10 research outputs found
Controllable Synthesis of 2D Perovskite on Different Substrates and Its Application as Photodetector
Perovskites have recently attracted intense interests for optoelectronic devices application due to their excellent photovoltaic and photoelectric properties. The performance of perovskite-based devices highly depends on the perovskite material properties. However, the widely used spin-coating method can only prepare polycrystalline perovskite and physical vapor deposition (PVD) method requires a higher melting point (>350 °C) substrate due to the high growth temperature, which is not suitable for low melting point substrates, especially for flexible substrates. Here, we present the controlled synthesis of high quality two-dimensional (2D) perovskite platelets on random substrates, including SiO2/Si, Si, mica, glass and flexible polydimethylsiloxane (PDMS) substrates, and our method is applicable to any substrate as long as its melting point is higher than 100 °C. We found that the photoluminescence (PL) characteristics of perovskite depend strongly on the platelets thickness, namely, thicker perovskite platelet has higher PL wavelength and stronger intensity, and thinner perovskite exhibits opposite results. Moreover, photodetectors based on the as-produced perovskite platelets show excellent photoelectric performance with a high photoresponsivity of 8.3 A·W−1, a high on/off ratio of ~103, and a small rise and decay time of 30 and 50 ms, respectively. Our approach in this work provides a feasible way for making 2D perovskite platelets for wide optoelectronic applications
Insights from Genetic Model Systems of Retinal Degeneration: Role of Epsins in Retinal Angiogenesis and VEGFR2 Signaling.
The retina is a light sensitive tissue that contains specialized photoreceptor cells called rods and cones which process visual signals. These signals are relayed to the brain through interneurons and the fibers of the optic nerve. The retina is susceptible to a variety of degenerative diseases, including age-related macular degeneration (AMD), diabetic retinopathy (DR), retinitis pigmentosa (RP) and other inherited retinal degenerations. In order to reveal the mechanism underlying these diseases and to find methods for the prevention/treatment of retinal degeneration, animal models have been generated to mimic human eye diseases. In this paper, several well-characterized and commonly used animal models are reviewed. Of particular interest are the contributions of these models to our understanding of the mechanisms of retinal degeneration and thereby providing novel treatment options including gene therapy, stem cell therapy, nanomedicine, and CRISPR/Cas9 genome editing. Role of newly-identified adaptor protein epsins from our laboratory is discussed in retinal angiogenesis and VEGFR2 signaling
Structural engineering of two-dimensional black phosphorus towards advanced photonic integrated circuits
Structural engineering is crucial for tuning the properties of artificial materials. As one of the most important two-dimensional (2D) materials, black phosphorus (BP) has been rediscovered in 2014 and attracted tremendous attentions all over the world. It shows great potentials in optoelectronic and integrated photonic applications due to the direct and tunable bandgap, high carrier mobility, and intrinsic anisotropy. However, some deficiencies are yet to be settled before its large-scale applications, such as the massive synthesis methods and structure–property relationship. To investigate the influence of structural engineering on the performance of 2D BP-based devices thoroughly, recent studies on deformation, atomic defects, superlattice, alloying, thickness and phase transition are maximality summarized in this review covering from the intrinsic properties to optoelectronic applications. Benefiting from the broad research in this field, challenges and opportunities of 2D BP for advanced integrated photonic applications are also provided, which supplies a useful reference to realize large-scale 2D BP-based all-optical communications in future
Fractal Etching of Graphene
An
anisotropic etching mode is commonly known for perfect crystalline
materials, generally leading to simple Euclidean geometric patterns.
This principle has also proved to apply to the etching of the thinnest
crystalline material, graphene, resulting in hexagonal holes with
zigzag edge structures. Here we demonstrate for the first time that
the graphene etching mode can deviate significantly from simple anisotropic
etching. Using an as-grown graphene film on a liquid copper surface
as a model system, we show that the etched graphene pattern can be
modulated from a simple hexagonal pattern to complex fractal geometric
patterns with sixfold symmetry by varying the Ar/H<sub>2</sub> flow
rate ratio. The etched fractal patterns are formed by the repeated
construction of a basic identical motif, and the physical origin of
the pattern formation is consistent with a diffusion-controlled process.
The fractal etching mode of graphene presents an intriguing case for
the fundamental study of material etching
Graphene–Bi<sub>2</sub>Te<sub>3</sub> Heterostructure as Saturable Absorber for Short Pulse Generation
Rapid
progresses have been achieved in the photonic applications
of two-dimensional materials such as graphene, transition metal dichalcogenides,
and topological insulators. The strong light–matter interactions
and large optical nonlinearities in these atomically thin layered
materials make them promising saturable absorbers for pulsed laser
applications. Either Q-switching or mode-locking pulses with particular
output characteristics can be achieved by using different saturable
absorbers. However, it remains still very challenging to produce saturable
absorbers with tunable optical properties, in particular, carrier
dynamics, saturation intensity as well as modulation depth, to suit
for self-starting, high energy or ultrafast pulse laser generation.
Here we report a new type of saturable absorber which is a van der
Waals heterostructure consisting of graphene and Bi<sub>2</sub>Te<sub>3</sub>. The synergetic integration of these two materials by epitaxial
growth affords tunable optical properties, that is, both the photocarrier
dynamics and the nonlinear optical modulation are variable by tuning
the coverage of Bi<sub>2</sub>Te<sub>3</sub> on graphene. We further
fabricated graphene–Bi<sub>2</sub>Te<sub>3</sub> saturable
absorbers and incorporated them into a 1.5 μm fiber laser to
demonstrate both Q-switching and mode-locking pulse generation. This
work provides a new insight for tailoring two-dimensional heterostructures
so as to develop desired photonic applications
Two-Dimensional CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> Perovskite: Synthesis and Optoelectronic Application
Hybrid organic–inorganic perovskite
materials have received
substantial research attention due to their impressively high performance
in photovoltaic devices. As one of the oldest functional materials,
it is intriguing to explore the optoelectronic properties in perovskite
after reducing it into a few atomic layers in which two-dimensional
(2D) confinement may get involved. In this work, we report a combined
solution process and vapor-phase conversion method to synthesize 2D
hybrid organic–inorganic perovskite (<i>i.e.</i>,
CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub>) nanocrystals as thin
as a single unit cell (∼1.3 nm). High-quality 2D perovskite
crystals have triangle and hexagonal shapes, exhibiting tunable photoluminescence
while the thickness or composition is changed. Due to the high quantum
efficiency and excellent photoelectric properties in 2D perovskites,
a high-performance photodetector was demonstrated, in which the current
can be enhanced significantly by shining 405 and 532 nm lasers, showing
photoresponsivities of 22 and 12 AW<sup>–1</sup> with a voltage
bias of 1 V, respectively. The excellent optoelectronic properties
make 2D perovskites building blocks to construct 2D heterostructures
for wider optoelectronic applications