An effective heterogeneous nanocatalyst was successfully designed by immobilization of tungstate ions (WO 4 2− ) onto the modified surface of carbon quantum dots (CQDs) with the 1-aminopropyl-3-methyl-imidazolium chloride ([APMim][Cl]). In this work, for the first time, the synthesized CQDs@IL/Cl − , via a facile one-step hydrothermal method, was used as an adsorbent and stabilizing support for tungstate ions. Characterization of the synthesized nanoparticles (NPs) by various physicochemical techniques illustrated that tungstate ions have been immobilized on the surface of IL-modified CQDs. With this novel nanocatalyst, a variety of primary, secondary alcohols, and other alcohol substrates have been efficiently oxidized to their corresponding aldehydes and ketones in yields of ≥88% with high selectivity (100%). In the presence of CQDs@IL/WO 4 2− as a recyclable nanocatalyst, all alcohol substrates without overoxidation to carboxylic acid were oxidized within 2 h, under a temperature of 70 °C with H 2 O 2 as the oxidant. The above catalyst can be readily recycled using a simple extraction and reused consecutive runs under the described reaction conditions without a considerable decrease in the activity and selectivity. In conclusion, this Article offers a novel application for CQD chemistry.
The Chang-Cooper discretization scheme for a class of Fokker-Planck equations is investigated. These equations of parabolic type govern the time evolution of the probability density function of stochastic processes, such that positivity of the density function and conservativeness of the total probability is guaranteed. It is shown that the Chang-Cooper scheme combined with backward first- and second-order finite differencing in time provides stable and accurate solutions that are conservative and positive. These properties are theoretically proven and validated by numerical experiments.
Achieving green and sustainable chemical processes by replacing organic solvents with water has always been one of the green chemistry goals and a challenging topic for chemists. However, the poor solubility of organic materials is a major limitation to achieving this goal, especially in alcohol oxidation. In this contribution, the development and design of amphiphilic catalysts via abundant, safe, cheaper, and more biocompatible sources have received notable attention. To this purpose, herein, our group successfully synthesized a new multifunctional amphiphilic carbon quantum dot (CQD) composed of 1-aminopropyl-3-methyl-imidazolium chloride ([APMim][Cl]), dodecylamine (DDA), and citric acid (CA) (denoted as CQDs@DDA-IL/Cl) using a one-pot hydrothermal route. The CQDs@DDA-IL/Cl was then utilized as an amphiphilic stabilizer for anchoring tungsten ions using an anion-exchange method (marked as CQDs@DDA-IL/W). The CQDs@DDA-IL/W as a reusable catalyst selectivity mediated the oxidation of alcoholic substrates with stoichiometric H2O2 in water solvent. The extraordinary performance of our catalyst was attributable to the coexistence of ionic liquid (IL) and DDA upon the surface of the CQDs@DDA-IL/W, which plays a main duty in the hydrophobic/hydrophilic balance, and significantly increase the catalyst compatibility in the aqueous medium with the purpose of removing organic solvents. As a result, the great mass transfer occurs in the two-phase medium using this amphiphilic nanocatalyst without any phase transfer catalyst (PTC) or other additives. The 100% selectivity, excellent turnover number (TON) and turnover frequency (TOF), high yield, almost complete and fast conversion of alcohol to the desired aldehydes and ketones without more oxidation, and easy and no-trouble isolation of product and catalyst are outstanding features of this catalytic system.
Continuous professional development (CPD) is important for teachers in attaining sustainable education. Accordingly, exploring teachersí perceptions could be a significant endeavor as teachersí beliefs impact their classroom practices, thereby, impacting student learning and, thus have educational implications. Therefore, this study was designed to investigate this fundamental issue via establishing professional development workshops to train teachers in order to promote sustainable professional growth. It examined 86 EFL teachersí beliefs and attitudes toward CPD before and after attending workshops for professional development. The data were collected through a questionnaire and a follow-up interview. Paired-samples t-tests were run to measure differences between responses of pre and post surveys. Moreover, raw frequencies and percentages were calculated in order to prioritize the items the teachers selected in each variable. The findings demonstrate that beliefs about CPD can change. Survey data collected before and after professional development workshops revealed a statistical significant shift in EFL teachersí beliefs. This finding was also supported by semi-structured interviews. In addition, the results also revealed that the participants perceived customized professional development programs with professional development framework as a beneficial tool to be included in the professional development programs. The study may have some pedagogical implications to be utilized in the educational process directed at sustainable professional development.
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