In a carbon-rich atmosphere, high-energy atoms bombard the Ni and Si surface, and reduce the free energy in the thermodynamic equilibrium of solid Ni–Si particles, considerably catalyzing the growth of Ni–Si nanocrystals. By controlling the carbon source content, a Ni3Si2 single crystal with high crystallinity and good homogeneity is stably synthesized. Electrochemical measurements indicate that the nanostructures exhibit an ultrahigh specific capacity of 835.3 C g−1 (1193.28 F g−1) at 1 A g−1; when integrated as an all-solid-state supercapacitor, it provides a remarkable energy density as high as 25.9 Wh kg−1 at 750 W kg−1, which can be attributed to the free-standing Ni3Si2/graphene skeleton providing a large specific area and NiOOH inhibits insulation on the electrode surface in an alkaline solution, thereby accelerating the electron exchange rate. The growth of the high-performance composite nanostructure is simple and controllable, enabling the large-scale production and application of microenergy storage devices.Recent developments in the synthesis of graphene-based structures focus on continuous improvement of porous nanostructures, doping of thin films, and mechanisms for the construction of three-dimensional architectures. Herein, we synthesize creeper-like NiThe online version of this article (10.1007/s40820-020-00527-w) contains supplementary material, which is available to authorized users. Electrical energy storage systems have become one of the key research objects that are studied to address current energy challenges such as the rapid consumption of fossil fuels, environmental pollution, and global warming , 2. Rech3S2 and Co9S8 double-size nanoparticles [3S2/carbon nanotubes [3S2@MoS2 core shell nanorods on Ni foam [2 nanocubes [3S2@Ni composites [3S2 nanorod arrays on Ni–graphene foams [2 electrodes have several disadvantages, such as low capacity, poor cycle life, large volume change rate, and solubility in electrolytes, limiting their use in supercapacitors [2 nanocube prepared via the microwave-assisted method has good cycle stability . However, the specific capacitance of the NiS2 nanocube is poor . Wang et al. [During the nanotechnology revolution of recent decades, one-dimensional nanostructures, such as nanowires, nanotubes, and nanorods, have attracted widespread attention because of their unique physical and chemical properties . The prearticles , hierarcanotubes , Ni3S2@M Ni foam , NiS2 naanocubes , Ni3S2@Nmposites , and Ni3ne foams . Howeverpacitors . For exapacitors  reportedg et al.  highligh3Si2 nanowires prepared via low-pressure chemical vapor deposition have a high specific capacitance (760 F g−1 at 0.5 A g−1) and low series resistance (0.93 Ω). By definition, high specific capacitance and low series resistance are key factors to mitigating the tradeoff between the power and energy densities. Therefore, nickel silicide can be used as a new electrode material to solve the limitations of traditional electrical double-layer capacitor materials in supercapacitor applications.Compared with other electrode materials, nickel silicide is advantageous because of its large mechanical stress tolerance, good electrical conductivity, and high electrochemical performance. It is a potential candidate material for supercapacitor electrodes. More importantly, its growth is compatible with and can be easily integrated into silicon process technology , 22. Acc3Si2/graphene using a simple and effective low-pressure all-solid melting-reconstruction chemical vapor deposition (LSRCVD) method. The Ni3Si2/NiOOH/graphene composite nanostructures were synthesized through a hydrothermal method. Based on systematic micromorphological characterization, the formation mechanism of the nanostructures is discussed to develop reliable and controllable nanostructure preparation technology. Under bombardment by high-energy particles in a carbon-rich environment, supersaturation of the Si precursor is decreased by using Ni as the substrate. The silicon vapor is cooled and crystallized on a molten nickel substrate to form Ni–Si nanostructures. By adjusting the carbon content and growth time, we successfully achieved Ni3Si2 nanocrystal growth in the axial direction and fabricated nanostructures with high surface areas under Ar gas etching. The electrochemical test confirms that the Ni3Si2/NiOOH/graphene composite exhibits extremely good performance. The specific capacitance of the Ni3Si2/NiOOH/graphene electrode reaches 835.3 C g−1 (1193.28 F g−1) at 1 A g−1. The fabricated all-solid-state supercapacitor exhibits a maximum energy density of 25.9 Wh kg−1 at 750 W kg−1. These properties are due to the following reasons: First, the Ni3Si2/graphene nanoskeleton possesses excellent mechanical strength and supports the entire electrode. Simultaneously, Ni3Si2 effectively guides the directional deposition of NiOOH with high crystal quality. NiOOH inhibits the insulation of the electrode surface in an alkaline solution and accelerates the electron exchange rate. Second, the interconnected nanostructures have large specific surface areas. Even if parts of the nanoflakes are disconnected from the substrate, the internal electronic circulation will still be protected by physical contact with adjacent nanostructures. Third, in a carbon-rich atmosphere, the surface free energy of solid Ni–Si particles in a thermodynamic equilibrium decreases and excess Ni rapidly diffuses into Ni–Si nanoparticles, which facilitates the formation of Ni–Si nanostructures. Nanoparticles grow in the radial direction to form creeper-like nanostructures. The creeper-like structure increases the specific surface area of the electrode material and the active sites, thereby inducing more redox reactions in the nickel substrate in addition to high conductivity, generating fast charge-transfer kinetics and thus better performance. Fourth, because of the self-supporting 3D porous nanostructure, electrons can traverse the entire electrode surface, creating a convenient electron transfer path for active nanomaterials, thereby improving the supercapacitor performance. The excellent electrochemical properties indicate the potential for integrated SC applications and marketization.Herein, we synthesized novel creeper-like Ni3Si2/graphene structure was fabricated using a laboratory-made low-pressure chemical vapor deposition (CVD) system. Initially, the surface of the Ni foam was sonicated in a 0.3 mol L−1 (NH4)2S2O8 solution for 5 min to remove contaminants and oxides. After washing with analytical-grade acetone, ethanol, and deionized water for 5 min each, the Ni foam was dried with nitrogen. Next, the cleaned Ni foam/Si (111) stack was placed into the quartz tube furnace of the CVD system at a base vacuum of ~ 0.1 Pa. Ultrahigh-purity hydrogen was injected into the furnace tube at a flow rate of 10 sccm. Subsequently, the nickel foam was heated from 30 to 1030 °C at a heating rate of 20 °C min−1. Once the temperature reached 1030 °C, ultrahigh-purity methane was introduced into the furnace tube (flow rate of 50 sccm) as the carbon source for 2 h. Second, the sample was cooled to 1000 °C and annealed for 1 h in a mixed atmosphere . The tube was then slowly cooled to ambient temperature at a cooling rate of ~ 5 °C min−1 under 10 sccm of hydrogen flow. Third, the Ni3Si2/NiOOH/graphene nanostructure was synthesized using a hydrothermal method. The metal foams were selectively etched in a mixture of 1 M FeCl3 and 2 M HCl at 60 °C overnight and free-standing Ni3Si2/graphene was obtained. Subsequently, 100 mg urea was uniformly dispersed in 40 mL deionized water by stirring for 1 h. The mixture was then transferred into a 60-mL Teflon-lined stainless-steel autoclave and the fabricated Ni3Si2/graphene was added to the mixture. The autoclave was subsequently sealed and maintained at 180 °C for 2 h. Once the reaction was completed, the autoclave was cooled to room temperature. Finally, the sample was clamped with tweezers and washed three times with deionized water and ethanol. The final product was obtained after drying overnight under vacuum at 80 °C. The mass of the graphene, Ni3Si2, and NiOOH are about 0.18, 0.26, and 0.26 mg, respectively. The detailed analysis process is in the supporting information.The creeper-like nanostructures were grown on commercial Ni foam in three steps. First, a hybrid Ni3Si2/graphene is similar to that of Ni3Si2/NiOOH/graphene, and the detailed process is in the supporting information.The synthesis process of NiOOH/graphene and Ni3Si2/NiOOH/graphene nanostructures were investigated via scanning electron microscopy (SEM) . The crystallinity of the materials was evaluated through high-resolution X-ray diffraction (XRD)  in Bragg (reflection) geometry and Cu Kα1 radiation (wavelength: λ = 1.54056 Å). The Raman spectrum was obtained with a Raman spectroscopy system  using an Ar+ laser (514 nm wavelength) as the excitation source. The elemental analyses of the composites were conducted via X-ray photoelectron spectroscopy (XPS) .The morphologies of the NiCyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) were performed using the CHI660 electrochemical workstation and a three-electrode test system including the active material as the working electrode, Ag/AgCl as the reference electrode, platinum mesh as the counter-electrode, and 3 M KOH as the electrolyte.Qs (C g−1) and specific capacitance Cg (F g−1) can be computed using Eqs. (I is the discharge current (A), m is the total weight (g) and Δt is the discharge time (s).Based on the GCD curves, the specific capacity Qs C g− and specing Eqs. :1\documeAll SC cell electrochemical measurements were performed using the prepared “sandwich” capacitor. The electrodes, cellulose diaphragms, and electrodes were stacked, and the active materials were in direct contact with the current collector. The electrolyte was gelatinous PVA-KOH.Cg) of the SC cell was calculated using the GCD curves and Eq. (E is the energy density (Wh kg−1) and P is the power density (W kg−1).The specific capacitance ( and Eq. . The ene and Eq.  and 4)::Cg) of t3Si2/NiOOH/graphene nanostructures were synthesized on 3D graphene/Ni foam using a three-step method. Figure 3Si2/NiOOH/graphene nanostructures.To ensure high purity and controllability, novel creeper-like Ni4 was decomposed through catalysis with the Ni foam and the carbon atoms dissolved in the 3D Ni foam. Simultaneously, the Si vapor mixed with Ni vapor in a carbon-rich environment, the formation of Ni–Si nanocores form from supersaturation of Ni/Si vapor, the nanocore melting, cooled and then condensed on the surface of the Ni foam. Several Ni–Si nanocores formed during condensation. In the second step, carbon atoms precipitated from the Ni foam and were transferred into graphene along the 3D Ni foam surface during annealing. During melting and condensation, the Ni–Si nuclei randomly merged and flowed on the graphene surface. Then, these nuclei grew radially and axially, forming a creeper-like nanoskeleton. In the third step, several Ni3Si2 units on the surface reacted with urea during the hydrothermal process to form NiOOH nanosheets, which dissolved in the solution. Ni3Si2 acts as the nanoframework to guide the deposition of NiOOH nanosheets, and a creeper-like nanostructure forms through the complex directional adhesion process.In the first step, CH3Si2 nanostructures using LSRCVD. The way to control the carbon content is to change the Ar flow rate. In the experiment, 12.5% carbon content atmosphere includes 10 sccm H2, 50 sccm CH4, 340 sccm Ar, 6.25% carbon content atmosphere includes 10 sccm H2, 50 sccm CH4, 740 sccm Ar, and 4.17% carbon content atmosphere includes 10 sccm H2, 50 sccm CH4, 1140 sccm Ar. During annealing, Ni–Si nanocrystals start to grow; the gas flow rate strongly affects the growth of the nanostructures, as shown in Fig. 2) condensed and crystallized as the crystal nucleus on the surface of the Ni foam , the crystallization mechanism changed to predominant axial growth . Because decreased number of carbon atoms increased the required surface free energy, Ni–Si nucleation became difficult. Figure The carbon content is one of the main factors affecting the synthesis of Ni3Si2 nanostructures using LSRCVD. Figure 3Si2 nanostructures for different growth times with 6.25% carbon content. Initially, mostly incomplete nanostructures were formed. In addition, the densities of the nanostructures were low, as shown in Fig. 3Si2 nanostructure growth.The annealing time is another key factor affecting the fabrication of Ni3Si2/NiOOH/graphene) and EDS images of the Ni3Si2/NiOOH/graphene creeper-like nanostructures. The lattice fringe distances of 0.25, 0.32, 0.33, and 0.46 nm in Fig. 3Si2 structure, respectively [Figure ectively . And theectively , 24. Fig3Si2/NiOOH/graphene , respectively. Compared with that of NiOOH/graphene, the intensity of the graphene and NiOOH peaks is much stronger than that of Ni3Si2/NiOOH/graphene, which could be caused by the presence of unrepaired defects such as lattice mismatch.Typical XRD patterns of the Ni3Si2/NiOOH/graphene materials were characterized via XPS. The survey scan spectra , Ni3Si2/NiOOH/graphene-1, -2 and -3 electrodes clearly differ owing to the significant contributions from Faradaic capacitance. The considerably extended discharge time of Ni3Si2/NiOOH/graphene-2 again proves their enhanced capacitance. The Nyquist plots obtained by EIS are composed of an arc in the high-frequency region and a straight line in the low-frequency region, which can be simulated by an equivalent circuit . Obviously, Ni3Si2/NiOOH/graphene-2 has minimal series (0.28 Ω) and contact resistances (0.8 Ω), which indicates better capacitance performance. It attributed to creeper-like Ni3Si2/graphene nanostructure has smaller crystal size and higher density. Electrolyte ions fully contact with the electrode and increase the effective specific surface area, and the creeper-like Ni3Si2/NiOOH/graphene electrode provides more active sites to store energy.To determine the electrochemical performance of the positive electrode, cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) of the Ni−1. The area of the CV curve of the electrode with Ni3Si2/NiOOH/graphene is larger than that of NiOOH/graphene and Ni3Si2/graphene, which indicates high capacitance. Notably, the three CV curves show different redox peaks at the same scanning rate because the Gibbs free energy of the surface redox reaction of Nip2/Nip3 differs. The relative redox process can be described using Eqs. (i) and scan rate (ʋ) using Eqs.  process, respectively. As shown in Fig. b values for the anode peaks in Ni3Si2/graphene and Ni3Si2/NiOOH/graphene are 0.69 and 0.59, respectively, indicating that the specific capacitances of the electrodes are based on both diffusion-controlled and pseudocapacitive behaviors. Adding NiOOH increases the size of the nanostructure and proportion of the current generated by the volume response. Therefore, the Ni3Si2/NiOOH/graphene electrode mainly exhibits diffusion control. The pseudocapacitive contribution can be investigated using the CV curves and Eqs. ::−1. The ing Eqs.  and 8)::−1. The and Eqs. :9\docume3Si2/NiOOH/graphene are shown in Fig. −1. Even at a high current density of 50 A g−1, the Coulomb efficiency can reach 86.93%. The specific capacity of the device at a current density of 1 A g−1 calculated from the discharge branch of the device is 835.3 C g−1 (1193.28 F g−1). The specific capacitance values of the electrodes were calculated based on their corresponding GCD curves, as shown in Fig. 3Si2/NiOOH/graphene electrode is much better than that of the Ni3Si2/graphene, and NiOOH/graphene electrodes because adding NiOOH provides more active sites and accelerates the ion exchange of the electrode surface in alkaline solution. The electrons react with NiOOH on the surface to generate Ni(OH)2 and OH−. Then, OH− reacts with Ni3Si2 to generate electrons and Ni3Si2(OH)3. It is a positive feedback process until the electrode material is transformed into Ni(OH)2 and Ni3Si2(OH)3. Additionally, the unique spatial structure of Ni3Si2 eases the agglomeration and deformation of NiOOH.In addition, the GCD curves of Ni3Si2/graphene, NiOOH/graphene, and Ni3Si2/NiOOH/graphene are shown in Fig. 3Si2/Graphene electrode, and Ni3Si2/NiOOH/Graphene electrode are 0.4, 0.97, and 0.36 Ω, respectively. The equivalent series resistance is 0.23, 0.28, and 0.47 Ω for the NiOOH/Graphene electrode, Ni3Si2/Graphene electrode, and Ni3Si2/NiOOH/Graphene electrode, respectively. Ni3Si2/NiOOH/graphene has the largest equivalent series resistance, which is due to the lattice mismatch at the interface of Ni3Si2 and NiOOH. In an alkaline environment, a protective layer of SiO2·2H2O and/or Ni2SiO4 can form on the surface of Ni3Si2. Because Ni2SiO4 and SiO2·2H2O are insulators, the charge transfer and diffusion processes on the electrode surface are suppressed [3Si2/graphene has the largest Warburg and charge-transfer resistances. NiOOH has excellent conductivity and prevents insulator production on the electrode surface, which considerably reduces difficulties in transporting charges. In the low-frequency region, the slope of the straight line indicates the difficulty of ion diffusion. The closer the angle between the line and the x-axis is to 90°, the higher the transmission efficiency of surface ions. The angle of the NiOOH/Graphene electrode, Ni3Si2/Graphene electrode, and Ni3Si2/NiOOH/Graphene electrode are 83.48°, 60.53°, and 79.70°. Overall, Ni3Si2/NiOOH/graphene has faster kinetics, higher conductivity, and a lower ion diffusion resistance during the charge–discharge process.The Nyquist plots of Ni3Si2/NiOOH/graphene was chosen to assemble symmetrical all-solid-state SCs and explore their energy storage performances. Figure −1), 126.3, 71.4, and 58.5 C g−1 at 0.3, 0.6, 1.2, and 3 mA cm−2, respectively. Figure −1 at 750 W kg−1, and the maximal power density is 7500 W kg−1 at 8.13 Wh kg−1. Compared with previous reports [3Si2/NiOOH/graphene all-solid-state SC exhibits higher energy and power densities. Therefore, the Ni3Si2/NiOOH/graphene all-solid-state SC can store more energy per unit weight and output a larger current density. Figure −2, 90.7% of the capacitance is maintained after 6000 cycles. From Fig. 3Si2 structure has not changed significantly, it demonstrates the durability of the Ni3Si2/NiOOH/graphene nanostructure. But a thin film is formed on the surface of the electrode to wrap the entire electrode. Figure 3Si2/NiOOH/graphene supercapacitors in series and charge the supercapacitor system to 2 V. When the voltage across the system reaches 2 V, disconnect the charging system and drive the LED light. In addition, Ni3Si2/NiOOH/graphene demonstrates superior specific capacitance by comparison with other materials . The all-solid-state SCs based on Ni3Si2/NiOOH/graphene nanostructures exhibit outstanding supercapacitor performance, exhibiting an extremely high-energy density (25.9 Wh kg−1 at 750 W kg−1). Even after 6000 cycles at 0.6 mA cm−2, only 10% of the capacitance is lost. This impressive electrochemical behavior indicates that creeper-like Ni3Si2/NiOOH/graphene nanostructures have great potential in the energy storage field.In summary, we successfully fabricated novel creeper-like NiSupplementary material 1 (PDF 629 kb)Below is the link to the electronic supplementary material.


The main findings of our study are determined differences in the ratio of pressure distribution on the inside and the outside foot and differences in kinematic parameters of the outside leg between elements. The mentioned analysis can provide an objective insight into the complexity of each element and provide guidelines for teaching process of those elements. This study determined the reasons for higher complexity of ST compared to PT based on the objective evaluation of biomechanical factors.There are numerous programs worldwide adapted for alpine ski beginners and they all share the same primary goal—inclusion of skiing beginners in alpine ski schools. The final elements of ski school taught in the parallel skiing technique are parallel turn and short turn. Synchronized analysis of kinetic and kinematic parameters of the parallel turn (PT) and short turn (ST) was conducted to determine the main biomechanical differences from a standpoint of foot pressure and lower limb angles. Both elements were performed by nine male ski instructors . Kinetic and kinematic analysis was conducted on 180 turns, 90 for each element. Differences in kinetic and kinematic parameters between parallel and short turns were tested by a paired  Alpine skiing is one of the most popular winter recreational activities . The aimEach ski school program is based on general principles of learning certain motor skills. Considering that skiing is a specific activity which consists of unnatural and uncommon movements for the human body, the principle of gradual learning is crucial. Ski elements are taught starting with simple ones, executed under slow speeds, and then progressing gradually towards more complex elements, which are executed under higher speeds ,7. Once The main unit which is continuously executed while skiing is the ski turn. According to authors who studied alpine skiing, it can be divided in two or three distinct phases ,9,10. StThe final elements of ski school taught in the parallel skiing technique are the parallel turn (PT) and short turn (ST). These elements are also used the most by recreational skiers while conquering the ski slope. Furthermore, their biomechanical characteristics are similar ,14. WhilAlthough numerous descriptions of the alpine skiing technique have been published, relatively little is yet known about the biomechanical factors that influence competitive performance . The numKinematic and kinetic analysis can provide a clear insight in the complexity of each movement while performing a ski turn, and it also allows comparisons between different types of turns ,16,17. BSki schools and ski coaches give their students and athletes feedback about their skiing performance, mainly based on subjective assessments. The Xsens system and pressure insoles can precisely determine biomechanical factors that influence the performance of each ski turn. They could therefore provide a better understanding of ski elements and consequently make the ski school teaching process and the development of young skiers more efficient. For that reason, synchronized analysis of kinetic and kinematic parameters of ST and PT was conducted to determine the main biomechanical differences from a standpoint of foot pressure and lower limbs angles. This analysis can provide an objective insight into the complexity of each element and offer some guidelines for the teaching process. Also, the results can help to clarify whether the usual methodical order of teaching the ST after PT is justified. We hypothesized that the ST is more complex in terms of the technique used, which is manifested in higher foot pressure and a different ratio of pressure distribution regarding the outside and inside foot. Also, regardless of their similarities in specific movements, we assumed there would be differences in kinematic parameters of lower limbs during the performance of ST and PT. Participants: The sample consisted of nine male ski instructors . Participants did not have any prior injuries that could affect skiing techniques or kinetic and kinematic variables in both ski elements. All participants were provided with a detailed explanation of the study procedures and they gave their written informed consent prior to the measuring procedure. The Faculty of Kinesiology, University of Zagreb (Croatia) Ethics Committee approved the study, which was performed following the ethical standards of the Declaration of Helsinki. Variables: Analysis of kinetic and kinematic parameters was conducted on two elements of parallel alpine ski school (PT and ST). A total of 180 turns were analyzed (90 in each element). The variable sample included 10 variables in total. The following kinetic variables were measured: maximum force of the right foot in the left turn (Max_F_R_LT); maximum force of the left foot in the left turn (Max_F_L_LT); maximum force of the left foot in the right turn (Max_F_L_RT); maximum force of the right foot in the right turn (Max_F_R_RT). All results are shown in newtons (N). The following kinematic variables were obtained (180° = knee and hip fully extended): angle of the right hip flexion in the left turn (Hip_R_LT); angle of the right knee flexion in the left turn (Knee_R_LT); angle of the left knee flexion in the left turn (Knee_L_LT); angle of the left hip flexion in the right turn (Hip_L_RT); angle of the left knee flexion in the right turn (Knee_L_RT); angle of the right knee flexion in the right turn (Knee_R_RT). All results are shown in degrees (°). All data were obtained in the final phase of each turn in both elements, precisely in the moment when skiers’ center of mass was at the lowest point and just before releasing the pressure on the outside ski a,b.To measure the kinetic variables, insoles designed for pressure detection  were used. Insoles are thin and light (2 mm), so they have a minimal influence on a skier’s performance during testing, which is especially important during more dynamic skiing, i.e., performance of advanced elements of ski techniques. For the purposes of this study, the sampling rate was set at 100 Hz. Data were derived from the corresponding Novel software  A previous study has confirmed the reliability and validity of Novel pressure insoles for analyzing foot pressure in alpine skiing ,27. Kinematic parameters were measured by a Xsens MVN Link inertial suit system. The system consists of 17 three-dimensional accelerometers/gyroscopes/magnetometers, battery and it was set at a 240 Hz output rate. Data were derived from the corresponding MVN BIOMECH software . Previous studies have confirmed the reliability and validity of the Xsens kinematic suit for analyzing kinematic parameters (joint angles) in alpine skiing ,20,21.Protocol of investigation: All instructors underwent the same protocol: measuring of anthropometric characteristics, adjusting the Xsens suit, adjusting pressure insoles inside the ski boots, a free skiing warm up run, a trial run in corridor for PT, measuring the performance of PT, a trial run in a corridor for ST and measuring the performance of ST.Anthropometric characteristics were used for calibration of the Xsens system. It was used according to the standard of procedure advised by the manufacturer . Standard calibration of pressure insoles was performed according to manufacturers’ advice . In order to synchronize both kinetic and kinematic systems, all turns were recorded with a video camera (Panasonic GH 5). For the purpose of synchronization, participants were asked to alternately lift their skis two times off the snow surface just before starting their descent. That was the starting moment when the time lapse of both systems was aligned.Overall testing was conducted for two days (four instructors on the first day and five on the following day). The study was performed in the morning hours to secure better snow conditions. The average incline of the slope was 20°. Participants had identical skiing equipment  during demonstration of both elements of ski technique. Both ski elements were performed on the selected part of the terrain, taking into consideration the characteristics of specific elements, in previously defined corridor of 15 m wide in the case of PT and 3 m wide in the case of ST . Particit-test was used. The results were considered significant when p < 0.05. With the use of the G*power program, the sample size (number of turns) was calculated (n = 90) that was needed for a measurement procedure with statistical significance of p ˂ 0.05; statistical power 0.8; effect size 0.3 and 2 groups.Statistical analysis: For the statistical analysis, program Statistica version 13.5.0.17  was used. Basic descriptive parameters were calculated for all measured variables. The normality of the data distribution was tested by the Kolmogorov–Smirnov test. For the detection of differences between the elements, a paired t-test are presented in Basic descriptive parameters of each tested variable along with results of paired p = 0.000; p = 0.000). Pressure force values of the outside foot in ST are higher than in PT . The force on the outside foot of ST represents 1.45 of mean body weight (MBW) of tested participants while the force of PT is 1.06 MBW. The force of the inside foot in the left turn was also higher while performing ST compared to PT . In relation to body weight, the measured force in ST was 0.92 MBW was 0.33 MBW in PT. p = 0.000, p = 0.000). The pressure force values of the outside foot in ST are higher than in PT . In relation to body weight, the measured force in ST was 1.37 MBW and was 1.10 MBW in PT. Furthermore, in ST the measured force of the inside foot was higher than in PT . In relation to body weight, the measured force in ST was 0.99 MBW and was 0.28 MBW in PT. In the right turn, a significant difference between the two observed elements was also determined in maximal force pressure of the outside and the inside foot (p = 0.002) in the left turn and in the left knee flexion angle (p = 0.036) in the right turn. At the end of each turn, the knee was more flexed i.e., the skier was in a lower position while performing the ST element . Significant differences regarding kinematic parameters between the two observed elements were found in the right knee flexion angle . Mean values of maximum pressure were higher in ST than in PT, in both feet, while performing elements on both the right and the left side. The ratio of foot pressure between the inside and the outside foot differed in the two observed elements. Foot pressure, although mainly on the outside foot, was significantly higher on the inside foot in ST when comparing the two elements . Higher foot pressure forces of the inside foot in ST could be explained by a higher complexity of the ski element. ST is executed in a more “choppy” fashion and, as was mentioned previously, it is commonly referred to as a short unfinished PT. Therefore, each phase of the turn and consequently the whole turn is performed in a shorter time interval. Each specific movement is executed faster and is performed automatically without preparing for each phase. Body weight is transferred faster from one to another outside ski. During that movement, a skier uses GRF in order to facilitate and speed up the transfer of the pressure from the outside leg to the new outside leg in the following turn. To ease the transfer movement and make it more efficient, the skier must use the inside foot, which will help him to master generated forces. Furthermore, at the end of the turn, the skier cannot control the speed by executing an uphill turn since the turn is unfinished by definition. High values of GRF detected at the end of the ST in this research are just another factor influencing the complexity of speed control. The steepness of the slopes increases the danger of injuries caused by a fall. Collision among skiers is dangerous, especially on steeper slopes where it is harder to stop the sliding after a fall. Therefore, ST is usually executed on the steep slopes by experienced skiers who mastered the speed control at the end of the turn. By using a narrow corridor, a skier minimizes the risk of collision with other skiers. On the other hand, when performing PT, the duration of the turn is longer and there is more time for adjusting movements in each phase of the turn. Also, a skier has more time to apply pressure on the ski surface at the right moment [There is a statistically significant difference between ST and PT in foot pressure forces, both on the outside and the inside foot (t moment . Generatp < 0.05), which is in accordance with data obtained in our research. The authors concluded the main reason for this difference was the lesser time in which the ST must be completed, without skidding which is manifested by an increase of GRF. The increase of GRF is also achieved by a higher edging angle, especially in the last phase of the turn. They suggested that while acquiring ST, the last phase of the turn should be short with a fast transfer of body mass to the other outside ski. While performing PT, the skier learns how to control the center of mass, pressure distribution and edging angle. After mastering the above mentioned techniques, the skier can achieve a high edging angle and utilize a high GRF to transfer the pressure to the new outside foot.Kim and Kim  comparedForce distribution analysis was conducted on elite ski instructors while performing slalom (SL) and giant slalom (GS) turn in a study of Lamontagne . His finIn a research conducted by Falda–Buscaiot et al. , the ratp = 0.002, p = 0.036). In ST it is very important to utilize the ground reaction force at the end of the turn in order to be faster in transition. Consequently, the skier must be in a lower position, i.e., his knee angle of the outside leg is smaller . Kröll et al. [Kinematic analysis showed significant differences between turns in knee angle values of the outside leg (l et al.  investigIn the previously cited study conducted by Kroll et al. , during Most of the kinetics and kinematics research addressed the issues of force application and changes in joint angles during dynamic performances of racers ,29,30,32Information about the timing of specific body movements which ensure optimal control of direction and speed could be crucial for accomplishing the aim of each alpine ski school—to enable skiers to be independent in mastering complex skiing elements. This research determined the reasons for higher complexity of ST compared to PT based on the objective evaluation of biomechanical factors that influence the performance of each element. Therefore, we confirmed that current methodical order of teaching ST after PT is justified. Based on our research, the turns performed in a narrow corridor are more complex due to their pressure distribution and lower body joint flexion, which is probably caused by a greater separation of movement in upper and lower body. Ski instructors and coaches should follow the methodical process from the beginning of teaching. All technical elements should be demonstrated and taught in a wide corridor with longer duration of each turn phase. This way, the students and athletes will have the necessary time to process and perform all the movements. Future studies should be focused on observing biomechanical factors of all the elements performed in narrow and wide corridors. Only then would it be possible to make a conclusion about the reasons beneath the complexity of performing a turn in a narrow corridor.The presented study is focused on kinematic and kinetic analysis of only two elements of alpine ski school. To make a conclusion about the complexity of elements and teaching methodology, it would be necessary to conduct measurements of each element included in alpine ski school program and every methodical exercise for teaching those elements. This would give ski instructors and coaches much more assurance when deciding upon the choice and the order of methodical exercises to use in the most efficient way to upgrade the teaching process of ski elements. Furthermore, it would be useful to determine pressure distribution on different areas of foot during performing different phases of the turn.The results of the conducted synchronized analysis of ski elements determined different ratio of pressure distribution between the elements. The pressure on the inside leg is relatively higher in ST compared to PT. Kinematic analysis pointed out differences in the knee angle of the outside leg, which has a role of controlling the speed and direction during descent. ST is more complex and skiers can only safely perform ST after mastering the optimal and balanced position with pressure dominantly on the outside ski recreational level alpine.Similar findings were determined in various alpine skiing studies focused on kinetic and kinematic analysis. Differences between those studies and the present one are participants and the type of analyzed turns. Although there are similarities between SL and GS and some elements of alpine ski school, it is important to be cautious when making conclusions about recreational skiing based on ski racers and their turns. Studies focused on alpine ski schools are necessary to determine crucial biomechanical factors influencing the performance of each element. It is important that ski instructors have that information because it can serve as a guideline for adapting their teaching process and make it more efficient, which will consequently reduce injuries.


Many eukaryotic species contain two separate molecular machineries for removing non-coding intron sequences from pre-mRNA molecules. The majority of introns (more than 99.5% in humans) are recognized and excised by the major spliceosome, which utilizes relatively poorly conserved sequence elements at the 5′ and 3′ ends of the intron that are used for intron recognition and in subsequent catalysis. In contrast, the minor spliceosome targets a rare group of introns (approximately 0.5% in humans) with highly conserved sequences at the 5′ and 3′ ends of the intron. Minor introns coexist in the same genes with major introns and while the two intron types are spliced by separate spliceosomes, the two splicing machineries can interact with one another to shape mRNA processing events in genes containing minor introns. Here, we review known cooperative and competitive interactions between the two spliceosomes and discuss the mechanistic basis of the spliceosome crosstalk, its regulatory significance, and impact on spliceosome diseases. Drosophila. More recently, an investigation of the genome of slime mold Physarum polycephalum revealed an exceptional case of >20,000 minor introns in a single genome  and ligation of coding sequences (exons) in pre-cursor messenger RNA (pre-mRNA), is carried out by a dynamic and complex machinery known as the spliceosome. The majority of metazoan organisms contain two parallel but analogous spliceosomes: the major or U2-dependent spliceosome which excises approximately 99.5% of introns, depending on the organism, and the minor or U12-dependent spliceosome which excises about 0.5% of introns. The respective intron types are similarly referred to as either major or U2-type introns, and minor or U12-type introns . The nume genome . The type genome . The orie genome . Nonethee genome . Interese genome . On the e genome . These pe genome .A key distinguishing feature between U12-type and U2-type introns is the conservation of intron recognition sequences i.e., the 5′ splice site (5′ss), 3′ splice site (3′ss) and the branch point sequence (BPS). Additionally, U2-type introns distinctively contain a polypyrimidine tract (PPT) upstream of the 3′ss. Splice site sequences are relatively weakly conserved in U2-type introns, which leads to more flexible splice site choices that fuel alternative splicing processes. In contrast, splice site sequences within U12-type introns are significantly more conserved , which tEfforts aimed at understanding the functional significance of U12-type introns have suggested that the splicing of minor introns is slower or less efficient than that of major introns and could be used as a rate-limiting step to control or fine-tune mRNA levels of MIGs . AccordiInteraction between the minor and major spliceosomes during pre-mRNA processing can lead to two opposing outcomes: cooperation or competition. Cooperative interactions can facilitate mutual activation of adjacent spliceosomes during splicing through exon and intron definition mechanisms. Alternatively, the two spliceosomes can compete with one another for access to introns that harbor splice site recognition sequences for both machineries. Under normal physiological conditions, competitive interactions can be identified by the alternate use of either U12-type or U2-type splice sites, which result in different mRNA isoforms. In contrast, cooperative interactions between the two spliceosomes are more challenging to identify, as they typically do not lead to changes in alternative splice site usage under physiological conditions, except in the few cases where such interactions have been exploited for regulatory purposes. Additionally, diseases affecting minor spliceosome functions lead to a variety of alternative splicing choices in both interaction types.At the mechanistic level, mutual interactions between the major and minor spliceosomes on the same pre-mRNA are predominantly mediated by exon definition interactions, in which the initial recognition of introns takes place by pairing splice sites across exons instead of introns . Subsequin vitro, between U1 snRNP and the minor spliceosome  are the main facilitators of these interactions . These iiceosome , and in and 3′ss .SNRNP48 and RNPC3 genes. These encode the U11-48K and U11/U12-65K proteins, respectively, that are components of the U11/U12 di-snRNP. Both genes contain a conserved sequence element in non-coding regions which include a tandem repeat of the U12-type 5′ss consensus sequence. The tandem 5′ss sequences are recognized by the U11 snRNP, but are not used as splicing donors by the minor spliceosome. Instead, the binding of the U11/U12 di-snRNP activates an upstream U2-type 3′ss (SNRNP48) due to inclusion of a PTC, or are retained in the nucleus due to an export-incompetent mRNA isoform (RNPC3)  . Notablyntiation , and is ntiation .Further evidence for cooperative interactions between the two spliceosomes has emerged from global transcriptome analyses of diseases which partially compromise the function of the minor spliceosome. A typical outcome in these diseases is intron retention resulting from splicing defects. However, several studies have also demonstrated that the splicing defects are not limited to U12-type introns but can also spread to the flanking U2-type introns  in a subCompetition between the two spliceosomes represents a special subclass of alternative splicing where an individual intron can be spliced by either the minor or the major spliceosome. In these instances, competing splice sites are typically in close proximity to one another on the pre-mRNA and the resulting mRNA isoforms are also often annotated in public databases. Depending on the positioning of the splice sites, such introns have been referred to as twintrons or nested introns, which both refer to instances where either minor or major intron is located within the other intron type . Nested prospero (pro) gene in Drosophila  or longer  mRNA isoforms. The resulting pro protein isoforms differ in the homeodomain region, which may affect DNA binding specificity  that is specific for the SRSFR10 protein and is involved in SRSF10 autoregulation. Levels of the functional SRSF10 isoform spliced by the minor spliceosome correlate not only with the activity of the minor spliceosome, but also with overall levels of other SR proteins, in a tissue-specific and developmental manner. This further suggests that regulation of the SR-protein family as a group, may be linked to the activity of the minor spliceosome   . The truif (RRM) .MAPK8-9) and for TMEM87a and TMEM87b genes. Here, competition between minor and major pathways leads to mutually exclusive incorporation of alternatively spliced exons into the mRNA. In the MAPK8/9 genes, U12-type and U2-type splice sites have an interlocked configuration where mutual competition of two U2-type 3′ss and two U12-type 5′ss leads to inclusion of either the alternative exon 6a or exon 6b   family genes (ctively) . In thisctively) . The difctively) , whereasctively) . A recene intron . Competipression , indicatCCDC84 gene  by e intron .MAPK12 and CENATAC cases with a shared 3′ss, there is another, albeit undetectable functional change upstream of the 3′ss. In the major pathway this region constitutes a pyrimidine-rich PPT recognized by the U2AF2 protein present in the U2AF1/2 heterodimer. In contrast, the minor spliceosome does not use the PPT or the U2AF1/2 heterodimer for intron recognition, but rather relies on BPS recognition by the U12 snRNA. A plausible explanation for the intron 3′ end compatibility between the two spliceosomes is that the minor intron BPS is also pyrimidine-rich and can, in a suitable context, also serve as a PPT for major introns, as suggested earlier (In both the  earlier .A unique case of competition has been described for the non-productive use of components of both splicing pathways to regulate the ratio between unspliced genomic RNA and subgenomic spliced mRNA species in the Rous Sarcoma Virus (RSV). The genomic RNA of this retrovirus contains an inhibitory splicing element designated the Negative Regulator of Splicing (NRS), the function of which is to suppress all splicing of the viral RNA to ensure production of unprocessed genomic RNA, that is subsequently packaged into virions . InteresHuman diseases that compromise functions of either spliceosome can have two differential outcomes in competitive contexts between the two spliceosomes. First, in cases of competitive intron recognition that leads to a balanced expression of spliceosome-specific mRNA isoforms, such as those described above, the most likely outcome is a shift in the balance between the isoforms. This effect may vary depending on the specific mutation/spliceosomal defect, and may be combined with other outcomes, such as alterations in exon definition mechanisms or increased levels of intron retention.An alternative possibility is the activation of cryptic splice sites near introns that do not display any obvious competition between the two spliceosomes. “Cryptic” in this context refers to splice sites that are not used under physiological conditions and are predictably also not annotated or documented in public databases. Thus, cryptic splice sites can be thought of as pseudo splices sites that are weaker in strength compared to authentic sites, and as such, are not efficiently recognized by the spliceosome in a context specific manner. Such splice sites tend to be activated as a consequence of mutations in either authentic splice sites or alternatively, in spliceosome components or regulators. Both lead to defects in splice site recognition either at the level of single introns, or more broadly . While cSNRNPE, RCD8/EDC4 and SLC9A8 genes  implicated in the Peutz-Jager Syndrome    and AP4Mal palsy  both of al palsy . In contal palsy . The stuUntil very recently, the outlook on the regulatory significance of the minor spliceosome functioning in parallel with the major spliceosome has been static. The main focus in the field has been on the inefficient splicing of U12-type introns under physiological conditions and the increased intron retention events observed in minor spliceosome diseases. However, rapidly accumulating transcriptomic data from an increasing number of minor spliceosome diseases is now challenging this narrow view by providing robust evidence of widespread crosstalk mechanisms between the minor and major spliceosomes, which were previously only reported in single-gene investigations. The fact that the locations of U12-type introns are known and highly conserved, presents a unique opportunity or lens through which the parallel functioning of both spliceosomes, particularly in exon and intron definition contexts, can be examined. Importantly, under physiological conditions, crosstalk between the two spliceosomes appears mostly to function as a mechanism for reinforcing constitutive splicing patterns through exon definition interactions, and to a lesser extent, as a mechanism for regulating balanced expression of mRNA isoforms that are dependent on either spliceosome. The less studied role of this crosstalk in regulating gene expression is particularly intriguing, as the few genes described here that utilize adjacent U12-and U2-type splice sites to regulate their expression, highlight an overlooked yet significant regulatory mechanism for some MIGs. Consequently, examining such crosstalk mechanisms has the potential to contribute to current understanding of the evolutionary significance of both spliceosomes functioning in parallel. Interestingly, for genes currently known to harbor these adjacent splice sites both cooperative and competitive outcomes have been observed, with the latter being more common. Competition between splice sites is a common occurrence for U2-type introns, due to the more degenerate splice sites in these introns and has been discussed extensively within the context of alternative splicing . In contMAPK8/9 (TMEM87a/b (In disease contexts the primary splicing defect can lead to additional defects in both competitive and collaborative interactions between the two spliceosomes. The occurrence of additional mRNA isoforms as a consequence of the loss of crosstalk between the two spliceosomes also influences the interpretation of transcriptomic data derived from minor spliceosome disease patient cells. A typical transcriptome-level workflow aims to identify the affected minor introns and MIGs, and optionally, use the intron retention levels to estimate the downregulation of MIGs for downstream analyses. Thus, the presence of novel transcripts arising from cryptic splice site usage and the loss of exon definition interactions can either exacerbate the effect on expression levels or lead to formation of mutant proteins, which may contribute to the pathology of the given disease. Additionally, the MAPK8/9  and TMEMMEM87a/b  examplesMEM87a/b  have demMEM87a/b .de novo events, such as KisSplice used in the CENATAC (At a more technical level, the activation and detection of cryptic splice sites poses an additional challenge for data analysis. Most software used in alternative splicing analyses rely on existing annotations when detecting alternative splicing events . As cryp CENATAC , we docu CENATAC , which iIn summary, recent transcriptome-wide investigations have uncovered a substantial number of crosstalk interactions between the major and minor spliceosomes. An outstanding question related to these splicing events concerns the identification of true regulatory events from cases representing opportunistic cryptic splice site activations. An additional unanswered question is whether either spliceosome can be regulated individually in a manner that would influence the crosstalk. There is some evidence of specific splicing factors such as hnRNP H/F and SRSF10 being linked to regulation of the minor spliceosome , but theBoth authors contributed equally to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Cell proliferation is an important cellular process for physiological tissue homeostasis and remodeling. The mechanisms of cell proliferation in response to pathological stresses are not fully understood. Mitochondria are highly dynamic organelles whose shape, number, and biological functions are modulated by mitochondrial dynamics, including fusion and fission. Mitofusin-2 (Mfn-2) is an essential GTPase-related mitochondrial dynamics protein for maintaining mitochondrial network and bioenergetics. A growing body of evidence indicates that Mfn-2 has a potential role in regulating cell proliferation in various cell types. Here we review these new functions of Mfn-2, highlighting its crucial role in several signaling pathways during the process of pathological cell proliferation. We conclude that Mfn-2 could be a new mediator of pathological cell proliferation and a potential therapeutic target. Cell proliferation is a precision–control process, which is essential for embryonic and postnatal development . Under pPreviously, mitochondria have been regarded as static and isolated organelles. More recently, they are found to undergo constant changes in morphology, including fission, fusion, and network formation, and they can also relocate to different parts in cells (trafficking); all of these processes are termed mitochondrial dynamics. Mitochondrial dynamics is essential to maintain the normal function of cells such as energy metabolism, calcium homeostasis, and reactive oxygen species generation . Mitochovia various pathways.Research in the past two decades or so have revealed that the mechanisms of mitochondrial dynamics are regulated by a group of highly conserved guanosine triphosphatases (GTPase) . MitofusIn this review, we summarized recent advancements in the study of mitochondrial fusion protein Mfn-2. We focus on the link between altered Mfn-2 and pathological cell proliferation.Current evidence indicates that Mfn-2 plays various roles in many cellular processes, including cell proliferation and cell death . Chen etAtherosclerosis is the main cause of cardiovascular diseases. It has been clearly demonstrated that the development and progression of atherosclerosis involve inflammation, abnormal proliferation of VSMCs, remodeling of the vascular wall, and evolution of occlusive plaques.via the inhibition of Erk/mitogen-activated protein kinase (Erk/MAPKs) signaling followed by cell cycle arrest. Cell transition from G0/G1 phase to S phase is one of the important characteristics for proliferation. EdU assay indicated that downregulation of Mfn-2 resulted in a significant decrease of G0/G1 phase cells and a synchronous increase of the percentage of S-phase cells in homocysteine-induced VSMCs, and overexpression of Mfn-2 obtained the contrary results, suggesting that cell cycle arrest at G0/G1 phase is responsible for the anti-proliferation effects of Mfn-2  and its receptors, inducing VSMCs to transform from quiescent state to secretion and proliferation state kt, etc. . One remkt, etc. . In Fengkt, etc. , which tIn patients diagnosed with type 2 diabetes, the incidence of atherosclerosis is high, and the expression of Mfn-2 in the muscle decreased; similar results are also observed in high-fat-diet mice. In addition, increasing the level of Mfn-2 could alleviate insulin resistance  through via autophagy, considering the role of Mfn-2 in the maintenance of MAM, more studies are required to provide evidence linking Mfn-2-mediated autophagy with VSMC proliferation in the future.As mentioned above, Mfn-2 is crucial in maintaining MAM structure. MAM is the central platform for the initiation of mitophagy and the formation of autophagosome . Chen anPulmonary hypertension is another pathological condition attributed to VSMC proliferation. Pathophysiological changes involve all three layers of pulmonary arteries during vascular remodeling. For instance, endothelial angiogenesis, smooth muscle cell hyperplasia and hypertrophy, adventitial fibroblast proliferation, myofibroblast differentiation, and extracellular matrix deposition have all been reported . The excThe role of Mfn-2 in pulmonary hypertension is complicated. via targeting Mfn-2 directly. Recent studies revealed that miRNAs play an important role in the pathogenesis of pulmonary hypertension by regulating ASMC proliferation . Several2+ transfer and inhibit cell proliferation in kidney cysts  is a cellular state in which the protein folding capacity of ER is overwhelmed due to increased protein load or disruption of the protein folding environment . It has  pathway . Ngoh et pathway . DownregA study from via the N-terminus  receptors (IP3R) and ryanodine receptors (RyRs) on the ER membrane  and entevia the Wnt/β-catenin pathway in bladder cancer. Mfn-2 knockdown increased the translocation of β-catenin into the nucleus, resulting in larger tumor volumes and a higher proliferation index. Pharmacological inhibition of the Mfn-2/mTORC2/Akt pathway attenuated tumor growth via various signaling pathways, there are currently no studies that figured out whether these pathways are related to mitochondria fusion. More studies on this topic may be necessary in the future.Although some evidence indicated that, in addition to fusion reaction, Mfn-2 has been reported to regulate cell proliferation (2)Although there are many evidence about the role of Mfn-2 in neoplastic diseases, the microenvironment may change the impact of Mfn-2 in different types of cancers. In the future, a more detailed analysis of Mfn-2 may be necessary.(3)Could altered Mfn-2 act as a potential biomarker in pathogenesis?via MAM formation and mitophagy to regulate cell proliferation and cell survival/death in different tissues. Many important questions await extensive investigation. In the future, studies on the role of Mfn-2 in cell proliferation may lead to the development of new strategies for treating various diseases, such as cancer and cardiovascular diseases.The machineries of mitochondrial fusion/fission and the significance of mitochondrial dynamics in regulating mitochondrial and cellular functions have been established. The mitochondrial fusion protein Mfn-2 regulates mitochondrial morphology, metabolism, calcium homeostasis, and mtDNA stability. Mfn-2 also plays a role YX and JL draft the manuscript. WW revised and polished the manuscript. XL supervised the review and established the whole frame. All authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


The Li−S batteries showed stabilized coulombic efficiency as high as 94% and excellent cyclic performance with an ultra low cyclic fading rate of 0.075% for the initial 280 cycles at a current density of 1.0 C. The improved electrochemical performance was ascribed to the enhanced conductivity by the connective graphene networks and the weakened shuttle effect by the special outer graphene layers. Mass production of the products was realized by the continuous FB−CVD process, which opens up new perspectives for large scale application of 3D graphene materials.Three−dimensional (3D) graphene with novel nano−architectures exhibits many excellent properties and is promising for energy storage and conversion applications. Herein, a new strategy based on the fluidized bed chemical vapor deposition (FB−CVD) process was proposed to prepare 3D graphene networks (3DGNs) with various nano−architectures. Specially designed SiC−C@graphene core/shell nanoparticles were prepared taking the advantages of the FB−CVD system, and 3DGNs with hierarchical nanostructures were obtained after removing the SiC core. The 3DGNs performed well as electrodes of lithium–sulfur batteries. The C–S cathode showed good rate performance at the current density of 0.1–2.0 C, and an initial discharge capacity of 790 mAhg Since its discovery in 2004, graphene has drawn increasing attention and has been intensively investigated due to its unique and excellent properties, such as huge specific surface area, high electrical conductivity and electron mobility, robust mechanical performance, good flexibility, high thermal conductivity, and efficient light absorption ,2,3. OveLithium–sulfur batteries are nowadays undergoing a tremendous number of investigations because of the highest theoretical capacity of elemental sulfur among cathode materials for secondary lithium batteries . However2O3 nanoparticles (NPs) have been used as templates for the catalyst−free CVD of graphene meso−sponge with monolayer graphene [Until now, several methods have been developed for fabricating 3DGNs, which could be divided into two categories: assembly of graphene sheets and direct synthesis from carbon sources . Assemblgraphene . 3DGNs pgraphene . Though To combine the construction of 3DGNs with hierarchical nanostructures in scientific perspective and the mass production in engineering perspective, we proposed a novel strategy by fluidized bed chemical vapor deposition (FB−CVD). SiC−C@graphene core/shell nanoparticles with novel nanostructures were first prepared via the FB−CVD process. After heat treated under high temperature and vacuum environment, high purity 3DGNs were obtained. The nano−architectures of the 3DGNs could be adjusted thanks to the different microstructures of SiC−C@graphene nanoparticles prepared at different experimental conditions. Sulfur with high loading was infiltrated into the 3DGNs via a melt−diffusion strategy to prepare the carbon/sulfur composite cathodes for lithium–sulfur batteries. The cathodes showed good discharge capacity, improved cyclic performance and excellent efficiency, demonstrating a great prospect of engineering application for the 3DGNs produced by the continuous FB−CVD process.−3 Pa. After heat treatment, SiC particles were evaporated and the carbon phase was remained to form 3D connective graphene net−cages. To investigate the effect of reaction atmosphere, propylene concentration and temperature on the microstructure of the products, different experimental conditions were conducted as shown in Preparation of the 3DGNs: The SiC−C@graphene nanoparticles were prepared by a fluidized bed chemical vapor deposition (FB−CVD) method. In a typical synthesis process, the reaction zone of the vertical fluidizing tube was heated at 1000 °C. Hexamethyldisilane (HMDS)  was used as the precursor to prepare SiC–C composite nanoparticles. HMDS was heated at 80 °C by a water bath to form vapor and then was carried into the furnace by argon. The other precursor of propylene was injected to the furnace at the same time. The products were collected by powder separator device which was connected to the gas outlet of the furnace. The obtained composite nanoparticles were then heated at 1950 °C for 3 h under a vacuum degree of 10Fabrication of 3DGNs/Sulfur Composites: The 3D graphene net−cages powder/sulfur composite cathodes were fabricated following a typical melt−diffusion strategy. The 3D graphene net−cages powder was firstly mixed with sulfur powder  with a mass ratio of 1:4 by milling. Subsequently, the mixture was placed in a sealed flask at 155 °C for 5 h to incorporate sulfur into the 3D graphene net−cages.−1 at room temperature. The differential scanning calorimetry (DSC) and thermogravimetry (TG) measurements were performed by a simultaneous thermal analysis apparatus  with a heating rate of 5 °C/min in different atmospheres.Characterizations: Microstructures of the product were observed by a field emission scanning electron microscope . The TEM images and corresponding selected area electron diffraction (SAED) patterns were obtained on a high resolution transmission electron microscope  at an acceleration voltage of 200 kV. The crystal structure of the samples was examined by X−ray diffraction (XRD) on a diffractometer using Cu Kα radiation . Raman scattering was excited employing a He–Ne laser (λ = 516 nm), and was collected by a micro−Raman spectrometer  in the wave number of 1000–3500 cmN−methyl−pyrrolidone dispersant by a magnetic stirrer for 24 h. The slurry was then coated onto an aluminum foil, followed by a vacuum drying for 6 h at 60 °C to obtain an areal sulfur loading of 1.1 mg·cm−2. Disks of 13.0 mm were punched as the working cathodes. A quantity of 25.0 μL electrolyte containing 1.0 M lithium bis (trifluoromethanesulfonyl)imide solution in 1,3−dioxolane/1,2−dimethoxyethane (1:1 v/v) was used to construct the Li–S cell. Lithium metal foil was used as the anode and the polypropylene membranes were used as the separators. The coin cells were tested in galvanostatic mode at various currents within a voltage range of 1.6–2.8 V using multichannel battery cycler . The cyclic performance was tested at a current density of 1.0 C. The capacities were calculated corresponding to the total mass of the cathodes slurry.Electrochemical Measurements: Li−S batteries were constructed to evaluate the electrochemical performance of 3D graphene net−cages as cathode scaffolds according to the procedure of the reference . The catThe spouted fluidized bed (FB) technology and chemical vapor deposition (CVD) method are combined to prepare C–Si based nanoparticles with hierarchical structures. Compared with conventional CVD route, the so−called spouted fluidized bed chemical vapor deposition (FB−CVD) method originally used for nuclear fuel particle coating, displays many advantages in the synthesis of nanostructured particles ,32,33,342 ratios. When 30% H2 was introduced into the furnace, which meant a decrease of the carbon content, the framework of the 3D graphene tended to open and lose the spherical shape, presenting a flower−like structure  graphene networks with novel nano−architectures were prepared by combining the FB−CVD process and subsequent heat treatment. Taking the advantages of the uneven temperature distribution of the fluidized bed and the rapid transport mechanism, core/shell structured SiC−graphene nanocomposites were prepared. The 3DGNs with different nano−architectures could be fabricated by adjusting the reaction atmosphere, temperature and precursors of FB−CVD. Novel 3D graphene net−cage nanostructures with interlaced graphene nanobelts and connected graphene shells were obtained from SiC−C@graphene nanocomposites. The 3DGNs performed well as electrodes of lithium–sulfur batteries with high sulfur loading, high discharge capacity, excellent cyclic performance and high efficiency. The hierarchical internal and external microstructures of the 3DGNs were responsible for the high electrochemistry performance by improving the conductivity, resisting the volume change and hindering the shuttle effect. This work provides a novel and effective synthesis strategy for the preparation 3DGNs with nano−architectures. These unique 3DGNs will find diverse applications in areas such as lithium−ion batteries, catalytic carriers and supercapacitors by fine structure design and integration with other functional materials. The realization of mass production by the FB−CVD process opens up new perspectives for large scale engineering application of the 3D graphene materials.


Aerogels have attracted significant attention recently due to their ultra-light weight porous structure, mechanical robustness, high electrical conductivity, facile scalability and their use as gas and oil absorbers. Herein, we examine the multi-functional properties of hybrid aerogels consisting of reduced graphene oxide (rGO) integrated with hexagonal boron nitride (hBN) platelets. Using a freeze-drying approach, hybrid aerogels are fabricated by simple mixing with various volume fractions of hBN and rGO up to 0.5/0.5 ratio. The fabrication method is simple, cost effective, scalable and can be extended to other 2D materials combinations. The hybrid rGO/hBN aerogels (HAs) are mechanically robust and highly compressible with mechanical properties similar to those of the pure rGO aerogel. We show that the presence of hBN in the HAs enhances the gas absorption capacities of formaldehyde and water vapour up to ~ 7 and > 8 times, respectively, as compared to pure rGO aerogel. Moreover, the samples show good recoverability, making them highly efficient materials for gas absorption applications and for the protection of artefacts such as paintings in storage facilities. Finally, even in the presence of large quantity of insulating hBN, the HAs are electrically conductive, extending the potential application spectrum of the proposed hybrids to the field of electro-thermal actuators. The work proposed here paves the way for the design and production of novel 2D materials combinations with tailored multi-functionalities suited for a large variety of modern applications. The GAs can also be used as reinforcing agents in composites, in sensors and nano-electronics, energy storage2, as cell growth promoters3, absorbers for the removal of food toxins4, in catalysis and biomedical applications among others1. Other materials such as hexagonal boron nitride (hBN) have also attracted significant attention for the fabrication of aerogels5 since their distinct properties as compared to GAs, pave the way for the development of new applications. For example, boron nitride based aerogels (BNAs) have been extensively used for the removal of organic and inorganic pollutants from aqueous solutions with high efficiency6. Moreover, BNAs possess high thermal conductivity and they remain stable up to 1000o C which make them attractive materials for applications required to perform reliably under harsh environments7. Besides graphene and boron nitride based aerogels, the area is highly active and other materials have also been tested, including silica9 and SnO210 based aerogels that show attractive properties and have been used in various applications.Graphene aerogels (GAs) have attracted significant attention recently since they are ultra-lightweight, mechanically robust, electrically conductive, perform well under harsh environment and as a result have found good use in various applications17. In this regard, hybrid aerogels (HAs) have started to gain attention and some efforts have already been reported in the literature for aerogels composed of combined graphene/boron nitride nano-sheets12, graphene/ boron nitride nanotubes13, graphene/MoS216 and others17. In particular, BNAs exhibit high thermal conductivity but low electrical conductivity,18 therefore, they are only suitable for applications as insulators. In contrast, reduced graphene oxide has both high thermal and moderate electrical conductivity and therefore its field of application differs than hBN. Both materials possess attractive mechanical properties, they are highly compressible and perform well as absorbers of gas and oil pollutants. It would be of great interest to create hybrid aerogels that retain the properties of the standalone materials or even develop hybrids that could outperform the efficiency of the homostructured materials.In an attempt to combine and exploit the distinct properties of dissimilar 2D materials, the fabrication of 2D hybrids could, under certain circumstances, impart new multi-functionalities and therefore has recently emerged as a very intense research field19. Bi et al.20 examined the efficiency of spongy graphene for oil absorption by floating the sample in liquid pollutants such as commercial petroleum products, fats and ketones, and the results showed high speed of absorption and efficient recovery. Similar experiments have been performed for thermally cross-linked Poly(acrylic acid)/rGO of low porosity as absorbers of various oils with high efficiency21, as well for pure graphene aerogels with density less than ~ 9 mg/cm322. An extensive discussion on the subject regarding carbon based absorbers can be found in reference19 and for hBN based materials in reference6. Boron nitride based porous materials have also been tested for the removal of substances from water. A foam like hBN structure was developed with density of ~ 30.4 mg/cm3 and proved very efficient for the removal/separation of a number of oils and chemicals by immersing the porous materials into contaminated water23. Similar experiments performed for another sponge like material made by few-layer hBN-coated melamine sponge which showed to possess very good recyclability performance24.One particular application of the aerogels is their use as volatile organic compounds (VOC) absorbers for the protection of museum artefacts such as paintings and other objects. It is worth noting that most artefacts owned by museums are often stored under hostile environmental conditions in deposits (e.g. in crates and boxes). It has been estimated that the largest museums typically display only about 5% of their collection at any time. This roughly 5% is usually rotated among the most important works the museums have, while other less significant works may never leave the storage area. Additionally, some artworks may be displayed but need preservation frequently in order that they survive, like works based on paper, which will fade if exposed to light. Both carbon and hBN aerogels have been tested as oil and organic absorbersHerein, we fabricate hybrid aerogels at various mix ratios composed of reduced graphene oxide (rGO) and hexagonal boron nitride (hBN) platelets using a freeze-drying approach. The method is cost effective and can be easily used for the fabrication of large-scale quantities, while it can be extended to the fabrication of other 2D materials as well. In this work we examine in detail the mechanical properties of the HAs as well the changes in the electrical conductivity induced by the presence of hBN. Furthermore, we investigate the efficiency of the proposed HAs as gas absorbers of formaldehyde, hydrochloric acid and acetic acid, as well their capacity for water vapour absorption. The results presented below show that the rGO/hBN hybrid aerogels possess good mechanical properties and reasonable electrical conductivities but, most importantly, certain combinations of these hybrids exhibit extremely high gas absorption capabilities.25 was followed herein for the fabrication of the rGO aerogels. Aqueous solution of GO was prepared by modified Hummer’s method27 and was subsequently diluted in water to obtain a concentration of 1 mg/mL. Hypophosphorous acid (H3PO2) and iodine (I2) of weight ratio GO: H3PO2:I2 equal to 1:100:10, were then added as the chemically reducing agents28. Subsequently the solution was placed in a furnace and heated to 80 °C for 8 h, resulting in a uniform gelation of the GO. The sample was then rinsed with water until a pH equal to 5, followed by freeze-drying for 48 h. For the fabrication of the HAs, another solution with boron nitride platelets of 1 mg/mL concentration was prepared in ethanol–water (50–50% w/w) and stirred for 10 min. Solutions with mixed GO and hBN with various concentrations of 0.9/0.1, 0.7/0.3 and 0.5/0.5 mg/mL were stirred and then the same steps as for the case of the pure GO were followed. We note that the addition of ethanol significantly stabilizes the mixed solution29 and assists to achieve uniform dispersions as seen in Fig. 13. It is noted that this approach cannot be used for the preparation of pure hBN aerogels, which points out to the crucial role of the presence of the GO which stabilizes the mixture. This is due to the gelation mechanism that involves the simultaneous reduction and self-assembly of the GO sheets, based on chemical reactions between the oxygen functional groups present at the surface of the GO and the chemical agents28. Thus, the hBN platelets that do not contain such groups on their surface simply attach to the GO sheets. The only complication is that the gelation time might be increased in the mixed solutions as discussed previously13. The density of the aerogels is found to be in the range of 13.9–23.4 mg/cm−3 without significant variation between samples.The approach presented previously by Hong et al.5/2 line. The analysed area was a spot with 3 mm diameter. The atomic ratios were calculated from the intensity (peak area) of the XPS peaks weighted with the corresponding relative sensitivity factors (RSF) derived from the Scofield cross-section taking into account the electron transport properties of the matrix,  and the energy analyser transmission function. For spectra collection and treatment, including fitting, the commercial software SpecsLab Prodigy  was used. The XPS peaks were deconvoluted with sum Gaussian-Lorenzian peaks after a Shirtey type background subtraction.The surface analysis measurements were performed in a UHV chamber (P ~ 5 × 10 − 10 mbar) equipped with a SPECS Phoibos 100-1D-DLD hemispherical electron analyser and a non-monochromatized dual-anode Mg/Al x-ray source for XPS. The XP Spectra were recorded with MgKa at 1253.6 eV photon energy and an analyser pass energy of 10 eV giving a Full Width at Half Maximum (FWHM) of 0.85 eV for Ag3d2O), hydrochloric acid or acetic acid were used as gas source each time. For the humidity measurements, vials full of water were placed similarly to the gases, while the relative humidity (RH) was measured independently and was found to be ~ 97%. All samples were initially dried at 200 °C for 2 h in order to remove their absorbed humidity and weighed into a high accuracy weight meter to measure their dried mass. Afterwards, the aerogels were loaded in a glass petri dish which was mounted inside the desiccator. The desiccator with the aerogels and the fuming gas was constantly inside a fume hood. Periodically, the mass of each sample was recorded by the weight meter, exactly next to the fume hood minimizing the exposure of the aerogels to the environment. The regeneration of the graphene and the graphene-hBN aerogels was performed by using a common electric hair dryer. During the regeneration process, the formed volatile vapour was removed with the assistance of the hood, as reported by Li et al.30.The gas absorption test was conducted in static conditions into a closed glass desiccator with an excess of pollutant, using a saturated vapour stream at room temperature. 100 mL of either formaldehyde  component concentration is calculated and from the peak intensities of C1s, O1s, P2p and N1s the (%) relative atomic ratio is obtained. Both sets of results are shown in Table 33. The C:O ratio for the 50/50 is almost the half of the pure GA which shows that the presence of hBN affects the reduction of the GO.In Fig. 34. The HAs show graphite peak at 2θ = 26° and also a clear peak at 27.3°, which are attributed to the (002) diffraction of hBN12. The position of the Raman peaks for the GO are ~ 1590 cm−1 and 1356 cm−1 corresponding to the G and D phonons, respectively35. The presence of hBN is also evident in the HA from an intense peak at 1366 cm−1 originating from the in-plane E2g phonon mode36. The intensity of the peak of the hBN is large due to the relatively large thickness (~ 2–3 μm) of the platelets.In Fig. −3 for all cases. In fact, this value is a prerequisite for classifying the 3D porous structure as an aerogel12. The structural characteristics of the integration of the rGO with the hBN, such as the attachment and wrapping of the hBN to the rGO, agrees very well with the results reported in other studies12.SEM images for all samples with various mixed ratios are given in Fig. The mechanical properties under compression for the hybrid structures of variable rGO/ hBN content were examined in detail and compared to those of the pure rGO aerogel. In Fig. −3 were tested and a compressive stress of ~ 1.5 kPa was measured at 50% of strain11. Elsewhere, rGO aerogels reinforced with boron nitride nanotubes of total density ~ 16 mg/cm−3, reached stress of ~ 12 kPa at ~ 75% of compressive strain13. We note that the mechanical properties of aerogels are linearly related to the density of the samples38, and the modulus for the GA of the present study agrees well with the analysis of reference37. Thus, the present HAs possess better mechanical performance as compared to reported results for other heterostructures13 since they have similar density or slightly higher, and in our case they reach much higher compressive stresses without failure.In a previous study, similar HAs with a smaller density of ~ 3.6 mg/cm39. The 90/10 hybrid exhibits almost half of this value of ~ 23.3 S/m, and with further increment of the amount of the hBN the conductivities do not vary a lot within the experimental error  and humidity of important artefacts in storage facilities  which is one of the main objectives of the present work.Both GAs and BNAs are highly efficient gas and oil absorbers45. Prior to exposing the samples to the gas/humid environment, care was taken to dry the samples by heating to 200 °C, followed by immediate measurements of their initial weight under dry conditions. The samples were then placed in a desiccator and exposed to saturated gas controlled environment, while their mass weight gain due to absorption was monitored by regular gravimetric measurements until the maximum mass increment was reached. More details can be found in the experimental section. From Fig. We tested the efficiency of the proposed hybrids and the GA for absorption of formaldehyde, hydrochloric acid and acetic acid, which are among the most commonly examined gases, as well the water vapour (humidity) absorption. Formaldehyde, in particular, is considered as a model polar VOC pollutant46. Formaldehyde is physiosorbed on graphene48, and this absorption is weak because of its small binding energy, large binding distance and small charge transfer from formaldehyde to the graphene sheets48. On the other hand, hBN (sponge like) exhibits superb formaldehyde absorption performance due to its high specific surface area and its abundant surface hydroxyls and amines46. Furthermore, the HAs are more hydrophilic compared to the rGO as deduced form the humidity absorption measurements discussed below, which also contribute to the high performance toward gaseous formaldehyde46. Additionally, chemisorption takes place on the hBN layers and contributes to high formaldehyde absorption via Cannizzaro-type disproportionation reactions, during which formaldehyde is converted into less toxic formic acid and methanol46. Another factor that can enhance the formaldehyde absorption is the surface properties of hBN. Hydrogen bonding between formaldehyde and hydroxyl or amine groups is very crucial in the absorption of formaldehyde50, while the formaldehyde molecules and hBN layers show both planar configuration, resulting in lower adsorption resistance46. Finally, formaldehyde has π-bonding between C and O atoms, while hBN also shows large 2D delocalized π-bonded structure. Consequently, π−π bonding interaction can occur between hBN and formaldehyde and this strong interaction enhances the absorption of the latter46.The high absorption of formaldehyde of the HAs can be mainly ascribed to the polarity of the molecules of formaldehyde. It is considered that materials with high specific surface area and a hydrophilic surface can be effective adsorbents for formaldehydeb = 0.29 eV51. When the formaldehyde molecules are adsorbed onto the neat rGO sheets, formaldehyde shows the preference to be located perpendicular to the sheet with H atoms close to the sheet, as shown in Fig. 52. Thus, graphene then becomes a n-type semiconductor, the valence electrons are increased and charge transfer from the electron donor molecules, formaldehyde, to the graphene sheets takes place51.As already mentioned, formaldehyde is known to be weakly physiosorbed on reduced graphene oxide sheets as a consequence of its small binding energy to graphene which is equal to E53. Formaldehyde exhibits larger adsorption energy and net charge transfer when is chemisorbed on doped graphene in comparison to a corresponding undoped graphene sheet. Specifically, for a boron-doped graphene sheet, the adsorption energy (Eads) and charge transfer (Q) are equal to − 0.543 eV and 0.239 e respectively, while the corresponding values for pristine graphene are − 0.137 eV and 0.094 eV, respectively53. This high adsorption energy is a strong indication that chemical bonds are created between the dopants  and O atom of formaldehyde. The reason behind this behaviour is the hybridisation between the dopants  and C atoms, around the two dopant atoms. Especially for boron, an overlap between B-2p and C-2p orbitals, with the energy ranging from − 3.810 to − 2.236 eV is observed53, which proves the appearance of a strong hybridization between B and C atoms around the doping atom. This strong orbital interaction between the p orbitals of B, N, and the C atoms also alters the magnetic properties of such systems53.As the amount of hexagonal boron nitride is gradually increased in the hetero-structured aerogel, the adsorption of formaldehyde increases (from 90/10% wt. to 50/50% wt.). This can be explained due to the strong chemisorption between the molecules of (adsorbed) formaldehyde and the ‘doped’ with hBN, graphene. It has been shown that doping graphene with boron (B) and nitrogen (N) atoms enhances the interaction between the graphene and formaldehyde significantly54. The related mechanism is shown in Fig. For the interaction between the boron nitride platelets and the formaldehyde, Cannizzaro-type disproportionation reaction of the latter has been reported to be dominant56 as can be deduced by the same approximately adsorption rates of all the hybrid aerogels that were examined in HCl, and neat rGO inside formaldehyde. It has been found that especially for a single chlorine atom, the bonding is ionic through the transfer of charge from graphene to chlorine adatom and creates a small local distortion in the underneath planar graphene55. The transfer of a single chlorine adatom on the surface of graphene is achieved almost without barrier. But, the anchoring of a graphene surface with Cl adatoms resulting in several conformations cannot be maintained because of the strong Cl-Cl interaction which in turn facilitates the desorption through the creation of Cl2 molecules.Regarding the adsorption of hydrochloric acid onto the examined pure rGO and hybrid aerogels, a weaker interaction between the HCl molecules and the surface of the prepared materials can be observed, as shown in Fig. 63. For comparison they are listed in the supporting information  was measured to be ~ 97% by the addition of a humidity sensor inside the chamber. Following the same procedure with the gas absorption measurements, the samples were firstly dried at 200° C and then being weighed periodically until they achieved a maximum absorption. As shown in Fig. As already mentioned, we cannot fabricate pure hBN aerogels with this approach, thus we cannot have a direct comparison for this case. The absorption results show that the two materials have different efficiencies depending on the specific vapour. The absorption efficiency is not compromised by mixing of the 2D materials, thus, in order to make as efficient absorbers as possible for a wide range of vapour concentrations, we need to use more than one material. Given the large availability of 2D materials with diverse properties, there is much room for the fabrication of novel highly efficient absorbers beyond the state-of-the-art. Moreover, these hybrids can be exploited in other applications for which electrical and thermal conductivities are required.46. Furthermore, the addition of hBN provides superior thermal conductivity to the HAs12, which make them promising materials for applications at elevated temperatures, further expanding their potential use. The HAs can be used as more efficient VOC absorbers for absorption of multiple compounds, in contrast to the standalone materials which are not efficient for all cases. All the above give the HAs a high degree of multi-functionality which enables their use in a plethora of applications, and, as demonstrated in the main text, the proposed aerogels can be used for protection of artefacts such as paintings in storage facilities in which a high concentration of humidity and VOCs is encountered.In summary, we presented a facile fabrication route for 2D hybrid aerogels comprising of rGO mixed with hBN platelets. The fabrication method is cost effective and scalable compared to high energy demanding methods for the fabrication of pure hBN aerogels, and can be used for mixing other 2D materials with rGO. The resulted HAs are mechanically robust with mechanical properties similar to those of pure GA. The HAs are electrically conductive, despite a decrease that occurs compared to the pure rGO aerogel, which can be useful for applications for which electrical conductivity is required. The most striking result is the very effective absorption capacity of the HAs of formaldehyde and humidity, which is 7–8 times higher compared to the pure GA and at least one order of magnitude higher than a pure hBN aerogelSupplementary Information.