Synthesis of graphene oxide-poly(2-hydroxyethyl methacrylate) composite by dispersion polymerization in supercritical CO2: adsorption behavior for the removal of organic dye

The use of a biocompatible and thermoresponsive polymer, poly(2-hydroxyethyl methacrylate) (PHEMA) grafted onto the surface of graphene oxide (GO) as an adsorbent for the removal of a cationic dye (methylene blue [MB]) from an aqueous solution is examined in this work. GO–PHEMA forms a hydrogel in water thus overcoming the problem faced by carbon-based adsorbent materials during post-treatment (i.e., separation of adsorbent from the aqueous phase). The GO–PHEMA composite was synthesized using a green approach through dispersion polymerization in supercritical CO₂. The successful preparation of this composite was confirmed by a series of characterization techniques. The adsorption behavior of the composite toward MB such as the effect of the adsorbent dosage, pH, contact time, dye concentration, and recyclability were observed. In addition, the adsorption isotherm, kinetics and thermodynamics were investigated. According to the experimental data, the adsorption parameters were found to fit well into the Freundlich adsorption isotherm with a correlation coefficient of 0.975 and a maximum predicted adsorption capacity of 39.41 mg g^?1 at 25 °C. The adsorption kinetics studies showed that the adsorption behavior followed a pseudo-second-order reaction. On the other hand, the thermodynamics studies showed that the adsorption of MB on GO–PHEMA composite followed spontaneous and endothermic adsorption process with an efficient adsorption temperature at 45 °C. The experimental results also showed that the GO–PHEMA composite could remove 99.8% of the dye in 45 min. Therefore, GO–PHEMA composite is a favorable green adsorbent for environmental applications.     

Synthesis, photochromic properties, and light-controlled metal complexation of a naphthopyran derivative

A light-controlled reversible binding switch based on photochromic 3H-naphtho[2,1-b]pyran is under development for studying cellular oscillatory calcium signals. The binding affinities of the closed and open forms of substituted naphthopyran 1 for Ca(2+), Mg(2+), and Sr(2+) in buffer were determined. The photochemically ring-opened form of the receptor exhibited increased affinity compared to the thermally stable closed form of the receptor. The binding affinity difference for Ca(2+) was approximately 77-fold at pH 7.6.     

Dependence of Hilbert coefficients

Let M be a finitely generated module of dimension d and depth t over a Noetherian local ring (A, \({\mathfrak{m}}\)) and I an \({\mathfrak{m}}\)-primary ideal. In the main result it is shown that the last t Hilbert coefficients \({e_{d-t+1}(I,M),\ldots, e_{d}(I,M)}\) are bounded below and above in terms of the first d ? t + 1 Hilbert coefficients \({e_{0}(I,M),\ldots,e_{d-t}(I,M)}\) and d.     

A molecular docking simulation study on potent inhibitors against Rhizoctonia solani and Magnaporthe oryzae in rice: silver-tetrylene and bis-silver-tetrylene complexes vs. validamycin and tricyclazole pesticides

Structural Chemistry - Rice, well known as the most important staple food source worldwide, is highly susceptible to many infectious diseases, especially rice sheath blight caused by fungus...     

Can Tetrylone Act in a Similar Fashion to Tetrylene in Ni(CO)2 Complexes? A Theoretical Study based on a Comparison using DFT Calculations

A comparison was made to investigate the structures and bonding of nickel complex that carry tetrylone and tetrylene ligands [(CO)₂Ni‐{E(PH₃)₂}] ( Ni1E ) and [(CO)₂Ni‐{NHE_Me}] ( Ni2E ) (E = C to Pb) using quantum chemical calculations at the BP86 level with various basis sets (SVP, TZVPP, TZ2P+). The nature of the Ni–E bonds was analyzed with charge‐ and energy decomposition methods. The structures of tetrylone complexes Ni1E exhibit an interesting trend with the ligands E(PH₃)₂ are bonded in a tilted orientation relative to the fragment Ni(CO)₂. In contrast, the calculated equilibrium structures of complexes Ni2E exhibit the NHE_Me ligands (E = C to Sn) bonded in a head‐on way to the Ni(CO)₂ fragment, while the bending angle gives the strongest side‐on bonded ligand NHPb_Me when E = Pb. The interesting trend of the bond dissociation energy (BDE) is observed for the tetrylone, which has the same trend BDEs compared with tetrylene complexes. The EDA‐NOCV results indicate that the tetrylone ligands {E(PH₃)₂} in complexes are similar to the tetrylene ligands NHE_Me as strong σ‐donors and weak π‐acceptors. The BDEs calculated for the Ni–E bonds in Ni1E and Ni2E show that the effect of bulky ligands may obscure the intrinsic Ni–E bond strength. The bonding analysis shows that the tetrylone ligands in Ni1E may act in a similar fashion to the tetrylene ligands in Ni2E . All complexes Ni1E and Ni2E are suitable targets for synthesis.     

Synthesis of polyaniline/Q-CdSe composite via ultrasonically assisted dynamic inverse emulsion polymerization

In this communication, polyaniline/CdSe quantum dots (PANI/Q-CdSe) composite was successfully synthesized via in situ ultrasonically assisted dynamic inverse emulsion polymerization. The synthesized PANI-coated Q-CdSe composite was characterized by field emission transmission electron microscopy showed that the CdSe quantum dots have an average size of around ca. 5 nm were dispersed in the PANI matrix. X-ray diffraction, Fourier transform infrared spectrum (FT-IR) and UV-visible spectrum were used to characterize the structure of the obtained PANI/Q-CdSe composite. FT-IR spectra indicated that the polymer was highly doped and existed in conducting emeraldine salt form. The obtained PANI/Q-CdSe composite showed significant improvement in the thermal behavior as indicated by TGA thermograph. The presented dynamic polymerization process is very fast and produces stable colloidal dispersion. This approach provides a one-step, simple, general, and inexpensive method for the preparation of PANI/Q-CdSe composite.     

Cooperative perfunctionalization and partial labeling of 6-azido-6-deoxy-α-cyclodextrin through copper(I)-catalyzed azide-alkyne cycloaddition

In a microwave and ligand-assisted cyclodextrin click cluster synthesis, we observed the cooperative perfunctionalization in the click reaction of 6-azido-6-deoxy-α-cyclodextrin under our optimized reaction conditions. MALDI-MS data and partial fluorescein labeling via the one-pot/stepwise methods confirmed the occurrence of cooperative perfunctionalization: the fully triazole-functionalized cyclodextrin click cluster became the major product with limited alkyne equivalents. To the best of our knowledge, this work constitutes the first example of a ‘cooperative’ click reaction of an azido-cyclodextrin. This cooperative perfunctionalization of cyclodextrin click clusters offers useful synthetic insights into the partial reporter labeling strategy using azido-cyclodextrin.     

Structured sublinear compressive sensing via belief propagation

Compressive sensing (CS) is a sampling technique designed for reducing the complexity of sparse data acquisition. One of the major obstacles for practical deployment of CS techniques is the signal reconstruction time and the high storage cost of random sensing matrices. We propose a new structured compressive sensing scheme, based on codes of graphs, that allows for a joint design of structured sensing matrices and logarithmic-complexity reconstruction algorithms. The compressive sensing matrices can be shown to offer asymptotically optimal performance when used in combination with orthogonal matching pursuit (OMP) methods. For reduced-complexity greedy reconstruction schemes, we propose a new family of list-decoding belief propagation algorithms, as well as reinforced and multiple-basis belief propagation (BP) algorithms. Our simulation results indicate that reinforced BP CS schemes offer very good complexity–performance tradeoffs for very sparse signal vectors.     

Gas sensor based on nanoporous hematite nanoparticles: Effect of synthesis pathways on morphology and gas sensing properties

The development of a low cost and scalable gas sensor for the detection of toxic and flammable gases with fast response and high sensitivity is extremely important for monitoring environmental pollution. In this work, we introduce two different synthesis pathways for the preparation of scalable Fe₂O₃ nanoparticles for gas sensor applications. One is co-precipitation and the other is hydrothermal method. The gas sensing properties of the α-Fe₂O₃ nanoparticles (NPs) fabricated by different synthesis pathways were studied and compared. The performance of the NPs in the detection of toxic and flammable gases such as carbon dioxide, ammonia, liquefied petroleum gas, ethanol, and hydrogen was evaluated. The Fe₂O₃ NP-based gas sensors exhibited high sensitivity and a response time of less than a minute to analytic gases. However, the NPs fabricated by the one-step direct method exhibited higher sensitivities than those generated by the α-Fe₂O₃ NPs obtained by co-precipitation synthesis possibly because of their nanoporous structure. This performance is attributed to the large specific surface area of the NPs, which results in higher sensitivity.