A 3-aminopropyltriethoxysilane Research Articles

Structural and morphological investigation of (R)-α-phenylethylammonium-oxalate in bulk vs. nanowires on a modified substrate surface.

A chiral organic insulator, (R)-α-phenylethylammonium-oxalate (RAPEAO), was prepared in the forms of single-crystal, powder and spin-coated layers on silicon substrate surfaces modified by plasma treatment or a (3-aminopropyl)triethoxysilane (APTES) polymer layer. For spin-coated samples, different deposition conditions have been investigated - various thicknesses controlled by speed and the number of repeated cycles, deposited continuously or by a layer-by-layer technique. The chemistry of this compound did not allow the deposition of the continuous thin film, yet, it caused the formation of a few nuclei on the substrate surface. Modification of the substrate with low temperature plasma caused the increased number of nuclei as well as enabled the growth of the nanowires, which was confirmed by atomic force microscopy (AFM) images. The same effect has been observed from the X-ray diffraction (XRD) measurements, where preferential growth of the studied compound in one direction was confirmed by grazing incidence, as well as wide reciprocal space mapping (WRSM). XRD studies confirmed the structural similarity of the compound, disregarding the compound form ranging from nanowires on the substrate to the bulk. Finally, the substrate covered by APTES thin film has had increased coverage of the substrate surface by the studied compound. Impedance spectroscopy revealed that the electrical conductivity of the sample in bulk at 20 °C is 6.3 × 10-15 (Ω cm)-1, indicating the insulating properties of the material.

Wearable Localized Surface Plasmon Resonance-Based Biosensor with Highly Sensitive and Direct Detection of Cortisol in Human Sweat

Wearable biosensors have the potential for developing individualized health evaluation and detection systems owing to their ability to provide continuous real-time physiological data. Among various wearable biosensors, localized surface plasmon resonance (LSPR)-based wearable sensors can be versatile in various practical applications owing to their sensitive interactions with specific analytes. Understanding and analyzing endocrine responses to stress is particularly crucial for evaluating human performance, diagnosing stress-related diseases, and monitoring mental health, as stress takes a serious toll on physiological health and psychological well-being. Cortisol is an essential biomarker of stress because of the close relationship between cortisol concentration in the human body and stress level. In this study, a flexible LSPR biosensor was manufactured to detect cortisol levels in the human body by depositing gold nanoparticle (AuNP) layers on a 3-aminopropyltriethoxysilane (APTES)-functionalized poly (dimethylsiloxane) (PDMS) substrate. Subsequently, an aptamer was immobilized on the surface of the LSPR substrate, enabling highly sensitive and selective cortisol capture owing to its specific cortisol recognition. The biosensor exhibited excellent detection ability in cortisol solutions of various concentrations ranging from 0.1 to 1000 nM with a detection limit of 0.1 nM. The flexible LSPR biosensor also demonstrated good stability under various mechanical deformations. Furthermore, the cortisol levels of the flexible LSPR biosensor were also measured in the human epidermis before and after exercise as well as in the morning and afternoon. Our biosensors, which combine easily manufactured flexible sensors with sensitive cortisol-detecting molecules to measure human stress levels, could be versatile candidates for human-friendly products.

GO-APTES-Cu (II) Schiff base complex as efficient heterogeneous catalyst for aerobic decarboxylation reaction of phenylacetic acids

In this paper, a 3-Aminopropyltriethoxysilane (APTES) immobilized graphene oxide nanocomposite was prepared using a simple robust method. A Cu (II) Schiff base complex was grafted on the nanocomposite. The chemical nature and structure of the final product were characterized by various common techniques. The final product acts as a heterogeneous catalyst for selective aerobic decarboxylation reaction of phenylacetic acid to benzaldehyde under ambient conditions. The heterogeneous catalyst may be reused at least 5 times without significant loss in its catalytic activity.

APTES-Modified Remote Self-Assembled DNA-Based Electrochemical Biosensor for Human Papillomavirus DNA Detection.

High-risk human papillomavirus (HPV) infection is an important cause of cervical cancer formation; therefore, being able to detect high-risk HPV (e.g., HPV-16) is important for the early treatment and prevention of cervical cancer. In this study, a combination of a 3-aminopropyltriethoxysilane (APTES) modified gold electrode and a super sandwich structure was creatively developed, resulting in the development of a biosensor that is both sensitive and stable for the detection of HPV-16. The electrochemical biosensor possesses a lower detection limit compared with previous studies with an LOD of 5.475 × 10−16 mol/L and it possesses a wide linear range from 1.0 × 10−13 mol/L to 1.0 × 10−6 mol/L (R2 = 0.9923) for the target DNA. The experimental data show that the sensor has good stability, and there is no significant decrease in the current response value after 7 days in the low-temperature environment. In addition, the sensor proved to be a powerful clinical tool for disease diagnosis because it showed good interference resistance in complex human serum samples.

Comparison of Physical Adsorption and Covalent Coupling Methods for Surface Density-Dependent Orientation of Antibody on Silicon

The orientation of antibodies, employed as capture molecules on biosensors, determines biorecognition efficiency and bioassay performance. In a previous publication we demonstrated for antibodies attached covalently to silicon that an increase in their surface amount Γ, evaluated with ellipsometry, induces changes in their orientation, which is traced directly using Time-of-Flight Secondary Ion Mass Spectroscopy combined with Principal Component Analysis. Here, we extend the above studies to antibodies adsorbed physically on a 3-aminopropyltriethoxysilane (APTES) monolayer. Antibodies physisorbed on APTES (0 ≤ Γ ≤ 3.5 mg/m2) reveal the Γ ranges for flat-on, side-on, and vertical orientation consistent with random molecular packing. The relation between orientation and Γ is juxtaposed for silicon functionalized with APTES, APTES modified with glutaraldehyde (APTES/GA) and N-hydroxysuccinimide-silane (NHS-silane). Antibody reorientation occurs at lower Γ values when physisorption (APTES) is involved rather than chemisorption (APTES/GA, NHS-silane). At high Γ values, comparable proportions of molecules adapting head-on and tail-on vertical alignment are concluded for APTES and the NHS-silane monolayer, and they are related to intermolecular dipole–dipole interactions. Intermolecular forces seem to be less decisive than covalent binding for antibodies on the APTES/GA surface, with dominant head-on orientation. Independently, the impact of glutaraldehyde activation of APTES on vertical orientation is confirmed by separate TOF-SIMS measurements.

Immobilization of a [CoIIICoII(H2O)W11O39]7- Polyoxoanion for the Photocatalytic Oxygen Evolution Reaction.

The ongoing transition to renewable energy sources and the implementation of artificial photosynthetic setups call for an efficient and stable water oxidation catalyst (WOC). Here, we heterogenize a molecular all-inorganic [CoIIICoII(H2O)W11O39]7– ({CoIIICoIIW11}) Keggin-type polyoxometalate (POM) onto a model TiO2 surface, employing a 3-aminopropyltriethoxysilane (APTES) linker to form a novel heterogeneous photosystem for light-driven water oxidation. The {CoIIICoIIW11}-APTES-TiO2 hybrid is characterized using a set of spectroscopic and microscopic techniques to reveal the POM integrity and dispersion to elucidate the POM/APTES and APTES/TiO2 binding modes as well as to visualize the attachment of individual clusters. We conduct photocatalytic studies under heterogeneous and homogeneous conditions and show that {CoIIICoIIW11}-APTES-TiO2 performs as an active light-driven WOC, wherein {CoIIICoIIW11} acts as a stable co-catalyst for water oxidation. In contrast to the homogeneous WOC performance of this POM, the heterogenized photosystem yields a constant WOC rate for at least 10 h without any apparent deactivation, demonstrating that TiO2 not only stabilizes the POM but also acts as a photosensitizer. Complementary studies using photoluminescence (PL) emission spectroscopy elucidate the charge transfer mechanism and enhanced WOC activity. The {CoIIICoIIW11}-APTES-TiO2 photocatalyst serves as a prime example of a hybrid homogeneous–heterogeneous photosystem that combines the advantages of solid-state absorbers and well-defined molecular co-catalysts, which will be of interest to both scientific communities and applications in photoelectrocatalysis and CO2 reduction.

Flexible liquid metal display using 3-Aminopropyl triethoxysilane-treated light emitting diodes (LEDs) array

In recent years, the fabrication of flexible electronic devices has been focused on the use eutectic gallium‑indium (EGaIn) liquid metal (LM) materials with polydimethylsiloxane (PDMS) microfluidics, which are less toxic. The flexible electronic devices offer the advantage of attaining various shapes as they are liquid at room temperature. However, discontinuities in the circuit occur while bending of the flexible LM circuit as EGaIn LM easily leaks into the space between the electrical components such as light-emitting diodes (LEDs) and PDMS microfluidic channels. Thus, the present study proposes use of a (3-Aminopropyl) triethoxysilane (APTES)-treatment method to create a circuit consisting of 100 μm channels based on EGaIn. The strategy enhances the bonding strength of surface mount device (SMD) such as LEDs and PDMS. The circuit mold to be patterned with the PDMS has been made with a 3D printer and coated with a polymer as buffer layer to allow the PDMS to detach the circuit mold easily. The change in resistance of the EGaIn LM by varying the bending angle from 0° to 60° is presented for one channel through the I-V curves. Additionally, effect of bending on the on/off state of an APTES-treated SMD type LED has been studied. Furthermore, the proposed method has been employed for developing a 5 × 1 LED array circuit. An Arduino has been employed to express a 5 × 5 LED array circuit in the form of letters. Hence, a flexible device with improved stability has been demonstrated using EGaIn LM that does not overflow while bending due to an enhanced binding force between the PDMS and SMD-type LEDs as a result of the APTES-treatment processing.

Optical Fiber Based Mach-Zehnder Interferometer for APES Detection.

A 3-aminopropyl-triethoxysilane (APES) fiber-optic sensor based on a Mach–Zehnder interferometer (MZI) was demonstrated. The MZI was constructed with a core-offset fusion single mode fiber (SMF) structure with a length of 3.0 cm. As APES gradually attaches to the MZI, the external environment of the MZI changes, which in turn causes change in the MZI’s interference. That is the reason why we can obtain the relationships between the APES amount and resonance dip wavelength by measuring the transmission variations of the resonant dip wavelength of the MZI. The optimized amount of 1% APES for 3.0 cm MZI biosensors was 3 mL, whereas the optimized amount of 2% APES was 1.5 mL.

Fabrication of a Kagomé-type MOF Membrane by Seeded Growth on Amino-functionalized Porous Al2 O3 Substrate.

In this study, we report an efficient fabrication method for the membrane of a metal-organic framework (MOF) (Kgm-OEt) which is one kind of kagomé-type MOF with a two-dimensional (2D) sheet structure having one-dimensional (1D) channels suitable for separation of H2 from other larger gases. The Kgm-OEt seed layer was created on an Al2 O3 substrate using layer-by-layer (LBL) growth, then a membrane was fabricated by secondary growth. The membrane on a 3-aminopropyltriethoxysilane (APTEs)-treated substrate obtained in this method was continuous and defect-free with the crystal orientation suitable for gas transportation, while the membrane grown on an unmodified substrate was loosely packed with unfavorable crystal orientation.

Simultaneously improved corrosion/wear resistances of Mg alloy through an ultra-thin Mg(OH)2/graphene-APTES coating

In order to expand the applied range of Mg alloy, a variety of coatings have been designed to improve their corrosion and wear resistance. Here, we report a 3-aminopropyl triethoxysilane (APTES) modified Mg(OH)2/reduced graphene oxide (RGO) hybrid coating with integrated anti-corrosion/wear property on Mg alloy, which is prepared by in-situ crystallization using a facile hydrothermal method. The ultra-thin Mg(OH)2/RGO layer with 250 nm exhibits a dual-structure, in which the inner layer is composed of Mg(OH)2, and then RGO sheets hybrid with Mg(OH)2 via the hydrogen bond to form the outer layer. The lubrication of RGO sheets and the high hardness of dense Mg(OH)2 give rise to the significant decrease of wear rate, which is two orders of magnitude less than that in Mg substrate. Next, the APTES layer effectively fills the pores and defects on the surface of Mg(OH)2/RGO via the Si-O-Mg and amide bond, and it forms a barrier film enriched with Si-O-Si bond via the self-crosslinking reaction. The effective combination of inorganic and organic layer contributes to the improved anti-corrosion property.

Assessment of physicomechanical properties of composite films based on a styrene-acrylic polymer, glycidyl ether, and a 3-aminopropyltriethoxysilane compatibilizer

The study concerns composite materials based on polymer mixtures of a styrene-acrylic polymer, glycidyl ether, and a 3-aminopropyltriethoxysilane (APTES) compatibilizer. The use of a silane-type compatibilizer improves the compatibility of the components and has been shown to significantly increase the degree of crosslinking of the composition components. In this work, the structural parameters of the polymer network of the composition components depending on the compatibilizer concentration were researched by the method of equilibrium swelling. The optimal concentration of the compatibilizer was found to maximize the degree of crosslinking with a minimal number of active chains. This fact proves that the crosslinking in the composition is complete and the molecule does not contain active sites that have not reacted with the compatibilizer. The swelling kinetics of the polymer composite films proves that with an increase in the degree of crosslinking, the swelling of the polymer films decreases. Polymer films with a low proportion of active chains practically do not swell after the crosslinking process.The article describes a possible mechanism of compatibilization involving 3-aminopropyltriethoxysilane as well as styrene-acrylic and glycidyl ether polymers. The 3-aminopropyltriethoxysilane compatibilizer has active functional groups that are located on opposite sides of the molecule; these are three active hydroxyl groups and one active amino group. Due to the presence of various functional groups, this compatibilizer can bind the polymers and thereby form strong polymer films.This gives grounds to assert that the control of the compatibilizer concentration and the degree of crosslinking of the composition components provide prospects for the creation of polymer films with high physical and mechanical characteristics due to the high interfacial adhesion of the components in the composition

Thermoresponsive Poly(vinyl methyl ether) (PVME) Retained by 3-Aminopropyltriethoxysilane (APTES) Network

Thermoresponsive polymers (TRP)s have been widely used for various applications from controlling membrane fouling in separation to cell/cell sheet harvesting in regenerative medicine. While poly(N-isopropylacrylamide) (pNIPAAm) is the most commonly used TRP, less expensive and easily processed poly(vinyl methyl ether) (PVME) also shows a hydrophilic to hydrophobic transition at 32-35 °C, near physiological conditions. In this study, we investigated the processing conditions for retaining a stable layer of PVME thin film on silica surfaces via entrapment in a 3-aminopropyltriethoxysilane (APTES) network. In addition, the thermoresponsive behaviors (TRB) of the retained PVME films were evaluated. Blend thin films of PVME/APTES with 90:10 and 50:50 mass ratios were spin-coated from their solutions in ethanol under ambient conditions and then annealed in a vacuum oven at 40, 60, 80, or 120 °C for 1, 2, or 3 days. The annealed films were then thoroughly rinsed with room temperature water and then soaked in water for 3 days. Our results showed that annealing at a temperature of ≥40 °C was necessary for retaining a PVME film on the surface. The higher annealing temperature led to greater film retention, probably due to the formation of a tighter APTES network. Regardless of processing conditions, all retained PVME films showed TRB, determined by water contact angles below and above the transition temperature of PVME. Additionally, particle attachment and protein adsorption on retained PVME films showed lower attachment or adsorption at room temperature as compared to that at 37 °C, and a greater difference was observed for the 90:10 blend where more PVME was consisted. Furthermore, human mesenchymal stem cells attached and proliferated on the retained PVME surfaces at 37 °C and rapidly detached at room temperature. These results illustrated the potential applications of PVME surfaces as thermoresponsive supports for low-fouling applications and noninvasive cell harvesting.

Plasmon expedited response time and enhanced response in gold nanoparticles-decorated zinc oxide nanowire-based nitrogen dioxide gas sensor at room temperature

A highly sensitive and rapidly responsive nitrogen dioxide (NO2) gas sensor based on gold (Au) nanoparticles (NPs)-decorated zinc oxide (ZnO) nanowires (NWs) is presented. The Au NPs decoration was conducted onto ZnO NWs with and without a (3-aminopropyl)triethoxysilane (APTES) layer on their surface by using the electrostatic force. The samples without the APTES layer exhibited high NO2 gas sensitivity (i.e. expedited response time and enhanced gas response) due to localized surface plasmon resonance (LSPR) of the Au NPs; in particular, the NO2 gas response and the response time were increased by three times and shortened by 86%, respectively, compared with the undecorated ZnO NWs. The presence of the APTES layer improved the Au NPs attachment, but hindering the gas adsorption on the ZnO NWs surface, as proven by the observed photocurrent and gas response. Our findings imply that the response time of semiconductor gas sensors can be remarkably expedited by the LSPR effect, which is useful for developing practical gas sensors.

Fabrication and characterization of silk fibroin coating on APTES pretreated Mg-Zn-Ca alloy.

To delay the degradation of magnesium alloys, silk fibroin as a natural organic polymer coating was fabricated on a 3-amino-propyltriethoxysilane (APTES) pretreated Mg-Zn-Ca alloy. APTES pretreatment coated the surface of magnesium alloys with amino groups, which can bond with functional groups in silk fibroin to form a compact coating/substrate interface. The influences of the APTES concentration and drying temperature on the coating adhesion and interface were investigated to explore the optimal parameters in the fabrication process. The nanoporous silk fibroin films completely covered the APTES pretreated Mg-Zn-Ca surface, which reached a thickness of ~7μm. The chemical states for the coated Mg-Zn-Ca alloy were compared to those of the bare Mg-Zn-Ca alloy and the APTES pretreated Mg-Zn-Ca alloy to illustrate the coating mechanism. During in vitro degradation and electrochemical measurements in simulated body fluid (SBF), the samples with the silk fibroin coating showed remarkably improved corrosion resistance and a slower degradation rate compared to those of the bare samples, suggesting that the silk fibroin coating was an effective protection coating for the substrates and can delay the degradation of magnesium alloys. Moreover, a model for the in vitro degradation was proposed. In vitro cell experiments confirmed the excellent biocompatibility of silk fibroin coated Mg-Zn-Ca structure.

Solid-phase colorimetric apta-biosensor for thrombin detection

Herein, we developed a solid-phase colorimetric apta-biosensor for thrombin detection. Aggregation of gold nanoparticles (AuNPs) deposited on a 3-aminopropyltriethoxysilane (APTES) substrate was utilized to form the colorimetric sensor. The APTES-coated substrate with primary aptamer (TBA1)-conjugated AuNPs (AuNP-TBA1) was used to construct the solid-phase sensing platform, where an enhancement of the localized surface plasmon resonance due to the AuNPs was observed upon incubation with a target molecule (thrombin). The introduction of secondary aptamer-conjugated AuNPs (AuNP-TBA2) induced plasmonic coupling of the AuNPs, resulting in significantly enhanced spectral signals and peak shifts and visually detectable color changes. This sensing platform not only includes several advantages, such as simplicity and rapid detection, but also allows naked-eye detection sensitivity at 3 μg/mL with no analytical equipment and a limit of detection of 1.33 μg/mL using UV–vis.

Reduction of Threshold Voltage Hysteresis of MoS2 Transistors with 3-Aminopropyltriethoxysilane Passivation and Its Application for Improved Synaptic Behavior.

Although molybdenum disulfide (MoS2) is highlighted as a promising channel material, MoS2-based field-effect transistors (FETs) have a large threshold voltage hysteresis (Δ VTH) from interface traps at their gate interfaces. In this work, the Δ VTH of MoS2 FETs is significantly reduced by inserting a 3-aminopropyltriethoxysilane (APTES) passivation layer at the MoS2/SiO2 gate interface owing to passivation of the interface traps. The Δ VTH is reduced from 23 to 10.8 V by inserting the 1%-APTES passivation layers because APTES passivation prevents trapping and detrapping of electrons, which are the major source of the Δ VTH. The reduction in the density of interface traps ( Dit) is confirmed by the improvement of the subthreshold swing (SS) after inserting the APTES layer. Furthermore, the improvement in the synaptic characteristics of the MoS2 FET through the APTES passivation is investigated. Both inhibitory and excitatory postsynaptic currents (PSC) are increased by 33% owing to the reduction in the Δ VTH and the n-type doping effect of the APTES layer; moreover, the linearity of PSC characteristics is significantly improved because the reduction in Δ VTH enables the synaptic operation to be over the threshold region, which is linear. The application of the APTES gate passivation technique to MoS2 FETs is promising for reliable and accurate synaptic applications in neuromorphic computing technology as well as for the next-generation complementary logic applications.

Microtribological properties of Ti 6Al 4V alloy treated with self-assembled dopamine and graphene oxide coatings

Abstract Ti 6Al 4V alloy is promising material as biomedical micro/nano–electromechanical systems. However, its poor microtribological properties have a negative impact on the micromachine stability. In this study, enhancements in anticorrosion and microtribological performances under dry and SBF lubrication are realized by grafting graphene oxide (GO) on the alloy surface. We further demonstrate that based on a 3-aminopropyltriethoxysilane (APTES) transition layer, the GO-coated sample with dopamine (DA) adhesive layer (APTES-DA-GO) exhibits better properties than those of the APTES-GO. Moreover, the anticorrosion and tribological mechanisms of the GO-coated samples were discussed. Analyses of worn surfaces show that the relative slip of GO sheets and entrapment of wear particles of the surface topography are the main factors contributing to the improved tribological behaviour.

An SPR Sensor Chip Based on Peptide-Modified Single-Walled Carbon Nanotubes with Enhanced Sensitivity and Selectivity in the Detection of 2,4,6-Trinitrotoluene Explosives.

In this study, we developed a surface plasmon resonance (SPR) sensor chip based on 2,4,6-trinitrotoluene (TNT) recognition peptide-modified single-walled carbon nanotubes (SWCNTs). The carboxylic acid-functionalized SWCNTs were immobilized on a 3-aminopropyltriethoxysilane (APTES)-modified SPR Au chip surface. Through π-stacking between the aromatic amino acids and SWCNTs, the TNT recognition peptide TNTHCDR3 was immobilized onto the surface of the SWCNTs. The peptide–SWCNTs-modified sensor surface was confirmed and evaluated by atomic force microscope (AFM) observation. The peptide–SWCNTs hybrid SPR sensor chip exhibited enhanced sensitivity with a limit of detection (LOD) of 772 ppb and highly selective detection compared with commercialized carboxymethylated dextran matrix sensor chips.

Adsorption Behavior of Gold Nanoparticles on Amino-terminated Micro Domains Fabricated on Quartz Substrate by Vacuum Ultra-violet Photolithography

Immobilization of gold nanoparticles (AuNPs) onto quartz is of considerable interest in optoelectronic applications. In this paper, we demonstrated a linear arrangement of AuNPs by controlling the function and optical properties at the microstructure of a quartz surface through formation of a 3-aminopropyltriethoxysilane (APS) self-assembled monolayer and the subsequent vacuum ultraviolet lithography. Citrate-capped AuNPs have been arranged on an APS-terminated surface by electrostatic attraction and in a VUV irradiated area by electrostatic repulsion. In addition, the density of AuNPs on along the boundary of the linear feature was higher than that in the center during the initial stage of immersion. The density of AuNPs along the linear feature became uniform over the entire surface with increasing immobilization time. These results induced the electrostatic interaction of negatively charged AuNPs on the interface between differently charged surfaces.

Interfacial Assembly of Robust TiO2 Nanosheets Onto Silica‐Modified Reduced Graphene Oxide for Highly Efficient Degradation of Organic Dyes

AbstractThe assembly of two‐dimensional (2D) transition‐metal oxides and reduced graphene oxide (RGO) has shown great potential in photocatalysis, energy storage, and photoelectric devices. In the work, we present a 3‐aminopropyltriethoxysilane (APTES)‐induced interfacial assembly route for preparation of a new type of 2D TiO2@RGO hybrid nanostructure. Benefiting from the electrostatic interaction between APTES and RGO, followed by the hydrolysis of APTES, an ultrathin SiO2 layer is first well grown into the surface of RGO. Subsequently, ultrathin TiO2 nanosheets (about 4 nm in thickness) are uniformly decorated onto the surface of silica‐modified RGO. These robust TiO2 nanosheets interconnect each other and form a unique net‐like architecture. Significantly, the TiO2@RGO products show superior structural stability. Consequently, the TiO2@RGO product annealed at 750 °C demonstrates an excellent photocatalytic activity and a good cycling life for degradation of organic dyes such as methyl orange (MO), rhodamine B (RhB) and methyl blue (MB) owing to the unique construction and enhanced synergistic effect.