Platinum(II) Phenylpyridyl Schiff Base Complexes as Latent, Photoactivated, Alkene Hydrosilylation Catalysts.

Photoactivated catalysts for the hydrosilylation of alkenes with silanes offer temporal control in manufacturing processes that require silicone curing. We report the development of a range of air-stable Pt(II) (salicylaldimine)(phenylpyridyl), [Pt(sal)(ppy)], complexes as photoinitiated hydrosilylation catalysts. Some of these catalysts show appreciable latency in thermal catalysis and can also be rapidly (10 s) activated by a LED UV-light source (365 nm), to give systems that selectively couple trimethylvinylsilane and hexamethylsiloxymethylsilane to give the linear hydrosilylation product. Although an undetectable (by NMR spectroscopy) amount of precatalyst is converted to the active form under UV-irradiation in the timescale required to initiate hydrosilylation, clean and reliable kinetics can be measured for these systems that allow for a detailed mechanism to be developed for Pt(sal)(ppy)-based photoactivated hydrosilylation. The suggested mechanism is shown to have close parallels with, but also subtle differences from, those previously proposed for thermally-activated Karstedt-type Pt(0) systems.

Unraveling the Steric Link to Copper Precursor Decomposition: A Multi-Faceted Study for the Printing of Flexible Electronics.

The field of printed electronics strives for lower processing temperatures to move toward flexible substrates that have vast potential: from wearable medical devices to animal tagging. Typically, ink formulations are optimized using mass screening and elimination of failures; as such, there are no comprehensive studies on the fundamental chemistry at play. Herein, findings which describe the steric link to decomposition profile: combining density functional theory, crystallography, thermal decomposition, mass spectrometry, and inkjet printing, are reported. Through the reaction of copper(II) formate with excess alkanolamines of varying steric bulk, tris-co-ordinated copper precursor ions: "[CuL3 ]," each with a formate counter-ion (1-3) are isolated and their thermal decomposition mass spectrometry profiles are collected to assess their suitability for use in inks (I1-3 ). Spin coating and inkjet printing of I1,2 provides an easily up-scalable method toward the deposition of highly conductive copper device interconnects (ρ = 4.7-5.3 × 10-7 Ω m; ≈30% bulk) onto paper and polyimide substrates and forms functioning circuits that can power light-emitting diodes. The connection among ligand bulk, coordination number, and improved decomposition profile supports fundamental understanding which will direct future design.

Tris(ß-ketoiminate) Aluminium(III) Compounds as Aluminium Oxide Precursors.

Precursor design is the crucial step in tailoring the deposition profile towards a multitude of functional materials. Most commercially available aluminium oxide precursors require high processing temperatures (>500 °C). Herein, we report the tuning of the decomposition profile (200-350 °C) of a range of octahedrally coordinated tris(ß-ketoiminate) aluminium complexes of the type [Al(MeCN(R)CHC=OMe)3 ], by varying the R substituents in the ligands. The complexes are derived from the reaction of trimethylamine alane (TMAA) and a series of N-substituted ß-ketoiminate ligands (R-acnacH, R=Me, Et, i Pr, Ph) with varying R-substituents sizes. When the more sterically encumbered ligand (R=Mes) was used, the Al atom became five-coordinate, therefore representing the threshold to octahedral coordination around the metal in these type of compounds, which, consequently, lead to a change of decomposition profile. The resulting compounds have been characterised by NMR spectroscopy, mass spectrometry, elemental analysis and single crystal X-ray diffraction. [Al(MeCN(Me)CHC=OMe)3 ] has been used as a single source precursor for the deposition of Al2 O3 . Thin films were deposited via aerosol assisted chemical vapour deposition (AACVD), with toluene as the solvent, and were analysed using SEM, EDX and XPS.

MODs vs. NPs: Vying for the Future of Printed Electronics.

This Minireview compares two distinct ink types, namely metal-organic decomposition (MOD) and nanoparticle (NP) formulations, for use in the printing of some of the most conductive elements: silver, copper and aluminium. Printing of highly conductive features has found purpose across a broad array of electronics and as processing times and temperatures reduce, the avenues of application expand to low-cost flexible substrates, materials for wearable devices and beyond. Printing techniques such as screen, aerosol jet and inkjet printing are scalable, solution-based processes that historically have employed NP formulations to achieve low resistivity coatings printed at high resolution. Since the turn of the century, the rise in MOD inks has vastly extended the range of potentially applicable compounds that can be printed, whilst simultaneously addressing shelf life and sintering issues. A brief introduction to the field and requirements of an ink will be presented followed by a detailed discussion of a wide array of synthetic routes to both MOD and NP inks. Unindustrialized materials will be discussed, with the challenges and outlook considered for the market leaders: silver and copper, in comparison with the emerging field of aluminium inks.

Low-Temperature Deposition of Highly Conductive Aluminum Metal Films on Flexible Substrates Using Liquid Alane MOD Precursors.

Metal-organic decomposition (MOD) precursor inks are emerging as the new route to low-temperature deposition of highly conductive metals, owing to the tunability of their decomposition. New methods of printing are being investigated to help negate the progressive issues of the electronics industry, not least the movement toward low-cost polymers and paper substrates. Informed precursor design is crucial if achieving materials capable of this is possible. In this work, the liquid MOD precursors, dimethylethylamine alane (DMEAA) and trimethylamine alane (TEAA), have been used to deposit a highly conductive aluminum (Al) metal with resistivities in the range of 4.10 × 10-5 to 5.32 × 10-7 Ω m (mean electrical resistivity of 8 × 10-6 Ω m, approximately 300 times more resistive than bulk Al metal), without the need for an additional solvent, at low temperatures (100 and 120 °C), on a range of substrates including glass, polyimide, polyethylene terephthalate, and paper. Conductive coatings have been analyzed using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and resistivity measurements; as a proof of concept, Al deposited on paper has been used in an electrical circuit. Results indicate that DMEAA is a better precursor, producing more conductive films, which is explained by its lower decomposition temperature and higher Al weight loading, indicating potential for significant industrial application.

A rugged, self-sterilizing antimicrobial copper coating on ultra-high molecular weight polyethylene: a preliminary study on the feasibility of an antimicrobial prosthetic joint material.

We report here for the first time how the combination of a precursor solution and low temperature (170 °C) aerosol assisted chemical vapour deposition were used to bond a copper coating to ultra-high molecular weight polyethylene (UHMWPE) and promote robustness. This metallic thin film remained intact on the UHMWPE substrate after the Scotch tape test and showed notable wear-resistance after 10 cycles of sand paper-abrasion. Antimicrobial assays against both Escherichia coli and Staphylococcus aureus revealed potent dark bactericidal activity with 99.999% reduction in bacterial number within 15 minutes. These results suggest that the modified UHMWPE could be a potential candidate for antimicrobial plastics and in the long term may find application in prosthetic joint applications.

Precursors for Atmospheric Plasma-Enhanced Sintering: Low-Temperature Inkjet Printing of Conductive Copper.

Bidentate diamine and amino-alcohol ligands have been used to form solid, water-soluble, and air-stable monomeric copper complexes of the type [Cu(NH2CH2CH(R)Y)2(NO3)2] (1, R=H, Y=NH2; 2, R=H, Y=OH; 3, R=Me, Y=OH). The complexes were characterized by elemental analysis, mass spectrometry, infrared spectroscopy, thermal gravimetric analysis, and single-crystal X-ray diffraction. Irrespective of their decomposition temperature, precursors 1-3 yield highly conductive copper features [1.5×10-6â€…Ω m (±5×10-7â€…Ω m)] upon atmospheric-pressure plasma-enhanced sintering.