Polymer nanoparticles with a sensitive CO2‐responsive hydrophilic/hydrophobic surface

Poly(methyl methacrylate) (PMMA) nanoparticles with a sensitive CO₂‐responsive hydrophilic/hydrophobic surface that confers controlled dispersion and aggregation in water were prepared by emulsion polymerization at 50 °C under CO₂ bubbling using amphiphilic diblock copolymers of 2‐dimethylaminoethyl methacrylate (DMAEMA) and N‐isopropyl acrylamide (NIPAAm) as an emulsifier. The amphiphilicity of the hydrophobic–hydrophilic diblock copolymer at 50 °C was triggered by CO₂ bubbling in water and enabled the copolymer to serve as an emulsifier. The resulting PMMA nanoparticles were spherical, approximately 100 nm in diameter and exhibited sensitive CO₂/N₂‐responsive dispersion/aggregation in water. Using copolymers with a longer PNIPAAm block length as an emulsifier resulted in smaller particles. A higher concentration of copolymer emulsifier led to particles with a stickier surface. Given its simple preparation and reversible CO₂‐triggered amphiphilic behavior, this newly developed block copolymer emulsifier offers a highly efficient route toward the fabrication of sensitive CO₂‐stimuli responsive polymeric nanoparticle dispersions. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2149–2156     

Analysis of new psychoactive substances in human urine by ultra‐high performance supercritical fluid and liquid chromatography: Validation and comparison

New psychoactive substances represent serious social and health problem as tens of new compounds are detected in Europe annually. They often show structural proximity or even isomerism, which complicates their analysis. Two methods based on ultra high performance supercritical fluid chromatography and ultra high performance liquid chromatography with mass spectrometric detection were validated and compared. A simple dilute‐filter‐and‐shoot protocol utilizing propan‐2‐ol or methanol for supercritical fluid or liquid chromatography, respectively, was proposed to detect and quantify 15 cathinones and phenethylamines in human urine. Both methods offered fast separation (<3 min) and short total analysis time. Precision was well <15% with a few exceptions in liquid chromatography. Limits of detection in urine ranged from 0.01 to 2.3 ng/mL, except for cathinone (5 ng/mL) in supercritical fluid chromatography. Nevertheless, this technique distinguished all analytes including four pairs of isomers, while liquid chromatography was unable to resolve fluoromethcathinone regioisomers. Concerning matrix effects and recoveries, supercritical fluid chromatography produced more uniform results for different compounds and at different concentration levels. This work demonstrates the performance and reliability of supercritical fluid chromatography and corroborates its applicability as an alternative tool for analysis of new psychoactive substances in biological matrixes.     

Effect of chemical parameters on pyrene degradation in soil in a pulsed discharge plasma system

Degradation of pyrene in soil in a net-to-net pulsed discharge plasma (PDP) system was reviewed. Effect of main chemical parameters, including air flow rate, pyrene concentration, initial pH and soil moisture content on pyrene degradation was examined. The obtained results show that 87.9% of pyrene could be removed under the condition of 60 min reaction; increasing of air flow rate within 1 L min⁻¹ was favorable for degradation; pyrene removal was decreased with the increase of initial pyrene concentration; oxidation of pyrene was more evident in acidic soil; enhancement of soil moisture content has no benefit on pyrene degradation.     

Fluorescence properties of riboflavin-functionalized mesoporous silica SBA-15 and riboflavin solutions in presence of different metal and organic cations

Riboflavin was covalently linked to mesoporous SBA-15 silica surface via grafting technique. Then fluorescence properties of the system obtained were analyzed in the presence of several metal and organic cations. Both quenching and strengthening of fluorescence as well as significant changes in the maximum fluorescence wavelength were observed. The results were compared with absorption and fluorescence data obtained for riboflavin water solutions.     

Crosslinked poly(ethylene oxide) containing siloxanes fabricated through thiol‐ene photochemistry

Homogenous amphiphilic crosslinked polymer films comprising of poly(ethylene oxide) and polysiloxane were synthesized utilizing thiol‐ene “ click ” photochemistry. A systematic variation in polymer composition was Carried out to obtain high quality films with varied amount of siloxane and poly(ethylene oxide). These films showed improved gas separation performance with high gas permeabilities with good CO₂/N₂ selectivity. Furthermore, the resulting films were also tested for its biocompatibility, as a carrier media which allow human adult mesenchymal stem cells to retain their capacity for osteoblastic differentiation after transplantation. The obtained crosslinked films were characterized using differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, FTIR, Raman‐IR , and small angle X‐ray scattering. The synthesis ease and commercial availability of the starting materials suggests that these new crosslinked polymer networks could find applications in wide range of applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1548–1557     

Nonlinear frequency response analysis: a recent review and perspectives

The nonlinear frequency response analysis (NFRA) can be seen as an extension of electrochemical impedance spectroscopy. NFRA gives a full and detailed representation of the system response and can establish a connection between model parameters and the experimentally observed phenomena. In this article, different theoretical NFRA approaches and the most recent application examples are discussed. A simple electrochemical example is used to showcase the benefits and disadvantages of analyzing the system response by using different approaches. In addition, it was shown how to extract experimental harmonic values and analyze them.     

基于学生群体心理测试系统的设计

心理测试的根本目的是为了让人们在测试过程中，产生某些特定行为，即个体对测试题目的反应，并根据这些行为反应来推论其相应的心理特性。在一定程度上帮助我们了解人类的心理活动，并从中得到帮助。因此，本文对基于学生群体心理测试系统的设计进行深入研究。     

Theoretical study of the structural,elastic and thermodynamic properties of chalcopyrite ZnGeP2

The structural, elastic, and thermodynamic properties of ZnGeP₂ with chalcopyrite structure are investigated using the pseudo-potentials plane wave method based on the density functional theory with the generalized gradient approximation. The lattice parameters (a, c and u) are directly calculated and agree well with previous experimental and theoretical results. The obtained negative formation enthalpy shows that ZnGeP₂ crystal has strong structural stability. We have also calculated the bulk modulus B and the elastic parameters (C₁₁, C₁₂, C₁₃, C₃₃, C₄₄, and C₆₆) which have not been measured yet. The accuracy and reliability of the calculated elastic constants of ZnGeP₂ crystal are discussed. In addition, the pressure and temperature dependencies of the lattice parameters, bulk modulus, Debye temperature, Grüneisen parameter, entropy, volume thermal expansion coefficient, and specific heat capacity are obtained in the ranges of 0–20 GPa and 0–1200 K using the quasi-harmonic Debye model. To our knowledge this is the first quantitative theoretical prediction of the thermodynamic properties for ZnGeP₂ compound and still awaits experimental confirmations.