SEM imaging of chiral nematic films cast from cellulose nanocrystal suspensions

Majoinen, Johanna; Kontturi, Eero; Ikkala, Olli; Gray, Derek G.

doi:10.1007/s10570-012-9733-1

Cited by 221 publications

(187 citation statements)

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“…[70][71][72][73][74][75] It is therefore not surprising that evaporative drying of dilute CNC dispersions spread on a wetting substrate normally results in inhomogeneous films. Several examples can be found in the literature, 15,29 and in the inset of Figure 5d, a film prepared by drying a 4.8 wt% wood-derived CNC suspension is shown. It has a characteristic texture with radially varying color (the origin of the color will be discussed below).…”

Section: Dried Cnc Filmsmentioning

confidence: 95%

“…22 However, progress in this area is hampered by a number of important phenomena that remain unexplained, as well as a few controversies regarding the self-organization of CNCs. For instance, the notion that the reflected color is due to a photonic bandgap resulting from the helical structure has been challenged based on observations of a helix that is too long for Bragg reflection to take place in the visible wavelength range, 29 and a surprising dependence on the ionic strength of the phase sequence and helical pitch has been observed in some systems. 30 One of the aims of this critical review is to emphasize the physics and physical chemistry-related issues involved in CNC self-assembly by comparing it with similar processes in suspensions of other nanorod classes.…”

Section: Introductionmentioning

confidence: 99%

“…(a) Shows the formation of a chiral nematic liquid crystal phase and its coexistence with an isotropic phase in a CNC suspension of 5 wt% (upper image). The helical arrangement of the nanorods is illustrated schematically next to a scanning electron microscopy image of an actual CNC helix (reproduced with permission from Majoinen et al, 29 Copyright ª 2012, Springer). Currently explored utilization schemes are exemplified by (b) the iridescence revealing the photonic crystal character of the film (reproduced with permission from Zhang et al, 15 Copyright ª 2012, SPIE) and (c) templating of the CNC-derived helical structure into inorganic materials (here, titanium dioxide) (reproduced with permission from Shopsowitz et al 84 Copyright ª 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).…”

Section: Introductionmentioning

confidence: 99%

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Cellulose nanocrystal-based materials: from liquid crystal self-assembly and glass formation to multifunctional thin films

et al. 2014

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Cellulose nanocrystals (CNCs), produced by the acid hydrolysis of wood, cotton or other cellulose-rich sources, constitute a renewable nanosized raw material with a broad range of envisaged uses: for example, in composites, cosmetics and medical devices. The intriguing ability of CNCs to self-organize into a chiral nematic (cholesteric) liquid crystal phase with a helical arrangement has attracted significant interest, resulting in much research effort, as this arrangement gives dried CNC films a photonic band gap. The films thus acquire attractive optical properties, creating possibilities for use in applications such as security papers and mirrorless lasing. In this critical review, we discuss the sensitive balance between glass formation and liquid crystal self-assembly that governs the formation of the desired helical structure. We show that several as yet unclarified observations-some constituting severe obstacles for applications of CNCs-may result from competition between the two phenomena. Moreover, by comparison with the corresponding self-assembly processes of other rod-like nanoparticles, for example, carbon nanotubes and fd virus particles, we outline how further liquid crystal ordering phenomena may be expected from CNCs if the suspension parameters can be better controlled. Alternative interpretations of some unexpected phenomena are provided, and topics for future research are identified, as are new potential application strategies. NPG Asia Materials (2014) 6, e80; doi:10.1038/am.2013.69; published online 10 January 2014Keywords: cholesteric; gel; glass; liquid crystal; nanocellulose; photonic crystal; self-assembly INTRODUCTION Nanomaterials based on renewable resources are attracting rapidly growing interest, both from a fundamental scientific point of view and from the perspective of developing novel structural and functional macroscopic materials. 1,2 Using nature-based nanomaterials offers ecological advantages, and the extraordinary mechanical performance and/or photonic crystal character of biological composites such as bone, nacre, wood, beetle scales and butterfly wings is also an important inspiration for the development of new multifunctional materials. [3][4][5] However, full utilization of the intrinsic properties of nanosized starting materials requires the development of robust and versatile synthetic and processing routes to control assembly over several length scales. [6][7][8] Cellulose, one of the most versatile and widely found biopolymers in nature, has been used by humans for millennia as a building material, an energy source, a component of clothing and for storing and sharing knowledge and culture. Today, cellulose materials are used in a wide range of applications, and the paper and pulp industry

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Section: Dried Cnc Filmsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Cellulose nanocrystal-based materials: from liquid crystal self-assembly and glass formation to multifunctional thin films

et al. 2014

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“…Gray с сотрудниками показал, что хиральная нематическая структура может сохраняться в пленках НКЦ при испарении растворителя в процессе, известном под английской аббревиатурой EISA (evaporationinduced self-assembly, т. е. самосборка, вызванная испарением) [11]. Пленки НКЦ обладают хиральностью на трех различных уровнях: на молекулярном уровне из-за асимметричных атомов углерода D-глюкозидных фрагментов; на наноуровне из-за скрученной морфологии отдельных кристаллов; и вследствие левозак-рученного хирального нематического дальнего порядка лиотропной жидкокристаллической фазы [12]. НКЦ представляют значительный интерес в качестве строительных блоков для создания супрамолекулярных иерархических структур вследствие уникального сочетания своих свойств (большая площадь поверхности, высокий модуль упругости, анизотропная форма частиц) [13].…”

Section: Introductionunclassified

Properties of Nanocrystalline Cellulose Obtained From Celluloses of Annual Plants

Воронова¹,

Суров²,

Рублева³

et al. 2017

Liq. Cryst. and their Appl.

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“…[1−27] In particular, cellulose nanocrystals (CNCs) are colloidal rods, having a typical lateral dimension of 5−10 nm and length of 50−300 nm. Above a critical aqueous concentration, they exhibit lefthanded chiral nematic (cholesteric) liquid crystallinity (LC) and optical iridescence, [4][5][6] which is preserved in dried films [4,28] . It allows templating for photonic materials using inorganics, nanoparticles, polymers, and pyrolyzed carbonized matter.…”

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confidence: 99%

Chiral Plasmonics Using Twisting along Cellulose Nanocrystals as a Template for Gold Nanoparticles

et al. 2016

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Nanocelluloses with native crystalline internal structures have attracted considerable interest due to their plant-based origin, high mechanical properties, modifiability, and chiral liquid crystallinity, which suggest novel functional sustainable materials. [1−27] In particular, cellulose nanocrystals (CNCs) are colloidal rods, having a typical lateral dimension of 5−10 nm and length of 50−300 nm. Above a critical aqueous concentration, they exhibit lefthanded chiral nematic (cholesteric) liquid crystallinity (LC) and optical iridescence, [4][5][6] which is preserved in dried films [4,28] . It allows templating for photonic materials using inorganics, nanoparticles, polymers, and pyrolyzed carbonized matter. [10,12,16,25,26] On the other hand, the CNCs have been suggested to possess a right-handed twist along their nanorod axis to explain the left-handed twist in their chiral LC. [6] Recently, the right-handed twist of individual CNCs and nanocelluloses of three different origins was observed by cryo-electron tomography (cryo-ET), and electron and atomic force microscopy [27,29] supported by molecular dynamics simulations [30−32] .Exploiting the twisting shape along the individual CNC nanorods could allow new optical functions in the nano/colloidal scale in dilute aqueous dispersions, i.e. not limited to the chiral LC based on the inter-rod assembly involving a larger length scale. Surprisingly, such optical findings have not been reported so far.Surface plasmons, i.e. collective oscillations of the conduction electrons on metal surfaces, allow physics and applications ranging from photonic devices, sensing, and solar cells to pharmacology. [33−37] In nanoparticles (NPs) the oscillations become coupled to allow a chiral plasmonic response, provided that they are sufficiently closely positioned and assembled in a chiral manner. This manifests in circular dichroism (CD) spectroscopy, which describes the difference in absorption between left-and right-handed circularly polarized light. The chiral coupling of surface plasmons induces a bisignated CD signal with a zerocrossing at the characteristic localized surface plasmon resonance wavelength of the isolated NPs. Such a Cotton effect is either dip−peak or peak−dip, depending on the handedness of chirality. [38−42] In chiral biological molecules, such as DNA, proteins and polypeptides, the CD signal is at ultraviolet wavelengths, whereas the CD signal of helical metal nanoparticle assemblies is at the visible wavelengths. This extends the applications to e.g. in biosensing. [37] Chiral nanoparticle assemblies have been shown using helical polymers, supramolecular fibers, and DNA-based constructs as templates. [40−42] In particular, a chiral plasmonic signal is obtained using DNA-origami to organize the nanoparticles in well-defined helices with tunable pitch, separation, and handedness. [40,41] Even if the above approaches are promising allowing in-depth tunable chiral plasmonic response, introducing rapid, scalable, and economic ways for producing chiral plas...

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SEM imaging of chiral nematic films cast from cellulose nanocrystal suspensions

Cited by 221 publications

References 12 publications

Cellulose nanocrystal-based materials: from liquid crystal self-assembly and glass formation to multifunctional thin films

Cellulose nanocrystal-based materials: from liquid crystal self-assembly and glass formation to multifunctional thin films

Properties of Nanocrystalline Cellulose Obtained From Celluloses of Annual Plants

Chiral Plasmonics Using Twisting along Cellulose Nanocrystals as a Template for Gold Nanoparticles

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