The extent of partial hydrolysis of tetraethyl propylene diphosphonate ester (TEPD) is altered by controlling the acid content during the formation of hybrid organic-inorganic TiO₂ nanoparticles. Depending on the degree of partial hydrolysis, the TEPD (derivatives)-TiO₂ bonding in the obtained materials is altered, as evidenced by solution and solid-state NMR.

Abstract

The hydrolysis of the phosphonate ester linker during the synthesis of hybrid (organic-inorganic) TiO₂ nanoparticles is important when forming porous hybrid organic-inorganic metal phosphonates. In the present work, a method was utilized to control the in-situ partial hydrolysis of diphosphonate ester in the presence of a titania precursor as a function of acid content, and its impact on the hybrid nanoparticles was assessed. Organodiphosphonate esters, and more specific, their hydrolysis degree during the formation of hybrid organic-inorganic metal oxide nanoparticles, are relatively under explored as linkers. Here, a detailed analysis on the hydrolysis of tetraethyl propylene diphosphonate ester (TEPD) as diphosphonate linker to produce hybrid TiO₂ nanoparticles is discussed as a function of acid content. Quantitative solution NMR spectroscopy revealed that during the synthesis of TiO₂ nanoparticles, an increase in acid concentration introduces a higher degree of partial hydrolysis of the TEPD linker into diverse acid/ester derivatives of TEPD. Increasing the HCl/Ti ratio from 1 to 3, resulted in an increase in degree of partial hydrolysis of the TEPD linker in solution from 4 % to 18.8 % under the applied conditions. As a result of the difference in partial hydrolysis, the linker-TiO₂ bonding was altered. Upon subsequent drying of the colloidal TiO₂ solution, different textures, at nanoscale and macroscopic scale, were obtained dependent on the HCl/Ti ratio and thus the degree of hydrolysis of TEPD. Understanding such linker-TiO₂ nanoparticle surface dynamics is crucial for making hybrid organic-inorganic materials (i. e. (porous) metal phosphonates) employed in applications such as electronic/photonic devices, separation technology and heterogeneous catalysis.

NiO/ZnO-derived MOF composite is used to modify carbon felt electrode. Alkaline zinc-based electrolyte is used as anolyte and catholyte and exhibits better redox reactions. The peak current ratio increases to 1.07 mA at 10 mA cm⁻² for the as-prepared material.

Abstract

NiO/ZnO composite derived metal-organic framework (MOF) is used as to modify carbon felt (CF) via a conventional solid-state reaction followed by ultrasonication. The prepared electrode material is used in zinc-hybrid redox flow batteries (RFBs) due to their high redox activity of Zn²⁺/Zn. The electrochemical performance of composite modified CF and pre-treated CF was studied by cyclic voltammetry (CV) in 0.5 M aqueous zinc chloride with 5 M potassium hydroxide solutions showed clear confirmation for enhanced electrocatalytic activity. The unique porous structure of NiO/ZnO-derived MOF with increased surface area improves the battery behavior significantlyThe peak current ratio for the as-prepared material is about 3 times higher than that of the pre-treated CF due to more active sites. Zinc-based RFB with modified CF electrode exhibited better electrochemical performance with voltage efficiency (VE, 88 %), which is higher than true redox flow batteries.

Weakly bound neon dimer, trimer and tetramers are studied at HF and CCSD(T) levels using Dunning, ANO and SIGMA-s basis sets. Their ground-state binding energies are studied along with some structural properties. SIGMA-s basis sets have been developed explicitly for this issue but in a manner that can be readily applied to other atoms for the study of larger weakly bound systems. The difficulties for attaining accurate results on these systems are assessed by the computation of total, atomization and correlation energies, as well as equilibrium distances, with several basis sets of increasing size, ranging from non-augmented to double-augmented versions. Extrapolations are proposed to predict stabilization energies and the results are compared with previously published data.

One of the emerging study areas to boost the heat transfer rates of the thermal devices is the further improvement of the thermophysical properties and thermal performance of ionic liquids (IL) by dispersing nanoparticles. This work provides a summary of the most recent research on the use of ionic liquid nanofluids as heat transfer fluids. Additionally, the methods for analyzing the thermophysical properties and creating IL nanofluids are discussed.

Abstract

Due to the improved thermophysical characteristics of ionic liquids (ILs), such as their strong ionic conductivity, negligible vapor pressure, and thermal stability at high temperatures, they are being looked at viable contender for future heat transfer fluids. Additionally, the dispersing nanoparticles can further improve the thermophysical characteristics and thermal performance of ionic liquids, which is one of the emerging research interests to increase the heat transfer rates of the thermal devices. The latest investigations about the utilization of ionic liquid nanofluids as a heat transfer fluid is summarized in this work. These summaries are broken down into three types: (a) the thermophysical parameters including thermal conductivity, viscosity, density, and specific heat of ionic liquids (base fluids), (b) the thermophysical properties like thermal conductivity, viscosity, density, and viscosity of ionic liquids based nanofluids (IL nanofluids), and (iii) utilization of IL nanofluids as a heat transfer fluid in the thermal devices. The techniques for measuring the thermophysical characteristics and the synthesis of IL nanofluids are also covered. The suggestions for potential future research directions for IL nanofluids are summarized.

For the purpose of predicting the structural and electronic properties of two-dimensional materials, a universal machine learning approach is reported.

Abstract

The growing number of studies and interest in two-dimensional (2D) materials has not yet resulted in a wide range of material applications. This is a result of difficulties in getting the properties, which are often determined through numerical experiments or through first-principles predictions, both of which require lots of time and resources. Here we provide a general machine learning (ML) model that works incredibly well as a predictor for a variety of electronic and structural properties such as band gap, fermi level, work function, total energy and area of unit cell for a wide range of 2D materials derived from the Computational 2D Materials Database (C2DB). Our predicted model for classification of samples works extraordinarily well and gives an accuracy of around 99 %. We are able to successfully decrease the number of studied features by employing a strict permutation-based feature selection method along with the sure independence screening and sparsifying operator (SISSO), which further supports the design recommendations for the identification of novel 2D materials with the desired properties.

Diversity in organometallic allenes: A structure-bonding study on two isomeric organometallic allenes [(μ-C)(Fe(CO)₄)₂] reveals a bis-pseudoallylic anionic delocalisation, similar to organic allene C(CH₂)₂, in the first case, and a typical three-center bis-allylic anionic delocalisation in the second one. A quantitative bonding analysis shows the transformation of the central carbon atom from a classical tetravalent coordinating center to a double σ-donor double π-acceptor ligand.

Abstract

Allenes (R₂C=C=CR₂) have been traditionally perceived to feature localized orthogonal π-bonds between the carbon centres. We have carried out quantum-mechanical studies of the organometallic allenes envisioned by the isolobal replacement of the terminal CH₂ groups by the d⁸ Fe(CO)₄ fragment. Our studies have identified two organometallic allenes viz. D_2d symmetric [(μ-C)(Fe(CO)₄)₂] (2) and D₃ symmetric [(μ-C)(Fe(CO)₄)₂] (3) with trigonal bipyramidal coordination at the Fe atoms. Compound 2 features the bridging carbon atom in an equatorial position with respect to the ligands on the TM centre, while 3 features the central carbon atom in an axial position. The bis-pseudoallylic anionic delocalisation proposed in the C2-C1-C3 spine of organic allene is retained in the organometallic allene 2, and is transformed to a typical three-centre bis-allylic anionic delocalisation in the organometallic allene 3. The topological analysis of electron density also indicates a bis-allylic anionic type delocalisation in the organometallic allenes. The quantitative bonding analysis using the EDA-NOCV method suggests a transition from classical electron-sharing bonding between the central carbon atom and the terminal groups in 1 to donor-acceptor bonding in 3. Meanwhile, both electron-sharing and donor-acceptor bonding models are found to be probable heuristic bonding representations in the organometallic allene 2.

Electronic states on the MoS₂ basal plane due to the formation of sulfur vacancies while annealing in hydrogen are revealed using ambient pressure XPS and DFT calculations. The XPS spectra shows the development of new components in Mo 3d due to the formation of sulfur vacancies with increasing temperature. The DFT calculations with appropriate vacancy models reproduce the core-level shifts.

Abstract

Sulfur vacancy on an MoS₂ basal plane plays a crucial role in device performance and catalytic activity; thus, an understanding of the electronic states of sulfur vacancies is still an important issue. We investigate the electronic states on an MoS₂ basal plane by ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and density functional theory calculations while heating the system in hydrogen. The AP-XPS results show a decrease in the intensity ratio of S 2p to Mo 3d, indicating that sulfur vacancies are formed. Furthermore, low-energy components are observed in Mo 3d and S 2p spectra. To understand the changes in the electronic states induced by sulfur vacancy formation at the atomic scale, we calculate the core-level binding energies for the model vacancy surfaces. The calculated shifts for Mo 3d and S 2p with the formation of sulfur vacancy are consistent with the experimentally observed binding energy shifts. Mulliken charge analysis indicates that this is caused by an increase in the electronic density associated with the Mo and S atoms around the sulfur vacancy as compared to the pristine surface. The present investigation provides a guideline for sulfur vacancy engineering.

Recently, we demonstrated that Pt catalyst complexes dissolved in the ionic liquid (IL) [C4C1Im][PF6] can be deliberately enriched at the IL surface by introducing perfluorinated substituents, which act like buoys dragging the metal complex towards the surface. Herein, we extend our angle-resolved X-ray photoelectron spectroscopy (ARXPS) studies at complex concentrations between 30 and 5%mol down to 1%mol and present complementary surface tension pendant drop (PD) measurements under ultra clean vacuum conditions. This combination allows for connec­ting the microscopic information on the IL/gas interface from ARXPS with the macroscopic property surface tension. The surface enrichment of the Pt complexes is found to be most pronounced at 1%mol. It also displays a strong temperature dependence, which was not observed for 5%mol and above, where the surface is already saturated with the complex. The surface enrichment deduced from ARXPS is also reflected by the pronounced decrease in surface tension with increasing concentration of the catalyst. We furthermore observe by ARXPS and PD a much stronger surface affinity of the buoy-complex as compared to the free ligands in solution. Our results are highly interesting for an optimum design of ionic catalyst solutions contact areas with a surrounding reactant/product phase, such as in SILP catalysis.

The contributions of the dichroism and birefringence to the SRS signal depend strongly on the energy level structure of the molecular sample. They can be separated experimentally by using an appropriate probe beam polarization analyzer installed in front of the photodetector (D).

Abstract

Dichroism and birefringence in Stimulated Raman Scattering (SRS) in polyatomic molecules were studied theoretically. General expressions describing the change of the polarization matrix of the probe laser beam transmitted through initially isotropic molecular sample excited by the pump laser beam have been derived. Arbitrary polarization states and propagation directions of the incoming pump and probe beams were considered. The expressions were written in terms of spherical tensor operators that allowed for separation of the field polarization tensor and the molecular part containing three scalar values of nonlinear optical susceptibility with =0,1,2. The geometry of almost collinear propagation of the pump and probe beams through the molecular sample was considered in greater details. It was shown that the dichroism and birefringence refer to the nonlinear optical susceptibility element and that their contributions to the SRS signal can be separated experimentally by using an appropriate probe beam polarization analyzer installed in front of the photodetector. Particular cases of the off-resonant SRS and resonant SRS have been considered. The results obtained were expressed in terms of the Stokes polarization parameters of the pump and probe beams.

DNA origami nanostructures are surprisingly stable in up to 5 % hydrogen peroxide over the course of three days and can thus be rendered catalytically active through efficient and reliable coupling to platinum nanoparticles.

Abstract

The DNA origami technique allows fast and large-scale production of DNA nanostructures that stand out with an accurate addressability of their anchor points. This enables the precise organization of guest molecules on the surfaces and results in diverse functionalities. However, the compatibility of DNA origami structures with catalytically active matter, a promising pathway to realize autonomous DNA machines, has so far been tested only in the context of bio-enzymatic activity, but not in chemically harsh reaction conditions. The latter are often required for catalytic processes involving high-energy fuels. Here, we provide proof-of-concept data showing that DNA origami structures are stable in 5 % hydrogen peroxide solutions over the course of at least three days. We report a protocol to couple these to platinum nanoparticles and show catalytic activity of the hybrid structures. We suggest that the presented hybrid structures are suitable to realize catalytic nanomachines combined with precisely engineered DNA nanostructures.