Creative Diagnostics provides CdSe/ZnS core-shell semiconductor quantum dots with emission range from 500 nm to 650 nm. Our CdSe/ZnS quantum dots are gradient alloyed semiconductor materials with size dependent optical/electronic properties, high fluorescence efficiency, low toxicity and easy cell absorb. Through surface passivation of high bandgap ZnS shell, low luminescence efficiency caused by defects and surface-trap states can be significantly minimized. Our CdSe/ZnS quantum dots can be used in highly sensitive cellular imaging, drug delivery and light emitting devices.