Narrow Results

In this paper, the effect of dewetted gold nanoparticles (AuNPs) on hexagonal boron nitride (hBN) is discussed along with the changes in surface plasmon resonance (SPR). Au is sputtered on monolayer hBN/SiO₂/Si substrate for a varied duration and subjected to thermal annealing. Monolayer hBN is verified by spectroscopic ellipsometry using the Tauc–Lorentz model, while the AuNPs are modeled using a combination of Gauss, Cody–Lorentz, and Tanguy dispersion laws. Sputtering of Au on hBN/SiO₂/Si results in a film-like layer compared to the one on SiO₂/Si. Before annealing, the improved uniformity of Au on hBN/SiO₂/Si diminished the SPR wavelength, ${\lambda }_{\mathrm{\text{spr}}}$, when the sputter duration exceeded 30 s, much sooner compared to 120 s from the one on SiO₂/Si. After annealing, the ${\lambda }_{\mathrm{\text{spr}}}$ is vibrant for all samples around 2.3 eV. Au dewetted more on hBN due to higher surface tension. Large dewetted AuNPs supported by hBN result in higher photon extinction at ${\lambda }_{\mathrm{\text{spr}}}$. The longest sputter duration of 120 s on hBN/SiO₂/Si (mean size 53 nm) exhibited an 11.2% higher extinction coefficient compared to the one on SiO₂/Si (mean size 39.6 nm). Findings support the advantages of preparing plasmonic AuNPs by dewetting on monolayer hBN.

In this study, gold nanoparticles were synthesized in a single step biosynthetic method using aqueous leaves extract of thymus vulgaris L. It acts as a reducing and capping agent. The characterizations of nanoparticles were carried out using UV-Visible spectra, X-ray diffraction (XRD) and FTIR. The surface plasmon resonance of the as-prepared gold nanoparticles (GNPs) showed the surface plasmon resonance centered at 550nm. The XRD pattern showed that the strong four intense peaks indicated the crystalline nature and the face centered cubic structure of the gold nanoparticles. The average crystallite size of the AuNPs was 14.93nm. Field emission scanning electron microscope (FESEM) was used to study the morphology of the AuNPs. AuNPs exhibited a spherical shape with diameters ranging 13–53nm. The synthesized stable gold nanoparticles showed more significant anticancer activity against MCF-7 and CAL-51 cells after 48h.

In this paper, homogenous gold nanoparticles (AuNPs) with a high density and a narrow size distribution were successfully fabricated on titanate nanowires (TNWs) scaffolds in the absence of organic capping agents. An ameliorated low-temperature hydrothermal method was used to prepare the TNWs scaffolds like bird's nest on the Ti substrate, and the nanowires diameter was about 30–80nm. Then, AuNPs were synthesized on the TNWs scaffolds with a deposition–precipitation urea (DPU) method. The TEM and XRD measurements indicated that well-crystallized face-centered cubic (fcc) AuNPs were homogeneously dispersed on TNWs, and AuNPs with average sizes of 2.7 nm and 4 nm were obtained, respectively for the theoretical gold loading 5 wt.% and 8 wt.%. Inspiringly, the 8%-AuNPs/TNWs catalyst could reduce 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) within 210 s, and exhibited better catalytic reduction performance than that of 5%-AuNPs/TNWs.

A novel sensitive and elective electrochemical sensor was developed to detect methyl parathion (MP) based on a glassy carbon electrode (GCE) modified with gold nanoparticles (AuNPs)/graphene nanocomposites film. The AuNPs were modified onto graphene sheets using NaBH₄ as a reductant. The obtained AuNPs/graphene nanocomposites were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical behavior of MP and interference studies were then investigated. Compared with metal ions and nitroaromatic compounds, which exist in environmental samples, the AuNPs/graphene/GCE exhibited high adsorption and strong affinity toward MP. Under optimized conditions, the oxidation peak current of MP was linear to its concentration within the range of 4.0 × 10^-7–8.0 × 10^-5 M, with a detection limit (S/N = 3) of 8.5 × 10^-8 M. These results indicated that the AuNPs/graphene nanocomposites displayed a synergic effect involving the catalytic characteristics of graphene and AuNPs nanocomposites, which can effectively improve the electrochemical properties of MP. Furthermore, the AuNPs also enhanced sensor sensitivity to MP. Therefore, the AuNPs/graphene/GCE could be a promising sensor for the fast, sensitive and selective detection of MP in real samples.