Nanoscale Morphology Research Articles

Morphology Tuning via Linker Modulation: Metal-Free Covalent Organic Nanostructures with Exceptional Chemical Stability for Electrocatalytic Water Splitting.

The development of synthetic routes for the formation of robust porous organic polymers (POPs) with well-defined nanoscale morphology is fundamentally significant for their practical applications. The thermodynamic characteristics that arise from reversible covalent bonding impart intrinsic chemical instability in the polymers, thereby impeding their overall potential. Herein, a unique strategy is reported to overcome the stability issue by designing robust imidazole-linked POPs via tandem reversible/irreversible bond formation. Incorporating inherent rigidity into the secondary building units leads to robust microporous polymeric nanostructures with hollow-spherical morphologies. An in-depth analysis by extensive solid-state NMR (1D and 2D) study on 1H, 13C, and 14N nuclei elucidates the bonding and reveals the high purity of the newly designed imidazole-based POPs. The nitrogen-rich polymeric nanostructures are further used as metal-free electrocatalysts for water splitting. In particular, the rigid POPs show excellent catalytic activity toward the oxygen evolution reaction (OER) with long-term durability. Among them, the most efficient OER electrocatalyst (TAT-TFBE) requires 314mV of overpotential to drive 10 mAcm-2 current density, demonstrating its superiority over state-of-the-art catalysts (RuO2 and IrO2).

Role of Nanoscale Morphology on the Efficiency of Solvent-Based Desalination Method

Brine desalination is important for minimizing the environmental impact of contaminated wastewater, yet current desalination techniques have high energy requirements. Solvent-based desalination (SBD) method, which is the process of extracting fresh water using an organic solvent, has existed for decades, yet has not reached competitive efficiencies. In this work, 10 organic solvents were tested for SBD efficacy via synergetic studies using bench-scale extraction experiments and molecular dynamics (MD) simulations. The SBD effectiveness was correlated to the computationally observed ability of the solvent to form one of the three morphologies in water: ordered, disordered, or partial nanoscale. We correlated that solvents that form ordered and disordered morphologies were not able to clean up the water. Solvents that were able to cause low salinity in water showed computationally observed partial nanoscale phase separation, where nanometer-scale aggregated solvent phases were able to effectively reject salt ions while capturing comparatively large amounts of water molecules. The formation of a partial nanoscale phase is likely driven by the solvent structure with bulky hydrocarbons adjacent to hydrophilic end groups. Our results make a step toward the rational design of solvents that may allow for efficient SBD and thus a low-cost source of fresh water.

An Investigation into the Effects of Electric Field Uniformity on Electrospun TPU Fiber Nano-Scale Morphology.

ANSYS Maxwell was used to replicate the conditions of two potential electrospinning configurations: a needle-plate and a parallel-plate configuration. Simulations showed that the electric field generated within the parallel-plate configuration was much more uniform than that within the needle-plate configuration. Both configurations were assembled and used electrospin fibers at three different spinning distances (10 cm, 12 cm, and 15 cm), at a consistent electric field strength of 1.7 kV/cm. Scanning electron microscopy was used to compare the morphologies of the fibers produced in both configurations in order to confirm whether a more uniform electric field yielded thinner fibers. The results show that the needle-plate configuration produced finer fibers than the parallel-plate configuration at all three spinning distances. However, there was no difference in the fiber diameters produced at the 12 and 15 cm spinning distances within the needle-plate configuration, implying thinning may only occur up to a certain distance in this configuration.

Boosting the H2–D2 Exchange Activity of Dilute Nanoporous Ti–Cu Catalysts through Oxidation–Reduction Cycle–Induced Restructuring

The use of nanoporous metals as catalysts has attracted significant interest in recent years. Their high‐curvature, nanoscale ligaments provide not only high surface area but also a high density of undercoordinated step edge and kink sites. However, their long‐term stability, especially at higher temperatures, is often limited by thermal coarsening and the associated loss of surface area. Herein, it is demonstrated that the nanoscale morphology of nanoporous Cu can be regenerated by applying oxidation/reduction cycles at 250 °C. Specifically, the morphological evolution and H2 dissociation activity of hierarchical nanoporous Cu catalysts doped with Ti during structural rearrangement triggered by oxidative and reductive atmospheres at elevated temperatures are studied. In addition to coarsening of the structure at elevated temperatures, oxidation at 400 °C causes an expansion of the ligaments. Subsequent reduction at 400 °C leads to the formation of particles and a drop in the H2 dissociation activity compared the fresh catalyst. However, performing the redox cycle at 250 °C reverses coarsening and boosts the H2 dissociation activity for the hydrogen–deuterium (H2–D2) reaction. Herein, the possibility to reverse coarsening is demonstrated, thereby mitigating the loss of activity frequently observed in nanoporous catalysts.

Rigid epoxy networks with very high intrinsic fracture toughness using a piperazine-based in-situ polymerization strategy

Various fillers and thermoplastics are often added to thermoset epoxies to improve toughness, but this may compromise their other properties or make synthesis difficult. In this study, brittle crosslinked epoxy networks are significantly toughened through in-situ polymerization of epoxy using piperazine, which reacts at moderately low temperatures in a catalyst-free one-pot method. Dynamic mechanical properties and nanoscale morphology suggest the mechanism for improved toughness is higher yielding near the crack tip due to increased molecular weight between crosslinks. The resulting toughness (KIC ∼ 2.12 MPa√m, GIC ∼ 1.96 kJ/m2) is higher than any other unfilled all-epoxy materials found in the literature.

Covalent Organic Framework Nanobowls as Activatable Nanosensitizers for Tumor-Specific and Ferroptosis-Augmented Sonodynamic Therapy.

Covalent organic frameworks (COFs) have attracted increasing attention for biomedical applications. COFs-based nanosensitizers with uniform nanoscale morphology and tumor-specific curative effects are in high demand; however, their synthesis is yet challenging. In this study, distinct COF nanobowls are synthesized in a controlled manner and engineered as activatable nanosensitizers with tumor-specific sonodynamic activity. High crystallinity ensures an ordered porous structure of COF nanobowls for the efficient loading of the small-molecule sonosensitizer rose bengal (RB). To circumvent non-specific damage to normal tissues, the sonosensitization effect is specifically inhibited by the in situ growth of manganese oxide (MnOx ) on RB-loaded COFs. Upon reaction with tumor-overexpressed glutathione (GSH), the "gatekeeper" MnOx is rapidly decomposed to recover the reactive oxygen species (ROS) generation capability of the COF nanosensitizers under ultrasound irradiation. Increased intracellular ROS stress and GSH consumption concomitantly induce ferroptosis to improve sonodynamic efficacy. Additionally, the unconventional bowl-shaped morphology renders the nanosensitizers with enhanced tumor accumulation and retention. The combination of tumor-specific sonodynamic therapy and ferroptosis achieves high efficacy in killing cancer cells and inhibiting tumor growth. This study paves the way for the development of COF nanosensitizers with unconventional morphologies for biomedicine, offering a paradigm to realize activatable and ferroptosis-augmented sonodynamic tumor therapy.

How clathrin-coated pits control nanoparticle avidity for cells.

The paramount relevance of clathrin-coated pits (CCPs) to receptor-mediated endocytosis of nanoparticles, extracellular vesicles, and viruses has made them the focus of many studies; however, the role of CCP geometry in the ligand-receptor interactions between multivalent nanoparticles and cells has not been investigated. We hypothesized the general dependence of nanoparticle binding energy on local membrane curvature to be expandable to the specific case of ligand-functionalized nanoparticles binding cell membranes, in the sense that membrane structures whose curvature matches that of the particle (e.g., CCPs) signficantly contribute to binding avidity. We investigated this hypothesis with nanoparticles that bind multivalently to angiotensin II receptor type 1, which is subject to clathrin-mediated endocytosis. When we used cholesterol extraction to prevent the action of CCPs, we found a 67 to 100-fold loss in avidity. We created a theoretical model that predicts this decrease based on the loss of ligand-receptor interactions when CCPs, which perfectly match nanoparticle geometry, are absent. Our findings shed new light on how cells "see" nanoparticles. The presence or absence of CPPs is so influential on how cells interact with nanoparticles that the number of particles required to be visible to cells changes by two orders of magnitude depending on CCP presence.

A fluorine functionalised phosphine based solid additive for morphology control and achieving efficient organic solar cells

A volatile solid additive (tris(pentafluorophenyl)phosphine) is used to modulate the nanoscale phase-separated morphology of a photoactive layer to fabricate an efficient organic photovoltaic device with a power conversion efficiency of 16.9%.

Constructing interface engineering and tailoring a nanoflower-like FeP/CoP heterostructure for enhanced oxygen evolution reaction.

The inexpensive and highly efficient electrocatalysts toward oxygen evolution reaction (OER) in water splitting electrolysis have displayed promising practical applications to relieve energy crisis. Herein, we prepared a high-yield and structurally regulated bimetallic cobalt-iron phosphide electrocatalyst by a facile one-pot hydrothermal reaction and subsequent low-temperature phosphating treatment. The tailoring of nanoscale morphology was achieved by varying the input ratio and phosphating temperature. Thus, an optimized FeP/CoP-1-350 sample with the ultra-thin nanosheets assembled into a nanoflower-like structure was obtained. FeP/CoP-1-350 heterostructure displayed remarkable activity toward the OER with a low overpotential of 276 mV at a current density of 10 mA cm-2, and a low Tafel slope of only 37.71 mV dec-1. Long-lasting durability and stability were maintained with the current with almost no obvious fluctuation. The enhanced OER activity was attributed to the presence of copious active sites from the ultra-thin nanosheets, the interface between CoP and FeP components, and the synergistic effect of Fe-Co elements in the FeP/CoP heterostructure. This study provides a feasible strategy to fabricate highly efficient and cost-effective bimetallic phosphide electrocatalysts.

Direct fabrication of NbS2 nanoflakes on carbon fibers by atomic layer deposition for ultrasensitive cardiac troponin I detection.

The sensitive detection of cardiac troponin I (cTnI) is of great significance for the early diagnosis of acute myocardial infarction (AMI). Herein, in order to fabricate an electrochemical biosensor for ultrasensitive cTnI detection, atomic layer deposition (ALD) was employed to directly deposit NbS2 nanoflakes (NFs) on carbon fiber paper (CFP). Due to the self-limiting reaction of ALD, NbS2NFs were deposited uniformly and accurately on the surface of carbon fibers by controlling the number of ALD cycles, which ensured ultrasensitive detection. Precise regulation of the nanoscale morphology and electrochemical performance of NbS2 nanoflakes via ALD cycles was observed in depth. Owing to the high surface area and conductivity, an anodic/cathodic current of ∼3.01 mA of NbS2NFs/CFP can be obtained. Subsequently, an electrochemical biosensor based on the excellent performance of NbS2NFs/CFP was fabricated. The ultrasensitive detection of cTnI in a linear range of 1 fM to 0.1 nM with a detection limit of 0.32 fM was achieved.

Restrained energetic disorder for high-efficiency organic solar cells via a solid additive

A new morphology regulation approach using solid additive, 1,3,5-trimethoxybenzene, can restrict energetic disorder and optimize the nanoscale morphology of organic solar cells, and achieves a high power conversion efficiency of 19.30%.

A Mini Review on the Development of Conjugated Polymers: Steps towards the Commercialization of Organic Solar Cells

This review article covers the synthesis and design of conjugated polymers for carefully adjusting energy levels and energy band gap (EBG) to achieve the desired photovoltaic performance. The formation of bonds and the delocalization of electrons over conjugated chains are both explained by the molecular orbital theory (MOT). The intrinsic characteristics that classify conjugated polymers as semiconducting materials come from the EBG of organic molecules. A quinoid mesomeric structure (D-A ↔ D+ = A-) forms across the major backbones of the polymer as a result of alternating donor-acceptor segments contributing to the pull-push driving force between neighboring units, resulting in a smaller optical EBG. Furthermore, one of the most crucial factors in achieving excellent performance of the polymer is improving the morphology of the active layer. In order to improve exciton diffusion, dissociation, and charge transport, the nanoscale morphology ensures nanometer phase separation between donor and acceptor components in the active layer. It was demonstrated that because of the exciton's short lifetime, only small diffusion distances (10-20 nm) are needed for all photo-generated excitons to reach the interfacial region where they can separate into free charge carriers. There is a comprehensive explanation of the architecture of organic solar cells using single layer, bilayer, and bulk heterojunction (BHJ) devices. The short circuit current density (Jsc), open circuit voltage (Voc), and fill factor (FF) all have a significant impact on the performance of organic solar cells (OSCs). Since the BHJ concept was first proposed, significant advancement and quick configuration development of these devices have been accomplished. Due to their ability to combine great optical and electronic properties with strong thermal and chemical stability, conjugated polymers are unique semiconducting materials that are used in a wide range of applications. According to the fundamental operating theories of OSCs, unlike inorganic semiconductors such as silicon solar cells, organic photovoltaic devices are unable to produce free carrier charges (holes and electrons). To overcome the Coulombic attraction and separate the excitons into free charges in the interfacial region, organic semiconductors require an additional thermodynamic driving force. From the molecular engineering of conjugated polymers, it was discovered that the most crucial obstacles to achieving the most desirable properties are the design and synthesis of conjugated polymers toward optimal p-type materials. Along with plastic solar cells (PSCs), these materials have extended to a number of different applications such as light-emitting diodes (LEDs) and field-effect transistors (FETs). Additionally, the topics of fluorene and carbazole as donor units in conjugated polymers are covered. The Stille, Suzuki, and Sonogashira coupling reactions widely used to synthesize alternating D-A copolymers are also presented. Moreover, conjugated polymers based on anthracene that can be used in solar cells are covered.

Probing Surfactant Bilayer Interactions by Tracking Optically Trapped Single Nanoparticles

AbstractSingle‐particle tracking and optical tweezers are powerful techniques for studying diverse processes at the microscopic scale. The stochastic behavior of a microscopic particle contains information about its interaction with surrounding molecules, and an optical tweezer can further facilitate this observation with its ability to constrain the particle to an area of interest. Although these techniques found their initial applications in biology, they can also shed new light on microscopic interface phenomena by unveiling nanoscale morphologies and molecular‐level interactions in real time, which are obscured in traditional ensemble analysis. Here, the application of single‐particle tracking and optical tweezers are demonstrated for studying molecular interactions at solid–liquid interfaces. Specifically, the surfactant behaviors at the water–glass interface are investigated by tracing gold nanoparticles that are optically trapped on these molecules. The underlying mechanisms governing the particle motion, which can be explained by hydrophobic interactions, disruptions, and rearrangements among surfactant monomers at the interfaces, are discovered. These interpretations are further supported by statistical analysis of an individual trajectory and comparison with theoretical predictions. The findings provide new insights into the surfactant dynamics and also illustrate the promise of single‐particle tracking and optical manipulation for studying nanoscale physics and chemistry of surfaces and interfaces.

Solvent-Vapor-Assisted Self-Assembly of Semiconducting Polymers at the Air–Liquid Interface: Impact on Nanoscale Morphology and Optoelectrical Anisotropy

Rapid evaporation of volatile solvents sometimes forcefully limits the time of molecular self-organization toward the growth of highly oriented semicrystalline thin films of organic semiconducting polymers (OSPs). We are reporting a unified approach harnessing the key advantages of the “floating-film transfer method” (FTM) along with the effect of solvent-vapor-assisted controlled evaporation of the solvents to fabricate a high-quality active semiconducting layer for better-performing organic field-effect transistors. To accomplish this, regioregular poly(3-hexylthiophene-2,5-diyl) has been used as a model OSP, and the fabricated films were thoroughly characterized using several tools to understand the structure–property correlation by exploring the fundamental properties. Oriented thin films thus fabricated exhibited highly “edge-on” oriented molecular packing with reduced interlamellar spacing, dh00, and extended π-conjugation length and lower exciton bandwidth. Moreover, quantum-dot-like aggregated nanostructuring within the crystalline domains, as evidenced by high-resolution transmission electron microscopy, forms a network of interconnected conductive pathways. This leads to enhanced field-effect mobility along the polymer backbone, μ|| = 0.0498 cm2 V–1 s–1, which is around five times higher than that of the thin films prepared by conventional FTM. Thus, our study demonstrated a facile route to obtain uniaxially oriented and highly crystalline OSP films suitable for solution-processed high-performance organic electronic device applications.

Nanoscale morphology and thermal properties of low insertion loss fiber Bragg gratings produced using the phase mask technique and a single femtosecond laser pulse.

Fiber Bragg gratings with a very low insertion loss are inscribed using the phase mask technique and a single infrared (800 nm) femtosecond laser pulse. The morphology of the resultant light-induced structural changes in the Ge-doped silica fiber (SMF-28) is analyzed using scanning electron microscopy. The electron microscopy images reveal that each Bragg grating period incorporates an elongated micropore embedded in a region of homogeneous material modification. The Bragg wavelength drift and reflectivity of fiber Bragg gratings produced with single pulses having the same energy but different duration (80 fs and 350 fs) are monitored for 1000 hours in the course of isothermal annealing at 1000°C. The annealing data demonstrate that both the isothermal Bragg wavelength drift and the decrease in the reflectivity of the fiber Bragg gratings under test are statistically slower for the 350 fs inscription pulses.

Bio-based semi-interpenetrating networks with nanoscale morphology and interconnected microporous structure

Creating new bio-based sustainable polymeric materials with similar or better performance than the petroleum-based counterparts has recently received considerable attention. It will have a significant positive impact on the environment and the sustainable polymer industry. This review article shows a relatively new method based on simultaneous in-situ polymerization and compatibilization of bio-based plant oil and biodegradable thermoplastic polymer to prepare semi-interpenetrating polymer networks (SINs) with unusual nano-scale morphology and interconnected porous structure will be summarized. The SINs were synthesized via cationic polymerization of tung oil in a homogenous solution of poly(ε-caprolactone) as a biodegradable, semi-crystalline, and biocompatible thermoplastic polymer. The degrees of miscibility, nanostructure morphology, and crystallinity was found to be composition-dependent. This relatively new blending method created a two-phase nanoscale morphology as small as 100 nm for blends with PCL contents of 20 and 30 wt.%. For higher PCL contents (e.g., 50 wt.% PCL blend), a co-continuous, interconnected microscale two-phase morphology was detected. The microporous structure of the SINs was also changed as a function of composition. For example, the interconnectivity and pore size was considerably decreased with increasing PCL content. Furthermore, a considerable decrease in the crystallization kinetics of PCL was observed as the PCL content is higher than or equal to 30 wt.%. While on the other hand, the crystallization kinetics accelerated significantly for 50 wt.%. This novel, low-cost strategy for preparing bio-based SINs with nanoscale morphology and interconnected three-dimensional cluster structures and desired properties should be widely used for creating new polymer systems.

Anion Effects on the Supramolecular Self-Assembly of Cationic Phenylalanine Derivatives.

Supramolecular hydrogels have emerged as a class of promising biomaterials for applications such as drug delivery and tissue engineering. Self-assembling peptides have been well studied for such applications, but low molecular weight (LMW) amino acid-derived gelators have attracted interest as low-cost alternatives with similar emergent properties. Fluorenylmethyloxycarbonyl-phenylalanine (Fmoc-Phe) is one such privileged motif often chosen due to its inherent self-assembly potential. Previously, we developed cationic Fmoc-Phe-DAP gelators that assemble into hydrogel networks in aqueous NaCl solutions of sufficient ionic strength. The chloride anions in these solutions screen the cationic charge of the gelators to enable self-assembly to occur. Herein, we report the effects of varying the anions of sodium salts on the gelation potential, nanoscale morphology, and hydrogel viscoelastic properties of Fmoc-Phe-DAP and two of its fluorinated derivatives, Fmoc-3F-Phe-DAP and Fmoc-F5-Phe-DAP. It was observed that both the anion identity and gelator structure had a significant impact on the self-assembly and gelation properties of these derivatives. Changing the anion identity resulted in significant polymorphism of the nanoscale morphology of the assembled states that was dependent on the chemical structure of the gelator. The emergent viscoelastic character of the hydrogel networks was also found to be reliant on the anion identity and gelator structure. These results demonstrate the complex interplay between the gelator and environment that have a profound and often unpredictable impact on both self-assembly properties and emergent viscoelasticity in supramolecular hydrogels formed by LMW compounds. This work also illustrates the current lack of understanding that limits the rational design of potential biomaterials that will be in contact with complex biological fluids and provides motivation for additional research to correlate the chemical structure of LMW gelators with the structure and emergent properties of the resulting supramolecular assemblies as a function of environment.

3D-printed HAp bone regeneration scaffolds enable nano-scale manipulation of cellular mechanotransduction signals

Nano-scale morphology on bone tissue engineering scaffold plays an essential role in cell behavior regulation and bone regeneration. In this study, patient-customized porous bone tissue engineering scaffolds were fabricated by 3D printing. Then functionalized nanorod morphologies were controllablyfabricated. The influence of nanorods geometrical cues on cellular behaviors and the mechanics of triggered osteogenesis were studied. In vitro studies indicated that the nanorods with a diameter of 30 nm accelerated cell proliferation and osteogenic differentiation. Yes-associated protein (YAP) was found involved in the cell sensing system, which regulates the cytoskeletal structure and gene expression. These results provided strong evidence that the surface nano-scale morphology triggered mechanotransduction related signals for promoting osteogenic differentiation. In vivo experiments indicated that the proposed 3D printed scaffolds with a nanorod coating promoted bone regeneration without exogenous cells and growth factors. This work provides a promising strategy for personalized bone tissue repair.

Fabrication of Chitosan-Based Network Polysaccharide Nanogels

In this study, we developed a method to fabricate chitosan-based network polysaccharides via the condensation between amino groups in water-soluble chitosan (WSCS) and a carboxylate-terminated maltooligosaccharide crosslinker. We previously reported on the fabrication of network-polysaccharide-based macroscopic hydrogels via the chemical crosslinking of water-soluble chitin (WSCh) with the crosslinker. Because the molecular weight of the WSCS was much smaller than that of the WSCh, in the present investigation, the chemical crosslinking of the WSCS with the crosslinker was observed at the nanoscale upon the condensation between amino and carboxylate groups in the presence of a condensing agent, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, and N-hydroxysuccinimide, affording nano-sized chitosan-based network polysaccharides. The occurrence of the crosslinking via the formation of amido linkages was supported by the IR analysis and 1H NMR measurements after the dissolution via acid hydrolysis in DCl/D2O. The products formed nanogels, whose sizes depended on the amino/carboxylate feed ratio. The nanoscale morphology and size of the products were evaluated via scanning electron microscopy, dynamic light scattering analyses, and transition electron microscopy. In the present study, we successfully developed the method to fabricate nanogel materials based on network polysaccharide structures, which can practically be applied as new polysaccharide-based 3D bionanomaterials.

Nanoscale surface dynamics of RF-magnetron sputtered CrCoCuFeNi high entropy alloy thin films

High entropy alloy (HEA) thin films of CrCoCuFeNi are grown on stainless steel substrate using radiofrequency (RF) magnetron sputtering method at different sputtering times (30, 60 and 90 minutes), substrate temperatures (room temperature, 100 and 200 deg. Celsius) and RF powers (100, 150 and 200 W). The nanoscale morphology and topography of the thin films are obtained using an atomic force microscopy (AFM) method. The average surface roughness, interface width, fractal and multifractal characteristics of the films are presented. It is shown that the average surface roughness and interface width decrease with the time of deposition while considering the combination of the other factors. The autocorrelation and height-height correlation functions reveal that these surfaces are self-affine and exhibit fractal characteristics. The increase in sputtering power, with different combinations of time and temperature, is related to large fractal dimension and small lacunarity coefficient. The increase in substrate temperature (for different combinations with time and RF power) is shown to enhance the spatial roughness of the HEA thin films. A multifractal analysis undertaken using generalized fractal dimension, mass exponent against moment order and multifractal spectrum reveal that all the films have a multifractal character; and the films deposited at high temperatures and powers exhibit the strongest multifractal behaviour.