Photodetectors with ultrahigh sensitivity based on the composite made with all carbon-based materials consisting of graphite quantum dots (QDs), and two dimensional graphene crystal have been demonstrated. Under light illumination, remarkably, a photocurrent responsivity up to 4 × 107 AW−1 can be obtained. The underlying mechanism is attributed to the spatial separation of photogenerated electrons and holes due to the charge transfer caused by the appropriate band alignment across the interface between graphite QDs and graphene. Besides, the large absorptivity of graphite QDs and the excellent conductivity of the graphene sheet also play significant roles. Our result therefore demonstrates an outstanding illustration for the integration of the distinct properties of nanostructured carbon materials with different dimensionalities to achieve highly efficient devices. Together with the associated mechanism, it paves a valuable step for the further development of all carbon-based, cheap, and non-toxic optoelectronics devices with excellent performance.
We report the first attempt at magnetic manipulation of the photoresponse in a one-dimensional device in which a highly sensitive ultraviolet photodetector, composed of tin dioxide nanowire (SnO 2 NW) and ferromagnetic nickel (Ni) electrodes, has been fabricated and characterized. Surprisingly, as the Ni electrodes were magnetized, the photocurrent gain was greatly enhanced by up to 20 times, which is far beyond all of the previously reported enhancement factors for functionalized NW photodetectors. The underlying mechanism enabling the enhanced gain is attributed to both oxygen molecules adsorbed and surface band-bending effects due to the migration of electrons to the surface of SnO 2 NW caused by the magnetic field of ferromagnetic electrodes. The novel approach presented here can provide a new route for the creation of highly efficient optoelectronic devices based on the coupling between ferromagnetic materials and nanostructured semiconductors.
Electric
vehicles (EVs) are poised to dominate the next generation
of transportation, but meeting the power requirements of EVs with
lithium ion batteries is challenging because electrolytes containing
LiPF6 and carbonates do not perform well at high temperatures
and voltages. However, lithium benzimidazole salt is a promising electrolyte
additive that can stabilize LiPF6 through a Lewis acid–base
reaction. The imidazole ring is not eligible for high-voltage applications
owing to its resonance structure, but in this research, electron-withdrawing
(−CF3) and electron-donating (−CH3) substitutions on imidazole rings were investigated. According to
the calculation results, the CF3 substitution facilitates
a high electron cloud density on imidazole ring structures to resist
the electron releases from bezimidazole in oxidation reactions. In
addition, through CF3 substitution, electrons are accepted
from the lattice oxygen (O2–) in lithium-rich layer
material and O– is converted by an electron released.
The O– is then adsorbed with the ethylene carbonate
and catalyzed to alkyl carbonate by Ni2+. The −CF3 substituted benzimidazole triggers a further reaction with
alkyl carbonate and forms a new polyionic liquid solid electrolyte
interphase on the cathode’s surface. Furthermore, the cycle
performance tested at 60 °C and 4.8 V showed that the CF3 substitution maintains the battery retention effectively
and exhibits almost no fading compared with both the blank electrolyte
and the CH3 substitution.
Via the integration of nanocomposites comprising I-III-VI semiconductor quantum dots (QDs) decorated onto a single SnO2 nanowire (NW), we successfully fabricate an ultrahigh-sensitivity and wide spectral-response photodetector. Under the illumination of He-Cd laser (325 nm) with the photon energy larger than the band gap of SnO2 nanowire, remarkably, an ultrahigh photocurrent gain up to 2.5 × 10(5) has been achieved, and an enhancement factor can reach up to 700% (cf. bare SnO2 NW) as light illumination onto the wire with an excitation intensity of 15 W/m(2). Also, a high gain value up to 1.3 × 10(5) is attained with the excited photon energy (488 nm) smaller than the band gap of SnO2 nanowire. Several key factors contribute to ultrahigh photocurrent gain and wide spectral response. First, the decorated quantum dot processes an inherent nature of a large absorption coefficient above its band gap. Furthermore, the single SnO2 nanowire provides an excellent conduction path for the photogenerated carriers as well as bears a large surface-to-volume ratio so that the coupling strength with quantum dots can be greatly enhanced. Most importantly, the spatial separation of photogenerated electrons and holes can be easily achieved due to the charge transfer arising from a type II band alignment between QDs and SnO2 NW. This work thus demonstrates a new approach in which by selectively decorating suitable QDs the photocurrent gain of SnO2 NWs can be greatly enhanced and extended to a wide spectral range of photoresponse previously inaccessible, providing a very useful guideline to create cheap, nontoxic, and highly efficient photodetectors.
A series of nanocrystalline
titanium (Ti) sub-oxides, including
TiO, Ti2O3, Ti3O5, and
Ti4O7, with high surface area and activity are
successively synthesized using a facile synthesis method that combines
the sol–gel and the energy-efficient vacuum-carbothermic (SG-VC)
processes. The combination results in synergy in producing nanomaterials
with high surface area (>100 m2 g–1),
good conductivity, and rich intra-grain defect features, giving the
oxides unique surface activities suitable for particular electrochemical
applications. The phase compositions of the resulting powders are
primarily determined by two process parameters, including the carbothermic
carbon (C) content, expressed as the C-to-Ti molar ratio of the reactant
powder, and the cooling protocol. Carbothermic C contents exceeding
a threshold of C/Ti ∼ 3.7 exclusively produced non-Magnéli
phase (MP) oxides including TiO and Ti2O3, while
the MP oxides, Ti3O5 and Ti4O7, can be formed only with lower C contents combined with selected
quenching protocols that kinetically limit oxygen replenishment during
cooling. Examples of the resulting MP Ti4O7 powder
exhibiting outstanding pseudocapacitive and oxygen evolution reaction
catalytic behaviors are demonstrated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.