Of 1-octadecanethiol Research Articles

A multifunctional heterogeneous superwettable coating for water collection, oil/water separation and oil absorption.

Herein, inspired by desert beetles, we fabricated a multifunctional heterogeneous superwettable coating (MHSC) for water collection and oily wastewater cleanup. The selective modifications of 1-octadecanethiol (ODT) treated CoO and P25 TiO2 nanoparticles (NPs) were prepared, so hydrophobic CoO NPs and superhydrophilic P25 NPs were combined on the MHSC, showing the water contact angle (WCA) of 156.5° and rolling-off angle (RA) of 6.4°. With the aid of waterborne polyurethane (WPU), five kinds of substrates (i.e., glass slide, dish, wood, fabric, sponge) spray-coated by MHSC displayed high-efficiency water collection rates (WCRs) of 18.1±0.7mgmin-1 cm-2. Moreover, MHSC coated fabric manifested robust oil/water separations with separation efficiencies (SEs) >99.7 % and fluxes ranged from 9.7 to 11.0Lm-2 s-1. Efficient oil sorption from oily water was obtained by MHSC coated sponge with oil absorption capacities (OACs) of 6.5-29.5gg-1. Further, even dealt with the treatments of mechanical destructions, extreme temperature and UV illumination, the coated materials remained stable performances.

Understanding the impact of Cu surface pre-treatment on Octadecanethiol-derived self-assembled monolayer as a mask for area-selective deposition

Atomic layer deposition (ALD) combined with self-assembled monolayer (SAM) passivation allows selective deposition on patterned substrates at the nanoscale, enabling bottom-up material fabrication for various applications. Selective chemisorption of 1-octadecanethiol (ODT) on Cu over SiO2 is exploited to achieve area selective deposition (ASD). Although the essential role played by SAM in preserving a confined material growth at higher ALD cycles is largely accepted, studies elucidating the influence of substrate properties on SAM’s ALD inhibition are lacking. In this work, Cu is treated either with acids or oxidizing agents to produce a multiplicity of surfaces, which differ in terms of composition and morphology. Using water contact angle, atomic force microscopy, x-ray photoelectron spectroscopy and cyclic voltammetry measurements, Cu substrates are characterized before and upon ODT deposition. The ODT layers formed on Cu are tested as a passivation means towards Hf3N4 ALD. The results stress the essential contribution of interface properties in forming dense thiol-SAM on metals, which is fundamental to a successful ASD process. It is here demonstrated that ODT on clean Cu cannot block Hf3N4 ALD at 150 °C, whereas on oxidized Cu the same organic layer prevents up to 19 nm Hf3N4 film growth before the Cu passivation is affected.

Effect of surface treatment on electrical properties of GaN metal–insulator–semiconductor devices with Al2O3 gate dielectric

This research proposes an economical and effective method of 1-octadecanethiol (ODT) treatment on GaN surfaces prior to Al2O3 gate dielectric deposition. GaN-based metal–insulator–semiconductor (MIS) devices treated by HCl, O2 plasma and ODT are demonstrated. ODT treatment was found to be capable of suppressing native oxide and also of passivating the GaN surface effectively; hence the interface quality of the device considerably improved. The interface trap density of Al2O3/GaN was calculated to be around 3.0 × 1012 cm−2 eV−1 for devices with ODT treatment, which is a relatively low value for GaN-based MIS devices with Al2O3 as the gate dielectric. Moreover, there was an improvement in the gate control characteristics of MIS-HEMTs fabricated with ODT treatment.

Formation of a mixed monolayer on a gold surface using fluorobenzenethiol and alkanethiol

Mixed monolayers consisting of 4-fluorobenzenethiolate and 1-octadecanethiolate on Au surfaces were formed by immersing in an ethanol solution of 4-fluorobenzenethiol (FBT), and subsequently by immersing in that of 1-octadecanethiol (ODT). To obtain systematically a mixed monolayer, the formation of FBT- and ODT-monolayers was investigated with respect to the reaction time and concentration of the solution. The monolayer formed on a Au surface was evaluated based on the work function, the water contact angle, and the X-ray photoelectron spectroscopy (XPS) spectra measured. The XPS measurement of substrates prepared for formation of a mixed monolayer exhibited F 1s and C 1s spectra supporting the presence of a mixed monolayer consisting of 4-fluorobenezenethiolate and 1-octadecanethiolate.

Thermal Effect on Positive Patterned Self-Assembled Monolayer Grown from a Droplet of Alkanethiol.

Atomic force microscope technique is widely used for the spatial narrow deposition of molecules inside the bare space of preexisting self-assembled monolayer (SAM) matrix. Using molecular dynamics simulation, we studied the formation of positively patterned SAM from a globule of 1-octadecanethiol (ODT) on predesigned SAM matrix of 1-dodecanethiol (DDT) and effect of temperature on it. The alkyl chains of ODT SAM were densely packed and ordered by means of chemisorption through sulfur atoms. The circular SAM of ODT contained defects due to the molecules those were standing upside down or trapped inside ODT SAM. We found that with the increase of temperature, these defects moved out by flipping of inverted ODT molecules or building spaces to be adsorbed on Au surface. The ODT molecules on the top of the pile of stable circular SAM or those are upside down and trapped disperse in a unique fashion namely serial pushing through which molecules firstly make a free space to enter inside the adsorbed thiol molecules and then push neighboring molecules to get enough space to be adsorbed on the gold surface. The stability of ODT SAM was confirmed by analyzing different structural properties such as tilt angle, tilt orientation. and backbone orientation. We also calculated the diffusion coefficient of the ODT molecules which were on the top of SAM island. © 2019 Wiley Periodicals, Inc.

Chemical Imaging of Self-Assembled Monolayers on Copper Using Compressive Hyperspectral Sum Frequency Generation Microscopy.

Sum frequency generation microscopy is a label-free optical imaging technique with intrinsic molecular vibrational contrast for surface studies. Recent developments of compressive sensing broad-band hyperspectral SFG microscopy have demonstrated the potential application for imaging monolayer at metal surfaces with micrometer spatial resolution. Here is presented the capability of chemical imaging of spatially patterned monolayers of 1-octadecanethiol (ODT) and 16-methoxy-1-hexadecanethiol (MeOHT) molecules assembled on a copper surface. The spatial distributions of the monolayer with vibrational-spectral contrast are well-demonstrated at different frequency regions through reconstruction of the hypercube using a 3-dimensional total variation regularization algorithm (3DTV). Spatial-chemical distributions of each component are also reconstructed directly from the compressive measurements by endmember unmixing (CEU) scheme. Compared to 3DTV algorithm, the reconstruction from CEU shows spatial distribution of each component on the surfaces, and demonstrates the ability to characterize the domains of mixed-molecules on surfaces.

Hierarchically structured self-supported latex films for flexible and semi-transparent electronics

Different length scale alterations in topography, surface texture, and symmetry are known to evoke diverse cell behavior, including adhesion, orientation, motility, cytoskeletal condensation, and modulation of intracellular signaling pathways. In this work, self-supported latex films with well-defined isotropic/anisotropic surface features and hierarchical morphologies were fabricated by a peel-off process from different template surfaces. In addition, the latex films were used as substrates for evaporated ultrathin gold films with nominal thicknesses of 10 and 20nm. Optical properties and topography of the samples were characterized using UV–vis spectroscopy and Atomic Force Microscopy (AFM) measurements, respectively. The latex films showed high-level transmittance of visible light, enabling the fabrication of semi-transparent gold electrodes. Electrochemical impedance spectroscopy (EIS) measurements were carried out for a number of days to investigate the long-term stability of the electrodes. The effect of 1-octadecanethiol (ODT) and HS(CH2)11OH (MuOH) thiolation and protein (human serum albumin, HSA) adsorption on the impedance and capacitance was studied. In addition, cyclic voltammetry (CV) measurements were carried out to determine active medicinal components, i.e., caffeic acid with interesting biological activities and poorly water-soluble anti-inflammatory drug, piroxicam. The results show that the fabrication procedure presented in this study enables the formation of platforms with hierarchical morphologies for multimodal (optical and electrical) real-time monitoring of length-scale-dependent biomaterial-surface interactions.

Generation of plasmonic Au nanostructures in the visible wavelength using two-dimensional parallel dip-pen nanolithography.

The fabrication and characterization of over millimeter (mm)-scale Au plasmonic structures are reported. Fishnet structures of Au are fabricated by the "bottom-up (direct deposition of alkanethiol)" and "top-down (wet-etching of Au)" combined approach using massively parallel dip-pen nanolithography (DPN). An array of two-dimensional (2D) parallel 55,000 pens was used for the DPN writing of 1-octadecanethiol (ODT) on an Au film in an area of 10 mm × 10 mm. The plasmonic resonance of the over millimeter-scale Au fishnet structures is shown at the visible region around 500 nm, which is measured by ellipsometrical experiments and theoretical finite-difference time-domain (FDTD) calculation. It was demonstrated that massive metal plasmonic structures can be conveniently obtained by using DPN, complementary with both e-beam lithography and nanoimprint lithography.

Role of Self-Assembled Monolayer Passivation in Electrical Transport Properties and Flicker Noise of Nanowire Transistors

Semiconductor nanowires have achieved great attention for integration in next-generation electronics. However, for nanowires with diameters comparable to the Debye length, which would generally be required for one-dimensional operation, surface states degrade the device performance and increase the low-frequency noise. In this study, single In(2)O(3) nanowire transistors were fabricated and characterized before and after surface passivation with a self-assembled monolayer of 1-octadecanethiol (ODT). Electrical characterization of the transistors shows that device performance can be enhanced upon ODT passivation, exhibiting steep subthreshold slope (~64 mV/dec), near zero threshold voltage (~0.6 V), high mobility (~624 cm(2)/V·s), and high on-currents (~40 μA). X-ray photoelectron spectroscopy studies of the ODT-passivated nanowires indicate that the molecules are bound to In(2)O(3) nanowires through the thiol linkages. Device simulations using a rectangular geometry to represent the nanowire indicate that the improvement in subthreshold slope and positive shift in threshold voltage can be explained in terms of reduced interface trap density and changes in fixed charge density. Flicker (low-frequency, 1/f) noise measurements show that the noise amplitude is reduced following passivation. The interface trap density before and after ODT passivation is profiled throughout the band gap energy using the subthreshold current-voltage characteristics and is compared to the values extracted from the low-frequency noise measurements. The results indicate that self-assembled monolayer passivation is a promising optimization technology for the realization of low-power, low-noise, and fast-switching applications such as logic, memory, and display circuitry.

Heat Transfer at Solid–Gas Interfaces by Photoacoustics at Brillouin Frequencies

We use time-resolved ellipsometry to investigate the rate of heat transfer at solid−gas interfaces through measurements of the amplitude and phase of acoustic waves at Brillouin frequencies, 100−400 MHz, at pressures 2 orders of magnitude higher than earlier comparable studies. An ultrafast optical pulse heats a thin metal film deposited on a sapphire substrate. Heat flow from the substrate into the gas causes expansion of the gas and generates an acoustic wave that is probed by off-null ellipsometry with subpicosecond time resolution. We compare the amplitudes and phases of photoacoustic signals generated in inert gases Ne, Ar, Kr, and Xe to a continuum theoretical model that includes the thermal accommodation coefficient α at the gas−solid interface. For the surfaces we have studied, bare Au and Au coated by a self-assembled monolayer of 1-octadecanethiol (ODT), this comparison between experiment and theory for the amplitude of the photoacoustic waves suggests that α values for bare and ODT-terminated Au are similar and α > 0.3. This conclusion is tentative, however, because the phases of the photoacoustic waves show systematic differences that are not predicted by the model. For tetrafluoroethane vapor (R-134a refrigerant), the photoacoustic signal generated by a Au surface coated with a hydrophilic (COOH-terminated) self-assembled monolayer is a factor of 2 larger than the photoacoustic signal generated by a hydrophobic (CH3-terminated) monolayer. We also report measurements of the ultrafast ellipsometry signals generated by the sudden desorption of physisorbed methanol and water on hydrophobic and hydrophilic self-assembled monolayers.

Introducing cymantrene labels into scattering scanning near-field infrared microscopy

In this paper we investigate metal-organic compounds as infrared (IR) active labels by scattering scanning near-field infrared microscopy (IR s-SNOM, often also abbreviated as s-SNIM) with a lateral resolution of 90 × 90 nm(2). Tailor-made IR spectroscopic probes based on cymantrene (CpMn(CO)(3) with Cp = η(5)-C(5)H(5)) conjugated to a cysteine-modified pseudoneurotensin (pNT-Cys-OH) peptide were prepared by automated microwave-assisted solid phase peptide synthesis (SPPS) and characterized by HPLC, ESI-MS and IR. Well-defined patterned self-assembled monolayers on a gold surface were prepared by microcontact printing of 1-octadecanethiol (ODT) followed by additional incubation in ethanolic solution of the cymantrene-peptide derivative. The self-assembled monolayers have been evidenced by infrared reflection absorption spectroscopy (IRRAS) and AFM. CO laser source radiation was tuned (1944, 1900, 1798 and 1658 cm(-1)) for imaging contrast with good matching correlation between spectroscopic and topographic patterns at specific characteristic metal carbonyl and amide bands (1944 cm(-1) (λ = 5.14 μm) and 1658 cm(-1) (λ = 6.03 μm)). Cymantrene probes provide an attractive method to tag a unique spectroscopic feature on any bio(macro)molecule. Introducing such probes into super-resolution IR s-SNOM will enable molecular tracking and distribution studies even in complex biological systems.

Spectroscopic and Microscopic Investigation of Gold Nanoparticle Formation: Ligand and Temperature Effects on Rate and Particle Size

We report a spectroscopic and microscopic investigation of the synthesis of gold nanoparticles (AuNPs) with average sizes of less than 5 nm. The slow reduction and AuNP formation processes that occur by using 9-borabicyclo[3.3.1]nonane (9-BBN) as a reducing agent enabled a time-dependent investigation based on standard UV-vis spectroscopy and transmission electron microscopy (TEM) analyses. This is in contrast to other borohydride-based syntheses of thiolate monolayer protected AuNPs which form particles very rapidly. We investigated the formation of 1-octadecanethiol (ODT) protected AuNPs with average diameters of 1.5-4.3 nm. By studying the progression of nanoparticle formation over time, we find that the nucleation rate and the growth time, which are interlinked with the amount of ODT and the temperature, influence the size and the size dispersion of the AuNPs. High-resolution TEM (HRTEM) analyses also suggest that the nanoparticles are highly single crystalline throughout the synthesis and appear to be formed by a diffusion-controlled Ostwald-ripening growth mechanism.

Thermal stability of thiol and silane monolayers: A comparative study

The stability of self-assembled monolayers (SAMs) at elevated temperatures is of considerable technological importance. The thermal stability of 1-octadecanethiol (ODT), 16-mercaptohexadecanoic acid (MHDA) and 1H,1H,2H,2H-perfluorodecanethiol (PFDT) SAMs on gold surfaces, and of 4-aminobutyltriethoxysilane (ABTES) and 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFDS) assembled on hydroxylated silicon surfaces, was studied by X-ray photoelectron spectroscopy (XPS). The samples were heated in ultrahigh vacuum to temperatures in excess of that required for SAM degradation. ODT monolayers were stable to ca. 110 °C, while MHDA and PFDT SAMs were stable to ca. 145 °C. ABTES SAMs were found to be indefinitely stable to 250 °C, while PFDS SAMs were stable to 350 °C. These studies demonstrate the advantages of using silane monolayers for moderate to high temperature applications and illustrate differences that arise due to the nature of the tail group. To demonstrate the feasibility of silanes for template-directed patterning, a hydroxylated silicon oxide surface containing microcontact-printed PFDS patterns was spin-coated with a mainly hydrophilic block copolymer. Annealing the surface at 90 °C for 2 h caused the block copolymer to dewet the hydrophobic PFDS-patterned regions and adsorb exclusively on the unpatterned regions of the surface.

Electrical detection of the biological interaction of a charged peptide via gallium arsenide junction-field-effect transistors

GaAs junction-field-effect transistors (JFETs) are utilized to achieve label-free detection of biological interaction between a probe transactivating transcriptional activator (TAT) peptide and the target trans-activation-responsive (TAR) RNA. The TAT peptide is a short sequence derived from the human immunodeficiency virus-type 1 TAT protein. The GaAs JFETs are modified with a mixed adlayer of 1-octadecanethiol (ODT) and TAT peptide, with the ODT passivating the GaAs surface from polar ions in physiological solutions and the TAT peptide providing selective binding sites for TAR RNA. The devices modified with the mixed adlayer exhibit a negative pinch-off voltage (V(P)) shift, which is attributed to the fixed positive charges from the arginine-rich regions in the TAT peptide. Immersing the modified devices into a TAR RNA solution results in a large positive V(P) shift (>1 V) and a steeper subthreshold slope ( approximately 80 mVdecade), whereas "dummy" RNA induced a small positive V(P) shift ( approximately 0.3 V) without a significant change in subthreshold slopes ( approximately 330 mVdecade). The observed modulation of device characteristics is analyzed with analytical modeling and two-dimensional numerical device simulations to investigate the electronic interactions between the GaAs JFETs and biological molecules.

Carbon Nanotube Monolayer Patterns for Directed Growth of Mesenchymal Stem Cells

Herein, wereport a method to control the adhesion and shape of MSCsusing monolayered CNT patterns. As a proof of concept, wepatterned various 1D nanostructures, including CNTs andNWs, on substrates, and MSCs were subsequently culturedand observed on the patterned substrates. In this work, self-assembled monolayer (SAM) patterns were first used todirect the assembly of single-walled CNTs (swCNTs) andmulti-walled CNTs (mwCNTs) on solid substrates. A self-limiting mechanism ensured the assembly of only a singlelayer of CNTs, without significant change of surface morphol-ogy. Importantly, the MSCs exhibited preferential growth onCNT patterns, and the cell culture results suggested that theCNT patterns did not have a harmful effect on the MSCs.Further, we demonstrated the growth of MSCs on swCNTpatterns between electrodes. These results clearly show thatCNT patterns have enormous potential as a new platform forbasic research and applications using stem cells.Figure 1 shows a schematic diagram depicting our experi-mental procedure for directed MSC growth. First, a non-polarSAM of 1-octadecanethiol (ODT) was patterned, while leav-ing some bare Au regions (Fig. 1A). SAM patterning on Aucan be achieved using dip-pen nanolithography (DPN)

Replacement of adsorbed alkanethiolate on Au with carboxyl-terminated thiol in solution: effect of alkyl chain length

We have investigated the effect of the alkyl chain length on the replacement of the self-assembled alkanethiolate on Au surface with carboxyl-terminated thiol dissolved in solution. Immersion time-dependent replacement of self-assembled alkanethiolates on Au substrate was monitored by lateral force microscope (LFM), contact angle measurement, and infrared spectroscopy (IRS). Both the self-assembled monolayers (SAM) of 1-octadecanethiol (ODT) and octanethiol (OT) were reacted with carboxyl-terminated 11-mercaptoundecanoic acid (MUA) molecules in ethanol. OT SAM was rapidly replaced by MUA molecules. More than 50% of OT molecules were replaced by MUA within the initial 50 h. In contrast, less than 10% of ODT molecules were replaced by MUA within the same time scale. This can be explained in terms of the relative stability between methyl- and carboxyl-terminated thiolates on Au surface, depending upon the chain length and the lateral hydrogen bonding.

Dip-Pen Nanolithography: What Controls Ink Transport?

The influence of temperature and humidity on the growth rates of 1-octadecanethiol (ODT) and 16-mercaptohexadecanoic acid (MHA) monolayers deposited onto a gold substrate has been systematically studied in the context of dip-pen nanolithography (DPN) experiments. By analyzing a statistically meaningful data set, we conclude that for both inks the deposition rate increases with increasing temperature, and that this temperature dependence is strongly affected by relative humidity, chemical nature of the ink and substrate, and writing speed. We attribute these observations to the different solubilities of the ink molecules in water (both the water in the meniscus and on the cantilever walls). In addition, we report a set of experiments that demonstrate meniscus formation even at 0% relative humidity due to residual water that moves to the point of contact between tip and sample.

High Resolution X-ray Photoelectron Spectroscopy Measurements of Octadecanethiol Self-Assembled Monolayers on Au(111)

We have measured high-resolution X-ray photoelectron spectroscopy (XPS) spectra of 1-octadecanethiol (ODT) self-assembled monolayers (SAMs) on a Au(111) surface in order to investigate the Au−S binding properties at the initial stage of SAM growth and after the desorption of the ODT from the Au surface. For the SAM prepared by the 1 min immersion into the ODT solution, we found new sulfur species around 161 eV and assigned it to isolated sulfur without C−S cleavage. We also confirmed the presence of a similar 161 eV peak in the S(2p) spectra after desorption of the ODT molecules. Furthermore, we observed a peak shift in the carbon 1s (C(1s)) peak, depending on the surface coverage of the ODT. In addition to the C(1s) peak of 285.1 eV which might correspond to alkyl chains of densely packed ODT molecules, another lower binding energy peak at 284.3 eV appeared after annealing. This lower C(1s) binding energy peak formation suggested that some of the alkyl chains for the remaining ODT molecules might be oriented parallel to the Au surface after annealing.