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The band gap energy of the calcined fibers increases significantly with addition of Mg ( 2 + ) along with an increase in the ultraviolet ( UV ) photoluminescence emission of the fibers .
 Chemical: Mg ( 2 + )
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: Mg ( 2 + )