5 research outputs found
Small Nanosized Oxygen-Deficient Tungsten Oxide Particles: Mechanistic Investigation with Controlled Plasma Generation in Water for Their Preparation
Formation and Optical Properties of Fluorescent Gold Nanoparticles Obtained by Matrix Sputtering Method with Volatile Mercaptan Molecules in the Vacuum Chamber and Consideration of Their Structures
This
paper proposes a novel methodology to synthesize highly fluorescent
gold nanoparticles (NPs) with a maximum quantum yield of 16%, in the
near-infrared (IR) region. This work discusses the results of using
our (previously developed) matrix sputtering method to introduce mercaptan
molecules, Ī±-thioglycerol, inside the vacuum sputtering chamber,
during the synthesis of metal NPs. The evaporation of Ī±-thioglycerol
inside the chamber enables to coordinate to the ānucleation
stageā very small gold nanoclusters in the gas phase, thus
retaining their photophysical characteristics. As observed through
transmission electron microscopy, the size of the Au NPs obtained
with the addition of Ī±-thioglycerol varied from approximately
2ā3 nm to approximately 5 nm. Plasmon absorption varied with
the size of the resultant nanoparticles. Thus, plasmon absorption
was observed at 2.4 eV in the larger NPs. However, it was not observed,
and instead a new peak was found at approximately 3.4 eV, in the smaller
NPs that resulted from the introduction of Ī±-thioglycerol. The
Au NPs stabilized by the Ī±-thioglycerol fluoresced at approximately
1.8 eV, and the maximum wavelength shifted toward the red, in accordance
with the size of the NPs. A maximum fluorescent quantum yield of 16%
was realized under the optimum conditions, and this value is extremely
high compared to values previously reported on gold NPs and clusters
(generally ā¼1%). To our knowledge, however, Au NPs of size
>2 nm usually do not show strong fluorescence. By comparison with
results reported in previous literature, it was concluded that these
highly fluorescent Au NPs consist of goldāmercaptan complexes.
The novel method presented in this paper therefore opens a new door
for the effective control of size, photophysical characteristics,
and structure of metal NPs. It is hoped that this research contributes
significantly to the science in this field
Small Nanosized Oxygen-Deficient Tungsten Oxide Particles: Mechanistic Investigation with Controlled Plasma Generation in Water for Their Preparation
Production of oxygen-deficient tungsten
oxide nanoparticles with
a diameter of around 10 nm have been successfully developed using
a microwave-induced plasma in liquid technique. The prepared blue-green
nanoparticles exhibit strong absorption in the visible region; thus,
these could be efficient visible-light photocatalysts. The high-angle
annular dark-field images revealed the dislocation of tungsten, which
causes oxygen deficiencies