Optimization of silica silanization by 3-aminopropyltriethoxysilane

Solid-State Glass Nanopipettes: Functionalization and Applications

Solid-state glass nanopipettes provide a promising confined space that offers several advantages such as controllable size, simple preparation, low cost, good mechanical stability, and good thermal stability. These advantages make them an ideal choice for various applications such as biosensors, DNA sequencing, and drug delivery. In this review, we first delve into the functionalized nanopipettes for sensing various analytes and the methods used to develop detection means with them. Next, we provide an in-depth overview of the advanced functionalization methodologies of nanopipettes based on diversified chemical kinetics. After that, we present the latest state-of-the-art achievements and potential applications in detecting a wide range of targets, including ions, molecules, biological macromolecules, and single cells. We examine the various challenges that arise when working with these targets, as well as the innovative solutions developed to overcome them. The final section offers an in-depth overview of the current development status, newest trends, and application prospects of sensors. Overall, this review provides a comprehensive and detailed analysis of the current state-of-the-art functionalized nanopipette perception sensing and development of detection means and offers valuable insights into the prospects for this exciting field.

Attachment of various-shaped polystyrene microplastics to silica surfaces: Experimental validation of the equivalent Cassini oval extended DLVO model

Microplastics (MPs) vary in shape and surface characteristics in the environment. The attachment of MPs to surfaces can be studied using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. However, this theory does not account for the shape MPs. Therefore, we investigated the attachment of spherical, pear-shaped, and peanut-shaped polystyrene MPs to quartz sand in NaCl and CaCl2 solutions using batch tests. The attachment of MPs to quartz sand was quantified using the attachment efficiency (alpha). Subsequently, alpha behaviors were interpreted using energy barriers (EBs) and interaction minima obtained from extended DLVO calculations, which were performed using an equivalent sphere model (ESM) and a newly developed equivalent Cassini model (ECM) to account for the shape of the MPs. The ESM failed to interpret the alpha behavior of the three MP shapes because it predicted high EBs and shallow minima. The alpha values for spherical MPs (0.62-1.00 in NaCl and 0.48-0.96 in CaCl2) were higher than those for pear- and peanut-shaped MPs (0.01-0.63 in NaCl and 0.02-0.46 in CaCl2, and 0.01-0.59 in NaCl and 0.02-0.40 in CaCl2, respectively). Conversely, the ECM could interpret the alpha behavior of pear- and peanut-shaped MPs either by changes in EBs or interaction minima as a function of orientation angles and electrolyte ionic strength. Therefore, the particle shape must be considered to improve the attachment analyses.

Crown ether decorated silicon photonics for safeguarding against lead poisoning

Lead (Pb2+) toxification is a concerning, unaddressed global public health crisis that leads to 1 million deaths annually. Yet, public policies to address this issue have fallen short. This work harnesses the unique abilities of crown ethers, which selectively bind to specific ions. This study demonstrates the synergistic integration of highly-scalable silicon photonics, with crown ether amine conjugation via Fischer esterification in an environmentally-friendly fashion. This realizes an integrated photonic platform that enables the in-operando, highly-selective and quantitative detection of various ions. The development dispels the existing notion that Fischer esterification is restricted to organic compounds, facilitating the subsequent amine conjugation for various crown ethers. The presented platform is specifically engineered for selective Pb2+ detection, demonstrating a large dynamic detection range, and applicability to field samples. The compatibility of this platform with cost-effective manufacturing indicates the potential for pervasive implementation of the integrated photonic sensor technology to safeguard against societal Pb2+ poisoning.

Microcapsule fabrication by ATRP at the interface of non-aqueous emulsions

We present soft-template encapsulation of salt hydrate phase change materials (PCMs) using modified silica particles to both stabilize emulsions and serve as initiators for organocatalyzed photoredox ATRP. The resulting core-shell structures have high core loading and are robust to thermal cycling. Critically, this strategy eliminates the need for a reagent in the core phase, thus preserving purity, and offers the ability to tailor shell composition for desired applications.

Analysis of Protein Cysteine Acylation Using a Modified Suspension Trap (Acyl-Trap)

Protein cysteine thiols undergo reversible S-acylation via a thioester linkage in vivo. S-palmitoylation, modification by C16:0 fatty acid, is a common S-acylation that mediates protein-membrane and protein-protein interactions critical to an array of biological processes, from homeostatic lung surfactant function to cellular transformation. The most widely used S-acylation assays, including acyl-biotin exchange (ABE) and acyl resin-assisted capture (Acyl-RAC), utilize blocking of free Cys thiols, hydroxylamine-dependent cleavage of the thioester and subsequent labeling of nascent thiol. ABE and Acyl-RAC have enabled both the proteome-wide identification of S-palmitoylation sites and basic biochemical studies. Yet, these assays generally utilize hundreds of micrograms to milligrams of input material and require numerous reagent removal and washing steps, making them laborious and ill-suited for high throughput and low input applications. To overcome this, we devised "Acyl-Trap", a suspension trap-based assay that utilizes a thiol-reactive quartz to enable buffer exchange and hydroxylamine-mediated S-acyl enrichment from 20-50 micrograms of input protein. The method is compatible with protein-level detection of Sacylated proteins as well as S-acyl site-based identification and quantification using on-quartz isobaric (tandem mass tag) labeling and LC-MS/MS. Also described are conditions for long-term hydroxylamine storage, which further expedites the assay and minimizes waste. More generally, Acyl-Trap serves as a proof-of-concept for PTM-tailored suspension traps suitable for both traditional intact protein detection and chemoproteomic workflows.

Unlocking Bio-Instructive Polymers: A Novel Multi-Well Screening Platform Based on Secretome Sampling

Biomaterials are designed to interact with biological systems to replace, support, enhance, or monitor their function. However, there are challenges associated with traditional biomaterials' development due to the lack of underlying theory governing cell response to materials' chemistry. This leads to the time-consuming process of testing different materials plus the adverse reactions in the body such as cytotoxicity and foreign body response. High-throughput screening (HTS) offers a solution to these challenges by enabling rapid and simultaneous testing of a large number of materials to determine their bio-interactions and biocompatibility. Secreted proteins regulate many physiological functions and determine the success of implanted biomaterials through directing cell behaviour. However, the majority of biomaterials' HTS platforms are suitable for microscopic analyses of cell behaviour and not for investigating non-adherent cells or measuring cell secretions. Here, we describe a multi-well platform adaptable to robotic printing of polymers and suitable for secretome profiling of both adherent and non-adherent cells. We detail the platform's development steps, encompassing the preparation of individual cell culture chambers, polymer printing, and the culture environment, as well as examples to demonstrate surface chemical characterisation and biological assessments of secreted mediators. Such platforms will no doubt facilitate the discovery of novel biomaterials and broaden their scope by adapting wider arrays of cell types and incorporating assessments of both secretome and cell-bound interactions. Key features • Detailed protocols for preparation of substrate for contact printing of acrylate-based polymers including O2 plasma etching, functionalisation process, and Poly(2-hydroxyethyl methacrylate) (pHEMA) dip coating. • Preparations of 7 mm × 7 mm polymers employing pin printing system. • Provision of confined area for each polymer using ProPlate® multi-well chambers. • Compatibility of this platform was validated using adherent cells [primary human monocyte-derived macrophages (MDMs)) and non-adherent cells (primary human monocyte-derived dendritic cells (moDCs)]. • Examples of the adaptability of the platform for secretome analysis including five different cytokines using enzyme-linked immunosorbent assay (ELISA, DuoSet®). Graphical overview.

Silicon-containing nanomedicine and biomaterials: materials chemistry, multi-dimensional design, and biomedical application

The invention of silica-based bioactive glass in the late 1960s has sparked significant interest in exploring a wide range of silicon-containing biomaterials from the macroscale to the nanoscale. Over the past few decades, these biomaterials have been extensively explored for their potential in diverse biomedical applications, considering their remarkable bioactivity, excellent biocompatibility, facile surface functionalization, controllable synthesis, etc. However, to expedite the clinical translation and the unexpected utilization of silicon-composed nanomedicine and biomaterials, it is highly desirable to achieve a thorough comprehension of their characteristics and biological effects from an overall perspective. In this review, we provide a comprehensive discussion on the state-of-the-art progress of silicon-composed biomaterials, including their classification, characteristics, fabrication methods, and versatile biomedical applications. Additionally, we highlight the multi-dimensional design of both pure and hybrid silicon-composed nanomedicine and biomaterials and their intrinsic biological effects and interactions with biological systems. Their extensive biomedical applications span from drug delivery and bioimaging to therapeutic interventions and regenerative medicine, showcasing the significance of their rational design and fabrication to meet specific requirements and optimize their theranostic performance. Additionally, we offer insights into the future prospects and potential challenges regarding silicon-composed nanomedicine and biomaterials. By shedding light on these exciting research advances, we aspire to foster further progress in the biomedical field and drive the development of innovative silicon-composed nanomedicine and biomaterials with transformative applications in biomedicine.

Bio-inspired polydopamine layer as a versatile functionalisation protocol for silicon-based photonic biosensors

Photonic biosensors have made major advances in recent years, achieving very high sensitivity, and progressing towards point-of-care deployment. By using photonic resonances, sensors can be label-free, which is particularly attractive for a low-cost technological realisation. A key remaining issue is the biological interface and the efficient and reliable immobilisation of binder molecules such as antibodies; many protocols are currently in use that have led to widely varying sensor performance. Here, we study a very simple and robust surface functionalisation protocol for silicon photonics, which is based on polydopamine, and we demonstrate both its simplicity and its high performance. The use of polydopamine (PDA) is inspired by molluscs, especially mussels, that employ dopamine to adhere to virtually any surface, especially in an aqueous environment. We studied the versatility of the PDA protocol by showing compatibility with 5 different disease biomarkers (Immunoglobulin (IgG), C-reactive protein (CRP), Tumour Necrosis factor-α (TNF-α), Interleukin-6 (IL-6), Matrix metalloproteinase (MMP-9) and show that the protocol is resistant to hydrolysis during incubation; the loss of functionality due to hydrolysis is a major issue for many of the functionalisation protocols commonly used for silicon-based sensors. The study using guided mode resonance-based sensors highlights the wide dynamic range of the protocol (0.01 ng/mL to 1 μg/mL), using IgG, CRP and MMP-9 protein biomarkers as exemplars. In addition, we show that the surface chemistry allows performing measurements in 10% human serum with a sensitivity as low as 10 ng/mL for IgG. We suggest that adopting this protocol will make it easier for researchers to achieve biofunctionalisation and that the biosensor community will be able to achieve more consistent results.

Volume-Confined Fabrication of Large-Scale Single-Crystalline Molecular Ferroelectric Thin Films and Their Applications in 2D Materials

With outstanding advantages of chemical synthesis, structural diversity, and mechanical flexibility, molecular ferroelectrics have attracted increasing attention, demonstrating themselves as promising candidates for next-generation wearable electronics and flexible devices in the film form. However, it remains a challenge to grow high-quality thin films of molecular ferroelectrics. To address the above issue, a volume-confined method is utilized to achieve ultrasmooth single-crystal molecular ferroelectric thin films at the sub-centimeter scale, with the thickness controlled in the range of 100-1000 nm. More importantly, the preparation method is applicable to most molecular ferroelectrics and has no dependency on substrates, showing excellent reproducibility and universality. To demonstrate the application potential, two-dimensional (2D) transitional metal dichalcogenide semiconductor/molecular ferroelectric heterostructures are prepared and investigated by optical spectroscopic method, proving the possibility of integrating molecular ferroelectrics with 2D layered materials. These results may unlock the potential for preparing and developing high-performance devices based on molecular ferroelectric thin films.

Surface chemistry applications and development of immunosensors using electrochemical impedance spectroscopy: A comprehensive review

Immunosensors are promising alternatives as detection platforms for the current gold standards methods. Electrochemical immunosensors have already proven their capability for the sensitive, selective, detection of target biomarkers specific to COVID-19, varying cancers or Alzheimer's disease, etc. Among the electrochemical techniques, electrochemical impedance spectroscopy (EIS) is a highly sensitive technique which examines the impedance of an electrochemical cell over a range of frequencies. There are several important critical requirements for the construction of successful impedimetric immunosensor. The applied surface chemistry and immobilisation protocol have impact on the electroanalytical performance of the developed immunosensors. In this Review, we summarise the building blocks of immunosensors based on EIS, including self-assembly monolayers, nanomaterials, polymers, immobilisation protocols and antibody orientation.

Chemical vapour deposition in narrow capillaries: Electro-osmotic flow control in capillary electrophoresis

BACKGROUND

In capillary electrophoresis (CE), the inner surface of fused-silica capillaries is commonly covalently modified with liquid silanes to control electroosmotic flow (EOF). This liquid phase deposition (LPD) approach is challenging for long and narrow-diameter capillaries (≥1 m, ≤25 μm ID) inhibiting commercial production. Here, we use chemical vapour deposition (CVD) to covalently modify capillaries with different silanes. Using a home-built CVD device, capillaries were modified with neutral (3-glycidyloxypropyl) trimethoxysilane (GPTMS), the weak base (3-aminopropyl) trimethoxysilane (APTMS), the weak acid 3-mercaptopropyltrimethoxysilane (MPTMS) and the neutral hydrophobic trichloro(1H,1H,2H,2H-perfluorooctyl) silane (PFOCTS). Gas-phase modification of GPTMS with acid and ammonia allowed further modification of the surface prior to molecular layer deposition (MLD) of poly(p-phenylene terephthalamide) (PPTA) using the self-limiting sequential reaction between terephthalaldehyde (TA) and p-phenylenediamine (PD) vapours.

RESULTS

Capillaries coated with GPTMS by CVD showed a greater reduction in EOF at all pH values than the conventional LPD. APTMS showed a reduction of the EOF at pH 9, with EOF reversal observed below pH 6. MPTMS provided a slightly lower EOF than an unmodified capillary at high pH, and a slightly higher EOF at lower pH. PFOCTS provided the most consistent EOF as a function of pH. The deposition of successive layers of PPTA resulted in increased surface coverage of the polymer and a greater reduction in EOF at pH higher than 5. The stability of a 10 μm ID GPTMS coated capillary was tested at pH 8.8 in a 200 mM CHES/Tris BGE for the separation of inorganic anions. Over 1.5 months of continuous operation (≈4130 runs), the reproducibility of the apparent mobilities for chloride, nitrite, nitrate and sulfate were 2.43%, 2.56%, 2.63% and 3.05%, respectively. The intra-day and inter-day column-to-column reproducibility and batch-to-batch reproducibility for all the coated capillaries ranged between 0.34% and 3.95%.

SIGNIFICANCE

The study demonstrates the superior performance of CVD coating for suppressing the EOF compared to LPD allowing the easy modification of long lengths of narrow capillary. The variation in silane, and the ability of MLD to modify and control the surface chemistry, provides a simple and facile method for surface modification. The stability of these coatings will allow long-term capillary electrophoresis monitoring of water chemistry, such as for monitoring fertiliser run-off in natural waters.

Universal and One-Step Modification to Render Diverse Materials Bioactivation

Bioactive materials that can support cell adhesion and tissue regeneration are greatly in demand in clinical applications. Surface modification with bioactive molecules is an efficient strategy to convert conventional bioinert materials into bioactive materials. However, there is an urgent need to find a universal and one-step modification strategy to realize the above transformation for bioactivation. In this work, we report a universal and one-step modification strategy to easily modify and render diverse materials bioactivation by dipping materials into the solution of dibutylamine-DOPA-lysine-DOPA (DbaYKY) tripeptide-terminated cell-adhesive molecules, β-peptide polymer, or RGD peptide for only 5 min. This strategy provides materials with a stable surface modification layer and does not cause an undesired surface color change like the widely used polydopamine coating. This one-step strategy can endow material surfaces with cell adhesion properties without concerns on nonspecific conjugation of proteins and macromolecules. This universal and one-step surface bioactivation strategy implies a wide range of applications in implantable biomaterials.

pH-Responsive Biomaterials for the Treatment of Dental Caries-A Focussed and Critical Review

Dental caries is a common and costly multifactorial biofilm disease caused by cariogenic bacteria that ferment carbohydrates to lactic acid, demineralizing the inorganic component of teeth. Therefore, low pH (pH 4.5) is a characteristic signal of the localised carious environment, compared to a healthy oral pH range (6.8 to 7.4). The development of pH-responsive delivery systems that release antibacterial agents in response to low pH has gained attention as a targeted therapy for dental caries. Release is triggered by high levels of acidogenic species and their reduction may select for the establishment of health-associated biofilm communities. Moreover, drug efficacy can be amplified by the modification of the delivery system to target adhesion to the plaque biofilm to extend the retention time of antimicrobial agents in the oral cavity. In this review, recent developments of different pH-responsive nanocarriers and their biofilm targeting mechanisms are discussed. This review critically discusses the current state of the art and innovations in the development and use of smart delivery materials for dental caries treatment. The authors' views for the future of the field are also presented.

Quantitative Elasticity Mapping of Submicron Silica Hollow Particles by PeakForce QNM AFM Mode

Silica hollow spheres with a diameter of 100-300 nm and a shell thickness of 8±2 nm were synthesized using a self-templating amphiphilic polymeric precursor, i.e., poly(ethylene glycol)-substituted hyperbranched polyethoxysiloxane. Their elastic properties were addressed with a high-frequency AFM indentation method based on the PeakForce QNM (quantitative nanomechanical mapping) mode enabling simultaneous visualization of the surface morphology and high-resolution mapping of the mechanical properties. The factors affecting the accuracy of the mechanical measurements such as a local slope of the particle surface, deformation of the silica hollow particles by a solid substrate, shell thickness variation, and applied force range were analysed. The Young's modulus of the shell material was evaluated as E=26±7 GPa independent of the applied force in the elastic regime of deformations. Beyond the elastic regime, the buckling instability was observed revealing a non-linear force-deformation response with a hysteresis between the loading and unloading force-distance curves and irreversible deformation of the shell at high applied forces. Thus, it was demonstrated that PeakForce QNM mode can be used for quantitative measurements of the elastic properties of submicon-sized silica hollow particles with nano-size shell thickness, as well as for estimation of the buckling behaviour beyond the elastic regime of shell deformations.

A highly sensitive and selective detection of 2,4,6-trinitrotoluene (TNT) using a peptide-functionalized silicon nanowire array sensor

A highly sensitive and specific detection of 2,4,6-trinitrotoluene (TNT), a typical nitrated aromatic explosive, was demonstrated by a silicon nanowire (SiNW) array sensor. The SiNW array devices were self-assembled and functionalized with the anti-TNT peptide to obtain unique sensitivity toward TNT. Also, the effect of the biointerfacing linker's chemistry and Debye screening with varied ionic strength of phosphate buffer solution (PBS) on TNT binding response signals were investigated. The optimization of the peptide-functionalized SiNW array sensor showed high sensitivity for TNT with a detection limit of 0.2 fM, the highest sensitivity reported to date. These initial promising results may help accelerate the development of portable sensors for femtomolar level TNT detection.

"Grafting-To" Covalent Binding of Plasmonic Nanoparticles onto Silica WGM Microresonators: Mechanically Robust Single-Molecule Sensors and Determination of Activation Energies from Single-Particle Events

We hereby present a novel "grafting-to"-like approach for the covalent attachment of plasmonic nanoparticles (PNPs) onto whispering gallery mode (WGM) silica microresonators. Mechanically stable optoplasmonic microresonators were employed for sensing single-particle and single-molecule interactions in real time, allowing for the differentiation between binding and non-binding events. An approximated value of the activation energy for the silanization reaction occurring during the "grafting-to" approach was obtained using the Arrhenius equation; the results agree with available values from both bulk experiments and ab initio calculations. The "grafting-to" method combined with the functionalization of the plasmonic nanoparticle with appropriate receptors, such as single-stranded DNA, provides a robust platform for probing specific single-molecule interactions under biologically relevant conditions.

Revisiting Alkoxysilane Assembly on Silica Surfaces: Grafting versus Homo-Condensation in Solution

Silica surface functionalization is often done through the condensation of functional silanes on silanols, silica surfaces' terminal groups. APTES, aminopropyltriethoxysilane, is widely used due to its assumed high reactivity with silanols, kinetically promoted by the catalytic action of the terminal amine function. Here, we revisit, based on a quantitative analysis by solid-state ²⁹Si NMR, the assembly of this silane on silica surfaces to investigate whether its presence results from grafting, i.e., hetero-condensation with silanol groups or from homo-condensation of silane molecules in solution leading to polycondensates physisorbed on silica. We investigate the interaction of APTES with a crystalline layered silicate, ilerite, and with amorphous nonporous silica. We also studied a second silane, cyanopropyltrichlorosilane (CPTCS), terminated with a nitrile group. Our results undoubtedly prove that while CPTCS is grafted on the silica surface, the presence of APTES on silica and silicate materials is only marginally associated with silanol consumption. The analysis of the signal related to silicon atoms from silanes (Tⁿ species) and those from silica (Qⁿ species) allowed for the accurate estimation of the extent of homo-condensation vs grafting based on the ratio of T-O-T/Q-O-T siloxane bridges. These findings deeply question the well-established certainties on APTES assembly on silica that should no longer be seen as grafting of alkoxysilane by hetero-condensation with silanol groups but more accurately as a homo-condensed network of silanes, predominantly physisorbed on the surface but including some sparse anchoring points to the surface involving less than 6% of the overall silanol groups.

Silicone-Based Multifunctional Thin Films with Improved Triboelectric and Sensing Performances via Chemically Interfacial Modification

The development of triboelectric nanogenerators (TENGs) technology has advanced in recent years. However, TENG performance is affected by the screened-out surface charge density owing to the abundant free electrons and physical adhesion at the electrode-tribomaterial interface. Furthermore, the demand for flexible and soft electrodes is higher than that for stiff electrodes for patchable nanogenerators. This study introduces a chemically cross-linked (XL) graphene-based electrode with a silicone elastomer using hydrolyzed 3-aminopropylenetriethoxysilanes. The conductive graphene-based multilayered electrode was successfully assembled on a modified silicone elastomer using a cheap and eco-friendly layer-by-layer assembly method. As a proof-of-concept, the droplet-driven TENG with the chemically XL electrode of silicone elastomer exhibited an output power of approximately 2-fold improvement owing to its higher surface charge density than without XL. This chemically XL electrode of silicone elastomer film demonstrated remarkable stability and resistance to repeated mechanical deformations like bending and stretching. Moreover, due to the chemical XL effects, it was used as a strain sensor to detect subtle motions and exhibited high sensitivity. Thus, this cheap, convenient, and sustainable design approach can provide a platform for future multifunctional wearable electronic devices.

Polymer Brushes on Silica Nanostructures Prepared by Aminopropylsilatrane Click Chemistry: Superior Antifouling and Biofunctionality

In nanobiotechnology, the importance of controlling interactions between biological molecules and surfaces is paramount. In recent years, many devices based on nanostructured silicon materials have been presented, such as nanopores and nanochannels. However, there is still a clear lack of simple, reliable, and efficient protocols for preventing and controlling biomolecule adsorption in such structures. In this work, we show a simple method for passivation or selective biofunctionalization of silica, without the need for polymerization reactions or vapor-phase deposition. The surface is simply exposed stepwise to three different chemicals over the course of ∼1 h. First, the use of aminopropylsilatrane is used to create a monolayer of amines, yielding more uniform layers than conventional silanization protocols. Second, a cross-linker layer and click chemistry are used to make the surface reactive toward thiols. In the third step, thick and dense poly(ethylene glycol) brushes are prepared by a grafting-to approach. The modified surfaces are shown to be superior to existing options for silica modification, exhibiting ultralow fouling (a few ng/cm2) after exposure to crude serum. In addition, by including a fraction of biotinylated polymer end groups, the surface can be functionalized further. We show that avidin can be detected label-free from a serum solution with a selectivity (compared to nonspecific binding) of more than 98% without the need for a reference channel. Furthermore, we show that our method can passivate the interior of 150 nm × 100 nm nanochannels in silica, showing complete elimination of adsorption of a sticky fluorescent protein. Additionally, our method is shown to be compatible with modifications of solid-state nanopores in 20 nm thin silicon nitride membranes and reduces the noise in the ion current. We consider these findings highly important for the broad field of nanobiotechnology, and we believe that our method will be very useful for a great variety of surface-based sensors and analytical devices.

Enhanced adsorption and recyclability of surface modified hydrophobic silica aerogel with triethoxysilane: removal of cefixime by batch and column mode techniques

Amine modified pumice-derived silica aerogel (AMPDSA) was synthesized and grafted up to 6.52 [Formula: see text] with (3-aminopropyl) triethoxysilane for cefixime antibiotic adsorption. Using Response surface methodology, at the pH of 3, the maximum removal of cefixime of 80.42% for an initial concentration of 3.56 mg L^-1 was achieved at an equilibrium time of 150 min. The compliance of various kinetic and isotherm models for the batch sorption system was corroborated from the correlation coefficient (R²) values. The maximum adsorption capacity of 19.76 mg g^-1 and 49.63 mg g^-1 was calculated for Langmuir and Khan isotherm models, respectively. The removal by fixed-bed column as a function of flow rate, initial cefixime concentration, and bed height was also performed. The maximum adsorption capacity of column with the bed height of 15 cm was found to be 31 mg g^-1 at the flow rate of 10 mL min^-1 for the initial concentration of 20 mg L^-1. The compliance of Thomas model with the column sorption was observed. The characterization using SEM, BET, and XRD was carried out for the virgin and regenerated AMPDSAs. The regeneration experiments confirmed the ability of AMPDSA for its cefixime removal efficiency of 80% up to eight cycles.

Review: 3-Aminopropyltriethoxysilane (APTES) Deposition Methods on Oxide Surfaces in Solution and Vapor Phases for Biosensing Applications

Surface functionalization and bioreceptor immobilization are critical processes in developing a highly sensitive and selective biosensor. The silanization process with 3-aminopropyltriethoxysilane (APTES) on oxide surfaces is frequently used for surface functionalization because of beneficial characteristics such as its bifunctional nature and low cost. Optimizing the deposition process of the APTES layer to obtain a monolayer is crucial to having a stable surface and effectively immobilizing the bioreceptors, which leads to the improved repeatability and sensitivity of the biosensor. This review provides an overview of APTES deposition methods, categorized into the solution-phase and vapor-phase, and a comprehensive summary and guide for creating stable APTES monolayers on oxide surfaces for biosensing applications. A brief explanation of APTES is introduced, and the APTES deposition methods with their pre/post-treatments and characterization results are discussed. Lastly, APTES deposition methods on nanoparticles used for biosensors are briefly described.

A nitric oxide and hydrogen sulfide dual-donating nanosystem for highly synergistic gas-radiotherapy against hepatocellular carcinoma

A drug delivery system (DDS) based on gold-capped mesoporous silica nanoparticles (MSN) is fabricated for loading NOSH-aspirin, a nitric oxide (NO) and hydrogen sulfide (H₂S) dual-donating cytotoxic molecule. The liver targeting and tumor microenvironment responsive properties of the nanosystem enable, for the first time, the concurrent delivery of NO and H₂S from a DDS into hepatocellular carcinoma (HCC) cells. Combined gas-radiotherapy (GT-RT) from drug-loaded DDS (NOSH@MSN-Au-Gal) and X-ray irradiation shows highly synergistic anti-cancer activity against both normoxic and hypoxic HCC cells. Further studies revealed that the combined GT-RT not only retains the well-known anticancer mechanism of NO, H₂S, and X-ray individually, but also alleviates HCC hypoxia via NO- and H₂S- involved unique pathways. In mice, the GT-RT greatly slows the growth of both subcutaneous and orthotopic HCC tumors and shows high biocompatibility. The current work is expected to promote the clinical application of combined GT-RT as an effective cancer treatment.

Cyclic Epipedography─Monitoring Contact Angle Changes in Dipping a Microsphere into a Liquid and Lifting from It

We propose cyclic epipedography to monitor the wetting characteristics of a microsphere on a stem with a liquid by tracking the level of a liquid line on the sphere when the sphere is dipped into and lifted from the liquid, and therefore the level of the liquid plane at infinity changes with respect to the sphere. Analysis of still images of a video taken with a horizontally held microscope determines the two levels. The sphere allows viewing of the liquid line without being obscured by the meniscus the liquid forms with its container's wall. A nearly perfect sphere is fabricated by melting the tip of a silica optical fiber while being rotated to form a ball 0.5-0.6 mm across. A dip-lift cycle is represented by a cyclic epipedogram─a closed loop in a plot of the level of the liquid line as a function of the level of the liquid plane. The position and shape of the loop allow us to estimate the contact angle at different stages in the dip-lift cycle. We applied the method to a hydroxylated silica microsphere in water, and the same sphere reacted with octylchlorosilane. Then, the method was applied to monitor the progress of the reaction of aminopropyldimethylethoxysilane with surface silanol. We find that the amphiphilic aminopropylsilane makes the surface conform to the environment. In air, the hydrophobic portion comes on top, while in water, hydrophilic part faces the surroundings. This conformity-caused Janus characteristics of the surface were almost absent with the hydroxylated silica and weak with the octylsilane-treated silica.

Optimizing Plasmonic Gold Nanorod Deposition on Glass Surfaces for High-Sensitivity Refractometric Biosensing

Owing to high surface sensitivity, gold nanorods (AuNRs) are widely used to construct surface-based nanoplasmonic biosensing platforms for label-free molecular diagnostic applications. A key fabrication step involves controlling AuNR deposition onto the target surface, which requires maximizing surface density while minimizing inter-particle aggregation, and is often achieved by surface functionalization with a self-assembled monolayer (SAM) prior to AuNR deposition. To date, existing studies have typically used a fixed concentration of SAM-forming organic molecules (0.2-10% v/v) while understanding how SAM density affects AuNR deposition and resulting sensing performance would be advantageous. Herein, we systematically investigated how controlling the (3-aminopropyl)triethoxysilane (APTES) concentration (1-30% v/v) during SAM preparation affects the fabrication of AuNR-coated glass surfaces for nanoplasmonic biosensing applications. Using scanning electron microscopy (SEM) and UV-visible spectroscopy, we identified an intermediate APTES concentration range that yielded the highest density of individually deposited AuNRs with minimal aggregation and also the highest peak wavelength in aqueous solution. Bulk refractive index sensitivity measurements indicated that the AuNR configuration had a strong effect on the sensing performance, and the corresponding wavelength-shift responses ranged from 125 to 290 nm per refractive index unit (RIU) depending on the APTES concentration used. Biosensing experiments involving protein detection and antigen-antibody interactions further demonstrated the high surface sensitivity of the optimized AuNR platform, especially in the low protein concentration range where the measurement shift was ~8-fold higher than that obtained with previously used sensing platforms.

Intermolecular charge transfer enhances the performance of molecular rectifiers

Molecular-scale diodes made from self-assembled monolayers (SAMs) could complement silicon-based technologies with smaller, cheaper, and more versatile devices. However, advancement of this emerging technology is limited by insufficient electronic performance exhibited by the molecular current rectifiers. We overcome this barrier by exploiting the charge-transfer state that results from co-assembling SAMs of molecules with strong electron donor and acceptor termini. We obtain a substantial enhancement in current rectification, which correlates with the degree of charge transfer, as confirmed by several complementary techniques. These findings provide a previously enexplored method for manipulating the properties of molecular electronic devices by exploiting donor/acceptor interactions. They also serve as a model test platform for the study of doping mechanisms in organic systems. Our devices have the potential for fast widespread adoption due to their low-cost processing and self-assembly onto silicon substrates, which could allow seamless integration with current technologies.

Label-Free Imaging of Single Proteins and Binding Kinetics Using Total Internal Reflection-Based Evanescent Scattering Microscopy

Single-molecule detection can push beyond ensemble averages and reveal the statistical distributions of molecular properties. Measuring the binding kinetics of single proteins also represents one of the critical and challenging tasks in protein analysis. Here, we report total internal reflection-based evanescent scattering microscopy with label-free single-protein detection capability. Total internal reflection is employed to excite the evanescent field to enhance light-analyte interaction and reduce environmental noise. As a result, the system provides wide-field imaging capability and allows excitation and observation using one objective. In addition, this system quantifies protein binding kinetics by simultaneously counting the binding of individual molecules and recording their binding sites with nanometer precision, providing a digital method to measure binding kinetics with high spatiotemporal resolution. This approach does not employ specially designed microspheres or nanomaterials and may pave a way for label-free single-protein analysis in conventional microscopy.

Amphiphilic Polymer Conetwork Gel Films Based on Tetra-Poly(ethylene Glycol) and Tetra-Poly(ε-Caprolactone)

The preparation and investigation of gel films from a model amphiphilic polymer conetwork (ACN) grant a deeper control and understanding of the structure–property relationship in the bulk phase and at the interface of materials with promising applications. In order to allow the simultaneous transport of hydrophilic and hydrophobic substances, polymeric networks with finely distributed hydrophilic and hydrophobic components are very suitable. When designing new soft materials such as coatings, in addition to the structure in the bulk phase, the structure at the interface plays a critical role. In this study, two alternating tetra-arm star polymers poly(ε-caprolactone) (tetra-PCL-Ox) and amino-terminated poly(ethylene glycol) (tetra-PEG-NH2) form an amphiphilic polymer conetwork. The correlation between different synthesis strategies for gel films of this ACN model system and their resulting properties will be described. Through various spin coating techniques, control over film thickness and roughness is achievable and highlights differences to macroscopic gel samples. Atomic force microscopy (AFM) measurements reveal the effect of solvents of different polarities on the swelling ability and surface structure. This correlates with AFM investigations of the mechanical properties on ACN gel films, demonstrating a strong effect on the resulting elastic modulus E, depending on the presence or absence of a good solvent during synthesis. Furthermore, a higher E modulus is obtained in the presence of the selective solvent water, compared to the non-selective solvent toluene. This observation is explained through selective swelling of the tetra-arm star polymers displaying a different hydrophobicity.

Kinetic, Isotherm, and Equilibrium Investigation of Cr(VI) Ion Adsorption on Amine-Functionalized Porous Silica Beads

The hexavalent chromium (Cr(VI)) ion adsorption properties were conferred to porous silica beads by introducing alkylamine chains through functionalization with an aminosilane coupling agent, [3-(2-aminoethylamino)propyl]triethoxysilane (AEAPTES), or with an epoxysilane coupling agent, (3-glycidyloxypropyl)triethoxysilane (GOPTES), and polyfunctional amine compounds or poly-ethylenimines (PEIs). The presence of amino groups on the silica beads was confirmed by XPS and the amount of amino groups increased to 0.270 mmol/g by increasing the AEAPTES concentration and/or reaction time. The adsorption capacity of the silica beads functionalized with AEAPTES was the maximum at the initial pH value of 3.0 and the initial adsorption rate increased with an increase in the temperature. The adsorption capacity increased with an increase in the amount of amino groups at pH 3.0 and 30 °C. The adsorption behavior obeyed the pseudo-second order kinetic model and was well expressed by the Langmuir isotherm. These results support that Cr(VI) ion adsorption is accomplished through the electrostatic interaction between protonated amino groups and HCrO4- ions. In addition, the adsorption capacity further increased to 0.192–0.320 mmol/g by treating the GOPTES-treated silica beads with triethylenetetramine, pentaethylenehexamine, or PEI. These empirical, equilibria, and kinetic aspects obtained in this study support that the porous silica-based adsorbents prepared in this study can be applied to the removal of Cr(VI) ions.

Evanescent scattering imaging of single protein binding kinetics and DNA conformation changes

Evanescent illumination has been widely used to detect single biological macromolecules because it can notably enhance light-analyte interaction. However, the current evanescent single-molecule detection system usually requires specially designed microspheres or nanomaterials. Here we show that single protein detection and imaging can be realized on a plain glass surface by imaging the interference between the evanescent lights scattered by the single proteins and by the natural roughness of the cover glass. This allows us to quantify the sizes of single proteins, characterize the protein-antibody interactions at the single-molecule level, and analyze the heterogeneity of single protein binding behaviors. In addition, owing to the exponential distribution of evanescent field intensity, the evanescent imaging system can track the analyte axial movement with high resolution, which can be used to analyze the DNA conformation changes, providing one solution for detecting small molecules, such as microRNA. This work demonstrates a label-free single protein imaging method with ordinary consumables and may pave a road for detecting small biological molecules.

Detection of siloxane thin films on glass substrate using IR ratio-reflectance spectrum

In case of thin films of siloxane obtained from different organo-silane derivatives (alkoxy and chloro) on soda lime silica glass substrates, IR-ATR and IR-SR could not detect the organic functional groups of the coating. This becomes even more problematic for the case of tetraethoxysilane (when fully hydrolyzed), the coating of which possesses the same functional groups as the glass substrate. In this work we propose to employ the so-called ratio-reflectance spectra in the v(Si-O) wavenumber region, where both glass and the siloxane coating give most prominent bands, important for the evaluation of the quality of coating formation and qualitative knowledge on its structure. We show that the reflectance-absorbance spectra obtained from the ratio-reflectance spectra are in direct connection to the structure of the siloxane network which depends not only on the chemical nature of the parent silane, but also on the dipping time and the solvent composition. Some characteristics of the reflectance-absorbance spectra, like the appearance of a two well defined bands at 1110 and 975 cm^-1, can be correlated to the film morphology and bridging oxygen number. We support our conclusions using principal component analysis of reflectance spectra, contact angle, AFM and SEM measurements.

Improvement of Mesenchymal Stromal Cell Proliferation and Differentiation via Decellularized Extracellular Matrix on Substrates With a Range of Surface Chemistries

Decellularized extracellular matrix (dECM) deposited by mesenchymal stromal cells (MSCs) has emerged as a promising substrate for improved expansion of MSCs. To date, essentially all studies that have produced dECM for MSC expansion have done so on tissue culture plastic or glass. However, substrate surface chemistry has a profound impact on the adsorption of proteins that mediate cell-material interactions, and different surface chemistries can cause changes in cell behavior, ECM deposition, and the in vivo response to a material. This study tested the hypothesis that substrate surface chemistry impacts the deposition of ECM and its subsequent bioactivity. This hypothesis was tested by producing glass surfaces with various surface chemistries (amine, carboxylic acid, propyl, and octyl groups) using silane chemistry. ECM was deposited by an immortalized MSC line, decellularized, and characterized through SDS-PAGE and immunofluorescence microscopy. No significant difference was observed in dECM composition or microarchitecture on the different surfaces. The decellularized surfaces were seeded with primary MSCs and their proliferation and differentiation were assessed. The presence of dECM improved the proliferation of primary MSCs by ~100% in comparison to surface chemistry controls. Additionally, the adipogenesis increased by 50–90% on all dECM surfaces in comparison to surface chemistry controls, and the osteogenesis increased by ~50% on the octyl-modified surfaces when dECM was present. However, no statistically significant differences were observed within the set of dECM surfaces or control surfaces. These results support the null hypothesis, meaning surface chemistry (over the range tested in this work) is not a key regulator of the composition or bioactivity of MSC-derived dECM. These results are significant because they provide an important insight into regenerative engineering technologies. Specifically, the utilization of dECM in stem cell manufacturing and tissue engineering applications would require the dECM to be produced on a wide variety of substrates. This work indicates that it can be produced on materials with a range of surface chemistries without undesired changes in the bioactivity of the dECM.

Electrochemical and X-ray Photoelectron Spectroscopy Surface Characterization of Interchain-Driven Self-Assembled Monolayer (SAM) Reorganization

Herein, we report a combined strategy encompassing electrochemical and x-ray photoelectron spectroscopy (XPS) experiments to investigate self-assembled monolayer (SAM) conformational reorganization onto an electrode surface due to the application of an electrical field. In particular, 3-mercaptopriopionic acid SAM (3MPA SAM) modified gold electrodes are activated with a 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysulfosuccinimide (NHSS) (EDC-NHSS) mixture by shortening the activation time, from 2 h to 15/20 min, labelled as Protocol-A, -B and -C, respectively. This step, later followed by a deactivation process with ethanolamine (EA), plays a key role in the reaction yields (formation of N-(2-hydroxyethyl)-3-mercaptopropanamide, NMPA) but also in the conformational rearrangement observed during the application of the electrical field. This study aims at explaining the high performance (i.e., single-molecule detection at a large electrode interface) of bioelectronic devices, where the 3MPA-based SAM structure is pivotal in achieving extremely high sensing performance levels due to its interchain interaction. Cyclic voltammetry (CV) experiments performed in K4Fe(CN)6:K3Fe(CN)6 for 3MPA SAMs that are activated/deactivated show similar trends of anodic peak current (IA) over time, mainly related to the presence of interchain hydrogen bonds, driving the conformational rearrangements (tightening of SAMs structure) while applying an electrical field. In addition, XPS analysis allows correlation of the deactivation yield with electrochemical data (conformational rearrangements), identifying the best protocol in terms of high reaction yield, mainly related to the shorter reaction time, and not triggering any side reactions. Finally, Protocol-C’s SAM surface coverage, determined by CV in H2SO4 and differential pulse voltammetry (DPV) in NaOH, was 1.29 * 1013 molecules cm−2, being similar to the bioreceptor surface coverage in single-molecule detection at a large electrode interface.

Fire-Resistant and Hierarchically Structured Elastic Ceramic Nanofibrous Aerogels for Efficient Low-Frequency Noise Reduction

Traffic noise has been regarded as one of the most annoying pollutions that induce severe hazards to human health, both physiological and psychological. The commonly used fibrous noise absorption materials are limited by their large density, poor sound absorption ability at low frequencies, and unsatisfactory fire-resistant ability. Here, we develop hierarchically structured elastic ceramic electrospun nanofibrous aerogels, which possess lightweight properties (density of 13.29 mg cm^-3) and superior low-frequency sound absorption ability (NRC value of 0.59). Specifically, the obtained ceramic electrospun nanofibrous aerogel is nonflammable on exposure to fire and can be compressed and quickly recover to its original height without any visible damage. Moreover, the resultant aerogels could be facilely and efficiently manufactured into designed shapes on a large scale, demonstrating their potential for industrialization. The successful design of such ceramic-based bulk materials may provide new insights for the further development of the next-generation high-efficiency sound-absorbing products.

The Elaboration of Effective Coatings for Photonic Crystal Chips in Optical Biosensors

Here, we propose and study several types of quartz surface coatings designed for the high-performance sorption of biomolecules and their subsequent detection by a photonic crystal surface mode (PC SM) biosensor. The deposition and sorption of biomolecules are revealed by analyzing changes in the propagation parameters of optical modes on the surface of a photonic crystal (PC). The method makes it possible to measure molecular and cellular affinity interactions in real time by independently recording the values of the angle of total internal reflection and the angle of excitation of the surface wave on the surface of the PC. A series of dextrans with various anchor groups (aldehyde, carboxy, epoxy) suitable for binding with bioligands have been studied. We have carried out comparative experiments with dextrans with other molecular weights. The results confirmed that dextran with a Mw of 500 kDa and anchor epoxy groups have a promising potential as a matrix for the detection of proteins in optical biosensors. The proposed approach would make it possible to enhance the sensitivity of the PC SM biosensor and also permit studying the binding process of low molecular weight molecules in real time.

High Sensitivity Label-Free Quantitative Method for Detecting Tumor Biomarkers in Human Serum by Optical Microfiber Couplers

Label-free optical fiber immunosensors have attracted widespread attention in recent decades due to their high sensitivity. However, nonspecific adsorption in serum has remained a critical bottleneck in existing label-free fiber optic biosensors, which hinders their widespread use in diagnostics. In addition, individual differences in clinical human serum (HS) negatively impact biosensing results. In this work, the modified serum preadsorption strategy was applied to reduce nonspecific adsorption by forming a saturated antifouling interface on an optical microfiber coupler (OMC). Furthermore, to reduce the effect of the differences between individual HS samples, we proposed a new method where Sigma HS was used as a wavelength shift reference due to being close to clinical serum compared to other serums. Sigma HS was used first to reduce the differences in immune sensors before performing a clinical sample test in which quantitative detection was achieved based on the independent calibration of several sensors with wide dynamic ranges via dissociation processes. The individual differences in 25% HS were corrected by 30% Sigma HS. As a proof of concept, the label-free OMC immune sensor demonstrates good sensitivity and specificity for the detection of carcinoembryonic antigen (CEA) in 25% Sigma HS at different concentrations. The detection limit of CEA reached as low as 34.6 fg/mL (0.475 fM). Additionally, label-free quantitative detection of CEA using this OMC immune sensor was verified experimentally according to the calibration line, and the results agree well with clinical examination detection. To our knowledge, it is the first study to employ an OMC immune sensor in point-of-care label-free quantitative detection for clinical HS.

Highly effective enzymes immobilization on ceramics: Requirements for supports and enzymes

Enzyme immobilization is a well-known method for the improvement of enzyme reusability and stability. To achieve very high effectiveness of the enzyme immobilization, not only does the method of attachment need to be optimized, but the appropriate support must be chosen. The essential necessities addressed to the support applied for enzyme immobilization can be focused on the material features as well as on the stability and resistances in certain conditions. Ceramic membranes and nanoparticles are the most widespread supports for enzyme immobilization. Hence, the immobilization of enzymes on ceramic membrane and nanoparticles are summarized and discussed. The important properties of the supports are particle size, pore structure, active surface area, volume to surface ratio, type and number of reactive available groups, as well as thermal, mechanical, and chemical stability. The modifiers and the crosslinkers are crucial to the enzyme loading amount, the chemical and physical stability, and the reusability and catalytical activity of the immobilized enzymes. Therefore, the chemical and physical methods of modification of ceramic materials are presented. The most popular and used modifiers (e.g. APTES, CPTES, VTES) as well as activating agents (GA, gelatin, EDC and/or NHS) applied to the grafting process are discussed. Moreover, functional groups of enzymes are presented and discussed since they play important roles in the enzyme immobilization via covalent bonding. The enhanced physical, chemical, and catalytical properties of immobilized enzymes are discussed revealing the positive balance between the effectiveness of the immobilization process, preservation of high enzyme activity, its good stability, and relatively low cost.

Au Nanoflowers for Catalyzing and In Situ Surface-Enhanced Raman Spectroscopy Monitoring of the Dimerization of p-Aminothiophenol

In this work, we demonstrated a facile approach for fabrication of Au nanoflowers (Au NFs) using an amino-containing organosilane, 3-aminopropyltriethoxysilane (APTES), as a shape-directing agent. In this approach, the morphology of the Au particles evolved from sphere-like to flower-like with increasing the concentration of APTES, accompanied by a red shift in the localized surface plasmon resonance peak from 520 to 685 nm. It was identified that the addition of APTES is profitable to direct the preferential growth of the (111) plane of face-centered cubic gold and promote the formation of anisotropic Au NFs. The as-prepared Au NFs, with APTES on their surface, presented effective catalytic and surface-enhanced Raman scattering (SERS) performances, as evidenced by their applications in catalyzing the dimerization of p-aminothiophenol and monitoring the reaction process via in situ SERS analysis.

Nanomagnetic approach applied to microalgae biomass harvesting: advances, gaps, and perspectives

Microalgae biomass is a versatile option for a myriad of purposes, as it does not require farmable land for cultivation and due of its high CO₂ fixation efficiency during growth. However, biomass harvesting is considered a bottleneck in the process because of its high cost. Magnetic harvesting is a promising method on account of its low cost, high harvesting speed, and efficiency, which can be used to improve the results of other harvesting methods. Here, we present the state of the art of the magnetic harvesting method. Detailed approaches involving different nanomaterials are described, including types, route of synthesis, and functionalization, variables that interfere with harvesting, and recycling methods of nanoparticles and medium. In addition to discussing the overall perspectives of the method, we provide a guideline for future research.

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.

Riboflavin Surface Modification of Poly(vinyl chloride) for Light-Triggered Control of Bacterial Biofilm and Virus Inactivation

Poly(vinyl chloride) (PVC) is the most used biomedical polymer worldwide. PVC is a stable and chemically inert polymer. However, microorganisms can colonize PVC producing biomedical device-associated infections. While surface modifications of PVC can help improve the antimicrobial and antiviral properties, the chemically inert nature of PVC makes those modifications challenging and potentially toxic. In this work, we modified the PVC surface using a derivative riboflavin molecule that was chemically tethered to a plasma-treated PVC surface. Upon a low dosage of blue light, the riboflavin tethered to the PVC surface became photochemically activated, allowing for Pseudomonas aeruginosa bacterial biofilm and lentiviral in situ eradication.

Covalent Immobilization of Organic Photosensitizers on the Glass Surface: Toward the Formation of the Light-Activated Antimicrobial Nanocoating

Two highly efficient commercial organic photosensitizers—azure A (AA) and 5-(4-aminophenyl)-10,15,20-(triphenyl)porphyrin (APTPP)—were covalently attached to the glass surface to form a photoactive monolayer. The proposed straightforward strategy consists of three steps, i.e., the initial chemical grafting of 3-aminopropyltriethoxysilane (APTES) followed by two chemical postmodification steps. The chemical structure of the resulting mixed monolayer (MIX_TC_APTES@glass) was widely characterized by X-ray photoelectron (XPS) and Raman spectroscopies, while its photoactive properties were investigated in situ by UV–Vis spectroscopy with α-terpinene as a chemical trap. It was shown that both photosensitizers retain their activity toward light-activated generation of reactive oxygen species (ROS) after immobilization on the glassy surface and that the resulting nanolayer shows high stability. Thanks to the complementarity of the spectral properties of AA and APTPP, the effectiveness of the ROS photogeneration under broadband illumination can be optimized. The reported light-activated nanocoating demonstrated promising antimicrobial activity toward Escherichia coli (E. coli), by reducing the number of adhered bacteria compared to the unmodified glass surface.

Functionalization and Characterization of Silicon Nanowires for Sensing Applications: A Review

Silicon nanowires are attractive materials from the point of view of their electrical properties or high surface-to-volume ratio, which makes them interesting for sensing applications. However, they can achieve a better performance by adjusting their surface properties with organic/inorganic compounds. This review gives an overview of the main techniques used to modify silicon nanowire surfaces as well as characterization techniques. A comparison was performed with the functionalization method developed, and some applications of modified silicon nanowires and their advantages on those non-modified are subsequently presented. In the final words, the future opportunities of functionalized silicon nanowires for chipless tag radio frequency identification (RFID) have been depicted.

Facile synthesis and immobilization of functionalized covalent organic framework-1 for electrochromatographic separation

Inspired by the outstanding functions of 3-aminopropyltriethoxysilane (APTES), which can be used for functionalization of both covalent organic frameworks (COFs) and substrate surfaces, herein, a proof-of-concept demonstration was carried out by one-step synthesis and immobilization of COF-1 in capillary. COF-1 was grown on the inner wall of capillary using APTES, which played a triple role of catalyst, stabilizer, and connecting arm during the process. The immobilization of COF-1 on silicon surface was confirmed by scanning electron microscopy. Moreover, COF-1 modified capillary (COF-1@capillary) column exhibited excellent performance in the electrochromatographic separation of amino acids. High resolution and separation efficiency (225,378 plates/m for 4-methylbiphenyl) were successfully achieved. Separation of methylbenzene, styrene, ethylbenzene, chlorobenzene, 1,2-dichlorobenzene, 1,2,4-trichlorobenzene, 4-methylbiphenyl, naphthalene, and 4-vinylbipheny in the electro-driven mode confirmed the successful growth of COF-1 on the inner wall of capillary. The developed facile method for the immobilization of COF-1 may pave the way for further application prospects of boron-based COFs.