Hybrid Organic-inorganic Monolith Research Articles

Toward High-Efficient Chiral Separation Using Hierarchically Porous HROP@Silica-Gel-Sheet Composite.

Separating racemates is still a great challenge for their similarity in chemical structures and physicochemical properties. Despite exhibiting a significant potential in the adsorption separation due to their intrinsic characteristics, hierarchically porous materials utilized in enantioseparation have rarely been reported to date. Furthermore, the molding of such materials together with their hybrid organic-inorganic monoliths is generally required to meet various prerequisites in diverse large-scale industrial applications, but without sacrificing their inherently hierarchical architectures. In this work, a three-dimensional hierarchically porous organic-inorganic composite was simply and feasibly prepared via integrating the micro/meso-porous hyper-cross-linked resin organic polymer (HROP) with macroporous silica gel sheet (SGS), followed by a chiral selector postmodification, named as HROP@SGS. Racemic 1-phenylethanol, ibuprofen, and naproxen could be separated only using such a piece of HROP@SGS as the filler with a solid phase extraction technique. Herein, HROP@SGS exhibited extraordinary chiral resolution performances and succeeded in achieving a complete chiral resolution. Our findings suggest that this simple strategy proposed by us, that is, combining the chiral micro/mesoporous organic materials with macroporous inorganic substrates, can be employed to prepare an unprecedented enantioseparation material, which has a promising potential in large-scale industrial applications, such as fixed-bed and membrane separation.

Recent development of hybrid organic-silica monolithic columns in CEC and capillary LC.

As an attractive alternative to organic and silica monoliths, hybrid organic-inorganic monolith somewhat combines the advantages of them, such as high surface area, excellent mechanical strength, and thermal stability. We have reviewed the preparation and application of hybrid monoliths in 2011 and 2013. The preparation approaches have been mainly summarized into three categories: (1) common sol-gel process using trialkoxysilanes and tetraalkoxysilanes as precursors; (2) "one-pot" process of alkoxysilanes and organic monomers simultaneously via sol-gel chemistry and free radical polymerization; and (3) other polymerization of silane-containing monomers. Herein, we would focus on the recent progress and development of preparation approaches, mainly covering the literatures since July of 2012. First, the direct synthesis approach of hybrid monoliths via sol-gel chemistry and following postmodification was an important route to fabricate various monolithic stationary phases, particularly, to modify the hybrid monoliths containing amino, epoxy, vinyl, and other groups. Second, "one-pot" process, as a novel preparation approach of hybrid monoliths, was further developed in the past 2 years, in which various organic functional monomers, not only water-soluble monomers, but also hydrophobic monomers could be added in the preparation system. Other polymerization techniques in the preparation of organic monolithic materials, particularly, free radical polymerization and ring-opening polymerization, were successfully transferred to fabricate the hybrid monoliths by using silane-containing monomers including POSS monomers or other self-synthesized monomers.

Preparation of a hybrid organic-inorganic monolith for extraction and purification of quercetin and myricetin from Chamaecyparis obtusa

A new hybrid organic-inorganic monolithic cartridge was synthesized and used as the selective sorbent for the extraction and purification of quercetin and myricetin from Chamaecyparis obtusa via a solid-phase extraction method. The morphology of the monolithic material was examined by field emission-scanning electron microscopy and a Brunauer-Emmett-Teller(BET) test. The adsorption capacity of the obtained material for quercetin and myricetin was investigated by fitting the adsorption data to four different adsorption equations, of which the Langmuir-Freundlich isotherm was selected as the most suitable model. Under optimized conditions, good calibration curves were observed at nine concentrations ranged from 0.5 μg/mL to 100.0 μg/mL of quercetin and myricetin. The extraction recovery ranged from 74.5% to 84.6% and the inter- and intra-day relative standard deviations were <6%. This type of hybrid monolith has potential for the separation and purification of bioactive compounds from natural plant extracts.

Hybrid organic–inorganic monolithic enzymatic reactor with SBA-15 nanoparticles incorporated

A novel enzymatic reactor was prepared by incorporating SBA-15 nanoparticles into hybrid organic-inorganic monolith and immobilizing trypsin with glutaraldehyde as bridging reagent. Preparation and operation conditions including nanoparticles percentage and residence time were optimized to improve the digestion efficiency. The digestion products were characterized by Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (MALDI-TOF-MS) with sequence coverage of 50%, 93% and 71% for bovine serum albumin, myoglobin and cytochrome C, while consuming only about 19s in dynamic mode. Compared with enzymatic reactor without nanoparticles incorporated, the enzymatic reactor with SBA-15 nanoparticles embedded achieved higher digestion efficiency by introducing more trypsin, which was originated from combination of SBA-15 nanoparticles and hybrid organic-inorganic monolith.

Immobilized antibody on a hybrid organic–inorganic monolith: Capillary immunoextraction coupled on-line to nanoLC-UV for the analysis of microcystin-LR

A complete characterization of a highly selective miniaturized immunosorbent (mIS) coupled on-line to nanoLC-UV is presented. A hybrid organic–inorganic monolith was synthesized in a 100μm i.d. capillary via a sol–gel process using tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) as precursors. After an activation step, monoclonal antibodies specific for microcystin-LR (MC-LR), the model molecule, were grafted on this porous media. The resulting mIS was coupled on-line to nanoLC-UV. Specific retention of MC-LR on the mIS was demonstrated with extraction recovery above 70% in pure water. Synthesis and grafting were repeated leading to reproducible extraction yields. The capacity of one of the prepared sorbents was determined as being 375pg. This miniaturized device was then applied to the selective extraction of MC-LR from blue-green algae extracts and revealed to be effective in isolating MC-LR from these complex samples thus improving the reliability of its analysis at the trace level.

Extraction of Astaxanthin from Shrimp Waste using Response Surface Methodology and a New Hybrid Organic-Inorganic Monolith

A 17-run Box-Behnken design (BBD) with three factors was used to improve the conditions for extracting astaxanthin from shrimp waste. The astaxanthin level was determined by high performance liquid chromatography (HPLC) using a C18 column and a UV detector at 476 nm. The mean extraction yield of astaxanthin at the improved conditions (extraction time 1.4 h, extraction temperature 72.4°C, and liquid-solid ratio 27.3) was 98.7 ± 2.6 µg g−1. A solid-phase extraction (SPE)-HPLC method was developed with a new hybrid organic-inorganic hybrid monolith for further purification of astaxanthin from shrimp waste. The SPE recoveries were ranging from 81.3 ± 2.4% to 86.5 ± 3.3%, and the intra-day and inter-day relative standard deviations (RSDs) of the proposed method were less than 4.3 ± 0.5% and 4.8 ± 0.2%, respectively. BBD increased the extraction efficiency and shortened extraction times significantly. SPE-HPLC with hybrid monolith showed good selectivity and purified astaxanthin from shrimp waste.

Preparation and applications of hybrid organic–inorganic monoliths: A review

This review presents an overview of the properties of hybrid organic-inorganic monolithic materials and summarizes the recent developments in the preparation and applications of these hybrid monolithic materials. Hybrid monolithic materials with porosities, surface functionalities, and fast dynamic transport have developed rapidly, and have been used in a wide range of applications owing to the low cost, good stability, and excellent performance. Basically, these materials can be divided into two major types according to the chemical composition: hybrid silica-based monolith (HSM) and hybrid polymer-based monolith (HPM). Compared to the HPM, HSM monolith has been attracting most wide attentions, and it is commonly synthesized by the sol-gel process. The conventional preparation procedures of two type's hybrid organic-inorganic monoliths are addressed. Applications of hybrid organic-inorganic monoliths in optical devices, capillary microextraction (CME), capillary electrochromatography (CEC), high performance liquid chromatography (HPLC), and chiral separation are also reviewed.

Synthesis of propyl‐functionalized hybrid monolithic silica capillaries and evaluation of their performances in nano‐LC and CEC

During the last decade, silica monolithic capillaries have focused more and more attention on miniaturized separation techniques like CEC, nano-LC, and chip electrochromatography owing to their unique chromatographic properties and to their possible in situ synthesis. Nevertheless, the preparation of conventional silica-based individual monolithic columns is time consuming, owing to the individual steps involved, including the synthesis of the silica matrix and its subsequent on-column chemical grafting. The hybrid organic-inorganic monoliths, whose synthesis is based on the polycondensation of siloxane with organosiloxane precursors, seems to be an attractive alternative since their direct synthesis leads to silica monoliths with organic moieties covalently linked to the inorganic silica matrix through hydrolytically stable Si-C bonds. This study describes the synthesis of hybrid monoliths using propyltrimethoxysilane (C3-TriMOS) as a new kind of silica coprecursor to subsequently increase the hydrophobicity of the stationary phase. The influence of several experimental parameters (pH, gelation temperature, relative proportion of the precursors) on the textural (skeleton and macropore size) and chromatographic properties (efficiency, retention, and electroosmotic mobility) of the obtained monoliths are discussed. The results show that the optimal coprecursor incorporation is obtained after a postgelation step during which the condensation of the C3-TriMOS coprecursor is favored by an increase in the pH medium. Thermal hydrolysis of urea previously added to the polymerization mixture allows this in situ pH increase. These hybrid monoliths present hydrophobic properties and allow the separation of test mixtures in the RP mode without any further modification. Moreover, they present excellent efficiencies since reduced plate height as low as 5 and 15 microm are obtained in the electrodriven mode (CEC) and in the hydrodynamic one (nano-LC), respectively.

Sol-gel synthesis of hybrid organic-inorganic monoliths doped with colloidal CdSe/ZnS core-shell nanocrystals

Colloidal CdSe/ZnS core-shell nanocrystals, with a narrow size distribution, were dispersed in a hybrid sol resulting from the hydrolysis of tetraethylorthosilicate and 3-glycidoxypropyltrimethoxysilane (GLYMO). In order to reduce the gelation time and the exposure of the nanoparticles to air, several catalysts of the GLYMO epoxy ring opening were employed for the sol preparation, such as imidazole, methyl-imidazole, pyridine, benzylamine, propylamine. The role of the various catalysts was monitored by optical absorption measurements in the near infrared region, by observing the evolution of the epoxy bands. Imidazole was found to provide the fastest gelation and the best results in terms of bubble disappearance from the gel structure. The variation in the optical properties of the semiconductor nanoparticles embedded in the matrix was monitored as a function of the gelation time and was compared to the optical absorption and photoluminescence spectra of the nanoparticles dissolved in a chloroform solution. A decrease in the gelation-time results in a closer resemblance between the optical properties of the CdSe/ZnS doped monoliths and those of the particles dissolved in the solvent, before incorporation in the matrix. The photoluminescence of the CdSe/ZnS nanocrystals is not bleached after they are trapped in the glassy matrix.