Self-assembled Nanofilms Research Articles

Cascaded dual-parameter SPR fiber sensor for RI and pH simultaneous detection based on Ag film and an Ag/self-assembled nanofilm structure

To achieve more accurate analysis and detection of changes in liquid parameters, we propose a dual-parameter surface plasmon resonance (SPR) sensor that can measure refractive index (RI) and pH simultaneously. In this paper, we compare and analyze the transmission spectrum when the SPR effect is excited by the cladding mode of a photonic crystal fiber (PCF) and the core mode of the no-core fiber. The results show that the SPR effect excited using the cladding mode is stronger and the sensor has better loss peaks, which is more conducive to realizing the detection of the external environment. Therefore, the sensor uses PCF as the substrate and utilizes a cascade composite film structure, and the area where a silver film is deposited on the surface of the PCF is selected as the RI sensing area. Another part of the PCF, after the silver film is deposited, uses a high-sensitivity polyacrylic acid/chitosan self-assembled nanofilm as the pH-sensitive film. Experimental results show that the maximum sensitivity is 4122.44 nm/RIU and -57.82 nm/pH when the RI range is between 1.333 and 1.385 and the pH range is between 3.11 and 8.63, respectively. In addition, we experimentally verified that the sensor had good stability and repeatability. The design of the sensor provides new possibilities for real-time monitoring and precise control, helping to advance scientific research and the development of industry.

Optical pH Sensor Based on a Long-Period Fiber Grating Coated with a Polymeric Layer-by-Layer Electrostatic Self-Assembled Nanofilm.

An optical fiber pH sensor based on a long-period fiber grating (LPFG) is reported. Two oppositely charged polymers, polyethylenimine (PEI) and polyacrylic acid (PAA), were alternately deposited on the sensing structure through a layer-by-layer (LbL) electrostatic self-assembly technique. Since the polymers are pH sensitive, their refractive index (RI) varies when the pH of the solution changes due to swelling/deswelling phenomena. The fabricated multilayer coating retained a similar property, enabling its use in pH-sensing applications. The pH of the PAA dipping solution was tuned so that a coated LPFG achieved a pH sensitivity of (6.3 ± 0.2) nm/pH in the 5.92-9.23 pH range. Only two bilayers of PEI/PAA were used as an overlay, which reduces the fabrication time and increases the reproducibility of the sensor, and its reversibility and repeatability were demonstrated by tracking the resonance band position throughout multiple cycles between different pH solutions. With simulation work and experimental results from a low-finesse Fabry-Perot (FP) cavity on a fiber tip, the coating properties were estimated. When saturated at low pH, it has a thickness of 200 nm and 1.53 ± 0.01 RI, expanding up to 310 nm with a 1.35 ± 0.01 RI at higher pH values, mostly due to the structural changes in the PAA.

Stretchable and Lithography-Compatible Interconnects Enabled by Self-Assembled Nanofilms with Interlocking Interfaces.

Stretchable interconnects with miniature widths are vital for the high-density integration of deformable electronic components on a single substrate for targeted data logic or storage functions. However, it is still challenging to attain high-resolution patternability of stretchable conductors with robust circuit fabrication capability. Here, we report a self-assembled silver nanofilm firmly interlocked by an elastomeric nanodielectric that can be photolithographically patterned into microscale features while preserving high stretchability and conductivity. Both silver and dielectric nanofilms are fabricated by layer-by-layer assembly, ensuring wafer-scale uniformity and meticulous control of thicknesses. Without any thermal annealing, the as-fabricated nanofilms from silver nanoparticles (AgNPs) exhibit conductivity of 1.54 × 106 S m-1 and stretchability of ∼200%, which is due to the impeded crack propagation by the underlying PU nanodielectrics. Furthermore, it is revealed that AgNP microstrips defined by photolithography show higher stretchability when their widths are downscaled to 100 μm owing to confined cracks. However, further scaling restricts the stretchability, following the early development of cracks cutting across the strip. In addition, the resistance change of these silver interconnects can be decreased using serpentine architectures. As a demonstration, these self-assembled interconnects are used as stretchable circuit boards to power LEDs.

Analysis of Expression of Diabetic Nephropathy-Related Protein and Stem Cell Tissue Repair Under Nano Membrane Concentration Technology

This study aimed to study protein expression in diabetic nephropathy (DN) rats and stem cell tissue repair based on nanomembrane concentration technology. Based on the polymer porous self-assembled nanomembrane technology, the content of total protein and albumin in the serum of rats in the control and experimental groups were measured. The obtained images were adopted to analyze the expression of cytoplasmic proteins and membrane proteins, and then the mechanism of stem cell tissue repair function was studied. The results showed that at 56 weeks of age, in contrast to control group, the total protein content in the serum of the experimental group evidently decreased. At 36 weeks of age, the cytoplasmic protein samples of diabetic rats in the experimental group were subjected to three two-dimensional protein electrophoresis. It was found that there were about 701 spots in each gel, and the matching rate was about 87.5%. In contrast to control group, 16 cytoplasmic proteins and 23 membrane proteins of the experimental group changed. The results of the differentially expressed protein analysis indicated that the change trends of protein spots. Based on polymer porous self-assembled nano-film technology, the expression of differential proteins in DN rats was analyzed, which would supplement new research assistance to the mechanism of DN.

Synthesis of upconverting nanosheets derived from Er-Yb and Tm-Yb Co-doped layered perovskites and their layer-by-layer assembled films

Here, we investigated the structure and upconversion (UC) properties of new-type of single oxide nanosheets, derived from the Er3+/Yb3+ and Tm3+/Yb3+ co-doped Ruddlesden-Popper type layered perovskites, and their layer-by-layer (LBL) self-assembled nanofilms. The single oxide nanosheets, obtained by exfoliation of the proton-exchanged K2La2Ti3O10, had the thickness in the range of 2–3 nm indicating good consistency with the theoretical thickness and lateral size from 500 nm up to 2 µm. Er3+/Yb3+, Tm3+/Yb3+ and Tm3+/Er3+co-doped nanosheets were used as building blocks of the multilayer films deposited by layer-by-layer procedure. The LBL films composed of 2.5 % Er3+ + 5 % Yb3+, 2.5 % Tm3+ + 20 % Yb3+, 2.5 % Tm3+ + 20 % Er3+ after 60 sequences have shown a white emission confirmed by the CIE chromaticity diagram. The possible UC energy transfer of LBL films fabricated after 30 sequences using the nanosheets derived from the 2.5 % Er3+ + 5 % Yb3+ co-doped layered perovskites was also suggested. The number of photons participating in the UC process was confirmed as two-photon for both green and red UC emissions due to the 4F9/2 →4I15/2 and 2H11/2, 4S3/2→ 4I15/2 transitions, respectively.

Influence of the nature of the alkanethiol terminal group on the electrochemical stability and blocking ability of self-assembled nanofilms on Au electrode

We studied the effect of the nature of the terminal group of thiols with the same chain length HS (CH2)8 – R (R: -CH3, -CH2OH, -NH2) on the electrodesorption behaviour of well-formed SAMs (the self-assembled monolayers), their stability and blocking ability using voltammetry and chronoamperometry. The nature of the terminal functional group determines the surface properties of SAM and provides the basis for subsequent interactions (for example, with peptides, proteins, DNA) in order to create sensors and bioagents. For the studied thiols, the hydrophilicity of the end groups increases in the series -CH3<< -NH2 ≤ -CH2OH; they also differ in polarity and the possibility of protonation of the amino group. For thiols with -CH3 and -CH2OH groups, an increase in the hydrophilicity of the terminal group leads to the formation of less stable and less ordered films. The replacement of carbon by nitrogen with approximately the same hydrophilicity of the groups (-CH2OH and -NH2) leads to the formation of a more stable film consisting of molecules in the same energy state, butwith poorer insulatingproperties.

Fiber-Optic SPR pH Sensor Based on MMF–NCF–MMF Structure and Self-Assembled Nanofilm

A fiber-optic pH sensor, based on layer-by-layer (LBL) self-assembly and surface plasmon resonance (SPR) technology, is proposed and experimentally confirmed. This article proposes poly (diallyldimethylammonium chloride) (PDDA) as the pretreatment solution for the surface of the gold film and the highly sensitive polyacrylic acid/chitosan (PAA/CS) self-assembled nanomembrane as the pH-sensitive film. It has been experimentally verified that the sensor can detect pH from 3.18 to 11.84 and it exhibits a high average sensitivity of 32.31 nm/pH in this range. In addition, experiments have confirmed that the sensor has attractive stability, repeatability, and hysteresis characteristics.

Solution-Based Synthesis of Layered Two-Dimensional Oxides as Broadband Emitters.

Preparing transition-metal oxides in their two-dimensional (2D) form is the key to exploring their unrevealed low-dimensional properties, such as the p-type transparent superconductivity, topological Mott insulator state, existence of the condensed 2D electron/hole gas, and strain-tunable catalysis. However, existing approaches suffer from the specific constraint techniques and precursors that limit their product types. Here, we report a solution-based method to directly synthesize KNbO2 in 2D by an out-of-the-pot growth process at low temperature, which is observed directly in real time. The developed method can also be applied to other 2D ternary oxide syntheses, including CsNbO2 and composited NaxK1-xNbO2, and it can be extended to the preparation of self-assembled nanofilms. In addition, We demonstrate the emission of broadband photoluminescence (PL, λ ∼ 350-800 nm) from as-synthesized single-crystal 2D KNbO2 sheets down to a single unit cell thickness. The ultra-broadband emission is ascribed to the self-trapped excitation state (STEs) from the in-phase distortion of the NbO6 octahedrons in 2D NbO2- layers. Beyond the broader luminescent range and the robust material thermal stability of niobates, the absence of sample size restrictions and the large aspect ratio of the 2D oxide sheets will provide opportunities in miniaturizing and advancing 2D-materials integrated optoelectronic devices.

Synthesis of polycyclosiloxanes with varying catechol substitution ratios for controllable Ag nanoparticles adsorption

We synthesized polycyclosiloxanes with varying catechol substitution ratios (CFPSs) and investigated silver nanoparticles (AgNPs) adsorption ability on their self-assembled nanofilm. The nanoparticle adsorption ability as a function of the catechol substitution ratio was examined using SEM and a tape peeling test. It was evidenced that the substitution ratio of the catechol units was directly proportional to the surface density of AgNPs adsorbed on CFPS nanofilms.

Synthesis of gold nanoparticles, their interfacial self-assembly, and plasma welding: A solution-processable strategy to interdigital electrodes

This study reports a solution-processable strategy to interdigital electrodes (IDEs), via integrating synthesis of gold nanoparticles (AuNPs), interfacial self-assembly, and plasma welding. Particularly, we found that the usual plasma cleaning process can effectively weld AuNPs, making the self-assembled, patterned AuNP film form a highly interconnected, porous IDEs composed of hyperboloid ligaments. With high conductivity and abundant active sites, the IDEs can serve as glucose sensor (detection limit, 493 μM) and also electrodes in perovskite photodetector (responsivity, 1.60 mA/W; raise/decay time, 0.544/0.866 s). These results offer a new pathway to broaden the applications of diverse self-assembled nanofilms.

Excellent inhibition performance of low-toxicity Dibenzyldithiocarbamic Acid Zinc Salt self-assembled nano-film for copper corrosion in sulfuric acid

The toxicities of corrosion inhibitors were evaluated by the method of Quantitative Structure Activity Relationships (QSARs) and the results show that Dibenzyldithiocarbamic Acid Zinc Salt (ZBTC) is a low-toxicity corrosion inhibitor. The film of ZBTC was fabricated on a copper surface by self-assembling and used to protect against copper corrosion in 0.5 M H2SO4 solution. Electrochemical tests, morphological characterizations (especially ellipsometer measurements), and theoretical calculation were utilized to investigate the inhibition performance and mechanism. The results indicate that the ZBTC had been strongly absorbed on the copper surface to form a hydrophobic film with thickness of 15.15 nm, which obeys the Langmuir isothermal adsorption. The superior corrosion inhibition efficiency of ZBTC SAM reached to 99.72% at a short self-assembly time (30 min).

Synergistic water lubrication effect of self-assembled nanofilm and graphene oxide additive

In this study, a pretreatment method was proposed to enhance the lubrication effect of GO as additives. During pretreatment, 3-aminopropyltriethoxysilane (3-APS) nanofilm was successfully fabricated on substrate surface by self-assembled technique. The 3-APS nanofilm with amino groups can chemically adsorb the GO nanosheets in water. Thus the graphene oxide sheets could deposit on 3-APS nanofilm quickly and last longer, forming durable tribofilms on sliding contact areas. Scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS) and water contact angle (WCA) characterizations revealed the successful preparation of 3-APS nanofilm. Importantly, tribological investigations indicated that under the synergistic effect of 3-APS nanofilm and GO additives, the friction coefficient and the wear rate decreased by 43.6% and 79.7%, compared to those of albronze lubricated by deionized water. Control experiments by respectively using GO additive, and 3-APS nanofilm were performed as well. It is found that using 3-APS nanofilm and GO additives together exhibits the best tribological performances among all the samples. Furthermore, GO tribofilms were detected on wear tracks and relative lubricating mechanisms were elucidated.

Natural Deposition Strategy for Interfacial, Self-Assembled, Large-Scale, Densely Packed, Monolayer Film with Ligand-Exchanged Gold Nanorods for In Situ Surface-Enhanced Raman Scattering Drug Detection.

Liquid interfacial self-assembly of metal nanoparticles holds great promise for its various applications, such as in tunable optical devices, plasmonics, sensors, and catalysis. However, the construction of large-area, ordered, anisotropic, nanoparticle monolayers and the acquisition of self-assembled interface films are still significant challenges. Herein, a rapid, validated method to fabricate large-scale, close-packed nanomaterials at the cyclohexane/water interface, in which hydrophilic cetyltrimethylammonium bromide coated nanoparticles and gold nanorods (AuNRs) self-assemble into densely packed 2D arrays by regulating the surface ligand and suitable inducer, is reported. Decorating AuNRs with polyvinylpyrrolidone not only extensively decreases the charge of AuNRs, but also diminishes repulsive forces. More importantly, a general, facile, novel technique to transfer an interfacial monolayer through a designed in situ reaction cell linked to a microfluidic chip is revealed. The self-assembled nanofilm can then automatically settle on the substrate and be directly detected in the reaction cell in situ by means of a portable Raman spectrometer. Moreover, a close-packed monolayer of self-assembled AuNRs provides massive, efficient hotspots to create great surface-enhanced Raman scattering (SERS) enhancement, which provides high sensitivity and reproducibility as the SERS-active substrate. Furthermore, this strategy was exploited to detect drug molecules in human urine for cyclohexane-extracted targets acting as the oil phase to form an oil/water interface. A portable Raman spectrometer was employed to detect methamphetamine down to 100 ppb levels in human urine, exhibiting excellent practicability. As a universal platform, handy tool, and fast pretreatment method with a good capability for drug detection in biological systems, this technique shows great promise for rapid, credible, and on-spot drug detection.

Electrochemical nanoarchitectonics through polyaminobenzylamine-dodecyl phosphate complexes: redox activity and mesoscopic organization in self-assembled nanofilms.

Molecular design and preparation of redox active films displaying mesoscopic levels of organization represents one of the most actively pursued research areas in nanochemistry. These mesostructured materials are not only of great interest at the fundamental level because of their unique properties but they can also be employed for a wide range of applications such as electrocatalysts, electronic devices, and electrochemical energy conversion and storage. Herein, we introduce a simple and straightforward strategy to chemically modify electrode surfaces with self-assembled electroactive polyelectrolyte-surfactant complexes. These assemblies are composed of amino-appended polyaniline and monododecyl phosphate. The complexes were deposited by spin-coating and the films were characterized by spectroscopic and X-ray-based techniques: XRR, GISAXS, WAXS, and XPS. The films presented a well-defined lamellar structure, directed by the strong interaction between the phosphate groups and the positively charged amine groups in the polyelectrolyte. These films also displayed intrinsic electroactivity in both acidic and neutral solutions, showing that the polymer remains electroactive and ionic transport is still possible through the stratified and hydrophobic coatings. The stability and enhanced electroactivity in neutral solutions make these assembled films promising building blocks for the construction of nanostructured electrochemical platforms.

Interfacial self-assembly approach of plasmonic nanostructures for efficient SERS and recyclable catalysts applications

We report on a simple and general interfacial self-assembly approach to fabricate plasmonic superlattice sheets in extremely large scale, which can be up to ca. 50 cm2, based on different types of noble metal nanoparticles. The self-assembled nanofilms exhibit exciting plasmonic properties with mirror-like reflectance, represented by vivid colour changes. More important, such superlattice sheets can be easily transferred and explored as highly efficient Shape-dependent Surface Enhanced Raman Scattering(SERS) substrates, as well as flexible and recyclable shape-dependent substrate-supporting nanocatalysts sheets. The conversion of 4-NPH were kept as high as 95% after the nanocatalyst sheets were used for six cycles. The interfacial self-assembly method can be exploited for develop-ment of optical and nanocatalysts devices such as flexible colour filters, molecular sensors and flexible plasmonic nanofilms.

An Environmentally Benign Antimicrobial Coating Based on a Protein Supramolecular Assembly.

The use of antimicrobial materials, for example, silver nanoparticles, has been a cause for concern because they often exert an adverse effect on environmental and safety during their preparation and use. In this study, we report a class of green antimicrobial coating based on a supramolecular assembly of a protein extracted from daily food, without the addition of any other hazardous agents. It is found that a self-assembled nanofilm by mere hen egg white lysozyme has durable in vitro and in vivo broad-spectrum antimicrobial efficacy against Gram-positive/negative and fungi. Such enhanced antimicrobial capability over native lysozyme is attributed to a synergistic combination of positive charge and hydrophobic amino acid residues enriched on polymeric aggregates in the lysozyme nanofilm. Accompanied with high antimicrobial activity, this protein-based PTL material simultaneously exhibits the integration of multiple functions including antifouling, antibiofilm, blood compatibility, and low cytotoxicity due to the existence of surface hydration effect. Moreover, the bioinspired adhesion mediated by the amyloid structure contained in the nanofilm induces robust transfer and self-adhesion of the material onto virtually arbitrary substrates by a simple one-step aqueous coating or solvent-free printing in 1 min, thereby allowing an ultrafast route into practical implications for surface-functionalized commodity and biomedical devices. Our results demonstrate that the application of pure proteinaceous substance may afford a cost-effective green biomaterial that has high antimicrobial activity and low environmental impact.

Self-assembled gold nanofilms as a simple, recoverable and recyclable catalyst for nitro-reduction

A facile method to prepare gold nanofilms (AuNFs), from hexaazamacrocycle (L) stabilized AuNPs, by self-assembly at liquid/liquid interfaces is developed. A vial coated with AuNFs was used as a recoverable and reusable catalytic reservoir for nitro-reduction reactions in water under ambient conditions.

Comparative Analysis of Triazine Self-Assembled Nanofilm with/without Fluorine Substituent on Copper Alloy Surface

Comparative Analysis of Triazine Self-Assembled Nanofilm with/without Fluorine Substituent on Copper Alloy Surface

Self-assembled nanofilm of 1,2-dihydro-3-(octadecylthio)benzotriazine on copper for corrosion protection

The self-assembled nanofilm of 1,2-dihydro-3-(octadecylthio)benzotriazine (DOTBT) was formed on fresh copper surface obtained by etching with 7 N nitric acid at a room temperature of 30 °C. The conditions for formation of the DOTBT nanofilm have been optimized by electrochemical impedance and electrochemical quartz crystal nanobalance (EQCN) studies. The DOTBT nanofilm on copper surface was characterized by contact-angle measurement, X-ray photoelectron spectra (XPS), reflection absorption FTIR spectra and atomic force micrographs (AFM). It is inferred that formation of DOTBT film is due to chemisorption of DOTBT on copper surface through nitrogen and subsequent complex formation between DOTBT and Cu + ions. Corrosion protection ability of DOTBT nanofilm was evaluated in dilute aqueous NaCl solution using electrochemical impedance, potentiodynamic polarization, weight-loss and XPS studies. These studies inferred that the DOTBT film protects effectively copper from corrosion. Potentiodynamic polarization studies revealed that the DOTBT film inhibits corrosion by controlling the cathodic reaction. The mechanism of corrosion protection of copper by DOTBT nanofilm is discussed in this paper.

BEHAVIOR OF ARTICULAR CHONDROCYTES ON NANOENGINEERED SURFACES

In tissue engineering, surface modification has becomes one of the leading methods to enhance initial cell attachment and subsequent cellular growth, differentiation and tissue formation. This work studied growth and behavior of primary bovine articular chondrocytes on self-assembled multilayer nanofilms composed of: polyelectrolytes [poly(styrene sulfonate) (PSS), poly-L-lysine (PLL), poly-D-lysine (PDL), chondroitin sulfate (CS), poly(ethyleneimine) (PEI), poly(dimethyldiallylammonium chloride) (PDDA), poly(ethylene glycol) amine (PEG - NH2)] and proteins [bovine serum albumin (BSA), collagen, fibronectin, laminin]. These biomaterials were used to build mono-, bi-, and tri-layer nanofilm architectures. Potential cytotoxic effects were assessed using Live/Dead assay and cell proliferation was quantified using MTT assay. Bright field and fluorescence microscopy were used to analyze chondrocyte morphology. ImageJ software was used to analyze the number, mean area, circularity and Feret's diameter of viable cells. Cumulative results demonstrated that chondrocyte growth; proliferation and functionality were dependent on initial cell density, nanofilm thickness and material composition of nanofilms.