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Polymer membranes have a wide variety of applications, ranging from water treatment to energy storage. Many of these applications require precise control over the membrane porosity and surface chemistry. In this study, we explore the modification of isoporous polycarbonate (PC) track-etched membranes (PCTEs) by atomic layer deposition (ALD) and sequential infiltration synthesis (SIS) to tune the pore size and the pore wall surface chemistry. We first performed a detailed study of Al2O3 ALD and SIS in PCTE using a variety of in situ and ex situ measurements. We discovered that short precursor exposure times are critical to achieve conformal Al2O3 ALD in the PCTE nanopores, while longer precursor exposure times resulted in Al2O3 SIS within the bulk of the PC leaving the membranes brittle. Next, we tuned the PCTE pore size via Al2O3 ALD and studied its effect on the water contact angle and the water permeance. We found that the membranes became more hydrophilic, and the permeance decreased with increasing ALD Al2O3 cycles. Finally, we studied the effect of hydrophilic (SnO2)/hydrophobic (In2O3) ALD metal oxide coatings on membrane properties. We found that the most hydrophilic SnO2 showed the highest water flux and the least hydrophilic In2O3 showed the lowest water flux through the PCTE membranes. Our results demonstrate that ALD is an effective method to tune the surface and transport properties of PCTE membranes, but care must be exercised to avoid SIS and bulk modification of the polymer. [ABSTRACT FROM AUTHOR]

New complexes MoO2(tBuAMD)2 (1) and WO2(tBuAMD)2 (2) (AMD = acetamidinato) are synthesized and fully characterized as precursors for atomic layer deposition (ALD). They contain metal-oxo functionalities not previously utilized in ALD-type growth processes and are fully characterized by 1H and 13C NMR, X-ray diffraction (XRD), Fourier transform infrared, thermogravimetric analysis, single-crystal XRD, and elemental analysis. Guided by quartz-crystal microbalance studies, ALD growth methodologies for both complexes have been developed. Remarkably, these isostructural compounds exhibit dramatic differences in ALD properties. Using 1 and O3, amorphous, ultrathin molybdenum oxynitride (MoON) films are grown on Si(100) wafers. Using 2 and H2O yields amorphous WO3 films on Si(100) wafers that crystallize as WO3 nanowires upon annealing. Although 1/H2O and 2/O3 growth was attempted, effective ALD growth could only be obtained with 1/O3 and 2/H2O, underscoring reactivity differences in these precursors. Film thicknesses, compositions, and optical and electrical parameters are characterized by variable angle spectroscopic ellipsometry, X-ray reflectivity, grazing incidence X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and atomic force microscopy techniques. The hitherto unknown ALD chemistry of group VI metal-oxo compounds lays a foundation for their use in the ALD synthesis of heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

New strategies to synthesize nanometer-scale silicon dioxide (SiO 2 ) patterns have drawn much attention in applications such as microelectronic and optoelectronic devices, membranes, and sensors, as we are approaching device dimensions shrinking below 10 nm. In this regard, sequential infiltration synthesis (SIS), a two-step gas-phase molecular assembly process that enables localized inorganic material growth in the targeted reactive domains of polymers, is an attractive process. In this work, we performed in situ Fourier transform infrared spectroscopy (FTIR) measurements during SiO 2 SIS to investigate the reaction mechanism of trimethylaluminum (TMA) and tri(tert-pentoxy) silanol (TPS) precursors with polymers having ester functional groups (poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), polycaprolactone (PCL), and poly(t-butyl methacrylate) (PBMA)), for the purpose of growing patterned nanomaterials. The FTIR results show that for PMMA and PEMA, a lower percentage of functional groups participated in the reactions and formed weak and unstable complexes. In contrast, almost all functional groups in PCL and PBMA participated in the reactions and showed stable and irreversible interactions with TMA. We discovered that the amount of SiO 2 formed is not directly correlated with the number of interacting functional groups. These insights into the SiO 2 SIS mechanism will enable nanopatterning of SiO 2 for low-dimensional applications., Competing Interests: The authors declare no competing financial interest., (© 2024 American Chemical Society.)

Membranes are among the most promising technologies for energy-efficient and highly selective separations, and the surface-charge property of membranes plays a critical role in their broad applications. Atomic layer deposition (ALD) can deposit materials uniformly and with high precision and controllability on arbitrarily complex and large substrates, which renders it a promising method to tune the electrostatics of water/solid interfaces. However, a systematic study of surface-charge properties of ALD-grown films in aqueous environments is still lacking. In this work, 17 ALD-grown metal-oxide films are synthesized, and a comprehensive study of their water stability, wetting properties, and surface-charge properties is provided. This work represents a resource guide for researchers and ultimately for materials and process engineers, seeking to tailor interfacial charge properties of membranes and other porous water treatment components.

Atomic layer deposition (ALD) of the well-known Al 2 O 3 on a LiCoO 2 system is compared with that of a newly developed AlW x F y material. ALD coatings (∼1 nm thick) of both materials are shown to be effective in improving cycle life through mitigation of surface-induced capacity losses. However, the behaviors of Al 2 O 3 and AlW x F y are shown to be significantly different when coated directly on cathode particles versus deposition on a composite electrode composed of active materials, carbons, and binders. Electrochemical impedance spectroscopy, galvanostatic intermittent titration techniques, and four-point measurements suggest that electron transport is more limited in LiCoO 2 particles coated with Al 2 O 3 compared with that in particles coated with AlW x F y . The results show that proper design/choice of coating materials (e.g., AlW x F y ) can improve capacity retention without sacrificing electron transport and suggest new avenues for engineering electrode-electrolyte interfaces to enable high-voltage operation of lithium-ion batteries., Competing Interests: The authors declare no competing financial interest.