Two novel diarylethene derivatives bearing a rhodamine unit have been successfully synthesized. Their unique multi-addressable switching characteristics as induced by chemical and optical dual inputs stimulation were observed using UV and FL measurements. The two diarylethenes showed excellent photochormism with alternating UV/vis light irradiation. Addition of trifluoroacetic acid (TFA) protonated the diarylethenes, which resulted in good photochromism and notable fluorescence change via the FRET mechanism. Subsequent addition of triethanolamine base would neutralize and return both their protonated open-ring and closed-ring isomers to their original forms. It was found that the diarylethene bearing a rhodamine unit linked by a benzhydrazide bridge group was more sensitive, efficient and reacted faster to protonation by TFA when compared to the benzamide bridged derivative. Furthermore, the benzhydrazide bridged diarylethene derivative was found to be selective towards Cr(III), Al(III), or Ca(II) with significant color and fluorescence changes.

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rity labeling, encryption, anticounterfeiting, and so on. [1,2] Diverse photonic structures have been reported, such as photonic crystals and Bragg stacks. [3,4] Generally, the iridescent colors produced by photonic crystals or Bragg stacks can be altered by changing either the particles' size, the spacing among particles in photonic crystals, or the thickness of overlapped layers in a Bragg stack in response to a stimulus. [5] Among them, chiral nematic liquid crystals with the ability to self-assembly into helical structures can selectively reflect the incident light. [4,6] Typically, cellulose nanocrystals (CNCs), derived from biomass via sulfuric acid hydrolysis or 2,2,6,6-tetramethylpiperidinyloxy (TEMPO)-mediated oxidation, possess the intriguing ability to self-assembly into a chiral nematic liquid crystals phase in sufficiently concentrated solutions. [7,8] Aqueous CNCs suspensions can be turned into iridescent solid films with a left-handed helical structure upon air-drying. The reflected light with certain wavelengths by solid CNCs films could be controlled by changing the helical pitch in suspensions via introducing electrolytes, varying the evaporation rate and substrates, coassembly of CNCs with polymeric networks, applying sonication, mechanical shearing, electrical or magnetic field. [9][10][11] In order to use the photonic properties of CNCs, many efforts have been devoted during the past few years to developing the uniform long-range helical order and homogeneous structure color by manipulating the pitch size and the chiral nematic organization in solid CNCs films. Various nanocomposite hydrogels, [4] films, [11] and elastomer [8] have been prepared in previous studies by evaporation-induced self-assembly (EISA) of CNCs together with various polymers. However, the procedures of EISA are highly sensitive, sophisticated and often require long time to concentrate a CNCs suspension to the desired concentration of above 10 wt%. In addition, various techniques, such as electromagnetic field and circular shear flow, also proved to facilitate chiral nematic alignment and improve the uniformity in helix orientation. [10,12] Despite these advances, most of color changes can only be realized in aqueous suspensions via the alteration of the pitch sizes of helical structures, which also limit their applications as solid optical

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