Presentation Information
[P03-331]Structural control and catalytic applications of AuNP–Dipeptide Composites with Different Peptide Sequences
○Naoaki Hiramatsu1, Asuka Inada1, Kaoru Ohe1, Tatsuya Oshima1 (1. University of Miyazaki (Japan))
Keywords:
Peptide,nanomaterial,AuNPs,Catalyst,4-NP
[Purpose]
Gold nanoparticles (AuNPs) have attracted considerable attention because of their facile synthesis, high stability, and excellent catalytic activity. However, many surfactants used for controlling the particle size of AuNPs exhibit strong cytotoxicity and often hinder surface modification, which limits their practical applications. To overcome these limitations, we developed gold–dipeptide nanocomposites (Au–Pep) using histidine-containing peptides as reducing agents. Histidine residues exhibit strong metal-coordination ability through their imidazole groups, enabling effective interactions with metal ions. In addition, peptides possess high flexibility in molecular design and structural diversity, making them promising candidates for controlling nanoparticle formation. In this study, we investigated the synthesis and catalytic properties of Au–Pep composites prepared using histidine-containing dipeptides.
[Method]
The ligand peptides (HE and HF) used for the synthesis of Au–Pep were prepared by Fmoc-based solid-phase peptide synthesis. After purification, the peptides were used as reducing and coordinating agents for the preparation of gold nanoparticle composites. Au–Pep composites were synthesized by reacting dipeptides (HE and HF) with Au(III) ions in aqueous solution. The resulting nanocomposites were characterized by several analytical techniques. UV–Vis spectroscopy was used to evaluate the optical properties and confirm the formation of gold nanoparticles through surface plasmon resonance (SPR). Powder X-ray diffraction (XRD) measurements were performed to analyze the crystalline structure of the nanoparticles.
[Results]
UV–Vis spectra of the synthesized Au–Pep solutions exhibited a characteristic surface plasmon resonance (SPR) absorption band around 600 nm, confirming the formation of AuNPs. XRD analysis further revealed diffraction peaks corresponding to crystalline gold. The catalytic performance of the nanocomposites was evaluated using the reduction of 4-nitrophenol (4-NP) as a model reaction. Au–Pep samples containing lower amounts of peptide showed higher catalytic activity in the reduction of 4-NP.
[Consideration]
Kinetic analysis indicated that decreasing the peptide/Au molar ratio resulted in a lower activation energy for the reaction. This enhancement in catalytic activity is attributed to structural changes in the nanocomposite surface. A lower peptide/Au ratio likely leads to smaller primary AuNPs and an increased effective reaction area, thereby facilitating catalytic reactions.
[Conclusion]
These findings demonstrate that the particle size of AuNPs and the structure of Au–Pep nanocomposites can be controlled by adjusting the peptide concentration during synthesis. Furthermore, the surface structure and surface area of AuNPs significantly influence their catalytic activity. Peptide-based nanocomposites therefore provide a promising strategy for designing functional gold nanoparticle catalysts with tunable structures and catalytic properties.
Gold nanoparticles (AuNPs) have attracted considerable attention because of their facile synthesis, high stability, and excellent catalytic activity. However, many surfactants used for controlling the particle size of AuNPs exhibit strong cytotoxicity and often hinder surface modification, which limits their practical applications. To overcome these limitations, we developed gold–dipeptide nanocomposites (Au–Pep) using histidine-containing peptides as reducing agents. Histidine residues exhibit strong metal-coordination ability through their imidazole groups, enabling effective interactions with metal ions. In addition, peptides possess high flexibility in molecular design and structural diversity, making them promising candidates for controlling nanoparticle formation. In this study, we investigated the synthesis and catalytic properties of Au–Pep composites prepared using histidine-containing dipeptides.
[Method]
The ligand peptides (HE and HF) used for the synthesis of Au–Pep were prepared by Fmoc-based solid-phase peptide synthesis. After purification, the peptides were used as reducing and coordinating agents for the preparation of gold nanoparticle composites. Au–Pep composites were synthesized by reacting dipeptides (HE and HF) with Au(III) ions in aqueous solution. The resulting nanocomposites were characterized by several analytical techniques. UV–Vis spectroscopy was used to evaluate the optical properties and confirm the formation of gold nanoparticles through surface plasmon resonance (SPR). Powder X-ray diffraction (XRD) measurements were performed to analyze the crystalline structure of the nanoparticles.
[Results]
UV–Vis spectra of the synthesized Au–Pep solutions exhibited a characteristic surface plasmon resonance (SPR) absorption band around 600 nm, confirming the formation of AuNPs. XRD analysis further revealed diffraction peaks corresponding to crystalline gold. The catalytic performance of the nanocomposites was evaluated using the reduction of 4-nitrophenol (4-NP) as a model reaction. Au–Pep samples containing lower amounts of peptide showed higher catalytic activity in the reduction of 4-NP.
[Consideration]
Kinetic analysis indicated that decreasing the peptide/Au molar ratio resulted in a lower activation energy for the reaction. This enhancement in catalytic activity is attributed to structural changes in the nanocomposite surface. A lower peptide/Au ratio likely leads to smaller primary AuNPs and an increased effective reaction area, thereby facilitating catalytic reactions.
[Conclusion]
These findings demonstrate that the particle size of AuNPs and the structure of Au–Pep nanocomposites can be controlled by adjusting the peptide concentration during synthesis. Furthermore, the surface structure and surface area of AuNPs significantly influence their catalytic activity. Peptide-based nanocomposites therefore provide a promising strategy for designing functional gold nanoparticle catalysts with tunable structures and catalytic properties.
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