研究目的
To demonstrate a simple and non-expensive dip-coating technique for preparing transparent and birefringent cellulose nanocrystal (CNC) films from aqueous suspensions, and to characterize their polarization properties using Mueller-matrix transmission spectroscopic ellipsometry.
研究成果
Birefringent CNC films were successfully fabricated using dip-coating, exhibiting transparency and linear birefringence with effective values around 0.021–0.026 in the visible range. The method is simple, non-expensive, and promising for applications in optical biomimetics and retarder films.
研究不足
The study is limited by the specific conditions of dip-coating (e.g., withdrawal speeds, CNC concentration), potential inhomogeneities at film edges, and the absence of chiral phase due to short drying times. Optimization of parameters for tailored birefringence is ongoing.
1：Experimental Design and Method Selection:
The study used dip-coating to prepare CNC films, hypothesizing that dragging forces during deposition align CNC. Mueller-matrix ellipsometry was employed for polarization characterization, with differential decomposition to analyze properties.
2：Sample Selection and Data Sources:
CNC suspensions were derived from hydrolyzed filter paper (Whatman 40). Glass slides (Corning 2947) served as substrates. Data included spectroscopic measurements and microscopy images.
3：0). Glass slides (Corning 2947) served as substrates. Data included spectroscopic measurements and microscopy images. List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment included a dual rotating compensator ellipsometer (RC2, J.A. Woollam Co.), FilmTek 3000 system (SCI, Inc.), AFM (Innova, Bruker), X-ray diffractometer (Rigaku/Dmax2100), ATR infrared spectrometer (Spectrum GX, Perkin Elmer), SEM (Phillips XL 30), and a home-made dip-coating apparatus. Materials included filter paper, sulfuric acid, water, and glass substrates.
4：Experimental Procedures and Operational Workflow:
CNC suspensions were prepared by hydrolyzing filter paper with sulfuric acid, followed by dilution, centrifugation, and dialysis. Films were dip-coated at withdrawal speeds of 10 and 20 cm/min, dried at room temperature, and characterized using various spectroscopic and microscopic techniques.
5：Data Analysis Methods:
Mueller matrix data were analyzed using differential decomposition to extract polarization properties like linear birefringence. Statistical analysis included standard deviation for transmittance measurements.
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dual rotating compensator ellipsometer
RC2
J.A. Woollam Co., Inc.
Used for transmission Mueller-matrix measurements at normal incidence to characterize polarization properties of the films.
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atomic force microscopy system
Innova
Bruker
Used to acquire AFM images in tapping mode to observe surface morphology and alignment of CNC films.
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X-ray diffractometer
Dmax2100
Rigaku
Used for X-ray diffraction data to confirm the crystalline structure of cellulose in the films.
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ATR infrared spectroscopy system
Spectrum GX
Perkin Elmer Inc.
Used for attenuated total reflection infrared spectroscopy measurements to verify molecular integrity of cellulose.
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glass substrate
2947
Corning
Used as substrates for dip-coating CNC films.
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FilmTek system
3000
SCI, Inc.
Used for transmittance irradiance measurements at normal incidence in the spectral range of 250–840 nm.
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scanning electron microscopy system
XL 30
Phillips
Used for cross-sectional SEM images to determine film thickness and morphology.
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gold deposition system
desk V
Denton Vacuum
Used to deposit a thin layer of gold on samples to avoid charging during SEM acquisition.
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filter paper
Whatman 40
Whatman
Used as the source of cellulose for preparing CNC suspensions through hydrolysis.
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