As shown in Fig. 6C, there was no photoacoustic signal from the normal sites of mice and the tumor site of the mice pre-treated with the CBS inhibitor aminooxyacetic acid (AOAA, 100 nmol) after injection of Si@BODPA, while a photoacoustic signal was observed in the tumors of the mice without and with pretreatment with a CBS activator (S-adenosyl-l-methionine), indicating that Si@BODPA can be used for detection of H2S in vivo. Here, CBS is linked to neoplasm.