Antistatic Structural Color and Photoluminescent Membranes from Co-assembling Cellulose Nanocrystals and Carbon Nanomaterials for Anti-counterfeiting

Abstract

Static charges on optical anti-counterfeiting membranes may lead to materials structural changes, dust stain aggravation, and misreading of optical information. Incorporating conductive particles is a common way to transfer accumulative charges, but the key issue is how to achieve high dispersion and effective distribution of particles. According to the strategy of assembly-induced structural colors, cellulose nanocrystals (CNCs) were employed as a solid emulsifier to stabilize hydrophobic carbon nanoparticles (CNPs) in aqueous media; subsequently, by solvent-evaporation-modulated co-assembly under a condition of 30 °C and 20 RH%, the binary suspensions containing 2 wt% CNC and CNPs with the equivalent concentration relative to CNC ranged from 1:40 to 1:10 were used to prepare antistatic composite membranes. Surface chemistry regulation of CNCs was applied to optimize the dispersibility of CNPs and the orientation of assembled CNC arrays, and the hydrophilic CNCs were more favorable for dispersion and assembly of binary suspension systems. Meanwhile, one-dimension carbon nanotube (CNT) and zero-dimension carbon black (CB) were found to show better dispersibility than two-dimension graphene, which was verified by a semiquantitative theoretical study. Moreover, the stable binary systems of CNT/CNC and CB/CNC were chosen for co-assembly as membranes, and the uniaxial orientation could be optimized as the full-width of 9.8° at half-maximum deviation angle while the surface resistivity could also drop down to 3.42 × 102 Ω·cm·cm−1. The structural color character of such paper-homology and antistatic-integrated membranes contributes to optical information hiding-and-reading, and shows great potential as optical mark recognition materials for electrostatic discharge protective packaging and anti-counterfeiting applications.