Rapid and sensitive detection of Hg2+ with a SERS-enhanced lateral flow strip.

Mercury ions are some of the most toxic heavy metal ions widely distributed in the environment. Hg2+ cannot be degraded by microorganisms and can accumulate in the body through the food chain, posing a great threat to human health. Herein, a method combining surface-enhanced Raman scattering (SERS) with a lateral flow strip (LFS) (SERS-LFS) was developed for the rapid and quantitative analysis of Hg2+. The recognition of Hg2+ by the LFS depends on a specific T-Hg-T strategy. Rhodamine 6G (R6G), as a SERS reporter, was assembled on the surface of Au@Ag core-shell nanoparticles, which served as an effective SERS substrate on both the T and C lines of the LFS. Using this SERS-LFS, the presence of target Hg2+ could be measured through the appearance of an orange color on the T line of the LFS. Furthermore, with the direct measurement of SERS on the T lines of the LFS, the SERS signal could be collected even at a low concentration of Hg2+, at which point the signal on the T lines could not be observed. Based on the intensities of the characteristic peak at 1513 cm-1 of R6G collected on the T lines of the LFS, a linear relationship was obtained in the range of 0.01 nM to 1 nM, and the detection limit of the LFS was greatly improved by at least 20 times over the colorimetric results of the traditional LFS based on naked-eye observation. More importantly, this SERS-LFS did not affect the intrinsic simplicity of the LFS. This developed SERS-LFS holds great potential in practical routine screening in food safety and environmental monitoring.

Simultaneous and accurate screening of multiple genetically modified organism (GMO) components in food on the same test line of SERS-integrated lateral flow strip.

Herein, a surface-enhanced Raman scattering (SERS)-integrated LFS platform was developed for rapid and simultaneous screening of multiple genetically modified organism (GMO) components (promoter, codon, and terminator) in soybean. Research demonstrated that, on the same test line (T line) of single LFS, three different GMP components can be well distinguished with the help of three SERS nano tags. Good linear correlations between SERS signal and concentration of each GMO component were also obtained for quantitative analysis. Of greater importance, whether these multiple analytes coexisted or not, varied in the same concentration trend or not, these multiple GMP components can be rapidly (15 min) and accurately screened with satisfied sensitivity and specificity by decoding the signals on the same T line. We envision that this decoding platform can further improve the potential of LFS and SERS for practical applications and provide a promising alternative for multiple screening of GMO identification in food.

Solution combustion synthesis of ternary Ni/WC/C composites with efficient electrocatalytic oxygen reduction performance.

In this paper, a fast processing route involving a wet-chemical method (solution combustion synthesis, SCS) and carbonization in a CH4 environment was demonstrated, through which nanosized Ni/WC/C powder with an average size of 80 nm was obtained. In the catalyst powder, Ni was evenly distributed and it could form NiOOH to promote catalysis, and an amorphous carbon (C) layer with a thickness of <10 nm was formed on the surface of the composite particles, improving the stability of the Ni/WC powder and promoting electron transport. Due to the characteristics of uniformity and a large specific surface area and the synergistic effect of Ni, WC, and C, this powder showed significantly improved ORR catalytic activity in alkaline solution. When the amount of Ni doping was 15 wt%, the composite powder showed the smallest particle size and the best ORR catalytic performance. Its cathode peak potential was -0.31 V and the half wave potential was -0.34 V. The number of electrons transferred in the ORR reaction was 3.6. This work provided a fast and cheap method for the preparation of multicomponent composite catalyst materials.

MXene (Ti3C2Tx) and Carbon Nanotube Hybrid-Supported Platinum Catalysts for the High-Performance Oxygen Reduction Reaction in PEMFC.

The metal-support interaction offers electronic, compositional, and geometric effects that could enhance catalytic activity and stability. Herein, a high corrosion resistance and an excellent electrical conductivity MXene (Ti3C2Tx) hybrid with a carbon nanotube (CNT) composite material is developed as a support for Pt. Such a composite catalyst enhances durability and improved oxygen reduction reaction activity compared to the commercial Pt/C catalyst. The mass activity of Pt/CNT-MXene demonstrates a 3.4-fold improvement over that of Pt/C. The electrochemical surface area of Pt/CNT-Ti3C2Tx (1:1) catalysts shows only 6% drop with respect to that in Pt/C of 27% after 2000 cycle potential sweeping. Furthermore, the Pt/CNT-Ti3C2Tx (1:1) is used as a cathode catalyst for single cell and stack, and the maximum power density of the stack reaches 138 W. The structure distortion of the Pt cluster induced by MXene is disadvantageous to the desorption of O atoms. This issue can be solved by adding CNT on MXene to stabilize the Pt cluster. These remarkable catalytic performances could be attributed to the synergistic effect between Pt and CNT-Ti3C2Tx.

Oxidative stress caused by lead (Pb) induces iron deficiency in Drosophila melanogaster.

Toxic elements exposure disturbs the homeostasis of essential elements in organisms, but the mechanism remains elusive. In this study, we demonstrated that Drosophila melanogaster exposed to Lead (Pb, a pervasive environmental threat to human health) exhibited various health defects, including retarded development, decreased survival rate, impaired mobility and reduced egg production. These phenotypes could be significantly modulated by either intervention of dietary iron levels or altering expression of genes involved in iron metabolism. Further study revealed that Pb exposure leads to systemic iron deficiency. Strikingly, reactive oxygen species (ROS) clearance significantly increased iron uptake by restoring the expression of iron metabolism genes in the midgut and subsequently attenuated Pb toxicity. This study highlights the role of ROS in Pb induced iron dyshomeostasis and provides unique insights into understanding the mechanism of Pb toxicity and suggests ideal ways to attenuate Pb toxicity by iron supplementation therapy or ROS clearance.

Pd/MXene(Ti3C2Tx)/reduced graphene oxide hybrid catalyst for methanol electrooxidation.

A key challenge in developing direct methanol fuel cells is the fabrication of electrocatalysts with high activity and long durability. Herein, we report a performance enhanced electrocatalyst of nanoscale Pd on MXene (Ti3C2Tx) and reduced graphene oxide (rGO). The mass activity of Pd/Ti3C2Tx-rGO (1: 1) hybrid toward methanol oxidation reaction is 753 mA mg-1, which is 1.7 times than that of Pd/C (446 mA mg-1). Additionally, the current density of Pd/Ti3C2Tx-rGO (1:1) catalyst contains 212 mAmg-1 which is nine times higher than that of Pd/C (23 mA mg-1) after 7200 s. The Pd/Ti3C2Tx-rGO (1:1) catalyst exhibits excellent cycling stability and long-term life. These remarkable catalytic performances are attributed to the role of Ti3C2Tx and rGO in enhancing the catalytic activity surface area and rapid mass/charge transfer due to the synergistic effect between Pd and Ti3C2Tx/rGO.

Preparation and Performance of Sintered Fe-2Cu-2Mo-0.8C Materials Containing Different Forms of Molybdenum Powder.

Fe-2Cu-2Mo-0.8C powder mixtures were prepared by mixing Fe, Cu and C elemental powders with different forms of Mo-containing powder (pure Mo powder, prealloyed Mo-Fe powder and mechanically alloyed Mo-Fe powder, respectively). The powder mixtures were warm pressed under different pressures and temperatures. Properties of the green compacts and the sintered parts were tested to investigate the effects of the different ways of introducing molybdenum. The test results show that a green density of 7.32 g/cm³ was obtained for Fe-2Cu-2Mo-0.8C powder mixtures containing mechanically alloyed Mo-Fe powders, under a warm compaction pressure of 800 MPa and warm pressing temperature of 120 °C, respectively. The sintered Fe-2Cu-2Mo-0.8C specimens added with mechanically alloyed Mo-Fe powders had a density of 7.31 g/cm³, a hardness of 95 HRB and a tensile strength of 618 MPa, respectively. Compared with the sintered samples, added Mo in the forms of pure Mo and prealloyed Mo-Fe powder, the sintered parts added with mechanically alloyed Mo-Fe powders had more uniform microstructure, better mechanical and wear-resistant properties.

Polybenzimidazole/Mxene composite membranes for intermediate temperature polymer electrolyte membrane fuel cells.

This report demonstrated the first study on the use of a new 2D nanomaterial (Mxene) for enhancing membrane performance of intermediate temperature (>100 °C) polymer electrolyte membrane fuel cells (ITPEMFCs). In this study, a typical Ti3C2T x -MXene was synthesized and incorporated into polybenzimidazole (PBI)-based membranes by using a solution blending method. The composite membrane with 3 wt% Ti3C2T x -MXene showed the proton conductivity more than 2 times higher than that of pristine PBI membrane at the temperature range of 100 °C-170 °C, and led to substantial increase in maximum power density of fuel cells by ∼30% tested at 150 °C. The addition of Ti3C2T x -MXene also improved the mechanical properties and thermal stability of PBI membranes. At 3 wt% Ti3C2T x -MXene, the elongation at break of phosphoric acid doped PBI remained unaffected at 150 °C, and the tensile strength and Young's modulus was increased by ∼150% and ∼160%, respectively. This study pointed out promising application of MXene in ITPEMFCs.

Fabrication of CsxFA1-xPbI3 Mixed-Cation Perovskites via Gas-Phase-Assisted Compositional Modulation for Efficient and Stable Photovoltaic Devices.

Over the past few years, significant attention has been focused on HC(NH2)2PbI3 (FAPbI3) perovskite due to its reduced band gap and enhanced thermal stability compared with the most studied CH3NH3PbI3 (MAPbI3). However, FAPbI3 is sensitive to moisture and also encounters a serious structural phase-transition from photoactive α-phase to photoinactive δ-phase. Herein, we first develop a novel FAI gas-phase-assisted mixed-cation compositional modulation method to fabricate CsxFA1-xPbI3 perovskite solar cells (PSCs), and realize the structural stabilization of α-phase FAPbI3 with the incorporation of smaller inorganic Cs+ ions. Through the setting of different Cs+ contents (x = 0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.50) along with a moderate FAI vapor deposition process, a series of CsxFA1-xPbI3 films with consistent compositions are fabricated, which perfectly resolves the main blocking problems of the conventional solution approach, such as difficulty in compositional control and rough film morphology. Meanwhile, we find that the Cs+ amount is crucial for generating phase-pure CsxFA1-xPbI3 (0 < x < 0.30) while higher contents result in phase segregation. Consequently, the optimum amount of Cs+ (x = 0.15) is verified, and Cs0.15FA0.85PbI3 shows the smallest unit cell volume and good moisture-resistant feature. Correspondingly, the highest power conversion efficiency (PCE) of 14.45% based on Cs0.15FA0.85PbI3 PSCs is successfully achieved in this work.

A novel transformation route from PbS to CH3NH3PbI3 for fabricating curved and large-area perovskite films.

We present a new transformation route from PbS to CH3NH3PbI3 for the facile preparation of perovskites with all kinds of shapes via vapor-assisted chemical bath deposition (VACBD). As such, curved and large-area CH3NH3PbI3 films with high quality are successfully achieved, which are suitable for the manufacturing scale-up of perovskite solar cells.

Solvent Engineering for Ambient-Air-Processed, Phase-Stable CsPbI3 in Perovskite Solar Cells.

Inorganic CsPbI3 perovskite solar cells (PSCs) owning comparable photovoltaic performance and enhanced thermal stability compared to organic-inorganic hybrid perovskites have attracted enormous interest in the past year. However, it is still a challenge to stabilize the desired black α-CsPbI3 perovskites in ambient air for photovoltaic applications. Herein, sequential solvent engineering including the addition of hydroiodic acid (HI) and subsequent isopropanol (IPA) treatment for fabricating stable and working CsPbI3 PSCs is developed, and a novel low-temperature phase-transition route from new intermediate Cs4PbI6 to stable α-CsPbI3 is also released for the first time. As such, the as-prepared PSCs give a relatively high power conversion efficiency (PCE) of 4.13% (reverse scan), and the steady-state power output of 1.88% is confirmed for the selected cell with an initial PCE of 3.13%. To the best of our knowledge, this is the first demonstration of fabricating CsPbI3 inorganic PSCs under fully open-air conditions.

Chemical Synthesis and Oxide Dispersion Properties of Strengthened Tungsten via Spark Plasma Sintering.

Highly uniform oxide dispersion-strengthened materials W-1 wt % Nd2O3 and W-1 wt % CeO2 were successfully fabricated via a novel wet chemical method followed by hydrogen reduction. The powders were consolidated by spark plasma sintering at 1700 °C to suppress grain growth. The samples were characterized by performing field emission scanning electron microscopy and transmission electron microscopy analyses, Vickers microhardness measurements, thermal conductivity, and tensile testing. The oxide particles were dispersed at the tungsten grain boundaries and within the grains. The thermal conductivity of the samples at room temperature exceeded 140 W/m·K. The tensile tests indicated that W-1 wt % CeO2 exhibited a ductile-brittle transition temperature between 500 °C and 550 °C, which was a lower range than that for W-1 wt % Nd2O3. Surface topography and Vickers microhardness analyses were conducted before and after irradiations with 50 eV He ions at a fluence of 1 × 1022 m-2 for 1 h in the large-powder material irradiation experiment system. The grain boundaries of the irradiated area became more evident than that of the unirradiated area for both samples. Irradiation hardening was recognized for the W-1 wt % Nd2O3 and W-1 wt % CeO2 samples.

Mechanical properties and microstructural change of W-Y2O3 alloy under helium irradiation.

A wet-chemical method combined with spark plasma sintering was used to prepare a W-Y2O3 alloy. High-temperature tensile tests and nano-indentation microhardness tests were used to characterize the mechanical properties of the alloy. After He-ion irradiation, fuzz and He bubbles were observed on the irradiated surface. The irradiation embrittlement was reflected by the crack indentations formed during the microhardness tests. A phase transformation from α-W to γ-W was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Polycrystallization and amorphization were also observed in the irradiation damage layer. The W materials tended to exhibit lattice distortion, amorphization, polycrystallization and phase transformation under He-ion irradiation. The transformation mechanism predicted by the atomic lattice model was consistent with the available experimental observations. These findings clarify the mechanism of the structural transition of W under ion irradiation and provide a clue for identifying materials with greater irradiation resistance.

Uniform, stable, and efficient planar-heterojunction perovskite solar cells by facile low-pressure chemical vapor deposition under fully open-air conditions.

Recently, hybrid perovskite solar cells (PSCs) have attracted extensive attention due to their high efficiency and simple preparing process. Herein, a facile low-pressure chemical vapor deposition (LPCVD) technology is first developed to fabricate PSCs, which can effectively reduce the over-rapid intercalating reaction rate and easily overcome this blocking issue during the solution process. As a result, the prepared uniform perovskite films exhibit good crystallization, strong absorption, and long carrier diffusion length. More strikingly, CH3NH3PbI3 absorbers by LPCVD demonstrate excellent moisture-resistant feature even under laser illumination and high-temperature conditions, which indicates that our proprietary method is very suitable for the future low-cost, nonvacuum production of the new generation photovoltaic devices. Finally, high efficiency of 12.73% is successfully achieved under fully open-air conditions. To the best of our knowledge, this is the first report of efficient PSCs with such a high humidity above 60%.