Among them, Na 3 V 2 (PO 4 ) 3 (NVP) has been identified so far as the most interesting one as it possesses satisfactory energy density and high power for extended cycle life. Its crystal structure can be described as a 3D framework of VO 6 octahedra and PO 4 tetrahedra connected to each other by common corners forming so-called "lantern units" along the c direction of the commonly used hexagonal cell. Sodium cations were described as randomly disordered over two sodium sites (Na(1), 6b and Na(2), 18e) [18] until Chotard et al. discovered that below 280 K, the so called α-NVP form crystallized in a monoclinic superstructure due to a fully ordered distribution of Na +[19] similar to the ordering previously reported in α-Na 3 Ti 2 (PO 4 ) 3 . [51] The synthesis of Na 3 V 2 (PO 4 ) 3 was first reported by Delmas. [20] Gopalakrishnan [21] later on reported on the possible extraction of three Na + toward the novel sodium-free V IV V V (PO 4 ) 3 composition. Afterward, the electrochemical extraction of Na + from Na 3 V 2 (PO 4 ) 3 to NaV 2 (PO 4 ) 3 (with a theoretical capacity of 117.6 mAh g −1 at 3.4 V vs Na/Na) was extensively investigated. [22][23][24][25][26] A large number of special treatments (e.g., carbon coating, particle shape controlling) was also proposed to improve battery performances. [27][28][29][30][31] It is important to note that only 2Na formula unit −1 have been completely removed from the structure during charging up to now. A possible activation of the V 4+/5+ redox couple at higher voltages may also contribute to the increasing of the energy density of NVP-based materials, as demonstrated in a series of works by using a metal substitution of a part of V 3+ in the structure of NVP. In recent years, several elements have been chosen for the partial substitution of V into the crystal structure of this promising material (such as Ni, [32][33][34] Al, [35,36] Fe 3+ , [34,37] Zr 4+ , [38] Mn 3+ , [39] Mn 2+ , [34,40] Cr 3+ , [41][42][43] Ti 4+ , [44][45][46] Mo 6+ , [47] and Mg 2+[48] ).In this work, Mn 2+ was used as a substituting ion to enhance the capacity of the Na 3 V 2 (PO 4 ) 3 cathode material. Inspired by the recent work of Zhou et al., [34] nearly single-phase Na 4 MnV(PO 4 ) 3 (98.5 wt%) powders were synthesized and studied structurally and electrochemically in details. In operando X-ray diffraction (XRD) studies during electrochemical operation show for the first time that Na 4 MnV(PO 4 ) 3 can deliver 156 mAh g −1 toward the new composition NaMnV(PO 4 ) 3 . Results and DiscussionThe crystal structure of Na 4 MnV(PO 4 ) 3 has been fully determined using high-resolution synchrotron powder XRD (SXRD) dataThe mixed Mn 2+ /V 3+ Na-super-ionic-conductor (NASICON) cathode material Na 4 MnV(PO 4 ) 3 is prepared by solid-state reaction at 800 °C under argon. When used as a positive electrode in Na batteries, this material can exchange three electrons for two transition metals, that is, yielding a high gravimetric capacity of 156 mAh g −1 on charge when the upper cutoff voltage is set to 4.3 V...

Nanotechnology-based pesticide formulations can improve the utilization rate of pesticides and reduce their negative effects on the environment. In this work, prochloraz was encapsulated within the pores of mesoporous silica nanoparticles (MSNs) attached covalently chitosan on the surface as gatekeepers via a silane coupling agent to prepare MSNs-chitosan@prochloraz nanoparticles. The results demonstrated that the obtained nanoparticles had a relatively high loading efficiency of prochloraz (25.4% w/w) and enhanced the light stability of prochloraz effectively. The nanoparticles showed excellent esterase and pH dual-responsive properties with controlled release behavior. The biological activity survey confirmed that the acid and enzyme produced by infected fruit can easily open the "gate" guarded by chitosan to achieve esterase and pH triggered on-demand pesticide release. Compared with prochloraz emulsifiable concentrate, preharvest application of MSNs-chitosan@prochloraz nanoparticles possessed a longer duration and a better antifungal activity against citrus diseases. The toxicity of the nanoparticles to zebrafish was reduced more than 6-fold compared with that of prochloraz technical. These results demonstrated that the MSNschitosan@prochloraz nanoparticles had potential as an environmentally friendly preharvest treatment agent in agricultural application.