Improving the Autofluorescence of Lophira alata Woody Cells via the Removal of Extractives.

The autofluorescence phenomenon is an inherent characteristic of lignified cells. However, in the case of Lophira alata (L. alata), the autofluorescence is nearly imperceptible during occasional fluorescence observations. The aim of this study is to investigate the mechanism behind the quenching of lignin's autofluorescence in L. alata by conducting associated experiments. Notably, the autofluorescence image of L. alata observed using optical microscopy appears to be quite indistinct. Abundant extractives are found in the longitudinal parenchyma, fibers, and vessels of L. alata. Remarkably, when subjected to a benzene-alcohol extraction treatment, the autofluorescence of L. alata becomes progressively enhanced under a fluorescence microscope. Additionally, UV-Vis absorption spectra demonstrate that the extractives derived from L. alata exhibit strong light absorption within the wavelength range of 200-500 nm. This suggests that the abundant extractives in L. alata are probably responsible for the autofluorescence quenching observed in the cell walls. Moreover, the presence and quantity of these extractives have a significant impact on the fluorescence intensity of lignin in wood, resulting in a significant decrease therein. In future studies, it would be interesting to explore the role of complex compounds such as polyphenols or terpenoids, which are present in the abundant extractives, in interfering with the fluorescence quenching of lignin in L. alata.

Pore-Rich Cellulose-Derived Carbon Fiber@Graphene Core-Shell Composites for Electromagnetic Interference Shielding.

Because of serious electromagnetic pollution caused by the widespread use of radio frequency equipment, the study of electromagnetic interference (EMI) shielding materials has been a long-standing topic. Carbon fiber and graphene composites have great potential as EMI shielding materials due to their unique microstructure and electrical conductivity. In this work, a novel kind of core-shell composite is fabricated based on the pore-rich pine needles-derived carbon fibers (coded as PNCFs) core and the graphene shell. The pore-rich PNCFs are created by KOH activation, and the integration between the pore-rich PNCFs and the graphene relies on a plasma-enhanced chemical vapor deposition (PECVD) method. The conductivity of the pore-rich PNCFs@graphene core-shell composite reaches 4.97 S cm−1, and the composite has an excellent EMI shielding effectiveness (SE > 70 dB over X-band (8.2−12.4 GHz)) and achieves a maximum value of ~77 dB at 10.4 GHz, which is higher than many biobased EMI shielding materials in the recent literature. By calculation and comparison, the large absorption loss (accounting for 90.8% of total loss) contributes to reducing secondary radiation, which is quite beneficial for stealth uses. Thus, this work demonstrates a promising design method for the preparation of green high-performance composites for EMI shielding and stealth applications (such as warcrafts, missiles, and stealth wears).

A Brief Review of Transparent Wood: Synthetic Strategy, Functionalization and Applications.

Severe pressure from energy consumption and serious pollution from non-renewable resources have urged human beings to develop green and energy-efficient materials. Transparent wood, consisting of original wood channel structure filled with resins, has favorable environmental friendliness and high transparency and haze, which holds huge potential in various important fields. Herein, a brief review of the current research activities centered on the development of transparent wood is provided. This review begins with an introduction to the background of transparent wood. Next, the cellular wall structure of wood and the synthetic strategy of transparent wood (including decolorization and impregnation) are summarized. Furthermore, the functionalization of transparent wood through doping nanomaterials or modifying resins is highlighted, and the relationship between the physicochemical properties and the potential uses (like optoelectronics, building materials, and furniture decoration) of transparent wood is clarified. Finally, a brief overview of the prospects and challenges for transparent wood is provided.

Softened Wood Treated by Deep Eutectic Solvents.

Due to its good physical properties, softened wood (SW) has been widely used in the fields of home furnishing, interior decoration, and construction, such as decorative panels, softened wood flooring, wooden bricks, and softened wood furniture. However, traditional methods of wood softening often fail to meet the requirements of enterprises for softening wood. Here, inspired by the research related to wood softening, we propose a method for directly preparing softened wood (SW) using a new type of "ionic liquid" eutectic solvent (DES) owing to its low cost, environmental friendliness, recyclability, and other advantages. To improve the adaptability of the study, a total of five types of DESs were designed and prepared, and by the microwave-assisted DES treatment of natural wood (NW), the purpose of softening wood was achieved. Then, we conducted a series of comparative analyses and performance tests on NW and SW, including microscopic images, chemical composition, color difference, and mechanical properties. The results show that the wood softened by DES has become a highly porous network structure, and partial lignin, hemicellulose, and cellulose have been removed. At the same time, different degrees of color change, lower hardness, excellent mechanical flexibility, and a compression rebound rate of up to about 90% are obtained. The above-mentioned various properties of SW provide great potential for its application in wood products.

Study on the Properties of Partially Transparent Wood under Different Delignification Processes.

Two common tree species of Betula alnoides (Betula) and New Zealand pine (Pinups radiata D. Don) were selected as the raw materials to prepare for the partially transparent wood (TW) in this study. Although the sample is transparent in a broad sense, it has color and pattern, so it is not absolutely colorless and transparent, and is therefore called partially transparent. For ease of interpretation, the following "partially transparent wood" is referred to as "transparent wood (TW)". The wood template (FW) was prepared by removing part of the lignin with the acid delignification method, and then the transparent wood was obtained by impregnating the wood template with a refractive-index-matched resin. The goal of this study is to achieve transparency of the wood (the light transmittance of the prepared transparent wood should be improved as much as possible) by exploring the partial delignification process of different tree species on the basis of retaining the aesthetics, texture and mechanical strength of the original wood. Therefore, in the process of removing partial lignin by the acid delignification method, the orthogonal test method was used to explore the better process conditions for the preparation of transparent wood. The tests of color difference, light transmittance, porosity, microstructure, chemical groups, mechanical strength were carried out on the wood templates and transparent wood under different experimental conditions. In addition, through the three major elements (lignin, cellulose, hemicellulose) test and orthogonal range analysis method, the influence of each process factor on the lignin removal of each tree species was obtained. It was finally obtained that the two tree species acquired the highest light transmittance at the experimental level 9 (process parameters: NaClO2 concentration 1wt%, 90 °C, 1.5 h); and the transparent wood retained most of the color and texture of the original wood under partial delignification up to 4.84-11.07%, while the mechanical strength with 57.76% improved and light transmittance with 14.14% higher than these properties of the original wood at most. In addition, the wood template and resin have a good synergy effect from multifaceted analysis, which showed that this kind of transparent wood has the potential to become the functional decorative material.

Study on the Colorimetry Properties of Transparent Wood Prepared from Six Wood Species.

Transparent wood (TW) was prepared by directly impregnating the wood cell wall and cavity with index-matched prepolymerized methyl methacrylate (MMA). In this process, lignin is retained compared with the preparation of transparent wood in the past, making the production faster and more energy-efficient. The innovation lies in that the prepared transparent wood retains the natural color and texture of the wood while transmitting light, especially under the illumination of a specific light source, which exist as the special visual effects. In order to enhance the practicality of the research and effectively expand the types of home decoration materials, six common wood species with different densities were selected in the experiment. Then the characteristics and mechanisms of wood, that is, color difference, light transmittance, microstructure, changes of chemical functional groups, and tensile strength, before and after PMMA impregnating were compared and analyzed. It is concluded that the light transmittance and mechanical properties of the wood have been improved, and a good synergistic effect between wood and PMMA has been confirmed by the analysis of scanning electron microscopy and infrared spectroscopy. The above highlights make pervious to transparent wood, which has the potential as an excellent functional decorative material.

A facile hydrothermal method-fabricated robust and ultralight weight cellulose nanocrystal-based hydro/aerogels for metal ion removal.

Heavy metal ion contamination, in particular that associated with Pb2+, Cd2+, and Cu2+, poses a considerable threat to aquatic environments and human health. To obtain a highly efficient adsorbent, in this work, a facile hydrothermal method was applied to prepare acrylic acid grafted onto cellulose nanocrystal (AA-g-CNC) hydro/aerogel as an adsorbent for Pb2+, Cd2+, and Cu2+ removal. The obtained AA-g-CNC hydrogels withstood up to 0.821 MPa of compression and showed good reciprocating performance when the deformation reached 40%. The as-formed AA-g-CNC aerogels had highly porous honeycomb structure, with many functional groups and a high zeta potential, all of which are essential features for an effective adsorbent. The maximum Pb2+, Cd2+, and Cu2+ removal capacities of AA-g-CNC aerogels reached 1026, 898.8, and 872.4 mg/g respectively. Their adsorption followed the Freundlich isotherm model and fitted well with pseudo-second-order kinetic models. The adsorption mechanism mainly attributed to electrostatic chelation between metal ions with sulfonate and carboxylate groups.

Effect of H2O2 Bleaching Treatment on the Properties of Finished Transparent Wood.

Transparent wood samples were fabricated from an environmentally-friendly hydrogen peroxide (H2O2) bleached basswood (Tilia) template using polymer impregnation. The wood samples were bleached separately for 30, 60, 90, 120 and 150 min to evaluate the effects on the changes of the chemical composition and properties of finished transparent wood. Experimental results showed decreases in cellulose, hemicellulose, and lignin content with an increasing bleaching time and while decreasing each component to a unique extent. Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) analysis indicated that the wood cell micro-structures were maintained during H2O2 bleaching treatment. This allowed for successful impregnation of polymer into the bleached wood template and strong transparent wood products. The transparent wood possessed a maximum optical transmittance up to 44% at 800 nm with 150 min bleaching time. Moreover, the transparent wood displayed a maximum tensile strength up to 165.1 ± 1.5 MPa with 90 min bleaching time. The elastic modulus (Er) and hardness (H) of the transparent wood samples were lowered along with the increase of H2O2 bleaching treatment time. In addition, the transparent wood with 30 min bleaching time exhibited the highest Er and H values of 20.4 GPa and 0.45 GPa, respectively. This findings may provide one way to choose optimum degrees of H2O2 bleaching treatment for transparent wood fabrication, to fit the physicochemical properties of finished transparent wood.

Hydrothermal Synthesis of Cellulose Nanocrystal-Grafted-Acrylic Acid Aerogels with Superabsorbent Properties.

In this work, we applied a fast and simple method to synthesize cellulose nanocrystal (CNC) aerogels, via a hydrothermal strategy followed by freeze drying. The characteristics and morphology of the obtained CNC-g-AA aerogels were affected by the hydrothermal treatment time, volume of added AA (acrylic acid), and the mass fraction of the CNCs. The formation mechanism of the aerogels involved free radical graft copolymerization of AA and CNCs with the cross-linker N,N'-methylene bis(acrylamide) (MBA) during the hydrothermal process. The swelling ratio of the CNC-g-AA aerogels was as high as 495:1, which is considerably greater than that of other polysaccharide-g-AA aerogels systems. Moreover, the CNC-g-AA aerogels exhibited an excellent methyl blue (MB) adsorption capacity and the ability to undergo rapid desorption/regeneration. The maximum adsorption capacity of the CNC-g-AA aerogels for MB was greater than 400 mg/g. Excellent regeneration performance further indicates the promise of our CNC-g-AA aerogels as an adsorbent for applications in environmental remediation.