could be quenched by Ni2þ due tothestrongcoordinationinteraction
between thepyrocatecholstructureofQDs–DAandNi2þ. Inthepresenceof L-histidine, Ni2þ preferredto
bind with L-histidine duetohighaffinity ofNi2þ to L-histidine andthephotoluminescenceintensityof
QDs–DAwasrecovered.Therecovered