ERBB2 and breast cancer: The 9-nm nanocrystals are selected as a model probe for diagnosis of cancer and functionalized with a shell made of a conjugated ligand for Herceptin, a cancer-specific antibody, which binds to the receptor tyrosine-protein kinase erbB-2 protein HER2/neu receptor characteristic of cells in breast cancers (as demonstrated by binding to the breast cancer cell line SK-BR-3 ) which is known to over-express the HER2/neu marker.