6 research outputs found
Ice-Assisted Transfer of Carbon Nanotube Arrays
Decoupling the growth and the application
of nanomaterials by transfer
is an important issue in nanotechnology. Here, we developed an efficient
transfer technique for carbon nanotube (CNT) arrays by using ice as
a binder to temporarily bond the CNT array and the target substrate.
Ice makes it an ultraclean transfer because the evaporation of ice
ensures that no contaminants are introduced. The transferred superaligned
carbon nanotube (SACNT) arrays not only keep their original appearance
and initial alignment but also inherit their spinnability, which is
the most desirable feature. The transfer-then-spin strategy can be
employed to fabricate patterned CNT arrays, which can act as 3-dimensional
electrodes in CNT thermoacoustic chips. Besides, the flip-chipped
CNTs are promising field electron emitters. Furthermore, the ice-assisted
transfer technique provides a cost-effective solution for mass production
of SACNTs, giving CNT technologies a competitive edge, and this method
may inspire new ways to transfer other nanomaterials
Observation of Charge Generation and Transfer during CVD Growth of Carbon Nanotubes
Carbon
nanotube (CNT) is believed to be the most promising material for next
generation IC industries with the prerequisite of chirality specific
growth. For various approaches to controlling the chiral indices of
CNTs, the key is to deepen the understanding of the catalytic growth
mechanism in chemical vapor deposition (CVD). Here we show our discovery
that the as-grown CNTs are all negatively charged after Fe-catalyzed
CVD process. The extra electrons come from the charge generation and
transfer during the growth of CNTs, which indicates that an electrochemical
process happens in the surface reaction step. We then designed an
in situ measurement equipment, verifying that the CVD growth of CNTs
can be regarded as a primary battery system. Furthermore, we found
that the variation of the Fermi level in Fe catalysts have a significant
impact on the chirality of CNTs when different external electric fields
are applied. These findings not only provide a new perspective on
the growth of CNTs but also open up new possibilities for controlling
the growth of CNTs by electrochemical methods
Laser-Induced Flash-Evaporation Printing CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> Thin Films for High-Performance Planar Solar Cells
Organicâinorganic
hybrid perovskites have been emerging
as promising light-harvesting materials for high-efficiency solar
cells recently. Compared to solution-based methods, vapor-based deposition
technologies are more suitable in preparing compact, uniform, and
large-scale perovskite thin films. Here, we utilized flash-evaporation
printing (FEP), a laser-induced ultrafast single source evaporation
method employing a carbon nanotube evaporator, to fabricate high-quality
methylammonium lead iodide perovskite thin films. Stoichiometric films
with pure tetragonal perovskite phase can be achieved using a controlled
methylammonium iodide to lead iodide ratio in evaporation precursors.
The film crystallinity and crystal grain growth could further be promoted
after postannealing. Planar solar cells (0.06 cm<sup>2</sup>) employing
these perovskite films exhibit a champion power conversion efficiency
(PCE) of 16.8% with insignificant hysteresis, which is among the highest
reported PCEs using vapor-based deposition methods. Large-area (1
cm<sup>2</sup>) devices based on such perovskite films also achieved
a stabilized PCE of 11.2%, indicating the feasibility and scalability
of our FEP method in fabricating large-area perovskite films for other
optoelectronic applications
New Approach to Low-Power-Consumption, High-Performance Photodetectors Enabled by Nanowire Source-Gated Transistors
Power
consumption makes next-generation large-scale photodetection
challenging. In this work, the source-gated transistor (SGT) is adopted
first as a photodetector, demonstrating the expected low power consumption
and high photodetection performance. The SGT is constructed by the
functional sulfur-rich shelled GeS nanowire (NW) and low-function
metal, displaying a low saturated voltage of 0.61 V ± 0.29 V
and an extremely low power consumption of 7.06 pW. When the as-constructed
NW SGT is used as a photodetector, the maximum value of the power
consumption is as low as 11.96 nW, which is far below that of the
reported phototransistors working in the saturated region. Furthermore,
benefiting from the adopted SGT device, the photodetector shows a
high photovoltage of 6.6 Ă 10â1 V, a responsivity
of 7.86 Ă 1012 V Wâ1, and a detectivity
of 5.87 Ă 1013 Jones. Obviously, the low power consumption
and excellent responsivity and detectivity enabled by NW SGT promise
a new approach to next-generation, high-performance photodetection
technology
Vapor-Condensation-Assisted Optical Microscopy for Ultralong Carbon Nanotubes and Other Nanostructures
Here
we present a simple yet powerful approach for the
imaging
of nanostructures under an optical microscope with the help of vapor
condensation on their surfaces. Supersaturated water vapor will first
form a nanometer-sized water droplet on the condensation nuclei on
the surface of nanostructures, and then the water droplet will grow
bigger and scatter more light to make the outline of the nanostructure
be visible under dark-field optical microscope. This vapor-condensation-assisted
(VCA) optical microscopy is applicable to a variety of nanostructures
from ultralong carbon nanotubes to functional groups, generating images
with contrast coming from the difference in density of the condensation
sites, and does not induce any impurities to the specimens. Moreover,
this low-cost and efficient technique can be conveniently integrated
with other facilities, such as Raman spectroscope and so forth, which
will pave the way for widespread applications
Epitaxial Growth of Aligned and Continuous Carbon Nanofibers from Carbon Nanotubes
Exploiting the superior properties
of nanomaterials at macroscopic scale is a key issue of nanoscience.
Different from the integration strategy, âadditive synthesisâ
of macroscopic structures from nanomaterial templates may be a promising
choice. In this paper, we report the epitaxial growth of aligned,
continuous, and catalyst-free carbon nanofiber thin films from carbon
nanotube films. The fabrication process includes thickening of continuous
carbon nanotube films by gas-phase pyrolytic carbon deposition and
further graphitization of the carbon layer by high-temperature treatment.
As-fabricated nanofibers in the film have an âannual ringâ
cross-section, with a carbon nanotube core and a graphitic periphery,
indicating the templated growth mechanism. The absence of a distinct
interface between the carbon nanotube template and the graphitic periphery
further implies the epitaxial growth mechanism of the fiber. The mechanically
robust thin film with tunable fiber diameters from tens of nanometers
to several micrometers possesses low density, high electrical conductivity,
and high thermal conductivity. Further extension of this fabrication
method to enhance carbon nanotube yarns is also demonstrated, resulting
in yarns with âŒ4-fold increased tensile strength and âŒ10-fold
increased Youngâs modulus. The aligned and continuous features
of the films together with their outstanding physical and chemical
properties would certainly promote the large-scale applications of
carbon nanofibers