[en] In this work we investigated the influence of different deposition angles on the structural and magnetic properties of nickel thin films obtained by Glancing Angle Deposition. The films were deposited onto glass substrates at the angles of 65° and 85°. The structure of the films was studied by scanning electron microscopy, atomic force microscopy and X-ray diffraction, while the magnetic properties were analyzed using magneto-optical Kerr effect microscopy (MOKE). It was found that the variation in the deposition angle has a great influence on the porosity, crystallinity and surface roughness of the Ni films. The obtained changes in microstructure were correlated with the variation in the magnetic properties. MOKE measurements revealed that the thinner films, deposited at the angle of 85°, have a 2.5 times higher coercivity in comparison with the films deposited at the lower angle, which can be ascribed to their higher porosity. © 2019 Elsevier Ltd

[en] Herein, the facile fabrication of a novel 3D macroporous structure of graphitic carbon nitride composed of self-assembled 2D nitrogen vacancy engineered nanosheets have been reported. The synthesis of the defect-engineered structure was achieved upon the addition of ethylene glycol during the solid-state synthesis process. The photocatalyst was characterized through a wide range of characterization techniques. The macroporous structure exhibited superior photocatalytic efficiency towards tetracycline antibiotic degradation under LED light illumination. The defect-engineered material (4EGCN) exhibited a 3.3-fold superior degradation rate coefficient of 0.010 min⁻¹, compared to the degradation rate coefficient (0.003 min⁻¹) of the bulk counterpart. This superior photocatalytic performance could be accredited to the extended visible light extraction efficiency, increased suppression efficacy of charge carriers, and porous structure. Moreover, the photocatalyst showed excellent stability even after five cycles of photocatalytic tetracycline degradation. Further, a probable degradation mechanism has been proposed according to the observations of the radical scavenging experiments.

[en] Thermal stimulus-responsive NiTi-based shape memory alloys, which undergo reversible, diffusion-less martensitic phase transformation, have emerged as important functional materials. Amongst them, Ni-rich NiTiHf high temperature shape memory alloys exhibit martensitic phase transformation temperatures well above 100 °C, making them suitable for high temperature applications. However, during repeated thermal cycles their transformation temperatures show instabilities which limit their practical applications. Here, we perform thermal cycling experiments at fixed as well as variable heating/cooling rates on the Ni_50.3Ti_29.7Hf₂₀ alloy which is heat-treated at different temperatures. We successfully minimized the variations in phase transformation temperatures to an acceptable range by aging the alloy below 500 °C for 3 h. We further show that this minimization correlates well with high activation energy required for the phase transformation elucidating the physical reason behind this observation. Our results pave the way forward for designing Ni-rich NiTiHf shape memory alloys with a stable functional response.

[en] Symmetric 2D Mesoporous Graphitic Carbon spinel cobalt ferrite (CoFe₂O₄/2D-C) with high porosity has been fabricated via a facile and swift sucrose template microwave combustion process followed by an additional annealing treatment. The CoFe₂O₄/2D-C composite comprises carbon coated spinel cobalt ferrite with densely connected porous layered structure facilitating fast electron and ion transport. Benefiting from such an inimitable structure, CoFe₂O₄/2D-C is employed as supercapacitors electrode material and exhibited a high specific capacitance (1318.1 Fg⁻¹ at 2.5 A g⁻¹ current density) and energy density (77.3 W h kg⁻¹) with an excellent electrochemical capacity retention of 97.2 % after 4000 cycles. Power law which expresses the dependence of peak CV current on scan rate at fixed potential confirmed that, the charge storage mechanism for the electrode material (CoFe₂O₄/2D-C) is influenced congruently by both the capacitive and diffusive controlled process which promoted an efficient energy storage for CoFe₂O₄/2D-C. Accordingly, this outstanding performance put forward its application as an effective material for electrochemical capacitors.

[en] In this paper, we have elaborated Cu₂Fe_1-x Co_xSnS₄ (CFCTS) thin films (x = 0%, 25%, 50%, 75% and 100%) by spray pyrolysis technique on glass substrates. The effect of varying (Fe/Co) ratio on chemical composition, morphological, structural, optical and electrical properties has been investigated using energy dispersive X-ray spectrometry (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, spectrophotometer and Hall Effect measurements respectively. XRD results have shown that the change in (Fe/Co) ratio leads to the transformation of stannite CFTS (x = 0%) to stannite CCTS (x = 100%) with the same preferred orientation (112) plan. CFTS and CCTS phases have been confirmed by Raman peaks located respectively at 318 and 325 cm^-1. A uniform and dense distribution of CCTS thin film were observed by scanning electron microscopy (SEM). Estimated band gap values of CFTS and CCTS thin films were equal to 1.46 eV and 1.32 eV respectively. Electrical resistivity value was decreased from 5.82 10^-3 Ω.cm for CFTS thin film to 5 10^-3 Ω.cm for CCTS thin film. These experimental results allow us to consider CFTS and CCTS as good candidates to be used as absorber materials in solar cell devices. Photocatalytic activities of CCTS thin film, CCTS/SnO₂:F, CCTS/In₂S₃ and CCTS/In₂S₃/SnO₂:F heterojunctions have been investigated under sun light irradiation using methylene blue (MB) as representative pollutant dye. It was found that the photodegradation rate was near to 86% in the presence of CCTS /In₂S₃ / SnO₂:F heterojunction after 4 hours which leads to considering it as a good candidate to implement eco-friendly, sun-powered devices for removing organic pollution in waste water. for photocatalysis applications.

[en] Here we present unique features of metal ion treated tungsten disulphide (WS₂) nanosheets. Through chemical exfoliation of bulk WS₂, multilayered WS₂ nanosheets were prepared and drop casted on finger like Cu (Copper) electrodes, thereby fabricating 2D material-based sensor units. Later, I-V characteristics of the units were investigated with and without heavy metal ion treatment. In case of Zn²⁺ ions, the sensor unit shows prominent negative resistance in the positive potential region of the I-V characteristics., which was further quantified by taking the difference between the peak and valley point of the negative resistance region to selectively detect Zn²⁺ ions. Accordingly, the response of the novel scheme was visualized by plotting calibration curve for Zn²⁺ ions, accompanied by analysis of the influence from other interfering ions through I-V characteristics. Excellent selectivity towards Zn²⁺ ions, with limit of detection 0.94 ± 0.05 ppb was found. Sensitivity of 0.63 ± 0.05 µA per ppb was achieved, accompanied by a rapid response.

[en] Harvesting triplet excitons via room temperature phosphorescence (RTP) from purely organic chromophores has been a formidable challenge, which has a potential applications in displays, lighting, and bio-imaging. Herein, a simple phthalimide phosphor derivative is reported, which exhibits visible cyan emissive phosphorescence in solution-processable thin films and orange-red emitting phosphorescence in the crystalline state. Presence of carbonyl group and the bromine atom in the molecular design effectively increases the inter-system crossing (ISC) and spin-orbit coupling efficiency (SOC) between singlet and triplet states, which play a crucial role in achieving efficient phosphorescence under ambient conditions.

[en] A new kind of lead halide perovskites (LHPs) with aggregation induced emission (AIE) feature is developed. These LHPs are nonemissive when they disperse in good solvent (DMF), but show high brightness when they aggregate in water. The morphology of LHPs changes from nanometer-sized irregular shape to micrometer-sized needle-like, and then to stick-like with increasing water fraction. However, their AIE is quenched by only a few pM of dispersed gold nanoparticles (AuNPs). Dopamine (DA) induces aggregation of AuNPs, resulting in AIE recovery of LHPs. A good linear range of DA is obtained from 0.5 to 50 μM with the limit of detection (LOD) 0.12 μM. In the catalysis of tyrosinase (TYR), DA is oxidized to dopaquinone, resulting in the fluorescence quenching of LHPs again. Therefore, this system is further used for monitoring TYR activity and evaluating inhibitor of TYR. Finally, this method is successfully applied to detecting DA in urine samples.

[en] In this work, the ZnS QDs, Bi/β-Bi₂O₄ and ZnS/Bi/β-Bi₂O₄ nanocomposite were synthesized through a facile precipitation, solvothermal and wet impregnation route respectively. The combination of bare ZnS QDs with Bi/β-Bi₂O₄ nanocomposite exhibits superior photocatalytic activity against toxic pollutants (MB & Rh B) and it’s attributed to the increased light-absorption capacity, efficient charge transfer process, extraordinary exciton separation, less photogenerated electron-hole recombination. The ZnS/Bi/β-Bi₂O₄ nanocomposite was found to be 3 times more efficient as a photocatalyst than pristine ZnS QDs. Besides, this composite demonstrates good stability for photocatalytic activities, no substantial decomposition of activity is being observed after 5 cycle’s run devoid of a main defeat in their performance. Scavenger test were also implemented in order to appreciate the possible mechanism of photodegradation. This superior photocatalytic activity and stability may offer a new sight in the improvement of a photocatalyst with large efficiency for practical application of wastewater treatment.

[en] A series of centrosymmetric and acentric whitlockite-type stoichiometric phosphates Ca₈MEr(PO₄)₇, M = Ca²⁺, Mg²⁺, Zn²⁺ and Ca_9-xZn_xLa_0.9(PO₄)₇:0.1Er³⁺ were synthesized through the high-temperature solid state route. The obtained phases were studied by a combination of methods including Synchrotron powder X-ray diffraction, dielectric spectroscopy, second harmonic generation, luminescence spectroscopy. There are two single-phase regions of polar (0 ≤ x < 0.5) and nonpolar (0.6 ≤ x ≤ 1) crystal structures were distinguished in Ca_9-xZn_xLa_0.9(PO₄)₇:0.1Er³⁺. These areas are separated by a two-phase region (0.5 ≤ x < 0.6). It was shown, that under Ca²⁺ → Zn²⁺ substitution a transformation from ferroelectric to antiferroelectric properties was occurred. The luminescence properties of the Ca₈MEr(PO₄)₇ were characterized by NIR spectroscopy at 300 K and at 5 K. It was concluded that the crystal site engineering in Er³⁺-containing β-Ca₃(PO₄)₂-type hosts offering a promising way to obtain efficient NIR phosphors.