A 3-aminopropyltrimethoxysilane Research Articles

Unstructured Self-Assembled Molecular Lamella Induces Ultrafast Thermal Transfer through a Cathode/Separator Interphase in Lithium-Ion Batteries

Thermal issues associated with lithium-ion batteries (LIBs) can dramatically affect their life cycle and overall performance. However, the effective heat transfer is deeply restrained by the high thermal resistance across the cathode (lithium cobalt oxide, LCO)-separator (polyethylene, PE) interface. This work presents a new approach to tailoring the interfacial thermal resistance, namely, unstructured self-assembled lamella (USAL). Compared to the popular self-assembled monolayers, although the USAL gives a redundant interface and amorphous molecule patterns, it can also provide many benefits, including easy assembly, more thermal bridges, and ready pressurization. Three small organic molecules (SOMs) were assembled into an LCO-PE interface, providing unique functional groups, -NH2, -SH, and -CH3, to illustrate its energy conversion efficiency. Through molecular dynamics simulations, our results show that the USAL can facilitate interfacial heat transfer remarkably. A 3-aminopropyl trimethoxysilane (APTMS)-coated LCO-PE system with 11.4 Å thickness demonstrates the maximum enhancement of thermal conductance, about 320% of the pristine system. Such enhancement is attributed to the developed double heat passages by strong non-bonded interactions across LCO-SOM and PE-SOM interfaces, a tuned temperature field, and high compatibility between SOMs and PE. Importantly, due to SOMs' amorphous morphology, the pressure can be imposed and further enhance the interfacial heat transfer. Results show the improved thermal conductance rises the most for the APTMS-coated LCO-PE system with 11.4 Å thickness at 10 GPa, almost 685% higher than that of the pristine system. The high efficiency of heat transfer comes as a result of the enhanced binding strength across the LCO-SOM and SOM-PE interface, the reduced phonon scattering in PE and SOMs, and the high LCO stiffness. These investigations are expected to provide a new perspective for modulating the heat transfer across the interphase of LIBs and achieve more effective thermal management for the multi-material system.

Multilayer Growth of Porphyrin-Based Polyurea Thin Film Using Solution-Based Molecular Layer Deposition Technique.

Controllable synthesis of organic thin film materials on solid surfaces is a challenging issue in the research field of surface science, as it is affected by several physical parameters. In this work, we demonstrated a solution-based molecular layer deposition (MLD) approach to prepare porphyrin-based covalent organic molecular networks on a 3-aminopropyl trimethoxysilane (APTMS) modified substrate surface using the urea coupling reaction between 1,4-phenylene diisocyanate (1,4-PDI) and 5,10,15,20-tetrakis-(4-aminophenyl) porphyrin (H2TAPP) at room temperature (22 ± 2 °C). Multilayer growth was investigated under different relative humidity (RH) conditions of the reaction chamber. Sequential molecular growth at low relative humidity (≤10% RH) was observed using UV-vis absorption spectroscopy and atomic force microscopy (AFM). The high-RH condition shows limited film growth. Infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS) revealed the polyurea bond formation in sequential multilayer thin films, demonstrating that stepwise multilayer film growth was achieved using the urea coupling reaction.

Protein, cell and bacterial response to atmospheric pressure plasma grafted hyaluronic acid on poly(methylmethacrylate).

Hyaluronic acid (HA) has been immobilised on poly(methyl methacrylate) (PMMA) surfaces using a novel dielectric barrier discharge (DBD) plasma process for the purposes of repelling protein, cellular and bacterial adhesion in the context of improving the performance of ophthalmic devices. Grafting was achieved by the following steps: (1) treatment of the PMMA with a DBD plasma operating at atmospheric pressure, (2) amine functionalisation of the activated polymer surface by exposure to a 3-aminopropyltrimethoxysilane (APTMS) linker molecule and (3) reaction of HA with the surface bound amine. The mechanism and effectiveness of the grafting process was verified by surface analysis. XPS data indicates that the APTMS linker molecule binds to PMMA via the Si-O chemistry and has the required pendant amine moiety. The carboxylic acid moiety on HA then binds with this -NH2 group via standard carbodiimide chemistry. ToF-SIMS confirms the presence of a coherent HA layer the microstructure of which is verified by AFM. The plasma grafted HA coating surfaces showed a pronounced decrease in protein and cellular adhesion when tested with bovine serum albumin and human corneal epithelial cells, respectively. The ability of these coatings to resist bacterial adhesion was established using Staphylococcus aureus NTC8325. Interestingly, the coatings did not repel bacterial adhesion, indicating that the mechanism of adhesion of bacterial cells is different to that for the surface interactions of mammalian cells. It is proposed that this difference is a consequence of the specific HA conformation that occurs under the conditions employed here. Hence, it is apparent that the microstructure/architecture of the HA coatings is an important factor in fabricating surfaces intended to repel proteins, mammalian and bacterial cells.

Competitive Attachment of Gold Nanoparticles on an Indium Tin Oxide Electrode.

Fundamental aspects of the attachment of gold nanoparticles (AuNPs) onto a 3-aminopropyltrimethoxysilane (APTMS) modified indium tin oxide (ITO) electrode were explored using commercially available Au colloid solutions of 5, 10 and 20 nm. In particular, competitive attachments of AuNPs were observed using mixed solutions of two Au colloids. Consequently, it was found that smaller AuNPs are easily attached on an APTMS modified ITO. On the other hand, the result of the stepwise attachments showed that after the surface was modified by the first AuNPs, the second AuNPs have difficulty attaching. This means, if surface connecting -NH2 terminals of APTMS are once occupied, further modification or exchange of the attached AuNPs would not be easy. From the present results, a contaminant amount of smaller AuNPs is considered to be a practical problem in modifying ITO surfaces by AuNPs.

Chitosan-Coated Fe<sub>3</sub>O<sub>4</sub> Magnetic Nanoparticles as Carrier of Cisplatin for Drug Delivery

A synthesis method for a chitosan-coated magnetic drug-delivery system of cisplatin is proposed. Here, cisplatin was conjugated to the surface of Magnetite (Fe3O4) nanoparticles via a (3-Aminopropyl)-trimethoxysilane (APTS) coupling agent. To reduce the cytotoxic effect of cisplatin, the magnetic drug was then encapsulated in chitosan (CS-cisplatin-Fe3O4) through the water/oil (W/O) emulsion method. The CS-cisplatin-Fe3O4 nanoparticles were synthesized in a spherical shape with a diameter of 190 nm. The cytotoxicity assay was performed using HeLa cells. The cisplatin uptake of the cells was determined using High Performance Liquid Chromatography (HPLC) to calculate the drug content. The controlled release of cisplatin was demonstrated by regulating the dissolution and diffusion of the drug through the chitosan matrix.

Detection of prostate-specific antigen with biomolecule-gated AlGaN/GaN high electron mobility transistors

In order to improve the sensitivity of AlGaN/GaN high electron mobility transistor (HEMT) biosensors, a simple biomolecule-gated AlGaN/GaN HEMT structure was designed and successfully fabricated for prostate specific antigen (PSA) detection. UV/ozone was used to oxidize the GaN surface and then a 3-aminopropyl trimethoxysilane (APTES) self-assembled monolayer was bound to the sensing region. This monolayer serves as a binding layer for attachment of the prostate specific antibody (anti-PSA). The biomolecule-gated AlGaN/GaN HEMT sensor shows a rapid and sensitive response when the target prostate-specific antigen in buffer solution was added to the antibody-immobilized sensing area. The current change showed a logarithm relationship against the PSA concentration from 0.1 pg/ml to 0.993 ng/ml. The sensitivity of 0.215% is determined for 0.1 pg/ml PSA solution. The above experimental result of the biomolecule-gated AlGaN/GaN HEMT biosensor suggested that this biosensor might be a useful tool for prostate cancer screening.

Studies of the chemical and electrical properties of fullerene and 3-aminopropyltrimethoxysilane based low-k materials

Among an extremely large number of possible fullerene applications in the field of electronics, optics and photovoltaics, C60-cages are also considered as a promising dopant for low dielectric constant (low-k) materials. In this study, we incorporated C60 species into a 3-aminopropyltrimethoxysilane (APTMS) based material. We prepared thin films by spin coating. Using X-ray photoelectron spectroscopy we analyzed the time-related interactions between the components of the prepared samples and the influence of the C60 replacement by its better soluble derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) on the chemical properties of the material. We applied atomic force microscopy to investigate the surface texture and thicknesses of the obtained films. In order to obtain information concerning the electrical properties of the material we performed capacitance-voltage characterization. We have proven that the increase of C60 species realized by PCBM incorporation within the APTMS-based matrix reduces the dielectric constant of the examined films while preserving its homogeneity.

Lithographically structured biological recognition structures for immunosensing and single cell analytics

AbstractThe preparation of structured antibody layers was shown. For this purpose, a (3‐aminopropyl)‐trimethoxysilane (APTMS) monolayer on a silicon wafer was pholithographically structured. To the APTMS structures, IgG antibodies can easily be attached via glutaraldehyde coupling. To prevent unspecific bonding to the bare silicon substrate, a commercial blocking agent has to be used.

Self-Assembly of 3-Aminopropyltrimethoxysilane to Improve the Efficiency of Dye-Sensitized Solar Cells

A dye-sensitized solar cell (DSSC) based on a 3-aminopropyltrimethoxysilane (APTS)-modified TiO2 electrode was fabricated. This cell generated a short current of 18.32 mA•cm^(-2), an open voltage of 775.9 mV, and its overall photo-to-electricity conversion efficiency was 9.15% under 100 mW•cm^(-2) white light irradiation from a xenon lamp. The three DSSC parameters for the bare TiO2 electrode were found to be 18.08 mA•cm^(-2), 749.9 mV, and 7.70%. Compared with the unmodified solar cell, the overall conversion efficiency improved by 18.8% and the fill factor improved from 0.57 to 0.64. This improvement is attributed to the inhibition of the back reaction at the interface between the semiconductor and the electrolyte. The dark current-applied voltage curve shows that the onset voltage shifts from -0.30 to -0.40 V, which indicates a reduction in defects and surface states on the TiO2 surface because of the presence of APTS. Furthermore, special experiments were conducted to investigate the interaction among TiO2, APTS, and the cis-Ru(dcpyH2)2(SCN)2 dye. In these experiments, APTS and the dye were self-assembled onto a TiO2 electrode in layers. The interaction was characterized by X-ray photoelectron spectroscopy (XPS). Qualitative and quantitative results showed that the -OCH2CH3 was partially removed and it formed mono-bridge or bi-bridge Si-O-Ti bonds. The cis-Ru(dcpyH2)2(SCN)2 dye adsorbed onto APTS through an electrostatic interaction between -COOH and -NH2 from the dye. FT-IR spectra further confirmed this inner interaction.

Surface forces and protein adsorption on dextran- and polyethylene glycol-modified polydimethylsiloxane

Dextran and polyethylene glycol (PEG) are often covalently bound to the surface of polydimethylsiloxane (PDMS) for the purpose of modifying its hydrophilicity and biocompatibility. In this work, the effects of the dextran and PEG on the morphology, wetting, and surface charge of the resulting surfaces were quantified and correlated with changes in the amount of fibrinogen and albumin adsorbed from aqueous solution. PDMS films were functionalized in a microwave oxygen plasma to create surface hydroxyl groups that were subsequently aminated by incubation in a (3-aminopropyl)trimethoxysilane (APTES) solution. Oxidized dextran and PEG-aldehyde were linked to the surface amines via reductive amination. This process resulted in low surface coverage of immobilized PEG in the end-on conformation and a more uniform and dense distribution of side-on immobilized dextran. The immobilized dextran reduced the contact angle of the PDMS film from 109° to 80° and neutralized the zeta potential over the pH range from 3 to 11. An atomic force microscope was used to measure the interaction force between the modified PDMS and a model hydrophobic surface (polystyrene latex) and a model hydrophilic surface (silica) in aqueous solution to show that van der Waals and hydrophobic attractive forces are the dominant forces for protein adsorption in this system. The PEG- and dextran-modified PDMS were exposed to BSA and fibrinogen to test their resistance to protein adsorption. The coatings were ineffective at reducing the adsorption of either molecule, and the dextran-modification of the PDMS caused more BSA to adsorb than in the case of the unmodified PDMS.

Controlling growth density and patterning of single crystalline silicon nanowires

This study examines the usage of well-patterned Au nanoparticles (NPs) as a catalyst for one-dimensional growth of single crystalline Si nanowires (NWs) through the vapor-liquid-solid (VLS) mechanism. The study reports the fabrication of monolayer Au NPs through the self-assembly of Au NPs on a 3-aminopropyltrimethoxysilane (APTMS)-modified silicon substrate. Results indicate that the spin coating time of Au NPs plays a crucial role in determining the density of Au NPs on the surface of the silicon substrate and the later catalysis growth of Si NWs. The experiments in this study employed optical lithography to pattern Au NPs, treating them as a catalyst for Si NW growth. The patterned Si NW structures easily produced and controlled Si NW density. This approach may be useful for further studies on single crystalline Si NW-based nanodevices and their properties.

Effects of Solvents on Poly(3,4-Ethylenedioxythiophene) (PEDOT) Thin Films Deposited on a (3-Aminopropyl)Trimethoxysilane (APS) Monolayer by Vapor Phase Polymerization

This study examined the effects of THF (tetrahydrofuran)-EtOH (ethanol) binary solvents on the formation of conducting poly (3,4-ethylenedioxythiophene) (PEDOT) nanofilms on (3-aminopropyl)trimethoxysilane (APS)-coated SiO2 surfaces by vapor phase polymerization (VPP). Rutherford backscattering spectrometry (RBS) showed that the spin-coated FeCl3 oxidants consisted of Fe, Cl, C, and O. The carbon in the oxidant film was attributed to the inclusion of solvent in the film, and the FeCl3 oxidant spin-coated film with a THF-EtOH ratio of 1 had a higher level of C than the film spin-coated with a pure EtOH solvent. The inclusion of solvent affected the formation of the subsequent PEDOT film, thereby influencing the film properties, such as the conductivity and surface morphology. Increasing the THF/EtOH ratio to 0.5 tended to minimize the surface roughness while further increase beyond this resulted in increased surface roughness, thus indicating the existence of an optimum THF/EtOH ratio. The highest conductivity (525 S/cm) was obtained in the PEDOT films deposited with THF:EtOH (wt. %) = 1.|In addition, the PEDOT films showed poor adhesion on the oxidant films deposited from a 50–50 wt. % solvent, possibly due to shielding effects of the THF solvent present between the PEDOT and APS monolayer.

Adhesion and Particle Deformation of Submicron-Sized Latex Particles on Hydrophobically Modified Solid Substrates at Room Temperature

Two- and three-dimensional colloid arrays were fabricated using three different kinds of monodisperse poly(styrene/sodium p-styrenesulfonate) (poly(St/NaSS) (i.e., high- and low-charged un-cross-linked, and low-charged cross-linked poly(St/NaSS) particles) on 3-aminopropyltrimethoxysilane (APTMS)-modified glass substrates at 20 °C. The array patterns were investigated by field-emission scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV−vis spectroscopic analyses. The adhesive force measured by AFM analysis revealed negligible attractive force between APTMS and the poly(St/NaSS) particles. The adhesion force measured between a 3-aminopropyltrimethoxysilane (APTMS)-modified SiNx tip and the self-assembled particle arrays was in good agreement with the attractive force calculated using the Lifshitz theory with the appropriate Hamaker constants. The cross-linked poly(St/NaSS) particles on the APTMS-modified glass substrate showed mainly hexagonal and square-lattice-free patterns without...

An exploratory study of the effects of the dielectric-barrier-discharge surface pre-treatment on the self-assembly processes of a (3-Aminopropyl) trimethoxysilane on glass substrates

X-ray photoelectron spectrometry (XPS), Fourier transform infrared spectrometry (FTIR), secondary-ion-mass spectrometry (SIMS) and contact angle measurement have been used in study of the enhancement effect of substrate pre-treatment by dielectric-barrier-discharge (DBD) for the self-assembly of a (3-Aminopropyl) trimethoxysilane (APTS) on glass substrates. In results, the concentration of the APTS molecules self-assembled on the surfaces of both the acetone-washed and the DBD-treated substrates were more than three times of that on the as-supplied substrate. Meanwhile, the self-assembly (SA) layers grown on the DBD-treated substrates have the best quality compared to those grown on the substrates pre-treated in other ways in terms of the silane-substrate bonding and the order of arrangement of the silane molecules.

Investigation of the Core−Shell Interface in Gold@Silica Nanoparticles: A Silica Imprinting Approach

The nature of the self-assembled core-shell interface in gold@silica nanoparticles synthesized via a 3-aminopropyltrimethoxysilane (APTMS) route is investigated using materials synthesis as a sensitive tool for elucidating interfacial composition and organization. Our approach involves condensation of the gold@silica nanoparticles within a silica framework for synthesis of a composite gold-silica material containing approximately 30 wt % gold. This material contains one of the highest gold loadings reported, but maintains gold core isolation as ascertained via a single surface plasmon resonance absorption band frequency corresponding to that of gold nanoparticles in dilute aqueous solution. The immobilized gold cores are subsequently etched using cyanide anion for the synthesis of templated porosity, which corresponds to the space that was occupied by the gold. Characterization of immobilized amines is performed using probe molecule binding experiments, which demonstrate a lack of accessible amines after gold removal. Solid-state 13C CPMAS NMR spectroscopy on these materials demonstrates that the amount of amine immobilization must be less than 10% of the expected yield, assuming that all of the APTMS becomes bound to the gold nanoparticle template. These results require a core-shell interface in the gold@silica nanoparticles that is predominantly occupied by inorganic silicate species, such as Si-O-Si and Si-OH, rather than primary amines. Such a result is likely a consequence of the weak interaction between primary amines and gold in aqueous solution. Our method for investigating the core-shell interface of gold@silica nanoparticles is generalizable for other interfacial structures and enables the synthesis of bulk imprinted silica using colloidal templates.

Open tubular capillary electrochromatography using capillaries coated with films of alkanethiol-self-assembled gold nanoparticle layers

We have used alkanethiol self-assembly and dithiol layer-by-layer (LBL) self-assembly processes to prepare an Au nanoparticle (NP)-coated open tubular capillary electrochromatography (OTCEC) column for the separation of three neutral steroid drugs (testosterone, progesterone, and testosterone propionate). The CEC column was fabricated through LBL self-assembly of Au NPs on a 3-aminopropyltrimethoxysilane (APTMS)-modified fused-silica capillary and subsequent surface functionalization of the Au NPs through self-assembly of alkanethiols. We investigated the electrochromatographic properties of the resulting Au NP-coated CEC column using a “reversed phase” test mixture of three steroid drugs. We found that the key factors affecting the separation performance were the number of Au NP layers, the length of the carbon-atom chain of the alkanethiol self-assembled on the Au NPs, the percentage of organic modifier, and the pH of the running electrolyte. This study reveals that the self-assembly of alkanethiols and dithiols onto Au NPs provides stationary phases for CEC separation that are easy to prepare and whose retention behavior is highly controllable and reproducible. We believe that our findings will contribute to further studies of the application of nanotechnology to separation science.

In vitro haemocompatibility and stability of two types of heparin-immobilized silicon surfaces

Heparin was covalently immobilized onto a silicon surface by two different methods, carbodiimide-based immobilization and photo-immobilization. In the former method, a (3-aminopropyl) trimethoxysilane (APTMS) self-assembled monolayer (SAM) or multilayer was first coated onto the silicon surface as the bridging layer, and heparin was then attached to the surface in the presence of water-soluble carbodiimide. In the latter method, an octadecyltrichlorosilane (OTS) SAM was coated on the silicon surface as the bridging layer, and heparin was modified by attaching photosensitive aryl azide groups. Upon UV illumination, the modified heparin was then covalently immobilized onto the surface. The hydrophilicity of the silicon surface changed after each coating step, and heparin aggregates on APTMS SAM and OTS SAM were observed by atomic force microscopy (AFM). In vitro haemocompatibility assays demonstrated that the deposition of APTMS SAM, APTMS multilayer and OTS SAM enhanced the silicon's haemocompatibility, which was further enhanced by the heparin immobilization. There is no evident distinction regarding the haemocompatibility between the heparin-immobilized surfaces by both methods. However, heparin on silicon with APTMS SAM and multilayer as the bridging layers is very unstable when tested in vitro with a saline solution at 37 °C, due to the instability of APTMS SAM and multilayer on silicon. Meanwhile, photo-immobilized heparin on silicon with OTS SAM as the bridging layer showed superb stability.

Doxorubicin Uptake and Release from Microgel Thin Films

We report investigations on the thermally regulated uptake and release of the chemotherapeutic drug doxorubicin from microgel thin films. A spin coating, layer-by-layer (scLbL) assembly approach was used to prepare thin films composed of thermoresponsive poly(N-isopropylacrylamide-co-acrylic acid) (pNIPAm-AAc) microgels by alternatively exposing a 3-aminopropyltrimethoxysilane (APTMS) functionalized glass substrate to polyanionic pNIPAm-AAc microgels and polycationic poly(allylamine hydrochloride) (PAH). Using this method, 10, 20, and 30 microgel layer films were constructed with uniform layer buildup, as confirmed by quartz crystal microgravimetry (QCM). The films were subsequently loaded with doxorubicin by cycling the temperature of the film in an aqueous doxorubicin solution between 25 and 50 degrees C. Release characteristics were then examined using UV-vis spectroscopy, which revealed temperature-dependent release properties.

On-line Chloride Interference Removal for Arsenic Determination in Waste Water and Urine by ICP-MS Using a Modified Capillary

The determination of arsenic in environmental samples like waste waters from industrial effluents and in biological samples like urine is very important due to the toxic nature of some of its species at moderate levels of exposure. The objective of this study was to evaluate the capability of modified anionic capillaries to remove chloride for ICP-MS determination of arsenic, which causes spectral interference due to formation of 40 Ar 35 Cl + . Also high chloride content gives non-spectral interferences. The results indicate that arsenic at a concentration higher than 1 µg L m 1 in a matrix with a chloride content up to 600 mg L m 1 can be accurately determined using a 3-aminopropyltrimethoxysilane (APTMS) modified capillary connected to a microconcentric nebuliser (MCN). The interference level of chloride is considerably reduced due to its retention in the capillary. The method has been successfully applied and validated for waste water and by recovery tests for urine (diluted 1 : 15) samples.