▎ 摘　　要

Functionalization of GQDs is expected to enhance the optoelectronic properties which are beneficial to explore their applications in the field of semiconductors, sensors, electronics, etc., Tyrosine is a versatile zwitterionic aromatic amino acid, which could improve the optical and electronic properties of the pristine GQDs. The tyrosine functionalized GQDs are synthesized in two different methods via in-situ and post-modification methods to study their characteristics and are named them as IS-Tyr-GQDs and PM-Tyr-GQDs respectively. The structural, morphological, assembly, surface functional group, and optical characteristics are analyzed and compared to study the changes in the characteristics of the prepared functionalized GQDs. The characteristic properties of the IS-Tyr-GQDs and PM-Tyr-GQDs are contrasting and vary in size, morphology, absorbance wavelength, crystal-linity, and emission behavior. The interesting result is that IS-Tyr-GQDs are crystalline fused spherical shape with 14-15 nm in size and PM-Tyr-GQDs are partially crystalline with cinctured-berry of 4-5 nm in size. Although the functional moiety is the same IS-Tyr-GQDs are excitation dependent with redshift whereas, PM-Tyr-GQDs are excitation independent with blue shift. AFM, HRTEM, XPS, XRD, and Raman spectroscopic analyses confirm the formation of two-dimensional (2D) Tyr-GQDs. Liquid Chromatography-Mass Spectra recorded evidence of the purity of the compound synthesized. Both IS-Tyr-GQDs and PM-Tyr-GQDs distinction in properties brings their diverse applications in bioimaging, biosensing, electronics, fabrication, and development of sensors.