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Surface functionalization is an effective approach to improve and enhance the properties of dental materials. A review of atomic layer deposition (ALD) in the field of dental materials is presented. ALD is a well-established thin film deposition technique. It is being used for surface functionalization in different technologies and biological related applications. With film thickness control down to Ångström length scale and uniform conformal thin films even on complex 3D substrates, high quality thin films and their reproducibility are noteworthy advantages of ALD over other thin film deposition methods. Low temperature ALD allows temperature sensitive substrates to be functionalized with high quality ultra-thin films too. In the current work, ALD is elaborated as a promising method for surface modification of dental materials. Different aspects of conventional dental materials that can be enhanced using ALD are discussed. Also, the influence of different ALD thin films and their microstructure on the surface properties, corrosion-resistance, antibacterial activity, biofilm formation, and osteoblast compatibility are addressed. Depending on the stage of advancement for the studied materials reported in the literature, these studies are then categorized into four stages: fabrication & characterization, in vitro studies, in vivo studies, and human tests. Materials coated with ALD thin films with potential dental applications are also presented here and they are categorized as stage 1. The purpose of this review is to organize and present the up to date ALD research on dental materials. The current study can serve as a guide for future work on using ALD for surface functionalization and resulting property tuning of materials in real world dental applications. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract Statement of problem Maxillofacial prostheses made of silicone elastomers undergo undesirable color degradation over time. How this color change can be prevented is unclear. Purpose The purpose of this in vitro study was to evaluate the ability of an oxide nanocoating to prevent color degradation of maxillofacial silicone elastomers after artificial accelerated aging. Material and methods A silicone elastomer with functional intrinsic pigment was tested. Specimens (N=20) were fabricated, and half of them were coated with a nanolayer of titanium dioxide (TiO 2) using atomic layer deposition. Both coated and noncoated specimens (control) were exposed to artificial aging at 450 kJ/m2 of total energy. Changes in the color of all the specimens with and without TiO 2 nanocoating were measured before and after the atomic layer deposition coating and before and after aging. The obtained color data were analyzed by using independent t tests and the 1-sample t test (α=.05). Results Color change (ΔE1=3.4 ±1.4) was observed for the silicone elastomers after the specimens were surface coated with TiO 2 nanofilm, although this change was not statistically significant (P =.369) compared with the acceptability threshold (ΔE=3.0). Upon exposure to artificial aging, the noncoated control specimens underwent color change (ΔE2=2.5 ±0.7, P =.083 compared with the acceptability threshold). The specimens with TiO 2 nanocoated surface experienced the least color change (ΔE3=1.4 ±0.6) when subjected to artificial aging, and this change was significantly lower (P <.001) than the established acceptability threshold of ΔE=3.0. In addition, the chemical analyses confirmed that the TiO 2 nanocoating remained on the surface after exposure to artificial aging. Conclusions TiO 2 nanocoating was shown to be effective in reducing color degradation of the silicone elastomer exposed to artificial aging for 120 hours with 450 kJ/m2 of total energy. [ABSTRACT FROM AUTHOR]

Abstract: Nitric oxide (NO) aided Si0.85Ge0.15 wet-oxynitridation has been performed at 400–700 °C, while the wet-NO feed gas was preheated to higher temperatures before entering the reaction zone. X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy data suggests that both nitrogen and oxygen incorporation increases within the dielectric bulk with increasing wet-oxynitridation temperature, while there is no apparent germanium segregation towards the dielectric/substrate interface at all temperatures studied. Moreover, angle-resolved XPS analysis suggests that wet-oxynitridation at temperatures higher than 600 °C volatilizes some germanium oxide from the surface region, while silicon monoxide is outgassed from the dielectric bulk and accumulates near the surface. Nitrogen incorporation is found to hinder germanium segregation. Z-contrast imaging with scanning transmission electron microscopy shows that oxynitrides grown in wet-NO have sharp interfaces with bulk Si0.85Ge0.15, while the roughness of the dielectric/Si0.85Ge0.15 substrate interface is less than 2 Å. These results are discussed in the context of an overall mechanism of SiGe wet-oxynitridation. [Copyright &y& Elsevier]

Abstract: The nature of the Si–O bonds, composition, and film strain changes in thermally nitrided silicon dioxides in NH3 at 1000 °C and 1 atm is investigated with Fourier transform infrared spectroscopy and spectroscopic ellipsometry. Shifts of the transverse optical and longitudinal optical phonons of O in Si–O–Si bridging bonds are the results of both compositional and strain within the silicon dioxide matrix. Red shifts during the initial nitridation period are followed by blue shifts at longer nitridation times. Red shifts can be explained by nitrogen incorporation and strain accumulation, while bulk film strain relaxation in nitrided oxides is most likely responsible for the blue shifts. [Copyright &y& Elsevier]

• Derived a group contribution method for Atomic Layer Deposition (ALD). • Computed UNIFAC interaction parameters for functional groups of ALD precursors. • Developed computer-aided molecular design along with ALD. • Used UNIFAC interaction parameters of functional groups to design new precursors. • Designed novel titanium precursors for ALD with enhanced properties. Nanomaterials and nanostructures with multi-functional properties found widespread applications such as electronics, optics, and coatings that can be fabricated using Atomic Layer Deposition (ALD). ALD is a vapor phase deposition technique to generate thin films of metals and metal oxides on a substrate. In this process, a precursor, which often comprises of organic functional groups that surround the depositing metal, chemisorbs on the substrate or reacts with the surface sites and with each other. Precursor chemisorption on the substrate leads ALD to be a self-limiting process. Thus, the precursor(s) should be chosen in a way to enhance deposition based on the ALD conditions. For a given application, it is practically impossible to carry out a large number of experiments using numerous precursors with varied deposition conditions to find the one that maximizes the growth rate in ALD. In addition, only existing precursors can be tested experimentally. The overall objective of this work is to develop a computational tool for the in-silico design of precursor materials using adsorbate solid solution theory (ASST). In the first part of this paper, we apply the ASST to derive properties of the functional groups present in the precursor using a new Group Contribution Method (GCM). The GCM is successfully derived and compared with the experimental data from ALD. The method shows good agreement and is useful for the design of novel materials. In the second part of this paper, using the thermodynamic properties as obtained from GCM, we develop a computer-aided molecular design (CAMD) framework for the optimal design of novel precursor materials with enhanced deposition properties for the ALD of metal oxides and metals. The metaheuristic efficient ant colony optimization algorithm (EACO) developed in-house is used for both parts. CAMD is a combinatorial optimization methodology, where molecules with optimal desired properties are generated from functional groups. The precursor selection optimization problem is posed as a mixed integer nonlinear programming problem, which is solved using EACO. The ALD growth kinetics is used as an objective of optimization and a solution is validated with thermodynamic constraints. Along with the number of groups, the temperature is also included in the optimization framework as decision variables. Forty-one novel titanium precursor molecular structures for ALD are generated with growth rates ranging from 1.23 Å/cycle to as high as 1.65 Å/cycle. Thus, these precursors have shown growth rates higher than the known titanium precursors. ALD growth rate is found to be a function of the combination of the precursor functional groups as well as temperature with a complex correlation among them. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Ag ALD parameters were tailored to create a stable, antibacterial coating. • Ag ALD did not change the optimal surface hydrophobicity of pristine filter media. • Deposited silver particulates on N95 filter media is stable against washing methods. • 1100 Ag ALD cycles at 90 °C suppressed S. aureus biofilm formation. • Ag-containing ALD can be a key strategy to improve long-term service life of masks. Due to the COVID19 outbreak, there has been increasing interest in tailoring, modifying and improving conventional personal protective equipment to increase their service life and make them more effective against viruses and bacteria. Here, atomic layer deposition (ALD) was used to functionalize the filter of N95 mask with nano-islands of silver. X-ray photoelectron spectroscopy and x-ray absorption fine structure were used for ALD silver characterization; microbiological assay was conducted to study the effectiveness of the deposited silver against the air-borne pathogen Staphylococcus aureus (S. aureus). Results showed that silver ALD successfully functionalized the N95 mask at 90 and 120 °C for two different numbers of ALD cycles (1100 and 1500 cycles). The deposited silver nano-islands were stable on the N95 filter media against washing. The leaching of silver nano-islands was studied using inductively coupled plasma mass spectrometry of phosphate-buffered saline solution after soaking the mask in it over predetermined times. <9% of Ag was removed after a maximum time of 4 h that was investigated. Antimicrobial tests showed that for samples functionalized with 1100 ALD cycles of Ag, 76% reduction in S. aureus colony-forming units content was observed after 24 h of biofilm development on the mask surfaces. [ABSTRACT FROM AUTHOR]

[Display omitted] • Surface, mechanical, and biological properties of TiO 2 /ZrO 2 ALD on PMMA is studied. • Synergistic effects of thin films of mixed oxides over single oxides are presented. • Mixed TiO 2 /ZrO 2 films show better antimicrobial activity than single oxides. • Coatings protect PMMA from wear and thermal effects and improve its nanohardness. • Enhanced functionalization of PMMA for biomedical and engineering applications. Titanium(IV) oxide (TiO 2) and zirconium(IV) oxide (ZrO 2) are well-known materials for their biocompatibility, hydrophilicity, antimicrobial activity, and excellent mechanical properties. Polymethyl methacrylate (PMMA), on the other hand, has many applications in medicine, biomedical systems, and engineering. However, its poor surface and mechanical properties limit its applications. The purpose of this study is how functionalization of PMMA would provide surface protection and reduce microbial adherence and biofilm formation. Hence, low-temperature Atomic Layer Deposition (ALD) was used to deposit TiO 2 , ZrO 2 , and TiO 2 /ZrO 2 mixed oxides nanofilms on PMMA substrates. Surface composition was examined and Ti:Zr ratios were calculated through x-ray photoelectron spectroscopy. The coatings increased wettability and slightly enhanced nanohardness of PMMA. No significant change was observed in the surface roughness of PMMA after ALD. The nanocoatings protected the PMMA surface from thermal and brushing challenges by maintaining wettability, surface roughness, and film integrity. Additionally, compared to control, the mixed oxides with 1:2 cycle ratio of TiO 2 :ZrO 2 showed a significant reduction on all bacterial and fungal initial adhesion and biofilm formation, while the TiO 2 film provided reduction at initial fungal adhesion. Thus, TiO 2 /ZrO 2 ALD on PMMA could enhance its surface, mechanical, and biological properties, preparing it for biomedical and engineering applications. [ABSTRACT FROM AUTHOR]

Abstract: Direct physical linkage of MAGUKs to the actin cytoskeleton was first established by the interaction of erythrocyte p55 with the FERM domain of protein 4.1R. Subsequently, it was reported that p55 binds to a 51-amino acid peptide, encoded by exon 10, located within the FERM domain of protein 4.1R. In this study, we investigated the nature of the p55–FERM domain binding interface and show that p55 binds to a second 35-amino acid peptide, encoded by an alternatively spliced exon 5, located within the FERM domain of protein 4.1R. Competition and Surface Plasmon Resonance-binding measurements suggest that the peptides encoded by exons 5 and 10 bind to independent sites within the D5 domain of p55. Interestingly, the full length 135 kDa isoform of protein 4.1R containing both exons 5 and 10 was targeted exclusively to the plasma membrane of epithelial cells whereas the same isoform without exon 5 completely lost its membrane localization capacity. Together, these results indicate that p55 binds to two distinct sites within the FERM domain, and the alternatively spliced exon 5 is necessary for the membrane targeting of protein 4.1R in epithelial cells. Since sequences similar to the exon 5-peptide of protein 4.1R and D5 domain of p55 are conserved in many proteins, our findings suggest that a similar mechanism may govern the membrane targeting of other FERM domain containing proteins. [Copyright &y& Elsevier]

Zirconia atomic layer deposition (ALD) using zirconium 2 -methyl 2 -butoxide (ZMB) and ethanol is reported for the first time. The process selectively deposits a uniform ZrO 2 film on silicon with a high deposition rate (∼2 Å/cycle), without any deposition on copper at a relatively low temperature (200 °C) and up to at least 200 cycles. This is the largest thickness of inherently surface selective ZrO 2 ALD ever reported (∼400 Å) and is at least 10 times more selective than that achieved using a similar deposition process but with a different precursor, tris (dimethylamino)cyclopentadienyl Zirconium (ZyALD™). The selectively deposited ZrO 2 films were characterized using spectral ellipsometry, X-ray photoelectron spectroscopy, extended X-ray absorption fine structure spectroscopy (EXAFS), atomic force microscopy and energy dispersive spectroscopy obtained during scanning electron microscopy and scanning transmission electron microscopy. Surface characterization techniques employed here confirmed the chemical nature and topography of the deposited ZrO 2 , whereas EXAFS showed the ZrO 2 to be amorphous on silicon having local bonding structure similar to that of ZrO 2 deposited with ZyALD™ precursor. [Display omitted] • Zirconia atomic layer deposition (ALD) using zirconium 2-methyl 2-butoxide (ZMB) and ethanol is reported for the first time. • Inherently selective Zirconia ALD on silicon and not on copper is demonstrated for the first time with the ZMB/Ethanol system. • Use of X-ray absorption, electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy and spectroellipsometry • Inherently selective ALD Zirconia nanofilm thickness is ten- to fifteen-fold higher than that of any material reported to date. [ABSTRACT FROM AUTHOR]