Near-infrared luminescence lanthanide complexes

which are found potential application in laser system and fibre communication

have recently draw more attention than ever.We suggest that near-infrared luminescent lanthanide complexes could also find application in rare earth ions fluorospectrometry and fluorescence immunoanalysis.The advantage layes in the low interference by coexist rare earth ions and can improve the reliability.In the present work

Ln-PAN(Ln=Yb

3+

Nd

3+

and Er

3+

and PAN=1-(2-pyridylazo)-2-naphthol)complexes were synthesized and characterized by elemental analysis.Their near-infrared luminescence properties both in solid form and in solution were studied with a self-made luminescence determination system.It was found that near-infrared luminescence of Yb

3+

and Er

3+

complexes could be strongly sensitized by coordination of PAN

while that of Nd

3+

complex could not be sensitized.An energy transfer mechanism was proposed to explain the near-infrared luminescence properties of Ln-PAN complexes.The difference between emission energy level of Yb

3+

Nd

3+

and Er

3+

gives the different match effects with the triplet energy level of PAN.The luminescence intensity change dramatically with solvent

and ethanol solution gives the most intense emission.The fluorescence in ethanol solution is stronger than that in solid form

which was attributed to the concentration quenching effect.Unlike luminescent complexes of the commonly used lanthanide complexes of Tb

3+

Eu

3+

Sm

3+

and Dy

3+

which could only be excited with UV light

Ln-PAN(Ln=Yb

3+

Nd

3+

and Er

3+

)complexes could be excited with whole spectrum range of visible light

and this is a great advantage in choose light source for luminescence analysis.The near-infrared luminescence of a mixed Ln-PAN(Ln=Yb

3+

Nd

3+

and Er

3+

)solution also be determined independently

it shows there is no interference among the fluorescence of the three lanthanide ions.