High-temperature electrochemical sensors based on stabilized zirconia play an important role in the control of exhaust emissions and the improvement of product quality and productivity. This paper ...gives an overview about high temperature oxygen sensor, auxiliary electrode type sensor, and mixed potential gas sensor. The response theories of a variety of sensors are elucidated. The related measurement ranges and application examples of oxygen sensors are presented. Since air pollution regulations are being reinforced in many countries, the worldwide demand for oxygen sensors is expected to be growing. Without appropriate solid electrolyte, auxiliary electrode type sensors are developed for measuring phosphorus, sulfur, silicon, manganese and chromium in melt and CO2, NOx and SOx in gas. We have described recent advances in improving the sensitivity, selectivity and long-term stability of mixed potential gas sensors which could be obtained by selecting suitable SE materials. This paper also reviews the limiting factors in measurement, the properties of stabilized zirconia and the role of electrode configuration in electrochemical sensors.
•Paper presents a review of electrochemical sensors based on stabilized zirconia.•Limiting factors in measurements are discussed.•Critical work of the state-of-the-art in the electrochemical sensors is presented.•Electrode reaction at the TPB and gas diffusion within electrode are discussed.
As an emerging building unit, carbon dots (CDs) have been igniting the revolutionaries in the fields of optoelectronics, biomedicine, and bioimaging. However, the difficulty of synthesizing CDs in ...aqueous solution with full‐spectrum emission severely hinders further investigation of their emission mechanism and their extensive applications in white light emitting diodes (LEDs). Here, the full‐color‐emission CDs with a unique structure consisting of sp3‐hybridized carbon cores with small domains of partially sp2‐hybridized carbon atoms are reported. First‐principle calculations are initially used to predict that the transformation from sp3 to sp2 hybridization redshifts the emission of CDs. Guided by the theoretical predictions, a simple, convenient, and controllable route to hydrothermally prepare CDs in a single reaction system is developed. The prepared CDs have full‐spectrum emission with an unprecedented two‐photon emission across the whole visible color range. These full‐color‐emission CDs can be further nurtured by slight modifications of the reaction conditions (e.g., temperature, pH) to generate the emission color from blue to red. Finally a flexible LEDs with full‐color emission by using epoxy CDs films is developed, indicating that the strategy affords an industry translational potential over traditional fluorophores.
A novel multi‐color‐emissive carbon dots (CDs) with two‐photon fluorescence are developed in aqueous solution for the first time by slight modifications of the reaction conditions. Theoretical calculations combined with experiments show that the photoluminescence mechanism of the multi‐color‐emissive CDs is the size change and the conversion of sp3 to sp2 hybridization.
Due to the complex core-shell structure and variety of surface functional groups, the photoluminescence (PL) mechanism of carbon dots (CDs) remain unclear. o-Phenylenediamine (oPD), as one of the ...most common precursors for preparing red emissive CDs, has been extensively studied. Interestingly, most of the red emission CDs based on oPD have similar PL emission characteristics. Herein, we prepared six different oPD-based CDs and found that they had almost the same PL emission and absorption spectra after purification. Structural and spectral characterization indicated that they had similar carbon core structures but different surface polymer shells. Furthermore, single-molecule PL spectroscopy confirmed that the multi-modal emission of those CDs originated from the transitions of different vibrational energy levels of the same PL center in the carbon core. In addition, the phenomenon of "spectral splitting" of single-particle CDs was observed at low temperature, which confirmed these oPD-based CDs were unique materials with properties of both organic molecules and quantum dots. Finally, theoretical calculations revealed their potential polymerization mode and carbon core structure. Moreover, we proposed the PL mechanism of red-emitting CDs based on oPD precursors; that is, the carbon core regulates the PL emission, and the polymer shell regulates the PL intensity. Our work resolves the controversy on the PL mechanism of oPD-based red CDs. These findings provide a general guide for the mechanism exploration and structural analysis of other types of CDs.
The study aimed to explore the relationship between miR-9-5p and ESR1, and clarify the underlying functional mechanism in the occurrence and development of hepatocellular carcinoma (HCC). Expression ...data including miRNAs and mRNAs of HCC downloaded from TCGA database were processed for differential analysis, and corresponding clinical data were collected for survival analysis to identify the target miRNA miR-9-5p. Bioinformatics databases were applied for predicting downstream target mRNAs of miR-9-5p. qRT-PCR was used to evaluate expression of miR-9-5p. Western blot was used to detect protein expression of ESR1. MTT, wound healing assay and Transwell assay were used to detect HCC cell proliferation, migration and invasion, respectively. Dual-luciferase reporter gene assay was used to identify the targeting relationship between miR-9-5p and ESR1. Research suggested that miR-9-5p was highly expressed in HCC cells but ESR1 was poorly expressed. Overexpression of miR-9-5p could improve the proliferation, invasion and migration of cells. Dual-luciferase reporter assay showed that ESR1 was the downstream target of miR-9-5p in HCC. Overexpression of miR-9-5p markedly reduced ESR1 mRNA and protein levels in HCC cells, whereas inhibition of miR-9-5p expression produced the contrary results. Silencing ESR1 could noticeably reverse the effect of miR-9-5p knockdown on the proliferation, migration and invasion of HCC cells. As an oncogene, miR-9-5p fostered the proliferation, migration and invasion of HCC cells by targeting and inhibiting ESR1 expression.
The feasibility of producing high-density sintered magnesia with a one-step sintering method was investigated by utilizing finely ground magnesite as raw materials for direct flotation. The mechanism ...of flotation desilication of microfine grain magnesite was investigated by combining microstructure and chemical properties. The results showed that dodecylamine (DDA) has a sorting effect on magnesite reverse flotation desilication. Under the premise of 150 mg/L sodium polyacrylate (PAANa) as an inhibitor and 300 mg/L DDA as a collector, the content and recovery rate of MgO can reach 83.91% and 78.78%, respectively. When sodium oleate (NaOL) was used as a collector, the recovery rate of MgO was only 49.22%; therefore, it is unsuitable for magnesite purification. The flotation effect was affected because MgO particles and SiO2 particles agglomerated in the flotation process. The flotation agent cannot work for a single element but works for the mineral agglomerate. While collecting Si elements, the agglomerated MgO was also brought into the froth layer, making flotation impossible.
Zirconia-based electrolyte is considered to be the most reliable candidate as oxide-ion electrolyte for oxygen sensor, oxygen pump, and solid-oxide fuel cell. The electrical property and stability of ...zirconia-based electrolyte depend strongly on dopant type and concentration. In this review, phase diagrams, electrical properties, and the latest developments of zirconia-based electrolyte with different dopant are discussed. The methods used to increase oxide-ion conductivity and decrease the electronic conductivity of stabilized zirconia are also discussed.
(4YSZ)
(Fe
O
)
and 9 mol% Y
O
stabilized ZrO
(9YSZ) were synthesized by co-precipitation method and their crystalline structure, microstructure, electronic conductivity, total conductivity were ...characterized. A limiting current oxygen sensor was assembled with (4YSZ)
(Fe
O
)
dense diffusion barrier and 9YSZ solid electrolyte by Pt sintered-paste method. Influences of temperature (T), oxygen concentration (x(O
)) and water vapor pressure (p(H
O)) on sensing characteristics of the limiting current oxygen sensor were investigated. The crystalline structure of (4YSZ)
(Fe
O
)
and 9YSZ belong to cubic structure with Formula: see text. The total conductivity of (4YSZ)
(Fe
O
)
is higher than that of 9YSZ and the electronic and total conductivities of the samples meet the linear relationship with 1000/T. The limiting current oxygen sensor exhibits excellent sensing characteristics under test conditions. The effects of T, x(O
) and p(H
O) are as follows: Log(I
·T) depends linearly on 1000/T, I
depends linearly on x(O
) and I
is not significantly dependent on p(H
O).
: Various carbon contents in the MgO-C refractory were studied with respect to the oxidation resistance and the wetting behavior with slag. The bulk density, apparent porosity, cold crushing ...strength, oxidation rate, and mass loss rate of the fired MgO-C refractories with various carbon contents were measured and compared. The wetting and penetration behavior of the cured MgO-C refractory with the molten slag were observed in-situ. The contact angle and the shape parameters of molten slag, including the apparent radius, height, and volume were compared. The results showed that the regenerated MgO effectively restrained the carbon oxidation in the MgO-C refractory, which was more evident at the low carbon content refractory. The contact angle between the MgO-C refractory and the molten slag increased as the carbon content increased. The increased contact angle decreased the penetration of the molten slag.
Currently, there is a strong drive to discover alternative materials that exhibit room‐temperature phosphorescence (RTP) for displays, bioimaging, and data security. Ideally, these materials should ...be nontoxic, cheap, and possess controllable photoluminescent properties. Carbon dots (CDs) possess each of these characteristics, but to date, less attention has been paid to their RTP mechanism. Herein, we synthesized a series of CDs by self‐crosslinking and carbonization of precursor. The resultant CDs were luminescent and exhibited a bright, micro‐second afterglow lifetime. To increase the RTP, a second microwave processing step was used to coat the CDs with polyvinyl alcohol (PVA), polyacrylamide (PAM), or tetraethyl orthosilicate (TEOS), producing CDs@PVA, CDs@PAM, and CDs@TEOS composites. The core–shell structure acted to enhance crosslinking at the surface of the CDs to boost the RTP, creating abundant energy levels for intersystem crossover. In situ X‐ray photoelectron spectroscopy verified electron transfer during luminescence. Finally, we present a design rule that can be used to tune the quantum yields and RTP lifetime of CDs, based on the effective stabilization of triplet excited states through the extent and strength of cross‐linking. This simple strategy provides a flexible route for guiding the further development of CDs with tailored RTP properties for various applications.
We propose a method to enhance phosphorescence emission by crosslinking. By controlling the degree and strength of crosslinking, the phosphorescence emission of carbon dots (CDs) can be tunable, and the CDs with the highest degree of crosslinking achieve a quantum yield of 55.49 and a lifetime of 750 ms.
Using the co-precipitation method to synthesize (CeO2)0.95(Y2O3)0.05 (YDC) and solidreaction method to synthesize (CeO2)0.75(ZrO2)0.25 (ZDC), and the crystal structure, micro-structure,total ...conductivity and electronic conductivity of the two materials was measured with X-raydiffraction (XRD), scanning electron microscope (SEM), DC van der Pauw and Hebb-Wagnermethods. A limiting current oxygen sensor was prepared with YDC solid electrolyte and a ZDCdense diffusion barrier layer by employing platinum pasting bonding. Sensing characteristics ofthe sensor were obtained at different conditions, including temperature (T), oxygen concentration(x(O2)) and water vapor pressure (p(H2O)), and the influence of various conditions on sensingperformance was studied. The long-term stability of the sensor was measured in an oxygen concentration of 1.2% and at a temperature of 800 °C for 120 h. XRD results show that the phase structure of both YDC and ZDC belongs to the cubic phase. SEM results show that both YDC and ZDC layers are dense layers, which are then qualified to be the composition materials of the sensor. The limiting current (IL) of the sensor is obtained and the sensor exhibits good sensing characteristics to satisfy the Knudsen model. Log(IL·T) depends linearly on 1000/T with a squared correlation coefficient (R2) of 0.9904; IL depends linearly on x(O2) with an R2 of 0.9726; and sensing characteristics are not affected by p(H2O). It was found that the oxygen sensor has good long-term stability.
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