Linear Birefringent Films of Cellulose Nanocrystals Produced by Dip-Coating

Mendoza-Galván, A.; Tejeda-Galán, Tania; Domínguez-Gómez, Amos B; Mauricio-Sánchez, Reina Araceli; Järrendahl, Kenneth; Arwin, Hans

doi:10.3390/nano9010045

Cited by 27 publications

(22 citation statements)

References 32 publications

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“…Other authors used a similar method based on convective-shear assembly to obtain the same alignment effect of CNC on gold and silica substrates [16]. Dip coating of non-sonicated CNC suspensions also produce birefringent films, as reported by our group [17].…”

Section: Introductionmentioning

confidence: 54%

Quantification of Optical Chirality in Cellulose Nanocrystal Films Prepared by Shear-Coating

et al. 2021

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Evaporation-induced-self-assembly is widely used to produce chiral cellulose nanocrystal (CNC) free-standing films reflecting left-handed polarized light. Research on supported chiral CNC films is rather scarce. The reflection and/or transmission of unpolarized light are the most common optical techniques used to characterize the selective reflection of CNC films whereas the use of techniques to quantify chiral properties is limited. Here, the fabrication of chiral CNC films supported on glass substrates by a shear-coating method, as well as a full characterization of their polarization properties, are reported. Optical chirality is evidenced in films, showing a brilliant blue structural color when viewed through a left-handed polarizer and darkness through a right-handed polarizer. Mueller-matrix data in the reflection and transmission modes are used to quantitatively characterize the structural origin of color in the films. The quantification of the linear and circular birefringence, as well as circular dichroism, is performed by analytical inversion of the Mueller matrix data in the transmission mode and regression analysis using Tellegen constitutive equations. The equivalence of the two methods to quantify the structural chirality in CNC films is demonstrated. The swelling of films in water and kinetics during drying is studied by reflection spectroscopy.

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Section: Introductionmentioning

confidence: 54%

Quantification of Optical Chirality in Cellulose Nanocrystal Films Prepared by Shear-Coating

et al. 2021

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“…Additionally, dip-coated mixtures of CNC and carbon-based nanomaterials (nanoparticles, nanotubes, and graphene) for anti-counterfeiting have been reported [ 26 ]. Dip coating of non-sonicated CNC suspensions produced birefringent films as reported by our group [ 27 ].…”

Section: Introductionmentioning

confidence: 67%

“…The preparation of the suspensions followed the procedure previously reported in the literature [ 7 , 27 ]. Ashless filter paper (Whatman 40) was chosen as the source of cellulose.…”

Section: Methodsmentioning

confidence: 99%

“…In nanostructured CNC films, the latter property is related to the structural chirality of CNC in a helicoidal arrangement. In previous studies carried out in our group, the elementary polarization properties of dip-coated [ 27 ] and free-standing [ 28 ] CNC films were addressed by a Mueller-matrix approach. Additionally, other authors used Mueller-matrix measurements to study the circular dichroism of chiral nematic films of CNC loaded with metallic nanoparticles [ 29 ].…”

Section: Introductionmentioning

confidence: 99%

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Shear-Coated Linear Birefringent and Chiral Cellulose Nanocrystal Films Prepared from Non-Sonicated Suspensions with Different Storage Time

et al. 2021

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Nanocelluloses are very attractive materials for creating structured films with unique optical properties using different preparation techniques. Evaporation-induced self-assembly of cellulose nanocrystals (CNC) aqueous suspensions produces iridescent films with selective circular Bragg reflection. Blade coating of sonicated CNC suspensions leads to birefringent CNC films. In this work, fabrication of both birefringent and chiral films from non-sonicated CNC suspensions using a shear-coating method is studied. Polarization optical microscopy and steady-state viscosity profiles show that non-sonicated CNC suspensions (concentration of 6.5 wt%) evolve with storage time from a gel-like shear-thinning fluid to a mixture of isotropic and chiral nematic liquid crystalline phases. Shear-coated films prepared from non-sonicated fresh CNC suspensions are birefringent, whereas films prepared from suspensions stored several weeks show reflection of left-handed polarized light. Quantification of linear and circular birefringence as well circular dichroism in the films is achieved by using a Mueller matrix formalism.

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“…This dependence can be explained by the fact that veins and other structures are made of highly oriented polymers that present certain anisotropic (birefringent or dichroic) response. The components that mainly provide birefringent response in plants (as well as dichroism when some pigments are present) are the cellulose fibrils, and in particular, the microcrystals of which cellulose fibrils are made of [ 52 – 55 ]. These microcrystals tend to be oriented in the direction of the large structures.…”

Section: Resultsmentioning

confidence: 99%

Depolarizing metrics for plant samples imaging

et al. 2019

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Optical methods, as fluorescence microscopy or hyperspectral imaging, are commonly used for plants visualization and characterization. Another powerful collection of optical techniques is the so-called polarimetry, widely used to enhance image contrast in multiple applications. In the botanical applications framework, in spite of some works have already highlighted the depolarizing print that plant structures left on input polarized beams, the potential of polarimetric methods has not been properly exploited. In fact, among the few works dealing with polarization and plants, most of them study light scattered by plants using the Degree of Polarization (DoP) indicator. Other more powerful depolarization metrics are nowadays neglected. In this context, we highlight the potential of different depolarization metrics obtained using the Mueller matrix (MM) measurement: the Depolarization Index and the Indices of Polarimetric Purity. We perform a qualitative and quantitative comparison between DoP- and MM-based images by studying a particular plant, the Hedera maroccana. We show how Mueller-based metrics are generally more suitable in terms of contrast than DoP-based measurements. The potential of polarimetric measurements in the study of plants is highlighted in this work, suggesting they can be applied to the characterization of plants, plant taxonomy, water stress in plants, and other botanical studies.

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Linear Birefringent Films of Cellulose Nanocrystals Produced by Dip-Coating

Cited by 27 publications

References 32 publications

Quantification of Optical Chirality in Cellulose Nanocrystal Films Prepared by Shear-Coating

Quantification of Optical Chirality in Cellulose Nanocrystal Films Prepared by Shear-Coating

Shear-Coated Linear Birefringent and Chiral Cellulose Nanocrystal Films Prepared from Non-Sonicated Suspensions with Different Storage Time

Depolarizing metrics for plant samples imaging

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