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Ru single atoms induce surface-mediated discharge in Na-O(2 )batteries
No full textSodium (Na) O-2 batteries have high energy density and low cost. However, high polarization, complex discharge products, and low Coulombic efficiency (CE) lead to poor cyclability. Here, we proposed an atomically dispersed Ru catalyst on nitrogen-doped graphene for Na-O-2 batteries. The catalysts enable the discharge to proceed via a surface-mediated route, which leads to uniform deposition of Na2-xO2 and low polarization during recharge. The first-principle calculation revealed that Ru-N-4 complex in the catalyst has strong chemical adsorption to intermediate superoxides, facilitating uniform deposition and enhancing rapid kinetics. In contrast, Ru nanoparticles, despite the catalytic activity, induce bulk deposition via a solution-mediated route because the exposed graphene surface shows weak interaction to superoxides, thereby lowering CEs and cyclability. In brief, the atomically-dispersed Ru catalyst endows Na-O-2 batteries with excellent electrochemical properties via a surface-mediated discharge. (C) 2021 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences
A two-step approach to phosphogypsum decomposition: Oxidation of CaS with CO2
No full textCO2 is proposed as an oxidant in a two-step phosphogypsum decomposition process, to oxidize the intermediate product of CaS into CaO. Isothermal and non-isothermal tests are conducted at a thermogravimetric analyzer combined with a Fourier transform infrared spectroscopy to reveal the reaction mechanism of CaS oxidation with CO2. During the course of non-isothermal process, several side reactions have been observed at low temperatures with CaCO3 and CaSO4 formations. CaS cannot be fully converted into CaO owing to the liquid melt formed by the mixture of CaSO4 and CaS. Full conversion into CaO is observed in the isothermal tests. The reaction order model fits the description of CaS oxidation into CaO with CO2, which is validated by both isothermal and non-isothermal data. In comparison with pure CaS, the CaS prepared from PG has a relatively lower reaction temperature with CO2, indicating the presence of impurities may have a catalytic effect
J-aggregation enhanced thermally activated delayed fluorescence for amplified spontaneous emission
No full textModulation of excited-state energy-level structures through controlled molecular stacking arrangement provides an effective strategy for tuning fluorescence and thermally activated delayed fluorescence (TADF) amplified spontaneous emission (ASE) but remains a critical challenge. Herein, we report the regulation of fluorescence and TADF ASE in organic crystalline polymorphs by controlling the excited-state dynamics through aggregate effects. Experimental and theoretical studies show that green crystals emit green fluorescence ASE, while red crystals emit red TADF ASE because a higher degree of J-aggregation in red crystals significantly results in a substantial decrease of energy gaps between singlet and triplet to 0.24 eV for the realization of a reverse intersystem crossing process. Our results suggest that molecular packing presents a powerful approach to tailor radiative channels that is fundamentally important for tuning fluorescence and TADF ASE in pure organic crystals
A Review of Microbial Mediated Iron Nanoparticles (IONPs) and Its Biomedical Applications
No full textNanotechnology is a booming avenue in science and has a multitude of applications in health, agriculture, and industry. It exploits materials' size at nanoscale (1-100 nm) known as nanoparticles (NPs). These nanoscale constituents are made via chemical, physical, and biological methods; however, the biological approach offers multiple benefits over the other counterparts. This method utilizes various biological resources for synthesis (microbes, plants, and others), which act as a reducing and capping agent. Among these sources, microbes provide an excellent platform for synthesis and have been recently exploited in the synthesis of various metallic NPs, in particular iron. Owing to their biocompatible nature, superparamagnetic properties, small size efficient, permeability, and absorption, they have become an integral part of biomedical research. This review focuses on microbial synthesis of iron oxide nanoparticles using various species of bacteria, fungi, and yeast. Possible applications and challenges that need to be addressed have also been discussed in the review; in particular, their antimicrobial and anticancer potentials are discussed in detail along with possible mechanisms. Moreover, some other possible biomedical applications are also highlighted. Although iron oxide nanoparticles have revolutionized biomedical research, issues such as cytotoxicity and biodegradability are still a major bottleneck in the commercialization of these nanoparticle-based products. Addressing these issues should be the topmost priority so that the biomedical industry can reap maximum benefit from iron oxide nanoparticle-based products
A promising catalytic solution of NO reduction by CO using g-C3N4/TiO2: A DFT study
No full textThe direct catalytic reduction of nitric oxide (NO) by carbon monoxide (CO) to form harmless N-2 and CO2 is an ideal strategy to simultaneously remove both these hazardous gases. To investigate the feasibility of using graphitic carbon nitride/titanium dioxide (g-C3N4/TiO2) to catalyze the NO reduction by CO, we systematically explore the effect of the interfacial coupling between g-C3N4 and TiO2 on the photo-induced carrier separation, the light absorption, and the surface reaction for the NO reduction by using density functional theory. The g-C3N4/TiO2 is predicted to have a better photocatalytic activity for NO reduction than g-C3N4, due to the enhanced light absorption intensity and the accelerated separation of the photo excited electron-hole pairs. By comparing the reaction routes on g-C3N4/TiO2 and g-C3N4, the results indicate that the introduction of TiO2 can keep the surface reaction process intact with the NO dissociation (N2O formation) being the rate-determining (crucial) step. Moreover, TiO2 can facilitate the desorption of NO reduction products, avoiding the deactivation of g-C3N4. This work shows that the composition of TiO2 into g-C3N4 provides a promising catalyst in NO reduction by CO. (C) 2021 Elsevier Inc. All rights reserved
National Key Research and Development Projects (Intergovernmental International Cooperation in Science and Technology Innovation Program)[2018YFE003400]
No full textState Key Laboratory of Multiphase Complex Systems, the Institute of Process Engineering, Chinese Academy of Sciences[MPCS-2021-A-05]
No full textThe Overexpression of Phasin and Regulator Genes Promoting the Synthesis of Polyhydroxybutyrate in Cupriavidus necator H16 under Nonstress Conditions
No full textCupriavidus necator H16 is an ideal strain for polyhydroxybutyrate (PHB) production from CO2. Low-oxygen stress can induce PHB synthesis in C. necator H16 while reducing bacterial growth under chemoautotrophic culture. The optimum growth and PHB synthesis of C. necator H16 cannot be achieved simultaneously, which restricts PHB production. The present study was initiated to address the issue through comparative transcriptome and gene function analysis. First, the comparative transcriptome of C. necator H16 chemoautotrophically cultured under low-oxygen stress and nonstress conditions was studied. Three types of genes were discovered to have differential levels of transcription: those involving PHB enzymatic synthesis, PHB granulation, and regulators. Under low-oxygen stress conditions, acetoacetyl-coenzyme A (CoA) reductase gene phaB2, PHB synthase gene phaC2, phasins genes phaP1 and phaP2, and regulator genes uspA and rpoN were upregulated 3.0-, 2.5-, 1.8-, 2.7-, 3.5-, and 1.6-fold, respectively. Second, the functions of upregulated genes and their applications in PHB synthesis were further studied. It was found that the overexpression of phaP1, phaP2, uspA, and rpoN can induce PHB synthesis under nonstress conditions, while phaB2 and phaC2 have no significant effect. Under the optimum conditions, the PHB percentage content in C. necator H16 was increased by 37.2%, 28.4%, 15.8%, and 41.0%, respectively, with overexpression of phaP1, phaP2, uspA, and rpoN, and the corresponding PHB production increased by 49.8%, 42.9%, 47.0%, and 77.5%, respectively, under nonstress chemoautotrophic conditions. Similar promotion by phaP1, phaP2, uspA, and rpoN was observed in heterotrophically cultured C. necator H16. The PHB percentage content and PHB production were increased by 54.4% and 103.1%, respectively, with the overexpression of rpoN under nonstress heterotrophic conditions.
IMPORTANCE Microbial fixation of CO2 is an effective way to reduce greenhouse gases. Some microbes, such as C. necator H16, usually accumulate PHB when they grow under stress. Low-oxygen stress can induce PHB synthesis when C. necator H16 is autotrophically cultured with CO2, H-2, and O-2, while under stress, growth is restricted, and total PHB yield is reduced. Achieving the optimal bacterial growth and PHB synthesis at the same time is an ideal condition for transforming CO2 into PHB by C. necator H16. The present study was initiated to clarify the molecular basis of low-oxygen stress promoting PHB accumulation and to realize the optimal PHB production by C. necator H16. Genes upregulated under nonstress conditions were identified through comparative transcriptome analysis and overexpression of phasin, and regulator genes were demonstrated to promote PHB synthesis in C. necator H16