In recent years, investigations of the phase transition behavior of semiconducting nanoparticles under high pressure has attracted increasing attention due to their potential applications in sensors, electronics, and optics. However, current understanding of how the size of nanoparticles influences this pressure-dependent property is somewhat lacking. In particular, phase behaviors of semiconducting CdS nanoparticles under high pressure have not been extensively reported. Therefore, in this work, CdS nanoparticles of different sizes are used as a model system to investigate particle size effects on high-pressure-induced phase transition behaviors. In particular, 7.5, 10.6, and 39.7 nm spherical CdS nanoparticles are synthesized and subjected to controlled high pressures up to 15 GPa in a diamond anvil cell. Analysis of all three nanoparticles using in-situ synchrotron wide-angle X-ray scattering (WAXS) data shows that phase transitions from wurtzite to rocksalt occur at higher pressures than for bulk material. Bulk modulus calculations not only show that the wurtzite CdS nanomaterial is more compressible than rocksalt, but also that the compressibility of CdS nanoparticles depends on their particle size. Furthermore, sintering of spherical nanoparticles into nanorods was observed for the 7.5 nm CdS nanoparticles. Our results provide new insights into the fundamental properties of nanoparticles under high pressure that will inform designs of new nanomaterial structures for emerging applications.

The use of zinc oxide (ZnO) nanostructures as a photocatalyst for the degradation of organic pollutants in water has received significant attention over the recent years. However, synthesis methods for producing ZnO nanostructures are generally costly, complicated, and hazardous to the environment. In this work, we demonstrate the synthesis of ZnO nanostructures by a simple hot water treatment (HWT) method and the photocatalytic activity of the hence produced nanostructures. HWT is a one-step, low-cost, eco-friendly, and scalable nanostructure growth method. By HWT, various metal-oxide nanostructures can be produced simply by the interaction of metals with hot water without the need for any chemical additives in the solution. Growth of metal-oxide nanostructures by HWT involves the formation of metal-oxides and their release from the surface of the metal into water, the migration of the metal-oxides in water, and their re-deposition at a different part of the metallic surface, which initiates the growth of nanostructures. In this study, we used zinc powder and plates for producing the ZnO nanostructures by HWT in DI water at 75°C. Scanning electron microscopy and X-ray diffraction were utilized to verify the formation of ZnO nanostructures. Zinc plates produced a suspension of ZnO nanostructures in water, while on the other hand, zinc powder resulted in ZnO nanostructures grown on the powder surface as well as standalone ZnO nanostructures also mixed in water. We used these nanostructures + water suspensions for our photocatalytic degradation studies. Methylene blue (MB) was used as a model organic pollutant. We mixed the ZnO nanostructure suspension with MB and exposed it to UV light. The degradation of MB was observed by measuring its absorbance values using a UV-Visible spectrophotometer over a period of 4 hours. We observed a 20% decrease in the concentration of MB in 4 hours when nanostructured Zn/ZnO powder suspension was used, and a 30% decrease was achieved when ZnO nanostructure-only suspension produced from zinc plates was used. MB alone was also exposed to UV light for the same period as a control experiment, and we did not observe any significant decrease in its concentration. These results indicate that the hot water treatment method presents a very simple, cost-effective, scalable, and eco–friendly alternative for the synthesis of ZnO nanostructures for photocatalytic water treatment applications.

We report on the synthesis, properties, and ion conductivity of a solid polymer electrolyte produced from polytetrahydrofuran (PTHF) photo-crosslinked with 3,4-epoxycyclohexylmethyl 3ʹ,4ʹ-epoxycyclohexane carboxylate (Epoxy), via an active monomer mechanism that facilitates the reaction of the native hydroxyl and epoxide end-groups. Crosslinked samples were loaded with different quantities of lithium tetrafluoroborate (LiBF4) and evaluated by electrochemical spectroscopy impedance (EIS) to determine their ionic conductivity. An increase in lithium salt loading led to an increase in ionic transport, reaching competitive conductivities of up to 10-3 S/cm at temperatures typical for battery operation. Thermal analysis confirms the amorphous structure and high thermal stability (30-90°). The mechanical analysis shows the materials possess suitable stiffness for applications. The results demonstrate a new synthetic route to tunable crosslinked networks for a broad range of chemical building blocks to achieve high lithium-ion conduction and attain desirable thermal and mechanical properties.

Mesoporous-TiO2:Sb layers were developed by sol-gel and spin-coating techniques for their application as photoanodes in SSSCs. The effect of Sb doping (4 mol%) and PVP loading (0.2-0.4 g) on the optical, structural, morphological, and chemical properties were studied. SEM results showed that the morphology, porosity, and particle size in the mp-TiO2:Sb depend on the amount of polymer and Sb doping. In particular, the doping decreases the porosity and particle size. XRD patterns showed well-defined reflections resembling the anatase crystalline structure. The crystallite size was of 22.61 and 16.27 nm for the undoped layers with 0.2 and 0.4 of PVP, which decreased to 17.69 and 7.93 nm for the doped ones. It was not observed the presence of Sb2O3 or Sb metallic, indicating Sb ions were inserted in the TiO2 lattice by substitution of Ti ions. Analysis of XPS spectra showed the presence of Ti4+, O2-, and Sb3+ in the mp-TiO2:Sb layers. The optical bandgaps of the mp-TiO2:Sb were in the range of 3.14-3.33 eV. The evaluation of the mp-TiO2:Sb layers as photoanodes in the Sb2Se3-sensitized solar cells gives a Voc of 261 mV, a Jsc of 3.92 mA/cm2, and a PCE of 0.71%.

The binary metal oxides are increasingly used as supercapacitor electrode materials in energy storing devices. Particularly NiCo2O4 has shown promising electrocapacitive performance with high specific capacitance and energy density. The electrocapacitive performance of these oxides largely depends on their morphology and electrical properties governed by their energy band-gaps and defects. The morphological structure of NiCo2O4 can be altered via the synthesis route, while the energy band-gap could be altered by doping. Also, doping can enhance crystal stability and bring in grain refinement, which can further improve the much-needed surface area for high specific capacitance. Given the above, this study evaluates the electrochemical performance of Ca-doped Ni1-xCaxCo2O4 (0 ≤ x ≤ 0.8) compounds. This stipulates promising applications for electrodes in future supercapacitors.

Recently, two-dimensional layered structures, especially MoS2 has come out as the most investigated electrode material for batteries and supercapacitors, possessing well preserved in-plane covalent bonding, leading to extraordinary mechanical elasticity within the layers as well as outstanding firmness along the c-axis. The present work is aimed to fabricate vertically aligned edge exposed molybdenum disulfide nanoflakes on the surface of the self-standing hydrophilic carbon nanotubes, using a two-step process involving a chemical route and magnetron sputtering techniques for flexible supercapacitor application. These hybrid heterostructures have been characterized using XRD, FESEM, and cyclic voltammetry. In the aqueous electrolyte of 1M Li2SO4, the symmetric device revealed very high areal capacitance of 182.5 mF/cm2 and 155 mF/cm2, at scan rates of 2 and 5 mV/s, respectively. The device shows high energy density of 365 mWh/cm2.

The REE (rare-earth-elements) cerium (Ce) is the most abundant earth-crust element and their oxides have great attention in the form of nanocrystalline nature with superior physical and chemical properties. Pure and Co (1%, 3% and 5%) doped CeO2 nanoparticles (NPs) synthesized by co-precipitation technique were characterized through X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), UV-visible spectroscopy. XRD shows face-centred-cubic (FCC) crystal symmetry with average crystallite size 6–12 nm. HRTEM exhibits almost identical cubical shaped particles with average size 4–10 nm. Tuned band-gap may be observed from UV-visible spectrum of CeO2-NPs upon Co (1%, 3% & 5%) incorporation. Enhancement of the photocatalytic activity observed for Co-doped (1%, 3% & 5%) to the degradation of methylene-blue (MB) dye under visible-light absorption.

Surface modification of Engelhard titanosilicate (ETS-10) with silver (Ag) was carried out in efforts to promote the photocatalytic activity of ETS-10 towards the degradation of methylene blue (MB) under visible light irradiation. The core-shell heterostructure encapsulates the Ag nanoparticles, which would otherwise dislodge from the surface of ETS-10. The Ag@ETS-10 core-shell heterostructured photocatalyst was prepared by the photodeposition of Ag nanoparticles onto ETS-10 crystals to form the Ag-ETS-10 core, followed by secondary growth of ETS-10 shell using the Ag-ETS-10 as seeds. Ag@ETS-10 showed absorption in the visible light region, as well as a red shift in the UV region, compared to the unmodified ETS-10. The extent of shell growth depended on the seeding level. Increasing the seeding level from 1 wt.% to 50 wt.% resulted in a decreased mode of the particle size distribution of the products, and thus a decreased shell thickness. The Ag@ETS-10 photocatalyst grown using 50 wt.% seeding level (i.e., ∼0.1 μm shell) showed higher photocatalytic activity in the photodegradation of MB under visible light irradiation (k = 0.0159 min-1) than the unmodified ETS-10 sample (k = 0.007 min-1). However, the Ag@ETS-10 photocatalyst grown using 1 wt. % seeding levels (i.e., ∼ 0.8 μm shell) showed lower photocatalytic activity compared to the Ag@ETS-10 photocatalyst grown using 50 wt.% seeding level (i.e., ∼ 0.1 μm shell). This was attributed to the suppression of the plasmon resonance peak when a thicker ETS-10 shell was grown around the Ag-ETS-10 core.

Silicon has attracted particular attention as a potential high capacity material for lithium based batteries. However, the application of Si-based electrodes remains challenging, in major part due to its significant irreversible energy loss during cycling. Here isothermal microcalorimetry (IMC) is demonstrated to be a precise and operando characterization method for tracking a battery's thermal behaviour and deconvoluting the contributions from electrochemical polarization, entropy change, and parasitic reactions. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and x-ray powder diffraction (XRD) further elucidate the Si reactivity in conjunction with the IMC.