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Biomimetic Synthesis of Gelatin Polypeptide-Assisted Noble-Metal Nanoparticles and Their Interaction Study

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ABSTRACT

Herein, the generation of gold, silver, and silver–gold (Ag–Au) bimetallic nanoparticles was carried out in collagen (gelatin) solution. It first showed that the major ingredient in gelatin polypeptide, glutamic acid, acted as reducing agent to biomimetically synthesize noble metal nanoparticles at 80°C. The size of nanoparticles can be controlled not only by the mass ratio of gelatin to gold ion but also by pH of gelatin solution. Interaction between noble-metal nanoparticles and polypeptide has been investigated by TEM, UV–visible, fluorescence spectroscopy, and HNMR. This study testified that the degradation of gelatin protein could not alter the morphology of nanoparticles, but it made nanoparticles aggregated clusters array (opposing three-dimensional α-helix folding structure) into isolated nanoparticles stabilized by gelatin residues. This is a promising merit of gelatin to apply in the synthesis of nanoparticles. Therefore, gelatin protein is an excellent template for biomimetic synthesis of noble metal/bimetallic nanoparticle growth to form nanometer-sized device.

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a, b TEM images of gelatin-Ag–AuNPs with different ratios of silver to gold synthesized at 80°C. a nAg/nAu = 2.4, : 2 mL, : 1 mL; b nAg/nAg = 1.2, : 2 mL, : 2 mL, the inset in b is magnification of the image marked by pane in b; c UV–vis spectra of Ag–AuNPs, AgNPs and AuNPs. (1) AgNPs (Cgelatin: 0.4 wt%, : 2 mL), (2) Ag–AuNPs in Figure 12a, (3) Ag–AuNPs in Figure 12b, (4) AuNPs (Cgelatin: 0.4 wt%, : 2 mL); d XRD of gelatin-Ag–AuNPs film dried at room temperature under vacuum. Peaks marked with stars arise from gelatin organic phase.
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Figure 12: a, b TEM images of gelatin-Ag–AuNPs with different ratios of silver to gold synthesized at 80°C. a nAg/nAu = 2.4, : 2 mL, : 1 mL; b nAg/nAg = 1.2, : 2 mL, : 2 mL, the inset in b is magnification of the image marked by pane in b; c UV–vis spectra of Ag–AuNPs, AgNPs and AuNPs. (1) AgNPs (Cgelatin: 0.4 wt%, : 2 mL), (2) Ag–AuNPs in Figure 12a, (3) Ag–AuNPs in Figure 12b, (4) AuNPs (Cgelatin: 0.4 wt%, : 2 mL); d XRD of gelatin-Ag–AuNPs film dried at room temperature under vacuum. Peaks marked with stars arise from gelatin organic phase.

Mentions: Bimetallic nanoparticles have recently attracted great research interests due to their potential applications in technologies such as catalysis, electronics and optical devices. The chemical and physical properties of bimetallic particles can be tuned not only by varying their size but also their composition. We synthesized Ag–Au bimetallic nanoparticles by using gelatin co-reduction action due to the fact that gelatin can be used as a reducing and stabilizing agent for gold and silver ion. Figure 12 showed that Au–Ag alloy clusters including isolated nanoparticles with different dimensions were embedded in gelatin polypeptide templates. Figure 12c showed Ag–Au clusters synthesized by using gelatin as a stabilizing and reducing agent are intermixed structures [35]. As the plasmon frequency of intermixed bimetallic clusters varies smoothly with composition between that of the pure Ag and pure Au clusters, the plasmon absorbance band of Ag–Au nanoparticles (Curve 2, 3 in Figure 12c) has been shifted to correspond with pure AgNPs (Curve 1) and AuNPs (Curve 4). Furthermore, Figure 12d showed the XRD pattern obtained for the Au–Ag nanoparticles-modified gelatin. Here, four different characteristic peaks obtained were Ag (110), Au (110), Au–Ag (111), Au–Ag (200). All these four XRD peaks clearly validate the presence of Au–Ag bimetallic nanoparticles [36]. And the XRD intensity of Au–Ag alloy nanoparticles decreased greatly compared to the single metal nanoparticles. This difference is mainly because atoms in Au–Ag alloy have insignificant deviations from an ideal fcc lattice [37].


Biomimetic Synthesis of Gelatin Polypeptide-Assisted Noble-Metal Nanoparticles and Their Interaction Study
a, b TEM images of gelatin-Ag–AuNPs with different ratios of silver to gold synthesized at 80°C. a nAg/nAu = 2.4, : 2 mL, : 1 mL; b nAg/nAg = 1.2, : 2 mL, : 2 mL, the inset in b is magnification of the image marked by pane in b; c UV–vis spectra of Ag–AuNPs, AgNPs and AuNPs. (1) AgNPs (Cgelatin: 0.4 wt%, : 2 mL), (2) Ag–AuNPs in Figure 12a, (3) Ag–AuNPs in Figure 12b, (4) AuNPs (Cgelatin: 0.4 wt%, : 2 mL); d XRD of gelatin-Ag–AuNPs film dried at room temperature under vacuum. Peaks marked with stars arise from gelatin organic phase.
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Figure 12: a, b TEM images of gelatin-Ag–AuNPs with different ratios of silver to gold synthesized at 80°C. a nAg/nAu = 2.4, : 2 mL, : 1 mL; b nAg/nAg = 1.2, : 2 mL, : 2 mL, the inset in b is magnification of the image marked by pane in b; c UV–vis spectra of Ag–AuNPs, AgNPs and AuNPs. (1) AgNPs (Cgelatin: 0.4 wt%, : 2 mL), (2) Ag–AuNPs in Figure 12a, (3) Ag–AuNPs in Figure 12b, (4) AuNPs (Cgelatin: 0.4 wt%, : 2 mL); d XRD of gelatin-Ag–AuNPs film dried at room temperature under vacuum. Peaks marked with stars arise from gelatin organic phase.
Mentions: Bimetallic nanoparticles have recently attracted great research interests due to their potential applications in technologies such as catalysis, electronics and optical devices. The chemical and physical properties of bimetallic particles can be tuned not only by varying their size but also their composition. We synthesized Ag–Au bimetallic nanoparticles by using gelatin co-reduction action due to the fact that gelatin can be used as a reducing and stabilizing agent for gold and silver ion. Figure 12 showed that Au–Ag alloy clusters including isolated nanoparticles with different dimensions were embedded in gelatin polypeptide templates. Figure 12c showed Ag–Au clusters synthesized by using gelatin as a stabilizing and reducing agent are intermixed structures [35]. As the plasmon frequency of intermixed bimetallic clusters varies smoothly with composition between that of the pure Ag and pure Au clusters, the plasmon absorbance band of Ag–Au nanoparticles (Curve 2, 3 in Figure 12c) has been shifted to correspond with pure AgNPs (Curve 1) and AuNPs (Curve 4). Furthermore, Figure 12d showed the XRD pattern obtained for the Au–Ag nanoparticles-modified gelatin. Here, four different characteristic peaks obtained were Ag (110), Au (110), Au–Ag (111), Au–Ag (200). All these four XRD peaks clearly validate the presence of Au–Ag bimetallic nanoparticles [36]. And the XRD intensity of Au–Ag alloy nanoparticles decreased greatly compared to the single metal nanoparticles. This difference is mainly because atoms in Au–Ag alloy have insignificant deviations from an ideal fcc lattice [37].

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Herein, the generation of gold, silver, and silver–gold (Ag–Au) bimetallic nanoparticles was carried out in collagen (gelatin) solution. It first showed that the major ingredient in gelatin polypeptide, glutamic acid, acted as reducing agent to biomimetically synthesize noble metal nanoparticles at 80°C. The size of nanoparticles can be controlled not only by the mass ratio of gelatin to gold ion but also by pH of gelatin solution. Interaction between noble-metal nanoparticles and polypeptide has been investigated by TEM, UV–visible, fluorescence spectroscopy, and HNMR. This study testified that the degradation of gelatin protein could not alter the morphology of nanoparticles, but it made nanoparticles aggregated clusters array (opposing three-dimensional α-helix folding structure) into isolated nanoparticles stabilized by gelatin residues. This is a promising merit of gelatin to apply in the synthesis of nanoparticles. Therefore, gelatin protein is an excellent template for biomimetic synthesis of noble metal/bimetallic nanoparticle growth to form nanometer-sized device.

No MeSH data available.


Related in: MedlinePlus