Superior Catalytic Performance of Gold Nanoparticles Within Small Cross-Linked Lysozyme Crystals

Abstract

Bionanomaterials synthesized by bio-inspired templating methods have emerged as a novel class of composite materials with varied applications in catalysis, detection, drug delivery, and biomedicine. In this study, two kinds of cross-linked lysozyme crystals (CLLCs) of different sizes were applied for the in situ growth of Au nanoparticles (AuNPs). The resulting composite materials were characterized by light microscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The catalytic properties of the prepared materials were examined in the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). It was found that the size of the AuNPs increased with an increase in Au loading for both small and large crystals. In addition, small crystals favored homogeneous adsorption and distribution of the metal precursors. And the size of the AuNPs within small crystals could be maintained below 2.5 nm by managing the HAuCl4/lysozyme molar ratio. Furthermore, the lysozyme functional groups blocked the AuNP activity sites, therefore reducing their catalytic activity. This effect was more pronounced for small AuNPs. Moreover, the mass transfer of reactants (4-NP) from solution to AuNPs within the crystals restricted their catalytic reduction, leading to superior catalytic performance of the AuNPs within small cross-linked lysozyme crystals (Au@S-CLLCs) compared to those within large cross-linked lysozyme crystals (Au@L-CLLCs) at similar Au loadings. Finally, an increase in Au loading clogged the crystal channels with increased quantities of larger aggregated AuNPs, thus impeding the catalytic performance of Au@S-CLLCs.

Mineralization and Self‐assembly of Gold Nanoparticles using Sulfur Amino Acid Modified Hierarchically Porous Metal‐Organic Frameworks

“…Gold nanoparticles are usually fixed on a carrier to prevent the gold nanoparticles from aggregating in the reaction and facilitate recycling. We used the gold nanoparticle‐loaded catalyst AuNP@HP‐UiO‐66‐C and AuNP@HP‐UiO‐66‐M to catalyze the reduction of 4‐nitrophenol (4‐NP) to 4‐aminophenol (4‐AP) [12] . In the reaction, 4‐NP can be adsorbed on the surface of gold nanoparticles, which can act as an electron transfer medium, transferring electrons from electron donor BH 4 ‐ to electron acceptor 4‐NP, thus reducing 4‐NP to 4‐AP.…”

“…We used the gold nanoparticle-loaded catalyst AuNP@HP-UiO-66-C and AuNP@HP-UiO-66-M to catalyze the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). [12] In the reaction, 4-NP can be adsorbed on the surface of gold nanoparticles, which can act as an electron transfer medium, transferring electrons from electron donor BH 4 to electron acceptor 4-NP, thus reducing 4-NP to 4-AP. 4-NP has a strong absorption peak at 400 nm, which can be detected by the UV-Vis spectrum.…”

Biomolecule‐Directed Carbon Nanotube Self‐Assembly

“…In particular, cross-linked lysozyme crystals (CLLCs) were prepared by encapsulating several metal and semiconducting NPs, with potential applications in catalysis, optical devices, and electron conduction. [105,106] A method was developed to incorporate a peptide-SWCNT hydrogel within CLLCs to take advantage of the strength and electronic conductivity of the SWCNTs at the macroscale. [100] First, SWCNTs were dispersed into a peptide hydrogel (Fmocdiphenylalanine) by a pH switch protocol.…”

Protein crystal based materials for nanoscale applications in medicine and biotechnology

“…To do this, they used cross‐linked lysozyme crystals to template the assembly of a synthetic hydrogel while monitoring the gel synthesis process and crystal stability via X‐ray diffraction. In addition to templating hydrogels, protein crystals have been used as molds during the synthesis of both quantum dots (Wei et al, ) and carbon dots (England, Patil, & Mann, ) with tunable fluorescence, or to grow and coordinate gold nanoclusters (Kowalski et al, ; Liang et al, ; M. Liu et al, ; Wei et al, ; Wei & Lu, ) and luminescent lanthanide complexes (Y. Zhang et al, ). There have been many other accounts of stabilized protein crystals being utilized as effective biotemplating scaffolds and catalytic vessels for the assembly of organometallic complexes and biohybrid materials.…”