Table 1.

Some examples of sensors for Cu²⁺ ion selectivity.

Materials	Cu2+ Selectivity	Detection Limit	Proposed Mechanism	Ref.
Helicene dye bearing hydrazine	good	2.6 ppb	photoinduced electron transfer	[53]
2,3-diaminophenazine, 1,2-diamino-anthraquinone, 2,4-dinitrophenylhydrazine	good	0.15 × 10−9 M/L	paramagnetic effect	[54]
Coumarin-based fluorogenic probe bearing the 2-picolyl unit	good	0.5 µM	quenching mechanism	[55]
Zinc-doped AgInS2 quantum dots	good	27.3 nM	electron transfer	[52]
Poly (methacrylic acid) (PMAA)-templated AgNCs	good	8 nM	quenching mechanism	[47]
DNA–AgNCs	/	1.4 mM	marvelous fluorescent enhancement in the presence of histidine	[57]
DNA-Cu/AgNCs	good	2.7 nM	static quenching mechanism	[58]
8PEG-AgNCs	good	50 nM	quenching mechanism	This work