Observation of High-Frequency Raman Modes in FeCl3- and Zn-Intercalated MoS2 Flakes.

In place of the widely studied graphene, monolayer or few-layer MoS2 flakes are promising materials for next-generation optoelectronic devices. MoS2 has attracted increasing attention in physics and its applications because of its capacity to undergo indirect-to-direct band gap transition. Raman spectroscopy is a useful and versatile tool to probe the physical properties of pristine and intercalated MoS2. This study investigates for the first time the multiphoton modes of FeCl3- and Zn-intercalated few-layer MoS2 at high frequencies of 1513 and 1732 cm-1 for FeCl3-MoS2 and 1341 and 1604 cm-1 for Zn-MoS2. The substrates interact with MoS2 during intercalation. The Raman peak intensities of the intercalated samples vary with intercalation time while keeping the peak position nearly constant. This finding is interesting and suitable for studying other 2D layered materials.

Study on the Electrochemical Reaction Mechanism of ZnFe2O4 by In Situ Transmission Electron Microscopy.

A family of mixed transition-metal oxides (MTMOs) has great potential for applications as anodes for lithium ion batteries (LIBs). However, the reaction mechanism of MTMOs anodes during lithiation/delithiation is remain unclear. Here, the lithiation/delithiation processes of ZnFe2O4 nanoparticles are observed dynamically using in situ transmission electron microscopy (TEM). Our results suggest that during the first lithiation process the ZnFe2O4 nanoparticles undergo a conversion process and generate a composite structure of 1-3 nm Fe and Zn nanograins within Li2O matrix. During the delithiation process, volume contraction and the conversion of Zn and Fe take place with the disappearance of Li2O, followed by the complete conversion to Fe2O3 and ZnO not the original phase ZnFe2O4. The following cycles are dominated by the full reversible phase conversion between Zn, Fe and ZnO, Fe2O3. The Fe valence evolution during cycles evidenced by electron energy-loss spectroscopy (EELS) techniques also exhibit the reversible conversion between Fe and Fe2O3 after the first lithiation, agreeing well with the in situ TEM results. Such in situ TEM observations provide valuable phenomenological insights into electrochemical reaction of MTMOs, which may help to optimize the composition of anode materials for further improved electrochemical performance.

Electromanipulating water flow in nanochannels.

In sharp contrast to the prevailing view that a stationary charge outside a nanochannel impedes water permeation across the nanochannel, molecular dynamics simulations show that a vibrational charge outside the nanochannel can promote water flux. In the vibrational charge system, a decrease in the distance between the charge and the nanochannel leads to an increase in the water net flux, which is contrary to that of the fixed-charge system. The increase in net water flux is the result of the vibrational charge-induced disruption of hydrogen bonds when the net water flux is strongly affected by the vibrational frequency of the charge. In particular, the net flux is reaches a maximum when the vibrational frequency matches the inherent frequency of hydrogen bond inside the nanochannel. This electromanipulating transport phenomenon provides an important new mechanism of water transport confined in nanochannels.

Mo doping-enhanced dye absorption of Bi2Se3 nanoflowers.

A simple solvothermal approach is explored to prepare Bi2-xMoxSe3 nanostructures by employing N,N-dimethylformamide (DMF) as the solvent. Mo plays an important role in the assembly of the Bi2-xMoxSe3 nanostructures from nanoplates to nanoflowers. Structural and morphological studies indicate that the resulting products are large specific surface area single-crystalline Bi2-xMoxSe3 nanoflowers self-assembled from thin nanoplates during the reaction process. The absorption properties of the as-prepared samples are investigated with Rhodamine B (RhB) as dye, and it is found that the Bi1.85Mo0.15Se3 nanoflowers show an optimal adsorption capacity, implying that Mo doping not only changes the morphologies of the nanostructures but also enhances their absorption behaviors.

Novel mechano-luminescent sensors based on piezoelectric/electroluminescent composites.

A high-sensitivity mechano-luminescent sensor was fabricated on the basis of piezoelectric/electroluminescent composites. The working principle of this mechano-luminescent sensor was elucidated by analyzing the relationship between the piezoelectric-induced charges and the electroluminescent effects. When a stress is applied on the piezoelectric layer, electrical charges will be induced at both the top and bottom sides of the piezoelectric layer. The induced electrical charges will lead to a light output from the electroluminescent layer, thus producing a mechano-luminescence effect. By increasing the vibration strength or frequency applied, the mechano-luminescence output can be obviously enhanced. Mechano-luminescence sensors have potential in smart stress-to-light devices, such as foot-stress-distribution-diagnosis systems and dynamic-load-monitors for bridge hanging cables.