en تخصصي Special پژوهشي Research In this study, silver nanoparticles were chemically synthesized and deposited on glass substrates using a reducing agent of sucrose, at 50&deg;C. Different characterizations including atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), and Raman spectroscopy were obtained to study silvery substrates. Then, the silvery substrates were used as the SERS substrates to detect vibrational modes of phenylalanine amino acid&nbsp;up to the concentration of 10^-7&nbsp;M. The importance of phenylalanine amino acid&nbsp;detection is due to the early diagnosis of phenylketonuria in neonates.&nbsp;Therefore, the blood plasma of a healthy neonate and a neonate with phenylketonuria disease were adsorbed on the SERS substrates. They enhance the intensity of molecular vibration peaks of phenylalanine amino acid&nbsp;of two kinds of blood plasmas. The intensities of molecular vibrations of unhealthy plasma are stronger than healthy plasma due to the higher concentrations of phenylalanine amino acid, which is the sign of&nbsp;Phenylketonuria&nbsp;disease.<br> <br> &nbsp; SERS Biological Sensors, Silver Nanostructures, Phenylalanine, Blood Plasma, Phenylketonuria. 31 38 http://ijop.ir/browse.php?a_code=A-10-557-2&slc_lang=en&sid=1 Vahid Eskandari vahid.22345@gmail.com 10031947532846003116 10031947532846003116 No Nanoscience and Nanotechnology Research Center, University of Kashan, Kashan, Iran Nafiseh Sharifi sharifi@kashanu.ac.ir 10031947532846003117 10031947532846003117 Yes Photonic and Plasma group, Physics Department, University of Kashan, Kashan, Iran