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Photocatalytic synthesis of H2O2 is an advantageous and ecologically sustainable alternative to the conventional anthraquinone process. However, achieving high conversion efficiency without sacrificial agents remains a challenge. In this study, two covalent organic frameworks (COF−O and COF−C) were prepared with identical skeletal structures but with their pore walls anchored to different alkyl chains. They were used to investigate the effect of the chemical microenvironment of pores on photocatalytic H2O2 production. Experimental results reveal a change of hydrophilicity in COF−O, leading to suppressed charge recombination, diminished charge transfer resistance, and accelerated interfacial electron transfer. An apparent quantum yield as high as 10.3 % (λ=420 nm) can be achieved with H2O and O2 through oxygen reduction reaction. This is among the highest ever reported for polymer photocatalysts. This study may provide a novel avenue for optimizing photocatalytic activity and selectivity in H2O2 generation. [ABSTRACT FROM AUTHOR]

Photocatalytic synthesis of H2O2 is an advantageous and ecologically sustainable alternative to the conventional anthraquinone process. However, achieving high conversion efficiency without sacrificial agents remains a challenge. In this study, two covalent organic frameworks (COF−O and COF−C) were prepared with identical skeletal structures but with their pore walls anchored to different alkyl chains. They were used to investigate the effect of the chemical microenvironment of pores on photocatalytic H2O2 production. Experimental results reveal a change of hydrophilicity in COF−O, leading to suppressed charge recombination, diminished charge transfer resistance, and accelerated interfacial electron transfer. An apparent quantum yield as high as 10.3 % (λ=420 nm) can be achieved with H2O and O2 through oxygen reduction reaction. This is among the highest ever reported for polymer photocatalysts. This study may provide a novel avenue for optimizing photocatalytic activity and selectivity in H2O2 generation. [ABSTRACT FROM AUTHOR]

[Objective] The rapid development of nuclear technology and the continuous expansion of nuclear energy applications have focused engineering research on the conceptual design and shielding calculations of advanced reactors. The development of third-generation advanced modular small reactors has elevated the requirements for the types of neutron-shielding materials, equipment quality, and compactness of design. For shielding, these materials must exhibit good neutron and y-ray slowing down and absorption performance and have excellent mechanical properties to ensure structural integrity during long-term operation. Traditional shielding materials mostly rely on simple high-hydrogen-content compounds, high-density metal, and boron-containing concrete materials. However, when shielding small solid-state reactors, they gradually exhibit shortcomings in physical and mechanical performances. Addressing the inadequacies in the design and application research of composite shielding solutions for current small solid-state reactors, lightweight materials with excellent composite shielding performance can effectively meet the radiation shielding needs in complex geometric structures and operational scenarios. [Methods] This study selected lightweight materials with excellent performance for a single-tube neutron radiation detection system and conducted relevant performance experiments. Theoretical values and experimental results were cross validated through uncertainty simulations. After a comprehensive comparison of the physical performances and processing costs of neutron slowing down and absorption materials, coupled with discussions on the feasibility of neutron-shielding experiments in an experimental environment, boron carbide, titanium hydride, and zirconium hydride were chosen as the shielding materials for this experiment. Special-sized containers were customized, and samples encapsulated in organic glass and PVC materials were prepared. Performance tests of the shielding materials were conducted by counting the number of neutrons at counter positions in the single-tube neutron radiation detection system. The experimental data, including counting averages (n/s), sample variance, and the characterized shielding effectiveness, were recorded, summarized, and analyzed in detail. Subsequently, the detection system was modeled using the independently developed reactor Monte Carlo code by the REAL team at Tsinghua University. Monte Carlo particle transport simulations were used to validate the consistency between experimental and theoretical data. [Results] The experimental results indicate the following findings: 1) The shielding enclosure device comprising PVC material has virtually no impact on background neutron counts, while the use of organic glass material leads to a substantial effect, reaching 5%-6%. 2) Under the experimental conditions, boron carbide exhibits a noticeable absorption effect on neutrons, with a 3 mm thickness already achieving a considerable absorption effect at nearly an order of magnitude. 3) Under equivalent experimental conditions, the shielding effectiveness of titanium hydride and zirconium hydride is unsubstantial. However, titanium hydride slightly outperforms zirconium hydride. This superiority is observed because, in hydrogen-containing materials, titanium hydride and zirconium hydride have the same proportion of hydrogen nuclei. Because of the slightly higher neutron absorption cross-section of titanium nuclei compared to zirconium nuclei, the absorption effect makes titanium hydride slightly better than zirconium hydride in overall shielding effectiveness. 4) The experimental data collected align well with Monte Carlo simulation calculations, indicating the correctness of the experimental approach in this study.[Conclusions] The data and conclusions obtained from this study on lightweight shielding materials with specific characteristics apply to other novel shielding systems and devices. The research indicates that under equivalent irradiation conditions, shielding effectiveness increases in the order of boron carbide, titanium hydride, and zirconium hydride. Simulations and experiments provide guidance and validation, establishing a solid theoretical foundation for introducing composite diffusive shielding materials into portable small nuclear power systems. [ABSTRACT FROM AUTHOR]

Hepatocellular carcinoma (HCC) is a malignant tumor leading cancer-associated high mortality worldwide. Unfortunately, the most commonly used drug therapeutics not only lack of target ability and efficiency, but also exhibit severe systemic toxicity to normal tissues. Thus, effective and targeted nanodrug of HCC therapy is emerging as a more important issue. Here, we design and develop the novel nanomicelles, namely Mannose-polyethylene glycol 600-Nitroimidazole (Man-NIT). This micelle compound with high purity comprise two parts, which can self-assemble into nanoscale micelle. The outer shell is selected mannose as hydrophilic moiety, while the inner core is nitroimidazole as hydrophobic moiety. In the cell experiment, Man-NIT was more cellular uptake by HCCLM3 cells due to the mannose modification. Mannose as a kind of glucose transporter 1 (GLUT1) substrate, can specifically recognize and bind to over-expressed GLUT1 on carcinoma cytomembrane. The nitroimidazole moiety of Man-NIT was reduced by the over-expressed nitroreductase with reduced nicotinamide adenine dinucleotide phosphate (NADPH) as the cofactor, resulting in transient deletion of NADPH and glutathione (GSH). The increase of reactive oxygen species (ROS) in HCCLM3 cells disturbed the balance of redox, and finally caused the death of tumor cells. Additional in vivo experiment was conducted using twenty-four male BALB/c nude mice to build the tumor model. The results showed that nanomicelles were accumulated in the liver of mice. The tumor size and pathological features were obviously improved after nanomicelles treatment. It indicates that namomicelles have a tumor inhibition effect, especially Man-NIT, which may be a potential nanodrug of chemotherapeutics for HCC therapy. [ABSTRACT FROM AUTHOR]

To address the problem that anechoic coatings frequently fall off from modern submersible hulls and are detrimental to the realization of underwater acoustic stealth, this paper focuses on the broadband sound absorbing of acoustic coverings in debonding states from fully bonded span to fully shedded conditions. Based on the non-uniform waveguide theory, subdomain splitting approach, and wave propagation theory in layered media, a global transfer matrix method (TMM) is developed for predicting the sound absorption of a composite overburden with periodic cavities in all peeling situations. Meanwhile, the corresponding acoustic-structure fully coupled finite element (FE) simulation and hydroacoustic impedance tube-based absorption experiment are sequentially performed for the lining in a semi-bonded state to comprehensively verify the accuracy and reliability of the present analytical methodology. Then, the influence laws of debonding states, material properties, and geometric parameters on the global absorption performance are investigated in depth to reveal the multiple energy dissipation mechanisms. The results show that the shedding state primarily affects the sound absorption characteristics of anechoic coatings in the low- to mid-frequency band below 7 kHz. [ABSTRACT FROM AUTHOR]