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Cellulose nanocrystals (CNCs) have drawn considerable attention for their use in optical and sensor applications due to their appealing properties of chiral nematic photonic structures. However, the flexibility and water instability of neat CNC chiral nematic films are questionable and compromise their outstanding properties. We propose a room-temperature process for fabricating flexible, water-stable chiral nematic CNC films. Aqueous glutaraldehyde (GA) was first mixed with CNCs, and then free-standing films were formed by evaporation-induced self-assembly. The chiral nematic dry films that formed were then exposed to hydrochloric acid vapor for subsequent GA cross-linking with CNCs. The GA cross-linked CNC films had a highly ordered chiral nematic organization. The enhanced water stability of the films was demonstrated by using GA cross-linked CNC films as freestanding template substrates for conducting polymers (polypyrrole) and metal oxides (iron oxide) to form flexible chiral nematic photonic hybrids.

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In this research, we report a polypyrrole (PPy) multilayer-laminated cellulose network aimed at the costeffective removal of aqueous potentially toxic metal ions with high adsorption efficiency and good adsorbent recyclability. The preparation of conformal adsorbent coatings on a fibrous cellulose network was accomplished by performing multiple cycles of simple dip-coating of a non-toxic oxidant and vapor-phase polymerization of PPy. The resultant PPy multilayer-deposited cellulose exhibited stable adhesion between the vapor-deposited PPy and the underlying cellulose support even in a strongly acidic solution. Using this non-hazardous hybrid adsorbent, mercury ions could be efficiently adsorbed over a large pH range with a maximum specific adsorption capacity of 31.689 mg g À1 , either in the form of a thick suspended adsorbent for large-scale decontamination or a thin dripper-type membrane for portable water purification. Furthermore, the PPy multilayer-laminated cotton fabric enabled the largescale repetitive removal of mercury ions (100 ppm, 1 liter) with efficiency above 91%. This study suggests that the PPy-cotton hybrid may serve as a large-scale, economical, and recyclable decontamination platform for efficient removal of highly potentially toxic metal ions (e.g., Hg(II) and Cr(VI)), which could be beneficial for water purification, particularly in resource-limited locations.Scheme 1 A schematic illustration of fabrication of PPy-cellulose hybrid materials. J. Mater. Chem. AThis journal is