摘要 : The trace-level detection of tetracyclines (TCs) in food products is essential to ensure food safety and public health. Herein, we prepared the methionine-doped carbon quantum dots (Met-CQDs) using citric acid as the precursor. Met-CQDs exhibited a Gaussian unimodal peak centered at 440 nm in the fluorescent excitation spectrum, along with a remarkable greenish-blue emission and a fluorescent quantum yield of 33.5 %. Furthermore, the presence of TC (the quencher) caused a rapid quenching of the fluorescence of Met-CQDs, accompanying with a color transition from light blue to dark bule as TC concentrations increased. The coloring variation was also detected by the images captured by smartphones and RGB analysis software, facilitating portable detection of TC utilizing Met-CQDs as a fluoroprobe. The findings indicate that the Met-CQDs based fluoroprobe exhibits high selectivity, rapid response (only ∼1 min) according to an "ON-OFF" sensing model. This fluorescence sensing method gave a low detection limit (LOD) of 0.032 μM and excellent linearity for TC in the concentration range of 0.1–500 μM. Also, the smartphone-based fluorescence-visualizing approach displayed good linearity with a LOD of 0.33 μM. The interactions between this fluoroprobe and TC occurred by virtue of both inner filter effect (IFE) and static-quenching principle. The average recovery for TC in the milk, honey, and tap water samples was determined to be 98.46 ± 1.71 % by a fluorometric method. Overall, both fluorometric and RGB approaches demonstrate strong correlation with conventional LC-MS/MS, and thus the as-fabricated Met-CQDs are promising for the preliminary screening of TCs' residues in food products.

摘要 : Simultaneously dispersing phosphide crystallites and multiple heteroatoms in hollow carbon is a significant yet challenging task for achieving high-performance oxygen electrocatalysts of zinc-air batteries. Herein, a simple wrapping-pyrolysis strategy is proposed to prepare Co 2 P/CoP embedded in N, P, S triply-doped hollow carbon (Co 2 P/CoP@NPS-HC). Co 2 P/CoP@NPS-HC composite features hollow polyhedral structure populated with numerous catalytically active Co 2 P/CoP nanoparticles and N, P, S heteroatoms. This optimized catalyst exhibits excellent activity for oxygen reduction reaction, with a half-wave potential of 0.82 V vs. RHE, and impressive enhancement for oxygen evolution reaction, indicated by an overpotential of 400 mV at 10 mA cm −2 . Moreover, Co 2 P/CoP@NPS-HC catalyst exhibits greater durability and superior methanol tolerance compared to commercial Pt/C. The excellent bifunctional electrocatalytic performance of Co 2 P/CoP@NPS-HC catalyst is attributed to the synergistic effect of uniformly dispersed Co 2 P/CoP nanoparticles and N, P, S triply-doped hollow carbon structure. The former provides abundant catalytically active sites, while the latter offers a high accessible specific surface area, as well as enhances catalytic activity and electronic conductivity due to its altered charge distribution.

摘要 : The minichannel boiling in a pumped two-phase fluid loop is an efficient thermal management for modern fighter jets in hypergravity environment. A variable-speed rotating platform is constructed to simulate the hypergravity environment. An experiment of the mechanically pumped two-phase fluid loop is conducted to investigate the flow boiling characteristics of minichannel evaporator under hypergravity conditions, with a focus on the centripetal and centrifugal radial flow modes. In addition, the dynamic heat transfer performance of the evaporator under centrifugal and centripetal flow modes is quantitatively evaluated by the average wall temperature, heat transfer coefficient, critical hypergravity acceleration. The results indicate that, the role of hypergravity in minichannel flow boiling in centripetal flow mode differs from that in the centrifugal flow mode. In the centripetal flow mode, the wall temperature of minichannel evaporator exhibits the "L"-shaped trend with respective to the hyper-gravitational acceleration, suggesting that hyper-gravitational acceleration contributes to heat transfer enhancement. In the centrifugal flow mode, an increase in hyper-gravitational acceleration leads to an overall "V"-shaped trend in the wall temperature of evaporator, indicating that there is optimum boiling performance at an appropriate hyper-gravitational acceleration. In addition, the critical hypergravity acceleration increases as the rise of flow rate in the centrifugal flow mode, no critical hypergravity acceleration is observed in the centripetal flow mode.

摘要 : In commercial buildings, implementing precooling measures before office hours in summer can effectively meet the thermal comfort needs of employees. However, in multi-zone environments, differences in the cooling rates between regions often exacerbate the heat transfer interference between zones, increasing the complexity of the precooling system and leading to energy waste with limited cooling capacity. To overcome these challenges, we have developed a novel multi-zone precooling control method, which integrates deep reinforcement learning (DRL) to optimize the heat transfer process by adjusting the Air Handling Units (AHUs) valve openings, thus achieving uniform precooling across the building. Comparisons with traditional precooling control methods demonstrate the effectiveness of the proposed method. The results show that, under conventional conditions, compared with the rule-based control (RBC) and proportional integral derivative (PID) methods, the precooling time is reduced by 11.4% and 5.8%, respectively, the complexity of heat transfer is reduced by 77.6% and 64.1%, and energy consumption is reduced by 14.5% and 9.3%. In addition, the study analyzes the influence of environmental parameters on precooling optimization. The findings indicate that weather conditions have the most substantial impact on short-term precooling performance, followed by building thermal performance and cooling conditions.

摘要 : The design of self-supporting structure is particularly important to improve the stability and electrochemical performance of hydrogen evolution reaction electrode. Here, a facile strategy for building novel ultra-stable 0D-2D-3D integrated self-supporting electrode with high conductivity, sufficient diffusion channels and large reactive surface area was proposed. In the heterostructure, 2D Ti 3 C 2 T x flakes in-situ synthesized on 3D network porous Ti 3 AlC 2 surface which provides the multiple reactive surface areas and aggregation resistance to facilitating 0D ultrafine Pt nanoparticles uniform anchorage. Combined with structural characterization and first-principles calculations revealed that, the highly dispersed ultrafine Pt synergistically coupling strong metal-support interactions creates a unique multifunctional catalytic interface with high stability and atomic utilization efficiency of Pt to promote the HER in acidic and seawater. The resultant self-supporting electrode (support 0.48 wt% Pt) exhibits much superior activity to 10 % commercial Pt/C (loaded on foam nickel) in 0.5 M H 2 SO 4 (55 mV@10 mA cm −2 ) and simulate seawater (196 mV@10 mA cm −2 ) while reducing the Pt usage by 15 times. Meanwhile, the electrode also illustrates outstanding stability under high current densities (100 h@100 mA cm −2 ). This study provides a new design idea for developing integrated self-supporting catalytic electrodes to meet the durability of hydrogen evolution reaction applications in harsh environments.

摘要 : 3D printed monolithic catalysts have attracted increasing attention in the petrochemical industry due to their advantages of the freedom of configuration, the rapidity of fabrication and the control of the fluid properties of the reaction medium. However, this remains challenging in constructing of micromorphology, reliable manufacturing, and adaptive functionality. Herein, inspired by the function of acicular plant fractal structure, we have developed bionic multistage monolithic catalysts based on direct photo-curing 3D printing technology. We also design two configuration strategies for static and dynamic oxidative desulfurization of fuels. Below the catalyst surface, the porous structure prepared by the hard template method can increase the specific surface area of the catalyst to disperse the active center and adsorb organic sulfur to strengthen the oxidation effect. The 3D-MoWO/PC-CE monolithic catalyst shows excellent activity in the static reaction with 100% sulfur removal. Above the catalyst surface, microcrystalline cellulose is introduced in-situ in 3D printed ink to build needle-like structures to enhance mass transfer efficiency and reduce surface pressure in dynamic fixed bed reaction. This work provides valuable ideas for the fabrication of efficient monolithic catalysts in various reactions.

摘要 : The mechanical behavior of Methane Hydrate-Bearing Sediment (MHBS) is essential for the safe exploitation of Methane Hydrate (MH). In particular, the pore size and physicochemical characteristics of MHBS significantly influence its mechanical behavior, especially in clayey grain-cementing type MHBS. This study employs the Distinct Element Method (DEM) to investigate both the macroscopic and microscopic mechanical behavior of clayey grain-cementing type MHBS, focusing on variations in pore size and physicochemical characteristics. To accomplish this, we propose a Thermo-Hydro-Mechanical-Chemical-Soil Characteristics (THMCS) DEM contact model that incorporates the effects of pore size and physicochemical characteristics on the strength and modulus of MH. This THMCS model is validated using experimental data available in the literature. Using the proposed contact model, we conducted a series of investigations to explore the mechanical behavior of MHBS under conventional loading paths, including isotropic and drained triaxial tests using the DEM. The numerical results indicate that smaller pore sizes and lower water content—key physicochemical characteristics resulting from variations in electrochemical properties and the intensity of the electric field—can lead to reduced shear strength and stiffness due to the increased breakage of aggregates and weakened cementation. Additionally, heating was found to further accelerate the process of structural damage in MHBS.

摘要 : Vanadium-based oxides have good application prospects in aqueous zinc ion batteries (AZIBs) due to their structures suitable for zinc ion extraction and intercalation. However, their poor conductivity limits their further development. The d-band center plays a key role in promoting adsorption of ions, which promotes the development of electrode materials. Here, a series of MoV 2 O 8 compounds with oxygen defect (O d -MoV 2 O 8 ) were synthesized by a simple hydrothermal process and a subsequent vacuum calcination process through strict control of the deoxidation time. Theoretical calculations reveal that the abundant oxygen vacancies in MoV 2 O 8 effectively regulate the d-band center of the zinc ion adsorption site. This precise control of the d-band center enhances the zinc ion adsorption energy of MoV 2 O 8, lowers the migration energy barrier for zinc ions, and ultimately significantly boosts zinc storage performance. The specific capacity is as high as 282.4 mAh/g after 100 cycles at 0.1 A/g, and it also shows excellent performance and outstanding cycle life. In addition, the maximum energy density of O d -MVO-0.5 (MoV 2 O 8 sample deoxidized for 0.5 h) is 343.3 Wh kg −1 . Importantly, the mechanism of Zn 2+ storage in O d -MoV 2 O 8 was revealed by the combination of in situ and ex situ characterization techniques.

摘要 : A coupled thiosulfate-driven denitrification and anammox (TDDA) process was established to remove nitrogen from wastewater. It was optimized in an up-flow anaerobic sludge blanket reactor using synthetic wastewater, and its reliability was then verified with actual wastewater. The results demonstrated that nitrate, nitrite, and ammonium could be synergistically removed, and the highest total nitrogen removal efficiency reached 97.8% at a loading of 1.39 kgN/(m 3 ·d). Anammox bacteria, primarily Candidatus_Brocadia, were the main contributors to nitrogen removal, while sulfur-oxidizing bacteria such as Thiobacillus and Rhodanobacter played a supportive role. By optimizing substrate conditions to enhance the anammox process, the coupled system attained higher abundances of functional genes such as napA, nirS, hzs, soxXA, and soxYZ, along with the corresponding microbial species. The data suggested that microbial cross-feeding and self-adaptation strategies were key to efficient nitrogen removal by TDDA.

摘要 : Photo-Fenton process is acknowledged for its high efficiency and technical feasibility in water treatment; however, its application is constrained by the addition of iron ions and hydrogen peroxide (H 2 O 2 ). Herein, an efficient photo-self-Fenton system with coating Fe-doped carbon dots (Fe-CDs) on the surface of highly crystalline C 3 N 5 (HC-C 3 N 5 ) nanosheets was developed for degradation of tetracycline (TC) under visible light irradiation. Experimental results reveal that Fe-CDs not only serve as active sites for facilitating superior light-induced charge separation and transfer towards the in-situ generation of H 2 O 2 over HC-C 3 N 5, but also provide the solid-phase Fe species for maximizing the activation of in-situ generated H 2 O 2 to produce highly oxidative OH and O 2 – species towards the photo-self-Fenton reaction. This research presents a novel design approach of utilizing a Fe-CDs-based photo-self-Fenton system for efficient wastewater treatment.