# Optical Chirality Determined from Mueller Matrices
## 2 Materials and Methods  
### Samples and Sample Preparation  
Anhydrous D-glucose (J. T. Baker Chemicals B. V., Landsmeer, The Netherlands) was dissolved in distilled water to a concentration of 0.25 g/mL. An \(\alpha\)-quartz plate with a diameter of 12.5 mm and nominal thickness of 1 mm was purchased from Changchun Boxin Photoelectric Co., Ltd., Chang Chun, China. The actual thickness was measured with a caliper and found to be 1.075 \(\pm\) 0.005 mm.  
The liquid crystal sample consists of a cholesteric glassy liquid crystal (ChGLC) sandwiched between two 3-mm thick glass substrates coated with buffed polyimide layers. The ChGLC in this study was Bz3 ChN synthesized using Scheme 1 in [PERSON] et al. [10]. The material was heated beyond its clearing temperature and degassed. The isotropic material was deposited on a buffed polyimide glass substrate.  
The second glass substrate was placed on top, and a small force was applied to spread the ChGLC film to the thickness of 10 \(\upmu\)m as determined by silica micro-rods. Upon slight cooling to below the clearing temperature, a shearing force was applied to the glass substrates to align the ChGLC along the polyimide. The device was thermally annealed for 2 h at 200 \({}^{\circ}\)C after which it was quenched. A mono-domain Bz3 ChN film is capable of circularly polarizing light with a selective reflection band centered at 410 nm.  
Specimens of the scarab beetle _Cetonia aurata_ ([PERSON], 1758) were collected just outside Linkoping in Sweden. The inside of one of the elytra from each specimen was mechanically cleaned with a scalpel to remove the endocuticle for improved transmission. The thickness of the optical active part of a cuticle varies slightly from beetle to beetle and also from position to position on an elytron. A thickness value of 20 \(\upmu\)m was found by scanning electron microscopy [7] and was used for the samples studied here.  
The film of cellulose nanocrystals (CNC) was prepared with ashless filter paper (Whatman grade 40) as the source of cellulose. The paper was ground in a coffee mill 3 times, each for 35 s. The hydrolysis was performed with concentrated sulfuric acid (64 wt\(\%\)) with a ratio of 8.75 mL of acid per gram of paper at 45 \({}^{\circ}\)C for 120 min. The reaction was stopped by adding distilled water at 4 \({}^{\circ}\)C using 10 times the volume of hydrolysis solution. After resting for 24 h in a refrigerator, the diluted solution was decanted, and the recovered slurry was centrifuged three times with distilled water at 9000 rpm for 10 min each.  
The paste of cellulose nanocrystals was dialyzed against 3 L of distilled water changing the water every 24 h until a neutral pH was reached in the water. The final pH of the nanocrystals inside the dialysis membrane was in the range of 3-4. The concentration of CNC was determined gravimetrically, and a suspension with 1.5 wt\(\%\) of CNC was prepared and mechanically dispersed at 9000 rpm for 10 min. The CNC suspension was stored for one month before the film was cast by pouring 2.5 mL of CNC suspension in a petri dish with a 3 cm diameter. The evaporation-induced self-assembly was performed at laboratory conditions. Mueller-matrix measurements were performed six months after preparation. A thickness of 20 \(\upmu\)m was evaluated with scanning electron microscopy.