Week 11: Montse & Jo

Montse

An explanation of the tests were performed the tea samples are as follow. First the samples sent contained two different types of stains; the first group had stains made with tea bags and the second group had stains made with mold.

The tea stain samples were further divided into two different groups based on the type of paper that was used to prepare them; one paper was thick and the other was very thin.  To perform the tests, four different stain samples were chosen; two with the thick paper and two with the thin paper. Figure 1 shows the four samples used.

First, to assess differences in the chemical composition between the two types of papers, a Furier Transform Infrared (FTIR) scan was performed. This technique allows identification of different functional groups, such as hydroxyl substituents, carbonyl substituents, and ether substituents, among others. The results showed that both papers have a similar chemical composition and it is consistent with the reported FTIR spectra of hemicellulose1-2. (Figure 2)

Next, the stains were visualized under a microscope using different magnifications. A picture of each one of the samples was taken using a Wolfe dissecting microscope, followed by a picture using a B3 Professional Miotic microscope (Eyepiece WF 10X / 20mm and objective 4X / 0.10 (WD 17mm)).  It can be seen that the fibers in the paper from samples 2 and 3 are much thicker and dense compared to the paper from samples 1 and 4. Also, the coloration for samples 2 and 3 is more pronounced compared to samples 1 and 4 (Figures 3-6). An interesting side note is that if one looks at the amplified pictures individually, it is hard to identify them as paper fibers. There can be many interpretations for that picture (See figures 7-10).

The next experiment was to determine the contact angle for each one of the paper samples. The contact angle was measured using the Pendant drop experiment and the OneAttension software. The contact angle for the thick paper was 89.87 o ± 0.66 and for the thin paper it was 0 o. This observation was very interesting due to the fact that both materials are the same (which should predict the same contact angle). A possible explanation for this is the fact that the thick paper has fibers that are highly packed, which in turns decreases its porosity. The following pictures (Figure 11-13) were collected while performing the experiment.

The next experiment was to extract the tea with different solvents and see if different pigments could be extracted with the intention of isolating different pigments that had different colors (to possibly use them as pigments for a “watercolor that is paint like”). Two different varieties of tea were used for the extraction: the YuLuYanCha and the Laoshan black tea. The solvents used were water, ethanol, ethyl acetate and hexanes. Figure 14 shows the extraction solutions; the front row shows the extractions of Laoshan black tea and the back row shows the extractions of YuLuYanCha. The solvents used for the extraction are in the back row. In order from right to left are: water, ethanol, ethyl acetate and hexanes (most polar to least polar).
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As it was predicted, various pigments were extracted when solvents with different polarities were used. To check the stability of the color, the solutions were photographed after 72 hours (Figure 15 samples are shown in the same order). The color appears to remain similar to the original test (a further test is coming to check if colors are the same). Figure 16 shows the YuLuYanCha tea after extraction (left) and before extraction (right). A picture of tea and epigallocatechin gallate drawn with those pigments was shown in the previous blog.
Also, Jo and I have continued to plan the Sci-Art exhibit.



References
1.    Célino, A.; Gonçalves, O.; Jacquemin, F.; Fréour, S., Qualitative and quantitative assessment of water sorption in natural fibres using ATR-FTIR spectroscopy. Carbohydrate polymers 2014, 101, 163-170.
2.    Ciolacu, D.; Ciolacu, F.; Popa, V. I., Amorphous cellulose—structure and characterization. Cellulose chemistry and technology 2011, 45 (1), 13.