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Coatings 2018, 8(4), 141; https://doi.org/10.3390/coatings8040141

Article
Self-Assembled Composite Langmuir Films via Fluorine-Containing Bola-Type Derivative with Metal Ions
1
Hebei Key Laboratory of Applied Chemistry, School of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, China
2
State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China
3
State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
*
Author to whom correspondence should be addressed.
Received: 17 January 2018 / Accepted: 12 April 2018 / Published: 14 April 2018

Abstract

:
The design and preparation of functional bolaamphiphile-based composite films are of key importance for application in a wide variety of fields. This study demonstrates a new approach to constructing composite films by the Langmuir-Blodgett (LB) method using a fluorine-containing bola-type diacid derivative with different metal ions. The bola-type molecule we used could be spread on water surfaces and metal ion subphases to fabricate various nanostructured ultrathin films. The obtained data demonstrated that the employed metal ions, including Ag(I), Cu(II), and Eu(III) ions in subphase solutions, can regulate the organized molecular stacking and form interfacial nanostructures deposited in LB films. It was found that the interfacial coordinating interactions can easily occur between carboxyl groups in a molecular skeleton with metal ions in the formed composite films. The formation of composite films was confirmed by changes in the surface pressure-area isotherms, morphologies, and spectra of the transferred LB films. While various research works have achieved the regulation of functions and nanostructures of sophisticated bola-type compounds, we here demonstrate a simple routine to modulate the nanostructures and organized packing of bola-type compounds composite films by changing the metal ions in subphase solutions.
Keywords:
composite Langmuir film; nanostructure; bola-type diacid; fluorine-containing spacer; self-assembly; metal ion coordination

1. Introduction

Bolaamphiphiles, which include two functional headgroups generally connected by some alkyl chains [1,2,3,4,5,6,7], have attracted much attention due to their special chemical and interfacial behaviors in different self-assembled nanostructures [8,9,10]. Different from typical amphiphilic compounds, bola-type molecules demonstrate changeable conformations at different interfacial situations [11,12,13]. These properties make them extremely suitable for applications in in nanotechnology, electronics, and gene and drug delivery [14,15,16,17,18]. For example, Lin et al. reported the preparation of a dual-responsive bola-type supramolecular amphiphile via complexation between pillar[5]arene and bolaform naphthalimide, which demonstrated good drug-loading efficiency and obvious improved anticancer properties [15].
In addition, the air/water interface can provide a good environment for many molecules/building blocks to construct supramolecular assemblies in a controlled manner [19,20,21,22]. To date, Langmuir and Langmuir-Blodgett (LB) techniques are considered well-known methods to fabricate organized ultrathin films at the air/water interface [23,24,25,26,27,28,29,30,31,32]. Moreover, in comparison to other self-assembly techniques [33,34], special two-dimensional (2D) and three-dimensional (3D) nanostructures can also be fabricated by the LB technique [35,36,37]. In our previous report, some bola-type diacid compounds with an alkyl spacer could react with metal ions to obtain new nanostructures in organized films [38]. Due to the novel ability of carboxylic groups to fabricate interfacial 2D patterns with metal ions, as a subsequent and interesting work, here we have designed and prepared self-assembled composite films of aromatic diacid with large conjugated spacers on different metal ion subphases.
In this paper, we investigated a new compound, 4,4′-(hexafluoroisopropylidene)bis(benzoic acid) (abbreviated as FA), which contains benzoic acid units as headgroups connected with a fluorine-containing CF3 spacer. We characterized this bola-type compound in organized Langmuir films based on the following. Firstly, the functional carboxylic headgroups demonstrated coordinating reactions with various metal ions and could be utilized to fabricate new interfacial nanostructures. Secondly, to investigate the possible packing of bolaform molecules with special spacers, we added the CF3 segment to the spacer in the molecular skeleton. Finally, owing to various coordinating modes with metal ions, the formed interfacial morphologies changed significantly. The investigation of the interfacial self-assembly of different bola-type amphiphiles in Langmuir films demonstrated an important driving force to finish this work.
By utilizing the Langmuir–Blodgett technique, the self-assembled composite films from FA molecules and different metal ions were fabricated and investigated. The prepared nanostructures can be regulated via interfacial coordination with various metal ions. The interfacial interactions and surface structures in the obtained LB films were characterized by many spectral and morphological methods. Lastly, a reasonable model was speculated. Our present research work could provide a platform for new explorations into the fabrication of self-assembled composite films using bola-type compounds.

2. Materials and Methods

2.1. Materials

The materials used in the experiment, including 4,4’-(hexafluoroisopropylidene)bis(benzoic acid) (98%, abbreviated as FA), silver nitrate (AR, 99.8%), copper nitrate trihydrate (Cu(NO3)2·3H2O), and Europium chloride hexahydrate (EuCl3·6H2O), were purchased from Sigma-Aldrich Chemicals (Shanghai, China), Aladdin Chemicals (Shanghai, China), and TCI Shanghai Chemicals, and used as received. The water we employed was prepared from a Millipore Milli-Q Plus purification system. The solvents used throughout the experimental procedure, such as ethanol and chloroform, were obtained from Sinopharm Chemical Reagent Co., Ltd. (Beijing, China).

2.2. Preparation of Composite Langmuir Films

The fabrications of spreading Langmuir films were prepared using a KSV-NIMA Mini-trough LB system [39,40,41]. The trough was thoroughly cleaned using solvents such as chloroform and ethanol, and then filled with pure water or metal ion solutions (0.50 mM) as subphases. Some amount of chloroform solution of FA (0.90 mg/mL) was carefully spread onto the surface using a glass syringe. After waiting 20 min for solvent evaporation and interfacial reaction with metal ions, the surface pressure-area (π–A) isotherms were obtained with a fixed compression speed of 10 cm2/min at room temperature. The FA monolayers were transferred by a horizontal lifting method onto quartz, glass, and CaF2 plates for UV-Vis, XRD, and FT-IR spectral measurements, respectively. One layer of the monolayer film was transferred onto the fresh cleaved mica surface by vertically dipping with a speed of 2 mm/min [42,43].

2.3. Characterization

The nanostructures of the obtained Langmuir films were characterized by a field-emission scanning electron microscope (SEM, S-4800II, Hitachi, Ibaraki, Japan) as well as a transmission electron microscope (TEM, HT7700, Hitachi High-Technologies Corporation, Ibaraki, Japan). The components in films were characterized via a scanning electron microscope (SEM) Field Emission Gun FEI QUANTA FEG 250 (FEI Corporate, Hillsboro, OR, USA) with energy dispersive spectroscopy (EDS) for qualitative chemical analysis. Atomic force microscopy (AFM) images were obtained by a Nanoscope model Multimode 8 Scanning Probe Microscope (Veeco Instrument, Santa Barbara, CA, USA). X-ray photoelectron spectroscopy (XPS) studies were measured on an ESCALab 250Xi (Thermo Fisher Scientific, San Jose, CA, USA) using a 200 W Al Ká monochromated radiation source. X-ray diffraction was measured on an X-ray diffractometer (SMART LAB, Rigaku, Akishima, Japan) using Cu Kα X-ray radiation. FT-IR spectra were conducted on a Fourier infrared spectroscopy (Thermo Nicolet Corporation, Madison, WI, USA) by transferring the obtained multilayer films on CaF2 plates as substrates.

3. Results and Discussion

Figure 1 demonstrates the surface pressure-area (π–A) isotherms of the used FA monolayers from pure water and different metal ions subphases at room temperature, respectively. The curve of pure water surface showed that the surface pressure of FA monolayer increased with compression up to the final surface pressure value of about 16 mN/m. It can be easily observed that when FA was spread on metal ions subphases, the onset and maximum values of surface pressure increased. Interestingly, it should be noted that the surface pressure from the FA-Cu composite Langmuir film showed a sharp increment with an extrapolating molecular area of 0.21 nm2/molecule and a maximum pressure value of 47 mN/m, which indicated that the formed FA-Cu composite films showed more stable characteristics than the other two composite films. Compared with the case on pure water, the significant differences of the isotherms suggested the occurrence of interfacial coordination between carboxyl groups in FA molecules with metal ions in subphase solutions.
In order to characterize the self-assembled morphology and large-area uniformity of FA Langmuir films, AFM images were performed by transferring the films onto a newly cleaved mica substrate. For FA film from pure water surface transferred at 10 mN/m, some aggregates with some holes could be clearly observed, as shown in Figure 2. In addition, for the monolayer LB films of FA from metal ion subphases, as shown in Figure 3, big changes appeared in the morphologies. For the films from the Ag(I) ion subphase, twisted fiber-like nanostructures formed and stacked more densely at high surface pressure. As for the FA-Cu composite Lanmguir film, flat slice aggregates with a diameter of several hundreds of nanometers appeared. In the case of the FA-Eu film, morphologies of dot-like aggregates and blocks were found. In addition, the curves of section analysis in the AFM data demonstrated the height change in the transferred monolayer, and provided useful information about molecular stacking and self-assembly. The present obtained plot curves in the AFM results indicated that the film height in composite films with three used metal ions showed a more organized distribution than that of the film fabricated on the pure water surface. Moreover, the multilayer and monolayer LB films of FA composite films from different subphases were further characterized by SEM and TEM techniques, as shown in Figure 4. Similar morphological changes were obviously observed. In addition, the C, F, and Cu elemental mappings of the prepared monolayer FA-Cu composite film were performed and are shown in Figure 5. It was found that a large number of anchored Cu ions were well distributed onto the obtained composites films. Moreover, the TEM iamge and C/F/Cu elemental mapping of FA-Cu composite film in Figure 6 further confirm the presence and the good distribution of FA molecules and Cu ions in the obtained composite films. It can be reasonably speculated that Cu(II) ions successfully loaded on the FA-Cu composite films via intermolecular corodiantion interaction. The above nanostructural results were in good agreement with the speculation of π–A isotherms, suggesting that there occurred some interfacial coordination interaction between FA molecules and metal ions in the prepared composite films.
To investigate the chemical state and elemental composition in the obtained composite films, the X-ray photoelectron spectra (XPS) of the obtained films were measured and are shown in Figure 7. Firstly, the survey measurement from 0 to 1200 eV for the composite films showed the characteristic C(1s), O(1s), and F(1s) elemental peaks for FA molecules [44,45,46,47,48]. In addition, characteristic Ag(3d), Cu(2p), and Eu(3d) peaks appeared on different metal ions subphases, respectively. Also, according to the relative elemental areas of C(1s), F(1s), and metal ions, the molar ratios of the FA molecule to different metal ions were calculated, giving values of 1:1.86, 1:0.93, and 1:0.46 for FA-Ag, FA-Cu, and FA-Eu composite films, respectively. The above results demonstrated the successful preparation of FA coordinated Langmuir films with used metal ions and different coordination modes in obtained LB composite films.
In addition, the FT-IR spectra of multilayer LB films were also investigated with the data shown in Figure 8. For the films transferred from metal ions subphases, strong vibration bands were observed at 1643 and 1467 cm−1 for FA-Ag films, 1609 and 1401 cm−1 for FA-Cu films, and 1549 and 1413 cm−1 for FA-Eu composite films, respectively. These two bands could be due to the symmetric and antisymmetric stretching vibration of COO groups, respectively [37,38]. According to a previous report from Nakamoto, the number of frequency separations between the symmetric and antisymmetric stretching of COO groups could be utilized as an indicator of interaction types between the carboxylate headgroup and metal ions, to investigate bridging bidentate, monodentate, and chelating bidentate, et al. [49]. The separation number is usually in the range of 200–300 cm−1 for monodentate types, and below 110 cm−1 for chelating bidentate types [37,49]. In the present investigation, the different separation numbers indicated the different coordination reactions between FA molecules with different metal ions.
In addition, broad vibration bands appeared in range of 3000–3500 cm−1 for the obtained FA-Eu composite films, revealing centered peak positions at 3353 and 3186 cm−1. This demonstrated that the composite films contained different types of hydrogen bonding interactions between FA molecules in FA-Eu composite films [37,38]. In addition, the obvious peak at 1658 cm−1 assigned to C=O vibration also showed that there were non-coordinated carboxyl groups in films, which can form hydrogen bonding forces between FA molecules in the prepared films. It could be concluded from the above data that when FA molecules were spread on Eu(III) ions subphase, FA molecules could closely pack one-by-one via intermolecular hydrogen bonding interaction and coordination reaction with Eu(III) ions. However, the coordination process with Eu(III) ions seemed incomplete and still retained a certain amount of carboxyl groups in the formed FA-Eu composite films.
Moreover, Figure 9 shows the XRD patterns of the transferred multilayer LB films of FA from different subphases. Only the curve of FA-Cu composite films showed an obvious diffraction peak centered at 16.1°, which corresponded to the layer distance of 0.55 nm from the calculation of Bragg’s law equation [50,51,52,53]. This indicated the difference of molecular packing modes between the formed FA-Cu organized films with other composite films.
Combined with the above results, the formation process and the self-assembly modes with metal ions of FA composite Langmuir films were proposed, as shown in Figure 10. As mentioned in the above discussion, the XPS measurement demonstrated that 1:2 type and 1:1 type composites were fabricated for FA films on Ag(I) or Cu(II) ion subphases, respectively. In consideration of various conditions, such as coordinating modes with different metal ions and the possible intermolecular stacking in interfacial films, it is rational to speculate that for the Cu(II)-composite film, FA molecules were connected via coordinating interaction through carboxyl groups to fabricate a polymer-like nanostructure, constructing the flat slice nanostructures via strong π–π stacking. In addition, for the case of the Ag(I)-composite film, FA molecules were packed and aligned via cooperative multi-interactions, including coordination reactions with Ag(I) ions, spatial hindrance between the CF3 groups, and partial π–π stacking in aromatic benzene moieties.
In addition, these reasonable molecular arrangements showed good agreement with the results of π–A data and structural characterizations. For example, when FA molecules were self-assembled from the Eu(III) ion subphase, partial carboxyl groups in FA molecules could coordinate with Eu(III) ions, as was confirmed by the above IR data. However, the coordinating process seemed to be incomplete due to the spatial limitation on the two-dimension surface. Therefore, dot-like aggregates were observed, demonstrating phenomena similar to those previously reported for nanostructures from bolaform compounds with metal ions [37,38]. In addition, it should be noted that 3D nano-architectures from bolaamphiphiles with long alkyl chains in molecular structures were usually formed upon compression at the air/water interface [11,50]. In the present case of FA-Eu composite films, the lack of alkyl chains and hydrophobicity from fluorine-containing molecular structures helped to induce the overlap of the neighboring molecules to aggregate and form dot-like domains or nanostructures.

4. Conclusions

In summary, here we designed and investigated the spreading behaviors of a self-assembled fluorine-containing bola-type diacid derivative at the air/water interface. The used bola-type molecules could fabricate organized composite ultrathin films with Ag(I), Cu(II), and Eu(III) ions in subphase solutions. It was interesting to find that different coordinating modes could regulate the stacking modes of the used bolaform molecules in the prepared composite films. The obtained composite films were characterized by various morphological and spectral methods and demonstrated different nanostructures and aggregations. Some rational interfacial self-assembly mechanisms were proposed to explain the formation process of the prepared composite films. Various composite films fabricated via interfacial self-assembly have been designed and prepared to construct organized arrays for use in potential applications, such as catalytic materials, sensors, etc. [54,55,56,57,58,59,60,61,62,63]. The present research provides a platform for new explorations into the construction of self-assembled composite films via interfacial coordination using LB techniques.

Acknowledgments

This work was financially supported by the National Natural Science Foundation of China (Nos. 21473153 and 51771162), the Support Program for the Top Young Talents of Hebei Province, China Postdoctoral Science Foundation (No. 2015M580214), and the Scientific and Technological Research and Development Program of Qinhuangdao City (No. 201701B004).

Author Contributions

Tifeng Jiao and Jingxin Zhou conceived and designed the experiments; Nianrui Qu, Shuxin Sun, Qianran Zhao, and Ruirui Xing performed the experiments; Nianrui Qu, Tifeng Jiao, and Jingxin Zhou analyzed the data; Faming Gao, Lexin Zhang, and Qiuming Peng contributed reagents/materials/analysis tools; Nianrui Qu and Tifeng Jiao wrote the paper.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Fuhrhop, J.H.; Wang, T. Bolaamphiphiles. Chem. Rev. 2004, 104, 2901–2938. [Google Scholar] [CrossRef] [PubMed]
  2. Fuhrhop, J.H.; Matthieu, J. Routes to functional vesicle membranes without proteins. Angew. Chem. Int. Ed. 1984, 23, 100–113. [Google Scholar] [CrossRef]
  3. Fuhrhop, J.H.; Fritsch, D. Bolaamphiphiles form ultrathin, porous and unsymmetric monolayer lipid membranes. Acc. Chem. Soc. 1986, 19, 130–137. [Google Scholar] [CrossRef]
  4. Escamilla, G.H.; Newkome, G.R. Bolaamphiphiles: From golf balls to fibres. Angew. Chem. Int. Ed. 1994, 33, 1937–1940. [Google Scholar] [CrossRef]
  5. Li, Y.; Liu, M. Induced chirality of supramolecular assemblies of some amphiphiles with beta-cyclodextrin through the interaction at the air/water interface. J. Colloid Interface Sci. 2007, 306, 386–390. [Google Scholar] [CrossRef] [PubMed]
  6. Shen, Z.; Wang, T.; Liu, M. Macroscopic chirality of supramolecular gels formed from achiral tris(ethyl cinnamate) benzene-1,3,5-tricarboxamides. Angew. Chem. Int. Ed. 2014, 53, 13424–13428. [Google Scholar] [CrossRef] [PubMed]
  7. Zhang, L.; Lu, Q.; Liu, M. Fabrication of chiral Langmuir-Schaefer films from achiral TPPS and amphiphiles through the adsorption at the air/water interface. J. Phys. Chem. B 2003, 107, 2565–2569. [Google Scholar] [CrossRef]
  8. Fuhrhop, J.H.; David, H.H.; Mathieu, J.; Liman, U.; Winter, H.J.; Boekema, E. Bolaamphiphiles and monolayer lipid membranes. J. Am. Chem. Soc. 1986, 108, 1785–1791. [Google Scholar] [CrossRef]
  9. Iwaura, R.; Yoshida, K.; Masuda, M.; Yase, K.; Shimizu, T. Spontaneous fiber formation and hydrogelation of nucleotide bolaamphiphiles. Chem. Mater. 2002, 14, 3047–3053. [Google Scholar] [CrossRef]
  10. Iwaura, R.; Yoshida, K.; Masuda, M.; Mayumi, O.K.; Yoshida, M.; Shimizu, T. Oligonucleotide-templated self-assembly of nucleotide bolaamphiphiles: DNA-like nanofibers edged by a double-helical arrangement of A-T base pairs. Angew. Chem. Int. Ed. 2003, 42, 1009–1012. [Google Scholar] [CrossRef] [PubMed]
  11. Zhang, L.; Jiang, S.; Liu, M. Configuration and photochemical reaction of a bolaamphiphilic diacid with a diazo resin in monolayers and Langmuir-Blodgett films. J. Colloid Interface Sci. 2003, 261, 417–422. [Google Scholar] [CrossRef]
  12. Yamaguchi, K.; Moriya, A.; Kinoshita, M. Peculiar membrane morphologies of archaebacterial lipid models: 1,1′-polymethylenebis(2-alkyl-sn-glycero-3-phosphocholine). Biochim. Biophys. Acta 1989, 1003, 151–160. [Google Scholar] [CrossRef]
  13. Yamaguchi, K.; Sakamoto, Y.; Moriya, A.; Yamada, K.; Higuchi, T.; Kinoshita, M. Archaebacterial lipid models. Highly thermostable membranes from 1,1′-(1,32-dotriacontamethylene)-bis(2-phytanyl-sn-glycero- 3-phosphocholine). J. Am. Chem. Soc. 1990, 112, 3188–3191. [Google Scholar] [CrossRef]
  14. Cuvier, A.S.; Berton, J.; Stevens, C.V.; Fadda, G.C.; Babonneau, F.; Van Bogaert, I.N.A.; Soetaert, W.; Pehau-Arnaudet, G.; Baccile, N. pH-triggered formation of nanoribbons from yeast-derived glycolipid biosurfactants. Soft Matter 2014, 10, 3950–3959. [Google Scholar] [CrossRef] [PubMed]
  15. Lin, X.; Jia, K.K.; Wang, Y.C.; Shao, W.; Yao, C.H.; Peng, L.M.; Zhang, D.M.; Hu, X.Y.; Wang, L.Y. Dual-responsive bola-type supra-amphiphile constructed from water-soluble pillar[5]arene and naphthalimide-containing amphiphile for intracellular drug delivery. ACS Appl. Mater. Interfaces 2017, 9, 4843–4850. [Google Scholar]
  16. Kang, Y.T.; Cai, Z.G.; Tang, X.Y.; Liu, K.; Wang, G.T.; Zhang, X. An Amylase-responsive bolaform supra-amphiphile. ACS Appl. Mater. Interfaces 2016, 8, 4927–4933. [Google Scholar] [CrossRef] [PubMed]
  17. Van Bogaert, I.N.A.; Buyst, D.; Martins, J.C.; Roelants, S.L.K.W.; Soetaert, W.K. Synthesis of bolaform biosurfactants by an engineered Starmerella bombicola yeast. Biotechnol. Bioeng. 2016, 113, 2644–2651. [Google Scholar] [CrossRef] [PubMed]
  18. Smith, T.J.; Wang, C.X.; Abbott, N.L. Redox-triggered mixing and demixing of surfactants within assemblies formed in solution and at surfaces. J. Colloid Interface Sci. 2017, 502, 122–133. [Google Scholar] [CrossRef] [PubMed]
  19. Yuan, J.; Liu, M. Chiral molecular assemblies from a novel achiral amphiphilic 2-(heptadecyl) naphtha[2,3]imidazole through interfacial coordination. J. Am. Chem. Soc. 2003, 125, 5051–5056. [Google Scholar] [CrossRef] [PubMed]
  20. Liu, Y.; Wang, T.; Huan, Y.; Li, Z.; He, G.; Liu, M. Self-assembled supramolecular nanotube yarn. Adv. Mater. 2013, 25, 5875–5879. [Google Scholar] [CrossRef] [PubMed]
  21. Cao, H.; Zhu, X.; Liu, M. Self-assembly of racemic alanine derivatives: Unexpected chiral twist and enhanced capacity for the discrimination of chiral species. Angew. Chem. Int. Ed. 2013, 52, 4122–4126. [Google Scholar] [CrossRef] [PubMed]
  22. Deng, M.; Zhang, L.; Jiang, Y.; Liu, M. Role of achiral nucleobases in multicomponent chiral self-assembly: Purine-triggered helix and chirality transfer. Angew. Chem. Int. Ed. 2016, 55, 15062–15066. [Google Scholar] [CrossRef] [PubMed]
  23. Yang, J.; Choi, M.K.; Kim, D.H.; Hyeon, T. Designed assembly and integration of colloidal nanocrystals for device applications. Adv. Mater. 2016, 28, 1176–1207. [Google Scholar] [CrossRef] [PubMed]
  24. Yonamine, Y.; Cervantes-Salguero, K.; Minami, K.; Kawamata, I.; Nakanishi, W.; Hill, J.P.; Murata, S.; Ariga, K. Supramolecular 1-D polymerization of DNA origami through a dynamic process at the 2-dimensionally confined air-water interface. Phys. Chem. Chem. Phys. 2016, 18, 12576–12581. [Google Scholar] [CrossRef] [PubMed]
  25. Kim, M.S.; Ma, L.; Choudhury, S.; Moganty, S.S.; Wei, S.; Archer, L.A. Fabricating multifunctional nanoparticle membranes by a fast layer-by-layer Langmuir-Blodgett process: Application in lithium-sulfur batteries. J. Mater. Chem. A 2016, 4, 14709–14719. [Google Scholar] [CrossRef]
  26. El Garah, M.; Dianat, A.; Cadeddu, A.; Gutierrez, R.; Cecchini, M.; Cook, T.R.; Ciesielski, A.; Stang, P.J.; Cuniberti, G.; Samori, P. Atomically precise prediction of 2D self-assembly of weakly bonded nanostructures: STM insight into concentration-dependent architectures. Small 2016, 12, 343–350. [Google Scholar] [CrossRef] [PubMed]
  27. Lotito, V.; Zambelli, T. Approaches to self-assembly of colloidal monolayers: A guide for nanotechnologists. Adv. Colloid Interface Sci. 2017, 246, 217–274. [Google Scholar] [CrossRef] [PubMed]
  28. Toor, A.; Feng, T.; Russell, T.P. Self-assembly of nanomaterials at fluid interfaces. Eur. Phys. J. E 2016, 39, 57. [Google Scholar] [CrossRef] [PubMed]
  29. Hao, L.J.; Fu, X.L.; Li, T.J.; Zhao, N.R.; Shi, X.T.; Cui, F.Z.; Du, C.; Wang, Y.J. Surface chemistry from wettability and charge for the control of mesenchymal stem cell fate through self-assembled monolayers. Colloid Surf. B 2016, 148, 549–556. [Google Scholar] [CrossRef] [PubMed]
  30. He, W.L.; Fang, F.; Ma, D.M.; Chen, M.; Qian, D.J.; Liu, M.H. Palladium-directed self-assembly of multi-titanium(IV)-porphyrin arrays on the substrate surface as sensitive ultrathin films for hydrogen peroxide sensing, photocurrent generation, and photochromism of viologen. Appl. Surf. Sci. 2018, 427, 1003–1010. [Google Scholar] [CrossRef]
  31. Hoffmann-Vogel, R. Imaging prototypical aromatic molecules on insulating surfaces: A review. Rep. Prog. Phys. 2018, 81, 016501. [Google Scholar] [CrossRef] [PubMed]
  32. Zhu, L.; Chen, F.; Ma, X.Y.; Qiang, X.; Li, Z.G.; Dong, C.; Zang, D.Y. Tadpole-shaped POSS-based copolymers and the aggregation behavior at air/water interface. Adv. Condens. Matter Phys. 2018, 3787843. [Google Scholar] [CrossRef]
  33. Liu, Y.; Hou, C.; Jiao, T.; Song, J.; Zhang, X.; Xing, R.; Zhou, J.; Zhang, L.; Peng, Q. Self-assembled AgNP-containing nanocomposites constructed by electrospinning as efficient dye photocatalyst materials for wastewater treatment. Nanomaterials 2018, 8, 35. [Google Scholar] [CrossRef] [PubMed]
  34. Zhou, J.; Gao, F.; Jiao, T.; Xing, R.; Zhang, L.; Zhang, Q.; Peng, Q. Selective Cu(II) ion removal from wastewater via surface charged self-assembled polystyrene-Schiff base nanocomposites. Colloid Surf. A-Physicochem. Eng. Asp. 2018, 545, 60–67. [Google Scholar] [CrossRef]
  35. Luo, X.; Ma, K.; Jiao, T.; Xing, R.; Zhang, L.; Zhou, J.; Li, B. Graphene oxide-polymer composite Langmuir films constructed by interfacial thiol-ene photopolymerization. Nanoscale Res. Lett. 2017, 12, 99. [Google Scholar] [CrossRef] [PubMed]
  36. Liu, M.H.; Cai, J.F. Silver(I) ion induced reverse U-shape monolayers of poly(methylenebis(benzimidazoles)) at the air/water interface. Langmuir 2000, 16, 2899–2901. [Google Scholar] [CrossRef]
  37. Lu, Q.; Luo, Y.; Li, L.; Liu, M. Self-assembled supramolecular architecture of a bolaamphiphilic diacid on the subphases containing Ag(I) and Eu(III) metal ions. Langmuir 2003, 19, 285–291. [Google Scholar] [CrossRef]
  38. Jiao, T.; Liu, M. Supramolecular nano-architectures and two-dimensional/three-dimensional aggregation of a bolaamphiphilic diacid at the air/water interface. Thin Solid Films 2005, 479, 269–276. [Google Scholar] [CrossRef]
  39. Duan, P.; Qin, L.; Liu, M. Langmuir-Blodgett films and chiroptical switch of an azobenzene-containing dendron regulated by the in situ host-guest reaction at the air/water interface. Langmuir 2011, 27, 1326–1331. [Google Scholar] [CrossRef] [PubMed]
  40. Zhou, X.; Cao, H.; Yang, D.; Zhang, L.; Jiang, L.; Liu, M. Two-dimensional alignment of self-assembled organic nanotubes through Langmuir–Blodgett technique. Langmuir 2016, 32, 13065–13072. [Google Scholar] [CrossRef] [PubMed]
  41. Xie, F.; Zhuo, C.; Hu, C.; Liu, M. Evolution of nanoflowers and nanospheres of zinc bisporphyrinate tweezers at the air/water interface. Langmuir 2017, 33, 3694–3701. [Google Scholar] [CrossRef] [PubMed]
  42. Guo, P.; Zhang, L.; Liu, M. A supramolecular chiroptical switch exclusively from an achiral amphiphile. Adv. Mater. 2006, 18, 177–180. [Google Scholar] [CrossRef]
  43. Huang, X.; Li, C.; Jiang, S.G.; Wang, X.S.; Zhang, B.W.; Liu, M.H. Self-assembled spiral nanoarchitecture and supramolecular chirality in Langmuir-Blodgett films of an achiral amphiphilic barbituric acid. J. Am. Chem. Soc. 2004, 126, 1322–1323. [Google Scholar] [CrossRef] [PubMed]
  44. Jiang, J.; Meng, Y.; Zhang, L.; Liu, M. Self-assembled single-walled metal-helical nanotube (M-HN): Creation of efficient supramolecular catalysts for asymmetric reaction. J. Am. Chem. Soc. 2016, 138, 15629–15635. [Google Scholar] [CrossRef] [PubMed]
  45. Guo, R.; Jiao, T.; Li, R.; Chen, Y.; Guo, W.; Zhang, L.; Zhou, J.; Zhang, Q.; Peng, Q. Sandwiched Fe3O4/carboxylate graphene oxide nanostructures constructed by layer-by-layer assembly for highly efficient and magnetically recyclable dye removal. ACS Sustain. Chem. Eng. 2018, 6, 1279–1288. [Google Scholar] [CrossRef]
  46. Liu, C.; Yang, D.; Jin, Q.; Zhang, L.; Liu, M. A chiroptical logic circuit based on self-assembled soft materials containing amphiphilic spiropyran. Adv. Mater. 2016, 28, 1644–1649. [Google Scholar] [CrossRef] [PubMed]
  47. Liu, M.; Zhang, L.; Wang, T. Supramolecular chirality in self-assembled systems. Chem. Rev. 2015, 115, 7304–7397. [Google Scholar] [CrossRef] [PubMed]
  48. Zhou, J.; Liu, Y.; Jiao, T.; Xing, R.; Yang, Z.; Fan, J.; Liu, J.; Li, B.; Peng, Q. Preparation and enhanced structural integrity of electrospun poly(ε-caprolactone)-based fibers by freezing amorphous chains through thiol-ene click reaction. Colloid Surf. A-Physicochem. Eng. Asp. 2018, 538, 7–13. [Google Scholar] [CrossRef]
  49. Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coordination Compounds; Wiley: New York, NY, USA, 1986. [Google Scholar]
  50. Duan, P.F.; Li, Y.G.; Jiang, J.; Wang, T.Y.; Liu, M.H. Towards a universal organogelator: A general mixing approach to fabricate various organic compounds into organogels. Sci. China Chem. 2011, 54, 1051–1063. [Google Scholar] [CrossRef]
  51. Lu, X.; Tao, L.; Song, D.; Li, Y.; Gao, F. Bimetallic [email protected] nanorods based ultrasensitive acetylcholinesterase biosensor for determination of organophosphate pesticides. Sens. Actuators B Chem. 2018, 255, 2575–2581. [Google Scholar] [CrossRef]
  52. Song, J.; Xing, R.; Jiao, T.; Peng, Q.; Yuan, C.; Möhwald, H.; Yan, X. Crystalline dipeptide nanobelts based on solid-solid phase transformation self-assembly and their polarization imaging of cells. ACS Appl. Mater. Interfaces 2018, 10, 2368–2376. [Google Scholar] [CrossRef] [PubMed]
  53. Huo, S.; Duan, P.; Jiao, T.; Peng, Q.; Liu, M. Self-assembled luminescent quantum dots to generate full-color and white circularly polarized light. Angew. Chem. Int. Ed. 2017, 56, 12174–12178. [Google Scholar] [CrossRef] [PubMed]
  54. Zhao, F.P.; Repo, E.; Meng, Y.; Wang, X.T.; Yin, D.L.; Sillanpaa, M. An EDTA-beta-cyclodextrin material for the adsorption of rare earth elements and its application in preconcentration of rare earth elements in seawater. J. Colloid Interface Sci. 2016, 465, 215–224. [Google Scholar] [CrossRef] [PubMed]
  55. Mostafa, M.S.; Bakr, A.S.A.; El Naggar, A.M.A.; Sultan, E.S.A. Water decontamination via the removal of Pb (II) using a new generation of highly energetic surface nano-material: Co+2Mo+6 LDH. J. Colloid Interface Sci. 2016, 461, 261–272. [Google Scholar] [CrossRef] [PubMed]
  56. Catala, L.; Mallah, T. Nanoparticles of Prussian blue analogs and related coordination polymers: From information storage to biomedical applications. Coord. Chem. Rev. 2017, 346, 32–61. [Google Scholar] [CrossRef]
  57. Galanti, A.; Kotova, O.; Blasco, S.; Johnson, C.J.; Peacock, R.D.; Mills, S.; Boland, J.J.; Albrecht, M.; Gunnlaugsson, T. Exploring the Effect of Ligand Structural Isomerism in Langmuir-Blodgett Films of Chiral Luminescent Eu-III Self-Assemblies. Chem. Eur. J. 2016, 22, 9709–9723. [Google Scholar] [CrossRef] [PubMed]
  58. Ermakova, E.V.; Meshkov, I.N.; Enakieva, Y.Y.; Zvyagina, A.I.; Ezhov, A.A.; Mikhaylov, A.A.; Gorbunova, Y.G.; Chernyshev, V.V.; Kalinina, M.A.; Arslanov, V.V. Effect of metalation-demetalation reactions on the assembly and properties of 2D supramolecular arrays of tetrapyridylporphyrin and its Zn(II)-complex. Surf. Sci. 2017, 660, 39–46. [Google Scholar] [CrossRef]
  59. Das, K.; Kundu, S. Subphase pH induced monolayer to multilayer collapse of fatty acid Salt Langmuir monolayer at lower surface pressure. Colloid Surf. A-Physicochem. Eng. Asp. 2016, 492, 54–61. [Google Scholar] [CrossRef]
  60. He, W.L.; Chen, J.L.; Chen, M.; Qian, D.J. Interfacial self-assembly, characterization, electrochemical, and photo-catalytic properties of porphyrin-ruthenium complex/polyoxomelate triad hybrid multilayers. Colloid Surf. A 2016, 509, 1–10. [Google Scholar] [CrossRef]
  61. Li, S.Y.; Du, L.; Wei, Z.M.; Wang, W.X. Aqueous-phase aerosols on the air-water interface: Response of fatty acid Langmuir monolayers to atmospheric inorganic ions. Sci. Total Environ. 2017, 580, 1155–1161. [Google Scholar] [CrossRef] [PubMed]
  62. Todosijevic, M.N.; Brezesinski, G.; Savic, S.D.; Neubert, R.H.H. Sucrose esters as biocompatible surfactants for penetration enhancement: An insight into the mechanism of penetration enhancement studied using stratum corneum model lipids and Langmuir monolayers. Eur. J. Pharm. Sci. 2017, 99, 161–172. [Google Scholar] [CrossRef] [PubMed]
  63. Adams, E.M.; Champagne, A.M.; Williams, J.B.; Allen, H.C. Interfacial properties of avian stratum corneum monolayers investigated by Brewster angle microscopy and vibrational sum frequency generation. Chem. Phys. Lipids 2017, 208, 1–9. [Google Scholar] [CrossRef] [PubMed]
Figure 1. Surface pressure-area isotherms of Langmuir films of compound FA on pure water surface (a) and metal ions subphases with a concentration of 0.5 mM (b, AgNO3; c, Cu(NO3)2; d, EuCl3). The inserted picture represents the molecular structure and the three-dimensional (3D) space-filling model of the FA molecule.
Figure 1. Surface pressure-area isotherms of Langmuir films of compound FA on pure water surface (a) and metal ions subphases with a concentration of 0.5 mM (b, AgNO3; c, Cu(NO3)2; d, EuCl3). The inserted picture represents the molecular structure and the three-dimensional (3D) space-filling model of the FA molecule.
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Figure 2. Atomic force microscopy (AFM) image with section analysis of the transferred monolayer film of compound FA from pure water at a pressure of 8 mN/m.
Figure 2. Atomic force microscopy (AFM) image with section analysis of the transferred monolayer film of compound FA from pure water at a pressure of 8 mN/m.
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Figure 3. AFM images with section analysis of the transferred monolayer Langmuir-Blodgett (LB) films of compound FA from different metal ion subphases: (a,b), 5 and 15 mN/m, Ag(I) ions; (c,d), 5 and 25 mN/m, Cu(II) ions; (e,f), 5 and 15 mN/m, Eu(III) ions.
Figure 3. AFM images with section analysis of the transferred monolayer Langmuir-Blodgett (LB) films of compound FA from different metal ion subphases: (a,b), 5 and 15 mN/m, Ag(I) ions; (c,d), 5 and 25 mN/m, Cu(II) ions; (e,f), 5 and 15 mN/m, Eu(III) ions.
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Figure 4. SEM images of the transferred multilayer and TEM images of the transferred monolayer films of compound FA from different subphases: (a,e), 8mN/m, pure water surface; (b,f), 15 mN/m, Ag(I) ions; (c,g), 25 mN/m, Cu(II) ions; (d,h), 15 mN/m, Eu(III) ions.
Figure 4. SEM images of the transferred multilayer and TEM images of the transferred monolayer films of compound FA from different subphases: (a,e), 8mN/m, pure water surface; (b,f), 15 mN/m, Ag(I) ions; (c,g), 25 mN/m, Cu(II) ions; (d,h), 15 mN/m, Eu(III) ions.
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Figure 5. SEM image of the prepared monolayer FA-Cu composite film (a), and C/F/Cu elemental mapping (bd).
Figure 5. SEM image of the prepared monolayer FA-Cu composite film (a), and C/F/Cu elemental mapping (bd).
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Figure 6. TEM images of the prepared monolayer FA-Cu composite film with C/F/Cu elemental mapping.
Figure 6. TEM images of the prepared monolayer FA-Cu composite film with C/F/Cu elemental mapping.
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Figure 7. X-ray photoelectron spectroscopy (XPS) curves of the transferred multilayer LB films of compound FA from different subphases.
Figure 7. X-ray photoelectron spectroscopy (XPS) curves of the transferred multilayer LB films of compound FA from different subphases.
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Figure 8. IR spectra of the transferred multilayer FA composite films from various subphase solutions.
Figure 8. IR spectra of the transferred multilayer FA composite films from various subphase solutions.
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Figure 9. XRD patterns of the transferred multilayer LB films of compound FA from different subphases.
Figure 9. XRD patterns of the transferred multilayer LB films of compound FA from different subphases.
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Figure 10. Schematic illustrations of self-assembly processes in FA coordinated Langmuir films.
Figure 10. Schematic illustrations of self-assembly processes in FA coordinated Langmuir films.
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