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a b s t r a c tThe different mechanisms of CO 2 methanation on Ni(111) surfaces have been investigated by density functional theory with and without the formation of CO as an intermediate. The most stable adsorption configurations of all reaction species (O, OH, CO, CH, CH 2 , CH 3 , CH 4 , HCOO, C(OH) 2 , CH 2 O, etc.) in three paths of CO 2 methanation adsorbed on the Ni(111) surface are described. The energy barriers and reaction energies for the overall processes involved in the various paths are presented. The rate-determining steps for the three mechanisms are HCOO→CO + OH for path 1, CO → C + O for path 2 and CO 2 + 2H → C(OH) 2 for path 3 with maximum energy barriers of 306.8 kJ/mol, 237.4 kJ/mol and 292.3 kJ/mol, respectively. Path 2 is therefore the optimum of the three mechanisms. The path starts with CO 2 dissociation into CO and O, CO decomposition into C and O species and C species hydrogenation to form CH 4 : CO 2 → CO + O → C + O + 4H → CH 2 + 2H → CH 3 + H → CH 4 .

Developing functional nanoagents for achieving the combination of microwave dynamic therapy (MDT) and microwave thermal therapy (MTT) is highly desirable due to the advantages of improving the therapeutic effect on tumors and minimizing the side effects. Metal-organic frameworks (MOFs), as emerging porous materials, exhibit many intriguing properties for application in biomedicine. Herein, new-style flexible Mn-doped zirconium metal-organic framework (Mn-ZrMOF) nanocubes (NCs) with the average size of about 60 nm were prepared easily by a one-pot hydrothermal method. Due to the strong inelastic collision of ions confined in a large number of micropores, the Mn-ZrMOF NCs were demonstrated to be an effective microwave-sensitive agent with a high thermal conversion efficiency up to 28.7%, which is the highest one of the recently reported microwave-sensitive agents. This is the first report of determining the microwave thermal conversion efficiency, which can be used to evaluate, compare, and predict the microwave sensitivity of different microwave-sensitive agents. More importantly, such Mn-ZrMOF NCs generate abundant reactive oxygen species (ROS) of hydroxyl radicals under microwave irradiation. As such, the Mn-ZrMOF NCs efficiently suppress the tumor cell growth in vivo and in vitro under mild microwave irradiation for the synergic effect of MTT and MDT. This work paves the way for developing nanoagents that are responsive to microwave irradiation, producing ROS and improving thermal effects to realize the noninvasive MTT and MDT treatment in clinics.

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The cytotoxic reactive oxygen species (ROS) generated by photoactivated sensitizers have been well explored in tumor therapy for nearly half a century, which is known as photodynamic therapy (PDT). The poor light penetration depth severely hinders PDT as a primary or adjuvant therapy for clinical indication. Whereas microwaves (MWs) are advantageous for deep penetration depth, the MW energy is considerably lower than that required for the activation of any species to induce ROS generation. Herein we find that liquid metal (LM) supernanoparticles activated by MW irradiation can generate ROS, such as •OH and •O 2 . On this basis, we design dual-functional supernanoparticles by loading LMs and an MW heating sensitizer ionic liquid (IL) into mesoporous ZrO 2 nanoparticles, which can be activated by MW as the sole energy source for dynamic and thermal therapy concomitantly. The microwave sensitizer opens the door to an entirely novel dynamic treatment for tumors.

The present study describes the synthesis of monodispersed PbSe and PbS nanocrystals by a facile, less hazardous and inexpensive approach. In this study, Se and S powder are used as chalcogenide precursors instead of trioctylphosphine-selenium (TOPSe) and hexamethyldisilthiane (TMS), which are toxic and expensive. The chalcogenide precursors used in this method are inexpensive and air-stable, which not only reduces the cost of the experiment, but also simplifies the synthesis process. Monodispersed PbSe and PbS nanocrystals with spherical, cubic and cuboctahedral shapes were obtained, and the size of the nanocrystals can be tuned in a wide range (6-25 nm for PbSe and 10-80 nm for PbS) via tuning the concentration of oleic acid (OA) and oleyamine (OAm). The mechanism of the size control and shape evolution is discussed. The concentration of OA and OAm is found to play an important role in deciding the size and shape of the nanocrystals in the nucleation and growth process.

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