Investigation of organic materials for lithium batteries

University of Technology Sydney. Faculty of Science.The performances of lithium-based batteries can be significantly influenced by the electrolyte and cathode materials. In this PhD project, functional organic materials were synthesised and applied as electrolyte and cathode components for lithium-ion (Li-ion) and lithium-oxygen (Li-O₂) batteries to improve overall performances. Theoretically, organic materials can be tailored with functional groups to fit various purposes, making them suitable for battery applications. Post-synthesis techniques such as field emission scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy were used to characterise the physical properties. Electrochemical analyses including galvanostatic discharge-charge method, cyclic voltammetry, linear sweep voltammetry, and impedance spectroscopy were conducted to determine the electrochemical performance of the materials. Porous polymer membranes based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) are prepared using the breath-figure method. The as-prepared PVDF-HFP porous membrane showed a highly ordered honeycomb-like structure. The highly porous structure could absorb large quantities of liquid electrolyte, resulting in a high ionic conductivity. Moreover, the non-combustible PVDF-HFP membrane could significantly enhance safety properties of Li-ion batteries compared to the one using a conventional Celgard separator. The combination of the PVDF-HFP membrane with liquid electrolyte resulted in a higher capacity and prolonged cycle life. Further investigation on coating poly(methyl methacrylate) (PMMA) on PVDF-HFP porous membranes to achieve hierarchical structures with sandwich-like morphology was carried and studied. By the combination of porous PVDF-HFP and PMMA with higher affinity towards liquid electrolyte, the ionic conductivity was further improved. As a result, the electrochemical performance of Li-ion battery was significantly enhanced. A bi-functional organic catalyst poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) was synthesized by a two-step method. The unique properties of PTMA during n-doping and p-doping could facilitate the discharge and charge processes, respectively. It was discovered that the discharge capacity increased and the charge over-potential was reduced. The mechanism investigation showed that it was the functional N-O radical interacting with oxygen and Li₂O₂ to catalyse the battery reactions. As a result, the cycling life of the Li-O₂ battery was significantly prolonged. Further investigation of employing co-polymers as binder in the cathode for Li-O₂ batteries was carried out. The binder was synthesized by co-polymerizing methyl methacrylate (MMA) and 2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate (TMA) monomers. The ratio between both monomers was also studied. The results indicated that the direct contact of co-polymer binder and liquid electrolyte would transfer it into a gel polymer electrolyte membrane which enabled the catalytic N-O radical group to function as restricted redox mediator. The electrochemical performance of Li-O₂ batteries can be further enhanced by employing PTMA. An investigation of the mechanism when tetrathiafulvalene (TTF) was used in Li-O₂ batteries in the presence of LiCl was studied. It is revealed that the addition of LiCl in the electrolyte completely changed the functional mechanism of TTF in Li-O₂ batteries. Instead of functioning as a solution-based redox mediator, the combination of TTF and LiCl resulted in a deposition of an organic conductor on the surface of Li₂O₂, providing additional ways for electron transference. As a result, the cycling efficiency was improved, and with the use of porous graphene as cathode material the cycle life was prolonged

A Convolutional-Transformer Network for Crack Segmentation with Boundary Awareness

Cracks play a crucial role in assessing the safety and durability of manufactured buildings. However, the long and sharp topological features and complex background of cracks make the task of crack segmentation extremely challenging. In this paper, we propose a novel convolutional-transformer network based on encoder-decoder architecture to solve this challenge. Particularly, we designed a Dilated Residual Block (DRB) and a Boundary Awareness Module (BAM). The DRB pays attention to the local detail of cracks and adjusts the feature dimension for other blocks as needed. And the BAM learns the boundary features from the dilated crack label. Furthermore, the DRB is combined with a lightweight transformer that captures global information to serve as an effective encoder. Experimental results show that the proposed network performs better than state-of-the-art algorithms on two typical datasets. Datasets, code, and trained models are available for research at https://github.com/HqiTao/CT-crackseg

The Double-Edged Sword Effect of Abusive Supervision on Subordinates’ Innovative Behavior

Existing studies on the relationship between abusive supervision and innovative behavior do not present a united picture. Drawing up the antecedent-benefit-cost framework and social cognitive theory, we tried to explain the contradictory relationships between them based on the mediating mechanism. Results showed that abusive supervision discouraged subordinates’ innovative behavior through reducing subordinates’ psychological safety but promoted subordinates’ innovative behavior through enhancing challenge-related stress

Identification and validation of microRNAs as endogenous controls for quantitative polymerase chain reaction in plasma for stable coronary artery disease

Background: Circulating microRNAs (miRNAs) have been proved to serve as biomarkers for diagnosis and assessment of prognosis of coronary artery disease (CAD). Reverse transcription quantitative polymerase chain reaction (RT-qPCR) is a widely-used technique to estimate expression levels of circulating miRNAs. Selection of optimal endogenous control (EC) remains critical to obtain reliable qPCR data of miRNAs expression. However, reference controls for normalization of circulating miRNA in CAD are still lacking. The purpose of this study was to identify stably expressed miRNAs to normalize RT-qPCR data derived from plasma in stable CAD.Methods: We identified 10 stably expressed candidate ECs by combining miRNA microarray screening and literature screening. These 10 candidate ECs were estimated by RT-qPCR and the data were analyzed by NormFinder and BestKeeper algorithm.Results: Two most stable ECs were identified as EC candidates and they were subsequently validated in another larger cohort. The 2 candidates were also validated by normalizing the expression levels of miR-21. In general, they were superior to the commonly used reference gene RNU6 in quantification cycle (Cq) value, stability value and normalization effect.Conclusions: Our results demonstrated that miR-6090 and miR-4516 can be used as reference genes for plasma miRNA analysis in stable CAD

Photothermal catalysis: From fundamentals to practical applications

Photothermal catalysis is an innovative approach that integrates photochemical and thermocatalytic processes to enable an efficient use of full-spectrum sunlight in catalyzing various chemical reactions for energy conversion and environmental governance. This approach has demonstrated competitive performance and energy efficiency compared to conventional techniques, making it suitable for large-scale applications. In this review, we will comprehensively examine the fundamentals and classification of photothermal catalysis and discuss detailed design principles of various types of photothermal catalysts, focusing on enhancing solar light absorption, improving internal electric field for more energetic hot carriers (EHC) and localized thermal energy (LTE), interfacial engineering for robust and directed EHC transferring, and regulating EHC and LTE for continuous 24/7 operation. We will also report photothermal catalysis in a diverse range of chemical reactions. Moreover, we will introduce the latest technologies for synthesizing robust photothermal catalysts and advanced solar concentrators for pilot testing in the production of solar fuels at scale. Finally, the future opportunities and challenges of the promising but fledging field will be discussed, which is expected to transform conventional chemical industries into a clean and sustainable manner

Switching of the Microglial Activation Phenotype Is a Possible Treatment for Depression Disorder

Major depressive disorder (MDD) is a common emotional cognitive disorder that seriously affects people’s physical and mental health and their quality of life. Due to its clinical and etiological heterogeneity, the molecular mechanisms underpinning MDD are complex and they are not fully understood. In addition, the effects of traditional drug therapy are not ideal. However, postmortem and animal studies have shown that overactivated microglia can inhibit neurogenesis in the hippocampus and induce depressive-like behaviors. Nonetheless, the molecular mechanisms by which microglia regulate nerve regeneration and determine depressive-like behaviors remain unclear. As the immune cells of the central nervous system (CNS), microglia could influence neurogenesis through the M1 and M2 subtypes, and these may promote depressive-like behaviors. Microglia may be divided into four main states or phenotypes. Under stress, microglial cells are induced into the M1 type, releasing inflammatory factors and causing neuroinflammatory responses. After the inflammation fades away, microglia shift into the alternative activated M2 phenotypes that play a role in neuroprotection. These activated M2 subtypes consist of M2a, M2b and M2c and their functions are different in the CNS. In this article, we mainly introduce the relationship between microglia and MDD. Importantly, this article elucidates a plausible mechanism by which microglia regulate inflammation and neurogenesis in ameliorating MDD. This could provide a reliable basis for the treatment of MDD in the future

Two−dimensional nanomaterials confined single atoms: New opportunities for environmental remediation

Two−dimensional (2D) supports confined single−atom catalysts (2D SACs) with unique geometric and electronic structures have been attractive candidates in different catalytic applications, such as energy conversion and storage, value−added chemical synthesis and environmental remediation. However, their environmental applications lack of a comprehensive summary and in−depth discussion. In this review, recent progresses in synthesis routes and advanced characterization techniques for 2D SACs are introduced, and a comprehensive discussion on their applications in environmental remediation is presented. Generally, 2D SACs can be effective in catalytic elimination of aqueous and gaseous pollutants via radical or non−radical routes and transformation of toxic pollutants into less poisonous species or highly value−added products, opening a new horizon for the contaminant treatment. In addition, in−depth reaction mechanisms and potential pathways are systematically discussed, and the relationship between the structure−performance is highlighted. Finally, several critical challenges within this field are presented, and possible directions for further explorations of 2D SACs in environmental remediation are suggested. Although the research of 2D SACs in the environmental application is still in its infancy, this review will provide a timely summary on the emerging field, and would stimulate tremendous interest for designing more attractive 2D SACs and promoting their wide applications

Photocatalytic reforming of lignocellulose: A review

Biomass has been considered as a promising energy resource to combat the exhaustion of fossil fuels, as it is renewable, sustainable, and clean. Photocatalytic reforming is a novel technology to utilize solar energy for upgrading biomass in relatively mild conditions. This process efficiently reforms and recasts biomass into hydrogen and/or valuable chemicals. To date, lignocellulose, including cellulose, hemicellulose and lignin, has attracted extensive studies in facile photocatalytic valorisation. This review summarizes and analyzes the most recent research advances on photoreforming of lignocellulose to provide insights for future research, with a particular emphasis on the reformation of lignin because of its 3D complex and stubborn structure. The structure of lignin contains a dominant linkage, i.e., β-O-4. The breakage of β-O-4 linkage can be proceeded by two steps, e.g., oxidization and reduction, according to the sequence of photoexcited holes and electrons. Thus, this review discusses two-step and integrate step dissociation strategies along with the rationally chosen photocatalysts. The challenges of the photocatalysts, solvent, and post-treatment were identified, and potential solutions to these challenges were provided

Platinum single atoms anchored on ultra-thin carbon nitride nanosheets for photoreforming of glucose

Photoreforming of biomass is a fascinating process that harnesses renewable sunlight and biomass to produce hydrogen under ambient conditions, holding a significant promise for future energy sustainability. However, the main challenge lies in developing highly active and stable photocatalysts with high light harvesting efficiency. In this study, we adopted a simple yet effective approach that combines thermal exfoliation and photodeposition to anchor Pt single atoms onto ultra-thin g-C3N4 nanosheets (MCNN). The incorporation of Pt single atoms induced a distinct red-shift in the visible light region, augmenting the solar energy absorption capacity, while the enlarged surface area of g-C3N4 nanosheets improved the mass transfer. Moreover, the enhanced photoelectric properties further contributed to the superior performance of Pt-MCNN-3.0 % in the photoreforming of glucose for hydrogen evolution. Remarkably, Pt-MCNN-3.0 % demonstrated an impressive hydrogen generation rate, approximately 59 times higher than that of MCNN, after a 3 h visible-light irradiation, maintaining a satisfied photo-stability. This work addresses the critical need for design of efficient photocatalysts, bringing us one step closer to realizing the potential of biomass photoreforming as a sustainable and clean energy conversion technology