Interest For Many Applications Research Articles

Abnormally High Graphitic Crystallization of Cellulose Nanocrystals.

Cellulose nanocrystals (CNCs) are currently of great interest for many applications, such as energy storage and nanocomposites, because of their natural abundance. A number of carbonization studies have reported abnormal graphitization behavior of CNCs, although cellulose is generally known as a precursor for hard carbon (nongraphitizable carbon). Herein, we report a spray-freeze-drying (SFD) method for CNCs and a subsequent carbonization study to ascertain the difference in the structural development between the amorphous and crystalline phases. The morphological observation by high-resolution transmission electron microscopy of the carbonized SFD-CNC clearly shows that the amorphous and crystalline phases of CNC are attributed to the formation of hard and soft carbon, respectively. The results of a reactive molecular dynamics (RMD) study also show that the amorphous cellulose phase leads to the formation of fewer carbon ring structures, indicative of hard carbon. In contrast, the pristine crystalline cellulose phase has a higher density and thermal stability, resulting in limited molecular relaxation and the formation of a highly crystalline graphitic structure (soft carbon).

Cold-Flow Properties of Estolides: The Older (D97 and D2500) versus the Mini-(D5773 and D5949) Methods

There is growing research on developing new and sustainable lubricants. Sustainable lubricants with adequate cold-flow properties are of particular interest for many applications. One limitation of the established methods for measuring cold flow properties is the large volume needed to test samples. This makes initial screening of many hard-to-synthesize samples difficult. In the current study, we compared the results of the older, widely accepted ASTM methods D97 (pour point, PP) and D2500 (cloud point, CP) to the newer, smaller-volume, and easier-to-perform methods D5949 and D5773 for bio-based base oils (estolides and iso-estolides). The CP results were in good agreement for less colored samples, but D5773 gave lower values for some darker (Gardner color >8) samples, especially esters. The D5949 showed a tendency to report slightly higher PP, especially for the lower values. Viscosities and densities in a wide temperature range (15 to 120 °C) were also measured. The surface tensions were estimated by a literature group method. Viscosity and density effects can only partially explain the differences in the PP values from the two methods. In conclusion, the newer mini-methods are an acceptable substitution when larger volumes are not accessible, unless the sample is too dark.

Bioinspired Nanotubular Structures by Soft-Template Electropolymerization: 3,4-(2,3-naphtylenedioxy)Thiophene Monomers Quenched to Form Dimers

Preparing well-ordered nanotubes on materials surface is a great of interest in many applications. Bio-inspired and theoretical approaches show that porous structures such as nanotubes are key parameters for both surface hydrophobicity and water adhesion. Here, a very easy soft-template electropolymerization approach is used to form nanotubular structures, followed by a bioinspired strategy to control the wetting properties. Fully conjugated monomers based on 3,4-(2,3- naphtylenedioxy)thiophene (NaphDOT) core grafted with many rigid aromatic groups such as phenyl, naphthalene, pyrene, pyrrole, were synthesized. Then, electropolymerization is carried out with these monomers, followed by surface and morphologies characterization of corresponding polymers. We show that even if just dimers are formed by electropolymerization, the resulting polymer can be sufficiently insoluble to form structured films. 3,4-(2,3-naphtylenedioxy)thiophene (NaphDOT) is chosen as a judicious example, due to strong <i>π</i>-stacking interactions, and also their capacity to form nanotubular structures by soft template-electropolymerization in the presence of water (H<sub>2</sub>O). Here, different substituents, polymerizable or not, are grafted on the 2-position of thiophene. Films are formed with all the studied substituents. Nanotubular structures are especially observed with the following substituents: hydroxyl, pyrene and pyrrole, but in the presence of H<sub>2</sub>O. We study also their influence on the surface hydrophobicity.

Multivariate Machine Learning Models of Nanoscale Porosity from Ultrafast NMR Relaxometry.

Nanoporous materials are of great interest in many applications, such as catalysis, separation, and energy storage. The performance of these materials is closely related to their pore sizes, which are inefficient to determine through the conventional measurement of gas adsorption isotherms. Nuclear magnetic resonance (NMR) relaxometry has emerged as a technique highly sensitive to porosity in such materials. Nonetheless, streamlined methods to estimate pore size from NMR relaxometry remain elusive. Previous attempts have been hindered by inverting a time domain signal to relaxation rate distribution, and dealing with resulting parameters that vary in number, location, and magnitude. Here we invoke well-established machine learning techniques to directly correlate time domain signals to BET surface areas for a set of metal-organic frameworks (MOFs) imbibed with solvent at varied concentrations. We employ this series of MOFs to establish a correlation between NMR signal and surface area via partial least squares (PLS), following screening with principal component analysis, and apply the PLS model to predict surface area of various nanoporous materials. This approach offers a high-throughput, non-destructive way to assess porosity in c.a. one minute. We anticipate this work will contribute to the development of new materials with optimized pore sizes for various applications.

Multivariate Machine Learning Models of Nanoscale Porosity from Ultrafast NMR Relaxometry

AbstractNanoporous materials are of great interest in many applications, such as catalysis, separation, and energy storage. The performance of these materials is closely related to their pore sizes, which are inefficient to determine through the conventional measurement of gas adsorption isotherms. Nuclear magnetic resonance (NMR) relaxometry has emerged as a technique highly sensitive to porosity in such materials. Nonetheless, streamlined methods to estimate pore size from NMR relaxometry remain elusive. Previous attempts have been hindered by inverting a time domain signal to relaxation rate distribution, and dealing with resulting parameters that vary in number, location, and magnitude. Here we invoke well‐established machine learning techniques to directly correlate time domain signals to BET surface areas for a set of metal‐organic frameworks (MOFs) imbibed with solvent at varied concentrations. We employ this series of MOFs to establish a correlation between NMR signal and surface area via partial least squares (PLS), following screening with principal component analysis, and apply the PLS model to predict surface area of various nanoporous materials. This approach offers a high‐throughput, non‐destructive way to assess porosity in c.a. one minute. We anticipate this work will contribute to the development of new materials with optimized pore sizes for various applications.

Geometrically tunable architected materials designed from prismatic rotating units

An exotic property of some mechanical metamaterials is their negative Poisson's ratio which is of interest for many applications, from biomedical to aeronautic. This work investigates how a mechanical metamaterial evolved from equilateral triangular rotating prisms changes its Poisson's ratio according to the orientation of the reference units with respect to the tensile loading direction (aligned or 45° rotated, respectively). Different configurations are investigated through kinematic analysis, which describes hinged couplings in the linked vertices of the prisms. The best configurations emerging from the kinematic analysis were converted into chiral architectures: Three-dimensional printed physical prototypes were tested under uniaxial compression and the results compared with finite element predictions. The experimental results showed a remarkably different deformation behaviour between the metamaterial designs, with a good qualitative agreement with the numerical simulations. High values of auxetic response are observed for the configuration whose cells are aligned with the load, while a low auxetic and less sensitive geometry variation behaviour was observed for the rotated cell architecture. This rotated configuration also exhibits the significant achievement of mechanical properties which are approximately independent of the geometry variations.

Activation of alkyl hydroperoxides by manganese complexes of tmtacn for initiation of radical polymerisation of alkenes.

The activation of alkyl hydroperoxides to generate radicals is a key step in the initiation of radical polymerisations in many industrial applications, not least protective coatings. Cobalt soaps (Co(ii) alkyl carboxylates) are highly effective catalysts under ambient conditions but viable alternatives based on less scarce catalysts are desirable, with especially iron and manganese catalysts showing potential. Manganese complexes of the ligand N,N',N″-trimethyl-1,4,7-triazacyclononane (tmtacn) are long established as catalysts for organic oxidations with H2O2, however their reactivity with alkyl hydroperoxides is less studied especially in apolar solvents. Here we show that this family of complexes can be employed as catalysts for the decomposition of alkyl hydroperoxides in apolar solvents such as styrene/methyl methacrylate mixtures and resins based on styrene/bisphenol-A based diglycidyl ether bismethacrylate (BADGE-MA). The progress of alkene polymerisation in crosslinking resins is followed by Raman spectroscopy to establish its dependence on the oxidation state of the manganese catalyst used, as gelation time and onset of autoacceleration are of particular interest for many applications. We show, through reaction progress monitoring with UV/vis absorption and Raman spectroscopy, that the stability of the manganese complexes in the resin mixtures has a substantial effect on curing progress and that the oxidation state of the resting state of the catalyst is most likely Mn(ii), in contrast to reactions with H2O2 as oxidant in which the oxidation state of the resting state of catalyst is Mn(iii). Manganese complexes of tmtacn are shown to be capable initiators of alkene radical polymerisations, and their rich coordination and redox chemistry means that resin curing kinetics can potentially be tuned more readily than with cobalt alkyl carboxylates.

(Digital Presentation) Metal Alloy Nanoparticles Dispersed in Amorphous Titanosilicate for Hydrogen Evolution Reaction Catalyst with Much Lower Overpotential Than That of Benchmark Catalyst in a Wide pH Range

Different kinds of metallic nanoparticles (Pd, Pt, Au, Cu, Ag etc.) are widely used in Electrochemical, Optoelectronic and Photovoltaic applications to harvest sunlight in order to increase the efficiency of devices.ETS-10, which is a synthetic microporous material consisting of –Ti-O-Ti-O-Ti- quantum wires running along [110] and [1-10] direction in polymorph B, has been of great interest in many applications like Electrochemical, Optoelectronic and Photovoltaic applications, due to its so unique (it contains periodically positioned quantum wires [-O-Ti(O-)4-O-] with a diameter (d) of ∼0.67 nm running along the two perpendicular directions in the crystal, tetrahedral framework structures and compostion, well defiend acidity, uniform pores, highly cation exchange selectivity, and good thermal stability are widely used as commercial catalysts, ion exchangers, and adsorbants) properties.As a results, Tafel slop clearly indicated that performance was much better than pure Pt plate and the quite stable upto 72 hours at all pH conditions. Figure 1

PEO-b-PNBA in-situ functionalized mesoporous silica films and their light- and pH-controlled ionic mesopore accessibility

Multistimuli-responsive, in-situ functionalized mesoporous silica films were fabricated by evaporation-induced self-assembly through physical entrapment of the functional template poly(ethylene oxide)-b-poly(2-nitrobenzyl acrylate) (PEO-b-PNBA). The light-cleavable and pH-responsive block copolymer PEO-b-PNBA simultaneously serves as structure-directing agent and for in-situ polymer functionalization of the generated mesopore space. The use of different PEO-b-PNBA compositions results in highly filled hybrid mesoporous silica films with different pore sizes, porosity, and polymer chain sequence within the mesopores. Based on these structural variations and the polymer chain sequence the ionic permselectivity of the silica-polymer hybrid thin films is adjusted. The side chains of the template PNBA block can be deprotected upon irradiation, hereby releasing pH-responsive carboxylic acid groups. The irradiation energy and irradiation time-dependent deprotection allows gradually controlled charge regulation in mesopores. This approach of in-situ functionalization using multistimuli-responsive PEO-b-PNBA block copolymers facilitates the fabrication of multi-responsive hybrid mesoporous silica films and bears high potential for the production of complex, hierarchical, multifunctional mesoporous materials. This fabrication method including direct functionalization of mesoporous structures is of high interest for many applications based on controlled molecular transport in nanoscale pores, such as sensing, separation, or catalysis.

Electronic frequency shifting enables long, variable working distance optical coherence tomography.

Increased imaging range is of growing interest in many applications of optical coherence tomography to reduce constraints on sample location, size, and topography. The design of optical coherence tomography systems with sufficient imaging range (e.g., 10s of centimeters) is a significant challenge due to the direct link between imaging range and acquisition bandwidth. We have developed a novel and flexible method to extend the imaging range in optical coherence tomography using electronic frequency shifting, enabling imaging in dynamic environments. In our approach, a laser with a quasi-linear sweep is used to limit the interferometric bandwidth, enabling decoupling of imaging range and acquisition bandwidth, while a tunable lens allows dynamic refocusing in the sample arm. Electronic frequency shifting then removes the need for high frequency digitization. This strategy is demonstrated to achieve high contrast morphological imaging over a > 21 cm working distance range, while maintaining high resolution and phase sensitivity. The system design is flexible to the application while requiring only a simple phase correction in post-processing. By implementing this approach in an auto-focusing paradigm, the proposed method demonstrates strong potential for the translation of optical coherence tomography into emerging applications requiring variable and centimeter-scale imaging ranges.

Toward Compact Motorized Lens: Switch and Focus a Filter Wheel with Single Piezoelectric Tube

AbstractMultispectral cameras (MSCs) have the capability of detecting and analyzing features invisible to human eyes and are of interest for many applications. However, the traditional MSC suffers from bulkiness since the light filtering and optical focusing mechanisms are independent. Herein, it proposed an integrated strategy that implements two functions through a tunable filtering‐focusing mechanism (TFFM), driven by two degrees of freedom (two‐DOF) piezoelectric tube actuator (PTA). The TFFM can realize light filtering and optical focusing through the rotary and linear motions of PTA. The configuration of PTA is presented, and the working principle is discussed. Then, prototypes of PTA and TFFM are developed, weighing merely 5.5 and 8 g, sizing of Ø7 × 21.4 mm and Ø35 × 7 mm, demonstrating the merits of lightweight and miniaturization. Experiments validate the effectiveness of TFFM, including multispectral images acquired with 0.1 s through rotary motion, focused images obtained with a linear speed of 60.2 mm−1s, and a series of images with different sharpness and wavelengths. The sharpness evaluation algorithms are adopted to determine the sharpest image. The work contributes to reducing the volume of MSC systems with multifunctionalities while keeping the devices simple, providing a practical and effective solution for the integrated design of MSC.

Solvation dynamics of choline fluoride in ethylene glycol – Water mixtures

Due to their favorable physical properties, deep eutectic solvents (DESs) have been of interest in many applications in the energy and industry sectors. In this study, we investigate the new deep eutectic solvent ethalineF (a 1:2 M ratio of choline fluoride:ethylene glycol) and the effect of water addition on the solvation dynamics compared to the better known ethaline (a 1:2 M ratio of choline chloride:ethylene glycol). Femtosecond transient absorption spectroscopy and NMR diffusometry were used to study the solvation dynamics. 19F NMR spectra were obtained for ethalineF solutions with different water additions. The 19F NMR spectra show two fluorine signals; one can be assigned to fluoride anions solvated by EG and the other signal to fluoride anions associated with the much heavier and less mobile choline cation. Density, viscosity, conductivity, and ET(30) polarity measurements are also provided for ethalineF. The nuclear spin nature of fluorine atom permits to measure the self-diffusion coefficient of the negative ion in addition of the cation diffusion in a choline halide based deep eutectic solvent system. This allows to calculate the NMR-predicted conductivities σNMR. The obtained ion dissociation coefficients αD at different water concentrations suggest a partial ion dissociation which was commensurate with the relatively low ion conductivity. The observed modest conductivity of ethalineF is explained in terms of ion association as well as the gradual increase in conductivity caused by the addition of water.

Evidence of interstitial-mediated boron self-diffusion in boron carbide

Boron carbide is an important high-temperature material with interesting structural and functional properties. However, self-diffusion is very poorly known on this material, and also the few impurity diffusion studies, devoted in particular to helium and lithium, overlook the possible diffusion coupling with intrinsic defects. In this paper we present a study of boron self-diffusion in boron carbide based on first principles calculations and kinetic cluster expansion. Our results show that boron self-diffusion may occur with a migration activation energy on the order of 1.5–1.6 eV and with a global activation energy between 4 and 5.5 eV, depending on the doping conditions, which is significantly lower than the self-diffusion activation energies in other semiconducting carbides, like silicon carbide.We believe that our results are of interest for many applications of boron carbide and for tuning the best conditions for controlling the synthesis routes at specific stoichiometries for boron carbide.

Visual analysis of interface deformation in multiphase flow

In multiphase flows, the evolution of fluid-fluid interfaces is of interest in many applications. In addition to fluid dynamic forces governing the flow in the entire volume, surface tension determines droplet interfaces. Here, the analysis of interface kinematics can help in the investigation of interface deformation and the identification of potential breakups. To this end, we developed a visualization technique using metric and shape tensors to analyze interface stretching and bending. For interface stretching, we employ the eigenpairs of the metric tensor defined for the deformation rate of the fluid surface. For interface bending, we present a technique that locally captures the interface curvature change in terms of a shape tensor, extracting its principal directions and curvatures. We then visualize interface deformation by combining both representations into a novel glyph design. We apply our method to study multiphase flow simulations with particular emphasis on interface effects. These include the interplay between fluid dynamics and surface tension forces leading to breakup processes following droplet collisions, as well as droplet-droplet interactions of different fluids where Marangoni convection along the surface is explicitly taken into account.Graphical abstract

Variability of travel time of solute particles in single fractures with spatially variable aperture

The arrival time of solutes from the source to a prescribed compliance boundary is a global transport quantity that is of practical interest in many applications, such as risk assessment for environmentally sensitive sites in regulatory analyses. Estimates of uncertainty are necessary and can play an important role in the decision-making process. The objective of this work is therefore to quantify the variability of solute travel time in individual fractures with spatially variable apertures. The variability of solute transport in fractures is largely determined by the heterogeneity of the apertures of naturally occurring rock fractures. To model solute transport, the fracture apertures and flow fields are considered as spatial random functions. Using the relationship between the two-dimensional depth-averaged solute conservation equation and the Fokker-Planck equation, it is possible to formulate the solute convection velocity in such a way that a general expression for the solute travel time variance can be developed by taking into account the effects of the variation in fracture aperture. A closed-form expression for the variance of travel time in the mean flow direction is derived for the case of advection-dominated solute transport. This derived expression allows the analysis of the effects of the variation of the fracture aperture on the variability of the solute travel time.

Unveiling the origin of n-type doping of natural MoS2: carbon

MoS2 has attracted intense interest in many applications. Natural MoS2 and field-effect transistors made of it generally exhibit n-type characteristics, but its origin is unknown. Herein, we show that C is the origin of the universal n-type doping of natural MoS2. Photoemission spectroscopies reveal that while many MoS2 samples with C detected are n-type, some without C exhibit p-type characteristics. The C-free, p-type MoS2 changes to n-type over time with the concurrent appearance of C that is out-diffused from bulk, indicating that C induces the n-type doping. The C-origin is verified by C-deposition and supported by theoretical calculations. This carbon appears as nanometer-scale defects frequently observed in scanning tunneling microscopy. In addition, we propose, based on the calculations, that S vacancies are responsible for the p-type characteristics, which contrasts with the widespread belief. This work provides new perspectives on MoS2 doping and presents a new direction for fabricating reliable MoS2 devices.

A functionality switchable meta-device: from perfect reflection to perfect absorption

Tunable meta-devices trigger immense interest in many applications like biosensing, thermal camouflage, radiative cooling, thermal emitting, infrared imaging, and energy harvesting. This paper presents a polarization-independent broadband tunable absorbing and reflecting meta-device using a phase change material Germanium-Antimony-Tellurium (GST). The proposed design manifests high absorptivity >80% over a broadband range of wavelength spanning the mid-IR regime. Furthermore, by changing the phase of GST material from crystalline to amorphous with the help of external stimuli, the absorbance of the device was reduced to almost zero in the range from 4 μm to 12 μm. To previse the angular constancy of the meta-absorber, the absorptivity was scrutinized under different incidence angles in both transverse magnetic (TM) and transverse electric (TE) polarizations which manifested the robustness of the proposed meta-absorber. As a result, the proposed absorber has tunable broadband absorbance and angular stability, which proclaim great potential in applications such as thermal camouflage, radiation detection, thermal emitter, and stealth technology, etc.

Inducing differences in modification degree and binding mode of organophosphonic acid grafted titania by changing pH and hydrocarbon chain length

Organically modified metal oxide surfaces are of interest in many applications since they combine the advantages of metal oxide supports (structural properties, chemical and mechanical stability) and organic functionalities (for specific surface interactions). Although surface modification with organophosphonic acids (PAs) with an alkyl or aminoalkyl functional group on TiO2 has been investigated previously, knowledge of the synthesis-properties correlation (e.g. the binding mode of the PAs) is still lacking, especially for functional group-surface interactions. These are however important as they can influence functional group availability in applications such as (metal) sorption. In this work, the dependence of modification degree and phosphorus chemical environment on pH and chain length (C1 to C6) was investigated with TGA, ICP-OES, nitrogen/argon sorption, XPS, and solid-state 31P NMR and DFT calculations. The TGA and the ICP-OES results showed a clear impact of pH on surface modification degrees, with a different response for modification with alkyl- and aminoalkylphosphonic acids, featuring a more rapid decrease in modification degrees from pH 2 upwards for the alkylphosphonic acids compared to the aminoalkylphosphonic acids. Moreover, a clear correlation can be found between the aminoalkyl chain length and the NH2/NH3+ ratio. In addition, a positive correlation between the modification degree and the protonation degree of the amine group is observed for aminomethylphosphonic acid (AMPA) and 2-aminoethylphosphonic acid (2AEPA) modified samples, while this is absent for longer alkyl chains. This is supported by DFT calculations that indicate that the most stable binding modes of AMPA and 2AEPA grafted on the anatase (101) surface include hydrogen bonds between NH3+ and the surface oxygen atoms, in contrast, the most stable binding modes for 3-aminopropylphosphonic acid (3APPA), 4-aminobutylphosphonic acid (4ABPA), and 6-aminohexylphosphonic acid (6AHPA) grafted on the anatase (101) surface involve a Lewis acid-base interaction between NH2 and a surface Ti site.

Morphology-controlled atmospheric pressure plasma synthesis of zinc oxide nanoparticles for piezoelectric sensors

Zinc oxide nanoparticles, especially those with a high aspect ratio (i. e., nanorods and nanowires), are of great interest for many applications as they are piezoelectric, photocatalytic and antimicrobial. In the present study, a plasma flight-thru synthesis method was developed that allows controlling the particle size and shape of the zinc oxide nanoparticles. In a direct current thermal plasma reactor operated at atmospheric pressure, zinc powder injected into the plasma jet was molten, vaporized and oxidized, which allowed growing zinc oxide nanoparticles. The particle spectrum ranged from small nanospheres to nanorods, nanowires and multipodic nanoparticles such as tetrapods. The influence of the oxygen rate and the plasma power (correlated to the discharge current) on the particle morphology was studied, and the feasibility of the nanowire-like particles as piezoelectric sensor material was investigated. Piezoelectric test sensors, equipped with the plasma-synthesized zinc oxide nanowires, successfully responded to mechanical stimulation after poling.

Divergent directed evolution of a TetR-type repressor towards aromatic molecules.

Reprogramming cellular behaviour is one of the hallmarks of synthetic biology. To this end, prokaryotic allosteric transcription factors (aTF) have been repurposed as versatile tools for processing small molecule signals into cellular responses. Expanding the toolbox of aTFs that recognize new inducer molecules is of considerable interest in many applications. Here, we first establish a resorcinol responsive aTF-based biosensor in Escherichia coli using the TetR-family repressor RolR from Corynebacterium glutamicum. We then perform an iterative walk along the fitness landscape of RolR to identify new inducer specificities, namely catechol, methyl catechol, caffeic acid, protocatechuate, L-DOPA, and the tumour biomarker homovanillic acid. Finally, we demonstrate the versatility of these engineered aTFs by transplanting them into the model eukaryote Saccharomyces cerevisiae. This work provides a framework for efficient aTF engineering to expand ligand specificity towards novel molecules on laboratory timescales, which, more broadly, is invaluable across a wide range of applications such as protein and metabolic engineering, as well as point-of-care diagnostics.