Search

A novel neptunyl(VI) phosphate compound, (NpO2)3(PO4)2(Terpy), was synthesized by hydrothermal reaction. It crystallizes in the orthorhombic space group Pca21 with unit-cell parameters a = 13.9944 Å, b = 12.1989 Å, c = 13.1277 Å, V = 2241.1 Å3, and Z = 4. Related to the layered structure of the uranophane topology, it contains the first reported (NpVIO2)2(PO4)22− sheets, which are bonded via π–π interactions between the NpVIO2(Terpy)2+ ligands that are perpendicular to the sheets. [ABSTRACT FROM AUTHOR]

Decades of research unveiled the unlimited potential of metal–organic frameworks (MOFs). Nevertheless, the hazardous and expensive production involving massive amounts of organic solvents has severely limited their widespread industrial adoption. Herein, the advantages of two eco-friendly strategies, base-assisted synthesis and modulated hydrothermal chemistry, were complementarily integrated, with the acetate anion introduced as a mild and efficacious modulator to regulate the coordination and tailor the crystallization pathway(s). The green, rapid, and scalable synthesis of a dual-ligand Zn-MOF was thereby achieved in water media, featuring an unprecedented space–time yield of 24 ton per m3 per day and a batch size exceeding a kilogram (i.e., 1.2 kg). Owing to its strong affinity toward CH4, the acquired Zn-MOF demonstrated a considerable CH4/N2 separation capacity under ambient conditions. This study not only facilitates the green and scalable production of MOFs but also offers a cost-effective adsorbent for CH4 recovery. [ABSTRACT FROM AUTHOR]

The sonohydrothermal (SHT) treatment is an innovative technique allowing the simultaneous coupling of low frequency ultrasound and hydrothermal conditions for the synthesis of materials. The aim of the present work was to investigate, for the first time, the synthesis of zeolite A and its formation mechanism under SHT conditions. The zeolite synthesis was carried out under sonohydrothermal conditions using a specially designed reactor that allows the application of ultrasonic irradiation at 20 kHz in an autoclave-type reactor heated up to 200 °C under autogenous pressure. The conversion kinetics of the amorphous hydrogel to zeolite A and its further conversion to sodalite were studied. Syntheses were performed in the SHT reactor at 80 and 100 °C, varying the synthesis time from 15 minutes to several hours. The required time to obtain fully crystalline zeolite A under sonohydrothermal conditions was only 25 minutes, highlighting a significantly improved crystallization rate compared to silent conditions (a 9.6-fold kinetic gain). In addition, the resulting zeolite A has smaller particles and a more homogeneous particle size distribution than the zeolite synthesized by hydrothermal treatment. These results can be explained by the sonofragmentation of the amorphous gel and the concomitant enhanced mass transfer of the building units at the interface between the crystallite surface and the solution resulting from the acoustic cavitation activity under SHT conditions. Compared to classical hydrothermal heating, a drastic kinetic increase of the transformation of zeolite A into the more stable sodalite phase was also observed under sonohydrothermal conditions. [ABSTRACT FROM AUTHOR]

New cesium cerium(IV) iodate Cs2Ce(IO3)6 was successfully prepared by applying a hydrothermal technique from starting reagents CsF, CeO2, H5IO6 and HIO3 at 230 °C. Cs2Ce(IO3)6 was analyzed via single crystal and powder XRD, EDX, IR spectroscopy and thermal analysis. The new compound crystallizes in the monoclinic space group C2/c with a = 14.0652(3) Å, b = 8.1890(2) Å, c = 17.7211(4) Å, β = 103.601(2)°, V = 1983.99(8) Å3, and Z = 4. The crystal structure of Cs2Ce(IO3)6 consists of CeO8 square antiprisms sharing their apexes and edges with trigonal pyramidal IO3− groups to form layers [Ce(IO3)6]2− parallel to the ab plane. These layers are further stabilised by a 12-vertex polyhedron, CsO12, situated in their voids. The IR spectrum of Cs2Ce(IO3)6 displays iodate group bands. According to DTA analysis, cesium cerium(IV) iodate exhibits high thermal stability in the air at temperatures up to 414 °C. [ABSTRACT FROM AUTHOR]

Nanomaterials are emerging as important contributors in various applications and can be used especially in environmental catalysis. Herein, a brief summary on the basic knowledge of supercritical hydrothermal synthesis (SCWHS) is presented, including the synthesized functional nanomaterials, the effects of different experimental conditions on the properties of nanoparticles, and examples of their applications in environmental catalysis, highlighting the environmental and economic advantages of SCWHS. This review focuses on supercritical water as an environmentally friendly particle engineering tool for the production of high-quality, high-yield nanoparticles and the possibility of achieving their continuous production in industry. Nanoparticles are nucleated within a short time and their particle size can be controlled by SCWHS. Therefore, attention is given to the relationship between the formation and experimental conditions, as well as the properties of the obtained material in terms of particle size, surface area, crystallinity, morphology and surface properties. In addition, SCWHS can combine organic wastewater treatment, waste resource utilization and nanoparticle synthesis, and the in situ-generated nanoparticles can promote the oxidation of organic wastewater and the resourceful conversion of solid wastes as well as have production value as a by-product. The work may provide guidance for the further development of SCWHS, preparation of functional nanomaterials, and exploration of multiple applications. [ABSTRACT FROM AUTHOR]

The development of advanced efficient and durable non-precious metal-based anode catalysts for photo-assisted direct methanol fuel cells remains a significant challenge. In this study, Ce-doped Co3O4 (Ce–Co3O4) was prepared by a three-step process involving hydrothermal synthesis, cation exchange and calcination. The introduction of Ce can not only induce more Co3+ with oxidation properties, but also expand the light absorption range and improve the separation efficiency of photogenerated electron–hole pairs. In an alkaline solution and under visible light irradiation, Ce–Co3O4 showed high current density (31.4 A g−1), high photo-response current (3.52 A g−1) and good long-term stability (the current density retention was 82% after 13 h under visible light irradiation). The reaction mechanism for the photo-assisted methanol oxidation was investigated by a series of optical characterization studies (UV-vis diffuse reflectance spectroscopy, Mott–Schottky, photoluminescence spectroscopy, and electron paramagnetic resonance). The results indicated that the strong oxidative photogenerated hole (h+), ˙OH, and ˙O2− were beneficial for the oxidation of methanol and COads. This study provides a good idea for the design of efficient non-precious metal based anode catalysts for photo-assisted direct methanol fuel cells. [ABSTRACT FROM AUTHOR]

The preparation of synthetic (Zr,U)SiO4 solid solution is challenging, as the conventional high-temperature solid-state method limits the solubility of uranium (4 ± 1 mol%) in the orthosilicate phase due to its thermodynamic instability. However, these compounds are of great interest as a result of (Zr,U)SiO4 solid solutions, with uranium contents exceeding this concentration, being observed as corium phases formed during nuclear accidents. It has been identified that hydrothermal synthesis pathways can be used for the formation of the metastable phase, such as USiO4. The investigation carried out in this study has indeed led to the confirmation of metastable (Zr,U)SiO4 compounds with high uranium contents being formed. It was found that (Zr,U)SiO4 forms a close-to-ideal solid solution with uranium loading of up to 60 mol% by means of hydrothermal treatment for 7 days at 250 °C, at pH = 3 and starting from an equimolar reactant concentration equal to 0.2 mol L−1. A purification procedure was developed to obtain pure silicate compounds. After purification, these compounds were found to be stable up to 1000 °C under an inert atmosphere (argon). The characterisation methods used to explore the synthesis and thermal stability included powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) and Raman spectroscopies, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). [ABSTRACT FROM AUTHOR]

Transition metal oxide nanocomposites with heterostructures have gained a lot of attention for use in supercapacitors owing to their low cost, high surface area, fast transport of ions and electrons and high specific capacitance due to efficacious interplay between the electrode and the electrolytes. In this study, we fabricated tri-metallic Cu, Mn, Ni(CMNO), bi-metallic Mn, Ni(MNO) and mono-metallic Ni(NO) oxides through a facile hydrothermal route. All the fabricated materials were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDX), and their electrochemical properties were studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge–discharge (GCD). The CMNO material showed remarkable electrochemical performance with a specific capacitance of 790.63 F g−1 at a current density of 1 A g−1, surpassing the performance of MNO (438.4 F g−1) and NO (290.82 F g−1). Furthermore, CMNO showed high cycling stability with a retention of 96.7% specific capacitance after 8000 cycles. Based on remarkable and unique properties, the CMNO material is regarded as a promising material for new-generation pseudo-capacitor applications. [ABSTRACT FROM AUTHOR]

Heteroatom (such as Ti, Sn, Zr, and Hf) zeolites that contain Lewis acid site (LAS) centers with tetrahedral coordination confined in micropores with various topologies are able to catalyze reactions distinct from those catalyzed by Brønsted acid sites (BASs). In particular, these LAS centers are able to coordinate with two oxygen atoms of one or two oxygenated molecules on a single LAS simultaneously, which are suitable for the conversion of biomass-derived oxygenates via unique reaction pathways, and have been widely explored in the conversion of biomass-derived oxygenates to value-added products. In this review, methods of conventional hydrothermal synthesis, improved direct synthesis (such as interzeolite transformation and dry gel conversion) and post-synthesis (such as solid-state ion change, structural reconstruction and grafting) are compared. Next, approaches for the qualification and quantification of the location (framework or extra-framework), fine structure (closed or open), and acidity of heteroatom centers are summarized. Thereafter, we present the applications of Lewis acid zeolites in the conversion of platform oxygenates of hexoses, furan derivatives and acid derivatives via reactions of isomerization, Meerwein–Ponndorf–Verley reduction, oxidation, and ketonization. Notably, the integration of multiple steps into a one-pot cascade reaction for the conversion of oxygenates (for example, glucose to 5-hydroxymethylfurfural and furfural to γ-valerolactone) mediated by the synergy of LASs and BASs or metal sites is also discussed. Finally, the opportunities and challenges in the low-cost synthesis and large-scale application of Lewis acid zeolites for the green and sustainable synthesis of chemicals are proposed. [ABSTRACT FROM AUTHOR]

LiFeOHS is a material with Li2(OH)2 layers intercalated between Fe2S2 planes. Its hydrothermal synthesis in various concentrations of LiOH yields materials with a high non-stoichiometry of the Li/Fe ratio which can be explained by partial substitution of Li+ for Fe2+ in the Li2(OH)2 layers. Thermogravimetry, X-ray diffraction and Mössbauer studies indicate that the charge balance is obtained by substitution of hydroxyl ions OH− by oxide ions O2−. This material has been tested as an electrode for lithium-ion batteries against lithium metal. Specific capacities above 200 mA h g−1 at C/10 are achieved, involving 1 lithium per chemical formula when cycled between 1 V and 3 V vs. lithium. The first irreversible discharge leads to the insertion of one lithium atom and the evolution of hydrogen gas while iron remains in its +2-oxidation state. An original Li2OFeS oxysulfide is formed. The following reversible oxidation/reduction cycles involve the Fe3+/Fe2+ redox couple between the two limiting compositions: Li2OFeIIS and LiOFeIIIS. [ABSTRACT FROM AUTHOR]

X-ray detectors based on scintillators are widely used in the fields of medical imaging, high-energy physics, geological exploration, and industrial detection. The development of scintillation materials with different characteristics has become the focus of considerable research interest. Herein, we report a facile hydrothermal synthesis of Gd- and Eu-codoped LiLuF4 microcrystals (MCs), which exhibit strong luminescence of Eu3+ ion characteristic emission, characterized by distinct red fluorescence emission. The research shows that Gd3+ co-doping effectively improved the sensitivity and light yield of LiLuF4:Eu MCs by regulating the proportion of co-doping ions. In addition, the detection limit is 140.72 nGy s−1 for LiLuF4:Eu,Gd MCs, approximately 39 times lower than the dose requirement of medical diagnosis. Based on LiLuF4:Eu,Gd MCs with the superior scintillation properties, a MC-composited film with 250 μm thickness was prepared by a direct coating method. The uniform and high-loading scintillation film exhibits outstanding imaging performance with a high spatial resolution of 14.8 LP mm−1, which confirms the application potential of X-ray imaging. [ABSTRACT FROM AUTHOR]

To improve the complexity and low catalytic performance and reduce the high cost of the traditional electrode preparation process for the sodium borohydride electro-oxidation reaction (BOR), in this work, a self-supported and efficient electrode material grown on nickel foam (CoNi/Co3O4/NF) was successfully designed using a simple hydrothermal synthesis method accompanied by the electrodeposition process. Benefiting from the three-dimensional nanoarray structure of CoNi/Co3O4/NF and the uniform distribution of Co and Ni modulating active sites by electrodeposition, the catalytic activity towards NaBH4 exhibits high efficiency. CoNi/Co3O4 exhibits excellent catalytic performance (up to 2157 mA cm−2 in 2 mol L−1 NaOH and 0.3 mol L−1 NaBH4), a high electrochemically active surface area (62.5 cm−2), and a low activation energy (15.56 kJ mol−1). The CoNi/Co3O4/NF electrode was further investigated on a direct sodium borohydride–hydrogen peroxide fuel cell (DBHPFC), which exhibited a maximum power density of 108.5 mW cm−2 and excellent stability. The excellent performance is mainly due to its unique nanoarray structure and electrodeposition distribution of Co and Ni active sites, which increases the electrochemical surface area and enhances the contact between the electrode and the electrolyte. [ABSTRACT FROM AUTHOR]

Recently, layered rare-earth hydroxides (LRHs) have received growing attention in the field of theranostics. We have previously reported the hydrothermal synthesis of layered terbium hydroxide (LTbH), which exhibited high biocompatibility, reversible uptake of a range of model drugs, and release-sensitive phosphorescence. Despite these favourable properties, LTbH particles produced by the reported method suffered from poor size-uniformity (670 ± 564 nm), and are thus not suitable for therapeutic applications. To ameliorate this issue, we first derive an optimised hydrothermal synthesis method to generate LTbH particles with a high degree of homogeneity and reproducibility, within a size range appropriate for in vivo applications (152 ± 59 nm, n = 6). Subsequently, we apply this optimised method to synthesise a selected range of LRH materials (R = Pr, Nd, Gd, Dy, Er, Yb), four of which produced particles with an average size under 200 nm (Pr, Nd, Gd, and Dy) without the need for further optimisation. Finally, we incorporate Gd and Tb into LRHs in varying molar ratios (1 : 3, 1 : 1, and 3 : 1) and assess the combined magnetic relaxivity and phosphorescence properties of the resultant LRH materials. The lead formulation, LGd1.41Tb0.59H, was demonstrated to significantly shorten the T2 relaxation time of water (r2 = 52.06 mM−1 s−1), in addition to exhibiting a strong phosphorescence signal (over twice that of the other LRH formulations, including previously reported LTbH), therefore holding great promise as a potential multi-modal medical imaging probe. [ABSTRACT FROM AUTHOR]

Supercapacitors are regarded as promising electrochemical energy storage solutions due to their multiple advantages. In this study, we report simple hydrothermal synthesis of nanostructured MnMoO4 (MMO) using CTAB and PVA as structure-directing agents, which is then employed as an electrode material in high-performance asymmetric supercapacitors. This resulted in the formation of morphologies analogous to nanoflakes (for CTAB; MMO-C), nanosheets (for PVA; MMO-P), and nanobundles (without a surfactant; MMO). MMO-C has a nanoflake-like structure with a large surface area, and an increasing number of electroactive surface sites and contact areas at the electrode–electrolyte interface. This results in a higher specific capacitance than other electrodes, measuring 919.6 F g−1 and 505 F g−1 at 1 A g−1 and 10 A g−1, respectively. It also exhibits extended cycling performance, with 94.1% retention after 10 000 cycles. The fabricated MMO-C//activated carbon (AC) asymmetric supercapacitor (ASC) device achieved a high specific capacitance of 111.9 F g−1 at 1 A g−1 in an operational potential window of 0–1.5 V. The ASC also has a high specific energy of 39.45 W h kg−1 at a specific power of 837.66 W kg−1 while retaining 90.3% of its initial capacitance after 10 000 cycles. A red LED was also turned on for 120 seconds when two ASCs were connected in series. [ABSTRACT FROM AUTHOR]

Chiral surfaces are an object of interest due to their application in catalysis, separation and sensors. Such surfaces can exhibit chirality on the molecular or supramolecular level. Previously, we have studied the thermodynamic features of adsorption on non-porous surfaces with supramolecular chirality. However, for their application in enantiomer separation, enantioselectivity and capacity should be greater. Porous adsorbents are promising for this purpose. In this work, the enantioselectivity of copper borophosphate LiCu2[BP2O8(OH)2] was studied. This zeotype material was obtained by hydrothermal synthesis without any source of chirality. Supramolecular chirality was achieved by spontaneous symmetry breaking via Viedma ripening. XRD and SEM were used to prove the synthesis accuracy. Enantioselectivity during adsorption was studied using the adsorption isotherms of α-pinene and limonene enantiomer analysis. The experimental isotherms were approximated by Langmuir, Dubinin–Radushkevich, Freundlich and Fowler–Guggenheim equations. The t-test was used to prove the reliability of the differences in enantiomer adsorption. The isosteric heats of adsorption were calculated from the adsorption isotherms. The data obtained have shown the ability of the LiCu2[BP2O8(OH)2] surface to recognize both α-pinene and limonene enantiomers. The molecules of α-pinenes adsorbed without pores, with the maximum enantioselectivity coefficient of 1.23 at 80 °C. Limonene molecules adsorbed in pore volume as single molecules or 1D chains. This phenomenon was proved by analysis of isosteric heats. The enantioselectivity of copper borophosphate to limonenes and α-pinenes was similar. The ability of pores with supramolecular chirality (and without molecular chirality) to recognize enantiomers was discovered in this paper for the first time. [ABSTRACT FROM AUTHOR]

Zeolites are a class of catalysts with specific pore structures as well as different pore sizes, which are now widely used in various shape-selective catalytic reactions. In this paper, a uniform micro/mesoporous core–shell composite HZSM-@MCM-41 comprising zeolite was successfully prepared by coating mesoporous MCM-41 shells on nanosized ZSM-5 cores using a two-step hydrothermal method. Nanoscale ZSM-5 cores with different acidity were successfully prepared by changing the Si/Al of the initial solution of pristine ZSM-5, and three different thicknesses of MCM-41 shell layers were easily encapsulated on the surface of ZSM-5 with different acidity by varying the amount of silicon source added in the secondary hydrothermal crystallization process. The synthesized series of micro-mesoporous core–shell catalysts were also applied to the catalytic fast pyrolysis in lignin. In the catalytic fast pyrolysis of lignin, the mesoporous structure promoted the transition of biomass pyrolysis intermediate to liquid products, and the acidity of the HZSM-5 core facilitated their catalytic transformation to aromatic hydrocarbons. Among all the tested catalysts, the HZ@M-80-ll catalyst with an internal Si/Al = 80 and MCM-41 shell thickness of ∼25 nm exhibited the highest production of light aromatics and phenols. [ABSTRACT FROM AUTHOR]

Chiral surfaces are an object of interest due to their application in catalysis, separation and sensors. Such surfaces can exhibit chirality on the molecular or supramolecular level. Previously, we have studied the thermodynamic features of adsorption on non-porous surfaces with supramolecular chirality. However, for their application in enantiomer separation, enantioselectivity and capacity should be greater. Porous adsorbents are promising for this purpose. In this work, the enantioselectivity of copper borophosphate LiCu2[BP2O8(OH)2] was studied. This zeotype material was obtained by hydrothermal synthesis without any source of chirality. Supramolecular chirality was achieved by spontaneous symmetry breaking via Viedma ripening. XRD and SEM were used to prove the synthesis accuracy. Enantioselectivity during adsorption was studied using the adsorption isotherms of α-pinene and limonene enantiomer analysis. The experimental isotherms were approximated by Langmuir, Dubinin–Radushkevich, Freundlich and Fowler–Guggenheim equations. The t-test was used to prove the reliability of the differences in enantiomer adsorption. The isosteric heats of adsorption were calculated from the adsorption isotherms. The data obtained have shown the ability of the LiCu2[BP2O8(OH)2] surface to recognize both α-pinene and limonene enantiomers. The molecules of α-pinenes adsorbed without pores, with the maximum enantioselectivity coefficient of 1.23 at 80 °C. Limonene molecules adsorbed in pore volume as single molecules or 1D chains. This phenomenon was proved by analysis of isosteric heats. The enantioselectivity of copper borophosphate to limonenes and α-pinenes was similar. The ability of pores with supramolecular chirality (and without molecular chirality) to recognize enantiomers was discovered in this paper for the first time. [ABSTRACT FROM AUTHOR]

FeNbO4 sonocatalysts were successfully synthesized by a simple hydrothermal route at pH values of 3, 5, 7, 9 and 11. The catalysts were characterized by XRD, XPS, TEM, SEM, N2 adsorption and DRS to analyse the effect of pH parameters on the physicochemical properties of the materials during hydrothermal synthesis. The sonocatalytic activity of FeNbO4 microspheres was evaluated by using acid orange 7 (AO7) as the simulated contaminant. The experimental results showed that the best sonocatalytic degradation ratio (97.45%) of organic dyes could be obtained under the conditions of an initial AO7 concentration of 10 mg L−1, an ultrasonic power of 200 W, a catalyst dosage of 1.0 g L−1, and a pH of 3. Moreover, the sonocatalysts demonstrated consistent durability and stability across multiple test cycles. After active species capture experiments and calculation of the energy band, a possible mechanism was proposed based on the special Fenton-like mechanism and the dissociation of H2O2. This research shows that FeNbO4 microspheres can be used as sonocatalysts for the purification of organic wastewater, which has a promising application prospect. [ABSTRACT FROM AUTHOR]

NIR luminescent materials have garnered widespread attention because of their exceptional properties, with high tissue penetration, low absorption and high signal-to-noise ratio in the field of optical imaging. However, producing nanophosphors with high quantum yields of emitting infrared light with wavelengths above 1000 nm remains a significant challenge. Here, we prepared a nanoscale ZnGa2O4:xCr3+,yNi2+ phosphor with good luminescence performance in near-infrared emission, which was synthesized via a hydrothermal method and subsequent calcination process. By co-doping with Cr3+ and Ni2+, the ZnGa2O4 phosphor shows a strong broadband emission of 1100-1600 nm in the second near-infrared (NIR-II) region, owing to the energy transfer from Cr3+ to Ni2+ with an efficiency up to 90%. Meanwhile, a near-infrared phosphor-conversion LED (NIR pc-LED) device is fabricated based on the ZnGa2O4:0.8% Cr3+,0.4%Ni2+ nanophosphor, which has under 100 mA input current, an output power of 23.99 mW, and a photoelectric conversion efficiency of 7.53%, and can be effectively applied in imaging and nondestructive testing. Additionally, the intensity ratio of INi/ICr of ZnGa2O4:0.8% Cr3+,0.4%Ni2+ with its high sensitivity value of 4.21% K-1 at 453 K under 410 nm excitation, indicates its potential for thermometry application. [ABSTRACT FROM AUTHOR]

This paper details the preparation of an aluminum-based organic metal complex doped with fluorine and nitrogen (2-Ml/Al–F–N). The synthesis method combines hydrothermal synthesis and calcination for modification. The catalyst was thoroughly characterized for its composition, structure, and morphology using various techniques, including XRD, FT-IR, XPS, SEM, TEM, and others. The electrochemical performance of the material was assessed using an electrochemical workstation, and gas chromatography was employed to analyze the results. DFT calculations were used to compute the material's properties and energy barrier diagram. The findings demonstrate that the catalyst exhibits a carbon nanoline morphology and showcases high catalytic activity in the CO2RR to CO. Notably, the catalyst exhibits excellent performance with a maximum current density of 14.08 mA cm−2 and a peak faradaic efficiency of 90.1% at −1.1 V vs. RHE. The active sites are predominantly located within the nanoline structure. The DFT calculations reveal that the introduction of ammonium fluoride during the synthesis process leads to the formation of a highly efficient fluorinated aluminum metal catalytic center derived from nonahydrate aluminum nitrate. This specific structure demonstrates excellent hydrogen suppression properties and effectively lowers desorption energy barriers, which enhances the CO2RR activity and promotes the electrocatalytic reduction of CO2 to CO. [ABSTRACT FROM AUTHOR]

The document is a contents list for the journal CrystEngComm, which focuses on the design and understanding of solid-state and crystalline materials. The contents list includes various articles on topics such as the growth of gold-based nanostructures, the synthesis of energetic pentazolate salt, and the investigation of additives on calcium carbonate crystallization. The journal is published by The Royal Society of Chemistry, a leading chemistry community. The document also mentions other journals in the field of environmental science and provides information about the organization's charitable work. [Extracted from the article]

Monoclinic AgTbW2O8:Eu3+ crystals were prepared by a simple one-step hydrothermal method. The phase, morphology and luminescence properties of the obtained phosphors were systematically characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and photoluminescence (PL). The effects of solution pH, W/Tb molar ratios and reaction temperatures as well as reaction times on the size and morphology of the final products were discussed, and the possible formation mechanism of the almond-like structure was proposed. The down-conversion luminescence properties and energy transfer behavior of the AgTbW2O8:Eu3+ phosphors were studied under ultraviolet light excitation. The emission lights were obtained from green to yellow-green to yellow to red by setting different ratios of Tb3+/Eu3+. The temperature-dependent fluorescence test data showed that AgTbW2O8:Eu3+ phosphors have good temperature stability. In addition, by doping alkali metal ions Li+, Na+, and K+ in AgTbW2O8:Eu3+ phosphors, it is found that the luminescence intensity of phosphors doped with alkali metal ions is enhanced compared with that of phosphors without alkali metal ions, and the phosphor doped with K+ has the largest luminescence intensity, which is due to the introduction of K+ making the crystal field produce the greatest asymmetry. [ABSTRACT FROM AUTHOR]

New polar K2NbO2F3 crystals were obtained under mild hydrothermal conditions, which differ from the higher temperature synthesis of previously known Nb-containing oxyfluorides. X-ray diffraction analysis of the single crystal, performed in the polar space group Pna21, is consistent with the existence of the second harmonic generation (SHG) effect in powders. A monotonous increase in SHG power in samples with increasing powder grain size indicates phase matching of neodymium laser radiation and its second harmonic. However, SHG is relatively small and does not exceed a third of the intensity of standard KH2PO4 powders. The weakness of the second-order optical nonlinearity in K2NbO2F is related to the strong pseudo-symmetry of the crystal structure, corresponding to the space group Pnam-D2h16, and thus the structure is very close to centrosymmetric. Structural evidence for the polarity of the K2NbO2F3 crystal is the subtle differences in the Nb–O bonds along the c axis in the (NbO3F3) octahedra, together with the presence of similar differences in the K1–O bonds. Extremely weak, close to the detection limit, very small deviations from the centrosymmetry of the entire structure also correlate with the existence of an almost second-order irreversible transformation of K2NbO2F3 into a centrosymmetric phase at temperatures 50–60 °C below the decomposition temperature of the substance at 560 °C. [ABSTRACT FROM AUTHOR]

At present, the rational design and facile synthesis of highly active and low-cost photocatalysts are still facing great challenges. Herein, a series of Zn0.5Cd0.5S/NiS (x mol%) composite photocatalysts have been synthesized via a simple and mild one-pot hydrothermal method. Compared with pure Zn0.5Cd0.5S, the NiS-loaded samples exhibit enhanced photocatalytic hydrogen generation performance, in which the Zn0.5Cd0.5S/NiS-5% sample has the highest H2 production rate of 10 855 ± 461 μmol h−1 g−1 with a quantum yield of 11.82% at 365 nm, which is almost 6.3 times higher than that of pristine Zn0.5Cd0.5S. The high activity of the Zn0.5Cd0.5S/NiS nanosheets may be attributed to their distinct nanostructure, including a short transfer distance of photoinduced charge carriers, a large number of unsaturated surface atoms, and a large surface area. Moreover, the added NiS nanoparticles served as an effective cocatalyst to promote photoinduced electron transfer and enhance the surface kinetics of H2 evolution. Our work provides a simple and effective route for the preparation of sulphur-based photocatalysts, which can significantly improve the efficiency of hydrogen production from water. [ABSTRACT FROM AUTHOR]

The synthesis of highly efficient NiFe-layered double hydroxides (NiFe-LDHs) to catalyze the oxygen evolution reaction (OER) is urgent and challenging. Herein, NiFe–FeCl3-x and NiFe–FeCl2-x samples (where FeCl3 and FeCl2 represent the Fe sources and x represents the imposed reaction time: 6, 12, and 24 h) were prepared via one-pot hydrothermal synthesis using Fe sources characterized by Fe(III) or Fe(II) valence states. In the presence of triethanolamine, when FeCl3 was used as the Fe source, pure NiFe-LDH was obtained, whose crystallinity increased with increasing hydrothermal treatment time. In contrast, when FeCl2 was used as the Fe source, a mixture of NiFe-LDH, Fe2O3, and trace amounts of Fe3O4 was obtained. The content of NiFe-LDH in the mixture increased under longer hydrothermal treatment and NiFe–FeCl3-x catalysts exhibited better OER performance than NiFe–FeCl2-x catalysts. Specifically, NiFe–FeCl3-6 afforded the highest OER performance with an overpotential of 246.8 mV at 10 mA cm−2 and a Tafel slope of 46.1 mV dec−1. Herein, we investigated the effects of the valence state of Fe precursors on the structures and OER activities of the prepared catalysts; the mechanism of NiFe-LDH formation via hydrothermal synthesis in the presence of triethanolamine was also proposed. [ABSTRACT FROM AUTHOR]

The presence of sulfamethoxazole (SMX) in natural waters has become a significant concern recently because of its detrimental effects on human health and the ecological environment. To address this issue, it is of utmost urgency to develop a reliable method that can determine SMX at ultra-low levels. In our research, we utilized PVP-induced shape control of a hydrothermal synthesis method to fabricate layer-like structured VS2, and employed it as an electrode modification material to prepare an electrochemical sensor for the sensitive determination of SMX. Thus, our prepared VS2 electrodes exhibited a linear range of 0.06–10.0 μM and a limit of detection (LOD) as low as 47.0 nM (S/N = 3) towards SMX detection. Additionally, the electrochemical sensor presented good agreement with the HPLC method, and afforded perfect recovery results (97.4–106.8%) in the practical analysis. The results validated the detection accuracy of VS2 electrodes, and demonstrated their successful applicability toward the sensitive determination of SMX in natural waters. In conclusion, this research provides a promising approach for the development of electrochemical sensors based on VS2 composite materials. [ABSTRACT FROM AUTHOR]

Upconversion luminescence (UCL) is a fluorescence process where two or more lower-energy photons convert into a higher-energy photon. Lanthanide (Ln3+)-doped UCL materials often suffer from weak luminescence, especially when directly synthesized by a hydrothermal (HT) process due to the existing hydroxyl group and undesirable arrangement of dopants within host lattices which quench luminescence and limit energy transfer. Therefore, additional heat treatment processes are required to enhance their UCL emission, even though direct hydrothermal synthesis without further heat treatment has the advantages of low energy consumption, fast synthesis, and wide applicability to generate UCL materials. In this study, via a HT process without annealing, we have produced Yb3+ and Er3+ co-doped SrMoO4 submicron spindles with a strong green UCL emission which can be seen with the naked eye, which HT produced oxide-based UCL materials often fail to demonstrate. We have investigated different HT synthesis conditions, such as temperature, time, pH and dopant composition, which control the nucleation, growth, lattice structure arrangement, and ultimately their UCL properties through XRD, SEM, EDS and UCL measurements. The bright green UCL from the SrMoO4:Yb,Er submicron spindles is further enhanced by post-synthesis annealing within a molten NaNO3/KNO3 system to prevent particle size growth. The green UCL intensity from the annealed SrMoO4:Yb,Er submicron spindles surpasses samples produced by the solid-state method and is comparable to that from the commercial NaYF4:Yb,Er sample. We have further studied the temperature-dependent luminescence of both the HT-prepared and molten-salt annealed SrMoO4:Yb,Er submicron spindle samples. The strong UCL from our SrMoO4:Yb,Er submicron spindles could warrant their candidacy for bioimaging and anticounterfeiting applications. [ABSTRACT FROM AUTHOR]

Natural photosynthetic biosystems, with elaborate spatial structures, possess substantial specific surface areas and strong light-scattering abilities and provide a blueprint for the fabrication of photocatalysts for efficiently capturing and utilizing solar energy. However, mimicking sophisticated natural structures by a rational design is a great challenge. Herein, we report a facile and universal symbiosis hydrothermal synthesis strategy for obtaining biomimetic volvox-like double-core nested hollow materials. The nested hollow materials possessed the special notched "mother–twin" core–shell structure and the core numbers could be well controlled by adjusting the amount of precursor. The notched double-core hollow ZnO/CdS (mother–twin HZC) was facilely constructed by the direct chemical deposition of CdS nanosheets on the double-core hollow ZnO (mother–twin HZ). The notched complex spatial heterostructure possessed a multiple light-reflection capability (improving the utilization of solar energy), tight interfacial contact (favoring charge migration), and a high surface-to-volume ratio (providing sufficient active sites for H2 production). Both the Z-scheme ZnO/CdS heterostructures and the special nested hollow structure could synergistically enable achieving a remarkable hydrogen generation rate (up to 18.70 mmol g−1 h−1) under visible-light irradiation, exceeding that of the reported similar ZnO/CdS heterostructure without co-catalysts. [ABSTRACT FROM AUTHOR]

Upconversion luminescence (UCL) is a fluorescence process where two or more lower-energy photons convert into a higher-energy photon. Lanthanide (Ln3+)-doped UCL materials often suffer from weak luminescence, especially when directly synthesized by a hydrothermal (HT) process due to the existing hydroxyl group and undesirable arrangement of dopants within host lattices which quench luminescence and limit energy transfer. Therefore, additional heat treatment processes are required to enhance their UCL emission, even though direct hydrothermal synthesis without further heat treatment has the advantages of low energy consumption, fast synthesis, and wide applicability to generate UCL materials. In this study, via a HT process without annealing, we have produced Yb3+ and Er3+ co-doped SrMoO4 submicron spindles with a strong green UCL emission which can be seen with the naked eye, which HT produced oxide-based UCL materials often fail to demonstrate. We have investigated different HT synthesis conditions, such as temperature, time, pH and dopant composition, which control the nucleation, growth, lattice structure arrangement, and ultimately their UCL properties through XRD, SEM, EDS and UCL measurements. The bright green UCL from the SrMoO4:Yb,Er submicron spindles is further enhanced by post-synthesis annealing within a molten NaNO3/KNO3 system to prevent particle size growth. The green UCL intensity from the annealed SrMoO4:Yb,Er submicron spindles surpasses samples produced by the solid-state method and is comparable to that from the commercial NaYF4:Yb,Er sample. We have further studied the temperature-dependent luminescence of both the HT-prepared and molten-salt annealed SrMoO4:Yb,Er submicron spindle samples. The strong UCL from our SrMoO4:Yb,Er submicron spindles could warrant their candidacy for bioimaging and anticounterfeiting applications. [ABSTRACT FROM AUTHOR]

Low charge carrier separation efficiency is one of the key factors restricting photocatalytic hydrogen evolution performance. It is an effective strategy to build heterojunctions to steer charge migration. Herein, a series of x-SnS2/SnS-Cd0.5Zn0.5S (x-SS-CZS) nanosphere composites with varying mass ratios of SnS2/SnS (SS) were prepared through in situ hydrothermal synthesis. Moreover, XRD, TEM, and XPS were used to characterize the 3D core–shell SS-CZS multi-heterojunction composite. The 5-SS-CZS heterojunction composite with 5 wt% content of SS exhibits a remarkable hydrogen evolution rate of 168.85 mmol g−1 h−1, which is 5.4 times higher than that of pristine twin CZS (31.08 mmol g−1 h−1) and 1.9 times higher than that of 5-SnS2-CZS (88.21 mmol g−1 h−1). Furthermore, the composite catalyst showed excellent photostability after four cycles of reactions under visible light illumination. The apparent quantum yield at λ = 420 nm could reach up to 24.78%. The excellent hydrogen evolution performance of 5-SS-CZS nanospheres is ascribed to the following factors: (1) a core–shell catalyst with broad spectral absorption improves light utilization efficiency, (2) hybrid material with large surface area provides more active sites and shows the highest H2 activity, (3) a multi-heterojunction composite extends the lifetime of photoinduced carriers and accelerates charge separation and migration, and (4) SS as a hole trapping agent enhances the photocatalytic stability performance. This work proposes a possible photocatalytic mechanism, while also providing a novel approach for the synthesis of highly active and stable photocatalysts. [ABSTRACT FROM AUTHOR]

This study utilized a hydrothermal method and air calcination to prepare a bimetallic metal–organic framework (MOF) derived Co3O4/SnO2 nanocomposite material, which was employed as a sensing material for ethanol detection. The structure, elemental composition, and surface morphology of Co3O4/SnO2 nanocomposite materials were defined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Compared to SnO2 nanoparticles derived from metal–organic frameworks, the bimetallic metal–organic framework-derived Co3O4/SnO2 nanocomposite material exhibits significantly superior ethanol sensing performance. At 225 °C, the response value (R = Ra/Rg) to 100 ppm ethanol is 135, demonstrating excellent repeatability, selectivity and stability. Gas sensitivity assessment findings indicate that the 3 at% (Co/Sn) Co3O4/SnO2 nanocomposite is an excellent gas sensing material, providing strong technical support for ethanol detection and environmental monitoring. [ABSTRACT FROM AUTHOR]

The synthesis of barium and strontium stannates in the process of decomposition of hydrothermally obtained precursors has been investigated. It was found that endothermic weight loss during the synthesis of barium stannate occurs in two stages, whereas during the synthesis of strontium stannate it occurs in one stage. From the summary of the results of thermogravimetric analysis, X-ray diffraction, and Mössbauer spectroscopy, the composition and local structure of X-ray amorphous phases are proposed. It is shown that the improvement of the crystal structure of the perovskite phases of MSnO3 (M = Ba, Sr) and the symmetry of the local environment of 119Sn continues up to high temperatures (1250–1500 °C) and is associated with the elimination of defects in the anion sublattice. The photocatalytic activity of hydrothermal phases MSn(OH)6 and their thermolysis products has been studied and was found not to be directly related to the specific surface area of the photocatalysts. The degradation of rhodamine B (RhB) occurs during the "dark" stages of catalysis due to the interaction of the dye with reactive oxygen species (mainly singlet oxygen). At the first stage, the decomposition of the RhB photochromic system is observed, whereas at the final stage of bleaching the dye is deethylated. [ABSTRACT FROM AUTHOR]

A microwave-assisted hydrothermal solution synthesis methodology is used to prepare 3D hierarchical flowery TiO2 microspheres quickly and without calcination. The X-ray diffraction analysis showed that the microspheres are crystallized in the anatase form. Scanning electron microscopy showed that the anatase 3D hierarchical flowery TiO2 microspheres comprised many nm-thick petal-like features evenly distributed in each microsphere. The use of microwaves (for only 10 min at 200 W) acted as the additional source of energy that resulted in the accelerated growth of flowery TiO2 microspheres that otherwise would require long durations to form under only hydrothermal conditions. The microspheres exhibited a large specific surface area of 87.58 m2 g−1 and unique pore characteristics, making them suitable for photocatalysis. In this context, the measured photodegradation efficiency of the 3D hierarchical flowery anatase-TiO2 microspheres in degrading methylene blue dye was as high as 98%. [ABSTRACT FROM AUTHOR]

Electrocatalytic nitrogen reduction (NRR) for artificial ammonia synthesis under ambient conditions is considered a promising alternative to the traditional Haber–Bosch process. However, it still faces multiple challenges such as the difficulty of N2 adsorption and activation and limited Faraday efficiency. In this work, a bimetallic oxide MnMoO4 was prepared by a hydrothermal method and low temperature calcination. The influence of the sintering temperature on the microstructure (crystallinity and oxygen vacancies) of the oxide and its NRR properties were systematically explored. The results showed that MnMoO4 sintered at 500 °C had the highest concentration of OVs and showed excellent NRR performance, with the highest NH3 yield (up to 12.28 μg h−1 mgcat−1), high Faraday efficiency (23.04% at −0.30 V vs. RHE), and good stability at −0.40 V vs. RHE, and the catalytic performance was about two times higher than that of Mn2O3 and MoO3. It is also superior to other bimetallic oxide NRR electrocatalysts reported in some cases. In addition, we also explored the ratio between Mn and Mo metals, and the catalytic effect was the best when Mn : Mo = 1 : 1. Due to the synergistic effect between Mn and Mo metals and the large number of OVs present internally, the catalytic activity for the NRR was largely improved. This study suggests that the bimetallic oxide MnMoO4 may be a promising NRR electrocatalyst. [ABSTRACT FROM AUTHOR]

Spinel-type inorganic pigments with intensive color and chemical/thermal stability are showing extensive applications that could be further broadened by color manipulation and improvement of the material properties through nanosizing. In this study, we report the supercritical hydrothermal synthesis of nonstoichiometric spinel-type cobalt gallate nanoparticles (Co–Ga NPs) with controlled color. Without the conventional calcination procedure, NPs with greenish-blue, blue, and yellowish-green colors were synthesized from precursor solutions at pH 7, 9, and 11, respectively, with a low Co/Ga molar ratio of 0.25. X-ray diffraction, scanning/transmission electron microscopy, and inductively coupled plasma-atomic emission spectroscopy methods suggest that the products were spinel-type cobalt gallate NPs with high crystallinity and a nonstoichiometric composition. Based on an X-ray absorption fine structure investigation, the prepared nonstoichiometric Co–Ga NPs were found to have different cationic configurations from stoichiometric CoGa2O4 produced by a solid-state reaction during calcination. Meanwhile, the degrees of distortions at tetrahedral and octahedral sites in the NPs were evaluated by Raman spectroscopy. In particular, nonstoichiometric Co–Ga NPs with a blue color were prepared without calcination for the first time and were found to have lower tetrahedral cobalt occupancy but comparable octahedral cobalt occupancy and larger polyhedral distortions at tetrahedral sites when compared to calcined CoGa2O4. We also discuss strategies that could realize Co–Ga NPs with a more brilliant blue color using the present technique based on an investigation of the growth process. [ABSTRACT FROM AUTHOR]

A strategy involving organic photocatalytic conversion using hydrothermal synthesis of high-entropy oxide (HEO) (CoCuZnMnNa)Ox nanoparticles was developed. Under mild conditions, HEO nanoparticles were driven by visible light to achieve ideal yields and selectivity in sulfide oxidative coupling reactions and benzimidazole cyclization reactions, with a wide substrate range. This study is expected to contribute to the use of high-entropy oxides in organic photocatalysis. [ABSTRACT FROM AUTHOR]

Regarding issues such as the removal of Al and resource utilization of phosphorus iron, a recycling process is proposed in this paper in which spent cathode materials and Al foil are leached by low-concentration acids, then Al is selectively precipitated, and finally the lithium iron phosphate material is synthesized by a one-step hydrothermal synthesis method after being prepared in a certain liquid ratio. Each influencing factor in the processes of acid leaching and precipitation of Al was investigated, and the corresponding mechanism and elemental direction were analyzed. The experimental results showed that the ideal leaching effect could be achieved using low concentrations of sulfuric acid, at leaching rates of 99.98%, 99.12%, 99.16%, and 22.44% for lithium, iron, phosphorus, and Al, respectively, under optimal conditions. Al was selectively precipitated in the form of Al phosphate, and the removal rate could reach more than 99.71%. This experimental scheme significantly reduces the necessary amounts of acid and alkali, produces less slag, is carried out using a compact process, and realizes the efficient recycling of lithium iron phosphate resources. [ABSTRACT FROM AUTHOR]

As one of the state-of-the-art solid Lewis acid catalysts, the Sn-beta stannosilicate zeolite is increasingly applied in the field of biomass conversion. Due to the similar framework structures between FAU and beta topology, the efficient hydrothermal synthesis of Sn-beta zeolites from low-cost FAU zeolites should be possible via an interzeolite transformation method. In the present work, a well-crystallized Sn-beta zeolite was rapidly synthesized via a novel interzeolite transformation method without the aid of beta seeds, and its structural evolution was systematically investigated by tracking the crystallization time. These results indicated that the nanosized Sn-beta zeolite framework contained four-fold coordinated Sn species, along with abundant intercrystalline mesopores. In addition, the glucose isomerization performance of the Sn-beta zeolite catalyst was evaluated and compared with that of traditional fluoride-mediated Sn-beta-F and gas–solid isomorphous substituted Sn-beta-PS zeolites with similar Sn contents. The fructose yield results demonstrated the superior performance of the Sn-beta catalyst. Further, the reaction parameters (reaction temperature, catalyst dosage, and reaction time) were optimized, and the excellent reusability of the Sn-beta zeolite was demonstrated by almost complete regeneration and restoration of the catalytic performance via calcination. This resultant Sn-beta zeolite was an active and stable heterogeneous catalyst for the isomerization of glucose into fructose. This work provides some guidance for the design and synthesis of nanosized metallosilicate zeolites via interzeolite transformation, focusing on the promotion effects of zeolite nucleation and crystallization. [ABSTRACT FROM AUTHOR]

The Keggin phosphotungstic acid (PW12) embedded metal–organic framework copper benzene-1,3,5-tricarboxylate (CuBTC), CuBTC@PW12, was fabricated by a facile hydrothermal synthesis technique. With a unique tetrakaidecahedron structure and multiple active sites, the obtained CuBTC@PW12 exhibited peroxidase-mimicking activity, which promoted a novel strategy for qualitative and quantitative detection of hydrogen peroxide (H2O2) and sequential sensing of ascorbic acid (AA) via colorimetric evolution. Notably, with the advantages of strong redox performance of POMs and the unique porous structure of metal organic frameworks (MOFs), as peroxidase mimics, CuBTC@PW12 achieved highly selective and sensitive detection of H2O2via oxidizing TMB to a blue oxidation product (ox-TMB), with a limit of detection of 2.67 μM within the 0.01 to 1.0 mM scale. Concomitantly, the AA can be monitored consecutively by reducing the ox-TMB with fading blue color quantitatively with a limit of detection at 0.15 μM in the range of 0.01–0.10 μM. The recoveries for the determination of AA in human serum were obtained at 94.63–105%. These results manifested that CuBTC@PW12 could be used as a peroxide-mimetic enzyme for the continuous detection of H2O2 and AA with the advantages of simplicity, efficiency, sensitivity and accuracy. [ABSTRACT FROM AUTHOR]

In this work, a photoelectrochemical (PEC) aptamer sensor using a TiO2/AgInS2/ZnS composite material as a photoelectric active anode substrate and NiCo-MOF@Au as a quenching element is constructed to detect Hg2+. Titanium dioxide (TiO2) was prepared by hydrothermal synthesis. The prepared TiO2 consists of rod-like aggregations with a unique structure and large specific surface area. TiO2/AgInS2/ZnS composites with higher photochemical activity were obtained by modifying AgInS2 quantum dots on the surface under electrostatic force and ZnS modification by the successive ionic layer adsorption and reaction (SILAR) method. The constructed PEC aptamer sensing platform has good sensing performance for Hg2+, and the detection limit is as low as 34 fM, showing high selectivity and reproducibility. At the same time, the application of this method in actual environmental samples is evaluated and satisfactory results are obtained. Therefore, the developed photoelectrochemical aptamer sensor provides a promising technique for the detection of Hg2+ in the environment. [ABSTRACT FROM AUTHOR]

Oxide semiconductors with mixed-valence states generally exhibit excellent optoelectronic and photochemical properties due to facile charge transfer in redox reactions. In this work, we investigate the effects of mixed alkali on the optical absorption, luminescence spectra and photocatalytic abilities of (Na1−xKx)Sb3O7 nanoparticles. All the samples are fabricated using a simple one-step hydrothermal method. The structural studies show that the largest substitution of K+ ions in (Na1−xKx)Sb3O7 is at x = 0.3. In hydrothermal synthesis, the mixed arrangement of K+ and Na+ in (Na1−xKx)Sb3O7 has an influence on the crystal shape of particles. NaSb3O7 develops into a regular cube shape. With the increase of K+ ions in (Na1−xKx)Sb3O7, the edges and corners of the cube are further ground off, resulting in irregularly spherical particles. This mixed-alkali antimonite belongs to a p-type indirect allowed transition semiconductor, and the optical band gap is 2.71 eV (x = 0.3). The intrinsic luminescence of NaSb3O7 is detected at 540 nm, which is nearly quenched in Na0.7K0.3Sb3O7. It is demonstrated that the substitution of K+ in NaSb3O7 significantly increases the photodegradation of RhB solutions. There are two types of Sb cations, i.e., Sb5+ and Sb3+ mixed in the structure. The improved photocatalysis is attributed to the charge mediators between Sb5+/Sb3+ couples. The experiment shows that co-doping cations in antimonite oxides may be one of the strategies to improve photochemical properties. [ABSTRACT FROM AUTHOR]

In this work, a photoelectrochemical (PEC) aptamer sensor using a TiO2/AgInS2/ZnS composite material as a photoelectric active anode substrate and NiCo-MOF@Au as a quenching element is constructed to detect Hg2+. Titanium dioxide (TiO2) was prepared by hydrothermal synthesis. The prepared TiO2 consists of rod-like aggregations with a unique structure and large specific surface area. TiO2/AgInS2/ZnS composites with higher photochemical activity were obtained by modifying AgInS2 quantum dots on the surface under electrostatic force and ZnS modification by the successive ionic layer adsorption and reaction (SILAR) method. The constructed PEC aptamer sensing platform has good sensing performance for Hg2+, and the detection limit is as low as 34 fM, showing high selectivity and reproducibility. At the same time, the application of this method in actual environmental samples is evaluated and satisfactory results are obtained. Therefore, the developed photoelectrochemical aptamer sensor provides a promising technique for the detection of Hg2+ in the environment. [ABSTRACT FROM AUTHOR]

Oxide semiconductors with mixed-valence states generally exhibit excellent optoelectronic and photochemical properties due to facile charge transfer in redox reactions. In this work, we investigate the effects of mixed alkali on the optical absorption, luminescence spectra and photocatalytic abilities of (Na1−xKx)Sb3O7 nanoparticles. All the samples are fabricated using a simple one-step hydrothermal method. The structural studies show that the largest substitution of K+ ions in (Na1−xKx)Sb3O7 is at x = 0.3. In hydrothermal synthesis, the mixed arrangement of K+ and Na+ in (Na1−xKx)Sb3O7 has an influence on the crystal shape of particles. NaSb3O7 develops into a regular cube shape. With the increase of K+ ions in (Na1−xKx)Sb3O7, the edges and corners of the cube are further ground off, resulting in irregularly spherical particles. This mixed-alkali antimonite belongs to a p-type indirect allowed transition semiconductor, and the optical band gap is 2.71 eV (x = 0.3). The intrinsic luminescence of NaSb3O7 is detected at 540 nm, which is nearly quenched in Na0.7K0.3Sb3O7. It is demonstrated that the substitution of K+ in NaSb3O7 significantly increases the photodegradation of RhB solutions. There are two types of Sb cations, i.e., Sb5+ and Sb3+ mixed in the structure. The improved photocatalysis is attributed to the charge mediators between Sb5+/Sb3+ couples. The experiment shows that co-doping cations in antimonite oxides may be one of the strategies to improve photochemical properties. [ABSTRACT FROM AUTHOR]

α-FeOOH (goethite) with a nanorod morphology has been synthesized successfully by a hydrothermal method, and further calcinated (6 h at 520 °C) to obtain α-Fe2O3 (hematite) nanoparticles of spherical shape morphology. The synthesized α-FeOOH and α-Fe2O3 nanoparticles were subjected to various characterization techniques (X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-Vis diffuse reflectance spectroscopy (UV-DRS), photoluminescence (PL) spectroscopy, liquid chromatography with mass spectrometry (LCMS), dynamic light scattering (DLS) and zeta potential (ZP), thermogravimetry analysis (TGA), differential thermal analysis (DTA), X-ray photoelectron spectrometer (XPS), N2 adsorption–desorption isotherms (BET), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDAX) and transmission electron microscopy (TEM)). Meanwhile, the as-synthesized α-FeOOH and α-Fe2O3 nanoparticles were used to degrade hazardous organic cationic dyes such as brilliant green (BG) and rhodamine B (RhB) under sunlight. It was observed from the study that BG (96%, 110 min) and RhB (93%,90 min) show responsive degradation in the presence of α-FeOOH nanorods. Besides this, 99% (100 min) and 99.4% (80 min) BG and RhB get degraded using α-Fe2O3 nanoparticles, respectively. Overall, α-Fe2O3 nanoparticles were a more prominent photocatalyst for the degradation of BG and RhB than α-FeOOH nanorods. [ABSTRACT FROM AUTHOR]

Two novel bismuth oxosalts, β-Bi3O3(VO4) and KBi5O5(PO4)2, synthesized hydrothermally crystallize in the triclinic space group P1¯ with a = 5.7337 (6), b = 7.1029 (8), c = 9.298 (1) Å, α = 80.334 (3), β = 78.576 (3), γ = 68.557° (3), V = 343.58 (7) Å3, Z = 8 and in the monoclinic P21/c space group with a = 8.0264 (6), b = 5.4616 (4), c = 27.769 (2), β = 95.697 (2), V = 1211.29 (16) Å3, Z = 4, respectively. Their crystal structures are built on corrugated layers formed of the linkage of oxo-centered OBi4 or OBi4, OBi5 and O(Bi,K)4 tetrahedra sharing edges surrounded by isolated vanadate/phosphate groups. β-Bi3O3(VO4) is suggested to be a high-pressure polymorph with a more symmetric crystal structure than the α-modification; this agrees with the trend of decreasing structural complexity with increasing pressure. Raman and photoluminescence spectra were measured for β-Bi3O3(VO4) and KBi5O5(PO4)2. The first one exhibits a weak emission at room temperature in the red-near-infrared region with a maximum at 650–660 nm, whereas the second bismuth oxosalt emits in the green orange range with a peak at 550 nm. [ABSTRACT FROM AUTHOR]

Although ZrSiO4 is the most well-known compound in the zircon-structured family (space group I41/amd), the experimental conditions for preparing pure and well-crystallized phases that are doped with a tetravalent element via hydrothermal synthesis have never been clearly discussed in the literature. With the aim to answer this question, the experimental conditions of the preparation of ZrSiO4 and (Zr,Ce)SiO4 were investigated in order to synthesize well-crystallized and pure phases. A multiparametric study has been carried out using soft hydrothermal conditions with variables including reactant concentration, initial pH of the reactive medium, and duration of the hydrothermal treatment. Pure ZrSiO4 was obtained through hydrothermal treatment for 7 days at 250 °C, within a large acidity range (1.0 ≤ pH ≤ 9.0) and starting from CSi ≈ CZr ≥ 0.2 mol L−1. As hydrothermally prepared zircon structured phases can be both hydrated and hydroxylated, its annealed form was also studied after heating to 1000 °C. Based on these results, the synthesis of (Zr,Ce)SiO4 solid solutions was also investigated. The optimal hydrothermal conditions to acquire pure and crystallized phases were as follows: 7 days at 250 °C with initial pH = 1 and concentration of the reactants equal to 0.2 mol L−1. This led to Zr1−xCexSiO4 solid solutions with the incorporated Ce content up to 40 mol%. Samples were characterized using multiple methods, including laboratory and synchrotron PXRD, IR and Raman spectroscopies, SEM, and TGA. Moreover, it was found that these phases were thermally stable in air up to at least 1000 °C. [ABSTRACT FROM AUTHOR]

Triclinic NaCe(WO4)2 with oxygen monovacancies and divacancies has been successfully prepared via a facile cetyltrimethyl ammonium bromide (CTAB)-assisted hydrothermal technique. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy have been employed to determine the unit cell and microstructure of the NaCe(WO4)2. The oxygen vacancies, structural distortion etc. have been investigated using Fourier-transform infrared, Raman and X-ray photoelectron spectroscopies. The synthesized samples exhibit an intense blue emission at 434 nm due to the 5d–4f transition of Ce3+ within the CeO8 dodecahedra, while the emission at 485 nm is ascribed to the 5d–4f transition within CeO7. It has also been identified that two emissions at 451 and 520 nm come from CeO6. Additionally, we find that the temperature of the hydrothermal reaction guides the formation of CeO7 and CeO6. In contrast to a previous ethylenediamine tetraacetic acid (EDTA)-assisted synthesis of NaCe(WO4)2 that results in a predominant green emission, our samples exhibit strong violet emissions indicating that less CeO7 and CeO6 is formed when using CTAB. We have also conducted ab initio calculations using density-functional theory, which reveals that the valence and conduction bands comprise of the O 2p orbitals and a O 2p–Ce 5d hybridization, respectively. The Ce 5dz2, 5dyz and 5dxz orbitals mostly facilitate the 5d–4f transition within the CeO7 and CeO6 polyhedra. Commission Internationale de I'Eclairage coordinates are found in the blue region with a correlated color temperature (CCT) of ∼7715 K indicating the potential for α-NaCe(WO4)2 to be used in cold solid state lighting applications. Finally, we also observe that the oxygen vacancies can act as active centers for the adsorption of molecular oxygen, which in consequence leads NaCe(WO4)2 to have gas sensing properties. [ABSTRACT FROM AUTHOR]

The key step for hydrogen production through water electrolysis is the development of highly efficient and inexpensive oxygen evolution reaction (OER) catalysts. In this work, we report the successful synthesis of a nanostructured Fe-doped cobalt-based telluride (Fe-doped CoTe2) catalyst on Co foam by a simple one-step hydrothermal synthesis method, which shows excellent OER performance. The influences of Fe doping amounts and reaction temperatures on the morphology, structure, composition, and the OER performance of cobalt-based tellurides have been systematically studied. The optimal sample Co@0.3 g FeCoTe2-200 exhibits a low overpotential of 300 mV at a current density of 10 mA cm−2, and a small Tafel slope of 36.99 mV dec−1, outperforming the undoped cobalt telluride catalysts (Co@CoTe2-200). The Co@0.3 g FeCoTe2-200 electrode also reveals a small overpotential degradation of around 26 mV after an 18-hour continuous OER process. These results unambiguously confirm that Fe doping helps improve the OER activity and long-term catalytic stability. The superior performance of nanostructured Fe-doped CoTe2 can be attributed to the porous structure and the synergistic effect of Co and Fe elements. This study provides a new approach for the preparation of bimetallic telluride catalysts with enhanced OER performance, and Fe-doped CoTe2 holds substantial promise for use as a high-efficiency, cost-effective catalyst for alkaline water electrolysis. [ABSTRACT FROM AUTHOR]

Obtaining white light from a single-component phosphor is still a significant challenge due to the complex energy transfer between multiple luminescent centers. Herein, white light emission is obtained in a single-component lutetium tungstate without any doping elements. By tuning the pH values during the hydrothermal synthesis, the orthorhombic Lu2W3O12 transformed into monocline Lu6WO12 and rhombohedra Lu6WO12. Only the monoclinic Lu2WO6 phase emitted light, whereas the other two phases did not. The main reason was that the exciton binding energy of Lu2WO6 was larger than that of Lu2W3O12 and Lu6WO12. Except for the 480 nm intrinsic emission of Lu2WO6, new long-wavelength excitation and emission bands were observed with the center at 340 nm and 520 nm. Based on the first-principle calculation, this new photoluminescence band comes from the electron transition between the local states of oxygen vacancies and valence band. Owing to this new broad-band emission, the white light LED lamp is fabricated by combining Lu2WO6 phosphor synthesized at pH values of 4.5 and 6 and 365 nm LED chips. The CIE coordinates of the pc-WLEDs are (0.346, 0.359) and (0.380, 0.380), respectively, and both are located in the white light region. Our research demonstrated a facile way to obtain a single-component white light emission phosphor without any doping components for pc-WLED applications. [ABSTRACT FROM AUTHOR]

Herein, we present a one-step hydrothermal synthesis approach towards the production of pure MnWO4, which is driven by visible light to produce HClO. Significantly, our findings demonstrate the first successful implementation of noble-metal-free materials for photocatalytic chlorine production in natural seawater. This discovery has immense potential for various applications. [ABSTRACT FROM AUTHOR]