Diode laser spectroscopic studies of biological materials using absorption and emission techniques

Abstract

Two diode lasers with optical spectroscopic properties for absorption and emission spectroscopy have been used as sources in the study of economically important biological materials. In the emission spectroscopy a fluorosensor with a diode lasing at 396 nm was used to conduct in-vivo and in-vitro water-stressed study on the leaves of male and female plants by recording their chlorophyll fluorescence induction kinetics at the red and far-red bands as well as their ratios. Using the chlorophyll fluorescence induction kinetics curves in combination with multivariate data analysis method, discrimination and classification models were formulated which made it possible to differentiate and classify the sexes of the nutmeg plant which can be used as a tool for the early sex prediction of the plant. In the absorption spectroscopy molecular oxygen in some fruits and wood species were probed by means of GAs in Scattering Medium Absorption Spectroscopy (GASMAS) technique using a continuous diode laser emitting at 760 nm. The wavelength modulation second derivative absorption signals of the oxygen gas were measured relative to their direct absorption signals and a ratio established. This ratio was found to be directly proportional to the gas concentration in the scattering medium under study. For the wood the equivalent optical path lengths in different directions reflected its anisotropic nature while the differences in equivalent optical path length were found to relate to their densities. The different time constants obtained for the fruits and wood species is a potential technique for identifying and characterizing these species.