Exploring Applications and Preparation Techniques for Cellulose Hydrogels: A Comprehensive Review.

Cellulose hydrogels, formed either through physical or chemical cross-linking into a three-dimensional network from cellulose or its derivatives, are renowned for their exceptional water absorption capacities and biocompatibility. Rising demands for sustainable materials have spurred interest in cellulose hydrogels, attributed to their abundant supply, biodegradability, and non-toxic nature. These properties highlight their extensive potential across various sectors including biomedicine, the food industry, and environmental protection. Cellulose hydrogels are particularly advantageous in applications such as drug delivery, wound dressing, and water treatment. Recent large-scale studies have advanced our understanding of cellulose preparation and its applications. This review delves into the fundamental concepts, preparation techniques, and current applications of cellulose hydrogels in diverse fields. It also discusses the latest advances in nano-lignin-based hydrogels, providing a comprehensive overview of this promising material and offering insights and guidance for future research and development.

Molten Alkali-Assisted Formation of Silicate Gels and Its Application for Preparing Zeolites.

Fly ash was used as raw material to prepare zeolites through silicate gels, assisted by the hydrothermal method. The silicate gels could be effectively formed in a few minutes in a molten alkali environment. The zeolites could be prepared by using these silicate gels through the hydrothermal method, which realizes the transformation from useless materials to highly valuable materials. The obtained zeolites were applied to the removal of ammonium in water, achieving the highvalue utilization of fly ash. The synthesized zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrum (EDS), thermogravimetric (TG), and Fourier transform infrared (FTIR) spectroscopy. The study on the adsorption and removal of ammonium in water shows that the adsorption of ammonium is more in line with pseudo first-order kinetics, and the adsorption mainly occurs in the first 20 min. The adsorption can reach equilibrium in 30 min, and the maximum adsorption capacity can reach 49.1 mg/g. The adsorption capacity of ammonium has the best performance at pH = 5. Furthermore, within a certain range, an increase in temperature is beneficial for the removal of ammonium.

Two new sesterterpenoids from Atractylodes japonica Koidz. ex Kitam.

Two new sesterterpenoids, atractylodes japonica terpenoid acid I (1) and atractylodes japonica terpenoid aldehyde I (2), were isolated from the rhizomes of Atractylodes japonica Koidz. ex Kitam together with ten known compounds (3-12). Their structures were elucidated on the basis of comprehensive spectroscopic analysis (1D/2D NMR, HRESIMS and IR). In addition, all of these isolated compounds were evaluated for their cytotoxic activities against human gastric cancer cell MGC-803 and human hepatocellular cancer cell HepG-2. Most of them exhibited moderate to weak inhibitory effects with IC50 values in the range of 25.15-88.85 µM except for 9-12.

Octylammonium Iodide Induced in-situ Healing Behavior at Perovskite / Carbon Interface: the "Slow-Release Effect" Caused by Carbon Black Adsorption.

"Perovskite / Carbon" interface has remained a key bottleneck for the hole-conductor-free perovskite solar cells based on carbon-electrode (CPSCs), due to problems like loose physics contact, defects, energy mismatch, poor chemical coupling, etc. A previous study shows that octylammonium iodide (OAI) blending in carbon paste induced a kind of "in-situ healing" effect for "perovskite / carbon" interface, and improved power conversion efficiency from ≈13% to >19%. Here the beneath mechanism is further explored by careful examination of the interaction between OAI molecule and carbon black (CB) nanoparticles. It comes to show that, the famous "CB adsorption" plays a key role during the "healing" processes. Due to CB adsorption behavior, the mass ratio between OAI and CB influences much on the healing effect. By suitably adjusting the mass ratio between OAI and CB, and increasing the light harvest of perovskite, an efficiency of 19.41% is achieved for the hole-conductor-free CPSCs. Device efficiency and the charge-extraction and recombination process are tracked with the storage period, continuous improvement appears for devices assembled by relatively higher CB mass. A kind of "slow-release effect" is revealed during the OAI-induced "in-situ healing" process, which is caused by the famous "CB adsorption" behavior.

Liquid-phase catalyst pre-seeding for controlled growth of layered MoS2 films over a large area via chemical vapor deposition.

We introduce an innovative method that facilitates precise control of high-quality molybdenum disulfide (MoS2) growth, extending up to three layers, on a large scale. This scalable growth is realized by employing solution-based catalysts and precursors in conjunction with chemical vapor deposition (CVD). The catalyst not only diminishes the precursor's activation energy and melting temperature but also augments the overall reaction rate. By regulating the concentration ratio, we directly manipulate the precursor concentrations, thereby promoting clean growth. This unique control mechanism, as delineated in this study, is unprecedented. Our findings confirm that the catalyst introduction does not compromise the quality of the resulting samples. Field effect transistors (FETs) fabricated from the synthesized MoS2 display superior electrical properties; they exhibit a high carrier mobility of 32.1 cm2 V-1 s-1 and an on/off current ratio of 108, signifying their promising electrical performance. Accordingly, our findings suggest that the solution-based CVD strategy presented herein can be potentially utilized for the integration of FETs into a multitude of practical applications.

Octylammonium Iodide Induced In-situ Healing at "perovskite/Carbon" Interface to Achieve 85% RH-moisture Stable, Hole-Conductor-Free Perovskite Solar Cells with Power Conversion Efficiency >19.

"Perovskite/carbon" interface is a bottle-neck for hole-conductor-free, carbon-electrode basing perovskite solar cells due to the energy mismatch and concentrated defects. In this article, in-situ healing strategy is proposed by doping octylammonium iodide into carbon paste that used to prepare carbon-electrode on perovskite layer. This strategy is found to strengthen interfacial contact and reduce interfacial defects on one hand, and slightly elevate the work function of the carbon-electrode on other hand. Due to this effect, charge extraction is accelerated, while recombination is obviously reduced. Accordingly, power conversion efficiency of the hole-conductor-free, planar perovskite solar cells is upgraded by ≈50%, or from 11.65 (± 1.59) % to 17.97 (± 0.32) % (AM1.5G, 100 mW cm-2 ). The optimized device shows efficiency of 19.42% and open-circuit voltage of 1.11 V. Meanwhile, moisture-stability is tested by keeping the unsealed devices in closed chamber with relative humidity of 85%. The "in-situ healing" strategy helps to obtain T80 time of >450 h for the carbon-electrode basing devices, which is four times of the reference ones. Thus, a kind of "internal encapsulation effect" has also been reached. The "in situ healing" strategy facilitates the fabrication of efficient and stable hole-conductor-free devices basing on carbon-electrode.

Polyvinyl Pyrrolidone Induced "Confinement Effect" on PbI2 and the Improvement on Crystallization and Thermal Stability of Perovskite.

Polyvinyl pyrrolidone is blended in PbI2 with varied concentration, so as to study the coarsening dynamics of perovskite during the two-step growth method. It is observed that polyvinyl pyrrolidone hinders the crystallization of PbI2 and helps to form a more amorphous PbI2 matrix, which then improves perovskite crystallization. As the blending concentration increases from 0 to 2 mM, average crystallite/grain size of perovskite increases from 40.29 nm/0.79 µm to 84.35 nm/1.02 µm while surface fluctuation decreases slightly from 25.64 to 23.96 nm. The observations are caused by the "confinement effect" brought by polyvinyl pyrrolidone on PbI2 . Elevating blending concentration of polyvinyl pyrrolidone results in smaller PbI2 crystallites and more amorphous PbI2 matrix, thus reducing the diffusion/reaction barrier between PbI2 and organic salt and favoring perovskite crystallization. As blending concentration increases from 0 to 2 mM, the device efficiency rises from 19.76 (± 0.60) % to 20.50 (± 0.89) %, with the optimized value up to 22.05%, which is further improved to 24.48% after n-Octylammonium iodide (OAI)-basing surface modification. The study enlarges the scope of "confinement effect" brought by polymer molecules, which is beneficial for efficient and stable perovskite solar cell fabrication.

Ultralow Lattice Thermal Transport and Considerable Wave-like Phonon Tunneling in Chalcogenide Perovskite BaZrS3.

Chalcogenide perovskites provide a promising avenue for nontoxic, stable thermoelectric materials. Here, the thermal transport and thermoelectric properties of BaZrS3 as a typical orthorhombic perovskite are investigated. An extremely low lattice thermal conductivity κL of 1.84 W/mK at 300 K is revealed for BaZrS3, due to the softening effect of Ba atoms on the lattice and the strong anharmonicity caused by the twisted structure. We demonstrate that coherence contributions to κL, arising from wave-like phonon tunneling, lead to an 18% thermal transport contribution at 300 K. The increasing temperature softens the phonons, thus reducing the group velocity of materials and increasing the scattering phase space. However, it simultaneously reduces the anharmonicity, which is dominant in BaZrS3 and ultimately improves the particle-like thermal transport. In addition, via replacement of the S atom with Se- and Ti-alloying strategy, the ZT value of BaZrS3 is significantly increased from 0.58 to 0.91 at 500 K, making it an important candidate for thermoelectric applications.

Enhanced photocatalytic activity of magnetically recyclable spherical Fe3O4/Cu2O S-scheme heterojunction.

In this study, magnetically recyclable spherical Fe3O4/Cu2O particles comprising S-scheme heterojunctions were prepared by a simple hydrothermal approach using n-type semiconductor Fe3O4 as precursor and p-type semiconductor Cu2O. A Fenton-like system was thus constructed via the addition to Fe3O4/Cu2O of hydrogen peroxide. A rhodamine B (RhB) solution was used to simulate polluted wastewater, and photocatalytic RhB removal experiments were conducted under visible light irradiation. Powder X-ray diffractometry, vibrating-sample magnetometry, nitrogen adsorption-desorption, transmission electron microscopy, and X-ray photoelectron spectroscopy experiments were conducted to characterise Fe3O4 and Fe3O4/Cu2O composite. The band gap of Fe3O4/Cu2O was 1.76 eV, narrower than that of Fe3O4 (2.14 eV). The effects of the pH, sample dosage, hydrogen peroxide concentration, and RhB initial concentration on RhB removal were investigated. According to evidence, under the optimum reaction conditions, the RhB removal rate was 99.4%. The Fe3O4/Cu2O composite exhibited good photocatalytic efficacy even after four cycles of testing. Based on the results of free radical capture experiments, hydroxyl radicals and holes cooperated as main reactive species in the photocatalytic system. The Fe3O4/Cu2O photocatalyst can be easily removed based on magnetism, and it has been proven to be very effective for the degradation of RhB under both UV and visible light irradiation.

Functional Aerogels Composed of Regenerated Cellulose and Tungsten Oxide for UV Detection and Seawater Desalination.

Functional aerogels composed of regenerated cellulose and tungsten oxide were fabricated by implanting tungsten-oxide nanodots into regenerated cellulose fiber. This superfast photochromic property benefitted from the small size and even distribution of tungsten oxide, which was caused by the confinement effect of the regenerated cellulose fiber. The composite was characterized using XRD and TEM to illustrate the successful loading of tungsten oxide. The composite turned from pale white to bright blue under ambient solar irradiation in five seconds. The evidence of solar absorption and electron paramagnetic resonance (EPR) demonstrated the fast photochromic nature of the composite and its mechanism. Furthermore, carbon fiber filled with preferential growth tungsten-oxide nanorods was obtained by annealing the photochromic composite in a N2 atmosphere. This annealed product exhibited good absorption across the whole solar spectrum and revealed an excellent photothermal conversion performance. The water evaporation rate reached 1.75 kg m-2 h-1 under one sun illumination, which is 4.4 times higher than that of pure water. The photothermal conversion efficiency was 85%, which shows its potential application prospects in seawater desalination.

Structural Variations of Metal Oxide-Based Electrocatalysts for Oxygen Evolution Reaction.

Electrocatalytic oxygen evolution reaction (OER), an important electrode reaction in electrocatalytic and photoelectrochemical cells for a carbon-free energy cycle, has attracted considerable attention in the last few years. Metal oxides have been considered as good candidates for electrocatalytic OER because they can be easily synthesized and are relatively stable during the OER process. However, inevitable structural variations still occur to them due to the complex reaction steps and harsh working conditions of OER, thus impending the further insight into the catalytic mechanism and rational design of highly efficient electrocatalysts. The aim of this review is to disclose the current research progress toward the structural variations of metal oxide-based OER electrocatalysts. The origin of structural variations of metal oxides is discussed. Based on some typical oxides performing OER activity, the external and internal factors that influence the structural stability are summarized and then some general approaches to regulate the structural variation process are provided. Some operando methods are also concluded to monitor the structural variation processes and to identify the final active structure. Additionally, the unresolved problems and challenges are presented in an attempt to get further insight into the mechanism of structural variations and establish a rational structure-catalysis relationship.

Efficient excitation of hybrid modes on a double-layer graphene with metallic slit grating.

The excitation of double-layer hybrid plasmonic modes is investigated by the finite element method. The hybrid modes, verified as the standing even order of both symmetric and anti-symmetric modes, are effectively generated. There are several advances in comparison with using the Si grating: the metallic grating not only compensates phase mismatch, but also acts as a magnetic polariton. The dependences of each hybrid mode on the geometric parameters are analyzed respectively. Interestingly, a second spectra splitting occurs at each hybrid resonant mode with an obliquely incident light. At last, the excitation efficiency can be further enhanced to 90% using the Salisbury screen. The proposed hybrid system can be utilized to design various double-layer graphene-based plasmonic devices, including tunable optical switches, thermal emitters, multiband absorbers, sensors, etc.

First-Principles Study of the Ferromagnetic Properties of Cr2CO2 and Cr2NO2 MXenes.

Massive attention has been paid to MXenes due to their intriguing properties and potential diverse applications. Extensive studies using first-principles calculations on the electronic structures of MXenes Cr2CO2 and Cr2NO2 were performed in this paper. Based on the accurate Heyd-Scuseria-Ernzerhof (HSE) calculations, Cr2CO2 is clarified to be a ferromagnetic semiconductor; meanwhile, Cr2NO2 is a half-metallic material, which is consistent with previous results. In particular, by analyzing the contribution of the orbitals to the band structures and density of states, the basic mechanism of ferromagnetism was analyzed in detail. Our theoretical work might promote the spintronics study and application of Cr-contained MXenes.

Fabrication of diverse carbon forms and their reversed applications in hexane/water separation.

Melamine foam is an important material in production and life. A series of porous carbon foams were obtained through a simple carbonization process of melamine foam at different temperatures. The carbon foams obtained at the carbonization temperature of 400 and 600 °C reveal a hydrophobic and even super-hydrophobic property (water contact angle larger than 150°) with a hexane adsorption much larger than that of melamine foam. However, the carbon foam obtained at the carbonization temperature of 800 °C reveals a super-hydrophilic property (water contact angle smaller than 5°) due to its severest shrinkage during the carbonization process. Interestingly, this series of carbon foams have an excellent performance in oil adsorption. However, the carbon membranes derived from the 800 °C carbon foam reveals oleophobicity under water (the adsorbed water at the surface was extremely important), which allows the penetration of water and blocks the infiltration of hexane at the same time. These different carbon forms have reversed applications in hexane/water separation.

Si2Ge: A New VII-Type Clathrate with Ultralow Thermal Conductivity and High Thermoelectric Property.

Based on global particle-swarm optimization algorithm and density functional theory methods, we predicted an alloyed Si2Ge compond with body centered tetragonal type VII clathrate (space group I4/mmm) built by a truncated octahedron fromed by six quadrangles and eight hexagons ([4668]). Si2Ge clathrate is 0.06 eV/atom lower than VII Si clathrate and thermally stable up to 1000 K. It has an indirect band gap of 0.23 eV, high p-doping Seebeck coefficient and n-doping electrical conductivity. It owns a low lattice thermal conductivity of 0.28 W/mK at 300 K because of its weak bonding and strong anharmonic interaction of longitudinal acoustic and low-lying optical phonons. The moderate electronic transport properties together with low lattice thermal conductivity results in a high optimal thermoeletric performance value of 2.54 (1.49) at 800 (1000) K in n (p)-doped Si2Ge.

A Flexible, Self-Floating Composite for Efficient Water Evaporation.

A flexible, self-floating W18O49/carbon foam composite is fabricated by calcining melamine foam with W18O49 as an adsorbate in N2 atmosphere. This self-floating property is simply realized by a carbonization process other than the complicated surface modification process. The simple synthesis procedure helps to increase not only the solar absorption but also the retention of W18O49 in the porous net structure. This composite absorbs almost the whole solar spectrum and generates localized heat at the surface, which is beneficial for water evaporation. Its water evaporation rate is 6.6 times higher than that of pure water. It has a stable cyclic performance over ten cycles under the illumination of simulated sunlight (500 W Xe lamp). Its flexibility makes it easy to reuse and transfer, which is evaluated by the bending deformation test. The W18O49/carbon foam composite is a prospective material in solar energy conversion field, and the preparation procedure is feasible to scale-up.

Different Atomic Terminations Affect the Photocatalytic Nitrogen Fixation of Bismuth Oxybromide: A First Principles Study.

We have systematically investigated the electronic structures and activation capacities of BiOBr {001} facets with different atomic terminations by means of DFT methods. Our calculations reveal that oxygen vacancies (OVs) give a significant boost in band edges of the O-terminated BiOBr {001} facets, and excess electrons induced by OVs could exceed the reduction potentials of high-energy N2 intermediates. Interestingly, the Bi-terminated BiOBr {001} facets may be good candidates for photocatalytic nitrogen fixation due to the stronger activation ability of N2 molecules comparing with O-terminated BiOBr {001} facets with OVs. Moreover, the Bi-terminated BiOBr {001} facets may tend to yield NH3 instead of N2 H4 .

Photothermal Conversion of W18O49 with a Tunable Oxidation State.

W18O49 with a tunable oxidation state was prepared by addition of NaNO3 or NaBH4 as a redox agent in the solvothermal system. The addition of redox agents has no influence on the crystallization of W18O49. The obtained W18O49 structures keep their morphology as a bundle of nanowires with a regular hexagonal on the cross-section. W18O49 exhibits strong valence-dependent absorption features in the near-IR region. Reduced W18O49 with more W5+ has a higher concentration of oxygen vacancies, which enhances the localized surface plasmon resonance effect. Reduced W18O49 exhibits a high photothermal conversion efficiency of 59.6 % and has good photothermal stability.

Porous TiO2 Assembled from Monodispersed Nanoparticles.

Porous TiO2 were assembled by evaporating or refluxing TiO2 colloid, which was obtained by dispersing the TiO2 nanoparticles with a crystallite size (d XRD) of 3.2 nm into water or ethanol without any additives. Porous transparent bulk TiO2 was obtained by evaporating the TiO2-C2H5OH colloid at room temperature for 2 weeks, while porous TiO2 nanospheres were assembled by refluxing the TiO2-H2O colloid at 80 °C for 36 h. Both of the porous TiO2 architectures were pore-size-adjustable depending on the further treating temperature. Porous TiO2 nanospheres exhibited enhanced photocatalysis activity compared to the nanoparticles.

Magnetic photocatalysts with a p-n junction: Fe3O4 nanoparticle and FeWO4 nanowire heterostructures.

Magnetic n-type semiconductor Fe3O4 nanoparticle and p-type semiconductor FeWO4 nanowire heterostructures were successfully synthesized without any surfactants or templates via a facile one-step hydrothermal process at 160 °C. The heterojunction structure and morphology were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Magnetic measurements indicated the coexistence of ferrimagnetic behavior of Fe3O4 and weak antiferromagnetic behavior of FeWO4. The degradation of methylene blue (MB) under UV-Visible light irradiation was studied as a model experiment to evaluate the catalytic activity of the Fe3O4/FeWO4 heterostructure p-n junctions. The decomposition efficiency was 97.1% after one hour UV-Visible irradiation. This magnetic photocatalyst can be easily recovered from the solution using a permanent magnet and redispersed by removing the magnet.