A novel polymer waveguide (active waveguide) type optode possessing th
e advantages of both selective analyte determination and optical signa
l propagation was developed. The noteworthy concept of this active wav
eguide is the integration of plural functions into the planar waveguid
e itself, such as molecular recognition, color change, and light propa
gation. In order to demonstrate this concept, the analyte sensing laye
r is utilized as the light propagating layer. An ion-selective optode
membrane consisting of a plasticized poly(vinylchloride) (PVC) membran
e containing a neutral ionophore and a color changeable lipophilic ani
onic dye was used as the planar active waveguide sensing layer. The pr
inciple of the response of this active waveguide is based on the measu
rement of the output light signal intensity in which this light is pro
pagated through the color changeable PVC membrane phase, and its inten
sity is decreased by interaction with the analyte ions. In this report
, calcium and sodium ion-sensitive waveguides were prepared based on o
ur developed neutral ionophores. Comparison of the experimental respon
ses between the novel active waveguide optode and a commonly utilized
conventional waveguide optode based on evanescent wave spectrometry de
monstrated that the sensitivity of the active waveguide optode is obvi
ously greater than that of the conventional waveguide optode. This con
cept of an active waveguide fully demonstrates the advantageous proper
ty of a planar waveguide with respect to highly sensitive and selectiv
e optical chemical sensing.