Convenient Chemical Method Research Articles

Zirconium induced surfaces frustrated Lewis acid-base pairs for BiOBr boosting CO2 photoreduction

Conversion of CO2 to carbon-based fuels via photocatalytic reduction, as a prospective approach, could alleviate energy shortages and environmental problems. However, the adsorption and activation of CO2 in the process of photocatalytic CO2 reduction are still great challenge. Herein, Zr isomorphous substituted BiOBr catalyst with surface frustrated Lewis acid-base pairs (SFLPs) are formed by a convenient chemical method. The photocatalytic activity of CO2 reduction for optimal Zr-BiOBr is significantly improved, with CO yield of 185.7 μmol·g−1·h−1 and CH4 of 0.7 μmol·g−1·h−1, being 9.2 - fold and 3.2 - fold higher than that of original BiOBr, respectively. It is found that zirconium is considered as Lewis acid site and lattice oxygen as Lewis base site, which could effectively boost the adsorption and activiation of CO2 molecules. This work not only demonstrates that construction of SFLPs for catalyst could be taken as an effective tactics for CO2 adsorption and activation, but also suggests a possible photocatalytic mechanism in depth.

ZIF-12 @ polypyrrole nanowires for selective detection of cadmium ions in water samples

Cadmium ion detection is an important area of research since it is associated with numerous diseases in humans and the environment. In this study, selective Cd2+ ion detection using polypyrrole and ZIF-12 was investigated using the square wave voltammetry technique. A convenient chemical method is used to polymerize the pyrrole to form a composite, which provides a better electroactive surface area of 24.5 x 10-3 m2 for the ZIF-12@Ppy composite modified GCE. The –NH2 functional group in polypyrrole makes good adsorptive property for Cd2+ ion capture with a detection range of 10 µM to 5 mM, the regression equation of y = 0.0102 x + 43.289, and low detection limit of approximately 50 nM as a result of enhanced electrocatalytic activity. The good anti-interference properties, repeatability, and stability of the prepared composite successfully demonstrated for the detection of Cd2+ ions in real samples from various water sources. Overall, these studies provide good insights into the development of an effective device for the detection of Cd2+ ions using polypyrrole and ZIF-12 platform.

Modifying surface frustrated Lewis pairs of BiOBr by La3+ replacing Bi3+ for expediting CO2 photoreduction

Photocatalytic reduction of carbon dioxide has attracted remarkable attention. However, the photocatalytic efficiency is restricted to the poor capacity of adsorption and activation for CO2 molecules on the surface of catalyst. Herein, La isomorphous substituted BiOBr is prepared by a convenient chemical method with La3+ replacing Bi3+. For CO2 photoreduction, the La-substituted BiOBr shows CO yield of 154.4 μmol·g−1·h−1, being 7.1-fold as higher as original BiOBr. Experimental and calculation results manifest that surface frustrated Lewis acid and base sites of La3+-O2− pairs are formed on the surface of BiOBr with adulteration of La and increased oxygen vacancies, which could be conductive to the adsorption and activation for CO2 molecules. This work not only suggests a possible mechanism for photocatalytic reduction of CO2, but also opens up a new opportunity for the preparation of efficient catalysts for CO2 reduction.

The Molecular Basis of Heat-Stable Enterotoxin for Vaccine Development and Cancer Cell Detection.

Heat-stable enterotoxin (STa) produced by Enterotoxigenic E. coli is responsible for causing acute diarrhea in infants in developing countries. However, the chemical synthesis of STa peptides with the native conformation and the correct intra-molecular disulfide bonds is a major hurdle for vaccine development. To address this issue, we herein report on the design and preparation of STa analogs and a convenient chemical method for obtaining STa molecules with the correct conformation. To develop an STa vaccine, we focused on a structure in a type II β-turn in the STa molecule and introduced a D-Lys residue as a conjugation site for carrier proteins. In addition, the -Glu-Leu- sequence in the STa molecule was replaced with a -Asp-Val- sequence to decrease the toxic activity of the peptide to make it more amenable for use in vaccinations. To solve several issues associated with the synthesis of STa, such as the formation of non-native disulfide isomers, the native disulfide pairings were regioselectively formed in a stepwise manner. A native form or topological isomer of the designed STa peptide, which possesses a right-handed or a left-handed spiral structure, respectively, were synthesized in high synthetic yields. The conformation of the synthetic STa peptide was also confirmed by CD and NMR spectroscopy. To further utilize the designed STa peptide, it was labeled with fluorescein for fluorescent detection, since recent studies have also focused on the use of STa for detecting cancer cells, such as Caco-2 and T84. The labeled STa peptide was able to specifically and efficiently detect 293T cells expressing the recombinant STa receptor (GC-C) protein and Caco-2 cells. The findings reported here provide an outline of the molecular basis for using STa for vaccine development and in the detection of cancer cells.

Detection of trace mercury ions in water by a novel Raman probe

The convenient chemical method for sensing mercury ion (Hg2+) has drawn significant attention in recent researches. Herein we report a simple, ultrasensitive and inexpensive protocol to detect trace mercury ions in water without complicatedly tagging, based on the facile synthesis of a nanocomposition, which is constructed with inositol hexaphosphate (IP6) stabilized gold nanoparticles (Au NPs) modified by crystal violet (CV) as Raman signal molecule and tri-sodium citrate (TC) as reducer, shortly named CV/TC/IP6/Au NPs. A possible mechanism for the Raman probe is the decreasing intensity of SERS band at 1173cm−1 of crystal violet (CV) with Hg2+ addition due to the reduction of Hg2+ by TC to Hg atom whose competition with CV molecules at the IP6/Au NPs surface, resulting in CV molecules detachment from the surface. The proposal Raman probe shows an unprecedented limit of detection (LOD) of 0.5pM for Hg2+. This SERS-based method of Hg2+ determination could be expected to have wide-range applications in many areas such as analysis of trace Hg2+ in river water.

ChemInform Abstract: Design and Functionality of Colloidal‐Crystal‐Templated Materials—Chemical Applications of Inverse Opals

AbstractReview: 289 refs.

Design and functionality of colloidal-crystal-templated materials—chemical applications of inverse opals

Templating with colloidal crystals composed of monodisperse spheres is a convenient chemical method to obtain porous materials with well-ordered periodicity and interconnected pore systems. The three-dimensionally ordered macroporous (3DOM) products or inverse opals are of interest for numerous applications, both for the optical properties related to structural color of these photonic crystal materials and because of their bicontinuous nanostructure, i.e., a continuous nanostructured skeleton with large interfacial area and a three-dimensionally interconnected pore system with low tortuosity. This review outlines various synthetic methods used to control the morphology of 3DOM materials with different compositions. It highlights aspects of the choice of colloidal particles, assembly of the colloidal crystal template, infiltration and processing, template removal, and other necessary modifications to enhance the functionality of the materials. It also considers syntheses within the confinement of 3DOM materials and summarizes characterization methods that are particularly useful in the analysis of 3DOM materials. The review then discusses chemical applications of 3DOM materials, namely sorption and controlled release, optical and electrochemical sensors, solar cells, lithium ion batteries, supercapacitors, fuel cells, and environmental and chemical fuel catalysis. A focus is on structural features and materials properties that enable these applications.

Room temperature synthesis and characterization of ultralong Cd(OH)2 nanowires: a simple and template-free chemical route

Ultralong Cd(OH)2 nanowires were fabricated in high yield by a convenient chemical method using alkali medium at room temperature without using any templates. The preparation conditions induce a unilateral growth of nanowires, despite the absence of any template. The length of the nanowires reached several hundreds of micrometers, giving an aspect ratio of a few thousands. The X-ray diffraction shows that the Cd(OH)2 nanostructures crystallized in the wurtzite structure without any special orientation. The photoluminescence spectrum of Cd(OH)2 nanostructures appears as two emission bands: one related to green emission at 475–510 nm, and the other related to deep level emission at 510–540 nm. Also the formation mechanisms of the nanowires are presented. The growth mechanism involves the irreversible and specifically oriented self-assembly of primary nanocrystals and results in the formation of the nanowires.

Mechanism of fluorescence energy transfer in aqueous solution cadmium sulfide quantum dots

Cadmium sulfide (CdS) quantum dots (QDs) prepared by a convenient chemical method have been characterized using absorption, fluorescence, and photoluminescence excitation techniques. The photoluminescence excitation studies show that there is an electron transfer from the surface adsorbate (thiourea) to CdS QDs in aqueous solution. The excitation band with peak maximum at 5.8 eV is assigned to the electronic transitions in the chemisorbed thiourea, whereas the excitation band between 3.45 and 3.7 eV corresponds to the band-to-band transition within the nanocrystalline CdS host. The absorption spectroscopy of the CdS QD solutions shows a strong absorption peak which is generated from thiourea. The band-edge fluorescence of the CdS QDs has also been investigated. It is shown that the fluorescence property of the CdS QDs can be enhanced by adding cadmium chloride (CdCl2) solution.

Chemoenzymatic synthesis of 2-chloro-4-nitrophenyl β-maltoheptaoside acceptor-products using glycogen phosphorylase b

In the present work, we aimed at developing a chemoenzymatic procedure for the synthesis of β-maltooligosaccharide glycosides. The primer in the enzymatic reaction was 2-chloro-4-nitrophenyl β-maltoheptaoside (G 7-CNP), synthesised from β-cyclodextrin using a convenient chemical method. CNP-maltooligosaccharides of longer chain length, in the range of DP 8–11, were obtained by a transglycosylation reaction using α- d-glucopyranosyl-phosphate (G-1-P) as a donor. Detailed enzymological studies revealed that the conversion of G 7-CNP catalysed by rabbit skeletal muscle glycogen phosphorylase b (EC 2.4.1.1) could be controlled by acarbose and was highly dependent on the conditions of transglycosylation. More than 90% conversion of G 7-CNP was achieved through a 10:1 donor–acceptor ratio. Tranglycosylation at 37 °C for 30 min with 10 U enzyme resulted in G 8→12-CNP oligomers in the ratio of 22.8, 26.6, 23.2, 16.5, and 6.8%, respectively. The reaction pattern was investigated using an HPLC system. The preparative scale isolation of G 8→11-CNP glycosides was achieved on a semipreparative HPLC column. The productivity of the synthesis was improved by yields up to 70–75%. The structures of the oligomers were confirmed by their chromatographic behaviours and MALDI-TOF MS data.

Chemoenzymatic preparation of 2-chloro-4-nitrophenyl β-maltooligosaccharide glycosides using glycogen phosphorylase b

In the present work, we aimed to develop a new chemoenzymatic procedure for the synthesis of β-maltooligosaccharide glycosides. The primer in the enzymatic reaction was 2-chloro-4-nitrophenyl β-maltoheptaoside (G 7-CNP), which was synthesised from β-cyclodextrin (β-CD) using a very convenient chemical method [E. Farkas, L. Jánossy, J. Harangi, L. Kandra, A. Lipták, Carbohydr. Res., 303 (1997) 407–415]. Shorter chain length CNP-maltooligosaccharides in the range of dp 3–6 were prepared using rabbit skeletal muscle glycogen phosphorylase b (EC 2.4.1.1). Detailed enzymological investigations revealed that the conversion of G 7-CNP was highly dependent on the conditions of phosphorolysis. A 100% conversion of G 7-CNP was achieved during 10 min in 1 M phosphate buffer (pH 6.8) at 30 °C with the tetramer glycoside (77%) as the main product. Phosphorolysis at 10 °C for 10 min resulted in 89% conversion and G 4-, G 5-, and G 6-CNP oligomers were detected in the ratio of 29:26:34%, respectively. The reaction pattern was investigated using an HPLC system. The preparative scale isolation of G 3→6-CNP glycosides was achieved by size-exclusion column chromatography (SEC) on Toyopearl HW-40 matrix. The productivity of the synthesis was improved by yields of up to 70–75%.

The cofactor Mg 2+—a key switch for effective continuous enzymatic production of GDP-mannose using recombinant GDP-mannose pyrophosphorylase

The aim of the presented work is the chemoenzymatic synthesis of GDP-mannose (GDP-Man). Mannose-1-phosphate (Man-1-P) is synthesised by a very convenient chemical method and is activated with GTP and recombinant GDP-mannose pyrophosphorylase (GDP-Man PP) to give GDP-Man. The productivity of the process is improved using reaction engineering techniques. Detailed kinetic studies, modelling of the reaction and simulations of different reaction systems revealed that besides a strong product inhibition the cofactor Mg 2+ is a key switch for effective enzymatic synthesis. Using a two-stage cascade of enzyme membrane reactors, GDP-Man could be produced continuously with a space-time yield of 28 g L −1 d −1 and an enzyme consumption of 0.9 U g −1, which means a six-fold improvement related to batch synthesis.

Convenient chemical method for measuring mean temperature at sites of degradation studies in the field

(...) A method which employs the hydrolysis of potassium ethyl xanthate requires only a milligram balance; a previous version (Ashworth 1980) is inconvenient because the user is restricted to a weekly schedule of site visits. We have modified the method to allow the user to visit sites at intervals of any convenient duration up to 10 days at 25 o C, 1 month at 15 o C or 3 months at 5 o C. (...)

ASSAY OF THYROIDAL ACTIVITY BY A CLOSED VESSEL TECHNIQUE

The work of Harington & Randall [1929] provided a convenient chemical method, based on the estimation of acid-insoluble iodine, for the assay of dried thyroid preparations. This method appears to be satisfactory for thyroid preparations, in which all the acid-insoluble iodine is thyroxine iodine. As a result, the biological assay of thyroidal activity has been much neglected and has mainly been used for determining the activity of substances related to thyroxine. In the last few years, artificially iodinated proteins (mostly iodinated casein), which possess high thyroidal activity, have come into use. These iodinated proteins contain a large amount of acid-insoluble iodine, and it is evident that only a small and variable proportion of it represents thyroxine or other substance with similar activity [Deanesly & Parkes, 1945b]. Chemical assay of such preparations is thus of little value, and the whole problem of the biological assay of thyroidal activity has had