▁main ▁properties , ▁a ▁very ▁high ▁surface ▁to ▁volume ▁ratio , ▁and ▁a ▁relatively ▁defect ▁free ▁structure ▁at ▁the ▁mole cular ▁level . ▁This ▁first ▁property ▁makes ▁electro sp un ▁material ▁suitable ▁for ▁activities ▁requiring ▁a ▁high ▁degree ▁of ▁physical ▁contact , ▁such ▁as ▁providing ▁sites ▁for ▁chemical ▁re actions , ▁or ▁the ▁capture ▁of ▁small ▁s ized ▁partic ulate ▁material ▁by ▁physical ▁ent ang lement ▁– ▁fil tr ation . ▁The ▁second ▁property ▁should ▁allow ▁electro sp un ▁fib ers ▁to ▁approach ▁the ▁theoretical ▁maximum ▁strength ▁of ▁the ▁sp un ▁material , ▁opening ▁up ▁the ▁possibility ▁of ▁making ▁high ▁mechanical ▁performance ▁composite ▁materials . ▁ ▁Fil tr ation ▁ ▁The ▁use ▁of ▁nan of iber ▁web s ▁as ▁a ▁filtering ▁medium ▁is ▁well ▁established . ▁Due ▁to ▁the ▁small ▁size ▁of ▁the ▁fib ers ▁London - V an ▁Der ▁Wa als ▁forces ▁are ▁an ▁important ▁method ▁of ▁ad hes ion ▁between ▁the ▁fib ers ▁and ▁the ▁captured ▁materials . ▁Pol ym er ic ▁nan of ib ers ▁have ▁been ▁used ▁in ▁air ▁fil tr ation ▁applications ▁for ▁more ▁than ▁seven ▁dec ades . ▁Because ▁of ▁poor ▁bulk ▁mechanical ▁properties ▁of ▁thin ▁nan ow eb s , ▁they ▁are ▁laid ▁over ▁a ▁fil tr ation ▁medium ▁substr ate . ▁The ▁small ▁fi ber ▁diam eters ▁cause ▁s lip ▁flows ▁at ▁fi ber ▁surfaces , ▁causing ▁an ▁increase ▁in ▁the ▁inter ception ▁and ▁in ert ial ▁imp action ▁effic ien cies ▁of ▁these ▁composite ▁filter ▁media . ▁The ▁en hanced ▁fil tr ation ▁efficiency