Potential Precursor Alternatives to the Pyrophoric Trimethylaluminium for the Atomic Layer Deposition of Aluminium Oxide

New precursor chemistries for the atomic layer deposition (ALD) of aluminium oxide are reported as potential alternatives to the pyrophoric trimethylaluminium (TMA) which is to date a widely used Al precursor. Combining the high reactivity of aluminium alkyls employing the 3-(dimethylamino)propyl (DMP) ligand with thermally stable amide ligands yielded three new heteroleptic, non-pyrophoric compounds [Al(NMe₂)₂(DMP)] ( 2 ), [Al(NEt₂)₂(DMP)] ( 3 , BDEADA) and [Al(NiPr₂)₂(DMP)] ( 4 ), which combine the properties of both ligand systems. The compounds were synthesized and thoroughly chemically characterized, showing the intramolecular stabilization of the DMP ligand as well as only reactive Al−C and Al−N bonds, which are the key factors for the thermal stability accompanied by a sufficient reactivity, both being crucial for ALD precursors. Upon rational variation of the amide alkyl chains, tunable and high evaporation rates accompanied by thermal stability were found, as revealed by thermal evaluation. In addition, a new and promising plasma enhanced (PE)ALD process using BDEADA and oxygen plasma in a wide temperature range from 60 to 220 °C is reported and compared to that of a modified variation of the TMA, namely [AlMe₂(DMP)] (DMAD). The resulting Al₂O₃ layers are of high density, smooth, uniform, and of high purity. The applicability of the Al₂O₃ films as effective gas barrier layers (GBLs) was successfully demonstrated, considering that coating on polyethylene terephthalate (PET) substrates yielded very good oxygen transmission rates (OTR) with an improvement factor of 86 for a 15 nm film by using DMAD and a factor of 25 for a film thickness of just 5 nm by using BDEDA compared to bare PET substrates. All these film attributes are of the same quality as those obtained for the industrial precursor TMA, rendering the new precursors safe and potential alternatives to TMA.     

Evaluation of 1st and 2nd generation of poly(amidoamine) dendrimer functionalized carbon nanotubes for the efficient removal of neptunium

Journal of Radioanalytical and Nuclear Chemistry - Herein, sorption of pentavalent neptunium from aqueous acidic solution was carried out onto 1st and 2nd generation of poly(amidoamine) dendrimer...     

Spectral statistics of random Schrödinger operator with growing potential

In this work we investigate the spectral statistics of random Schrödinger operators acting on where are i.i.d random variables distributed uniformly on [0,1].     

Spectrofluorimetric study on in vitro interaction between calcium phosphate nanoparticle and salmon testis DNA

Cocrystalline TiO₂ nanoblossoms having enhanced photocatalytic activities have been facilely grown via a one-step solvothermal process on titanium foil in mixed solvents of water and ethylene glycol. By varying the volume ratio of two solvents, we have controlled the morphological, the structural, and the optical properties of TiO₂ nanoblossoms. Our prepared TiO₂ nanoblossoms have been found to have both the anatase and the rutile crystal structures acting as nanoscale p–n junctions, which help to enhance catalytic performances via forming inner electric fields. In particular, TiO₂ nanoblossoms grown in the 1:1 volume mixture of water and ethylene glycol have been found to have the best-defined nanoscale p–n junctions, showing the best photocatalytic activity consequentially.     

Spectrophotometric determination of europium in aqueous samples and interference of Fe3+, UO22+ and Th4+ and other complexing agents on determination

Journal of Radioanalytical and Nuclear Chemistry - Due to the high neutron absorption cross section, Eu is having stringent specification limits in U, Pu and Th based nuclear fuel materials....     

Strategy to design aqueous-soluble iron-oxide molecular cluster and nanostructure using polyoxometalate ligand scaffold

Profound availability of iron on earth crust and diversely accessible redox states, makes it a significant metal ion in biology as well as to design molecular catalysts and nanostructured materials. Low-oxidation potential and prone to hydrolysis in an aqueous medium, predominantly in neutral to basic pH, of the divalent iron in the active site of the catalysts, results in the formation of bulk and/or colloidal ferric-hydroxide, oxy-hydroxide, and -oxide. However, nature has developed its own strategy to preserve iron-oxide cluster core, e.g., Ferritin, without aggregation in physiological pH via designing protein scaffold as protector ligand. Although molecular iron-oxo clusters, isolated by using small organic ligands, are depicted as potent catalysts, they usually don't sustain under catalytic turnover condition. In this context, the isolation of multinuclear iron-oxo clusters soluble in water and their subsequent catalysis in the aqueous phase remains a perdurable challenge. Polyoxometalates (POM) are themselves small metal-oxo cluster anions where the metals are in the highest valent-state and a diverse POM structure can be obtained simply by varying the metal ions. Depending on the structure of the POM, the available terminal or bridging oxo groups can act as donor atoms to one or more iron centers. Consequently, a variety of iron clusters can be stabilized by using POM scaffold. Thereby, polyoxoanions, extremely aqueous-soluble and oxidatively inert under reaction conditions, behaved as versatile ligand platform to stabilize iron clusters of different nuclearity (n = 2–30) in water. Moreover, different possible structures and diversity in chemical property by varying hetero atoms or metal ions led to the isolation of a unique aqueous soluble iron-oxide and/or iron-oxy-hydroxide nanostructure where a significant number of polyoxoanions were covalently attached, making them extremely soluble nanostructures. This review summarizes the adapted synthetic strategies to isolate such molecular and nano-scopic iron clusters stabilized by POM anions and describes their stability in an aqueous medium and showcases their prospective applications in different emerging areas.     

Mechanistic aspects of ligand substitution on <Emphasis Type="Italic">cis</Emphasis>-diaqua(<Emphasis Type="Italic">cis</Emphasis>-1,2-diaminocyclohexane)platinum(II) by Glycine-<Emphasis Type="SmallCaps">l</Emphasis>-Leucine

The kinetics of the interaction of glycine-l-leucine (Glyleu) with cis-[Pt(cis-dach)(OH₂)₂]²⁺ (dach = 1,2-diaminocyclohexane) has been studied spectrophotometrically as a function of [cis-[Pt(cis-dach)(OH₂)₂]²⁺], [Glyleu] and temperature at pH 4.0, where the complex exists predominantly as the diaqua species and Glyleu as a zwitterion. The substitution reaction shows two consecutive steps: the first is the ligand-assisted anation and the second is the chelation step. The activation parameters for both the steps were evaluated using Eyring’s equation. The low ∆H₁^≠ (51.9 ± 2.8 kJmol⁻¹) and large negative value of ∆S₁^≠ (−152 ± 8 JK⁻¹mol⁻¹) as well as ∆H₂^≠ (54.4 ± 1.7 kJmol⁻¹) and ∆S₂^≠ (−162 ± 5 JK⁻¹mol⁻¹) indicate an associative mode of activation for both the aqua ligand substitution processes.