Self-assembly of gibberellic amide assemblies and their applications in the growth and fabrication of ordered gold nanoparticles

Novel TiO2-Supported Gold Nanoflowers for Efficient Photocatalytic NOx Abatement

In this study, we pioneered the synthesis of nanoflower-shaped TiO2-supported Au photocatalysts and investigated their properties. Au nanoflowers (Au NFs) were prepared by a Na-citrate and hydroquinone-based preparation method, followed by wet impregnation of the derived Au NFs on the surface of TiO2 nanorods (TNR). A uniform and homogeneous distribution of Au NFs was observed in the TNR + NF(0.7) sample (lower Na-citrate concentration), while their distribution was heterogeneous in the TNR + NF(1.4) sample (higher Na-citrate concentration). The UV-Vis DR spectra revealed the size- and shape-dependent optical properties of the Au NFs, with the LSPR effect observed in the visible region. The solid-state EPR spectra showed the presence of Ti3+, oxygen vacancies and electron interactions with organic compounds on the catalyst surface. In the case of the TNR + NF(0.7) sample, high photocatalytic activity was observed in the H2-assisted reduction of NO2 to N2 at room temperature under visible-light illumination. In contrast, the TNR + NF(1.4) catalyst as well as the heat-treated samples showed no ability to reduce NO2 under visible light, indicating the presence of deformed Au NFs limiting the LSPR effect. These results emphasized the importance of the choice of synthesis method, as this could strongly influence the photocatalytic activity of the Au NFs.

Chitosan nanoparticles as carrier systems for the plant growth hormone gibberellic acid

This work concerns the development of nanocarriers composed of alginate/chitosan (ALG/CS) and chitosan/tripolyphosphate (CS/TPP) for the plant growth regulator gibberellic acid (GA₃). ALG/CS nanoparticles with and without GA₃ presented mean size of 450±10nm, polydispersity index (PDI) of 0.3, zeta potential of -29±0.5mV, concentrations of 1.52×10¹¹ and 1.92×10¹¹ nanoparticles mL^-1, respectively, and 100% encapsulation efficiency. CS/TPP nanoparticles with and without GA₃ presented mean size of 195±1nm, PDI of 0.3, zeta potential of +27±3mV, concentrations of 1.92×10¹² and 3.54×10¹² nanoparticles mL^-1, respectively, and 90% encapsulation efficiency. The nanoparticles were stable during 60days and the two systems differed in terms of the release mechanism, with the release depending on factors such as pH and temperature. Bioactivity assays using Phaseolus vulgaris showed that the ALG/CS-GA₃ nanoparticles were most effective in increasing leaf area and the levels of chlorophylls and carotenoids. The systems developed showed good potential, providing greater stability and efficiency of this plant hormone in agricultural applications.

ELLAGIC ACID DIRECTED GROWTH OF Au–Pt BIMETALLIC NANOPARTICLES AND THEIR CATALYTIC APPLICATIONS

In this work, we report the facile formation of bimetallic nanoparticles of Au–Pt in the presence of the plant polyphenol ellagic acid (EA). It was found that EA formed micro-fibrillar assemblies, which aggregated into micro-bundles under aqueous conditions. Those micro-bundles acted as templates for the growth of Au nanoparticles, as well as bimetallic Au–Pt nanoparticles biomimetically. At higher concentrations of EA, it was observed that in addition to forming fibrous micro-bundles, columnar assemblies of EA were formed in the presence of the metal nanoparticles. The formation of the assemblies was found to be concentration dependent. It appears that upon binding to metal ions and subsequent formation of the nanoparticles, morphological changes occur in the case of EA assemblies. The morphological changes observed were probed by electron microscopy. Further, the ability of the materials to degrade the toxic aromatic nitro compound 2-methoxy-4-nitroaniline was explored, where 50% degradation was observed within 15 min, indicating that such hybrid materials may have potential applications in environmental remediation.