absorbers, sensors, gas separation, etc. In the current paper, several recent developments have been highlighted and reviewed regarding the fabrication and characterization of siliceous/non-siliceous mesoporous materials via various synthetic approaches. Furthermore, the availability of diverse functionalization methods has been reviewed to provide comprehensive approaches for synthesizing new generations of suitably modified mesoporous materials with superior structural, physicochemical, and textural characteristics.

Since 1990 and the invention of the very first generation of ordered mesoporous silica materials, several innovative methodologies have been applied to synthesize, characterize, and modify silica/non-silica mesoporous materials.

Biocompatible Periodic Mesoporous Ionosilica Nanoparticles with Ammonium Walls: Application to Drug Delivery

Periodic mesoporous ionosilica nanoparticles with ammonium walls were synthesized exclusively from a trisilylated ammonium precursor. The nanoparticles display a uniform particle size, together with a high specific surface area and an ordered hexagonal pore architecture. Completely biocompatible in vitro and in vivo, the nanoparticles are efficiently endocytosed by RAW 264.7 macrophages and used as carrier vehicles for anionic drugs. Diclofenac-loaded ionosilica nanoparticles are very efficient in inhibiting lipopolysaccharides-induced inflammation.