8 research outputs found
Colloidal Synthesis of Wurtzite Cu<sub>2</sub>ZnSnS<sub>4</sub> Nanorods and Their Perpendicular Assembly
The quaternary copper chalcogenide Cu<sub>2</sub>ZnSnS<sub>4</sub> is an important emerging material for the development of
low-cost
and sustainable solar cells. Here we report a facile solution synthesis
of stoichiometric Cu<sub>2</sub>ZnSnS<sub>4</sub> in size-controlled
nanorod form (11 nm × 35 nm). The monodisperse nanorods have
a band gap of 1.43 eV and can be assembled into perpendicularly aligned
arrays by controlled evaporation from solution
Investigations into the Electrochemical, Surface, and Electrocatalytic Properties of the Surface-Immobilized Polyoxometalate, TBA<sub>3</sub>K[SiW<sub>10</sub>O<sub>36</sub>(PhPO)<sub>2</sub>]
Surface anchoring of an organic functionalized
POM, TBA<sub>3</sub>KÂ[SiW<sub>10</sub>O<sub>36</sub>(PhPO)<sub>2</sub>] was carried out
by two methods, the layer-by-layer (LBL) assembly technique by employing
a pentaerythritol-based rutheniumÂ(II) metallodendrimer as a cationic
moiety and also by entrapping the POM in a conducting polypyrrole
film. The redox behavior of the constructed films was studied by using
cyclic voltammetry and electrochemical impedance spectroscopy. The
surface morphologies of the constructed multilayers were examined
by scanning electron microscopy and atomic force microscopy. X-ray
photoelectron spectroscopy was conducted to confirm the elements present
within the fabricated films. The multilayer assembly was also investigated
for its catalytic efficiency towards the reduction of nitrite
Biomineralization Mechanism of Gold by Zygomycete Fungi Rhizopous oryzae
In recent years, there has been significant progress in the biological synthesis of nanomaterials. However, the molecular mechanism of gold biomineralization in microorganisms of industrial relevance remains largely unexplored. Here we describe the biosynthesis mechanism of gold nanoparticles (AuNPs) in the fungus Rhizopus oryzae. Reduction of AuCl<sub>4</sub><sup>–</sup> [Au(III)] to nanoparticulate Au<sup>0</sup> (AuNPs) occurs in both the cell wall and cytoplasmic region of R. oryzae. The average size of the as-synthesized AuNPs is ∼15 nm. The biomineralization occurs through adsorption, initial reduction to Au(I), followed by complexation [Au(I) complexes], and final reduction to Au<sup>0</sup>. Subtoxic concentrations (up to 130 μM) of AuCl<sub>4</sub><sup>–</sup> in the growth medium increase growth of R. oryzae and induce two stress response proteins while simultaneously down-regulating two other proteins. The induction increases mycelial growth, protein yield, and AuNP biosynthesis. At higher Au(III) concentrations (>130 μM), both mycelial and protein yield decrease and damages to the cellular ultrastructure are observed, likely due to the toxic effect of Au(III). Protein profile analysis also confirms the gold toxicity on R. oryzae at high concentrations. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis shows that two proteins of 45 and 42 kDa participate in gold reduction, while an 80 kDa protein serves as a capping agent in AuNP biosynthesis
Selective Phase Transformation of Wurtzite Cu<sub>2</sub>ZnSn(SSe)<sub>4</sub> (CZTSSe) Nanocrystals into Zinc-Blende and Kesterite Phases by Solution and Solid State Transformations
A wide range of physical properties
from optoelectronic (e.g.,
band gap) to structural (e.g., hardness) can be affected without changing
the composition of a solid but just by altering the crystal phase.
Here, we report a selective structural phase transition of metastable
wurtzite CZTSSe nanocrystals into more stable phases such as zinc
blende and kesterite using solution and solid state transformations,
respectively. The phase transformation pathways are selective, with
the wurtzite to zinc-blende transition not occurring because of thermal
annealing or the wurtzite to kesterite transition because of solution
transformation. We show the importance of both ligand chemistry and
temperature to lowering the barrier for rapid conversion from one
phase to another in this system. The phase transitions are accompanied
by changes in the band gap with values for each calculated by cyclic
voltammetry
High Density Growth of Indium seeded Silicon Nanowires in the Vapor phase of a High Boiling Point Solvent
Herein, we describe the growth of Si nanowires (NWs)
in the vapor
phase of an organic solvent medium on various substrates (Si, glass,
and stainless steel) upon which an indium layer was evaporated. Variation
of the reaction time allowed NW length and density to be controlled.
The NWs grew via a predominantly root-seeded mechanism with discrete
In catalyst seeds formed from the evaporated layer. The NWs and substrates
were characterized using transmission electron microscopy (TEM), scanning
electron microscopy (SEM), X-ray diffraction (XRD), scanning transmission
electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX),
and X-ray photoelectron spectroscopy (XPS). The suitability of the
indium seeded wires as anode components in Li batteries was probed
using cyclic voltammetric (CV) measurements. The route represents
a versatile, glassware-based method for the formation of Si NWs directly
on a variety of substrates
Silver-Modified η‑Al<sub>2</sub>O<sub>3</sub> Catalyst for DME Production
Herein,
an in situ DRIFT technique was used to study the reaction
mechanism of methanol dehydration to dimethyl ether (DME). Moreover,
the effect of silver loading on the catalytic performance of η-Al<sub>2</sub>O<sub>3</sub> was examined in a fixed bed reactor under the
reaction conditions where the temperature ranged from 180 to 300 °C
with a WHSV = 48.4 h<sup>–1</sup>. It was observed that the
optimum Ag loading was found to be 10% Ag/η-Al<sub>2</sub>O<sub>3</sub> with this novel catalyst also showing a high degree of stability
under steady-state conditions, and this is attributed to the enhancement
in both the surface Lewis acidity and the hydrophobicity
Silver-Modified η‑Al<sub>2</sub>O<sub>3</sub> Catalyst for DME Production
Herein,
an in situ DRIFT technique was used to study the reaction
mechanism of methanol dehydration to dimethyl ether (DME). Moreover,
the effect of silver loading on the catalytic performance of η-Al<sub>2</sub>O<sub>3</sub> was examined in a fixed bed reactor under the
reaction conditions where the temperature ranged from 180 to 300 °C
with a WHSV = 48.4 h<sup>–1</sup>. It was observed that the
optimum Ag loading was found to be 10% Ag/η-Al<sub>2</sub>O<sub>3</sub> with this novel catalyst also showing a high degree of stability
under steady-state conditions, and this is attributed to the enhancement
in both the surface Lewis acidity and the hydrophobicity
Surface Immobilization of a Tetra-Ruthenium Substituted Polyoxometalate Water Oxidation Catalyst Through the Employment of Conducting Polypyrrole and the Layer-by-Layer (LBL) Technique
A tetra Ru-substituted polyoxometalate
Na<sub>10</sub>[{Ru<sub>4</sub>O<sub>4</sub>(OH)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>}Â(γ-SiW<sub>10</sub>O<sub>36</sub>)<sub>2</sub>] (Ru<sub>4</sub>POM) has been successfully immobilised onto
glassy carbon electrodes and indium tin oxide (ITO) coated glass slides
through the employment of a conducting polypyrrole matrix and the
layer-by-layer (LBL) technique. The resulting Ru<sub>4</sub>POM doped
polypyrrole films showed stable redox behavior associated with the
Ru centres within the Ru<sub>4</sub>POM, whereas, the POM’s
tungsten-oxo redox centres were not accessible. The films showed pH
dependent redox behavior within the pH range 2–5 whilst exhibiting
excellent stability towards redox cycling. The layer-by-layer assembly
was constructed onto polyÂ(diallyldimethylammonium chloride) (PDDA)
modified carbon electrodes by alternate depositions of Ru<sub>4</sub>POM and a RuÂ(II) metallodendrimer. The resulting Ru<sub>4</sub>POM
assemblies showed stable redox behavior for the redox processes associated
with Ru<sub>4</sub>POM in the pH range 2–5. The charge transfer
resistance of the LBL films was calculated through AC-Impedance. Surface
characterization of both the polymer and LBL Ru<sub>4</sub>POM films
was carried out using atomic force microscopy (AFM), X-ray photoelectron
spectroscopy (XPS), and scanning electron microscopy (SEM). Initial
investigations into the ability of the Ru<sub>4</sub>POM LBL films
to electrocatalytically oxidise water at pH 7 have also been conducted