A number of CaHfO3 modified BiFeO3-0.33BaTiO3 (BF-0.33BT-xCH) lead-free piezoceramics were fabricated through the solid-state sintering method and comprehensively investigated in this work. Under the ...optimal sintering temperature, all compositions display a typical perovskite structure in a pseudo-cubic phase with slightly larger lattice parameters as the CH content increases. The electrical resistivity is highly enhanced due to the addition of CH. Microstructures, including the grain morphology, core-shell structure, and chemistry inhomogeneities, are demonstrated upon different BF-0.33BT-xCH compositions. In particular, the core-shell structures with non-uniform element distributions in the compositions can be eliminated by adding sufficient CH content (x > 0.05). The highest saturation polarization (40.1 μC/cm2), remnant polarization (26.8 μC/cm2), and converse piezoelectric coefficient (290 pm/V) are achieved in the BF-0.33BT-0.01CH piezoceramic, which are significantly enhanced in comparison with the undoped BF-0.33BT piezoceramic. With further increasing the CH content, the piezoelectric properties of BF-0.33BT-xCH ceramics decline rapidly, and they start to exhibit characteristics of relaxor ferroelectrics.
BiFeO3–BaTiO3 is a promising lead-free piezoelectric ceramic, exhibiting high Curie temperature and superior electrochemical characteristics. In this work,
(
1
−
x
)
BiFeO3–xBaTiO3 (BF–xBT,
x
=
0
.
2
...6
, 0.28, 0.30, 0.32, 0.34, 0.36) ceramics were fabricated using the conventional solid-state reaction method through precise composition control. Multiple characterization techniques, including X-ray powder diffraction (XRD), scanning electron microscope (SEM), and electrical property testing systems, were applied to systematically examine the crystallographic structure, microstructure, as well as the dielectric, ferroelectric and piezoelectric properties of the BF–xBT ceramics. The XRD results confirm that all compositions exhibit a typical perovskite structure, transitioning from a single rhombohedral phase to a rhombohedral–cubic phase mixture as the BT content increases. SEM shows apparent core–shell microstructures in the ceramics. Notably, the results demonstrated that the BF–0.30BT ceramic exhibits the maximum piezoelectric constant (
d
3
3
)
∼
2
1
7
pC/N, while the BF–0.34BT ceramic displays the maximum converse piezoelectric constant
(
d
3
3
∗
)
∼
3
2
3
pm/V, which highlights the suitability of BF–BT ceramics for high-performance piezoelectric applications.
The interface oxygen vacancies (IOVs) not only enormously reduce the transport resistance of photo-generated carriers at the BiOI/BiOCl heterostructure interface but also boost the nonrdical process, ...and thus the excellent catalytic performance for electrophilicity contaminants (TC-HCl) and insecticidal activity for rotifers were obtained.
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•IOVs concentration, active species contribution and 1O2 forming path were established.•Transport resistance of photo-induced carriers was reduced by appropriate IOVs.•Superior catalytic performance and insecticidal activity due to the boosted nonradical process.•Structure-activity relationship of IOVs concentration and catalytic activity was constructed.
Boosting nonradical (1O2, e− and h+) process to enhance the selective degradation for electrophilicity contaminants is an ingenious strategy. Herein, BiOI/BiOCl heterojunction with rational interface oxygen vacancies (IOVs) concentration was successfully synthesized by ultrasonic method. Moreover, multi-characterization and interference experimental unveiled that the appropriate IOVs concentration can not only effectively reduce the transport resistance of photo-induced carriers but also boost the nonradical process. Thus, BOC-5 can remove 84% (20 mg/L) tetracycline hydrochloride (TC-HCl) in 1 h and present wonderful insecticidal performance for rotifers. Simultaneously, the quantitative methods of IOVs concentration, the contribution of the active species to the catalytic performance and the contribution of different 1O2 source to the total 1O2 were established for the first time. Furthermore, the structure–activity relationship between the IOVs concentration and the catalytic properties was firstly constructed. This work provides an inventive idea to purify water pollutants and disinfestation by boost nonradical process via interface defect engineering.
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•A novel thiophene-based COF was synthesized for the first time at room temperature.•A method coupling MSPE with derivatization-assisted GC–MS was developed for the sensitive analysis ...of estrogens.•Harnessing programmable π-π stacking to boost extraction capacity of COF was first presented.•Low detection limits and good recoveries were obtained in the detection of estrogens in water samples.
Under room temperature conditions, a novel thiophene-based magnetic covalent organic framework (COF) was ingeniously synthesized for the first time, utilizing an uncomplicated and benign Schiff base reaction between 4,4′,4″,4‴-(pyrene-1,3,6,8-tetrayl)tetraaniline (PyTTA) and 2,2′-dithiophene-5,5′-dicarboxaldehyde (BTDA), with Fe3O4 serving as the magnetic nucleus. The fabricated Fe3O4@Py-BTDA COF nanocomposite displays superior crystallinity, homogenous pore size distribution, elevated magnetic responsiveness, and extraordinary thermal and chemical stability, which is an ideal sorbent for magnetic solid phase extraction (MSPE) of estrogens in environmental water samples. The presence of thiophene groups within the Fe3O4@Py-BTDA COF significantly bolsters the π-π interaction between the COF and the target analytes, and meanwhile provides sufficient hydrophobic sites and unique p-π interactions, thus becoming a crucial factor in augmenting the extraction efficiency of estrogens. Due to the high boiling point of estrogens, derivatization is necessary before gas chromatography–mass spectrometry (GC–MS) analysis. So, the conditions of derivatization, extraction and desorption were then systematically optimized. Under the optimal MSPE conditions, a rapid and sensitive method coupling MSPE with GC–MS was developed for the analysis of five estrogens in environmental water samples. The method showed good linearity (r2 > 0.9997) in the range of 0.05–100 μg L−1, low detection limits (4.0–7.0 ng/L), good spiked recoveries (91.56 %-105.80 %), and satisfactory relative standard deviations (RSD, less than 7.4 %). In addition, the method was successfully applied to the determination of estrogens in Yangtze River water, East Lake water, and tap water, with the recoveries in the range of 81.33 %-113.95 % and the RSDs in the range of 0.12 % to 7.69 % at different spiked levels. Estrone (E1) and estradiol (E2) were detected in the Yangtze River water with concentrations of 0.31 μg L−1 and 0.08 μg L−1. And, the prepared Fe3O4@Py-BTDA COF nanocomposite still provides good extraction effect after five cycles of application. The developed method is rapid, simple, sensitive, and environmentally friendly, and has good application in the analysis and determination of estrogens in environmental water samples.
As typical emerging contaminants, pharmaceuticals and personal care products (PPCPs) are extensively present in the environment with generally trace levels. The continuous emissions and potential ...hazards of PPCPs have caused primary concerns worldwide. Therefore, it is crucial to develop some simple, facile, sensitive and efficient sample pretreatment and analysis methods for the determination of PPCPs. In this review, the sample preparation techniques for PPCPs in different environmental media are summarized, including liquid-liquid extraction (LLE), pressurized liquid extraction (PLE), liquid-phase microextraction (LPME), microwave-assisted extraction (MAE), solid phase extraction (SPE), magnetic solid phase extraction (MSPE) and so on. Furthermore, the most commonly adopted analytical methods for the identification and quantification of PPCPs were reviewed including gas chromatography (GC), high-performance liquid chromatography (HPLC) and some coupling analytical techniques with mass spectrometry (MS). This review gives an insight into recent advances in the determination of PPCPs in the different environmental samples.
•Research progress in PPCPs analysis as Emerging contaminants is reviewed.•Discuss the occurrence of PPCPs in different environments.•Pretreatment methods of PPCPs in samples from various environmental matrices were discussed.•Advanced instrumental analysis techniques for a wide range of applications are discussed.
The OVs concentration of novel CQDs/BiOCl schottky heterojunction can be regulated via introduce CQDs. Therefore, the as-prepared sample present excellent photocatalytic performance due to the ...transformation efficiency of the photo-induced carriers was greatly enhanced under the coupling of rational OVs, point discharge effect, and interfacial electric field.
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•The novel CQDs/BiOCl with rational OVs was fabricated by using maltitol as carbon source.•The transformation efficiency of photo-induced carriers was dramatically enhanced under the coupling of rational OVs, interfacial electric field and point discharge effect .•The contribution of the free radicals to the photocatalytic activity was thoroughly calculated.
Increasing the migration and separation efficiencies of photogenerated carriers can enormously enhance photocatalytic properties. Thus, a novel CQDs/BiOCl nanocomposite with rich oxygen vacancies (OVs) was effectively synthesized via a hydrothermal method by using maltitol as a carbon source to address these issues. The photocatalysts were characterized by XRD, SEM, TEM, FT-IR, BET, XPS, PL, EIS, I-t, DRS and ESR. The experimental results demonstrate that BOC-1 can purify 72% tetracycline hydrochloride (10 mg/L, TC-HCl) within 60 min, which is 4 times higher than pure BiOCl. Moreover, photocatalytic mechanism was thoroughly studied and verified that the cooperation of point discharge effect (PDE) and rational OVs concentration induced by carbon quantum dots (CQDs) can significantly enhance the migration and separation of photo-induced carriers, thereby leading to high photocatalytic activity of the as-prepared nanocomposites. In addition, the contribution of the free radicals was comprehensively calculated based on trapping experiments. the contributions of ·OH, ·O2- and 1O2 are 6.38%, 48.94% and 8.51%, respectively. This study provides a promising strategy to boosting the photoinduced carrier transfer properties by the coupling of point discharge effect and defect engineering.
Abstract
BiFeO
3
–SrTiO
3
(BF–ST) ceramics have been considered a novel class of lead‐free dielectric materials exhibiting notable dielectric constants and remarkable thermal stability. In this work, ...we fabricated a series of (1 −
x
)BF–
x
ST (0.32 ≤
x
≤ 0.44) ceramics near the morphotropic phase boundary and comprehensively investigated their microstructure and electrical properties, which seeks to optimize the piezoelectric performance. As the ST content increases, a gradual reduction in the rhombohedral phase fraction is observed alongside a corresponding increase in the cubic phase fraction. Although
x
= 0.38, the maximum grain size of 5.66 μm is obtained, accompanied by a distinctive heterogeneous core–shell microstructure, which demonstrates a high remanent polarization of 51.2 μC/cm
2
and a maximum
d
33
value of 72 pC/N. Furthermore, impedance spectroscopy analysis reveals the formation of a conductive core and a nonconductive shell within the sample. These findings highlight the potential of optimized BF–ST ceramics as promising alternatives to lead‐based piezoelectric materials, offering exceptional ferroelectric and piezoelectric properties.
Abstract The investigation of lead‐free ceramics with exceptional piezoelectric properties holds great importance in the substitution of lead‐based materials, hence promoting the development of green ...technology and fostering an environmentally sustainable society. This study successfully synthesized two series of Bi(Mg 2/3 Nb 1/3 )O 3 (BMN)‐modified BiFeO 3 –BaTiO 3 (BF–BT) lead‐free piezoelectric ceramics using the conventional solid‐state reaction approach. The phase structure, microstructure, dielectric, and piezoelectric properties of these ceramics were comprehensively investigated. A typical perovskite structure is observed in all probed compositions, and the associated phase structure undergoes a gradual transition from a rhombohedral‐cubic phase mixture to a cubic‐dominant phase structure as increases the content of BMN and BT. All compositions exhibit obvious core–shell microstructures with inhomogeneous element distributions. Most importantly, the BF–0.30BT–0.005BMN and BF–0.34BT–0.03BMN piezoelectric ceramics presented remarkable values for the piezoelectric coefficient (225 pC/N) and converse piezoelectric coefficient (396 pm/V), respectively. These findings highlight the potential of BMN‐modified BF–BT ceramics for use in high‐performance piezoelectric applications.
In many studies, the properties of BiFeO3–BaTiO3 (BF–BT) ceramics vary greatly using different raw reagents, which makes it challenging to obtain reliable and repeatable properties of BF–BT‐based ...devices. In this work, 0.7BiFeO3–0.3BaTiO3 (0.7BF–0.3BT) ceramics were fabricated by a conventional solid‐phase synthesis using TiO2 reagents with varied purities of 98%, 99%, 99.9%, and 99.99%, respectively. The phase structure, microstructure, ferroelectric, and piezoelectric properties were comprehensively studied. All compositions of the ceramics exhibit a pseudo‐cubic phase perovskite structure, and the fraction of the rhombohedral phase increases with increasing the TiO2 purity. Additionally, backscattered electron images and energy‐dispersive spectroscopy revealed an obvious core–shell structure within grains. In particular, the 0.7BF–0.3BT ceramics prepared with 98% purity TiO2 exhibited superior ferroelectric and piezoelectric properties, d33 ∼ 220 pC/N and d33∗$d_{{\mathrm{33}}}^{\;*}$ ∼ 230 pm/V. The ceramics prepared with higher purity TiO2 suffered from severe leakage conduction, which can be well addressed by adding excess TiO2. Our work reveals the importance of different grades of purity TiO2 on the electrical properties of BF–BT ceramics.
Abstract In many studies, the properties of BiFeO 3 –BaTiO 3 (BF–BT) ceramics vary greatly using different raw reagents, which makes it challenging to obtain reliable and repeatable properties of ...BF–BT‐based devices. In this work, 0.7BiFeO 3 –0.3BaTiO 3 (0.7BF–0.3BT) ceramics were fabricated by a conventional solid‐phase synthesis using TiO 2 reagents with varied purities of 98%, 99%, 99.9%, and 99.99%, respectively. The phase structure, microstructure, ferroelectric, and piezoelectric properties were comprehensively studied. All compositions of the ceramics exhibit a pseudo‐cubic phase perovskite structure, and the fraction of the rhombohedral phase increases with increasing the TiO 2 purity. Additionally, backscattered electron images and energy‐dispersive spectroscopy revealed an obvious core–shell structure within grains. In particular, the 0.7BF–0.3BT ceramics prepared with 98% purity TiO 2 exhibited superior ferroelectric and piezoelectric properties, d 33 ∼ 220 pC/N and ∼ 230 pm/V. The ceramics prepared with higher purity TiO 2 suffered from severe leakage conduction, which can be well addressed by adding excess TiO 2 . Our work reveals the importance of different grades of purity TiO 2 on the electrical properties of BF–BT ceramics.
