Luminescence最新文献

Bioluminescence inhibition (BLI) measurements in bioluminescent bacteria (BB) is perceived as a potential qualitative and quantitative indicator of hazardous materials. Acute but minor fluctuations in osmolarity and pH do not affect the living systems significantly. However, significant BLI is observed from marine BB due to acute osmolarity or pH changes that may affect the bioassay sensitivity. Often, real samples have low pH and osmolarity, interfering with the hazard assessment based on the principles of BLI. This anomaly in BLI measurements may lead to false positives. Therefore, modifications in existing analytical methods to overcome such practical constraints are envisaged. In the present research, a marine BB was utilized to study the luminescence reversal effect when exposed to stressful environments such as hypotonic (deionized water), acidic (50 μM to 50 mM HCl), and 0.1-100 ppm of Hg(II) for 0-30 min. Postincubation, the calcium alginate immobilized bioluminescent bacteria (biophotonic beads) were transferred to Boss media to observe any luminescence enhancement. The results showed that osmotic shock and low-strength acidic environments (50 μM to 0.5 mM HCl) at specified incubation times were not detrimental to the biophonic beads regarding luminescence response.

The present study introduces the idea of a novel fluorescence-based imaging technique combined with a microfluidic platform that enables a precise control of dark transient state populations of fluorescent probes flowing over a uniform, top flat supergaussian excitation field with a constant flow rate. To demonstrate the imaging capability of the proposed detection method, numerical simulations have been performed by considering laser, microscope and flow parameters of experimental setup together with photophysical model and electronic transition rates of fluorescent dyes. As an output data to be assessed, fluorescence image data is simulated numerically for bromine-free carboxyfluorescein and its brominated derivatives having different numbers of bromine atoms. Based on the magnitudes of applied excitation irradiances and flow rates, which can be manually controlled by user during experiments, the presence of dark state populations can appear as broadening, shifts and decays in normalized fluorescence intensity signals that are computed from simulated fluorescence images. As such changes in signals become more pronounced upon an increase in the degree of bromination, it is elicited that heavy atom effect can be resolved by properly tuning excitation powers of laser and flow rates. Proposed imaging method has potential to provide invaluable means to conventional fluorescence methods and can open up new perspectives in biomedical research.

Er³⁺-doped BaF₂ single crystals were investigated with two primary aims: first, to probe the infrared emissions from the ⁴I_11/2 level (around 1.0 μm) under 1500-nm excitation and, second, to use the crystal to enhance the efficiency of silicon-based solar cells through upconversion mechanism. Upon excitation at 1500 nm, the upconversion emission spectrum of the Er³⁺-doped BaF₂ single crystals, recorded in the range of 480-1080 nm, exhibited two well-structured visible bands at 538 and 650 nm, along with a strong near infrared emission at 971 nm. This strong 971-nm emission has an emission cross-section of approximately 0.23 × 10^-20 cm². As with any phenomenon inherent to energy transfer by upconversion, the ⁴I_11/2 fluorescence decay exhibits a rise time followed by a long decay of approximately 15 ms and a positive optical gain from the low values of the population inversion coefficient, which could potentially give rise to laser emission from this level. When we place our crystal on a photovoltaic device illuminated by 1500-nm wavelength radiation, we record a photocurrent of 300 μA at an illumination power of 85 mW. This indicates that the Er³⁺-doped BaF₂ crystal is highly suitable for significantly enhancing the efficiency of silicon-based solar cells.

Mercury ions (Hg²⁺) seriously harm the central nervous system of humans, leading to brain damage and even heart failure and death. Therefore, effective detection of Hg²⁺ in water quality has become an urgent research field. It is very important to develop economically efficient fluorescent sensors to achieve rapid and sensitive detection of Hg²⁺. Therefore, the high fluorescence quantum yield fluorescent carbon dots (CDs) with amide group were prepared. The process of preparing CDs was regulated by multiple key factors (carbon source, proportion, time), and the CDs with the best fluorescence performance were selected. It was comprehensively characterized, including fluorescence performance, surface structure, phase, and morphological characteristics. The amide group endows CDs with the ability to act as both donors and acceptors for hydrogen bonding, forming complexes with metal ions, thus making them suitable for the detection of Hg²⁺. It is worth noting that CDs can quickly detect Hg²⁺ within 1 min, and there is a good linear relationship within the ranges of 0.001-200 μM and 200-500 μM. The detection limit of UC-CDs is 8.2 nM. This study provides a fluorescent sensor with fast reaction, excellent sensitivity, and selectivity for the efficient detection of Hg²⁺ in water.

Bioluminescence is a functional property used by many marine organisms for multilateral communications. In the Arabian Sea, the dinoflagellate Noctiluca scintillans (Macartney) Kofoid and Swezy, 1921, contributes gradually to the bioluminescent potential (BP) of the phytoplankton community. Experiments, field sampling, and remote sensing were employed, to estimate the seasonal variation of the BP and the abundance of cells in the northwestern Arabian Sea. An experimental setup for BP measurements integrated a "Chelsea Instruments" GlowTracka sensor, which required ~5 N. scintillans cells to obtain a statistically robust signal. Plankton were sampled with 200-μm mesh size nets, in the upper mixed layer. Also, N. scintillans cells were counted in Niskin bottle samples collected from the deep chlorophyll maximum. The remotely sensed chlorophyll-a concentration was analyzed, for the period from 2000 to 2022. A positive linear relationship between the abundance of N. scintillans cells in experiments and their BP was elucidated. Peaks of BP in experiments fit the Northeast and Southwest Monsoon periods and so did the N. scintillans abundance peaks in situ. These findings showed that BP may serve as an indicator of N. scintillans abundance and biomass in the northwestern Arabian Sea.

Hypochlorous acid (HClO) is released by immune cells in the immune system, and it helps the body fight off infections and inflammation by killing bacteria, viruses, and other pathogens. However, tissue damage or apoptosis may also be induced by excess HClO. On this basis, we designed the probe TPE-NS by choosing tetraphenylethylene (TPE) as the luminescent unit and dimethylthiocarbamoyl chloride as the recognition site. By Gaussian's transition state calculations, HClO will cut off the photoinduced electron transfer (PET) effect of TPE-NS by hydrolysis reaction, thus emitting strong fluorescence. TPE-NS has rapid recognition and excellent specificity for HClO, and the limit of detection is 7.27 μM. Finally, TPE-NS was successfully used for the visualization of endogenous and exogenous HClO in cell experiments.

Spectroscopic properties of Tb-doped and Tb-Ag codoped lithium tetraborate (LTB) glasses with Li₂B₄O₇ (or Li₂O-2B₂O₃) composition are investigated and analysed using electron paramagnetic resonance (EPR), optical absorption, photoluminescence (PL) and photoluminescence excitation (PLE) spectra, PL decay kinetics and absolute quantum yield (QY) measurements. PL spectra of the investigated glasses show numerous narrow emission bands corresponding to the ⁵D₄ → ⁷F_J (J = 6-0) and ⁵D₃ → ⁷F_J (J = 5-3) transitions of Tb³⁺ (4f⁸) ions. The most intense PL band of Tb³⁺ ions at 541 nm (⁵D₄ → ⁷F₅ transition) is characterised by a lifetime slightly exceeding 2.6 ms. PL spectra of the Ag-containing glass show two broad weakly resolved emission bands in the violet-green spectral range attributed to Ag⁺ ions and nonplasmonic Ag nanoclusters. Decay kinetics of these bands are nonmonoexponential, characterised by an average lifetime in the microsecond range. A significant enhancement of the PL intensity and PL QY of Tb³⁺ ions was observed in Tb-Ag codoped LTB glass in comparison with Tb-doped LTB glass. The excitation energy transfer (EET) mechanisms from Ag⁺ ions and Ag nanoclusters to Tb³⁺ ions were explored.

In this paper, a series of BaSrCaWO₆:x%Mn⁴⁺, y%La³⁺ (x = 0.1, 0.5, 0.6, 1.5; y = 0, 5, 10, 15, 20) red-emitting phosphors were synthesized by the high-temperature solid-state method. The structure and optical properties of the samples were systematically studied by the characterizations of x-ray diffraction (XRD), scanning electron microscope (SEM), UV-Vis spectra, photoluminescence (PL) spectra, photoluminescence excitation (PLE) spectra, and quantum efficiency (QE). It was found that the addition of La³⁺ ions plays significant roles on the luminous performance of phosphors as compared with the nonluminous BaSrCaWO₆:Mn (BSCW:Mn), which can be attributed to the Mn²⁺ → Mn⁴⁺ oxidation process induced by La³⁺ doping. The BSCW:0.5%Mn, 15%La³⁺ phosphor exhibited a strong emission peak at 685 nm with a CIE chromaticity coordinate at (0.720, 0.279), which is suitable for application in indoor plant cultivations. The BSCW:0.5%Mn, 15%La³⁺ phosphor exhibited an IQE of 47.8% and a high absorption efficiency of 72.8% with the EQE of 34.8%. Besides, the phosphor also showed the thermal stability with the emission intensity at 423 K being 48% of the emission intensity at 298 K. These results indicate that the synthesized BSCW:0.5%Mn, 15%La³⁺ phosphor could be a potential phosphor to be applied in plant growth LEDs.

Currently, the development of red Mn⁴⁺-activated fluoride luminescent materials attracts a lot of attention in optical thermometry sensors, solid lighting, display, and plant growth areas. Nevertheless, the thermal stability of Mn⁴⁺-activated fluoride luminescent materials is still a crucial issue. Herein, a new red Rb₂NaVF₆:Mn⁴⁺ luminescent material with outstanding thermal stability was successfully synthesized through the facial coprecipitation method. Mn⁴⁺ ions prefer to occupy VF₆ octahedra based on the accurate Rietveld refinement results. Accordingly, the as-prepared Rb₂NaVF₆:Mn⁴⁺ exhibits a broad absorption region from 300 to 500 nm with a maximum of 468 nm, matching well with the near-ultraviolet and blue InGaN chip. Upon 468 nm excitation, Rb₂NaVF₆:Mn⁴⁺ can emit narrow-band red light at 632 nm. Notably, Rb₂NaVF₆:Mn⁴⁺ shows superior antithermal quenching properties, of which the integrated intensities at 175°C can realize as high as 140% than that at 25°C. Owing to the diverse thermal quenching behavior between anti-Stokes and Stokes emission, Rb₂NaVF₆:Mn⁴⁺ displays promising candidates in optical thermometry sensors with a relative sensitivity S_r of 0.49%. This study offers new insight into developing antithermal quenching red Mn⁴⁺-activated fluoride luminescent materials.