A method for immobilizing amino-group containing molecules onto surfaces and devices having immobilized isocyanate-group containing molecules prepared by the method are disclosed. The method comprises reacting a surface (i.e., glass surface) having free hydroxyl groups with a silyl isocyanate derivatizing agent to provide immobilized reactive moieties, the agent having a formula: (R.sub.1O)(R.sub.2O)(R.sub.3O)Si--X--NCO wherein R.sub.1, R.sub.2 and R.sub.3 are independently represents C.sub.1-C.sub.6 alkyl, phenyl, or aryl substituted with one or more groups selected from the group consisting of C.sub.1-C.sub.6 alkyl and C.sub.1-C.sub.6 alkoxy; X represents linear or branched C.sub.1-C.sub.20 alkyl or aryl substituted with one or more groups selected from the group consisting of C.sub.1-C.sub.6 alkyl and C.sub.1-C.sub.6 alkoxy, optionally substituted with one or more heteroatoms comprising oxygen, nitrogen, and sulfur and reacting the immobilized reactive moieties with the amino group-containing molecule so as to immobilize said molecule on the surface. Devices having a surface with immobilized molecules such as nucleic acids or proteins are useful for detection of target analytes in a sample.