Cerium phosphate nanotubes: synthesis, characterization and biosensing

Facile synthesis of flower-like CePO4 with a hierarchical structure for the simultaneous electrochemical detection of dopamine, uric acid and acetaminophen

A flower-like CePO4 with a hierarchical structure was hydrothermally prepared for electrochemical sensing of dopamine, uric acid and acetaminophen.

A glassy carbon electrode modified with cerium phosphate nanotubes for the simultaneous determination of hydroquinone, catechol and resorcinol

A nafion film containing cerium phosphate nanotubes was pasted onto a glassy carbon electrode (GCE) to obtain a sensor for hydroquinone (HQ). The morphologies and components of the coating were characterized by transmission electron microscopy, scanning electron microscopy and energy-dispersive spectroscopy. Cyclic voltammetry and differential pulse voltammetry (DPV) showed the specific surface of the electrode to be significantly increased and the electron transfer rate to be accelerated. The modified GCE was applied to the determination of hydroquinone (HQ) via DPV. The oxidation current increases linearly in the 0.23 μM to 16 mM HQ concentration range which is as wide as five orders of magnitude. The limit of detection is 0.12 μM (based on a signal-to-noise ratio of 3), and the sensitivity is 1.41 μA·μM^-1 cm^-2. The method was further applied to the simultaneous determination of HQ, catechol and resorcinol. The potentials for the three species are well separated (20, 134, and 572 mV vs SCE). Average recoveries from (spiked) real water samples are between 95.2 and 107.0%, with relative standard deviations of 0.9~2.7% (for n = 3) at three spiking levels. The method was validated by independent assays using HPLC. Graphical abstract ᅟ.

L. A, Arunkumar P, Ahmed W, Ryu S, Cha SW, Babu KS. Structure dependent luminescence, peroxidase mimetic and hydrogen peroxide sensing of samarium doped cerium phosphate nanorods

Samarium doped cerium phosphate nanorods exhibit enhanced peroxidase mimetic activity and hydrogen peroxide sensing.

Transcription of Nanofibrous Cerium Phosphate Using a pH-Sensitive Lipodipeptide Hydrogel Template

A novel and simple transcription strategy has been designed for the template-synthesis of CePO₄·xH₂O nanofibers having an improved nanofibrous morphology using a pH-sensitive nanofibrous hydrogel (glycine-alanine lipodipeptide) as structure-directing scaffold. The phosphorylated hydrogel was employed as a template to direct the mineralization of high aspect ratio nanofibrous cerium phosphate, which in-situ formed by diffusion of aqueous CeCl₃ and subsequent drying (60 °C) and annealing treatments (250, 600 and 900 °C). Dried xerogels and annealed CePO₄ powders were characterized by conventional thermal and thermogravimetric analysis (DTA/TG), and Wide-Angle X-ray powder diffraction (WAXD) and X-ray powder diffraction (XRD) techniques. A molecular packing model for the formation of the fibrous xerogel template was proposed, in accordance with results from Fourier-Transformed Infrarred (FTIR) and WAXD measurements. The morphology, crystalline structure and composition of CePO₄ nanofibers were characterized by electron microscopy techniques (Field-Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy/High-Resolution Transmission Electron Microscopy (TEM/HRTEM), and Scanning Transmission Electron Microscopy working in High Angle Annular Dark-Field (STEM-HAADF)) with associated X-ray energy-dispersive detector (EDS) and Scanning Transmission Electron Microscopy-Electron Energy Loss (STEM-EELS) spectroscopies. Noteworthy, this templating approach successfully led to the formation of CePO₄·H₂O nanofibrous bundles of rather co-aligned and elongated nanofibers (10⁻20 nm thick and up to ca. 1 μm long). The formed nanofibers consisted of hexagonal (P6₂22) CePO₄ nanocrystals (at 60 and 250 °C), with a better-grown and more homogeneous fibrous morphology with respect to a reference CePO₄ prepared under similar (non-templated) conditions, and transformed into nanofibrous monoclinic monazite (P21/n) around 600 °C. The nanofibrous morphology was highly preserved after annealing at 900 °C under N₂, although collapsed under air conditions. The nanofibrous CePO₄ (as-prepared hexagonal and 900 °C-annealed monoclinic) exhibited an enhanced UV photo-luminescent emission with respect to non-fibrous homologues.

Preparation of Cerium Orthophosphate Nanosphere by Coprecipitation Route and Its Structural, Thermal, Optical, and Electrical Characterization

Cerium orthophosphate (CePO4) nanoparticles were synthesized via wet chemical coprecipitation technique using cerium nitrate hexahydrate for Ce3+ ion and ammonium dihydrogen phosphate for PO43- ion source. X-ray diffraction (XRD) analysis suggests that the material belongs to monoclinic crystal system with crystallite size of 49.3 nm. Scanning electron microscope (SEM) and transmission electron microscope (TEM) reveal the surface morphology of the prepared nanoparticles as nanospheres having grain size in the range of 30–50 nm. The energy dispersive X-ray analysis (EDAX) gives elemental composition present in the grown nanomaterial. Thermogravimetric analysis suggests that the structural phase transition is above 800°C. The optical properties include UV-VIS-NIR absorption and the photoluminescence spectrum shows the absorption and emission peaks in the ultraviolet region. The dielectric constant (ε/ ) and ac conductivity properties were investigated with regard to change in temperature (40 to 500°C) and frequency (5 kHz to 1 MHz). The dielectric measurement indicates that the transition is diffused and the activation energy values decrease suggesting that the conduction mechanism is due to hopping of the charge carriers from one site to another.

Iron phosphate nanostructures synthesized by microwave method and their applications in biosensing

A fast, simple microwave heating method has been developed for synthesizing iron phosphate (FePO(4)) nanostructures. The nanostructures were characterized and confirmed by transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS), x-ray powder diffraction (XRD), Fourier transform infrared (FT-IR), and UV-vis spectroscopy. The morphology and the size of the nanomaterials are significantly influenced by the concentration of the precursors and the kinds of surfactants. The nanostructures have been employed as an electrode substrate to immobilize myoglobin (Mb) and to facilitate the direct electron transfer (DET) reaction of the protein. After being immobilized on the nanomaterials, Mb can keep its natural structure and undergo effective DET reaction with a pair of well-defined redox peaks at - (330 ± 3.0) mV (pH 6.8) and an apparent electron transfer rate constant of 5.54 s(-1). The Mb-FePO(4)/GC electrode displays good features in the electrocatalytic reduction of H(2)O(2), and thus can be used as a biosensor for detecting substrates with a low detection limit (5 ± 1 µM), a wide linear range (0.01-2.5 mM), a high sensitivity (ca. 85 ± 3 µA mM(-1) cm(-2)), as well as good stability and reproducibility. Therefore, FePO(4) nanomaterials can become a simple and effective biosensing platform for the integration of proteins/enzymes and electrodes, which can provide analytical access to a large group of enzymes for a wide range of bioelectrochemical applications.