Zinc-8-hydroxyquinoline intercalated in calcium bentonite: A promising DO sensor

Zn(II) and 8-hydroxyquinoline were made to react in an in situ solid−solid reaction in the interlayer space of Ca-bentonite from Thailand, resulting in [Zn(8-hydroxyquinoline)₂]²⁺, the well known -Znq₂. X-ray diffraction patterns showed that the interlayer space of the bentonite increased from 1.56 to 1.67 nm on going from Zn(II)-bentonite to Znq₂-bentonite, which confirmed the intercalation of Znq₂ in bentonite. The intercalated Znq₂-bentonite compound was mixed with a solution of polystyrene in toluene and coated as a film on a polystyrene sheet. The fluorescence intensity of Znq₂-bentonite film was measured in the presence of dissolved oxygen (DO). It was found that the fluorescence intensity of the film decreased as dissolved oxygen increased, which is a promising result for developing an optical dissolved oxygen sensor (DO sensor). The fluorescence quenching by oxygen followed the Stern-Volmer plot.     

基于光纤的溶解氧浓度荧光测定法

针对溶解氧浓度微量探测的现实需求,提出了一种基于荧光猝灭原理、利用多孔光纤实现的溶解氧浓度测定新方法。该方法将钌联吡啶[Ru（dpp）₃]Cl₂掺杂的凝胶薄膜修饰在多孔光纤的内壁上,制备了一种溶解氧测定探头并对其测试性能进行表征。光纤贯穿整个长度的孔洞结构既可以作为敏感膜的载体,也可以作为待测物流过的通道和反应场所。与传统测试方法相比,该测试探头的多孔道结构显著提高了比表面积,指示剂可以与溶解氧直接反应,提高了探头的敏感性并且具有微量探测的潜力。实验结果表明,在0~20 mg/L的浓度范围内,Stern-Volmer曲线近似线性,响应敏感度I₀/I为3.6,响应时间为200 ms。该测试方法在溶解氧微量探测领域具有重要用途。     

Dissolved oxygen sensor by using Ru-fluorescence indicator and a U-shaped plastic optical fiber

A dissolved oxygen (DO) sensor based on U-shape plastic optical fiber (POF) and dichlorotris (1, 10- phenanthroline) ruthenium ([Ru(dpp)3]2 ) as an oxygen indicator was described. Fluorescence intensity and lifetime were measured when the sensor was soaked into a water bath blasted with air with varied O2/N2 ratios. The influence of Ru concentration, annealing time and U-shaped POF curve radius on the system sensitivity was also studied. A two-layer model was proposed to analyze the deviation from linear relation described by Stern-Volmer equation, and to explain the deviation and the dependence of the fluorescence on curvature of U-shape POF. By fitting the experimentally measured sub-linear relation ofτ0/τ ratio versus oxygen concentration, the proportion of effectively sensitive layer and the Stern-Volmer coefficient can be evaluated to be f = 0.59 and Ksv = 0.61 typically.     

Ratiometric fluorescent nanoparticles for sensing temperature

A ratiometric type of fluorescent nanoparticle was prepared via an encapsulation–reprecipitation method. By introducing an alkoxysilanized dye as a reference, the nanoparticles (NPs) give both a green and a red fluorescence under one single-wavelength excitation. The resulted ratiometric fluorescence is found to be highly temperature-dependent in the physiological range (25–45 °C), with an intensity temperature sensitivity of ?4.0%/°C. Given the small size (20–30 nm in diameter) and biocompatible nature (silica out layer), such kind of NPs were very promising as temperature nanosensors for cellular sensing and imaging.     

Effect of cobalt doping on structural,optical and redox properties cerium oxide nanoparticles

Cobalt-doped ceria nanoparticles were synthesized using the polyol method under co-precipitation hydrolysis. The structural, morphological, optical and redox properties were observed to investigate the influence of different concentration of cobalt ion doping on the prepared CeO₂ nanomaterials in terms of X-ray diffraction, field-emission transmission electron microscopy, thermogravimetric analysis, Fourier-transform infrared spectroscopy, UV/vis absorption spectroscopy and temperature program reduction techniques. The optical band gap energy was calculated from the optical absorption spectra for doped ceria nanoparticles, which have been found to be 2.68, 2.77, and 2.82 eV for the 2, 4, and 7 mol% Co ion-doped CeO₂ nanoparticles, respectively. As observed, the band gap energies increases as the doping Co ion concentrations increased, which could be due to significant increased oxygen vacancies with Co doping. The synergistic interaction between Co and CeO₂ was the main factor responsible for high catalytic activity of cobalt-doped CeO₂ model catalysts.     

Properties of stable nonstoichiometric nanoceria produced by thermal plasma

Thermally stable blue nonstoichiometric nanoceria was produced by feeding nanoceria with an average size of 50 nm into a DC thermal plasma reactor. The effects of different plasma power levels and atmospheres were investigated. XRD results showed the ceria lattice parameter increased with plasma power. SEM and TEM results showed that the shape of nanoparticles changed after plasma treatment; the blue nonstoichiometric nanoceria had highly regular shapes such as triangular pyramids and polyhedral in contrast to the irregular shape of the raw nanoceria. Significant downshift was found in the Raman spectra of the plasma products, with a 7.9-cm^?1 shift compared with raw nanoceria, which was explained by the reduction of Ce⁴⁺. X-ray photoelectron spectroscopy results showed that the Ce³⁺ fraction increased from 14% in the raw nanoceria to 38–39% for the product CeO_2-x , indicating the high reduction state on the ceria surface. It was determined that this blue nonstoichiometric nanoceria was stable up to 400 °C in air, but the color changed to pale yellow after 4 h at 500 °C in air indicating oxidation to CeO₂. Additionally, this novel stable nano-CeO_2-x caused a red shift in the UV-visible absorption results; a 48-nm red shift occurred for the nonstoichiometric nanoceria produced at 15 kW compared with the raw nanoceria. The band gap was calculated to be 2.5 eV while it was 3.2 eV for the raw nanoceria, indicating that this novel stable blue nonstoichiometric nanoceria should be a promising material for optical application.     

Effect of temperature on the synthesis of silver nanoparticles with polyethylene glycol: new insights into the reduction mechanism

Polyethylene glycol (PEG) molecules act as a reducing and stabilizing agent in the formation of silver nanoparticles. PEG undergoes thermal oxidative degradation at temperatures over 70 °C in the presence of oxygen. Here, we studied how the temperature and an oxidizing atmosphere could affect the synthesis of silver nanoparticles with PEG. We tested different AgNO₃ concentrations for nanoparticles syntheses using PEG of low molecular weight, at 60 and 100 °C. At the higher temperature, the reducing action of PEG increased and the effect of PEG/Ag⁺ ratio on nanoparticles aggregation changed. These results suggest that different synthesis mechanisms operate at 60 and 100 °C. Thus, at 60 °C the reduction of silver ions can occur through the oxidation of the hydroxyl groups of PEG, as has been previously reported. We propose that the thermal oxidative degradation of PEG at 100 °C increases the number of both, functional groups and molecules that can reduce silver ions and stabilize silver nanoparticles. This degradation process could explain the enhancement of PEG reducing action observed by other authors when they increase the reaction temperature or use a PEG of higher molecular weight     

基于荧光淬灭原理的光纤氧传感器的实验研究

基于荧光淬灭原理的光纤氧传感器一直是许多研究工作的重点。介绍了一种制作简单、成本低的光纤氧传感器制造方法。该方法基于荧光淬灭原理，在光纤末端涂覆荧光材料铂八乙基卟啉(PtOEP)实现的。传感器中荧光材料被395nm的紫光激发，并由Y形光纤引导，使用广州犀谱光电USB2000+光谱仪记录荧光的发光强度时序图。最后得到的PtOEP的(I₀/I₁₀₀)-1的值为0.78，即光纤氧传感器的灵敏度为0.78，而且，斯特恩-沃尔默(Stern-Volmer)图显示出很好的线性特性。从氧气到空气环境的响应时间为24 s，从空气环境到氧气的响应时间是5 s。结果表明，基于荧光淬灭原理的光纤氧传感器具有较高的灵敏度和更快的响应时间。     

Biocompatibility selenium nanoparticles with an intrinsic oxidase-like activity

Selenium nanoparticles (SeNPs) are considered to be the new selenium supplement forms with high biological activity and low toxicity; however, the molecular mechanism by which SeNPs exert the biological function is unclear. Here, we reported that biocompatibility SeNPs possessed intrinsic oxidase-like activity. Using Na₂SeO₃ as a precursor and glutathione as a reductant, biocompatibility SeNPs were synthesized by the wet chemical reduction method in the presence of bovine serum albumin (BSA). The results of structure characterization revealed that synthesized SeNPs were amorphous red elementary selenium with spherical morphology, and ranged in size from 25 to 70 nm size with a narrow distribution (41.4 ± 6.7 nm). The oxidase-like activity of the as-synthesized SeNPs was tested with 3,3′,5,5′-tetramethylbenzidine (TMB) as a substrate. The results indicated that SeNPs could catalyze the oxidization of TMB by dissolved oxygen. These SeNPs showed an optimum catalytic activity at pH 4 and 30 °C, and the oxidase-like activity was higher as the concentration of SeNPs increased and the size of SeNPs decreased. The Michaelis constant (K _m) values and maximal reaction velocity (V _max) of the SeNPs for TMB oxidation were 0.0083 mol/L and 3.042 μmol/L min, respectively.     

Magnetically Reusable and Well-dispersed Nanoparticles for Oxygen Detection in Water

In this study, we aimed to synthesize magnetically well-dispersed nanosensors for detecting dissolved oxygen (DO) in water, and explore their biological applications. Firstly, we synthesized two kinds of magnetic nanoparticle with average sizes of approximately 82 nm by one-step emulsion polymerization: polystyrene magnetic nanoparticles (Fe₃O₄@Os1-PS) and polymethylmethacrylate magnetic nanoparticles (Fe₃O₄@Os1-PMMA). Both types of nanoparticle present good dispersibility and fluorescence stability. The nanoparticles could be used as oxygen sensors that exhibited a high DO-sensitivity response in the range 0-39.30 mg/L, with a strong linear relationship. The nanoparticles have good magnetic properties, and so they could be recycled by magnet for further use. Recovered Fe₃O₄@Os1-PS still presented high stability after continued use in oxygen sensing for one month. Furthermore, Fe₃O₄@Os1-PS was employed for detecting the bacterial oxygen consumption of Escherichia coli (E-coli) to monitor the metabolism of bacteria. The results show that Fe₃O₄@Os1-PS provide high biocompatibility and non-toxicity. Polystyrene magnetic nanoparticles therefore present significant potential for application in biological oxygen sensing.

     

Synthesis of amino-group functionalized superparamagnetic iron oxide nanoparticles and applications as biomedical labeling probes

Superparamagnetic iron oxide (SPIO) nanoparticles were synthesized by coprecipitation technique and further functionalized with amino-group to obtain amino-group functionalized (amino-SPIO) nanoparticles. The X-ray diffraction results reveal the structure of amino-SPIO nanoparticles, from which the average iron core diameter is approximately 10 nm by calculation; while Zetasizer reveals their hydrodynamic diameter are mainly distributed in the range of 40?C60 nm. These nanoparticles can be taken up by liver tissue, resulting in dramatically darkening of liver tissue under T2-magnetic resonance imaging (MRI). The spin?Cspin relaxivity coefficient of these nanoparticles is 179.20 mM^?1 s^?1 in a 1.5 T magnetic resonance system. In addition, amino-SPIO nanoparticles were conjugated to Tat (FITC) peptide and incubated with neural stem cells in vitro, the authors can detect the positive-labeling (labeled) neural stem cells showing green fluorescence, which indicates Tat (FITC) peptide-derivated amino-SPIO nanoparticles are able to enter cells. Furthermore, it was also find significant negative T2 contrast enhancement when compared with the non-nanoparticles-labeled neural stem cells in T2-weighted MRI. The amino-SPIO nanoparticles show promising potential as a new type of labeling probes, which can be used in magnetic resonance-enhanced imaging and fluorescence diagnosis.     

Oxygen Diffusion into Multiwalled Carbon Nanotube Doped Polystrene Latex Films Using Fluorescence Technique

This study examines the oxygen diffusion into polystyrene (PS) latex/multiwalled carbon nanotube (MWNT) nanocomposite films (PS/MWNT) consisting of various amounts of MWNT via steady state fluorescence technique (SSF). PS/MWNT films were prepared from the mixture of MWNT and pyrene (P)-labeled PS latexes at various compositions at room temperature. These films were then annealed at 170 °C above glass transition (T_g) temperature of PS. Fluorescence quenching measurements were performed for each film separately to evaluate the effect of MWNT content on oxygen diffusion. The Stern-Volmer equation for fluorescence quenching is combined with Fick’s law for diffusion to derive the mathematical expressions. Diffusion coefficients (D) were produced and found to be increased from 1.1?×?10^?12 to 41?×?10^?12 cm²s^?1 with increasing MWNT content. This increase was explained via the existence of large amounts of pores in composite films which facilitate oxygen penetration into the structure.     

EPR and Magnetization Studies of Polymer-Derived Fe-Doped SiCN Nanoceramics Annealed at Various Temperatures: Blocking Temperature,Superparamagnetism and Size Distributions

X-band EPR spectra on SiCN ceramics, doped with Fe(III) ions, annealed at 800 °C, 1000 °C, 1100 °C, 1285 °C, and 1400 °C have been simulated to understand better their magnetic properties, accompanied by new magnetization measurements in the temperature range of 5–400 K for zero-field cooling (ZFC) and field cooling (FC) at 100C. The EPR spectra reveal the presence of several kinds of Fe-containing nanoparticles with different magnetic properties. The maxima of the temperature variation of ZFC magnetization were exploited to estimate (i) the blocking temperature, which decreased with annealing temperature of the samples and (ii) the distribution of the size of Fe-containing nanoparticles in the various samples, which was found to become more uniform with increasing annealing temperature, implying that more homogenous magnetic SiCN/Fe composites can be fabricated by annealing at even higher temperatures than 1400 °C to be used as sensors. The hysteresis curves showed different behaviors above (superparamagnetic), below (ferromagnetic), and about (butterfly shape) the respective average blocking temperatures, 〈T_B〉. An analysis of the coercive field dependence upon temperature reveals that it follows Stoner–Wohlfarth model for the SiCN/Fe samples annealed above 1100 °C, from which the blocking temperatures was also deduced.     

Properties of pulsed laser deposited nanocomposite NiO:Au thin films for gas sensing applications

Nanocomposite thin films formed by gold nanoparticles embedded in a nickel oxide matrix have been synthesized by a new variation of the pulsed laser deposition technique. Two actively synchronized laser sources, a KrF excimer laser at 248 nm and an Nd:YAG laser at 355 nm, were used for the simultaneous ablation of nickel and gold targets in oxygen ambient. The structural, morphological, and electrical properties of the obtained nanocomposite films were investigated in relation to the fluence of the laser irradiating the gold target. The nanocomposite thin films were tested as electrochemical hydrogen sensors. It was found that the addition of the gold nanoparticles increased the sensor sensitivity significantly.     

CdSe-ZnS quantum dots as temperature sensors during thermal coagulation of bovine serum albumin (BSA) solder

Laser tissue soldering (LTS) has variously interesting applications such as wound closure, anastomosis of blood vessels, and sealing corneal wounds. Since tissue properties such as optical absorption or thermal conductivity may differ, temperature control is essential to obtain full coagulation and to minimize thermal side effects. In this article, a non-invasive technique is proposed for temperature sensing by using CdSe-ZnS quantum dots (QDs) dissolved in protein solder, namely bovine serum albumin (BSA). The temperature measurement is conducted by monitoring the change in the photoluminescence spectra of the QDs. It is shown that the peak emission wavelength of about 653 nm of CdSe-ZnS QDs shifts linearly in a temperature range from 30 °C to 70 °C, with a coefficient of 0.153 nm?°C^?1 with increasing temperature. The wavelength shift can be determined by applying a small spectrometer with a CCD-array detector. The uncertainty associated with this method is estimated to be less than 6 °C in temperature. As the temperature increases, the measured signal strength initially remains constant and then falls off abruptly when exceeding 55 °C. The signal drop correlates with a phase change from a clear, low-scattering protein solution to strong-scattering solid material.     

Dielectric anomalous response of water at 60 °C

Recently, the paraelectric response of water was investigated in the range 0–100 °C. It showed an almost perfect Curie–Weiss behaviour up to 60 °C, but a slight change in slope of 1/ε_d versus T at 60 °C was overlooked. In this work, we report optical extinction measurements on metallic (gold and silver) nanoparticles dispersed in water, annealed at various temperatures in the range from 20 to 90 °C. An anomalous response at 60 °C is clearly detectable, which we associate to a subtle structural transformation in the water molecules at that temperature. This water anomaly is also manifested by means of a blue shift in the longitudinal surface plasmon resonance of the metallic nanoparticles for the solutions annealed at temperatures higher than about 60 °C. A reanalysis of 1/ε_d (T) for water in the whole temperature range leads us to conclude that the water molecule undergoes a subtle transformation from a low temperature (0–60 °C) configuration with a dipole moment μ₁ = 2.18 D (close to the molecular dipole moment of ice) to a high temperature (60–100 °C) configuration with μ₂ = 1.87 D (identical to the molecular dipole moment in water vapour).     

Low temperature microwave sintering of yttrium and samarium co-doped ceria solid electrolytes for IT-SOFCs

Nanocrystalline co-doped ceria Ce_0.8Sm_0.2?xY_xO_2?δ solid electrolytes for intermediate-temperature solid oxide fuel cells (IT-SOFCs) were synthesized through sol–gel auto-combustion method. The prepared samples were sintered via microwave sintering at 1200 °C for 1 h. The X-ray diffraction analysis of co-doped ceria system reveals formation of the samples with a single-phase cubic fluorite structure. The lattice parameter values were calculated from X-ray diffraction patterns. The calculated crystallite sizes of all the samples were found to be in the range of 17 and 28 nm. Surface morphologies and elemental analysis of all the samples were carried out by using SEM and EDS analysis. The existence of chemical bonding in the samples was studied by FTIR spectroscopy. The presence of oxygen vacancies and evaluation of their concentration in the material was carried out using Raman spectroscopy analysis. Electrical properties of all the samples were analyzed by impedance spectroscopy. It was found that microwave sintered co-doped ceria sample Ce_0.8Sm_0.1Y_0.1O_2?δ exhibits the highest total ionic conductivity with minimum activation energy among all the compositions and conventional sintered sample. Therefore, it can be concluded that the microwave sintered Ce_0.8Sm_0.1Y_0.1O_2?δ sample may be useful as a promising electrolyte material for the IT-SOFCs.     

Growth and magnetic behavior of bismuth substituted yttrium iron garnet nanoparticles

Crystal growth and the magnetic properties of bismuth substituted yttrium iron garnet (Bi-YIG) nanoparticles were studied with particular focus on the bismuth composition dependence of the magnetic properties of the particles and the effects of annealing on the garnet phase formation. The Bi-YIG nanoparticles of 47–67 nm in size can be chemically synthesized when they are annealed at 650–850 °C. Both the lattice constant and the magnetization of the garnet nanoparticles linearly increase when the bismuth composition in the Bi-YIG particles increases. We have found that chemically synthesized nanoparticles transform from the amorphous to the garnet phase when annealed at temperatures below 650 °C, while the onset of magnetic moment of iron in the garnet nanoparticles is observed slightly above 650 °C. According to Mössbauer effect measurements, the hyperfine fields of ⁵⁷Fe at the tetrahedral and octahedral sites in the garnet are 39 and 48 T, respectively.     

牛血红蛋白与纳米雄黄相互作用的光谱研究

采用紫外-可见吸收光谱、荧光光谱研究牛血红蛋白(bovine hemoglobin,简称BHb)与纳米雄黄的相互作用。从紫外-可见吸收光谱可观察到,随着纳米雄黄浓度的增加,牛血红蛋白406 nm附近的特征Soret吸收带红移至413 nm,且强度逐渐降低。强度的降低表明纳米雄黄可能使部分血红素辅基逐渐从它们的键腔中脱离出来。特征峰位的红移推测为纳米雄黄中的砷结合了血红蛋白中的氧,诱导血红蛋白脱氧,变成脱氧血红蛋白,其构象由R态转变成T态。由荧光光谱研究可以得出随着纳米雄黄浓度的增加,牛血红蛋白338 nm处的荧光强度逐渐减弱,Stern-Volmer方程分析表明,纳米雄黄静态猝灭牛血红蛋白的内源荧光。紫外-可见吸收光谱与荧光光谱的计算结果均表明,牛血红蛋白与纳米雄黄的结合常数k的数量级达到109。     

Optical quantum transmitter with finesse of 30 at 800-nm central wavelength using microring resonators

A microring resonator (MRR) system incorporating an add/drop system is presented. The finesse of the proposed system can be determined using the full width at half maximum (FWHM) and free spectrum range (FSR) of the generated multiple soliton pulses. The central wavelength of the bright input soliton pulse has been selected as 800 nm, at which a ring system with better sensitivity shows high finesse that is suitable for applications to many optical communication systems such as optical transmitters and sensors. Simulation results show that FSR of 0.3 nm and 1.1 ns and FWHM of 10 pm and 36.6 ps could be obtained. Therefore, a system with finesse of 30 can be obtained; in such a system, the MRR system shows high performance. This system can be used in optical communication networks as a transmitter system for optical soliton pulses with finesse of 30, and theses pulses can be detected via an optical receiver.