Detecting acetone is vital for both environmental safety and human health. However, many existing detection methods suffer from bulky equipment, complex processes, and limited efficiency. Metal oxide ...semiconductor (MOS) based gas sensors, particularly WO3, have gained attention due to their portability, cost-effectiveness, and sensitivity. In this study, we successfully synthesize a series of 1D hierarchical core-shell metal oxide semiconductor MOS@WO3 structures (MOS: TiO2, WO3, and SnO2) via a hydrothermal method employing self-assembly. Notably, the TiO2@WO3 sensor exhibits an exceptional response value (Ra/Rg = 23.6) at a concentration of 50 ppm for acetone. It also demonstrates a rapid response recovery time (12/35.5 s) and a remarkably low detection limit, as low as 10 ppb (Ra/Rg = 1.29). This exceptional sensing performance is attributed to the large specific surface area, abundant oxygen vacancy, narrow bandgap, additional depletion layer of the heterostructure, and the main conduction channel in the shell of TiO2@WO3 NCs. This study not only promotes acetone sensor development but also contributes to innovative layered core-shell material fabrication methodologies.
•One-dimensional hierarchical core-shell MOS@WO3 nanocomposites are prepared.•TiO2@WO3 nanocomposites show excellent performance in detecting acetone.•The sensing properties are attributed to hierarchical and core-shell heterostructure.
•Thermal treatment of mallee wood cylinders at 150–260°C was studied.•Aromatic ring structures were formed at the temperature as low as 150°C.•The abundance of aromatics trapped in resultant chars ...varied with the location of cylinder.•The fused aromatic ring structures has polar functionalities.
Aromatics are important components in the tars from biomass gasification or in bio-oil from pyrolysis. This study investigated the formation of polycyclic aromatics during the thermal treatment of mallee wood at low temperature. The formation of tar was negligible below 200°C but became significant above 230°C. At the same time, the abundance of aromatics also became significant above 230°C. In addition, it was found that some aromatics were formed even at temperatures as low as 150°C. These aromatics were trapped in the resultant chars but could be extracted with solvents (i.e. methanol/chloroform). The abundance of trapped aromatics was different between the outer surface and the centre of the char (cylinder shape). FT-IR and UV-fluorescence analysis revealed that the aromatics contained polar functionalities (e.g. carbonyl groups) on the benzene rings. Some unsaturated hydroxyl aldehyde/ketone intermediates were formed in parallel with the aromatics.
Strain engineering is a powerful tool that can modulate semiconductor device performance. Here, we demonstrate that the bandgap of thin film (∼40 nm) black phosphorus (bP) can be continuously tuned ...from 2.9 to 3.9 μm by applying an in-plane uniaxial strain, as evidenced by mid-infrared photoluminescence (PL) spectroscopy. The deduced bandgap strain coefficients are ∼103 meV %–1, which coincide with those obtained in few-layer bP. On the basis of first-principles calculations, the origin of the uniaxial tensile strain-induced PL enhancement is suggested to be due to the increase in both the effective mass ratio (m e */m h *) and the bandgap, leading to the increment of the radiative efficiency. Moreover, the mid-infrared PL emission remains perfectly linear-polarized along the armchair direction regardless of tensile or compressive strain. The highly tunable bandgap of bP in the mid-infrared regime opens up opportunities for the realization of mid-infrared light-emitting diodes and lasers using layered materials.
Abstract Exploration of molecular catalysts with the atomic‐level tunability of molecular structures offers promising avenues for developing high‐performance catalysts for the electrochemical ...co‐reduction reaction of carbon dioxide (CO 2 ) and nitrite (NO 2 − ) into value‐added urea. In this work, a binuclear cobalt phthalocyanine (biCoPc) catalyst is prepared through chemical synthesis and applied as a C─N coupling catalyst toward urea. Achieving a remarkable Faradaic efficiency of 47.4% for urea production at –0.5 V versus reversible hydrogen electrode (RHE), this biCoPc outperforms many known molecular catalysts in this specific application. Its unique planar macromolecular structure and the increased valence state of cobalt promote the adsorption of nitrogenous and carbonaceous species, a critical factor in facilitating the multi‐electron C─N coupling. Combining highly sensitive in situ attenuated total reflection surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRAS) with density functional theory (DFT) calculations, the linear adsorbed CO (CO L ) and bridge adsorbed CO (CO B ) is captured on biCoPc catalyst during the co‐reduction reaction. CO B , a pivotal intermediate in the co‐reduction from CO 2 and nitrite to urea, is evidenced to be labile and may be attacked by nitrite, promoting urea production. This work demonstrates the importance of designing molecular catalysts for efficient co‐reduction of CO 2 and nitrite to urea.
•We construct a fine-grained classification dataset of wet Age-related macular degeneration (AMD).•A knowledge-driven deep learning model, KFWC, is proposed to improve accuracy in fine-grained ...disease classification with insufficient data.•KFWC can detect 10 signs of lesions on medical images and can diagnose two subtypes of wet-AMD.•Multiple experiments demonstrate the effectiveness and interpretability of the proposed KFWC.
Automated diagnosis using deep neural networks can help ophthalmologists detect the blinding eye disease wet Age-related Macular Degeneration (AMD). Wet-AMD has two similar subtypes, Neovascular AMD and Polypoidal Choroidal Vasculopathy (PCV). However, due to the difficulty in data collection and the similarity between images, most studies have only achieved the coarse-grained classification of wet-AMD rather than a fine-grained one of wet-AMD subtypes. Therefore, designing and building a deep learning model to diagnose neovascular AMD and PCV is a great challenge.
To solve this issue, in this paper, we propose a Knowledge-driven Fine-grained Wet-AMD Classification Model (KFWC) to enhance the model's accuracy in the fine-grained disease classification with insufficient data. We innovatively introduced a two-stage method. In the first stage, we present prior knowledge of 10 lesion signs through pre-training; in the second stage, the model implements the classification task with the help of human knowledge. With the pre-training of priori knowledge of 10 lesion signs from input images, KFWC locates the powerful image features in the fine-grained disease classification task and therefore achieves better classification.
To demonstrate the effectiveness of KFWC, we conduct a series of experiments on a clinical dataset collected in cooperation with a Grade III Level A ophthalmology hospital in China. The AUC score of KFWC reaches 99.71%, with 6.69% over the best baseline and 4.14% over ophthalmologists. KFWC can also provide good interpretability and effectively alleviate the pressure of data collection and annotation in the field of fine-grained disease classification for wet-AMD.
The model proposed in this paper effectively solves the difficulties of small data volume and high image similarity in the wet-AMD fine-grained classification task through a knowledge-driven approach. Besides, this method effectively relieves the pressure of data collection and annotation in the field of fine-grained classification. In the diagnosis of wet-AMD, KFWC is superior to previous work and human ophthalmologists.
Furan, an important product from catalytic pyrolysis of biomass, has the potential to be further converted into value-added chemicals or biofuels. This study investigated the conversion of furan into ...benzofuran over a Broensted acid catalyst (Amberlyst 70) at 140-190 degree C in various solvents. With water as the solvent, furan could barely make its way to benzofuran as its polymerization dominated. With methanol as the solvent, the polymerization of furan was suppressed and benzofuran formation was enhanced substantially. This is because in methanol, the reactive intermediates (i.e., aldehydes) were stabilized and their involvement in polymerization reactions was suppressed. Other alcohols showed similar effects on suppressing polymerization. In dimethyl sulfoxide (DMSO), the polymerization of furan was also effectively suppressed. However, furan was not converted to benzofuran but to levulinic acid via a distinct reaction route.
This study investigated the effects of thermal pretreatment and ex-situ grinding on the production of bio-oil and biochar from the pyrolysis of mallee wood cylinders in a fluidised-bed reactor. The ...wood cylinders were firstly pretreated at 150–380°C and were then crushed into small particles before further pyrolysis at 500°C. Thermal pretreatment alone for wood cylinders could not promote the bio-oil yield. Combined thermal pretreatment at low temperatures and subsequent grinding facilitated the formation of bio-oil and minimised the formation of biochar. This is because the thermal pretreatment and grinding partially destroyed the cell wall structure and improved the mass transfer of volatiles exiting from the particles during the subsequent pyrolysis. However, if the pretreatment temperature was above 260°C, the biochar yields increased due to the cross-linking and charring reactions. These charring reactions compromised the beneficial effects of grinding, leading to decreases in the formation of bio-oil. The balance between thermal pretreatment and grinding needed to be delicately managed to maximise the formation of bio-oil. The pretreatment temperature would significantly affect the composition of bio-oil from the ex-situ grinding pyrolysis. The controlled pretreatment temperature could somewhat “activate” lignin or cause cross-linked bonds in biomass which was responsible for the formation of aromatics.
•Effects of thermal treatment and grinding on pyrolysis of wood cylinders were studied.•The bio-oil yield was not promoted by the thermal treatment of wood cylinders.•Low temperature treatment with ex-situ grinding greatly promoted bio-oil formation.•High temperature treatment compromised beneficial effects of grinding on bio-oil yield.•Balance between pretreatment and grinding was responsible for the bio-oil formation.
•Mineral acid and solid acid catalyst affect the esterification of bio-oil in varied ways.•Conversion of sugars and phenolics are sensitive to the dispersion of H+.•Etherification reactions are ...sensitive to concentration of H+.
The different catalytic behaviour of solid acid catalyst and mineral acid catalyst towards the acid-treatment of bio-oil was investigated. The hydrogen ions in the mineral acid catalyst such as sulfuric acid homogeneously dispersed in the reaction medium made the conversion of main components of bio-oil including carboxylic acids, sugars and phenolics more efficient. In comparison, there was a steric hindrance for these components of bio-oil to access the hydrogen located in the local surface of the solid acid catalyst such as Amberlyst 70. This negatively affected their conversions during the acid-treatment. However, the inhomogeneous distribution of hydrogen ions from Amberlyst 70 in the reaction medium created high concentration of hydrogen ions in the local vicinity of the solid catalyst surface of the catalyst, which is found to be crucial for the occurrence of the etherification reactions. Understanding how the dispersion of hydrogen ions of catalyst affect the esterification of bio-oil can provide useful information for the development of the effective catalysts for upgrading of bio-oil.
•Aromatics in bio-oil behave differently in water and methanol during the thermal treatment.•GC–MS results indicated the different reaction behaviour of mono-phenolics in bio-oil.•Acetic acid and ...formic acid have negligible effect on the behaviour of aromatics.•Amberlyst 70 with strong acidity can exert strong effects on the behaviour of aromatics.
The main components in bio-oil behave differently during the thermal treatment in water or in methanol. Water cannot stabilize the aromatics in bio-oil. Consumption of the aromatics with mono-ring and two fused benzene rings and the formation of the aromatics with three or more fused benzene ring aromatics were observed during the thermal treatment in water. In methanol, the fluorescence intensities of the mono-ring, the aromatics with the two fused ring structures and three-ring aromatics increased. Methanol could stabilize the aromatics and retain them in the reaction medium. The conversion of mono-ring phenolics in thermal treatment of bio-oil in water and their formation in methanol was further confirmed with GC–MS measurement. In addition, it was found that the effects of acetic acid and formic acid on the conversion of the aromatics in bio-oil were negligible. This was probably due to the relative weak acidities of acetic acid and formic acid or the presence of the internal heavy carboxylic acids in bio-oil. However, the conversion of the aromatics in bio-oil was significantly promoted by the strong acids such as Amberlyst 70.
Structural changes in partially gasified char during low-temperature gasification in air were investigated using Fourier transform infrared/Raman and X-ray photoelectron spectroscopies. Two kinds of ...chars prepared from the gasification of mallee wood in 15% H2O–Ar at 600 and 900 °C were gasified in air at 375 °C in a thermogravimetric analyzer, separately. The breakage of large aromatic ring systems, the consumption of cross-linking structures, and the formation of dangling structures indicated the destruction of the aromatic ring systems of char with the progress of gasification in air. In addition, the oxidation of char was very significant at the initial stage (char conversion of <10%) of gasification in air, which was mainly due to the newly formed aromatic C–O structures. The newly formed aromatic C–O structure was also mainly responsible for the continuously increased total oxygen content, the total Raman intensity, and the total infrared (IR) intensity of char with the progress of gasification in air. Moreover, because of the different structural stabilities between the char prepared at 600 and 900°C, two kinds of aromatic C–O structures were formed during gasification in air. Some could greatly enhance the Raman scattering ability, while some could promote the IR absorption of the char.
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