Resonant Raman Scattering and Optical Absorption Studies of Zn(II) Impurities in L-Alanine Single Crystal

TL;DR

This study investigates how Zn(II) impurities affect the vibrational and optical properties of L-Alanine single crystals using resonant Raman scattering and absorption spectroscopy, revealing impurity interactions and bandgap estimations.

Contribution

It introduces a combined spectroscopic approach to analyze transition metal impurities in amino acid crystals, providing insights into impurity positioning and electronic interactions.

Findings

Resonant enhancement of vibrational modes near UV absorption band.

Estimation of bandgap at 3.8 eV consistent with absorption data.

Identification of impurity interactions with amino and carboxyl groups.

Abstract

We present a study of low-concentration Zn (II) impurities in L-Alanine Single Crystal (ZNLA) employing resonant Raman scattering and optical absorption spectroscopy. By analyzing the relative integrated intensity of the selective vibrational modes, we observe a resonant enhancement of Raman-active modes near the UV absorption band, associated with vibrations of the amino and carboxyl groups in ZNLA. These findings suggest that zinc cations occupy an interstitial position coordinated by amino and carboxyl groups. Also, ZNLA single crystal shows a strong antiresonance behavior for some modes associated with amino and carboxyl groups. The antiresonance model in the cross-section allowed the estimation of the bandgap to be 3.8 eV, which perfectly agrees with the direct bandgap obtained from the absorption spectrum (3.75 eV). Finally, our approach proves to be useful for detecting interactions between transition metal ion impurities and intramolecular structures in other transition metal-doped organic amino acid systems.