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Kinetic stabilization of cellulose nanocrystals in a photocurable prepolymer for application as an adhesion promoter in UV-curable coatings
摘要： Cellulose nanocrystals (CNC) at low loading levels were shown to reinforce a photocurable coating resulting in improved adhesion. A polyether polyol containing CNC at loading levels of up to 1.8 wt% was grafted with 3-isopropenyl-α,α-dimethylbenzyl isocyanate to functionalize it with a photocurable group. The nanoparticles were kinetically stabilized in the rapidly forming prepolymer of high viscosity. Photoinitiators and a difunctional reactive diluent were added to produce optically transparent coatings and free films upon irradiation by ultraviolet (UV) light. This allowed evaluation of the effects of CNC at low loading levels in a glassy polymer matrix obtained through a rapid cure system. Incorporation of CNC nanoparticles in the polymer matrix resulted in an average improvement in adhesive strength of 154% while enhancing tensile strength by an average of 16%. The technique described could be used as a new approach to reduce adhesive failure in UV-curable coatings without sacrificing their mechanical strength.
关键词： Coatings,Nanoreinforcement,UV curing,Nanocomposite,Adhesion promoter,Cellulose nanocrystals
更新于2025-11-21 11:01:37
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Tessellation of Chiral-Nematic Cellulose Nanocrystal Films by Microtemplating
摘要： In biological architectures, material properties are optimized by the hierarchical structuring of components with a multiscaled order, from the nano- to the macroscales. Such designs enable, for instance, programmed yield points that maximize toughness. However, research efforts in biomimetic materials have focused on the assembly of nano- or macrostructures individually. In this study, high strength cellulose nanocrystals (CNCs), assembled into chiral-nematically ordered structures, are tiled into a higher level, macro-sized, architecture by topographical templating. As templates, two meshed architectures with distinct feature sizes are evaluated, and the optomechanical properties of the resulting films are compared to featureless, flat, CNC films. Controlling capillary stresses arising during CNC assembly is shown to enable control over the orientation of the chiral-nematic director across the topography of the template. Tuning the specific reflections and multiscaled fracture propagation is demonstrated for the microtemplated CNC films. The latter phenomenon contributed to enhancing the toughness of the material through a high tortuosity of fracture propagation in all (x, y, z) directions. The presented findings are expected to pave the way towards the incorporation of current research in cellular metamaterials with the research focusing on the generation of nanoscaled biomimetic constructs.
关键词： tessellation,conformability,biomimetic,hierarchical,cellulose nanocrystals
更新于2025-11-21 11:01:37
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Composite up-conversion luminescent films containing a nanocellulose and SrF2:Ho particles
摘要： The synthesis of up-conversion luminescent composite films based on a nanocellulose matrix containing Sr1-xHoxF2+x particles was proposed. The combination of sulfuric acid hydrolysis and ultrasonication allowed us to synthesize a series of stable nanocellulose dispersions from various raw materials (powdered sulphate bleached wood pulp, Blue Ribbon filter paper, and microcrystalline cellulose Avicel). The size distribution of cellulose nanoparticles in the aqueous dispersions was determined. Cellulose nanocrystals (CNC) and/or cellulose nanofibrils (CNF) dispersions were used to fabricate thin films by solution casting followed by solvent evaporation under ambient conditions. The size and shape of cellulose nanoparticles, surface morphology, crystallinity index of nanocellulose, polymerization degree, and optical properties were studied. By mixing aqueous dispersions of CNC with up-conversion Sr1-xHoxF2+x particles, homogeneous suspensions were obtained. Finally, a solution casting technique was used to prepare CNC/Sr1-xHoxF2+x and CNC/CNF/Sr1-xHoxF2+x nanocomposite films. CNC/CNF dispersions were utilized for the production of flexible, durable, transparent composite films. The synthesized nanocomposites demonstrated intense red luminescence upon Ho3+ excitation by 1912 nm laser radiation. The obtained up-conversion luminescent composite films can be considered as a promising material for photonics, in particular for near-IR laser labeling and radiation visualization, luminescent sensorics.
关键词： Nanocomposites,Up-conversion luminescent films,Cellulose nanofibrils,Cellulose nanocrystals,SrF2:Ho3+
更新于2025-09-23 15:23:52
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Synthesis of Carbon Nanodots from Cellulose Nanocrystals Oil Palm Empty Fruit by Pyrolysis Method
摘要： Biomass such as cellulose is one of the most common abundant organic materials on the Earth. Biomass has carbon chain that could be an excellent choice for the fabrication of carbon materials. Cellulose nanocrystal is nano-sized cellulose and could become the potential source in fabricating carbon nanodots that are affected by pyrolysis temperature. In fact, the size and temperature are essentially important to synthesize the carbon nanodots. This research is contributed to synthesize this material, and to investigate the effect of temperature. The percentage of cellulose nanocrystals and carbon nanodots obtained are less than 50%. Carbon nanodots are synthesized by pyrolysis method and cellulose nanocrystals are fabricated by membrane method. TEM analysis shows that cellulose nanocrystals are nano-sized. Under UV light source, the samples show fluoroscencing colours i.e. blue to green. From this research it can be concluded that the temperature affects the characteristics of carbon nanodots produced by pyrolysis method.
关键词： Pyrolysis,Cellulose Nanocrystals,Fluorescent,Carbon Nanodots
更新于2025-09-23 15:23:52
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Photonic Titanium dioxide film obtained from hard template with chiral nematic structure for environmental application
摘要： In the present work, mesoporous TiO2 with a photonic structure was elaborated using cellulose nanocrystals (CNCs) as a biotemplate by two-step hard template methods. This strategy enables to replicate the chiral nematic (CN) structure of the photonic films (biotemplate) in TiO2 films. A series of iridescent CNCs films with different weight ratios of silica/CNCs composite photonic films were prepared via evaporation induced self-assembly (EISA) method. The films showed iridescent color and tuneable Bragg reflection wavelengths by solely changing the ratio between the silica and the CNCs biotemplate. Polarized optical microscopy (POM) performed on hydride SiO2/CNCs films showed a birefringence and typical fingerprint of chiral nematic structure. This birefringence was also observed for TiO2 films obtained using SiO2 films as a hard template, which suggested the transfer of the chiral nematic structure in TiO2 materials. Afterwards, their optical, morphological and electronic properties were studied by scanning electron microscope (SEM), POM, energy-dispersive X-ray spectroscope (EDX) and time resolved microwave conductivity (TRMC). The photocatalytic activities were evaluated by following the phenol degradation using high performance liquid chromatography (HPLC). The results showed that the structuration of the TiO2 film using a chiral nematic SiO2 film as hard template enhances the photocatalytic performance compared to non-structured mesoporous TiO2.
关键词： hard template,cellulose nanocrystals,iridescent film,evaporation induced self-assembly,light harvesting,phenol degradation,chiral nematic structure
更新于2025-09-23 15:22:29
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Modular Nanocomposite Films with Tunable Physical Organization of Cellulose Nanocrystals for Photonic Encryption
摘要： Reported herein is the novel achievement of uniform and tunable interference colors of nanocomposite films containing organized cellulose nanocrystals (CNCs) from dynamic hydrogel precursors. Homogeneous and amendable interference colors with broad range are obtained either by stacking the nanocomposite films to adjust the amount of CNCs in the propagation pathway of light or by regulating the rotation angles between the individual films to alter the relative organization of CNCs within the system. Moreover, the precise and controllable patterned CNC composite films with multicolors in one film are facilely fabricated for the first time from the patterned hydrogel precursors. Based on this stacking/rotation-method, these patterned nanocomposite films with tunable interference colors can be further applied as fundamental elements for optical encryption by establishing a ternary-coded decimal system with encoded decimal numerals, paving the way for the development of photonic functional materials based on CNCs.
关键词： nanocomposites,interference colors,cellulose nanocrystals,photonic materials,encryption
更新于2025-09-23 15:19:57
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Ionically Modified Cellulose Nanocrystal Self-Assembled Films with a Mesoporous Twisted Superstructure: Polarizability and Application in Ion-Gated Transistors
摘要： Mesoporous structures made of cellulose nanocrystals (CNCs) and their self-assembly into films is of great interest not only due to their abundancy and sustainability but also due to their ease of chemical modification and nanoscale bio mimicry capabilities. However, their implementation in (opto)electronic devices requires further understanding on how these self-assembled twisted mesoporous superstructures respond to electrical stimulus. In this regard, this work focusses in the infiltration with three distinct alkali ions (Li+, Na+ and K+) to yield films with improved electrochemical response when compared to pristine ones, while preserving their photonic character. Electrochemical characterization shows capacitances of up to 2.5 μF cm-2 allowing for their integration as solid-state gate electrolytes in amorphous indium-gallium-zinc-oxide transistors, resulting in low operating voltages (< 2 V), On/Off ratios of up to 6 orders of magnitude and high saturation mobilities >10 cm2 V-1 s-1. Devices fabricated on Na+ and K+ infiltrated CNC films present the best characteristics, indicating pure capacitive charging of the semiconductor. The insights presented here contribute to applications in solid-state ionics in mesoporous structures or the combination of optically active electrolytes capable of providing unique functionalities in ion-gated transistors and circuitry.
关键词： Self-assembly,Mesoporous Structures,Cellulose Nanocrystals,Ion Gated Transistors,Photonics
更新于2025-09-12 10:27:22
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Plasmonic Metamaterial Gels with Spatially Patterned Orientational Order via 3D Printing
摘要： Optical properties can be programmed on mesoscopic scales by patterning host materials while ordering their nanoparticle inclusions. While liquid crystals are often used to define the ordering of nanoparticles dispersed within them, this approach is typically limited to liquid crystals confined in classic geometries. In this work, the orientational order that liquid crystalline colloidal hosts impose on anisotropic nanoparticle inclusions is combined with an additive manufacturing method that enables engineered, macroscopic three-dimensional (3D) patterns of co-aligned gold nanorods and cellulose nanocrystals. These gels exhibit polarization-dependent plasmonic properties that emerge from the unique interaction between the host medium’s anisotropic optical properties defined by orientationally ordered cellulose nanocrystals, from the liquid crystal’s gold nanorod inclusions, and from the complexity of spatial patterns accessed with 3D printing. The gels’ optical properties that are defined by the interplay of these effects are tuned by controlling the gels’ order, which is tuned by adjusting the gels’ cellulose nanocrystal concentrations. Lithe optical responsiveness of these composite gels to polarized radiation may enable unique technological applications like polarization-sensitive optical elements.
关键词： liquid crystals,optical properties,nanoparticles,plasmonic properties,cellulose nanocrystals,gold nanorods,3D printing
更新于2025-09-12 10:27:22
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Cellulose-Based Microparticles for Magnetically Controlled Optical Modulation and Sensing
摘要： Responsive materials with birefringent optical properties have been exploited for the manipulation of light in several modern electronic devices. While electrical fields are often utilized to achieve optical modulation, magnetic stimuli may offer an enticing complementary approach for controlling and manipulating light remotely. Here, the synthesis and characterization of magnetically responsive birefringent microparticles with unusual magneto-optical properties are reported. These functional microparticles are prepared via a microfluidic emulsification process, in which water-based droplets are generated in a flow-focusing device and stretched into anisotropic shapes before conversion into particles via photopolymerization. Birefringence properties are achieved by aligning cellulose nanocrystals within the microparticles during droplet stretching, whereas magnetic responsiveness results from the addition of superparamagnetic nanoparticles to the initial droplet template. When suspended in a fluid, the microparticles can be controllably manipulated via an external magnetic field to result in unique magneto-optical coupling effects. Using a remotely actuated magnetic field coupled to a polarized optical microscope, these microparticles can be employed to convert magnetic into optical signals or to estimate the viscosity of the suspending fluid through magnetically driven microrheology.
关键词： magneto-optical properties,polarized light,cellulose nanocrystals,microfluidics,microparticles
更新于2025-09-11 14:15:04
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Recent advances in the manipulation of circularly polarised light with cellulose nanocrystal films
摘要： Significant advances have been made to control the iridescence and the selective reflection of left circularly polarised (LCP) light, and transmission of right circularly polarised (RCP) light of solid films prepared from cellulose nanocrystals (CNCs). However the manipulation of the photonic properties of the CNCs films, which reflect both RCP and LCP light is less investigated. Solid films prepare from natural sources as CNCs have advantageous characteristics that are absent in other synthetic structures, such as wide availability and renewability. Here we review and compare recent research activity involving the production and characterization of photonic band gap structures resulting from an anisotropic layer inserted between two cholesteric layers with different helical pitches but the same handedness. We make connections between systems existing in Nature and synthetic ones with the hope of advancing in the production and manipulation of CNCs-based photonic structures.
关键词： Cellulose nanocrystals,Photonics,Circularly polarised light,Bio-inspired materials,Iridescence,Liquid crystals
更新于2025-09-10 09:29:36