Summary of Hg²⁺ detection on paper-based analytical devices.

Method	Measurement	Linearity (μg mL−1)	LOD (μg mL−1)	Conditions	Lifetime	Sample	Ref.
AgNPls	Colorimetric, Photoshop	5–75	0.12	Added CuSO4, boiling	—	Drinking and tap water	52
Pyridylazo indicators	Colorimetric, Photoshop	—	10	pH 6.5	Over 2 months	Sewage water	53
SPR of ssDNA modified AuNPs	Colorimetric, ImageJ	0–0.02	0.01	pH 9	Added NaCl (protected aggregation)	Pond and river water	54
Curcumin nanoparticles	Colorimetric, Photoshop	0.01–0.4	0.003 (addition 50 times)	pH 7, phosphate buffer	Over 6 months in solution	Tap and waste water	55
AgNPs, double layer	Colorimetric, ImageJ	0.05–7	1	—	—	Drinking and tap water	56
PtNPs and TMB	Colorimetric, electrical readout system	0.005–0.1	0.002	—	Over 6 months in solution	Pond and tap water	57
Dithizone in NaOH	Distance-based	1–30	0.93	pH 9, added masking agent	Over 7 days	Whitening, cream	32
Silicon nanocrystals and carbon dots	Ratiometric fluorescent (semi-quantitative)	0–0.02 (repeated 20 times reagent)	0.002	—	—	Tap and lake water	58
AgNPs	Colorimetric, smartphone application	0–0.004	0.002	—	—	River water	59
Nitrogen doped carbon dots (EDTA)	Fluorescence quenching, ImageJ	0.02–10	0.02	pH 4–9	Added NaCl for stability	Tap water in solution (not apply in paper device)	48
Nitrogen-doped carbon dots (ethylenediamine)	Fluorescence quenching, distance-based	0.005–1	0.005	No effect (pH 3–11)	Over 5 months on paper	Drinking, pond and tap water	Our work