Composite Langmuir-Blodgett Films Research Articles

Fabrication and Self-Assembly Behavior of BPEF and BBPEF Composite Langmuir-Blodgett Films with Photovoltaic Conversion Properties.

The LB films prepared through the Langmuir-Blodgett (LB) technique are of significant importance for the fabrication of functional films such as optoelectronic materials and sensors. In this study, 9,9-bis (4-(2-hydroxy-ethoxy) phenyl) fluorene (BPEF) and 9,9-bis [3-phenyl-4-(β-hydroxy-ethoxy) phenyl] fluorene (BBPEF) were combined with saffron T (ST), methylene blue (MB) and Rhodamine B (RhB) dyes by LB technique to prepare ordered composite films. The nanostructures and morphologies of the composite films were analyzed by transmission electron microscopy (TEM) and atomic force microscopy (AFM). It was found that the films exhibited distinct aggregation morphologies. The UV-VIS absorption spectra showed that the concentration of dye molecules had a significant effect on the spectral characteristics. The contact Angle test shows that the prepared composite films are hydrophobic. The photovoltaic conversion performance of LB composite films was studied by transient photocurrent response experiments. It was found that BPEF/dye and BBPEF/dye composite films exhibited significant responses in photocurrent. In particular, BPEF/RhB and BBPEF/RhB composite films demonstrated excellent photoresponsive performance. This study used LB technology in combination with BPEF and BBPEF to demonstrate enhanced photocurrent and stable performance of LB film, which provided ideas for expanding the application range of materials.

Facile preparation and study of supramolecular architecture of an efficient nanocomposite LB film AHSM/SA based on azo-functionalized hockey stick-shaped mesogen at air-water and air-solid interface

Hockey stick-shaped mesogens are fascinating thermotropic liquid crystal systems owing to their exceptional supramolecular assembly properties and shape anisotropy compared to conventional rod-and bent-shaped mesogens. In this article, we present an investigation of the supramolecular organization of a new azo-functionalized hockey stick-shaped mesogen with stearic acid at the air-water interface and air-solid interfaces by applying the Langmuir-Blodgett film deposition method. The incorporation of stearic acid can change the molecular organization of azo-functionalized hockey stick-shaped mesogen at an aqueous interface through hydrophobic-hydrophobic interactions and form a supramolecular nanostructure at the solid interface. The interfacial nature of the Langmuir monolayer was studied by recording the isotherm (surface pressure area, π–A), which was further analyzed by using Brewster angle microscopy. The significant reduction in molecular area, increased surface pressure, and lower isotherm slope of the AHSM/SA composite mixture indicate the hybrid AHSM/SA monolayer's greater stability compared to pure AHSM. BAM images of the AHSM/SA composite signify nanostructure aggregates formed by the interaction of AHSM and SA molecules at the air-water interface. Field emission scanning electron microscopic analysis of composite films revealed the formation of supramolecular domains. The impact of changing the surface pressure and the number of depositions on the morphology of the composite film surface was monitored using field emission scanning electron microscopy. The supramolecular H-type aggregation of azo-functionalized hockey stick-shaped mesogen and stearic acid molecules in the composite LB film was characterized using UV–visible absorption and steady-state fluorescence spectroscopy. The adsorption of stearic acid onto azo-functionalized hockey stick-shaped mesogen via hydrophobic interactions was confirmed by Fourier transform infrared spectroscopy of the composite Langmuir Blodgett film. Further, Raman spectroscopy of the LB films of the AHSM/SA composites is distinct from the pristine film components due to the merging of signals at similar wave numbers for both SA and AHSM with a lack of typical packing pattern further supported by PXRD studies of the films.

Preparation of Langmuir-Blodgett composite films based on Bisphenol fluorene and Epoxy bisphenol fluorene with photovoltaic properties

The Langmuir-Blodgett (LB) technique can be used to obtain highly ordered arrangement and assembly of high polymer molecular chains, and the obtained LB films exhibit the controllable structures and special physicochemical properties. Here, we successfully prepared the composite LB films based on bisphenol fluorene (BPF) and epoxy bisphenol fluorene (DGPF) by LB technique, as well as explored the microstructures of the composite LB films by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The different aggregation states of various dye molecules in the composite LB films are investigated by UV–vis. Interestingly, the composite LB film electrodes exhibit promising photoelectrochemical properties. In particular, BPF/MB and DGPF/MB LB films show better photoelectric conversion efficiency. It is attributed to the ordered arrangement of BPF and DGPF and their effective aggregation with dye molecules, which improves the light absorption ability and charge transfer efficiency of the materials. Therefore, the prepared LB films based on the synthetic polymers BPF and DGPF are expected to play an important role in microelectronics.

Preparation of Langmuir-Blodgett composite films based on sericin protein and silk fibroin with good surface-enhanced Raman scattering and photovoltaic properties

In this work, the self-assembled films of sericin protein (SP), silk fibroin (SF), and dye molecules were prepared by the Langmuir-Blodgett (LB) technique. Surface-enhanced Raman scattering (SERS) experiments demonstrated that the SP/saffron T (ST)-80 and SF/ST-60 composite LB films exhibited good Raman enhancement characteristics with enhancement factors (EFs) of 5.74×104 and 7.05×104, respectively. The relative standard deviations (RSDs) of Raman intensity were 7.19% and 18.40%, respectively, confirming the uniformity of the composite LB films. Furthermore, photoelectric conversion efficiencies indicate that the electrodes fabricated from SP/ST and SF/ST film electrodes have high carrier rates and good photocurrent generation properties. This study provides novel insights into the fabrication of multifunctional SP/dye and SF/dye composite LB films, demonstrating their potential applications in SERS and photovoltaic conversion.

Self-assembled composite Langmuir-Blodgett films of carbon nanotubes: An approach to enhance surface-enhanced Raman scattering and photoelectric performance

Self-assembly is a technique that utilizes non-covalent interactions between molecules to assemble into ordered nano-scale aggregates from disordered states. Langmuir-Blodgett (LB) technique is one of the commonly applied methods for constructing molecular assemblies at gas-liquid interfaces. In this study, a series of ordered composite films of amino-functionalized carbon nanotubes (MWCNTs-NH2) and different dye molecules were prepared using LB technique. The surface-enhanced Raman scattering (SERS) performance of MWCNTs-NH2/dye composite films was investigated. The experimental results showed that MWCNTs-NH2/Methylene blue (MB) composite film exhibited good SERS enhancement performance for Rhodamine 6 G (R6G) molecules with an enhanced factor (EF) of 2.16 × 105, and had certain repeatability and uniformity, making it suitable for the detection of trace molecule. The photoelectric conversion efficiency of MWCNTs-NH2/dye composite films were also explored. MWCNTs-NH2/MB composite film not only exhibited the highest photocurrent value but also had the smallest impedance compared with the other films, indicating that it had lower impedance, better carrier transport rate, and more stable performance. This work provides an effective method for fabricating the composite LB films based on the carbon nanotubes with great SERS and photoelectric conversion efficiency.

Chemical gas sensor, surface enhanced Raman scattering and photoelectrics of composite Langmuir-Blodgett films consisting of polypeptide and dye molecules

Langmuir-Blodgett (LB) technology has attracted increasing interest to generate intelligent biomaterials combined with novel peptide molecules. In this work, the composite films based on palmitoyl pentapeptide-4 (PP4) and phthalocyanine dye molecules were prepared by LB technique. The aggregation forms of phthalocyanine dye molecules and the structures/properties of composite films were studied. UV-Vis, FT-IR and SEM and other characterizations proved that the LB films are successfully composited, which may be due to the H-bonding, π-π stacking and electrostatic forces. Interestingly, the TPPS/PP4 LB films show excellent acid-alkali gas response. In addition, the surface-enhanced Raman scattering (SERS) demonstrate that the TsNiPc/PP4 LB film exhibits surface-enhancing properties for crystal violet (CV) molecules. Furthermore, the result demonstrate that the prepared LB films show good photocurrent generation efficiency. This work provides new clues for the preparation of self-assembled films and their applications as gas sensors, SERS and photoelectric device.

Interfacial aggregation behavior of novel carbazole-based composite Langmuir-Blodgett films for photoelectric conversion and catalytic performance

The development of multifunctional film materials from novel organic small molecules has attracted the attention of researchers. In this study, novel carbazole organic molecules (CS-14, CS-38 and CS-39) were successfully composited with TsNiPc and TPPS subphases into multilayer films by LB technology. The nanostructure and morphology of the composite films were successfully assembled and analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). In addition, the stability of the composite film was proved by UV–vis spectroscopy and Fourier transform infrared spectroscopy. The results demonstrate that Langmuir films are transferred to the surface of substrates in different aggregated morphologies. In addition, the self-assembled LB film electrodes exhibit excellent photoelectrochemical performance. The photoelectric conversion of the multilayer films transferred to ITO (indium tin oxide) was tested, and CS-38/TsNiPc Langmuir film exhibits a stronger photoelectric conversion effect. The electrolysis reaction of LB films to water was also tested. Further analysis shows that the composite films with TsNiPc as the subphase all showed better catalytic performance than the composite films with TPPS as the subphase. Therefore, the prepared LB film has the potential to become an optoelectronic functional ultrathin film device.

Preparation of composite Langmuir-Blodgett films based on carbon spheres and wide applications for acid/alkaline gas sensor, surface enhanced Raman scattering and photoelectrics

Through this study, a variety of carbon spheres/dye (CS/dye) composite films were prepared based on the Langmuir-Blodgett (LB) technology. The prepared CS/dye composite films were tested for acid and alkali gases discoloration characteristics. The CS/CR composite film shows good acid/alkaline gas sensing performances, and its characteristic absorption peaks have a significant movement in the UV–vis spectrum. In addition, the surface enhancement of the Raman scattering (SERS) experiment proves the good Raman enhancement performance of the prepared composite LB film with the enhanced factor (EF) of 8.5×104. The relative standard deviation of Raman intensity is 24.74 %, indicating the good reproducibility and uniformity of composite film, which makes it applicable to the detection of trace molecules. Furthermore, the CS/NR composite film has a current density of 1217 μA/cm2 when the potential voltage is 1 V, indicating that the composite film has a high carrier transfer rate, which provides a reference for further exploration of optoelectronic devices of CSs system.

Gas-Responsive and Self-Powered Visual Composite Langmuir–Blodgett Films for Ultrathin Gas Sensors

The complex and variable environments are challenging the development of related detection and analysis. Ammonia (NH3) and hydrogen chloride (HCl) gases are both commonly used in industry, but they are considered to be toxic and corrosive substances that can threaten human health and the environment. Therefore, it is necessary here to develop a convenient, sensitive, and reliable sensor device for acid-alkali gas detection. Herein, we propose the synthesis strategy of an ultrathin film gas sensor based on the pH-responsive, self-powered, and visible composite Langmuir-Blodgett (LB) films. In our work, the LB films with nanometric thicknesses are obtained based on the sensitive materials of two novel carbazole structural sensitizers (abbreviated as CS-35 and CS-37) and several dye molecules. The composite LB films are formed with Carbazole samples and dye molecules through hydrogen bonding, π-π stacking, synergistic electrostatic interactions, and hydrophobic interactions, existing as J-aggregate or H-aggregate. The formation of high-quality and uniform Langmuir films is confirmed with transmission electron microscope (TEM), UV-vis spectrum, atomic force microscopy (AFM), and other measurements. In addition, based on the simple protonation and deprotonation, the prepared LB films can be assembled into a visual sensor for the response of pH gases. The response is confirmed by the study of ultraviolet spectroscopy and electrical output in vertical contact separation mode, which potentially unlocks a sustainable future for the application of ultrathin self-powered gas sensors.

Sensing of Alphacypermethrin Pesticide Using Modified Electrode of Chitosan-Silver Nanowire Nanocomposite Langmuir Blodgett Film

ABSTRACT We report on the sensing of a hazardous pesticide alphacypermethrin (ACM) using electrochemical technique through a nanocomposite film modified electrode. The nanocomposite film comprising of octadecylamine, chitosan, polyvinyl alcohol-silver nanowires and haemoglobin, shortly (OCPAH), was prepared by Langmuir–Blodgett (LB) film deposition technique on various substrates and electrodes. The composite LB film was characterised by UV-visible spectroscopy and scanning electron microscopy, which confirms the stable and multilayer film. The LB film modified electrode was used for sensing ACM pesticide by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV) techniques. The achieved sensing parameters such as limit of detection as 14 nM, 5 nM and 10 nM; linear range as 10–100 nM, 10–40 nM and 50–100 nM/10–100 nM; and sensitivity as 0.418 µA/nM/cm2, 0.259 µA/nM/cm2 and 0.271 µA/nM/cm2 for CV, DPV and SWV techniques, respectively. The reported sensor is found to have stability of 74% upto 20 cycles, the relative standard deviation (RSD) value for metal ion/organic interference species as 2% and for real samples are within 1.4% using CV technique. The reported nanocomposite-based ACM pesticide sensor will open up new options for research on LB film nanocomposite-based sensing of different organophosphorus groups of pesticides.

Construction of Multifunctional and Adjustable Langmuir-Blodgett Composite Films Containing Black Phosphorus with High Stability for Optically Electrical Applications.

Fabrication of composite thin-film materials based on black phosphorus (BP) will greatly broaden the applications of BP in various areas. However, it is still a challenge to prepare a BP-based composite film with good stability and controllable structure. In this work, a series of BP-based composite Langmuir-Blodgett (LB) films are prepared by the self-assembly of polyethyleneimine (PEI)-modified BP nanosheets (BPNSs) (BPNS-PEI) and dye molecules. The presence of PEI greatly improves the stability of BPNSs. As for BPNS-PEI and dye molecules, the electrostatic interactions or π-π stacking interactions ensure the formation of stable composite LB films. Due to the protonation and deprotonation of amino groups, the synthesized BPNS-PEI/dye composite films show a sensitive response to acid and alkali gases, which shows wide application prospects as a highly sensitive gas sensor. Furthermore, surface-enhanced Raman scattering (SERS) proves that the prepared LB films exhibit good reproducibility and obvious Raman enhancement effect on rhodamine 6G molecules. In addition, due to the high carrier transfer rate of the obtained composite films, they possess enhanced photocurrent generation performance than pure BPNS-PEI and pure dye films. The current work demonstrates an effective method for preparing the ordered self-assembled BP-based composite LB films with good SERS and photoelectric conversion performance.

Self-Assembled Black Phosphorus-Based Composite Langmuir-Blodgett Films with an Enhanced Photocurrent Generation Capability and Surface-Enhanced Raman Scattering Properties.

In this work, Langmuir–Blodgett (LB) composite thin films were successfully prepared using black phosphorus nanosheets (BPNS) and dye molecules. Black phosphorus (BP) was first exfoliated in isopropanol solution to form BPNS, and then, BPNS were modified with 4-azidobenzoic acid (Az-BPNS) to improve their stability. The characterization results showed that the synthesized Az-BPNS-dye LB films have a uniform and ordered structure. In addition, the synthesized Az-BPNS-dye LB films exhibit excellent photoelectrochemical performance, and Az-BPNS-methylene blue (MB) produces higher photocurrent compared to Az-BPNS-Neutral red (NR) films. The current work shows an effective way to prepare functionalized BP-based materials and provide evidence for their application in optoelectronic devices.

Facile preparation of self-assembled black phosphorus-based composite LB films as new chemical gas sensors

In recent years, the researches on the modification and functionalization of black phosphorus (BP) materials have attracted more and more attention. In this study, few-layers BP nanosheets (BPNS) were prepared by a simple liquid exfoliation method. However, BPNS has the disadvantages of easy oxidation and poor stability, which will also affect the performance of BP. Therefore, 4-azidobenzoic acid was used to modify the BPNS to improve the stability of BP. In addition, 4-azidobenzoic acid modified BPNS (f-BPNS) and dye molecules can form a composite Langmuir-Blodgett (LB) film through electrostatic interaction or π-π stacking forces. UV–vis, Atomic force microscopy (AFM) and other characterizations were used to prove the successful preparation of the f-BPNS-dye composite LB film. It should be noted that the obtained uniform and dense composite films showed good sensitivity to acid and alkali gas. Moreover, the f-BPNS-dye composite films can still maintain high performance after 10 cycles of acid-alkali tests, indicating that the prepared films have high stability. This work provides a new direction for the preparation of new two-dimensional composite materials and their application in gas sensors.

Preparation and High Photocurrent Generation Enhancement of Self-Assembled Layered Double Hydroxide-Based Composite Dye Films.

Understanding photocurrent conversion of layered double hydroxide (LDH) materials will be a key step in the future application of these materials to light-capturing molecular devices. In the present study, ultrathin nickel-iron layered double hydroxide/dye (NF-LDH/dye) Langmuir-Blodgett (LB) semiconductor films were prepared using an LB device and deposited on an indium tin oxide (ITO) substrate as a photoanode. The photoelectric conversion efficiency of the prepared LB semiconductor film materials was tested. A comparative experiment was performed to effectively explore the photoelectric conversion performances of the LB semiconductor film materials. Specifically, the NF-LDH cast film electrode, the dye cast film electrode, and an ultrathin composite LB film electrode were used as typical samples to explore photoelectric conversion performances. The electrochemical workstation was used to study the photocurrent density, linear scanning voltammetry curve, and electrochemical impedance spectroscopy of LB film electrodes with different layers. The results show that the film electrode cast by LDH alone or dye alone produces weak photocurrent. The photoelectric conversion efficiency of the LB film electrode is enhanced due to the different dyes' molecular structures and/or aggregations on the surface of LDH with various morphological patterns. The combined NF-LDH/dye composite LB film photoelectrode can generate a photocurrent that is 2-5 times stronger than the raw material, and the stable use efficiency is more than 92%. Present obtained composite LB films demonstrated a uniform morphology and good photoelectric conversion ability. This work provides a useful reference for the field of LDH semiconductor optoelectronic devices and solar cells.

Facile Synthesis of Self-Assembled NiFe Layered Double Hydroxide-Based Azobenzene Composite Films with Photoisomerization and Chemical Gas Sensor Performances.

Two kinds of layered double hydroxide (LDH) Langmuir composite films containing azobenzene (Azo) groups were successfully prepared by Langmuir–Blodgett (LB) technology. Then, an X-ray diffractometer (XRD), a transmission electron microscope (TEM), and an atomic force microscope (AFM) were used to investigate the structures of NiFe-LDH and the uniform morphologies of the composite LB films. The photoisomerization and acid–base gas sensor performances of the obtained thin film samples were tested by infrared visible (FTIR) spectroscropy and ultraviolet visible (UV–vis) spectroscropy. It is proved that the Azo dye molecules in the composite film are relatively stable to photoisomerization. In addition, the prepared composite films have high sensing sensitivity and good recyclability for acid–base response gases. The present research proposes a new clue for designing thin film materials for chemical gas response with good stability and sensitivity.

Facile synthesis of self-assembled carbon nanotubes/dye composite films for sensitive electrochemical determination of Cd(II) ions

A new type of voltammetric sensor material has been fabricated via a facile self-assembled method. A modified glassy carbon electrode (GCE) by phenylsulfonic groups grafted multi-walled carbon nanotubes (CNT-SO3H) with dye molecules via Langmuir–Blodgett (LB) assembling (CNT-SO3H/dye-LB/GCE) were prepared for detecting trace levels of cadmium (Cd2+) ions by square wave anodic stripping voltammetry. The synergy effect between CNT-SO3H and dye as well as orderly aggregates in composite LB films contributed to greatly enhancing the determination performance. Under selected conditions, voltammetric response of the fabricated electrochemical sensor in 0.1 M acetate buffer solution containing Bi3+ ions for Cd2+ ions was linear with its concentration in the range 0.1 to 1.2 μM, with a detection limit of 0.08 μM. In addition, the preparation process of self-assembled composite film modified electrodes was simple, non-toxic, exhibiting higher sensitivity and potential application prospects in aspects of heavy metal ions detection and environmental analysis.

Preparation and self-assembly of graphene oxide-dye composite Langmuir films: Nanostructures and aggregations

Graphene oxide (GO)-based nanocomposite films via facile and appropriate self-assembly methods have demonstrated many potential applications in wide fields. This study demonstrates a facile and clean route to prepare graphene oxide-dye composite films using Langmuir-Blodgett (LB) technique at room temperature. By electrostatic interaction between cationic dye molecules and negatively charged GO sheets as well as π-π interactions, GO-dye composite LB films were formed spontaneously. As a soft platform for dye molecules, GO sheets induce dye molecules to self-assemble and form highly ordered structures containing H-aggregates and/or J-aggregates. The morphological characterization results show the formation of GO-dye composite films with smooth and dense surfaces. And the spectral results reveal that dye molecules stack in well-organized aggregates on the surface of GO sheets corresponding to monomers in bulk solution. The present research work about GO-dye composite films by LB method may provide new clues to prepare organized composite films and demonstrate potential applications in many fields.

Formation and tribological properties of composite Langmuir–Blodgett films of stearic acid with molybdenum disulfide and amorphous carbon

The morphology and tribological properties of Langmuir–Blodgett mono- and bilayers of stearic acid with particles of molybdenum disulfide (MoS2) and amorphous carbon (С), prepared on silicon and steel substrates by horizontal deposition (stearic acid–MoS2 and stearic acid–С monolayers) and by the “roll” technique (stearic acid–MoS2/stearic acid–С bilayers), were studied. Incorporation of C and MoS2 particles into the structure of a stearic acid film enhances its wear resistance by a factor of 2.8 and 5.5, respectively. The presence of MoS2 and С particles and of their aggregates of size from ~220 nm to 16.3 μm in stearic acid layers was confirmed by atomic force microscopy.

Architecture effects of glucose oxidase/Au nanoparticle composite Langmuir-Blodgett films on glucose sensing performance

The Langmuir-Blodgett (LB) deposition technique is employed to prepare nano-composite films consisting of glucose oxidase (GOx) and gold nanoparticles (AuNPs) for glucose sensing applications. The GOx and AuNPs are co-adsorbed from an aqueous solution onto an air/liquid interface in the presence of an octadecylamine (ODA) template monolayer, forming a mixed (GOx-AuNP) monolayer. Alternatively, a composite film with a cascade architecture (AuNP/GOx) is also prepared by sequentially depositing monolayers of AuNPs and GOx. The architecture effects of the composite LB films on the glucose sensing are studied. The results show that the presence of AuNPs in the co-adsorption system does not affect the adsorption amount and preferred conformation (α-helix) of GOx. Furthermore, the incorporation of AuNPs in both composite films can significantly improve the sensing performance. However, the enhancement effects of the AuNPs in the two architectures are distinct. The major effect of the AuNPs is on the facilitation of charge-transfer in the (GOx-AuNP) film, but on the increase of catalytic activity in the (AuNP/GOx) one. Therefore, the sensing performance can be greatly improved by utilizing a film combining both architectures (AuNP/GOx-AuNP).

A new voltammetric sensor for sensitive and selective determination of xanthine based on DNA and polyaniline composite Langmuir–Blodgett film

DNA–polyaniline (PAn) complex Langmuir–Blodgett film modified glassy carbon electrode (GCE) was used as a new voltammetric sensor (DNA/PAn-LB/GCE) for xanthine (XA) detection. The characteristic of DNA/PAn-LB film was studied by electrochemical impedance spectroscopy and scanning electron microscope. Electrochemical behaviors of XA at the sensor were studied in pH 7.0 phosphate buffer solutions by cyclic voltammetry and differential pulse anodic voltammetry. The results showed that this new modified electrode exhibited an excellent immunity from uric acid and hypoxanthine interference and a new sensitive and selective electroanalytical method for XA was proposed with wider linear range. Under the optimum conditions, the calibration curve for XA was obtained over the range of 7.0×10−8–1.0×10−5molL−1, with the detection limit of 3.0×10−8molL−1. The practicability of this method was demonstrated by determining the concentration of XA in human serum samples.