Perovskite-Structured BiFeO₃ Nanoparticles with Abundant Oxygen Vacancies for Selective <i>n</i>‑Butanol Gas Sensing

N-butanol, a standard volatile organic compound (VOC) gas with toxicity and flammability, seriously endangers human life and health. It is imperative to achieve rapid and trace detection of n-butanol. Oxygen vacancies have been proven to be an essential factor for VOC gas adsorption at the surface of metal oxide semiconductor (MOS) gas sensors. In view of the above, BiFeO3 (BFO) nanoparticles with abundant oxygen vacancies were prepared via simple sol–gel and annealing. Crystal structure, morphology, and compositions were systematically analyzed by a series of characterizations (XRD, SEM, HRTEM, EPR, and XPS). The response of the synthesized BFO-2 sensor reached 19.37 to 100 ppm n-butanol with a detection limit of 0.28 ppm at an optimal operating temperature of 280 °C. In addition, BFO-2 also has a fast response time, good stability and repeatability, and favorable selectivity to n-butanol. It is crucial to systematically explore the excellent selectivity of BFO sensors due to their abundant oxygen vacancies and large intrinsic crystal defects. Herein, adjusting the calcination temperature is one constructive strategy to tune the oxygen vacancy, which would prompt the gas sensing performance of BFO sensors to n-butanol

Thermodynamic criteria of the end-of-life silicon wafers refining for closing the recycling loop of photovoltaic panels

The collected end-of-life (EoL) silicon wafers from the discharged photovoltaic (PV) panels are easily contaminated by impurities such as doping elements and attached materials. In this study, the thermodynamic criteria for EoL silicon wafers refining using three most typical metallurgical refining processes: oxidation refining, evaporation refining, and solvent refining were systemically and quantitatively evaluated. A total of 42 elements (Ag, Al, Au, B, Be, Bi, C, Ca, Ce, Co, Cr, Cu, Fe, Ga, Gd, Ge, Hf, In, La, Mg, Mn, Mo, Na, Nb, Ni, Os, P, Pb, Pd, Pt, Re, Ru, Sb, Sn, Ta, Ti, U, V, W, Y, Zn, Zr) that are likely to be contained in the collected EoL silicon-based PV panels were considered. The principal findings are that the removal of aluminum, beryllium, boron, calcium, gadolinium, hafnium, uranium, yttrium, and zirconium into the slag, and removal of antimony, bismuth, carbon, lead, magnesium, phosphorus, silver, sodium, and zinc into vapor phase is possible. Further, solvent refining process using aluminum, copper, and zinc as the solvent metals, among the considered 14 potential ones, was found to be efficient for the EoL silicon wafers refining. Particularly, purification of the phosphorus doped n-type PV panels using solvent metal zinc and purification of the boron doped p-type PV panels using solvent metal aluminum are preferable. The efficiency of metallurgical processes for separating most of the impurity elements was demonstrated, and to promote the recycling efficiency, a comprehensive management and recycling system considering the metallurgical criteria of EoL silicon wafers refining is critical.</p

Vascular Geometry Reconstruction.

<p>(A) Reconstructed 3D patient-specific LAD models. (B) The construction of the non-CT models (C) The patient-specific LAD models (red) and the corresponding non-tortuous artery models (blue).</p

Highly Selective and ppb-Level Butanone Sensors Based on SnO₂/NiO Heterojunction-Modified ZnO Nanosheets with Electron Polarity Transport Properties

Gas sensors require the construction of composites with high reactivity to reduce the detection limit, but this can lead to a broad-spectrum response between the adsorbed oxygen and the target gas, making it difficult to improve selectivity. In this study, the phenomenon of electron polar transport properties of the two-dimensional heterojunction material is first discovered in gas sensing and utilized to greatly improve the selectivity of butanone sensors. Ultra-thin porous ZnO nanosheets modified with SnO2/NiO heterogeneous particles are synthesized to achieve 20 ppb detection limits for butanone with a response of 328 to 100 ppm butanone, which is the lowest known detection limit. The combination of reaction kinetics and liquid chromatography–mass spectrometry reveals a good synergistic catalytic effect of SnO2/NiO heterogeneous particles, which may contribute to the high response and low detection limit of butanone. Finally, the possible mechanism for the generation of electron polar transport phenomenon is analyzed in the two-dimensional heterojunction material. This work provides a novel perspective for achieving both selectivity and detection limits in gas sensors, with universal applicability and application potential

The velocity vectors at the maximal flow rate frames for CT models during rest and exercise conditions.

<p>Time frames were: t = 0.47 s for rest condition and t = 0.35 s for exercise condition (the maximal dilatation condition).</p

The flow rate and downstream perfusion pressure for two cases under resting condition.

<p>The flow rate and downstream perfusion pressure for two cases under resting condition.</p

The flow rate and downstream perfusion pressure for two cases during exercise.

<p>non-CT: non-CT models during exercise condition; CT-M: CT models during the maximal dilatation condition; CT-A: CT models with the auto-regulation effect during exercise condition.</p

The AMDDP for all simulated cases at rest and during exercise.

<p>The AMDDP for all simulated cases at rest and during exercise.</p

Boundary conditions.

<p>(A) The inlet pressure waveform at rest (blue) and during exercise (red). (B) The LV pressure waveform at rest (blue) and during exercise (red). (C) The lumped parameter model.</p

The resistances for all simulated cases at rest and during exercise.

<p>The resistances for all simulated cases at rest and during exercise.</p