Amides 2 Aminopropyltriethoxysilane 2 Ammonium compounds 2 Aqueous media 2 Bromine compounds 2 Cetyltrimethylammonium bromide 2 Crosslinker 2 Cu(II) sensor Europium 2 Europium(III) 2 Gels 2 Glass slides 2 Glass transition 2 Hybrid materials 2 In-situ 2 Iron compounds 2 Luminescence 2 Luminescence quenching 2 Metal ions 2 Organic precursor 2 Ppb levels 2 Quenching 2 Sensor device 2 Sensors 2 Silicon compounds 2 Sol-gel 2 Sol-gel process 2 Sol-gel technique 2 Sol-gels 2 Sols 2