15621
The photocatalytic properties of this film were evaluated by voltammetric , UV - Vis spectrophotometric and gas chromatographic measurements following the decomposition rate of suitably selected molecular probes , such as 4 - hydroxybenzoic acid and methylene blue .
 Chemical: 4 - hydroxybenzoic acid; Chemical: methylene blue
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: 4 - hydroxybenzoic acid; Chemical: methylene blue