Facile fabrication of polymer-inorganic hybrid particles with various morphologies by combination of hydrolytic condensation process with radiation seeded emulsion polymerization

A novel approach was proposed to the synthesis of poly(styrene-divinyl benzene-acrylic acid)/poly [3-(methacryloxy)propyl trimethoxysilane-styrene] [P(St-DVB-AA)/P(MPS-St)] hybrid particles. The morphologies of the particles could be tuned from raspberry-like to snowman-like by simply changing the feeding amount of second monomer or inorganic precursor. The fabricated raspberry-like ones could be modified to obtain hydrophobic surface with a contact angle up to 146°. And the snowman-like ones could be used as solid surfactant to stabilize water/styrene (W/St) mixtures, thus hierarchical porous materials could be obtained after the polymerization of monomer phase. The preliminary application of such soap-free block materials in oil-polluted water treatment was also investigated.

Compressed antisolvent process for polymer coating of drug-loaded aerogel nanoparticles and study of the release behavior

The overall objective of the present work was to modulate the release behavior of drug-impregnated silica particles from almost instantaneous release to a more sustained delivery, prolonged during several hours. Triflusal was chosen as a model drug of the low biodisponibility type. The process is based in the coating with Eudragit® RL 100 polymer of aerogel-like silica particles. Materials were processed in compressed CO₂ by using the batch and semicontinuous antisolvent coating methods. Triflusal release from Eudragit-coated aerogel particles was compared with the dissolution profiles recorded for pristine triflusal and for triflusal impregnated into polymer or non-coated aerogel particles. The release profiles were determined by high-performance liquid chromatography. Eudragit-coated materials presented an intermediate drug-release rate between this obtained for the infused polymer and that of the impregnated aerogel particles. Diffusion-governed mechanisms were found for the studied aerogel-like systems after fitting the release data to both Korsmeyer-Peppas and Baker-Lonsdale equations. The major advantage of the compressed CO₂ antisolvent approach was the ability to physically coat very fine particles (<100 nm). Moreover, the stability of the studied drug in water increased after coating. Figure

Schematic representation of the antisolvent CO₂ particle coating and release behavior of the obtained hybrid products     

pH-triggered PMAA-b-HTPB-b-PMAA copolymer micelles: physicochemical characterization and camptothecin release

pH-sensitive poly(methacrylic acid)-block-hydroxyl-terminated polybutadiene-block-poly(methacrylic acid) block copolymers were synthesized by atom transfer radical polymerization of t-butyl methacrylate and follow-up acidolysis. The copolymers can spontaneously assemble into stable and nearly spherical micelle aggregates in aqueous solution, with hydrodynamic diameters (D _h ) from 51 to 92 nm and critical micelle concentration of 3.90–7.76 mg L^?1. Zeta potentials were found to be increased with increasing (monomer)/(initiator) molar ratios. A pH-dependent phase behavior is produced at approximately 5.4–5.6, as determined by D _h and I ₃₃₅/I ₃₃₂ fluorescence intensity ratios. The in vitro camptothecin (CPT) release was compositional and pH dependent, and the cumulative CPT release below pH 7.2 was higher than that in pH 7.4. They could inhibit the premature burst CPT release. The copolymer micelles were low in cytotoxicity even at a micellar concentration of 800 mg L^?1, and therefore they may be used as potential drug-delivery carriers.

Microfluidic robotic device coupled with electrochemical sensor field for handling of paramagnetic micro-particles as a tool for determination of plant mRNA

The expression of genes responsible for the biosynthesis of stress proteins corresponds to the exposition of an organism to abiotic and/or biotic stress. We utilize two types of paramagnetic particles for isolation of total mRNA from early somatic embryos of Norway Spruce (Picea abies /L./ Karst.) and maize plants (Zea mays L.) treated with cadmium(II) ions. The paramagnetic particles were evaluated for analysis of real samples, and poly-adenine was used as a model mRNA. Various approaches (from non-automatic to fully automatic) were tested in terms of handling the particles.

Facile fabrication of snowman-like Janus particles with asymmetric fluorescent properties via seeded emulsion polymerization

This paper presents a facile method for the preparation of snowman-like Janus particles (SJP) with asymmetric fluorescent property via seeded emulsion polymerization, in which in situ formed raspberry-like cadmium sulfide/poly(styrene–divinylbenzene–acrylic acid) nanocomposite particles (RNP) were used as the seeds. The as-prepared RNP and SJP have been thoroughly characterized by transmission electron microscopy, field-emission scanning electron microscopy, thermogravimetric analysis, X-ray powder diffraction, Fourier transform infrared, ultraviolet visible, and photoluminescent spectrometry. It is found that the size ratio of the polymer bulge/inorganic seed part could be continuously tuned as well as the composition of polymer bulges by changing the composition of monomer mixtures and monomer/seed weight ratio. The obtained Janus particles possess amphiphilic properties which can be further used as solid surfactants to stabilize W/O emulsions and successively to construct hierarchical structured materials. Meanwhile, their asymmetric fluorescent properties may be exploited to detect their assembled situation and orientation at the oil–water interface of emulsions as well as at the surface of hierarchical structured materials.

Surface molecular imprinting for chemiluminescence detection of the organophosphate pesticide chlorpyrifos

We report on a surface molecular imprinting strategy for synthesizing core-shell particles whose shell is imprinted with chlorpyrifos (CPF). The particles were prepared by copolymerization of the methacryloyl groups on the surface of silica particles modified with 3-methacryloxypropyl trimethoxysilane a functional monomer and a cross-linking agent. The imprinted particles exhibit larger binding capacity, faster binding kinetics, and higher recognition selectivity for CPF. Combined with highly sensitive chemiluminescence assay, the method was applied to the determination of CPF with a detection limit of 0.92?nM which is about 2 orders of magnitude lower than that by conventional CL method. The method also displays repeatability for more than 200 times.

Preparation and characterization of an imprinted monolith by atom transfer radical polymerization assisted by crowding agents

A method based on reverse atom transfer radical polymerization (R-ATRP) and molecular crowding has been used for design and synthesis of monolithic molecularly imprinted polymers (MIPs) capable of recognizing ibuprofen (IBU). 4-Vinylpyridine (4-VP) was used as the functional monomer, and ethylene glycol dimethacrylate (EDMA) was the crosslinking monomer. Azobisisobutyronitrile (AIBN)–CuCl₂–N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) was used as the initiating system. Compared with conventional radical polymerization-based IBU-MIPs, the imprinting effects of the obtained IBU-MIPs was enhanced, suggesting the merit of combination of reverse ATRP and molecular crowding. In addition, it was found that the polymerization time of the molecularly imprinted monolithic column, the amount of template, the degree of crosslinking, and the composition of mobile phase greatly affected retention of the template and the performance of molecular recognition .

An efficient electrochemical disinfection of E. coli and S. aureus in drinking water using ferrocene–PAMAM–multiwalled carbon nanotubes–chitosan nanocomposite modified pyrolytic graphite electrode

This work reported an efficient electrochemical treatment for drinking water disinfection using a pyrolytic graphite electrode modified with ferrocenyl tethered poly(amidoamine) dendrimers–multiwalled carbon nanotubes–chitosan nanocomposite. The influence parameters of electrochemical disinfection of Escherichia coli and Staphylococcus aureus, such as applied potential and sterilization time, were investigated. Further investigation indicated that almost all (99.99 %) of the initial bacteria were killed after applying a low potential of 0.4 V for 10 min. During the electrochemical disinfection process, the oxidized form of ferrocene was formed on electrode, which played a key role in the disinfection towards E. coli and S. aureus. Hence, the proposed method may provide potential application for the disinfection of drinking water.

Charge Detection Mass Spectrometry with Resolved Charge States

Charge detection mass spectrometry (CDMS) measurements have been performed for cytochrome c and alcohol dehydrogenase (ADH) monomer using a modified cone trap incorporating a cryogenically cooled JFET. Cooling the JFET increases its transconductance and lowers thermal noise, improving the signal to noise (S/N) ratio. Single ions with as few as 9 elementary charges (e) have been detected. According to simulations, the detection efficiency for ions with a charge of 13 e is 75 %, and for charges above 13 e the detection efficiency rapidly approaches 95 %. With the low limit of detection achieved here, adjacent charge states are easily resolved in the m/z spectrum, so the accuracy and precision of the image charge measurements can be directly evaluated by comparing the measured image charge to the charge deduced from the m/z spectrum. For ADH monomer ions with 32 to 43 charges, the root mean square deviation of the measured image charge is around 2.2 e. Ions were trapped for over 1500 cycles. The number of cycles detected appears to be limited mainly by collisions with the background gas.

Improved DFT-Based Interpretation of ESI-MS of Aqueous Metal Cations

We present results showing that our recently developed density functional theory (DFT)-based speciation model of the aqueous Al³⁺ system has the potential to improve the interpretations of ESI-MS studies of aqueous metal cation hydrolytic speciation. The main advantages of our method are that (1) it allows for the calculation of the relative abundance of a given species which may be directly assigned to the signal intensity in a mass spectrum; (2) in cases where species with identical m?z ratios may coexist, the assignment can be unambiguously assigned based on their theoretical relative abundances. As a demonstration of its application, we study four pairs of monomer and dimer aqueous Al³⁺ species, each with identical m/z ratio. For some of these pairs our method predicts that the dominant species changes from the monomer to the dimer species under varying pH conditions.

Low molecular weight aromatic compounds possessing nonflammable and flammable characteristics in calcium fluoride nanocomposite matrices after calcination at 800 °C

Calcium chloride reacted with potassium fluoride in the presence of low molecular weight aromatic compounds (ArH) such as bisphenol AF, bisphenol A, bisphenol F, biphenyl, and 1-(2-naphthyl)ethanol under alkaline conditions to afford new calcium fluoride/ArH composites. Dynamic light scattering and field emission scanning electron micrographs measurements show that these calcium fluoride/ArH composites are nanometer size-controlled fine particles and have a good dispersibility and stability in water, tetrahydrofuran, 1,2-dichloroethane, methanol, dimethyl sulfoxide, N,N-dimethylformamide, and 2-propanol. Interestingly, aromatic compounds possessing acidic hydroxyl groups in the calcium fluoride nanocomposites were found to exhibit a nonflammable characteristic even after calcination at 800 °C, although the corresponding aromatic compounds possessing neither acidic hydroxyl groups nor hydroxyl groups in the nanocomposites exhibited a usual flammable characteristic under similar conditions. In contrast, calcium fluoride/ArH nanocomposites, which were prepared under no catalytic conditions, afforded a clear weight loss corresponding to the contents of ArH in the composites to exhibit a usual flammable characteristic.

Extraction of tributyltin by magnetic molecularly imprinted polymers

We have prepared core-shell magnetic molecularly imprinted polymer nanoparticles for recognition and extraction of tributyl tin (TBT). The use of particles strongly improves the imprinting effect and leads to fast adsorption kinetics and high adsorption capacities. The functional monomer acrylamide was grafted to the surface of Fe₃O₄ nanospheres in two steps, and MIP layers were then formed on the surface by creating a MIP layer on the surface consisting of poly(ethyleneglycol dimethacrylate) with a TBT template. The particles were characterized in terms of morphological, magnetic, adsorption, and recognition properties. We then have developed a method for the extraction of TBT from spiked mussel (Mytilidae), and its determination by liquid chromatography-tandem mass spectrometry. The method has a limit of detection of 1.0 ng?g^?1 (n?=?5) of TBT, with a linear response between 5.0 and 1,000 ng?g^?1. The proposed method was successfully applied to the determination of trace TBT in marine food samples with recoveries in the range of 78.3–95.6 %.

Influence of secondary preparative parameters and aging effects on PLGA particle size distribution: a sedimentation field flow fractionation investigation

Poly(lactic-co-glycolic acid) particles in the 200–400-nm size range were formulated through nanoprecipitation and solvent evaporation methods. Different concentrations of the polymer and stabilizer (Pluronic® F 68) were tested in order to identify the best conditions for making poly(lactic-co-glycolic acid) particles of suitable size, stable in time, and to be used as carriers for brain-targeting drugs. The particles with the best characteristics for delivery system design were those formulated by nanoprecipitation with an organic/water phase ratio of 2:30, a polymer concentration of 25 mg/mL, and a surfactant concentration of 0.83 mg/mL; their surface charge was reasonably negative (approximately -27 mV) and the average size of the almost monodisperse population was roughly 250 nm. Particle characterization was obtained through ζ-potential measurements, scanning electron microscope observations, and particle size distribution determinations; the latter achieved by both photon-correlation spectroscopy and sedimentation field flow fractionation. Sedimentation field flow fractionation, which is considered more reliable than photon-correlation spectroscopy in describing the possible particle size distribution modifications, was used to investigate the effects of 3 months of storage at 4 °C had on the lyophilized particles.

Poly(ethylene oxide)–poly(ethylene imine) block copolymers as templates and catalysts for the in situ formation of monodisperse silica nanospheres

Block copolymers based on poly(ethylene oxide) (PEO) and poly(ethylene imine) (PEI) are efficient catalysts/templates for the formation of uniform silica nanoparticles. Addition of tetraethylorthosilicate to a solution of PEO–PEI or PEI–PEO–PEI block copolymers results in the formation of silica particles with a diameter of ca. 30 nm and narrow size distribution. The particles precipitated with the diblock copolymers can be redispersed in water after isolation as individual nanoparticles. Evidently, block copolymers based on PEO and PEI serve as excellent templates for the biomimetic and “soft” synthesis of silica nanoparticles.

An approach to core–shell nanostructured materials with high colloidal and chemical stability: synthesis, characterization and mechanistic evaluation

Silver–polypyrrole (PPy) core–shell nanoparticles have been fabricated by a facile one-step “green” synthesis using silver nitrate as an oxidant and soluble starch as an environmentally benign stabilizer and co-reducing agent. The morphology and optical properties of the particles were significantly affected by the reaction temperature, soluble starch concentration, and ratio of pyrrole monomer to AgNO₃ oxidant. The core–shell nanoparticles exhibited outstanding dispersive properties in deionized water due to residual starch, as compared with PPy nanoparticles in which starch was absent. The mechanism of core–shell nanoparticle formation was elucidated through TEM imaging vs. reaction time. The colloidal and chemical stability of the nanoparticles was demonstrated in a variety of solvents, including acids, bases, and ionic and organic solvents, through monitoring the localized surface plasmon resonance of the nanoparticles. Furthermore, the catalytic properties of these silver–PPy core–shell nanoparticles were also demonstrated.

Kinetic and Thermodynamic Control of Protonation in Atmospheric Pressure Chemical Ionization

For p-(dimethylamino)chalcone (p-DMAC), the N atom is the most basic site in the liquid phase, whereas the O atom possesses the highest proton affinity in the gas phase. A novel and interesting observation is reported that the N- and O-protonated p-DMAC can be competitively produced in atmospheric pressure chemical ionization (APCI) with the change of solvents and ionization conditions. In neat methanol or acetonitrile, the protonation is always under thermodynamic control to form the O-protonated ion. When methanol/water or acetonitrile/water was used as the solvent, the protonation is kinetically controlled to form the N-protonated ion under conditions of relatively high infusion rate and high concentration of water in the mixed solvent. The regioselectivity of protonation of p-DMAC in APCI is probably attributed to the bulky solvent cluster reagent ions (S_nH⁺) and the analyte having different preferred protonation sites in the liquid phase and gas phase.

Quinolinium ionic liquid-modified silica as a novel stationary phase for high-performance liquid chromatography

A novel stationary phase based on quinolinium ionic liquid-modified silica was prepared and evaluated for high-performance liquid chromatography. The stationary phase was investigated via normal-phase (NP), reversed-phase (RP), and anion-exchange (AE) chromatographic modes, respectively. Polycyclic aromatic hydrocarbons, phthalates, parabens, phenols, anilines, and inorganic anions were used as model analytes in chromatographic separation. Using the newly established column, organic compounds were separated successfully by both NP and RP modes, and inorganic anions were also separated completely by AE mode. The obtained results indicated that the stationary phase could be applied in different chromatographic modes, with multiple-interaction mechanism including van der Waals forces (dipole–dipole, dipole–induced dipole interactions), hydrophobic, π–π stacking, electrostatic forces, hydrogen bonding, anion-exchange interactions, and so on. The column packed with the stationary phase was applied to analyze phthalates and parabens in hexane extracts of plastics. Tap water and bottled water were also analyzed by the column, and nitrate was detected as 20.1 and 13.8 mg L^?1, respectively. The results illustrated that the stationary phase was potential in practical applications.

New monolithic stir-cake-sorptive extraction for the determination of polar phenols by HPLC

A novel porous monolith has been prepared and used as a sorbent in stir-cake-sorptive extraction (SCSE). The monolithic material was prepared by in-situ copolymerization of allyl thiourea (AT) and divinylbenzene (DB) in the presence of dimethylformamide as a porogen solvent. To optimize the polymerization conditions, different monoliths with different ratios of functional monomer to porogenic solvent were prepared, and their extraction efficiency was investigated in detail. The monolith was characterized by elemental analysis, scanning electron microscopy, mercury intrusion porosimetry, and infrared spectroscopy. Analysis of polar phenols in environmental water samples by a combination of ATDB-SCSE and HPLC with diode-array detection was selected as a model for the practical application of the new sorbent. Several extraction conditions, including extraction and desorption time, pH, and ionic strength of the sample matrix were optimized. The results showed that the new monolith had high affinity for polar phenols and could be used to extract them effectively. Under the optimum conditions, low detection (S/N?=?3) and quantification (S/N?=?10) limits were achieved for the phenols, within the ranges 0.18–0.90 and 0.59–2.97 μg L^?1, respectively. The linearity of the method was good, and the method enabled simple, practical, and low-cost extraction of these analytes. The distribution coefficients between ATDB and water (K _ATDB/W) were calculated for the phenolic compounds and compared with K _O/W. Finally, the proposed method was successfully applied to the determination of the compounds in three environmental water samples, with acceptable recovery and satisfactory repeatability.

Hydrophilic molecularly imprinted polymers for bisphenol A prepared in aqueous solution

We have prepared a hydrophilic molecularly imprinted polymer (MIP) for the hydrophobic compound bisphenol A (BPA) in aqueous solution using 3-acrylamido-N,N,N-trimethylpropan-1-aminium chloride (AMTC) as the functional monomer. Under redox-polymerization conditions, BPA forms an ion-pair with AMTC, which was confirmed by ¹H-NMR titration. The imprinting effect in aqueous solution was evaluated by comparison of this material with the corresponding non-imprinted polymer (NIP) and with a control polymer (CP) bearing no AMTC. The MIP showed the highest activity among the three polymers, and the imprinting factors as calculated from the amount of BPA bound to the MIP divided by the amounts bound to NIP and CP, respectively, are 1.8 and 6.0. The MIP was selective for BPA in aqueous solution, while structurally related compounds are not recognized. Such a selectivity for a hydrophobic compound is rarely observed in aqueous medium because non-specific binding of BPA inevitably leads to hydrophobic interaction.

Chiral separation of racemic mandelic acids by use of an ionic liquid-mediated imprinted monolith with a metal ion as self-assembly pivot

A new chiral stationary phase based on molecularly imprinted polymers (MIP) was prepared in ionic liquid by use of the metal pivot concept. Imprinted monoliths were synthesized by use of a mixture of R-mandelic acid (template), 4-vinylpyridine, ethylene glycol dimethacrylate, and several metal ions as pivot between the template and functional monomer. A ternary mixture of dimethyl sulfoxide–dimethylformamide–[BMIM]BF₄ containing metal ions was used as the porogenic system. Separation of the enantiomers of rac-mandelic acid was successfully achieved on the MIP thus obtained, with resolution of 1.87, whereas no enantiomer separation was observed on the imprinted monolithic column in the absence of metal ions. The effects of polymerization conditions, including the nature of the metal ion and the ratios of template to metal ions and template to functional monomer, on the chiral separation of mandelic acid were investigated. The results reveal that use of metal ions as a pivot, in combination with ionic liquid, is an effective method for preparation of a highly efficient MIP stationary phase for chiral separation.