[en] Here we report the utilization of p-p isotype heterojunctions for improving the CO₂ gas sensing performance of polyaniline (Pani)/hierarchical mesoporous LaFeO₃ (LFO) at room temperature and high humidity (~90%). Our findings show that the partial protonated of Pani and different wt% of LFO have a significant effect on CO₂ gas sensing. The Pani/LFO nanocomposite (PLFO) gas sensor with 10 wt% LFO exhibited 13.20 times higher gas sensitivity to 20,000 ppm of CO₂ compared to pure Pani gas sensor. All of the sensors had a dynamic response to 5000, 10,000 and 20,000 ppm of CO₂ gas at ~90% humidity. The good long-term stability after one year is observed for the sensor based on PLFO. Moreover, CO₂ gas mechanism of the PLFO sensors were studied in details. The advantages of p-p heterojunctions could provide a new perspective for CO₂ gas sensing applications.

[en] One of the most important challenges in Nano-scale spintronics is the production of intrinsic two-dimensional ferromagnetic half-metals with large spin gaps and high Curie temperatures. Here, by using firs-principles calculation we predict two-dimensional transition metal hydrides M_nH_m (M: V, Cr, Fe, and Co) have different magnetic properties in various space groups. Our results show the magnetic ground state of VH₃, FeH₃ and CoH₃ in space group P/4nmm, Cr₂H₃, Fe₂H₃ and Co₂H₃ in space group of P-3 m1 is ferromagnetic while V₂H₃ and CrH₃ in space group of P-3 m1 and P/4nmm respectively, are antiferromagnetic. In particular Co₂H₃ monolayer is 100% spin polarized intrinsic ferromagnetic half metal with spin gap of 3.2 eV and Cr₂H₃ can also change to half-metal by doping a small amount of electric charge with a band gap of 4.2 eV. The delocalized and unpaired d electrons around the Fermi level act as the chief source of magnetism and half metallicity. The Curie temperature, calculated utilizing the mean-field approximation, is 485 and 227 K for Co₂H₃ and Cr₂H₃ monolayers respectively so it can be concluded that Co₂H₃ and Cr₂H₃ monolayers are promising candidates for spintronic applications.

[en] In this study, we have successfully synthesized self-assembled LaFeO₃ (LFO) microsphere photocatalysts by hydrothermal method at two different temperatures in order to study the surface-morphology modification and photocatalytic activity. The self-assembled LFO microspheres have been characterized by X-ray diffraction, Fourier transform infrared spectroscopy, atomic force microscopy, thermogravimetric analysis, high-resolution transmission electron microscopy, UV–Vis spectroscopy, field emission scanning electron microscopy, Brunauer–Emmett–Teller analysis and photoluminescence spectroscopy. The results show that the surface-morphology modification of self-assembled microspheres has a significant effect on the degradation of methylene blue under sunlight irradiation. The enhancement of photocatalytic activity of LFO microspheres composed of nanorods was attributed to their high specific surface area (15.06 m²g⁻¹), low tensile strain and high charge separation efficiency as evidenced by PL spectrum. The surface roughness has increased from 23.96 to 61.36 nm after surface modification from nanoparticle to nanorod in the self-assembled microspheres, respectively. The great durability and stability of photocatalyst were sustained over three cycles, indicating this structure has a potential application in wastewater treatment.

[en] Polypyrrole (PPy)–Zn₂SnO₄ nanocomposites have been prepared using dodecylbenzene sulfonic acid as a dopant by chemical oxidative polymerization for different weight percentages of Zn₂SnO₄ nanoparticles (0–20 wt%). The physicochemical characterization confirmed well-formed DBSA doped PPy–Zn₂SnO₄ nanocomposites with globule—like morphology and high porosity. Moreover, the UV–Vis spectrum revealed a blue shift for nanocomposites with respect to pure PPy, reflecting the modified electronic states as a result of effective interaction between PPy and Zn₂SnO₄ nanoparticles. All of the synthesized nanocomposites had a good thermal stability below 200 °C (< 4% weight loss). We applied the synthesized nanocomposites as a resistive sensor to detect the ethanol vapor. The results demonstrate that PPy–Zn₂SnO₄ (10 wt%) nanocomposite has the highest DC conductivity and response at room temperature. Also, it shows a linear response, appropriate recovery time and reproducibility. The excellent long-term stability (about 30% less than the initial experiment) after 7 months is observed for the sensor based on PPy–Zn₂SnO₄ (10 wt%), which makes it convenient for practical applications.

[en] Adsorptive potential of maghemite decorated multiwalled carbon nanotubes (MWCNTs) for the removal of cadmium ions from aqueous solution was investigated. The magnetic nanoadsorbent was synthesized using a versatile and cost effective chemical route. Structural, magnetic and surface charge properties of the adsorbent were characterized using FTIR, XRD, TEM, VSM analysis and pH_P_Z_C determination. Batch adsorption experiments were performed under varied system parameters such as pH, contact time, initial cadmium concentration and temperature. Highest cadmium adsorption was obtained at pH 8.0 and contact time of 30 min. Adsorption behavior was kinetically studied using pseudo first-order, pseudo second-order, and Weber–Morris intra particle diffusion models among which data were mostly correlated to pseudo second-order model. Adsorbate-adsorbent interactions as a function of temperature was assessed by Langmuir, Freundlich, Dubinin–Radushkevich (D-R) and Temkin isotherm models from which Freundlich model had the highest consistency with the data. The adsorption capacity increased with increasing temperature and maximum Langmuir’s adsorption capacity was found to be 78.81 mg g"−"1 at 298 K. Thermodynamic parameters and activation energy value suggest that the process of cadmium removal was spontaneous and physical in nature, which lead to fast kinetics and high regeneration capability of the nanoadsorbent. Results of this work are of great significance for environmental applications of magnetic MWCNTs as promising adsorbent for heavy metals removal from aqueous solutions.Graphical Abstract

[en] Highlights: • Spin-dependent electronic transport properties on single ferrocene molecule. • Highly effect of anchoring atoms on the control of spin transport properties. • Observation of high spin-filtering and negative differential resistance behaviors. Spin transport properties of a single ferrocene molecule connected between gold electrodes by amine (NH₂), sulfur (S) and titanium (Ti) linkers are investigated using density functional theory through a non-equilibrium Green’s function approach. The results clearly reveal that the anchoring groups can significantly modify the spin-dependent properties due to shift of the frontier orbitals. This will give rise to some interesting phenomena including robust spin-filtering effect and obvious negative differential resistance behavior. Importantly, the linkers dramatically influence the bias region of spin-filtering diagram. The numerical results suggest that such single molecular junctions would be efficiently implemented for developing spintronic devices.

[en] Graphical abstract: - Highlights: • Polyaniline/titania (rutile) nanocomposite (TPNC) was synthesized by a chemical oxidative polymerization method. • Surface morphology and titania (rutile) wt% in TPNC sensors were significant factors for H₂ gas sensing. • TPNC sensors could be used for H₂ gas sensing at different R.H. humidity. • TPNC Sensors exhibited considerable sensitive, reversible and repeatable response to H₂ gas at environmental conditions. - Abstract: The resistance-based sensors of polyaniline/titania (rutile) nanocomposite (TPNC) were prepared by spin coating technique onto an epoxy glass substrate with Cu-interdigited electrodes to study their hydrogen (H₂) gas sensing features. Our findings are that the change of the surface morphology, porosity and wt% of titania in TPNCs have a significant effect on H₂ gas sensing of sensors. All of the sensors had a reproducibility response toward 0.8 vol% H₂ gas at room temperature, air pressure and 50% relative humidity. A sensor with 40 wt% of titania nanoparticles had better response/recovery time and the response than other sensors. Moreover, H₂ gas sensing mechanism of TPNC sensors based contact areas and the correlation of energy levels between PANI chains and the titania grains were studied