Comparing the light response of D-glucose in polyacrylamide hydrogel and water in NIR spectral region by using an LED based portable device

The spectral properties of the molecules depend on the matrix in which the interactions with other molecules inside the matrix affect the vibrational and rotational modes of the molecule. In this study, an absorption-based system was designed to show how the absorbance properties of the glucose change in polyacrylamide (PAAm) hydrogel when compared with water. The measurements were performed at different wavelengths; 960 nm, 1450 nm, 1550 nm, and 1950 nm and it was observed that the system is sensitive to glucose at the wavelengths of 1450 and 1950 nm in PAAm hydrogel, whereas it is only sensitive at 1450 nm in water which is due to the high absorbance of water at 1950 nm. In PAAm hydrogel, water molecules mostly gather around the polymer chains via electrostatic interactions and the absorbance of water decreases which results in an increasing absorbance of glucose. According to the results, the responsivity of the system at 960 and 1550 nm, which are the wavelengths commonly used in LED-based systems for measuring glucose in literature, is not high enough for reliable glucose measurements when compared with 1450 and 1950 nm.