Table 1.

Correlation of silk optical properties with structural and mechanical properties

Material	Morphology	Fibroin tertiary structure	Silk II content	Silk II alignment	Mechanical	Optical	References
Natural Silk Fibers	Filamentous thin	Silk I, Silk II	High (55%)	High	Flexible, high tensile strength	Extreme blue-shifted fluorescence, SHG	[36]
Fibroin Solution	Amorphous	Silk I	None-Low	None	-	Highly red-shifted fluorescence, no SHG	[45]
Fibroin Film	Amorphous, thin	Silk I	None-Low	None	Stiff	Red-shifted Fluorescence, no SHG	[15,43]
Fibroin Film (solvent treated)	Amorphous, thin	Silk I, Silk II	Medium-High (20%)	High with compression	Stiff	Blue-shifted fluorescence, SHG when compressed	[15,43]
Hydrogel	Heterogeneous microstructures, Thick	Silk I, Silk II	Htgn (40–50%)	None	Flexible, weak	Highly blue-shifted fluorescence, no SHG	[45, 44]
Scaffold	Porous, Thick	Silk I, Silk II	Medium (22%)	Some	Flexible, strong	Highly blue-shifted fluorescence, SHG along pores	[19,25,40]