Table 2.

The biopolymers and conducting polymers based on surface plasmon resonance for metal ion detection.

Metal Ion	Type of Polymers	Linear Range	Limit of Detection	References
Fe3+	Chitosan thin film	4.477 µM–1.79 nM	4.477 µM	[58]
Cr6+	Gold nanoparticles/chitosan composite	192.322 µM–4.808 nM	192.322 µM	[71]
Hg2+	Chitosan cross-linked glutaraldehyde solution	Hg2+: 2.493–498.529 µM	Hg2+: 2.493 µM	[72]
Cu2+		Cu2+: 7.868 µM–1.573 nM	Cu2+: 7.868 µM
Cu2+	Chitosan cross-linked glutaraldehyde solution	Cu2+: 7.868 µM–1.573 mM	Cu2+: 7.868 µM	[73]
Zn2+		Zn2+: 7.648 µM–1.529 mM	Zn2+: 7.648 µM
Mn2+		Mn2+: 9.101 µM–1.820 mM	Mn2+: 9.101 µM
Pb2+	Immobilized p-tert-butylcalix[4]arene-tetrakis in chitosan thin film	0.144–24.131 µM	0.144 µM	[74]
Pb2+	Crosslinked chitosan	2.413–482.625 µM	2.413 µM	[75]
Pb2+	Gold–chitosan–graphene oxide nanostructured thin films	0.145–24.131 µM	0.145 µM	[76]
Zn2+	Chitosan–tetrabutyl thiuram disulfide	0.153–76.476 µM	0.153 µM	[77]
Pb2+	Chitosan–graphene oxide	0.483–24.131 µM	0.483 µM	[78]
Pb2+	Gold/silver/gold/chitosan–graphene oxide	Pb2+: 0.483–24.131 µM	Pb2+: 0.483 µM	[79]
Hg2+		Hg2+: 0.499–24.926 µM	Hg2+: 0.499 µM
K+	Valinomycin doped chitosan–graphene oxide thin film	0.0256 µM–2.557 mM	0.0256 µM	[80]
Co2+	Immobilized 4-(2-pyridylazo) resorcinol in chitosan–graphene oxide composite thin film	0.169 µM–1.696 mM	0.169 µM	[80]
Co2+	Cadmium sulfide quantum dots–graphene oxide–chitosan nanocomposite thin film	0.169–169.684 µM	0.169 µM	[82]
Pb2+	Chitosan–glutathione coated sensor probe	4.826–33.784 µM	6.274 µM	[83]
Pb2+	Gold nanoparticle kappa-carrageenan and chitosan	0.048–24.131 µM	0.048 µM	[84]
Fe2+	Chitosan/hydroxyl-functionalized graphene quantum dots thin film	8.953 µM–1.79 mM	8.953 µM	[85]
Hg2+	Chitosan/carboxyl-functionalized graphene quantum dots thin film	2.493–498.529 µM	2.493 µM	[86]
Pb2+	Chitosan–poly(amidoamine) dendrimer composite thin film	0.483–2.413 µM	0.483 µM	[87]
Cu2+	Chitosan/poly(acrylic acid) bilayers	3.147 µM–7.868 mM	0.1054 µM	[88]
Cu2+	Silver/gold composite film modified by modified-chitosan (MCS) thin film	15.737–78.683 µM	0.283 µM	[89]
Co2+	Chitosan–graphene oxide/cadmium sulphide quantum dots active layer	0.169 µM–1.696 mM	0.169 µM	[90]
Co2+	Chitosan–graphene oxide–cadmium sulfide quantum dots composite thin film	1.697 µM–1.696 mM	1.697 µM	[91]
Cu2+	Nanocrystalline cellulose modified by hexadecyltrimethylammonium bromide and graphene oxide composite thin film	157.366–944.198 µM	157.366 µM	[92]
Ni2+	Nanocrystalline cellulose–graphene oxide-based nanocomposite	0.170–170.378 µM	0.170 µM	[93]
Zn2+	Modified-nanocrystalline cellulose/graphene oxide	0.153–152.952 µM	0.153 µM	[94]
Hg2+	Polypyrrole and 2-mercaptobenzothiazole	0.498–49.853 µM	0.0498 µM	[95]
Cu2+	Polypyrrole thin film	Cu2+: 1.574–314.733 µM	Cu2+: 1.574 µM	[96]
Fe3+		Fe3+: 1.791–358.134 µM	Fe3+: 1.791 µM
Hg2+	Polypyrrole multi-walled carbon nanotube composite layer	Hg2+: 0.498–498.529 µM	Hg2+: 0.498 µM	[97]
Pb2+		Pb2+: 0.483–482.625 µM	Pb2+: 0.483 µM
Fe2+		Fe2+: 1.791 µM–1.79 mM	Fe2+: 1.791 µM
Pb2+	Gold nanoparticles/graphene oxide/polyaniline nanocomposites film	0.145–14.479 µM	0.145 µM	[98]
Al3+	Polypyrrole multiwalled carbon nanotube composite layer	3.706 µM–3.706 mM	3.706 µM	[99]
Mn2+	Nanocomposite of polypyrrole and zinc oxide over silver	0–0.2 M	0.673 µM	[100]
Cu2+	Polypyrrole–chitosan layer	1.574 µM–1.573 mM	1.574 µM	[101]
Hg2+	Polypyrrole–chitosan conducting polymer composite	2.493 µM–59.824 µM	2.493 µM	[102]
Pb2+
Fe3+	Polypyrrole–chitosan layer	1.791 µM–1.343 mM	1.791 µM	[103]
Zn2+	Polypyrrole–chitosan	Zn2+: 0.153–59.824 µM	Zn2+: 0.153 µM	[104]
Ni2+		Ni2+: 0.170 µM–1.277 mM	Ni2+: 0.170 µM
Cd2+	Polypyrrole and chitosan/ITO/silver	-	Cd2+: 1.29 nM	[105]
Pb2+			Pb2+: 1.58 nM
Hg2+			Hg2+: 2.93 nM
Ni2+ Fe2+ Co2+ Al2+ Mg2+ Hg2+ Pb2+	Polypyrrole–chitosan/nickel–ferrite nanoparticle composite layer	-	Ni2+, Fe2+, Co2+: 17.3 nM Al2+, Mg2+: 37.1 nM Hg2+, Pb2+: 4.82 nM	[106]
V	Polypyrrole–chitosan–cobalt ferrite nanoparticles composite layer	0.0133–1334.721 µM	13.3 nM	[107]