Treated metal oxide particles and toner compositions

A toner composition comprising toner particles and metal oxide particles treated with at least a charge modifying agent, wherein the charge modifying agent is represented by the following formula:

• An-Zc—Yb—Ar(EW)a
• wherein Ar represents an aromatic group, EW represents an electron withdrawing group, Y represents a spacer group, Z represents an alkylene group, An represents an anchor group, a is an integer from 1 to 5, b is 0 or 1, and c is 0 or 1,
• wherein Y is —N(R)—, —N(R)C(O)—, —C(O)N(R)—, —OC(O)—, —C(O)O—, —O—, —S—, —CH═N—, —N═CH—, —N═N—, or —S(O)2—, wherein R represents hydrogen or a substituted or unsubstituted aryl or alkyl group,
• An is represented by XdSiR′(3-d), wherein X represents equal or different hydroloyzable groups or a siloxane group, R′ represents hydrogen or a substituted or unsubstituted aryl or alkyl group, and d is an integer from 1 to 3, and
• the metal oxide particles are silica, alumina, ceria, titania, or a mixture thereof.