Intrinsic Photoluminescence from Gels Containing Amine or Amide Chemical Groups

Gels obtained through the sol–gel procedure by mixing an alkoxide with a carboxylic acid emit intense intrinsic photoluminescence when the alkoxide contains an amine or amide group. However, also simple polyether chains with two end amino groups but no alkoxysilane groups gel by interaction with carboxylic acids and also emit photoluminescence. Luminescence emission in these gels could be justified by a model similar to the emission of Green Fluorescent Protein. According to this model, amide groups, abundant in these gels, go through multiple reactions with other amide or amino groups so that they could yield conjugated species that are capable to emit photoluminescence. This model could open the possibility to synthesize a great variety of photoluminescent species based on amine-carboxylate interactions.