Fig. 1

Appearances of O1/W primary emulsions loaded with menthol prepared under different Tween 80 contents and different oil-water ratios after standing for different time, in which the content of Tween 80 is 3% （a）; 4% （b）; and 5% （c）, respectively"

Fig. 2

Appearances of O1/W/O2 double emulsions loaded with menthol prepared under different Span 80 contents and different mass ratios of the O1/W primary emulsion loaded with menthol to the outer oil phase O2 （ζ） after standing for different time, in which the content of Span 80 is 3% （a）; 4% （b）; and 5% （c）, respectively"

Fig. 3

Appearances of O1/W primary emulsions loaded with menthol （a） and O1/W/O2 double emulsions loaded with menthol （b） without dye, with lemon yellow, and with Nile red （from the left to the right）, respectively"

Fig. 4

Optical microscopic images of O1/W/O2 double emulsion loaded with menthol （a）; Inverted fluorescence microscope images of the emulsions: O1/W primary emulsion loaded with menthol （b）; O1/W/O2 double emulsion loaded with menthol （c）; Laser confocal microscopy images of O1/W/O2 double emulsion loaded with menthol （d）"

Fig. 5

Appearances of O1/W/O2 double emulsions loaded with menthol under different conditions: after centrifugation at different speeds （r/min） （a）; after standing at room temperature for different times （b）"

Fig. 6

UV-Visible absorption spectra after reaction between menthol solutions with different mass concentrations and sulfuric acid solution of p-dimethylaminobenzaldehyde （a）; The relation curve between the absorption intensity at λ=550 nm after reaction of mentholwith p-dimethylaminobenzaldehyde and the corresponding mass concentration of menthol （b）"

Fig. 7

UV-Visible spectra of menthol in O1/W/O2 double emulsion （a）; Loading rate variation of O1/W/O2 double emulsion for menthol after standing at room temperature for different times （b）"

Fig. 8

Thermogravimetric analysis of O1/W/O2 double emulsion loaded with menthol （a）; Temperature characteristic curve of menthol release from the O1/W/O2 double emulsion loaded with menthol （b）"

Tab. 1

Analysis of the thermogravimetric results for O1/W/O2 double emulsion loaded with menthol"