A review of experimental and modeling techniques to determine properties of biopolymer-based nanocomposites

The nonbiodegradable and nonrenewable nature of plastic packaging has led to a renewed interest in packaging materials based on bio-nanocomposites (biopolymer matrix reinforced with nanoparticles such as layered silicates). One of the reasons for unique properties of bio-nanocomposites is the difference in physics at nanoscale as compared to that at macroscale. Therefore, the effect of nanoscale on the properties of bio-nanocomposites is discussed. Properties of bio-nanocomposites are governed by the extent of dispersion of nanoparticles in the biopolymer matrix and interaction between nanoparticles and the biopolymer. Selection of proper technique to determine properties of these bio-nanocomposites is very critical in assessing their performance. Experimental techniques (tensile testing, barrier property measurement, dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, rheological measurement) to determine the mechanical, barrier, thermal, and rheological properties of bio-nanocomposites are discussed in terms of methodology, interpretation of results, and application in studying the properties of bio-nanocomposites. Mathematical modeling plays an important role in predicting the properties of bio-nanocomposites and comparing them to the measured properties. This comparison helps in better understanding the mechanism for much improved properties of bio-nanocomposites. Mathematical modeling is also helpful in understanding the effects of different parameters on the properties of bio-nanocomposites. Therefore, the article describes mathematical modeling of mechanical and barrier properties of bio-nanocomposites using analytical micromechanics.     

Changes in lycopene and beta carotene contents in aril and oil of gac fruit during storage

Gac fruits were physically measured and stored under ambient conditions for up to 2 weeks to observe changes in carotenoid contents (lycopene and beta carotene) in its aril. Initial concentrations in the aril of lycopene were from 2.378 mg/g fresh weight (FW) to 3.728 mg/g FW and those of beta carotene were from 0.257 to 0.379 mg/g FW. Carotenoid concentrations in the aril remained stable after 1 week but sharply declined after 2 weeks of storage. Gac oil, pressed from gac aril, has similar concentrations of lycopene and beta carotene (2.436 and 2.592 mg/g, respectively). Oil was treated with 0.02% of butylated hydroxytoluene, or with a stream of nitrogen or untreated then stored in the dark for up to 15 or 19 weeks under different temperatures (5 °C, ambient, 45 and 60 °C). Lycopene and beta carotene in control gac oil degraded following the first-order kinetic model. The degradation rate of lycopene and beta carotene in the treated oil samples were lower than that in the control oil but the first-order kinetic was not always followed. However, both lycopene and beta carotene degraded quickly in gac oil with the first-order kinetic under high temperature conditions (45 and 60 °C) regardless of the treatments used.     

Using Specific Displacements to Analyze Motion without Calibration

Considering the field of un-calibrated image sequences and self-calibration, this paper analyzes the use of specific displacements (such as fixed axis rotation, pure translations,...) or specific sets of camera parameters. This allows to induce affine or metric constraints, which can lead to self-calibration and 3D reconstruction.A uniformed formalism for such models already developed in the literature plus some novel models are developed here. A hierarchy of special situations is described, in order to tailor the most appropriate camera model to either the actual robotic device supporting the camera, or to tailor the fact we only have a reduced set of data available.This visual motion perception module leads to the estimation of a minimal 3D parameterization of the retinal displacement for a monocular visual system without calibration, and leads to self-calibration and 3D dynamic analysis.The implementation of these equations is analyzed and experimented.     

An Integrated Process for D-Sorbitol Production over NiO/TiO2 Supported Ru Nanocatalyst: A Greener Approach

The catalytic transformation of D-glucose towards D-sorbitol is a well-established process in the biorefinery industry. Normally, this batch-wise hydrogenation over metallic catalysts suffers from several troubles such as low yielding and facile catalyst deactivation. To address these challenges, we, hereby fabricated 5NiO/TiO₂-supported Ru nanocatalysts (Ru-5NiO/TiO₂, 1.0 and 5.0 wt% Ru) and examined their efficacy in the continuous-flow reduction of D-glucose aqueous solution (20 wt%) to produce D-sorbitol for the first time. In this study, D-glucose conversion and D-sorbitol yield were represented as a function of residence time, where the feeding rate of D-glucose was systematically controlled to maximize the outcome of D-sorbitol. Remarkably, D-glucose was fully converted to 99.0% selectivity of D-sorbitol under optimized reaction conditions (100 °C, 8 MPa H₂ with a flow rate of 100 L h^?1). The experimental results showed that the mean activity and specific rate of 1.0 wt% Ru-5NiO/TiO₂ were achieved as 731.3 mmol h^??1 g^??1 and 1030.7 mmol h^?1 g^?1, respectively, which surpassed those of monometallic Ru-based catalysts (1.0 wt% Ru/TiO₂, 1.0 wt% Ru/SiO_2, and 1.6 wt% Ru/C). Moreover, the stability of 1.0 wt% Ru-5NiO/TiO₂ nanocatalyst was sustained for long-term operation (>?360 h) and no leaching of ruthenium was highly acknowledged.

Graphical Abstract

     

Fabrication of Zein-Based Fibrous Scaffolds for Biomedical Applications—A Review

Zein, which accounts for around 80% of the total protein composition in corn, is a biocompatible and biodegradable substance derived from renewable sources. Although insoluble in water, its amphiphilic characteristics are utilized to generate nanoparticles, nanofibers, microparticles, and even films. Numerous recent studies have demonstrated the potential of zein as a prospective biomaterial to develop fibrous scaffolds for biomedical functions owing to its biocompatibility, fibrous formation, and encapsulating qualities. Fabrication of zein-based fibrous scaffolds for biomedical applications is achieved by a wide variety of techniques, including electrospinning, wet spinning, freeze drying, and additive manufacturing. This article overviews current advancements in manufacturing techniques for zein-based fibrous scaffolds. In addition, it summarizes the most recent biomedical applications and research activities utilizing zein-based fibrous scaffolds. Overall, zein is proposed as a potential biomaterial for the production of fibrous scaffolds that stimulate cell adhesion and proliferation in a number of exciting biomedical applications due to its biodegradability, biocompatibility, and other unique features related to its structure.     

Relationship between pore fluid velocity distribution and pore size distribution

This study investigated the normalized velocity magnitude distribution and normalized pore volume distribution in different porous media with porosity between 13.5% and 85%, including sandstones, carbonates, synthetic silica, sphere packings and fiber scaffolds. It was found that both velocity magnitude and pore size follow the same distribution. These results allow the prediction of the velocity distribution in a porous medium when its pore structure is known or tuning the velocity by controlling the pore structure.     

MoxWx–1S2 Nanotubes for Advanced Field Emission Application

Transition metal dichalcogenide (TMDC) nanotubes complement the field of low-dimensional materials with their quasi-1D morphology and a wide set of intriguing properties. By introducing different transition metals into the crystal structure, their properties can be tailored for specific purpose and applications. Herein, the characterization and a subsequent preparation of single-nanotube field emission devices of Mo_xW_x-1S₂ nanotubes prepared via the chemical vapor transport reaction is presented. Energy-dispersive X-ray spectroscopy, Raman spectroscopy, and X-ray diffraction  indicate that the molybdenum and tungsten atoms are randomly distributed within the crystal structure and that the material is highly crystalline. High resolution transmission electron microscopy  and electron diffraction (ED) patterns further corroborate these findings. A detailed analysis of the ED patterns from an eight-layer nanotube reveal that the nanotubes grow in the 2H structure, with each shell consists of one bilayer. The work function of the nanotubes is comparable to that of pure MoS₂ and lower of pure WS₂ NTs, making them ideal candidates for field emission applications. Two devices with different geometrical setup are prepared and tested as field emitters, showing promising results for single nanotube field emission applications.     

A Metal-Organic Framework Incorporating Eight Different Size Rare-Earth Metal Elements: Toward Multifunctionality À La Carte

Multi-metallic multivariate (MTV) rare earth (RE) metal−organic frameworks (MOFs) are of interest for the development of multifunctional materials, however examples with more than three RE cations are rare and obstructed by compositional segregation during synthesis. Herein, this work demonstrates the synthesis of a multi-metallic MTV RE MOF incorporating two, four, six, or eight different RE ions with different sizes and in nearly equimolar amounts and no compositional segregation. The MOFs are formed by a combination of RE cations (La, Ce, Eu, Gd, Tb, Dy, Y, and Yb) and a 1,7-di(4-carboxyphenyl)-1,7-dicarba-closo-dodecaborane (mCB-L) linker. The steric bulkiness and acidity of mCB-L is crucial for the incorporation of different size RE ions into the MOF structure. Demonstration of the incorporation of all RE cations is performed via compositional and structural characterization. The more complex MTV MOF, including all eight RE ions (mCB-8RE), are also characterized using optical, thermal, and magnetic techniques. Element-selective X-ray absorption spectroscopy and X-ray Magnetic Circular Dichroism measurements allow us to characterize spectroscopically each of the eight RE ions and determine their magnetic moments. This work paves the way for the investigation of MTV MOFs with the possibility to combine RE ions à la carte for diverse applications.     

Flexible Nanoarchitectonics for Biosensing and Physiological Monitoring Applications

Flexible and implantable electronics hold tremendous promises for advanced healthcare applications, especially for physiological neural recording and modulations. Key requirements in neural interfaces include miniature dimensions for spatial physiological mapping and low impedance for recognizing small biopotential signals. Herein, a bottom-up mesoporous formation technique and a top-down microlithography process are integrated to create flexible and low-impedance mesoporous gold (Au) electrodes for biosensing and bioimplant applications. The mesoporous architectures developed on a thin and soft polymeric substrate provide excellent mechanical flexibility and stable electrical characteristics capable of sustaining multiple bending cycles. The large surface areas formed within the mesoporous network allow for high current density transfer in standard electrolytes, highly suitable for biological sensing applications as demonstrated in glucose sensors with an excellent detection limit of 1.95 µm and high sensitivity of 6.1 mA cm⁻² µM⁻¹, which is approximately six times higher than that of benchmarking flat/non-porous films. The low impedance of less than 1 kΩ at 1 kHz in the as-synthesized mesoporous electrodes, along with their mechanical flexibility and durability, offer peripheral nerve recording functionalities that are successfully demonstrated in vivo. These features highlight the new possibilities of our novel flexible nanoarchitectonics for neuronal recording and modulation applications.     

Effect of Different Solvents on the Synthesis of Resorcinol–Formaldehyde and g-C3N4 Composite as Photocatalyst for Degradation of Methylene Blue

Carbon nitride, a hot spot in metal-free material, has been widely studied for various fields of application. Various efforts have been made to improve the photocatalytic activity of carbon nitride, including cross-linking with other kinds of polymers. In this study, Resorcinol – Formaldehyde (RF) resins were chosen to modify carbon nitride because they can act as a sacrificial agent to create the Z-scheme catalytic system with carbon nitride. The novelty of this study is using polyol solvents to synthesize nano-fragments Resorcinol–Formaldehyde. The goal of this work was to study the influence of polyol solvents on the formation of RF polymer and the photocatalytic performance of RF-modified carbon nitride. Scanning electron microscope (SEM) images suggested that nano-fragments RF resins that were synthesized in ethylene glycol and glycerol were able to deposit densely on the surface and in pores of carbon nitride as nano-fragments, while RF obtained from hydrothermal had the morphology of microspheres and only anchored on the surface of carbon nitride. In terms of BET (Brunauer–Emmett–Teller) surface area, E-RFCN had the largest value in four samples (72.3 m² g^?1) and was the only sample that had the BET value higher than that of pristine carbon nitride (26.9 m² g^?1). Regarding the photocatalytic activity, E-RFCN was the optimal sample that could completely remove MB in the solution within 40 min in H₂O₂/visible light conditions. Furthermore, the catalyst could work effectively in a wide pH range from 5 to 9, and could be reused for 4 cycles. By conducting radical scavenging experiments, it was founded that ?OH, photoinduced holes (h?+) and ?O₂^? contributed to MB decomposition by the order: h?+??>??OH?>??O₂^?. Finally, the hypothesis for the effect of polyol solvents on the polymerization of RF and the RF-carbon nitride cross-linking had been proposed.