Phys.org June 2, 2022 Single-molecule devices provide a reliable platform for exploration of the intrinsic properties of matters at the single-molecule level. The regulation of the electrical properties of single-molecule devices will be a key factor in enabling further advances in the development of molecular electronics. In this review article researchers in China introduce the optoelectronic effects that are involved in single-molecule devices, including photoisomerization switching, photoconductance, plasmon-induced excitation, photovoltaic effect, and electroluminescence. They summarize the optoelectronic mechanisms of single-molecule devices, with particular emphasis on the photoisomerization, photoexcitation, and photo-assisted tunneling processes. Discussion on the opportunities and challenges arising in […]
Tag Archives: S&T China
Generating ultra-violet lasers with near-infrared light through ‘domino upconversion’ of nanoparticles
Phys.org May 19, 2022 Direct ultraviolet lasing is constrained by the fabrication challenge and operation cost. Researchers in China have developed a strategy for the indirect generation of deep-ultraviolet lasing through a tandem upconversion process. They developed a core–shell–shell nanoparticle to achieve deep-ultraviolet emission at 290 nm by excitation in the telecommunication wavelength range at 1550 nm. The ultra large anti-Stokes shift of 1260 nm (~3.5 eV) stems from a tandem combination of distinct upconversion processes that are integrated into separate layers of the core–shell–shell structure. By incorporating the core–shell–shell nanoparticles as gain media into a toroid microcavity, single-mode lasing at 289.2 nm was realized […]
Release of two new datasets related to climate in Central Asia
Phys.org May 23, 2022 Researchers in China have derived a high-resolution (9 km) climate projection dataset over Central Asia (HCPD-CA) from dynamically downscaled results based on multiple bias-corrected global climate models. It contains four geostatic variables and 10 meteorological elements that are widely used to drive ecological and hydrological models. The reference and future periods are 1986–2005 and 2031–2050, respectively. The carbon emission scenario is Representative Concentration Pathway (RCP) 4.5. The evaluation showed that the data product has good quality in describing the climatology of all the elements in CA despite some systematic biases. Main features of projected climate changes over […]
Chinese team breaks distance record for quantum secure direct communication
Phys.org April 20, 2022 Researchers in China have designed an elaborate physical system and protocol with much enhanced performance for quantum secure communication. The design increased the secrecy capacity greatly by achieving an ultra-low quantum bit error rate of <0.1%, one order of magnitude smaller than that of existing systems. Compared to previous systems, the proposed scheme used photonic time-bin and phase states, operating at 50 MHz of repetition rate, which can be easily upgraded to over 1 GHz using current on-the-shelf technology. Their experiments demonstrated that the proposed system could tolerate more channel loss, from 5.1 dB, which is about 28.3 km in […]
Electronic nanogenerator tattoos as human-machine interfaces
Nanowerk April 19, 2022 Although triboelectric nanogenerators (TENGs) have proven to be excellent candidates for wearable energy harvesters, they commonly face the hurdles of poor adhesion to skin and relative thick in geometry up to several cm. Researchers in China have introduced tattoo-like triboelectric nanogenerators (TL-TENGs) made with ultrathin materials with outstanding mechanical property of high robustness and thickness of tens of μm. They have remarkable electrical characteristics, with open-circuit voltage and short circuit current reaching up to ≈180 V and ≈2.2 μA under constant tapping (≈16 kPa), respectively. With the well structural mechanics designs, the TL-TENGs can be customized […]
Achieving higher performance with potassium ion battery
Phys.org April 14, 2022 Low temperature aqueous batteries (LT-ABs) have attracted extensive attention in recent years. However, they suffer from electrolyte freezing, slow ionic diffusion and sluggish interfacial redox kinetics at low temperature. In a review article researchers in China discussed the physicochemical properties of aqueous electrolytes in terms of phase diagram, ion diffusion and interfacial redox kinetics to guide the design of low temperature aqueous electrolytes (LT-AEs). They introduced the characteristics of equilibrium and non-equilibrium phase diagrams to analyze the antifreezing mechanisms and propose design strategies for LT-AEs. To understand and regulate the ion diffusion kinetics they reviewed the […]
Optimizing silicon structure to reduce reflection
Nanowerk April 14, 2022 Researchers in China examined changes in the porous structure of silicon to make it less reflective and thus a better material for solar absorbing technology. Currently, the reflectivity of porous silicon prepared using electrochemical methods is around 5 to 10 per cent, with the lowest reflectivity being 4.7 per cent for light in the wavelength range of 300 to 1000 nanometres. They calculated and compared the surface reflectivity of porous silicon structures with different pore sizes. They discovered that the porous silicon structure when prepared under the optimal corrosion parameters can achieve an average reflectivity as […]
Shapeable carbon fiber networks with hierarchical porous structure for high-performance Zn-I2 batteries
Nanowerk March 16, 2022 Although aqueous rechargeable zinc-iodine batteries (ZIBs) emerged as a promising energy storage alternative they suffer from the severe shuttle effect of polyiodide and poor reversibility, leading to the poor cycling lifetime and potential safety issues. Researchers in China found that the assembly of Al-based metal-organic frameworks (Al-MOFs) in the presence of polyacrylonitrile (PAN) via electrospinning technique enabled the formation of Al-MOF/PAN fibers. With the subsequent pyrolysis, the hierarchical porous carbon fibers with nitrogen doping (NPCNFs) are prepared for loading iodine. The confinement effect of the porous carbon network and the nitrogen doping, inhibits the shuttle effect […]
Researchers develop silicon cuboid nanoantenna
Phys.org March 21, 2022 The Purcell effect is commonly used to increase the spontaneous emission rate by modifying the local environment of a light emitter. Researchers in China studied the scattering cross section, polarization charge distribution, and electromagnetic field distribution for electromagnetic plane wave illuminating the silicon dielectric cuboid nanoantenna and identified simultaneous existence of electric dipole (ED), magnetic dipole (MD) and electric quadrupole (EQ) emission resonance modes in this nanoantenna. When they calculated the Purcell factor of ED, MD, and EQ emitters with different moment orientations as a function of radiation wavelength by placing these point radiation source within […]
Revealing thermal runaway routes in lithium-sulfur batteries
EurekAlert March 14, 2022 Researchers in China investigated the thermal runaway behavior of Li-S pouch cells from the materials level and found that the thermal runaway route starts from cathode-induced reactions and then gets accelerated by reactions from the anode. The solvent vaporization was verified to dominate pressure building up during thermal runaway. Li-S batteries employing varied electrolytes with different thermal stabilities, even inorganic all solid-state electrolytes, all undergo rapid thermal runaway at a narrow temperature range due to the intrinsic thermal features of the sulfur cathode and Li metal anode sublimating, melting, and cross-reacting at high temperatures. According to […]