A Facile Synthesis of Silver-Coated Composite Particles by Swelling Surface Method

We report a facile and rapid method for fabrication of composite particles consisting of a polystyrene (PS) core and a uniform silver shell. The process involves the PS colloid surface swelling, the anchoring of silver ions and nanoparticles onto the surfaces, and the subsequent growth of metal seeds in a short period. The present approach has the advantages of simplicity and high efficiency. The TEM images show the morphology of the obtained PS core-silver shell particles, and their chemical composition and crystallinity are analysed by x-ray diffraction. To our knowledge, this is the first study based on swelling PS surface for synthesis of silver-coated PS particles and may be implemented for preparing other metal-coated PS particles.     

COVID-19空气传播的动力学研究

基于病毒在空气中主要的存在形式是依附于人体正常呼吸或者咳嗽、打喷嚏所形成的微小液滴.本文主要考虑了半径在0.05～100μm范围内的液滴在平静空气中的动力学行为,发现当液滴的半径接近100μm时,在平静空气中的停留时间小于2 s,咳嗽和打喷嚏时喷出的液滴可以将病毒最远携带至0.61 m处;而当液滴半径范围在1～10μm时,悬浮的液滴会携带病毒在空气中存在长达3.7 h;而当液滴半径接近病毒线度时,病毒会在平静的空气中存在25天,同时也会在空气中发生相对明显的扩散.