In situ synthesis of gold nanoparticles using tryptophan enantiomers for determination of enantiomeric composition.
- 1Department of Analytical Chemistry, Faculty of Chemistry and Petroleum Sciences, Bu-Ali Sina University Hamedan Iran [email protected].
Abstract
This paper reports a simple one-step colorimetric method for distinguishing l- and d-tryptophan based on the in situ formation of gold nanoparticles (AuNPs) in the presence of Cu²⁺. The tryptophan enantiomers act as both reducing and stabilizing agents, generating different nanoparticle aggregation behaviors and visible color changes. l-Tryptophan causes strong aggregation and a purple color, while d-tryptophan yields dispersed particles and a light pink color, enabling visual and spectrophotometric enantiomeric discrimination. At each fixed total tryptophan concentration, the absorbance at 570 nm increased with increasing d-Trp mole fraction, allowing the enantiomeric composition to be estimated. Separate linear relationships between absorbance and d-Trp mole fraction were obtained at total tryptophan concentrations ranging from 104 µM to 3.3 mM. TEM analysis showed predominantly discrete particles for d-tryptophan and extensively associated particles for l-tryptophan, with mean primary-particle sizes of approximately 43 and 47 nm, respectively. These optical and morphological observations establish distinct enantiomer-dependent endpoint colloidal states but do not, by themselves, identify their chiroptical origin. The integrated synthesis-detection approach provides a rapid and inexpensive proof-of-concept for estimating enantiomeric composition in compositionally defined d-Trp/l-Trp mixtures. Selectivity in the presence of other amino acids, reducing substances, chelating agents, or complex matrix components was not evaluated in the present study.
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BibTeX
@article{radmanesh2026situ,
title = {{In situ synthesis of gold nanoparticles using tryptophan enantiomers for determination of enantiomeric composition.}},
author = {Rozhin Radmanesh and Mazaher Ahmadi and Tayyebeh Madrakian and Abbas Soloki},
journal = {RSC advances},
year = {2026},
month = oct,
doi = {10.1039/d5ra09954d},
url = {https://europepmc.org/article/MED/42846972},
note = {CC BY-NC},
}
RIS
TY - JOUR
TI - In situ synthesis of gold nanoparticles using tryptophan enantiomers for determination of enantiomeric composition.
AU - Rozhin Radmanesh
AU - Mazaher Ahmadi
AU - Tayyebeh Madrakian
AU - Abbas Soloki
PY - 2026
DA - 2026/10/07
JO - RSC advances
DO - 10.1039/d5ra09954d
UR - https://europepmc.org/article/MED/42846972
AB - This paper reports a simple one-step colorimetric method for distinguishing l- and d-tryptophan based on the in situ formation of gold nanoparticles (AuNPs) in the presence of Cu²⁺. The tryptophan enantiomers act as both reducing and stabilizing agents, generating different nanoparticle aggregation behaviors and visible color changes. l-Tryptophan causes strong aggregation and a purple color, while d-tryptophan yields dispersed particles and a light pink color, enabling visual and spectrophotometric enantiomeric discrimination. At each fixed total tryptophan concentration, the absorbance at 570 nm increased with increasing d-Trp mole fraction, allowing the enantiomeric composition to be estimated. Separate linear relationships between absorbance and d-Trp mole fraction were obtained at total tryptophan concentrations ranging from 104 µM to 3.3 mM. TEM analysis showed predominantly discrete particles for d-tryptophan and extensively associated particles for l-tryptophan, with mean primary-particle sizes of approximately 43 and 47 nm, respectively. These optical and morphological observations establish distinct enantiomer-dependent endpoint colloidal states but do not, by themselves, identify their chiroptical origin. The integrated synthesis-detection approach provides a rapid and inexpensive proof-of-concept for estimating enantiomeric composition in compositionally defined d-Trp/l-Trp mixtures. Selectivity in the presence of other amino acids, reducing substances, chelating agents, or complex matrix components was not evaluated in the present study.
SN - 2046-2069
ER -