Table 1.

Summary of representative reports of fluorescent nanoprobes for metal ions sensing.

Type of nanomaterialsa		Analytes	Detection mechanisma	Detection limit	Reference
Noble metal nanomaterials	Metal NPs	Pb2+	fluorescence quenching	0.51 nM	76
			fluorescence enhancement	1.5 nM	83
		Hg2+	fluorescence enhancement	0.32 μM	80
				30 nM	88
			NSET	2 nM	92
		Zn2+	fluorescence enhancement	0.76 μM	81
		Cu2+	FRET	0.3 nM	82
				9.83 pM	87
		K+	FRET	100 μM	90
		Tb3+	FRET	N. A.	93
	Metal NCs	Hg2+	fluorescence quenching	0.5 nM	114
		Cu2+	fluorescence quenching	5 nM	110
		Pb2+	fluorescence quenching	2 nM	126
		Fe3+	AIFQ	3.5 μM	132
Upconversion nanoparticles		Hg2+	LRET	0.06 nM	156
				41 nM	158
		Pb2+	FRET	80 nM	161
			fluorescence enhancement	20 nM	162
		Cu2+	FRET	1 μM	166
Semiconductor nanoparticles	Undoped QDs	Cu2+	fluorescence quenching	7.1 nM	195
			fluorescence enhancement	2.75 nM	220
		Pb2+	fluorescence enhancement	0.2 nM	216
		Ca2+	FRET	2 μM	219
	Doped QDs	Hg2+	fluorescence enhancement	0.18 nM	232
		Ag+	NSET	7.9 nM	233
		Fe2+	fluorescence quenching	3 nM	234
Carbon Materials	CDs	Hg2+	fluorescence enhancement	20 nM	246
			fluorescence quenching	0.1 μM	247
	GQDs	Cu2+	fluorescence quenching	282.9 nM	255
		Cr6+	fluorescence quenching	40 nM	257
	CNTs	Ag+	fluorescence enhancement	1 nM	268
		Hg2+	FRET	15 nM	264
		Ag+		18 nM
		Pb2+		20 nM
	Graphene	Hg2+	fluorescence enhancement	0.92 nM	261
		Ag+	FRET	20 nM	279
		Hg2+		5.7 nM

^aNPs: nanoparticles; NCs: nanoclusters; CDs: carbon dots; GQDs: graphene quantum dots; CNTs: carbon nanotubes; NSET: nanometal surface energy transfer; FRET: fluorescence resonance energy transfer; N. A.: Not available; AIFQ: aggregation-induced fluorescence quenching; LRET: luminescence resonance energy transfer