A near-infrared fluorescent probe for evaluating endogenous hydrogen peroxide during ischemia/reperfusion injury.

Hydrogen peroxide (H2O2), as a major component of reactive oxygen species (ROS), plays an important role in normal physiological processes. A H2O2 burst also occurs in the ischemia/reperfusion (I/R) process and causes a series of physiological and pathological injuries. Therefore, it is important to determine concentration fluctuations of H2O2. Here we develop a ratiometric fluorescent probe, Cy-ArB, which shows high selectivity and sensitivity toward H2O2. The fluorescence response of the probe is triggered by the reaction of borate esters with H2O2, and this process releases a near-infrared heptamethine cyanine fluorophore which has the ability of mitochondrial tracing. Hence, the probe can be used for real-time monitoring of H2O2 fluctuations in the mitochondrial respiration chain. Finally, we explore the fluctuations of H2O2 in cells and in vivo during the I/R process using the probe Cy-ArB. The results of our experiments prove that our probe is a potential candidate for clinical surgery pre-evaluation.

An Electrostatically Self-Assembled Thin Film Made of Zn-Substituted Tungstoborate and Rhodamine B with Photoelectrochemical Properties.

An electrostatically self-assembled multilayer thin film consisting of alternating layers of Keggin polyoxometalate of Zn-substituted tungstoborate (BW11Zn) and Rhodamine B (RhB) has successfully been prepared on a quartz and indium-tin oxide (ITO) glass substrate. The ultraviolet-visible (UV-vis) absorption spectra demonstrated that the electrostatically self-assembled film of (BW11Zn/RhB)n was uniformly deposited layer by layer, and the RhB molecules in the film formed the J-aggregation. The photoelectrochemical investigations showed that the films generated stable cathodic photocurrents that originated from RhB, and the maximal cathodic photocurrent density generated by an eight-layer film was 4.9 µA/cm2 while the film was irradiated with 100 mW/cm2 polychromatic light of 730 nm > λ > 325 nm at an applied potential of 0 V versus a saturated calomel electrode.

Improvement and formation of UV-induced damage on LBO crystal surface during long-term high-power third-harmonic generation.

We demonstrate the improvement and formation of UV-induced damage on LBO crystal output surface during long-term (130 h) high-power (20 W) high-repetition-rate (80 kHz) third-harmonic generation. The output surface was super-polished (RMS surface roughness <0.6 nm) to sub-nanometer scale super smooth roughness. The surface lifetime has been improved more than 20-fold compared with the as-polished ones (RMS surface roughness 4.0~8.0 nm). The damage could be attributed to the consequence of thermal effects resulted from impurity absorptions. Simultaneously, it was verified that the impurities originated in part from the UV-induced deposition.

Synthesis of indium borate and its application in photodegradation of 4-chlorophenol.

Indium borate has been prepared by a sol-gel method. The structure, morphology, and photophysics of the resultant photocatalysts have been studied via the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), and diffuse reflectance UV-visible light spectroscopy. These photocatalysts have been used to photodegrade 4-chlorophenol. The photocatalytic activity depends on the annealing temperature during preparation. It is found that borates can exhibit a high photodegradation activity under UV-light irradiation, for which the efficiency can be higher than that of as-prepared TiO(2). This is explained according to the results of fluorescence spectra and valence band X-ray photoelectron spectroscopy (XPS). It is confirmed by the results of time-resolved photoluminescence decay spectra; i.e., the lifetime of electrons and holes involved in the radiative process can be longer for the borates than that for TiO(2). This implies that indium borate can be a promising photocatalyst for future applications in treatment of environment contaminants.

On the luminescence of Ce3+, Eu3+, and Tb3+ in novel borate LiSr4(BO3)3.

This paper reports on the photoluminescence (PL) and time-resolved properties of Ce(3+), Eu(3+), and Tb(3+) in novel LiSr(4)(BO(3))(3) powder phosphors. Ce(3+) shows an emission band peaking at 420 nm under 350-nm UV excitation. Energy transfer from Ce(3+) to Mn(2+) takes place in the co-doped samples. Eu(3+) shows red emission under near UV excitation. LiSr(4)(BO(3))(3):Eu(3+) phosphor could be a suitable candidate for phosphor-converted solid state lighting. The luminescence lifetime is 2.13 ms for Eu(3+) in LiSr(4)(BO(3))(3):0.001Eu(3+). As Eu(3+) concentration increasing, the decay curves deviate from exponential behavior. Tb(3+) shows the strongest (5)D(4)→(7)F(5) emission line at 540 nm. Decay curves of (5)D(4)→(7)F(5) and (5)D(3)→(7)F(5) emission with different Tb(3+) concentrations were also measured. Cross-relaxation process is discussed based on the decay curves.

Multiple pulse nanosecond laser induced damage study in LiB3O5 crystals.

Multiple pulse nanosecond laser induced damage in the bulk of LiB3O5 (LBO) crystals was investigated at 1064 nm, 532 nm and 355 nm. Scanning electron microscopy of cleaved damage sites confirmed the presence of different zones that have already been reported in the case of KH2PO4 (KDP). Multi pulse measurements reveal a strong decrease of the damage threshold with increasing pulse number at 1064 nm (fatigue effect). A weaker fatigue effect was observed at 532 nm and no fatigue effect was found at 355 nm. This observation is best explained by an inherently statistical light matter interaction generating laser induced damage. Finally, a polarization dependent damage threshold anisotropy was evidenced at all three wavelengths, being strongest at 1064 nm. The results indicate the importance of Li+ vacancy stabilized color centers for the damage mechanism.

Optimization of Pr3+, Tb3+, and Sm3+ co-doped (Y0.65Gd0.35)BO3:Eu0.05(3+) VUV phosphors through combinatorial approach.

A combinatorial approach was used to systematically investigate the effect of trace Pr(3+), Tb(3+), or Sm(3+) on the VUV photoluminescence of Eu(3+) in the Pr(3+), Tb(3+), or Sm(3+) co-doped (Y(0.65)Gd(0.35))BO(3):E(3+)(0.05). We found that Pr(3+) and Tb(3+)increases the VUV photoluminescent efficiency, while Sm(3+) decreases the efficiency. The optimized composition was identified to be between 7 x 10(-6) and 3 x 10(-4), and the corresponding efficiency improvement is about 15%. Scale-up experiments confirmed the results in the combinatorial materials libraries.

SYNTHESIS, OPTICAL PROPERTIES AND THERMOLUMINESCENCE DOSIMETRY FEATURES OF MANGANESE DOPED Li2B4O7 NANOPARTICLES.

Lithium tetraborate (Li2B4O7) nanoparticles (NPs) doped with manganese (Mn) were prepared for the first time by the solid-state sintering method. NPs were characterized using X-ray diffraction, scanning electron microscopy, photoluminescence and thermoluminescence (TL) techniques. The synthesized NPs exhibited highest TL response at 0.3 wt% of Mn dopant under gamma irradiation. TL dose response is linear for the absorbed dose from 1 Gy to 20 kGy and beyond this range behaves sub-linear. Such feature makes the synthesized nanophosphor as a promising material for high-dose dosimetry applications. Low fading and good reusability were obtained for the synthesized NPs. Tm-Tstop and computerized glow curve deconvolution procedures were utilized to identify the component TL glow peaks and kinetic parameters of the produced phosphor. Other TL dosimetry features of the prepared NPs are also presented and discussed.

Structure and photoluminescent properties of microstructural YBO3 : Eu3+ nanocrystals.

YBO3 : Eu3+ nanocrystals (NCs) were prepared by a hydrothermal method and characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. The results demonstrate that morphology and structure of the NCs varied strongly with hydrothermal temperature. Their luminescent properties were investigated in comparison to the bulk. A large number of NO3- groups were adsorbed at the surface of hydrothermal products, which acted as luminescent killers; Two symmetry sites of Eu3+ ions in NCs, the interior and the surface sites, were identified by the site-selective excitation and time-resolved emission experiments; The intensity ratio of 5D0-7F2 to 5D0-7F, of EU3+ at the surface site increased greatly than that at the interior site; as a result, the chromaticity was improved; The total radiative transition rate of 5D0-sigmaJ7FJ for Eu3+ at the surface site was 3-5 times larger than that at the interior.

Individual monitoring based on magnesium borate.

Valuable features of magnesium borate sintered solid thermoluminescence dosemeters (TLDs), such as near tissue- equivalence, high sensitivity, and good performances for X, gamma, beta and neutron dosimetry, were developed and produced by the Institute of Nuclear Sciences, Vinca. These features form the basis for using this type of TLDs successfully for legal personal dosimetry control in Serbia for the past 27 y. The dosimetric properties of this TL material are presented in this study.

Comparative study of LiF:Mg,Cu,Na,Si and Li2B4O7:Cu,Ag,P TL detectors.

Recently, two new types of 'tissue equivalent' thermoluminescent detectors (TLDs) have aroused attention: LiF:Mg,Cu,Na,Si and Li2B4O7:Cu,Ag,P. In this work the characteristics of both detectors were compared with the characteristics of the well-known type LiF:Mg,Ti detector, TLD-100. The following properties were investigated: the glow curve structures, relative sensitivity, batch homogeneity and uniformity, detection threshold, reproducibility of the response, linearity in the wide dose range and fading. Also, the energy dependence for medium and low energy X rays was determined in the range of mean energies between 33 and 116 keV. The results confirmed 'tissue equivalency' of both new types in the investigated range of photon energies. LiF:Mg,Cu,Na,Si detector has very high sensitivity (approximately 75 times higher than that of TLD-100) and is convenient for use in a very low range of doses. Li2B4O7:Cu,Ag,P detector shows some improvements in comparison with the previously prepared types of lithium borate. The most important is the five times higher sensitivity than that of TLD-100. This detector is also very promising, especially in medical dosimetry.

Radiation-induced defects in manganese-doped lithium tetraborate phosphor.

Lithium tetraborate doped with manganese synthesised by solid-state sintering technique exhibits a dosimetric peak at 280°C. The high-temperature glow curve results in no fading for three months. The sensitivity of Li2B4O7:Mn is determined to be 0.9 times that of TLD-100. The infrared spectrum of this phosphor indicates the presence of bond vibrations corresponding to BO4 tetrahedral and BO3 triangles. The mechanism for thermoluminescence in this phosphor was proposed based on the thermoluminescence (TL) emission spectra, kinetic analysis of TL glow curves and electron paramagnetic resonance (EPR) measurements on non-irradiated and gamma-irradiated phosphors. It was identified that oxygen vacancies and Boron oxygen hole centre (BOHC) are the electron and hole trap centres for TL in this phosphor. When the phosphor is heated, the electrons are released from the electron trap and recombine with the trapped holes. The excitation energy during the recombination is transferred to the nearby Mn(2+) ions, which emit light at 580 nm.

Dosimetric characteristics of Li2B4O7:Cu,Ag,P solid TL detectors.

The main dosimetric characteristics are presented of newly prepared tissue-equivalent, highly sensitive thermoluminescent detector, Li,B4O7:Cu,Ag,P in the form of sintered pellets, developed at the Institute of Nuclear Sciences, Vinca. As a result of an advancement in the preparation procedure by the sensitising of basic copper activated lithium borate TL material, significant improvement in the TL sensitivity of Li2B4O7:Cu,Ag,P was gained. The glow curve of Li,B4O7:Cu,Ag,P consists of well defined main dosimetric peak situated at about 185-190 degrees C with the TL sensitivity which is about four to five times higher than that of LiF:Mg,Ti (TLD-100). From the experimental results a very wide linear dose response range, up to 10(3) Gy is evident. Dosimetric characteristics make sintered solid Li,B4O7:Cu,Ag,P TL detectors very promising for different dosimetry applications particularly in medical dosimetry and also for individual monitoring.

Thermoluminescent spectra of rare earth doped MgB4O7 dosemeters.

This paper presents X ray excited TL spectra of magnesium borate doped with either single rare earth ions Dy or Tm, or co-doped with Dy/Tm, Tm/Mn or Dy/Tb. Intrinsic emission from the host material is in the UV/blue region at approximately 375 nm, with a tail extending to 200 nm. The main dosimetric peak is detected at approximately 180 degrees C but slight differences are noted between the glow peak maxima from the different rare earth ions and there were changes following thermal treatments. The results are discussed according to the interaction between trapping and rare earth sites.

Main dosimetric characteristics of some tissue-equivalent TL detectors.

The aim of this work was to determine important dosimetric characteristics of several types of the most interesting tissue-equivalent thermoluminescent detectors (TLDs). Special attention was given to the determination of energy dependence for medium and low energy X rays. The following types of TLDs were investigated: (a) two new types based on lithium borate: Li2B4O7:Cu,In and Li,B4O7:Cu,In,Ag; (b) two types of the recently developed highly sensitive LiF:Mg,Cu,P material: TLD-700H and GR 200A and (c) two well known types of LiF:Mg,Ti detectors: TLD-100 and TLD-700. In order to determine their photon energy response characteristics, TLDs previously calibrated with 137Cs gamma rays were simultaneously irradiated with X ray beams in the range of effective energies between 33 and 116 keV. Measured energy responses (relative to air), normalised to those to 137Cs photons were compared with calculated data. Although the deviations of the measured data from the 'theoretical' predictions are different for all the investigated TLDs, there is no large difference in 'tissue-equivalency' between them.

High resolution emission spectra of TL materials.

High resolution emission spectra of several TL materials, that are commonly used in dosimetry, were measured using a low cost fibre optic spectrometer containing a 2048 pixel CCD array. The spectra were taken from 177 to 890 nm with a wavelength resolution of 1.3 nm. This allowed for line width discrimination and the resolution of transitions that have not been seen so far. For rare earth doped materials like CaF2:Tm (TLD-300) and CaF2:Dy (TLD-200) the spectral lines were compared to the energy levels measured by Dieke and Crosswhite leading to the identification of most of the transition lines.

Response of a lithium gadolinium borate scintillator in monoenergetic neutron fields.

Accurate estimation of neutron dose requires knowledge of the neutron energy distribution in the working environment. Existing neutron spectrometry systems, Bonner spheres for example, are large and bulky, and require long data acquisition times. A portable system that could indicate the approximate neutron energy spectrum in a short time would be extremely useful in radiation protection. A composite scintillator, consisting of lithium gadolinium borate crystals in a plastic scintillator matrix, produced by Photogenics is being tested for this purpose. A prototype device based on this scintillator and digital pulse processing electronics has been calibrated using quasi-monoenergetic neutron fields at the low-scatter facility of the UK National Physical Laboratory (NPL). Energies selected were 144, 250, 565, 1400, 2500 and 5000 keV, with correction for scattered neutrons being made using the shadow cone technique. Measurements were also made in the NPL thermal neutron field. Pulse distributions collected with the digitiser in capture-gated mode are presented, and detection efficiency and energy resolution derived. For comparison, neutron spectra were also collected using the commercially available Microspec N-Probe from Bubble Technology Industries, which consists of an NE213 scintillator and a 3He proportional counter.

Clinical comparison between the bleaching efficacy of light-emitting diode and diode laser with sodium perborate.

The aim of this clinical study was to test the efficacy of a light-emitting diode (LED) light and a diode laser, when bleaching with sodium perborate. Thirty volunteers were selected to participate in the study. The patients were randomly divided into two groups. The initial colour of each tooth to be bleached was quantified with a spectrophotometer. In group A, sodium perborate and distilled water were mixed and placed into the pulp chamber, and the LED light was source applied. In group B, the same mixture was used, and the 810 nm diode laser was applied. The final colour of each tooth was quantified with the same spectrophotometer. Initial and final spectrophotometer values were recorded. Mann-Whitney U-test and Wicoxon tests were used to test differences between both groups. Both devices successfully whitened the teeth. No statistical difference was found between the efficacy of the LED light and the diode laser.