Fig. 1. Modulation of multiple neuronal population with trichromatic UCNPs.

a Schematic showing NIR trichromatic upconversion mediated multicolor optogenetics. Channelrhodopsins and trichromatic UCNPs were introduced into specific brain areas. 980, 808, and 1532 nm NIR light can penetrate brain tissue and excite the trichromatic UCNPs respectively, which would emit corresponding 475, 540, and 650 nm visible color and activate the matching neuronal population. b Schematic showing the CW NIR excited multicolor emission of trichromatic UCNPs and the mixture of monochromatic UCNPs with correspondent photographs under three NIR excitation. NIR laser of 980, 808, or 1532 nm only generates one corresponding color in trichromatic UCNPs with dissipation core-shell structure, namely blue, green, and red emission. A mixture of conventional monochromatic UCNPs under NIR excitation. 808 and 980 nm NIR light induce two or three color bands emission.