The 10 most-cited articles in The Journal of Physical Chemistry, 2020

Nanomaterials, which promote the generation of reactive oxygen species (ROS) and precipitate the onset of oxidative stress responsible for the development of a variety of adverse conditions, have a great prospect for various nanomedicine applications. In this paper, for the first time, we report the pro-oxidant activity of GdYVO₄:Eu³⁺ and GdVO₄:Eu³⁺ nanoparticles (NPs) in water solutions without any external stimuli (in the darkness). This dark pro-oxidant activity is shown to be associated with superoxide (O₂•–) and hydroxyl radical (•OH) generation and is dependent on the size of NPs and, consequently, the concentration of surface defects, such as oxygen vacancies VO. For small 2 nm GdYVO₄:Eu³⁺ NPs, strong O₂•– and •OH radical production has been revealed, whereas for larger GdVO₄:Eu³⁺ NPs, low level of O₂•– and negligible level of •OH radical production have been detected during the sample storage in the darkness. The possible mechanisms of the dark ROS generation in ReVO₄:Eu³⁺ NPs are considered.

Co₃O₄ nanoparticles with smaller particle size can expose more active sites to react with electrolytes, thereby exhibiting better supercapacitive performance. However, the size of Co₃O₄ nanoparticles is difficult to be effectively controlled in traditional carbon matrices. Herein, P, N-codoped carbon matrices with ultrahigh surface area and abundant nanocavities are used as a novel host to confine the growth of Co₃O₄ nanoparticles. The Co₃O₄/carbon composites with high redox activities of Co₃O₄ are successfully obtained, in which Co₃O₄ nanoparticles are strongly anchored in the carbon matrices, resulting in the enhancement of the composites’ capacitive performance (1310 F g–¹ at 0.5 A g–¹). Meanwhile, the strong anchoring effect of the carbon host on Co₃O₄ nanoparticles because of the rich doping elements and the confinement effect of the nanocavities ensure long-term stability (92% capacitance retention after 5000 cycles). Furthermore, the assembled asymmetric supercapacitor using this composite as the cathode material and activated carbon as the anode material delivers a high…

The transfer mechanism of photogenerated charges (e– and h⁺) has always been a research hotspot of the photocatalysis field. Here, a series of WO₃/ZnO composite photocatalysts with different ratios were synthesized, and importantly, the transfer mechanism of photoexcited charges was systematically studied. By performing various characterizations, the direct Z-scheme of WO₃/ZnO was proposed, and the results verified that the immanent electric field formed between WO₃ and ZnO semiconductors is the inner impetus of charge transfer. This work distinguished the transfer mechanism of photogenerated charges in the heterojunction photocatalyst by the relative p–n junction theory and can also provide guidance for the construction and application of novel heterojunction photocatalysts in theory and practice.

Different from two-dimensional (2D) transition-metal dichalcogenides, 2D transition-metal trichalcogenides with a quasi-one-dimensional chain offer additional advantages in electronics and optoelectronics. Based on the recent experimental synthesis of few layers of ZrS₃, we present a comparative study on the electron and phonon transport properties of bulk and monolayer ZrS₃ by using the first-principles calculations combined with the Boltzmann transport theory. The anisotropic electrical conductivity is obtained because of the different carrier effective masses along different directions, and consequently, a larger power factor along the y direction is achieved for both p-type and n-type. The multivalley degeneracy valence band contributes to the large Seebeck coefficient and the high power factor for holes. The carriers of electrons with higher mobility along the Γ–Y direction are responsible for the better transport properties of electrons than holes. In addition, the dimensionality reduction in the crystal structure enhances the phonon scattering and decreases the phonon group…

The band gap is an important parameter that determines light-harvesting capability of perovskite materials. It governs the performance of various optoelectronic devices such as solar cells, light-emitting diodes, and photodetectors. For perovskites of a formula ABX₃ having a non-zero band gap, we study nonlinear mappings between the band gap and properties of constituent elements (e.g., electronegativities, electron affinities, etc) using alternating conditional expectations (ACE)—a machine learning technique suitable for small data sets. We also compare ACE with other machine learning methods: decision trees, kernel ridge regression, extremely randomized trees, AdaBoost, and gradient boosting. The best performance is achieved by kernel ridge regression and extremely randomized trees. However, ACE has an advantage that it presents its results in a graphic form, helping in interpretation. The models are trained with the data obtained from density functional theory calculations. Different statistical approaches for feature selection are applied and compared: Pearson correlation,…

Bifunctionality is a key feature of many industrial catalysts, supported metal clusters and particles in particular, and the development of such catalysts for the CO₂ reduction reaction (CO₂RR) to hydrocarbons and alcohols is gaining traction in light of recent advancements in the field. Carbon-supported Cu nanoparticles are suitable candidates for integration in the state-of-the-art reaction interfaces, and here, we propose, synthesize, and evaluate a bifunctional Ni–N-doped-C-supported Cu electrocatalyst, in which the support possesses active sites for selective CO₂ conversion to CO and Cu nanoparticles catalyze either the direct CO₂ or CO reduction to hydrocarbons. In this work, we introduce the scientific rationale behind the concept, its applicability, and the challenges with regard to the catalyst. From the practical aspect, the deposition of Cu nanoparticles onto carbon black and Ni–N–C supports via an ammonia-driven deposition precipitation method is reported and explored in more detail using X-ray diffraction, thermogravimetric analysis, and hydrogen temperature-programmed…

Fabrication of white light-emitting nanophosphors with high luminous efficacy is an urgent need for the next-generation lighting industry and display systems. While rare-earth ions have been frequently utilized as dopants to fabricate semiconducting and dielectric nanophosphors, the limited abundance of rare-earth elements on our planet demands a search for suitable alternatives. Here, we report the fabrication of ZnS nanoparticles co-doped with Co²⁺ and Mn²⁺ transition metal ions which manifest intense near-white light emission under ultraviolet excitation. While the nanophosphors could be fabricated through a simple low-temperature two-step chemical process, both the color and intensity of their emission can be tuned just by varying the molar concentration of the two dopant ions. The variation of the emission color and its intensity in the nanophosphors due to the dopant ion concentration has been explained considering the interband energy transfer from Mn²⁺ ions to Co²⁺ ions and creation of deep level defect states in the host nanocrystals. The synthesis process utilized in the…

TiO₂ nanoarray (TNA) is usually used to improve the energy storage performance of the polymer composite; however, owing to the paradox between polarization and breakdown strength, the discharged energy density of TNA-based composite is always restricted. In this study, a novel bilayer composite with excellent energy storage performance has been designed and fabricated by combining aligned TNA and random TiO₂ nanowires (TO NWs) with poly(vinylidene fluoride) (PVDF) matrix. Interestingly, a superior discharged energy density of 16.13 J/cm³ was obtained in the (5 vol % TO NWs/TNA)–PVDF composite, which is 2.0 times higher than that of pure PVDF matrix (8.23 J/cm³) due to the simultaneously improved polarization and breakdown strength. Additionally, the corresponding energy efficiency remains high (77.37%) owing to the nonferroelectric characteristics of the TO fillers and the suppressed leakage current density. Considering the excellent and sharply incremental discharged energy density and superior energy efficiency of the (5 vol % TO NWs/TNA)–PVDF composite, this demonstrated work…

Two-dimensional transition-metal oxides have been widely explored as catalysts in high-capacity nonaqueous lithium–oxygen batteries due to their excellent electrochemical performance in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), but little attention has been paid to non-transition-metal oxides. Here, we employ density functional methods based on the Perdew–Burke–Ernzerhof (PBE) functional with dispersion correction and the Heyd–Scuseria–Ernzerhof hybrid functional (HSE06) to investigate the mechanisms of the nucleation and decomposition processes of Li₄O₂(s), i.e., discharge and charge processes on single-layer Tl₂O (SL-Tl₂O) in lithium–oxygen batteries. HSE06 with the spin–orbital coupling effect is adopted to calculate the band gap of SL-Tl₂O. It is demonstrated that the spin–orbital coupling effect is significant in predictions of not only electronic but also thermodynamic properties for heavy-element compounds such as Tl₂O. The formation of LiO₂(s) is initiated by the adsorption of oxygen molecules instead of lithium atoms on the surface. The…

B-site doping of organic–inorganic perovskites is an effective way to improve its optoelectronic properties; however, it is rarely reported for perovskite single crystals. Here, we report the B-site doping of MAPbBr₃ single crystals with erbium (Er) via a simple antisolvent vapor-assisted crystallization method. The Er-doped MAPbBr₃ single crystal exhibits significantly enhanced photoluminescence (PL) and photoconductivity compared with the undoped sample. Low-temperature PL spectroscopy reveals that Er-doping creates a shallow acceptor level inside the band gap of MAPbBr₃, which contributes to significantly enhanced PL emission because of bound excitons. Furthermore, Er-doping also effectively lowers the deep trap density and improves the conductivity and mobility of the single crystal. Consequently, the Er-doped MAPbBr₃ single crystal photodetector shows responsivity and external quantum efficiency approximately 5 times higher than those of the undoped device. The effective improvement of optoelectronic properties of the MAPbBr₃ single crystal by Er-doping may benefit a wide range…