ChemPhysMater最新文献

We investigated the polaron-assisted nonadiabatic dynamics in protonated TiO₂, as well as the polaron-H₂O coupling and its effects on the relaxation of photogenerated electrons. We observed that different polaron hopping regimes result in varied nonadiabatic couplings and relaxations of excited electrons from the conduction band minimum to the gap states of protonated TiO₂, with a weak dependence on the actual trapping site of the polaron. Surface-adsorbed H₂O molecules can attract polarons toward the adsorbed Ti sites, with the coupling between H₂O and the polaron being inversely proportional to their distance. Our findings suggest that the lifetime of the photogenerated charge carriers can be extended by reducing the polaron-H₂O distances, with expected benefits to the efficiency of the reduced TiO₂ samples for photocatalytic applications.

In this study, various chemical treatments were performed on clay-rich media to investigate their effects on hydrogen adsorption performance. We unequivocally demonstrated that acid-treated samples exhibited significant structural changes compared with those treated with alkali solutions. Gas adsorption isotherms and powder X-ray diffraction analyses clearly revealed that the acid treatment of clayey materials not only increased their surface area, but also enhanced hydrogen sorption uptake, increased interstratification, and reduced particle size. Most importantly, we succeeded in rationalizing the improvement in hydrogen uptake by sequentially applying purification, followed by acid treatment.

Pickering emulsions were prepared by phacoemulsification in an ice water bath with squalene as the oil phase and an aluminum adjuvant as the particle stabilizer. The effects of formulation and process conditions on the size and distribution of the Pickering emulsions were investigated. Pickering emulsions prepared under the optimal prescription and process conditions were mixed with a peptide antigen to obtain a peptide vaccine. The optimal prescription and process condition of the Pickering emulsion is as follows: squalene as the oil phase, ultra-pure water as the water phase with 5 mg/mL aluminum adjuvant, and an ultrasonication time of 4 min at 200 W power. BALB/c mice were immunized with the peptide vaccine, and the ability of the Pickering emulsion as an immunological adjuvant to improve the efficacy of the peptide vaccine was evaluated. Under optimal conditions, a Pickering emulsion with a small particle size (430.8 nm), uniform distribution (polydispersion index of 16.9%), and zeta potential of 31.5 mV, was obtained. Immunological results showed that the serum specific antibody level in the vaccinated group reached 1×10⁴ after three immunizations. The proportion of CD4⁺T cells and CD4/CD8 cells was significantly higher (P<0.05) in the vaccinated groups than the blank control group. Further, cytokine (TNF-α) secretion decreased in the aluminum adjuvant and Pickering emulsion groups but increased in the Freund's adjuvant group. All three vaccinated groups of mice exhibited low but detectable levels of IFN-γ secretion.

In the present study, we calculated the elastic, mechanical, and thermo-physical properties of Zirconium Nitride (ZrN)/Magnesium Oxide (MgO) (001) nanostructures in the temperature range of 50∼300 K using higher-order elastic constants. With two fundamental factors, nearest-neighbor distance and hardness parameter, in this temperature range, the second-and third-order elastic constants (SOECs and TOECs) are estimated using the Coulomb & Born-Mayer potential. The computed values of SOECs have been used to calculate Young's modulus, thermal conductivity, Zener anisotropy, bulk modulus, thermal energy density, shear modulus, and Poisson's ratio to assess the thermal and mechanical properties of the ZrN/MgO (001) nanostructured layer. Additionally, SOECs are used to calculate the wave velocities for shear as well as longitudinal modes of propagation along crystalline orientations <100>, <110>, and <111> in these temperature ranges. The temperature-dependent Debye average velocity, hardness, melting temperature, and ultrasonic Grüneisen parameters (UGPs) were evaluated. The fracture/toughness (B/G) ratio in the current investigation was greater than 1.75, indicating that the ZrN/MgO (001) nanostructured layer was ductile in this temperature range. The selected materials fully satisfied the Born mechanical stability requirement. At this ambient temperature, it has been computed how long thermal relaxation takes to complete and how ultrasonic waves are attenuated by thermo-elastic relaxation and phonon-phonon interaction mechanisms. These results, in combination with other well-known physical properties, can be applied to the non-destructive testing of materials for various industrial applications such as microelectronic devices, optical coatings, batteries, and solar cells.

With the fabrication of high-performance thermoelectric (TE) materials, developments are being made in enhancing the figure of merit, zT, of TE materials. Liquid-like binary copper selenide (Cu₂Se) chalcogenides recently gained significant recognition because of their anomalous but fascinating electrical and thermal transport performances. In this study, a facile synthesis technique was adopted in fabricating Cu₂Se nanoparticles using a rapid microwave-assisted hydrothermal route at different reaction times. The results were compared with those of the Cu₂Se solid-state (SS) sample synthesized using the traditional melting and annealing technique. X-ray diffraction patterns revealed successful synthesis of nanoparticles and a phase transition from orthorhombic α-phase and cubic β-phase to a single orthorhombic structure after hot-pressing. Scanning electron microscopic images revealed that although the grain sizes of the nanoparticle (NP) bulk samples increased with the reaction time of the microwave hydrothermal process, the grain sizes were significantly smaller than that of the SS sample. Additionally, NP bulk samples exhibited plenty of nano-grains and pores that are absent in the SS sample. The size and distribution of the grains and pores were measured to study their effects on the transport of carriers and phonons. The NP30 sample exhibited the highest power factor of 983.3 µW K⁻² m at 673 K among the NP samples, exhibiting intermediate values of resistivity and Seebeck coefficient that are close to those of the SS sample. Moreover, the NP samples exhibited appreciably lower thermal conductivity than the SS sample that is attributed to strengthened phonon scattering. The minimum thermal conductivity of the NP05 sample, 0.78 WK⁻¹ m⁻¹ at 348 K, is 1.7 times lower than that of the SS sample. Finally, a maximum zT of 0.56 at 673 K, being approximately 1.3 times higher than that of the SS sample owing to the optimized thermal conductivity, was achieved for the NP30 sample. This value is comparable to or higher than that reported for Cu₂Se synthesized using the traditional SS method. Investigations revealed that the proposed microwave hydrothermal synthesis technique is a facile, rapid, and reliable method that results in Cu₂Se alloys with excellent TE performance.

The direct electrolytic splitting of abundant seawater instead of scarce freshwater is an ideal strategy for producing clean and renewable hydrogen (H₂) fuels. The oxygen evolution reaction (OER) is a vital half-reaction that occurs during electrochemical seawater splitting. However, OER suffers from sluggish four-electron transfer kinetics and competitive chlorine evolution reactions in seawater. Noble metal-based catalysts such as IrO₂ and RuO₂ are considered to have state-of-the-art OER electrocatalytic activity, but the low reserves and high prices of these noble metals significantly limit their large-scale application. Recently, efforts have been made to explore efficient, robust, and anti-chlorine-corrosion non-noble-metal OER electrocatalysts for seawater splitting such as oxides, hydroxides, phosphides, nitrides, chalcogenides, alloys, and composites. An in-depth understanding of the fundamentals of seawater electrolysis and the design principle of electrode materials is important for promoting seawater-splitting technology. In this review, we first introduce fundamental reactions in seawater electrolytes. Subsequently, construction strategies for OER electrocatalysts for seawater splitting are introduced. Finally, present challenges and perspectives regarding non-noble-metal OER electrocatalysts for commercial H₂ production by seawater splitting are discussed.

The electromagnetic wave absorption capabilities of an absorber depend on its dielectric and magnetic components, which determine its interfacial polarization, conductivity loss, magnetic loss, and other such mechanisms. In this study, a comprehensive review of the electromagnetic wave and material interaction was conducted. Moreover, for a better understanding of the trends and evolutionary developments in the study of the electromagnetic wave absorber, 23300 documents dated between 1990 and 2020 were examined, which were obtained from Scopus using the keywords of “electromagnetic wave absorption” and “microwave absorption”. The data search in Scopus was conducted using the related keywords in the search bar for titles and abstracts. These results demonstrate that the majority of research regarding electromagnetic wave absorbers was conducted in China, which was followed by the United States. The number of published documents regarding the electromagnetic wave absorption field significantly increased between 1990 and 2020; these documents were mostly published as journal articles. With respect to the journal activity, the most productive journal was the “Journal of Alloys and Compounds”, with a total of 592 articles. In addition, graphene and titanium dioxide were determined to be the materials that were most studied in the field of electromagnetic wave absorption.

Because switchable water is difficult to apply directly for oil removal, an enhanced approach to improve oil removal is proposed using a surfactant-free microemulsion (SFME) containing switchable water. The SFME is formed using switchable water (aqueous N, N-dimethylethanolamine (DMEA) or N,N-dimethylbutylamine (BDEA)) and a hydrophobic amine (N-butyldiethanolamine (DMBA)). The single-phase region for preparing the SFME is determined using a ternary phase diagram, and the microstructure types are distinguished using the conductivity method. The pH changes and dynamic laser scattering test results demonstrate that the SFME exhibits irreversible transformation behavior regulated by CO₂. Moreover, the recovered SFME containing BDEA has a microstructure with a smaller particle size after removing the CO₂ by bubbling N₂ at 65 °C, which is attributed to the higher proportion of DMEA than that of BDEA. In addition, dodecane and diesel oil are shown to dissolve in the SFME, and the oil solubility of the SFME increases with increasing oil phase (DMBA) content. The interface free energy theory reveals that the oil is more easily detached with the addition of SFME than with switchable water only owing to the reduced interface free energy of oil on the solid surface. Thus, an enhanced approach for removing oil is proposed to wash oil sands, where the oil removal efficiency of switchable water can be improved by using SFMEs containing switchable water.

Cobalt sulfides are considered as promising candidates for lithium-ion battery (LIB) anode materials with high energy densities. Their energy storage mechanism is widely understood to involve the traditional intercalation and conversion reaction. However, these conventional mechanisms are unable to explain the storage capacities of certain materials which exceed the theoretical limit. Here, utilizing advanced in situ magnetometry to detect the magnetization evolution of Co_1-xS LIBs in real time, it is demonstrated that the Co-catalytic lithium storage process and interfacial space charge storage mechanism are strongly related to the additional capacity of cobalt sulfides. During discharge, a Co/Li₂S interface is formed, wherein the Co nanoparticles and Li₂S could store a large amount of polarized electrons Li⁺, respectively. Subsequently, the electrons stored in Co are transferred to the polymeric film, forming radical anions and contributing extra capacity. These findings reveal the charge storage mechanisms of transition metal sulfides and highlight the critical role of magnetic testing in the investigation of energy storage mechanisms.

The development of polymer solar cells (PSCs) for the donor materials based on benzo[1,2-b:4,5-b′]dithiophene (BDT) has significantly boosted the power conversion efficiency (PCE). However, the PCE of polymer donor materials for benzo[1,2-b:4,5-b′]difuran (BDF)-based lags far behind that of their BDT analogs. To further explore efficient copolymers based on BDF units, a two-dimensional (2D) side-chain strategy was proposed to investigate the atom-changing effects on the copolymer donors for the properties of electron and optical. In this study, we designed and synthesized three new BDF-based copolymer donor materials, named PBDF-C, PBDF-O, and PBDF-S. Owing to the balanced charge transport and favorable phase separation of PBDF-S:Y6, a high PCE of 13.4%, a short-circuit current (J_sc) of 25.48 mA cm⁻², an open-circuit voltage (V_oc) of 0.721 V, and a fill factor (FF) of 72.6% was obtained. This research demonstrates that the BDF building block has great potential for constructing conjugated copolymer donors for high-performance PSCs and that 2D side-chain modification is a facile approach for designing high-performance BDF-based copolymer materials.