Tabrizi B, D’Elia V, Del Gobbo S, Jabbour GE. Microwave-Assisted Non-aqueous and Low-Temperature Synthesis of Titania and Niobium-Doped Titania Nanocrystals and Their Application in Halide Perovskite Solar Cells as Electron Transport Layers

Undoped and Nb-doped TiO₂ nanocrystals are prepared by a microwave-assisted non-aqueous sol-gel method based on a slow alkyl chloride elimination reaction between metal chlorides and benzyl alcohol. Sub-4 nm nanoparticles are grown under microwave irradiation at 80 °C in only 3 h with precise control of growth parameters and yield. The obtained nanocrystals could be conveniently used to cast compact TiO₂ or Nb-doped TiO₂ electron transport layers for application in formamidinium lead iodide-based photovoltaic devices. Niobium doping is found to improve the cell performance by increasing the conductivity and mobility of the electron transport layer. At the same time, a measurable decrease in parasitic light absorption in the low wavelength portion of the spectrum was observed.

Importance of Clean Surfaces on the Catalyst: SnS2 Nanorings for Environmental Remediation

The focus of the work is the synthesis of SnS₂ nanomaterials with (peg-SnS₂NF) and without (sf-SnS₂NR) the involvement of the organic template and the comparative study of their catalytic activities. The synthesis of these materials was achieved in a single-step procedure aided by hexamethyldisilazane (HMDS). These nanoparticles were subjected to X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, and UV-vis spectroscopy analyses to investigate their structural, topographical, surface, and optical properties. The present work suggests that the surfactant-free SnS₂ nanoring (sf-SnS₂NR) catalyst has lower surface area compared to the poly(ethylene glycol)-stabilized SnS₂ nanoflower (peg-SnS₂NF) catalyst but shows high activity under visible light for the photoreduction of Cr(VI) and the photocatalytic degradation of organic dyes. The work exposed the importance of the clean surfaces on the catalyst and is expected to have a high impact on the photocatalytic activity of the SnS₂ nanomaterial. The study also endorses the utility of the HMDS-assisted synthetic method for the production of multifunctional semiconductor tin disulfide nanomaterials with multiple potential applications.

Physico-chemical investigation of ZnS thin-film deposited from ligand-free nanocrystals synthesized by non-hydrolytic thio-sol-gel

Ultra-small and monodispersed zinc sulfide nanocrystals (NCs) (d ≤ 3 nm) have been prepared without the use of any surfactants by a synthetic route using benzyl mercaptan as a source of sulfur. The prepared NCs are dispersible in highly polar solvents and display the capability to closely pack-up in a bulky film. The NCs were characterized by TEM, XRD and UV-vis optical absorption as well as by steady-state and time-resolved photoluminescence (PL) spectroscopies. Uniform films of ZnS were spin-coated on glass and ITO-glass substrates using a NCs dispersion in N,N-dimethylformamide. The NCs and the resulting films were characterized by morphological and optoelectronic probing techniques such as AFM, SEM, diffuse reflectance, PL and photoelectron spectroscopy in air. These physical investigations confirmed that the chalcogenide NCs grown by this method have the potential to be utilized directly as photocatalysts and are potentially useful building-blocks/starting materials for the fabrication of semiconductor thin films for optoelectronic applications such as LED, luminescent screens, field effect transistor and solar cells. Insights on the chemistry involved in the NCs growth have been provided revealing that their formation proceeds through a mechanism involving a thioether elimination reaction.

Ethers as Oxygen Donor and Carbon Source in Non-hydrolytic Sol-Gel: One-Pot, Atom-Economic Synthesis of Mesoporous TiO2 -Carbon Nanocomposites

Mesoporous TiO₂ -carbon nanocomposites were synthesized using an original non-hydrolytic sol-gel (NHSG) route, based on the reaction of simple ethers (diisopropyl ether or tetrahydrofuran) with titanium tetrachloride. In this atom-economic, solvent-free process, the ether acts not only as an oxygen donor but also as the sole carbon source. Increasing the reaction temperature to 180 °C leads to the decomposition of the alkyl chloride by-product and to the formation of hydrocarbon polymers, which are converted to carbon by pyrolysis under argon. The carbon-TiO₂ nanocomposites and their TiO₂ counterparts (obtained by calcination) were characterized by nitrogen physisorption, XRD, solid state ¹³ C NMR and Raman spectroscopies, SEM, and TEM. The nanocomposites are mesoporous with surface areas of up to 75 m²  g^-1 and pore sizes around 10 nm. They are composed of aggregated anatase nanocrystals coated by an amorphous carbon film. Playing on the nature of the ether and on the reaction temperature allows control over the carbon content in the nanocomposites. The nature of the ether also influences the size of the TiO₂ crystallites and the morphology of the nanocomposite. To further characterize the carbon coating, the behavior of the carbon-TiO₂ nanocomposites and bare TiO₂ samples toward lithium insertion-deinsertion was investigated in half-cells. This simple NHSG approach should provide a general method for the synthesis of a wide range of carbon-metal oxide nanocomposites.

Ultrafast Synthesis and Coating of High-Quality β-NaYF4:Yb3+,Ln3+ Short Nanorods

An ultrafast route to prepare up-converting single β-phase NaYF₄:Yb³⁺,Ln³⁺ (Ln: Er, Tm, or Tb) short nanorods (UCNRs) of high quality was developed. This new procedure affords reactive-surface nanorods that are easily coated by direct injection of suitable capping ligands. Thus highly crystalline nanorods with excellent UC fluorescence and good solvent-selective dispersion are obtained, which represents a significant advance in the field and enlarges their use for biomedical and other technological applications. Unlike other methodologies, the short reaction time provides a kinetic control over crystallization processes, and the β-phase and rod morphology is preserved regardless of the optically active Ln³⁺ ion. The UC emission was finely tuned by using the most popular Yb³⁺/Tm³⁺ and Yb³⁺/Er³⁺ pairs. More importantly, UCNRs doped with the unusual Yb³⁺/Tb³⁺ pair, with no ladder-like energy levels, provided a nice emission upon near-infrared excitation, which constitutes the first example of phonon-assisted cooperative sensitization to date in pure β-NaYF₄ nanocrystals.

A general nonaqueous sol-gel route to g-C3N4-coupling photocatalysts: the case of Z-scheme g-C3N4/TiO2 with enhanced photodegradation toward RhB under visible-light

The g-C₃N₄-coupling TiO₂ photocatalysts with controllable particle size as well as the interface contact were prepared by a general nonaqueous sol-gel method. The structural and morphological features of g-C₃N₄/TiO₂ were investigated through the X-ray diffraction, Fourier transformed infrared spectra, scanning electron microscopy and transmission electron microscopy, respectively. It is found the TiO₂ nanoparticles with a size of 7.3 ± 1.6 nm are uniformly anchored on the surface of the g-C₃N₄ nanosheets in isolation. The photocatalytic properties of as-prepared g-C₃N₄/TiO₂ were tested by degradation of Rhodamine B (RhB) under visible light, and an enhanced activity is observed. The mechanism of the enhanced activity was further investigated through N₂ adsorption-desorption isotherms, UV-vis spectra, photoluminescence spectra, photoelectrochemical measurements, radical trapping experiments and X-ray photoelectron spectroscopy. Furthermore, the photocatalytic performances of obtained g-C₃N₄/TiO₂ under sunlight were also evaluated in aspects of degradation efficiency and stability. The results indicate that the obtained g-C₃N₄/TiO₂ is one promising photocatalyst for practical applications. The study of as-prepared g-C₃N₄/TiO₂ also implies that the present method could be a general route of g-C₃N₄-coupling photocatalysts.

Matching the organic and inorganic counterparts during nucleation and growth of copper-based nanoparticles – in situ spectroscopic studies

Closing the loop: initially, the reactivity of benzyl alcohol determines the nucleation of Cu nanoparticles, but as soon as they start to form they begin to catalyze the condensation of benzyl alcohol to dibenzylether.

In-situ and tunable nitrogen-doping of MoS2 nanosheets

Molybdenum disulfide (MoS₂) nanosheets have unique physical and chemical properties, which make it a perfect candidate for next generation electronic and energy storage applications. Herein, we show the successful synthesis of nitrogen-doped MoS₂ nanosheets by a simple, effective and large-scale approach. MoS₂ nanosheets synthesised by this method show a porous structure formed by curled and overlapped nanosheets with well-defined edges. Analysis of the nanosheets shows that they have an enlarged interlayer distance and high specific surface area. X-ray photoelectron spectroscopy analysis shows the nanosheets have Mo-N bond indicating successful nitrogen doping. The nitrogen content of the product can be modulated by adjusting the ratio of starting materials easily within the range from ca. 5.8 to 7.6 at%.

Morphology controlled synthesis of SnS₂ nanomaterial for promoting photocatalytic reduction of aqueous Cr(VI) under visible light

A mild, template free protocol has been demonstrated for SnS2 nanoflake formation at the gram level from SnCl2 and thioacetamide (TAA). The SnS2 nanoflakes congregate to nanoflowers and nanoyarns with variable TAA concentrations. BET measurements reveal that the synthesized nanomaterials are highly porous having very high surface area, and the nanoflower has higher surface area than the nanoyarn. The synthesized nanomaterial finds application for promoting photoreduction of extremely toxic and lethal Cr(VI) under visible light irradiation due to their porous nature. The nanoflowers photocatalyst is proved to be superior to nanoyarn due to the increased surface area and higher pore volume. It was also inferred that increased pH decreased the reaction rate. The present result suggests that the morphology-dependent photoreduction of Cr(VI) by SnS2 nanomaterial under visible light exposure will endorse a new technique for harvesting energy and purification of wastewater.

Zinc blende versus wurtzite ZnS nanoparticles: control of the phase and optical properties by tetrabutylammonium hydroxide

We demonstrated phase control, mediated by the presence of tetrabutylammonium hydroxide, in the growth of ZnS crystals by using a cost effective MAS method; a very moderate temperature (140 °C) and a very fast reaction time are sufficient to produce nanostructures with a good degree of crystallinity.