Effect of in-situ application of ultrasonic waves during formation of silver nanoparticles embedded in phospholipid membrane

Effect of in-situ application of ultrasonic waves (up to 1MHz) on the Ag nanoparticles spontaneously produced inside the 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) membrane by thermal evaporation of Ag was studied by placing the membrane on a ultrasonic transducer during the metal deposition. Application of the ultrasonic vibration promoted spatial ordering of the deposited nanoparticles due to the induced phase transition from L-alpha to H-II for DOPE. Arising from the agitation effect, particle size refinement, which depended on the amplitude of the ultrasonic vibration, was observed. It was also shown that a stiff gel state 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) membrane can be made locally permeable to incident Ag atoms by introducing DOPE molecules into the DPPC membrane as the Ag nanoparticles preferentially nucleated in the DOPE-rich region. Application of ultrasonic vibration with increasingly higher amplitude or frequency made the Ag nanoparticles uniformly distributed in the DPPC, suggesting that the permeability of the DPPC membrane can be temporarily increased without permanently damaging the membrane by addition of liquid crystalline lipids and subsequent application of ultrasonic waves. (C) 2013 AIP Publishing LLC.This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MEST) (No. 2012000815)