By using the positive charged polystyrene (PS) microsphere as template, mono-disperse amino-(-NH(2)) functionalized hollow silica microspheres (HSMS-NH(2)) with similar to 1310 nm in diameter and uniform shells were successfully prepared with a modified sol-gel process. The amino functionalized silica were coated on the PS microspheres via ammonia catalysis, co-hydrolysis and condensation of TEOS and APTES, and then the PS templates were selectively dissolved in THF solution to form the functional hollow microspheres. The controllable thickness (35-85 nm) and amino density (2.46 x 10(-5)-6.18 x 10(-5) mol/g) of the shells could be facilely tuned by changing the amount of TEOS and APTES. In vitro ultrasound images of as-prepared HSMS-NH(2) with different concentrations in the physiological saline solution were further investigated. The obvious signal enhancement indicates that as-prepared HSMS-NH(2) has a great potential application for ultrasound imaging. (C) 2011 Elsevier Inc. All rights reserved.