Selected-Control Hydrothermal Synthesis and Formation Mechanism of Monazite- and Zircon-Type LaVO4 Nanocrystals

Lanthanum vanadate-based carbon nanocomposite as an electrochemical probe for amperometric detection of theophylline in real food samples

Theophylline (THP) is an emerging drug for chronic obstructive pulmonary disease whose side effects can be greatly affected by caffeine-containing real foods. Because an overdose of this substance can cause respiratory and neurological damage, producing a fast and accurate analytical procedure is critical. Based on a cutting-edge hybrid nanocomposite, this study was used to construct an electrochemical sensor for the accurate detection of THP. Spectroscopy and morphological investigation supported the easy synthesis of tetragonal-LaVO₄ (t-LV) nanopellets and LV@CNF hybrid nanocomposite. To detect THP, a highly dispersed LV@CNF nanocomposite was modified on a glassy carbon electrode as a sensing substrate. By amperometric technique, the sensor shows a wide linear range of 0.01-1070 μM, low limit of detection (2.63 nM), and sensitivity (0.228 μA μM^-1 cm^-2). Finally, the current technique was successfully used to identify THP in real food samples (chocolate, coffee and black tea).

Electrocatalytic oxidation and amperometric determination of sulfasalazine using bimetal oxide nanoparticles-decorated graphene oxide composite modified glassy carbon electrode at neutral pH

Cube-shaped samarium orthovanadate (SmVO₄) nanoparticles were interconnected with a graphene oxide sheet (GOS) using a simple and eco-friendly method to generate a SmVO₄@GOS nanocomposite. SmVO₄ was characterized using various spectroscopic and microscopic techniques, which confirmed the wrapping of GOS around the SmVO₄ nanoparticles. SmVO₄@GOS was then used to modify a glassy carbon electrode (GCE), which was evaluated for its electrochemical performance toward the assay of sulfasalazine (SSZ), an antibiotic drug. Cyclic voltammetry and amperometry were both used for the assay of SSZ using the SmVO₄@GOS-modified GCE at pH 7. The modified amperometric sensor is more sensitive, with a low detection limit (2.16 nM) and wide linear range of 20 nM-667 μM (Ag/AgCl). The electrochemical oxidation of SSZ was tested with blood serum and urine samples at physiological pH with recoveries in the range 96.1-98.6%. It indicates that the modified electrochemical sensor has good sensitivity and practical applicability toward SSZ detection. In the field of non-enzymatic sensors, SmVO₄@GOS/GCE provides a highly promising performance. Therefore, the electrochemical sensors have capacity for extensive analytical applications in biomedical devices.

Rare-Earth Doping in Nanostructured Inorganic Materials

Impurity doping is a promising method to impart new properties to various materials. Due to their unique optical, magnetic, and electrical properties, rare-earth ions have been extensively explored as active dopants in inorganic crystal lattices since the 18th century. Rare-earth doping can alter the crystallographic phase, morphology, and size, leading to tunable optical responses of doped nanomaterials. Moreover, rare-earth doping can control the ultimate electronic and catalytic performance of doped nanomaterials in a tunable and scalable manner, enabling significant improvements in energy harvesting and conversion. A better understanding of the critical role of rare-earth doping is a prerequisite for the development of an extensive repertoire of functional nanomaterials for practical applications. In this review, we highlight recent advances in rare-earth doping in inorganic nanomaterials and the associated applications in many fields. This review covers the key criteria for rare-earth doping, including basic electronic structures, lattice environments, and doping strategies, as well as fundamental design principles that enhance the electrical, optical, catalytic, and magnetic properties of the material. We also discuss future research directions and challenges in controlling rare-earth doping for new applications.

Malate-aided selective crystallization and luminescence comparison of tetragonal and monoclinic LaVO4:Eu nanocrystals

With malate (Mal2-) as a new type of chelate, tetragonal (t-) and monoclinic (m-) structured LaVO4:Eu crystals (∼10-60 nm) were selectively crystallized as nanosquares and nanorods via a hydrothermal reaction at 200 °C for 24 h. The effects of the Mal2-:(La,Eu)3+ molar ratio, solution pH and Eu3+ content on the phase structure and crystal morphology were systematically investigated and elucidated. The competition between OH- and Mal2- toward rare earth ions was discussed to play a critical role in phase selection, and the t-phase can only be fabricated at pH ∼ 6-8 with the assistance of Mal2-. The optimal Eu3+ content for luminescence was determined to be ∼5 at% under the VO43- → Eu3+ energy transfer mechanism. Experimental comparison showed that t-(La0.95Eu0.05)VO4 (λex = 275 nm, λem = 620 nm) emits ∼5.3 times as strong as m-(La0.95Eu0.05)VO4 does (λex = 313 nm, λem = 616 nm), while theoretical analysis revealed that the 5D0 level of Eu3+ has a quantum efficiency of ∼80% for the former and ∼70% for the latter. Besides, the t- and m-(La0.95Eu0.05)VO4 nanocrystal phosphors were analyzed to have fluorescence lifetimes of ∼1.53 ± 0.01 and 2.28 ± 0.01 ms for their 620 and 616 nm red emissions, respectively.

Microwave-assisted hydrothermal synthesis and spectroscopic characteristics of a Lu4Hf3O12:Pr scintillator

Microwave-assisted hydrothermal synthesis of Pr-doped Lu₄Hf₃O₁₂ nanopowders fabricates the products of different morphology. PL and RL in ceramics shows the Pr³⁺ emission.

Fluorescent LaVO4:Eu3+ micro/nanocrystals: pH-tuned shape and phase evolution and investigation of the mechanism of detection of Fe3+ ions

LaVO₄:Eu³⁺ micro/nanocrystals with various shapes were hydrothermally synthesized by adjusting the pH of the system at 180 °C for 12 h in the presence of ethylenediaminetetraacetic acid (EDTA).

Three-Dimensional Porous Iron Vanadate Nanowire Arrays as a High-Performance Lithium-Ion Battery

Development of three-dimensional nanoarchitectures on current collectors has emerged as an effective strategy for enhancing rate capability and cycling stability of the electrodes. Herein, a new type of three-dimensional porous iron vanadate (Fe0.12V2O5) nanowire arrays on a Ti foil has been synthesized by a hydrothermal method. The as-prepared Fe0.12V2O5 nanowires are about 30 nm in diameter and several micrometers in length. The effect of reaction time on the resulting morphology is investigated and the mechanism for the nanowire formation is proposed. As an electrode material used in lithium-ion batteries, the unique configuration of the Fe0.12V2O5 nanowire arrays presents enhanced capacitance, satisfying rate capability and good cycling stability, as evaluated by cyclic voltammetry and galvanostatic discharge-charge cycling. It delivers a high discharge capacity of 293 mAh·g(-1) at 2.0-3.6 V or 382.2 mAh·g(-1) at 1.0-4.0 V after 50 cycles at 30 mA·g(-1).

Catechin assisted phase and shape selection for luminescent LaVO4 zircon

Catechin conformers enhance luminescence from rare earth orthovanadates by tuning the structures in 0, 1 and 2 dimensions with a preferred tetragonal phase.

Bi(x)La(1-x)VO4 solid solutions: tuning of electronic properties via stoichiometry modifications

BixLa1-xVO4 solid solutions were obtained in the form of fine powder via a microwave-assisted hydrothermal route. The presence of a solid solution in the studied system was confirmed using X-ray diffraction (XRD) and optical spectroscopy techniques. Pure BiVO4 and LaVO4 were obtained in the monoclinic form, whereas solid solutions in the tetragonal, zircon-type structure. The optical band gap dependence on the composition of the solid solution is parabolic, thus there is a possibility to tune this parameter in a wide concentration range, from 2.4 to 4.0 eV. An absorption coefficient maximum is also concentration-dependent, possibly, due to the structural disorder of the samples. Solid solutions with Bi(3+) concentration between 11.94 and 32.57 at.% exhibit intense, green luminescence. This indicates the presence of Bi-originated electronic states within the band gap. The value of the conduction band edge potential, measured by both electrochemical impedance spectroscopy and work function measurements, is concentration-independent. Moreover, solid solutions exhibit a photoelectrochemical photocurrent switching effect, thus they may be promising materials for molecular electronics and as dioxygen activators.

A general procedure to synthesize highly crystalline metal oxide and mixed oxide nanocrystals in aqueous medium and photocatalytic activity of metal/oxide nanohybrids

A conventional and general route has been exploited to the high yield synthesis of many kinds of highly crystalline metal oxide and mixed oxide nanocrystals with different morphologies including belt, rod, truncated-octahedron, cubic, sphere, sheet via the hydrothermal reaction of inorganic precursors in aqueous solution in the presence of bifunctional 6-aminohexanoic acid (AHA) molecules as a capping agent. This method is a simple, reproducible and general route for the preparation of a variety of high-crystalline inorganic nanocrystals in scale-up. The shape of inorganic nanocrystals such as CoWO(4), La(2)(MoO(4))(3) can be controlled by simply adjusting the synthesis conditions including pH solution and reaction temperature. Further, by tuning precursor monomer concentration, the mesocrystal hierarchical aggregated microspheres (e.g., MnWO(4), La(2)(MoO(4))(3)) can be achieved, due to the spontaneous assembly of individual AHA-capped nanoparticles. These obtained AHA-capped nanocrystals are excellent supports for the synthesis of a variety of hybrid metal/oxide nanocrystals in which noble metal particles are uniformly deposited on the surface of each individual nanosupport. The photocatalytic activity of Ag/TiO(2) nanobelts as a typical hybrid photocatalyst sample for Methylene Blue degradation was also studied.