Bleaching Rate Research Articles

Coordination-enhanced photochromism in dysprosium dinuclear complexes with photomodulated single-molecule magnet behavior

We report the synthesis of a pyrazine-based bis-tridentate diarylethene (DAE) ligand and the corresponding dinuclear yttrium and dysprosium complexes that all show T-type photochromism. Large changes in the photochromic behaviour are induced by metal coordination, including a tuning of the bleaching rate by several orders of magnitude, characterized through VT-NMR and supported by theoretical calculations. The dysprosium dinuclear complex shows a single-molecule magnet (SMM) behaviour, under an external applied magnetic field, significantly modulated upon photoisomerization. This feature is further analyzed through ab initio calculations.

STUDY OF THE Ni(OH)2 ELECTROCHROMIC PROPERTIES OF FILMS DEPOSITED ON FTO GLASS WITH AN ADDITIONAL CONDUCTING LAYER

This work attempts to evaluate the influence of substrate conductivity on electrochromic and electrochemical properties of Ni(OH)2/PVA composite films, including coloration and bleaching rate. The conductivity of FTO glass was improved by depositing a silver gird with differing line densities. For deposition of the silver lines, aerosol jet printing method was used. As a result, few electrochromic films were deposited onto bare FTO glass and FTO glass with silver grid deposited onto it. In order to investigate deposited electrochromic films, the cyclic voltammetry with simultaneous recording of the optical characteristics is used. The optical characteristics of films were rather close to each other. At the same time, their electrochemical properties are different. It is found that the additional peaks observed is that of silver, which is electrochemically active in used potential window. In addition it was observed that during electrochemical cycling of Ni(OH)2/PVA deposited on substrates with silver grid, the last changed color from shiny metallic to black color. It is proposed that color changes of silver grid caused by silver transforming to Ag2O or AgO and back to metallic silver. It is found, that for small areas of electrochromic platings, substrate resistivity has a negligible effect on coloration and bleaching rates. The coloration and bleaching rates for Ni(OH)2/PVA films deposited onto the bare substrate, the substrate with a silver grid (1 cm cell size) and the substrate with a silver grid (0.5 cm cell size) were: –1.45, –1.71, –1.40 and 1.1, 0.75, 0.84 %∙s-1. It is suggested that the effect of substrate conductivity will clearly be seen when the physical sizes of substrate increase. Also it was underlined that for further experiments for effect definition of substrate resistivity on electrochromic properties inherit conductive materials should be used

Error correction due to background subtraction in ratiometric calcium measurements with CCD camera

BackgroundCa2+ plays an important role in many physiological processes and an accurate study of these signals is important. In modern fluorescence microscopy, a charge-coupled device (CCD) camera is widely deployed for calcium imaging. The ratiometric method is used for the fluorescence dye Fura-2 and Grynkiewitz's formula (Grynkiewicz et al., 1985) is commonly used to convert fluorescence to free Ca2+ concentration ([Ca2+]). But the need to subtract the background signal can lead to a big error in ratiometric calcium measurements. When the error due to background subtraction occurs, the fluorescence ratio of 340 nm divided by 380 nm lights may be twice as large as the actual value. Under conditions when the excitation intensity is not adjusted to ensure the same throughput of the objective lens for ultraviolet dye illumination, the indicator does not gradually bleach out for channels with a wavelength of 340 nm and 380 nm light, which lead to an additional error in determining the concentration of Ca2+. New methodHere we present a new approach for calculating [Ca2+] from the ratiometric fluorescence of Fura-2 dye imaged by a CCD camera. It is designed to optimize [Ca2+] measurements with photobleaching correction without background subtraction error. A mathematical method is also provided for removing the existing underestimated value of fluorescence at an excitation wavelength of 340 nm and compensating for the bleaching rate for both channels with wavelengths of 340 nm and 380 nm using a power function. ResultsIn cultured neurons, the calculations of the free Ca2+ concentration during Ca2+ transients estimated by the old and new methods, determine it to the same extent. This comparison was made under conditions without errors through background subtraction. If there is this error, the old method calculates [Ca2+] with a much higher, rather than the actual value. ConclusionsWe present a modified Grynkiewitz's formula for calculation [Ca2+] for ratiometric dye, such as Fura-2 imaged by a CCD camera, with photobleaching correction without background subtraction error.

Oxidative Catalysis by TAMLs: Obtaining Rate Constants for Non-Absorbing Targets by UV-Vis Spectroscopy.

Understanding the catalysis of oxidative reactions by TAML activators of peroxides, i. e. iron(III) complexes of tetraamide macrocyclic ligands, advocated a spectrophotometric procedure for quantifying the catalytic activity of TAMLs for colorless targets (kII ', M-1 s-1 ), which is incomparably more advantageous in terms of time, cost, energy, and ecology than NMR, HPLC, UPLC, GC-MS and other similar techniques. Dyes Orange II or Safranin O (S) are catalytically bleached by non-excessive amount of H2 O2 in the presence of colorless substrates (S1 ) according to the rate law: -d[S]/dt=kI kII [H2 O2 ][S][TAML]/(kI [H2 O2 ]+kII [S]+kII '[S1 ]). The bleaching rate is thus a descending hyperbolic function of S1 : v=ab/(b+[S1 ]). Values of kII ' found from a and b for phenol and propranolol with commonly used TAML [FeIII {o,o'-C6 H4 (NCONMe2 CO)2 CMe2 }2 (OH2 )]+ are consistent with those for S1 (phenol, propranolol) obtained directly by UPLC. The study sends vital messages to enzymologists and environmentalists.

Treatment of hot-dip galvanization by coagulation-flocculation, adsorption and by new hybrid process coagulation-flocculation/adsorption using lime-(chitosan-epichlorohydrin)/activated carbon based on dates stones

In this work, we conducted a study that is to bleach wastewater loaded with ions, while using and optimizing the process of hybridized treatment of liquid effluents by of coagulation-flocculation/adsorption (CF-ADS). According to the separate optimization of flocculation processes (optimum dose of the flocculant (chitosan cross-linked by epichlorohydrin (chitosan-ECH))) and adsorption (activated carbon based on dates stones), we combined the two methods in order to increase performance fading exploited wastewater. The results of the rate of elimination separated by the methods of coagulation-flocculation, adsorption and are respectively of the order of 88.17% and 96.17% for the zinc and of the order of 83.68% and 95.4% for copper. While the results of the bleaching obtained by the hybrid method CF-ADS have shown that the bleaching rate was calculated as around 99.14% for zinc and of the order of 96.8%,for the copper, obviously very interesting with respect to the coagulation-flocculation(CF) and adsorption(ADS) used separately.

Photobleaching of Phthalocyanine Molecules within a Complex with Colloidal Quantum Dots

Fluorescent nanoparticles are currently considered as promising enhancers of photodynamic activity of traditional photosensitizers in procedures for photodynamic therapy of cancer and inactivation of pathogens. On the one hand, such nanoparticles act as a nanoplatform for target delivery of dye molecules to cells; on the other hand, they act as light-harvesting antennas that increase the effective absorption cross-section of the dye. This paper investigates the effect of semiconductor CdSe/ZnS quantum dots coated with a polymer shell on the photostability of zinc or aluminum polycationic phthalocyanines. It was shown that the rate of photobleaching of phthalocyanines increases significantly in the presence of quantum dots both under direct illumination of phthalocyanine by red light and under the quantum dot-mediated illumination by blue light. This effect can be explained by the fact that phthalocyanine inside the polymer shell of the quantum dot is the primary target for the attack by reactive oxygen species. The rate of bleaching of the chemical trap of reactive oxygen species, 4-nitroso-N,N-dimethylaniline, in a phthalocyanine solution increases in the presence of the quantum dot under red light illumination. We believe that the chemical trap is concentrated in the polymer shell of the quantum dot, which increases the probability of its damage by active oxygen species generated by phthalocyanine. Since the diffusion of reactive oxygen species from the polymer shell of the nanoparticle into the surrounding solution is slow, the use of quantum dots as an enhancer of the photodynamic action of phthalocyanines can be effective only in the absence of significant steric obstacles to the diffusion of reactive oxygen species to the target molecules of photodynamic inactivation.

Alarming the impacts of the organic and inorganic UV blockers on endangered coral's species in the Persian Gulf: A scientific concern for coral protection

Abstract Coral reefs provide many benefits to the society, including ecological nest for aquatic species, medicine ingredient, and protection of coastlines from flooding and storms. Organic and inorganic UV filters (UVfs) are key ingredients in a variety of sunscreen and personal care products, which are massively released to natural waters by marine tourism. Reports are alarming UVfs cause fast bleaching of coral reefs in the Persian Gulf at a tiny concentration (less than 10 µl L−1). Here, for the first time, the evidence pertaining to the impacts of UVfs on corals in the Persian Gulf is highlighted. Based on the existing field reports, laboratory experiments and increasing trend f tourism, corals of Kish Island in Iran are seriously threatened. Here, Kish is a study model that highlights the alarming impacts of UVfs on the endangered population of corals in all Gulf countries. This study found a positive relation between the number of visitors to the island and the bleaching rate of stony coral.

Enhanced visible-light photocatalytic activity of anatase-rutile mixed-phase nano-size powder given by high-temperature heat treatment.

Nano-size EVONIK AEROXIDE® P25 titanium dioxide, TiO2, powder was heat-treated at temperatures, 700–900°C, in air. An X-ray diffraction study showed that the P25 powder is composed of approximately 20 and approximately 80 mass% of rutile and anatase phases, respectively. It was also shown that the transformation from anatase to rutile induced by high-temperature heat treatment was almost completed at 750°C, whereas a small amount (less than 3 mass%) of anatase phase was still left even in the powder heat-treated at 900°C. The transformation behaviour was consistent with results obtained by Raman scattering spectroscopy. Raman experiments also indicated that high-temperature heating induced the formation of oxide ion vacancies. Powders were dispersed in methyl orange (MO) aqueous solution, and the bleach rate of MO was measured to evaluate photocatalytic activity under ultraviolet (UV)- and visible-light irradiation. After the heat treatment, the UV-light photocatalytic performance sharply deteriorated. Interestingly, visible-light photocatalytic activity was enhanced by high-temperature heating and reached the highest performance for an 800°C-heated sample, indicating that the P25 powder obtained high visible-light photocatalytic performance after heat treatment. Even after 900°C heat treatment, the photocatalytic performance was higher than that of as-received powder. Enhancement of photocatalytic activities was discussed in relation to visible light absorption and charge carrier transfer.

Assessment of p-nitroso dimethylaniline (pNDA) suitability as a hydroxyl radical probe: Investigating bleaching mechanism using immobilized zero-valent iron nanoparticles

Use of p-nitroso dimethylaniline (pNDA) as a selective hydroxyl radical (OH) probe compound has been extensively reported in the literature for evaluating the performance of the catalysts used in Advanced Oxidation Processes (AOPs). Some recent studies speculated that pNDA might be oxidized by other oxidizing species, and might also be directly reduced. This study, for the first time, investigates pNDA bleaching mechanism by an Fe0-containing composite, capable of causing both reduction and Fenton-like oxidation. The composite consisted of Santa Barbara-15 (SBA-15) mesoporous silica as the supporting medium for nZVI immobilization (nZVI/SBA-15). The quantity of iron in the composite was optimized by synthesizing four various nZVI/SBA-15 samples with different iron to silica weight ratios and comparing their pNDA bleaching efficiency. Kinetic studies showed a pseudo-second-order model for pNDA bleaching using all nZVI/SBA-15 samples. The effects of OH scavengers and dissolved oxygen concentration on pNDA bleaching rate were examined. FTIR analysis of pNDA solutions showed different molecular structures for pNDA bleached under different DO conditions, leading to the conclusion that pNDA is susceptible to reductive bleaching. Results demonstrated that when using pNDA as a probe for free radicals’ generation assessment, the reductive potential of the catalysts needs to be considered.

Hydroxyl radical formation in the hybrid system of photocatalytic fuel cell and peroxi-coagulation process affected by iron plate and UV light.

The hybrid electrochemical system of photocatalytic fuel cell - peroxi-coagulation (PFC-PC) is a combined technology of advanced oxidation process (AOP) which involve the hydroxyl radical formation for simultaneous degradation of organic pollutant and electricity generation. The p-nitrosodimethylaniline (RNO) spin trapping technique was applied by analyzing the RNO bleaching performance to detect the OH at the PFC and PC reactors. The presence of UV light showed higher RNO bleaching rate at the PFC reactor (11.7%) with maximum power density (Pmax=3.14mWcm-2). Results revealed that the optimum of maximum power density was observed at iron plate size of 30cm2. UV light became a limiting factor in the PFC system as a power source in the PFC-PC system. Meanwhile, iron plate plays an important role to supply the soluble Fe2+ ions by oxidation process and become a suitable catalyst for in-situ production of H2O2 and OH through the PC process to degrade the organic molecules.

Ecotoxicological responses of a reef calcifier exposed to copper, acidification and warming: A multiple biomarker approach

Multiple global and local stressors threat coral reefs worldwide, and symbiont-bearing foraminifera are bioindicators of reef health. The aim of this study was to investigate single and combined effects of copper (Cu) and climate change related stressors (ocean acidification and warming) on a symbiont-bearing foraminifer by means of an integrated biomarker analysis. Using a mesocosm approach, Amphistegina gibbosa were exposed for 25 days to acidification, warming and/or Cu contamination on a full orthogonal design (two levels each factor). Cu was the main factor increasing bleaching and respiration rates. Warming was the main cause of mortality and reduced growth. Calcification related enzymes were inhibited in response to Cu exposure and, in general, the inhibition was stronger under climate change. Multiple biological endpoints responded to realistic exposure scenarios in different ways, but evidenced general stress posed by climate change combined with Cu. These biological responses drove the high values found for the ‘stress index’ IBR (Integrated Biomarker Response) – indicating general organismal health impairment under the multiple stressor scenario. Our results provide insights for coral reef management by detecting potential monitoring tools. The ecotoxicological responses indicated that Cu reduces the tolerance of foraminifera to climate change (acidification + warming). Once the endpoints analysed have a high ecological relevance, and that responses were evaluated on a classical reef bioindicator species, these results highlight the high risk of climate change and metal pollution co-exposure to coral reefs. Integrated responses allowed a better effects comprehension and are pointed as a promising tool to monitor pollution effects on a changing ocean.

A High-Throughput Image Correlation Method for Rapid Analysis of Fluorophore Photoblinking and Photobleaching Rates.

Super-resolution fluorescence imaging based on localization microscopy requires tuning the photoblinking properties of fluorescent dyes employed. Missing is a rapid way to analyze the blinking rates of the fluorophore probes. Herein we present an ensemble autocorrelation technique for rapidly and simultaneously measuring photoblinking and bleaching rate constants from a microscopy image time series of fluorescent probes that is significantly faster than individual single-molecule trajectory analysis approaches. Our method is accurate for probe densities typically encountered in single-molecule studies as well as for higher density systems which cannot be analyzed by standard single-molecule techniques. We also show that we can resolve characteristic blinking times that are faster than camera detector exposure times, which cannot be accessed by threshold-based single-molecule approaches due to aliasing. We confirm this through computer simulation and single-molecule imaging data of DNA-Cy5 complexes. Finally, we demonstrate that with sufficient sampling our technique can accurately recover rates from stochastic optical reconstruction microscopy super-resolution data.

Quantifying the colour loss of green field pea (Pisum sativum L.) due to bleaching.

Post-harvest change in the colour of green field pea (Pisum sativum L.) is undesirable as this impacts the visual quality and market value of the seed. To date, there is no standard, objective method to determine bleaching. Therefore, the aim of this study was to develop an objective method for scoring bleaching based on colour reflectance spectra, measured both by spectrophotometer and multispectral Image Analysis (IA). Green field pea seeds were sorted into samples of uniform colour and these were used to train the model. Spectra calculated from multispectral images (with colour bands at 405,470,530,590,660 and 850nm) were matched to the spectrophotometer output through multiple linear regression. All spectra were transformed to emphasize the wavelength regions most impacted during bleaching, following which two critical reflectance values were scaled to a single bleaching score. The bleaching assessment method was tested in a time-course experiment comprising seeds from five green-pea genotypes stored for six months. Each sample was divided into two so that half of the seeds were stored in the dark and the remainder were exposed to controlled light to exaggerate bleaching. Throughout this period, the samples were imaged at six-weekly intervals. Assessment of bleaching by the IA method agreed well with spectrophotometer measurements, achieving a Lin’s concordance statistic of 0.99 and 0.96 for the calibration and time-course samples respectively. The IA method proved more versatile because assessments could be made on individual seeds enabling the computation of bleaching uniformity within each sample. This method captured differences between genotypes in the extent, rate and uniformity of bleaching. All genotypes exhibited susceptibility to bleaching when stored under the controlled light conditions. Excell was observed to be the most susceptible genotype with the greatest bleaching-rate and OZB1308 displayed the most colour-stability.

High performance in electrochromic amorphous WOx film with long-term stability and tunable switching times via Al/Li-ions intercalation/deintercalation

Lithium ion (Li+) aggregation in the amorphous tungsten oxide (a-WOx) film is the main cause of the electrochromic (EC) device failure. This has hindered a-WOx films goes towards industrialization on behalf of the giant EC performance and long-term reliability. A novel kind of electrolytes consisted of Aluminum ions (Al3+) and Lithium ions (Li+) used for electrochromic sputtered a-WOx films is presented. With the newly designed Al3+/Li+ co-existed electrolytes, the optical transmittance modulation can be largely enhanced compared with Li+, meanwhile, the problem of degradation after long-term cycling for a-WOx induced by Li ions-trapping is able to be solved. Furthermore, the utilization of Al3+ brings slow switching kinetics at the ions extraction step to the films compared with Li+, which supplies a new method to modulate the bleaching rate by applying adjustable Al3+/Li+ ratio of electrolytes and a tunable and controllable switching time is easily achieved in this work. This Al3+/Li+ co-based electrolyte opens a new way to design and control the high contrast, long-lived cycling stability and changeable switching time EC devices based on a-WOx films.

An o-hydroxyl aldehyde structure based naphthalimide derivative: Reversible photochromic properties and its application in ClO- detection in living cells.

A bifunctional organic compound 2-butyl-6-hydroxy-1,3-dioxo-2,3-dihydro-1H-benzo[de] isoquinoline-5-carbaldehyde (BHC) with photochromic properties in solid state and probe detection for ClO- in complete water solution was synthesized and fully characterized. A 'white-yellow-white' reversible photochromic behavior could be observed when alternating UV/vis light irradiation on the solid BHC powder. Good fatigue resistance and adjustable bleaching rate were shown when heating conditions changes. In addition, BHC displayed a high selectivity and low detection limit (1.16 × 10-8 M) for ClO-. The photoluminescent fluorescence "on-off" recognition result can be easily identified and BHC has been tested for safely imaging living cells and detecting hypochlorite anion in vitro and vivo. A better water solubility of BHC effectively reduces damage caused by organic solvent in cell imaging progress.

Reversible photochromic tetraphenylethene-based Schiff base: Design, synthesis, crystal structure and applications as visible light driven rewritable paper and UV sensor

“Paper” plays an important role in the development and spread of civilization. However, massive use of paper has led to nonnegligible negative influence on environment. Recently, great progresses have been made in the fields of rewritable paper that has enormous potential in alleviating the increasing demand for paper. Therefore, we report a new photochromic tetraphenylethene-based Schiff base derivative 2-ethoxy-6-(((4-(1,2,2-triphenylvinyl)phenyl)imino)-methyl)phenol (TPENOEt). TPENOEt exhibits reversible photochromic behavior, fast response, simple synthetic step, lower cost and excellent fatigue resistance. The bleaching rate of TPENOEt is tunable by longer wavelength light, white light irradiation and elevated temperature. The fluorescence of TPENOEt is weak in solid state, which increases obviously after grinding with a pestle accompanied by reduced photochromic efficiency and longer response time. These results provide a new view to get insight into the relationship between packing style and fluorescence/photochromism property of Schiff base derivatives. TPENOEt is successfully applied as a visible light driven rewritable paper, 410 nm violet light can serve as a pen, while 420–590 nm visible light and white light is employed as the eraser. The recorded information will be erased in about 15 s after white light irradiation and will be self-erased in 20 min in daylight and in about 15 days in dark. Moreover, TPENOEt can also serve as a UV strength sensor for naked eye detection of UV radiation pollution.

New coumarin- and phenoxazine-based fluorescent probes for live-cell STED nanoscopy.

The potential of live-cell stimulated emission depletion (STED) nanoscopy has not yet been fully exploited. Currently, the main limitation is the small number of fluorophores and probes that can sustain high light intensity/high dose employed in STED. Namely, fluorophores suitable for STED nanoscopy must be bright and highly photostable and exhibit a large Stokes shift. To expand the list of available probes, we synthesized and evaluated several new membrane probes for live-cell STED nanoscopy. Of the tested probes, probes MePyr500, ThiaCN545 and NB640 not only allow high-resolution STED images, but also partition into the intracellular membranes relatively quickly, thus lacking the selectivity of labelling solely the plasma membrane. During experiments, cytotoxicity was observed merely with the probe ThiaCN545, which blebs the plasma membrane. In comparison with commercially available CellMask Orange and STAR RED (KK114) DPPE, all our tested probes exhibited better photostability with the exception of NB640, which had the fastest bleaching rate of all tested probes. The best overall results can be assigned to the probe MePyr500, providing high-resolution STED images as well as high photostability with no noticeable cytotoxicity, making it an excellent candidate for further development.

Dynamic Measurement of Nanoflows: Analysis and Theory of an Optofluidic Flowmeter.

Scientists must overcome fundamental measurement problems if microfluidic devices are to become reliable and commercially viable. In particular, microfluidic devices require precise control over operating conditions such as flow-rate, υυ , which is difficult to measure continuously and in situ. Given the small scales involved, state-of-the-art approaches generally require accurate models to infer υυ on the basis of indirect measurements. However, such methods necessarily introduce model-form errors that dominate at the nL/min scale being targeted by the community. To address these problems, we develop a robust and largely assumption-free scaling method that relates the fluorescence efficiency of fluorophores to υυ through a dosage parameter ξ, which depends on the flow rate and laser power. Notably, we show that this scaling relationship emerges as a universal feature from a general class of partial differential equations (PDEs) describing the experimental setup, which consists of an excitation beam and fluorescence detector. As a result, our approach avoids uncertainties associated with most modeling assumptions, e.g. the exact system geometry, the flow profile, the physics of fluorescence, etc. Moreover, the corresponding measurements remain valid down to the scale of 10 nL/min, with some devices potentially capable of reaching 1 nL/min. As an added benefit, the measurement procedure is mathematically simple, requiring a few trivial computations, as opposed to the full solution of a PDE. To support these claims, we discuss and quantify uncertainties associated with our method and present experimental results that confirm its validity.

Ag/Ag2O as a Co-Catalyst in TiO2 Photocatalysis: Effect of the Co-Catalyst/Photocatalyst Mass Ratio

Mixtures and composites of Ag/Ag2O and TiO2 (P25) with varying mass ratios of Ag/Ag2O were prepared, employing two methods. Mechanical mixtures (TM) were obtained by the sonication of a suspension containing TiO2 and Ag/Ag2O. Composites (TC) were prepared by a precipitation method employing TiO2 and AgNO3. Powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirmed the presence of Ag(0) and Ag2O. The activity of the materials was determined employing methylene blue (MB) as the probe compound. Bleaching of MB was observed in the presence of all materials. The bleaching rate was found to increase with increasing amounts of TiO2 under UV/vis light. In contrast, the MB bleaching rate decreased with increasing TiO2 content upon visible light illumination. XRD and XPS data indicate that Ag2O acts as an electron acceptor in the light-induced reaction of MB and is transformed by reduction of Ag+, yielding Ag(0). As a second light-induced reaction, the evolution of molecular hydrogen from aqueous methanol was investigated. Significant H2 evolution rates were only determined in the presence of materials containing more than 50 mass% of TiO2. The experimental results suggest that Ag/Ag2O is not stable under the experimental conditions. Therefore, to address Ag/Ag2O as a (photo)catalytically active material does not seem appropriate.

Pump wavelength dependence and thermal effect of photobleaching of BAC-Al in bismuth/erbium codoped aluminosilicate fibers.

Photobleaching of IR luminescence of BAC-Al at 1180nm under various irradiation wavelengths (532, 633, 710, 830, and 980nm) is observed for the first time, to the best of our knowledge. It is found that the bleaching rate increases along with the increasing photon energy. The photobleaching of BAC-Al at 532nm irradiation is described as a two-photon process, evidenced by the quadratic dependence of the bleaching rate on the launched power. The photoinduced reduction on absorption bands of BAC-Al (700nm) and BAC-Si (816nm) is observed, revealing the higher stability for BAC-Al to laser irradiation. The thermal annealing effect on the bleached BAC-Al is also investigated; strong luminescence quenching of BAC-Al at the high temperature (500°C) is shown instead of the recovery. The underlying mechanism for photobleaching and thermal quenching of BAC-Al is analyzed and discussed.