Commercially　available　fumed　silica　(F-SiO2)　was　hydrophobised　in　situ　via　the　interaction　with　a　cationic　gemini　surfactant,　ethanediyl-α,ω-bis(tetradecyldimethyl-ammonium　bromide)　(14-2-14),　in　aqueous　solution.　The　effect　of　this　surfactant　modification　was　far　higher　that　carried　out　by　its　corresponding　monomer,　tetradecyltrimethylammonium　bromide　(C14TABr).　The　mechanism　of　modification　was　assumed　according　to　zeta　potential　measurements　and　observations　of　physical　appearance.　These　particles　were　used　to　generate　and　stabilize　aqueous　foams.　Both　the　foaming　efficiency　and　the　stabilising　ability　of　F-SiO2/14-2-14　all　exceeded　that　of　F-SiO2/C14TAB.　In　the　gemini　case,　the　synergism　and　competition　between　the　particles　and　the　free　surfactant　molecules　for　their　adsorption　at　the　foam　film　were　found,　which　resulted　in　two　peaks　in　the　foam　stability　curve.　Dilational　rheology　of　the　films　was　measured　using　an　oscillating　drop　technique.　There　were　also　two　maxima　in　the　dilational　elasticity　for　the　F-SiO2/14-2-14　system,　respectively　corresponding　to　each　maximum　in　foam　stability.　©　The　Royal　Society　of　Chemistry　2016.