Self-assembly Technique Research Articles

Unique and efficient modulation of polycarbazole thin film surface morphology by electrochemical, photochemical and self-assembly techniques

Surface morphology significantly impacts the performance of conducting polymers by influencing charge transport, electromechanical properties, and diffusion dynamics. Understanding and controlling surface morphology is crucial for optimizing the performance of conducting polymers in various applications. In this work, we synthesized for the first time the Azo-SH molecule containing azobenzene, thiol and carbazole groups, thus enabling it photoactivity, electroactivity and self-assembly properties. By integrating the photosensitive azobenzene and the thiol-terminated functional molecule into the electroactive carbazole group, it has been obtained unique surface morphologies that modulating effectively and efficiently via electrochemical, photochemical and self-assembly. The electroactive and photoactive polymer films obtained by electropolymerization were characterized by AFM, e-QCM, electrochemical impedance and XPS techniques. This study has demonstrated as a proof of concept that the surface properties of thin films formed with all-in-one type molecules can be modified by electrochemical, photochemical and self-assembly techniques. Surface morphology modulation of thin films by including wettability, polarity, dipole moment and other properties would provide a powerful approach to prepare functional organic devices.

Polymerization-Induced Self-Assembly for the Synthesis of Polyisoprene-Polystyrene Block and Random Copolymers: Towards High Molecular Weight and Conversion.

In this study, reversible addition-fragmentation chain- transfer (RAFT) polymerization combined with the polymerization-induced self-assembly (PISA) technique is used to synthesize polyisoprene (PI)-based block and random copolymers with polystyrene (PS), aiming for high molecular weight and monomer conversion. The focus is to optimize the polymerization conditions to overcome the existing challenge of cross-linking and Diels-Alder reactions during the polymerization of isoprene, which typically constrain the reaction conversion and molecular weight of the final polymers. Using a poly(methacrylic acid) (PMAA) macroRAFT agent synthesized in ethanol at 80°C, random and block copolymers of PS-PI with a target molecular weight of 50000gmole-1 and a high monomer conversion of ≈80% are achieved under optimized conditions in water-emulsion at 35°C. 1H nuclear magnetic resonance (NMR) verified the successful synthesis as well as the high content of 1,4 microstructure in polyisoprene. The thermal analysis via differential scanning calorimetry indicated distinct glass transitions for the microphase-separated PI-PS block copolymer, while a single transition for PI-PS random copolymer, indicating no microphase separation. Furthermore, dynamic light scattering analysis together with transmission electron microscopy provided further insight into the self-assembled emulsion nanoparticles of the polymers indicating a particle size in the range 70 to 130nm.

Hierarchy-constructed superhydrophobic and transparent coating modified intraocular lens by layer-by-layer self-assembly for glistening reduction and antiadhesion

Intraocular lens (IOL) implantation surgery is the most effective treatment for cataract. However, glistening formed by the incoming liquid microvacuoles can significantly damage postoperative visual quality after prolonged implantation, for which there is still lack of effective clinical treatment. In this study, inspired by the amazing water-repellency of natural superhydrophobic surface, a functionalized IOL material modified with the superhydrophobic and transparent coating was prepared using layer-by-layer electrostatic self-assembly technique combined with fluorination. After the alternate deposition of multiple cationic/anionic polyelectrolytes and silica nanoparticles of varying sizes on IOL materials, the constructed multilayered films with special surface roughness were further fluorinated to reduce surface energy. In addition to its excellent superhydrophobicity and transparency, this multilayered coating could efficiently eliminate the glistening formation of IOL under accelerated condition in vitro. Furthermore, the in vitro experiments with water droplets, cells, and bacteria suggested the superior antiadhesion property of such coating modified materials. The biocompatibility evaluation, both in vitro and in vivo, demonstrated the great biocompatibility of the materials modified with superhydrophobic and transparent coating. Therefore, this multilayered coating with excellent superhydrophobic and transparent characteristics can provide an available approach aiming at anti-glistening and antiadhesion of IOL materials. Advances in the fabrication process of surface coating with specific functions will enhance the practical application and clinical success of modified IOLs.

Preparation, characterization, stability and application of the H-type aggregates lutein/whey protein/chitosan nanoparticles

Natural lutein is liposoluble and has powerful antioxidant activity, which can be self-aggregated to form H-type aggregates in organic-water systems. However，its application is limited by poor solubility and high instability. Here, whey proteins/chitosan-coated H-type aggregates lutein nanoparticles (NPs) were fabricated via a bottom-up layer-by-layer self-assembly technique. The optimal conditions for the preparation of the NPs (173.3 nm) were determined by the Dynamic Light Scattering and UV–vis spectroscopy. Briefly, three proteins (WPI and WPC and BSA) were used to fabricate polysaccharide-protein nanocarriers to encapsulate the lutein. These spectroscopy studies indicated that chitosan and BSA formed hydrophobic microdomain by the intermolecular electrostatic attraction force with remarkable changes of secondary structure in protein. The morphology revealed that the NPs were nearly spherical. The EE of the NPs was ≥90.4 %, with a LC of up to 28.3 %. Lutein in NPs can be stabilized as H-type aggregates at different temperatures and pH-values. Additionally, the cytotoxicity test of the NPs on L929 and Caco-2 cells showed that NPs had low cytotoxicity in a limited concentration range. Results indicated that whey protein/chitosan-coated lutein nanoparticles significantly improved water dispersion and stability of lutein and its aggregates, thus broadening their application in nutrient delivery system.

Hyaluronic acid/lactoferrin–coated polydatin/PLGA nanoparticles for active targeting of CD44 receptors in lung cancer

Traditional chemotherapeutic drugs lack optimal efficacy and invoke severe adverse effects in cancer patients. Polydatin (PD), a phytomedicine, has gradually gained attention due to its antitumor activity. However, its low solubility and poor bioavailability are still cornerstone issues. The present study aimed to fabricate and develop hyaluronic acid/lactoferrin–double coated PD/PLGA nanoparticles via a layer-by-layer self-assembly technique for active targeting of CD44 receptors in lung cancer. Different molecular weights (M.wt.) of HA (32 and 110 kDa) were exploited to study the relationship between the HA M.wt. and the NPs targeting efficacy. The optimized formulations were fully characterized. Their cytotoxicity and cellular uptake were investigated against A549 cell line by CCK-8 kit and fluorescence imaging, respectively. Finally, HA110/Lf-coated PD/PLGA NPs (F9) were subjected to a competitive inhibition study to prove internalization through CD44 overexpressed receptors. The results verified the fabrication of F9 with a particle size of 174.87 ± 3.97 nm and a zeta potential of −24.37 ± 1.19 mV as well as spherical NPs architecture. Importantly, it provoked enhanced cytotoxicity (IC50 = 0.57 ± 0.02 µg/mL) and superior cellular uptake efficacy. To conclude, the current investigation lays the foundation for the prospective therapeutic avenue of F9 for active targeting of CD44 receptors in lung cancer.

Layered MXene Films via Self-Assembly.

MXene has attracted significant attention as a 2D material family due to its metallic conductivity and abundant surface functional groups and has been extensively studied and applied as bulk materials and microscale thin films. MXene possesses ionizable surfaces and edges, as well as high surface area. Its customizable dispersibility demonstrates unique advantages in self-assembly solution processing. Recent studies have demonstrated the application value of layered MXene films at the nanoscale thickness and the reliance of processing on self-assembly techniques. However, this field currently lacks sufficient attention. Here, the regulatory mechanisms are summarized for the preparation of layered MXene films through self-assembly techniques, as well as introduce their applications. Moreover, the future challenges of large-scale applications of MXene self-assembly techniques are proposed. It is believed that this review would provide a dynamic and promising path for the development of layered MXene self-assembly techniques.

Fe(OH)3/Ti3C2Tx nanocomposites for enhanced ammonia gas sensor at room temperature

Two-dimensional material (2D material) MXene has great application potential in gas sensors because of its excellent controllable performance and vast specific surface area. In this study, we used a straightforward in-situ electrostatic self-assembly technique to create Fe(OH)3/Ti3C2Tx nanocomposites, which were then used to fabricate gas sensors for ammonia detection at room temperature (25 ℃). Several characterization methods were performed aimed at determining the surface appearance and construction of the nanocomposites, and the sensing characteristics and mechanism were also systematically examined. The findings demonstrate the effective incorporation of amorphous Fe(OH)3 nanoparticles on the surface of Ti3C2Tx. Additionally the nanocomposites of Fe(OH)3/Ti3C2Tx have considerably higher specific surface area than pure Ti3C2Tx, hence offering more active NH3 adsorption sites. The response of the sensor to 100 ppm NH3 was 48.6% at room temperature, which was 9.3 times more higher than that of pure Ti3C2Tx. The sensors also have the advantages of long-term stability (33 days), low NH3 detection limit (500 ppb), and rapid recovery time (85 s) and response times (78 s). It is anticipated that this work will be helpful for developing the new generation of wearable ammonia sensors at room temperature.

Temperature dependence of gold nanostar particles morphology and its SERS application

ABSTRACT Gold nano-star particles (GNS) have broad application prospects in Raman enhancement, photovoltaic, and catalysis fields because of the hot spot effect of their tip structure. However, metal nanoparticles will accumulate heat during applications of high-power laser-focused irradiation, which may lead to the morphological degradation of the nanoparticles. In this paper, we have studied the effect of annealing temperature on the surface tip structure of GNS. Firstly, GNS with the multi-tip structure were synthesised by the two-step method, and GNS thin films were prepared by self-assembly technique without auxiliaries. By means of SEM characterisation, the film is found to be compact and uniform. Secondly, we systematically studied the morphology degradation of GNS at 100°C, 150°C, 200°C and 250°C. The results show that the tip of GNS does not change obviously until the temperature reaches 200°C. Then the four kinds of GNS films were used as surface-enhanced Raman scattering (SERS) substrates, and their Raman enhancement properties have been studied with adenine as the analyte, and stronger Raman enhancement effect can be found for the tip of nanoparticles. For a SERS substrate corresponding to an annealing temperature of 100°C, we have obtained the limit sensitivity of adenine molecule of 10−9 M. Finally, the surface electric field distribution and local resonance spectrum curves of four kinds of gold nanoparticles with different tip sizes were simulated theoretically by using the finite element method, and the results are consistent with the experimental data.

Synthesis And Efficiency Evaluation of Chitosan-Alginate Hydrogel Polyelectrolyte Complex Filter for Treatment of Oil Spillage

Crude oil spills pose considerable environmental concerns thereby demanding the development of effective, sustainable, and eco-friendly remediation solutions. In this study, we synthesized and evaluated the efficiency of a biodegradable polymer filter using sodium alginate and chitosan for the treatment of oil spillage. The sodium alginate-chitosan hydrogel polyelectrolyte complex (SACHPC) filter was synthesized via dipping method using a layer-by-layer self-assembly technique integrated with cotton wool as the filter medium. The efficiency of the filter was evaluated based on flow rate of recovered oil and reusability of the filter. Simulated oil spillage of 0.5 M was subjected to filtration using the SACHPC filter. The flow rate was determined based on the time taken for 1 L of oil to pass through the filter. The SACHPC filter exhibited underwater superoleophobic behaviour with exceptional filtration efficiency (> 98.3%) in acidic, neutral and alkaline conditions (pH 3, 7 and 11). The flow rate of the filter was 120 mL/min, while the third-use filter exhibited a decrease flow rate of 50 ml/min. Moreover, the filter achieved an impressive crude oil recovery rate of 85%. X-ray diffraction analysis confirmed crude oil adsorption in the presence of an amorphous phase while scanning electron microscopy analysis revealed the structural morphology of the SACPHC filter. Overall, the SACHPC filter maintained high filtration efficiency thereby offering a sustainable strategy for oily wastewater purification and oil spill clean-up.

Fabrication and Characterization of Graphene Oxide – Cadmium Sulphide Nanocomposite Coating for Corrosion Inhibition of Mild Steel Specimen

Abstract The oil and gas sector play a significant role in the Sultanate of Oman’s economic growth and contribute major revenue. Corrosion is a global concern and that strongly affects the industrial sectors. The corrosion problems in oil pipelines would be successfully resolved by means of novel control techniques. This research focused on the fabrication of Graphene oxide (GO) - Cadmium sulphide (CdS) nanocomposite for controlling corrosion in mild steel specimen. Graphene oxide was synthesized from Alovera extract by carbonization process. GO - CdS nanocomposite was prepared and deposited on a mild steel pipe by self-assembly technique. The coated material was used for stability studies at varying pH conditions and exposure period followed by corrosion studies. The testing methods adopted are Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Energy Dispersive X-Ray analysis (EDX), and Fourier Transform Infrared Spectroscopy (FTIR). Wet/Dry test and Atmosphere tests were conducted to examine the performance of coating material towards corrosion. The atomic force microscope (AFM) operated in non-contact mode was used to study surface topology of the coated specimen. From the outcome of the corrosion studies, it was established that the GO- CdS Nano composites thin film acted as an ecofriendly corrosion inhibitor to enhance the lifespan of the mild steel pipe. This novel research is aligned with the United Nations Sustainability Goals (UNSD - 9: Industry, Innovation and Infrastructure & UNSDG 12 – Responsible consumption and production) and Oman vision 2040. The results from the study validates that the GO - CdS thin films coated on mild steel pipe could be a viable solution to corrosion issues in oil pipelines owing to their good film stability, minimum film thickness, high durability, and ecofriendly approach.

Osteogenic and osteoclastic differentiation by control release of adenosine within PEI/HA/Collagen composite coatings

In virtue of the rapid metabolism and short half-life of adenosine (AD) in the human body, it is highly desired to explore new adenosine delivery system with controlled and steady release capacity. In this study, composite coatings consisting of polyethyleneimine (PEI), hyaluronic acid (HA) and collagen type I (COL-1) on titanium substrate surface are developed by layer-by-layer self-assembly technique, in which different concentrations of AD are encapsulated. In-vitro release study demonstrated a steady and sustained release of AD from the composite coating system. Adenosine within composite coatings depicted a concentration-dependent regulatory effect on the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and osteoclastic differentiation of mouse leukemia cells of monocyte macrophage (RAW264.7) cells. All of these coatings exhibited good cell viability and promoted osteoblast cell proliferation. Among various composite coatings, the optimized coating specimen with loading of 65 μg AD (AD2) exhibits the best osteoconductive and osteoinductive activities with significantly enhanced osteoblast-associated gene expressions, and increased alkaline phosphatase (ALP) activity and calcium deposits. On the other hand, AD2 specimen shows the activity of inhibiting osteoclast differentiation and osteobclast-associated gene expressions as well as suppressing tartrate-resistant acid phosphatase (TRAP) activity. The superior performance of AD/PEI/HA/COL composite coatings indicated that this coating system could be useful for bone tissue engineering.

Barium titanate/ZnAl-layered double hydroxide catalysts for piezoelectrically enhanced photocatalytic degradation of coexisting pollutants and antibiotic resistance genes

Composite materials consisting of BaTiO₃/ZnAl-layered double hydroxide (LDH) were synthesized utilizing a combination of self-assembly and hydrothermal techniques, displaying outstanding piezoelectric characteristics. When subjected to ultrasonic vibration and visible light (VSL) irradiation, these composites demonstrated superior piezoelectric photocatalytic capabilities, achieving degradation rates of 99 % for NTP and a complete 100 % for TC within a span of 45 minutes. The presence of ultrasonic vibration induces polarized electric fields within the ZnAl-LDH and BaTiO₃ components. These fields support the maintenance of the intrinsic electric field strength across the heterojunction interfaces, facilitating the expedited migration of photogenerated carriers. Consequently, this enhances the efficiency of carrier separation and fosters a synergistic catalytic effect attributed to dual piezoelectricity when exposed to VSL. This investigation highlights the potential of piezoelectric photocatalysis in efficiently removing pollutants, suggesting its applicability in the treatment of municipal wastewater and sterilization processes, and offers innovative perspectives for advancing piezoelectric photocatalyst development.

Design of multiple anti-fouling and honeycomb-like NH2-AgBiS2 @g-C3N4 hydrogel layer onto PAN fiber membrane for multicomponent pollutant-oil-water emulsion treatment

Nano-structured hydrogel with unique anti-oil fouling property exhibits big advantage in oil/water separation, but its application in complex oily wastewater (contain oils, organic matter, bacteria, etc.) cleanup is hampered by the insufficient capabilities in multi-antifouling and synergistic treatment. Herein, we constructed the amino-rich NH2-AgBiS2/PANI (polyaniline)-g-C3N4 based multi-functional hydrogel functional layer onto the polyacrylonitrile (PAN) fiber membrane via polyphenol-mediated chitosan gelation and vacuum-assisted self-assembly techniques. The unique honeycomb-like structure and super-wetting feature synergistically contributed to the powerful oil resistance and flux breakthrough of composite membrane. Such membrane achieved superior permeability (up to 3558 L−1 m−2 h−1) for various SDS-stabilized oil-in-water emulsions and remarkable synergistic treatment efficiency of multicomponent pollutant-oil-water emulsion. The rational design of hydrogel layer on membrane surface intensified the photo-response ability and multiple electron transport channels, which offered the favorable photocatalytic self-cleaning performance towards degradation of organic dyes. According to the free radical quenching and EPR experiments, the photocatalytic mechanism was proposed. In addition, the inhibition rate of E. coli could reach 100 % under illumination of 24 h. Therefore, the integration of ultra-low oil adhesion, photocatalytic self-cleaning, and antibacterial features endows membrane with exceptional multiple anti-fouling performance, exhibiting unique advantages over traditional membranes in handling complex membrane fouling issues.

Barrier Membrane with Janus Function and Structure for Guided Bone Regeneration.

Guided bone regeneration (GBR) technology has been demonstrated to be an effective method for reconstructing bone defects. A membrane is used to cover the bone defect to stop soft tissue from growing into it. The biosurface design of the barrier membrane is key to the technology. In this work, an asymmetric functional gradient Janus membrane was designed to address the bidirectional environment of the bone and soft tissue during bone reconstruction. The Janus membrane was simply and efficiently prepared by the multilayer self-assembly technique, and it was divided into the polycaprolactone isolation layer (PCL layer, GBR-A) and the nanohydroxyapatite/polycaprolactone/polyethylene glycol osteogenic layer (HAn/PCL/PEG layer, GBR-B). The morphology, composition, roughness, hydrophilicity, biocompatibility, cell attachment, and osteogenic mineralization ability of the double surfaces of the Janus membrane were systematically evaluated. The GBR-A layer was smooth, dense, and hydrophobic, which could inhibit cell adhesion and resist soft tissue invasion. The GBR-B layer was rough, porous, hydrophilic, and bioactive, promoting cell adhesion, proliferation, matrix mineralization, and expression of alkaline phosphatase and RUNX2. In vitro and in vivo results showed that the membrane could bind tightly to bone, maintain long-term space stability, and significantly promote new bone formation. Moreover, the membrane could fix the bone filling material in the defect for a better healing effect. This work presents a straightforward and viable methodology for the fabrication of GBR membranes with Janus-based bioactive surfaces. This work may provide insights for the design of biomaterial surfaces and treatment of bone defects.

Chemically Powered Nanomotors with Magnetically Responsive Function for Targeted Delivery of Exosomes.

Janus structure plays a crucial role in achieving chemically driven nanomotors with exceptional motion performance. However, Janus-structured chemically driven nanomotors with magnetic responsiveness are commonly fabricated by sputtering metal films. In the study, a self-assembly technique is employed to asymmetrically modify the surfaces of magnetic silica (SiO2@Fe3O4) nanoparticles with platinum nanoparticles, resulting in the formation of this kind nanomotors. Compared to platinumfilm, platinum nanoparticles exhibit a larger surface area and a higher catalytic activity. Hence, the nanomotors demonstrate improved diffusion capabilities at a significantly lower concentration (0.05%) of hydrogen peroxide (H2O2). Meanwhile, exosomes have gained attention as a potential tool for the efficient delivery of biological therapeutic drugs due to their biocompatibility. However, the clinical applications of exosomes are limited by their restricted tropism. The previously obtained nanomotors are utilized to deliver exosomes, greatly enhancing its targetability. The drug doxorubicin (DOX) is subsequently encapsulated within exosomes, acting as a representative drug model. Under the conditions of H2O2 concentration at the tumor site, the exosomes exhibited a significantly enhanced rate of entry into the breast cancercells. The utilization of the nanomotors for exosomes presents a novel approach in the development of hybrid chemically and magnetically responsive nanomotors.

Ti3C2 quantum dots-modified oxygen-vacancy-rich BiOBr hollow microspheres toward optimized photocatalytic performance

The Ti3C2 quantum dots (QDs)/oxygen-vacancy-rich BiOBr hollow microspheres composite photocatalyst was prepared using solvothermal synthesis and electrostatic self-assembly techniques. Together, Ti3C2QDs and oxygen vacancies (OVs) enhanced photocatalytic activity by broadening light absorption and improving charge transfer and separation processes, resulting in a significant performance boost. Meanwhile, the photocatalytic efficiency of Ti3C2 QDs/BiOBr-OVs is assessed to investigate its capability for oxygen evolution and degradation of tetracycline (TC) and Rhodamine B (RhB) under visible-light conditions. The rate of oxygen production is observed to be 5.1 times higher than that of pure BiOBr-OVs, while the photocatalytic degradation rates for TC and RhB is up to 97.27% and 99.8%, respectively. The synergistic effect between Ti3C2QDs and OVs greatly enhances charge separation, leading to remarkable photocatalytic activity. Furthermore, the hollow microsphere contributes to the enhanced photocatalytic performance by facilitating multiple light scatterings and providing ample surface-active sites. The resultant Ti3C2QDs/BiOBr-OVs composite photocatalyst demonstrates significant potential for environmental applications.

Construction and Preparation of the Novel ADN/CL-20 Cocrystal via Directional Hydrogen Bonding Design for Turning Hygroscopicity.

Ammonium dinitramide (ADN), as a novel and environmentally friendly oxidizer, has strong hygroscopicity when exposed to high-humidity air, which seriously hinders its application in solid propellants. Modification of oxidizers by cocrystallization is an effective strategy to improve the hygroscopicity of energetic components. In this paper, the theoretical simulation of ADN/CL-20 cocrystals was developed via a directional hydrogen bonding design to establish a cocrystal with improved hygroscopicity. Intermolecular interaction analyses reveal that hydrogen bonds and van der Waals interactions synergistically lead to the formation of cocrystals. The ADN/CL-20 cocrystal was prepared experimentally by the spray drying self-assembly technique, and the corresponding thermal analysis and sensitivity properties were conducted to illustrate the thermal stability and high safety. Furthermore, the critical relative humidity (CRH) measurement was carried out to evaluate the hygroscopicity of the cocrystal, exhibiting a certain degree of antihygroscopic effect with a CRH of 65%. The hydrogen bonds formed between ADN and CL-20 saturate the ammonium ions of ADN, further preventing ADN from absorbing water molecules in the air. The ADN/CL-20 cocrystal has high specific impulse characteristics (Isp: 272.6 s). Accordingly, this work clearly demonstrates that the ADN/CL-20 cocrystal is expected to be used in a solid propellant to make up for the deficiency of the ADN oxidizer.

Use of tyrosinase nanobiosensor for detection of atrazine and simazine and its application in real water samples

ABSTRACT This study presents the development and characterization of cantilever nanobiosensors functionalized with the tyrosinase enzyme (0.05–0.001%) for the detection of atrazine and simazine in water. The optimization of tyrosinase activity through precise immobilization and sensitive layer adjustments was evaluated. Topographical analysis revealed the successful immobilization of the tyrosinase enzyme using the self-assembled monolayer technique, enhancing sensor sensitivity. Upon comparing the enzyme concentrations, it was found that the 0.006% exhibited remarkable results, including a limit of detection (LOD = 0.0080 ppb) and a limit of quantification (LOQ = 0.0267 ppb), along with enhanced storage stability for 15 days for atrazine detection. For simazine, the nanobiosensor exhibited high sensitivity (8.1532 nm/ppb) and LOD (0.0117 ppb). They demonstrated excellent reversibility (99%) over six cycles and selectivity against interfering pesticides commonly found in agricultural environments, indicating their suitability for complex sample matrices. Real water samples met regulatory standards for atrazine levels, further validating the efficacy of the nanobiosensors in detecting pesticide contamination. The enzymatic nanobiosensor achieved recoveries ranging from 97 to 101%, indicating high reproducibility. These findings demonstrate the potential of the developed nanobiosensors for sensitive and reliable pesticide detection in environmental monitoring, with implications for future applications.

Self-Assembled Plasmonic Structural Color Colorimetric Sensor for Smartphone-Based Point-Of-Care Ammonia Detection in Water.

Monitoring chemical levels is crucial for safeguarding both the environment and public health. Elevated levels of ammonia, for instance, can harm both humans and aquatic ecosystems, often indicating contamination from agriculture, industry, or sewage. Developing portable, high-resolution, and affordable methods for in situ monitoring of ammonia is thus imperative. Plasmonic sensors offer a promising solution, detecting ammonia by correlating changes in their optical response to the target analyte's concentration. While they are highly sensitive and can be fabricated in a variety of portable and user-friendly formats, some still require reagents or expensive optical equipment, which hinder their widespread adoption. Here, we present a self-assembled nanoplasmonic colorimetric sensor capable of directly detecting ammonia concentrations in aqueous matrices. The proposed sensor exploits the plasmonic resonance of the nanostructures to transduce changes in the chemical environment into alterations in color, offering a label-free method for real-time analysis. The sensor is fabricated using a self-assembling technique compatible with low-cost mass production based on aluminum and aluminum oxide, ensuring affordability and avoiding the use of other toxic chemicals. We developed a model to predict ammonia concentrations based on visible color change of the sensor, achieving a detection limit of 8.5 ppm. Furthermore, to address the need for on-site detection, we integrated smartphone technology for real-time color change analysis, eliminating the need for expensive, bulky optical instruments. Indeed, our approach offers a cost-effective, portable, and user-friendly solution for ammonia detection in water without the need for chemical reagents or spectrometers, making it ideal for field applications. Interestingly, this platform extends its applicability beyond ammonia detection, enabling the monitoring of various chemicals using a smartphone, without the need for any additional costly equipment.

Achieving High-Performance Polymer-Wrapper-Free Aligned Carbon Nanotube Field-Effect Transistors Through Degradable Polymer Wrapping and Efficient Removal Techniques.

Semiconducting carbon nanotubes (s-CNTs) have emerged as a promising alternative to traditional silicon for ultrascaled field-effect transistors (FETs), owing to their exceptional properties. Aligned s-CNTs (A-CNTs) are particularly favored for practical applications due to their ability to provide higher driving current and lower contact resistance compared with individual s-CNTs or random networks. Achieving high-semiconducting-purity A-CNTs typically involves conjugated polymer wrapping for selective separation of s-CNTs, followed by self-assembly techniques. However, the presence of the polymer wrapper on A-CNTs can adversely impact electrical contact, gating efficiency, carrier transport, and device-to-device variations, necessitating its complete removal. While various methods have been explored for polymer removal, accurately characterizing the extent of removal remains a challenge. Traditional techniques such as absorption spectroscopy and X-ray photoelectron spectroscopy (XPS) may not accurately depict the remaining polymer content on A-CNTs due to their inherent detection limits. Consequently, the performance of FETs based on pure polymer-wrapper-free A-CNTs is unclear. In this study, we present an approach for preparing high-semiconducting-purity and polymer-wrapper-free A-CNTs using poly[(9,9-dioctylfluorenyl-2,7-dinitrilomethine)-(9,9-dioctylfluorenyl-2,7-dimethine)] (PFO-N-PFO), a degradable polymer, in conjunction with a modified dimension-limited self-alignment process (m-DLSA). Comprehensive transmission electron microscopy (TEM) characterizations, complemented by absorption and XPS characterizations, provide robust evidence of the successful near-complete removal of the polymer wrapper via a cleaning procedure involving acidic degradation, hot solvent rinsing, and vacuum annealing. Furthermore, top-gated FETs based on these high-semiconducting-purity and polymer-wrapper-free A-CNTs exhibit good performance metrics, including an on-current (Ion) of 2.2 mA/μm, peak transconductance (gm) of 1.1 mS/μm, low contact resistance (Rc) of 191 Ω·μm, and negligible hysteresis, representing a significant advancement in the CNT-based FET technology.