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Soil biofumigation with brassica plant residues has been shown to significantly suppress soilborne pathogen. However, little published data reported the impact of biofumigation on microbial community structure in pepper (Capsicum annuum L.) production systems under field conditions. Biofumigation with rapeseed (Brassica napus 'Dwarf Essex') meal and chemical fumigation with dazomet were tested to control the pepper disease caused by Phytophthora capsici. BF treatment showed the lowest disease incidence among these treatments. Effects on soil bacterial and fungal communities were assessed by denaturating gradient gel electrophoresis and the results showed that the biofumigation increased bacterial diversity and decreased fungal diversity. There was a negative correlation between soil bacterial diversity and disease incidence and a positive correlation between soil fungal diversity and disease incidence. Cloning of the microbial community showed that the microbial community structures were altered by biofumigation. Soil was also evaluated for their chemical properties. Biofumigation increased soil content of total N, NO3(-)-N, available P and available K. A significant correlation between soil microbial community structures and soil chemical properties was found. Overall, these results indicated that biofumigation reduced disease incidence of pepper through altering soil microbial community structures.

The interfacial interaction of the colloidal NPs in solution is closely related to the surface charge, which heavily influences the NP synthesis, colloidal stabilization and various applications. [2] In general, the inorganic core of colloidal NPs in solutions possess a net electric charge at the interface, which can attract dissolved heterogeneously-charged crystal-constituting ions and solvent molecules by electrostatic interaction, thus constructing the electrical double layer and rendering the NPs well-dispersed (Figure 1a). The presence of surface charge can also physically or chemically adsorb the dissolved molecules such as organic dyes at the NP interface, which restructures the energy dissipation pathways between the colloidal NPs and outside world. However, although much efforts had been devoted to understanding the interfacial interactions of NPs, comparable study taking into account the motion states of the particles is still rare. For example, the colloidal NPs could experience Brownian motion in stationary solution, flowing in fluid, as well as keeping static when being adhered on macroscopic objects, depending on the specific environments in applications such as biodetection, bioimaging, and printable electronics. [3] Albeit of its fundamental importance, the specific role of particle moving on the interfacial reactions of colloidal NPs is ambiguous up to now and as always been ignored for most cases.The sum frequency generation (SFG) vibrational spectroscopy, a second-order nonlinear optical technique, has been proved to be powerful for probing the interfacial molecules in view of its inherent interface selectivity and high sensitivity. [4] In this work, combined in situ spectroscopies based on SFG and photoluminescence (PL) characterization were adopted to reveal the unprecedented effect of particle moving to the interfacial adsorption of colloidal fluoride nanocrystals in great detail. Comparative results of the proof-of-concept experiments for the ligand-free NaYF 4 :Yb,Er upconverting (UC) nanocrystals reveal that the particle moving in aqueous solution reversibly alter the surface charge. More importantly, it is found that the motion state of the NPs determines molecular arrangement of Rhodamine B (RhB) at the particle interface, which significantly affect the energy transfer from the colloidal NPs to the adsorbed dyes.

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