Hybrid Nanofilm Research Articles

Construction of an Au/g-C3N4/GO/Au substrate by a layer-by-layer assembly approach for surface-enhanced Raman spectroscopy

In this work, an Au/g-C3N4/GO/Au hybrid nanofilm for surface-enhanced Raman scattering (SERS) substrate application was prepared by a facile layer-by-layer assembly technique using nanosheet-structured graphitic carbon nitride (g-C3N4), graphene oxide (GO) and 40 nm-gold nanoparticles (Au NPs). The effects of composition, assembly sequence and assembly cycles on the SERS performance were optimized to achieve the SERS-active substrate. The detection limit of Au/g-C3N4/GO/Au substrate for crystal violet and rhodamine 6 G probe molecules reached as high as 10−8 M, with good stability and uniformity. Its further application in food colorants detection (erythrosine, carmine and temptation red) had successfully met the national food safety standards and the quantitative detection for erythrosine and temptation red had also been established. Based on finite-difference time-domain element simulation and density functional theory quantum chemical calculation, the mechanism of the SERS effect of the substrate was unveiled, which is attributed to the combination of electromagnetic enhancement effect of Au nanoparticle aggregates and chemical enhancement effect of GO and g-C3N4. Notably, water droplet evaporation induced Raman enhancement was observed on the Au/g-C3N4/GO/Au substrate. This can be ascribed to the inhomogeneous evaporation of the droplet that promotes the enrichment of the probe molecules into the center of the droplet. This novel enhancement strategy provides a new idea for further improving detection sensitivity of SERS substrate materials.

Carreau Hybrid Nanofilm Flow Over a Stretching Sheet with Suction/Injection Effect

Carreau Hybrid Nanofilm Flow Over a Stretching Sheet with Suction/Injection Effect

Synthesis of a novel multifunctional montmorillonite/L-malic-acid/curcumin/bacterial cellulose hybrid nanofilm with excellent heat insulation, antibacterial activity and cytocompatibility

Synthesis of a novel multifunctional montmorillonite/L-malic-acid/curcumin/bacterial cellulose hybrid nanofilm with excellent heat insulation, antibacterial activity and cytocompatibility

Tailoring the flow properties of inhaled micronized drug powders by atomic and molecular layer deposition

For dry powder inhaled formulations, good flow behaviour is vital in re-dispersing the powder. However, inhaled drug powders with a particle size below 10 µm are classified as highly cohesive materials with poor flow characteristics. Here we demonstrate how to alter the flow properties of micronized budesonide powders by depositing different materials (organic, inorganic, and hybrid organic–inorganic) in the forms of nanoscale films onto the drug particles using atomic/molecular layer deposition (ALD/MLD) coatings. The angle of repose (static) and pneumatic delivery measurements were performed to access the flow characteristics. The flowability can be effectively improved with the growth of inorganic nanofilm (SiO2, TiO2, or Al2O3) via ALD and hybrid nanofilm (titanicone) via combined ALD-MLD coating. This improvement is reflected by the decrease in the angle of repose and minimum pick-up velocity (Upu), as well as promoting the pneumatic delivery of a much larger amount of drug powders after ALD or hybrid coating. In contrast, the organic PET coated budesonide via MLD exhibits comparable poor flow characteristics as the uncoated budesonide. Rather than being transported in individual particles, the uncoated or PET-coated budesonide powders are pneumatically delivered in form of complex clusters with a size of over 500 μm, whereas the ALD budesonide is dispersed in form of small agglomerates (<100 μm). Despite the difference in agglomerate size, entraining behaviors of all samples agree well with the prediction of Kalman’s pick-up Zone I correlation. The inorganic nanofilm deposited via ALD alters the surface chemistry to reduce the inter-particle forces measured by atomic force microscopy, giving rise to an improved drug delivery performance. Nanoscale surface modification of dry powder particles has good potential for inhaled drug delivery enhancement.

Detection of Proton Carriers in Tyrosine-Rich Peptide Thin Film

Traditional Von Neumann structure, where memory and computational units are separated, is now facing significant difficulties in terms of power consumption and computing speed in big data era. Therefore, human brain-like computing architecture is now paid attention in research field owing to its high parallelism, fault tolerance and robustness1-2. In this biological system, synaptic weight which plays crucial role in memory and learning is modulated by ionic species, especially protons transmitted between synapses. Here, we focused on short length peptide Y7C (YYACAYY) thin film which induces proton coupled electron transfer (PCET) due to its Tyrosine-rich structure. The Y7C film has shown an interesting behavior in which electrical conductivity varies with humidity3-4. By this modulation, bimodal memristor using both of voltage and humidity5 input and synaptic transistor which shows dynamic reponses through humidity have been demonstrated, but direct relation between current and proton conduction is still ambiguous. Therefore, we measured transient current flow between Pd and Au electrode and detected proton conduction of Y7C film.In previous studies, voltage & humidity controlled Y7C bimodal memristor has been reported. However, since the current regulation through humidity showed insufficient response than that through voltage, a definite relationship between moisture and current needs to be defined. To achieve that, thin film of the peptide material dissolved in Trifluoroacetic acid (TFA) 99% solution was spin coated on SiO2/Si substrate. By measuring the transient current of the Y7C film, presence of temporary charge carriers was observed. Also, the electrical impedance spectroscopy (EIS) of peptide layer showed a semicircle and a nonvertical tail, which indicate ionic conduction through the film. Lastly, film characterization of Y7C thin layer unveiled that the corresponding ions are protons as originally targeted. This research has showed principles of peptide thin film’s current increment driven by both of humidity and voltage through electrochemical reaction. Fig.1. Transient charge flowing through Y7C thin film measured in various atmospheric conditions and electrodes Acknowledgment This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2020R1A2C2004864). References Pakkenberg B, Pelvig D, Marner L, Bundgaard M J, Gundersen H J G, Nyengaard J R and Regeur L 2003 Exp. Gerontol. 38 95Abbott L F and Nelson S B 2000 Nat. Neurosci. 3 1178Lee, Jaehun, et al. "Proton conduction in a tyrosine‐rich peptide/manganese oxide hybrid nanofilm." Advanced Functional Materials 27.35 (2017): 1702185.Sung, Taehoon, et al. "Effects of proton conduction on dielectric properties of peptides." RSC advances 8.59 (2018): 34047-34055.Song, Min-Kyu, et al. "Proton-enabled activation of peptide materials for biological bimodal memory." Nature Communications 11.1 (2020): 1-8. Figure 1

Synthesis and Structure of a Two-Dimensional Palladium Oxide Network on Reduced Graphene Oxide.

New nanostructures often reflect new and exciting properties. Here, we present an two-dimensional, hitherto unreported PdO square network with lateral dimensions up to hundreds of nanometers growing on reduced graphene oxide (rGO), forming a hybrid nanofilm. An intermediate state of dissolved Pd(0) in the bacterium S. oneidensis MR-1 is pivotal in the biosynthesis and inspires an abiotic synthesis. The PdO network shows a lattice spacing of 0.5 nm and a thickness of 1.8 nm on both sides of an rGO layer and is proposed to be cubic or tetragonal crystal, as confirmed by structural simulations. A 2D silver oxide analog with a similar structure is also obtained using an analogous abiotic synthesis. Our study thus opens a simple route to a whole new class of 2D metal oxides on rGO as promising candidates for graphene superlattices with unexplored properties and potential applications for example in electronics, sensing, and energy conversion.

The nanophotonic machinal cavity and its hydrogen sensing application

Hydrogen, a clean energy carrier, possesses great potential to be an alternative fuel in the future. However, it also has a reputation for being explosive and dangerous. Thus, in the realization of hydrogen energy utilization, hydrogen safe storage and transport are the main issues which currently need to be solved at present. For safety, hydrogen leaks or concentration variations should be monitored accurately and timely during storage or transport. Among the many sensors, the optical hydrogen sensor can satisfy demands of safety, online detection, undisturbed surrounding, and lack of spark. Hence, a fiber-based nanophotonic machinal cavity (NPMC) is proposed and proved that it can be used for hydrogen sensing. This cavity is composed of two mirrors: One is fiber-air interface, another is gold (Au)/palladium (Pd) hybrid nanofilm, herein, Au film with low elastic modulus is employed as a reflective mirror and support substrate of Pd component. Since Pd-hydrogen reactions can induce deformation on this hybrid nanofilm, which will change the resonant characteristics of the cavity, Pd functions as hydrogen-sensitive nanomaterial. Experimentally, Au/Pd hybrid nanofilm-based NPMCs are prepared and used to demonstrates the feasibility of hydrogen sensing. The experimental results reveal that this proposed NPMC maintains advantages of reusable, durable, fast response/recovery (12/1s), low limit of detection (0.1%) and widely linear detection range (1–3.5%) in hydrogen sensing application. This intrinsically safe, miniaturized fiber optic device can be used in space constrained and hazardous environments.

Crack Suppression in Conductive Film by Amyloid-Like Protein Aggregation toward Flexible Device.

A fatal weakness in flexible electronics is the mechanical fracture that occurs during repetitive fatigue deformation; thus, controlling the crack development of the conductive layer is of prime importance and has remained a great challenge until now. Herein, this issue is tackled by utilizing an amyloid/polysaccharide molecular composite as an interfacial binder. Sodium alginate (SA) can take part in amyloid-like aggregation of the lysozyme, leading to the facile synthesis of a 2D protein/saccharide hybrid nanofilm over an ultralarge area (e.g., >400cm2 ). The introduction of SA into amyloid-like aggregates significantly enhances the mechanical strength of the hybrid nanofilm, which, with the help of amyloid-mediated interfacial adhesion, effectively diminishes the microcracks in the hybrid nanofilm coating after repetitive bending or stretching. The microcrack-free hybrid nanofilm then shows high interfacial activity to induce electroless deposition of metal in a Kelvin model on a substrate, which noticeably suppresses the formation of microcracks and consequent conductivity loss during the bending and stretching of the metal-coated flexible substrates. This work underlines the significance of amyloid/polysaccharide nanocomposites in the design of interfacial binders for reliable flexible electronic devices and represents an important contribution to mimicking amyloid and polysaccharide-based adhesive cements created by organisms.

Ultrathin poly (vinyl alcohol)/MXene nanofilm composite membrane with facile intrusion-free construction for pervaporative separations

Molecular separations using synthetic membranes have been widely recognized as energy-efficient processes relative to conventional separation technologies. Rational design of the membrane structures for attainment of exceptionally permselective materials is highly beneficial in this respect. Herein, an ultrathin organic-inorganic hybrid nanofilm is formed on a hydrophobic polytetrafluoroethylene porous substrate through a facile and scalable solution casting process, thereby realizing an intrusion-free composite structure. Nanosizing Ti3C2Tx MXene and sulfosuccinic acid are incorporated as nanofiller and crosslinker to manipulate the structural rigidity and free-volume property by polymer-nanofiller interaction and polymer chain crosslinking while simultaneously rendering outstanding membrane transport property, selectivity and stability. The synthesized nanofilm composite membrane with thickness down to ≈230 nm, comparable with the lateral dimension of small-sized MXene (≈142 nm), exhibits outstanding pervaporative separation of water from various aqueous-ion or -alcohol mixtures with high throughput that is around 5–70 times of other reported polymer-based membranes. Transport modelling of this hybrid nanofilm suggests that ultralow-resistance permeation behavior induced by MXene nanosheets dominates as the nanofilm thickness approaches the filler size.

Hybrid nanofilms as topical anesthetics for pain-free procedures in dentistry

Topical anesthetics are widely applied in order to relieve the discomfort and anxiety caused by needle insertion and other painful superficial interventions at the oral cavity. So far, there are no commercially available effective topical anesthetic formulations for that purpose, and the most of developments are related to hydrophilic and low mucoadhesive forms. Therefore, we have prepared different hybrid nanofilms composed of biopolymer matrices (chitosan, pectin, and chitosan-pectin) blended with nanostructured lipid carriers (NLC) loading the eutectic mixture of 5% lidocaine–prilocaine (LDC–PLC), in order to fulfill this gap in the market. These dual systems were processed as hybrid nanofilms by the solvent/casting method, and its mucoadhesive, structural and mechanical properties were detailed. The most appropriate hybrid nanofilm combined the advantages of both pectin (PCT) and NLC components. The resultant material presented sustained LDC–PLC release profile for more than 8 h; permeation across porcine buccal mucosa almost twice higher than control and non-cytotoxicity against 3T3 and HACAT cell lines. Then, the in vivo efficacy of PCT/NLC formulation was compared to biopolymer film and commercial drug, exhibiting the longest-lasting anesthetic effect (> 7 h), assessed by tail flick test in mice. These pectin-based hybrid nanofilms open perspectives for clinical trials and applications beyond Dentistry.

Sucrose concentration sensor based on MoS2 nanofilm and Au nanowire array enhanced surface plasmon resonance with a graphene oxide nanosheet

A method of sucrose concentration detection based on surface plasmon resonance is proposed. Thus, what we believe to be a novel prism coupling structure is designed for a sucrose concentration sensor utilizing the unique feature of graphene oxide to sucrose in water, and a ${{\text{MoS}}_2}$MoS2-graphene oxide hybrid nanofilm is chosen to enhance surface plasmon resonance based on Au nanoparticles. The thickness of each layer for the designed structure is analyzed to get the optimal value by the finite element method, so that the sensitivity of the sucrose concentration sensor is able to be improved greatly. The optimal thickness of each layer is given, for which the sensitivity of the surface plasmon resonance sucrose concentration sensor can reach as high as 0.16°/% concentration within the detection range of sucrose concentration, 0%–70% concentration. The relationship between the sucrose concentration and the surface plasmon resonance angle are obtained within the detection range of the sucrose concentration.

Sn-Triggered Two-Dimensional Fast Protein Assembly with Emergent Functions.

The discovery of a general strategy for organizing functional proteins into stable nanostructures with the desired dimension, shape, and function is an important focus in developing protein-based self-assembled materials, but the scalable synthesis of such materials and transfer to other substrates remain great challenges. We herein tackle this issue by creating a two-dimensional metal-protein hybrid nanofilm that is flexible and cost-effective with reliable self-recovery, stability, and multifunctionality. As it differs from traditional metal ions, we discover the capability of Sn2+ to initiate fast amyloid-like protein assembly (occurring in seconds) by effectively reducing the disulfide bonds of native globular proteins. The Sn2+-initiated lysozyme aggregation at the air/water interface leads to droplet flattening, a result never before reported in a protein system, which finally affords a multifunctional 2D Sn-doped hybrid lysozyme nanofilm with an ultralarge area (e.g., 0.2 m2) within a few minutes. The hybrid film is distinctive in its ease of coating on versatile material surfaces with endurable chemical and mechanical stability, optical transparency, and diverse end uses in antimicrobial and photo-/electrocatalytic scaffolds. Our approach provides not only insights into the effect of tin ions on macroscopic self-assembly of proteins but also a controllable and scalable synthesis of a potential biomimic framework for biomedical and biocatalytic applications.

Amperometric H2O2 sensor based on gold nanoparticles/poly (celestine blue) nanohybrid film

The present paper demonstrates a significant hybrid nanofilm using gold nanoparticles (GNPs) and poly celestine blue (PCB) as an effective sensing material for hydrogen peroxide (H2O2). The surface assembly of the nanocatalyst GNPs provides greater surface area for improved layering of PCB on the electrode surface. Cyclic voltammetry, UV visible spectroscopy and field emission scanning electron microscopy studies confirmed the structure and morphology of the synthesized GNPs. Cyclic voltammetric characterization of the fabricated GNPs/PCB electrode was performed and under optimal conditions they exhibited enhanced electrochemical sensing towards H2O2 with better sensitivity and detection limit as 0.22 µA/µM and 3.9 × 10−6 M (S/N = 3). The interference studies using the GNPs/PCB modified electrode interprets the selectivity of the electrode towards H2O2. The proposed sensor was highly stable and was effectively applied for analysis of H2O2 in real samples.

Planar waveguide nanolaser configured by dye-doped hybrid nanofilm on substrate

Dye-doped hybrid silicate/titanium nanofilms on the glass substrate structures of asymmetrical waveguides were studied by way of laser systems. The threshold, spatial and spectral features of the laser oscillation of genuine and hollow waveguides were determined. The pattern of stimulated radiation included two concurrent processes: single-mode waveguide lasing and lateral small divergence emission. Comparison of the open angle of the lateral beams and grazing angles of the waveguide lasing mode provides an insight into the effect of leaky mode emission followed by Lummer–Gehrcke interference.

Tannic Acid/Fe3+/Ag Nanofilm Exhibiting Superior Photodynamic and Physical Antibacterial Activity.

Silver nanoparticles (AgNPs) enwrapped in the biologically safe tannic acid (TA)/Fe3+ nanofilm are synthesized by an ultrafast, green, simple, and universal method. The physical antibacterial activity and photodynamic antibacterial therapy (PAT) efficacy of the TA/Fe3+/AgNPs nanofilm were investigated for the first time, which exhibited a strong physical antibacterial activity as well as great biocompatibility, through in vitro and in vivo studies. The results disclosed that this hybrid coating could possess high PAT capabilities upon irradiation under a visible light of 660 nm, which is longer than those of previously reported green and blue sensitization light, thus allowing deeper light penetration into biological tissues. Electron spin resonance (ESR) spectra proved that the PAT efficacy of the TA/Fe3+/AgNPs nanofilm was associated with the yields of singlet oxygen (1O2) under the irradiation of visible light (660 nm). A higher PAT efficiency of 100 and 94% against Escherichia coli and Staphylococcus aureus could be achieved within 20 min of illumination under 660 nm visible light, whereas the innate physical antibacterial activity of AgNPs could endow the implants with long-term prevention of bacterial infection. The mechanism of PAT may be associated with the formation of oxidative stress and oxidative damage to key biomolecules (proteins and lipids) in bacteria. Our results reveal that the synergistic action of both PAT and physical action of AgNPs in this hybrid nanofilm is an effective way to inactivate bacteria, with minimal side effects.

Proton Conduction in a Tyrosine‐Rich Peptide/Manganese Oxide Hybrid Nanofilm

Proton conduction is an essential process that regulates an integral part of several enzymatic catalyses and bioenergetics. Proton flows in biological entities are sensitively controlled by several mechanisms. To understand and manipulate proton conduction in biosystems, several studies have investigated bulk proton conduction in biomaterials such as polyaspartic acid, collagen, reflectin, serum albumin mats, and eumelanin. However, little is known about the bulk proton conductivity of short peptides and their sequence‐dependent behavior. Here, this paper focuses on a short tyrosine‐rich peptide that has redox‐active and cross‐linkable phenol groups. The spin‐coated peptide nanofilm is immersed in potassium permanganate solution to induce cross‐linking and oxidation, simultaneously leading to hybridization with manganese oxide (MnOx). The peptide/MnOx hybrid nanofilm can efficiently transport protons, and its proton conductivity is ≈18.6 mS cm−1 at room temperature. This value is much higher than that of biomaterials and comparable to those of other synthetic proton‐conducting materials. These results suggest that peptide‐based hybrid materials can be a promising new class of proton conductor.

Direct growth of Fe3O4-MoO2 hybrid nanofilm anode with enhanced electrochemical performance in neutral aqueous electrolyte

To enhance the electrochemical energy storage performance of supercapacitors (SCs), the current researches are general directed towards the cathode materials. However, the anode materials are relatively less studied. In the present work, Fe3O4-MoO2 (FO-MO) hybrid nano thin film directly grown on Ti substrate is investigated, which is used as high-performance anode material for SCs in Li2SO4 electrolyte with the comparison to pristine Fe3O4 nanorod array. The areal capacitance of FO-MO hybrid electrode was initially found to be 65.0mFcm−2 at 2mVs−1 and continuously increased to 260.0% after 50 cycles of activation. The capacitance values were considerably comparable or higher than many reported thin-film iron oxide-based anodes in neutral electrolyte. With the protection of MoO2 shell, the FO-MO electrode developed in this study also exhibited excellent cyclic stability (increased to 230.8% after 1000 cycles). This work presents a promising way to improve the electrochemical performance of iron oxide-based anodes for SCs.

Biomimetic Sensors: Vectorially Imprinted Hybrid Nanofilm for Acetylcholinesterase Recognition (Adv. Funct. Mater. 32/2015)

Biomimetic Sensors: Vectorially Imprinted Hybrid Nanofilm for Acetylcholinesterase Recognition (Adv. Funct. Mater. 32/2015)

Vectorially Imprinted Hybrid Nanofilm for Acetylcholinesterase Recognition

Effective recognition of enzymatically active tetrameric acetylcholinesterase (AChE) is accomplished by a hybrid nanofilm composed of a propidium‐terminated self‐assembled monolayer (Prop‐SAM) which binds AChE via its peripheral anionic site (PAS) and an ultrathin electrosynthesized molecularly imprinted polymer (MIP) cover layer of a novel carboxylate‐modified derivative of 3,4‐propylenedioxythiophene. The rebinding of the AChE to the MIP/Prop‐SAM nanofilm covered electrode is detected by measuring in situ the enzymatic activity. The oxidative current of the released thiocholine is dependent on the AChE concentration from ≈0.04 × 10−6 to 0.4 × 10−6m. An imprinting factor of 9.9 is obtained for the hybrid MIP, which is among the best values reported for protein imprinting. The dissociation constant characterizing the strength of the MIP‐AChE binding is 4.2 × 10−7m indicating the dominant role of the PAS‐Prop‐SAM interaction, while the benefit of the MIP nanofilm covering the Prop‐SAM layer is the effective suppression of the cross‐reactivity toward competing proteins as compared with the Prop‐SAM. The threefold selectivity gain provided by i) the “shape‐specific” MIP filter, ii) the propidium‐SAM, iii) signal generation only by the AChE bound to the nanofilm shows promise for assessing AChE activity levels in cerebrospinal fluid.

Sandwiched confinement of quantum dots in graphene matrix for efficient electron transfer and photocurrent production.

Quantum dots (QDs) and graphene are both promising materials for the development of new-generation optoelectronic devices. Towards this end, synergic assembly of these two building blocks is a key step but remains a challenge. Here, we show a one-step strategy for organizing QDs in a graphene matrix via interfacial self-assembly, leading to the formation of sandwiched hybrid QD-graphene nanofilms. We have explored structural features, electron transfer kinetics and photocurrent generation capacity of such hybrid nanofilms using a wide variety of advanced techniques. Graphene nanosheets interlink QDs and significantly improve electronic coupling, resulting in fast electron transfer from photoexcited QDs to graphene with a rate constant of 1.3 × 109 s−1. Efficient electron transfer dramatically enhances photocurrent generation in a liquid-junction QD-sensitized solar cell where the hybrid nanofilm acts as a photoanode. We thereby demonstrate a cost-effective method to construct large-area QD-graphene hybrid nanofilms with straightforward scale-up potential for optoelectronic applications.