Advanced Strategies to Improve Performances of Molybdenum-Based Gas Sensors

Molybdenum-based materials have been intensively investigated for high-performance gas sensor applications.Particularly,molybdenum oxides and dichalcogenides nanostructures have been widely examined due to their tunable structural and physicochemical properties that meet sensor requirements.These materials have good durability,are naturally abundant,low cost,and have facile preparation,allowing scalable fabrication to fulfill the growing demand of susceptible sensor devices.Significant advances have been made in recent decades to design and fabricate various molybdenum oxides-and dichalcogenides-based sensing materials,though it is still challenging to achieve high performances.Therefore,many experimental and theoretical investigations have been devoted to exploring suitable approaches which can significantly enhance their gas sensing properties.This review comprehensively examines recent advanced strategies to improve the nanostructured molybdenum-based material performance for detecting harmful pollutants,dangerous gases,or even exhaled breath monitoring.The summary and future challenges to advance their gas sensing performances will also be presented.

Synergetic influence of ex-situ camphoric carbon nano-grafting on lithium titanates for lithium ion capacitors

The present study provides detailed experimental results on the synthesis and characterization of carbonized lithium titanate spinel（LTO） composites as electrode materials for lithium ion capacitor.The LTO particles were grafted with a porous carbon layer obtained from the pyrolysis of camphor.The graphitic nature of the carbon was confirmed through Raman spectroscopy.The relative contributions from the capacitive and diffusion controlled processes underlying these electrodes were mathematically modeled.Electron transport mechanism underlying these electrodes was determined by measuring the work functions（φ） of LTO and carbon grafted LTO using ultraviolet photoelectron spectroscopy.These carbon grafted LTO composites exhibited an energy density of 330 m Wh L-1and a peak power density of 2.8 k W L-1,when employed as electrodes in coin cells with excellent cycling stability at the end of 4000 cycles.

Manufactured nanoparticle:A prediction model for understanding PM2.5 toxicity to human

Epidemiological studies have demonstrated that chronic exposure to polluted concentration of fine ambient particulate matter(PM2.5)can induce markedly harmful effects on human health,however,an enormous research effort is still need to the comprehensive understanding of PM2.5 induction of new negative health outcomes.Recently,Maher and colleges[1]from Environmental Magnetism and Paleomagnetism at Lancaster University

Bioresorbable magnesium-based alloys containing strontium doped nanohydroxyapatite promotes bone healing in critical sized bone defect in rat femur shaft

Magnesium-based biomaterials have been in extensive research for orthopedic applications for decades due to their optimal mechanical features and osteopromotive nature;nevertheless,rapid degradation restricts their clinical applicability.In this study,pristine magnesium was purified(P-Mg)using a melt self-purification approach and reinforced using indigenously synthesized nanohydroxyapatite(HAP,0.6 wt.%)and strontium substituted nanohydroxyapatite(SrHAP,0.6 wt.%)using a low-cost stir assisted squeeze casting method to control their degradation rate.Using electron back-scattered diffraction(EBSD)and X-ray diffraction(XRD)examinations,all casted materials were carefully evaluated for microstructure and phase analysis.Mechanical characteristics,in vitro degradation,and in vitro biocompatibility with murine pre-osteoblasts were also tested on the fabricated alloys.For in vivo examination of bone formation,osteointegration,and degradation rate,the magnesium-based alloys were fabricated as small cylindrical pins with a diameter of 2.7 mm and a height of 2 mm.The pins were implanted in a critical-sized defect in a rat femur shaft(2.7 mm diameter and 2 mm depth)for 8 weeks and evaluated by microCT and histological evaluation for bone growth and osteointegration.When compared to P-Mg and P-MgHAP,micro-CT and histological analyses revealed that the P-MgSrHAP group had the highest bone formation towards the periphery of the implant and hence maximum osteointegration.When the removed pins from the bone defect were analyzed using GIXRD,they displayed hydroxyapatite peaks that were consistent with bio-integration.For P-Mg,P-MgHAP,and P-MgSrHAP 8 weeks after implantation,in vivo degradation rates derived from micro-CT were around 0.6 mm/year,0.5 mm/year,and 0.1 mm/year,respectively.Finally,P-MgSrHAP possesses the requisite degradation rate as well as sufficient mechanical and biological properties,indicating that it has the potential to be used in the development/fabrication of biodegradable bioactive orthopaedic implants.

Theoretical study of CO2 hydrogenation to methanol on isolated small Pdx clusters

CO2 hydrogenation to methanol on small size Pdxclusters(x = 7, 9 and 13) has been studied using density functional theory calculations. It has been found that in contrast to metallic Pd system, these small Pdxclusters can interact well with CO2 molecule. CO2 molecule can be adsorbed with a bidendate configuration on the Pdxclusters. The formation of CO2 bidendate adsorption configuration facilitates the first step of CO2 hydrogenation reaction on the clusters. The energy profiles for formate pathway and reverse water gas shift + CO hydrogenation pathways on Pdxclusters are quite similar with Cu(111) surface, except for the first and last hydrogenation steps where the Pdxclusters have lower activation energies. This improvement causing the Pdxclusters to have a tolerable turn over frequencies values. In general, the usage of Pd in the form of small size cluster can improve the catalytic performance of metallic Pd for the CO2 hydrogenation to methanol because small size Pd cluster can act not only as an H2 dissociation center but also as a CO2 hydrogenation center.

Higher open-circuit voltage set by cobalt redox shuttle in SnO_2 nanofibers-sensitized CdTe quantum dot solar cells

In this study, we report an efficient CdTe-SnOquantum dot（QD） solar cell fabricated by heat-assisted drop-casting of hydrothermally synthesized CdTe QDs on electrospun SnOnanofibers. The as-prepared QDs and SnOnanofibers were characterized by dynamic light scattering（DLS）, UV–Vis spectroscopy,photoluminescence（PL） spectra, X-ray diffraction（XRD） and transmission electron microscopy（TEM）. The SnOnanofibers deposited on fluorine-doped tin oxide（SnO） and sensitized with the CdTe QDs were assembled into a solar cell by sandwiching against a platinum（Pt） counter electrode in presence of cobalt electrolyte. The efficiency of cells was investigated by anchoring QDs of varying sizes on SnO. The best photovoltaic performance of an overall power conversion efficiency of 1.10%, an open-circuit voltage（Voc）of 0.80 V, and a photocurrent density（JSC） of 3.70 m A/cmwere obtained for cells with SnOthickness of5–6 μm and cell area of 0.25 cmunder standard 1 Sun illumination（100 m W/cm）. The efficiency was investigated for the same systems under polysulfide electrolyte as well for a comparison.

Selectivity of CO_(2)reduction reaction to CO on the graphitic edge active sites of Fe-single-atom and dual-atom catalysts:A combined DFT and microkinetic modeling

We study the carbon dioxide reduction reaction(CO_(2)RR)activity and selectivity of Fe single-atom catalyst(Fe-SAC)and Fe dual-atom catalyst(Fe-DAC)active sites at the interior of graphene and the edges of graphitic nanopore by using a combination of DFT calculations and microkinetic simulations.The trend of limiting potentials for CO_(2)RR to produce CO can be described by using either the adsorption energy of COOH,CO,or their combination.CO_(2)RR process with reasonable reaction rates can be achieved only on the active site configurations with weak tendencies toward CO poisoning.The efficiency of CO_(2)RR on a catalyst depends on its ability to suppress the parasitic hydrogen evolution reaction(HER),which is directly related to the behavior of H adsorption on the catalyst’s active site.We find that the edges of the graphitic nanopore can act as potential adsorption sites for an H atom,and in some cases,the edge site can bind the H atom much stronger than the main Fe site.The linear scaling between CO and H adsorptions is broken if this condition is met.This condition also allows some edge active site configurations to have their CO_(2)RR limiting potential lower than the HER process favoring CO production over H2 production.

Sensing system for mimicking cancer cell–drug interaction

Biomarker discovery for early detection and therapy of diseases has been blooming for the past two decades.Following the identification of new biomarkers,research and development of sensing platforms has started to become more urgently needed recently,in both laboratory and clinical settings.

Temperature-feedback upconversion nanocomposite creates a new strategy for photothermal therapy

An upconversion nanocomposite containing photothermal material that can be served as an ideal probe to real-time monitor microscopic temperature during photothermal therapy(PTT)in biological system was described in a paper on Nature Communications[1].This temperature-feedback upconversion nanocomposite is shown to be able to reach high temperature at microscopic scale as to implement PTT for cancer treatment while keeping the temperature of lesion at low level to prevent damage to normal tissue in real biosystems.

Near infrared light triggered nitric oxide releasing platform based on upconversion nanoparticles for synergistic therapy of cancer stem-like cells

Near infrared(NIR) light-driven nitric oxide(NO) release nano-platform based on upconversion nanoparticles(UCNPs) and light sensitive NO precursor Roussin's black salt(RBS) was fabricated to generate NO upon 808 nm irradiation. The application of 808 nm laser as the excitation source could achieve better penetration depth and avoid overheating problem. The combination of UCNPs and RBS could realize the on-demand release of NO at desired time and location by simply controlling the output of NIR laser.Cellular uptake results showed that more nanoparticles were internalized in cancer stem-like cells(CSCs)rather than non-CSCs. Therefore, a synergistic cancer therapy strategy to eradicate both CSCs and nonCSCs simultaneously was developed. Traditional chemo-drug could inhibit non-CSCs but has low killing efficiency in CSCs. However, we found that the combination of NO and chemotherapy could efficiently inhibit CSCs in bulk cells, including inhibiting mammosphere formation ability, decreasing CD44^+/CD24^- subpopulation and reducing tumorigenic ability. The mechanism studies confirmed that NO could not only induce apoptosis but also increase drug sensitivity by declining drug efflux in CSCs. This UCNPsbased platform may provide a new combinatorial strategy of NO and chemotherapy to improve cancer treatment.

Bottom-up construction of highly ordered mesoporous graphene frameworks

Graphene,a two-dimensional(2D)sheet of carbon atoms,has attracted increasingly greater attention since its first isolation in 2004[1].Apart from the excellent electrical conductivity,graphene also possesses an exceptionally high specific surface area(*2,630 m2/g),which makes it particularly suitable for applications in electrochemical energy storage devices such as lithium-ion batteries(LIBs)and supercapacitors[2,3].However,graphene sheets

Photoanode Activity of ZnO Nanotube Based Dye-Sensitized Solar Cells

Vertical ZnO nanotube （ZNT） arrays were synthesized onto an indium doped tin oxide （ITO） glass substrate by a simple electrochemical deposition technique followed by a selective etching process. Scanning electron microscopy （SEM） showed formation of well-faceted hexagonal ZNT arrays spreading uniformly over a large area. X-ray diffraction （XRD） of ZNT layer showed substantially higher intensity for the （0002） diffraction peak, indicating that the ZnO crystallites were well aligned with their c-axis. Profilometer measurements of the ZNT layer showed an average thickness of -7 μm. Diameter size distribution （DSD） analysis showed that ZNTs exhibited a narrow diameter size distribution in the range of 65-120 nm and centered at -75 nm. The photoluminescence （PL） spectrum measurement showed violet and blue luminescence peaks that were centered at 410 and 480 nm, respectively, indicating the presence of internal defects. Ultra-violet （UV） spectroscopy showed major absorbance peak at ,-348 nm, exhibiting an increase in energy gap value of 3.4 eV. By employing the formed ZNTs as the photo-anode for a dye-sensitized solar cell （DSSC）, a full-sun conversion efficiency of 1.01% was achieved with a fill factor of 54%. Quantum efficiency studies showed the maximum of incident photon-to-electron conversion efficiency in a visible region located at 590-550 nm range.

Nanotechnology in the programmed cell therapy:nowhere to escape of cancer

For lymphomas,the transport of chemotherapeutic drugs usually meets physical barriers to the lymph nodes where disseminated tumor cells frequently reside.But new findings show that autologous T cells as live vectors combined with nanotechnology-based drug delivery can provide a novel opportunity for the improved chemotherapy toward lymphomas.

Solidifying framework nucleic acids

Living organisms have developed their unique strategies during the natural evolution for building hard tissues with minerals,including silica,calcium carbonate,calcium phosphate,and ferric oxide [1].Such biomineralized materials generally have complex hierarchical structures with excellent mechanical properties.Although bioinspired approaches have led to the creation of well-defined synthetic structural materials ranging from micro to macro scales,the rational design of discrete biomimetic structures at the nanoscale remains a grand challenge.