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Appl Surf Sci 2017 Oct 12;419:778-787. Epub 2017 May 12.

Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, 844 N 16th St, Lincoln, NE 68588, USA.

A detailed structural and chemical analysis of a class of self-organized surface structures, termed aggregated nanoparticle spheres (AN-spheres), created using femtosecond laser surface processing (FLSP) on silicon, silicon carbide, and aluminum is reported in this paper. AN-spheres are spherical microstructures that are 20-100 μm in diameter and are composed entirely of nanoparticles produced during femtosecond laser ablation of material. AN-spheres have an onion-like layered morphology resulting from the build-up of nanoparticle layers over multiple passes of the laser beam. Read More

Appl Surf Sci 2018 Jul 3;447:535-541. Epub 2018 Apr 3.

Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, United States.

Solution-based lithographic surface modification of an organic monolayer on a solid substrate is attained based on selective area photo-reduction of copper (II) to copper (I) to catalyze the azide-alkyne dipolar cycloaddition "click" reaction. X-ray photoelectron spectroscopy is used to confirm patterning, and spectroscopic results are analyzed and supplemented with computational models to confirm the surface chemistry. It is determined that this surface modification approach requires irradiation of the solid substrate with all necessary components present in solution. Read More

Appl Surf Sci 2018 Oct 24;455:438-445. Epub 2018 May 24.

University of Delaware, Department of Chemistry and Biochemistry, Newark, DE, USA.

Amechanism of thermal dry etching process of cobalt thin films by using 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (hexafluoroacetylacetone, hfacH) was investigated. This process, relevant to atomic layer etching (ALE) technology directed towards oxidized cobalt films, requires adsorption of molecular organic precursor, such as hfacH, at moderate temperatures and is often thought of as releasing water and Co(hfac) at elevated temperatures. The reaction was analyzed in situ by temperature-programmed desorption (TPD) and the resulting surface was investigated ex situ by X-ray photoelectron spectroscopy (XPS). Read More

Appl Surf Sci 2017 Jan 1;392:950-959. Epub 2016 Sep 1.

Center for Biomedical Engineering, Department of Chemical and Biological Engineering, University of New Mexico, United States.

When poly(-isopropyl acrylamide) (pNIPAM) is tethered to a surface, it can induce the spontaneous release of a sheet of mammalian cells. The release of cells is a result of the reversible phase transition the polymer undergoes at its lower critical solution temperature (LCST). Many techniques are used for the deposition of pNIPAM onto cell culture substrates. Read More

Appl Surf Sci 2017 Feb 15;396:1170-1176. Epub 2016 Nov 15.

Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.

Femtosecond laser surface processing is a technology that can be used to functionalize many surfaces, imparting specialized properties such as increased broadband optical absorption or superhydrophilicity/superhydrophobicity. In this study, two unique classes of surface structures, below surface growth (BSG) and above surface growth (ASG) mounds, were formed by femtosecond laser surface processing on amorphous and polycrystalline NiNb with two different grain sizes. Cross sectional imaging of these mounds revealed thermal evidence of the unique formation processes for each class of surface structure. Read More

Appl Surf Sci 2016 Nov;387:89-102

Department of Environmental Technology, Faculty of Chemistry, University of Gdansk, 63 Wita Stwosza St., 80-308 Gdansk, Poland.

TiO nanotubes arrays (NTs), obtained via electrochemical anodization of Ti foil, were modified with monometallic (Cu, Bi) and bimetallic (AgCu) nanoparticles. Different amounts of metals' precursors were deposited on the surface of NTs by the spin-coating technique, and the reduction of metals was performed via gamma radiolysis. Surface modification of titania was studied by EDS and XPS analysis. Read More

Appl Surf Sci 2016 Dec 25;388(A):461-467. Epub 2015 Nov 25.

Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA.

This work presents an approach for producing a high-coverage single monolayer of magnetic nanoparticles using "click chemistry" between complementarily-functionalized nanoparticles and a flat substrate. This method highlights essential aspects of the functionalization scheme for substrate surface and nanoparticles to produce exceptionally high surface coverage without sacrificing selectivity or control over the layer produced. The deposition of one single layer of magnetic particles without agglomeration, over a large area, with a nearly 100% coverage is confirmed by electron microscopy. Read More

Appl Surf Sci 2016 Aug 31;378:301-307. Epub 2016 Mar 31.

National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.

Low temperature Si epitaxy has become increasingly important due to its critical role in the encapsulation and performance of buried nanoscale dopant devices. We demonstrate epitaxial growth up to nominally 25 nm, at 250°C, with analysis at successive growth steps using STM and cross section TEM to reveal the nature and quality of the epitaxial growth. STM images indicate that growth morphology of both Si on Si and Si on H-terminated Si (H: Si) is epitaxial in nature at temperatures as low as 250 °C. Read More

Appl Surf Sci 2016 Mar;365:180-190

Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT, USA; Blackrock Microsystems, Salt Lake City, UT, USA.

In various applications such as neural prostheses or solar cells, there is a need to alter the surface morphology of high aspect ratio structures so that the real surface area is greater than geometrical area. The change in surface morphology enhances the devices functionality. One of the applications of altering the surface morphology is of neural implants such as the Utah electrode array (UEA) that communicate with single neurons by charge injection induced stimulation or by recording electrical neural signals. Read More

Appl Surf Sci 2015 Dec;359:911-916

Department of Chemistry, Michigan State University, East Lansing, MI 48840.

Surface initiated atom transfer radical polymerization (ATRP) of substituted styrenes leads to rapid synthesis of uniform and thick substituted polystyrene brushes (>100 nm in 1 hour) from gold surface. High growth rates were observed for styrenes substituted with electron withdrawing groups in meta/para positions. The effects seen in surface and solution polymerizations are similar for styrenes with electron withdrawing groups, and for electron donors in ortho and para positions. Read More

Appl Surf Sci 2015 Dec 8;357 Pt A:452-458. Epub 2015 Sep 8.

Center for Superconducting and Magnetic Materials, Department of Materials Science and Engineering, The Ohio State University, Columbus, OH USA 43210.

High quality, -axis oriented, MgB thin films were successfully grown on 6H-SiC substrates using pulsed laser deposition (PLD) with subsequent annealing. To obtain high purity films free from oxygen contamination, a dense Mg-B target was specially made from a high temperature, high pressure reaction of Mg and B to form large-grained (10~50 µm) MgB. Microstructural analysis via electron microscopy found that the resulting grains of the film were composed of ultrafine columnar grains of 19-30 nm. Read More

Appl Surf Sci 2015 Jul;343:166-171

Department of Chemistry, University of Massachusetts Lowell, 1 University Ave., Lowell, MA 01854, United States ; KTH-Royal Institute of Technology, Department of Chemistry, Teknikringen 30, S-10044 Stockholm, Sweden.

Covalently immobilized poly(4-vinylphenol) (PVP) monolayer films were fabricated by spin coating PVP on perfluorophenyl azide (PFPA)-functionalized surface followed by UV irradiation. The pH-responsive behavior of these PVP ultrathin films was evaluated by ellipsometry, quartz crystal microbalance (QCM) and surface plasmon resonance (SPR). By monitoring the responses of these films to pH , the ionization constant of the monolayer thin films was obtained. Read More

Appl Surf Sci 2014 Aug;311:684-689

Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, MD, USA.

Stent migration occurs in 10-40% of patients who undergo placement of esophageal stents, with higher migration rates seen in those treated for benign esophageal disorders. This remains a major drawback of esophageal stent therapy. In this paper, we propose a new surface modification method to increase the adhesion between self-expandable metallic stents (SEMS) and tissue while preserving their removability. Read More

Appl Surf Sci 2014 Dec;321:205-213

Department of Biomedical Engineering, The University of Memphis, Memphis, TN 38152, USA USA.

The present study discusses the design, development and characterization of electrospun Tecoflex EG 80A class of polyurethane nanofibers and the incorporation of multiwalled carbon nanotubes (MWCNTs) to these materials. Scanning electron microscopy results confirmed the presence of polymer nanofibers, which showed a decrease in fiber diameter at 0.5% wt. Read More

Appl Surf Sci 2014 Jan;289(100):407-416

Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9, A-1060 Vienna, Austria.

A novel operation mode for time of flight-secondary ion mass spectrometry (ToF-SIMS) is described for a TOF.SIMS 5 instrument with a Bi-ion gun. It features sub 100 nm lateral resolution, adjustable primary ion currents and the possibility to measure with high lateral resolution as well as high mass resolution. Read More

Appl Surf Sci 2012 Nov;261

Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195.

Ultra-thin self-assembled monolayer (SAM)-oxide hybrid dielectrics have gained significant interest for their application in low-voltage organic thin film transistors (OTFTs). A [8-(11-phenoxy-undecyloxy)-octyl]phosphonic acid (PhO-19-PA) SAM on ultrathin AlO (2.5 nm) has been developed to significantly enhance the dielectric performance of inorganic oxides through reduction of leakage current while maintaining similar capacitance to the underlying oxide structure. Read More

Appl Surf Sci 2013 May;273(100):706-716

School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, PR China.

A novel hybrid mesoporous aluminosilicate sieve (HMAS) was prepared with fly ash and impregnated with zeolite A precursors. This improved the mercury adsorption of HMAS compared to original MCM-41. The HMAS was characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, Fourier transform infrared (FTIR) analysis, transmission electron microscopy (TEM) images and Si and Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectra. Read More

Appl Surf Sci 2012 Oct;258(24):10123-10127

Institute of Physical Chemistry, University of Innsbruck, Innrain 52a, A-6020 Innsbruck, Austria.

Reflectance difference spectroscopy (RDS) is applied to follow in situ the preparation of clean and carburized W(1 1 0) surfaces and to study the temperature-induced transition between the R(15 × 3) and R(15 × 12) carbon/tungsten surface phases. RDS data for this transition are compared to data obtained from Auger-electron spectroscopy and low-energy electron diffraction. All techniques reveal that this transition, occurring around 1870 K, is reversible with a small hysteresis, indicating a first-order-like behaviour. Read More

Appl Surf Sci 2011 Nov;258(3):1235-1241

Division of Surface and Corrosion Science, Royal Institute of Technology (KTH), Drottning Kristinas väg 51, SE-100 44 Stockholm, Sweden.

Complementary surface and near-surface analytical techniques have been used to explore a brass (Cu-20Zn) surface before, during, and after exposure in air at 90% relative humidity. Volta potential variations along the unexposed surface are attributed to variations in surface composition and resulted in an accelerated localized growth of ZnO and a retarded more uniform growth of an amorphous CuO-like oxide. After 3 days the duplex oxide has a total mass of 1. Read More

Appl Surf Sci 2011 Apr;257(13):5605-5612

Center for Materials Research (CMR), Norfolk State University, Norfolk, Virginia 23504.

Cobalt Chromium (Co-Cr) alloys has been widely used in the biomedical arena for cardiovascular, orthopedic and dental applications. Surface modification of the alloy allows us to tailor the interfacial properties to address critical challenges of Co-Cr alloy in medical applications. Self assembled monolayers (SAMs) of Octadecylphosphonic acid (ODPA) have been used to form thin films on the oxide layer of the Co-Cr alloy surface by solution deposition technique. Read More

Appl Surf Sci 2009 May;255(15):6832-6839

Biological Engineering Program, Utah State University, 4105 Old Main Hill, Logan, Utah (U.S.A.).

Scanning tunneling microscopy (STM) lithography was utilized to investigate a 12-mer HS-ssDNA self-assembled Au (111) surface. Under low sample bias and high tunneling current, the repeated scanning resulted in the growth of nanostripes. The stripe orientation, the stripe width, and the spacer width between adjacent nanostripes were found to be dependent on their relative locations from dislocation points where two adjacent gold terraces overlap. Read More

Appl Surf Sci 2010 Jan;256(6):1832-1836

National ESCA and Surface Analysis Center for Biomedical Problems (NESAC/BIO), Departments of Bioengineering and Chemical Engineering, University of Washington, 98195 Seattle, WA, U.S.A.

Well-defined and homogeneous, contamination-free self-assembled monolayers (SAMs) were fabricated by the chemisorption of lip-NH--CH-N=N--CH-COOH (lip = α-lipoyl) onto gold. This adsorbate species is composed of a 1,2-dithiolane-based headgroup, an azobenzene-based (and hence photochromic) spacer unit and a carboxylic acid functional group. The SAM constituents are covalently attached to the substrate by the bidentate thiolate anchor groups and exhibit a strongly tilted binding configuration. Read More

Appl Surf Sci 2008 Dec;255(4):1170-1173

Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY, 14260-3000 USA.

Biodegradable polymers are of interest in developing strategies to control protein drug delivery. The protein that was used in this study is Keratinocyte Growth Factor (KGF) which is a protein involved in the re-epithelialization process. The protein is stabilized in the biodegradable polymer matrix during formulation and over the course of polymer degradation with the use of an ionic surfactant Aerosol-OT (AOT) which will encapsulate the protein in an aqueous environment. Read More

Appl Surf Sci 2008 Dec;255(14):1068-1070

Department of Chemistry, Penn State University, University Park, PA 16802, United States.

The effect of incident angle on the quality of SIMS molecular depth profiling using C(60) (+) was investigated. Cholesterol films of ~300 nm thickness on Si were employed as a model and were eroded using 40 keV C(60) (+) at an incident angle of 40° and 73° with respect to the surface normal. The erosion process was characterized by determining at each angle the relative amount of chemical damage, the total sputtering yield of cholesterol molecules, and the interface width between the film and the Si substrate. Read More

Appl Surf Sci 2008 Dec;255(4):1298-1304

Department of Chemistry, Penn State University, 104 Chemistry Building, University Park, PA 16802, United States.

Sample preparation is central to acquiring meaningful molecule-specific images with SIMS, especially when submicron lateral resolution is involved. The issue is to maintain the distribution of target molecules while attempting to introduce biological cells or tissue into the high vacuum environment of the mass spectrometer. Here we compare freeze-drying, freeze-etching, freeze-fracture and trehalose vitrification as possible strategies for these experiments. Read More

Appl Surf Sci 2008 Dec;255(4):816-818

Department of Chemistry, The Pennsylvania State University, 104 Chemistry Building, University Park, PA 16802, United States.

Molecular depth profiling and three-dimensional imaging using cluster projectiles and SIMS have become a prominent tool for organic and biological materials characterization. To further explore the fundamental features of cluster bombardment of organic materials, especially depth resolution and differential sputtering, we have developed a reproducible and robust model system consisting of Langmuir-Blodgett (LB) multilayer films. Molecular depth profiles were acquired, using a 40-keV C(60) (+) probe, with LB films chemically alternating between barium arachidate and barium dimyristoyl phosphatidate. Read More

Appl Surf Sci 2008 Dec;255(4):1190-1192

Department of Chemistry, The Pennsylvania State University, 104 Chemistry Building, University Park, PA 16802, United States.

With the chemical imaging capability of ToF-SIMS, biological molecules are identified and localized in membranes without any chemical labels. We have developed a model membrane system made with supported Langmuir-Blodgett (LB) monolayers. This simplified model can be used with different combinations of molecules to form a membrane, and thus represents a bottom-up approach to study individual lipid-lipid or lipid-protein interactions. Read More

Appl Surf Sci 2008 ;255(4):1158-1161

Department of Chemistry, Penn State University, 104 Chemistry Building, University Park, PA 16802.

We report the use of SIMS imaging to quantify the relative difference in the amount of lipid between two sections, the plasma membrane and the cytoplasm, of single cells from two different populations. Cells were each labeled with lipophillic dyes, frozen, fractured and analyzed in a ToF-SIMS mass spectrometer equipped with a 40 keV C(60) (+) ion source. In addition to identifying cells from separate populations, the lipophilic dyes can be used as a marker for the outer leaflet of the cell membrane and therefore as a depth finder. Read More

Appl Surf Sci 2008 Dec;255(4):929-933

Department of Chemistry, University Park, PA 16802, United States.

Phagocytosis is a major component of the animal immune system where apoptotic cellular material, metabolites, and waste are safely processed. Further, efficient phagocytosis by macrophages is key to maintaining healthy vascular systems and preventing atherosclerosis. Single-cell images of macrophage phagocytosis of red blood cells, RBCs, and polystyrene microspheres have been chemically mapped with TOF-SIMS. Read More

Appl Surf Sci 2006 Jul;252(19):6716-6718

Department of Chemistry, The Pennsylvania State University, 104 Chemistry Bldg., University Park, PA 16802, United States.

There is an increased interest in how lipids interact with each other, especially in the lateral separation of lipids into coexisting liquid phases as this is believed to be an attribute of raft formation in cell membranes. ToF-SIMS has shown itself to be an excellent tool for investigating cellular and model membrane systems and will be perhaps the most powerful one for investigating raft formation. Results from our laboratory show the capability of ToF-SIMS at identifying unequivocally the content of coexisting liquid lipid phases. Read More