In the lab，I use fluorescence spectrometer for the ratiometric fluorescence measurement which needs to measure optical intensity at two different wavelenghts.
However, the fluorescence spectrometer is expensive and huge. I am wondering how to build a portable device for the ratiometric fluorescence measurement?
If you don’t mind losing the flexibility of scanning the spectrum or rapidly changing ex/em bands, you would build a 2-band fluorescence colorimeter. You’d need two emission filters and one or two excitation filters, arranged around your cuvette so that the excitation and emission light paths intersect at a 90 degree angle in the sample. Of course, you’d need an excitation source and either two photodetectors or a means of manually switching the emission filter, plus the electronics to capture the photodetector output and do the ratiomatric comparison.