We describe a new process for preparing porous solid phase microextraction (SPME) coatings by the sputtering of silicon onto silica fibers. The microstructure of these coatings is a function of the substrate geometry and mean free path of the silicon atoms, and the coating thickness is controlled by the sputtering time. Sputtered silicon structures on silica fibers were treated with piranha solution (a mixture of concd H2SO4 and 30% H2O2) to increase the concentration of silanol groups on their surfaces, and the nanostructures were silanized with octadecyldimethylmethoxysilane in the gas phase. The attachment of this hydrophobic ligand was confirmed by X-ray photoelectron spectroscopy and contact angle goniometry on model, planar silicon substrates. Sputtered silicon coatings adhered strongly to their surfaces, as they were able to pass the Scotch tape adhesion test. The extraction time and temperature for headspace extraction of mixtures of alkanes and alcohols on the sputtered fibers were optimized (5 min and 40 °C), and the extraction performances of SPME fibers with 1.0 or 2.0 μm of sputtered silicon were compared to those from a commercial 7 μm poly(dimethylsiloxane) (PDMS) fiber. For mixtures of alcohols, aldehydes, amines, and esters, the 2.0 μm sputtered silicon fiber yielded signals that were 3–9, 3–5, 2.5–4.5, and 1.5–2 times higher, respectively, than those of the commercial fiber. For the heavier alkanes (undecane–hexadecane), the 2.0 μm sputtered fiber yielded signals that were approximately 1.0–1.5 times higher than the commercial fiber. The sputtered fibers extracted low molecular weight analytes that were not detectable with the commercial fiber. The selectivity of the sputtered fibers appears to favor analytes that have both a hydrophobic component and hydrogen-bonding capabilities. No detectable carryover between runs was noted for the sputtered fibers. The repeatability (RSD%) for a fiber (n = 3) was less than 10% for all analytes tested, and the between-fiber reproducibility (n = 3) was 0–15%, generally 5–10%, for all analytes tested. The repeatabilities of our sputtered fibers and the commercial 7 μm PDMS fiber are essentially the same. Fibers could be used for at least 300 extractions without loss of performance. More than 50 compounds were identified in a gas chromatography–mass spectrometry headspace analysis of a real world botanical sample with the 2.0 μm fiber.

Low energy ion scattering (LEIS) probes the elemental composition of the outermost atomic layer of a material and provides static depth profiles of the outer ca. 10 nm of surfaces. Its extreme surface sensitivity and quantitative nature make it a powerful tool for studying the relationships between surface chemistry and surface related phenomena such as wetting, adhesion, contamination, and thin film growth. The high depth resolution obtained in LEIS in its static and sputter depth profile modes are useful for studying the layer structures of thin films. LEIS instrumentation has improved significantly in recent years, showing dramatic increases in its sensitivity and further expanding its potential applications. In this article, we provide a practical introduction to the technique, including a discussion of the basic theory of LEIS, LEIS spectra, LEIS instrumentation, and LEIS applications, including catalysts, solid oxide fuel cells (SOFCs), and thin films in integrated circuits.

Here, we report the most comprehensive characterization of nanodiamonds (NDs) yet undertaken. Five different samples from three different vendors were analyzed by a suite of analytical techniques, including X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), inductively coupled plasma mass spectrometry (ICP-MS), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), Brunauer-Emmett-Teller (BET) surface area measurements, and particle size distribution (PSD) measurements. XPS revealed the elemental compositions of the ND surfaces (83–87 at.% carbon and 12–14 at.% oxygen) with varying amounts of nitrogen (0.4–1.8 at.%), silicon (0.1–0.7 at.%), and tungsten (0.3 at.% only in samples from one vendor). ToF-SIMS and ICP showed metal impurities (Al, Fe, Ni, Cr, etc. with unexpectedly high amounts of W in one vendor’s samples: ca. 900 ppm). Principal component analyses were performed on the ToF-SIMS and ICP data. DRIFT showed key functional groups (–OH, C=O, C–O, and C=C). BET showed surface areas of 50–214 m2/g. XRD and TEM revealed PSD (bimodal distribution and a wide PSD, 5–100 nm, for one vendor’s samples). XRD also provided particle sizes (2.7–27 nm) and showed the presence of graphite. EELS gave the sp2/sp3 contents of the materials (37–88 % sp3). PSD measurements were performed via differential sedimentation of the particles (mean particle size ca. 17–50 nm). This comprehensive understanding should allow for improved construction of nanodiamond-based materials.

We describe the derivatization of uncross-linked and cross-linked layer-by-layer (LbL) assemblies of polyelectrolytes (polyallylamine hydrochloride and polyacrylic acid) with sulfydryl groups via Traut’s reagent (2-iminothiolane). This thiolation was optimized with regards to temperature, concentration, and pH. The stability of the resulting –SH groups in the air was determined by X-ray photoelectron spectroscopy (XPS). This air oxidation has obvious implications for the use of thiol–ene reactions in materials chemistry, and there appears to be little on this topic in the literature. Three main S 2s signals were observed by XPS: at 231.5 eV (oxidized sulfur), 227.6 eV (thiol groups), and 225.4 eV (thiolate groups). Due to their rapid oxidation, we recommend that thiolated surfaces be used immediately after they are prepared. As driven by 254 nm UV light, thiol groups on polyelectrolyte multilayers react with 1,2-polybutadiene (PBd), and residual carbon–carbon double bonds on adsorbed PBd similarly react with another thiol. In the case of a fluorinated thiol, surfaces with high water contact angles (ca. 120°) are obtained. Modest exposures to light result in derivatization, while longer exposures damage the assemblies. Polyelectrolyte–thiol–PBd–thiol assemblies delaminate from their substrates when immersed for long periods of time in water. Surface silanization with an amino silane prevents this delamination and leads to stable assemblies. These assemblies withstand various stability tests. Techniques used to analyze the materials in this study include X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), atomic force microscopy (AFM), and contact angle goniometry.

•UTLC plates prepared by low-pressure CVD of SiNx onto carbon nanotube templates.•Very fast separations.•Detailed method development.•Plates show a high degree of reusability/robustness.•Detection by ambient mass spectrometry: DESI and DART.Microfabrication of ultrathin-layer chromatography (UTLC) plates via conformal deposition of silicon nitride by low-pressure chemical vapor deposition onto patterned carbon nanotube (CNT) scaffolds was demonstrated. After removal of the CNTs and hydroxylation, the resulting UTLC phase showed no expansion or distortion of their microfeatures and the absence/reduction of remaining nitrogenic species. Developing time of a mixture of lipophilic dyes on this UTLC plates was 86% shorter than on high-performance thin-layer chromatography (HPTLC) plates. A water-soluble food dye mixture was also separated resulting in low band broadening and reduced developing time compared to HPTLC. For the latter example, mobile phase optimization on a single UTLC plate consisted of 14 developments with different mobile phases, each preceded by a plate prewashing step. The same plate was again reused for additional 11 separations under varying conditions resulting in a development procedure with a mean separation efficiency of 233,000 theoretical plates/m and a reduced mobile phase consumption of only 400 μL. This repeated use proved the physical robustness of the ultrathin layer and its resistance to damage. The layer was highly suited for hyphenation to ambient mass spectrometry, including desorption electrospray ionization (DESI) mass spectrometry imaging and direct analysis in real time (DART) mass spectrometry.

The plan view is used in crystallography and materials science to show the positions of atoms in crystal structures. However, it is not widely used in teaching general chemistry. In this contribution, we introduce the plan view, and show these views for the simple cubic, body-centered cubic, face-centered cubic, hexagonal close packed, CsCl, NaCl, diamond cubic, ZnS, and CaF2 unit cells. A survey administered to college-level general chemistry students indicates that the plan view helps them to better understand crystal structures.

•We introduce a new figure of merit for XPS narrow scans: the equivalent width (EWXPS).•EWXPS is less subjective and involves lesser user bias than traditional peak fitting.•EWXPS is responsive to changes in chemical states of materials.•EWXPS could be used for quality control and comparing spectra from similar samples.•EWXPS has the potential to be part of an expert software system for machine interpretation of spectra.X-ray Photoelectron Spectroscopy (XPS) is a widely used surface analytical tool that provides information about the near surface regions of materials. And while indispensable for XPS data analysis, peak fitting of narrow scans is often a fairly subjective exercise. Herein we introduce the equivalent width (EW) as an additional and less subjective figure of merit for XPS narrow scans. We believe that this parameter will prove particularly useful for analyzing series of similar or nominally identical spectra, perhaps as a component of an expert software system for the machine interpretation of spectra. It also appears to be useful, shedding light on the chemical state of materials, when additional information about a sample is known. The EWXPS is simply defined as the area of a narrow scan divided by the height of the maximum of its peak envelope. To limit any ambiguity in EWXPS for a series of spectra, we may also list the peak position of the maximum of the envelope (PEmax). The potential usefulness and limitations of the EWXPS and PEmax parameters are demonstrated by their application to the narrow scans of: (i) four sets of ozone-treated carbon nanotubes (EWXPS ∼ 2.11–2.16 eV for a Shirley background, and up to 2.88 eV for no background, PEmax ∼ 284.4–284.5 eV), (ii) a series of silicon wafers with different oxide thicknesses (EWXPS ∼ 1.5–2.8 eV, PEmax ∼ 99–103 eV), (iii) hydrogen-terminated silicon before and after derivatization with pentyl groups, and after annealing of the pentyl-modified material (EWXPS ∼ 0.7–1.0 eV, PEmax ∼ 25.9–26.1 eV), and (iv) five nanodiamond samples, where three of the spectra showed charging (EWXPS ∼ 2.6–4.9 eV, PEmax ∼ 272.7–293.9 eV). In this final example, EWXPS was plotted against PEmax to identify the region corresponding to the materials that showed the least charging. EWXPS and PEmax appear to correlate with the expected chemistries of all the systems studied. We calculate EWXPS using a Shirley baseline and with no baseline at all. In setting the baseline limits for EWXPS, we consider the derivative of C 1s narrow scans. We also show the application of EWXPS to single, fitted components within a narrow scan.

•We apply the equivalent and autocorrelation widths and variance to XPS narrow scans.•This approach is complementary to traditional peak fitting methods.•It is bias free and responsive to subtle chemical changes in spectra.•It has the potential for machine interpretation of spectra and quality control.•It has the potential for analysis of complex spectra and tracking charging/artifacts.X-ray photoelectron spectroscopy (XPS) is widely used in surface and materials laboratories around the world. It is a near surface technique, providing detailed chemical information about samples in the form of survey and narrow scans. To extract the maximum amount of information about materials it is often necessary to peak fit XPS narrow scans. And while indispensable to XPS data analysis, even experienced practitioners can struggle with their peak fitting. In our previous publication, we introduced the equivalent width (EWXPS) as both a possible machine automated method, one that requires less expert judgment for characterizing XPS narrow scans, and as an approach that may be well suited for the analysis of complex spectra. The EWXPS figure of merit was applied to four different data sets. However, as previously noted, other width functions are also regularly employed for analyzing functions. Here we evaluate two other width functions for XPS narrow scan analysis: the autocorrelation width (AWXPS) and the variance (σXPS2). These widths were applied to the same four sets of spectra studied before: (a) four C 1s narrow scans of ozone-treated carbon nanotubes (CNTs) (EWXPS: ∼2.11–2.16 eV, AWXPS: ∼3.9–4.1 eV, σXPS2: ∼5.0–5.2 eV, and a modified form of σXPS2, denoted σXPS2*: ∼6.3–6.8 eV), (b) silicon wafers with different oxide thicknesses (EWXPS: ∼1.5–2.9 eV, AWXPS: ∼2.28–4.9, and σXPS2: ∼0.7–4.9 eV), (iii) hydrogen-terminated silicon surfaces, before and after modification with pentyl groups, and after annealing of the pentyl-terminated surface (EWXPS: ∼0.7–1.0 eV, AWXPS: ∼1.2–1.6 eV, and σXPS2: ∼0.12–0.19 eV), and (iv) C 1s narrow scans from five different nanodiamond samples, three of which showed charging (EWXPS: ∼2.6–4.8 eV, AWXPS: ∼3.8–6.9 eV, and σXPS2: ∼1.6–4.2 eV). All three of the width functions showed similar trends, except in the case of the C 1s spectra of the CNT samples, which were the most complex spectra evaluated, where σXPS2 showed poor correlation with the corresponding O/C ratios. Accordingly, we favor EWXPS and AWXPS. EWXPS is advantageous because it is conceptually simple, giving the most intuitive results. AWXPS has the advantage of not requiring the user to specify the height of the function at its maximum, which will be affected by noise. Because these functions are based on different mathematical operations/algorithms, best practices may involve the calculation of both widths for a set of narrow scans. The standard deviation, σXPS, i.e., the square root of the variance, was also examined. As expected, it gave results similar to σXPS2.

The traditional assignment of oxidation states to organic molecules is problematic. Accordingly, in 1999, Calzaferri proposed a simple and elegant solution that is based on the similar electronegativities of carbon and hydrogen: hydrogen would be assigned an oxidation state of zero when bonded to carbon. Here, we show that X-ray photoelectron spectroscopy, a core electron spectroscopy that is sensitive to oxidation states of elements, generally agrees with his suggestion. We also list the typical (IUPAC) rules for assigning oxidation states, review recent suggestions of Loock and Steinborn that are based on Pauling’s earlier approach, discuss the traditional (IUPAC and Pauling–Loock–Steinborn) assignments of oxidation states to organic molecules, review Calzaferri’s suggestion, introduce X-ray photoelectron spectroscopy (XPS), show the general agreement of Calzaferri’s suggestion with XPS results, provide supporting examples from the literature, and discuss the limitations of Calzaferri’s recommendation vis-à-vis XPS results. We conclude by recommending that either (i) Calzaferri’s suggestion be implemented into the current IUPAC rules or (ii) the Loock definition be explanded to deal specifically with atoms with similar electronegativities.Keywords: Analytical Chemistry; First-Year Undergraduate/General; Misconceptions/Discrepant Events; Organic Chemistry; Oxidation State; Physical Chemistry; Second-Year Undergraduate; Textbooks/Reference Books; Upper-Division Undergraduate;

•A Bi–Te–Se thin film is characterized by spectroscopic ellipsometry (SE).•The SE data are obtained using interference enhancement.•Modeling of the SE data is guided by results from other techniques.•Atomic force and scanning electron microscopy reveal rough, grainy films.•X-ray diffraction and X-ray reflectivity confirm film composition and SE modeling.Conventional magnetic tape is the most widely used medium for archival data storage. However, data stored on it need to be migrated every ca. 5 years. Recently, optical discs that store information for hundreds, or even more than 1000 years, have been introduced to the market. We recently proposed that technology in these optical discs be used to make an optical tape that would show greater permanence than its magnetic counterpart. Here we provide a detailed optical characterization of a sputtered thin film of bismuth, tellurium, and selenium (BTS) that is a proposed data storage layer for these devices. The methodology described herein should be useful in the future development of related materials. Spectroscopic ellipsometry (SE) data are obtained using interference enhancement, and the modeling of this data is guided by results from atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray reflectivity (XRR). By AFM, ca. 40 nm BTS films show ca. 10 nm roughness. SEM images also suggest considerable roughness in the films and indicate that they are composed of 13.1 ± 5.9 nm grains. XRD confirms that the films are crystalline and predicts a grain size of 17 ± 2 nm. XRD results are consistent with the composition of the films — a mildly oxidized BTS material. Three models of increasing complexity are investigated to explain the SE data. The first model consists of a smooth, homogeneous BTS film. The second model adds a roughness layer to the previous model. The third model also has two layers. The bottom layer is modeled as a mixture of BTS and void using a Bruggeman effective medium approximation. The upper layer is similarly modeled, but with a gradient. The first model was unable to adequately model the SE data. The second model was an improvement — lower MSE (4.4) and good agreement with step height measurements. The third model was even better — very low MSE (2.6) and good agreement with AFM results. The third SE model predicted ca. 90% void at the film surface. XRR modeling of the film agreed well with the predictions from SE. The uniquenesses of the SE models were confirmed.

A novel write-once-read-many (WORM) optical stack on Mylar tape is proposed as a replacement for magnetic tape for archival data storage. This optical tape contains a cosputtered bismuth–tellurium–selenium (BTS) alloy as the write layer sandwiched between thin, protective films of reactively sputtered carbon. The composition and thickness of the BTS layer were confirmed by Rutherford Backscattering (RBS) and atomic force microscopy (AFM), respectively. The C/BTS/C stack on Mylar was written to/marked by 532 nm laser pulses. Under the same conditions, control Mylar films without the optical stack were unaffected. Marks, which showed craters/movement of the write material, were characterized by optical microscopy and AFM. The threshold laser powers for making marks on C/BTS/C stacks with different thicknesses were explored. Higher quality marks were made with a 60× objective compared to a 40× objective in our marking apparatus. The laser writing process was simulated with COMSOL.Keywords: bismuth; carbon; data storage; optical tape; selenium; sputter; tellurium;

We describe a method for plasma cleaning silicon surfaces in a commercial tool that removes adventitious organic contamination and enhances silane deposition. As shown by wetting, ellipsometry, and XPS, hydrogen, oxygen, and argon plasmas effectively clean Si/SiO2 surfaces. However, only hydrogen plasmas appear to enhance subsequent low-pressure chemical vapor deposition of silanes. Chemical differences between the surfaces were confirmed via (i) deposition of two different silanes: octyldimethylmethoxysilane and butyldimethylmethoxysilane, as evidenced by spectroscopic ellipsometry and wetting, and (ii) a principal components analysis (PCA) of TOF-SIMS data taken from the different plasma-treated surfaces. AFM shows no increase in surface roughness after H2 or O2 plasma treatment of Si/SiO2. The effects of surface treatment with H2/O2 plasmas in different gas ratios, which should allow greater control of surface chemistry, and the duration of the H2 plasma (complete surface treatment appeared to take place quickly) are also presented. We believe that this work is significant because of the importance of silanes as surface functionalization reagents, and in particular because of the increasing importance of gas phase silane deposition.

Some of us recently described the fabrication of thin layer chromatography (TLC) plates from patterned carbon nanotube (CNT) forests via direct infiltration/coating of the CNTs by low pressure chemical vapor deposition (LPCVD) of silicon from SiH4, followed by high temperature oxidation of the CNTs and Si. Herein we present an improved microfabrication process for the preparation of these TLC plates. First, a few nanometers of carbon and/or a thin film of Al2O3 is deposited on the CNTs. This method of priming the CNTs for subsequent depositions appears to be new. X-ray photoelectron spectroscopy confirms the presence of additional oxygen after carbon deposition. After priming, the plates are coated by rapid, conformal deposition of an inorganic material that does not require subsequent oxidation, i.e., by a fast pseudo atomic layer deposition (ψ-ALD) of SiO2 from trimethylaluminum and tris(tert-butoxy)silanol. Unlike devices described previously, faithful reproduction of the features in the masks is still observed after oxidation. A bonded, amino phase on the resulting plates shows fast, highly efficient separations of fluorescent dyes (plate heights in the range of 1.6–7.7 μm). Extensive characterization of the new materials by TEM, SEM, EDAX, DRIFT, and XPS is reported. A substantially lower process temperature for the removal of the CNT scaffold is possible as a result of the already oxidized materials used.Highlights► Fast, highly efficient (Hobs range of 1.6–7.7 μm) separations rivaling those of HPLC. ► Rapid deposition of an inorganic material that does not require oxidation. ► For the first time a bonded phase deposited on microfabricated TLC plates. ► Extensive characterization by TEM, SEM, EDAX, DRIFT, and XPS.

A new stationary phase for reversed-phase high performance liquid chromatography (RP HPLC) was created by coating spherical 3 μm carbon core particles in a layer-by-layer (LbL) fashion with poly(allylamine) (PAAm) and nanodiamond. Unfunctionalized core carbon particles were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and Raman spectroscopy. After LbL of PAAm and nanodiamond, which yields ca. 4 μm core–shell particles, the particles were simultaneously functionalized and cross-linked using a mixture of 1,2-epoxyoctadecane and 1,2,7,8-diepoxyoctane to obtain a mechanically stable C18/C8 bonded outer layer. Core–shell particles were characterized by SEM, and their surface area, pore diameter, and volume were determined using the Brunauer–Emmett–Teller (BET) method. Short stainless steel columns (30 × 4.6 mm i.d.) were packed and the corresponding van Deemter plots obtained. The Supporting Information contains a MATLAB program used to fit the van Deemter data. The retentions of a suite of analytes were investigated on a conventional HPLC at various organic solvent compositions, pH values of mobile phases, including extreme pH values, and column temperatures. At 60 °C, a chromatogram of 2,6-diisopropylphenol showed 71 500 plates/m (N/m). Chromatograms obtained under acidic conditions (pH 2.7) of a mixture of acetaminophen, diazepam, and 2,6-diisopropylphenol and a mixture of phenol, 4-methylphenol, 2-chlorophenol, 4-chlorophenol, 4-bromophenol, and 1-tert-butyl-4-methylphenol are presented. Retention of amitriptyline, cholesterol, and diazinon at temperatures ranging from 35 to 80 °C and at pH 11.3 is reported. A series of five basic drugs was also separated at this pH. The stationary phase exhibits considerable hydrolytic stability at high pH (11.3) and even pH 13 over extended periods of time. An analysis run on a UHPLC with a “sandwich” injection appeared to reduce extra column band broadening and gave best efficiencies of 110 000–120 000 N/m.

Porous graphitic carbon (PGC) particles were functionalized/passivated in situ in packed beds at elevated temperature with neat di-tert-amylperoxide (DTAP) in a column oven. The performance of these particles for high performance liquid chromatography (HPLC) was assayed before and after this chemistry with the following analytes: benzene, toluene, ethyl benzene, n-propyl benzene, n-butyl benzene, p-xylene, phenol, 4-methylphenol, phenetole, 3,5-xylenol, and anisole. After the first functionalization/passivation, the retention factors, k, of these compounds decreased by about 5% and the number of theoretical plates (N) increased by ca. 15%. These values of k then remained roughly constant after a second functionalization/passivation but a further increase in N was noticed. In addition, after each of the reactions, the peak asymmetries decreased by ca. 15%, for a total of ca. 30%. The columns were then subjected twice to methanol at 100 °C for 5 h at 1 mL/min. After these stability tests, the values of k remained roughly constant, the number of plates increased, which is favorable, and the asymmetries rose and then declined, where they remained below the initial values for the unfunctionalized columns. Functionalized and unfunctionalized particles were characterized by scanning electron microscopy and BET measurements, which showed no difference between the functionalized and unfunctionalized materials, and X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS), where ToF-SIMS suggested some chemical differences between the functionalized and unfunctionalized materials. In particular ToF-SIMS suggested that the expected five-carbon fragments from DTAP exist at higher concentrations on DTAP-functionalized PGC. First principle calculations on model graphitic surfaces suggest that the first addition of a DTAP radical to the surface proceeds in an approximately isothermal or slightly favorable fashion, but that subsequent DTAP additions are then increasingly thermodynamically favorable. Thus, this analysis suggests that the direct functionalization/passivation of PGC with DTAP is plausible. Chemometric analyses of the chromatographic and ToF-SIMS data are also presented.Highlights► Di-tert-amylperoxide was used to functionalized/passivate the surface of PGC. ► PCA demonstrated a change in the N, Assym.10%, and k after reacting with DTAP. ► PCA of ToF-SIMS data suggests the attachment of DTAP formed radicals to PGC.

Self-assembly of organic thiols is the most common way to introduce functional groups onto gold surfaces. Although the gold–sulfur (Au–S) bond is moderately strong (∼45 kcal/mol), it is also prone to oxidation, which substantially weakens the Au–S interaction. In this work, we describe the creation of more robust molecular assemblies on gold. As a first step, a thiolated monolayer is prepared on gold with an α,ω-dithiol. Experiments are also reported for a mercaptosilane monolayer on silicon dioxide. An oligomer of polybutadiene (PBd) was then tethered to these surfaces using thiol–ene chemistry. Residual groups on the PBd are then reacted with thiols, including octadecanethiol (ODT), 1H,1H,2H,2H-perfluoroalkanethiol, and a thiol-terminated 25-mer of DNA. Little nonspecific adsorption of a non-thiolated DNA oligomer was observed. Surface characterization was performed with X-ray photoelectron spectroscopy (XPS), contact angle goniometry, time-of-flight secondary ion mass spectrometry (ToF-SIMS), and spectroscopic ellipsometry. A thiol–gold monolayer and an analogous assembly of the same thiol tethered to gold through PBd on a dithiol monolayer were both exposed to air and light for 2 weeks and then rinsed with water. The monolayer on gold was removed in this process, while the thiol in the assembly appeared unaffected.

A highly durable optical disk has been developed for data archiving. This optical disk uses tellurium as the write layer and carbon as a dielectric and oxidation prevention layer. The sandwich style CTeC film was deposited on polycarbonate and silicon substrates by plasma sputtering. These films were then characterized with AFM, SEM, TEM, EELS, and ellipsometry and were tested for writability and longevity. Results show the films were uniform in physical structure, stable, and able to form permanent pits. Data was written to a disk and successfully read back in a commercial DVD drive.Keywords: archival; carbon; data storage; DVD; optical disk; tellurium

We describe direct polymer attachment to hydrogen and deuterium-terminated diamond (HTD and DTD) surfaces using a radical initiator (di-tert-amyl peroxide, DTAP), a reactive monomer (styrene) and a crosslinking agent (divinylbenzene, DVB) to create polystyrene encapsulated diamond. Chemisorbed polystyrene is sulfonated with sulfuric acid in acetic acid. Surface changes were followed by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). Finally, both polystyrene-modified DTD and sulfonated styrene-modified DTD were used in solid phase extraction (SPE). Percent recovery and column capacity were investigated for both phenyl (polystyrene) and sulfonic acid treated polystyrene SPE columns. These diamond-based SPE supports are stable under basic conditions, which is not the case for silica-based SPE supports.

We report the first attachment of polymers with pendant vinyl groups to hydrogen-terminated silicon(111) (Si(111)-H); 1,2-polybutadiene (Mw = 3200−3500 g/mol) was attached to Si(111)-H under mild conditions at room temperature with visible light. We also report the partial functionalization, in solution, of 1,2-polybutadiene with various thiols using thiol−ene chemistry and the subsequent attachments of these compounds to Si(111)-H. The partially functionalized or unfunctionalized polybutadienes allow further functionalization at the surface through their unreacted carbon−carbon double bonds. We present this as a useful strategy for silicon surface modification. Surfaces were characterized with contact angle goniometry, spectroscopic ellipsometry, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and atomic force microscopy (AFM).

In spite of advances in solid-phase extraction (SPE) technology there are certain disadvantages to current SPE silica-based, column packings. The pH range over which extraction can occur is limited and each column is generally only used once. New diamond-based reversed SPE phases (C18, C8, and perfluorinated) were developed in our laboratories. Studies were done which show that these phases do not have the same limitations as traditional silica-based stationary phases. The synthesis and properties of these diamond-based phases are presented, and the stability, percent recovery, and column capacity are given for the C18 phase.

Here we present a straightforward patterning technique for silicon: subsurface oxidation for micropatterning silicon (SOMS). In this method, a stencil mask is placed above a silicon surface. Radio-frequency plasma oxidation of the substrate creates a pattern of thicker oxide in the exposed regions. Etching with HF or KOH produces very shallow or much higher aspect ratio features on silicon, respectively, where patterning is confirmed by atomic force microscopy, scanning electron microscopy, and optical microscopy. The oxidation process itself is studied under a variety of reaction conditions, including higher and lower oxygen pressures (2 and 0.5 Torr), a variety of powers (50−400 W), different times and as a function of reagent purity (99.5 or 99.994% oxygen). SOMS can be easily executed in any normal chemistry laboratory with a plasma generator. Because of its simplicity, it may have industrial viability.

Although polydimethylsiloxane (PDMS) transfer during microcontact printing (μCP) has been observed in previous reports, which generally focused on only one or a few different substrates, in this work we investigate the extent of PDMS transfer onto a series of surfaces with a wide range of hydrophobicities using an uninked, unpatterned PDMS stamp. These surfaces include clean silicon, clean titanium, clean gold, “dirty” silicon, polystyrene, Teflon, surfaces modified with PEG, amino, dodecyl, and hexadecyl monolayers, and also two loose molecular materials. The PDMS transferred onto planar surfaces is, in general, easily detected by wetting and spectroscopic ellipsometry. More importantly, it is detected by time-of-flight secondary ion mass spectrometry (ToF-SIMS) because of the sensitivity of this technique to PDMS. The effect of surface free energy on PDMS transfer in microcontact printing is investigated, and the relationship between the amount of PDMS in ToF-SIMS spectra and the surface tensions of initial surfaces is revealed. We show that PDMS transfer can be applied as a probe of surface free energies using ToF-SIMS, where PDMS preferentially transfers onto more hydrophilic surface features during stamping, with little being transferred onto very hydrophobic surface features. Multivariate curve resolution (MCR) analysis of the ToF-SIMS image data further confirms and clarifies these results. Our data lend themselves to the hypothesis that it is the free energy of the surface that plays a major role in determining the degree of PDMS transfer during μCP.

This paper documents time-of-flight secondary ion mass spectrometry (ToF−SIMS) analyses of 34 different coal samples. In many cases, the inorganic Na+, Al+, Si+, and K+ ions dominate the spectra, eclipsing the organic peaks. A scores plot of principal component 1 (PC1) versus principal component 2 (PC2) in a principal components analysis (PCA) effectively separates the coal spectra into a triangular pattern, where the different vertices of this pattern come from (i) spectra that have a strong inorganic signature that is dominated by Na+, (ii) spectra that have a strong inorganic signature that is dominated by Al+, Si+, and K+, and (iii) spectra that have a strong organic signature. Loadings plots of PC1 and PC2 confirm these observations. The spectra with the more prominent inorganic signatures come from samples with higher ash contents. Cluster analysis with the K-means algorithm was also applied to the data. The progressive clustering revealed in the dendrogram correlates extremely well with the clustering of the data points found in the scores plot of PC1 versus PC2 from the PCA. In addition, this clustering often correlates with properties of the coal samples, as measured by traditional analyses. Partial least-squares (PLS), which included the use of interval PLS and a genetic algorithm for variable selection, shows a good correlation between ToF−SIMS spectra and some of the properties measured by traditional means. Thus, ToF−SIMS appears to be a promising technique for the analysis of this important fuel.

We report the preparation of highly conductive polyaniline (PANi) fibers produced via a wet-spinning process into different coagulation solvents or solutions. To the best of our knowledge, this paper shows the first successful spinning of PANi fibers into an aqueous environment where no post-doping of the fiber is needed. Aqueous solutions of different salts, small anionic molecules, small cationic molecules, polycations, and polyanions are studied. Best results are obtained using an aqueous solution of a polyanion as a coagulation bath. The resulting fibers exhibit good length, stability, and morphology. An in depth study of the relationship between the fiber properties and the concentration of a polyanion in the aqueous bath (poly(sodium 4-styrenesulfonate), PSS) is performed. It is shown that PSS solutions stabilize the PANi fibers without dramatically changing the conductivity of the fibers. It is believed that this stabilization is a result of numerous ionic interactions between cationic centers on the PANi and anionic groups on the polyanion. This new preparation method should be industrially viable.