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Interfacial Properties and Aggregates of Novel Redox-Active Surfactant to Synthesize Silver Nanoparticles at the Air/Water Interface
Abstract
An anionic and amphiphilic molecule, AQua (AQ-NH-(CH2)10COOH; where AQ is anthraquinone), which has two stimuli responsive functional-groups, can form self-assembled interfacial aggregates at the air-water interface and, their morphologies can be controlled by changing the subphase conditions such as the pH of the subphase. These interfacial morphologies may be altered from planar structures to wormlike aggregates which is a very rare observation in the literature. Moreover, the unique functional groups of AQua give possibility to reduce metal cations and allow the formation of organic/inorganic nanocomposite structures at the interface. In this context, formation of silver nanoparticles (AgNPs) via AQua-based self-assembled structures at the interface was studied using Langmuir techniques. The kinetics of the reduction process as well as the effect of various parameters were systematically examined. This study demonstrates that interfacial configuration of the AQua molecule at the interface as well as its orientation has a vital role in the morphology of either organic or inorganic self-assemblies formed. The morphology may be adjusted and designed interfacial structures may be obtained. The interfacial properties of AQua, a novel material, may be used in a wide variety of fields such as biotechnology, medicine, energy and pharmaceuticals.
Although having been increasingly studied, there is still controversy as to when the addition of nanoparticles could improve the drag reduction performance of polymer drag reducer and particularly what is the underlying mechanism from the fluid dynamics viewpoint. The drag reduction effects of adding SiO2 nanoparticles to various polymer polyacrylamide (PAM) solutions were examined in this work. The optimal combination of SiO2 nanoparticles with cationic polyacrylamide was confirmed. Interestingly, the addition of SiO2 nanoparticles to cationic polyacrylamide solution was shown to be quite efficient for reducing drag, but only at higher flow rates with Reynolds numbers more than 6000, below which the nanoparticle addition is even negative. The addition of SiO2 nanoparticles to the PAM solution is supposed to play a dual role. The first is an increase in flow resistance caused by the Brownian motion of nanoparticles, while the second is a decrease in flow resistance caused by acting as nodes to protect the polymer chain from shear-induced breaking under high shear action. At optimal nanoparticle concentration and under higher Reynolds numbers, the later effect is dominant, which could improve the drag reduction performance of polymer drag reducers. Our work should serve as a guide for the application of natural gas fracturing, where the flow rate is frequently very high.
Memristive devices have shown promising applications in various fields (e.g., non‐volatile memory, reconfigurable switches, and bio‐inspired neuromorphic computing). Despite the significant advances in this field, the exploration of nanomaterials with tunable composition, thickness, dimension, and conductivity for memristive devices is still in great necessity. Here, the transformation of the ultrathin film polydopamine (PDA) obtained at air/water interface from amorphous to quasi‐ordered structure is revealed. Owing to the unique feature, the self‐assembled PDA film at air/water interface is firstly employed as the active material in constructing write‐once‐read‐many‐times (WORM) memory devices. With an increase in the applied electric field, the device shows a switching from high resistance state (HRS, OFF state) to low resistance state (LRS, ON state) with a high ON/OFF current ratio of >103. Furthermore, the abundant amidogen and phenolic hydroxyl group enable the in situ Ag nanoparticle decoration on the PDA film, which can be further used in the construction of anisotropic volatile memristors with a high ON/OFF current ratio (>104), exceptional stability and good integrability. The potential application of polydopamine film obtained at air/water interface in fabricating organic resistive memory device with a high ON/OFF current ratio over 103 is shown. When decorated with Ag nanoparticles, this film can be further used in the construction of anisotropic volatile memristors with high ON/OFF current ratio (>104), exceptional stability and good integrability.
The welding and sintering of nanomaterials is usually achieved at high temperatures and high pressures. Here, it is found that merging of metal nanoparticles occurs under ambient conditions in an aqueous solution via protein bonding. It is discovered that the silver nanoparticles from the in situ reduction of silver ammonium ions by glucose undergo confined nucleation and growth and are bound by ultrathin amyloid‐like β‐sheet stacking of lysozyme. This merging of silver nanoparticles creates a freestanding large‐area (e.g., 400 cm2) 2D silver film at the air/water interface with a purity up to 98% and controls nanoscale thickness. This reaction system is general to other proteins and metals, and shows the great ability for controlled synthesis of highly reflective and highly conductive silver films with elongation nearly 10 times higher than that of pure metal without protein bonding. The ultrathin protein‐bonding layer functions as a key mediator to dynamically tune the silver conductance in response to external pressures and strains. The sensors exhibit ultrasensitive capability for stealth transmission of Morse code and for silent speech recording via the detection of tiny vibrations of the human throat. This approach will shed light on the development of protein bonding of a given material for bespoke functions. A freestanding metal film forms under ambient conditions in an aqueous solution via protein bonding. The ultrathin protein‐bonding layer functions as a key mediator to dynamically tune the silver conductance in response to external pressures and strains. Sensors exhibit ultrasensitive capability for stealth transmission of Morse code and for silent speech recording via the detection of tiny vibrations of the human throat.
The hybrid conducting polymers (HCPs) possesses unusual properties of both conducting polymers (CPs) and organic/inorganic nanoparticles, which drawn much attraction to the scientist and researchers. The processing of HCPs have helped in overcoming the drawbacks associated with CPs such as poor processability, solubility, stability and low yield. In view of this, the present review article highlights the important synthesis techniques of HCPs and their conduction mechanism. Additionally, much attention has been paid to their diverse applications in energy storage devices, EMI shielding, sensors, biomedicals, anti-corrosive coatings. Finally, the future prospects and current challenges of such polymers have also been overviewed. © 2017 The Korean Society of Industrial and Engineering Chemistry.
We describe herein the significance of a sodium citrate and tannic acid mixture in the synthesis of spherical silver nanoparticles (AgNPs). Monodisperse AgNPs were synthesized via reduction of silver nitrate using a mixture of two chemical agents: sodium citrate and tannic acid. The shape, size and size distribution of silver particles were determined by UV–Vis spectroscopy, dynamic light scattering (DLS) and scanning transmission electron microscopy (STEM). Special attention is given to understanding and experimentally confirming the exact role of the reagents (sodium citrate and tannic acid present in the reaction mixture) in AgNP synthesis. The oxidation and reduction potentials of silver, tannic acid and sodium citrate in their mixtures were determined using cyclic voltammetry. Possible structures of tannic acid and its adducts with citric acid were investigated in aqueous solution by performing computer simulations in conjunction with the semi-empirical PM7 method. The lowest energy structures found from the preliminary conformational search are shown, and the strength of the interaction between the two molecules was calculated. The compounds present on the surface of the AgNPs were identified using FT-IR spectroscopy, and the results are compared with the IR spectrum of tannic acid theoretically calculated using PM6 and PM7 methods. The obtained results clearly indicate that the combined use of sodium citrate and tannic acid produces monodisperse spherical AgNPs, as it allows control of the nucleation, growth and stabilization of the synthesis process.
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The online version of this article (doi:10.1007/s11051-017-3973-9) contains supplementary material, which is available to authorized users.
Recent advances in nanoscience and nanotechnology radically changed the way we diagnose, treat, and prevent various diseases in all aspects of human life. Silver nanoparticles (AgNPs) are one of the most vital and fascinating nanomaterials among several metallic nanoparticles that are involved in biomedical applications. AgNPs play an important role in nanoscience and nanotechnology, particularly in nanomedicine. Although several noble metals have been used for various purposes, AgNPs have been focused on potential applications in cancer diagnosis and therapy. In this review, we discuss the synthesis of AgNPs using physical, chemical, and biological methods. We also discuss the properties of AgNPs and methods for their characterization. More importantly, we extensively discuss the multifunctional bio-applications of AgNPs; for example, as antibacterial, antifungal, antiviral, anti-inflammatory, anti-angiogenic, and anti-cancer agents, and the mechanism of the anti-cancer activity of AgNPs. In addition, we discuss therapeutic approaches and challenges for cancer therapy using AgNPs. Finally, we conclude by discussing the future perspective of AgNPs.
Using two-phase (water–toluene) reduction of AuCl4– by sodium borohydride in the presence of an alkanethiol, solutions of 1–3 nm gold particles bearing a surface coating of thiol have been prepared and characterised; this novel material can be handled as a simple chemical compound.
Silver/alanine nanocomposites with varying mass percentage of silver have been produced. The size of the silver nanoparticles seems to drive the formation of the nanocomposite, yielding a homogeneous dispersion of the silver nanoparticles in the alanine matrix or flocs of silver nanoparticles segregated from the alanine crystals. The alanine crystalline orientation is modified according to the particle size of the silver nanoparticles. Concerning a mass percentage of silver below 0.1%, the nanocomposites are homogeneous, and there is no particle aggregation. As the mass percentage of silver is increased, the system becomes unstable, and there is particle flocculation with subsequent segregation of the alanine crystals. The nanocomposites have been analyzed by transmission electron microscopy (TEM), UV-Vis absorption spectroscopy, X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy and they have been tested as radiation detectors by means of electron spin resonance (ESR) spectroscopy in order to detect the paramagnetic centers created by the radiation. In fact, the sensitivity of the radiation detectors is optimized in the case of systems containing small particles (30 nm) that are well dispersed in the alanine matrix. As the agglomeration increases, particle growth (up to 1.5 μm) and segregation diminish the sensitivity. In conclusion, nanostructured materials can be used for optimization of alanine sensitivity, by taking into account the influence of the particles size of the silver nanoparticles on the detection properties of the alanine radiation detectors, thus contributing to the construction of small-sized detectors.
Organic-inorganic hybrid materials do not represent only a creative alternative to design new materials and compounds for academic research, but their improved or unusual features allow the development of innovative industrial applications. Nowadays, most of the hybrid materials that have already entered the market are synthesised and processed by using conventional soft chemistry based routes developed in the eighties. These processes are based on: a) the copolymerisation of functional organosilanes, macromonomers, and metal alkoxides, b) the encapsulation of organic components within sol-gel derived silica or metallic oxides, c) the organic functionalisation of nanofillers, nanoclays or other compounds with lamellar structures, . The chemical strategies (self-assembly, nanobuilding block approaches, hybrid MOF (Metal Organic Frameworks), integrative synthesis, coupled processes, bio-inspired strategies, ) offered nowadays by academic research allow, through an intelligent tuned coding, the development of a new vectorial chemistry, able to direct the assembling of a large variety of structurally well defined nano-objects into complex hybrid architectures hierarchically organised in terms of structure and functions. Looking to the future, there is no doubt that these new generations of hybrid materials, born from the very fruitful activities in this research field, will open a land of promising applications in many areas: optics, electronics, ionics, mechanics, energy, environment, biology, medicine for example as membranes and separation devices, functional smart coatings, fuel and solar cells, catalysts, sensors, .
The creation of nanoscale materials for advanced structures has led to a growing interest in the area of biomineralization. Numerous microorganisms are capable of synthesizing inorganic-based structures. For example, diatoms use amorphous silica as a structural material, bacteria synthesize magnetite (Fe3O4) particles and form silver nanoparticles, and yeast cells synthesize cadmium sulphide nanoparticles. The process of biomineralization and assembly of nanostructured inorganic components into hierarchical structures has led to the development of a variety of approaches that mimic the recognition and nucleation capabilities found in biomolecules for inorganic material synthesis. In this report, we describe the in vitro biosynthesis of silver nanoparticles using silver-binding peptides identified from a combinatorial phage display peptide library.
Recently, nanomaterial-based adhesives have arised as alternatives to be used in the industrial field or to provide the next generation of biomedical adhesives with their enhanced mechanical properties and adhesion strengths. In this work, we developed a method for achieving adhesion between two PDMA (Poly dimethylacrylamide) hydrogel surfaces by using different nanomaterial-based adhesive dispersions with different sizes and shapes that have high mechanical adhesion strength. We obtained a new adhesive consisting of a lipid-based nanotube formed by the special custom-made molecule AQua (C25H29NO4) and measured the adhesion force between the hydrogel surfaces. Our results revealed that lipid AQua nanotube dispersions, which also has a high potential as drug delivery agents, showed efficient adhesion by strongly binding the hydrogel strips together and exhibit better adhesive effects in comparison with other nanomaterials that are used for this purpose. This high adhesion capability is also valid for various hydrogels that have different chemical properties or rigidities and soft tissues such as calf livers. So, the system developed here is believed to have a usage potential in different industrial and biomedical areas.
The “flipping method” is a new straightforward way to both adsorb and organize microparticles at a liquid interface, with ultralow amounts of surfactant and no other external force than gravity. Here we demonstrate that it allows one to adsorb a variety of inorganic nanoparticles at an air/water interface, with an organization, directly controlled by the surfactant concentration, ranging from amorphous to highly crystalline two-dimensional assemblies. With micromolar amounts of a conventional cationic surfactant (Dodecyltrimethylammonium bromide, DTAB), nanoparticles of different compositions (silica, silver, gold), sizes (down to 100 nm) and shapes (spheres, cubes) adsorb from the bulk and directly organize at the air/water interface, resulting in marked optical properties such as reflectivity or intense structural coloration.
Nanomaterials (NMs) have gained prominence in technological advancements due to their tunable physical, chemical and biological properties wtih enhanced performance over their bulk counterparts. NMs are categorized depending on their size, composition, shape, and origin. The ability to predict the unique properties of NMs increases the value of each classification. Due to increased growth of production of NMs and their industrial applications, issues relating toxicity are inevitable. The aim of this review is to compare the man-made (engineered) and naturally occurring nanoparticles (NPs) and nanostructured materials (NSMs) to identify their nanoscale properties and to define the specific knowledge gaps related to the risk assessment of the NPs and NSMs in the environment. The review presents an overview of NMs history and classifications as well as profiling various sources of NPs and NSMs from natural to synthetic and their toxic effects towards mammalian cells and tissues. Additionally, the types of toxic reactions associated with NPs and NSMs and the regulations implemented by different countries to reduce the risks are also discussed.
The antimicrobial property of silver nanoparticles (AgNPs) is believed to be associated to their interaction with biointerfaces such as microbial cell membranes, encouraging research on the identification of membrane sites capable of AgNPs binding. Although significant progress has been made in that regard, the exact molecular mechanism of action is yet to be fully understood. In this study, AgNPs dispersed in aqueous media and stabilized with polyvinylpyrrolidone were incorporated in Langmuir monolayers of selected lipids that served as cell membrane models. Results from pressure-area isotherms, vibrational spectroscopy and Brewster angle microscopy revealed condensation of glycoside-free lipid monolayers, evidencing that the AgNPs interact mostly with the lipid hydrophilic head groups. In contrast, the monolayers of systems containing glycoside derivatives were found to expand upon AgNPs incorporation, indicating that the glycosidic compounds might facilitate the incorporation of these nanoparticles in cellular membranes. These data can be therefore correlated with the possible toxicity and microbicide effect of AgNPs in lipidic surfaces of mammalian and microbial membranes.
This review article provides an overview of hybrid and nanocomposite materials used as biomaterials in nanomedicine, focusing on applications in controlled drug delivery, tissue engineering, biosensors and theranostic systems. Special emphasis is placed on the importance of tuning the properties of nanocomposites, which can be achieved by choosing appropriate synthetic methods and seeking synergy among different types of materials, particularly exploiting their nanoscale nature. The challenges in fabrication for the nanocomposites are highlighted by classifying them as those comprising solely inorganic phases (inorganic/inorganic hybrids), organic phases (organic/organic hybrids) and both types of phases (organic/inorganic hybrids). A variety of examples are given for applications from the recent literature, from which one may infer that significant developments for effective use of hybrid materials require a delicate balance among structure, biocompatibility, and stability.
Atmospheric aerosol particles composed of a mixture of organic and inorganic compounds are common and constitute an important fraction of air pollutants. In this study, the activities of common atmospheric inorganic ions (Ag(+), Zn(2+), Fe(3+), Fe(2+), Ca(2+) and Al(3+)) and fatty acid molecules (stearic acid and arachidic acid) at air-aqueous interface were investigated by Langmuir methods and infrared reflection-absorption spectroscopy (IRRAS). In the presence of different inorganic ions, surface pressure-area isotherms of the Langmuir films showed compressed or expanded characteristics. IRRAS spectra confirmed that the existence of inorganic ions in the fatty acid monolayer changes the surface properties of aqueous-phase aerosols. Formation of different coordination types of carboxylates at the air-water interface alters the dissolution and partitioning behavior, which has significant influence of Raoult effect on nucleating cloud droplets. Our work displays the relationship between structure and surface properties for aqueous-phase aerosols and implies an efficient method for further understanding of their formation mechanism and potential atmospheric implications.
Lipid nanotubes are the preferred structures for many applications, especially biological ones, and thus have attracted much interest recently. However, there is still a significant need for developing more lipid nanotubes that are reversibly controllable to improve their functionality and usability. Here, we presented a two-way reversible morphology control of the nanotubes formed by the recently designed molecule AQUA (C25H29NO4). Due to its special design, the AQUA has both pH-sensitive and redox-active characters provided by the carboxylic acid and anthraquinone groups. Upon chemical reduction, the nanotubes turned into thinner ribbons and this structural transformation was significantly reversible. The reduction of the AQUA nanotubes also switched the nanotubes from electrically conductive to insulative. Nanotube morphology can additionally be altered by decreasing the pH below the pKa value of the AQUA, at ∼4.9. Decreasing the pH caused the gradual unfolding of the nanotubes and the inter-layer distance in the nanotube’s walls increased. This morphological change was fast and reversible at a wide pH range, including the physiological pH. Thus, the molecular design of the AQUA allowed for an unprecedented two-way and reversible morphology control with both redox and pH effects. These unique features make AQUA a very promising candidate for many applications, ranging from electronics to controlled drug delivery.
Lipid nanotubes (LNTs) are one of the most advantageous structures for drug delivery and targeting. LNTs formed by a specially designed molecule called AQUA (AQ-NH-(CH2)10COOH (AQ: anthraquinone group) is used for drug delivery, and doxorubicin (DOX) is the drug selected. DOX and AQUA have some similarities in their molecular structures, so a significant amount of DOX can be loaded to LNTs. The AQUA LNTs are pH responsive, and drug loading increased almost linearly by increasing the pH, reaching a maximum value (96%) at pH 9.0. In terms of drug release, lower pHs are preferred. Drug-loaded LNTs are also mixed with four different gels (chitosan, alginate, hydroxypropyl methylcellulose and polycarbophil) to use the advantages of these gels. The drug release efficiency is studied using a Franz diffusion cell in which sheep colon membranes and dialysis membranes are utilized. The amount of released DOX from the chitosan gel formulations was quite high. Sodium alginate gels had lower release and slower diffusion of DOX. The cytotoxic effect of DOX-loaded AQUA LNTs has also been determined on cell cultures. Our new lipid nanotubes are a non-toxic, effective, biodegradable, biocompatible, stable and promising system for drug delivery and can be used for colonic administration of DOX for the treatment of colorectal cancer (CRC).
Self-assembly is the autonomous organization of components into patterns or structures without human intervention. Self-assembling processes are common throughout nature and technology. They involve components from the molecular (crystals) to the planetary (weather systems) scale and many different kinds of interactions. The concept of self-assembly is used increasingly in many disciplines, with a different flavor and emphasis in each.
Self-assembly programmed by molecular structure and guided dynamically by energy dissipation is a ubiquitous phenomenon in biological systems that build functional structures from the nanoscale to macroscopic dimensions. This paper describes examples of one-dimensional self-assembly of peptide amphiphiles and the consequent biological functions that emerge in these systems. We also discuss here hierarchical self-assembly of supramolecular peptide nanostructures and polysaccharides, and some new results are reported on supramolecular crystals formed by highly charged peptide amphiphiles. Reflecting on presentations at this Faraday Discussion, the paper ends with a discussion of some of the future opportunities and challenges of the field.
In this paper some of the recent work directed at possible commercial applications for monolayer and multilayer Langmuir-Blodgett films is described. A number of the application areas are covered in detail. These include: second-order nonlinear optics; sensors; membranes; and electronic devices.
We demonstrate the formation of gold nanocrystals of different morphologies using alkylated tyrosine (AT) as a reducing agent at a liquid-liquid and air-water interface. The reduction of aqueous chloroaurate ions occurs in a single step wherein the AT molecule plays the multifunctional role of a phase transfer, reducing and capping agent. Gold nanoparticles formed at the air-water interface are very thin, flat sheet or ribbon-like nanostructures, which are highly oriented in the (111) direction. On the other hand, reduction of aqueous chloroaurate ions at a liquid-liquid interface by AT molecules present in the organic phase yielded nanoparticles having predominantly spherical morphology but with no specific crystallographic orientation. The difference in morphology of the nanoparticles may be due to the different orientational and translational degrees of freedom of the AT molecules and gold ions at these two interfaces. The AT-capped gold nanoparticles were characterized by UV-vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and nuclear magnetic resonance spectroscopy ( 1 H NMR), while the LB films of flat gold sheets were also studied by X-ray photoemission spectroscopy (XPS).
Self-assembled lipid nanotubes arouse lots of interest due to their exceptional properties such as very simple production procedures, large variety of applications and high biocompatibility. In this study, the new eccentric but simple molecule, AQua (AQ-NH-(CH(2))(10)COOH; where AQ is anthraquinone), which integrates redox-active and pH sensitive character with nanotube forming capability has been designed. AQua forms self-assembled nanotubes by the chiral symmetry-breaking mechanism, in a high yield in the presence of ethanolamine. The nanotubes obtained in AQua-ethanolamine mixture are stable with time and resistant against drying and dilution at constant pH. However, pH change with dilution (without pH control) causes the unfolding of the nanotubes indicating the pH sensitive character. Existence of redox active anthraquinone group along with the carboxylic acid moiety gives the probability of reversibly controllable character to our nanotubes. The effect of the base type which is used to adjust the pH of the dispersion has also been investigated, and helix-tube-ribbon mixture is obtained when NaOH is used instead of ethanolamine. Although there are limited number of studies particularly in the field of reversibly controllable and/or redox active lipid nanotubes, controlled self-assembly and disassembly of these appreciable aggregates are very important for their usage in special applications. Thus, this study is hoped to be one of the remarkable studies for the development of reversibly controllable, redox active self assembled nanotubes.
High aspect ratio peptide nanofibers have potential as biodegradable vehicles for drug delivery. We report here the synthesis of four self-assembling peptide amphiphiles (PAs) containing a lysine ε-amine-derivatized hydrazide that was systematically placed at different positions along the backbone of the peptide sequence C(16)V(2)A(2)E(2) (where C(16) = palmitic acid). Hydrazones were formed from each hydrazide by condensation with the solvatochromic dye 6-propionyl-2-dimethylaminonaphthalene (Prodan), which is typically used to probe cell membranes. All four compounds were found to self-assemble into nanofibers, and Prodan release was measured from filamentous gels prepared by screening PA charges with divalent cations. Near zero-order release kinetics were observed for all nanofibers, but release half-lives differed depending on the position of the fluorophore in the PA sequence. Dye release kinetics were rationalized through the use of cryogenic transmission electron microscopy, small-angle X-ray scattering, fluorescence spectroscopy, fluorescence anisotropy, circular dichroism, and partition coefficient calculations. Relative release rates were found to correlate directly with fluorophore mobility, which varied inversely with packing density, degree of order in the hydrophobic PA core, and the β-sheet character of the peptide.
TiO2 nanosized clusters have been prepared by the Langmuir−Blodgett technique starting from the n-octadecylamine−titanyl oxalate complex. The floating film morphology has also been investigated by Brewster angle microscopy (BAM). The presence of TiO2 in the subphase promotes the formation of aggregates of n-octadecylamine on the subphase surface. LB films initially contain TiO2 nanosized clusters embedded in the organic amorphous matrix; their structural evolution induced by thermal annealing has been investigated. UV−vis spectroscopy, high-resolution transmission electron microscopy (HRTEM), and small area electron diffraction (SAD) characterization methods are used as synergic techniques giving complementary information regarding both structural features and photophysical properties.
We report a new fabrication method of a thin polymer film with regular array of micropores (honeycomb film). A honeycomb film was fabricated by depositing a dilute solution of an amphiphilic polymer on water surface. The honeycomb film transferred onto a solid substrate was characterized by atomic force microscopy. By this fabrication method, it was possible to control film area, pore diameter, and film thickness. The pore size depended upon the evaporation time of the polymer solution spread on water surface. The thickness of a honeycomb film was controlled by spreading area of the polymer solution. The spreading behavior was influenced by the water temperature. The film area was proportional to the volume of spread polymer solution and controlled by changing the sub-phase temperature, too. When the polymer solution was simply cast on a solid substrate, a thin polymer layer remained in the bottom of the honeycomb pores. On the other hand, the honeycomb film fabricated on water surface has no bottom layer in its pores. A self-standing honeycomb mesh is formed by the “on-water spreading” method.
Silver particulate films have been prepared by exposing aqueous silver nitrate solutions, coated by monolayers and contained in a Lauda film balance, to formaldehyde (HCHO). Monolayers, prepared from dihexadecyl phosphate (1), dioctadecyldimethylammonium bromide (2), n-C16H33C(H)[CON(H)(CH2)(2)NH2](2) (3), and (C18H37N+(CH2CH2SHBr- (4), have been characterized by surface pressure vs surface area and surface potential vs surface area isotherms. Silver particulate film formation was found to be influenced by the concentration of AgNO3, the time of exposure to formaldehyde, the type of monolayer used, the pH of the subphase, and the presence of ammonia or CuCl2 in the subphase. Under similar conditions, the rate of silver particle growth under monolayers increased in the order 2 < 4 < 1 < 3. Silver particulate films, formed under monolayers, were quantitatively transferred to solid substrates (by horizontal lifting) and characterized thereon by absorption spectroscopy, optical microscopy, X-ray diffraction, and electrical measurements prior and subsequent to annealing them at 300 degrees C. Silver particulate films remained stable for weeks under the monolayers and for months subsequent to their transfer onto substrates. Analyzing the optical microscopic images of silver clusters, grown under monolayers prepared from 1 and 3 (and subsequently transferred to quartz slides), led to fractal dimensions of 1.51 +/- 0.13 and 1.68 +/- 0.25, respectively, in the relatively short-range scale, indicating a crossover to nonfractal structures during growth. Increasing the time of HCHO exposure shifted the absorption band of silver particles, grown under monolayers prepared from 1, from 270 to 440 nm, signifying the transition of the initially formed small nonmetallic clusters to larger metallic aggregates. Particles grown under monolayers prepared from 3 developed a narrow apparent absorption minimum at 321 nm (interband transition) upon prolonged exposure to HCHO, signaling the presence of rough silver surfaces with large surface-to-volume ratios. The resistivity of relatively thick silver particulate films, generated by the HCHO exposure of an aqueous 5 x 10(-2) M AgNO3 solution (coated by a monolayer prepared from 3), was determined to be 1.59 x 10(-6) Omega cm on solid substrates.
Isolated subunits from the crystalline cell surface (S layer) proteins of Bacillus sphaericus CCM2177 could be recrystallized into large coherent double layers at the air-water interface and as monolayers on dipalmitoylpho-phatidylcholine and dipalmitoylphosphatidylethanolamine (DPPE) monolayer films spread on a Langmuir-Blodgett (LB) though. The recrystallized S layer proteins and the S layer/DPPE layers could be chemically cross-linked from the subphase with glutaraldehyde. This cross-linking step enhanced the stability of the recrystallized S layer protein films and the composite S layer/DPPE layers considerably for subsequent handling procedures. By transferring a second phospholipid film onto the S layer/DPPE layers it was possible to mimic the structural principle of those archaeobacterial cell envelopes which are exclusively composed of a plasma membrane and a closely associated S layer. The high stability of S layer supported lipid membranes and the possibility for producing this composite structure on a large scale by standard LB techniques open new ways for exploiting structural and functional principles of membrane associated and integrated molecules.
Gold nanorings were prepared at the air/water interface through reduction of AuCl4− ions by UV-light irradiation or formaldehyde gas treatment at room temperature templated by thin films of phthalocyanine derivatives. Silver nanorings were produced at the air/water interface via reduction of Ag+ ions by UV-light irradiation templated by poly(9-vinylcarbazole) (PVK) thin films. These nanostructures were investigated by transmission electron microscopy (TEM), selective-area electron diffractometry (SAED), and high-resolution TEM (HRTEM). It was found that the gold nanorings are composed of close-packed nanoplates whose (1 1 0) crystal planes are parallel to the air/water interface; while silver rings are composed of nanoparticles. It is demonstrated that the ring-like aggregates formed by parallel linear supramolecules of the phthalocyanine derivatives and the ring-like structure of PVK supramolecules are responsible for the formation of the gold and silver nanorings, respectively.
Dialkoxy derivatives of anthraquinone (AQ), dicyano-anthraquinone (DCAQ) and tetracyanoanthraquinone (TCAQ) were synthesized and their associated electrochemical, optical and self-assembling properties were investigated as candidates for n-type materials. AQ shows UV absorption features, whereas both DCAQ and TCAQ exhibit bathochromic and hyperchromic electronic transitions into the visible region. The electron accepting strength of the three compounds was established by cyclic voltammetry as -1.52 V, -1.3 V and -0.9 V vs. ferrocene/ferricenium for AQ, DCAQ and TCAQ, respectively. All three quinones displayed quasireversible, two sequential one-electron transfer redox reactions. DFT calculations of DCAQ and TCAQ demonstrate structural changes upon reduction, which is supported by spectroelectrochemical experiments. Furthermore, the structural changes result in different absorption profiles and show potential as electrochromic materials. Finally, both AQ and DCAQ show liquid crystalline phases and importantly, DCAQ exhibits both a smectic liquid crystalline and a soft crystal phase between -6 °C and 85 °C, which offers promise as a self-assembling n-type material.
A new type of polymer-assisted self-assembly of nanospheres at a water-air interface was uncovered. By adding merely 1-3 ppm of polyethylene oxide in the water, the polystyrene nanospheres, applicable to diameters ranging from 100 nm to 1 μm, were found to gradually move closer to each other and eventually form a close-packed structure confirmed from its diffraction pattern. As it turns out, polyethylene oxides are adsorbed onto the surface of polystyrene nanospheres, giving rise to the effective screening of coulomb repulsive force between nanospheres followed by the onset of polymer-bridging effect as demonstrated from the strong suppression of Brownian motion. The resulting monolayer of close-packed polymer/nanospheres hybrid at the water-air interface with area size more than 1 cm(2) are robust and can be transferred to a substrate of any kind without serious breaking due to surface tension tearing. Our finding may provide a further extension to the scope of nanosphere lithography technique.
The syntheses of six room-temperature discotic liquid crystals based on an alkoxy-anthraquinone (AQ) framework is described. Differential scanning calorimetry, X-ray diffraction (XRD), and cross-polarized microscopy were used to identify phases and confirm phase-transition temperatures. Cross-polarized microscopy results suggest columnar discotic structures at room temperature. However, the AQ derivatives also undergo mesophase-to-mesophase transitions, which are attributed to rectangular- to hexagonal-columnar discotic transitions based on XRD analysis. Furthermore, some of the compounds display remarkable liquid crystalline phase stability that spans from -50 to 150 degrees C, a useful temperature range for organic materials applications. The different AQ derivatives did not exhibit electronic perturbations, as all compounds have absorption onsets of approximately 400 nm. Finally, solution cyclic voltammetry of the AQ derivatives was carried out to determine the redox potentials, diffusion coefficients, and electron transfer rate constants. All AQ derivatives had E(1/2) values that ranged between -1.52 and -1.70 V vs Fc/Fc(+). Diffusion coefficients and electron transfer rates for all AQ derivatives ranged between 0.4 and 7.1 x 10(-6) cm(2) x s(-1) and 0.9 and 5.2 x 10(-3) cm x s(-1), respectively.
Winnik, Manners, and others have reported that crystalline diblock copolymers can be used to self-assemble a range of complex hierarchical micellar nanostructures. The type of micellar structure that is formed depends on a number of factors such as relative size of the two blocks and the thermodynamics of interaction between the two blocks and the solvent. It is also found that the use of block copolymers with more complex structures such as three-armed star terpolymers, allows access to multicomponent micelles. Winnik and team members probed the potential of crystallization-driven polymerization concept to access much more complex micellar-like architectures. It is found that deposition of crystalline homopolymer poly(ferrocenyldimethylsilane) (PFS) onto a surface and exposing the crystalline surface to the cylindrical-micelle- forming brushes of the cylindrical micellar grow from the step edges on the surface.
Pure-lipid films at the water interface have surface-pressures vs. area isotherms that are often interpreted as involving first-order phase transitions from a condensed region to a liquid-expanded region. Two phases are presumed to coexist in the intermediate part of the isotherm. We constructed a film balance that could be placed on the stage of an epifluorescence microscope. A dipalmitoyl phosphatidylcholine film containing a low concentration of a fluorescent lipid probe showed an inhomogeneous fluorescence distribution in the so-called liquid-expanded region of the isotherm. Only the intermediate and condensed regions could be prepared so as to be optically homogeneous below 25 degrees C. We investigated membrane flow and lateral lipid diffusion in the membrane on the trough. The isotherms and isochores were measured. The results require, at least, a modified description of the monolayer structure in various regions of the isotherms. The solid-condensed region corresponds to a gel phase of the lipids where there is no flow in the membrane, lateral diffusion is low, the compressibility is low, and the membrane is optically homogeneous. The "liquid-condensed/liquid-expanded" region appears to be a homogeneous membrane where lateral diffusion and membrane flow are both rapid. This is a region of high compressibility. The "liquid-expanded" region is not homogeneous as seen under the microscope, and the flow of the surface layer can be very fast.
The organization of hydrophobized colloidal gold nanoparticles at air-water interface and the formation thereafter of lamellar, multilayer films of the gold nanoparticles by the Langmuir-Blodgett technique is described in this paper. The hydrophobization of the colloidal particles was accomplished by the direct chemisorption of laurylamine molecules on aqueous colloidal gold nanoparticles during a phase-transfer process. While monolayers of the laurylamine-capped gold nanoparticles at the air-water interface were not amenable to layer-by-layer transfer onto solid supports, it was observed that addition of the water-insoluble amphiphile octadecanol to the gold nanoparticle solution improved the stability of the monolayer at the interface as well as the multilayer assembly protocol. The organization of the gold nanoparticles at the air-water interface was followed by surface pressure-area isotherm measurements while the formation of multilayer films of the nanoparticles by the Langmuir-Blodgett technique was monitored by quartz crystal microgravimetry, UV-vis spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy.
A seed-mediated growth method was used to control the morphology and dimensions of Au nanocrystals by the manipulation of the experimental parameters in aqueous solution at room temperature. This chemical route produces various structural architectures with rod-, rectangle-, hexagon-, cube-, triangle-, and starlike profiles and branched (such as bi-, tri-, tetra-, and multipod) Au nanocrystals of various dimensions in high yield in the presence of a single surfactant, cetyltrimethylammonium bromide.
The need to improve miniaturization and device performance in the microchip and microelectronics industry has recently inspired many investigations into supramolecular chemistry. Specifically, the ability to precisely control the inner and outer diameters of self-assembled lipid nanotubes (LNTs) directly determines their suitability for technological applications. Understanding how structural variation affects nanotube dimensions at the molecular level would facilitate a more efficient and systematic approach to generating rationalized tubular libraries. This review summarizes recent advances as well as approaches to controlling the dimensions of lipid and polymer nanotubes, focusing on the outer and inner diameters, lengths, and membrane wall thickness. Some of the methods considered include chiral molecular self-assembly, packing-directed self-assembly, polymer assembly, molecular sculpting, and templated synthesis using a pore.
Nanofibrillar micellar structures formed by the amphiphilic hyperbranched molecules within a Langmuir monolayer were utilized as matter for silver nanoparticle formation from the ion-containing water subphase. We observed that silver nanoparticles were formed within the multifunctional amphiphilic hyperbranched molecules. The diameter of nanoparticles varied from 2-4 nm and was controlled by the core dimensions and the interfibrillar free surface area. Furthermore, upon addition of potassium nitrate to the subphase, the Langmuir monolayer templated the nanoparticles' formation along the nanofibrillar structures. The suggested mechanism of nanoparticle formation involves the oxidation of primary amino groups by silver catalysis facilitated by "caging" of silver ions within surface areas dominated by multibranched cores. This system provides an example of a one-step process in which hyperbranched molecules with outer alkyl tails and compressed amine-hydroxyl cores mediated the formation of stable nanoparticles placed along/among/beneath the nanofibrillar micelles.
The monodisperse silver nanoparticles were synthesized by one-step reduction of silver ions in the alkaline subphase beneath vitamin E (VE) Langmuir monolayers. The monolayers and silver nanocomposite LB films were characterized by surface pressure-area (pi-A) isotherms, transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-vis), selected area electron diffraction (SAED), Fourier transform infrared transmission spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), respectively. The results showed that the limiting area/VE molecule on different subphases varied. The phenolic groups in the VE molecules were converted to a quinone structure, and the silver ions were mainly reduced to ellipsoidal and spherical nanoparticles. The arrangement of the nanoparticles changed from sparseness to compactness with reaction time. The electron diffraction pattern indicated that the silver nanoparticles were face-centered cubic (fcc) polycrystalline. Silver nanocomposite LB films with excellent quality could be formed on different substrates, indicating that the transfer ratio of monolayer containing silver nanoparticles is close to unity. The dynamic process of reduction of silver ions by VE LB films was also studied through monitoring the conductivity of an Ag2SO4 alkaline solution.
The growth of gold nanoparticles by reduction by citrate and ascorbic acid has been examined in detail to explore the parameter space of reaction conditions. It is found that gold particles can be produced in a wide range of sizes, from 9 to 120 nm, with defined size distribution, following the earlier work of Turkevich and Frens. The reaction is initiated thermally or in comparison by UV irradiation, which results in similar final products. The kinetics of the extinction spectra show the multiple steps of primary and secondary clustering leading to polycrystallites.
Phase-contrast transmission electron microscopy (PC-TEM) and quick freezing method have been combined to study the initial growing process of a self-assembled lipid nanotube in water. The PC-TEM enabled us to detect thin lamellar edge structure and the very fast growth of the newborn edge to a thin tube with high contrast. The thin tube acts as a core structure for further growth into thick complete lipid nanotube. The initially formed nanotube structure is denoted as a "core tube". The core tube has uniform wall structure that consists of five lamellar layers and the inner and outer diameters of the core tube are 130 and 180 nm, respectively. The evaluated lamellar spacing of 4.6 nm is well compatible with that measured by X-ray diffraction. We also discussed the molecular packing of the nanotube from the pitch angle determined by the PC-TEM images, X-ray diffraction pattern in wide-angle region, and IR spectroscopy. The subcell structure of the nanotube is assigned to an orthorhombic type. The twisting angle between the neighboring lipid molecules is determined as ca. 0.26 degrees for the first time; it is a crucial parameter for the formation of a lipid nanotube in chiral packing but has not been elucidated before.
How the interaction of PVP-stabilized Ag nanoparticles with models of cellular membranes at the air-water interface is modulated by the monolayer composition
- da Silva
Micelles make a living
- Rowan
Investigation of The Physical Interactions of Surfactant-Modified Nanoparticles with a Model Cell Membrane, Chemical Engineering
- D Demir
D. Demir, Investigation of The Physical Interactions of Surfactant-Modified
Nanoparticles with a Model Cell Membrane, Chemical Engineering, Hacettepe
University Institute of Science and Technology, Ankara, 2011.
- J Jeevanandam
- A Barhoum
- Y S Chan
- A Dufresne
- M K Danquah
J. Jeevanandam, A. Barhoum, Y.S. Chan, A. Dufresne, M.K. Danquah, Review on
nanoparticles and nanostructured materials: history, sources, toxicity and
regulations, Beilstein J. Nanotechnol. 9 (2018) 1050-1074.
- H D M Follmann
- A F Naves
- R A Araujo
- V Dubovoy
- X Huang
- T Asefa
- R Silva
- O N Oliveira
H.D.M. Follmann, A.F. Naves, R.A. Araujo, V. Dubovoy, X. Huang, T. Asefa,
R. Silva, O.N. Oliveira, Hybrid materials and nanocomposites as multifunctional
biomaterials, Curr. Pharm. Des. 23 (2017) 3794-3813.