Unidirectional Growth Research Articles

Bulk growth of unidirectional 1, 3, 5-Triphenylbenzene (TPB) single crystal for fast neutron detection by time of flight technique

The organic scintillator crystal 1,3,5-Triphenylbenzene (TPB) is a promising material for high-energy particle detection applications. The bulk size of unidirectional (<100> plane) TPB cylindrical crystal was grown by the unidirectional growth technique and their optical properties were analyzed to couple with a photomultiplier tube for detector device fabrications. The gamma retorts of the grown cylindrical crystal were tested with varying gamma energy sources ranging from 356 to 1275 keV. The Time of flight (TOF) experimental setup was constructed with a grown TPB crystal and Neutron-Gamma discrimination was demonstrated with a 252Cf fission source. The developed TPB crystal exhibits strong timing characteristics operates consistently and offers a great capability for discrimination over gamma radiations.

Sankaranarayanan-Ramasamy (SR) technique L- threonine lithium chloride single crystal: Unidirectional growth, optical and mechanical studies

L-Threonine Lithium Chloride (LTLC), an effective semi-organic NLO material, was successfully produced as a bulk single crystal using the Sankaranarayanan Ramasamy (SR) process. According to a study of a single crystal's X-ray diffraction, LTLC crystallises in an orthorhombic system with space group P212121. From the powder XRD method, unidirectional development along the plane (110) was established. The optical absorption spectra reveals that LTLC has a broad bandgap of 3.75 eV and is very transparent over the whole visible region. On the magnified crystal, photoconductivity measurements show positive photoconductivity. According to the photoluminescence investigation, LTLC emits green light with a wavelength of 535 nm. Vickers microhardness testing was done to determine the crystal's mechanical strength. At different temperatures and frequencies, the dielectric constant and dielectric loss were calculated. In addition to the density functional theory (DFT) calculations such as frontier molecular orbital’s (FMOs), analysis was carried out. Utilizing Kurtz's Nd:YAG Laser, powder testing is another method used to assess the produced crystal's SHG activity.

One-dimensional γ-Al2O3 growth from the oxidation of NiAl

We report an oxide nanowire growth phenomenon that morphologically resembles the vapor-liquid-solid process but with a fundamentally different mechanism. This is demonstrated with the high-temperature NiAl oxidation that results in the unidirectional γ-Al2O3 growth with a NiO nanoparticle at the nanowire tip. The NiO nanoparticle surface serves as the active site for dissociative O2 adsorption that produces an inward flux of atomic oxygen toward the γ-Al2O3/NiAl interface for γ-Al2O3 growth by reacting with bottom-up diffusing Al3+ cations. The nanowire lengthening follows the parabolic kinetics with the upward lattice diffusion of Al3+ cations in the γ-Al2O3 nanowires as the rate-limiting factor.

UNDERSTANDING THE BUILT-UP EVOLUTION AND COMPLEXITY OF FAST-GROWING BUILT-UP AGGLOMERATION USING THE CENTROID SHIFT MODEL AND FRACTAL DIMENSION

Abstract. Understanding Built-up evolution and complexity over time is attained to exercise sustainable development and smart implementations in the future. The Spatiotemporal evolution of built-up analysis is carried out using the centroid shift model considering the geometry of the built-up from 1975 to 2019 (1975, 1990, 1999, 2009, and 2019). The centroid shift indicates the trajectory of the growth pattern and the future direction of growth. The study area experienced a unidirectional growth pattern till 2009, considering 1975 as the base year, and by 2019 the growth direction shifted by 3.52 degrees, and the overall centroid shift magnitude was 2.42 km2. The non-Euclidean geometric nature of the physical world puts forward fractal geometry to understand the complexity of built-up. The mean fractal dimension index shows the growth type in the study area; a directional approach towards the mean fractal dimension provides a critical understanding of the complexity around the built-up Centroid. Among all the eight directions considered, NW_W showed maximum built-up growth with infilling growth type, and the E_SE direction showed a significant jump in an area with external expansion by 2019. This direction indicates the future growth direction. The study concludes that complexity analysis critically enhances the spatiotemporal dynamics of built-up evolution.

Single‐Orientation Epitaxy of Quasi‐1D Tellurium Nanowires on M‐Plane Sapphire for Highly Uniform Polarization Sensitive Short‐Wave Infrared Photodetection

AbstractTellurium (Te), an elemental van der Waals semiconductor, has intriguing anisotropic physical properties owing to its inherent quais‐1D crystal structure. Synthesizing ultrathin Te crystal with uniform orientation is important to its large‐scale device applications, but that remains a great challenge. Herein, the nanoscale grooves‐induced unidirectional epitaxy growth of 1D Te nanowires via physical vapor deposition on the annealed m‐plane sapphire is demonstrated. By enhancing the annealing temperature from 1000 to 1300 °C, nanoscale grooves on m‐plane sapphire arising along the [100] direction and gradually distinct, and the corresponding Te nanowires grown on them turns from random to uniform, finally achieving nearly 95% unidirectional Te nanowires. The as‐grown Te nanowires possess high crystallinity with clearly chiral helical chains along the c‐axis direction and reveal thickness‐tunable bandgap with prominent linear‐dichroic. As results, the Te nanowire‐based photodetectors demonstrate a broadband photoresponse from visible (532 nm) to short‐wave infrared (2530 nm), with high responsivity of 327 A W−1 as well as strong and uniform polarization sensitivity (anisotropic ratio = 2.05) to 1550 nm light. The high crystallinity and superior anisotropy of Te nanowires, combined with the orientation‐controlled preparation endows it with great feasibility for constructing chip‐scale multifunctional optoelectronic devices.

A novel two-step route to unidirectional growth of multilayer MoS2 nanoribbons

Alkali-assisted chemical vapour deposition (CVD) of transition metal dichalcogenides (TMDs) has been shown to promote the growth of large single crystals of TMD monolayers. The morphology control of TMDs is a key parameter for the scalable synthesis of versatile layered materials. This work demonstrates that the alkali-assisted synthesis provides a route toward fabricating highly crystalline MoS2 nanoribbons. Our proposed method involves a vapour-liquid–solid phase reaction between MoOx(2 < x < 3) precursors grown by Pulsed Laser Deposition (PLD) and metal alkali halide (i.e., NaF). The growth process evolves via the emergence of the Na–Mo–O liquid phase, which mediates the formation of MoS2 multilayer nanoribbons in a sulfur-rich environment. Moreover, the as-grown MoS2 nanoribbons are surrounded by mono- and multilayer triangles of MoS2 and exhibit a preferential alignment defined by both MoS2 crystal symmetry and the underlying Al2O3 substrate. In addition, we observe a significant built-in strain in the as-grown MoS2 nanostructures, which increase in magnitude from the multilayer nanoribbons to the triangular monolayers, and which can be effectively released upon transfer onto another substrate. The growth method developed here can enable flexibility in designing nanoelectronic devices based on TMDs with tunable dimensions.

Unidirectional domain growth of hexagonal boron nitride thin films

Two-dimensional van der Waals (2D-vdW) layered hexagonal boron nitride (h-BN) has gained tremendous research interest over recent years due to its unconventional domain growth morphology, fascinating properties and application potentials as an excellent dielectric layer for 2D-based nano-electronics. However, the unidirectional domain growth of h-BN thin films directly on insulating substrates remains significantly challenging because of high-bonding anisotropicity and complex growth kinetics than the conventional thin films growth, thus resulting in the formation of randomly oriented domains morphology, and hindering its usefulness in integrated nano-devices. Here, ultra-wide bandgap h-BN thin films are grown directly on low-miscut atomically smooth highly insulating c-plane sapphire substrates (without using any metal catalytic layer) by pulsed laser deposition, showing remarkable unidirectional triangular-shape domains morphology. This unidirectional domain growth is attributed to the step-edge guided nucleation caused by reducing the film-substrate interfacial symmetry and energy, thereby breaking the degeneracy of nucleation sites of random domains, as revealed by the density functional theory (DFT) calculations. Through extensive characterizations, we further demonstrate the excellent single crystal-like functional properties of films. Our findings might pave the way for feasible large-area direct growth of electronic-quality h-BN thin films on insulating substrates for high-performance 2D-electronics, and in addition would be beneficial for hetero engineering of 2D-vdW materials with emergent phenomena.

Research progress of hydrogels as delivery systems and scaffolds in the treatment of secondary spinal cord injury.

Secondary spinal cord injury (SSCI) is the second stage of spinal cord injury (SCI) and involves vasculature derangement, immune response, inflammatory response, and glial scar formation. Bioactive additives, such as drugs and cells, have been widely used to inhibit the progression of secondary spinal cord injury. However, the delivery and long-term retention of these additives remain a problem to be solved. In recent years, hydrogels have attracted much attention as a popular delivery system for loading cells and drugs for secondary spinal cord injury therapy. After implantation into the site of spinal cord injury, hydrogels can deliver bioactive additives in situ and induce the unidirectional growth of nerve cells as scaffolds. In addition, physical and chemical methods can endow hydrogels with new functions. In this review, we summarize the current state of various hydrogel delivery systems for secondary spinal cord injury treatment. Moreover, functional modifications of these hydrogels for better therapeutic effects are also discussed to provide a comprehensive insight into the application of hydrogels in the treatment of secondary spinal cord injury.

Theoretical and Experimental Investigation of In Situ Grown MOF‐Derived Oriented Zr‐Mn‐oxide and Solution‐Free CuO as Hybrid Electrode for Supercapacitors

AbstractRecently metal‐organic framework (MOF) derived electrode materials have grown considerable research interest in the field of supercapacitor (SC) technology. Herein, MOF‐derived Zr‐Mn‐oxide is successively combined with solution‐free CuO nanowires not only to avoid the structural limitations of MOF but also to fabricate a positive‐negative hybrid electrode material. The MOF‐derived mixed metal oxide prepared through in situ fabrication allows the uniform and unidirectional growth of oriented Zr‐Mn‐oxide@CuO@Cu. The hybrid electrode exhibited over 100% stability after 20,000 cycles in a three‐electrode setup with a wide potential window range of 1.2 V (−0.6 to 0.6 V). Further, the obtained Zr‐Mn‐oxide@CuO@Cu hybrid electrode exhibited 14.1‐ and 5.5‐fold higher capacity over its MOF‐derived Zr‐Mn‐oxide counterpart (−0.6 to 0.1 V) and CuO (0.0 to 0.5 V), respectively. Additionally, the hybrid device with hybrid Zr‐Mn‐oxide@CuO@Cu as the positive electrode and reduced graphene oxide as the negative electrode also displayed promising energy and power densities. Furthermore, density functional theory calculations are employed to study the hybrid electrode material's properties. Overall, the unidirectional and vertically aligned MOF‐derived Zr‐Mn‐oxide@CuO@Cu hybrid electrode material with notable electrochemical performance can be useful for the fabrication of next‐generation supercapacitor electrodes.

Detailed structural and topological analysis of SnBi2Te4 single crystal

We report herein the successful synthesis of the topological material SnBi2Te4 in single-crystal form. Phase purity and unidirectional growth are evident from X-ray diffraction (XRD) patterns acquired from a powdered sample and a crystal flake. The crystalline morphology has also been visualized by acquiring a field-emission scanning electron microscope (FESEM) image. The crystal has been thoroughly characterized by means of Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements. The topological properties of SnBi2Te4 have been probed through magneto-transport measurements. SnBi2Te4 has been found to exhibit a small but non-saturating magneto-resistance (MR) up to ±12 T. The low-field magnetoconductivity (MC) of SnBi2Te4 at 2 K can be well explained through the Hikami–Larkin–Nagaoka (HLN) formalism, which confirms the presence of a weak anti-localization (WAL) effect in its crystal. Moreover, the non-trivial topological character has been evidenced through first-principles calculations using density functional theory (DFT), with and without spin-orbit coupling (SOC) protocols. A significant change in the bulk electronic band structure is observed upon the inclusion of SOC parameters, signifying topological properties of SnBi2Te4. Its topological non-trivial character has also been verified through calculation of Z2 invariants and the surface states spectrum in the (111) plane.

Role of Different Solvents and Tailor-Made Additives in Asymmetry in Growth Rates along the Opposite Ends of the Polar Axis: The Riddle of α-Resorcinol

Understanding the mechanism of unidirectional growth of polar acentric materials along the polar axis has been an important issue so far. To this end, we computationally examine the role of various tailor-made additives in aqueous, acetic acid, and acetone solutions to elucidate the underlying mechanism of asymmetry in the growth of α-resorcinol crystals. A simulated annealing method followed by periodic density functional theory using the B3LYP method augmented with an empirical dispersion term has been employed to determine the solute–surface, solvent–surface, and additive–surface interfaces. The adsorption energies of different molecular auxiliaries in various step configurations on oxygen-rich {01̅1̅} and hydrogen-rich {011} faces have been determined to examine different adsorption pathways before obtaining the rate of growth. Considering that crystallization is a thermally activated process that involves the kinetic and thermodynamic aspects of the adsorption of different molecular auxiliaries at the interface, the rate of growth along the opposite ends of the polar axis has been calculated to determine growth anisotropy. We have constructed eight different step configurations (¢1–¢8) on the (011) and (01̅1̅) faces to determine the adsorption pathways of the resorcinol molecule. It has been found that the adsorption of different auxiliaries in ¢1, ¢4, and ¢1 step configurations would determine the growth rate of oxygen-rich faces from aqueous, acetic acid, and acetone solutions, respectively. Our results show that the oxygen-rich faces grew 9 and 6 times faster than the hydrogen-rich faces from aqueous and acetone solutions, respectively. However, the growth rate of the oxygen-rich faces is nearly 3 orders of magnitude lower than that of the hydrogen-rich faces during acetic acid-mediated crystallization. Our study suggests that the solvent adsorption energy toward the oxygen-rich faces is not strong enough to explain the experimentally observed growth disruption of the oxygen-rich faces from acetic acid solution. We find that the strongly adsorbed acetic acid on the oxygen-rich faces rotates one of the hydroxyl groups of the surface molecule from anti to the syn position, which causes an appreciable delay in their growth. Moreover, adsorption of different auxiliaries in the ¢6 step configuration would determine the growth rate of hydrogen-rich faces from aqueous, acetic acid, and acetone solutions. The adsorption energies of water, acetic acid, acetone, and different conformers/tailor-made additives in various step configurations have also been evaluated to determine the effect of these auxiliaries on the unidirectional growth along the polar axis. Our results show that the asymmetry in growth decreases with increasing saturation temperatures and supersaturation, which is consistent with the experimental results. Increased concentrations of β- and γ-phase conformers of resorcinol and orcinol lead to increased asymmetry from aqueous growth. However, asymmetry from aqueous growth decreases with increasing concentrations of 2-methylresorcinol and pyrogallol. Our findings clearly show that the growth asymmetry increased from 9 to 1 in aqueous solution containing 20% pyrogallol at a temperature of 25 °C, which is in good agreement with the experimental observation. The asymmetry in growth from aqueous and acetone solutions decreases with increasing supersaturation. On the other hand, the asymmetric growth induced by acetic acid increases with increasing supersaturation, which clearly suggests that the solvent interaction on oxygen-rich faces is higher than that on hydrogen-rich faces.

Modeling gross motor developmental curves of extremely and very preterm infants using the AIMS home-video method

BackgroundMotor development is one of the first signals to identify whether an infant is developing well. For very preterm (VPT) infants without severe perinatal complications, little is known about their motor developmental curves. AimsExplore gross motor developmental curves from 3 until 18 months corrected age (CA) of VPT infants, and related factors. Explore whether separate profiles can be distinguished and compare these to profiles of Dutch term-born infants. Study designProspective cohort study with parents repeatedly recording their infant, using the Alberta Infant Motor Scale (AIMS) home-video method, from 3 to 18 months CA. SubjectsForty-two Dutch infants born ≤32.0 weeks gestational age and/or with a birthweight (BW) of <1500 g without severe perinatal complications. Outcome measuresGross motor development measured with the AIMS. ResultsIn total 208 assessments were analyzed, with 27 infants ≥five assessments, 12 with <four, and three with one assessment. Sigmoid-shaped gross motor curves show unidirectional growth and variability. No infant or parental factors significantly influenced motor development, although a trend was seen for the model where lower BW, five-minute Apgar score <7, and Dutch native-speaking parents were associated with slower motor development. Three motor developmental profiles of VPT infants were identified, early developers, gradual developers, and late bloomers, which until 12 months CA are comparable in shape and speed to profiles of Dutch term-born infants. ConclusionsVPT infants show great intra- and interindividual variability in gross motor development, with three motor profiles being distinguished. From 12 months CA onwards, VPT infants appear to develop at a slower pace. With some caution, classifying infants into motor developmental profiles may assist clinical decision-making.

Soft-template electropolymerization of 3,4-(2,3-naphtylenedioxy)thiophene-2-acetic acid esters favoring dimers: Controlling the surface nanostructure by side ester groups

A series of the esters of 3,4-(2,3-naphtylenedioxy)thiophene-2-acetic acid (NaphDOT-R) have been synthesized, with varying the structure of the ester fragments in the molecules (fluoroalkyl groups and different aromatic moieties: benzene, naphthalene, carbazole and pyrene). Their anodic oxidation by cyclic voltammetry scanning between –1 and +2.0 V led to electrochemical deposition of the films on the electrode surface which show different surface morphology. NaphDOT-R derivatives can be divided into two groups: (1) the monomers with fluoroalkyl and benzyl ester groups can only dimerize with depositing insoluble dimers on the electrode surface, whereas (2) monomers with condensed aromatic moieties (naphthalene, carbazole and pyrene) in the ester fragment undergo further electropolymerization involving these groups. The surfaces of the deposited films were studied by scanning electron microscopy toward their roughness and wettability. The influence of water on the electropolymerization process and the surface nanostructures is discussed through TEM observations of the micellar template in the electropolymerization solutions. No template was nevertheless detected for NaphDOT-Pyr in dichloromethane, which electropolymerization leads to the formation of aggregated spherical nanoparticles or tree-like surface nanostructures (3D), whereas in dichloromethane saturated with water, unidirectional (1D) growth of vertically aligned nanotubes was observed. The wettability studies on electrodeposited films with three probe liquids (water diiodomethane and hexadecane) showed that they are generally slightly hydrophobic and oleophilic, while the structure of the side ester group and the deposition conditions effect on the quantitative parameters of the surface roughness and wettability.

In-situ comparison of interface instability of basal and edge planes during unidirectional growth of sea ice

The evolutions of water/ice interface with distinct ice orientations are one of the central problems in sea ice growth. Some misunderstandings prevailed in previous hypothesis on morphological evolution of sea ice, which need the validation with carefully designed experiments. Up to now, there is no in-situ comparison of unidirectional freezing behavior between distinct ice orientations, which makes the previous hypothesis on sea ice growth skeptical about its physical basis. The aim of this paper is to provide an in-situ comparison of unidirectional growth behavior of lamellar sea ice between basal and edge planes. Our experiment is realized by a delicate design of parallel freezing samples with two specified ice orientations in a modeled sea water under an imposed thermal gradient. The planar instability as well as the unidirectional cellular/dendritic growth patterns of water/ice interfaces of basal and edge plane ice are compared. It is found that the instability grows faster for edge plane ice, which is addressed by an incubation time coupled with the surface tension anisotropy. In addition, two types of tilted growth patterns of sea ice after planar instability are observed simultaneously, which are suggested to stem from distinct physical origins and provide a new insight into the tilted growth of cellular/dendritic ice. Collectively, these experimental results are suggested to promote our understanding of morphological evolution of unidirectional growth of sea ice, as well as its diverse relevance to many other areas involving ice growth.

Numerical Analysis of Nucleation and Growth of Stray Grain Formation during Laser Welding Nickel-Based Single-Crystal Superalloy Part II: Solidification Cracking Diminution through Single-Crystallinity Control

The effect of thermo-metallurgical factors, such as heat input and welding configuration, on solidification cracking driving forces nearby dendrite tip, such as solidification temperature range and columnar/equiaxed transition (CET) was thermodynamically and kinetically discussed with aid of comprehensive numerical analysis for multicomponent melt-pool solidification during laser processing under non-equilibrium solidification conditions to better understand problematical solidification cracking phenomena. By using (001)/[100] welding configuration, axisymmetrical distributions of columnar/equiaxed transition and solidification temperature range alongside solidification interface are homogeneously produced on both sides of weld pool. By using (001)/[110] welding configuration, nonaxisymmetrical distributions are heterogeneously produced, and are able to bring about infelicitous microstructure degradation. Unidirectional region of [001] columnar dendrite is more prone to epitaxial growth without morphology transition to conservatively better crystallography-assisted single-crystal growth. Unidirectional epitaxial growth is collapsed, and onset of stray grain nucleation and solidification cracking eventuates in [100] region of equiaxed dendrite growth. Low heat input relatively broadens portion of unidirectional columnar dendrite, where stray grain is infrequently nucleated and grown, and thus morphology transition seldom happens, as long as undercooling and solidification temperature range alongside dendrite tip are sufficient low to challengingly develop crackless dendrite growth and high-quality weld by thermometallurgy-aided single-crystallinity control. Auspicious (001)/[100] welding configuration simultaneously abates overall stray grain nucleation and constricts solidification temperature range nearby fusion boundary to wane microstructure heterogeneity. Conversely, plenteous stray grain formation is kinetically attained and extensive solidification temperature range nearby fusion boundary is thermodynamically obtained by problematical (001)/[110] welding configuration to metallurgically induce pernicious equiaxed dendrite and disintegrate dendrite growth. Moreover, the mechanism of solidification cracking diminution as consequence of appropriate optimization of thermo-metallurgical determinants during multicomponent nickel-based single-crystal superalloy melt-pool non-equilibrium solidification is also proposed. The potent consistency between the predicted and experimented results is exceedingly tenable.

Age structure and growth pattern of a high-altitude lizard population based on age determination by skeletochronology.

Age determination provides crucial data regarding the life history of a species. Skeletochronology is considered to be a reliable method for age determination but is seldom applied to the genus Phrynocephalus (Agamidae) as it requires careful bone histological analysis to determine the formation of the lines of arrested growth (LAGs). We analyzed LAGs in different bones of Phrynocephalus vlangalii, a small, high-altitude lizard, and demonstrated that the phalanges are the best materials for skeletochronology in this species. We also found that the proximal half of the phalangeal diaphysis exhibits the most complete LAGs because of the unidirectional longitudinal growth of the phalange. Histologically, as the embryo bone that developed during the embryonic period was preserved even in very old individuals, no LAGs were eroded by endosteal resorption in the phalanges. The maximum age was 4yearsfor males and 5years for females. It was determined that the age at maturity was 3years for males and 2 or 3years for females. On the basis of age determination, the age structures of both sexes were compared, and age-specific growth differences between the sexes were also analyzed. No differences in the snout-vent length were observed between sexes in any age group. However, the tail length of males aged 3 and above was significantly longer than that of females. Thus, the use of phalanges in the age determination of P. vlangalii is effective and can be widely applied to the ecological studies of this species as well as other small lizards.

A study of the phase transition by the electrical resistivity and photocurrent on TGS crystal grown using the unidirectional growth method of Sankaranarayanan–Ramasamy

A study of the phase transition by the electrical resistivity and photocurrent on TGS crystal grown using the unidirectional growth method of Sankaranarayanan–Ramasamy

Exploring the "Living" Growth of Block Copolymer Nanofibers from Surface-Confined Seeds by In Situ Solution-Phase Atomic Force Microscopy.

Living crystallization-driven self-assembly of polymeric and molecular amphiphiles is of growing interest as a seeded growth route to uniform 1D, 2D, and more complex micellar nanoparticles with controlled dimensions and a range of potential applications. Although most studies have been performed using colloidally stable seeds in bulk solution, growth of block copolymer (BCP) nanofibers from seeds confined to a surface is attracting increased attention. Herein, we have used atomic force microscopy (AFM) to undertake detailed studies of the growth of BCP nanofibers from immobilized seeds located on a Si surface. Through initial ex situ AFM studies and in situ AFM video analysis in solution, we determined that growth occurred in four stages, whereby an initial surface-bound growth regime transitions to surface-limited growth. As the nanofiber length increases, surface influence is diminished as the newly grown micelle segment is no longer bound to the Si substrate. Finally, a surface-independent regime occurs where nanofiber growth continues into bulk solution. In addition to the anticipated nanofiber elongation, our studies revealed occasional examples of AFM tip-induced core fragmentation. In these cases, the termini of the newly formed fragments were also active to further growth. Furthermore, unidirectional growth was detected in cases where the seed was oriented at a significant angle with respect to the surface, thereby restricting unimer access to one terminus.

Carbon-based aerogel in three-dimensional polyurethane scaffold: The effect of in situ unidirectional aerogel growth on piezoresistive properties

Carbon-based aerogels (CA) with durable piezoresistive properties possess great promise for applications in wearable electronics. However, it is still a great challenge to fabricate high performance aerogel sensors due to the limits of mechanical properties. We recently developed a novel strategy to build aerogel/foam hybrid structure that can effectively enhance the mechanical properties of aerogel-based sensors. Herein, CA/polyurethane foam (PUF) composite was fabricated via in situ unidirectional freeze-drying process starting from a carbon nanotubes (CNTs)/graphene oxide (GO) aqueous dispersion stabilized with chitosan (CS) which was filled into the porosity of an open cell PUF. The resulting composite shows a microscopic anisotropy in the CA with electrical conductivity as high as 10.54 S m−1. The piezoresistive sensitivity of the resulting composite can be simply modulated over a wide range from 1.1 to 3.6 by adequately selecting its initial pre-strain. The CA/PUF composite exhibits excellent compressible resilience at the strain of 50% for at least 100 cycles. In addition, the sensor was successfully applied for detecting various human motions. These unique properties make the realized composite a promising candidate for effective flexible piezoresistive strain sensors in wearable applications.

Growth onset of perylene-based nanocrystals

The wide application of organic nanocrystals requires a deeper understanding of their nucleation mechanisms. In particular, the onset of nucleation still needs to be elucidated, although tremendous efforts have already been made in both experimental and simulation studies. In this research, we conduct molecular dynamics (MD) simulations, supported by quantum mechanical (DFT) calculations, to understand the mechanisms of the nucleation onset of organic perylene nanocrystals. Our DFT calculations indicate that face-to-face and face-to-edge molecular stacking can ultimately lead to the formation of a herringbone-style perylene nanocrystal. On the other hand, the results of MD simulations show the formation of clusters, which continues with the crystal nucleation in the form of unidirectional or multidirectional growth, depending on the feeding rate of perylene molecule in vacuum. This research helps to better understand the control of the growth of organic nanocrystals in modern nanotechnology.