Evaluation of Acridine in Nafion as a Fluorescence-Lifetime-Based pH Sensor

2003 ◽  
Vol 57 (1) ◽  
pp. 73-79 ◽  
Author(s):  
Alan G. Ryder ◽  
Sarah Power ◽  
Thomas J. Glynn
Keyword(s):  
Excited State ◽  
Fluorescence Lifetime ◽  
Light Emitting Diode ◽  
Ph Sensor ◽  
Average Lifetime ◽  
Ph Sensing ◽  
Light Emitting ◽  
Ph Response ◽  
Ph Values ◽  
The Impact

We report a novel fluorescence-lifetime-based pH sensing method that utilizes acridine incorporated into Nafion (AcNaf) as the fluorescent indicator. The AcNaf sensor is excited using a 380 nm light emitting diode (LED) and the fluorescence lifetimes are measured at 450 and 500 nm. The fluorescence behavior of acridine as a function of pH in aqueous phosphate buffers and incorporated into the Nafion membrane has been investigated. The results show that incorporating acridine into Nafion changes the apparent ground-state pKa from ∼5.45 to ∼9, while the apparent excited-state pKa* is only slightly changed (∼9.4 in 0.1 M phosphate buffer). The AcNaf film shows a good pH response with a change in average lifetime of ∼19 ns (at an emission wavelength of 450 nm) over the pH 8 to 10 range. We also show that excited-state protonation does not occur in the AcNaf sensor film and that chloride quenching cannot occur because of the permselective nature of Nafion. We also discuss how the unique structure of Nafion affects the fluorescence behavior of acridine at various pH values and examine the impact of buffer concentration on apparent pKa and pH sensing ability.

scholarly journals Photocatalytic Degradation of Sulfolane Using a LED-Based Photocatalytic Treatment System

Catalysts ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 624
Author(s):  
Sripriya Dharwadkar ◽  
Linlong Yu ◽  
Gopal Achari
Keyword(s):  
Photocatalytic Degradation ◽  
Oil And Gas ◽  
Light Emitting Diode ◽  
Tap Water ◽  
Aqueous Media ◽  
Ultrapure Water ◽  
Light Emitting ◽  
Degradation Rates ◽  
Reduced Graphene ◽  
The Impact

Sulfolane is an emerging industrial pollutant detected in the environments near many oil and gas plants in North America. So far, numerous advanced oxidation processes have been investigated to treat sulfolane in aqueous media. However, there is only a few papers that discuss the degradation of sulfolane using photocatalysis. In this study, photocatalytic degradation of sulfolane using titanium dioxide (TiO2) and reduced graphene oxide TiO2 composite (RGO-TiO2) in a light-emitting diode (LED) photoreactor was investigated. The impact of different waters (ultrapure water, tap water, and groundwater) and type of irradiation (UVA-LED and mercury lamp) on photocatalytic degradation of sulfolane were also studied. In addition, a reusability test was conducted for the photocatalyst to examine the degradation of sulfolane in three consecutive cycles with new batches of sulfolane-contaminated water. The results show that LED-based photocatalysis was effective in degrading sulfolane in waters even after three photocatalytic cycles. UVA-LEDs displayed more efficient use of photon energy when compared with the mercury lamps as they have a narrow emission spectrum coinciding with the absorption of TiO2. The combination of UVA-LED and TiO2 yielded better performance than UVA-LED and RGO-TiO2 for the degradation of sulfolane. Much lower sulfolane degradation rates were observed in tap water and groundwater than ultrapure water.

scholarly journals Near-Infrared pH Sensor Based on a SPEEK–Polyaniline Polyelectrolyte Complex Membrane

Proceedings ◽  
2018 ◽  
Vol 3 (1) ◽  
pp. 11 ◽  
Author(s):  
Nedal Y. Abu-Thabit
Keyword(s):  
Polyelectrolyte Complex ◽  
Near Infrared ◽  
Response Times ◽  
Oxidative Polymerization ◽  
Ph Sensor ◽  
Ph Sensing ◽  
Ph Values ◽  
Sensing Applications ◽  
Ph Range ◽  
Speek Membrane

A polyelectrolyte complex (PEC) membrane based on sulfonated poly (ether ether ketone) and polyaniline (SPEEK-PANI) was developed for pH sensing applications. Aniline was polymerized in the presence of the SPEEK membrane by using in situ chemical oxidative polymerization to yield an ionically crosslinked SPEEK-PANI membrane. The fabricated membrane exhibited sensitivity in the physiological pH range of 2–8. The PEC membrane pH sensor showed good absorption properties in the near-infrared region (NIR). The membrane showed fast response during a de-doping process (≈90 s), while longer response times are essential for doping processes from the alkaline/neutral pH region to the acidic pH region, which is attributed to the presence of highly acidic sulfonic acid groups with a high buffering capacity in the PEC membrane. The SPEEK-PANI membrane exhibited slightly higher water uptake compared to the neat SPEEK membrane. The membrane exhibited good stability, as it was stored in 1M HCl solution for more than 2 years without physical or visual deterioration. A preconditioning step in 1M HCl ensured that the results were reproducible and allows the pH sensor to be used repeatedly. The PEC sensor membranes are suitable for applications that start at low pH values and move upwards to higher pH values in the 2–8 pH range.

Efficient deep-blue non-doped organic light-emitting diode with improved roll-off of efficiency based on hybrid local and charge-transfer excited state

RSC Advances ◽  
2016 ◽  
Vol 6 (74) ◽  
pp. 70085-70090 ◽  
Author(s):  
Haichao Liu ◽  
Qing Bai ◽  
Weijun Li ◽  
Yachen Guo ◽  
Liang Yao ◽  
...  
Keyword(s):  
Excited State ◽  
High Efficiency ◽  
Light Emitting Diode ◽  
Blue Emission ◽  
Light Emitting ◽  
Organic Light Emitting Diode ◽  
Deep Blue ◽  
Organic Light ◽  
Slow Roll ◽  
Donor Acceptor

Acceptor–donor–acceptor triphenylamine–phenanthroimidazole derivate (TPA–2PPI) servers as an emitter, whose device exhibits deep-blue emission, high efficiency and slow roll-off of efficiency.

Spin-Dependent Recombination in PPV and Polyfluorene LEDs

2002 ◽  
Vol 725 ◽  
Author(s):  
Anoop S. Dhoot ◽  
Neil C. Greenham
Keyword(s):  
Excited State ◽  
Quantum Efficiency ◽  
Light Emitting Diode ◽  
Careful Study ◽  
Crucial Importance ◽  
Polymer Leds ◽  
Light Emitting ◽  
Formation Probability ◽  
Triplet Excitons ◽  
Triplet Absorption

AbstractIn a polymer light-emitting diode, the fraction of excitons formed as singlets is of crucial importance in determining the quantum efficiency. We have shown that it is possible to measure excited state absorptions due to triplet excitons and polarons in working polymer LEDs, and we are able to quantify the triplet generation rate by measuring the strength of the triplet absorption. Here, we show that by careful study of singlet emission and triplet absorption in an LED based on a poly(p-phenylenevinylene) derivative we can obtain an accurate value of 83±7% for the singlet formation probability, significantly higher than the value of 25% predicted by simple spin statistics. We extend these measurements to devices based on poly(dioctyl-fluorene), where we find similarly high values for the singlet formation probability. In devices using the polyfluorene copolymer F8BT, we find that the triplet absorption is extremely small, consistent with even higher singlet formation probabilities.

The impact of LED illumination on antioxidant properties of sprouted seeds

2011 ◽  
Vol 6 (1) ◽  
pp. 68-74 ◽  
Author(s):  
Giedrė Samuolienė ◽  
Akvilė Urbonavičiūtė ◽  
Aušra Brazaitytė ◽  
Gintarė Šabajevienė ◽  
Jurga Sakalauskaitė ◽  
...  
Keyword(s):  
Light Emitting Diode ◽  
Antioxidant Properties ◽  
Radical Scavenging ◽  
Triticum Aestivum L ◽  
Alpha Tocopherol ◽  
Antioxidant Compounds ◽  
Light Emitting ◽  
Radish Sprouts ◽  
Sprouted Seeds ◽  
The Impact

AbstractThe objective of this study was to evaluate the effect of the light emitting diode (LED) spectra on the antioxidant properties of sprouted wheat (Triticum aestivum L.), radish (Raphanus sativus L.), and lentil (Lens esculenta Moenh.) seeds. Lighting experiments were performed under controlled conditions (PPFD - 100 μmol m−2 s−1; 12 h photoperiod; 27°C). The LED conditions used were: L1 - 638 nm; L2 - 455 nm, 638 nm, 669 nm, 731 nm (basal components); L3 - basal + 385 nm; L4 - basal + 510 nm and L5 - basal + 595 nm. Wheat and lentil sprouts were shown to accumulate less phenolic compounds and were more sensitive to light spectral differences when compared to radish sprouts. The antioxidant properties and contents of antioxidant compounds in seeds germinated in the dark were significantly lower than LED treated seeds. The higher content of total phenols and significant increase in alpha-tocopherol and vitamin C concentration resulted in altered DPPH free-radical scavenging capacity. Therefore we conclude that the LED spectra, based on basal components supplemented with green (510 nm) light can improve the antioxidant properties of sprouted seeds of lentil and wheat. The highest antioxidant properties of radish seeds were caused by radiation with supplemental amber (595 nm) light.

scholarly journals Impact of the light-curing source and curing time on the degree of conversion and hardness of a composite

2013 ◽  
Vol 1 (1) ◽  
pp. 91
Author(s):  
Anderson Catelan ◽  
Caetano Tamires ◽  
Boniek Castillo Dutra Borges ◽  
Giulliana Panfiglio Soares ◽  
Bruno de Castro Ferreira Barreto ◽  
...  
Keyword(s):  
Physical Properties ◽  
Light Emitting Diode ◽  
Knoop Hardness ◽  
High Irradiance ◽  
Degree Of Conversion ◽  
Curing Time ◽  
Light Emitting ◽  
Light Curing ◽  
Ft Ir ◽  
The Impact

Adequate physical properties of the resinous materials are related to clinical longevity of adhesive restorations. The aim of this investigation was to assess the impact of light-curing source and curing time on the degree of conversion (DC) and Knoop hardness number (KHN) of a composite resin. Circular specimens (5 x 2 mm) were carried out (n = 7) of the Filtek Z250 (3M ESPE) composite. The specimens were light-cured by quartz-halogen-tungsten (QTH) XL 3000 (3M ESPE, 450 mW/cm2) or light-emitting diode (LED) Bluephase 16i (Vivadent, 1390 mW/cm2) for 20, 40, or 60 s. After 24 h, absorption spectra of composite were obtained using Spectrum 100 Optica (Perkin Elmer) FT-IR spectrometer in order to calculate the DC and, KHN was performed in the HMV-2T (Shimadzu) microhardness tester under 50-g load for 15 s dwell time. DC and KHN data were subjected to 2-way ANOVA and Tukey’s test at a pre-set alpha of 0.05. The LED showed highest DC and KHN values than QTH (p < 0.05). The increase of curing time improved the DC and KHN, all curing times with statistical difference (p < 0.05). The use of light-curing units with high irradiance and/or the time of cure increased may improve the physical properties of resin-based materials.

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