Photonic bandgap of inverse opals prepared from core-shell spheres

Table 1 Compositions of PS-silica core-shell spheres and properties of the corresponding photonic crystals

Code	TEOS (M)	Opal			Inverse opal
Code	TEOS (M)	λ_m^a(nm)	d_m^b(shell thickness) (nm)	d_s^c(shell thickness) (nm)	λ_m^d(nm)	d_a^e(nm)	Shrinkage ratio^f(%)
PC0	0	530	224 ± 2.9 (0)	223.4 (0)	348	190.5	14.7
PC3	0.03	564	242 ± 2.6 (20)	241.2 (17.8)	428	200.6	10.2
PC6	0.06	586	250 ± 4.2 (26)	252.4 (29.0)	501	220.6	1.3
PC9	0.09	606	262 ± 3.2 (38)	262.5 (39.1)	528	218.3	2.3

^aWavelength of stop band maximum for the opal structure, observed from Figure3; ^bdiameter of core-shell spheres, measured from SEM images; ^cdiameter of core-shell spheres, calculated from Equation 1; ^dwavelength of stop band maximum for the inverse opals, measured from the UV–vis spectra; ^ediameter of air spheres, calculated from Equation 1, assuming that the thickness of the shell was fixed; ^festimated from the ratio of d_a to the pristine diameter of the PS spheres.