I am working with nano-cellulose and aramid thin films and people are measuring the UV absorbance of thin films using ultraviolet (UV)–Vis-near infra- red light spectrophotometer. Are these instrument same as the ones used for finding UV absorbance of solutions? Is there any separate procedure to measure for films?
@Sangeeta Sankhla,
The measurements on liquids and on thin films using a UV-VIS-Nir spectrophotometer are slightly different. The sample holders for liquid samples are not suitable for thin film samples. The aperatures for thin film samples must be smaller than your thin film samples. Otherwise it gives inaccurate results.
Dear Sangeeta Sankhla
The UV-vis-NIR spectrophotometer will have a separate sample holder (that comes with separate chamber, just like for solid samples in the same instrument) where you can place the thin films and record the absorbance. Knowing the refractive index of the film you can calculate the thickness and vise versa. However, you can still measure the absorbance of coated films in an instrument which does not have a separate sample holder to get crude information. This can be performed exactly the way UV-vs absorbance is recorded, but with replacing the cuvette with substrate and sample. Regards.
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