Authors：Hee-Sung Jeong, Chun-Yeol You, Byoung Jin Suh, Kyung-Pil Kim, Jiwon Jang, Seungyeop Jeong, Jae-Hak Choi and Jaseung Koo
Journal：Journal of Nanoparticle Research
Abstract：Using a simple and facile method, we precisely controlled the two-dimensional layered array structure of graphene oxide (GO)–iron oxide (Fe3O4) nanoparticle hybrid multilayer films and investigated the correlation between the assembled structure of the hybrid films and their magnetic properties. GO–Fe3O4 nanoparticle hybrids were obtained via the ligand exchange of oleic acid-functionalized Fe3O4 nanoparticles with GO at the gas–liquid interface. Hybrids of oriented Fe3O4 nanoparticles and GO monolayers spontaneously formed at the gas–liquid interface, which were subsequently deposited on solid substrates using the Langmuir–Schaefer (LS) technique. Two-dimensional superlattices of GO–Fe3O4 nanoparticle hybrids were fabricated through repeated LS deposition of the nanoparticle monolayer with a hexagonal array structure sandwiched between GO monolayers. The magnetic properties of the GO–Fe3O4 multilayer were measured using SQUID magnetometry. From the field cooling/zero field cooling results, we found that the 2D superlattice-like layered structure of the GO–Fe3O4 multilayer facilitates the layer-dependent properties in the out-of-plane field case due to the dipolar interactions between the top and bottom layers.
Authors：Herbert Winnischofer, Elizangela C. Cesca, Alejandro E. P. Mendoza, Iolanda P. Araújo, Eduard Westphal, Daniela Z. Mezalira, Débora T. Baloghd and Osvaldo N. Oliveira Jr.
Journal：Journal of the Brazilian Chemical Society
Abstract：The molecular control in Langmuir-Blodgett (LB) films may be exploited in charge storage electrodes provided a suitable choice of molecular architecture and components is made. In this paper, we employed a naphtyl-1,3,4-oxadiazole amphiphile (NFT1) and its complex [Ru(bpy)2NFT1]PF6 (RuNFT1) (bpy = 2,2’-bipyridine) in heterostructured LB films in a proof‑of-principle production of charge storage. The optimized architecture contained a one-layer RuNFT1 deposited on a 9-layer NFT1 LB film, where the efficient packing of NFT1 inferred from spectroscopic measurements and Brewster angle microscopy (BAM) images was considered as relevant for ion diffusion. This packing was achieved owing to the π-stacking warranted by the planarity of the NFT1 naphtyl 1,3,4-oxadiazole ring, as confirmed with density functional theory (DFT) calculations. The top layer of the redox-active RuNFT1 provided an additional contribution with its Faradaic charge storage to the double layer capacitance of NFT1. Taken together, these results demonstrate that synergy may be achieved in combining distinct compounds in LB films toward efficient charge storage.
Authors：I. A. Reznik, A. S. Zlatov, P. O. Il’in, R. A. Zakoldaev, S. A. Moshkalev and A. O. Orlova
Journal：Optics and Spectroscopy
Abstract：Determination of regular features of mechanisms underlying interactions of nanostructured materials is one of the most important problems on the way to create the new generation of efficient photovoltaic devices. In this paper, we study the luminescent and photoelectric properties of hybrid structures that are formed on the basis of multilayer graphene nanoribbons and semiconductor quantum nanocrystals of the 0D dimension, CdSe/ZnS core/shell quantum dots, and 2D-dimension CdSe nanoplates. It is shown that the multiexponential decay of the exciton luminescence of CdSe nanoplates at room temperature is determined by the occurrence of delayed luminescence, which is caused by the presence of trap states on the surface of nanoplates. It is found that, in dry layers of nanoplates on a dielectric substrate and in the composition of hybrid structures with graphene nanoribbons, the efficiency of delayed exciton luminescence of nanoplates increases. It is shown that the rate of increase in the photoconductivity in hybrid structures based on CdSe nanoplates is an order of magnitude higher than the rate of this process in similar structures based on CdSe/ZnS quantum dots, which indicates the formation of an effective energy/charge transfer channel from nanoplates to graphene nanoribbons.
Authors： Anna Chachaj-Brekiesz, Anita Wnętrzak, Sara Włodarska, Ewelina Lipiec and Patrycja Dynarowicz-Latka
Journal：The Journal of Steroid Biochemistry and Molecular Biology
Abstract：Systematic studies on the influence of selected ring–oxidized (7α–hydroxycholesterol, 7α–OH; 7β–hydroxycholesterol, 7β–OH; 7–ketocholesterol, 7–K) and chain–oxidized (25–OH) sterols on lipid layer of myelin were performed. Myelin sheath was modeled as five–component Langmuir monolayer (Chol:PE:SM:PS:PC 50:20:12:9:9). Particular oxysterols have been incorporated into the model myelin sheath by replacing cholesterol totally or partially (1:1). The effect of oxysterol incorporation was characterized with surface pressure and electric surface potential – area isotherms and visualized with Brewster angle microscopy (BAM) and atomic force microscopy (AFM). It has been noticed that model myelin loses its homogeneous structure (due to the appearance of domains) at physiological bilayer conditions (30–35 mN/m). In the presence of oxysterols, the fluidity of myelin model increases and the organization of lipids is altered, which is reflected in the decrease of electric surface potential changes (ΔV). The strongest myelin/oxysterol interactions have been observed for 7–K and 25–OH, being the most cytotoxic oxysterols found in biological tests.
Authors：Tej B. Limbu, Basant Chitara, Martha Garcia Cervantes, Yu Zhou, Shengxi Huang, Yongan Tang and Fei Yan
Journal：The Journal of Physical Chemistry C
Abstract：MXenes have attracted great attention as promising substrates for surface-enhanced Raman scattering (SERS) applications. However, the underlying SERS mechanism has not been a focus of any investigation. Herein, we report the first systematic experimental study on the SERS activity of Ti3C2TX nanosheets with thickness ranging from 5 to 120 nm, using methylene blue (MB) as a probe molecule. The experimental and mathematical modeling results show that the Raman enhancement factor (EF) increases monotonically with the increasing thickness of Ti3C2TX nanosheets, however, it falls drastically around a sheet thickness of 0.8 µm and 1.0 µm under 532 and 633 nm laser excitations, respectively. The Raman EF reaches a maximum value around a thickness of 2.0 µm, suggesting that a maximum EF can be achieved with a 2.0 µm-thick Ti3C2TX film substrate. The thickness-dependence of the Raman enhancement can be accounted for by the adsorption and intercalation of MB molecules into the interlayer spacing of Ti3C2TX. Furthermore, by combining experimental observations and numerical calculation, we confirm that the charge transfer mechanism is dominantly responsible for Raman enhancement on Ti3C2TX. Additionally, we report an observation of resonance coupling of charge transfer and molecular transition as a contributing factor to the higher EF obtained with a 633 nm laser excitation. Taken together, these findings have significant implications for cost and performance optimization in designing MXene-based SERS substrates for next-generation chemical and biological sensing platforms.
Authors：Dorota Matyszewska, Ewa Nazaruk and Richard A.Campbell
Journal：Journal of Colloid and Interface Science
Abstract：We quantify directly here for the first time the extents of interactions of two different anthracycline drugs with pure and mixed lipid monolayers with respect to the surface pressure and elucidate differences in the resulting interaction mechanisms. The work concerns interactions of doxorubicin (DOx) and idarubicin (IDA) with monolayers of the zwitterionic DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) and negatively charged DMPS (1,2-dimyristoyl-sn-glycero-3-phospho-L-serine (sodium salt)) as well as a 7:3 mixture of the two lipids. These drugs are used in current cancer treatments, while the lipid systems were chosen as phosphocholines are the major lipid component of healthy cell membranes, and phosphoserines are the major lipid component that is externalized into the outer leaflet of cancerous cell membranes. It is shown that DOx interacts with DMPS monolayers to a greater extent than with DMPC monolayers by lower limits of a factor of 5 at a surface pressure of 10 mN/m and a factor of 12 at 30 mN/m. With increasing surface pressure, the small amount of drug (∼ 0.3 µmol /m2) bound to DMPC monolayers is excluded from the interface, yet its interaction with DMPS monolayers is enhanced until there is even more drug (∼ 3.2 µmol /m2) than lipid (∼ 2.6 µmol /m2) at the interface. Direct evidence is presented for all systems studied that upon surface area compression lipid is reproducibly expelled from the monolayer, which we infer to be in the form of drug-lipid aggregates, yet the nature of adsorption of material back to the monolayer upon expansion is system-dependent. At 30 mN/m, most relevant to human physiology, the interactions of DOx and IDA are starkly different. For DOx, there is a conformational change in the interfacial layer driven by aggregation, resulting in the formation of lateral domains that have extended layers of drug. For the more lipophilic IDA, there is penetration of the drug into the hydrophobic acyl chain region of the monolayer and no indication of lateral segregation. In addition to the Langmuir technique, these advances were made as a result of direct measurements of the interfacial composition, structure and morphology using two different implementations of neutron reflectometry and Brewster angle microscopy. The results are discussed in terms of the prevention of drug penetration through cell membranes by passive diffusion as well as activation of drug removal mechanisms related to multidrug resistance.
Authors：Maximilian M. Schmidt, Steffen Bochenek, Alexey A. Gavrilov, Igor I.Potemkin,
and Walter Richtering
Journal：arXiv preprint arXiv:2007
Abstract：The role of electrostatics on the interfacial properties of polyelectrolyte microgels has been discussed controversially in the literature. It is not yet clear if, or how, Coulomb interactions affect their behavior under interfacial confinement. In this work, we combine compression isotherms, atomic force microscopy imaging, and computer simulations to further investigate the behavior of pH-responsive microgels at oil-water interfaces. At low compression, charged microgels can be compressed more than uncharged microgels. The in-plane effective area of charged microgels is found to be smaller in comparison to uncharged ones. Thus, the compressibility is governed by inplane interactions of the microgels with the interface. At high compression, however, charged microgels are less compressible than uncharged microgels. Microgel fractions located in the aqueous phase interact earlier for charged than for uncharged microgels because of their different swelling perpendicular to the interface. Therefore, the compressibility at high compression is controlled by out-of-plane interactions. In addition, the size of the investigated microgels plays a pivotal role. The charge-dependent difference in compressibility at low compression is only observed for small but not for large microgels, while the behavior at high compression does not depend on the size. Our results highlight the complex nature of soft polymer microgels as compared to rigid colloidal particles. We clearly demonstrate that electrostatic interactions affect the interfacial properties of polyelectrolyte microgels.
Authors：Fernando Augusto de Souza Furtado and Luciano Caseli
Journal：Thin Solid Films
Abstract：The adsorption of the enzyme galactose oxidase onto stearic acid Langmuir monolayers was investigated with surface pressure-area isotherms, Brewster Angle Microscopy and polarization-modulated infrared reflection-absorption spectroscopy. The enzyme was incorporated in the monolayer at low surface pressures, expanding the lipid films, and further monolayer compression expelled it from the contact with the air phase and repositioned the enzyme below the lipid polar heads. The enzyme-lipid system was then stabilized by electrostatic interactions, leading the monolayer to condense at higher surface pressures, reducing the number of interfacial aggregates. The lipid-enzyme interactions at the interface made the monolayer less viscoelastic and more disordered as pointed by the reduced compressional modulus and decreased trans/gauche ratio for the lipid acyl chains. Also, the secondary structures of the adsorbed enzyme were kept as demonstrated with infrared spectroscopy. The condensed enzyme-lipid monolayer was transferred to solid supports as Langmuir-Blodgett films and the enzyme activity was detected, being preserved for one month. These results show how the molecular organization provided by the ultrathin films can help maintain the catalytic activity for immobilized enzymes, which is important, general speaking, for nanotechnology and biosensing manufacturing.
Authors：Darvina C. K. Lim, Faridah L. Supian & Yanuar Hamzah
Journal：Journal of Materials Science: Materials in Electronics
Abstract：A layered composites of calixarene, namely, THC4-rGO, was produced fromcalixarene-25,26,27,28-tetrol (THC4) and reduced graphene oxide (rGO) usingthe Langmuir–Blodgett (LB) technique. THC4 and rGO were prepared in asolution form first, then by using the LB technique to form LB films which werethen deposited onto a quartz surface for Raman and electrical study. Langmuirproperty such as surface pressure-area (P-A) isotherms of THC4 and rGO wereused to study the intermolecular interactions at air–water interface. Ramanspectroscopy was used to observe the crystallinity of the composites. The electricalproperties by using four-point probe, i.e., I–V curves, resistivity, andconductivities of the rGO and THC4-rGO were analyzed to illustrate theenhanced properties. The results from this study can be utilized for the potentialapplication of electronic sensors using calixarene.
Authors：Darvina C. K. Lim, Faridah L. Supian, and Yanuar Hamzah
Journal：Biochimica et Biophysica Acta (BBA)
Abstract：The interactions of liquid-crystalline nanoparticles based on lipid-like surfactants, glyceryl monooleate, monoolein (GMO) and 1,2,3-trihydroxy-3,7,11,15-tetramethylhexadecane, phytantriol (PT) with selected model lipid membranes prepared by Langmuir technique were compared. Monolayers of DPPC, DMPS and their mixture DPPC:DMPS 87:13 mol% were used as simple models of one leaflet of a cell membrane. The incorporation of cubosomes into the lipid layers spread at the air-water interface was followed by surface-pressure measurements and Brewster angle microscopy. The cubosome – membrane interactions lead to the fluidization of the model membranes but this effect depended on the composition of the model membrane and on the type of cubosomes. The interactions of PT cubosomes with lipid layers, especially DMPS-based monolayer were stronger compared with those of GMO-based nanoparticles. The kinetics of incorporation of cubosomal material into the lipid layer was influenced by the extent of hydration of the polar headgroups of the lipid: faster in the case of smaller, less hydrated polar groups of DMPS than for strongly hydrated uncharged choline of DPPC. The membrane disrupting effect of cubosomes increased at longer times of the lipid membrane exposure to the cubosome solution and at larger carrier concentrations. Langmuir monolayer observations correspond well to results of studies of HeLa cells exposed to cubosomes. The larger toxicity of PT cubosomes was confirmed by MTS. Their ability to disrupt lipid membranes was imaged by confocal microscopy. On the other hand, PT cubosomes easily penetrated cellular membranes and released cargo into various cellular compartments more effectively than GMO-based nanocarriers. Therefore, at low concentrations, they may be further investigated as a promising drug delivery tool.
Authors：E. P. Kolesovaa, F. M. Safina, V. G. Maslova, A. Dubavika, Y. K. Gun’kob, and A. O. Orlovaa
Journal：Optics and Spectroscopy
Abstract：The efficiency of the electron transfer in hybrid structures based on quantum dots of differentarchitectures was studied. Electron transfer efficiency was estimated by two independent methods from theside of the electron donor (quantum dot) and acceptor (Titania nanoparticles). Structures based on coreCdSe QDs with small diameter demonstrate the highest efficiency of electron transfer and ROS generation.The presence of the dark fraction of QDs in the ensemble reduces the functionality of hybrid structures andlimits their practical applicability.
Authors：Elsa M. Materon, Gustavo F. Nascimento , Flavio M. Shimizu, Amanda S. Cˆamara ,
Bianca Sandrino, Ronaldo C. Faria, Osvaldo N. Oliveira Jr.
Journal：Colloids and Surfaces B: Biointerfaces
Abstract：The fight against drug resistance in chemotherapy requires a molecular-level understanding of the drug interactionwith cell membranes, which today is feasible with membrane models. In this study, we report on theinteraction of gemcitabine (GEM), a pyrimidine nucleoside antimetabolite used to treat pancreatic cancer, withLangmuir films that mimic healthy and cancerous cell membranes. The cell membrane models were made witheight compositions of a quaternary mixture containing 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC),1,2-dipalmitoyl-sn-glycero-3-phosphoserine (DPPS), sphingomyelin (SM), and cholesterol (CHOL). The relativeconcentration of SM was increased so that four of these compositions represented cancerous cells. GEM wasfound to increase the mean molecular area, also increasing their surface elasticity, with stronger interactionsbeing observed for membranes corresponding to cancerous cells. More specifically, GEM penetrated deepest inthe membrane with the highest SM concentration (40 mol%), as inferred from polarization-modulated infraredreflection absorption spectroscopy (PM-IRRAS). This finding was confirmed with molecular dynamics simulationsthat also indicated how GEM approaches the membrane, which could be useful for guiding the design ofdrug delivery systems. The experimental and simulation results are consistent with the preferential attachment ofGEM onto cancerous cells and highlight the role of SM on drug-cell interactions.
Authors：Yongping Shan, Lu Liu, Yang Liu, Hauke Harms, and Lukas Y. Wick
Journal：Environmental Technology & Innovation
Abstract：Increasing wastewater generation rates and micro-pollutant levels in environmental matrices constrain energy-efficient and fast control technologies. In this study, different optical and geometrical photocatalytic reactor (PCR) design have been investigated experimentally using BPA molecule as a model pollutant. N-TiO2, Ni-N-TiO2, Sn-N-TiO2, Ni-Sn-C-N-TiO2 and -Ni-Sn-C-N-TiO2 nano-layered thin films (TFs) have been produced and employed as immobilized nano-catalysts. An ultrasound-assisted fluorine (F) etching method was applied to Sn and Ni co-doped TFs. The synthesized TFs were characterized by SEM-EDX, AFM, XPS, FT-IR and UV-vis spectroscopies. Three different types of PCRs with different geometrical and optical design were operated using different light sources, wavelengths and technologies. A box type photoreactor, vertical and horizontal coated quartz tubular reactors (CQTRs) were fabricated and their performances were evaluated considering BPA degradation kinetics and unit energy consumption figures (, kJ energy used mg−1 BPA). Vis, UV A, UV C lamps and SMD 5050 blue (450 nm) and UV (365 nm) LEDs were employed as irradiation sources to initiate photocatalytic reactions. The highest pseudo first-order reaction rate (k) and the lowest value were obtained by -Sn-Ni-C-N-TiO2, positioned in vertical type reactor under UV LED irradiation as 20.5 min and 56 kJ mg−1 BPA respectively. Whereas, the highest BPA degradation rate (k) and the lowest value for the box type reactor under 257 nm UV C irradiation were estimated as 20.3 min−1 and 1,581 kJ mg−1 BPA respectively for -Sn-Ni-C-N-TiO2. Although similar reaction rates were obtained for both reactor types, energy consumption was lowered approximately 28-fold in the developed vertical positioned reactor system in addition to several other benefits. While UV LED based-PCR yielded elevated levels of BPA removal efficiency, 257 nm UV C irradiation did not contribute to BPA degradation when positioned vertically. Furthermore, obtained experimental results also revealed that -Sn-Ni-C-N-TiO2 has significant potential to function under solar irradiation.