4 research outputs found
One-Step Synthesis of Antioxidative Graphene-Wrapped Copper Nanoparticles on Flexible Substrates for Electronic and Electrocatalytic Applications
In
this study, we report a novel, one-step synthesis method to fabricate
multilayer graphene (MLG)-wrapped copper nanoparticles (CuNPs) directly
on various substrates (e.g., polyimide film (PI), carbon cloth (CC),
or Si wafer (Si)). The electrical resistivities of the pristine MLG-CuNPs/PI
and MLG-CuNPs/Si were measured 1.7 × 10<sup>–6</sup> and
1.4 × 10<sup>–6</sup> Ω·m, respectively, of
which both values are ∼100-fold lower than earlier reports.
The MLG shell could remarkably prevent the Cu nanocore from serious
damages after MLG-CuNPs being exposed to various harsh conditions.
Both MLG-CuNPs/PI and MLG-CuNPs/Si retained almost their conductivities
after ambient annealing at 150 °C. Furthermore, the flexible
MLG-CuNPs/PI exhibits excellent mechanical durability after 1000 bending
cycles. We also demonstrate that the MLG-CuNPs/PI can be used as promising
source-drain electrodes in fabricating flexible graphene-based field-effect
transistor (G-FET) devices. Finally, the MLG-CuNPs/CC was shown to
possess high performance and durability toward hydrogen evolution
reaction (HER)
Growth of Large-Area Graphene Single Crystals in Confined Reaction Space with Diffusion-Driven Chemical Vapor Deposition
To synthesize large-area graphene
single crystals, we specifically
designed a low-pressure chemical vapor deposition (LPCVD) reactor
with confined reaction space (L 22 mm × W 13 mm × H 50 μm).
Within the confined reaction space, a uniform distribution of reactant
concentrations, reduced substrate roughness, and the shift of growth
kinetics toward a diffusion-limited regime can be achieved, favoring
the preparation of large-area, high-quality graphene single crystals.
The gas flow field and mass transport pattern of reactants in the
LPCVD system simulated with a finite element method support the advantages
of using this confined reaction room for graphene growth. Using this
space-confined reactor together with the optimized synthesis parameters,
we obtained monolayer, highly uniform, and defect-free graphene single
crystals of up to ∼0.8 mm in diameter with the field-effect
mobility of μ<sub>EF</sub> ∼ 4800 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup> at room temperature. In addition,
structural design of the confined reaction space by adjusting the
reactor’s dimensions is of facile controllability and scalability,
which demonstrates the superiority and preference of this method for
industrial applications
The Effects of Fluorine-Contained Molecules on Improving the Polymer Solar Cell by Curing the Anomalous S‑Shaped <i>I</i>–<i>V</i> Curve
In this study, we investigate the
effects of fluorinated polyÂ(3,4-ethylene dioxythiophene):polyÂ(styrenesulfonate)
buffer layer on the performance of polymer photovoltaic cells. We
demonstrate for the first time, the deterioration of the device performance
can be effectively mended by modifying the interface between the active
layer and buffer layer with heptadecafluoro-1,1,2,2-tetra-hydro-decyl
trimethoxysilane (PFDS) and perfluorononane. Device performance shows
a substantial enhancement of short-circuit current from 7.90 to 9.39
mA/cm<sup>2</sup> and fill factor from 27% to 53%. The overall device
efficiency was improved from 0.98% to 3.12% for PFDS modified device.
The mechanism of S-shape curing is also discussed. In addition, the
stability of modified devices shows significant improvement than those
without modification. The efficiency of the modified devices retains
about half (1.88%) of its initial efficiency (4.1%) after 30 d compared
to the unmodified ones (0.61%), under air atmosphere
High <i>K</i> Nanophase Zinc Oxide on Biomimetic Silicon Nanotip Array as Supercapacitors
A 3D trenched-structure metal–insulator–metal
(MIM)
nanocapacitor array with an ultrahigh equivalent planar capacitance
(EPC) of ∼300 μF cm<sup>–2</sup> is demonstrated.
Zinc oxide (ZnO) and aluminum oxide (Al<sub>2</sub>O<sub>3</sub>)
bilayer dielectric is deposited on 1 μm high biomimetic silicon
nanotip (SiNT) substrate using the atomic layer deposition method.
The large EPC is achieved by utilizing the large surface area of the
densely packed SiNT (∼5 × 10<sup>10</sup> cm<sup>–2</sup>) coated conformally with an ultrahigh dielectric constant of ZnO.
The EPC value is 30 times higher than those previously reported in
metal–insulator–metal or metal–insulator–semiconductor
nanocapacitors using similar porosity dimensions of the support materials