Search Results (9)

We report a comprehensive investigation of the photophysical properties of Hoechst 33258 (HOE) embedded in polyvinyl alcohol (PVA) films. HOE displays a bright, highly polarized, blue fluorescence emission centered at 430 nm, indicating effective immobilization within the polymer matrix of PVA. Its fluorescence quantum yield is notably high (~0.74), as determined relative to a quinine sulfate standard. In addition, we observed that HOE-doped PVA films exhibit room temperature phosphorescence (RTP) that remains visible for several seconds after UV excitation ceases. The slightly negative phosphorescence anisotropy implies that the triplet–singlet radiative transition is orthogonal to the singlet–singlet transition governing fluorescence. Notably, we observed that direct triplet-state excitation at longer wavelengths (beyond the primary absorption band) produces highly polarized RTP. We believe this possibility of direct triplet-state excitation opens new avenues for studying RTP in polymer-immobilized molecules. Full article

Coastal concrete structures, such as cross-sea bridges and tunnels, are susceptible to the penetration of chloride ions, which can lead to the deterioration of the passive film on the rebar surface, consequently accelerating the corrosion process. Conventional methods for monitoring chloride ions typically require in situ drilling for sample collection, thereby compromising efficiency and accuracy. Additionally, real-time monitoring and early warning cannot be achieved. To address these challenges, this work introduces a fluorescent-probe-based fiber optic sensor for monitoring chloride levels in concrete structures. Quinine sulfate was chosen as the fluorescent material due to its exceptional sensitivity to chloride ions and its stability in concrete environments. The proposed sensor was manufactured using sol–gel and 3D-printing techniques. Tests were conducted using concrete simulation fluid and cement mortar specimens. The results demonstrate that the sensitivity of the proposed sensor is greater than 0.01 M, and its accuracy in penetration depth measurement is better than 3 mm. The findings confirm that the designed fiber optic sensor based on quinine sulfate enables real-time monitoring of chloride ions in concrete structures, offering high sensitivity (0.1% in concentration and 2.7 mm in terms of penetration depth), unique selectivity (as it is immune to other ions whose concentrations are 10 times higher than those of Cl⁻), and a compact size (10 × 20 mm). These attributes render it promising for practical engineering applications. Full article

The direct infusion of bitter solutions in the gastrointestinal tract can reduce the secretion of orexigenic hormones and influence appetite and food intake. We aimed to explore whether oral ingestion of the bitter tastant hydroxychloroquine sulfate can exert similar effects. Ten lean adult women were included in this double-blind, randomized, two-visit, crossover study. After an overnight fast, each volunteer received film-coated tablets containing 400 mg of hydroxychloroquine sulfate (Plaquenil^®) or placebo. Plasma-ghrelin, -motilin, -insulin and blood-glucose concentrations were determined every 10 min before and 30 min after feeding; appetite was scored every 10 min. Hunger scores were investigated with a special interest 50–60 min after the ingestion of hydroxychloroquine sulfate, right before a rewarding chocolate milkshake was offered to drink ad libitum. Compared with the placebo, hydroxychloroquine sulfate tended to reduce hunger at the time of interest (p = 0.10). No effect was found upon subsequent milkshake intake. Motilin plasma concentrations were unaltered, but acyl-ghrelin plasma concentrations decreased after the ingestion of hydroxychloroquine sulfate (t = 40–50; p < 0.05). These data suggest that the oral intake of hydroxychloroquine sulfate tablets reduces subjective hunger via a ghrelin-dependent mechanism but does not affect motilin release, hedonic food intake or insulin levels in healthy women. Full article

Precipitation is considered a key factor influencing the fluorescent dissolved organic matter (FDOM) of urban rivers. However, the multiple effects of precipitation on FDOM in urban rivers and the long-term impacts of precipitation on the spatial patterns of FDOM are seldom known. Spatiotemporal variations of FDOM at 36 sites from the urban rivers of Jinan City during dry and wet seasons were investigated in this study. Four components were identified using an excitation–emission matrix and parallel factor analysis. Overall, the total fluorescence intensities in dry and wet seasons ranged from 6.59 to 35.7 quinine sulfate units (QSU) and 3.42 to 69.3 QSU, respectively. Significant variations were found for different components that C2 and C3 declined but C4 increased in the wet season (p < 0.05). The temporal variations for different components could be explained by the different combined effects of precipitation dilution and flushing. Three different reference FDOM sources, including background water, spring water, and wastewater treatment plant (WWTP) outlets, were illustrated using principal coordinate analysis (PCoA). The places of FDOM in most sites were more closed to the PCoA location of WWTP outlets in the dry season while central shifted in the wet season. The changes of FDOM sources in the wet season could be explained by the mixed effect of precipitation. In conclusion, this study provided new insights into the multiple impacts of precipitation on FDOM in urban river systems, and also data support for precise pollution discharge and water resource management. Full article

Prior work suggests humans can differentiate between bitter stimuli in water. Here, we describe three experiments that test whether beer consumers can discriminate between different bitterants in beer. In Experiment 1 (n = 51), stimuli were intensity matched; Experiments 2 and 3 were a difference from control (DFC)/check-all-that-apply (CATA) test (n = 62), and an affective test (n = 81). All used a commercial non-alcoholic beer spiked with Isolone (a hop extract), quinine sulfate dihydrate, and sucrose octaacetate (SOA). In Experiment 1, participants rated intensities on general labeled magnitude scales (gLMS), which were analyzed via ANOVA. In Experiment 2, participants rated how different samples were from a reference of Isolone on a 7-point DFC scale, and endorsed 13 attributes in a CATA task. DFC data were analyzed via ANOVA with Dunnett’s test to compare differences relative to a blind reference, and CATA data were analyzed via Cochran’s Q test. In Experiment 3, liking was assessed on labeled affective magnitude scales, and samples were also ranked. Liking was analyzed via ANOVA and rankings were analyzed with a Cochran–Mantel–Haenszel test. Experiment 1 confirmed that samples were isointense. In Experiment 2, despite being isointense, both quinine (p = 0.04) and SOA (p = 0.03) were different from Isolone, but no significant effects were found for CATA descriptors (all p values > 0.16). In Experiment 3, neither liking (p = 0.16) or ranking (p = 0.49) differed. Collectively, these data confirm that individuals can discriminate perceptually distinct bitter stimuli in beer, as shown previously in water, but these differences cannot be described semantically, and they do not seem to influence hedonic assessments. Full article

Two novel highly fluorescent hyperbranched polybenzobisthiazole amides with a donor–acceptor architecture and large Stokes shift were rationally designed and synthesized. The chemical structures of the prepared hyperbranched polymers were characterized using Fourier Transform Infrared Spectroscopy (FTIR) analysis, Hydrogen Nuclear Magnetic Resonance (¹H-NMR) analysis, and Gel Permeation Chromatography (GPC) analysis. These two polymers were soluble in dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF), and their DMSO and DMF solutions emitted strong green light (517–537 nm) with high quantum yields (QYs) and large Stokes shifts. Their relative fluorescence QYs in the DMSO solution were calculated as 77.75% and 81.14% with the Stokes shifts of 137 nm (0.86 eV) and 149 nm (0.92 eV) for HP–COOH and HP–NH₂, respectively, using quinine sulfate as the standard. In the DMF solution, the QYs of HP–COOH and HP–NH₂ were calculated as 104.65% and 118.72%, with the Stokes shifts of 128 nm (0.79 eV) and 147 nm (0.87 eV), respectively. Their films mainly emitted strong blue light with the maximum emission wavelengths of 436 nm and 480 nm for HP–COOH and HP–NH₂, respectively. The Stokes shifts for HP–COOH and HP–NH₂ films were 131 nm (0.42 eV) and 179 nm (0.86 eV), respectively. They are promising candidates for luminescent solar concentrators and blue light emitting materials. Full article

Algal biofuels are investigated as a promising alternative to petroleum fuel sources to satisfy transportation demand. Despite the high growth rate of algae, predation by rotifers, ciliates, golden algae, and other predators will cause an algae in open ponds to crash. In this study, Chlorella kessleri was used as a model alga and the freshwater rotifer, Brachionus calyciflorus, as a model predator. The goal of this study was to test the selective toxicity of the chemical, quinine sulfate (QS), on both the alga and the rotifer in order to fully inhibit the rotifer while minimizing its impact on algal growth. The QS LC₅₀ for B. calyciflorus was 17 µM while C. kessleri growth was not inhibited at concentrations <25 µM. In co-culture, complete inhibition of rotifers was observed when the QS concentration was 7.7 µM, while algal growth was not affected. QS applications to produce 1 million gallons of biodiesel in one year are estimated to be $0.04/gallon or ~1% of Bioenergy Technologies Office’s (BETO) projected cost of $5/gge (gallon gasoline equivalent). This provides algae farmers an important tool to manage grazing predators in algae mass cultures and avoid pond crashes. Full article

A series of a new type of Schiff bases 1–7, derived from 2-phenyl-3-amino-4(1H)-quinolinone and R-salicyladehyde derivatives wherein R = 3-hydroxy (1), 3,4-dihydroxy (2), 3-methoxy (3), 3-carboxy (4), 3-allyl (5), 5-chloro (6), and 5-nitro (7), was synthesized and structurally characterized. Each of the molecules 1, 3 and 7 consists of three planar moieties (i.e., a quinolinone and two phenyl rings), which are mutually oriented differently depending on the appropriate substituent R and the extent of non-covalent contacts stabilizing the crystal structures. The compounds were studied for their fluorescence properties, where compound 6 yielded the strongest intensity both in the solid phase and in 100 μM ethanol solution with a quantum yield of φ = 3.6% as compared to quinine sulfate used as a standard. The in vitro cytotoxicity of these compounds was tested against the human osteosarcoma (HOS) and breast adenocarcinoma (MCF7) cell lines, revealing no activity up to the concentration of 50 µM. Full article

This study presents results from field surveys performed over various seasons in a large, eutrophic, shallow lake (Lake Taihu, China) using an in situ chromophoric dissolved organic matter (CDOM) fluorescence sensor as a surrogate for other water quality parameters. These measurements identified highly significant empirical relationships between CDOM concentration measured using the in situ fluorescence sensor and CDOM absorption, fluorescence, dissolved organic carbon (DOC), chemical oxygen demand (COD) and total phosphorus (TP) concentrations. CDOM concentration expressed in quinine sulfate equivalent units, was highly correlated with the CDOM absorption coefficient (r² = 0.80, p < 0.001), fluorescence intensities (Ex./Em. 370/460 nm) (r² = 0.91, p < 0.001), the fluorescence index (r² = 0.88, p < 0.001) and the humification index (r² = 0.78, p < 0.001), suggesting that CDOM concentration measured using the in situ fluorescence sensor could act as a substitute for the CDOM absorption coefficient and fluorescence measured in the laboratory. Similarly, CDOM concentration was highly correlated with DOC concentration (r² = 0.68, p < 0.001), indicating that in situ CDOM fluorescence sensor measurements could be a proxy for DOC concentration. In addition, significant positive correlations were found between laboratory CDOM absorption coefficients and COD (r² = 0.83, p < 0.001), TP (r² = 0.82, p < 0.001) concentrations, suggesting a potential further application for the real-time monitoring of water quality using an in situ CDOM fluorescence sensor. Full article