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Diatom testing is considered a useful method for providing supportive evidence for the diagnosis of drowning in forensic pathology. However, various factors remain controversial for recognizing diatoms, such as being time-consuming and laborious and influencing the consistency of the results. Given the absence of precise and well-defined studies on this subject, this study aimed to determine the relationship between the ability to identify diatoms and researchers with different technical backgrounds. A total of 55 samples from 18 cases, including water, lungs, liver, and kidneys, were treated using the microwave digestion-vacuum filtration-automated scanning electron microscopy (MD-VF-Auto SEM), which was used to compare diatom analyses among three groups of well-trained forensic pathologists (FPs), trained junior employees (JEs), and new trainees (TEs). In addition to achieving similar accuracy of positive findings from drowning cases, counting efficiency was evaluated based on taxonomy records and counting time after viewing more than 5500 diatom images. In contrast to the higher counting efficiency of the JE group than that of the TE group, we observed a statistically significant difference (p < 0.05) in the diatom classification between these two groups. Based on our experiments, an efficient analysis for automatically identifying and classifying diatoms is urgently required. •Particular experimental data deliberated on time-consuming and laborious diatom analysis.•This research provided new evidence for the relationship on the ability of different forensic experts in diatoms test.•New index applied to assess counting proficiency contributed to reveal the difference from trainees in diatom analysis.•Special training necessarily guarantees accurate identification of diatom and drowning diagnosis.

Resource reutilization of industrial waste mud has encountered challenges due to its high water content, enhanced fluidity, and inherent difficulty in segregating mud and water phases. The author first screened out efficient flocculants through flocculation dehydration tests and then adopted the technology of vacuum filtration combined with electroosmosis dehydration to conduct deep dehydration of waste mud. Among them, the independently designed vacuum filtration electroosmosis system effectively solves the problems of easy clogging and bending of the traditional system. On this basis, geopolymer fluid solidified soil was prepared using dehydrated mud, furnace slag, and fly ash as raw materials, and the influencing factors of its long-term service performance were studied. It was confirmed that the efficient treatment capacity of the combined dehydration technology for industrial waste mud, and the geopolymer fluid solidified soil prepared from dehydrated mud has engineering application potential. This research provides a reference for the resource utilization of industrial waste mud.

Porous electrode composite materials with a large surface area and suitable pore size, as well as a short diffusion distance of electrolyte ions in the pore channels, are greatly desired for supercapacitor electrodes. Porous silicon composite zinc oxide nanoparticles with a high cycling performance and stability have been prepared by vacuum filtration, combined with homogenizing and hydrothermal methods. The composite material has a 3.9 mF/g specific capacitance, which is an increase of 40 times when compared to pure porous silicon. The results show that the composite materials can effectively passivate the porous silicon surface, improving the porous silicon capacitor's characteristics and stability. This investigation is helpful in understanding the surface modification of porous silicon, and also indicates a potential method for designing porous electrode composite materials based on porous silicon and zinc oxide nanoparticles.The vacuum filtration was chosen to prepare porous silicon composite ZnO nanoparticles materials. It shows that ZnO adheres to the surface of the porous silicon and the inside of the pore walls more uniformly. The specific capacitance of the composite material is 3.9 mF/g, which is 40 times higher than that of pure porous silicon. The modified electrode not only has improved capacitance characteristics but also has good stability. Testing the impedance of the electrode shows that the modified electrode resistance has been improved to a certain extent, while the surface stability and the charge and discharge performance of the composite electrode have been greatly improved. Experiments showed that the use of ZnO can effectively improve the electrical properties of porous silicon, which provides ideas and experimental references for further expanding the application fields of porous silicon.

Graphene aerogel (GA) is widely used in electronic devices owing to its light weight, elasticity, and excellent thermal conductivity. GA has been prepared using various methods. However, the preparation process is complex and the thickness is hard to control, which limits its application. There is an urgent need for a new and simple method to fabricate graphene aerogel. Herein, we describe a novel strategy for fabricating GA via a vacuum filtration–ice template freeze-drying method. The stability of graphene oxide slurry (GOS) was changed by using hydrochloric acid (HCl, 0.12 mol/L), and then GA was quickly obtained by vacuum filtration–ice template freeze drying and graphitization. The obtained GA reveals a symmetrical hyperbolic structure in the vertical direction, giving it excellent thermal and electrical conductivity and good compression performance. The electrical conductivity is up to 14.87 S/cm and the thermal conductivity is 1.29 W m−1 K−1 when the density is 36 mg cm−3. The pressure only needs 0.013 MPa when the strain of GA is 50%. GA has considerable potential for the application of supercapacitors owing to the high conductivity and low density.

Graphene-based materials can have well-defined nanometer pores and can exhibit low frictional water flow inside them, making their properties of interest for filtration and separation. We investigate permeation through micrometer-thick laminates prepared by means of vacuum filtration of graphene oxide suspensions. The laminates are vacuum-tight in the dry state but, if immersed in water, act as molecular sieves, blocking all solutes with hydrated radii larger than 4.5 angstroms. Smaller ions permeate through the membranes at rates thousands of times faster than what is expected for simple diffusion. We believe that this behavior is caused by a network of nanocapillaries that open up in the hydrated state and accept only species that fit in. The anomalously fast permeation is attributed to a capillary-like high pressure acting on ions inside graphene capillaries.

We report a facile and cost-effective approach to develop self-standing reduced Graphene Oxide (rGO) film based optical sensor and its low-temperature performance analysis where midgap defect states play a key role in tuning the crucial sensor parameters. Graphite oxide (GO) is produced by modified Hummers’ method and reduced thermally at 250 °C for 1 h in Argon atmosphere to obtain rGO. Self-standing rGO film is prepared via vacuum filtration. The developed film is characterized by HRTEM, FESEM, Raman, and XRD techniques. The developed sensor exhibits highest sensitivity towards 635 nm illumination wavelength, irrespective of the operating temperature. For a given excitation wavelength, photoresponse study at low temperature (123K–303K) reveals inverse relationship between sensitivity and operating temperature. Highest sensitivity of 49.2% is obtained at 123 K for 635 nm laser at power density of 1.4 mW/mm 2 . Unlike sensitivity, response- and recovery-time demonstrate directly proportional dependence with operating temperature. Power dependent studies establish linear relation between power-density and sensitivity, and a safe limit beyond which sample heating prolongs the recovery time. Wavelength-dependent studies shows that proposed sensor can efficiently operate from visible to near NIR region. To the best of our knowledge such rGO based optical sensor performance at low temperature had not been reported earlier.

Microbial fuel cells (MFCs) are expected to be the next green energy systems, which can harvest chemical energy existing in domestic waste. In this research, a two-chambered microbial fuel cell (MFC) was developed. On the anode side, an activated carbon-based electrode with biofilms of yeast cells was used as the anode. On the cathode side, potassium ferricyanide was used as catholyte, and buckypaper (BP) was used as the cathode electrode. Many researchers made BP by the chemical vapor deposition method, which is high-cost. In this research, the vacuum filtration method was used to reduce the fabrication cost of BP. The power density of the MFCs using different cathode materials was compared: (1) 2.8 µW/cm2 of carbon sheet, (2) 3.2 µW/cm2 of carbon sheet-coated carbon nanotubes (CNTs) and (3) 4.3 µW/cm2 of two-layer BP. Based on the experimental results, the surface area of BP might be much larger than that of the carbon sheet-coated CNTs.

HighlightsA flexible and lightweight microwave absorber was prepared by a vacuum filtration method.The remarkable microwave absorbency makes the absorber paper attractive in wireless wearable electronics field.Developing a flexible, lightweight and effective electromagnetic (EM) absorber remains challenging despite being on increasing demand as more wearable devices and portable electronics are commercialized. Herein, we report a flexible and lightweight hybrid paper by a facile vacuum-filtration-induced self-assembly process, in which cotton-derived carbon fibers serve as flexible skeletons, compactly surrounded by other microwave-attenuating components (reduced graphene oxide and Fe3O4@C nanowires). Owing to its unique architecture and synergy of the three components, the as-prepared hybrid paper exhibits flexible and lightweight features as well as superb microwave absorption performance. Maximum absorption intensity with reflection loss as low as − 63 dB can be achieved, and its broadest frequency absorption bandwidth of 5.8 GHz almost covers the entire Ku band. Such a hybrid paper is promising to cope with ever-increasing EM interference. The work also paves the way to develop low-cost and flexible EM wave absorber from biomass through a facile method.

The one-dimensional character of electrons, phonons and excitons in individual single-walled carbon nanotubes leads to extremely anisotropic electronic, thermal and optical properties. However, despite significant efforts to develop ways to produce large-scale architectures of aligned nanotubes, macroscopic manifestations of such properties remain limited. Here, we show that large (>cm 2 ) monodomain films of aligned single-walled carbon nanotubes can be prepared using slow vacuum filtration. The produced films are globally aligned within ±1.5° (a nematic order parameter of ∼1) and are highly packed, containing 1 × 10 6 nanotubes in a cross-sectional area of 1 μm 2 . The method works for nanotubes synthesized by various methods, and film thickness is controllable from a few nanometres to ∼100 nm. We use the approach to create ideal polarizers in the terahertz frequency range and, by combining the method with recently developed sorting techniques, highly aligned and chirality-enriched nanotube thin-film devices. Semiconductor-enriched devices exhibit polarized light emission and polarization-dependent photocurrent, as well as anisotropic conductivities and transistor action with high on/off ratios. Large films of aligned and closely packed single-walled carbon nanotubes can be prepared through slow vacuum filtration, and used to create terahertz polarizers, thin-film transistors, polarized light emission devices, and polarization-sensitive detectors.

Creating artificial matter with controllable chirality in a simple and scalable manner brings new opportunities to diverse areas. Here we show two such methods based on controlled vacuum filtration - twist stacking and mechanical rotation - for fabricating wafer-scale chiral architectures of ordered carbon nanotubes (CNTs) with tunable and large circular dichroism (CD). By controlling the stacking angle and handedness in the twist-stacking approach, we maximize the CD response and achieve a high deep-ultraviolet ellipticity of 40 ± 1 mdeg nm −1 . Our theoretical simulations using the transfer matrix method reproduce the experimentally observed CD spectra and further predict that an optimized film of twist-stacked CNTs can exhibit an ellipticity as high as 150 mdeg nm −1 , corresponding to a g factor of 0.22. Furthermore, the mechanical rotation method not only accelerates the fabrication of twisted structures but also produces both chiralities simultaneously in a single sample, in a single run, and in a controllable manner. The created wafer-scale objects represent an alternative type of synthetic chiral matter consisting of ordered quantum wires whose macroscopic properties are governed by nanoscopic electronic signatures and can be used to explore chiral phenomena and develop chiral photonic and optoelectronic devices. Methods for generating macroscopic chiral matter struggle with limited scalability. Here, the authors show two vacuum filtration methods - twist stacking and mechanical rotation - to align carbon nanotubes into chiral structures at wafer scale with tunable circular dichroism.