A Janus silica cage was synthesized by selectively grafting an ionic liquid (IL) and poly‐N‐isopropylacrylamide (PNIPAM) (lower critical solution temperature (LCST)≈32 °C) onto the exterior and interior sides of the mesoporous SiO2 shell. The paramagnetic core inside the cavity is responsible for magnetic collection. The PW12O403? anion is further conjugated onto the IL side by anion exchange. The Janus cage acts as a thermal‐responsive reactor for catalytic oxidization of dibenzothiophene (DBT) in the presence of H2O2. The sulfide in the model oil can be completely decomposed at 25 °C, whilst the oxidative products are more dissoluble in water and preferentially captured inside the Janus cage. The Janus cage reactor could be regenerated at high temperature above 32 °C after releasing the products. 相似文献
Core-shell structured SiO2/poly(N-isopropylacrylamide) (SiO2/PNIPAM) microspheres were successfully fabricated through hydrolysis and condensation reaction of tertraethyl or-thosilicate (TEOS) on the surface of PNIPAM template at 50 oC. The PNIPAM template can be easily removed by water at room temperature so that SiO2 hollow microspheres were finally obtained. The transmission electron microscope and scanning electron microscope observations indicated that SiO2 hollow microspheres with an average diameter of 150 nm can be formed only if there are enough concentration of PNIPAM and TEOS, and the hy-drolysis time of TEOS. FTIR analysis showed that part of PNIPAM remained on the wall of SiO2 because of the strong interaction between PNIPAM and silica. This work provides a clean and efficient way to prepare hollow microspheres. 相似文献
In this work, a new surface‐initiating system was constituted on the surfaces of cross‐linked polyvinyl alcohol (CPVA) microspheres, and on this basis, papain surface‐imprinted material was successfully prepared in aqueous solution. CPVA microspheres were modified with chlorethamin as reagent, and so a mass of primary amino group was introduced onto CPVA microspheres. Whereupon, a surface initiating system (−NH2/S2O82−) was formed at the interface between the microspheres and aqueous solution, in which papain as template protein, 4‐styrene sulfonate (SSS) as functional monomer, N,N′‐methylenebisacrylamide (MBA) as cross‐linker and (NH4)2S2O8 as initiator were all dissolved. In neutral solution, the polypeptide chains of papain as a basic protein were positively charged, and the molecules of anionic monomer SSS would spontaneously gather around papain polypeptide chain, forming complex by right of strong electrostatic interaction. The free radicals produced on CPVA microspheres initiated the monomer SSS around papain polypeptide chain and the cross‐linker MBA to produce graft/cross‐linking polymerization, and at the same time, papain macromolecules were embed in the cross‐linked networks. As a result, the graft/cross‐linking polymerizing of SSS and the molecule imprinting of papain were synchronously carried out, and papain surface‐imprinted material, MIP‐PSSS/CPVA microspheres, was obtained. The experimental results show that the papain surface‐imprinted material has excellent binding affinity and high recognition selectivity for papain. The binding capacity of MIP‐PSSS/CPVA microspheres for papain reaches 44 mg/g, and relative to another basic protein, trypsin (TRY) as contrast protein, the selectivity coefficient of MIP‐PSSS/CPVA microspheres for papain is 14.35, displaying very high recognition specificity. 相似文献
We present a protocol for the preparation of surface‐imprinted polymer microspheres by core–shell precipitation polymerization for the enantioseparation of (S)‐amlodipine. In this work, submicron mesoporous silica microspheres were prepared with gemini cationic surfactant as soft template. Molecularly imprinted polymers were coated on the silica supports with a low level of crosslinking, and the thickness of the thin‐walled imprinted shell was about 45 nm. The material showed fast binding kinetics for (S)‐amlodipine (within only 20 min for complete equilibrium), and the saturation adsorption capacity reached 309.2 mg/g, indicating the good accessibility of binding sites and improved mass transfer for target molecule. The imprinted microspheres exhibited an appreciable enantiomeric excess of (S)‐amlodipine of 11.3% when used as a glass chromatography column for the enantioseparation of (S)‐amlodipine from amlodipine besylate without extra chiral additives. The surface‐imprinted materials display potentially amplification for industrial enantioseparation of (S)‐amlodipine. 相似文献
The surface imprinting technique has been developed to overcome the mass‐transfer difficulty, but the utilization ratio of template molecules in the imprinting procedure still remains a challengeable task to be improved. In this work, specifically designed surface‐imprinted microspheres were prepared by a template‐oriented method for enantioseparation of amlodipine besylate. Submicron mesoporous silica microspheres were surface‐modified with double bonds, followed by polymerizing methacrylic acid to generate carboxyl modified mesoporous silica microspheres (PMAA@SiO2). Afterwards, PMAA@SiO2 was densely adsorbed with (S )‐amlodipine molecules to immobilize template molecules through multiple hydrogen bonding interactions. Then surface molecular imprinting was carried out by cross‐linking the carboxyl group of PMAA@SiO2 with ethylene glycol diglycidyl ether. The surface‐imprinted microspheres showed fast binding kinetics of only 20 min for equilibrium adsorption, and the saturation adsorption capacity reached 137 mg/g. The imprinted materials displayed appreciable chiral separation ability when used as column chromatography for enantioseparation of amlodipine from amlodipine besylate, and the enantiomeric excess of (S )‐amlodipine reached 13.8% with only 2.3 cm column length by no extra chiral additives. Besides, the imprinted materials exhibited excellent reusability, and this allows the potential application for amplification production of amlodipine enantiomer. 相似文献
A series of poly( N-isopropyl acrylamide) (PNIPAM) samples with molecular weight ranging from 2.23×10~4 to 130×10~4 and molecular weight distribution M_w/M_n≤1.28 were obtained by free radical polymerization and repeat precipitation fractionation. The molecular weight M_w, second virial coefficient A_2 as well as the mean-square-root radius of gyration 〈S~2〉 for PNIPAM samples in tetrahydrofuran (THF) were determined by light scattering, and the relations were estimated at A_2 ∞ M_w~0.25) and 〈S~2〉~(1/2)=1.56×10~(-9) M_w~(0.56). The intrinsic viscosity for THF solution and methanol solution of PNIPAM samples was measured and the Mark-Houwink equations were obtained as [η]=6.90×10~(-5) M~(0/73) (THF solution) and [η]=1.07×10~(-4) M~(0.71) (methanol solution). The above results indicate that both THF and methanol are good solvents for PNIPAM. The limit characteristic ratio C_∞ for PNIPAM in the two solutions was determined to be 10.6 by using Kurata-Stockmayer equation, indicating that the f 相似文献
Temperature‐sensitive imprinted and non‐imprinted hydrogels composed of N‐isopropylacrylamide (NIPA) and 2‐acrylamido‐2‐methyl‐propanosulfonic acid (AMPS) have been prepared by free‐radical crosslinking copolymerization in aqueous solution at three different temperatures: 10 °C (below the lower critical solution temperature, LCST), 33 °C (at the LCST), and 40 °C (above the LCST). Myoglobin (Mb, MW 17 kDa) is used as the template biomolecule. The effects of the initial concentration and adsorption time over the Mb adsorption capacity of the hydrogels have been analyzed and found to be strongly dependent on the preparation temperature (Tprep). The maximum Mb adsorption for the imprinted hydrogel prepared at 10 °C is 97.40 ± 2.35 mg Mb · g−1 dry gel in 0.32 mg · mL−1 Mb solution at 22 °C. Moreover, batch adsorption equilibrium and selectivity studies have been performed using a reference molecule, hemoglobin (Hb, MW 65 kDa). The imprinted hydrogels have a 2.8–3.3 times higher adsorption capacity for Mb than the non‐imprinted hydrogels prepared at the same Tpreps, and also have a 1.8–2.7 times higher selectivity for the imprinted molecule.
A novel sensor for the determination of parathion‐methyl based on couple grafting of functional molecular imprinted polymers (MIPs) was fabricated which is developed by anchoring the MIP layer on surfaces of silica particles embedded CdSe quantum dots by surface imprinting technology. The synthesized molecular imprinted silica nanospheres (CdSe@SiO2@MIP) allow a high selectivity and sensitivity of parathion‐methyl via fluorescence intensity decreasing when the MIP material rebinding the parathion‐methyl molecule. Compared with the MIP fabricated in traditional method, the template of parathion‐methyl was easier to remove from the CdSe@SiO2@MIP imprinted material. Under optimal conditions, the fluorescence intensity of parathion‐methyl at the imprinted sensor was detected by spectrofluorophotometer. The relative fluorescence intensity of CdSe@SiO2@MIP decreased linearly with the increasing concentration of parathion‐methyl ranging from 0.013 mg·kg−1 to 2.63 mg·kg−1 with a detection limit (3δ) of 0.004 mg·kg−1 (S/N=3), which is lower than the MIP in tradition. The imprinted film sensor was applied to detect parathion‐methyl in vegetable samples without the interference of other organophosphate pesticides and showed a prosperous application in the field of food safety. 相似文献
This study presents a new synthetic method for fabricating yolk@shell‐structured barium magnesium silicate (BMS) particles through a template‐engaged solid‐state reaction. First, as the core template, (BaMg)CO3 spherical particles were prepared based on the coprecipitation of Ba2+ and Mg2+. These core particles were then uniformly shelled with silica (SiO2) by using CTAB as the structure‐directing template to form (BaMg)CO3@SiO2 particles with a core@shell structure. The (BaMg)CO3@SiO2 particles were then converted to yolk@shell barium magnesium silicate (BMS) particles by an interfacial solid‐state reaction between the (BaMg)CO3 (core) and the SiO2 (shell) at 750 °C. During this interfacial solid‐state reaction, Kirkendall diffusion contributed to the formation of yolk@shell BMS particles. Thus, the synthetic temperature for the (BaMg)SiO4:Eu3+ phosphor is significantly reduced from 1200 °C with the conventional method to 750 °C with the proposed method. In addition, the photoluminescence intensity of the yolk@shell (BaMg)SiO4:Eu3+phosphor was found to be 9.8 times higher than that of the conventional (BaMg)SiO4:Eu3+ phosphor. The higher absorption of excitation light by the structure of the yolk@shell phosphor is induced by multiple light‐reflection and ‐scattering events in the interstitial void between the yolk and the shell. When preparing the yolk@shell (BaMg)SiO4:Eu3+ phosphor, a hydrogen environment for the solid‐state reaction results in higher photoluminescence efficiency than nitrogen and air environments. The proposed synthetic method can be easily extended to the synthesis of other yolk@shell multicomponent metal silicates. 相似文献
ABSTRACTIn this work, a magnetic molecularly imprinted polymer (Fe3O4@SiO2@MIPs) was prepared via a surface-imprinted method for the determination of the triazines in environmental water samples combined with high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer showed that the Fe3O4@SiO2@MIPs was successfully synthesised and exhibited superparamagnetism. The isotherm adsorption, selectivity and adsorption kinetics experiments showed that the Fe3O4@SiO2@MIPs exhibited excellent specific recognition and fast adsorption equilibrium for triazines. The adsorption process is spontaneous and endothermic. The isotherm adsorption was consistent with Scatchard model and adsorption kinetic fit pseudo-second-order kinetic model. Under the optimised adsorption conditions, the Fe3O4@SiO2@MIPs was directly used to selectively enrich six triazines in environmental water samples. The enrichment volume was up to 500 mL, and the matrix effects were down to 0.7–12.4%. The built method has excellent linearities in the range of 0.25–500 ng L?1 with R2 in the range of 0.998–0.999, lower limit of detections (0.02–0.08 ng L?1) and higher precision (2.4–7.2%). The Fe3O4@SiO2@MIPs is expected to be widely applied to the direct enrichment of triazines in bulk environmental water samples. 相似文献
We explore here an approach to mimic the structures and biological functions of protein loops in small synthetic molecules, by grafting the loop of interest onto an organic template comprising a bicyclic diketopiperazine, prepared by the formal coupling of (2S,4S)-4-aminoproline (Pro(NH2)) and aspartic acid (Asp). The Fmoc-protected template 4 is used to prepare cyclo(-Ala1-Asn2-Pro3-Asn4-Ala5- Ala6-Temp-) ( 5 ) and cyclo(-Ala1-Arg2-Gly3-Asp4-Temp-) ( 6 ) (where Temp = template derived from 4 ), containing the Asn-Pro-Asn-Ala (NPNA) and Arg-Gly-Asp (RGD) motifs. The conformational properties of these molecules are studied in aqueous solution by NMR and simulated-annealing methods. The NPNA motif, an immunodominant epitope on the circumsporozoite surface protein of the malaria parasite Plasmodium falciparum, is shown to adopt a stable type-I β-turn in 5 . The template in 5 adopts a preferred conformation with Pro(NH2)χ1 ≈? ?35° and the Asp moiety χ1 ≈? 70°. A different template conformation is inferred for 6 , with Pro(NH2)χ1 ≈? 0°, but the ARGD loop appears by NMR to undergo rapid conformational averaging. Solid-phase binding assays reveal that 6 displays modest antagonist activity towards both the integrin αIIbβ3 and αvβ3 receptors. 相似文献
A highly selective imprinted amino-functionalized silica gel microsphere was prepared by a simple molecular imprinting technique with a sol–gel process. Theophylline was used as template; 3-aminopropyltrimethoxysilane (APTMS) as functional monomer and tetraethylorthosilicate (TEOS) as reticulating agent. These theophylline imprinted silica microspheres were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron micrographs (SEM), thermogravimetric analysis (TGA), and high performance liquid chromatography (HPLC) in detail. The results showed that monodispersive APTMS-silica imprinted microspheres with size of 250 nm were synthesized successfully. Two kind of binding sites exist between the sol–gel imprinted microspheres and theophylline with KD and Qmax for the higher affinity binding parameters was 1.89 μg/mL and 7.47 μg/mg dry polymers, and for the lower affinity binding sites were found to be 0.18 μg/mL and 3.47 μg/mg dry polymers, respectively. Packed in column, the imprinted microspheres were employed to extract theophylline from green tea successfully. 相似文献
We aim to develop novel photoresponsive surface molecularly imprinted polymer (SIMP) microspheres, an SiO2‐SIMP, for the photocontrolled extraction of uric acid from biological samples. The SiO2‐SMIP was prepared on silica microspheres by surface polymerization and characterized by using scanning electron microscopy, transmission electron microscopy, FTIR spectroscopy, thermogravimetric analysis, nitrogen adsorption–desorption analysis, and UV‐visible spectroscopy. The SiO2‐SMIP microspheres showed a photocontrolled uptake and release of uric acid in NaH2PO4 buffer upon alternate irradiation at 365 and 440 nm. The SiO2‐SMIP microspheres were able to photocontrollably extract uric acid from complicated biological samples for concentration analysis with no significant interference encountered and it exhibited very good recognition ability and fast binding kinetics toward uric acid. 相似文献