Sustainable versatile chitin aerogels: facile synthesis, structural control and high-efficiency acoustic absorption.

Bio-based materials with excellent acoustic absorption properties are in great demand in architecture, interior, and human settlement applications for efficient noise control. In this study, crayfish shells, a form of kitchen waste, are utilized as the primary material to produce ultralight and multifunctional chitin aerogels, which effectively eliminate noise. Different replacement solvents and freezing rates were employed to regulate the porous structures of chitin aerogels, and their resulting acoustic absorption performance was investigated. Results demonstrate that employing deionized water as the replacement solvent and utilizing a common-freeze mode (frozen via refrigerator at -26 °C) can produce chitin aerogels with larger porosity (96.26%) and apertures, as well as thicker pore walls. This results in superior broadband acoustic absorption performance (with a maximum absorption coefficient reaching 0.99) and higher Young's modulus (28 kPa). Conversely, chitin aerogels solvent-exchanged with tert-butyl alcohol or subjected to quick-freeze mode (frozen via liquid nitrogen) exhibit smaller porosity (92.32% and 94.84%) and apertures, thereby possessing stronger diffuse reflection of visible light (average reflectance of 94.30% and 88.18%), and enhanced low-frequency (500 to 1600 Hz) acoustic absorption properties. Additionally, the acoustic absorption mechanism of fabricated chitin aerogels was predicted using a simple three-parameter analysis Johnson-Champoux-Allard-Lafarge (JCAL) model. This study presents a novel approach to developing multifunctional biomass materials with excellent acoustic absorption properties, which could have a wide range of potential applications.

Effects of Freeze-Drying Processes on the Acoustic Absorption Performance of Sustainable Cellulose Nanocrystal Aerogels.

Cellulose aerogels have great prospects for noise reduction applications due to their sustainable value and superior 3D interconnected porous structures. The drying principle is a crucial factor in the preparation process for developing high-performance aerogels, particularly with respect to achieving high acoustic absorption properties. In this study, multifunctional cellulose nanocrystal (CNC) aerogels were conveniently prepared using two distinct freeze-drying principles: refrigerator conventional freezing (RCF) and liquid nitrogen unidirectional freezing (LnUF). The results indicate that the rapid RCF process resulted in a denser CNC aerogel structure with disordered larger pores, causing a stronger compressive performance (Young's modulus of 40 kPa). On the contrary, the LnUF process constructed ordered structures of CNC aerogels with a lower bulk density (0.03 g/cm3) and smaller apertures, resulting in better thermal stability, higher diffuse reflection across visible light, and especially increased acoustic absorption performance at low-mid frequencies (600-3000 Hz). Moreover, the dissipation mechanism of sound energy in the fabricated CNC aerogels is predicted by a designed porous media model. This work not only paves the way for optimizing the performance of aerogels through structure control, but also provides a new perspective for developing sustainable and efficient acoustic absorptive materials for a wide range of applications.

Mushroom poisoning outbreaks in Guizhou Province, China: a prediction study using SARIMA and Prophet models.

Mushroom poisoning is a public health concern worldwide that not only harms the physical and mental health of those who are poisoned but also increases the medical and financial burden on families and society. The present study aimed to describe and analyze the current situations and factors influencing mushroom poisoning outbreaks in Guizhou province, Southwest China, between January 2012 and June 2022, and to predict the future trends of its occurrence. Our study provides a basis for the rational formulation of prevention and control and medical resource allocation policies for mushroom poisoning. The epidemiological characteristics and factors influencing mushroom poisoning incidence were analyzed using descriptive epidemiological methods and the chi-squared test, respectively. Then, future occurrence trends were predicted using the SARIMA and Prophet models. In total, 1577 mushroom poisoning incidents were recorded in Guizhou Province, with 7347 exposures, 5497 cases, 3654 hospitalizations, and 93 fatalities. The mortality rate was 4.45% in 1 ~ 6 years higher than other age groups. There were notable geographic and seasonal characteristics, with the number of occurrences much higher in rural areas (1198) than in cities (379), and poisoning cases were more common during the rainy season (June to September). The mortality rate of household poisoning cases was 1.86%, with the most deaths occurring in households. Statistically significant differences were observed in the incidence across various cities, periods, and poisoning locations (P < 0.05). Both models had advantages and disadvantages for prediction. Nevertheless, the SARIMA model had better overall prediction results than the Prophet model (R > 0.9, the residual plot of the prediction results was randomly distributed, and RMSESARIMA < RMSEProphet). However, the prediction result plot of the Prophet model was more explanatory than the SARIMA model and could visualize overall and seasonal trends. Both models predicted that the prevalence of mushroom poisoning would continue to increase in the future; however, the number of fatalities is generally declining. Seasonal patterns indicated that a high number of deaths from gooseberry mushroom poisoning occurred in October. The epidemiological trends of mushroom poisoning remain severe, and health education on related knowledge must be strengthened in rural areas, with June to October as the key prevention and control phase. Further, medical treatment of mushroom poisoning cases with clinical symptoms should pay attention to inquiries to check whether the mushroom is similar in appearance to the Amanita, particularly in October.

Two-dimensional ß-noble-transition-metal chalcogenide: novel highly stable semiconductors with manifold outstanding optoelectronic properties and strong in-plane anisotropy.

In this work, five two-dimensional (2D) noble-transition-metal chalcogenide (NTMC) semiconductors, namely ß-NX (N = Au, Ag; X = S, Se, Te), were designed and predicted by first-principles simulations. Structurally, the monolayer ß-NX materials have good energetic, mechanical, dynamical, and thermal stability. They contain two inequivalent noble-transition-metal atoms in the unit cell, and the N-X bond comprises a partial ionic bond and a partial covalent bond. Regarding the electronic properties, the ß-NX materials are indirect-band-gap semiconductors with appropriate band-gap values. They have tiny electron effective masses. The hole effective masses exhibit significant differences in different directions, indicating strongly anisotropic hole mobility. In addition, the coexistence of linear and square-planar channels means that the diffusion and transport of carriers should be anisotropic. In terms of optical properties, the ß-NX materials show high absorption coefficients. The absorption and reflection characteristics reveal strong anisotropy in different directions. Therefore, the ß-NX materials are indirect-band-gap semiconductors with good stability, high absorption coefficients, and strong mechanical, electronic, transport, and optical anisotropy. In the future, they could have great potential as 2D semiconductors in nano-electronics and nano-optoelectronics.

Tuning the Electronic and Optical Properties of the Novel Monolayer Noble-Transition-Metal Dichalcogenides Semiconductor ß-AuSe via Strain: A Computational Investigation.

The strain-controlled structural, electronic, and optical characteristics of monolayer ß-AuSe are systematically studied using first-principles calculations in this paper. For the strain-free monolayer ß-AuSe, the structure is dynamically stable and maintains good stability at room temperature. It belongs to the indirect band gap semiconductor, and its valence band maximum (VBM) and conduction band minimum (CBM) consist of hybrid Au-d and Se-p electrons. Au-Se is a partial ionic bond and a partial polarized covalent bond. Meanwhile, lone-pair electrons exist around Se and are located between different layers. Moreover, its optical properties are anisotropic. As for the strained monolayer ß-AuSe, it is susceptible to deformation by uniaxial tensile strain. It remains the semiconductor when applying different strains within an extensive range; however, only the biaxial compressive strain is beyond -12%, leading to a semiconductor-semimetal transition. Furthermore, it can maintain relatively stable optical properties under a high strain rate, whereas the change in optical properties is unpredictable when applying different strains. Finally, we suggest that the excellent carrier transport properties of the strain-free monolayer ß-AuSe and the stable electronic properties of the strained monolayer ß-AuSe originate from the p-d hybridization effect. Therefore, we predict that monolayer ß-AuSe is a promising flexible semiconductive photoelectric material in the high-efficiency nano-electronic and nano-optoelectronic fields.

Strain-dependent optical properties of the novel monolayer group-IV dichalcogenides SiS2semiconductor: a first-principles study.

We studied the structural, electronic, and optical characters of SiS2, a new type of group IV-VI two-dimensional semiconductor, in this article. We focused on monolayer SiS2and its characteristic changes when different strains are applied on it. Results reveal that the monolayer SiS2is dynamically stable when no strain is applied. In terms of electronic properties, it remains a semiconductor under applied strain within the range from -10% to 10%. Besides, its indirect band-gap is altered regularly after applying a strain, whereas different strains lead to various changing trends. As for its optical properties, it exhibits remarkable transparency for infrared and most visible light. Its main absorption and reflection regions lie in the blue and ultraviolet areas. The applied uniaxial strain causes its different optical properties along the armchair direction and zigzag direction. Moreover, the tensile strain could tune its optical properties more effectively than the compressive strain. When different strains are applied, the major changes are in blue and ultraviolet regions, but only minor changes can be found in infrared and visible regions. So its optical properties reveal good stability in infrared and visible regions. Therefore, SiS2has a promising prospect in nano-electronic and nano-photoelectric devices.

Topological phase transition and tunable electronic properties of hydrogenated bismuthene: from single-layer to double-layer.

Planar bismuthene grown on SiC substrate provides a promising candidate to engineer van der Waals double-layer (DL) made of two dimensional (2D) topological insulators. We perform systematical calculations in DL hydrogenated bismuthene (H-Bi) that can be used to simulate the experimentally grown planar bismuthene to explore realizable 2D topological insulator van der Waals DL. Two possible geometry configurations of AA- and AB-stacked DL H-Bi are investigated. Due to pseudo Jahn-Teller effect, AB-stacked DL H-Bi has a strong interlayer coupling interaction and shows buckled lattice. Particularly, both AA- and AB-stacked DL H-Bi are topologically trivial rather than topologically nontrivial. The physical origin of the trivial topology is clarified by analyzing orbital composition. We discuss how the electronic properties are modified by interlayer coupling, external strain, and metal atom intercalation. It is also found that, for AB-stacked DL H-Bi, metal atom intercalation gives rise to novel multiple Rashba splitting near the valence band top, which is expected to manipulate the same spin in different planar bismuthene layers. Our results present various and tunable electronic properties of van der Waals DL H-Bi and allow for probing into multiple Rashba effect in 2D inversion-asymmetric topological insulators.

Strain-tunable electronic and optical properties of novel anisotropic green phosphorene: a first-principles study.

The effect of in-layer strain on the optical and electrical properties of monolayer green phosphorene, a new anisotropic two-dimensional (2D) material, has been systematically studied. The studied strain includes in-layer uniaxial strain and biaxial strain. Green phosphorene can be viewed as a combination of black and blue phosphorene segments in regular order. We adopt the HSE06 method to correct the calculated results. The results reveal that, firstly, strain-free monolayer green phosphorene is a stable direct band gap 2D semiconductor with the anisotropic optical property. The transmittance of infrared and visible light along the zigzag direction is better than that along the armchair direction. However, the transmittance of the UV-light along the armchair direction is better than that along the zigzag direction. Secondly, the optical properties, such as the absorption coefficient and reflectivity, along armchair and zigzag direction respond very differently to the various applied strains. As for the electronic properties, the band gap exhibits different changing trends by applying either in-layer biaxial strain or uniaxial strain in different directions. Besides, the near-band-edge electronic orbitals exhibit different bond nature in different directions. These results suggest that green phosphorene shows strong anisotropy in electronic and optical properties. By calculating and comparing the energies of near-band-edge states after applying different strains on green phosphorene, the reason for the anisotropy of the new 2D material is analyzed. This study implies that the electronic and optical properties of green phosphorene, a stable direct band gap anisotropic semiconductor, could be efficiently tuned by in-layer biaxial or uniaxial strain. Therefore, green phosphorene can be used in linear polarizers and other anisotropic photoelectric devices.

Topologically nontrivial phase and tunable Rashba effect in half-oxidized bismuthene.

Bismuth based (Bi-based) materials exhibit promising potential for the study of two-dimensional (2D) topological insulators or quantum spin Hall (QSH) insulators due to their intrinsic strong spin-orbit coupling (SOC). Herein, we theoretically propose a new inversion-asymmetry topological phase with tunable Rashba effect in a 2D bismuthene monolayer, which is driven by the sublattices half-oxidation (SHO). The nontrivial topology is identified by the SHO induced p-p band inversion at the Γ point, the Z2 topological number, and the metallic edge states. Interestingly, the SOC opens a band gap as large as 0.26 eV at Γ, which is twice as large as that of the freestanding bismuthene monolayer, revealing a predominant contribution of the orbital filtering effect. Inversion-symmetry breaking leads to a substantial Rashba constant of 11.5 eV Å near the valence band top, which is about twice as large as that of the freestanding bismuthene monolayer due to the SHO effect. In particular, the topological insulator-to-topological semimetal phase-transition and the tunable Rashba effect were achieved by exerting a moderate strain. We demonstrate that 3% stretching is the most desirable strain to obtain superior properties. Hexagonal boron nitrogen (h-BN) is proposed to serve as a suitable substrate for SHO-Bi in practical applications. Our findings not only provide a new route to engineering a 2D inversion-asymmetry topological insulator but also represent a significant advance in the exploration of 2D Bi-based topological materials.

Anisotropic optical properties induced by uniaxial strain of monolayer C3N: a first-principles study.

The optical properties, structural properties and electronic properties of a new two-dimensional (2D) monolayer C3N under different strains are studied in this paper by using first-principles calculations. The applied strain includes in-layer biaxial strain and uniaxial strain. The monolayer C3N is composed of a number of hexagonal C rings with N atoms connecting them. It is a stable indirect band gap 2D semiconductor when the strain is 0%. It could maintain indirect semiconductive character under different biaxial and uniaxial strains from ε = -10% to ε = 10%. As for its optical properties, when the uniaxial strain is applied, the absorption and reflectivity along the armchair and zigzag directions exhibit an anisotropic property. However, an isotropic property is presented when the biaxial strain is applied. Most importantly, both uniaxial tensile strain and biaxial tensile strain could cause the high absorption coefficient of monolayer C3N to be in the deep ultraviolet region. This study implies that strain engineering is an effective approach to alter the electronic and optical properties of monolayer C3N. We suggest that monolayer C3N could be suitable for applications in optoelectronics and nanoelectronics.

Electronic and magnetic properties of 3D transition-metal atom adsorbed arsenene.

To utilize arsenene as the electronic and spintronic material, it is important to enrich its electronic properties and induce useful magnetic properties in it. In this paper, we theoretically studied the electronic and magnetic properties of arsenene functionalized by 3D transition-metal (TM) atoms (TM@As). Although pristine arsenene is a nonmagnetic material, the dilute magnetism can be produced upon TM atoms chemisorption, where the magnetism mainly originates from TM adatoms. We find that the magnetic properties can be tuned by a moderate external strain. The chemisorption of 3D TM atoms also enriches the electronic properties of arsenene, such as metallic, half-metallic, and semiconducting features. Interestingly, we can classify the semiconducting feature into three types according to the band-gap contribution of spin channels. On the other hand, the chemisorption properties can be modified by introducing monovacancy defect in arsenene. Present results suggest that TM-adsorbed arsenene may be a promising candidate for electronic and spintronic applications.

Tuning the electronic properties of bilayer group-IV monochalcogenides by stacking order, strain and an electric field: a computational study.

As the isoelectronic counterpart of phosphorene, monolayer group IV-VI binary MX (M = Ge, Sn; X = Se, S) compounds have drawn considerable attention in recent years. In this paper, we construct four high-symmetry stacking models for bilayer MX to tune their electronic properties. We systematically explore the dynamical and thermal stabilities of all bilayer MX. It is found that five of them are possible at room temperature. Then, we perform first-principles calculations to study how the bilayer structure affects their electronic properties. The results demonstrate that the electronic properties of MX materials can be modulated by forming bilayer structures. Their bandgap can be tuned over a wide range from 0.789 to 1.617 eV, and an indirect-to-direct transition occurs in three cases. Considering the flexibility of bilayer MX, we utilize in-plane uniaxial tensile strain to adjust their band structures and achieve much more indirect-to-direct bandgap transitions. The realization of direct bandgaps will be helpful for their application in next-generation high-efficiency modern nano-optoelectronic and photovoltaic devices. We also study the responses of different bilayer MX to an external vertical electric field. It is found that their bandgaps decrease rapidly with the increase of the electric field.

Emerging novel electronic structure in hydrogen-Arsenene-halogen nanosheets: A computational study.

Based on first-principles calculations including spin-orbit coupling, we investigated the stability and electronic structure of unexplored double-side decorated arsenenes. It has been found that these new double-side decorated arsenenes, which we call "hydrogen-arsenene-halogen (H-As-X, X is halogen)", are dynamically stable via the phonon dispersion calculations except H-As-F sheets. In particular, all of H-As-X nanosheets are direct band gap semiconductors with a strong dispersion near the Fermi level, which is substantially different from the previous works of double-side decorated arsenenes with zero band gaps. Our results reveal a new route to change the band gap of arsenene from indirect to direct. Furthermore, we also studied bilayer, trilayer, and multilayer H-As-Cl sheets to explore the effects of the layer number. The results indicate that bilayer, trilayer, and multilayer H-As-Cl sheets display novel electronic structure, namely multi-Dirac cones character, and the Dirac character depends sensitively on the layer number. It is noted that the frontier states near the Fermi level are dominantly controlled by the top and bottom layers in trilayer and multilayer H-As-Cl sheets. Our findings may provide the valuable information about the new double-side decorated arsenene sheets in various practical applications in the future.

Unexpected electronic structure of the alloyed and doped arsenene sheets: First-Principles calculations.

We study the equilibrium geometry and electronic structure of alloyed and doped arsenene sheets based on the density functional theory calculations. AsN, AsP and SbAs alloys possess indirect band gap and BiAs is direct band gap. Although AsP, SbAs and BiAs alloyed arsenene sheets maintain the semiconducting character of pure arsenene, they have indirect-direct and semiconducting-metallic transitions by applying biaxial strain. We find that B- and N-doped arsenene render p-type semiconducting character, while C- and O-doped arsenene are metallic character. Especially, the C-doped arsenene is spin-polarization asymmetric and can be tuned into the bipolar spin-gapless semiconductor by the external electric field. Moreover, the doping concentration can effectively affect the magnetism of the C-doped system. Finally, we briefly study the chemical molecule adsorbed arsenene. Our results may be valuable for alloyed and doped arsenene sheets applications in mechanical sensors and spintronic devices in the future.

The electronic properties of impurities (N, C, F, Cl, and S) in Ag3PO4: A hybrid functional method study.

The transition energies and formation energies of N, C, F, Cl, and S as substitutional dopants in Ag3PO4 are studied using first-principles calculations based on the hybrid Hartree-Fock density functional, which correctly reproduces the band gap and thus provides the accurate defect states. Our results show that NO and CO act as deep acceptors, FO, ClO, and SP act as shallow donors. NO and CO have high formation energies under O-poor condition therefore they are not suitable for p-type doping Ag3PO4. Though FO, ClO, and SP have shallow transition energies, they have high formation energies, thus FO, ClO, and SP may be compensated by the intrinsic defects (such as Ag vacancy) and they are not possible lead to n-type conductivity in Ag3PO4.

[Biological dressing with human hair keratin-collagen sponge-poly 2-hydroxyethyl methacrylate composite promotes burn wound healing in SD rats].

OBJECTIVE: To develop a composite material containing human hair keratin (HHK), collagen sponge (inner layer) and poly 2-hydroxyethyl methacrylate (PHEMA) film that allows sustained release of polydatin and test its effect as a biological dressing in promoting burn wound healing in SD rats. METHODS: Three HHK materials with fast, moderate, and low degradation rates were mixed at the ratio of 4:3:3 to prepare a reticular structure, which was processed into a composite material with bovine tendon-derived collagen sponge, and further complexed with HEMA film containing PD prepared by polymerization. Degree II burn wound was induced in SD rats by scalding and within postburn day 2-5, the wounds were cleansed and covered with the composite material or with glutaraldehyde-treated porcine skin (positive control). At week 1, 2, 4, 6 and 8 following wound dressing, 6 full-thickness skin samples were harvested from the wounds for histological observation and immunohistochemical detection of collagen and elastic fibers, and the wound healing time and healing rate were recorded. RESULTS: The prepared collagen sponge film was transparent and porous (50-300 microm in diameter) and allowed sustained PD release into normal saline within 48 h. Compared with the porcine skin, the composite material reduced exudation and maintained ideal moisture of the wound, and significantly shortened the wound healing time (P=0.000). On day 7, 14, and 21 following dressing, the composite material and porcine skin significantly increased the wound healing rate as compared with the negative control group (P=0.000), and on day 14, the composite achieved significantly greater healing rate than the porcine skin (P<0.05). CONCLUSION: HHK-collagen sponge-PHEMA/PD composite as a dressing material promotes burn wound healing in rats by allowing in vivo construction of tissue engineered epidermis. PHEMA is feasible for sustained drug delivery in this composite.

[Studies on design, synthesis and biodegradation of carrier for colon-site specific, drug delivery system].

AIM: To design and synthesize a novel vector for colon-site specific drug delivery system and investigate the relationship between the biodegradation properties and composition of materials in the simulated colon fluid. METHODS: The azocopolymer P (HEMA-MMA-MAA) was synthesized using 2-hydroxyethylmethacrylate (HEMA), methyl methacrylate (MMA) and methacrylic acid (MAA) as comonmer, azobisisobutyronitrilel (AIBN) as initiator, cross-linked with divinylazobezene (DVAB). The chemical structure of the synthesized series of azocopolymer is examined by UV, FTIR spectroscopy and nuclear magnetic resonance data. Their swelling behavior is evaluated by the swelling equilibrium parameter Q, the biodegradation tests of the materials were carried out at physiologically relevant buffer designed to mimic the colon environment. The biodegradation properties were assessed using the differential scanning calorimeters (DSC) and gel permeation chromatography (GPC) and the morphology on the surface of materials before and after degradation was observed by scanning electron microscopy (SEM). RESULTS: The swelling equilibrium parameter Q increased with increasing the contents of HEMA and MAA in the materials. The degradation behavior was relevant to the ratio of three components in the copolymers. CONCLUSION: This materials may become a good carrier for the colon-site specific drug delivery system if the contents of commoners HEMA, MMA and MAA are adjusted reasonably.

Synthesis of p, p'-divinylazobenzene.

OBJECTIVE: To synthesize p, p'-divinylazobenzene (DVAB). METHOD: Wittig reagent was initially synthesized using P-nitrobenzyl bromide and triphenylphosphine, followed by reaction with formaldehyde to produce p-nitro styrene, which was then deoxidized by Zn/NaOH for the final product of DVAB. RESULTS: Fourier transform infrared spectroscopy, nuclear magnetic resonance and element analysis were employed to identify the structure of DVAB, and the lambda(max) as determined by ultraviolet spectroscopy occurred at 357 nm. CONCLUSIONS: The synthesis procedure of DVAB was therefore optimized with high yield.