12500
While conducting toxicity tests with nano titanium dioxide , the authors found that test suspensions were being contaminated with aluminum and titanium from tip erosion during direct sonication .
 Chemical: titanium dioxide; Chemical: aluminum; Chemical: titanium
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: titanium dioxide; Chemical: aluminum; Chemical: titanium