Abstract
In general, biochemical sensors based on photonic cavities are used to detect changes in the refractive index of the environment. In this study, however, a GaInAsP semiconductor photonic-crystal nanolaser sensor that we recently developed was found to detect not only the environmental refractive index but also the surface charge. In contrast to the pH sensitivity we reported previously, this is an ultra-sensitive detection mechanism capable of identifying proteins and deoxyribonucleic acids (DNA) at a femtomolar-order or lower concentrations. When the device is exposed to plasma or DNA solutions, the laser wavelength simultaneously changes with the zeta potential and the flat-band potential of the semiconductor surface. This indicates that the charged functional groups on the surface, which are formed by these treatments, modify the Schottky barrier near the semiconductor surface, trap the excited carriers in the barrier, and change the refractive index of the semiconductor via the carrier effects. These findings also suggest that some other photonic sensors may also exhibit similar electrochemical and optoelectronic effects.
Highlights
Biosensors detect biomolecules such as proteins and deoxyribonucleic acids (DNAs) in a solution through a change in some physical quantity of the sensor
When the concentration is of the order of picomolar or lower, the shift in the resonance wavelength or resonance angle must be explained differently because the index change produced by the adsorption would be too small
To the best of our knowledge, no studies have been conducted to directly measure the number of molecules adsorbed on the surface by other means, to estimate the environmental and modal index changes, and to confirm the resonance shift that arises from these index changes
Summary
Biosensors detect biomolecules such as proteins and deoxyribonucleic acids (DNAs) in a solution through a change in some physical quantity of the sensor In this decade, various photonic biosensors based on optical resonance, which do not require labels such as fluorescent molecules or colorimetric substances, have been studied and developed [1,2,3,4,5]. Various photonic biosensors based on optical resonance, which do not require labels such as fluorescent molecules or colorimetric substances, have been studied and developed [1,2,3,4,5] These sensors detect the target through a shift in the resonance wavelength or resonance angle of light when the target molecules are adsorbed on the sensor.
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