Surface Modification Of Substrates Research Articles

Surfactant-Free Interface Suspended Gold Graphitic Surface-Enhanced Raman Spectroscopy Substrate for Simultaneous Multiphase Analysis.

Simultaneous multiphase detection of multiplex analytes is important, albeit challenging, especially in pharmaceuticals analysis since drugs with lipid and water solubility were often administrated together for synergistic therapy. Surface-enhanced Raman spectroscopy (SERS) is a label-free and sensitive tool for multiplex analytes detection at multiphase interfaces. However, the requirements of inducers or surfactant surface modification of the SERS substrate have restricted extensive applications. Herein, we developed a graphene-isolated-Au-nanocrystal based multiphase analysis system. Unexpectedly, the gold graphitic SERS substrate can simply suspend at the interface of the different phase without the involvement of any surfactant. Therefore, the proximity of substrate with analyte molecules remains unaffected. Such suspended substrate not only ensures sensitive SERS detection but also enables the enrichment of analytes from the different phase simultaneously without interference. Moreover, the graphitic shell of the SERS substrate has a unique vibration band located in the Raman biological silence region which is utilized as the internal standard and improves the SERS quantification accuracy. Efficient ex vivo multiphase enrichment and detection of mimic lipid- and water-soluble drugs injected into mice were demonstrated with such gold graphitic substrate, showing the potential of this simultaneous multiplex pharmacokinetic analysis.

Fabrication and properties characterization of BaSi2 thin-films thermally-evaporated on Ge (100) modified substrates

The fabrication of orthorhombic barium disilicide (BaSi2) thin-films on modified germanium (Ge) substrates by thermal evaporation method was demonstrated, in which the surface modification of Ge substrate was performed by a simple chemical etching method. The effects of etching time on crystalline quality and optical properties of the BaSi2 films were investigated. The results revealed that the substrate modification has positive impact in improving the crystalline quality, reducing the light reflection, and increasing the absorption of the BaSi2 thin-films. Etching time was optimized at 15 min, considering the trade-off between crystalline quality and optical properties. Minority carrier-lifetime of the evaporated film on Ge substrate achieved 3.17 μs, which is among the high value obtained for thin BaSi2 films.

Reliable surface modification of dental plastic substrates to reduce biofouling with a photoreactive phospholipid polymer

ABSTRACTPlastic substrates have been widely applied in clinical settings for dental treatments. These substrates should be strong enough for long‐term implantation in the oral cavity and should be resistant to biofouling. We developed a new photoreactive phospholipid polymer to reduce biofouling on dental plastics via a photochemical reaction. Poly(methyl methacrylate) (PMMA) and poly(ether ether ketone) (PEEK) were used as dental plastics. To determine the antibiofouling properties on the polymer surface, the phospholipid polymer was covalently immobilized on the substrates by UV irradiation. We evaluated the antibiofouling properties by observing the protein adsorption and cell and bacterial adhesion. Significant protein adsorption and cell adhesion appeared on the bare PMMA and PEEK substrates but decreased dramatically after surface modification with the phospholipid polymer. Thus, this photoreactive polymer shows potential for conferring dental plastics with antibiofouling properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46512.

(Invited) Additives in Cu Plating for Microelectronics Applications

Electrodeposition is a prevailing method in fabrication of Cu interconnects in microelectronics due to its ability to fill complex structures having a wide range of critical dimensions. A typical acidified Cu electrolyte contains a number of additives, organic and inorganic species in ppm amounts, with a specific role in the plating process. The additives in Cu plating have been extensively studied in the past couple of decades, and grouped according to their role in filling/creating features for microelectronics applications. This categorization is not a uniform one, and it might differ from author to author. In one popular convention, organic additives in the so-called three-component plating bath are named accelerator, suppressor and leveler, with their names hinting at how they influence Cu deposition. Ultimately, it is thanks to these additives that defect-free Cu features ranging from tens of nanometers to hundreds of micrometers can be economically fabricated. However, it is not enough to successfully fill a given single feature. The same has to be done for all the features on a 300 mm wafer, and then performed reproducibly over and over again. So, one needs to monitor the state of the electrolyte, i.e. of all the bath constituents, and either replace or replenish the electrolyte when the need arises. Additives could also have a strong influence on the physical properties of the deposit and therefore have a strong influence on the post-plating processing results. An additive that promotes void-free deposition of Cu structures in the end might not be used in a production line if it creates issues in the processing steps following electrodeposition. In our presentation we focus on a number of specific examples showing the effect of additives on nucleation and growth of Cu, propagation of Cu fronts on resistive substrates, post-plating processing, and their use in substrate surface modifications. A closer look is taken into in situ microscopic and electrochemical techniques and their use in studies of electrochemical nucleation and growth of Cu. We discuss advantages and drawbacks of potential step and galvanostatic deposition techniques in determining nucleation and growth parameters, and selection criteria for additive sets for a given plating task. We demonstrate that substrate surface modifications prior to plating could help simplify bath composition, i.e. eliminate need for some additives in the electrolyte, or improve the filling performance of the given plating bath. We also give examples of additives that promoted void-free filling of features but also influenced physical/mechanical properties of the final product in such a way that rendered it unusable in a specific application.

Solid-Surface Modification with Two-Dimensionally Ordered Oriented Molecular Films

The surface properties of solid substrates have a considerable impact on many physical, chemical, and electrochemical events occurring at a materials interface, and thus the control of chemical and physical properties of solid surfaces (e.g., surface morphology and energy, wettability, and adhesiveness) provides a key technology in many practical applications. As a useful approach for this purpose, the formation of self-assembled monolayers (SAMs) has widely been used, which relies on specific bonding between polar functional groups of organic molecules and outermost surface elements of inorganic substrates. However, this approach cannot be applied for the modification of polymer substrate surfaces, which are devoid of any effective binding site against polar functional groups. Here we report a new type of organic surface modifier consisting of a paraffinic tripodal triptycene, which undergoes controlled self-assembly not only on inorganic substrates but also on polymer substrates, resulting in a completely oriented molecular thin film like SAMs. The formation of this molecular film does not rely on specific chemical bonding but on a unique assembling property of the molecular building block capable of forming 2D (hexagonal triptycene array) + 1D (layer stacking) structure regardless of the types of substrates. In this presentation, an application of this molecular film to organic electronic devices, which can enhance device performances, will also be described.

Surface characterization of copper substrates modified with carboxyl terminated phosphonic acids

The surface modification of copper substrates by means of liquid phase reaction with 1H, 1H, 2H, 2H-perfluorooctanephosphonic acid, 6-phosphonohexanoic acid and 16-phosphonohexadecanoic acid is investigated. The substrate preparation is based on common industrial methods and avoids a separate oxidation step of the copper surface prior to modification. Analysis and characterization of the surfaces were performed using various physico-chemical methods. The film formation of a fluoroalkyl phosphonic acid and two carboxyl terminated phosphonic acids on the copper surface was proven by X-ray photoelectron spectroscopy, infrared spectroscopy, SEM/EDX as well as water contact angle measurements. For 16-phosphonohexadecanoic acid a higher film thickness was obtained compared to 6-phosphonohexanoic acid. Hydrogen bonds between adjacent carboxylic terminated phosphonic acids lead to multilayer formation. In additional experiments, these phosphonic acids were investigated as adhesion promoters in copper / epoxy resin laminates in order to replace conventional surface roughening processes. For these laminates, the peel strength was significantly higher when the copper surface was functionalized with 16-phosphonohexadecanoic acid.

The Effect of Laminin Surface Modification of Electrospun Silica Nanofiber Substrate on Neuronal Tissue Engineering.

In this study, we first synthesized a slow-degrading silica nanofiber (SNF2) through an electrospun solution with an optimized tetraethyl orthosilicate (TEOS) to polyvinyl pyrrolidone (PVP) ratio. Then, laminin-modified SNF2, namely SNF2-AP-S-L, was obtained through a series of chemical reactions to attach the extracellular matrix protein, laminin, to its surface. The SNF2-AP-S-L substrate was characterized by a combination of scanning electron microscopy (SEM), Fourier transform–infrared (FTIR) spectroscopy, nitrogen adsorption/desorption isotherms, and contact angle measurements. The results of further functional assays show that this substrate is a biocompatible, bioactive and biodegradable scaffold with good structural integrity that persisted beyond 18 days. Moreover, a synergistic effect of sustained structure support and prolonged biochemical stimulation for cell differentiation on SNF2-AP-S-L was found when neuron-like PC12 cells were seeded onto its surface. Specifically, neurite extensions on the covalently modified SNF2-AP-S-L were significantly longer than those observed on unmodified SNF and SNF subjected to physical adsorption of laminin. Together, these results indicate that the SNF2-AP-S-L substrate prepared in this study is a promising 3D biocompatible substrate capable of sustaining longer neuronal growth for tissue-engineering applications.

Application of surface analysis methods to study alignment mechanism and orientation of liquid crystals

This review highlights the importance of surface analytical methods in the elucidation of liquid crystal alignment mechanism with the focus on two aspects. In the first part, this review examines current literature related to studies of surface modification of substrates with the goal of creating beneficial interactions with liquid crystals resulting in their alignment. The second part of the paper highlights surface studies of various aspects of surface orientation and properties of aligned liquid crystal layers on various substrates.

Surface functionalization and manipulation of mesoporous silica adsorbents for improved removal of pollutants: a review

This review presents a broad overview of recent advances in the surface modification of mesoporous silica substrates for improved adsorption capacity and selectivity for both organic and inorganic wastewater pollutants.

Exploration of the modification of carbon-based substrate surfaces in aqueous rechargeable zinc ion batteries.

The hydrophobic surfaces of carbon-based substrates lead to a huge interface impedance in aqueous rechargeable zinc ion batteries (ZIBs). Herein, we try to regulate the morphology and investigate the effects of polar groups on the substrate surface. With the treated substrate, the cyclic and rate performances of MnO2 electrodes are improved by ∼42.5% and 97 mA h g−1.

Surface modification of bulk titanium substrates for biomedical applications via low-temperature microwave hydrothermal oxidation.

Micro-to-nanoscale surface topographies of orthopaedic and dental implants can affect fluid wetting and biological response. Nanoscale features can be superimposed on microscale roughness of titanium (Ti) surfaces at high temperatures, resulting in increased osteoblast differentiation. However, high temperatures can compromise mechanical properties of the bulk material. Here, we have developed a novel low-temperature microwave hydrothermal (MWHT) oxidation process for nanomodification of microrough (SLA) Ti surfaces. Nanoscale protuberances (20 -100 nm average diameter) were generated on SLA surfaces via MWHT treatment at 200°C in H2 O, or in aqueous solutions of H2 O2 or NH4 OH, for times ranging from 1 to 40 h. The size, shape, and crystalline content of the nanoprotuberances varied with the solution used and treatment time. The hydrophilicity of all MWHT-modified surfaces was dramatically enhanced. MG63 and normal human osteoblasts (NHOsts) were cultured on MWHT-treated SLA surfaces. While most responses to MWHT-modified surfaces were comparable to those seen on SLA controls, the MWHT-generated nanotopography reduced osteocalcin production by NHOst cells, suggesting that specific nanotopographic characteristics differentially mediate osteoblast phenotypic expression. MWHT processing provides a scalable, low-temperature route for tailoring nanoscale topographies on microroughened titanium implant surfaces with significantly enhanced wetting by water, without degrading the microscale surface structure of such implants. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 782-796, 2018.

Improved electrochemical properties of morphology-controlled titania/titanate nanostructures prepared by in-situ hydrothermal surface modification of self-source Ti substrate for high-performance supercapacitors

AbstarctTi substrate surface is modified into two-dimensional (2D) TiO2 nanoplatelet or one-dimensional (1D) nanorod/nanofiber (or a mixture of both) structure in a controlled manner via a simple KOH-based hydrothermal technique. Depending on the KOH concentration, different types of TiO2 nanostructures (2D platelets, 1D nanorods/nanofibers and a 2D+1D mixed sample) are fabricated directly onto the Ti substrate surface. The novelty of this technique is the in-situ modification of the self-source Ti surface into titania nanostructures, and its direct use as the electrochemical microelectrode without any modifications. This leads to considerable improvement in the interfacial properties between metallic Ti and semiconducting TiO2. Since interfacial states/defects have profound effect on charge transport properties of electronic/electrochemical devices, therefore this near-defect-free interfacial property of Ti-TiO2 microelectrode has shown high supercapacitive performances for superior charge-storage devices. Additionally, by hydrothermally tuning the morphology of titania nanostructures, the electrochemical properties of the electrodes are also tuned. A Ti-TiO2 electrode comprising of a mixture of 2D-platelet+1D-nanorod structure reveals very high specific capacitance values (~7.4 mF.cm−2) due to the unique mixed morphology which manifests higher active sites (hence, higher utilization of the active materials) in terms of greater roughness at the 2D-platelet structures and higher surface-to-volume-ratio in the 1D-nanorod structures.

Surface modification of porous substrates for oil/water separation using crosslinkable polybenzoxazine as an agent

Efficient separation of both immiscible and emulsified oil/water mixtures is achieved by collaborating polybenzoxazine (PBz) with commercially available substrates in this work. Possessing intrinsic low surface energy, crosslinked PBz coating endows various substrates (sponges, filter paper, and ceramic membrane) with surface hydrophobicity and oleophilicity and enables oil-selective penetration. The as-prepared sponge (CR-PBz-sponge) could effectively remove oil floating on water and oil under water with high absorption capacities (up to 120 times its own weight) and good recyclability. The PBz-coated filter paper (CR-PBz-filter paper) is applicable to efficient large-scale oil/water separation based on its high fluxes (about 5000–6000Lm−2h−1) on a wide range of organic solvents and oils. CR-PBz-ceramic membrane shows great effectiveness in removal of tiny water droplets from water-in-oil emulsion and reduces the water contents of the treated oil to the levels of the natural water solubility of the oils. Based on its separation efficiency, processing simplicity, substrate versatility and low cost, the technique of using PBz as coating material to fabricate oil/water separation materials is promising in practical and industrial concerns.

Surface Modification of Polymer Substrates for Biomedical Applications.

While polymers are widely utilized materials in the biomedical industry, they are rarely used in an unmodified state. Some kind of a surface treatment is often necessary to achieve properties suitable for specific applications. There are multiple methods of surface treatment, each with their own pros and cons, such as plasma and laser treatment, UV lamp modification, etching, grafting, metallization, ion sputtering and others. An appropriate treatment can change the physico-chemical properties of the surface of a polymer in a way that makes it attractive for a variety of biological compounds, or, on the contrary, makes the polymer exhibit antibacterial or cytotoxic properties, thus making the polymer usable in a variety of biomedical applications. This review examines four popular methods of polymer surface modification: laser treatment, ion implantation, plasma treatment and nanoparticle grafting. Surface treatment-induced changes of the physico-chemical properties, morphology, chemical composition and biocompatibility of a variety of polymer substrates are studied. Relevant biological methods are used to determine the influence of various surface treatments and grafting processes on the biocompatibility of the new surfaces—mammalian cell adhesion and proliferation is studied as well as other potential applications of the surface-treated polymer substrates in the biomedical industry.

Impact of short duration, high-flow H2 annealing on graphene synthesis and surface morphology with high spatial resolution assessment of coverage

Treatment of graphene growth substrates with H2 has long been known to impact the quality of deposited graphene. However, the parameters for hydrogen treatment that are considered the optimum – very long anneals under low hydrogen concentrations – are often undesirable for practical reasons. In this paper we optimize anneal parameters for fast anneals of <1 h, via investigation of both substrate surface modification and graphene growth quality using a number of traditional and novel experimental techniques. Our results indicate a dual effect of H2 annealing on the surface morphology of the copper substrate, and consequent graphene growth quality, whereby H2 passivates and smoothens the Cu surface, causing it to become morphologically more favorable for graphene growth, but may in large quantities make the surface less chemically favorable, limiting the quality of grown graphene. Moreover, we use a novel method based on Atomic Force Microscopy (AFM) for higher spatial resolution analysis of the homogeneity of graphene using maps of the Hamaker coefficient.

Surface modification of titanium substrates for enhanced osteogenetic and antibacterial properties

The insufficient osseointegration and bacterial infection of titanium and its alloys remain the key challenges in their clinic applications, which may result in failure implantation. To improve osteogenetic and antibacterial properties, TiO2 nanotube arrays were fabricated on titanium substrates for loading of antibacterial drug. Then, TiO2 nanotube arrays were covered with chitosan/sodium alginate multilayer films. The successful construction of this system was verified via scanning electron microscopy and contact angle measurement. The cytocompatibility evaluation in vitro, including cytoskeleton observation, cell viability measurement, and alkaline phosphatase activity assay, confirmed that the present system was capable of accelerating the growth of osteoblasts. In addition, bacterial adhesion and viability assay verified that treated Ti substrates were capable of reducing the adhesion of bacteria. This study may provide an alternative to develop titanium-based implants for enhanced bone osseointegration and reduced bacterial infection.

Cellulose Nanocrystals with Tethered Polymer Chains: Chemically Patchy versus Uniform Decoration

The site-specific surface modification of colloidal substrates, yielding "patchy" nanoparticles, is a rapidly expanding area of research as a result of the new complex structural hierarchies that are becoming accessible to chemists and materials scientists through colloidal self-assembly. The inherent directionality of cellulose chains, which feature a nonreducing and a reducing end, within individual cellulose nanocrystals (CNCs) renders them an interesting experimental platform for the synthesis of asymmetric nanorods with end-tethered polymer chains. Here, we present water-tolerant reaction pathways toward patchy and uniformly modified CNC hybrids based on atom transfer radical polymerization (ATRP) and initiators that were linked to the CNCs with carbodiimide-mediated coupling and Fischer esterification, respectively. Various monomers, including N-isopropylacrylamide (NIPAM), [2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC), and sodium 4-vinylbenzenesulfonate (4-SS), were polymerized from both types of initiator-modified CNCs, yielding chemically patchy and uniform CNC hybrids, via surface-initiated ATRP (SI-ATRP). Interestingly, the stereochemistry of tethered PNIPAM was affected by the precise location of ATRP initiating sites, as evidenced by 1H NMR and circular dichroism (CD) spectroscopy. This effect may be related to the inherent right-handed chirality of CNCs. CNC/PMETAC hybrids were labeled with gold nanoparticles (AuNPs) in order to visualize the precise location of polymer tethers via cryo-electron microscopy. In some instances, the AuNPs were indeed concentrated at the end groups of the patchy CNC hybrids.

Surface modification of polymeric substrates to enhance the barrier properties of an Al2O3 layer formed by PEALD process

Aluminum oxide (Al2O3) layers were deposited on various polymeric substrates by a low frequency plasma-enhanced atomic layer deposition (PEALD) process. Polyethylene naphthalate (PEN), polyethylene terephthalate (PET), and polyethersulfone (PES) were tested as substrates for barrier films. Each substrate has its own characteristics to have influences on the Al2O3 layer formation and penetration into the substrate, which greatly affected the barrier properties. Prior to the deposition process, polymeric substrates were pretreated in argon and oxygen plasmas, and surface energy was leveled up due to the formation of polar group. Characterizations of the Al2O3 layer by Time of Flight - Secondary Ion Mass Spectrometry (ToF-SIMS) revealed that plasma treatment lowered the level of OH− in Al2O3 layer. X-ray photoelectron microscopy (XPS) confirmed that A12p peak of Al2O3 layer was shifted to a higher core level by plasma treatment. Density of the layer on the plasma treated surface was greater than that of untreated surface. It was found that plasma treatment of the surface had significant effects on the formation of the Al2O3 layer, which much improved the barrier performance. Optical transmittance was little affected by plasma treatment and PEALD process. After oxygen plasma pretreatment, the WVTR of the Al2O3 layer deposited on the plasma-treated PEN substrate was around 7.2 × 10−4 g/m2day, which is significantly lower than that of the untreated substrate.

Area-selective Surface Modification of Si Substrates with a Fluorescent Organophosphonic Acid Using the Differences in Reactivities of Their Surface Terminal Groups

Area-selective surface modification of Si substrates bearing OH- and H-terminated areas by fluorescent 1-pyrenylphosphonic acid (PYPA) was achieved using chlorobenzene at 140 °C for 2 h in an autoclave. The OH-terminated area was successfully modified, as shown by X-ray photoemission spectroscopy and contact angle measurement, while no reaction proceeded between PYPA and the H-terminated area. SiO2 nanoparticles were reacted with PYPA under the same conditions to form Si–O–P bonds, suggesting that dehydration coupling proceeded between the OH-terminated area and PYPA.

Effects of the surface modification of polyurethane substrates on genotoxicity and blood activation processes

The aim of this study was to determine the mutagenic and thrombogenic potential of a material composed of a thin coating deposited on a polymeric substrate. In this work, a surface was modified in a manner that would mimic the function of cellular niches. Finally, the surfaces should actively capture and differentiate progenitor cells from the blood stream. Thin films with 10 to 500nm thicknesses were deposited by unbalanced, pulsed DC magnetron sputtering on smooth polyurethane. Such high energy conditions led to a stiffening of the polymer surface layers by pseudodiffusion during the initial stages of film growth. Both the high intrinsic film stress due to high energy film growth and the huge difference in the elastic properties of the films and polymer substrates resulted in hierarchical and self-adapting nanowrinkling. Surface modifications of synthetic materials for future use in regeneration of the circulatory system must be tested in terms of their thrombogenicity and mutagenicity. Point mutations in many cases can lead to many serious haematologic complications. Genotoxicity was determined by testing for reverse histidine mutations in selected strains of Salmonella typhimurium. The analysis was performed in the presence and absence of metabolic activation system S9 containing liver microsomal fraction of rats. Based on these results, no mutagenicity of the tested material was observed. The interaction of blood and the material under dynamic conditions was described. Blood from above the analysed surface was collected after the test, and the quality of the blood was assessed along with the type of cellular response to the surface. In the obtained results of the coagulation processes, it was found that the tested material reduced the process of platelet activation under hydrodynamic conditions in comparison to the control material, polyurethane.