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Due to the lacks of lysosome localization group and reaction/interaction site for hypochlorite (ClO

The shape of the mesoporous silica particles is rich and colorful. It has long been believed that the macroscopic structure of mesoporous silica particles is formed by continuously building microstructural units and growing them step by step. However, in this work, it is found that the growth process of mesoporous silica particles is not linear but stepped. The mesoporous silica particles grow up by repeating the process of “rapid construction of framework structure first and then slow construction of fine structure”. The size of the mesoporous silica particles only grows stepwise when constructing the framework structure, but remains almost unchanged during subsequent fine structure construction. During the growth of the mesoporous silica particles, about one-sixth of the time is used to construct the framework structure, and the rest of the time is spent on the construction of fine structure.

As an important post-translational modification of proteins, phosphorylation plays a key role in regulating a variety of complicated biological reactions. Owing to the fact that phosphopeptides are low abundant and the ionization efficiency could be suppressed in mass spectroscopic detection, highly efficient and selective enrichment methods are essential to identify protein phosphorylation by mass spectrometry. Here, we develop novel titanium oxide coated core shell mesoporous silica (CSMS@TiO

We present here a novel nano-channel confined biomimetic nanozyme/bioenzyme system, which is prepared by co-immobilizing polyoxometalates (vanadomolybdophosphoric heteropoly acid, PMoV

A novel conjugated polymer PProDOT(MeEO)2 based on dioxythiophene with symmetric double ethoxymethyl pendant groups was successfully synthesized through electrochemical polymerization. The polymer film exhibits reversible electrochromism switching between broadly absorbing bluish black neutral state (− 0.1 V) and transmissive sky blue oxidized state (0.7 V). The symmetric double short-chain ethoxymethyl substitution pattern was utilized to realize the broadly absorbing bluish black neutral state of the polymer film. The electrochemical, spectroelectrochemical, and electrochromic switching properties of the polymer film were studied in detail.

The synthesis and electrochromic properties of a novel regiosymmetric polymer based on 3,4-ethylenedioxythiophene, poly(2,3-bis(bromomethyl)-2,3-dihydrothieno[3,4-b][1,4]dioxine) (PEDOT(MeBr)2) were highlighted. The monomer was electrochemically polymerized via repetitive cycling between 0 and 1.8 V in lithium perchlorate (LiClO4)–acetonitrile (ACN) electrolytic medium. The corresponding polymer was characterized by FTIR spectra, scanning electron microscopy, cyclic voltammetry, UV–Vis-NIR spectroscopy and colorimetry. It features a reversible redox process and demonstrates a stable blue-to-transmissive electrochromic behavior with very low driving potentials (−0.1 and 0.65 V). Additionally the polymer film exhibits enhanced optical contrast (60% at 669 nm) and improved coloration efficiency (183.1 cm2/C at 100% full contrast during bleaching process) which are higher than those of PEDOT, a relatively longer response time compared with PEDOT and reasonable redox stability.

A new magenta-to-transmissive electrochromic polymer, poly(3,4-bis(3-bromopropoxy)thiophene) (PBBrPOT) was synthesized by electrochemical polymerization and its electrochromic properties were characterized in detail. Compared with the representative “large-volume alkyl substituents” strategy, herein we use bromines as the end-capping groups of two propoxyl substituents on the 3- and 4- position of the thiophene ring to introduce more steric repulsion within the polymer chains, and therefore obtain a magenta neutral state of the polymer. The PBBrPOT film shows a set of reasonable electrochromic features, including low driving potentials (−0.1 V and 0.9 V), appropriate transmittance change (38% at 556 nm), but a relatively longer response time in bleaching process (t95 = 6.5 s).

Monodispersed core-shell silica spheres with fibrous shell structure and tunable pore size were prepared by using a one-pot oil-water biphase method. The pore size could be tuned from 7 nm to 37 nm by using organic solvents with different polarities as oil phase. The spheres synthesized by using benzene as organic solvent had the maximum pore size of 37 nm and possessed a surface area of 61 m2 g−1. The obtained wide pore core-shell silica spheres were applied for rapidly separating small molecules, peptides, small proteins, and large proteins with molecular weight up to 200 kDa. Since the pore size of the core-shell silica spheres was sufficiently large for the free access of all the solutes, sharp and symmetric peaks were obtained. The separation performance was as high as 264,531 plates m−1 for fluorene. The great efficient separation demonstrates that the wide pore core-shell silica spheres have a great potential for rapid analysis of both small and large solutes with high performance liquid chromatography.

We report a highly uniform porous layer open tubular (PLOT) column for capillary electrochromatography (CEC) analysis. The PLOT column is easily fabricated using a single-step in-situ biphasic reaction, producing homogeneous porous-layer modified surface with ∼240 nm thickness in a 50 μm-id capillary. CEC performance of the PLOT column has been investigated and optimized under various experimental parameters. Using a mixture of naphthalene and biphenyl as the test sample, we show that the PLOT column exhibits good separation efficiency with resolution >3.0 and theoretical plate numbers over 6 × 104, as well as good intra-/inter-day repeatability and column-to-column repeatability. The column has been successfully applied for CEC analysis of three different types of samples without any further modification of the columns, including complicated peptide products from tryptic-digestion of proteins (lysozyme and BSA), β-blockers (basic samples) and polycyclic aromatic hydrocarbons (neutral samples). Efficient separation has been achieved, which could be attributed to the enhanced surface-to-volume ratio of the PLOT column that will increase the interaction between solid phase and mobile phase in CEC. In addition, base-line separation of neutral samples indicates the reversed phase chromatographic property of the PLOT column, which could be induced by the residue of hexadecyltrimethylammonium bromide used in the fabrication process. Our study show that the present PLOT column is a promising approach that can significantly enhance CEC separation efficiency and could be of potential value in analysis of various different samples.

As an important post-translational modification of proteins, phosphorylation plays a key role in regulating a variety of complicated biological reactions. Owing to the fact that phosphopeptides are low abundant and the ionization efficiency could be suppressed in mass spectroscopic detection, highly efficient and selective enrichment methods are essential to identify protein phosphorylation by mass spectrometry. Here, we develop novel titanium oxide coated core shell mesoporous silica (CSMS@TiO2) nanocomposites for enrichment of phosphopeptides with simultaneous exclusion of massive proteins. The CSMS@TiO2 nanocomposites have essential features, including uniform 1.0 μm diameter, 120 nm thick shell, 7.0 nm mesopores perpendicular to the surface, large surface area of 77 m2/g and pore volume of 0.15 cm3/g, therefore can greatly improve the sensitivity for identifying phosphopeptides by capillary electrophoresis-mass spectrometry. The proposed CSMS@TiO2 nanocomposites are applied for analysis of β-casein tryptic digest and bovine serum albumin (BSA) protein mixture, respectively. The results show that the number of phosphopeptides detected is tremendously increased by using CSMS@TiO2 nanocomposite, proving selectively enriching phosphopeptides due to the size-exclusive and specific interaction of the TiO2-modified mesopores. The enrichment of the phosphopeptides is achieved even for the digests at very low concentration of β-casein (1 fmol/μL). This research would open up a promising idea to utilize mesoporous materials in peptidomics analysis.

Because of their extremely low amount in complex samples, it is quite challenging to accurate determine residues of phosphorus-containing amino-acid-like herbicides (PAAHs) in food products. Here we develop novel core-shell mesoporous silica (CSMS) microspheres coated by titanium dioxide (CSMS@TiO2) for extraction and enrichment of PAAHs in baby foods. After the dispersive solid phase extraction (d-SPE), sheathless capillary electrophoresis-mass spectrometry (sheathless CE-MS) is utilized to achieve efficient separation and sensitive detection. The synthesized CSMS@TiO2 composites are characterized by various spectroscopic techniques, proving TiO2 is uniformly distributed onto the channel surface of CSMS. The composites have essential features that are favorable for adsorption of the analytes on the material for d-SPE, including uniform diameter (1.0 μm with a shell thickness of 133 nm), large perpendicular mesopores (15.6 nm), high surface area (101.1 m2/g) and large pore volume (0.4 cm3/g). Taking glyphosate, glufosinate and their main metabolites (aminomethylphosphonic acid and 3-methylphosphinicopropionic acid) as analytes, selective and efficient enrichment is achieved by CSMS@TiO2-based d-SPE through the affinity interaction between titanium dioxide and phosphate groups. Sensitive detection of target compounds is achieved with low limits of quantitation (LOQs) between 0.3–1.6 ng/mL and excellent inter/intra-day repeatability. The compounds in nine different commercial baby foods from local markets are analyzed using the proposed method. Good recoveries of 82.3–102.6% are achieved with low RSDs (n = 5) of 2.1–8.3%. Our study indicates that the proposed CSMS@TiO2-based d-SPE combined with sheathless CE-MS is an accurate and reliable approach for sensitive determination of trace-amount PAAHs and their metabolites in complex samples.

Whether as a microelement or a highly toxic metal ion, it has a standing demand to the development of simple, facile and sensitive platform for copper ion (Cu(II)) assay. Here we reported the use of 2,4,6-trihydrazinyl-1,3,5-triazine (THT) and citric acid (CA) as precursors to fabricate carbon dots (C-dots) through one-spot hydrothermal approach at 200 °C for 10 h. The maximum excitation and emission wavelengths at ∼355 and ∼440 nm, respectively, of the triazine-doped C-dots with ∼27.6 % QY were observed. The functional groups such as −COOH and -NH2 anchored on the surface of the C-dots, which led to the pH-dependent emission behavior. Also, they can coordinate with Cu(II) to form an absorbent complex, quenching the blue fluorescence of the triazine-doped C-dots by inner filter effect, and the aggregation-induced quenching also contributed to the fluorescence decay. A chemosensory platform for Cu(II) with an 8.6 nM detection limit in a concentration ranging from 0.01–12.5 μM was therefore established. The triazine-doped C-dots were successfully applied in not only the determination in environment but also the imaging in cell of Cu(II), demonstrating their excellent applicability.

A hybrid material was prepared from a metal-organic framework (MOF) and core-shell silica by using a kinetic controlling approach. The nanocrystalline MOF (HKUST-1) was prepared from 1,3,5-benzenetricarboxylate and copper(II) by tuning the reaction rate via the fraction of ethanol in the solvent. After the reaction rate was reduced to a certain degree, the pore surface would be well covered with Cu(II), which initiated the formation of a nanocrystalline HKUST-1. The resulting hybrid material was packed into a stainless-steel column (4.6 × 150 mm) and used as a stationary phase in high performance liquid chromatography. SiO2@dSiO2-HKUST-1 combined the merits of the high separation performance of the core-shell particles and the unique selectivity of the HKUST-1 nanocrystals. A separation efficiency as high as almost 140,000 plates per meter was achieved for the model analyte styrene. The material was stable and exhibited a highly reproductivity. The relative standard deviations of column-to-column, intra-day, and inter-day reproducibility of the SiO2@dSiO2-HKUST-1 packed columns for the retention time of styrene were 4.7%, 0.3%, and 0.4%, respectively.

An anionic water-soluble poly(3,4-propylenedioxythiophene) derivative (PProDOTCB-salt) with double-Y shaped carboxyl-containing side chains has been applied as a colorimetric sensor to detect Fe3+ in 100% aqueous solutions. The Fe3+-induced disassembly of inter-chain aggregates, conformation changes, intra-chain aggregation of PProDOTCB-salt and its colorimetric and fluorescent responses have been studied by absorption and fluorescence spectroscopy. The results indicate that Fe3+ can be detected with the naked eye through the color change of polymer solutions from purple to faint yellow. In addition the Fe3+ detection ability of the sensor is unaffected with the presence of other commonly coexistent ions.

A novel fibrous mesoporous silica nanoparticles (fSiO2) stationary phase grafted with polymer (Poly (2-(dimethylamino) ethyl methacrylate) (PDMAEMA) was developed for open tubular capillary electrochromatography (OT-CEC). The preparation procedure included synthesizing fSiO2 through biphase stratification approach, removing the surfactants, silanization and in situ graft polymerization with monomers via atom transfer radical polymerization (ATRP). Subsequently, PDMAEMA-modified mesoporous silica nanoparticles (P-fSiO2)/ethanol solution was immobilized onto the inner surface of the pretreated capillary and functionalized with octadecylsilane to fabricate the open-tubular column. Separation of polycyclic aromatic hydrocarbons (PAHs) and proteins were carried out to evaluate the performance of the column in CEC. The run-to-run, day-to-day and column-to-column reproducibility in terms retention time of naphthalene was 1.9%, 2.2%, and 3.7%, respectively. The effects of solvent concentration and pH on the separation were evaluated. The method was also used for the separation of real bio-sample, egg white proteins.

Core-shell silica particles with fibrous shell structure and tunable pore size were prepared by using a dul-template method. The pore size of the core-shell silica particles was affected greatly by the amount of octadecylamine, which as used as cosurfactant. The pore size could be enlarged from 7.1 nm to 22.3 nm while keeping the unique fibrous shell structure. After derivatized with C18, the separation performances of these particles with a wider pore size were investigated. The column efficiency was as high as 219,789 plates m−1 for dimethylnaphthalene. Baseline separation of proteins ranging in size from 12 to 66 kD was achieved within 5 min. The separation results demonstrate that the synthesized core-shell silica particles would be a promising packing material in the rapid and high-resolution separation of both small solutes and macromolecules.

Based on a detailed study of the hydrolysis process of tetrabutyl orthotitanate (TBOT), TiO

Inspired by the conversion from organics or biomass to fluorescent carbon dots (C-dots), the use of pesticide 4-chlorophenol (4-CP) as a precursor to prepare C-dots has been reported. The as-prepared chlorine-doped C-dots display a brightly blue emission at ∼445 nm with ∼22.8% quantum yield. Also, the surface of C-dots enriches functional groups, such as phenolic hydroxyl and carboxylic acid, etc., which can capture ferric ion (Fe(III)), resulting in the quenching of blue fluorescence of C-dots through an inner filter effect. The quantitative assay for Fe(III) was therefore realized by this probe with a 0.36 μM detection limit in the 0.6–25 μM concentration range. Most significantly, the cytotoxicity on Hela cells indicates the 4-CP-derived C-dots have a negligible cytotoxicity. The C-dots were applied in detection in environmental samples and imaging in Hela cells of Fe(III), demonstrating their good applicability, low toxicity and good biocompatibility, and providing an alterative approach to totally eliminate the harm of chlorophenols (CPs).

Silica intercalated graphene-silica composites (G/SiO2) were prepared by one-step hydrothermal method. In the previously reported one-step method for synthesizing G/SiO2 composites (eg. Bull. Mater. Sci., 37 (2014), 589–595; Applied Surface Science 259 (2012), 566–573), graphene needs to be synthesized first and then used to prepare G/SiO2 composites. In this work, neither the preparation of graphene nor the use of graphite as a carbon source is required for the preparation of G/SiO2 composites. Instead, organic solvent (such as toluene, xylene, mesitylene, n-hexane, n-heptane, and cyclohexane) was directly used as the carbon source, and the growth and recombination of graphene and SiO2 were achieved simultaneously through a one-step hydrothermal method. In a hydrothermal reaction vessel, the mixture consisting of organic solvent, TEOS, H2O, and surfactant was uniformly stirred, and then reacted at 160 °C for 4 h to prepare G/SiO2 composite. The influence of the type of organic solvent, hydrothermal reaction temperature, and calcination temperature on the structure of G/SiO2 composites were studied. The morphology and structure of G/SiO2 composites were characterized by FESEM, TEM, and Raman. The formation mechanism of G/SiO2 composite was proposed. G/SiO2 composite was then grown directly on the SiO2 spheres and used as stationary phase for high performance liquid chromatograph separation. Mixture of hydrocarbons was well separated under reversed phase condition.

Resource utilization of starch fermentation wastewater is facing the challenge that is short of trash to treasure approach with high efficiency except for the fodder production. Here we reported the use of starch fermentation wastewater as a precursor to prepare carbon materials. When the carbonization temperature being set at 180 °C, the S,-N-doped C-dots with ~24.5% of quantum yield and a green emission at ~518 nm were obtained. The functional groups on the surface of S,-N-doped C-dots can coordinate with free ferric ion (Fe(III)), and the excited electron of C-dots can be captured by 3d orbit of Fe(III), which, together with the assistance of inner filter effect, resulted in the quenching of green fluorescence of S,-N-doped C-dots. A sensing platform for Fe(III) was therefore established with a 3.2 nM detection limit in 0.01 to 16 µM concentration range. When the carbonization temperature being enhanced to 200 °C, the carbon microspheres with ~3.3–6.9 μm in diameter were gained. The carbon microspheres own benign outer hydrophilicity and inner hydrophobicity, and can efficiently remove the dyes in solution through π-π stacking, hydrogen bond and electrostatic effect, exhibiting a good adsorption capacity with ~188 mg/g and a rapid absorption equilibrium within 60 min. The S,N-doped C-dots and carbon microspheres were applied in Fe(III) determination in environmental samples and solution decolorization, respectively, demonstrating their good applicability, and opening up a promising door for the magnificent transition from fermentation wastewater to valuable resource.

In this work, open-tubular capillary column coated with zeolite imidazolate framework-8 (ZIF-8) nanocrystals was prepared by a layer-by-layer method. The coating was formed by growing ZIF-8 nanocrystals on either bare fused silica capillary wall or the capillary column premodified with amino groups. The shape and the thickness of the coating formed by using these two methods were almost the same. However, the coverage of the ZIF-8 crystals on the bare fused silica capillary wall was higher than that on the capillary column premodified with amino groups. The ZIF-8 coated capillary column was evaluated for open-tubular capillary electrochromatography. The effect of pH value, buffer concentration, and applied voltage on the separation of phenols was investigated. Good separation of nine phenolic isomers was achieved because of the strong interaction between unsaturated Zn sites and phenols. The column performance for o-nitrophenol was as high as 208 860 plates m(-1) . The run-to-run, day-to-day, and column-to-column reproducibility of retention time and resolution for p-nitrophenol and o-nitrophenol were very good with RSDs of less than 6.5%.

Graphene oxide (GO) has been considered as a promising stationary phase for chromatographic separation. However, the very strong adsorption of the analytes on the GO surface lead to the severe peak tailing, which in turn resulting in decreased separation performance. In this work, GO and silica nanoparticles hybrid nanostructures (GO/SiO2 NPs@column) were coated onto the capillary inner wall by passing the mixture of GO and silica sol through the capillary column. The successful of coating of GO/SiO2 NPs onto the capillary wall was confirmed by SEM and electroosmotic flow mobilities test. By partially covering the GO surface with silica nanoparticles, the peak tailing was decreased greatly while the unique high shape selectivity arises from the surface of remained GO was kept. Consequently, compared with the column modified with GO (GO@column), the column modified with GO and silica nanoparticles through layer-by-layer method (GO-SiO2 NPs@column), or the column modified with silica nanoparticles (SiO2 NPs@column), GO/SiO2 NPs@column possessed highest resolutions. The GO/SiO2 NPs@column was applied to separate egg white and both acidic and basic proteins as well as three glycoisoforms of ovalbumin were separated in a single run within 36 min. The intra-day, inter-day, and column-to-column reproducibilities were evaluated by calculating the RSDs of the retention of naphthalene and biphenyl in open-tubular capillary electrochromatography. The RSD values were found to be less than 7.1%.

We propose a new capillary electrophoresis (CE)-based open-tubular immobilized enzyme microreactor (OT-IMER) and its application in acetylcholinesterase (AChE) assays. The IMER is fabricated at the capillary inlet (reactor length of ∼1 cm) with the inner surface modified by a micropore-structured layer (thickness of ∼220 nm, pore size of ∼15–20 nm). The use of IMER accomplishes the enzymatic reaction and separation/detection of the products in the same capillary within 3 min. The feasibility of the proposed method is evaluated via online analysis of the activity and inhibition of AChE enzymes. Such method exhibits good reproducibility with relative standard deviation (RSD) of less than 4% for 20 runs, and the enzyme remains over 82% of the initial activity after usage of 7 days. The IMERs are successfully applied to detect the organophosphorus pesticide, paraoxon, in three types of vegetable juice samples with a limit of detection of as low as 61 ng mL−1. Results show that the spiked samples are in the range of 89.6–105.9% with RSD less than 2.7%, thereby indicating its satisfactory level of accurate and reliable analysis of real samples by using the proposed method. Our study indicates that, with combination of advantages of both porous-layer capillary and CE OT-IMER, the proposed method is capable to enhance enzymatic reactions and to achieve rapid analysis with simple instrumentation and operation, thus would pave the way for extensive application of CE-based IMERs in a variety of bioanalysis.

Immobilized enzyme micro-reactors (IMERs) are of vital importance in developing miniaturized bioanalytical systems and have promising applications in various biomanufacturing. An inherent limitation in designing IMERs is the one-dimensional cylindrical geometry of micro-channels that offers limited exposed surface area for molecular reorganization and enzyme immobilization. In this study, we report a robust capillary-IMER based on a three dimensional porous layer open tubular (3D-PLOT) column which is prepared by an easy-to-control surface modification strategy via single-step in situ biphasic reaction. The 3D-PLOT column with highly uniform porous geometry and narrow distribution of porosity can greatly enhance the surface-area-to-volume ratio of the micro-channels, showing the beneficial effects for enzyme immobilization to enhance reaction efficiency and shorten analysis time. Taking trypsin as a model enzyme, enzymatic activities of immobilized enzyme are analyzed. We compare enzyme assays using the proposed 3D-PLOT-IMER with those using normal capillary-IEMR without surface modification as well as free trypsin. The 3D-PLOT-IMER exhibits excellent stability and inter/intra-day reproducibility, and these characteristics imply the reliability of the proposed IMERs for accurate enzyme assay. The feasibility of the proposed method for potential application in biological analysis is demonstrated by coupling the 3D-PLOT-IMER with a nano-LC-MS/MS system for online digestion of standard proteins, cell extraction and living Hela cells. Our study show that the surface modification with the proposed 3D-porous layer is a simple and efficient approach for enzyme immobilization, and could be widely suitable for different kinds of IMERs.

Monodispersed silica spheres with solid core and fibrous shell were successfully synthesized using a biphase reaction. Both the thickness and the pore size of the fibrous shell could be finely tuned by changing the stirring rate during synthesis. When stirring was adjusted from 0 to 800 rpm, the thickness of the shell could be tuned from 13 to 67 nm and the pore size from 5 to 16 nm. By continuously adjusting the stirring rate, fibrous shells with hierarchical pore structure ranged from 10 to 28 nm and thickness up to 200 nm could be obtained in one pot. We demonstrate that fibrous shells with controllable thickness and pore size could be coated on silica cores with diameters from 0.5 to 3 μm while maintaining the monodispersity of the particles. As a result of the unique fibrous structure, the BET surface area could reach ∼233 m(2) g(-1) even though the shell thickness was less than 150 nm. The core-shell particles were modified with C18, packed, and then used in high-performance liquid chromatography (HPLC) separation, showing separation performance as high as 2.25 × 10(5) plates m(-1) for naphthalene and back pressure as low as 5.8 MPa. These silica microspheres with fibrous shells are expected to have great potential for practical applications in HPLC.

MCM-41 silica particles with rich morphologies were prepared in a strong basic solution under a variety of conditions. It was found that the morphology of mesostructured silica was mainly affected by the rate difference between silica condensation and mesostructure formation. The effect of various parameters such as types and amounts of the cosolvents, degree of the dilution, amount of the surfactant, and pH value on the size of rate difference was studied systematically. Depending on the rate difference between silica condensation and mesostructure formation, mesoporous MCM-41 particles with various morphologies could be achieved, including spheres, hexagonal rods, spiral, orange, and gyroid.

Core-shell mesoporous silica (CSMS) microspheres with tunable mesopores in the shell are highly desired in various bioapplications. With novel CSMS microspheres that are synthesized using a convenient two-phase process, we report in this study the analysis of low molecular-weight (MW 2 /g), large pore volume (0.12 cm 3 /g) and excellent water dispersibility. The CSMS microsphere-based enzyme nanoreactors have been fabricated by immobilizing trypsin on the pore channels of the CSMS microspheres using either physical absorption or covalent binding via thiol or aldehyde group with a high loading capacity of 11.8–6.1 mg/g. Due to the unique fibrous pore structure, low MW proteins can enter the channels in the shell to interact with immobilized trypsin, followed by analysis of the digestion products using MALDI-TOF MS or electrophoresis (CE) techniques. The properties and analytical performance of different trypsin-immobilized CSMS microspheres has been systematically evaluated. The results show that the peptide-sequence coverage of the smaller protein is enhanced by using trypsin-CSMS microspheres, indicating the size-dependent digestion which results from the size-exclusion interaction of the mesopores against the high-MW proteins. The present study would pave the way for further applications of mesoporous materials in proteome analysis.

Metal-organic frameworks (MOFs) have been emerged as promising stationary phases for separations. However, the irregular shapes and wide size distribution of MOF particles have led to the high column backpressure and low column efficiency. We described here a kinetic controlling method to deposit zeolitic imidazolate framework (ZIF-8) onto the pore surface using core-shell silica spheres as support. By varying the volume ratio of N,N-dimethylformamide and methanol, the formation speed of ZIF-8 crystals were greatly suppressed, resulting in the growth of very thin layer (∼3.4nm) of ZIF-8 nanocrystals on the pore surface of the spheres instead of freedom growth of micron sized crystals in the solution. Thus prepared hybrid particles combined the merits of high selectivity of MOFs and the high separation performance of core-shell silica spheres. As a result, separation performance as high as 210000 plates/m for a mixture of xylene isomers was achieved.

Silica spheres covered with rods perpendicular to the particle surface were prepared by a simple one-pot sol-gel process. Thus prepared rods-on-sphere silica particles possessed core-shell structure. Compared to other core-shell silica particles in which the shell was synthesized by the time-consuming multiple-step layer-by-layer coating technique, the shell of our rods-on-sphere particles was formed by directly grown rods from the silica spheres. The coverage of the rods on the particle surface could be tuned by changing the amount of water in the reaction. The rods on the particle surface increased the surface roughness which may help decreasing the A-term. Therefore, the calcined and modified rods-on-sphere silica particles were packed into stainless steel columns and then assessed for the separation of various samples including small molecules and proteins. In comparison with a commercially available Kromasil column, the pressure of the rods-on-sphere column is much lower under the same separation conditions, while the column efficiency was comparable. The separation results demonstrate that rods-on-sphere silica particles are a type of new and highly promising packing stationary phase for high performance liquid chromatography.

Hierarchical mesoporous silica spheres (HS) were prepared by a simple sol–gel method and used for the removal of methylene blue from aqueous solutions. The macrostructure of HS can be tuned simply by adding different amounts of ethanol as a reactant. The prepared HS were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, nitrogen adsorption–desorption isotherms, and thermogravimetric analysis. The results showed that HS possessed both macropores and mesopores, with an average diameter of 5.6 μm, a surface area of 2280 m2 g−1, and a pore volume of 1.15 cm3 g−1. The influence of pH, temperature, dosage of adsorbent, and initial methylene blue (MB) concentration on the adsorption behavior were investigated. The experimental results showed that HS exhibited a high adsorption capacity (654.5 mg g−1) and extremely rapid adsorption rate (

This is the first time when protein-imprinted polymers are prepared with "pending templates." The polymers were synthesized in the presence of a real sample (chicken egg white), rather than any known commercial proteins. Compared with a simultaneously synthesized nonimprinted control polymer, the polymers show higher adsorption capacity for abundant components (as "pending templates") in the original sample. Chromatography experiments indicated that the columns made of the imprinted polymers could retain abundant species (imprinted) and separate them from those not imprinted. Thus, the sample could be split into dimidiate subfractions with reduced complexities. "Pending template imprinting" suggests a new way to investigate molecular imprinting, especially to dissect, simplify, and analyze complicated samples through a series of polymers just imprinted by the samples per se.

In this paper, open-tubular capillary column coated with graphene oxide (GO) was prepared through ionic adsorption of negatively charged GO nanosheets onto the capillary wall pre-modified with positively charged poly(diallydimethylammonium chloride) (PDDA). Thus prepared coating was very stable and could endure over 200 separations. The electroosmotic flow (EOF) characteristics of bare fused silica capillary column, PDDA coated column, and GO-PDDA coated column (GO-PDDA@column) were investigated by varying the percentage of methanol in buffer and the buffer pH value. The run-to-run, day-to-day, and column-to-column reproducibilities of EOF on GO-PDDA@column were satisfying with relative standard deviation values of less than 2% in all cases. The stationary phase displays a characteristic reversed-phase behavior. The GO-PDDA@column was also used to separate proteins in egg white. Both basic and acidic proteins were separated in a single run.

In this study, a method for the determination of alkylamine carbonate (AAC) nonionic-anion oil displacement agent in oil-field water was developed for the first time, involving pre-column derivatization using a novel labeling agent and HPLC with diode-array detection. The derivatization and chromatographic separation conditions were investigated thoroughly. The analyte was labeled with 4-methoxybenzenesulfonyl fluoride at 50 °C for 20 min. When the method was applied in the determination of C18A5C (an AAC oil displacement agent containing eighteen alkyl and five amino groups) a linear calibration curve was obtained from 1.0 to 100.0 μg mL-1 with a correlation coefficient of more than 0.999 and a detection limit of 0.05 μg mL-1. In the determination of real oil-field water samples, the recovery range of C18A5C was 91.8% to 96.2%, and the intra-day and inter-day relative standard deviations were 2.9-3.5% and 3.8-4.3%, respectively. The experimental results demonstrate that this method, with its merits of simplicity in pretreatment, rapidity in derivatization, and stability of the derivatives, can be employed in the analysis of C18A5C and has potential application in the detection of other oil displacement surfactants containing amino groups. It is of great significance to develop a fast, easy-to-operate, sensitive and reliable method for environmental impact assessment. © The Royal Society of Chemistry 2013.

Nonporous thiol-functionalized silica spheres (SiO2 SH) were prepared by hydrolysis of 3-mercaptopropyltrimethoxysilane. Then, sulfonic acid functionalized silica microspheres (SiO2 SO3H) were prepared through direct oxidization of SiO2 SH by H2O2 and used as adsorbent. The structure and surface of the adsorbent were investigated by field emission scanning electron microscopy, N2 adsorption–desorption isotherm, Fourier transform infrared spectroscopy and electron diffraction spectroscope. The BET surface area of the particles is only 1.58 m2/g. However, the content of thiol group on particle surface was as high as 36% (wt%). It was found that the SiO2 SO3H could effectively remove heavy metal ions (Pb2+, Cd2+, and Cu2+) in solution through electrostatic interaction. When SiO2 SO3H with the particle size of 0.95 μm was used as adsorbent, the adsorption capacity for Pb2+, Cd2+, and Cu2+ reaches 635, 499, and 260 mg/g, respectively. The strong adsorption ability of SiO2 SO3H can be attributed to the nonporous particles with rich sulfonic group facilitating the mass transport of metal ions to the active sites. The adsorption isotherm data obey the Freundlich model. Kinetics of the metal ions removal was found to follow pseudo-second-order rate equation. pH values have only small influence on the adsorption capacity in the studied pH range. Consecutive adsorption–desorption experiments showed that SiO2 SO3H could be reused with only a slight loss in the adsorption capacity.

The graphene oxide (GO) is carbon based material that has high surface area, high adsorption ability, and is stable at high temperature. In this work, the GO phase was prepared and used for gas chromatographic separation. GO nanosheets were covalently bonded onto the inner surface of fused silica capillary column using 3-aminopropyldiethoxymethyl silane as cross-linking agent. The prepared GO nanosheets were characterized with TEM and the GO coating was characterized with SEM. As a high performance stationary phase, GO provides not only a high surface area to increase the phase ratio but also rich functional groups for the formation of hydrophobicity, hydrogen bonding, and π-π electrostatic stacking interactions with volatile aromatic or unsaturated organic compounds. Thus, mixtures of a wide range of organic compounds including alcohols and aromatic compounds were well separated and an efficiency of 1990 theoretical plates per meter for anisole was obtained on GO coated 1.0m×200μm i.d. fused silica capillary column. The experimental results demonstrate that GO coated capillary columns are promising for gas chromatographic separation.

Previously, we have prepared nanoflake-like tin disulfide (SnS2) and used for the immobilization of proteins and biosensing. We have now modified an electrode with a composite consisting of nanoflake-like SnS2 decorated with gold nanoparticles (Au-NPs) and have immobilized glucose oxidase (GOx) on its surface in order to study its direct electrochemistry. Scanning electron microscopy, electrochemical impedance spectroscopy, Fourier transform IR spectroscopy and cyclic voltammetry were used to examine the interaction between GOx and the AuNP-SnS2 film. It is shown that the composite film has a larger surface area and offers a microenvironment that facilitates the direct electron transfer between enzyme and electrode surface. The immobilized enzyme retains its bioactivity and undergoes a surface-controlled, reversible 2-proton and 2-electron transfer reaction, with an apparent electron transfer rate constant of 3.87 s -1. Compared to the nanoflake-like SnS2-based glucose sensor, the GOx-based biosensor exhibits a lower detection limit (1.0 :M), a better sensitivity (21.8 mA M -1 cm -2), and a wider linear range (from 0.02 to 1.3 mM). The sensor displays excellent selectivity, good reproducibility, and acceptable stability. It was successfully applied to reagentless sensing of glucose at −0.43 V.

A method was established to monitor organic reactions by micellar capillary electrokinetic chromatography (MEKC). After optimizing conditions such as the composition of the solvents, the surfactant, and the apparent pH (pH*) of the system, the method was utilized to analyze the reaction of glycidyl methacrylate (GMA) and allyl amine. The main products were identified in the electropherograms. The reaction procedure was monitored in real time. This method was found to have common applicability, being able to separate and detect nonaqueous soluble, nonionic, and low-UV-Vis absorbance compounds. It provides a rapid and low-cost way to understand organic reactions and to direct synthesis works.

Monodispersed hybrid silica spheres with particles sizes up to 4 μm were obtained by controlling the number of nuclei generated in the initiation phase of particle formation using a two-step sol–gel method. This method has two advantages: (i) the particle size can be tuned easily just by variation of the amount ammonia added in the step of precursor hydrolysis, and (ii) the amount of precursor used to prepare particles with the same diameter is at least ten times lower than with traditional methods. The effects of stirring speed and stirring time on the resulting particle size were also studied.

This paper reports on a new strategy to coat fused silica capillaries through ionic adsorption of gold nanoparticles (AuNPs) on a polyelectrolyte multilayer (PEM) modified capillary wall. The coating was constructed in situ by alternating rinses with positively charged poly(diallydimethylammonium chloride), negatively charged poly(sodium-4-styrenesulfonate), and positively charged AuNPs. After self-assembly of n-octadecanethiol onto the surface of AuNPs, the modified capillary was investigated as a new medium for the separation of neutral analytes and proteins in open-tubular capillary electrochromatography (OT-CEC). The surface coverage of the capillary wall was increased using the high density of AuNPs which were dynamically capped with 4-dimethylaminopyridine (DMAP). The chromatographic performance of the column coated with positively charged AuNPs was remarkably improved compared with a column modified with negatively charged AuNPs. The coating was robust over more than 810 runs in this study and also showed high stability against 0.01 M NaOH, 0.01 M HCl, and electrolyte concentrations up to 70 mM. The run-to-run, day-to-day, and capillary-to-capillary reproducibilities of electroosmotic flow were satisfying with relative standard deviation values of less than 1% in all cases. The AuNP-coated PEM modified capillary column not only showed good performance for neutral analytes but also was suitable for the analysis of both basic and acidic proteins.

A rapid, low-cost, high sensitive and quantitative method to detect valiolamine in a medium for microbial culture, involving derivatization with a new labeling reagent, 4-methoxybenzenesulfonyl fluoride (MOBS-F), followed by reverse-phase high-performance liquid chromatography with ultraviolet (UV) detection with simple operation procedure. 4-Methoxybenzenesulfonyl chloride (MOBS-Cl) and 2-nitrobenzenesulfonyl chloride (NBS-Cl) were compared with MOBS-F as novel reagents in this paper, and the MOBS-F was chosen as the most suitable derivatization reagent. The column was thermostatic at 35 °C, the mobile phase flow-rate was 1.0 mL/min and the detection wavelength was 240 nm. For a biological sample, the separation of the derivatives was achieved using a gradient mobile system. The elution program is 88% phosphate buffer (50 mM; pH = 3.0) and 12% methanol for 23 min, then 70% of phosphate buffer and 30% methanol for another 15 min and finally 88% of phosphate buffer and 12% of methanol for 5 min to re-equilibrate the column. The optimized conditions of the derivatization were as follows: derivatization reaction temperature 30 °C; derivatization reaction pH value 11.0, reaction time 10 min and MOBS-F concentration higher than 1.5 mg/mL for standard solutions and higher than 5.0 mg/mL for the biological sample. Calibration curves were linear in the range of 0.050-25 μg/mL for the standard solutions and 1.0-75 μg/mL for the biological sample. The sensitive analytical method is helpful to control the biotechnological process of voglibose production and product quality control. © 2010 Elsevier B.V. All rights reserved.

Bare nonporous silica particles with diameter around 1 microm were prepared. A 20 cm section of a total length of 45 cm capillary (100 microm i. d.) was packed electrokinetically and the separation performance of basic compounds was investigated in the pressurized capillary electrochromatography (pCEC) system using 1 microm nonporous bare silica spheres as stationary phase and acetonitrile-water as mobile phase. The effects of the composition of the mobile phase, the concentration of the buffer, pH value, applied voltage and so on on the separation performance were investigated. The experimental results demonstrated that the bare silica column showed a typical reversed phase separation mechanism when it was used for separation of basic compounds. The separation performance changed slightly with changing buffer concentration. Since the degree of dissociation of the basic compounds depended greatly on the pH value, the interaction between the compounds and stationary phase changed with the changing of pH value, thereby changing the resolution of the compounds. The separation performance increased with the increase of applied voltage. A column efficiency of 35 000 for o-toluidine was obtained when a voltage of 1 kV was applied.