Attachment of 3-(Aminopropyl)triethoxysilane on silicon oxide surfaces: dependence on solution temperature

Synergistic effect of silane cross-linker (APTEOS) on PVA/gelatin blend films for packaging applications

The objective of this work is to fabricate hydrogel films which are biodegradable and also fit for packaging applications. The hydrogel films were prepared by the reaction of polyvinyl alcohol and gelatin with and without 3-aminopropyltriethoxysilane (APTEOS) cross-linker. The hydrogel films were then characterized by FTIR spectroscopy, degree of swelling, TGA, SEM analysis and mechanical testing. The FTIR spectra of the hydrogel films confirmed the presence of both polymers and hydrogen bonding between them. TGA analysis confirmed the increase in thermal stability with the increase of cross-linker amount. SEM analysis confirmed the increase in uniformity of structure with the increase of cross-linker amount. The increase in cross-linker amount resulted in decrease of degree of swelling and increase of tensile strength. The biodegradability of hydrogel films was evaluated by performing soil burial test and found to be decreased with the increase of cross-linker amount. In order to balance the tensile strength and biodegradability, the optimum amount of cross-linker was determined which resulted in the formation of the best performing film. Finally, our best performing film was compared with other hydrogel films reported in the literature. Hence, the hydrogel films cross-linked with APTEOS are biodegradable, having high tensile strength and suitable for packaging purpose.

Optimized microwave-assisted functionalization and quantification of superficial amino groups on porous silicon nanostructured microparticles

This work presents an optimized microwave (MW)-assisted method for the chemical functionalization of porous silicon particles (PSip). 3-(Aminopropyl)triethoxysilane (APTES) was grafted on previously stabilized PSip. The functionalization efficiency was studied and optimized in terms of reaction time (Rt) and reaction temperature (RT) using a central composite design (CCD). The effect of MW irradiation on the surface coverage was found to strongly depend on the PSip surface chemistry, Rt, RT, and percentage of APTES. Quantification of grafted amino groups was performed by the ninhydrin method (NHIM); confirming the results by thermogravimetric analysis (TGA). Reacting with 5% APTES solution at 95 °C for 26 min was the best functionalization conditions. The efficiency of PSip-APTES prepared under the optimized conditions was compared to those functionalized by the traditional method; MW irradiation increases by 39% the number of functional groups grafted onto the PSip surfaces with the additional benefit of having a drastic reduction in Rt.

Expanding the Limits of Photodynamic Therapy: The Design of Organelles and Hypoxia-Targeting Nanomaterials for Enhanced Photokilling of Cancer

Photodynamic therapy (PDT) is a minimally invasive clinical protocol that combines a nontoxic photosensitizer (PS), appropriate visible light, and molecular oxygen for cancer treatment. This triad generates reactive oxygen species (ROS) in situ, leading to different cell death pathways and limiting the arrival of nutrients by irreversible destruction of the tumor vascular system. Despite the number of formulations and applications available, the advancement of therapy is hindered by some characteristics such as the hypoxic condition of solid tumors and the limited energy density (light fluence) that reaches the target. As a result, the use of PDT as a definitive monotherapy for cancer is generally restricted to pretumor lesions or neoplastic tissue of approximately 1 cm in size. To expand this limitation, researchers have synthesized functional nanoparticles (NPs) capable of carrying classical photosensitizers with self-supplying oxygen as well as targeting specific organelles such as mitochondria and lysosomes. This has improved outcomes in vitro and in vivo. This review highlights the basis of PDT, many of the most commonly used strategies of functionalization of smart NPs, and their potential to break the current limits of the classical protocol of PDT against cancer. The application and future perspectives of the multifunctional nanoparticles in PDT are also discussed in some detail.

Comprehensive Characterization of APTES Surface Modifications of Hydrous Boehmite Nanoparticles

Hydrous boehmite (γ-AlOOH) nanoparticles (BNP) show great potential as nanoscale filler for the fabrication of fiber reinforced nanocomposite materials. Notably, the particle-matrix interaction has been demonstrated to be decisive for improving the matrix-dominant mechanical properties in the past years. Tailoring the surface properties of the nanofiller enables to selectively design the interaction and thus to exploit the benefits of the nanocomposite in an optimal way. Here, an extensive study is presented on the binding of (3-aminopropyl)triethoxysilane (APTES), a common silane surface modifier, on BNP in correlation to different process parameters (concentration, time, temperature, and pH). Furthermore, a comprehensive characterization of the modified BNP was performed by using elemental analysis (EA), thermogravimetric analysis (TGA) coupled with mass spectrometry (TGA-MS), and Kaiser's test (KT). The results show an increasing monolayer formation up to a complete surface coverage with rising APTES concentration, time, and temperature, resulting in a maximal grafting density of 1.3 molecules/nm². Unspecific multilayer formation was solely observed under acidic conditions. Comparison of TGA-MS results with data recorded from EA, TGA, and KT verified that TGA-MS is a convenient and highly suitable method to elucidate the ligand binding in detail.

Triethoxysilane-derived SiOx-assisted structural reinforcement of Si/carbon nanotube composite for lithium-ion battery

Herein, triethoxysilane-derived SiOx is used as a robust adhesive anchor to bind Si nanoparticles (NPs) and carbon nanotubes (CNTs) to prepare a structurally reinforced Si/CNT microsphere composite. The chemical reaction between the silanol groups of triethoxysilane with the hydroxyl groups on the Si surface and acid-treated CNTs induce strong chemical bonds between the Si NPs and CNTs and among neighboring CNTs, facilitating electron-conduction pathways and structural integrity of the composite, even under severe stress/strain. Thus, the structurally reinforced Si/CNT/SiOx microsphere composite exhibits superior cyclability: ∼88% of its initial capacity of 1112 mA h g-1 is retained after 100 cycles at 0.5 A g-1. Moreover, the Si/CNT/SiOx composite exhibits a negligible change in electrode thickness after 100 cycles. The stable electrochemical behavior and negligible change in the electrode thickness are attributed to the maintenance of the electron-conduction pathways and structural integrity of the Si/CNT/SiOx composite, enabled by the binding of neighboring CNTs with the SiOx anchor.

Surface Functionalization of Platinum Electrodes with APTES for Bioelectronic Applications

The interface between electronic components and biological objects plays a crucial role in the success of bioelectronic devices. Since the electronics typically include different elements such as an insulating substrate in combination with conducting electrodes, an important issue of bioelectronics involves tailoring and optimizing the interface for any envisioned applications. In this paper, we present a method for functionalizing insulating substrates (SiO₂) and metallic electrodes (Pt) simultaneously with a stable monolayer of organic molecules ((3-aminopropyl)triethoxysilane (APTES)). This monolayer is characterized by high molecule density, long-term stability, and positive surface net charge and most likely represents a self-assembled monolayer (SAM). It facilitates the conversion of biounfriendly Pt surfaces into biocompatible surfaces, which allows cell growth (neurons) on both functionalized components, SiO₂ and Pt, which is comparable to that of reference samples coated with poly-L-lysine (PLL). Moreover, the functionalization greatly improves the electronic cell-chip coupling, thereby enabling the recording of action potential signals of several millivolts at APTES-functionalized Pt electrodes.

A practical guide to rapid-prototyping of PDMS-based microfluidic devices: A tutorial

Micro total analytical systems (μTAS) are attractive to multiple fields that include chemistry, medicine and engineering due to their portability, low power usage, potential for automation, and low sample and reagent consumption, which in turn results in low waste generation. The development of fully-functional μTAS is an iterative process, based on the design, fabrication and testing of multiple prototype microdevices. Typically, microfabrication protocols require a week or more of highly-skilled personnel time in high-maintenance cleanroom facilities, which makes this iterative process cost-prohibitive in many locations worldwide. Rapid-prototyping tools, in conjunction with the use of polydimethylsiloxane (PDMS), enable rapid development of microfluidic structures at lower costs, circumventing these issues in conventional microfabrication techniques. Multiple rapid-prototyping methods to fabricate PDMS-based microfluidic devices have been demonstrated in literature since the advent of soft-lithography in 1998; each method has its unique advantages and drawbacks. Here, we present a tutorial discussing current rapid-prototyping techniques to fabricate PDMS-based microdevices, including soft-lithography, print-and-peel and scaffolding techniques, among other methods, specifically comparing resolution of the features, fabrication processes and associated costs for each technique. We also present thoughts and insights towards each step of the iterative microfabrication process, from design to testing, to improve the development of fully-functional PDMS-based microfluidic devices at faster rates and lower costs.

Chemical insight into the adsorption of reactive wool dyes onto amine-functionalized magnetite/silica core-shell from industrial wastewaters

Fe₃O₄ NPs are synthesized by the co-precipitation technique. Moreover, the pristine was coated by silica layer and then functionalized by 3-aminopropyltrimethoxysilane (APTS). The sample possessed saturation magnetization with value equals 37 emu/g which made them to easily separate using external magnet. FT-IR, TGA, EDX, and VSM confirmed the aminosilane loading. The surface topography and composition were characterized using XRD, TEM, SEM, BJH, and BET methods. Where adsorption capacity of the surface toward the removal of four commercial reactive wool dyes (RD), Itowol black (IB), Itowol Red (IR), Sunzol black (SB), and Lanasol blue (LB) have been investigated. The influence variables such as pH, adsorbent dose, dye concentration, and temperature were calculated. Where experimental results fitted to Langmuir isotherm model with q_max equals 161.29, 151.51, 123.45, and 98.20 mg/g, for IR, LB, SB, and IB respectively. The results showed that the RD adsorption described by pseudo-second-order kinetics. The calculated thermodynamic parameters indicated that RD adsorption onto Fe₃O₄@SiO₂-NH₂ was spontaneous and exothermic in nature. The possible mechanisms monitoring RD adsorption on the surface included hydrogen bonding and electrostatic interactions. The reusability of adsorbent carried with four cycles without releasing of magnetite and thus excluding the potential hazardous of nanomaterial to the environment. Graphical abstract.

A signal-on electrochemical aptasensor based on silanized cellulose nanofibers for rapid point-of-use detection of ochratoxin A

An innovative ultrasensitive electrochemical aptamer-based sensor was developed for ochratoxin A (OTA) detection in cold brew coffee through revolutionary combination of nanofibers, electrochemical method, and aptamer technologies. The assembly of the aptasensor was based on the activation of silanized cellulose nanofibrous membranes as a supporting matrix for methylene blue (MB) redox probe-labeled aptamer tethering. Cellulose nanofibrous membranes were regenerated by deacetylating electrospun cellulose acetate nanofibrous membranes with deacetylation efficacy of 97%, followed by silanization of the nanofiber surfaces by using (3-aminopropyl)triethoxysilane (APTES). A replacement of conventionally casted membranes by the nanofibrous membranes increased the active surface area on the working electrode of a screen-printed three-electrode sensor by more than two times, consequently enhancing the fabricated aptasensor performance. The developed aptasensor demonstrated high sensitivity and specificity toward OTA in a range 0.002-2 ng mL^-1, with a detection limit of 0.81 pg mL^-1. Moreover, the assembled aptamer-based sensor successfully detected OTA in cold brew coffee samples without any pretreatment. The aptasensor exhibited good reusability and stability over long storage time. Graphical abstract.

Antibody Immobilization in Zinc Oxide Thin Films as an Easy-Handle Strategy for Escherichia coli Detection

The antibody immobilization compatible with low-cost materials and label-free strategies is a challenge for biosensor device fabrication. In this study, ZnO thin film deposition was carried out on corning glass substrates by ultrasonic spray pyrolysis at 200 °C. The thin films were analyzed as platforms for enteropathogenic Escherichia coli (E. coli EPEC) antibody immobilization. The modification of thin films from the functionalization and antibody immobilization steps was visualized using Fourier transform infrared spectroscopy (FTIR) spectroscopy, and surface changes were observed by atomic force microscopy. The obtained FTIR spectra after functionalization showed a contribution of the amino group (NH₂) derived from silane (3-aminopropyltrimethoxysilane). The antibody immobilization showed an amide I conserved signal corresponding to the C=O stretching vibrations and the amide II signal related to the N-H scissor vibration mode. In this way, the signals observed are correlated with the presence of antibody immobilized on the film. The ZnO film morphology changes after every stage of the process and allows observing the antibody distribution on the immobilized surface. In order to validate the antibody recognition capability as well as the E. coli EPEC detection in situ, polymerase chain reaction was used.

Utilizing molecular resonance-localized surface plasmon resonance coupling for copper ion detection in plasma

The rapid, point-of-care detection of copper in plasma can greatly aid in a large number of diseases where copper has been implicated to be an important factor, such as cancer, Alzheimer's and Diabetes mellitus. Localized surface plasmon resonance (LSPR) technologies show promise in the inexpensive detection of copper, whereas previous platforms are plagued with selectivity and sensitivity issues. Herein, we have created a sensitive and selective on-chip copper sensor which can produce a colorimetric reading in 60 minutes. The selectivity of the assay is based on 'Click' chemistry and is shown to have little interference with other metal ions present in plasma. The sensitivity of the assay is generated from the coupling of the molecular resonance of a dye and the LSPR of the gold nanoparticles. The assay is capable of measuring copper concentrations in human plasma as low as 4 μM and the linear range of sensitivity, 4 to 20 μM, is in the physiologically relevant range. This robust, colorimetric assay should prove useful in a point-of-care setting.

Study on Functionality and Surface Modification of a Stair-Step Liquid-Triggered Valve for On-Chip Flow Control

Distinctive from other forms of microfluidic system, capillary microfluidics is of great interest in autonomous micro-systems due to its well-engineered fluidic control based on capillary force. As an essential component of fluidic control in capillaric circuits, micro-valves enable sequential fluidic operations by performing actions such as stopping and triggering. In this paper, we present a stair-step liquid-triggered valve; the functionality of the valve and its dependencies on geometry and surface modification are studied. The surface contact angle of the microfabricated valves that are coated by polyethylene glycol (PEG) or (3-Aminopropyl) triethoxysilane (APTES) is evaluated experimentally, and the corresponding reliability of the valve structure is discussed. Moreover, the variation in the surface contact angle over time is investigated, indicating the shelf time of the device. We further discuss the overall fluidic behavior in such capillary valves, which benefits the capillaric circuit designs at the initial stage.

Competitive Adsorption between a Polymer and Solvents onto Silica

In polymer nanocomposites, particle-polymer interactions play a key role both in the processing and in the final properties of the obtained materials. Specifically, for silica, because of the surface polarity, surface modification is commonly used to improve the compatibility with apolar polymer matrices in order to prevent agglomeration. In this work, a new way to investigate the polymer-silica affinity and determine dispersibility parameters (HDP) of silica particles in the 3D Hansen space using a solvent approach is proposed. These parameters are estimated from the assessment of the stability of suspensions in a set of organic solvents. Based on the respective locations of the solvent, polymer, and silica representative points in the 3D Hansen space, the adsorption of a given polymer in solution in a given solvent can be predicted. This is shown with the industrial precipitated silica Zeosil 1165MP in combination with polystyrene and polybutadiene. It is shown that silanization of the silica particles decreases the adsorption of polystyrene, even though because of this surface treatment, silica comes closer to polystyrene in the Hansen space. This counter-intuitive effect is rationalized based on the consideration of an adsorption parameter χ_S computed from the relative locations of the solvent, polymer, and particles in the 3D Hansen space. Basically, this parameter is related to the respective distances of the solvent and polymer representative points to that of the particle in the Hansen space.

Lyophilization enabled disentanglement of polyethylenimine on rambutan-like silica nanoparticles for enhanced plasmid DNA delivery

Polyethylenimine (PEI) functionalization onto nanoparticles is a widely used strategy for constructing particulate vectors for gene delivery. However, how to control the conformation of PEI chains and the resultant impact on gene transfection efficiency remains largely unexplored. Herein, we report that drying methods dramatically affect the conformation of PEI chains modified on the surface of silica nanoparticles and consequently the plasmid DNA transfection performance. Specifically, lyophilization renders less entangled PEI compared to commonly used vacuum drying as evidenced by an elevated glass transition temperature. The lyophilization induced disentangled conformation is likely associated with the solid-to-gas phase transition drying mechanism, which removes the bound crystal water content and thus reduces hydrogen bonding between amines. Moreover, we find that the stretched PEI chains on the surface of rambutan-like silica nanoparticles promote their binding capacity towards plasmid DNA molecules and thereby enhanced gene delivery and transfection efficiency. Our findings have provided new understanding about amine based polymers modified on nanoparticles, and have significant implications on the design of efficient particulate vectors for gene delivery.

Controlled Silanization: High Molecular Regularity of Functional Thiol Groups on Siloxane Coatings

A comparative study on deposition and molecular regularity of two organosilanes, i.e., commercially available (3-mercaptopropyl)trimethoxysilane (MPTMS) and newly developed mercaptopropylsilatrane (MPS), was conducted in this work. MPTMS and MPS were applied to modify silicon surfaces to characterize their deposition kinetics, surface morphology, thickness, and elemental composition and the reactivity of thiol end groups based on gold-thiol and thiol-ene chemistries. MPS possesses a tricyclic caged structure and a transannular N → Si dative bond, making it chemically stable and controllable to avoid fast hydrolysis and aggregation in solution. The results indicate that MPS allows faster deposition and better formation of thin and homogeneous films than MPTMS. More importantly, the functional thiol groups on MPS coatings enable immobilization of a large amount of gold nanoparticles and effective thiol-ene photopolymerization with zwitterionic sulfobetaine acrylamide. Postmodification on silanized surfaces with MPS endows excellent plasmonic and antifouling properties, potentially leading to valuable applications to biosensing and biomaterials. The work demonstrated the feasibility and applicability of the functional silatrane molecule for surface silanization in a controlled manner.

Facile synthesis of an aminopropylsilane layer on Si/SiO2 substrates using ethanol as APTES solvent

(3-aminopropyl)triethoxysilane (APTES) is a commonly used organosilane on surface functionalization of silicon oxide surfaces. However, its deposition process from solution-phase usually involves the use of toluene, which has often been identified as crucial for the formation of an aminopropylsilane monolayer. Toluene is ranked as a problematic solvent in the guide developed by a group referred to as the solvent sub-team of CHEM21. In this work, we propose a facile synthetic route for functionalizing a silicon substrate with APTES via solution-phase approach using only solvents that are classified as recommended. The influence of the APTES concentration, reaction times and different post-deposition conditions using acetic acid and methanol were studied in order to evaluate the quality and thickness of the organosilane layers.•

The method uses ethanol as APTES solvent for functionalizing silicon dioxide surfaces and only uses solvents classified as recommended.

•

The method uses a solution phase approach, does not require complicated equipment and can be prepared at room temperature.

Controlling the Dynamics of Ionic Liquid Thin Films via Multilayer Surface Functionalization

The structural dynamics of planar thin films of an ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BmimNTf₂) as a function of surface charge density and thickness were investigated using two-dimensional infrared (2D IR) spectroscopy. The films were made by spin coating a methanol solution of the IL on silica substrates that were functionalized with alkyl chains containing head groups that mimic the IL cation. The thicknesses of the ionic liquid films ranged from ∼50 to ∼250 nm. The dynamics of the films are slower than those in the bulk IL, becoming increasingly slow as the films become thinner. Control of the dynamics of the IL films can be achieved by adjusting the charge density on substrates through multilayer network surface functionalization. The charge density of the surface (number of positively charged groups in the network bound to the surface per unit area) is controlled by the duration of the functionalization reaction. As the charge density is increased, the IL dynamics become slower. For comparison, the surface was functionalized with three different neutral groups. Dynamics of the IL films on the functionalized neutral surfaces are faster than on any of the ionic surfaces but still slower than the bulk IL, even for the thickest films. These results can have implications in applications that employ ILs that have electrodes, such as batteries, as the electrode surface charge density will influence properties like diffusion close to the surface.

Fundamental Insights into the Covalent Silane Functionalization of NiFe Layered Double Hydroxides

Layered double hydroxides (LDHs) are a class of 2D anionic materials exhibiting wide chemical versatility and promising applications in different fields, ranging from catalysis to energy storage and conversion. However, the covalent chemistry of this kind of 2D materials is still barely explored. Herein, the covalent functionalization with silanes of a magnetic NiFe-LDH is reported. The synthetic route consists of a topochemical approach followed by anion exchange reaction with surfactant molecules prior to covalent functionalization with the (3-aminopropyl)triethoxysilane (APTES) molecules. The functionalized NiFe-APTES was fully characterized by X-ray diffraction, infrared spectroscopy, electron microscopy, thermogravimetric analysis coupled with mass spectrometry and ²⁹ Si solid-state nuclear magnetic resonance, among others. The effect on the electronic properties of the functionalized LDH was investigated by a magnetic study in combination with Mössbauer spectroscopy. Moreover, the reversibility of the silane-functionalization at basic pH was demonstrated, and the quality of the resulting LDH was proven by studying the electrochemical performance in the oxygen evolution reaction in basic media. Furthermore, the anion exchange capability for the NiFe-APTES was tested employing Cr^VI , resulting in an increase of 200 % of the anion retention. This report allows for a new degree of tunability of LDHs, opening the door to the synthesis of new hybrid architectures and materials.

On-Demand Release of Protective Agents Triggered by Environmental Stimuli

The aim of this study was to develop smart materials with stimuli-responsive properties for the long-term protection of steel. The idea was to obtain a tailored and controlled release of protective agents in response to the environment stimuli. First, the protective efficacy of three inhibitors containing a carboxylic moiety, such as p-aminobenzoic (pAB), succinic (SA), and caffeic (CA) acids, was investigated in alkaline chloride solutions. The results revealed that pAB is the most effective protective agent, significantly better than SA and CA. It is surprising that the steel surface in the pAB solution remains unchanged even after 5 months of corrosion treatment, whereas the formation of degradation products in the SA and CA solutions was observed after only 6 days. Based on these findings, pAB was selected and used for the functionalization of silica nanoparticles and layered double hydroxides (LDHs) that can act as delivery vehicles and as an inhibitor reservoir. Specifically, pAB was chemisorbed on silica amino groups via an amide bond, and this makes possible a gradual inhibitor release induced by an alkaline environment. The intercalation of pAB in its anionic form into the LDHs structure is responsible for a completely different behavior since the release is induced by chloride ions and occurs by an anionic exchange reaction. Thus, these materials play a dual role by acting as an inhibitor reservoir and by capturing chlorides. These findings reveal that it is possible to create a reservoir of corrosion inhibitors gradually released on demand based on the chemical environment. The stimuli-responsive properties and the complementary protective action of inhibitor-loaded silica and LDHs make them attractive for the long-term protection of steel and open the way for innovative solutions in the preservation of concrete cultural heritage.

Mutated Human P-Selectin Glycoprotein Ligand-1 and Viral Protein-1 of Enterovirus 71 Interactions on Au Nanoplasmonic Substrate for Specific Recognition by Surface-Enhanced Raman Spectroscopy

Protein tyrosine sulfation is a common post-translational modification that stimulates intercellular or extracellular protein-protein interactions and is responsible for various important biological processes, including coagulation, inflammation, and virus infections. Recently, human P-selectin glycoprotein ligand-1 (PSGL-1) has been shown to serve as a functional receptor for enterovirus 71 (EV71). It has been proposed that the capsid viral protein VP1 of EV71 is directly involved in this specific interaction with sulfated or mutated PSGL-1. Surface-enhanced Raman spectroscopy (SERS) is used to distinguish PSGL-1 and VP1 interactions on an Au nanoporous substrate and identify specific VP1 interaction positions of tyrosine residue sites (46, 48, and 51). The three tyrosine sites in PSGL-1 were replaced by phenylalanine (F), as determined using SERS. A strong phenylalanine SERS signal was obtained in three regions of the mutated protein on the nanoporous substrate. The mutated protein positions at (51F) and (48F, 51F) produced a strong SERS peak at 1599–1666 cm−1, which could be related to a binding with the mutated protein and anti-sulfotyrosine interactions on the nanoporous substrate. A strong SERS effect of the mutated protein and VP1 interactions appeared at (48F), (51F), and (46F, 48F). In these positions, there was less interaction with VP1, as indicated by a strong phenylalanine signal from the mutated protein.

Study on flame retardancy and smoke suppression of PET by the synergy between Fe2O3 and new phosphorus-containing silicone flame retardant

To reduce the environmental hazard from the flame retardant, a halogen-free phosphorus-containing silicone flame-retardant poly N, N dimethylene phosphate aminopropyl siloxane (PDPSI) was prepared following the Mannich reaction. Then, PDPSI and ferric oxide (Fe2O3) were used for the preparation of synergistic flame-retardant polyethylene terephthalate (PET). The flame-retardant test results revealed that at 2% PDPSI/Fe2O3 content and 1:2 mass ratio of PDPSI to Fe2O3, the limit oxygen index value of the PDPSI/Fe2O3/PET composite material was 27.9%, reaching the flame-retardant level and passing the V-0 rating in the UL-94 test. In addition, the PDPSI/Fe2O3/PET composites had a char residue content of 17.5% at 700°C, an increase of 30.6% compared to that of the pristine PET. In the cone calorimeter test, the addition of PDPSI/Fe2O3 significantly reduced the peak heat release rate (PHRR), total heat release (THR) rate, and total smoke production (TSP) value of the resulting PET composites. PHRR and THR decreased by 66.05% and 14.3%, respectively. The TSP value decreased from 14.4 m2 to 8.1 m2, a decrease of 43.8%. The scanning electron microscopy images and Fourier-transform infrared spectra of the char residue showed a significant synergy between Fe2O3 and PDPSI, changing the structure of the carbon layer in continuous and dense form, thus the flame retardancy and smoke suppression of the PET composites improved. In addition, the tensile strength of the PET composite was 42.11 MPa, which was only 1.84% less than that of the pristine PET.

Gold Nanoparticle Self-Aggregation on Surface with 1,6-Hexanedithiol Functionalization

Here we study the morphology and the optical properties of assemblies made of small (17 nm) gold nanoparticles (AuNPs) directly on silicon wafers coated with (3-aminopropyl)trimethoxysilane (APTES). We employed aliphatic 1,6-hexanedithiol (HDT) molecules to cross-link AuNPs during a two-stage precipitation procedure. The first immersion of the wafer in AuNP colloidal solution led mainly to the attachment of single particles with few inclusions of dimers and small aggregates. After the functionalization of precipitated NPs with HDT and after the second immersion in the colloidal solution of AuNP, we detected a sharp rise in the number of aggregates compared to single AuNPs and their dimers. The lateral size of the aggregates was about 100 nm, while some of them were larger than 1μm. We propose that the uncompensated dipole moment of the small aggregates appeared after the first precipitation and acts further as the driving force accelerating their further growth on the surface during the second precipitation. By having such inhomogeneous surface coating, the X-ray reciprocal space maps and modulation polarimetry showed well-distinguished signals from the single AuNPs and their dimers. From these observations, we concluded that the contribution from aggregated AuNPs does not hamper the detection and investigation of plasmonic effects for AuNP dimers. Meantime, using unpolarized and polarized light spectroscopy, the difference in the optical signals between the dimers, being formed because of self-aggregation and the one being cross-linked by means of HDT, was not detected.

Facile Synthesis of Graphene from Waste Tire/Silica Hybrid Additives and Optimization Study for the Fabrication of Thermally Enhanced Cement Grouts

This work evaluates the effects of newly designed graphene/silica hybrid additives on the properties of cementitious grout. In the hybrid structure, graphene nanoplatelet (GNP) obtained from waste tire was used to improve the thermal conductivity and reduce the cost and environmental impacts by using recyclable sources. Additionally, functionalized silica nanoparticles were utilized to enhance the dispersion and solubility of carbon material and thus the hydrolyzable groups of silane coupling agent were attached to the silica surface. Then, the hybridization of GNP and functionalized silica was conducted to make proper bridges and develop hybrid structures by tailoring carbon/silica ratios. Afterwards, special grout formulations were studied by incorporating these hybrid additives at different loadings. As the amount of hybrid additive incorporated into grout suspension increased from 3 to 5 wt%, water uptake increased from 660 to 725 g resulting in the reduction of thermal conductivity by 20.6%. On the other hand, as the concentration of GNP in hybrid structure increased, water demand was reduced, and thus the enhancement in thermal conductivity was improved by approximately 29% at the same loading ratios of hybrids in the prepared grout mixes. Therefore, these developed hybrid additives showed noticeable potential as a thermal enhancement material in cement-based grouts.

Interfacial separation of concentrated dye mixtures from solution with environmentally compatible nitrogenous-silane nanoparticles modified with Helianthus annuus husk extract

The capacity of an adsorbent to bind and remove dye from solution greatly depends on the type of functionalization present on the nanoparticles surface, and its interaction with the dye molecules. Within this study, nitrogenous silane nanoparticles were hydrothermally synthesized resulting in the formation of rapid and highly efficient adsorbents for concentrated mixed dyes. The amorphous silane nanoparticles exhibited a monolayer based mechanism of mixed dye adsorption with removal capacities between 416.67 and 714.29 mg/g of adsorbent. Dye removal was predominantly due to the electrostatic attraction between the positively charged silane nanoparticles (13.22-8.20 mV) and the negatively charged dye molecules (-54.23 mV). Addition of H. annuus extract during synthesis resulted in three times the surface area and 10 times increased pore volume compared to the positive control. XPS analysis showed that silane treatments had various nitrogen containing functionalities at their surface responsible for binding dye. The weak colloidal stability of silane particles (13.22-8.20 mV) was disrupted following dye binding, resulting in their rapid coagulation and flocculation which facilitated the separation of bound dye molecules from solution. The suitability for environmental applications using these treatments was supported by a bacterial viability assay showing >90% cell viability in treated dye supernatants.

Bottom-Up Masking of Si/Ge Surfaces and Nanowire Heterostructures via Surface-Initiated Polymerization and Selective Etching

The fully bottom-up and scalable synthesis of complex micro/nanoscale materials and functional devices requires masking methods to define key features and direct the deposition of various coatings and films. Here, we demonstrate selective coaxial lithography via etching of surfaces (SCALES), an enabling bottom-up process to add polymer masks to micro/nanoscale objects. SCALES is a three-step process, including (1) bottom-up synthesis of compositionally modulated structures, (2) surface-initiated polymerization of a conformal mask, and (3) selective removal of the mask only from regions whose underlying surface is susceptible to an etchant. We demonstrate the key features of and characterize the SCALES process with a series of model Si/Ge systems: Si and Ge wafers, Si and Ge nanowires, and Si/Ge heterostructure nanowires.

An Optical Microfiber Biosensor for CEACAM5 Detection in Serum: Sensitization by a Nanosphere Interface

The detection of carcinoembryonic antigen (CEA)-related cell adhesion molecules 5 (CEACAM5) is significant in cancer prewarning. Early diagnosis can effectively alleviate the danger of cancer. Point-of-care testing (POCT) has become a competitive technology for early detection. Fiber optic biosensors have great potential as POCT tools. However, their limits of detection (LODs) are not sufficient to afford ultralow concentration detection at the early stage. Herein, this work presents an optical microfiber sensor functionalized by a polystyrene@gold nanosphere (PS@Au nanosphere) interface for a synergistic sensitization effect to detect the ultralow CEACAM5 concentrations in serum at the early stage. The sensor's LOD achieves 3.54 × 10^-17 M in pure solution and 5.27 × 10^-16 M in serum, with the sensitization effect coupled with surface area enlargement and electromagnetic enhancement of interface. This LOD is about 6 orders of magnitude lower than that of current methods. It can be employed to detect the biomarkers at ultralow concentrations present in serum in the early stages of cancer. As the interfacial synergistic sensitization strategy is suitable for refractive index (RI)-based optical transducers, this work provides new opportunities to employ fiber optic biosensors as effective POCT tools.

Dependence of deposition method on the molecular structure and stability of organosilanes revealed from degrafting by tetrabutylammonium fluoride

We probe the structure of self-assembled monolayers (SAMs) comprising organosilanes deposited on flat silica-based surfaces prepared by liquid and vapor deposition by removing the organosilane molecules gradually from the underlying substrate via tetrabutylammonium fluoride (TBAF). Removal of organosilanes from the surface involves the cleavage of all pertinent Si-O bonds that anchor the organosilane molecules to the SAM, i.e., direct organosilane-surface linkages and in-plane crosslinks between neighboring organosilanes. We gain insight into the organosilane structure and stability by monitoring the organosilane density as a function of exposure time to TBAF. Degrafting of trifunctional chloro- and methoxy-alkylsilanes deposited from solution yields similar degrafting kinetics. We observe fast degrafting for organosilane SAMs deposited from the vapor phase, indicating that SAMs prepared in this manner form more loosely packed arrays, with less in-plane connectivity, compared to their solution-deposited counterparts. Bulkier, fluorinated silanes form more stable SAMs due to their ability to readily align and form a network with few aggregates and a relatively high fraction of surface bonds. The addition of a polymer brush to an anchored organosilane molecule demonstrates that increased bond tension accelerates the degrafting process despite the increased diffusion resistance.

Surface Enhanced CdSe/ZnS QD/SiNP Electrochemical Immunosensor for the Detection of Mycobacterium Tuberculosis by Combination of CFP10-ESAT6 for Better Diagnostic Specificity

In this study, an electrochemical immunosensor was introduced for the detection of tuberculosis (TB) via utilization of a modified electrode containing a quantum dot (CdSe/ZnS QD) and functionalized silica nanoparticles (SiNPs) on screen-printed carbon electrode (SPCE) CdSe/ZnS QD/SiNPs/SPCE, by employing indirect enzyme-linked immunosorbent assay (ELISA). Here, the fabricated electrode was linked to the biocatalytic action of enzyme catalase through antigen–antibody binding for the detection of the antigen (CFP10–ESAT6) by means of producing a differential pulse voltammetry (DPV) current. The characterization and cyclic voltammetry (CV) of the modified electrode showed good electrochemical behavior and enhanced high electron transfer between the electrode and analyte. Moreover, the active surface area was 4.14-fold higher than the bare SPCE. The developed method showed high selectivity towards CFP10–ESAT6 compared with the other TB proteins. The detection of CFP10–ESAT6 also showed a linear response towards different concentrations of CFP10–ESAT6 with R² = 0.9937, yielding a limit of detection (LOD) of as low as 1.5 × 10⁻¹⁰ g/mL for a linear range of 40 to 100 ng/mL of CFP10–ESAT6 concentration. The proposed method showed good reproducibility of target analyte with a relative standard deviation of 1.45%.

The Prevailing Role of Hotspots in Plasmon-Enhanced Sum-Frequency Generation Spectroscopy

The plasmonic amplification of nonlinear vibrational sum frequency spectroscopy (SFG) at the surfaces of gold nanoparticles is systematically investigated by tuning the incident visible wavelength. The SFG spectra of dodecanethiol-coated gold nanoparticles chemically deposited on silicon are recorded for 20 visible wavelengths. The vibrational intensities of thiol methyl stretches extracted from the experimental measurements vary with the visible color of the SFG process and show amplification by coupling to plasmon excitation. Because the enhancement is maximal in the orange-red region rather than in the green, as expected from the dipolar model for surface plasmon resonances, it is attributed mostly to hotspots created in particle multimers, in spite of their low surface densities. A simple model accounting for the longitudinal surface plasmons of multimers allows the recovery of the experimental spectral dispersion.

Single-molecule detection of biomarker and localized cellular photothermal therapy using an optical microfiber with nanointerface

For early-stage diagnostics, there is a strong demand for sensors that can rapidly detect biomarkers at ultralow concentration or even at the single-molecule level. Compared with other types of sensors, optical microfibers are more convenient for use as point-of-care devices in early-stage diagnostics. However, the relatively low sensitivity strongly hinders their use. To this end, an optical microfiber is functionalized with a plasmonic nanointerface consisting of black phosphorus-supported Au nanohybrids. The microfiber is able to detect epidermal growth factor receptor (ErbB2) at concentrations ranging from 10 zM to 100 nM, with a detection limit of 6.72 zM, enabling detection at the single-molecule level. The nanointerface-sensitized microfiber is capable of differentiating cancer cells from normal cells and treating cancer cells through cellular photothermal therapy. This work opens up a possible approach for the integration of cellular diagnosis and treatment.

Adsorption of bentazone and imazapyc from water by using functionalized silica: Experimental and computational analysis

In this study, silica and functionalized silica materials (3-aminopropyl and 3-mercapto derivatives) were successfully used for the removal of the pesticides bentazone and imazapyc from aqueous solutions. Adsorbent materials were characterized by BET isotherms and FT-IR spectroscopy (confirming the functionalization), and their equilibrium adsorption capacity was evaluated at different ionic strengths. It is observed that the maximum adsorption capacities decrease in the order 3-aminopropyl-derivative > silica >3-mercaptopropyl derivative. An increase in ionic strength produces an enhancement in the removal of pesticides. All isotherms are Ib-type and follow the Langmuir model, suggesting a monolayer physical adsorption process.

A new silanizing agent tailored to surface bio-functionalization

Amino-terminated surfaces can be effectively obtained by means of silanizing agents, realizing surfaces suitable for the purification of biomarkers of several pathologies. Since the level of biomarkers, such as microRNAs and cell-free DNA, into circulation may be extremely low, new and ameliorated capturing molecules and protocols are highly required. In this work, a new silane, acetone-imine propyl trimethoxysilane (AIPTMS), is synthesized with a simple and elegant reaction, via the nucleophilic addition of the primary amino group to the carbonyl group of acetone. AIPTMS and APTMS were used to silanize silicon oxide surfaces, which were characterized chemically (XPS) and morphologically (AFM). The two types of surfaces were chemically similar, but behaved very differently both for surface morphology and functional properties. The AIPTMS-modified surface was indeed very smooth and homogeneous with respect to the APTMS-modified surface. Moreover, the AIPTMS surface captured larger amounts of nucleic acids almost immediately after preparation, while APTMS-based functional surfaces needed longer time to reach comparable efficiency. AIPTMS shows several advantages over standard aminosilanes, as it realizes a more homogeneous surface coverage that, in turn, produces an improved response towards the capture of nucleic acids. AIPTMS is a very promising reagent for the reliable and reproducible preparation of active biofunctional surfaces for the purification and analysis of circulating biomarkers.

Surface Functionalization toward Biosensing via Free-Standing Si-OH Bonds on Nonoxidized Silicon Surfaces

Usually hydroxyl groups present on top of oxidized silicon served as binding centers for a silanization reaction toward surface functionalization. In this study, we developed a novel surface functionalization strategy where hydroxyl functionalization on nonoxidized silicon surfaces are obtained. These surfaces were stable for several weeks even in ambient air at room temperature. This high stability indicates a strong spatial isolation of the hydroxyl groups because they keenly tend to undergo a condensation reaction, forming silicon oxide. To prove the applicability of the obtained hydroxylated silicon surface, we further modified the hydroxyl groups with a commonly used silane molecule, (3-aminopropyl)triethoxysilane (APTES). The functional amino groups of the APTES layer bonded to the surface were subsequently altered by N-maleoyl-β-alanin to generate a surface highly specific for the immobilization of thiol-containing biomolecules (like thiolated single-stranded DNA or cysteine-tagged proteins). All modification steps have been investigated by IR spectroscopic ellipsometry measurements.

Concentration of hepatitis A virus in milk using protamine-coated iron oxide (Fe3O4) magnetic nanoparticles

Hepatitis A virus (HAV) continues to be the leading cause of viral hepatitis. HAV outbreaks have been linked to the consumption of milk, but methods for HAV detection in milk are very limited. We developed a method to concentrate HAV in milk using protamine-coated iron oxide (Fe₃O₄) magnetic nanoparticles (PMNPs). In this study, protamine was covalently coated on the surface of the MNPs (20-30 nm) by a three-step chemical reaction. The successful linkage of protamine to the MNPs was confirmed by Fourier transform infrared spectroscopy (FTIR), zeta potential, and transmission electron microscopy (TEM). When used for concentrating HAV from 40 mL of milk, 50 μL of PMNPs were added to the sample and mixed for 20 min by gentle rotation, followed by a magnet capture for 30 min. The captured PMNPs were washed with glycine buffer (0.05 M glycine, 0.14 M NaCl, 0.2% (v/v) Tween 20, pH 9.0) and HAV RNA was extracted using the QIAamp MinElute Virus Spin Kit and quantified by real-time RT-PCR. The method showed a detection limit of 8.3 × 10⁰ PFU of HAV in milk. The whole concentration procedure could be completed in approximately 50 min. The developed method was simple, inexpensive, and easy-to-perform.

Biofunctionalized cellulose paper matrix for cell delivery applications

The present study delineates the preparation, characterization, and application of (3-Aminopropyl)triethoxysilane (APTES)/Caprine liver-derived extracellular matrix (CLECM) coated paper matrix for cell delivery. Here, we exploited positively charged surface of the paper matrix (as imparted by APTES derivatization) to improve the biological responses of the cells. Our results demonstrated that the functionalized paper matrixes favored the adhesion, growth, and proliferation of multiple cell types including normal, transformed, cancerous, and stem cells as compared to the pristine paper matrix. Upon implantation into the mice model, the developed paper matrix supported infiltration of the host cells and vasculature without showing any evidence of significant systemic toxicity. Moreover, the cells cultured on the paper matrix, when delivered to the CAM and mouse models, showed an enhanced vascular network around the substrate, thereby confirming its potential to deliver the cells in vivo. Together, the study confirms that the reported paper-based platform is easy to fabricate, cheap, portable and could efficiently be applied to cell delivery applications for either tissue repair or the development of humanized animal model.

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 V_TH) from interface traps at their gate interfaces. In this work, the Δ V_TH 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 V_TH 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 V_TH. The reduction in the density of interface traps ( D_it) 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 V_TH and the n-type doping effect of the APTES layer; moreover, the linearity of PSC characteristics is significantly improved because the reduction in Δ V_TH 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.