Abstract
We report the use of thin-film organic photodiodes as integrated optical detectors for microscale chemiluminescence. The copper phthalocyanine–fullerene (CuPc–C
60) small molecule photodiodes have an external quantum efficiency of ∼30% at 600–700
nm, an active area of 2
mm
×
8
mm and a total thickness of ∼2
mm. Simple detector fabrication, based on layer-by-layer vacuum deposition, allows facile integration with planar chip-based systems. To demonstrate the efficacy of the approach, CuPc–C
60 photodiodes were used to monitor a peroxyoxalate based chemiluminescence reaction (PO-CL) within a poly(dimethylsiloxane) (PDMS) microfluidic device. Optimum results were obtained for applied reagent flow rates of 25
μL/min, yielding a CL signal of 8.8
nA within 11
min. Reproducibility was excellent with typical relative standard deviations (R.S.D.) below 1.5%. Preliminary quantitation of hydrogen peroxide yielded a detection limit of ∼1
mM and linearity over at least three decades. With improved sensitivity and when combined with enzymatic assays the described integrated devices could find many applications in
point-of-care diagnostics.