Nanofilm Surface Research Articles

Effect of an Electric Double Layer on the Adsorption and Catalytic Properties of the Ytterbium Nanofilm Surface

Effect of an Electric Double Layer on the Adsorption and Catalytic Properties of the Ytterbium Nanofilm Surface

SERS detection of shikonin dye by metal-coordinated tethering on gold nanofilm

We developed a spectroscopic detection method of dye molecules by combining surface-enhanced Raman spectroscopy (SERS) and a metal-coordinated tethering method. In order to mimic the surface of cellulose fiber, a gold nanofilm (AuNF) surface was modified with hydroxyl groups, and then treated following a tethering process to form a metal ion-mediated dye ligand complex (Al3+-shikonin dye complex) on the AuNF. Then, the colloidal gold nanoparticles (AuNPs) were dropped and dried to form SERS hot-spots, where shikonin locates in the interstitial gap between AuNP and AuNF. The SERS enhancement factor (EF) of AuNP-on-AuNF was calculated to be 4.4 × 107 via SERS measurement of 4-mercaptobenzoic acid (4-MBA). The SERS heatmap of shikonin from the ‘dyed AuNP-on-AuNF’ substrate showed that shikonin was uniformly tethered on AuNF surface in the same way as the dyeing of dye molecules on cellulose fibers. Furthermore, the spectral differences were observed between ‘dyed AuNP-on-AuNF’ and salt-induced AuNP aggregates due to the difference in vibrational modes between dyed shikonin and free shikonin. This method can apply to various natural dyes owing to the versatility of the dyeing method with a metal ion. Moreover, SERS libraries obtained using this method can directly compare with dyes tethered on fibers.

Composite membranes with nanofilms assembled on nanofiber supports for high-performance nanofiltration with antibacterial property

Nanofiltration has been widely applied in the field of desalination, wastewater treatment and water softening as an emerging and promising membrane separation technology. In order to break the trade-off effect between selectivity and permeability, we develop a novel thin-film composite nanofiltration membrane via a one-step interfacial assembly strategy of PDA/PEI nanofilms on nanofiber substrates. The ultrathin PDA/PEI nanofilm is defect-free, acting as the selective layer for ion sieving. The nanofiber substrate with high porosity provides plenty of mass transfer channels to reduce the membrane resistance, resulting in a enhanced water permeability of 18.1 L m-2 h-1 bar-1, which is 3 times higher than that prepared with commercial substrates. Attributed to the universally adhesive property of PDA, the PDA/PEI nanofilm can well integrate with the nanofiber substrate, enhancing the interfacial interaction strength and thus the composite structure stability. As a versatile platform, the abundant Ag nanoparticles are immobilized onto the PDA/PEI nanofilm surface, endowing the membrane with significant antibacterial property. This is of importance for membrane antifouling during the long-term and practical applications. This work could pave a facile way to develop advanced nanofiltration membranes with outstanding separation performance and various functions.

Perfluorooctanoyl chloride engineering toward high-flux antifouling polyamide nanofilms for desalination

Nanofiltration (NF) membranes with high flux and superior antifouling performance are in great demand for water purification. Low-surface-energy fluorine materials have attracted significant attention in the fabrication of antifouling nanofiltration membranes. However, their inferior water affinity usually leads to the sacrifice of membrane water permeability. Herein, we explored perfluorooctanoyl chloride (PFOC) as a reactive additive in the organic phase during support-free interfacial polymerization (IP) to engineer fluorinated polyamide (FPA) nanofilms, which were further transferred onto porous substrates for thin-film composite (TFC) membranes. PFOC can participate in the interfacial polymerization process, leading to an enlarged pore size of the FPA nanofilm. The resultant TFC membrane displayed water permeance of 28.5 ± 0.7 L m−2 h−1 bar−1, about twice as high as that of the pure polyamide (PA) membrane while maintaining Na2SO4 rejection above 98.5% and NaCl rejection below 15.0%. Moreover, the existence of low-surface-energy perfluoroalkyl chains on the FPA nanofilm surface can endow the TFC membrane with superior antifouling properties with a higher flux recovery ratio and lower flux decline ratio against oil/water emulsions (FRR = 97.9%, DRt = 9.5%) and bovine serum albumin (FRR = 98.5%, DRt = 13.9%). Our approach may enlighten a new avenue on engineering high-flux antifouling TFC membranes with fluorine materials.

The Ripple Effect of Graphite Nanofilm on Stretchable Polydimethylsiloxane for Optical Sensing.

Graphene-based optical sensing devices have been widely studied for their broad band absorption, high carrier mobility, and mechanical flexibility. Due to graphene’s weak light absorption, studies on graphene-based optical sensing thus far have focused on hybrid heterostructure devices to enhance photo-absorption. Such hybrid devices need a complicated integration process and lead to deteriorating carrier mobility as a result of heterogeneous interfaces. Rippled or wrinkled graphene has been studied in electronic and optoelectronic devices. However, concrete demonstrations of the impact of the morphology of nanofilms (e.g., graphite and graphene) associated with light absorption in optical sensing devices have not been fully examined. This study explored the optical sensing potential of a graphite nanofilm surface with ripples induced by a stretchable polydimethylsiloxane (PDMS) supporting layer under different stretch:release ratios and then transferred onto silicon, both under experimental conditions and via simulation. The optical sensing potential of the rippled graphite nanofilm was significantly enhanced (260 mA/W at the stretch–release state of 30%), as compared to the pristine graphite/PDMS (20 mA/W at the stretch–release state of 0%) under laser illumination at a wavelength of 532 nm. In addition, the results of our simulated computation also confirmed the improved light absorption of rippled graphite nanofilm surface-based optical sensing devices, which was comparable with the results found in the experiment.

Advanced Optical Detection through the Use of a Deformably Transferred Nanofilm

Graphene has been extensively investigated in advanced photodetection devices for its broadband absorption, high carrier mobility, and mechanical flexibility. Due to graphene’s low optical absorptivity (2.3%), graphene-based photodetection research so far has focused on hybrid systems to increase photoabsorption. However, such hybrid systems require a complicated integration process and lead to reduced carrier mobility due to heterogeneous interfaces. Crumpled or deformed graphene has previously been reported in electronics and optoelectronics. However, a depth study on the influence of the morphology of nanofilms (e.g., graphite or graphene) related to light absorption in photodetection devices has not been demonstrated yet. Here, we present an interesting study in terms of the effect of the deformable surface and the smooth surface of a nanofilm transferred onto Si through two transfer strategies using isopropanol injection and nitrogen blowing (to form a deformable nanofilm surface) and deionized water injection and van der Waals interaction (to form a smooth nanofilm surface). As a result, optical detection in the case of the deformable nanofilm surface was enhanced significantly (~100%) compared with that of the smooth nanofilm surface in the visible laser wavelength (532 nm). In addition, evidence from the computational simulation also firmly affirms an advancement in the optical detection of deformed nanofilm-surface-based photodetection devices compatible with the experimental results.

Scanning Tunneling Microscopy of the Ytterbium Nanofilm Surface and Layers of Oxygen Molecules Adsorbed on It

The surfaces of Yb–Si(111) and O–Yb–Si(111) structures (with a thickness of ytterbium nanofilms of 16 monolayers (6.08 nm)) have been investigated for the first time using scanning tunnel microscopy, which has provided data on the morphology and phase composition of these surfaces. It is found that, prior to oxygen adsorption, the nanofilms exhibit a high degree of homogeneity over their thickness, grow in accordance with a mechanism very close to the layer-by-layer growth, and have a homogeneous crystalline structure. After oxygen adsorption, an island layer of oxygen molecules is formed with a thickness of 0.112 nm. It is shown that the nanofilms morphology in the regions of the film surface coated by a monomolecular oxygen film changes significantly, while the morphology of the surface regions uncoated with the adsorbed layer remains unchanged.

Copper-mediated synergistic catalytic titanium dioxide nanofilm with nitric oxide generation and anti-protein fouling for enhanced hemocompatibility and inflammatory modulation

Nitric oxide (NO) has become a highly compelling therapeutic gas for treating vascular diseases due to its versatile functions to vascular responses. Currently, NO biomimetic materials are successfully established through loading catalyst (i.e., Se, Cu) with the vehicle to decompose endogenous NO donors in blood continuously. However, current NO biomimetic materials are susceptible to the non-specific protein fouling, resulting in undesired therapeutic inefficiency with the observation of attenuated or even blocked NO catalytic activities. Herein, we produced a multifunctional nanofilm with dual catalysis based on the vascular stent platform via simply doping one kind of metal (Cu) as cocatalyst into anatase TiO2 crystal. Beneficial synergistic interactions between two kinds of catalysis are reported in this work. The nanofilm surface is endowed with photoinduced super hydrophilic conversion and controlled NO catalytic release simultaneously. The super hydrophilic surface shows the excellent self-cleaning ability to resist protein fouling. Importantly, the maintenance of the protein-resistant surface can effectively improve the NO catalytic release and reduce inflammatory stimuli, contributing to enhanced hemocompatibility. The optimum doping amount of Cu (TiO2@Cu1, 0.77 wt.%) is determined through the characterization of adjustable photoinduced hydrophilic conversion and appropriate NO catalytic generation within the effective physiological concentration. After vascular implantation in rats, the TiO2@Cu1 nanofilms achieved elevated performances on antithrombosis, reducing the intima hyperplasia area and promoting rapid reendothelialization at 4 weeks. This study provides a valuable guideline for NO-biomimetic materials used for blood contact devices and paves the way for the surface modification for vascular implants.

In Situ Evaluation of Kinetics and Interaction Mechanism between Chenodeoxycholic Acid and N719 on Dye-Sensitized Nanofilm Surface

The photoanode of a dye-sensitized solar cell is composed of titanium dioxide and a dye adsorbed on the surface. Dye molecules, such as N719 dye, usually agglomerate due to H bond and other factors...

An in situ exchange mechanism for dye molecules and cations at the nano-semiconductor film/electrolyte interface

This communication uses electrochemical quartz crystal microbalance (EQCM) in combination with the potentiostatic method to study the in situ exchange mechanism for dye molecules and cations on the nano-film surface under a constant potential. The relationship between dye molecule desorption mass and charge was analyzed. A theoretical model was established to obtain the important parameters of cation exchange number and apparent valence electron number during dye desorption, and the microscopic desorption mechanism of the dye is further revealed.

Mechano-signalling, induced by fullerene C60 nanofilms, arrests the cell cycle in the G2/M phase and decreases proliferation of liver cancer cells.

Introduction and objectiveDegradation of the extracellular matrix (ECM) changes the physicochemical properties and dysregulates ECM–cell interactions, leading to several pathological conditions, such as invasive cancer. Carbon nanofilm, as a biocompatible and easy to functionalize material, could be used to mimic ECM structures, changing cancer cell behavior to perform like normal cells.MethodsExperiments were performed in vitro with HS-5 cells (as a control) and HepG2 and C3A cancer cells. An aqueous solution of fullerene C60 was used to form a nanofilm. The morphological properties of cells cultivated on C60 nanofilms were evaluated with light, confocal, electron and atomic force microscopy. The cell viability and proliferation were measured by XTT and BrdU assays. Immunoblotting and flow cytometry were used to evaluate the expression level of proliferating cell nuclear antigen and determine the number of cells in the G2/M phase.ResultsAll cell lines were spread on C60 nanofilms, showing a high affinity to the nanofilm surface. We found that C60 nanofilm mimicked the niche/ECM of cells, was biocompatible and non-toxic, but the mechanical signal from C60 nanofilm created an environment that affected the cell cycle and reduced cell proliferation.ConclusionThe results indicate that C60 nanofilms might be a suitable, substitute component for the niche of cancer cells. The incorporation of fullerene C60 in the ECM/niche may be an alternative treatment for hepatocellular carcinoma.

Electrostatic Nature of Size Dependences of Adsorption Properties of Ytterbium Nanofilms Grown on the Surface of Silicon: the CO–Yb–Si(111) System

The adsorption of CO molecules onto ytterbium nanofilms with their thickness varying from 1 to 16 monolayers is studied. The dependences of the number of adsorbed CO molecules (adsorption isotherms) and the work function of ytterbium films on the dose of carbon monoxide are examined. It is demonstrated that both the number of adsorbed molecules and the work function depend (under equal conditions) on the nanofilm thickness; in other words, a size effect is revealed. It is found that this size effect is induced by the electrostatic interaction between the conduction electrons of ytterbium and the electrons localized on the nanofilm surface, which establish bonding between the surface and CO molecules. This interaction depends on the film thickness and limits the number of CO molecules that may be adsorbed onto the surface of a film with a given thickness.

Электростатическая природа размерных зависимостей адсорбционных свойств нанопленок иттербия, выращиваемых на поверхности кремния: система CO-Yb-Si(111)

AbstractThe adsorption of CO molecules onto ytterbium nanofilms with their thickness varying from 1 to 16 monolayers is studied. The dependences of the number of adsorbed CO molecules (adsorption isotherms) and the work function of ytterbium films on the dose of carbon monoxide are examined. It is demonstrated that both the number of adsorbed molecules and the work function depend (under equal conditions) on the nanofilm thickness; in other words, a size effect is revealed. It is found that this size effect is induced by the electrostatic interaction between the conduction electrons of ytterbium and the electrons localized on the nanofilm surface, which establish bonding between the surface and CO molecules. This interaction depends on the film thickness and limits the number of CO molecules that may be adsorbed onto the surface of a film with a given thickness.

Transfilm passivation of a silicon–ytterbium nanofilms interface with chemisorbed CO and O2 molecules

Passivation of a silicon–ytterbium nanofilm interface with СО and О2 molecules chemisorbed on the opposite side of films is studied. The transfilm inhibition of silicides is found to be caused by the Coulomb interactions between the localized electrons forming the donor–acceptor bonding of molecules with films and the conductivity electrons of ytterbium (6s-band). This interaction increases the energy of the chemisorbed molecules–ytterbium films system. At a given amount of chemisorbed molecules this increase is higher for the thinner rather than thicker films. This correlation with the film thickness favors the lack of chemical interaction between silicon and ytterbium, when СО and О2 molecules are chemisorbed on the nanofilm surface.

Ultrathin Co3O4 nanofilm as an efficient bifunctional catalyst for oxygen evolution and reduction reaction in rechargeable zinc-air batteries.

Two-dimensional (2D) nanocatalysts with a large specific surface area and efficient charge conductivity are promising candidates for catalyzing the sluggish oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), which are at the heart of various electrochemical energy conversion and storage technologies. Here, we report the synthesis of an ultrathin Co3O4 nanofilm with a thickness of nearly 1.8 nm via a surfactant- and template-free facile hydrothermal route. The proposed synthesis strategy can be extended to the preparation of 2D NixCo3-xO4 and FexCo3-xO4 nanostructures. The synthesized Co3O4 nanofilm exhibited bifunctional activity that was superior to that of the counterpart Co3O4 nanoparticles, including a lower overpotential and higher reduction and evolution current densities, and demonstrated faster catalytic kinetics over the 2D nanofilm surface. In comparison with precious metal-based catalysts, to achieve an OER current density of 40 mA cm-2 the overpotential of the nanofilm (461 mV) was lower than that of RuO2 (526 mV), whereas the ORR on the nanofilm proceeded via a dominant 4e- transfer mechanism, which is similar to that of commercial carbon-supported Pt (Pt/C). The Co3O4 nanofilm enabled the assembly of rechargeable Zn-air batteries with a lower overpotential (0.72 V), higher round-trip efficiency (62.7%), and a longer cycle lifetime (175 cycles). The remarkable bifunctional activity contributes to an increase in the number of electrochemically active sites, a large interfacial contact area with the electrolyte, and the enrichment of Co3+ ions on the surface, which facilitates the adsorption and activation of oxygen-containing species. This study should shed light on the future development of new electroactive materials with optimized 2D nanostructures to enhance the overall bifunctional ORR/OER performance of rechargeable metal-air batteries.

Highly Sensitive Electrochemical Bioassay for Hg(II) Detection Based on Plasma-Polymerized Propargylamine and Three-Dimensional Reduced Graphene Oxide Nanocomposite

In this study, a nanocomposite consisting of three-dimensional reduced graphene oxide (3D-rGO) and plasma-polymerized propargylamine (3D-rGO@PpPG) was prepared and used as a highly sensitive and selective DNA sensor for detecting Hg2+. Given the high density of amino groups in the resultant 3D-rGO@PpPG nanocomposite, thymine-rich and Hg2+-targeted DNA was preferentially immobilized on the fabricated sensor surface via the strong electrostatic interaction between DNA strands and the amino-functionalized nanocomposites, followed by detecting Hg2+ through T–Hg2+–T coordination chemistry between DNA and Hg2+. The results of electrochemical measurements revealed that the anchored amount of DNA strands anchored on the 3D-rGO@PpPG nanofilm surface affects the determination of Hg2+ in aqueous solution. It showed high sensitivity and selectivity toward Hg2+ within concentrations ranging from 0.1 to 200 nM and displayed a low detection limit of 0.02 nM. The new strategy proposed also provides high selectivity of Hg2+ against other interfering metal ions, good stability, and repeatability. The excellent applicability of the developed sensor confirms the potential use of plasma-modified nanofilms for the detection of heavy metal ions in real environmental samples and water.

Temperature transformations of optical spectra in semiconductor flat heterostructures with quantum wells.

The results of theoretical study of the temperature dependence of a long-wave range fundamental absorption edge in flat nanoheterostructures with a single quantum well (nanofilms) are adduced. The quantum well is assumed to be rectangular, of finite depth, and with unstrained heterojunctions as the nanofilm surface. Energies of electrons, holes, and excitons have been calculated within the framework of the effective mass model using the Green functions techniques, with account of their interaction with polar optical phonons confined within a quantum well. Numerical calculations are performed for nanofilms β-CdS/β-HgS/β-CdS and Al0.3Ga0.7As/GaAs/Al0.3Ga0.7As. It is shown that interaction with optical phonons causes a long-wave shift of the threshold frequency of the fundamental absorption band and a shift of exciton peaks by hundreds of Å for the first mentioned nanofilm and by dozens of Å for the second one, which is characterized by lower magnitudes of the constants of the electron-phonon coupling. The shift magnitude, as well as the height and half-width of the exciton absorption band, changes when the temperature exceeds 80 and 100 K, respectively.

Atmospheric Pressure Plasma Polymerization of Super-Hydrophobic Nano-films Using Hexamethyldisilazane Monomer

The super-hydrophobic nano-films were synthesized by atmospheric pressure plasma jet using hexamethyldisilazane. In this paper, the atmospheric pressure plasma jet reacting with air was used to determine the formation of plasma polymerized nano-film. The atmospheric pressure plasma polymerized nano-film surface properties were determined by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and atomic forced microscopy. Specifically, it has been observed that atmospheric pressure plasma polymerization with the appropriate monomer gas flow rate cause the formation of the super-hydrophobic film. The surface properties of atmospheric pressure plasma polymerized nano-films were determined as the Cassie–Baxter state. It was examined that super-hydrophobic nano-film surface exhibits the organosilicon sphere stacking structure. Such sphere stacking structure does not only cause the hydrophobicity, it also stabilizes the Cassie regime, and thus favors the water repellency.

Complex study of titanium nano-films prepared by magnetron sputtering

The oxidation of Ti films with thickness from 5 to 100 nm was performed in air at room temperature. The thickness and roughness of metal and oxide layers were determined by neutron and X-ray reflectometry. The thin titanium films were found to be oxidized to a greater depth; than the thick ones. However the metal layer was found to exist even in the thinnest (5 nm) samples, as the direct measuring of electrical resistance of the films has confirmed. The optimal parameters of titanium films utilizable in polarizing coatings of neutron optics were estimated. The AFM data on the microrelief and the phase homogeneity of the Ti nano-film surface were obtained.

Biocompatible TiO2 nanoparticle-based cell immunoassay for circulating tumor cells capture and identification from cancer patients

We demonstrate the isolation of circulating tumor cells (CTCs) with a biocompatible nano-film composed of TiO2 nanoparticles. Due to the enhanced topographic interaction between nano-film and cancer cell surface, cancer cells (HCT116) spiked into PBS and healthy blood can be recovered from the suspension, whose efficiencies were respectively 80% and 50%. Benifit from the biocompatibility of this nano-film, in-situ culture of the captured cancer cells is also available, which provides an alternative selection when the capture cell number was inadequate or the sample cannot be analyzed immediately. For the proof-of-concept study, we use this nano-film to separate the circulating tumor cells from the colorectal and gastric cancer patient peripheral blood samples and the captured CTCs are identified by a three-colored immunocytochemistry method. We investigated the cancer cells capture strength at the nano-bio interface through exposing the cells to fluid shear stress in microfluidic device, which can be utilized to increase the purity of CTCs. The result indicated that 50% of the captured cells can be detached from the substrate when the fluid shear stress was 180dyncm(-2). By integration of this CTCs capture nano-film with other single cell analysis device, we expected to further explore their applications in genome sequencing based on the captured CTCs.