Production Of Active Sites Research Articles

Effect of organic carboxylates in coal on the production of active sites and coal self-ignition behavior

The heat release of coal oxidation lead to the thermal decomposition of carboxylic groups, which include carboxylic acid and carboxylate. However, few researchers have studied the effect of the decomposition of intrinsic carboxylate structure on coal self-ignition process. In this work, different coal samples were selected and treated with alkali solutions to form organic carboxylate structures, and the thermal decomposition of the raw and alkali-treated coals followed by the room temperature oxidation process were analyzed. The effect of the carboxylate structures on the thermal behavior, elemental distribution, and functional groups of coal was also studied by means of TGA, FTIR, XPS and EPR. The results showed that the carboxylic groups in coal were transformed into carboxylate structures by ion exchange. In addition, highly reactive free radical active sites were produced and accumulated along with the decomposition of carboxylates, thus accelerating the self-heating of coal. In the room-temperature oxidation experiment, the temperature of alkali-treated Wulan coal was spontaneously raised by 13.9℃, while that of raw coal was 4.3 ℃. The results showed that the thermal decomposition of organic carboxylate played an important role in promoting the spontaneous combustion of coal, and acid pretreatment could be a potential method to effectively inhibit the coal self-ignition process.

Carbon cloth/transition metals-based hybrids with controllable architectures for electrocatalytic hydrogen evolution - A review

Recently, the demand for energy consumption has been increasing exponentially due to the exhaustion of fossil fuels in the environment. This is the foremost technical challenge to the researchers to progress clean and alternative sustainable energy sources. Among various kinds of energy sources, an environment-friendly fuel, hydrogen is recognized as a favorable energy carrier to reduce the necessity on fossil fuels and protect the environment by reducing the discharge of greenhouse and other toxic gases. Thus, effective production and storage of hydrogen through a cost-effective and significant approach are the important factors of sustainable hydrogen production. Electrocatalytic water splitting is a favorable method for the hydrogen evolution reaction (HER), which requires an efficient and strong electrocatalyst to accelerate the kinetics of HER. To date, the well-developed electrocatalysts for HER activity are Pt-group metals, but, these electrocatalysts are inadequate and more expensive. In recent years, significant improvement has been achieved in the development of carbon cloth-based HER electrocatalysts as a replacement to Pt-based catalysts for hydrogen production in acidic medium. In this review, we mainly focused on the recent growth in the establishment of carbon-cloth functionalized transition metal (Fe-, Co-, Ni-, Mo-, and W-) based electrocatalysts towards the enhancement of HER activity. Depending on the results, we believed that the transition metal-based electrocatalysts have been appearing as fascinating and future alternative catalysts due to their morphology improvements, synergistic effects, a significant enhancement in the production of active sites, charge transfer efficiency, and superior HER activity with great durability. In addition, we outline the remarkable challenges and future prospects in this inspiring field.

Fluorometric titration assay of affinity of tight-binding nonfluorescent inhibitor of glutathione S-transferase.

To determine inhibition constant (K(i)) of tight-binding inhibitor, the putative method estimated an apparent K(i) from the response of initial rates to total concentrations of the inhibitor considering its depletion during binding for conversion into the true K(i), but was impractical with glutathione S-transferase of sophisticated kinetics. A fluorometric titration assay of dissociation constant (K(d)) was thus proposed. Schistosoma japonicum glutathione S-transferase (SjGST) action on a nonfluorescent divalent pro-inhibitor and glutathione yielded a divalent product in active site to act as a tight-binding inhibitor, whose binding quenched fluorescence of SjGST at 340 nm under the excitation at 280 nm. K(d) was estimated from the response of fluorescence of SjGST at 340 nm to total concentrations of the divalent product considering its depletion during binding. By fluorometric titration assay, K(d) of two tested nonfluorescent divalent products varied from subnanomolar to nanomolar, but both were resistant to change of SjGST levels and consistent with their apparent K(i) estimated via the putative method. Hence, fluorometric titration assay of K(d) of nonfluorescent tight-binding inhibitors/ligands was effective to GST and may be universally applicable to common enzymes/proteins; affinities of tight-binding inhibitors of GST can be approximated by their apparent K(i) estimated via the putative method.

Reaction chemistry at the Si (100) surface—control through active-site manipulation

Thermal desorption methods have been used to investigate the interaction of propylene (C3H6) with Si(100)-(2×1). The adsorption characteristics depend strongly on the availability of active sites at the Si(100) surface. Reactivity is enhanced by production of active sites during ion prebombardment. Adsorption of C3H6 to a disordered, ion-bombarded Si(100) surface results in nearly complete dissociation of C3H6 for ion fluences as small as 1015 Ar+ ions/cm2. In contrast, for a thermally annealed and ordered Si(100) surface, only 65% of the C3H6 dissociates. The remainder of the propylene chemically bonds to the surface as an undissociated molecule which desorbs intact at 550 K. The increase in reactivity is due to an increase in dissociative chemisorption which occurs at defect sites produced by ion bombardment. Reactivity is suppressed by capping of active sites using atomic hydrogen preadsorption. Hydrogen passivates the Si(100) surface by occupation of silicon dangling bonds, which prevents adsorption of C3H6. By controlling the number and kind of active surface sites in this way, it is possible to manipulate the reactive ability of the Si(100) surface.