Materials For Many Potential Applications Research Articles

Facile Synthesis of Hollow Glass Microsphere Filled PDMS Foam Composites with Exceptional Lightweight, Mechanical Flexibility, and Thermal Insulating Property.

The feature of low-density and thermal insulation properties of polydimethylsiloxane (PDMS) foam is one of the important challenges of the silicone industry seeking to make these products more competitive compared to traditional polymer foams. Herein, we report a green, simple, and low-cost strategy for synthesizing ultra-low-density porous silicone composite materials via Si-H cross-linking and foaming chemistry, and the sialylation-modified hollow glass microspheres (m-HM) were used to promote the HM/PDMS compatibility. Typically, the presence of 7.5 wt% m-HM decreases the density of pure foam from 135 mg/cm-3 to 104 mg/cm-3 without affecting the foaming reaction between Si-H and Si-OH and produces a stable porous structure. The optimized m-HM-modified PDMS foam composites showed excellent mechanical flexibility (unchanged maximum stress values at a strain of 70% after 100 compressive cycles) and good thermal insulation (from 150.0 °C to 52.1 °C for the sample with ~20 mm thickness). Our results suggest that the use of hollow microparticles is an effective strategy for fabricating lightweight, mechanically flexible, and thermal insulation PDMS foam composite materials for many potential applications.

Revealing the Superior Electrocatalytic Performance of 2D Monolayer WSe2 Transition Metal Dichalcogenide for Efficient H2 Evolution Reaction

AbstractH2 evolution reaction (HER) requires an electrocatalyst to reduce the reaction barriers for the efficient production of H2. 2D transition metal dichalcogenides (2D TMDs) have emerged as a pinnacle group of materials for many potential applications, including HER. In this work, a pristine 2D monolayer WSe2 TMD is computationally designed using the first principle‐based hybrid density functional theory (DFT) to investigate its structural, electronic properties and the electrocatalytic performance for HER. The possible Volmer‐Heyrovsky and Volmer‐Tafel reaction mechanisms for HER at the W‐edge of the active site of WSe2 are studied by using a nonperiodic finite molecular cluster model W10Se21. The study shows that the pristine 2D monolayer WSe2 follows either the Volmer‐Heyrovsky or the Volmer‐Tafel reaction mechanisms with a single‐digit low reaction barrier about 6.11, 8.41 and 6.61 kcal mol−1 during the solvent phase calculations of H•‐migration, Heyrovsky and Tafel transition (TS) states, respectively. The lower reaction barriers, high turnover frequency (TOF) ≈ 4.24 × 106 s−1 and 8.86 × 107 s−1 during the Heyrovsky and Tafel reaction steps and the low Tafel slope 29.58 mV dec−1 confirm that the pristine 2D monolayer WSe2 might be a promising alternative to platinum group metals (PGM) based electrocatalyst.

Structural and impedance spectroscopy characterization of Stannic oxide electronic system

Stannic oxide (SnO2) is explored as one well-known material for many potential applications due to its unique electronic properties. The objective is to focus on structural and electrical characteristics of SnO2 electronic material, synthesized through the high-temperature solid-state principle. The sample has a tetragonal system, which is revealed by the X-ray diffraction technique. Different electrical parameters are comprehensively analyzed with the help of impedance spectrometer. The studied material has a relatively high dielectric constant and low tangent loss which furnish it as a suitable applicant for electronic applications.

An Ultra‐Strong, Water Stable and Antimicrobial Chitosan Film with Interdigitated Bouligand Structure

AbstractNatural polymeric materials are an attractive potential replacement for non‐biodegradable plastics. However, one of the main challenges for high‐end applications of these materials, is to maintain their high mechanical properties in a watery environment. Here, inspired by the reinforcement principle of multiscale architecture in natural crab exoskeletons, an ultra‐strong and hydrostable film is developed through a top‐down method directly from the crab shell. The resulting chitosan film exhibits an outstanding isotropic tensile strength of ≈220 MPa and a superior wet strength of ≈70 MPa, which is significantly higher than that of conventional polysaccharide‐based materials and many commercially used plastics. Its excellent mechanical properties are due to the realization of strong interactions between chitosan fibrils even in wet conditions through interdigitation and densification processes without other additives. Additionally, it also possesses outstanding transparency, flexibility, antimicrobial ability, and biodegradability, making it a promising high‐performance and eco‐friendly material for many potential applications.

The Effect of Annealing on the Optoelectronic Properties and Energy State of Amorphous Pyrochlore Y2Ti2O7 Thin Layers by Sol–Gel Synthesis

Pyrochlore titanate (Y2Ti2O7) is a promising material for a wide range of applications in optoelectronics and photocatalysis due to its advantageous chemical, mechanical, and optical properties. To enhance its potential for such uses, however, a high-quality and scalable synthesis method is required. We here investigate the crystallization of sol–gel produced Y2Ti2O7 layers. We observe a transition of the amorphous pyrochlore phase at annealing temperatures below 700 °C. The transmittances of the Y2Ti2O7 thin layers annealed at 400 to 700 °C are approximately 92.3%. The refractive indices and packing densities of Y2Ti2O7 thin layers annealed at 400–700 °C/1 h vary from 1.931 to 1.954 and 0.835 to 0.846, respectively. The optical bandgap energies of Y2Ti2O7 thin layers annealed at 400–700 °C/1 h reduce from 4.356 to 4.319 eV because of the Moss–Burstein effect. These good electronic and optical properties make Y2Ti2O7 thin layers a promising host material for many potential applications.

Transient Chemical Activation of Covalent Bonds for Healing of Kinetically Stable and Multifunctional Organohydrogels

Transient Chemical Activation of Covalent Bonds for Healing of Kinetically Stable and Multifunctional Organohydrogels

Structure Effects Induced by High Mechanical Compaction of STAM‐17‐OEt MOF Powders

AbstractMetal‐organic frameworks (MOFs) are promising materials for many potential applications, spacing from gas storage to catalysis. However, the powder form they are generally made of is not suitable, mainly because of the low packing density. Powder compaction is therefore necessary, but also challenging because of its typical mechanical fragility. Indeed, generally, MOF powders undergo irreversibly damages upon densification processes, for example partially or totally loosing microporosity and catalytic activity. In this work, we have deeply studied the compaction effects on the flexible Cu(II)‐based MOF STAM‐17‐OEt (Cu(C10O5H8) ⋅ 1.6 H2O), whose chemical composition is close to that of HKUST‐1, obtaining that, by contrast, STAM‐17‐OEt is extremely suitable for mechanical compaction processes with pressures up to 200 MPa, which increase its packing density and its catalytic activity, and then also preserve the characteristic porosity, flexibility and water stability of STAM‐17‐OEt. The results are supported by many experimental techniques including EPR spectroscopy, PXRD diffraction, CO2 isotherms studies and catalytic tests.

Two dimensional ferromagnetic semiconductor: monolayer CrGeS3

Recently, two-dimensional ferromagnetic semiconductors have been an important class of materials for many potential applications in spintronic devices. Based on density functional theory, we systematically explore the magnetic and electronic properties of CrGeS3 with the monolayer structures. It is found that the bandgap of spin-up state is 1.01 eV when it is 1.07 eV in spin-down state. The exchange splitting is calculated as 0.67 eV (2.21 eV by HSE06 functional), which originates from bonding hybridized states of Cr eg-S p and unoccupied Cr t2g-Ge p hybridization. After that, the comparison of total energy between different magnetic states ensures the ferromagnetic ground state of monolayer CrGeS3. The reason of the magnetic states originates mainly from the competition between antiferromagnetic direct neighboring Cr–Cr exchange and ferromagnetic superexchange mediated by S atom. And the results also show the magnetic moment of 6 per unit cell, including two Cr atoms. Besides, we estimate that the monolayer CrGeS3 possesses the Curie temperature of 161 K by mean-field theory. The results suggest that monolayer CrGeS3 crystals will possess potential applications in nanoscale spintronics.

Al-Doped TiO2 Nanotube Arrays Achieved by Using Low Boiling AlCl3 as a Dopant Source for Supercapacitors

One-dimensional TiO2 nanotube arrays (TiO2 NTAs) fabricated by anodization of titanium have been considered as promising materials for many potential applications. However, TiO2 NTAs generally suffer from poor electrochemical properties due to limited electrical conductivity of TiO2. For this reason, various approaches to preparing nonmetal-doped and metal-doped TiO2 have been developed. Nevertheless, these reported methods were mainly appropriate for self-doping and nonmetal doping of TiO2. For the metal doping, some difficulties such as multiple steps, harsh reaction conditions, or expensive facilities were often encountered. Here, we propose a novel strategy to realize the metal doping of TiO2 NTAs by using a low boiling metal compound as a dopant source. As an example, through heating the as-anodized TiO2 NTAs together with AlCl3 in a confined space, the Al3+ ions are incorporated into the TiO2 lattice in the form of substitution of Ti4+ by Al3+. Moreover, the AlCl3 vapor treatment route can achieve adherent TiO2 NTA films on Ti substrate. The as-prepared Al-doped TiO2 NTA electrode delivers an average capacitance of 12.48 mF cm−2 at 100 mV s−1, which is ∼2.5 times higher than that of untreated TiO2 NTAs. Also, the Al-doped electrode shows an excellent rate capability and long-term cycling stability.

Effect of Annealing on the Surface Morphology, Optical and and Structural Properties of Nanodimensional Tungsten Oxide Prepared by Coprecipitation Technique

Tungsten oxide (WO3) nanoparticles with monoclinic structure have been synthesized by using an inexpensive coprecipitation process. The obtained nanoparticles were annealed at 400°C, 500°C, 600°C, 700°C, 800°C, and 900°C for 1 h under the same physical conditions. The morphology, structure, and optical properties of the synthesized nanoparticles were studied by x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), ultraviolet–visible (UV–Vis) spectrophotometry, and Raman spectroscopy. The XRD results confirmed that the synthesized nanomaterial was crystalline in nature with monoclinic phase. The crystallite size varied from 14 nm to 87 nm when changing the annealing temperature. Williamson–Hall analysis was used to investigate the change in lattice strain and crystallite size. The optical performance was investigated by using UV–visible spectroscopy. The bandgap of the prepared nanomaterials varied from 2.51 eV to 3.77 eV with the annealing temperature, due to the variation of the effect of oxygen vacancies on the electronic band structure. SEM revealed formation of uniform and irregular-sized nanoparticles. HRTEM analysis revealed that the nanoparticles grew along the [002] plane with d-spacing of 0.39 nm for the material annealed at 500°C and along the [200] plane with spacing of 0.36 nm when annealed at 800°C. The crystalline nature of the synthesized nanomaterial was confirmed by uniform and clear fringes obtained in TEM micrographs. The correlation between the peak position and width of the key band at 806 cm−1 in Raman spectroscopy band is discussed. These enhancements in the properties of WO3 nanomaterial make it an efficient material for many potential applications, e.g., in photocatalysis, electro- and photochromic devices, etc.

Photosensitizing Metal-Organic Layers for Efficient Sunlight-Driven Carbon Dioxide Reduction.

Metal-organic layers (MOLs), a free-standing monolayer version of two-dimensional metal-organic frameworks (MOFs), have emerged as a new class of 2D materials for many potential applications. Here we report the design of a new photosensitizing MOL, Hf12-Ru, based on Hf12 secondary building units (SBUs) and [Ru(bpy)3]2+ (bpy = 2,2'-bipyridine) derived dicarboxylate ligands. After modifying the SBU surface of Hf12-Ru with M(bpy)(CO)3X (M = Re and X = Cl or M = Mn and X = Br) derived capping molecules through carboxylate exchange reactions, the resultant Hf12-Ru-Re and Hf12-Ru-Mn MOLs possess both [Ru(bpy)3]2+ photosensitizers and M(bpy)(CO)3X catalysts for efficient photocatalytic CO2 reduction. The proximity of the MOL skeleton to the capping ligands (1-2 nm) facilitates electron transfer from the reduced photosensitizer [Ru(bpy)3]+ to MI(bpy)(CO)3X (M = Re, Mn) catalytic centers, resulting in CO2 reduction turnover numbers of 8613 under artificial visible light and of 670 under sunlight. MOLs thus represent a novel platform to assemble multifunctional materials for studying artificial photosynthesis.

Graphyne and Its Family: Recent Theoretical Advances.

Graphyne and its family are new carbon allotropes in 2D form with both sp and sp2 hybridization. Recently, the graphyne with different structures have attracted great attentions from both experimental and theoretical communities, especially because the first successful synthesis of graphdiyne, which is a typical member of the graphyne family. In this review, recent theoretical progresses in the research of the graphyne family are summarized. More specifically, we systematically introduce the structural, mechanical, band, electronic transport, and thermal properties of graphyne and its family, as well as their possible applications, such as gas separation, water desalination and purification, anode material for ion battery, H2 storage, and catalysis application. Several related theoretical methods are also reviewed. The coexistence of sp and sp2 hybridization and the unique atom arrangement of the graphyne family members bring many novel properties and make them promising materials for many potential applications.

Self-assembly of repeat proteins: Concepts and design of new interfaces.

In nature, assembled protein structures offer the most complex functional structures. The understanding of the mechanisms ruling protein-protein interactions opens the door to manipulate protein assemblies in a rational way. Proteins are versatile scaffolds with great potential as tools in nanotechnology and biomedicine because of their chemical, structural, and functional versatility. Currently, bottom-up self-assembly based on biomolecular interactions of small and well-defined components, is an attractive approach to biomolecular engineering and biomaterial design. Specifically, repeat proteins are simplified systems for this purpose. In this work, we provide an overview of fundamental concepts of the design of new protein interfaces. We describe an experimental approach to form higher order architectures by a bottom-up assembly of repeated building blocks. For this purpose, we use designed consensus tetratricopeptide repeat proteins (CTPRs). CTPR arrays contain multiple identical repeats that interact through a single inter-repeat interface to form elongated superhelices. Introducing a novel interface along the CTPR superhelix allows two CTPR molecules to assemble into protein nanotubes. We apply three approaches to form protein nanotubes: electrostatic interactions, hydrophobic interactions, and π-π interactions. We isolate and characterize the stability and shape of the formed dimers and analyze the nanotube formation considering the energy of the interaction and the structure in the three different models. These studies provide insights into the design of novel protein interfaces for the control of the assembly into more complex structures, which will open the door to the rational design of nanostructures and ordered materials for many potential applications in nanotechnology.

Cellular carbon microstructures developed by using stereolithography

Additive manufacturing has attracted much attention to generate structures containing ordered cells and customized shapes with various materials. A simple method was proposed to develop net-shape cellular carbon microstructures (CCMs) with controllable low shrinkage by using stereolithography. The polymer architectures, made of photosensitive resins, and sodium chloride were directly used as carbon precursors and granular support during carbonization, respectively. In addition, graphite powder was introduced into the granular support, which significantly enhances the mechanical property and electrical conductivity of the CCMs, and low graphite content has no significant effect on the volume shrinkage. The extremely high-porosity CCMs without distortion and breakage were obtained, showing controllable low volume shrinkage (44%–52%) with extremely low carbon yield (6%). The microstructure, mechanical property and electrical conductivity were measured and compared. It was found that the CCMs with graphite particles attaching on their surfaces show smooth surfaces with fewer defects, and possess great mechanical property (compressive stress and elastic modulus are 0.36 Mpa and 23.9 Mpa, respectively) and electrical conductivity (0.43 S/cm), which makes them promising materials for many potential applications.

Theoretic Study on Dispersion Mechanism of Boron Nitride Nanotubes by Polynucleotides.

Due to the unique electrical and mechanical properties of boron nitride nanotubes (BNNT), BNNT has been a promising material for many potential applications, especially in biomedical field. Understanding the dispersion of BNNT in aqueous solution by biomolecules is essential for its use in biomedical applications. In this study, BNNT wrapped by polynucleotides in aqueous solution was investigated by molecular dynamics (MD) simulations. Our results demonstrated that the BNNT wrapped by polynucleotides could greatly hinder the aggregation of BNNTs and improve the dispersion of BNNTs in aqueous solution. Dispersion of BNNTs with the assistance of polynucleotides is greatly affected by the wrapping manner of polynucleotides on BNNT, which mainly depends on two factors: the type of polynucleotides and the radius of BNNT. The interaction between polynucleotides and BNNT(9, 9) is larger than that between polynucleotides and BNNT(5, 5), which leads to the fact that dispersion of BNNT(9, 9) is better than that of BNNT(5, 5) with the assistance of polynucleotides in aqueous solution. Our study revealed the molecular-level dispersion mechanism of BNNT with the assistance of polynucleotides in aqueous solution. It shades a light on the understanding of dispersion of single wall nanotubes by biomolecules.

Polyaniline–graphene oxide nanocomposites: Influence of nonconducting graphene oxide on the conductivity and oxidation‐reduction mechanism of polyaniline

ABSTRACTThe present endeavor focuses on the unusual interactions between polyaniline and graphene oxide (PANi–GO) which radically affects the properties of nanocomposites as it is an emerging material for many potential applications. A series of nanocomposites have been synthesized by varying the weight percentage of highly nonconducting GO with respect to aniline which exhibit superior properties in terms of shelf life, processability and conductivity due to the synergistic effect of GO and PANi. A comparison of the resistances of samples reveal that though as‐synthesized GO is insulating (80 MΩ), when added to PANi (283 kΩ) in small amounts yields conducting composites (50–280 Ω). Up to 5 weight % concentration, GO renders conductivity to the composite probably by increasing the doping level of PANi. Nonetheless, no further increase in conductivity observed on addition of more than 5 wt% GO in the composite has dictated us to unravel the structure property relationship between PANi and GO, where GO facilitates the formation of partially reduced phase of PANi, thereby restricting the electronic transport. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3778–3786

Synthesis and photocatalytic properties of multi-morphological AuCu3-ZnO hybrid nanocrystals

Noble metal–semiconductor hybrid nanocrystals represent an important class of materials for many potential applications, especially for photocatalysis. The utilization of transition metals to form alloys with noble metals can not only reduce the preparation costs, but may also offer tunable optical and catalytic properties for a broader range of applications. In this study, we report on the solution synthesis of AuCu3–ZnO hybrid nanocrystals with three interesting morphologies, including urchin-like, flower-like and multipod-like nanocrystals. In the synthetic strategy, Au–Cu bimetallic alloy seeds formed in situ are used to induce the heteroepitaxial growth of ZnO nanocrystals on the surface of bimetallic alloy cores; thus different types of morphologies can be achieved by controlling the reaction conditions. Through high-resolution transmission electron microscopy observations, well-defined interfaces between ZnO and AuCu3 are observed, which indicate that ZnO has a (0001) orientation and prefers to grow on AuCu3 {111} facets. The as-prepared hybrid nanocrystals demonstrate morphology- and composition-dependent surface plasmon resonance (SPR) absorption bands. In addition, much higher photocatalytic efficiency than pure ZnO nanocrystals is observed for the hybrid nanocrystals in the degradation of methylene blue. In particular, the multipod-like AuCu3–ZnO hybrid nanocrystals show the highest catalytic performance, as well as more than three times higher photocurrent density than the pure ZnO sample. The reported synthetic strategy provides a facile route to the effective combination of a plasmonic alloy with semiconductor components at the nanoscale in a controlled manner.

A simple approach for fabrication of interconnected graphitized macroporous carbon foam with uniform mesopore walls by using hydrothermal method

Three-dimensional (3D) highly interconnected graphitized macroporous carbon foam with uniform mesopore walls has been successfully fabricated by a simple and efficient hydrothermal approach using resorcinol and formaldehyde as carbon precursors. The commercially available cheap polyurethane (PU) foam and Pluronic F127 were used as a sacrificial polymer and mesoporous structure-directing templates, respectively. The graphitic structure of carbon foam was obtained by catalytic graphitization method using iron as catalyst. Three different carbon foams such as graphitized macro-mesoporous carbon (GMMC) foam, amorphous macro-mesoporous carbon (AMMC) foam and graphitized macroporous carbon (GMC) foam were fabricated and their physicochemical and mechanical properties were systematically measured and compared. It was found that GMMC possess well interconnected macroporous structure with uniform mesopores located in the macroporous skeletal walls of continuous framework. Besides, GMMC foam possesses a well-defined graphitic framework with high surface area (445m2/g), high pore volume (0.35cm3/g), uniform mesopores (3.87nm), high open porosity (90%), low density (0.30g/cm3) with good mechanical strength (1.25MPa) and high electrical conductivity (11S/cm) which makes it a promising material for many potential applications.

Copper plasmonics and catalysis: role of electron-phonon interactions in dephasing localized surface plasmons.

Copper metal can provide an important alternative for the development of efficient, low-cost and low-loss plasmonic nanoparticles, and selective nanocatalysts. However, poor chemical stability and lack of insight into photophysics and plasmon decay mechanisms has impeded study. Here, we use smooth conformal ALD coating on copper nanoparticles to prevent surface oxidation, and study dephasing time for localized surface plasmons on different sized copper nanoparticles. Using dephasing time as a figure of merit, we elucidate the role of electron-electron, electron-phonon, impurity, surface and grain boundary scattering on the decay of localized surface plasmon waves. Using our quantitative analysis and different temperature dependent measurements, we show that electron-phonon interactions dominate over other scattering mechanisms in dephasing plasmon waves. While interband transitions in copper metal contributes substantially to plasmon losses, tuning surface plasmon modes to infrared frequencies leads to a five-fold enhancement in the quality factor. These findings demonstrate that conformal ALD coatings can improve the chemical stability for copper nanoparticles, even at high temperatures (>300 °C) in ambient atmosphere, and nanoscaled copper is a good alternative material for many potential applications in nanophotonics, plasmonics, catalysis and nanoscale electronics.

Single-Walled Carbon Nanotubes Do Not Pierce Aqueous Phospholipid Bilayers at Low Salt Concentration

Because of their unique physical, chemical, and electrical properties, carbon nanotubes are an attractive material for many potential applications. Their interactions with biological entities are, however, not yet completely understood. To fill this knowledge gap, we present experimental results for aqueous systems containing single-walled carbon nanotubes and phospholipid membranes, prepared in the form of liposomes. Our results suggest that dispersed single-walled carbon nanotubes, instead of piercing the liposome membranes, adsorb on them at low ionic strength. Transmission electron microscopy and dye-leakage experiments show that the liposomes remain for the most part intact in the presence of the nanotubes. Further, the liposomes are found to stabilize carbon nanotube dispersions when the surfactant sodium dodecylbenezenesulfonate is present at low concentrations. Quantifying the interactions between carbon nanotubes and phospholipid membranes could not only shed light on potential nanotubes cytotoxicity but also open up new research venues for their use in controlled drug delivery and/or gene and cancer therapy.