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Abstract: The gadolinium iron garnet (GdIG, Gd3Fe5O12) and yttrium iron garnet (YIG, Y3Fe5O12), and their GdIG X :YIG1− X composites, were obtained by a new solid-state procedure. The microstructure of the samples was studied by X-ray powder diffraction and Rietveld refinement, Vickers microhardness and scanning electron microscopy. The density and microhardness behavior were studied as a function of the lattice parameters for the composite samples. In the present work, the magnetic and dielectric properties of the GdIG X :YIG1− X composite at radio and microwave frequencies were also studied. The magnetic permeability and dielectric permittivity and loss properties for the composite GdIG X :YIG1− X showed good potential for use in components, when one is looking for moderate ε r′ and μ r′ materials with low loss in the radio-frequency and microwave range. [Copyright &y& Elsevier]

Abstract: Y3Fe5O12 (YIG) crystal has many attractive characteristics, such as low dielectric loss, narrow resonance linewidth in microwave region and also possesses a good saturated magnetization value. Composite technology in general sets out to combine materials in such a way that the properties of the composite are the optimum for a particular application. The different materials work together to give a composite of unique properties. In this work, we present the preparation procedure (obtaining) of the GdIG X :YIG1− X ferrimagnetic ceramic matrix composite by mechanical alloying and calcinations. Besides that, we study its properties by X-ray powder diffraction, infrared, Micro-Raman, 57Fe Mössbauer spectroscopy and hysteresis loop measurements. [Copyright &y& Elsevier]

Abstract: Capacitance–voltage and capacitance–frequency characteristics of the metal/n-GaN/metal Schottky contacts with Au, Al and Ag electrodes were investigated as a function of the temperature and external electric field in the frequency range from 100 to 300kHz. Forward capacitance–voltage measurements were carried out in the frequency range from 100Hz to 20MHz. The temperature capacitance coefficient and the electrical tunability were measured as a function of the external DC field for all contacts. The capacitance and dielectric loss measurements show relaxation peaks from 4 to 11kHz for some electrodes, indicating that interfacial effects play an important role in the electrical properties of the GaN Schottky barrier contact. Low-frequency relaxation studies were conveniently used to probe interfacial characteristics of the contacts. [Copyright &y& Elsevier]

Abstract: In this work, we report electrical measurements of CaCu3Ti4O12 (CCTO) and (BaTiO3–barium titanate, BTO) thick films. The dielectric constant (K) measurements shows that the BTO thick film present a higher K compared to CCTO compound, in the range of frequencies under study. However, for the composite film (CCTO50 and CCTO50T films), one has an unexpected result; the dielectric constant is higher for all the frequencies under study. The BTO–CCTO composite films do not obey the empirical mixing rule. These electric properties were also studied in the temperature range of 80–300K. For the CCTO film, two relaxation processes were detected. The calculated activation energy was around 0.51eV for temperatures above 200K. One second relaxation process was observed on cooling below 200K with activation energy around 0.061eV. For the composite film CCTO50T, both relaxation processes are still present. Therefore, these measurements confirm the potential use of such materials for small high dielectric planar devices. These films are also attractive for capacitor applications and certainly for microelectronics, microwave devices (cell mobile phones, for example), where the miniaturization of the devices is crucial. [Copyright &y& Elsevier]

In this paper, we will study the effect of the presence of CCTO (CaCu3Ti4O12) in the dielectric permittivity and loss of barium titanate (BTO-BaTiO3) thick films. These films were prepared in two layers geometry using the screen printing technique on Al2O3 substrates. Mechanical alloying followed by the solid state procedure has been used successfully to produce powders of CCTO (CaCu3Ti4O12) used in the films. We also look at the effect of the grain size of the BTO and CCTO in the final properties of the film. These samples were studied using X-ray diffraction, scanning electron microscopy (SEM), Raman and infrared spectroscopies. We also did a study of the dielectric permittivity (K) and loss (D) in the medium-frequency (MF) range (100 Hz–1 MHz), of the films. The role played by firing process in the film preparation and the crystallite size of CCTO and BTO in the dielectric constant and structural properties of the films are discussed. Therefore, these measurements confirm the potential use of such materials for small high dielectric planar devices. These films are also attractive for capacitor applications and certainly for microelectronics, microwave devices (cell mobile phones, for example), where the miniaturization of the devices is crucial. [Copyright &y& Elsevier]

In this paper we will study the effect of the presence of hydroxyapatite (HA—Ca10(PO4)6(OH)2) on the dielectric permittivity and losses of the barium titanate (BTO—BaTiO3) thick films. These films were prepared in two layers geometry using the screen printing technique on Al2O3 substrates. Mechanical alloying has been used successfully to produce nanocrystalline powders of hydroxyapatite (HA) used in the films. We also look for the effect of the grain size of the BTO and HA on the final properties of the film. The samples were studied using X-ray diffraction, scanning electron microscopy (SEM), Raman and infrared spectroscopies, dielectric permittivity and losses measurements. The study of the dielectric permittivity and losses was done in the radio-frequency range (100 Hz–10 MHz). The role played by the firing process in the film preparation and the crystallite size of HA and BTO on the dielectric constant and structural properties of the films are discussed. [Copyright &y& Elsevier]

The structural and dielectric characterization of the Ca 3 ZrSi 2 O 9 (CZS) ceramic compound and the Ca 3-x Ba x ZrSi 2 O 9 (BaCZS) solid solution were investigated for their application in radiofrequency (RF) and microwave (MW) antenna devices. All of the samples were synthesized using the solid-state route. The structural characterization of the samples was performed by X-ray powder diffraction pattern. Infrared and Raman spectroscopy were used to correlate the absorption bands of the main chemical bonds in the materials. Scanning electron microscopy was used to examine the surface and microstructure of the samples. Dielectric properties at MW and RF ranges were analyzed using the Hakki-Coleman and Silva-Fernandes-Sombra methods. The CZS electrocemaric showed a dielectric relative permittivity (ε') of 10.96, a dielectric loss (tan δ) of 8.28 × 10−4 at 10.20 GHz, and a resonant frequency temperature coefficient (τ f) of −44.30 ppm °C−1. The influence of Ba ions on the CZS phase was evaluated using molar ratio variations (x = 0.15, 0.30, and 0.45), denotated as Ca 2.85 Ba 0.15 ZrSi 2 O 9 , (0.15BaCZS), Ca 2.70 Ba 0.30 ZrSi 2 O 9, (0.30BaCZS), and Ca 2.55 Ba 0.45 ZrSi 2 O 9 (0.45BaCZS), respectively. Among these samples, 0.45BaCZS showed a τ ƒ of approximately zero (−5.78 ppm °C−1), demonstrating an improvement in the material with the addition of Ba. Preliminary tests at MW and RF showed that the permittivity values and dielectric losses varied accordingly with the increase in the proportion of barium, as well as τ ƒ. For the dielectric resonator antenna (DRA) tests, the samples operated below −10 dB, between 6.57 and 7.7 GHz, behaving like materials used in microwaves devices for C-Band applications. [ABSTRACT FROM AUTHOR]

In this work, the Y 3 TaO 7 weberite-type structure was synthesized by solid state reaction at 1773 K for 6 h, and its crystalline phase was characterized using X-ray diffraction (XRD). Morphological analysis was performed using scanning electron microscopy (SEM). Electrical characterization of the electroceramics was investigated with temperature variation employing complex impedance spectroscopy (CIS). The Nyquist diagram was fitted employing one resistor (R) – constant phase element (CPE) associations correlating to grain boundary. Activation energy (E a) values for the relaxation processes were determined as 1.07, 1.06 and 1.15 eV for imaginary impedance (Z″), imaginary electrical modulus (M") and conductivity (σ′), respectively, indicating a consistent thermo-activated conduction process. The temperature coefficient of the resonant frequency (τ f) was found to be 31.24 ppm.K−1, suggesting for the development of new dielectric materials with τ f ∼ 0. The performance of the dielectric resonator antenna (DRA) was assessed through numerical simulation, demonstrating a strong correlation in impedance and operating frequency at 5.01 GHz. This study aims to facilitate the design of Y 3 TaO 7 -based materials, offering significant potential for applications in microelectronic devices in the radiofrequency (RF) and microwave (MW) range. [ABSTRACT FROM AUTHOR]

In this work, we reported the synthesis of carbon quantum dots (CQDs) with high fluorescent quantum yield (90.7 %). These nanoparticles were applied in a turn-off/turn-on sensor able to detect cyanide ions. In this sensing strategy, Fe3+ ions were added to the aqueous suspension of CQDs to quench the fluorescence of the system, which was recovered from the presence of cyanide ions. Furthermore, a sensor array was developed using the LDA chemometric tool, to classify different species present in cookie formulations, including gluten. The turn-off/turn-on sensor proved to be sensitive and effective for detecting cyanide ions, with a detection limit of 3.77 ppm. This high sensibility and selectivity allowed quantifying the analyte in a real sample of tap water. [Display omitted] • A fluorescent nanoprobe with ultra-high quantum yield (90.7 %) for sensing of allergens and toxic substances was obtained. • Carbon Quantum Dots (CD-90) synthesized by one-step hydrothermal treatment and showed high fluorescence signal at 440 nm. • CD-90 were used as fluorescent nanoprobes in the construction of a sensor array for detection of gluten in cookies samples. • Fe3+ ions quenched the fluorescence of CD-90, which was recovery by adding CN − ions. • CN − ions were identified in tap water sample with recovery of 94.8 % and RSD of 7.34 %. [ABSTRACT FROM AUTHOR]

Despite significant efforts by scientists in the development of advanced nanotechnology materials for smart diagnosis devices and drug delivery systems, the success of clinical trials remains largely elusive. In order to address this biomedical challenge, magnetic nanoparticles (MNPs) have gained attention as a promising candidate due to their theranostic properties, which allow the simultaneous treatment and diagnosis of a disease. Moreover, MNPs have advantageous characteristics such as a larger surface area, high surface-to-volume ratio, enhanced mobility, mass transference and, more notably, easy manipulation under external magnetic fields. Besides, certain magnetic particle types based on the magnetite (Fe 3 O 4) phase have already been FDA-approved, demonstrating biocompatible and low toxicity. Typically, surface modification and/or functional group conjugation are required to prevent oxidation and particle aggregation. A wide range of inorganic and organic molecules have been utilized to coat the surface of MNPs, including surfactants, antibodies, synthetic and natural polymers, silica, metals, and various other substances. Furthermore, various strategies have been developed for the synthesis and surface functionalization of MNPs to enhance their colloidal stability, biocompatibility, good response to an external magnetic field, etc. Both uncoated MNPs and those coated with inorganic and organic compounds exhibit versatility, making them suitable for a range of applications such as drug delivery systems (DDS), magnetic hyperthermia, fluorescent biological labels, biodetection and magnetic resonance imaging (MRI). Thus, this review provides an update of recently published MNPs works, providing a current discussion regarding their strategies of synthesis and surface modifications, biomedical applications, and perspectives. [Display omitted] • Diverse synthesis methods control properties of magnetic nanoparticles for biomedical applications. • Surface functionalization with polymers enhances stability, dispersibility, and compatibility. • Encapsulation enables controlled release of therapeutic agents under external stimuli. • Multifunctional nanoparticles offer potential for simultaneous imaging and therapy (theranostics). • Nanoparticles could be tailored for targeted drug delivery to tumor cells. [ABSTRACT FROM AUTHOR]

Abstract Yttrium iron garnet and calcium titanate (Y 3 Fe 5 O 12 -CaTiO 3 , YIG-CTO) ceramic composite were obtained according to the well-established solid-state route. This system was studied by complex impedance spectroscopy as a function of temperature. All samples showed a thermo-activated relaxation with energy activation between 1.10 and 1.70 eV. The CaTi 0.6 Fe 0.4 O 2.8 phase is formed during sintering process, which influences in the electrical behavior of the samples. Nyquist diagrams were adjusted by two equivalent circuits in series to represent electric response. The YIG-CTO system was also used to design a dielectric resonator antenna (DRA) for microwave applications. The results indicate that DRA YIG-CTO-based presented an operation frequency range around 1–7 GHz, and reflection coefficient below −38 dB. From obtained results, the YIG-CTO composite is a great candidate for usage in electronic devices, operating in the C-band, such as WiFi and ISM band applications. Highlights • Composites demonstrate ferrimagnetic behavior due to Y 3 Fe 5 O 12 phase. • Y 3 Fe 5 O 12 –CaTiO 3 composite can be used as Class 1 ceramic capacitors due to its high thermal-stability. • Resonators can be used in C-band applications: satellite communication, Wi-Fi devices and weather radar systems. [ABSTRACT FROM AUTHOR]

TiO 2 is a common inorganic filter used in sunscreens due to its photoprotective effect on the skin against UV radiation. However, the use of this kind of material in cosmetics is limited by its inherent photocatalytic activity. It is known that coating on TiO 2 surface can improve some features. Although, many of the methodologies used for this purpose are still laborious and time-consuming. Thus, this work reports a novel, easy, cheap and fast strategy to coat TiO 2 particles by using a sonochemistry approach, aiming to decrease photocatalytic activity and to enhance colloidal stability. For this proposal, SiO 2 , Al 2 O 3 , ZrO 2 and sodium polyacrylate (PAANa) were used to tune the surface of commercial TiO 2 particles and they were applied in a sunscreen formulation. The samples were characterized by XRPD, FT-IR, DLS, EDS, SEM and TEM. The photocatalytic activity and UV-shielding ability were also evaluated. The sunscreen formulations were prepared and characterized by zeta potential, DLS, and Sun Protection Factor (SPF). FT-IR, EDS, and charge surface of the particles confirmed the success of the sonochemistry coating. Additionally, TiO 2 @Al 2 O 3 , TiO 2 @SiO 2 and TiO 2 @PAANa show a lower photocatalytic activity than original TiO 2 with similar UV-shielding ability. The sunscreens produced with the coated TiO 2 have similar SPF to the one with commercial TiO 2 . Specifically, the sunscreen with TiO 2 @PAANa shows an increase in colloidal stability. Herein, the incorporation of the sonochemical-coated TiO 2 particles in sunscreen formulations may produce sunscreens with better aesthetic appearance and a greater health security due to its lower free radicals production. [ABSTRACT FROM AUTHOR]

Multiple forms of detecting Co2+ are reported in this work to quantify these ions in real blood plasma samples. Carbon Quantum Dots (CQDs) were used as a fluorescent nanoprobe. The CQDs were obtained from a bottom-up approach using a hydrothermal method and choline chloride and branched poly(ethyleneimine) as precursor molecules. Several spectroscopic and structural characterizations were performed. The efficient fluorescence quenching of CQDs related to the Co2+ ion was used for the detection of the analyte, generating a sensing strategy with a limit of detection (LOD) of 0.98 μmol L−1. Furthermore, the interaction between the Co2+ ion with the CQDs resulted in the color change of the solution from colorless to pale yellow. Thus, a colorimetric Co2+ sensor was also developed, since there was an absorption band at 315 nm attributed to the formation of the complex CQD + Co2+. The colorimetric method showed an excellent sensitivity to Co2+, with a LOD of 3.01 μmol L−1. In addition, Principal Component Analysis (PCA) together with Linear Discriminant Analysis (LDA) were used successfully to distinguish different concentrations of Co2+ and different interfering ions present in the solution. Finally, a real sample of blood plasma was properly treated and doped with different concentrations of Co2+, which was successfully quantified via fluorescent method. Therefore, the CQDs obtained in this work are a powerful and versatile Co2+ detection tool. • A fluorescent nanoprobe with high selectivity for multi-way sensing of cobalt was obtained through one-pot synthesis. • N-CD-Ch quantify Co2+ ions by fluorescence quenching and chemometric tools. • Co2+ with N-CD-Ch shows color pale yellow and a colorimetric sensor was developed. • Co2+ was identified in blood plasma sample with recovery of 100.9% and RSD of 0.9%. [ABSTRACT FROM AUTHOR]

The Sr 3 MoO 6 (SMO) double perovskite has been studied due to its photoluminescence properties. Herein, the aim of this work is to study the dielectric properties of the SMO in radiofrequency (RF). From impedance spectra, we proposed an equivalent circuit using three associations of R-CPE in parallel. We also evaluated its performance as a microwave device (dielectric resonator antenna - DRA). The SMO-based DRA operated at 3.71 GHz (frequency of operation antenna), with reasonable gain (5.00 dBi) and directivity (5.70 dBi), where these values are close to the ones presented by commercial antennas. Additionally, a numerical simulation is performed to obtain the main parameters for proper device application. Based on our results, SMO electroceramic shows important properties, which can be used for devices operating in the S-band such as weather radar, surface ship radar and communications satellites. [ABSTRACT FROM AUTHOR]

Ni 0.5 Zn 0.5 Fe 2 O 4 nanocrystals were successfully synthesized under different pure hydrothermal conditions (no organic solvent). The effects of the NaOH content and reaction time on the growth mechanism, as well as structural, morphological and magnetic properties were investigated. High-resolution electron microscopy transmission (HRTEM) revealed the formation of the nanocrystals, mainly via oriented attachment or in addition by a coalescence mechanism depending on the NaOH concentration (3.7–5.2 M). This secondary mechanism was found to give rise to defects in the network and structural disorder on the surface of the nanocrystals. By extending the reaction time (6–24 h), a morphology transition from truncated-hexagonal to rounded structures was seen, which evidenced a self-integration mechanism to achieve the most stable shape. Moreover, preferential exposure of the (111) plane was observed. Electrochemical measurements using [Fe(CN) 6 ] 3─/4─ to check the surface status further supported this statement. This indicated an adsorption effect of the NaOH on the surface of the MNPs allowing an oriented growth of the nanocrystals. In addition, the blocking temperature ( T B ) was affected by different factors (rearrangement of the atoms on the surface or increase of the magnetically-ordered core) depending on the hydrothermal conditions used. [ABSTRACT FROM AUTHOR]

In this study, we report the synthesis and application of polyethylenimine, ethylenediamine branched-functionalized carbon quantum dots (CQDs.BPEI) for protein sensing. These carbon-based nanoparticles were found to act as a protein-responsive platform. On this basis, the CQDs.BPEI system was able to detect eight different proteins (four metallic and four non-metallic), even using concentrations in the range of 5–40 nM, depending on the analyte protein. The fluorescence titrations performed at 298 and 310 K displayed fluorescence quenching, which can be explained through a collisional mechanism. It was also possible to conclude that the fluorescence quench comes from the amino acid residues on the surface of the proteins. To further check the potential of the system, we developed a “nose”-based methodology to identify proteins. Using materials, such as copper acetate and ethylenediaminetetraacetic acid, our chemical “nose” approach was able to discriminate 40 nM proteins in phosphate buffered saline (pH 7.4). In this case, the identification accuracy of the random unknown set was 83%. Overall, the results evidence the potential of CQDs.BPEI as a protein-responsive probe to detect and identify proteins. [ABSTRACT FROM AUTHOR]

Chitosan-based magnetite nanocomposites were synthesized using a versatile ultrasound assisted in situ method involving one quick step. This synthetic route approach results in the formation of spheroidal nanoparticles (Fe 3 O 4 ) with average diameter between 10 and 24 nm, which were found to be superparamagnetic with saturation magnetization (Ms) ranges from 32–57 emu g −1 , depending on the concentration. The incorporation of Fe 3 O 4 into chitosan matrix was also confirmed by FTIR and TG techniques. This hybrid nanocomposite has the potential application as electrochemical sensors, since the electrochemical signal was excepitionally stable. In addition, the in situ strategy proposed in this work allowed us to synthesize the nanocomposite system in a short time, around 2 min of time-consuming, showing great potential to replace convencional methods. Herein, the procedure will permit a further diversity of applications into nanocomposite materials engineering. [ABSTRACT FROM AUTHOR]

Objectives Enamel resin infiltrants are biomaterials able to treat enamel caries at early stages. Nevertheless, they cannot prevent further demineralization of mineral-depleted enamel. Therefore, the aim of this work was to synthesize and incorporate specific hydroxyapatite nanoparticles (HAps) into the resin infiltrant to overcome this issue. Methods HAps were prepared using a hydrothermal method (0 h, 2 h and 5 h). The crystallinity, crystallite size and morphology of the nanoparticles were characterized through XRD, FT-IR and TEM. HAps were then incorporated (10 wt%) into a light-curing co-monomer resin blend (control) to create different resin-based enamel infiltrants (HAp-0 h, HAp-2 h and HAp-5 h), whose degree of conversion (DC) was assessed by FT-IR. Enamel caries lesions were first artificially created in extracted human molars and infiltrated using the tested resin infiltrants. Specimens were submitted to pH-cycling to simulate recurrent caries. Knoop microhardness of resin-infiltrated underlying and surrounding enamel was analyzed before and after pH challenge. Results Whilst HAp-0 h resulted amorphous, HAp-2 h and HAp-5 h presented nanorod morphology and higher crystallinity. Resin infiltration doped with HAp-2 h and HAp-5 h caused higher enamel resistance against demineralization compared to control HAp-free and HAp-0 h infiltration. The inclusion of more crystalline HAp nanorods (HAp-2 h and HAp-5 h) increased significantly ( p < 0.05) the DC. Significance Incorporation of more crystalline HAp nanorods into enamel resin infiltrants may be a feasible method to improve the overall performance in the prevention of recurrent demineralization (e.g. caries lesion) in resin-infiltrated enamel. [ABSTRACT FROM AUTHOR]

This work investigates the microstructure and magnetic–dielectric properties of the CaTiO 3 (CTO) and Y 3 Fe 5 O 12 (YIG) composite ceramic. CTO is a paramagnetic ceramic, presents a positive value of Resonant Frequency Temperature Coefficients ( τ f ) and has high dielectric permittivity ( ε r ) while YIG is ferromagnetic, has low ε r and negative τ f values. Therefore, it is expected that the composite from these individual phase shows new properties, or a mix of them derived from each component. X-ray powder diffraction (XRPD), Scanning Electron Microscope (SEM), Raman and 57 Fe Mössbauer spectroscopy were performed to confirm the phases of the composites. The dielectric and magnetic properties in Radio-Microwave frequencies were studied by impedance spectroscopy using different geometries. It was observed a densification improvement resulting from the insertion of the CTO in composites and a chemical reaction between YIG and CTO phases. This new composite has potential applications in bulk and thick/thin films devices. [ABSTRACT FROM AUTHOR]

In this study, magnetic nanobiocomposites were prepared in different proportions and produced with galactomannan (GM), magnetic nanoparticles of NiZn and glycerol (GL). The microstructure and morphology of the samples were characterized by Scanning Electron Microscopy (SEM), X-ray powder diffraction, Fourier transform infrared (FTIR) spectroscopy, Thermal analysis (TG) and Differential scanning calorimetry (DSC). The magnetic and dielectric behavior of the films was studied by Vibrating sample magnetometer (VSM) and Impedance spectroscopy. The results showed efficient incorporation of NiZn in the polymer matrix. The degradation profiles presented thermal events that were confirmed by endothermic and exothermic processes from DSC measurements. Films presented saturation magnetization (M s ) range from 6 to 17 emu/g and superparamagnetic behavior. It was observed that the values of dielectric constant increased as a function of the nanoparticles concentration in the bionacomposite. Thus, this kind of biocomposite could be used as a versatile magnetic-dielectric in microwave devices. [ABSTRACT FROM AUTHOR]

Abstract: Na[Ru(SO3)(TCNQ)(bpy)2] and [Ru(SO3)(bpy)2(TCNE)] complexes were synthesized and characterized by means of electrochemical techniques and electronic, vibrational and electron paramagnetic resonance (EPR) spectroscopies. Vibrational data indicated a metallocyclopropane configuration for TCNE while TCNQ ligand is coordinated through the nitrile fragment. EPR data indicated the reduced state for the metal centers and for the TCNQ ligand (TCNQ−). The values of the potentials assigned to the redox processes associated to the TCNX ligands indicated a decrease in the electron transfer barrier. Data of dielectric measurements hinted that TCNQ containing complex is more polarized than the TCNE containing compound. Impedance spectroscopy measurements indicated a temperature-dependent relaxation process for both the complexes. However, for TCNQ containing complex, the results suggested the transition from long-range to short-range mobility. In addition, two values of activation energy (2.0 and 0.6eV) were calculated for this complex suggesting a phase transition process. [Copyright &y& Elsevier]

Abstract: A new synthetic route was used to obtain bismuth rare earth tungstates: BiREWO6, where RE = Y, Gd and Nd. These materials were obtained by microwave radiation in air at 900–1100 °C for 10 min, depend on the rare earth composition in the ceramic. Structural characterization was performed by X-ray powder diffraction, Infrared and Raman spectroscopy. It was observed that all samples are isostructural materials with monoclinic phase with space group A12/m1 and member of the Aurivillius family, as Bi2WO6 ferroelectric phase. It was observed moderated values for dielectric measurements ( and 0.018 < tg δ > 0.079) at microwaves frequencies, which can be used as Dielectric Resonator Antenna or for size reduction of the electric device. [Copyright &y& Elsevier]

Eu3+ – Tb3+ co-doped Sr 3 MoO 6 (SMO) phosphors have been synthesized by solid-state reaction. Powder X-ray diffraction (PXRD) and Scanning electron microscopy (SEM) were used for the characterization of the synthesized materials, and no significant structural changes have been observed. Photoluminescence (PL) was obtained under the 290 nm excitation where a strong energy transfer from host to active ions and weak energy transfer between the active ions with prominent emission from respective active ions. The fluorescence intensity ratio (FIR) was evaluated as a function of temperature in the range of 14 and 300 K using Eu3+/Tb3+ ratio to obtain absolute (S A) and relative (S R) sensitivities. SMO:Eu/Tb presented maximum S A of 0.0029 K−1 at 300 K and S R of 0.24% K−1 at 300 K, demonstrating that investigated system could be used in temperature sensing applications at low temperature. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the CaCu3Ti4O12 (CCTO) ceramic phase was synthesized by microwave heating in a much shorter time compared to the conventional heating methods. The results indicate that microwave processing is a promising method for preparing CCTO ceramics. CCTO was prepared using a domestic microwave oven operated at 2.45GHz with 800W. After a few minutes of microwave irradiation the formation of CCTO was confirmed by X-ray powder diffraction. The CCTO ceramic was studied in the medium-frequency (MF) range (100Hz–1MHz) and in the microwave range of frequencies. The experimental and theoretical characteristics of the dielectric resonator antenna are investigated. [Copyright &y& Elsevier]

• Highly fluorescent FM-CDs have shown maximum emission wavelength at 435 nm. • FM-CDs proved to be excellent nanoprobes for analysis of additives in food. • Detection of food additives by FM-CDs and LDA algorithm was successfully performed. • The identification in pickled olives samples was performed with 100 % of accuracy. A robust fluorescence-based sensing strategy was designed considering relevance of analyzing chemical additives in industrialized food. In this study, a sensing approach was developed using fluorescent carbon quantum dots (CQDs) as a chemometric tool. CQDs were synthesized by a simple one-step hydrothermal route using the American natural seed Caelsalpinia pulcherrima , and further characterized regarding their chemical structure. Five food additives were identified, citric acid, lactic acid, ascorbic acid, sodium benzoate and potassium sorbate, which showed a highly sensitive response with a limit of detection (LOD) as low as 252 ng mL−1. The sensing platform was designed using the supervised method for recognizing patterns of linear discriminant analysis (LDA), where we could identify different concentrations of additives, after optimization of experimental parameters. Furthermore, the sensing strategy successfully identified all tested additives in a pickled olives sample with 95 % of confidence, where 100 % of combinations were correctly identified based on classification matrix. Overall, the obtained results evidence the accuracy and potential of CQDs-based fluorescence sensing in the identification of food additives. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) have a large number of technological applications, such as photonic devices, molecular diagnostics, antimicrobial coating and biomedical devices. These nanomaterials can be synthesized using common fungi, which represents a green approach with the additional advantage of biocompatibility. Here we applied Tip-Enhanced Raman Spectroscopy (TERS) to obtain optical characterization with resolution beyond the diffraction limit of AgNPs produced by Rhodotorula glutinis and Rhodotorula mucilaginosa fungi. Those fungi are conventional found in ordinary soil of north part of Brazil, which biosynthesize core-shell AgNPs with protein-capping layer. With TERS we were able to investigate with lateral resolution of few nanometers the size and structure of the protein capping layer, how it interacts with the Ag core, and how sensitive the system (core + protein) is to visible light illumination. Despite the complex data generated which depends on the orientation of the protein, which is highly, it was possible to detect the stretching of the S - S sulfur bridge in amino acids. This stretch band is induced by a trans C α - S conformation acid on Rm-AgNPs, thus showing the potential of characterization of TERS in nanobiosystems. [ABSTRACT FROM AUTHOR]

• CQD and AgNP were combined to develop a pesticides sensing strategy using FRET phenomenon. • A fast pesticide identification was applied in real samples of rice, carrot, orange and pepper. • The sensibility of the sensing strategy achieved 250 ng.mL−1. In this work, a fluorescent sensing strategy was developed for identification of pesticides in food, which was obtained thought the interaction of carbon quantum dots (CQDs) and silver nanoparticles (AgNPs). The CQDs were synthesized from riboflavin according to an experimental design. On this basis, the most appropriate samples were selected and structurally characterized, where AgNPs efficiently quench the fluorescence of CQDs due a fluorescence resonance energy transfer (FRET). The CQDs was titrationed with AgNPs (Ag@PAA and Ag@bPEI), determining the best concentration of quenching (0.228 and 3.030 pmol.L−1, respectively). Furthermore, a strategy of sensing was developed in order to identify the pesticides propanyl, parathion, dimethoate, chlorpyrifos and pyrimicarb, which were also verified in real samples of rice, carrot, orange and pepper. The results were analyzed by linear discriminant analysis (LDA), obtaining different response patterns against pesticide concentrations, with confidence level of 95%. After that, assays were performed using lower concentrations of the analytes. It was verified that in pepper extract, the sensibility of the sensing strategy was 250 ng.mL−1. Therefore, the CQDs synthesized in this work may be considered a powerful tool to identify pesticides in food samples. [ABSTRACT FROM AUTHOR]