SiO2 Matrix Research Articles

Efficient Thermal Management with Selective Metamaterial Absorber for Boosting Photothermal CO2 Hydrogenation under Sunlight.

Photothermal catalytic CO2 hydrogenation is a prospective strategy to simultaneously reduce CO2 emission and generate value-added fuels. However, the demand of extremely intense light hinders its development in practical applications. Herein, this work reports the novel design of Ni-based selective metamaterial absorber and employs it as the photothermal catalyst for CO2 hydrogenation. The selective absorption property reduces the heat loss caused by radiation while possessing effectively solar absorption, thus substantially increasing local photothermal temperature. Notably, the enhancement of local electric field by plasmon resonance promotes the adsorption and activation of reactants. Moreover, benefiting from the ingenious morphology that Ni nanoparticles (NPs)are encapsulated by SiO2 matrix through co-sputtering, the greatly improved dispersion of Ni NPs enables enhancing the contact with reaction gas and preventing the agglomeration. Consequently, the catalyst exhibits an unprecedented CO2 conversion rate of 516.9mmol gcat -1 h-1 under 0.8W cm-2 irradiation, with near 90% CO selectivity and high stability. Significantly, this designed photothermal catalyst demonstrates the great potential in practical applications under sunlight. This work provides new sights for designing high-performance photothermal catalysts by thermal management.

Enhancing SiGeSn nanocrystals SWIR photosensing by high passivation in nanocrystalline HfO2 matrix

SiGeSn nanocrystals (NCs) in oxides are of considerable interest for photo-effect applications due to the fine-tuning of the optical bandgap by quantum confinement in NCs. We present a detailed study regarding the silicon germanium tin (SiGeSn) NCs embedded in a nanocrystalline hafnium oxide (HfO2) matrix fabricated by using magnetron co-sputtering deposition at room temperature and rapid thermal annealing (RTA). The NCs were formed at temperatures in the range of 500–800 °C. RTA was performed to obtain SiGeSn NCs with surfaces passivated by the embedding HfO2 matrix. The formation of NCs and β-Sn segregation were discussed in relation to the deposition and processing conditions by employing HRTEM, XRD and Raman spectroscopy studies. The spectral photosensitivity exhibited up to 2000 nm in short-wavelength infrared (SWIR) depending on the Sn composition was obtained. Comparing to similar results on GeSn NCs in SiO2 matrix, the addition of Si offers a better thermal stability of SiGeSn NCs, while the use of HfO2 matrix results in better passivation of NCs increasing the SWIR photosensitivity at room temperature. These results suggest that SiGeSn NCs embedded in an HfO2 matrix are a promising material for SWIR optoelectronic devices.

Microstructure analysis of quartz fiber reinforced SiO2 matrix composites by X-ray computed tomography

This paper presents the microstructure of quartz fiber reinforced SiO2 matrix (SiO2f/SiO2) wave-transparent composites characterized by X-ray computed tomography (XCT) and the impregnation of silica sol by conducting permeability and pore network model analyses. Results show that in 2.5D woven structural preform silica gel mainly flowed along the extension direction of weft yarns during impregnation, and the permeability rate in this direction reached 368.49μm2. Attributing to the large pore size, large throat radius and good pore connectivity, impregnation of this preform was more uniform, resulting in a small final porosity of the composite (2.32%). Comparatively speaking, in stitched structural preform silica sol flowed primarily between the layers of fiber cloths, achieving a maximum permeability rate of 36.47μm2, but along the direction of stitching fiber yarns permeability rate was only 5.23μm2. Small throat radius and pore size of fiber preform led to poor impregnation effect and a total porosity of 11.85%. Preform structure plays a crucial role in the densification process of SiO2f/SiO2 composites prepared by sol-gel method.

Nanoscale dielectric properties of TiO2 in SiO2 nanocomposite deposited by hybrid PECVD method

In this paper, nanocomposites (TiO2 in SiO2) are produced by an advanced hybrid aerosol-PECVD method based on direct liquid injection of a non-commercial colloidal solution in an O2 / hexamethyldisiloxane (HMDSO) low-pressure plasma. Dielectric properties are investigated at nanoscale using techniques derived from Atomic Force Microcopy in terms of relative dielectric permittivity, charge injection and transport. Results show that a concentration in TiO2 up to 14% by volume makes it possible to increase the relative dielectric permittivity up to 4.8 while maintaining the insulating properties of the silica matrix. For a TiO2 concentration in the range 15%–37% by volume, the relative dielectric permittivity increases (up to 11 for 37% TiO2 by volume) and only few agglomerated nanoparticles lowering the insulating properties are observed. For TiO2 concentration above 40% by volume, the relative dielectric permittivity still increases but the quantity of agglomerated nanoparticles is very high, which greatly increases the charge transport dynamic and degrades the insulating properties. Finally, 37% of TiO2 by volume in the SiO2 matrix appears to be the best compromise, between high dielectric permittivity and low leakage current for the MIM applications aimed.

Enhancing the dielectric and thermal properties of polytetrafluoroethylene-based composites through designing and constructing a novel interfacial structure

Polytetrafluoroethylene (PTFE) is widely used as a fundamental core material for high-frequency and high-speed signal transmission fields due to its excellent dielectric properties. However, the high coefficient of thermal expansion (CTE) characteristic of PTFE severely limits its practical application. The CTE of PTFE can be reduced by filling with SiO2, which is always accompanied by a rapid deterioration of dielectric properties due to the poor interfacial compatibility between SiO2 and PTFE matrix. In this paper, the challenge of synergistic regulation of dielectric and CTE properties for PTFE-based composites is overcome by constructing an interfacial structure with physical interactions. Micro-mesoporous SiO2 (mSiO2) is prepared and introduced as a filler, compared with smooth surface SiO2 (sSiO2), the presence of micro-mesoporous in mSiO2 allows PTFE molecular chains to be adsorbed on the surface or in the pore channels of mSiO2, which improves the interfacial combination of the mSiO2/PTFE composites through the physical interaction between mSiO2 and PTFE. The results show that mSiO2/PTFE composite exhibits a lower CTE (58 ppm °C−1) while maintaining a lower dielectric constant (εr, 2.29, 30 GHz) with dielectric loss (tan δ, 2.31 × 10−3, 30 GHz) at a filler addition of 30 vol%, as compared with that of the sSiO2/PTFE composites. This work provides a new strategy for fabricating PTFE-based composites with low CTE as well as low εr and tan δ.

Electrically induced direct to indirect exciton transition in CdTe/CdMnTe concentric double quantum ring rooted in SiO2 matrix

Effect of electric field and ring dimension on the localization of direct and indirect exciton formed inside a CdTe/CdMnTe Concentric Double Quantum Ring (CDQR) has been studied using variational technique. The whole double ring structure is embedded inside a SiO2 matrix to enhance exciton localization. Electric field applied along the axial (z) axis tilts the band structure which promotes the carrier localization more in the edges than in the center of the ring. Thus, the stronger electric field gives a triangular confinement to the carrier in the edges which enhances the carrier stability. Along with the effect of electric field the ring dimension which determines the stability of the exciton retains has been estimated through the mean square distance. The effect of the location of the constituent carriers on the excitonic stability and the efficient carrier transfer from inner ring to outer ring has been calculated for both symmetric and asymmetric ring dimensions. Height of the ring has been varied to understand its effect on the localization of both direct and indirect exciton.

Redistribution of dopants between amorphous and crystalline phases in ZrO2–SiO2 nanoceramics

AbstractExtensive efforts have been devoted to investigate the distribution of dopants in ceramics. However, one critical question remained barely explored, which is the redistribution of dopants between amorphous and crystalline phases during fast sintering of ceramics. Here we address this gap by observing the redistribution of five selected dopants (Y, Ce, Yb, Hf, and Ta) in ZrO2–SiO2 nanoceramics during sintering. We designed two groups of experiments: In group one, dual‐phase amorphous particles were sintered with multicomponent crystalline ones. The former particles were ZrO2–SiO2 glass, whereas the latter ones consisted of ZrO2 solid‐solution nanocrystallites (SSNCs) embedded in an oxide glass containing Zr, Si, Y, Ce, Hf, Yb, and Ta. In group two, dual‐phase crystalline particles were sintered with multicomponent amorphous ones. The former particles were composed of ZrO2 nanocrystallites (NCs) embedded in an amorphous SiO2 matrix, whereas the latter ones were oxide glass containing Zr, Si, Y, Ce, Hf, Yb, and Ta. Redistribution of the dopants from the glass to ZrO2 NCs occurred in the two groups, that is, the five dopants migrated from the glass matrix into the ZrO2 NCs, forming ZrO2 SSNCs. The redistribution of the dopants not only increased the configuration entropy of the ZrO2 NCs but also benefited the network structure integrity of SiO2 glass. The dopant redistribution process was driven by the minimization of the studied material's free energy. The reported results are important for understanding the redistribution behaviors of dopants and are expected to provide new insights to design new ceramics via the multielement co‐doping strategy.

Structural Si3N4-SiO2 glass ceramics with bioactive and anti-bacterial properties

Silicon nitride-based bioceramics have been investigated for biomedical applications due to their good thermo-mechanical, tribological and antibacterial properties. However, biological properties, such as bioactivity that promotes the interaction with tissue, are also important. Silicon dioxide has been found to promote bioactivity. With the aim of combining both advantages, a new Si3N4-SiO2 glass ceramic was developed. Three different compositions were synthesized and sintered by spark plasma sintering. The results showed that β-Si3N4 crystalline is well distributed in the SiO2 matrix. 70SiN samples exhibited the highest mechanical properties with a flexural strength of 452 ± 33 MPa and a toughness of 6.4 ± 0.5 MPa∙m1/2. 50SiN samples exhibited the best bacteriostatic effect due to the synergistic effect of surface chemistry and topography. Apatite was observed on the surfaces of all groups. This study shows that the newly developed Si3N4-SiO2 glass ceramics exhibit promising mechanical and biological properties for biomedical applications.

Metal oxide hybridization enhances room temperature phosphorescence of carbon dots-SiO2 matrix for information encryption and anti-counterfeiting.

Room temperature phosphorescent (RTP) carbon dot (CD) materials have been widely used in various fields, but it is difficult to achieve a long lifetime, high stability and easy synthesis. In particular, realizing the phosphorescence emission of CDs using a metal oxide (MO) matrix is a challenge. Here, solid gels are synthesized via in situ hydrolysis, and then RTP CDs are synthesized based on a SiO2 matrix (CDs@SiO2) and hybridized with a MO matrix (CDs@SiO2-MO) by high-temperature calcination. Among the materials synthesized, Al2O3 matrix RTP CDs (CDs@SiO2-Al2O3) have a long phosphorescence lifetime of 689 ms and can exhibit yellow-green light visible to the naked eye for 9 s after the UV light (365 nm) is turned off. Compared with the green phosphorescence of CDs@SiO2, the yellow-green phosphorescence lifetime of CDs@SiO2-Al2O3 is enhanced by 420 ms. In addition, CDs@SiO2-Al2O3 maintains good stability of phosphorescence emission in water, strongly oxidizing solutions and organic solvents. As a result, CDs@SiO2-Al2O3 can be applied to the field of information encryption and security anti-counterfeiting, and this work provides a new, easy and efficient synthesis method for MO as an RTP CD matrix.

Controlling photoluminescence of silicon quantum dots using pristine-nanostates formation

This study investigates the effective control of photoluminescence (PL) of silicon nanocrystals (Si–NCs) embedded in a SiO2 matrix, with a specific focus on tuning the luminescent wavelength profile and intensity for silicon-based optoelectronic applications. By manipulating the composition ratio (x) of SiOx, the well-known simultaneous changes in PL peak position and intensity were observed after annealing. To preserve the desired wavelength characteristics and enhance the luminesce intensity, we propose a novel approach to generate pristine nanostates (PNs) for Si-NC formation using proton irradiation (PI). The application of proton irradiation was found to be successful in significantly increasing PL intensity while strongly suppressing the peak position shifts. Through extensive spectroscopic analysis including PL, X-ray photoelectron spectroscopy, and absorption spectroscopy, we investigate specific defect states in the SiOx matrix, and identified as PNs. We interpret that these PNs consist of self-trapped exciton, E′ center, non-bridging oxygen hole center, and oxygen-deficiency center states. In the as-grown sample, the PNs promote appropriate phase separation and play a significant role in stabilizing the structure during the subsequent annealing processes. This study elucidates the Si-NC formation mechanism by enhancing O-diffusion-induced phase separation, a process accelerated in SiOx with controlled PNs. The proposed PI-induced PNs offer a novel pathway for developing Si-based optoelectronic devices with desired characteristics in the operating wavelength range. These findings open up promising possibilities for advanced silicon-based optoelectronic applications.

Effect of Ca2+ doping and annealing temperature on the structure, morphology and magnetic behavior of CaxCo1-xFe2O4/SiO2 nanocomposites

Co-doped ferrites are promising functional materials for many practical applications and their physical properties can be tailored by changing their composition. This study assesses the structure, morphology and magnetic properties of CaxCo1-xFe2O4/SiO2 (x = 0.0–0.5) nanocomposites (NCs) obtained by sol–gel method and annealed at different temperatures (400, 800 and 1200 °C). The effect of Ca2+ doping on the properties of nano-structured Ca-Co ferrite embedded in the SiO2 matrix was investigated by thermogravimetry and differential thermal analysis, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy, Brunauer-Emmett-Teller surface area, inductively coupled plasma optical emission spectrometry, atomic force microscopy (AFM) and magnetic measurements. The thermal analysis showed the formation of metal succinates up to 200 °C and of ferrite above 280 °C. The presence of poorly crystalline ferrite accompanied by silicates at low annealing temperatures and of highly crystalline ferrite accompanied by SiO2 and Ca silicates at high annealing temperatures was identified by XRD. The increased Ca2+ doping led to a decrease in the structural parameters estimated by XRD and the surface area. The AFM images revealed that the NCs have a crystalline core covered by a layer of amorphous SiO2. The hysteresis loop shape indicated the superparamagnetic-like and ferromagnetic behavior of the obtained NCs. The magnetic properties improved with the increase in annealing temperature and depended on the particle size and dopant content. The NCs with low Ca2+ content annealed at 800 °C still show appreciable hysteresis, but doping with high Ca2+ contents drastically affects the magnetic properties.

Solution processed PANI-rGO-SiO2 nanocomposite with inflated electron injection and transport capabilities as ETL for OLED applications

PANI-rGO-SiO2 nanocomposite as an ETL with varying concentrations of SiO2 was synthesized via oxidative in-situ polymerization process. Their structural and optical properties were investigated by XRD, FESEM, FTIR, Photoluminescence and UV–Vis. Spectroscopy. The PANI depicted a nanofiber-like structure with uniform distribution. The optical band gap of the optimized PGS1 nanocomposite was estimated ∼ 3.01 eV in the visible region of electromagnetic spectrum. TGA results revealed lesser weight loss ∼ 12 % in case of PGS1 nanocomposite than PANI. The light absorption was found at 481 nm in blue region due to charge transfer of SiO2 and PANI-rGO matrix. The current density of PGS1 nanocomposite was observed 76 % greater than pristine PANI using J-V characteristics which showed greater capacities to transfer electron from cathode into emissive layer. These results elucidate that the optimized PGS1 nanocomposite is a compatible candidate for an electron transport layer (ETL) in OLED applications.

Effects of Lanthanum Substitution and Annealing on Structural, Morphologic, and Photocatalytic Properties of Nickel Ferrite.

Nanoparticles of NiLaxFe2-xO4 ferrite spinel incorporated in a SiO2 matrix were synthesized via a sol-gel method, followed by annealing at 200, 500, and 800 °C. The resulting materials were characterized via XRD, AFM, and BET techniques and evaluated for photocatalytic activity. The XRD diffractograms validate the formation of a single-phase cubic spinel structure at all temperatures, without any evidence of secondary peaks. The size of crystallites exhibited a decrease from 37 to 26 nm with the substitution of Fe3+ with La3+ ions. The lattice parameters and crystallite sizes were found to increase with the rise in La3+ content and annealing temperature. Isotherms were employed to calculate the rate constants for the decomposition of malonate precursors to ferrites and the activation energy for each ferrite. All nanocomposites have pores within the mesoporous range, with a narrow dispersion of pore sizes. The impact of La content on sonophotocatalytic activity was evaluated by studying Rhodamine B degradation under visible light irradiation. The results indicate that the introduction of La enhances nanocomposite performance. The prepared Ni-La ferrites may have potential application for water decontamination.

Effect of La3+ on thermal, structural and morphological properties of Zn–Co ferrite spinel-based pigments

The paper discusses the structural, morphological, and chromatic characteristics of La3+ substituted Fe3+ in Zn–Co–La ferrite embedded in a SiO2 matrix, synthesized through a sol-gel method. The thermal behavior of reactants during the synthesis process revealed the formation of metallic oxalate up to 200 °C and their decomposition into metal oxides that further react and form ferrites. The rate constants of oxalate decomposition into ferrites calculated using the isotherms at 160, 200, 240, and 280 °C decrease with increasing temperature and depend on the Fe3+ substitution with La3+ in Zn–Co–La ferrite. The XRD patterns showed a nano-crystalline, single-phase structure formation. The lattice constant increased from 8.431 Å to 8.466 Å, and the crystallite size registered a growth from 35 to 64 nm with the increase in La3+ cations concentration. FT-IR spectra revealed the existence of the M − O stretching bands from Zn–Co–La ferrite and the formation of SiO2 matrix. Transmission electron microscopy revealed spherically-shaped ferrite particles,with particle sizeraging from,38 to 67 nm. The particle size increases with increasing the La content. The lightness of pigments is low and increases by embedding in opaque ceramic glazes. Synthesized NCs were tested for their potential application as pigments in the ceramic industry through their incorporation into glazes. This evaluation included assessing their color using CIELAB coordinates.

Zwitterionic liquid-based gel electrolyte for high performance lithium metal battery at low temperatures

Gel electrolyte (GE) gains intensive attentions for lithium metal battery, especially those targeting to use at low temperatures. The liquid medium, as the core component, of most gel electrolytes (GEs) is organic liquid or ionic liquid, always suffering from serious safety issue and low transference number (t+). The low t + aggravates concentration polarization and thus leads to the increase of overpotential and undesirable side reactions. Herein, zwitterionic liquid (ZIL) with high stability and safety is prepared by mixing zwitterion (ZI) and lithium salt. The ZIL is then encapsulated into a SiO2 matrix to fabricate novel gel electrolyte (SiGE-ZIL). The low freezing point and strong mobility of ZIL confer SiGE-ZIL a high conductivity of 3.36 × 10−4 S cm−1 at −40 °C. Importantly, the large dipole moment of ZI effectively accelerates the dissociation of lithium salt, permitting a high t+ of 0.553 at −40 °C, which is 2.3 times of that of the analogous ionic liquid. The assembled LiFePO4/Li battery exhibits an excellent cycling stability with a capacity of 91.6 mAh g−1 at 600th cycle at 0.5C and 0 °C. Especially at −20 °C, the capacity can reach 67.1 mAh g−1 at 600th cycle under 0.5C, surpassing most of GE-based batteries.

Influence of La3+ substitution on the structure, morphology and magnetic properties of CoLaxFe2−xO4@SiO2 nanocomposites

Structural tuning of CoFe2O4 nanoparticles by doping with rare earth (La3+) ions stands out as a novel technique to tune their physical properties and to provide new nanocomposites for various applications. CoLaxFe2−xO4 (x = 0.0; 0.3; 0.6; 0.9; 1.2; 1.5) nanoparticles embedded in SiO2 (40 wt%) matrix were synthesized by sol-gel method and annealed at 400, 800 and 1200 °C. The effect of Fe3+ substitution by La3+ on the structure, morphology and magnetic properties of nano-structured Co-La ferrite embedded in the SiO2 matrix was investigated by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) surface area, atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and magnetic measurements. The annealing at low temperatures led to poorly crystalline ferrites, while the annealing at high temperatures directed highly crystalline ferrites accompanied by secondary phases. The crystallite size, dislocation density and porosity increased, while the lattice parameter, unit cell volume and hopping lengths decreased with the increase in La3+ content. By substituting Fe3+ ion with La3+ ion, the specific surface area decreased from 244 m2/g to 111 m2/g at 400 °C, reaching values below 0.5 m2/g at 800 and 1200 °C. The AFM revealed a spherical-shaped crystalline core covered by an amorphous SiO2 layer. The TEM images revealed spherical shape nanoparticles of size increasing with La3+ content and annealing temperature. The average particle size measured by AFM ranged between 14 nm and 72 nm, which is in good agreement with the XRD. SEM indicated that the ferrite nanoparticles were nearly spherical and had varying agglomeration degrees. The saturation magnetization, remanent magnetization, coercivity, squareness, magnetic moment per formula unit and anisotropy constant decreased with the increase in La3+ content and increased with the increase in crystallite size. By incorporating La3+ in the ferrite system, the gradual change from hard (CoFe2O4 @SiO2) to soft (CoLa1.5Fe0.5O4 @SiO2) magnetic ferrite occured. The magnetic properties of low La3+ content ferrites recommend them for a wide range of applications.

Unlocking a Dual-Channel Pathway in CO2 Hydrogenation to Methanol over Single-Site Zirconium on Amorphous Silica.

Converting CO2 into methanol on a large scale is of great significance in the sustainable methanol economy. Zirconia species are considered to be an essential support in Cu-based catalysts due to their excellent properties for CO2 adsorption and activation. However, the evolution of Zr species during the reaction and the effect of their structure on the reaction pathways remain unclear. Herein, single-site Zr species in an amorphous SiO2 matrix are created by enhancing the Zr-Si interaction in Cu/ZrO2 -SiO2 catalysts. In situ X-ray absorption spectroscopy (XAS) reveals that the coordination environment of single-site Zr is sensitive to the atmosphere and reaction conditions. We demonstrate that the CO2 adsorption occurs preferably on the interface of Cu and single-site Zr rather than on ZrO2 nanoparticles. Methanol synthesis in reverse water-gas-shift (RWGS)+CO-hydro pathway is verified only over single-dispersed Zr sites, whereas the ordinary formate pathway occurs on ZrO2 nanoparticles. Thus, it expands a non-competitive parallel pathway as a supplement to the dominant formate pathway, resulting in the enhancement of Cu activity sixfold and twofold based on Cu/SiO2 and Cu/ZrO2 catalysts, respectively. The establishment of this dual-channel pathway by single-site Zr species in this work opens new horizons for understanding the role of atomically dispersed oxides in catalysis science.

Unlocking a Dual‐Channel Pathway in CO2 Hydrogenation to Methanol over Single‐Site Zirconium on Amorphous Silica

AbstractConverting CO2 into methanol on a large scale is of great significance in the sustainable methanol economy. Zirconia species are considered to be an essential support in Cu‐based catalysts due to their excellent properties for CO2 adsorption and activation. However, the evolution of Zr species during the reaction and the effect of their structure on the reaction pathways remain unclear. Herein, single‐site Zr species in an amorphous SiO2 matrix are created by enhancing the Zr−Si interaction in Cu/ZrO2‐SiO2 catalysts. In situ X‐ray absorption spectroscopy (XAS) reveals that the coordination environment of single‐site Zr is sensitive to the atmosphere and reaction conditions. We demonstrate that the CO2 adsorption occurs preferably on the interface of Cu and single‐site Zr rather than on ZrO2 nanoparticles. Methanol synthesis in reverse water‐gas‐shift (RWGS)+CO‐hydro pathway is verified only over single‐dispersed Zr sites, whereas the ordinary formate pathway occurs on ZrO2 nanoparticles. Thus, it expands a non‐competitive parallel pathway as a supplement to the dominant formate pathway, resulting in the enhancement of Cu activity sixfold and twofold based on Cu/SiO2 and Cu/ZrO2 catalysts, respectively. The establishment of this dual‐channel pathway by single‐site Zr species in this work opens new horizons for understanding the role of atomically dispersed oxides in catalysis science.

Facile fabrication of silica nanoparticles with incorporation of AIEgen and coreactant as self-enhanced electrochemiluminescence probes for sensitive immunoassay of microcystin-LR

Microcystin-LR (MC-LR) is an algae toxin that poses a serious threat to human health because of its multiorgan toxicity, genotoxicity, and carcinogenicity. Herein, we develop an electrochemiluminescent (ECL) immunosensor for MC-LR detection on the basis of aggregation-induced ECL (AIECL)-assisted self-enhancement strategy. The probe used in this assay is prepared by simultaneously encapsulating AIEgens (namely 1,1,2,2-tetra(4-carboxylbiphenyl)ethylene (H4TCBPE) and its coreactant 2-(dibutylamino)ethanol (DBAE)) into silica to form ternary H4TCBPE@SiO2-DBAE nanoparticles. DBAE can function as a catalyzer to accelerate the in situ formation of SiO2 matrix and an intracoreactant to react with H4TCBPE for the generation of an intense ECL emission as a result of shortened electron transfer pathway and decreased energy loss. We further prepare a biocompatible and electroactive Ti3C2Tx/MoS2/Au hybrid that acts as the immuosensing substrate to accelerate interfacial electron transfer and conjugate the captured antibody (Ab1). Both Ab1-coated Ti3C2Tx/MoS2/Au and antibody (Ab2)-labeled H4TCBPE@SiO2-DBAE can interact with target MC-LR to obtain a sandwich immunosensor. This immunosensor enables quantitative detection of MC-LR antigen with a detection limit of 31 fg/mL and a broad linear range from 50 fg/mL to 10 ng/mL. The proposed strategy opens up a new avenue to fabricating new self-enhanced ECL emitters for sensitive monitoring of environmental microcystins.

Heterogeneity effects in micro-beam XRF scanning spectroscopy of binary powdered mixtures and lake sediments

Micro-beam X-ray fluorescence (XRF) scanning spectroscopy is very useful for analyzing heterogeneous samples from earth and environmental sciences with high spatial resolution. However, XRF intensity depends on grain size and mineralogical composition, known as the heterogeneous effect, although little quantitative evaluation has been conducted. In this study, the binary powdered mixtures of Fe2O3 in the CaCO3 or SiO2 matrix with nine grain size fractions (0.3–605 μm), four Fe2O3 concentrations (5–20 wt%), and fine-grained sedimentary cores from Lake Baikal were used for analysis, using a scanning X-ray analytical microscope (SXAM), and then evaluated by making a simple modification of the Berry–Furuta–Rhodes model. The results of binary powdered samples show that the Fe intensity decreases as the grain size increases, but if the grain size is constant, its intensity has a linear relationship with the composition of Fe2O3. The experimental data are in good agreement with theoretical curves. The theory predicts that if a phase that contains fluorescent elements has narrow ranges of concentration and grain size, the micro-beam XRF spectroscopy enables highly precise calibration from the XRF intensity to element concentration. The theoretical curves of the Lake Baikal sediment core suggest that the Fe intensity has about a 30% maximum difference in the median grain size range of 3.9–28.2 μm. This variation appears in a scatter of regression between Fe intensity and concentration, but it scarcely affected the XRF intensity variability of sediment composition.