Significant Decrease In Fluorescence Research Articles

Microwave Synthesis of Carbon Quantum Dots from Arabica Coffee Ground for Fluorescence Detection of Fe3+, Pb2+, and Cr3.

In this study, carbon quantum dots (CQDs), which were synthesized from arabica coffee ground-derived activated carbon, have been successfully employed as a fluorescence sensor to detect Fe3+ ions. CQDs were fabricated using microwave heating for 5-10 min, which emitted vibrant blue light at 455 nm when exposed to excitation at 365 nm. Dynamic light scattering (DLS) analysis revealed that the average size of CQDs was 10.12 nm with a quantum yield of 6.01%. Fluorescence detection was developed for sensing Fe3+, Pb2+, and Cr3+ ions. The addition of the three metal ions resulted in a decrease in the fluorescence (FL) intensity of the CQDs, with the addition of Fe3+ ions demonstrating a more significant decrease in FL compared to the addition of both Cr3+ and Pb2+ ions. The results indicated that the CQDs synthesized from activated carbon of arabica coffee waste performed as a selective fluorescent detector for Fe3+ ions, with a detection limit of 0.27 μM.

Investigation of biofluorescence produced by the red king crab Paralithodes camtschaticus

AbstractBiofluorescence is widely documented in marine organisms, yet few studies exist for decapods. After observing the king crab Paralithodes camtschaticus biofluoresces, we carried out studies on two separately maintained groups of male crabs under controlled conditions. Hyperspectral imaging on Group 1 (n = 18) examined the exoskeleton, whereas fluorospectrometry examined the hemolymph of Group 2 animals (n = 19). Both groups were investigated for fluorescence signals before and after exposure to a live shipping transportation simulation. The spines, chelae, eyestalks and cervical grooves of the cardiac region of P. camtschaticus fluoresce in the green spectra (∼500 nm), while the arthrodial membranes of the joints fluoresce in the red spectrum (∼680 nm). After the shipping simulation, we observed a significant decrease in fluorescence in the eyestalks (p = 0.009), while the cervical grooves showed a less significant change (p = 0.01). The hemolymph examined with 21 excitation wavelengths (250–350 nm) emitted fluorescence in ∼400–550 nm spectrum. We found a significant increase (p < 0.05) in fluorescence for 16 excitation wavelengths after transport simulation. The results presented in this study indicate that king crab fluorescence changes due to external stimuli. Fluorospectroscopy or hyperspectral imaging technology may serve as an effective early indicator of preclinical stress in these commercially important decapods.

КВАНТОВЫЕ ТОЧКИ СУЛЬФИДА КАДМИЯ, ПОЛУЧЕННЫЕ С ИСПОЛЬЗОВАНИЕМ БЕЛКОВ-ПОРИНОВ, КАРРАГИНАНОВ, ХИТОЗАНОВ И ЛИПОПОЛИСАХАРИДОВ

Quantum dots (QDs) are a new generation of fluorochromes with significant advantages over traditional organic dyes. QDs based on CdS are promising materials for optics, optoelectronics, biology, and medicine. QDs in the form of colloidal solutions are of great scientific and practical interest. CdS quantum dots were synthesized by chemical condensation in an aqueous solution using Yersinia pseudotuberculosis porin proteins, positively (chitosan) and negatively (carrageenan, lipopolysaccharide) charged polysaccharides. The maxima of the emission spectra for all samples were 450 nm, which indicates the same QD size; is determined by the size of the "cells" of the grid matrix, which limit the size of the QD. It was shown that the fluorescence intensity of QDs synthesized in LPS solutions was two times higher than that of other samples. The fluorescence of the samples and the maxima of the emission spectra (450 nm) are preserved during intensive dialysis against buffers, which indicates the stability of QDs and the possibility of using the obtained labeled preparations. Keeping samples at pH 3 leads to a significant decrease in fluorescence, especially for acidic polysaccharides. Anionic oxygen of phosphate, hydroxyl groups of sugar, nitrogen atoms can interact with metal ions, which are precursors (precursors) for CdS nanocrystals. It was found that the interaction with porin-specific IgG leads to a significant change in the luminescence intensity of QD-porin samples. This is of interest from the point of view of chemical sensing and opens the prospect of using QD-labeled porin-based nanostructures as biosensors.

Dibenzothiazole appended 4-hydroxyphenyl acrylonitrile as a highly selective visual and fluorimetric detection of cyanide ion

A new colorimetric, fluorescent chemosensor 2-(benzo[d]thiazol-2-yl)-3-(3-(benzo[d]thiazol-2-yl)-4-hydroxyphenyl)acrylonitrile (DBTH) with a D-π-A framework has been developed for the detection of cyanide anion (CN−). DBTH can display a high degree of selectivity and sensitivity towards CN− relative to a wide variety of competing anions. DBTH undergoes a color change from colorless to brown after reaction with CN− because of a strong blue shift in the absorption peak at 353 nm. The interaction between blue-fluorescent DBTH and CN− results in a significant decrease in fluorescence. The nucleophilic addition of CN− is the cause of the optical response of DBTH to CN−. The hypothesized mechanism was supported by 1H NMR titrations, mass spectroscopy, and DFT calculations. The detection limit of the probe is (colorimetrically 8.4 nM and fluorometrically 8.9 nM), which is less than the threshold of 1.9 μM set by the World Health Organization (WHO) for CN− ions in an aqueous solution. DBTH coated test kits were developed for on-site detection of cyanide ion that have the added benefit of being solid-supported chemosensors.

Quantitative and Qualitative Assessment of Fluorescence in Aesthetic Direct Restorations.

Currently available direct restoration materials have been developed to have improved optical properties to interact with light in the same manner as the natural tooth. The objective of this study was to investigate the fluorescence of different enamel resin composites. In the present study, nine brands of enamel composites were tested in vitro, some of which are cited by manufacturers as having color adjustment potential. Fluorescence spectra of the composite specimens and the human natural enamel were measured with a fluorescence spectrophotometer immediately after preparation and after 6 months. Qualitative data of the specimens were also collected. Statistical analyses were conducted by Kruskal–Wallis and Mann–Whitney U nonparametric tests (p < 0.05). Almost all tested resin composites presented a significant decrease in the fluorescence values after a period of 6 months. There was no significant decrease in fluorescence in the case of Harmonize™ resin composite samples, which presented the lowest initial fluorescence values. The highest value in the reduction of the initial fluorescence intensity after 6 months (22.95%) was observed for the Charisma® specimens. Composites with a color adjustment did not perform significantly better than other composites in terms of reduction in fluorescence intensity.

Exploiting Rhizobium for Cadmium Sulphide Nanoparticle Synthesis: Heterologous Expression of an Escherichia coli DH10B Enzyme, YbdK [EC: 6.3.2.2] in Sinorhizobium fredii NGR234

Escherichia coli DH10B has 1.1 kb ybdK gene which is responsible for encoding YbdK enzyme that possess a Gamma glutamyl cysteine synthetase activity. ybdK gene was ligated downstream of a constitutive derepressed lac promoter of a low copy number plasmid vector pBBR1MCS-2, giving rise to a recombinant plasmid pPAT. Sinorhizobium fredii NGR234 transformed with pPAT showed an augmented production of glutathione which in turn increased the production of cadmium sulphide nanoparticles to some extent. Also, a heterologous expression of YbdK in Sinorhizobium fredii NGR234 improved the oxidation status of bacterial cells which is confirmed by fluorescence microscopy images and fluorometry. Genetically modified (GM) cells stained by DCFDA showed a significant decrease in fluorescence compared to wild type (WT) cells. Physical and chemical properties of the nanoparticles produced by the pPAT transformed Sinorhizobium fredii NGR234 differed significantly compared to wild type (WT) Sinorhizobium fredii NGR234. Comparative analysis of the nanoparticles by FTIR and SEM analysis revealed the functional groups attached to nanoparticles and average nanoparticle size respectively. Nanoparticles synthesized by genetically modified (GM) bacteria were about 3 times smaller in size compared to those produced by wild type (WT) rhizobium. FTIR analysis revealed an augmented presence of peptide with the nanoparticles produced by GM bacteria compared to those produced by the WT bacteria. XRD data revealed that biosynthesized CdS nanoparticles are face centered crystalline particles which was confirmed by comparing the peaks to standard JCPDS data (JCPDS card no. 10-454).

Patterns of telomere length with age in African mole-rats: New insights from quantitative fluorescence in situ hybridisation (qFISH).

Naked mole-rats Heterocephalus glaber (NMRs) are the longest-lived rodent and also resist the normal signs of senescence. In a number of species, cellular ageing has been correlated with a reduction in telomere length, yet relatively little is known about telomeres and their age-related dynamics in NMRs and other African mole-rats. Here, we apply fluorescence in situ hybridisation (FISH) to quantify telomeric repeat sequences in the NMR, the Damaraland mole-rat, Fukomys damarensis (DMR) and the Mahali mole-rat, Cryptomys hottentotus mahali (MMR). Both terminal and non-terminal telomeric sequences were identified in chromosomes of the NMR and DMR, whilst the MMR displayed only terminal telomeric repeats. Measurements of tooth wear and eruption patterns in wild caught DMRs and MMRs, and known ages in captive bred NMRs, were used to place individuals into relative age classes and compared with a quantitative measure of telomeric fluorescence (as a proxy for telomere size). While NMRs and MMRs failed to show an age-related decline in telomeric fluorescence, the DMR had a significant decrease in fluorescence with age, suggesting a decrease in telomere size in older animals. Our results suggest that among African mole-rats there is variation between species with respect to the role of telomere shortening in ageing, and the replicative theory of cellular senescence.

The Effect of Cellular Coenzyme Q10 Deficiency on Lysosomal Acidification.

Coenzyme Q10 (CoQ10) deficiency currently represents the only treatable mitochondrial disorder, however, little is known about how it may affect other organelles. The lysosome has been found to have a large concentration of CoQ10 localised at its membrane; additionally, it has been suggested that it plays a role in the normal acidification of the lysosomal lumen. As a result, in this study we assessed the effect of CoQ10 deficiency on lysosomal acidification. In order to investigate this, a neuronal cell model of CoQ10 deficiency was established via the treatment of SH-SY5Y cells with para-aminobenzoic acid (PABA). This method works through the competitive inhibition of the CoQ10 biosynthetic pathway enzyme, CoQ2. A single 1 mM (5 days) treatment with PABA resulted in a decrease of up to 58% in cellular CoQ10 (p < 0.05). It was found that this resulted in a significant decrease in fluorescence of both the LysoSensor (23%) and LysoTracker (35%) probes used to measure lysosomal pH (p < 0.05). It was found that subsequent treatment with CoQ10 (5 µM, 3 days) was able to restore cellular CoQ10 concentration (p < 0.005), which was associated with an increase in fluorescence from both probes to around 90% of controls (p < 0.05), suggesting a restoration of lysosomal pH. This study provides insights into the association between lysosomal pH and cellular CoQ10 status and the possibility that a deficit in the status of this isoprenoid may result in an impairment of lysosomal acidification.

Aggregation-Induced Emission Enhancement of CdSe QDs by Protamine and its Application to Sensitively and Selectively Detect Heparin

Background: Heparin, it is commercially used as an anticoagulant in surgical procedures for the prevention of blood clotting. However, overdose and prolonged use of heparin often induce potentially fatal bleeding complication. So, it is of crucial importance to monitor closely heparin levels for the sake of health. In this work, a sensitive fluorescence sensing platform to detect heparin was set up based on MPA-CdSe QDs (quantum dots) and protamine enhanced fluorescent system. Methods: The image of CdSe QDs was taken on a JEM-2100 transmission electron microscope (JEOL Ltd.). The fluorescence spectrum was recorded on a FluoroMax-4 fluorescence spectrophotometer (Horiba, USA). UV–vis absorption spectrum was recorded using a Shimadzu UV-2450 Spectrophotometer (Tokyo, Japan). A vortex mixer IKA MS3 digital was selected to mix the solution. Results: Under optimized conditions, the linear response to detect heparin ranges from 0.06 to 14 µg mL-1 with a detection limit of 8 ng mL-1. The approach showed a highly selective response to heparin in the presence of 16 interfered substances. Conclusion: A simple method for the detection of heparin was developed based on MPA-CdSe QDs and protamine enhanced fluorescent system. The electrostatic effect between MPA-CdSe QDs and protamine resulted in strong fluorescence enhancement from the MPA-CdSe QDs. Moreover, the addition of heparin could cause a significant fluorescence decrease due to the strong affinity of protamine and heparin. Under optimal conditions, this method displayed a low detection limit and good selectivity over other substances.

Nitrogen-doped carbon dots synthesized from acrylic acid and ethylenediamine for simple and selective determination of cobalt ions in aqueous media

Fluorescent nitrogen-doped carbon dots (NCDs) with a quantum yield of 22.7% and an average size of about 4.28 nm were hydrothermally synthesized using acrylic acid and ethylenediamine in one pot. When excited at 350 nm, the NCDs showed a strong emission peak centered at 425 nm, corresponding to blue fluorescence. Interestingly, for NCDs, significant decrease in fluorescence was observed upon addition of cobalt ions (Co2+). On the basis of this particular phenomenon, the synthesized NCDs are demonstrated as an effective fluorescence probe for the selective and quantitative analysis of low concentration Co2+ in a linear range of 1.0–60 µM. Limit of detection (LOD) is 0.25 µM. Further detailed investigations on the interactions of NCDs with Co2+ as quencher by using various techniques (UV–vis absorption and time-resolved fluorescence techniques) confirmed that the fluorescence quenching is mainly induced by the interaction of between Co2+ and some functional groups of NCDs.

Quantum dots based imprinting fluorescent nanosensor for the selective and sensitive detection of phycocyanin: A general imprinting strategy toward proteins

Molecular imprinting as a versatile technology has gained popularity in various fields for diverse species; however, protein imprinting still remains challenging due to some inherent problems but is potentially rewarding work. Herein, we reported a facile strategy to imprint phycocyanin (PC), as a template, using quantum dots (QDs) co-capped by thioglycollic acid and glutathione directly as functional monomer via dopamine self-polymerization, which effectively simplified the imprinting process and afforded easy accessibility to recognition sites. The resulting QDs based imprinting nanosensor showed significant fluorescence decrease of QDs within less than 16s upon binding PC owing to the ultrathin imprinting layer (ca. 3nm), leading to a high detectability down to 0.075μM. An excellent linearity was found within the wide range of 0.8–8.0μM (R2=0.9935). Good recognition selectivity toward PC was displayed over other possible competing molecules, with a high imprinting factor of 7.3. Seawater and lake water samples spiked with PC were also analyzed, presenting satisfactory recoveries ranging from 90.8–110.1% with precisions below 4.6%, indicating the practicality of the imprinting nanosensor for accurately rapid nanoscale monitoring of algae blooms. By using another protein, bovine haemoglobin (BHb), as a convincing support model, the present study can provide a simple and general imprinting strategy toward various concerned proteins through rationally utilizing diverse functionalization and interactions.

A graphene-phthalocyanine hybrid as a next photoactive layer

Highly dispersible graphene was hybridized with a phthalocyanine derivative via covalent linkage to create a new type of donor-acceptor hybrid exhibiting photoinduced charge separation. Graphene is beneficial for the hybridization due to its easy functionalization and the unique electron accepting ability. A phthalocyanine (PC) derivative, pyrazine-based silicon phthalocyanine dichloride, possessing rich π-conjugated macrocycle was used for the electron donating purpose. The hybrid molecule showed a significant decrease in fluorescence of π-conjugated PC, implying an efficient photoinduced charge transfer occurring within the covalently-linked molecular structure consisting of “donor-acceptor”. The graphene-PC hybrid molecule has also been demonstrated as an active layer material in organic photovoltaic device as well. Thus our results indeed underline the efficacy of the molecular level heterojunction of the covalently linked graphene-PC molecule in a single cell and will open new opportunities ahead for active layers research to go beyond conventional bulk-heterojunction (BHJ).

The Neurotoxic Effect of Manganese on Dopamine Post‐Synaptic Receptors Are Reversed by Taurine

Manganese (Mn), a neurotoxin causing the human disease Manganism, a Parkinson's‐like syndrome, disrupts dopamine neurotransmission in the brain. The neurotoxic mechanism of action is not fully resolved. Reports postulate manganese toxicity is more related to post‐synaptic dopamine D2 receptors (D2DR) dysfunction, than degeneration of dopamine neurons. Gill lateral ciliated cells of Crassostrea virginica are innervated by cilio‐inhibitory dopamine nerves via the branchial nerve and have D2DR type post‐synaptic receptors. Our previous physiological work found Mn treatments block the cilio‐inhibitory effect of dopamine on gill lateral cells and our immunohistofluorescence work with FITC‐labeled 2° antibodies against anti‐D2DR showed Mn treatments reduced FITC fluorescent intensity in gill lateral cells. The results suggest that either Mn toxicity causes a loss of D2DR number or a structural disruption of receptor integrity. Currently there is no effective clinical treatment for Manganism. There are reports the drug p‐aminosalicylic acid (PAS) alleviates some of the symptoms and our physiological and immunohistofluorescence studies with C. virginica showed PAS reversed the toxic action of Mn on the animals' dopaminergic system. Recently the amino acid taurine has been shown to alleviate symptoms in a number of neurodegenerative diseases. In the present study we hypothesize taurine would reverse the neurotoxic effect of Mn on gill lateral cell D2DR in C. virginica. To test this C. virginica were treated for 3 or 5 days with Mn (500 μM) followed by 3 or 5 days with taurine (500 μM), respectively. Gills were excised and treated for immunohistofluorescence as previously done. Briefly, gills were fixed in paraformaldehyde, exposed to rabbit anti‐D2DR 1° antibodies followed by FITC‐labeled goat anti‐rabbit 2° antibodies, paraffin embedded, sectioned at 10 μm and visualized on a fluorescence microscope. Fluorescence intensity was quantified using ImageJ software from NSF. Results show fluorescence intensity in gill cells of animals treated with Mn had a statistically significant decrease in fluorescence, 66% less than non‐Mn treated controls. Animals treated with 3 days of Mn followed by 3 days of taurine had gill cells showing only an 18% reduction in fluorescence intensity compared to controls. Animals treated 5 days with Mn followed by 5 days with or without taurine gave similar results. The study indicates taurine was able to reverse the Mn induced loss of post‐synaptic D2DR fluorescence similarly to what occurred with PAS treatments. The neuroprotective mechanism of taurine needs to be further investigated. This immunohistological study suggests taurine may be a promising therapeutic agent in the treatment of Manganism in humans.Support or Funding InformationThis work was supported in part by PSC‐CUNY grant 690340047, 2R25GM06003 of the Bridge Program of NIGMS and a Carnegie Foundation award.

Analysis of the Color and Fluorescence Alterations of Enamel and Dentin Treated With Hydrogen Peroxide

The aim of this study was to evaluate the effect of hydrogen peroxide whitening on fluorescence and color of bovine enamel and dentin. Twenty five dentin discs and 25 enamel discs, with 6 mm diameter and 1 mm thick, were obtained. Direct fluorescence (spectrofluorophotometry) and color (spectrophotometry) were assessed. After fluorescence and color baseline measurements, specimens were immersed in a 35% hydrogen peroxide (HP) solution for 1 h. This procedure was repeated after 7 days. Final fluorescence and color measurements were performed after the second immersion. Chemical characterization of 5 additional specimens was also performed. Data were submitted to repeated analysis of variance and Tukey's test for fluorescence and unpaired t-test for color and chemical components (p<0.05). Fluorescence decreased significantly in dentin specimens after whitening. Enamel presented lower fluorescence than dentin at baseline, but this parameter did not decrease after whitening. Color changes were observed for both substrates, with significantly greater whitening effect in dentin (ΔE=10.37) (p<0.001). Whitening by hydrogen peroxide induced significant decrease in fluorescence of tooth dentin and promoted significant color changes in dentin and enamel with more accentuated outcomes in dentin.

Thiophene aldehyde-diamino uracil Schiff base: A novel fluorescent probe for detection and quantification of cupric, silver and ferric ions

A new Schiff base from the condensation of 5,6-diamino-1,3-dimethyluracil with 5-methylthiophene-2-carboxaldehyde was synthesized. The compound was characterized by spectral data (UV–Vis, IR, 1H NMR, fluorescence, MS). Ethanolic solutions of the Schiff base exhibit a strong fluorescence emission at 385nm (λex=341nm), and have been employed as a “turn-off” fluorescent probe for selective detection of Ag+, Cu2+ and Fe3+ ions in presence of other cations such as Na+, K+, Ca2+ and Mg2+ ions abundant in natural water. The interaction between the tested compound and copper, silver or iron ions is associated with a significant fluorescence decrease, showing detection limits of 2.1–14.2ppb. Under optimal conditions, the developed sensor was successfully employed to determine Ag+, Cu2+ and Fe3+ ions in real samples and proved to be selective and sensitive.

PTH(1-34) Treatment Increases Bisphosphonate Turnover in Fracture Repair in Rats.

Bisphosphonates (BP) are antiresorptive drugs with a high affinity for bone. Despite the therapeutic success in treating osteoporosis and metabolic bone diseases, chronic BP usage has been associated with reduced repair of microdamage and atypical femoral fracture (AFF). The latter has a poor prognosis, and although anabolic interventions such as teriparatide (PTH(1-34) ) have been suggested as treatment options, there is a limited evidence base in support of their efficacy. Because PTH(1-34) acts to increase bone turnover, we hypothesized that it may be able to increase BP in turnover in the skeleton, which, in turn, may improve bone healing. To test this, we employed a mixture of fluorescent Alexa647-labelled pamidronate (Pam) and radiolabeled (14) C-ZA (zoledronic acid). These traceable BPs were dosed to Wistar rats in models of normal growth and closed fracture repair. Rats were cotreated with saline or 25 μg/kg/d PTH(1-34) , and the effects on BP liberation and bone healing were examined by X-ray, micro-CT, autoradiography, and fluorescent confocal microscopy. Consistent with increased BP remobilization with PTH(1-34) , there was a significant decrease in fluorescence in both the long bones and in the fracture callus in treated animals compared with controls. This was further confirmed by autoradiography for (14) C-ZA. In this model of acute BP treatment, callus bone volume (BV) was significantly increased in fractured limbs, and although we noted significant decreases in callus-bound BP with PTH(1-34) , these were not sufficient to alter this BV. However, increased intracellular BP was noted in resorbing osteoclasts, confirming that, in principle, PTH(1-34) increases bone turnover as well as BP turnover.

Effect of tablets containing probiotic bacteria (Lactobacillus reuteri) on early caries lesions in adolescents: a pilot study.

The objective of the study was to investigate the effect of tablets containing probiotic lactobacilli on early caries lesions in adolescents with quantitative light-induced fluorescence (QLF). 36 healthy adolescents of both sexes (12-17 years of age) were enrolled and randomly allocated to a placebo-controlled trial with two parallel groups. The test group received two tablets daily containing two strains of Lactobacillus reuteri (DSM 17938 and ATCC PTA 5289) for a period of three months, while the control group got identical placebo tablets without live bacteria. The primary outcome was QLF-readings (change in fluorescence, ΔF and lesion area, mm2) at baseline and after 3 months, conducted at two buccal sites of each individual, pre-selected with clearly visible clinical signs of enamel demineralisation (white spots). Significantly more premolars were allocated to the placebo group, while the test group had more incisors (P<0.05). There were no statistically significant differences in fluorescence values between the groups, neither at baseline, nor at the follow-up. There was however a significant decrease in fluorescence over time in the test group, but not in the placebo group (P<0.05). No alterations of the lesion area (ΔA) were found in any group. The inter-examiner intra-class correlation coefficient-value for QLF-readings was excellent. No side- or adverse effects were reported during the intervention period. This pilot study found a significant decrease over time in the test group. However, no statistically significant differences in fluorescence values between the groups were found. Hence, the null hypothesis could not be rejected.

Water dispersible, non-cytotoxic, cross-linked luminescent AIE dots: Facile preparation and bioimaging applications

Fluorescent organic nanoparticles have attracted great current research interest due to their superior properties as compared with small organic dyes and fluorescent inorganic nanoparticles. However, fluorescent organic nanoparticles based on conventional organic dyes often result in significant fluorescence decrease due to the notorious aggregation-caused quenching effect. On the other hand, these fluorescent organic nanoparticles obtained from self-assembly are normally not stable in diluted solution. Therefore, the development of novel fluorescent organic nanoparticles which could overcome these limitations is highly desirable for their practical biomedical applications. In this work, water dispersible, non-cytotoxic and cross-linked luminescent polymeric nanoparticles based on aggregation induced emission dyes were prepared via one pot emulsion polymerization. These cross-linked luminescent polymeric nanoparticles emitted strong red fluorescence and were highly stable in diluted aqueous solution, making them highly potential for various biomedical applications.

Integrating physicochemical information to follow the transformations of biomass upon torrefaction and low-temperature carbonization

Morphological and structural changes of different types of biomass after torrefaction and low-temperature carbonization processes have been investigated using a variety of characterization techniques comprising Fourier-Transform infrared spectroscopy (FTIR), gas adsorption at different pressures, thermogravimetry, optical and scanning electron microscopy techniques together with chemical analysis. The biomasses selected included softwood chips (pine), hardwood chips (acacia, eucalyptus, forest residues from eucalyptus) and olive stone. Torrefaction led to the enrichment of carbon and a decrease in reactivity, accompanied by a decrease in the hydrogen- and oxygen-bearing functionalities and a slight increase in aromatization. This was physically reflected in cell-wall shrinkage, resulting in a brittle, well-defined vegetal structure with moderate microporosity, in which slight increase in cell-wall reflectance and significant decrease in fluorescence have been produced. Carbonization at 450°C in turn led to a further loss of oxygen functionalities and a large increase in aromaticity, reflecting the virtual disappearance of hemicellulose and cellulose. This caused a significant increase in optical reflectance, loss of fluorescence and development of both meso- and microporosity generating an isotropic solid with a disordered structure similar to that of industrial charcoal. The microscopy techniques also showed the heterogeneity of the treated samples in terms of reflectance distribution or fluorescence properties, which cannot be assessed by bulk characterization techniques. They indicated a greater heterogeneity in the sample treated at torrefaction temperatures. The different characterization techniques have revealed minor differences between hardwood and softwood behavior, essentially attributed to resinous impregnations in the latter, whereas greater differences were observed between woods and olive stone due to significant differences in their internal and external structure.

Photodegradation of luminescence in organic-ligand-capped Eu3+:LaF3 nano-particles

The luminescence from europium doped lanthanum trifluoride (Eu3+:LaF3) nano-crystals can be greatly enhanced by capping with β-diketonate organic ligands. Here, we report on photo-stability measurements for the case of nano-crystals capped with thenoyltrifluroacetone (TTA) and compared with those capped with an inactive ligand, oleic acid. With exposure to UV pump light, we observed significant decrease in fluorescence and change in emission spectrum of the TTA-capped nano-particles whilst the fluorescence lifetime remained approximately constant. After a dose of order 70 kJ cm−2, the luminescence level was similar to that of oleic acid capped nano-crystals. We discuss possible mechanisms.