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Thermal Shock Synthesis of Metal Nanoclusters within On-the-fly Graphene Particles
摘要： Metal nanoclusters (1-10 nm) have drawn great attention due to their potential applications including energy storage, catalysis, nanomedicine and electronic devices. However, manufacturing ultra-small metal nanoparticles at high concentrations in an unaggregated state is not a solved problem. Here we report an aerosol-based thermal shock technique for in situ synthesis of well-dispersed metal nanoclusters in on-the-fly graphene aerosols. A rapid thermal shock to the graphene aerosol has been used to nucleate and grow the metal nanoclusters with subsequent quenching to freeze the newly formed nanoclusters in the graphene aerosol matrix. A characteristic time analysis comparison with experiment shows that the nanocluster formation is governed by nucleation and subsequent surface growth, and that the graphene retards coagulation, enabling unaggregrated metal nanoclusters. The method is generic, and we show the formation of sub-10 nm Ni, Co and Sn nanoclusters. This continuous aerosol-based thermal shock technique offers considerable potential for the scalable synthesis of well-dispersed and uniform metal nanoclusters stabilized within a host matrix. As an example of potential application, we demonstrate very favorable catalytic properties.
关键词： thermodynamics,in situ growth,growth mechanism,thermal shock synthesis,kinetics,metal nanoclusters
更新于2025-09-19 17:15:36
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Structural characterization and thermal degradation of poly(methylmethacrylate)/zinc oxide nanocomposites
摘要： This work is based on the preparation of composites of poly(methylmethacrylate) with zinc oxide nanoparticles synthesized by solution casting method. Chloroform cast poly(methylmethacrylate) films containing different amounts of ZnO nanoparticles were characterized by XRD, SEM, UV-vis spectroscopy, FTIR spectroscopy and TGA. The results show that ZnO nanoparticles with a size of 24 nm were fairly dispersed in the polymer matrix. The obtained material had UV shielding capability with optical transparency. Thermal characterization shows that, the nanocomposites were more thermally stable than pure PMMA presenting three degradation steps. Apparent kinetic parameters were determined for each degradation step using peak fitting methodology. According to activation energies, ZnO particles affect simultaneously but oppositely the kinetics of underlying degradation reactions. Thermal stability of the PMMA/ZnO nanocomposites was the result of the overall balance in favor of the inhibiting effect of ZnO.
关键词： PMMA,polymer nanocomposites,activation energy,ZnO nanoparticles,degradation kinetics,TGA
更新于2025-09-19 17:15:36
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Ligand binding kinetics at histamine H3 receptors by fluorescence-polarization with real-time monitoring
摘要： Growing evidence recommends incorporating the concept of drug-target residence times within drug development and screening programs. For many targets, systematic research for binding kinetics is emerging and reported, as in case of the histamine H3 receptor. Alternatively, fluorescent methods based on Foerster resonance energy transfer have been reported recently but application of fluorescence polarization to kinetics of unlabeled ligands is not known to us. Thus, we established a radiolabel-free, real-time resolving method that is compatible to high-throughput-screening programs with the objective to explore the underlying binding kinetics. This method takes benefit of bodilisant as H3 receptor ligand. Thereby, we detected short residence times around 5 min for the H3 receptor ligands ciproxifan, clobenpropit, thioperamide as well as pitolisant. Monitoring association rates, remarkably slower association rate constants were examined for ciproxifan and thioperamide when compared to those of pitolisant or clobenpropit. The affinities for the ligands derived by the kinetic approach differ from affinity estimates in literature using radiolabeled agonists in displacement assays. Further investigation raised exceptional pharmacological properties, consistent with occurrence of secondary binding sites at the H3 receptor. Validation of resulting affinity constants was successfully performed by displacement assays based on fluorescence polarization with bodilisant. Thereby, measurements of receptor kinetics of prominent inverse agonists were obtained.
关键词： drug-target residence time,H3 receptor,fluorescence polarization,histamine,receptor kinetics
更新于2025-09-19 17:15:36
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Time-resolved laser-flash photolysis Faraday rotation spectrometer: a new tool for total OH reactivity measurement and free radical kinetics research
摘要： The total OH reactivity (k’OH) is an important parameter for quantitative assessment of the atmospheric oxidation capacity. Although laboratory measurement of k’OH has been achieved 20 years ago, the instruments required are often costly and complex. Long-term atmospheric observations remain challenging and elusive. In this work, a novel instrument combining laser-flash photolysis with a mid-infrared Faraday rotation spectrometer (LFP-FRS) has been developed for the measurement of k’OH and for studying gas phase free radical kinetics. The reactor is composed of a Herriott-type optical multipass cell, and OH radicals were generated by flash photolysis of ozone with a 266 nm pulsed Nd:YAG laser. The decay of the OH signal was directly measured with a time-resolved FRS spectrometer at 2.8 μm. The overlapping pathlength between the pump beam and probe beam was 25 m. High performance was achieved by subtracting the signals before and after flash photolysis to eliminate interferences caused by H2O absorption and background drift. The optimum precisions (1σ) of OH concentration and k’OH measurement were 4×106 molecule cm-3 and 0.09 s-1 over data acquisition times of 56 s and 112 s, respectively. The performance of the system was evaluated by the reaction of OH with CO and NO. The measured rate coefficients (kOH+CO and kOH+NO) were in good agreement with values reported in the literature. The developed LFP-FRS provides a new, high precision, and highly selective tool for atmospheric chemistry research of OH radicals and other transient paramagnetic free radicals such as HO2 radicals.
关键词： atmospheric oxidation capacity,total OH reactivity,laser-flash photolysis,free radical kinetics,Faraday rotation spectrometer
更新于2025-09-19 17:13:59
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Effective charge kinetics steering in surface plasmons coupled two-dimensional chemical Au/Bi2WO6-MoS2 heterojunction for superior photocatalytic detoxification performance
摘要： Developing and designing a rational heterojunction with efficient charge kinetics properties have been a research hotspot for improving photocatalytic performance. Herein, a surface plasmons coupled two-dimensional chemical Au/Bi2WO6-MoS2 heterojunction was synthesized. In thus a system, Au nanoparticles are tightly attached to the sides of Bi2WO6 nanosheets, conducting a HEI effect with additional visible light response to inject “hot electrons” into Bi2WO6, resulting in additional charge generation. Meanwhile, few-layer MoS2 nanosheets were chemically assembled onto ultrathin Bi2WO6 nanosheets via interfacial S-O bonds to form a intimate 2D-2D nanojunction, the separated and injected electrons on the surface of Bi2WO6 were further directional transfer to MoS2 nanosheets through S-O bonds for detoxification of heavy metal ions Cr(VI), and the corresponding holes left on Bi2WO6 nanosheets were applied for simultaneous degradation of tetracycline antibiotic. The photocatalytic detoxification activity of Au/Bi2WO6-MoS2 was nearly 4.84, 3.47 and 1.90 times higher than that of pristine Bi2WO6, Au/Bi2WO6 and Bi2WO6-MoS2 composites, which could be ascribed to the effective charge kinetics steering and well manipulation of charge flow by virtue of the rational structural and compositional features. This work provides a new perspective for the construction of high-activity detoxification photocatalysts through steering charge kinetics.
关键词： chemical heterojunction,Bi2WO6,charge kinetics steering,Photocatalysis,hot electrons inject
更新于2025-09-19 17:13:59
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Optimizing the Phase-Separated Domain Size of the Active Layer via Sequential Crystallization in All-Polymer Solar Cells
摘要： Proper domain size of the active layer plays a key role in determining the exciton dissociation and charge transport in all polymer solar cells (all-PSCs). However, fine-tuning the domain size remains challenging due to low glass transition temperature and negligible mixing entropy in polymer blends. Herein, we systematically studied the influence of “crystallization kinetics” on the domain size and proposed that if donor and acceptor crystallize simultaneously, it is prone to form large domain size; while if sequential crystallization of donor and acceptor occurs, a fine phase separation structure with proper domain size can be obtained. Taking PBDB-T/PNDI blends for instance, the domain size was decreased by using sequential crystallization, meanwhile, the crystallinity and molecular orientation were optimized as well, boosting the power conversion efficiency (PCE) from 6.55% to 7.78%. This work provides a novel way to finely tune the heterojunction phase separation structures.
关键词： domain size,crystallization kinetics,sequential crystallization,all-polymer solar cells,phase separation
更新于2025-09-19 17:13:59
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Direct Laser Etching Free‐Standing MXene‐MoS <sub/>2</sub> Film for Highly Flexible Micro‐Supercapacitor
摘要： The biomass hydrolysis residue (BHR) is the residue consisting of mainly lignin after the biomass-to-ethanol process. A combustion kinetic comparison of the biomass material (BM), BHR, and three main components (lignin, cellulose, and hemicellulose) is studied by thermogravimetry (TG) using the Kissinger method and Flynn?Wall?Ozawa (FWO) method under five different heating rates. The results show that the ignition temperature (Ti) and burnout temperature (Tb) of BHR are both higher than those of BM. BM burns more sufficient than BHR because it contains more fixed carbon content. The results show that the activation energy calculated by the Kissinger method for the corn cob hydrolysis residue (CCHR), corn straw hydrolysis residue (CSHR) and corn cob (CC) is 188.08, 192.76 and 205.76 kJ/mol, respectively. The results calculated by the FWO method show that, when the mass conversion (α) is small, EBHR > EBM, as α increases, E of BM gradually exceeds that of BHR. This could explain the phenomenon why BHR ignites earlier than BM but burns out later than BM. The power law (P4 and P2) reaction models are proper to describe the experimental behavior of BHR and BM, respectively. This paper also verifies that, on the premise of an accurate measurement of the three main components in BM and BHR, the TG curves and kinetic parameters of BM and BHR can be predicted.
关键词： thermogravimetry,combustion kinetics,biomass hydrolysis residue,Flynn?Wall?Ozawa method,Kissinger method
更新于2025-09-19 17:13:59
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A UV‐LEDs based photomicroreactor for mechanistic insights and kinetic studies in the norbornadiene photoisomerization
摘要： In this work, we report a simple and inexpensive UV-LEDs based photomicroreactor assembly constructed by commercially available components. The photoisomerization of norbornadiene to quadricyclane was selected to validate this novel photomicroreactor design. Mass transport limitation was eliminated and indicated by dimensionless numbers Fo and DaII, and photons loss was evaluated considering the absorption and reflection of the microreactor walls. The solvents, photosensitizers and light sources selections were optimized for achieving better photochemical performance and mechanistic insights. The detailed comparison between the high-pressure mercury arc lamp and the UV-LEDs strip revealed great potential of UV-LEDs as appealing light source for photochemical transformations. Moreover, the reaction mechanism was thoroughly discussed and illustrated by the Jablonski diagram indicating electronic states transitions. According to possible intermediate steps, a kinetic model was proposed with the reaction rate constant being correlated with the photon flux, which is valuable for process optimization and further understanding reaction mechanisms.
关键词： photosensitization,reaction kinetics,microreactor,mass transport,UV-LED
更新于2025-09-19 17:13:59
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Dynamics of Yb2+ to Yb3+ ion valence transformations in Yb:YAG ceramics used for high-power lasers
摘要： Due to the good thermal-mechanical and luminescence properties, Yb:YAG ceramics are suitable as thin-disk lasers; however, their efficiency is limited by the presence of Yb2t ions, which entail parasitic energy transfer from Yb3t formation in Yb:YAG ceramics prepared by solid-state reaction sintering. The samples were prepared by air annealing, the oxidation of the material leads to recharging Yb2t ion to its trivalent state. The activation energy was determined by Jander to be Ea(D) ? 2.7 ? 0.2 eV, which is in good agreement with the activation energy for oxygen diffusion in the YAG lattice. It was concluded that the recharging of Yb2t ion to its trivalent state in YAG ceramics is limited by the oxygen self-diffusion through the grain volume, and the oxygen vacancy alone and/or together with the presence of antisites can be proposed as Yb2t charge compensation mechanism in the YAG ceramics, unlike the YbAG single crystals, where tetravalent impurities are responsible for charge compensation.
关键词： Yb:YAG,Optical ceramics,Oxidation kinetics
更新于2025-09-19 17:13:59
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Fundamentals of three-dimensional Yb-fiber Nd:YAG laser machining of structural bone
摘要： This work aims to understand the fundamental aspects of the laser-bone interaction in three-dimensional laser machining of the bone through an integrated experimental-computational approach. The study introduces 3-dimensional laser machining of bones through multi-laser passes and attempts to establish the dimensional control over the laser-machined cavity through a finite element method based multi-physics computational model. A continuous wave Yb-fiber Nd:YAG laser (λ = 1064 nm) was employed with laser fluences ranging from 5:31 J/mm2 to 25:46 J/mm2 generated in combination of laser power (400 W–700 W) and machining speed (50 mm/s–250 mm/s). In multi-laser pass machining, the optimum fill spacing of 0.2 mm was identified for higher machining rates with low deviation from linearity of machined edge (d = 9 μm). This resulted in high machining rates ranging from 16:49 + 0:2 mm3/s to 45:26 + 0:66 mm3/s for a given range of laser fluence. The optimization for machining efficiency and physical attributes of the machined cavity were comprehended through thermodynamics and kinetics of the laser interaction with the bone based on the computational model for varying laser processing parameters.
关键词： bone,kinetics,Yb-fiber Nd:YAG laser,laser machining,computational model,three-dimensional,thermodynamics
更新于2025-09-16 10:30:52