Studying the effect of concentration on spectral and optical properties of chitosan polymer. Periodicals of Engineering and Natural Sciences, [S. l.], v. 11, n. 1, p. 134–143, 2025. DOI: 10.21533/pen.v11.i1.84. Disponível em: https://pen.ius.edu.ba/index.php/pen/article/view/84. Acesso em: 1 may. 2026.