Silica nanoparticles have been studied extensively in biomedical field due to their high biocompatibility,controllable morphology and so on.They can be used both as the drug carrier and imaging vehicle.Here,an aminated ultra-small silica nanoparticle based system is developed with various functionalities.Multiple molecules including fluorophore,folic acid,and antibody are coupled to this system to achieve specific applications such as bacterial/cell labelling and recognition.