Resin	Ni(II) ion precursor	Ni(II) content		N/Ni	Complex color	DR UV-Vis-NIR λ_max, nm
Resin	Ni(II) ion precursor	wt.%	mmol/g	N/Ni	Complex color	DR UV-Vis-NIR λ_max, nm
	NiCl₂∙6H₂O				bright green	1264, 766, 414
	Ni(AcO)₂∙4H₂O				yellow	1120, 674, 392
2.1	NiCl₂∙6H₂O	4.65	0.79	2.95	green	988, 610
2.2	NiCl₂∙6H₂O	4.79	0.82	3.98	blue	1008, 615, 383
2.3	NiCl₂∙6H₂O	4.72	0.80	4.95	sapphire	1005, 583, 307
2.1	Ni(AcO)₂∙4H₂O	4.88	0.83	3.10	green	1019, 615, 370
2.2	Ni(AcO)₂∙4H₂O	4.65	0.79	4.13	blue	966, 598, 366
2.3	Ni(AcO)₂∙4H₂O	4.80	0.82	4.83	violet	980, 568, 358