Green sonochemical synthesis and fabrication of cubic MnFe2O4 electrocatalyst decorated carbon nitride nanohybrid for neurotransmitter detection in serum samples

The binary nanomaterials and graphitic carbon based hybrid has been developed as an important porous nanomaterial for fabricating electrode with applications in non-enzymatic (bio) sensors. We report a fast synthesis of bimetal oxide particles of nano-sized manganese ferrite (MnFe₂O₄) decorated on graphitic carbon nitride (GCN) via a high-intensity ultrasonic irradiation method for C (30 kHz and 70 W/cm²). The nanocomposites were analyzed by powder X-ray diffraction, XPS, EDS, TEM to ascertain the effects of synthesis parameters on structure, and morphology. The MnFe₂O₄/GCN modified electrode demonstrated superior electrocatalytic activity toward the neurotransmitter (5-hydroxytryptamine) detection with a high peak intensity at +0.21 V. The appealing application of the MnFe₂O₄/GCN/GCE as neurotransmitter sensors is presented and a possible sensing mechanism is analyzed. The constructed electrochemical sensor for the detection of 5-hydroxytryptamine (STN) showed a wide working range (0.1–522.6 μM), high sensitivity (19.377 μA μM⁻¹ cm⁻²), and nano-molar detection limit (3.1 nM). Moreover, it is worth noting that the MnFe₂O₄/GCN not only enhanced activity and also promoted the electron transfer rate towards STN detection. The proposed sensor was analyzed for its real-time applications to the detection of STN in rat brain serum, and human blood serum in good satisfactory results was obtained. The results showed promising reproducibility, repeatability, and high stability for neurotransmitter detection in biological samples.     

Ultrasonic-assisted preparation and characterization of magnetic ZnFe2O4/g-C3N4 nanomaterial and their applications towards electrocatalytic reduction of 4-nitrophenol

Nanoball-structured ferromagnetic zinc ferrite nanocrystals (ZnFe₂O₄ NPs) entrapped with graphitic-carbon nitride (g-C₃N₄) was produced via straightforward and facile sonochemical synthetical technique (titanium probe; 100 W/cm² and 50 KHz). The morphological (SEM), elemental (EDS), diffraction (XRD), XPS, and electrochemical studies (CV) have been carry out to verify the nanostructure and shape of the materials. The ZnFe₂O₄ NPs/g-C₃N₄ electrode (GCE) was constructed which displayed outstanding electrochemical ability towards toxic 4-nitrophenol (NTP). A sensitive, selective, reproducible, and durable electrochemical NTP sensor was developed by ZnFe₂O₄ NPs/g-C₃N₄ modified electrode. The modified sensor exhibited a high sensitivity and 4.17 nanomolars of LOD. It’s greater than the LOD of previously reported NTP modified sensors. The real-time experiments of the modified electrochemical (ZnFe₂O₄ NPs/g-C₃N₄ electrode) sensor were successfully explained in various water (river and drinking) samples and its showed high standard recoveries. Therefore, sonochemical synthetical method and fabrication of modified electrode were developed this work based on environmental analysis of NTP sensor.     

Facile synthesis of copper ferrite nanoparticles with chitosan composite for high-performance electrochemical sensor

Herein, the synthesis of copper ferrite nanoparticles (CuFe₂O₄ NPs)/chitosan have been prepared by sonochemical route under ultrasonic irradiation bath at 40 kHz and 50 W. A high sensitive and stable modified electrochemical sensor was developed using a composition of copper ferrite nanoparticles coordinated with biopolymer through a facile ultrasound approach. Besides, power and frequency parameters are highly important for sonochemical synthesis and specifically structure, and size of the nanomaterials development during the ultrasonic irradiation time. In this work, ultrasonic bath was used to synthesis of CuFe₂O₄ nanomaterial at 40 kHz with 1 h. CuFe₂O₄/chitosan was characterized by FESEM, EDX, XRD and electrochemical methods. Furthermore, 8-hydroxyguanine is one of biomarker by oxidative stress. The concentrations of 8-hydroxyguanine within a cell are a measurement of oxidative stress in human body. Consequently, the measurement of 8-hydroxyguanine in blood serum samples with high specificity is of greatest importance. The CuFe₂O₄/chitosan modified electrode is displayed a low detection limit of 8.6 nM and long linear range (0.025–697.175 µM).     

Spectroscopic characteristics of the Nd3+ ions in garnet crystals

The article deals with the research of oscillator strengths and the Ω_t (t=2,4,6) intensity parameters of Nd³⁺ doped garnet crystals. It has been found that the absorption intensity of the ⁴I_9/2→⁴G_5/2, ²G_7/2 hypersensitive transition in the Ca₃(NbGa)₅O₁₂ crystals doped with Nd³⁺ is considerably higher than the corresponding values in the following garnet crystals: Y₃Al₅O₁₂:Nd, (GdY)₃(ScAl)₅O₁₂:Nd, Gd₃(ScAl)₅O₁₂:Nd and (GdСa)₃(GaZr)₅O₁₂:Nd. It has been established also that the Ω₂ intensity parameter of the Ca₃(NbGa)₅O₁₂:Nd crystals is one order of magnitude higher compared to the same parameter for the other garnet crystals. These effects in the Ca₃(NbGa)₅O₁₂:Nd crystals are explained by the presence of the Nd³⁺ ions optical sites with a symmetry of local environment C₂, C_2v, C₁.     

Intense visible luminescence from Nd-doped yttrium oxysulfide

We report on a novel luminescent phenomenon in Y₂O₂S doped with Nd³⁺. After irradiation by a 261 nm ultraviolet (UV) light into the Y₂O₂S host lattice, the Nd³⁺-doped Y₂O₂S phosphor emits intense blue luminescence in the visible light region. Moreover, this blue luminescence can also be obtained by exciting directly into the Nd³⁺ energy absorption itself. XRD, photoluminescence, and fluorescence decay curve are used to characterize the synthesized phosphor. The spectroscopic data indicate that all the visible emission peaks are originated from the electrical transitions of Nd³⁺, and the strong luminescence of the Nd³⁺ is considered to be due to an efficient energy transfer from the Y₂O₂S host lattice to the Nd³⁺ in Y₂O₂S:Nd³⁺. The optimum concentration for the luminescence Nd³⁺ is determined to be 1 mol% of Y³⁺ in Y₂O₂S host. The critical energy transfer distance has been calculated by the concentration quenching and the possible luminescent process of this blue luminescence-emitting phosphor is also investigated.     

Thermoelectric power and ac conductivity of A-type Nd2O3

Measurement of thermoelectric power Θ of pressed pellets of A-type Nd₂O₃ from 550 to 1180K and electrical conductivity (σ) at dc, 50 Hz, 1.542 kHz and 3 kHz at different temperatures is reported. It is concluded that electrical conduction at high temperature (T>600K) in this solid is due to positive large polarons in O²⁻ : 2p (valence) band and negative intermediate polarons in Nd³⁺ : 5d (conduction band). The energy band gap of the solid has been found to be 2.44 eV. At low temperatures, conduction by hopping of charge carriers from one impurity centre to another has been predicted.     

A sonochemical synthesis of SrTiO3 supported N-doped graphene oxide as a highly efficient electrocatalyst for electrochemical reduction of a chemotherapeutic drug

A sonochemical based green synthesis method playa powerful role in nanomaterials and composite development. In this work, we developed a perovskite type of strontium titanate via sonochemical process. SrTiO₃ particles were incorporated with nitrogen doped graphene oxide through simple ultrasonic irradiation method. The SrTiO₃/NGO was characterized by various analytical methods. The nanocomposite of SrTiO₃/NGO was modified with laser-induced graphene electrode (LIGE). The SrTiO₃/NGO/LIGE was applied for electrochemical sensor towards chemotherapeutic drug detection (nilutamide). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques have been used to examine the electrochemical performance of nilutamide (anti-cancer drug). DPV was found to be more sensitive and found to exhibit a sensitivity 8.627 µA µM⁻¹ cm⁻² for SrTiO₃/NGO/LIGE with a wide linear range (0.02–892 µM) and low Limit of detection (LOD: 1.16 µM). SrTiO₃/NGO/LIGE has been examined for the detection of nilutamide in blood serum and urine samples and obtained a good recovery in the range of 97.2–99.72 %. The enhanced stability and selectivity and practical application results indicates the suitability of SrTiO₃/NGO/LIGE towards the detection of nilutamide drug in pharmaceutical industries.     

Luminescence of neodymium-doped yttria

Pulsed cathodoluminescence of Nd³⁺: Y₂O₃ nanopowders of the cubic and monoclinic phases and the ceramics synthesized from these nanopowders has been investigated in the spectral range 350–850 nm. It is found that the IR emission band of neodymium ions in the Nd³⁺: Y₂O₃ cubic phase is located at λ₁ ≈ 825 nm. When there is a monoclinic phase admixture, two additional luminescence bands of Nd³⁺ arise in the spectrum at λ₂ ≈ 750 nm and λ₃ ≈ 720 nm. The emission spectrum of all Nd³⁺: Y₂O₃ materials also contains a wide intrinsic band of yttrium oxide at λ ≈ 485 nm; however, the presence of neodymium decreases the intensity of this band and increases the its structurization. It is suggested that the structure of this band in Nd³⁺: Y₂O₃ materials is mainly determined by local absorption (self-absorption) of neodymium ions.     

Spectroscopic properties of Nd—doped phosphate glass with a high emission cross section

Neodymium doped phosphate glasses have been prepared by the semi-continuous melting technique. Their absorption and emission spectra have been recorded at room temperature. The Judd－Ofelt theory has been applied to evaluate the stimulated emission cross sections of ⁴F_3/2→⁴I_11/2 transition for Nd³⁺. The higher stimulated emission cross section, 4.0×10^-20cm², is obtained. The fluorescence decays of the ⁴F_3/2→⁴I_11/2 transition of Nd³⁺ are measured for the samples doped (0.7－10) wt% of Nd₂O₃ at room temperature. The concentration quenching of Nd-doped phosphate glass is mainly attributed to cross-relaxation and energy migration. The site-dependent properties of fluorescence spectra and the fluorescence lifetime of the Nd³⁺-doped phosphate glass (with 2.2wt%Nd₂O₃) are studied using laser-induced fluorescence line narrowing techniques, and the site-to-site variations of optical properties are observed at low temperature.     

Cation disorder and structural studies on Bi4−x Nd x Ti3O12 (0.0≤x≤2.0)

Here we report the results of combined powder X-ray and neutron diffraction studies of Bi_4?x Nd _x Ti₃O₁₂ (0.0 ≤ x ≤ 2.0) compositions. The parent Bi₄Ti₃O₁₂ has an orthorhombic lattice (space group: B2cb) with unit cell parameters a = 5.4432(5) Å, b = 5.4099(5) Å and c = 32.821(2) Å, and V = 966.5(1) ų. This orthorhombic lattice is retained in all the studied compositions. The unit cell parameters gradually decrease with Nd³⁺ ion concentration with a discontinuity at x = 0.75. Orthorhombicity of the lattice decreases with increase in Nd³⁺ content in the lattice. The orthorhombic unit cell parameters for a representative Bi₂Nd₂Ti₃O₁₂ composition are: a = 5.3834(9), b = 5.3846(9) and c = 32.784(1) Å. The observed orthorhombic distortion at x = 2.0 is very small and thus the crystal structure apparently has a pseudo-tetragonal lattice. In addition, Nd³⁺ preferentially substitutes in the perovskite slab of the Aurivillius structure. The fraction of Nd³⁺ in the fluorite slab increases with increase in Nd³⁺ contents.     

Optical and electronic polarizability investigation of Nd-doped soda-lime silicate glasses

This paper reports on different physical and optical properties of Nd³⁺-doped soda-lime silicate glass. The glasses containing Nd³⁺ in (65−x)SiO₂:25Na₂O:10CaO:xNd₂O₃ (where x=0.0-5.0 mol%) have been prepared by the melt-quenching method. In order to understand the role of Nd₂O₃ in these glasses the density, molar volume, refractive index and optical absorption were investigated. The results show that the density and molar volume of the glasses increase with an increase in Nd₂O₃ concentration and consequently generate more non-bridging oxygen (NBOs) into glass matrix. The optical absorption spectra were measured in the wavelength range from 300 to 700 nm and the optical band gaps were determined. It was found that the optical band gap decreases with an increase in Nd₂O₃ concentration. On the basis of the measured values of density and refractive index, the Nd³⁺ ion concentration in glasses, the polarizability of oxide ions and optical basicity were theoretically determined.     

A novel graphene-chitosan-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> nanocomposite modified sensor for sensitive and selective electrochemical determination of a monoamine neurotransmitter epinephrine

A novel sensitive electrochemical sensor has been developed by modification of glassy carbon electrode (GCE) with graphene (GRP), chitosan (CHIT), and bismuth oxide (Bi₂O₃) nanoparticles. The morphological characteristics of nanocomposite (GRP-CHIT-Bi₂O₃ or GCB) were studied by scanning electron microscope and atomic force microscopy. The electrochemical behavior of epinephrine at nanocomposite modified GCE (GCB/GCE) was investigated in pH 7.4 phosphate buffer solution using cyclic voltammetry and square wave voltammetry. GCB/GCE showed an enhancement in the current response as compared to bare GCE. Electrochemical impedance spectra showed a reduction of charge transfer resistance and higher electrocatalytic behavior of the sensor. The electrooxidation process of epinephrine at the modified sensor was found to be diffusion controlled. GCB/GCE showed a linear response to epinephrine in the range 100 to 500 nM. The limit of detection and limit of quantification were found to be 3.56 and 11.85 nM, respectively, which is lower than many other sensors reported for epinephrine in literature. The modified sensor showed high sensitivity (1.3 nA/nM) and selectivity for epinephrine. The method was employed for quantification of epinephrine in pharmaceutical formulation and human blood serum samples.     

Hexagonal-like NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> nanostructure based high-performance supercapacitor electrodes

A novel approach of double hydroxide-mediated synthesis of nickel cobaltite (NiCo₂O₄) electro-active material by the hydrothermal method is reported. The obtained NiCo₂O₄ electro-active material displays the spinel cubic phase and hexagonal-like morphology. Thermogravimetry analysis confirms the thermal stability of the electrode material. The functional groups and phase formation of NiCo₂O₄ have been confirmed by FT-IR and Raman spectral analysis. The modified NiCo₂O₄ electrode exhibits the highest specific capacitance of 767.5 F g^?1 at a current density of 0.5 A g^?1 in 3 M KOH electrolyte and excellent cyclic stability (94 % capacitance retention after 1000 cycles at a high current density of 5 A g^?1). The excellent electrochemical performance of the electrode is attributed to the hexagonal-like morphology, which contributes to the rich surface electro-active sites and easy transport pathway for the ions during the electrochemical reaction. The attractive Faradic behavior of NiCo₂O₄ electrode has been ascribed to the redox contribution of Ni²⁺/Ni³⁺ and Co²⁺/Co³⁺ metal species in the alkaline medium. The symmetrical two-electrode cell has been fabricated using the NiCo₂O₄ electro-active material with excellent electrochemical properties for supercapacitor applications.     

Synthesis and characterization of ZnCo2O4 nanomaterial for symmetric supercapacitor applications

ZnCo₂O₄ nanomaterial was prepared by co-precipitation method and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), and galvanostatic charge–discharge tests at various current densities. It is shown that the crystal structure and surface morphology play an important role in the enhancement of the specific capacitance. The TEM results clearly indicate that the prepared material shows aggregated particles. The particle size powder was about 50 nm, and SEM pictures indicate a porous morphology. The electrochemical behavior of ZnCo₂O₄ was characterized by mixing equal proportion of carbon nanofoam (CNF). From CV, it is concluded that the combination of redox and pseudo-capacitance increases the specific capacitance up to 77 F g⁻¹ at 5 mV s⁻¹ scan rate. The ZnCo₂O₄-based supercapacitor cell has good cyclic stability and high coulombic efficiency.     

Nd photoluminescence study of Nd-doped Si-rich silica films obtained by reactive magnetron sputtering

Nd³⁺-doped silicon-rich silicon oxide (SRSO) thin films have been fabricated by reactive magnetron sputtering of a pure silica target topped with Nd₂O₃ chips. The concentration of Nd ions in the deposited layers is controlled by the number of Nd₂O₃ chips, whereas the incorporation of silicon excess is monitored by the hydrogen partial pressure, P_H2, introduced in the Ar plasma, owing to the ability of hydrogen to reduce the oxygen released by the sputtering of the silica target. Photoluminescence (PL) experiments were made at room temperature using a nonresonant excitation line from an Ar laser. The influences of Nd³⁺ content and P_H2 have been studied to optimize the Nd³⁺ emission. PL spectra reveal a two order of magnitude enhancement of the Nd³⁺ emission around both 0.9 and 1.1 μm, when Si nanoclusters (Si-nc) are formed in the same Nd³⁺-doped matrix. The dependence of the Nd³⁺ PL with P_H2 and Nd concentration is indicative of the occurrence of an efficient energy transfer from the Si-nc to the rare earth ions. The radiative lifetime is also deduced and commented in the light of Nd³⁺-Si-nc coupling.     

Facile sonochemical synthesis of rutile-type titanium dioxide microspheres decorated graphene oxide composite for efficient electrochemical sensor

In this reports the facile and green synthesis of rutile-type titanium dioxide nanoparticles decorated graphene oxide nanocomposite via the ultrasonication process (frequency: 50 kHz, Power: 100 W/cm² and Ultrasonic type: Ti-horn). Because, the sonochemical synthesis method is simple, non-explosive and harmless method than other conventional technique. Furthermore, the synthesized material was characterized by various analytical techniques including FESEM, EDX, XRD, EIS and electrochemical methods. Then, the synthesized TiO₂ MPs@GOS composite was applied for the electrocatalytic detection of theophylline (TPL) using CV and amperometric (current-time) techniques. Captivatingly, the modified sensor has excellent electrocatalytic performance with the wider linear range from 0.02 to 209.6 µM towards the determination of theophylline and the LOD and sensitivity of the modified sensor was calculated as 13.26 nM and 1.183 μA·µM⁻¹·cm⁻², respectively. In addition, a selectivity, reproducibility and stability of the TiO₂ MPs@GOS modified GCE were analyzed towards the determination of theophylline molecule. Finally, the real time application of TiO₂ MPs@GOS modified theophylline sensor was established in serum and drug samples.     

Spectroscopy and energy balance of the Nd<Subscript>2</Subscript>O<Subscript>3</Subscript> selective emission upon the laser thermal excitation

The laser thermal melting of powders is used to fabricate selective emitters (SEs) that represent Nd₂O₃ and Y₂O₃-Nd₂O₃ polycrystals on quartz holders. The SEs are stable under atmospheric conditions upon multiple heating by laser radiation up to the melting point. The spectral shape and integral intensity of the selective heat radiation (SHR) of the Nd₂O₃ microcrystalline powder and the Nd₂O₃ and Y₂O₃-Nd₂O₃ polycrystals are experimentally studied in the near-IR and visible spectral ranges versus the intensity of the laser thermal excitation at a wavelength of 10.6 μm in comparison with the absorption and luminescence spectra of the YAG:Nd³⁺ and YAlO₃:Nd³⁺ single crystals. The SHR spectra are determined by the vibronic transitions between the electronic states ² G _7/2-⁴F_3/2 ⁴I_11/2 and ⁴I_9/2 of the Nd³⁺ ions that are thermally excited due to the multiphonon transitions from the ground state. The energy balance of the SE laser thermal heating is experimentally investigated. The coefficient of the laser energy conversion to the Nd³⁺ SHR is measured, and the emissivity of the SEs that can be used for the study of the thermophotovoltaic generators and the optical excitation of the laser-active media in the near-IR spectral range is estimated.     

Luminescence and excitation spectra of YAG:Nd excited by synchrotron radiation

The low-temperature 4f²5d→4f³ fast emission of Nd³⁺ from YAG:Nd³⁺ has been studied under excitation by synchrotron radiation. Additionally, 4f³→4f³ luminescence of Nd³⁺ has been observed and assigned to transitions from the ²F(2)_5/2 and ⁴F_3/2 multiplet terms. The observed experimental spectra of Nd³⁺ d-f emission and f-d excitation are well simulated by crystal-field calculations.     

High Quantum Efficiency of Nd3+ Ions in a Phosphate Glass System using the Judd–Ofelt Theory

The optical properties of trivalent neodymium embedded in a P₂O₅–Al₂O₃–Na₂O–K₂O phosphate glass system, synthesized by the fusion method, are studied. Absorption, luminescence, lifetime, and Raman spectroscopy measurements were performed and the Judd–Ofelt theory was applied to determine optical parameters such as the quantum efficiency and the stimulated emission cross section of the Nd³⁺-doped glass system. This structure has high quantum efficiency at low Nd³⁺ concentrations, comparable to the efficiency of a commercial YAG:Nd³⁺ crystal. We discuss the mechanisms responsible for the high quantum efficiency observed in the proposed phosphate glass system.     

Gamma-ray irradiation effect on the absorption and luminescence spectra of Nd:GGG and Nd:GSGG laser crystals

Laser crystals Nd³⁺:Gd₃Ga₅O₁₂ (Nd:GGG) and Nd³⁺:Gd₃Sc₂Ga₃O₁₂ (Nd:GSGG) were grown by Czochralski method. The influence of gamma-ray irradiation on their absorption and luminescence spectra has been investigated. Two additional absorption (AA) bands induced by gamma-ray irradiation appear in the spectra of Nd:GGG crystal while only a very weak AA band appears for the Nd:GSGG crystal. This indicated that Nd:GSGG crystal has stronger ability to resist the color center formation by irradiation. The intensity of the excitation and emission spectra of Nd:GGG crystal decrease after the irradiation of 100 Mrad gamma-ray. In contrast, a luminescence strengthening effect was observed in Nd:GSGG crystal after exposure to the same irradiation dose. The results showed that the Nd:GSGG crystal is a promising candidate used under radiation environments such as in outer space.