I am new to the site, A couple of points of reference for your review . QD'S can be charged both negatively or positively. Thanks for the invite Chessmite http://koppensgroup.icfo.es/2012konstantatoshybrid.pdf http://adsabs.harvard.edu/abs/2009PCCP...11.5962E http://www.narcis.nl/research/RecordID/OND1335152/Language/en Regards SUNYN75